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The adoption of wireless communications and, in particular, Wi-Fi, at the lowest level of the factory automation hierarchy has not increased as fast as expected so far, mainly because of serious issues concerning determinism. Actually, besides the random access scheme, disturbance and interference prevent reliable communication over the air and, as a matter of fact, make wireless networks unable to support distributed real-time control applications properly. Several papers recently appeared in the literature suggest that diversity could be leveraged to overcome this limitation effectively. In this paper a reference architecture is introduced, which describes how seamless link-level redundancy can be applied to Wi-Fi. The framework is general enough to serve as a basis for future protocol enhancements, and also includes two optimizations aimed at improving the quality of wireless communication by avoiding unnecessary replicated transmissions. Some relevant solutions have been analyzed by means of a thorough simulation campaign, in order to highlight their benefits when compared to conventional Wi-Fi. Results show that both packet losses and network latencies improve noticeably., preprint, 13 pages (Winner of the "2017 Best Paper Award for the IEEE Transactions on Industrial Informatics")

In this paper, we propose a method to estimate user’s movement path using Wi-Fi authentication log. Large organization often have many Wi-Fi access points (APs) which are centrally managed by a wireless LAN controller, usually with roaming feature. While the user moves around the area covered by the Wi-Fi network, the AP they connect to will change. Each time the connected AP change, an authentication such as 802.1x is performed. The credentials such as user ID and password are sent to an authentication server via the controller. This allows the controller to know who has connected to which access point and when. Our method is to track a certain person’s movement path from the authentication log afterword. Assuming the authentication log is recorded where the roaming occurred, the area where the device was at point could be estimated. By combining with the structure of the building, we are able to roughly estimate the user’s movement path.

In this chapter, we investigate the channel assignment problem (CAP) that is critical in wireless communication applications. Researchers strive to develop algorithms that are able to effectively assign limited channels to a number of cells with nonhomogeneous demands. Inspired by the recent success of metaheuristics, a hybrid ant colony optimisation (HACO) is proposed in this chapter. The HACO embodies several problem-dependent heuristics including ordering, sequential packing, and a local optimiser into an ACO framework. The advantages of this hybrid are two-fold. First, the EMC constraints can be effectively handled by the problem-dependent heuristics instead of using a penalty function as observed in other works which may lengthen the elapsed time in order to reach convergence. Second, the embedded heuristics serve as intensification strategies conducted by the metaheuristic framework and help improve the generated solutions from different view points. The performance of the HACO algorithm is evaluated on the Philadelphia benchmark set, such that it can be compared to that of existing approaches. It is observed from the experimental results that the HACO algorithm can solve optimally six of the eight benchmark problems and obtain near-optimal solutions for the other two problems which have been known to be the most difficult in the literature. For practical reasons, we only allow the HACO algorithm to run for a relatively short time compared to that used by other approaches. It is plausible to get a better result if more computational time is allocated.

© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works On-chip communication remains as a key research issue at the gates of the manycore era. In response to this, novel interconnect technologies have opened the door to new Network-on-Chip (NoC) solutions towards greater scalability and architectural flexibility. Particularly, wireless on-chip communication has garnered considerable attention due to its inherent broadcast capabilities, low latency, and system-level simplicity. This work presents ORTHONOC, a wired-wireless architecture that differs from existing proposals in that both network planes are decoupled and driven by traffic steering policies enforced at the network interfaces. With these and other design decisions, ORTHONOC seeks to emphasize the ordered broadcast advantage offered by the wireless technology. The performance and cost of ORTHONOC are first explored using synthetic traffic, showing substantial improvements with respect to other wired-wireless designs with a similar number of antennas. Then, the applicability of ORTHONOC in the multiprocessor scenario is demonstrated through the evaluation of a simple architecture that implements fast synchronization via ordered broadcast transmissions. Simulations reveal significant execution time speedups and communication energy savings for 64-threaded benchmarks, proving that the value of ORTHONOC goes beyond simply improving the performance of the on-chip interconnect.

In wireless networks, seamless roaming allows a mobile user (MU) to utilize its services through a foreign server (FS) when outside his home server (HS). However, security and efficiency of the aut...

Wireless LAN controller (WLC) is used to manage and control Access points (APs) in Wireless local area network (WLAN). Proxy mobile IPv6 (PMIPv6) protocol supports network-layer mobility in WLC based WLAN. However, it introduces extra delay in delivering packets from the APs to the WLC. We use Mobile access gateway (MAG) chain to reduce packet delay. The handoff delay and packet delivery delay under the proposed scheme are derived, based on which we formulate the delay minimization problem whose solution leads to the optimal MAG chain length. Numerical analysis results indicate that the proposed scheme outperforms the existing scheme in terms of delay in the case when the delay between Local mobility anchor (LMA) andWLC is relatively greater than the delay between two neighboring WLCs. The proposed scheme is able to reduce packet loss resulting from the traditional handoff procedure introduced in the PMIPv6 protocol and that due to delay limitation.

Sensor network protocol stacks require the addition or adjustment of functions based on customer requirements. Sensor network protocols that require low delay and low packet error rate (PER), such as wireless control networks, often adopt time division multiple access (TDMA). However, it is difficult to add or adjust functions in protocol stacks that use TDMA methods. Therefore, to add or adjust functions easily, we propose NES-SOURCE, a compact wireless control network protocol with a fast path-switching function. NES-SOURCE is implemented using carrier sense multiple access/collision avoidance (CSMA/CA) rather than TDMA. Wireless control networks that use TDMA prevent communication failure by duplicating the communication path. If CSMA/CA networks use duplicate paths, collisions occur frequently, and communication will fail. NES-SOURCE switches paths quickly when communication fails, which reduces the effect of communication failures. Since NES-SOURCE is implemented using CSMA/CA rather than TDMA, the implementation scale is less than one-half that of existing network stacks. Furthermore, since NES-SOURCE’s code complexity is low, functions can be added or adjusted easily and quickly. Communication failures occur owing to changes in the communication environment and collisions. Experimental results demonstrate that the proposed NES-SOURCE’s path-switching function reduces the amount of communication failures when the communication environment changes owing to human movement and others. Furthermore, we clarify the relationships among the probability of a changing communication environment, the collision occurrence rate, and the PER of NES-SOURCE.

The recent popularization of mobile devices has increased the amount of communication traffic. Hence, it is necessary both in academia and industry to research load distribution methods for mobile networks. An evaluation environment for large-scale networks that behaves like a practical system is necessary to evaluate these methods, and either a physical environment or simulation environment can be used. However, physical and simulation environments each have their advantages and disadvantages. A physical environment is suitable for practical operation because it is possible to obtain data from a real environment. In contrast, the cost for a large number of nodes and the difficulty of field preparation are its disadvantages. Reproducing radio propagation is also a challenge. Network simulators solve the disadvantages of the physical environment by modeling the entire evaluation environment. However, they do not exactly reproduce the physical environment because the nodes are abstracted. This article presents an evaluation environment that combines a network simulator and virtual machines with virtual wireless Local Area Network (LAN) devices. The virtual machines reproduce the physical environment with high fidelity by running the programs of the physical machines, and the virtual wireless LAN devices make it possible to emulate wireless LAN communication using default operating system drivers. A network simulator and virtual machines also reduce the cost for nodes, ease the burden of field preparation, and reproduce radio propagation by modeling the evaluation environment. In the evaluation, the proposed method decreased the difference from the physical environment to 5% in terms of transmission control protocol throughput. In the case of user datagram protocol, the proposed method decreased the difference from the physical environment down to 1.7%. The number of virtual machines available on a host machine and the practical use of the proposed method are also discussed.

At present, the need for internet access in public area using wireless connections is increasing drastically and this should be supported by good network infrastructure. Wireless network is one of the best alternative in building a practical internet network. WDS is a system to develop wireless internet network without having to use cable as its backbone for access point but instead utilize wireless path from its access point. The problems that often arise in the design of wireless LAN network is the poor signal received by the user due to the installation of an access point that is poor location-wise. This is because at some point it is very difficult to install Access point using cable because the distance is too far from the existing router. In this paper, we propose to use three scenario of WDS mode to compare its performance. We investigate three different topology policy models of the WDS Bridge point-to-point, WDS Bridge point to multipoint and WDS repeater. The use of these three topologies aims to reach locations that are not covered by wireless LAN network, in addition this method can save the use of network resources such as LAN cables. Based on the simulation results, it is found that the topology point to point gives better value but it generated higher delays. The delay generated on point to point is higher than other topologies. Meanwhile, the measurement results are not much different on topology point to multipoint with repeater topology. The point to multipoint topology is slightly better than the repeater of the three QoS parameters.

The multi-packet reception (MPR) technique enables access points to correctly receive simultaneously transmitted packets. Therefore, the network saturation throughput can be significantly improved by introducing MPR into wireless local area networks (WLANs). In this letter, we develop a novel analytical model to evaluate the saturation throughput of a WLAN with MPR. In contrast to previous models, we adopt the stationary distribution of backoff counter value after a generic overlapping transmission process to characterize the behavior of a contending station. Then, we derive the saturation throughput based on this distribution. Comparisons with simulation results show that our analytical model provides a close evaluation of the saturation throughput. Moreover, the impacts of several parameters on the saturation throughput are also investigated using the proposed model.

Although full-duplex transmission can be helpful for enhancing wireless link capacity, it may require extra energy to overcome the residual self-interference. In this paper, we investigate the tradeoff between energy consumption and delay in a multichannel full-duplex wireless LAN. The goal is to minimize the energy consumption while keeping the traffic queues stable. With Lyapunov optimization, we develop a throughput optimal online scheme to achieve the goals with optimized channel assignment, transmission scheduling, and transmission mode selection. We study the influence of full-duplex transmissions on the network capacity region, prove the optimality of the proposed algorithm, and derive upper bounds for the average queue length and energy consumption, which demonstrate the energy-delay tradeoff in such systems. The proposed algorithm and the capacity region analysis are validated with simulations.

Just like Ethernet before, IEEE 802.11 is now transcending the borders of its usage from the office environment toward real-time communication on the factory floor. However, similar to Ethernet, the availability of synchronized clocks to coordinate and control communication and distributed real-time services is not a built-in feature in WLAN. Over the years, this has led to the design and use of a wide variety of customized protocols with varying complexity and precision, both for wired and wireless networks, in accordance with the increasingly demanding requirements from real-time applications. This survey looks into the details of synchronization over IEEE 802.11 with a particular focus on the infrastructure mode which is most relevant for industrial use cases. It highlights the different parameters which affect the performance of clock synchronization over WLAN and compares the performance of existing synchronization methods to analyze their shortcomings. Finally, it identifies new trends and directions for future research as well as features for wireless clock synchronization which will be required by the applications in the near future.

In this paper, we design a protocol to communicate data reliably in harsh environments. Robust data transmission with high accuracy is imperative in industrial wireless networks. The communication over a radio link in such environment gets affected by noisy surroundings. In order to maintain the high quality of services in these networks, cooperation and adaptability at a cross layer are introduced in proposed scheme. The collaborative coding used in proposed protocol; combine the data packets of network sources to improve channel capacity. This reduces the routing overheads and enhances the network gains along with the introduction of minimum delay. The performance of the network is evaluated using parameters such as throughput, reliability, channel utilization, energy, and latency for different network sizes. Results of the proposed protocol are observed and compared with the industrial wireless communication standard Wireless HART (WHART). In rest of the paper, the proposed ‘Cross Layer Cooperative Industrial Protocol’ will be termed as “XLCI Protocol”. Results shows that XLCI protocol improves the network throughput by 53%, reliability by 40%, channel capacity by 40%, also energy consumption is reduced by 70% and latency is improved by 46%, as compared to WHART.

Device authentication is a critical and challenging issue for the emerging Internet of Things (IoT). One promising solution to authenticate IoT devices is to extract a fingerprint to perform device authentication by exploiting variations in the transmitted signal caused by hardware and manufacturing inconsistencies. In this paper, we propose a lightweight device authentication protocol [named speaker-to-microphone (S2M)] by leveraging the frequency response of a speaker and a microphone from two wireless IoT devices as the acoustic hardware fingerprint. S2M authenticates the legitimate user by matching the fingerprint extracted in the learning process and the verification process, respectively. To validate and evaluate the performance of S2M, we design and implement it in both mobile phones and PCs and the extensive experimental results show that S2M achieves both low false negative rate and low false positive rate in various scenarios under different attacks.

In this paper, a novel Medium Access Control (MAC) protocol for industrial Wireless Local Area Networks (WLANs) is proposed and studied. The main challenge in industry automation systems is the ultra-low network latency with a target upper bound in the order of 1 ms while maintaining high network reliability and availability. The novelty of the proposed wireless MAC protocol resides in its similar latency performance as its counterpart in wired industrial LAN. First, the functional design of the MAC protocol is introduced. Then its performance results gained from hardware implementation (SystemC and VHDL) on an FPGA platform are presented. Finally, a real-time communication module which achieves the ultra-low latency required in industrial automation is described.

The time to frequency protocol is the first frequency-domain contention protocol in wireless LANs, and has attracted a great deal of attention, since it can improve channel efficiency significantly. However, this protocol mainly provides a uniform service by letting each user conduct channel contention over the same frequency-domain range. In this paper, we first propose a novel weighted frequency-domain contention (WFC) scheme for service differentiation. In WFC, different frequency-domain ranges are assigned to different users to achieve weighted channel access opportunity, and a signature-assisted method is employed to completely exclude collisions. We then develop a theoretical framework to study the performance of WFC. With this framework, we can evaluate system throughput, optimize system parameter settings, and achieve proportional fairness. Extensive simulations verify that our theoretical model is very accurate.

A load balancing mechanism can adjust the load distribution among access points (APs) and improve resource utilization for dense wireless local area networks (WLANs). In this paper, we propose a semi-matching-based load balancing scheme for the IEEE 802.11 dense WLANs. The proposed scheme runs in a centralized controller. The controller judges whether the load is unevenly distributed according to the collected channel busy time ratio information of the entire network, and triggers the load balancing mechanism accordingly. In order to realize load balancing among APs and maximize the overall network throughput, we model the station to AP association problem as a weighted bipartite graph matching problem and find the optimal semi-matching using the Kuhn-Munkres (K-M) algorithm. Simulation results show that the proposed scheme achieves performance improvement comparing with traditional schemes.

Serving a Dynamic Host Configuration Protocol (DHCP) request with some additional services package may cause a conventional wireless router consumes more memory resources. High memory usage would break the DHCP request process if the wireless router becomes busy. In this paper, the centralized DHCP servers is proposed to overcome this situation. In term of Cisco product there is Wireless LAN Controller that can solve that situation. In this research, we suggest an open source solution for this situation. The original master and backup algorithm are modified to reserve DHCP request. DHCP master server serves many connected network under the main router. The modification of original master and backup algorithm is located in resource allocation calculation in the main router. Computer agent checks the memory of the main router to decide a diversion of DHCP pool to the backup router. Run test results show that the proposed method has an acceptable lease time. It can handle 254 DHCP requests within only 0.6 seconds longer than the conventional method. Further, the number of client that could be reserved by the proposed method is better than the method used in OpenWRT router, which is about 100 more clients successfully receive their IP.

A simple wavelength-division-multiplexing passive optical network is proposed in this paper. By simply designing the remote node, the virtual-ring local area network (LAN) services transmitted among optical network units are realized. And coupled with conventional broadband light source and spectrum-sliced technology, the network can support the LAN services in a cost-effective way. More particularly, the whole wavelength band of downstream services can also be reused for LAN services by selecting a special port of Arrayed Waveguide Grating. The simulation results indicate the 10 Gb/s LAN communication in this network can be achieved with the help of forward error correction.

Wireless networks are today employed as complementary access technology, implemented on the last hop towards the Internet end-user. The shared media that wireless deployments provide and which is relevant to interconnect multiple users has a limited technical design, as only one device can be served per unit of time, design aspect that limits the potential applicability of wireless in dense environments. This paper proposes and evaluates a novel MAC-layer mechanism that extends current wireless networks with the possibility to perform downstream transmission to multiple devices within a single transmission time-frame, resulting in improved fairness for all devices. The mechanism, which is software-defined, is backward-compatible with current wireless standards and does not require any hardware changes. The solution has been validated in a realistic testbed, and the paper provides details concerning the computational aspects of our solution; a description of the implementation; and results extracted under different realistic scenarios in terms of throughput, packet loss, as well as jitter.

In uplink wireless local area networks (WLANs) with multi-packet reception (MPR) which can be implementable with multi-user multiple-input multiple-output techniques, partial successes among simultaneous transmissions may frequently occur due to frame errors. This causes an increase in the contention window size only for the failed stations (STAs) under the binary exponential backoff algorithm, and a severe unfairness problem in terms of channel access opportunity may occur among the STAs with different frame error rates. In this letter, we propose a novel medium access control (MAC) protocol to support fair channel access in uplink WLANs with MPR. Analysis and simulation results show that our proposed MAC protocol can significantly improve the fairness in terms of both channel access opportunity and throughput.

In wireless local area network, all transmissions are preceded by clear channel assessment (CCA), which determines the availability of wireless medium. Ideally, CCA should enable concurrent transmissions, whenever possible, to improve network capacity via spatial reuse. However, current CCA method is inherently limited in exploiting spatial reuse. Only the received signal strength of an incoming frame is utilized for CCA, and hence, the feasibility of a concurrent transmission should be determined without the knowledge of the frame’s transmitter, the corresponding receiver, etc. In this letter, we propose a novel CCA method which utilizes additional information delivered in the physical layer header to properly determine the feasibility of concurrent transmissions. Simulation results show that the proposed method increases network throughput by up to 54% by promoting spatial reuse.

As a promising solution for handling super dense wireless networks, wireless local area networks (WLANs) have been intensively considered due to their wide availability. However, the contention-based MAC protocol in WLANs should be modified because of its inefficiency. To this end, we consider a recently proposed novel MAC protocol called the renewal access protocol (RAP). With the RAP, we analyze two strategies for resolving collisions efficiently and achieving optimal throughput performance in super dense WLANs: strategies without and with grouping. First, we analyze the asymptotic behavior of the RAP itself (i.e., without grouping) as the number of terminals goes to infinity. We show that the RAP can achieve optimal throughput even in super dense WLANs and the relevant optimal access probability can be derived in a closed form. Second, we propose a grouping strategy in the RAP called the grouped RAP (G-RAP). While a grouping strategy in the IEEE 802.11ah standard is based on time division, our G-RAP is based on transmission attempts. So the G-RAP does not waste channel resources. We show that the G-RAP achieves the optimal network throughput for any group structure if terminals use the optimal access probability that we derive. Our analytical results are validated by simulation.

Cooperation is always required in every filed of communication nowadays because neither a single layer, nor a single protocol is able to perform well in a network. In this work, cooperation has been performed using Medium Access Layer (MAC) using the concept of Rely Node. Although it has been claimed previously that cooperative scheme always promises a higher throughput and lower delay performances still here, a medium access control scheme known as C-MAC (Customize-Medium Access Control) has been proposed, where the neighbours, i.e. the relay node is selected not only assuming higher data rate, but also based on its reliability factor, power constraints, throughput, packet forwarding ratio, delay, which leads to motivate for better decision to deciding whom to co-operate with. The overall system has become reliable with an increased lifetime of the network.

Network virtualization is an emerging technology for solving the rigidity of the physical network infrastructure. The innovative technique virtualizes all resources in the network, including the network links and nodes, and provides a number of virtual networks on a single network infrastructure. In order to realize a virtual network, a thorough and complete monitoring of all resources in the network should be performed firstly. OpenFlow is an open source stack for network virtualization. However, it is impossible to apply OpenFlow to AP-based legacy wireless LAN environment because OpenFlow targets ethernet-based LAN environment. In this paper, we implement an adaptor-styled virtual switch for AP-based wireless LAN through customizing the Open vSwitch which is a virtual switch of OpenFlow. The evaluation test results show that the implemented OpenFlow stack operates successfully. The implemented OpenFlow stack can now be plugged immediately in existing AP-based wireless LAN environment and plays network resource monitoring. In the future, we can develop wireless LAN virtualization applications on the wireless OpenFlow stack.