1.Multiuser Channel Estimation

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Block I. Block II. Block III. Antenna. Matrix Products. Data. Multiuser Detection. Decoder. Block IV. Correlation Matrices (Per Bit). Inverse. Detected Bits. A 0 H A 1 O(K 2 N). Delay. M U X. d. Decision Feedback. Multistage Detection (Per Window). Multiple Users. R br - PowerPoint PPT Presentation

Text of 1.Multiuser Channel Estimation

  • IMPLEMENTING CHANNEL ESTIMATION ALGORITHMS ON HARDWARE Sridhar Rajagopal, Suman Das and Joseph R. Cavallaro1.Multiuser Channel Estimation5.Task Decomposition3 .Base-station Receiver2.Third Generation Communication Systems6. Exploiting Pipelining and Parallelism7. Meeting Real-Time Requirements4. DSP Implementation TI TMSC6701, projected at 250 MHz. 1953 cycles available for detection of 1 bit assuming data rate of 128 Kbps. In-depth profiling to find bottlenecks. Multiuser Detection needs to performed continuously to meet data rate requirementsChannel Estimation can be updated less frequentlySingle DSP does not meet real-time requirementsMultiuser Detection - Bottleneck! Multiuser Channel EstimationNeed to know the Channel for proper detectionDelays and Amplitudes of each user and each pathSend sequence of known bits (Pilot / Preamble)Pilot Code-Multiplexed with DataPilot Time-Multiplexed with DataMultiuser DetectionUse knowledge of channel for reliable detection

    Multiple UsersMultiple Access InterferenceMultipath DelaysFadingAdditive White Gaussian NoiseChannel EffectsMultiuser Channel Estimation MethodsSubspace Maximum Likelihood Joint Estimation and DetectionComputationally EfficientBetter BER Performance W-CDMA - Wideband CDMA (5 MHz) 3G Communication SystemsIntegrating Multimedia CapabilitiesQuality of Service (QoS) Multi-rate ServicesHigher Data Rates 2048,384,144 KbpsN - Spreading Code LengthK - Number of UsersA - [A0 A1] - Channel EstimateD - Multiuser Detection Windowr - Received bits of K usersCan be Data or Pilot (with interference/fading)b - Known Pilot bits at the receiverd - Detected Data bitsData - Data synchronized with d ParametersAccelerating the blocks in Multistage Detection to meet real-time requirements.Graph shows the data rates achieved by different levelsof acceleration for multiuser detection.Task ATask B

    Spreading Factor

    Number of Bits / Frame

    Data Rate




    1024 Kbps



    128 Kbps



    16 Kbps

    ECE Industrial Affiliates, Rice University 1999