Interpretting Signal Level

[Kalle Valo]

ext christopher <christopher at codeopoly.com> writes:

> Thanks for writing back, but I'm still unsure about how I should use
> your answer. I'll try to better describe what I meant.
>
> In the current driver, the sm_drv.c file has the sm_monitor_rx()
> function which prepares the AVS header. In particular, it has this line:
> "avs->ssi_signal = cpu_to_be32(hdr->rssi & 0x7f)"
>
> Questions: 
>
> 1. Is the rssi field in the hdr (for the current driver) the same as
> rcpi (in your upcoming driver)? In other words, I see in your new
> driver the stlc45xx_rx_data() function sets up status.signal and
> status.qual using rcpi. I want the same thing, but in the existing
> driver. I will simply use rssi and then do the .signal and .qual
> calculations in user space.

Most probably they are not the same. I haven't investigated cx3110x
monitor mode at all, so I'm basically guessing here.

> 2. Upon receipt of the frame in my application and evaluation of the
> AVS header with the signal value, can I write something like:
> int dBm_for_this_frame = header->ssi_signal / 2 - 110;
> int qual_for_this_frame = header->ssi_signal * 100 / 140;

You can try to guess the correct equation yourself. Put N800/N810 to a
fixed location, connect to the AP in managed mode and check the rssi
with iwconfig. Next put the device to monitor mode, keep it on the
same fixed location and check signal level from received beacons. Now
you can compare your results to the reference point. 

Signal strength value from iwconfig should be correct, because our UI
uses the same value.

> 3. If that is reasonable, then I guess the ranges aren't clear to me
> yet. Is it fair to re-state your dBm ranges as this:
> strong dBm: -50 and values greater (i.e., going towards 0)
> good dBm: values between -51 and -75
> weak dBm: anything smaller than -75

Yes, that's what I was thinking. But please note that these number are
only something which I quickly came up based on experience, I didn't
give them a second thought. So handle with care :)

-- 
Kalle Valo