1 Introduction
A series of new services have been added to WCDMA R6: WSS (Wideband Speech Service), PSS (Packet-switch Streaming Service), MMS (MulTImedia Messaging Service), and IMS (IP MulTImedia Services). The common feature of these new services is the support for multimedia, which is precisely the focus and advantages of WCDMA R6. In fact, the MSS and PSS standards are the standards specifically formulated by 3GPP for the huge market after short messages (SMS), and its significance is significant.
WCDMA R6 will provide an all-IP network for the core network. In this way, an IP multimedia network supporting audio and video services is formed. The network can guarantee the quality of service (QoS) of the provided audio and video services, and also supports seamless integration of audio and video communications. In this way, it has the following two effects on WCDMA traffic analysis.
First, compared to traditional request / response HTTP traffic, multimedia streams usually have a longer duration. In general, the multimedia stream uses the UDP protocol as the lower layer transmission protocol, which slows the response to network congestion. Therefore, the traffic characteristics of multimedia streams are very different from web traffic. As multimedia streaming traffic increases, network performance will be significantly affected. Therefore, the support of WCDMA R6 new services for multimedia has greatly increased the requirements for system bandwidth, and added a lot of pressure to the design and configuration of system resources. In order to design a new network and rationally allocate system resources, people need to understand the flow characteristics and flow models of WCDMA new services.
Secondly, these new services have greatly enriched customers' options and needs. In order to use system resources more efficiently and meet various requirements of different customers, the importance of QoS for WCDMA R6 has risen accordingly to an unprecedented height. In order to effectively improve QoS in the WCDMA R6 network, people also need to understand the flow characteristics and flow models of WCDMA new services.
Starting from the above two aspects, WCDMA R6 operators and equipment suppliers urgently need to understand the flow characteristics and flow models of WCDMA new services, which is also the focus of this article.
2 3G mobile communication network new business network traffic model
The new services of WCDMA R6 include WSS, PSS, IMS, and MMS. Among them, PSS is a packet switching business flow service, IMS is a real-time IP multimedia service, and MMS is a non-real-time multimedia messaging service.
Among these three new services, WSS is an audio service stream, and the rest are multimedia streams, which are discussed separately in this article.
2.1 Network traffic model of WSS service
WSS is the audio service flow, including the user's voice call. Although the available bandwidth has increased in WCDMA R6, this has no effect on the behavior of users' voice calls. Therefore, the flow characteristics of WSS still conform to the traditional voice call flow model.
Voice call behavior is represented by alternating active and quiet periods, and an event-driven state model (see Figure 1) is used to characterize these two random periods. In fact, the active period and the quiet period conform to the negative exponential distribution. TacTIve indicates that the call is active and the average time to send on the uplink, and Tsilent indicates that the call is quiet and the average time to receive on the downlink. And, the average of the two meets: Tsilent + TacTIve = 3s. This makes the active period of a call channel approximately 50% to 60%. It should be noted here that all mobile users' call behavior has nothing to do with each other.
Figure 1 Call behavior model
As shown in FIG. 2, the mean value of the session duration of a voice call service is tD, Speech = 120, and the session duration conforms to a negative exponential distribution. And during this period, the establishment of the connection of the session will monopolize the relevant resources of the system.
Figure 2 Voice business service model
2.2 Network traffic model of PSS, IMS and MMS services
As WCDMA R6 increases the available bandwidth, these new services can provide multimedia services for mobile devices at the same time, and support the following multiple media types: audio service streams (including voice), video service streams, static pictures, 2D and 3D graphics And animation, text (including simple text types and complex text types, such as descriptive fonts, colors, and sizes), synthesized audio streams, and metadata (Metadata).
In this way, we can divide the traffic of these new services into data traffic (including the last five types of the above media types, because they are all transmitted in the form of data streams), video traffic and audio traffic These 3 categories. Of course, in terms of traffic, the first two account for the vast majority.
PSS, IMS, and MMS services provide services through streaming mechanisms such as data traffic, video traffic, and audio traffic.
For audio streams, you can use the ON / OFF model that meets the truncated Pareto distribution to describe:
(1)
(2)
The specific parameters of the model are:
◠Session period: Pareto distribution with shape parameter α = 1.6 and mean value m = 2.4s.
◠Intermittent period between two sessions: exponential distribution of parameter λ = 36 / 0.16K, K is the average number of audio connections established by a user
â— Session data transmission rate: 20kbit / s.
â— Packet size: 500bytes.
â— ON period: the parameter is exponentially distributed in 0.2s.
â— OFF period: a certain value, the mean value m = 2.4s.
Introduction
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