Special issue on adaptive antennas for wireless communications (original) (raw)

Adaptive subband arrays for multipath fading mitigation

1998

In high-speed digital mobile communications, inter-symbol interference (ISI) due to multipath fading and co-channel interference (CCI) become two significant problems that decrease the communication quality and limit the communication capacity. Adaptive array alone or together with temporal equalizations or diversity techniques are promising methods to suppress both of the ISI and CCI so that the communication performance can be greatly improved, and, it also leads to the increase of communication capacity.

Multiple antenna systems: frontier of wireless access

2004 IEEE 15th International Symposium on Personal, Indoor and Mobile Radio Communications (IEEE Cat. No.04TH8754), 2004

Multiple antenna systems are the new frontier for wireless communications including the actually third generation mobile communication systems, called Universal Mobile Telecommunication System (UMTS), the wireless LAN and the wireless PAN up to the future 4G mobile system focused on seamlessly integration of the existing wireless technologies. The use of multiple antenna systems improves the overall system performance in term of capacity and spectrum efficiency achieving high data rate wireless services. The paper highlights the two main techniques: smart antennas with adaptive beamforming to cancel the interference signals (from other users or multipath) and MIMO systems to exploit the space-time properties of wireless channels.

Multiple-antenna communication systems: an emerging technology

Canadian Journal of Electrical and Computer Engineering, 2004

A recent development in wireless communications is the application of multiple-input multiple-output (MIMO) systems to radio communications via use of multiple antennas. In order to investigate the technology's potential, an experimental MIMO system which contains two four-element antenna arrays (4 × 4) has been developed at the University of Alberta. The system is used to obtain MIMO channel measurements in a typical indoor office environment in the ISM band (902-928 MHz). Measurement campaigns were performed using different antenna spacings and two different types of antenna: half-wavelength (λ/2) centre-fed dipoles and dual polarized patches. The measurements are used to calculate channel capacities for an indoor 4 × 4 MIMO system. The measurements confirm the high capacity potential of a MIMO channel, with ergodic capacity of approximately 21 bits per channel use available with either antenna type at a signal-to-noise ratio of 20 dB if the antenna element separation is λ/2 or larger. An introduction to basic MIMO theory, a discussion of the University of Alberta wireless MIMO testbed, and observations regarding the measured indoor MIMO channel are presented in the paper.

Spectral efficiency of FDMA/TDMA wireless systems with transmit and receive antenna arrays

IEEE Transactions on Wireless Communications, 2002

In recent years, the ever growing need for higher capacity in wireless systems has fueled the interest in exploiting the spatial dimension-through the use of antennas arrays-to improve the utilization of the available radio spectrum. As a result, a large number of space-time techniques have been proposed wherein arrays are used to mitigate interference and enhance signal levels. More recently, information theory has shown that, with spatial data multiplexing, very large spectral efficiencies can be attained in multipath channels using transmit and receive antenna arrays. In this paper, the system benefit of using transmit and receive arrays in multicell scenarios is evaluated as a function of both the propagation environment and the number of antennas. Our results confirm the potential for very large system spectral efficiencies associated with the use of transmit and receive arrays, in particular in interference-limited rich-multipath conditions wherein the ability to perform interference mitigation-leading to tighter spectral reuse-and spatial data multiplexing grows with the number of antennas. In environments free of multipath, the potential is smaller but still very significant, associated with interference mitigation and signal enhancement only, since spatial data multiplexing is no longer possible.

Multi-user MIMO systems: The future in the making

Potentials, IEEE, 2009

V ery few technologies have had as much impact on the trajectory of evolution of wireless communication systems as Multiple Input Multiple Output (MIMO) systems. MIMO systems have already been employed in the existing 802.11n and 802.16e standards resulting in a huge leap in their achievable rates. A relatively recent idea of extending the benefits of MIMO systems to multi-user scenarios seems promising in the context of achieving high data rates envisioned for future cellular standards after 3G. Although substantial research has been done on the theoretical front, recent focus is on making multi user MIMO (MU-MIMO) practically realizable. It offers an enormous scope for further research in the coming years. As in the case of any evolving technology in communication systems, the literature concerning MU-MIMO systems involves complex mathematical analysis, making it difficult for an ordinary reader to comprehend. This article aims at giving an insight into MU-MIMO systems-its concept, fundamentals, and trends including an overview of important research results. It is intended at giving a good start to amateurs interested in being part of the community that shapes the future of wireless systems.