Simulation of Real under Both S-ALOHA and R T Random Access Protocols Ziad A. El-Sahn, Julien Penon, and Leslie A. Rusch Centre d'optique, Photonique et Laser (COPL) Département de Génie Électrique et de Génie Informatique Université Laval, Québec, QC, GK 7P4. ziad.el-sahn.@ulaval.ca http://agora.ulaval.ca/~ziels 2 November 2006 December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada Motivation Most research and experiments in OCDMA have focused on the physical layer. However, a few authors have examined the optical link layer. Simulation Data Link Layer Physical Layer Experiment 2 November 2006 December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada 2
Presentation Outline Experiment Protocols 2 November 2006 December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada Optical CDMA Networks Users transmit simultaneously and asynchronously Soft-capacity on demand (large no. of codes) An alternative to WDMA and TDMA for PONs Sub-Gb/s rates for FTTH applications Potentially low cost December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada 4 2
Attractions of Efficient use of bandwidth All CDMA advantages Incoherent sources Simple electronics Balanced detection Encoding with FBGs Low cost December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada 5 Basic Idea of Frequency Encoding 2 2 A( ω) Power Transmitted Encoded Light Balanced Detection A( ω) A( ω) D. Zaccarin, and M. Kavehrad, IEEE Photonics Technology Letters. (99) December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada 6
Encoding Using FBGs 6 5 4 2 2 4 5 6 2 4 5 6 Z.Wei, H. M. H. Shalaby, and H. G. Shiraz, IEEE J. Lightwave Technology. (200) S. Ayotte, M. Rochette, J. Magné, L. A. Rusch, and S. LaRochelle, IEEE J. Lightwave Technology. (2005) Broadband Light Source (CW) Chirped FBG 2 4 5 6 J. Penon, S. Ayotte, L. A. Rusch, and S. LaRochelle, Conf. on Lasers and Electro-Optics (CLEO). (2006) December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada 7 7 x 622 Mbps Transmission Data Generation Pattern Generator EDF Source BPF EAM BPF Error Detector LPF RF Amplifier Detection Process V+ -2 2 VOD - db DEC# 0 0 0 0 C-DEC# 0 0 0 VOA 0 db 5 db 542.5 nm 542.5 nm ~ 0 nm ~ 0 nm December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada 8 4
Back-to-Back Performance BER 0-2 0-4 0-6 0-8 0 interferers interferer 2 interferers interferers 4 interferers 5 interferers 6 interferers Intensity Noise 0-0 Error Free -0-28 -26-24 -22-20 -8-6 -4 Received power by desired user [dbm] 2 2 - NRZ PRBS at 622 Mbps (Back-to-Back) December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada 9 The Need for MAC in OCDMA Coordination between users Higher throughput Lower delay Avoid the complexity in PHY layer Support of differential QoS Resource allocation and DBA December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada 0 5
ALOHA CDMA Protocol - p o - p r D. Raychaudhuri, IEEE Transactions on Communications. (98) December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada The R T Protocol (-A)(- ) Acknowledgement Mode Reception Mode H. M. H. Shalaby, IEEE J. Lightwave Technology. (2004) December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada 2 6
Throughput and Delay Simulation December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada Throughput vs. Offered Load 7 Near Optimal R T, -25 dbm Throughput, (packets/slot) 6 5 4 2 R T, -0 dbm ALOHA CDMA, -25 dbm ALOHA CDMA, -26 dbm ALOHA CDMA, -27 dbm ALOHA CDMA, -28 dbm Traditional S-ALOHA The R T provides ~ 5 db improvement over ALOHA CDMA The R T is more stable in terms of throughput 0 0 2 4 5 6 7 Offered load, (packets/slot) December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada 4 7
Delay vs. Throughput 5 4.5 0.4 4 0.2.5 0. ALOHA CDMA, -25 dbm ALOHA CDMA, -26 dbm ALOHA CDMA, -27 dbm R T, -25 dbm R T, -0 dbm ALOHA CDMA,.045-25 dbm ALOHA CDMA, -26 dbm.04 ALOHA CDMA, -27 dbm ALOHA CDMA, -28 dbm.05.0 R T, -25 dbm R T, -0 dbm Large delay at low power Delay (slots) Delay (slots) 0.082.5 0.06 2 Delay (slots).025 The R T is more stable in terms of delay.02 0.04.5 0.02 0.5 0 0 2 4 5 6 7 0 2 4 5 6 7 0 Throughput (packets/slot) Throughput (packets/slot) 0 2 4 5 6 7 ALOHA CDMA Throughput (packets/slot).05.0.005 Acceptable delay slot = ~.6 μs R T Protocol December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada 5 Summary We simulated the throughput and delay of an experimental 7 622 Mbps system. Both ALOHA CDMA and R T protocols were considered. The R T provides a 5 db improvement over the ALOHA CDMA. The R T is more stable in terms of throughput and delay compared to the ALOHA CDMA. December 5, 2006 IEEE LEOS Annual 2006, Montréal, Québec, Canada 6 8