MAC Layer Scheduling Research Articles

Simulation and analysis of C-V2X data transmission in different traffic scenarios based on MAC layer scheduling algorithms

With the rapid development of communication technology, vehicles are becoming more and more intelligent, and Vehicle to Vehicle (V2V) communication has become an important cornerstone for the future intelligence of vehicles. Because of the high-reliability and low-latency characteristics of 5G networks, many applications can be realized by using Vehicle to Network (V2N) communications. Different applications have different requirements for Quality of Service (QoS), which should be met by the network, and the base station can use different scheduling methods to satisfy these different requirements. This paper focuses on the scheduler at the MAC layer in 5G base stations. The scheduler must handle both video signals and other communication signals transmitted by the vehicle, and must also consider Hybrid Automatic Repeat reQuest (HARQ) retransmissions. We performed a C-V2X signaling network transmission simulation by using OMNeT++. We considered urban and motorway, two public transportation scenarios. Different types of data are set to be transmitted in two scenarios. We used different scheduling schemes for data scheduling, then investigated the performance of these scheduling schemes for transmitting data. The methods and simulation experiments mentioned in this paper are important for practical generalization.

Toward Protecting 5G Sidelink Scheduling in C-V2X Against Intelligent DoS Attacks

5G Cellular Vehicle-to-Everything (5G C-V2X) is emerging as the globally dominant connected vehicle technology. One critical application of 5G C-V2X is the direct exchange of safety-critical messages between vehicles to prevent crashes and correspondingly reduce roadway injuries and fatalities. While current C-V2X security protocols concern only message payloads, we expose vulnerabilities in the physical-layer attributes and decentralized MAC-layer scheduling algorithm of 5G C-V2X by developing two stealthy denial-of-service (DoS) attacks to exploit them. These low-duty-cycle attacks dramatically degrade C-V2X availability, increasing the likelihood of prolonged travel times and even vehicle crashes. We further develop detection and mitigation techniques for each attack, in part by exploiting new C-V2X features of 3GPP Rel-17. We experimentally evaluate our attacks and countermeasures in a hardware testbed composed of USRPs and state-of-the-art C-V2X kits as well as through extensive network and roadway simulations, showing that within seconds of initiation our attacks can reduce a target’s packet delivery ratio by 90% or that of the C-V2X channel to under 25%. We further evaluate our machine-learning detection and low-cost mitigation techniques, showing the latter completely thwart one attack and reduce the impact of the other by 80%, providing insight towards developing a more robust 5G C-V2X.

Delay-Based Resource Allocation With Fairness Guarantee and Minimal Loss for eMBB in 5G Heterogeneous Networks

Heterogeneity is defined as one of the core merits in the 5th Generation (5G) mobile systems. Such a trait is prominent in modern 5G traffic scenarios, i.e., enhanced Mobile Broadband (eMBB), where coarse Quality of Service (QoS) profiles need to be satisfied over the shared transmission channel. For that, Radio Resource Management (RRM) became a challenging problem that should be figured out based on the traffic scenario. Extensive efforts dwelled in the literature attempt to solve the resource allocation problem in the downlink channel by maximizing the gain for a certain aspect in the QoS profile. This, however, poses a challenge for 5G-related traffic scenarios such that multi-dimension QoS shall be attainable. Therefore, in this paper, a Delay-aware Resource Allocation for Guaranteed Fairness and minimal Loss (DRAGFL) is proposed to enhance the QoS for Real-Time (RT) services in eMBB 5G Heterogeneous Networks. The ultimate objective of DRAGFL is to maintain a steadily low latency for delay-sensitive flows without restraining the service fairness and the data loss in the overload states. DRAGFL enhances the efficiency of the MAC layer scheduler throughout three phases. Firstly, generating delay-derived weight matrix of the resources blocks to radio bearers from eMBB different classes. Then, greedy-based flows prioritization for Resource Blocks (RBs) assignment. Finally, the data rate of the RT and Non RT (NRT) flows is further emphasized through a channel-aware principle that is invoked conditioning to the remaining radio resources and available data to be scheduled in the interval. The performance evaluation using system-level simulations reveals prominent gains of DRAGFL in sustaining a steadily low end-to-end delay in the high congestion states. Moreover, it maintains ideal states of service fairness with low data loss for different traffic loads to indicate a promising MAC scheduler for the developing scenarios of 5G.

Designing an Energy Efficient Clustering in Heterogeneous Wireless Sensor Network

Designing an energy-efficient scheme in a Heterogeneous Wireless Sensor Network (HWSN) is a critical issue that degrades the network performance. Recharging and providing security to the sensor devices is very difficult in an unattended environment once the energy is drained off. A Clustering scheme is an important and suitable approach to increase energy efficiency and transmitting secured data which in turn enhances the performance in the network. The proposed algorithm Energy Efficient Clustering (EEC) works for optimum energy utilization in sensor nodes. The algorithm is proposed by combining the rotation-based clustering and energy-saving mechanism for avoiding the node failure and prolonging the network lifetime. This shows MAC layer scheduling is based on optimum energy utilization depending on the residual energy. In the proposed work, a densely populated network is partitioned into clusters and all the cluster heads are formed at a time and selected on rotation based on considering the highest energy of the sensor nodes. Other cluster members are accommodated in a cluster based on Basic Cost Maximum flow (BCMF) to allow the cluster head for transmitting the secured data. Carrier Sense Multiple Access (CSMA), a contention window based protocol is used at the MAC layer for collision detection and to provide channel access prioritization to HWSN of different traffic classes with reduction in End to End delay, energy consumption, and improved throughput and Packet delivery ratio(PDR) and allowing the cluster head for transmission without depleting the energy. Simulation parameters of the proposed system such as Throughput, Energy, and Packet Delivery Ratio are obtained and compared with the existing system.

Supporting Asymmetric Transmission for Full-Duplex Smart-Home Networks

In smart home networks, the traffic is often asymmetric (i.e., the uplink traffic load of a node is not equal to its downlink traffic load). This paper is concerned with how to achieve asymmetric transmission for a full-duplex (FD) IoT network (where the AP and nodes are FD-enabled). Most existing related schemes considered a partial FD network consisting of an FD AP and half-duplex (HD) nodes and achieved asymmetric transmission via PHY-layer mechanisms such as power control. However, for an FD network, the MAC-layer scheduling mechanism might be better to achieve asymmetric transmission than the PHY-layer power-control mechanism which will introduce complex interference management. To this end, we propose a simple and novel MAC scheduling scheme called AT-MAC to support asymmetric transmission in an FD IoT network. In our design, we differentiate uplink-dominant (UD) and downlink-dominant (DD) nodes. Upon receiving a packet, a receiver determines whether to execute a reverse transmission to the peer or to initiate a new transmission to a third node according to the type of UD and DD nodes. Next, we develop a theoretical framework to evaluate the throughput of AT-MAC. The extensive simulations verify that our design is very effective (namely, it can achieve the asymmetric transmission, while fully utilizing the FD gain to maximize the system throughput and lower the packet delay) and our theoretical model is very accurate. This paper is very helpful for designing quality-of-service-oriented FD MAC protocols.

Two-level QoS-aware frame-based downlink resources allocation for RT/NRT services fairness in LTE networks

In LTE, bandwidth resources allocation became a huge burden to be handled, as both of RT and NRT traffic should be processed fairly to satisfy their diverse QoS requirements. To tackle this issue in particular, in this work, we propose a fairness-based resources allocation method named Frame-based Game Theory (FGT), which can be flexibly implemented as an upper level in LTE downlink MAC layer; before the PRBs allocation function. Basically, FGT aim is to allow involved classes with different QoS requirements to fairly gain a part of the available channel resources to transmit their flows. Adhere, on every LTE-frame, a cooperative game scenario is designed. Wherein, Shapley formula is used to distribute the available amount of data within RT and NRT traffic classes. Then, conforming to these assigned resources portions to each traffic class, PRBs allocation process is triggered every TTI for the selected flows. In this work, we adopted some of the recent PRBs allocation methods as a lower level scheduler in order to illustrate a complete idea of MAC layer scheduling functions, and also to effectively evaluate FGT performance. Simulation results on various scenarios show that, fairness index for flows from different classes is increased when FGT is considered. The results also conveyed outperforming QoS indices for FGT on RT and NRT service in terms of throughput, PLR, as well as cell spectrum efficiency.

Performance Analysis of MAC Layer Scheduling Schemes for IMM Applications Over High Speed Wireless Campus Network in IEEE802.11e

In IMM traffic, while establishing a voice or video conversation, the sender and the receiver (the participants) should be mutually benefited by ensuring QoS like minimum data loss, sharing sufficient bandwidth and achieving high throughput over the WCN. To improve the network performance, scheduling mechanism is a challenging issue in the transmission of IMM traffic and it still needs to be solved over WCN. This paper aims to employ three different MAC layer scheduling mechanisms such as FIFO, RED and WRED for analysing the performance over the network, based on variation of traffic load in IEEE802.11e, and to evaluate the proposed schedulers' performance using different performance metrics in WCN. Here, the traffic load is varied by increasing the packet size and the traffic arrival rate, respectively. In order to analyse the network performance, the simulation has been done in QualNET 5.1 simulator. In the simulator, the mobility model is chosen as 'Random Waypoint' to change the node position randomly and the application as CBR. Simulation results show that increasing the packet size enables RED and WRED schedulers to perform better than FIFO in terms of all the performance metrics. On the other hand, increasing the traffic arrival rate helps to enhance the performance of the FIFO scheduler compared to the FIFO scheduling mechanism in the previous case. It is conclusive through the performance analyses that all three schedulers perform comparatively better when the traffic arrival rate is increased compared to increasing the packet size.

E-MiLi: Energy-Minimizing Idle Listening in Wireless Networks

WiFi interface is known to be a primary energy consumer in mobile devices, and idle listening (IL) is the dominant source of energy consumption in WiFi. Most existing protocols, such as the 802.11 power-saving mode (PSM), attempt to reduce the time spent in IL by sleep scheduling. However, through an extensive analysis of real-world traffic, we found more than 60 percent of energy is consumed in IL, even with PSM enabled. To remedy this problem, we propose Energy-Minimizing idle Listening (E-MiLi) that reduces the power consumption in IL, given that the time spent in IL has already been optimized by sleep scheduling. Observing that radio power consumption decreases proportionally to its clock rate, E-MiLi adaptively downclocks the radio during IL, and reverts to full clock rate when an incoming packet is detected or a packet has to be transmitted. E-MiLi incorporates sampling rate invariant detection, ensuring accurate packet detection and address filtering even when the receiver's sampling clock rate is much lower than the signal bandwidth. Further, it employs an opportunistic downclocking mechanism to optimize the efficiency of switching clock rate, based on a simple interface to existing MAC-layer scheduling protocols. We have implemented E-MiLi on the USRP software radio platform. Our experimental evaluation shows that E-MiLi can detect packets with close to 100 percent accuracy even with downclocking by a factor of 16. When integrated with 802.11, E-MiLi can reduce energy consumption by around 44 percent for 92 percent of users in real-world wireless networks.

A learning automata-based uplink scheduler for supporting real-time multimedia interactive traffic in IEEE 802.16 WiMAX networks

Worldwide interoperability for microwave access (WiMAX) is one of the most challenging forthcoming technologies providing broadband wireless access (BWA) which promises its users high Quality of Service (QoS) for supporting interactive real-time multimedia services. One of the most important enablers for this is the MAC layer scheduling. For WiMAX, no scheduling algorithm has been standardized and has been left open for the vendors to implement as per their own needs, thereby facilitating the differentiation between their products. Some of the most important metrics for an efficient scheduling algorithm are throughput, delay, jitter (time variation of delay), and packet loss. In this paper, we propose a learning automata (LA)-based scheduling algorithm for WiMAX uplink real-time multimedia interactive traffic in a point to multipoint (PMP) architecture. The main objective of the work presented in the paper is to present the design of an efficient algorithm for providing QoS to real-time uplink traffic. The results of simulation based performance evaluation studies show that the proposed algorithm results in an increase of throughput and decrease in delay and packet loss for real-time service flows as compared to other non-real-time traffic.

Research on QoS of ertPS of 802.16e Scheduling Algorithms

ertPS is an extension of rtPS and combines the efficiency of UGS and rtPS. Based on ertPS, base station can provide the active authorization unicast as UGS, and better than UGS. In OPNET environment, we model and simulate ertPS of moble WiMAX MAC layer scheduling algorithms based on IEEE 802.16e protocol. The simulation results compare the performance of ertPS with UGS on load, delay, delay variation and etc., and analyze QoS according to IEEE 802.16e protocol.

A Unified MAC and Routing Framework for Multichannel Multi-interface Ad Hoc Networks

Improving the capacity of wireless networks is critical and challenging. Although wireless standards such as IEEE 802.11 allow the use of multiple channels at the physical layer, current Media Access Control (MAC) and routing protocols of mobile ad hoc networks have mainly been developed to run over one channel. In this paper, we design a unified MAC and routing framework to exploit the temporal and frequency resources to significantly improve the throughput of ad hoc networks. Our joint channel assignment and routing scheme searches for an efficient transmission path, taking into account the constraints due to the limited number of available channels and radio interfaces and the impact of MAC-layer scheduling. Channel maintenance schemes are proposed to adapt the path and channel assignment in response to the changes of network topology and channel condition, as well as feedback from the MAC layer. Given the routing path and channel assignment, our scheduling scheme at the MAC layer explores the resources at the time domain to coordinate transmissions within an interference range to maximize channel usage, reduce channel access competition among nodes assigned to the same channel, coordinate radio interface usage to avoid unnecessary channel switching, and support load balancing. Complemented with the scheduling algorithm, a prioritized transmission scheme is presented to resolve collisions from multiple nodes scheduled to transmit on the same channel in the same time period and to reduce the transmission delay of mission-critical packets and message broadcast, which help further improve network performance. Our simulations demonstrate that our integrated MAC and routing design can efficiently utilize the channel resources to significantly improve the throughput of multichannel multi-interface ad hoc networks.

Design and Implementation of Hybrid MAC-Based Robust Architecture for Wireless Sensor Network

In this letter, we propose an energy efficient hybrid architecture, the Hybrid MAC-based Robust Architecture (HMR), for wireless sensor networks focusing on MAC layer's scheduling and adaptive security suite as a security sub layer. A hybrid MAC layer with TDMA and CSMA scheduling is designed to prolong network life time, and the multi-channel TDMA based active/sleep scheduling is presented. We also present the security related functionalities needed to employ a flexible security suite to packets dynamically. Implementation and testbed of the proposed framework based on IEEE 802.15.4 are shown as well.

A Class of Cross-Layer Optimization Algorithms for Performance and Complexity Trade-Offs in Wireless Networks

In this paper, we solve the problem of a joint optimal design of congestion control and wireless MAC-layer scheduling using a column generation approach with imperfect scheduling. We point out that the general subgradient algorithm has difficulty in recovering the time-share variables and experiences slower convergence. We first propose a two-timescale algorithm that can recover the optimal time-share values. Most existing algorithms have a component, called global scheduling, which is usually NP-hard. We apply imperfect scheduling and prove that if the imperfect scheduling achieves an approximation ratio rho, then our algorithm produces a suboptimum of the overall problem with the same approximation ratio. By combining the idea of column generation and the two-timescale algorithm, we derive a family of algorithms that allows us to reduce the number of times the global scheduling is needed.

SyncWUF: An Ultra Low-Power MAC Protocol for Wireless Sensor Networks

In wireless sensor networks, power consumption is one of the key design issues because a large number of sensor nodes are powered by cheap batteries. Switching the RF transceiver, which is one of the biggest power consumers in a sensor node, to low-power sleep mode as much as possible has been proven to be a very efficient way to save power with a factor of tens or even hundreds. So far, several schemes have been proposed to reduce the duty cycle of the RF transceiver by MAC layer scheduling. Among them, the wake-up-frame scheme and the WiseMAC are two very efficient protocols based on the so-called preamble sampling technology. This paper proposes combining these two schemes to obtain a further optimized low-power MAC protocol, called SyncWUF, for low-traffic wireless sensor network. Analytical and simulation results prove that our proposal achieves significant battery lifetime gain in different application cases without negatively affecting other important system parameters such as channel capacity and latency

SyncWUF: An Ultra Low-Power MAC Protocol for Wireless Sensor Networks

In wireless sensor networks, power consumption is one of the key design issues because a large number of sensor nodes are powered by cheap batteries. Switching the RF transceiver, which is one of the biggest power consumers in a sensor node, to low-power sleep mode as much as possible has been proven to be a very efficient way to save power with a factor of tens or even hundreds. So far, several schemes have been proposed to reduce the duty cycle of the RF transceiver by MAC layer scheduling. Among them, the wake-up-frame scheme and the WiseMAC are two very efficient protocols based on the so-called preamble sampling technology. This paper proposes combining these two schemes to obtain a further optimized low-power MAC protocol, called SyncWUF, for low-traffic wireless sensor network. Analytical and simulation results prove that our proposal achieves significant battery lifetime gain in different application cases without negatively affecting other important system parameters such as channel capacity and latency

QoS support for integrated services over CATV

Cable TV has emerged as a promising access network infrastructure for the delivery of voice, video, and high-speed data traffic. A central issue in the design of protocols for CATV networks is to support different levels of QoS for diverse user applications. While CATV service providers and equipment have standardized, in the so-called MCNS protocol, the basic network architecture and interfaces, issues in the MAC layer for QoS support are likely to be left for differentiation in vendor products. This article first presents an overview of the basic CATV network architectural assumptions and the set of QoS requirements for supporting integrated services over CATV. It then discusses a MAC layer scheduling protocol that can efficiently multiplex constant bit rate traffic, such as voice over IP with guaranteed delay bound, and best-effort traffic, such as data services with minimum bit rate guarantee, while achieving fairness on any excess available bandwidth. The performance of this algorithm is illustrated by simulation results using Opnet. We also discuss a dynamic polling mechanism that enhances the link utilization while preserving delay bounds for latency-critical traffic.