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... have been numerous industrial initiatives and academic projects either directly or indirectly working with vertical mobility. The term vertical mobility was first introduced by the Daedalus/BARWAN 2 =-=[1]-=- project at University of California Berkeley. Fig. 2 shows the conceptual architecture of vertically overlapping heterogeneous wireless networks, illustrating also the various domains of operation fo...

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... kbps of GSM data up to the 2 Mbps theoretical rate of UMTS. So far the dominating packet radio service over the cellular GSM core network in Europe has been GPRS (General Packet Radio Service). GPRS =-=[21]-=- uses exactly the same physical radio channels as GSM and only new logical GPRS radio channels are defined. The allocation of these channels is flexible: from 1 to 8 radio interface timeslots can be a...

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...to the new IPv6 protocol. The academic networking community started to get interested at the same times about providing mobility across heterogeneous networks. Network layer solutions using Mobile IP =-=[3]-=- attracted many academic projects as it provided a quick-start to demonstrate and experiment with a real-life testbed. Testbed setups in most cases consisted of a set of laptops equipped with wireless...

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...lic Internet, and by designing and configuring the local test network, the setup was ready. The early academic releases of Mobile IP provided in the Internet with open source codes were MosquitoNET 4 =-=[4]-=-, an implementation of Mobile IPv4 on the Linux OS at Stanford University, and Monarch 5 ,an implementation of both Mobile IPv4 and Mobile IPv6 on the BSD OS at Carnegie Mellon University. 2 Bay Area ...

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...n is QoS due to handoff delay caused by message exchanges, multiple database accesses, and negotiation-renegotiation processes affecting the performance of both upper-layer protocols and applications =-=[12]-=-. This type of problema requires considerations at many layers of the communications: priority-based routing at the network layer, delay budget calculations and the optimization of individual paramete...

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...e this next generation to be realized around 2010 and based around five elements: fully converged services, ubiquitous mobile access, diverse user devices, autonomous networks and software dependency =-=[5]-=-. In this vision, the seamless connection of heterogeneous networks include cellular data, 3G, WLAN/HIPERLAN, short range PAN/LAN/MAN and broadcast DVB/DAB services integrated through an IP based core...

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...ation level connectivity is “kept alive”. Mobile IP handoff can be optimized by avoiding triangle routing problem and smoothed through FAs using binding updates to reduce packet loss during a handoff =-=[75]-=-. Sometimes handoff optimization can be RAN specific [76], indicating the need to separately consider optimization of vertical, horizontal, macro and micro mobility and their variations in heterogeneo...

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...ified into macro- ands41 micro-mobility, as well as into horizontal and vertical mobility. Wireless connection diversity can be interconnected using data link layer events on an L2 peer-to-peer basis =-=[44]-=-. System architecture design also relates to selecting appropriate mobility protocols to suite specific mobility scenarios. An overall design may utilize the best features of the available technical s...

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...ff triggering in wireless networks, a selection or combination of some of these may be appropriate. RSS measurement algorithms are characterized by low computation complexity, but adaptive algorithms =-=[103]-=- have potential for more intelligent decisions improving the performance. Adaptive algorithms include pattern recognition [104], neural networks [105] and fuzzy logic [106] algorithms. The author of t...

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... time MH spends in one cell, whereas the dwell-timer is a handoff algorithm parameter to adjust how long the MH will persist in a specific cell. Dwell-time can be modelled as a system level parameter =-=[111]-=-. Application session duration is another parameter to consider, as discussed in [110]. It is commonly modelled using a negative exponential distribution with parameter μ. This distribution may not be...

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...d mobile executed handoff (MEHO), respectively. In GSM the measurements of alternative BSs is made by the MH, but the decision is made in the BS/MSC , thus resulting in mobile assisted handoff (MAHO) =-=[66]-=-. Another case is network assisted handoff (NAHO) [67] where the network can aid handoff decisions controlled by the MH. The handoff process itself can be characterized as hard [68] or soft [69]. As i...

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...doff delay, number of handoffs and lost packets. These are mainly single-user specific measures. At the network or cell level, performance measures such as network load and blocking rates can be used =-=[102]-=-. This thesis studies the use of simple-to-implement algorithms based on using a dwell-timer in a vertical mobility scenario as the basis for analysis and uses mean throughput as the main performance ...

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... OSI model including network layer (L3), link layer (L2) and cross-layer (L3 + L2) solutions [42]. In addition transport and upper OSI layer solutions exists, such as mobile middleware based on CORBA =-=[43]-=-. Mobility scenarios can be classified into macro- ands41 micro-mobility, as well as into horizontal and vertical mobility. Wireless connection diversity can be interconnected using data link layer ev...

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...on criteria can be dependent on path loss, cell type, candidate cell capacity, or combination of them. Velocity is an important metric as it has effects on radio and network level mobility parameters =-=[93]-=-. In an extreme case, the MH may be travelling in a train [94]. The HDE may use in addition parameters such as network load [95] or economical factors such as price [96]. These metrics form a rich set...

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... and averaging the handoff performance can be significantly improved [99, 100]. Practical implementations usually favour suboptimal rather than optimal algorithms due to the implementation complexity =-=[101]-=-. Algorithm performance can thus be compromised to some extent to favour a simpler and more light-weight implementation. Algorithm performance can be measured in proportion to throughput, handoff dela...

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... proxy). Without optimization router discovery, duplicate address detection (DAD) and the registration of new addresses are too inefficient to support seamless inter-domains45 handoffs in Mobile IPv6 =-=[83]-=-. Whether or not Mobile IP is used in vertical handoff, the handoff procedure needs elaboration. Especially, a delay budget needs to be carefully considered. Various sources of delays (packet latencie...

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... communication. In addition, IEEE 802.16 (WiMAX) and IEEE 802.20 (WWAN) aim at higher data rates over longer distances. In the wireless local area networks (WLAN), the IEEE 802.11 family of standards =-=[23]-=- has been most successful and so far has dominated the markets in this area.s36 Table 3. Range and PHY data rates for 802.11b WLAN. Transmits Rate/ Range “High speed” 11 Mbps “Medium speed” 5.5 Mbps “...

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...) technologies. In this hybrid communication scenario, multihomed mobile nodes may communicate with each other using an ad hoc protocol while preserving Internet connectivity through IP micromobility =-=[54]-=-. However, service stability and reachability may become an issue in such a highly mixed environment. An overall communications architecture may be needed to support different network appliances withi...

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...RSS measurements a number of algorithms can be used, such as dwell-timer and hysteresis based. With the optimal value of hysteresis and averaging the handoff performance can be significantly improved =-=[99, 100]-=-. Practical implementations usually favour suboptimal rather than optimal algorithms due to the implementation complexity [101]. Algorithm performance can thus be compromised to some extent to favour ...

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...at they all build on the TCP/IP model. The Internet Protocol (IP) has two versions (v4 and v6). IPv4 is currently dominant, but the transition to from IPv4 to IPv6 is expected to take place gradually =-=[64]-=-. It is also worth mentioning that global roaming among different 3Gs43 standards (e.g., UMTS and CDMA2000) can be achieved through IP level interworking [65]. 2.3.2 Handoff strategies Handoff (or han...

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...r derived froms48 RSS, and Bit Error Rate (BER) values to know the channel quality. The availability to a middleware type of HDE implementation may be only through a relative signal quality indicator =-=[89]-=-. Block Error Rate (BLER) has been used to indicate MAC layer events. The probability of packet retransmission is equal to the probability of any of the transport blocks that the packets consist of [9...

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...9]. Block Error Rate (BLER) has been used to indicate MAC layer events. The probability of packet retransmission is equal to the probability of any of the transport blocks that the packets consist of =-=[90]-=-. The power control [91] of the MH can be another optimization criteria in conjunction with handoff, this being another metric for the algorithms to consider affecting signal quality and power consump...

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...ER) has been used to indicate MAC layer events. The probability of packet retransmission is equal to the probability of any of the transport blocks that the packets consist of [90]. The power control =-=[91]-=- of the MH can be another optimization criteria in conjunction with handoff, this being another metric for the algorithms to consider affecting signal quality and power consumption. In target cell det...

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...can be another optimization criteria in conjunction with handoff, this being another metric for the algorithms to consider affecting signal quality and power consumption. In target cell determination =-=[92]-=- the cell selection criteria can be dependent on path loss, cell type, candidate cell capacity, or combination of them. Velocity is an important metric as it has effects on radio and network level mob...

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...ation of heterogeneous networks, including multiple overlapping (more than 2) radio technologies, as discussed in Paper VII. Cellular networks in Europe have evolved through 2G (GSM data), 2G+ (HSCSD =-=[20]-=-), 2.5G (GPRS), 2.75G (EDGE) to 3G (UMTS/WCDMA), providing data rates from the 9.6 kbps of GSM data up to the 2 Mbps theoretical rate of UMTS. So far the dominating packet radio service over the cellu...

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...m may be adaptive in proportion to some temporal variations in changing system parameters (e.g., changing conditions in the radio channel). These algorithms may use a cost criterion (or cost function =-=[70]-=-) to determine rules for optimal handoff decision. IP mobility solutions use similar hard and soft handoff strategies, but relate the terminology to network layer phenomenon such as packet latency and...

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...RSS measurements a number of algorithms can be used, such as dwell-timer and hysteresis based. With the optimal value of hysteresis and averaging the handoff performance can be significantly improved =-=[99, 100]-=-. Practical implementations usually favour suboptimal rather than optimal algorithms due to the implementation complexity [101]. Algorithm performance can thus be compromised to some extent to favour ...

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...whole system architecture design is mobility management. As elaborated in Chapter 2.3, mobility management in the next generation all-IP based wireless systems uses hierarchical network architectures =-=[14]-=-, both in horizontal and vertical planes. Mobility management across B3G networks, where “access is the killer application” [15], can be conceptually divided into several subtopics such as mobility an...

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...e multiple users and real-time traffic is present, and performance can degrade down to 10-30 % of the nominal values, especially in the case of real-time applications used in a multi-user environment =-=[24]-=-. Performance is enhanced in IEEE 802.11g and IEEE 802.11a standards that employ OFDM (Orthogonal Frequency Division Multiplexing) technology. OFDM transmits multiple signals simultaneously over a sin...

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...ility management decisions in addition to mobile navigation services. The usage of geolocation information in location aided routing schemes has been proposed for example in the context of geocasting =-=[36]-=- and location-aware ad hoc networking [37]. Packets can be geocasted to a specific geographic area, or an ad hoc routing protocol can use location information as a metric for routing decisions. There ...

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...cro-mobility can be solved with Mobile IP [45, 46] type solutions, whereas micro-mobility protocols include HMIP (Hierarchical Mobile IP) [47], IDMP (Intra-Domain Mobility Protocol) [48], Cellular IP =-=[49, 50]-=- and HAWAII (Handoff-Aware Wireless Access Internet Infrastructure) [49]. Fast handoff with micro-mobility becomes an issue when the MH changes is network attachment frequently, which is the case when...

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...cation Channel Admission Control (CAC), channel assignment, power control and handoff, adapting to the time and space variant changes in signal quality, network load and other environmental variables =-=[108]-=-. Fig. 12. Vertical mobility model. The vertical mobility model in Fig. 12 illustrates how several independent micro-cells (representing different wireless access technologies) can be overlaid by macr...

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...n be modelled with multidimensional birth-death processes [109]. Changes in the handoff process can be seen as variations in system states. Following the formulation logic and principles presented in =-=[110]-=-, state vgz of a single cell in the vertical mobility model is a sequence of integers, which can be written as Z ntuples forming a multi-dimensional state space of dimension Z·W: v11, v12, … v1w, … v1...

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...g also the various domains of operation for the subnetworks in the overall architecture. Development around providing mobility to the famous Internet protocol suite TCP/IP started in the early 1990’s =-=[2]-=-. The Internet Engineering Task Force (IETF) established a work group 3 for providing mobility support at first for the basic IPv4 protocol, and then later to the new IPv6 protocol. The academic netwo...

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...core network. Implementing this type of integrated system invokes many challenges in mobile handset design, wireless system discovery, terminal mobility, topological fault tolerance and survivability =-=[6]-=-. Realization of the envisioned B3G or 4G systems and technologies requires unified efforts in the areas of standardization and development of the enabling technologies, providing access network conve...

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...bling technologies, providing access network convergence in an evolutionary manner, designing system architectures with considerations on application, protocols, location, authentication and security =-=[7]-=-. The fragmented nature of the heterogeneous radio spectrum calls for new software defined reconfigurable radio concepts utilizing economical smart and adaptive antennas in MIMO radio channels, multi-...

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...aptive antennas in MIMO radio channels, multi-standard (3G/4G/802.11/GPS/Bluetooth) transceiver architectures, wideband OFDM/multi-carrier modulation, and other advanced solutions implemented in RFIC =-=[8]-=-. They will provide new performance in achieving data rates up to 100 Mbps and support for streaming, multicasting, and downloads of 5-20Mbps even when travelling at 200 km/hr, over an IP-centric netw...

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...n travelling at 200 km/hr, over an IP-centric network. Terminal implementation technologies include system-on-chip (SoC) and system-in-a-package (SiP) technologies with reconfigurable building blocks =-=[9]-=-. From the service aspect one has to find a balance between public and private service domains by adapting multiple standards and service environments (home, office, outdoors, indoors) across multiple...

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...utdoors, indoors) across multiple operators and service provider domains with ensured QoS, data privacy and information integrity, and taking into account user profile ands31 terminal characteristics =-=[10]-=-. This requires a service architecture that supports integrated mobility management for heterogeneous wireless network environment, session control and mobility, AAA (Authorization, Authentication and...

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...ent for heterogeneous wireless network environment, session control and mobility, AAA (Authorization, Authentication and Accounting) functionality, and profile based personalizable service management =-=[11]-=-. In order to achieve end-to-end QoS, the system architecture has to consider the handoff process in particular. During the handoff between heterogeneous systems the mobile user may experience signifi...

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...n all-IP based wireless systems uses hierarchical network architectures [14], both in horizontal and vertical planes. Mobility management across B3G networks, where “access is the killer application” =-=[15]-=-, can be conceptually divided into several subtopics such as mobility and interworking scenarios [16], handoff control strategies, handoff algorithms, handoff performance measures, handoff methodology...

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...e have been a wide variety of wireless access network technologies developed during the past decade. As described in Table 1, wireless data access can be provided over heterogeneous wireless networks =-=[17]-=-. Some of the wireless network standards have aimed at specific market regions such as North-America, Europe and Asia, especially in cellular networks. In local and personal area networks there are so...

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...ided into wireless local area networks (WLAN), wireless personal area networks (WPAN), wireless metropolitan area networks (WMAN) and wireless wide area networks (WWAN), including cellular, satellite =-=[18]-=- and envisioned stratospheric [19] networks.sTable 1. Wireless data access in heterogeneous wireless network standards. 34 Network Standard Data rate (PHY) Frequency band Cellular networks GSM data (2...

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...orks (WLAN), wireless personal area networks (WPAN), wireless metropolitan area networks (WMAN) and wireless wide area networks (WWAN), including cellular, satellite [18] and envisioned stratospheric =-=[19]-=- networks.sTable 1. Wireless data access in heterogeneous wireless network standards. 34 Network Standard Data rate (PHY) Frequency band Cellular networks GSM data (2G) 9,6 kbps 900/1800/1900 MHz WLAN...

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...acity modulation and coding schemes. However, the practical performance of these cellular data systems is usually much lower than the nominal rates, even down to ten times lower than the nominal rate =-=[22]-=-. As shown in Table 1, wireless local and personal area networking standards include IEEE 802.11 (WLAN), IEEE 802.15 (Bluetooth), IEEE 802.15.3 (WPAN), IEEE 802.15.4 (Zigbee), ETSI BRAN HIPERLAN and H...

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...e transmission power. Further enhancements are due to the standards IEEE 802.11i for WLAN security, and IEEE 802.11e for providing QoS support in the WLAN environment. The Bluetooth 1.1 specification =-=[25]-=- enables 721 kbps data rates, but it is also upgrading to support higher data rates. The Bluetooth Special Interest Group's (SIG) has adopted Enhanced Data Rate (EDR) specifications, which replaces th...

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...wo models in the literature for the integration of WLAN into cellular networks, tight and loose coupling models. These two models represent the current R&D means to achieve global mobility management =-=[26]-=-. As illustrated in Fig. 4, the loose coupling model facilitates vertical mobility management in the IP stack, putting emphasis on implementing roaming, mobility and security management in the network...

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...Fr. Rel L1 bis L1 bis IP BB L2 BB L1 802.11 PHY 802.3 PHY 802.3 PHY SGSN GGSN on the LAN IP GTP UDP IP BB L2 Fig. 4. Loose coupling protocol architecture of GPRS/EDGE and 802.11 WLAN. As described in =-=[27]-=-, vertical mobility management in the tight coupling model can be interfaced below the LLC in the GPRS signalling model, and WLAN roaming can be implemented as micro-mobility within the area of an SGS...

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... Gn and Iu. The tight coupling model may be more favourable for operators as the mobility, security, QoS, billing and authentication features of GPRS/UMTS are facilitated over the WLAN access channel =-=[28]-=-. Standardization of WLAN-Cellular interworking is undertaken by standardization groups such as 3GPP [29], 3GPP2, IETF and ITU-R. For example, the IEEE 802.11 working group has defined six scenarios f...

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...g and integrating possibilities among heterogeneous wireless networks. The first one with imminent deployment is the integration of digital audio and video broadcasts (DAB/DVB) into cellular networks =-=[32]-=-. Integration holds possibilities for hybrid solutions ranging from device-based integration to network-level integration [33]. In Finland there has been a pilot program to test what is called the fou...

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...mobile navigation services. The usage of geolocation information in location aided routing schemes has been proposed for example in the context of geocasting [36] and location-aware ad hoc networking =-=[37]-=-. Packets can be geocasted to a specific geographic area, or an ad hoc routing protocol can use location information as a metric for routing decisions. There are also proposals for position assisted h...

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...eocasted to a specific geographic area, or an ad hoc routing protocol can use location information as a metric for routing decisions. There are also proposals for position assisted handoff algorithms =-=[38, 39]-=-. These examples suggest the integration of location-awareness to the integrated system architecture. In general, the combination of multi-network connectivity integrated with location technologies pr...

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...eocasted to a specific geographic area, or an ad hoc routing protocol can use location information as a metric for routing decisions. There are also proposals for position assisted handoff algorithms =-=[38, 39]-=-. These examples suggest the integration of location-awareness to the integrated system architecture. In general, the combination of multi-network connectivity integrated with location technologies pr...

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...proaching, the dormant WLAN interface can be woken up when the mobile user is approaching it, and closed down when passing away from the hotspot. An example of a multi-interface device is provided in =-=[40]-=-. When the interface is brought up, a mechanism such as MAC layer sensing [41] can be used to help connection management. In the next section, mobility management issues in heterogeneous systems are d...

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...approaching it, and closed down when passing away from the hotspot. An example of a multi-interface device is provided in [40]. When the interface is brought up, a mechanism such as MAC layer sensing =-=[41]-=- can be used to help connection management. In the next section, mobility management issues in heterogeneous systems are discussed including architectural and communication aspects, having emphasis on...

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... Distance, Location Mobility management in heterogeneous networks can take place in different layers of the OSI model including network layer (L3), link layer (L2) and cross-layer (L3 + L2) solutions =-=[42]-=-. In addition transport and upper OSI layer solutions exists, such as mobile middleware based on CORBA [43]. Mobility scenarios can be classified into macro- ands41 micro-mobility, as well as into hor...

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...ultihoming. Macromobility is referred to also as interdomain mobility, and micromobility as intradomain mobility. From the integration point of view, at L3 macro-mobility can be solved with Mobile IP =-=[45, 46]-=- type solutions, whereas micro-mobility protocols include HMIP (Hierarchical Mobile IP) [47], IDMP (Intra-Domain Mobility Protocol) [48], Cellular IP [49, 50] and HAWAII (Handoff-Aware Wireless Access...

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...adomain mobility. From the integration point of view, at L3 macro-mobility can be solved with Mobile IP [45, 46] type solutions, whereas micro-mobility protocols include HMIP (Hierarchical Mobile IP) =-=[47]-=-, IDMP (Intra-Domain Mobility Protocol) [48], Cellular IP [49, 50] and HAWAII (Handoff-Aware Wireless Access Internet Infrastructure) [49]. Fast handoff with micro-mobility becomes an issue when the M...

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... of view, at L3 macro-mobility can be solved with Mobile IP [45, 46] type solutions, whereas micro-mobility protocols include HMIP (Hierarchical Mobile IP) [47], IDMP (Intra-Domain Mobility Protocol) =-=[48]-=-, Cellular IP [49, 50] and HAWAII (Handoff-Aware Wireless Access Internet Infrastructure) [49]. Fast handoff with micro-mobility becomes an issue when the MH changes is network attachment frequently, ...

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...cro-mobility can be solved with Mobile IP [45, 46] type solutions, whereas micro-mobility protocols include HMIP (Hierarchical Mobile IP) [47], IDMP (Intra-Domain Mobility Protocol) [48], Cellular IP =-=[49, 50]-=- and HAWAII (Handoff-Aware Wireless Access Internet Infrastructure) [49]. Fast handoff with micro-mobility becomes an issue when the MH changes is network attachment frequently, which is the case when...

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... changes is network attachment frequently, which is the case when the velocity of the MH is high or the serving area is small. Micromobility protocols also facilitate IP paging. Regional registration =-=[51]-=- and hierarchical schemes have been presented as partial solutions for this. A post-registration method [52] has been introduced to improve the performance of hierarchical solutions. In general, micro...

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...ing area is small. Micromobility protocols also facilitate IP paging. Regional registration [51] and hierarchical schemes have been presented as partial solutions for this. A post-registration method =-=[52]-=- has been introduced to improve the performance of hierarchical solutions. In general, micromobility solutions enhance Mobile IP functionality by locally reducing handoff latency through minimizing th...

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...ng handoff latency through minimizing the signalling load and, e.g., providing a new CoA with minimal latency. Limited multicast has been considered as a solution to improve micromobility performance =-=[53]-=-. Fig. 7 illustrates a vertical micromobility scenario where the BS and AP represent different RAN (Radio Access Network) technologies. In this hybrid communication scenario, multihomed mobile nodes m...

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...neous RANs and administrative domains. A spontaneous communication architecture with plug-and-play features can utilize, e.g., a service gateway to connect multiple technologies and networks together =-=[55]-=-.sBS1 42 AP1 BS2 AP2 Fig. 7. Vertical micromobility with a hybrid ad hoc networking scenario. There are a number of other proposals for macro- and micromobility protocols with certain optimized featur...

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...cially with latency and security sensitive applications. For example, Session Initiation Protocol (SIP) supports terminal, service and personal mobility at the session layer level and can be combined =-=[56]-=- with Mobile IP, with possibilities of end-to-end adaptation for vertical handoff [57]. On the contrary, mSCTP (mobile Stream Control Transmission Protocol) [58] provides a transport layer solution as...

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...on Protocol (SIP) supports terminal, service and personal mobility at the session layer level and can be combined [56] with Mobile IP, with possibilities of end-to-end adaptation for vertical handoff =-=[57]-=-. On the contrary, mSCTP (mobile Stream Control Transmission Protocol) [58] provides a transport layer solution as an alternative for L3 solutions. The Host Identification Protocol (HIP) [59] is anoth...

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...ession layer level and can be combined [56] with Mobile IP, with possibilities of end-to-end adaptation for vertical handoff [57]. On the contrary, mSCTP (mobile Stream Control Transmission Protocol) =-=[58]-=- provides a transport layer solution as an alternative for L3 solutions. The Host Identification Protocol (HIP) [59] is another proposal for enabling vertical mobility above L3. It provides an additio...

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... handoff [57]. On the contrary, mSCTP (mobile Stream Control Transmission Protocol) [58] provides a transport layer solution as an alternative for L3 solutions. The Host Identification Protocol (HIP) =-=[59]-=- is another proposal for enabling vertical mobility above L3. It provides an additional cryptographic-based name space for Internet hosts and an API. HOPOVER (HandOff Protocol for OVERlay networks) [6...

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...9] is another proposal for enabling vertical mobility above L3. It provides an additional cryptographic-based name space for Internet hosts and an API. HOPOVER (HandOff Protocol for OVERlay networks) =-=[60]-=- provides QoS features for Mobile IP by enabling resource reservation through wireless RSVP (ReSerVation Protocol). SMIP (Seamless Mobile IP) [61] extends Mobile IP by introducing a Decision Engine (D...

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... API. HOPOVER (HandOff Protocol for OVERlay networks) [60] provides QoS features for Mobile IP by enabling resource reservation through wireless RSVP (ReSerVation Protocol). SMIP (Seamless Mobile IP) =-=[61]-=- extends Mobile IP by introducing a Decision Engine (DE) making handoff decisions for intradomain routing. Other solutions enable context transfer during handoff [62]. Context information can be for e...

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...tocol). SMIP (Seamless Mobile IP) [61] extends Mobile IP by introducing a Decision Engine (DE) making handoff decisions for intradomain routing. Other solutions enable context transfer during handoff =-=[62]-=-. Context information can be for example AAA parameters. Providing this type of context information prior or during the handoff enables making the new network attachment with all services in use in a ...

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... parameters. Providing this type of context information prior or during the handoff enables making the new network attachment with all services in use in a seamless and secure manner. It is argued in =-=[63]-=- that mobile multimedia streaming in multihomed environments (i.e., the MH has a network interface to more than one administrative domain) can benefit from using bicasting (i.e., sending the same pack...

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... IPv6 is expected to take place gradually [64]. It is also worth mentioning that global roaming among different 3Gs43 standards (e.g., UMTS and CDMA2000) can be achieved through IP level interworking =-=[65]-=-. 2.3.2 Handoff strategies Handoff (or handover) is an event when a mobile station moves from one wireless cell to another. It can be classified into horizontal (intra-system) and vertical (inter-syst...

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... the measurements of alternative BSs is made by the MH, but the decision is made in the BS/MSC , thus resulting in mobile assisted handoff (MAHO) [66]. Another case is network assisted handoff (NAHO) =-=[67]-=- where the network can aid handoff decisions controlled by the MH. The handoff process itself can be characterized as hard [68] or soft [69]. As it is wellknow from “traditional” horizontal handoffs, ...

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...ted handoff (MAHO) [66]. Another case is network assisted handoff (NAHO) [67] where the network can aid handoff decisions controlled by the MH. The handoff process itself can be characterized as hard =-=[68]-=- or soft [69]. As it is wellknow from “traditional” horizontal handoffs, hard handoff refers to a brake in the communication while making a handoff (brake-before-make), whereas soft handoff has a conn...

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...MAHO) [66]. Another case is network assisted handoff (NAHO) [67] where the network can aid handoff decisions controlled by the MH. The handoff process itself can be characterized as hard [68] or soft =-=[69]-=-. As it is wellknow from “traditional” horizontal handoffs, hard handoff refers to a brake in the communication while making a handoff (brake-before-make), whereas soft handoff has a connection to bot...

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...l handoff decision. IP mobility solutions use similar hard and soft handoff strategies, but relate the terminology to network layer phenomenon such as packet latency and packet loss. Lossless handoff =-=[71]-=- means that no packets are lost while making the handoff. Fast handoff [72] refers to low packet latency, which is the reason why this class is also referred to as low-latency handoff [73]. Seamless h...

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... strategies, but relate the terminology to network layer phenomenon such as packet latency and packet loss. Lossless handoff [71] means that no packets are lost while making the handoff. Fast handoff =-=[72]-=- refers to low packet latency, which is the reason why this class is also referred to as low-latency handoff [73]. Seamless handoff [74] means that the transition to a new network attachment is transp...

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...ess handoff [71] means that no packets are lost while making the handoff. Fast handoff [72] refers to low packet latency, which is the reason why this class is also referred to as low-latency handoff =-=[73]-=-. Seamless handoff [74] means that the transition to a new network attachment is transparent to the user. Application level connectivity is “kept alive”. Mobile IP handoff can be optimized by avoiding...

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...that no packets are lost while making the handoff. Fast handoff [72] refers to low packet latency, which is the reason why this class is also referred to as low-latency handoff [73]. Seamless handoff =-=[74]-=- means that the transition to a new network attachment is transparent to the user. Application level connectivity is “kept alive”. Mobile IP handoff can be optimized by avoiding triangle routing probl...

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...ff can be optimized by avoiding triangle routing problem and smoothed through FAs using binding updates to reduce packet loss during a handoff [75]. Sometimes handoff optimization can be RAN specific =-=[76]-=-, indicating the need to separately consider optimization of vertical, horizontal, macro and micro mobility and their variations in heterogeneous wireless access network cases.s44 Several aspects can ...

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...rigger vertical handoff. For this various mobility metrics can be employed as a specific algorithm. The decision about when and how this transition (or handoff) is executed is aided by handoff policy =-=[77]-=-. For example, the priority can be set to provide the fastest network connection to the mobile user, or the cheapest. Policy parameters can be weighted as a set of tuples (factor, weight) [78]. For ex...

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... policy [77]. For example, the priority can be set to provide the fastest network connection to the mobile user, or the cheapest. Policy parameters can be weighted as a set of tuples (factor, weight) =-=[78]-=-. For example, WLAN can be set as high priority, so that is used always when available, or alternatively handoff is made only when no latency or communication break sensitive application is active [79...

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...78]. For example, WLAN can be set as high priority, so that is used always when available, or alternatively handoff is made only when no latency or communication break sensitive application is active =-=[79]-=-. Thus different mobility and application scenarios require different optimization aspects. Considering the WLAN priority model, it would be preferable to seamlessly and automatically switch to a high...

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...ate proof-of-concepts, and extensive vertical mobility test runs have not been deployed by the author, although the author has been involved with educational contribution in preparing such test cases =-=[80, 81]-=-. Results from the empirical and simulation studies complement the technical solutions discussed in this chapter providing more tools and knowledge for holistic system design and mobility engineering....

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...ate proof-of-concepts, and extensive vertical mobility test runs have not been deployed by the author, although the author has been involved with educational contribution in preparing such test cases =-=[80, 81]-=-. Results from the empirical and simulation studies complement the technical solutions discussed in this chapter providing more tools and knowledge for holistic system design and mobility engineering....

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... is necessary for seamless mobility and handoff. Different delay components (detection, configuration, registration) resulting in vertical macromobility performance with Mobile IPv6 are elaborated in =-=[82]-=-. It is shown that fast RA (Router Advertisement) with RA caching can benefit vertical handoff performance, especially when used with TCP level enhancements (e.g., TCP proxy). Without optimization rou...

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...d IPv4 and IPv6 specific mobility signalling such as binding updates (BU) and router advertisements (RA). For optimizing the handoff decision, one should minimize the delay budget through a proactive =-=[85]-=- approach where as much as possible is done prior to the handoff. Then, when minimal handoff delay is enabled, the optimal handoff instant should be considered. For the decision making algorithm cross...

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...adigm is described in the following. 1000s46 2.3.3 Vertical handoff characteristics The handoff procedure in general includes events such as registration, association, reassociation, and dissociation =-=[86]-=-. The vertical handoff procedure involves these same basic events. Fig. 8 illustrates the vertical handoff procedure. Working in WLAN Working in UMTS Decision Engine A B C Prepare Ready for UMTS Yes N...

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...llows the application to prepare for the coming handoff by, e.g., momentarily increasing buffer size [71] and potentially inform upper layer protocols such as to tailor the TCP congestion window size =-=[87]-=- or other mechanisms to improve the performance during handoff. Finally, output C (Handoff) indicates that a handoff is needed and the handoff procedure to the overlay network (UMTS) is invoked. The u...

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...ional horizontal handoff scenario, Received Signal Strength (RSS) or its relative equivalent RSSI (Received Signal Strength Indicator) has usually been the primary monitored metric. Also the distance =-=[88]-=- from a BS is used in conjunction, indicating the existence of location-aware handoff algorithms. In GSM, both the MH and BS monitor the RSSI, which is a scaled number derived froms48 RSS, and Bit Err...

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...e cell capacity, or combination of them. Velocity is an important metric as it has effects on radio and network level mobility parameters [93]. In an extreme case, the MH may be travelling in a train =-=[94]-=-. The HDE may use in addition parameters such as network load [95] or economical factors such as price [96]. These metrics form a rich set of potential metrics to be considered in the design of HDE fu...

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...metric as it has effects on radio and network level mobility parameters [93]. In an extreme case, the MH may be travelling in a train [94]. The HDE may use in addition parameters such as network load =-=[95]-=- or economical factors such as price [96]. These metrics form a rich set of potential metrics to be considered in the design of HDE functionalities, enabling context-aware handoff decisions [97]. The ...

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...work level mobility parameters [93]. In an extreme case, the MH may be travelling in a train [94]. The HDE may use in addition parameters such as network load [95] or economical factors such as price =-=[96]-=-. These metrics form a rich set of potential metrics to be considered in the design of HDE functionalities, enabling context-aware handoff decisions [97]. The HDE can utilize a reconfigurable state ma...

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... load [95] or economical factors such as price [96]. These metrics form a rich set of potential metrics to be considered in the design of HDE functionalities, enabling context-aware handoff decisions =-=[97]-=-. The HDE can utilize a reconfigurable state machine (as introduced in Paper I) to tailor rules for different mobility and application scenarios. The state machine can utilize or implement specific al...

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...hes have been used, such as a predefined threshold of WLAN RSS, where the threshold is set to a value at which the transmission and reception of IP control information is close to becoming unreliable =-=[98]-=-. However, article [98] points out that “the intelligence of the switching algorithm could be improved”. As discussed in Paper II, based on RSS measurements a number of algorithms can be used, such as...

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...are characterized by low computation complexity, but adaptive algorithms [103] have potential for more intelligent decisions improving the performance. Adaptive algorithms include pattern recognition =-=[104]-=-, neural networks [105] and fuzzy logic [106] algorithms. The author of this thesis has designed and implemented an experimental proof-of-concept vertical macromobility testbed for Mobile IPv4 using a...

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...w computation complexity, but adaptive algorithms [103] have potential for more intelligent decisions improving the performance. Adaptive algorithms include pattern recognition [104], neural networks =-=[105]-=- and fuzzy logic [106] algorithms. The author of this thesis has designed and implemented an experimental proof-of-concept vertical macromobility testbed for Mobile IPv4 using a fuzzy logic algorithm,...

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...ty, but adaptive algorithms [103] have potential for more intelligent decisions improving the performance. Adaptive algorithms include pattern recognition [104], neural networks [105] and fuzzy logic =-=[106]-=- algorithms. The author of this thesis has designed and implemented an experimental proof-of-concept vertical macromobility testbed for Mobile IPv4 using a fuzzy logic algorithm, as presented in Paper...

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... delay, the ratio of effective data rates and the reduction to nominal rates for a single user. Fig. 11. Moving-out transition from WLAN to cellular. While there are location-aided handoff algorithms =-=[107]-=-, location-awareness is considered in this thesis only in the architecture when preparing the MH for approaching vertical handoff. Due to the fact that the RSS variation at the edge of the WLAN cell i...