Transcript Lecture 06

NETE0510
Physical Layer Protocols and
Access Technologies
Supakorn Kungpisdan
[email protected]
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Communications
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Virtual Tributary (VT)
 VTs are the building blocks of the SPE
 VTxx designates VTs of xx Mbps
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Virtual Tributary (VT)
7 VT groups (VTGs) per STS-1, each
VTG contain
• 4 VT1.5s  1 STS-1 can carry 28
DS1s
• 3 VT2s  1 STS-1 can carry 21 E1s
• 2 VT3s
•1 VT6
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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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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-C, EIA-232-E, ITU-T V.24/V.28
 RS-232-C and EIA-232-E are defined by the Electronic
Industries Association (EIA) as synchronous interface
standards for use with the physical layer
 D-shaped 25-pin connector DTE interface to voice-grade
modems (DCE)
 ITU V.24/V.28 is similar to RS-232-C and provides the
international version of the RS-232-C standard
 V.24 defines physical interface and V.28 defines electrical
interface
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RS-232
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T1/E1 Framing and Formating
 A T1 circuit operates at a speed of 1.544 Mbps  circuit
capacity
 Throughput is less than 1.536 Mbps
 Took twisted wire pairs and accommodated 24 voice
conversations instead of one with the use of multiplexers
 24 channels, 8 bits per channel, in a time frame of 125
µs
 192 bits + 1 framing bit = 193 bits per T1 frame
 T1 transmits 8000 frames per second
 E1 is European standard of the T1
 Offer 2.048-Mbps bandwidth
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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 directchannel interface
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HSSI (cont’d)
Fiber-optic modem
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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 the 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: 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
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Gigabit Ethernet
 1000 Mbps
 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-5) encoding along with four wire
pairs, able to provide 250 Mbps per pair
 Can transmit signal for 100 m over twister-pair cable and
longer with fiber-optic cable
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Gigabit Ethernet (cont’d)
 1000BaseT: use 4-pair CAT-5 balanced copper cabling and a 5level 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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Step-index Profile
The proportion between diameters of core and cladding e.g. 62.5/125 (µm)
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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:
Independent or ad-hoc  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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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.
 Coaxial cable connections are also available
 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)
MDI: medium dependent interface used
to connect to other hub or switch
without crossover cable required
Media access unit
(provide logical ring)
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Physical Media Comparison
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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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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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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 T1
 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, $-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 BRI provides one of the best disaster
discovery alternatives for services such as FR
and IP (VPNs and Internet access)
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ISDN Basics
 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
NT1 or NT2
Terminal Adapter
ISDN router (TE1)
ISDN PCI card
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ISDN Reference Points
 R — References the connection between a non-ISDN
compatible device Terminal Equipment type 2 (TE2)and
a Terminal Adapter (TA), for example an RS-232- serial
interface.
 S — References the points that connect into the
customer switching device Network Termination type 2
(NT2) and enables calls between the various types of
customer premises equipment.
 T — Electrically identical to the S interface, it references
the outbound connection from the NT1 to the ISDN
network or Network Termination type 1 (NT1).
 U — References the connection between the NT1 and
the ISDN network owned by the telephone company.
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ISDN Access Options
TE1
TE1
ISDN router
TE2
TE1
ISDN router
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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
 PRI
23 64-kbps bearer (B) channels and one 64-kbps
signaling channel (North America) 23B+D
30B+D for international
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 fullduplex 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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T1 Frame Structure
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E1 PRI Frame Structure
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ISDN Protocol Model
 Primary ISDN architecture concepts consists of multiple
devices connecting through an ISDN network termination
device (TE) into the central office environment where
information services are provided
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ISDN Information Services Concept
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ISDN Protocol Architecture
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ISDN Protocol Architecture
ISDN introduced the notion of multiple
planes:
Bearer service (or user plane)
Control plane
Management plane
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ISDN Protocol Architecture
 The user protocol (or bearer service) is Layer 1 for
circuit-mode, Layer-2 for frame-mode, and Layer 3 for
packet-mode services
 Intermediate nodes might provide only physical
connectivity.
 The purpose of control plane is to establish, configure,
and release the user plane capabilities
 The management plane is responsible for monitoring the
status, configuring the parameters, and measuring the
performance of the user and control planes
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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 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: 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
 Physical Layer Protocols and Interfaces
 Accessing the Network
 Copper Access Technologies
 Cable Access Technologies
 Fiber Access Technologies
 Air Access Technologies
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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 Cable
Ground 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 supported 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 telephpony, 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
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Equipment Associated with Cable Access
 2 types of equipments required
Cable modem on the customer end
Cable-Modem Termination System (CMTS) at the cable
provider’s end
 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
kms
Use a tuner to separate data channels from cable TV
programming
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Equipment Associated with Cable Access
 CMTS
Located at the cable provider’s headend
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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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
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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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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
 Physical Layer Protocols and Interfaces
 Accessing the Network
 Copper Access Technologies
 Cable Access Technologies
 Fiber Access Technologies
 Air Access Technologies
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Air Access Technologies
Mobile wireless technologies include
cellular and wireless LAN
Fixed wireless technologies include pointto-point, fixed radio, and satellite
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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
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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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Questions?
Next Lecture
Common Protocols and Interfaces
in the LAN Environment
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