Performance Comparison of Downlink Packet Scheduling Algorithms in LTE Network

Long Term Evolution (LTE) was introduced by the Third-Generation Partnership Project (3GPP) and is considered as the latest step towards the fourth generation of radio technology. This paper investigates the performance of well-known packet scheduling algorithms such as Proportion Fair (PF), Maximum- Largest Weighted Delay First (M-LWDF), Exponential Proportion Fair (EXP/PF), Frame Level Scheduler (FLS), Exponential rule (EXP rule), and Logarithmic rule (LOG Rule) in terms of delay, throughput, and packet loss ratio (PLR) by using the LTE-Sim open source simulator. Different traffic types are used, and Simulation results show that in video traffic, FLS and EXP algorithms provide a higher system throughput compared to other algorithms while keeping the delay and packet loss ratio small. However, in the case of best-effort traffic, results show a high delay and PLR with low throughput. The main contribution of this paper is to determine the appropriate downlink scheduling algorithm for VOIP, video, and best-effort traffics in 3GPP LTE

Adaptive frame structure and OFDMA resource allocation in mobile multi-hop relay networks

The objective of this thesis research is to optimize network throughput and fairness, and enhance bandwidth utilization in wireless mobile multi-hop relay (MMR) networks. To enhance bandwidth utilization, we propose an adaptive OFDMA frame structure which is used by the base station and the non-transparent relay stations. To optimize throughput and fairness, we develop an adaptive OFDMA allocation algorithm by using the proposed adaptive OFDMA frame. The effectiveness of the proposed schemes has been verified by numeric simulations. Providing ubiquitous coverage with wireless metropolitan area networks (WMANs) can be costly, especially in sparsely populated areas. In this scenario, cheaper relay stations (RSs) can be used to provide coverage instead of expensive base stations (BSs). The RS extends the coverage area of traditional BSs. This sort of network is known as a wireless MMR network. This thesis focuses on MMR networks that use orthogonal frequency division multiple access (OFDMA) and time division duplex (TDD) as a multiple access scheme and a duplex communication technique (e.g., WiMAX). The use of OFDMA resources (e.g., OFDMA symbols and subcarriers) and how they are shared in current schemes can reduce system capacity and network throughput in certain scenarios. To increase the capacity of the MMR network, we propose a new protocol that uses an adaptive OFDMA frame structure for BSs and RSs. We also propose adaptive OFDMA resource allocation for subscriber stations (SSs) within a BS or RS. We derive the maximum OFDMA resources that RSs can be assigned and synchronize access zones and relay zones between a superior station and its subordinate RSs. This is bounded by three properties defined in this thesis: a data relay property, a maximum balance property, and a relay zone limitation property. Finally, we propose max-min and proportional fairness schemes that use the proposed adaptive frame structure. The proposed scheme is the first approach that incorporates the adaptive technique for wireless MMR networks. We evaluate our scheme using simulations and numerical analysis. Results show that our technique improves resource allocation in wireless MMR networks. Further, in asymmetric distributions of SSs between access zones and relay zones, the proposed OFDMA allocation scheme performs two times better than the non-adaptive allocation scheme in terms of average max-min fairness and 70% better in terms of average throughput.Ph.D.Committee Chair: Dr. John A. Copeland; Committee Member: Dr. George F. Riley; Committee Member: Dr. Henry L. Owen; Committee Member: Dr. Mary Ann Ingram; Committee Member: Dr. Patrick Trayno

Packet scheduling algorithms in LTE systems

University of Technology Sydney. Faculty of Engineering and Information Technology.There has been a huge increase in demand towards improving the Quality of Service (QoS) of wireless services. Long Term Evolution (LTE) is a development of the Third-Generation Partnership Project (3GPP) with the aim to meet the needs of International Telecommunication Union (ITU). Some of its aspects are highlighted as follows: increase in data rate, scalable bandwidth, reduced latency and increase in coverage and capacity that result in better quality of service in communication. LTE employs Orthogonal Frequency Division Multiple Access (OFDMA) to simultaneously deliver multimedia services at a high speed rate. Packet switching is used by LTE to support different media services. To meet the QoS requirements for LTE networks, packet scheduling has been employed. Packet scheduling decides when and how different packets are delivered to the receiver. It is responsible for smart user packet selection to allocate radio resources appropriately. Therefore, packet scheduling should be cleverly designed to achieve QoS that is similar to fixed line services. eNodeB is a node in LTE network which is responsible for radio resource management that involves packet scheduling. There are two main categories of application in multimedia services: RT (Real Time) and NRT (None Real Time) services. RT services are either delay sensitive (e.g. voice over IP), loss sensitive (e.g. Buffered Video) or both (delay &loss sensitive) for example video conferencing. Best effort users are an example of NRT services that do not have exact requisites and have been allocated to spare resources. Reaching higher throughput has sometimes resulted in unfair allocation to users who are located far from the base station or users who suffer from bad channel conditions. Therefore, a sufficient trade-off between throughput and fairness is essential. The scarce bandwidth, fading radio channels and the QoS requirement of the users, makes resource allocation a demanding issue. Different scheduling approaches have been suggested for different service demands described briefly throughout the thesis. Initially, a comprehensive literature review of existing work on the packet scheduling topic has been accomplished in this thesis to realize the characteristics of packet scheduling and the resource allocation for the wireless network. Many packet scheduling algorithms developed to provide satisfactory QoS for multimedia services in downlink LTE systems. Several algorithms considered in this thesis include time and frequency domain algorithms and their way of approach has been investigated. The next objective of this thesis is to improve the performance of packet scheduling in LTE downlink systems. A new packet scheduling algorithm has been introduced in this thesis. A study on VoLTE (Voice over LTE), video streaming and best effort traffic under three different scheduling algorithms has been conducted. Heterogeneous traffic based on precise modelling of packets has been used in the simulation. The main resource allocation and assignment technique used in this work namely Dynamic Subcarrier Allocation scheme is shown to provide a solution to solve the cross layer optimisation problem. It depends on Channel Quality Information (CQI) and has been broadly investigated for single carrier and multicarrier wireless networks. The problem is based on the maximisation of average utility functions. Different scheduling algorithms in this method consider to be utility functions. The throughput, fairness and Packet Loss Ratio have been considered as the requirements for examining the performance of algorithms. Simulation results show that the proposed algorithm significantly increases the performance of streaming and best effort users in terms of PLR and throughput. Fairness has also been improved with less computational complexity compared to previous algorithms that have been introduced in this thesis

Downlink scheduling and resource management for best effort service

Abstract. Throughput performance and geographical service fairness of best effort service used for downlink of a 802.16e based TDD-OFDMA sectored cellular networks are evaluated in conjunction with different scheduling schemes and frequency reuse plans. The OFDM systems are based on two multiple access schemes, which are the OFDM-TDM and OFDMA, and considered scheduling schemes are round robin, max C/I, PF and G-fair schedulers with adaptive rate control. The 3-sectored 1 FA, 3-sectored 3 FA, and 6-sectored 3 FA plans are compared in terms of throughput, capacity, and geographical service fairness, which assist in determining the choice of a scheduling and frequency reuse plan

Subcarrier and Power Allocation in WiMAX

Worldwide Interoperability for Microwave Access (WiMAX) is one of the latest technologies for providing Broadband Wireless Access (BWA) in a metropolitan area. The use of orthogonal frequency division multiplexing (OFDM) transmissions has been proposed in WiMAX to mitigate the complications which are associated with frequency selective channels. In addition, the multiple access is achieved by using orthogonal frequency division multiple access (OFDMA) scheme which has several advantages such as flexible resource allocation, relatively simple transceivers, and high spectrum efficient. In OFDMA the controllable resources are the subcarriers and the allocated power per subband. Moreover, adaptive subcarrier and power allocation techniques have been selected to exploit the natural multiuser diversity. This leads to an improvement of the performance by assigning the proper subcarriers to the user according to their channel quality and the power is allocated based on water-filling algorithm. One simple method is to allocate subcarriers and powers equally likely between all users. It is well known that this method reduces the spectral efficiency of the system, hence, it is not preferred unless in some applications. In order to handle the spectral efficiency problem, in this thesis we discuss three novel resources allocation algorithms for the downlink of a multiuser OFDM system and analyze the algorithm performances based on capacity and fairness measurement. Our intensive simulations validate the algorithm performances.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Investigation of efficient resource allocation schemes for WiMAX networks

This thesis was submitted for the degree of Master of Philosophy and was awarded by Brunel University on 9 July 2008.WiMax (Worldwide Interoperability for Microwave Access) is a promising wireless technology with the aim of providing the last mile wireless broadband access designed for both fixed and mobile consumers as an alternative solution to the wired DSL and cable access schemes. The purpose of this research project is to investigate efficient resource allocation algorithms for WiMax. To achieve this goal, we investigate efficient PHY layer Partial Usage of SubCarriers (PUSC) allocation as well as MAC layer piggyback bandwidth request mechanisms. At the PHY layer we proposed improvements on the Uplink and Downlink PUSC subcarrier allocation scheme. For the Uplink PUSC we suggested a method by allocating different frequencies to neighbouring cells in combination with the Integer Frequency Reuse (IFR) and Fractional Frequency Reuse (FFR) in order to reduce interferences and collisions. The simulation results exhibit that collision rates can be reduced to zero for both IFR and FFR patterns with the proposed improvement by assuming that perfect power control is used in the system. In addition, there is no collision at cell edges. The results also show that FFR patterns achieve lower inter-cell interference and higher capacities as compared to the IFR patterns. For the Downlink PUSC we introduced an offset scheme with the purpose of increasing the number of users in the system. At the MAC layer we propose an improvement on the piggyback bandwidth request mechanism by increasing the size of the piggyback bandwidth request in order to reduce the number of bandwidth requests and hence improve the resource utilisation. The simulation results demonstrate that our improved scheme achieves higher throughput, less delay and packet loss rates as compared to the standardised piggyback bandwidth request mechanism

Priority-Based Resource Allocation for Downlink OFDMA Systems Supporting RT and NRT Traffics

Efficient radio resource management is essential in Quality-of-Service (QoS) provisioning for wireless communication networks. In this paper, we propose a novel priority-based packet scheduling algorithm for downlink OFDMA systems. The proposed algorithm is designed to support heterogeneous applications consisting of both real-time (RT) and non-real-time (NRT) traffics with the objective to increase the spectrum efficiency while satisfying diverse QoS requirements. It tightly couples the subchannel allocation and packet scheduling together through an integrated cross-layer approach in which each packet is assigned a priority value based on both the instantaneous channel conditions as well as the QoS constraints. An efficient suboptimal heuristic algorithm is proposed to reduce the computational complexity with marginal performance degradation compared to the optimal solution. Simulation results show that the proposed algorithm can significantly improve the system performance in terms of high spectral efficiency and low outage probability compared to conventional packet scheduling algorithms, thus is very suitable for the downlink of current OFDMA systems

Mobile WiMAX Performance Investigation

Although the Mobile-WiMAX technology is being deployed in the United States, Europe, Japan, Korea, Taiwan and in the Mideast, there are still ongoing discussions about the potential of this technology. What is really remarkable, in fact, with regard to the Mobile-WiMAX profile, is the high number of degrees of freedom that are left to manufacturers. The final decision on a lot of very basic and crucial aspects, such as, just to cite few of them, the bandwidth, the frame duration, the duplexing scheme and the up/downlink traffic asymmetry, are left to implementers. It follows that the performance of this technology is not clear yet, even to network operators. This consideration motivated our work, which is focused on the derivation of an analytical framework that, starting from system parameters and implementation choices, allows to evaluate the performance level provided by this technology, carefully taking all aspects of IEEE802.16e into account. In particular, the analysis starts from the choices to be made at the physical layer, among those admitted by the specification, and "goes up" through the protocol pillar to finally express the application layer throughput and the number of supported voice over IP (VoIP) users, carefully considering "along the way" all characteristics of the the medium access control (MAC) layer, the resource allocation strategies, the overhead introduced, the inherent inefficiencies, etc

Performance comparison of downlink packet scheduling algorithms in LTE network

Long Term Evolution (LTE) was introduced by the Third-Generation Partnership Project (3GPP) and is considered as the latest step towards the fourth generation of radio technology.This paper investigates the performance of well-known packet scheduling algorithms such as Proportion Fair (PF), Maximum- Largest Weighted Delay First (M-LWDF), Exponential Proportion Fair (EXP/PF), Frame Level Scheduler (FLS), Exponential rule (EXP rule), and Logarithmic rule (LOG Rule) in terms of delay, throughput, and packet loss ratio (PLR) by using the LTE-Sim open source simulator. Different traffic types are used, and Simulation results show that in video traffic, FLS and EXP algorithms provide a higher system throughput compared to other algorithms while keeping the delay and packet loss ratio small. However, in the case of best-effort traffic, results show a high delay and PLR with low throughput.The main contribution of this paper is to determine the appropriate downlink scheduling algorithm for VOIP, video, and best-effort traffics in 3GPP LTE