在毫微米波段下使用最佳化理論之混合式空間分割多重接取波束形成技術

Abstract

使用平面天線陣列來呈現射頻及基頻混合式空間分割多重接取(SDMA)的波束形成架構，此平面天線陣列的每個單元天線都有相位移位器，把陣列分區為許多區塊且每個區塊可共享一個數位處理路徑。為了壓抑波束圖形的旁瓣輻射及維持使用者的訊號與干擾及雜訊比(SINR)，最佳化理論被應用在設計此混合式空間多重接取的波束形成。兩種設計方式如下：一種為在限制所有使用者的SINR下令其使用之傳送能量為最小；而另一種為在總傳送能量限制下令其所有使用者中最差的SINR要最大。考慮實際上會遇到的不同影響因素，依據此兩種設計方式，我們可以進一步的討論對於兩個使用者的SDMA系統之下的混和式波束形成技術的可行性及效能。此外，在某些程度的波束誤差下，兩種強健型波束形成技術可用來確保每個使用者的SINR。模擬結果顯示出，使用最佳化理論可有效改善混合式波束形成技術的SINR及指向性，此外，混和式波束形成技術擁有強健性去對抗一些延伸的影響因素，如相位變動、波束誤差及通道不確定性。

A radio-frequency and baseband hybrid beamforming (HBF) scheme is presented for spatial division multiple access (SDMA) of 60GHz applications using planar antenna arrays (PAA). PAA with phase shifters for each element antenna is partitioned into sub-blocks and each block is applied a common baseband beamforming weight. To suppress the grating lobes of beam pattern and to maintain the signal to interference plus noise ratio (SINR) of users in the SDMA system, we study the design of this HBF using convex optimization. Two design criteria are considered herein: one minimizes the transmit power subject to a SINR constraint, and the other maximizes the worst case SINR subject to a total power constraint. Based on these two criteria, the feasibility and performance of HBF are extensively studied for a two-user SDMA system, taking into account various factors faced in practice. Moreover, to ensure the SINR of each user under a certain degree of beam misalignment, two robust HBF schemes are also proposed according to the design criteria. Simulation results show that both the SINR and directivity of HBF can be significantly improved by making use of the convex optimization technique. In addition, the HBF scheme is robust to some extend to phase variations, beam misalignment and channel uncertainties.