Wireless Overlay Networks Research Articles

CSVAG: Optimizing Vertical Handoff Using Hybrid Cuckoo Search and Genetic Algorithm-Based Approaches

One of the primary challenges that wireless technology in the present generation is facing is always best connected (ABC) service. This is possible only when the wireless overlay networks follow a cooperative and coordinated process. Vertical handoff is one such process. Concerning this process, the main challenge is to develop algorithms that take care of optimal connection management with proper resource utilization for uninterrupted mobility. In this paper, we develop a new hybrid cuckoo search (CS) and genetic algorithm (GA) that maximizes the performance of heterogeneous wireless systems in terms of minimizing latency, handover failure probability, and enhancing the throughput. We focus on an optimized simulation framework to demonstrate the advantage of our hybrid model. It can be discerned from the simulation analysis that the proposed hybrid technique increases throughput by 17% and 8% compared to the cuckoo search and genetic algorithms applied individually. The performance of the proposed scheme is promising for applications wherein the handoff mechanisms have to be optimized to control frequent handoffs to further reduce the power consumption of user equipment.

IRONWAN: Increasing Reliability of Overlapping Networks in LoRaWAN

LoRaWAN deployments follow an ad-hoc deployment model that has organically led to overlapping communication networks, sharing the wireless spectrum, and completely unaware of each other. LoRaWAN uses ALOHA-style communication where it is almost impossible to schedule transmission between networks belonging to different owners properly. The inability to schedule overlapping networks will cause inter-network interference, which will increase node-to-gateway message losses and gateway-to-node acknowledgement failures. This problem is likely to get worse as the number of LoRaWAN networks increase. In response to this problem, we propose IRONWAN, a wireless overlay network that shares communication resources without modifications to underlying protocols. It utilises the broadcast nature of radio communication and enables gateway-to-gateway communication to facilitate the search for failed messages and transmit failed acknowledgements already received and cached in overlapping network's gateways. IRONWAN uses two novel algorithms, a Real-time Message Inter-arrival Predictor, to highlight when a server has not received an expected uplink message. The Interference Predictor ensures that extra gateway-to-gateway communication does not negatively impact communication bandwidth. We evaluate IRONWAN on a 1000-node simulator with up to ten gateways and a 10-node testbed with 2-gateways. Results show that IRONWAN can achieve up to 12\% higher packet delivery ratio (PDR) and total messages received per node while increasing the minimum PDR by up to 28\%. These improvements save up to 50\% node's energy. Finally, we demonstrate that IRONWAN has comparable performance to an optimal solution (wired, centralised) but with 2-32 times lower communication costs. IRONWAN also has up to 14\% better PDR when compared to FLIP, a wired-distributed gateway-to-gateway protocol in certain scenarios.

Safety monitoring method of vehicle bridge stress structure based on wireless sensing technology

In the safety monitoring of bridge stress structure, the influence of surrounding environment and noise interference will cause the change of monitoring node coverage and affect the monitoring accuracy. Based on wireless sensor technology, a safety monitoring method of vehicle bridge stress structure is proposed. The interpolation fitting method is used to calculate the stress value of the sensor, and the optimal layout of the sensor is determined with the minimum deflection transfer error as the objective function. Probability sensing model is used to establish wireless overlay network, and wireless sensing technology is used to collect monitoring data. Based on the monitoring data, the static and dynamic response equation is established to establish the finite element model of bridge stress structure. The first level early warning threshold is determined according to the monitoring data under the normal operation state of the bridge, and the second level early warning threshold is determined according to the most unfavorable load distribution of the finite element model, so as to complete the bridge safety monitoring. The experimental results show that the average deformation deviation of the monitoring method proposed in this paper is 0.26mm, which is 0.77mm and 1.22mm smaller than the monitoring methods based on machine vision and GPS differential positioning technology, indicating that the monitoring method in this paper is more accurate and meets the safety requirements of bridge engineering.

Secure Overlay Routing for Large Scale Networks

Probabilistic key pre-distribution schemes have recently emerged as major tools of addressing secure routing challenge in wireless networks. In our previous work, we propose an algorithm capable of finding optimal secure paths in overlay wireless networks. An important concern related to that algorithm is the scalability of the solution for large scale networks containing thousands of nodes. In this paper, we propose two alternative solutions for the previously formulated problem of secure overlay routing that can effectively scale to thousands of nodes. The first one is a deterministic Dijkstra-based algorithm analytically proven to find the optimal path with a time complexity much lower than that of the original algorithm. The second alternative is an approximation method capable of finding a near optimal path with an accuracy of 99 percent compared to the optimal path. At the cost of a space complexity in the order $O(n \log ^3n)$, this algorithm can find the near optimal path with a linear time complexity compared to quadratic or multiplicative time complexity associated with the first algorithm proposed in this paper. Experimental results using a number of different key pre-distribution schemes confirm our analytical findings.

An Improved Delay Resistant Adaptive Multicasting Strategy for High Definition Video Delivery in Wireless Overlay Network

The Multimedia based application services have been getting attention in recent years in various fields. These services require a stringent delay resistant protocol in order to provide the best Quality of Service to end users. Existing protocols are predominantly designed using load balancing, tree, multi-tree and mesh based mechanisms. These mechanisms suffer in the presence of channel noise and incur more delay due to improper multicasting techniques adopted. Overlay network using hybrid (tree over mesh) structure along with multicasting strategies are used to address this issue. In this paper, an Improved Delay Resistant Adaptive Multicasting (IDRAM) model which adopts hybrid overlay creation, sub-packet based multi path transmission technique and error correction based on Forward Error Correction along with arbitrary IDRAM-A and selective IDRAM-S multicasting techniques are proposed and evaluated. Simulation is conducted to calculate frame success ratio, throughput, number of packet retransmission and transmission delay. The results obtained prove that IDRAM-S outperforms better than IDRAM-A and existing sub packet based multi path techniques. The number of retransmission requests made by IDRAM-S is reduced compared to the existing model. This reduction in the number of retransmission enables in minimizing end to end delay and thereby achieve stringent delay constraints associated with multimedia data delivery.

Local connectivity for heterogeneous overlaid wireless networks

We study the local connectivity, i.e., the node isolation probability of two coexisting wireless ad hoc networks (a primary network vs. a secondary network), where two users can communicate if the signal-to-interference ratio (SIR) at the receiver is larger than a threshold. Assuming the primary users are distributed as a Poisson point process (PPP) and the secondary users are distributed as a Matern cluster process (MCP), we investigate the impact of network parameters on the node isolation probability. Upper and lower bounds for the node isolation probability of the heterogeneous overlaid networks are presented. We also study the node isolation probability when the primary users are distributed as a MCP and the secondary users are distributed as a PPP. Numerical and simulation results indicate that the secondary user’s local connectivity has a performance degradation due to the heterogeneity of the secondary network, while the local connectivity is improved due to the heterogeneity of the primary network.

SmartHO: mobility pattern recognition assisted intelligent handoff in wireless overlay networks

Handoff management providing continuous mobility services is important for end-users in wireless overlay networks. The existing studies focus on improving the handoff performance with little attention to determine the current mobility pattern to provide different advanced services for end-users, and the handoff process is not intelligent as well. Due to the randomness and fuzziness of human mobility, predicting the mobility is still an open issue. In this paper, a mobility pattern recognition assisted intelligent handoff (SmartHO) is proposed. By exploring the regularity and rationality in the seemingly random daily itinerary and analyzing the typical mobility patterns, a spatial---temporal mobility pattern model is firstly constructed, and the mobility pattern recognition algorithm based on the joint space---time correlation then is designed. In different handoff cases, the specific handoff optimization strategies corresponding to the mobility patterns are employed to make the handoff process more intelligent. With the configurations from the authors real life, the simulations conducted on the NS-2 platform show that SmartHO outperforms FHMIPv6 in the critical handoff performance metrics.

Rate Allocation Based on Coalition Formation Game in Low Power Collaborative Transmission

To realize collaborative transmission in wireless overlay access networks, the question of rate allocation arises as how to divide the traffic flow among heterogeneous networks. Different networks role as game players and they try to transmit the traffic flow by a cooperative method. Power costs and transmission capabilities in heterogeneous networks are different according to terminal position, network load etc, so the grand coalition is not always beneficial and the coalition structure should be adjusted in time. With the power cost introduced in the utility function, the rate allocation is formulated in a coalition formation game framework in the paper. The stable coalition structure is formed with the merge-and-split rule, then the utility is distributed to different players and the transmission rates in different networks are determined. Such a process continues until the end of the traffic transmission. The theoretical and experimental results are presented to validate our proposed method. Compared with the Nash Bargaining Solution and the Shapley value, the coalition structure can be adjusted with the terminal position through the new scheme and then the highest coalition utility can be obtained with low power cost. Moreover, the proposed method turns to be the bargaining game framework if the power cost is not considered.

Improving Management Performance of P2PSIP for Mobile Sensing in Wireless Overlays

Future wireless communications are heading towards an all-Internet Protocol (all-IP) design, and will rely on the Session Initiation Protocol (SIP) to manage services, such as voice over IP (VoIP). The centralized architecture of traditional SIP has numerous disadvantages for mobile ad hoc services that may be possibly overcome by advanced peer-to-peer (P2P) technologies initially developed for the Internet. In the context of mobile sensing, P2PSIP protocols facilitate decentralized and fast communications with sensor-enabled terminals. Nevertheless, in order to make P2PSIP protocols feasible in mobile sensing networks, it is necessary to minimize overhead transmissions for signaling purposes, which reduces the battery lifetime. In this paper, we present a solution to improve the management of wireless overlay networks by defining an adaptive algorithm for the calculation of refresh time. The main advantage of the proposed algorithm is that it takes into account new parameters, such as the delay between nodes, and provides satisfactory performance and reliability levels at a much lower management overhead than previous approaches. The proposed solution can be applied to many structured P2P overlays or P2PSIP protocols. We evaluate it with Kademlia-based distributed hash tables (DHT) and dSIP

Multi-Antenna Spatial Multiplexing in Overlaid Wireless Networks: Transmission Capacity Analysis

Multi-Antenna Spatial Multiplexing in Overlaid Wireless Networks: Transmission Capacity Analysis

Case study on handoff strategies for wireless overlay networks

One of the most challenging topics for next‐generation wireless networks is the process of vertical handoff since many of wireless technologies overlap each other and build a heterogeneous topology. Several parameters, pertaining to user/application requirements and network conditions, such as data rate, service cost, network latency, speed of mobile, and etc. must be considered in the handoff process of heterogeneous networks along with RSSI information. In this paper, adaptive fuzzy logic‐based vertical handoff decision‐making algorithms are presented for wireless overlay networks which consist of GSM/GPRS/Wi-Fi/UMTS/WiMAX technologies. The parameters data rate, monetary cost, speed of mobile and RSSI information are processed as inputs of the proposed fuzzy‐based systems. According to these parameters, an output value, which varies between 1 and 10, is produced. This output value is utilized to determine whether a handoff process is necessary or not and to select the best candidate access point in the vicinity. The results show that, compared to the traditional RSSI‐based algorithm significantly enhanced outcomes can be achieved for both user and network as a consequence of the proposed fuzzy‐based handoff systems. The simulation results are also compared with those of classical MADM (Multiple Attribute Decision Making) method, i.e. SAW (Simple Additive Weighting). According to the results obtained, the proposed vertical handoff decision algorithms are able to determine whether a handoff is necessary or not, properly, and select the best candidate access network considering the aforementioned parameters. Moreover, fuzzy‐based algorithm noticeably reduces the number of handoffs compared to SAW‐based algorithm.

Throughput and delay scaling laws for mobile overlaid wireless networks

In this paper, we study the throughput and delay scaling laws over two coexisting mobile networks. The primary network consists of n randomly distributed primary nodes which can operate as if the secondary network is absent. However, the secondary network with a higher density m=nβ, β>1 is required to adjust its protocol. By considering that both the primary and the secondary networks move according to random walk mobility model, we propose a multi-hop transmission scheme, and show that the secondary network can achieve the same throughput and delay tradeoff scaling law as in stand-alone network Ds(m)=Θ(mλs(m)). Furthermore, for primary network, it is shown that the tradeoff scaling law is given by Dp(n)=Θ(nlognλp(n)), when the primary node is chosen as relay node. If the relay node is a secondary node, the scaling law is Dp(n)=Θ(nβlognλp(n)). The novelties of this paper lie in: (i) detailed study of the delay scaling law for the primary network in the complex scenario where both the primary and the secondary networks are mobile; (ii) the impact of buffer delay on the two networks due to the presence of preservation region. We explicitly analyze the buffer delay and obtain an expression as DSRII(m)=Θ(1/nβ−1as(m)).

WCayleyCCC: A Robust Wireless Overlay Network with Simple Routing and Small-World Features

Recent wireless systems research has focused on building highly usable data searching in wireless overlay networks. Short query paths, small routing tables, and robustness constitute the most prominent design objectives for the overlay topology. In this paper, we introduce a general group theoretic method and define a new Cayley graph. We then use these constructs to derive a novel wireless overlay structure. WCayleyCCC, our proposed overlay network, has many desirable features, including short query paths, compact routing tables, high clustering, and robustness. Because of its symmetry, our design offers simpler routing (searching) and several other desirable properties compared with many previously proposed wireless overlay networks, such as MChord. Performance evaluation results, reported in this paper, quantify the advantages of WCayleyCCC in terms of query path length, routing table size, clustering, and robustness relative to some recent proposals. WCayleyCCC is particularly useful in distributed computing under relatively stable conditions such as wireless mesh networks.

EVM as Generic QOS Trigger for Heterogeneous Wireless Overlay Networks

Fourth Generation (4G) Wireless System will integrate heterogeneous wireless overlay systems i.e. interworking of WLAN/ GSM/ CDMA/ WiMAX/ LTE/ etc with guaranteed Quality of Service (QoS) and Experience (QoE).QoS(E) vary from network to network and is application sensitive. User needs an optimal mobility solution while roaming in Overlaid wireless environment i.e. user could seamlessly transfer his session/ call to a best available network bearing guaranteed Quality of Experience. And If this Seamless transfer of session is executed between two networks having different access standards then it is called Vertical Handover (VHO). Contemporary VHO decision algorithms are based on generic QoS metrics viz. SNR, bandwidth, jitter, BER and delay. In this paper, Error Vector Magnitude (EVM) is proposed to be a generic QoS trigger for VHO execution. EVM is defined as the deviation of inphase/ quadrature (I/Q) values from ideal signal states and thus provides a measure of signal quality. In 4G Interoperable environment, OFDM is the leading Modulation scheme (more prone to multi-path fading). EVM (modulation error) properly characterises the wireless link/ channel for accurate VHO decision. EVM depends on the inherent transmission impairments viz. frequency offset, phase noise, non-linear-impairment, skewness etc. for a given wireless link. Paper provides an insight to the analytical aspect of EVM & measures EVM (%) for key management subframes like association/re-association/disassociation/ probe request/response frames. EVM relation is explored for different possible NAV-Network Allocation Vectors (frame duration). Finally EVM is compared with SNR, BER and investigation concludes EVM as a promising QoS trigger for OFDM based emerging wireless standards.

A Pre-Emptive Horizontal Channel Borrowing and Vertical Traffic Overflowing Channel Allocation Scheme for Overlay Networks

In this paper, a channel allocation scheme is studied for overlay wireless networks to optimize connection-level QoS. The contributions of our work are threefold. First, a channel allocation strategy using both horizontal channel borrowing and vertical traffic overflowing (HCB-VTO) is presented and analyzed. When all the channels in a given macro-cell are used, high-mobility real-time handoff requests can borrow channels from adjacent homogeneous cells. In case that the borrowing requests fail, handoff requests may also be overflowed to heterogeneous cells, if possible. Second, high-mobility real-time service is prioritized by allowing it to pre-empt channels currently used by other services. And third, to meet the high QoS requirements of some services and increase the utilization of radio resources, certain services can be transformed between real-time services and non-real-time services as necessary. Simulation results demonstrate that the proposed schemes can improve system performance.

Design and evaluation of flow handoff signalling for multihomed mobile nodes in wireless overlay networks

With the increasing deployment of wireless overlay networks, a mobile node with a range of network interfaces can be connected to multiple heterogeneous or homogeneous access networks simultaneously. Such host multihoming technology can be exploited to distribute (or hand off) application flows among the most appropriate interfaces and access networks dynamically to achieve end-to-end seamless, robust and even quality-of-service-aware communications for mobile users. It is essential that an efficient and effective flow handoff signalling scheme be in place. Nevertheless, little prior work has addressed this problem sufficiently in a systematic way and little performance evaluation is readily available. We propose a set of signalling procedures for a comprehensive, flexible yet standard-oriented flow handoff solution. Two candidate schemes are designed by extending and optimising related IETF work based on Mobile IPv6 or Network Mobility (NEMO). Theoretical analyses are performed and numerical results are then presented with a focus on signalling loads to compare the two proposals and to demonstrate that the designs can largely meet the requirements on desired signalling performance. Preliminary implementations and experimental results are also reported to validate the concepts of the designs, investigate the flow handoff signalling delays and verify the effectiveness of the policy-based flow handoff support for typical real-time and non-real-time applications.

Context-Aware Streaming Video System for Vertical Handover over Wireless Overlay Network

Streaming video would become a popular form of transferring video over next-generation wireless overlay networks. As transport protocol for streaming video, TCP- friendly rate control (TFRC) is generally used. Using both TCP congestion response function and current network conditions, TFRC adjusts transmission rate so as to achieve maximum TCP-friendly throughput. However, TFRC is less responsive to changes in handover between wireless overlay networks, since it was designed for applications that would prefer to maintain a slowly-changing transmission rate. Also, the transferred streaming video could be degraded owing to the service interruption time occurred during vertical handover (VHO) process. In this paper, a new cross-layer TFRC streaming video system is demonstrated for VHO over wireless overlay network. The proposed system consists of a VHO based TFRC server and a TFRC client with VHO decision function. The proposed TFRC server uses explicit VHO messages for faster rate adaptation to a new target network. Also, the proposed TFRC client decides on switching time between different overlay networks by using handoff metrics obtained from multi-layers. The simulation results show that the proposed streaming video system provides better QoS and throughput supports than the conventional TFRC scheme during VHO .

TCP Congestion Control with ACK-Pacing for Vertical Handover

In this paper, we discuss TCP performance in a wireless overlay network where wireless LANs and cellular networks are integrated. In the overlay network, vertical handover, where a mobile node changes its access link during a session, is one of the most important technologies. When a vertical handover occurs, throughput performance of a TCP flow is degraded due to not only packet losses during the handover, but drastic change of its bandwidth-delay product. In this paper, we propose an ACK-pacing mechanism for TCP congestion control to improve the performance degradation. The proposed system is receiver-driven, so no modification is required to the mechanism of TCP sender. In the proposed system, a TCP receiver adjusts a transmission rate of ACKs according to the relationship between bandwidth-delay products before and after a handover. Since the ACK-clocking mechanism of TCP adjusts the transmission rate of TCP segments, the TCP receiver can seamlessly adjust its congestion window size to the new bandwidth-delay product. Computer simulation results show that the proposed system can improve the TCP performance during the vertical handover.

Dynamic guard channel allocation scheme for calls in WONs

Future wireless networks will provide ubiquitous communication services to a large number of mobile users. The design of such networks is based on heterogeneous wireless overlay networks that allow efficient use of the limited available spectrum, and also cover different ranges of coverage areas. A dynamic guard channel allocation scheme for calls in wireless overlay networks is developed. The new scheme considers the mobility, current location of mobile terminals, and bandwidth status in allocating bandwidth for new calls in order to guarantee the quality of service for all calls.

Improving handoff performance in wireless overlay networks by switching between two-layer IPv6 and one-layer IPv6 addressing

In wireless/mobile networks, users freely change their service points, while they are communicating with other users. In order to support the mobility of mobile nodes, Mobile IPv6 (MIPv6) is proposed by the Internet Engineering Task Force (IETF), in which a mobile node must inform its home agent the binding of its home address and the current care-of-address (CoA). The home agent forwards packets to CoA when it receives packets for the mobile node. There is a significant problem in MIPv6 due to its inability to support micromobility caused by long delays and high packet losses during a handoff. Hierarchical Mobile IPv6 (HMIPv6) is proposed to separate mobility into micromobility [within one domain or within the same mobility anchor point (MAP)] and macromobility (between domains or between MAPs). HMIPv6 reduces handoff latency by employing a hierarchical network structure and minimizing the location update signaling with external network. The two-layer network structure of HMIPv6 is very suitable for supporting the vertical handoff and the horizontal handoff in wireless overlay networks. Wireless overlay networks can consist of two layers. Functions of access routers can be implemented in low-layer networks and functions of MAPs can be implemented in high-layer networks. Or we can have an access router collocated with a low-layer network and an MAP collocated with a high-layer network. In either way, the micromobility in HMIPv6 is equal to the horizontal handoff in wireless overlay networks and the macromobility in HMIPv6 is equal to the vertical handoff in wireless overlay networks. However, a significant delay still occurs in macromobility management. This paper considers handover operations. We analyze the handoff delay and find that the DAD time represents a large portion of handoff delay. We also note that we can assign a unique on-link care-of address (LCoA) to each mobile node and switch between one-layer IPv6 and two-layer IPv6 addressing. By this way, we propose a Stealth-time HMIP (SHMIP) which can reduce the effect of the DAD time on the handoff delay and, thus, reduce the handoff time significantly. To further reduce packet losses, we also adopt prehandoff notification to request previous MAP to buffer packets for the mobile node. By simulations, we show that the proposed scheme can realize low handoff delays and low packet losses during macromobility.