Modelling multi-packet multi-receiver spectrum sharing using D-OFDM in software-defined networks

Abstract

Cognitive radio (CR) technology has been proposed to solve the inefficient spectrum utilization resulted from the traditional fixed spectrum allocation strategy used in wireless systems. Through dynamic and opportunistic spectrum access, CR users can significantly improve spectrum utilization. Most of existing spectrum access schemes designed for CR networks (CRNs) targeted either uni-cast transmission or multi-cast transmission paradigm. Such transmission paradigms allow a CR user to transmit the same data packet over multiple channels to a receiver or a group of receivers. However, existing designs cannot support simultaneous transmissions of multiple distinct packets to different receivers. This new transmission paradigm can be realised using the Discrete Orthogonal Frequency Division Multiplexing (D-OFDM) technology, where each CR transmitter can send multiple different packets to several (multiple) receivers over different channels. In this paper, we investigate the problem of assigning channels to CR transmitters with D-OFDM capabilities, each with multiple packets to be simultaneously sent to multiple receivers. Specifically, we formulate the channel assignment problem as an optimization problem with the goal of achieving the maximum possible network sum-rate. Then, we optimally solve the optimization problem based on standard linear programming methods. To realize our channel assignment in a distributed way, we propose an admission control spectrum access mechanism that allows communicating CR users to exchange their control information. Simulation experiments are carried out to reveal the effectiveness of the proposed protocol compared to previous protocols. The results reveal that significant performance improvement can be achieved by utilizing the D-OFDM technology, in which CR users are allowed to simultaneously transmit multiple packets to multiple receivers.