Wireless communication systems are well known in the art. In traditional wireless communication systems, real time services are typically implemented using a circuit switched infrastructure in conjunction with at least one dedicated wireless resource. A current trend in the industry, however, is the use of so-called packet switched infrastructures in support of wireless communication systems. In particular, the use of the Internet Protocol (network) is important to the communications of a wireless communication system utilizing packet switched infrastructure.
In such a system, wireless computers or communication units typically communicate with a wireless or radio access network (RAN) that in turn communicates with a packet switched networking forming a part of the infrastructure, such as the Internet or World Wide Web. Often, the target of the communication unit, such as a mobile computer, is a client, such as a mobile subscriber unit, coupled to the packet switched network. For the mobile computer to establish communications with another communication unit, the mobile computer needs an IP address, which is used to identify the source of communications. When radio coverage to the RAN is unavailable, the communication unit, such as the mobile computer, is unable to retrieve an IP address from the packet switched network; however, the mobile computer still requires an IP address to communicate with either the mobile subscriber unit or with the packet switched network regardless of the state of radio coverage.
Currently, solutions to address the need of the mobile computer to have connectivity to the mobile subscriber unit regardless of RAN coverage are imperfect. One solution uses Network Address Port Translation (NAPT) to allow the mobile computer and the mobile subscriber unit to communicate regardless of RAN coverage. A serious limitation of such a solution is that many applications and protocols associated with either the mobile computer or the mobile subscriber unit do not operate with NAPT. Thus, regardless of whether RAN coverage is available, many applications and protocols associated with the mobile computer or the mobile subscriber unit will not operate. Another solution requires that the mobile computer and the mobile subscriber unit maintain multiple connections to the packet switched network so that if one connection is unavailable, then another connection will still allow for communications. Such a solution, known in the art as multi-homing, is expensive and requires duplicating communication connections.
As a result, there exists a need for a method and apparatus for maintaining communications when a radio access network link is unavailable.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to each other. Further, where considered appropriate, reference numerals have been repeated among the figures to indicate identical elements.