WO2008026182A2

WO2008026182A2 - Method and apparatus for enhanced active time calculation on a cdma access gateway

Info

Publication number: WO2008026182A2
Application number: PCT/IB2007/053488
Authority: WO
Inventors: Michael Borella; Chandra Warrier
Original assignee: Utstarcom, Inc.
Priority date: 2006-08-31
Filing date: 2007-08-29
Publication date: 2008-03-06
Also published as: WO2008026182A3

Abstract

Active time determination for wireless communication system usage is described herein (Fig 2) In one embodiment, a preferred method of determining active time of a wireless data session compπses the steps of receiving at least one airlink start message (300), including a final airlink start message, receiving a trigger indication to restart usage accounting and responsively sending a first accounting stop message to a AAA server (120), the first accounting stop message including an accumulated AAA active time attribute, wherein a value of the AAA active time attribute includes a duration of the time from the final airlink start message to the time of the trigger indication, sending an accounting start message associated with the restart usage accounting, receiving an airlink stop message having an airlink active time attribute, and transmitting a second accounting stop message associated with the restarted usage accounting to the AAA server, the second accounting stop message including an accumulated AAA active time attribute, wherein a value of the AAA active time attribute excludes a duration of the time from the final airlink start message to the time of the received indication

Description

Method and Apparatus for Enhanced Active Time Calculation on a CDMA Access Gateway

BACKGROUND

1. Technical Field

The claims and examples of embodiments relate to methods and systems for accounting for subscriber usage of a wireless communication system.

2. Description of Related Art

Increasingly, people are connecting to the Internet using mobile devices. For example, laptop computers are used by business travelers, and cellular telephones and personal digital assistants are used by people from many locations to access information about such topics as sports and weather. To accomplish this communication, these devices typically connect - physically or wirelessly - to a network that has been established wherever they are.

To handle this connectivity, a mobile device, or mobile node, typically obtains an Internet Protocol ("IP") address. The IP address may be simple IP address, or may be a mobile one, which is used in conjunction with a protocol known as the Mobile Internet Protocol ("Mobile IP"). Mobile IP enables mobile nodes to maintain a static or at least semipermanent IP address, to which other devices can transmit data bound for the mobile nodes, no matter where the mobile nodes happen to be currently attached to the Internet. Mobile IP is described in RFC 3344, "IP Mobility Support for IPv4," (August 2002), which is incorporated herein by reference.

In Mobile IP, each mobile node has a "home network," on which sits a device known as the mobile node's home agent ("HA"). Under standard IP routing, all data addressed to a mobile node will be routed to the mobile node's HA. When the mobile node is on its home network, the HA will send any such data to the mobile node, as would a typical router. When a mobile node is on another network, known as a "foreign network," the mobile node informs the HA of its location. In that case, the HA sends any data addressed to the mobile node to a device on the foreign network known as a foreign agent ("FA"), which delivers the data to the mobile node. The FA also routes data sent from the mobile node over the Internet to its intended destination. The FA typically resides on what is referred to as a packet data serving node ("PDSN"). Users of these mobile nodes are typically billed by their particular Internet Service Provider (ISP) for using the provider's packet-data communication service. In the case of cellular wireless devices, the ISP is typically also the provider of cellular wireless service to the device generally. Thus, users typically have a particular service plan with their service provider that includes packet-data service. To accurately compute bills for their users, service providers require accurate user data-service records ("UDR"), regardless of whether that usage took place on the mobile node's home network, on one or more foreign networks, or a combination of the two.

In a 3 G data network, the packet control function ("PCF") and the radio access network ("RAN") track the airlink usage by a mobile node for a mobile session. This information is transported by the PCF to the PDSN in Al l messages in a so-called "active time" attribute. The PDSN typically sums the received active time attributes and transports the calculated active time to the access authentication and accounting (AAA) server in accounting messages.

There are instances, however, where the active time reported by the PCF is not an accurate measure of the subscriber's usage time, and errors in accounting may occur. Consequently, an improvement is desired.

SUMMARY

An improved mechanism for active time determination is described herein. In one embodiment, a preferred method of determining active time of a wireless data session comprises the steps of: receiving at least one airlink start message, including a final airlink start message; receiving a trigger indication to restart usage accounting and responsively sending a first accounting stop message to a AAA server, the first accounting stop message including an accumulated AAA active time attribute, wherein a value of the AAA active time attribute includes a duration of the time from the final airlink start message to the time of the trigger indication; sending an accounting start message associated with the restarted usage accounting; receiving an airlink stop message having an airlink active time attribute; and transmitting a second accounting stop message associated with the restarted usage accounting to the AAA server, the second accounting stop message including an accumulated AAA active time attribute, wherein a value of the AAA active time attribute excludes a duration of the time from the final airlink start message to the time of the received indication.

The trigger indication may be an indication of a PPP renegotiation initiated by a mobile node, the radio access network, such as the PDSN, or other network entity that may require or request datalink characteristics other than those associated with the current PPP link. The trigger indication may also be a time of day ("TOD") trigger, or other system attribute, associated with changes in billing rates. The trigger indication to restart usage may also be an attribute overflow trigger, to prevent overflow of the accumulated time attribute.

In an alternative embodiment, the method of determining active time of a wireless data session may comprise the steps of: at a PDSN, establishing a persistent radio-network- to-PDSN connection having multiple portions, each portion having a cumulative airlink active time duration, and wherein delineations between portions are determined by the PDSN; and, generating a AAA accounting message associated with each portion of the persistent radio-network-to-PDSN connection, where each of the plurality of accounting messages includes the cumulative active time duration for the respective portion, and wherein the cumulative active time durations are determined from airlink active time attributes received from the radio network, and wherein at least one airlink active time attribute is associated with two portions of the persistent radio-network-to-PDSN connection.

In this embodiment the PDSN determines the delineation between portions of the persistent radio-network-to-PDSN in response to a trigger indication, such as PPP renegotiation, TOD, attribute overflow, etc. The airlink active time attribute that is associated with two portions of the persistent radio-network-to-PDSN connection is preferably divided into a first amount and a second amount, the first amount being a time duration between the receipt of an airlink start message and a trigger indication, and wherein the first amount and second amount are incorporated into different accounting messages. The second amount may then be determined by subtracting the first amount from the airlink active time attribute.

These as well as other aspects, advantages, and alternatives will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagram of a wireless data communication system that utilizes preferred embodiments of the active time determination methods.

Figure 2 is an exemplary call-flow diagram of a preferred embodiment of the active time determination system.

Figures 3 and 4 are exemplary flow diagrams of preferred methods of active time determination.

DETAILED DESCRIPTION

1. Overview

A given data session over a wireless network may comprise a number of different airlink sessions between a mobile node 102 and a radio access network ("RAN"). The airlink active time for a given airlink session is reported by the PCF to the PDSN. The PDSN maintains an active time record by accumulating the airlink active times of the various airlink sessions. Upon call termination, the PDSN sends an accounting message to the AAA server indicating the total active time. There are also scenarios where a PDSN will send accounting messages to the AAA without a trigger from the PCF and therefore will not have the current active time information. Examples of such scenarios are PPP renegotiation, TOD trigger, etc. In these scenarios the PDSN computes active time on its own, based on prior active time received from the PCF, state information (active or dormant) and timestamps of various state change events and triggers that cause accounting message generation.

2. Example Architecture

In wireless mobile communication systems, each mobile node (e.g., laptop, cell phone, etc.) is assigned an IP address. The IP address may be a simple IP address, or a Mobile IP address. In simple IP, the IP address is associated with a PDSN or other packet data gateway device (referred to collectively herein as a PDSN). Data intended for the mobile may be routed across a network to the PDSN, and then forwarded to the mobile node. In Mobile IP, the IP address is typically associated with a home network, and information is routed between a foreign agent ("FA") that resides on the PDSN to a home agent ("HA") on the home network. Entities seeking to transmit data to a mobile node may transmit the data to the mobile node's home address on the home network, whereupon the HA transmits the data to the FA/PDSN (typically via a data tunnel). In either case, the mobile node typically begins the process of establishing data connectivity by establishing a data link, such as a point-to-point protocol (PPP) connection, with the PDSN.

Figure 1 is a simplified block diagram of an example of a communications system, in accordance with examples of embodiments. It should be understood that this and other arrangements described herein are set forth only as examples. Those skilled in the art will appreciate that other arrangements and elements (e.g., machines, interfaces, functions, orders, and groupings of functions, etc.) can be used instead, and some elements may be omitted altogether. Further, many of the elements described herein are functional entities that may be implemented as discrete or distributed components or in conjunction with other components, and in any suitable combination and location. Various functions described herein as being performed by one or more entities may be carried out by hardware, firmware, and/or software. Various functions may be carried out by a processor executing instructions stored in memory.

As shown in Figure 1, the communications system 100 includes a mobile node 102, a radio access network ("RAN"), which may comprise a base transceiver station ("BTS") 106, a base station controller ("BSC") and packet control function ("PCF") 108. System 100 also includes a packet data serving node ("PDSN") 110, a packet switched network 116, and authentication, authorization and accounting ("AAA") server 120, and may optionally include a mobile switching center ("MSC") 112, a Public Switched Telephone Network (PSTN) 114, and home agent ("HA") 118.

The mobile node 102 may be any device capable of packet-data communication via PDSN 110, and arranged to function as a simple IP mobile node, or a Mobile IP mobile node in communication with HA 118. As examples, the mobile node 102 may be a cellular telephone, a personal digital assistant (PDA), a computer, a desktop computer, or a laptop computer. The mobile node 102 may also itself be a foreign agent, arranged to serve some number of other mobile nodes. As a further example, the mobile node 102 could be a router, such as a wireless router. The mobile node 102 may take other forms as well, without departing from the scope of the claims. In the preferred examples of embodiments described herein, the mobile node 102 is a cellular telephone.

The PSTN 114 is a circuit-switched network for routing calls between telephones over conventional telephone lines, and is well known in the art. The packet-switched network 116 may include one or more wide area networks (WANs), one or more local area networks (LANs), one or more public networks such as the Internet, one or more private networks, one or more wired networks, and/or one or more wireless networks. Devices in communication with the network 116 may transmit and receive data using a packet-switched protocol such as the Internet Protocol (IP), and may be identified by an address such as an IP address.

To provide service to the mobile node 102, the BTS 106 provides a wireless coverage area, and communicates over a wireless air interface 104 with the mobile node 102 in the coverage area. The communication between the BTS 106 and the mobile node 102 may occur in a digital format, such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Global System for Mobile Communications (GSM), 3rd Generation (3G) wireless communications, or Institute of Electrical and Electronics Engineers (IEEE) 802. Hx, or an analog format, such as Advanced Mobile Phone Service (AMPS). Some examples of embodiments use a digital format known as cdma2000®, described in "CDMA 2000® Series," TIA/EIA/IS-2000 Series, Release A (2000), which is incorporated herein by reference.

The BTS 106 may be controlled by the BSC/PCF 108, which, in turn, may be controlled by the MSC 112. The MSC 112 may be connected to the PSTN 114, and may use a signaling system, such as SS7, to route calls through the PSTN 114. The MSC 112 may be able to communicate with one or more Home Location Registers (HLRs) (not shown) and one or more Service Control Points (SCPs) (not shown), typically via one or more Signal Transfer Points (STPs) (not shown).

The mobile node 102 uses the AAA server 120 for authentication for access to wireless data resources, which may also include voice over IP services in an all IP packet network (i.e., where MSC 112 is not required in order to provide voice services). To enable the mobile node 102 to engage in packet-data communication over the packet-switched network 116, the BSC/PCF 108 includes a packet control function (PCF), and the PDSN 110 connects the BSC/PCF 108 to the network 116. The PDSN may include foreign agent functionality. As such, this description at times refers to the PDSN with respect to functions typically carried out by a FA. The communication between the BSC/PCF 108, the MSC 112, and the PDSN 110 may conform to "Wireless IP Network Standard," 3GPP2 P.S0001-A v3.0 (July 2001) and "Interoperability Specification (IOS) for cdma2000 Access Network Interfaces," 3GPP2 A.S0011-17-A v2.0.1 (December 2003), which are incorporated herein by reference.

Briefly, under these specifications, the mobile node 102 may request access to the network 116 by sending a packet-data origination request to the MSC 112. The MSC 112 then signals to the BSC/PCF 108, which in turn signals to the PDSN 110. The PDSN 110 and the mobile node 102 then negotiate to establish a data link. If this is successful, a data link, such as a point-to-point protocol (PPP) connection, is established between the mobile node 102 and the PDSN 110. The PDSN 110 may then act as a network access server, providing the mobile node 102 access to the packet-switched network 116. 3. Example Accounting Methods

The PDSN calculates active time from the information received from the PCF. The computed active time is then included in accounting messages transmitted to the AAA. The following sections describe the PDSN procedures for various events. The terminology used for active time in various procedures is as follows:

active-time-airlink attribute = the value of active time sent by the PCF in airlink messages

active-time = The active time saved in the usage data record (UDR) data structure in the PDSN

active-time-aaa attribute = The active time value in the AAA attribute in accounting messages

During any given data call, the mobile node may establish numerous airlink sessions with the radio access network. This is because typical data sessions often do not require continuous data transmission and receipt, such as during Web browsing. During periods of inactivity, the airlink resources may not be needed, and thus are made available to other users of the system. During this time, however, the call remains active in a persistent session is present between the PCF and the PDSN. The persistence of the session is indicated by a so- called active stop message. The PDSN receives an active stop airlink in the following events:

• Dormancy

• Airlink parameter change

• From the source PCF once handoff is completed and Al 1 session disconnected with source

• Al l termination When the mobile node requires an airlink for data transmission, it re-establishes the airlink with the RAN, and resumes its PPP session with the PDSN. To inform the PDSN of airlink status, the PCF provides airlink start and airlink stop messages at the beginning and end of each airlink session. The airlink start and stop messages are indicative of airlink usage time, and in particular, the airlink stop messages include the active-time attribute associated with just-terminated airlink session. The PDSN accumulates the values of the active times reported by the PCF, and when the PCF reports that the mobile node has ended the data call, the PDSN reports the accumulated active-time as an active-time-aaa attribute in an accounting stop message to the AAA server.

However, under certain circumstances to PDSN may initiate accounting stop messages on its own initiative, and at points in time that are unknown to the PCF. Indeed, the supplemental accounting stop messages occur at points in time during an active airlink session, and effectively divide the call, or persistent RAN-PDSN session, into two or more portions. These supplemental accounting stop messages may be triggered by any number of events or circumstances, the most common of which include PPP renegotiation, time of day triggers, and attribute overflow events. The PDSN therefore, may not simply rely upon active-time-airlink attributes reported by the PCF, but must accurately account for the cumulative active-times associated with different portions of the persistent radio-access- node-to-PDSN session.

Figure 2 is a simplified block diagram of an example of an accounting flow diagram, in accordance with examples of embodiments. In particular, Figure 2 is a call diagram 200 of the method when the trigger event is a PPP renegotiation. The PCF 202 is on the left side of Figure 2 while the PDSN 204 is represented by the center box, and the AAA server 206 is on the right side of Figure 2. At time t=0, message 208 indicates to the PDSN that a new persistent RAN-PDSN session is to be established. Message 210 indicates that the simple IP, or mobile IP, setup has been completed. PDSN 204 then sends accounting start message 212 to the AAA server 206. Message 214 at time t=100 is an airlink stop message from the PCF indicating that the airlink has been terminated, and that the active-time for that particular airlink session was 100 seconds. At this point, additional airlink start and stop messages may be received, indicative of additional airlink sessions. These additional airlink sessions are not depicted in Figure 2 for purposes of clarity. At time t=200, airlink start message 216 is received indicating that the airlink has been reinitiated with the mobile node.

At time t= 250, a trigger indication is received in the form of a PPP renegotiation message 218. The PDSN is configured to respond to this indication performing certain accounting functions. In particular the PDSN 204 reports the accumulated airlink active-time up to that point, and restarts the accumulation of airlink active -time. The PDSN does this by calculating the accumulated time of all the individual airlink sessions (if more than one), and including the incremental time from which the last airlink start message was received (which is airlink start message 216 in the example of Figure 2) up to the time that the trigger indication was received. PDSN 204 then sends accounting stop message 220 to the AAA server 206, and includes the accumulated active-time for the first portion of the persistent session.

Once the PPP renegotiation has completed as indicated by message 222, the PDSN 204 sends an accounting start message 224 to the AAA server 206. Upon receipt of the next airlink stop message, which will include an airlink active-time attribute, PDSN 204 does not use the entire value of the airlink active -time attribute when determining the cumulative active-time. Rather, PDSN 204 subtracts the incremental time duration from the PCF- reported airlink active-time value that has previously been incorporated in the accumulated active-time as reported in accounting stop message 220. In the example of Figure 2, at time t=300, the airlink stop message 226 is also a deregistration message, indicating that the PDSN should send an accounting stop message to the AAA server 206. On the other hand, had the message 226 been simply an airlink stop message, at this point additional airlink start and airlink stop messages may be received and their airlink active -time attributes be included in the accumulated active-time at PDSN 204.

With respect to Figure 3, a preferred method 300 of determining active time of a wireless data session comprises the steps of: 302 receiving at least one airlink start message, including a final airlink start message. The final airlink start message is the "final" start message associated with the first portion of the persistent RAN-PDSN session. This corresponds to airlink start message 216 of Figure 2.

At step 304 a trigger indication is received, and is interpreted as a request to restart usage accounting. The trigger indication may be an indication of a PPP renegotiation initiated by a mobile node, the radio access network, such as the PDSN, or other network entity that may require or request datalink characteristics other than those associated with the current PPP link. One example of the need to renegotiate PPP is if the mobile was initially registered as a simple IP device, but now requires features and functionality associated with mobile IP. Other circumstances associated with PPP renegotiation are well understood in the art. The trigger indication may also be a time of day ("TOD") trigger, or other system attribute, and may be associated with changes in billing rates. That is, for service plans that provide for different billing rates during different times of the day, the PDSN must be able to provide separate accounting information associated with the portions of a single call that spans two different time periods. The trigger indication to restart usage may also be an attribute overflow trigger, to prevent overflow of the accumulated time attribute.

In response, at step 306, the PDSN responsively sends a first accounting stop message to a AAA server, the first accounting stop message including an accumulated AAA active time attribute, wherein a value of the AAA active time attribute includes a duration of the time from the final airlink start message to the time of the trigger indication. This incremental time from the final airlink start message to the time of the trigger indication is preferably calculated by the PDSN may use timestamps associated with the final airlink start message, and the receipt of the trigger indication.

At step 308, the PDSN sends an accounting start message associated with the restarted usage accounting. At step 310, the PDSN receives an airlink stop message from the PCF, having an airlink active-time attribute. Because the PCF was unaware that the PDSN had terminated the accounting associated with a first portion of the persistent RAN-PDSN session, the active -time attribute inaccurately reflects the unaccounted for active-time. Thus, upon receipt of a deregistration message, the PDSN transmits a second accounting stop message associated with the restarted usage accounting to the AAA server, and the message takes into account the incremental portion of time already accounted for. That is, the second accounting stop message includes an accumulated AAA active time attribute, wherein the AAA active-time attribute excludes a duration of the time from the final airlink start message to the time of the received trigger indication.

In an alternative embodiment, the method 400 of determining active time of a wireless data session is described with reference to Figure 4. At step 402, the PDSN establishes a persistent radio-network-to-PDSN connection having multiple portions, each portion having a cumulative airlink active time duration. In this embodiment the PDSN determines the delineation between portions of the persistent radio-network-to-PDSN in response to a trigger indication, such as PPP renegotiation, TOD, attribute overflow, etc., as described herein.

At step 404, the PDSN generates a AAA accounting message associated with each portion of the persistent radio-network-to-PDSN connection. Each of the accounting messages includes the cumulative active-time duration for the respective portion, and the cumulative active time durations are determined from airlink active time attributes received from the radio network, and wherein at least one airlink active time attribute is associated with two portions of the persistent radio-network-to-PDSN connection. The airlink active-time attribute that is associated with two portions of the persistent radio-network-to-PDSN connection is preferably divided into a first amount and a second amount, the first amount being a time duration between the receipt of an airlink start message and a trigger indication, and wherein the first amount and second amount are incorporated into different accounting messages. The second amount may then be determined by subtracting the first amount from the airlink active time attribute.

Exemplary embodiments of the invention have been described above. Those skilled in the art will appreciate that changes may be made to the embodiment described without departing from the true spirit and scope of the invention as defined by the claims.

Claims

CLAIMSWe claim:

1. A method of determining active time of a wireless data session comprising the steps of: receiving at least one airlink start message, including a final airlink start message; receiving a trigger indication to restart usage accounting and responsively sending a first accounting stop message to a AAA server, the first accounting stop message including an accumulated AAA active time attribute, wherein a value of the AAA active time attribute includes a duration of the time from the final airlink start message to the time of the trigger indication; sending an accounting start message associated with the restarted usage accounting; receiving an airlink stop message having an airlink active time attribute; and transmitting a second accounting stop message associated with the restarted usage accounting to the AAA server, the second accounting stop message including an accumulated AAA active time attribute, wherein a value of the AAA active time attribute excludes a duration of the time from the final airlink start message to the time of the received indication.

2. The method of claim 1 wherein the step of receiving a trigger indication to restart usage comprises receiving an indication of a PPP renegotiation.

3. The method of claim 2 wherein the PPP renegotiation is initiated by a mobile node.

4. The method of claim 1 wherein the step of receiving a trigger indication to restart usage comprises receiving a time of day trigger.

5. The method of claim 1 wherein the step of receiving a trigger indication to restart usage comprises receiving an attribute overflow trigger.

6. A method of determining active time of a wireless data session comprising the steps of: at a PDSN, establishing a persistent radio-network-to-PDSN connection having multiple portions, each portion having a cumulative airlink active time duration, and wherein delineations between portions are determined by the PDSN; and, generating a AAA accounting message associated with each portion of the persistent radio-network-to-PDSN connection, where each of the plurality of accounting messages includes the cumulative active time duration for the respective portion, and wherein the cumulative active time durations are determined from airlink active time attributes received from the radio network, and wherein at least one airlink active time attribute is associated with two portions of the persistent radio-network-to-PDSN connection.

7. The method of claim 6 wherein the PDSN determines the delineation between portions of the persistent radio-network-to-PDSN in response to a trigger indication.

8. The method of claim 7 wherein the trigger indication is the occurrence of a PPP renegotiation.

9. The method of claim 7 wherein the trigger is a time of day trigger.

10. The method of claim 7 wherein the trigger is an attribute overflow trigger.

11. The method of claim 6 wherein the at least one airlink active time attribute that is associated with two portions of the persistent radio-network-to-PDSN connection is divided into a first amount and a second amount, the first amount being a time duration between the receipt of an airlink start message and a trigger indication, and wherein the first amount and second amount are incorporated into different accounting messages.

12. The method of claim 11 wherein the second amount is determined by subtracting the first amount from the at least one airlink active time attribute.