The demand for wireless mobile communications services is growing at an explosive rate, with the anticipation that communication to a mobile device anywhere on the globe at all times will be available in the near future. An array of antennas mounted on vehicles, ships, aircraft, satellites, and base stations is expected to play an important role in fulfilling the increased demand of channel requirement for these services, as well as for the realization of the dream that a portable communications device the size of a wristwatch be available at an affordable cost for such services. This paper is the first of a two-part study. It provides a comprehensive treatment, at a level appropriate to nonspecialists, of the use of an antenna array to enhance the efficiency of mobile communications systems. It presents an overview of mobile communications as well as details of how an array may be used in various mobile communications systems, including land-mobile, indoor-radio, and satellite-based systems. It discusses advantages of an array of antennas in a mobile communications system, highlights improvements that are possible by using multiple antennas compared to a single antenna in a system, and provides details on the feasibility of antenna arrays for mobile communications applications.

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Applications of antenna arrays to mobile communications. I. Performance improvement, feasibility, and system considerations

Wireless communications are transmitted from at least two radioterminals (110a, 110b) to a base station (120) co-channel over a return link using a return link alphabet. Wireless communications are also transmitted from the base station to the at least two radioterminals over a forward link using forward link alphabet that has more symbols than the return link alphabet. The co=channel signal are deciphered at the receiver, while the radio terminal can use a smaller return link alphabet, which can reduce the power dissipation at the radiotermials.

Co-channel wireless communication methods and systems using nonsymmetrical alphabets

A satellite is used to route push-to-send messages among terrestrial base stations. Reduced push-to-send delays thereby may be provided, when a source push-to-send radioterminal is widely separated from a destination push-to-send radioterminal. Satellite routing only may be used when the source push-to-send radioterminal and the destination push-to-send radioterminal are not communicating with a single terrestrial base station or with a group of terrestrial base stations that are proximate one another. A destination base station that is communicating with the destination push-to-send radioterminal may be determined at the satellite, at a satellite gateway and/or at a central server.

Satellite assisted push-to-send radioterminal systems and methods

A new approach for joint data estimation and channel tracking for multiple-input multiple-output (MIMO) channels is proposed based on the decision-directed recursive least squares (DD-RLS) algorithm. RLS algorithm is commonly used for equalization and its application in channel estimation is a novel idea. In this paper, after defining the weighted least squares cost function it is minimized and eventually the RLS MIMO channel estimation algorithm is derived. The proposed algorithm combined with the decision-directed algorithm (DDA) is then extended for the blind mode operation. From the computational complexity point of view being O(3) versus the number of transmitter and receiver antennas, the proposed algorithm is very efficient. Through various simulations, the mean square error (MSE) of the tracking of the proposed algorithm for different joint detection algorithms is compared with Kalman filtering approach which is one of the most well-known channel tracking algorithms. It is shown that the performance of the proposed algorithm is very close to Kalman estimator and that in the blind mode operation it presents a better performance with much lower complexity irrespective of the need to know the channel model.

https://link.springer.com/content/pdf/10.1155%2FWCN%2F2006%2F43275.pdf

Decision-directed recursive least squares MIMO channels tracking

A system for communications on an extraterrestrial body may include a space-based component and an ancillary extraterrestrial component on the extraterrestrial body. The space-based component may be configured to provide wireless communications with a plurality of radioterminals located on the extraterrestrial body over a satellite frequency band wherein the space-based component includes at least one satellite orbiting the extraterrestrial body. The ancillary extraterrestrial component may be configured to provide wireless communications with the plurality of radioterminals located on the extraterrestrial body. Moreover, the ancillary extraterrestrial component may reuse at least one satellite frequency of the satellite frequency band, and the space-based component and the ancillary extraterrestrial component may be configured to relay communications therebetween. Related methods are also discussed.

Communications systems and methods including emission detection

The spatial filtering properties of adaptive antenna arrays in wireless networks make it possible to confine the radio energy associated with a given user to a small addressed volume. This reduces the overall level of co-channel interference within the service area and ultimately leads to an increase in capacity for interference limited systems. In addition, by using the antenna array to spatially separate and reject multipath energy, the resulting delay spread can be significantly reduced offering the possibility of service in areas which would otherwise be restricted by time dispersion. The article show that adaptive antenna arrays, when applied to a DECT system, can increase service provision to areas which would otherwise be limited by multipath propagation. Furthermore, the use of spatial filtering allows the possibility of multiple users on the same frequency and time slot by minimising co-channel interference from other users. The capacity increase achievable can be as much as seven times.

http://ieeexplore.ieee.org/iel3/3160/8978/00396208.pdf

Capacity and service extension for future wireless networks using adaptive antennas

Results highlighting the capacity enhancement and service or range extension of a wireless communication network employing adaptive antenna technology are presented. The picocellular service area was modelled using ray tracing techniques, and it has been shown that the maximum RMS delay spread was reduced from > 100 ns to < 30 ns by employing a beamformer with an associated array capable of forming multiple 15° wide beams. In addition, a seven-fold increase in the overall spectrum efficiency was predicted.

P Guemas

Papers

Capacity and service extension for future wireless networks using adaptive antennas

Capacity and service extension for wireless networks using adaptive antennas