----- Message d'origine ---- De : Philip Levis <[EMAIL PROTECTED]> À : [EMAIL PROTECTED] Cc : tinyos-help@millennium.berkeley.edu Envoyé le : Vendredi, 5 Septembre 2008, 4h05mn 28s Objet : Re: [Tinyos-help] LQI measurments with Tmote-Sky sensor?
On Sep 4, 2008, at 9:45 AM, <[EMAIL PROTECTED]> <[EMAIL PROTECTED]> wrote: > Hi, > > I'am using Tmote Sky sensors and I need some help about LQI > measurments. > To calculate LQI values I use Delta application with the trawler > tool. I' have some remarks. > with a maximum of power transmission (0dbm) and distance of 3 > meters, I found stronge values. However, in the literature we speak > about a value between 50 and 110 > then I' have these questions: > 1)- why values upper than 110 and lower then 50 even under perfect > conditions. > 2)- Why values are very large (few thousands)? However in the > standard 802.15.4 it is mentioned that the LQI value is an integer > between 0 and 255 (on 8bits) > 3)- Since the LQI is calculated when a packet is received, how about > the packet when the value is higher than 110 or especially 255. (is > it droped, is a bad packet, is it normal to calculate to calculate a > very high value (thousands))? > 4)- is there an other mean to calculate LQI values without using > Trawler? is a manner to debug this directly in a console? > 5)- Are the values on the Trawler tool the true calculated values > of LQI?. > > thanks for your help in advance. > Denzel The values Delta is reporting are probably not raw LQI readings from the radio, rather those values put through MultihopLQI's link quality function: uint16_t adjustLQI(uint8_t val) { uint16_t result = (80 - (val - 50)); result = (((result * result) >> 3) * result) >> 3; return result; } Phil In moteiv/tos/lib/MultiHopLQI/MultiHopLQIM.nc, I found this function : uint16_t correlation(uint8_t v) { uint16_t c = (80 - (v - 40)); c = (((c * c) >> 3) * c) >> 3; return c; } someone knows why the difference between the two functions AdjustLQI and correlation? ..... (v-50)); vs. ..... (v-40)); thanks in
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