Wireless data links and wireless power transfer (WPT) have become emerging topics in IoT applications. A simple-structure high-efficiency rectenna is the key technology for wirelessly powered IoT receivers. Herein, we explore a unified co-design technique that synergizes wideband circular polarization (CP) antennas with high-frequency Gallium Arsenide (GaAs) Schottky diodes across the 10–20-GHz range. Our approach involves a systematic study of the rectifier’s nonlinear behavior over wide frequency ranges, followed by the identification of an effective antenna candidate for co-design. This strategy effectively obviates the need for matching networks, filters, and extra components typically found in conventional wideband rectennas. Consequently, we present a co-design example: the proposed CP antenna, featuring a measured impedance bandwidth of 11.65–16.9 GHz (36.8%), a 3-dB axial ratio bandwidth (ARBW) of 12.55–16.9 GHz (29.54%), and a measured peak gain of 8.5 dBic. This design integrates CP magneto-electric (ME)-dipole units with rectifier topologies. Measured results show an RF-DC efficiency of over 50% within the 11–14.6 GHz (28%) and 10–18 dBm power range, with a maximum conversion efficiency of 61%. This design approach holds broad applicability for all wideband rectennas, offering notable advantages in terms of simplicity, efficiency, and compactness.

A comprehensive review of metamaterials and metasurfaces for wireless power transfer (WPT) and wireless energy harvesting (WEH) is presented in this article. According to the features of the electromagnetic field from the source to the receiver, WPT is divided into nonradiative near-field technology and radiative (near and far-field) technologies. Many different and important designs are reviewed and compared. It is shown that metamaterials and metasurfaces can significantly improve the power transfer efficiency and operational distance for WPT systems. They can also improve the energy conversion efficiency of wireless energy harvesters by making the reception less sensitive to incident wave angle and polarization. A rectenna is a critical element for both WPT and WEH. It is shown that metamaterial-based rectennas can achieve a higher RF to dc conversion efficiency. Furthermore, metamaterials can also be used as either parasitic elements or loading components to improve WEH performance in terms of circuit size, beamwidth, and conversion efficiency. Future development directions and opportunities of metamaterials and metasurfaces for WPT and WEH are also proposed in this article.

In this paper, we investigate an open topic of a multiuser single-input-multiple-output (SIMO) generalized frequency division multiplexing (GFDM) system in the presence of carrier frequency offsets (CFOs) and in-phase/quadrature-phase (IQ) imbalances. A low-complexity semi-blind joint estimation scheme of multiple channels, CFOs and IQ imbalances is proposed. By utilizing the subspace approach, CFOs and channels corresponding to$U$users are first separated into$U$groups. For each individual user, CFO is extracted by minimizing the smallest eigenvalue whose corresponding eigenvector is utilized to estimate channel blindly. The IQ imbalance parameters are estimated jointly with channel ambiguities by very few subcarriers. The proposed scheme is feasible for a wider range of receive antennas number and has no constraints on the assignment scheme of subsymbols and subcarriers, modulation type, cyclic prefix length and the number of subsymbols per GFDM symbol. Simulation results show that the proposed scheme significantly outperforms the existing methods in terms of bit error rate, outage probability, mean-square-errors of CFO estimation, channel and IQ imbalance estimation, while at much higher spectral efficiency and lower computational complexity. The Cramér-Rao lower bound is derived to verify the effectiveness of the proposed scheme, which is shown to be close to simulation results.

This article presents an innovative belt antenna with an electromagnetic band-gap (EBG) ground plane made of textile materials. The antenna can be applied in a smart belt system to set up a communication link with other electronic devices and/or host a variety of sensors to track human motions. The proposed belt antenna works at 2.45 GHz in the industrial, scientific, and medical radio band for Bluetooth low energy communications. Considering the effect the human body would have on the performance of a belt antenna, a textile ground plane is designed to be integrated into the trouser fabric behind the belt to provide isolation from the body and simultaneously improve antenna radiation characteristics. Through the application of the ground plane, the belt antenna achieves a maximum realized gain of 7.94 dBi and a minimum specific absorption rate of 0.04 W/kg at 0.5 W input power. During the design process, characteristic mode analysis is used to explore the underlining principle and further optimize the antenna performance. Two typical EBG structures are analyzed in detail for this application scenario. The suspended transmission line method is used to evaluate EBG performance variations when the textile ground plane is bent. A prototype of such a system is fabricated and tested. Experimental results shows that the belt antenna, together with the textile EBG ground plane, is an excellent candidate for a smart belt system with desirable radiation pattern, efficiency, and safety limit.

We propose a low-complexity semi-blind joint multi- carrier frequency offset (CFO) and multi-channel estimation scheme for uplink generalized frequency division multiple access (GFDMA) systems. To the best of our knowledge, this is the first work to investigate the estimation of both CFOs and channels for a wide range of GFDMA systems, allowing arbitrary carrier assignment, modulation type and cyclic prefix length, and a wide range of the number of receive antennas. Thanks to the orthogonality between noise subspace and each signal subspace of U users, a complex U-CFO and U-channel estimation problem is decomposed into 2U one-dimensional problems, and solved in a semi-blind manner. Also, the multi-CFO compensation is performed at receiver rather than transmitter, avoiding spectral overhead due to feedback of multiple CFOs. Simulation results show that the proposed scheme significantly outperforms the existing methods in terms of bit error rate (BER) and root-mean-square-errors (RMSEs) of CFO and channel estimation, at much lower computational complexity than the existing methods.

We propose a robust semi-blind estimation scheme of channel and carrier frequency offset (CFO) for generalized frequency division multiplexing (GFDM) systems. This, to the best of our knowledge, is the first work to propose an integral solution to channel and full-range CFO for a wide range of GFDM systems. Based on the derived equivalent system model with CFO included implicitly, a subspace based method is proposed to perform initial channel estimation blindly, which requires only a small number of received symbols to achieve the second order statistics of the received signal. Then, CFO estimation and channel ambiguity elimination are undertaken in series by utilizing a small number of nulls and pilots in a single sub-symbol. Both channel and CFO estimations are more robust against inter-carrier interference (ICI) and inter-symbol interference (ISI) caused by the nonorthogonal filter of GFDM, compared to the existing methods. The proposed scheme achieves a bit error rate (BER) performance close to the ideal case with perfect CFO and channel estimations especially at medium and high signal-to-noise-ratios (SNRs).

Broadband power line communication (BPLC) and television white space (TVWS) are regarded as promising candidates for indoor broadband applications of the Internet of Things. However, they share the access to the very high frequency (VHF) band, which could cause harmful interference and performance degradation to each other. In this paper, a TVWS regulated BPLC system is proposed for point-to-multipoint downlink communication, which integrates the requirement of primary user sensing and the permissible transmission power spectral density (PSD) for TVWS users into the BPLC standard, regarding VHF band access. This integration guarantees minimum interference level between TVWS and BPLC and allows higher transmission PSD for BPLC users in VHF, and hence higher capacity and coverage for BPLC.

We propose an iterative semi-blind (ISB) receiver structure to enable ultra-reliable low-latency communications in short-frame full-duplex (FD) systems with carrier frequency offset (CFO). To the best of our knowledge, this is the first paper to propose an integral solution to channel estimation and CFO estimation for short-frame FD systems by utilizing a single pilot. By deriving an equivalent system model with the CFO included implicitly, a subspace-based blind channel estimation is proposed at the initial stage, followed by CFO estimation and channel ambiguities elimination. Then, the refinement of channel and the CFO estimates is conducted iteratively. The integer and fractional parts of CFO in the full range are estimated as a whole and in closed-form at each iteration. The proposed ISB receiver significantly outperforms the previous methods in terms of frame error rate, mean square errors of channel estimation and CFO estimation and output signal-to-interference-and-noise ratio, while at a halved spectral overhead. Cramér-Rao lower bounds are derived to verify the effectiveness of the proposed ISB receiver structure. It also demonstrates high-computational efficiency as well as the fast convergence speed.

We propose an iterative semi-blind carrier frequency offset (CFO) estimation, self-interference (SI) cancelation and signal detection scheme for full-duplex (FD) orthogonal frequency division multiplexing (OFDM) systems. To the best of our knowledge, this is the first work to consider signal detection of FD systems in the presence of both CFO and SI. The CFO estimation, SI cancelation and signal detection are performed initially by a subspace based semi-blind method, which are then enhanced significantly by performing iterations among them. Its CFO compensation is performed on the desired signal estimate, avoiding the introduction of CFO to the SI. The pilots for the desired signal and SI are carefully designed to enable simultaneous transmission of them to achieve FD training mode. Simulation results show that, the proposed iterative scheme, with much lower training overhead, demonstrates a significant performance enhancement over the existing methods. By utilizing the second order statistics of the received signal, a much superior bit error rate (BER) performance can be achieved compared to the case with perfect SI cancelation and CFO compensation. Its output signal-to- interference-and-noise-ratio (SINR) is close to that with perfect SI cancelation, and robust against the input signal-to-interference ratio (SIR).

A joint multi-carrier frequency offset (CFO) and multi- time of arrival (TOA) estimation algorithm for multiuser single-input multiple-output (SIMO) orthogonal frequency division multiplexing (OFDM) systems is proposed. With carefully designed pilots, multiple CFOs and TOAs of K users are separated jointly, dividing a complex 2K-dimensional estimation problem into 2K low-complexity mono-dimensional estimation problems. Two CFO estimation approaches, including a low-complexity closed-form solution and a high-accuracy null-subcarrier assisted accurate estimation approach, are proposed, where the integer and fractional parts of each CFO are estimated as a whole rather separately. Each TOA is estimated regardless of CFO by exploring the features of the inter-carrier interference matrix. The Cramer-Rao lower bounds (CRLBs) of multi-CFO and mutli-TOA estimation are derived for the first time for SIMO OFDM systems. Simulation results show that the proposed CFO and TOA estimators provide higher estimation accuracy than the existing approaches. They also achieve performances close to the CRLBs especially at high signal-to-noise-ratios (SNRs).

Motivated by the high data rate requirement, full- duplex (FD) multiple-input multiple-output (MIMO) has attracted much attention in both academia and industry. However, FD and MIMO techniques require high power consumption. To strike the balance between the data rate and power consumption, we propose a novel hybrid duplexing strategy, in which antennas are distributed across the service areas and are capable of working in hybrid modes of FD, half- duplex (HD) and sleeping mode, leading to higher energy efficiency (EE) than FD mode only due to enhanced degree of freedom. Based on the hybrid duplexing strategy, we maximize system EE by jointly designing transmitting/receiving chains' activation/deactivation at DAs, downlink beamformer, and uplink transmission power. Novel optimization algorithms are developed. Simulation results confirm that the hybrid duplexing distributed antenna (DA) system provides significant EE improvement over the conventional centralized FD MIMO system, showing its green evolution and applicability to future network deployment.

To address the problem of unbalanced received signal-to-interference-and-noise ratio (SINR) at relay and destination nodes in wireless power transfer (WPT)- supported relay system, we propose a novel asymmetric full-duplex (FD) decode-and-forward (DF) WPT relay strategy, where the transmission time slots are not necessarily identical. By introducing asymmetric time slots, higher degree of freedom is obtained than the conventional symmetric WPT relay system. Furthermore, based on the asymmetric strategy, we develop a spectral efficiency (SE)- oriented resource allocation algorithm by jointly designing time slots, transmission power at source and relay. Simulation results show that the proposed asymmetric system demonstrates higher SE than the symmetric WPT-powered FD and the time- switching based FD relay systems. Besides, more energy can be harvested at the relay node by the proposed system benefiting from the enhanced degree of freedom, showing its applicability in WPT-powered relay systems.

Broadband power line communication (PLC) is a promising solution for the convergence of Internet, data and video transmissions for in-home networking. Narrowband interference (NBI) is one of the crucial affecting factors of PLC systems and requires accurate modeling. In this paper, the narrowband interference for PLC is investigated using both measurement and modeling approaches. A novel three- dimensional (3D) Markov chain (MC) based statistical model is developed, to model the occurrence of NBI which is associated with the traffic of certain radio users. An intensive performance analysis on the impact of the NBI on PLC is provided. The effectiveness of the proposed model is verified by measured results. The 3D MC model can be used for optimizing future cognitive PLC networks, through simulation-based approaches.

We propose a semi-blind precoding aided maximum likelihood (ML) carrier frequency offset (CFO) estimation method and a precoding aided equalization based on independent component analysis (ICA) receiver structure for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) wireless communication systems. By carefully designing a constant in the precoding process, the power between reference data and source data can be balanced to enable ML CFO estimation and ambiguity elimination for the ICA output signals at the receiver. This proposed semi-blind non-redundant structure is much more bandwidth-and-energy efficient than the pilot aided ML CFO estimation method, as no real-time training or extra transmission power is required. Simulation results show that the proposed scheme provides a bit error rate (BER) performance the same as the performance of the pilot aided ML CFO estimation method, and close to the ideal case with perfect channel state information (CSI) and no CFO.

Energy efficiency (EE) is an important issue at 60 GHz due to high power consumption of devices working at such high frequency. In this paper, we investigate EE optimization for full-duplex (FD) decode-of-forward (DF) relay-assisted 60 GHz multiuser indoor networks. In contrast to the existing spectral efficiency (SE) optimization, our scheme maximizes system EE for FD relaying system under cross-layer constraints, addressing the typical problems at 60 GHz, such as the effect of imperfect channel estimation due to serious signal blockage. A low-complexity EE-orientated optimization algorithm is proposed, by which the transmission power, subcarriers and throughput are allocated jointly across multiple users. Simulation results verify our analytical results and confirm that the proposed algorithm achieves a higher EE than the SE-oriented approach, while offering a comparable SE. Also, FD relaying with the proposed algorithm outperforms HD relaying in terms of both EE and SE. In addition, a much lower throughput outage probability is guaranteed by the proposed algorithm, showing its robustness against channel estimation errors. A full range of power consumption sources and imperfect self-interference cancellation are considered to rationalize our analysis.

Broadband power line communication (BPLC) is a promising technology for indoor broadband communication networks. However, BPLC has restricted transmission power in the very high frequency (VHF) band in order to avoid harmful interference to existing wireless services. In this paper, a new hybrid multiple-input multiple-output (MIMO) system is proposed between BPLC and TV white space (TVWS) channels to enhance the system capacity over BPLC in VHF. In order to satisfy the interference limit at the TV primary user (PU) receiver (Rx), an iterative precoding algorithm is proposed to enhance the overall ergodic capacity. Simulation results verify the effectiveness of the proposed hybrid system over the previous cognitive BPLC system.

Power line communication (PLC) network is a promising solution for smart grid and home broadband applications. However, its topology is not always available and is time‐varying due to frequent load changes. The existing topology estimation approaches require installation of a large number of PLC modems or suffer limited resolution. Moreover, they are designed for static PLC networks and need to be repeated at a regular basis to combat topology changes. The authors propose a high‐resolution and low‐complexity dynamic topology estimation scheme for time‐varying indoor PLC networks, which consists of three parts: (i) a time‐frequency domain reflectometry based path length estimation method, which requires measurement at a single PLC modem and achieves a much higher resolution than the frequency domain reflectometry based method; (ii) a node‐by‐node greedy algorithm for topology reconstruction, which is much more computationally efficient than the existing peak‐by‐peak searching algorithm; (iii) an impulsive noise assisted dynamic topology re‐estimation method, which results in a significant complexity reduction over fixed‐frequency re‐estimation.

Energy-efficiency (EE)-oriented green communication design is an important issue at 60 GHz due to high power consumption of devices working at such a high frequency. In this paper, we investigate EE-oriented resource allocation for full-duplex (FD) decode-and-forward relay-assisted 60-GHz multiuser indoor systems. In contrast to the existing spectral efficiency (SE)-oriented designs, our scheme maximizes the EE for a FD relaying system under cross-layer constraints, addressing the typical problems at 60 GHz, such as the intermittent signal blockage caused by the small wavelength of millimeter-wave. A low-complexity EE-orientated resource allocation algorithm is proposed, by which the transmission power allocation, subcarrier allocation, and throughput assignment are performed jointly across multiple users. Simulation results verify our analytical results and confirm that the FD relaying with the proposed algorithm achieves a higher EE than the FD relaying with SE-oriented approaches, while offering a comparable SE. In addition, a much lower throughput outage probability is guaranteed by the proposed resource allocation algorithm, showing its robustness against channel estimation errors. A full range of power consumption sources and imperfect self-interference cancellation are considered to rationalize our analysis.

Parking in major cities, particularly with dense traffic, directly effects the traffic flow and people's life. In this paper, we introduce a new smart parking system that is based on intelligent resource allocation, reservation, and pricing. The proposed system solves the current parking problems by offering guaranteed parking reservations with the lowest possible cost and searching time for drivers and the highest revenue and resource utilization for parking managers. New fair pricing policies are also proposed that can be implemented in practice. The new system is based on mathematical modeling using mixed-integer linear programming (MILP) with the objective of minimizing the total monetary cost for the drivers and maximizing the utilization of parking resources.

Power line communication (PLC) is a promising solution for smart grid and smart home applications. However, the topology of a PLC network is not always available, and it is often hard to obtain. The existing topology estimation approaches either require installation of a large number of PLC modems or have a limited resolution. We propose a time-frequency domain reflectometry (TFDR) based topology estimation scheme for PLC networks, which requires measurement at only one PLC modem and has a much higher resolution than the frequency domain reflectometry (FDR) based method. We also propose an enhanced topology reconstruction algorithm, which is much more computationally efficient than a reference searching algorithm.

We provide a comprehensive energy efficiency (EE) analysis of the full-duplex (FD) and half-duplex (HD) amplify-and-forward (AF) relay-assisted 60-GHz dual-hop indoor wireless systems, aiming to answer the question of which relaying mode is greener (more energy efficient) and to address the issue of EE optimization. We develop an opportunistic relaying mode selection scheme, where FD relaying with one-stage self-interference cancellation (passive suppression) or two-stage self-interference cancellation (passive suppression + analog cancellation) or HD relaying is opportunistically selected, together with transmission power adaptation, to maximize the EE with given channel gains. A low-complexity joint mode selection and EE optimization algorithm are proposed. We show a counter-intuitive finding that with a relatively loose maximum transmission power constraint, FD relaying with two-stage self-interference cancellation is preferable to both FD relaying with one-stage self-interference cancellation and HD relaying, resulting in a higher optimized EE. A full range of power consumption sources is considered to rationalize our analysis. The effects of imperfect self-interference cancellation at relay, drain efficiency, and static circuit power on EE are investigated. Simulation results verify our theoretical analysis.

We propose a joint independent component analysis (ICA) based equalization and carrier frequency offset (CFO) estimation scheme for orthogonal frequency division multiple access (OFDMA) systems, which requires only a single pilot, resulting in a very low spectral overhead. On the one hand, a low-complexity ambiguity elimination method is proposed in the ICA equalized signals. By designing and exploring a fixed order of correlation in the transmitted signals, the permutation ambiguity problem is solved, while the remaining quadrant ambiguity is eliminated by one pilot symbol. One the another hand, linear CFO estimation is performed with a closed-form solution based on the phase difference between adjacent rows in the CFO-corrupted channel structure. Simulation results show that the proposed semi-blind ICA based scheme not only outperforms some existing CFO estimation approaches, but also provides a bit error rate (BER) performance, comparable to the ideal case with perfect channel state information (CSI) and no CFO.

We propose a low-complexity frequency synchronization approach for semi-blind independent component analysis (ICA) based coordinated multi-point (CoMP) orthogonal frequency division multiplexing (OFDM) systems, with multiple carrier frequency offsets (CFOs). The key idea is to introduce a short pilot for both multi-CFO estimation and ambiguity elimination in the ICA equalized signals. First, by minimizing the cross-correlation between original pilots and received pilots with implicit phase rotation correction, the one-dimensional search based CFO estimation can be performed without trial ICI compensation and channel state information (CSI). Second, by maximizing the real part of the cross-correlation between ICA equalized pilots and original pilots, the same pilots can be used again to eliminate the permutation and quadrant ambiguity in the ICA equalized signals. Simulation results show that, with a very low training overhead of 2%, the proposed multi-CFO estimation approach outperforms existing methods. Also, the proposed semi-blind CoMP system can achieve a bit error rate (BER) performance close to the ideal case with perfect CSI and no CFO.

The existing Bernoulli-Gaussian (BG) model describes the impulsive noise samples for power line communication (PLQ as independent and identically distributed (i.i.d.). In practice, impulses often occur in bursts and have memory. In this paper, the impulsive noise for PLC is investigated using both measurement and modeling approaches. To the best of our knowledge, this is the first work to model the correlation between consecutive impulses for PLC, using a hybrid model which includes the weighted contributions of deterministic and random patterns of individual impulses in a burst. The occurrence dependence between bursts and between impulses in a burst is described by an enhanced two-level Markov Chain (MQ based model. An intensive performance analysis of the proposed models is provided. The effectiveness of the models is verified by measured results.

We propose a semi-blind multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system, with a precoding aided carrier frequency offset (CFO) estimation approach, and an independent component analysis (ICA) based equalization structure. A number of reference data sequences are carefully designed offline and are superimposed to source data via a non-redundant linear precoding process, which can kill two birds with one stone, without introducing any extra total transmit power and spectral overhead. First, the reference data sequences are selected from a pool of carefully designed orthogonal sequences. The CFO estimation is to minimize the sum cross-correlation between the CFO compensated signals and the rest orthogonal sequences in the pool. Second, the same reference data enable elimination of the permutation and quadrant ambiguity in the ICA equalized signals by maximizing the cross-correlation between the ICA equalized signals and the reference data. Simulation results show that, without extra bandwidth and power needed, the proposed semi-blind system achieves a bit error rate (BER) performance close to the ideal case with perfect channel state information (CSI) and no CFO. Also, the precoding aided CFO estimation outperforms the constant amplitude zero autocorrelation (CAZAC) sequences based CFO estimation approach, with no spectral overhead.

We propose an optimal asymmetric resource allocation (ARA) algorithm for the decode-and-forward (DF) dualhop multi-relay Long Term Evolution Advanced (LTE-Advanced) system in the downlink, with orthogonal frequency division multiplexing (OFDM) transmission. Our work is different in that the time slots for the two hops via each of the relays are designed to be asymmetric, i.e., with K relays in the cell, a total of 2K time slots may be of different durations, which enhances the degree of freedom over the previous work. Also, a destination may be served by multiple relays at the same time to enhance the transmission diversity. Moreover, closed-form results for optimal allocation are derived, which requires only limited feedback information. Simulation results show that, thanks to the multi-relay, multi-user and time diversities, the proposed ARA scheme can provide a much better performance than the scheme with symmetric time allocation, as well as the scheme with asymmetric time allocation for a system composed of independent single-relay sub-systems, especially when the relays are close to the source.

We propose a joint semi-blind equalization and inter-carrier interference (ICI) mitigation scheme for multiple carrier frequency offsets (CFOs) corrupted signals in carrier aggregation (CA) based multiple access coordinated multi-point (CoMP) systems with OFDMA. The CFO-induced ICI is mitigated implicitly via the independent component analysis (ICA) based semi-blind equalization, without requiring an explicit process of estimation of multiple CFOs. Only a small number of pilots are used to resolve the remaining indeterminacies in the ICA equalized signals, introducing a very low training overhead. Simulation results show that the proposed semi-blind ICA based equalization scheme provides a bit error rate (BER) performance closed to the ideal case with perfect CSI and no CFO, and also outperforms the approach with the constant amplitude zero autocorrelation (CAZAC) sequences based explicit CFO estimation.

We propose an orthogonal frequency division multiplexing (OFDM) based semi-blind coordinated multi-point (CoMP) system, with a low complexity estimation approach for multiple carrier frequency offsets (CFOs), and an equalization structure based on the independent component analysis (ICA). Our work is different in that a small number of well-designed pilot symbols are employed to kill two birds with one stone. On the one hand, using the structure of pilots, a complex multi-dimensional search for multiple CFOs is divided into a series of low-complexity mono-dimensional searches. On the other hand, the cross-correlation between the transmitted and the received pilot symbols is explored to allow elimination of the remaining ambiguity in the ICA equalized signals. Simulation results show that with a low training overhead of 3.1%, the proposed semi-blind system can achieve a bit error rate (BER) performance close to the ideal case with perfect channel state information (CSI) and no CFO at the receiver.

In this paper, we propose a novel asymmetric resource allocation (RA) scheme for the decode-and-forward (DF) multi-relay based Long Term Evolution Advanced (LTE-Advanced) system, with the orthogonal frequency division multiplexing (OFDM) modulation. Given a fixed total transmit time duration, the time slot durations for the two hops via each of the K relays are designed to be asymmetric, which increases the degree of freedom for transmission significantly. We propose an optimal algorithm to maximise the system capacity, with joint asymmetric time allocation, power allocation, and subcarrier selection/allocation. Simulation results show that the proposed asymmetric RA scheme provides an enhanced performance over algorithms with symmetric time slot allocation, and it is also robust against the variation of relay nodes' locations.

An asymmetric resource allocation (ARA) scheme for the downlink wireless multi-destination relay systems with orthogonal frequency division multiplexing (OFDM) modulation is proposed. Unlike the previous work, the transmission durations at the source (base station) and the relay are designed to be asymmetric, which enhances the degree of freedom for transmission. Therefore, the proposed ARA scheme achieves a higher system capacity than existing symmetric RA schemes. Simulation results demonstrate that the proposed asymmetric time allocation has a significant effect on the system performance with a large number of users, a long source-to-destination distance, and when there is a significant difference between the source-to-relay and the relay-to-destination distances.

The authors propose an optimal resource allocation (RA) scheme for wireless multi-destination relay systems with orthogonal frequency division multiplexing (OFDM) modulation. The authors work is different in that they consider a practical downlink OFDM-based relay network, where a relay is used to help the source (base station) communicate with multiple out-of-range destinations (users), rather than a single destination (user) as assumed in most previous work. The proposed optimal RA scheme consists of subchannel allocation (SA), subchannel pairing and joint source–relay power allocation (PA). In particular, it is shown that both SA and joint source–relay PA play a dominant role in the three steps of RA. It is also demonstrated that the shorter the distance between the source and the relay, the more impact of multiuser diversity on the system capacity. By employing SA and joint source–relay PA only, a near-optimal performance can be achieved. This work can be extended to the multi-hop, multi-relay and multi-destination uplink/downlink OFDM system.

We propose an optimal asymmetric resource allocation scheme with limited feedback for wireless relay systems based on orthogonal frequency division multiplexing (OFDM) modulation. Unlike the previous work, we assume that the bits transmitted over the same subchannel from the source to the relay may be distributed over different subchannels when being forwarded from the relay to the destination. This not only increases the degree of freedom for transmission, but also reduces the transmission overhead significantly because the amount of feedback information required is independent of the number of subchannels. Furthermore, the transmission durations at the source and the relay are designed to be asymmetric, which also enhances the degree of freedom for transmission. Simulation results show that the proposed optimal asymmetric resource allocation scheme achieves a higher system capacity, and has less sensitivity to channel estimation errors than the previous work. It also demonstrates a fast convergence speed.

We propose an adaptive cross-layer design for the downlink multiuser orthogonal frequency division multiplexing (OFDM) systems, to maximize the weighted sum capacity of all users, where each user has multiple heterogeneous traffic queues simultaneously. A packet dependent (PD) scheduling scheme is employed at the medium access control (MAC) layer, which determines the packet transmission order by assigning different weights to different packets, and is shown by simulations more efficient than the previous methods where all packets in a queue have the same weight. The weight design in PD scheduling considers the delay, size and quality of service (QoS) priority level of packets. Each user weight employed in resource allocation at the physical (PHY) layer is obtained by summing up the weights of selected packets for the user. By properly choosing the number of packets used for weight calculation, the proposed cross-layer design requires a much lower overall complexity than the conventional queue based designs. It is also proven to achieve the maximum system stability region. Furthermore, simulation results show that the proposed suboptimal resource allocation algorithm provides a near-optimal performance while requiring a relatively low complexity.

We propose a dynamic resource allocation scheme for a wireless cooperative network based on orthogonal frequency division multiplexing (OFDM) modulations with limited feedback. The amount of the feedback information required from the relay to the source in the proposed scheme is independent of the number of subchannels, which results in a dramatic reduced overhead over conventional resource allocation schemes. Furthermore, the transmission durations at the source and the relay are designed to be asymmetric, which enhances the degree of freedom for transmission. Simulation results show that the proposed resource allocation scheme achieves a higher system capacity, and has less sensitivity to channel estimation errors than the previously proposed schemes based on subchannel paring and power allocation. It also has a fast convergence speed. An intensive performance analysis is provided for the proposed resource allocation scheme.

We propose the optimal resource allocation for wireless multi-destination relay systems with orthogonal frequency division multiplexing (OFDM) modulation, which includes subchannel allocation (SA), subchannel pairing (SP), and joint source-relay power allocation (PA). Our work is different in that we consider a practical downlink OFDM based cooperative network, where the relay is used to help the source (base station) to communicate with multiple destinations (users) rather than a single destination as assumed in the previous work. Simulation results demonstrate that the proposed optimal resource allocation outperforms other resource allocation schemes in terms of the system capacity. This work can be extended to multi-relay multi- destination uplink/downlink OFDM relay systems.

We describe a novel application framework to reduce the effects of ink-bleed in old documents. This task is treated as a classification problem where training-data is used to compute per-pixel likelihoods for use in a dual-layer Markov Random Field (MRF) that simultaneously labels image pixels of the front and back of a document as either foreground, background, or ink-bleed, while maintaining the integrity of foreground strokes. Our approach obtains better results than previous work without the need for assumptions about ink-bleed intensities or extensive parameter tuning. Our overall framework is detailed, including front and back image alignment, training-data collection, and the MRF formulation with associated likelihoods and intra- and interlayer cost computations.

We propose a novel packet batch dependant cross-layer scheduling scheme for the downlink multiuser orthogonal frequency division multiplexing (OFDM) system, which significantly outperforms the existing queue dependant scheduling scheme over a wide range of signal-to-noise (SNR) in terms of the system bandwidth efficiency, best-effort (BE) traffic throughput and quality of service (QoS) traffic delay, while requiring a lower complexity. Our batch dependant scheduling also provides a better tradeoff between the QoS traffic and BE traffic. It is also shown to guarantee the system stability.

We propose a novel cross-layer optimization scheme for the downlink multiuser orthogonal frequency division multiplexing (OFDM) system. The proposed maximum weighted capacity (MWC) based resource allocation at the physical (PHY) layer can provide a much better QoS than the previous resource allocation schemes, while maintaining the highest or nearly highest capacity and costing a similar complexity. In particular, the more fluctuation in different users' data arrival rates, the more advantages of MWC in both QoS and capacity. Besides, our proposed delay satisfaction (DS) scheduling at the medium access control (MAC) layer allows more than one connection to be served in each slot, which is more efficient than conventional scheduling.

The location and identification of unexploded ordnance (UXO) from magnetometer measurements have long been an area of active research interest. Ground surface methods, which are widely used for objects buried in shallow depths, become ineffective for objects deep in the soil because the object's anomalous field diminishes rapidly with distance, and interference by metal debris on the ground surface is significant. For the location and identification of deeply buried UXO, a total-field magnetometer equipped with a cone penetrometer technology (CPT) drilling system is employed in this paper. A novel inversion method is developed to extract information from individual and multiple CPT profiles. Compared with conventional inversion methods providing a single minimum as an estimate, this approach tests the likelihood distribution over the anticipated solution space, hence providing reliability. Real-world data are collected from a test site for the location and identification of a specific target. All experiments and simulations demonstrate the superior capability of this technique in solving real-world problems when only limited data points are available.

The packet priority calculation method, also referred to as packet selection policy, is a necessary component for sorted priority based packet schedulers. A new packet priority calculation method, called smallest middle-point finish time first (SMFF), is proposed. An analysis model, called packet rate proportional server plus (PRPS+), based on the packet rate proportional server (PRPS) is developed to act as the start point for the discussion on the SMFF. It is shown that the packet schedulers based on sorted-priority can be modeled by the PRPS+ class, (such as weighted fair queuing, start-time fair queuing, self clocked fair queuing and worst-case fair weighted fair queuing); it is demonstrated that the scheduling fairness is improved if their priority calculation methods are replaced by SMFF.

We propose a simple power allocation (PA) scheme for wireless MIMO systems with layered space-time equalization (LSTE), which aims at minimizing the overall BERs for all data streams. This so-called MIN-BER PA scheme significantly outperforms the uniform power (UP) case in a wide range of RMS delay spreads and at high SNR, with little loss in computational complexity and bandwidth efficiency. Compared to EQ-BER PA, MIN-BER PA yields close performance, but requires much less complexity especially at high SNR. Closed-form results are provided for MIN-BER PA, based on which intensive performance analysis is made, including BER performance and signal detection ordering for LSTE with PA.

The family of repetition coded (RC) multicarrier system has a few members, such as multicarrier code division multiple access and intercarrier interference self-canceling scheme etc. This paper investigates three modes of the RC-OFDM system in the presence of unknown block fading channel. Relying on the code redundance, blind channel identification and equalization algorithms are developed. In the multitransmitter system, frequency-domain optimum precedes are proposed to solve the channel ambiguity. Simulation results are provided to corroborate the theoretical analysis.

The existing method for sampling a modulated signal is the same as that for a non-modulated message signal. Therefore, the quadrature sampling rate for a modulated signal must be larger than its bandwidth. However, a new algorithm, which can recover completely a DC-free message signal from an FM signal at a sampling rate less than its bandwidth, is presented. The new sampling rate limit is also discussed. The investigation shows that the current sampling theorem does not present an optimal sampling rate for recovering the message signal from an FM signal and further modification of the theorem might be needed.

With various building dielectric parameters, simulation results obtained using a ray-tracing method for both the narrowband and wideband indoor channel characterisation are presented. Effects of different building dielectric parameters on the channel characteristics are shown for the same building in terms of the predicted path-loss and RMS delay spread (/spl tau//sub rms/) of the channel impulse response. Simulation results demonstrate that channel /spl tau//sub rms/ is more sensitive to the building dielectric parameters compared with the path-loss characteristic. This indicates that the information on building dielectric parameters with higher accuracy is required for indoor channel /spl tau//sub rms/ prediction.

A new orthogonal multicarrier bandwidth modulation (OMBM) scheme is proposed in this paper. The distinct feature of this scheme is that the frequency domain data is used to decide the number of orthogonal subcarriers for wireless transmissions. Different bandwidth of the OMBM symbol in the time domain reflects on the different data in the frequency domain. A discrete Fourier transform (DFT) based minimum mean square error (MMSE) estimator is employed to conduct the bandwidth detection. Analysis and simulation results demonstrate that the OMBM scheme is a flexible modulation structure and not sensitive to noise interference. Some properties and possible application of the OMBM code are also introduced.

A calibration technique for free-space measurement of the permittivity and conductivity has been developed, taking account of antenna-medium coupling. Thus, the accuracy is improved compared to previously used calibration. Two examples are given to illustrate this improvement.