EXP Rule Research Articles

APredictive Resource Allocation for Wireless Communications Systems.

Using event-driven computer simulations, we test a predictive resource allocation scheme for broadband wireless communications systems based on the Kalman Filter. We implemented the filter in six different scheduling algorithms and selected the best performing of them (EXP Rule and FLS) for a detailed analysis. We considered several simulation scenarios with velocities ranging from 0 to 350 km/h representing pedestrian, vehicular and high-speed train scenarios. We also considered different traffic profiles by changing the number of mobile devices between 10 and 250. Our simulations showed improvement in throughput, spectral efficiency, and a decrease in packet loss rates for two schedulers: the EXP Rule and the Frame Level Scheduler. Our predictor can be applied to any wireless system that performs centralized resource allocation based on data rate or any other quantity that needs to be estimated for resource distribution in a network.

Introduction of a Novel Hybrid Weighted Exponential Logarithm-Maximum Throughput (HWEL-MT) Scheduler for QoS Improvement of LTE/4G Cellular Networks

The real-time broadcast of multimedia contents such as VoIP and video traffics in recent cellular networks is increasingly becoming common. In this regard, LTE networks with the objective of providing high speed data along with QoS assurance have been introduced. To perform this, schedulers in order to allocate of the resources to the traffics are used as channel-aware/QoS-aware. The most important and effective schedulers are EXP RULE and E2M RULE for this type of networks but still requires improving of QoS parameters to reach an optimal level of performance. In this paper aims to improve the packet loss rate (PLR), latency and throughput parameters especially and improve the other QoS parameters generally in the downlink LTE networks, a new scheduler called Hybrid Weighted Exponential Logarithm-Maximum Throughput (HWEL-MT) RULE method has been proposed. By performing simulations and comparisons between output results of EXP-Rule, E2M RULE and HWEL-MT RULE schedulers for VoIP, video and best effort traffics, we have totally concluded that the proposed HWEL-MT scheduler is able to improve PLR, delay, throughput, fairness and spectral efficiency more than two other examined methods. The results have been presented and compared by implementing a LTE network included 5---70 mobile users in open source LTE-Sim software.

A Review of MAC Scheduling Algorithms in LTE System

The recent wireless communication networks rely on the new technology named Long Term Evolution (LTE) to offer high data rate real-time (RT) traffic with better Quality of Service (QoS) for the increasing demand of customer requirement. LTE provide low latency for real-time services with high throughput, with the help of two-level packet retransmission. Hybrid Automatic Repeat Request (HARQ) retransmission at the Medium Access Control (MAC) layer of LTE networks achieves error-free data transmission. The performance of the LTE networks mainly depends on how effectively this HARQ adopted in the latest communication standard, Universal Mobile Telecommunication System (UMTS). The major challenge in LTE is to balance QoS and fairness among the users. Hence, it is very essential to design a down link scheduling scheme to get the expected service quality to the customers and to utilize the system resources efficiently. This paper provides a comprehensive literature review of LTE MAC layer and six types of QoS/Channel-aware downlink scheduling algorithms designed for this purpose. The contributions of this paper are to identify the gap of knowledge in the downlink scheduling procedure and to point out the future research direction. Based on the comparative study of algorithms taken for the review, this paper is concluded that the EXP Rule scheduler is most suited for LTE networks due to its characteristics of less Packet Loss Ratio (PLR), less Packet Delay (PD), high throughput, fairness and spectral efficiency.

A performance analysis on packet scheduling schemes based on an exponential rule for real-time traffic in LTE

Abstract Long-Term Evolution (LTE) was implemented to fulfill and satisfy users’ needs as well as their demands for an improvised, fast and efficient Quality of service (QoS). A minimal aggregate of waiting time in return would give users a better Quality of experience (QoE). Real-time service packet scheduling is an important process in allocating resources to users. An efficient packet scheduling scheme will be able to cater fairly and efficiently to its users in the LTE network. Hence, studies are performed focusing on real-time traffic which includes video as well as Voice over Internet Protocol (VoIP) transmissions. In this work, the existing exponential rule (EXP rule) is utilized to benchmark our proposed packet scheduling techniques so that we are able to further evaluate the scheduling performance. In response to the increasing likelihood of losing packets in the EXP rule’s algorithm and maximizing the throughput rate, several schemes have been experimented with. The proposed schemes include 1) simplified EXP rule (sEXP Rule), 2) modified EXP rule (mEXP Rule), 3) EXP rule with maximum throughput (MT) (EXP_MT Rule), and 4) enhanced EXP rule with MT (E2M). By adding MT as a weight to the EXP rule, the throughput is maximized, thus providing higher throughput rates for real-time and non-real-time traffic. The simulation results show that the sEXP rule has a better performance in throughput, packet loss rate (PLR), and spectral efficiency for video traffic. Aside from this, our proposed E2M rule performs better than the benchmark EXP rule and outperforms the other proposed schemes, as well. It is observed that the E2M rule has better QoS support for real-time transmission in terms of delay, packet loss, throughput and spectral efficiency, within the LTE network. Hence, our proposed E2M rule is an enhancement of the benchmark EXP rule, which is commonly used in LTE packet scheduling.

Performance Analysis of Service Based Scheduler in LTE OFDMA System

Long Term Evolution (LTE) is the wireless broadband technology developed by Third Generation Partnership Project (3GPP) to support higher data rate. Resource scheduling in LTE plays an important role in deciding the overall network performance. In this paper, a new scheduling approach called Service Based Scheduler (SBS) is proposed that is suitable for real time services. In this method, two tag values called maximum tag value (Tmax) and minimum tag value (Tmin) are estimated for the packets based on the type of bearers. Tmax is calculated for Guaranteed Bit Rate (GBR) bearers and Tmin is calculated for non GBR bearers. Then, separate ascending sorted lists are formed for Tmax and Tmin. The packets from the Tmax list are allocated first in spite of users' channel condition. After the allocation of packets from Tmax list, if the current Transmit Time Interval (TTI) has more resources, then packets from Tmin list are allocated strictly based on users' channel conditions. The proposed scheduling approach provides better performance for real time services compared to other schemes like Proportional Fairness (PF), Modified Largest Weighted Delay First (MLWDF), Exponential rule (EXP rule) and Logarithmic rule (LOG rule).

PERFORMANCE COMPARISON OF PACKET SCHEDULING ALGORITHMS FOR VIDEO TRAFFIC IN LTE CELLULAR NETWORK

In this paper we have studied downlink packet scheduling algorithms proposed for LTE cellular networks. The study emphasize on three most promising scheduling algorithms such as: FLS, EXP rule and LOG rule. The performance of these three algorithms is conducted over video traffic in a vehicular environment using LTE-Sim simulator. The simulation was setup with varying number of users from 10 - 60 in fixed bounded regions of 1 km radius. The main goal this study is to provide results that will help in the design process of packet scheduler for LTE cellular networks, aiming to get better overall performance users. Simulation results show that, the FLS scheme outperforms in terms of average system throughput, average packet delay, PLR; and with a satisfactory level of fairness index.

Delay-Optimal Opportunistic Scheduling and Approximations: The Log Rule

This paper considers the design of multiuser opportunistic packet schedulers for users sharing a time-varying wireless channel from performance and robustness points of view. For a simplified model falling in the classical Markov decision process framework, we numerically compute and characterize mean-delay-optimal scheduling policies. The computed policies exhibit radial sum-rate monotonicity: As users' queues grow linearly, the scheduler allocates service in a manner that deemphasizes the balancing of unequal queues in favor of maximizing current system throughput (being opportunistic). This is in sharp contrast to previously proposed throughput-optimal policies, e.g., Exp rule and MaxWeight (with any positive exponent of queue length). In order to meet performance and robustness objectives, we propose a new class of policies, called the Log rule, that are radial sum-rate monotone (RSM) and provably throughput-optimal. In fact, it can also be shown that an RSM policy minimizes the asymptotic probability of sum-queue overflow. We use extensive simulations to explore various possible design objectives for opportunistic schedulers. When users see heterogenous channels, we find that emphasizing queue balancing, e.g., Exp rule and MaxWeight, may excessively compromise the overall delay. Finally, we discuss approaches to implement the proposed policies for scheduling and resource allocation in OFDMA-based multichannel systems.

Large Deviations Sum-Queue Optimality of a Radial Sum-Rate Monotone Opportunistic Scheduler

A centralized wireless system is considered that is serving a fixed set of users with time varying channel capacities. An opportunistic scheduling rule in this context selects a user (or users) to serve based on the current channel state and user queues. Unless the user traffic is symmetric and/or the underlying capacity region a polymatroid, little is known concerning how performance optimal schedulers should tradeoff <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">maximizing current service rate</i> (being opportunistic) versus <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">balancing unequal queues</i> (enhancing user-diversity to enable future high service rate opportunities). By contrast, with currently proposed opportunistic schedulers, e.g., MaxWeight and Exp Rule, a radial sum-rate monotonic (RSM) scheduler de-emphasizes queue-balancing in favor of greedily maximizing the system service rate as the queue-lengths are scaled up linearly. In this paper, it is shown that an RSM opportunistic scheduler, p-Log Rule, is not only throughput-optimal, but also maximizes the asymptotic exponential decay rate of the sum-queue distribution for a two-queue system. The result complements existing optimality results for opportunistic scheduling and point to RSM schedulers as a good design choice given the need for robustness in wireless systems with both heterogeneity and high degree of uncertainty.