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" True Vendor-Neutral WISP Consulting-Training-Troubleshooting Phone (VoIP Over Broadband Wireless) 818-227-4220 www.ask-wi.com --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "SOCALWUG" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/SOCALWUG SOCALWUG website: http://www.socalwug.org -~----------~----~----~----~------~----~------~--~---
