Ismael Gutierrez

Joint Transmit Antenna and space-time coding selection for WiMAX MIMO systems

In this paper the combination of Transmit Antenna Selection with Linear Dispersion Code Selection is studied. Two optimization criteria are proposed (bit error rate minimization and throughput maximization). The performance of the proposed spatial link adaptation scheme is evaluated under low mobility environments concluding that maximum spatial diversity is achieved as well as a smooth transition between codes with low spatial multiplexing rate and high spatial diversity (suitable for low SNR), to codes with high multiplexing rate but low diversity order (suitable for high SNR) maximizing the overall system throughput1.

System level evaluation for WiMAX IEEE 802.16m

This paper presents a system level simulator for the evaluation of WiMAX IEEE 802.16m technologies in a multi-cellular environment. This simulator is a quite powerful tool which allows quantifying the benefits of proposed air interface technologies on overall system performance using several metrics. As a case of study, the paper conducts performance evaluation of WiMAX IEEE 802.16m contiguous and distributed sub-channelization modes. The results obtained show a clear advantage for the distributed mode in term of system throughput but not in term of number of simultaneously active users. Similarly, many different cases of study can be further conducted using this simulation platform, which will yield crystal clear conclusions on the performance of WiMAX IEEE 802.16m system.

Low complexity soft demapping for non-binary LDPC codes

This article focuses on non-binary wireless transmission, where non-binary refers to the use of non-binary Low Density Parity Check (LDPC) codes for Forward Error Correction. The complexity of the non-binary soft demapper is addressed in particular when one non-binary Galois Field (GF) symbol spreads across multiple Quadrature Amplitude Modulation (QAM) symbols and Space-Time Block Code (STBC) codewords. A strategy is devised to guarantee an efficient mapping at the transmitter, together with an algorithm at the receiver for low complexity soft Maximum Likelihood demapping. The proposed solution targets a trade-off between performance and complexity, and removes any restriction on the setting of the GF order, QAM constellation order, and STBC scheme. This makes the non-binary LDPC codes even more appealing for potential use in practical wireless communication systems.

On the performance of non-binary LDPC with MIMO in practical systems

This paper aims at assessing the performance of non-binary LDPC codes with MIMO techniques in practical systems (e.g. MIMO 2×2 systems). More specifically, we compare two approaches at the receiver side, a first linear approach (using linear equalizer) and a second less common approach making “soft” use of the maximum likelihood (ML) criterion. Moreover, this paper also tries to assess the suitability of non-binary LDPC for combination with MIMO techniques, as compared to competing binary FEC schemes such as Duo Binary Turbo Codes. This is done by quantifying the gain achieved by non binary LDPC with either Alamouti or Spatial multiplexing techniques, in comparison to DBTC, and with reference to the single antenna context.

Performance of NB-LDPC and DBTC codes with channel estimation and SNR mismatch

This paper compares the robustness of Non-Binary LDPC and Duo-Binary Turbo Code schemes against impairments in the estimation of the channel coefficients, and the noise power. This study considers both types of mismatches separately and jointly. The scenario of simulation also takes into account the distortions introduced by a High Power Amplifier (HPA) and the Inter-Carrier-Interference (ICI) caused by a mobile channel. The communication system under analysis is the OFDM-based WINNER wireless model. The results show that Non-Binary LDPC codes provide even better performance than DBTC in the case of non perfect channel knowledge.

Spectral Efficiency Using Combinations of Transmit Antenna Selection with Linear Dispersion Code Selection

In this paper the objective is to enhance the spectral efficiency using combinations of transmit antenna selection with Linear Dispersion Code Selection. Both bit error rate minimization and throughput maximization criteria are here examined. The performance of the proposed spatial link adaptation scheme is evaluated under low mobility environments concluding that in case of linear receivers the transmit antenna code selection scheme with the combination of adaptive modulation and coding achieves a noticeable SNR gain (up to 3dB) in a large SNR margin (SNR from 6 to 18dB), which could be considered as a potent technique to achieve a smooth transition between diversity and multiplexing in order to maximize the overall system throughput.

Spectral efficiency under Transmit Antenna and LDC selection with throughput maximization using WiMAX

In this paper the spectral efficiency using combinations of Transmit Antenna Selection with Linear Dispersion Code Selection (TACS) is studied. The selection criterion is defined in order to maximize the spectral efficiency while bounding the maximum error rate (Rate Adaptation). The performance of the proposed spatial link adaptation scheme is evaluated under low mobility environments concluding that in case of linear receivers (e.g. MMSE) the TACS scheme with adaptive coding and modulation achieves a noticeable SNR gain (up to 3dB) in a wide SNR range (from 6 to 18dB), and could be considered as a powerful technique to achieve a smooth transition between diversity and multiplexing in order to maximize the overall system throughput1.

Linear Dispersion Codes Selection Using WiMAX over Uncorrelated MIMO Rayleigh Channel

In this paper the combination of Transmit Antenna Selection with Linear Dispersion Code Selection is proposed and analysed. The bit error rate metric criterion is proposed (bit error rate minimization and throughput maximization) to evaluate the performances. The performance of the proposed spatial link adaptation scheme is evaluated under low mobility environment and MIMO uncorrelated Rayleigh channel. Concluded analysis shown that maximum spatial diversity is achieved as well as a smooth transition between codes with low spatial multiplexing rate and high spatial diversity (suitable for low SNR), and codes with high multiplexing rate but low diversity order (suitable for high SNR) in order to maximize the overall system throughput.