  This paper considers a multipair amplify-and-forward massive MIMO relaying
system with low-resolution ADCs at both the relay and destinations. The channel
state information (CSI) at the relay is obtained via pilot training, which is
then utilized to perform simple maximum-ratio combining/maximum-ratio
transmission processing by the relay. Also, it is assumed that the destinations
use statistical CSI to decode the transmitted signals. Exact and approximated
closed-form expressions for the achievable sum rate are presented, which enable
the efficient evaluation of the impact of key system parameters on the system
performance. In addition, optimal relay power allocation scheme is studied, and
power scaling law is characterized. It is found that, with only low-resolution
ADCs at the relay, increasing the number of relay antennas is an effective
method to compensate for the rate loss caused by coarse quantization. However,
it becomes ineffective to handle the detrimental effect of low-resolution ADCs
at the destination. Moreover, it is shown that deploying massive relay antenna
arrays can still bring significant power savings, i.e., the transmit power of
each source can be cut down proportional to $1/M$ to maintain a constant rate,
where $M$ is the number of relay antennas.
