Emerging Applications of CDMA

Advisor: Prof. Michael Pursley

Direct-sequence spread-spectrum modulation has been employed in many recent communications and navigation systems. This modulation can provide multiple-access capability, improved performance on multipath channels, precise time-of-arrival information, and protection against various forms of interference. When used to provide multiple-access capability (perhaps in addition to other benefits), direct-sequence spread spectrum is often referred to as CDMA. It is clear that CDMA will continue to be a cornerstone for future cellular communications and navigation systems. It is a key feature in emerging third- and fourth-generation cellular systems, and CDMA continues to be the modulation of choice for the Global Positioning System (GPS). New signal designs and receiver processing techniques are being devised for future CDMA cellular systems, and CDMA will be used in the new GPS civil signal at frequency L5 (1176.45 MHz).

The student will investigate the benefits of direct-sequence spread spectrum as it applies to cellular communications and navigation. Based on technical articles and many patents that have been issued for cellular communications equipment and GPS receivers, the student will learn about implementation techniques for CDMA and examine tradeoffs in the design of several of the subsystems in CDMA transmitters and receivers. In addition to cellular communications and GPS systems, the DARPA low-cost packet radio (LPR) and ITT's handheld multimedia terminal (HMT) will provide concrete examples to enhance the student's research experience. Issues such as the selection of spreading sequences, the design of rake receivers for multipath channels, acquisition and tracking requirements, and the choice of error-control coding method will be investigated by the student. The student will also examine emerging standards for third- and fourth-generation CDMA cellular systems and new advances in technology that are being incorporated into CDMA systems.