Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-05-26
2003-07-15
Le, Thanh Cong (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S067150, C455S067700
Reexamination Certificate
active
06594487
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reception device for a radio communication system for receiving subscriber signals via a radio interface wherein the reception device contains a device for determining a number of active subscribers from a total number of subscribers that are assigned to the radio interface and further contains a detection device for detecting at least one subscriber signal.
2. Description of the Prior Art
Radio communication systems serve for the transmission of subscriber signals via a radio interface with the assistance of high-frequency oscillations. Such radio communications systems are, for example, mobile radio telephone networks or devices for wireless subscriber connection to a fixed network. When the subscriber signals of various subscribers are transmitted via the radio interface, it is called a multi-subscriber message transmission system. Time-division multiplex, frequency-division multiplex or code-division multiplex methods can be employed for separating the subscribers. It is also possible to combine these methods.
When, according to a multi-subscriber message transmission system, for example, K different subscribers are allocated to the radio interface formed by a channel, the corresponding reception device must be able to undertake a separation of the subscriber signals. Depending on the number of different subscribers, this leads to a considerable detection outlay in the reception device, since the actual conditions on the radio interface are unknown to the reception device.
U. Mitra, H. V. Poor, “Neural Network Techniques for Multi-User Demodulation”, Proceedings of the international conference on neural networks, San Francisco, Mar. 28-Apr. 1, 1994, Vol. 3, pp. 1538-1543, and B. Aazhang, B.-P. Paris, “Neural Networks for Multi-User Detection in Code-Division Multiple-Access Communications”, IEEE Transactions on Communications, Vol. 40, No. 7, Jul. 1, 1992, pp. 1212-1222, disclose detection principles for CDMA transmission methods suitable for a different number of subscribers. EP-A-0 526439 discloses a CDMA receiver wherein only the strongest signals are evaluated. Further, P. Jung, B. Steiner, “Konzept eines CDMA-Mobilfunksystems mit gemeinsamer Detektion für die dritte Mobilfunkgeneration”, Nachrichtentechnik/Elektronik 45 (1995), March/April 1995, pp. 24-27, discloses a CDMA transmission method in time slots.
The invention present is, present therefore present direct toward reducing the detection outlay.
SUMMARY OF THE INVENTION
The inventive reception device for a radio communication system for the reception of subscriber signals via a radio interface contains a device for determining the plurality K′ of active subscribers from a set of K subscribers allocated to the radio interface and contains a detection device for detecting at least one subscriber signal. A signal mix present at the reception device can be processed better and the subscriber signals can be detected better since, given a plurality K′<K of active subscribers, the set of subscribers to be taken into consideration in the detection is reduced.
According to an embodiment of the present invention, the reception is improved further when the device for determining the K′ active subscribers is connected such to the detection device that the plurality K′ of active subscribers and their identity is communicated to the detection device. When the K′ active subscribers are known to the detection device on the basis of their identify, then a plurality K-K′ of subscribers can remain out of consideration in the separation of the subscriber signals.
When the subscriber signals arrive at the reception device by radial blocks, then the device for determining the K′ active subscribers advantageously determines these from the subscriber signals related to radial blocks. Since the plurality of the K′ active subscribers can change from radial block to radial block, a determination of the K′ active subscribers from the subscriber signals constantly gives the reception device current values that are required for the detection. Some other signaling regarding the plurality of K′ active subscribers thereby need not be undertaken. A plurality of radial blocks can be combined for a higher measuring position in this evaluation related to radial blocks.
The inventive reception device is particularly advantageous when the subscriber signals are primarily separated by a fine structure. Such a fine structure is established, for example, in the code-division multiplex method (CDMA-code division multiple access) since a subscriber-related code is allocated to every subscriber at the transmission side. As the corresponding reception device knows at least the code of the at least one subscriber signal.
The separation of the subscribers thus occurs via their subscriber code. The subscriber signals are modulated with this subscriber code. When the subscriber signals, as disclosed, for example, by German Letters Patents DE 41 21 356 C2 or DE 43 29 320 A1, are detected according to what is referred to as the JD (joint detection) CDMA method, then it is particularly significant that the plurality of subscriber codes to be taken into consideration is reduced. The inventive reception device offers particular advantages here.
According to a further embodiment of the reception device, the device for determining the K′ active subscribers is connected such to the detection device that the fine structures of the K′ active subscribers are communicated to the detection device. The fine structures that are thus communicated serve the JD-CDMA detection algorithm for separating one or more subscriber signals accordingly the influence of the respectively other K′−1 active subscribers is also taken into consideration. The device for determining the K′ active subscribers is advantageously configured such that a respective test quantity is determined from the K possible subscriber signals and is compared to a threshold. Which of the K subscribers is, in fact, active at the moment derives from this comparison.
According to an a further embodiment, this test quantity has been determined from a quantity proportional to the energy of a channel pulse response of the respective subscriber signal. A channel model of the reception device is required for distortion-correction of subscriber signals, for which reason a channel pulse response is determined for each subscriber signal and the channel model can be balanced accordingly. The energy of the channel pulse response or, respectively, equivalent quantities such as the power, is a suitable quantity for determining the activity of a subscriber. Alternatively, the test quantity quantity can be determined from a sum of the amounts of samples of the respective subscriber signals; for example, of the data-bearing part of the subscriber signal. Given a digital transmission, samples from which the subscriber signals are subsequently to be reconstructed are identified at the reception device. A conclusion about the activity of the respective subscriber is all the more reliable the more strongly the samples contrast with noise on the radio interface.
According to further embodiments of the present invention, the test quantity can be determined from a data-carrying part of the respective subscriber signal (particularly suitable when no balance values are available), i.e. from the samples for corresponding data symbols, or from a test sequence of the respective subscriber signal. A test sequence is thereby a plurality of symbols that is sent by the respective transmission device in addition to the transmitted data and that is known undistorted at the reception device. For example, the reception device can determine the channel pulse response from a comparison of known test sequence to received test sequence.
When the set of possible fine structures is limited, then the advantage arises for the reception device that the set of K subscribers can als
Klein Anja
Nasshan Markus
Bell Boyd & Lloyd LLC
Cong Le Thanh
Nguyen Thuan T.
Siemens Aktiengesellschaft
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