Craig Birkmaier wrote: > Once again we have caught Bert shooting from the > hip, at a target he missed by a mile. Once again, lack of understanding of the subject matter causes Craig to get all confused and to hype up what is fairly straighforward. First of all, I was quoting the original article, posted by Bill Sheppard. That article had not mentioned anything about COFDM. As to this: > What it IS, is a creative use of broadcast OFDM > technology to ENHANCE the existing two-way CDMA > infrastructure in a backward compatible way, > delivering MANY of the services and benefits that > I have been advocating via the "spectrum utility" > concept. The original concept was to transmit both one-way TV and two-way cellular service using cdma2000. The TV signals would use regular TV-like broadcast towers. However, in order to allow for efficient frequency reuse for the two-way cellular service, the cellular service could not possibly also make use of the big stick(s). THEREFORE, replacing the CDMA big stick with a COFDM big stick is easy enough to do, especially when DVB-H already exists to make this an efficient proposition for hand-helds. So there's no "backward compatible" mumbo jumbo involved here at all. It is just a way of reapportioning the 700 MHz frequency band they bought to provide the two services they want to sell. > Using CDMA unicast is highly inefficient, both > in terms of spectral efficiency and power > consumption, Bull. CDMA is only less spectrally efficient than COFDM *if* you use COFDM at 16-QAM or better. That's because the CDMA downlink uses QPSK (uplink BPSK). So you trade off robustness for bit rate. But "highly inefficient" is clearly an exaggeration. With CDMA, they might create multiple channels with orthogonal spreading codes. With COFDM, they might instead create a single broadcast channel, and have receivers tune into different subchannels of that one band. > The physical infrastructure that Qualcom will > use is virtually identical to that which I have > been describing for COFDM-based SFNs for DTV. > Transmission will come from "one or a small > number of towers," potentially using tall > buildings in urban areas. Oh, PLEASE! Own up to having been spreading illogical ideas nd misinformation, will you? The infrastructure they are talking about is simply big sticks, for the TV portion. Physics doesn't care whether the tower is used for normal DTT or for this mobile TV service, especially because they are using the UHF band! Tall towers and high power are essential for efficient broadcast. Tall towers result in lower propagation losses, and high power is needed for range. They said nothing about using only buildings for the big stick or big sticks. That was your editorial addition. (In NYC, that might even work, just as regular DTT towers do.) Bert ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.