Digital Signal Processing Reference
In-Depth Information
Fig. 6.1
Focus of this chapter is on the run time control challenge for cognitive radio. Actions are
taken based on a monitoring of the environment (channel and application state) and based on this
information the optimal configuration point is selected based on a DT model
Fig. 6.2
Centrally controlled
point-to-multipoint LAN
topology with uplink and
downlink communication
6.2 Anticipation Through Design Time Modeling
In this section, we follow the design steps considered in the design flow proposed
in Chap. 3 to achieve the required performance at minimal QoS for the cognitive
radios. Consider a wireless network as in Fig.
6.2
where multiple nodes are cen-
trally controlled by an AP. Each node (such as a handheld video camera) desires
to transmit or receive frames in real-time and it is the AP's responsibility to assign
channel-access grants. The resource allocation scheme within the AP specifies each
user's system configuration settings for the next transmission based on the feedback
of the system state from the current transmission. It must ensure that the nodes meet
their performance constraints by delivering their data in a timely manner while con-
suming minimal energy. The problem is first stated formally and a specific example
is provided further in this chapter. The network consists of
n
flows
F
1
,F
2
,...,F
n
}
with periodic delay-sensitive frames or jobs. For notational simplicity, we assume
a one-to-one mapping of flows to nodes, but the method is also applicable to more
flows per node.
The design time steps, the focus of this chapter, are discussed in the next subsec-
tions. First, it is required to define the control dimensions or the available flexibility.
Next, the system scenarios need to be determined or what scenarios the cognitive
radio is expected to encounter. Then, the relevant cost, resource and quality dimen-
sions need to be defined. They define what the cognitive radio should adapt for.
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