In a wireless communication network, a Physical Cell ID (PCI) is a unique sequence that identifies cells in the physical layer, and the role of the PCI is scrambling synchronization channels, so that the terminal can obtain cell identity while detecting synchronization channels. Because of the one to one relationship between the PCI and the primary synchronization sequence (PSS) as well as the secondary synchronization sequence (SSS), according to the 3rd Generation Partnership Project (3GPP) agreement, a long term evolution (LTE) system has a total of 504 PCIs available. These 504 PCIs are identified by different PSSs and SSSs, respectively. The 504 PCIs have been divided into 168 groups represented by 168 SSSs, i.e., group identifications. Each group has three identities represented by three PSSs. The three identities of each group are generally allocated to different cells under control of the same base station.
In the fourth generation mobile communication system and the LTE-advanced system, in addition that the macro cells need to occupy a part of PCI resources, a part of PCI resources also needs to be allocated to femtocells, relay stations and microcells as well as other heterogeneous nodes. In the areas where base stations are deployed densely, PCI resources may be insufficient. The approach generally used to solve the problem of insufficient resources is multiplexing PCI so as to ensure that PCI can be configured for each base station, while multiplexing PCI also brings multiplexing interferences to the network, i.e., too densely configuring PCI will make two cells which multiplex PCI so close that it will cause interference.
Further, through the cross-correlation study of PCI code, it is found that the cross-correlation of SSSs which identify PCI is not perfect. In the case of poor network environment, PCI will be interfered by other PCI which is produced by SSS shifting, and the smaller the displacement is, the greater the interference is, and this also makes it difficult to properly identify the synchronization signal. Thus, for adjacent cells, it is necessary to configure PCIs which are identified by SSSs with larger displacement. In other words, the PCI resources with smaller displacement are tried to be allocated to the nodes with greater distance to avoid the interference caused by the undesirable code property.
USPTO Backgrounds
USPTO Backgrounds