30 5 2012 9 JOURNAL OF APPLIED SCIENCES Electronics and Information Engineering Vol. 30 No. 5 Sept. 2012 DOI: 10.3969/j.issn.0255-8297.2012.05.005 710064 (wide code division multiple access, WCDMA) (interleaving differential minimum mean square error, IDMMSE). WCDMA (differential minimum mean square error, IDMMSE).. DMMSE. IDMMSE MMSE. TN914.4 0255-8297(2012)05-0466-07 Interleaving Differential MMSE Multiuser Detection Based on Cyclic-stationary Period FENG Xing-le, LI Wei, JIANG Yun-guo School of Information Engineering, Chang an University, Xi an 710064, China Abstract: To suppress multiple access interference (MAI) in wide code division multiple access (WCDMA) systems in a fast fading channel, an interleaving differential MMSE multiuser detection method based on the cyclo-stationary period is proposed. According to typical characteristics of two-layered spreading modulation in WCDMA, the update criterion of coefficients is based on the cyclo-stationary period, instead of the spread factor. As the proposed method can characterize the pattern of MAI properly, improved performance can be achieved. Moreover, interleaving is involved to let the symbols with the same comprehensive spread sequence be transmitted consecutively to ensure that the channel gains of successive symbols keep constant in the fast fading channel. Simulation results show the performance is improved without increasing the system complexity, and Doppler shift is better dealt with. Keywords: wide code division multiple access (WCDMA), multiuser detection, differential minimum mean square error (IDMMSE), cyclo-stationary period, interleave (code division multiple access, CDMA) [1]. (minimum mean square error MMSE). (wide code division multiple access WCDMA). WCDMA MMSE. [2] 2011-04-24 2011-09-11 (No.61271262) (No.IRT0951) (No.2011K06-28) (No.20090205120002) (No.CHD2012JC069, No.CHD2012TD011) MIMO E-mail: xlfeng@chd.edu.cn
5 467 MMSE. [3] (high speed downlink packet access, HSDPA) (least mean square, LMS). [4] MMSE. [5] (direct sequencecode division multiple access, DS-CDMA) (differential minimum mean square error, DMMSE). [6] MMSE. MMSE [5] DMMSE DS- CDMA WCDMA WCDMA DMMSE DMMSE. DMMSE DMMSE. DMMSE. 1 1.1 WCDMA WCDMA (dedicated physical data channel, DPDCH) (dedicated physical control channel, DPCCH). WCDMA 1 (orthogonal variable spreading factor, OVSF) DPDCH DPCCH 2. WCDMA 1. 1 k. K v k (i) = K d k (i τ k )S k (mod (i/(p/g))) k=1 + n(i) (1) 1 Figure 1 System model
468 30 d k (i) = f k (i) [β I x k (i)c k,i + jβ Q y k (i)c Q,k ] (2) 1 (1) (2) k. 1 DPDCH DPCCH i x k (i) y k (i) OVSF C k,i C k,q β I β Q d k (i). x k (i) y k (i) C k,i C k,q OVSF C k,i C k,q x k (i) y k (i) f k (i) k i j. 2 1 d k (i) k S(2) S k S k (mod (i/(p/g))) u k (i) mod( ). S(2) S k OVSF C k,i. d k (i) G G S k P S k P/G S k (mod (i/(p/g))) k i G d k (i) n(i). u k (i) v k (i). u k (i) 2.2. 1.2 Jake [7]. 6 ( ) ( ) m m h [m] = h = h f s 4f d = f ( ) d 3 m Γ 2π 4 4πfd 2 14 J 1 4 ( π 2 m ) (3) f d f s = 4f d Γ (γ) = 1 (1+1/λ) z γ 1+γ/λ J 1 (γ) = 4 λ=1 λ=0 ( γ ) 1 4 +2λ 2 1 1 4 [7]. ( 1) λ λ!γ(1/4+λ+1) 1.3 WCDMA v k (i) û k (i) k [S k (mod (i/(p/g)))] H d k (i) G 1 ẑ k (i) G. k. k DPDCH DPDCH DPCCH.. ẑ k (i) G 1 ẑ k (i) G 1 w k (i) i x k (i) = w k (i) H ẑ k (i) (4) ẑ k (i) G x k (i) x k (i). w k (i). 2 IDMMSE 2.1 DMMSE DMMSE DS-CDMA [8] arg min{e[ x k (i 1) w k (i), ẑ k (i) w k x k (i) w k (i 1), ẑ k (i 1) 2 ]} (5) s.t. E[ w k (i), ẑ k (i) 2 ] = w H k Rw k = 1 (6) E [ ] w k (i), ẑ k (i) = wk H(i) ẑ k(i) R = E[ẑ k (i)ẑk H (i)]. (5). (5) (6). DMMSE.
5 469. DS-CDMA. G OVSF G. WCDMA G P. WCDMA OVSF S(2) 2. i G C k,i S k S k (mod (i/(p/g))). DMMSE ( G ) C k,i S(2) S k (mod (i/(p/g))) DMMSE WCDMA. 2 x k (i) x k (i (P/G)) x k (i (P/G)) x k (i) [9] DMMSE argmin{e[ x k (i (P/G)) w k (i), ẑ k (i) w x k (i) w k (i (P/G)), ẑ k (i (P/G)) 2 ]} (7) 2 Figure 2 Comprehensive spread sequence DMMSE (5) DMMSE (7) w k (i P/G) w k (i 1) w k (i). 2.2 IDMMSE DMMSE. w k (i (P/G)) w k (i) P/G DMMSE. u k (i) u k (i (P/G)) MMSE (interleave differential minimum mean square error, IDMMSE) u k (i) u k (i P/G), DMMSE. 3. u k (i) N (P/G) u k (i) G. P /G 1 2 N N.. u k (i) u k (i (P/G)). DMMSE. (7) x k (i) x k (i (P/G)).
470 30.. 3 Figure 3 Interleaving register matrix x k (i) x k (i (P/G)). NP /G x k (i) x k (i P/G). 2.3 (7) [10] LMS (normalized least mean squares, NLMS) DMMSE NLMS e k (i) = x k (i)w k (i (P/G)) H ẑ k (i (P/G)) x k (i (P/G))w k (i (P/G)) H ẑ k (i) (8) M(i) = ηm(i (P/G)) + (1 η)ẑ k (i) H ẑ k (i) (9) w k (i) = (w k (i (P/G)) + µ M(i)ẑk(i)ẑ k (i)x (i (P/G))e k (i)) w k (i (P/G)) H ẑ k (i (P/G)) (10) η M(i) * sgn () T. 4 4 IDMMSE Figure 4 Flow diagram of IDMMSE 3 3.1 3GPP [11] MATLAB WCDMA. Walsh 256 S(2) 32 8 DPDCH 1/32 DPCCH 0.733 3/256 0 256. 3 1) [2] MMSE MMSE. 2) DMMSE_NLMS (7) w k (i (P/G)) w k (i) P/G, DMMSE. 3) IDMMSE_NLMS DMMSE_NLMS x k (i) x k (i (P/G)), IDMMSE.
5 471 DMMSE IDMMSE M(i)=0.1 η=0.5 µ=0.001. 1 G 3 (symbol error ratio, SER). 900 MHz 30 km/h f d =25 Hz G=32. 5 DMMSE SER MMSE IDMMSE SER DMMSE. DMMSE IDMMSE x k (i) x k (i (P/G)) DMMSE. 6 Figure 6 Effect of Doppler shift on the performance 5 3 Figure 5 SER comparasion of three algrithms 2 3. E b /N o =10 db K=4 G=32. 6 3 SER. MMSE DMMSE SER 0.5 IDMMSE x k (i) x k (i P/G) SER. 3, 3. E b /N o =10 db K=4 f d =30 Hz. 7 G x k (i) x k (i (P/G)) x k (i) x k (i (P/G)) SER. 7 Figure 7 Effect of spread factor on the performance 3.2 DMMSE MMSE DMMSE MMSE. 1 DMMSE MMSE. 1 Table 1 Complexity comparasion of two algorithms MMSE 3 G 2 G DMMSE 7 G 2 3 G IDMMSE N (P/G). (P/G)
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