Cognitive Radio with Unidirectional Transmitter and Receiver - - PowerPoint PPT Presentation

NCP Bi NCP Bi-

• weekly Meeting

weekly Meeting

Cognitive Radio with Unidirectional Transmitter and Receiver Cooperation

Speaker: Shih-Chun Lin* Co-Authors: Pin-Hsun Lin# , Hsuan-Jung Su# and Yao-Win Hong* * Institute of CE, National Tsing-Hua University

#Dept. of EE, National Taiwan University

Date : Apr. 9, 2010

Outline Outline

• Introduction and System Model
• Cognitive Radio with Unidirectional

Transmitter (UT) Cooperation

• Cognitive Radio with Unidirectional

Transmitter and Receiver (UTR) Cooperation

• Numerical examples
• Conclusion

NCP Bi NCP Bi-

• weekly Meeting

weekly Meeting

Introduction and System Model Introduction and System Model

Interference Interference-

• Mitigation Based

Mitigation Based Cognitive radio Cognitive radio

[Interference avoidance] [Interference mitigation]

[Courtesy from N. Devroye, P. Mitran and V. Tarokh, Limits on Communication in a Cognitive Radio Channel," IEEE Communications Magazine, 2006]

Simultaneously Silence

Cognitive radio with coexistence constraint Cognitive radio with coexistence constraint

• A. Jovicic and P. Viswanath, “Cognitive radio: An information-theoretic perspective,” IEEE
• Trans. Inform. Theory, vol. 55, no. 9, pp. 3945–3958, Sept. 2009

3 4 2 PR-TX PR-RX CR-TX CR-RX 1

• Jovicic & Vishwanath’s cognitive radio signaling:

– PR’s signal non-causally known at the CR-TX – Single user decoder at the PR RX – CR-TX relays PR’s signal to maintain PR’s rate, and uses the dirty paper coding (DPC) to cancel the interference from PR

DPC

Motivation : (cont Motivation : (cont’ ’d) d)

• Pros of [JV09] : Optimal when |H24

|< |H23 |

• Cons of [JV09] :

– ` ` Noisy’’ relaying of the PR’s signal may be inefficient when |H24 | is large or CR’s power is high – Assume |H12 |> > |H14 | to neglect decoding delay at Node 2 – The complexity of practical dirty paper coding (DPC) implementations may be still inhibitive in current communication systems.

NCP Bi NCP Bi-

• weekly Meeting

weekly Meeting

Cognitive Radio with Unidirectional Cognitive Radio with Unidirectional Transmitter (UT) Cooperation Transmitter (UT) Cooperation

Unidirectional Transmitter (UT) Cooperation Unidirectional Transmitter (UT) Cooperation

• Three phase protocol (Half-duplex Node 2 and 3)
• Add two phases to JV scheme :

– Phase 1 : Listening – Phase 3 : “Clean” relaying

UT Cooperation UT Cooperation

• Phase 1: Node 2 listens and decodes PR’s message
• Phase 2: Node 2 transmits the DPC encoded signal
• Phase 3: Node 2 relays “clean” signals

DPC with SI X1 relay X1

Transmitter Side Transmitter Side-

• Information Constraint

Information Constraint

• Successful listening

at Phase 1 : To attain enough mutual information at Node 2

R1 (Rate of PR)

Coexistence Constraint Coexistence Constraint

• Although the SNR at the three phases are different, from

[CP89], Node 4 can still use single user decoder with rate R1 if the “average SNR” over three phases are large enough

• [JV06] neglected the listening phase, thus the conventional

Shannon coding theorem worked

R1

• T. M. Cover and S. Pombra, “Gaussian feedback capacity,” IEEE Trans. Inform. Theory,
• vol. 35, no. 1, pp. 37–43, Jan. 1989.

Achievable rate of UT Achievable rate of UT

• If the system parameters selected meet previous

constraints, then by the classical DPC result, the following rate is achievable by UT

NCP Bi NCP Bi-

• weekly Meeting

weekly Meeting

Cognitive Radio with Unidirectional Cognitive Radio with Unidirectional Transmitter and Receiver (UTR) Transmitter and Receiver (UTR) Cooperation Cooperation

Unidirectional transmitter and receiver Unidirectional transmitter and receiver (UTR) cooperation (UTR) cooperation

• Besides UT, the UTR cooperation has advantages

– Diversity from H34 – Works when H12 is low and decode at Node 2 fail – CR user uses the conventional MAC encoder/decoder instead

• f the complex DPC

UTR Cooperation UTR Cooperation

• Phase 1: Node 2 and Node 3 listens and decodes

PR’s message

• Phase 2: Node 2 transmits
• Phase 3: Node 2 and Node 3 relays “clean” signals

Conventional Gaussian signal relay X1

Achievable rate of UTR

• From [LU06], the transmitted signal in Phase 2 is optimal for

MAC with common msg = > using conventional MAC decoder

• If the system parameters selected meet constraints as those

in UT, we can use the achievable rate of the MAC channel to find the UTR achievable rate.

MAC with common message

• N. Liu and S. Ulukus, “Capacity region and optimum power control strategies for fading Gaussian

multiple access channels with common data,” IEEE Trans. Commun., pp 1815–1826, 2006.

NCP Bi NCP Bi-

• weekly Meeting

weekly Meeting

Numerical examples Numerical examples

• UT V.S. JV
• UTR V.S. JV

Environments (UT V.S. JV) Environments (UT V.S. JV)

3 4 2 1

1+ j 1/4H12 H12

2

H12

5 . 1

H12 H12

2 / 1

• Same average power:

Total power of Node 2 & 3 of UTR at Phase 3 meets

• |H24

|> |H34 | UT is better than UTR

UT V.S. JV UT V.S. JV

Environments (UTR V.S. JV) Environments (UTR V.S. JV)

3 4 2 1

1+ j 1/4H12 H12

2

H12

2 2

H12 H12

2 / 1

Same average power with JV: : |H34 |> |H24 | UTR is better than UT

UTR V.S. JV UTR V.S. JV

Conclusion Conclusion

• We proposed two new cooperation methods for

CR system with coexistence constraint , i.e, the UT and UTR cooperation

• The key ideas are

– relay “clean” signals in the last phase – Receiver cooperation

• Numerical examples confirm the rate gains of the

proposed protocols

Future works Future works

• Parameter optimization
• High SNR analysis
• Extensions to ergodic Rayleigh fading channels

Thanks and Questions !