Satellite Communication Networking

Chapter 26

    The first beneficiary of satellite communication system was the military forces for they can communicate each group during operations. They used also this for agriculture, forestry, geology, and even environmental science. For agriculture they used satellite communication in order to determine the productive from non productive yields. All this improves yield and prevents the waste of valuable chemicals. This practice is well established in America. They also used satellite communication networking for infrared vision, satellite based navigation, such as GPS.

        The process begins at an earth station,, an installation design to transmit and receives signal from a satellite in orbit around the earth. Then the earth station send an information via high powered, high frequency range signal to satellite and receives and retransmit the signals back to earth where they are receive by other earth stations in the coverage area of the satellite. This scenario is also mentioned during our national tour in Subic satellite station. The area that receives the signal of useful strength from the satellite is called satellite footprint.  Then the transmission process from the earth station to the satellite is called the uplink and the system from the satellite to the earth station is called downlink.     

       

        The satellite frequency has three common uses, the C-band, Ku-band, and the Ka-band. C-band and Ku-band are the most common frequency spectrums used by today’s satellite. The frequency and the wavelength are inversely proportional to each other. If the frequency increases the wavelength will decrease. For the design of antenna, consider the frequency and wavelength. The wavelength increases, larger antenna are required to receive the signal.

         Majority of satellite in orbit around the earth are positioned at a point of 22,300 miles above the earth’s equator in Geosynchronous Earth Orbit or GEO. This satellite can maintain an orbit with a period of rotation around the earth with exactly equal to 24 hours. The reason of this is that the satellite revolve at the same rotational speed of the earth, they appear stationary from the earth surface. That’s why the antenna that they are using doesn’t need to move after they have been properly aimed at a target satellite in the sky.

         Medium Earth Orbit is an innovation of communication. It gives rise to the new orbits and totally new system design. It has been proposed that the orbit distance of about 8,000 miles. The signals travel from MEO satellite travel a shorter distance which translates to improve signal strength at the receiving end. If the signal travels in a shorter distance the delay was reduced and it accommodates the needs of the system faster. That why it is better to use a MEO for satellite purposes.

      Low Earth Orbit or LEO is divided into 3 categories. First is called little LEO, second is big LEO, third is mega LEO. LEOs will orbit at a distance of 500 to 1000 miles above the earth. They consider this as a short distance, that’s why it can’t cause any delay for transmission. It could take .05 seconds and further reduces the need for sensitivity for the receiving equipment. The little LEO will operate in the 800 MHz range, big LEO will operate in the two GHz or above range, then the mega LEO will operate in the 20 to 30 GHz range. The mega LEO has a higher frequency associated that’s why it is capable of carrying more capacity and much capability for real time. If we say real time it means that it operates always at the present time.   

THIRD- GENERATION (3G) WIRELESS SYSTEM

CHAPTER25

      Wired system is a good and reliable technique to be use for transmitting data and information. But now a days wireless system developed in order to produce a good communication system like wired communication. To come up this wireless system, 3G as made for the revolution existing Time Division Multiple Access (TDMA) operators must evolve their network to take advantage of mobile multimedia application and the eventual shift to all IP architecture. The operators begin to the next step in the evolution process to enhanced data for global environment or EDGE. Their are some application of existing TDMA including online e-mail, access to the worldwide web, enhanced short message service, wireless imaging with instant photos or graphics, video services, document or information sharing, surveillance, voice messaging via internet, and broadcasting.

      For 3G technology operators skip for using step of EDGE, instead they proceed to UMTS or Universal Mobile Telecommunication Services. They do this because EDGE is one step closer to UMTS. It provides higher data rates than GPRS and introduces a new modulation scheme called 8-Phase Shift Keying (PSK). The time division multiple Access community also adopted EDGE for the migration to UMTS.  UMTS is a part of the ITU IMT- 2000 vision of a global family of 3G mobile communications systems. It plays a big role for creating the future mass market for high quality wireless multimedia communications that will approach 2 billions users worldwide by the year of 2010. UMTS also modulate concept that takes full advantage of the converging existing and future information network, device and services. UMTS help mobile communications to move forward from where we are today into 3G services and deliver speech, data, pictures, graphics, video communication, and other services to the users.

       UMTS is one of the major 3G mobile communication systems that is being developed within the framework which has been defined by the ITU and is known as IMT-2000.It will also support many major telecommunications operators and manufacturers because it has a unique opportunity to create a mass market for highly personalized and user friendly mobile access to the nearer future. It helps a lot to the end user because it gives more benefits to make the task of the users easier. It evolves mobile technology in terms of capability and advancement of the systems. The success of UMTS requires new technology, partnership and addressing of many commercial and regulatory issues. It will also enable wireless knowledge workers, delivering high value broadband information, commerce, and entertainment services to users via fixed, wireless and satellite networks. UMTS will also increase the speed of convergence between voice, data, and multimedia to deliver new service and more opportunities.

       Other way of developing wireless system is called WCDMA, it is a 3G mobile wireless technology offering much higher data speeds to mobile and portable wireless device than commonly offered in today’s market. It supports mobile portable voice, image, data, and video communication at up to 2 Mbps or 384 Kbps. The process of this uses digital signal and transmitted in coded, spread spectrum mode over a broad range of frequencies. WCDMA also offers very high capacity with 50 to 80 voice channels per 5 MHz carrier with 8 channels per carrier with 200 KHz for GSM. To achieve this high data rates WCDMA requires wide frequency bands that is allocated, one for sending data from the terminal and one for the receiving data on the terminal.         

GENERAL PACKET RADIO SERVICE (GPRS)

Chapter 24

   The demand for communication is now increase, and need innovation process in order to produce a fast and reliable communication industry. If these things happen, the services will be more efficient and more effective especially to those subscribers who are engage in business. The GSM help the growing of data traffic in general all point to a significant business opportunity for GSM operators. That’s why subscribers of this system increase. But as always, users need changes and improvement of what they are using. They want a high speed and broader band communication so that they can make their task easier and faster.

     Now a new communication system is made in order to improve the needs of the users. This device is the General Packet Radio Service or (GPRS) it is the key milestone for GSM data. The price of this is chipper that the end users can really afford to subscribe. Before the people decide to choose communication technique, they first consider the price then the durability and reliability of the product is their second basis.

     GPRS also extends the packet data capabilities of the GSM network from packet data on signaling channel service. GPRS is also fit in with the existing GSM PLMN as well as the packet data networks. PLMN provides wireless access to wired packet data network. GPRS use for short message services or SMS components to provide SMS over GPRS. It will provide a seamless network infrastructure for operation and maintenance of the network. GPRS gives mobile users faster data speed and particularly good internet traffic. It will enable voice and data calls to be handled simultaneously. Users can have 342 always on connectivity to the mobile internet enjoying high speed delivery of e-mails with large file attachments, web surfing, and access to corporate Local Area Network.

    

      GPRS was also defined as a provider for true packet radio service on GSM networks by the European Telecommunication Standards Institute. GPRS was developed to enable GSM operators to meet the growing demands for wireless packet data service that is a result of the explosive growth of the internet and corporate intranets. Application of this network require relatively high throughput and are characterize by bursty traffic patterns and asymmetrical throughput needs. Example of these is web browsing, it is a result of burst of network traffic while information is being transmitted or received followed by long idle periods while the data is being sent from the client device than is being sent from the client device to the server.

      GPRS roaming use for calls and SMS messages, the growth of using this is very fast because many countries adopted this technique in order to support those who are communicating in one country to another. This roaming is considered as a multibillion business according to those who are engage in this business. The GPRS PLMN enables mobile users to roam within a geographic coverage area and receive continuous wireless packet data services. The user will move while actively sending and receiving data or may move during periods of inactivity. Either way the network tracks the location of the MS so that incoming packets can be routed to MS when they arrived. The GPRS PLMN interfaces with the MS via the air interface. It will initially provided using an enhanced version of standards GSM interface. The operators will now evolve their network to incorporate more advanced radio interfaces in the future so that they can deliver higher data rates to the end users. The GPRS PLMN interfaces as an overlay to traditional public packet data network using standards Packet Data Protocol (PDS).