Handover In 4 G Networks


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  • Scalability of handover framework to handle increased handovers without compromising latency performanceFlexibility to support various 4G deployments
  • Mobility framework designed to cover: all possible deployment scenarios enable and optimize handover between IEEE 802.16m Bss handover from an IEEE 802.16e BS to an IEEE 802.16m BS (note: under a legacy ASN network) intra-BS zone switch between LZone and Mzone
  • Exception HandlingThe handover is considered failedMS performs cell reselectionMS performs network re-entry procedure or initial network entry procedure
  • Seamless handover is a network re-entry procedure:Exchange of PDUs between MS and BS before network re-entrySupports data integrity protectionNot demanding full uplink synchronization from MS to BSRequires coordination serving and target BSsEBB handover is an optimized hard handover procedure:Network re-entry to the target BS during the negotiated network re-entry procedure intervalsCommunication with serving BS until the completion of the network re-entryLegacy supported handover provides:Backward compatibilitySupport mobility capability across coexisting legacy and advanced networks.Multicarrier handover:Capability of BSs and MSs to operate over multiple carriers upon a common MAC layerResults in high data rate service and cell capacity increaseCombined with seamless handover allows zero tolerance of data interruption time
  • One or two iterations to avoid excessive scheduling overhead
  • One or two iterations to avoid excessive scheduling overhead
  • Handover from a 16e BS to a 16m Mixed Mode BS
  • (Access Service Network)
  • (Access Service Network)
  • Seamless handover mode:Minimizes complexity and delayPotential loss of Service Data Units (SDUs)Appropriate for loss-tolerant but delay-sensitive data (e.g. VoIP)Lossless handover mode:Guarantees in-sequence packet delivery during handoverRetransmits any unacknowledged PDUs prior to handoverAppropriate for dealy-tolerant services (e.g. FTP)
  • TSG SA WG2 Architecture is in charge of developing the Stage 2 of the 3GPP network. Based on the services requirements elaborated by SA1, SA2 identifies the main functions and entities of the network, how these entities are linked to each other and the information they exchange. The output of SA2 is used as input by the groups in charge of the definition of the precise format of messages in Stage 3
  • Handover In 4 G Networks

    1. 1. Department of Digital SystemsMsc.Digital Communications and Networks<br />HANDOVERIN 4G NETWORKS<br />OikonomakisSpyridon<br />PantelopoulouCharikleia<br />
    2. 2. Structure of Presentation<br />Handover Basics<br />Handover in and between 4G networks<br />Handover procedures IEEE 802.16m<br />Advanced handover features IEEE 802.16m<br />Legacy supported handover IEEE 802.16m<br />Handover Framework 3GPP LTE-Advanced<br />Interworking between IEEE 802.16m & 3GPP LTE-Advanced<br />Conclusions<br />
    3. 3. The Term Handover<br />The process of transferring an ongoing call or data session from one channel to another in a cellular network.<br />Basic reasons why a handover might be conducted:<br />The user has moved out of range<br />The base station is full<br />It is a key component in cellular network mobility management as it requires a specific latency on server interruption time. <br />
    4. 4. Handover Framework Requirements<br />Latency and Flexibility<br />Scalability of handover framework to handle increased handovers without compromising latency performance<br />Handling networks with heterogeneous BS entities (pico / femtocells)<br />Optimizations to allow handover to multicarrier-capable devices.<br />
    5. 5. IEEE 802.16m & 3GPP LTE - Advanced<br />Physical layer frame of IEEE 802.16m designed with legacy of IEEE 802.16e <br /><ul><li>allowing operation:
    6. 6. Either on separate frequency assignments
    7. 7. Or on the same frequency assignment with proper time-division zone partitioning between them (LZone, Mzone)
    8. 8. Providing legacy access service network (ASN) support mode (plug-and-play)</li></ul>LTE – Advanced designed with legacy of GSM/EDGE, GERAN and UMTS<br /><ul><li>handover and cell reselection to/from the legacy systems through treating them as inter-RAT networks.</li></li></ul><li>Handover in UMTS and WiMAX<br />E-UTRAN<br />IEEE – 802.16m<br />
    9. 9. Deployment scenarios ieee – 802.16m<br />a) greenfield deployment (new spectrum) b) mixed deployment, carrier reuse c) mixed deployment, carrier overlay<br />
    10. 10. IEEE – 802.16e & IEEE – 802.16m COEXISTENCE ARCHITECTURE<br />
    11. 11. OVERALL HANDOVER PROCEDURES <br /><ul><li>Completion
    12. 12. Exception Handling</li></ul>Preparation and Initiation<br />Execution<br />
    13. 13. ADVANCED HANDOVER FEATURES IEEE 802.16m<br />Goal: To reduce latency during handover in physical and MAC layers and provide a better end-user experience<br />Advanced handover enhancements based on the general handover call flow:<br />Seamless Handover<br />EBB Handover (Entry Before Break)<br />Newly introduced in the IEEE 802.16m air interface protocol:<br />Legacy Supported Handover<br />Multicarrier Handover<br />
    14. 14. EBB handover procedures<br />General EBB handover procedures: a) single-carrier b) multicarrier<br />
    15. 15. Legacy Supported Handover IEEE 802.16m (1)<br />There are four possible scenarios for handover:<br /><ul><li>Handover from a 16e BS to 16m BS:</li></ul>16e BS to mixed-mode16m BS<br />16e BS to advanced only 16m BS<br /><ul><li>Handover from a 16m BS to 16e BS :</li></ul>advanced only 16m BS to 16e BS<br />mixed-mode 16m BS to legacy 16e BS<br />
    16. 16. Legacy Supported Handover IEEE 802.16m (2)<br />Handover procedure from an IEEE 802.16e BS to a mixed-mode IEEE 802.16m BS<br />
    17. 17. Legacy Supported Handover IEEE 802.16m (3)<br />Handover from a 16e BS to a 16m Only BS (direct handover)<br />Case of the largest interruption time due to lack of the demanded BSs’ interfaces<br />Legacy ASN :<br />Security update is a typical intra-16m handover case<br />Requires capability negotiation and MAC context setup<br />16m ASN:<br />Requires full network entry<br />
    18. 18. Legacy Supported Handover IEEE 802.16m (4)<br />Handover from a 16m BS to a 16e BS<br />Either the 16m MS performs legacy handover to the 16e BS through the Lzone<br />Or the 16m MS performs direct handover to the 16e BS through the MZone<br />
    19. 19. The Handover Framework of 3GPP LTE-Advanced<br />Hard handover is similar to IEEE 802.16m<br />Differences: <br />Allows only BBE (Break Before Entry) operation<br />Handover initiation and target selection are more tightly controlled by the network<br />Supports seamless and lossless handover<br />User procedure can be assigned in a per resource bearer (RB) manner<br />Packet Data Convergence Protocol (PDCP) handles differently the data forwarding at the UE and eNodeB sides in different modes<br />
    20. 20. Interworking Between IEEE 802.16m and 3GPP LTE-Advanced (1)<br />Handover from IEEE 802.16m to 3GPP LTE-Advanced can use tow layer-2 protocols:<br />IEEE 802.16m generic MAC layer-2 transfer tunnel<br />IEEE 802.21 media-independent handover protocol<br />Given these frameworks and MAC layer control signaling there can be support of:<br />single-radio handover<br />dual radio handover<br />
    21. 21. Interworking Between IEEE 802.16m and 3GPP LTE-Advanced (2)<br />Handover from 3GPP LTE-Advanced to IEEE 802.16 family supports dual radio procedure via layer 3 transport.<br />The 3GPP Service and Architecture 2 (SA2) specification requires layer 3 handover signaling for UE to preregister with WiMAX network.<br />Disadvantage: No layer-2 radio access network 2 (RAN2) specification defined to optimize handover<br />
    22. 22. Conclusions<br />Reducing service interruption time is becoming more in next-generation wireless systems.<br />IMT-Advanced Systems provide advanced handover mechanisms in order to provide enhanced user experience during handover.<br />Important requirement when design IEEE 802.16m and 3GPP systems is:<br />Legacy supported mobility management<br />All previously described advanced features of handover mechanisms enhance the user experience by:<br />Reducing handover interruption time<br />Diminishing the coverage hole<br />