An experimental study of network performance impact of increased latency in software defined radios

Software Defined Radios are becoming more and more prevalent. Especially in the radio amateur community, Software Defined Radios are a big success. The wireless industry also has considerable interest in the dynamic reconfigurability and other advantages of Software Defined Radios. Our research focuses on the latency of Software Defined Radios and its impact on throughput in modern wireless protocols. Software Defined Radio systems often employ a bus system to transfer the samples from a radio frontend to the processor which introduces a non-negligible latency. Additionally, the signal processing calculations on general-purpose processors introduce additional latencies that are not found on conventional radios. This work concentrates on one particular Software Defined Radio system called GNU Radio, an open source Software Defined Radio application, and one of its hardware components, the Universal Software Radio Peripheral (USRP), and analyzes its receive and transmit latencies. We will use these measurements to characterize the performance impact on IEEE 802.15.4 implementation in GNU Radio. Additionally, we present two Software Defined Radio implementations of short-range radio standards, a FSK scheme used in the Chipcon CC1000 radio, and the physical layer of IEEE 802.15.4. We use these implementations for round trip time measurements and introduce two sample applications, a physical layer bridge between the FSK scheme and IEEE 802.15.4, and a dual channel receiver that receives two radio channels concurrently.