Advanced Signal Processing for Ultra-Wide-Band (UWB) Communications in Wireless Networks

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

Advanced Signal Processing for Ultra-Wide-Band (UWB) Communications in Wireless Networks Following the February 2002 order by the Federal Communications Commission, ultra-wide- band (UWB) communications technology has emerged as the leading standard for very high data rate applications in wireless networks. The technology will allow the wireless connection of multiple devices at very high rates and at low power consumption. UWB will allow the transmission of video, audio, and other data traffic among devices at rates that may reach 480Mbps. For example, UWB could stream real-time video content from a PC or a consumer electronics device, such as a camcorder, a DVD player or a personal video recorder, to a flat-screen HDTV display without the need for wires. In order for this technology to become widely adopted it is necessary to maintain the costs of UWB devices low. A major challenge arises from the signal distortions that are introduced during the analog processing as a result of manufacturing imperfections. The effects of such distortions will be compounded in future high-performance wireless networks due to the higher silicon integration, lower power consumption, larger bandwidth, and higher carrier frequency. There are at least two strategies to address this diffculty. One strategy is generally costly and relies on building more reliable front-end radios. The second strategy, which is one of the objectives of this proposal, is to model and cancel signal distortions by using advanced signal processing and compensation algorithms in the digital domain. This research proposes a systematic way for modeling distortion effects, exploiting the distortion models in receiver design, developing enhanced OFDM receivers that counter-balance the effects of distortions and that improve the range of UWB devices, investigating theoretical limits of performance, and also implementing and testing the developed algorithms on an FPGA testbed. Objectives. (1) Develop distortion models and distortion cancellation techniques for UWB de- vices by using advanced signal processing algorithms in the digital domain. (2) Develop enhanced OFDM receivers for UWB communications by jointly addressing the issues of improved range, improved channel estimation, and distortion compensation. (3) Use the developed distortion can- cellation receivers for both single user and multi-user (space-time coded) communications scenarios. (4) Investigate theoretical limits of performance and effects of distortion on system performance. (5) Pursue a proof-of-concept implementation of a UWB system on an FPGA by using the developed algorithms in order to investigate the models and the algorithms for improved performance. Intellectual Merit of the Proposed Activity. The PI and his research group have extensive research experience on different aspects of advanced signal processing, communications, and adaptive system design. The proposed research activity is creative in several respects: (1) It recognizes the need to address signal distortions introduced by analog processing as a step towards maintaining the cost of UWB devices low. (2) It recognizes the importance of cancelling distortion in the digital domain, as opposed to the analog domain. (3) It studies the effects of major sources of distortion (including IQ imbalances, phase noise, and transmitter and receiver nonlinearities) on algorithm development and performance. (4) It addresses major performance hurdles such as enhanced channel estimation in order to incorporate distortion models, the design of distortion-robust OFDM-based SISO and MIMO (space-time coded) communications, and the need for improved range for UWB devices due to their limited transmit power. (5) It pays attention to the intricate balance between algorithm complexity and hardware implementation. Broader Impacts of the Proposed Activity. The broader impacts of the proposed research are as follows: (1) It has significant implications on the information technology infrastructure of the nation by making the promising UWB technology widely spread at lower costs. (2) It contributes to the development of ultra-high-speed wireless networks for PC peripherals, consumer electronics, home networking, and mobile devices at data rates that may reach 480Mbps. (3) It trains both graduate and undergraduate students in an area of fundamental relevance to future communications systems. (4) The results of the research will be widely disseminated online and via publications in archival journals and conference proceedings, and also via demonstrations of the hardware testbed. A-1