| Summary: | To cope with the exploding demand for higher data rate and the heavier asymmetry of downlink (DL) and uplink (UL) traffic, dynamic time-division duplex (DTDD) has been proposed, where the time resources can be adjusted dynamically between DL and UL transmission. However, the strict synchronization requirements in DTDD bring extra overhead. In this paper, a bidirectional dynamic network (BDN) with massive multiple input multiple output is studied, in which DL and UL transmission can occur simultaneously. Under imperfect channel-state information, the closed-form expressions for the UL achievable rates with maximum ratio combination (MRC) and zero-forcing (ZF) receivers as well as the DL achievable rates with maximum ratio transmission (MRT) and ZF beamforming are derived in both BDN and DTDD systems. Based on these expressions, we compare the spectral efficiency of BDN and DTDD systems. Numerical results show that the simulation results match well with the closed-form expressions in both BDN and DTDD systems. Furthermore, BDN is more spectral efficient than DTDD. ZF achieves better performance in spectral efficiency than MRC and MRT.
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