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CONCLUSION AND FUTURE WORK
The major outcome of this research effort is to analyse the feasibility and benefits of achieving seamlessness with the proposed decentralized approach augmenting the conventional centralized approach for heterogeneous networks. In lieu of this, the outcomes achieved include
- A Hybrid Approach (Linux Kernel Module and SCTP) to decrease the latency during Vertical Handoff process and IP mobility to achieve seamless continuity.
- Location Awareness in Hybrid Approach to reduce the triggering of unnecessary handoffs during vertical handoff that result in performance degradation.
Contributions of the Present Work
In this thesis, several aspects and approaches for seamless continuity are discussed. The major contributions of the work carried out in this thesis are:
- Different approaches to achieve seamless continuity in heterogeneous networking environment.
- A brief review on the open issues and challenges related to seamless continuity.
- Design and development of daemon based decentralized approach for intranet environment.
- Design and development of an efficient and fast method known as kernel based decentralized approach for improving the latency during handoffs.
- Development of Stream Control Transmission Protocol (SCTP) approach for addressing dynamic address reconfiguration in heterogeneous environment.
- Design and development of a novel hybrid method using the combination of SCTP and kernel module.
- Development of a location aware method to incorporate into the hybrid approach for heterogeneous networks.
The proposed solution is a hybrid approach to achieve seamless session continuity in heterogeneous networks. This approach is completely decentralized complementing the centralized approach which is completely based on server agents. It can be applied to both intra and Internet environment without any changes to the network layer. To prove this approach for seamlessness, testing was done on three network interfaces Ethernet (eth), WLAN (wlan), WCDMA (wcdma).
A vertical handoff daemon was developed to achieve seamlessness over heterogeneous networks. This daemon application runs as a background process at the user space and it also takes care of the handoff process between various radio interfaces. Firstly, this proposed daemon continuously polls for the registered interfaces and then checks the status (live or dead) of these devices. Later, it also updates the status to the network layer of the protocol stack to keep the service continuing between the mobile device and the server. The designed architecture is well suited for all the IP based multimedia applications but running only in intranet environment. IP mobility is an issue which has to be still addressed which cannot be solved in this approach.
To achieve seamless continuity over heterogeneous networks, this proposed solution is a combination of Stream Control Transmission Protocol (SCTP) and Linux kernel module. This kernel module gets registered with the Linux kernel and updates the status of various interfaces by signalling the SCTP application running at the user level. This SCTP application will then accomplish the handoff process between various network interfaces.
The reason behind this approach is SCTP has an advantage of IP address reconfiguration which solves the IP mobility issue and Kernel module has an advantage of latency. This accomplishes the handoff process in a faster and elegant fashion. But this will not solve the problem of unnecessary triggering of handoffs. In this regard the following handoff decision process was integrated into hybrid approach to improve performance while achieving seamlessness.
Location based Handoff Decision
This proposed algorithm is completely based on location based information. This is a research effort to study the feasibility of location based solution which consists of combining the conventional handoff decision with a location based evaluation mechanism. This mechanism relies on positioning method for obtaining mobile user position fixes. Once the user’s location, speed and direction are calculated, the evaluation mechanism will predict the user’s path. It will then decide whether the user will remain in the same network coverage area for necessary duration to result in performance improvement. If not, this proposed evaluation method will notify the mobile device to trigger a handoff. The knowledge on user’s location, speed and direction is necessary to prevent inefficient and unnecessary handoffs.
In this research effort, a seamless vertical handoff system across heterogeneous networks is presented. It is implemented in current Linux operating system. In the proposed system, the handoff latency is much shorter than other current systems focusing on the issue of vertical handoff. Different from other vertical handoff systems, handoff agents or servers are not required in this system. Only with the mobile host itself, the vertical handoff can be realized. Moreover, the overhead during handoff is also quite low. The system is evaluated through a series of experiments. The experimental results demonstrated the handoff is handled in a fast and elegant manner.
The proposed system is tested in the real-world analyses. The experiments were conducted under different environments and evaluated with various multimedia applications. This work is not only for home network solution but it is extended to an Internet solution. Moreover, prior to triggering handoff, the algorithm’s ability to predict user direction, speed and visit to WLAN coverage area allowed it to provide an observable benefit both on user’s perspective and also on network’s perspective. This location based evaluation of the algorithm helped to not only prevent the occurrence of unnecessary handoffs which would result in performance degradation but also reduce wastage of resources.
The novel hybrid decentralized approach based on location awareness presented in this work handled the issues of latency, dynamic address reconfiguration and unnecessary triggering of handoffs for seamless continuity in heterogeneous networks.
Keeping in view the wide proliferation of heterogeneous networks and high level of interworking required for next generation mobile users, the scope of the future work can be more focussed on pursuing open challenges such as battery power consumption, Quality of Service (QoS) and security for effective ubiquitous experience and seamless continuity.
Battery power consumption of the mobile client is a significant criterion for handoff. Whenever the battery power drops to particular threshold, the mobile client should immediately shift to lower power demand network interface.
As the demand for multimedia applications increases there is a need to guarantee QoS such as high available bandwidth, Bit Error Rate (BER), network load balancing, Signal to Noise ratio (SNR) and so on.
Security is another important criterion which needs to be addressed. Hence, when handoff data is exchanged between devices it is always preferable to have network with high level of encryption.
In this research effort, some work was done on best Access Point selection algorithm. With the enormous increase of WLAN AP’s everywhere, there is a need to look at new approaches to select the best AP among multiple AP’s for achieving horizontal handoffs.
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