Mobile TV design scheme based on digital TV broadcasting network

There are three types of mobile TV, one is based on the analog TV broadcast network, the other is based on the mobile communication network, and the other is based on the digital broadcast network. The first solution is to add an analog TV module to the mobile phone to receive analog TV broadcast programs. Because the effect is not satisfactory, it is not easy to be accepted by consumers. Solutions based on mobile communication networks are further divided into unicast solutions based on 2.5G mobile communication networks and multicast solutions based on 3G mobile communication networks. The unicast solution uses the 3GPP standard video format to provide on-demand, live, and carousel services through streaming media servers, such as the WAP portals of China Mobile and China Unicom. Multicast solutions such as Qualcomm's MediaFLO, the solution calculates the load of the mobile network, performs reasonable network scheduling, and controls the playing time of media programs and the way of program transmission. There are three major standards for mobile TV based on digital television broadcasting networks: DVB-H (Digital Video Broadcasting-Handheld) in Europe, ISDB-T (Integrated Services Digital BroadcasTIng-Terrestrial) in Japan, and T-DMB (Terrestrial-Digital MulTImedia) in South Korea. BroadcasTIng). China’s national standards have not yet been officially promulgated

Currently, T-DMB has been opened and operated in South Korea, with more than 300,000 users. Beijing, Guangdong and Shanghai are already building experimental T-DMB networks. DVB-H has also begun operations in several European countries. This article discusses the mobile phone TV solution based on the digital TV broadcasting network, which is a mobile digital TV mobile phone solution composed of TI's DM275, HOLLYWOOD DTV1OOx and TSC2110 mobile phone platforms. This solution is under development.

Mobile digital TV mobile phone design plan

The mobile digital TV handset contains two sub-systems: DVB-H mobile digital TV sub-system and GSM/GPRS communication sub-system, as shown in Figure 1. The two sub-systems use the application processor as the host to control the DVB-H mobile digital TV receiver and the GSM/GPRS communication module.

手机电视分为3种，一种是基于模拟电视广播网的方案，另一种是基于移动通信网的技术方案，还有一种是基于数字广播网的方案。第一种方案是在手机上加上模拟电视模块来接收模拟电视广播节目，由于效果不尽人意，不易被消费者接受。基于移动通信网的方案又分为基于2.5G移动通信网的单播方案和基于3G移动通信网的多播方案。单播方案使用3GPP标准视频格式，通过流媒体服务器提供点播、直播、轮播服务，如中国移动和中国联通的WAP门户。多播方案如美国高通公司的MediaFLO，该方案通过计算移动网的负载，进行合理网络调度，控制媒体节目的播放时间和节目传输方式。基于数字电视广播网的手机电视有3大标准：欧洲的DVB-H(Digital Video Broadcasting-Handheld)、日本的ISDB-T(Integrated Services Digital BroadcasTIng-Terrestrial)和韩国的T-DMB(Terrestrial-Digital MulTImedia BroadcasTIng)。中国的国家标准目前还没有正式颁布。

目前，T-DMB在韩国已经开通运营，已有超过30万的用户。北京、广东和上海已经在建T-DMB实验网。DVB-H在几个欧洲国家也开始运营。本文讨论的是基于数字电视广播网手机电视的方案，由TI的DM275，HOLLYWOOD DTV1OOx及TSC2110手机平台组成的移动数字电视手机方案，本方案正在开发过程中。

移动数字电视手机设计方案

移动数字电视手机包含两个分系统：DVB-H移动数字电视分系统和GSM/GPRS通信分系统，如图1所示。两个分系统以应用处理器为主机，控制DVB-H移动数字电视接收器和GSM/GPRS通信模块。

图1　移动数字电视手机方框图

移动数字电视分系统

移动数字电视系统由包含调谐器、解调器的移动数字电视接收器和应用处理器两部分组成，如图2所示。

图2　数字电视模块功能方框图

移动数字电视接收器的输入是来自于天线的射频广播信号，其输出是MPEG-2传输码流(TS)或IP数据包。它们再输入到应用处理器进行视频和音频的解压缩，并在LCD上进行显示。移动数字电视接收器与应用处理器(TI DM275)接口上的数据通信分为两类：(1)控制与状态交换。应用处理器对接收器启动程序下载、配置；接收器对应用处理器进行运行信息和状态的报告。(2)数据流。传送要解码的信道信号，包括从接收器输送给应用处理器的数字视频、数字语音和数据。上面两类数据在一个物理接口或两个物理接口上传送。物理接口模式有3种，如表1所列。

表1　物理接口模式

下面讨论接收器与应用处理器的SDIO接口方式，如图3所示。

图3　接收器以4位数据线SDIO接口方式

SDIO接口模式时，控制和状态报告及数据流都是通过SDIO来交换的，分为4位和1位数据接口模式，如表2所列。

表2　SDIO接口模式

DM275上集成的DSP内核为TMS320C54x，CPU内核为ARM7TDMI。DM275是支持H.264／MPEG-4 AVC(以下简称H.264)编解码处理的便携终端DSP，特点是集成负责MPEG-2传输码流分离处理的专用电路。

DM275是TI的TMS320DM270后续产品。内含102MHz TMS320C54x DSP处理器和88MHz ARM7TDMI微控制器双核结构。增加了分离MPEG-2传输码流的处理电路，还使得负责部分影像数据解码处理的专用电路iMX也支持H.264解码处理。

DM275的编解码处理能力如下：(1)编码处理。MPEG-4Simple Profile：640×480像素，30帧/s；MPEG-4 Advanced Simple Profile：320×480像素，30帧/s。(2)解码处理。H.264：352×288像素，30帧/s；MPEG-4 Advanced Simple Profile：720×480像素，30帧/s；MPEG-2：720×480像素，30帧/s；DivX：720×480像素，30帧/s；WMV(Windows Media Video)9：720×480像素，30帧/s。

DM275具有多种外部接口：USB、UART、MMC/SD、SPI、SDRAM、LCD。可以直接带CCD或CMOS摄像头。由于DM275灵活的编程特性和很强的信号处理能力，可以适应各种制式的移动电视标准的需要，适合移动电视多媒体手机的应用。

GSM/GPRS通信分系统

GSM/GPRS通信分系统由射频、基带构成，基带又由模拟基带和数字基带构成。基带还要控制外围电路，包括SIM卡、键盘、闪存、SRAM。电源管理、充电管理、语音的输入输出等也是由基带控制。本模块基于TEXAS INSTRUMENTS的TSC2110平台。TI的手机平台是世界上使用最为广泛的手机平台，北京首信股份有限公司在TI的手机平台上研发手机有超过5年的历史，具有丰富的TI平台开发经验。因此，选用TSC2110能够快速地集成移动数字电视手机。

GSM/GPRS通信分系统与移动数字电视分系统的连接

GSM/GPRS通信分系统和移动数字电视分系统之间的连接方式如图4所示，是将GSM/GPRS的数字基带与移动数字电视应用处理器通过16位并行数据线和17位并行地址线相连。DM275工作在外部主处理模式，GSM/GPRS数字基带通过外部主CPU接口访问DM275。DM275能够工作在旁路模式，对DM275停止供电，GSM/GPRS数字基带可以直接驱动LCD显示，减小待机功耗。

图4　GSM/GPRS通信分系统与移动数字电视分系统的连接图

移动数字电视测试方案

移动数字电视手机的测试，包括GSM/GPRS通信功能的测试和DVB-H数字电视功能的测试。GSM/GPRS通信功能的测试方案非常成熟，这里仅讨论DVB-H电视功能测试。MDTV的测试包括工作验证和性能验证。工作验证是指在理想条件下的信号的完整接收；性能验证是指在DVB-H终端的信号接收能力。

DVB-H/T工作验证基本要求

(1)播送1个电视节目的DVB-H/T信号；(2)完全MPE FEC；(3)时间分片(TIME SLICING)；(4)支持PSI/SI；(5)工作在UHF频段。对于性能验证则还需要支持VHF和L波段及插入衰减。

DVB-H/T工作验证简单装置

在DVB-H/T工作验证的简单装置中，所有数据录好存在计算机中，并传送到提供射频信号的调制器中，这个装置可以与发送内容毫无关系地来评估DVB-H/T接收器。装置如图5所示。

图5　DVB-H/T工作验证简单装置

笔记本电脑存储录好的数据流，并通过USB送到调制器。有两种结构的录制数据流：(1)为DVB-T录制的数据流。格式为MPEG-2的视频音频流封装到MPEG-2传输码流文件中，这个文件包含PSI/SI表。(2)为DVB-H录制的数据流。H.264视频和AAC音频格式封装到MPEG-2的传输码流文件中，也包含PSI/SI表。

DVB-T/H射频调制器将DVB异步比特流转化为射频信号，它执行下列功能：上变频，调制，整个DVB-H/T物理层参数的全面控制。建议使用Enensys的NN6-1161调制器。

被评估的DVB-H/T接收器通过USB或SDIO，SPI与计算机或嵌入式平台连接。计算机起两个作用：接收多媒体流并播放；诊断检索和DVB-H/T接收器的监控。安装在计算机上的软件包可以播放内容并检索诊断。软件包还容许用户监视和控制下列参数：射频调谐器参数(频率、增益等)；解调器控制参数(如FFT模式、保护间隔等)；DVB-H/T连接层(MPE-FEC)参数(如BURST大小、时间片长度等)。

DVB-H/T工作验证的高级装置

DVB-H/T工作验证的高级装置如图6所示。笔记本电脑存储录好的数据流并通过网络连接输出。数据流以H.264格式记录并通过RTP/UDP发送。IP封包器(IPE)将IP流转化为DVB异步比特流。执行下列任务：多协议封包，节包装，时间分片，PSI/SI插入。IP封包器建议使用DataPlanet的DP14502。

图6　DVB-H/T工作验证高级装置

DVB-T/H射频调制器将DVB异步比特流转化为射频信号，它执行下列功能：上变频，调制，整个DVB-H/T物理层参数的全面控制。建议使用Enensys的NN6-1161调制器。

DVB-H/T的性能验证装置

这个装置使用R&S的广播测试系统SFU，如图7所示。这个装置还可以用做控制与空中接口直接相关的信道参数的高级平台，这些参数有输出电平、衰减、射频频率扫描、衰落影响、加性噪声等。

图7　DVB-H/T的性能验证装置

R&S的广播测试系统提供完整的DVB-H/T信号，包括可以配置不同的播送模式和调制参数。测试系统输出的射频信号可以直接输入到DVB-H接收器或者传送到空中。DVB-H接收器输出的传输码流回送到广播测试系统，比较发送和接收的数据以获得中间条件下的DVB-H接收器性能。这个装置主要用于测信道衰减条件下的解码信号质量，也就是提供评价验证DVB-H接收器的性能手段。

Figure 1 Block diagram of mobile digital TV handset

Mobile digital TV subsystem

The mobile digital TV system consists of a mobile digital TV receiver including a tuner and a demodulator and an application processor, as shown in Figure 2.

Figure 2 　 Digital TV module functional block diagram

The input of the mobile digital TV receiver is the radio frequency broadcast signal from the antenna, and the output is the MPEG-2 transport stream (TS) or IP data packet. They are then input to the application processor for decompression of video and audio, and displayed on the LCD. The data communication on the interface between the mobile digital TV receiver and the application processor (TI DM275) is divided into two categories: (1) Control and state exchange. The application processor downloads and configures the startup program of the receiver; the receiver reports operating information and status of the application processor. (2) Data flow. Transmit the channel signal to be decoded, including digital video, digital voice and data sent from the receiver to the application processor. The above two types of data are transmitted on one physical interface or two physical interfaces. There are 3 physical interface modes, as listed in Table 1.

Table 1 　 Physical interface mode

The following discusses the SDIO interface between the receiver and the application processor, as shown in Figure 3.

Figure 3 　 The receiver uses a 4-bit data line SDIO interface

In SDIO interface mode, control and status reports and data streams are exchanged through SDIO, which are divided into 4-bit and 1-bit data interface modes, as listed in Table 2.

Table 2 　 SDIO interface mode

The integrated DSP core on DM275 is TMS320C54x, and the CPU core is ARM7TDMI. DM275 is a portable terminal DSP that supports H.264/MPEG-4 AVC (hereinafter referred to as H.264) encoding and decoding processing, and is characterized by integrating a dedicated circuit responsible for MPEG-2 transmission stream separation processing.

DM275 is the follow-up product of TI's TMS320DM270. Contains 102MHz TMS320C54x DSP processor and 88MHz ARM7TDMI microcontroller dual-core structure. The processing circuit for separating the MPEG-2 transmission code stream is added, and the dedicated circuit iMX responsible for the decoding processing of part of the image data also supports the H.264 decoding processing.

DM275's encoding and decoding processing capabilities are as follows: (1) Encoding processing. MPEG-4 Simple Profile: 640×480 pixels, 30 frames/s; MPEG-4 Advanced Simple Profile: 320×480 pixels, 30 frames/s. (2) Decoding processing. H.264: 352×288 pixels, 30 frames/s; MPEG-4 Advanced Simple Profile: 720×480 pixels, 30 frames/s; MPEG-2: 720×480 pixels, 30 frames/s; DivX: 720×480 Pixels, 30 frames/s; WMV (Windows Media Video) 9: 720×480 pixels, 30 frames/s.

DM275 has a variety of external interfaces: USB, UART, MMC/SD, SPI, SDRAM, LCD. Can directly bring CCD or CMOS camera. Due to the flexible programming features and strong signal processing capabilities of DM275, it can adapt to the needs of various mobile TV standards and is suitable for mobile TV multimedia mobile phone applications.

GSM/GPRS communication subsystem

The GSM/GPRS communication subsystem is composed of radio frequency and baseband. The baseband is composed of analog baseband and digital baseband. The baseband also controls the peripheral circuits, including the SIM card, keyboard, flash memory, and SRAM. Power management, charging management, voice input and output, etc. are also controlled by the baseband. This module is based on the TSC2110 platform of TEXAS INSTRUMENTS. TI's mobile phone platform is the most widely used mobile phone platform in the world. Beijing Capitel Co., Ltd. has developed mobile phones on TI's mobile phone platform for more than 5 years and has rich experience in TI platform development. Therefore, choosing TSC2110 can quickly integrate mobile digital TV phones.

Connection of GSM/GPRS communication subsystem and mobile digital TV subsystem

The connection method between the GSM/GPRS communication subsystem and the mobile digital TV subsystem is shown in Figure 4. It is to connect the GSM/GPRS digital baseband and the mobile digital TV application processor through a 16-bit parallel data line and a 17-bit parallel address line. Connected. DM275 works in the external main processing mode, and the GSM/GPRS digital baseband accesses DM275 through the external main CPU interface. DM275 can work in bypass mode, stop power supply to DM275, GSM/GPRS digital baseband can directly drive LCD display to reduce standby power consumption.

Figure 4 　 GSM/GPRS communication subsystem and mobile digital TV subsystem connection diagram

Mobile digital TV test plan

The testing of mobile digital TV phones includes GSM/GPRS communication function testing and DVB-H digital TV function testing. The test plan of GSM/GPRS communication function is very mature, only discuss DVB-H TV function test here. MDTV testing includes work verification and performance verification. Work verification refers to the complete reception of signals under ideal conditions; performance verification refers to the signal reception capability of the DVB-H terminal.

Basic requirements for DVB-H/T work verification

(1) Broadcast a DVB-H/T signal of a TV program; (2) Complete MPE FEC; (3) Time SLICING; (4) Support PSI/SI; (5) Work in UHF frequency band. For performance verification, support for VHF and L bands and insertion attenuation are also required.

DVB-H/T work verification simple device

In a simple device for DVB-H/T work verification, all data is recorded in a computer and transmitted to a modulator that provides radio frequency signals. This device can evaluate DVB-H/T reception regardless of the content of the transmission. Device. The device is shown in Figure 5.

Figure 5 　 DVB-H/T work verification simple device

The notebook computer stores the recorded data stream and sends it to the modulator via USB. There are two types of recorded data streams: (1) The recorded data stream for DVB-T. The video and audio stream in the format of MPEG-2 is encapsulated into an MPEG-2 transport stream file, which contains the PSI/SI table. (2) Data stream recorded by DVB-H. H.264 video and AAC audio formats are encapsulated into MPEG-2 transport stream files, and PSI/SI tables are also included.

The DVB-T/H radio frequency modulator converts the DVB asynchronous bit stream into a radio frequency signal. It performs the following functions: up-conversion, modulation, and comprehensive control of the entire DVB-H/T physical layer parameters. It is recommended to use Enensys' NN6-1161 modulator.

The DVB-H/T receiver being evaluated is connected to a computer or embedded platform via USB or SDIO, SPI. The computer plays two roles: receiving and playing multimedia streams; diagnostic retrieval and monitoring of DVB-H/T receivers. The software package installed on the computer can play content and retrieve diagnostics. The software package also allows users to monitor and control the following parameters: RF tuner parameters (frequency, gain, etc.); demodulator control parameters (such as FFT mode, guard interval, etc.); DVB-H/T connection layer (MPE-FEC) parameters (Such as BURST size, time slice length, etc.).

Advanced device for DVB-H/T work verification

The advanced device for DVB-H/T work verification is shown in Figure 6. The notebook computer stores the recorded data stream and outputs it through a network connection. The data stream is recorded in H.264 format and sent via RTP/UDP. IP packetizer (IPE) converts IP streams into DVB asynchronous bit streams. Perform the following tasks: multi-protocol packaging, section packaging, time slicing, PSI/SI insertion. It is recommended to use DataPlanet's DP14502 for the IP packetizer.