MXPA00007865A - Method and system for selecting control channels from base stations located near a border between radio telecommunications networks - Google Patents

Abstract

A method and system for selecting control channels from base stations located near a border (71) between radio telecommunications network (C,O). The system includes a first mobile switching center MSC (33) that services and controls a coverage area associated with a first radio telecommunications network (C), a plurality of base stations (34-49) located within the first radio telecommunications network, and a plurality of base stations (55-67) located within the second radio telecommunications network (D). Additionally, the system includes redirection logic (35) located within the first MSC which determines if a mobile station MS (69) from the second radio telecommunications network is attempting to access a base station in the first radio telecommunications network which is adjacent to the border between the first and second radio telecommunications networks and redirects the MS to access a control channel from a base station located within the second radio telecommunications network. The system may also include a second MSC with redirection logic for redirecting mobile stations to their home radio telecommunications network.

Description

"METHOD AND SYSTEM FOR SELECTING CONTROL CHANNELS OF BASE STATIONS PLACED NEAR A MARGIN BETWEEN THE RADIO TELECOMMUNICATION NETWORKS " BACKGROUND OF THE INVENTION TECHNICAL FIELD OF THE INVENTION This invention relates to radio telecommunication systems and, more particularly, to a method and system for selecting control channels of the base stations placed near a range between the networks of radio telecommunications.

DESCRIPTION OF THE RELATED TECHNIQUE In a radio telecommunications network, when a mobile station (MS) originates a call, the MS scans for a control channel with the strongest signal. When the MS is operating along a range where two radio telecommunications networks having different network operators are placed adjacently, the MS can give access to an analog control channel from a base station in a neighboring network in time from the network which MS is running. For example, an MS operating near a margin within its base network may receive a stronger signal from a base station placed across the margin in a neighboring network and may give access to the neighboring network as a result. Several problems arise when an MS gives access to a control channel from a different operator. First, the MS is loaded by a different network operator, instead of its originating network operator. Second, higher regimes such as vagrant charges may result. In addition, the operator of the originating network loses revenues to which it is legitimately enabled since the MS is still operating within the coverage area of the home network of the MS. The MS may also lose the ability to give access to the features found in its home network. Another serious problem arises when the mobile station operates along the margin of two competing networks. In an attempt to recover lost revenue, network operators currently reinforce the transmitting power from their base stations in order to "capture" the mobile stations operating along the margin. Increasing the power of a base station in a network can lead the network operator to reinforce the power from its base stations, literally causing a "power war" between the base stations of the margin. The increase of transmitter power in the base stations of the margin leads to increased mutual radio interference along the margin, decreasing the operation of both networks. It would be advantageous to have a system and method that prevents mobile stations from operating within their home network near a margin with a neighboring network, to give access to analog control channels from a neighboring network. While there are no known prior art teachings of a solution to the aforementioned deficiency and inconveniences as given herein, a reference of the prior art which discusses the subject matter having some relation to the issues discussed herein is U.S. Patent No. 4,905,301 issued to Krolopp and others (Krolopp). Krolopp discloses a mobile telephone which compares a system identification transmitted in a control channel of a desired network and the identification of the system transmitted in an access channel during the access process of the mobile telephone. Access is allowed only if the identification of the control channel system and the identification of the access channel system coincide. Krolopp does not disclose or suggest a system or method to correctly select the control channels of the base stations placed near a margin between the radio telecommunications networks. Krolopp only discloses a mobile telephone which compares a system identification of the proposed control channel with a system identification obtained during the initialization of the mobile telephone. Even when Krolopp can be used to restrict a mobile phone from operating in selected control channels, suffers from several disadvantages. The mobile phone must be modified to compare the system identifications. In addition, if the mobile telephone is connected in a coverage area where the control channels of the adjacent network have the strongest signal, the mobile telephone will give access to the control channel of the adjacent network, since the identification of the preferred system It is established when the mobile phone is connected. In fact, if the mobile phone is connected in the adjacent network, the mobile phone will only allow access to the control channels with a system identification associated with the adjacent network, even when the mobile phone returns to the home network. Therefore, Krolopp only solves the problems of a mobile station that transmits near a margin when the mobile station is first energized in its home network. In addition, if the mobile phone in Krolopp is actually placed in the adjacent network, the mobile phone will deny access to the more intense control channels, thus losing the admission of the operator of the adjacent network who has a legitimate right to the lost revenue. . In this way, it would be a distinct advantage if there were a system and method that prevents mobile stations from operating within the originating network along a margin, from erroneously giving access to analogue control channels from another network with an operator different.

COMPENDIUM OF THE INVENTION In one aspect, the present invention is a system for selecting a control channel for a mobile station (MS) operating close to a margin between a first radio telecommunications network and a second radio telecommunications network. The system includes a first mobile switching center (MSC) serving and controlling an area associated with the first radio telecommunications network, a first plurality of base stations placed near the first radio telecommunications network, and a second plurality of base stations placed within the second radio telecommunications network. In addition, the system includes a means for determining whether the MS is trying to provide access to a control channel from a base station in the first plurality of base stations, and a means for redirecting the MS to access a channel of control. control from a base station in the second plurality of base stations. In another aspect, the present invention is a method of selecting a control channel for an MS operating within a first radio telecommunications network along a range between a first radio telecommunications network and a second telecommunications network of radio. The first radio telecommunications network includes a first mobile switching center (MSC) and a first plurality of base stations. In addition, the second radio telecommunications network includes a second MSC and a second plurality of base stations. The method first begins with the second MSC determining whether the MS is trying to give access to a control channel from a base station of the second plurality of base stations. Next, the second MSC re-directs the MS to give access to a control channel from a base station in the first plurality of base stations, at 'determining that the MS is trying to give access to a control channel from a base station in the second plurality of base stations.

In another aspect, the present invention is a method for selecting a control channel for an MS operating within a first radio telecommunications network along a range between the first radio telecommunications network and a second telecommunications network. of radio. The first radio telecommunications network includes a first mobile switching center (MSC) and a first plurality of base stations. In addition, the second radio telecommunications network includes a second MSC and a second plurality of base stations. First, the MS tries to give access to a first control channel from one of the second plurality of base stations. Next, the second MSC determines whether the MS is associated with the first radio telecommunications network. The second MSC then determines whether the first control channel is associated with a margin base station that is adjacent to the margin between the first radio telecommunications network and the second radio telecommunications network, by determining that the MS is associated with The first radio telecommunications network. The second MSC then selects a list of alternate control channels by determining that the first control channel is associated with a margin base station. The list includes control channels of the base stations of the margin in the first radio telecommunications network and controls the channels from the base stations in the second radio telecommunications network that are not the base stations of the margin. Next, the second MSC sends a message redirected to the MS. The redirected message includes the list of alternative control channels and directs the MS to try to give access to one of the alternative control channels in the list. In still another aspect, the present invention is a system for selecting a control channel for an MS operating near a margin between the first radio telecommunications network and a second radio telecommunications network. The system includes an MSC that services and controls a coverage area associated with the first radio telecommunications network, a first plurality of base stations placed within the first radio telecommunications network, and a second plurality of base stations placed within the second radio telecommunications network, and a means for storing a list of associated directory numbers with mobile stations that have the second radio telecommunications network as their home network. The system also includes a means for determining whether the MS is trying to provide access to a base station that is adjacent to the margin between the first radio telecommunications network and the second radio telecommunications network in the first plurality of stations, base, a means for determining a plurality of alternative control channels from the second plurality of base stations and a means for redirecting the MS to provide access to a control channel from the plurality of alternative control channels.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and its numerous objects and advantages will become more apparent to those skilled in the art with reference to the following drawings, together with the accompanying specification, in which: Figure 1 (Prior Art) is a simplified functional diagram illustrating the components of an existing radio telecommunications system for a mobile station placed near a margin between two networks that are served by different operators; Figure 2 is a simplified functional diagram illustrating the components of a radio telecommunications system for a mobile station positioned near a margin between two networks that are serviced by different operators in a preferred embodiment of the present invention; and Figure 3 is a flow chart indicating the steps of the method for selecting the control channels near a margin between two radio telecommunications networks in accordance with the teachings of the present invention.

DETAILED DESCRIPTION OF THE MODALITIES The present invention is a system and method for selecting the control channels near a margin between two radio telecommunications networks. Figure 1 is a simplified functional diagram illustrating the components of an existing radio 1 telecommunication system for a mobile station (MS) 25 positioned near a margin 27 between two analog cellular networks that are served by different operators. The radio telecommunications system 1 includes a Network A having a mobile switching center A (MSC-A) 5 serving the base stations (BS) 7-13. The existing radio telecommunications system 1 also includes a Network B having a mobile switching center-B (MSC-B) 15 which serves the BSs 17-23. MS 25 operates within the radio telecommunications system 1 and margin 27 separates Network A from Network B. It should be understood that in actual practice, there may be many more base stations in each network, but for illustrative purposes, only a few margin base stations have been shown. The MS 25 is a mobile station whose "origin" network is Network A. The MSC-A typically serves the MS 25 when the MS 25_ is within the coverage area of the Network A. When the MS 25 originates a call , it scans for a control channel with the strongest signal. Once the MS 25 determines which base station has the strongest signal, it gives access to the control channel in order to establish a call. Problems arise, however, when MS 25 operates near margin 27. Even though MS 25 operates near margin 27, MS 25 can detect the strongest signal strength from one of the base stations of Network B 17 -23, and give access to a control channel from the neighboring B network. For example, if MS 25 is still physically positioned as shown within the coverage area of Network A, still near margin 27, it can give access to a control channel associated with one of the closest base stations 19 or 21 placed in Network B. This results in MS 25 incurring additional fees or fees to give access to a different network and incorrectly withdrawing the revenue from Network A. In order to retain the income generated from MS 25, each network operator increases the transmitting power of its margin base stations in order to "capture" the MS 25. Figure 2 is a simplified functional diagram illustrating the components of a radio telecommunications system 31 for a mobile station ( MS) 69 placed near a margin 71 between two analog cellular networks which are serviced by different operators in a preferred embodiment of the present invention. The radio telecommunications system 31 includes a Network C having a mobile switching center-C (MSC-C) 33 with a redirection logic circuit 35., and base stations (BS) 37-49. In addition, the radio telecommunications system 31 includes a Network D having a mobile switching center-D (MSC-D) 51 with redirection logical station 53, and BSs 55-67. MS 69 operates within the radio telecommunications system 31, and margin 71 separates Network C from Network D. It should be understood that in actual practice, there may be many more base stations in each network, but for illustrative purposes , only a few margin base stations have been shown. The base stations 37-43 are all placed near the margin 71 and are designated as the margin base stations. The base stations 45-49 are base stations neighboring the margin base stations, but are located further away within the coverage area of the Network C. Within the MSC-C, the redirection logic circuit 35 includes a base data containing directory numbers used by the mobile stations whose home network is Network D. The list of flag numbers can be indicated by a prefix "located at the beginning of a telephone number of the mobile station. For example, a mobile station, which is associated with Network D, can have a number such as 555-1313.The prefix, "555", can be an indicator that the mobile station is associated with Network D. The MSC -C would store the prefix "555" co or an indicator to determine a directory number with flags In addition to storing the directory numbers with flags, the redirection logic circuit 35 determines when a mobile station, such as a MS 69, which has a directory number with flags is trying to give access to a control channel associated with one of the margin base stations of Network C, 37-43. When the redirect logic circuit 35 determines this, the redirection logic circuit 35 sends a redirect message to the MS 69 denying access to the requested control channel and redirecting the MS 69 to try to give access in a different control channel. Within Network D is MSC-D 51 which has control of BSs 55-67. The base stations 55-61 are all located near the edge 71 and are designated as the margin base stations. The base stations 63-67 are base stations neighboring the margin base stations, but are located furthest from the coverage area of the Network D. Within the MSC-D, the redirection logic circuit 53 includes a base of data containing the flagged directory numbers used by mobile stations whose home network is Network C. The list of flagged directory numbers may be indicated by a prefix found at the beginning of a mobile station telephone number as it is described in the foregoing. In addition to storing the directory numbers with flag, the redirection logic circuit 53 determines when a mobile station having a directory number with flag is trying to give access to a control channel associated with one of the base stations of margin of Network D 55-61. When the redirect logic circuit 53 determines this, the redirect logic circuit 53 sends a redirected message to the mobile station denying access to the requested control channel and redirecting the mobile station to a control channel associated with another base station . Although Figure 2 illustrates both MSCs with a redirection logic circuit, only one MSC is required to have a redirection logic circuit in order to prevent a mobile station from another mobile station from incorrectly accessing one of its base stations. However, in order for both networks to prevent their mobile stations from erroneously accessing the control channels from another network, both MSCs must have a redirection logic circuit. When only one MSC has a redirection logic circuit, only one network is protected from inadvertent access by a mobile station associated with another network. For example, if the MSC-D has a redirection logic circuit, but the MSC-C does not have a redirection logic circuit, the MS 69 will be prevented from erroneously accessing the base stations from Network D. However, if a The mobile station associated with Network D mistakenly tries to gain access with a margin base station of Network C, the MSC-C would not redirect the mobile station back to its own network. Therefore, in the preferred mode, both MSCs would have a redirection logic circuit. Using both networks the redirection logic circuit, both networks obtain income for which they have a legitimate right.Still referring to Figure 2, the operation of the radio telecommunications system 31 will be explained. In an exemplary scenario, the MS 69 is a mobile station whose home network is Network C. The location of the MS 69 may vary through the radio telecommunications system 31. When the MS 69 is operating near the edge 71, but it is still within the coverage area of Network C, the MS 69 can receive a more intense signal from one of the base stations of margin 55-61 within Network D, and therefore tries to obtain access to one of the control channels associated with BSs 55-61. When the MS 69 tries to gain access to a control channel associated with one of the margin base stations 55-61, the associated MSC-D, through the redirection logic circuit 53, recognizes that the directory number of the MS 69 is flagged, indicating that MS 69 is associated with Network C. Then, the MSC-D determines whether MS 69 is attempting to give access to a control channel associated with one of the base stations of margin of the Network D 55-61. If the MSC-D determines that the MS 69 is trying to give access to one of its margin base stations, the MSC-D sends a redirect message to the MS 69. The redirection message includes a list of candidate control channels and instructs the MS to try to give access in a control channel from the list of candidate control channels. The list of candidate control channels which may be as many as six in a preferred embodiment includes the candidate control channels associated with the base stations of margin 37-43 within Network C, as well as the control channels candidate associated with base stations placed more deeply within the coverage area of Network D, such as base stations 63-67. The MS 69 then tries to give access to the control channel with the strongest signal among the candidate control channels. If MS 69 is located near margin 71, but still within the physical coverage area of Network C, MS 69 will possibly give access to a margin base station associated with Network C, since the signal will be more that the signals from the base stations 63-67 placed furthest within the coverage area of Network D. In the situation where the MS 69 actually roams to the coverage area of Network D, the MS 69 of new will try to give access to one of the base stations of margin 55-61 associated with Network D. The MSC-D then recognizes that MS 69 is associated with Network C determining that the directory number of MS 69 is a flag number of the MSC-D database. The MSC-D then determines that the MS 69 is trying to give access to one of its base stations of margin 55-61. The MSC-D sends a redirection message giving instructions that MS 69 try to give access in a control channel from the list of data control channels. The MS 69 then tries to give access to the control channel with the strongest signal from among the candidate control channels. If MS 69 has actually moved within the coverage area of Network D, MS 69 will give access to one of the base stations located furthest away within the coverage area of Network D, for example, one of the Base stations 63-67. In this situation, MS 69 actually falls within the coverage area of Network D and, therefore, it must legitimately use Network D, thus allowing Network D to collect the revenue to which it is entitled. Figure 3 is a flow chart indicating the steps of the method for selecting the control channels near a margin between two radio telecommunications networks in accordance with the teachings of the present invention. With reference to Figures 2 and 3, the method will now be described. In step 81, the MS 69 originates a call within the radio telecommunications system 31. MS 69 tries to give access to the control channel with the strongest signal. Then, in step 83, an MSC, for example the MSC-D, receives the - request for access to the control channel associated with one of the base stations of Network D (ie, one of the base stations BS 55-67). Then, in step 85, it is determined whether a directory number associated with MS 69 is a flag number. This is achieved when the MSC-D stores all the directory numbers associated with Network C, the neighboring network within the redirection logic circuit 53. The list of directory numbers with flag can be indicated by a prefix that is at the beginning of a telephone number of the mobile station. If it is determined that the MS 69 is not associated with a flagged directory number, the method moves to step 87 where the MSC-D then allows the MS 69 to access the requested control channel with the strongest signal. For example, MS 69 would not be associated with the flagged directory number if MS 69 were from Network D or from a network that is not a margin network other than Network C. In this situation, the MS 69 would allow to use the requested control channel. However, if it is determined in step 85 that MS 69 is associated with a flag directory number, the method moves from step 85 to step 89 where the MSC-D, through the redirection logic circuit 53 determines whether the control channel that MS 69 is - trying to use is associated with one of the margin base stations of the MSC-D (ie, one of the base stations 55-61). If it is determined that the requested control channel is not associated with one of the margin base stations (eg, MS 69 is trying to access one of the base stations 63-67), the method moves to step 91 where MSC-D allows MS 69 to have access to the requested control channel. This would occur when MS 69 was deep within the coverage area of Network D and there is no ambiguity as to the side on which margin 71 of MS 69 is placed. However, if it is determined that the channel of requested control is associated with a margin BS (ie, one of the base stations 55-61), the method moves from step 89 to step 93 where the MSC-D, through the redirection logic circuit 53, Select a list of candidate control channels. The list, which may include as many as six numbers, includes control channels associated with the base stations from the margin base stations within the C network (BSs 37-43), as well as the base stations located furthest away within the network D, such as the base stations 63-67.

Then, in step 95, the MSC-D sends a redirect message to the MS 69. The redirect message denies access to the control channel requested by the MS 69, sends the list of candidate control channels, as well as gives instructions to MS 69 to try to gain access with one of the control channels in the list. Next, in step 97, MS 69 gives access to one of the control channels of the candidate list with the strongest signal. If the MS 69 is actually still in the coverage area of Network C, the MS 69 will possibly give access to a control channel from one of the base stations placed within Network C. However, if the MS 69 has moved within the coverage area of Network D, MS 69 will possibly give access to a control channel in a deeper way within the coverage area of Network D, such as a control channel associated with one of base stations 63-65. The radio telecommunications system 31 offers several advantages in relation to the existing system. When the MS 69 is placed within the coverage area of the Network C, the radio telecommunications system 31 prevents inadvertent access of a base station from another network, such as Network D. However, if the MS 69 in reality is located within the coverage area of Network D, the radio telecommunications system 31 will correctly allow MS 69 to access a base station within the coverage area of Network D. Therefore, it is believed that that the operation and construction of the present invention will be apparent from the foregoing description. Even when the method and system shown and described have been characterized as being preferred, it will be readily apparent that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined in the following claims.

Claims (18)

1. A system for selecting a control channel for a mobile station (MS) operating near a margin between a first radio telecommunications network and a second radio telecommunications network, the MS operates within a coverage area of the second radio telecommunications network, the system comprising: a first mobile switching center (MSC) serving and controlling a coverage area associated with the first radio telecommunications network; a first plurality of base stations placed within the first radio telecommunications network; a second plurality of base stations placed within the second radio telecommunications network; means within the first MSC to determine whether the MS is trying to give access to a control channel from a base station in the first plurality of base stations while the MS is placed within the coverage area of the second network of radio telecommunications; means for redirecting the MS to give access to a control channel from a base station of the second plurality of base stations, by determining that the MS is trying to inappropriately access a control channel from a control station. basis of the first plurality of base stations.

2. The system for selecting a control channel for an MS of claim 1, wherein the means for determining whether the MS is trying to incorrectly access a control channel from a base station in the first plurality of monitoring stations. The base includes means for determining whether the MS is attempting to provide access to a base station in the first plurality of base stations remaining adjacent to the margin between the first radio telecommunications network and the second radio telecommunications network.

3. The system for selecting a control channel for an MS of claim 2, further comprising a means for determining whether the MS is associated with the second radio telecommunications network. The system for selecting a control channel for an MS of claim 3, wherein the means for determining whether the MS is associated with the second radio telecommunications network includes a means for storing a list of directory numbers associated with the mobile stations that have the second radio telecommunications network as their home network. The system for selecting a control channel for an MS of claim 4, wherein the means for redirecting the MS to give access to a control channel from a base station in the second plurality of base stations includes a means to determine a plurality of alternative control channels, the plurality of alternative control channels include control channels from the second plurality of base stations. The system for selecting a control channel for an MS of claim 5, wherein the means for redirecting the MS to give access to a control channel from a base station of the second plurality of base stations includes a means to send a redirect message to the MS, the redirect message including a list of the plurality of alternative control channels. The system for selecting a control channel for an MS of claim 1, wherein the means for determining whether the MS is trying to inappropriately access a control channel from a base station in the first plurality of control stations. base, is one - logical redirection function placed within the first MSC. The system for selecting a control channel for an MS of claim 7 further comprising: a second MSC serving and controlling a coverage area associated with the second radio telecommunications network; means for determining whether the second MS that is associated with the first radio telecommunications network is trying to incorrectly access a control channel from a base station in the second plurality of base stations while the second MS is placed within the coverage area of the first radio telecommunications network; and means for redirecting the MS to give access to a control channel from a base station in the first plurality of base stations, by determining that the MS is trying to incorrectly access a control channel from a base station of the second plurality of base stations. The system for selecting a control channel for a mobile station (MS) of claim 8, wherein the means for determining whether the second MS is trying to incorrectly access a channel of - - control from a base station of the second plurality of base stations includes a means for determining whether the second MS is attempting to give access to a base station in the second plurality of base stations remaining adjacent to the margin between the first network of radio telecommunications and the second radio telecommunications network. The system for selecting a control channel for a mobile station (MS) of claim 9 which further comprises a means for determining whether the second MS is associated with the first radio telecommunications network. The system for selecting a second control channel for an MS of claim 10 wherein the means for determining whether the second MS is associated with the first radio telecommunications network includes a means for storing a list of associated directory numbers with mobile stations that have the first radio telecommunications network as their home network. The system for selecting a control channel for an MS of claim 11, wherein the means for redirecting the second MS to provide access to a control channel from a base station of the first plurality of base stations includes a means for determining a second plurality of alternative control channels, the alternative control channels including the control channels from the first plurality of base stations. The system for selecting a control channel for an MS of claim 12, wherein the means for redirecting the second MS to provide access to a control channel from a base station of the first plurality of base stations includes a means for sending a redirect message to the second MS, the redirect message includes a second list of the second plurality of alternative control channels. The system for selecting a control channel for an MS of claim 8, wherein the means for determining whether the second MS is attempting to incorrectly access a control channel from a base station of the second plurality of base stations, is a logical redirection function placed within the second MSC. 15. A method for selecting a control channel for a mobile station (MS) operating within a first radio telecommunications network along a margin between the first radio telecommunications network and the second radio telecommunications network , the first radio telecommunications network has a first mobile switching center (MSC) and a first plurality of base stations, and the second radio telecommunications network has a second MSC and a second plurality of base stations, the method comprising the steps of: determining, by means of the second MSC, whether the MS is attempting to incorrectly access a control channel from one of the second plurality of base stations while the MS is placed within the coverage area of the first radio telecommunications network; and redirecting by the second MSC, the MS to give access to a control channel from one of the first plurality of base stations when determining that the MS is trying to give access to a control channel from one of the second plurality of stations of base. The method for selecting a control channel for an MS of claim 15, wherein the step of determining by the second MSC, if the MS is trying to incorrectly access a control channel from a -second plurality of stations base includes: determining by the second MSC, whether the MS is associated with the first radio telecommunications network; and determining, by the second MSC, whether the MS is requesting a control channel from a base station at the second plurality of base stations remaining adjacent to the margin between the first radio telecommunications network and the second telecommunications network of radio, when determining that the MS is associated with the first radio telecommunications network. The method for selecting a control channel for an MS of claim 16, wherein the step of redirecting by means of the second MSC, the MS accessing a control channel from one of the first plurality of base stations includes : selecting, through the second MSC, a list of alternative control channels, the list includes control channels from the first plurality of base stations; and sending via the second MSC, a redirect message to the MS instructing the MS to give access to a control channel from a list of alternative control channels. 18. The method for selecting a control channel for an MS of claim 17, further comprising, after the step of sending via the second MSC, a redirect message to the MS, the step of providing access, through the MS, to a control channel from the list of alternative control channels with the strongest signal. "_ 19 .. A method for selecting a control channel for a mobile station (MS) operating within a first radio telecommunications network along a margin between the first radio telecommunications network and the second radio network. radio telecommunications, the first radio telecommunications network has a first mobile switching center (MSC) and a first plurality of base stations, and the second radio telecommunications network has a second MSC and a second plurality of base stations , the method comprises the steps of: treating by the MS of improperly accessing a first control channel from one of the second plurality of base stations while the MS is located within a coverage area of the first radio telecommunications network; determining by the second MSC whether the MS is associated with the first radio telecommunications network; determining by the second MSC whether the first control channel is associated with a margin base station that is adjacent to the margin between the first radio telecommunications network and the second radio telecommunications network, by determining that the MS is associated with the first radio telecommunications network; selecting from the second MSC a list of alternative control channels by determining that the first control channel is associated with a margin base station, the list includes control channels from the margin base stations in the first telecommunications network radio and the control channels of the base stations in the second radio telecommunications network that are not the margin base stations; and send a redirect message from the second MSC to the MS, including the redirect message the list of alternative control channels and direct the MS to try to give access to one of the alternative control channels in the list. 20. A system for selecting a control channel for a mobile station (MS) operating along a range between a first radio telecommunications network and the second radio telecommunications network, the system comprising: a first mobile switching (MSC) serving- and controlling a coverage area associated with the first radio telecommunications network; a first plurality of base stations placed within the first radio telecommunications network; a second plurality of base stations placed within the second radio telecommunications network; a means within the first MSC for storing a list of directory numbers associated with the mobile stations having the second radio telecommunications network as their home network: a means for determining whether the MS is trying to incorrectly access a station of base remaining adjacent to the margin between the first radio telecommunications network and the second radio telecommunications network in the first plurality of base stations while the MSC is located within the coverage area of the second radio telecommunications network; a means for determining a plurality of alternative control channels, the alternative control channels include control channels from the second plurality of base stations; and a means for redirecting the MS to give access to a control channel from the plurality of alternative control channels.