CPE 426 Computer Networks

1
CPE 426 Computer Networks

• Week 16 Last
• Chapter 16 Wireless NW Technologies

2
TOPICS

• Chapter 16 Wireless NW Technologies
• Introduction
• ISM
• PAN
• ISM Bands
• WLAN
• Standard
• Architecture
• Contension
• Wireless MAN and WiMax
• Wireless WAN
• Cellular Technologies
• VSAT
• GPS

3
16.2 Wireless Networks Taxonomy

• ??????????????????????????????????????????????????
  ????????
• ????????????????????????? License ????????
  License
• ??????? Wireless Technologies ????????? PAN ?????
  WAN

4
16.2 Wireless Networks Taxonomy
5
16.3 Personal Area Network

• ??????????????????????? ??????????????????????????
  ???????????????????
• Handset ??? Telephone
• Mouse ??? Keyboard
• ?????????????? 3 ????

6
16.4 ISM Wireless Bands Used By LANs and PANs

• ?????????????????????????????????????????????????
  Industrial, Scientific ??? Medical Group
  ?????????????????????? License ???????????????
  WLAN ??? PAN

7
16.5 Wireless LAN Technologies ??? WIFI

• ??????????????????? IEEE 802.11
• ?? 1999 ??????????????????? Wireless
  ??????????????????? Wi-Fi Alliance
• Non-Profit Organization ??????????????????????????
  ? Wireless ???????????????? IEEE 802.11
• ??????????????????? Wi-Fi Alliance ????????????

8
16.5 Wireless LAN Technologies ??? WIFI
9
16.6 Spread Spectrum Techniques

• ??????????????????? Spread Spectrum ?????
• ????? Performance ???????
• ??????????????????????? Noise
• ??? Bandwidth ????????????????????????
• ?? 3 Technologies
• DSSS ???????????? Digital ?????????(Exclusive
  OR) Code ????????? Pseudorandom Sequence
• FHSS ????????? Analog ???????????????????????????
  ?????????????????????????????
• OFDM ????????? FDM ???????? ?????????????????????
  ?????????????? Orthogonal ??? ????????????????????
  ?????????????

10
16.6 Spread Spectrum Techniques
11
16.7 Wireless LAN Standard ?????(IEEE
802.11-2007)
12
16.8 Wireless LAN Architecture

• ?????????? Access Point (Base Station),
  Interconnection Mechanism (Switch or Router) ???
  Nodes (Wireless Station)
• ???????????????????????
• Ad Hoc Wireless Host ?????????????????????????
  Base Station
• Infrastructure ???? Host ???????????????????
  Base Station
• Set ??? Computer ??????????????????????????????
  Access Point ????? BSS (Basic Service Set)

13
16.8 Wireless LAN Architecture
14
16.9 Overlap, Association and 802.11 Frame Format

• ??? Access Point ????????????????? ???????????
  Dead Zone
• ?????? Access Point ???????????????????????
  Overlap ???? Host ??????????????????????????????
  Access Point
• ???????????? Host ????????????? Association
  ????????????? Access Point
• Frame ??? 802.11 ?????????????? MAC Address
  ??????? Access Point ??? Router

15
16.9 Overlap, Association and 802.11 Frame Format
16
16.10 Coordination ??????? Access Point

• Access Point ??????????????????????
  ?????????????????????????????????????
  ???????????????????????????? ?????????????????????
  
• Handoff (Hand Over) ???????????????????????????
  ????????????? Association ????? AP ???????
• ????????????? Signal Strength ??????????????????
• ?? AP ???????????? ???????? Mechanism ??? Access
  Point ???????? Computer ??????????????????????????
  ????? ???????? Association ??? Access Point
  ????????????????????

17
16.11 Contention-Free Access

• PCF (Point Coordination Function) ?????? AP
  ???????????????? BSS ?????????????????????????????
  ???????????????????? ??????????????????????????
  ?????????????????? WLAN
• DCF (Distributed Coordinated Function)
  ?????????????????? BSS ????? Random Access
  Protocol ????????? 802.11 ????? CSMA/CA ???
  ??????????????????????? RTS(Request to Send)
  ????????????? CTS (Clear to Send) ???? ???????????

18
16.11 Contention-Free Access

• CSMA/CA Timing ????????? 802.11
• Host ???????? ????????? Channel ???????????? DIFS
  Distributed Inter-Frame Space 50 Microsecond
  (SIFS2 Slot Time)
• Host ?????????????????????? RTS
• AP(???? Host ???????) ??????????? RTS
  ??????????????????? SIFS (Short Inter-Frame Space
  10 us) ??????? CTS ??????
• Host ??????????? CTS ?????????????????? SIFS
  ????????????????????????????????? Slot Time
• ????? Slot Time 20 us
• ??????????????????????????? ??????????? SIFS
  ?????? Ack
• ???????????? Ack ?????????????? ??????? Backoff
  ??? Retransmission

19
16.11 Contention-Free Access
20
16.12 Wireless MAN Technologies and WiMax

• ?????????????????????????????????????????? ???
  IEEE 802.16 ???????????? WiMax ???????????????????
  ????????????? WiMax Forum ????????????????????????
  ?
• ????? Version ???????????????????????
• Fixed WiMax, IEEE 802.16-2004 ?????????????????
  Access Point ???????????????? Handoff
  ??????????????????????????????????????????????????
  ?????????
• Mobile WiMax, IEEE 802.16e-2005 ????? Handoff
  ??????? AP ??????????????????? Laptop ???? Cell
  Phone ???
• WiMax ??????????????????????????????? Last Mile
  ???????????????? Backhaul ????????????????????????
  ??? Site ???????????

21
16.12 Wireless MAN Technologies and WiMax
22
16.12 Wireless MAN Technologies and WiMax

• The key features of WiMAX can be summarized as
  follows
• Uses licensed spectrum (i.e., offered by
  carriers)
• Each cell can cover a radius of 3 to 10 Km
• Uses scalable orthogonal FDM
• Guarantees quality of services (for voice or
  video)
• Can transport 70 Mbps in each direction at short
  distances
• Provides 10 Mbps over a long distance (10 Km)

23
16.13 PAN Technologies and Standard

• IEEE 802.15

24
16.13 PAN Technologies and Standard

• Bluetooth
• The IEEE 802.15.1a standard evolved after vendors
  created Bluetooth technology as a short-distance
  wireless connection technology
• The characteristics of Bluetooth technology are
• Wireless replacement for cables (e.g., headphones
  or mouse)
• Uses 2.4 GHz frequency band
• Short distance (up to 5 meters, with variations
  that extend the range to 10 or 50 meters)
• Device is master or slave
• Master grants permission to slave
• Data rate is up to 721 Kbps

25
16.13 PAN Technologies and Standard

• Ultra Wideband (UWB)
• The idea behind UWB communication is that
  spreading data across many frequencies
• requires less power to reach the same distance
• The key characteristics of UWB are
• Uses wide spectrum of frequencies
• Consumes very low power
• Short distance (2 to 10 meters)
• Signal permeates obstacles such as walls
• Data rate of 110 at 10 meters, and up to 500 Mbps
  at 2 meters
• IEEE unable to resolve disputes and form a single
  standard

26
16.13 PAN Technologies and Standard

• Zigbee
• The Zigbee standard (802.15.4) arose from a
  desire to standardize wireless remote control
  technology
• especially for industrial equipment
• Because remote control units only send short
  command
• high data rates are not required
• The chief characteristics of Zigbee are
• Wireless standard for remote control, not data
• Target is industry as well as home automation
• Three frequency bands used (868 MHz, 915 MHz, and
  2.4 GHz)
• Data rate of 20, 40, or 250 Kbps, depending on
  frequency band
• Low power consumption
• Three levels of security being defined

27
16.14 Short Distance Communication Technologies
????

• ?????????? InfraRED ??? RFID
• InfraRED
• InfraRED technology is often used in remote
  controls
• and may be used as a cable replacement (e.g., for
  a wireless mouse)
• The Infrared Data Association (IrDA) has produced
  a set of standards that are widely accepted
• The chief characteristics of the IrDA technology
  are
• Family of standards for various speeds and
  purposes
• Practical systems have range of one to several
  meters
• Directional transmission with a cone covering 30
  Degree
• Data rates between 2.4 Kbps (control) and 16 Mbps
  (data)
• Generally low power consumption with very-low
  power versions
• Signal may reflect from surfaces
• but cannot penetrate solid objects

28
16.14 Short Distance Communication Technologies
????

• Radio Frequency Identification (RFID)
• RFID technology uses an interesting form of
  wireless communication to create a mechanism
• A small tag contains identification information
• that a receiver can pull from the tag
• Some features of RFID
• Over 140 RFID standards exist for a variety of
  applications
• Passive RFIDs draw power from the signal sent by
  the reader
• Active RFIDs contain a battery
• which may last up to 10 years
• Limited distance
• although active RFIDs extend farther than passive
• Can use frequencies from less than 100 MHz to
  868-954 MHz
• Used for
• inventory control, sensors, passports, and other
  applications

29
16.15 Wireless WAN Technologies

• ????????
• Cellular Communication System
• Satellite Communication System

30
16.15.1 Cellular Communication System

• ????????????????????? Voice ?????? Mobile Phone
• ?????????? Cell ???????????? PTN
• ??????????????????????????????????? Data ????
• Architecture ????? Cell ??????????
• Tower
• ???????? Tower ?????????????? Mobile Switching
  Center ?????????????????????????????????????
  Handoff ??????? Cell
• Tower ????? Omnidirectional Antenna
  ??????????????????? (??????????)
• Cell ????? Cell ?????????????????????????
  ?????????
• ???????????????????? Cell ?????????
  ???????????????????????

31
16.15.1 Cellular Communication System
32
16.16 Cell Clusters and Frequency Reuse

• ???????? Cell ???????????????????????????????????
  ????? Cell ???????????? Cluster ????? Cluster
  ???????????????????????????????
• ????????????????????????????????? Cell
  ??????????????
• 7 cell cluster ???????????????????? ?????????????

33
16.16 Cell Clusters and Frequency Reuse
34
16.17 Generations of Cellular Technologies

• 1G, 2G, 2.5G, 3G, 3.5G, 4G
• 1G
• Began in the late 1970s, and extended through the
  1980s
• Originally called cellular mobile radio
  telephones
• used analog signals to carry voice 
• 2G and 2.5G
• Began in the early 1990s and continues to be used
• The main distinction between 1G and 2G arises
• because 2G uses digital signals to carry voice
• The label 2.5G is used for systems that extend a
  2G system
• to include some 3G features

35
16.17 Generations of Cellular Technologies

• 1G, 2G, 2.5G, 3G, 3.5G, 4G
• 3G and 3.5G
• Began in the 2000s
• Focuses on the addition of higher-speed data
  services
• A 3G system offers download rates of 400 Kbps to
  2 Mbps, and is intended to support applications
  such as web browsing and photo sharing
• 3G allows a single telephone to roam across the
  world
• 4G
• Began around 2008
• Focuses on support for real-time multimedia
• such as a television program or high-speed video
• They include multiple connection technologies
• such as Wi-Fi and satellite
• at any time, the phone automatically chooses the
  best connection technology available

36
16.17 Generations of Cellular Technologies

• A variety of standards have evolved
• (many attempted to choose an approach and create
  a standard)
• The European Conference of Postal and
  Telecommunications Administrators chose a TDMA
  technology known as Global System for Mobile
  Communications (GSM)
• In the United States, each carrier created a
  network with its own technology
• Motorola invented a TDMA system known as iDEN
• Most US and Asian carriers adopted a CDMA
  approach that was standardized as IS-95A
• Japan created a TDMA technology known as PDC
• Figure 16.18 summarizes major 2G standards
• and some of the 2.5G standards that evolved

37
16.17 Generations of Cellular Technologies
38
16.17 Generations of Cellular Technologies

• The standards listed in the figure each provide a
  basic communication mechanism over which many
  services can operate
• General Packet Radio Service (GPRS) for Internet
  access
• Short Message Service (SMS) is used for texting
• Wireless Application Service (WAP) is used to
  access Internet
• Multimedia Messaging service (MMS) is used for
  multi-media
• GPRS technologies have been further developed
  that use more sophisticated modulation and
  multiplexing techniques (to increase data rates)
• Enhanced Data rate for GSM Evolution (EDGE)
• known as Enchanced GPRS (EGPRS), offers higher
  transfer rates
• EDGE Evolution provides higher rates

39
16.17 Generations of Cellular Technologies

• Service providers pushed to make technologies
  interoperable
• the industry consolidated many of the approaches
  from 2G into a few key standards
• IS-136, PDC, IS-95A, and EDGE all influenced the
  design of UMTS, a technology that uses Wideband
  CDMA (WCDMA)
• IS-95B was extended to produce CDMA 2000, as in
  Figure 16.19
• Several standards evolved for 3G data services
• EVDO (Evolution Data Optimized or Evolution Data
  Only) and EVDV emerged at approximately the same
  time
• They combine CDMA and FDM to increase the overall
  performance
• High-Speed Downlink Packet Access (HSDPA) offers
  download speeds of 14 Mbps

40
16.17 Generations of Cellular Technologies
41
16.18 VSAT Satellite Technology

• ???????????????????????????????????????????
  ???????? ???????????????? Commercial ???????????
• VSAT (Very Small Aperture Terminal)
  ?????????????????????????????????????????????
  ??????????
• ??????????????????????????????????????????????????
  ???????????
• VSAT ?????????????? 3 ???? ???????????????????????
  ?????????????????

42
16.18 VSAT Satellite Technology
43
16.19 GPS Satellites

• Global Positioning System ????????????
  ????????????????????????
• Accuracy between 2-20 meters
• (military ones have higher accuracy)
• 24 total satellites orbit the earth
• Satellites arranged in six (6) orbital planes
• Provides time synchronization
• that can be used in some communications

44
HW 10(Last) Chapter 16

• Download
• ?????????????????????????? ???????????????????
  5-310

45
End of Chapter Week 16

• Course Ends
• Final Exam
• Up to Week 16
• ??????????? Midterm ???? MT ?????????
  ???????????? IP Address
• No Calculator
• ????????? Final 50 (6 ??? 60 ?????)
• ??????????????????????? ????????
• IP Subnet ????????????? ?????????? Midterm

46
End of Chapter Week 16

• Final Exam List
• 1. IP Address and Subnetting
• 2. TCP/UDP
• 3. Routing General
• 4. IP Routing
• 5. QoS and IP Telephony
• 6. NW Security and WLAN