波束域5G系統之使用者分群技術研究

隨著4G通訊發展成熟，5G通訊也成為世界矚目焦點，巨量天線是5G技術中最熱門的研究議題。基地台用巨量天線同時服務大量使用者，遇到的問題（1）若使用天線通道的訊號處理，需大量領航訊號，通道呈現高度頻率選擇性，系統效能大幅減低，（2）高階MU-MIMO技術下系統龐大的複雜度。波束群多重進接（Beam-group Division Multiple Access, BgDMA）系統在波束域處理訊號，解決頻率選擇性，大幅減少領航訊號密度及通道估測數，且藉由使用者分群將互相干擾嚴重的使用者分在同一群組中，預編碼時可有效降低複雜度且消除干擾更有效率。本論文提出多階段使用者分群，第一階段用極低複雜度的方法將可能互相干擾嚴重的使用者分在同一群組；第二階段用使用者通道資訊將維度過大群組拆散以限制MU-MIMO的複雜度，第一方法利用使用者通道功率增益，第二方法利用使用者通道正交性，來將過大群組拆開；第三階段把維度過小且互相干擾的群組合併以改善系統效能，第一方法把波束重疊數量多的群組合併，第二方法把維度過小的群組再次經過第一階段使用者分群。結果顯示使用多階段使用者分群與沒有使用者分群且使用所有波束相差約200倍以上的系統複雜度，在降低大量複雜度之下，更多高複雜度的預編碼、干擾消除或使用者排程可以在實際系統中使用。

關鍵字

第五代移動通信系統；分波束群多重進接；巨量天線；使用者分群

並列摘要

With the development of 4G (4th generation) systems, 5G (5th generation) sys-tems have come into focus. The technology of large-scale antenna is one of the most popular research areas in 5G systems. When a large number of antenna-equipped eNB serves a lot of users simultaneously, there are some problems: (1) Per anten-na-channel signal processing needs a large number of pilots for channel estimation, and frequency selective of the channel causes performance degradation. (2) High-complexity in high-order MU-MIMO processing. BgDMA (Beam-group Division Multiple Access) is a one 5G system that re-solves channel’s frequency selectivity in the beam-domain, reduces number of ref-erence signals for channel estimation, and puts the UEs with severe interference to each other into the same group by user grouping to lower the MU-MIMO complexi-ty. In this thesis, a multi-stage user grouping is proposed for BgDMA system. Step 1 puts the UEs with severe interference to each other into same group in a very low-complexity way. Step 2 breaks the oversized groups through the channel’s pow-er gain or orthogonality to limit MU-MIMO complexity. Step 3 combines the under-sized groups through the number of overlapped beams or going to Step 1 again to improve performance. Numerical results show that the proposed method can provide good tradeoff between performance and complexity.

並列關鍵字

5G ； BgDMA ； large-scale antenna ； User grouping

參考文獻

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波束域5G系統之使用者分群技術研究

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