1 / 46

Wireless Network Devices

Wireless Network Devices. MIS 4700 Dr. Garrett. WLAN Radio Components. Common Components. Radio transmitter and receiver, or transceiver Also called a radio modulator / demodulator (modem) Antenna. 802.11 Radio Functions. Modulation Generates a carrier wave and modulates the wave

egil
Download Presentation

Wireless Network Devices

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Wireless Network Devices MIS 4700 Dr. Garrett

  2. WLAN Radio Components

  3. Common Components • Radio transmitter and receiver, or transceiver • Also called a radio modulator / demodulator (modem) • Antenna

  4. 802.11 Radio Functions • Modulation • Generates a carrier wave and modulates the wave • Spread-spectrum encoding • Combines data stream into a bit sequence with a higher data rate to form what is called a chipping code • Increases the ability to withstand interference

  5. 802.11 Radio Functions • Physical (PHY) layer splitting • Physical Layer Convergence Protocol (PLCP) sublayer • Senses the carrier to see if it is in use • Physical Medium Dependent (PMD) sublayer • Carries the modulated signal • MAC controller • Runs MAC layer protocols that buffer incoming and outgoing packets along with channel access and management

  6. Interference • Interference is the biggest issue in wireless communications • Causes intermittent reception and connectivity problems • In-channel interference is caused by other devices that emit signals in the same frequency

  7. IEEE 802.11 Modulation Methods

  8. WLAN Devices

  9. Wireless Network Adapters • May be an internal or external device • Form factors include: • Internal expansion card, network interface cards (NICs) • Internal integrated network adapters • External PC Card network adapters • External USB network adapters

  10. Key Characteristics of Wireless NICs • Interface type (internal, USB, PCI, etc.) • Wireless standard (802.11a, 802.11b, 802.11g, Bluetooth, etc.) • Antenna type (detachable, non-detachable) • Power output (40mW, 50mW, 200mW) • Power modes (PSP, CAM)

  11. Advantages and Disadvantages of Common Wireless NIC Types

  12. Advantages and Disadvantages of Common Wireless NIC Types

  13. Expansion Card Wireless NIC • Most common until recently • Installed inside a computer case, in a PCI slot in most instances

  14. Wireless NICs An IEEE 802.11b wireless NIC expansion card (Photo courtesy of D-Link Systems, Inc.) Verify the 802.11x standard of a wireless NIC before installing it. (Original photo courtesy of Cisco Systems, Inc.)

  15. Network Adapter Wireless Standards • The IEEE 802.11b and 802.11g standards are mostly compatible, but 802.11a is not compatible with either 802.11b or 802.11g. • The 802.11b-Plus standard is proprietary • Bluetooth  is not compatible with any of the 802.11 standards.

  16. Antenna Type • Non-detachable is most common • Detachable antennas may be more useful for a site survey An expansion card wireless NIC with a connection jack for an external WLAN antenna (Photo courtesy of D-Link Systems, Inc.)

  17. Power Output • Higher output power provides greater RF range • Output power ranges from 30 to 200 milliWatts (mW) • Interference may become a factor when using higher output power • Power consumption may be a factor for a laptop

  18. Power Modes • Constantly Awake Mode (CAM) • Useful when connected to a power source but may drain a battery quickly • Power Savings Polling (PSP) • Allows NIC to be put to sleep to conserve power when not in use • Fast PSP • Combines CAM and PSP features • Maximum Power Saving (MaxPSP) • Periodically awakened to retrieve network traffic

  19. Properties of Wireless Connection

  20. Wireless Networks Tab

  21. Proprietary Wireless Network • Proprietary software to monitor wireless networks is often provided with the wireless card The Linksys PCI Network Monitor is a proprietary wireless network management and monitoring tool.

  22. Wireless NICs and Linux • Most of the newer Linux versions provide support for 802.11b wireless cards • 802.11g access points are compatible with 802.11b wireless NICs • When choosing a wireless NIC check to make sure it is compatible with Linux and that a device driver is available • If there is no device driver available, you may try the wireless utilities called wireless-tools.26 by Jean Tourrilhes

  23. Almost all PC card wireless NICs are type II 68-pin cards PC Card/PCMCIA NICs

  24. PC Card NIC Guidelines • Use the operating system to stop or disable the card before removing it • Ensure the orientation of the card before inserting it to avoid damaging the pins • Use the push buttons or ejectors to remove a card – not pliers or other gripping device

  25. USB Network Adapters • Universal Serial Bus (USB) connectors come in two types: • Direct connect • Cable connect A USB network adapter that connects directly to a computer (Photo courtesy of Cisco Systems, Inc.) A USB network adapter that is connected to a computer with a USB cable (Photo courtesy of Belkin Corporation)

  26. Access Point • Distribution point, hub, and bridge for wireless NICs within its range • Includes a radio transceiver, wireline 802.3 interface, bridging circuitry or software • Provides a communications link between a wireless node and other wireless and wired network services and resources

  27. AP Considerations • Coverage to provide linkage for every wireless LAN station in its cell • Placement location is best if higher • Network mode • Ad-hoc if wireless devices will roam • Infrastructure if position is relatively static • Thin or fat devices

  28. Thin and Fat APs • Fat • Provides all of the functions required for WLAN connectivity: • Authentication • Encryption • Management • Thin • Provides RF-to-RF linkage and radio-to-wire converter • A central controller handles all other intelligent, or fat, services

  29. Multiradio APs • Support two or more WLAN standards simultaneously An access point with multiple built-in WLAN radios (Photo courtesy of Intermec Technologies Corp.)

  30. Bridging APs • Connect two or more LANs together in a point-to-point or point-to-multipoint topology

  31. Stealth APs • Do not broadcast their SSID for security reasons – only those knowing the SSID may connect

  32. Wireless Repeaters • Attenuation is the weakening of a signal as it travels further from its source • Wireless repeaters receive a transmitted signal and retransmit the signal with its original strength restored • Repeaters add latency, or delay, to the signal

  33. Bridges • A bridge creates a crossover point between two LANs or LAN segments operating on the same networking protocol • Learning bridges maintain a table of what network nodes lie on – only packets headed to other nodes are allowed thru • Wireless bridges are commonly used to provide a connection point between the WLANs in two buildings of a campus area network

  34. Bridging Tables A bridge uses the entries in its bridging table to route messages arriving from different networks or network segments

  35. Wireless Bridges Wireless bridges are used to link buildings in a campus area network setting

  36. Wireless Switch • Wireless switches are like multi-port bridges but smarter • A switch creates and maintains switching tables that allow it to manage network bandwidth • Switches use Spanning Tree Protocol (STP) to prevent loops in the network • Messages are forwarded through the switch using packet switching

  37. Packet Switching • Cut-through switching • Switch begins forwarding the message as soon as the source and destination addresses are read • Fast-forward switching • Switch begins forwarding the message as soon as the destination address is read • Store-and-forward switching • Switch reads entire message before forwarding it • Fragment-free switching • Reads first 64 bytes of the message which helps it identify collision packets

  38. Virtual LANs • Switches may create Virtual LANs (VLANs) • Logically creates groups of devices or users • Does not require a device or user to be geographically or functionally fixed

  39. Routers • Routers determine the best path to take through a network and then switch the packet A message is routed across the Internet until it arrives at the router servicing the destination node address.

  40. Routing Tables • Routers use a routing table to determine what port a packet needs to be switched out of to reach its destination • Routing entries are created in two ways: • Static routes are manually defined by the network administrator • Dynamic routes are learned by talking to other routers through routing protocols

  41. Routing Tables • Routing tables include: • remote network addresses • ports to use to get to remote networks • gateway of last resort

  42. Wireless Routers • Wireless routers are also called gateways • Most wireless routers are connected to a wired network in addition to communicating with wireless devices • Combines the functions of a wireless access point and a typical router to allow connections among multiple networks • Routers use information in the IP packet header to route packets

  43. Wireless Routers • Additional features of wireless routers include: • Network Address Translation (NAT) • Port-based access control • Firewall

  44. Wireless Gateways • A gateway is a network device that joins two networks • Functions of a wireless gateway include: • Advanced routing • Switching • Security A wireless gateway is used as the base station in hot spot networks. (Photo courtesy of 3Com Corporation.)

  45. WLAN Antennas • A dipole antenna built into most wireless NICs, access points, and routers is adequate for small businesses and homes • An external antenna is necessary for more advanced applications

  46. Antenna Considerations • Nearby metal, walls, large furniture, trees, and other objects may affect signal • Nearby RF interference may be picked up • Many RF antennas are polarized vertically, so horizontal polarization may be better • Cable connections should be free of splices and connectors as much as possible

More Related