Turbo Multiuser Detection Group Members: -Bhushan G. Jagyasi -Himanshu Soni

Single user detection b 1 (.) b 2 (.) b n (.) g1 g2 gn Modula- -tion AWGN Modula- -tion b^ 1 (.) b^ 2 (.) b^ n (.) g1 g2 gn Decision Reciever / Detector Noisy Channel r(t) Received signal, r(t) = b1g1f1+ b2g2f2+ ……bngnfn + n(t) After detector y(t)=b^1(t) = b1.g1.g1. f1+ b2.g2.g1.f2+ ……bn.gn.g1.fn + n o.g1

Received signal for jth user

Turbo Principal Concatenated coding and iterative decoding. Encoder Decoder

’Turbo’ in turbo-codes, does not apply to the code itself, but to the iterative way of decoding. The title Turbo is taken from the principle of the turbo engine. Iterating the soft output of the convolutional code decoder back to the multiuser detector, a turbo multiuser detector architecture is created

Transmitter block diagram [ From reference 3]

Receiver block diagram (Turbo MUD) r(t) [ From reference 3]

SISO block diagram [ From reference 3]

SISO implementation Output of Soft interference cancellation, yk(i), where,

MMSE filtering output, Where,

Log likelihood calculation where, It is used as feedback for soft interference canceller Conditional Probability Log likelihood ratio

Results Results are for following parameters  No of users=5  No. of user bits =1000  Channel noise= 16 db for all users  Receiver noise = 20 db  No. of iterations= 5

Constellation plots (User 1)

BER Plot (For one sample path ) For 5 user Signal to channel Noise ratio in dB---- 

Average BER Plot (For ten sample path ) For 10 user Signal to channel Noise ratio in dB----  BER

Average BER Plot For 5 user Signal to channel Noise ratio in dB----  BER

References 1] Shimon Mosavi, “ Multiuser detection for DS-CDMA Communications”, IEEE Communication Magazine, pp ,Oct ] H.Vincent Poor, “Turbo Multiuser Detection: An Overview”,IEEE 6 th international symposium on spread-spectrum technology and appliation, pp ,Sept 6-8, ] Gebrben Heinen, “ Turbo multiuser Detection Architectures”, M.Sc. Thesis, Dec ] Xiaodong Wang and H.Vincent Poor, “Iterative (Turbo) Soft Interference cancellation and Decoding for Coded CDMA”, IEEE transaction on communications, vol.47, No.7, July 1999, pp ,