Ratio Scheduling Research Articles

Channel and Delay Weighted Response Ratio Scheduler for 5G and Beyond Systems

Channel and Delay Weighted Response Ratio Scheduler for 5G and Beyond Systems

Maximum Rate Scheduling With Adaptive Modulation in Mixed Impulsive Noise and Additive White Gaussian Noise Environments

This article proposes an opportunistic scheduling scheme based on adaptive modulation for users in a mixed noise environment, where some users are under additive white Gaussian noise (AWGN) and other users are exposed to impulsive noise. Unlike the scenario, where all the users are in an AWGN environment, the maximum signal-to-noise ratio (SNR) scheduler does not provide the maximum capacity if users are in a mixed noise environment. In the proposed scheduling scheme, called maximum rate scheduler, the user with the highest rate (or highest modulation order), instead of highest SNR, is selected. To evaluate the performance of the proposed scheduling scheme, the analyses of average spectral efficiency, outage probability and system capacity are provided along with a simple calculation of SNR thresholds for adaptive modulation in an impulsive noise environment satisfying target symbol error rate (SER). Simulation results illustrate that system capacity with the proposed scheduling given target SER = 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> and the average spectral efficiency are improved by 156% and 124%, respectively, at SNR = 5 dB when a strong impulsive noise is present.

Task Offloading and Trajectory Control for UAV-Assisted Mobile Edge Computing Using Deep Reinforcement Learning

Mobile Edge Computing (MEC) has been widely employed to support various Internet of Things (IoT) and mobile applications. By leveraging the advantages of easily deployed and flexibility of Unmanned Aerial Vehicle (UAV), one of MEC primary functions is employing UAVs equipped with MEC servers to provide computation supports for the offloaded tasks by mobile users in temporally hotspot areas or some emergent scenarios, such as sports game areas or destroyed by natural disaster areas. Despite the numerous advantages of UAV carried with a MEC server, it is restricted by its limited computation resources and sensitive energy consumption. Moreover, due to the complexity of UAV-assisted MEC system, its computational resource optimization and energy consumption optimization cannot be achieved well in traditional optimization methods. Furthermore, the computational cost of the MEC system optimization is often exponentially growing with the increase of the MEC servers and mobile users. Therefore, it is considerably challenging to control the UAV positions and schedule the task offloading ratio. In this paper, we proposed a novel Deep Reinforcement Learning (DRL) method to optimize UAV trajectory controlling and users’ offloaded task ratio scheduling and improve the performance of the UAV-assisted MEC system. We maximized the system stability and minimized the energy consumption and computation latency of UAV-assisted the MEC system. The simulation results show that the proposed method outperforms existing work and has better scalability.

Regret Benefit Ratio Link Scheduler for Wireless Backhaul With Directional Antennas

With huge bandwidth available in the mmWave band, wireless backhaul at mmWave frequencies can be a promising backhaul solution for small cells densely deployed underlying the homogeneous macrocells. With multiple links under such mmWave wireless network, it is desired to have a scheduling mechanism that can effectively improve the capacity of network with Quality of Service (QoS) considered. In this paper, we propose the regret benefit ratio scheduler (RBRS) that can maximize the number of links with their QoS requirements satisfied. Our proposed indicator, called regret benefit ratio (RBR), allows us to simultaneously maximize the QoS benefit and minimize contention among links under directional antennas. We design RBRS for a time slot based centralized control mmWave network in which we utilize RBR to find suitable concurrent transmission links for every single time slot. Furthermore, we also propose a distributed scheme under Carrier-sense multiple access with collision avoidance (CSMA/CA), which implements the RBR by prioritizing Medium Access Control (MAC) contention window to provide better concurrent transmission support while achieving the QoS-aware capability. Simulations in the 73-GHz band are conducted to demonstrate the superior performance of our algorithm under different criteria.

Improved Scheduling Mechanisms for Synchronous Information and Energy Transmission.

Wireless energy collecting technology can effectively reduce the network time overhead and prolong the wireless sensor network (WSN) lifetime. However, the traditional energy collecting technology cannot achieve the balance between ergodic channel capacity and average collected energy. In order to solve the problem of the network transmission efficiency and the limited energy of wireless devices, three improved scheduling mechanisms are proposed: improved signal noise ratio (SNR) scheduling mechanism (IS2M), improved N-SNR scheduling mechanism (INS2M) and an improved Equal Throughput scheduling mechanism (IETSM) for different channel conditions to improve the whole network performance. Meanwhile, the average collected energy of single users and the ergodic channel capacity of three scheduling mechanisms can be obtained through the order statistical theory in Rayleig, Ricean, Nakagami-m and Weibull fading channels. It is concluded that the proposed scheduling mechanisms can achieve better balance between energy collection and data transmission, so as to provide a new solution to realize synchronous information and energy transmission for WSNs.

DO‐Fast: a round‐robin opportunistic scheduling protocol for device‐to‐device communications

AbstractIn this paper, we consider the distributed opportunistic scheduling problem for the Orthogonal Frequency Division Multiplexing OFDM‐based device‐to‐device (D2D) communications, where D2D links contend for access to the dedicated spectrum with limited assistance from cellular infrastructures. Particularly, a synchronous distributed opportunistic scheduling protocol under fairness constraints (DO‐Fast) is prompted. In DO‐Fast, a round‐robin strategy is integrated with the opportunistic scheduling to tackle the trade‐off between system throughput and access fairness. Moreover, without instantaneous channel state information at receivers, we incorporate a priority allocation scheme, where access priorities are assigned randomly in a local fashion. Consequently, DO‐Fast is robust against imperfect channel estimates and inaccurate channel state information ordering. In addition, the opportunistic strategy in DO‐Fast is distinguished from the existing ones in that efficient spatial reuse is exploited by allowing concurrent transmissions based on the signal‐to‐interference ratio scheduling criterion. Meanwhile, access opportunities are moderately granted for poor quality links by the round‐robin strategy for fairness considerations. We analyze and compare three practical scheduling strategies in terms of the access probability. We also evaluate access fairness through Jain's Index. It is shown via numerical and simulation results that DO‐Fast could achieve efficient spectrum utilization and guarantee the short‐term fairness. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Deadline Maximum Signal to Interference Ratio Scheduling Algorithm for WiMAX

The IEEE 802.16 standard, which is called Worldwide Interoperability for Microwave Access (WiMAX) is a low cost solution for Internet access in metropolitan and rural areas; it provides both high throughput and large coverage broadband wireless access. Although it defines five service level classes to support real-time and bandwidth demanding applications, each class is associated with a set of Quality of Service (QoS) parameters. However, the standard does not specify which scheduling algorithm should be used to serve packets. Due to the wireless channel variability, scheduling mechanisms widely studied for wired networks are not suitable for IEEE 802.16 networks. In this paper, we introduce Deadline maximum Signal to Interference Ratio scheduler , which makes bandwidth allocation decisions based on information about the channel quality and deadline. Simulation results show the proposed approach gains more delivering packet and decreases the average end to end delay and improve the fairness index.

Multi-User Scheduling Method Considering Fairness and Mitigation of Multi-Cell Interference for Multi-Hop Cellular System

In order to improve the cell boundary throughput performance and to extend the coverage area, relaying transmission with relay stations (RSs) is becoming a promising architecture for the next generation cellular systems. However, if RSs are operated in every cell, the interference between cells increases and the throughput improvement effect with RSs is prone to be restricted. In this paper, we propose a scheme reducing the interference from other cells by using packet transmission control. This packet transmitting control technique is realized by the compound scheduling technique with the Proportional fair (PF) scheduling and the Maximum Carrier-to-Interference power Ratio (Max CIR) scheduling. The proposed scheme can improve the throughput around the cell boundary by controlling the timing of transmission of each cell with appropriate power and user assignment. The simulation results show that the proposed method can also improve the fairness of user throughput and system throughput considering the users of whole cell.

Scheduling Algorithm to Optimize Jobs in Shop Floor

Problem statement: The ratio scheduling algorithm to solve the allocation of jobs in the shop floor was proposed. The problem was to find an optimal schedule so as to minimize the maximum completion time, the sum of distinct earliness and tardiness penalties from a given common due date d. Approach: The objective of the proposed algorithm was to reduce the early penalty and the late penalty and to increase the overall profit of the organization. The proposed method was discussed with different possible instances. Results: The test results showed that the algorithm was robust and simple and can be applied for any job size problem. Conclusion: The proposed algorithm gave encouraging result for the bench mark instances when the due date is less than half of the total processing time.

Adaptive Subframe Partitioning and Efficient Packet Scheduling in OFDMA Cellular System with Fixed Decode-and-Forward Relays

The integration of multihop relays with orthogonal frequency-division multiple access (OFDMA) cellular infrastructures can meet the growing demands for better coverage and higher throughput. Resource allocation in the OFDMA two-hop relay system is more complex than that in the conventional single-hop OFDMA system. With time division between transmissions from the base station (BS) and those from relay stations (RSs), fixed partitioning of the BS subframe and RS subframes can not adapt to various traffic demands. Moreover, single-hop scheduling algorithms can not be used directly in the two-hop system. Therefore, we propose a semi-distributed algorithm called ASP to adjust the length of every subframe adaptively, and suggest two ways to extend single-hop scheduling algorithms into multihop scenarios: link-based and end-to-end approaches. Simulation results indicate that the ASP algorithm increases system utilization and fairness. The max carrier-to-interference ratio (Max C/I) and proportional fairness (PF) scheduling algorithms extended using the end-to-end approach obtain higher throughput than those using the link-based approach, but at the expense of more overhead for information exchange between the BS and RSs. The resource allocation scheme using ASP and end-to-end PF scheduling achieves a tradeoff between system throughput maximization and fairness.

Behavioral characterization of mice lacking GIRK/Kir3 channel subunits

G protein-gated inwardly rectifying K(+) (GIRK/Kir3) channels mediate the postsynaptic inhibitory effects of many neurotransmitters and drugs of abuse. The lack of drugs selective for GIRK channels has hindered our ability to study their contributions to behavior. Here, we assessed the impact of GIRK subunit ablation on several behavioral endpoints. Mice were evaluated with respect to open-field motor activity and habituation, anxiety-related behavior, motor co-ordination and ataxia and operant performance. GIRK3 knockout ((-/-)) mice behaved indistinguishably from wild-type mice in this panel of tests. GIRK1(-/-) mice and GIRK2(-/-) mice, however, showed elevated motor activity and delayed habituation to an open field. GIRK2(-/-) mice, and to a lesser extent GIRK1(-/-) mice, also displayed reduced anxiety-related behavior in the elevated plus maze. Both GIRK1(-/-) mice and GIRK2(-/-) mice displayed marked resistance to the ataxic effects of the GABA(B) receptor agonist baclofen in the rotarod test. All GIRK(-/-) mice were able to learn an operant task using food as the reinforcing agent. Within-session progressive ratio scheduling, however, showed elevated lever press behavior in GIRK2(-/-) mice and, to a lesser extent, in GIRK1(-/-) mice. Phenotypic differences between mice lacking GIRK1, GIRK2 and GIRK3 correlate well with the known impact of GIRK subunit ablation on neurotransmitter-gated GIRK currents, arguing that most neuronal GIRK channels contain GIRK1 and/or GIRK2. Altogether, our data suggest that GIRK channels make important contribution to a range of behaviors and may represent points of therapeutic intervention in disorders of anxiety, spasticity and reward.

Effect of cooperative and selection relaying schemes on multiuser diversity in downlink cellular systems with relays

In this paper, we investigate the effect of cooperative and selection relaying schemes on multiuser diversity in downlink cellular systems with fixed relay stations (RSs). Each mobile station (MS) is either directly connected to a base station (BS) and/or connected to a relay station. We first derive closed-form solutions or upper-bound of the ergodic and outage capacities of four different downlink data relaying schemes: A direct scheme, a relay scheme, a selection scheme, and a cooperative scheme. The selection scheme selects the best access link between the BS and an MS. For all schemes, the capacity of the BS-RS link is assumed to be always larger than that of RS-MS link. Half-duplex channel use and repetition based relaying schemes are assumed for relaying operations. We also analyze the system capacity in a multiuser diversity environment in which a maximum signal-to-noise ratio (SNR) scheduler is used at a base station. The result shows that the selection scheme outperforms the other three schemes in terms of link ergodic capacity, link outage capacity, and system ergodic capacity. Furthermore, our results show that cooperative and selection diversity techniques limit the performance gain that could have been achieved by the multiuser diversity technique.

Control point policy: part 1–efficiency within make-to-order environments

The recognition of the desire for punctual delivery of products has lead to the use of the service level as a common performance criterion for measuring the proportion of products that meet due dates specified by the customer. To successfully increase the service level, a manufacturing system may respond more quickly to orders by reducing the levels of in-process inventory in the system and hence decrease throughput times. This paper examines the use of the recently developed Control Point Policy (CPP) in improving service levels in re-entrant, ‘make-to-order’ manufacturing systems and compares its effectiveness with that of the Critical Ratio scheduling rule. Simulation studies have been undertaken to provide insight into how and when to apply the CPP policy within such environments with results indicating that, in cases requiring small storage areas between machines, the CPP results in better service level performance.

Random Unitary Beamforming With Partial Feedback for MISO Downlink Transmission Using Multiuser Diversity

In this paper, we study the problem of downlink transmission in multiple-input-single-output (MISO) wireless communication systems using multiuser diversity. There are antennas at the base station (BS) and single-antenna receivers. The performance of multiuser diversity depends on the number of users that have independent channel realizations. It is well known that increasing the number of users improves the performance at the expense of increasing feedback that is proportional to the number of users. For sufficiently large K, the capacity scales like M log log K. When K is large, increasing feedback limits practical applications of the multiuser diversity. Our approach is to reduce the feedback by selecting a threshold for the linfin-norm of the normalized cross-correlation (||zk||infin) between the users' channel and the beamforming matrix based on the random unitary beamforming. The average amount of feedback per time slot is real numbers and integers which does not change with K. To improve fairness, an equal ratio scheduling algorithm which could serve the users with different rate requirements is developed. Monte Carlo simulation results is provided to verify the performance of the proposed algorithm.

Golden ratio scheduling for flow control with low buffer requirements

A method of flow control that requires very few buffers to be allocated at each node to virtual circuits (or sessions) that have to transverse many links is described. Transmissions are scheduled using the golden ratio policy of A. Itai and Z. Rosberg (1984). It is shown that the buffer requirements of a session grow at most logarithmically with the number of slots allotted to it. As an immediate consequence, intra-network delays are bounded.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Learning to Live with Variable Ratio Scheduling: The Career of a Horse Player*

Although adaptations to variable ratio scheduling are an inevitable aspect of sustained gambling, the long term significance of this phenomena has not been researched adequately. Linking ethnographic data collection and social learning analysis, the author presents a career portrayal of regular horse race gamblers that describes how they deal with differential reinforcement. Over time, most horse players develop strategies that allow them to continue their gambling careers despite the low probability of financial success. The career portrayal also identifies reward factors that help explain the persistence at gambling demonstrated by inveterate horse players.

Note—On Anomalies in Dynamic Ratio Type Scheduling Rules: A Clarifying Analysis

Previous authors have shown that dynamic ratio scheduling rules do not always behave as intended. A recent proposal by Adam and Surkis (Adam, N. R., J. Surkis. 1980. Priority update intervals and anomalies in dynamic ratio type job shop scheduling rules. Management Sci. 26 (12, December) 1227–1237.) to correct such anomalies is shown to be in error. The reason why such anomalies occur is clarified and a rule which prevents such anomalies is presented.

Optimal Control Solution of the Automotive Emission-constrained Minimum Fuel Problem

The automotive industry is confronted with the conflicting goals of improving fuel economy, reducing exhaust emissions, and maintaining vehicle driveability. Difficulties arise in the application of optimal control theory to this problem because transient models of the fuel, emission, and driveability responses do not exist. To circumvent these difficulties, the mathematical models are replaced by a sophisticated experimental test setup. To demonstrate the applicability of the optimal control approach without a mathematical model, the problem of the hot-start optimization of fuel economy subject to emission constraints problem is solved. Air-fuel ratio and spark advance are employed as the controls. Operational considerations necessitate the direct incorporation of the feedback control functions into the gradient-type solution algorithm. For this case, the results show that the oxides of nitrogen (NOx) are controlled primarily through air-fuel ratio scheduling. The soîution of this problem demonstrates the feasibility of the experimental optimal control approach. The second problem involves the cold-start portion of the Federal Test Procedure (FTP). The transient influences of the engine and catalytic converter warmup are analyzed by the optimization procedure and are reflected in the optimal feedback functions. For this case, the control of hydrocarbons (HC) and carbon monoxide (CO) is accomplished by minimizing engine-out concentrations immediately after startup. As the system warms up, the controls are gradually adjusted to reduce the fuel rate and to take advantage of the oxidation in the exhaust manifold and catalytic converter. The NOX control is accomplished primarily through lean air-fuel ratio scheduling during hot operation. Finally, the hot-start optimization program is generalized to include an explicit surge-type driveability constraint on the controls. Comparison of the results of the hot-start problems reveals the trade-off between fuel economy and driveability. The imposition of the driveability constraint results in emission control primarily by retarding the spark advance and less by lean air-fuel ratio scheduling. Consequently, the driveability constraint causes a slight fuel economy penalty.

Note—Author's Reply to Graves' Note on the Paper “Critical Ratio Scheduling: An Experimental Analysis”

Author's Reply to Graves' Note on the Paper (Berry, W. L., V. Rao. 1975. Critical ratio scheduling: an experimental analysis. Management Sci. 22 (2, October) 192–201).

Note—A Note on “Critical Ratio Scheduling: An Experimental Analysis”

A recent journal article [Berry, W. L., Rao, V. 1975. Critical ratio scheduling: an experimental analysis. Management Sci. 22 (2, October) 192–201.] by Berry and Rao on job shop scheduling reported some counterintuitive results concerning the use of dynamic operating information in making priority scheduling decisions. The results of the article, based on a simulation experiment, indicate that dynamic information on queue waiting time at individual machines and on the inventory status of individual items fails to improve the performance of the production system. In fact, the reported performance of the dynamic rule was inferior to the static rules in five out of six cases. The purpose of this note is to call attention to the possibility that it is Berry and Rao's construction and/or use of this information, and not the value of the information itself, which is in question.