( if we consider different small areas.
we have more than one channel in a specific region, like channel 1 is better than other channels,while in some other region channel 1 is poor than other channels)
Dear,
Cognitive (or smart) radio networks like xG’s xMaxsystem are an innovative approach to wireless engineering in which radios are designed with an unprecedented level of intelligence and agility. This advanced technology enables radio devices to use spectrum (i.e., radio frequencies) in entirely new and sophisticated ways. Cognitive radios have the ability to monitor, sense, and detect the conditions of their operating environment, and dynamically reconfigure their own characteristics to best match those conditions.
Using complex calculations, xMax cognitive radios can identify potential impairments to communications quality, like interference, path loss, shadowing and multipath fading. They can then adjust their transmitting parameters, such as power output, frequency, and modulation to ensure an optimized communications experience for users.
For more information , check this link:
http://www.xgtechnology.com/technology/cognitive-radio-networks/
The very first criterion about channel quality is the noise level: whether stemming from channel interference, other transmitters on the same channel or other sources does not matter. This level is easily assessed by just 'listening'.
Further on you may try to establish a link on a channel with an acceptable noise level to check for other parameters like multipath propagation, channel attenuation etc.
'Cognitive' or 'smart' is not magic - only the experience of decades of radio operations 'put into the devices'.
Hi Saba,
You first have to know what you want to transmit over the channel and how you intent to do that. If you know you link parameters (transmit power, bandwidth, minimum SINR required at the receiver) , you can than look at each available channel and see if the link will be successful in that channel, considering the interference and noise in that channel.
Kindest regards, Ben
Hello Saba
The answer to this question depends on your network topology (you have cognitive users only or also you have cognitive BSs) and also it depends if your cognitive users are mobile or stationary because the quality of the same channel will differ if the user is moving due to the fading effects. But simply if you want to know the quality of the channel that you will use this can be done during the sensing time. If the channel is not occupied then you can know the quality of the channel using the preambles.
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