1310 bridge - signal strength and signal quality

robinhepburn · ‎11-08-2007

I'm sure I'm not the first to ask but I can't seem to find an answer anywhere.

I have a point-to-point link with 1310 bridges and external 10dBi YAgi antennas. The distance is 4.47km and the user experience is poor. I don't have the enable password as this is lost so I'm going to have to password recover (i.e. wipe back to factory defaults) the bridges just to get into them.

I need to formulate a plan for addressing this and need some insight on what is going on from the little knowlege I have. The command show dot11 stat client-traffic shows me a signal strength of 77 and a signal quality of 24. Retries are around 11%. What do these SS and SQ figures actually mean? I speak dB but these are clearly not dB so what are they and how do I convert these to something meaningful? This wireless link is 3500Km away in a remote African location so I need a good idea of what I need to do before I get there. I can't just take a bucket-load of kit with me due to customs and regulatory issues and I won't be able to source anthing in-country either so here knowlege is everything.

Advice appreciated.

drolemc · ‎11-14-2007

Problems in Bridged networks can be mainly due to RF interference between the two bridges. We need to identify the source which is causing this RF interference and remove it to improve signal strength. There are a couple of good documents on Cisco.com on troubleshooting bridged networks.

The documents are available at http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a0080094c6e.shtml

http://www.cisco.com/en/US/products/hw/wireless/ps469/products_tech_note09186a0080508551.shtml

bbxie · ‎11-14-2007

SS is a measurement of how strong the signal strength is, it is ofen measured as how many dBm(in your case is -77dBm)(0 dBm = 1 mW,PdBm = 10*Log10(PdBm/1mW); SQ means SNR(Signal/Noise ratio),it is measured as how many dB(dB = 10 Log10 (P2/P1))(20dB means P2 is 100 times P1).

10dBi Yagi antenna is not good enough to support p2p 1310 bridge in 4.47km distance(even with no antenna cable lose, it will run on 12Mbps in such a distance)(you can use cisco's "Outdoor Bridge Range Calculation Utility" to calculate how far each antenna support). Other things need to take care is to make sure there's no obstacles between the bridges(WiFi bridge need line of sight,that's why WiMAX is becoming more and more popular in outdoor area) and you have aligned the antennas to a suitable angle(that's the most time-consuming part).