The Verification Of Multicast Beamforming Technology And Its Energy Efficient Design For Cache-Enabled Cloud RAN

Multicast plays an important role in wireless networks to delivery a common message to multiple users simultaneously.Multicast beamforming can further boost the system perfor-mance by utilizing channel state information?CSI?at the base station?BS?equipped with mul-tiple antennas.This paper provides a validation of multicast beamforming over actual channels measured in the Shanghai Jiao Tong University?SJTU?campus wireless network,a FDD LTE network.We first build a receiver prototype using USRP N210 and LabVIEW for channel mea-surement.A single base station with 4 antennas and 3 singleantenna receivers are considered.Based on the measured actual CSI,we then evaluate the performance of multicast beamform-ing under the quality of service?QoS?problem formulation,which is to minimize the transmit power consumption subject to an individual Signal to Noise Ratio?SNR?constraint for each user receiver.This problem is NP-hard.The Semi-Definite Relaxation?SDR?approach is adopted to find an solution close to primitive solution.Experimental results demonstrate that multi-cast transmission using a single beamformer provides significant power gain over unicast trans-mission with multiple beamformers under the same QoS constraints in our considered campus network.This thesis also consider a base station switch control strategy proplem based on a content-centric transmission design in a cloud radio access network by incorporation multicastiong and caching.Based on this existing formulation,we then consider BS switch on/off control strategy.Specifically,when existing a base station that don't serve any user,we can turn it off.Thus we can reduce the total network cost through reducing the static power consumption of the base station.In the existing work,users requesting the same content form a multicast group and are served by a same cluster of base stations?BSs?cooperatively.And each BS has a local cache,and it acquires the requested contents either from its local cache or from the central processor via backhaul links.The existing work investigate the dynamic contentcentric BS clustering and multicast beamforming with respect to both channel condition and caching status.Based on that,we formulate a mixed-integer nonlinear programming problem of minimizing the weighted sum of backhaul cost and BS power under the quality-of-service constraint for each multicast group.Then,as the existing work,we reformulate an equivalent sparse multicast beamforming?SBF?problem.By adopting smoothed l₀-norm approximation and other techniques,the SBF problem is transformed into the difference of convex programs and effectively solved using the convex–concave procedure algorithms.Simulation results demonstrate significant advantage of the proposed BS switch on/off control strategy.