Multi-channel Scheme Research Articles

Efficient Multichannel Communications in Wireless Sensor Networks

This article demonstrates how to use multiple channels to improve communication performance in Wireless Sensor Networks (WSNs). We first investigate multichannel realities in WSNs through intensive empirical experiments with Micaz motes. Our study shows that current multichannel protocols are not suitable for WSNs because of the small number of available channels and unavoidable time errors found in real networks. With these observations, we propose a novel tree-based, multichannel scheme for data collection applications, which allocates channels to disjoint trees and exploits parallel transmissions among trees. In order to minimize interference within trees, we define a new channel assignment problem that is proven NP-complete. Then, we propose a greedy channel allocation algorithm that outperforms other schemes in dense networks with a small number of channels. We implement our protocol, called the Tree-based, Multichannel Protocol (TMCP), in a real testbed. To adjust to networks with link quality heterogeneity, an extension of TMCP is also proposed. Through both simulation and real experiments, we show that TMCP can significantly improve network throughput and reduce packet losses. More important, evaluation results show that TMCP better accommodates multichannel realities found in WSNs than other multichannel protocols.

Analytical Study of the Impact of the Mobility Node on the Multi-channel MAC Coordination Scheme of the IEEE 1609.4 Standard

Analytical Study of the Impact of the Mobility Node on the Multi-channel MAC Coordination Scheme of the IEEE 1609.4 Standard

Multichannel Ultrasonic Data Communications in Air Using Range-Dependent Modulation Schemes.

There are several well-developed technologies of wireless communication such as radio frequency (RF) and infrared (IR), but ultrasonic methods can be a good alternative in some situations. A multichannel airborne ultrasonic data communication system is described in this paper. ON-OFF keying (OOK) and binary phase-shift keying (BPSK) modulation schemes were implemented successfully in the system by using a pair of commercially available capacitive ultrasonic transducers in a relatively low multipath indoor laboratory environment. Six channels were used from 50 to 110 kHz with a channel spacing of 12 kHz, allowing multiple 8-bit data packets to be transmitted simultaneously. The system data transfer rate achieved was up to 60 kb/s and ultrasonic wireless synchronization was implemented instead of using a hard-wired link. A model developed in the work could accurately predict ultrasonic signals through the air channels. Signal root mean square (rms) values and system bit error rates (BERs) were analyzed over different distances. Error-free decoding was achieved over ranges up to 5 m using a multichannel OOK modulation scheme. To obtain the highest data transfer rate and the longest error-free transmission distance, a range-dependent multichannel scheme with variable data rates, channel frequencies, and different modulation schemes, was also studied in the work. Within 2 m, error-free transmission was achieved using a five-channel OOK with a data rate of 63 kb/s. Between 2 and 5 m, six-channel OOK with 60 kb/s data transfer rate was error free. Beyond 5 m, the error-free transmission range could be extended up to 10 m using three-channel BPSK with a reduced data rate of 30 kb/s. The situation when two transducers were misaligned using three-channel OOK and BPSK schemes was also investigated in the work. It was concluded that error-free transmission could still be achieved with a lateral displacement of less than 7% and oblique angles of less than 7°, and three-channel BPSK proved to be more robust than three-channel OOK with transducer misalignment.

Flashing displays: user-friendly solution for bootstrapping secure associations between multiple constrained wireless devices

Future healthcare systems, smart homes, and similar will involve a large number of smart inter-connected wireless devices (such as wireless sensor nodes). One of the major challenges to securing these systems presents loading initial cryptographic credentials into a relatively large number of wireless devices. Furthermore, many of these technologies involve low-cost and highly interface constrained devices (lacking usual wired interfaces, displays, keypads, and alike). We propose two novel multichannel key deployment schemes for wireless networks that only require a presence of a light source device, such as a multi-touch screen (tablet or smartphone device). The first key deployment scheme is based on secret key cryptography and is suitable for interface/resource-constrained wireless devices. The second scheme assumes a strong attacker and requires the use of public key cryptography. In both our solutions, we use one-way visible light channel of multi-touch screens (flashing displays) to initialize devices in a secure, usable, and scalable way. From the user's perspective, this boils down to placing the devices on the multitouch screen after which the remaining process is fully automatized. We showed through the experiments with 48 users that our solution is user-friendly and scales linearly with the number of nodes. Copyright © 2015 John Wiley & Sons, Ltd.

Absolute positioning by multi-wavelength interferometry referenced to the frequency comb of a femtosecond laser

A multi-wavelength interferometer utilizing the frequency comb of a femtosecond laser as the wavelength ruler is tested for its capability of ultra-precision positioning for machine axis control. The interferometer uses four different wavelengths phase-locked to the frequency comb and then determines the absolute position through a multi-channel scheme of detecting interference phases in parallel so as to enable fast, precise and stable measurements continuously over a few meters of axis-travel. Test results show that the proposed interferometer proves itself as a potential candidate of absolute-type position transducer needed for next-generation ultra-precision machine axis control, demonstrating linear errors of less than 61.9 nm in peak-to-valley over a 1-meter travel with an update rate of 100 Hz when compared to an incremental-type He-Ne laser interferometer.

GaS: A Gateway Scheduling-Based Beamforming Scheme for Handoff Support in Wireless Mesh Networks

Fast handoff support is a basic requirement for an Internet-based wireless mesh network (WMN), aiming to guarantee mobile users continuous connection to the Internet, regardless of their physical locations or moving trajectory. Due to the multihop transmission of network-layer handoff signaling packets, handoff performance in WMNs can be largely degraded by the increasing number of wireless hops as well as the channel access contentions between data and signaling packets in the mesh backbone. However, these issues are ignored in existing handoff solutions and multichannel medium-access control schemes. In this paper, we address the seamless handoff support from a different perspective and propose a gateway scheduling-based (GaS) beamforming scheme for handoff support in single-radio multichannel multihop WMNs. Our proposed beamforming scheme can realize single-hop handoff signaling packet transmissions and eliminate the channel contentions between data and signaling packets. Simulation results show that the total handoff delay is significantly improved using our proposed GaS beamforming scheme under various scenarios, as compared with existing handoff solutions in multihop WMNs. In addition, due to the single-hop transmission of signaling packets, the signaling overhead in the wireless mesh backbone can be substantially reduced.

An Efficient Secure Multichannel Traffic Management Scheme in 2.4 GHz Home Automation Network with IoT Functions

A home automation system integrates electrical devices in a house with each other. In this paper, an efficient secure multichannel traffic management scheme for wireless home automation networks with IoT (Internet of Things) functions is proposed. The mechanism includes a channel resource optimization scheme by the centralized channel assignment algorithms and an intrusion detection scheme for security enhancement with the traffic management. We evaluated the performance of the mechanism by using the wireless data measured on real wireless home networks. The simulation results show that the scheme can effectively manage the multi-channel status of the networks and detect the intrusion attacks, which improve the overall network performance.

Design of a Multi-Channel Random Demodulator for Wideband Signals

The wideband signals in most important applications are sparse or compressible in some sense. A multi-channel scheme for random demodulator without integrator is introduced in this paper. This architecture is based on compressive sensing (CS) and random demodulator (RD), and overcomes the problem of the integrator’s switching scheme injects noise into the signal and deteriorates the reconstructed signal of the RD, which has the same reconstruction guarantees by similar algorithms with the basic RD because the measurement matrix between their is identical, and which resolves some of the practical issues present in prior work. The results of simulation indicate that multi-tone signal can be successful reconstructed at sampling rate downs to 1/10 of the Nyquist-rate, which represents an up to 90% savings in the bandwidth and the storage memory.

A Multi-channel Scheduling Scheme for Collision-Free High-Rate WPANs

Ultra wide-band (UWB) technologies are being feverishly developed in the technical community. UWB devices are expected to operate at rates of up to 0.5 Gb/s and communicate with other devices at a range of up to 10 m. Thus, UWB technologies are being developed as core technology for high-speed wireless personal area networks. The salient features of UWB networks--high-rate communications, low interference with other radio systems, and low power consumption--bring many benefits to users. Thus, they enable consumers to experience new applications such as wireless universal serial bus for connecting personal computers to their peripherals and the consumer---electronics in people's living rooms. However, if multiple WiMedia logical link protocol Service Sets (WSSs) coexist in an adjacent area, various conflicts among independent WSSs can occur frequently. In order to solve this problem, we propose a multi-channel scheduling scheme (MCS) for the coexistence of adjacent WSSs. The proposed MCS scheme can scan new idle channel and detect its time offset where a WSS device can transmit a new beacon frame and data frames without conflicts. We also evaluate the performance of the proposed MCS scheme through various simulations in terms of several metrics. Simulation results demonstrate that the MCS scheme can minimize the possibility of data frame collisions by efficiently managing the multiple available channels in a hybrid manner combining proactive and reactive methods.

Adaptive Interference-Aware Multichannel Assignment for Shared Overloaded Small-Cell Access Points Under Limited Feedback

This paper proposes a reduced-complexity multichannel assignment scheme for short-range cellular systems. It treats the scenario when a number of small-cell (e.g., femtocell) access points (APs) can be shared to serve active scheduled users. The APs employ isotropic antenna arrays and operate using an open-access control strategy. To improve the reuse ratio of physical resources, the APs are assumed to occupy a single physical channel, wherein coordination among them is infeasible. On the other hand, to improve the spatial coverage, a scheduled user can be served by a single transmit channel from an AP at a time. For the case of overloaded APs and when the feedback links are capacity limited, the scheme attempts to identify the suitable transmit channels from the deployed APs in an adaptive manner such that certain performance and/or processing load limits are satisfied. The effects of some system and design parameters on the outcomes of the scheme are thoroughly discussed. Novel results for the statistics of the resulting interference power are presented, from which results for some performance measures and processing loads are obtained. Numerical and simulations results are provided to clarify the achieved gains, as compared with related models under different operating conditions.

Performance and Reliability Evaluation of BSM Broadcasting in DSRC with Multi-Channel Schemes

IEEE 1609.4 protocol defines a channel switching mechanism to enable a single radio operating efficiently on multiple channels to support both safety and non-safety services. Basic safety message (BSM) is transmitted only through the control channel at regular intervals. In this paper, we propose an analytic model based on interacting semi-Markov process (SMP) to evaluate both Medium Access Control (MAC) and application level performance and reliability of safety message broadcasting incorporating the impact of multi-channel operations. Message service time distribution is derived using Laplace-Stieltjes transform based on the proposed model. Due to the cyclic interactions between the SMP models for vehicles contending the same channel, fixed-point iteration is used to obtain converged solutions. Subsequently, MAC and application-level performance and reliability metrics are derived based on the converged solutions. Channel fading with path loss is taken into consideration in this derivation. The analytic models are validated through extensive simulations in NS2 to verify the effectiveness and accuracy of our proposed fixed-point iteration based model decomposition. The effects of channel switching mechanism and channel fading are also evaluated by comparing with other analytic models.

A Multi-Channel Fusion Based Newborn Seizure Detection

We propose and compare two multi-channel fusion schemes to utilize the information extracted from simultaneously recorded multiple newborn electroencephalogram (EEG) channels for seizure detection. The first approach is known as the multi-channel feature fusion. It involves concatenating EEG feature vectors independently obtained from the different EEG channels to form a single feature vector. The second approach, called the multi-channel decision/classifier fusion, is achieved by combining the independent decisions of the different EEG channels to form an overall decision as to the existence of a newborn EEG seizure. The first approach suffers from the large dimensionality problem. In order to overcome this problem, three different dimensionality reduction techniques based on the sum, Fisher’s linear discriminant and symmetrical uncertainty (SU) were considered. It was found that feature fusion based on SU technique outperformed the other two techniques. It was also shown that feature fusion, which was developed on the basis that there was inter-dependence between recorded EEG channels, was superior to the independent decision fusion.

A multichannel scheme in smooth scattering theory

In this paper we develop the scattering theory for a pair of self-adjoint operators \mbox{ A_{0}=A_{1}\oplus\dots \oplus A_{N} } and A=A_{1}+\dots +A_{N} under the assumption that all pair products A_{j}A_{k} with j\neq k satisfy certain regularity conditions. Roughly speaking, these conditions mean that the products A_{j}A_{k} , j\neq k , can be represented as integral operators with smooth kernels in the spectral representation of the operator A_{0} . We show that the absolutely continuous parts of the operators A_{0} and A are unitarily equivalent. This yields a smooth version of Ismagilov's theorem known earlier in the trace class framework. We also prove that the singular continuous spectrum of the operator A is empty and that its eigenvalues may accumulate only to "thresholds'' of the absolutely continuous spectra of the operators A_{j} . Our approach relies on a system of resolvent equations which can be considered as a generalization of Faddeev's equations for three particle quantum systems.

An Adaptive Channel Scheduling Design for Multi-Hop Handoff Delay Reduction in Internet-Based Wireless Mesh Networks

Seamless handoff support is an essential issue to ensure continuous communications in multi-hop wireless mesh networks (WMNs). Due to the multi-hop transmission of network-layer handoff signaling packets, the handoff performance in WMNs can be largely degraded by the long queueing delay and medium access delay at each mesh router, especially when the backbone traffic volume is high. However, this issue is ignored in existing handoff solutions and multi-channel allocation schemes. In this paper, we address the seamless handoff support from a different perspective and propose a novel channel allocation design in hierarchical WMNs to reduce the queueing delay and medium access delay of handoff signaling packets over multi-hop wireless links and to improve the average channel utilization simultaneously. Both analytical and OPNET simulation results show that the performance of the average channel utilization and total handoff delay can be improved significantly using our proposed channel allocation scheme under various scenarios, as compared to other existing channel allocation and handoff solutions in multi-hop WMNs.

Improvement on a Multi-Channel Broadcast Encryption Scheme

Broadcast encryption provides a convenient method to distribute digital content to subscribers over an insecure broadcast channel so that only the qualified users can recover the data. In some broadcast encryption based systems such as pay-TV, multiple ciphertext headers (via multiple channels) are needed since the sender needs to send various contents to different groups of subscribers. Each receiver needs to store all headers in order to switch channel fluently. Recently, Phan et al. described a multi-channel broadcast encryption scheme, in which the sender encapsulates multiple ephemeral keys into one ciphertext header so that each receiver only stores one ciphertext header and still can recover various ephemeral keys for different contents. We present an improvement on their scheme, which will reduce the size of public key and the computation cost for decryption. The improved scheme can be used to construct efficient dynamically privileged broadcast encryption system.

A Fair Scheme for Multi-channel Selection in Vehicular Wireless Networks

In recent years, the IEEE 802.11p/1609 wireless access in vehicular environments standards adopt the dedicated short-range communications multi-channel architecture for vehicular wireless networks. To utilize the multi-channel architecture, each vehicle equipped with two sets of transceivers can operate concurrently on three different channels. For example, in cluster-based multi-channel schemes, a cluster head vehicle coordinates and assigns an appropriate channel to its cluster members. However, these schemes are unsuitable for a single channel device performing on only one RF channel at a time which would waste channel resource and increase time to allocate a channel. Another approach, called LEACH-based scheme, selects channels randomly and ensures that each channel is selected once within a round in each vehicle. However, this leads to a situation that different vehicles might select the same channel in short-term duration. In this paper, we propose a multi-channel selection scheme, called minimum duration counter (MDC) scheme, which could apply to a single channel device, while utilizing the multi-channel architecture of an 802.11p/1609 network. In addition, we compare the MDC scheme with pure random (PR) and LEACH-based schemes in terms of fairness index (FI) and utilization to emphasize the fairness and to balance the traffic of multi-channel usage. Furthermore, we analyze the counter overflow probability distribution and propose solutions to the MDC scheme. Numerical results show that our scheme outperforms the PR and LEACH-based schemes in terms of multi-channel usage, traffic balancing, and fairness.

A SNR-based Multi-channel Multicast Scheme for Popular Video in Wireless Networks

Multi-channel multicast/broadcast solution is used to improve Quality of Service (QoS) /Quality of Experience (QoE) of Video-on-Demand (VoD) service in mobile Internet Protocol Television (IPTV) applications. In this paper, a SNR-based multi-channel multicast scheme (SBMM) for popular video in wireless networks is proposed. Different from the existing fast data broadcasting scheme (FB), the wireless channel Signal Noise Ratio (SNR) is taken into account in SBMM. The higher-SNR channel is assigned with a higher channel rate. The higher-rate channel is used to transmit higher priority chunks, through which users’ waiting time is reduced and bandwidth utilization is improved. Simulation results show that 22.11% of FB’s start-up delay is reduced in average by SBMM and 49.52% at most. Moreover, 4.01% of FB’s download time is reduced in average by SBMM and 8.25% at most in the price of a small increase in buffer requirements. The additional space taken is 2.11% of the total video size in average and 6.19% at most. At the same time, SBMM can use bandwidth effectively through delivering chunks according to different priorities. As hardware technology develops, it is reasonable to reduce users’ waiting time further in the price of a small increase in buffer requirements.

Performance Evaluation of Multi-Channel Operation For Safety And Non-Safety Application On Vehicular Ad Hoc Network IEEE 1609.4

The IEEE 1609.4 standard for Vehicular ad hoc network has been proposed to enhance the IEEE 802.11p MAC to support multi-channel operation. Multi-channel operation separate safety and non-safety related applications on a different channel. The vehicles must periodically switch between control channel and service channel to concurrently exchange the safety and non-safety related messages so that the problem of contention between applications can be avoided. In this work we measure the performance of both safety and non-safety related applications on multi-channel operations and compared to the single-channel operation. We analyze the performance of safety message dissemination model for two distinct cases: single-hop and multi-hop. Our experiment shows that multi-channel operation can provide better QoS performance than single channel. Using of the multi channel scheme can reduce the level of contention between safety and non safety applications that impact the amount of packet loss is reduced by 47% than single channel

The Unbalance Current Effect Caused by Non-Uniform Inductors in the Multi Phase Converter with a Single Current Sensor

To get less ripple of output voltage and reduce the inductor current capacity, the multi-channel scheme is a popular structure in the high power converter. By sharing the total current to multi channels, the channel current will be inversely proportional to the number of channels. Normally, the inductor of each channel is proposed to be uniform when the design procedure, and the inductor current of each channels also be supposed to be equal. And, the single current sensor structure will be considered, due to the cost reduction and the designed simplification. However, in real implementation, the inductance of each channels are different, and such kind of difference will cause some unexpected effect when using a single current sensor. To make sure the activity of the circuit as expectation, some non-uniform inductor effects in multi channel converter will be discussed in this paper. First, the measure method of the inductance error ratios in each channel will be proposed in the single current sensor scheme. Then, the unbalance current effect of the non-uniform inductance in the single sensor scheme will be discussed. The simulation results will be provided in this paper, which results will show the inductance measurement workable and the unexpected current obviously.

Position Tracking and Attitude Stable Control for an Unmanned Quadrotor Vehicle

A simplified dynamic model of the quadrotor is established. A multi-channel control scheme based on PID and dynamic inversion is proposed. Four channels are designed to achieve the position tracking and attitude stabilization of the quadrotor. A simulation shows the validity and good features of the control strategy.