The new generation of satellites is high throughput satellites (HTS). It has many times more throughput of the traditional FSS satellites allocating the same amount of frequency on orbit . The throughput of these satellites is high by taking advantage of frequency reuse and multiple spot beams. The cost per bit is reduced irrespective of spectrum choice . ADS is replaced by FTTH for access performance as a new standard. . Throughput in this scenario is information delivery speed (bits/sec) which depends upon:
Bandwidth (MHz): It is increased by using frequency reuse phenomena.
Efficiency (bits/sec per MHz): This is the amount of error-free information in the allocated bandwidth, which can be achieved by using spot beams.
One of the fundamental differences in the architecture of HTS and traditional satellites is the use of multiple spot beams for the coverage of a specific desired location, unlike the previous wide beams. These spots beams have two major benefits .
High Gain (Transmit/Receive): The directivity in spot beams is high so the gain is higher compared to traditional wide beams. A narrow beam results in increased power due to which user terminals become smaller and higher order modulation becomes possible, thus higher data rate transmission per unit is achieved.
Frequency Re-Use: The desired service location can be covered by multiple spot beams. The same frequency band and polarization can be used by several beams which mean an increase in the capacity of the satellite system for a specific frequency band allocated to the system. Four color schemes are the best settlement between performance and system capacity however three and seven color scenario is also be implemented for frequency reuse . Dividing no of spots of spots beam antenna by no of colors gives the frequency reuse factor of spot beam antenna. The capacity of spot beam antenna is frequency reuse factor times more than a large contour single beam.
This capacity increase is attained without raising DC power and RF but just with a little amendment in the satellite . In Single feed per beam SFB antennas the multiple beams are produced by a single horn. Active or passive lenses and single oversized designed reflector are used to produce overlapping spot beams to evade holes in the coverage area . Multiple spot beam antennas MSB uses arrays of small horns to generate beams so using only one reflector overlapping spots can be achieved which pointer reduction in cost and mass.
High throughput satellites (HTS) system is classified into different generation according to its capacity.
The first generation of HTS gives around a few tens of Gbits/s while the 2nd HTS generation produces one hundred Gbits/s approximately e.g. KA-SAT, Via Sat 1, Echo-star etc. . Several hundreds of Gbit/s will be offered by the third generation. It will boost the capability of the system and optimization of the satellite and system resources, providing quality close to fiber to the home  . KA-SAT is the new generation satellite of Ka-band of HTS system. It provides services for broadband and TV broadcasting as well . It has 82 spots covering a large area using frequency-reuse factor 20-times. This system uses small user terminals for Asymmetric digital subscriber line (ADSL). Its capacity is over 90 Gbit/s. It was the first HTS Ka-band satellite launched with this much capacity on 26 Dec 2010 and its commercial operation was started on 31 May 2011.