MPEG-4编解码算法及其视频性能分析

3G移动终端要求能够提供包含语音、数据和图像的多媒体业务，为此3GPP制定了第一个适合3G系统的基于电路交换的多媒体终端模型——3G-324M规范，该模型支持MPEG-4视频处理，它具有高压缩比和容错编码特性。在研究MPEG-4编解码算法基础上进行了MPEG-4视频编码的性能测试。     

3G电路域视频质量问题分析及初步解决思路

从3G电路域业务实现所采用的3G-324M协议入手,对3G电路域业务经常出现的视频质量问题进行了详细分析,并提出了初步解决思路。     

Wireless video applications in 3G and beyond

This article surveys wireless video applications that have been commercialized recently or are expected to go to market in 3G (and beyond) mobile networks, mainly covering error control technologies in view of "wireless video." We introduce several related 3GPP standards including circuit-switched multimedia telephony, end-to-end packet-switched streaming, multimedia messaging service, and multimedia broadcast /multimedia service. We also review the supporting technologies for those four applications. The article concludes with a discussion of error control and rate control adaptability to network QoS variation, which is distinct from wired networks and critical to wireless networks. With respect to MBMS, we point out that required cell transmission power is crucial when realizing meaningful multicast coverage, and suggest a system that integrates different unicast and multicast networks, application-layer data repair, and transmission scheduling.     

Transmission algorithm for video streaming over cellular networks

2.5G and 3G cellular networks are becoming more widespread and the need for value added services increases rapidly. One of the key services that operators seek to provide is streaming of rich multimedia content. However, network characteristics make the use of streaming applications very difficult with an unacceptable quality of service (QoS). The 3GPP standardization body has standardized streaming services that will benefit operators and users. There is a need for a mechanism that will enable a good quality multimedia streaming that uses the 3GPP standard. This paper describes an adaptive streaming algorithm that uses the 3GPP standard. It improves significantly the QoS in varying network conditions while monitoring its performance using queueing methodologies. The algorithm utilizes the available buffers on the route of the streaming data in a unique way that guarantees high QoS. The system is analytically modeled: the streaming server, the cellular network and the cellular client are modeled as cascaded buffers and the data is sequentially streamed between them. The proposed Adaptive streaming algorithm (ASA) controls these buffers’ occupancy levels by controlling the transmission and the encoding rates of the streaming server to achieve high QoS for the streaming. It overcomes the inherent fluctuations of the network bandwidth. The algorithm was tested on General Packet Radio Service (GPRS), Enhanced Data rates for GSM Evolution (EDGE) and Universal Mobile Telecommunication System (UMTS) networks. The results showed substantial improvements over other standard streaming methods used today.     

One-pass GPRS and IMS authentication procedure for UMTS

Universal Mobile Telecommunications System (UMTS) supports Internet protocol (IP) multimedia services through IP multimedia core network subsystem (IMS). Since the IMS information is delivered through the general packet radio service (GPRS) transport network, a UMTS mobile station (MS) must activate GPRS packet data protocol (PDP) context before it can register to the IMS network. In the Third-Generation Partnership Project (3GPP) specifications, authentication is performed at both the GPRS and the IMS networks before an MS can access the IMS services. We observe that many steps in this 3GPP "two-pass" authentication procedure are identical. Based on our observation, this paper proposes an one-pass authentication procedure that only needs to perform GPRS authentication. At the IMS level, authentication is implicitly performed in IMS registration. Our approach may save up to 50% of the IMS registration/authentication traffic, as compared with the 3GPP two-pass procedure. We formally prove that the one-pass procedure correctly authenticate the IMS users.     

基于3G-324M和SIP的3G可视电话互通研究

可视电话业务对网络带宽、时延抖动和丢包率都有较高的要求。中国目前的第三代移动通信技术（3G）网络制式使用不同的无线技术,这使得3G网络中可视电话业务在实现的技术方式上也不同。此处主要研究3G网络中基于3G-324M和SIP协议为基础的电路域和分组域可视电话的实现技术,包括控制协议和呼叫流程。同时针对各自不同的实现方式探讨互通的具体形式,在深入分析可视电话互通理论的基础上设计了互通网关的结构,这对于实现不同制式下的可视电话业务互通具有重要的参考价值。     

浅谈IP多媒体子系统业务平台

文章研究了3GPP在UMTSRel5、Rel6演进版本中提出的IP多媒体子系统(IMS),描述了IMS在基于分组域上提供电话和非电话业务的系统架构。IMS的提出对固网和移动网络的融合起到了很大的推动作用,研究基于IMS的统一业务平台对下一代业务平台体系架构具有一定参考意义。     

Wireless Security

This paper describes the security features incorporated into the third generation (3G) mobile system developed in 3GPP, specifically the enhancements to the shared secret symmetric authentication scheme as used in GSM. The proposed security architecture for the Internet multimedia subsystem (IMS) based on and built upon Internet applications, services and protocols, is then described. Finally, the paper describes some early work by 3GPP to integrate public key security mechanisms into 3G, while maintaining the global reach and call set-up performance, that mobile users now take for granted.     

An access-aware pricing strategy for the evolved packet system

The evolved packet system (EPS) integrates third generation partnership project (3GPP) and non-3GPP wireless access networks to provide mobile users with ubiquitous access to a diverse set of multimedia services. As we know, 3GPP and non-3GPP access networks differ significantly with respect to bandwidth capacity, coverage range, and service cost. It is crucial to enable efficient load balancing between 3GPP and non-3GPP access networks to improve resource utilization, and still maximize revenue generation. From an economic point of view, pricing plays an important role in achieving load balancing in the EPS. This paper proposes an access-aware pricing strategy for the EPS to achieve load balancing between 3GPP and non-3GPP access networks and to maximize revenue generation for network operators. In addition, this paper develops an analytical model for the system using the proposed access-aware pricing strategy. With the analytical model, this paper also proposes an iterative method for determining the optimal pricing that maximizes revenue generation in the EPS. The analytical model is verified by simulation.     

Effective Radio Resource Management for MBMS in UMTS Networks

Broadcast and multicast offer a significant improvement of spectrum utilization, and becomes particularly important where information channels are shared among several users. Mobile cellular environments are expected to evolve with the technological approaches necessary to facilitate the deployment of multimedia services, such as streaming, file download and carousel services. The perspective that video streaming in wireless networks services is an attractive service to end-users has spurred the research in this area. To provide for a video delivery platform in UMTS, the Third Generation Partnership Project (3GPP) addressed this problem with the introduction of the Multimedia Broadcast and Multicast Services (MBMS) in 3GPP Release 6. In this document we analyse several effective radio resource management techniques to provide MBMS, namely, use of non-uniform QAM constellations, multi-code and macro-diversity to guarantee the optimal distribution of QoS depending on the location of mobiles.     

CDMA EVDO网络中的QoS保障机制研究

随着3G无线分组网络的飞速发展,基于移动终端的实时多媒体业务需求也日趋广泛.如何保障诸如流媒体直播和可视通话等QoS要求较高的业务,必将成为一个重要的课题.对CDMA EVDO网络中的QoS保障机制进行了初步探讨,阐述了CDMA EVDO网络的QoS实现架构,并以终端MS源发呼叫的QoS协商过程为例,描述了其信令流程.     

IP multimedia subsystems in 3GPP and 3GPP2: overview and scalability issuesP

The Internet has experienced tremendous expansion in the past several years. Demands for IP multimedia services are emerging. The third-generation (3G) wireless networks aim to support mobile users with numerous Internet services. 3G standards organizations are developing IP multimedia subsystems (IMS) to achieve seamless integration between Internet and 3G networks. Moreover, the collaboration between IETF, 3GPP, and 3GPP2 is essential to the development of IMS for next-generation networks. This article first provides an overview of 3GPP and 3GPP2 IMS and illustrates the IMS requirements, architectures, and functional models. We then discuss potential scalability issues in IMS. This article provides guidance for constructing a robust and scalable IMS.     

LTE Part I: Core network

Current cellular networks based on Third Generation Partnership Project (3GPP) and 3GPP2 technologies provide evolution from circuit-switched technologies, originally developed for voice communications, to packetswitched technologies. Next-generation networks need to deliver IP-based services (voice, video, multimedia, data, etc.) for all kinds of user terminals while moving between fixed (fiber, DSL, cable) and wireless (3GPP-based, 3GPP2-based, IEEE-based) access technologies, and roaming between various operator networks. Users expect the network to originate, terminate, and maintain a session while the user is moving and roaming. Services have to be delivered to users based on serving network functionality (quality of service [QoS], bandwidth, etc.), availability, and user preferences. The network and users must be protected through various authentication, encryption, and other security mechanisms at the access, network, and application layers. Mobility has to be provided through coordinated link, network, and application layer mobility mechanisms that ensure user expectations of service performance are met. Requirements on the radio technology include improved performance as well as reduced system and device complexity. 3GPP Release 8 specifies the architecture to meet the above requirements.     

Efficient slice‐aware H.264/AVC video transmission over time‐driven priority networks

This paper proposes a multimedia streaming architecture that combines network and video technologies to handle video traffic over multi‐hop access networks. In this context, resource overprovision typical of current quality of service approaches will become a limiting factor because of the increasing spread of bandwidth‐intensive multimedia applications. The proposed scheme adopts a time‐driven priority scheduling at network nodes and exploits slice classification at the video encoder to differentiate packets. The service guarantees offered by time‐driven priority, together with the packet classification, significantly reduce congestion and increase the video quality at the receiver with respect to the traditional differentiated services (DiffServ) approach, also achieving high resource utilization. This is an important result, as current DiffServ‐based architectures are far from obtaining such resource utilization in conjunction with reasonable delays and jitters. Copyright © 2013 John Wiley & Sons, Ltd.     

3G移动可视电话系统设计

介绍了3G移动可视电话的设计架构模式,基于Window CE操作系统,结合VTApp、3G-324M协议栈、音视频设备驱动、RIL和双端口RAM等相关模块,实现了可视电话这一复杂的多媒体应用系统的运行,描述了相关模块的工作原理与设计思路,并通过对呼出流程图加以介绍的方式,对可视电话系统的运行流程加以阐述。     

MPEG-4 Video Transmission over Wireless Networks: A Link Level Performance Study

With the scalability and flexibility of the MPEG-4 and the emergence of the broadband wireless network, wireless multimedia services are foreseen to become deployed in the near future. Transporting MPEG-4 video over the broadband wireless network is expected to be an important component of many emerging multimedia applications. One of the critical issues for multimedia applications is to ensure that the quality-of-service (QoS) requirement to be maintained at an acceptable level. This is further challenged in that such a service guarantee must be achieved under unreliable and time-varying wireless channels. In this paper we study the link level performance of MPEG-4 video transmission over the uplink of an unreliable wireless channel. We introduce the discrete time batch Markovian arrival process (DBMAP) with two types of arrivals to model the MPEG-4 video source, which takes into account the inherent nature of the adaptiveness of the video traffic. We prove that in a hidden Markov modeled (HMM) wireless channel with probabilistic transmission, the service time for an arbitrary radio link control (RLC) burst follows phase type (PH-type) distribution. We show that the link level performance of a wireless video transmission system can be modeled by a DBMAP/PH/1 priority queue, and present computation algorithm and numerical results for the queueing model. Extensive simulations are carried out on the queueing behavior of the video transmission buffer, as well as on the packet level error behavior of the video data. The results demonstrate that video quality can be substantially improved by preserving the high priority video data during the transmission.     

SIP在3G网络中的应用

第三代移动通信系统是能提供多种类型IP数据业务的通信系统.会话起始协议SIP是3G的IP多媒体子系统中提供多媒体业务的核心技术.文章首先介绍了SIP的基本工作原理,然后对3GPP UMTS R5定义的IMS进行了简要描述,最后详细阐述了SIP在IMS提供服务的过程及对漫游用户的处理.     

Standardization of the AMR wideband speech codec in 3GPP and ITU-T

3GPP and ITU-T have standardized a multi-rate codec for wideband speech conversational applications. Following a competitive selection process, the adaptive multirate wideband (AMR-WB) specifications were approved in March 2001 as part of 3GPP release 5. The ITU-T Study group 16 approved the same wideband coding algorithm as Recommendation G.722.2 and its Annexes.     

Application-Level QoS Negotiation and Signaling for Advanced Multimedia Services in the IMS

The IP multimedia subsystem (IMS) has been recognized as a reference next-generation network architecture for offering multimedia services over an Internet Protocol (IP)-based infrastructure. One of the key benefits of the IMS is efficient and flexible introduction of new services and access to third-party application providers, thanks to standard interfaces and standardized service capabilities. To support novel media-rich applications across a wide range of user devices and access networks, IMS must support negotiable quality of service (QoS) for IP multimedia sessions. In this article, we describe the application-level QoS signaling as specified by the 3GPP and propose some enhancements based on advanced QoS parameter matching and optimization functionality to be included along the signaling path. We outline various signaling flow scenarios and discuss them in the context of a case study involving an IMS-supported 3D virtual environment, featuring a treasure-hunt-like game.     

IMS关键技术及业务应用研究

3GPP UMTS体系标准的R5版本中引入的IMS是为支持移动多媒体业务而设计,是第三代移动通信核心网络的重要组成部分。论文首先对IMS的关键技术做了归纳总结,然后重点介绍了IMS的安全功能。在此基础上讨论了IMS中的业务架构和基本业务。