----- Message d'origine ----
De : Philip Levis <[EMAIL PROTECTED]>
À : [EMAIL PROTECTED]
Cc : [email protected]
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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