From jeffl@comix.santa-cruz.ca.us Sat Nov 28 01:16:11 PST 1998 Article: 36469 of ba.internet From: jeffl@comix.santa-cruz.ca.us (Jeff Liebermann) Newsgroups: ba.internet Subject: Re: Ricochet Wireless 2.4ghz Service Date: Mon, 02 Nov 1998 07:23:22 GMT Organization: Committee To Maintain an Independent Xenix Lines: 116 Message-ID: <36445046.52759130@news.ricochet.net> References: <363c8c4d.1183274@news.ricochet.net> <1dhrum7.dlt4ndqzn2fuN@[192.168.1.2]> <363BEDDE.5DA9E966@rahul.net> Reply-To: jeffl@comix.santa-cruz.ca.us NNTP-Posting-Host: 204.179.134.49 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: 909991545 F7W8ZAFJM8631CCB3C usenet58.supernews.com X-Complaints-To: newsabuse@supernews.com X-Newsreader: Forte Agent 1.5/32.451 Path: news1.meer.net!news3.best.com!news1.best.com!su-news-hub1.bbnplanet.com!news.gtei.net!newsfeed.berkeley.edu!Supernews73!supernews.com!Supernews69!not-for-mail Xref: news1.meer.net ba.internet:36469 On 31 Oct 1998 21:11:17 PST, Me Again wrote: >I have heard rummors that one can get faster speeds (up >to 128k) *now*. Not possible with the 900MHz Ricochet units. The basic data rate from modem to poletop is about 100Kbits/sec. In order to simulate full duplex with a half duplex radio, the rate is half of that plus turn-around delay which is about 40Kbits/sec max. However, 40Kbits/sec is the native maximum data rate to the RS-232 serial port. PPP has some overhead and methinks 38Kbits/sec is about the limit under ideal conditions. The poletops talk to each other and the WAP's (Wired Access Points) at roughly twice this rate. (Note: I'm not sure of the exact numbers). The new 2.4GHz radios have more spectrum (80Mhz) and less restrictive FCC regulations to deal with. The basic data rate is something like 300Kbits/sec which blunders downward to about 125Kbits/sec thruput. The question that always comes up is why such a *LOW* data rate. With 80MHz to play with, you could easily do 1.5Mbits/sec (T1) without much difficulty. It seems that information bandwidth can be traded for distance (assuming a fixed bit error rate, tx power, rx sensitivity, antenna gains, and path loss). Want to go twice as fast? No problem, just cut your range in half. If you cut the range in half, it would require 4 times as many pole tops to cover a given area. The 2.4GHz ISM band is a strange block of frequencies shared with all manner of unfriendly signal sources. The worst is the common microwave oven the leaks RF in this band. Foliage attenuation and water vapour absorption is signifigent at 2.4GHz. Multipath distortion is going to be a problem. It's going to be interesting. My guess is that if you can't physically see a pole top, it's not going to work. The Stanford reference refers to the "Starmode" which effectively spoofs the acknowledgements and therefore requires radically fewer turnaround delays and no duplex emulation. You can get about 80Kbits/sec with Starmode. >Is this if you are within a close distance to the new >antennas mentioned above? Exactly where are those new antennas? :-) Look for a white box hung on light poles directly under the light sensor (that turns on the street light and powers the poletop radio). The new boxes have two antennas that vary in configuration. If you want to know where your friendly local poletops are actually located, fire up your Ricochet modem and connect to the serial port with a terminal emulator. Type AT and it should return OK. Then type: ATS?! 300:Version 301:Serial # 304:Baud Rate 305:Numeric Name 306:Unique Name 310:Expected Links 311:Best Links 313:Max Data Size 314:ATA Timeout 316:Path Life 317:Path Cache Size 318:Net Timeout 319:Starmode Caps 320:Active Baud Rate 321:Ring Delay 322:Connect Password 323:User Inactivity 324:Starmode Tx Q 325:Battery Voltage 326:System Inactivity 327:Sleep Mode 328:OOB IP Addr 330:Service Password 1 331:Service Password 2 340:Connection Method 360:Status Icons 361:Serial Lines 362:NS Attributes 390:Mfrg Pn 391:R3 Date 392:R5 Date 393:Mfrg Pn Rev 400:Boots 800:Modem Control 802:Bridge Config 803:Phone # Limit 804:Phone # OK For a list of commands. The latitude and longitude of the radios you hear is reported by: ATS311? Lat: 37.082805 Long: -122.095184 Color: 0 41 -038 Lat: 37.129755 Long: -122.086515 Color: 0 31 -090 Lat: 37.129755 Long: -122.086515 Color: 0 124 -092 OK The last two columns are important. Using the top line, the "41" is the average propogation delay (as would be reported by ping). The "-038" is the approximate signal strength in dBm (decibels below 1milliwatt into 50 ohms). The -038dbm is fairly strong because the poletop is on my roof. The -090dbm is useable, but not great. Use your street atlas map to figure out where the radios are located. The lat/long is NOT exact, but the radio will be fairly close. >I bought a ricochet modem (I think it's the SE model, it looks like the >one pictured at http://www.metricom.com/products/ )about 2 years ago and >haven't had a software upgrade in a while. All I can find on their >website is a FAQ entry that says: Try: http://www.ricochet.net/support There are downloadable flash ram update utility at: http://www.ricochet.net/ricochet/support/modemsw/ Oh-oh. There was a Jan 98 update. If you don't hear from me again, it didn't work. >Q: If I buy a Ricochet modem now, will it work with Metricom's >next-generation, high-speed network? > >A: Subscribers, using current Ricochet modems, will experience both >speed and performance gains through the new high-speed network. In order >to obtain end-user throughput speeds of 128 kbps or higher, subscribers >will need to purchase a new modem. The increase in overall performance will come from the increased bandwidth between the poletops and the WAP at 2.4GHz and the elimination of the congestion caused by using the same frequencies between the customer modem <-> poletop and poletop <-> WAP. Later... Dr Who is playing on the TV. -- Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 (831)699-0483 pgr (831)426-1240 fax (831)336-2558 home http://www.cruzio.com/~jeffl WB6SSY jeffl@comix.santa-cruz.ca.us jeffl@cruzio.com