Wireless Future - Telenor

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88 domain, it attaches to a new leaf in the hierarchy. Establishment of the correct path then essentially consists of propagating a new route establishment message up the tree towards the least common ancestor (LCA) of the current and old leaf nodes. Thus, the latency involved in the intra-domain update process is defined by the latency of communication between the leaf and the LCA (In the worst case it is as high as the latency between the leaf node and the ingress point). Cellular IP and Hawaii differ in the way the route update and refreshes are provided to the nodes. We further describe these protocols in the following sections. Additionally they differ in the way they interwork with Mobile IP. We note that these schemes were designed for IPv4 but can be adapted for IPv6. Here we only describe the version for IPv4. 3.2.2 Cellular IP Cellular IP [4] provides local mobility and fast handoff support, relying on Mobile IP for macro-mobility. The Cellular IP network consists of a set of Cellular IP routers, several base stations which are also Cellular IP enabled, and a Cellular IP gateway (see Figure 3-1). Every base station is IP addressable and the Gateway acts as a Foreign Agent. The main idea behind Cellular IP (CIP) is that the IP address (Home Address) of the Terminal equipment is used as the user identity within the Cellular IP domain (one domain per gateway), and uplink user traffic packets (from the MS to the Gateway) update the path to the user. The following provides a summary of the main procedures specific to Cellular IP. Mobility States: The MH is either in idle state or in active state. When an idle MH receives an IP packet (paged from the network) it moves from idle mode to active mode and sends a route update packet. When a subsequent packet is received, the active state timer is reset. When this timer times out, the MS goes back to idle. In active state, any Packet Data Unit (PDU) sent uplink will update the route from the MS to the gateway. A PDU can be a traffic PDU or a control PDU (route update message) if the route update timer has timed out. Whenever a traffic- PDU is sent this timer is reset. Thus in active state at least one IP packet is sent during a time equal to the value of the route update timer. In idle state paging updates are sent instead of route updates. The paging update is meant to update the paging cache of the nodes on the path. Route updates or paging updates uses ICMP. Cellular IP routing: When a node receives an uplink packet, it reads the source address and updates the corresponding cache and then routes the packet towards the gateway. When a downlink packet is received, a node checks the cache. If the routing cache has not been updated the node is paged. Otherwise it sends to the next node that is indicated in the binding table. Handovers: Inter-gateway handoff is like a new registration at a new gateway. The location information at the old gateway expires and is not explicitly removed. There are two options for intra domain handoffs, hard and semi-soft. • In hard handoff, when the MH decides to handoff it sends a hard handoff route update message (for security reasons, an uplink packet is not sufficient) to the new base station. This route update heads towards the gateway. Each Cellular IP node along the way creates a new entry in its routing cache for the mobile node (or updates the existing entry). When the message reaches the LCA, the old entry is replaced by the new entry, pointing towards the new base station. At this point, the handoff is complete, and the route cache entries along the path from the LCA to BS 1 are left to expire when they time-out. Meanwhile packets are sent to the old base station and are thus lost. • Semi-soft handoff addresses the problem of packet loss by requiring the mobile to switch back to the old base station for a short period, the semi-soft period, while waiting for the semi-soft route update to reach the crossover node. When the LCA is reached, a new entry (second entry) for the mobile node is created in the route cache. Hence, during the semi-soft period, packets are forwarded to both base stations. When the semi-soft period is over, the mobile node switches back to the new base station and sends a hard handoff route update which eventually removes the entry towards the old base station in the LCA. Security Cellular IP ensures the integrity and confidentiality of mobility related control messages. To ensure that, only authenticated packets can establish or change cache mappings in a Cellular IP network and all control packets, i.e. paging and routing update messages, must be authenticated. Data packets can only refresh existing mappings. This of course reduces the signalling efficiency of the original scheme in which the main benefit was to have the data packets acting as control packets to update the route. 3.2.3 Hawaii In Hawaii [5] the addressing is different from CIP. The mobile host is assigned a co-located care-of address from its foreign domain and packets are tunnelled to the care-of address by a Home Agent in its home domain. When moving within the foreign domain, the mobile host keeps Telektronikk 1.2001
Router 1 Router 0 its care-of address. Hawaii maintains the paths in the domain through the specific path set-up mechanism that is described below. Registration Phase When the Mobile powers up it sends a Mobile IP registration message to the BS covering the area the MS is camping on. The BS triggers a registration procedure towards the HA which is located within the home domain of the MH. After completion of that procedure (assumed here valid) the BS sends a path set up message (Hawaii specific message) up to the gateway via a default route. Every router on that path will set its host based forwarding entries for the MH colocated care-of address. Then the BS sends an acknowledgement to the MH. The forwarding entries are kept as soft state meaning they expire after a certain time. They are kept alive by hopby-hop refresh messages. Handover When the MS moves to another cell the new path has to be established and the old path has to disappear in the network. Two schemes are defined (see Figure 3-2). The first one, the forwarding path set up scheme, is optimised for networks where the mobile host cannot receive/ transmit from/to different base stations (macro diversity), e.g. TDMA based systems. The second one, the non-forwarding path set-up scheme, is optimised for networks where macro diversity is possible (e.g. CDMA). • Forwarding scheme. The packets are forwarded from the old BS to the new BS while the new path is not set-up. When the MH enters a new cell it sends a Mobile IP registra- Telektronikk 1.2001 A B C 4 3 6 A A B 5 2 B Router 2 Old BS A A New BS B B Mobile user 7 1 Router 1 Router 0 tion message that includes the old base station’s address. When receiving this message the new BS sends a Hawaii message to the old BS. The old BS changes the forwarding entry for the MH to the uplink router (router 1), which is specified in its routing table, and forwards the message to that router. This router will do the same and forward the message further along the way towards the new BS. The message will eventually reach the new BS. The new BS sends a reply to the MS and the handover procedure is completed. • Non-forwarding scheme. The MH sends a Mobile IP registration to the new BS which sends a Hawaii message to the old BS. This message is transmitted hop-by-hop and every router on the path between the new and the old BS will create/update its entry for the MH accordingly. When the message has reached the LCA the path is diverted. Meanwhile the packets are received by the MH on the old air interface which the MS is able to receive from if macro-diversity functionality is implemented. No packet loss is therefore experienced. The old BS will send an acknowledgement to the new BS after receiving the message. The handover procedure is then completed. 3.2.4 Analysis The strong point of these techniques is that tunnelling within the domain is not necessary. Tunnelling is detrimental to the transport efficiency in the domain. Within the cellular IP network, routing is host-based. Hence Cellular IP or Hawaii nodes must be special routers that have a special routing function. In particular the nodes A B C 4 5 2 A A B 3 6 B Router 2 Old BS A A New BS B B Mobile user 1 7 Figure 3-2 The two handover mechanisms of Hawaii 89
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Telektronikk Volume 97 No. 1 - 2001
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Per Hjalmar Lehne (42) obtained his
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Stein Svaet (41) is Senior Research
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Pbit/day 6 150 125 100 75 50 25 0 F
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8 Video communication as a utility
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10 The idea of reconfigurable mobil
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12 Switched lobe Dynamically phased
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Figure 10 The All IP vision Figure
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16 The IP world has some problems t
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18 Abbreviations and acronyms less
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Jorge Pereira (40) obtained his Eng
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(Millions) Figure 1 Exponential gro
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24 Defining Generation based upon D
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Multi-mode Terminal by Software Rad
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distribution layer possible return
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30 A Co-Ordinated Approach to 4G As
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Figure 2 Applications will grow fas
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Figure 5 Evolution from multi-mode
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Operator/Provider download librarie
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Page 44 and 45: Figure 3 Two arrays with M and N el
Page 46 and 47: Figure 5 Cumulative probability dis
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Page 50 and 51: 48 Conclusion The challenge of prov
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Page 58 and 59: 56 7 Conclusion and Further Researc
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Page 66 and 67: 64 4 BRAIN homepage. (2001, March 6
Page 68 and 69: Figure 2 The Bluetooth protocol sta
Page 70 and 71: Figure 5 A Bluetooth radio module i
Page 72 and 73: 70 • Instant postcard: A Bluetoot
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Page 76 and 77: Table 1 Allocated HiperLAN bands (i
Page 78 and 79: Figure 4 Basic MAC frame structure
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Page 84 and 85: 82 5 References 1 CEPT. ERC Decisio
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Page 110 and 111: Figure 2 The first use case diagram
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Page 116 and 117: Figure 10 Initiating call from PSTN
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Page 134 and 135: Figure 2 Needs and Related Services
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Anne Lise Lillebø (52) is Adviser
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140 with other SDOs (Standards Deve
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142 Box 2 - ETNO Declaration We, th
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Arve Meisinset (52) is Senior Resea
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146 In ITU-T we have seen needs to
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148 Each viewpoint constitutes a se
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Figure 2 UML class diagrams for tra
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152 The functionality describing th
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