Archived from groups: alt.cellular.sprintpcs (
More info?)
paul@wren.cc.kux.edu wrote in message news:<b9na70prrrdc4cch3vr584bee2kg0mhfjh@4ax.com>...
> On Thu, 8 Apr 2004 01:20:55 -0400, "Donkey Agony" <root@[127.0.0.1]>
> wrote:
>
> >http://ptech.wsj.com/ptech.html
>
> Rolling out EV-DO is an interesting and risky venture for multiple
> reasons.
>
> Part of the carrier's spectrum is dedicated to data only with EV-DO.
> This implies that, even under "emergency loads", which the FCC is
> encouraging carriers to handle, that EV-DO spectrum is "untouchable"
> for voice.
>
> The carriers using EV-DO hope that that data-only spectrum will be
> well utilized. That remains to be seen and is another risk.
Currently, VZW's trial deployments in D.C. & San Diego are both
CDMA1xEV-DO 1900. Undoubtedly, D.C. & San Diego were selected as test
markets due to two factors: VZW holds a PCS D or PCS E 10 MHz license
overlapping its Cellular B-side license in each market, and D.C.'s BAM
Lucent infrastructure versus San Diego's AirTouch Nortel
infrastructure allows VZW to test both vendor's EV-DO solutions. The
more important conclusion, however, is that VZW has currently
relegated EV-DO to PCS spectrum that was of little if any consequence
to its voice or 1xRTT data capacity. However, VZW does not possess
coincident PCS licenses across all of its major Cellular markets (no
supplementary PCS spectrum in Charlotte, Denver, Detroit,
Indianapolis, Phoenix, Portland, St. Louis, San Francisco, Seattle, et
al.) Thus, particularly in those markets, voice/1xRTT capacity could
potentially suffer if existing CDMA1x 800 carrier channels are
subsequently
devoted to EV-DO.
FYI, if you are interested to know in which markets VZW does hold PCS
spectrum, the maps that XFF & I have created are well-documented:
http://people.ku.edu/~cinema/wireless/vzw_pcs.html
http://people.ku.edu/~cinema/wireless/vzw_pcs_block.html
> One would think that Verizon Wireless would, eventually, like to
> migrate their especially heavy peak-load voice areas to EV-DV for the
> gains in voice capacity. Since EV-DV is also data capable,
> simultaneously, in the same spectrum, does EV-DO have a long term
> future for carriers that don't have entirely separate frequency ranges
> for it?
Assuredly, 1xEV-DV - in the true spirit of CDMA - is the more
efficient technology at balancing both voice & data capacity. Though
there is some irony involved in the following statement - since both
EV-DV & EV-DO use time-division scheduling techniques to dramatically
improve Ec/Io thus also increase instantaneous data throughput - the
hubristic flaw of EV-DO reminds me much of the inefficiency of GSM or
IS-136 TDMA. In CDMA, unused capacity - in the form of power - can be
fully distributed to other active users. But in the TDMA
air-interfaces, unused timeslots sit inefficiently vacant. Since
EV-DO dedicates carrier channels entirely to data, any unusued data
capacity also sits inefficaciously disengaged and unavailable to
voice, regardless of proportional demand.
My primary concern - for both EV-DO & EV-DV - is that neither will
ultimately be able to deliver upon promised broadband-like speeds.
Shannon's classic equation shows us that capacity cannot simply be
manufactured via technology alone. Increased capacity can only be
distributed via fundamental improvements in bandwidth,
signal-to-noise, or to a lesser degree also modulation agility - the
last of which is closely-tied to signal-to-noise.
The 1.2288 MHz channel at hypothetically 6 dB S/N can support a
maximum capacity of approximately 2.85 Mbps. If the S/N can somehow
be refined to 9 dB, theoretical capacity jumps to about 3.89 Mbps.
Regardless, however, that capacity will be divided amongst all users
of the channel. The greater the number of users, the less throughput
available to each individual user. The overall channel capacity may
be in the multi-megabit range - which is an impressive result over
little more than a 1 MHz wireless channel - but no single user will
approach that speed.
In a nutshell, there is no alchemy involved in either EV-DO or EV-DV.
Neither is a magic bullet. As the number of users of 3G data services
will increase, the multi-megabit capacity will be continually
subdivided into smaller & smaller individual pieces. As usage
multiplies, only increased bandwidth - additional 3G spectrum
allocation - or improved signal-to-noise - more frequent spatial
re-use (i.e. cell-splitting) - will maintain broadband-like 3G data
capacity per user.
Andrew
--
Andrew Shepherd
cinema@ku.edu
cinema@sprintpcs.com
http://www.ku.edu/home/cinema/
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