Investigating Latency in GNU Software Radio with USRP Embedded Series SDR Platform

Software-Defined Radio (SDR) is a radio technology that most of conventional radio components are implemented in software. Besides the advantages like re-configurability and flexibility, a SDR system has to face a critical challenge on real-time processing due to high jitter and latency. Thus, understanding latency in SDR systems is very important. This paper focuses on investigating the latency of a popular SDR platform - GNU Software Radio with a new Universal Software Radio Peripherals (USRP) device -USRP Embedded Series E100. This research investigates and analyzes the reasons of the delays by considering all the buffering mechanisms in the platform. After that, we verify and quantify them by using three experimental methods. The first method is to calculate the whole delay of the SDR system by measuring the round-trip time (RTT). The second method measures subparts of the whole latency by using timestamp during a packet transmission process. The third approach is designated to measure the latency of the hardware part and bus communication part. We believe this study offers the better understanding of the latency in a new embedded USRP series - USRP E100 with GNU Software Radio platform.