Channels In IEEE Research Articles

Performance Analysis of Cooperative Spectrum Sensing using Empirical Mode Decomposition and Artificial Neural Network in Wireless Regional Area Network

Background: Radio spectrum is natural and the most precious means in wireless communication systems. Optimal spectrum utilization is a key concern for today's cutting-edge wireless communication networks. The impending problem of the lack of available spectrum has prompted the development of a new idea called “Cognitive Radio” (CR). Cooperative spectrum sensing (CSS) is utilized to improve the detection performance of the system. Several fusion algorithms of decision-making are proposed for sensing the licensed user, but they do not work well under low signal-to-noise ratio (SNR). Objectives: To address the issue of poor detection performance under low SNR, Empirical mode decomposition (EMD) and artificial neural network (ANN) based CSS under Rayleigh multipath fading channel in IEEE 802.22 wireless regional area network (WRAN) is proposed in this paper. Method: In this work, we propose the use of ANN as a fusion center. First, the received signal's energy is calculated using EMD. The computed energy, SNR, and false alarm probability are combined to form a data set of 2048 samples. They are utilized to train Levenberg- Marquardt back propagation training algorithm-based feed-forward neural network (FFNN). Using this trained network, CSS in WRAN is simulated under Rayleigh multipath fading. Results: Simulation results show that the proposed CSS method based on EMD-ANN outperforms the standard fast Fourier transform (FFT) and EMD detection-based cooperative spectrum sensing with a hard "OR" fusion at low SNR. With Pf =0.01, 100% detection accuracy with proposed techniques is obtained at SNR= -22dB. Conclusion: The findings show that the suggested approach outperforms EMD and FFT based energy detection scheme-based traditional CSS in low SNR environments.

Noise-Canceling Channel Estimation Schemes Based on the CIR Length Estimation for IEEE 802.11p/OFDM Systems

This paper investigates methods for noise-canceling channel estimation (NC-CE) to track rapid time-varying channels in IEEE 802.11p/orthogonal frequency division multiplexing (OFDM) systems. To this end, we introduce a novel three-step channel estimation technique based on the estimated length of the channel impulse response (CIR). This approach aims to surpass the performance of conventional designs that rely on constructed data pilots (CDPs). In the first step, we not only eliminate noise components but also estimate the channel frequency responses (CFRs) of virtual subcarriers for long preamble parts. Moving on to the second step, we incorporate a modified CDP method without a frequency-domain reliability test and interpolation, taking into account the CFRs of virtual subcarriers obtained at the previous OFDM symbol time. The final step can be implemented as the operation of the inverse fast Fourier transform (IFFT)/nulling/FFT to reduce noise components from the CFRs obtained in the second step and generate CFRs for virtual subcarriers to be used in the next symbol time. The results of our simulations validate the effectiveness of our proposed channel estimation schemes.

Sensors Scheduling for Remote State Estimation Over an Unslotted CSMA/CA Channel

This article investigates the sensor selection problem for remote state estimation. A set of sensors measures a process's state and sends the measurements to a remote estimator over an unslotted carrier sense multiple access/collision avoidance (CSMA/CA) channel in IEEE 802.15.4-based wireless body area networks. This article aims to answer which sensors should be selected according to probability so that the state estimation error covariance and the energy consumption of sensors can be optimized. A common assumption in most existing methods about sensor scheduling is that the packet loss process is unrelated to the channel input. This article analyzes the relationship between channel input and packet loss rate by modeling the communication process. A scheduling scheme is proposed to increase channel utilization from the perspective of sensor information fusion. Then the constraint on the performance metrics is presented. By transforming the sensor selection problem into a constrained optimization problem, the solution to the optimization problem is obtained by a numerical algorithm. Finally, the validity of the model and the feasibility of the sensor scheduling are demonstrated by a numerical simulation.

A two stage cascode LNA using modified derivative superposition technique in [formula omitted] HBT with an IIP3 of 2 dBm and NF of 4.8 dB for IEEE 802.11ad standard

A two stage cascode Low Noise Amplifier (LNA) is designed in 130 nm SiGe HBT. The work focuses on achieving a low Noise Figure (NF), high linearity, and high gain for the LNA in the frequency band of 57.24 GHz-65.88 GHz to be operated in all the four channels of IEEE 802.11ad standard. A modified Derivative SuperPosition technique is used in the first stage of the cascaded LNA to improve the linearity of the circuit. Post layout Electromagnetic (EM) simulation results of the proposed LNA achieves a peak gain of 20.19dB at 59.5GHz, linearity (IIP3) of 2dBm at the maximum gain and also achieved a NF of 4.1dB - 4.8dB in the operating band of frequency. DC power consumption of the proposed circuit is 9.2mW from a supply voltage of 1.2V, with an area occupancy of 311μm×298μm.

Partially Overlapping Channel Assignment Using Bonded and Non-Bonded Channels in IEEE 802.11n WLAN

Nowadays, wireless local area network (WLAN) has become prevalent Internet access due to its low-cost gadgets, flexible coverage and hassle-free simple wireless installation. WLAN facilitates wireless Internet services to users with mobile devices like smart phones, tablets, and laptops through deployment of multiple access points (APs) in a network field. Every AP operates on a frequency band called channel. Popular wireless standard such as IEEE 802.11n has a limited number of channels where frequency spectrum of adjacent channels overlaps partially with each other. In a crowded environment, users may experience poor Internet services due to channel collision i.e., interference from surrounding APs that affects the performance of the WLAN system. Therefore, it becomes a challenge to maintain expected performance in a crowded environment. A mathematical model of throughput considering interferences from surrounding APs can play an important role to set up a WLAN system properly. While set up, assignment of channels considering interference can maximize network performance. In this paper, we investigate the signal propagation of APs under interference of partially overlapping channels for both bonded and non-bonded channels. Then, a throughput estimation model is proposed using difference of operating channels and received signal strength indicator (RSSI). Then, a channel assignment algorithm is introduced using proposed throughput estimation model. Finally, the efficiency of the proposal is verified by numerical experiments using simulator. The results show that the proposal selects the best channel combination of bonded and non-bonded channels that maximize the performance.

Channel Assignment Based on CSMA-Aware Interference Model With Overlapped Channels in Multiradio Multichannel Wireless Mesh Networks

Multi-radio Multi-channel Wireless Mesh Networks (MRMC WMNs) implemented on IEEE 802.11 standards are widely used owing to their adaptability in practical network scenarios. The channel assignment problem in MRMC WMNs has been extensively studied. However, in most of the existing works, only orthogonal wireless channels are considered owing to the complexity of the channel assignment problem, which results in a low level of spatial utilization. This paper introduces partially overlapping channels into the CSMA-aware interference and shared link capacity models to fully exploit the spectrum resource and improve network capacity, utilizing both orthogonal channels and partially overlapping channels in IEEE 802.11 2.4 GHz bands. We formulate this problem as a mixed-integer linear program (MILP). We propose a traffic-demand-aware collision-free partially overlapping channel assignment (TAC-POCA), which uses all the available channels and achieves collision-free end-to-end flow transmissions to attain load balance. Simulation results show that TAC-POCA leads to better utilization of the spectrum resource and throughput improvement in both grid and random topology networks than in the case of using only orthogonal channels.

An Adaptive Channel Hopping and Dynamic Superframe Selection Scheme With QoS Considerations for Emergency Traffic Transmission in IEEE 802.15.6-Based Wireless Body Area Networks

In modern days, as medical technology advances and the world’s population grows, healthcare has been undergoing crucial changes. The common practice of clinical treatment is gradually being overhauled by ubiquitous healthcare systems. The wireless body area networks (WBANs) are becoming increasingly important for future healthcare applications. According to the human physiological information, WBAN not only sends the real-time notification to the user but also decreases the transmission delay of patient information to the physician for the medical decision. As medical emergency information must be transmitted after a disaster occurrence, the number of WBANs and emergency traffic increase in the particular area. In the situations, a large number of WBANs may be close to each other, thus causing inter-WBAN interference and increasing the transmission delay. Therefore, in this paper, we propose a dynamic channel and superframe selection scheme (DCSSS) in IEEE 802.15.6 WBANs. DCSSS records the channel interference degree which is used to adaptively select different superframe structures and to effectively transmit data. It mitigates the inter-WBAN interference to improve the transmission delay and QoS violation. Additionally, it increases the chance of successful data transmission before the deadline of the data as well as reduces power consumption.

An Insight of Backoff Algorithms in Wireless Networks

The IEEE 802.11 MAC is liable for the scheme of channel accessing. It decides the performance of the WLAN and DCF is the central strategy. Stations that need to get to the divert may partake in a disseminated manner by means of CSMA/CA in the MAC layer. Packet collision can’t be totally avoided because of the nodes which are in scattered manner. MAC layer uses a BEB scheme for CA (collision avoidance).. Nodes are experiencing a collision in common channel in IEEE 802.11 and must have to backoff for a arbitrary time and selected consistently from CW. The contention window is maintained dynamically by BO algorithms. Network performance is decreased due to a sudden change in window size. Different existing algorithms for backoff and comparision among the algorithms are shown in the manuscript.

Chinese Character-Shaped Artistic Patch Antenna

This contribution presents a novel design of a circularly polarized (CP) array antenna composed of the Chinese character-shaped artistic patches: Zhong and Guo . Namely, the CP Zhong-shaped patch and the Guo-shaped patch join together via a feeding network to form a two-element antenna array. This is the Chinese country name of China printed in the boldfaced SimHei font. Attributed to its artistic nature, this is the first design that breaks the design principles of CP antenna array, wherein, first, nonidentical radiating elements are used, and second, nonrotated elements are excited with quadrature phases. The experimental results in combination with simulations validate that the Zhong–Guo artistic antenna exhibits a unidirectional gain of 8.2 dBic with an operating bandwidth of 0.72 GHz. The achieved bandwidth sufficiently covers the 14 channels of IEEE 802.11 at 2.4 GHz wireless local area network band.

A New Data Pilot-Aided Channel Estimation Scheme for Fast Time-Varying Channels in IEEE 802.11p Systems

The channel estimation in the IEEE 802.11p vehicle-to-everything (V2X) communication systems is generally a challenging task due to high mobility and insufficient number of pilots. Conventional data pilot-aided channel estimation schemes are difficult to apply in practice due to high complexity and the error propagation problem. In this correspondence paper, we propose a new data pilot-aided channel estimation scheme to overcome both issues. To this end, we develop a state feedback decision algorithm that enables us to extract reliable data pilots within a few received symbols. As a result, we can minimize both the error propagation effect and the computational complexity. We verify the complexity gain of the proposed scheme through the complexity analysis. Finally, we demonstrate the accuracy of the proposed channel estimation scheme in terms of the packet error rate performance.

Co-existence Issue in IoT Deployment using Heterogeneous Wireless Network (HetNet): Interference Mitigation using Cognitive Radio

In today’s era of Machine-to-Machine (M2M) communication, where a tiny embedded device is having enough functionality and computational power to be network enabled for various applications aided with sensors, relays, and actuators to make Internet-of-Things (IoT) a reality. IoT is not a technology by itself rather a vision to interconnect every single piece of intelligent electronics using existing LAYER-I and II data communication standards and the internet based on OSI Layer Architecture. In the context of deployment of such IoT networks, it is imperative; a heterogeneous wireless network will be most viable for the need of different application-specific scenarios. The primary goal of this paper is to propose a Cognitive Radio (CR) Algorithm for mitigation of interference based on the analytical and empirical model of packet error rate (PER) for IEEE 802.15.4 network in the presence of IEEE 802.11 b/g/n network operating in the 2.4 GHz unlicensed industrial scientific medical (ISM) frequency band. The power spectral density (PSD) of three standards widely deployed IEEE 802.11 b/g/n are considered for determining the interference power of overlapping channels of IEEE 802.11 b/g/n. To create a test-bed for an Empirical Model Digi’s XBEE® 802.15.4 Zigbee modules is used for IEEE 802.15.4 and Intel/ Qualcomm (Atheros) WiFi Alliance adaptors are considered and IEEE 802.11 to validate the analytical model.

5G: performance and evaluation of FS‐FBMC against OFDM for high data rate applications at 60 GHz

This study presents a frequency spreading filter bank multi-carrier (FS-FBMC) waveform as a potential candidate for the fifth generation (5G) network applications at millimetre-waves (mmWaves). The proposed model is developed based on the orthogonal frequency division multiplexing (OFDM) waveform standardised by IEEE 802.15.3c for 60 GHz high data-rate applications. The effects of non-linearities of power amplifiers (PAs) at 60 GHz for both OFDM and FS-FBMC are presented and compared using a realistic PA model. In particular, the sensitivity of both transmission schemes to the non-linear effects is investigated and its impact on the performance degradation in terms of output-power-backoff, is characterised over typical indoor line-of-sight, kiosk and residential, 60 GHz IEEE channel models. The assessment metrics considered are bit error rate and out-of-band emissions. This study concludes radio access schemes for future communication generations, i.e. 5G may employ OFDM for up-link and FS-FBMC for down-link due to the sensitivity to PA non-linearities of both waveforms.

Frequency hopping in IEEE 802.15.4 to mitigate IEEE 802.11 interference and fading

In this paper, we investigate the issues of initialization and deployment of wireless sensor networks (WSNs) under IEEE 802.11b/g interference and fading channels using frequency hopping (FH). We propose an FH algorithm for WSNs, which is implemented and tested with a pair of nodes employing IPv6 over low power wireless personal area networks (6LoWPAN) standard. The merits and demerits of the proposed FH scheme in WSNs are studied under strong IEEE 802.11b/g interference and frequency selective fading channels. We compare the performance results of the proposed FH scheme with those obtained by single-channel radio in WSNs, and show that FH maintains very reliable data rates in the presence of adverse conditions where the single-channel radio fails. We determine a minimum center frequency offset of channels between IEEE 802.15.4 and IEEE 802.11b/g-based networks, which guarantees the error free network operation of IEEE 802.15.4 using a single channel. We design a second FH procedure comprising only four free channels (15, 20, 25, and 26) of IEEE 802.15.4 standard, and show that in the presence of nearby IEEE 802.11b/g interference, the IEEE 802.15.4 data rate using this method is always 98% and more.

On the Goodness of Using Orthogonal Channels in WLAN IEEE 802.11 in Realistic Scenarios

Due to the high density of Wi‐Fi networks, especially in the unlicensed 2.4 GHz frequency band, channel assignment has become a critical duty for achieving a satisfactory user experience. Probably, the main peculiarity of Wi‐Fi networks is the partial overlap of the radio channels that can be used by access points. For that reason, a number of works avoid cochannel interferences by using only channels which are far enough from each other to have no interferences, the so‐called orthogonal channels. However, there is a range of choices between using the whole spectrum and using only orthogonal channels. In this work we evaluate the influence of the choice of channel set in realistic settings, using both optimization and heuristic approaches. Results show that the optimizer is not able to achieve better results when using the whole spectrum instead of restricting to only the orthogonal channels. In fact, the optimizer uses mainly the orthogonal channels when they are available, while the heuristics considered lose performance when more channels are available. We believe this insight will be useful to design new heuristics for Wi‐Fi channel assignment.

A Circular-Polarization Reconfigurable Meng-Shaped Patch Antenna

In this paper, we introduce a reconfigurable artistic patch antenna with unidirectional circular-polarization (CP) radiation. The novel geometry composed of a Chinese character Meng shaped patch and dual L-shaped feeding probes that are connected to a PIN-diode-based switching circuit. The simulated and experimental results show that the proposed antenna achieves the operating bandwidth from 2.4 to 2.5 GHz that covers dynamically the 14 channels of IEEE 802.11/b/g/b/ax. By switching the L-probes, either left-handed CP or right-handed CP can be generated to cover different seven-channel blocks in order to enhance the channel efficiency. A broadside realized gain varying between 5-6 dBic and an efficiency of -0.5dB were recorded. The proposed antenna holds an overall dimension of 0.72λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.72λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.12λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> with an aperture efficiency of 59% at 2.45 GHz.

Self-Coexistence among IEEE 802.22 Networks: Distributed Allocation of Power and Channel.

Ensuring self-coexistence among IEEE 802.22 networks is a challenging problem owing to opportunistic access of incumbent-free radio resources by users in co-located networks. In this study, we propose a fully-distributed non-cooperative approach to ensure self-coexistence in downlink channels of IEEE 802.22 networks. We formulate the self-coexistence problem as a mixed-integer non-linear optimization problem for maximizing the network data rate, which is an NP-hard one. This work explores a sub-optimal solution by dividing the optimization problem into downlink channel allocation and power assignment sub-problems. Considering fairness, quality of service and minimum interference for customer-premises-equipment, we also develop a greedy algorithm for channel allocation and a non-cooperative game-theoretic framework for near-optimal power allocation. The base stations of networks are treated as players in a game, where they try to increase spectrum utilization by controlling power and reaching a Nash equilibrium point. We further develop a utility function for the game to increase the data rate by minimizing the transmission power and, subsequently, the interference from neighboring networks. A theoretical proof of the uniqueness and existence of the Nash equilibrium has been presented. Performance improvements in terms of data-rate with a degree of fairness compared to a cooperative branch-and-bound-based algorithm and a non-cooperative greedy approach have been shown through simulation studies.

Towards 5G: Performance evaluation of 60 GHz UWB OFDM communications under both channel and RF impairments

Detailed analysis on the impact of RF and channel impairments on the performance of Ultra-Wideband (UWB) wireless Orthogonal Frequency Division Multiplexing (OFDM) systems based on the IEEE 802.15.3c standard, for high data-rate applications using the 60 GHz millimetre frequency band is presented in this paper. This frequency band, due to the large available bandwidth is very attractive for future and 5G wireless communication systems. The usage of OFDM at millimetre-wave (mmWaves) frequencies is severely affected by non-linearities of the Radio Frequency (RF) front-ends. The impact of impairments is evaluated, in terms of some of the most important key performance indicators, including spectral efficiency, power efficiency, required coding overhead and system complexity, Out-Of-Band Emissions (OOBEs), Bit Error Rate (BER) target and Peak Signal-to-Noise Ratio (PSNR). Additionally, joint distortion effects of coexisting Phase-Noise (PN), mixer IQ imbalances and Power Amplifier (PA) non-linearities, on the performance degradation of a mmWave radio transceiver, combined with various multipath fading channels, are investigated. Subsequently, the power efficiency of the system is evaluated by estimating values of the PA Output-Power-Backoff (OBO) needed to meet the requirements for the Transmit Spectrum Mask (TSM) and BER target. Finally, a comparison of the system overall performance between uncoded and coded OFDM systems combined with Quadrature Amplitude Modulations (16 and 64 QAM) and its maximum operable range are evaluated by transmitting a Full HD uncompressed video frame under five different RF impairment conditions over a typical LOS kiosk 60 GHz IEEE channel model.

A Channel Assignment Extension of Active Access-Point Configuration Algorithm for Elastic WLAN System and Its Implementation Using Raspberry Pi

Recently, Wireless Local-Area Network (WLAN) has become prevailing as it provides flexible Internet access to users with low cost through installation of several types of access points (APs) in the network. Previously, we proposed the active AP configuration algorithm for the elastic WLAN system using heterogeneous APs, which dynamically optimizes the configuration by activating or deactivating APs based on traffic demands. However, this algorithm assumes that any active AP may use a different channel from the other ones to avoid interferences, although the number of non-interfered channels in IEEE 802.11 protocols is limited. In this paper, we propose the extension of the AP configuration algorithm to consider the channel assignment to the active APs under this limitation. Besides, AP associations of the hosts are modified to improve the network performance by averaging loads among channels. The effectiveness of our proposal is evaluated using the WIMNET simulator in two topologies. Finally, the elastic WLAN system including this proposal is implemented using Raspberry Pi for the AP. The feasibility and performance of the implementation are verified through experiments using the testbed.

An Improved OFDM Scheme for Service Channels of Vehicular Ad-Hoc Networks

In order to enhance the efficiency and reliability of transmitting varying application messages in intelligent transportation system, we presented an improved Orthogonal Frequency Division Multiplexing (OFDM) scheme for service channels of IEEE 802.11p Vehicular Ad-Hoc Networks, which combined OFDM technique with identity authentication and dynamic sub-carriers allocation algorithm. OFDM sub-channels could be adaptively adjusted according to the load status of service channels and different QoS requirements. The implementation method of proposed scheme was discussed in detail, and the performance was verified by theoretical analysis and simulation.

Multivariate Control Chart for the Detection of MAC Layer Misbehavior in Mobile ad Hoc Networks

The share nature of the transmission channel in IEEE 802.11 makes the network vulnerable to several attacks like the MAC layer misbehavior which can be similar to denial of service attack. In this way cheating node by choosing smaller backoff timer attempts to increase its resources at the expense to other stations which respect the protocol.In this paper, we suggest a novel detection scheme of such attack using a multivariate control chart currently exist in industrial management with a large success. Our proposed strategy comes to replace the univariate Shewhart control chart which already exists in the literature research for the detection of greedy nodes, because it reduces the number of control chart. As we will prove by NS-2 simulations, the proposed mechanism doesn’t require any modification to the 802.11 standard, it works in real time and very easy in implementation though it appears somewhat complicated because of the computation of the mean and the covariance matrix in the absence of the MAC layer misbehavior attack.