Optimal MFSK signalling for Reed-Solomon codedfrequency-hopped multiple-access communications

We analyzed the bit error probability of a single RS codeword with symbol overlapping. By symbol overlapping, we mean that the bits in each modulation symbol can belong to 2 or more RS symbols and vice versa. We propose two novel designs for Reed-Solomon (RS) coded modulation with symbol overlapping. For an RS code with symbol size GF(2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sup> ), the information bits are first RS coded. For the first strategy, the coded bits are matrix interleaved prior to modulation and for the second strategy, the RS symbols are matrix interleaved and the resulting coded symbols are shifted circularly by n/2 bits prior to modulation. In this paper, we considered a M = 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sup> -ary modulation scheme. The received signal is demodulated appropriately, de-interleaved and RS decoded. The decoded symbols are interleaved and sent to the demodulator where it makes use of the decoded symbols from other codewords to re-demodulate the signals. This process is repeated until there is no improvement in the bit error rate. It is observed that this simple coded modulation design scheme has about 0.5 dB better performance than one that does not employ symbol overlapping over an AWGN channel at bit error rate of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . An improvement of 1 dB is observed over a Rayleigh fading channel

In this paper, we investigate a novel beam direction-based modulation transmit scheme for millimeter-wave (mmWave) communication systems equipped with distributed antennas, and propose an enhanced space-domain index modulation (ESDIM) scheme, in which the number of beamforming directions (BDs) for transmitting information bits can be one or two. The ESDIM system jointly utilizes the combination of the index of BDs and signal constellations to transmit information bits, in which one or two beam directions are considered. In addition, we propose power allocation (PA) aided schemes for ESDIM to further improve the system reliability by reducing the system symbol error rate (SER), where three constraints to the transmit power for beamforming are investigated. To be specific, a total transmit power constraint (TTPC) and two per-beamforming power constraints (PBPC) are considered. We first propose a suboptimal PA algorithm for the TTPC-PA aided ESDIM scheme using a powerful solver based on advanced algebra theories, which only considers the PA aspects for a given selected beamforming pair. Then, we extend the TTPC-PA aided scheme to the average per-beamforming power constraint (APBPC)-PA aided scheme and the strict per-beamforming power constraint (SPBPC)-PA aided scheme. Simulation results show that the proposed schemes improve the system SER performance compared to other existing counterparts.

Sparse vector coding (SVC) is a promising short-packet transmission method for ultra reliable low latency communication (URLLC) in next generation communication systems. In this paper, a dual-mapping SVC (DM-SVC) based short packet transmission scheme is proposed to further enhance the transmission performance of SVC. The core idea behind the proposed scheme lies in mapping the transmitted information bits onto sparse vectors via block and single-element sparse mappings. The block sparse mapping pattern is able to concentrate the transmit power in a small number of non-zero blocks thus improving the decoding accuracy, while the single-element sparse mapping pattern ensures that the code length does not increase dramatically with the number of transmitted information bits. At the receiver, a two-stage decoding algorithm is proposed to sequentially identify non-zero block indexes and single-element non-zero indexes. Extensive simulation results verify that proposed DM-SVC scheme outperforms the existing SVC schemes in terms of block error rate and spectral efficiency.

Forward error correction (FEC) is a key capability in modern satellite communications that provide the system designer with the needed flexibility to comply with the different applications' requirements. Reed-Solomon (RS) codes are well known for their ability to optimize between the system power, bandwidth, data rate, and the quality of service. This paper introduces an efficient decoding scheme for decoding the RS codes adhering to the Consultative Committee for Space Data Systems (CCSDS) standards based on Justesen's construction of concatenation. To maintain the standard output size, the proposed scheme first encodes every m - 1 bits using the single-parity-check (SPC) code, while the RS code encodes K SPC codewords into N symbols that are of the same size as CCSDS standard. Decoding on the inner SPC code is based on maximum-likelihood decoding Kaneko algorithm, while for the proposed coding scheme, the reduced test-pattern Chase algorithm is adapted for decoding the outer RS code. The simulation results show the coding gains of 1.4 and 7 dB compared with the algebraic decoding of RS codes over the AWGN and Rayleigh fading channels, respectively. Moreover, the adopted reduced test-pattern Chase algorithm for decoding the RS code achieves an overall complexity reduction of 40% compared with the conventional Chase decoding algorithm.

The conventional matched filter (MF) correlation receiver for direct sequence spread spectrum transmissions is reconsidered from the theoretical point of view of robust distributed detection (decision fusion). Separate chip-by-chip decisions on the transmitted information bit of interest are generated. The individual decisions are then optimally fused to produce the final decision on the transmitted bit. It is proven that the majority-vote strategy is the statistically optimal fusion rule for additive white Gaussian noise channels. An exact closed form expression is given for the probability of error induced by the majority-vote receiver. It is shown that the performance is independent of the identity of the active interfering user population, that is signatures and signature cross-correlations, in DS-CDMA environments. This perfect robustness with respect to the identity of the multiuser interference component is coupled by significant resistance toward occasional high-power jamming (equivalently occasional natural severe channel imperfections) or outlier-prone background noise, or both. Some numerical studies illustrate these theoretical findings.

The performance of coded multi-pulse pulse position modulation (MPPM) consisting of m slots and 2 pulses, denoted as (m, 2) MPPM, with imperfect slot synchronization is analyzed. Convolutional codes and Reed-Solomon (RS) codes are employed for (m, 2) MPPM, and the bit error probability of coded (m, 2) MPPM in the presence of the timing offset is derived. In each coded (m, 2) MPPM, we compare the performance of some different code rate systems. Moreover, we compare the performance of both systems at the same information bit rate. It is shown that in both coded systems, the performance of code rate-1/2 coded MPPM is the best when the timing offset is small. Further, convolutional coded (m, 2) MPPM on the constraint length k/spl ges/7 performs better than Reed-Solomon coded (m, 2) MPPM for the same code rate. >

Permutation index-quadrature spatial modulation: A spectral efficient spatial modulation for next generation networks

This paper proposes and analyzes a maximum aposteriori probability (MAP) coherent detector for Walsh-Hadamard multiplexed binary antipodal signals, based on vector detection at the code-length size of the Walsh-Hadamard codes. Tight bounds on the bit error probability that are analytically derived or numerically computed, together with simulation results, show significant performance gain over symbol-by-symbol MAP detection for either one-dimensional or two-dimensional system configurations that lead to pulse amplitude modulation (PAM) and quadrature amplitude modulation (QAM) rectangular constellations, respectively. In addition, the proposed system with MAP vector detection, presents great performance enhancement compared to standard binary phase shift keying (BPSK) modulation under identical information bit rate and mean power constraints, at a cost of higher instant power and moderate detection complexity.

A principal component combining with differential detector (PCC–DD) is proposed to demodulate M-ary DPSK signals in diversity systems. Exact average bit error probability (BEP) of binary DPSK signals over Rayleigh fading channels for the PCC–DD is obtained in closed form and is shown to agree with the results of simulations. Approximate average BEP of quadrature and octal DPSK signals over Rayleigh fading channels for the PCC–DD are also derived and are shown to be close to those from simulations. It is also shown that PCC–DD outperforms the well known DPSK demodulator that contains a set of differential detectors followed by equal gain combining (DD–EGC) over Rayleigh fading channels in terms of low-average BEP. The performance gain of the PCC–DD over the DD–EGC is large when the signal is binary DPSK, and is very small when the signal is either quadrature or octal DPSK.

The performance of a multi-user chaos-based direct sequence code division multiple access (DS-CDMA) communication system with a sequence synchronisation unit incorporated is examined. Synchronisation is achieved through code acquisition and maintained through the code tracking phase. The performance of the proposed system is evaluated in a Rayleigh fading channel with additive white Gaussian noise and interuser interference. Results are compared to a fade-free channel. It is shown that, although the system is robust to the influence of noise and interuser interferences, it fails to satisfy the maximum allowable bit error rate limit of 10−3 in the Rayleigh fading channel.

The asymptotic performance of Reed-Solomon (RS)-coded M-ary orthogonal signaling with ratio-threshold test (RTT) type demodulation in a Rayleigh-fading channel is considered. We show that the minimum E~/sub b//N/sub 0/ needed for error-free communication is eln2 (2.75 dB) with RTT, and 4.79 (6.8 dB) with hard decisions. The optimum code rate that minimizes the required E~/sub b//N/sub 0/ is e/sup -1/ with RTT and 0.46 with hard decision, and the optimum ratio threshold approaches 1 for large M. Next, we investigate the fundamental limit in a direct-sequence spread-spectrum multiple-access (DS/SSMA) system employing an M-ary orthogonal code of length N=Mm, which is obtained by spreading every row of an M/spl times/M Hadamard matrix with a user-specific random sequence of length N. We derive the minimum E~/sub b//N/sub 0/ for error-free communication as a function of the number of users, the optimum code rate that minimizes E~/sub B//N/sub 0/, and the maximum limit on the total information transmission rate. Then, we consider a multirate DS/SSMA system, where a population of users simultaneously transmit at different power levels a variety of traffic types of different information rates. We derive the minimum required E~/sub B//n/sub 0/ and the optimum code rate for each traffic type.

Straightforward implementation of a maximum likelihood decoder implies a complexity that grows algebraically with the inverse of error probability. Forney has suggested an approach, concatenation, for which error probability decreases exponentially with increasing complexity. This paper presents the results of an evaluation of a particular concatenation system, structurally similar to the hybrid system of Falconer, employing a Reed-Solomon outer code and an inner convolutional code. The inner decoder is a Viterbi decoder of constraint length less than the corresponding encoding constraint length (nonmaximum likelihood). The outer decoder assumes one of three possible forms, all employing the likelihood information developed by the inner decoder to assist in outer decoding. Error corrections and erasure fill-ins achieved by the outer decoder are fed back to the inner decoder. Performance is evaluated through computer simulation. The three outer decoders are found to provide approximately the same performance, all yielding low error probabilities at rates somewhat above R <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">comp</inf> of sequential decoding and at signal energy to noise density ratios per information bit around 1.7 dB.

A semiconductor laser diode direct detection optical communication system suitable for use in an intersatellite communication link was constructed, and its performance was measured. The system used Q = 4 pulse position modulation (PPM) to transmit binary source data at a rate of 25 Mbit/s and contained a low-noise silicon avalanche photodiode (APD) as a photodetector. Use of the conventional Gaussian model for the output of the low-noise APD (RCA C30902S) was shown to be inappropriate under low-background radiation levels because its use caused a severe underestimate of the optical APD gain and an overestimate of a system bit error rate. A numerical procedure was developed that made use of the Conradi distribution for the APD output which gave good agreement with the results of the experimental measurements of system performance. A slot clock recovery subsystem was also provided in the receiver. It consisted of a nonlinearity which is easy to implement and a narrow bandpass filter centered at the slot clock frequency. Use of the recovered timing signal showed no penalty in the minimal input optical power required to maintain a specified error rate. The system achieved a bit error rate of 10−6 at a received signal level corresponding to an average of 60 detected photons per transmitted information bit (120 photons per PPM symbol).

In this paper, we study transmit codebook designs for spatial modulation with analog phase shifters. The proposed spatial modulation with analog phase shifters can send more spatial symbols than conventional spatial modulation, while reserving the low complexity of single RF-chain MIMO structure. The main idea is to transmit N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> different phase-shifted copies of a digitally modulated signal through N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> transmit antennas. In each time slot, the transmitted information bits are divided into two groups. The first group of the bits is mapped to the digitally modulated signal symbol. The second group of the bits is mapped to the spatial symbol, which determines the phase shift of each antenna. The transmit signal designs are carried out in open loop and closed loop scenarios, respectively. In open loop scenario, the transmit codebook is designed in two steps, i.e., generate the optimal spatial codebook according to Grassmannian line packing criterion, and find the optimal tradeoff between the cardinality of spatial codebook and the modulation order of signal symbol. In the closed loop scenario, the transmit codebook is designed according to the structure of Huffman tree. Extensive simulation results are given to validate the effectiveness of the proposed scheme in open loop scenario and close loop scenario, respectively.

Transmission efficiency, defined as the ratio of successfully transmitted information bits to overall bits transmitted, can be used for evaluating the transmission performance of wireless links. As a function of received signal to noise ratio (SNR), transmission efficiency is determined by physical layer technologies, such as channel coding, interleaving, modulation and other error-recovery techniques of wireless links. In this paper we first analyze the form of transmission efficiency function in wireless links, then based on that we propose an adaptive coding scheme that maximizes the transmission efficiency according to wireless channel conditions (received SNR). Simulation results show that with the proposed adaptive coding, transmission efficiency of wireless links can be significantly enhanced.