[Tinyos-help] Correlation between LQI and RSSI

[Philip Levis]

Hm. I think that's a packet close to the edge of reception  
sensitivity. Different noise floors (a few dB variation) at different  
nodes can therefore cause SNR changes that will see significant  
shifts in chip correlation.

Phil

On Jan 27, 2008, at 7:37 PM, Omprakash Gnawali wrote:

> Here is a small fraction of data form an experiment I did using Tmotes
> a few days ago - each node logged the lqi and rssi of each packet it
> received from different transmitters. Based on this data, if you read
> a value of 212 as rssi field, there is no guarantee that you will have
> a particular lqi value. The lqi could be as low as 56 (with a small
> probability) or as high as 107 (also with a small probability), more
> like that the lqi's will be in the 90's to about 105.
>
> # pkts, rssi, lqi
>     498 212 100
>     514 212 101
>     495 212 102
>     445 212 103
>     399 212 104
>     308 212 105
>     131 212 106
>      30 212 107
>      11 212 56
>       8 212 57
>       8 212 60
>      10 212 61
>      16 212 62
>      25 212 63
>      33 212 64
>      27 212 65
>      32 212 66
>      40 212 67
>      54 212 68
>      51 212 69
>      57 212 70
>      66 212 71
>      72 212 72
>      84 212 73
>     101 212 74
>     115 212 75
>     115 212 76
>     153 212 77
>     141 212 78
>     181 212 79
>     179 212 80
>     207 212 81
>     212 212 82
>     234 212 83
>     244 212 84
>     276 212 85
>     286 212 86
>     320 212 87
>     347 212 88
>     365 212 89
>     399 212 90
>     440 212 91
>     457 212 92
>     461 212 93
>     562 212 94
>     577 212 95
>     552 212 96
>     522 212 97
>     558 212 98
>     487 212 99
>
> - om_p
>
> On Jan 27, 2008 4:20 PM, Daria Wotzka (Geb. Zmarzly)
> <Daria.Zmarzly at gmx.net> wrote:
>> The bug was following: "(...)the LQI byte was overwritten by the RSSI
>> byte.(...)"  but it means that RSSI and LQI have to have exactly same
>> values; my LQIs are in range of 70-130 and RSSIs in range of 220-240.
>> Could it be still due to the same bug? (Packet payload was 80 bytes)
>>
>> Daria
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