Development of Software for Ephemeris Data Generation, Transmission and Reception via DVB-T2

Vektor, an R&D center based in Russia, commissioned Promwad to develop special software for a simulator to generate, transmit and receive high-precision ephemeris time data via DVB-T2.

The designed system uses a ready-made network of television towers as base stations to calculate navigational corrections and transmit them over the air. The software helps test simulators in different modes of operation to ensure required values for communication range, data transmission speed and delay.
 

Customer

Vector, a specialized experimental design house for systems and measuring tools, engaged in R & D in telematics, as well as manufacturing, introduction and maintenance of telematics equipment.
 

Objective

Development of special software (SS) for a simulator for generating, transmitting and receiving high-precision ephemeris data (ED) via a digital television broadcasting channel, DVB-T2.
 

Solution

1. Development stages

The development process involved several stages.

Stage 1

Creation of a working prototype of a system for transmitting GPS / GLONASS navigation corrections (ED – high-precision ephemeris data) over a DVB-T2 channel. Adjustment and testing of basic modes of operation. Experimental testing in different modes of operation to make sure the required performance for communication distance and data rate is achieved. Creation of operational and program documentation.

The hardware and software complex should provide the following functions:

  • Generation a transport stream in real time, which would contain at least one TV program and a data stream of navigation information packed in DSM CC sections
  • Emission (transmission) of generated DVB-T2 data
  • Reception of DVB-T2 data
  • Extraction of navigation information and the TV program from the digital stream
  • Sending the customer navigation corrections
     

Stage 2

Development of special software (SS) for a simulator for generating, transmitting and receiving IP packets of digital networks over the DVB-T2 channel, name code “Gateway DVB-T2 SS”.

This special software should provide the following functions:

  • Generation of a transport stream in real time, which would contain at least one TV program and a data stream of navigation information packed in DSM CC sections, including IP packets routed to a special virtual network interface
  • Emission (transmission) of generated DVB-T2 data
  • Reception of DVB-T2 data
  • Extraction of transmitted IP packets from the digital stream
  • Forwarding received network packets to the customer through a physical network interface
  • IP traffic should be transmitted at a speed of no less than 10 Mbit / sec for IP packets of 1,480 bytes
     

2. Functional diagram of the solution

Diagram 1. Correction transmission system prototype (ephemeris data — ED)
 
 
The system consists of the following functional units:
  • Multiplexer (generates a transport stream in real time)
  • Modulator (transmits a generated DVB-T2 stream over the air)
  • TV STB (receives a DVB-T2 stream over the air, plays it, extracts navigation information from the stream and transmits it)
  • Test PC (simulates the source and receiver of navigation information and is also used to control the modulator)

Diagram 2. DVB-T2 SS Gateway Layout

 

3. Hardware

A special feature about the hardware part of the system is that it uses the STiH251-HDK, a standard evaluation board, as an STB; the TVB597A, a third-party hardware and software complex, as a modulator; and a standard PC as a multiplexer and the source and receiver of navigation data. In addition, the system was tested using the Javad JNS100GG base station and the NAVIS NV08 navigation receiver.
 

4. Software

The special features of the software multiplexer are:

  • Encapsulation of navigation corrections into packets according to the sequence: UDP - IP - MPE – TS
  • Generation of a specific program for the data stream
  • Data buffering before sending in order to reduce the repetition rate of TS data packets (because the STB packet filter cannot handle  the stream of ~> 1,000 packets / sec)
  • Sending buffered data if there are no new data coming for a certain time
  • Automatic start-up of the multiplexer and the modulator when the PC multiplexer is enabled  
  • Automatic installation of multiplexer and modulator software

The modulator software was further improved to add PEPI stream playback. In other respects, the modulator software was used without modification.

The special features of the STB software are:

  • Use of software for a home digital TV STB design, as base software
  • Use of the PTI subsystem for data stream reception
  • Use of two streams for data reception and transmission
  • Automatic adaptation of STB basic firmware

Test versions of the modulator and STB software were developed to test transmission delays. The test version of modulator software was created in two versions - one with double-stream processing (navigation data reading stream and multiplexer stream) and the other with non-blocking data reading.

The second stage involved the creation of an IP DVB-T2 gateway prototype based on developed the technology. IP packets are received and sent by means of traffic routing with the Linux kernel through TUN virtual interfaces on the transmitting and receiving side. High-speed transmission is ensured through data buffering on the sending side, as well as through sending data in DVB-T2 sections of 3KB.
 

Advantages

  • Experimental testing is possible for simulators in different operational modes in order to ensure that the requirements for communication range, data rate and data transmission delay are achieved
  • The designed system helps use the existing network of TV towers as base stations for navigation corrections calculation and their transmission over the air

 

Interfaces and technologies

DVB-T/T2, MPEG2-TS, UDP, MPE

Software

STLinux-2.4, kernel-2.6.32, STAPISDK-A38.1