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for further development and implementation. In
the rest of this chapter we explore these areas and
apply our results for efficient video distribution
over WiMAX networks.
network is either to be told or to constantly poll
for new nodes. Although WiMAX has a large
bandwidth capability, the poll method will cre-
ate a greater amount of overhead than the first
method (which only requires a single broadcast
message from the base station). This should take
the form of a list of all client stations complete
with their IP and MAC addresses. This list gets
added to every time a new client station registers
with the base station. The network manager can
poll nodes either individually, in a broadcast or
at the request of the node (station initiated poll).
This research will adopt a unicast polling method
(individually poll) in order to maintain the current
list of active nodes.
While any WiFi node could act as the base
station, the implementation of an NMS within
the base station of WiMAX makes the hardware
required for a base station different to that of a
client unit. So the number of nodes able to become
the base station will be restricted and not every
node will try and become the base station.
WiMAX Network
Management System
WiMAX has a defined Network Management
System that is instantiated in the base station. The
protocols for resource allocation and manage-
ment are already defined in the 802.16 standard
(Wood, 2006), therefore this research does not
propose to modify them or create new ones, but
instead to utilise them as they are. These protocols
include network registration, authentication and
resource allocation. Priority traffic will therefore
be sent using a Non-Real-Time Polling Service
QoS algorithm, Real-time traffic will be sent us-
ing the Unsolicited Grant Service or Real-Time
Polling Service based on the current utilisation
of the network. If the network is heavily utilised
then UGS services may have to be changed to
rtPS services in order to maintain the network
throughput in an efficient way. Finally, Best Effort
traffic will obviously use the Best Effort service
for transmission.
WiMAX Network Topology
and Simulation Results
The first and simplest simulation scenario of
WiMAX network is the scenario with thee users
connected to the BS that are sending data served
by different service classes (Tarter, 2008). The
uplink throughput is analysed (Figure 1).
The three users simultaneously transmit infor-
mation with the following QoS and data rates:
2Mbps data rate for the UGS (unsolicited grant
service), 1Mbps served by the real-time Pooling
Service (rtPS) and 20kbps served by best effort
service (BE).
As presented WiMAX does guarantee QoS by
setting a certain service type. The following sec-
tions present a new technique for efficient video
distribution over WiMAX networks based on the
feature of the QoS reliability.
WiMAX Node Attrition Strategy
WiMAX 802.16 is not designed to support emer-
gency services and as such has a weakness similar
to WiFi, in that it relies on a central base station. In
contrast to WiFi where packets can flow between
client stations directly, the base station in WiMAX
is required in all communications. This will change
with the advent of the 802.16j standard of WiMAX,
but for the time being, WiMAX networks cannot
be used in the mesh network architecture. They
are limited to the star topology.
As data transfer between nodes is only via the
base station, the only way for client nodes within
a network to discover other nodes within the same
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