Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1997-06-30
2001-05-29
Vincent, David R. (Department: 2661)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C455S452200
Reexamination Certificate
active
06240079
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for data transmission in a time division multiple access (TDMA) mobile communication system, comprising the step of assigning one or more time-slots to a mobile station for data transmission depending on the data transfer rate required by an application using the mobile station.
BACKGROUND OF THE INVENTION
In mobile telecommunication systems of the time division multiple access (TDMA) type, time-division communication takes place on the radio path in successive TDMA frames, each of which consists of several time-slots. In each time-slot, a short information packet is sent in form of a radio frequency burst which has a finite duration and which consists of a set of modulated bits. The time-slots are mainly used for conveying control channels and traffic channels. On the traffic channels, speech and data are transmitted. On the control channels, signalling between a base station and mobile subscriber stations is carried out. An example of a TDMA radio system is the Pan-European mobile communication system GSM (Global System for Mobile Communications).
For communication in conventional TDMA systems, each mobile station is assigned one channel time-slot for data or speech transmission. Thus, the GSM system, for instance, may have up to eight parallel connections to different mobile stations on a same carrier frequency. The maximum data transfer rate on one traffic channel is restricted to a relatively low level, depending on the available channel bandwidth, as well as the channel coding and error correction used in the transmission. In the GSM system, for instance, the user rate is 9.6 kbit/s or 12 kbit/s. In addition, in the GSM system a so-called half-rate (max. 4.8 kbit/s) traffic channel may be chosen for low speech coding rates. A half-rate channel is established when a mobile station communicates in a certain time-slot only in every second time-slot, i.e. at half-rate. A second mobile station communicates in every second time-slot of the same frame. The capacity of the system in terms of the number of subscribers may thus be doubled, in other words, up to 16 mobile stations may communicate simultaneously on the same carrier frequency.
In the last few years, the need for high-speed data services in mobile communication networks has remarkably increased. Data transfer rates of at least 64 kbit/s would be required for utilizing ISDN (Integrated Services Digital Network) circuit switched digital data services, for example. Data services of the public network PSTN, such as modems and telefax terminals of class G3, require higher transfer rates, such as 14.4 kbit/s. One of the growing areas of mobile data transfer that requires higher transfer rates than 9.6 kbit/s is the mobile video service. Services of this kind include e.g. security control by cameras, and video databases. The minimum data transfer rate in video transfer may be, for instance, 16 or 32 kbit/s.
The data transfer rates of the present mobile communication networks are not, however, adequate to satisfy these new needs.
One way to solve the problem is to use multiple TDMA time-slots for communication with a mobile station. In this way, one mobile station may transmit and receive data at higher data transfer rates by multiplexing the data to multiple time-slots (traffic channels). This is termed as multi-slot access technique.
When multiple time-slots are used for communication with one mobile station, problems arise if a sufficient number of traffic channels in not available. This may occur in the call set-up phase or in a handover. Handover refers to transferring the mobile station from one channel onto another channel of the same cell or an adjacent cell during an ongoing call. A problem arises if the mobile station is operating at a high data transfer rate, and the new cell can not provide after the handover a data transfer rate as high as that of the previous cell. One solution would be to interrupt the connection if the quality i.e. the data transfer rate of the data transfer service is not adequate in the call set-up or handover, or after-the handover. However, this solution is not acceptable.
SUMMARY OF THE INVENTION
An object of the present invention is to relieve the problems caused by capacity restrictions in a mobile communication network which employs the multi-slot access technique in data transmission.
This is achieved with the method for data transmission in a time division multiple access (TDMA) mobile communication system comprising the step of assigning one or more time-slots to a mobile station for data transmission, depending on the data transfer rate required by an application using the mobile station. The method is characterized by determining minimum and maximum requirements for the data transfer rate of the user data for the connection, and by dynamically adjusting the channel configuration consisting of one or more time-slots and assigned to the mobile station for a data call, within the limits of said minimum and maximum requirements of the data channel, depending on a varying allocation level of the resources of a mobile communication network.
In the invention, the data transfer rate of a data call is dynamically adjusted depending on the resources of the network in a mobile communication system employing a so-called multi-slot access technique, by determining minimum and maximum requirements for the transfer rate of the user data, in addition to the presently specified parameters used for establishing a data call. These requirements may include the following parameters: the required level of service (data transfer rate) and the desired level of service (data transfer rate). The desired level of service determines the data transfer rate the mobile station wishes to be able to use. Simultaneously, the desired data transfer rate is also the maximum data transfer rate to be allowed for the mobile station. The required level of service determines the minimum data transfer rate that must be provided for ensuring the continuity of data transmission. If the required data transfer rate cannot be provided, the call set-up is interrupted or the data call is interrupted. These parameters allow the mobile communication network to reduce the data transfer rate if the cell is not capable of providing the desired data transfer rate in connection with call set-up or handover. Thus, the number of calls interrupted or prevented due to the lack of resources decreases.
Instead of transferring the parameters, the mobile station may indicate said minimum and maximum requirements to the mobile communication network in a number of alternative ways, such as by indicating the level of service. The minimum and the maximum requirements used are then selected in accordance with the indicated level of service in the mobile communication network.
In accordance with the present invention, the mobile communication network is able to modify the channel configuration of the data call and thus also the data transfer rate to a desired level once the network resources required therefor are released. In a preferred embodiment of the invention, the mobile communication network may, during a call, or after a call set-up or a handover, modify the channel configuration assigned to a data call to provide down to the minimum required data transfer rate, for releasing network resources in the mobile communication network for serving other traffic, such as new data calls.
REFERENCES:
patent: 4887265 (1989-12-01), Felix
patent: 4949395 (1990-08-01), Rydbeck
patent: 5070536 (1991-12-01), Mahany et al.
patent: 5128959 (1992-07-01), Bruckert
patent: 5200956 (1993-04-01), Pudney et al.
patent: 5483676 (1996-01-01), Mahany et al.
patent: 5513183 (1996-04-01), Kay et al.
patent: 5535207 (1996-07-01), Dupont
patent: 5654969 (1997-08-01), Wilhelmsson
patent: 5742592 (1998-04-01), Scholefield et al.
patent: 2112762 (1994-07-01), None
patent: 332 818 (1989-09-01), None
patent: 615 393 (1994-09-01), None
Hamalainen Jari
Honkasalo Zhi-Chun
Jokinen Harri
Posti Harri
Vainikka Jari
Nokia Telecommunications Oy
Pillsbury & Winthrop LLP
Vincent David R.
LandOfFree
Data transmission method in a TDMA mobile communication system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Data transmission method in a TDMA mobile communication system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Data transmission method in a TDMA mobile communication system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2541771