March 2018 DISTRIBUTION 21
Tips for building a working DTT infrastructure
There are many factors that will influence the complexity , cost and time to deploy a digital terrestrial television ( DTT ) network .
Harmonic , which has worked on more than 80 projects in over 60 countries globally , recommends that broadcasters take into account these key considerations : n What is the % population coverage target ? This will have a huge impact on the number of transmitters to be deployed in a country . n Is indoor reception a goal ? Is reception on a portable device an objective ? Is receiving DTT in a car an objective ? All these points impact the modulation parameter choice , as well as the number of broadcasted channels . n Is it a multi-frequency network ( MFN ) or single-frequency network ( SFN )? This will have an impact on the cost of the signal distribution network and the edge / tower devices , especially if regionalisation is required .
The regionalisation of the various channels — is it a full channel replacement , local news only , or local ad insertion ? n What is the distribution network to the towers ? It could be satellite or IP , and so on . n Is it free-to-air , free-to-view or a pay- TV network ? n In the case of satellite distribution , does the operator also want the DTT distributed signal to be received from satellite , as well as over DTT , to offer 100 % population coverage , as required by some regulators ?
According to Yan Mostovoy , director , contribution and distribution solutions , Harmonic , the company has had the biggest DTT market share since 1998 . In many of these DTT projects , Harmonic has gone beyond playing the role of just a technology
Harmonic has had the biggest
DTT market share worldwide since 1998 , with more than 80 projects in over 60 countries , revealed Yan
Mostovoy , director , contribution and distribution solutions , Harmonic .
vendor , and has also acted as an advisor , he added . “ We provide our customers with an end-to-end DTT solution that includes the most advanced features and technologies , such as headend processing and efficient distribution with any types of regionalisation needs , for any types of distribution network and for both MFN and SFN signals ,” he told APB . “ We also participate and contribute to DVB-T / T2 standardisation efforts , and are active in developing unique features and capabilities for DTT , which puts us in a leading position against our competition .”
And while Mostovoy agreed that Asia- Pacific may be lagging behind other regions when it comes to deploying DTT , he pointed out that out of 46 APAC countries , states or islands , 26 are successfully delivering DTT services in one way or another .
“ The region is diversified in adopting DTT standards ,” Mostovoy also observed . “ China has deployed DTMB , South Korea ATSC , Japan and the Philippines ISDB-T , and the rest , DVB-T / T2 . Harmonic was involved in many of the DTT projects in the region , particularly those in Thailand , Singapore , Indonesia , Malaysia , Vietnam , Taiwan , China and Australia .” reception , at least as a best effort service .”
Where Europe is concerned , the analogue switch off ( ASO ) has been a long gone conclusion in many countries . Some have gone further by making a second DTT transition , going from DVB-T and MPEG-2 to DVB-T2 and H . 264 or HEVC / H . 265 , Dr Siebert points out .
He highlights Germany as a case in point , where 2017 saw the introduction of the country ’ s second-generation DTT system , which utilises DVB-T2 and HEVC / H . 265 to bring HD and more services to the end-user . “ To plan the transition , the relevant
sideration of any DTT deployment today , as being the need for bidirectional IP connectivity with all towers and remote sites . “ This IP network opens the door for central network management and control , resulting in a significant Opex savings for both the distribution and contribution portions of the operation .”
Beyond the transmission equipment itself , each and every device , device parameter or functionality at the tower sites can be reached : off-air probes , windspeed monitors , thermometers , oil level tanks of diesel generators , CCTV and so on .
A full-scale IP bidirectional network also allows a single Network Operations Centre ( NOC ) to correlate alarms or monitor trends and , therefore , make responses proactive instead of reactive . Massart elaborates : “ The significant Opex savings come from not having to dispatch skilled personnel continuously for stakeholders came together in a round table approach ,” Dr Siebert describes . “ A wide range of interest groups participated in the planning : public and private broadcasters , network operators , the consumer electronics and retail industry , German regulators and even consumer organisations representing the interest of the end-users .”
All relevant aspects were discussed and agreed during the round table discussions , including : business cases , frequency planning , transition scenarios , transmission parameters , AV coding , receiver specification and perhaps of most relevance , financing and time schedules .
each and every event . “ Travelling to towers high up in the mountains or in winter conditions or , in some remote cases , to islands by helicopter , is a costly undertaking , which can be avoided by full remote control .”
This IP pipe can be provided by a VSAT network , such as the Newtec Dialog platform , which provides a feature that allows the VSAT Forward IP pipe to be merged into the video distribution stream while preserving compatibility with the DTT / DTH overlay . Capex savings are also possible as this merged carrier can be received by a single VSAT modem generating the video distribution carrier , with the T2-MI streams for DVB-T2 distribution , as well as setting up the local IP network .
“ Smart solutions such as Newtec Dialog allow convergence of the video distribution and IP networking components , resulting in Capex savings on tower level , as well as Opex savings ,” Massart concluded .
Compliance of the TV receivers and sets to the new specification was then demonstrated by a logo , defined and administered by the round table . This was closely followed by an intensive marketing campaign informing end-users about the changes to come .
Within a nine-hour period on March 29 last year , the switchover to the new system took place without any major flaws , Dr Siebert reports . “ There are , of course , many ways for the transition to a new system , and Germany can only serve as an example ,” he emphasises . “ Nevertheless , there may be elements of the German approach that could be considered for other regions , such as Asia-Pacific .”
According to the Asia-Pacific Broadcasting Union ( ABU ), as of January this year , only a meagre five countries in the Asia-Pacific region have completed a full ASO . Calling this a “ surprising statistic ”, Dr Siebert says : “ Only a handful of countries [ in APAC ] have gone through ASO , while others appear to be struggling with their DTT transition , even as people in the region have continued to embrace digital broadcast TV .”
While he acknowledges that each country in APAC needs to define its own road to DTT and ASO , there appears to be no major obstacles standing in the way of the DTT transition . “ Digital services via cable and satellite are popular , and as well , there are commercial DTT networks in many countries in APAC ,” Dr Siebert explains . “ There is certainly no shortage of inexpensive receiver equipment based on DVB specifications ( the majority of countries in Asia- Pacific have chosen DVB standards for their DTT transition ), and the region has plenty of experienced engineers with the know-how to
WiB , or Wideband Broadcast , is a new DTT architecture with the potential to reduce Opex and Capex for a terrestrial network , and to increase the bandwidth for a given set of frequencies . set up DTT networks .”
In today ’ s digital age where viewing habits continue to evolve , it is imperative that broadcasters are armed with the mechanisms to interact , get analytics and build loyalty among audiences — all of which are difficult to achieve without going digital , because analogue transmission lacks return paths that can be integrated with modern broadcast services .
For broadcasters who are running digital services alongside analogue ones , they need to give due consideration to the actual costs of running simulcast operations — is this truly economically viable and sustainable over a long period of time ?
A new digital terrestial network architecture , however , may well allow broadcasters to make a more cost-effective transition to DTT . WiB , or Wideband Broadcast , is a new DTT architecture with the potential to reduce Opex and Capex for a terrestrial network , and to increase the bandwidth for a given set of frequencies .
Dr Siebert details : “ Before WiB , the typical approach for terrestrial network planning is to not reuse the same frequencies for adjacent transmitters , because , except for single frequency networks ( SFNs ), the receiver would see the signal as noise ”
The WiB approach , however , is based on the concept that all transmitters in a network use all available frequencies , which means that there will be interference
from adjacent transmitters . “ To compensate for the interference , a very robust modulation scheme like QPSK needs to be used , resulting in a lower data rate in the typical 8MHz channel ,” Dr Siebert continues . “ Consequently , the bandwidth needs to be increased to wideband channels beyond the usual 6MHz or 8MHz bandwidth . Furthermore , additional interference reduction measures , like directional antennas or Layer Division Mutiplexing ( LDM ), are needed .”
To further analyse the potential of WiB , the DVB Project has set up a special Study Mission Group ( SMG ). And while the DVB Project ’ s work on WiB is at an early stage , first simulations have demonstrated that with WiB , transmission power can be reduced by up to 90 %. “ This would result in significant Capex and Opex cost savings for terrestrial networks . Furthermore , it seems to be possible that the overall capacity of a network could be increased with the new concept ,” Dr Siebert reports , while highlighting that more research is required to identify and confirm WiB ’ s full potential .
“ Assuming that the current prediction on reduced power and increased capacity are confirmed , WiB will be the first technology after DVB-T2 to significantly improve DTT networks , and could play a major role in spectrum discussions and network planning in the years to come ,” he concludes .