tailieunhanh - Hệ thống 3G và mạng không dây thông minh P6

In this book we have discussed the performance implications adaptive antenna arrays of and adaptive modulation techniques both FDMARDMA and CDMA cellular mobile commuin nications networks. In Chapter 3 we investigated antenna arrays and adaptive beamforming commenced, in Section considering the possible applications antenna arraysand of their related benefits. | Third-Generation Systems and Intelligent Wireless Networking . Blogh L. Hanzo Copyright 2002 John Wiley Sons Ltd ISBNs 0-470-84519-8 Hardback 0-470-84781-6 Electronic Chapter Conclusions and Further Research Summary and Conclusions In this book we have discussed the performance implications of adaptive antenna arrays and adaptive modulation techniques in both FDMA TDMA and CDMA cellular mobile communications networks. In Chapter 3 we investigated antenna arrays and adaptive beamforming algorithms. We commenced in Section by considering the possible applications of antenna arrays and their related benefits. The signal model used was then described in Section and a rudimentary example of how beamforming operates was presented. Section highlighted the process of adaptive beamforming using several different temporal reference techniques along with the approaches used in spatial reference techniques. The challenges that must be overcome before beamforming for the downlink becomes feasible were also discussed in Section . Results were presented showing how the SMI ULMS and NLMS beamforming algorithms behaved for a two element adaptive antenna in conjunction with varying eigenvalue spread and reference signal length. The SMI algorithm was shown to converge rapidly irrespective of the eigenvalue spread. The performance of the ULMS beamformer was shown to be highly dependent upon the input signal power presented to the antenna rendering it impractical. However the NLMS algorithm was found to be far superior in this respect and it was later shown to approach the performance of the SMI beamformer for a three element adaptive array. A low SNR gives a poor estimate of the received signal s cross-correlation matrix resulting in similar performance for all three algorithms. However as the SNR improves the SMI technique guarantees a stronger interference rejection. The SMI algorithm is more complex for a large number of antenna elements but for a .