Cross Layer Optimization Techniques

9 May 2008

Department of Electrical Engineering & Computer Science

EECS 983 Class Project

Ramya NaiduSarvesh Kumar.V

Asifuddin MohammadPiyush Upadhyay

9 May 2008 Cross Layer Optimization Techniques 2

Cross Layer Optimization TechniquesOutline

• Introduction• UDP segment Size adaptation• Knobs and Dials Simulation Framework• TCP segment size adaptation

– Issues– Effect of ARQ on TCP performance– Effect of FEC/ARQ on TCP performance

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Cross Layer Optimization TechniquesIntroduction

• Cross Layer Optimization [CLO]:– An approach that coordinates protocol

behavior at different layers with a goal to maximize the overall performance [4]

– Knobs and Dials• Dials pass information from lower to

higher layer• Knobs pass info from higher to lower layer

• CLO Technique considered: – Transport layer with Physical Layer

interaction– Segment size with BER

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Cross Layer Optimization Techniques

Outline• Introduction• UDP segment Size adaptation• Knobs and Dials simulation framework• TCP segment size adaptation

– Issues– Effect of ARQ on TCP performance– Effect of ARQ/FEC on TCP performance

• Hardware Implementation

9 May 2008 Cross Layer Optimization Techniques 5

Cross Layer Optimization Techniques UDP Segment Size adaptation

• Adapt UDP segment size as BER of the link changes

• Initial Analysis of effect on throughput• Simulation parameters

– Number of nodes 2– CBR/UDP– Rate 1Mbps– Link Capacity 1Mbps– Simulation time 50s– Error Model Uniform

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Cross Layer Optimization Techniques UDP Segment Size adaptation

9 May 2008 Cross Layer Optimization Techniques

Cross Layer Optimization TechniquesUDP Segment Size adaptation

• Initial Analysis with UDP lead to two directions• Building the knobs and dials simulation

framework• Study the complications when extending this

scheme to TCP

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Cross Layer Optimization Techniques

Outline• Introduction• UDP segment Size adaptation• Knobs and Dials Simulation Framework• TCP segment size adaptation

– Issues– Effect of ARQ on TCP performance– Effect of ARQ/FEC on TCP performance

• Hardware Implementation

Knobs and Dials Simulation Framework

Knobs and Dials Simulation Framework

• Step 1: Node 1 Sends packets to Node 2

9 May 2008 Cross Layer Optimization Techniques

Knobs and Dials Simulation Framework

9 May 2008 Cross Layer Optimization Techniques

• Step 2: Computer BER from received packets and update the dial matrix

Knobs and Dials Simulation Framework

9 May 2008 Cross Layer Optimization Techniques

• Step 3: Write the BER from dial matrix to the dial packet (Out of band signaling)

Knobs and Dials Simulation Framework

• Dial Packet format used

• Choice of Inband Vs Out of band signalling has to be made• Dial Packet format should be decided if out of band

signaling is used

9 May 2008 Cross Layer Optimization Techniques

Knobs and Dials Simulation Framework

• Step 4: Read the BER value from the dial packet and write it to the dial matrix of node 1

9 May 2008 Cross Layer Optimization Techniques

Knobs and Dials Simulation Framework

• Step 5: Read the BER value from the dial matrix of N1 and compute the new segment size

9 May 2008 Cross Layer Optimization Techniques

Knobs and Dials Simulation Framework

• Step 6: Write the new segment size to the knob matrix (An unused knob) and transmit with this size

9 May 2008 Cross Layer Optimization Techniques

Simulation Challenges

• Creating a new signaling protocol for out of band signaling <solved>

• Building knob and dial hashes at each node <solved>

• Accessing packet headers <solved>• Obtaining a Tcl handle to C++ class variables

to enable per packet processing <solved>• Per packet processing <Yet to be solved>

9 May 2008 Cross Layer Optimization Techniques

Knobs and Dials Simulation Framework

• Issues to be addressed:– Complexity at each node– Overhead due to extra signaling (Out of band) – Loss of Signaling packets– RTT of the link– Changes to framework in case of multi-hop network

with multiple interfaces at nodes

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Cross Layer Optimization Techniques

Outline• Introduction• UDP segment Size adaptation• Knobs and Dials Simulation Framework• TCP segment size adaptation

– Issues– Effect of ARQ on TCP performance– Effect of ARQ/FEC on TCP performance

• Hardware Implementation

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Cross Layer Optimization Techniques TCP Segment Size adaptation

• TCP with Link layer reliability – Effect of ARQ on TCP– Effect of FEC/ARQ on TCP

• TCP without Link layer reliability

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Cross Layer Optimization Techniques Effect of ARQ on TCP

• ARQ persistency and TCP RTO– ARQ with low persistency does not improve TCP

throughput– High persistency improves TCP performance [2]– Problems of ARQ with high persistency [1]

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Cross Layer Optimization Techniques Effect of ARQ/FEC on TCP

• Throughput improvement is more significant due to ARQ than due to FEC in an ARQ/FEC scheme [2]

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Cross Layer Optimization Techniques TCP without link layer reliability

• LL retransmission does not always improve TCP throughput [1]

• This motivates the study of segment size adaptation

Simulation Challenges

• Implementing FEC in ns2 < Yet to be solved >• Hacking the ns2 error model code<Yet to be

solved>

9 May 2008 Cross Layer Optimization Techniques

Future Work

• Extending the simulations to multi-hop scenarios

• Study the impacts of cross-layering signaling• Extending the framework for other knobs and

dials

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Cross Layer Optimization Techniques

Outline• Introduction• UDP segment Size adaptation• TCP segment size adaptation

– Issues– Effect of ARQ on TCP performance– Effect of ARQ/FEC on TCP performance

• Hardware Implementation

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References

• [1] Kim Hyogon, Changhoon Han. "Reducing TCP response time in face of wireless uplink losses." IEEE VTC'01 1(2001): 262-266.

• [2] A.Chockalingam, Michael Zorzi. "Wireless TCP Performance with Link Layer FEC/ARQ." IEEE ICC'99 2(1999): 1212-1216.

• [3] Jin-Hee Choi, Jin-Ghoo Choi,Chuck Yoo. "Dynamic Segment Size Adjustment for TCP performance in cellular networks." ICEE'05 (2005): 95-96.

• [4] A.Warrier,L.Le and I.Rhee. “Cross-Layer Optimization made practical”. Broadnets 2007(Invited paper)

• [5] Gary J. Minden, Joseph B. Evans, Leon Searl, Daniel DePardo, Victor R. Petty, Rakesh Rajbanshi, Jordan Guffey, Qi Chen, Timothy Newman, Frederick Weidling, Dinesh Datla, Brett Barker, Megan Peck, Brian Cordill, Alexander M. Wyglinski, and Arvin Agah, “KUAR: A Flexible Software-Defined Radio Development Platform,” Second IEEE Symposium on New Frontiers in Dynamic Spectrum Access Networks (Dublin, Ireland), April 2007.

References

• [6]Minden, G.J.   Evans, J.B.   Searl, L.S.   DePardo, D.   Rajbanshi, R.   Guffey, J.   Qi Chen   Newman, T.R.   Petty, V.R.   Weidling, F.   Peck, M.   Cordill, B.   Datla, D.   Barker, B.   Agah, A. ” COGNITIVE RADIOS FOR DYNAMIC SPECTRUM ACCESS - An Agile Radio for Wireless Innovation” IEEE communication Magazine, May 2005, Vol. 45,issue 5.

9 May 2008 Cross Layer Optimization Techniques