Evaluation of Wireless Mesh Network Handoff Approaches for Public Safety and Disaster Recovery Networks
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I. INTRODUCTION
Temporary communications infrastructure is often required
by the Public Safety and Disaster Recovery (PSDR) workers
when they arrive at the scene of a disaster. Wireless mesh
networks are ideal for establishing this temporary communications
infrastructure [1] as they provide broadband connectivity
over a wide area and can be rapidly deployed (due to their selfconfiguring
and self-healing functionality). In wireless mesh
networks there are typically two categories of node present:
mesh clients and mesh routers [2].


II. BACKGROUND
In order for a client device to change its access router, a
handoff must occur at layer-2 of the network stack. A layer-
3 hand-off may also be required if the new access router is
in a different subnet. Layer-3 handoffs are quite specific to
the protocol used, whereas layer-2 handoffs all modify the
default handoff behavior described in IEEE 802.11 a/b/g (the
predominant networking standards used by existing wireless
mesh networks). As such, we only cover layer-2 handoffs in
this section.


III. PSDR NETWORK STRUCTURE AND
REQUIREMENTS
In Public Safety and Disaster Response scenarios, an hierarchical
network structure is used to ensure scalability.
At the bottom layer of the hierarchy are Personal Area
Networks (PAN). These correspond to small wireless networks
connecting various sensors and communication devices together
on a PSDR worker.


IV. EVALUATION OF EXISTING CLIENT HANDOFF
APPROACHES
In this section of the paper we use the requirements given in
Section III to evaluate handoff approaches operating at layer-
2, layer-3 and those that are operate across these layers (i.e.
are cross-layer). We do not include the approaches used within
commercial mesh networking products as the necessary details
are not readily available.


VI. CONCLUSION
The SAFECOM Statement of Requirements reports [5][4],
issued by the US Department of Homeland Security, provide
a strict set of performance requirements for Public Safety
and Disaster Response networks. We evaluated existing client
device handoff techniques for wireless mesh networks using
a subset of these requirements, namely: (1) handoffs of client
devices between IANs should not lead to packet loss, (2) the
handoff can only induce less than 14ms latency, and (3) the
approach must be scalable.