Inter-satellite communication (ISC) is a critical component of low Earth orbit (LEO) satellite communication systems, enabling seamless data exchange between satellites within the same or across different orbital planes. This paper investigates the impact of position and attitude perturbations caused by gravitational forces, theJ2effect, aerodynamic torques, and Earth’s magnetic field between inter-orbital LEO satellite pairs on ISC channels. It reveals that such perturbations significantly degrade the LEO ISC link performance at the terahertz (THz) band. To address this challenge, a novel statistical symbol-level power and modulation adaptation (SSL-PMA) algorithm is proposed to mitigate the effects of the perturbations, enhance spectral efficiency, and reduce transmission power consumption under varying perturbation levels. Simulation results demonstrate that the proposed algorithm achieves substantial spectral efficiency gains over conventional adaptive and non-adaptive schemes, maintaining bit error rate (BER) performance comparable to or better than that of fixed modulation schemes across different perturbation levels. Notably, transmission power savings of up to 40% are achieved at inter-plane angles of 90◦ and 150◦, with slightly lower savings at 30◦. These findings highlight the potential of the proposed SSL-PMA algorithm for efficient and adaptive transmission in future THz-band inter-satellite communication systems.

Millimeter wave (mmWave) technology promises unprecedented capacity and ultra-low latency for wireless communications. However, mmWave systems confront challenges, including high costs, power consumption, and accurate carrier synchronization, significantly limiting mmWave-based applications. The emerging over-the-air modulation (OTAM) technique has recently demonstrated cost-effective and low-power mmWave communication by utilizing channel attenuation difference characteristics to achieve an ASK-like modulation effect. Despite these advancements, the wireless beam modulation (WBM) system based on the OTAM technique suffers from nonlinear interference caused by random phase offsets when supporting multi-node spatial division multiplexing (SDM) access. To address the challenges, we propose a moment-based analysis (MBA) framework to reduce carrier synchronization requirements, enabling the WBM system to linearize nonlinear spatial interference under coarse carrier synchronization. Within the MBA framework, we further develop a moment-based interference cancellation (MBML-IC) algorithm based on the maximum likelihood criterion. The MBML-IC algorithm eliminates interference in the energy domain, thereby supporting multi-node SDM access for the WBM system. Simulation experiments validate the performance improvements regarding the system bit error rate (BER). Besides, the proposed MBA framework and MBML-IC algorithm empower the WBM system to employ lower-precision, cost-effective, and low-power mmWave components, enhancing energy efficiency.

Inter-satellite communication (ISC) is an essential part of LEO satellite communication systems, allowing satellites to communicate with each other in the same or different orbital planes. This paper presents a prediction model to estimate the distance and Doppler shift between two LEO satellites in different orbital planes. Using this prediction model, a channel model for rapidly changing inter-orbital ISC channels is established. Moreover, a novel dynamic symbol-level power and modulation pre-adaptation (SL-PMPA) algorithm is proposed to achieve power-efficient high throughput transmission under the rapidly changing ISC channel. Simulation results demonstrate that compared to conventional transmission modulation schemes, the proposed dynamic SL-PMPA algorithm not only significantly enhances the throughput under the same BER threshold, but also effectively reduces the transmission power.

To support emerging smart applications, joint communication and sensing (JCAS) integrates sensing into communications to save resources and provide a wider sensing service. Although there have been many works in this area, almost all of them are based on the sometimes impractical assumption that the position of the transmitter is known. In this paper, we propose a low-complexity multi-target-aided method for uplink MIMOOFDM sensing in a cluttered environment with an unknown transmitter’s position. Specially, we form the signal received at the base station (BS) as a fourth-order tensor, and after clutter suppression, we adopt a low-rank CANDECOMP/PARAFAC (CP) decomposition to perform parameter estimations. Through theory analysis, our CP decomposition satisfies the condition of uniqueness. Simulation results show that the proposed method can achieve better normalized mean square error performance than the existing methods and even approach a similar performance with the ideal case benchmark.

Using DNA as the medium to store information has recently been recognized as a promising solution for long-term data storage. While several system prototypes have been demonstrated, the error characteristics in DNA data storage are discussed with limited content. Due to the data and process variations from experiment to experiment, the error variation and its effect on data recovery remain to be uncovered. To close the gap, we systematically investigate the storage channel, i.e., error characteristics in the storage process. In this work, we first propose a new concept named sequence corruption to unify the error characteristics into the sequence level, easing the channel analysis. Then we derived the formulations of the data imperfection at the decoder including both sequence loss and sequence corruption, revealing the decoding demand and monitoring the data recovery. Furthermore, we extensively explored several data-dependent unevenness observed in the base error patterns and studied a few potential factors and their impacts on the data imperfection at the decoder both theoretically and experimentally. The results presented here introduce a more comprehensive channel model and offer a new angle towards the data recovery issue in DNA data storage by further elucidating the error characteristics of the storage process.

DNA code design aims to generate a set of DNA sequences (codewords) with minimum likelihood of undesired hybridizations among sequences and their reverse-complement (RC) pairs (cross-hybridization). Inspired by the distinct hybridization affinities (or stabilities) of perfect double helix constructed by individual single-stranded DNA (ssDNA) and its RC pair, we propose a novel similarity significance (SS) model to measure the similarity between DNA sequences. Particularly, instead of directly measuring the similarity of two sequences by any metric/approach, the proposed SS works in a way to evaluate how more likely will the undesirable hybridizations occur over the desirable hybridizations in the presence of the two measured sequences and their RC pairs. With this SS model, we construct thermodynamically stable DNA codes subject to several combinatorial constraints using a sorting-based algorithm. The proposed scheme results in DNA codes with larger code sizes and wider free energy gaps (hence better cross-hybridization performance) compared to the existing methods.

DNA has become an attractive medium for long-term data archiving due to its extremely high storage density and longevity. Short single-stranded DNAs, called oligonucleotides (oligos), have been designed and synthesized to store digital data. Previous works designed the oligos with a pair of primer binding sites (PBSs) (each with a length of around 200) attached at the two ends of each basic readable data block. The addition of PBSs decreases the data density significantly because in the current DNA synthesis, the maximum length of a synthesized oligo in good quality is around 200. Furthermore, the maximum homopolymer run allowed by the existing experiments has been reported to be three nucleotides. In this work, to increase the data density, we have devised and tested an oligo design for DNA-based storage with the basic readable data block appended by a single PBS at one end only, while allowing the maximum homopolymer run to be increased to 4. We also present an oligo assembly algorithm that can reconstruct oligos with a single PBS from the error-prone raw readouts obtained from the sequencing process. We have conducted a wet lab experiment to validate the proposed design, where we tested with 398KB of data stored into 10,750 oligos. The experimental results show that it is possible to recover over 99 percent of the oligo sequences without error, which proves that one PBS is sufficient for implementing a DNA-based data storage system with maximum homopolymer run relaxed to 4. The use of single PBS leads to a significant data density gain from 14.3 to 140.2 percent over the existing short-strand DNA data storage schemes by reserving more nucleotides for storing information bits.

Global Navigation Satellite System (GNSS) Radio Occultation (RO) is an atmospheric remote sensing technique that improves global weather forecasting, climate monitoring, and ionospheric studies. Planetary boundary layer height (PBLH) is a crucial parameter in modeling the troposphere. Space-based GNSS RO has been used in detecting the PBLH with receivers onboard low earth orbit satellites. This paper presents a method of PBLH detection using GNSS signal amplitude measured by a mountaintop-based RO (MRO) system on the summit of Haleakala, Hawaii. The estimated PBLHs are comparable with those derived from space-based RO measurements, space-borne lidar, and local radiosonde profiles. With advantages such as having dense temporal and spatial coverage, low-cost, and an easy-to-implement algorithm, the MRO-based signal amplitude method can be a useful addition to existing methods and could contribute to regional weather study.

In this letter, we provide a new framework for semiblind interference alignment (SBIA) in multi-input-single-output broadcast channels (MISO-BC) where the transmitter receives channel feedback from only one receiver (referred to as supernode). The supernode is called so because it has reconfigurable antennas as well as a feedback mechanism to the transmitters. All other receivers neither have reconfigurable antennas nor provide any kind of feedback to the transmitter. We provide a linear precoding scheme using interference alignment (IA) for this new framework for some classes of MISO-BC, and show that the degrees of freedom (DoF) gain is higher than the traditional orthogonal transmission schemes such as time-division-multiple-access (TDMA). Our proposed SBIA can also be applied to the two-user X-channel for which it is DoF-optimal.

Recently, a transmission strategy was designed for the K-user interference channel (IC) without CSI at the transmitters (CSIT) but aided by a relay which knows the global CSI, where it was shown that K - 1 relay antennas are required to attain the maximum network DoF. In this paper, we derive general IA feasibility conditions for a single relay-aided IC with CSI at both the relay and the transmitters. Our result shows that except for the special case of K = 3 users, providing CSI to the transmitters still requires K - 1 relay antennas to achieve the maximum network DoF. Next, we design the minimum-sum-mean-squareerror (MSMSE) and weighted-sum-rate (WSR) maximizing precoders for the relay-aided IC network without CSIT which show higher sum-rate in the finite-SNR region compared to the IA precoding. Further, a so-called scaled-IA initialization is proposed for the MSMSE and the WSR algorithms which not only preserves the network DoF but also saves the power at the relay considerably compared to the MSMSE and the WSR schemes with random initializations. Extensive simulation results in both symmetric and asymmetric networks show that the MSMSE precoder shows better BER performance than both the IA and the WSR algorithms for low-to-moderate data rates.

Energy is scarce in mobile computing devices including wearable and implantable devices in a wireless body area network. In this paper, an adaptive routing protocol is developed and analyzed which minimizes the energy cost per bit of information by using the channel information to choose the best strategy to route data. In this approach, the source node will switch between direct and relayed communication based on the quality of the link and will use the relay only if the channel quality is below a certain threshold. The mathematical model is then validated through simulations which shows that the adaptive routing strategy can improve energy efficiency significantly compared with existing methods.

Techniques that could be used to monitor human motion precisely are helpful in various applications such as rehabilitation, gait analysis, and athletic performance analysis. This paper focuses on the 3-D foot trajectory measurements based on a wearable wireless ultrasonic sensor network. The system consists of an ultrasonic transmitter (mobile) and several receivers (anchors) with fixed known positions. In order not to restrict the movement of subjects, a radio frequency (RF) module is used for wireless data transmission. The RF module also provides the synchronization clock between mobile and anchors. The proposed system measures the time-of-arrival (TOA) of the ultrasonic signal from mobile to anchors. Together with the knowledge of the anchor's position, the absolute distance that the signal travels can be computed. Then, the range information defines a circle centered at this anchor with radius equal to the measured distance, and the mobile resides within the intersections of several such circles. Based on the TOA-based tracking technique, the 3-D foot trajectories are validated against a camera-based motion capture system for ten healthy subjects walking on a treadmill at slow, normal, and fast speeds. The experimental results have shown that the ultrasonic system has sufficient accuracy of net root-mean-square error ( 4.2 cm) for 3-D displacement, especially for foot clearance with accuracy and standard deviation ( 0.62 ±7.48 mm) compared to the camera-based motion capture system. The small form factor and lightweight feature of the proposed system make it easy to use. Such a system is also much lower in cost compared to the camera-based tracking system.

In this paper, for the K-user interference relay channel (IRC) with transmitters and relays having no and global channel state information (CSI), respectively, a minimum sum mean squared error (MSMSE) based relay precoder is proposed. It is shown that MSMSE outperforms interference alignment (IA) relay precoder in sum rate at low to mid signal-to-noise ratio (SNR) regions as well as in bit error rate (BER) at all SNR regions for small and moderate sizes of Gray encoded constellations.

In this paper, a new method for measuring and monitoring human body joint angles, which uses wearable ultrawideband (UWB) transceivers mounted on body segments, is proposed and investigated. The model is based on providing a high ranging accuracy (intersensor distance) between a pair of transceivers placed on the adjacent segments of the joint center of rotation. The measured distance is then used to compute the joint angles based on the law of cosines. The performance of the method was compared with a flexible goniometer by simultaneously measuring joint flexion-extension angles at different angular velocities, ranging between 8 and 90(°) /s. The measurement errors were evaluated by the average differences between two sets of data (ranging from 0.8(°) for slow movement to 2.8(°) for fast movement), by standard deviation (ranging from 1.2(°) to 4.2(°) for various movement speeds) and by the Pearson correlation coefficient (greater than 0.99) which demonstrates the very good performance of the UWB-based approach. The experimental results have shown that the system has sufficient accuracy for clinical applications, such as rehabilitation.

We provide the degrees of freedom (DoF) characterization for the three-user MT× MRmultiple-input-multipleoutput (MIMO) interference channel (IC) with rank-deficient channel matrices, where each transmitter is equipped with MTantennas and each receiver with MRantennas, and the interfering channel matrices from each transmitter to the other two receivers are of ranks D1and D2, respectively. One important intermediate step for both the converse and achievability arguments is to convert the fully-connected rank-deficient channel into an equivalent partially-connected full-rank MIMO-IC by invertible linear transformations. As such, existing techniques developed for full-rank MIMO-IC can be incorporated to derive the DoF outer and inner bounds for the rank-deficient case. Our result shows that when the interfering links are weak in terms of the channel ranks, i.e., D1+ D2≤ min(MT, MR), zero forcing is sufficient to achieve the optimal DoF. On the other hand, when D1+ D2> min(MT, MR), a combination of zero forcing and interference alignment is in general required for DoF optimality. The DoF characterization obtained in this paper unifies several existing results in the literature.

This paper studies the achievable rate region of the K-user Gaussian multiple-input single-output interference channel (MISO-IC) with interference treated as noise, when improper or circularly asymmetric complex Gaussian signaling is applied. By exploiting the separable rate expression with improper Gaussian signaling, we propose a separate covariance and pseudo-covariance optimization algorithm, which is guaranteed to improve the users' rates over the conventional proper or circularly symmetric complex Gaussian signaling. In particular, for the pseudo-covariance optimization, the semidefinite relaxation (SDR) technique is applied to provide a high-quality approximate solution. For the special case of two-user MISO-IC, the SDR technique yields the optimal pseudo-covariance solution.

This paper studies the transmit optimization for the K-user Gaussian single-input single-output interference channel (SISO-IC), with the interference treated as Gaussian noise and by applying improper or circularly asymmetric complex Gaussian signaling. The transmit optimization with improper Gaussian signaling involves not only the signal covariance as in the conventional proper or circularly symmetric complex Gaussian signaling, but also the signal pseudo-covariance, which is conventionally set to zero in proper Gaussian signaling. By utilizing the rate-profile method, the achievable rate region of the K-user SISO-IC is characterized by solving a sequence of minimum-weighted-rate maximization (MinWR-Max) problems, which are non-convex and thus difficult to be solved globally optimally. By applying the semidefinite relaxation (SDR) technique, we propose an efficient approximate solution, which jointly optimizes the covariance and pseudo-covariance of the transmitted signals. Simulation results demonstrate the effectiveness of the proposed algorithm for the K-user SISO-IC with improper Gaussian signaling.

In wireless sensor networks, nodes can retransmit their neighbours' packets to provide redundancy and decrease packet error rate. However, this comes at the expense of increased energy consumption in the cooperating nodes. Cooperation between nodes in routing data is a necessity in sensor networks. This work exploits features of UWB-IR modulations to create redundancy in wireless sensor networks. We introduce a physical layer coding framework for UWB-IR and compare it with conventional UWB-IR modulation in terms of energy usage. Simulation results show that the proposed methods can decrease the energy usage of the nodes while enhancing packet error rate performance of the system.

An accurate approach in locating a source based on the intersections of hyperboloids defined by the time difference of arrival (TDOA) of a signal received at a number of reference nodes is proposed and investigated. The demonstrated system consists of a UWB transmitter, irradiating a UWB Gaussian pulse, and eight coherent receivers where positions are known. Techniques like optimal template-based estimator used for time delay estimation are discussed. The effect of errors in range measurement on the accuracy of positioning is reduced by adopting Taylor-series-based minimization procedures. Furthermore, we evaluate the performance of the proposed method by comparing with traditional LSE minimization procedure in both simulation and experimental results. The experimental results show that the target positioning error is only about (0.7198±0.271)cm (mean±standard deviation), which is accurate for potential applications such as robot navigation, personal tracking and monitoring.

In this paper, beamforming design is considered for a K-user multiple-input-multiple-output interference channel (MIMO-IC) under limited channel feedback budget at the users. Using a geometrical framework, an analytical expression for the upper bound on the total rate loss due to limited channel feedback is derived. The rate loss is a function of the total feedback budget available to the receiver, the strength of the desired and the interfering links at the users and the network parameters. This rate loss upper bound metric is then minimized at each receiver locally by allocating the feedback bits optimally among the links observed by it. We obtain an interesting result that under limited channel feedback budget at the users, interference alignment (IA) may not be the appropriate beamforming strategy. Based on the feedback bit allocation policy to minimize the rate loss upper bound at the receiver and the corresponding channel quantization error statistics at the transmitter, an improved beamformer design is proposed. The proposed beamformer shows a higher throughput gain compared to all other existing schemes.

This paper studies the achievable rate region of the K-user Gaussian multiple-input single-output interference channel (MISO-IC) with the interference treated as noise, when improper or circularly asymmetric complex Gaussian signaling is applied. The transmit optimization with improper Gaussian signaling involves not only the signal covariance matrix as in the conventional proper or circularly symmetric Gaussian signaling, but also the signal pseudo-covariance matrix, which is conventionally set to zero in proper Gaussian signaling. By exploiting the separable rate expression with improper Gaussian signaling, we propose a separate transmit covariance and pseudo-covariance optimization algorithm, which is guaranteed to improve the users' achievable rates over the conventional proper Gaussian signaling. In particular, for the pseudo-covariance optimization, we establish the optimality of rank-1 pseudo-covariance matrices, given the optimal rank-1 transmit covariance matrices for achieving the Pareto boundary of the rate region. Based on this result, we are able to greatly reduce the number of variables in the pseudo-covariance optimization problem and thereby develop an efficient solution by applying the celebrated semidefinite relaxation (SDR) technique. Finally, we extend the result to the Gaussian MISO broadcast channel (MISO-BC) with improper Gaussian signaling or so-called widely linear transmit precoding.

In direct sequence-code division multiple access (DS-CDMA) systems over frequency-selective channels, blind joint equalisation and multiuser detection has been the focus subject of research by many researchers. In this scheme, only the desired user's spreading code and timing information are available to the receiver. The two-stage constant modulus algorithm (CMA)-based receiver proposed, implements an adaptive blind joint equalisation and multiuser detection without explicit channel estimation. The first stage of the algorithm can be seen as a linear combination of blind adaptive minimum output energy (MOE) detectors based on total data correlation matrix. In this study, the authors adopt a MOE detector based on interference correlation matrix instead of total data correlation matrix to improve the performance of the first-stage detector, thus achieving an improved two-stage CMA-based blind joint equalisation and multiuser detection algorithm. In addition, the convergence of the proposed adaptive algorithm is analysed. Both the analysis and computer simulation verify the performance improvement of our proposed algorithm.

Wireless body area network (WBAN) is an interesting application of sensor networks which can revolutionize our interaction with the outside world. WBAN like any other sensor network suffers limited energy resources and hence preserving the energy of the nodes is of great importance. Unlike typical sensor networks WBANs have few and dissimilar sensors. In addition, the body medium has its own propagation characteristic which means that the existing solution for preserving energy in wireless sensor networks might not be efficient in WBANs. The quality of the links between the nodes in WBAN is changing frequently due to the moving nature of the body. This can pose a major problem especially in the energy efficiency merit. In this work we have proposed an opportunistic scheme to exploit the body movements during the walking to increase the life time of the network. The results show that comparing to the existing methods this work can increase the life time of the network.

High-rate space-time block codes (STBC with code rate >; 1) in multi-input multi-output (MIMO) systems are able to provide both spatial multiplexing gain and diversity gain, but have high maximum likelihood (ML) decoding complexity. Since group-decodable (quasi-orthogonal) code structure can reduce the decoding complexity, we present in this paper systematic methods to construct group-decodable high-rate STBC with full symbol-wise diversity gain for arbitrary transmit antenna number and code length. We show that the proposed group-decodable STBC can achieve high code rate that increases almost linearly with the transmit antenna number, and the slope of this near-linear dependence increases with the code length. Comparisons with existing low-rate and high-rate codes (such as orthogonal STBC and algebraic STBC) are conducted to show the decoding complexity reduction and good code performance achieved by the proposed codes.

In this paper, we present a new class of spacetime block code, called shift-orthogonal space-time block codes (SOSTBC), which can maintain orthogonality (hence symbolwise linear decoding) in asynchronous wireless relay networks, under both amplify-and-forward (AF) and decode-and-forward (DF) relaying schemes. The definitions, systematic constructions and properties of SOSTBC are presented. We also present some simulation results to illustrate its effectiveness in achieving full asynchronous cooperative diversity.

Spatial multiplexing code (SMC) has high transmission code rate but also high maximum likelihood (ML) decoding complexity. To overcome this disadvantage, we propose 2-group decodable SMC with full symbol-wise diversity for arbitrary number of transmit antennas. In this paper, unbalanced 2-group decodable SMC is first constructed and used to construct balanced 2-group decodable SMC. The rates of both the unbalanced/balanced 2-group decodable SMCs approach Ntasymptotically when T ¿ Ntwhere Ntis the number of transmit antennas and T is the code length. To our best knowledge, this is the first time that 2-group decodable SMCs are constructed systematically.

In this paper, we explore the application of cooperative communications in ultra-wideband (UWB) wireless body area networks (BANs), where a group of on-body devices may collaborate together to communicate with other groups of on-body equipment. Firstly, time-domain UWB channel measurements are presented to characterize the body-centric multipath channel and to facilitate the diversity analysis in a cooperative BAN (CoBAN). We focus on the system deployment scenario when the human subject is in the sitting posture. Important channel parameters such as the pathloss, power variation, power delay profile (PDP), and effective received power (ERP) crosscorrelation are investigated and statistically analyzed. Provided with the model preliminaries, a detailed analysis on the diversity level in a CoBAN is provided. Specifically, an intuitive measure is proposed to quantify the diversity gains in a single-hop cooperative network, which is defined as the number of independent multipaths that can be averaged over to detect symbols. As this measure provides the largest number of redundant copies of transmitted information through the body-centric channel, it can be used as a benchmark to access the performance bound of various diversity-based cooperative schemes in futuristic body sensor systems.

Based on the refinement-only fast subspace tracking (RO-FST) algorithm to adaptively estimate the signal sub-space, a blind adaptive SVD-based minimum-mean-square-error (MMSE) multiuser detector is proposed in this paper for asynchronous direct-sequence code-division-multiple-access (DS-CDMA) systems over multipath fading channels. Numerical results show that the proposed detector gives low computational complexity and good performance in terms of signal-to-interference-plus-noise ratio (SINR) and bit-error-rate (BER). In addition, we apply the perturbation analysis of the proposed adaptive detector to derive the closed-form expressions for the mean-square error (MSE) and SINR. The analytical results are shown to match well with the simulation results.

We propose a blind user identification detection (UID) scheme based on linear prediction algorithm for asynchronous direct-sequence code-division multiple-access systems over multipath fading channels. Numerical results show that both the false alarm rate and bit error rate of the proposed algorithm are better than those of the existing subspace-based UID algorithms.

This paper presents an approach based on a preprocessing technique that allows the conventional subspace tracking method to be adapted to the case of coherent or highly correlated multipath signals in fading channels. The preprocessing technique, known as temporal smoothing, makes use of the independent fading property of the signal paths to decorrelate them. It gives better resolution than the common spatial smoothing methods in tracking the directions of the coherent paths.

Subspace-based direction finding techniques, such as MUSIC, encounter great difficulty when the received signals on the antenna array are coherent. This problem can be solved by conventional spatial smoothing methods, which require at least 3M/2 antennas to resolve M coherent signals. A previously proposed preprocessing approach called temporal smoothing requires only M+1 antennas given M coherent signals. In this letter, a block-sampling temporal smoothing scheme is introduced, and we derive the MSE in the bearing estimation with temporal smoothing. Finally, the performance of the temporal smoothing is compared with the spatial smoothing.

The synergy between frequency arid phase modulation (FPM) using trellis-coded modulation (TCM) leads to greater gains than can be achieved using conventional TCM/MPSK modulation. An iterative structure is introduced into a TCM/FPM scheme to give a new scheme, the Turbo TCM/FPM scheme. Simulation results show that the new scheme can achieve a significant performance improvement with respect to the Turbo TCM 8PSK and TCM/FPM schemes, respectively, in a DS/SSMA system over a multipath Rician fading channel.

The conventional maximum a posteriori receiver for coded code-division multiple-access (CDMA) systems has exponential computational complexity in terms of the number of users and the memory of the channel code. In this letter, we propose a low-complexity soft-input soft-output (SISO) multiuser detector based on the reduced-state a posteriori probability algorithm. Per-survivor processing and soft interference cancellation are used to remove the residual past and future interference in the branch metric computation. The complexity of the proposed receiver is related to the reduced memory of the CDMA channel and can be adjusted according to the complexity/performance tradeoff. Simulation results show that for asynchronous convolutionally coded systems, the proposed receiver can achieve the near-single-user performance for moderate to high signal-to-noise ratios.

The convergence rate of an adaptive filter is one of the key elements which determines the performance of the filter in a moderately slow time-varying channel. In this paper a new blind minimum mean-square error (MMSE) linear detector based on the modified stochastic gradient descent (SGD) algorithm is presented. The proposed detector is simple, robust and has a faster convergence rate than the conventional SGD algorithm.

We propose iterative multiuser detectors for asynchronous code-division multiple-access with parallel-concatenated convolutional codes (turbo codes) and with serially concatenated convolutional codes (SCCC). At each iteration we update and exchange the extrinsic information from the multiuser detector and channel decoders and regenerate soft information between constituent convolutional decoders. Simulation results show that with the proposed structure, near-single-user performance can be achieved. We also propose two reduced-complexity techniques, i.e., the reduced-state iterative multiuser detector based on the T-MAP algorithm and the iterative interference canceler based on a noise-whitening filter. Simulation results show a small performance degradation for these two techniques, particularly for the T-MAP receiver.

Linear block codes over Gaussian integers and Eisenstein integers were used for coding over two-dimensional signal space. A group of Gaussian integers with 2/sup 2n/ elements was constructed to code quadrature amplitude modulation (QAM) signals such that a differentially coherent method can be applied to demodulate the QAM signals. This paper shows that one subgroup of the multiplicative group of units in the algebraic integer ring of any quadratic number field with unique factorization, modulo the ideal (P/sup n/), can be used to obtain a QAM signal space of 2p/sup 2n-2/ points, where p is any given odd prime number. Furthermore, one subgroup of the multiplicative group of units in the quotient ring Z[/spl omega/]/(p/sup n/) can be used to obtain a QAM signal space of 6p/sup 2n-2/ points; one subgroup of the multiplicative group of units in the quotient ring Z[i](p/sup n/) can be used to obtain a QAM signal space of 4p/sup 2n-2/ points which is symmetrical over the quadrants of the complex plane and useful for differentially coherent detection of QAM signals; the multiplicative group of units in the quotient ring Z[/spl omega/]/(2/sup n/) can be used to obtain a QAM signal space of 3/spl middot/2/sup 2n-2/ points, where i=/spl radic/-1, /spl omega/=(-1+/spl radic/-3)/2=(-1+i/spl radic/3)/2, p is any given odd prime number, Z[i] and Z[/spl omega/] are, respectively, the Gaussian integer ring and the Eisenstein integer ring. These multiplicative groups can also be used to construct block codes over Gaussian integers or Eisenstein integers which are able to correct some error patterns.

This paper deals with the optimization of the design and radio network resource planning for cellular mobile communication systems. The key element to be considered for mobile network planning is cost. A hierarchical optimization planning method (HOP) is utilized since there are so many factors like system performance, terrain features, base station parameters, and cost factors which are involved in the large-scale system design. We present a three-level optimization approach for designing a cellular mobile system. It determines the cell number, cell site allocation, and the specific base station parameters in order to minimize the total system cost and to comply with the required system performance. The problem is formulated as a large combinatorial optimization model which can determine the optimal number of cells and select the best base stations' locations. The simulated annealing approach is developed to solve the hard combinatorial problem. Simulation results demonstrate the feasibility and effectiveness of the HOP approach for radio network planning.

For (n,q)=p/sup s/, where p=ch(F/sub q/), s/spl ges/1, V a q/sup m/-ary repeated-root cyclic code of length n with generator polynomial g(x), we give a partial answer about whether the q-ary image of V is cyclic or not with respect to a certain basis for F/sub q/m over F/sub q/.

With the trend towards higher performance in cellular networks, traffic control methods that assign available channel to cells dynamically provide more benefits than the conventional fixed assignment in generating better capacity and lesser forced termination. Previous studies of dynamic methods are based mainly on event driven simulation. A theoretical model for a cellular mobile communication system is presented in the paper. The comparison techniques are illustrated by examining a channel borrowing scheme. The characteristics obtained from the dynamic model and from event driven simulation are in agreement.>