Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1998-03-12
2001-03-13
Olms, Douglas W. (Department: 2732)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S280000, C370S324000, C342S088000
Reexamination Certificate
active
06201819
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for transmitting data packets from mobile stations to base stations in mobile radio systems operated by the time-division multiplex method.
2. Description of the Prior Art
For the transmission of data between two communication terminals, recourse can be made to connection-oriented concepts and concepts based on virtual (logical) links. In the case of connection-oriented data transmissions, physical resources have to be provided between the two communication terminals during the entire time of the data transmission.
In the case of data transmission via logical links, the permanent provision of physical resources is unnecessary. An example of such data transmission is packet data transmission. Here, a logical link between the two communication terminals exists during the entire duration of the data transmission, but physical resources are provided only during the actual transmission times of the data packets. This process is based on the fact that the data is sent in short data packets, between which longer pauses can occur. In the pauses between the data packets, the physical resources are available for other logical links. With respect to one logical link, physical resources are saved.
The packet data transmission process is suitable in particular for communication systems with limited physical resources, whenever short data packets have to be transmitted only sporadically. For example in mobile radio systems, such as the GSM mobile radio system, the physical resources are restricted in terms of frequency range (number of frequency channels) and time slots. Accordingly, such physical resources have to be used efficiently.
The GSM mobile radio system operates by the time-division multiplex method, with the result that time slots within a frequency channel can be divided between various communication terminals. In a communication relationship between a base station, which is further connected to a communication network, and a mobile station, it must be ensured that the information items sent by the various mobile radio stations arrive in the base station in conformity with the time slots. Since the distance, and consequently the delay, between mobile station and base station may well differ and/or changes if the mobile station moves, it is necessary to calculate a timing advance which influences the time of sending for the respective time slot in the mobile station.
The GSM system was conceived for voice transmission. In a voice transmission, information items are constantly exchanged between mobile station and base station. There is, therefore, no difficulty in determining the timing advance sufficiently frequently on the basis of the constantly exchanged information items.
However, the amount of signalling which voice transmission involves, and which can be used also for the determination of the timing advance, is inappropriately high, for packet data transmission. A process for packet data transmission in which the timing delay is determined before each transmission of the data packet is known from Telia AB/Telia Research, from the GPRS Conference from 10 to Jan. 12, 1995. As emerges from page 8, items 3 and 4 of the updating procedure, the mobile station sends an access data packet on an access channel GACH, whereupon the base station determines the timing advance and sends the determined timing advance to the mobile station via an acknowledgement channel GCCH. The timing advance must consequently still be determined relatively frequently. Also, accesses to the access channel and acknowledgement channel are necessary in this case, or these channels have to be separately provided.
SUMMARY OF THE INVENTION
The present invention is directed toward reducing the amount of signalling in packet data transmission in mobile radio systems.
The process according to the present invention utilizes the fact that a mobile station moves towards or away from the base station usually only at low speeds. Consequently, the signal delay between mobile station and base station also changes only gradually, with the result that no abrupt changes to the timing advance are necessary. In view of this fact, the determination of the timing delay can be linked to the satisfying of certain decision criteria. Such criteria relate to the period of time between timing delay determinations if the transmission of the data packets is performed with a small guard time, i.e., the guard time is less than the maximum permissible signal delay between mobile station and base station.
The guard time is, by definition, the time between the end of a transmitted data packet and the end of the associated time slot. It ensures that, if there is a small discrepancy between the arrival of the data packet and the pattern of the time slots of the base station, a collision of the data packets of two time slots cannot occur. For example, for a GSM system this means that, with a small guard time of, for example, 8.25 bits (about 30 &mgr;s) and a mobile station moving away from the base station at 36 km/h, once a timing advance has been set it does not lead to any collision of data packets for up to 7 minutes, even without any correction.
A guard time of 10 to 50 &mgr;s in a time slot in the GSM system at the same time also represents an efficient sharing of the resource of time. The relatively long period of time during which data packet collisions are avoided by the timing delay, once it has been set, can be used to achieve the effect that the decision criteria are satisfied only by the end of a period which can be set by means of parameters. Irrespective of the data packets actually sent, the timing advance is recalculated, and the mobile station is set to it, only at relatively great intervals. The amount of signalling is in this case small and no additional delay occurs before the transmission of a data packet.
As an alternative to this, the decision criteria may also be satisfied by the fact that, when sending a data packet, and the last determination of the timing advance was a predetermined period of time before A specifically set period is in this case replaced by testing, before each sending of a data packet, whether only a tolerable period of time has elapsed since the last determination of the timing advance. Under certain circumstances, the frequency of the determination of the timing advance may be additionally restricted, but an additional checking effort is necessary before each sending of a data packet.
The test packet of which the arrival at the base station is used as a basis for determining the timing advance advantageously contains an identification which indicates that only the timing advance is to be determined. The base station recognises from this that from then on no technical radio resources have to be assigned. It is also possible to dispense with additional signallings when sending the determined timing delay if the confirmation of reception of data packets is also used for sending the said timing advance.
Further advantageous refinements of the process according to the present invention may also be realized. In particular, the process according to the present invention is suitable for use in GSM mobile radio systems, whereby applications such as a mobile office with E-mail, fax, file transfer, point-of-sale implementations, fleet management, traffic control systems and other similar applications can be realised.
Additional features and advantages of the present invention are described in, and will be apparent from, the Detailed Description of the Preferred Embodiments and from the Drawings.
REFERENCES:
patent: 3742498 (1973-06-01), Duun
patent: 5295152 (1994-03-01), Gudmundson et al.
patent: 5301188 (1994-04-01), Kotzin et al.
patent: 5802105 (1998-09-01), Tiedemann, Jr. et al.
patent: 5959980 (1999-09-01), Scott
patent: 40 11 341 A1 (1991-10-01), None
patent: 0 533 636 A2 (1993-01-01), None
patent: 2 277 232 (1994-10-01), None
patent: WO 94/05094 (1994-03-01), None
Bell Boyd & Lloyd LLC
Hom Shick
Olms Douglas W.
Siemens AG
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