Mabruk Gheryani

Design of an Adaptive MIMO System using Linear Dispersion Code

In this paper, we present a new adaptation scheme for MIMO systems using linear dispersion code. The statistics of signal-to-interference-noise for a MIMO transceiver using linear dispersion code and linear minimum-mean-square-error (MMSE) receiver over a Rayleigh fading channel is studied. The associated probability density function of the signal-to interference-noise is derived and verified. The average BER over MIMO fading channel for a given constellation using the MMSE receiver is calculated numerically. The numerical and simulation results match very well. With the statistics as a guideline, we study new design of selection-mode adaptation using a linear dispersion code. A new adaptive parameter, called space-time symbol rate, can be applied due to the use of linear dispersion code. An adaptive algorithm for the selection-mode adaptation is proposed. Based on the proposed algorithm, two adaptive techniques using constellation and space-time symbol rate are studied, respectively. If constellation and space-time symbol rate are considered jointly, more selection modes can be available. Theoretical analysis demonstrates that the average transmission rate of selection-mode adaptation can be improved in this case. Simulation results are provided to show the benefits of our new design.

Multi-Dimensional Beamforming for Adaptive MIMO Systems

A novel scheme called multi-dimensional beamforming is proposed for adaptive MIMO systems, which can achieve higher capacity than eigen-beamforming when more feedback bandwidth is available. Theoretical analysis and numerical results show that multi-dimensional beamforming improves capacity as compared to eigen-beamforming at relatively high signal-to-noise ratio. By extension of the existing beamforming scheme to multi-dimension, we are able to concatenate the scheme with space-time codes. Simulation results are also provided to evaluate the concatenated schemes with linear space-time codes at various data rates in terms of bit error rate.

Error Performance of Linear Dispersion Codes

In this paper, we present a study of error performance of linear dispersion codes. First, an upper bound of average error probability is derived for any signal-to-noise ratio. Based on this bound, a tight upper bound of average error probability at high signal-to-noise ratio is further derived to show the diversity advantage of linear dispersion codes. The tight bound demonstrates the relationship of error probability to constellation size and space-time symbol rate. The bound at high signal-to-noise ratio is verified by simulation results.

Capacity Analysis of Full Rate Linear Dispersion Codes

In this paper, we have studied capacity of linear dispersion codes in frequency-flat Rayleigh fading environments. An exact analytical formula of the ergodic capacity was derived for the full-rate linear dispersion code. The ergodic capacity was given in terms of signal-to-noise ratio and multiple antenna dimension. The exact analytical expression is verified by simulation results. This study will be of benefit to the design and study of linear dispersion code.

Coded cooperative networks with channel estimation technique

This paper proposes a coherent distributed convolutional-based coding scheme with channel estimation based on pilot signals. Instead of transmitting the second frames on orthogonal sub-channels from the source and relay nodes to the destination, we used Alamouti scheme in the second frame. In particular, we assume that the channel state information is estimated at all nodes involved in the transmission process. Assuming decode-and-forward (DF) relaying, we derived upper bounds on the bit error rate (BER) for M-ary phase shift keying (M-PSK) transmission with channel estimation errors. Our analytical results have shown that a performance close to perfect channel knowledge can be obtained when the number of pilot symbols increases. At low pilot to noise ratio (PNR), the proposed scheme cannot provide significant performance improvements. Finally, the performance of the system degrades significantly. This diversity degradation is attributed to the channel estimation errors made at the relay and destination nodes.

Distributed convolutional-based coding for system non-idealities

This paper proposes a coding scheme for cooperative networks in the non-ideal case with system imperfections where the source and relays share their antennas to create a virtual transmit array to transmit towards their destination. We focus on the problem of coding for the relay channels. While the relays may use several forwarding strategies, including amplify-and-forward (AF) and decode-and-forward (DF), we focus on coded DF relaying. In particular, we consider the case when all the nodes estimate the channel state information in the transmission process. We derive upper bounded expressions for the bit error rate (BER) assuming M-ary phase shift keying (M-PSK) transmission. It is shown that the performance is degraded due to the presence of channel estimation error. However, the observations made in ideal scenarios still hold for the non-ideal case. Also our analytical results have shown that a performance close to perfect channel knowledge can be obtained when the number of pilot symbols kp increases. Also, with kp pilot symbols, the performance was shown to approach the perfect channel knowledge case at high pilot to noise ratio (PNR) (Eb/N0). Finally, at low PNR, the proposed scheme cannot provide significant performance improvements.

Power allocation strategy for MIMO system based on beam-nulling

In this paper, we propose a scheme called “beam-nulling” using the same feedback bandwidth as beamforming but with higher capacity. In the beam-nulling scheme, the eigenvector of the weakest subchannel is fed back and then signals are sent over a generated subspace orthogonal to the weakest subchannel. Hence, the scheme can achieve high capacity. The capacities of water-filling, equal power, beamforming and beam-nulling are compared through theoretical analysis and numerical results. It is shown that at medium signal-to-noise ratio, beam-nulling approaches the optimal waterfilling scheme. Additionally, the existing beamforming and new proposed beam-nulling can be extended if more than one eigenvector is available at the transmitter. The new extended schemes are called multi-dimensional (MD) beamforming and MD beam-nulling. Theoretical analysis and numerical results in terms of capacity are also provided to evaluate the new extended schemes.

Design of adaptive MIMO system using linear dispersion code

In this paper, we develop a new design for adaptation of linear dispersion code. A new adaptive parameter called spacetime symbol rate is applied in our design. We have studied the statistics of signal-to-interference-noise of a linear MMSE receiver over a Rayleigh fading channel. The average BER for a given constellation using the MMSE receiver is calculated numerically. With the statistics as a guideline, two adaptive techniques using constellation and space-time symbol rate are studied, respectively. If constellation and space-time symbol rate are considered jointly, more selection modes can be available. Theoretical analysis demonstrates that the average transmission rate of the joint adaptation can be improved in this case. Simulation results are provided to show the benefits of our new design.

SINR Analysis for Full-Rate Linear Dispersion Code Using Linear MMSE

We have studied the statistics of signal-to- interference-noise for a MIMO transceiver using full-rate linear dispersion code and linear minimum-mean-square-error (MMSE) receiver over a Rayleigh fading channel. The associated probability density function of the signal-to-interference-noise is derived, which will benefit the future study, such as error- rate probability. Simulation results are provided to verify the theoretical analysis.