- 著者
- Ryo TAKAHASHI Hidenori MATSUO Sijie XIA Qiang CHEN Fumiyuki ADACHI
- 出版者
- The Institute of Electronics, Information and Communication Engineers
- 雑誌
- IEICE TRANSACTIONS on Communications (ISSN:09168516)
- 巻号頁・発行日
- vol.E106-B, no.9, pp.748-757, 2023-09-01
Cell-free massive MIMO (CF-mMIMO), which cooperatively utilizes a large number of antennas deployed over a communication area, has been attracting great attention as an important technology for realizing 5G-advanced and 6G systems. Recently, to ensure system scalability and mitigate inter-user interference in CF-mMIMO, a user-centric (UC) approach was investigated. In this UC approach, user-centric antenna-sets are formed by selecting appropriate antennas for each user, and postcoding is applied to reduce the strong interference from users whose antenna-sets overlap. However, in very high user density environments, since the number of interfering users increases due to increased overlapping of antenna-sets, the achievable link capacity may degrade. In this paper, we propose a user-cluster-centric (UCC) approach, which groups neighborhood users into a user-cluster and associates the predetermined number of antennas to this user-cluster for spatial multiplexing. We derive the uplink postcoding weights and explain the effectiveness of the proposed UCC approach in terms of the computational complexity of the weight computation. We also compare the uplink user capacities achievable with UC and UCC approaches by computer simulation and clarify situations where the UCC approach is effective. Furthermore, we discuss the impact of the number of interfering users considered in the zero-forcing and minimum mean square error postcoding weight computation on the user capacity.
- 著者
- Yuta Seki Fumiyuki Adachi
- 出版者
- The Institute of Electronics, Information and Communication Engineers
- 雑誌
- IEICE Communications Express (ISSN:21870136)
- 巻号頁・発行日
- pp.2018XBL0028, (Released:2018-03-22)
- 被引用文献数
- 1
In this paper, we propose an adaptive minimum mean square error filtering combined with singular value decomposition (MMSE-SVD) for OFDM downlink multi-user multi-input multi-output (MU-MIMO) transmission. During data transmission, base station (BS) updates the multi-user MMSE transmit filter by using linear channel prediction, while user equipments (UEs) update their eigenmode receive filters, constructed by SVD, by using decision feedback adaptive channel estimation. The uncoded BER performance achievable by adaptive MMSE-SVD is evaluated by computer simulation. It is shown that proposed adaptive MMSE-SVD can increase an allowable maximum Doppler frequency (fDT) for keeping BER<10-2 by about 4 times.