Enhancing the performance of random access MAC protocols for low-cost SDRs

Abstract

Software Defined Radio (SDR) is a technology which facilitates experimentation and the practical realization of novel wireless communication systems. Especially low-cost SDRs, however, experience high communication delays due to the connection between the radio hardware and the host computer. This delay hinders the implementation of Medium Access Control (MAC) protocols. In Carrier Sense Multiple Access (CSMA) based protocols, especially the Clear Channel Assessment (CCA) as well as the subsequent channel access phase are subject to strict temporal constraints. In this paper, we present two strategies that address both issues and aim to enhance the performance and efficiency of CSMA protocols implemented on low-cost SDRs. The first approach employs a dedicated spectrum sensing engine as a CCA agent for the SDR. The second strategy optimizes the frame transmission path inside the SDR. Experimental results indicate that both strategies have a positive impact on reducing the slot time parameter of the CSMA MAC.

AVATARS: a software-defined radio based teleoperating cyber-physical system for disaster environment exploration

“…To reduce the RTT for the ARQ protocol using the low-cost SDR platform, an optimized frame transmission path is designed in [22] by pre-modulating the transmission frame. In [23], a dedicated spectrum sensing engine is designed to enhance the sensing speed of a pure software implementation of a CSMA-based MAC protocol.…”

“…Even the dedicated hardware can improve the performance of SDR implementation, there are some additional hardware costs. In this paper, to overcome the processing delay of the low-cost USRP platform and improve the communication efficiency, we not only optimize the frame transmission path as in [22], we also employ the packets pipelining transmission. Moreover, the transmission of robot control information and channel switching information wastes communication throughput if using the existing Zigbee or WiFi protocols.…”

“…The LIFS time (T LIFS ) is the processing delay of each packet, and the SIFS time (T SIFS ) is the processing delay of the ACK. Due to the switching and processing delay of the USRP platform [5,6,18,22], the RTT for a single packet transmission easily adds up to tens and hundreds of milliseconds, which lead to a low communication efficiency. Figure 3(b) shows details of the packets pipelining and accumulative acknowledgment strategy adopted in the wireless link.…”

Towards an Open Source IEEE 802.11p stack: A full SDR-based transceiver in GNU Radio

“…This issue can, however, be circumvented by implementing the CSMA/CA on the FPGA, which is possible since the SDR has an on-board flash where it can store a frame and handle the channel access in hardware. A basic CSMA implementation for the N210 with a non standard PHY that demonstrates this possibility has been presented in [20].…”