Paul Guinand

High-performance low-memory interleaver banks for turbo-codes

A new method of designing high-performance, low-memory, interleaver banks for turbo-codes is presented. The new interleavers are called dithered relative prime (DRP) interleavers. Only a small number of parameters are required to both store and implement each interleaver in the bank. The error rate performance is similar to that achieved by other good interleaver designs that typically require the storage of all K indexes for each interleaver of length K.

Space-time coding in mobile Satellite communications using dual-polarized channels

The use of dual-orthogonal polarization (horizontal/vertical or circular right-hand/left-hand polarizations) can increase the rate of transmission of satellite communication systems by a factor of two. However, the cross polar discriminations (XPDs) of the satellite and earth station antennas may be large enough to severely interfere between the two polarizations. In this paper, we investigate the use of space-time coding techniques in satellite-land mobile systems using dual-polarized transmit and receive antennas. In particular, we show that we can achieve significant gains by using layered space-time coding concepts and iterative detection and decoding receivers in communications systems employing polarization diversity channels in the presence of line-of-sight components.

Estimating the minimum distance of turbo-codes using double and triple impulse methods

A long-standing problem for turbo-codes has been the efficient and accurate determination of the distance spectrum, or even just the minimum distance, for specific interleavers. This letter compares a number of distance estimation techniques and introduces two new approaches based on iterative processing. The new approaches are more reliable and are particularly useful for long blocks with high minimum distances. Distance measurement results are presented for random, high-spread random (HSR) and dithered relative prime (DRP) interleavers.

Performance of an MLSE-based early stopping technique for turbo codes

A crucial issue in the practical application of turbo codes is decoding complexity. A common approach to reducing decoding complexity is to stop the iterative decoding process early. It is demonstrated that an early stopping technique based on maximum-likelihood sequence estimation (MLSE) can significantly reduce average decoder processing. Specifically, it is shown that an 8-state turbo code with 512 data bits and a nominal code rate of 1/3 can be decoded in less than 2 iterations on average when E/sub b//N/sub 0/ /spl ges/ 2 dB (packet error rate /spl ap/ 10/sup -7/). This reduction is achieved with virtually no loss in error rate performance relative to performing a large fixed number of iterations.

Approaching near-capacity on a multi-antenna channel using successive decoding and interference cancellation receivers

In this paper, we address the problem of designing multirate codes for a multiple-input and multiple-output (MIMO) system by restricting the receiver to be a successive decoding and interference cancellation type, when each of the antennas is encoded independently. Furthermore, it is assumed that the receiver knows the instantaneous fading channel states but the transmitter does not have access to them. It is well known that, in theory, minimum-mean-square error (MMSE) based successive decoding of multiple access (in multi-user communications) and MIMO channels achieves the total channel capacity. However, for this scheme to perform optimally, the optimal rates of each antenna (per-antenna rates) must be known at the transmitter. We show that the optimal per-antenna rates at the transmitter can be estimated using only the statistical characteristics of the MIMO channel in time-varying Rayleigh MIMO channel environments. Based on the results, multirate codes are designed using punctured turbo codes for a horizontal coded MIMO system. Simulation results show performances within about one to two dBs of MIMO channel capacity.

Separable concatenated convolutional codes: The structure and properties of a class of codes for iterative decoding

In this paper a brief overview of the concept of iterative processing is provided. Then a code construction for convolutional codes, that results in a signal structure amenable to iterative processing, is studied. This construction is analogous to product coding for block codes. It is shown that the construction shares a number of properties with the product coding construction, including the property that it is commutative. The relationship between the free distance and the interleaving factors is examined, and then exemplified with computer simulation results.

Estimating the minimum distance of large-block turbo codes using iterative multiple-impulse methods

A difficult problem for turbo codes is the efficient and accurate determination of the distance spectrum, or even just the minimum distance, for specific interleavers. This is especially true for large blocks, with many thousands of data bits, if the distance is high. This paper compares a number of recent distance estimation techniques and introduces a new approach, based on using specific event impulse patterns and iterative processing, that is specifically tailored to handle long interleavers with high spread. The new method is as reliable as two previous iterative multiple-impulse methods, but with much lower complexity. A minimum distance of 60 has been estimated for a rate 1/3, 8-state, turbo code with a dithered relative prime (DRP) interleaver of length K = 65 536. Copyright

Approaching near-capacity on a multi-antenna channel using multirate encoding and successive decoding receivers

We address the problem of designing multirate codes for a multiple-input and multiple-output (MIMO) system by restricting the receiver to be a successive decoding and interference cancellation type, when each of the input signals is encoded independently. It is assumed that the receiver knows the instantaneous fading channel states but the transmitter does not have access to them. We design a multirate coded MIMO system using punctured turbo codes and demonstrate the efficiency of the proposed scheme using simulation results. In particular, the simulation results show performance within 2 dB of MIMO channel capacity.

An Alternative Approach to the Design of Interleavers for Block Turbo Codes

In this paper we describe two methods of interleaving for use with generalized product block codes that can be decoded using a “turbo” decoding strategy. These methods are designed to avoid certain specific error patterns. One method has a number theoretic basis while the other uses finite projective planes. Simulation results are presented.

Separable concatenated codes with iterative map filtering

In practice, very efficient signalling over radio channels requires more than designing very powerful codes. It requires designing very powerful codes that have special structure so that practical decoding schemes can be used with excellent, but not necessarily optimal, results. Examples of two such approaches include the concatenation of convolutional and Reed-Solomon coding, and the use of very large constraint-length convolutional codes with reduced-state decoding. In this paper, powerful codes are obtained by using simple block codes to construct multidimensional product codes. The decoding of multidimensional product codes, using separable symbol-by-symbol maximum a posteriori (MAP) “filters”, is described. Simulation results are presented for three-dimensional product codes constructed with the (16,11) extended Hamming code. The extension of the concept to concatenated convolutional codes is given. The relationship between the free distance and the interleaving factors is examined, and then exemplified with computer simulation. Potential applications are briefly discussed.