Application Note HARRIS - DTC-98053D. March 2002

Transcription

1 REMOTE CONTROL OF THE DVB-T COFDM MODULATORS FROM THE MULTIPLEXING SITE NIT UPDATE OPTION HARRIS - DTC-98053D March 2002 Centre Espace Performance-Alphasis-F SAINT GREGOIRE CEDEX Tel:+33 (0) Fax:+33 (0) itis@harris.com

2 INTRODUCTION With the non stop development of the DVB-T market, the networks are becoming more and more important in terms of number of equipment and the operators look for some flexible tools to configure and control the entire network. HARRIS has implemented some specific designs dedicated to control any COFDM modulators (VCAST) from the multiplexing site (from the VSFN adapter). DVB-T NETWORK ORGANIZATION The DVB-T network consists of several COFDM Modulators, located on different transmitter sites. In case of a Single Frequency Network (SFN), the SFN adapter is required to insert into the MPEG-TS stream some time information, needed to align the different transmitter signal. VIDEO SOURCE MPEG-2 ENCODER COFDM ENCODER V-CAST UHF TRANSMITTER VIDEO SOURCE MPEG-2 ENCODER MPEG-2 MUX SFN ADAPTER DISTRIBUTION NETWORK DVB-T RECEIVER V-TER MPEG-2 DECODER VIDEO MONITOR VIDEO SOURCE MPEG-2 ENCODER COFDM ENCODER V-CAST UHF TRANSMITTER DVB group has defined a specific MPEG packet, called the Mega-Frame Initialization Packet (MIP), which carries the different time information requested to synchronize the transmitter. Moreover, the MIP packet definition enables to control the COFDM modulators from the multiplexing site. The MIP control can be used in MFN networks to configure all the CODM modulators from a single point, or in a SFN to control modulators and to ensure the time synchronization. REQUIREMENTS TO REMOTE CONTROL THE COFDM MODULATOR Flexibility to perform the DVB-T testing Because the DVB-T system is quite new, the network operator focus on making some field tests to measure its performances for several configurations. The goal is to provide a good reception quality with the maximum useful bit rate. The large number of the DVB-T parameters (FFT size, Guard Interval, Coding rate, Constellation type,...) makes this kind of tests very complex. Each time any change is required, the SFN adapter and all the COFDM modulators have to be reconfigured. DVB-T installation and tuning is now easier and faster The DVB-T SFN tuning consists in adjusting the internal delays of the COFDM modulators to ensure the best reception results on the coverage area. In practice, the reception quality is measured at different places of the coverage area and the static delay of the COFDM modulators may be adjusted to ensure the best performance. Page 2/10 DTC98053D.doc March 2002

3 Each transmitter may be muted in order to measure the SFN behaviour. During this set-up, it is very suitable to be able to remote control all the COFDM modulators from a unique site. Thanks to the Remote Control from MIP packet, the installation and the set-up of the SFN become easier and faster. For the DVB-T tuning, the main applications of the remote control are : Adjust the Static Delay of each transmitter Mute the transmitter (i.e. mute the COFDM modulator IF output) Change the DVB-T mode Switch the COFDM modulator into the test mode (local PRBS or Test Pattern Insertion) Enable/Disable the SFN mode to make a single transmitter test THE MIP PACKET DEFINITION The MIP packet has been defined in the TS V1.1.2 document from DVB group. Several parameters have been specified and are dedicated to be sent to the COFDM modulator according different fields : FIELD Parameter type Implemented in VCAST Synchronization_ID MFN/SFN Yes TPS_MIP Constellation Yes Hierarchy Information Yes Code rates (HP & LP) Yes Guard Interval Yes Transmission mode Yes RF channel Bandwidth Yes Priority of the transport stream Optional parameters Time Offset Optional Yes Frequency Offset Optional No Power function Optional No Function Proprietary functions Yes Yes HARRIS IMPLEMENTATION HARRIS has implemented the control of VCAST from the MIP packet in order to provide the maximum flexibility for the user. This feature is available from the version shown below : VCAST FIRMWARE V1.30 VCAST-OPE Software V1.10 VSFN FIRMWARE V1.10 VSFN-OPE Software V1.10 In order to cope with the other different ways to control VCAST (manual, remote via RS232), an Authorization Table is created. The VCAST parameters are gathered into Group of functions and the Authorization Table specifies the source to control each of them. This mode is called the Partial Remote Control. From the SFN adapter it is possible to force VCAST into the remote control from MIP mode. In that case all the functions are controlled from MIP. This mode is identified as the Total Remote Control. March 2002 DTC98053D.doc Page 3/10

4 Addressing VCAST Any VCAST can be addressed individually thanks to the standardized Transmitter Identifier field. This field consists of 16 bits set to during factory tests. The user must set its own identifier to enable the individual control of the equipment. use VCAST-OPE/OPERATION/SYSTEM CONFIG menu, use the front panel VCAST Control Modes There are three different modes to control VCAST : Manual Mode : VCAST configuration is locally set from the front panel RS232 Mode : VCAST configuration is set from the VCAST-OPE software (direct or remote link) MPEG2-TS Mode : This mode is set in pair with one of the previous modes. It authorizes some parameters to be controlled from the MIP packets according to the Authorization Table, defined by the user (Partial Remote Control). In case the control from MIP is forced from VSFN (Total Remote Control), this mode is automatically enabled. VCAST Authorization Table This table defines the way one specific Group of Function is configured (RS232/MANUAL or MPEG2-TS). The user must set-up this table before starting the remote control from MIP. use VCAST-OPE/OPERATION/SYSTEM CONFIG menu The source of every Groups of Function is set to Manual/RS232 during factory tests. HARRIS Group of Function Appendix A presents the VCAST parameters which are gathered into Group of Functions. A large number of private functions have been developed in order to provide the full remote control of the equipment. Moreover the three following functions are necessary to change the VCAST control mode from VSFN : Function Restriction Comments Equipment Control No restriction Changes the control mode via MIP. Transmitter Identifier MPEG2-TS Mode Changes the Transmitter Identifier via MIP Authorization Table Setup MPEG2-TS Mode Sets or resets the Authorization Table via MIP These specific functions are not part of the Group of Function table because they are not controlled from the Authorization Table. Page 4/10 DTC98053D.doc March 2002

5 APPLICATION 1 : PARTIAL REMOTE CONTROL V-SFN DISTRIBUTION NETWORK V-CAST TRANSMIT RS232 RS232 VCAST PRELIMINARY SET-UP : 1 Switch to RS232 Control Mode 2 Set the specific Transmitter Identifier 3 Configure the Authorization Table 4 Enable the MPEG-TS Control Mode VSFN-OPE VCAST-OPE The Partial Remote Control authorizes to configure some parameters of the VCAST from VSFN. It means that the other parameters are still set from either the front panel (Manual Mode) or from VCAST-OPE (RS232 Mode). On each VCAST, the transmitter Identifier must be defined (use the front panel or the OPE s/w) and the Authorization T able must be set-up (can only be done with the OPE s/w). Example : Control the Static Delay from MIP (Partial Remote Control) A- Preliminary configuration of VCAST A.1 Run VCAST-OPE software A.2 Switch VCAST mode to RS232 (OPERATION/SYSTEM CONFIG/CONTROL = RS232) A.3 Check the Transmitter Identifier (OPERATION/SYSTEM CONFIG) A.4 Select the Group of Functions relative to the Static Delay adjustment (OPERATION/SYSTEM CONFIG/GROUP OF PARAMETERS/NETWORK MANAGEMENT) A.5 Enable the control from MIP (MPEG2-TS VIA MIP + CHANGE) A.6 Switch VCAST mode to RS232/MANUAL + MPEG2-TS (OPERATION/SYSTEM CONFIG/CONTROL) B- Static Delay Adjustment from VSFN B.1 Run VSFN-OPE software B.2 Add a new parameter into MIP (OPERATION/NETWORK SETTINGS/ADD/MIP FUNCTION MENU) B.3 Specify the Transmitter Identifier and the label (MIP FUNCTION MENU) B.4 Define the function : SEND MODE = ONE SHOT(*) GROUP OF FUNCTION = NETWORK MANAGEMENT FUNCTION = STATIC DELAY VALUE = XXXX µs B.5 Download the PC data base into VSFN (OPERATION/NETWORK SETTINGS/DOWNLOAD) (*) SEND MODE : Specifies the periodicity of the parameter (DISABLED/SINGLE SHOT/REPETITIVE) March 2002 DTC98053D.doc Page 5/10

6 APPLICATION 2 : TOTAL REMOTE CONTROL V-SFN DISTRIBUTION NETWORK V-CAST TRANSMIT RS232 NO VCAST PRELIMINARY SET-UP VSFN-OPE The Total Remote Control consists in forcing VCAST into the control mode from MIP. In other words, it consists in setting the MPEG2-TS source in the VCAST Authorization Table for every functions. This is useful when the user doesn t want to make any specific local configuration on VCAST. All the VCAST configuration is done from the MIP parameters specification in the VSFN-OPE software. In that case, the specific private function AUTHORIZATION TABLE is used as follow : VALUE Forbid Config via MIP Full Config via MIP Restricted Configuration via MIP Disable the control from MIP Comments VCAST configuration is set from PC (RS232) or from the front panel VCAST can be fully configured from the MIP function. The private function of the DVB-T settings group are disabled to avoid any interference with the MIP mandatory section Disable the control from the Optional and MIP functions Enable the control from the MIP private function Note : If a parameter is not specify by MIP, the value specified from the Front Panel (Manual mode) or from the PC (RS232 Mode) is kept. Example1 : Control the DVB-T Mode of all VCAST using the MIP field B- Enable VCAST control from MIP B.1 Run VSFN-OPE software B.2 Add a new parameter into MIP (OPERATION/NETWORK SETTINGS/ADD/MIP FUNCTION MENU) B.3 Specify the Transmitter Identifier and the label (MIP FUNCTION MENU) B.4 Enable the control of the VCAST from MIP : SEND MODE = ONE SHOT GROUP OF FUNCTION = PRIORITY FUNCTION = EQUIPMENT CONTROL VALUE = ENABLE MPEG2-TS VIA MIP Page 6/10 DTC98053D.doc March 2002

7 C- Force the Authorization Table to MPEG2-TS (full control) Remote control of the DVB-T COFDM Modulators C.1 Add a new parameter into MIP (OPERATION/NETWORK SETTINGS/ADD/MIP FUNCTION MENU) C.2 Specify the Transmitter Identifier and the label (MIP FUNCTION MENU) C.3 Define the function : SEND MODE = ONE SHOT GROUP OF FUNCTION = PRIORITY FUNCTION = AUTHORIZATION TABLE VALUE = FULL CONFIGURATION VIA MIP C.4 Download the PC data base into VSFN (OPERATION/NETWORK SETTINGS/DOWNLOAD) The mode specified for the SFN adapter is sent through the MIP section to VCAST. When the user changes the SFN DVB-T mode, VCAST automatically reconfigures. Note : As no Transmitter Identifier is used for the MIP section all VCAST will be reconfigured Example2 : Control the DVB-T Mode of a specific VCAST using the DVB-T Settings functions If the Authorization Table value is set to RESTRICTED CONFIG FROM MIP (C.3), the DVB-T mode is then derived from the function of DVB-T settings group. In that case it is necessary to add the following parameters to specify the new DVB-T mode and to Restart VCAST to valid the mode : B.1... B.4 C- Force the Authorization Table to MPEG2-TS (Restricted control) C.1 Add a new parameter into MIP (OPERATION/NETWORK SETTINGS/ADD/MIP FUNCTION MENU) C.2 Specify the Transmitter Identifier and the label (MIP FUNCTION MENU) C.3 Define the function : SEND MODE = ONE SHOT GROUP OF FUNCTION = PRIORITY FUNCTION = AUTHORIZATION TABLE VALUE = RESTRICTED CONFIGURATION VIA MIP D- Change the DVB-T mode (8K to 2K) D.1 Add a new parameter into MIP (OPERATION/NETWORK SETTINGS/ADD/MIP FUNCTION MENU) D.2 Specify the Transmitter Identifier and the label (MIP FUNCTION MENU) D.3 Define the function : SEND MODE = ONE SHOT GROUP OF FUNCTION = DVB-T SETTINGS FUNCTION = TRANSMISSION MODE VALUE = 2K FFT E- Restart VCAST after any change in the DVB-T mode E.1 Add a new parameter into MIP (OPERATION/NETWORK SETTINGS/ADD/MIP FUNCTION MENU) E.2 Specify the Transmitter Identifier and the label (MIP FUNCTION MENU) E.3 Define the function : SEND MODE = ONE SHOT GROUP OF FUNCTION = RESET OR RESTART FUNCTION = RESTART E.6 Download the PC data base into VSFN (OPERATION/NETWORK SETTINGS/DOWNLOAD) March 2002 DTC98053D.doc Page 7/10

8 NIT TABLE UPDATE The NIT table is generated by the MPEG Multiplexer and coveys information relating to the characteristics of the network. IRDs may be able to store the NIT information in order to minimize the access time when switching between channels. As an option, the NIT table can be updated on VSFN or on VCAST. MPEG2-TS NIT TABLE DISTRIBUTION DVB-MUX V-SFN NETWORK V-CAST TRANSMIT NIT UPDATE NIT UPDATE MIP FRONT PANEL VSFN-OPE VCAST-OPE The NIT table is specified in the document prets of March In DVB-T application the Terrestrial Delivery System Descriptor carried by the NIT Table describes how the multiplex is broadcasted ONAIR : Terrestrial Delivery System Descriptor field Center Frequency (ONAIR Frequency) Bandwidth Constellation (1) Hierarchy Information (1) HP Code rate (1) LP Code rate (1) Guard Interval (1) Transmission Mode (FFT size) (1) Other Frequency Flag Action on VSFN or VCAST Set by user Updated from VSFN or VCAST Option Set to zero (1) This parameter is automatically updated after any change in the DVB-T Settings (since the NIT Update is enabled) NIT update on VSFN In this case the NIT table will be broadcasted by all the transmitters connected to VSFN The NIT update option must be enabled (VSFN-OPE/ADMINISTRATION/FACTORY SETTINGS) The NIT update can be disabled or enabled (VSFN-OPE/OPERATION/SFN SETTINGS) The Center Frequency can be set by user (VSFN-OPE/OPERATION/SFN SETTINGS/CHANGE) All the other fields are automatically updated from the VSFN DVB-T settings Page 8/10 DTC98053D.doc March 2002

9 NIT update on VCAST (RS232 or MANUAL modes) It enables to broadcast a specific NIT at one transmitter site (MFN application) The NIT update option must be enabled (VCAST-OPE/ADMINISTRATION/FACTORY SETTINGS) The NIT update can be disabled or enabled (VCAST-OPE/OPERATION/MAIN SETTINGS) The Center Frequency can be set by user (VCAST-OPE/OPERATION/MAIN SETTINGS/CHANGE) All the other fields are automatically updated from the active VCAST DVB-T settings NIT update on VCAST (Control from MIP) The NIT update option must be enabled (VCAST-OPE/ADMINISTRATION/FACTORY SETTINGS) The control from MIP must be enabled (MPEG2-TS enabled) The group of functions NETWORK MANAGEMENT must be controlled from MIP in the Authorization Table On VSFN the parameter NIT UPDATE must be sent to VCAST (VSFN-OPE/OPERATION/NETWORK SETTINGS/GROUP OF FUNCTION = NETWORK MANAGEMENT/FUNCTION=NIT UPDATE/VALUE=NIT UPDATE) The center frequency can be indicated by the function NIT CENTER FREQUENCY (VSFN-OPE/OPERATION/NETWORK SETTINGS/GROUP OF FUNCTION = NETWORK MANAGEMENT/FUNCTION=NIT CENTER FREQUENCY/VALUE= XXXX) The VSFN-OPE MIP data base must be downloaded into VSFN (VSFN-OPE/NETWORK SETTINGS/DOWNLOAD) All the other fields are automatically updated from the active VCAST DVB-T settings March 2002 DTC98053D.doc Page 9/10

10 APPENDIX A : HARRIS GROUP OF FUNCTIONS Group of functions Function Function Type in MIP Packet MIP section Constellation Hierarchy information Code rate HP stream Code rate LP stream Guard interval Transmission mode SFN Synchronization Optional MIP section Transmitter Time Offset (Static Delay) Optional DVB-T Settings Constellation Hierarchy information Code rate HP stream Code rate LP stream Guard interval Transmission mode Network Management Static Delay NIT Center Frequency NIT Update Output Selection Output Type Test Mode Operation Mode Test Stream PRBS Type Advanced Settings Input Stuffing Packets Stuffing Packet Adaptation PCR Restamping Muting All Outputs Spectrum Inversion SFN Synchronization Front Panel Display PPS Edge Mute Conditions Reset and Restart Reset of V-CAST Restart of V-CAST Real Time Clock Equipment Date Equipment Time Page 10/10 DTC98053D.doc March 2002