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Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
Overview of Wireless Networks Anuj Puri
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Overview of Wireless Networks Anuj Puri

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  • 1. Overview of Wireless Networks Anuj Puri
  • 2. Outline
    • Projections of wireless growth
    • Cellular Networks
    • Wireless LANs and Bluetooth
    • WAP
    • Ad Hoc wireless networks
  • 3. HUGE EXPECTATIONS AND INVESTMENT IN M-DATA
    • PCs
    • TV households
    • Mobile phone subscribers
    • Millions of subscribers worldwide
    • U.K. licenses
    • German licenses
    • French licenses
    • UMTS license fee to date (not ex-haustive)
    • European UMTS spectrum auctions
    • $ Billions
  • 4. SUCCESS OF I-MODE IN JAPAN
    • Feb 22, 1999 start
    • Aug 8
    • Nov 18
    • Dec 23
    • May 31,
    • 2000
    • i-Mode has already exceeded 12 million subs
    • Number of i-mode subscribers
    • Thousands
  • 5. Outline
    • Projections of wireless growth
    • Cellular Networks
    • Wireless LANs and Bluetooth
    • WAP
    • Ad Hoc wireless networks
  • 6. Cellular Networks
    • Mobile phones (internet access)
    • Cellular concept
      • Frequency reuse
      • Handoffs
  • 7. Organization of Cellular Networks BS – modulation, antenna MSC – switching HLR – information (location) about “home” users VLR – information about visiting users BS (base station) MSC (mobile switching center) HLR (home location register) VLR (visitor location register)
  • 8. How does a call get to the mobile ?
    • Suppose (510) 643 - 1111 is roaming in the (703) area code
    • Cell phone registers with the (703) MSC, which adds it to (703) VLR and informs the (510) HLR of the location of the cell phone
    • A call comes in for (510) 643 – 1111. Then (510) MSC queries its HLR, and directs the call to the (703) MSC
    • The (703) MSC forwards the call to the mobile
  • 9. Handoff MSC HLR VLR
    • Mobile is associated with BS A
    • It continuously monitors the signal strength from BS A,
    • and BS B
    • When the signal strength from BS B becomes stronger,
    • it associates with BS B
    BS B BS A
  • 10. Evolution of cellular industry First Generation Analog Voice AMPS Second Generation Digital Voice GSM, IS-95, IS-136, PDC Third Generation Packet data W-CDMA, EDGE, CDMA2000
  • 11. MULTIPLE MIGRATION PATHS ARE AVAILABLE
    • 2G
    * Footnote Source: Sources
    • 2.5G
    • 3G
    • 3+G
    • 4G
    • PDC
    • GSM
    • TDMA
    • (IS-136)
    • CDMA (IS-95A/B)
    WCDMA
    • HSPDA
    • OFDM
    • Software radio
    • Array antennas
    • GPRS
    • EDGE
    • CdmaOne
    • 1XRTT
    • 1XEVDO/HDR
    • 1 xtreme
    • cdma2000
    • MC-3X
  • 12. 3G Networks BS B BS A SGSN SGSN GGSN Access Network Physical layer/ MAC IP based Core Network Routing/network handoff
  • 13. Mobile IP
    • Home Agent (HA) – keeps track of where the mobile is (similar to GGSN)
    • Foreign Agent (FA) – delivers packets to the mobile in the foreign network (similar to SGSN)
    • All packets for mobile arrive at HA which “tunnels” them to mobile’s FA
    • When mobile moves to a new location, it informs its HA of the new FA
  • 14. Outline
    • Projections of cellular growth
    • Cellular Networks
    • Wireless LANs and Bluetooth
    • WAP
    • Ad Hoc wireless networks
  • 15. Wireless LANs and Bluetooth
    • For indoor use or operation over small areas
    • Operates in ISM (Industrial Scientific and Medical) Band
    • Spread Spectrum techniques
  • 16. Main Components of 802.11 Roaming Medium Access Control Physical Layer
  • 17. Physical Layer
    • Operate in unlicensed bands
      • In U.S., 900 MHz, 2.4 GHz, 5.7GHz
      • Various restrictions on use
    • Spread Spectrum techniques
      • Direct Sequence Spread Spectrum
      • Frequency Hopping Spread Spectrum
  • 18. Medium Access Layer
    • Why not use Ethernet protocol ?
      • Sender cannot detect collision
        • senders power overwhelms other transmitters
        • carrier sense does not necessarily mean collision
      • Receiver has a better idea of whether a collision is happening
      • Hidden Terminal / Exposed Terminal Problem
  • 19. Hidden and Exposed Terminals A B C A and B can hear each other B and C can hear each other A and C can not hear each other Both A and C want to transmit to B (Hidden Terminal) B wants to transmit to A when C is transmitting to someone else (Exposed Terminal)
  • 20. MACA A wants to transmit to B - A sends a RTS to B - B replies with a CTS - A sends data to B RTS: contains the length of data CTS: also contains the length of data Everyone hearing RTS stays quiet for CTS Everyone hearing CTS remains quiet for RTS
  • 21. 802.11 MAC
    • CSMA/CA (Carrier Sense / Collision Avoidance)
      • Carrier Sense (check to see if someone is transmitting)
      • Collision Avoidance (RTS-CTS-Ack)
    • Acknowledgments at link level
    • Fragmentation and Reassembly
  • 22. Basic Scheme RTS CTS Data ACK NAV (RTS) NAV (CTS) Defer Access Back-off Window
  • 23. Some Terminology Access Point Access Point Basic Service Set (BSS) Extended Service Set (ESS) Distribution System
  • 24. Bluetooth
    • Master-slave architecture
    • Frequency hopping system
    • System design for cheap production
  • 25. Outline
    • Projections of cellular growth
    • Cellular Networks
    • Wireless LANs and Bluetooth
    • WAP
    • Ad Hoc wireless networks
  • 26. WAP (or the web for small wireless devices)
    • Why not use wired web infrastructure (html, http, tcp) ?
      • HTML too feature rich for small devices
      • TCP may have too much overhead for low bandwidth wireless links
    • WAP (Wireless Application Protocol)
      • An optimized stack for wireless applications
      • Mobile talks with the WAP gateway
      • WAP gateway talks with the web server on the internet
  • 27. WAP Architecture WAP Gateway Internet Web Server WAP HTTP/TCP
  • 28. WAP Stack Bearer Services SMS, CSD WDP (Datagram Protocol) WTP (Transaction Protocol) WSP (Session Protocol) WML, etc IP TCP/UDP HTTP HTML
  • 29. Gateways/Proxies for Wireless Devices ? 2 nd Generation: Low speed data, small displays  WAP 3 rd Generation: Higher speed, IP address for each station  Proxy/ Gateway ? Gateway Internet Web Server
  • 30. Outline
    • Projections of wireless growth
    • Cellular Networks
    • Wireless LANs and Bluetooth
    • WAP
    • Ad Hoc wireless networks
  • 31. Ad Hoc Wireless Networks
    • No base stations or infrastructure required
    • Multi-hop wireless networks
      • Each node can talk with a neighbor
    • Applications
      • Sensor networks
      • Intelligent control applications (i.e, IVHS)
  • 32. Ad Hoc Wireless Networks
    • MAC schemes
    • Addressing
    • Routing
  • 33. Geographical Routing Algorithm
    • Assumptions:
    • Each node knows its own position and its neighbors’ position
    • Nodes don’t know the global topology
    • Destination address is a geographical position to which the packet is to be delivered
    Geographical network
  • 34. A Simple Routing Algorithm Routing Decision: Route to the neighbor which is nearest to the packet destination Source Destination
  • 35. Problem with Simple Routing Source Destination
    • Simple routing doesn’t always work
    • The Geographical routing algorithm is an extension of the
    • simple routing algorithm.
    Wall
  • 36. Routing Tables Routing Table for Station n: (x,y) position Neighbor a (12,4) b Position of n - Position of neighbor a a
    • Routing Algorithm:
    • Packet arrives for position p
    • at node n
    • Node n finds the position to
    • which p is closest and forwards
    • to the corresponding neighbor
    Position of neighbor b
    • Routing Tables:
    • Routing tables contain some
    • additional entries beside neighbors
  • 37. Route Discovery
    • Packet gets “stuck” when a node does not have a neighbor to which it can forward the packet
    • When a packet is stuck, a Route Discovery is started to destination D
    • A path p = s(0) s(1)...s(k) is found to D
    • Entry [ position(D), s(i+1) ] is added to the routing table of s(i)
  • 38. Example Pos(A) = (1,1) Pos(B) = (2,2) Pos(C) = (3,1) Links: A ---- B B ---- C A B C Pos(A) --- Pos(B) B Pos(B) --- Pos(A) A Pos(C) C Pos(C) --- Pos(B) B
    • A gets a packet for Pos(C)
    • A forwards it to B because pos(B) is closer to pos(C)
    • B forwards it to C because pos(C) is closer to pos(C)
    Pos(C) Pos(C) Pos(C)
  • 39. Route Discovery Pos(A) = (1,1) Pos(B) = (2,2) Pos(C) = (3,1) Pos(D) = (2.5,0) Links: A ---- B B ---- C C ---- D B C
    • A gets a packet for Pos(D)
    • Packet gets stuck at A because Pos(A) is closest to Pos(D)
    • Initiate route discovery for D from A
    • Update the routing tables and forward the packet
    Pos(D) Pos(D) A D Pos(A) --- Pos(B) B Pos(D) --- Pos(C) C Pos(B) --- Pos(A) A Pos(C) C Pos(C) --- Pos(B) B Pos(D) D Pos(D) Pos(D) Pos(D) Pos(D) B Pos(D) C
  • 40. Theorem: There are no cycles in the routing tables. --- Think of the routing entry [ position(D), a] as a path with end point D. Then we are always following a path whose end point is closer to the destination then the end point of the previous path.
  • 41. A Geometrical View Routing Table for Station n: (x,y) position Neighbor a (12,4) b Position of n - Position of neighbor a a Position of neighbor b Vornoi View : n a b (12,4)
    • Route discovery is initiated if packet destination falls within
    • the cell containing station n
    • Each route discovery causes the cell with station n to get split
  • 42. Routing Table Size
    • How many “splits” before station n is alone in its cell ?
      • Each split reduces the cells area ~ 1/2
      • The cell’s area when station n is alone in the cell ~ 1/N
      • where N is the number of stations in a unit area
      • => log(N) splits before station n is alone in its cell
    • Each split causes a route discovery
    • Each route discovery causes L entries to be added to the routing
    • tables where L is the average route discovery path length
    • => O( L log(N) ) entries in routing table of each station
  • 43. Outline
    • Projections of wireless growth
    • Cellular Networks
    • Wireless LANs and Bluetooth
    • WAP
    • Ad Hoc wireless networks

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