Higher Order Sectorization in LTE Downlink with 3GPP Release 10 Closed Loop MIMO Transmission Techniques

An extensive evaluation on the system performance of a conventional LTE wide beam tri-sector site network exploiting 3GPP Rel. 10 advanced closed loop MIMO transmission techniques (CL-MIMO) with that of a Higher Order Sectorized (HOS) network has been carried out. The investigation emphasizes on a system performance assessment under realistic conditions. These include a real MCS link adaptation with HARQ processes, adaptive scheduling algorithms, standardized CL-MIMO with the corresponding feedback mechanism and antenna characteristics as parameterized by the antenna manufacturers. The fundamentals of HOS is first explained on the basis of a simple single transmit antenna system per sector. Then antenna diversity is introduced into the system. System performance comparison for a practical network with a fixed number of transmit antenna elements per site (24 Tx antenna elements/site) is carried out for various network layouts applying either MIMO and/or HOS. For the latter 2 variants of deployments are considered: hard-sectorization, where multiple antenna elements with narrower beam width are used to cover smaller sub-sectors and soft-sectorization, in which fixed beam forming by means of pre-coding weights applied on an antenna array is exploited for sector forming. Constraint to Rel. 10 feedback mechanism, numerical results indicate advantages in deploying HOS over CL-MIMO usage, provided that large antenna array with suitable pattern characteristics for forming virtual sectors are available.