标题: UMTS即时计费协定之研究
A Study on UMTS Online Charging Protocol
作者: 林一平
LIN JASON YI-BING
国立交通大学资讯工程学系(所)
公开日期: 2010
摘要: 在第三代无线通讯系统Universal Mobile Telecommunications System(UMTS),当使用
者(User Equipment;UE)经由整合封包无线电服务General Packet Radio Service(GPRS)
网路开始使用预付式服务时,闸道GPRS 支援节点Gateway GPRS Support Node(GGSN)
会向即时计费系统Online Charging System(OCS)请求预支费用。此计费控制的方法乃
由GGSN 和OCS 在Gy 介面使用Diameter 计费协定中的计费控制请求Credit Control
Request(CCR)与计费控制答覆Credit Control Answer(CCA)信息來达成。
当GGSN 的预支费用罄,GGSN 会执行预留费用操作,向OCS 请求更多的费用。此时,
进行中的服务会先被暂停,直到从OCS 获得费用才能继续。而延迟处理服务中传送的
使用者封包,将会降低服务的品质。为了解决这个问题,本计画提出一个名为“提早预
留费用”的机制Credit Pre-reservation Mechanism(CPM)。这个方法定义了一个边界參
數δ。当GGSN 预留的预支费用少于δ时,GGSN 将会提早执行预留费用操作,使得在此
操作执行时,GGSN 还是可以继续处理使用者封包。
在CPM 机制,如果δ的值设太小,GGSN 的预支费用很快会用完,而进行中的服务就会
在执行预留费用操作时被暂停。但如果δ的值设太大,则一个进行中的服务会预留太多
费用,那么OCS 的费用就会被很快消耗。这样,新产生的服务要求可能就无法被接受,
而正在执行的服务也可能被强迫终止。在本研究计画中,我们描述了數学推导和模拟兩
种模型來量测CPM 的效能表现。除此之外,我们将在GGSN 节点以及IP 多媒体子网路
之节点建置以Diameter 协定为基础的CCR 及CCA 信息及执行程序。并实作CPM 机
制。此外,我们也使用TTCN-3 实作Diameter 之一致性测试工具,进而测试及分析计费
系统与各服务节点间运作时之效能。
In Universal Mobile Telecommunications System (UMTS), when a User Equipment (UE)
originates a prepaid session through the General Packet Radio Service (GPRS), the Gateway
GPRS Support Node (GGSN) will request an amount of prepaid credit from the Online
Charging System (OCS). The credit control is achieved by exchanging Diameter Credit
Control Request (CCR) and Credit Control Answer (CCA) messages through the Gy
interface between the GGSN and the OCS.
When the credit units are depleted at the GGSN, a reserve units operation is executed to
request additional credit units. The session must be suspended until extra credit units are
granted from the OCS. Delayed processing of user packets at the GGSN may seriously
degrade the quality of service (QoS). To resolve this issue, we propose the Credit
Pre-reservation Mechanism (CPM). In the CPM, we define a threshold δ. When the remaining
credit c of the session is not larger than δ, the GGSN conducts the RU operation to request
extra credit from the OCS. During the RU operation, the GGSN continues to process the user
packets.
In the CPM, if δ is set too small, then the credit units are likely depleted and the service
must be suspended during the RU operation. If δ is set too large, many credit units are
reserved in the active sessions, and the credit in the OCS is consumed fast. Therefore, a
newly incoming session has less chance to be served, and an in-progress session is likely to
be force-terminated. In this work, we will propose both analytic and simulation models to
investigate the performance of the CPM. We also implement the Diameter charging protocol
in the GGSN nodes and other IP multimedia service nodes, and the CPM mechanism in the
application server. We will implement the Diameter conformance test tool based on Testing
and Test Control Notation version 3 (TTCN-3). Through the conformance testing and the
analysis, we will investigate the performance between the OCS and the service nodes.
官方说明文件#: NSC97-2221-E009-143-MY3
URI: http://hdl.handle.net/11536/100411
https://www.grb.gov.tw/search/planDetail?id=1985546&docId=324115
显示于类别:Research Plans


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