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Chapter 4 Architectures of distributed systems

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Chapter 4 Architectures of distributed systems Powered By Docstoc
					Chapter 4 IEEE 802.16 (WiMAX)
    Outline

   4.1 Overview
   4.2 IEEE 802.16 Physical Layer
   4.3 IEEE 802.16e Scalable OFDMA
   4.4 IEEE 802.16e MIMO-OFDM
   4.5 WiMAX vs. HSDPA
   4.6 IEEE 802.16e MAC Power Saving Mode
   4.7 WiMAX QoS and Handover Mechanism
   4.8 WiMAX Security


              Vehicle Communication Networks and Protocols   2
4.1 Overview
Wireless network technology

           Wireless Wide Area Network
                   IEEE 802.20


        Wireless Metropolitan Area Network
               IEEE 802.16 (WiMAX)


            Wireless Local Area Network
                IEEE 802.11 (WiFly)



          Wireless Personal Area Network
                802.15.1 (Bluetooth)
                  802.15.3 (UWB)
                 802.15.4 (ZigBee)


           Vehicle Communication Networks and Protocols   4
    WiMAX introduction

   What is WiMAX?
       Worldwide Interoperability for Microwave Access
        (WiMAX)
       Created by the WiMAX Forum (established in June 2001)
            A standards-based technology enabling the
             delivery of last mile wireless broadband
             access as an alternative to cable and DSL.

   IEEE 802.16
       An IEEE standard for Wireless Metropolitan Area
        Networks (WirelessMAN)


                    Vehicle Communication Networks and Protocols   5
              WiMAX standards history
                                              • Original fixed wireless broadband for 10-66GHz:
                               802.16           Line-of-Sight only (LOS), Point-to-Multi-Point
                                                (PMP) applications
                             (Dec 2001)
      802.16c
       (2002)                                  • Extension for 2-11GHz: Targeted for Non-Line-
                               802.16a           of-Sight (NLOS), Point-to-Multi-Point
• System profiles for 10-                        applications like “last mile” broadband access
  66GHz                      (Jan 2003)


                             802.16-2004       • System profiles and errata for 2-11GHz
                            (802.16REVd)
                              (Oct 2004)

                            802.16e-2005      • Combined fixed and mobile wireless broadband
   Inactive                                     for <11GHz
                              (802.16e)
   Active
                             (Dec 2005)
                                  Vehicle Communication Networks and Protocols                    6
WiMAX basic data

Standard         802.16              802.16-2004                   802.16e-2005

Frequency                               2-11GHz                2-11GHz for fixed
               10-66GHz
  band                                                         2-6GHz for mobile

                                                                   Fixed and mobile
Application    Fixed LOS              Fixed NLOS
                                                                        NLOS


 Data rate    32~134Mbps               1~75Mbps                       1~15Mbps


 Physical     Single Carrier        Single Carrier,                 Single Carrier,
  Layer           only             OFDM, OFDMA                     OFDM, OFDMA

                                     4~6Mile (Max.
  Range         1~3 Mile                                              1~3 Mile
                                        30Mile)

                    Vehicle Communication Networks and Protocols                      7
    WiMAX spectrum status
   WiBRO (Feb. 2002): 2.3~2.4GHz
       Korea
   America: 2.5~2.7GHz
       U.S.
       Canada
       Singapore
       Israel
       Taiwan
   Europe: 3.4~3.6GHz
       Europe
       China
       Hong Kong


                    Vehicle Communication Networks and Protocols   8
4.2 IEEE 802.16 Physical
Layer
    Duplexing schemes (1/3)

   Time-Division Duplex (TDD)
       Downlink (DL) & Uplink (UL) on the same channel
       Transmit and receive separate in time
   Frequency-Division Duplex (FDD)
       Downlink & Uplink on different channels
       Supported full duplex SS & half duplex SS
            SS: Subscriber station




                    Vehicle Communication Networks and Protocols   10
        Duplexing schemes (2/3)

       TDD: DL and UL share the same frequency

                                      Time


             Frame n-1               Frame n                     Frame n+1




                         DL                       DL
                       Subframe                 Subframe


TTG = Transmit Transition Gap
RTG = Receive Transition Gap           TTG                       RTG
                         Vehicle Communication Networks and Protocols        11
    Duplexing schemes (3/3)

   FDD: both DL and UL transmit simultaneously,
    but on different frequencies.
                                 Time


        Frame n-1               Frame n                     Frame n+1


                                   DL
      Frequency A               SubFrame
                                                            Guard Band

                                   UL
      Frequency B               SubFrame


                    Vehicle Communication Networks and Protocols         12
    The physical layer (1/3)

   WiMAX supports four PHYs
       Single Carrier (SC): for 10-66GHz
       Single Carrier Access (SCa): for 2-11GHz
       Orthogonal Frequency Division Multiplexing (OFDM)
       Orthogonal Frequency Division Multiple Access
        (OFDMA)




                   Vehicle Communication Networks and Protocols   13
      The physical layer (2/3)

Standard            Frequency band               PHY           Duplexing

WirelessMAN-SC      10-66GHz                     SC            TDD, FDD

WirelessMAN-SCa     2-11GHz                      SCa           TDD, FDD

WirelessMAN-OFDM    2-11GHz Licensed             OFDM          TDD, FDD

WirelessMAN-OFDM    2-11GHz Unlicensed           OFDM          TDD

WirelessMAN-OFDMA   2-11GHz Licensed             OFDMA         TDD, FDD

WirelessMAN-OFDMA   2-11GHz Unlicensed           OFDMA         TDD


                      Vehicle Communication Networks and Protocols         14
    The physical layer (3/3)

   SC/SCa



                  Freq.
                                 Time


   OFDM
                  (subcarrier)
                   Freq.




                                 Time

   OFDMA
                  (subchannel)
                   Freq.




                                 Time


               Vehicle Communication Networks and Protocols   15
       WirelessMAN-OFDM (1/4)
      It is based on OFDM modulation
      It is designed for NLOS operation in the frequency
       bands 2~11GHz
      Efficiently fast Fourier transform (FFT) implementation
      Wide bandwidth transmission




                                                                FDM
OFDM spectrum     OFDM spectrum
                                                                     save of bandwidth
(single bit)
                                                                OFDM
                      Vehicle Communication Networks and Protocols                       16
    WirelessMAN-OFDM (2/4)

   An OFDM Symbol




   Subcarrier types
       Data subcarriers: for data transmission
       Pilot subcarriers: for various estimation purposes
       Null subcarriers: no transmission, for guard bands, non-
        active subcarriers and the DC subcarrier
                     Vehicle Communication Networks and Protocols   17
    WirelessMAN-OFDM (3/4)

   OFDM symbol parameter
       256 FFT size
            200 are used
                 192 data subcarriers
                 8 pilot subcarriers
            28 lower frequency guard subcarriers
            27 higher frequency guard subcarriers
       DC carrier is not used



                       Vehicle Communication Networks and Protocols   18
    WirelessMAN-OFDM (4/4)

   The advantages of OFDM
       High data transmission rate
       High bandwidth efficiency
   The disadvantages of OFDM
       Sensitive to carrier frequency offset
       High Peak to Average Power Ratio (PAPR)




                    Vehicle Communication Networks and Protocols   19
    WirelessMAN-OFDMA (1/3)

   Based on OFDM modulation
   Subchannel
       A set of subcarriers forms a subchannel
       The subcarriers may and may not be adjacent




                    Vehicle Communication Networks and Protocols   20
    WirelessMAN-OFDMA (2/3)

   An OFDMA Symbol




   Subcarrier types
       Data subcarriers: for data transmission
       Pilot subcarriers: for various estimation purposes
       Null subcarriers: no transmission at all, for guard bands
        and DC carrier
                     Vehicle Communication Networks and Protocols   21
    WirelessMAN-OFDMA (3/3)

   OFDMA symbol parameter
       FFT size: 2048, 1024, 512, 128
   OFDMA supports multi-user to transmit data at
    the same time
       Downlink: One BS transmits data to multiple SSs.
       Uplink: Multiple SSs transmit data to one BS.




                    Vehicle Communication Networks and Protocols   22
4.3 IEEE 802.16e Scalable
OFDMA
    IEEE 802.16e scalable OFDMA(1/3)

   OFDMA-PHY
       Mobile WiMAX based on OFDMA-PHY
       Optimal performance in channel bandwidths ranging from
        1.25 MHz to 20 MHz
       Scalability is supported by adjusting the size of FFT size
            If the available bandwidth increases, the
             FFT size is also increased
            The subcarrier spacing is always 10.94kHz
       The allocation of different subcarrier keeps the product
        cost low


                     Vehicle Communication Networks and Protocols   24
    IEEE 802.16e scalable OFDMA(2/3)

   OFDMA Scalable parameters Table




               Vehicle Communication Networks and Protocols   25
    IEEE 802.16e scalable OFDMA(3/3)

   Subchannelization
       Subchannel is a group of available subcarriers
       OFDMA-PHY allows subchannelization in both the
        uplink and the downlink
       Subchannel is the minimum frequency resource-unit
        allocated by the base station.
            Different subchannels may be allocated to
             different users as a multiple-access
             mechanism.




                    Vehicle Communication Networks and Protocols   26
        Subcarrier allocation

   Downlink
       Partial Usage of Subchannels (DL-PUSC)
       Full Usage of Subchannels (DL-FUSC)
       Optional Full Usage of Subchannels (DL-OFUSC)
       Band AMC (Adaptive Modulation and Coding)
   Uplink
       Partial Usage of Subchannels (UL-PUSC)
       Optional Partial Usage of Subchannels (UL-OPUSC)
       Band AMC


                      Vehicle Communication Networks and Protocols   27
      Subcarriers permutation

     A permutation is a method of mapping physical
      subcarriers to logical subchannels
     Uplink and downlink can have different
      permutations
                                                                     Subchannel




Physical Index                                       Logical Index


                  Vehicle Communication Networks and Protocols                    28
       Full usage of subchannels
       (DL-FUSC、 DL-OFUSC)
           Subchannel 1                        Subchannel 2


                   …                                  …
Time



                                                                                       Symbol n



                                                                                       Symbol n+1


       Frequency
                             Constant Set Pilot                   Variable Set Pilot
                                Subcarrier                            Subcarrier

                          Vehicle Communication Networks and Protocols                       29
          Partial usage of subchannels (DL-PUSC)
       Frequency




         Cluster                                                             Cluster

                                      ……                                                Odd Symbol

                                                                                        Even Symbol

Time           Group 1                                                        Group 6


                   …                                                           …
                         Subchannel (2 culsters from a group)




                              Vehicle Communication Networks and Protocols                    30
         Partial usage of subchannels (UL-PUSC)
   Frequency




              Tile
           Structure
Time


          Group 1                                                       Group 6

               …                                                         …


                                                                              Pilot subsarrier


                       Subchannel (6 tile from a group)
                              Vehicle Communication Networks and Protocols                       31
         Optional partial usage of subchannels
         (UL-OPUSC)
   Frequency




Time


          Group 1                                                    Group 6

               …                                                      …


                                                                           Pilot subsarrier


                    Subchannel (6 tile from a group)
                           Vehicle Communication Networks and Protocols                       32
             DL/UL-band AMC
             (adaptive modulation and coding)
   Frequency




Time                ………
             Bin                       Bin
              1                         N
       bin


                                                                   3 X 2 ACM
 1 X 6 ACM                  2 X 3 ACM                              Subchannel
 Subchannel                 Subchannel

                                                                       6 X 1 ACM
                                                                       Subchannel

                        Vehicle Communication Networks and Protocols                33
4.4 IEEE 802.16e MIMO-
OFDM
    What is MIMO (1/3)

   MIMO is multiple-input multiple-output
    communication
   MIMO is a kind of new Intelligent
    antennas
       It uses multiple transmitter and multiple receiver
        to improve the performance of radio
        communication.



                   Vehicle Communication Networks and Protocols   35
          What is MIMO (2/3)
amplification




                a. Normal Sine Wave




                b. Multipath Interference


                         Vehicle Communication Networks and Protocols   36
 What is MIMO (3/3)


                       stream
  BS                                                       Client


Old BS to Client – transmit and receive 1 stream only



                       stream
                       stream
MIMO
                                                           Client
                           …..




 BS
        …..




                                                    …..
MIMO BS to Client - transmit and receive many stream concurrently
                  Vehicle Communication Networks and Protocols      37
           MIMO vs. intelligent antenna
                                      Stream 1
transmitter                                                                         receiver
                                      Stream 1
               IA                                                              IA




                                           …..
                     …..




                                                                    …..
              Intelligent Antenna : Single-Input Multi-Output (SIMO)




transmitter                           Stream 1                                      receiver
                                      Stream 2
           MIMO                                                            MIMO
                                           …..
                      …..




                                                                   …..
                                                                   …..
     …..




                                                                                    …..
              MIMO Antenna : Multi-Input Multi-Output (MIMO)

                                Vehicle Communication Networks and Protocols                   38
    Functions of MIMO (1/3)

   MIMO technology can be divided into two main
    functions
       Spatial multiplexing
       Spatial diversity




                    Vehicle Communication Networks and Protocols   39
    Functions of MIMO (2/3)
   Spatial multiplexing
       In spatial multiplexing, a high rate signal is split into multiple lower
        rate streams
            Each stream is transmitted from a different
             transmit antenna in the same frequency channel.
            If these signals arrive at the receiver antenna
             array with sufficiently different spatial
             signatures, the receiver can separate these
             streams, creating parallel channels for free.
       Spatial multiplexing can solve the problem of higher Signal to Noise
        Ratio (SNR) by increasing channel capacity greatly.




                        Vehicle Communication Networks and Protocols               40
    Functions of MIMO (3/3)

   Spatial diversity
       In Spatial diversity, it can increase the quality of signals
        by using multiple channel at the transmitter and receiver to
        reduce fading.




                     Vehicle Communication Networks and Protocols   41
    Advantages of MIMO

   MIMO technology have many advantages in
    wireless communications
       MIMO doesn't need additional bandwidth or transmit
        power and can significantly increase the data throughput
        and link range.
       MIMO increases the efficiency of spectral (offers more
        bits per second and per Hertz of bandwidth) and link
        reliability.




                     Vehicle Communication Networks and Protocols   42
    MIMO-OFDM

   MIMO-OFDM is a new technology which
    combine the advantages of MIMO and OFDM
       Higher communication quality
            MIMO-OFDM provide better performance to
             noise, interference and multi-path.
       Higher spectral efficiency
            MIMO-OFDM can increase spectral efficiency
             without additional bandwidth or transmit
             power.




                     Vehicle Communication Networks and Protocols   43
4.5 WiMAX vs. HSDPA




     Vehicle Communication Networks and Protocols   44
    WiMAX

   WiMAX (IEEE 802.16) stands for Worldwide
    Interoperability for Microwave Access
   It is a kind of wireless MAN
   The characteristics of WiMAX are
       long distance (max range 50 km)
       high data rates (up to 70 Mbit/s)
       Deploy fast
       Low cost



                     Vehicle Communication Networks and Protocols   45
  IEEE 802.16 family
                  802.16/16a                 802.16d                    802.16e
Spectrum          10 ~ 66GHz                 < 11GHz                    < 6GHz

 Channel       Line of Sight only     None of Sight only None of Sight only
Conditions
 Bit Rate       32~134 Mbps in         Up to 75 Mbps in             Up to 20 Mbps in
                28MHz channel           20MHz channel                5MHz channel
                  bandwidth               bandwidth                    bandwidth

Modulation      Single Carrier          OFDM 256 sub-                 1x Scalable
                                           carriers                     OFDMA
 Mobility            Fixed                    Fixed                     Portable
 Channel       20, 25 and 28MHz          Scalable 1.5 to            Scalable 1.25 to
Bandwidths                                  20MHz                       20MHz

Typical Cell       2 ~ 5 km               7 to 10km                     1 ~ 5km
  Radius                                Max range 50km
                     Vehicle Communication Networks and Protocols                      46
    HSDPA

   HSDPA stands for High Speed Download
    Packet Access
       Also called as “3.5G”
   HSDPA has been specified in the 3rd
    Generation Partnership Project (3GPP) release
    5
   It is a mobile telephony communications
    protocol which based on W-CDMA technology.
    (W-CDMA is a type of 3G cellular network.)


                    Vehicle Communication Networks and Protocols   47
         WiMAX vs. HSDPA(1/3)

        Bit rate and cell radius
              802.16/16a            802.16d                  802.16e       HSDPA
 Bit Rate     32~134 Mbps       Up to 75 Mbps           Up to 20 Mbps     14.4 Mbit/s
                in 28MHz          in 20MHz                 in 5MHz
                 channel           channel                 channel
               bandwidth         bandwidth               bandwidth

Cell Radius     2 ~ 5 km           7 to 10km                 1 ~ 5km      0.5 ~ 5 km
                                   Max range
                                      50km




                           Vehicle Communication Networks and Protocols                 48
    HSDPA vs. WiMAX(2/3)
   Mobility
       WiMAX offers high bit rate
       Originally, it was designed for fixed communication
       802.16e is the mobile WirelessMAN standard
       3G/HSDPA was designed for mobile telephony
        communications, so it supports good mobility.
   Cost
       HSPDA is based on W-CDMA technology. It can upgrade
        old 3G station without deploying new station.




                    Vehicle Communication Networks and Protocols   49
    WiMAX vs. HSDPA(3/3)

   Market trends
       The market trends of 3G/HSDPA network is to offer the
        public voice service and multimedia business, realize the
        personal cell-phone in the whole world, area and country.
        HSPDA usually is used for browsing on the Internet or
        downloading larger video files.
       The market trends of WiMAX is to offer portable wireless
        wideband, extend the connection of WLAN effectively,
        suitable for deploying in the outskirts, countryside that
        can't be covered effectively by xDSL and CableModem.



                    Vehicle Communication Networks and Protocols   50
4.6 IEEE 802.16e MAC Power
Saving Mode
    IEEE 802.16e MAC power saving mode (1/2)

   The power saving mode allows mobile stations
    to operate for longer durations
   The power saving is achieved by turning off
    parts of the MSs when the communication is
    idle
   It defines signaling methods that allow the MS
    to retreat into a sleep mode or idle mode when
    inactive.



                Vehicle Communication Networks and Protocols   52
    IEEE 802.16e MAC power saving mode (2/2)

   Power management
       Awake mode
            MS and BS continuously process
             downlink/uplink traffics
            Perform handover to support the mobility
       Sleep mode
            MS may power down, scan neighbor BS(s),
             conduct handover/network re-entry or listen
             the broadcasting message
       Idle mode (optional)
            MS and BS close all connections, all air
             resources
            MS monitors down link periodically.

                     Vehicle Communication Networks and Protocols   53
        Mode transition diagram
                                         State Machine
Power off                              -MSS / BS: Buffer empty time > a specified time
                                       -MSS: Entering MSS sleeping


                         Awake                                             Sleep
                         Mode           -MSS: Entering MSS listening
                                                                           Mode
    Power on                            -MSS: UL User data
                                                                                         Power off
                                        -BS: Sleep interval expired &
                                             DL data buffered


                                                   -BS / MSS: Buffer empty time > a specified time
        -BS / MSS: Paging, Location Update
        -MSS: UL User data

                                                    Idle
                                                    Mode
                                                                        Power off

                                   Vehicle Communication Networks and Protocols                      54
    Sleep mode
   Objective
       Minimize MS power usage
       Reduce the usage of BS air interface
   Implementation of sleep-mode
       Optional for MS
       Mandatory for BS
   3 types of Power Saving Classes
       Power Saving Type I
       Power Saving Type II
       Power Saving Type III


                    Vehicle Communication Networks and Protocols   55
       Sleep mode operations
Frame received and MS state




   Active            Sleep          Listen           Sleep             Listen        Active




•MS Normal Tx or Rx           • MS sleeps for number of              • MS Listens for number of
•MS requests BS to enter      frames called sleep interval.          frames called listening
sleep mode to save power.     • No MS Tx or Rx during                interval.
•Sleep mode „start frame‟     this interval.                         • management MSG
is indicated.                 • Power saving classes                 received from BS
                              supported provide flexible             • scan neighbor BS(s)
                              wake up methods



                             Vehicle Communication Networks and Protocols                         56
          Power saving type I
          Enter the sleep mode when start frame is received
          Fixed listening windows size
          Sleep window size =
           min (previous sleep window size•2, final-sleep window
           size)


          Initial Sleep    Listening     2*Initial Sleep      Listening     Final-Sleep    Listening
          Window Size
                           Window         Window Size         Window        Window Size    Window


normal     sleep          Listening          sleep           Listening      sleep         Listening normal


         Start

                                       Vehicle Communication Networks and Protocols                     57
         Power saving type II

        Enter the sleep mode when start frame is
         received
        Fixed listening windows size
        Fixed sleep window size (equal to initial-sleep
         window size)
         Initial Sleep                    Initial Sleep                 Initial Sleep
           Window         Listening         Window         Listening      Window         Listening
              Size        Window               Size        Window            Size        Window


normal      sleep        Listening           sleep        Listening        sleep        Listening    normal




    Start


                                      Vehicle Communication Networks and Protocols                        58
         Power saving type III

        Enter the sleep mode when start frame is
         received
        Sleep window size = Final-sleep window size

                                Final-Sleep
                                  Window
                                    Size


normal                             sleep                            normal




    Start




                     Vehicle Communication Networks and Protocols        59
    Idle mode (optional)
   Idle mode is an optional feature and can be negotiated
    between BS and MS
   It allows MS to receive DL broadcast messages
    periodically without registering at a BS
   MS is restricted to scan the network at discrete intervals
       MS is not required to perform the normal operations
   Benefits
       For MS: save power and operation resources
       For BS: provide a simple method for alerting the MS to pending MS-
        directed DL traffic




                       Vehicle Communication Networks and Protocols      60
    Idle mode operations(1/2)
   BSs are divided into logical groups called paging groups
       An MS in idle mode periodically monitors the DL transmission of the
        network to determine the paging group of its current location.
   If MS moves to a new paging group
       The MS performs a paging group update
       It informs the network of the current paging group in which it is
        present.
   If there is pending downlink traffic, the network has to
    establish a connection with an MS in idle mode
       The network needs to page the MS only in all the BSs belonging to the
        current paging group



                        Vehicle Communication Networks and Protocols        61
    Idle mode operations(2/2)

   The paging area should be large enough so that
       The MS is not required to perform a paging area update
        too often
   The paging area should be small enough so
    that
       The paging overhead associated with sending the page on
        multiple BSs is low enough




                    Vehicle Communication Networks and Protocols   62
Paging area example




     Paging                Paging                  Paging
     Group 1               Group 2                 Group 3




     Cell Site




                 Vehicle Communication Networks and Protocols   63
4.7 WiMAX QoS and
Handover Mechanism
    Service flows

   A service flow is a unidirectional flow of packets
       The QoS of the flow is uniquely identified by a 32-bit
        integer – SFID
   There is a one-to-one mapping between active
    service flows (32-bit SFID) and transport
    connections (16-bit CID).




                     Vehicle Communication Networks and Protocols   65
    Service scheduling

   Unsolicited Grant Service (UGS)
   Real-time Polling Service (rtPS)
   Extended real-time Polling Service (ertPS)
   Non-real-time Polling Service (nrtPS)
   Best Effort (BE)




                Vehicle Communication Networks and Protocols   66
    Service types (1/5)

   Unsolicited Grant Service (UGS)
       Used for real-time data with fixed packet size and periodic
        arrivals
       QoS parameters
            Maximum Sustained Rate
            Maximum Latency Tolerance
            Jitter Tolerance
       Support Constant Bit Rate (CBR) services, such as T1/E1
        emulation, and Voice over IP (VoIP) without silence
        suppression


                     Vehicle Communication Networks and Protocols   67
    Service types (2/5)

   Real-time Polling Service (rtPS)
       Used for near real-time data with variable-sized packets
        and periodic arrivals
       QoS parameters
            Minimum   Reserved Rate
            Maximum   Sustained Rate
            Maximum   Latency Tolerance
            Traffic   Priority
       Support real-time services such as MPEG video or VoIP
        with silence suppression


                       Vehicle Communication Networks and Protocols   68
    Service types (3/5)
   Extended real-time Polling Service (ertPS)
       Similar to rtPS, used for near real-time data with variable-
        sized packets and periodic arrivals
            The process for handling jitter is required
       QoS parameters
            Minimum Reserved Rate
            Maximum Sustained Rate
            Maximum Latency Tolerance
            Jitter Tolerance
            Traffic Priority
       Support real-time services such as VoIP with silence
        suppression

                     Vehicle Communication Networks and Protocols   69
    Service types (4/5)

   Non-real-time Polling Service (nrtPS)
       Used for delay tolerant traffic
       Require some minimum data rate
       The BS polls nrtPS connections on an fixed interval
       QoS parameters
            Minimum Reserved Rate
            Maximum Sustained Rate
            Traffic Priority
       Support non-real-time services that require variable size
        data grant burst types on a regular basis such as FTP


                     Vehicle Communication Networks and Protocols   70
    Service types (5/5)

   Best Effort (BE)
       Used for streams with no data rate guarantees
       QoS parameter
            Maximum Sustained Rate
            Traffic Priority




                    Vehicle Communication Networks and Protocols   71
    QoS mechanisms

   Classification
       Mapping from MAC service data units (SDU) fields (e.g
        MAC address or other field) to CID and SFID
   Scheduling
       Downlink scheduling module
       Uplink scheduling module




                    Vehicle Communication Networks and Protocols   72
      Classification
Subscriber Station (SS)                                   Base Station (SS)

       Applications
                                                                                           Traffic
                Data traffic           Traffic                                             from
                                       from SS                                             Internet
 CID/SFID Classification                                CID/SFID Classification




                                                     CID
                                                     CID
                                                     CID
                                                     CID
                                                     CID
                                                     CID
                                                     CID
                                                     CID
                                                     CID
                                                     CID
CID
CID
CID
CID
CID
CID
CID
CID
CID
CID




                                       Queues
UGS   rtPS   ertPS   nrtPS   BE                        UGS    rtPS    ertPS   nrtPS   BE



                               Vehicle Communication Networks and Protocols                       73
    Scheduling

   Downlink scheduling module
       All queues are in BS
   Uplink scheduling module
       Queues are distributed among SSs
       Queue states and QoS requirements are obtained through
        BW requests
       Scheduling algorithms are not defineded in standard
        document




                    Vehicle Communication Networks and Protocols   74
    QoS parameters
   Traffic priority
        The value (0 .. 7) specifies the priority assigned to a service flow.
   Maximum sustained rate
        Specifies the peak information rate of the service flow in bits per second.
   Maximum traffic burst
        Specifies the maximum burst size that can be transported.
   Minimum reserved rate
        The rate in bits per second specifies the minimum amount of data to be
         transported on the service flow when averaged over time.
   Tolerated jitter
        Specifies the maximum delay variation (jitter) for the service flow.
   Maximum latency
        Specifies the maximum latency between the reception of a packet by the BS
         or SS on its network interface and the forwarding of the packet to its RF
         interface.



                           Vehicle Communication Networks and Protocols                75
    Handover procedure (1/2)
   Handover
       An mobile station (MS) migrates from the air-interface
        provided by one BS to the air interface provided by
        another BS.
   Handover situations
       To obtain higher signal quality.
       To obtain higher QoS.




                     Vehicle Communication Networks and Protocols   76
    Handover procedure (2/2)
   Network topology acquisition
       Network topology advertisement
       MS scan the neighboring BSs
   Handover process
       Cell reselection
       Handover decision and initiation
       Handover cancellation
       Termination with the serving BS
       Drops during handover
       Network entry/re-entry


                    Vehicle Communication Networks and Protocols   77
         Handover state machine

Cell Reselection


         MS decides to add/drop BS


HO Decision &           Target Scanning &                    Network             Termination of
  Initiation             Synchronization                     Re-entry               Service

         MS begins to                MS scans and                  MS reenters          MS terminates
         handover with target        synchronizes with the         new network          with the
         BS                          target BS                                          serving BS



                                                  MS cancels the
                                                  handover process
                                                                                         End HO
                                        HO Cancellation


                                 Vehicle Communication Networks and Protocols                     78
4.8 WiMAX Security
    Architecture
   Encapsulation protocol
       A set of cryptographic suites
       The rules for applying those algorithms to a MAC PDU
        payload
   Key management protocol
       Privacy Key Management (PKM)
       Secure distribution of keying data from the BS to the SS
       There are 2 kinds of key
            Authorization Key (AK)
                 Shared key between the SS and the BS.
            Traffic Encryption Key (TEK)
                 PKM exchange key (Encrypted by AK)



                       Vehicle Communication Networks and Protocols   80
Security sublayer


  RSA-based             Authorization /            EAP encapsulation /
 authentication           SA control                 decapsulation

                  PKM control management


                                      Control message processing
 Traffic data encryption /
 authentication processing                    Message authentication
                                                   processing
                             PHY SAP


                  Vehicle Communication Networks and Protocols           81
          MAC PDU format



HT=0 → Generic MAC Header
EC → Encryption control
Type → Subheader/Payload type
ESF → Extended subheader field
CI → CRC Indicator
EKS → Encryption Key Sequence
LEN → Length
(header+payload+CRC)
CID → Connection ID
HCS → Header Check Sequence




                                 Generic MAC header format
                                 Vehicle Communication Networks and Protocols   82
MAC management message format




         Vehicle Communication Networks and Protocols   83
    PKM protocol
   802.16e-2005 supports two PKM protocols
       PKM version 1
       PKM version 2
   PKM supports two authentication protocol
    mechanisms:
       RSA protocol (support is mandatory in PKMv1, support is
        optional in PKMv2)
       Extensible Authentication Protocol (optional)




                    Vehicle Communication Networks and Protocols   84
PKM process


           1. Authentication


SS                                                      BS
            2. Key exchange



           3. Data encryption




         Vehicle Communication Networks and Protocols        85
    PKM version 1

   Security Association (SA)
       The set of security information between the BS and SSs
        for supporting secure communications.
       Three SA types:
            Primary
            Static
            Dynamic
       Identified using SAID




                       Vehicle Communication Networks and Protocols   86
     PKM version 1 authentication

SS                                                        BS

                Authentication
                 Information                            •Verify CA Certificate
                [CA-Certificate]

            Authorization Request                       •Verify SS Certificate

     [SS-Certificate, Security-Capabilities,            •Determine KEK (Key Encryption
                                                        Key)
     SAID]
                                                        •Generate AK
             Authorization Reply
                                                        •Encrypt AK with SS’s public-key
      [AK, Key-Lifetime, Key-Sequence-
                                                        •Send encrypted AK back
      Number, SA-Descriptor(s), PKM
      Configuration settings (optional)]
                       Vehicle Communication Networks and Protocols                    87
     PKM version 1 - TEK exchange
     (PMP mode)

SS                                                    BS


              Key Request
       [Key-Sequence-Number, SAID,
       HMAC-Digest]

                Key Reply                           •Encrypt TEK with KEK from AK
     [Key-Sequence-Number, SAID, TEK-
     Parameters, HMAC-Digest]


             Encrypted Data

                   Vehicle Communication Networks and Protocols                     88
     PKM version 1 - TEK exchange
     (Mesh mode)

SS                                                      SS


               Key Request
     [SS Certificate, SAID, HMAC-Digest]


                 Key Reply                            •Encrypt TEK with SS’s public key
     [Key-Sequence-Number, SAID, TEK-
     Parameters, HMAC-Digest]


              Encrypted Data

                     Vehicle Communication Networks and Protocols                    89
    PKM version 2

   PKMv2 offers more enhanced features
       MBS (Multicast and Broadcast Services)
       Key hierarchy
       New cryptographic technology
   The derivation of authorization key (AK) is
    based on RSA and EAP
   BS has a certificate
       It can authenticate itself to the MS by mutual
        authentication


                     Vehicle Communication Networks and Protocols   90
    Key hierarchy (1/2)

   The PKMv2 defines hierarchy for keys
       Pre-PAK (pre-Primary AK) yielded by the RSA-based
        authorization process
       MSK yielded by the EAP based authentication process
       MBSAK from which keys used to protect MBS traffic are
        derived.




                    Vehicle Communication Networks and Protocols   91
     Key hierarchy (2/2)

Pre-PAK: pre-Primary AK           MTK: MBS Transport Key

AK: Authorization                 EIK: EAP Integrity Key

MAK: Multicast and                MGTEK: MBS Group Traffic
Broadcast Service AK              Encryption Key
KEK: Key Encryption Key           TEK: Traffic Encryption Key
GKEK: Group Key                   GTEK: Group Traffic Encryption
Encryption Key                    Key



                    Vehicle Communication Networks and Protocols   92
      Cryptographic technology
                      PKMv1                              PKMv2
Data En/Decryption    56 bit CBC-Mode DES                56 bit CBC-Mode DES
                                                         128 bit CCM-Mode AES
                      128 bit CCM-Mode AES               128 bit CBC-Mode AES
                                                         128 bit CTR-Mode AES
Data Authentication   Not Support                        128 bit CCM-Mode AES
Key Generation        Not Define                         Dot16KDF
Key En/Decryption     128bit EDE-Mode 3-DES              128bit EDE-Mode 3-DES
                      1024 bit RSA                       1024 bit RSA
                      128 bit ECB-Mode AES               128 bit ECB-Mode AES
                                                         128 bit AES-Key-Wrap



                         Vehicle Communication Networks and Protocols            93
     PKMv2 SA-TEK 3-Way handshake

MS                                                                  BS

                      SA-TEK-Challenge

     [BS_Random, KeySeqNo, AKID, KeyLifeTime, H-C/MAC]

                       SA-TEK-Request

        [BS_Random, KeySeqNo, AKID, SecurityCapabilities,
        SecNegParam, PKMConfSettings, H-C/MAC]
                       SA-TEK-Response
     [BS_Random, KeySeqNo, AKID, SA-TEKUpdate, FrameNo,
     SADescriptors, SecNegParam, H-C/MAC]
                     Vehicle Communication Networks and Protocols        94
    V1 v.s. V2
   Authentication & authorization
       It improves single authentication to become mutual
        authentication between SS and BS
       It reduces the possibility of fake BS attack.
   Data privacy
       IEEE 802.16e add secure encryption standard such as
        AES-key-wraps.
   Key exchange
       Update the finite state machine (FSM) of the key
        exchange
                     Vehicle Communication integrity and
        Add new method to protect Networks and Protocolssupport MBS.

                      Vehicle Communication Networks and Protocols     95
    Problem
   Replay attack
       PKMv2 adds random number generated by MS and BS to
        protect message from replay attack.
       However, the TEK sequence number length remains two
        bit long as PKMv1
            It still   is easy to suffer from replay
             attack.
   Security supporting mobility
       IEEE 802.16e does not define the pre-authentication
        mechanism explicitly to solve time-consuming
        authentication operation.



                    Vehicle Communication Networks and Protocols   96
    Data encryption

   DES - CBC encryption
       General data transmission
   AES - CCM encryption
       High-level security data transmission
   AES - CTR encryption
       For broadcast and multicast




                     Vehicle Communication Networks and Protocols   97
         DES in CBC mode

       GMH                      Plaintext Payload                             CRC
                                                     Every Block<= 64bits
Value from     Plaintext         Plaintext         ………            Plaintext
   TEK         Block(0)          Block(1)                         Block(n)
parameter


      CBC-IV


                DES(K)           DES(K)                           DES(K)



               Ciphertext       Ciphertext         ………           Ciphertext
                Block(0)         Block(1)                         Block(n)




      GMH                     Ciphertext Payload                              CRC

                            Vehicle Communication Networks and Protocols            98
        AES in CCM mode
Authentication
             Bytes 0     1    2      3     4   5    6    7      8     9      10    11   12     13   14    15   16

  Block(0)         Flag      Generic MAC Header           Reserved                Packet Number      Data LEN



                                                   Data Length

         Packet        GMH PN                           DATA                                 ICV    CRC



                                   Every Block = 16 Bytes             Block(n)
                                                                      10 Bytes
                                                             Zero Padding

                         Plaintext         Plaintext      ………               Plaintext
                         Block(1)          Block(2)                         Block(n)
  Block(0)
                                                                                                        Get Least
                                                                                                    significant 8 bytes


  AES(K)                          AES(K)                       AES(K)                   AES(K)            16Bytes
                                                                                                          Output



                                         Vehicle Communication Networks and Protocols                                     99
            AES in CCM mode
encryption       Bytes 0    1      2     3     4      5    6      7      8   9     10     11      12   13     14     15     16


       Block(0)        Flag      Generic MAC Header               Reserved               Packet Number         Counter




  Packet     GMH      PN                                   DATA                                         ICV         CRC




       Plaintext Block(1)       Plaintext Block(2)                Plaintext Block(n-1)         Plaintext Block(n)
           (16 Bytes)               (16 Bytes)            ……           (16 Bytes)                  (10 Bytes)
                                                                                                                              ICV Block




     AES(K)                     AES(K)                      AES(K)                      AES(K)
                                                                                                                   AES(K)
Counter+1
                       Counter+2                     Counter+(n-1)               Counter+(n)
      Block(1)
                              Block(2)                      Block(n-1)                   Block(n)                  Block(0)

    PN++
            Ciphertext Block(1) Ciphertext Block(2)            Ciphertext Block(n-1) Plaintext Block(n)            ICV Ciphertext
 GMH PN
                (16 Bytes)          (16 Bytes)
                                                          ……        (16 Bytes)           (10 Bytes)                Block (16 Bytes)
                                                                                                                                      CRC

                                              Vehicle Communication Networks and Protocols                                                  100
      AES in CTR mode
          Bytes 0     1      2      3      4    5     6     7    8      9    10    11    12      13   14    15     16


Counter Block             Nonce                     Nonce                   Nonce                  Nonce


                      4 Bytes
                                                                                                           Counter counts after
                          Nonce                                 DATA
                                                                                                            encrypt one block



        Plaintext Block(1)       Plaintext Block(2)               Plaintext Block(n-1)        Plaintext Block(n)
            (16 Bytes)               (16 Bytes)           ……           (16 Bytes)                 (10 Bytes)




        AES(K)                   AES(K)                                AES(K)                     AES(K)

         Counter                 Counter                               Counter                     Counter
         Block+1                 Block+2                             Block+(n-1)                  Block+(n)



                Ciphertext Block(1) Ciphertext Block(2)                  Ciphertext Block(n-1) Plaintext Block(n)
GMH    Nonce
                    (16 Bytes)          (16 Bytes)
                                                                ……            (16 Bytes)           (10 Bytes)
                                                                                                                  CRC

                                        Vehicle Communication Networks and Protocols                                        101

				
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