Field of the Invention

The present invention relates to radio telecommunication systems and, more particularly, to a cellular mobile radio telecommunication system for completing a call in the absence of an available radio communication channel.

Background of the Invention

In many scarcely populated areas of the world it is economically not feasible to deploy radio access units or radio base stations for a mobile radio telecommunications network providing a number of radio communication channels sufficiently for placing a call by each and every user or subscriber at each time of the day.

Users or subscribers living in these areas are fully aware of this fact and accept a situation in which they might need to wait for sometime till a radio communication channel of a radio access unit becomes available for completing a call. In general, the time to wait for an available radio channel can take seconds up to even minutes of valuable time. Lack of communication channel resources may also arise in intermediate equipment, such as radio repeaters and radio link equipment, such as mini link equipment, by which the radio access unit connects to a network access unit.

Users or subscribers that are today faced with a radio access unit lacking resources receive a network congestion tone or congestion signal without any further information as to the future availability of resources for completing the call. Accordingly, such

users need to redial over and over again until their call can be completed over a free radio communication channel.

The worst case appears if a call has to be completed between two or even more radio users or subscribers, because in such a case a free radio communication channel for both the calling party and the called party has to be available for completing the call.

In the present description, call completion is the process of establishing a telecommunication link between a calling party and a called party, either a voice connection or a data connection, dependent on the type of communication to be exchanged between the parties.

It will be appreciated that repeatedly dialling is not friendly to the users or subscribers of a radio telecommunication system, and puts a high load on signalling resources of the radio telecommunication system, in particular the radio access units thereof. Moreover, a user may eventually decide not to complete a call at all, leading to loss of revenues for the operator of the radio telecommunication system and/or an operator of a fixed or landline telecommunication system such as a Public Switched Telephone Network (PSTN) or an Integrated Services Digital Network (ISDN), for example.

Summary of the Invention

It is a first object of the present invention to provide an improved method of completing a call in a radio telecommunication system, in particular a cellular mobile radio telecommunication system, between a mobile calling party and a fixed called party in the absence of an available radio communication channel for the calling party.

It is a second object of the present invention to provide a method of completing a call in a radio telecommunication system, in particular a cellular mobile radio telecommunication system, between a

fixed calling party and a mobile called party in the absence of an available radio communication channel for the called party.

It is a third object of the present invention to provide a method for completing a call in a radio telecommunication system, particular a cellular mobile radio telecommunication system, between a mobile calling party and a mobile called party, in absence of an available radio communication channel for at least one of the calling party and the called party.

It is a fourth object of the present invention to provide a radio telecommunication system, in particular a cellular mobile radio telecommunication system, comprising a network access unit and a plurality of radio access units each arranged for providing radio communication service to a plurality of remote radio communication devices in geographically limited areas or cells.

It is a fifth object of the present invention to provide a radio telecommunication system, in particular a cellular mobile radio telecommunication system, comprising a network access unit and a plurality of radio access units each arranged for providing radio communication service to a plurality of remote radio communication devices in geographically limited areas or cells.

It is a sixth object of the present invention to provide a radio telecommunication system, in particular a cellular mobile radio telecommunication system, comprising a network access unit and a plurality of radio access units each arranged for providing radio communication service to a plurality of remote radio communication devices in geographically limited areas or cells.

A further object of the present invention is to provide a radio access unit or radio base station and a network access unit or Radio Exchange (RE) or Mobile Switching Centre (MSC) for operating in such a radio telecommunication system.

The above-mentioned first object of the present invention

is achieved by a method of completing a call in a radio telecommunication system, in particular a cellular mobile radio telecommunication system, between a mobile calling party and a fixed called party in the absence of an available radio communication channel for the calling party, the method comprising the steps of:

- establishing the unavailability of a radio communication channel,

- providing a message informing the calling party of the unavailability of a radio communication channel,

- monitoring the availability of a radio communication channel, and

- informing a party of completing the call if a radio communication channel becomes available.

The above-mentioned second object of the present invention is achieved by a method of completing a call in a radio telecommunication system, in particular a cellular mobile radio telecommunication system, between a fixed calling party and a mobile called party in the absence of an available radio communication channel for the called party, the method comprising the steps of:

- establishing the unavailability of a radio communication channel,

- providing a message informing the calling party of the unavailability of a radio communication channel,

- monitoring the availability of a radio communication channel, and

- informing a party of completing the call if a radio communication channel becomes available.

The above-mentioned third object of the present invention is achieved by a method of completing a call in a radio telecommunication system, in particular a cellular mobile radio telecommunication system, between a mobile calling party and a mobile called party in the absence

of an available radio communication channel for at least one of the calling party and the called party, the method comprising the steps of:

- establishing the unavailability of at least one radio communication channel,

- providing a message informing the calling party of the unavailability of a radio communication channel,

- monitoring the availability of radio communication channels for both the calling party and the called party, and

- informing a party of completing the call if the radio communication channels become available.

Instead of simply informing the calling party by a congestion tone or signal of a lack of resources for completing a call, in accordance with the present invention, a message is provided to the calling party informing same of the unavailability of a radio communication channel, such that the calling party is fully informed about the cause of the none-completion of the call. Further, after a call has been placed by the calling party, the availability of a radio communication channel, or radio communication channels in the case of a call to both a mobile calling party and a mobile called party is monitored, and if a radio communication channel or radio communication channels become available, a party to the initially placed call is informed that the call actually can be completed.

With the improved method according to the present invention, calling parties do not need to redial over and over again for finding themselves an available radio communication channel for completing the call. Instead of this, a party to the call is informed of the completion of the call once sufficient radio communication channel resources are available. It will be appreciated that the method according to the present invention is not only more user friendly then the prior art method discussed above, but also significantly reduces the load on the signalling resources of the radio telecommunication system, either or

both in the radio access unit and the radio network unit associated with a party.

In accordance with the present invention, either or both the calling party and the called party can be informed of the availability of radio communication channel resources for completing the call. In particular, by informing not only the calling party but also the called party of the availability of completing the call, the chance that a call will be completed as soon as possible radio communication channel resources are available, is greatly enhanced.

Further, by informing the calling party with a message concerning the actual cause of the non-completion of the call, the calling party, from experience, can make an assessment of the time within which most probably the call can be completed, which is in particular applicable to users in scarcely populated areas.

In a yet further embodiment of the method according to the present invention, also the called party is informed of the unavailability of a radio communication channel. By this measure, not only the called party is informed that a calling party is attempting to complete a call, but the called party can likewise make an assessment of the time within which a call from the calling party may be expected after the receipt of such a message.

It will be appreciated that a more informative message of the unavailability of a radio communication channel as the cause for the non-completion of a call, instead of a simple congestion tone, is to the benefit of both parties. Not only from the perspective of enhancing the chance of the actual completion the call but also from the point of user friendliness.

In a further embodiment of the invention, the message for informing a party of the unavailability of a radio communication channel is a text message, in particular a message provided by a Short Messaging Service (SMS) or Unstructured Supplementary Service Data (USSD) or other

messaging service such as a packet switched messaging service of an operating radio communication system in accordance with the Global System for Mobile communications (GSM) radio communication system or a Wide Band Code Division Multiple Access (WCDMA) radio communication system.

In a yet further embodiment of the invention, a party may be informed about the availability of completing a call by a text message, by a voiced message and/or by automatically completing a call between the called party and the calling party. In the case of a text message, the message can be provided by SMS or USSD of a GSM or WCDMA radio communication system, for example. Because a radio communication channel or radio communication channels are available for completion of the call, either or both parties may also be informed by a voiced message of the availability of completing the call. Such a voiced message may be provided separately or in addition to a text message.

Instead of providing a separate message or in addition to the provision of a separate message, parties may be informed by automatically completing the call and, in a further embodiment of the method according to the invention, the actual completion of the call may be under the decision of the calling party, by providing the calling party with a text or spoken menu of measures to select from, for example.

It will be appreciated that, for informing parties of actual completion of the call, information needs to be stored identifying the calling party, the called party and the radio access unit or radio access units lacking radio communication channel resources. To this end, the user or subscriber numbers of the calling party and the called party and an identification number of the radio access unit or radio access units involved can be stored. Storage of such information is well known in radio telecommunication systems, for which no further clarification is required.

In a preferred embodiment of the method according to the invention, the information identifying the parties is stored in a call

completion queue. A party may be informed of completing the call dependent on the position of the call in the call completion queue.

In a yet further embodiment of the invention, the call completion queue operates in a First In First Out (FIFO) modus. Either party may be informed as to the position of the call in the call completion queue.

Monitoring whether a radio communication channel or radio communication channels become available is preferably implemented in the radio access unit, as an additional function together with a reporting function for reporting, by the radio access unit, of the availability of a radio communication channel. However, those skilled in the art will appreciate that, dependent on the architecture of the radio communication system and the communication and signalling protocol used, the monitoring function may be implemented in the network access unit, for example, or in an Intelligent Network to which the radio communication system connects.

In accordance with the fourth object of the present invention, there is provided a radio telecommunication system, in particular a cellular mobile radio telecommunication system, comprising a network access unit and a plurality of radio access units each arranged for providing radio communication service to a plurality of remote radio communication devices in geographically limited areas or cells, the system comprising means for establishing the unavailability of a radio communication channel for completing a call between a radio communication device of a mobile calling party and a fixed called party, messaging means for informing the calling party of the unavailability of a radio communication channel, monitoring means for monitoring the availability of a radio communication channel, and means for informing a party of completing the call if a radio communication channel becomes available.

In accordance with the fifth object of the present invention, there is provided a radio telecommunication system, in

particular a cellular mobile radio telecommunication system, comprising a network access unit and a plurality of radio access units each arranged for providing radio communication service to a plurality of remote radio communication devices in geographically limited areas or cells, the system comprising means for establishing the unavailability of a radio communication channel for completing a call between a radio communication device of a mobile called party and a fixed calling party, messaging means for informing the calling party of the unavailability of a radio communication channel, monitoring means for monitoring the availability of a radio communication channel, and means for informing a party of completing the call if a radio communication channel becomes available.

In accordance with the sixth object of the present invention, there is provided a radio telecommunication system, in particular a cellular mobile radio telecommunication system, comprising a network access unit and a plurality of radio access units each arranged for providing radio communication service to a plurality of remote radio communication devices in geographically limited areas or cells, the system comprising means for establishing the unavailability of a radio communication channel for completing a call between a radio communication device of a mobile calling party and a radio communication device of mobile called party, messaging means for informing-a calling party of the unavailability of a radio communication channel, monitoring means for monitoring the availability of radio communication channels for both the calling party and the called party, and means for informing a party of completing the call if the radio communication channels become available.

In further embodiments of the radio telecommunication system according to the present invention, the messaging means are arranged for also informing the called party of the unavailability of a radio communication channel. The messaging means are preferably arranged for providing a text message, in particular a message provided by a Short Messaging Service (SMS) or Unstructured Supplementary Service Data (USSD)

or other messaging service such as a packet switched messaging service in a Global System for Mobile communications (GSM) radio communication system or a Wide Band Code Division Multiple Access (WCDMA) radio communication system.

In a yet further embodiment of the radio telecommunication system according to the invention, means are provided for informing either or both the calling party and the called party of completing a call, if a radio communication channel or radio communication channels becomes or are available. Such means, in accordance with the present invention, can likewise be arranged for providing a text message, in particular a message provided by an SMS or USSD or other service of a GSM or WCDMA radio communication system.

In a further embodiment of the invention of the means for informing a party of the completion of a call may be arranged for providing a voiced message, whether or not in combination with a text message. The means for informing a party of the completion of a call, in accordance with a yet further embodiment of the present invention, can be arranged for automatically completing a call between the parties and, preferably, these means are arranged for completing the call at the decision of the calling party.

In the case of non-completion of multiple calls, the radio telecommunication system according to the invention can be advantageously provided with storage means for storing calls in a call completion queue. The means for informing a party of completing the call may be operatively connected to the storage means and arranged for informing a party dependent on the position of the call in the call completion queue.

By operating the storage means, in accordance with a still further embodiment of the radio telecommunication system of the invention, for operating in a First In First Out (FIFO) modus, calls are completed in the order as wherein they have been placed. In the case of storage means holding a call completion queue, the messaging means are

advantageously arranged for providing a message informing a party of the position of the call in the call completion queue.

The radio telecommunication system according to the present invention, in another embodiment thereof, may comprise means for completion of a call under control of a calling party.

The above-mentioned means for establishing the unavailability of a radio communication channel for completing a call, the monitoring means, the messaging means, the means for informing a party of completing the call, and the storage means can be arranged in either or both the radio access units and the radio network unit of the radio telecommunication system according to the invention. In the case of locating the monitoring means in a radio access unit, the monitoring means are arranged for reporting the availability of a radio communication channel or radio communication channels to the network access unit. In the context of the present invention, these means as a whole are designated by the acronym CCANU (Call Completion At Network Unavailability).

Instead of or in addition to the implementation of the CCANU means in the radio communication network, all or part of the CCANU means may be implemented in an intelligent network (IN) infrastructure of a fixed or landline communication system. It wil be appreciated that the present invention may operate between users of different radio communication networks, which connect via such an IN architecture.

Those skilled in the art will appreciate that the CCANU means can be implemented either in hardware or in software and by a combination of both hardware and software.

The invention further provides a radio access unit and a network access unit arranged as disclosed above, for use in a radio telecommunication system of the present invention, for performing the improved method for completing a call, as disclosed above.

The above-mentioned and other features an advantages of the

invention will be best understood from the following description with reference to the enclosed drawings.

Brief Description of the Drawings

Figure 1 shows, in a schematic and illustrative manner, a cellular radio telecommunication system in accordance with the present invention operating in accordance with the Global System for Mobile (GSM) communications.

Figure 2 shows a simplified block diagram of an embodiment of a radio access unit operating in accordance with the present invention.

Figure 3 shows a simplified block diagram of an embodiment of a network access unit operating in accordance with the present invention.

Figure 4 shows in a time diagram an embodiment of the method according to the present invention.

Detailed Description of the Embodiments

Without the intention of a limitation, the invention will now be explained by its application in a cellular radio communication system, such as a cellular radio telecommunication system operating in accordance with the Global System for Mobile communications (GSM) standard. However, the invention is generally applicable in radio communication systems, both cellular and cordless radio communication systems, either using Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA) or Code Division Multiple Access (CDMA) radio communication channels for providing voice and/or data communication between a mobile calling party and a mobile called party, a mobile calling party and a fixed called party and a fixed calling party

and a mobile called party.

The term mobile calling party or mobile called party is used for identifying a user or subscriber using radio communication devices or equipment, such as a radio telephone and/or a radio data terminal for completing a call. The term fixed party identifies a user or subscriber of a fixed or landline telecommunication system, such as the Public Switched Telephone Network (PSTN), the Integrated Services Digital Network (ISDN) or any other public or private landline telephone system or network.

Figure 1 shows a typical architecture of a GSM system 10, comprising several functional entities, the functions and interfaces of which are specified in applicable protocols. The GSM system 10 can be divided into three general parts.

First, the radio communication devices or Mobile Equipment (ME) 11, such as mobile telephones and/or mobile radio data transmission devices, carried by the user or subscriber of the GSM system 10. Note that in rural areas, for example, the radio communication devices can be fixedly installed, for example.

Second, the radio access units or radio base stations subsystem, which controls the radio or Um-interface 16 with the mobile equipment 11. The main part of the radio base stations subsystem is formed by a Base Station Controller (BSC) 14 and Base Transceiver Stations (BASS) 15 which connect 12 to a BSC 14. Each BTS 15 provides service to a geographically limited area or cell 13. The cells 13 are preferably arranged such that a wide geographic area is completely covered by a plurality of adjacent cells 13. However, in scarcely populated areas or rural areas the capacity of radio base station subsystems 14, 15 may be limited to arrive at an economically feasible network architecture.

A third and major part of the GSM system 10 is the network subsystem 20, comprising a network access unit or Mobile Switching Centre

(MSC) 21, which performs switching of calls between the radio base station subsystems 13, 14 and the Public Switch Telephone Network (PSTN) or Integrated Service Digital Network (ISDN) 17.

The network subsystem 20 further comprises a Home Location Register (HLR) 22 and a Visitor Location Register (VLR) 23 which, together with the MSC 21 provide call-routing and roaming capabilities of the GSM system 10. The VLR 23 contains selected administrative information from the HLR 22, necessary for call control and provision of subscriber services for each ME 11, currently located in the geographically area controlled by a VLR 23. For authentication and security purposes, an Equipment Identity Register (EIR) 24 and an Authentication Centre (AuC) 25 are provided in the network subsystem 20. The EIR 24 is a data base containing a list of valid ME 11 of the system 10 and the AuC 25 is a protected data base storing a copy of secret keys of each ME 11. The MSC 21 connects to the BSC 14 through a so-called A- interface 18. The BASS 15 connect to the BSC 14 across a so-called Abis- interface 19.

At the radio Um-interface 16, the GSM system 10 operates following a combination of Time and Frequency Division Multiple Access (TDMA/FDMA)..The FDMA part involves the division by frequency of available transmission bandwidth into a plurality of Radio Frequency (RF) carriers. One or more carrier frequencies are assigned to each BTS 15, for completing calls with a ME 11. To avoid interference between communications in adjacent or neighbouring cells 13, the number of carrier frequencies to each BTS 15 is limited. Each of the carriers is further divided in time, using a TDMA scheme, providing a plurality of duplex radio communication channels for completing calls, either voice or data calls, with an ME 11.

For signalling purposes between the radio base station subsystems 14, 15 and the ME 11, a separate signalling protocol is implemented in the GSM system 10. Signalling between the different

entities in the fixed part of the GSM system, such as between the HLR 22 and the VLR 23, is accomplished by the so-called Mobile Application Part (MAP). MAP is built on top of the Transaction Capabilities Application Part (TCAP), the top layer of Signalling System number 7. Across the Um- interface 16, signalling is implemented as a modified version of the so- called Link Access Procedure-D (LAPD) signalling protocol for the D channel used in ISDN, called LAPDm. To this end, suitable signalling and control means are implemented in the radio base station subsystems 14, 15, which are known to those skilled in the art. These systems are not specifically shown in figure 1 in order not to complicate the figure.

In accordance with the present invention, the BTS 15 and/or the BSC 14 and/or the MSC 21 are provided with additional means, in the context of the present invention designated as call Completion At Network Unavailability (CCANU), arranged for implementing the method of the invention of completing a call in the GSM system 10 in the absence of an available radio communication channel for a calling party. In figure 1, the CCANU means are indicated by broken lines and designated by reference numerals 26, 27 and 28, respectively. The CCANU means may, in addition to or instead of, completely or partly, be implemented in the PSTN or ISDN 17, which may form part of an intelligent network architecture, as designated by reference numerals 20.

In figure 2, a simplified block diagram is shown of a radio base station subsystem 14, 15 in accordance with the present invention, wherein the means 26, 27 are further specified. Only those means are shown which directly relate to the present invention. Those skilled in the art will appreciate that the BSC 14 and BTS 15 may comprise further means for completing calls, which are known perse in the prior art of record of GSM systems and networks. It will be appreciated that such means are herein incorporated by reference. In figure 2, reference numeral 30 discloses means for establishing the unavailability of a radio communication channel at the Um-interface 16 of a BTS 15 for completing a

call between a calling party and a called party, at least one of which avails himself or herself of a mobile radio communication device or ME 11.

Reference numeral 31 designates monitoring means for monitoring whether a radio communication channel becomes free or available at the Um-interface 16. It will be appreciated that the monitoring means 31 are operatively connected to the means 30 for establishing the unavailability of a radio communication channel. In this embodiment, the monitoring means 31 are arranged for reporting the availability of a radio communication channel to the network access unit or MSC 21.

As mentioned in the preamble, lack of radio communication resources can also arise in the event that intermediate equipment between the network subsystem 20 and the radio base stations subsystem 14, 15 runs out of resources, such as for example a radio repeater or radio link equipment, such as mini link equipment. It will be appreciated that the monitoring means 31 are arranged for monitoring the availability of a radio channel for such intermediate devices.

Reference numeral 32 refers to messaging means for providing a message to a calling party and/or a called party informing same of the unavailability of a radio communication channel for completing a call. Likewise, the messaging means 32 are operatively connected to the means 30. The message will be provided to the ME 11 via the signalling means or a dedicated radio communication channel.

Reference numeral 33 designates means for informing a party of completing a call, once a radio communication channel becomes available. It will be appreciated that means 33 are operatively connected to the monitoring means 31.

Reference numeral 34 designates storage means, for storing information such as subscriber numbers (A-number/B-number) identifying the calling party and/or the called party and/or an identification number

or the like of a radio base station subsystem involved in the completion of a call. Note that in the case of a call between mobile users or mobile subscribers, two or more radio base station subsystems 14, 15 can be involved in the completion of the call, of which relevant identification information needs to be stored.

The messaging means 32 are advantageously arranged for providing a text message to either one or all the parties involved in a call by means of a Short Messaging Service (SMS) or Unstructured Supplementary Service Data (USSD) as implemented in the GSM radio system 10. In the case of a message to be transmitted to a fixed party, i.e. a party connected to a landline telecommunication network or another radio communication system operating in a different standard than GSM, a text message using a protocol suitable for transmission and receipt in such telecommunication system will be provided to the party or parties involved, such as a packet switched messaging service in a Wide Band Code Division Multiple Access (WCDMA) radio communication system.

Likewise, the means 33 for informing a party of the availability of completing the call, can be arranged for providing a text message using a suitable messaging service for a respective party involved in a call .

The means 33 may also be arranged for automatically completing a call, once a radio communication channel or radio communication channels (have) become available, by setting up a call between a calling party and the called party, dependent on the information stored in the storage means 34, for example.

The actual completion of the call can be at the decision of the original calling party, for example, by informing this party that the call will be completed if the party accepts same. It is then up to this party to decide whether to actually complete the call.

Because a radio communication channel is available at the completion of a call, instead of a text message, a voiced message can be

provided to the parties informing them of the availability of the call completion. For example a voiced selection menu or the like.

The storage means 34 are advantageously arranged for maintaining a call completion queue such that, if a call can not be completed, due to unavailability of a radio communication channel, this call will be placed in the queue. That is, the relevant identification information of the call is placed in the queue. The call completion can be operated in a number of modes, such as a First In First Out (FIFO) modus. However, other modes can be applied for completing a call, dependent upon priorities, for example. Such priorities may be based on the urgency of a call or can be provided as a special service to mobile subscribers or mobile users, upon specific payment or the like, for example.

Figure 3 shows in a schematic block diagram an implementation of the means 30-34 in the network subsystem 20, more particularly in the network interface unit or MSC 21.

In a practical embodiment of the system according to the invention, the means 30-31 may be distributed over the BSC/BTS 14, 15 and the MSC 21 and can be implemented in hardware, in software or a combination of hardware and software.

Instead of or in addition to the implementation the means 30-34 in the radio base stations subsystem 14, 15 and/or the network subsystem 20, these means may be implemented in other parts of the mobile radio communication system 10 and/or the fixed or landline communication system 17. In particular, in the case of an Intelligent Network (IN) infrastructure, comprising Service Control Point or Signal Control Point (SCP) and Service Switching Point (SSP) equipment making up the fixed or landline communication system 17, part or all of the means 30-34 may be implemented in SCP equipment, for example. In particular, the messaging means and the means for informing that a radio channel becomes available, inclusive means for automatically completing the call, may be implemented

in the IN infrastructure.

In general, the radio communication system connects to a core network, comprising SSP equipment, which in turn connects to a so- called service network, comprising SCP equipment. The CCANU means according to the invention can be advantageously implemented in the service network, such that the invention can be used independent of a particular radio access network involved or in the case of calls between different radio access networks of different operators, different protocols, and the like.

For messaging purposes, packet switched services may be advantageously used for the purpose of the invention.

In the time diagram shown in figure 4, the different steps of the improved method for completing a call in a radio telecommunication system, according to the present invention, are illustratively shown. In figure 4, time is running from the top of the figure to the bottom of the figure. Steps which are consecutive in time are arranged from the top to the bottom of the figure. These steps are indicated by arrows, which point in the direction of the communication flow between the several units or means involved. In figure 4, for the same or functionally equivalent units or means, like reference numerals are used as in figures 1-3.

Referring to figure 4, arrow 40 indicates a call set-up from an ME 11 as the calling party or A-party, via the Um-interface 16 and a BTS 15 towards a BSC 14. The BSC 14, in this embodiment of the invention, is equipped with means 30 for establishing the availability of a radio communication channel. In the event that no radio communication channel is available for completing the call set-up 40, the MSC 21 will be informed by the BSC 14, of the unavailability of a radio communication channel, via the A-interface 18, indicated by arrow 41.

In accordance with the present invention, failure of the call set-up triggers messaging means 32 for providing a message to the

calling party using the ME 11. The triggering of the messaging means 32 is indicated by arrow 42. Arrow 43 indicates a transmission of a message to the calling party 11, for example: "You have temporarily no access to the network". In addition to the transmission of a message to the calling party 11, also a message may be transmitted by the messaging means 32 to the called party or B-party 35, indicated by arrow 44. This message may read, for example: "A person with phone number xxx is trying to call you, call set-up will be delayed due to network temporarily unavailability".

In the event of a fixed calling party establishing a call to a mobile called party, while lack of radio channel resources is established, the messaging means 32 will provide a message to the fixed called party reading, for example: "The party you are calling has temporarily no access to the network". The mobile called party may receive the same message as indicated above in connection with arrow 44.

In the event of a mobile calling party and a mobile called party, both using an ME 11 of the same or different radio communication networks, it will be appreciated that each BSC 14 associated with each ME 11 involved in a call can trigger the messaging means 32 in the case of unavailability of radio communication channel resources. In such a case it is advantageously to have the messaging means 32 operated centrally for a radio communication system 10, for example implemented in the network access unit or MSC 21 or the PSTN/ISDN 17 or any other applicable fixed telecommunication network connection to the radio system.

If a call is put into a call completion queue, the messaging means may provide a message informing a party of the position of the call in the queue, accompanied by an approximate waiting time, for example.

In the event that the means 30 establish the unavailability of the radio communication channel or radio communication channels, monitoring means 31 are triggered for monitoring whether a radio channel or radio channels become available or free. In figure 4 this is indicated

by arrow 45. It is assumed that the monitoring means 31 are arranged at the BSC 14. However, the monitoring means 31 may also be implemented in the MSC 21, for example, such that a real time triggering implementation and a near-real time non-triggering implementation for the completion of a call is possible.

Once a radio channel or radio channels are available, means 33 are triggered by the monitoring means 31, for informing either or both the calling party and the called party of the availability of completing a call, as indicated by arrow 46.

The means 33 may provide a message, either a text message or a voiced message, to initiate one or both parties involved in the call to complete the call; indicated by arrows 47 and 48 in figure 4.

In addition to the messages 47, 48, the means 33 can be arranged for automatically completing a call by triggering the MSC 21, for example, as indicated by arrow 49. The MSC 21 then will operate in accordance with the applicable signalling and communication protocol for completing the call.

It will be appreciated that, dependent on the implementation of the means 30-34 in accordance with the present invention, the time diagram of figure 4 will slightly change as to the origin and the destination of the several steps or arrows.

The present invention is not limited to the embodiments as disclosed above, and can be modified and enhanced by those skilled in the art beyond the scope of the present invention as disclosed in the appended claims without having to apply inventive skills.