– This paper provides a comprehensive study of interleave-division multiple-access (IDMA) systems. The IDMA receiver principles for different modulation and channel conditions are outlined. A semi-analytical technique is developed based on the density evolution technique to estimate the bit-error-rate (BER) of the system. It provides a fast and relatively… (More)
—This paper presents an asynchronous interleave-division multiple-access (IDMA) scheme, in which users are distinguished by different chip-level interleaving methods instead of by different signatures as in a conventional code-division multiple-access (CDMA) scheme. A very low-cost iterative detection algorithm is derived for the IDMA scheme based on a… (More)
—This paper is concerned with a class of low-rate codes constructed from Hadamard code arrays. A recursive encoding principle is employed to introduce an interleaving gain. Very simple trellis codes with only two or four states are sufficient for this purpose, and the decoding cost involved in the trellis part is typically negligible. Both simulation and… (More)
—This letter is concerned with the implementation issue of the sum-product algorithm (SPA) for decoding the low density parity check codes. It is shown that the direct implementation of the original form of SPA is sensitive to the quantization effect. We propose a parity likelihood ratio technique to overcome the problem. It is shown that for comparable… (More)
—We show that the capacity of a Gaussian multiple access channel can be approached by interleaved low-rate codes together with a simple chip-by-chip iterative decoding strategy. Based on a rate 1/69 code and with a total of 35 simultaneous users (the aggregate rate 1/2), performance of BER = 10 5 is observed at 0 1 4 dB, which is close to the corresponding… (More)
In this correspondence, we introduce a new class of low-rate error correction codes called zigzag Hadamard (ZH) codes and their concatenation schemes. Each member of this class of codes is specified by a highly structured zigzag graph with each segment being a Hadamard codeword. The ZH codes enjoy extremely simple encoding and very low-complexity… (More)
This paper presents a family of space-time codes employing interleavers to separate signals from different antennas. Noticeable performance improvement has been observed compared with existing schemes. An iterative detection algorithm is derived. The complexity involved is very low, and increases only linearly with the number of transmit antennas.
We study a multi-layer space-time code based on random interleaving and proper power allocation. We show that, theoretically, the proposed code can achieve capacity for any transmission rate by superimposing many ideal low-rate codes. We also show that, with practically available codes, the proposed scheme can achieve performance close to the theoretical… (More)