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

Dzmitry Kliazovich Sept. 11, 2007 TCP over Infrastructure WiFi LL-ACKTCP Data Mobile Node (MN) Base Station (BS) Channel Contention LL-ACKTCPACK WiFi (IEEE ) 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

Dzmitry Kliazovich 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

Dzmitry Kliazovich 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

Dzmitry Kliazovich 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

Dzmitry Kliazovich 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 ) IP Network TCP Data PHY Headers LL Headers TCP ACK PHY Headers LL Headers Overhead reduction

Dzmitry Kliazovich 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

Dzmitry Kliazovich 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

Dzmitry Kliazovich 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 = to ) Wireless channel (BER = to )

Dzmitry Kliazovich 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

Dzmitry Kliazovich 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

Dzmitry Kliazovich 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)

Dzmitry Kliazovich Sept. 11, 2007 Evaluation Results Simulation Setup  Ns2 simulator with ARQ proxy extensions  IEEE b 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 11 Mb/s ARQ Proxy ARQ Client

Dzmitry Kliazovich Sept. 11, 2007 Evaluation Results Throughput performance Improvement: 20% Improvement: up to 100% VoIP and Multimedia Applications TCP file transfer, Ethernet MTU

Dzmitry Kliazovich Sept. 11, 2007 Evaluation Results Round Trip Time (RTT) improvement Order of milliseconds

Dzmitry Kliazovich Sept. 11, 2007 Evaluation Results High error rate tolerance

Dzmitry Kliazovich 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

Dzmitry Kliazovich 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

Dzmitry Kliazovich 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)

Dzmitry Kliazovich 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

Dzmitry Kliazovich 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

Dzmitry Kliazovich Sept. 11, 2007 Evaluation: 3G LTE scenario Round Trip Time (RTT) Hash value errors

Dzmitry Kliazovich Sept. 11, 2007 Current Activities and Future Work ARQ proxy material (Available)  ARQ proxy for WiFi (IEEE )  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 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.

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

Dzmitry Kliazovich Sept. 11, 2007 Thank you!