Solid State Circuits Society

October 18, 2007

Our speaker was   Mr. Jason A. Trachewsky, (Senior Technical Director of Broadcom), and the topic of his presentation was “A 2×2 MIMO Baseband for High-Throughput Wireless Local-Area Networking (802.11n) “

Abstract

The new IEEE 802.11n draft introduces physical layer (PHY) and media access controller (MAC) layer improvements to enable transmission of two independent data streams of coded OFDM with constellations from BPSK to 64-QAM and code rates from 1/2 to 5/6 at average TCP throughputs 7 times greater than 802.11a or 802.11g using two transmit antennas and slightly more than double the bandwidth. In addition to the maximum data rate increase, the 802.11n draft provides modes to increase the range of moderate data rate links through diversity combining and spatial multiplexing and MAC aggregation techniques to reduce layer-2 overhead.

A flexible single-chip fully-integrated 2×2 MIMO baseband PHY and MAC is presented. The PHY is capable of transmitting up to two information streams generated from one rate-1/2 64-state convolutional encoder and fully-flexible MIMO block interleaver on up to two transmit antennas. The convolutional encoder includes a puncturing engine to create rate-2/3, 3/4, and 5/6 codes. Single-stream modes may use one or two active antennas with cyclic shift transmitter diversity employed when two antennas are simultaneously active and transmitter selection diversity employed when one antenna is active; the cyclic shift and selection algorithm are fully programmable. The PHY can receive transmissions of one information stream with a single-receiver-path maximum-likelihood decoder, with or without receiver selection diversity, or a maximal ratio combiner (MRC) followed by a maximum-likelihood decoder. It can receive two information streams with a novel dual-antenna maximum-likelihood decoder, providing second-order diversity for each stream. It also includes logic to map more than two receiver antennas to the two receiver RFIC inputs for additional selection diversity gains. The MAC includes standard-compliant frame aggregation and block acknowledgement capabilities to vastly improve efficiency at high PHY rates.

The talk will cover technical specifications of the baseband processor, an overview of some of the key algorithms that the high throughputs possible, and some measured results.
BiographyJason Trachewsky is currently a Broadcom Fellow and Senior Technical Director in Broadcom’s Office of the CTO and is investigating new wireless technologies. Prior to his current position, he was Senior Director of Engineering for the Wireless LAN Business Unit at Broadcom. In that role, he was responsible for Broadcom’s R&D for 802.11 products from 802.11b through the 802.11n MIMO wireless LAN standard and made several contributions to the 802.11n drafts. Prior to Broadcom, he was with Epigram, Inc., which was acquired by Broadcom in 1999, and Applied Signal Technology, Inc. He received a BSEE from Stanford University in 1991.

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