[问题] How to obtain RSSI value from wireless access point

[aruba]

Hi All,

Does anyone know how to read the RSSI(received signal strength indicator)value from a typical AP in a WLAN environment?

TIA,

 

[LLMI]

For a WLAN Access Point(AP) or a Mobile station, they are similar,

There is a WLAN (11b or 11a, currently most are 11b, called Wi-Fi) transceiver module in the AP. In the module, there are two parts: RF transceiver and baseband modem. The RSSI is a signal indicating the RF(Radio Frequency) receiving power. Therefore, the signal is from the RF receiving path.It is an analog signal.
Mostly the signal is from IF (Intermediate Frequency) transceiver after the IF amplifier.

Currently, there are two solutions for WLAN RF transceiver:
1.Single chip: zero-IF or 300 or 374MHz IF (mostly). Check the chip part number, then read the spec, there must have a pin for RSSI (output) on the chipset. In some modules, baseband processor reads the signal. But some don't. According to 802.11b and 11a standard, it is necessary to read it.

2.Multi-chip solution: like "Intersil" early version. There are several chips to complete the RF transceiver function. The RSSI signal is from IF chip. Reading the IF chip spec, you will find a pin for the RSSI signal.

Then it's easy, get a ADC, read it into your processor.

 

[aruba]

Thank you for the info, LLMI.

I am trying to develop an application run on a fixed node in WLAN. The application needs to get the RSSI from all Access Points that connects to the WLAN. I heard that IWSPY utility on Linux can read the RSSI digitized value. I don't want to attached a ADC to each AP for this. Do you know any vender that provides software interface (such as API) for application to call?

Thanks again,

Aruba

 

[LLMI]

如果你不CARE 硬件, 只要在电脑里读软接口,

1. 不管是PCI 或是USB, IEEE802.11b 协议中有一个Rx_VECTOR.其中第二项(也可能是第四项,我记不清了)就是RSSI,自己编写接口软件去读即可.
2. 如果想买接口软件,或许看看这两个,

http://www.wildpackets.com/support/knowledge_base/airopeek

http://www.ozetechnology.com/goodies/Wireless.shtml

3. 你的AP 生产厂家应有接口测试软件,其中应有RSSI.

关于软件方面,我不在行.

 

[aruba]

十分感谢你所给的详细解释。