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Nó được thành lập bởi Sony Ericsson, IBM, Intel, Toshiba và Nokia, và sau đó tham gia của nhiều công ty khác là thành viên liên kết hoặc nhận nuôi con nuôi. Bluetooth công nghệ đã đóng một phần trong Tiếng nói tăng qua IP (VOIP) cảnh, với tai nghe Bluetooth được sử dụng như | FUNDAMENTALS OF SINGLE-CARRIER CDMA TECHNOLOGIES 117 R 3 4 and additional redundancy is transmitted with the second transmission. The following puncturing matrices are used 1 represents that the bit at that position is transmitted and 0 represents that it is not transmitted 51 111111 000000 P1 100000 P2 011110 000100 1 100 1 1 For CC the same packet with puncturing matrix P1 is transmitted until a positive acknowledge ACK is received. For IR the puncturing matrix P1 is used for the first transmission and P2 for the second transmission and the order repeated for further transmissions. Code combining is employed if the same packet is transmitted more than once. For reference the throughput obtained with coherent rake combining is also plotted the throughput degrades drastically when the number L of paths increases. With the increase in L the frequency-selectivity of the channel gets stronger and the orthogonality distortion is severer. Hence the throughput decreases with the increase in L. However with MMSE-FDE the throughput is almost insensitive to L. This is because MMSE-FDE can partially restore the code orthogonality which is distorted due to the frequency selectivity of the channel and obtain the frequency diversity gain. For L 1 the throughput is lower with MMSE-FDE compared to rake combining due to the GI insertion loss. However in broadband channels characterized by time- and frequency-selective fading the MMSE-FDE has a better performance. REFERENCES 1 F. Adachi M. Sawahashi and H. Suda Wideband DS-CDMA for next generation mobile communications systems IEEE Commun. Mag. Vol. 36 No. 9 pp. 56-69 Sept. 1998. 2 Y. Kim et al. Beyond 3G vision requirements and enabling technologies IEEE Commun. Mag. Vol. 41 No. 3 pp.120-124 Mar. 2003. 3 M. Helard R. Le Gouable J-F. Helard and J-Y. Baudais Multicarrier CDMA techniques for future wideband wireless networks Ann. Telecommun. vol. 56 pp. 260-274 2001. 4 S. Hara and R. Prasad Overview of multicarrier CDMA IEEE Commun.
