| 摘要 |
The application relates to the detection of local cell identifier collision by a base station. For identification purposes, each base station in the network (200) may be assigned or otherwise select a local cell identifier (e.g., a physical cell identifier (PCI), a pilot pseudorandom number (PilotPN), or some other type of identifier) intended to be unique in a given geographical region. Because of its limited geographical reach, the local cell identifier can be use a relatively small number of bits and still be in principle (locally) unique in a given area. However, for the same reasons, the quantity of local cell identifiers defined in a given system is limited (e.g., on the order of one to several hundred in some systems). Meanwhile, femto base stations, such as the femto base stations (210) and (212) in FIG. 2, may be deployed in potentially large numbers throughout homes, apartment buildings, office buildings, etc., and by individual consumers without the central planning conventionally used in macro networks to coordinate the distribution of local cell identifiers. Thus, identifier conflict among base stations in femto networks as well as mixed networks, and the problems associated therewith, have the potential to be more widespread and more detrimental than in conventional macro networks where deployment and base station identification is more closely controlled. In one particular type of conflicting use, referred to as identifier "collision," two base stations in close proximity to one another may inadvertently use the same local cell identifier in a manner that causes a user device in that region to concurrently receive signals (e.g., pilot signals) comprising the same local cell identifier from two otherwise distinct base stations. The resulting identifier collision between femto base stations (210) and (212) may lead to several problems. Therefore, the application proposes to detect collision as follows. The femto base station (210) detects that the PCI received in the RRCConnectionReestablishmentRequest message matches its own PCI (i.e., the PCI of the femto base station (210)) but that the c-RNTI does not match any of the c-RNTIs that the femto base station (210) has assigned to any user devices that it is serving (e.g., the user device (222)). Accordingly, the femto base station (210) determines that the RRCConnectionReestablishmentRequest message is in fact intended for another neighboring base station using the same PCI as itself (i.e., the femto base station (212) in this example, although its identity may be unknown to the femto base station (210)). |
