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Interference Mitigation in Wireless Systems

Interference Mitigation in Wireless Systems:

Wireless communication is the fastest growing sector of the communication industry. Over the last decade, small portion of unlicensed spectrum has encouraged innovations in wireless networking including wireless LAN, Mesh, blue tooth, and so on. These wireless device has become popular in recent years and has received wide deployments.The known fact is that the devices operating in same band create interference to others and hurt overall system performance. Therefore we need to have some adaptive algorithms through which wireless device can adapt their transmission parameters according to their operating environment. One solution is, for a given system in which K users operate in a signal space dimension N (aka processing gain in CDMA system), assign orthogonal signatures to the users when the number of users K is less than or equal to N. And assign precoders such that they satisfy the GWBE when the number of users K > N.

MotivationCommunication channel refers to the medium used to transfer information from a transmitter to a receiver. Communication channels can be either wire-line or wireless. Wire-line channels physically connect the transmitter to the receiver through wire, making them more private and less prone to interference. In wireless communications, electromagnetic waves or RF carry a signal over the communication path, without using the wires. The wireless communication channels might consist of the wave guide, the atmosphere, the free space or even the sea, through which the radio waves propagate subjected to reflection, refraction, diffraction and/or absorption. Wireless channels are thus, more public, with the transmitter radiating a signal that can be received by any antenna in close proximity. Hence interference and noise are much more prevalent in wireless communication. Moreover, when a signal passes through the transmission medium, it gets scattered so that the signal will vary randomly or fade, due to the effect of propagation environment. Wireless communication is the fastest growing sector of communication industry. Over the last decade, small portion of unlicensed spectrum has encouraged innovations in wireless networking including wireless LAN, Mesh, blue tooth, and so on. These wireless device has become popular in recent years and has received wide deployments.The known fact is that the devices operating in same band create interference to others and hurt overall system performance. Therefore we need to have some adaptive algorithms through which wireless device can adapt their transmission parameters according to their operating environment. One solution is, for a given system in which K users operate in a signal space dimension N (aka processing gain in CDMA system), assign orthogonal precoders/signatures to the users when K is less than or equal to N. And assign precoders such that they satisfy the Generalized Welch Bound Equality (GWBE). In order to avoid abrupt change in transmitter due to which the receiver cannot change its receiver filter so fast, the incremental or gradient descent strategies towards the best solution are few example solutions. 



















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