The Design And Implementation Of The Multi-frequency Multi-standard Digital TV Drive Test System

In recent years, the development of digital television was fast, more and more people begin to pay attention to it. Terrestrial digital TV is a type of digital TV system, whose program transmission depends on single-frequency or SFN (single-frequency network) and the terminal demodulation with STB. China’s national standard DTMB and multimedia broadcasting CMMB is building the network and is in an application stage. It has covered most of the first-tier cities and is being extended to the second and third tier cities. With the increase in coverage requirements, we need to bulid a system and continued to network debugging, network optimization, network maintenance, etc. So the test has become one of the important aspects of network conditions. In this paper, based on single frequency network, combined with the demand for network coverage testing, achieved a drive test system with network coverage simulation, real-time multi-frequency multi-format signal acquisition and data processing.First the paper researched the system architecture and the key technology of China DTMB terrestrial digital TV and multimedia broadcasting CMMB system. Then made a presentation on their networking mode, terrestrial digital television transmission channel and propagation model.Followed by in-depth study of single frequency network coverage, simulated the single frequency network coverage area. Basis on the theory of single-frequency network coverage, complete the coverage area of simulation methods and algorithms.Finally, designed and completed the drive test systems. The drive test system is consists of three parts, they are covering analog part, signal measurement part and data processing part. Coverage simulation was completed based in part of the theory of a single frequency network. Signal measurement part using a GPS receiver, the DTMB receivers, CMMB receiver and spectrum analyzer as hardware data acquisition equipment, and the personal computer as a data receiving and processing software platform. In software systems use USB and serial interface to acquire data. Use pictureBox controls and GDI+technology to complete electronic map and to achieve data storage by DataTable and file reading and writing. The whole systems use the multi-threading technology. Part of the data processing has used WebGIS technology based on Google map API. The various modules of the system closely integrated together to achieve the goal of terrestrial digital television network coverage testing.The designed Digital TV drive test system is of great operation, stability, and high reliability. At the same time it has a coverage prediction function can help testers to determine the test route, greatly reducing the test blindness. And its multi-standard multi-frequency measurement characteristics at the same time improve the efficiency of the testing, At last, the powerful data processing help testers faster to identificate of network coverage. The system can fully applied to our terrestrial digital TV and multimedia broadcast television network testing, which is important for the development of China’s terrestrial digital TV.