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Uncoordinated Optical Multiple Access using IDMA and Nonlinear TCM

UCLA Electrical Engineering Department-Communication Systems Laboratory. Uncoordinated Optical Multiple Access using IDMA and Nonlinear TCM. PIs: Eli Yablanovitch, Rick Wesel, Ingrid Verbauwhede, Bahram Jalali, Ming Wu Students whose work is discussed here:

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Uncoordinated Optical Multiple Access using IDMA and Nonlinear TCM

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  1. UCLA Electrical Engineering Department-Communication Systems Laboratory Uncoordinated Optical Multiple Access using IDMA and Nonlinear TCM PIs: Eli Yablanovitch, Rick Wesel, Ingrid Verbauwhede, Bahram Jalali, Ming Wu Students whose work is discussed here: Juthika Basak, Herwin Chan, Miguel Griot, Andres Vila Casado, Wen-Yen Weng

  2. OCDMA Coding Architecture 1.2 Gbps 2 Gbps 60 Mbps Reed Solomon (255, 237) Trellis Code 1/20 int OR channel 93 Mbps 5 other tx Correct extra errors Separate different transmitters Asychronous Access code Communication Systems Laboratory

  3. The system Reed Solomon (255, 237) sync Trellis Code 1/20 int 5 other tx For uncoor-dinated access To distinguish between users Initial synchroni-zation of tx-rx pair OR channel To bring final BER to 1e-9 BER Tester Reed Solomon (255, 237) Trellis Code 1/20 int Bit align sync Large feedback loop for rx synchronization Communication Systems Laboratory

  4. Experimental Setup FPGA XMIT 1 AMP AMP Optical MOD AMP FPGA XMIT 2 AMP Optical MOD AMP AMP Optical MOD FPGA XMIT 3 Optical to Electrical AMP AMP Optical MOD FPGA XMIT 4 D Flip-Flop AMP AMP Optical MOD FPGA XMIT 5 AMP AMP Optical MOD FPGA XMIT 6 FPGA RCV 1 Communication Systems Laboratory

  5. Six Users Communication Systems Laboratory

  6. Communication Systems Laboratory

  7. Probability of amplitudes for 6-users Communication Systems Laboratory

  8. Asynchronous users Communication Systems Laboratory

  9. Receiver Ones Densities for this code. Communication Systems Laboratory

  10. Performance results • FPGA implementation: • In order to prove that NL-TCM codes are feasible today for optical speeds, a hardware simulation engine was built on the Xilinx Virtex2-Pro 2V20 FPGA. • Results for the rate-1/20 NL-TCM code are shown next. • Transfer Bound: • Wen-Yen Weng collaborated in this work, with the computation a Transfer Function Bound for NL-TCM codes. • It proved to be a very accurate bound, thus providing a fast estimation of the performance of the NL-TCM codes designed in this work. Communication Systems Laboratory

  11. 6-user BER 10-5 C-Simulation Performance Results: 6-user OR-MAC Communication Systems Laboratory

  12. 6-user BER 10-5 6-user OR-MAC:Simulation, Bound, FPGA (no optics) Communication Systems Laboratory

  13. Results: observations • An error floor can observed for the FPGA rate-1/20 NL-TCM. • This is mainly due to the fact that, while theoretically a 1-to-0 transition means an infinite distance, for implementation constraints those transitions are given a value of 20. • Trace-back depth of 35. • Additional coding required to lower BER to below 10-9. Communication Systems Laboratory

  14. Dramatically lowering the BER : Concatenation with Outer Block Code • Optical systems deliver a very low BER, in our work a is required. • Using only a NL-TCM, the rate would have to be very low. • A better solution is found using the fact that Viterbi decoding fails gradually, with relatively high probability only a small number of bits are in error. • Thus, a high-rate block code that can correct a few errors can be attached as an outer code, dramatically lowering the BER. Block-Code Encoder NL-TCM Encoder Z-Channel Block-Code Decoder NL-TCM Decoder Communication Systems Laboratory

  15. Reed-Solomon + NL-TCM : Results • A concatenation of the rate-1/20 NL-TCM code with (255 bytes,247 bytes) Reed-Solomon code has been tested for the 6-user OR-MAC scenario. • This RS-code corrects up to 8 erred bits. • The resulting rate for each user is (247/255).(1/20) • The results were obtained using a C program to apply the RS-code to the FPGA NL-TCM output. Communication Systems Laboratory

  16. C-Simulation Performance Results: NL-TCM only, 100-user OR-MAC Communication Systems Laboratory

  17. Current Status • Decreased optical speed from 2 to 1.2 Gbps because FPGA can’t keep up at 2 Gbps. • Single Amplifier Results: • 2-Amplifier system in progress. • We need more amplifiers for six users. Last night, worked for 4 users, but two users need more power. Communication Systems Laboratory

  18. Results • Demonstrated scalability to 100 users in a C simulation. • Working on our 6-user optical implementation. Communication Systems Laboratory

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