Motorola BluetoothTM Solution to Interference Rejection and Co-existence with 802.11

Dr. Weizhong Chen

Motorola, Inc. WITC, SPS, Austin, Texas

Friday, October 18th, 3:00 PM, ENS 637

fwc003@email.sps.mot.com

Abstract

BluetoothTM is a low cost and low power wireless connectivity technology operating in the 2.4GHz unlicensed ISM band. One of the important challenges to BluetoothTM adopters is interference rejection and co-existence with other WLAN standards like 802.11. This presentation describes Motorola's Bluetooth solution that addressed these challenges. The actual performance measured from the chip set indicate that Motorola's solution provides over 10dB gain over the competitors in the market place.

Motorola's interference rejection solution is achieved via high performance signal detection algorithms. These high performance algorithms not only increase BluetoothTM performance, but also reduce its interference to 802.11 due to its reduction of re-transmission.

The high performance signal detection algorithms include the joint detection of the access code, timing and carrier in baseband, and the Maximum Likelihood Sequence Estimation (MLSE) symbol recovery with carrier tracking. The joint detection uses the 64 symbols of the entire sync word to derive the carrier, instead of the 4 symbols of the preamble in a conventional approach, significantly improving the carrier estimation in an interference environment. The BluetoothTM channel has unrecoverable Inter Symbol Interference (ISI). Conventional slicing detection is optimal only with 0-ISI channels. MLSE is an optimal packet waveform matching detection by trying all possible bit patterns. ISI is included into its optimization. Thus MLSE allows for the use of an exceptionally narrow selectivity filter to reject interference and AWGN.

Motorola's interference rejection performance is not at the price of extensive processing that increases the silicon cost and power consumption. The joint detection gate count is compatible with a conventional solution for the access code detection and timing sync, and the MLSE symbol recovery gate count is negligible in current silicon technology. Motorola's solution relies on its unique, powerful, and efficient algorithms.

Biography

Dr. Weizhong Chen is a Distinguished Member of Technical Staff with Wireless Integration Technology Center (WITC), Semiconductor Products Sector. He received his Ph.D. from Texas A&M University in Electrical Engineering in December 1994. Dr. Chen was the baseband architect for Motorola's two-way paging base station systems between 1995 and 1999. From December 1999 to June 2002, he was the chief modem architect for Motorola's Bluetooth chipset. Currently, Dr. Chen is the technical leader for the WLAN-802.11b modem design team. Dr. Chen has 9 issued US patents and 8 pending. Before joining Motorola, Dr. Chen also published 6 papers in various IEEE Journals and conferences.

Dr. Chen developed the Bluetooth receiver architecture, JD/MLSE (Joint Detection and Maximum Likelihood Sequence Estimation) for the Motorola's Bluetooth chipset, which is well known in the industry. The JD/MLSE receiver provides a low-cost/power solution with superior interference rejection performance in the 2.4GHz ISM band.

A list of Wireless Networking and Communications Seminars is available at from the ECE department Web pages under "Seminars". The Web address for the Wireless Networking and Communications Seminars is http://signal.ece.utexas.edu/seminars