Transcript Lecture 06

Course Outline
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Data Communications: Past to Future
Understanding the Standards and Their Makers
Introduction to Transmission Technologies
Multiplexing and Switching Technologies
Optical Networking
Midterm Revision
Physical Layer Protocols and Access Technologies (28/7/07)
Data-link layer and Protocols (28/7/07)
LANs and Hi-speed LANs (4/8/07)
ISDN (11/8/07)
Frame Relay (18/8/07)
ATM (25/8/07)
Wireless LANs and Cellular Networks (1/9/07)
Common Protocols and Interfaces in the Upper Layers (TCP/IP)
(8/9/07)
Presentation (15/9/07)
NETE0510: Communication Media and Data
Communications
1
NETE0510
Physical Layer Protocols and
Access Technologies
Supakorn Kungpisdan
[email protected]
NETE0510: Communication Media and Data
Communications
2
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
NETE0510: Communication Media and Data
Communications
3
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 voicegrade 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
NETE0510: Communication Media and Data
Communications
4
RS-232
NETE0510: Communication Media and Data
Communications
5
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
NETE0510: Communication Media and Data
Communications
6
RS-232 (cont’d)
HW flow
control
NETE0510: Communication Media and Data
Communications
7
NETE0510: Communication Media and Data
Communications
8
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.
NETE0510: Communication Media and Data
Communications
9
25-pin RS232 Pinouts
(Shield ground)
NETE0510: Communication Media and Data
Communications
10
Data Transmission
NETE0510: Communication Media and Data
Communications
11
9-pin RS232 Pinouts
NETE0510: Communication Media and Data
Communications
12
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.
NETE0510: Communication Media and Data
Communications
13
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
NETE0510: Communication Media and Data
Communications
14
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.
NETE0510: Communication Media and Data
Communications
15
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
NETE0510: Communication Media and Data
Communications
16
HSSI (cont’d)
Fiber-optic modem
Rack
NETE0510: Communication Media and Data
Communications
17
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)
NETE0510: Communication Media and Data
Communications
18
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
NETE0510: Communication Media and Data
Communications
19
Comparisons
of Ethernet
Cabling
Specifications
NETE0510: Communication Media and Data
Communications
20
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
NETE0510: Communication Media and Data
Communications
21
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 4pair 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
NETE0510: Communication Media and Data
Communications
22
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
NETE0510: Communication Media and Data
Communications
23
Step-index Profile
The proportion between diameters of core and cladding e.g. 62.5/125 (µm)
NETE0510: Communication Media and Data
Communications
24
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
NETE0510: Communication Media and Data
Communications
25
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
standardized 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)
MDI port: medium dependent interface
used to connect to other hub or switch
without crossover cable required
Media access unit
(provide logical ring)
NETE0510: Communication Media and Data
Communications
26
Physical Media Comparison
NETE0510: Communication Media and Data
Communications
27
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
NETE0510: Communication Media and Data
Communications
28
Wireless LAN (cont’d)
NETE0510: Communication Media and Data
Communications
29
Wireless LAN (cont’d)
NETE0510: Communication Media and Data
Communications
30
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
NETE0510: Communication Media and Data
Communications
31
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)
NETE0510: Communication Media and Data
Communications
32
Consumer or Residential Alternatives
NETE0510: Communication Media and Data
Communications
33
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
xDSL
64-128 kbps
CATV
20-40 Mbps
16 kbps–55.2
Mbps
CATV = Cable Television
POTS = Plain Old Telephone Service
NETE0510: Communication Media and Data
Communications
34
Corporate or Business Access
Alternatives
 Copper
All consumer methods
DS1, FT3, DS3
ISDN
 Fiber
DS3
SONET OC-N
NETE0510: Communication Media and Data
Communications
35
Corporate or Business Access
Alternatives
NETE0510: Communication Media and Data
Communications
36
Outline
 Physical Layer Protocols and Interfaces
 Accessing the Network
 Copper Access Technologies
 Cable Access Technologies
 Fiber Access Technologies
 Air Access Technologies
NETE0510: Communication Media and Data
Communications
37
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
NETE0510: Communication Media and Data
Communications
38
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
NETE0510: Communication Media and Data
Communications
39
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
NETE0510: Communication Media and Data
Communications
40
Dialup or Legacy Analog Modem
NETE0510: Communication Media and Data
Communications
41
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
NETE0510: Communication Media and Data
Communications
42
ISDN (cont’d)
NETE0510: Communication Media and Data
Communications
43
ISDN Devices
NETE0510: Communication Media and Data
Communications
44
ISDN Devices
NT1 or NT2
Terminal Adapter
ISDN router (TE1)
ISDN PCI card
NETE0510: Communication Media and Data
Communications
45
ISDN Reference Points
 R — References the connection between a non-ISDN
compatible device TE2 and a TA, for example an RS-232serial 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
NETE0510: Communication Media and Data
Communications
46
ISDN Access Options
TE1
TE1
ISDN router
TE2
TE1
ISDN router
NETE0510: Communication Media and Data
Communications
47
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
NETE0510: Communication Media and Data
Communications
48
ISDN: BRI
NETE0510: Communication Media and Data
Communications
49
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
NETE0510: Communication Media and Data
Communications
50
ISDN: PRI
NETE0510: Communication Media and Data
Communications
51
DSL
DSLAM: DSL Access Multiplexer
NETE0510: Communication Media and Data
Communications
52
DSL Types
NETE0510: Communication Media and Data
Communications
53
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
NETE0510: Communication Media and Data
Communications
54
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
NETE0510: Communication Media and Data
Communications
55
Advantages of DSL
 Always on connection
 Simultaneous voice and data communications
 Higher speed than legacy V.92 modem
 Not require new wiring
NETE0510: Communication Media and Data
Communications
56
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
NETE0510: Communication Media and Data
Communications
57
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
NETE0510: Communication Media and Data
Communications
58
Outline
 Physical Layer Protocols and Interfaces
 Accessing the Network
 Copper Access Technologies
 Cable Access Technologies
 Fiber Access Technologies
 Air Access Technologies
NETE0510: Communication Media and Data
Communications
59
Cable Access Technologies
 Enable people to view cable TV and get high-speed
internet over the same (coax) access circuit
NETE0510: Communication Media and Data
Communications
60
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
NETE0510: Communication Media and Data
Communications
61
Coaxial Cable
Ground and protecting the core from electrical noise
and crosstalk, a signal overflow from an adjacent wire
NETE0510: Communication Media and Data
Communications
62
Two-way Cable System
NETE0510: Communication Media and Data
Communications
63
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
NETE0510: Communication Media and Data
Communications
64
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
NETE0510: Communication Media and Data
Communications
65
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
NETE0510: Communication Media and Data
Communications
66
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
NETE0510: Communication Media and Data
Communications
67
CMTS (cont’d)
NETE0510: Communication Media and Data
Communications
68
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.
NETE0510: Communication Media and Data
Communications
69
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.
NETE0510: Communication Media and Data
Communications
70
Outline
 Physical Layer Protocols and Interfaces
 Accessing the Network
 Copper Access Technologies
 Cable Access Technologies
 Fiber Access Technologies
 Air Access Technologies
NETE0510: Communication Media and Data
Communications
71
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
NETE0510: Communication Media and Data
Communications
72
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
NETE0510: Communication Media and Data
Communications
73
Outline
 Physical Layer Protocols and Interfaces
 Accessing the Network
 Copper Access Technologies
 Cable Access Technologies
 Fiber Access Technologies
 Air Access Technologies
NETE0510: Communication Media and Data
Communications
74
Wireless Internet Access
NETE0510: Communication Media and Data
Communications
75
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
NETE0510: Communication Media and Data
Communications
76
Cellular Hierarchical Model
NETE0510: Communication Media and Data
Communications
77
Evolution of Cellular Technologies
NMT = Nordic Mobile Telephony
TACS = Total Access Communications System
AMPS = Advanced Mobile Phone System
PDC = 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
NETE0510: Communication Media and Data
Communications
78
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
NETE0510: Communication Media and Data
Communications
79
Questions?
Next Lecture
Data-link Layer and Protocols
NETE0510: Communication Media and Data
Communications
80