Wireless telecommunication networks are known. In such networks, mobile communication devices (for example, mobile telephones) are operable to communicate with base stations provided by network providers.
In known wireless telecommunication networks, radio coverage is provided to network connectable devices, such as mobile telephones, or wireless devices such as tablets, within areas known as cells. A base station is located in each cell to provide radio coverage. Typically, network connectable devices in each cell are operable to receive information and data from a base station and to transmit information and data to a base station.
User equipment roam through the wireless communications network. Base stations are typically provided which support areas of radio coverage. A number of such base stations are provided and are distributed geographically in order to provide a wide area of coverage to user equipment.
When user equipment is within an area served by a base station, communications may be established between the user equipment and the base station over associated radio links.
Traditional base stations provide coverage in relatively large geographical areas and those cells are often referred to as macro cells. It is possible to provide a heterogeneous network (HetNet) where smaller-sized cells are provided within macro cells, as illustrated in FIG. 1. Such smaller sized cells are sometimes referred to as low-power nodes (LPN), home nodeBs (HNB) micro cells, pico cells or femto cells. One way to establish a small cell is to provide a small cell base station that provides coverage having a relatively limited range within the coverage area of the macro cell. The transmission power of a small cell base station is relatively low and, hence, each small cell provides a small coverage area compared to that of a macro cell and covers, for example, an office or a home.
Such small cells are typically provided where the communications coverage provided by the macro cell is poor or where a user wishes to use an alternative communications link provided locally, by the small cell base station, to communicate with the core network, and/or to increase capacity within a network.
Deployment of small cells in a wireless communication network can assist a network in relation to handling capacity in high traffic areas, for example, so-called hot spot areas. An ability to offload traffic to a small cell or cells located in a high traffic area of a network may be particularly useful to a network operator.
Although HetNet deployments may offer advantages, unexpected consequences of such deployments may occur. It is desired to address those consequences.
“UMTS; UTRAN architecture for 3G home node B stage 2” (3GPP TS25.467 version 10.6.0 release 10) discloses a way of providing soft handovers between small cell base stations via an Iurh interface, which involves a target cell being added to an active set of a UE under control of the serving node.
EP1773075 discloses a fast cell selection method for high speed downlink packet access system, in which a target node is detected and a radio link is established between the terminal and the target base station and the terminal updates its active set with the target base station. This is done under control of the serving radio network control.
WO2005/125260 relates to a system where handover is controlled centrally and discloses a smooth hard handover method in which radio links are prepared in selected base stations for potential communication with a mobile station. A radio link in the prepared state will have a dedicated physical control channel set up but not a dedicated physical data channel. The dedicated physical channel control need be set up only in the downlink direction.