1. Arsany Guirguis and Mustafa El-Nainay Alexandria University
Channel Selection Scheme for Cooperative Routing Protocols in Cognitive Radio Networks
Arsany Guirguis and Mustafa El-Nainay
Alexandria University
Presented by: Arsany Guirguis January 29th, 2017

2. Agenda Introduction Related Work System Model CSCR Details
Performance Evaluation
Conclusion

3. Cognitive Radio Networks (CRNs): What and Why?
Spectrum is scarce.
Spectrum is underutilized.
Primary Users (PUs) and Secondary Users (SUs).
Recently, some cooperation-based protocols were proposed to work in the CRNs [1].
SUs can construct cooperative groups to enhance the transmission quality at the destination and null the transmission at PUs.
Existing cooperation-based techniques ignored choosing the best channel to use.

4. Motivating Example Cooperative group of 3 SUs – 6 PUs - 3 channels.
Which channel is the best?
All group members should operate on the same channel (frequency).

5. Related Work
A lot of approaches to choose the best channel, each with different metric, in the context of CRNs [2].
Formulated as an optimization problem:
Minimum transmission power without being considered a noise [3].
Maximize the achievable capacity [4].
A brute force search for the best channel
The least end-to-end delay [5].
The least congested channel with PUs [6].

6. The Need to Extend
All (cooperative) group nodes should operate on the same channel.
Some important parameters were not taken into consideration in the formulations proposed in the mentioned publications.
PUs activities.
Switching delay.
SUs flows interference on each other.

7. What we propose
CSCR: a Channel Selection scheme for Cooperative Routing protocols in CRNs.
The channel selection algorithm aims at choosing the channel that achieves:
the best achievable capacity for SUs flows,
the least interference between SUs flows and each other,
the least impact on surrounding PUs, and
the minimum channel switching delay.

8. System Assumptions SUs can sense and detect PUs activities.
Slow fading wireless channels. Channel coefficients remain constant for short time.
Channel switching delay depends on the difference between source and target channels.
Channels are non-overlapping.
PUs and SUs are stationary.
SUs know their locations, their neighbors’ locations, and the final destination location.

9. Adding CSCR to Route Discovery Phase
Each group in the network chooses independently in the group construction phase the optimal channel for data transmission.
Based on that, the routing metric is given by:
𝐿𝐶 𝑖𝑗 = 𝐶 𝑖𝑗 𝑁 𝑛 +𝛽 𝑁 𝑓 − 𝑁 𝑛 ∗ 𝑃 𝑝𝑢 ∗ 𝑇 𝑠𝑤𝑖𝑡𝑐ℎ
𝑃 𝑝𝑢 : Activity probability of surrounding PUs.
𝑇 𝑠𝑤𝑖𝑡𝑐ℎ : Switching delay cost.
Other symbols are related to Undercover protocol [1].
We extended the cooperation-based protocols in two ways: 1- Update the routing metric. 2- Update the flow of sequences to adapt to choosing the best channel.

10. The group construction part
CSCR Algorithm Flow

11. To count valid channels
CSCR Algorithm Flow
The valid channels are those whose using will not affect the other running secondary flows on the same node.

12. Loop on all channels and check if they are valid
CSCR Algorithm Flow

13. If valid, proceed to gp construction
If invalid, add to a list
CSCR Algorithm Flow

14. If no valid*, try invalid. Else, finish
CSCR Algorithm Flow
* rare case

15. Simulation Setup Used NS2 [7] for evaluation.
SUs and PUs are randomly distributed in the deployment area.
ON-OFF model for PUs with exponentially-distributed parameters.
Nodes run IEEE MAC protocol.
Compare against Undercover [1] (cooperation- based) and LAUNCH [8] (channel-aware).

16. Results: Changing Number of SUs
- Increasing the number of SUs increases the goodput and control overhead.
- CSCR outperforms other protocols with a limited overhead.
(a) Goodput
(b) Control Overhead

17. Results: Changing Number of PUs
- Increasing the number of PUs decreases the goodput (CSCR is better).
- Delay follows goodput (due to queuing) except LAUNCH (interweave model).
(a) Goodput
(b) End-to-end Delay

18. Conclusion
We propose CSCR which is a channel selection scheme for cooperative routing protocols in Cognitive Radio Networks.
Choosing the channel is done in the route discovery phase along with the group construction.
Results show that CSCR always outperforms existing protocols in terms of network goodput, in some cases, by more than 150%, end-to-end delay, and the packet delivery ratio.
The cooperative group and the operating channel are selected in a way that increases the achievable capacity, decreases the interference between secondary users flows, avoids the primary users activity areas, and decreases the channel switching delay.
Simulation experiments are carried using NS2.
Specifically, the proposed scheme can enhance the network goodput, in some cases, by more than 150%, as compared to other related protocols.

19. References
[1] Arsany Guirguis, Mohammed Karmoose, Karim Habak, Mustafa El-Nainay, and Moustafa Youssef, “Cooperation-based routing in cognitive radio networks,” arXiv preprint arXiv: , [2] Elias Z Tragos, Sherali Zeadally, Alexandros G Fragkiadakis, and Vasilios A Siris, “Spectrum assignment in cognitive radio networks: A comprehensive survey,” Communications Surveys & Tutorials, IEEE, vol. 15, no. 3, pp. 1108–1135, [3] Deepak R Joshi, Dimitrie C Popescu, and Octavia A Dobre. Joint spectral shaping and power control in spectrum overlay cognitive radio systems. Communications, IEEE Transactions on, 60(9): , [4] Haythem Ahmad Bany Salameh. Throughput-oriented channel assignment for opportunistic spectrum access networks. Mathematical and Computer Modelling, 53(11): , [5] Won-Yeol Lee and Ian F Akyldiz, “A spectrum decision framework for cognitive radio networks,” IEEE TMC, vol. 10, no. 2, pp. 161–174, [6] Wooseong Kim, Andreas J Kassler, Marco Di Felice, and Mario Gerla. Urban-x: towards distributed channel assignment in cognitive multi-radio mesh networks. In Wireless Days (WD), 2010 IFIP, pages IEEE, [7] S. Floyd S. McCanne. NS network simulator. os.asp. [8] Karim Habak, Mohammed Abdelatif, Hazem Hagrass, Karim Rizc, and Moustafa Youssef, “A location-aided routing protocol for cognitive radio networks,” in ICNC. IEEE, 2013, pp. 729–733.

20. Thank You!