Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1999-03-17
2001-10-30
Trost, William (Department: 2683)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S525000
Reexamination Certificate
active
06311074
ABSTRACT:
The invention is directed to a base station for communication connections to mobile stations via radio interfaces and to a method for covering a cell of a cellular mobile radiotelephone system.
Mobile communication systems, for example mobile radiotelephone systems such as the GSM (Global System for Mobile communication) mobile radiotelephone system, enable the setup of communication connections from and to mobile subscribers in that information are transmitted via a radio interface. Various methods for separating the subscribers can be utilized on the radio interface, including time-division multiplex and frequency-division multiplex methods.
In mobile radiotelephony, the information on the radio interface are transmitted with electromagnetic waves. After the transmission over the radio interface, only a part of the energy is absorbed by the reception antenna of the receiving radio station. In a typical use environment of a mobile communication system, the transmitted information are subject to various disturbances on the radio interface. The information send from the transmitting station reach a receiving station over various propagation paths, so that the signal components of various propagation paths superimpose at the receiving station. Moreover, occlusions can considerably impede the transmission of information from a transmitting station to the receiving station. Interferers in the frequency band of the respective communication connection also lead to a deterioration of the quality of the received signals.
European Letters Patent 0 617 861 B1 discloses a method for improving the radio cell illumination in a cellular mobile radiotelephone system. In this method, the information of a communication connection are transmitted to a mobile station with a single carrier frequency from a plurality of radio stations, typically three branches of a base station, at the edge of a cell to be covered. The signals of the individual branches superimpose at the mobile station and thereby lead to an improvement in the quality of the communication connection. The signals sent from the mobile station are received by all branches of the base station covering the cell and are subjected to a diversity-combination method. The connection from the mobile station to the base station can thus also be improved.
However, a considerable outlay arises due to this configuration of a base station since, compared to a base station that comprises an omnidirectional characteristic in the middle of a cell or compared, too, to conventional sector cells, triple the number of transmission and reception devices must be offered. An improvement of the transmission quality is thus only possible with a greatly increased circuit-oriented outlay, so that the method is very expensive for a mobile radiotelephone network operator.
The invention is based on the object of specifying a base station and a method for covering a cell of a cellular mobile radiotelephone system that, upon retention of the advantages of the multiple connection, reduce the outlay for covering a cell. This object is achieved by the base station according to the features of patent claim
1
and by the method according to the features of patent claim
11
. Advantageous developments can be derived from the subclaims.
According to the invention, a base station for communication connections to mobile stations via radio interfaces contains at least one combination means.
At least two base station branches for the coverage of a cell are connected to this combination means. The combination means is provided for monitoring the transmission quality for a communication connection between a mobile station and the at least two base station branches. Corresponding to the identified transmission quality for a communication connection, the combination means undertakes an activation or, respectively, deactivation of further base station branches. The activation or, respectively, deactivation ensues in both transmission directions. When a base station branch is add [sic], then the information transmission between this base station branch and the mobile station in both directions for said communication connection ensues in addition to the information transmission that is already ensuing via the previously activated base station branches.
As a result of the flexible cut-in or, respectively, out of additional base station branches, the transmission quality can be improved or, respectively, it is possible to reduce the outlay for base station branches required for a communication connection given adequate transmission quality. No separation of the two transmission directions thereby ensues; rather, both transmission directions are switch [sic] in common. It is thereby possible to release a transmission and reception unit in a base station branch. The evaluation and [sic] of the monitored transmission quality and the triggering of the cut-in or, respectively, out of branches can also be initiated by a control means outside the combination means. A signal combination, for example addition, and distribution of the reception signals of the individual branches always advantageously occurs in the combination means.
The identify [sic] transmission quality is checked overall for the individual branches and for the communication connection. Which branches are required for assuring an adequate transmission quality and which are not required can thus be determined. The corresponding branches are activated or, respectively, deactivated for the connection under consideration. The activation and deactivation ensues in both transmission directions. The transmission and reception equipment that have been released at the deactivate [sic] branch can be used for a communication connection of a different mobile station due to the release in both transmission directions; i.e. transmission and reception equipment are not reserved at all branches during the existence of a communication connection but are dynamically cut in or, respectively, out as needed. It is thus possible to better utilize transmission and reception equipment, i.e. undertake savings, upon retention of the advantages of multiple coverage.
Upon employment of standard radio propagation models and of the model of the reception power addition in the signal combination, the percentage of connections that require additional branches (for example, reception level lower than the average level in the cell) and wherein the additional branches effect a substantial improvement of the reception conditions (for example, reception level improvement of more than 1 dB) was found by simulations. As a typical result, one thereby obtains:
Connections with one branch: 65%,
Connections with two branches: 25%, and
Connections with three branches: 10%.
The average number of branches per connection is thus 1.45. Only about 1.5 instead of three branches are thus needed on average and a savings of 50% for transmission and reception equipment can be realized by the inventive base station.
In the inventive base station, a base transmission/reception station or sector antenna that was disconnect [sic] for a communication connection is cutted [sic] in on a different carrier frequency for a further communication connection. As a result of this design, an improved utilization of the transmission and reception equipment of the base station and an improved utilization of the system resources for the purpose of enhancing the network capacity derive. The transmission equipment of a base station are advantageously fashioned such that a switching of the carrier frequency is possible related to time slots given a time-division multiplex method. A dynamic allocation of a logical channel [sic] to a physical channel thus ensues for each time slot.
In the inventive base station, the base station branches are formed by base transmission/reception stations that are respectively arranged at the edge of the cell or, alternatively, by sector antennas to which different sectors of a cell are
Bell Boyd & Lloyd LLC
Perez-Gutierrez Rafael
Siemens Aktiengesellschaft
Trost William
LandOfFree
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