Methods for determining a number of control channels in a cell

Details Methods for determining a number of control channels in a cell Methods for determining a number of control channels in a cell

1998-10-27

2001-08-07

Nguyen, Lee (Department: 2683)

Telecommunications

Transmitter and receiver at separate stations

Plural transmitters or receivers

C455S451000, C455S452200

Reexamination Certificate

active

06272352

ABSTRACT:

This application claims priority under 35 U.S.C. §§119 and/or 365 to 9703930-9 filed in Sweden on Oct. 28, 1997; the entire content of which is hereby incorporated by reference.
TECHNICAL FIELD
The present invention relates to methods of reconfigurating a cell in a cellular mobile radio system wherein each cell includes a prescribed minimum number of dedicated control channels (SDCCH) used for signalling and a number of traffic channels (TCH), where a traffic channel can be converted to a dedicated control channel and vice versa.
BACKGROUND OF THE INVENTION
It is previously known in a cellular mobile radio system to reconfigurate a cell by temporarily utilizing an empty traffic channel as a control channel.
U.S. Pat. Nos. 5,299,198 and 5,513,183 show a TDMA system in which the number of control channels can be increased by using the traffic channels (see e.g. the Abstract).
WO93/10600 discloses a method of temporarily using a traffic channel as a control channel. The decision for this is made based on comparisons of the traffic density with given threshold values (see the abstract and pages 8, lines 17 to page 9 line 9 and page 15 line 24 to page 17, line 8).
DE 31 30 176 A1 discloses a method in a cellular TDMA-system to convert traffic channels to control channels in dependence on the traffic load. More specific, in dependence on the ratio: number of time slots
umber of subscribers in a cell.
SUMMARY OF THE INVENTION
The previously known techniques as e.g. mentioned above to configure the needed number of dedicated control channels, especially the signalling channels in every cell, is based on manually calculating the expected signalling traffic based on traffic models, current traffic distribution and statistics about handovers and congestion rates.
The number of signalling channels is often overdimensioned to avoid congestion. There are ways to overcome short periods of such congestion by using a traffic channel as a signalling channel. This, however, implies the use of a whole time slot instead of using only a fraction of a time slot.
Some cells carry more signalling traffic than others do. Cells at a border of a location area (LA) need more such channels than other cells. This is due to the fact that when a mobile crosses an LA border it is triggered to notify the network about its new location. This is done using a signalling channel and therefore causes heavy load on these channels. Cells with a high amount of SMS traffic do also need more signalling channels than other cells. These factors must be taken into account when dimensioning the number of signalling channels.
When there is congestion on signalling channels, new calls needing signalling channels in order to be set up may use a traffic channel i.e. a whole time slot. The congestion of signalling channels is therefore highly undesireable. This result in that an operator must over-dimension the signalling channels. However, since a cell always is given a fixed number of channels (traffic+signalling) the trade-off is fewer channels to be used as traffic channels available to carry the payload. This will seriously affect the operator's revenue. To overcome the problem with congestion on dedicated control channels, in particular the Stand Alone Dedicated Control Channel SDCCH in the GSM-system, it is allowed to use a traffic channel TCH for the signalling procedure. This will save the incoming call. However, a TCH uses a whole time slot for its configuration, while one SDCCH subchannel only uses ⅛ of it. The use of TCH for signalling is thus not desireable unless for short duration as unpredictable traffic peaks.
One object of the present invention is to meet the above mentioned problems by automatically and dynamically reconfigure a cell in a cellular mobile radio system with new or less signalling channels on demand.
Another object of the present invention is to carry out an automatic reconfiguration on a long term basis in order to take care of the fluctuations in the signalling traffic.
One advantage with the present invention as compared with prior art reconfigurations is that reconfiguration either from a traffic channel to a signalling channel or vice versa is done only in the case certain conditions are fulfilled and thus that unnecessary reconfiguration in a cell can be avoided.
Another advantage is that unnecessary reconfigurations created by the “fast loop” method mentioned below can be reduced.


REFERENCES:
patent: 5235598 (1993-08-01), Sasuta
patent: 5239678 (1993-08-01), Grube et al.
patent: 5299198 (1994-03-01), Kay et al.
patent: 5513183 (1996-04-01), Kay et al.
patent: 5729534 (1998-03-01), Jokinen et al.
patent: WO 93/10600 (1993-05-01), None
patent: WO 95/19687 (1995-07-01), None

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