co channel interference

[muhsi_2015]

Hi,

1

AP 1 Channel 36 rssi- 86

AP 2 Channel 36 rssi -51

In the above case the client which is connected to AP will face  slowness due to CCI when  AP1 is  talking to another client ? 

2

AP 3 Channel 40 rssi- 62

AP 4 Channel 40 rssi -56

Thanks

[Ric Beeching]

I guess the easy answer here is yes there will be some slowdown due to the CCI. It would be better to have your APs configured across different separated channels e.g. 36,40,44,58 etc

[muhsi_2015]

HI,

if ap1 is communicating with station A , and station B also wants to communicate with AP2 

What will happen , how the CCA-CS works?

Thanks

[Ric Beeching]

Because wireless is a half-duplex medium the APs and Stations will use CSMA/CA techniques to prevent collisions on the same channel by listening for traffic at the same time as they intend to transmit. Something like this may occur:

1) Station A wants to talk to AP1 and "listens for traffic" on channel

2) Station A might send a Request To Send (RTS) packet out to check for any other activity on that channel.

3) A Clear To Send (CTS) packet may come back which will permit Station A to send traffic

4) Station A sends traffic and Station B, which has heard that Station A is sending traffic, will wait for a certain period of time before trying to send its own traffic.

5) When Station B begins to send traffic, Station A will have to wait. 

Now this is assuming all the clients on the channel can 'hear' each other and also support the timers put in place to prevent collisions. In a lot of environments (mostly 2.4GHz), technologies like Bluetooth and Zigbee don't care about waiting to transmit and they will always send their traffic regardless, creating more interference in that band.

[muhsi_2015]

Hi,

Thanks for the reply . 

Could you brief what is  82 dBm in the below text 

The thresholds for both carrier sense and energy detection are predefined in the standard. For 802.11a the carrier sensitivity is ­82 dBm and the energy detection threshold is ­62 dBm.

Thanks