1.Multiuser Channel Estimation

1. Block I Block II Block III Antenna Matrix Products Data Multiuser Detection Decoder Block IV Correlation Matrices (Per Bit) Inverse Detected Bits A0HA1 O(K2N) Delay M UX d Decision Feedback Multistage Detection (Per Window) Multiple Users Rbr O(KN) + RbbAH = Rbr O(K2N) Demod -ulator A0HA0 O(K2N) b d Channel Estimation MUX MUX Rbr O(KN) O(DK2Me) Pilot M UX data’ b (known) RbbAH = Rbr O(K2N) A1HA1 O(K2N) d Rbb O(K2) pilot The Wireless Channel AHr O(KND) data Noise + MAI Channel Estimation Base Station Task A Task B Direct Path Reflected Paths Multiuser Detection Time User 1 User 2 Block III Block IV Matrix Products A0HA1 O(DK2Me) AHr A0HA0 A1HA1 1 1 d data K K 8.Real-Time Implementation FPGA High Performance Processors VLSI DSP 5 x 10 Data Rates for Different Levels of Pipelining and Parallelism 3 2.5 (Parallel A) (Parallel+Pipe B) (Parallel A) (Pipe B) (Parallel A) B 2 A B Sequential A + B Data Rates 1.5 Data Rate Requirement = 128 Kbps 1 Joint Work with Praful Kaul (UIUC) Parthasarathy Ranganathan Dr. Sarita Adve (UIUC) 0.5 DSP + FPGA 0 9 10 11 12 13 14 15 Number of Users IMPLEMENTING CHANNEL ESTIMATION ALGORITHMS ON HARDWARESridhar Rajagopal, Suman Das and Joseph R. Cavallaro 1.Multiuser Channel Estimation 3 .Base-station Receiver 5.Task Decomposition Channel Effects • Multiple Users • Multiple Access Interference • Multipath Delays • Fading • Additive White Gaussian Noise Parameters • N - Spreading Code Length • K - Number of Users • A - [A0 A1] - Channel Estimate • D - Multiuser Detection Window • r - Received bits ofKusers • Can beDataor Pilot(with interference/fading) • b - KnownPilotbits at the receiver • d - DetectedDatabits • Data’ - Datasynchronized with d • Multiuser Channel Estimation Methods • Subspace • Maximum Likelihood • Joint Estimation and Detection • Computationally Efficient • Better BER Performance 6. Exploiting Pipelining and Parallelism 4. DSP Implementation • Multiuser Channel Estimation • Need to know the Channel for proper detection • Delays and Amplitudes of each user and each path • Send sequence of known bits (Pilot / Preamble) • Pilot Code-Multiplexed with Data • Pilot Time-Multiplexed with Data • Multiuser Detection • Use knowledge of channel for reliable detection • 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 requirements • Channel Estimation • can be updated less frequently • Single DSP does not meet real-time requirements • Multiuser Detection - Bottleneck! Task B Task A 2.Third Generation Communication Systems Accelerating the blocks in Multistage Detection to meet real-time requirements. • W-CDMA - Wideband CDMA (5 MHz) • 3G Communication Systems • Integrating Multimedia Capabilities • Quality of Service (QoS) • Multi-rate Services • Higher Data Rates • 2048,384,144 Kbps 7. Meeting Real-Time Requirements Graph shows the data rates achieved by different levels of acceleration for multiuser detection.