Karl Molnar & Eric Wang

Dr. Karl Molnar
Dr. Eric Wang

Ericsson Company

Thursday, April 15
4:30 - 6:00 PM
Room 1001 EECS

Interference Cancellation for TDMA Digital Cellular Systems

Dr. Karl Molnar

Performance in TDMA digital cellular systems is often limited by interference, specifically by one or two dominant interfering users. In order to improve system performance (capacity) or call quality, this interference must either be avoided or mitigated for both uplink and downlink reception. In this talk, we give a description of the techniques used to handle interference for the IS-136 system. For uplink reception, traditional diversity reception is combined with equalization to perform interference cancellation through space-time processing. This technique is further combined with fixed beamforming to provide significant gains in fast fading and dispersive environments. For the downlink, fixed beamforming is used to statistically improve carrier to interference levels at the handset by only transmitting energy towards the desired mobile user. Further improvements can be obtained by cancelling interference at the handset. Under the restriction that there is only one antenna available for reception, joint detection is considered for cancelling the remaining, dominant interferers.

Physical Layer of W-CDMA

Dr. Yi-Pin Eric Wang

Standardization of third generation cellular systems is underway. Wideband CDMA (W-CDMA) has been chosen as the basic radio access technology for third generation cellular systems in Europe and Japan. This access technology is based on direct-sequence spread spectrum technique using 5 MHz bandwidth. Compared to second generation narrowband CDMA, W-CDMA offers improvement in both coverage and capacity. In this talk, physical layer specification of W-CDMA will be presented. Important features of W-CDMA are highlighted. In addition, the major difference between W-CDMA and IS-95 is identified. Finally, key research topics for W-CDMA are listed.

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