Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
2000-10-02
2001-11-20
Patel, Ajit (Department: 2662)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C331S143000, C331S143000, C331S143000, C331S143000
Reexamination Certificate
active
06320854
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for allocating a radio channel in a radio communications system. The radio communications system uses radio channels, which are in each case formed by at least one timeslot for transmitting information. The invention further relates to a corresponding radio communications system.
The allocation of radio channels to mobile stations in a radio communications system is normally carried out by radio stations which supply radio resources to the mobile stations or radio subscribers in their associated radio cells. The information is transmitted, via a radio interface, on the allocated radio channel, which is in each case formed by at least one timeslot. Channel allocation problems occur whenever interference occurs among the mobile stations and/or the radio stations, or between a mobile station and a radio station. Particularly in the case of radio communications systems having a frequency repetition interval (reuse cluster) equal to unity, the high interference level means that a soft handover, that is to say connection relaying, is required, in which the mobile stations or radio subscribers at cell boundaries must be supplied with radio resources simultaneously from at least two radio stations. This results in radio stations being networked with one another and results in a considerable additional signaling complexity. Furthermore, the overall capacity of the radio communications system is reduced by subscribers or mobile stations who or which remain in such a soft-handover area.
Published European Patent Application EP 0 411 878 A2 discloses a configuration for managing the power control for radio channels in a radio communications system having a number of base stations and mobile stations. In this case, the radio channels are each allocated an individual transmission/reception power level as a function of the prevailing transmission conditions.
Published British Patent Application GB 2 288 517 A discloses a radio communications system, in which the interference levels of the radio channels are monitored, and are compared with a reference level. A new channel is then chosen if this channel has a level which is lower than the reference level.
A method for a dynamic allocation of transmission channels under different conditions in a communications system is described in the article “Distributed Measurement-based Dynamic Channel Assignment for Personal Communications”, IEEE, volume 2, No. CONF.45, Jul. 25, 1995. An allocation algorithm is proposed, which operates on the principle of a least possible interference.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and a radio communications system for allocating a radio channel which overcome the disadvantages of the heretofore-known methods and systems of this general type and which increase the efficiency of the channel allocation and avoid the disadvantages of a soft handover.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for allocating a radio channel in a radio communications system, the method includes the steps of:
providing radio channels for a transmission of information, the radio channels being formed by at least a respective one of a plurality of timeslots;
performing a channel allocation by allocating, with a radio station, a given one of the radio channels for a downlink direction to a mobile station as a function of a channel allocation pattern, the channel allocation pattern indicating transmission power levels for the plurality of timeslots; and
correcting, with the mobile station, the channel allocation as a function of an interference pattern indicating interference power levels in the plurality of timeslots.
In other words, based on a channel allocation in a radio communications system with timeslots, the invention provides that a radio station allocates the radio channel for the downlink direction to a mobile station as a function of a channel allocation pattern which indicates the transmission power levels for the timeslots, and that the mobile station corrects the allocation of the radio channel, controlled by the mobile station, as a function of an interference pattern which indicates the interference power levels in the timeslots.
The allocation process results in the transmission power level being distributed as uniformly as possible between the timeslots which are provided for the connection from the radio station in the downlink direction, as a function of the occupancy of the timeslots in accordance with the channel allocation pattern. The combination with the possibility of correcting the allocated timeslot—to a timeslot with a lower interference power level on the basis of the interference pattern—under the control of the mobile station allows to avoid a disadvantageous soft handover, even with a frequency repetition interval (cluster reuse) equal to unity, which is critical for interference. The mobile station preferably uses a rapid MAHO method (Mobile Assisted Handover) for correction.
According to another mode of the invention, in the situation where the interference pattern at the mobile station has a high interference power level for the timeslot of the allocated radio channel, the mobile station initiates a switching from the allocated timeslot to another timeslot with a lower interference power level.
In accordance with another mode of the invention, the mobile station initiates a switching from a given one of the timeslots assigned to a given one of the radio channels to another one of the timeslots having a lower interference power level than the given one of the timeslots, if the interference pattern at the mobile station has a high interference power level for the given one of the timeslots.
In accordance with yet another mode of the invention, the interference pattern is formed by superimposing channel allocation patterns of a plurality of radio stations, in particular of adjacent radio stations.
In accordance with a further mode of the invention, the transmit information is distinguished on the basis of a subscriber-specific fine structure in one of the timeslots for a simultaneous transmission of the information to a plurality of mobile stations.
In accordance with another mode of the invention, spread codes in accordance with a CDMA (Code Division Multiple Access) method are used for the subscriber-specific fine structure.
In accordance with yet another mode of the invention, spatial incidence directions of training sequences in accordance with an SDMA (Spatial Division Multiple Access) method are used for the subscriber-specific fine structure.
In accordance with a further mode of the invention, the timeslots are organized in accordance with a TDMA access method or a TDD (Time Division Duplex) access method and the radio channels are formed from the timeslots of the TDMA access method or the timeslots of the TDD access method.
In accordance with another mode of the invention, the radio station allocates one of the radio channels for an uplink direction to the mobile station as a function of the interference pattern generated from received timeslots.
In accordance with yet another mode of the invention, the radio station selects one of the radio channels currently having a lowest interference power level for a connection to a further mobile station.
A combination of the method based on a timeslot structure—for example a TDMA or TDD method—with a subscriber-specific fine structure in order to distinguish information transmission in one and the same timeslot—for example for the CDMA (Code Division Multiple Access) method or the SDMA (Space Division Multiple Access) method—is particularly advantageous.
With the objects of the invention in view there is also provided, a radio communications system for allocating a radio channel, including:
a mobile station; and
a radio station operatively connected to the mobile station, the mobile station and the radio station being configured for use with radio channels ea
Färber Michael
Haardt Martin
Klein Anja
Kottkamp Meik
Mohr Werner
Greenberg Laurence A.
Lerner Herbert L.
Patel Ajit
Siemens Aktiengesellschaft
Stemer Werner H.
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