- 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
- Keiko Ohnari Kazumasa Okada Osamu Higuchi Hidenori Matsuo Hiroaki Adachi
- 出版者
- The Japanese Society of Internal Medicine
- 雑誌
- Internal Medicine (ISSN:09182918)
- 巻号頁・発行日
- vol.57, no.20, pp.3021-3024, 2018-10-15 (Released:2018-10-15)
- 参考文献数
- 17
- 被引用文献数
- 1 6
An 82-year-old woman developed neck weakness and dysarthria with antibodies against acetylcholine receptor (AChR) and low-density lipoprotein receptor-related protein 4 (LRP4). Myasthenia gravis (MG) was diagnosed by edrophonium and repetitive nerve stimulation tests. Her symptoms resolved completely by immunotherapy. One year later, she presented with muscle weakness and bulbar palsy accompanied by atrophy and fasciculation. Her tendon reflexes were brisk, and Babinski's sign was positive. She was diagnosed with probable amyotrophic lateral sclerosis (ALS). Immunotherapy did not improve her symptoms, and she ultimately died of respiratory failure. MG and ALS may share a pathophysiology, including anti-LRP4 antibodies at the neuromuscular junction.