Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Patent
1995-11-13
1998-01-20
Eisenzopf, Reinhard J.
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
455502, 370331, H04B 726, H04J 316
Patent
active
057110034
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns a method of intercellular transfer between two cells of a cellular mobile radio network such as a GSM (Global System for Mobile communications) network. When a mobile station moves from one cell to another neighboring cell of a mobile radio network, each cell having a base transceiver station, the continuity of the call in progress may need to be preserved, and the frequency used for exchanging speech data (or signalling data) between a mobile station (hereinafter called a "mobile") and a base transceiver station changes on moving from one cell to another neighboring cell. A method used to achieve this continuity is known as "handover" in the GSM system.
The following description uses the terminology of the GSM system. For more information, reference may be made to the proceedings of the "Digital Cellular Mobile Communication Seminar" held in Nice from 16 through 18 Oct. 1990.
FIG. 1 is a diagrammatic representation of part of the structure of a GSM network made up of a plurality of cells, of which only three cells C1, C2 and C3 are shown. A mobile MS (for example a mobile telephone in a vehicle) moves around within the coverage area of the GSM network.
A cell of a GSM network corresponds in practise to the geographical coverage of a base transceiver station with which it is associated and which is therefore located at its center. Each base transceiver station comprises one or more transceivers, each associated with an antenna and processing equipment. As shown in FIG. 1, the geographical coverages of the stations partially overlap.
The cells C1, C2 and C3 are associated with respective base transceiver stations BTS1, BTS2 and BTS3. The latter are controlled by a base station controller BSC. The functions of the BSC include frequency management and management of the channels available on the various frequencies at each base transceiver station. The combination of a BSC and the associated base transceiver stations is called a base station system (BSS). There can be a plurality of BSC, each controlling a predetermined number of base transceiver stations. Each BSC is connected to a mobile services switching center (MSC), which constitutes the master structure of a GSM network. Thus a given MSC can control the operation of several BSS constituting a public land mobile network (PLMN).
A network of this kind operates in the following manner: the mobile MS sends signals in the form of streams of digital data or packets called bursts to the station BTS1 while it is in cell C1 and the station BTS1 transmits information extracted from these bursts to the BSC which in turn transmits the information to its destination via the MSC. The destination can be a fixed station or another mobile.
Each burst of data, for example speech data, is transmitted in a time slot of 577 .mu.s duration, eight successive time slots constituting one frame. Eight mobiles MS can therefore communicate on the same radio channel, i.e. on the same carrier frequency, because the GSM network uses the time division multiple access (TDMA) principle. Between two and four radio channels are usually assigned to each base transceiver station and between 16 and 32 time slots or channels are therefore available for transmission in each cell. The same goes for reception.
Because the TDMA principle is used, it is vital in the GSM system to ensure that the time slots assigned to each mobile MS in a given cell are in a given order. A mobile MS and its base transceiver station BTS each have their own internal clock. It is therefore necessary to allow for the time shift due to the propagation time of radio waves between the mobile MS and its base station BTS to prevent the mobile MS transmitting data during the time slot (i.e. on the channel) assigned to another mobile MS (the duration of a time slot is 577 .mu.s and a radio wave travels 300 m in 1 .mu.s).
When the mobile MS is in cell C1 it receives signals not only from the base transceiver station BTS1 but also from BTS2 and BTS3. The GSM system pro
REFERENCES:
patent: 5128925 (1992-07-01), Dornstetter et al.
patent: 5309439 (1994-05-01), Roos
patent: 5345448 (1994-09-01), Keskitalo
patent: 5355515 (1994-10-01), Sicher
R. Mouly et al, "The Pseudo-Synchronisation, a Costless Feature to Obtain the Gains of a Synchronised Cellular Network", Mobile Radio Conference, Oct. 1991, Nice (France) pp. 51-55.
Alcatel Mobile Communication France
Eisenzopf Reinhard J.
Kincaid Lester G.
LandOfFree
Method for determining timing advance during handover does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for determining timing advance during handover, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for determining timing advance during handover will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-734344