1. Presented by Mohamad Haidar, Ph.D. May 13, 2009 Moncton, NB, Canada
Power Management and Bandwidth Allocation in a Cognitive Wireless Mesh Network
Presented by
Mohamad Haidar, Ph.D.
May 13, 2009
Moncton, NB, Canada

2. Table of Content Introduction Problem statement Proposed Approach
Problem Formulation
Parameters and Assumptions
Simulation Results
Conclusion
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3. Introduction Cognitive Radio:
It is a transceiver device that is able to understand and react to its operating environment.
It is aware of channel conditions and activity.
It changes its operating parameters to enable reliable, interference free, communications.
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4. Problem Statement
Measurements consistently show that some bands are under-utilized in some areas at some times.
Careful consideration should be given to the Primary User (PU) in order not to induce additional interference.
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5. Proposed Approach Heuristic algorithm:
Sort Secondary Users (SUs) in ascending order according to highest BW request. This could be justified as giving a higher priority to SUs with high BW requests (Video and Voice vs. Data)
Add SUs to the licensed spectrum as long as the interference level at the PU does not exceed a pre-defined threshold value and BW requests of SUs do not exceed the PU BW.
In order to allow spectrum efficiency, power transmitted at SUs is dropped down as long as the data rate communication is still supported for the communication link between any two SUs.
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6. Problem Formulation
NLIP Model:
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7. Parameters and Assumptions
Locations of SUs and PUs are known.
Communication activities between SUs are known.
SUs operate on 2.4 GHz and PU operate on 700 MHz.
Centralized infrastructure: The algorithm is run at the central server and decisions are multicast to intended SUs in order to instruct them about their respective frequencies or channels (along with the BW allocation on the licensed spectrum), and their transmitted power levels.
Average data rate requests of each SU is known from which BW request can be calculated from the Shannon-Hartley theorem.
Exchange of control information and signaling between SU nodes is beyond the scope at this moment.
Information about the existence of the PU at the particular frequency and time is already known.
SUs are assumed to be equipped with dual-antenna. Smooth switching between one antenna and the other.
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8. Results
Scenario 1
Tx Power at all SU nodes and PU = 20 dBm
PU BW = 12 MHz
Interference threshold is -80 dBm
SU Transmitter/Receiver Number
SU Transmitter Power (dBm)
SU Bandwidth Request (MHz)
3 / 1 8 2
14 / 13
1.9
13 / 11 11
1.8
1 / 16 6
0.4
tolerated interference at the PU is dBm < -80 dBm
BW Utilization ≈ 50%
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9. Results (cont’d) Scenario 2
SU Transmitter/Receiver Number
SU Transmitter Power (dBm)
SU Bandwidth Request (MHz)
12 / 7 3
4.80
14 / 13
4.10
13 / 11 7
3.00
tolerated interference at the PU is dBm < -80 dBm
BW Utilization ≈ 99.5%
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10. Results (cont’d)
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11. Conclusion and Future Work
power management and spectrum utilization algorithm has been presented to allow SUs to opportunistically access the licensed spectrum.
Future work:
Control information and signalling
Mobility of SUs
Distributed approach rather than a centralized one.
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