KR20050044738A - Apparatus and method of using a ciphering key in a hybrid communications network - Google Patents

Abstract

A method of using a ciphering key in a mobile station (18) from a first base station (12) in a first cellular communications system controlled by a first mobile switching control (10) station to a second base station in a second, different cellular system controlled by a second mobile switching control station is described. The method comprises generating for the mobile station a cipher key for use by the mobile station during communication in the second cellular communications system. The cipher key is generated by the mobile station from a private key assigned to the mobile station for the second cellular communications system and from a random number generated by the second cellular communications system. The cipher key is then communicated to the first mobile system and a private long code is generated for use by the mobile station during communication in the first cellular communications system.

Description

APPARATUS AND METHOD OF USING A CIPHERING KEY IN A HYBRID COMMUNICATIONS NETWORK}

 This application prioritizes "Apparatus and Method Affecting Handoff Between Other Cellular Communication Systems", filed December 7, 2001, filed February 4, 2002. US Patent Application No. 10 / 077,502, "Apparatus and Method Affecting Handoff Between Different Cellular Communication Systems" and US Patent Application No. 60 / 350,401, filed Jan. 17, 2002, using "GSM-1xMSC." GSM authentication, encryption, and other feature support in CDMA 1x networks.

The present invention generally relates to a method and apparatus for using an encryption key.

The so-called code division multiple access (CDMA) modulation technique is only one of several techniques for facilitating communication in which multiple system users exist. Although other techniques such as time division multiple access (TDMA), frequency division multiple access (FDMA) and AM modulation schemes such as amplitude companded single sideband (ACSSB) are available, CDMA has significant advantages over these other modulation techniques. Has The use of CDMA technology in a multiple access communication system is disclosed in US Pat. No. 4,901,307, entitled "Spectrum Spread Multiple Access Communication System Using Satellite or Terrestrial Repeater," which is assigned to this assignee and hereby incorporated by reference. Is cited.

U.S. Patent No. 4,901,307 describes the use of code division multiple access (CDMA) spread spectrum communication signals to allow users of multiple mobile telephone systems, each with one transceiver, to control satellite repeaters or terrestrial base stations (known as cell base stations or cell-sites). Disclosed is a multiple access technique for communicating over. Using CDMA communication, the frequency spectrum can be reused many times, thereby increasing system user capacity. The use of CDMA technology results in much higher spectral efficiency than can be achieved using other multiple access technologies.

In a typical cellular telephone system, the available frequency band is typically divided into channels of 30 kHz bandwidth while analog FM modulation techniques are used. The system service area is divided into cells of geographically variable size. Available frequency channels are divided into sets, each of which generally contains the same number of channels. Frequency sets are assigned to cells in a manner that minimizes the possibility of common-channel interference. For example, assume a system where there are seven frequency sets and the cells are hexagonal of the same size. The frequency set used in one cell will not be used in the six nearest or neighboring cells around that cell. Moreover, one intra-cell frequency set will not be used in the next nearest neighbor cells of the 12 that cell.

In a typical cellular system, the implemented handoff scheme is to allow one call or other form of connection (ie, data link) to continue when the mobile station crosses the boundary between the two cells. Handoff from one cell to another is initiated when the receiver handling the call or connection in the cell base station recognizes that the received signal strength from the mobile station has fallen below a predetermined threshold. Low signal strength indication means that the mobile station should be close to the cell boundary. When the signal level falls below a predetermined threshold, the base station asks the system controller to determine whether the adjacent base station has received a mobile station signal having a better signal strength than the current base station.

The system controller sends a message with a handoff request to the neighbor base station in response to the current base station query. Base stations adjacent to the current base station use specific scanning receivers to find signals from mobile stations on a particular channel. If one of the neighbor base stations reports the appropriate signal level to the system controller, a handoff will be attempted.

Next, the handoff is initiated when an idle channel is selected from the channel set used at the new base station. The control message is sent to the mobile station companding it to switch from the current channel to the new channel. At the same time, the system controller switches the call from the first base station to the second base station.

In a typical system, the call will not continue unless the handoff to the new base station is successful. There are several reasons why a failure may occur during handoff. Handoff may fail when there are no idle channels available in the neighbor cell to compose the call. The handoff fails if the other base station reports that it is listening to the mobile station in question, in fact when this base station is listening to another mobile station using the same channel in a completely different cell. This error report causes the call to switch to the wrong cell, and typically one of these signal strengths is insufficient to maintain communication. Moreover, if the mobile station does not listen to the command to switch channels, the handoff will fail. Deletion experiences often lead to handoff failures often doubting the reliability of the system.

Another common problem in conventional telephone systems arises when the mobile station is close to the boundary between two cells. In this situation, the signal level tends to perturb at both base stations. This signal level perturbation results in a "ping-pong" situation where repeated requests are placed and received between two base stations. These additional unnecessary handoff requests increase the probability that the mobile station incorrectly listens for channel switch commands or no commands at all. Moreover, the ping-pong situation increases the probability of a call dropping if inadvertently delivered to a cell where all channels are currently used and thus cannot be used to accept a handoff.

U. S. Patent No. 5,101, 501, entitled “Method and Apparatus for Providing Soft Handoff in a CDMA Cellular Telephone System”, assigned to the assignee and incorporated by reference for reference, is provided with a mobile station via one or more cell base stations during handoff. A method and system for providing communication are disclosed. In such an environment, communication within the cellular system is not hindered by the actual handoff from the base station corresponding to the cell away from the mobile station to the base station corresponding to the cell into which the mobile station will enter. This type of handoff is considered a "soft" handoff in communication between a mobile station and cell base stations in which two or more base stations or sectors of the base stations simultaneously transmit to the mobile station. The use of such "soft" handoff techniques has been found to substantially reduce the occurrence of a ping-pong situation in which repeated handoff requests are formed between a pair of base stations.

An improved soft handoff technique is disclosed in U.S. Patent No. 5,267,261 entitled " Mobile Station Assisted Soft Handoff in CDMA Cellular Communication Systems, " which is assigned to the assignee and is hereby incorporated by reference. Soft handoff techniques are improved by measuring at the mobile station the strength of the "pilot" signals transmitted by each base station in the system. These pilot strength measurements assist the soft handoff process by facilitating the identification of viable base station handoff candidates.

Improved soft handoff techniques define that the mobile station monitors the signal strength of pilots from neighboring base stations. When the measured signal strength exceeds a given threshold, the mobile sends a signal strength message to the system controller through the base station with which the mobile station will communicate. The command message from the system controller to the new base station and the mobile station establishes simultaneous communication over the new and current base stations. When the mobile station detects that the pilot signal strength corresponding to at least one base station with which the mobile station is communicating falls below a predetermined level, the mobile station transmits the specified signal strength indicating the base station through the base station with which it is communicating. Report to the system controller. The command message from the system controller to the identified base station and mobile station terminates communication through that base station but continues communication with other base stations or base stations.

Although the above techniques are suitable for call transfer between cells in the same system, a more complex situation develops as the mobile station moves from another cellular system to a cell served by a base station. One conflicting factor in this "system to system" handoff is that adjacent cellular systems often have dissimilar characteristics. For example, adjacent cellular systems will often operate at different frequencies and maintain different levels of base station output power or pilot strength. This difference precludes the mobile station from performing similar operations with pilot strength comparisons and existing mobile station-assisted soft handoff techniques.

When resources cannot be used to perform intersystem soft handoff, the handoff timing of a call or connection from one system to another becomes important if the service remains uninterrupted. That is, intersystem handoff should be performed at a time when successful transmission of a call or connection between systems is likely. In this handoff, referred to herein as a hard handoff, the connection between the mobile station and one system must be broken before communication between the mobile station and the other system begins. This means that a handoff should be attempted only when, for example:

(i) when the idle channel is available in the new cell

(ii) the mobile station is in range of the new cell base station but before it has lost contact with the current cell base station;

(iii) when the mobile station is in a position to receive a command to switch channels.

Ideally, each such intersystem hard handoff will be performed in a manner that minimizes the possibility of "pinging" handoff requests between base stations of other systems. However, this makes it difficult to identify when and through which base station the mobile station should be supplied with new frequency and channel information and instructed to transmit the current call or connection as a result of the failure of the current handoff process.

These and other drawbacks of current intersystem handoff techniques compromise the quality of cellular communications and further degrade performance as the number of competing cellular systems rapidly increases. Thus, there is a need for an intersystem handoff technique that can reliably instruct the handoff of a call or connection between base stations of other cellular communication systems.

U.S. Patent No. 5,697,055, assigned to Mobile Assignee Soft Handoff in CDMA Cellular Communication Systems, which is assigned to the assignee and is hereby incorporated by reference, is a system-to-system communication between the first and second cellular systems. A method and system for performing handoff is disclosed. At the mobile station, the quantifiable parameter of the signal transmitted by the second base station of the second system is measured. When the measured value of the quantifiable parameter passes the first predetermined level, the mobile station communicates a signaling amount message through the first base station of the first system to the first mobile switching control station.

The channel request message is then communicated from the first mobile switching control station to a second mobile switching control station in the second system. At the second base station, the quantifiable parameter of the signal received from the mobile station is also measured. The second base station establishes communication with the mobile station when the measured value of the quantifiable parameter passes at a predetermined level. Optionally, the signal strength of the first pilot signal transmitted by the first base station is measured at the mobile station. The handoff request message is then sent to the second base station when the measured signal strength of the first pilot signal is below the second predetermined level, so that mobile station communication is established. The provision of a voice link between the mobile station switching control stations enables the transmission of the current connection between the first and second cellular systems and the intersystem soft handoffs to be performed.

This arrangement works well for situations where both systems are CDMA-based and can thus perform soft handoffs, but in terms of how to handle in-system handoffs when one or more systems are unable to perform such handoffs. The problem remains. For example, the so-called GSM standard does not have any mechanism for soft handoff. Therefore, there is a problem in handing off a call using an air interface from a CDMA network to a GSM network. Moreover, GSM authentication cannot be performed because CDMA 2000 mechanisms cannot transmit the data required to perform GSM authentication. Encryption in GSM is different from encryption in CDMA 2000.

One way to solve this problem is to change the GSM to affect handoffs to non-GSM systems, for example CDMA systems. However, GSM has been set up for a long time by comparison, and operators will not want to make expensive changes to existing equipment to perform adjacent incompatible systems. If new messages are added to the error interface in support of dual-mode mobile stations, changes should be made to support these new messages. Clearly, this is undesirable from the operator's point of view.

Another problem associated with handoff between CDMA and GSM systems is that CDMA and GSM authentication use two different methods and keys. The authentication methods in GSM and CDMA 1X are basically the same, but the keys have different sizes. CDMA 1X has additional procedures such as unique attempt and count methods, which prevent channel hijack and replay attacks, respectively.

1 is a schematic representation of a cellular system.

2 is a schematic representation of the boundary between two cellular systems.

3 is a schematic diagram of a dual mode mobile station;

4 is a schematic representation of data exchange in a GSM system.

5 is a schematic diagram of a single mode mobile station.

The present invention solves the above problems.

According to one aspect of the invention, a movement is from a first base station in a first cellular communication system controlled by a first mobile switching control station to a second base station in a second other cellular system controlled by a second mobile switching control station. A method of using a domestic encryption key is provided, the method comprising generating an encryption key for a mobile station for use by the mobile station during communication in a second cellular communication system, the encryption key comprising the second cellular communication system. Generated by the mobile station from an encryption key assigned to the mobile station and from a random number generated by the second cellular communication system, for communicating the encryption key to the first mobile station and for use by the mobile station during communication within the first cellular communication system. Generating a personal long code for the mobile station.

According to another feature of the invention, a mobile station is operable to receive and transmit signals with a base station in a first cellular communication system, and a mobile station during communication within a cellular communication system, receiving random numbers generated by the second cellular communication system. A controller is provided for generating an encryption key for a mobile station for use by a mobile station, wherein the encryption key is generated from an encryption key assigned to the mobile station for the cellular communication system and from a random number received.

Thus, a way to enable the CDMA physical layer in a GSM system without requiring significant changes to the GSM mobile service switching center (MSC) is to reuse the GSM authentication method for the CDMA physical layer. This offers the advantage that the system does not need to support two different types of authentication centers, two types of SIM cards, and the like.

The above and further features of the present invention are set forth in the appended claims, which will become apparent with advantages in light of the following detailed description of exemplary embodiments of the invention given with reference to the accompanying drawings.

1 is a schematic diagram of an exemplary cellular telephone system. The illustrated system typically uses one of several multiple access modification techniques to facilitate communication between multiple system mobile stations or mobile telephones and base stations. Such multiple access communication system technologies include AM modulation schemes such as time division multiple access (TDMA), frequency division multiple access (TDMA), code division multiple access (CDMA), and amplitude companded single sidebands. For example, the CDMA spread spectrum modulation technique disclosed in U. S. Patent No. 4,901, 307 mentioned has significant advantages over other modulation techniques for multiple access communication systems and is therefore desirable.

In a typical CDMA system, each base station transmits a unique pilot signal, which includes the transmission of a "pilot carrier" on that pilot channel. The pilot signal is an unmodulated direct sequence spread spectrum signal that is always transmitted by each base station using a common pseudorandom noise (PN) spreading code. The pilot signal allows mobile stations to obtain initial system synchronization, or timing, in addition to providing a phase reference for coherent demodulation and a signal strength measurement used for handoff determination. Pilot signals, such as those sent by each base station, can often be the same PN spreading code but have different code phase offsets.

In the system shown in FIG. 1, a system controller and switch 10, also referred to as a mobile switching center (MSC), is typically an interface and processing circuit for providing system control to a number of base stations 12, 14, 16 (not shown). City). The controller 10 also controls routing telephone calls from the public switched telephone network (PSTN) to the appropriate base station for transmission to the appropriate mobile station. The controller 10 also controls routing calls from the mobile stations through the at least one base station to the PSTN. The controller 10 directs calls between mobile users through the appropriate base station (s) because these mobile stations typically do not communicate directly with each other.

The controller 10 is connected to base stations by various means such as dedicated telephone lines, fiber optic links, or by microwave communication links. In FIG. 1, these three exemplary base stations 12, 14, 16 are shown with an exemplary mobile station 18 that includes a cellular telephone. Arrows 20a and 20b define possible communication links between base station 12 and mobile station 18. Arrows 22a and 22b define a possible communication link between base station 14 and mobile station 18. Similarly, arrows 24a and 24b define possible communication links between base station 16 and mobile station 18.

Base station service areas or cells are designed within geographic shapes such that the mobile station is closest to one base station. When the mobile station is idle, i.e., no call is made, the mobile station continues to monitor pilot signal transmissions from each neighboring base station. As shown in FIG. 1, pilot signals are transmitted to mobile station 18 by base stations 12, 14, 16 over communication links 20b, 22b, 24B, respectively. The mobile station then determines in which cell it is located by comparing the pilot signal strengths transmitted from these particular base stations.

In the example shown in FIG. 1, the mobile station 18 is considered to be closest to the base station 16. When the mobile station 18 initiates the call, a control message is sent to the nearest base station here, the base station 16. When the base station 16 receives the call request message, it signals to the system controller 10 and passes the number of calls. The system controller 10 then connects the call to the desired recipient via the PSTN.

If the call is initiated in the PSTN, the controller 10 sends the call information to all base stations in the area. The base stations again send a paging message to the desired recipient mobile station. When the mobile listens for a page message, it responds to a control message sent to the nearest base station. This control message signals the system controller that this particular base station is in communication with the mobile station. Controller 10 then routes the call to the mobile station through the nearest base station.

If mobile station 18 moves out of the coverage area of the initial base station, i.e., base station 16, it will want to continue the call by routing the call through another base station. During the handoff process, there are other ways of initiating a handoff call or routing through another base station.

In the base station initialization handoff method, the initial mobile station, i.e., mobile station 16, recognizes that the signal transmitted by mobile station 18 falls below a certain threshold level. Base station 16 then sends a handoff request to system controller 10, which relays the request to all neighboring base stations 12, 14 of base station 16. The controller-transmission request includes channel related information and includes the PN code sequence used by the mobile station 18. Base stations 12 and 14 tune the receiver to the channel used by the mobile station and typically measure signal strength using digital techniques. If one of the base station 12, 14 receivers reports a signal stronger than the initial base station report signal strength, a handoff is established for that base station.

Optionally, the mobile station itself initiates a so-called mobile-assisted handoff. The base stations each transmit a pilot signal, which, together with others, identifies the base station. The mobile station has a search receiver used to scan pilot signal transmissions of adjacent base stations 12 and 14 in addition to other functions. If the pilot signal of one of the neighbor base stations 12, 14 is found to be stronger than the given threshold, the mobile station 18 now sends a message about this effect to the base station 16.

Next, the mobile station can communicate with one or more base stations 12, 14, 16 through a dialogue process between the mobile station and the base station. During this process, the mobile station identifies and measures the signal strength of the received pilot signals. This information communicates with the MSC through the base station (s) with which the mobile station is communicating. Upon receiving this information, the MSC initiates or terminates the connection between the mobile station and the base station, thus affecting the mobile station-assisted handoff.

The above process is regarded as a "soft" handoff in which the mobile station simultaneously communicates through one or more base stations. During soft handoff, the MSC combines or selects signals received from each base station with which the mobile unit communicates as it moves between other cells. In a similar manner, the MSC relays signals from the PSTN to each base station with which the mobile unit is communicating. Mobile station-assisted handoffs tend to be more complex if the mobile station is located within the coverage area of two or more base stations that are not the same cellular system, ie not controlled by the same MSC.

One method for performing handoff between base stations in other systems is described with reference to FIG. 2, which is a CDMA cellular system (eg, IS-95 1X) and GSM mobile switching under the control of a CDMA mobile switching center MSCc. Shown schematically is a cellular communication network 30 comprising a GSM cellular system under center MSCg control. In FIG. 2, five such exemplary base stations B1A through B5A are located schematically in cells C1A through C5A of the CDMA system, respectively, and five base stations B1B through B5B each represent cells of the GSM system ( C1B to C5B). Although the cells C1A to C5A and the cells C1B to C5B are shown in a circle for convenience of illustration, the cells may be designed in other forms and may actually have a shape according to the topography and topography of the area in which they are located. have. What the cells C1A through C3A and C1B through C3B follow is called "boundary" cells because these cells are close to the boundary between the first and second cellular systems. This design allows the remaining cells in each system to be conveniently referred to as "inner" cells.

The following description will be given with reference to a base station capable of receiving and responding to a signal from a base station in CDMA and GSM cellular systems. However, any form of communication system may be used, such as CDMA One, CDMA2000, CDMA2000 1x, CDMA 2000 3x, High Data Rate Principles (HDR), CDMA 1xEV, CDMA 1xEVDO, TDMA, TDSCDMA, W-CDMA, GPRS and others. You will see that there is. To this end, the mobile station is configured with a dual-band transceiver having a receive chain that is tunable to different operating frequencies of both cellular systems. A schematic diagram of this mobile station is shown in FIG. 3 of the accompanying drawings. As shown, the mobile station 40 includes an antenna 42 coupled via a duplexer 44 to a CDMA transmit and receive chain 46 and a GSM transmit and receive chain 48. Transmit / receive chains 46 and 48 are common for separate CDMA and GSM systems. The chains output appropriately demodulated and converted data to general purpose baseband circuit 50 and receive data for transmission from baseband circuit 40. The transmit / receive chains 46 and 48 are controlled by a controller 52 that switches between the two chains in response to command signals from a CDMA or GSM system. Thus, in this embodiment, both chains are not active at the same time. In another embodiment, both chains are active at the same time.

In another embodiment, the mobile station consists of a single transceiver having a receive chain tunable to one of two cellular systems. A schematic diagram of such a mobile station is given in FIG. 5 of the accompanying drawings. As shown, the mobile station 53 includes an antenna 54. Duplexer 55 is coupled to CDMA transmit and receive chain 56 (if it has a CDMA handset). Otherwise, the mobile station 53 is connected to the GSM transmit and receive chain 57. The transmit / receive chains 56 and 57 are conventional for their respective CDMA and GSM systems. The chain output is the output of the appropriate demodulated and converted data to a commercial baseband circuit 58 and receives data for transmission from the baseband circuit 58. The transmit / receive chain, chain 56 or chain 57 is controlled by controller 59.

Referring to Figure 2, the CDMA Mobile Switching Center (MSCc) controls the routing of telephone calls from the public switched telephone network (PSTN) to the appropriate base stations B1A to B5A for transmission to designated mobile stations. The CDMA Mobile Switching Center (MSCc) also controls the routing of calls from the mobile stations in the coverage area of the first cellular system to the PSTN via at least one base station. The GSM mobile switching center MSCg operates in a similar manner to control the operation of the base stations B1B to B5B and to route calls between the PSTN and the GSM cellular system. Control messages and the like are communicated between MSCc and MSCg via in-system data link 34.

When a mobile station is located in the inner cells of a CDMA system, the mobile station is typically programmed to monitor pilot signal transmissions from each neighboring (ie, inner and / or boundary) base station. Next, the mobile station determines in which cell it is located by comparing the pilot signal strength transmitted from surrounding base stations. When the mobile station approaches the border of the inner cell, the mobile station-assisted handoff is disclosed, for example, in the manner disclosed in US Pat. No. 5,267,262.

Another situation arises when the mobile station is located in one of the boundary cells C1A to C3A or C1B to C3B. As an example, consider a case where a mobile station is located in cell C2A but is close to cell C2B. In this example, the mobile station starts receiving available signal levels from base station B2B, which is reported back to base station B2B and to any other base station (s) with which the mobile station is currently communicating. The time at which the available signal levels are received by the mobile or base station by measuring one or more quantifiable parameters of the received signal (e.g., signal strength, signal to noise ratio, frame erasure rate, bit error rate and / or relative time delay). Is determined. This mechanism is similar to the method disclosed in the aforementioned US Pat. No. 5,697,055.

If both systems are CDMA systems, the handoff mechanism disclosed in US Pat. No. 5,697,055 can be used to affect handoff between cell C2A and cell C2B. However, there is a problem that a mechanism for handing off a call using an air interface from a CDMA network to a GSM network does not currently exist. GSM authentication cannot be performed because CDMA mechanisms cannot transmit the data required for GSM authentication. Encryption in GSM is different from encryption in CDMA. If new messages are added to the air interface in support of dual-mode mobile stations, changes must be made to these new messages. This is not desirable.

The solution to this problem uses a generic message containing instructions that the mobile station can transfer from the CDMA network to the GSM network. General messages must be able to carry the data needed to affect GSM authentication and encryption. Preferably, other auxiliary characteristics in GSM should be supported by a general message. In other words, established GSM protocols must be maintained completely to minimize any change in existing GSM systems. Part of the handoff operation includes establishing a subscriber identity, and once the handoff has been affected, it is necessary to maintain signaling and data confidentiality for the physical connection (encryption). The definition and operation requirements of subscriber identity authentication are given in GSM 02.09.

The authentication process is used to set up an encryption key. Therefore, the authentication process is performed after the network establishes subscriber identity and before the channel is encrypted. Two network functions are necessary to achieve this, ie the authentication process itself and management of authentication and encryption keys in the system.

To this end, a tunneling mechanism can be performed at any time (in handoff situations and in non-handoff situations) and is unidirectional or bidirectional. One type of tunneling mechanism is typically not checked by the GSM base station controller (BSC) but so called ADDS (Application Data Transfer Service) messages and short data bursts for transparent delivery within the CDMA system GSM parameters required by the dual mode mobile station. Messages. The use of ADDS messages allows a general payload along with data bursts to be transmitted between the mobile service switching center (MSC) or other network elements (eg SMS, Location Location Server, OTASP) of the networks. The system uses it to transfer GSM information end-to-end between the network and the mobile station without any change to the CDMA BSCc or BTS.

In the network deployment shown in FIG. 2, ADDS messaging is used to convey GSM handoff data, such as timing information and authentication data from MSCc, to the mobile station via BSCc. The mobile station then uses so-called MAP (Mobile Application Protocol) messages to deliver handoff data to MSCg in the GSM network. This requires only minor changes to MSCg in order to enable it to translate the data into MAP messages and thus control the mobile station. Other alternatives for passing data are of course also possible.

When the mobile station is located at the boundary between CDMA and GSM systems (eg, within cell C2A and adjacent cell C2B), the mobile station sends back to MSCc to inform MSCc of the situation causing the mobile station to handoff to the GSM system. Begin the handoff process by sending a message.

The cell database (not shown) is used as part of the handoff process. This database is used to provide the mobile station with the necessary information to the GSM network, thereby allowing handoff as needed between the CDMA MSC and GSM.

In GSM systems, two types of handoff are available, synchronous and asynchronous. It is desirable to easily implement asynchronous handoff. Therefore, the mobile station is instructed that the handoff will be asynchronous handoff to GSM. After the handoff command is received by the mobile station, the mobile station first transmits several access bursts until the mobile station receives the MAP handoff message back to the CDMA MSCc so that GSM authentication data can be generated and provided to the mobile station. Transmit to controller BSCg. GSM has a burst of data to assist in requiring timing for mobile and has a process for asynchronous handoff. Therefore, the ADDS message includes an "Active Time" message that defines a specific time for the handoff that has occurred. Only when this data is received will the mobile station begin normal transmission.

Another problem in the handoff between CDMA and GSM is that CDMA and GSM authentication use two different methods and keys. The authentication method in GSM and CDMA 1X is basically the same, but the keys have different sizes. CDMA 1X has a unique attempt and count method, which prevents channel hijack and replay attacks, respectively. In order for the CDMA physical layer to be used in a GSM system without requiring significant changes to the GSM MSCg, GSM authentication methods must be reusable through the CDMA physical component. This has the advantage that the system does not have to support two different types of authentication centers, two types of SIM cards, and the like.

The authentication process consists of a series of exchanges between the system and the mobile station. The system sends an unexpected number of RANDs to the mobile station. Next, the mobile station calculates the resulting SRES, known by the signature of the RAND number, using an algorithm known as the A3 algorithm. The A3 algorithm uses RAND and individual subscriber authentication key Ki to calculate the SRES. Subscriber authentication key Ki is assigned when the customer first subscribes to the service and is stored in the subscriber identity module (SIM) card and home positioning register (HLR) of the system. Ki is the private key in encryption and therefore can never be transmitted over the network. Finally, the mobile sends a signature SRES that is validated.

Note that the mentioned use of the encryption key and authentication process is independent of the handoff process. 4 of the accompanying drawings shows how authentication is affected in the GSM MSC. The authentication key in GSM is called Ki and is 128 bits long. The network generates a random number (RAND), which is 128 bits long. RAND and Ki are input to the A3 algorithm and calculate a 32-bit result (SRES) from the input data. The RAND number is sent to the mobile station via error messages. In a GSM system, each mobile station comprises a smart card, a so-called subscriber identity module (SIM) card. Standard SIM commands for authentication are specified in GSM 11.11. These commands are allowed to be executed unless they interfere with the correct functioning of the GSM application. If the SIM is removed from the mobile station during the call, the call is immediately terminated as specified in GSM 11.11.

The mobile station SIM also calculates the SRES by applying the A3 algorithm to the received number of RAND and locally stored copies of Ki. The calculation result is again an SRES and should be the same as the SRES calculated by the network. Therefore, the resulting SRES is sent by the mobile station to the network which is compared with the value of the SRES calculated by the network. If the values of the two SRES are the same, the mobile station is authenticated. In the system of FIG. 2, the RAND number is sent using the ADDS messages over the air interface, with the result that the SRES is sent again.

 The value of SRES is used in an algorithm known as A8 to calculate a 64-bit cipher or cipher and key Kc. The Kc key generated by the GSM authentication and encryption algorithm by the mobile station SIM is applied to the CDMA physical layer instead of the personal long code mask normally generated using the CDMA CAVE algorithm. 64-bit Kc keys are uniquely mapped to 42-bit personal long codes and are thus used as the basis for a "personal long code mask" to provide voice privacy. The private long code mask is passed around the CDMA messages and translated in no different way than when generated from the CAVE algorithm. This approach to voice privacy allows the system to maintain unique authentication centers and unique SIM forms within the hybrid CDMA / GSM network.

GSM performs encryption at the frame level. Every frame is encrypted using a frame number and a 64-bit Kc key, and the key is derived as described with reference to FIG. The frame number and Kc mask are applied to every frame. In a CDMA 1X system, encryption is performed using a 42-bit private long code. In the hybrid system of FIG. 2, the Kc key is used to derive a 42-bit long code mask and has a mapping algorithm that maps between Kc and the private long code. This mapping is done in MSCc and simply tells the BSC which private long code to use.

ADDS operation enables the delivery of transparent services between terrestrial network elements (eg, MSC, SNS, PDC) and mobile stations. The system uses this operation to pass authentication information RAND to the MS and SRES back to the MSC. ADDS messaging operations are performed from the MSCc to the BSCc, allowing data to be sent to the mobile station through the paging channel. The ADDS forwarding operation is performed from the NSCc to the MSCc and allows data to be transferred from the mobile station to the network via an access channel. ADDS forwarding operations are performed from MSCc to NSCc or from BSCc to MSCc, allowing data to be transmitted between the mobile station and the network over a traffic channel. The ADDS parameter is defined as "ADDS user part", which contains a 6-bit "data bus type" that contains the format of the application data message. ADDS operations use ADDS user part parameters that contain service-specific data. The authentication operation uses the ADDS user portion to carry authentication data. The described system uses a new form of data burst called "GSM-MAP authentication" that is translated according to the mobile station.

Note that the exemplary embodiments are implemented whenever a database for storing information included in the authentication process comes out of the receiving end or whenever connected by the receiving end. The processor of the example embodiments is used to implement one encryption scheme with one user that is different from another. The basic implementation of the example embodiment is performed without the need for a physical connection to mediate resources because communication with individual users occurs over a wireless medium.

Those skilled in the art will appreciate that various exemplary logical blocks, modules, circuits, and algorithms described in connection with the embodiments described herein may be implemented as electronic hardware, computer software, or a combination of both. Several exemplary components, blocks, modules, circuits, and steps have been described generally in terms of their functionality. These functions are implemented in hardware or software, depending on the design constraints for the particular application and the overall system. Those skilled in the art will appreciate that interchange of hardware and software is possible under these circumstances and will know the best way to implement the described functionality for each particular application. For example, the various illustrative logic blocks, flow diagrams, windows, and steps described in connection with the described embodiments may be implemented in an application specific integrated circuit (ASIC), programmable logic device, discrete gate or transistor logic such as registers in a FIFO, firmware It is implemented or executed in hardware or software having a processor that executes an instruction set, a field programmable gate array (FPGA) or other programmable logic device, and a combination thereof. The processor may preferably be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller or state machine. The software resides in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROM, DVD-ROM, registers or other magnetic or optical storage media. Those skilled in the art will appreciate that the data, instructions, instructions, information, signals, bits, symbols, and chips referred to in the above description are preferably voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or combinations thereof. It can be seen that it can be expressed as.

Therefore, the embodiments described through the present invention described through the preferred embodiments are for illustrative purposes only, and the spirit and scope of the present invention as disclosed by the appended claims and equivalents thereof by those having appropriate knowledge and skills. You can see that it is possible without departing.

Claims (16)

In a system having a mobile station from a first base station in a first cellular communication system controlled by a first mobile switching control station and a second base station in a second other cellular system controlled by a second mobile switching control station, Generating an encryption key for the mobile station to be used by the mobile station during communication in the second cellular communication system, the encryption key being from the private key assigned to the mobile station for the second cellular communication system and the second Generated from a random number generated by the cellular communication system; Communicating the encryption key to a first mobile system; And Generating a personal long code for the mobile station to be used by the mobile station during communication in the first cellular communication system. 2. The method of claim 1, wherein the first system comprises a channel for transferring data between the system and the mobile station, the method further comprising: transmitting the encryption key to the system using the channel for data transfer. How to include more. 3. The method of claim 2, wherein the channel is a paging channel. The method of claim 1, wherein the first cellular communication system is controlled by a first mobile switching control station, and the second cellular communication system is controlled by a second mobile switching control station, The method is: Measuring a parameter of a signal transmitted by the first base station at the mobile station; Measuring a parameter of a signal transmitted by the second base station at the mobile station; Communicating a signal quality message from the mobile station to the first mobile switching control station via the first base station when the parameters reach a predetermined situation; Generating information about a channel request message for the second mobile switching control station by the first mobile switching control station; Communicating the information from the first mobile switching control station to the mobile station; Generating a channel request message for the second mobile switching control station from the information from the first mobile switching control station at the mobile station; And Communicating the channel request from the mobile station to the second mobile switching control station. 5. The method of claim 4, further comprising generating channel information for the mobile station at the second mobile switching control station that identifies a channel in the second communication system. 6. The method of claim 5, wherein the method further comprises establishing communication between the mobile unit and the second base station in the identified channel. 7. The method of claim 6, further comprising establishing communication between the mobile unit and the first base station. The method of claim 4, wherein the parameter corresponds to a signal strength. 5. The method of claim 4, wherein the first cellular communication system is a CDMA system. 10. The method of claim 9, wherein the second cellular communication system is a GSM system. As a mobile station, A transceiver chain operative to receive and transmit signals with a base station in a ruler communication system; And Receive a random number generated by the cellular communication system; And A controller for generating a cryptographic key for the mobile station to be used by the mobile station during communication within the cellular communication system, the cryptographic key from the private key assigned to the mobile station for a second cellular communication system and from the received random number Created-Mobile station containing-. In a system having a first base station from a first cellular communication system controlled by a first mobile switching control station to a second other cellular system controlled by a second mobile switching control station, Means for generating an encryption key for the mobile station to be used by the mobile station during communication in the second cellular communication system, the encryption key being from the private key assigned to the mobile station for the second cellular communication system and Generated from a random number generated by the two cellular communication system; Means for communicating the encryption key to the first mobile system; And Means for generating a personal long code for the mobile station used by the mobile station during communication in the first cellular communication system. 13. The apparatus of claim 12, wherein the first system includes a channel for transferring data between the system and the mobile station, wherein the device means for transmitting the encryption key to the system using the channel for data transfer. Device further comprising. The apparatus of claim 13, wherein the channel is a paging channel. 13. The apparatus of claim 12, wherein the first communication system is a CDMA system. 16. The apparatus of claim 15, wherein the second cellular communication system is a GSM system.