Sayed Ali Khodam Hoseini

arXiv2018

Joint Resource Allocation and Antenna Selection In the Uplink of OFDMA Networks

The problem of joint sub-channel, power control and antenna selection in the uplink of OFDMA networks is investigated. The corresponding optimization problem is a non convex mixed integer non-linear problem(MINLP). To tackle the problem, an iterative two-step optimization problem is devised. First,~Having fixed the selected antenna as well as the associated power of each user,~a sub-channel assignment problem using the so-called Hungarian method is proposed. Second, the joint power and antenna selection problem is extended into a more elegant form through adding a penalty term to the objective function forcing the relaxed boolean variables associated with antenna selection problem to take binary values. To this end, the problem is restated as a difference of two concave function (DC programming) and is effectively solved in an iterative manner. The foregoing procedure is iteratively repeated until approaching a fixed network throughput. Simulation results demonstrate the superiority of the proposed method w.r.t. the exhaustive search with fixed power control mechanism.

cs.IT↗

arXiv2016

Minimizing The Expected Distortion Using Multi-layer Coding Approach In Two-Hop Networks

This work concerns minimizing the achievable distortion of a Gaussian source over a two-hop block fading channel under mean square-error criterion. It is assumed that there is not a direct link between transmission ends and the communication is carried out through the use of a relay, employing the Decode and Forward (DF) strategy. Moreover, for both of transmitter-to-relay and relay-to-destination links the channel statistics are merely available at the corresponding receivers, while the channel gains are not available at the affiliated transmitters. It is assumed that a Gaussian source is hierarchically encoded through the use of successive refinement source coding approach and sent to the relay using a multi-layer channel code. Similarly, the relay transmits the retrieved information to the destination through the use of a multi-layer code. Accordingly, in a Rayleigh block fading environment, the optimal power allocation across code layers is derived. Numerical results demonstrate that the achievable distortion of the proposed multi-layer approach outperforms that of single-layer code. Moreover, the resulting distortion of DF strategy is better than Amplify and Forward~(AF) strategy for channel mismatch factors greater than one, while the resulting distortion has a marginal degradation for channel mismatch factors lower than one.

cs.IT↗