"There are three kinds of mobile TV. One is based on analog TV broadcasting network, the other is based on mobile communication network, and the other is based on digital broadcasting network. The first scheme is to add an analog TV module to the mobile phone to receive analog TV broadcasting programs. Due to the unsatisfactory effect, it is not easy to be accepted by consumers. The schemes based on mobile communication network are divided into unicast scheme based on 2.5G mobile communication network and multicast scheme based on 3G mobile communication network. The unicast scheme uses the 3GPP standard video format and provides on-demand, live and rotation services through the streaming media server, such as the WAP Portal of China Mobile and China Unicom. The multicast scheme, such as mediaflo of Qualcomm, calculates the load of the mobile network, carries out reasonable network scheduling, and controls the playing time and transmission mode of media programs. There are three major standards for mobile TV based on digital TV broadcasting network: DVB-H (digital video broadcasting handheld) in Europe, ISDB-T (integrated services digital broadcasting terrestrial) in Japan and T-DMB (terrestrial digital multimedia broadcasting) in Korea. China's national standards have not been officially promulgated yet. At present, T-DMB has been put into operation in Korea and has more than 300000 users. T-DMB experimental networks are already under construction in Beijing, Guangdong and Shanghai. DVB-H is also operational in several European countries. This paper discusses the mobile digital TV mobile phone scheme based on digital TV broadcasting network, which is composed of TI's dm275, Hollywood dtv1oox and tsc2110 mobile phone platform. This scheme is under development. Design scheme of mobile digital TV mobile phone mobile digital TV mobile phone includes two subsystems: DVB-H mobile digital TV subsystem and GSM / GPRS communication subsystem, as shown in Figure 1. The two subsystems take the application processor as the host to control DVB-H mobile digital TV receiver and GSM / GPRS communication module. Fig. 1 block diagram of mobile digital TV mobile phone mobile digital TV subsystem mobile digital TV system is composed of mobile digital TV receiver and application processor including tuner and demodulator, as shown in Fig. 2. Fig. 2 functional block diagram of digital TV module the input of mobile digital TV receiver is RF broadcast signal from antenna, and its output is MPEG-2 transmission code stream (TS) or IP packet. They are then input to the application processor for video and audio decompression and displayed on the LCD. The data communication on the interface between mobile digital TV receiver and application processor (Ti dm275) can be divided into two categories: (1) control and state exchange. The application processor downloads and configures the receiver startup program; The receiver reports the operation information and status of the application processor（ 2) Data flow. Transmit channel signals to be decoded, including digital video, digital voice and data transmitted 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 three physical interface modes, as listed in Table 1. Table 1 physical interface mode SDIO interface mode between receiver and application processor is discussed below, as shown in Figure 3. Fig. 3 when the receiver adopts 4-bit data line SDIO interface mode, control, status report and data flow are exchanged through SDIO, which is divided into 4-bit and 1-bit data interface modes, as listed in Table 2. Table 2 DSP core integrated on SDIO interface mode dm275 is TMS320C54x and CPU core is ARM7TDMI. Dm275 is a portable terminal DSP supporting h.264/mpeg-4 AVC (hereinafter referred to as H.264) codec processing. It is characterized by integrating a special circuit responsible for MPEG-2 transmission code stream separation processing. Dm275 is a subsequent product of TI's tms320dm270. It contains 102mhz TMS320C54x DSP processor and 88mhz ARM7TDMI microcontroller dual core structure. The processing circuit for separating MPEG-2 transmission code stream is added, and the special circuit IMX responsible for decoding some image data also supports H.264 decoding processing. The encoding and decoding processing capabilities of dm275 are as follows: (1) encoding processing. MPEG-4Simple 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 and LCD. It can be directly equipped with CCD or CMOS camera. Due to its flexible programming characteristics and strong signal processing ability, dm275 can meet the needs of various mobile TV standards and is suitable for the application of mobile TV multimedia mobile phones. GSM / GPRS communication subsystem GSM / GPRS communication subsystem consists of RF and baseband, and baseband consists of analog baseband and digital baseband. Baseband also controls peripheral circuits, including SIM card, keyboard, flash memory and SRAM. Power management, charging management, voice input and output are also controlled by baseband. This module is based on tsc2110 platform of Texas Instruments. Ti's mobile platform is the most widely used mobile platform in the world. Beijing Shouxin Co., Ltd. has developed mobile phones on TI's mobile platform for more than 5 years and has rich experience in Ti platform development. Therefore, the selection of tsc2110 can quickly integrate mobile digital TV mobile phones. Connection between GSM / GPRS communication subsystem and mobile digital TV subsystem the connection mode between GSM / GPRS communication subsystem and mobile digital TV subsystem is shown in Figure 4. The digital baseband of GSM / GPRS and mobile digital TV application processor are connected through 16 bit parallel data line and 17 bit parallel address line. The dm275 operates in the external main processing mode, and the GSM / GPRS digital baseband accesses the dm275 through the external main CPU interface. Dm275 can work in bypass mode and stop power supply to dm275. GSM / GPRS digital baseband can directly drive LCD display to reduce standby power consumption. Figure 4 connection diagram between GSM / GPRS communication subsystem and mobile digital TV subsystem mobile digital TV test scheme mobile digital TV mobile phone test, including GSM / GPRS communication function test and DVB-H digital TV function test. The test scheme of GSM / GPRS communication function is very mature. Only DVB-H TV function test is discussed 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 receiving capability of DVB-H terminal. Basic requirements for DVB-H / t work verification (1) broadcast DVB-H / T signal of one TV program（ 2) Full MPE FEC（ 3) Time slicing（ 4) Support PSI / Si（ 5) It works in UHF band. For performance verification, it is also necessary to support VHF and L-band and insertion attenuation. Simple device for DVB-H / t work verification in the simple device for DVB-H / t work verification, all data is recorded and stored in the computer and transmitted to the modulator providing RF signal. This device can evaluate the DVB-H / T receiver regardless of the transmission content. The device is shown in Figure 5. Figure 5 DVB-H / t work verification simple device laptop stores the recorded data stream and sends it to the modulator through USB. There are two kinds of recorded data streams: (1) recorded data stream for dvb-t. The video and audio stream in MPEG-2 format is encapsulated into the MPEG-2 transmission code stream file, which contains psi / Si table（ 2) Data stream recorded for dvb-h. H. 264 video and aac audio formats are encapsulated into MPEG-2 transmission stream files, and PSI / Si tables are also included. DVB-T / h RF modulator converts DVB asynchronous bit stream into RF signal. It performs the following functions: up conversion, modulation and overall control of the parameters of the whole DVB-H / T physical layer. It is recommended to use enensys nn6-1161 modulator. The evaluated DVB-H / T receiver is connected to the computer or embedded platform through USB or SDIO, SPI. The computer plays two roles: receiving and playing multimedia streams; Diagnostic retrieval and monitoring of DVB-H / T receiver. Packages installed on your computer can play content and retrieve diagnostics. The software package also allows the user to monitor and control the following parameters: RF tuner parameters (frequency, gain, etc.); Demodulator control parameters (such as FFT mode, protection 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 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 through RTP / UDP. IP packetizer (IPE) converts IP stream into DVB asynchronous bit stream. Perform the following tasks: multi protocol packet, section packaging, time slicing, PSI / Si insertion. Dp14502 of dataplanet is recommended for IP packer. Figure 6 DVB-H / t work verification advanced device DVB-T / h RF modulator converts DVB asynchronous bit stream into RF signal. It performs the following functions: up conversion, modulation and overall control of the parameters of the whole DVB-H / T physical layer. It is recommended to use enensys nn6-1161 modulator. DVB-H / T performance verification device, which uses R & s broadcast test system SFU, as shown in Figure 7. The device can also be used as an advanced platform for controlling channel parameters directly related to the air interface, such as output level, attenuation, RF frequency scanning, fading effect, additive noise, etc. Fig. 7 the broadcast test system of the DVB-H / T performance verification device R & S provides a complete DVB-H / T signal, including different broadcast modes and modulation parameters. The RF signal output by the test system can be directly input to the DVB-H receiver or transmitted to the air. The transmission code stream output by the DVB-H receiver is sent back to the broadcast test system, and the transmitted and received data are compared to obtain the performance of the DVB-H receiver under intermediate conditions. This device is mainly used to measure the decoded signal quality under the condition of channel attenuation, that is, to provide a means to evaluate and verify the performance of DVB-H receiver., Technology Zone
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