MXPA00001715A - Method and apparatus for reconfiguring control channel provision within a cellular telephone system - Google Patents

Abstract

In response to the blocking (100) of a base station (18) control channel, an attempt is first made to recover (102) the channel (perhaps using a deblock). If the recovery should fail, a reconfiguration of the control channel from a control channel transceiver to a selected traffic channel transceiver is effectuated. The traffic channel transceiver that is selected preferably is of the same type as the control channel transceiver and has as many idle channels as possible (108). Alternatively, the selected traffic channel transceiver may have a different type with as many idle channels as possible (112). The configuration and frequency of the selected traffic channel transceiver are then replaced (116) with the configuration and frequency of the control channel transceiver to complete the reconfiguration. The control channel is then deblocked (118) and the traffic channel(s) previously supported by the found transceiver are blocked.

Description

METHOD AND APAPATO PECQNFIGUPAR THE DISPOSITION OF CHANNELS OF CONTROL IN A CELLULAR TELEPHONE SYSTEM BACKGROUND OF THE INVENTION Technical Field of the Invention The present invention relates to cellular telephone systems, and in particular, to a method and apparatus for reconfiguring a control channel of a cellular telephone system.

Description of the Related Art Cellular telephone systems divide a large service area into different smaller geographical areas called "cells" each usually in the size range from about half to about 20 kilometers in diameter. Each cell is at least contiguous and / or overlaps with multiple adjacent cells to offer virtually continuous coverage throughout the service area. A base station is provided for each of the cells. Each base station includes a plurality of transceivers, with each transceiver capable of operating independently at a different, assigned, radio frequency selected from the cellular frequency band. Through the transceivers, the base stations are connected in simultaneous radio frequency communications on these channels with a plurality of mobile stations operating within the area of the associated cell. The base stations further communicate by data links and voice trunks with a central control station, commonly known as a mobile switching center, which functions to selectively connect the telephone calls to the mobile stations through the base stations and , in general, control the operation of the system. The frequencies assigned to a cell support at least one control channel (CCH) and a plurality of voice and data (traffic) channels (TCH). In an analog cellular telephone system, such as the known advanced mobile telephony service (AMPS) communication system, there is an analog communications channel with frequency division multiple access (FDMA) (control or traffic) by frequency . In a digital cellular telephone system, such as the D-AMPS or Global System for Mobile (GSM) communication systems, however, there is a plurality of digital communication channels with time division multiple access (TDMA) by frequency. The control channel serves as the service access point for mobile stations for the cellular telephone system. Then, to offer continuous telephony service to subscribers, it is imperative that failures in the control channel are avoided. These failures, for example, can occur when the control channel is automatically blocked by a fault detected in the hardware (ie, in the transceiver). Many cells support the use of a backup control channel that is then used in the case of a failure as such. The backup control channel may be provided by an alternate transceiver that is activated when the transceiver that supports the control channel fails. This solution is not preferred, however, because it requires the inclusion of expensive additional hardware in each base station. In contrast, if the alternate transceiver consists of one of the other transceivers in the base station that supports one or more traffic channels, the reconfiguration may result in the loss of calls currently being handled by the alternate transceiver. There is a need then for a reconfiguration procedure that takes into account aspects of call loss when the backup control channel is activated. In addition, in some cases it is not necessary to reconfigure. Accordingly, there is a need for a procedure to handle blocking of control channels that evaluates other options (such as unlocking or recovery) before committing to a reconfiguration.

COMPENDIUM OF THE INVENTION To solve the above aspects and others, the present invention responds to the blocking of a control channel rlp od-a ri? n ha co nri morn -i t? - | - O-n t- a t-? l? -? r-p HTnor-a v o l channel. Tp l recovery can be carried out through an unlocking. If the recovery fails, the control channel is reconfigured from the non-operational control channel transceiver to another transceiver at the base station that supports the traffic channels. The transceiver selected for the reconfiguration of preference is that traffic channel that supports the transceiver having the same type of control channel transceiver with as many inactive channels as possible. Otherwise, the selected transceiver has a different type with as many inactive channels as possible. Once the selected transceiver has been found, its configuration and frequency are replaced with the configuration and frequency of the transceiver of the control channel. The control channel is then unlocked in this selected transceiver, and previously supported traffic channels are blocked. Meanwhile, the control channel transceiver maintains its configuration and frequency until the time when the equipment becomes operational again. At this time, it returns to support the control channel, and the selected transceiver returns to its original configuration and frequency.

BRIEF DESCRIPTION OF THE DRAWINGS It is possible to obtain a more complete understanding of the method and apparatus of the present invention by referring to the following detailed description when taken in conjunction with the accompanying drawings, wherein: FIGURE 1 is a schematic diagram of a system of cell phone; FIGURE 2 is an exemplary transceiver configuration for a base station; and FIGURE 3 is a flow chart illustrating an operation of the reconfiguration in a control channel according to the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS Reference is now made to FIGURE 1, where a schematic diagram of a cellular telephone system is shown. An arbitrary geographical region (hereinafter "the service area") is divided into a plurality of contiguous cells 10 represented schematically by hexagons. A cellular service area can cover a large geographic region, and in many cases there will be a need for a large number of cells. Sometimes the number of cells needed will exceed the number of cells provided by dividing the available frequencies in the allocated cellular frequency band between the cells in such a way to handle the expected subscribers' use per cell. In cases like these there simply are not enough frequencies for single assignment to the included cells. Then, to provide sufficient call handling capacity in the entire service area, the cells are grouped into groups of cells and the frequencies are divided and reused in each of the groups according to a certain frequency assignment plan. Each of the cells 10 in a cellular telephone system as illustrated in FIGURE 1 includes at least one base station (BS) 18 configured to facilitate radio frequency communications with mobile stations 20 moving throughout the service area. The base stations 18 are illustrated being located at or near the center of each of the cells 10. However, depending on the geography and other known factors, the base stations 18 may instead be located on or near the periphery of, or otherwise away from the centers of each of the cells 10. In. In such cases, the base stations 18 can transmit and communicate with the mobile stations 20 located within the cells 10 using directional rather than omnidirectional antennas. The base stations 18 are connected by communication links 16 (and perhaps through a base station controller, not shown) to at least one of the mobile switching centers (MSC) 22 which operates to control the operation of the system providing cellular communications with mobile stations 20. Each base station 18 includes a plurality of transceivers (not shown, see FIGURE 2) capable of operating independently at different radio frequencies of the cellular frequency band assigned to the cell. The operation of the mobile switching center 22 and the base station 18 for providing cellular telephone services is well known to those skilled in the art and will not be described further. Now with reference to FIGURE. 2, wherein an exemplary transceiver configuration for a base station 18 is shown. The base station 18 includes a plurality of transceivers (Tx) 26. Each transceiver 26 in turn operates at a selected frequency (or more particularly a pair of frequencies). associated partners for uplink and downlink communications, respectively). The base station 18 further includes a control module 28 that regulates the operation and configuration of the transceiver 26. Among other well-known transceiver control operations related to assisting in the provision of cellular telephone service, the control module 28 further instructs the each transceiver 26 in terms of frequency (ie, the pair of frequencies) that it must use for operation. In this sense, the transceivers 26 of each base station 18 can be selectively tuned in response to the instruction of the control module 28. At least one of the transceivers 26 (1) in the base station 18 is assigned to support a control channel for the cell . Depending on the type of cell phone system established, this specific transceiver 26 (1) can also support one or more voice channels (traffic) for the cell. In an analog cellular telephone system, such as the known advanced mobile telephone service communication system (AMPS), where there is an analog communications channel with frequency division multiple access (FDMA) by frequency, the transceiver 26 (1) assigned to support the control channel only supports this control channel. Then each of the remaining transceivers 26 (2) supports an analog voice (traffic) channel per cell. In a digital cellular telephone system, such as the known D-AMPS or Global System for Mobile (GSM) communication systems, where there is a plurality of digital communication channels with time division multiple access (TDMA) by frequency, the transceiver 26 (1) assigned to support the control channel supports this control channel as well as a plurality of digital voice (traffic) channels. The rest of the transceivers 26 (2) each also supports a plurality of digital voice (traffic) channels. In a telephone system rp l n l a r a l l e r i n i "i p" i + "=? 1 or í tnp '~> Hnhl or nri tran s r; on t- Q? ~ F. (1) assigned to support an analog control channel supports only this control channel, and another transceiver 26 (1) assigned to support a digital control channel supports this control channel as well as a plurality of digital voice channels (traffic). The rest of the transceivers 26 (2) each supports a single voice channel (traffic) for analog mode or a plurality of voice (traffic) channels for digital mode. The control module 28 monitors the operation of the transceiver 26 and detects cases of hardware failure. In response to this, the control module implements an automatic blocking function to disable the use of channels (control and / or traffic) supported by the failed transceiver 26. An indication of the blocking event may also be provided to the switching center mobile. The establishment of an automatic block with respect to a transceiver 26 (2) supporting one or more voice channels (traffic) affects the ability of the base station 18 to handle communications with the mobile station. The operation of another normal way of the base station 18 continues. Establishing automatic blocking with respect to a transceiver 26 (1) by supporting a control channel, however, can return the base station 18 completely inoperable since the control channel is used as the access point to the system. cellular telephony for the mobile stations served. By or i Q? rfiiionf '3 ^ o Horio nr-p c -l- a r a t on? n n no pc pc or a a a al al al al al al con ((((((canal??????? canal? canal? canal? canal? canal? canal? canal Now with further reference to FIGURE 3, where a flow chart illustrating an operation of the reconfiguration of the control channel according to the present invention is shown. With the establishment in step 100 by means of the control module 28 of the automatic blocking of the channel with respect to a transceiver 26 (1) supporting a control channel (digital or analog), first the control module tries in step 102 recover blocked channel (maybe through an unlock). Other operations and recovery procedures are well known in the art, and will not be described in more detail herein. If the recovery fails, as determined in decision step 104, reconfiguration 106 of the control channel is performed. The reconfiguration action 106 includes searching in step 108 another transceiver 26 (2) in the base station 18 of the same type as the transceiver supporting the blocked channels, which only supports the traffic channels, and has as many channels of inactive traffic as possible. By "the same type" it is understood that the transceiver 26 (2) having the same number of logical channels as the blocked channel transceiver 26 (1) supporting the control channel. The transceivers of the same type 26 are nro fori} p? If the logical channels do not change as a result of reconfiguration, transceivers are preferred 26 (2) only of traffic channels to ensure that the reconfiguration does not eliminate any other control channel supported by the base station 18. Transceivers 26 with inactive traffic channels are preferred as this minimizes disturbances for the resulting subscriber communications (calls) The service provider can selectively set a threshold value for the number of inactive traffic channels that must be present for the transceiver 26 (2) to take it into consideration, if a transceiver 26 (2) can not be found, as determined in decision step 110, the action of the reconfiguration in step 106 further includes hn p a r on al s 1 1 9 nf rn Ir? Tí onÍOi "f¡Ì O) on the oc base 18 not the same type as the transceiver that supports blocked channels, which supports only traffic channels, and that has as many inactive traffic channels (limited by the threshold) as possible. transceiver 26 (2) suitable in step 108 or step 112, as determined in decision steps 110 or 114, the configuration and frequency of transceiver 26 (2) with appropriate reconfiguration, found are replaced in step 116 with the configuration and frequency of the blocked channel transceiver 26 (1) This substitution operation requires the control module 28 to instruct the found transceiver 26 (2) to perform a new frequency tuning.After the replacement is complete, the control channel previously blocked is unlocked (along with any equally supported traffic channel that was also blocked), and the traffic channel (s) supported by the reconfiguration transceiver are blocked (step 118). If no transceiver is found with adequate reconfiguration 26 (2) (see, the decision steps 110 and 114) no reconfiguration is performed (step 120).

Meanwhile, the transceiver 26 (1) maintains its control channel configuration and frequency assignment waiting for the time when the equipment again becomes operational (path 122). At this point a new substitution is made (step 116) to the original configurations and frequencies for the transceivers 26 (1) and 26 (2). The previously blocked traffic channels are then unblocked (step 118). A more complete understanding of the present invention can be obtained by examining two examples in connection with the execution of the FIGURE process. 3. In a first example, suppose that the present invention goes roan l i v a nn roanoftO 3. n? a osf-a r i rín has «p nfrorianH? analog cellular telephone service as the communication system of the advanced mobile telephony service (AMPS) known, where there is an analog communications channel with frequency division multiple access (FDMA) by frequency. The base station accordingly includes a transceiver 26 (1) assigned to support the control channel, along with a plurality of the remaining transceivers 26 (2) each supporting an analog voice (traffic) channel. A failure of the transceiver 26 (1) assigned to support the control channel is detected and, in step 100, the automatic blocking of the control channel is performed. Then, in step 102 an attempt is made to recover the blocked channel. Assuming that this fails (step 104), a reconfiguration 106 of the control channel is performed. First, another transceiver 26 (2) of the same type as the transceiver 26 (1) assigned to support the control channel, which supports only traffic channels, and which is inactive, is in step 108. If in the step 108 there is no transceiver 26 (2), another transceiver 276 (2) of a different type such as the transceiver 26 (1) assigned to support the control channel, which only supports traffic channels, and it is inactive, it is in step 112. Assuming now that it is (preferably from step 108) a transceiver 26 (2) like this, the configuration and frequency of the transceiver 26 (1) assigned to support the control channel blocked replaced (step 116) the configuration and frequency of the found transceiver 26 (2). This replacement operation requires the transceiver 26 (2) to perform a new frequency tuning to the frequency of the assigned control channel. Once the replacement is complete, the previously blocked control channel is unblocked, and the traffic channel formerly supported by the transceiver 26 (2) found is blocked (step 118). Finally, when the transceiver 26 (1) again becomes operational, it returns (path 122) its support of the operation of the control channel. The substitution is reversed (step 116) to the previous configurations and frequencies, and the traffic channel supported by the transceiver 26 (2) is unlocked (step 118). In a second example, suppose that the present invention is made with respect to a base station offering digital cellular telephony service such as the known D-AMPS or Global Systems for Mobile (GSM) communication systems, where there is a plurality of digital channels of communications with multiple time division (TDMA) access by frequency. The base station accordingly includes a transceiver 26 (1) assigned to support the control channel and a plurality of digital voice channels (traffic) together with a plurality of remaining transceivers 26 (2) each supporting a plurality of digital channels of voice (traffic). A failure of the assigned transceiver 26 (1) is detected to support the control channel and the plural traffic channels and the automatic blocking of the control / traffic channels is performed in step 100. Then, in step 102 an attempt is made to recover the blocked channels. Assuming that this fails (step 104), a reconfiguration 106 of the control channel is performed. First, another transceiver 26 (2) of the same type as the transceiver 26 (1) assigned to support the control / traffic channels, which only support the traffic channels, and has more than one threshold number of channels of traffic. inactive traffic, is searched in step 108. If in step 108 no transceiver 26 (2) is found, in step 112 another transceiver 26 (2) of a different type such as the assigned transceiver 26 (1) is searched to support the control channel, which supports only traffic channels, and has more than one threshold number of inactive traffic channels. Assuming now that a transceiver 26 (2) is thus (preferably in step 108), the configuration and frequency of the transceiver 26 (1) assigned to support the blocked control / traffic channels replaces (step 116) the configuration and frequency of the transceiver 26 (2) found.

This replacement operation requires the transceiver 26 (1) to perform a frequency retune to the frequency of the assigned control channel. Once the substitution is complete, the previously blocked control / traffic channels are unblocked, and the traffic channels formerly supported by the transceiver 26 (2) found are blocked (step 118). Finally, when the transceiver 26 (1) again becomes operational, its control channel operation support (path 122) returns. A replacement is made (step 116) again to the previous configurations and frequencies, and the traffic channels supported by the transceiver 26 (2) are unblocked (step 118). Although the method and apparatus of the present invention have been illustrated in the accompanying drawings and described in the aforementioned detailed description, it will be understood that the invention is not limited to the described mode (s), but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as established and defined by the following clauses.

Claims (22)

1. RE I VIND I CAC I ONE S 1 . TTn mof-nrl < The channel includes the steps of: responding to a blockage of a control channel supported by a first transceiver at a base station by searching a second transceiver in the base station that supports as many inactive traffic channels as possible, replace a configuration and frequency of the second transceiver with a configuration and frequency of the transceiver, and unblock the control channel that is now supported by the second transceiver 2. The method as recited in claim 1 further includes the step of blocking the one or more traffic channels formerly supported by the second transceiver and now supported by the first transceiver 3. The method as mentioned in Claim 1 further includes the step of first attempting a recovery of the blocked control channel before searching for the second transceiver 4. The method as in claim 1 wherein the Searching the second transceiver comprises the step of searching for a second transceiver having the same type as the first transceiver with as many inactive traffic channels as possible. 5. The method as in reix7indication 4 wherein the same type comprises a second transceiver having the same number of logical channels as the first transceiver. The method as in claim 4, wherein the step of searching further comprises the step of searching for a second transceiver having a different type as the first transceiver with as many inactive traffic channels as possible. The method as in claim 1, wherein the step of searching the second transceiver comprises the step of searching for a second transceiver having more than one threshold number of inactive traffic channels. 8. The method as in claim 1 further i? P l p -F > The second transceiver after the termination of the block related to the first transceiver 9. A base station for a cell comprises: a selectively tunable transceiver supporting a control channel of the cell; plurality of second selectively tunable transceivers each supporting at least one traffic channel of the cell, and a control module operating in response to a blocking of the control channel to select a certain transceiver of the plurality of second selectively tunable transceivers having as many channels of inactive traffic as possible and reconfigure the control channel support for the certain second transceiver having the second transceiver adopted a configuration and frequency of the first transceiver 10. The base station as in claim 9, wherein the control module it is also operating to select the certain second transceiver d e the plurality of second transceivers having more than threshold number of inactive traffic channels. The base station as in claim 9, wherein the control module is further operable to select this certain second transceiver from the plurality of second transceivers having the same type as the first transceiver with as many inactive traffic channels as possible. The base station as in claim 11, wherein the same type comprises a second transceiver having the same number of logical channels as the first transceiver. The base station as in claim 11, wherein the control module is further operable to select this certain second transceiver from the plurality of second transceivers having a different type as the first transceiver with as many inactive traffic channels as possible. The base station as in claim 9 wherein the control module is further operating to restore an earlier frequency and configuration of the second transceiver after the termination of the first block related to the first transceiver. 15. A method for reconfiguring the control channel comprises the steps of: responding to a blocking of a control channel supported by a first transceiver at a base station by searching for a second transceiver at the base station that supports more than one number threshold of inactive traffic channels; replace a configuration and frequency of the second transceiver with a configuration and frequency of the first transceiver; and unblock the control channel that is now supported by the second transceiver. 16. The method as in claim 15 further includes the step of unlocking the traffic channels formerly supported by the second transceiver. 17. The method as in claim 15 further includes the step of first attempting a recovery of the blocked control channel before searching for the second transceiver. 18. The method as in claim 15, wherein the step of searching the second transceiver comprises the step of searching for a second transceiver having the same number of logical channels as the first transceiver. 19. The method as in claim 15 further includes the step of restoring the configuration and frequency of the second transceiver after the termination of the lock related to the first transceiver. 20. A base station for a cell comprises: a first transceiver supporting a control channel of the cell; a plurality of second selectively tunable transceivers each supporting at least one traffic channel of the cell; and a control module operating in response to a blocking of the control channel to select a certain transceiver from the plurality of second selectively tunable transceivers having more than one threshold number of inactive traffic channels and reconfiguring the control channel support for the certain second transceiver having adopted the certain second transceiver a configuration and frequency of the first transceiver. 21. The base station as in claim 20, wherein the control module is further operating to select this certain second transceiver from the plurality of second transceivers having the same number of logical channels as the first transceiver. 22. The base station as in claim 20, wherein the control module is further operating to restore an earlier frequency and configuration of the second transceiver after the termination of the block related to the first transceiver.