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Technology Stocks : Terayon Communications Systems -- Ignore unavailable to you. Want to Upgrade?

To: Shawn Fisher who wrote (32)	8/7/1998 6:12:00 PM
From: Geof Hollingsworth	Respond to of 48

Hi Shawn, Let me chime in with what I remember, and I expect Bernard can then put us both on the right track! I have seen the noise/throughput graphs from the meetings a few weeks ago, but don't have a copy. In general, your concept is right-S-CDMA gives slightly better throughput (bits/hertz) than QPSK in the upstream for ingress in the noise region you indicated (<19db but greater than 0), including the notch-filter approach proposed by Broadcom. QAM16 is not relevant here (only used in upstream). They are both significanly inferior to VC/DMT in that noise range, and VC/DMT continues to perform (at degraded performance levels) long after the S/N would knock both QPSK and S-CDMA off the air. As a result, expect the terms of engagement to shift, with Broadcom (and perhaps Terayon) arguing that strong ingress noise is not that big a problem in cable plants when the committee gets together next month.

To: Shawn Fisher who wrote (32)	8/7/1998 6:47:00 PM
From: Bernard Levy	Read Replies (1) \| Respond to of 48

Hi Shawn: Your interpretation is correct. To be able to transmit a large number of bits per Hz per second through the use of a high order QAM 64 or 256 QAM, you need a high signal to noise ratio. 256 QAM can transmit 40Mb/sec per 5MHz downstream channel, i.e. 8 bits/Hz/sec. The existing Terayon modem offers only about 14 Mb/sec downstream and upstream, but it can accommodate a lot of noise. Terayon is claiming that their next generation S-CDMA modem will offer 40Mb/sec downstream and 30 Mb/sec upstream per 5Mhz channel, but I find this claim had to believe because it would require spreading a high-order QAM signal. I have never seen CDMA applied to high-order QAM (current wireless CDMA systems use QPSK). I think that ultimately, cleaning the channel is the best option as you suggest. S-CDMA buys time for cash-strapped operators, but in the long run, cable companies will want an upgraded plant. Best regards, Bernard Levy