Tuan A. Tran

A generalized linear quasi-ML decoder of OSTBCs for wireless communications over time-selective fading channels

We propose a novel generalized linear quasi-maximum-likelihood (quasi-ML) decoder for orthogonal space-time block codes (OSTBCs) for wireless communications over time-selective fading channels. The proposed decoder computes the decision statistics based on the channel-state information and completely removes the intertransmit-antenna interference to provide excellent diversity advantage when the channel varies from symbol to symbol. It is shown that when the channel is quasi-static, the proposed decoder is the optimum ML decoder for OSTBCs. The theoretical bit-error probabilities of the proposed decoder are given and it is shown that the proposed decoder does not exhibit error floors at high signal-to-noise ratios like the decoder proposed in and . Simulation results for various channel-fading rates are presented to verify the theoretical analysis.

A generalized simplified ML decoder of orthogonal space-time block code for wireless communications over time-selective fading channels

We propose a novel generalized simplified maximum-likelihood (ML) decoder of orthogonal space-time block code (OSTBC) for wireless communications over time-selective fading channels. The proposed decoder computes the decision statistics based on the channel state information (CSI) and completely removes the inter-transmit-antenna interference (ITAI) and provides diversity advantage when the channel varies from one signaling interval to another. It is shown that when the channel is quasi-static, the proposed decoder becomes the optimum ML decoder for OSTBC. We derive a tight theoretical upper bound for bit error probability of the proposed decoder. We show theoretically that the proposed decoder does not exhibit error floors at high signal-to-noise ratios (SNR). Simulation results for various channel-fading rates are presented to verify our theoretical analysis and demonstrate robust performance of the proposed decoder.

Sum of arbitrarily correlated Gamma variates and performance of wireless communication systems over Nakagami-m fading channels

The probability density function (PDF) and the moment generating function (MGF) of a sum of squares of arbitrarily correlated, non-identically distributed Nakagami-m random variates, with non-identical and non-integer fading orders are derived. The authors proposed a simple method to determine a good truncation of the PDFs infinite sum and the associated truncation error. The derived results can be used to analyse a number of performance measures of diversity combining techniques in wireless communication systems over Nakagami-m fading channels.

A robust and low-complexity transceiver for space-time block coding multiuser wireless communications systems

This paper proposes a novel, robust and low complexity transceiver for space-time block coding multiuser communications system. The users are grouped, and users in a group share the same signature called group signature (GS). Signals from all the groups are transmitted simultaneously. At the receiver, signals coming from a particular group are separated by the respective group filters (GF). The separated groups are inter-group interference free. The signal of each user in each group is recovered by iterative soft interference cancellation and decoding techniques (see Wang, X. and Poor, H.V., IEEE Trans. Commun., vol.47, no.7, p.1046-61, 1999). Computer simulation shows that the performance of our system approaches the performance of a single-user communications system. The proposed transceiver offers robust performance at very low complexity and low bandwidth expansion.

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.

Performance of MRC over Nakagami-m fading channels with arbitrary branch correlation, non-identical and non-integral fading orders

We derive the PDF and MGF of the sum arbitrarily correlated, non-identically distributed gamma random variates. The derived PDF and MGF include the case of non-identical but non-integral fading orders. The derived results can be used to analyze a number of performance measures of diversity combining techniques for wireless communications over Nakagami-m fading channels. We derive, as an example, the exact bit error probability of MRC receivers over Nakagami-m fading channels for arbitrary PSK and square QAM signal constellations with coherent detection.

Orthogonal space-time block codes: performance analysis and comparisons

We derive a simple method to directly compute the exact bit error probabilities (BEPs) of orthogonal space-time block codes (OSTBCs) over Rayleigh fading channels for arbitrary I-PSK and square I-QAM signal constellations with coherent detection. Based on the derived BEPs, we study the performance of various OSTBCs for numerous numbers of receive antennas and bit rates. Our analysis shows that even at low bit rates and with only a single receive antenna, OSTBC for four transmit antennas would be the best choice for most practical cases. Furthermore, if the receiver has multiple antennas, OSTBCs for more than four transmit antennas only degrade performance while adding more complexity. We conclude that in most cases, OSTBCs for four transmit antennas or less should be the choice.

Combined space-time trellis-coded modulation and group multiuser detection

We propose a robust transceiver for space-time trellis coded modulation multiuser communications. Users in our system are divided into a number of groups using the group signatures proposed in Tran et al. (2002). The multiuser detection at the receiver is performed in group fashion after the group interference cancellation. The trellis decoding and multiuser detection are performed jointly in an iterative manner. Computer simulation results show that our receiver approaches single-user performance after three iterations. The computational complexity per user per code symbol of our receiver is much lower than the receiver proposed in Lu et al. (2000). We conclude that the proposed transceiver is robust and has low complexity for wireless multiuser communications systems.

Performance comparison between the use of group signatures and robust error correction codes in wireless multiuser communication systems

We investigate the performances of two wireless multiuser space-time block coding (STBC) communication systems. In the first system, the notion of group signature (GS) proposed by Tran and Sesay (see IEEE Vehicular Technology Conference (VTC2002-Spring), Alabama, USA, May 2002) is applied and in the second system, all users communicate on the same channel and no GS is used. In both systems, a 4-state convolutional code is concatenated with the space-time block code proposed by Alamouti (see IEEE J. Select. Areas Commun., vol.16, no.8, p.1451-58, 1998). In the second system, the bandwidth allocated to the use of GS in the first system is allocated for the use of a stronger convolutional code such that both systems utilize the same bandwidth. Computer simulation results show that the first system, with the use of GSs, significantly outperforms the second system in the region of low signal-to-noise ratios, at the same hardware and computational complexities.