HARI PRJ1

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					 VERTICAL HANDOVER APPROACHES
BASED ON IEEE 802.21 MIH STANDARDS
  For HETEROGENEOUS NETWORKS




            Presented by
          M.HARIKRISHNAN(EC1106)

           Under the Guidance of
            Dr.G.SIVARADJE
                    OBJECTIVE

 The design goal of this project is to provide an
  efficient vertical handover decision algorithm based
  on IEEE 802.21 standard for best quality of service.

 Seamlessly transfer to best access link among all
  available candidate with no perceivable interruption.

 Probability of     handover failure, unnecessary
  Handover initiation, Ping-Pong effect should be
  minimized.
  HANDOVER DECISION BASED ON IEEE
       802.21 MIH STANDARDS
 The decision to initiate handovers in 3G networks has
  traditionally based on the received signal strength and
  availability of resources in a new cell.

 Such traditional handover decisions use RSS as the only
  criteria.

 In order to enable seamless vertical handovers, IEEE 802.21
  aims to improve user experience of MTs by enabling
  handovers between heterogeneous technologies while
  maintaining session continuity.
                       CONTINUED

 In a heterogeneous network, handover decisions could also
  be initiated for other reasons including RSS, network
  connection time, security, bandwidth, data rate and user
  preferences.
VERTICAL HANDOVER DECISION BASED ON
         MIHF(MIES,MICS,MIIS)
                          CONTINUED

 MIH can provide Link up, Link down and Link going down events (MIES)
  to monitor the link status continuously.

 Handoff is prepared if the link going down, then the MIH user provides
  MICS command to the users to switch links.

 The ASCONF-Path Failure sends from MN to CN to notify that the IP
  address is going to fail.

 The client gets the available network information from the information
  server through MIIS queries and responses.

 Best candidate is selected. MN sends ASCONF-Delete old IP to indicate
  CN to delete old IP address and add new IP address
  VERTICAL HANDOVER DECISION BASED ON
             MIH STANDARD

 The above mentioned idea is implemented based on
  conditional probability of link down (RSSi-1) and link going
  down (RSSi).

 For assumption, in a time (i-1) mobile station is in WLAN
  coverage, therefore RSS value is greater than the RSS
  threshold and in a time i mobile station is not in WLAN
  coverage, therefore RSS value is less than the RSS threshold.

 The probability of handover from WLAN to cellular network
  is predicted by conditional probability
                                    CONTINUED

   •          Assume
         RSSi <RSSthr = x and RSSi-1 >RSSthr =y

         P{RSSi <RSSthr ,RSSi-1 >RSSthr }=P(x,y)

       Therefore,                                                                         2
                    1                 1       x − µx   2        x − µx   y − µy   y − µy
P x, y    =                  exp −                         − 2ρ                 +
              2Πσx σy   1−ρ2       2(1 − ρ2     σx                σx       σy       σy


 Thus the probability of handover from WLAN to Cellular networks was found and
 will reduces the number of handover occurring by taking periodic RSS sample into
 account.
        MINIMIZATION OF HANDOVER FAILURE
     PROBABILITY AND UNNECESSARY HANDOVER
                (RSS MEASUREMENT)
 In order to maintain seamless user roaming and optimize network resource
  usage, it is desirable to minimize handover failures and unnecessary
  handovers.

 It takes various network parameters in to account, AP power level, RSS
  samples, radius of the network, and velocity of mobile terminal etc.

 RSS measurement fluctuates because of fading (Fast and shadow fading)
  and affects accuracy of time prediction.

 To reduce the impact of shadow fading, collect more RSS samples and
  average them in a sliding window.
                                      CONTINUED

 Log distance path loss model is given by
         Yj (i)=Pj -L j (i)-A j (i)

  Pj - power transmitted from BSj,
  Lj(i) - mean path-loss
  Aj(i) - shadowing loss

 The Received Signal Strength is estimated by
                                       lop
          RSSi =Ptx +Pref -10nlog              +ε
                                       d ref
  Ptx - transmitted power from AP
  n - path loss exponent
    - Gaussian distributed random
MEAN RSS VARIATION DUE TO SHADOW FADING
       WITH RESPECT TO DISTANCE


                        40
                                                                              Beta=3
                        20                                                    Beta=4
                                                                              Beta=5
                         0                                                    Beta=8

                        -20
  RSS Variation (dB)




                        -40

                        -60

                        -80

                       -100

                       -120

                       -140
                              0   10   20   30   40     50     60   70   80   90   100
                                                   Distance (m)
HANDOVER FAILURE PROBABILITY


                                 0.18
                                            Fixed RSS method
                                 0.16       Hysteresis method
                                            MIH method
                                 0.14
  Handover failure probability




                                 0.12

                                  0.1

                                 0.08

                                 0.06

                                 0.04

                                 0.02

                                   0
                                        0            50                        100     150
                                                  Velocity of Mobile Terminal (km/h)
PROBABILITY OF UNNECESSARY HANDOVER


                                         0.25
                                                    Fixed RSS method
                                                    Hysteresis method
                                          0.2       MIH method
      Unnecessary Handover probability




                                         0.15




                                          0.1




                                         0.05




                                           0
                                                0            50                        100     150
                                                          Velocity of Mobile Terminal (km/h)
                     CONCLUSION

 A IEEE 802.21 Media Independent Handover scheme has
  been presented for seamless vertical handover between
  heterogeneous networks for best QoS.

 Results show that proposed method outperforms the existing
  methods which are based on received signal strength and
  hysteresis margin.

 The probability of unnecessary handover and handover failure
  for the proposed method is minimized by considering shadow
  fading and velocity of the mobile terminals into account.
                               REFERENCES
[1]      Daniel Corujo, Carlos Guimaraes, Bruno Santos and Rui L. Aguiar,”Using an Open-
Source       IEEE 802.21 Implementation for Network-Based Localized Mobility
Management”, IEEE         Communication Magazine, pp. 114-123, 2011.
[2]         Xiaohuan Yan, Y.Ahmet Sekercioglu, and Sathya Narayanan, “A Survey of
Vertical Handover Decision Algorithms in Fourth Generation Heterogeneous Wireless
Networks”, Computer Networks, Vol. 54, pp. 1848-1863, 2010.
[3]      A. H. Zahran, B. Liang, and A. Saleh,”Signal Threshold Adaptation for Vertical
Handoff in Heterogeneous Wireless Networks, Mobile Networks and Applications”, 11(4):
pp. 625–640, August 2006.
[4] S. Mohanty and I. F. Akyildiz,” A Cross-layer (layer2 + 3) Handover Management
Protocol     for Next-Generation Wireless Systems”, IEEE Transactions on Mobile
Computing, 5:1347–1360, October 2006.
[5] X. Yan, N. Mani, and Y. A. Sekercioglu, ”A Traveling Distance Prediction Based Method
to Minimize Unnecessary Handovers from Cellular Networks to WLANs”, IEEE
Communications letters, 12(1): pp. 14–16, January 2008.

				
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posted:11/15/2012
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