tailieunhanh - Advanced Trends in Wireless Communications Part 3

Tham khảo tài liệu 'advanced trends in wireless communications part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 60 Advanced Trends in Wireless Communications Channel capacity For fading channels the ergodic channel capacity characterizes the long-term achievable rate averaged over the fading distribution and depends on the amount of available channel state information CSI at the receiver and transmitter Alouini Goldsmith 1999a . Two adaptive transmission schemes are considered Optimal rate adaptation with constant transmit power ORA and optimal simultaneous power and rate adaptation OPRA . Under the ORA scheme that requires only receiver CSI the capacity is known to be given by Alouini Goldsmith 1999a 1 o Cora taWo f y ln 1 y y 40 In order to obtain an analytical expression of C qra for the considered DS-CDMA system we first make use of the infinite series representations of the PDF of Y given by 28 . Then by expressing the exponential and the logarithm in terms of Meijer-G functions Prudnikov et al. 1986 Eq. Prudnikov et al. 1986 Eq. and applying the result given in Prudnikov et al. 1986 Eq. the following expression for the capacity may be obtained 1 3 rr 1 1 1-U-k 1 U L G Cm I C -ụ V F. 3 2 L 1 0 J 41 CCRA ln2 n AB ụ L Ĩk r ũ where cm i i is the Meijer-G function Gradshteyn Ryzhik 2000 Eq. . For the OPRA scheme the capacity is known to be given by Alouini Goldsmith 1999a Eq. 7 r Y CHOPRA I log2 fY Y dY 42 Jyb Y0 where Y0 is the cutoff SNR below which transmission is suspended. By substituting 28 to 42 expressing the logarithm and the exponential in terms of Meijer-G functions Prudnikov et al. 1986 Eq. Prudnikov et al. 1986 Eq. and with the help of Prudnikov et al. 1986 Eq. C opra may be obtained as U L o G 0 3 1 1 1--U-k 1 r C -ụ V 3 2 lY0 0 0 J 43 c qpra ln2n AlBl Lĩk r ũ In Figure 6 the average of a triple-branch MRC diversity system under the ORA transmission scheme is illustrated versus Y1 for n 2 and ụ . An exponentially power decay profile with 5 0 1 is considered. The average channel capacity is .