HeterogeneousNetworkModel创新.PDFVIP

Chapter 2 Heterogeneous Network Model and Preliminaries 2.1 A System Model for Heterogeneous Networks A two-tier heterogeneous network model in LTE is studied throughout this book. As shown in Fig. 2.1, consider downlink communications in a heterogeneous cellular network with high transmit power macro evolved Node Bs (MeNB) and low transmit power small evolved Node Bs (SeNB) or relay nodes (RN). Each macro cell is divided into several sectors served by directional antennas. Within each macro cell sector, there are several SeNBs or RNs uniformly distributed. Denote the total number of macro cell sectors in the system as Nc and the number of uniformly deployed SeNBs/RNs in each sector as Nr . UEs are uniformly distributed in the network with an average of Nu active UEs in each sector. The SeNBs/RNs have full radio resource management (RRM) functionalities as well as data relaying capability. Decode-and-forward relaying scheme is assumed. A UE can be either associated with a MeNB or a SeNB/RN. Denote a UE associated with a MeNB as a M-UE and a UE associated with a SeNB/RN as a S-UE/R-UE. The communication link between a MeNB and a UE is termed as a direct link, the link between a SeNB/RN and a UE as an access link, and the link between a MeNB and a SeNB/RN as a backhaul link. The backhaul link could be wired or wireless, could be ideal or non-ideal with ideal backhaul featuring a typical transmission delay of several micro seconds while non-ideal backhaul featuring a transmission delay ranging from several milli-seconds to ten of milli-seconds. For the wireless backhaul, the backhual link could be out-of-band backhaul or in-band backhaul. With in-band backhual, the backhaul link shares the same radio resource as the direct/access link. The total frequency band can be divided into several sub-bands with each sub- band being assigned to one of the