MXPA00005671A - Paging method for a multi-line terminal in a fixed cellular system - Google Patents

Abstract

A communication system provides telephone service to subscriber units through a private branch exchange (PBX) and a fixed cellular terminal (FCT) that operates within a digital cellular network. The cellular network transmits page information over one or more physical channels that are subdivided into digital control channels (DCCH) that include one or more logical paging channels (PCHs). The FCT includes a number of cellular terminals (CTs) incorporated in multi-line terminals (MLTs). The MLTs connect the subscriber units to the CTs, at least one of which receives the page information on at least one PCH.

Description

"RADIOLOCALIZATION METHOD FOR A TERMINAL OF MULTIPLE LINES IN A FIXED CELLULAR SYSTEM" TECHNICAL FIELD _ This invention: usually relates to the field of communication systems and, more particularly, to a communication system that provides telephone service using a Fixed Cell Terminal (FCT).

BACKGROUND In many parts of the world, telephone service is not easily available due to inadequate or non-existent infrastructure, and people who want the service have to wait for a long period of time to obtain it. In order to solve this problem, many service providers are installing terminals that are known as Fixed Cellular Terminals (FCT), which combine the technology in the private branch office telephone exchange (PBX) and cellular technology, to provide telephone service to through a cellular network. An FCT includes a Multiple Line Terminal (MLT) and a PBX that together provide telephone service - - to a group of subscribers through a cellular network. In the FCT, a group of subscriber units, such as conventional wired telephones, are multiplexed through the PBX to a number of cellular terminals (CTs) incorporated in the MLT. This provision accelerates the installation of telephone infrastructure at distant locations, where conventional wiring telephone service is not available. For example, a known FCT provides telephone service to 100 subscribers using an MLT that has 16 CTs. A control unit - in the MLT it coordinates the selection of main lines and the communication with the PBX. Under this provision, each MLT serves a group of subscriber units that can receive or initiate calls through the cellular network. When a call is addressed to a specific subscriber number of a conventional FCT, the cellular network transmits a radiolocation containing the number of the called subscriber through a control channel. Each of the CTs that functions to direct or originate a call to and from any of the subscriber units is programmed to respond to the radiolocations addressed to the group of subscriber numbers assigned to a corresponding MLT. Conventional FCTs are implemented using two types of cellular networks. The first type of cellular network is - an analog cellular network, such as an AMPS network, which modulates the analog voice and control signals in physical radio frequency (RF) channels that are linked to the CTs and a central controller of the cellular network with one another. Under this implementation, the CTs of an MLT are tuned to a known radiofrequency control channel for receiving and transmitting the analog control information, such as the radiolocation information and the voice channel information carrying a voice call. Once the control information is received for the called subscriber unit, the MLT selects an unoccupied CT to handle the call. FCTs are also implemented in a second type of cellular network that uses a hybrid of analog and digital technology. One of these hybrid cellular network standards is defined by IS-54 of Telecommunication Industry Associated (TIA). This hybrid cellular network uses one or more analog physical channels to communicate the control information. The voice and data signals, however, communicate digitally through logical channels that are formed by subdividing a physical frequency channel into a predetermined number of time slots. In many digital systems, the logical channels carry digital voice and traffic data using a Time Division Multiple Access (TDMA) technique. Similar to analog cellular networks, CTs of the FCT that work with the hybrid cellular network, which tune to a physical control channel designated to receive the analog control information., including the radiolocation information. There is also a third type of cellular network, which is completely digitized. This type of cellular network uses logical channels to communicate the voice or digital data as well as the control information. A digital cellular standard is defined by the TIA IS-136 standard, which is being rapidly adopted throughout the world. A cellular network implemented using the IS-136 standard transmits the control information through the digital control channels (DCCHs) that carry the radiolocation information through the logical radiolocation channels (PCHs). Under the IS-136 standard, a Mobile Switching Center (MSC) performs a predefined PCH calculation algorithm to assign the PCHs. In order to locate the PCHs, the MSC applies a number of defined parameters, including each mobile identification number of the mobile station (MIN, to the PCH calculation algorithm.) Due to the arbitrary nature of the MIN pair, however, - the PCH calculation algorithm produces arbitrary results.Therefore, unlike the first two types of cellular networks that transmit radiolocation information through a known physical control channel, the radiolocation information in an IS-136 system can be dispersed In addition, in addition to being scattered in multiple logical channels of a physical channel DCCH, a cell, depending on the cell configuration of the cellular network, can distribute the PCH channels through up to 8 physical channels DCCH The arbitrary nature of CH complicates allocation through one or more physical channels, the implementation of an FCT using a channel of digital control Unlike the analog and hybrid cellular networks, which have a fixed control channel to which the CTs can be easily tuned to receive the radiolocation information, the radiolocation information in an existing digital cellular network is carried in the PCHs that are not fixed. Since the MLT is responsible for answering calls addressed to a large group of subscriber numbers, e.g., up to 100 subscriber numbers, its associated CTs must calculate a PCH for each subscriber number based on an assigned MIN pair. Due to arbitrarily assigned logical PCHs, theoretically, each mobile station must monitor each PCH in all DCCHs. Even when the CT - has the ability to monitor each PCH, to carry out the PCH allocation algorithm for each pair of MIN of a large group of subscriber numbers, eg, of 100, within the duration of the logical channel, which under the standard of IS-136 is approximately 640 ms, it is beyond the processing power of existing CTs. In addition, if the allocated PCHs are dispersed through two or more physical channels, the existing CTs, without modifications in the hardware and software, are unable to simultaneously monitor the PCHs through the multiple physical channels. Due to the wide acceptance of digital cellular networks, it is desired to implement the FCT under a standard that defines a digital control channel, without essentially modifying an existing infrastructure. Therefore, there is a need for a communication system that allows the operation of the FTC in an existing cellular network using the digital control channels.

COMPENDIUM The present invention addressing this need is exemplified in a communication system that includes a cellular network that transmits the radiolocation information through one or more physical channels that are subdivided into digital control channels (DCCHs), which include one or more logical radiolocation channels (PCHs). A fixed cellular terminal (FCT) with a number of subscriber units, each having a corresponding subscriber number, and a number of cellular terminals (CTs) communicates with the cellular network through the DCCHs. At least, a multi-line terminal (MLT) that connects with the subscriber's units and with the CTs that receive the radiolocation information in at least one PCH through at least one of the CTs. According to some of the more detailed features of the invention, the radiolocation information addressed to all the subscriber units that are connected to the MLT is transmitted through the common PCH. Preferably this is carried out by executing a PCH calculation algorithm to assign the PCH. Under this provision, the PCH is calculated based on an MLT identification (MLT ID), which is assigned to the MLT. When the radiolocation information is transmitted, the subscriber number of a unit of the called subscriber is transmitted through an assigned PCH. In accordance with another embodiment of the invention, a CT is reserved to receive the radiolocation information through all the PCHs. Under this modality, each CTs ignores the radiolocation information. The reserved TC supplies the radiolocation information to the MLT, which assigns one of the other CTs to answer a call. Other features and advantages of the present invention will become apparent from the following description of the preferred embodiment, which is taken together with the accompanying drawings. - DETAILED DESCRIPTION _ Referring to Figure 1, a communication system 10 in accordance with the present invention provides a telephone see to the subscribers using a digital cellular network 12. In a preferred unit, the cellular network 12 is implemented essentially in accordance with the standard TIA IS-136, which is incorporated by reference in this way. Therefore, the operation of the cellular network 12 is described to the extent necessary for the understanding of the present invention. Although the present invention is described as being covered using the IS-136 standard, those skilled in the art will appreciate that the present invention could be advantageously used in a wide variety of other digital communication systems, such as those based on the PDC standards. or GSM.

The communication system 10 provides a telephone see to the fixed subscriber units 18 that communicate with the cellular network 12 through a fixed cellular terminal (FCT) that connects them with a number of Multiple Line Terminals (MLTs) 22 through PBX 2. In a well-known way, the cellular network 12 communicates the digital voice, the data and the control information through the physical channels that subdivide into a number of logical control channels. In addition, the communication system provides cellular service to the subscribers that carry the mobile stations 14 while they march within the communication cells 16 of the cellular network 12. The cellular network 12 is a hierarchical network with multiple levels to manage the calls. Using an assigned set of uplink and downlink radio frequency channels, which are subdivided into logical control channels, the mobile stations 14 and the MLTs 22 participate in the calls using the assigned logical channels. A Mobile Service Switching Center (MSC) 26 is responsible for sending calls from a point of origin to a destination. In particular, the MSC 26 is responsible for the establishment, control and termination of calls. The MSC 26 that also communicates with a public switched telephone network (PSTN) 28, or another network - public and private, which connects with conventional telephones 30. A subscriber database 32, which is accessible through MSC 26, maintains the records corresponding to each subscriber of communication system 10. Comparing a number of the called subscriber , for example, with one originating via a telephone 30 against the subscriber's database 32, the MSC 26 determines whether a call is handled or not. At a lower hierarchical level, the MSC 26 is connected to a group of base station controllers (BSCs) 34, which are primarily responsible for mobility management. For example, based on the strength of the received signal given, a BSC 34 determines whether a delivery should be initiated, the process by which the calls are kept ~ without noticeable interruption. At an even lower hierarchical level, each of the BSCs 34 controls a group of base transceiver stations (BTSs) 38. Through the antennas 37 and 35, the BTSs 38 mainly provide wireless links for transmitting and receiving bursts of data through the logical channels. Each BTS 38 includes one or more transceivers (not shown) that use the physical channels to service a specific common geographic area, such as one or more of the communication cells 16.

Referring to Figure 2, a functional diagram of an MLT 22 is shown as including a terminal unit 39 having a number of cellular terminals (CTs) 40 and a control unit 42. In an exemplary embodiment, the MLT 22 includes sixteen CTs 40 to serve 100 units of the subscriber 18. The control unit 42 includes a processor 44 which controls the total operation of the MLT 22 and faces the CTs 40 through a CT interface 46, which in an exemplary embodiment of The invention uses a serial communication protocol to provide communication between the control unit 42 and the CTs 40. The MLT 22 interconnects with the PBX 24 through a PBX interface 48. The PBX 24 routes the calls to and from from the subscriber units 18 through the CTs 40 of the MLT 22. The CTs 40 are interconnected with the cellular network 12 in a manner similar to that of the mobile stations 14 of Figure 1. A radiofrequency unit 41, which includes a passive device that combines the outputs of the CTs with a single antenna 35, receives and transmits the radiofrequency signals to and from the cellular network in accordance with the IS-136 standard. In this exemplary embodiment, using the sixteen CTs 40, the MLT 22 is responsible for routing calls to and from the 100 units of the subscriber 18 through the PBX 24. A maintenance and operation controller (O &M) controls the operation and maintenance of one or more of the MLTs 22 in a well-known manner. As described above, each physical channel is subdivided into a number of logical channels consisting of time intervals during which the voice * or digital data and control information are communicated.

Referring to Figure 3a, a physical channel subdivided into six time slots is shown to form a 40-ms TDMA frame or frame. The voice or digital data is communicated through the digital logical traffic (DTC) channels, and the control information is transmitted through the digital control channels (DCCH) The DCCHs used to transmit the control information to the CTs 40 (and the mobile stations 14) are known as DCCH Forwards (FDDCH). In contrast, the DCCHs used to receive the control information from the CTs 40 are known as the Reverse DCCH (RDDCH). Each FDDCH includes a number of TDMA Superbusters. Figure 3b shows a TDMA Supermachine consisting of sixteen 40-ms TDMA frames for a total length of 640 s. Each superframe FDDCH consists of an ordered sequence of logical channels, including F-BCCH, E-BCCH, S-BCCH, reserved slots, and SPACH. The F-BCCH contains data elements that may be related to radiolocation, such as the continuation of - radiolocation and the calculation information of PCH. The SPACH time intervals serve as the radiolocation intervals in the FDCCH. All radiolocations of the mobile station are received in these slots. A predefined minimum and maximum number of these logical channels can be included in each FDDCH overframe. For example, a minimum of 3 and a maximum of 10 intervals of F-BCCH can be included in an FDCCH overframe. Similarly, each FDCCH overframe can include a minimum of 2 and a maximum of 28 SPACH time slots. In accordance with one embodiment of the present invention, a method for radiolocating a subscriber unit causes the MSC to transmit all radiolocations directed to an MLT in a common PCH, which is used by all CTs 40 within the MLT to monitor radiolocations. . More particularly, the radiolocation method of the invention allocates an MLT ID to each of the MLTs, which are connected to a corresponding group of units of the subscriber 18 through the PBX 24. In an exemplary embodiment, the MLT IDs are assigned to the MLTs using the 50 O i M controller (shown in Figure 2). Instead of the MIN / ESN pair, the CTs 40 and the MSC 26 all use a corresponding MLT ID, which is associated with a corresponding group of the subscriber numbers, to calculate the common PCH. Based on a so-called subscriber number, the MSC 26 applies an MLT ID associated with the number of the called subscriber to the calculation algorithm PCH to calculate an appropriate PCH. In the MLT, the CTs 40 also use their assigned MLT IDs to calculate their assigned PCH. Because the MSC 26 and the CTs 40 of a specific MLT 22 use the same MLT ID, the PCH calculation algorithm produces the same PCH. Then, the CTs 40 are tuned to the calculated PCH and monitor for radiolocations directed to the subscriber units 18, which are connected to their corresponding MLTs 22. Once they are radiolocated by the MSC 26, the unemployed CTs 40 compare the number of the transmitted subscriber against a list of subscriber numbers assigned to their corresponding MLTs 22. If a match is found, the idle CTs 40 direct the subscriber number to the control unit 42. The control unit 42 routes the subscriber's number to the PBX 24, which alerts the subscriber unit 18 causing it to sound. If more than one unoccupied CTs 40 responds to the radiolocation, using an arbitrary block 52 (shown in Figure 2), the control unit 42 selects one of the unoccupied CTs 40 to handle the call. Under an exemplary embodiment of the invention, a single field called "MLT ID" is added to the subscriber database 32. For each FCT subscriber number, the MLT_ID field contains a value corresponding to an MLT ID of an MLT 22 to which the subscriber units 18 are assigned. In other words, the subscriber database 32 associates the numbers of the FCT subscriber as an MLT ID. Preferably, the MLT_ID field is added to each subscriber number regardless of whether they are FCT subscriber numbers or non-FCT subscribers. However, it could be appreciated that the MLT_ID field could only be added for the FCT subscribers. In an exemplary embodiment, the corresponding MLT_ID fields of the subscriber numbers that are not FCT may not contain any value. When a call is detected, the MS 26 queries a number of the subscriber received in its subscriber database 32. If found, the MSC 26 checks the corresponding MLT_ID field. If this field was loaded with an MLT ID value, the MSC 26 calculates a PCH based on the MLT ID associated with the subscriber number of the unit 18 of the called subscriber. Using the calculated PCH channel, the MSC 26 transmits a radiolocation that includes the subscriber number of the unit 18 of the called subscriber. Therefore, the MSC 26 only uses the MLT ID to select a PCH. Once selected, a corresponding subscriber number is used to radiolocate a unit of the called subscriber.

- - In this manner, the MSC 26 radiolocates each unit 18 of the subscriber, which is assigned to an MLT, using a single PCH that is calculated based on the MLT ID. The advantage of this solution through using a specific MIN from the list of 100 already assigned to the MLT, is that it is independent of non-FCT subscribers and does not require the MSC to distinguish between FCT and non-FCT subscribers. This allows MSC 26 to radiolocate all subscriber types in network 12 without requiring significant configuration modification in existing MSC 26 or mobile stations 14. In another embodiment of the invention, MLTs operate without being assigned in MLT ID. Instead, the processing of the radiolocations received through the PCHs is downloaded to the processor of the control unit 42, which has a higher processing power than that of the CTs 40. Even when the CTs 40 are capable to monitor each SPACH interval in the DCCH, they are not able to process the radiolocations. The CTs 40 must read each message of each slot and compare it against a large list of stored subscriber numbers, for example 100 numbers of the fan. Since each SPACH could contain 5 radiolocations, under this scenario, a CT 40 must perform 500 comparisons for each SPACH slot of 20 ms. With the maximum of 28 SPACH slots, - - theoretically, the TC would need to complete up to 14,000 comparisons in 560 ms. As described above, the processors of the existing CTs do not have this high processing power. In addition, if an "Additional DCCH Information" element is communicated through F-DCCH, the CTs may be required to monitor radiolocations of up to 8 different physical DCCHs simultaneously, or multiple logical DCCHs on the same frequency. Current CTs are also unable to simultaneously monitor different physical channels. Therefore, in accordance with this embodiment of the invention, one of the CTs 40 of MLT 22 is reserved for PCH supervision. The reserved TC is only responsible for monitoring the radiolocations at each PCH in the overframe. The reserved TC does not perform any comparison or other processing on the radiolocation information. All other CTs not reserved in the MLT would ignore any of the radiolocations found in a superframe. The reserved TC passes all the radiolocation information received at each PCH to the control unit 42 for processing. Under this modality, the reserved TC acts as a unit to collect data in the MLT 22. By receiving the radiolocation information from the reserved TC, the control unit 42 compares the MIN transmitted in the radiolocation information with a list of numbers of the corresponding subscriber contained in the control unit 42. If a match is found, the control units 42 select nn idle CT as the main line to handle the received radiolocation and send the radiolocation to the selected CT 40. The selected CT 40 would then respond to the radiolocation as if it had received it from the MSC 26 under a normal cellular environment. Preferably, if a reserved TC becomes inoperative, the control unit 42 reserves a different TC to monitor the PCH. If a cell uses multiple DCCHs, up to 8 CTs 40 may be designated as the reserved CTs. Alternatively, multiple receivers can be incorporated into the radio frequency unit 41 (shown in Figure 2) to monitor multiple DCCHs. From the foregoing description, it will be appreciated that the two embodiments of the invention allow the implementation of an FCT using an existing digital cellular network to provide telephone service for subscriber units through a PBX. Using the MLT separate IDs in the PCH calculation algorithms of the CTs and the MSC, one embodiment of the invention forces the radiolocations of the subscriber units in a common PCH. In this way, the expense associated with the - - management of the arbitrary PCH assignment. In the other embodiment, the present invention reduces the monitoring load of all the PCHs through the CTs by designating a reserved TC, which monitors and discloses the radiolocation information received through all the PCHs to the control unit. This embodiment of the invention, therefore, discharges the processing requirement to monitor the radiolocations transmitted in arbitrary channels from the CTs to the most powerful processor of the control unit. Accordingly, both embodiments of the invention allow the implementation of a FCT operating with a cellular network using a digital control channel. Although the invention has been described in detail with reference to only one preferred embodiment, those skilled in the art will appreciate that various modifications can be made without departing from the invention. Accordingly, the invention is defined solely by the following claims which are intended to cover all equivalents thereof.

Claims (14)

CLAIMS:

1. A communication system comprising: a cellular network that transmits the radiolocation information through one or more physical channels that are subdivided into digital control channels (DCCH) that include one or more of the logical radiolocation channels (PCHs); a fixed cellular terminal (FCT) that includes: a number of units of the subscriber each having a corresponding subscriber number; a number of cellular terminals (CTs); at least one multi-line terminal (MLT) that connects to the subscriber units and to the CTs, wherein at least one of the CTs receives the radiolocation information in at least one PCH.

The method of claim 1, wherein the radiolocation information addressed to all subscriber units that are connected to the MLT is transmitted through a common PCH.

The method of claim 1, further comprising the step of carrying out an algorithm of the PCH calculation to assign at least one PCH, wherein at least one PCH is calculated based on an ML-identification (MLT) ID), which is assigned at least one MLT.

4. The method of claim 2, further comprising the step of transmitting the subscriber number of a unit of the called subscriber through a PCH. assigned.

The method of claim 1, further including the step of reserving a CT to receive the radiolocation information through all the PCHs, wherein the other CTs ignore the radiolocation information.

6. The method of claim 5, wherein the MLT assigns one of the other CTs to answer a call.

7. A method for calling the subscriber units having corresponding subscriber numbers through an MLT connected with at least one TC, comprising: assigning an MLT ID to the MLT; receive the radiolocation information by at least one CT in a PCH that is assigned based on the MLT ID.

The method of claim 7, further comprising the step of selecting at least one CT to process a call.

The method of claim 7, which further includes the step of assigning the PCH carrying out. a PCH calculation algorithm using the MLT ID.

10. The method of claim 7, further comprising the step of transmitting the radiolocation information including the subscriber number of a unit of the called subscriber.

11. A method for radiolocating a number of subscriber units having corresponding subscriber numbers through the MLT, comprising: determining an MLT ID associated with a subscriber number; assign a PCH to transmit the radiolocation information based on the MLT ID; and assign a PCH to receive the radiolocation information based on the MLT ID.

12. A communication system that provides communication capability to a number of subscriber units having corresponding subscriber numbers, comprising: a number of MLTs having corresponding MLT unique IDs where each MLT ID is associated with a group of numbers of the subscriber; an MSC that "allocates the PCHs to radiolocate the subscriber units based on the MLT IDs; and the CTs that receive the radiolocation information through the assigned PCHs."

13. An MLT, comprising: a plurality of CTs, wherein at least one of the CTs is reserved to receive the radiolocation information in a plurality of PCHs, a control unit that receives the radiolocation information from a reserved CT and assigns one of the other CTs to handle a call addressed to a subscriber unit

14. A method for radiolocating the subscriber units having corresponding subscriber numbers, comprising: assigning an MLT ID to at least one MLT, associating the MLT IDs with the subscriber's numbers, receiving a call to an subscriber unit called; determine an MLT ID associated with the subscriber number of the called subscriber unit; assign a PCH based on the MLT ID; transmit the information of the subscriber; directed di-location in the called subscriber unit; and receiving the radiolocation information in a calculated channel based on the MLT ID.