Baseband design and implementation for micro/pico base stations (mBS) in 5G ultra-dense network (UDN) is studied.Low cost is an essential requirement for mBS baseband in UDN.Digital baseband cost of ASIC/ASIP (Application Specific Integrated Circuit / Instruction-set processor) is of the most uncertainty in mBS system.However,the actual costs and hardware feasibility of the baseband are yet unknown to network deployers and researchers.In this paper,we studied the baseband hardware system design and implementation for low-cost mBS.We analyzed popular baseband algorithms and architectures for both full-digital and hybrid beamforming (BF) for UDN.We then proposed feasible chip-level solutions for the baseband with up to 128-antenna BS system,and estimated their implementation cost.Results show that among full-digital BF algorithms,zero-forcing is a choice of high performance and low cost;for hybrid BF,4×32 architecture (32 RF chains) provides good reduction in baseband cost with acceptable performance loss,thus it can be a preferable solution under low cost consideration.The proposed system planning method can also be used for the design of other related systems.
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