FAST OPPORTUNISTIC DISTRIBUTED RESOURCE REALLOCATION FOR ESTABLISHED CONNECTIONS IN A MULTIHOP NETWORK
BACKGROUND OF THE INVENTION  1. Field of the Invention
 The present invention relates in general to a multihop network that implements a reactive routing protocol which is used by nodes to continuously adapt resources of the multihop network in response to topology changes in the multihop network so as to optimize the performance of a connection between a source node and a destination node.
 2. Description of Related Art
 A problem inherent with multihop networks (wireless ad hoc networks) is that they have a topology that changes over time because the nodes are mobile which can lead to a connection breaking between two nodes relaying traffic for a specific connection. There are several other reasons why a topology changes over time in addition to moving nodes. For example, topology changes may occur even without nodes moving such as variations caused by moving objects on which radio waves reflect or changes in the communication media. These topology changes include, for example, channel variations (of own and/or interfering channels), traffic pattern changes, transmit pattern changes and resource allocation changes. To adapt to these topology changes, the multihop networks can employ either a proactive routing protocol or a reactive routing protocol. In multihop networks that employ a proactive routing protocol, the topology changes are typically adapted to by continuously updating the routing paths between the nodes. And, in multihop networks that employ a reactive routing protocol, the routing paths between the nodes are first set up in what is usually denoted the route discovery phase. Once the path setup is complete, the route maintenance phase takes over. This phase is responsible for maintaining paths between active source/destination pairs in the face of topological changes, for example when two nodes on the path towards the destination node have moved apart too far which causes the connection to break then a route repair procedure (part of the route maintenance phase) is invoked as a rescue operation to try and repair the connections between the nodes. If this rescue operation is not successful, then a new route discovery round has to be performed. Examples of reactive routing protocols include AODV (Ad Hoc on Demand Distance Vector) and DSR (Dynamic Source Routing) that were developed within IETFs MANET workgroup are described in the following articles:
 C. Perkins, E. M. Royer and S. R. Das, "Ad Hoc On-demand Distance Vector Routing", RFC 3561, July 2003.
 D. Johnson and D. Maltz, "Dynamic Source Routing in Ad Hoc Wireless Networks", draft-ietfmanet-dsr-09.txt, April 2003.
 The contents of these articles are hereby incorporated by reference herein.
 Although these routing protocols generally work well they still have a drawback in which they fail to do enough to optimize the performance of a connection between two nodes. Accordingly, there is a need for a
multihop network that implements a new reactive routing protocol which optimizes the performance of a connection between two nodes. This need and other needs are satisfied by the multihop network, node and method of the present invention.
BRIEF DESCRIPTION OF THE INVENTION
 The present invention includes a multihop network that implements a reactive routing protocol which enables nodes to continuously adapt network resources in a distributed/opportunistic manner in response to a topology change within the multihop network so as to optimize the performance of a connection between a source node and a destination node. The types of resources that can be adapted include for example: (1) a route; (2) a channel; and/or (3) physical layer parameters. And, the different types of topology changes that can occur include for example: (1) movement of a node; (2) quality variations in a channel between the source node and the destination node; (3) changes in traffic patterns in the multihop network; (4) changes in transmit patterns (e.g., power, beamforming direction) in the multihop network; and (5) changes in resource allocations in the multihop network (100, 400).
BRIEF DESCRIPTION OF THE DRAWINGS
 A more complete understanding of the present invention may be had by reference to the following detailed description when taken in conjunction with the accompanying drawings wherein:
 FIG. 1 is a block diagram that illustrates an exemplary multihop network which has nodes that implement a reactive routing protocol in accordance with the present invention;
 FIG. 2 is a flowchart illustrating the steps of a preferred method for implementing the reactive routing protocol within the multihop network of FIG. 1 in accordance with the present invention;
 FIG. 3 is a block diagram of an exemplary beacon that can be transmitted from an active node within the multihop network of FIG. 1 in accordance with step 202 of the method of FIG. 2; and
 FIGS. 4A-4D are block diagrams illustrating different ways the reactive routing protocol can be used to adapt a route between a source node and a destination node in the multihop network of FIG. 1.
DETAILED DESCRIPTION OF THE DRAWINGS
 Referring to FIG. 1, there is disclosed a block diagram of an exemplary multihop network 100 that has nodes 102a, 1026 . . . 102a (17 shown) which implement a reactive routing protocol in accordance with method 200 of the present invention. As shown, the multihop network 100 has multiple nodes 102a, 1026 . . . 102a that operate in a wireless medium where traffic sent between two nodes 102a and 102m (for example) is called a flow 104 (one shown). The node originating the transfer of data in a flow 104 is called a source node 102a and the node terminating the data is called a destination node 102m. The multihop network 100 can have zero, one or a multitude of flows 104 at each instant between any two nodes 102a, 1026 . . . 102a. Each flow 104 is carried in a connection 106 where only one