System and method of siphoning messages from a mobile network to an alternative network

(54) (56) (57)

Assignee

INVENTOR

AGENT

NAME

Winphoria Networks Inc., 3 Highwood Drive

Tewksbury MA 01876 US

Shamim A Naqvi, Morrisstown NJ 07960 US Kumar K Vishwanathan, Windham NH 03087 US Rangamani Sundar, NH 03087 US Murali Aravamudan, Windham NH 03087 US Ehrner & Delmar Patentbyrå AB

System and method of diversion messages from a network to an alternate network

Windham mobile

CALLED PUBLICATIONS: - - SUMMARY:

A proxy switch, communication methods and communication logic for use in a mobile network are described. A proxy switch is used between a base station subsystem and a mobile switching center. It receives signaling messages and either returns them, blocks them, converts them, ebbs divert them to an alternative network. A proxy switch includes signaling message management logic for sending and receiving signaling messages to and from the MSCin on a first signaling link and sending and receiving messages to and from the BS on a second signaling link; wherein the second signaling link has a mapped equivalent to the first link. Message intercept logic detects whether a signaling message from an MSC Ar is a Change Over Order (COO) indicating that the MSC will not receive signaling messages on the first signaling link. The message intercept logic also prevents the COO message from being forwarded to the BS and generates and sends a Change Over Acknowledge (COA) confirmation message on the COO message to the MSC. Signal message redirect logic receives signaling messages on the second signaling link and provides control information contained therein to the alternative communication network after the message receive logic detects the COO; and carrier circuit redirection receives information from a carrier circuit corresponding to the second signaling link and routes the information to the alternative communication network

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The numbers in parentheses indicate the INID code.

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SUMMARY

A proxy switch, communication methods and communication logic for use in a mobile network are described. A proxy switch is used between a base station subsystem and a mobile switching center. It receives signaling messages and either returns them, blocks them, converts them, or redirects them to an alternative network. In addition to providing an opportunity to remove load in the form of mobile traffic, it provides a platform for new communication services. A proxy switch includes signaling message management logic for sending and receiving signaling messages to and from the MSC on a first signaling link and transmitting and receiving messages to and from the BS on a second signaling link; wherein the second signaling link has a mapped equivalent to the first link. Message intercept logic detects whether a signaling message from an MSC is a Change Over Order (COO) indicating that the MSC will not receive signaling messages on the first signaling link. The message interception logic also prevents the COO message from being forwarded to the BS and generates and sends a Change Over Acknowledge (COA) confirmation message on the COO message to the MSC. Signal message redirect logic receives signaling messages on the second signaling link and provides control information contained therein to the alternative communication network after the message reception logic detects the COO; and carrier circuit redirection logic receives information from a carrier circuit corresponding to the second signaling link and routes the information to the alternative communication network.

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Background of the invention

1st Field of the Invention

This invention relates to mobile communications and, more specifically, to the use of a proxy switch in a mobile communications network to improve the capacity and cost-effectiveness of the communications network and to provide a platform for new mobile services.

2nd Adjacent technology

All modern mobile communication systems have a hierarchical structure, where a geographical coverage area is divided into a number of geographical areas called cells. Referring to Figure 1, each cell is preferably served by a Base Transceiver Station (BTS) 102a. A plurality of BTSs 102b-n are interconnected via fixed links 104a-n to a base station controller (BSC) 106a controller. The BTSs and BSCs are sometimes referred to collectively as Base Station Subsystem BS 107. A plurality of BSCs 106b-n can be connected to a mobile switching center (Mobile Switching Center, MSC) 110 via fixed links 108a-n.

The MSC 110 acts as a local switch (with additional features for managing mobility management requirements, discussed below) and communicates with the telephone network (PSTN) 120 through trunk groups. In US mobile networks, the concepts of home MSC and a port MSC (Gateway MSC, G-MSC) are used. The home MSC is the MSC corresponding to the switch associated with a mobile station (MS); this association is based on the telephone number, for example, the area code of the mobile station. (The Home MSC is responsible for the CPR discussed below). The G-MSC, on the other hand, is the switch used to connect an MS call to the PSTN. As a consequence, sometimes the home MSC and G-MSC are the same unit, but sometimes not (for example, when the MS roams). Usually, a visitor location register (Visiting Location Register, VLR) 116 is placed together with the MSC 110 and a logical singular CPR is used in the mobile network. As explained below, CPR and VLR are used to store many types of subscriber information and profiles.

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Ί • ···· · ·

A number of radio channels 112 are associated with the entire coverage area.

The radio channels are divided into channel groups allocated to individual cells. The channels are used to transmit signaling information and to establish call connections and the like, and to transmit speech or data information as soon as a call link has been established.

At a relatively high level of abstraction, mobile network signaling comprises at least two main aspects. One aspect involves the signaling between an MS and the rest of the network. By 2G (2G is the industry name for the second generation) and subsequent technology, this signaling refers to access methods used by the MS (eg time division multiple access, TDMA);

code division multiple access (CDMA), radio channel assignment, authentication, etc. A second aspect involves the signaling among various devices in the mobile network, such as e.g. the signaling among MSCs, VLRs, CPRs, etc. The second part is sometimes referred to as Mobile Application Part (MAP) especially when used in conjunction with number 7 signaling (SS7).

Various forms of signaling (as well as data and voice communication) are transmitted and received in accordance with different standards. For example, the Electronics Industries Association (EIA) and the Telecommunications Industry Association (TIA) have defined many US standards, such as IS-41, which is a MAP standard. By analogy, CCITT and ITU have defined international standards, such as GSM-MAP, which is an international MAP standard. Information on these standards is well known and can be found from relevant organizations as well as in the literature, see for example,

Forests, SIGNALING IN TELECOMMUNICATIONS NETWORK (Wiley 1998).

To deliver a call from an MS 114, a user dials the number and press send on a cellular phone or other mobile station. Mobile station 114 transmits the dialed number indicating the service requested to the MSC 110 via base station 107. The MSC 110 checks with an associated VLR 116 (described below) to determine whether mobile station 114 is allowed to use the requested service. The G-MSC directs the call to the local exchange, for the user who dialed the number, in PSTN 120. The local exchange alerts the dialed user terminal and a response signal is routed back to mobile station 114 through the responsible MSC 110 (serving MSC) which then closes

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526 491 voice connection to the mobile station. As soon as the set of call is completed, the call can bend.

To deliver a call to a mobile station 114, (assuming the call comes from PSTN 120), the PSTN user dials the telephone number associated with the mobile station. At least by US standards, PSTN 120 directs the call to the mobile station's home MSC (which both can and cannot be the one responsible for the MS). The MSC then asks the CPR 118 to determine which MSC is currently responsible for the mobile station. This also works to inform the responsible MSC that a call is imminent. The home MSC then directs the call to the responsible MSC. The responsible MSC searches (page) the MS via the appropriate BS. The mobile station responds and appropriate signaling links are set up.

During a call, the BS 107 and mobile station 114 may cooperate to change channels or BTS 102, if needed, e.g. due to signal conditions. These changes are known as handoffs, and they include their own types of known messages and signaling.

One aspect of MAP includes mobility management. Other BSs and MSCs may be needed and used to serve a mobile station, as mobile station 114 roams to different locations. Mobility management ensures that the G-MSC has the subscriber profile and other information that the MSC needs to handle (and charge) calls correctly. For this purpose, MSCs use a Visiting Location Register (VLR) 116 and a Home Location Register (HLR) 118. The CPR is used to store and obtain, among other things, the mobile identification number (MIN), the electronic serial number (ESN), MS status and MS service profile. The VLR stores similar information except it stores an MSC identification that identifies the G-MSC. In addition, under appropriate MAP protocols, location update procedures (or registration reports) are performed so that the home MSC of a mobile subscriber knows its user's location. These procedures are used when an MS roams from one location to another, or when an MS is turned on and registers itself to gain access to the network. For example, a location update procedure may proceed with the MS 114 sending a location update request to VLR 116 via BS 107 and MSC 110. VLR 116 sends a location update message to the HLR 118 responsible for

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526 491 • · · · · · ·· · ·· ··

The MS 114, and the subscriber profile are downloaded from the CPR 118 to the VLR 116. The MS 114 receives confirmation of a successful location update. The CPR 118 requests that the VLR (if anything) that had previously had profile data to delete data related to the relocated mobile station 114.

Figure 2 shows in greater detail the signaling and user interface between a BS 107 and an MSC 110 in a CDMA mobile network. BS 107 communicates signaling information using the Al interface. The A2 interface transmits user traffic (e.g. voice signals) between the MSC switch component 204 and BS 107. The A5 interface is used to provide a user traffic connection for circuit switched data calls (as opposed to voice calls) between the source BS and the MSC. .

As the number of base stations or the number of subscribers grows, the load on the MSC 110 increases. This increased load forces the service provider to add greater capacity to the system. Adding more capacity usually means that the service provider adds more switch modules to the MSC or places additional MSCs on the network. Both options include significant costs.

In addition, subscribers require newer services, for example, data calls to the Internet. For some of these services, MSCs are not cost effective as they are primarily developed for voice calls. Integration of new services into the MSC is complicated or impossible because many MSC software architectures use their own designs or closed designs. This means that the software logic necessary to provide the services cannot be easily added to the MSC 110. Often, a switch additive is used to provide such services. For example, an Inter-Working Function (IWF) is an add-on for directing a data call to the Internet. Both modes -integrating functionality in the MSC or adding a side-trunk add-on - include the MSC when delivering the service. As new services are expected to drive up the demands, it is likely that integration of new services through MSC modifications or through sidetrack additions will aggravate network blockage at the MSC and require costly MSC resources.

SUMMARY OF THE INVENTION The invention provides systems and methods for mobile communication. Switching operations are performed between at least one mobile switching center (MSC)

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526 491 and at least one base station subsystem (BS). The switching, according to one aspect of the invention, allows communication traffic to be diverted to or from an alternative network. According to one aspect of the invention, logic at the switching site interprets messages indicating when diversion should occur.

According to one aspect of the invention, traffic is diverted to an alternative communication network from a mobile communication network with at least one BS, at least one MS, at least one MSC and at least one switch. The switch sends and receives signaling messages to and from the MSC on a first signaling link and transmits and receives messages to and from the BS on a second signaling link; wherein the second link has a mapped equivalent to the first link. The switch detects whether a received message is a change over order (COO) message from the MSC, indicating that the MSC will not receive signaling messages on the first signaling link, and the switch generates and sends a confirmation message (Change Over Acknowledge, CO A) on COO message to MSC. After detecting the COO message, the switch receives signaling messages on the second signaling link and provides control information contained therein to the alternative communication network. In addition, after the detection of the COO message, the switch receives information from a carrier circuit corresponding to the second signaling link and directs the information to the alternative communication network.

According to another aspect of the invention, a proxy switch comprises signaling message processing logic for transmitting and receiving signaling messages to and from the MSC on a first signaling link and transmitting and receiving messages to and from the BS on a second signaling link; wherein the second link has a mapped equivalent to the first link. Message reception logic detects whether a signaling message from an MSC is a COO message indicating that the MSCr will not receive signaling messages on the first signaling link. The message reception logic also prevents the COO message from being forwarded to the BS and generates and sends a COA message to the MSC. Signaling Message Rerouting logic

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526 491 • · · ···· · · receives signaling messages on the second signaling link and provides control information contained therein to the alternative communication network after the message intercept logic detects the COO message; and the carrier circuit redirect logic receives information from a carrier circuit corresponding to the second signaling link and directs the information to the alternative communication network.

Brief description of the drawings

In the drawings, Figure 1 is a system diagram of a prior art mobile network;

Figure 2 illustrates a prior art interface between a BS and a mobile switching center in a prior art mobile network;

Figures 3A-B illustrate a proxy switch and certain sets in a mobile web according to preferred embodiments of the invention;

Figure 4 illustrates a typical data plan of a proxy switch according to a preferred embodiment of the invention;

Figure 5 illustrates message diversion logic for a proxy switch according to a preferred embodiment of the invention;

Figure 6 illustrates software process architecture for a proxy switch according to a preferred embodiment of the invention;

Figure 7 illustrates software process architecture for a proxy switch according to a preferred embodiment of the invention;

Figure 8 illustrates software module architecture for certain processes for a proxy switch according to a preferred embodiment of the invention; and Figures 9-11 are simplified diagrams to show message flow and software process collaboration.

Detailed description

Preferred embodiments of the invention provide a proxy switch and method for its use in a mobile communications network. The proxy switch is preferably positioned between an MSC and a BS, transparent to other components, meaning that neither the BS nor the MSC need to know the proxy switch or need to change its behavior or functionality due to the existence of the proxy switch. Instead, the BS and MSCs can be operated as they usually do, regardless of the existence of the proxy switch.

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·· ····

One of the benefits of the proxy switch is that it can help avoid blocking in a mobile network. For example, the proxy switch can be used (a) to direct communications from an MS to a network before arriving at an MSC and (b) to send diverted traffic to the desired destination via an alternative network, such as a packet-based network. Similarly, the proxy switch can be used to deliver communications to an MS from an alternative network. As a consequence, costly MSC and PSTN resources can be avoided and the proxy switch can be used to increase network capacity cost-effectively.

In addition, the proxy switch defines a set of functions that enable new communication services to be provided to the network. For example, by using the proxy switch, new call parking services can be integrated into the mobile network.

Figure 3A shows a preferred deployment of a proxy switch 300, where the proxy switch 300 is positioned between BS 107 and MSC 110. Only a subset of trunks 306 which transmit user traffic needs to be terminated in the proxy switch; other trunks 308 can directly connect the MSC 110 and BS 107. All control links 312 from BS 107 are terminated in the proxy switch 300. The proxy switch includes a control plane 302 and a data plane 304 (also known as a carrier plane). Control plane 302 handles all signaling traffic, and data plane 304 handles all user traffic for the trunks connected to the proxy switch.

According to the preferred deployment, the proxy switch 300 communicates according to the same signaling protocol on both sides of the control plane 302. For example, in the embodiment suitable for use in CDMA technology, the signaling links 312 between the BS 107 and the proxy switch 300 carry information according to the IS-634 / IOS Interface. Likewise, the signaling links 314 between the MSC 110 and the proxy switch 300 carry information according to the Al interface. This situation differs from other mobile switching complexes such as MSC or BS where different signaling standards are used for communication on different sides of the switch. For example, the MSC has Al interfaces on one side of the complex and communicates according to SS7 / ISUP on the other (ie, the PSTN side of the switch).

According to other embodiments, the proxy switch terminates new input interfaces A8, A9, and output interfaces A10, All for CDMA2000 for packet-based transmission

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526 491&gt; · · ·· ···· • ···· · traffic, both signaling and user traffic. Current MSCs do not support these input interfaces.

The proxy switch's data plane 304 uses the same standards on each side of the switch. The BS side trunks 306, in the CDMA embodiments, communicate according to the A2 and A5 interfaces, depending on whether numbers or data are transmitted on the trunks, likewise, the MSC side trunks 307 use the same interface. Unlike the MSC which has A2 / A5 on one side but communicates according to PSTN 64kb / s pulse code modulation standards on the other side.

In addition, while all the other devices in a mobile network use their own point codes within their signaling (point codes are used as unique identifiers in the network), in some embodiments, the proxy switch 300 does not use its point code and instead uses the point codes contained in the received messages. By using the BS or MSC point codes, instead of the proxy switch point code, the proxy switch transparency is enabled.

According to some embodiments, there is no equivalent between an MSC and a proxy switch. A number of BS can work against a single proxy switch.

Figure 3B shows another preferred deployment. In the deployment of FIG. 3B, the proxy switch 300 may be in communication with more than one MSC 100-110k. The control plane 302 of the proxy switch 300, like that in the deployment of Figure 3a, can receive control signals 312a-n from a plurality of BSs 107a-n. In addition, the data plane 304 can receive trunks 306a-n from a plurality of BSs. Unlike the deployment of Figure 3a, the system of Figure 3b receives and transmits information on the signaling links 314j-k to multiple MSCs 10-10-k.

The set of Figure 3b can be configured to better distribute the load in the system, to improve reliability (by providing an alternative connection to an MS), and to provide services that consistently match a user profile. According to an embodiment using the set of Figure 3B, the system can be configured so that calls from a given caller are routed to an MSC that handles most of the user's traffic (as opposed to only the geographical location where the user puts on his or her MS 114). This determination can be based on statistical monitoring or can be configured in a user profile. By configuring the system so, the amount can

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526 491 ΡΓ: ί.ΐ · =; ···· = ':? · Π Q • · · · · · · · ·· «·· location update messages and the like is reduced. In other embodiments, the proxy switch can be configured so that calls are routed to MSCs that are relatively underutilized. In this way, system administrators can better track the load in the entire communication system during handling. In addition, calls can be routed to MSCs that provide services consistent with a given user profile.

The proxy switch 300 comprising software that accepts all signaling messages and, depending on the message and the state of the system, performs at least one of the following:

1st for the message, further unchanged to the MSC or BS addressed in the message;

2nd intercept messages between the MSC and the BS;

3rd for some intercepted messages: converts the intercepted messages to another message and sends the converted message instead of the original intercepted message to the MSC or BS addressed in the received message;

4th redirects the message from the mobile and PSTN based network to an alternate network.

These types of actions performed in each of the cases along with the events that trigger the actions are described below.

In many cases, especially when a message from an MS 114 is diverted and traffic is routed to an alternate network, the proxy switch 300 can act as an MSC 110. In such a role, the proxy switch fulfills the responsibilities and roles that a traditional MSC would have. Some of these functions and roles relate to mobility management. Consider the case of a roaming MS; as it roams from one cell to another, it can roam to a cell handled by another MSC, resulting in a handoff between the source and target MSCs. If the proxy switch 300 has diverted the message and the call / session has been routed to an alternate network, the handoff must be handled by the proxy switch analogous to the way the handoff would be handled with a conventional MSC. The proxy switch must ensure that appropriate databases are updated with the new MS mode. Another function of the proxy switch concerns the allocation of resources. Especially when an MS initiates a message requesting one

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526 491 new call / session, appropriate circuits (channels) must be assigned for this session. Depending on the system configuration and the state of the system, the proxy switch makes such assignments analogously to the way conventional MSC assignment circuits do.

Figure 4 shows a typical set where the proxy switch 300 is connected to several alternative networks, e.g. an IP backbone 412 or an alternative circuit based network 414, e.g. another carrier. These alternative networks can be used to transmit voice and / or data traffic to desired destinations while avoiding PSTN 120 together with costly resources in the MSC 110 in whole or in part. Alternatively, these arrangements can be used so that circuit-switched traffic can be transported away to another network; For example, circuit-linked traffic from Nashua, NH can be transported to one. MSc in Waltham MA. They can also be used to connect to other networks. For example, IP backbone 412 can communicate with IP voice network 418 or internet 416. As will be explained below, when traffic is diverted to an alternative network, both control information (e.g. from signaling messages) and speech or data from the carrier circuits on the links 306 are sent via an alternate network.

To support these typical sets and to maintain transparency, preferred embodiments of the invention provide some core functionality. These core functions allow traffic to be diverted from the trunks 306 before reaching the MSC 110; enables the introduction of traffic on trunks 306 from alternative networks; enables transparent operation; acts as a building block for higher layer applications; and / or support procedures related to error recovery.

Standard procedures exist for error handling of signaling links between BS 107 and MSC 110. According to these procedures, both the BS and the MSC are considered as equal elements, as element 1 and element 2. Both elements retain two sets of numbers, referred to as the forward sequence number (Forward Sequence Number). , FSN) and Backward Sequence Number (BSN).

FSN identifies the last message sent to an element and BSN identifies the last message received from an element. For example, suppose there are two signaling links, SLCO and SLC1, between element 1 and element 2. If element 1 has FSN = 5 and element 2 has BSN = 3, then element 1 knows that it has sent all messages up to and including message 5 to element 2; element 2 knows that it has received all messages up to and including

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526 491 message 3. If SLCO breaks and element 1 detects such a violation, element 1 sends a Change Over Order (COO) message to element 2 requesting element 2 to change to link SLC1. Element 2 responds with a COA (Change Over Acknowledged, change confirmed). BSN numbers based on which missing message can be returned are included in these messages. For example, in the example above, messages 4 and 5 needed to be returned to element 2.

Procedure for automatic triggering of diversion based on COO messages

According to certain embodiments of the invention, the proxy switch can dynamically determine when the system can benefit from redirecting (or directing) messages to an alternative network (see, e.g., 400, Figure 4). For example, according to one embodiment of the invention, the proxy switch 300 monitors the signaling bandwidth directly or indirectly as a measure of the system bandwidth (e.g., reduced signaling bandwidth translated into reduced system bandwidth). In one embodiment, Change Over Order (COO, change order) from the MSC can be used as a signal for blocking at the MSC, or at least that the bandwidth to / from the MSC is adversely affected until the affected link recovers and traffic changes back to that link. Thus, the proxy switch 300 interprets a COO message as a triggering event to slow down traffic to the MSC, and in response, initiate traffic diversion to an alternative network connected to the proxy switch.

A form of typical logic in this is shown with reference to Figure 5. The proxy switch 805 creates a set of FSN and BSN counters for each of the links to the MSC 110 and to the BS 107. Each of the messages to or from the BS is intercepted and the sequence numbers are updated 810 accordingly. If the proxy switch 300 detects 815 a COO message from MSCr 110, then the proxy switch 300 intercepts that message 820 and does not allow it to pass to the BS

107.1 in this example, only the COO message reflects the requested change and does not indicate that messages need to be returned. The proxy switch 300 then generates a COA message 825 with modified BSN numbers for the MSC and sends the COA message 830 to the MSC 110. The modified sequence numbers are those created by the proxy switch during processing of the messages, similar to that described above. The MSC now believes that its COO has been performed. The communication bandwidth between the MSC and the BS is lower

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as a consequence of the change, as fewer signaling links are available.

Although the bandwidth between the proxy switch 300 and the MSC can be adversely affected as a result of the COO described above, the bandwidth between the BS 107 and the proxy switch 300 is negatively affected. The proxy switch can benefit from the context by diverting traffic to an alternative network. The proxy switch thus initiates diversion 835 of the traffic for traffic generated from the BS side of the proxy switch. There are many types of alternative networks that can be used to transmit numbers as well as data traffic from an MS 114 (see eg Figure 4). If there are multiple types of alternative networks connected to the proxy switch, the proxy switch can then select the type of the alternative network based on the communication type, e.g. data or numbers. Upon initiation of diversion, the proxy switch will configure the data plane required to direct certain carrier circuit traffic to appropriate alternative networks (as described below). For example, VoIP device 404 can be configured with information extracted from signaling messages.

Traffic diversion continues for the given session. The proxy switch 300 then retains the FSN, BSN numbers as described above. All COO messages from BS 107 are then intercepted and a COA is generated and sent to the BS, while retaining the FSN and BSN counters.

All COO messages from MSC 110 are received 850 and checked to see if they indicate that the MSC is again ready to receive traffic on the previously dropped link, ie to see if the COO message is a message saying it has changed back . If there is such a message, the proxy switch interprets this as the MSC can again handle high-level traffic and act to reconnect the diverted links and traffic. (If the COO message is not a message that says it was changed back, there may be another change message indicating a context that could benefit from additional traffic diversion.) If it is a return change message, a new COO 855 will be generated with modified BSN and is transmitted 860 to BS 107. The modified BSN is maintained by the proxy as discussed above. The proxy switch 300 then waits and receives a COA message 865 from BS 107. A new COA message is then generated 870 with modified BSN numbers and sent

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875 to the MSCm 110. The proxy switch then ends the traffic diversion procedure. The control plane instructs the data plane accordingly.

According to certain embodiments, the decision to divert traffic may include other assumptions. For example, the alternative network may provide QoS guarantees that can be considered by the proxy switch logic. In one embodiment, only diversion occurs at session boundaries. If a call is to be diverted, it is diverted at the origin of the call.

The above description presumed that the COO was sent as an indication of network blocking. According to one embodiment of the invention, the logic as described above was equipped for automatic derivation with error handling logic described in relation to Figures 7a-b. In this embodiment, the proxy switch executes 300 each time it receives a COO from the MSC retransmission logic discussed above. However, COO messages from the BS are always treated as a failure in the signaling link, and the retransmission logic is executed but no diversion.

hardware Architecture

Referring to both Figures 3 and 4, preferred embodiments of the proxy switch 300 include a control plane 302 and a data plane 304. The control plane comprises a combination of process hardware and associated software.

The data plane includes large hardware that responds to commands from the control plane.

The control plane includes programmable signaling cards (e.g., PMC 8260 available from Force Systems) to receive signaling information from the signaling links 312,314 and to perform the initial processing thereof. The initial processing involves transmitting and terminating information on the signaling links and extracting, under program control, the message information contained in the signaling messages. As soon as the message information is retrieved, the signaling cards cause the message information to be passed to a programmable processor card (eg RPC 3305 and 3306 available from Radisys) which is then responsible for performing the proxy switch's functionality in response thereto as described above.

The control plane is constructed with passive fault tolerance mechanisms. These mechanisms ensure that in case of catastrophic failure on the control plane, the signaling links

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which is received by one side of the control plane to be passed over to the other side. Accordingly, if the control plane breaks, the links are passed across the control plane and the BSC and MSC can communicate in conventional manner.

The data plane 304 according to a typical embodiment is shown in Figure 4. It includes a DACS 402, a Voice over IP device 404, a data termination module 406 (eg to terminate AS data in CDMA networks), a PPP relay device 408, and a PPP termination device 410. The various devices can be packaged on one or more modules.

DACS 402 receives the carrier circuits of the trunks 30 and terminates the information received on the trunks; it also transmits numbers and data on these trunks.

Ports pre-equipped with DACS 402 are connected to VoIP 404 and data terminator 408. Data terminator 408, in turn, is connected to PPP relay 408, which in turn communicates with PPP terminator 410. In addition, the data plane can also be used to connect to alternative circuit based networks , e.g. to redirect traffic to a circuit MSC in another regional network.

All data plan units receive control information from control plane 302 via control channels 401 used to transmit information according to H.248 or Media Gateway Control Protocol (MGCP). The control channel, is used, among other things, to inform DACS 402 about how to maintain the carrier circuits. For example, a given input circuit from BS 107 is mapped to an output port on one of the devices. The control channel is also used to transmit control information to the various devices. For example, the signal information includes control information such as destination IP addresses that can be used to create destination addresses required by the VoIP device. This information can then be used by the VoIP device to deliver voice information received from DACS by packing the information accordingly and transmitting it according to appropriate protocols, e.g. RTP / UDP / IP.

The data plane is constructed with passive fault tolerance mechanisms. These mechanisms ensure that in case of failure on the data plane, the trunks received by one side of the DACS will be passed to the output trunks connected to the MSC. Accordingly, if

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the data plane breaks down, the trunks pass over the data plane and the BSC.n and the MSC can communicate in a conventional manner.

Miukvaru architecture

Referring to Figures 9-10, according to a preferred embodiment, the control lance software executes session leader processes and communication processes. The session manager processes include a Proxy Session Manager (PSM) 904 and a Core Session Manager (CSM) 1002. The communication process includes SS7 Message Handler (SS7MsgHdlr) 902 an and IP Message Handler (IPMsgHdlr) 906 an. As the names show, session managers include logic for managing and managing call sessions, while message managers include logic for managing messages. Message Manager encapsulates the logic for managing messages so that other software does not need to know special message management details. Similarly, session managers encapsulate the logic of session management, so that other software such as message managers do not need to know session state or the like.

The processes SS7MsgHdlr and IPMsgHdlr are responsible for accepting incoming messages and sending outgoing messages. The former accepts and sends signaling messages from and to the MSC 110 and / or the BS 107. The latter SS7MsgHdlr and IPMsgHdlr accept and send control messages to the data plane. The PSM process 904 handles all calls or sessions that are call-through or non-diverted calls. The CSM process 1002 handles all calls or sessions diverted through the proxy switch 300. The CSM process 1002 as such provides largely the same functionality as the circuit MSC and a BS in that it responds similar to an MSC on messages from the BS: et, and responds to messages from the MS as if it were a BS. Generally, there are multiple PSM and CSM processes running simultaneously on different processor boards to provide the necessary scalability and performance. Additional software processes are provided for error safety and reliability. In the diagrams they are referred to as PSM '904' and CSM '1002'. The purpose of these "important" processes is to provide error security for other PSM and CSM processes. In one embodiment, each of the PSMs and CSMs has a shadow PSM '/ CSM' process that provides shadow coverage. If a PSM or CSM process fails, the corresponding shadow PSM '/ CSM' process is designed to take over from the failed process.

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Referring to Figure 6, as signaling messages arrive from the BSC and MSC, those of an SS7MsgHdlr 902a-n executing on the SS7 processor board are handled. There is an SS7MsgHdlr associated with any signaling link to or from the proxy switch. The SS7 processor cards (mentioned above) extract sufficient information from the signaling message to identify a corresponding SS7MsgHdlr to which the signaling message is transmitted.

SS7MsgHdlr receives the messages and assigns a (preferably) unique logical reference number to this message. This reference number is later used to identify subsequent messages that belong to the same ongoing call / session. The assigned logical reference number is communicated back to the software system running in the BS or MSC (eg SCCP protocol stack) which then uses this reference number in all messages belonging to this call / session.

After processing the above, then SS7MsgHdlr 902 selects a PSM 904 to handle the message. In one embodiment, the SS7MsgHdlr examines the point code of the device transmitting the message and selects a PSM associated with that code. For example, a table can be used to store such conditions.

PSM 904 then determines whether this message is for a call / session to be diverted. In one embodiment, this determination is made by examining the service selection field, contained in the message, which distinguishes between data sessions and voice calls. In another embodiment, this determination is made by examining the numbers, for the caller and the caller, to ascertain whether both are mobile numbers. In a further embodiment, this determination is made by examining the number of the caller to determine if the caller has selected a VoIP service provider. As soon as the determination has been made to divert this call / session, for the PSM 904 message to CSM 1002. If it is determined that this call / session is not diverted, PSM generates a message that is used to send it back to the MSC : n or BS via SS7MsgHdlr processes.

The PSM processes 904 can also communicate via an internal protocol to the CSM processes 1002, see e.g. Figure 7. The internal protocol for a preferred embodiment is stateless and text-based. As above, PSM handles them

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526 491 sessions / conversations that are not distracting. As soon as it finds a session / call that is divertable / t for that content of that session / call to a CSM process. The CSM process is responsible for handling all calls / sessions that are distracting. CSM communicates with the data plane via standard control protocols such as H.248 and MGCP (Media Gateway Control Protocol).

The internal architecture of PSM and CSM processes is similar. Referring to Figure 8, incoming messages are received by the network interface module 1102. The network interface module then transmits the message to the protocol engine 1104. For example, this engine 1104, according to CDMA embodiments, is responsible for encoding and decoding messages according to the IS-634 protocol.

The state machine module 1106 is responsible for handling messages and registering the state according to the protocol. For example, according to a given protocol, a given message represents a known state transition according to that protocol. The state machine module 1106 includes the logic for registering the state and implementing the state transitions.

The active directory module 1108 interacts with the external mobility management functions of the MSC and is responsible for obtaining and updating subscriber profiles and other user / subscriber data. In a traditional MSC, the Visiting Location Register (VLR) is typically located together with the MSC; The VLR contains subscriber information (profiles) currently roaming within the area covered by the MSC. In addition, the MSC is connected to another database, called the Home Location Register (CPR), which contains all subscribers who are home to the current network. When a subscriber roams and enters an area covered by the MSC, the MSC requests from the CPR to send the subscriber's profile and store it in the (local) VLR. When the subscriber clears from the area covered by the MSC (to an area covered by another MSC), the subscriber profile is deleted. The active directory module in the proxy switch acts as a client to the CPR database, requests subscriber profiles from the CPR for subscribers roaming into the area covered by the proxy switch, and updates the local database, i.e. the active directory module and its associated database acts / acts as a traditional VLR for roaming subscribers).

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The Media Gateway Controller (MGC) module 1110 interacts with the proxy switch's data plan 304 via open control protocols, such as Η.248 and MGCP. Upon receiving the request from the IS-634 state machine module 1106, MGC 1110 sends a message in the H.248 or MGCP protocol to the data plane 304 to perform the requested actions. In one embodiment, the so-called TDM-VoIP case, it instructs these action messages from MGC 1110 to the data plane, the data plane to receive incoming circuit (TDM) traffic at an inbound port and convert it to RTP / UDP / IP packets and send it out from one of the exit ports. Accordingly, in this embodiment, incoming circuit traffic is packaged and transmitted as packets. This embodiment can be used to make circuit switched calls, and transports them as Voice over IP (VoIP) calls. In another embodiment, the so-called TDM-TDM case, MGC 1110 instructs data plane 304 to receive incoming circuit-switched (TDM) traffic at an input port and switches out as circuit-switched (TDM) traffic from an output port. In this case, incoming circuit-switched traffic is maintained as circuit-switched and switched to an alternate circuit-switched network.

Figures 9-11 are used to illustrate the above concepts with simplified diagrams. The figures are used to show different interactions for the software processes in response to signaling messages. Carrier circuits are excluded from some of the figures in order to simplify. In addition, only a few examples of PSM and CSM processes are presented for the purpose of simplification.

Figure 9 is used to display the control flow as a new call message is initiated from BS 107 to MSC 110, and to display a throughput call. A walkthrough call is a call in which the proxy switch 300 is not responsible for handling the call and is passed through to handle the MSC 110. The proxy switch 300 is transparent to this call (although it can change point codes, for example, to handle relocation of the MSC (s) explained with reference to Figure 3B). The BS 107 sends 1205 a service request (such as a CSR) intended for the MSC 110. The service request includes a service option field specifying whether this is a voice call or a data call request. The proxy switch receives this message (because it is in the signal path between the BSC and the MSC); in particular, the SS7MsgHdlr process 902 receives the call, assigns a unique local reference number to the message (it is the initial message for a potential ongoing call request), and directs 1210

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<img file="SE526491C2_D0007.tif" />

it to PSM process 904 for further processing. PSM process 904 decodes the incoming message and uses the IS-634 state machine (for CDMA embodiments) to determine whether this call should be diverted (for example to an alternate network) or allowed to be handled by the MSC 110. Since the call in this example is not to be diverted, the message is encoded and sent back 1215 to SS7MsgHdlr process 902.1, an embodiment, the communication protocol between SS7MsgHdlr and the PSM processes is a stateless text-based protocol that provides a session log for the abstraction level (relative to the abstraction level). The SS7MsgHdlr process 902 then forwards the 1220 IS-634 message to the MSC 110. The MSC processes this message and responds to 1225. This response is also received by the proxy switch 300, but since this response is related to an ongoing but non-diverting call (as determined by the local reference number assigned to the initial CSR request message described above), the SS7MsgHdlr does not need process 902 forwards this message to PSM 904. Instead, SS7 MsgHdlr 1230 transmits this message transparently to BS 107. All further exchanges regarding this call are allowed to pass transparently between the BS and the MSC except for a Call Release message at the end of the call. In response to a Call Release, the proxy switch 300 guarantees that the call disconnection is performed including the disposition of the local reference number. The call disconnect message is also sent to the BS 107 through the proxy switch so that the BS can continue with its disconnection process.

Figure 10 is used to show the case when a call message is initiated by BS 107 to MSC 110 and is also used to display proxy trunks, i.e. trunks controlled and assigned by MSC 110. BS 107 sends a 1305 service request intended for the MSC 110. The proxy switch receives this message and the SS7 MsgHdlr process 902 receives the call, assigns a unique local reference number to this message, and directs it to the PSM process 904 for further processing. PSM process 904 decodes the incoming message and determines whether this call should be diverted (for example to an alternate network) or allowed to be handled by the MSC 110. Since the call in this example is not to be diverted, the message is encoded and returned 1315 to SS7MsgHdlr process 902. SS7MsgHdlr process 902 1320 returns the message to the MSC 110. The MSC 110 responds to 1325 on the crush set request by assigning a

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526 491 channel to the call (as described above). This channel assignment is received by the proxy switch 300 which forwards the 1330 assignment to the PSM 904, which in turn responds to 1335 having registered this assignment 1330. The proxy switch then sends the channel assignment request to the BS 107. 1340 all further exchanges regarding this call between the BSC: n and the MSC are allowed to pass transparently through the proxy switch until the Call Release message is transmitted. The call disconnect message triggers the shutdown process in the proxy switch.

Figure 11 is used to show the case of a diverted call. A derived call is a call initiated by BS 107 that is received and redirected to an alternate network of the proxy switch. In such an example, all signaling of the proxy switch is handled and the trunks that handle user traffic are controlled by the proxy switch. BS 107 sends a service request for the MSC 110 to 1405. The proxy switch receives this message and assigns a unique local reference number to the message, directing it 1410 to the PSM process 904 for further processing. The PSM process 904 decodes the incoming message and uses the IS-634 state machine (for CDMA embodiments) to determine whether the call should be diverted. Since the call in this example is to be diverted to an alternative network, 1415 PSM sends the message to CSM process 1002. CSM process 1002 now begins to behave like a conventional MSC and issues 1420 a channel assignment for this call, assigning a trunk between the BS and the proxy switch's data plan. The channel assignment is sent in 1435 to SS7MsgHdlr. The SS7MsgHdlr process sends this channel assignment information to the BS 1430 so that the BS can use it for user traffic. CSM also sends a message to the proxy switch's data plane (as described above using H.248 or MGCP protocols) and directs it to receive incoming user traffic on the assigned channel and redirects it to an alternate network. As described above, in one embodiment, the alternative network may be an IP network. All further exchanges occur between the BSC and the CSM process until the call disconnection command is issued by the MSC, which causes the release of resources (the disconnection process).

In another embodiment, the software architecture can only use a single process to perform the proxy functions rather than using two different processes (PSM and CSM). In such an embodiment, the PSM process alone determines, as before, whether a call should be diverted or not. If it is not a diverting call,

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Ι · «· · is allowed to continue to the MSC. If it is a divert call, the PSM handles the call itself and sends and accepts messages from BS 107 and MSC 110. In other words, PSM acts in such an embodiment as an MSC and BS 107 and handles all signaling messages in the this respect. The PSM process as such provides much the same functionality as the circuit-switched MSC and as a BS 107 in that it responds similarly to an MSC to messages from BS 107, and responds to messages from the MS as if it were a BS 107.1 In general, there are multiple PSM processes running simultaneously on different processor boards to provide the necessary scalability and performance. Additional software processes are provided for error safety and reliability. The purpose of these processes is to provide error security for other PSM processes. In one embodiment, each PSM has a shadow process that provides shadow coverage. If a PSM process goes wrong, the corresponding shadow process is designed to take over from the process that went wrong.

variations

The embodiments described above facilitate all the realization of a transparent switch. However, sub-sets of functionality also provide advantages over prior art. For example, a switch partially visible to the network may still offer many of the advantages discussed above.

In addition, the embodiments have been partially described in relation to CDMA protocols, but the embodiments can also be modified to work with GSM, IS-136 and / or other 2G and 3G protocols.

Connecting trunks from the proxy switch to the MSC is optional.

By describing a typical embodiment, it will be apparent to those skilled in the art that changes can be made to the embodiment described without departing from the scope of the invention.

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