Tung X. Lai

SPC07-3: An Iterative QR-SIC Receiver for Concatenated Space Frequency Coding Schemes in Severe Multipath Channels

This paper studies an efficient receiver design for concatenated space-frequency coded orthogonal frequency division multiplexing (OFDM) systems under severe multipath channels. The proposed receiver utilizes a turbo-like iterative QR decomposition based successive interference cancellation (QR-SIC) algorithm that exploits both spatial and frequency diversity inherent in the multipath multiple-input multiple output (MIMO) channel. Performance of the proposed receiver is evaluated via Monte Carlo simulations. Our results show that the proposed iterative QR-SIC scheme attains excellent performance improvements in severe multipath fading channels. In addition, the proposed scheme attains manageable receiver complexity since we only consider a maximum of 2-3 iterations.

Performance Analysis and Multi-Stage Iterative Receiver Design for Concatenated Space- Frequency Block Coding Schemes

This paper presents performance analysis and computationally efficient receiver design for concatenated space-frequency block coded orthogonal frequency division multiplexing (SFBC-OFDM) systems. Firstly, we present a simple method to approximate the theoretical bit error rate performance of the optimal maximum likelihood (ML) receiver for concatenated SFBC-OFDM systems. Next, we propose a low complexity multistage iterative QR decomposition based successive interference cancellation (QR-SIC) detector for OFDM systems employing the concatenated SFBC strategy. The proposed detector utilizes a Turbo-like iterative QR-SIC algorithm that exploits both spatial and frequency diversities inherent in multi-input multioutput (MIMO) multi-path fading channels. The performance of the proposed QR-SIC receiver is evaluated via Monte Carlo simulations. Our results show that the performance of the proposed receiver can approach the theoretical BER performance of the optimal ML receiver at high signal-to-noise ratios. In addition, we also compare the performance and complexity of the proposed QR-SIC detector with a Turbo-based maximum aposteriori (MAP) demodulator. These comparisons show that the proposed QR-SIC scheme performs reasonably well with respect to the MAP demodulator at higher iterations while attaining a much lower complexity than the MAP demodulator.

Performance analysis of space time block coded systems over frequency selective Rayleigh fading channels

This paper studies a different approach to the performance analysis of arbitrary space time block coded over frequency selective Rayleigh fading channels for single carrier (SC) systems. We first analyzed the performance of space time block code (STBC) systems only, and then, the performance of STBC concatenated with channel codes systems. The pairwise error probability (PEP) is derived for arbitrary STBC over the generalized frequency selective Rayleigh fading channels. The approximation of a bit error probability (BEP) is then computed by using the union bound. The simulation results are also given to verify the analytical performance. It is shown that the theoretical results and the simulation results of the STBC systems are identical for all SNRs

Single-carrier concatenated space-time block coded transmissions over selective-fading channels

We propose single-carrier transmission systems for STBC coded and concatenation of a FEC code with a STBC over ISI fading channels. The proposed receivers rely on iterative successive interference cancellation technique, which avoids the disadvantages of multicarrier systems. Simulation results show that for the STBC only system, the proposed receiver outperforms the OFDM receiver under the power constraint scenario. For the concatenated coding system, the proposed receiver outperforms the OFDM receiver when there is more than one receive antenna.

Analytical BER Analysis of the Space Time Block Coded Systems in Frequency Selective Rician Fading Channels

This paper presents a different approach to analyze the performance of an arbitrary linear STBC system over frequency-selective generalized Rician fading channels with single carrier transmissions. First, the performance of STBC without channel coding over ISI Rician fading channels is analyzed. Then, the performance of channel-coded STBC systems over ISI channels is analyzed. In the analyses, pairwise error probability (PEP) and bit error probability (BEP) are derived and approximated. The approximation of the BEP is computed by using the union bound. Extensive simulation and numerical results are provided to verify the theoretical performance analyses. It is shown that the theoretical analyses and simulation results agree with one another well even at low SNRs

Space-time block coding over frequency selective fading channel in the downlink WCDMA system

Space-time block coding (STBC) is a promising candidate for the next generation cellular communications standard, especially in the downlink system. In the downlink WCDMA system, multiple access interference (MAI), which impairs performance of the receiver, can be eliminated by channel chip level equalization. In this paper, different schemes for STBC over frequency selective fading channels in downlink WCDMA systems are introduced. Simulation results show that the combination of channel chip equalization and STBC (symbol level as well as chip level) provides better performance.

Groupwise Recursive Channel Estimation for Space-Frequency Block Coded OFDM Systems in Doubly Selective Fading Channels

In this paper, we propose two computationally efficient groupwise recursive channel estimation algorithms for channel encoded SFBC-OFDM systems in doubly (i.e., frequency and time) selective fading channels. The first of these algorithms is based on the recursive least squares (RLS) principle whereas the second one employs the minimum mean square error (MMSE) criterion. To reduce the computational complexity associated with the groupwise recursive channel estimation schemes, we propose an inverse QR decomposition (IQR) algorithm based on scaled Givens rotations. The performance of the proposed algorithms is evaluated via simulations and compared to the case with perfect channel state information (CSI) knowledge at the receiver. The simulations show that the proposed algorithms perform reasonably close to the perfect CSI case under various channel conditions.

On the performance of the space time coded WCDMA downlink system over multi-path fading channel

This paper presents performance results of space-time block coding (STBC) in the downlink WCDMA with linear receivers at the terminal. We analyze the bit-error probability performance for this system in frequency selective fading channels. We also present some numerical results. The results show that much better performance is achieved when linear channel equalization at the chip level is employed at the terminals receiver instead of the conventional Rake receiver. For example, for voice conversations at a BER of 10/sup -3/, the capacity can be doubled by using channel chip equalizer.

On performance of time-hoping impulse radio system with space time coding

Impulse radio (IR) is a promising candidate for short-range, high data rate multiple-access wireless communications. In a multiuser scenario, there are pulses collisions between the signal of the desire user and the interfering users, which degrade the system performance. In this paper, space-time block coding (STBC) is employed in the IR system to exploit space-time diversity for improving performance. Several types of receivers are also proposed and their performances are studied.

On the iterative multiuser receivers for time hoping impulse radio communication systems

The iterative multiuser detection methods are proposed for time hoping impulse radio (TH-IR) communications systems by drawing the similarity between the digital PAM IR and the conventional spread spectrum systems, i.e. DS-CDMA. These iterative multiuser receivers overcome the problem of pulse collisions in the IR system that causes the collapse of the conventional receiver. Two different receiver structures are proposed and their performance is studied and compared with the single user case. It is shown that the performance of these iterative receivers approach that of the single user receiver after only a few (two or three) iterations