Wireless Local Area Network Interference Research Articles

Two‐layer modelling of IEEE 802.11x channel occupancy

AbstractLow power IoT communication signals (e.g., Bluetooth and ZigBee) may seriously suffer from the presence of high‐power co‐channel interference like wireless local area network (WLAN) signal. They may effectively avoid WLAN interference by exploiting dynamic characteristics of WLAN traffic. Representing the arrival/departure of WLAN users using an M/M/m/m queueing structure, the characterization of large‐scale dynamics of WLAN channel occupancy is considered. The characterization of small‐scale dynamics of WLAN channel occupancy is also considered by generating WLAN signal using a two‐state semi‐Markovian process. Simulation results show that the proposed model generates WLAN signal having similar statistical characteristics to those of real WLAN signal.

A Wrench-Shaped UWB Antenna Yielding Dual Notched Bands for WLAN Application

A wrench-shaped ultrawideband (UWB) antenna with dual notched bands is proposed and investigated. The antenna has a wrench-shaped patch and two T-shaped slots on the ground, realizing the required UWB band. To achieve the dual notched band characteristics in upper and lower wireless local area network (WLAN) bands, an Omega-shaped slot is etched on the feedline and a novel composite right/left-handed electromagnetic bandgap (CRLH-EBG) structure is built on the ground. Measured results present an operating frequency band from 3.04 to 11.4 GHz, with two notched bands of 5.1–5.4 GHz (uplink of WLAN band) and 5.7−5.985.7-5.98 GHz (downlink of WLAN band), respectively. Both measured and simulated results of the proposed antenna are exhibited, promising that the antenna applies to UWB applications and can precisely overcome WLAN interference.

WLAN interference signal recognition using an improved quadruple generative adversarial network

Cross-technology interference sources poses a great challenge for improving throughputs of wireless local area networks (WLAN) and wireless interference signal recognition (WISR) can provide a precondition for mitigating this problem. The quadruple generative adversarial network (QGAN) has shown its prevailing performance for specific emitter identification (SEI). In this paper, an enhanced collaborative learning mechanism is proposed to improve QGAN's performance for WISR. ACGAN is involved in the Improved-QGAN architecture to substitute original GAN, and loss functions are further optimized for generative, representation and classification sub-networks. Besides, a lightweight model based on knowledge distillation (KD) is presented to reduce memory consumption and computational complexity at inference phase. Numerical results indicate that the proposed Improved-QGAN outperforms the other baseline algorithms both on the experimental dataset and benchmark dataset.

WLAN Interference Identification Using a Convolutional Neural Network for Factory Environments

Factory communication systems require highly re- liable links with predictable performance and quality of service in order to avoid outages that can damage the production-line process. Communication anomalies can be caused by narrowband interference which is difficult to identify and track from the time- domain information only. This paper describes a methodology for classifying increasing severity and types of interference in order to improve throughput prediction. Received signal strength (RSS) data is collected from both a ray-tracing simulation and a Wireless Local Area Network (WLAN) measurement campaign with a transmitter mounted on an actual automated guided vehicle (AGV). Scalogram time-frequency images are computed from the RSS signal and a convolutional neural network (CNN) is then trained to recognize the spectral features and enable the interference classification. The block random interference could be correctly classified on over 65% of the occasions in the ray- traced channel at 30 dB SNR.

Design of printed monopole antenna with band notch characteristics for ultra‐wideband applications

A novel design of printed monopole antenna for the ultra-wideband (UWB) applications with band notch characteristics at wireless local area network (WLAN) and X-band satellite communication system has been proposed in this manuscript. Two different types of feed lines, that is, simple and tapered are used to excite the proposed antenna. Initially, designed antenna is excited by using simple 50 Ω transmission line after that tapered transmission line is introduced to enhance the impedance matching throughout the UWB frequency range (3.1-10.6 GHz). A comparison of designed antenna with simple and tapered feed line on the basis of impedance matching has also been made in this article, and found that later case reports better impedance matching in terms of Voltage Standing Wave Ratio (VSWR) bandwidth (2.45-12.0 GHz). Further, the notch bands are embodied into the designed antenna by using two split ring slots and one horizontal slot. The antenna with outer ring slot rejects the WLAN frequency band and antenna with inner ring junks the X-band satellite communication signal. The notch frequency has been adjusted by optimizing the dimensions of split ring slots as well as horizontal slot, which are incised on the structure of proposed antenna. By adjusting all the parameters of the etched slots of proposed antenna, dual band notched characteristics centered at frequencies 5.4 and 7.4 GHz has been achieved. Designed antenna is also compact (30 × 30 mm2) and capable to suppress the interference of WLAN and X-band satellite communication signal from the entire range of UWB passband. The proposed antenna is designed on low cost FR4 glass epoxy substrate with 1.6 mm thickness and dielectric constant 4.4. Antenna is designed and simulated by using HFSS V13 simulator and further, it is fabricated and tested for the validation of results. Simulated and measured results are also juxtaposed and found in good agreement with each other.

Planar quasi‐Yagi antenna with band rejection based on dual dipole structure for UWB

Aiming to realise an end-on-fire antenna with band rejection for ultra-wideband (UWB) system, a planar quasi-Yagi antenna with dual-dipole structure is proposed. The antenna comprises of a coupling transition structure, two stripes and a dual-dipole connected by a coplanar stripline. The compact arrangement of the dual-dipole generates reverse currents at some specific frequency points on their edges, giving rise to phase offsets in far field. This mechanism is used to design band rejection. Simulated and measured results show that the proposed antenna has a bandwidth from 3.08 to 11.1 GHz, which covers the whole UWB band. Meanwhile, the antenna achieves a band rejection from 5.12 to 6.08 GHz, which avoids wireless local area network interference. In pass-band, the antenna achieves a moderate gain, from 4.6 to 7.1 dBi.

WLAN interference self‐optimization using som neural networks

SummaryIn order to suppress the interference in local area networks, this paper presents a Wireless Local Area Networks (WLAN) interference self‐optimization method based on a Self‐Organizing Feature Map (SOM) neural network model. This method trains the model by using original data sets as the initial vector set and using the whole Signal to Interference plus Noise Ratio (SINR) vector generated by the change of one Wireless Access Point (AP) channel as the basic feature. After the training, the SOM neural network can quickly locate the fault AP and optimize the network according to the changes of the network environment. Simulation results reveal that the proposed scheme can efficiently locate the AP where interference happens and optimize the interference with an improved user experience. Copyright © 2016 John Wiley & Sons, Ltd.

An Adaptive WLAN Interference Mitigation Scheme for ZigBee Sensor Networks

We propose an adaptive interference avoidance scheme that enhances the performance of ZigBee networks by adapting ZigBees' transmissions to measured wireless local area network (WLAN) interference. Our proposed algorithm is based on a stochastic analysis of ZigBee operation that is interfered with by WLAN transmission, given ZigBee and WLAN channels are overlaid in the industrial, scientific, and medical (ISM) band. We assume that WLAN devices have higher transmission power than ZigBee devices. Then, the high transmission power of WLAN devices causes the capture effect when WLAN and ZigBee transmit simultaneously. On the other hand, ZigBee performs backoff during clear channel assessment (CCA) operation if the WLAN is transmitting its frames on the channel. We adopt a widely used WLAN queueing/transmission model that is based on a Markov chain concept. We model a ZigBee device's operation using the Markov chain that includes WLAN interference statistically derived from the WLAN queueing/transmission model. Our proposed algorithm is evaluated in a simulated ZigBee network in the presence of varying WLAN interference. Numerical results show that our WLAN interference mitigation scheme finds the ZigBee control parameters, among a candidate set, which enhances ZigBee network performance compared to the conventional ZigBee operation.

Range impairments of multi-band OFDM UWB communication systems in the presence of OFDM-based WLAN interference

In this paper, a closed form expression for the bit error rate performance of the multi-band orthogonal frequency division multiplexing (MB-OFDM) ultra wideband (UWB) communication system in the presence of interference is analytically analysed. The considered channel is the Saleh-Valenzuela multipath fading channel model. The interference is modelled as the OFDM-based IEEE802.11n wireless local area networks (WLANs). The dependence of the bit error rate performance of the MB-OFDM UWB communication system on the transmission range along with the impact of interference is also analytically investigated. Numerical results are validated with the aid of simulations. It is shown that the range performance of the MB-OFDM UWB communication system is severely deteriorated due to the presence of such interference.

Performance Evaluation of IEEE 802.15.4 Protocol Under Coexistence of WiFi 802.11b

Abstract ZigBee (IEEE 802.15.4) is a wireless mesh networking protocol low in cost, power, data rate, and complexity. To access Lo- cal Area Networks (LAN), 802.11b/g standard is used all over the world as Wi-Fi (Wireless Fidelity) standard. IEEE 802.15.4 Wireless Sensor Networks (WSNs) and IEEE 802.11b/g Wireless Local Area Networks (WLANs) are often collocated, causing a coexistence. The coexistence occurs because these networks share the same 2.4 GHz Industrial, Scientific, and Medical (ISM) band. A Simulation model has been introduced which completely reflects the ZigBee and WiFi coexistence. We have proposed frequency agility based interference avoidance algorithm . However, algorithm detects interference and adaptively switch nodes to safe channel for dynamically avoid WLAN interference with lower latency and energy consumption. The performance of ZigBee under WiFi is empirically evaluated in terms of the packet error rate (PER) and bit error rate (BER). The Simulation results us- ing frequency agility algorithm demonstrate that the design guideline can efficiently mitigate the effect of WiFi interference and enhance the performance of ZigBee networks.

Performance Analysis of ISA100.11a Under Interference From an IEEE 802.11b Wireless Network

Recently, the International Society of Automation (ISA) released ISA100.11a as an open standard for reliable wireless networks for industrial automation. ISA100.11a operates in the 2.4-GHz industrial, scientific, and medical (ISM) unlicensed band, and may suffer from interference from other radio technologies operating in the same band. This coexistence issue can lead to significant degradation of ISA100.11a performance. In this work, the performance of the ISA100.11a industrial wireless network under interference from an IEEE 802.11b wireless local area network (WLAN) is evaluated. An analytical model for the coexistence between ISA100.11a and IEEE 802.11b is suggested. The packet error rate (PER) and average end-to-end delay are evaluated, where the PER is obtained from the bit error probability and collision time, whereas the average end-to-end delay is investigated from the waiting time in buffer and the transmission time. Simulation results from the OPNET modeler are presented to validate the numerical analysis. It is demonstrated that ISA100.11a achieves acceptable PER and satisfies the delay requirement for industrial process control and monitoring, even under significant WLAN interference.

Performance improvement in ZigBee-based home networks with coexisting WLANs

In recent years, a large diversity of network-enabled devices have been widely prevalent in home environment. With the prevalence of such devices, wireless home networks enable monitoring and control applications for home user comfort and efficient home management. In the home network, alarm signals must be delivered in real-time to the residents or to the emergency services and some home control applications require the response time to be on the order of a few hundred milliseconds for optimal user experience. Most recently, ZigBee has emerged as one of the most promising technologies for wireless home networking because it is targeted at applications that require a low data rate and long battery life, which are also the features of home network applications. However, its usage in close proximity to Wireless Local Area Networks (WLANs) introduces coexistence problems, resulting in failing to fulfil the response time required by the home control applications. To overcome this problem, we propose to control the WLAN traffic when there exist ongoing ZigBee transmissions and the maximum tolerable delay is not met due to the WLAN interference. We aim to guarantee that the delay experienced by ZigBee sensors (especially, for alarm signals) does not exceed the maximum tolerable delay, while maintaining as high throughput as possible in the WLANs. The simulation results demonstrate that our proposed algorithm can enhance the delay performance of ZigBee networks by mitigating the effect of WLAN interference and improve the throughput in the WLANs.

Developing ZigBee Deployment Guideline Under WiFi Interference for Smart Grid Applications

Smart grid is an intelligent power generation, distribution, and control system. ZigBee, as a wireless mesh networking scheme low in cost, power, data rate, and complexity, is ideal for smart grid applications, e.g., real-time system monitoring, load control, and building automation. Unfortunately, almost all ZigBee channels overlap with wireless local area network (WLAN) channels, resulting in severe performance degradation due to interference. In this paper, we aim to develop practical ZigBee deployment guideline under the interference of WLAN. We identify the “Safe Distance” and “Safe Offset Frequency” using a comprehensive approach including theoretical analysis, software simulation, and empirical measurement. In addition, we propose a frequency agility-based interference avoidance algorithm. The proposed algorithm can detect interference and adaptively switch nodes to “safe” channel to dynamically avoid WLAN interference with small latency and small energy consumption. Our proposed scheme is implemented with a Meshnetics ZigBit Development Kit and its performance is empirically evaluated in terms of the packet error rate (PER) using a ZigBee and Wi-Fi coexistence test bed. It is shown that the empirical results agree with our analytical results. The measurements demonstrate that our design guideline can efficiently mitigate the effect of WiFi interference and enhance the performance of ZigBee networks.

Interference Mitigation in IEEE 802.15.4-A Cluster Based Scheduling Approach

Problem statement: In universal networking environments; two or more heterogeneous communication systems coexisting in a single place. Especially, Wireless Local Area Networks (WLANs) based on IEEE 802.11b specifications and Wireless Personal Area Networks (WPANs) based on IEEE 802.15.4 specifications need to coexist in the same Industrial, Science and Medial (ISM) band. If the WPAN communication coverage is expanded using a cluster-tree network topology, then the 802.15.4 network is more susceptible to interference from neighboring WLANs. Approach: In this study, we propose an adaptive transmission power aware cluster scheduling algorithm using multiple channels in a WPAN in the presence of WLAN interference. Results: The algorithm includes node identification, channel allocation, clustering and time scheduling. To evaluate the performance of the proposed algorithm, the performance metrics such as Bit error, Packet Error Rate (PER), Throughput, Average End-End Delay and Average Jitter is measured through Qualnet simulation. PER is calculated from bit error rate. The simulation results are compared with the conventional TDMA scheme. Conclusion/Recommendations: The measurement result shows that the proposed algorithm is effective in an IEEE 802.15.4 cluster-tree network in the presence of multiple IEEE 802.11 interferers.

Inter and Intra Cluster Scheduling for Performance Analysis of Coexistence Heterogeneous Networks

In ubiquitous networking environments, we generally need two or more heterogeneous communication systems coexisting in a single place. Especially, wireless local area networks (WLANs) based on IEEE 802.11b specifications and wireless personal area networks (WPANs) based on IEEE 802.15.4 specifications need to coexist in the same Industrial, Science and Medial (ISM) band. If the WPAN communication coverage is expanded using a cluster-tree network topology, then the 802.15.4 network is more susceptible to interference from neighboring WLANs. In this paper, we propose an adaptive transmission power aware cluster scheduling algorithm using multiple channels in a WPAN in the presence of WLAN interference. The algorithm includes node identification, channel allocation, clustering and time scheduling. To evaluate the performance of the proposed algorithm, the performance metrics such as Bit error, Throughput, Average End-End Delay and Average Jitter is measured through Qualnet simulation. The measurement result shows that the proposed algorithm is effective in an IEEE 802.15.4 cluster-tree network in the presence of multiple IEEE 802.11 interferers.

Adaptive frequency hopping for bluetooth robust to WLAN interference

In this letter, we propose a new adaptive frequency hopping (AFH) scheme for Bluetooth to mitigate interference from IEEE 802.11x based wireless local area network (WLAN). To fast classify available channels for the Bluetooth, we first group the Bluetooth channels according to the channel allocation of WLAN and classify groups instead of Bluetooth channels. Then, we employ a moving average technique to estimate the status of Bluetooth channels in groups more accurately. The performance of the proposed scheme is verified by computer simulation. Simulation results show that the proposed AFH scheme significantly outperforms conventional schemes.

Channel Clustering and Probabilistic Channel Visiting Techniques for WLAN Interference Mitigation in Bluetooth Devices

Since Bluetooth and wireless local area network (WLAN) technologies both operate at the 2.4-GHz industrial, scientific, and medical (ISM) band, the two types of devices may suffer from mutual interference and performance degradations. In this paper, we propose two new techniques, channel clustering and probabilistic channel visiting, to effectively improve the existing coexistence and interference mitigation mechanisms. The channel clustering technique employs statistical pattern recognition to classify the status of Bluetooth channels more accurately. The probabilistic channel visiting is used to more equitably allocate the channel resources between Bluetooth and WLAN devices. The effectiveness of these techniques is quantified by simulations. Results show that both techniques are beneficial in improving the performance of the existing mechanisms.