We discuss three structures of modified low-density parity-check (LDPC) code ensembles designed for transmission over arbitrary discrete memoryless channels. The first structure is based on the well known binary LDPC codes following constructions proposed by Gallager and McEliece, the second is based on LDPC codes of arbitrary (q-ary) alphabets employing modulo-q addition, as presented by Gallager, and the third is based on LDPC codes defined over the field GF(q). All structures are obtained by applying a quantization mapping on a coset LDPC ensemble. We present tools for the analysis of non-binary codes and show that all configurations, under maximum-likelihood decoding, are capable of reliable communication at rates arbitrarily close to channel capacity of any discrete memoryless channel. We discuss practical iterative decoding of our structures and present simulation results for the AWGN channel confirming the effectiveness of the codes.

This paper proposes a class of full space diversity full rate space–time turbo codes. Both parallel concatenated and serially concatenated codes are designed. A rank theory proposed by the authors earlier is employed to check the full space diversity of the codes. The simulations show that the space–time turbo codes can take full advantage of space diversity and time diversity if they are available in the channels. We also study the robustness of performance of both turbo codes and trellis codes in space–time correlated fading channels.

Space–time coding has been studied extensively as a powerful error correction coding for systems with multiple transmit antennas. An important design goal is to maximize the level of space diversity that a code can achieve. Toward this goal, the only systematic algebraic coding theory so far is binary rank theory by Hammons and El Gamal for binary phase-shift keying (BPSK) modulated codes defined over binary field and quaternary phase-shift keying (QPSK) modulated codes defined over modulo four finite ring. To design codes with higher bandwidth efficiency, we develop an algebraic rank theory to ensure full space diversity for PP quadrature and amplitude modulated (QAM) codes for any positive integer. The theory provides the most general sufficient condition of full space diversity so far. It includes the BPSK binary rank theory as a special case. Since the condition is over the same domain that a code is defined, the full space diversity code design is greatly simplified. The usefulness of the theory is illustrated in examples, such as analyses of existing codes, constructions of new space–time codes with better performance, including the full diversity space–time turbo codes.

Introduction: Recently, there has been a surge of interests in the design of the so called \space{time " codes which take advantage of both the spatial diversity provided by multiple antennas and the temporal

Abstrucr- This paper proposes a class of full space diversity QI’SK space-time codes based on parallel concatenated convolutional (turbo) codes. A rank criterion of full space diversity is used in the design. Com-pared with space-time trellis codes, the simulations show it has robust]per-formance at both quasi-static fading channel and time varying fading chan-nel. I.

| This paper derives conditional probability density functions (PDFs) and computes numerical capacity curves for the following discrete two-dimensional (2D) channels: (a) a slow-fading Rayleigh channel with discrete carrier tracking by a phase locked loop (PLL), where the PLL signal-to-noise ratio (SNR) is proportional to the fading amplitude squared; (b) an additive white Gaussian noise (AWGN) channel with a PLL; and (c) a fast-fading Rician channel with carrier phase estimation for the line-of-sight (LOS) path only. All three channel models assume independent fading of successively received symbols. Capacity calculations are performed for equiprobable signaling with two 8-ary amplitude-modulated phase-shift-keyed (AM-PSK) constellations, and three 16-ary constellations. On the Rayleigh and AWGN channels, the AM-PSK constellations give gains between 2 and 11 dB over PSK, at SNRs between 5 and 40 dB. For the Rician channel, AM-PSK gives a capacity gain over PSK of up to 0.75 bit at hig...

SufJicient conditions to ensure QAM space-time codes achieve full space diversity in quasi-static fading channel are pre-sented. The conditions are on code words or generator matrices instead of on every code word pair. This sim-

In this paper, we design parallel concatenated convolutional codes (PCCCs) for trellis coded modulation (TCM) over the following discrete two-dimensional (2D) channels: (a) a slow-fading Rayleigh channel with discrete carrier tracking by a phase locked loop (PLL), where the PLL signal-to-noise ratio (SNR) is proportional to the fading amplitude squared; (b) an additive white Gaussian noise (AWGN) channel with a PLL; and (c) a fastfading Rician channel with carrier phase estimation for the line-of-sight (LOS) path only. For the fast-fading Rician channel, we show that the pairwise sequence error probability for maximum likelihood (ML) decoding of M-ary phase shift keying (M-PSK) is a function of squared Euclidean distance, and use this fact to derive performance bounds on M-PSK TCM. We then design turbo-TCM codes at 1 bit/symbol/Hz for 8-PSK and two-radius 8-QAM constellations. Simulation results on the partially coherent Rayleigh and AWGN channels show that the 8-QAM codes have a 1.5 t...

Satellite networks have signi cant advantages over terrestrial networks. Satellites provide unique advantages such as remote coverage with rapid deployment, distance insensitivity, bandwidth-on-demand, immunity to terrestrial disasters, o ering broadband links. Broadband satellite networks will play an important role in the rapidly evolving information infrastructure. However, there are several obstacles which need to be overcome so that broadband satellite networks can operate in full service. The objective of this survey is to present the state-of-the-art in broadband satellite networks by focusing on link access methods, error control schemes and TCP problems and to point out open research problems.

... technique for trellis coded modulation (TCM). Although this technique directly assigns constellation points to the branches of the trellis, it has been shown that the same optimal code can be accomplished by a convolutional code with a mapper that assigns a series of coded bits to a constellation point. This notion has remained with the appearance of turbo codes. Therefore, parallel concatenated trellis coded modulation (PC-TCM) has been traditionally designed using parallel concatenated convolutional codes with a bits-to-symbol mapper. This paper shows that for higher-order modulations using linear codes is too restrictive. Parallel Concatenated Nonlinear Trellis Coded Modulation (PC-NLTCM) which directly assigns constellation points as output-labels to the branches of the trellis can outperform PC-TCM. Simulation results are shown