Performance Enhancement of the CSMA/CA MAC Mechanisms Using a Reject Request to Send (RRTS) Message for 3.5 GHz Shared Spectrum Systems

The federal communications commission (FCC) has addressed a three-tiered spectrum access system (SAS) in the so called innovation band (3.5 GHz) which foresees besides the priority access licenses (PAL) an unlicensed spectrum access as general authorized access (GAA). In this context, the SAS assigns the spectrum to the PAL and GAA systems which are citizens broadband radio service devices (CBSDs). Thus, the issue of finding a scheme that achieves an optimal spectrum access among the CBSDs and their nodes in term of maximizing the throughput is addressed. In this paper we present the design and results of a broadcast message termed reject request to send (RRTS) based on the IEEE 802.11 distributed coordination function (DCF) mechanisms for SAS with efficient spectrum access in respect to maximize the system throughput for GAA CBSDs in an unlicensed spectrum. The system improvement shows how the RRTS message can be used in a minimum intrusive way to enhance the system throughput compared with the state-ofthe-art (SoA) DCF scheme. Moreover, the suggested scheme is able to handle a large number of accessing nodes because our scheme is robust against the number of nodes which opens a new perspective for high connection density in a SAS context and beyond 5G.