Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Patent
1997-05-23
1999-02-02
Eisenzopf, Reinhard J.
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
455560, 455561, 455524, H04B 106
Patent
active
058677917
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to macro diversity in a digital mobile radio communication system, and in particular to an up link macro diversity method and apparatus in such a system.
BACKGROUND
In conventional digital cellular mobile radio communication systems a mobile station communicates with only one base station at each given time. However, recently it has been suggested to use so called macro diversity in such systems. This concept means that in the down link direction several base stations send the same information blocks to a mobile station, which combines the sent blocks into a final received block. In the up link direction a mobile station transmits an information block which is received at several base stations. The received blocks are transmitted to a common node in the land system, for example a mobile services switching center, where the received blocks are combined into a final received block. These procedures increase the reliability of the received information blocks, since the information has now travelled along different paths, one of which may distort the information less than the other.
A drawback of these up link diversity methods is that the received information blocks from several base stations have to be sent to the mobile services switching center, which reduces the capacity of the land system.
SUMMARY
An object of the present invention is therefore to provide an up link macro diversity method and apparatus in a digital cellular mobile radio communication system in which the capacity of the land system is increased by reducing the amount of information that has to be transferred between base stations and the next node of the land system of said communication system, for example a mobile services switching center.
One way to combine information blocks from several base stations is to use only the information from the "best" block. In such a case it would be unnecessary to transfer the information of discarded blocks between base stations and the mobile services switching center. Thus, the present invention is based on the idea that instead of transferring all the received blocks, it is sufficient to calculate a quality measure for each block and to transfer only these quality measures. The quality measures received by the mobile services switching center are then compared, and the base station from which the best quality measure was received is ordered to transfer its information block.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention, together with further objects and advantages thereof, may best be understood by making reference to the following description taken together with the accompanying drawings, in which:
FIG. 1 is a block diagram of a part of a digital cellular mobile radio communication system illustrating the concepts of the present invention;
FIG. 2 is a diagram illustrating the signal transfer between base stations and a mobile services switching center operating in accordance with the present invention; and
FIG. 3 is a flow chart illustrating the method in accordance with the present invention.
DETAILED DESCRIPTION
The present invention will now be described with reference to a digital cellular radio communication system of TDMA type. However, the invention is not restricted to such systems, but is also applicable to other digital cellular systems, such as CDMA systems.
In FIG. 1 a mobile MS transmits information blocks, which are received at two base stations BS1 and BS2. The received signals are demodulated and decoded in accordance with conventional methods, and the resulting information blocks BL1 and BL2, respectively, are stored in respective buffers BUF1 and BUF2. In a preferred embodiment an information block is a frame, which typically corresponds to 10-40 ms of speech/data. Microprocessor controllers MPC1 and MPC2, respectively, retrieve relevant bits over bit retrieval lines B for calculating and outputting corresponding quality measures Q1 and Q2, respectively, of the stored blocks BL1 and BL2.
Here the concept quality measur
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Aokz Makoto
Eisenzopf Reinhard J.
Telefonaktiebolaget LM Ericsson
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