CHAPTER 27

Low−Earth−Orbit Satellites (LEOs)

A low Earth orbit (LEO) is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km. Given the rapid orbital decay of objects below approximately 200 km, the commonly accepted definition for LEO is between 160–2,000 km (100–1,240 miles) above the Earth's surface. The sideways speed needed to achieve a stable low earth orbit is about 7.8 km/s, but reduces with altitude.

Satellite systems are employed for telephone and data communications. There are geostationary satellites flying in high orbit (22,000 miles) where they can maintain the same position above the earth's surface at all times. The only problem, with such high-flying satellites is that there is a noticeable delay in real-time communications, and the power requirement to communicate with the satellites is too high for portable devices.

LEOs are more practical for mobile communication devices like mobile phones, PDAs, and automobile communication systems. An LEO satellite orbits in a relatively low earth orbit of a few hundred miles. In this orbit, the round-trip time for transmission is minimal, as are the power requirements for earth-bound communication devices. The downside of LEO satellites is that a fleet of them is required. Because of their low orbit, they move faster relative to a point on the surface, so a fleet of LEO satellites is required to maintain communications over a single point. As one LEO moves out of position, the other moves in. Each satellite covers an area that could be compared to a cell in a cellular system, except that the cell moves as the satellite orbits.

Space debris

The LEO environment is becoming congested with space debris. This has caused growing concern in recent years, since collisions at orbital velocities can be damaging or dangerous, and can produce more space debris in the process (Kessler Syndrome). The Joint Space Operations Center, part of United States Strategic Command (formerly the United States Space Command), currently tracks more than 8,500 objects larger than 10 cm in LEO,[4] however a limited Arecibo Observatory study suggested there could be approximately one million objects larger than 2 millimeters, which are too small to be visible from Earth.

ORBITAL DISTANCES

Any satellite can achieve orbit at any distance from the earth if its velocity is sufficient to keep it from falling to earth. The farter the satellite is from the earth, the longer it takes for a transmission to reach the satellite. The altitudes at which satellites can orbit are split into two categories:

Ø  Low Earth Orbit (LEO)

Ø  Medium Earth Orbit (MEO)

LOW EARTH (LEO)

Satellites in low earth orbit (LEO) satellites complete one orbit roughly every 90 minutes at a height of between 100 and 500 miles above the earth's surface. This means that they are fast moving ( >17,000mph) and sophisticated ground equipment must be used to track the satellite. This makes for expensive antennas that must track the satellite and lock to the signal while moving.

MIDDLE EARTH (MEO)

Most of the satellites in middle earth orbit circle the earth at approximately 6,000 to 12,000 miles above the earth in an elliptical orbit around the poles of the earth. Any orbit that circles around the poles is refered to as a 'polar orbit'. Polar orbits have the advantage of covering a different section of the earth's surface as they circle the earth. As the earth rotates, satellites in polar orbits can cover the entire surface of the earth. Fewer satellites are required to create coverage for the entire earth, as these satellites are higher and have a larger footprint. Spy satellites typically use middle earth, polar orbits to cover as much of the earth's surface as possible from one satellite.

GEOSTATIONARY/GEOSYNCHRONOUS (GEO)

 At 22,240 miles above the earth, craft inserted into orbit over the equator and traveling at approximately 6,880 miles per hour around the equator following the earths rotation. This allows these satellites to maintain their relative position over the earth's surface. Since the satellite follows the earth, and takes 24 hours to complete it's orbit around the earth, geostationary orbits are also called geosynchronous.

http://www.answers.com/topic/low-earth-orbit

http://www.linktionary.com/l/leo.html

http://en.wikipedia.org/wiki/Low_Earth_orbit

CHAPTER 25

THIRD- GENERATION (3G) WIRELESS SYSTEM

The 3G (UMTS and CDMA2000) research and development projects started in 1992. In 1999, ITU approved five radio interfaces for IMT-2000 as a part of the ITU-R M.1457 Recommendation; WiMAX was added in 2007.

There are evolutionary standards (EDGE and CDMA) that are backwards-compatible extensions to pre-existing 2G networks as well as revolutionary standards that require all-new network hardware and frequency allocations. The cell phones used utilise UMTS in combination with 2G GSM standards and bandwidths, but do not support EDGE. The latter group is the UMTS family, which consists of standards developed for IMT-2000, as well as the independently developed standards DECT and WiMAX, which were included because they fit the IMT-2000 definition.

3G systems will provide access, by means of one or more radio links, to a wide range of telecommunication services supported by the fixed telecommunication networks and to other services that are specific to mobile users. A range of mobile terminal types will be encompassed, linking to terrestrial and/or satellite-based networks, and the terminals may be designed for mobile or fixed use.

3G is the next generation of wireless network technology that provides high speed bandwidth (high data transfer rates) to handheld devices. The high data transfer rates will allow 3G networks to offer multimedia services combining voice and data. Specifically, 3G wireless networks support the following maximum data transfer rates:

1. 2.05 Mbits/second to stationary devices.

2. 384 Kbits/second for slowly moving devices, such as a handset carried by a

walking user.

3. 128 Kbits/second for fast moving devices, such as handsets in moving vehicles.

3G networks offer users advantages such as:

1. New radio spectrum to relieve overcrowding in existing systems.

2.More bandwidth, security, and reliability.

3. Interoperability between service providers.

4. Fixed and variable data rates.

5. Asymmetric data rates.

6. Backward compatibility of devices with existing networks.

7. Always-online devices.  3G will use IP connectivity, IP is packet based (not

circuit based).

8. Rich multimedia services.

UMTS offers teleservices (like speech or SMS) and bearer services, which provide the capability for information transfer between access points. It is possible to negotiate and renegotiate the characteristics of a bearer service at session or connection establishment and during ongoing session or connection. Both connection oriented and connectionless services are offered for Point-to-Point and Point-to-Multipoint communication.

Bearer services have different QoS parameters for maximum transfer delay, delay variation and bit error rate. Offered data rate targets are:

1.144 kbits/s satellite and rural outdoor

2.384 kbits/s urban outdoor

3.2048 kbits/s indoor and low range outdoor

UMTS network services have different QoS classes for four types of traffic:

> Conversational class (voice, video telephony, video gaming)

> Streaming class (multimedia, video on demand, webcast)

> Interactive class (web browsing, network gaming, database access)

> Background class (email, SMS, downloading)

UMTS will also have a Virtual Home Environment (VHE). It is a concept for personal service environment portability across network boundaries and between terminals. Personal service environment means that users are consistently presented with the same personalised features, User Interface customisation and services in whatever network or terminal, wherever the user may be located. UMTS also has improved network security and location based services.

http://www.umtsworld.com/technology/overview.htm

http://transition.fcc.gov/3G/

http://www.silicon-press.com/briefs/brief.3g/brief.pdf

CHAPTER 24

 GENERAL PACKET RADIO SERVICE (GPRS)

GPRS is a best-effort service, implying variable throughput and latency that depend on the number of other users sharing the service concurrently, as opposed to circuit switching, where a certain quality of service (QoS) is guaranteed during the connection. In 2G systems, GPRS provides data rates of 56–114 kbit/second.[3] 2G cellular technology combined with GPRS is sometimes described as 2.5G, that is, a technology between the second (2G) and third (3G) generations of mobile telephony.[4] It provides moderate-speed data transfer, by using unused time division multiple access (TDMA) channels in, for example, the GSM system. GPRS is integrated into GSM Release 97 and newer releases.

GPRS usage is typically charged based on volume of data. This contrasts with circuit switching data, which is typically billed per minute of connection time, regardless of whether or not the user transfers data during that period.

GPRS data is typically supplied either as part of a bundle (e.g., 5 GB per month for a fixed fee) or on a pay-as-you-use basis. Usage above the bundle cap is either charged per megabyte or disallowed. The pay-as-you-use charging is typically per megabyte of traffic.

General Packet Radio Services (GPRS) is a packet-based wireless communication service that promises data rates from 56 up to 114 Kbps and continuous connection to the Internet for mobile phone and computer users. The higher data rates allow users to take part in video conferences and interact with multimedia Web sites and similar applications using mobile handheld devices as well as notebook computers. GPRS is based on Global System for Mobile (GSM) communication and complements existing services such circuit-switched cellular phone connections and the Short Message Service (SMS).

Protocols supported

GPRS supports the following protocols:

1. Internet protocol (IP). In practice, built-in mobile browsers use IPv4 since IPv6 was not yet popular.

2. Point-to-point protocol (PPP). In this mode PPP is often not supported by the mobile phone operator but if the mobile is used as a modem to the connected computer, PPP is used to tunnel IP to the phone. This allows an IP address to be assigned dynamically to the mobile equipment.

3. X.25 connections. This is typically used for applications like wireless payment terminals, although it has been removed from the standard. X.25 can still be supported over PPP, or even over IP, but doing this requires either a network based router to perform encapsulation or intelligence built in to the end-device/terminal; e.g., user equipment (UE).

When TCP/IP is used, each phone can have one or more IP addresses allocated. GPRS will store and forward the IP packets to the phone even during handover. The TCP handles any packet loss (e.g. due to a radio noise induced pause).

Hardware

Devices supporting GPRS are divided into three classes:

Class A

Can be connected to GPRS service and GSM service (voice, SMS), using both at the same time. Such devices are known to be available today.

Class B

Can be connected to GPRS service and GSM service (voice, SMS), but using only one or the other at a given time. During GSM service (voice call or SMS), GPRS service is suspended, and then resumed automatically after the GSM service (voice call or SMS) has concluded. Most GPRS mobile devices are Class B.

Class C

Are connected to either GPRS service or GSM service (voice, SMS). Must be switched manually between one or the other service.

A true Class A device may be required to transmit on two different frequencies at the same time, and thus will need two radios. To get around this expensive requirement, a GPRS mobile may implement the dual transfer mode (DTM) feature. A DTM-capable mobile may use simultaneous voice and packet data, with the network coordinating to ensure that it is not required to transmit on two different frequencies at the same time.

http://en.wikipedia.org/wiki/General_Packet_Radio_Service

http://searchmobilecomputing.techtarget.com/definition/GPRS

Chapter 18

MMDS and LMDS

      The  Multichannel Multipoint Distribution Service (MMDS) is a broadcasting and communications service that operates in the ultra-high-frequency (UHF) portion of the radio spectrum between 2.1 and 2.7 GHz. MMDS is also known as wireless cable. It was conceived as a substitute for conventional cable television (TV). However, it also has applications in telephone/fax and data communications. Allows two-way voice, data and video streaming. It operates at a lower frequency than LMDS (typically within specified bands in the 2-10GHz range) and therefore has a greater range and requires a less powerful signal than LMDS. MMDS is a less complicated, cheaper system to implement.

     

         MMDS band uses microwave frequencies from 2 GHz to 3 GHz in range. Reception of MMDS-delivered television signals is done with a special rooftop microwave antenna and a set-top box for the television receiving the signals. The antenna usually has an integrated down-converter to transmit the signals at frequencies compatible with terrestrial TV tuners down on the coax (much like on satellite dishes where the signals are converted down to frequencies more compatible with standard TV coaxial cabling), some larger antennas utilise an external down-converter. The receiver box is very similar in appearance to an analogue cable television receiver box. is a wireless telecommunications technology, used for general-purpose broadband networking or, more commonly, as an alternative method of cable television programming reception.

Transmission line

   Transmission line is a specialized cable designed to carry alternating current of radio frequency, that is, currents with a frequency high enough that their wave nature must be taken into account. Transmission lines are used for purposes such as connecting radio transmitters and receivers with their antennas, distributing cable television signals, and computer network connections.

        

          Local Multipoint Distribution Service (LMDS) is an ideal solution for bringing high-bandwidth services to homes and offices within the last-mile—an area where cable or optical fibre may not be convenient or economical. Having architectural similarities with cellular networks, LMDS is a fixed (non-mobile) point-to-multipoint wireless access technology that typically operates in the 28 GHz band and offers Line-of-Sight (LoS) coverage up to 3-5 km. Depending on the local licensing regulations in a country, such broadband wireless systems may operate anywhere from 2 to 42 GHz. Though data transfer rates for LMDS can reach 1.5 to 2 Gbps, in reality it is designed to deliver data at speeds between 64 Kbps to 155 Mbps (as against 9.6 Kbps offered by 2G cellular networks like GSM), a more realistic downstream average being around 38 Mbps. At such speeds, LMDS may be the key to bringing multimedia data—supporting voice connections, the Internet, videoconferencing, interactive gaming, video streaming and other high-speed data applications—to millions of customers worldwide over the air.

              

The services possible with LMDS include the following:

· Voice dial−up services

· Data

· Internet access

· Video

Head-End Equipment

The Head-End equipment can be broken down into two main categories:

Digital television equipment and Internet and VoIP equipment.

   

     The digital television equipment can provide MPEG-2 encoded video/audio streams from live television feeds, and optionally from video servers with VOD or other pre-recorded content.  The encoded streams are multiplexed into a DVB compliant MPEG-2 ASI transport stream and delivered to the transmission site through a variety of distribution networks including IP networks, microwave links and satellite delivery.

          The Internet and VoIP Head-End equipment requires a robust IP network connection to the DOCSIS 2.0/3.0 Wireless Modem Termination System at the transmission site.  The connection must exceed the total bandwidth   (>30Mbit/sec) of the wireless data network.

http://en.wikipedia.org/wiki/Local_Multipoint_Distribution_Service 

http://www.angelfire.com/nd/ramdinchacha/DEC00.html

http://www.uniquesys.com/MMDS/MMDS_Triple_Play.php

http://www.digital-kaos.co.uk/forums/f10/what-mmds-simple-explanation-23214/

http://www.mobilecomms-technology.com/projects/mmds/

Chapter 17

                               

      Microwave− and Radio−Based Systems

        A radio base system (1000) is multi-path-connected to a plurality of mobile terminal devices to transmit/receive signals. When a communication channel establishment request is sent from one of the plurality of mobile terminal devices, a control unit (80) detects the presence or absence of a mobile terminal device to which a communication channel is already connected for each of a plurality of slots.

           Microwave frequencies range from 300 MHz to 30 GHz, corresponding to wavelengths of 1 meter to 1 cm.  These frequencies are useful for terrestrial and satellite communication systems, both fixed and mobile.  In the case of point-to-point radio links, antennas are placed on a tower or other tall structure at sufficient height to provide a direct, unobstructed line-of-sight (LOS) path between the transmitter and receiver sites. In the case of mobile radio systems, a single tower provides point-to-multipoint coverage, which may include both LOS and non-LOS paths.  LOS microwave is used for both short- and long-haul telecommunications to complement wired media such as optical transmission systems.

         Microwaves are widely used for point-to-point communications because their small wavelength allows conveniently-sized antennas to direct them in narrow beams, which can be pointed directly at the receiving antenna. This allows nearby microwave equipment to use the same frequencies without interfering with each other, as lower frequency radio waves do.

  

   Advantages:

Ø  High frequency of microwaves gives the microwave band a very large information-carrying capacity.

Ø  The microwave band has a bandwidth 30 times that of all the rest of the radio spectrum.

     Disadvantage:

Ø  Microwaves are limited to line of sight propagation.

Ø  They cannot pass around hills or mountains as lower frequency radio waves can.

  

Principles and Operation

Microwave Link Structure

        

      The basic components required for operating a radio link are the transmitter, towers, antennas, and receiver. Transmitter functions typically include multiplexing, encoding, modulation, up-conversion from baseband or intermediate frequency (IF) to radio frequency (RF), power amplification, and filtering for spectrum control. Receiver functions include RF filtering, down-conversion from RF to IF, amplification at IF, equalization, demodulation, decoding, and demultiplexing. To achieve point-to-point radio links, antennas are placed on a tower or other tall structure at sufficient height to provide a direct, unobstructed line-of-sight (LOS) path between the transmitter and receiver sites.

Microwave System Design

    

     The design of microwave radio systems involves engineering of the path to evaluate the effects of propagation on performance, development of a frequency allocation plan, and proper selection of radio and link components. The frequency allocation plan is based on four elements: the local frequency regulatory authority requirements, selected radio transmitter and receiver characteristics, antenna characteristics, and potential intrasystem and intersystem RF interference.

 Microwave Propagation Characteristics

       

     The various phenomena associated with propagation, such as multipath fading and interference, affect microwave radio performance.  The modes of propagation between two radio antennas may include a direct, line-of-sight (LOS) path but also a ground or surface wave that parallels the earth's surface, a sky wave from signal components reflected off the troposphere or ionosphere, a ground reflected path, and a path diffracted from an obstacle in the terrain.

       A simple and cost-effective demultiplexing approach for a subcarrier multiplexed radio-over-fiber (RoF) system is proposed, analyzed, and experimentally demonstrated. A microwave photonic filter based on multiple optical sources is integrated into the RoF system, and by simply controlling the time delay in the remote antenna unit, the subcarrier with desirable frequency can be filtered out, and undesirable ones are suppressed. An experimental demonstration has been carried out by implementing a two-optical-source-based microwave photonic filter in an RoF downlink transmitting a 2.5-GHz subcarrier modulated with 150-Mb/s on-off keying (OOK) data, showing that it works well as a subcarrier demultiplexer. The proposed demultiplexing approach enjoys high flexibility, tunability, and cost-effectiveness and has good potential applications in the multiplexed RoF systems.

http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=5711628

http://www.eogogics.com/talkgogics/tutorials/microwave-line-of-sight-systems

http://www.google.com.ph/search?q=Microwave%E2%88%92+and+Radio%E2%88%92Based+Systems&hl=tl&rlz=1C1ECBA_enPH471PH471&prmd=imvns&source=lnms&tbm=isch&ei=kqs8T_S6OLCRiQfNv823BA&sa=X&oi=mode_link&ct=mode&cd=2&ved=0CBQQ_AUoAQ&biw=1366&bih=624

Chapter 16

       

                                                                    xDSL

       DSL   is a family of technologies that provide internet access by transmitting digital data over the wires of a local telephone network. In telecommunications marketing, the term DSL is widely understood to mean Asymmetric Digital Subscriber Line (ADSL), the most commonly installed DSL technology. DSL service is delivered simultaneously with wired telephone service on the same telephone line. This is possible because DSL uses higher frequency bands for data separated by filtering. On the customer premises, a DSL filter on each outlet removes the high frequency interference, to enable simultaneous use of the telephone and data.

       The data bit rate of consumer DSL services typically ranges from 256 kbit/s to 40 Mbit/s in the direction to the customer (downstream), depending on DSL technology, line conditions, and service-level implementation. In ADSL, the data throughput in the upstream direction, (the direction to the service provider) is lower, hence the designation of asymmetric service. In Symmetric Digital Subscriber Line (SDSL) services, the downstream and upstream data rates are equal.

       A DSL circuit provides digital service. The underlying technology of transport across DSL facilities uses high-frequency sinusoidal carrier wave modulation, which is an analog signal transmission. A DSL circuit terminates at each end in a modem which modulates patterns of bits into certain high-frequency impulses for transmission to the opposing modem. Signals received from the far-end modem are demodulated to yield a corresponding bit pattern that the modem retransmits, in digital form, to its interfaced equipment, such as a computer, router, switch, etc.

Benefits & Applications

Benefits

• High-speed data service

– DSL typically >10x faster than

56-kbps analog modem

• Always on connection

– No need to “dial-up”

• Uses existing copper wires

– Co-exists w/ POTS service

• Reasonably priced today and

getting cheaper

Applications

• High speed Internet access

• SOHO

• Multimedia, Long distance

learning, gaming

• Video on Demand

• VPN

• VoDSL

          Asymmetric digital subscriber line (ADSL) is a type of digital subscriber line technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. It does this by utilizing frequencies that are not used by a voice telephone call.[1] A splitter, or DSL filter, allows a single telephone connection to be used for both ADSL service and voice calls at the same time. ADSL can generally only be distributed over short distances from the telephone exchange (the last mile), typically less than 4 kilometres (2 mi),[2] but has been known to exceed 8 kilometres (5 mi) if the originally laid wire gauge allows for further distribution.

           IDSL is a system in which digital data is transmitted at 128 Kbps on a regular copper telephone line (twisted pair) from a user to a destination using digital (rather than analog or voice) transmission, bypassing the telephone company's central office equipment that handles analog signals. IDSL uses the Integrated Services Digital Network (Integrated Services Digital Network) Basic Rate Interface in ISDN transmission code.

           HDSL (High bit-rate Digital Subscriber Line), one of the earliest forms of DSL, is used for wideband digital transmission within a corporate site and between the telephone company and a customer. The main characteristic of HDSL is that it is symmetrical: an equal amount of bandwidth is available in both directions. HDSL can carry as much on a single wire of twisted-pair cable as can be carried on a T1 line (up to 1.544 Mbps) in North America or an E1 line (up to 2.048 Mbps) in Europe over a somewhat longer range and is considered an alternative to a T1 or E1 connection.

         SDSL (Symmetric Digital Subscriber Line) is high-speed Internet access service with matching upstream and downstream data rates. That is, data can be sent to the Internet from the client machine or received from the Internet with equal bandwidth availability in both directions.

         RADSL is an implementation of ADSL that automatically adjusts the connection speed to adjust for the quality of the telephone line. As line conditions change, you can see the speeds changing in each direction during the transmission.

         SHDSL technology can transport data symmetrically at data rates from 192 Kbps to 2,320 Kbps. SHDSL utilizes a single copper wire pair, making it an affordable DSL option attractive to small businesses.This service delivers voice and data services based on highly innovative communication technologies and will thus be able to replace older communication technologies such as T1, E1, HDSL, HDSL2, SDSL, ISDN, and IDSL in the future.

          VDSL was developed to support exceptionally high-bandwidth applications such as High-Definition Television (HDTV). VDSL is not as widely deployed as other forms of DSL service. However, VDSL can achieve data rates up to approximately 51,840 Kbps, making it the fastest available form of DSL.

http://compnetworking.about.com/od/dsldigitalsubscriberline/l/bldef_vdsl.htm

http://www.wisegeek.com/what-is-sdsl.htm

http://www.xilinx.com/esp/wired/optical/collateral/DSL.pdf

http://en.wikipedia.org/wiki/Digital_subscriber_line

Chapter 12

ASYNCHRONOUS TRANSFER MODE

    Asynchronous Transfer Mode (ATM) is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that use variable sized packets or frames. ATM provides data link layer services that run over a wide range of OSI physical Layer links. ATM has functional similarity with both circuit switched networking and small packet switched networking. It was designed for a network that must handle both traditional high-throughput data traffic (e.g., file transfers), and real-time, low-latency content such as voice and video. ATM uses a connection-oriented model in which a virtual circuit must be established between two endpoints before the actual data exchange begins. ATM is a core protocol used over the SONET/SDH backbone of the public switched telephone network (PSTN) and Integrated Services Digital Network (ISDN), but its use is declining in favour of all IP.

       Asynchronous Transfer Mode, a network technology based on transferring data in cells or packets of a fixed size. The cell used with ATM is relatively small compared to units used with older technologies. The small, constant cell size allows ATM equipment to transmit video, audio, and computer data over the same network, and assure that no single type of data hogs the line.

      ATM (asynchronous transfer mode) is a dedicated-connection switching technology that organizes digital data into 53-byte cell units and transmits them over a physical medium using digital signal technology. Individually, a cell is processed asynchronously relative to other related cells and is queued before being multiplexed over the transmission path.

            ATM creates a fixed channel, or route, between two points whenever data transfer begins. This differs from TCP/IP, in which messages are divided into packets and each packet can take a different route from source to destination. This difference makes it easier to track and bill data usage across an ATM network, but it makes it less adaptable to sudden surges in network traffic.

       Asynchronous Transfer Mode (ATM) represents a relatively recently developed communications technology designed to overcome the constraints associated with traditional, and for the most part separate, voice and data networks. ATM has its roots in the work of a CCITT (now known as ITU-T) study group formed to develop broadband ISDN standards during the mid-1980s. In 1988, a cell switching technology was chosen as the foundation for broadband ISDN, and in 1991, the ATM Forum was founded.

         The ATM Forum represents an international consortium of public and private equipment vendors, data communications and telecommunications service providers, consultants, and end users established to promote the implementation of ATM. To accomplish this goal, the ATM Forum develops standards with the ITU and other standards organizations.

       The first ATM Forum standard was released in 1992. Various ATM Forum working groups are busy defining additional standards required to enable ATM to provide a communications capability for the wide range of LAN and WAN transmission schemes it is designed to support. This standardization effort will probably remain in effect for a considerable period due to the comprehensive design goal of the technology, which was developed to support voice, data, and video on both local and wide area networks.

Benefits of ATM

      ATM provides a flexible and scalable solution to the increasing need for quality of service in networks where multiple information types (such as data, voice, and real-time video and audio) are supported. With ATM, each of these information types can pass through a single network connection.        

ATM can provide the following:

1.    High-speed communication

2.    Connection-oriented service, similar to traditional telephony

3.    Fast, hardware-based switching

4.    A single, universal, interoperable network transport

5.    A single network connection that can reliably mix voice, vedio, and data

6.    Flexible and efficient allocation of network bandwidth  

http://technet.microsoft.com/en-us/library/cc740081(WS.10).aspx

http://www.techfest.com/networking/atm/atm.htm

http://technet.microsoft.com/en-us/library/bb726929.aspx

http://www.webopedia.com/TERM/A/ATM.html

http://en.wikipedia.org/wiki/Asynchronous_Transfer_Mode