Phase locked loops (PLL) for RF carrier synthesis often employ oscillators that insert a considerable amount of time varying phase noise into the received signal. That noise must then be removed in digital basebandreceiver. This phase noise is an indivisible superposition of noise components from receiver and transmitter. Regarding to systems with multiple transmit and receive antennas (MIMO) and if multiple PLLs for carrier synthesis are used each of the superposed phase noise processes per transmit and receive antenna pair can be measured at the receiver. This paper provides a new scheme for high SNR scenarios that exploits spatial correlation between these overlaying phase noise processes at the receiver in order to improve estimation and compensation of the phase noise. Therefore the Wiener filter approach is applied.

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We examine the throughput of an opportunistic beamforming system with proportional fair scheduling and show for normally distributed channel fading states that for large numbers of users the average throughput of each user multiplied by the number of users approaches the maximum possible throughput of this user achievable by coherent beamforming, if round robin scheduling was used. Thus, we extend a proof by Viswanath et al. who showed this for discrete fading states. We give the average SNR of the scheduled user (averaged across the fading states) in closed form and the average throughput in form of an integral as a function of the number of transmit antennas and users. Simulations of this system confirm the analytical results. Finally, we show that for a large number of transmit antennas, the probability density function of the SNR of the scheduled user and therefore also the throughput asymptotically approach those of a system with a max SNR scheduler that always transmits to the user having the largest SNR and thus maximizes the total throughput.

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