Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W84/00—Network topologies
  • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
  • H04W84/04—Large scale networks; Deep hierarchical networks
  • H04W84/08—Trunked mobile radio systems

Definitions

• a reporting device operating in TEETRA network and configuration of the same in response with network load
• the invention relates to a reporting device operating in a TETRA network and to overload prevention means for a control channel.
• the control channel of a base station in a TCTRA network is a common resource for all terminals and devices in communication with the discussed base station.
• the control channel is used, for example, for establishing a phone call, clearing, transmitting short messages, as well as for signalling other information between a base station and terminals.
• the control channel of a base station may become congested for example by short messages sent by an automatic reporting device.
• Such devices may include, for example, telematic or telemetric devices which deliver reports at intervals specified in the configuration thereof.
• the above-mentioned congestion of a control channel may affect e.g. the ability of a telecommunications network to establish and uphold phone calls or other critical functions that require communication across the control channel.
• the TEETRA network, and the communication channel in particular, has a relatively modest data transfer capacity per base station. In a catastrophe situation, for example, the authorities often have a considerable number of TEETRA terminal devices set up within the range of a single base station.
• overstepping the transfer capacity of a base station causes trouble in all communication traffic within the base station's range.
• the base stations of a transport company's network can be heavily loaded as a result of tracking messages in the vicinity of traffic terminals, even though the continuous tracking of vehicles located in terminal areas is less important than the reliability of actual communication.
• a further objective is to keep up a sufficient reporting rate in any event.
• the system of the invention is able to configure dynamic reporting gaps for terminals by making use of the real-time or anticipatory load control of a base station in the process of specifying an appropriate reporting rate.
• the above- mentioned load control is used for detecting a potential overload in a base station control channel or a risk of developing something like that, on the basis of which the automatic reporting device can be dynamically re-configured for a lowered reporting frequency or the time instant for the transmission of its reports relative to the transmission time of other terminals can be optimized so as to burden the control channel as little as possible. This enables preventing a control channel overload, the telecommunications network being thereby able to maintain its normal operation.
• a load can also be estimated without load data delivered by a base station, in which case the load control can be located outside a TETRA network and be independent of the network's actual ability to send loading data from a base station.
• the estimation can be executed by measuring a network's operation as described hereinafter.
• the estimation can also be upgraded by means of geographic data for terminals and configuration data for terminals, which can be used as a basis for working out the amount of loading applied on base stations in a given region by reporting alone. If all control-channel loading terminals report the geographic data thereof to the load control, the loading data can be calculated with an adequate precision just on the basis of the geographic data and the transmission setups of the terminals.
• the method and system of the invention are able to maintain a reporting rate which is always sufficient for the reporting to be useful, while keeping it sufficiently low for an impending overload condition to avoid putting other vital communication traffic at risk.
• reporting involves geographic information for example in a disaster area
• the geographic reporting can be reduced to a very low level for example for as long as the terminal lies within the range of a severely loaded base station, and more accurate geographic reporting is not continued until after leaving the base station's range.
• the updating rate required of tracking is often relatively modest because, in any event, a TCTRA network enables establishing a group call to the terminals within the range, whereby operation can be coordinated even without precise geographic information.
• the usage of a control channel capacity is also influenced by the respective phases of devices when reporting. If, for example, 50 devices are reporting at ten-second gaps at the same absolute instant of time, the band usage will clearly exceed that of reporting sequentially at equal gaps. The former situation develops a peak of band usage, resulting in errors and repeated transmissions with a waste of transfer capacity. On the other hand, the latter situation provides an even distribution of load with respect to time with no resulting errors.
• the invention is based on two logical basic components. These components can be provided in physically separate devices or integrated in a single physical device. The components can be positioned in a terminal or in a telecommunications network or in devices in communication with a telecommunications network.
• a device configuration module is used for the control, transmission and optionally storage of configuration information specified by the reporting rate of an automatic reporting device.
• a load tracking module for a control channel monitors continuously the load of a telecommunications network and especially that of a control channel.
• the assembly also comprises:
• An automatic reporting device which sends reports by using a control channel in accordance with reporting parameters specified in a configuration message.
• An application which utilizes the information sent by the automatic reporting device and requests the system for a desired reporting rate.
• the system of the invention comprises means for monitoring the load of a telecommunications network, especially for monitoring the load of control channels in base stations, as well as for inferring an appropriate reporting rate and/or timing, in order to enable reconfiguring the transmission setups of automatic reporting devices in keeping with the load of a telecommunications network and especially a base station control channel and the reporting demand.
• Load control can be effected either by using prior known control methods for the load of a telecommunications network or the degree of load can be estimated on the basis of a number of errors, a transit delays or the variation of transit delay in reports transmitted by devices and received, i.e. the loading of a network is assessed indirectly by tracking its operation.
• Prediction can be effected by using, for example, the observation or knowledge of the fact that a large number of terminals are about to arrive in the vicinity of a certain base station.
• a TEETRA network is used in official service and for example in conducting operations in accidents, it is often possible to make a likely conclusion that a significant number of units approaching a scene of accident have their destination within the range of one base station, whereby the reporting rate of units already present within the range of said base station or those about to arrive therein can be reduced in anticipation until such time that the discussed units leave the base station's range or until there are no longer a large number of terminals within the base station's range. Consequently, the leadership in charge of coordinating the activities in a scene of accident is always aware of which units are currently for example in the vicinity of a base station located in the affected area and which units have left the area or on their way over there.
• the reporting rate of terminals present within the range of a base station located in the affected area is reduced in order to secure a reliable operation of voice communications.
• the terminal may independently send, along with a position data report, a message about the switch of base stations and thereafter the terminal may even self-configure itself to transmit geographic information at a slightly higher rate, even without a specific command.
• a terminal of the invention can be used for sending any automatic report.
• the terminal may increase the reporting rate independently for example to the average between a normal reporting rate and a commanded reporting rate upon proceeding to a cell next to the loaded base station, and the normal reporting rate is not picked up until within the range of a cell following that.
• Predicting a load preferably also involves the use of statistics associated with the data transfer of messages, because that is when the hazard of an overload can also be detected even if true loading data for a base station is not available.
• a load tracking module from which the device configuration module obtains a message about the loading of a network, and configuration messages sent by the device configuration module are received by an automatic reporting device of the invention, and the transmission timing of reports sent by the automatic reporting device is revised according to the configuration messages.
• a configuration message can be used for giving instructions or threshold values in order to revise the transmission timing of messages or reports, such as a transmission frequency, a minimum or maximum time gap between reports or a minimum or maximum magnitude of the revision to be reported or a phase for the transmission moment of reports, according to the configuration messages.
• the configuration module and the automatic reporting device constitute jointly a pair of devices according to the invention, whereby it is possible to avoid overloading a base station's control channel in a subsequently described manner and which jointly execute the method of the invention.
• Fig. 1 shows devices of the invention as part of a more extensive assembly.
• the numerals for phases and messages in the description refer to those shown in the figure.
• Fig. 1 includes an automatic reporting device A, a device configuration module B, a load tracking module D and an application E being in communication with the device configuration module.
• Numerals refer to messages, while letters are for devices or components in the system.
• Reference numerals 3, 6, 4 and 7 represent messages transmitted along a base station's control channel.
• a line C represents traffic in the control channel and the line crosses the messages sent along the control channel.
• the load tracking module D reads loading information F regarding the base station's control channel or the load tracking module makes conclusions about the magnitude of load by gathering information regarding transit delays or variation of transit delays, re-transmissions, numbers of errors in the system's messages or regarding the number of terminals to be located and presently within the range of a base station or regarding configuration data of the discussed terminals.
• Configuration data 1 contains a desired service level or parameters directly related to reporting rate, for example priority, time interval, speed of motion, distance to a preceding report or counter reading.
• the device configuration module B informs the load tracking module B of a new automatic reporting device A, of its identifier and priority or its reporting setups. This information can be used by the load tracking module for assessing a load.
• the load tracking module may in turn inform the configuration module of the identifier of a congested base station and of the identifiers of reporting devices that it is possibly aware of. In other words, load tracking can be practiced also with the aid of configuration data. Provided that the topology of a network is consistent with fig. 1, the data transfer between a load tracking module and a configuration module presents no problem.
• the modules may even be separate parts of one computer program.
• the device configuration module B sends a configuration message 3 to the automatic reporting device A.
• the device configuration module B may revise the original requested configuration parameters.
• the automatic reporting device Upon receiving the configuration message 3, the automatic reporting device starts a transmission of reports 4 in a manner determined in the configuration message 3. If, under a single base station, there are several devices with a comparatively high reporting rate, the base station's control channel may become overloaded and blocked by these messages.
• the load tracking module D may inform the device configuration module B at any time of a potential overload in the control channel of a given base station.
• This information 5 may contain, for example:
• the device configuration module configures the automatic reporting device A to modify its reporting to a less stressful level.
• the automatic reporting device A starts using new configuration data 6, thus revising the timing of transmissions 7 and the loading of a base station's control channel remaining within an acceptable range.
• the configuration data may also contain instructions for returning to a normal operating mode after the reporting device has for example left the range of a congested base station's cell.
• the load tracking module D updates the situation to the device configuration module B, which may proceed to further configure the devices A as necessary.
• the optimization of a time instant for the reporting function of a terminal can be effected for example as follows:
• the device configuration module and/or the load tracking module that the control channel of one base station has plenty of devices thereunder, which have an identical reporting rate or whose reporting rates are multiples of each other. Thus, there is a hazard of sending a multitude of messages almost simultaneously.
• the device configuration module supplies each of the above-mentioned terminals with a specific number representing a (cyclic) time instant linked to absolute time.
• the time instant is selected to be as discrete as possible for various terminals.
• a plurality of terminals are able to conduct reporting at the same communication rate, but within the range of one base station the distribution of messages is such that not many messages are delivered within a short period of time.
• the number of time instant can be defined for example within a cyclically repetitive time period.
• the terminals proceed to report at the time instants configured therein.
• the devices be supplied with new reporting requests appropriately timed to match the time instants.
• One way is to configure all devices present within the same range to report as consistently as possible at various time instants, in which case the reporting is quite consistent even without specific optimization.
• the reporting rate is defined at 100 seconds, ten terminals being given a command at the intervals of 10 seconds, the result being one message for approximately every ten seconds.
• the reporting rate can also be defined as a random time gap between transmissions and a convenient average transmission frequency. This is a simple approach and may function reliably for example when terminals have concentrated at the same time within the coverage range of several base stations and terminals switch base stations all the time.
• a random transmission gap eliminates periodic powerful peaks of loading, but does not eliminate random peaks of load.
• a terminal or an automatic reporting device may also supply information facilitating the estimation of a load. This information can be for example a time tagging or a sequence number for a message.
• a support for load tracking can be provided for example by information about whether transmissions of messages have failed and when messages have been attempted and when managed to get through.
• messages sent by a terminal can be used for measuring the functionality of a transmission path.
• a terminal is also capable of independently reducing the reporting rate whenever the transmission path is not fully functional, for example when the application does not respond normally or there is a high volume of errors. This does not actually warrant a response to the volume of traffic in the control channel itself, because the transmission path loading can also be caused by radio interference or the like external factor. Even in this case, it is sensible to reduce the network loading exactly as in the event of an overload.
• the terminal has specific configuration and load tracking modules in its software, i.e. some of the messages in the control channel of fig. 1 will be omitted and replaced by intra-terminal commands.
• the terminal reveals its independent decision about reducing a reporting rate and reveals the loading condition in the next message to inform the application and the rest of the system of the reason why the number of received messages is less than expected.
• An independent reduction of loading by the action of a terminal ensures that the system shall operate in a sensible manner also when the messages of the actual configuration module are blocked.
• Reduction of a reporting rate is preferred also when communication with the recipient of a report or with the configuration module is likely to dysfunction or when it seems that a base station is no longer in communication with the rest of a TEETRA network. At this time, it is advisable to avoid all unnecessary communication and attempts to re-establish a contact must be rather infrequent.
• the devices of a TEETRA network are able to communicate also locally without communicating with the entire network infrastructure, and hence, despite the breakup of a base station contact with the rest of the network, the control channel may nevertheless be congested and active. In this sense, a TETRA network is totally different from a GSM network as the latter does not function at all in this sort of situation.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)

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Cited By (1)

Citations (4)

• 2005
  • 2005-04-13 FI FI20050134U patent/FI6841U1/fi not_active IP Right Cessation
• 2006
  • 2006-04-11 EP EP06725915A patent/EP1875755A1/en not_active Withdrawn
  • 2006-04-11 WO PCT/FI2006/050140 patent/WO2006108921A1/en not_active Application Discontinuation

Patent Citations (4)

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