1. ARQ Proxy (for WiFi networks) Ischia island, Italy Sept. 11, 2007 Dzmitry Kliazovich Nadhir Ben Halima Fabrizio Granelli University of Trento, Italy

2. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 TCP over Infrastructure WiFi LL-ACKTCP Data Mobile Node (MN) Base Station (BS) Channel Contention LL-ACKTCPACK WiFi (IEEE 802.11) IP Network TCP Data PHY Headers LL Headers TCP ACK PHY Headers LL Headers Legend: Transmitted at Basic rate Transmitted at Data rate Application Data Acknowledgements at different layers

3. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 ARQ Proxy - Approach Idea: Substitute the transmission of TCP ACK packets with a short MAC layer request on the radio link for multilayer ARQ overhead reduction

4. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 ARQ Proxy - Approach TCP Data PHY/LL Headers LL-ACK Fixed Host (FH) IP Network ARQ Proxy MACARQ ClientMACTCP TCP Data Mobile Node (MN) Base Station (BS) TCP o Access TCP header o Get IP addr, port, etc. o Generate TCP ACK & store o Compute TCP ACK identification index Generate TCP ACK Index TCP DataTCPACK TCP ACK Index

5. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 ARQ Proxy – Packet Identification Hash values Frame Sequence Numbers Mobile Node (MN) Base Station (BS) LL-ACK PHY Header LL Header TCP data Sequence Control Address 3Address 4 Fragment Number B3B4 Bits: 412 B15 B0 Sequence Number Link layer ACK (LL-ACK) or

6. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 ARQ Proxy - Benefits Performance and System Capacity Increase LL-ACK TCP Data Mobile Node (MN) Base Station (BS) Channel Contention LL-ACK TCPACK WiFi (IEEE 802.11) IP Network TCP Data PHY Headers LL Headers TCP ACK PHY Headers LL Headers Overhead reduction

7. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 ARQ Proxy - Benefits Reduced RTT (Round Trip Time) Fixed Host (FH) IP Network Mobile Node (MN) Base Station (BS) TCP DataTCPACK Medium Access + TCP ACK Transmission over wireless channel

8. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 ARQ Proxy - Benefits End-to-end TCP semantics are maintained Fixed Host (FH) IP Network Mobile Node (MN) Base Station (BS) TCP DataTCPACKLL-ACK

9. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 ARQ Proxy - Benefits Higher channel error rates tolerance Fixed Host (FH) IP Network Mobile Node (MN) Base Station (BS) TCPACK No TCP ACK over wireless channel Wired channel (BER = 10 -6 to 10 -8 ) Wireless channel (BER = 10 -3 to 10 -1 )

10. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 ARQ Proxy - Benefits Mobility & Incremental deployment Fixed Host (FH) IP Network Mobile Node (MN) Base Station (BS) No TCP state related information is maintained ARQ Proxy ARQ Client

11. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 ARQ Proxy - Benefits Performance and system capacity increase Reduced RTT (Round Trip Time) End-to-end TCP semantics are maintained Higher channel error rates tolerance Full mobility support Incremental deployment & Co-existence

12. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 ARQ Proxy - Limitations TCP ACKs are not substituted:  During connection establishment and connection termination packets (identified by SIN and FIN flags)  For TCP ACK encapsulated into TCP data packet in case of bidirectional data transfer  For Duplicate TCP ACKs  TCP ACK advertising exhausted receive buffer resources (rwnd field)

13. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 Evaluation Results Simulation Setup  Ns2 simulator with ARQ proxy extensions  IEEE 802.11b physical layer, no RTS/CTS  Bottleneck buffer: 700 packets  TCP NewReno flows  Results averaged over 10 runs Fixed Host Mobile Node Base Station 100 Mb/s, 15 ms IEEE 802.11b @ 11 Mb/s ARQ Proxy ARQ Client

14. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 Evaluation Results Throughput performance Improvement: 20% Improvement: up to 100% VoIP and Multimedia Applications TCP file transfer, Ethernet MTU

15. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 Evaluation Results Round Trip Time (RTT) improvement Order of milliseconds

16. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 Evaluation Results High error rate tolerance

17. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 Motivation for Scenario Choice Why link layer ARQ as a feedback channel? Why TCP?  Accounts for more than 85% of Internet traffic* Why Infrastructure network scenario?  Over 95% of wireless links are on the last mile [*] C. Fraleigh at el. “Packet-level traffic measurements from the Sprint IP backbone,” IEEE Network, vol. 17, no. 6, pp. 6 – 16, Nov.-Dec. 2003.

18. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 Other Operation Scenarios  Single-hop Ad hoc network Fixed Network Infrastructure Fixed Source  Multi-hop network  Infrastructure network with relays ARQ Proxy

19. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 ARQ Proxy for 3G LTE Key features  Evolved radio access: OFDM, multiple antenna techniques  Evolved architecture: fewer nodes, reduced latency, low cost  Evolved networking: All-IP architecture, shared resources 3G Long-Term Evolution (LTE)

20. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 ARQ Proxy for 3G LTE ARQ Proxy: Use Hybrid ARQ (HARQ) feedback to substitute TCP ACK packets on the radio channel Hash values for packet identification TCP MAC TCP Data TCPACK ARQ Client HARQACK+ Generation Output queue Sniff TCPACK Hash value HARQ Protocol stack at the receiver

21. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 Evaluation: 3G LTE scenario Setup  Ns2 with Enhanced UMTS Radio Access Extensions (EURAE)  eNB and RNC are combined into a single node  Rayleigh fading with 300 meters between UE and eNB  Encapsulation overhead: TCP (20 bytes), IP (20 bytes), PDCP (1 byte), RLC (2 bytes), and PHY CRC (2 bytes)  Hash value size: 32 bits  TCP NewReno sources Metrics  Throughput and Round Trip Time (RTT) performance with different error rates

22. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 Evaluation: 3G LTE scenario Round Trip Time (RTT) Hash value errors

23. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 Current Activities and Future Work ARQ proxy material (Available)  ARQ proxy for WiFi (IEEE 802.11)  ARQ proxy for 3G LTE (Super-3G)  EU patent-pending D. Kliazovich, F. Granelli, S. Redana, and N. Riato, “Cross-Layer Error Recovery Optimization for 3G LTE Systems,” EP 07425087.9 D. Kliazovich, F. Granelli, S. Redana and N. Riato, “Cross-Layer Error Control Optimization in 3G LTE,” IEEE Global Communications Conference (GLOBECOM), Washington, DC, U.S.A, December 2007.

24. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 Current Activities and Future Work ARQ proxy material (Coming soon…)  ARQ proxy for WiMAX (IEEE 802.16) Adaptation and system level simulations  Proposal to 3GPP standardization group  Under consideration for next generation equipment produced by Nokia Siemens Network (NSN)

25. Dzmitry Kliazovich (kliazovich@dit.unitn.it) Sept. 11, 2007 Thank you!