Multimedia and Mobile Communication Laboratory. Outline Multimedia and Mobile Communication...

Multimedia and Mobile Communication Laboratory

Exploring Spectrum-aware On-demand Multi-path Routing

in Multi-radio Multi-hop Cognitive Radio Networks

XIAOFEI WANGTAEKYOUNG KWON, YANGHEE CHOI

MMLAB, SEOUL NATIONAL UNIVERSITY

2008.01.15


Introduction to CRN

Multi-radio Multi-path Routing in CRN

Evaluation

Conclusion

Outline


Introduction to CRN


Evaluation

Conclusion

Outline


1. Introduction to CRN

Cognitive Radio NetworkDynamic spectrum accessOpportunistically utilize spectrum resourcesActive monitoring, tuning, working


Primary Users (PU), Secondary Users (SU)○ PU can start transmission anytime○ SU has to use bands occupied by no PU

Art of SU’s life in CRN : Jump and fill in the blanks!


Introduction to CRN


Evaluation

Conclusion

Outline


Everything becomes difficult in “multi-hop”No one knows what happens 1-hop away!Much tougher in CRN

2. Multi-radio Multi-path

A

B CD E


Fundamental issues in multi-hop CRNRoute ConnectivityAchievable End-to-end ThroughputPU’s insertion and SU’s recovery

Let’s us multi-radio multi-path strategyTo provide higher probability of route survivalTo achieve times of end-to-end throughput“Spectrum-wise disjoint paths”To avoid intra-path & inter-path interference


Multiple Cognitive Radios1 for control signaling, M for data traffic

○ “Share” mode○ “Switch” mode

1 + N bands, N ≥ M Multiple Paths

Split transmission mannerDuplicated transmission manner


Multi-path in Multi-radio Multi-hop CRN


Spectrum PoolAll parameters of licensed/unlicensed bandsRadio and Band Usage Table (RBT)

B: Several available bands I: Number of flows that are using this band in this SUN: Number of flows that are using this band within 1- hop

neighborsR: Which radio is using this band in this SU“X” will be used to indicate PU occupation

Periodical exchange of hello message


A Multi-radio Multi-hop CRN ExampleExisting SU flows:

Current PU traffics:○ P1 : b1○ P2 : b4○ P3 : b5


Route Discovery (DSR-like)Attach its own RBT into the RREQ

○ New RREQ_ID or old RREQ_ID but with hop count ≤ previous one rebroadcast (multipath)

RREQ with RBTS

S

A B

D

FE

RREQ with RBTS RREQ with RBTS, E

RREQ with RBTS, A

RREQ with RBTS, E, F

RREQ with RBTS, A, B


RREQs arrives at DFirst RREQ

○ Primary Path (PP)Later RREQs

○ Candidate Path (CP)

Radio & band selectionPreference:

○ Idle radio > “Share” > “Switch”RBTs should be updated after

every comparison!


○ RBTS & RBTA RBTS’ & RBTA’

○ RBTA’ & RBTB RBTA’’ & RBTB’

○ RBTB’ & RBTD RBTB’’ & RBTD’ …

○ …


Path Evaluation Metrics:Hop Count:

○ NPP: Hop count of PP

○ NCP: Hop count of CP

Band Overlapping Factor: FCP

α: weight factor○ balancing how we emphasize the jointness of

paths


Finally, two paths are established:○ Primary Path:

○ Secondary Path: ( selected from CPs)

Data Striping:○ Packets will be splitted and transmitted

throughput different paths simultaneously

Dual path: odd / even


Recovery:

b1

S

F

P4

E

b4

Db3

b1

1

2 1 31

2

XStop transmitting to me, go other path!

Who is involved in this PU insertion?

New radio&band is assigned, let’s keep going

E3 ---- 3F2

b23


Introduction to CRN


Evaluation

Conclusion

Outline


3. Evaluation

MPMR vs. MPSR(SMR) vs. SPMRNS2802.11a, 6Mbps, UDP7 orthogonal channels from 11a:

○ 36, 44, 52, 60, 149, 157, 1653 radios2 paths


Maximum End-to-end Throughput:○ MPMR achieves much high end-to-end throughput○ MPSR uses single radio, low throughput○ SPMR uses one path, limited high throughput

MPSR( )


Recovery Evaluation○ P4 begins at 3 sec.○ E detects the insertion○ is interrupted○ E and F re-select b2

○ ~120 ms

E3 ---- 3F2


There is a degradation of throughput, for allMPSR achieves low throughput ( let’s ignore it…)SPMR transmission is terminatedMPMR keeps high speed transmission

MPMR SPMR MPSR(SMR)


Introduction to CRN


Evaluation

Conclusion

Outline


4. Conclusion

Multi-path Routing in Multi-radio Multi-hop Cognitive Radio NetworksRoute DiscoveryRadio/Band SelectionRoute Recovery

FinallyHigher route connectivityHigher end-to-end throughput


CurrentlyMassive simulationsDetailed evaluation

Future WorkMore efficient radio & band selection algorithmMore evaluation metrics of pathsFaster route recovery of SS’s trafficTry to cancel the extra radio for control signal

○ This is the most practical problem!


Thank You!

Q&A

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