S. Mukherjee (USA)

Maximal Ratio Combining, microdiversity, macrodiversity.

We consider a single mobile station in a wireless cellular network, and focus on the uplink. The mobile’s transmis sions can be received by more than one base station (BS). Each BS has multiple antennas and is assumed to perform maximal ratio combining (MRC) on them. Based on the signal to noise ratio (SNR) at the output of the combiner at each BS, a system controller (e.g., the RNC in UMTS) de cides to accept the received frame at exactly one BS and reject all other BSs. This is called “switching” and the chosen BS is the one with largest averaged received sig nal power over some time duration. Since switching can be quite costly in terms of signaling overhead, we impose a hysteresis threshold for switching, and we study the case where switching can only occur at certain periodic inter vals, called “switch-and-stay macrodiversity.” We provide an analytical expression for the probability of outage at any given location for the mobile, i.e., the probability that the SNR at the MRC output of whichever BS is selected by the system controller is less than some chosen threshold. We can then obtain numerically the dependence of this outage probability on parameters like the hysteresis threshold and the degree of microdiversity at each BS.

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