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[Discuss-gnuradio] Wireless data casting

From: Steve Schear
Subject: [Discuss-gnuradio] Wireless data casting
Date: Sun, 06 Feb 2005 00:03:23 -0800

Recently on the list there has been a simulating 802.11xx protocol thread using GnuRadio/USRP. I think two equal or even more interesting applications for GnuRadio would be to employ these devices to enable legal unlicensed datacasting (including Pod-casting-like capabilities) and VoIP.

Only relatively low data rates (e.g., 128 kbps) are need for reasonably good mp3 or similar audio compression.

If we assume a modulation with only 1 b/Hz efficiency and spread the signal across the available spectrum then a process gain of about 650 is possible at 2.4 GHz and 975 at 5.7 GHz bands. At these process gains CDMA is practical and they increase the effective EIRP by up to almost 30dB. Multiple codes may be used to enable multiple datacast stream and/or soft hand off between broadcast cells offering the same streams so metropolitan area coverage could be offered.

32 kbps is sufficient for toll quality PCM telephony. Process gains would be effectively doubled over datacasting. If higher efficiency voice coding methods are used another 2-4 fold improvement in process gains are achievable.


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