[SOCALWUG] Re: Reg WiF/WiMax questions

Thu, 02 Mar 2006 10:47:05 -0800

Is there really such a thing as WiFi operating "seamlessly"?  I assume that would be like the operation of cellular service.  Wireless computer interface to the Internet can be accomplished by "dial up" through the PSTN Cellular and that would be seamless, but other than that kind of service, if you move from one WiFi hot spot to another, the OS has to re-acquire connection via the new hot spot. 

I have two WAP's and would like to configure so that it would be seamless to move between them, anyone know how?


Richard, NCT
N6GPP

On 3/2/06, Jack Unger <[EMAIL PROTECTED]> wrote:

Roaming between access points may result in applications stopping
termporarily or dropping permanently.


Sankaran Somasundaram wrote:
> I have some basic question again. what are the problems that would arise
> with "seamless wi-fi"..One problem i know is interference because of the
> unregulated unlicensed region wi-fi operating in. what else could be the
> problems when a seamless wi-fi is promised?
>
> your help is appreciated.
>
> Thanks,
> Sankar
>
>
>
> On 2/28/06, Sankaran Somasundaram <[EMAIL PROTECTED]
> <mailto: [EMAIL PROTECTED]>> wrote:
>
>     Thanks a lot Kevin and Mr.Thompson.
>
>
>     On 2/27/06, Jim Thompson <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>
>     wrote:
>
>
>         kevincw01 wrote:
>
>>I don't beleive it's this simple.  One problem is that the range for
>>  802.11g is actually less than 802.11b at the maximum throughput.
>>
>         The primary reason for this is that at the maximum modulation speed
>         (54Mbps .vs 11Mbps) a much higher Eb/No (SNR) is required for
>         11g than
>         for 11b.
>
>         At (nearly) equivalent bit rates (12Mbps 11g .vs 11Mbps 11b) the
>         Eb/No
>         curves are almost identical.
>
>         If your environment has a high delay spread (lots of multipath),
>         then
>         11g's 800ns guard interval may get a signal through a lot
>         "farther" than
>         11b's nominal 110ns tollerance for delay spread.
>
>>So you have to decide, do you want the range for the max
>         throughput or at
>>just the point before it stops working?  Another problem is that the
>>power drain is largely dependent on the manufactuer's strength
>         of the
>>radio.  All radios are not the same strength.  Off the top of my
>         head,
>>I think many pcmcia 802.11b cards are 150mW but definiteily not all
>>(don't quote me on that, it's just a number floating around in
>         my head
>>that seems right).  So you'd probably have to take the average
>         here, or
>>maybe different numbers for different strengths...  Then
>         ofcourse the
>>cost is going to be all over the map, good luck on that one.
>>
>>
>         The original questions are unaswerable without a lot more
>         information.
>
>         However, the Eb/No (SNR) curves for the WiMax PHYs, operated in
>         unlicensed spectrum, at equivalent bit rates are approximately
>         the same,
>         and anyone operating WiMax or WiFi in unlicensed spectrum must
>         operate
>         under 47 CFR Part 15.247 (ISM) or 15.407 (U-NII), so there is *no*
>         inherent advantage of either WiMax or WiFi (compared to each other)
>         under these conditions.
>
>         If you don't believe me, I invite you to study the IEEE
>         documents carefully.
>
>         *most* 802.11b cards operated with 16-17dBm (32mW - 50mW) of
>         transmit
>         power.  There are specialty cards with 100mW or more of transmit
>         power
>         available.  All other things being equal, building a high-power
>         11g card
>         is more expensive than building a high-power 11b card, due to
>         peak-to-average power ratio issues.   Since WiMax also uses
>         OFDM, with
>         similar modulation envelopes, it will also face PAPR .vs linearity
>
>
>
>
>

--
Jack Unger ([EMAIL PROTECTED]) - President, Ask-Wi.Com, Inc.
Serving the License-Free Wireless Industry Since 1993
Author of the WISP Handbook - "Deploying License-Free Wireless WANs"
--
"Being a bit scattered tends to be a trait of highly imaginative people."  
The more you rattle the marbles around in your brain, the more creative new connections you make, as it were
– connections that might be lost on those focusing intently on just the red ones.
  - Ed Vogel, University of Oregon, Department of Neuroscience
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