在IEEE 802.11 網路上具有動態頻寬配置功能的雙向感知無線電媒介層多重存取協定

Abstract

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Recently, the CR technology has emerged as a recent breakthrough radio technology to address the spectrum underutilization and spectrum scarcity problem by providing means to utilize the spectrum holes (i.e., unused spectrum) in an intelligent way. Therefore, this technology could facilitate efficient utilization of the radio spectrum while provide highly reliable communication for all users of the targeted wireless networks. In this research, we propose a bi-directional CR MAC protocol for the CR users (CRUs) such that the CRUs can coexist with the primary users (PUs, i.e., IEEE 802.11 users) and flexibly use the spectrum holes without affecting the performances of PUs.

The proposed bi-directional CR MAC protocol is an extension of the CR MAC protocol proposed by TakChon Lou et al. [9] and Shie-Yuan Wang et al. [10]. Although both of these previous works have dramatically improved the spectrum efficiency, their studies fail to address the protocol degradation performance in delivering TCP flows. In addition, the main limitation of their protocols is that the bandwidth allocation for the CRUs has to be done statically. Therefore, in this research, we first address the problem of the TCP performance degradation over [10] and propose a basic scheme CR MAC protocol (BBi-MAC) as a remedy. Follow on, we work on an advanced scheme of the CR MAC protocol (ABi-MAC) which possesses the ability of reserving the bandwidth dynamically according to the CRUs’ bandwidth demand. Therefore, the ABi-MAC can further well utilize the spectrum holes of an IEEE 802.11 network and support synchronous two-way traffic flows with variable packet sizes. The performances of our proposed schemes are evaluated using both mathematical analysis and simulation. Both of the analytical and numerical results show that our proposed schemes can significantly enhance the aggregate throughputs of CRUs in an 802.11 network and dramatically improve the spectrum efficiency without degrading the performances of PUs.