General Interference Model Research Articles

Randomized Scheduling of Real-Time Traffic in Wireless Networks Over Fading Channels

Despite the rich literature on scheduling algorithms for wireless networks, algorithms that can provide deadline guarantees on packet delivery for general traffic and interference models are very limited. In this paper, we study the problem of scheduling real-time traffic under a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">conflict-graph interference model</i> with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">unreliable links</i> due to channel fading. Packets that are not successfully delivered within their deadlines are of no value. We consider traffic (packet arrival and deadline) and fading (link reliability) processes that evolve as an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">unknown</i> finite-state Markov chain. The performance metric is efficiency ratio which is the fraction of packets of each link which are delivered within their deadlines compared to that under the optimal (unknown) policy. We first show a conversion result that shows classical non-real-time scheduling algorithms can be ported to the real-time setting and yield a constant efficiency ratio. In particular, Max-Weight Scheduling () yields an efficiency ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1/2$</tex-math> </inline-formula> . We then propose randomized algorithms that achieve efficiency ratios strictly higher than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1/2$</tex-math> </inline-formula> , by carefully randomizing over the maximal schedules. Further, we propose low-complexity and myopic distributed randomized algorithms, and characterize their efficiency ratio. Simulation results are presented that verify that the randomized algorithms outperform classical ones such as and for scheduling real-time traffic over fading channels.

Mixed-Numerology Channel Division for Wireless Avionics Intracommunications

Increasing attention has been paid to the wireless avionics intracommunications (WAIC) on aircraft. The frequency band of 4200-4400 MHz is recommended to WAIC by the International Telecommunication Union Radio Communication Sector (ITU-R), which thereby comes with a new challenge of using the available frequency band effectively to cater for the massive communication needs in aircraft. To address this challenge, we propose the first channel design framework named mixed-numerology channel division (MNCD) specifically for WAIC. Furthermore, a general interference model has been proposed to better utilize the recommended frequency band. Extensive evaluations show that the proposed framework can be a promising solution for massive wireless communications in aircraft.

Electromagnetically induced transparency based on magnetic toroidal mode of dielectric reverse-symmetric spiral metasurfaces

The intriguing properties of the toroidal mode (TM) resonance can potentially promote a low-loss light–matter interaction. This study proposes an electromagnetically induced transparency (EIT) resonance with a high quality factor, which can reach 7798, and low mode volume can reach 0.009 μm3, high contrast ratio can reach nearly 100%, in the near-infrared region, which is generated by the magnetic TM in a reverse-symmetric coupling spiral metasurface. A two-oscillator model can only explain the influence of near-field coupling at the EIT point for weak coupling. Moreover, a multipole decomposition method shows that the excitation mechanism of EIT resonances originates from the destructive interference between the subradiant modes (magnetic toroidal dipole-electric quadrupole) and magnetic dipole resonance. Consequently, a new general extinction spectrum interference model is applied to fit all coupling conditions for both weak and strong coupling results that perfectly correspond to the multipole decomposition method. The results of this study could be useful in the analysis and understanding of the electromagnetic coupling characteristics of nanoparticles and provide a design approach for novel metasurfaces for low-loss optical applications.

Achieving Efficient Routing in Reconfigurable DCNs

Heavy and highly dynamic traffic demands in today's data center networks (DCNs) pose great challenges to efficient traffic engineering. With gigabit bandwidth, wireless communication technologies, such as free space optics and 60GHz wireless, are promising to augment DCNs and enable efficient traffic engineering. Complementary to the emerging reconfigurable architectures, we aim to achieve efficient routing and effectively balance the load with the performance guarantee. We derive a general interference model and propose a decomposition technique with proven performance guarantee and solve the load balancing problem in reconfigurable DCNs. In addition, we propose two solutions, WiRo and OFS, to flexibly reconfigure network topology and enable hybrid-routing with paths consisting of both stable wired links and flexible wireless links with different methods. Our measurement-facilitated and trace-driven simulations demonstrate that our solutions outperform existing flow scheduling algorithms with the average throughput of large flows increased by up to 190% and the average completion time reduced by up to 72.6%. Meanwhile, the average completion time of small flows is reduced by up to 64.5%.

Optic Flow and Tunnel Vision in the Detection Response Task.

In a driving simulator, a backwards counting task, a simple steering task, and a fully autonomous driving task were applied to study the independent effects of cognitive load, visual-cognitive-manual load, and optic flow on visual detection response task (vDRT) performance. The study was designed to increase the understanding of the processes underlying vDRT effects. The tunnel vision effect induced by a "steering while driving" task found in a previous study was investigated further in this experiment. Stimulus eccentricity and conspicuity were applied as within-subjects factors. Cognitive load, visual-cognitive-manual load, and optic flow all resulted in increased vDRT response time (RT). Cognitive load and visual-cognitive-manual load both increased RT but revealed no interaction of task by stimulus eccentricity. However, optic flow resulted in a task by stimulus eccentricity interaction on vDRT RT that was evidence of a tunnel vision effect. The results suggested that optic flow may be a factor responsible for tunnel vision while driving, although this does not support the tunnel vision model because it is unrelated to workload. However, the results supported the general interference model for cognitive workload. The results have implications for the diagnosticity of the vDRT. During driving tasks, tunnel vision effects may occur as a result of optic flow, and these effects are unrelated to workload.

General Stress-Strength Interference and Gamma Process Combined Method for Space Solar Cell Components Reliability Analysis

Space solar cell components always suffered from the complex and hostile space environment. The reliability of space solar cell components is important to ensure the mission success of space satellites. However, the current research mostly focuses on solar cells' degradation mechanisms. There is less research based on the performance parameters of space solar cell component's degradation to analyze its reliability. Therefore, a reliability analysis method based on the method of modeling the performance degradation of space solar cell components is proposed. By combining general stress-strength interference model and Gamma process, the reliability model of space solar cell components is established. The accelerated degradation test based on the equivalent particle dose is performed to simulate the radiation influence and verify the proposed method. Compared with the displacement damage dose method, the proposed method can further develop the reliability analysis based on performance degradation analysis. Moreover, the cover glass and interconnection are also taken into account together to form a completed component analysis. Through analyzing the cover glass and interconnection experiment results, the cover glass can affect the component reliability; whereas, the interconnection has little influence at the particle radiation condition. Based on the proposed method, the reliability is easier to calculate with the degradation of output power.

The Effects of Cognitive and Visual Workload on Peripheral Detection in the Detection Response Task.

The independent effects of cognitive and visual load on visual Detection Response Task (vDRT) reaction times were studied in a driving simulator by performing a backwards counting task and a simple driving task that required continuous focused visual attention to the forward view of the road. The study aimed to unravel the attentional processes underlying the Detection Response Task effects. The claim of previous studies that performance degradation on the vDRT is due to a general interference instead of visual tunneling was challenged in this experiment. vDRT stimulus eccentricity and stimulus conspicuity were applied as within-subject factors. Increased cognitive load and visual load both resulted in increased response times (RTs) on the vDRT. Cognitive load increased RT but revealed no task by stimulus eccentricity interaction. However, effects of visual load on RT showed a strong task by stimulus eccentricity interaction under conditions of low stimulus conspicuity. Also, more experienced drivers performed better on the vDRT while driving. This was seen as evidence for a differential effect of cognitive and visual workload. The results supported the tunnel vision model for visual workload, where the sensitivity of the peripheral visual field reduced as a function of visual load. However, the results supported the general interference model for cognitive workload. This has implications for the diagnosticity of the vDRT: The pattern of results differentiated between visual task load and cognitive task load. It also has implications for theory development and workload measurement for different types of tasks.

Task-irrelevant distractors in the delay period interfere selectively with visual short-term memory for spatial locations

Visual short-term memory (VSTM) enables the representation of information in a readily accessible state. VSTM is typically conceptualized as a form of "active" storage that is resistant to interference or disruption, yet several recent studies have shown that under some circumstances task-irrelevant distractors may indeed disrupt performance. Here, we investigated how task-irrelevant visual distractors affected VSTM by asking whether distractors induce a general loss of remembered information or selectively interfere with memory representations. In a VSTM task, participants recalled the spatial location of a target visual stimulus after a delay in which distractors were presented on 75% of trials. Notably, the distractor's eccentricity always matched the eccentricity of the target, while in the critical conditions the distractor's angular position was shifted either clockwise or counterclockwise relative to the target. We then computed estimates of recall error for both eccentricity and polar angle. A general interference model would predict an effect of distractors on both polar angle and eccentricity errors, while a selective interference model would predict effects of distractors on angle but not on eccentricity errors. Results showed that for stimulus angle there was an increase in the magnitude and variability of recall errors. However, distractors had no effect on estimates of stimulus eccentricity. Our results suggest that distractors selectively interfere with VSTM for spatial locations.

On the Performance of Largest-Deficit-First for Scheduling Real-Time Traffic in Wireless Networks

This paper considers the problem of scheduling real-time traffic in wireless networks. We consider ad hoc wireless networks with general conflict graph-based interference model and single-hop traffic. Each packet is associated with a deadline and will be dropped if it is not transmitted before the deadline. The number of packet arrivals in each time-slot and the maximum delay before the deadline are independent and identically distributed across time. We require a minimum fraction of packets to be delivered. At each link, we assume the link keeps track of the difference between the minimum number of packets that need to be delivered so far and the number of packets that are actually delivered, which we call the deficit. The largest-deficit-first (LDF) policy schedules links in descending order according to their deficit values, which is a variation of the longest-queue-first (LQF) policy for non-real-time traffic. We prove that the efficiency ratio of LDF, which is the fraction of the throughput region that LDF can achieve for given traffic distributions, can be lower-bounded by a quantity that we call the real-time local-pooling factor (R-LPF). We further prove that a lower bound on the R-LPF can be related to the weighted sum of the service rates, with a special case of 1/(β + 1) by considering the uniform weight, where β is the interference degree of the conflict graph. We also propose a heuristic consensus algorithm that can be used to obtain a good weight vector for such lower bounds for given network topology.

On Link Scheduling Under Blockage and Interference in 60-GHz Ad Hoc Networks

In this paper, we tackle the problem of minimum time length link scheduling in 60-GHz ad hoc wireless networks using directional antennas with directional beamforming, under both traffic demand and signal to interference and noise ratio constraints. Both single-hop and multi-hop cases are considered. For the single-hop scenario, a binary integer programming problem is formulated by incorporating a general interference model for directional transmissions and a Markov chain-based blockage model. Two effective solution algorithms are proposed, including a greedy algorithm that maximizes the instant throughput for each time slot, and a column generation-based algorithm that iteratively improves the current link schedule. For the multi-hop scenario, we develop a more complicated problem formulation incorporating both route selection and flow conservation constraints. We also develop an effective algorithm to solve the multi-hop problem. The performance of the proposed algorithms is validated with simulations.

Truthful Spectrum Auctions With Approximate Social-Welfare or Revenue

In cellular networks, a recent trend in research is to make spectrum access dynamic in the spatial and temporal dimensions for the sake of efficient utilization of spectrum. In one such model, the spectrum is divided into channels and periodically allocated to competing base stations using an auction-based market mechanism. An “efficient” auction mechanism is essential to the success of such a dynamic spectrum access model. A key objective in designing an auction mechanism is “truthfulness.” Combining this objective with an optimization of some social choice function (such as the social-welfare or the generated revenue) is highly desirable. In this paper, we design polynomial-time spectrum auction mechanisms that are truthful and yield an allocation with $O(1)$ -approximate social-welfare or revenue. Our mechanisms generalize to general interference models. To the best of our knowledge, ours is the first work to design polynomial-time truthful spectrum auction mechanisms with a constant-factor approximation of either the expected revenue or the social-welfare. We demonstrate the performance of our designed mechanism through simulations.

Opportunistic Scheduling and Channel Allocation in MC-MR Cognitive Radio Networks

In this paper, we use the Lyapunov optimization technique to develop scheduling policies for multiradio multichannel cognitive networks to optimize jointly the throughput and the average delay of a secondary network, with limited interference to primary users (PUs)' transmission. In particular, we consider three scenarios, including a static single-hop secondary network, a static multihop secondary network, and a mobile secondary network. For these cases, with the consideration of general mobility and interference models, we design efficient scheduling and channel allocation algorithms based on the concept of Lyapunov drift and give the corresponding performance bound. Furthermore, our theoretical analysis demonstrates that the proposed algorithms can achieve a flexible tradeoff between network throughput and average backlogs by using the Lyapunov optimization technique. Finally, the efficiency of the proposed algorithms is verified by the numerical simulations.

Approximation Algorithms for Throughput Maximization in Wireless Networks With Delay Constraints

We study the problem of throughput maximization in multihop wireless networks with end-to-end delay constraints for each session. This problem has received much attention starting with the work of Grossglauser and Tse (2002), and it has been shown that there is a significant tradeoff between the end-to-end delays and the total achievable rate. We develop algorithms to compute such tradeoffs with provable performance guarantees for arbitrary instances, with general interference models. Given a target delay-bound Δ(c) for each session c, our algorithm gives a stable flow vector with a total throughput within a factor of O(log Δ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> /loglog Δ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> ) of the maximum, so that the per-session (end-to-end) delay is O(((log Δ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> /loglog Δ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> )Δ(c)) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ), where Δ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> =max <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> {Δ(c)}; note that these bounds depend only on the delays, and not on the network size, and this is the first such result, to our knowledge.

A Low-Complexity Congestion Control and Scheduling Algorithm for Multihop Wireless Networks With Order-Optimal Per-Flow Delay

Quantifying the end-to-end delay performance in multihop wireless networks is a well-known challenging problem. In this paper, we propose a new joint congestion control and scheduling algorithm for multihop wireless networks with fixed-route flows operated under a general interference model with interference degree K. Our proposed algorithm not only achieves a provable throughput guarantee (which is close to at least 1/K of the system capacity region), but also leads to explicit upper bounds on the end-to-end delay of every flow. Our end-to-end delay and throughput bounds are in simple and closed forms, and they explicitly quantify the tradeoff between throughput and delay of every flow. Furthermore, the per-flow end-to-end delay bound increases linearly with the number of hops that the flow passes through, which is order-optimal with respect to the number of hops. Unlike traditional solutions based on the back-pressure algorithm, our proposed algorithm combines window-based flow control with a new rate-based distributed scheduling algorithm. A key contribution of our work is to use a novel stochastic dominance approach to bound the corresponding per-flow throughput and delay, which otherwise are often intractable in these types of systems. Our proposed algorithm is fully distributed and requires a low per-node complexity that does not increase with the network size. Hence, it can be easily implemented in practice.

The impact of network topology on delay bound in wireless Ad Hoc networks

We consider single channel wireless networks with interference constraint among the links that can be activated simultaneously. The traffic flows are assumed to be single hop. Delay performance of the well known throughput optimal maximum weight link scheduling algorithm has been studied recently. In this paper, we study the relation between network topology and delay of maximum weight link scheduling algorithm. First, we consider 1-hop interference model. Under this interference model, an upper bound for the average delay of packets is derived analytically in terms of edge chromatic number of the network graph. Then the results have been extended to the case of general interference model. Under this model of interference, an upper bound for delay as a function of chromatic number of conflict graph is derived. Since chromatic number and edge chromatic number are network topology parameters, the results show that how the upper bound of delay is affected by network topology. Simulation results confirm our analytical relations.

Belief Propagation Methods for Intercell Interference Coordination in Femtocell Networks

Interference coordination is a fundamental challenge in emerging femtocellular deployments. This paper considers a broad class of interference coordination and resource allocation problems for wireless links based on utility maximization with a general linear mixing interference model suitable for complex femtocellular systems. The resulting optimization problems are typically hard to solve optimally even using centralized algorithms but are an essential computational step in implementing rate-fair and queue stabilizing scheduling policies in wireless networks. We consider a belief propagation framework to solve such problems approximately. In particular, we construct approximations to the belief propagation iterations to obtain computationally simple and distributed algorithms with low communication overhead. Notably, our methods are very general and apply to, semi-static and dynamic interference coordination problems including the optimization of transmit powers, transmit beamforming vectors, fractional frequency reuse (FFR) and sub-band allocations to maximize the above objective. Numerical results for femtocell deployments demonstrate that such algorithms compute a very good operating point in typically just a couple of iterations.

A Refined Performance Characterization of Longest-Queue-First Policy in Wireless Networks

One of the major challenges in wireless networking is how to optimize the link scheduling decisions under interference constraints. Recently, a few algorithms have been introduced to address the problem. However, solving the problem to optimality for general wireless interference models is known to be NP-hard. The research community is currently focusing on finding simpler suboptimal scheduling algorithms and on characterizing the algorithm performance. In this paper, we address the performance of a specific scheduling policy called Longest Queue First (LQF), which has gained significant recognition lately due to its simplicity and high efficiency in empirical studies. There has been a sequence of studies characterizing the guaranteed performance of the LQF schedule, culminating at the construction of the σ-local pooling concept by Joo In this paper, we refine the notion of σ -local pooling and use the refinement to capture a larger region of guaranteed performance.

Delay Analysis and Optimality of Scheduling Policies for Multihop Wireless Networks

We analyze the delay performance of a multihop wireless network with a fixed route between each source-destination pair. We develop a new queue grouping technique to handle the complex correlations of the service process resulting from the multihop nature of the flows. A general set-based interference model is assumed that imposes constraints on links that can be served simultaneously at any given time. These interference constraints are used to obtain a fundamental lower bound on the delay performance of any scheduling policy for the system. We present a systematic methodology to derive such lower bounds. For a special wireless system, namely the clique, we design a policy that is sample-path delay-optimal. For the tandem queue network, where the delay-optimal policy is known, the expected delay of the optimal policy numerically coincides with the lower bound. We conduct extensive numerical studies to suggest that the average delay of the back-pressure scheduling policy can be made close to the lower bound by using appropriate functions of queue length.

Crossmodal semantic priming by naturalistic sounds and spoken words enhances visual sensitivity.

We propose a multisensory framework based on Glaser and Glaser's (1989) general reading-naming interference model to account for the semantic priming effect by naturalistic sounds and spoken words on visual picture sensitivity. Four experiments were designed to investigate two key issues: First, can auditory stimuli enhance visual sensitivity when the sound leads the picture as well as when they are presented simultaneously? And, second, do naturalistic sounds (e.g., a dog's "woofing") and spoken words (e.g., /dɔg/) elicit similar semantic priming effects? Here, we estimated participants' sensitivity and response criterion using signal detection theory in a picture detection task. The results demonstrate that naturalistic sounds enhanced visual sensitivity when the onset of the sounds led that of the picture by 346 ms (but not when the sounds led the pictures by 173 ms, nor when they were presented simultaneously, Experiments 1-3A). At the same SOA, however, spoken words did not induce semantic priming effects on visual detection sensitivity (Experiments 3B and 4A). When using a dual picture detection/identification task, both kinds of auditory stimulus induced a similar semantic priming effect (Experiment 4B). Therefore, we suggest that there needs to be sufficient processing time for the auditory stimulus to access its associated meaning to modulate visual perception. Besides, the interactions between pictures and the two types of sounds depend not only on their processing route to access semantic representations, but also on the response to be made to fulfill the requirements of the task.

Approximation Algorithms for a Link Scheduling Problem in Wireless Relay Networks with QoS Guarantee

The emerging wireless relay networks (WRNs) are expected to provide significant improvement on throughput and extension of coverage area for next-generation wireless systems. We study an optimization problem for multihop link scheduling with bandwidth and delay guarantees over WRNs. Our optimization problem is investigated under a more general interference model with a generic objective. The objective can be based on various kinds of performance indexes (e.g., throughput, fairness, and capacity), which can be determined by service providers. Through our theoretical analysis, the intractability and inapproximability of the optimization problem are shown. Due to the intractable computational complexity, we present efficient algorithms to provide a reasonable small approximation factor against any optimal solution even for a worst-case input. Furthermore, some experimental results indicate that our algorithms yield near-optimal performance in the average case.