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					Cellular Networks   Mobility              Mobile IP              Cellular Mobility   Take-Home Points




                    Mobility in Wireless Networks
                        Mobile IP and Cellular Networks


                                       Daniel Zappala

                                  Brigham Young University
                                Computer Science Department




                    Mobility in Wireless Networks     Daniel Zappala                            1/22
Cellular Networks       Mobility              Mobile IP              Cellular Mobility   Take-Home Points




       1    Cellular Networks


       2    Mobility


       3    Mobile IP


       4    Cellular Mobility


       5    Take-Home Points




                        Mobility in Wireless Networks     Daniel Zappala                            2/22
Cellular Networks      Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Questions of the Day




               How do Cellular networks work?
               How can a mobile user remain connected to the
               Internet?




                       Mobility in Wireless Networks     Daniel Zappala                            3/22
Cellular Networks   Mobility              Mobile IP              Cellular Mobility     Take-Home Points



Cellular Networks

                                                             cell
                                                                       geographical region
                                                                       covered by a cell tower
                                                                       CDMA or combined
                                                                       FDMA/TDMA - divide
                                                                       spectrum into frequency
                                                                       channels, divide each
                                                                       channel into time slots
                                                             mobile switching center
                                                                       connects cellular network
                                                                       to telephone network and
                                                                       Internet
                                                                       call setup
                                                                       mobility between cells and
                                                                       switches

                    Mobility in Wireless Networks     Daniel Zappala                              4/22
Cellular Networks       Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Cellular Standards


               2G systems: digital voice
                    GSM - FDMA/TDMA, most widely deployed, 200 countries, a
                    billion people
                    IS-95 - first CDMA-based cellular standard, developed by
                    Qualcomm
                    IDEN - TDMA, Nextel, merged with Sprint, being phased out
                    for CDMA2000
                    IS-136 - uses FDMA/TDMA, North America, Cingular and US
                    Wireless, being phased out for GSM, CDMA2000
               2.5G systems: voice and data channels
                    GPRS - evolved from GSM, packet-switched, 170 kbps (30-70
                    in practice)
                    CDMA2000 1xRTT - evolved from IS-95, 144 kbps



                        Mobility in Wireless Networks     Daniel Zappala                            5/22
Cellular Networks       Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Cellular Standards


               2.75G - almost 3G in speed
                    EDGE - another enhancement of GSM, 384 kbps, 2.75G
               3G: voice (circuit-switched) and data (packet-switched)
                    UMTS - W-CDMA, successor to GSM networks, 384 kbps - 2
                    Mbps, European, some Japan, Cingular in U.S.
                    CDMA2000 1xEV - CDMA2000 with high data rates - 3.1
                    Mbps up, 1.8 Mbps down, U.S., Japan, Korean, Canada –
                    Verizon, Sprint
               4G: 10 Mbps and up, seamless mobility between different
               cellular technologies, mesh networking, and lots of other
               dreams



                        Mobility in Wireless Networks     Daniel Zappala                            6/22
Cellular Networks        Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Mobility




               how fast is the user moving?
               does the user need to keep her IP address?
                    cellular or high speed car vs DHCP on a laptop
                    need to maintain Internet connections when user becomes
                    mobile: is it the application’s or TCP’s job?
               is infrastructure available?


                         Mobility in Wireless Networks     Daniel Zappala                            7/22
Cellular Networks   Mobility              Mobile IP              Cellular Mobility       Take-Home Points



Mobility Terminology



                                                                               home agent:
                                                                               entity that acts on
                                                                               behalf of mobile
                                                                               user while she is
                                                                               away
                                                                               foreign agent:
                                                                               entity that acts on
                                                                               behalf of mobile
                                                                               user in visited
                                                                               network



                    Mobility in Wireless Networks     Daniel Zappala                                8/22
Cellular Networks   Mobility              Mobile IP              Cellular Mobility       Take-Home Points



Mobility Terminology



                                                                               permanent
                                                                               address: address
                                                                               in home network
                                                                               care-of-address:
                                                                               address in the
                                                                               foreign network




                    Mobility in Wireless Networks     Daniel Zappala                                8/22
Cellular Networks        Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Approaches


               network-layer routing
                    routers advertise permanent address of mobile nodes via usual
                    routing algorithm
                    no changes to end systems
                    not scalable - breaks IP address aggregation
                    could separate routing from naming (Nimrod IPv6 proposal),
                    but this requires massive Internet architecture change
               application-layer routing
                    applications register with home network when they visit a
                    foreign network
                    indirect routing: home agent routes packets to foreign agent
                    direct routing: home agent tells correspondent about foreign
                    agent



                         Mobility in Wireless Networks     Daniel Zappala                            9/22
Cellular Networks       Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Indirect Routing




               transparent to correspondent


                        Mobility in Wireless Networks     Daniel Zappala                           10/22
Cellular Networks       Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Indirect Routing




               causes a triangle routing problem: forward path is different
               from the reverse path, may be inefficient and may cause
               problems with TCP
                        Mobility in Wireless Networks     Daniel Zappala                           11/22
Cellular Networks       Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Direct Routing




               solves triangle routing problem, but not transparent to
               correspondent

                        Mobility in Wireless Networks     Daniel Zappala                           12/22
Cellular Networks       Mobility      Mobile IP     Cellular Mobility   Take-Home Points



Direct Routing




               foreign agent chaining when mobile node moves to a new
               foreign network
               subsequent foreign networks just notify the anchor foreign
               agent
               used in GSM in Wireless Networks
                         Mobility               Daniel Zappala                    13/22
Cellular Networks        Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Mobile IP




               RFC 3220
               uses home agents, foreign agents, foreign agent registration,
               care-of-addresses, encapsulation
               three components
                    indirect routing
                    agent discovery
                    registration with home agent




                         Mobility in Wireless Networks     Daniel Zappala                           14/22
Cellular Networks         Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Mobile IP Agent Discovery

           foreign and
           home agents
           advertise
           services by
           broadcasting
           ICMP
           messages
           H, F bits:
           home and/or
           foreign agent
           R bit:
           registration
           required

                          Mobility in Wireless Networks     Daniel Zappala                           15/22
Cellular Networks   Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Mobile IP Registration Example




                    Mobility in Wireless Networks     Daniel Zappala                           16/22
Cellular Networks        Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Mobile TCP

               not possible with today’s operating systems
                    TCP sockets use source and destination IP addresses along
                    with ports to identify a connection
                    would need to replace socket API
               TCP performance over wireless may be bad
                    high packet loss over wireless due to bit errors, collisions,
                    handoff
                    TCP interprets loss as congestion, will slow down
               possible solutions
                    reliability at link layer
                    TCP awareness of wireless links – distinguish between
                    congestion and wireless loss, react properly
                    split the connection into two parts – wired and wireless, used
                    in cellular networks


                         Mobility in Wireless Networks     Daniel Zappala                           17/22
Cellular Networks   Mobility              Mobile IP              Cellular Mobility     Take-Home Points



Cellular Call to Mobile User

                                                                         home network:
                                                                         cellular provider
                                                                         network (e.g.
                                                                         Verizon)
                                                                         HLR: home location
                                                                         register - database
                                                                         with your profile
                                                                         (number, services,
                                                                         billing) and location
                                                                         VLR: visitor location
                                                                         register - database
                                                                         containing all users
                                                                         currently in network

                    Mobility in Wireless Networks     Daniel Zappala                             18/22
Cellular Networks   Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Cellular Mobility - Same MSC


                                                        goal: route call via new base
                                                        station with no interruption
                                                        motivation
                                                                connectivity
                                                                stronger signal from new BS
                                                                load balancing
                                                        cell phone measures signal
                                                        strength of all BS it can hear,
                                                        reports to current BS
                                                        handoff initiated by current BS




                    Mobility in Wireless Networks     Daniel Zappala                           19/22
Cellular Networks   Mobility              Mobile IP                  Cellular Mobility   Take-Home Points



Cellular Handoff Steps

                                                      1     old BS informs MSC of handoff,
                                                            list of 1+ new BS
                                                      2     MSC creates circuit to new BS
                                                      3     new BS allocates radio channel
                                                            for phone
                                                      4     new BS signals MSC that it is
                                                            ready
                                                      5     old BS tells phone to perform
                                                            handoff
                                                      6     phone activates new channel
                                                      7     phone signals MSC that handoff
                                                            is complete
                                                      8     MSC releases circuit to old BS
                    Mobility in Wireless Networks         Daniel Zappala                           20/22
Cellular Networks   Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Cellular Mobility - Different MSC




                    Mobility in Wireless Networks     Daniel Zappala                           21/22
Cellular Networks        Mobility              Mobile IP              Cellular Mobility   Take-Home Points



Take-Home Points



               many people now browse through mobile devices
               cellular standards keep providing faster data rates
                    phone calls may someday be dwarfed by Internet access, as
                    with landline phones
               mobile infrastructure can use indirect or direct routing
               mobile IP and cellular mobility both use indirect routing
                    cellular mobility has more complexity because it must maintain
                    a circuit




                         Mobility in Wireless Networks     Daniel Zappala                           22/22

				
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