Performance of Adaptive Modulation with Space-Time Block Coding and Imperfect Channel State Information over Rayleigh Fa
The performance analysis of adaptive MQAM/MPSK with space-time block coding (STBC) and imperfect channel state information (CSI) over Rayleigh fading channels is presented. The fading gain value is partitioned into a number of regions by which the modulat
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College of Electronic and Information Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, China 2 National Mobile Communications Research Laboratory Southeast University, Nanjing, China
Abstract. The performance analysis of adaptive MQAM/MPSK with spacetime block coding (STBC) and imperfect channel state information (CSI) over Rayleigh fading channels is presented. The fading gain value is partitioned into a number of regions by which the modulation is adapted according to the region the fading gain falls in. Under a target bit error rate (BER) and fixed power constraint, the fading gain switching thresholds and the probability density function of fading gain under imperfect CSI are respectively derived. Based on the above results, the closed-form expression for the SE is obtained. A tightly closed-form approximation of average BER is derived by means of the approximation of complementary error function. Computer simulations verify the effectiveness of the derived theoretical SE and BER expressions. Keywords: Adaptive modulation, Spectrum efficiency, Bit error rate, Spacetime coding, MQAM, MPSK.
1 Introduction With the fast development of modern communication techniques, the demand for high data rate service is grown increasingly in the limited radio spectrum. For this reason, the future wireless communication system will require spectrally efficient techniques to increase the system capacity. To satisfy this requirement, adaptive modulation (AM), as a powerful technique for improving the spectrum efficiency, has obtained fast development recently [1]. It can take advantages of the time-varying nature of wireless channels to transmit higher speeds under favorable channel conditions and to reduce throughout as the channel degrades by varying the transmit power, symbol rate, code rate, and their combination. Thus it can provide much higher spectrum efficiency without sacrificing bit error rate (BER) [2-5]. Moreover, multiple antennas technique is well known to offer improvements in spectrum efficiency along with diversity and coding benefits over fading channels. Especially, space-time coding in multi-antenna system provides effective transmit diversity for combating fading effects [6-9]. Hence, the effective combination of adaptive modulation and space-time coding techniques has received much attention in the literature [7-9, 2-3]. Discreterate adaptive MQAM scheme in conjunction with space-time block coding (STBC) H. Tan (Ed.): Knowledge Discovery and Data Mining, AISC 135, pp. 169–176. springerlink.com © Springer-Verlag Berlin Heidelberg 2012
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scheme with constant power over flat Rayleigh fading is studied in [7]. A general performance analysis of STBC with fixed and variable rate QAM is given in [8]. An adaptive coded modulation scheme with 2-antennas STBC is considered in [9] that make use of turbo code to improve the system coding gain. The performance of adaptive modulation with single antenna system is analyzed in [2]. The performance analysis of single-and multicar
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