Spectral - and energy-efficient two-stage cooperative multicast for LTE-advanced and beyond

Driven by the strong demand for mobile video services in future mobile communications systems, advanced multicast techniques such as cooperative multicast, CM, have been developed to support multimedia services with high spectral and energy efficiency. With path loss gain, spatial diversity, and time diversity, CM outperforms traditional multicast, TM, in various scenarios at the cost of additional signaling and location information. Assuming selective combining based on average received signal strength, SCA, and high user density, the design of spectral- and energy-efficient CM (SECM-H) is presented, which employs a mobile relay arrangement scheme based on sector ring structures. It is shown by numerical results that SECM-H could improve the spectral efficiency per Watt of TM by 75.3 percent. Moreover, using cyclic prefix combining instead of SCA, BS coordination and MR coordination could further enhance the spectral efficiency per Watt of SECM-H by 10.4 and 20.0 percent, respectively. The design of SECM with low user density (SECM-L) is also described. When the number of users is small, a try-best, or TB, MR selection scheme should be employed that chooses the successful mobile station closest to the unsuccessful mobile station as its MR. The spectral efficiency per Watt of SECM-L with TB increases rapidly with the number of users. Its performance is inferior to that of TM when there are fewer than 37 users, while about 60 percent enhancement can be achieved when there are 100 users.