Vertical handover

As explained in [15], handover is defined as the changing of the network point of attachment of a mobile device. When the device moves to a new point of attachment which is technologically identical to the previous point of attachment, this is called horizontal handover. An example of horizontal handover occurs when the calls on a 3G phone are moved from raie 3G Base-station to another 3G Base-station. Vertical handover is defined as a handover where the new point of attachment comprises a different technology when compared with the previous point of attachment. In this paper, we are primarily concerned with vertical handovers. 

However, since these networks have different characteristics in terms of speed, latency, and reliability, vertical handover will therefore have an impact on the network service experienced by ongrang applications and services as mobile nodes move around. Some applications such as multimedia may be able to adapt, while others may need support to deal with varying quality-of-service (QoS). This situation is also... 

As pointed out in [14], vertical handover can cause radical changes in QoS. Hence, it is important that as much control as possible is exercised by mobile devices to achieve optimum vertical handover. It is therefore necessary to develop new techniques which could make other layers of the protocol stack aware of impending handover decisions and, thus, allow them to take steps to minimize the effects. So a new QoS Framework is required which must be integrated with mobility mechanisms such as handover. 

Examples of such future frameworks are the Mobile Ethernet as described in [13], Ambient Networks explained in [8] and the Y-Conun framework highlighted in [12]. The Y-Comm group has been working oti introducing novel approaches to support a seamless and secure vertical handover in heterogeneous environments. This paper will consider the mechanisms introduced by the Y-Comm group to address mobility, QoS, and security issues and explains how these mechanisms could be integrated in the context of the Y-Comm framework. 

Given the future structure of the network as detailed in Figs. 16.1 and 16.2, vertical handover will occur between networks connected to the same core endpoint (called an intra-CEP handover) or between networks cmmected to adjacent core endpoints (called an inter CEP handover). In order to optimize the handover process, it is necessary to examine handover in detail. This advanced classification is shown in Fig. 16.3. 

As previously discussed, in order to support seamless and secure vertical handover in future, heterogeneous networks, there is a need for novel communicaticm frameworks, wherein different handover, security and QoS mechanisms could be integrated with the communicaticH) system. This section outlines the Y-Conun framework. 

In this section we look at how proactive handover is done in Y-Comm. This is detailed in Fig. 16.5. Vertical handover is faciUtated in Y-Comm using the three... 

The handover scenario is described as follows the PML polls the NML about networks in the local area. The NML sends this information about local networks and their topologies back to the PML. The PML uses this information to decide when, where, and to which network to handover and then gives that information to VHL to execute the handover at the chosen time. The VHL contacts the Reconfiguration layer in the core network to request a channel on the target Base-station. The RAL will acquire a channel on behalf of the mobile terminal. When the TBVH period expires, the VHL then instructs its NAL to handover. It is very important to see that the PML also informs the higher layers of impending handover, giving the new QoS, TBVH, and the IP address on the new network. This is used by the Handover Module in the QoS Framework to initiate QoS and security mechanisms to ensure a smooth vertical handover. 

This model facilitates secure vertical handover and attempts to prevent network resources from being abused and overloaded. This is done by monitoring resource requests and ensuring access to vulnerable components does not exceed the available QoS. 

This paper has explored mechanisms for building future networks. These systems will have to integrate mobility, via vertical handover, QoS, and security. The required mechanisms have been explored in the context of the Y-Comm architecture. Proactive handover mechanisms as well as QoS and Security were integrated to provide secure vertical handover. Future work will involve using the mechanisms detailed in this paper to build a prototype system. 

Aiash M, Mapp G, Lasebae A, Phan R, Loo J (2011) A formally verified AKA protocol for vertical handover in heterogeneous environments using Casper/FDR. EURASIP Journal on Wireless Communications and Networking 2012, 2012 57 doi 10.1186/1687-1499-2012-57... 

It is often specified that a certain percentage (90% 95%) of the primary consolidation must have occurred at the time of handover of the reclamation. It is noted that a requirement stipulating 100% consolidation is not realistic since settlement is a function of the logarithm of time. In fact the-time needed for occurrence of the last 5% consolidation settlement is, on an average, more or less equal to the time period required for occurrence of approximately 95% consolidation, even when vertical drains are installed. 

Specifications do not always consider or refer to secondary compression (creep). The contribution of the secondary compression to the total settlement can be considerable when thick very soft cohesive layers underlie the reclamation site. Vertical drains do not help to accelerate the secondary compression. Reduction of the secondary compression after handover can only be realized by means of a temporary preload that is in place for a sufficient long time period which is not always available... 

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