Channel-aware Scheduler Research Articles

Analysis for Joint Delay-Power Tradeoff with Buffer/Channel-Aware and Its FPGA Implementation in Wireless Sensor Networks

In this paper, we aim to investigate the delay-power tradeoff problem which is attracting widespread interest due to its importance in wireless technology. This research has two main objectives. First, to assess the effect of different system parameters on the performance metrics. Second, to provide a solution for this optimization problem. A two-state, slow-fading channel is categorized into good and bad channel states. An adaptive transmission and random data arrivals are considered in our model. Each channel category has its own Markov chain, which is used in modeling the system. A joint Buffer-Aware and Channel-Aware (BACA) problem was introduced. In addition, an enhanced iterative algorithm was introduced for obtaining a sub-optimal delay-power tradeoff. The results show that the tradeoff curve is piecewise linear, convex and decreasing. Furthermore, a channel-aware system was investigated to provide analysis of the effect of system parameters on the delay and power. The obtained results show that the dominant factors that control the system performance are based on the arrival rate and the channel goodness factor. Moreover, a simplified field programable gate array (FPGA) hardware implementation for the channel aware system scheduler is presented. The implementation results show that the consumed power for the proposed scheduler is 98.5 mW and the maximum processing clock speed is 190 MHz.

A Low-Complexity Scheduler to Improve the Number of Satisfied Video Streaming Users in LTE

The ongoing development of mobile communication networks has led to an expressive growth in capacity demand, mainly due to video streaming services, which together with the Internet of Things sector represent a challenge for the mobile network operators. Video streaming is already responsible for most of the Internet traffic, and the real-time video calling services are becoming increasingly common. The use of strict quality of service parameters can lead to global resource starvation, where no user can be served with the resources available. In case of network congestion is important to prevent global resource starvation problem and also serve as many users as possible with a reasonable quality of service while still ensuring a minimum of connectivity to other users. Considering this problem, this article presents a new channel-aware downlink packet scheduler for Long Term Evolution networks that aims to increase the number of satisfied real-time video streaming users. The performance evaluation was done through computer simulations, using peak signal-to-noise ratio (PSNR) to compare the quality delivered by competing algorithms, and the number of users who are given enough resources to play video with quality. The results indicate that the proposed method outperforms the commonly-used algorithms considering the number of satisfied users and average video PSNR, mainly under moderate-to-heavy traffic load conditions.

Multi-Layer FFR-Aided OFDMA-Based Networks Using Channel-Aware Schedulers

In orthogonal frequency-division multiple access (OFDMA) networks, the use of universal frequency reuse improves overall cell capacity at the cost of very high levels of inter-cell interference particularly affecting the users located in the cell-edge regions. In order to provide a better quality of experience to cell-edge users while still achieving high spectral efficiencies, conventional fractional frequency reuse (FFR) schemes split the cells into inner and outer regions (or layers) and allocate disjoint frequency resources to each of these regions by applying higher frequency reuse factors to the outer regions. Recently, multi-layer FFR-aided OFDMA-based designs, splitting the cell into inner, middle, and outer layers, have been proposed with the aim of further improving the throughput fairness among users. This paper presents an analytical framework allowing the performance evaluation and optimization of multi-layer FFR-aided OFDMA-based networks. Tractable mathematical expressions of the average spectral efficiency are derived and used to pose optimization problems allowing network designers to achieve the optimal trade-off between spectral efficiency and fairness. Analytical and simulation results clearly show that, irrespective of the channel-aware scheduler in use, multi-layer FFR-schemes can outperform the conventional two-layer FFR architectures.

Mitigating Cross-VM Side Channel Attack on Multiple Tenants Cloud Platform

Virtualization is a key enabling technology in cloud computing. Multiple tenants can share computing resource of cloud provider on demand. While sharing can reduce the expenses of computing, it brings security vulnerability as well since the isolation between different VMs could be violated through side-channel attacks. Recent researches point out that by leveraging memory bus contention, two colluded malware within different VMs (but on the same host) may use diversity of memory access latency as a covert channel to deliver security critical information, such as user passwords or credit card numbers, which can bypass access control policies enforced by the guest OS or even the hypervisor. The bandwidth of such covert channel could be up to hundreds of kilobytes per second, which is fast enough to transfer large data objects. In this paper we propose a covert channel aware scheduler that considers security as first class to mitigate such side- channel attack. The scheduler is able to control the execution time overlapping of different VMs, and can also inject noise periodically to mitigate the threat of potential side channels. We have built a prototype of the proposed scheduler that enables overlapping control and noise injection. The performance evaluations show that the overhead introduced is acceptable. Meanwhile, the new scheduler offers the user to dynamically configure scheduling parameters to adapt to diverse circumstances, in order to make a balance between performance and security. Index Terms—virtual machine, cloud computing, security, side channel attack, scheduling algorithm

Analysis of performance trade-offs for an adaptive channel-aware wireless scheduler

In this paper, we consider the scheduling problem where data packets from K input-flows need to be delivered to K corresponding wireless receivers over a heterogeneous wireless channel. Our objective is to design a wireless scheduler that achieves good throughput and fairness performance while minimizing the buffer requirement at each wireless receiver. This is a challenging problem due to the unique characteristics of the wireless channel. We propose a novel idea of exploiting both the long-term and short-term error behavior of the wireless channel in the scheduler design. In addition to typical first-order Quality of Service (QoS) metrics such as throughput and average delay, our performance analysis of the scheduler permits the evaluation of higher-order metrics, which are needed to evaluate the buffer requirement. We show that variants of the proposed scheduler can achieve high overall throughput or fairness as well as low buffer requirement when compared to other wireless schedulers that either make use only of the instantaneous channel state or are channel-state independent in a heterogenous channel.

The Effect of On-Off Scheduling to the Required Transmit Power in Systems with Fast Power Control

Physical layer channel-aware scheduling may significantly improve coverage and throughput of IP based services in wireless cellular networks, and the feasibility of such schedulers is actively studied within 3G and 4G systems. A channel-aware scheduler requires access to instantaneous channel state information in order to direct transmission to users with favorable channel conditions. In frequency division duplex (FDD) systems, this requires a fast feedback channel between mobile and base stations, and the overhead of the feedback control channel should be kept as low as possible. In this paper, we study the effect of control channel overhead to on-off scheduling (OOS) when fast transmit power control is applied in data and control channels. On-off scheduling is a simple channel-aware scheduling algorithm, where transmission to a user is suspended if the transmit power exceeds a given threshold. On-off scheduling is applied on the data channel while control channel is always on so that the scheduler is able to obtain channel state information from active users. The gain of OOS strongly depends on the power ratio between control and data channels, and increased interference due to control signaling and decreased interference due to channel-aware scheduling should be jointly considered in system design. Gains in the required transmit power are translated into gains in coverage and capacity assuming WCDMA parameters, and the results can be applied, e.g., when designing scheduling algorithms and corresponding signaling formats for WCDMA uplink.