 Hello everyone, my self-care brother, assistant professor, Department of Electronics and Telecommunication Engineering, Walsh and the Institute of Technology, Swalapur. Welcome to video lecture on very small aperture terminal that is also called the InShot vShot. Let us start with the learning outcomes first. At the end of this session, students will be able to draw and explain architecture of vShot earth station, discuss, advantage and limitations of vShot. What is vShot first? vShot is a small satellite earth station that transmits and receives data wise or video via satellite. That means, basically it is an earth station which is used to transmit and receive data wise etcetera via satellite. The very small component of vShot refers to the size of the vShot disk antenna typically about 60 centimeter to 3.8 meter. The small or very small refers to the size of the disk antenna. It requires or vShot requires no additional technology to operate it, vShot simply plugs into existing terminal equipment. What is the effect on frequency and transmitted power if size of the antenna decreases? Pause the video and write the answer. I think you might have written the answer. When I decrease the size of the antenna on the other hand, we need to increase the transmitting power also. We need to increase the frequency of the transmitting signal. So, decrease in antenna size cause the increase in transmitting power as well as a signal transmission frequency. Why is vShot? Early earth stations in commercial systems were very large and expensive. We need to make system more affordable to end user. We need to increase the transmit power from satellite and also higher frequency of transmission. This result into a smaller earth station antenna size required. That means in the earlier days, so it is a large and expensive satellite disk antennas use or satellite earth stations are used. These are very difficult to install and transporting also cumbersome. To make it easy for the end user by the cost of transmitting power increase as well as a higher frequency concentration, you can get it reduce the earth station antenna size. vShot implementations. There are several ways vShot service might be implemented. First one is one way which is used for TV broadcasting satellites where that is the only transmission or TV broadcasting stations have only transmission of the signals. There is no reception that is one way transmission. Split two way that is also called split IP implementation. Here there is a return link from user is not via the satellite example for this is direct TV. So, there is a two way but return link is not through satellite direct by the user. Third one is two way implementation. It comes up both up link as well as down link through satellite for up link earth station to satellite for down link from satellite to the earth station. So, in this video I am going to discuss only two way implementation. Two way implementations are further classified into two types. First one is star vShots are linked via a hub. Second means mesh vShots are linked together without going through a large hub. You can see these two diagrams this is a star vShot network. It comes up a central hub this is also called the master control station. So, there are several vShots are connected if anyone vShot want to transmit signals to or communicate with another vShot the first signal reaches to the hub and then to the another vShot. So, whereas in the mesh second diagram mesh architecture it does not have any hub it has several vShots. So, communication takes place from one vShot to another vShot. So, vShot star architecture you can see this diagram there is a master control station called hub. So, hub is situated on the earth station and several vShots are connected. If I want to communicate from one vShot to another vShot it should transmit first to the satellite and then to the hub again hub hub will retransmit back and to the satellite and it will transmit back to the another vShot. There is a communication takes place through central unit unit called hub. In star network architecture all of the traffic is routed via the master control station or called hub. If a vShot wishes to communicate with another vShot they have to go via the hub as we have discussed. So, if vShot wants to communicate with another vShot it should go through the hub. Necessity a a double hop link via the satellite first from vShot to the hub and then hub to the another vShot. Since all of the traffic radiates from the hub this architecture is referred to as a star network because here there is a hub is placed at the center. Then vShot mesh architecture in this there is no hub or central control station. So, one of the vShot acts as a control station here or several combinedly you can work together as a master control station or hub. In mesh architecture each of the vShots has ability to communicate directly with any of the other vShots. Since the traffic can go to or from any vShot this architecture is referred to as a mesh network. It will still be necessary to have network control and the duties of the hub can end either be handled by one of the vShots. So, some hub is required to control here. So, one of the vShot acts as a hub here. The master control station functions can be said among the vShots. What are the advantages and limitations of star network? First we shall see advantages. First one is it reduces the transferring of packets from the excessive number of nodes. Central hub facilitates the easy addition of new devices any vShot to be added here. So, central hub itself gives an option to add any vShot network. It is easy to understand install and navigate. So, very easy to understand because you can add it easily means you can install also and understand easily. Faulty parts can be easily detected and eliminated. One advantage is good advantage is any of the device or vShots goes that is faulty they can be detected and eliminated easily. It is interference free at the time of adding and removing devices when you add any of the new network or vShot. So, that in that time interference is free there is no interference in the system. What are the limitations? The function of the system is highly depends upon the central hub. So, totally the entire network depends on the hub. Any lapse in the central hub can result in the inoperability of entire system. If hub get any problem the entire system will not operate. Scalability relies on the capability of the central hub. The scalability factor depends on the that is capability of the central hub. Advantage and limitations of mesh network. Advantage first. The mesh topology helps more than one transmission of data from one node to another node simultaneously we can send the signal simultaneously from one node to another node. Provides privacy and security with point to point links here there is no central hub that is why directly can transmit from one point to another point or one link to another link. It is robust failure of one link does not affect the other system. There is no hub here. In the previous case if hub does not work then entire system will not operate. Here it is a robust system failure of one link does not affect the other system. Fault identification isolations are also easy. What are the limitations? This network configuration cannot create redundant network connections as there are some connections which are useless. The overall cost of the topology is also increased because of an excessive amount of cabling and need of IOPORs. The system cost in mesh network is increased because accessing of cable and need of IOPORs. Wiring is complex in this mesh network. These are some of the references I refer to prepare above PPT. Thank you.