Alamouti Technique Research Articles

Noise Cancellation for HIPERLAN/2 with Open Loop Transmit Diversity Technique

A new proposed method is presented, where multiple antennas have been applied into HIPERLAN/2 system in addition to employing space-time diversity technique, especially the Alamouti technique. The suggested approach is used to cancel or reduce the effect of the transmitted power using a feedback signal process within the transceiver unit, especially when the antennas are closely located and working in full-mode duplexing. Several parameters including the transmitted power, the received power, and the feedback accuracy have been considered for testing the performance of the system in term of the signal to noise ratio (SNR) versus bit error rate (BER). A software programme using MATLAB and Simulink is implemented to evaluate the proposed method. The results showed that the system performance is heavily dependent on the amount of the mismatch in the feedback, the received power, and the transmitted power. The performance of the system decreases as the feedback accuracy increases when the transmitted power and the received power are constant. At the same time, the performance of the system decreases as the transmitted power increases when the received power and the mismatch are constant. Finally, the increase in the received power enhances the system performance when the other parameters are constant.

A Novel Space–Time Coding Scheme Used for MIMO-SAR Systems

Attention has been devoted to multi-input-multi-output (MIMO) synthetic aperture radar (SAR) systems in recent years. The applications of MIMO-SAR systems that involve high-resolution wide-swath remote sensing, 3-D imaging, and multi-baseline interferometry are seriously limited by the ambiguous energy introduced by the imperfect orthogonal waveforms. The ambiguous energy degrades SAR image severely, because it can be accumulated from closely spaced scatters. In order to suppress the ambiguous energy, the space-time coding (STC) scheme using the Alamouti technique has been proposed recently. However, this scheme is based on the assumption that the channel responses are constant within the consecutive transmissions. For the time-variant channel responses caused by motion errors or other factors, there will be residual ambiguous energy and “ghost targets.” In this letter, a novel STC scheme suitable for MIMO-SAR systems is proposed. The performance of the proposed scheme is immune to the time-variant channel responses. Moreover, it can get more spatial diversities to enhance the MIMO SAR imaging applications. The proposed scheme is validated by numerical simulation results.

이동통신 기반의 재난경보 방송을 위한 동기식 협력통신 방식

이동통신망을 이용한 재난경보의 신속한 방송을 위해 CBS 기능이 이용된다. 본 논문에서는 이 CBS 기능을 위한 동기식 협력통신 방식을 제안한다. 특히 고속 전송을 위한 동기 방식과 데이터 복구 기법을 제안한다. 고속 전송 환경에서의 동기를 위해 주기 전치부가 있는 프리엠블이 이용되며 데이터 복구를 위해 SC-FDE와 유사한 주파수 영역에서의 Alamouti 기법을 이용한다. 모의실험 결과는 제안된 방식이 CBS에 매우 적합함을 보여준다. The CBS methodology has been utilized in order to make a rapid broadcast of emergency alert based on cellular systems. We present a synchronous cooperative communication method for the CBS. Especially, we suggest a synchronization scheme and a data recovery approach for high-rate cooperative communications. For the high-rate transfer of emergency alert, the cyclic prefix is added to the preamble for the synchronization. For the data recovery, the Alamouti technique is utilized on frequency domain, which is similar to SC-FDE. The simulation results confirm that our proposed scheme is very suitable for the CBS.

Modeling and performance evaluations of Alamouti technique in a single frequency network for DVB-T2

Abstract Alamouti space–frequency coding provides additional frequency diversity, especially in multipath propagation environments. This article addresses a new modeling of the Alamouti code multiple input single output (MISO) in a single frequency network(SFN) for two, three, and four transmitters, and different types of coding and modulations in the DVB-T2 (Digital Video Broadcasting Terrestrial second generation). Classical SFN, Alamouti MISO, and combined SFN with Alamouti MISO (called SFN-2x1 Alamouti MISO) are compared and analyzed. Performance evaluations are made for two, three, or four transmission antennas through 0-dB Echo profile, TU6 mobile channel, unbalanced received power and rotated constellation. The obtained results show clearly that the performance of an SFN network using 0-dB Echo profile with Alamouti MISO is only better than a pure SFN for two and three antennas. Moreover, an SFN based on four antennas (receiving from four antennas) has almost the same performance as SFN-2x1 Alamouti MISO.

A Simple and Robust Equal-Power Transmit Diversity Scheme

Spatial diversity techniques are now used in most wireless communications systems to improve robustness to signal fading. On the downlink of cellular systems, low-cost requirements of the user terminal tend to favor transmit diversity over receive diversity, and Alamouti's transmit diversity technique appears today in most wireless communications systems standards. But in terms of the total transmit power, Alamouti's technique loses 3 dB with respect to optimum transmit diversity which requires perfect Channel State Information (CSI) at the transmitter. In this paper, we introduce a simple transmit diversity technique that relies on simple power measurements at the receiver which comes very close to optimum transmit diversity performance when assuming perfect CSI is available at the transmitter while relaxing the transmit power requirements by 3 dB. In this technique, the same power is transmitted from the two antennas and the phase difference of the signals received from the two channels is constrained to be smaller than π/N, where N is a predefined parameter. Its performance is studied in narrowband fading channels, in OFDM systems operating on frequency-selective channels, and in the presence of channel estimation errors.