5. Mobile Networking Challenges 5.1 Mobile IP

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  • 5. Mobile Networking Challenges

    5.1 Mobile IPMobile IP IP . IP . Mobile IP . Mobile IP (Home Address) COA(Care of address) . , COA . , COA .

    Mobile Networking Challenges

  • Mobile IPWhen the mobile device moves to another area, it receives a care-of address (CoA) from foreign agent (FA).The foreign agent and home agent will coordinate to provide a connection as through the mobile device can still be reached via its home address.The home agent maintains a mapping between the mobile devices home address and foreign address.Any packet sent to the home address will put into an IP-in-IP tunnel by the HA, and forwarded to the foreign address. At the end of this tunnel is the FA, whose job is to decapsulate the packet and forward the orginal data to the mobile device.Mobile IP essentially offers a way to identify a mobile device using the same address when it moves to another location and cannot be serviced by its original home agent.

    Mobile Networking Challenges

  • Mobile IP

    Mobile Networking Challenges

  • Mobile IPv6Mobile Pv6 Mobile IPv4 CoA , .CoA . CoA , . . RR(Return Routability) MN CoA , CoA . MobileIPv6 .

    Mobile Networking Challenges

  • Mobile Networking Challenges

  • 5.2 Wireless TCPTCP provides connection-oriented service over packet switching networks. Acknowledgment schemes are used to ensure TCP connection reliability. Round-trip time (RTT) estimates allow dynamic adjustment of the sliding window in order to achieve maximum throughput.The flow control and congestion control mechanisms of TCP help the transport adapt to network conditions and endpoint characteristics.TCP assumes all packets losses are caused by congestion at links where buffers overrun and packets are dropped. Congestion control using slow-start, congestion avoidance, fast re-transmission, and fast recover are commonplace among many TCP implementations.

    Mobile Networking Challenges

  • 5.2.1 Wireless TCP ChallengesWireless communications have imposed a number of challenges on TCP, including:High packet drop rateUnreliable wireless linkMobilityResource-limited mobile deviceWireless link bandwidth vs. wired link bandwidth 5.2.2 Wireless TCP protocolWireless TCP can be enhanced in several ways, including TCP-split, link-layer-assisted TCP, and regular TCP modifications.

    Mobile Networking Challenges

  • Wireless TCP Protocols5.3 Convergence of Heterogeneous Wireless Networks Convergence Integration of cellular networks and wireless LAN hotspots Integration of wireless LAN and Bluetooth Integration of wireless LAN and cellular for enterprises Integration of wireless LAN and corporate IP private branch exchange (PBX)

    CategoryExamplesTCP-split

    Link-layer-assisted TCP

    TCP modificationI-TCPM-TCPSnoop/delay duplicated acknowledgementAIRMAILRLPEifelTCP SACKFast start

    Mobile Networking Challenges

  • 5.3.2 Internetworking System ArchitectureTightly coupled internetworkingA wireless LAN gateway is necessary to act as an agent for a group of access points.Loosely coupled internetworkingWireless LANs directly connect to the Internet and do not have any links to cellular core elements.Fig. 5.1

    Mobile Networking Challenges

  • 5.5 Wireless LAN and Bluetooth CoexistenceWireless LAN and Bluetooth boorativeth operate at 2.4-GHz unlicensed frequency band.The basic approaches can be divided into two categories: collaborative and noncollaborative.The collaborative approach aims to coordinate frequency use between two types of radios, thus requiring interprotocol communication that must be implemented on the same devices.The noncollaborative approach looks at only one side; that is, it tries to mitigate interference by reducing the chances of frequency overlapping, but it requires the acting device to detect interference or conduct interference estimation.

    Mobile Networking Challenges

  • 5.5 Mobile Next-Generation Networks5.5.1 Mobile IP for MacromobilityThe triangular routing path problem can be solved by allowing the home agent to notify the correspondent station the CoA of the mobile station in question using a binding update message.The corresponding station maintains what is called a binding cache for the latest known CoA of mobile station.Direct communication between the two parties can be performed within the home agents relay.

    Mobile Networking Challenges

  • Mobile IP enhancements.

    Mobile Networking Challenges

  • 5.5.2 Mobile IP for MicromobilityGFA is responsible for forwarding those packets to the foreign agent at that point of time, which further relays traffic to the mobile station.A domain root router for each domain is designated to handle intradomain and interdomain mobility.When the mobile station moves within the home domain, it performs a path update operation so as to build an updated path to the domain root router.When it moves to another domain, the domain root router of the new domain will act as the foreign agent to the mobile station, allowing intramobility within the foreign domain.

    Mobile Networking Challenges

  • Mobile IP regional registration and HAWAII.

    Mobile Networking Challenges

  • 5.3.3 Link Layer Mobility ManagementThe UMTS standard defines an optional network entity called gateway location register (GLR) for intersystem roaming. In UMTS, the service area is partitioned into gateway location areas (G-LAs), which are further divided into location areas (LAs), which are comprised of a number of cell sites.G-LA An HLR location update is performed when a mobile station crosses the boundary of a G-LA.LA A GLR location update is performed when a mobile station crosses the boundary of an LA.Cell A VLR location update is performed when a mobile station completes d movements between cells, where d is the movement threshold.

    Mobile Networking Challenges

  • Gateway location register (GLR) in UMTS.

    Mobile Networking Challenges

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