...This topic addresses some of the basic concepts for use of the license-exempt
spectrum in addition to considering some of the issues presented by this approach
to satisfying the needs of the public safety community.
In the event of localized incidents or even massive disasters, reliable, immediate
and efficient public safety communications between agencies and first responders
is crucial. The rapid deployment of seamless voice communications is mission critical
for first responders who may also need layouts or blueprints of buildings, the transfer
of real-time video at the scene, or geographical and other broadband data to carry
out missions effectively. However, ubiquitous coverage of anywhere and anytime public
safety communications has always been desired but more difficult in reality to accomplish.
Further, such critical communications must go beyond just voice-oriented communications
and now tend towards multimedia broadband applications that require higher bandwidths
during peak operations in real-time. .....
A wireless mesh network is a communications network composed of radio access nodes
organized in an overlapping mesh topology where each node relays or routes information
from other nearby nodes.1 Because of its nature as an infrastructure-less
distributed communications architecture for relaying traffic, the size and the range
of a network can be dynamically elastic but it simultaneously requires small transmit
power levels to restrain potential interference. ....
WLAN systems have become increasingly popular.....These applications bring attention
to the use of WLANs as an alternative method of public safety communications either
from an infrastructure perspective or as an emergency ad hoc method to gain communications
at the scene of an incident.
Even though the WLAN operational range is relatively short due to the 1 Watt transmit
power limitation and the interference restrictions, the capacity for high data rates
can be useful and has the additional advantage of lower cost. The wireless mesh
networking technology extends WLAN's ability to span wider end-to-end range. Mesh
networking not only extends range but also improves overall network capacity when
more nodes are added. For a mesh network architecture, two schemes are well developed:
Infrastructure-mesh and Client-mesh. These two types of mesh networks can be combined
to form a hybrid network. In fact, Client-mesh is also known as "Ad-hoc" where each
node relays other traffic to an access node (usually one of Infrastructure-mesh
nodes) that routes traffic outside the Ad-hoc network, most likely IP-based Internet
Recently, public safety agencies across the country have been able to leverage the
widely successful private sector wireless technology as a complementary solution
for disaster and municipal public safety communications.4 Examples include
Oklahoma City, Oklahoma; Silicon Valley, CA; Minneapolis, MN; and many others.5