WO2001024552A1

WO2001024552A1 - A method of and apparatus for assigning a unit identity

Info

Publication number: WO2001024552A1
Application number: PCT/IB2000/001351
Authority: WO
Inventors: Niels Peter Sandberg; Per Roed; Aage Sandfeld Jensen
Original assignee: Motorola A/S
Priority date: 1999-09-27
Filing date: 2000-09-25
Publication date: 2001-04-05
Also published as: AU7035100A; GB2354672A; GB9922750D0

Abstract

This invention relates to a method of and apparatus for assigning a unit identity to remote units (101-107) in a communication system (100). A remote unit (101) comprises means for selecting an identity (201) and broadcasting an identity request message. A second remote unit (103) will upon receiving the identity request message investigate whether the identity is already in use by the second remote unit. If so it will either transmit an identity request message or release the identity. The first remote unit (101) comprises means (211) for assigning the unit identity to the first remote unit (101) if no reject messages are received in response to the unit identity request. The invention is applicable to radio communication systems such as TETRA.

Description

A METHOD OF AND APPARATUS FOR ASSIGNING A UNIT

IDENTITY

Field of the Invention

This invention relates to a method of and apparatus for assigning a unit identity to a remote unit in a communication system in particular in a radio communication system such as TETRA (TErrestrial Trunked RAdio) or GSM (Global System for Mobile communication).

Background of the Invention

Radio communication systems are known where a plurality of remote units communicate with each other. These systems include TETRA (TErrestrial Trunked RAdio), and GSM (Global System for Mobile communication) communication systems. In both of these systems the remote units can communicate through a central station. In GSM for example, all communication between remote units is carried out by one remote unit transmitting to a central station (a base station), the signal being routed to a second central station which transmits the signal to a second remote unit. Specifically the central station may be the same for both remote units.

In TETRA it is furthermore possible for remote units to communicate directly with each other without any central station being involved. Specifically, a system can be envisaged without any central station and thus consisting only of a plurality of remote units.

In order to establish communication between specific remote units it must be possible to identify the remote units. Typically remote units therefore have a unique permanent identity which can be used for designating this remote unit. In addition remote units may often be assigned other identities such as for example a temporary identity and/or they may share an identity with other remote units. The latter enables group calls where a plurality of remote units are designated as recipients of a specific communication by using the common identity.

As an example, an identity may be assigned to all remote units by a group of workers performing a specific task. Information can then easily be communicated to this group of workers by using the common identity and no information as to which workers are included in the group are needed. When the task is completed the workers will move on to other tasks which may be different for different workers. A new identity may then be assigned depending on which specific task each individual worker is allocated.

In order for such a communication system to work, it is thus necessary to control assignment of identities so that conflicts are avoided. Typically, this is achieved by identities being assigned or at least monitored by a central processor, which contains information on which identities are allocated to which remote units. However, such a system requires a central data base which increases cost and complexity of the infrastructure. This may especially, be critical as some systems do not comprise any. centralised processor and a new processor must be included in the system simply to manage identity assignment. Furthermore, a central approach requires an increased amount of communication between central stations and thus increase the communication bandwidth requirements of the fixed infrastructure. As the cost of the communication within the fixed infrastructure can be very substantial this can be a very significant disadvantage.

A decentralised method of controlling the assignment of identities to remote units would therefore be advantageous. Summary of the Invention

The invention seeks to provide a method of and apparatus for assigning a unit identity to remote units which mitigates at least some of the above mentioned disadvantages.

According to a first aspect of the invention, there is provided a method of assigning a unit identity to a first remote unit in a communication system comprising a plurality of remote units, the method comprising the steps of: selecting a unit identity of the first remote unit locally to the first remote unit; broadcasting a unit identity request for the selected unit identity; and assigning the selected unit identity to the first remote unit if no reject messages are received in response to the unit identity request.

Preferably, the method further comprises the steps of: receiving the unit identity request at a second remote unit; and the second remote unit transmitting a reject message to the first remote unit if the unit identity is in use by the second remote unit, or alternatively deleting a unit identity in the second remote unit in response to receiving the unit identity request.

According to a second aspect of the invention there is provided an apparatus for assigning a unit identity to a remote unit in a communication system comprising a plurahty of remote units, the apparatus comprising: means for selecting the unit identity of a remote unit locally to the remote unit; means for broadcasting a unit identity request for the selected unit identity; and means for assigning the unit identity to the remote unit if no reject messages are received in response to the unit identity request. An advantage of the invention is thus that there is no requirement for a centralised processor for assignments of identities to the remote units.

Brief Description of the Drawings

An embodiment of the present invention is described below, by way of example only, with reference to the Drawings, in which:

FIG. 1 is an illustration of a communication system to which the current invention is applicable; and

FIG. 2 is an illustration of a remote unit in accordance with an embodiment of the invention.

Detailed Description of a Preferred Embodiment

Fig. 1 shows an embodiment of a radio communication system to which this invention is applicable. A number of remote units 101 — 107 communicate with each other in this example through a central unit 109. Alternatively the remote units 101 - 107 may communicate directly without any intermediary central unit. For example remote unit 101 may transmit directly to remote unit 107 and vice versa. This may be possible whether a central is present in the communication system or not. Typically, remote units are small portable terminals but any suitable communication device may be substituted without detracting from the current invention.

For simplicity, the central unit in the described embodiment is a simple repeater which receives the signal from a transmitting remote unit 101 and retransmit this signal to one or more receiving remote units 103- 107. However, in other embodiments the central unit can be significantly more complex and include the functionality for controlling the communication system. It can thus include data demodulators, switching circuitry, resource allocation units and more. It may furthermore be part of an interconnected network which routes calls between different central units as well as between different remote units served by the same central station. Examples of such more complex central units are the base stations of the Global System for Mobile Communications.

In communication systems comprising a number of remote units, each potentially in need of communicating with another of the remote units, it must be possible to identify each of the remote units. In many communication systems such as TETRA or GSM each remote unit has a unique identity number which identifies the remote unit. This can be a permanent identity allocated to the remote ^'unit when manufactured or can be assigned to the remote unit at a later state. In the latter case it may be possible to change the unique identity allocated to a specific remote unit but this will be done infrequently and the identity must remain a unique identity. In these cases a semi-permanent rather than a permanent identity may thus be used. When estabhshing a call, the communication system can use the unique identity to identify the desired remote unit. In systems such as GSM a mobile phone number is used by the user of the originating remote unit and the communication system translates this into the unique identity of the corresponding remote unit.

However, especially in many private mobile radio communication systems such as TETRA, a permanent unique identity is insufficient, and in addition to the unique identity, a temporary identity can be assigned to the remote units. These identities are not necessarily unique and can thus be shared between a plurahty of remote units. Furthermore they can be dynamically assigned and can thus change frequently. Also the same temporary identities will often be re-used and it is therefore necessary to have a method for assigning the temporary identities to the remote units without a conflict between different remote units occurring.

An example of a system using temporary identities is a private radio network used in an airport. In this example, a work identity is dynamically and temporarily assigned to a remote unit depending on which task is carried out by the user of this remote unit. For example an identity number can be made up from the service performed (mechanical checking, baggage handling, refueling), the flight number and the gate. An identity of 471116 can thus for example mean that the service performed is baggage handling (4 being the code for baggage handling), 711 is the flight number and the plane is at gate 16. When the user has completed the current task he will move on to the next task which will be a different flight number and a different gate (and possible a different task). Furthermore, the same identity code will reused the following day when the same service is performed on the same flight number of the same gate but possibly by a user having a different remote unit. The use of temporary, dynamically assigned and reuseable identities provides the benefit that another user can contact the bagage handler of flight 711 at gate 16 without knowing who is providing this service or which remote unit he is using.

Known methods for assigning temporary identities use a centralized data base from where the temporary identities are allocated. This increases the cost and complexity of the infrastructure and can be inflexible.

Fig 2 illustrates an embodiment in accordance with the current invention of a first remote unit 101. The first remote unit comprises means 201 for selecting a unit identity such as the temporary work identity described. The means 201 for selecting a unit identity is connected to a transmitter 203 which is connected to an antenna 205 through a duplexer 207. The same antenna 205 is through the duplexer 207 connected to a receiver 209 and the receiver output is connected to means 211 for assigning a unit identity to the remote unit.

In use, a desired temporary identity is selected in the means 201 for selecting a unit identity. Preferably these means incorporate a keypad or other input device by which the user of the first remote unit 101 can input a desired identity. Alternatively the desired identity can be selected by the first remote unit 101 according to specific rules without interacting with the user. The means 201 for selecting a unit identity creates a unit identity request message. This message includes control data necessary for the communication system and other remote units to detect and handle the message as a unit identity request. It furthermore includes data indicating the selected unit identity.

The unit identity request message is fed to the transmitter 203 of the first remote unit, and in one embodiment of the invention the transmitter 203 broadcasts this message directly to other remote units 103 — 109. The other remote units 103 — 107 receiving the unit identity request decode the message in order to identify the selected identity. The remote units 103-109 then compare the received identity with the identity or identities currently assigned or used by the respective remote unit 103 - 107. If the selected identity is already used or assigned the remote unit 103 - 107 will generate a reject message indicating that the selected identity code is already in use. This reject message will be transmitted back to the first remote unit 101, and received by the receiver 209. The received message is fed to the means 211 for assigning a unit identity to the remote unit, which upon receiving the message will prevent assignment of the selected unit identity to the first remote unit 101. Preferably this will be displayed to the user who can then select a different unit identity. In an alternative embodiment the remote units 103 — 109 transmit acknowledge signals if the selected identity is not in use and the first remote unit 101 assigns the selected unit identity only if acknowledge messages are received from all other remote units. In this case a reject message is thus made up by the absence of an acknowledge message.

In a different embodiment, a second remote unit 103 already having the selected unit identity assigned will upon receiving the unit identity request from the first remote unit 101 release the assignment of this unit identity. A second remote unit 103 receiving a unit identity request will thus delete this identity from the list of identities assigned to the second remote unit 103.

In a preferred embodiment both of these described embodiments are included simultaneously, so that upon receiving a unit identity request already assigned to a second remote unit 103, the second remote unit 103 will present the conflict to the user, who can then decide whether to release the assignment or reject the unit identity request. Alternatively the second remote unit 103 can automatically determine whether to reject or release the identity based on a defined set of rules without interfacing with the user. In a shghtly different embodiment the second remote unit 103 generates a reject message and transmits this to the first remote unit 101 when the selected unit identity is already assigned. Upon receiving this reject message, the first remote unit 101 makes a decision whether to abort the assignment of the selected unit identity or whether to request deletion of the assignment in the second remote unit 103. Again this decision can be automatic or can be based on a decision of the user of the first remote unit. If the decision is to request release of the assignment of the identity in the second remote unit, the first remote unit 101 generates and transmits a user identity delete message to the second remote unit 103, which in response releases the unit identity. It will be apparent to the person skilled in the art that different protocols and decision rules can be substituted without detracting from the current invention.

In one embodiment in accordance with the invention the communication between the remote units 101 — 107 is accomplished through a central station 109. In this case the first remote unit 101 will transmit the unit identity request to the central station 109 and the central station 109 will broadcast this to other remote units 103 - 109. These remote units 103 - 107 may upon receiving the unit identity request transmit a reject message to the central station 109 and the central station 109 will transmit this message back to the first remote unit 101. In such an embodiment all the communication between the remote units 101 — 107 may be via the central station 109 or alternatively only some of the communications may use the central station 109 whereas other communications are directly between the remote units 101 - 107.

Preferably in this embodiment, the broadcast from the central station 109 is repeated a number of times. For example, one unit identity request message received from the first remote unit can be broadcast at regularly intervals until a time out occurs or until a reject message is received, from a remote unit. Transmitting the message more than once has the advantage of improving the reliability of it being received by remote units who may temporarily be unable to receive the message. The probability of falsely assigning a used identity to the first remote unit is thereby reduced.

According to one embodiment of the invention, the remote units monitor and record the unit identity requests transmitted from other remote units. Over time the remote unit thereby builds up a database of already assigned identities. When selecting a new identity this information can be used in the remote unit either by using it in an automated decision process or alternatively by incorporating it in the interface with the user. Specifically, the user can enter a desired identity and if the database already has an entry indicating that the identity is in use by another remote station it can inform the user, who can then select a different identity. In this embodiment the communication system will preferably also include messages transmitted when an identity is released thereby enabling the remote unit to keep track of which identities are in use at any given instant.

The embodiments described above thus have the advantages of being simple to implement and requiring no centralised database or processor for assigning identities. Rather identity assignment is performed distributed by the remote units communicating with each other. The embodiments thus provide a simple and cheap solution to identity assignment with no infrastructure requirements.

It will be apparent that the invention is applicable to many communication systems including TETRA and GSM as well as non-radio systems such as fixed networks where users are allocated identities.

Claims

1. A method of assigning a unit identity to a first remote unit in a communication system comprising a plurality of remote units, the method comprising the steps of: selecting a unit identity of the first remote unit locally to the first remote unit; broadcasting a unit identity request for the selected unit identity; and assigning the selected unit identity to the first remote unit if no reject messages are received in response to the unit identity request.

2. A method of assigning a unit identity as claimed in claim 1 further comprising the step of: receiving the unit identity request at a second remote unit; and the second remote unit transmitting ^'a reject message to the first remote unit if the unit identity is in use by the second remote unit.

3. A method of assigning a unit identity as claimed in claim 2 further comprising the steps of: the first remote unit transmitting a user identity delete message in response to receiving the reject message from the second remote unit; and the second remote unit deleting a second user identity in response to receiving the user identity delete message from the first remote unit.

4. A method of assigning a unit identity as claimed in claim 1 further comprising the step of: receiving the unit identity request at a second remote unit; and deleting a unit identity in the second remote unit in response to receiving the unit identity request.

5. A method of assigning a unit identity as claimed in any of the claims 2 to 4 further comprising the step of presenting the unit identity request to the user of the second remote unit; and determining the response to the unit identity request in response to a user input.

6. A method of assigning a unit identity as claimed in any of the previous claims wherein the unit identity request is transmitted to a central station and the broadcast of the unit identity request is by the central station.

7. A method of assigning a unit identity as claimed in claim 6 wherein the central station repeatedly broadcasts the unit identity request.

8. A method of assigning a unit identity as claimed in any of the previous claims wherein the unit identity is a temporary unit identity and each of the plurality of remote units in addition has a unique permanently allocated identity.

9. A method of assigning a unit identity as claimed in any of the previous claims wherein at least one of the plurahty of remote units records the unit identity of received unit identity requests.

10. A method of assigning a unit identity as claimed in any of the previous claims wherein the communication system is a radio communication system.

11. An apparatus for assigning a unit identity to a remote unit in a communication system comprising a plurality of remote units, the apparatus comprising: means for selecting the unit identity of a remote unit locally to the remote unit; means for broadcasting a unit identity request for the selected unit identity; and means for assigning the unit identity to the remote unit if no reject messages are received in response to the unit identity request.

12. A method of assigning a unit identity substantially as hereinabove described with reference to or as shown in the drawings.

13. An apparatus for assigning a unit identity substantially as hereinabove described with reference to or as shown in the drawings.