Hello All, There is a notion of "detecting the signal" and "capturing the signal" based on the received signal strength. The packet reception success depends upon the noise on the channel too (SNR). For simplicity of this discussion, let us ignore noise for the time being.
According to the best of my knowledge, the only physical entitiy present(which impacts the discussion) in the data sheet of a wireless receiver is the "receiver sensitivity". If the received signal level is higher than this sensitivity (noise ~= 0), then the receiver is able to successfully receive the packet.
However, in certain research work and simulators, "capture threshold" and "reception threshold" variables are also introduced. Here is the main point of this topic. Are these abstract entities? In a simple scenario where a receiver is placed at some distance from transmitter. Is there a possibility of sensing the packet but not being able to decode it (assume noise ~= 0 again) ? If not, then the whole idea of capture threshold is meaningless. If yes, then why doesnt the wireless cards have it in their specs?
My thinking is that a signal can be captured properly if the demodulation phase succeeds. There is always something on the channel. If the demodulator can figure out the envelope wave (depending on the modulation type), it should be able to demodulate the wave and capture the digital content from the analog signal. Is there a possibility that we detect the envelope wave but still not able to demodulate? (Again assuming noise ~= 0). If this is so, then there can be carrier sensing but incorrect reception. Since the whole envelope wave is sent with the same power, is there any reason of not decoding it after detecting it.
Wlog, I guess we can assume that this effect can be stated even when any noise present on ths channel. There is still capture/detect effect, but now we have to consider SNR ratio instead of just signal strength.
Any pointers to this topic is greatly appreciated. Sorry if the question is very trivial to DSP/communication people! :)
Thanks and Regards, Vinay