[opendtv] Re: Analysis: WiMax Could Be "The New Radio"

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
  • Date: Fri, 20 May 2005 16:29:31 -0400

This qualifies as THE classic example of someone not putting

> WiMax has been designed to have a range of 30 miles from a
> single, well-located transmitter; within that range, data
> transfer rates are anticipated to be 70 Mbps. To put that
> in perspective, most radio stations use ISDN connections to
> retrieve high-quality audio from remote broadcasts.

So let's see. Mobile WiMax would most likely use the OFDM
option and frequencies below 11 GHz (starting at 2.3 GHz).
With the OFDM option, spectral efficiency is allowed to be
set to different settings, depending on robustness needs. As
of now, the range is 1 b/s/Hz to 5 b/s/Hz, which is achieved
in the usual way (BPSK, QPSK, 16-QAM, 64-QAM, with an
assortment of convolutional FEC as well as block RS codes
possible for each modulation mode, and optional turbo
convolutional coding too).

Normal digital radio does the same sort of thing, with the
same tradeoff between channel capacity and robustness, and
can operate even at frequencies in the MF, HF or VHF bands.
And the spectral efficiency is typically in the 1+ b/s/Hz

Because digital radio is aimed at streaming media and
mobility, it doesn't need to provide the wide range of setup
options WiMax provides (such as ATM framing, for example,
or 5 b/s/Hz spectral efficiency).

If you load radio stations into WiMax frequencies, you take
away capacity for two-way broadband subscribers using WiMax
and you waste the radio spectrum. If you modify the WiMax
standard to use radio frequencies, you are simply playing
musical chairs with spectrum.

> A single WiMax connection has the equivalent capacity of
> more than 500 ISDN lines. As a further comparison, many
> radio stations have T-1 connections to the Internet for
> their computer networks. A single WiMax connection would
> offer the equivalent of 60 T-1 lines, or seven DVD-quality
> video signals to each individual wireless user.

Proving what? If a radio station needs 128 Kb/s, it requires
no less spectrum on the WiMax frequencies than it would on
the radio frequencies, for equal robustness.

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