Seamless Indoor/Outdoor Positioning Using Digital Television Terrestrial Broadcasting (DTMB) Technology Integrated with GNSS

Jinsong Xu, Xiaochun Lu, Haitao Wu, Decai Zou

Abstract: Compare with outdoor positioning, indoor positioning has been overlooked by many investigators. While GNSS can be made to work indoors, the lower signal levels and poor multipath environment mean that performance is much worse than outdoors, and in some places there is no coverage at all. Indoor GNSS and cell-phone bearer positioning will be in general use for emergency calls from mobiles (E911/E112), but with an accuracy close to 100 m (which is sufficient for this particular service). In contrast to the GPS, the DTV signals are received from transmitters at relatively short distance, while the broadcast transmitters operate at levels up to the megawatts effective radiated power (ERP). Also the RF frequency of the DTV signal is much lower than the GPS, which makes it easier for the signal to penetrate buildings and other objects. So it is suitable for the precision positioning inside the building and the city center. The digital television terrestrial broadcasting (DTMB) is one of important standard about DTV, which is regulated by the national standard GB2006-20600. DTMB transmission system using time domain synchronous orthogonal frequency division multiplexing (TDS innovation OFDM) of single and multicarrier modulation. This modulation mainly for broadband transmission channel characteristics of terrestrial digital multimedia television broadcasting can achieve good performance in linear time-varying transmitter channel or frequency selective and time selective exist at the same time channel. Pseudo-random sequence (PN) is introduced in DTMB signal frame header, DTMB signal has more stronger correlation than other DTV standards. So DTMB is more suitable for precise indoor positioning. Integration of DTMB with GNSS can provide a seamless transition from outdoor to indoor position and vice-versa. The ranging accuracy expected from DTMB systems is expected to be better than 1m in severe multipath environments. The paper describes the concept of using the DTMB signal for indoor positioning and how it is proposed to ensure seamless operation with GNSS and crucial techniques of positioning system based on digital television terrestrial broadcasting is researched. Firstly, it proposal one acquisition and tracking method based on DTMB digital TV signal and the infrastructure of indoor positioning system based on DTMB is given. The operating principle of the indoor positioning system is very similar to that of a GNSS. Fixed terminals transmit accurately timed signals, along with information about the terminal’s location and the transmission time. The handset has both GNSS and indoor DTMB receiving terminals, and uses either or both so that the positioning service is seamless. Secondly, it analyzes the DTMB system structure and signal frame structure, and takes an example as PN420 mode to research the relationship of signal frame head original function. PN sequence in DTMB signals should be used for position location and multipath estimation under some circumstances. However, large position location error may be introduced when there is co-channel interference in the DTMB signal. In the presence of co-channel interference, multipath estimation is actually the linear combination of the multipath channel responses from all the DTMB transmitters on the same channel, since an identical PN sequence is used for all co-channel DTMB transmitters. Thirdly, the receiver design in baseband is fulfilled by analyzing the operation principle of receiver and validated on Xilinx Virtex-5 FPGA. Some key receiver techniques in baseband includes the digital filtering signal tracking, carrier tracking and code tracking, FIR filter and raise cosine filter is investigated. Based on some advantages of Field Programmable Gate Array (FPGA), Implementation of the receiver in baseband is used on FPGA hardware platform. Finally, the positioning result combined with the GNSS and the DTMB signal is achieved. The result is shown that the positioning combined with satellite navigation signal and the DTMB signal is precise in the complex city environments. It provides that combined positioning system with GNSS and digital television terrestrial broadcasting signal is realizable in complex circumstance of city.
Published in: Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014)
September 8 - 12, 2014
Tampa Convention Center
Tampa, Florida
Pages: 1646 - 1651
Cite this article: Xu, Jinsong, Lu, Xiaochun, Wu, Haitao, Zou, Decai, "Seamless Indoor/Outdoor Positioning Using Digital Television Terrestrial Broadcasting (DTMB) Technology Integrated with GNSS," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 1646-1651.
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