The art and popularity of wireless communications has grown significantly over recent years. Indeed, millions of people are engaging in voice and data communications using mobile stations such as cellular telephones and Personal Digital Assistants (PDAs). In principle, a user can communicate over the Internet or call anyone over the Public Switched Telephone Network (PSTN) from any place inside the coverage area of a cellular wireless network.
In a typical cellular wireless network, an area is divided geographically into a number of cells and cell sectors, each defined by a radio frequency (RF) radiation pattern from a respective antenna structure in the cellular wireless network. Within each cell sector, the RF radiation pattern provides an air interface over which mobile stations may communicate with the cellular wireless network. In turn, the cellular wireless network may communicate with one or more other networks, such as the PSTN or a packet-switched network (e.g., the Internet). As such, when a mobile station is positioned within the coverage area of the cellular wireless network (e.g., in given cell sector), the mobile station can communicate with entities on the other networks via the cellular wireless network.
The RF air interface of any given cell sector in the cellular wireless network is typically divided into a plurality of channels for carrying communications between the mobile stations and the cellular wireless network. For example, the RF air interface may include a plurality of forward-link channels, such as pilot channels, sync channels, paging channels, and forward-traffic channels, for carrying communications from the cellular wireless network to the mobile stations. As another example, the RF air interface may include a plurality of reverse-link channels, such as access channels and reverse-traffic channels, for carrying communications from the mobile stations to the cellular wireless network. However, the number of channels on the air interface, and thus the number of simultaneous communications the air interface can support, is limited by hardware and/or protocol constraints. As such, cellular wireless networks often try to conserve the limited supply of channels by assigning them on an as-needed basis.
One common way a cellular wireless network conserves channels is by employing a paging process to locate a given mobile station before assigning a channel to the given mobile station. More particularly, when the cellular wireless network receives a request to set up a communication with a given mobile station, the cellular wireless network may send a page message over a paging channel in each of a plurality of cell sectors for receipt by the given mobile station. In this respect, the cellular wireless network is able to locate the given mobile station using the paging channel in each cell sector, without tying up traffic channels.
Thereafter, if the given mobile station receives the page message in a given cell sector, the given mobile station may indicate its location in the given cell sector by sending a response back to the cellular wireless network over an access channel of the given cell sector. In turn, the cellular wireless network may then assign the given mobile station a traffic channel in the given cell sector by (i) reserving an available traffic channel for communication with the given mobile station, and (ii) sending the given mobile station a channel assignment message identifying the reserved traffic channel. Upon receipt of the channel assignment message, the given mobile station may then acquire the identified traffic channel, and communication over the traffic channel may begin shortly thereafter.
Although the paging process described above enables the cellular wireless network to conserve its limited supply of channels while locating mobile stations, the exchange of multiple paging messages, including delay between theses messages, may introduce latency into the communication setup process. This latency may be undesirable, especially for time sensitive applications such as Voice over IP (VoIP) and Push-to-Talk (PTT). As such, a cellular wireless network that reduces the latency in the communication setup process would be desirable.
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