A novel terminal-controlled handover scheme in heterogeneous wireless networks

Existing telemedicine systems that rely on single telecommunication network are unable to guarantee the user is always connected to healthcare professionals anywhere and anytime. The use of heterogeneous wireless networks can overcome this issue. However, the existing handover schemes are not efficient enough for telemedicine application. This is because the preference of telemedicine user might change based on the patient health conditions. In critical condition, the user preference might be biased toward the network QoS to optimize the quality of real-time telemedicine services. Conversely, the user would prefer the low cost network for transmitting the recorded health data to hospital server during non-critical situation. In this paper, an Improved Technique for Order of Preference by Similarity to Ideal Solution (I-TOPSIS) handover scheme is proposed for telemedicine services using heterogeneous wireless network. The proposed handover scheme is aware of patient health condition as well as user preference. It acts as user-preference based handover scheme and QoS based handover scheme during non-critical and critical condition, respectively. It overcomes the imperfections of the existing handover schemes in supporting telemedicine services.

The wireless network environment in the future is going to include various heterogeneous wireless networks. In a heterogeneous wireless network environment, vertical handoff processes caused by the movement of users are inevitable. However, the research related to how to achieve seamless vertical handoff and improve QoS guarantees in today's heterogeneous wireless networks is still something to work on. Therefore, this paper proposed the Advanced Vertical Handoff Translation Center (Advanced VHTC) architecture for Wi-Fi/WiMAX heterogeneous wireless networks, aiming to improve the quality of services in heterogeneous wireless networks by means of packet formats translation between heterogeneous wireless networks and the MIH-based seamless vertical handoff mechanism, which cut down the time for vertical handoff and obtain high quality and persistent connection service. Lastly, with the brilliant results of a complete simulation, this paper will show the performance in terms of delay, jitter, packets loss and throughput to prove that the Advanced VHTC for next generation heterogeneous wireless networks can provide good QoS guarantees and obtain persistent transmission with high performance while performing seamless vertical handoff.

Transferring a huge amount of data between different network locations over the network links depends on the network’s traffic capacity and data rate. Traditionally, a mobile device may be moved to achieve the operations of vertical handover, considering only one criterion, that is the Received Signal Strength (RSS). The use of a single criterion may cause service interruption, an unbalanced network load and an inefficient vertical handover. In this paper, we propose an enhanced vertical handover decision algorithm based on multiple criteria in the heterogeneous wireless network. The algorithm consists of three technology interfaces: Long-Term Evolution (LTE), Worldwide interoperability for Microwave Access (WiMAX) and Wireless Local Area Network (WLAN). It also employs three types of vertical handover decision algorithms: equal priority, mobile priority and network priority. The simulation results illustrate that the three types of decision algorithms outperform the traditional network decision algorithm in terms of handover number probability and the handover failure probability. In addition, it is noticed that the network priority handover decision algorithm produces better results compared to the equal priority and the mobile priority handover decision algorithm. Finally, the simulation results are validated by the analytical model.

It is envisaged that next generation wireless networks (NGWN) will be heterogeneous, consisting of multiple radio access technologies (RATs) coexisting in the same geographical area. In these heterogeneous wireless networks, mobile terminals of different capabilities (heterogeneous terminals) will be used by subscribers to access network services. We investigate the effect of using heterogeneous mobile terminals (e.g. single-mode, dual-mode, triple-mode, etc.) on call blocking and call dropping probabilities in cooperative heterogeneous wireless networks. We develop analytical models for heterogeneous mobile terminals and joint radio resource management in heterogeneous wireless networks. Using a two-class three-RAT heterogeneous wireless network as an example, the effect of using heterogeneous terminals in the network is evaluated. Results show the overall call blocking/dropping probability experienced by subscribers in heterogeneous wireless networks depends on the capabilities of mobile terminals used by the subscribers. In the worst case scenario, when all subscribers use single-mode mobile terminals, each subscriber is confined to a single RAT and consequently, joint radio resource management in heterogeneous wireless network has no improvement on new call blocking and handoff call dropping probabilities. However, in the best case scenario, when all subscribers use three-mode terminals, new class-1 call blocking probability decreases from 0.37 (for 100% single-mode terminals) to 0.05, at the arrival rate of 6 calls per minute. New class-2 call blocking probability also decreases from 0.8 to 0.52. Similarly, handoff class-1 call dropping probability decreases from 0.14 to 0.003, and handoff class-2 call dropping probability decreases from 0.44 to 0.09.

In next generation heterogeneous wireless networks, a user with a multi-mode terminal may have network access for different bearer services using various access technologies. In such a scenario, the user will select the best access network with good QoS and low cost. A profit-seeking network service provider, in order to maximize his revenue and be competitive in the market, has to efficiently utilize limited resources, and properly price the bearer services. Based on analysis and simulations, a simple allocation policy is proposed with the aim to maximize network capacity and user QoS, which can also simplify network selection process. In addition, the pricing policy for multi-services in heterogeneous wireless networks is also investigated in this paper.

Recently, there has been great interest in the community over heterogeneous wireless networks in order to support services with high quality. The integration of Wimax and Wi-Fi technologies in communication systems such as Voice ,FTP ,Video conducted heterogeneous system reveal that the proposed network selection technique can effectively decide the optimum network through making trade-offs among network condition, user preference while avoiding frequent handoffs. We identify vertical handover decision algorithm suitable for multimode mobile devices based on the Analytic Hierarchy Process (AHP) and evaluates its performance through simulation by Opnet. This paper gives a comparative analysis of two queuing systems FIFO and WFQ by showing the advantages of using suitable weight which was calculated by AHP. The simulation results show that WFQ technique has a superior quality than FIFO. It could be opportunity to network designers and suppliers are providing the resources to servers more efficient use.

Vertical handoff in next generation heterogeneous wireless networks is a multi-dimensional issue. In this article we propose a multi-dimensional adaptive SINR based vertical handoff algorithm (MASVH) which uses the combined effects of SINR, user required bandwidth, user traffic cost and utilization from participating access networks to make handoff decisions for multi-attribute QoS consideration. Simulation results confirm that the new MASVH algorithm improves the system performance in terms of higher throughput and lower dropping probability, as well as reduces the user traffic cost for accessing the integrated wireless networks.

Context-aware and priority-based user association and resource allocation in heterogeneous wireless networks

Wireless technology is a revolutionary advancement providing users with ubiquitous data and telephony access anywhere and anytime with no physical (PHY) connection. The currently deployed wireless networks like Wi-Fi, Worldwide Interoperability for Microwave Access (WiMAX), Universal Mobile Telecommunications Systems (UMTS), and Long Term Evolution (LTE) systems have different characteristics that make them complementary in terms of performance, coverage, and cost. This network variety presents an opportunity to provide better services to end users, given the advances in mobile terminals (MTs). To reach this goal, an appropriate automatic network selection (ANS) mechanism, which is able to always select the best access network, is needed. This consists of constantly monitoring any type of available access network, i.e., automatically selecting and switching to the best one, as the network that maximizes the users quality of experience, taking into account their preferences and the terminal and network conditions. ANS is a multidimensional decision-making problem that can be solved by finding an appropriate complex tradeoff between possibly conflicting criteria. In this paper, we propose an analytical model to capture the preferences of end users. Based on this model, we design an ANS mechanism that takes into account all aspects of the tradeoff between the quality of the connections, the preferences of the end users, and the cost. To highlight the benefits of our approach from the perspectives of both end users and network operators, we have implemented and tested the solution in a multitechnology simulator. Results show that the proposed solution outperforms mainstream approaches.

In this paper, the security of user domain including mobile terminal (MT) and user in heterogeneous wireless networks (HWN) are paid more attention. We introduce the trusted platform module (TPM) to ensure the terminal trustworthiness, while password, fingerprint and smartcard guarantee userpsilas identity. MT, user, and smartcard have been regarded as three separated entities, as well as the user including the owner and operator of MT have been distinguished. With the combination of TPM and CPK, the proposed scheme can implement TPM off-line identity attestation. A mutual authentication scheme among user/smartcard/MT is proposed to improve the security of the user domain and provide enhanced end-to-end security for MT to resist potential attacks from MT to user and resist possible attacks in HWN. The security and performance analyses show security, computation overhead and efficiency of this proposed scheme are enhanced.

In the next generation heterogeneous wireless networks, a user with a multi-interface terminal may have network access from different service providers using various technologies. Vertical Handover (VHO) is the capability to switch on-going connections from one Radio Access Network (RAN) to another. This switching is based on the discovered accesses, QoS constraints, operator policies, user preferences and available system capacity and utilization. Optimizing the VHO process is an important issue of research, which leads to reduction of network signaling and mobile device power loss and on the other hand improves network quality of service (QoS) and grade of service (GoS). In this paper, a decision support system is developed to address the VHO problem. This system combines fuzzy logic and TOPSIS, a MCDM algorithm, to the problem of VHO. This combination decreases the influence of the dissimilar, imprecise, and contradictory measurements for the VHO criteria coming from different sources. A performance analysis is done and results are compared with traditional algorithms for VHO. These results demonstrate a significant improvement with our developed algorithm.

Regarding of the problem of visible light communication (VLC) and WiFi heterogeneous network handover, most of the existing work focuses on the research of the vertical handover algorithm of heterogeneous networks, and the coordinated handover of horizontal handover (HHO) and vertical handover (VHO) of heterogeneous networks Strategies are rarely studied. Based on this, this paper proposes a new coordinated vertical handover (CVHO)scheme for heterogeneous networks. This scheme simplifies the motion model of the mobile terminal (MT), and proposes a handover algorithm to realize the coordinated handover of HHO and VHO of the network. The simulation results show that, compared with the traditional immediate vertical handover (IVHO)and dwell vertical handover (DVHO), this handover strategy can better meet the actual movement demands.

This paper proposes a heterogeneous wireless network with handover in the application layer. The proposed network requires no upgrade of wireless infrastructure and mobile terminals to convert the present homogeneous networks to the proposed heterogeneous network. Only installing application programs on the content server side and the mobile terminal side is required. The performance of the proposed network has been evaluated in a field trial using a mobile broadband wireless access (MBWA) air interface with wide coverage and a wireless local area network (WLAN) air interface with high throughput. The field trial results show that the maximum value of the handover outage time is only 170ms. The proposed heterogeneous wireless network is promising since both high throughput and wide coverage area are attained by a combination of the proposed handover scheme with the present homogeneous wireless networks.

In heterogeneous wireless networks (HWNs), it is important to select a currently optimal network for applications demanded by communicating Mobile Nodes (MNs) through Vertical Handover (VHO). VHO problem in HWNs is modeled as a multi-criteria decision making (MCDM) problem. VHO process is very vital in HWNs networks and thus demand the application of very efficient MCDM algorithms. The use of efficient MCDM algorithms for heterogeneous network selection can provide MNs with satisfactory Quality of Service (QoS). We propose a novel MCDM algorithm called MULTIplicative form with Multi-Objective Optimization Ratio Analysis (MULTIMOORA). The performance of the MULTIMOORA is validated by comparing it with SAW, GRA, VIKOR and TOPSIS algorithms for voice, file download and video streaming traffic classes. Simulation results show that MULTIMOORA outperforms SAW, GRA and VIKOR. Moreover, results show it has similar performance with TOPSIS, in term of accuracy for all the network traffics considered.

Many studies have shown that Vegas TCP has a better throughput and stability than Reno TCP in homogeneous networks with a single TCP flavor, but performs less well in heterogeneous networks in which two TCP flavors coexist. The progressive behavior of Reno TCP and the conservative behavior of Vegas TCP cause a bias when they are used simultaneously, and thus Vegas TCP fails to obtain a fair share of the bandwidth. This paper examines the origins of this bias and proposes a threshold-based congestion control mechanism designed to alleviate the resulting unfairness problem. The simulation results show that the proposed scheme achieves a higher throughput than the conventional Vegas TCP scheme and preserves the stability of the conventional scheme when used in heterogeneous wired and wireless networks.