Beacon Frames Research Articles

클러스트-트리 무선센서네트워크에서 비콘 프레임 충돌 회피를 위한 멀티채널 시분할 스케줄링

클러스트-트리 무선센서네트워크에서 비콘 프레임 충돌 회피를 위한 멀티채널 시분할 스케줄링

Low Duty-Cycling MAC Protocol for Low Data-Rate Medical Wireless Body Area Networks.

Wireless body area networks (WBANs) are severely energy constrained, and how to improve the energy efficiency so as to prolong the network lifetime as long as possible is one of the most important goals of WBAN research. Low data-rate WBANs are promising to cut down the energy consumption and extend the network lifetime. Considering the characteristics and demands of low data-rate WBANs, a low duty-cycling medium access control (MAC) protocol is specially designed for this kind of WBAN in this paper. Longer superframes are exploited to cut down the energy consumed on the transmissions and receptions of redundant beacon frames. Insertion time slots are embedded into the inactive part of a superframe to deliver the frames and satisfy the quality of service (QoS) requirements. The number of the data subsections in an insertion time slot can be adaptively adjusted so as to accommodate low data-rate WBANs with different traffic. Simulation results show that the proposed MAC protocol performs well under the condition of low data-rate monitoring traffic.

A detection method of WLAN security mechanisms based on MAC frame resolution

Security mechanism detection is not only an important content of vulnerabilities evaluation but also the foundation of key strength test for wireless local area network (WLAN). This paper analyzes the specifications of WLAN security mechanisms and points out the defects in design of security mechanisms detection algorithm based on the standards. By capturing and analyzing a large number of Beacon frames from different vendor’s access points (APs), we summarize the relevant fields and information elements in a Beacon frame, and present their values or status when an AP is set to every specific security mechanism. A detection algorithm of WLAN security mechanisms is proposed based on the experimental study result and the pseudo code of a reference implementation for the algorithm is designed. The validity of the algorithm is illustrated by examples, which shows it can detect every WLAN security mechanism accurately.

Exploiting Delay-Aware Load Balance for Scalable 802.11 PSM in Crowd Event Environments

This paper presents ScaPSM (i.e., Scalable Power-Saving Mode Scheduler), a design that enables scalable competing background traffic scheduling in crowd event 802.11 deployments with Power-Saving Mode (PSM) radio operation. ScaPSM prevents the packet delay proliferation of previous study, if applied in the crowd events scenario, by introducing a new strategy of adequate competition among multiple PSM clients to optimize overall energy saving without degrading packet delay performance. The key novelty behind ScaPSM is that it exploits delay-aware load balance to control judiciously the qualification and the number of competing PSM clients before every beacon frame’s transmission, which helps to mitigate congestion at the peak period with increasing the number of PSM clients. With ScaPSM, the average packet delay is bounded and fairness among PSM clients is simultaneously achieved. ScaPSM is incrementally deployable due to only AP-side changes and does not require any modification to the 802.11 protocol or the clients. We theoretically analyze the performance of ScaPSM. Our experimental results show that the proposed design is practical, effective, and featuring with significantly improved scalability for crowd events.

Modelling and analysis data fragmentation in IEEE 802.15.4 slotted CSMA/CA protocol without ACK mode

The low-rate wireless personal area networks (WPANs), as wireless sensor networks (WSNs), suffer from many constraints. The IEEE 802.15.4 standard proposes the slotted CSMA/CA as a communication channel access mechanism with collision avoidance that take into account the constraints of WPANs. In this paper, we propose to introduce a data fragmentation mechanism into slotted CSMA/CA to improve a bandwidth utilisation. The novelty, in this paper, is the use of the fragmentation mechanism to replace an acknowledgement frame after the transmission of the fragment and the remaining frame. The beacon frame is used to confirme the success transmission of a data fragment. To evaluate the performances of our proposition, we have developped a three dimension Markov chain which modelises the behaviour of the node using IEEE 802.15.4 with data fragmentation mechanism without using an ACK frame. The analytical results of the network throughput and the transmission success delay demonstrate the improvement of the bandwidth occupation.

Energy‐efficient beacon listening scheme for periodic vital signal monitoring

A new energy-efficient beacon listening scheme with a medium access control protocol is proposed for periodic vital signal monitoring in a wireless body area network system. The conventional system receives every beacon frame to adjust the protocol context; however, the proposed scheme receives only the necessary beacon frames. As a result, power consumption decreases by reducing idle listening times. The simulation results demonstrate that the proposed scheme reduces power consumption of the beacon mode to almost that of the non-beacon mode. Compared with the normal beacon mode, it reduces the power consumption by 25% when the traffic model is assumed to be electrocardiogram (ECG). This is suitable for devices monitoring periodic data such as an ECG application.

Regrouping algorithm to alleviate the hidden node problem in 802.11ah networks

An IEEE 802.11ah network has been designed to service a wide range of sensor network applications where a single access point (AP) covers a transmission range of up to 1 km and needs to support more than 8000 nodes. As a result, it has much more hidden node pairs compared to conventional 802.11a/b/g/n/ac networks. In addition, since nodes in power saving mode wake up simultaneously to send frames after receiving a beacon frame from the AP, the hidden node problem can become worse, resulting in frequent packet collisions and performance degradation. The 802.11ah standard proposes a group-based contention scheme to resolve the performance degradation problem, but it cannot resolve it appropriately.In this paper, we analyze the harmful impact of the hidden node problem on network performance and propose a new grouping algorithm to alleviate the performance degradation. Our proposed hidden matrix based regrouping (HMR) algorithm first finds hidden node pairs, and generates a hidden node matrix accordingly. Then it regroups hidden nodes to alleviate the hidden node problem using the hidden node matrix. Through extensive simulations, we show that our HMR algorithm eliminates most of hidden node pairs, thereby improving the performance of the 802.11ah network significantly in terms of the number of hidden node pairs and power-save poll (PS-Poll) transmission end time.

데이터링크 트리거에 의한 IP 핸드오버 성능 개선

In the traditional wireless LAN model, scan procedure to search a new AP starts when the predefined number of Rx failure of beacon frames are occurred. In this case, lots of data packet loss occur during MN`s handover because loss of the relatively longer data packet starts before the small-sized beacon loss. Newly developed scanning mechanism in this paper has the beacon counter that increases when the Rx power level of beacon frame is less than the threshold and the previous rx power level. New scan procedure starts when the counter exceeds the predefined number. Beacon Rx power threshold is verified and performance of the new WLAN model is evaluated under UDP and TCP traffic environment.

Distributed channel selection scheme based on the number of interfering stations in WLAN

In contention-based wireless local area networks (WLAN), adjacent WLAN access points (APs) and stations (STAs) using the same channel may degrade their performance due to contention. To solve this problem, researchers have studied various distributed channel selection schemes, where APs select the least congested channel among all available channels. However, the existing distributed channel selection schemes rarely consider contention from upstream transmission of STAs. Therefore, it is difficult to find the least congested channel in a WLAN environment where both upstream and downstream transmissions exist. In this paper, we propose a novel distributed channel selection scheme which decides a channel with minimum number of interfering STAs as the least congested channel. Unlike the existing schemes, the proposed scheme considers the contention from both downstream and upstream transmissions. In the proposed scheme, an AP can perceive the number of interfering STAs by receiving the beacon frames from its neighboring APs. For practical implementation of our proposed scheme, we also define the additional information elements of the beacon frame according to the IEEE 802.11 standard. By performing a system level simulation and experiment using a test bed, we evaluate and analyze the performance of the proposed scheme by comparing it with that of the least congested channel selection (LCCS) and the client-assisted channel assignment optimization (CACAO) schemes. The simulation result shows that the proposed scheme increases the network throughput by 11% and 20% compared to the LCCS and CACAO schemes, respectively. Under test environment, we confirm that the proposed scheme can enhance the data rate of AP up to three times comparing to that of the LCCS scheme.

A Beacon Transmission Power Control Algorithm Based on Wireless Channel Load Forecasting in VANETs.

In a vehicular ad hoc network (VANET), the periodic exchange of single-hop status information broadcasts (beacon frames) produces channel loading, which causes channel congestion and induces information conflict problems. To guarantee fairness in beacon transmissions from each node and maximum network connectivity, adjustment of the beacon transmission power is an effective method for reducing and preventing channel congestion. In this study, the primary factors that influence wireless channel loading are selected to construct the KF-BCLF, which is a channel load forecasting algorithm based on a recursive Kalman filter and employs multiple regression equation. By pre-adjusting the transmission power based on the forecasted channel load, the channel load was kept within a predefined range; therefore, channel congestion was prevented. Based on this method, the CLF-BTPC, which is a transmission power control algorithm, is proposed. To verify KF-BCLF algorithm, a traffic survey method that involved the collection of floating car data along a major traffic road in Changchun City is employed. By comparing this forecast with the measured channel loads, the proposed KF-BCLF algorithm was proven to be effective. In addition, the CLF-BTPC algorithm is verified by simulating a section of eight-lane highway and a signal-controlled urban intersection. The results of the two verification process indicate that this distributed CLF-BTPC algorithm can effectively control channel load, prevent channel congestion, and enhance the stability and robustness of wireless beacon transmission in a vehicular network.

Autonomous and adaptive beaconing strategy for multi‐interfaced wireless mobile nodes

AbstractAd hoc wireless communications rely on beaconing to manage and maintain several network operations and to share relevant network parameters among network nodes. Beacon frames are sent at the start of each beacon interval. The frequency of beaconing depends on whether beacon intervals are fixed size or may be adapted and regulated according to the perceived network and workload conditions. On the other hand, current mobile nodes usually embed several heterogeneous wireless interfaces that urge the design of an adaptive beaconing strategy. In this paper, we propose an autonomous and adaptive beaconing strategy for multi‐interfaced mobile wireless nodes that is capable of regulating the beacon interval size dynamically according to the perceived network conditions. The proposed strategy is based on a joint dynamic estimation of both the announcement traffic indication message (ATIM) window and the beyond‐ATIM window sizes for each beacon interval. Extensive simulations were conducted using OMNeT++ to ascertain the improvements achieved by autonomously regulating the entire beacon interval to take into account the network and workload conditions. Obtained results showed that the two proposed approaches improve significantly the efficiency of the network in terms of throughput, end‐to‐end delay, and power consumption. The proposed fixed beacon interval (fixed‐BI) approach stands as an enhanced version of the power‐saving multi‐channel MAC protocol (PSM‐MMAC). The proposed variable beacon interval (variable‐BI) approach, which regulates dynamically both of the ATIM and the beyond‐ATIM windows, outperforms both the fixed‐BI and the PSM‐MMAC. In particular, under nominal traffic loads, the end‐to‐end delay of the variable‐BI is much lower than those provided by the fixed‐BI and PSM‐MMAC. Copyright © 2015 John Wiley & Sons, Ltd.

On Minimizing Energy Consumption of Duty-Cycled Wireless Sensors

This letter considers an energy consumption minimization problem of duty-cycled wireless sensors which are associated with a central controller, say an access point (AP), in a single-hoped synchronous wireless sensor network (WSN). The cost function we propose consists of the energy consumed during periodic wake-ups for wireless sensors to check a beacon frame from the AP and the one consumed for them to receive packets waiting in the AP's queue. This letter provides an optimal sleep interval as a closed form solution of minimizing energy consumption, which is expressed as mean packet inter-arrival times, mean packet transmission times over erroneous wireless channel, and power consumption at each wake-up and a packet transmission.

Beacon-based channel assignment and jammer mitigation for MANETs with multiple interfaces and multiple channels

The capability of accessing multiple channels through multiple interfaces improve network capacity and is desirable for future Mobile Ad-Hoc Networks (MANETs). However, due to the presence of jammers as well as mobility and ad-hoc features, MANETs require distributed and efficient resource management for channel assignment. To address the channel assignment problem, which is a non-deterministic polynomial-time hard (NP-hard) problem, we propose a heuristic algorithm called Channel Assignment and JAmmer Mitigation (CA-JAM). The CA-JAM algorithm assigns a distinct channel for every interface of one station, and then all stations exchange the assignment information through beacon frames on every individual interface. When one station receives a beacon, the station organizes the information into tables. Therefore, each station, distributively, uses the table to reduce the number of neighboring stations using the same channel to avoid interference which in turn improves the throughput. The tables are also used to learn the disconnected neighbors due to jamming so as to mitigate the effect of jamming and maintain connectivity. CA-JAM is fully distributed with no use of control channel or central entity; thus, it improves connectivity and reduces interference by balancing stations over the available channels while mitigating jamming effects from multi channel multi interface MANETs. We confirm that CA-JAM outperforms existing protocols using the OPNET simulator.

CADMA: collision-avoidance directional medium access for vehicular ad hoc networks

Quick and accurate message transmission is an important research topic for vehicular ad hoc networks (VANET). Most studies assume that the periodic broadcast of beacon frames between vehicles increases the safety of the driver. In particular, there has been a lot of research into broadcasting based on carrier sense multiple access with collision avoidance (CSMA/CA) algorithms for medium access. However, the CSMA/CA algorithm is not an optimum technique for the VANET system, due to the transfer delay that occurs in inducing frequent collisions on transmission signals. In this paper, we propose a collision-avoidance directional medium access (CADMA) protocol and infrastructure-utilized clustering method for VANET to support reliable data transfer. In the proposed scheme, the CADMA protocol uses non-competitive transmission methods and cluster heads (CHs) to manage access by allocating the nodes resources. In addition, the roadside unit (RSU) helps with the clustering process. The simulation results indicate that the CADMA can reduce transmission delays and the collision rate of the broadcasting signal, and have shown that the CADMA can be effectively utilized for the VANET systems.

A passive self-configuration MAC protocol for supporting network management in IEEE 802.11-based multi-hop mobile ad hoc networks

This paper proposes a fully distributed self-configuration media access control (MAC) protocol for IEEE 802.11-based multi-hop mobile ad hoc networks. The proposed MAC protocol targets to determine proper stations to become supervisors to support network management. This study first formulates the supervisor determination problem as the virtual backbone construction problem. Because determining the optimal number of supervisors falls into the NP-complete problem, this study uses many rules to determine enough supervisors to support network management. The determined supervisors are divided into multiple sets, and the supervisors in a set need to transmit beacon frames in the specific beacon interval. Using the proposed rules, not all the stations need to transmit beacon frames in each beacon interval. Moreover, the neighboring supervisors do not transmit beacon frames in the same beacon interval, thereby avoiding network partitioning, saving battery power, and achieving reliable broadcast. Simulation results confirm that the proposed MAC protocol actually determines enough and minimum number of supervisors. Results also show that the proposed MAC protocol leads to less packet collisions and reduces energy consumption, compared with the IEEE 802.11 standard.

A statistical frame based TDMA protocol for human body communication.

BackgroundHuman body communication (HBC) using the human body as the transmission medium, which has been regarded as one of the most promising short-range communications in wireless body area networks (WBAN). Compared to the traditional wireless networks, two challenges are existed in HBC based WBAN. (1) Its sensor nodes should be energy saving since it is inconvenient to replace or recharge the battery on these sensor nodes; (2) the coordinator should be able to react dynamically and rapidly to the burst traffic triggered by sensing events. Those burst traffic conditions include vital physical signal (electrocardiogram, electroencephalogram etc.) monitoring, human motion detection (fall detection, activity monitoring, gesture recognition, motion sensing etc.) and so on. To cope with aforementioned challenges, a statistical frame based TDMA (S-TDMA) protocol with multi-constrained (energy, delay, transmission efficiency and emergency management) service is proposed in this paper.MethodsThe scenarios where burst traffic is often triggered rapidly with low power consumption and low delay is handled in our proposed S-TDMA. A beacon frame with the contained synchronous and poll information is designed to reduce the possibility of collisions of request frames. A statistical frame which broadcasts the unified scheduling information is adopted to avoid packet collisions, idle listening and overhearing. Dynamic time slot allocation mechanism is presented to manage the burst traffic and reduce the active period in each beacon period. An emergency mechanism is proposed for vital signals to be transmitted. The theory analysis is proceed and the result is evaluated in the hardware platform.ResultsTo verify its feasibility, S-TDMA was fully implemented on our independently-developed HBC platform where four sensor nodes and a coordinator are fastened on a human body. Experiment results show that S-TDMA costs 89.397 mJ every 20 s when the payload size is 122 bytes, 9.51% lower than Lightweight MAC (LMAC); the average data latency of S-TDMA is 6.3 ms, 7.02% lower than Preamble-based TDMA (PB-TDMA); the transmission efficiency of S-TDMA is 93.67%, 4.83% higher than IEEE 802.15.6 carrier sense multiple access/collision avoidance (CSMA/CA) protocol.ConclusionsWith respect to the challenges of HBC based WBANs, a novel S-TDMA protocol was proposed in this paper. Compared to the traditional protocols, the results demonstrate that S-TDMA successfully meets the delay and transmission efficiency requirements of HBC while keeping a low energy consumption. We also believe that our S-TDMA protocol will promote development of HBC in wearable applications.

Sleep More Without Losing the Network Connectivity

Extensive research efforts have been put to facilitate distraction free communication in intermittently connected networks. Nodes within this kind of network experiences frequent disconnections due to sparse deployment of nodes, mobility and node failures. Usually, nodes in intermittent network spend the time in listening network rather than transmitting or receiving any useful data. The energy consumed in the idle listening mode is one of the major reasons for battery drain in intermittent network. This paper addresses the energy consumption problem during idle listening and provides a better solution by designing a new structure for beacon interval with one beacon frame and checking out the neighbor table for the past record of encounters so as to decrease idle listening without losing network connectivity in the intermittent network. The actual performance of the proposed work is analyzed using the parameters packet delivery ratio, energy consumption and neighbor discovery in order to check the condition “sleep more without losing the network connectivity” is achieved.

A novel cheater and jammer detection scheme for IEEE 802.11-based wireless LANs

The proliferation of IEEE 802.11 networks has made them an easy and attractive target for malicious devices/adversaries which intend to misuse the available network. In this paper, we introduce a novel malicious entity detection method for IEEE 802.11 networks. We propose a new metric, the Beacon Access Time (BAT), which is employed in the detection process and inherits its characteristics from the fact that beacon frames are always given preference in IEEE 802.11 networks. An analytical model to define the aforementioned metric is presented and evaluated with experiments and simulations. Furthermore, we evaluate the adversary detection capabilities of our scheme by means of simulations and experiments over a real testbed. The simulation and experimental results indicate consistency and both are found to follow the trends indicated in the analytical model. Measurement results indicate that our scheme is able to correctly detect a malicious entity at a distance of, at least, 120 m. Analytical, simulation and experimental results signify the validity of our scheme and highlight the fact that our scheme is both efficient and successful in detecting an adversary (either a jammer or a cheating device). As a proof of concept, we developed an application that when deployed at the IEEE 802.11 Access Point, is able to effectively detect an adversary.

Intelligent Coordinator Selection Mechanism (ICSM) for IEEE802.15.4 Beacon-Enabled MAC Protocol in Mobile Wireless Sensor Networks

The IEEE802.15.4 beacon-enabled MAC protocol supports a simple coordinator selection mechanism (CSM) in static WSNs as well as mobile WSNs, where CSM normally selects the nearest coordinator. However, CSM is not suitable for constant moving node in mobile WSNs, where node will be switching coordinators too often due to strong mobility and low coverage range. In mobile WSNs, the node needs to select the best coordinator that has potential to provide longest connectivity period. This paper introduces the Intelligent Coordinator Selection Mechanism (ICSM) which supports the node to select the best coordinators. The proposed mechanism is based on link quality indicator (LQI) values of the received beacon frames from the nearby coordinators. The node selects the coordinator for association that has potential to provide the longest connectivity period. Our proposed ICSM reduces the energy consumption, enhance the association period and the throughput, and minimize the number of switching amongst the coordinators. The mobile node connectivity period is improved from 55% to 86% (static) and 94% (mobile), while the number of association attempts are reduced from 13% to 6% (static) and 2% (mobile) coordinators.

Channel estimation and transmit power control in wireless body area networks

Wireless body area networks have recently received much attention because of their application to assisted living and remote patient monitoring. For these applications, energy minimisation is a critical issue since, in many cases, batteries cannot be easily replaced or recharged. Reducing energy expenditure by avoiding unnecessary high transmission power and minimising frame retransmissions is therefore crucial. In this study, a transmit power control scheme suitable for IEEE 802.15.6 networks operating in beacon mode with superframe boundaries is proposed. The transmission power is modulated, frame-by-frame, according to a run-time estimation of the channel conditions. Power measurements using the beacon frames are made periodically, providing reverse channel gain and an opportunistic fade margin, set on the basis of prior power fluctuations, is added. This approach allows tracking of the highly variable on-body to on-body propagation channel without the need to transmit additional probe frames. An experimental study based on test cases demonstrates the effectiveness of the scheme and compares its performance with alternative solutions presented in the literature.