The Effect of Channel Estimation Error on the Throughput of Broadcast Channels

Abstract

In a broadcast channel in which one transmitter serves receivers, the capacity region highly depends on the amount of channel state information (CSI) at the transmitter. Assuming that the transmitter knows the SNR of all the receivers, opportunistic strategy maximizes the throughput (sum-rate) of the system. It is usually assumed that CSI is accurate, however, evaluating the SNR is basically an estimation problem in the receiver which cannot be done without error. In this paper, we analyze the effect of the noisy estimation of SNR on the throughput of a broadcast channel. We propose a generalization of the opportunistic transmission in which the transmitter still sends to the user with the highest estimated SNR, but backs off on the transmit rate based on the variance of the estimation error. We obtain the optimum amount of back off and compute the throughput for our scheduling scheme. Clearly, the estimation can be improved by using a longer training phase; however, longer training would deteriorate the throughput. In the final part of the paper, we address this trade off and obtain the optimum training strategy that maximizes the throughput of the system.

On imperfect CSI for the downlink of a two-tier network

“…Proof: The proof is provided in [23]. It follows from the claim that in (16), maximizing the argument of the integration maximizes the integration. The problem thus becomes that of finding…”

“…The system goodput is defined as the amount of information successfully received at the user terminal, without retransmissions. To maximize the achievable goodput, we propose a suboptimal transmission strategy based on rate backoff [16] to decrease the CSI mismatch in the system. We show that the maximum density of femtocells increases exponentially with the number of antennas at the macro base station and the quantization size for the limited feedback beamforming system.…”

Optimal wireless multiuser channels with imperfect channel state information

“…E.g., when power is fixed and only rate adaptation is considered the problem is reduced to the determination of the optimal backoff function; e.g. [3]. A second possibility is to fix a target outage probability and separate the optimization into the determination of a backoff function for target outage, followed by optimal power allocation [4].…”

A performance comparison of interference alignment and opportunistic transmission with channel estimation errors

“…In [7], an opportunistic transmission scheduling policy is shown to be robust to estimation errors from both stochastic approximation algorithm and imperfect measurement of channel conditions. Another study [8] considers a broadcast channel with estimation errors where the transmit node sends to the user with the highest estimated SNR but backs off on the transmit rate based on the variance of the estimation error. The performance of such a scheme relies heavily on the duration of training period.…”