MXPA97010490A - Telephone system mo - Google Patents

Abstract

A mobile telephone system consisting of a base transceiver station (BTS) that provides radio communication with a mobile telephone (MS) and also communicates with a control station (BSC) through a communication link in the form of a leased line that provides a first communication path (P1) with a predetermined bandwidth for signals communicated between the BTS and the BSC. A communication network in the form of an ISDN is used to provide a second communication path in a selectable manner (P2) between the BTS and the BSC to increase the available bandwidth for the signals during the peak demand periods. In order to accommodate different call connection times in the system through the leased line and the ISDN, the BSC / BTS are placed to produce the connection signals (CLI1, CLI2) that initiate billing to the same regardless of the path P1, P2 that is used to make the flame connection

Description

MOBILE PHONE S 1STE A DESCRIPTION PE THE INVENTION This invention relates to a mobile telephone system and to a method for providing a communication channel for mobile telephony, and has a particular application, although not exclusive, to digital mobile systems, for example the Global System for Mobile Communication systems ( GSM). In a conventional GSM mobile cellular telephone system, a mobile station (MS) such as a mobile handset communicates through a radio link with one of a number of fixed base transceiver stations (BTS) distributed in different geographic locations to through the coverage area of the system. BTS groups are connected to a base station controller (BSC) through wired lines. The BTS subgroups may be coupled through a station to the BSC. The BSC groups are coupled by means of respective wire lines to a mobile switching center (MSC). The MSC, in addition to being connected to other BSCs, has a connection to a public switched telephony network (PSTN). The system allows communication to be established between two MSs, or between an MS and a conventional telephone connected to the mobile system through the PSTN, or to another network. Conventionally, the wire lines used to connect each BTS to its station, or direct the BSC, are rented from a terrestrial telecommunications system provider. The leased line needs to have enough bandwidth for the peak data flow to flow when it occurs in the use in the network, with the result that during periods of low system utilization, the bandwidth of the line is not completely used. . However, the rented line is rented on a continuous basis rather than on its level of use and the cost effectiveness of the line decreases during periods of low usage. The so-called rented digital line E1 (or T1 in the United States) offers a bandwidth of 2 MB / s where considering that the data rates between a BTS and its associated station are of the order of 1 MB / s or less. Terrestrial system providers often offer digital leased lines, which can be leased with a fixed bandwidth of N x 64 kb / s, where N is an integer typically of 1 - 30. Those lower bandwidth leased lines are suitable to provide the connection between a BTS and the BSC, either by means of a station or directly. The leased line connection to a BTS suffers from some disadvantage that in order to provide sufficient bandwidth when the BTS is operating near its maximum utilization level, the bandwidth needs to be selected to be greater than is necessary for the levels of traffic that occur during most of the time. This increases the cost of the rented line. Similarly, a leased E1 / T1 line that can dial with peak levels between the station and the BSC may provide excessive capacity for the average traffic levels that may occur during normal levels of system utilization. Similarly, if the BTS capacity expands, additional bandwidth may be necessary, that is, another leased line may be required which will be inefficient and costly for the average traffic flow, although necessary to handle the flow levels of peak traffic. It is known, for example, from the Application for European Patent No. 0398183 (Northern Telecom) for a private telephone system having a communication link (e.g., a private link) to provide a first communication path for signals communicated between two system nodes to provide the nodes with connections additional for communication with a communications network (for example, a public network); and control means operable to selectively provide a second communication path, through the communications network, to increase the available bandwidth on the first communication path for the signals communicated between the nodes. For each call, the traffic can be carried on the first path or the second path, although the control signal between the mobile station and the termination of the network is always carried on the first path. This principle can be applied to the connections between a base transceiver station and a control station of a mobile telephone system, providing the communication link as a rented line, to provide the first communication path and provide the communication network as an integrated services digital network (ISDN) so that the second communication path can be selectively set through the ISDN to provide additional bandwidth for the signals in the event of high system utilization. The ISDN is billed to the user according to the amount of time it is used and the available bandwidth for the signals, can be increased by providing the second communication path, incurring only the cost for the time used for the second trajectory. In this way, the rented line can be selected to have a bandwidth that can be used on a relatively high usage scale during normal operation, because in the case of higher usage levels, the second path can be connected selectively to handle the additional "peak" bandwidth requirement that occurs during high levels of system usage. However, although the links between the base transceiver stations and the control stations form a private network, they carry the mobile telephone calls that support the tariff. This causes a problem, since when a call is connected through the system, the time required to establish the connection can typically be greater through the first path than through the second path, for example, where the first path comprises a rented line and the second path consists of an ISDN. Billing to the user is established by a "call-connection" signal that is typically relayed to the BTS to signal that the connection has been made and that billing can begin. Discrepancies may arise, either when the call-connection signal on the input line arrives first, in which case the MS user would be charged for the time between the arrival of the call-connection signal and the actual time of the connection on the ISDN. Conversely, if the call connection signal on the ISDN path was the one that arrived first (or the call-connection signal on the leased line falls above all, for example because the call is not answered) the The mobile network operator will be loaded for the ISDN link before the MS user is connected, thus incurring an unnecessary cost for the mobile network operator. Note that the ISDN call-connection signal only refers to the connection between the BTS and the BSC. According to the invention, a mobile telephone system comprising a base transceiver station for providing radio communication with one or more mobile stations is provided.; a control station for providing call connections between a mobile station and other network terminations; a communication link to provide a first communication path for signals communicated between the base transceiver station and the control station; the base transceiver station and the control station which also have connections for communication with a communication network; operable control means for selectively providing a second communication path, through the communication network, to increase the available bandwidth over the first communication path for the signals communicated between the base transceiver station and the control station; and means for initiating time billing for the corresponding first and second paths in a predetermined time relationship in response to the initiation of a dialed call connection between a mobile station and a network termination. According to another aspect, there is provided a method for providing a communication channel for mobile telephony, wherein a base transceiver station provides a radio communication with a mobile system and the base transceiver station provides communication with a control station; the method comprising a first communication path with a predetermined bandwidth for signals communicated between the base transceiver station and the control station through a fixed communication link, selectively providing a second communication path for the signals communicated between the base transceiver station and the control station, through a communication network to increase the available bandwidth of the signals; wherein the time billing is initiated for the first and second paths in a predetermined time relationship in response to the initiation of a dialed call connection. This provision ensures that there are no billing differences between the calls established through the ISDN path and the calls established through the rented line.

Preferably, the system has means for transmitting the respective call connection signals along the first and second communication paths in response to the establishment of the respective paths, and means to prevent the transmission of call connection signals until both paths are established and means responsive to receiving the call connection signals to initiate time-related billing for the first and second paths, respectively. Preferably, this can be achieved by placing the call connection signals that are transmitted along both the first and second communication paths from one end to the other so that they arrive at the other end substantially simultaneously. For the invention to be more fully understood one embodiment thereof will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic block diagram of a mobile telephone system in accordance with the invention; Figure 2 illustrates an alternative configuration in which a BTS is directly connected to the BSC without a station; Figure 3 illustrates a call connection protocol; Figure 4 illustrates in more detail the signal configurations used to communicate between the BTS and BSC shown in Figure 2; and Figure 5 is a graph illustrating the variations in bandwidth that occur over time for data communications between the BTS and BSC shown in Figure 2. Referring to Figure 1, a mobile GSM digital telephone network cellular is shown which includes a plurality of base transceiver stations BTS1, BTS2 distributed in various locations through the coverage area provided by the system. Each BTS1, 2 can communicate by digital cellular GSM technique with the mobile system such as the mobile handsets MS1, 2. As shown in Figure 1, BTS1 and BTS2 are connected by means of leased digital wire lines 1, 2 to a station H1 which is connected via wireline 3 to a BSC and an associated interconnection CC1. The BSC is connected by means of an additional line 4 to a mobile switching center MSC which is connected via lines 5, 6, 7 to additional network terminations, both mobile (by means of the additional MSCs, not shown) and fixed (by means of a conventional public switched telephone network PSTN). A conventional handset 8 is shown connected via line 9 to a digital local exchange DLE which is part of the PSTN. Figures 2 and 4 show a simplified network for illustrative purposes, having an individual mobile station (MS) and a base transceiver site (BTS), the last connector directly to the base location controller (BSC) (i.e. not via a station). The BTS and BSC have ISDN telephony connections. The BTS and BSC are under the control of a Network Management System (N M) that monitors and controls the operation of the cellular network. Figure 3 is a flow chart showing seven stages S1 to S7 occurring during call set-up. It should be noted that step S3 takes place in parallel with steps S2 and S4. Figure 5 is a graph of the bandwidth requirement for signal communication between the BTS and BSC as a function of time. The maximum bandwidth that can be handled by the path P1 is shown by the dotted line 20 and the additional bandwidth that can be provided by the path P2 is shown by the dotted line 21. Therefore, when the graph 22 is located below the line 20, the trajectory P1 can be used alone although the trajectory P2 is required for the striped areas 23 shown in the graph.

I I Referring now to Figure 1 in greater detail, leased lines 1, 2, 3 are usually rented from a land system provider. A conventional E1 digital rented line offers a bandwidth of 2 MB / s. However, the bandwidth for the data from the typical BTS is of the order of 1 MB / s and thus a rented line E1 would have an inefficient bandwidth utilization for the connection between each BTS and the associated station H1. An alternative offered by the terrestrial system providers is for the leased bandwidth on a base N x 65 kb / s for which the GSM system provider rents from the terrestrial system provider a bandwidth location of N x 64 kb / s on a continuous basis, N being a fixed integer selected depending on the usage regime of the BTS. Therefore, if the BTS is expected to handle a large number of calls, N will be selected at a relatively high value, considering that if BTS is located in a position where a lower rate can be expected, N will be selected to have a higher value low. Once selected by the system provider, N can not be easily changed. When renting a line in this way it is cheaper than a rented line E1 although the value of N needs to be selected carefully. It is understood that the usage regime of the GSM system varies greatly depending on a number of factors such as the time of day, although not all factors can be predicted; for example, users can be randomly distributed in the vicinity of a particular BTS at a particular time, thus raising the usage regime. The value of N for the line is then selected as a compromise between the maximum possible bandwidth required for the total capacity of the BTS and the average utilization rate that usually occurs for the BTS. However, this can lead to the inefficient use of the bandwidth of lines 1, 2, 3 with the disadvantage that the user of the GSM system has to rent more bandwidth than the one normally used, to work with the demand peak and therefore provide a satisfactory service to the users of the mobile system. As shown in Figure 1, a second signal communication path is provided between BTS1 and the associated station H1 through an ISDN digital integrated services network 10 (shown in Figure 1 in two portions 10a, 10b). This second communication path includes a first link 11 from station H1 to network 10a and a second link 12 from network 10a to BTS1. The corresponding links are provided for all the BTS connected to the station. Therefore, for BTS2, the link 13 together with the link 11 provide a corresponding second communication path to increase the first path 2. Therefore, according to the invention, the bandwidth for the first communication path P1 provided by the rented line 1, can be selected to have a lower value of N than hitherto so that its bandwidth is used more efficiently through normal use. In the event that the number of calls is increased so that a higher bandwidth is required between BTS1 and H 1, the system is operative to selectively establish a second communication path P2 through the I SDN 1 0a by means of the 1 1, 12 links thus increasing the available bandwidth. While the leased line is billed on a continuous time basis, the use of the ISDN is invoiced over the time for which it is connected, so that it is only necessary to pay for the ISDN during the period that the second communication path to through links 1 1 and 12 is really connected. Therefore, charges are incurred only while a connection is made with respect to the second communication path, so that the second path is paid only when necessary. Now considering the connection of the BSC, the bandwidth of several signals received at the station H1 are simultaneously transmitted and communicated to a third path through the leased line 3 for the BSC and its associated interconnection CC1. The combined bandwidth of the signals distributed by station H 1 is somehow greater than the bandwidth of the signals communicated between each individual BTS and the station so that the use of a leased line E1 for line 3 is appropriate. However, during periods of heavy system use, the bandwidth of the signals may exceed the available bandwidth of line 3. To overcome this problem, a fourth communication path can be established through ISDN 10 through the portion 10b, by means of the links 14, 15 in a manner similar to that described with reference to the BTS. In this way, a higher level of bandwidth utilization can be achieved for line 3, with the peak demand being conducted per channel through the ISDN through links 14, 15, during the periods of need, instead of a continuous base. Other architectures are possible. For example, the BTS base transceiver sites may be directly connected to the mobile switching center MSC. The ISDN or similar network can be used to increase the bandwidth on any of the links in those architectures. The communication signal protocols will now be described in greater detail with reference to Figure 2, which shows a simplified version of the network only with a BTS directly connected to the BSC, it is understood that the current network in practice will include many links, as exemplified in Figure 1. In Figure 2, the BTS is connected by a leased line P1 to the BSC and the connection can be established on the P2 path through the ISDN. The BTS is given on its own ISDN telephone number, in this example, 01999 643997. Similarly, the BSC is given with a telephone number BSC 01111 645444. The BTS can make a connection for the BSC via the ISDN by dialing of the appropriate telephone number, ie, BSC 01111 645444. The BSC can similarly form a connection to the BTS. Communication via ISDN is in accordance with a LAPD signal format over channel D in a manner known per se. An example of a call connection procedure will now be given in which the telephone MS initiates a connection for telephone 8, which in this example has the telephone number of 0111 274 6991. Referring to Figure 3, in step S1, the user of the mobile handset MS operates his dial pad to dial the telephone number of the telephone 8 (Figure 2) and press the "send" button to initiate the call. The signals are transmitted in the GSM form to the BTS and a call connection is established in a conventional manner on the first communication path P1 comprising the leased line N x 64 kb / s connected to the BSC, and then through the MSC on line 4, the PSTN on line 7 and therefore on telephone 8 through DLE and line 9. This is shown in step S2. Referring to Figure 2, the NM network management can determine that the bandwidth of the P1 path is insufficient to process the requested call connection and that it is appropriate to open a second communication path P2 through the ISDN. If this is the case, the BTS calls the BSC by means of the ISDN by transmitting the call signals for the telephone number 01 1 1 1 645444, as shown in step S3 in Figure 3. In general, there will be a difference of time between the time taken to open the P2 path through the ISDN and the call connection through the P1 path and the paths 4, 7 and 9. In particular, the call connection through the P1 path may not be completed if the call is not answered or the called party is busy on another call. To accommodate these different settling times, the BSC waits for an indication from the MSC that the call connection to the telephone 8 has been established, as shown in step S4, after which, in step S5, the BSC transmits the call connection signals C1, C2 back to the BTS on the paths P1 and P2 respectively, with the time controls selected so that the C1 and C2 arrive simultaneously at the BTS, as shown in step S6. Therefore, the time invoicing for the ISDN P2 route call is the same as that for the conventional P1 terrestrial route and there are no billing discrepancies. The described system also allows the telephone 8 calls the mobile station MS, in which case the connection on the path P2 is established by the call of the BSC to the BTS, that is, by the telephone number dialed 01000 643997. Similarly, the invention allows adequate control of the call disconnection signals for the paths P1 and P2. The call connection scheme is also configured to handle the deleted calls (when the MS moves out of the radio coverage area) and the handover (when a mobile station moves from one BTS to another). For security purposes, the BTS and the BSC are configured to verify the identity of the call stations by means of the ISDN using the call identification signals (CLI). If the call number does not correspond to a known BSC or BTS number, the system can register the call number so that the data can be sent to the NM network management system for review and, if the number occurs regularly, it can be taken the additional action if necessary. The configuration of the signals transmitted between the MS, BTS and BSC will now be described in greater detail with reference to Figure 4. The mobile handset MS when using the GSM techniques typically transmits in a data rate of 22.8 kb / s with coding 13 kb / s voice over a radio link to the BTS. For the rented line P1, the 4: 1 simultaneous transmission can be used. Line P1 typically has a bandwidth of N x 64 kb / s in which case 4 x 13 k is transmitted simultaneously at 1 x 64 k time intervals. For the P2 path, the channel called ISDN2 provides 2 x 64 kb / s channels available for the data transceiver which can therefore handle 8 calls transmitted simultaneously. The connection between the ISDN 10 and the BSC comprises 30 channels so that up to 15 BTS can be connected to the BSC each with 2 x 64 kb / s channels. Since the P2 path can handle more than one call simultaneously, the logic equipment is provided to ensure that no channels are in use before the P2 path is disconnected to avoid undesirable call disconnection. Also, a check can be made when a call is initially established, if the P2 path is already open for another call, to avoid unnecessary fixation of an additional path through the ISDN. In an alternative configuration, the data is transmitted between the MS and BTS at an average speed that is, with the voice at 7 kb / s in which case the 8: 1 simultaneous transmission can be used for the P1, P2 trajectories. On occasions of low demand, it is undesirable for the system to direct calls through the P2 path, because this leaves the capacity on the P1 path unused, which is already paid to be a rented line. The bandwidth requirement can be judged on a call-by-call basis, in which case the local network management can instruct the BTS / BSC if the P2 path is necessary. However, it is undesirable for the system to select the P1 path to carry a call if this would result in too little or no remaining capacity to set additional calls. It would be possible to transfer calls from one path to another while they are in progress, for example, if the capacity is required for more than one fix signaling on the P1 path, although the extra time required to make the signaling channel available on the Path P1 by transferring a call from path P1 to transfer P2 would increase call setup times unacceptably. It is therefore desirable to place the calls on the path P2 so that sufficient capacity always remains on the path P1 to handle at least the signaling required for the expected call traffic level. The decision to select the trajectory P2, to increase the available bandwidth, it can be done in a number of different ways. First, it can be done according to the time of day or some other appropriate period determined by the traffic flow trend analysis. As shown in Figure 5, the bandwidth requirement typically varies with the time and for some locations, it can be a recognizable or different day pattern, in which case the P2 path can be switched over the high usage periods predicted by the BTS / BSC or NM. Also, the management of local network at the level BTS / BSC can detect the traffic levels that rise towards the limit 20, at which time the second path P2 is switched to increase the available bandwidth. While the invention has been described in connection with a GSM network, other transceiver techniques can be used, for example in DSC 1800, PCS (DCS 1900), JDC DAMPS. The invention is also applicable to analog cellular systems.

Claims (25)

1. REIVIN DICACIONES 1 . A mobile telephone system comprising a base transceiver station (BTS1) for providing radio communication with one or more mobile stations (MS); a control station (BSC) for providing call connections between a mobile station (MS) and other network terminations; a communication link for providing a first communication path (P1, P3) for signals communicated between the base transceiver station (BTS) and the control station (BSC); the base transceiver station and the control station which also have connections for communication with a communication network; control means (NM) operable to selectively provide a second communication path, through the communication network, to increase the available bandwidth over the first communication path for signals communicated between the base transceiver station (BTS) and the control station (BSC); and means for initiating time billing for the first and second corresponding paths in a predetermined time relationship in response to the initiation of a dialed call connection between a mobile station MS and a network termination.
2. 2. A system, according to claim 1, including means for transmitting respective call connection signals (C1, C2) along the first and second communication paths (P1, P2) in response to the establishment of respective paths, means for preventing the transmission of the call connection signals (C1, C2) until both paths are established and the means (BTS) respond to the reception of the call contact signals to initiate the time-related saturation for the first and second trajectories respectively.
3. 3. A system, according to claim 2, including means for transmitting call connection signals (C1, C2) along the first and second communication paths (P1, P2) from one end to the other so that they arrive at the other end substantially simultaneously.
4. 4. A system, according to claims 1, 2 or 3, characterized in that the control means provide the second communication path in accordance with the time of day.
5. 5. A system, according to any preceding claim, characterized in that the control means include network management means for detecting the use of the first path and for selectively operating the connection of the second path in accordance with such use.
6. 6. A system, according to claim 5, characterized in that the control means are arranged to provide the second path if it is detected that the use of the first path exceeds a given level.
7. 7. A system, according to any preceding claim, characterized in that the control means include means that respond to a call attempt to determine if the first path offers sufficient bandwidth for the call, and if not, route the call through of the second trajectory.
8. 8. A system, according to any preceding claim, characterized in that for each connected call, the traffic is transported on the first path or the second path, in accordance with the operation of the control means (NM) although in any case the signaling of control between the mobile station (MS) and the network termination is carried by the first path.
9. 9. A system, according to any preceding claim, characterized in that the control station comprises a controller (BSC) for controlling the base transceiver station (BTS), the first and second communication paths being provided between the controller (BSC) ) and the base transceiver station (BTS). 1 0.
10. A system, in accordance with claim 9, characterized in that it includes a station (H1) to control a plurality of those base transceiver stations (BTS1, 2), the first and second communication paths (1 , 2; 1 1, 1 2, 1 3) that are provided between the station and the base transceiver station. eleven .
11. A system, according to claim 10, characterized in that it includes a plurality of base transceiver stations connected to the station, and respectively the first and second communication paths that are provided between the station and each of the transceiver stations and transceivers. base. 1 2.
12. A system, according to claim 11 or 12, characterized in that it includes a third communication path between the station and the controller (BSC) and means for selectively providing a fourth communication path through the network between the station and the controller (BSC).
13. 3. A method for providing a communication channel for mobile telephony, characterized in that a transceiver base station provides radio communication with a mobile system and the base transceiver station provides communication with a control station; the method comprising providing a first communication path with a predetermined bandwidth for signals communicated between the base transceiver station and the control station through a fixed communication link, selectively providing a second communication path for the signals communicated between the base transceiver station and the control station, through the communication network to increase the available bandwidth for the signals, where the time billing is initiated for the first and second trajectories in a time relation default in response to the initiation of a dialed call connection.
14. 14. One method, in accordance with the claim 13, characterized in that the call connection signals are transmitted along the first and second communication paths in response to the establishment of the respective connections and in which transmission of one or both of the call connection signals is prevented unless both connections are established. 1 5.
15. A method, in accordance with the claim 14, characterized in that the call connection signals are transmitted along the first and second communication paths from one end to the other so that they arrive at the other end substantially simultaneously and the time billing is initiated for the first and second paths respectively in response to the reception of the call connection signals. 1 6.
16. A method, according to the claim 1 3, 14 or 1 5, characterized in that the following communication path is provided in accordance with the time of day.
17. 7. A method according to claim 13, 14, 15 or 16, characterized in that the second path is selectively operatively connected in accordance with the degree of use of the first path.
18. 18. A method, according to claim 1 7, characterized in that the second path is provided if the detected use of the first path exceeds a given level.
19. 19. A method, according to claim 13, 14, 15, 16, 17 or 18, characterized in that the call is directed through the second path in response to a call attempt, even if the first path does not offer enough bandwidth for the call.
20. 20. A method, according to any of claims 13 to 19, characterized in that for each call, the traffic is transported on either the first path or the second path, although in any case the control signaling between the mobile station (MS) and the network termination is carried over the first path. twenty-one .
21. A method, according to any of claims 13 to 20, the first and second communication paths that are provided between a controller (BSC) and a base transceiver station (BTS) controlled by the controller (BSC).
22. 22. A method, according to claim 23, characterized in that the first and second communication paths are provided between a station (H1) and one or more base transceiver stations (BTS1, 2) controlled by the station (H1).
23. 23. A method, in accordance with the claim 22, characterized in that a fourth communication path is selectively provided through the network between the station and the controller (BSC) to increase a third communication path between the station and the controller (BSC).
24. 24. A mobile telephone system substantially as described with reference to the drawings.
25. 25. A method for providing a communication channel for mobile telephony, substantially as described with reference to the drawings.