Telecommunications – Receiver or analog modulated signal frequency converter – With wave collector
Patent
1995-04-26
1999-11-23
Eisenzopf, Reinhard J.
Telecommunications
Receiver or analog modulated signal frequency converter
With wave collector
455275, 455562, H04B 106
Patent
active
059916133
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for antenna selection control in a radio receiver and to an arrangement for antenna selection control in a radio receiver.
In the case of radio-frequency telecommunication in the gigahertz region, because of the propagation characteristics the transmission conditions are frequently very different within a small spatial region (centimeter region). The consequence of this is that in the case of moving systems the transmission conditions fluctuate strongly in time even at low speeds of, for example, approximately 1 m/s. In order to be able to achieve transmission which is as good as possible during movement even in regions with poor transmission conditions, a second, spatially offset antenna is installed at the base station, which second antenna, because of the spatial separation, provides other transmission conditions and to which it is possible to switch in this case (antenna diversity). Such an antenna control is provided in essence in the "Digital European Cordless Telecommunications System" (DECT) Standard (draft prETS 300 175-3: 1991, page 183/184). An antenna switch-over is provided in this standard on the basis of the quality of reception in the following cases:
The "burst-mode two-way communications system" has already been disclosed in European Patent Application EP 0 213 780 A2 (Application No.: 86306015.8). By contrast with the arrangement according to the invention, the known system has a plurality of transceiver devices having one threshold value arrangement each, which are connected to a switching element for switching over to one of two antennas. The threshold value arrangements realize a prescribed absolute threshold value (page 3, column 3, lines 55/56). The threshold value is, however, also to be adjustable from outside by means of software, and thus to be optimizable, it remaining open in the published European Patent Application how such an adjustment and optimization would have to be performed (column 3, lines 57/58; column 4, line 41). In particular, it also remains open whether such an optimization is performed by a single adjustment of the threshold value, for example during manufacture or upon commissioning of the apparatus, or is also performed in continuous operation. Obviously, only a single adjustment of the threshold value is provided, since it is stated in the European Patent Application that in practice the threshold value corresponds to that value at which reception is still just adequate ("worst-case service"), generally 15 dB below an average field strength at maximum range (column 4, lines 41-46).
In the known system, signal fades (drops in field strength) are detected by means of a rapid rate of change in the received field strength, this parameter being compared with values averaged over a plurality of time periods (column 4, lines 47-56). However, the averaging, provided for in this case, requires substantial computational outlay and a corresponding computing time. There is no provision in the known system to change the threshold value with rising field strength values.
Specifically, if appropriate systems contain two antennas, but only one receiver, there is the substantial problem for the control of the antenna switch-over that the quality of the signals received at both antennas cannot be measured simultaneously. The measurements have to be carried out one after the other in order to decide at which antenna signals of better quality of reception can be received. In this case, there is the difficulty, on the one hand, that a measurement at one antenna is bound up with the reception of a burst at this antenna, and that the measurement result "poor quality of reception" can lead to a loss of data. On the other hand, a further problem consists in that, depending on the speed of movement of the actual device or of a corresponding device to which there is a radio connection; and on the burst rate, the measurement result is valid only for a few bursts. A further difficulty consists in that the receiving conditio
REFERENCES:
patent: 4462099 (1984-07-01), Braun
patent: 5161252 (1992-11-01), Higuchi et al.
patent: 5239541 (1993-08-01), Maurai
"On The Radio Link Performance Of The Digital European Cordless Telecommunications (DECT) System", L.B. Lopes, Proceedings of Globecom 90, Dec. 2-5, 1990, pp. 1013-1017.
"Predictive Antenna Selection Diversity (PADS) For TDMA Mobile Radio", Y. Yamao et al, Proceedings of 1991 International Conference On Communications--ICC 91, Jun. 23-26, 1991, pp. 1480-1484.
"A Business Cordless PABX Telephone System On 800 MHz Based On The DECT Technology", C. Buckingham et al, IEEE Communications Magazine, vol. 29, No. 1, Jan. 1991, pp. 105-110.
Euscher Christoph
Pillekamp Klaus-Dieter
Armstrong Darnell R.
Eisenzopf Reinhard J.
Siemens Aktiengesellschaft
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