Civilian public safety organizations, such as municipal police squads, municipal fire departments, private security organizations, and other public service organizations, commonly utilize two-way radio communication systems that allow mobile nodes, such as police squad cars, fire trucks, individual patrollers with two-way radios, etc., to communicate with each other as well as with one or more geographically fixed nodes, such as a headquarters or precinct building. Such systems are, in essence, wireless local area networks (WLANs). Such systems are commonly used to carry voice communications, often using encrypted digital channels, as well as other data. For instance, squad cars often have PCs, laptop computers or other computing devices that can connect to the WLAN to download various forms of data, such as motor vehicle records for a particular driver or license plate, arrest records for particular individuals, bulletins from headquarters, photographs (such as mug shots), etc, from one or more central servers coupled to the WLAN (typically through a wired LAN). Often, the mobile nodes, such as squad cars maintain local copies of certain types of data, such as mug shots and bulletins.
In addition, the mobile nodes may, not only receive data from a central server, but send data to the central server. For instance, police officers may prepare and transmit arrest reports and other reports to the central server using the WLAN so that coworkers working in a precinct building can have more immediate access to such reports, rather than waiting for officers to physically return to the precinct before such reports can be entered (in a database maintained on the central server). This may also make record keeping more efficient since an officer can directly create an electronic version of the record, rather than preparing a hard copy of the report, which would then need to be entered into the database in a separate manual step when the officer returned to the precinct.
These types of WLANs typically cover a specific geographic area, such as a municipality or county. The area that such a network must cover often is larger than can be covered by a single fixed antenna because the power with which two way radios and related fixed antennas can transmit data is limited, not only by practical weight and power considerations (especially for the mobile nodes), but also by local state or national regulation. Accordingly, a plurality of antenna nodes positioned at geographically separate locations in the municipality might commonly be coupled to a wired LAN, each antenna having full-time haul back capabilities to the central server(s) via the wired LAN. Of course, the wired LAN (which may also be considered the wired portion of an overall LAN that also includes the wireless LAN) also typically would include other fixed nodes in addition to the antenna nodes, such as dispatchers and desktop computers that also communicate with the central server(s) and/or the mobile nodes. When a mobile node is within range of a fixed access point it communicates directly with the host (or central server) via the fixed access point. However, when a mobile node moves beyond transmission range of a fixed access point, it essentially cannot communicate with the WLAN until it returns within range of one of the fixed access points. Thus, if a central server has data to be transmitted to a particular mobile node or vice versa and that mobile node is out of radio transmission range of any fixed access point, that mobile node simply was unable to receive the data until the mobile node came back into radio range.
These types of WLANs commonly also incorporate a protocol by which two mobile nodes can directly communicate with each other on a peer-to-peer basis if they are within range of each other.
The cost of installing the infrastructure to support multiple remote fixed access points (e.g., antennas) for such WLANs can be substantial and includes costs such as leases on the lines necessary to connect the remote fixed access points to the wired portion of the LAN.
It often is economically infeasible to provide enough fixed access points (i.e., antennas) to fully cover an municipality. Accordingly, mobile nodes, e.g., squad cars, may be out of communication with headquarters and/or other mobile nodes for lengthy periods of time and, hence, be unable to receive potentially important data and updates.
Accordingly, it is an object of the present invention to provide an improved wireless communication system.
It is another object of the present invention to provide a WLAN that enables data to be indirectly transmitted between a mobile node and a server even when the mobile node is out of range of any fixed access point.
It is a further object of the present invention to provide a wireless communication system in which data can be transferred between a mobile node and a fixed access point through other mobile nodes.