Next generation heterogeneous wireless networks with QoS guarantees

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.

Heterogeneous wireless network (HWN) is an overlay structure of different wireless networks (WN). The WNs may differ in terms of coverage, capacity, underlying technology, service types, and network operators. In such a HWN environment, a mobile user (MU) equipped with multi-mode or multi-home terminal always wish to maintain connectivity with a wireless network which can provide best quality of experience (QoE). Similarly, the WN may allow the connectivity only to a MU which can provide highest revenue. This may leads to an event, called vertical handoff, where the MU leaves current WN and connect to another different WN. The conflicting goals of maximizing QoE and revenue simultaneously while performing a VHO necessitates the selection of mutually best MU and WN. Game theory is an efficient mathematical tool to model such situations where specific actions of decision makers lead to mutually conflicting consequences to each other. This paper, using a tutorial style, presented the game theory concepts and its application for VHO, type of games, and game solutions. It proposes, in specific, the noncooperative game formulations for three different VHO situations and their solutions using NASH for HWNs.

Multimode terminals designed for heterogeneous wireless networks (HWNs) have the capability to support two or more classes of calls simultaneously. When a multimode terminal having an ongoing call initiates a new class of call, the current radio access technology (RAT) may not support the new class of call thereby necessitating a vertical handoff to a RAT that can support both the current and the newly initiated call. However, vertical handoffs incur signaling overhead, handover delay, packet loss, and service disruption. Therefore, it is important to reduce the frequency of vertical handoffs in HWNs. This paper proposes a predictive algorithm that considers the current state and the possible future state of a multimode terminal in making RAT selection decisions, and thereby reduces the frequency of vertical handoffs in HWNs. The history of a user's call logs is used in making predictions about future states of the user's multimode terminal. The paper develops an analytical model to evaluate the performance of the proposed predictive RAT-selection algorithm, using a four-RAT HWN as an example, and considering three classes of calls namely voice, video, and data. Results show that the proposed predictive algorithm significantly reduces the frequency of vertical handoff calls when compared with non-predictive algorithm in HWNs.

With advances in variant wireless technologies, many mobile devices equipped with multiple interfaces have emerged. In such a multiple wireless network environment, it is desirable to enjoy streaming video with good quality and low cost. The challenge of providing such services is to take advantage of heterogeneous wireless network characteristics, including their bandwidth, packet lost probability and transmission cost. In this paper, we first present a detailed video distortion model to estimate the distortion experienced by service users. Based on this model, we then propose a 3-stage greedy algorithm, which determines the transmission sequences over two heterogeneous wireless networks, so that distortion controlled streaming video services can be provided with near-optimal cost. Experiment results show that the detailed video distortion model can keep the expected distortion under better control. Besides, the proposed 3-stage greedy algorithm provides a solution which meets the distortion and deadline constraints with the near-optimal cost

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.

SummaryNetwork selection mechanisms have a significant role in guaranteeing the QoS for users in a heterogeneous wireless networks environment. These mechanisms allow the selection of an optimal wireless network to satisfy the needs of users. Users are provided with the opportunity to select from multiple connectivity opportunities available all over various wireless networks. Furthermore, the network operators themselves can execute active selection strategies that facilitate proper decision making, in which user preferences are considered. This study proposes a new noncooperative competing game‐theoretic model and strategy space based on user preference. This model can solve network selection problems and capture the inter‐linkages of decisions taken by various networks. A generalized simple additive weighting method is incorporated into the framework of noncooperative game theory. In addition, the utility function is employed to assess the usefulness of the system. Simulation results and analysis illustrate the efficacy of the suggested model in attaining optimum network utility for heterogeneous wireless networks while optimizing user satisfaction. Copyright © 2014 John Wiley & Sons, Ltd.

Future-generation wireless networks have been envisioned as the integration of various wireless access networks, including both wireless wide area networks and wireless local area networks. In such a heterogeneous network environment, seamless mobility support is the basis of providing uninterrupted wireless services to mobile users roaming between various wireless access networks. Because of transparency to lower-layer characteristics, ease of deployment, and greater scalability, the application-layer-based session initiation protocol has been considered the right candidate for handling mobility in heterogeneous wireless networks. However, SIP entails application-layer transport and processing of messages, which may introduce considerable delay. As a case study of the performance of mobility management protocols in the heterogeneous wireless networks, we analyze the delay associated with vertical handoff using SIP in the WLAN-UMTS internetwork. Analytical results show that WLAN-to-UMTS handoff incurs unacceptable delay for supporting real-time multimedia services, and is mainly due to transmission of SIP signaling messages over erroneous and bandwidth-limited wireless links. On the other hand, UMTS-to-WLAN handoff experiences much less delay, mainly contributed by the processing delay of signaling messages at the WLAN gateways and servers. While the former case requires the deployment of soft handoff techniques to reduce the delay, faster servers and more efficient host configuration mechanisms can do the job in the latter case.

Decision making is the hot topic in business management. Recently, there have been investigations in Call Admission Control (CAC) to handle the handover events in wireless network environments. Wireless networks have been seen to support different handoff mechanisms, in which the user can switch from one wireless network to another such as from IEEE 802.11 to IEEE 802.16. Many wireless standards, such as IEEE 802.16e and IEEE 802.11, have been proposed to satisfy diverse requirements for mobile users.. Several strategies have been proposed to realize seamless handoff in the heterogeneous networks; in this paper, we analyze the performance of some novel intelligent handoff mechanisms with multiple attributes. The mobile set dynamically selects the optimal network and provides the user with high throughput of Quality of Service (QoS) as to minimize the blocking probability of the system in heterogeneous networks. We evaluate some intelligent handoff mechanisms such as Technique for Order Preference by Similarity to Ideal Solutions (TOPOSIS), Simple Additive Weight (SAW), Analytic Hierarchy Process (AHP) and Fuzzy Logic and Grey Relational Analysis (GRA). From the results, blocking probability and dropping rate can be referenced to support better QoS.

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.

Network reliability analyses have received much attention in heterogeneous wireless network performance evaluation during the last few years. In this paper, a method for heterogeneous wireless network reliability evaluation to meet the required levels of heterogeneous wireless network differences of various graph-theoretic connectivity measures is proposed. A concept of heterogeneous wireless network reliability degree is proposed and a heterogeneous wireless network reliability entropy-based method for analyzing the proposed reliability measure is discussed. This method is based on heterogeneous wireless network survivability and stability analyses. Its core is the computation of some heterogeneous wireless network combinatorial invariants. These invariants, once computed, directly provide pure and simple framework for computation of heterogeneous wireless network reliability. We illustrate how a new approach to assessing the performance of in heterogeneous wireless networks. Our results also illustrate how the characteristics of the heterogeneous wireless networks may affect the performance of the different measures. We also present some simulation results.

In a heterogeneous network consisting of diverse wireless access standards, vertical handoff (VHO) plays a major role in handling seamless data transfer. Vertical Handoff decision is based upon Received Signal Strength (RSS) measurements, where handoff (HO) decision is made individually without considering other HO user equipments (UE). This results in higher block rate and power consumption at the mobile devices. User mobility is an important factor that is to be considered in VHO decision, i.e., VHO is required only at lower speeds, and since high speed user velocity may cause unnecessary handovers that can degrade system capacity and QoS level. By considering UE velocity also, in making a HO decision, we can reduce the transmission cost and transmission time. This paper adopts the mathematical model based VHO prediction approach comprising a well defined objective function considering RSS, UE velocity, load and cost per user bandwidth. The system performance can be enhanced according to the user preferences by adjusting the weights in the defined objective function. Due to the high bandwidth and ease of networking we consider the wireless access standards: Wi-Fi and Wimax. The propagation model considered in this paper is Jake's model. The algorithm is simulated in MAT LAB and the performance of the network is evaluated in terms of user velocity and handover numbers.

A novel terminal-controlled handover scheme in heterogeneous wireless networks

Despite recent interests in developing vertical handoff decision algorithms, an essential component of the architecture of the next generation heterogeneous wireless networks, very few studies have so far reported any meaningful comparative performance analysis. This paper attempts to fill this gap in the literature by presenting a comprehensive study on the performance of three vertical handoff decision algorithms, namely, SAW (Simple Additive Weighting), TOPSIS (Technique for Order Preference by Similarity to Ideal Solution), and MDP (Markov Decision Process). We have used both analytical and simulation tools (ns-2.29) to evaluate and compare expected total QoS offerings in the mean duration of a service under different state transition probability distributions, user perception models on the importance of QoS parameters, and network switching costs. To our surprise, we have observed TOPSIS achieving the best performance despite MDP’s using the optimal policy. We suspect that the user satisfiability model used in MDP to estimate link rewards might have contradicted the underlying user perception model used to estimate normalised weight of each QoS parameter, which will be investigated in future.

At present, the fixed spectrum allocation is the accepted strategy employed by the wireless industry and regulators and a large number of spectrum resources have been wasted because of the traffic load variation in different heterogeneous wireless networks. Through the analysis of recent research about dynamic spectrum allocation (DSA), vertical handoff and multi-mode base stations, the authors have proposed the shared carrier vertical network transformation (SCVNT) algorithm, which is based on minimum total blocking probability (MTBP) or minimum redundant channel difference (MRCD). In order to evaluate the performance of SCVNT, the cellular system model and user mobility model are established, and using fixed channel allocation and dynamic channel allocation in each network, the theoretical analysis and simulation experiments are made in different user mobility conditions, different SCVNT judgment periods and different thresholds of the redundant channel difference. The results indicate that SCVNT can effectively reduce total blocking probability and enhance fairness in heterogeneous wireless networks with good compatibility and applicability.

As many access technologies develop, more and more heterogeneous wireless networks appear around us. In this case, when whole mobile networks move from the visiting network to another, the handoff attracts the attentions especially. The exited handoff methods with network mobility merely extended the scheme of handoff in MIPv6 or integrated the exited methods into the uniform scheme but it can not make the good effect to really and truly solve the fast and smooth (packet lossless) handoff in heterogeneous wireless networks. In this paper, the fast handoff scheme is given and it provides Multi-Mobile Router (MMR) with a vicinage table to keep information about their vicinages access router. Using this method, it performs the Fast Handoff with network mobility effectively in heterogeneous wireless networks. In addition, we introduce the new entity TCS (temporary control server) to manage MMR procedure in order to complete fast handoff and reduce the power consumption of MMR. By analysis and simulations, we demonstrate that fast handoff scheme has the better performance than Basic NEMO.