Reduced-Complexity Receiver Structures for Space–Time Bit-Interleaved Coded Modulation Systems

We propose a technique that enhances the bandwidth efficiency of the two transmit antenna differential space-time block code (DSTBC) by use of space-time block code (STBC) expansion and trellis coding. STBC expansion is realized by expanding the conventional Alamouti STBC using unitary matrix transformation. This is followed by trellis code-aided mapping of additional bits to space-time codes of the expanded set. Trellis code-aided mapping of additional bits enhances the bandwidth efficiency of the proposed DSTBC scheme. The proposed scheme sends more information bits in each transmitted space-time code than the conventional differential detection-aided DSTBC (CDD-DSTBC) scheme, and yet retains the same error performance. For each additional bit sent with the transmitted space-time codeword, the proposed scheme using 16QAM achieves a 12.5% increase in bandwidth efficiency, while the scheme using 64QAM realises an 8.3% increase. Simulation results demonstrate that the error performance of the proposed scheme tightly matches that of CDD-DSTBC with improvement in bandwidth efficiency. The bandwidth efficiency is enhanced at the expense of a moderate increase of the computational complexity at the receiver.

Joint iterative channel estimation and decoding for 16-QAM bit-interleaved coded modulation (BICM) is considered over frequency-flat fading channels. Estimates of the complex channel gain are derived first from known pilot symbols by optimum Wiener filtering and passed to the BICM iterative decoder as initial channel state information. After each decoding iteration, the channel estimates are refined using the extrinsic information fed back from the decoder. An advanced scheme called restart is developed to effectively reduce the bit error rate floor, by restarting the decoder after several iterations with the refined channel gain estimates. Motivated by the observation of the burst errors in the transmitted sequence, the restart algorithm is extended by concatenating Reed-Solomon codes with BICM. When RS (255, 223) code is used for BICM with 16-QAM modified set partitioning labeling and a 16-state code, the BER of 10/sup -6/ can be achieved at E/sub b//N/sub 0/ of 10.5 dB for normalized fade rate f/sub d/T/sub s/ = 0.02.

Experimental measurements have shown that the noise in many communication channels is non-Gaussian. Bit interleaved coded modulation (BICM) is very popular for spectrally efficient transmission. Recent results have shown that the performance of BICM using convolutional codes in non-fading channels can be significantly improved if the coded bits are not interleaved at all. This particular BICM design is called BICM trivial (BICM-T). In this paper, we analyze the performance of a generalized BICM-T design for communication over Gaussian mixture noise (GMN) channels. The results disclose that for an optimal bit error rate (BER) performance, the use of an interleaver in BICM for GMN channels depends upon the strength of the impulsive noise components in the Gaussian mixture. The results presented for 16-QAM show that the BICM-T can result in gains up to 1.5 dB for a target BER of 10 -6 if the impulsive noise in the Gaussian mixture is below a certain threshold level. The simulation results verify the tightness of developed union bound (UB) on BER performance.

A simple model for analysing channel estimation errors in space-time coding and modulation was constructed, and the Cramer-Rao bound expression for channel estimation errors was derived. It was also proved that the Cramer-Rao bound derived in the paper was a general and tight bound, as compared with the one given in the reported results of channel estimation errors. Moreover, the influence of channel estimation errors on the bit-error performance of space-time block coding and modulation was simulated by the Monte Carlo method showing that the losses of the performance caused by the channel estimation errors within the above Cramer-Rao bound are the minima in the losses of bit-error performance caused by all the channel estimation errors. This conclusion accorded with the analytical result in theory.

The application of bit-interleaved coded modulation (BICM) in combination with differential encoding and non-coherent reception over flat fading channels is assessed. Since the labeling plays a central role for BICM we propose a suitable definition of Gray labeling for differentially encoded transmission. We show that for multiple symbol detection such a Gray labeling does not exist. Finally, we illustrate the consequences on the capacity by comparing BICM and an optimum coded modulation scheme.

Bit-interleaved coded modulation (BICM) transceivers often use equally spaced constellations and a random interleaver. In this paper, we propose a new BICM design, which considers hierarchical (nonequally spaced) constellations, a bit-level multiplexer, and multiple interleavers. It is shown that this new scheme increases the degrees of freedom that can be exploited in order to improve its performance. Analytical bounds on the bit error rate (BER) of the system in terms of the constellation parameters and the multiplexing rules are developed for the additive white Gaussian Noise (AWGN) and Nakagami-m fading channels. These bounds are then used to design the BICM transceiver. Numerical results show that, compared to conventional BICM designs, and for a target BER of 10^{-6}, gains up to 3 dB in the AWGN channel are obtained. For fading channels, the gains depend on the fading parameter, and reach 2 dB for a target BER of 10^{-7} and m=5.

Impulsive, non-Gaussian noise is prevalent in wireless environments. We adopt an impulsive noise model over multi-input-multi-output (MIMO) channels and discuss receiver and code design over fading channels with impulsive noise. We derive code design criteria for the so-called genie-aided, and minimum distance receivers, both of which yield criteria identical to the nonimpulsive, Gaussian noise case. We also study the performance of certain space-time block codes (STBCs) and space-time trellis codes (STTC) over impulsive noise channels with the genie-aided receiver (GAR) and minimum distance receiver (MDR). The performance loss incurred by the impulsive nature of the noise is shown to increase with the diversity order for the MDR. To approximate the good performance of the practically unrealistic GAR, we propose a maximum a posteriori (MAP) receiver, whose performance can be tightly lower bounded by the GAR. We simplify the optimal MAP receiver by an approximation and show that for alt cases of practical interest, only 2 terms in the approximation are sufficient to get a near-MAP performance. Simulations corroborate our analytical findings

In this article, several extensions to an alternating space-time (ST) code (STC) physical layer security (PLS) scheme from the literature are proposed. These contributions include alternative orthogonal STCs as well as non-orthogonal and spatially-multiplexed (SM) STCs for improved bandwidth efficiency. Phase rotation (PR) algorithms are provided to build very large sets of unique alternative STCs for use with this scheme. Decoding methods are discussed for alternating non-orthogonal and SM STCs. Monte Carlo simulations are provided to compare bit error rate (BER) performance between different decoding methods. Secrecy system nomenclature is adapted to the alternative STCs and proposed algorithms. Information-theoretic security analysis including message and key equivocation is provided along with expected eavesdropper BER based on an assumed attack methodology. A comparison of security offered by the alternating STC PLS scheme with and without incorporation of proposed PR algorithms is performed. Substantially greater exhaustive key search attack complexity is achieved by using the PR algorithms proposed in this article.

In recent years, an Ultra Wideband (UWB) has attracted much attention in short range high speed wireless communications. Meanwhile, the single-carrier transmission with frequency domain equalization (SC-FDE) has also recently at- tracted much attention. It is reported that the SC-FDE sys- tem obtains an excellent performance as well as orthogonal frequency division multiplexing (OFDM), because the SC-FDE system has the advantage of frequency diversity gain even in strong frequency selective channels. However, in the SC-FDE system, the cyclic extension reduces the bandwidth efficiency. Thus, in the SC-FDE system, various methods to improve the bandwidth efficiency are reported. In this paper, we evaluate the improvement of bandwidth efficiency based on cyclic prefix (CP) reconstruction as a method of improving bandwidth efficiency of Ultra Wideband-Impulse Radio (UWB-IR) and Direct Sequence- Ultra Wideband (DS-UWB).

Classical Turbo code suffers from high error floor due to its small minimum Hamming distance (MHD). Newly-proposed 3D-Turbo code can effectively increase the MHD and achieve a lower error floor by adding a rate-1 post encoder, through which part of the parity bits from the classical Turbo encoder are further encoded. In this paper, a novel bit-interleaved coded modulation (BICM) system is proposed by combining rotated mapping QAM and 3D-Turbo code to effectively improve the performance of 3D-Turbo code over Raleigh fading channels. A 2D iterative soft demodulating-decoding algorithm is developed for the proposed BICM system. Simulation results show that the proposed system can obtain about 0.8-1.0 dB gain at bit error rate (BER) of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> , compared with the existing BICM system with Gray mapping QAM.

This chapter discusses fundamentals of information theory and channel coding (error correction coding ECC, Forward error correction FEC). First, key results of Shannon, including channel capacity and the relationship between transmit power and bandwidth, are discussed. Block codes multiply a block of data with an encoding matrix. For systematic codes, the resulting codeword consists of systematic bits and parity check bits. Decoding is achieved by multiplication with a parity check matrix and determination of the syndrome vector. Correction of errors within the correction sphere can be done, e.g., through lookup tables. Convolutional codes send the source data stream through shift registers and adders, a process described by a trellis diagram. Maximum-likelihood sequence estimation (Viterbi algorithm) determines the (transmit) bit sequence with best distance metric (Hamming or Euclidean) from the received signal. Methods for combining coding and higher-order modulation include trellis coded modulation (using set partitioning for code design) and bit-interleaved coded modulation (BICM). Turbo codes are close to capacity-achieving. They are based on transmitting differently interleaved convolutional codes; receivers use soft decoding of the constituent codes and iterative exchange of soft information (log-likelihood ratios). Low-density parity check codes (LDPCC) are decoded by belief propagation (message passing), where variable nodes and constraint nodes exchange beliefs about the codeword. In fading channels, (block or convolutional) interleaving is essential to provide diversity. From an information-theoretic point of view, in fading channels we can distinguish between the ergodic capacity and the outage capacity. If the channel state information is known at the transmitter, waterfilling is the optimum power allocation strategy. Automatic Repeat Request ARQ) and Hybrid ARQ (including chase combining or incremental redundancy) are described in the appendix.

The direct sequence (DS) spread spectrum communication technique is widely regarded as one of the most effective methods of mitigating the effects of a repeating jammer in military communications systems. The proposed system coupled DS with multiple frequency shift keying (DS/MFSK). It is comprised of a transmitter and a receiver. Non-coherent demodulation is examined, as are the spreading sequences in question. The effect of AWGN and Rayleigh fading channels on the proposed approach's bit error rate (BER) is examined. The investigation demonstrates that even with an 8 dB signal-to-noise ratio, superior outcomes can be achieved; this study's suggested endeavor is to create a novel transceiver system built on the DS/MFSK modular architecture. MFSK modulation prevents multiple-access interference, while DS is typically employed to boost system efficiency across erratic fading. Test results show that reliability on the AWGN channel decreases a little while reliability is greatly enhanced by Rayleigh fading. Moreover, notable improvements in bandwidth efficiency are achieved.

In this paper, we analytically derive the bit error rate (BER) for bit-interleaved coded modulation (BICM) under the assumption of a temporally correlated flat Rayleigh fading channel. We assume the channel state information (CSI) to be unknown at receiver side and consider a linear minimum mean-squared error (LMMSE) channel estimator that relies on periodically inserted pilot symbols. We give asymptotic results for both non-iterative BICM and BICM with iterative decoding (BICM-ID). Furthermore, we show that the interpretation of the channel estimation error as an SNR degradation holds true in these cases.

Scalable video multicast using inter-layered superposition and network-coded cooperation over MIMO relay systems

The IEEE 802.11a OFDM wireless local area network (WLAN) system aims to achieve code diversity in quasi-static frequency-selective fading channels by employing bit interleaved coded modulation (BICM). Since the time variation of the channel during a WLAN packet transmission is small and its frequency selectivity finite, the code diversity is limited by both the degree of the channel variation as well as by the code properties. This paper experimentally investigates the impact of channel frequency selectivity on the code-diversity performance of BICM, with and without 2/spl times/1 Alamouti transmit diversity. Using a simplified model of the finite frequency selectivity, we develop a mathematical framework to show that the code diversity is only probabilistically achieved. Our results indicate that for the frequency selectivity typically seen in indoor WLAN channels, using a channel code with larger d/sub free/ does not improve the packet error rate (PER) performance.