Array processing involves manipulation of signals induced on various antenna elements. Its capabilities of steering nulls to reduce cochannel interferences and pointing independent beams toward various mobiles, as well as its ability to provide estimates of directions of radiating sources, make it attractive to a mobile communications system designer. Array processing is expected to play an important role in fulfilling the increased demands of various mobile communications services. Part I of this paper showed how an array could be utilized in different configurations to improve the performance of mobile communications systems, with references to various studies where feasibility of apt array system for mobile communications is considered. This paper provides a comprehensive and detailed treatment of different beam-forming schemes, adaptive algorithms to adjust the required weighting on antennas, direction-of-arrival estimation methods-including their performance comparison-and effects of errors on the performance of an array system, as well as schemes to alleviate them. This paper brings together almost all aspects of array signal processing.

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Application of antenna arrays to mobile communications. II. Beam-forming and direction-of-arrival considerations

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

A location system for identifying locations of emitters (1) in a cellular telephone service area. Searching (4) identifies active emitters in the service area to find the coarse areas in which active emitters (1) are located, using selection criteria to designate one or more of the active emitters as selected emitters. Emitter signals are measured with a plurality of sensors (19) each sensor at a different location. Groups of the sensors are tasked, one group of tasked sensors for each corresponding selected emitter. Each tasked sensor takes a measurement on an emitter signal transmitted by the corresponding selected emitter. The measurements are processed (5) to determine the location of each selected emitter based on the measurements from the group of tasked sensors.

Method and apparatus for mobile emitter location

Processes and compositions are provided for decreasing emissions of mercury upon combustion of fuels such as coal. Various sorbent compositions are provided that contain components that reduce the level of mercury and/or sulfur emitted into the atmosphere upon burning of coal. In various embodiments, the sorbent compositions are added directly to the fuel before combustion; are added partially to the fuel before combustion and partially into the flue gas post combustion zone; or are added completely into the flue gas post combustion zone. In preferred embodiments, the sorbent compositions comprise a source of halogen and preferably a source of calcium. Among the halogens, iodine and bromine are preferred. In various embodiments, inorganic bromides make up a part of the sorbent compositions.

Reducing mercury emissions from the burning of coal

A method and apparatus for measuring the time difference of arrival between two received signals, each received signal being a time delayed version of a transmitted signal (12) as intercepted at two different sensors (24/124) where the transmitted signal is generated by a radio frequency transmitter (10). The apparatus includes a sensor (24) having a receiver (15) which receives a received signal and generates a receiver output signal, a decoder (27) which decodes an encoded signal transferred from another sensor (124) to generate a reconstructed signal (28) representative of the transmitted signal received at the other sensor (124) and a correlator (29) for correlating the reconstructed signal and the receiver output signal to determine a time difference of arrival (30) of the receipt of the transmitted signal at the respective sensors.

Time difference of arrival measurement system

The hardware implementation of an adaptive array as a technique for compensating multipath fading in mobile communications is described. The number of the antenna elements is four. The target communication system is modulated by 256 kbps Gaussian-filtered minimum shift keying (MSK) and has a time-division multiplexing (TDM) architecture with 24 time slots. Based on the digital beamforming concept, all of the signals and the array weights are digital-signal processed. The constant modulus algorithm (CMA) is employed for weight optimizing. In an additive white Gaussian noise channel, this system has 5.6-dB gain in an energy-per-bit-to-noise-density ratio at a bit error rate (BER) of 1.0*10/sup -3/, compared with a single antenna system. The result of the basic field test shows that the gain at a BER of 1.0*10/sup -3/ reaches 22.3 dB in a nonselective, slow Rayleigh fading channel given a 5 Hz maximum Doppler shift. >

An implementation of a CMA adaptive array for high speed GMSK transmission in mobile communications

This paper describes the performance of an adaptive array as a countermeasure to multipath fading for a 256 kbps Gaussian-filtered minimum shift keying (GMSK) mobile communication system operating in the 1.5 GHz band. An adaptive array having four antenna elements is implemented using the digital beam forming concept. The constant modulus algorithm (CMA) is employed for the adaptation process to ease the implementation. Measurements in central Tokyo of the bit error rate (BER) performance and an array pattern arising in the multipath environment are presented. Analysis of the array pattern confirms that the array succeeds in directing nulls to the delayed signals. BER performance shows an improvement in E/sub b//N/sub 0/, compared with that of a single antenna system, of 17.5 to 22 dB at a BER of 1.0*10/sup -2/ in a frequency-selective fading channel. >

BER performance of CMA adaptive array for high-speed GMSK mobile communication-a description of measurements in central Tokyo

The authors describe a hardware implementation of a GMSK/TDMA (Gaussian minimum-shift keying/time-division multiple-access) communication system and show the bit error rate (BER) performance of the system. This system employs a modulation data rate of 256 kb/s and accommodates 24 users/carrier. In order to reduce the effect of multipath fading, an adaptive array which has four antenna elements is implemented using a digital beamforming concept. All signal processing is carried out by digital signal processors. In an AWGN (additive white Gaussian noise) channel, this system has a 6-dB gain in input power at a BER of 1.0*10/sup -3/ compared with the ordinary system with only one antenna. A field test shows that the gain at a BER of 1.0*10/sup -3/ becomes 20 dB in a flat fading channel. >

A development of GMSK/TDMA system with CMA adaptive array for land mobile communications

The bit-error-rate (BER) performance of a constant modulus algorithm adaptive array for a Gaussian-filtered minimum shift keying/time division multiple access (GMSK/TDMA) system is described. The measurement was carried out in central and suburban Tokyo. The system uses a modulation data rate of 256 kb/s. In order to reduce the effect of multipath fading, an adaptive array of four antenna elements is implemented using a digital beam forming concept. The improvement in input power, compared with that of a single antenna system, reaches 16 dB in suburban Tokyo and 19 to 23 dB in central Tokyo at a BER of 1.0*10/sup -2/. Moreover, in central Tokyo, the irreducible error seen in the single antenna system is removed by the adaptive array. >

T. Shimura

Papers

An implementation of a CMA adaptive array for high speed GMSK transmission in mobile communications

BER performance of CMA adaptive array for high-speed GMSK mobile communication-a description of measurements in central Tokyo

A development of GMSK/TDMA system with CMA adaptive array for land mobile communications

BER performance of CMA adaptive array for a GMSK/TDMA system-a description of measurements in central Tokyo