1. Cross-Layer Protocol
최 종 훈

2. Contents What is cross-layer protocol? Why cross-layer protocol?
Cross-layer Design
Cautionary Perspective
Example
References

3. What is cross-layer protocol?
Layered architecture
Hierarchical
Independent
Forbid direct communication between nonadjacent layers
Cross-layer architecture
Violate the reference layered architecture
Dependent
Direct communication or sharing variables between nonadjacent layers
Performance gains
Figure 1. The layered OSI architecture

4. Why cross-layer protocol?
Characteristics of wireless systems
Unique problems created by wireless links
Small-scale channel variations
Large-scale channel variations
Possibilities of opportunistic communications on wireless links
Time-varying channel quality
New modalities of communication offered by the wireless medium
Broadcast nature of the channel

5. Cross-layer Design
Figure 2. Illustrating the different kinds of cross-layer design

6. Cross-layer Design Creation of new interfaces
Upward information flow
Downward information flow
Back-and-forth information flow
Merging of adjacent layers
Design coupling without new interfaces
Vertical calibration across layers

7. Cross-layer Interactions
Figure 3. Architectural blueprints for wireless communications

8. Cross-layer Interactions
Direct communication between layers
Runtime information sharing
Visible variables (e.g. protocol headers)
A shared database across layers
Service of storage/retrieval of information
Suitable for vertical calibration across layers
Completely new abstractions
New way to organize the protocols
Great flexibility

9. Cross-layer Feedback Link / MAC layer Network layer Transports layer
The number of retransmissions at the link layer
QoS (i.e. acceptable delay, packet loss)
Network layer
IP hand-off begin/end information
Transports layer
Packet loss data at TCP
TCP retransmission timer information
Application layer
Throughput

10. Cross-layer Feedback Physical layer Link/MAC layer Network layer
Battery status
Adapt its coding/modulation
Link/MAC layer
Control transmit power for reducing bit-error rate
Network layer
Bit-error rate information in order to switch another network interface with lower bit-error-rate
Application layer
Channel condition information
Various standard coding techniques for multi-media applications

11. Cross-layer Feedback Link / MAC layer Physical layer Network layer
Error control mechanisms based on current channel conditions
Frame length using channel condition information at PHY
Network layer
IP hand-off – delay
Reduce hand-off latency
Transport layer
TCP round-trip time or retransmission timer at transport layer
Retransmission information at link layer
Application layer
Different QoS requirements – priority
FEC/ARQ

12. Cross-layer Feedback Network layer Physical layer Link / MAC layer
Bit-error rate
Switch to another network interface
Link / MAC layer
Hand-off information
Reduce hand-off latency
Transport layer
Manipulate retransmission timer and avoid unnecessary packet retransmission
Application layer
Information about acceptable delay or throughput
Select the appropriate interface

13. Cross-layer Feedback Transport layer Link / MAC layer Network layer
Information about packets pending retransmission
Adjust round-trip time (RTT)/retransmission timeout (RTO)
Network layer
Hand-off information
Avoid timeout
Application layer
QoS requirements
Manipulate receiver window
Packet loss and throughput information
Adapt sending rate

14. Cross-layer Feedback Application layer Physical layer Link / MAC layer
Channel condition information
Various standard coding techniques for multi-media applications
Link / MAC layer
Prioritize frames
Network layer
Switch the network interface
Transport layer
Tune the receiver window
Higher throughput

15. Cautionary Perspective
Undesirable consequences on overall system performance
The importance of architecture
Stability
Robustness
Spaghetti design – hard to upkeep
Longer-term considerations
Longevity
Per unit cost

16. Example Ksentini, A., Naimi, M., Gueroui, A.,
“Toward an Improvement of H.264 Video Transmission over IEEE e through a Cross-Layer Architecture,”
IEEE Communications Magazine,
vol. 44, Issue 1, Jan. 2006, pp

19. Example Results analysis in EDCA in DCF mean loss rate is 16%

20. Example Results analysis in QoS architecture in EDCA in DCF
mean loss rate is 2%
in EDCA
mean loss rate is 13.75%
in DCF
mean loss rate is 27%

21. Example
Results analysis

22. References
Srivastava, V., Motani, M., “Cross-layer design: a survey and the road ahead,” IEEE Communications Magazine, vol. 43, Issue 12, Dec. 2005, pp
V. T. Raisinghani and S. Lyer, “Cross-Layer Design Optimizations in Wireless Protocol Stacks,” Computer Communications (Elsevier), vol. 27, no. 8, May 2004, pp
Shakkottai, S., Rappaport, T.S., Karlsson, P.C., “Cross-layer design for wireless networks,” IEEE Communications Magazine, vol. 41, Issue 10, Oct. 2003, pp
Kawadia, V., Kumar, P.R., “A cautionary perspective on cross-layer design,” IEEE Wireless Communications [see also IEEE Personal Communications], vol. 12, Issue 1, Feb. 2005, pp
Sedaghati-Mokhtari, Nasser, Bojnordi, Mahdi Nazm, Yazdani, Nasser, “Cross-Layer Design: A New Paradigm,” Communications and Information Technologies, ISCIT '06. International Symposium on Oct Sept , pp. 183 – 188.
Ksentini, A., Naimi, M., Gueroui, A., “Toward an Improvement of H.264 Video Transmission over IEEE e through a Cross-Layer Architecture,” IEEE Communications Magazine, vol. 44, Issue 1, Jan. 2006, pp