Ch 8 -  Chapter 8 OSI Physical Layer
Objectives <ul><li>Explain the  role  of Physical layer protocols and services in supporting communication across data net...
Role of the Physical Layer <ul><li>Encode  the binary digits that represent Data Link layer frames into  signals   </li></...
Purpose of the Physical Layer <ul><li>The OSI Physical layer provides the means to  transport the bits  that make up the D...
Physical Layer Elements <ul><li>The physical media and associated elements  </li></ul><ul><li>A representation of bits on ...
Physical Layer Operation <ul><li>The Physical layer may add its  own signals  to indicate the beginning and end of the fra...
Physical Layer Standards <ul><li>The Physical layer consists of hardware in the form of electronic circuitry, media and co...
Physical Layer Technologies <ul><li>Physical and electrical properties of the media  </li></ul><ul><li>Mechanical properti...
Functions of the Physical Layer <ul><li>Physical components  </li></ul><ul><ul><li>electronic hardware device, media and c...
Signals <ul><li>Each signal placed onto the media can occupy a specific amount of time, known as the  bit time  (or bit in...
Signaling Methods <ul><li>Bits are represented on the medium by changing either the  amplitude ,  frequency  or  phase  of...
Non Return to Zero (NRZ) Signaling <ul><li>The bit stream is transmitted as a series of voltage values </li></ul><ul><ul><...
Manchester Coding <ul><li>The bit values are represented as voltage transitions  </li></ul><ul><ul><li>a  low to a high  v...
Encoding  <ul><li>Encoding is the symbolic grouping of bits prior to being presented on the media  </li></ul><ul><ul><li>i...
Signal Patterns <ul><li>The signal patterns,  start  of frame,  end  of frame and frame  contents , are decoded into bits ...
Code Groups <ul><li>A code group is a consecutive  sequence of code bits  that are interpreted as  data bit  pattern  </li...
Advantages of Using Code Groups <ul><li>Reducing bit errors </li></ul><ul><ul><li>to properly detect an individual bit cor...
Advantages of Using Code Groups (cont’d) <ul><li>Distinguish  data bits  from  control bits   </li></ul><ul><ul><li>the sy...
Code Symbol <ul><li>In a 4B/5B code symbol, 4 bits of data are turned into a 5-bit code symbols for transmission </li></ul...
Data Carrying Capacity <ul><li>Bandwidth  </li></ul><ul><ul><li>the capacity of a medium to carry data is described as the...
Data Carrying Capacity (cont’d) <ul><li>Throughput  </li></ul><ul><ul><li>the measure of the  transfer of bits  across the...
*Data Carrying Capacity (cont’d) Ch 8 -
Physical Media Characteristics <ul><li>The standards for copper media define the type of media, bandwidth, type of connect...
Copper Media <ul><li>A  coaxial cable  has a single conductor that run through the centre of the cable that is encased by,...
External Signal Interference  <ul><li>Data is transmitted on copper wires as  electrical pulses   </li></ul><ul><li>The ti...
Limiting Interference <ul><li>Cable types with  shielding  or  twisting  of the pairs of wires are designed to  minimize s...
Unshielded Twisted Pair ( UTP ) <ul><li>UTP cabling consists of  four pairs  of color-coded wires twisted together and enc...
UTP Cabling Standards <ul><li>UTP cabling conforms to the standards established jointly by the Telecommunications Industry...
UTP Cable Types Ch 8 -
Coaxial Cables <ul><li>A widely used media in wireless and cable access technologies  </li></ul><ul><li>Coax cables are us...
Coaxial Cable Connectors <ul><li>There are different types of connectors used with coax cable </li></ul>Ch 8 -
Shielded Twisted-Pair (STP) Cable <ul><li>Each twisted pair is wrapped in a  foil shield  </li></ul><ul><li>The entire bun...
Copper Media Safety <ul><li>Electrical hazards  </li></ul><ul><ul><li>copper wires could conduct electricity in undesirabl...
Fiber Media <ul><li>Fiber optic uses either glass or plastic fibers to guide light impulses </li></ul><ul><ul><li>bits are...
Optical Fiber Implementation Issues <ul><li>More  expensive  than copper media over the same distance (but for a higher ca...
Optical Fiber Construction <ul><li>Optical fiber consists of a PVC  jacket  and a series of strengthening materials that s...
Single Mode  Optical Fiber <ul><li>Small core </li></ul><ul><li>Uses a  single ray  of light emitted from a laser </li></u...
Multimode Optical Fiber <ul><li>Larger core  than single mode cable (50 microns or greater) </li></ul><ul><li>Uses LED emi...
Wireless Media <ul><li>Carry electromagnetic signals at  radio  and  microwave  frequencies that represent binary digits  ...
Types of Wireless Networks <ul><li>IEEE 802.11 </li></ul><ul><ul><li>a wireless LAN technology commonly known as  Wi-Fi </...
Types of Wireless Networks (cont’d) <ul><li>IEEE 802.16 </li></ul><ul><ul><li>known as  WiMAX  (Worldwide Interoperability...
Wireless LAN Devices <ul><li>Wireless access point ( AP )  </li></ul><ul><ul><li>concentrates the wireless signals from us...
Wireless LAN Standards <ul><li>IEEE 802.11a  </li></ul><ul><ul><li>operates  in the  5 GHz  frequency band and offers spee...
Wireless LAN Standards (cont’d) <ul><li>IEEE 802.11g  </li></ul><ul><ul><li>operates  in the  2.4 GHz  frequency band and ...
Copper Media Connectors Ch 8 -
Correct Connector Termination <ul><li>It is essential that all copper media terminations be of  high quality  to ensure  o...
Fiber Media Connectors <ul><li>Straight-Tip  (ST) </li></ul><ul><ul><li>bayonet style connector widely used with  multimod...
Fiber Media Connectors <ul><li>Lucent Connector  (LC) </li></ul><ul><ul><li>a small connector that can be used with single...
Type of Cables Ch 8 -  OTDR  Optical time-domain reflector : Check Fiber Optic cable
Devices Name Ch 8 -
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  • This chapter introduces the general functions of the Physical layer as well as the standards and protocols that manage the transmission of data across local media.
  • The International Organization for Standardization (ISO) The Institute of Electrical and Electronics Engineers (IEEE) The American National Standards Institute (ANSI) The International Telecommunication Union (ITU) The Electronics Industry Alliance/Telecommunications Industry Association (EIA/TIA) National telecommunications authorities such as the Federal Communication Commission (FCC) in the USA
  • The figure depicts some of the purposes of signaling patterns.
  • Data transfer can be measured in three ways: bandwidth, throughput and goodput
  • As an example, consider two hosts on a LAN transferring a file. The bandwidth of the LAN is 100 Mbps. Due to the sharing and media overhead the throughput between the computers is only 60 Mbps. With the overhead of the encapsulation process of the TCP/IP stack, the actual rate of the data received by the destination computer, goodput, is only 40Mbps.
  • The susceptibility of copper cables to electronic noise can be limited by any one of the above methods.
  • The allocation of these addresses inside the networks should be planned and documented.
  • There are benefits to using a layered model to describe network protocols and operations.
  • The ISO 8877 specified RJ-45 connector is used for a range of Physical layer specifications, one of which is Ethernet. Another specification, EIA-TIA 568, describes the wire color codes to pin assignments (pinouts) for Ethernet straight-through and crossover cables.
  • Transcript of "Chapter8 "

    1. 1. Ch 8 - Chapter 8 OSI Physical Layer
    2. 2. Objectives <ul><li>Explain the role of Physical layer protocols and services in supporting communication across data networks </li></ul><ul><li>Describe the purpose of Physical layer signaling and encoding as they are used in networks </li></ul><ul><li>Describe the role of signals used to represent bits as a frame is transported across the local media </li></ul><ul><li>Identify the basic characteristics of copper , fiber , and wireless network media </li></ul><ul><li>Describe common uses of copper, fiber, and wireless network media </li></ul>Ch 8 -
    3. 3. Role of the Physical Layer <ul><li>Encode the binary digits that represent Data Link layer frames into signals </li></ul><ul><li>Transmit and receive these signals across the physical media – copper wires, optical fiber and wireless </li></ul>Ch 8 -
    4. 4. Purpose of the Physical Layer <ul><li>The OSI Physical layer provides the means to transport the bits that make up the Data Link frame across the network media </li></ul><ul><li>Creates the electrical, optical or microwave signal that represents the bits in each frame </li></ul><ul><li>Retrieve the signals, restore them to their bit representation and pass the bits up to the Data Link layer as a complete frame </li></ul>Ch 8 -
    5. 5. Physical Layer Elements <ul><li>The physical media and associated elements </li></ul><ul><li>A representation of bits on the media </li></ul><ul><ul><li>the type of signal depends on the type of media </li></ul></ul><ul><li>Encoding of data and control information </li></ul><ul><li>Transmitter and receiver circuitry on the network devices </li></ul>Ch 8 -
    6. 6. Physical Layer Operation <ul><li>The Physical layer may add its own signals to indicate the beginning and end of the frame </li></ul><ul><li>The signals can be in the form of electrical , light or radio pulses </li></ul>Ch 8 -
    7. 7. Physical Layer Standards <ul><li>The Physical layer consists of hardware in the form of electronic circuitry, media and connectors </li></ul><ul><li>The standards governing the hardware are defined by the relevant electrical and communications engineering organizations </li></ul><ul><ul><li>IEEE, EIA/TIA, ISO et al </li></ul></ul>Ch 8 -
    8. 8. Physical Layer Technologies <ul><li>Physical and electrical properties of the media </li></ul><ul><li>Mechanical properties (materials, dimensions, pin-outs) of the connectors </li></ul><ul><li>Bit representation by the signals (encoding) </li></ul><ul><li>Definition of control information signals </li></ul>Ch 8 -
    9. 9. Functions of the Physical Layer <ul><li>Physical components </li></ul><ul><ul><li>electronic hardware device, media and connectors </li></ul></ul><ul><li>Encoding </li></ul><ul><ul><li>a method of converting a stream of data bits into a predefined code </li></ul></ul><ul><ul><li>using predictable patterns helps to distinguish data bits from control bits and provide better media error detection </li></ul></ul><ul><li>Signaling </li></ul><ul><ul><li>generate the electrical, optical or wireless signals that represent the “1” and “0” </li></ul></ul>Ch 8 -
    10. 10. Signals <ul><li>Each signal placed onto the media can occupy a specific amount of time, known as the bit time (or bit interval) </li></ul><ul><li>A clock signal provides synchronization between the transmitter and receiver for successful delivery of the bits </li></ul><ul><ul><li>bits must be examined at specific times during the bit time </li></ul></ul>Ch 8 -
    11. 11. Signaling Methods <ul><li>Bits are represented on the medium by changing either the amplitude , frequency or phase of the signal </li></ul><ul><ul><li>e.g. with Non-Return to Zero, a 0 is represented by one voltage during the bit time and a 1 may be represented by another voltage during the bit time </li></ul></ul><ul><li>There are also methods of signaling that use transitions to indicate a logic level </li></ul><ul><ul><li>detect the voltage transitions in the middle of the bit time </li></ul></ul><ul><ul><li>Manchester coding indicates a 0 by a high to low voltage transition and a 1 by a low to high voltage transition in the middle of the bit time </li></ul></ul>Ch 8 -
    12. 12. Non Return to Zero (NRZ) Signaling <ul><li>The bit stream is transmitted as a series of voltage values </li></ul><ul><ul><li>a low voltage value represents a logic 0 </li></ul></ul><ul><ul><li>a high voltage value represents a logic 1 </li></ul></ul><ul><li>The NRZ signaling is suitable for slow speed data links </li></ul><ul><ul><li>uses bandwidth inefficiently and is susceptible to electromagnetic interference </li></ul></ul><ul><ul><li>boundaries between individual bits can be lost when a long strings of 1s or 0s are transmitted </li></ul></ul>Ch 8 -
    13. 13. Manchester Coding <ul><li>The bit values are represented as voltage transitions </li></ul><ul><ul><li>a low to a high voltage transition represents a logic 1 </li></ul></ul><ul><ul><li>a high to a low voltage transition represents a logic 0 </li></ul></ul><ul><li>Voltage transition must occur in the middle of each bit time </li></ul><ul><ul><li>this transition can be used to ensure the bit times at the receiving nodes are synchronized with the transmitting nodes </li></ul></ul><ul><li>Signaling method used by 10BaseT Ethernet </li></ul>Ch 8 -
    14. 14. Encoding <ul><li>Encoding is the symbolic grouping of bits prior to being presented on the media </li></ul><ul><ul><li>improve the efficiency at higher speed data transmission </li></ul></ul><ul><ul><li>detect errors more efficiently </li></ul></ul><ul><li>The Physical layer of a device needs to be able to detect legitimate data signals and ignore random non-data signals </li></ul><ul><li>Signal patterns that provide frame detection </li></ul><ul><ul><li>start and end of frame </li></ul></ul><ul><ul><li>valid data bits need to be grouped into a frame </li></ul></ul><ul><ul><li>random unframed signals due to noise or interference are not decoded </li></ul></ul>Ch 8 -
    15. 15. Signal Patterns <ul><li>The signal patterns, start of frame, end of frame and frame contents , are decoded into bits </li></ul>Ch 8 -
    16. 16. Code Groups <ul><li>A code group is a consecutive sequence of code bits that are interpreted as data bit pattern </li></ul><ul><ul><li>e.g. the code bits 10101 could represent the data bits 0011 </li></ul></ul><ul><ul><li>often used as an intermediary encoding technique for higher speed LAN technologies </li></ul></ul><ul><li>Code groups introduce overhead in the form of extra bits to transmit but improve the robustness of a communication link </li></ul>Ch 8 -
    17. 17. Advantages of Using Code Groups <ul><li>Reducing bit errors </li></ul><ul><ul><li>to properly detect an individual bit correctly, the receiver must know how and when to sample the signal </li></ul></ul><ul><ul><li>signal transitions are used for synchronization </li></ul></ul><ul><ul><li>code groups are designed so that the symbols force an ample number of bit transitions to synchronize the timing </li></ul></ul><ul><ul><li>ensures that not too many 1s or 0s are used in a row </li></ul></ul><ul><li>Limiting the effective energy transmitted </li></ul><ul><ul><li>the number of 1s and 0s in a string of symbols are evenly balanced, known as DC balancing </li></ul></ul><ul><ul><li>prevents excessive amounts of energy being injected into the media during transmission, thereby reducing the radiated interference </li></ul></ul><ul><ul><li>transmitting a long series of 1s, presence of energy, could overheat the transmitting laser and the photo diodes in the receiver </li></ul></ul>Ch 8 -
    18. 18. Advantages of Using Code Groups (cont’d) <ul><li>Distinguish data bits from control bits </li></ul><ul><ul><li>the symbols representing the data have different bit patterns than symbols for control </li></ul></ul><ul><ul><li>data symbols represent the data of the frame </li></ul></ul><ul><ul><li>control symbols are special codes injected by the Physical layer </li></ul></ul><ul><ul><li>invalid symbols are patterns not allowed on the media </li></ul></ul><ul><li>Better media error detection </li></ul><ul><ul><li>invalid symbols create long series of 1s or 0s </li></ul></ul><ul><ul><li>the receipt of an invalid symbol indicates a frame error </li></ul></ul>Ch 8 -
    19. 19. Code Symbol <ul><li>In a 4B/5B code symbol, 4 bits of data are turned into a 5-bit code symbols for transmission </li></ul>Ch 8 -
    20. 20. Data Carrying Capacity <ul><li>Bandwidth </li></ul><ul><ul><li>the capacity of a medium to carry data is described as the raw data bandwidth </li></ul></ul><ul><ul><li>digital bandwidth measures the amount of information that can flow from one place to another in a given amount of time </li></ul></ul><ul><ul><li>typically measured in kbps or Mbps </li></ul></ul><ul><ul><li>physical media properties, current technologies and the laws of physics are factors that can determine available bandwidth </li></ul></ul>Ch 8 -
    21. 21. Data Carrying Capacity (cont’d) <ul><li>Throughput </li></ul><ul><ul><li>the measure of the transfer of bits across the media over a given period of time </li></ul></ul><ul><ul><li>usually does not match the specified bandwidth </li></ul></ul><ul><ul><li>factors such as the amount of traffic, type of traffic, number of devices and media access methods can influence throughput </li></ul></ul><ul><li>Goodput </li></ul><ul><ul><li>the measure of useable data transferred over a given period of time </li></ul></ul><ul><ul><li>measures the effective transfer of user data between Application layer entities, such as a web server and a client web browser </li></ul></ul><ul><ul><li>goodput is throughput minus traffic overhead for establishing sessions, acknowledgements and encapsulation </li></ul></ul><ul><li>Goodput < Throughput < Bandwidth </li></ul><ul><li>BW – Theoretical, Throughput – Actual, Goodput - Data </li></ul>Ch 8 -
    22. 22. *Data Carrying Capacity (cont’d) Ch 8 -
    23. 23. Physical Media Characteristics <ul><li>The standards for copper media define the type of media, bandwidth, type of connectors, pin-outs and color code connections and maximum cable distance </li></ul>Ch 8 -
    24. 24. Copper Media <ul><li>A coaxial cable has a single conductor that run through the centre of the cable that is encased by, but separated from, a shield </li></ul><ul><li>Twisted pair cable consists of pairs of color-coded wires twisted together and encased in a plastic sheath </li></ul><ul><li>Networking media generally make use of modular jacks and plugs </li></ul><ul><ul><li>provide easy connection and disconnection </li></ul></ul>Ch 8 -
    25. 25. External Signal Interference <ul><li>Data is transmitted on copper wires as electrical pulses </li></ul><ul><li>The timing and voltages of these data signals are susceptible to interference or “noise” from outside the communication system </li></ul><ul><ul><li>these unwanted signals can distort and corrupt the data signals </li></ul></ul><ul><li>Radio waves and electromagnetic devices such as fluorescent lights , electric motors and other devices are potential sources of noise </li></ul>Ch 8 -
    26. 26. Limiting Interference <ul><li>Cable types with shielding or twisting of the pairs of wires are designed to minimize signal degradation due to electronic noise </li></ul><ul><li>Selecting the cable type or category most suited to protect the data signals in a given networking environment </li></ul><ul><li>Designing a cable infrastructure to avoid known and potential sources of interference in the building structure </li></ul><ul><li>Using cabling techniques that include proper handling and termination of the cables </li></ul>Ch 8 -
    27. 27. Unshielded Twisted Pair ( UTP ) <ul><li>UTP cabling consists of four pairs of color-coded wires twisted together and encased in a flexible plastic sheath </li></ul><ul><li>Twisting has the effect of canceling unwanted signals </li></ul><ul><ul><li>the unwanted signals present on the twisted pair wires are equal and in opposite magnitude </li></ul></ul><ul><li>The cancellation effect also helps to avoid interference from internal sources called crosstalk </li></ul><ul><ul><li>crosstalk is the interference caused by the magnetic field around adjacent pairs of wires </li></ul></ul>Ch 8 -
    28. 28. UTP Cabling Standards <ul><li>UTP cabling conforms to the standards established jointly by the Telecommunications Industry Association (TIA) and Electronics Industries Alliance (EIA) </li></ul><ul><li>TIA/EIA-568A stipulates the commercial cabling standards for LAN installation </li></ul><ul><ul><li>cable types, cable lengths, connectors, cable termination and methods of testing cable </li></ul></ul><ul><li>The electrical characteristics of copper cabling are defined by the Institute of Electrical and Electronic Engineers (IEEE) </li></ul><ul><ul><li>cables are placed into categories according to their ability to carry higher bandwidth rates </li></ul></ul><ul><ul><li>Category 5 ( Cat 5 ) cable is commonly used in 100Base-TX Fast Ethernet installations </li></ul></ul><ul><ul><li>Cat 6 is the recommended type for new building installations </li></ul></ul>Ch 8 -
    29. 29. UTP Cable Types Ch 8 -
    30. 30. Coaxial Cables <ul><li>A widely used media in wireless and cable access technologies </li></ul><ul><li>Coax cables are used to attach antennas to wireless devices </li></ul><ul><li>Traditional cable TV, transmitting in one direction, was composed completely of coax cable </li></ul><ul><li>Cable service providers are providing Internet connectivity with the combined use of fiber and coax , referred to hybrid fiber coax ( HFC ) </li></ul>Ch 8 -
    31. 31. Coaxial Cable Connectors <ul><li>There are different types of connectors used with coax cable </li></ul>Ch 8 -
    32. 32. Shielded Twisted-Pair (STP) Cable <ul><li>Each twisted pair is wrapped in a foil shield </li></ul><ul><li>The entire bundle of shielded twisted pairs are shielded in a braided shield and protected by a plastic jacket </li></ul><ul><li>STP provides better noise protection than UTP cabling at a higher cost </li></ul><ul><li>STP was the cabling structure specified for Token Ring network installations </li></ul>Ch 8 -
    33. 33. Copper Media Safety <ul><li>Electrical hazards </li></ul><ul><ul><li>copper wires could conduct electricity in undesirable ways </li></ul></ul><ul><ul><li>network cabling could present undesirable voltage levels when used to connect devices that have power sources with different ground potential </li></ul></ul><ul><ul><li>copper cabling may conduct voltages caused by lightning strikes to network devices </li></ul></ul><ul><li>Fire hazards </li></ul><ul><ul><li>cable insulation and sheaths may be flammable or produce toxic fumes when heated or burned </li></ul></ul>Ch 8 -
    34. 34. Fiber Media <ul><li>Fiber optic uses either glass or plastic fibers to guide light impulses </li></ul><ul><ul><li>bits are encoded as light impulses </li></ul></ul><ul><li>Capable of providing very large raw bandwidth rates </li></ul><ul><li>Media is immune to electromagnetic interference and will not conduct unwanted electrical currents due to grounding issues </li></ul><ul><li>Optical fibers are thin and have relatively low signal loss </li></ul><ul><li>Can operate at much greater lengths than copper without the need for signal regeneration </li></ul>Ch 8 -
    35. 35. Optical Fiber Implementation Issues <ul><li>More expensive than copper media over the same distance (but for a higher capacity) </li></ul><ul><ul><li>optical fiber is primarily used as backbone cabling for high-traffic point-to-point connections between data distribution facilities and for the interconnection of buildings in multi-building campus </li></ul></ul><ul><li>Different skills and equipment required to terminate and splice the cable infrastructure </li></ul><ul><li>More careful handling than copper media </li></ul>Ch 8 -
    36. 36. Optical Fiber Construction <ul><li>Optical fiber consists of a PVC jacket and a series of strengthening materials that surround the optical fiber and its classing </li></ul><ul><li>Light can only travel in one direction over optical fiber </li></ul><ul><ul><li>two fibers are required to support full-duplex operation </li></ul></ul><ul><li>Fiber-optic patch cables bundle together two optical fiber cables and terminate them with a pair of standard single fiber connectors </li></ul><ul><ul><li>straight tip (ST) </li></ul></ul><ul><ul><li>subscriber connector (SC) </li></ul></ul>Ch 8 -
    37. 37. Single Mode Optical Fiber <ul><li>Small core </li></ul><ul><li>Uses a single ray of light emitted from a laser </li></ul><ul><ul><li>laser light is uni-directional and travels down the center of the fiber </li></ul></ul><ul><ul><li>can transmit optical pulses for very long distances </li></ul></ul><ul><li>Less dispersion </li></ul><ul><li>Suited for long distance applications (up to 100 km or 62 miles) </li></ul>Ch 8 -
    38. 38. Multimode Optical Fiber <ul><li>Larger core than single mode cable (50 microns or greater) </li></ul><ul><li>Uses LED emitters that do not create a single coherent light wave </li></ul><ul><ul><li>LED enters the multimode fiber at different angles </li></ul></ul><ul><li>Allows greater dispersion and therefore loss of signal </li></ul><ul><ul><li>long fiber runs may result in pulses becoming blurred on reception </li></ul></ul><ul><li>Used for long distance application, but shorter than single-mode </li></ul><ul><ul><li>up to about 2km </li></ul></ul>Ch 8 -
    39. 39. Wireless Media <ul><li>Carry electromagnetic signals at radio and microwave frequencies that represent binary digits </li></ul><ul><li>Uses air or free space as the medium of data transport </li></ul><ul><li>Construction materials used in buildings and structures, and the local terrain can limit the effective coverage </li></ul><ul><li>Wireless is susceptible to interference </li></ul><ul><li>Network security is a major concern of wireless transmission </li></ul>Ch 8 -
    40. 40. Types of Wireless Networks <ul><li>IEEE 802.11 </li></ul><ul><ul><li>a wireless LAN technology commonly known as Wi-Fi </li></ul></ul><ul><ul><li>uses a contention system with CSMA/CA media access process </li></ul></ul><ul><li>IEEE 802.15 </li></ul><ul><ul><li>wireless personal area network(PAN) standard commonly known as Bluetooth </li></ul></ul><ul><ul><li>uses a device pairing process to communicate over distances of up to 100 meters </li></ul></ul>Ch 8 -
    41. 41. Types of Wireless Networks (cont’d) <ul><li>IEEE 802.16 </li></ul><ul><ul><li>known as WiMAX (Worldwide Interoperability for Microwave Access) </li></ul></ul><ul><ul><li>uses a point-to-multipoint topology to provide wireless broadband access </li></ul></ul><ul><li>Global System for Mobile Communications ( GSM ) </li></ul><ul><ul><li>includes Physical layer specifications for the implementation of the Layer 2 General Packet Radio Service ( GPRS ) protocol to provide data transfer over mobile cellular telephony networks </li></ul></ul>Ch 8 -
    42. 42. Wireless LAN Devices <ul><li>Wireless access point ( AP ) </li></ul><ul><ul><li>concentrates the wireless signals from users and connects, usually through a copper cable, to the existing copper-based network infrastructure </li></ul></ul><ul><li>Wireless NIC adaptors </li></ul><ul><ul><li>provides wireless communication capability to each network host </li></ul></ul>Ch 8 -
    43. 43. Wireless LAN Standards <ul><li>IEEE 802.11a </li></ul><ul><ul><li>operates in the 5 GHz frequency band and offers speeds of up to 54 Mbps </li></ul></ul><ul><ul><li>smaller coverage area and is less effective at penetrating building structures </li></ul></ul><ul><ul><li>not interoperable with 802.11 b and 802.11 g standards </li></ul></ul><ul><li>IEEE 802.11b </li></ul><ul><ul><li>operates in the 2.4 GHz frequency band and offers speeds of up to 11 Mbps </li></ul></ul><ul><ul><li>longer range and are better able to penetrate building structures than devices based on 802.11a standard </li></ul></ul>Ch 8 -
    44. 44. Wireless LAN Standards (cont’d) <ul><li>IEEE 802.11g </li></ul><ul><ul><li>operates in the 2.4 GHz frequency band and offers speeds of up to 54 Mbps </li></ul></ul><ul><ul><li>operate at the same radio frequency and range as 802.11b but with the bandwidth of 802.11a </li></ul></ul><ul><li>IEEE802.11n </li></ul><ul><ul><li>currently in draft form </li></ul></ul><ul><ul><li>proposed standard defines frequency of 2.4 GHz or 5 GHz </li></ul></ul><ul><ul><li>expected data rates are 100 Mbps to 210 Mbps with a distance range of up to 70 meters </li></ul></ul>Ch 8 -
    45. 45. Copper Media Connectors Ch 8 -
    46. 46. Correct Connector Termination <ul><li>It is essential that all copper media terminations be of high quality to ensure optimum performance with current and future network technologies </li></ul><ul><ul><li>there is the possibility of signal loss and the introduction of noise to the communication circuit each time copper cabling is terminated </li></ul></ul><ul><ul><li>each cable is a source of Physical layer performance degradation when improperly terminated </li></ul></ul>Ch 8 -
    47. 47. Fiber Media Connectors <ul><li>Straight-Tip (ST) </li></ul><ul><ul><li>bayonet style connector widely used with multimode fiber </li></ul></ul><ul><li>Subscriber Connector (SC) </li></ul><ul><ul><li>a connector that uses a push-pull mechanism to ensure positive insertion </li></ul></ul><ul><ul><li>widely used with single-mode fiber </li></ul></ul>Ch 8 -
    48. 48. Fiber Media Connectors <ul><li>Lucent Connector (LC) </li></ul><ul><ul><li>a small connector that can be used with single-mode and multimode fibers </li></ul></ul>Ch 8 -
    49. 49. Type of Cables Ch 8 - OTDR Optical time-domain reflector : Check Fiber Optic cable
    50. 50. Devices Name Ch 8 -

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