宏分集对于CDMA系统前向容量的影响

宏分集可以有效地克服大尺度衰落的影响.对于CDMA反向信道而言,采用宏分集可以有效地改善信道质量并提高反向容量.与此相比,有关宏分集对CDMA前向信道的影响的研究则并不多见.本文深入分析了多天线宏分集下的CDMA系统前向容量并发现,在传统CDMA系统中,无论采用何种功率分配方案,宏分集都会导致前向容量损失.在分析容量损失原因的基础上,我们进一步提出了一种新的发送分集方案.在该方案下,前向容量不仅得到较大的提高,而且会随着参与宏分集的基站数目的增多进一步增大.

Effect of Macrodiversity on CDMA Forward-Link Capacity

Macrodiversity is an effective means to overcome large-scale fading effects.Much of previous work focused on its benefits to the reverse link in CDMA systems.However,its effect on the forward link is less well understood.In this paper,we analyze the CDMA forward-link capacity with macrodiversity and the results show that macrodiversity causes forward-link capacity loss whatever power allocation scheme is adopted.Basd on the analysis of the cause of capacity loss,we further present a new transmission scheme,in which some joint control among the involved base stations is made to assure that the signals arrived at the desired mobile in phase and simultaneously.The simulation results show that in the new transmission scheme much higher capacity can be achieved with macrodiversity and the capacity increases rapidly with the number of involved base stations.