NETE0510: Communication Media and Data Communications 1 Course Outline 1.Data Communications: Past...

NETE0510: Communication Media and Data Communications

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Course Outline1. Data Communications: Past to Future2. Understanding the Standards and Their Makers3. Introduction to Transmission Technologies4. Multiplexing and Switching Technologies5. Optical Networking6. Midterm Revision7. Physical Layer Protocols and Access Technologies (28/7/07)8. Data-link layer and Protocols (28/7/07)9. LANs and Hi-speed LANs (4/8/07)10. ISDN (11/8/07)11. Frame Relay (18/8/07)12. ATM (25/8/07)13. Wireless LANs and Cellular Networks (1/9/07)14. Common Protocols and Interfaces in the Upper Layers (TCP/IP)

(8/9/07)15. Presentation (15/9/07)


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NETE0510Physical Layer Protocols and

Access Technologies

Supakorn [email protected]


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Physical Media

Three major types of physical media Copper

Twisted-pair, coaxial, twin-axial (twin-ax), broadband (used in CATV)

Fiber Resistance to electromagnetic signals, not affected by

crosstalk, interference, but require more protection Air

Point-to-point wireless, wireless LAN, cellular, microwave, or satellite


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RS-232, ITU-T V.24/V.28

EIA RS-232 (or EIA-232 or most recent TIA-232) are defined by the Electronic Industries Association (EIA) as synchronous interface standards for use with the physical layer D-shaped 25-pin connector (DB25) DTE interface to voice-

grade modems (DCE) TIA: Telecommunications Industry Association EIA: Electronic Industries Alliance

ITU V.24/V.28 is similar to RS-232 and provides the international version of the RS-232 standard V.24 defines physical interface and V.28 defines electrical

interface


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RS-232


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RS-232 (cont’d)

The standard does not define bit rates for transmission, although the standard says it is intended for bit rates lower than 20 kbps.

Many modern devices can exceed this speeed (38.4 kbps and 57.6 kbps being common, and 115.2 kbps and 230.4 kbps making occasional appearances) while still using RS232 compatible signal levels.

In general, terminals have male connectors with DTE pin functions, and modems have female connectors with DCE pin functions

Full RS232 requires 25-pin connector, whereas only 22 pins are used. Since most devices, especially PC, use only a few signals, smaller connectors can be used, e.g. 9-pin connector (DB9)

More about RS232 http://www.camiresearch.com/Data_Com_Basics/RS232_standard.html http://www.taltech.com/resources/intro-sc.html


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RS-232 (cont’d)HW flow control


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Connector Shell (Shield)

Pin 1 is wired to the connector shell (shield) The cable's shield is usually a foil blanket

surrounding all conductors running the length of the cable and joining the connector shells.

Pin 1 of the EIA232 specification, called out as "shield", may be separate from the earth ground usually associated with the connector shells.


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25-pin RS232 Pinouts

(Shield ground)


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Data Transmission


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9-pin RS232 Pinouts


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DB25-to-DB9 Adapter

Use this to adapt a 25-pin COM connector on the back of a computer to mate with a 9-pin serial DCE device, such as a 9-pin serial mouse or modem.


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DB9-to-DB25 Adapter

Use this to adapt a 9-pin COM connector on the back of a computer to mate with a 25-pin serial DCE devices, such as a modem


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Null Modem

Use this female-to-female cable in any application where you wish to connect two DTE devices (for example, two computers). A male-to-male equivalent of this cable would be used to connect two DCE devices.


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HSSI

HSSI is a physical interface at speeds up to 52 Mbps Become standard interface between DS3 rate of 45

Mbps and the OC-1 SONET interface of 51.84 Mbps for everything from WAN connectivity to a DTE-DCE direct-channel interface


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HSSI (cont’d)

Fiber-optic modem

Rack


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IEEE802 Physical Interfaces

3 common MAC physical interfaces for the IEEE 802 architecture model are: Ethernet (802.3) Token Ring (802.5) Wireless LAN (802.11)


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10-Mbps (Legacy) Ethernet

Many different types of Ethernet access: 1 Base5, 10Base2, 10Base5, 10BaseF

Each type defines both wiring and device terminating the end of the wiring

10Base5 (Thicknet) and 10Base2 (Thinnet) 10 refers to 10-Mbps Ethernet Base stands for baseband

Baseband signaling indicates that Ethernet signals are the only signals carried over the media system

Most common connectivity is via twisted-pair using 10BaseT or 100BaseT standards with no more than 100 m from central bus or switch


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Comparisons of Ethernet Cabling Specifications


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Fast Ethernet

100 Mbps, new preferred standard FastEthernet specifications include mechanisms for

autonegotiation of the media speed. Vendor can produce dual-speed Ethernet interfaces that can

be installed and run at either 10 Mbps or 100 Mbps automatically

Autonegotiation allows the devices to perform automatic configuration to achieve the best possible mode of operation over a link


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Fast Ethernet (cont’d)

Three media varieties 100BaseTX: uses 2-pair Category 5 UTP cable

TX segment type is a twisted-pair segment that uses two pairs of wires and is based on data grade twisted-pair physical medium standard developed by ANSI

100BaseFX: uses fiber-optic cable FX is based on fiber-optic physical medium standard developed

by ANSI and uses two strands of fiber cable 100BaseT4: early implementation of Fast Ethernet, uses 4-

pair Category 3, 4, or 5 UTP cable T4 segment type is a twisted-pair segment that uses four pairs

of telephone-grade twisted-pair wire, half-duplex 100BaseT2: full-duplex, 100 megabit over two pairs of

Category 3 Too late to make much of an impact


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Gigabit Ethernet

Idea when budget is tight but require higher bandwidth Employ all the same specifications defined by the

original Ethernet standard, including the same Ethernet frame format and size

1000BaseT physical layer provides 1-Gbps Ethernet signal transmission over four pairs of Cat-5 UTP cable

Use five-level (PAM (Pulse Amplitude Modulation)-5) encoding (5 voltage level: +2, +1, 0, -1, -2 V) along with four wire pairs, able to provide 250 Mbps per pair PAM-5 is used to reduce inter-symbol interference between the

unshielded pairs. Can transmit signal for 100 m over twister-pair cable and

longer with fiber-optic cable


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Step-index Profile

The proportion between diameters of core and cladding e.g. 62.5/125 (µm)


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Gigabit Ethernet (cont’d)

1000BaseT: use 4-pair CAT-5 balanced copper cabling and a 5-level coding scheme

1000BaseCX: use 150-ohm shielded copper cable and supports a max length of 25 m

1000BaseF: use fiber-optic 1000BaseFX: use 62.5/125 multimode fiber and supports a max

distance of 412 m 1000BaseSX: use 50/125 or 62.5/125 multimode fiber with max

distance of 550 m 1000BaseLX: use 9/125 single-mode, 50/125 multimode, or

62.5/125 multimode fiber with max distance of 5 kms 1000BaseZX: use 9/125 single-mode fiber with max distance of 100

kms 10-Gbps Ethernet: only fiber-optic cable


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Token Bus and Token Ring Physical interface for IEEE802.4 Token Bus and IEEE802.5 Token Ring is

the DB connector, interfacing with IBM Type 1 shielded twisted-pair cable. Token ring: Physical star, logical ring Uses special 3-byte frame called a token travelling around the ring. Coaxial cable connections are also available (for Token Bus) Token ring LAN speeds of 4, 16, 100 Mbps and 1 Gbps have been standardi

zed by the IEEE 802.5 working group. Token Ring is usually run in Type 1 (2-pair STP), Type 2 (4-pair STP), Type

3 (UTP), and Type 5 (fiber-optic cable)

Media access unit(provide logical ring)

MDI port: medium dependent interface used to connect to other hub or switch without crossover cable required


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Physical Media Comparison


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Wireless LAN (IEEE802.11)

IEEE802.11 specifies connectivity between LAN devices using radio-based equipment

802.11 is similar to 802.3 for wired LANs but use CSMA/CA instead of CSMA/CD

Collision detection cannot be used for radio frequency transmission because when a node transmits over the air, it cannot hear other nodes on the network

Support two types of operating configurations: Adhoc or independent do not need an access point Infrastructure need an access point

Access point acts as a bridge in a wired LAN


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Wireless LAN (cont’d)


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Wireless LAN (cont’d)


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Outline

Physical Layer Protocols and Interfaces Accessing the Network

Consumer Corporate or Business

Copper Access Technologies Cable Access Technologies Fiber Access Technologies Air Access Technologies


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Consumer or Residential Alternatives

Existing copper phone line: Plain old telephone service (POTS) Dialup ISDN Basic rate interface (BRI) DSL

Cable line Cable modem

Wireless Direct broadcast satellite (DBS) Very small aperture satellite (VSAT)


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Consumer or Residential Alternatives


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Last-Mile Link

The link that spans the last mile from the home to a network service provider

Such services typically connect a home to an existing network

Service Bandwidth

POTS 28.8-56 kbps

ISDN 64-128 kbps

xDSL 16 kbps–55.2 Mbps

CATV 20-40 Mbps

CATV = Cable TelevisionPOTS = Plain Old Telephone Service


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Corporate or Business Access Alternatives

Copper All consumer methods DS1, FT3, DS3 ISDN

Fiber DS3 SONET OC-N


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Corporate or Business Access Alternatives


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Outline

Physical Layer Protocols and Interfaces Accessing the Network Copper Access Technologies Cable Access Technologies Fiber Access Technologies Air Access Technologies


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UTP

A transmission repeater system over a four-wire twisted-pair is defined and called a t-carrier system e.g. T1 system

Signal and service is referred as a DS1 T1 circuits are brought to the customer location

via either copper or fiber UTP is very popular type of copper wiring


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UTP Ratings (EIA/TIA Standards)

Category 1 used for voice and low-speed data transmission up to 56 kbps

Category 2 Ideal for 4-Mbps token ring, RS-232, RS-422, and AS/400

Category 3 Ideal for telephone, 4-Mbps token ring, and 10BaseT applications

Category 4 Used for 16-Mbps token ring

Category 5 Suitable for 100BaseT Ethernet, 10-Mbps token ring, and OC-3 ATM

Category 5e Support speed up to 1.2 Gbps and typically used for Gigabit Ethernet

Category 6 Newly designed for Gigabit Ethernet and future apps


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Dialup or Legacy Analog Modem

Current standard for 56-Kbps modem is V.92 Prior to 56-Kbps modems, the best speed between two

modems was 33.6 Kbps. With V.90, connection speeds can exceed 50 Kbps

Up to 54 Kbps download, 33.6 Kbps upload V.92 provides 56 Kbps with enhancements:

Upload speed increased to 48 Kbps: improve video conferencing and file uploading

Startup time reduced from about 20 seconds to about 10 seconds

Internet call waiting Receive a call while the modem is still connected


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Dialup or Legacy Analog Modem


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ISDN

ISDN provides one of the best disaster discovery alternatives for services such as Fame Relay and IP (VPNs and Internet access)

Built on the TDM hierarchy developed for digital telephony

ITU-T defines two standards for physical interface to ISDN BRI (Basic Rate Interface) PRI (Primary Rate Interface)

The physical layer provides transmission capability, activation, and deactivation of terminal equipment (TE) and network termination (NT) data (D)-channel access for TE, maintenance functions, and channel status indications


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ISDN (cont’d)


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ISDN Devices


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ISDN Devices

Terminal Adapter

ISDN router (TE1)

NT1 or NT2

ISDN PCI card


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ISDN Reference Points

R — References the connection between a non-ISDN compatible device TE2 and a TA, for example an RS-232- serial interface. TE2 - TA

S — References the points that connect into the customer switching device NT2 and enables calls between the various types of customer premises equipment. NT2 – TE1, NT2 - TA

T — Electrically identical to the S interface, it references the outbound connection from the NT1 to the ISDN network or NT2. NT1 – NT2

U — References the connection between the NT1 and the ISDN network owned by the telephone company. NT1 – Telephone company


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ISDN Access Options

TE1ISDN router

TE1

TE1ISDN router

TE2


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BRI and PRI

BRI Provides two 64-kbps bearer (B)-channels for the carriage of

user data and one 16-kpbs control and network management D-channel

2B+D = (2x64 + 16) = 144 kbps Suitable for voice, data, and video (low rate)

PRI 23 64-kbps bearer (B) channels and one 64-kbps signaling

channel (North America) 23B+D (DS1 equivalent) 30B+D for international (E1 equivalent) Higher bandwidth or shared customer devices


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ISDN: BRI


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ISDN PRI (cont’d)

ISDN PRI provides a single 1.544 Mbps DS1 or a 2.048-Mbps E1 data rate channel over a full-duplex synchronous point-to-point channel using TDM hierarchy

DS1 data stream comprises 24 DS0 channels of 64 kbps each containing 23 B-channels at 64 kbps each and one D-channel at 64 kbps


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ISDN: PRI


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DSL

DSLAM: DSL Access Multiplexer


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DSL Types


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DSL Modem

The existing copper telephone network line connects the customer’s xDSL modem to a service provider model in the public network.

The xDSL modem can create the following three channel types: High-speed downstream channel ranging from 1.5 to 5.2

Mbps Medium-speed duplex channel ranging from 16 kbps to 2.3

Mbps POTS channel


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DSL Equipments

DSL modem Connect the customer across the local loop to the

provider’s DSL access multiplexer (DSLAM) Support routing, switching, or firewall functionality

DSLAM Use statistical multiplexing to combine many DSL lines Support different types of DSL in a single central office

with additional features e.g. IP routing or DHCP


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Advantages of DSL

Always on connection Simultaneous voice and data communications Higher speed than legacy V.92 modem Not require new wiring


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Disadvantages of DSL

Limitation of distance ADSL, ADSL Lite, IDSL, RADSL, UDSL: 18,000 ft HDSL, FDSL 2: 12,000 ft SDSL: 10,000 ft VDSL: 4,500 ft

The achievable high-speed downstream data rate depends on Length of twisted-pair line Presence of bridged taps (repeaters) and load coils (filters)

from the old party-line days Cross-coupled interference from other lines


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DSL Standards

The ANSI standard for ADSL is discrete multitone (DMT) DMT is a FDM that divides the data into 256 downstream and 32

upstream channels, each 4-kHz wide DMT constantly searches for the best channels for transmission and

reception and shifts the signals between the different channels QAM (Quadrature amplitude modulation) uses phase and amplitude

modulation to create 16 different channels Support two carriers having the same frequency buy differ in phase by

90 degrees Enable twice the rate of standard pulse amplitude modulation

CAP (Carrierless amplitude phase modulation): a version of QAM divides signals on the telephone line into three distinct bands: Voice conversation: 0-4 kHz Upstream channel: 25-160 kHz Downstream channel: 240 kHz – 1.5 MHz


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Outline



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Cable Access Technologies

Enable people to view cable TV and get high-speed internet over the same (coax) access circuit


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Coaxial Cable

Installed approx 60% of all homes in the US Less distance sensitive than DSL Coaxial cable is more resistant to interference

and attenuation than twisted-pair cabling Attenuation is the loss of signal strength, which begins

to occur as the signal travels further along a copper wire


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Coaxial CableGround and protecting the core from electrical noise and crosstalk, a signal overflow from an adjacent wire


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Two-way Cable System


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Two-way Cable Operation (cont’d)

Coaxial cable can carry hundreds of MHz of signals Each TV signal is supported by a 6-MHz channel on the

cable High-end coaxial cable supports 550 MHz carrying 75 TV

channels Recently install fiber from cable headend to distribution

channel, then transmit signals through coaxial cable Fiber supports 750 MHz to support more channels and

high-speed Internet, cable telephony, and interactive video services


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Two-way Cable System (cont’d)

To enable internet access, need to put data into a 6-MHz channel

The first user to connect to the Internet through a specific 6-MHz channel can use almost the entire bandwidth of that channel.

More users, performance drops Service provider resolve performance degradation by

adding a new channel and splitting the numbers of users on each channel

The average throughput is typically about 1 Mbps 2 types of equipments required

Cable modem on the customer end Cable-Modem Termination System (CMTS) at the cable

provider’s end


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Cable Modem

A set-top box device that supports, Internet access, cable TV programming, and telephone access to the PSTN

Provide high-speed Internet access through a cable TV network on average of 3-50 Mbps and a distance of 100 km

Use a tuner to separate data channels from cable TV programming


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CMTS

CMTS Located at the cable provider’s headend CMTS inserts IP packets from the Internet into MPEG frames

and transmits them to the cable modems via an RF signal Similar to DSLAM acting as a multiplexer combining traffic

from multiple users onto a single channel A CMTS supports up to as many as 2,000 connections to the

Internet through a single 6-MHz channel Support both upstream and downstream

Upstream data is transferred from the customer in a separate division of time not used by other customers

Downstream data is supported much like an Ethernet LAN


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CMTS (cont’d)


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CMTS (cont’d)

A CMTS performs packet format conversion and DHCP addressing. It may also provide routing, bridging, filtering and traffic shaping.

The combiner merges the TV programming feeds with the RF (radio freq) data from the CMTS.

A CMTS may provide filtering to protect against theft of service and denial of service attacks or against hackers trying to break into the cable operator's system.

It may provide traffic shaping in order to guarantee a specified quality of service (QoS) to selected customers.

A CMTS may also provide bridging or routing capabilities.


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Cable Modem Standards

In the US, Data Over Cable Service Interface Specification (DOCSIS) accepted by ITU in 1998 Has become ITU J.112

DOCSIS supports data services over a cable TV network using one 6-MHz channel in the 50-750 MHz spectrum range for downstream traffic the 5-42 MHz band for the upstream traffic

A DOCSIS-compliant CMTS enables customer PCs to dynamically obtain IP addresses by acting as a proxy and forwarding DHCP requests to DHCP servers.


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Outline



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Fiber Access Technologies

Preferred cable media for servicing access rates at DS3 and above

Wide range of fiber access solutions and technologies offered including SONET/SDH, ATM, MPLS (Multiprotocol Label Switching), and Ethernet/IP/PPP networks


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Services Offered via Fiber Access

DS3 service Support transmission of 44.736 Mbps of voice, data,

video, and/or switched services SONET/SDH access

Service providers offer SDH/SONET extension over fiber–optic cable at rates from T1/E1 to OC-12/STM-4

SONET/SDH is supported with a wide range of modems, multiplexers, multiservice access nodes, and converters


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Outline



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Wireless Internet Access


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Mobile Wireless

Cellular and analog network work using a hierarchical model consisting of base stations and antennas.

The area a base station covers is called a “cell” Macro cells are the largest of the cells and

provide extensive coverage, often first built to provide coverage

Micro cells support selected outdoor areas Pico cells are the smaller of the cells and are

built to provide capacity Usually cover the interior of buildings


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Cellular Hierarchical Model


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Evolution of Cellular Technologies

NMT = Nordic Mobile Telephony TACS = Total Access Communications SystemAMPS = Advanced Mobile Phone SystemPDC = Personal Digital Cellular (NTT DoCoMo)W-CDMA = Wideband Code Division Multiple Access (UMTS and FOMA (for NTT DoCoMo)EDGE = Enhanced Data Rates for GSM Evolution


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Fixed Wireless Wireless local loop (WLL) using radio technology has

been implemented for places too expensive to wire such as mountain, swamp, and rural cluster areas.

Multichannel multipoint distribution system (MMDS) A line-of-sight service that operates in the 2.1-2.7 GHz frequency

range Use microwave channels to distribute a varied range of

telecommunications services to subscribers Support 6-MHz channels Can reach up to 70 miles in flat area

Local multipoint distribution service (LMDS) Allocated at 27.5-29.5 GHz Provide two-way wireless cable TV and high-speed data service Similar to MMDA but use higher frequencies and has higher

transmission capacity Require only 6-inch antenna, but must be within 3-5 miles of the

subscriber’s house


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