ARQ Proxy for Cross-Layer Error Control Optimization in 3G LTE 26-30 November 2007 Washington, DC, USA ARQ Proxy for Cross-Layer Error Control Optimization in 3G LTE Dzmitry Kliazovich Fabrizio Granelli University of Trento, Italy Simone Redana Nicola Riato Nokia Siemens Networks S.p.A

Fabrizio Granelli (granelli@dit.unitn.it) Outline 3G Long-Term Evolution Background and features TCP over 3G LTE ARQ Proxy Multi-layer ARQ optimization Packet identification techniques Operation in WiFi and WiMAX Conclusions 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Fabrizio Granelli (granelli@dit.unitn.it) 3G LTE background 3G LTE (Long-Term Evolution) - an attempt to bring 4G technology into 3G spectrum Reason: challenge other advanced technologies (like WiMAX) meeting high data rate service demands 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

3G LTE: Targeted features High data rates 100 Mbps in DL (for 20 MHz band) – Efficiency 5 bps/Hz 50 Mbps in UL (for 20 MHz band) – Efficiency 3.5 bps/Hz Low Latency Between terminal and Radio control device (RAN): < 10 ms Recovery from idle mode: < 50 ms From standby mode: < 100 ms Mobility 15 km/h – optimized performance 120 km/h – high performance 350 km/h (or 500 km/h) – establish communication Flexible Channel Bandwidth 1.25 MHz, 5MHz, 10 MHz, 15 MHz and 20 MHz 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

3G LTE: Key Technologies Evolved Architecture Reduced number of nodes Low delay Evolved Radio Access OFDM for spectrum efficiency Multiple Antenna Techniques Evolved Link Layer One TCP/IP datagram mapped into one RCL packet ARQ + HARQ for error recovery 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Fabrizio Granelli (granelli@dit.unitn.it) TCP over 3G LTE Evolved Packet Core File Server Enhanced Node B User Equipment (eNB) (UE) IP TCP Data Header PHY/LL IP TCP Data TCP data packet Headers Header HARQ ACK TCP ACK Uplink Scheduling Request Unlink Grant HARQ ACK IP Header TCP PHY/LL Headers 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Fabrizio Granelli (granelli@dit.unitn.it) ARQ Proxy - Approach Idea: Substitute the transmission of TCP ACK packets with a short MAC layer request on the radio link 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Fabrizio Granelli (granelli@dit.unitn.it) ARQ Proxy - Approach Enhanced Node B (eNB) Evolved Packet Core User Equipment (UE) File Server TCP ARQ Proxy MAC MAC ARQ Client TCP TCP Data TCP Data PHY / LL Headers TCP Data Access TCP header Get IP addr, port, etc. Generate TCP ACK & store Generate TCP ACK TCP ACK Index TCP ACK Index HARQ ACK + TCP Index Compute TCP ACK identification index TCP ACK 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

ARQ Proxy – Packet Identification 3G LTE: Hash values WiFi: Frame Sequence Numbers PHY Header LL TCP data Sequence Control Address 3 Address 4 Fragment Number B3 B4 Bits: 4 12 B15 B0 Sequence Number Hybrid ARQ (HARQ-ACK) Enhanced Node B (eNB) or User Equipment (UE) HARQ ACK 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Fabrizio Granelli (granelli@dit.unitn.it) ARQ Proxy - Benefits Performance and System Capacity Increase Evolved Packet Core File Server Enhanced Node B User Equipment (eNB) (UE) IP TCP Data Header PHY/LL IP TCP Data Headers Header HARQ ACK Overhead reduction PHY/LL IP TCP IP TCP Headers Header ACK Header ACK HARQ ACK 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Scheduling + TCP ACK Transmission over radio channel ARQ Proxy - Benefits Reduced RTT (Round Trip Time) TCP Data File Server Evolved Packet Core Enhanced Node B User Equipment (eNB) (UE) TCP ACK Scheduling + TCP ACK Transmission over radio channel 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Fabrizio Granelli (granelli@dit.unitn.it) ARQ Proxy - Benefits End-to-end TCP semantics are maintained TCP Data File Server Evolved Packet Core User Equipment (UE) Enhanced Node B (eNB) TCP ACK Hash value 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

ARQ Proxy - Benefits Higher channel error rates tolerance Wired channel (BER = 10-6 to 10-8) Wireless channel (BER = 10-3 to 10-1) File Server Evolved Packet Core User Equipment (UE) Enhanced Node B (eNB) TCP ACK Hash value is smaller than TCP ACK 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

No TCP state related information is maintained ARQ Proxy - Benefits Mobility & Incremental deployment No TCP state related information is maintained File Server Evolved Packet Core User Equipment (UE) Enhanced Node B (eNB) 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Fabrizio Granelli (granelli@dit.unitn.it) 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 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

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) 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Fabrizio Granelli (granelli@dit.unitn.it) Evaluation Results Simulation Setup Enhanced UMTS Radio Access Extensions (EURAE) for Ns2 simulator To make it look like 3G LTE Node B and RNC are combined Modified link layer One-to-one mapping of IP packets into RLC PDUs Physical layer HSDPA with trace data for UE within 300 meters from eNB Header overhead: TCP (20 bytes), IP (20 bytes), PDCP (1 byte), RLC (2 bytes) File Server Evolved Packet Core User Equipment (UE) Enhanced Node B 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it) (eNB)

Fabrizio Granelli (granelli@dit.unitn.it) Evaluation Results Round Trip Time (RTT) improvement Order of milliseconds 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Fabrizio Granelli (granelli@dit.unitn.it) Evaluation Results No need to introduce additional error recovery for hash values 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Motivation for Scenario Choice Why link layer ARQ/HARQ as a feedback channel? Why TCP? Accounts for more than 85% of Internet traffic* Why cellular 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. 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Other Operation Scenarios ARQ Proxy ARQ Proxy . . . Single-hop Ad hoc network Multi-hop network ARQ Proxy Fixed Source Fixed Network Infrastructure Cellular network with relays 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Fabrizio Granelli (granelli@dit.unitn.it) ARQ Proxy for WiFi 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 IEEE 802.11b @ 11 Mb/s 100 Mb/s, 15 ms Fixed Host Base Station Mobile Node ARQ Proxy Client 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

VoIP and Multimedia Applications TCP file transfer, Ethernet MTU Evaluation Results Throughput performance Improvement: 20% Improvement: up to 100% VoIP and Multimedia Applications TCP file transfer, Ethernet MTU 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Fabrizio Granelli (granelli@dit.unitn.it) Evaluation Results Round Trip Time (RTT) Error rate tolerance 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Current Activities and Future Work ARQ proxy material (Available) ARQ proxy for 3G LTE (Super-3G) ARQ proxy for WiFi (IEEE 802.11) EU patent D. Kliazovich, N. Ben Halima, and F. Granelli, “Cross-Layer Error Recovery Optimization in WiFi Networks,” Tyrrhenian International Workshop on Digital Communication (TIWDC), Ischia island, Naples, Italy, September, 2007. D. Kliazovich, F. Granelli, S. Redana, and N. Riato, “Cross-Layer Error Recovery Optimization for 3G LTE Systems,” EP 07425087.9 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

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) 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)

Fabrizio Granelli (granelli@dit.unitn.it) Thank you! 26 - 30 November 2007 Fabrizio Granelli (granelli@dit.unitn.it)