Cellular wireless networks typically comprise user equipments (UE) such as mobile handsets which may communicate via a network interface comprising a radio transceiver to a network of base stations connected to a telecommunications network. Such cellular wireless networks have undergone rapid development through a number of generations of radio access technology. The initial deployment of systems using analogue modulation has been superseded by second generation (2G) digital systems such as GSM (Global System for Mobile communications), typically using GERA (GSM Enhanced Data rates for GSM Evolution Radio Access) radio access technology, and these systems have themselves been replaced by or augmented by third generation (3G) digital systems such as UMTS (Universal Mobile Telecommunications System), using the UTRA (Universal Terrestrial Radio Access) radio access technology. Third generation standards provide for a greater throughput of data than is provided by second generation systems; this trend is continued with the proposals by the Third Generation Partnership Project (3GPP) of the Long Term Evolution (LTE) system, using E-UTRA (Evolved UTRA) radio access technology, which offers potentially greater capacity and additional features compared with the previous standards.
A user equipment may have an interface to a second network, in addition to having an interface to cellular wireless network, which may be used for example to connect via a wireless link such as IEEE 802.11 WiFi to a wireless access point in a data network. The wireless link may be used, for example, for to provide a data connection such as an Internet connection. In some situations, such as in an aeroplane, the transceiver for communicating via the cellular wireless network may be disabled and the user may communicate using the WiFi link.
However, in many situations there is a tendency for users to keep the cellular radio transceiver enabled continuously, so that the user may receive calls or text messages using the cellular network. As a result, many user equipments remain continuously camped on the cellular wireless network, even at times when the user is unlikely to make a call, such as at night. The provisioning of wireless network infrastructure, such as base station transceivers, has to be sufficient to handle the signalling involved with a large number of user equipments which are continuously camped on the network. Even when a user equipment is not making or receiving a call, it may be required to send periodic idle mode signalling, such as periodic location area updates or routing area updates.
Increasingly, network operators are striving to reduce the power consumption of cellular wireless networks, and in order to do this, it is beneficial to reduce the number of network elements, in particular wireless transceivers, that are powered up in less busy times. However, the large number of user equipments that are continuously camped on the network reduces the scope for powering down network elements. The load on the conventional, high power consumption, cellular macrocell base stations may be reduced by the provisioning of low power femtocell base stations within the cellular network at user premises, to which a user equipment may handover when the user is at home. Alternatively, the user may turn off the user equipment so that incoming messages are dealt with by voice mail.