Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
2001-03-28
2004-01-27
Maung, Nay (Department: 2684)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S448000, C370S509000, C370S335000
Reexamination Certificate
active
06684079
ABSTRACT:
The present invention relates to a method for disturbance-free operation of at least two, preferably in-house UMTS (Universal Mobile Telecommunication System), base stations with partially overlapping radio fields in a telecommunications radio cell network, the base stations transmitting communications information using the CDMA (Code Division Multiple Access) multiple access method, and also to a base station and to a mobile station for disturbance-free operation in a universal mobile telecommunications system.
DESCRIPTION OF THE PRIOR ART
It is known, in wire-free communications systems, to utilize physical channels for the transmission of messages or data. By the utilization of such physical channels, the communications information, for example in the form of real time video voice data or recently real time data, is communicated via an air interface from a first station to a second station. In the case of duplex radio connections, information is also exchanged in the opposite direction via the same air interface.
Parameters of the physical channels are, for example, a specific time slot in a TDMA (Time Division Multiple Access) radio communications system, a specific carrier frequency utilized during the communication of the communications information in an FDMA (Frequency Division Multiple Access) radio communications system, and a specific code used to code the communications information for radio transmission in a CDMA (Code Division Multiple Access) radio communications system. Combinations of the known multiple access methods TDMA, FDMA and CDMA are also possible.
In a known mobile radio system, in particular the so-called GSM system (Global System for Mobile Telecommunication), the allocation of the radio channels via which communications information can be transmitted between a specific base station and a specific mobile part is performed centrally by a coordination unit. The coordination unit assigns a specific number of radio channels to the individual control units of the GSM base stations taking account of specific country conditions (e.g., the interference situation calculated a priori).
Furthermore, radio communications systems exist which work in so-called uncoordinated operation. In systems of this type, the radio channels are not allocated centrally for the entire system, rather the radio stations participating in a radio connection that is to be set up select for themselves the relevant channels from an existing channel supply according to specific criteria. One example of a radio station which works in the uncoordinated operation mentioned above is that which operates according to the DECT standard.
Thus, in known radio communications systems, in particular in a GSM, a system according to the DECT standard or in the future UMTS, duplex radio connections are set up in order to bidirectionally transmit data even at relatively high data rates, voice information or, generally, communications information of other services via a radio interface. Known methods include here, in particular, the so-called TDD (Time Division Duplex) method, in which a first radio channel and a second radio channel of the same duplex radio connection utilize different time slots of the same carrier frequency.
The third-generation mobile radio system UMTS is intended to cover both the conventional so-called outdoor range and in-house range. For the optimal functioning of a mobile radio system of this type, the envisaged resource planning is inherently provided, and explicit frequency planning is not necessary. While a handover to the adjacent base station is made under severe interference conditions (adjacent base station is a source of interference) in the outdoor range, this cannot happen with in-house base stations. Therefore, in this case an effective method of interference elimination (synchronization→midamble→interferences) is crucial for a high spectral efficiency of the system. In the case of a mobile radio system which covers both the quasi-public and the private sectors, the difficulty that arises for the operator is that home base stations installed in the private sector are not under the control of the operator and, therefore, cannot be controlled from the network.
In the case where, on account of such home base stations becoming increasingly widespread, such home base stations are located in direct proximity, which is the case for example in a multiple dwelling, the radio fields of the individual home base stations can then overlap, with the consequence of reciprocal interference and of limited or interference-impaired radio transmission.
In the DECT structure, that channel which allows an undisturbed connection set-up for data transmission is selected in a quasi self-organizing manner by the subscribers of the respective local network before the connection set-up. In the case where interference occurs, a channel changeover is made to a channel which is once again free from interference or freer from interference, such changeover generally being imperceptible to the user. Since the radio communication is realized under TDMA in the case of the DECT system, a channel changeover is not very problematic even in the absence of synchronization between the subscribers; i.e., in the event of a changeover to another base station.
Difficulties arise, however, when the CDMA multiple access method is intended to be used for a universal mobile radio system. In that case, the chip synchronism, i.e. the use of mutually orthogonal CDMA codes, is a prerequisite for preventing interference caused by the users or in order to obtain optimal spectral network efficiency. If a number of base stations are operated asynchronously in such a system, severe interference and, under certain circumstances, considerable losses of capacity shall be registered on account of the lack of orthogonality of the CDMA codes; particularly when, even in the in-house range, high-bit-rate data services are intended to be handled or taken up via the system.
Ep 0 865 172 A2 discloses a method for operating at least two overlaid wire-free communications systems, the two communications systems being at least one indoor and one outdoor communications system and, for interference-free operation of the two systems, existing radio connections in the in-house range being handled via time slots in accordance with a time division duplex method and, at the same time, these time slots being utilized in order to monitor radio channels utilized for existing radio connections in the outdoor range, with the result that rapid reaction to changing traffic requirements or reaction to interferences is possible.
It is an object of the present invention, therefore, to specify a method for disturbance-free operation of at least two in-house UMTS base stations with partially overlapping in-house radio fields in a telecommunications radio cell network, the assumption being that the base stations transmit communications information according to the CDMA principle; i.e., multiple access method. The present invention is intended to increase the spectral efficiency through optimal utilization of the network conditions, without the need for reserving a broad frequency spectrum specifically for the in-house application. At the same time, the present invention is intended to improve the signal or data transmission quality, so that even in a region of high local density of the base stations, there is sufficient channel capacity available for data transmission.
SUMMARY OF THE INVENTION
Accordingly, the method-pertaining basic concept of the present invention consists in the fact that the at least two participating base stations which have partially overlapping radio fields perform an autosynchronization procedure for the purpose of eliminating disturbing interferences precisely on account of the overlapping radio fields and the fact that it is no longer possible to fall back to two frequencies. Chip synchronism is achieved as the result of this autosynchronization procedure, and it is thus assured that orthogonality of the codes of the mult
Aretz Kurt
Bolinth Edgar
Kamperschroer Erich
Schwark Uwe
Bell Boyd & Lloyd LLC
Corsaro Nick
Maung Nay
Siemens Aktiengesellschaft
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