The Wireless communication system has a challenge of accommodating many users in a small area. With the advent of spread spectrum and hence CDMA, fixed bandwidth was used to accommodate many users by making use of certain coding properties over the bandwidth. However, the standardization of conventional DS-CDMA system has the major problem of multi-access interference (MAI). The MAI occurs in multi-access communication systems and is unavoidable because receiver's deal with information interferes with each other.
To overcome these limitations, Multi-user Detection (MUD) emerges as a promising approach to increase the system capacity over conventional CDMA receiver. MUD is basically the design of signal processing algorithms and these algorithms take into account the correlative structure of the MAI.
Keywords: CDMA, QPSK, GMSK, QAM, MAI, MUD
[...] Make a decision on user signal i , bi = Pb((i ) 0.5 Pb ( i 0.5 Based on this above steps, the algorithm is implemented under CDMA model to avoid local minima Implementation Probabilistic Data Association Algorithm for Multiuser detection in CDMA receiver is implemented in MATLAB 7.0 for different number of users and also different modulation techniques with different code. I. QPSK II. 16-QAM III. 64-QAM IV. GMSK The m/c specifications on which the computation of the above algorithm results are taken as under: Processor: Intel Pentium PIV 2.6 GHZ RAM: 512 MB RAM MBD: 865 Intel Chipset HDD: 80 GB HDD ~ = b + ~ = b e + b e + ~ y z j j z i i j Where ~ = W R y and ~ = W R z . [...]
[...] Figure shows comparison of & 64 users with gold code and Figure shows the profile plot for the same system model Modulation: 16QAM ,Channel: AWGN , Code : Gold 10 ii. Fig. Figure shows comparison of & 64 users with PN code and Figure shows the profile plot for the same system model BER 10 Modulation: 16QAM ,Channel: AWGN , Code : PN 10 2-user 4-user 8-user 16-user 64-user Eb/N0 Fig. 10 BER 10 - 2-user 4-user 8-user 16-user 64-user Eb/N0 Fig. [...]
[...] This algorithm is implemented for a limited number of user based on synchronus CDMA using MUD tecthniques. Also, Computer results shows that the PDA methos will be tested on a DSP platform and analyze the performance of it in a real time application. Future possible work for VHDL simulation and implementation in VLSI chip also possible REFERENCES 1. L. Hanzo, L-L. Yang , E-L Kuan, K.Yen. “Single and multi-carrier DS-CDMA”, IEEE Fumihiro Hasegawa, Speed and accuracy comparison of techniques for multi-user detection in synchronous CDMA.”, IEEE Peng Hui Tan, Multi-user based on reduced [...]
[...] Figure 13(a) shows comparison of & 64 users with Walsh code and Figure 13(b) shows the profile plot for the same system model Modulation: GMSK ,Channel: AWGN , Code : Walsh Fig. 11(a) 10 BER 10 - 2-user 4-user 8-user 16-user 64-user E b /N0 Fig. 13(a) Fig. 13(b) ii. Figure 14(a) shows comparison of & 64 users with PN code and Figure 14(b) shows the profile plot for the same system model Fig. 15(b) 3. CONCLUSION We can conclude based on the above results that as seen from the Figure The Eb/No curve for the and 16 users with PDA algorithms between 8 to 18 db is good enough (e.g. [...]
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