Today, entertainment is a booming business as media companies  are announcing introduction  of new TV Channels everyday.  This is also providing opportunities for growth to Satellite, Cable and Telecom companies.  DTH operators are increasing no. of TV Channels they can beam to their subscribers.  On the other hand MSOs are not behind in this race and are increasing no. of channels and enhancing reach with connectivity to near & far areas using  HFC and Fibre Optical Network.  It is well known fact that acquisition and processing of  TV programmes has 80% cost of a DHE/AHE as compared  to transmission & distribution equipment.  Fig-1 & Fig-2 shows details of Analogue & Digital Headend System.  It is quite evident from this that it, is economical to setup a Master Headend at one place and carry signals to distance locations over  Fibre Networks (SDH/SONET Networks) or Satellite using Headend in the Sky (HITS) approach.

HITS platform has already been launched by WWIL and more companies are waiting for this .  However, there is a limitation of using Satellite as limited no. of TV Channels (60-80) can be transmitted because of  x-ponder space.  With increased requirement of TV Channels including High Definition TV  use of HITS will find limitations.

Benefits of IP Networking

This Technology was developed for transporting large amount of telephone/data traffic as a replacement to Plesiochronous Digital Hierarchy  (PDH) or Asynchronous Transfer Mode (ATM) scheme where E1(2Mbits) /    E2(8Mbits)/E3(34Mbits) etc have been used.  Presently SONET/SDH networks are also carry ATM traffic.  SONET/SDH are based on circuit mode communication which provides constant bit rate and delay for all data streams.  For instance, SONET / SDH can be used to provide several Internet Service Providers (ISP) to share the same fibre optic without affecting each others traffic load.

SDH standards have been developed by International Telecommunication Union (ITU) known as G.707 standards and it is followed by ETSI in Europe while SONET are followed in USA.  It is not within the cope of this article to provide protocols & framing details.  However, Table-1 provides SONET/SDH data profiles.  It is clear that STM-0 provides 51.840Mbits capacity while STM-1 and 4 provides 155.520 and 622.080Mbits/S capacity.  STM-1 refers to Synchronous Transport Module Level-1 and it is the basic transmission format for SDH system.

It is clear that STM-4 can carry more than 150 TV Channels in digital format.  SDH profiles go upto STM-16, 64, 1024 which are 25, 10.00, 159.00 Gbits data rates respectively.  If STM-64 circuits are used, it is possible to send 2500 Digital TV Channels.  ( One standard TV Channel will occupy of  4.0-5.0Mbits data while High Definition will be approx 8-10Mbits.)