[show abstract][hide abstract] ABSTRACT: In receivers, IQ imbalances have significant effects on the performance of data transmission. Comparison of the performance of different types of orthogonal space-time block codes (OSTBC) in the presence of IQ imbalances show that different codes donpsilat have a same behavior. Although most codes have an acceptable performance in low imbalances, they canpsilat work properly in the presence of intensive non-idealities. Despite this general similarity, there are some differences in the behavior of the codes against non-idealities. Such differences make them suitable for different situations.
Personal, Indoor and Mobile Radio Communications, 2008. PIMRC 2008. IEEE 19th International Symposium on; 10/2008
[show abstract][hide abstract] ABSTRACT: In mobile communications, nonideal operation of the RF-IF chain has significant effects on the signal received by the BS. Since most beamforming algorithms use the received signal parameters to steer suitable beam, any error or uncertainty cause significant degradation in beamforming performance. In this paper, effects of some of the most important RF-IF chain errors occurred in down conversion process are investigated theoretically as well as by simulation. Our investigations show that the error caused by the difference between down converters, has a significant effect on the beamformer performance. It is shown that the RF-IF chain phase and amplitude errors have a more significant effect on the beamformer performance than the other errors. Because of the higher sensitivity of the phase of the received signal, phase error has the most significant effect.
Industrial Technology, 2006. ICIT 2006. IEEE International Conference on; 01/2007
[show abstract][hide abstract] ABSTRACT: In mobile communications, beamforming is one of the most efficient techniques to suppress undesired effects of the transmission channel. In a CDMA mobile communications system, there are some parameters such as PN code length of the CDMA signals and modulation type and order that usually are changed to increase the capacity and data bit rate. Variation of these parameters can change the beamformer performance. In this paper, effect of changing these parameters on the beamformer performance is investigated both theoretically and by using simulations. These investigations show that the above parameters have different effects on the beamformer performance
[show abstract][hide abstract] ABSTRACT: In mobile communications, transmission channel causes significant effects on the signal of mobile users received by the BTS. These changes can degrade the performance of the beamformer. In this paper, undesired effects of the transmission channel on the performance of the LS-CMA based beamformer are investigated both theoretically and through simulations. Investigations of this paper show that the effect of transmission channel on the beamformer performance depends on some parameters such as modulation technique used in the transmitter, mobile environment, and etc. But in general, phase error and angular spread have the worst effect on the beamformer performance.