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A reduced signaling scheme based on a new metric for opportunistic beamforming Disclosure Number: IPCOM000030024D
Original Publication Date: 2004-Aug-25
Included in the Prior Art Database: 2004-Aug-25

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A fundamental characteristic of the wireless channel is the fading of the channel strength due to constructive and destructive interference between multipaths. An important means to cope with channel fading is the use of diversity. Multiuser diversity is a form of diversity inherent in a wireless network, provided by independent time-varying channels across the different users. The diversity benefit is exploited by tracking the channel fluctuations of the users and scheduling transmissions to users when their instantaneous channel quality is near the peak. To increase this effect, additional channel fluctuation can be generated, e.g. by opportunistic beamforming. The core idea of opportunistic beamforming is to use a directive antenna system at the base station to generate random beam patterns which will be constant for a certain period until a new random beam pattern is chosen. As all cells act in the same way the interference that a mobile observes is based on the beam patterns in the cell that it is attached to (transmitting data to the mobile) and the beam patterns in the neighboring cells. As the cells vary their pattern from time to time the probability that a mobile observes good interference conditions is increased. The scheduling is based on the SINR (Signal to Interference-plus-Noise Ratio) that every mobile observes. Since the interference is usually modeled as noise, SINR is referred to as the SNR in the following.