Abstract
In traditional CSMA/CA-based MAC designs supporting successive interference cancellation (SIC), channel utilization is inefficient, because the inherited CSMA/CA-style contention approach often forces the whole channel to remain idle and the early released channel is not utilized. In this paper, we propose Multi-CQ, which is the first software-defined networking (SDN)-based MAC design for wireless LANs that supports SIC and significantly improves the channel utilization. Multi-CQ, adopting SDN’s functional separation idea and OFDMA, makes contention and data transmission be executed over two subchannels independently and concurrently, where the superposition coding are used for decoding combined signals, and multiple CQs (contention queues) are introduced to coordinate the concurrency. This concurrent execution greatly reduces the waste in channel contention. Next, adopting SDN’s central control idea, Multi-CQ controller selects nodes who can finish their frame transmissions in almost equal time, thereby improving the channel utilization. Finally, we develop a theoretical model to optimize bandwidth allocation for channel contention and data transmission. Extensive simulations verify the effectiveness of our design and the accuracy of our theoretical model. This study is also helpful to better design wireless MAC protocols supporting other advanced functionalities such as MU-MIMO.
Highlights
1) The serial execution of contention and transmission leads to low channel utilization and 2) transmissions without user selection leads to wasted successive interference cancellation (SIC) transmission capacity
In our design, which incorporates software-defined networking (SDN)’s functional separation concept, the concurrent execution of channel contention and data transmission is allowed over two subchannels
In applying SDN’s central control concept, we adopt a centralized control mechanism based on the contention queue to reduce the time disparities of concurrent frame transmission, thereby overcoming the second drawback
Summary
With the ongoing development of communications technologies, many physical layer designs have been implemented. As a 5G development potential technology, non-orthogonal multiple access (NOMA) [1], [2], [3], [4] has attracted great attention in recent years. The core technology of NOMA is successive interference cancellation (SIC). In this technology, multiple nodes can transmit their frames to a receiver simultaneously, and the receiver iteratively decodes the overlapping frames using SIC. SIC enables simultaneous transmission and it can effectively increase the channel capacity of a physical layer and significantly improve channel utilization. If N1 and N2 simultaneously transmit frames to an access point (AP), the AP first decodes the frame with the stronger signal (say, N1's frame) and decodes the frame with the weaker signal (say, N2's frame) after removing the strong signal from the mixed signal
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