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).    

    

MMDS and LMDS

   

    MMDS or Multichannel Multipoint Distribution Service is a wireless broadband technology for internet access, that’s why it also known as a wireless cable. In 1970s they already used MMDS for the support of their television set by giving a clearer signal to the users. For the transmission of the signal they used terrestrial bases radio transmitters and for the receiver they only used an exclusive small digital receiver. The transmission that they used depends on the line of sight. Each of the channels can transfer in a rate of 27 Mbps and that is high enough to support the users. For the non license channel it can take a 99 MHz, 2.4 GHz and 5.7 to 5.8 GHz over the license channels. The frequency that they used is in a range belong to ultra high frequency which is 2.1 to 2.7 GHz. As the same for wired connection cable used for TV, MMDS can act the same functions. The only thing to do for MMDS to be efficient like wired cable is to boost the power that they have so that it can produce a clear signal.

     MMDS has a limited frequency spectrum. The number of channels available in RF bands characterize MMDS network. It can allocate only 200 MHz frequency spectrum, it can reduce the number of channels in the system for TV signal using 6 MHz of bandwidth, 33 channels can be fit into the spectrum. 

     The MMDS works for giving a clear signal to the users and it can accommodate many subscribers. The signal that they are using has many sources like cable head ends. Satellite, terrestrial, and cable delivered programs comprises the material to be delivered over MMDS. All satellite delivered in baseband format are remodulated and subsequently up converted to microwave frequencies. The signal that has been deliver is always passes through a heterodyne processor prior to improve MMDS frequencies. The transmission of using the antenna has arranged of about 35 miles depending on the broadcast power. Operating power is about 1 to 100 watt range. But it is a line of sight service, even if it can take too much power still it can’t support the client were living around the mountain.

     LMDS or Local Multipoint Distribution Service use to support the demands of the people for high speed broadband communication. They support them especially if they are far from the main source of signal. LMDS is also wireless technology that is used to deliver the multiple service offered in some local areas. Example services of LMDS are, voice dial up services, data, internet access, and video. LMDS operate in a higher frequency; the radio signal is limited to 5 miles of point to point service. This makes somewhat like a cellular operation in the way the carrier layout their operation.

     Benefits of using LMDS are the one reason why many local providers use this. First benefit of this is that it is very cost effective and the subscribers can easily afford it. The investors now are not afraid to invest their money upon using this system. The implementation for LMDS is also faster and not takes too much time, this is also a good factor of dealing with this system. As we all know, every one of us needs faster and reliable broadband communications. That’s why this system can help us to achieve our desire.

Reference: Broadband Telecommunication Handbook: 2^nd edition by Regis Bates

MICROWAVE AND RADIO BASED SYSTEM

    Some people not aware of microwave radio dishes placed in some areas like towers or any buildings. Microwave operates in a frequency range of 300 Mhz to 300 Ghz and its size is about 1mm and 30 cm long. Before microwave used only in telephone transmission in order to help people in their communication. But now a days microwave evolved to many purposes, like what we have seen in some residences who are using microwave in their television set.

     There are many users of microwave system; one of this is the PCS or the cellular and Personal Communication Services industry. They uses microwave in order to improve their connections of components and for the expansion of their network. Microwave also can eliminate the monthly recurring charges. But microwave played in a very crucial role in the PCS industry if their systems use the 1.9 to 2.3 GHz frequency band. The users of this frequency band are the police, fire, electric utilities, and municipal organizations. To accommodate those users in a 2 GHz frequency band, a microwave was used to relocate the users in a new band as required by the FCC.

       Second user of microwave is the CAP market or the Competitive Access Providers. They offer a large distance access in their telephone service in order to support their customers but in the lower price. CAPs uses fiber optic in their connections but they also recognize the benefits using a microwave or wireless connection.

       Microwave use for radio and TV, we can now see the growing of digital services for televisions, like signal TV. They use microwave repeaters on the satellite to retransmit TV signals to the receiving stations. It will improve the reception of the picture and give many channels that can entertain the users.

       A laptop computer with a credit card size can now uses microwave to convert the messages into binary code for computer processing and convert back to microwave for transmission. It can be use as LAN in some areas like school campuses, airports and etc., microwave make this all possible.

      In using microwave always consider the bandwidth; use only the desire bandwidth that is enough to support your system. Remember that the higher the bandwidth that you are using the bigger the cost, that’s why don’t use bandwidth that is more than enough because some of this bandwidth would be wasted. You will notice if your bandwidth is enough if your data is keep moving and voice call coming is properly manage by your system.

    If you are using microwave you need to know if it is reliable or not because it can waste your time or even your money. Make sure that it is fast in terms of transmitting or receiving so that the delay during your work will be reduce.

Reference: Broadband Telecommunication handbook: second edition by Regis Bates.

xDSL: CHAPTER 16

Internet accesses before using ILEC or Incumbent Local Exchange Carriers has many problems including the ability of maintaining and preserving their installed base. ILEC want to have high speed communication ability and more correct internet access. That’s why they continue to find way to have a new technology that can solve their problem. ILEC have an installed base of unshielded twisted pair in the local loop, and because of this they invented a new technology called xDSL in order to exist the copper cable plant. DSL is known as digital subscriber line, the lower X stands for many variations. Those variations including the following, Asymmetrical DSL, ISDN or ISDL, High-bit rate DSL, Consumer DSL, Single High speed DSL, Rate-adaptive DSL, Very high- bit rate DSL, single DSL. But the most popular on variation is the Asymmetrical DSL because it supports the cable plant and it has a speed that varies depending on the quality of copper.

ADSL produced a high speed transmission using the twisted pair telephone lines and under the current technology it uses the speed between 1.5 to 6 Mbps. They said that in the future the ADSL will carry the speed of 8.192 Mbps and it is very possible to happen. The services that DSL provides are voice, multimedia, data, video, and internet streaming protocol service.

 ISDL or ISDN_DSL is a technique that uses digital and operating at two channels of 64 Kbps for voice or non voice and 16 Kbps for data channel for signaling, control and data packets. ISDN couldn’t catch faster but it is demandable because the carriers caught off- guard when users demand was moderate, escalated so quickly. 

HDSL is developed as more efficient way of transmitting; it does not require the repeater on a local loop above 12K. HSDL is more efficient because the bridge taps will not bother the service and the splices are left in place. It can deliver 1.544 Mbps.

SDSL provides a high speed communications using a single cable pair and a distance of not greater than 10K. Despite of this distance, SDSL can deliver a 1.544 Mbps on a single cable pair. Still it has an advantage to produce a god communication. The limitation of the distance of SDSL is now supported by the use of ADSL. Now the distance becomes 18K by the help of ADSL.

RADSL is made to develop the variations and speed of transmission. IT gives the flexibility to adopt the changing in each direction during the transmission. It can also provides 768 Kbps, that’s why ILEC used this.

CDSL provide only 1 Mbps in download direction and 160 Kbps for upward direction. But still the consumers want to use this because it does not need any splitter on the line.

SHDSL supports the repeaters which further increase the reach capability of some technologies. One of the advantage of SHDSL is that is has an increasing symmetrical bandwidth during installation. SHDL provides the services to the remote LAN access, Web-hosting, application sharing, and video conferencing.

VDSL is faster and more reliable to used, obviously we know that it is fast because the name of very high bit rate. It uses a fiber feed to deliver VDSL so that they can achieve the speed that they want.

Now we know how important those variation in providing the DSL to reach their goal and to satisfy the ILECs for the improvement of their technological device so it can carry the needs of the consumers or the end users. Fast and safe communication is the most important thing that the users needed, the secondary is the cost. That’s why this xDSL made in order to give what they want.

Reference: Broadband Telecommunication Handbook: 2^nd edition by Regis Bates

Asynchronous Transfer Mode (ATM)

ATM is an evolution from many other set of protocol, it is member of the fast packet switching family and this is what we call cell relay. It is called asynchronous because it is designed to carry any form of traffic and enables the traffic to be delivered asynchronously to the network. When traffic in the form of cells arrives, the cells are mapped into the network and transported to the next destinations.

They are using a combination of TDM or time division multiplexing with cells using reassigned slots and statistical TDM if there is no cells arrive. It uses virtual circuits, the permanent virtual circuit (PVC) and switched virtual circuits (SVC) to handle the connection. These two circuits are important factor for ATM because it will fix the size of cells employed and carry the traffic of the end users.

ATM also used to integrate voice, data, video and multimedia traffic on a single backbone network. The standards of voice, video and data have different standards and their data network is also separated when it is transmitted.

ATM gives excitement to the users because it has a higher bandwidth that can support their systems to overcome the problems that they encountered from the past technology. Obviously the capacity of ATM to give a good performance to the multimedia application is much different from the technique that they are using before because it is capable of higher bandwidth.

The speed of ATM at the start of using this is about 1.544 Mbps, today it already have 622 Mbps. As we observe the difference of the two is very far, the increased of the speed is now enough to convince the user to use ATM. But even the speed increased to much higher capability, they still find ways to reach 2.488Gbps for the future application. In order to inform the people that they reach their demands in using ATM is done by QoS capability.

For layer architecture ATM is different from the OSI, ATM only uses two layer. The two layers are the data link layer and the physical layer. ATM is said to be designed to run on a physical medium such as SONET.

We need to know the importance of ATM because it gives many benefits to the users. One of these benefits is the high speed communication, this is very important so that the needs and wants of the users will easily serve. To get this high sped communication the fast hardware-base switching is also very important because the proper switching help to increase the speed of communication.

The disadvantage of ATM is that it can cause much confusion because of their name, it is called asynchronous but it is related to synchronous transmission and their specification has similarities. It needs also many protocol points and interfacing so that it can support the older legacy system.

Reference: Broadband Telecommunication Handbook: 2^nd edition by Regis Bates