Optimizations for Push-to-Talk in Wireless Networks

Push-to-Talk or PTT is ideal for group communication in a cooperative work environment, since conversations tend to be terse, and single-point to multipoint communication is the norm. PTT is generally run using simple two-way devices communicating on a common channel. However, field experience has repeatedly exposed the need for better range and higher robustness, particularly since Departments of Public Safety and Medical Emergency Response Teams have come to rely heavily on this technology. PTT over a stable regulated carrier-grade wireless network such as 1xEVDO, GSM, or TDMA is therefore highly desirable. Unlike peer-peer half duplex communications and other low-cost alternatives run over unlicensed spectrum, providing PTT over regulated technologies such as 1xEVDO-Revision A is challenging. The foremost stumbling block is temporal resource allocation overheads during call setup. Call setup can take considerable time owing to network complexity and the state changes involved in setting up a Traffic Channel (TCH). This paper surveys a repertoire of optimization techniques that can be used to improve network performance metrics to acceptable limits for PTT deployment.