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Low-density parity-check (LDPC) codes are playing more and more important role in digital broadcasting standards due to their excellent error correction performance. In this paper, we study the combination of LDPC codes over GF(q) with q-ary modulations for bandwidth efficient transmission over AWGN channel and consider the design of the codes. Specifically, we develop the concept of quasi-regular codes, and propose an improved Monte Carlo method to optimize the quasi-regular codes. To justify the performance of our proposed scheme, simulation results are presented and analysed. Index Terms--Bandwidth efficient transmission, LDPC codes, Monte Carlo method, q-ary modulations.

Block turbo codes with trellis-based decoding are proposed for use in cell-based satellite communication. Shortened Reed--Muller (RM) codes are used as the component codes because their minimal trellis is known. Simulation results for RM turbo codes and shortened RM turbo codes are presented over additive white Gaussian noise and Rayleigh fading channels. The performance of the shortened codes with different shortening patterns are shown. In some cases, the codes have the unequal error protection property, useful in asynchronous transfer mode cell formatting. In order to test the suitability of the proposed coding scheme from a practical point of view, the effect of channel impairments, including channel signal-to-noise ratio mismatch and carrier phase offset, are investigated. Index Terms--Asynchronous transfer mode (ATM), Reed--Muller (RM) codes, trellis-based iterative decoding, turbo codes, unequal error protection (UEP).

In this paper, we present a novel method for data detection of M-ary phase shift keying (MPSK) in the presence of unknown carrier phase and additive white Gaussian noise. Here, the unknown carrier phase is rapidly changing and random. That is, the unknown phase changes from symbol to symbol in a nondeterministic manner. The rate of phase change is such that phase change over two symbol intervals is negligible, but it is not necessarily negligible over a longer interval. Our proposed system outperforms traditional differential phase shift keying (DPSK) by 1.5 dB at error probabilities of [10.sup.-3] and [10.sup.-4]. We also compare the performance of our scheme with that of multiple symbol differential detection (MSDD). Except under very slow phase change conditions, our scheme outperforms MSDD.

In conventional TCM schemes, for a rate of n bits per channel symbol, a 2(super n+1)-point constellation is used. In this work, we show that using constellations with less than 2(super n+1)-points, one can achieve a considerable coding gain in comparison to the traditional 2(super n+1)-point constellation. The increase in coding gain is due to a reduction in transmitted signal energy as a result of deleting some high power signals from the original 2(super n+1)-point constellation and reuse of some of the low power signals instead.

In this work, the effect of the frequency offset on the probability of miss for a packet radio modem, using the constant false alarm rate (CFAR) preamble detection scheme, is analyzed. The expression for the probability of miss for the general case, i.e., where there is a frequency offset, is derived. This general expression is then used to derive the expressions for the false alarm rate and the probability of miss for the special case, where the frequency offset is negligible. Several graphs depicting the probability of miss for different values of signal-to-noise ratio and frequency offset, are also included.