  We study low-signalling overhead scheduling for downlink coordinated
multi-point (CoMP) transmission with multi-antenna base stations (BSs) and
single-antenna users. By exploiting the asymmetric channel feature, i.e., the
pathloss differences towards different BSs, we derive a metric to judge
orthogonality among users only using their average channel gains, based on
which we propose a semi-orthogonal scheduler that can be applied in a two-stage
transmission strategy. Simulation results demonstrate that the proposed
scheduler performs close to the semi-orthogonal scheduler with full channel
information, especially when each BS is with more antennas and the celledge
region is large. Compared with other overhead reduction strategies, the
proposed scheduler requires much less training overhead to achieve the same
cell-average data rate.
