Olabisi E. Falowo

Review: Bandwidth aggregation in heterogeneous wireless networks: A survey of current approaches and issues

Future wireless networks are envisaged to consist of a variety of integrated and jointly managed radio access technologies (RATs). This is motivated by the complementary features of the individual RATs. When in the overlapping coverage of the integrated RATs, a multimode terminal can use them simultaneously, thus aggregating bandwidth to enhance performance of high-bandwidth applications. However, there are challenges that must be addressed to achieve efficient bandwidth aggregation. Packet reordering is the most dominant challenge. Packet reordering can lead to excessive delays that can affect real-time applications; it can also affect throughput of TCP applications adversely. To circumvent the reordering problem and other challenges associated with simultaneous use of the terminals multiple interfaces, bandwidth aggregation solutions are developed. This paper reviews existing bandwidth aggregation solutions in heterogeneous wireless networks. Challenges and several open research issues in the design of bandwidth aggregation approaches are also outlined. To the best of our knowledge, this is the first comprehensive review of existing bandwidth aggregation techniques in heterogeneous wireless networks. This paper, therefore, provides important lessons and information from current bandwidth aggregation solutions, which can be used to guide the development of more efficient bandwidth aggregation approaches.

Joint call admission control algorithms: Requirements, approaches, and design considerations

It is envisioned that next generation wireless network (NGWN) will be heterogeneous where different radio access technologies coexist. This vision of NGWN has led to the development of new call admission control (CAC) algorithms specifically designed for heterogeneous wireless networks. This paper reviews recent call admission control algorithms for heterogeneous wireless networks. Benefits and requirements of joint CAC (JCAC) algorithms are discussed. We examine eight different approaches for selecting the most appropriate radio access technology (RAT) for incoming calls in NGWN and classify the JCAC algorithms based on these approaches. The advantages and disadvantages of each approach are discussed. We analyze six different design considerations for JCAC algorithms. These design considerations are centralization, optimization, number of network selection criteria, call type, centricity, and prediction. A more thorough understanding of JCAC in heterogeneous wireless networks and its research trends may help one to design better JCAC algorithms.

Adaptive bandwidth management and joint call Admission control to enhance system utilization and QoS in heterogeneous wireless networks

The coexistence of different cellular networks in the same area necessitates joint radio resource management for enhanced QoS provisioning and efficient radio resource utilization. We propose adaptive bandwidth management and joint call admission control (JCAC) scheme for heterogeneous cellular networks. The objectives of the proposed adaptive JCAC scheme are to enhance average system utilization, guarantee QoS requirements of all accepted calls, and reduce new call blocking probability and handoff call dropping probability in heterogeneous wireless networks. We develop a Markov chain model for the adaptive JCAC scheme and derive new call blocking probability, handoff call dropping probability, and average system utilization. Performance of the proposed adaptive JCAC scheme is compared with that of nonadaptive JCAC scheme in the same heterogeneous wireless network. Results show an improvement in average system utilization of up to 20%. Results also show that connection-level QoS can be significantly improved by using the proposed adaptive JCAC scheme.

Joint Call Admission Control Algorithm for Fair Radio Resource Allocation in Heterogeneous Wireless Networks Supporting Heterogeneous Mobile Terminals

There is a problem of unfairness in allocation of radio resources among heterogeneous mobile terminals in heterogeneous wireless networks. Low-capability mobile terminals (such as single-mode terminals) sutTer high call blocking probability whereas high-capability mobile terminals (such as quad-mode terminals) experience very low call blocking probability, in the same heterogeneous wireless network. This paper proposes a joint call admission control (JCAC) algorithm to reduce this problem of unfairness. The proposed JCAC algorithm makes call admission decisions based on mobile terminal modality (capability), network load, and radio access technology (RAT) terminal support index. The objectives of the proposed JCAC algorithm are to reduce call blocking/ dropping probability, and ensure fairness in allocation of radio resources among heterogeneous mobile terminals in heterogeneous networks. We develop an analytical model to evaluate the performance of the proposed JCAC scheme in heterogeneous wireless networks and derive expression for call blocking/ dropping probability. The performance of the proposed JCAC algorithm is compared with that of other JCAC algorithm. Results show the proposed algorithm reduces call blocking/ dropping probability in the networks, and ensure fairness in allocation of radio resources among heterogeneous terminals.

PMIPv6 and MIH-enhanced PMIPv6 for mobility management in heterogeneous wireless networks

Next generation wireless networks will interwork hence combine resources of the available heterogeneous networks for connection support. Mobility across these networks will be inevitable. Thus, to support seamless connection migration between the networks, seamless handover is a necessary requirement. One of the requirements for ensuring seamless handover is the reduction of the delay that occurs during a handover procedure. Various mobility management protocols have been proposed and standardized to support mobility across heterogeneous networks but they cannot provide seamless handover in their current form. However, Proxy Mobile IPv6, which is a networked-based mobility management, goes a long way towards reducing handover delay. Enhancing it with a handover optimization mechanism, such as IEEE 802.21 MIH services, improves the handover performance even further. This paper therefore evaluates the performance of PMIPv6 versus PMIPv6 enhanced with MIH services. The results show that indeed PMIPv6 performs even better when enhanced with MIH in terms of reducing handover delay and reducing packet losses during handover across heterogeneous wireless networks.

Joint Call Admission Control for Next Generation Wireless Network

Next generation wireless network (NGWN) will be heterogeneous in nature where different radio access technologies (RATs) such as UMTS, WiMax, WLAN, etc, coexist. This coexistence necessitates joint radio resource management (JRRM). This paper focuses on joint call admission control (JCAC) for NGWN. Factors that determine a users preference for a particular RAT are discussed. We propose a JCAC algorithm which considers the users preference in making admission decision. A specific case where the user prefers to be served by the RAT which has the least service cost is modeled and evaluated using Markov decision process. The results obtained shows that overall service cost in heterogeneous network can be significantly reduced by using the proposed joint call admission control

Enhancing PMIPv6 for better handover performance among heterogeneous wireless networks in a micromobility domain

This paper analyzes the reduction of handover delay in a network-based localized mobility management framework assisted by IEEE 802.21 MIH services. It compares the handover signaling procedures with host-based localized MIPv6 (HMIPv6), with network-based localized MIPv6 (PMIPv6), and with PMIPv6 assisted by IEEE 802.21 to show how much handover delay reduction can be achieved. Furthermore, the paper proposes and gives an in-depth analysis of PMIPv6 optimized with a handover coordinator (HC), which is a network-based entity, to further improve handover performance in terms of handover delay and packet loss while maintaining minimal signaling overhead in the air interface among converged heterogeneous wireless networks. Simulation and analytical results show that indeed handover delay and packet loss are reduced.

Network selection in heterogeneous wireless networks using multi-criteria decision-making algorithms: a review

It is expected that next-generation wireless networks will provide a plethora of mobile wireless services to users and ubiquitous network coverage at all times. Meeting these expected goals requires that new and existing networks be seamlessly integrated together to form Heterogeneous Wireless Networks (HWNs). Thus, seamless and efficient handover mechanisms are pertinent for optimal network performance in HWNs; so that the mobile user can switch from one access network to another, in search of the best connection for the demanded services. The HWNs’ performance can be reduced, if efficient network selection is not achieved. In HWNs, network-selection decisions can be evaluated by using multi-criteria, or a single criterion. However, network selection and decision-making in HWNs often involves taking into account a large number of complex and conflicting network-decision factors, or criteria. Thus multi-criteria decision-making techniques are more efficient than single-criterion techniques. Multi-Criteria Decision-Making (MCDM) techniques comprise of a developed branch of operational research for assisting in the resolution of complex decision-making problems. MCDM is an important tool that has been used to model and analyze handover-decisions and network-selection problems in HWNs. This paper reviews and classifies the most significant MCDM algorithms that have been used to address the network decision-making problems in HWNs in terms of algorithmic approach, the type of calls, the cardinality of decision criteria employed, handover-control points and the types of network utilities. Comprehensive step-wise mathematical implementations of the reviewed MCDM schemes are presented, while pointing out their strengths and limitations. This paper review fills a research gap in the investigation on network-selection criteria’s interdependence and interactions, and their effects on criteria’s weight of importance. It then provides an insight into the importance of network-criteria weighting and the current research trend in the application of MCDM algorithms to network-selection problems in HWNs.

Network-based distributed mobility management: Design and analysis

Mobile IPv6 and its extensions including Proxy MIPv6 employ a centralized mobility anchor to handle mobility management of the mobile nodes. The mobility anchor is in charge of mobility routing, location management and home address allocation functions. Having all of these functions bundled in a single network entity brings performance issues such as non optimal routing via this centralized anchor, traffic bottleneck and single point of failure. Distributed mobility management is an alternative approach to overcome these issues. A network-based distributed mobility management scheme that co-locates the mobility routing function to distributed access routers with a mobility client function in different networks is presented. It provides an optimal path for both handover traffic and new traffic of the mobile nodes, and releases the burden from the centralized mobility anchor. The paper presents in detail the scheme and its principle of operation. Furthermore, it develops an analytical model to evaluate the performance of the scheme. Numerical results are presented to demonstrate better performance in terms of packet delivery cost, tunneling cost and total cost.

PMIPv6-HC: Handover Mechanism for Reducing Handover Delay and Packet Loss in NGWN

Next generation wireless networks will consist of interworking heterogeneous wireless access technologies that will be integrated over an IP-based infrastructure to provide network access ubiquity. In such a networking environment mobility particularly vertical handover between the heterogeneous wireless networks has to be supported. However, it is challenging to coordinate vertical handover within this diverse environment to ensure better handover performance in terms of handover delay and packet loss. Consequently, this paper proposes the idea of employing a handover coordinator between the heterogeneous networks that are affected in the handover process. The main idea is that dynamically coordinating handover procedures ahead of time among the affected networks will enhance overall handover performance. That is, coordinated handover procedures will be easy to handle proactively thus mitigating delays and packet loss during the actual handover period. The proposed handover coordinator utilizes a network-based mobility management protocol as a basis to effectively and efficiently handle vertical handovers in a localized heterogeneous wireless environment. Thus, the resulting network-based handover mechanism improves performance particularly in terms of ensuring that the handover between the heterogeneous wireless networks is transparent to active connections during the handover period. Simulation results show that handover coordination in network-based mobility managed heterogeneous wireless networks further reduces handover delay and packet loss hence improving handover performance.