Multiplex communications – Communication over free space – Combining or distributing information via time channels
Patent
1995-06-12
1998-04-14
Olms, Douglas W.
Multiplex communications
Communication over free space
Combining or distributing information via time channels
370350, H04J 316
Patent
active
057401683
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a radio link switching scheme suitable for an intra-base station radio link switching.
BACKGROUND ART
In recent years, the mobile communication for carrying out communications by utilizing radio links between base stations and mobile stations has come to be widely used. The service area of such a mobile communication is formed by a multiplicity of cells (or zones), where a base station is provided in each cell. Thus, usually, the mobile station which moves within a certain cell is going to carry out the communication through a prescribed radio link with the base station provided in that certain cell. Here, the radio link used is not necessarily fixed to a particular one, and will be switched as the need arises.
There are two types of the radio link switching required in the mobile communication, including the inter-base station radio link switching and an intra-base station radio link switching. The inter-base station radio link switching is executed in a case of changing the base station in communication with the mobile station, as the mobile station moves from a cell of the currently communicating base station to a neighboring cell of another base station. On the other hand, the intra-base station radio link switching is executed in a case the degradation of the radio link quality is caused by the interference from the other base station or mobile station. A conventional scheme for this intra-base station radio link switching will now be described.
In the digital mobile telephone system currently in practical use, the intra-base station radio link switching within one and the same base station is handled by the identical scheme as in the inter-base station radio link switching, which proceeds according to the sequence chart shown in FIG. 1 as follows.
Namely, while the base station and the mobile station are in communication by using the transceiver circuit of the base station, when this transceiver circuit detects the degradation of the quality of the radio link in use, this fact is notified to a control circuit of the base station in a form of a link switching request (step S101). In response, the control circuit makes the selection of unused wire link, frequency, and time-slot (step S103), and notifies the selected wire link to an exchanger station. Then, the exchange station makes the signal transmission with respect to the notified wire link in addition to the wire link currently in use (step S105) while the control circuit notifies the selected frequency and the time-slot to the transceiver circuit connected with the selected wire link.
The transceiver circuit which received this notice then generates the new radio link synchronization signal according to the notified frequency and the time-slot, and transmits the generated new radio link synchronization signal to the mobile station (step S107). In addition, the control circuit transmits the new radio link designation signal to the mobile station via the old radio link so as to notify the frequency and the time-slot of the new radio link (step S109).
Then, the control circuit of the mobile station notifies the notified new frequency and time-slot to the transceiver circuit of the mobile station such that this transceiver circuit switches the frequency and time-slot to the notified new frequency and time-slot (step S111). Then, this transceiver circuit receives the new radio link synchronization signal transmitted from the transceiver circuit of the base station to carry out the synchronization establishing processing for the new radio link (step S113), so as to establish the new radio link synchronization on the mobile station side and the base station side (steps S115 and S117).
When this synchronization is established, the base station stops the signal transmission to the old wire link, and releases the old wire link and radio link (step S119). Then, the communication through the newly set up radio link is started.
Now, in contrast to the intra-base station radio link switching in the TDMA-FDMA
REFERENCES:
patent: 5535425 (1996-07-01), Watanabe
patent: 5561852 (1996-10-01), Heeschen et al.
patent: 5574974 (1996-11-01), Almgren et al.
Hiroike Akira
Nakamura Takehiro
Umeda Narumi
NTT Mobile Communication Network Inc.
Olms Douglas W.
Patel Ajit
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