Combining Beamforming and Orthogonal Space-Time Block Coding

Abstract-Multiple transmit and receive antennas can be used in wireless systems to achieve high data rate communication. Recently, efficient space-time codes have been developed that utilize a large portion of the available capacity. These codes are designed under the assumption that the transmitter has no knowledge about the channel. In this work, on the other hand, we consider the case when the transmitter has partial, but not perfect, knowledge about the channel and how to improve a predetermined code so that this fact is taken into account. A performance criterion is derived for a frequency-nonselective fading channel and then utilized to optimize a linear transformation of the predetermined code. The resulting optimization problem turns out to be convex and can thus be efficiently solved using standard methods. In addition, a particularly efficient solution method is developed for the special case of independently fading channel coefficients. The proposed transmission scheme combines the benefits of conventional beamforming with those given by orthogonal space-time block coding. Simulation results for a narrow-band system with multiple transmit antennas and one or more receive antennas demonstrate significant gains over conventional methods in a scenario with nonperfect channel knowledge

Precoder design for space-time coded systems over correlated Rayleigh fading channels using convex optimization

A class of computationally efficient linear precoders for space-time block coded multiple-input multiple-output wireless systems is derived based on the minimization of the exact symbol error rate (SER) and its upper bound. Both correlations at the transmitter and receiver are assumed to be present, and only statistical channel state information in the form of the transmit and receive correlation matrices is assumed to be available at the transmitter. The convexity of the design based on SER minimization is established and exploited. The advantage of the developed technique is its low complexity. We also find various relationships of the proposed designs to the existing precoding techniques, and derive very simple closed-form precoders for special cases such as two or three receive antennas and constant receive correlation. The numerical simulations illustrate the excellent SER performance of the proposed precoders

Adaptive transmit eigenbeamforming with orthogonal space-time block coding in correlated space-time channels

Conventional space-time codes can provide a significant improvement in system performance only if the signal paths are spatially uncorrelated, a condition that is hardly met in practice. In this paper, we mitigate this condition by combining a technique of eigenbeamforming, based on the channel correlation matrix, with orthogonal space-time block codes (O-STBC) at the transmitter side of the link. No feedback information from the receiver (the mobile station) is utilized in the proposed structure. Simulation results using 4-ary PSK signaling showed that this idea outperforms existing techniques in both uncorrelated and correlated channels in terms of bit-error rate and symbol-error rate

A Closed-loop Cross-Layer Scheme for Wireless Multiuser Transmissions

AbstractTo improve transmission efficiency of wireless communication systems, cross-layer design is investigated, which can adapt to the dynamically variable wireless channel characters. In this paper, a novel cross-layer design for multi-user system is proposed to improve system performance. The Beamforming-MIMO cross-layer system is scheduled through combining multilevel adaptive modulation (AM) at physical layer with truncated automatic repeat request (ARQ) protocol at data link layer, and feed backing modulation mode, ARQ request and transmit weight vector from receiver, in order to improve multi-antennas system performance. This paper derives close-form expressions of the system spectral efficiency and the outage probability for wireless multiuser MIMO transmissions. It shows by simulation that, compared to Alamouti's cross-layer system and SISO cross-layer system, this cross-layer system can achieve better performance. And we analyze the impact of the transmit antenna number and mobile user number on the performance

A phase feedback based extended space-time block code for enhancement of diversity

In this paper we propose a generalization of extended orthogonal space-time block codes (EO-STBCs) for MIMO (multi-input/multi-output) channels using four transmit antennas for quasi-static flat fading channels. Since full rate and complex orthogonal space-time block codes (STBCs) do not exist for more than two transmit antennas, we propose a feedback based STBC scheme. In this scheme, phases of certain symbols are rotated according to the feedback from the receiver which is equivalent to rotating the phases of the corresponding channel coefficients. Simulation results show that this rotation phase feedback method achieves a satisfactory performance and outperforms the previous closed-loop space-time block codes, even when the feedback is quantized

Exploiting transmission spatial diversity in frequency selective systems with feedback channel

In this paper we address the design of a multiple transmit antenna system in which the Channel State Information (CSI) at the transmitter is not perfect. Two different approaches are analyzed one based on the Minimization of the Mean Square Error (MMSEj and the other based on the application of the Maximum Likelihood Sequence Estimation (MLSE). In both cases a Bayesian criterion is used in order to take into account the error between the CSI and the real channel. Finally, some simulation results and conclusions are provided, showing which is the gain of these approaches when the error between the CSI and the real channel is either Gaussian or uniform, where this last case corresponds to a quantization of the channel time response in order to transmit the CSI through a feedback channel from the receiver to the transmitter.Postprint (published version

Capacity Enhancement for High Data Rate Wireless Communication System

Wireless communication systems have advanced significantly in the past years and played an extremely important role in our society. It is rapidly becoming the most popular solution to deliver voice and data services due to flexibility and mobility that can be offered at moderate infrastructure costs. It is foreseen that future wireless communication system will experience an enormous increase in traffic due to increased number of users as well as new high bit rate data services (multimedia) being introduced. The increase in channel capacity and high transmission rates for wireless communications requires technologies for power saving and efficient frequency usability. One of the most promising techniques to achieve this is the Multiple Input Multiple Output (MIMO) system. This paper proposed a combined spatial multiplexing MIMO scheme with beamforming for high data rate wireless communication. The proposed transmission scheme combines the benefits of both techniques and the system was able to transmit parallel data streams as well as provide beamforming gain. Actually, these diverse techniques, share the same requirement of multiple antenna elements, but differ in the antenna element spacing necessary for the different schemes to work. Thus, smart antenna array was proposed as a possible solution and was adopted at both the transmitter and receiver. The proposed hybrid technique improved the system spectral efficiency performance significantly than the conventional MIMO, spatial multiplexing and beamforming techniques when used alone under the same simulation environment.DOI:http://dx.doi.org/10.11591/ijece.v4i5.645

Indoor off-body wireless communication: static beamforming versus space-time coding

The performance of beamforming versus space-time coding using a body-worn textile antenna array is experimentally evaluated for an indoor environment, where a walking rescue worker transmits data in the 2.45 GHz ISM band, relying on a vertical textile four-antenna array integrated into his garment. The two transmission scenarios considered are static beamforming at low-elevation angles and space-time code based transmit diversity. Signals are received by a base station equipped with a horizontal array of four dipole antennas providing spatial receive diversity through maximum-ratio combining. Signal-to-noise ratios, bit error rate characteristics, and signal correlation properties are assessed for both off-body transmission scenarios. Without receiver diversity, the performance of space-time coding is generally better. In case of fourth-order receiver diversity, beamforming is superior in line-of-sight conditions. For non-line-of-sight propagation, the space-time codes perform better as soon as bit error rates are low enough for a reliable data link