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Design Notes

Digital Video Broadcasting (DVB) System

Terrestrial (DVB-T) and Handheld (DVB-H)

This example illustrates a DVB transmitter, based on the ETSI EN 300 744, V 1.5.1 (2004-06) technical specifications, and a typical receiver implementation.

Configuration of the DVB Transmitter parameters is described below.

- TRANSMISSION_MODE determines the inner interleaving (Section 4.3.4) and signal constellation and mapping (Section 4.3.5). Available options are:

            - QPSK Non-hierarchical

            - 16QAM Non-hierarchical

            - 64QAM Non-hierarchical

            - 16QAM Hierarchical

            - 64QAM Hierarchical

- OPERATION_MODE is defined in Section 4.1 and can be set to:

            - 2K

            - 4K

            - 8K

            2K and 8K modes are defined for both DVB-T and DVB-H. 4K mode is used exclusively in DVB-H systems and is defined in Annex F.

- RANDOMIZE can disable randomization of input data, which may be useful for testing purposes. This is achieved by setting the RANDOMIZE parameter to Off.

- CODE_RATE determines the rate of the convolutional inner encoder. Available rates are:

            - 1/2

            - 2/3

            - 3/4

            - 5/6

            - 7/8

- MOD_ALPA determines constellation proportions (Section 4.3.5). It is always 1 for Non-hierarchical modes, so in this case it is ignored. The available settings for Hierarchical modes are:

            - 1

            - 2

            - 4

- CHANNEL_BW defines the standard channel spacing defined in Section 4.1. Available options are:

            - 8 MHz

            - 7 MHz

            - 6 MHz

            - 5 MHz

            5 MHz channel spacing is defined for use outside the traditional broadcast bands and parameters for operating with such spacing are given in Annex G.

- G determines the guard interval for the OFDM modulation. The available options are:

            - 1/4

            - 1/8

            - 1/16

            - 1/32

- TX_OUT_LEVEL determines the output level of the transmitter and is defined in units defined in Options/Project Options/Global Units, in the Power window.

- TX_CARRIER_FREQ determines the carrier frequency in units defined in Options/Project Options/Global Units, in the Frequency entry.

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Configuration of the DVB Receiver parameters is described below.

- TRANSMISSION_MODE determines the inner interleaving (Section 4.3.4) and signal constellation and mapping (Section 4.3.5). Available options are:

            - QPSK Non-hierarchical

            - 16QAM Non-hierarchical

            - 64QAM Non-hierarchical

            - 16QAM Hierarchical

            - 64QAM Hierarchical

- OPERATION_MODE is defined in Section 4.1 and can be set to:

            - 2K

            - 4K

            - 8K

            2K and 8K modes are defined for both DVB-T and DVB-H. 4K mode is used exclusively in DVB-H systems and is defined in Annex F.

- RANDOMIZE can disable randomization of input data, which may be useful for testing purposes. This is achieved by setting the RANDOMIZE parameter to Off.

- DEC_TYPE determines the decision type used in the receiver. Available options are:

            - Soft Decisions

            - Hard Decisions

- TRACEBACK determines the traceback length used in the Viterbi decoder.

====================================================================

This example implements a typical DVB Receiver with Soft or Hard Decision decoding. Bit Error Rate is measured for both data sources. For Hierarchical modes, the second BER block should be enabled and the first one disabled. The BER is plotted vs. the total signal power used for both data sources.

The test bench is mainly designed for BER evaluations. It also monitors the following measurements:

• TX spectrum at the output of the transmitter and at the input of the receiver

• IQ constellation at the the transmitter (before OFDM modulation)

• OFDM subcarriers at the transmitter (before OFDM modualtion)

Please note that BER measurements will run faster if these measurements are disabled.

Note: Data Source 2 is used only in Hierarchical transmission modes.  Furthermore, relative SNR for Data Source 1 and Data Source 2 depends on the particular Transmission Mode and Alpha paramter, and is different for each source.  Hence, the BER curves will reach lower BER values at different regions of the Total Signal Power axis.  It is recommended that BER_EXT modules on the main system diagram are enabled one at a time so that the BER simulation runs faster.

System Diagram - DVB System

Graph - TX Spectrum

Graph - OFDM Subcarriers

Graph - IQ Constellation

Graph - BER