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To: Bernard Levy who wrote (5771)	10/31/1999 8:52:00 PM
From: Hatim Zaghloul	Read Replies (4) \| Respond to of 12823

Bernard, OFDM is as you said, primarily a public domain technology. However all attempts to operate wideband OFDM in the late eighties had failed for three known shortcomings of OFDM: the peak to average ratio, synchronization since there are too many carriers to lock on only one and selective fading. Wi-LAN introduced and a simple method of whitening to reduce the peak to average ratio. This was patented in the Canadian patent. Wi-LAN introduced the concept of using an estimate of the frequency response of the channel as means to remove the effects of selective fading. This aspect is the main claim in the US and Canadian patens. Synchronization was solved by a number of companies. Wi-LAN opted for using a direct sequence header for OFDM. Wi-LAN has filed another patent on the use of the channel estimator to improve the performance of the forward error corrector. This was disclosed in a submission to the IEEE802.11 working group. As for DMT, Cisco itself published a paper indicating that OFDM is principally different than DMT: www.cisco.com/cpress/cc/td/cpress/design/rbb/ch02.htm I hope this gives some answers. Hatim

To: Bernard Levy who wrote (5771)	11/1/1999 4:46:00 AM
From: Peter Ecclesine	Read Replies (1) \| Respond to of 12823

Hi Bernard, I'm told there were Japanese researchers in the 1960s working on OFDM, but the concept has origins in the 1950s. TI was working with Clarity from late '97, using 175MHz 'C62s. The design was prototyped on PCI boards with more than four 'C62s to impliment the algorithms. OFDM algorithms pushed the DSPs of the era, and small changes in DMA modes had a large effect on the algorithms. (TI also consumed Amati, whose principals were familiar with Clarity's work.) petere TI continues to have interests in wireless voice, data and video(1394), and works closely with their largest (Nordic) customers.