On Mon, Jul 25, 2011 at 1:32 PM, Luis R. Rodriguez <mcgrof@xxxxxxxxx> wrote:
> On Thu, Jul 21, 2011 at 8:13 PM, MingAnn Ng <devil_eddie01@xxxxxxxxxxx> wrote:
>> Hi Luis,
>>
>> I am thinking of using the ACS application for channel selection on IBSS
>> network. I had run a test with the current git. But the result is not so
>> convincing.
>>
>> 10 surveys for 2412 MHz: 11.382248 12.847997 13.223471 13.403065
>> 13.454694 13.529891 12.556324 13.573309 13.616969 13.645601
>> 10 surveys for 2417 MHz: 12.678072 10.299560 -inf -inf 9.678072 -inf -inf
>> -inf -inf -inf
>> 10 surveys for 2422 MHz: -inf -inf -inf -inf -inf -inf -inf -inf -inf
>> -inf
>> 10 surveys for 2427 MHz: -inf -inf 12.192645 -inf -inf -inf -inf -inf
>> -inf -inf
>> 10 surveys for 2432 MHz: -inf 9.192645 12.777608 12.192645 12.192645 -inf
>> 12.192645 -inf 10.093109 12.192645
>> 10 surveys for 2437 MHz: 11.192645 -inf 11.000000 10.093109 10.093109
>> 11.192645 -inf 11.192645 -inf -inf
>> 10 surveys for 2442 MHz: 10.192645 10.093109 -inf 10.061401 11.192645
>> -inf -inf -inf 11.192645 10.093109
>> 10 surveys for 2447 MHz: -inf -inf -inf 11.777608 -inf 10.192645 -inf
>> -inf -inf -inf
>> 10 surveys for 2452 MHz: 11.192645 -inf -inf 11.192645 -inf -inf -inf
>> 13.777608 11.337035 10.830075
>> 10 surveys for 2457 MHz: 10.192645 -inf -inf -inf -inf -inf -inf -inf
>> -inf -inf
>> 10 surveys for 2462 MHz: 9.540568 9.192645 10.283793 8.476438 -inf -inf
>> -inf -inf 10.192645 -inf
>> 10 surveys for 2467 MHz: -inf -inf -inf -inf -inf -inf 9.752072 -inf -inf
>> -inf
>> 10 surveys for 2472 MHz: -inf -inf 10.192645 -inf -inf -inf -inf -inf
>> 7.714598 -inf
>> 10 surveys for 5180 MHz: 2.000000 1.830075 1.000000 0.678072 2.000000
>> 2.000000 2.000000 0.678072 2.000000 2.000000
>> 10 surveys for 5200 MHz: 2.000000 1.678072 2.000000 2.000000 2.000000
>> 2.000000 1.678072 2.000000 0.678072 0.678072
>> 10 surveys for 5220 MHz: 2.000000 1.415037 2.000000 0.000000 2.000000
>> 2.000000 1.678072 2.000000 2.000000 2.000000
>> 10 surveys for 5240 MHz: 3.000000 3.000000 3.000000 1.245112 3.000000
>> 3.000000 3.000000 2.678072 2.000000 3.000000
>> 10 surveys for 5260 MHz: 3.000000 2.000000 3.000000 3.000000 3.000000
>> 3.000000 2.000000 2.678072 2.000000 2.678072
>> 10 surveys for 5280 MHz: 3.000000 1.415037 3.000000 1.415037 1.678072
>> 2.000000 1.245112 3.000000 3.000000 2.678072
>> 10 surveys for 5300 MHz: 3.000000 3.000000 3.000000 1.415037 3.000000
>> 3.000000 3.000000 2.000000 3.000000 3.000000
>> 10 surveys for 5320 MHz: 3.000000 3.000000 3.000000 3.000000 3.000000
>> 2.678072 3.000000 1.415037 3.000000 2.000000
>> 10 surveys for 5500 MHz: -1.000000 -2.000000 -1.000000 -2.321928
>> -1.321928 -1.321928 -1.000000 -2.321928 -1.000000 -2.459432
>> 10 surveys for 5520 MHz: -2.392317 -1.169925 -1.169925 -0.807355
>> -1.906891 -1.169925 -1.169925 -1.169925 -1.700440 -0.807355
>> 10 surveys for 5540 MHz: -1.169925 -2.643856 -1.169925 -2.087463
>> -1.169925 -1.169925 -2.523562 -1.169925 -1.169925 -1.169925
>> 10 surveys for 5560 MHz: -1.169925 -1.169925 -2.643856 -1.169925
>> -1.321928 -1.169925 -1.459432 -1.700440 -2.087463 -1.169925
>> 10 surveys for 5580 MHz: -1.169925 -1.700440 -1.169925 -1.906891
>> -1.321928 -1.169925 -1.169925 -1.169925 -1.169925 -1.169925
>> 10 surveys for 5600 MHz: -1.169925 -1.169925 -1.169925 -2.643856
>> -0.807355 -2.459432 -1.459432 -1.169925 -1.169925 -1.169925
>> 10 surveys for 5620 MHz: -1.169925 -1.321928 -2.087463 -1.169925
>> -1.169925 -1.321928 -0.807355 -2.392317 -1.169925 -1.169925
>> 10 surveys for 5640 MHz: -2.643856 -1.321928 -1.169925 -2.857981
>> -1.169925 -0.584963 -1.169925 -1.169925 -1.169925 -3.643856
>> 10 surveys for 5660 MHz: -2.169925 -1.584963 -2.169925 -2.857981
>> -1.169925 -1.169925 -1.169925 -1.169925 -1.459432 -1.169925
>> 10 surveys for 5680 MHz: -1.169925 -1.169925 -2.643856 -2.700440
>> -1.169925 -1.169925 -1.169925 -1.169925 -0.807355 -1.700440
>> 10 surveys for 5700 MHz: -2.087463 -1.169925 -1.169925 -1.000000
>> -2.459432 -1.169925 -1.169925 -1.169925 -1.169925 -1.169925
>> 2412 MHz: 13.123357
>> 2417 MHz: -inf
>> 2422 MHz: -inf
>> 2427 MHz: -inf
>> 2432 MHz: -inf
>> 2437 MHz: -inf
>> 2442 MHz: -inf
>> 2447 MHz: -inf
>> 2452 MHz: -inf
>> 2457 MHz: -inf
>> 2462 MHz: -inf
>> 2467 MHz: -inf
>> 2472 MHz: -inf
>> 5180 MHz: 1.618622
>> 5200 MHz: 1.671229
>> 5220 MHz: 1.709311
>> 5240 MHz: 2.692318
>> 5260 MHz: 2.635614
>> 5280 MHz: 2.243133
>> 5300 MHz: 2.741504
>> 5320 MHz: 2.709311
>> 5500 MHz: -1.574714
>> 5520 MHz: -1.346398
>> 5540 MHz: -1.544436
>> 5560 MHz: -1.506274
>> 5580 MHz: -1.311873
>> 5600 MHz: -1.438962
>> 5620 MHz: -1.378062
>> 5640 MHz: -1.690221
>> 5660 MHz: -1.609185
>> 5680 MHz: -1.487164
>> 5700 MHz: -1.373637
>> Ideal freq: 2417 MHz
>>
>>
>> The ideal channel is 2417MHz. But there are many interference in 2.4G at my
>> testing place. the result for that channel is -inf.
>
> Right..
>
>> I did not understand the
>> outcome, maybe you can describe about -infinity and why that this result
>> occurs.
>
> Sure, so -inf means the calculation resulted in a value out of bounds
> by the used data type. The issue lies in the wide range of values that
> we run into for analysis in very noisy environments. One alternative I
> considered was to use __float128 instead of long double for the
> interference_factor but I was unable to figure out how to print these
> correctly.
>
>> will it be causing by scanning time for particular channel is too
>> short?
>
> Can you test with the latest ACS patches I posted for hostapd with
> debugging and see the values you get there?
Or you can try to split up the computation by using logarithm
identities as follows:
diff --git a/survey.c b/survey.c
index ef47f95..13defc8 100644
--- a/survey.c
+++ b/survey.c
@@ -274,10 +274,9 @@ static long double
compute_interference_factor(struct freq_survey *survey, __s8
{
long double factor;
- factor = survey->channel_time_busy - survey->channel_time_tx;
- factor /= (survey->channel_time - survey->channel_time_tx);
- factor *= (base_to_power(2, survey->noise - min_noise));
- factor = log2(factor);
+ factor = log2(survey->channel_time_busy - survey->channel_time_tx);
+ factor -= log2(survey->channel_time - survey->channel_time_tx);
+ factor += survey->noise + min_noise;
survey->interference_factor = factor;
Luis
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