To provide cellular wireless communication service, a wireless service provider or “wireless carrier” typically operates a radio access network (RAN) that defines one or more coverage areas in which mobile stations can be served by the RAN and can thereby obtain connectivity to broader networks such as the public switched telephone network (PSTN) and the Internet. A typical RAN may include one or more base transceiver stations (BTSs) (e.g., macro network cell towers and/or femtocells), each of which may radiate to define a cell and cell sectors in which mobile stations can operate. Further, the RAN may include one or more base station controllers (BSCs) (which may also be referred to as radio network controllers (RNCs)) or the like, which may be integrated with or otherwise in communication with the BTSs, and which may include or be in communication with a switch or gateway that provides connectivity with one or more transport networks. Conveniently with this arrangement, a cell phone, personal digital assistant, wirelessly equipped computer, or other mobile station that is positioned within coverage of the RAN can then communicate with a BTS and in turn, via the BTS, with other served devices or with other entities on the transport network.
Wireless communications between a mobile station and a serving BTS in a given coverage area will typically be carried out in accordance with one or more agreed air interface protocols that define a mechanism for wireless exchange of information between the mobile station and BTS. Examples of such protocols include CDMA (e.g., EIA/TIA/IS-2000 Rel. 0, A (commonly referred to as “IS-2000” or “1xRTT”), EIA/TIA/IS-856 Rel. 0, A, or other version thereof (commonly referred to as “IS-856”, “1xEV-DO”, or “EVDO”)), iDEN, WiMAX (e.g., IEEE 802.16), LTE, TDMA, AMPS, GSM, GPRS, UMTS, or EDGE, and others now known or later developed.
The air interface protocol will generally define a “forward link” encompassing communications from the BTS to mobile stations and a “reverse link” encompassing communications from mobile stations to the BTS. Further, each of these links may be structured to define particular channels, through use of time division multiplexing, code division multiplexing (e.g., spread-spectrum modulation), frequency division multiplexing, and/or some other mechanism.
The forward link, for example, may define (i) a pilot channel on which the RAN may broadcast a pilot signal to allow mobile stations to detect wireless coverage, (ii) system parameter channels (e.g., a sync channel) on which the RAN may broadcast system operational parameters for reference by mobile stations so that the mobile stations can then seek network access, (iii) paging channels on which the RAN may broadcast page messages to alert mobile stations of incoming communications, and (iv) traffic channels on which the RAN may transmit bearer traffic (e.g., application data) for receipt by mobile stations. And the reverse link, for example, may define (i) access channels on which mobile stations may transmit “access probes” such as registration messages and call origination requests, and (ii) traffic channels on which mobile stations may transmit bearer traffic for receipt by the RAN.
When a RAN receives an incoming communication for a mobile station, the RAN typically pages the mobile station via a paging channel in at least the coverage area in which the mobile station last registered. When a cellular wireless communication system seeks to page a mobile station (e.g., for an incoming call or for some other reason), a switch in the network may send the page message to numerous base stations in the switch's coverage area, with the hope that when the base stations broadcast the page message, the mobile station will receive the page message in one of the associated sectors, and will respond. Furthermore, to increase the chances that a mobile station receives a page, a RAN may re-send a page, possibly multiple times, in the event that an attempt to page a mobile station fails.
Once a mobile station is successfully paged, the RAN and mobile station typically proceed to set up a forward-link traffic channel between the BTS and the mobile station, via which the RAN can communicate with the mobile station. As part of this process, the RAN determines the transmit power to use for forward-link traffic. To do so, the RAN may first transmit at an initial transmit power, which is typically a constant power level that is preset at the RAN. The mobile station then evaluates the forward-link signal quality, such as by determining the frame error rate (FER), and reports back to the RAN. Then, depending on the signal quality, the RAN may increase or decrease the transmit power by a predetermined increment. The RAN and mobile station may then repeat this process until a satisfactory signal quality is achieved.