Recently, modified noisy gradient descent bit flipping (MNGDBF) algorithms have been proposed to eliminate the Gaussian random generators required in the original noisy gradient descent bit flipping (NGDBF) algorithm for the decoding of low-density parity-check (LDPC) codes. In this paper, a platform has been established for the hardware implementation of the LDPC encoder, the Gaussian noise channel generator and the decoder using MNGDBF decoding algorithms based on the use of field programmable gate array (FPGA). With 6-bit quantization, results show that the error performance achieved by hardware experiments is similar to that obtained by floating-point computer simulations. Moreover, we propose a new MNGDBF algorithm, in which the flipping condition is determined with the help of the summation of all inversion functions. Experimental results show that the proposed algorithm has superior performance than the original MNGDBF algorithm.

Abstract The original online fountain codes discard a large number of symbols that do not meet the requirements at the decoder. To improve channel utilization, this article proposes a new online fountain code. In the completion phase, the proposed code improves the receiving rules of encoded symbols, that is, the encoded symbols discarded in the original online fountain codes are selectively cached. Moreover, an optimal degree selection strategy of encoded symbols is obtained in the proposed scheme. The valid degree range of the proposed strategy is also analyzed, leading to an upper bound of cached events which eventually limits the number of feedbacks. The theoretical analysis and simulation results reveal that the proposed scheme outperforms two state‐of‐the‐art online fountain codes in terms of overhead factors, number of feedback transmissions, and encoding/decoding efficiency.

In this article, we investigate the performance of physical-layer network coding (PNC) with hierarchical modulation (HM) over a two-way relay channel (TWRC). While Gray mapping is the optimal for the bit-interleaved coded modulation (BICM) systems in point-to-point communications, the superimposed constellation at the relay in PNC transmission does not maintain the same characteristics as the original Gray mapping at the users. Thus, to address this issue and obtain the optimal mapping for PNC, we propose a Pseudo-Gray (Pe-Gray) constellation for the user-end hierarchical quadrature amplitude modulation (H-QAM). In particular, we develop the design criterion for the user constellation to avoid demodulation ambiguity and more importantly, to ensure that the superimposed constellation can be Gray-mapped. The achievable rate analysis and simulation results show that the proposed Pe-Gray can achieve significant performance gains of up to 2 dB over the conventional Gray, M3, and MSED constellations in power-imbalanced HM-BICM-PNC. The performance superiority of the Pe-Gray is further demonstrated over the power-imbalanced channels, which also suggests its enhanced robustness in wireless fading channels.

In this article, we explore the application of hybrid automatic repeat request (HARQ) within the intelligent reflection surface-assisted nonorthogonal multiple access (IRS-NOMA) system. We investigate the closed-form expressions for the outage probability of multiple users in the HARQ-assisted IRS-NOMA system, considering scenarios with perfect successive interference cancellation (pSIC) and imperfect successive interference cancellation (ipSIC), respectively. A definite integral approximation method for multidimensional functions based on Gauss-Chebyshev quadrature (GCQ) is proposed to conduct the performance analysis of the proposed HARQ-assisted IRS-NOMA system. Based on the asymptotic outage probability, the diversity order of multiple users for HARQ-assisted IRS-NOMA is obtained. Under the analytical results, the diversity order of the mth$(m\gt 1)$user for the HARQ-assisted IRS-NOMA with ipSIC is zero, and that of the mth user for the HARQ-assisted IRS-NOMA with pSIC is in connection with the number of reflecting elements and the number of transmission rounds. The simulation results are presented to substantiate the accuracy of the analytical results. The results demonstrate that: 1) the HARQ-assisted IRS-NOMA systems can achieve a significant gain compared with the IRS-NOMA systems; 2) the HARQ-assisted IRS-NOMA outperforms the HARQ-assisted IRS-orthogonal multiple access in terms of outage probability and diversity order; and 3) the HARQ with incremental redundancy (HARQ-IR)-assisted IRS-NOMA system has a better performance than the HARQ with chase combining (HARQ-CC)-assisted IRS-NOMA system.

In this paper, we construct non-binary codes of lengthNwhich correct errors under a non-binary segment-Nmaxburst-Ddeletion and maxburst-Sinsertion (NB-SBDI(N, D, S)) channel without knowing the codeword boundaries. In this NB-SBDI(N, D, S) channel, at most a single non-binary burst (a block of consecutive bits/symbols) of deletions or insertions of length up toDorS, respectively, exists in a block ofNconsecutive non-binary symbols. One code named as BM-DB-MDS consists of a maximum distance separable (MDS) code, a block of periodic de Bruijn (DB) symbols, and a block of proposed periodic binary marker (BM) patterns with a period ofS+D+ 2. The other code called BM-MDS code consists of a BM code and an MDS code. We show that the rates of BM-DB-MDS and BM-MDS codes achieve λ/λ+1 (1 - 1/2t), λ ∈ N+and 1 - 1/t, respectively, whenN→ +∞, where λ represent the MDS code shortening factor, and 1/tis the rough proportion of the maximum length of burst deletions or insertions allowed in a code.

Low-density parity-check (LDPC) codes with protograph-based raptor-like (PBRL) structure have been chosen as the data channel coding scheme for the fifth-generation (5G) enhanced mobile broad band (eMBB) services. However, these 5G LDPC codes are not optimized for the scenarios of Ultra Reliable and Low Latency Communications (URLLC) and massive Machine Type Communications (mMTC) in which small transport block sizes are usually used. In this paper, a new method is proposed to construct PBRL LDPC codes for URLLC and mMTC. This method incorporates degree-distribution optimization, base matrix derived from parity-check matrix of quadratic residue codes, masking technique and modified progressive-edge-growth (PEG) algorithm. Simulation results show that the proposed PBRL LDPC codes outperform 5G LDPC short codes in terms of error-correcting performance.

In this article, we present a coding method called expanding-window zigzag decodable fountain code with unequal error protection property (EWF-ZD UEP code) to achieve scalable multimedia transmission. The key idea of the EWF-ZD UEP code is to utilize bit-shift operation and expanding-window strategy to improve the decoding performance of the high-priority data without performance deterioration of the low-priority data. To provide more protection for the high-priority data, we precode the different importance level using LDPC codes of varying code rates. The generalized variable nodes of different importance levels are further grouped into several windows. Each window is associated with a selection probability and a bit-shift distribution. The combination of bit-shift and symbol exclusive-or operations is used to generate an encoded symbol. Theoretical and simulation results on input symbols of two importance levels reveal that the proposed EWF-ZD UEP code exhibits UEP property. With a small bit shift, the decoding delay for recovering high-priority input symbols is decreased without degrading the decoding performance of the low-priority input symbols. Moreover, according to the simulation results on scalable video coding, our scheme provides better basic video quality at a lower proportion of received symbols compared to three state-of-art UEP fountain codes.

In the future 6G integrated sensing and communication (ISAC) cellular systems, networked sensing is a promising technique that can leverage the cooperation among the base stations (BSs) to perform high-resolution localization. However, a dense deployment of BSs to fully reap the networked sensing gain is not a cost-efficient solution in practice. Motivated by the advance in the intelligent reflecting surface (IRS) technology for 6G communication, this paper examines the feasibility of deploying the low-cost IRSs to enhance the anchor density for networked sensing. Specifically, we propose a novel heterogeneous networked sensing architecture, which consists of both the active anchors, i.e., the BSs, and the passive anchors, i.e., the IRSs. Under this framework, the BSs emit the orthogonal frequency division multiplexing (OFDM) communication signals in the downlink for localizing the targets based on their echoes reflected via/not via the IRSs. However, there are two challenges for using passive anchors in localization. First, it is impossible to utilize the round-trip signal between a passive IRS and a passive target for estimating their distance. Second, before localizing a target, we do not know which IRS is closest to it and serves as its anchor. In this paper, we show that the distance between a target and its associated IRS can be indirectly estimated based on the length of the BS-target-BS path and the BS-target-IRS-BS path. Moreover, we propose an efficient data association method to match each target to its associated IRS. Numerical results are given to validate the feasibility and effectiveness of our proposed heterogeneous networked sensing architecture with both active and passive anchors.

Device-to-device (D2D) communications can allow different devices to communicate in short range, which greatly meets the demand of effective transmissions. In this paper, a spectral and energy-efficient carrier index keying-aided$M$-ary differential chaos cyclic shift keying (CIK-MDCCSK) system is proposed for D2D communications, where multiple cyclic-shifted$M$-ary information-bearing signals are superimposed and transmitted by a subcarrier, and extra keying bits are transmitted by indices of the selected subcarriers. Furthermore, a carrier keying detection and$M$-ary de-mapping algorithm is proposed to retrieve the information bits transmitted by$M$-ary symbols and indices of carrier keying. The bit error rate (BER) expressions of the proposed CIK-MDCCSK system are derived over the additive white Gaussian noise (AWGN) and D2D channels, and the optimal power coefficient is deduced for performance enhancement. Then, the spectral efficiency, energy efficiency, and complexity of CIK-MDCCSK are analyzed and compared to benchmark systems to show its superiority. Next, the proposed CIK-MDCCSK system is expanded into its enhanced version for more effective transmission without degrading the BER performance. It is demonstrated by performance comparisons that the proposed CIK-MDCCSK system can achieve more than twice energy efficiency and up to 3 dB gain in BER performance compared to state-of-the-art benchmarks.

The huge amount of data produced in the 6G networks not only brings new challenges to the reliability and efficiency of mobile devices but also drives rapid development of new storage techniques. With the benefits of fast access speed and high reliability, NAND flash memory has become a promising storage solution for the 6G networks. In this paper, we investigate a protograph-coded bit-interleaved coded modulation with iterative detection and decoding (BICM-ID) utilizing irregular mapping (IM) in the NAND flash-memory systems. First, we propose an enhanced protograph-based extrinsic information transfer (EPEXIT) algorithm to facilitate the analysis of protograph codes in the IM-BICM-ID systems. With the use of EPEXIT algorithm, a simple design method is conceived for the construction of a family of high-rate protograph codes, called irregular-mapped accumulate-repeat-accumulate (IMARA) codes, which possess excellent decoding thresholds and linear-minimum-distance-growth property. Furthermore, motivated by the voltage-region iterative gain characteristics of IM-BICM-ID systems, a novel read-voltage optimization scheme is developed to acquire accurate read-voltage levels, thus minimizing the decoding thresholds (in dB) of protograph codes. Analyses and simulations indicate that the proposed IMARA-aided IM-BICM-ID scheme and read-voltage optimization scheme remarkably improve the convergence and decoding performance of flash-memory systems. Thus, the proposed protograph-coded IM-BICM-ID can be viewed as a reliable and efficient storage solution for the new-generation mobile networks, such as Internet of Vehicles.

In this work, we develop a pair of rate-diverse encoder and decoder for a two-user Gaussian multiple access channel (GMAC). The proposed scheme enables the users to transmit with the same codeword length but different coding rates under diverse user channel conditions. First, we propose the row-combining (RC) method and row-extending (RE) method to design practical low-density parity-check (LDPC) channel codes for rate-diverse GMAC. Second, we develop an iterative rate-diverse joint user messages decoding (RDJD) algorithm for GMAC, where all user messages are decoded with a single parity-check matrix. In contrast to the conventional network-coded multiple access (NCMA) and compute-forward multiple access (CFMA) schemes that first recover a linear combination of the transmitted codewords and then decode both user messages, this work can decode both the user messages simultaneously. Extrinsic information transfer (EXIT) chart analysis and simulation results indicate that RDJD can achieve gains up to 1.0 dB over NCMA and CFMA in the two-user GMAC. In particular, we show that there exists an optimal rate allocation for the two users to achieve the best decoding performance given the channel conditions and sum rate.

This paper considers the joint device activity detection and channel estimation problem in a massive Internet of Things (IoT) connectivity system, where a large number of IoT devices exist but merely a random subset of them become active for short-packet transmission in each coherence block. In particular, we propose to leverage the temporal correlation in device activity, e.g., a device active in the previous coherence block is more likely to be still active in the current coherence block, to improve the detection and estimation performance. However, it is challenging to utilize this temporal correlation as side information (SI), which relies on the knowledge about the exact statistical relation between the estimated activity pattern for the previous coherence block (which may be imperfect with unknown error) and the true activity pattern in the current coherence block. To tackle this challenge, we establish a novel SI-aided multiple measurement vector approximate message passing (MMV-AMP) framework. Specifically, thanks to the state evolution of the MMV-AMP algorithm, the correlation between the activity pattern estimated by the MMV-AMP algorithm in the previous coherence block and the real activity pattern in the current coherence block is quantified explicitly. Based on the well-defined temporal correlation, we further manage to embed this useful SI into the denoiser design under the MMV-AMP framework. Specifically, the SI-based soft-thresholding denoiser with binary thresholds and the SI-based minimum mean-squared error (MMSE) denoiser are characterized for the cases without and with the knowledge of the channel distribution, respectively. Numerical results are given to show the significant gain in device activity detection and channel estimation performance brought by our proposed SI-aided MMV-AMP framework.

The classic trilateration technique can localize each target based on its distances to three anchors with known coordinates. Usually, this technique requires all the anchors and targets, e.g., the satellites and the mobile phones in Global Navigation Satellite System (GNSS), to actively transmit/receive radio signals such that the delay of the one-way radio signal propagated between each anchor and each target can be measured. Excitingly, this paper will show that the trilateration technique can be generalized to the scenario where one of the three anchors and all the targets merely reflect the radio signals passively as in radar networks, even if the propagation delay between the passive IRS and the passive targets is difficult to be measured directly, and the data association issue for multi-sensor multi-target tracking arises. Specifically, we consider device-free sensing in a cellular network consisting of two base stations (BSs), one passive intelligent reflecting surface (IRS), and multiple passive targets, to realize integrated sensing and communication (ISAC). The two BSs transmit the orthogonal frequency division multiplexing (OFDM) signals in the downlink and estimate the locations of the targets based on their reflected signals via/not via the IRS. We propose an efficient trilateration-based strategy that can first estimate the distances of each target to the two BSs and the IRS and then localize the targets. Numerical results show that the considered networked sensing architecture with heterogenous anchors can outperform its counterpart with three BSs.

Abstract By combining bit‐shift and exclusive‐or operations, a weighted zigzag decodable fountain code is proposed to achieve an unequal error protection property. In the proposed scheme, the input symbols of different importance levels are first pre‐coded into variable nodes using low‐density parity‐check codes. Then, bit‐shift operations prior to exclusive‐or are performed on the non‐uniformly selected variable nodes to generate encoded symbols. An analysis of the erasure probabilities based on the and‐or tree is further introduced. Simulation results show that by appropriately choosing the maximum bit‐shift amount, the proposed weighted zigzag decodable fountain codes can successfully recover the more important input symbols prior to the less important ones.

Protograph-based low-density parity-check Hadamard codes (PLDPC-HCs) are a new type of ultimate-Shannon-limit-approaching codes. In this paper, we propose a hardware architecture for the PLDPC-HC layered decoders. The decoders consist mainly of random address memories, Hadamard sub-decoders and control logics. Two types of pipelined structures are presented and the latency and throughput of these two structures are derived. Implementation of the decoder design on an FPGA board shows that a throughput of 1.48 Gbps is achieved with a bit error rate (BER) of$10^{-5}$at around$E_{b}/N_{0}=-0.40$dB. The decoder can also achieve the same BER at$E_{b}/N_{0}=-1.14$dB with a reduced throughput of 0.20 Gbps.

We propose a new type of ultimate-Shannon-limit-approaching codes called spatially coupled protograph-based low-density parity-check Hadamard convolutional codes (SC-PLDPCH-CCs), which are constructed by spatially coupling PLDPC-Hadamard block codes. We develop an efficient decoding algorithm that combines pipeline decoding and layered scheduling for the decoding of SC-PLDPCH-CCs, and analyze the latency and complexity of the decoder. To estimate the decoding thresholds of SC-PLDPCH-CCs, we first propose a layered protograph extrinsic information transfer (PEXIT) algorithm to evaluate the thresholds of spatially coupled PLDPC-Hadamard terminated codes (SC-PLDPCH-TDCs) with a moderate coupling length. With the use of the proposed layered PEXIT method, we develop a genetic algorithm to find good SC-PLDPCH-TDCs in a systematic way. Then we extend the coupling length of these SC-PLDPCH-TDCs to form good SC-PLDPCH-CCs. Results show that our constructed SC-PLDPCH-CCs can achieve comparable thresholds to the block code counterparts. Simulations illustrate the superiority of the SC-PLDPCH-CCs over the block code counterparts and other state-of-the-art low-rate codes in terms of error performance. For the rate-0.00295 SC-PLDPCH-CC, a bit error rate of 10−5is achieved at$E_{b}/N_{0} = -1.465$dB, which is only 0.125 dB from the ultimate Shannon limit.

Spectrum sharing in a cognitive radio system involves a secondary user updating transmit power for sharing spectrum with a primary user. The deep$Q$-network in the framework of deep reinforcement learning achieves transmit power control by a deep neural network for learning a nonlinear mapping from states to$Q$-values. Since a deep neural network is confronted with noise susceptibility, the deep$Q$-network produces deteriorative network parameters and volatile$Q$-values in the presence of contaminated states. In view of the positive effect of kernel least mean square (KLMS) for signal smoothing, we combine KLMS with the deep$Q$-network for smoothing network-generated outputs. Since an inappropriate step size of KLMS causes under-smoothing or over-smoothing issues, a weighting procedure using past$Q$-values is proposed for cooperating with KLMS. We assess the incremental ratio of the success rate of the smooth deep$Q$-network to that of the deep$Q$-network (RSR) in cognitive radios. Simulations show that RSR has averaged almost over 30% at the early stage of power control. In particular, the maximum RSR reaches almost over 80% or 180% at different scenarios of power control for the primary user. In addition, the smooth deep$Q$-network achieves an improved success rate in comparison with other algorithms.

This paper considers joint device activity detection and channel estimation in Internet of Things (IoT) networks, where a large number of IoT devices exist but merely a random subset of them become active for short-packet transmission at each time slot. In particular, to improve the detection performance, we propose to leverage the temporal correlation in user activity, i.e., a device active at the previous time slot is more likely to be still active at the current time slot. Despite the appealing temporal correlation feature, it is challenging to unveil the connection between the estimated activity pattern for the previous time slot (which may be imperfect) and the true activity pattern at the current time slot due to the unknown estimation error. In this paper, we manage to tackle this challenge under the framework of approximate message passing (AMP). Specifically, thanks to the state evolution, the correlation between the activity pattern estimated by AMP at the previous time slot and the real activity pattern at the previous and current time slot is quantified explicitly. Based on the well-defined temporal correlation, we further manage to embed this useful SI into the design of the minimum mean-squared error (MMSE) denoisers and log-likelihood ratio (LLR) test based activity detectors under the AMP framework. Theoretical comparison between the SI-aided AMP algorithm and its counterpart without utilizing temporal correlation is provided. Moreover, numerical results are given which show the significant gain in activity detection accuracy brought by the SI-aided algorithm.

Abstract This paper investigates the relay selection problem and proposes a three‐stage relay selection strategy with power allocation (TRSPA) for a spectrum‐sensing‐based full‐duplex (FD) user relaying cooperative non‐orthogonal multiple access (CNOMA) scheme. Uniformly‐distributed strong user relays in the investigated scheme help a weak user communicates with the base station in an efficient and reliable way. The proposed TRSPA strategy maximizes the transmission data rate of the selected relay while ensuring successful transmissions for the weak user by precisely narrowing down relay candidates step‐by‐step and dynamically allocating optimal power coefficients. Exact and asymptotic outage probabilities and ergodic rates are worked out. Accordingly, diversity orders and spatial multiplexing gains are derived. We further exploit the impact of self‐interference (SI) on TRSPA for FD‐CNOMA and then compare its performance with TRSPA applied in other relaying modes, that is half‐duplex and orthogonal multiple access. Finally, simulation results reveal that: (i) theoretical derivation results are correct; (ii) TRSPA always outperforms other relay selection strategies in terms of outage probability and ergodic rate; and (iii) TRSPA for FD‐CNOMA in a real‐world scenario achieves better performance than other relaying modes in spite of the adverse effect of SI in FD mode.

In this paper, we propose a new method to design low-density parity-check Hadamard (LDPC-Hadamard) codes — a type of ultimate-Shannon-limit approaching channel codes. The technique is based on applying Hadamard constraints to the check nodes in a generalized protograph-based LDPC code, followed by lifting the generalized protograph. We name the codes formedprotograph-basedLDPC Hadamard (PLDPC-Hadamard) codes. We also propose a modified Protograph Extrinsic Information Transfer (PEXIT) algorithm for analyzing and optimizing PLDPC-Hadamard code designs. The proposed algorithm further allows the analysis of PLDPC-Hadamard codes with degree- 1 and/or punctured nodes. We find codes with decoding thresholds ranging from −1.53 dB to −1.42 dB. At a BER of 10−5, the gaps of our codes to the ultimate-Shannon-limit range from 0.40 dB (for rate = 0.0494) to 0.16 dB (for rate = 0.003). Moreover, the error performance of our codes is comparable to that of the traditional LDPC-Hadamard codes. Finally, the BER performances of our codes after puncturing are simulated and compared.

We propose a novel type of ultimate-Shannon-limit-approaching codes, namely protograph-based low-density parity-check Hadamard (PLDPC-Hadamard) codes in this paper. We also propose a systematic way of analyzing such codes using Protograph EXtrinsic Information Transfer (PEXIT) charts. Using the analytical technique we have found a code of rate about 0.05 having a theoretical threshold of -1.42dB. At a BER of 10-5, the gaps of our code to the Shannon capacity for R=0.05 and to the ultimate Shannon limit are 0.25 dB and 0.40 dB, respectively.

In this article, we introduce an automatic stream computing reoptimization flow from ASICs to field-programmable gate arrays (FPGAs). Complex VLSI designs need to be prototyped and/or emulated on FPGAs. The main problem that we address in this article is that configurations optimized when targeting ASICs are often, as we will show in this article, highly un-optimal when remapped onto an FPGA. Thus, this article proposes a method to first generate a variety of dataflow configurations targeting an ASIC given multiple behavioral descriptions for high-level synthesis (HLS) and then, based on a compositional predictive model, automatically reoptimize the dataflow when mapped onto an FPGA. The experimental results show that our proposed method works well and that it is very fast.

Mobile sensor networks (MSNs) are good candidates for large-scale unattended surveillance applications. However, it is challenging to track moving targets due to their complex dynamic behaviors. Semiflocking algorithms have been proven to be efficient in controlling MSNs in both area coverage and target tracking applications. While many existing literatures on the study of semiflocking algorithms often assume an area of interest (AoI) to be regular and with unified traversal cost, the uneven and rough landscapes in real-life applications have imposed extra challenges and raised demands for new management strategies. In this article, a mobility map is used to incorporate different costs associated with irregular terrains which results in different maximum allowed speeds on nodes in different regions. In order to reduce target detection time and node energy consumption, a heuristic search algorithm is developed to find time-efficient and feasible paths between nodes and sensing targets. Under the proposed algorithm, nodes can effectively select a target to track or search for new targets in the AoI. Results of extensive experiments show that semiflocking-controlled nodes together with path planning can reach their targets faster with lower energy consumption compared to three exiting flocking-based algorithms.

The synchronization-correcting code proposed by Davey and MacKay (DM) consists of an outer code which corrects substitution errors and an inner watermark code which maintains synchronization. The inner watermark code converts each symbol into one of the lowest density sequences which is subsequently added to a predefined randomly-generated watermark sequence. We claim that the inner sparsified codebook can be optimized based on better distance property and lowest-density property, and the improvement can be significant under some specific cases. In order to verify our claim and to reduce the complexity of the inner decoder, a hard-decision decoding based on Hamming distance and a soft-decision decoding based on a new metric are proposed for the symbol-level decoder. Simulation results verify the claim that the system with the improved codebook design offers better performance in terms of symbol error rate, reduces decoding complexity and saves computational time.

One of the advantages of High-Level Synthesis (HLS), also called C-based VLSI-design, over traditional RT-level VLSI design flows, is that multiple micro-architectures of unique area vs. performance can be automatically generated by setting different synthesis options, typically in the form of synthesis directives specified as pragmas in the source code. This design space exploration (DSE) is very time-consuming and can easily take multiple days for complex designs. At the same time, and because of the complexity in designing large ASICs, verification teams now routinely make use of emulation and prototyping to test the circuit before the silicon is taped out. This also allows the embedded software designers to start their work earlier in the design process and thus, further reducing the Turn-Around-Times (TAT). In this work, we present a method to automatically re-optimize ASIC designs specified as behavioral descriptions for HLS to FPGAs for emulation and prototyping, based on the observation that synthesis directives that lead to efficient micro-architectures for ASICs, do not directly translate into optimal micro-architectures in FPGAs. This implies that the HLS DSE process would have to be completely repeated for the target FPGA. To avoid this, this work presents a predictive model-based method that takes as inputs the results of an ASIC HLS DSE and automatically, without the need to re-explore the behavioral description, finds the Pareto-optimal micro-architectures for the target FPGA. Experimental results comparing our predictive-model based method vs. completely re-exploring the search space show that our proposed method works well.

Semi-flocking algorithms have been demonstrated to be efficient in maneuvering MSNs in multi-target tracking tasks. In many real-world applications, targets can be assigned with different priorities according to their importance of being tracked. However, existing semi-flocking algorithms normally assume the importance of all targets to be identical, which may not allocate resources in an efficient manner. In this paper, we propose a target evaluation method that incorporates priorities of the targets in the assessment process. Based on the evaluation results, mobile agents decide to track a target or continue to scan the terrain via a probabilistic task switching mechanism. Simulation results indicate a higher effectiveness of the proposed method in target tracking and area coverage when compared with two existing semi-flocking algorithms.

As a bandwidth-efficient technique, bit-interleaved coded modulation with iterative demapping and decoding (BICM-ID) has attracted much research attention in the field of wireless communication. In this paper, we put forth a joint design of root-protograph (RP) low-density parity-check (LDPC) codes and BICM-ID, referred to as RP-based BICM-ID (RP-BICM-ID), over block-fading (BF) channels so as to boost the throughput under limited bandwidth. To preserve the full-diversity property of RP codes, we propose an efficient modulation strategy for the RP-BICM-ID system by taking the fading-block length into consideration. We also analyze the outage-probability limit of the RP-BICM-ID systems to establish the fundamental lower-limit on their word-error-rate (WER) performance. Moreover, we conceive a multi-level protograph extrinsic information transfer (ML-PEXIT) algorithm to derive the asymptotic WER and bit error rate (BER) of the RP-BICM-ID systems over BF channels. As a further insight, we develop a novel unequal-error-protection (UEP) bit-to-symbol (B2S) mapping scheme for the RP-BICM-ID systems, which gives rise to an additional performance improvement. Analyses and simulations show that the proposed RP-BICM-ID systems can not only realize desirable spectral efficiency, but also obtain near-outage-limit performance over BF channels. Therefore, the proposed RP-BICM-ID systems are very promising in achieving high-reliability and high-rate transmissions under slow-fading wireless-communication environments.

In this paper, a novel full-duplex cooperative non-orthogonal multiple access (FD CNOMA) system is proposed, where users intend to exchange messages with the assistance of a decode-and-forward relay. To characterize the potential performance gain brought by the proposed FD CNOMA scheme, the outage probability and ergodic rate are analyzed. Specifically, the closed-form expressions for the outage probabilities, diversity orders, ergodic rates, and system throughputs in delay-limited and delay-tolerant transmission modes are derived under the realistic assumption of imperfect self-interference cancellation. Furthermore, to present the comprehensive performance evaluation, both perfect and imperfect successive interference cancellations (SICs) are taken into consideration. Simulations are performed to validate the accuracy of the derivation results and to illustrate the outstanding performance of the proposed scheme in low signal-to-noise ratio region compared with half-duplex CNOMA system and cooperative orthogonal multiple access system. Our results show that under the conditions of both perfect and imperfect SICs, outage probability floors and ergodic rate ceilings exist for the proposed FD CNOMA scheme due to the inter-user interference among superimposed NOMA signals and the residual self-interference caused by the imperfect self-interference cancellation.

This paper investigates the effect of pin multiplexing on the resultant micro-architecture of synthesizable behavioral descriptions for High-Level Synthesis (HLS). A method is presented to find the most efficient pin assignments by assigning multiple logic inputs and outputs to the same physical ports such that the performance degradation and area overhead is minimized. The proposed method is a fast heuristic based on the scheduling results of HLS seen as a black box and hence is flexible enough to work with any HLS tool. Experimental results show that our proposed method is very efficient compared to an exhaustive search and a simulated annealing method at a fraction of the time and much better than randomly selecting the pins to be multiplexed.

Mobile sensor networks (MSNs) are useful in monitoring outdoor environments. Semi-flocking algorithms have been proven to be efficient in controlling MSNs in area sensing and target tracking applications. Even though outdoor environments may consist of irregular regions with different traverse costs, existing semi-flocking algorithms assume an area of interest (AoI) to be regular and with uniform costs. Such an assumption limits target tracking capabilities of a MSN. In this work, we model operating terrains using a mobility map that incorporates the speed limits of different sub-regions. To gather the required number of mobile sensor nodes for target tracking, an A* heuristic search algorithm is used to find time-efficient paths connecting nodes to targets. Nodes can acquire navigation information using the A*-based path planning module and then traverse along the time-efficient paths until they reach the targets. Simulation results verify the effectiveness of the proposed method over an existing semi-flocking algorithm.

Online fountain codes have been proven to require lower overhead and fewer feedbacks than growth codes for successful decoding. In an attempt to improve the intermediate symbol recovery rate, the authors propose sending a number of degree‐1 input symbols prior to the build‐up phase based on a simple application of probability theory. In addition, during the completion phase, received encoded symbols with three neighbouring white (un‐decoded) symbols are retained for decoding and updating the decoding graph later. The performance and characteristics of the proposed improved online fountain codes are compared to those of the original online fountain codes over an erasure channel. Simulation results reveal that the improved online fountain codes outperform the original fountain codes in terms of intermediate symbol recovery rate, average encoded symbols required to be generated by the sender, average feedback transmissions, and encoding/decoding efficiency.

Double protograph low-density parity-check code has been shown to be a good solution for joint source-channel coding. Moreover, the source code and channel code (as one code pair) can be jointly optimized to achieve a good bit error rate (BER) performance. In this paper, first, an optimal design criterion of this code pair based on an extended curve-fitting algorithm is proposed. Second, a joint optimization procedure which searches for both the optimal decoding threshold and the optimal code pair is presented. In addition, for short-to-moderate-length codewords, the finite-length effect cannot be ignored and the procedure has to be modified with a new notion named length-N decoding threshold. The protograph extrinsic information transfer analysis and the BER simulation have shown that our optimized code pairs acquire lower decoding thresholds than conventional code pairs. Moreover, the optimized code pairs with short-to-moderate-length codewords can mitigate the finite-length effect and obtain low length-N decoding thresholds.

Energy usage and data rate of differential chaos shift keying (DCSK) are both inefficient since half of the symbol duration is used to transmit reference. To improve the energy efficiency and data rate, we propose a new chaos modulation scheme which combines DCSK with code index modulation (CIM) referred to as CIM-DCSK. In the proposed scheme, a short reference signal is transmitted first. Then P repeated reference signals, which serve as information-bearing signals, are simultaneously modulated by an information bit and a Walsh code with a specific index which is determined by an extra information symbol. The analytical bit error rate (BER) performance of the proposed scheme is derived and verified by simulations. Further, we improve the performance of the proposed system by applying noise-reduction and optimizing power coefficients on the reference and the information-bearing signals of CIM-DCSK. Simulation and analytical results show that these optimization methods significantly boost the BER performances of the proposed schemes. Finally, the BER performances of the proposed systems are compared with that of the conventional DCSK system and the short reference DCSK (SR-DCSK) system. Numerical results show that the proposed schemes outperform both DCSK and SR-DCSK.

This paper investigates the puncturing pattern design of Hadamard codes. When designing the puncturing patterns, the minimum Hamming distance property and cross-correlation property of the punctured Hadamard codes are considered. The theoretical upper bound of the minimum Hamming distance is derived for the punctured Hadamard codes and an algorithm is subsequently proposed for searching punctured codes with the minimum distance approaching the bound. Another approach to design the punctured codes is to minimize the cross-correlations between punctured codewords. A new metric is defined to measure the overall severity of the cross-correlation based on which punctured codes with the “lowest” cross-correlations are found. Simulation results show that both techniques are effective in searching for good punctured Hadamard codes. As expected, moreover, the punctured codes found by minimizing the cross-correlation outperform those optimized by maximizing minimum Hamming distance when a-posteriori-probability decoding is used.

For channels that introduce substitution, insertion and deletion errors, one challenging problem for a code designer is to avoid false code synchronization. In other words, the probability of false codewords occurring should be minimized with appropriate code design. In this paper, we propose a new class of systematic comma free code called generalized F(n, s, t) code. We first prove that this code is a synchronous code and then we derive the probabilities of false synchronization when a substitution, insertion or deletion error occur. We compare the theoretical and simulation results under different parameters. We also compare the performance of our proposed code with the classical F code.

In this paper, we propose a parallel architecture of the imperfect maximum likelihood decoding (IMLD) method, called PIMLD. It is further implemented onto an FPGA and applied to decode the (24,12,8) extended Golay code. Experimental results show that the proposed PIMLD decoder achieves 12.0 Gb/s throughput at 500 MHz frequency. Moreover, the latency for the decoder is only 5 clock cycles.

Efficient path planning has an utmost importance in the domain of autonomous navigation. Even though shortest path planning has been well discussed in the past, the same techniques might not always be used to find the fastest path in outdoor environments due to the inability of mobile agents to travel at their peak speed everywhere in irregular terrains. Mobility maps are an effective way for dealing with such irregularities. In this paper, we first introduce a grid-based mobility maps for representing speed limitations in outdoor terrains. Then, we propose a heuristic for finding the fastest path on such maps. The proposed heuristic is proven to be both admissible and consistent. Therefore, it can be used with A*-like heuristic search algorithms for obtaining fastest paths efficiently. Simulation results provided in this paper verify the optimality of paths that are found with the help of the proposed heuristic.

A multi-mode QC-LDPC decoder is proposed to satisfy the 802.11n/ac WiFi standard. With code-specific design, the overall performance of the decoder is enhanced while ensuring an on-the-fly reconfigurable ability. The proposed architecture has been synthesized using an FPGA for measurements. A state-of-art error rate and implementation complexity are reported. Meanwhile, the throughput has been increased to range from 382 MHz to 1852 MHz.

The authors study the performance of protograph low‐density parity‐check (LDPC) codes over two‐dimensional (2D) intersymbol interference (ISI) channels in this study. To begin with, the authors propose a modified version of finite‐length (FL) extrinsic information transfer (EXIT) algorithm so as to facilitate the convergence analysis of protograph codes. Exploiting the FL‐EXIT analyses, the authors observe that the protograph codes optimised for 1D ISI channels, e.g. the 1D‐ISI protograph code, cannot maintain their advantages in the 2D‐ISI scenarios. To address this problem, the authors develop a simple design scheme for constructing a family of rate‐compatible improved protograph (RCIP) codes particularly for 2D‐ISI channels, which not only outperform the 1D‐ISI protograph code, but also are superior to the regular column‐weight‐3 code and optimised irregular LDPC codes in terms of the convergence speed and error performance. More importantly, such RCIP codes benefit from relatively lower error‐floor as well as linear encoding and fast decoding. Thanks to these advantages, the proposed RCIP codes stand out as better alternatives in comparison with other error‐correction codes for ultra‐high‐density data storage systems.

The M ‐ary differential‐chaos‐shift‐keying ( M ‐ary DCSK) system offers a good noise performance over an additive white Gaussian noise (AWGN) channel in the category of non‐coherent detection chaotic systems. However, the way that the M ‐ary DCSK system utilises the available Walsh codes results in a relatively low bandwidth efficiency (BE). Moreover, the number of delay elements required at the transmitter and receiver increases exponentially with the number of bits per symbol. To overcome the aforementioned problems, the authors propose a multilevel code‐shifted DCSK (MCS‐DCSK) system in this study. In the proposed MCS‐DCSK system, the reference chaotic signal and the information‐bearing chaotic signals are orthogonal and are transmitted in the same time slot. They show that the MCS‐DCSK system significantly outperforms the M ‐ary DCSK system in terms of BE and complexity. They also derive analytical bit‐error‐rate expressions for the MCS‐DCSK system over additive white Gaussian noise and multipath fading channels, and verify them with simulation results.

Mobile data offloading is an emerging technology to avoid congestion in cellular networks and improve the level of user satisfaction. In this paper, we develop a distributed market framework to price the offloading service, and conduct a detailed analysis of the incentives for offloading service providers and conflicts arising from the interactions of different participators. Specifically, we formulate a multileader multifollower Stackelberg game (MLMF-SG) to model the interactions between the offloading service providers and the offloading service consumers in the considered market framework, and investigate the cases where the offloading capacity of APs is unlimited and limited, respectively. For the case without capacity limit, we decompose the followers' game of the MLMF-SG (FG-MLMF-SG) into a number of simple follower games (FGs), and prove the existence and uniqueness of the equilibrium of the FGs from which the existence and uniqueness of the FG-MLMF-SG also follows. For the leaders' game of the MLMF-SG, we also prove the existence and uniqueness of the equilibrium. For the case with capacity limit, by considering a symmetric strategy profile, we establish the existence and uniqueness of the equilibrium of the corresponding MLMF-SG, and present a distributed algorithm that allows the leaders to achieve the equilibrium. Finally, extensive numerical experiments demonstrate that the Stackelberg equilibrium is very close to the corresponding social optimum for both considered cases.

Trax is a two-player game of simple rules but strategic depth. This article proposes an FPGA-based artificial intelligence for its endless version called Supertrax. An implementable algorithm is developed by combining several strategies and techniques functioning at various levels of software and hardware. These methods are developed using heuristics, multi-level pattern recognition, Monte-Carlo Tree Search, and path-based scheduling. A specific architecture has also been described to accommodate this algorithm. The proposal contributes a novel idea on this subject and its performance will be shown in the design competition to be held in FPT'15.

We develop a distributed market framework to price the offloading service, and conduct a detailed analysis of the incentives for offloading service providers and conflicts arising from the interactions of different participators. Specifically, we formulate a multi-leader multi-follower Stackelberg game (MLMF-SG) to model the interactions between the offloading service providers and the offloading service consumers in the considered market framework, and investigate the cases where the offloading capacity of APs is unlimited and limited, respectively. For the case without capacity limit, we decompose the followers' game of the MLMF-SG (FG-MLMF-SG) into a number of simple follower games (FGs), and prove the existence and uniqueness of the equilibrium of the FGs from which the existence and uniqueness of the FG-MLMF-SG also follows. For the leaders' game of the MLMF-SG, we also prove the existence and uniqueness of the equilibrium. For the case with capacity limit, by considering a symmetric strategy profile, we establish the existence and uniqueness of the equilibrium of the corresponding MLMF-SG, and present a distributed algorithm that allows the leaders to achieve the equilibrium. Finally, extensive numerical experiments demonstrate that the Stackelberg equilibrium is very close to the corresponding social optimum for both considered cases.

This paper considers physical-layer network coding (PNC) in vehicular ad-hoc network (VANET) to solve the problem of short contact time between fast-moving vehicles. PNC enables data exchange between nodes in a relay network within a short airtime, e.g., twice faster than relay networks based on traditional communication, and can be a powerful performance booster in VANET. One of the most important challenges in applying PNC to VANET, however, is the Doppler shift caused by vehicular motions. Doppler shift leads to carrier frequency offset (CFO) that induces inter-carrier interference (ICI) in OFDM systems. The ICI destroys the orthogonality of modulated symbols, causing degradation in PNC signal detection. This paper puts forth a detection method to mitigate the CFO/ICI effect on PNC. The method, referred to as BP-VPNC, makes use of a belief propagation (BP) algorithm to process the outputs of the OFDM correlators. BP extracts useful hidden information embedded in ICI to improve signal detection in VANET PNC. Our study shows that the BER performance of PNC VANET operated with BP-VPNC can be achieved close to that of traditional VANET at various CFO levels. These results suggest that with BP-VPNC, a potential shortcoming of PNC, vulnerability to CFO, can be circumvented, and that PNC can be used to overcome the short vehicular contact time in VANET.

To exchange information between two sources in a two‐way relaying network with multiple potential relays, most researches focus on two‐hop relay system with single‐relay‐selection (SRS) scheme. Comparing with SRS scheme, the authors first design a paired‐relay‐selection (PRS) scheme in which a pair of ‘best’ relays broadcast network‐coded information to other nodes (source or relay). They propose an optimal selection algorithm and a suboptimal algorithm that selects the pair of ‘best’ relays in the PRS scheme and they describe how the nodes exchange information in a frame consisting of four timeslots. Both the analytical and simulation results show that when the pathloss exponent is large and/or there is a sufficient number of relays to choose from, using two relay nodes can provide a lower outage compared with using only one relay node even under the same total transmit power in uniformly distributed relay networks. In addition, to reduce the overhead of the PRS scheme, they propose an iterative‐PRS (I‐PRS) scheme in which the paired relay is selected in an iterative and opportunistic way. Simulation results show that the I‐PRS scheme has nearly the same outage performance as the PRS scheme under time‐invariant channels and significantly outperforms the PRS scheme under time‐varying channels.

In this paper, we study the traffic performance in communication networks from a complex network perspective. The node usage probability is an effective metric for characterizing the traffic load distribution and how frequently a node is chosen to relay packets in a network. Based on the concept of node usage probability, we propose an effective routing strategy to maintain balanced traffic loads in the network nodes by avoiding overuse of certain nodes. Simulation results show that routing algorithms based on the proposed strategy can effectively balance traffic loads and improve the overall traffic performance.

In this paper, we propose two relay cooperation schemes for a Multiple Access Relay Channel (MARC). The proposed schemes make use of a lattice-based approach to block Markov encoding. The first scheme applies Compute-And-Forward (CAF) at the relay and Successive Interference Cancellation (SIC) at the destination; whereas the second one applies SIC at both the relay and the destination. A detailed analysis of the rates achieved by these two schemes is also provided. The schemes are further studied under two specific channel settings.

In this paper, efficient LDPC block-code decoders/simulators which run on graphics processing units (GPUs) are proposed. We also implement the decoder for the LDPC convolutional code (LDPCCC). The LDPCCC is derived from a predesigned quasi-cyclic LDPC block code with good error performance. Compared to the decoder based on the randomly constructed LDPCCC code, the complexity of the proposed LDPCCC decoder is reduced due to the periodicity of the derived LDPCCC and the properties of the quasicyclic structure. In our proposed decoder architecture, Γ (Γ is a multiple of a warp) codewords are decoded together, and hence, the messages of Γ codewords are also processed together. Since all the Γ codewords share the same Tanner graph, messages of the Γ distinct codewords corresponding to the same edge can be grouped into one package and stored linearly. By optimizing the data structures of the messages used in the decoding process, both the read and write processes can be performed in a highly parallel manner by the GPUs. In addition, a thread hierarchy minimizing the divergence of the threads is deployed, and it can maximize the efficiency of the parallel execution. With the use of a large number of cores in the GPU to perform the simple computations simultaneously, our GPU-based LDPC decoder can obtain hundreds of times speedup compared with a serial CPU-based simulator and over 40 times speedup compared with an eight-thread CPU-based simulator.

In this paper, we study the packet routing process in communication networks. For efficient and reliable data transmission, the traffic load should be as uniformly distributed as possible in the network and the average distance travelled by the data should be short. The Internet has been demonstrated to have small-world and scale-free properties in its topology. Under the shortest path routing strategy, the traffic intensity of high degree nodes is much higher, thus causing congestion of the whole network. We propose an adaptive routing algorithm, which takes into consideration both the network structure property and the dynamic traffic information. Simulation results show that the proposed algorithm can effectively balance the traffic in the network and improve the overall traffic performance.

To help exchanging information between two sources in a two-way relaying network with multiple relays, we consider selecting one “best” relay or a pair of “best” relays that broadcast network-coded information to other nodes (source or relay). Further, we assume that the multiple relays are random distributed in a one-dimensional or two-dimensional space between the sources and we take the path loss between the nodes into consideration. We also select the relay(s) based on the max-min criterion in both the Single Relay Selection (SRS) scheme and the Paired-Relay Selection (PRS) scheme. In particular, we propose a Distributed VIterbi Selection Algorithm (DVISA) that selects the pair of “best” relays in the PRS scheme and we describe how the nodes exchange information in a frame consisting of 4 time slots. Both our analytical and simulation results show that when the path-loss exponent is large and/or there is a sufficient number of relays to choose from, using two relay nodes can provide a lower outage compared with using only one relay node even under the same total transmit power.

The sufficient condition for a blindly interference-aligned 2-user 2 × 1 broadcast channel (BC) in homogeneous block fading to achieve its maximal 4/3 degree-of-freedom (DoF) is well understood. However, the condition for the general case, i.e., a homogeneous K-user 2 × 1 BC, to achieve the corresponding optimal 2K/2+K-1 DoF remains unsolved and is, thus, the focus of this paper. Here, a K-user 2×1 BC is said to be BIA-feasible if it achieves the optimal DoF via blind interference alignment (BIA). In this paper, we cast this general BIA-feasibility problem in the framework of finding solutions for a system of linear Diophantine equations. Then by studying the solvability of the Diophantine system, we derive the necessary and sufficient conditions on the K users' fading block offsets to ensure the BIA feasibility of the K-user BC. Using the results above, we also examine a 2 × 1 broadcast network with M homogeneous users, in which their offsets are independent of one another and are uniformly distributed over a coherence block. We show by simulations that when the network contains M = 11 homogeneous users, there is more than 95% chance of finding 3 users to form a BIA-feasible 3-user 2 × 1 BC. Furthermore, increasing M to infinity ensures a virtual multiple-input multiple-output (MIMO) channel to be formed from the DoF perspective.

This letter develops a log-likelihood-ratio-based decoder for a generalized joint channel-coding-and-physical-network coding used in a two-way relay system. Assuming that the same low-density parity-check codes are used at the source nodes, the proposed decoder shows identical error performance as the probability-domain-based decoder but with a much lower computational complexity.

ABSTRACT Low‐density parity‐check (LDPC) codes are very powerful error‐correction codes with capabilities approaching the Shannon's limits. In evaluating the error performance of an LDPC code, the computer simulation time taken becomes a primary concern when tens of millions of noise‐corrupted codewords are to be decoded, particularly for codes with very long lengths. In this paper, we propose modeling the parity‐check matrix of an LDPC code with compressed parity‐check matrices in the check‐node domain (CND) and in the bit‐node domain (BND), respectively. Based on the compressed parity‐check matrices, we created two message matrices, one in the CND and another in the BND, and two domain conversion matrices, one from CND to BND and another from BND to CND. With the proposed message matrices, the data used in the iterative LDPC decoding algorithm can be closely packed and stored within a small memory size. Consequently, such data can be mostly stored in the cache memory, reducing the need for the central processing unit to access the random access memory and hence improving the simulation time significantly. Furthermore, the messages in one domain can be easily converted to another domain with the use of the conversion matrices, facilitating the central processing unit to access and update the messages. Copyright © 2011 John Wiley & Sons, Ltd.

Radio coverage is limited by two parameters: (i) energy per bit radiated by the transmitter and (ii) BER performance of the receiver. In Ultra-Wideband Impulse Radio (UWB IR) the former is limited by the FCC Regulations while the latter depends on the detection algorithm. The fact that prevents the use of UWB IR devices in real applications is the unacceptable short radio coverage. The pulse compression technique, that simultaneously increases the maximum attainable energy per bit and introduces a processing gain at the receiver is proposed here to overcome this problem. As a result of pulse compression, the coverage of the new UWB chirp IR devices is 6-times longer than that of the conventional UWB IR devices, i.e., the radio coverage is extended from less than 10 meters up to 40 meters.

In this paper we study the performance of communication networks from a network science perspective. We consider in particular the effects of the choice of routing algorithms and the kind of network topology on selected areas of performance, and we also study the vulnerability of the networks when subject to selected attack strategies. Contrary to intuition, our results reveal that the removal of a certain number of high-degree nodes in a scale-free network with shortest path routing does not necessarily worsen the overall network performance. Moreover, the scale-free network can perform better when high-degree nodes are coordinated to provide exclusive service to a specific group of nodes.

Assortativity is an important structural characteristic of complex networks. In this paper, we propose a simple method to generate a network with the desired assortative coefficient but still keep the degree distribution unchanged. We simulate cases with different assortative coefficients and calculate the packet drop probability when the buffer size is limited. The simulation results indicate that assortativity has a significant effect on the traffic performance. Our study helps to understand how the network structure influences the traffic dynamics in complex networks.

Recently, there have been different applications, namely 10GBase-T Ethernet, video broadcasting and satellite communication, utilizing low-density parity-check (LDPC) codes as the forward-error-correction codes. The main reason is that the error performance of LDPC codes can be very close to the Shannon limit. LDPC codes can be further categorized into LDPC block codes (LDPC-BCs) and LDPC convolutional codes (LDPC-CCs). It has also been discovered that LDPC-CCs usually outperform LDPC-BCs. Simulation of LDPC-BCs and LDPC-CCs can take a lot of time because the decoding algorithms are relatively complex. Fortunately, the decoding steps can be performed in parallel. In this paper, we create three different platforms for simulating the error performance of LDPC-CCs. The first two platforms are run on a Central Processing Unit (CPU) while the third one involves the use of a Graphics Processing Unit (GPU). We show that using GPU can improve the simulation speed substantially.

In this paper, we propose an effective and efficient searching method for constructing quasi-cyclic low-density parity-check (QC-LDPC) codes with a desired girth g. We begin with an arbitrary QC-LDPC code with girth-4 and we evaluate only the number of cycles with length 4. When all the cycles with length 4 are removed by adjusting the elements of the QC-LDPC code, we form a QC-LDPC code with girth-6. Subsequently, we consider only the numbers of cycles with length 4 and length 6. In general, knowing that the current QC-LDPC code has a girth of g', we only consider the numbers of cycles with length up to g' even though g' may be smaller than the desired girth g. By using an adaptive cost function, which is defined as the number of cycles of length g', in the optimization/searching process, we are able to reduce the computational effort tremendously compared with Wang's searching algorithm [1]. Consequently, our proposed method can generate QC-LDPC codes with the desired girth much more efficiently.

In wireless communications, spatial diversity techniques, such as space-time block code and single-input multiple-output (SIMO), are employed to strengthen the robustness of the transmitted signal against channel fading. This article studies the performance of protograph-based low-density parity-check (LDPC) codes with receive antenna diversity. The authors first propose a modified version of the protograph extrinsic information transfer algorithm and use it for deriving the threshold of the protograph codes in a SIMO system. The authors then calculate the decoding threshold and simulate the bit-error rate (BER) of two protograph codes (accumulate-repeat-by-3-accumulate (AR3A) code and accumulate-repeat-by-4-jagged-accumulate (AR4JA) code), a regular (3,6) LDPC code and two optimised irregular LDPC codes. The results reveal that the irregular codes achieve the best error performance in the low signal-to-noise-ratio (SNR) region and the AR3A code outperforms all other codes in the high-SNR region. Utilising the theoretical analyses and the simulated results, the authors further discuss the effect of the diversity order on the performance of the protograph codes. Accordingly, the AR3A code stands out as a good candidate for wireless communication systems with multiple receive antennas.

In this study, the authors investigate the optimal sensing settings that can maximise the throughput of the cognitive radio (CR) users under the constraint that the signals from the primary users (PUs) are sufficiently protected. They focus on the throughput at the data link layer where end-to-end delivery of data packets is considered. Consequently, the throughput is defined as the rate at which correct data are received. They reconsider the tradeoff between the sensing settings and the throughput. They also separately perform optimisation on the throughput when cooperative spectrum sensing (CSS) is/is not used. In order to evaluate the throughput, they further derive the exact symbol-error-rate (SER) expressions in the presence of co-channel interference. After proving that the throughput functions are unimodal, they proposed two efficient and effective algorithms that can derive the optimal settings for maximising the throughput. Finally, the authors show that their numerical results and compare optimal results with those found by exhaustive searches. They conclude that their algorithms produce optimal results very close to those found by exhaustive searches.

Transmission error because of fading in the cognitive radio–fusion centre (CR–FC) links can severely degrade the performance of cooperative spectrum sensing. In this study, the upper and lower bounds of the overall false alarm probability and overall detection probability are derived as functions of the bit-error probabilities (BERs) of the CR–FC links. Based on these bounds, the constraints that the BERs of the CR–FC links should satisfy are addressed given the target overall false alarm probability or overall detection probability. Furthermore, channel coding schemes and cooperative schemes that provide reliable transmissions in the CR–FC links are studied. Particularly, inspired by the cluster-based cooperative spectrum sensing, a multi-user cooperative scheme is proposed. Finally, the relationship between the overall detection probability and the overall false alarm probability is investigated when the SNR of the primary user signal at each CR node is small.

We investigate the performance of the protograph low-density parity-check (LDPC) codes, which have been shown to possess simple structures and outstanding error performance over additive white Gaussian noise (AWGN) channels, over partial response (PR) channels using the finite-length extrinsic information transfer (EXIT) algorithm. Due to the intersymbol interference (ISI) caused by the PR channels, we observe that the conventional protograph LDPC codes do not perform well in terms of error rates. We further propose a new design scheme and construct three new types of protograph LDPC codes. Unlike conventional protograph LDPC codes in which the highest-degree variable nodes are punctured, the new protograph LDPC codes have their lowest-degree variable nodes punctured. Moreover, some edge re-connections are made in one of the proposed codes. The EXIT-chart analysis, the convergence analysis and the bit-error-rate simulation have shown that all three new codes outperform the conventional protograph LDPC codes. Moreover, two of the proposed codes are superior to the regular column-weight-3 LDPC code and thus they are good alternatives compared to other error-correction codes for use in data storage systems.

In this study, the authors propose a systematic method of designing low-density parity-check codes with deterministic unequal-error-protection characteristics over an additive white Gaussian noise channel. The proposed method optimises the code rate or the noise threshold while at the same time guaranteeing that different classes of code bits can achieve their respective target error probabilities within a specified number of decoding iterations. The authors also derive the necessary and sufficient stability condition for the optimisation method.

A low-density parity-check (LDPC) code can be described by a Tanner graph composed of symbol nodes and check nodes. Short cycles in the Tanner graph should be avoided because such cycles will degrade the performance of the decoder and hence increase the error rate. In most of the circumstances, cycles of length 4 can be totally eliminated in the Tanner graph when the LDPC code has been designed properly. Locally, for each variable node in the Tanner graph, the girth may take the value of 6 or 8, or even higher. In this study, the authors attempt to increase the local girths of a Tanner graph with an aim to improving the error performance of the code. The authors propose and analyse the ‘degree spectrum’ of the symbol nodes connecting to each of the check nodes. Based on the analysis, the authors can determine if the local girths can be further increased. The authors also propose simple ways to construct codes with higher local girths. Finally, the authors show the characteristics and the error performance of the codes constructed with the proposed methods.

Elementary trapping sets (ETSs) have been found to be the main cause of error floor in the decoding of low-density parity-check (LDPC) codes. Moreover, irregular LDPC codes that avoid harmful [w; u; e] ETSs have been constructed and have shown to possess superior error performance compared with other LDPC codes. In this paper, we attempt to evaluate irregular LDPC code performance under an additive white Gaussian noise channel within the high SNR region using the importance sampling (IS) approach in conjunction with the identification of [w; u; e] ETSs. For any given irregular LDPC code, we will first apply a three-step method that aims to search as many ETSs within the code as possible. Then, we will classify these ETSs into different groups based on their labels, i.e., [w; u; e]'s. Further, by dividing the error region into various sub-regions centered by ETSs, we apply the IS simulator to evaluate the error rate of each of the sub-regions. Based on the error rates of all the sub-regions, we can estimate the overall error rate of the LDPC code. Results have indicated that our proposed IS scheme can produce speed-up gains up to 3.9×109 times compared to Monte Carlo simulations.

In an opportunistic relaying mechanism, the "best" relay is selected to forward a received signal to the destination. In this paper, we propose a novel criterion to choose the "best" relay, namely the max-generalized-mean (MGM) selection criterion, which encompasses the max-min and the max-harmonic-mean (MHM) selection criteria. We then analyze the asymptotic outage probability of the selection decode-and-forward opportunistic relaying (SDF-OR) protocol under the proposed MGM selection criterion. Based on the asymptotic results, we show the conditions under which the MGM selection framework provides the full diversity. We further optimize the asymptotic outage probability by adjusting the parameters associated with the MGM selection criterion. We show that at high signal-to-noise-ratio (SNR), a lower outage probability can be accomplished by the MGM selection criterion compared with the max-min or the MHM selection criterion for the SDF-OR protocol.

Both the peak power and the average power of emission are limited in UWB systems in order to keep the interference caused in an already existing narrowband radio system low enough. It is frequently overlooked that these power limits have to be checked not over the transmitted UWB signal but at the output of a bandpass filter specified in the FCC regulations. A further constraint exists in the handheld cheap devices where the low supply voltage reduces even further the attainable energy available to carry one bit information. The bit energy determines the coverage, the larger the bit energy, the larger the coverage. Introducing a novel approach an exact link budget calculation is proposed here for UWB impulse radio. Since the NLOS coverage of impulse radio obtained from the link budget is less than 2 m, the implementation of WLAN systems is not feasible with UWB impulse radio devices. To increase the bit energy, the UWB carrier-based approach, where the duty cycle is considerably increased, is proposed here. More than 16-dB improvement in bit energy has been achieved by increasing the UWB carrier duration to 300 ns.

To satisfy the huge demand for unlicensed handheld wireless networking devices, the Federal Communications Commission (FCC, USA) made the application of ultra-wideband (UWB) technology possible in 2002. Since then an IEEE standard has already been approved for the physical layer of the UWB impulse radio networking devices. Because of the ultra-wideband property the design and implementation of UWB circuits and systems set up an enormous challenge for the circuit designers. Unfortunately, an exact specification has not yet been derived for the circuit designers. Starting from the FCC Regulations and the IEEE UWB standard this contribution derives the required specifications for the blocks of UWB transceivers. It shows that if CMOS technology is used then the coverage of UWB impulse radio is limited by the low supply voltage. To overcome this limit more than one UWB carrier pulse is used to keep transmitted energy per bit high enough but to reduce the required voltage swing below the supply voltage. The optimum value of delay to be set between the successive UWB pulses is also determined.

Since the coherent receivers are not feasible to implement low-cost ultra-wideband (UWB) impulse radio (IR) devices featuring extremely low power consumption, energy detector-based (ED-based) noncoherent receivers are more and more frequently chosen. The Pulse Polarity Modulation (PPM) scheme with a threshold compensated receiver is a promising candidate for the implementation of cheap and robust UWB IR devices. Unfortunately, the field tests and computer simulations have shown the well known fact that the noise performance of noncoherent demodulators is much behind that of their coherent counterparts. The poor noise performance results in a such a bad receiver sensitivity that prevents the use of noncoherent receivers in the majority of real applications. This contribution shows how the noise performance of noncoherent threshold compensated PPM receiver can be improved considerably by disabling the receiver outside of the UWB pulse where only channel noise and interference is observed. The novel receiver configuration, referred to as gated threshold compensated noncoherent PPM receiver offers an 8-dB improvement in receiver sensitivity.

Transmitted reference (TR) modulation scheme and the autocorrelation receiver offer a simple and robust transceiver configuration for ultra-wideband (UWB) communications. Unfortunately, the TR UWB system has a poor noise performance. The paper shows that the noise performance of a TR autocorrelation system can be improved considerably by placing a noise filter before the autocorrelation detector. The optimum frequency response of required noise filter is derived.

Low-density parity-check (LDPC) codes with scale-free (SF) symbol-node degree distribution have been shown to provide very good error performance. When the code rate becomes high, however, there will be a lot of degree-2 symbol nodes in the “pure” SF-LDPC codes. As a consequence, when the codes are constructed by connecting the symbol nodes with the check nodes, many small-size cycles will be formed. Such small-cycles will degrade the error performance of the codes. In this paper, we address the issue by imposing a new constraint on the design of high-rate SF-LDPC codes. We will compare the error rates of the constrained SF-LDPC codes and other optimized LDPC codes.

This paper firstly introduced some principles of the phase-shifting network of an electronically-steered smart antenna for TD-SCDMA systems. Secondly, we described the principle of a phase-shifter. The proposed phase-shifter is used in TD-SCDMA systems and is simulated by the Ansoft HFSS software. Simulation results show that the proposed phase-shifter can obtain better angle of phase-shifting. The phase-shifting network based on the proposed phase- shifter can also attain efficient downtilt angle.

This paper studies the problem of energy consumption minimization in wireless sensor networks (WSNs) under uncertainty in sensor node generated traffic. It is important to consider traffic uncertainty because WSNs designed for surveillance and monitoring applications typically operate in event-driven and query-driven modes for which the node generated traffic changes from instant to instant. The problem is formulated as a two-stage stochastic linear program with recourse where the objective is to minimize the sum of the energy cost expended on the carried traffic and the average energy cost of blocked traffic, under the constraint of a fixed energy budget at each node. The stochastic programming formulation lends to the consideration of two approaches for handling the randomly generated traffic: a deterministic approach in which all future generated random traffic are constrained by the link flows determined for the nominal traffic, and a stochastic approach where the link flows are adapted as the node generated traffic changes. Numerical results show that, compared to the deterministic approach, the stochastic approach provides up to 10% savings in network-level energy consumption and this is achieved without a loss in received data quality. The network-level energy savings translate to a prolonged network lifetime.

In this letter, we consider a cooperative communication network over Rayleigh fading channels. We assume that the amplify-and-forward (AF) and the selection decode-and-forward (SDF) opportunistic relaying methods are used and that the relay with the largest harmonic mean of the source-relay channel gain and the relay-destination channel gain is selected for forwarding the message to the destination. We derive the high-SNR outage probabilities, which are then compared with the simulation results. We also compare our analytical results with the high-SNR outage probabilities found when the max–min criterion is used to select the opportunistic relay.

Trapping sets (TSs) are known to cause error floors in regular and irregular low-density parity-check (LDPC) codes. By avoiding major error-contributing TSs during the code construction process, codes with low error floors can effectively be built. In it has been shown that TSs labeled as [w;u] are considered as being equivalent under the automorphism of the graph and are therefore contributing equally to the error floor. However, TSs with the same label [w;u] are not identical in general, particularly for the case of irregular LDPC codes. In this paper, we introduce a parameter e that can identify the number of "distinguishable" cycles in the connected subgraph induced by an elementary trapping set. Further, we propose a code construction algorithm, namely the Progressive-Edge-Growth Approximate-minimum-Cycle-Set-Extrinsic-message-degree (PEG-ACSE) method, that aims to avoid small elementary trapping sets (ETSs), particularly detrimental ETSs. We also develop theorems evaluating the minimum possible ETSs formed by PEG construction algorithms in general. We compare the characteristics of the codes built using the proposed method and those built using PEG-only or PEG-Approximate-minimum-Cycle-Extrinsic-message-degree (PEG-ACE) methods. Results from simulations show that the codes constructed using the proposed PEG-ACSE method produce lower error rates, particularly at the high signal-to-noise (SNR) region, compared with codes constructed using other PEG-based algorithms.

In this paper, we study a decode-and-forward two-way relaying network. We propose an opportunistic two-way relaying (O-TR) scheme based on joint network coding and opportunistic relaying. In the proposed scheme, one single "best relay" is selected by MaxMin criterion to perform network coding on two decoded symbols sent from two sources, and then to broadcast the network-coded symbols back to the two sources. The performance of the proposed scheme is analyzed, and verified through Monte Carlo simulations. Results show that the proposed scheme achieves a better performance compared to the fully-distributed space-time two-way relaying (FDST-TR), which has been identified as the best decode-and-forward two-way relaying method so far.

Dual-hop transmission systems employing fixed-gain amplify-and-forward (AF) relaying have been studied recently over Nakagami fading channels. These analyses, however, either have imposed certain constraints on the fading parameters or have not been totally accurate when evaluating the diversity order of the systems. In this letter, we will develop a methodology for evaluating the diversity order of such systems. The methodology can be easily extended to analyze fixed-gain AF relaying with multiple relays.

In this paper, we attempt to evaluate irregular LDPC code performance at the high SNR region using the importance sampling (IS) approach in conjunction with primary- trapping-set identification. Results have indicated that our proposed IS scheme can produce speed-up gains up to 3.9 x 109times compared with Monte Carlo simulations.

A large organization is composed of groups, which may represent departments, centers, administrative units, etc. In this paper, we analyze the internal call interactions among telephone numbers belonging to the same or different groups in a large organization. We observe that the node degree probabilities are almost the same for degrees less than 30 and they are found to obey a power-law when the degrees are large. Further, we find two typical cumulative probability distributions of the intergroup link weight for the group-nodes in the internal telephone group network and we also find that there is a limit to the group size. Based on the results, we propose a growth model using a combination of preferential and non-preferential attachments as well as group splitting. We show that the constructed network exhibits similar properties as the real-life internal telephone call/group network.

Sensor networks employ a large amount of wireless sensor nodes to provide sensing power with high redundancy. Such redundancy makes sensor networks robust under changing environments. However, without proper scheduling, the surplus sensing power will cost tremendous energy consumption to the wireless sensor nodes. A scheduling scheme based on social insect colonies is proposed here. The proposed scheme is a kind of adaptive ‘periodic on-off’ scheduling scheme that uses only local information for making scheduling decisions. The scheme is evaluated in terms of averaged detection delay, target 3-coverage hit-rate and energy consumption per successful target detection. Simulation results show that, when comparing with other generic scheduling schemes, the proposed scheme can reduce energy consumption from a minimum of 7.49% to a maximum of 90.81% and improve the target hit-rate from a minimum of 15.7% to a maximum of 58.9%. Optimisation of the network lifetime and other performances is possible by adjusting some parameters.

Cooperative communications has been recognised as an effective technique to combat multi-path fading impairment and to provide additional diversity advantage for small-size and low-power-consumption mobile terminals. A class of decode-and-forward (DF) relaying serial cooperative communications, in which each node is assumed to be able to determine whether the received signals can be successfully decoded or not, has recently been proposed and analysed over Rayleigh fading channels. Since the Nakagami fading channels represent a wide variety of realistic channels, such serial cooperative networks should be investigated over such channels before putting into real applications. In this paper, we analyse the performance of such serial cooperative transmission systems thoroughly over dissimilar Nakagami fading channels. We derive a closed-form symbol-error-rate expression for the case of M-ary phase shift keying (PSK) modulation. Moreover, we evaluate the system diversity property and investigate the achievable diversity order under two specific channel conditions. Finally, we perform simulations to verify the theoretical findings.

Study of complex networks has been conducted across many fields of science, including computer networks, biological networks and social networks. Characteristics of different types of complex networks such as random networks, regular-coupled networks, small-world networks and scale-free networks have been discovered by researchers. Application of such network properties to solve engineering problems, however, is still at the infancy stage. In this study, we make one of the first attempts in applying complex network theories to communications engineering. In particular, inspired by the shortest-average-path-length property of scale-free networks, we design short-length low-density-parity-check (LDPC) codes with an aim to shortening the average distance between any two variable nodes. We will also compare the error performance, both theoretically and by simulations, of the proposed codes with those of other well-known LDPC codes.

We analyze the performance of cooperative communication systems with opportunistic decode-and-forward for relaying and selection combining receiver at the destination. We derive an exact closed-form expression for the outage of the system over dissimilar Nakagami fading channels. Also, we study its asymptotic outage performance, based on which the optimum power allocations for the source and the relays are determined. Finally, we verify the theoretical results by simulations.

We analyze the performance of cooperative communication systems with opportunistic decode-and-forward for relaying and selection combining receiver at the destination. We derive an exact closed-form expression for the outage of the system over dissimilar Nakagami fading channels. Also, we study its asymptotic outage performance, based on which the optimum power allocations for the source and the relays are determined. Finally, we verify the theoretical results by simulations.

We analyze a serial cooperative transmission system with DF relaying over Nakagami fading channels. We consider a system in which the simple receivers will not estimate the amplitude of the received signals. Hence, signals are combined with equal gain before decoding. Moreover, the relays use a simple protocol when relaying the messages — they re-transmit the message if they can decode the received message correctly; otherwise, they do not transmit anything and remain idle. We will derive an exact expression for the asymptotic symbol error rate of the system and evaluate the diversity properties.

In this letter, we examine in detail a cooperative network with multiple relays. We investigate protocols that incorporate the opportunistic relaying technique, which selects the "best" relay among the M available relays. We evaluate the asymptotic outage performance of incremental amplify-andforward (IAF) when it is extended to the opportunistic relaying scenario. Moreover, we propose two new protocols, namely opportunistic incremental selection AF and opportunistic joint incremental selection relaying, and derive the corresponding asymptotic outage probabilities. Finally, we compare the analytical asymptotic outage probabilities and the simulated ones. We conclude that the OJISR protocol outperforms the other protocols.

Sensor networks with a large amount of sensor nodes usually have high redundancy in sensing coverage. The network lifetime can be further extended by proper scheduling and putting unnecessary sensor nodes into sleep mode. In this paper a bio-inspired scheduling scheme is proposed. The proposed scheme is a kind of adaptive "selective on-off" scheduling scheme which uses only local information for making scheduling decisions. The scheme is evaluated in terms of target 3-coverage hit-rate, averaged detection delay, and energy consumption per successful target detection. Simulation results show that our proposed scheme can reduce energy consumption by as much as 2/3 when comparing with other generic scheduling schemes while maintaining the detection delay and target hit-rate at a comparable level. Optimization of the network lifetime and other performances is possible by adjusting some parameters.

The authors investigate a cooperative network with three terminals. By exploiting a simple two-bit feedback message from the destination, two incremental relaying protocols are proposed, namely incremental selection amplify-and-forward (ISAF) and joint incremental selection relaying (JISR) with an aim to balance the load between the source and the relay. The authors derive the asymptotic outage probabilities of the two new protocols and find them to be lower than that of the incremental amplify-and-forward (IAF) protocol, which has been identified as the best protocol so far. Moreover, the spectral efficiencies of ISAF and JISR match that of IAF. Simulation results have verified the asymptotic performance of the protocols and have shown that JISR outperforms ISAF and IAF over all signal-to-noise ratio values.

In this paper, we extend the characteristic-function approach to derive an exact symbol error rate expression for the M-ary time-hopping orthogonal pulse position modulation (THPPM) ultra-wideband (UWB) system under the interference from multiple users. Monte Carlo simulations are then used to validate the analytical solutions. The results are found to be valid even when that the chip width is greater than the pulse duration. Moreover, the analytical results are compared to those found by Gaussian approximation and the Gaussian quadrature rule method. We further show that compared to a binary system, M-ary systems can produce better error rate performance.

It is natural to envisage that in a telephone network, some telephone numbers originate or receive more calls than others. Indeed, real-life data have verified the conjecture that the number of calls originated from or received by a telephone number in a network has a power-law property. Further, the number of calls made or received by the same telephone number can be very different. In this paper, we construct a self-growing complex network for modeling the aforementioned telephone call network. The complex network obtained is a directed and weighted network. Moreover, the nodes (telephone numbers) of the network exhibit power-law properties in the following aspects: total-degree, out-degree, in-degree, total-strength, out-strength and in-strength.

In this paper, the authors derive a symbol error rate expression for the M-ary TH-PPM UWB system under the interference from multiple users. Monte Carlo simulations are then used to validate the analytical solutions. Moreover, the analytical results are compared to those found by Gaussian approximation. The authors further show that compared to a binary system, M-ary systems can produce better error performance.

The performances of orthogonal space–time block codes (OSTBCs) over Rician–Nakagami channels are investigated. In particular, we derive closed-form symbol error probability (SEP) expressions for OSTBC systems in which M-ary phase-shift-keying modulation and M-ary quadrature-amplitude modulation are used. These SEP results are expressed in terms of Lauricella's multivariate hypergeometric functions, which can be easily evaluated numerically. When the Rician–Nakagami channel degenerates to the Rician–Rayleigh channel, or equivalently the Rayleigh fading channel, the closed-form SEP expressions are rewritten in terms of higher transcendental functions, that is, Gauss hypergeometric function and Appell hypergeometric function.

A novel approach to analyzing the performance of the V-BLAST multi-input multi-output systems with two transmit antennas is presented in this letter. Based on the properties of Wishart matrices, we derive the exact SNR distributions in the first and second detection steps when optimal detection ordering is used. Closed-form analytical expressions for the bit error rates are then given. The effect of optimal ordering on the diversity order and SNR is evaluated. The results are found to be consistent with those previously published by other researchers

The problem of traffic congestion in complex networks is studied. Two kinds of complex network structures, namely random graphs and scale-free networks, are considered. In terms of the structure of connection, random graphs are homogeneous networks whereas the scale-free networks are heterogeneous networks. For both types of networks, we introduce an additional scale-free feature in the load generation process such that a small number of nodes are more heavily loaded than others. A traffic model similar to the routing algorithm in computer networks is used in our simulation study. We show how the network structures and parameters influence the traffic congestion status.

In the study of low-density-parity-check (LDPC) codes, most researchers are interested in their bit error rate performance. However, block error rate (BLER) is another important measure of the system performance because it provides the rate at which the blocks/packets need to be re-sent again - the smaller the better. In this paper, we apply a simple feedback technique to the decoding of LDPC codes. Extensive simulations have been performed. Results show that the proposed method can effectively improve the BLER of the codes at the waterfall region while not degrading the BER performance at the high SNR region

An analytical approach to the performance analysis of the Vertical Bell Laboratories Space-Time (V-BLAST) multi-input multi-output (MIMO) systems with two transmit antennas is presented in this paper. We derive the exact SNR distribution in the first and second detection steps when optimal detection ordering is used. A closed-form analytical expression for the bit error rate (BER) is then given. The effect of the optimal ordering with two transmit antennas on the diversity order and SNR is also evaluated. Finally, we study the system performance under unbalanced transmit power.

In this paper, the throughput of B-networks is investigated. In the previous analysis by Lee and Yoon (1990), a systematic imbalance of internal link traffic was overlooked. By taking this into account, our analysis yields a more accurate prediction of the throughput of B-networks. The packet arrival rates at the links within the network are derived mathematically and solved using iterations. Throughputs of the unmodified and modified models are compared, together with simulation results. Throughputs of B-networks with different network sizes and traffic rates are also compared with the gamma and crossbar networks.

An analytical model is presented to study the effect of power control error in a CDMA cellular system. The forward link capacity and reverse link capacity are evaluated for perfect and imperfect power control cases. In our model, two forward link power control (nth-power-of-distance power control and optimum power control) and one reverse link power control schemes are examined. The effect of the dynamic range of transmission, moreover, has also been analyzed.