Actas JP2011 - Universidad de La Laguna

Actas XXII Jornadas de Paralelismo (JP2011) , La Laguna, Tenerife, 7-9 septiembre 2011rameter changes).• Predictive events (link going down).• Network initiated events (load balancing, operatorpreferences).A.2 Media Independent Information Service (MIIS)The MIIS allows the MIHF to discover its networkenvironment gathering information that the upperlayers make use of to make decisions. The informationelements refers to the list of available networks,location of Point of Attachment (PoA), operator ID,roaming partners, cost, security, QoS, PoA capabilities,and Vendor specific information, among others.A.3 Media Independent Command Service (MICS)The MICS allows the MIHU to take control overthe lower layers through a set of commands. Withthe information gathered by the MIES and MIIS, theMIHU decide to switch from one PoA to another.The commands allow not only to execute the handover,but to set different parameters in the lowerlayers elements. Depending on which entity has thehandover control, some services are more useful thanothers. The following commands are typically usedby the MICS:• MIH Handover Initiate. Used between networkand mobile device.• MIH Handover Prepare. Used between the oldnetwork (PoA) and the new network.• MIH Handover Commit. Used between networkand mobile device.• MIH Handover Complete. Used between networkand mobile device and network to network.A.4 AmendmentsIn order to fully provide handover services, the802.21 must be implemented into network devicesand mobile devices. The media specific amendmentsrequired by MIHF are defined as follows• Container for MIH messages for 802.11 are definedin the 802.11u [11]• Container for MIH messages for 802.16 are definedin the 802.16g [12]• The 3GPP-SAE (System Architecture Evolution)is working for 3GPP. [13]• The IEFT MIPSHOP (Mobility for IP: Performance,Signaling and Handoff Optimization) ishas defined the Transport for MIH Protocol [14]• 802.3 is desired.IV. Overview of the Vertical HandoverDecision Algorithm (VHDA)The VHO process considered in our experimentsuses the IEEE 802.21 standard at the first phase inorder to gather information, notify events and executecommands. For the decision phase, we haveused a VHDA that considers the availability and thebandwidth offered for the decision making process.Figure 4 shows the state diagram of the VHDA whenUpper Layers (L3 and above)SIP MIPv4 MIPv6 HIP ....Mobility ManagementMIHEventsLinkEventsMIH_SAPSmartTriggersMIH_Link_SAPMIH UsersMIHCommandsLinkCommandsLower Layers (L2 and below)Handover Management802.21 MIH FunctionHandoverMessagesInformationServiceInformationServiceProtocol and Device Hardware802.3 802.11 3GPP 802.16Fig. 3.InformationServiceIEEE 802.21 Architecture.selecting a candidate network to switch to. As observed,the MIHF set at the User Equipment (UE) iscontinuously sensing the interfaces. When an eventis triggered, and depending on the type of event, theVHDA performs different routines and subroutinesbased in MICS and MIES in order to select the bestcandidate network, or simply chooses the UMTS networkby default, due to the full UMTS coverage. Finally,considering the execution phase of the VHOprocess, we use Mobility support for Internet Protocolv.6 (MIPv6) to manage the mobility issues. Itis important to emphasize that the 802.21 events:LINK UP and LINK DOWN, determine the behaviorof the VHDA. When a LINK DETECTED eventoccurs, the user equipment will trigger other eventssuch as LINK UP if the technology detected is ableto offer more bandwidth, negotiating with the newbase station for the IP address; MIPv6 is in chargeof this negotiation and notification to different componentsof the system. All these processes requirecomplex actions which imply latency. On the otherhand, when a LINK DOWN event is detected, onlya notification is performed by the MIPv6 agent sincethe interface was already configured in a previousLINK UP. So, there is no added latency to theseprocesses.V. Simulation frameworkConsidering networking in general, there are severaltools for simulation. Nevertheless, consideringVHO in particular, there are only a few simulationtools available. To address this shortage, the NationalInstitute of Standards and Technology (NIST)has developed a tool for seamless mobility [15] based....JP2011-429