To cope with the ongoing trend in data traffic asymmetry of uplink (UL) and downlink (DL) transmissions, bidirectional dynamic networks (BDNs) have been proposed to facilitate simultaneous UL and DL communications. Moreover, the large-scale distributed antenna system (L-DAS) is considered to improve the spectral efficiency (SE). Aiming at maximizing the SE in the BDN with the L-DAS, in this paper, we propose a novel distributed antenna (DA) clustering strategy named flexible antenna clustering (FAC) to allow each user to choose the most effective DAs. This also provides a low-complexity solution to solve the antenna clustering problem in the L-DAS. In FAC, the operation mode (UL or DL transmission) of the DAs can be flexibly changed, which is determined by the baseband processor units. By taking both the homogeneous and heterogeneous interferences into consideration, we propose two novel metrics for the user and DA selection orders. To the best of our knowledge, this is the first time that the user selection order is considered in solving the antenna clustering problem. Compared with the time division duplex system, our FAC strategy used in the BDN is verified to have improved efficiency in achieving better SE performance. Therefore, the BDN with the L-DAS is suitable in practical communication systems thanks to its SE gain. Based on these results, we further provide some specific suggestions for the practical network configuration.
- Massive multi-input-multiple-output (MIMO)
- antenna clustering
- distributed antenna system (DAS)