手机电视业务与多媒体广播组播业务标准

介绍了各种手机电视业务支撑技术和标准,就基于数字广播网、卫星广播网、移动蜂窝网络的手机电视技术进行了详细阐述。     

Estimation of accurate effective loss rate for FEC video transmission

We propose an algorithm for adjusting data transmission parameters, such as the packet size and the code rate of forward error correction (FEC), to obtain maximum video quality under dynamic channel conditions. When determining transmission parameters, it is essential to calculate an accurate effective loss rate that reflects FEC recovery failures and over-deadline packets. To this end, we analyze the delays caused by FEC coding and the potential packet size variations. In our analysis, we consider the effect of delayed transmission of video packets incurred by the parity packets as well as the encoder and decoder buffers. With the analysis reflecting the delay effect, we are able to accurately estimate the delay patterns of all video packets. Based on the analysis results, we establish an accurate model for estimating the effective loss rate. Simulations show that the proposed effective loss rate model accurately estimates the effective loss rate and significantly improves the reconstructed video quality at the receiver.     

Multicast Broadcast Services Support in OFDMA-Based WiMAX Systems [Advances in Mobile Multimedia]

Multimedia stream service provided by broadband wireless networks has emerged as an important technology and has attracted much attention. An all-IP network architecture with reliable high-throughput air interface makes orthogonal frequency division multiplexing access (OFDMA)-based mobile worldwide interoperability for microwave access (mobile WiMAX) a viable technology for wireless multimedia services, such as voice over IP (VoIP), mobile TV, and so on. One of the main features in a WiMAX MAC layer is that it can provide'differentiated services among different traffic categories with individual QoS requirements. In this article, we first give an overview of the key aspects of WiMAX and describe multimedia broadcast multicast service (MBMS) architecture of the 3GPP. Then, we propose a multicast and broadcast service (MBS) architecture for WiMAX that is based on MBMS. Moreover, we enhance the MBS architecture for mobile WiMAX to overcome the shortcoming of limited video broadcast performance over the baseline MBS model. We also give examples to demonstrate that the proposed architecture can support better mobility and offer higher power efficiency.     

WCDMA中承载MBMS的几种方法

首先介绍了WCDMA系统中支持MBMS的系统结构,分析了使用DSCH信道带来的缺点,随后提出了其他一些技术,如等级分割、长TTI和STTD技术,采用这些技术可以大大降低基站FACH信道的发射功率,最后提出了利用多播信道和专用信道的组合提供MBMS业务。     

Cross-Layer Modeling for QoS-Driven Multimedia Multicast/Broadcast over Fading Channels in [Advances in Mobile Multimedia]

In this article we propose a cross-layer design model for multimedia multicast/broadcast services to efficiently support the diverse quality of service requirements over mobile wireless networks. Specifically, we aim at achieving high system throughput for multimedia multicast/broadcast while satisfying QoS requirements from different protocol layers. First, at the physical layer, we propose a dynamic rate adaptation scheme to optimize the average throughput subject to the loss rate QoS constraint specified from the upper-layer protocol users. We investigate scenarios with either independent and identically distributed (i.i.d.) or non-i.i.d. fading channels connecting to different multicast receivers. Then, applying the effective capacity theory at the data link layer, we study the impact of the delay QoS requirement (i.e., QoS exponent) on the multimedia data rate of mobile multicast/broadcast that our proposed scheme can support. Also presented are simulation results which show the trade-off among different QoS metrics and the performance superiority of our proposed scheme as compared to the other existing schemes.     

3G移动网络中的组播与广播

手机电视业务可以使用户在移动终端上观看电视节目。目前的手机电视都是以点到点(PtoP)的方式通过流媒体技术来实现的。但是,随着手机电视业务市场的不断拓展,简单的点到点方式已经无法满足需求,因此移动网络需要具有点到多点(PtoM)实现方式的广播,组播能力。本文简单介绍了3GPP和3GPP2中定义的新移动广播,组播业务,详细说明了其网络架构和具体的无线承载方式。     

Layer 7 Multimedia Proxy Handoff Using Anycast/Multicast in Mobile Networks

Proxies can improve the quality of service (QoS) of clients in the three-tier networking architecture. However, it is more complicated to apply the server-proxy-client networking architecture to mobile networks for multimedia streaming because mobile clients possess the "keeping moving" characteristic. Therefore, the three-tier architecture in mobile networks must take user mobility into consideration, i.e., mobile clients should be able to switch to a proxy dynamically. In this paper, application-layer proxy handoff (APH) is defined to have applications be executed smoothly when mobile clients move in the server-proxy-client architecture. First, APH employs application-layer anycast to select one of the candidate proxies as the next proxy based on 1) the network condition between the mobile client and each candidate proxy and 2) the load balance among the candidate proxies. Second, APH utilizes IPv6 multicast to switch the session from the original proxy to the next proxy smoothly and to forward the available cache unsent in the original proxy to the next proxy for keeping the original session continuous     

A Load-aware Scheme for Providing Heterogeneous Multimedia Broadcast/Multicast Service (Het-MBMS)

As the utilization efficiency of network resource arouse the interests of researchers, Multimedia Broadcast Multicast Service (MBMS) with its inherent nature brings mobile wireless communications enter a new era. On the other hand, Next Generation Wireless Network (NGWN) trends to integrate multiple Radio Access Technologies (RATs) to optimize the overall network performance. In case, handover performance becomes a vital indicator of mobility experience of User Equipment (UE). Contrast to conventional vertical handover, the problem we facing is how to seamlessly handover for MBMS to provide heterogeneous MBMS (Het-MBMS). In order to address this problem, this paper proposes a new functional entity called Media Independent Broadcast Multicast Service Center (MIBM-SC), by the extensions and enhancements of Broadcast/Multicast-Service Center (BM-SC) and Media Independent Information Service (MIIS). Additionally, a network selection and a cell transmission mode selection schemes are proposed. Both schemes are based on a load-aware network capacity estimation algorithm to select the best target network and the best cell transmission mode. NS-2 based simulation validates that the proposed scheme enables to provide Het-MBMS and it improves the handover performance in terms of packet loss rate, throughput, handover delay, cell load, and bandwidth usage and Peak Signal-to-Noise Ratio (PSNR). Meanwhile, the total consumption of downlink power is reduced.     

Multimedia Broadcast Multicast Service Performance and its Enhancements in WCDMA Networks

Multimedia Broadcast Multicast Service (MBMS) in Wideband Code Division Multiple Access (WCDMA) networks is used to transmit information from one source to vast amount of recipients. The MBMS technique eases the load of the network and therefore allows network to serve more subscribers. The very aim of this study is to evaluate the performance of Release 6 MBMS and its performance enhancements in WCDMA networks. Special attention will be focused on macro and receive diversity which are considered in addition to time diversity provided by long interleaving as enhancements on MBMS performance. 3GPP Release 6 specifications for MBMS introduce two macro diversity schemes: soft and selective combining. The effect of those combining scheme concepts together with and without receive diversity provided by multiple receive antennas are examined. Also, a concept closely related to the receive diversity called Rx-switching i.e., turning the another receive antenna off in good channel situations for power saving purposes is studied. The system level performance of MBMS point-to-multipoint (p-t-m) mode is evaluated with dynamic system level tool in which e.g., mobility of users and interactions of the radio resource management functionalities are explicitly taken into account. Our studies indicate that macro diversity brings significant gains to the MBMS performance. Receive diversity together with macro diversity schemes improves the performance even more and therefore enhances the cell throughput that MBMS can offer. Furthermore, based on the findings of this study it seems that 2Rx Rake receiver can operate with a single antenna significant amount of time without sacrificing desired coverage and thus provide clear power saving opportunities.

多媒体多播组播单频网中免干扰动态信道分配

为了避免多媒体多播组播单频网(MBSFN)区域内部和区域之间的干扰,进一步提高频谱效率,该文提出一种改进的基于噪声调节时滞噪声混沌神经网络(NHNCNN)的动态信道分配方法。首先,根据MBSFN区域的特殊拓扑结构,重新定义了4种电磁兼容限制函数,在此基础上精心构建了免干扰的NHNCNN能量函数。其次对NHNCNN的稳态判定进程加以改进以提高系统的收敛速度。特别地,采用类二分法联合NHNCNN去搜索最小信道分配总数。仿真结果表明,利用富足的NHNCNN时滞、噪声和混沌神经动力,所提算法能有效地搜索到合理解,并最终找到全局最优解,提高了频谱效率。与现有方法相比,所提算法能够实现更好的收敛速度和合理解率。     

An ARQ/FEC coding scheme for land mobile communication

This paper describes the development of a laboratory test unit that implements a new Type I/II ARQ scheme for use on a land mobile forward satellite link. Investigation of channel characteristics showed that it was possible to use convolutional coding to combat random errors, but it was also necessary to employ an ARQ scheme in order to overcome fades due to signal blockage. The hardware development used commercial 68000-based VME cards as well as special-purpose cards to perform the functions of Viterbi decoding and packet synchronization. Results are presented for the hardware operating with Gaussian noise as time limitations excluded the use of satellite fading simulation. In order to ensure a high degree of data integrity error detection was applied to the data packets such that a residual error rate of less than 10^?11 should result. This was not able to be verified due to the limited time. However, long term tests did indicate that an error rate less than 10^?8 was achieved.     

广播网络中基于补丁流的丢包恢复机制研究

现有的数字广播网络由于没有回传通道,发送端无法知悉传输过程中的丢包状况。接收端处在广播网络的不同位置,常常因处于小区边缘或受障碍物遮挡等原因造成信号减弱,从而导致丢包率提高。该文提出了一种基于pFEC (patching Forward Error Correction,补丁FEC)的丢包恢复机制,来解决单向广播网络的丢包问题。该方法利用蜂窝移动网络的双向信道来传输补丁流,提供自适应的FEC来降低丢包率。这种方式可以在广播业务中为不同位置的用户提供不同的丢包恢复能力。理论建模及仿真结果显示,在蜂窝移动网络丢包率不高的情况下,pFEC机制能够有效应对个别用户突发的丢包,从而提高广播业务整体的可靠性和服务质量。     

基于QoS保证的广播/组播OFDM系统资源分配策略

该文提出了一种基于服务质量(QoS)保证的次优广播/组播OFDM系统资源分配算法。算法在最优分配原则的基础上采用不同广播/组播业务目标速率作为约束条件,并以业务组中最差接收用户传输速率作为搜索目标,使得业务组中全部用户达到QoS要求,算法的公平性及有效性得到提高;同时采用时频格作为分配算法中的基本资源单位,以降低分配算法的复杂度。仿真结果表明,改进分配策略的系统吞吐量性能接近最优广播/组播分配算法,提高了广播/组播系统资源分配的公平性。     

Improved FEC Code Based on Concatenated Code for Optical Transmission Systems

The improved three novel schemes of the super forward error correction(super-FEC) concatenated codes are proposed after the development trend of long-haul optical transmission systems and the defects of the existing FEC codes have been analyzed. The performance simulation of the Reed-Solomon(RS)+Bose-Chaudhuri-Hocguenghem(BCH) inner-outer serial concatenated code is implemented and the conceptions of encoding/decoding the parallel-concatenated code are presented. Furthermore, the simulation results for the RS(255,239)+RS(255,239) code and the RS(255,239)+RS(255,223) code show that the two consecutive concatenated codes are a superior coding scheme with such advantages as the better error correction, moderate redundancy and easy realization compared to the classic RS(255,239) code and other codes, and their signal to noise ratio gains are respectively 2～3dB more than that of the RS(255,239)code at the bit error rate of 1×10 -13 . Finally, the frame structure of the novel consecutive concatenated code is arranged to lay a firm foundation in designing its hardware.     

WDM光传送网络中数字包封与前向纠错分析

为适应多种不同格式信号 (如 ATM、SDH、IP等 )透明传送的需要 ,高速 WDM光传送网络采用数字包封技术。按照 RS纠错码编码规则 ,采用相应的编码形式可纠正一定的突发误码。WDM光网络系统的 TDM数字包封采用 RS纠错码编码 FEC应用形式。分析了 TDM数字包封的基本原理及 RS纠错码编码 FEC的纠错性能特性。     

The Role of HAPs in Supporting Multimedia Broadcast and Multicast Services in Terrestrial-Satellite Integrated Systems

New-generation telecommunications systems are expected to meet the rising user exigencies of mobility and ubiquitous access to multimedia services. As a consequence, 3GPP consortium has introduced the Multimedia Broadcast and Multicast Service (MBMS) concept into 3G/beyond-3G networks. Supporting MBMS in next generation hybrid wireless platforms becomes a challenging issue due to high traffic load deriving from both signaling message exchange and data transmission between multicast sources (BM-SC) and end users. Therefore, in this context, key research issues are surely: effective exploitation of the limited radio spectrums available, coordination of users accessing radio resources, as well as provisioning of desired QoS guarantees. Given the high mobility profiles typical of UMTS users, it clearly appears that the cited target performance can only be achieved through networking solutions based on an overlapped terrestrial-HAP-satellite coverage. An inter-working scenario where HAPs operate in synergy with the UMTS terrestrial and satellite segments seems to be the most promising solution to provide mobile users with MBMS services. Our work, dealing with architectural design options, takes into account many metrics relevant to aspects, such as: frequency allocation, costs in terms of resource utilization, signaling traffic load, number and location of customers, reliability, possible retransmission paths, user mobility, and QoS.Giuseppe Araniti received a degree in Electronic Engineering from the University of Reggio Calabria, Italy, in 2000. He received the Ph.D. in Electronic Engineering from the same University, in March 2004. He is currently a junior researcher at the D.I.M.E.T., of the University of Reggio Calabria, Italy. His major area of research is the traffic and resource management in third and fourth generation mobile radio systems.Antonio Iera graduated in Computer Engineering at the University of Calabria, Italy, in 1991 and received a Master Diploma in Information Technology from CEFRIEL, Italy, in 1992 and a Ph.D. degree from the University of Calabria, Italy, in 1996.Since 1997 he has been with the University of Reggio Calabria, Italy, first as an Assistant Professor and then as an Associate Professor. Currently, he is Professor at the same University. His research interests include Personal Communications Systems, Enhanced Wireless and Satellite Systems.Antonella Molinaro received a degree in Computer Engineering from the University of Calabria, Italy, in 1991, a Master degree in Information Technology from CEFRIEL, Italy, in 1992, and a Ph.D. degree from the University of Calabria, Italy, in 1996. Since 1998 she has been an Assistent Professor first at the University of Messina and then at the University of Calabria. She is currently an Associate Professor at the University Mediterranea of Reggio Calabria, Italy. Her interests include mobile radio systems and inter-working wireless-wired networks.     

一种TD-SCDMA系统多媒体广播／组播下行接收算法——Chip级合并算法

给出了一种适用于TD-SCDMA系统的多媒体广播/组播(MBMS)业务下行接收检测算法.这种检测算法 通过对多个小区的数据在Chip级进行合并,一方面可以避免TDD模式下MBMS广播业务之间的同频干扰问题;另 外,可以利用Chip级合并提供处理增益.因此该方法可以使多个小区在一个时隙中发送高速的MBMS业务,有较高系统利用率.     

长距离高速光纤通信中的FEC技术及其研究进展

前向纠错编码是实现长距离高速光纤通信的关键技术。本文结合ITU—T的最新标准G．707，G．709和G．97分析了三种光纤通信中的编码方案，介绍了光纤通信的前向纠错技术编码的最新研究进展。     

Sliding‐window forward error correction using Reed‐Solomon code and unequal error protection for real‐time streaming video

Forward error correction (FEC) techniques are widely used to recover packet losses over unreliable networks in real‐time video streaming applications. Traditional frame‐level FEC encodes 1 video frame in each FEC coding window. By contrast, in the expanding‐window FEC scheme, high‐priority frames are included in the FEC processing of the following frames, so as to construct a larger coding window. In general, expanding‐window FEC improves the recovery performance of FEC, because the high‐priority frame can be protected by multiple windows and the use of a larger coding window increases the efficiency. However, the larger window size also increases the complexity of the coding and the memory space requirements. Consequently, expanding‐window FEC is limited in terms of practical applications. Sliding‐window FEC adopts a fixed window size in order to approximate the performance of the expanding‐window FEC method, but with a reduced complexity. Previous studies on sliding‐window FEC have generally adopted an equal error protection (EEP) mechanism to simplify the analysis. This paper considers the more practical case of an unequal error protection (UEP) strategy. An analytical model is derived for estimating the playable frame rate (PFR) of the proposed sliding‐window FEC scheme with a Reed‐Solomon erasure code for real‐time non‐scalable streaming applications. The analytical model is used to determine the optimal FEC configuration which maximizes the PFR value under given transmission rate constraints. The simulation results show that the proposed sliding‐window scheme achieves almost the same performance as the expanding‐window scheme, but with a significantly lower computational complexity.