34 **5.6. Conclusions**

35 In this section, we investigate a possibility to employ both the orthogonal unified complex 36 Hadamard transform spreading sequences and the WH real spreading sequences in the DS-37 CDMA downlink wireless communication system using the GR constructed based on the 38 GASP and carry out a comparative analysis. The SINR at the GR output in the DS-CDMA Signal Processing by Generalized Receiver in DS-CDMA Wireless Communications Systems 71 Signal Processing by Generalized Receiver in DS-CDMA Wireless Communications Systems http://dx.doi.org/10.5772/58990 149

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13 conditions.

14 *5.5.3. Effect of MAI*

1 *5.5.2. Effect of different fading channels*

148 Contemporary Issues in Wireless Communications

33 have verified our theoretical analysis.

34 **5.6. Conclusions**

2 Figure 13 shows the BER performance of the DS-CDMA downlink wireless communication 3 system employing the GR with the unified complex Hadamard transform spreading 4 sequences and WH spreading sequences over different channels, including the AWGN 5 channel, Rayleigh fading channel, and Ricean fading channel with the factor *F* 5 . It can be 6 seen that in all the channels under consideration, the DS-CDMA downlink wireless 7 communication system employing the GR with the unified complex Hadamard transform 8 spreading sequences has the better BER performance, especially in the high SNR region. 9 Also, we can see a great superiority under employment of the GR in the DS-CDMA 10 downlink wireless communication system with the unified complex Hadamard transform 11 spreading sequences and WH spreading sequences over the implementation of the Rake 12 receiver in the DS-CDMA downlink wireless communication system under the same

15 To show the effect of MAI, Fig.14 depicts the BER performance of the DS-CDMA downlink 16 wireless communication system employing the GR with the unified complex Hadamard 17 transform spreading sequences and WH spreading sequences as a function of the number of 18 active users *K*. The BER performance of the DS-CDMA downlink wireless communication 19 system employing the GR with the unified complex Hadamard transform spreading 20 sequences is better than that of the DS-CDMA downlink wireless communication system 21 employing the GR with the WH spreading sequences at the high SNR and all the chosen 22 values of *K*. Although the advantage brought by using the unified complex Hadamard 23 transform spreading sequences in the DS-CDMA downlink wireless communication system 24 employing the GR fades gradually with the increase of MAI. For example, under the large 25 number of users and small SNR, the BER performance of the DS-CDMA downlink wireless 26 communication system employing the GR with the unified complex Hadamard transform 27 spreading sequences is comparable to that of the DS-CDMA downlink wireless 28 communication system employing the GR with the WH spreading sequences in the low 29 SNR region. Also, for all cases, a great superiority of the GR implementation in the DS-30 CDMA downlink wireless communication system with the unified complex Hadamard 31 transform spreading sequences and WH spreading sequences in comparison with 32 employment of the Rake receiver in the same system is evident. These results in simulations

35 In this section, we investigate a possibility to employ both the orthogonal unified complex 36 Hadamard transform spreading sequences and the WH real spreading sequences in the DS-37 CDMA downlink wireless communication system using the GR constructed based on the 38 GASP and carry out a comparative analysis. The SINR at the GR output in the DS-CDMA

**Figure 13.** BER performance as a function of SNR *Eb N*<sup>0</sup> 2 in different channels (*K* 10, *L* 4) , 3 MMRC.

1

4

5 **Figure 14.** BER performance as a function of the number of users *K*. Rayleigh fading channel, MMRC, 6 *L* 4 .

7 downlink wireless communication system with the unified complex Hadamard transform 8 spreading sequences is independent of the phase offsets between different paths. The SINR 9 at the GR output in the DS-CDMA downlink wireless communication system with the WH

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1 real spreading sequences is a function of the squared cosine of path phase offsets. By this 2 reason, the employment of the orthogonal unified complex Hadamard transform spreading 3 sequences in the DS-CDMA downlink wireless communication system using the GR 4 provides the better BER performance with respect to the DS-CDMA downlink wireless 5 communication system using the GR with the WH real spreading sequences, especially, at 6 high SNRs. Evaluation of the BER performance demonstrating the benefits of employment 7 of the unified complex Hadamard transform spreading sequences and MMRC weights in 8 the GR employed by the DS-CDMA downlink wireless communication system has been 9 carried out over simulation. Comparative analysis of employment of the GR and Rake 10 receiver in the DS-CDMA downlink wireless communication system with the orthogonal 11 unified complex Hadamard transform spreading sequences and the WH real spreading 12 sequences has been performed over simulation. Comparison showed a great superiority in 13 favor of the GR.
