Packet Scheduling Study For Heterogeneous Traffic In Downlink 3gpplte System

Long-Term Evolution (LTE), an emerging and promising fourth generation mobile technology, is expected to offer ubiquitous broadband access to the mobile subscribers. In this paper, the performance of Frame Level Scheduler (FLS), Exponential (EXP) rule, Logarithmic (LOG) rule and Maximum-Largest Weighted Delay First (M-LWDF) packet scheduling algorithms has been studied in the downlink 3GPP LTE cellular network. To this aim, a single cell with interference scenario has been considered. The performance evaluation is made by varying the number of UEs ranging from 10 to 50 (Case 1) and user speed in the range of [3, 120] km/h (Case 2). Results show that while the number of UEs and user speed increases, the performance of the considered scheduling schemes degrades and in both case FLS outperforms other three schemes in terms of several performance indexes such as average throughput, packet loss ratio (PLR), packet delay and fairness index.

Due to copyright restrictions, the access to the full text of this article is only available via subscription.

Two novel packet scheduling algorithms, the basic and modified priority and fairness (BPF and MPF)-based packet scheduling algorithms, are proposed in this paper for adaptive modulation and coding (AMC)-based orthogonal frequency division multiple access (OFDMA) systems. In the proposed algorithms, various user traffics are transmitted in a sequence determined by their priorities on subchannels while jointly considering fairness among users and subchannels. Simulation results show that the proposed algorithms increase the number of supported users satisfying the same underlying quality of service (QoS) requirements than some existing packet scheduling algorithms in literature.

OFDM (Orthogonal Frequency Division Multiplexing) is a well-known multicarrier modulation technique that allows high-rate data transmissions over multipath broadband wireless channels. By usingOFDM, a high-rate data stream is split into a number of lower-rate streams that are simultaneously transmitted on different orthogonal subcarriers. Thus, the broadband channel is decomposed into a set of parallel frequency-flat subchannels; each one corresponding to an OFDM subcarrier. In a single user scenario, if the channel state is known at the transmitter, the system performance can be enhanced by adapting the power and data rates over each subcarrier. For example, the transmitter can allocate more transmit power and higher data rates to the subcarriers with better channels. By doing this, the total throughput can be significantly increased. In a multiuser scenario, different subcarriers can be allocated to different users, which constitutes an orthogonal multiple access method known as OFDMA (Orthogonal Frequency Division Multiple Access). OFDMA is one of the principal multiple access schemes for broadband wireless multiuser systems. It has being proposed for use in several broadband multiuser wireless standards like IEEE 802.20 (MBWA: http://grouper.ieee.org/groups/802/20/), IEEE 802.16 (WiMAX: http://www.ieee802.org/16/, 2011) and 3GPP-LTE (http://www.3gpp.org/). This chapter focuses on the OFDMA broadcast channel (also known as downlink channel), since this is typically where high data rates and reliability is needed in broadband wireless multiuser systems. In OFDMA downlink transmission, each subchannel is assigned to one user at most, allowing simultaneous orthogonal transmission to several users. Once a subchannel is assigned to a user, the transmitter allocates a fraction of the total available power as well as a modulation and coding (data rate). If the channel state is known at the transmitter, the system performance can be significantly enhanced by allocating the available resources (subchannels, transmit power and data rates) intelligently according to the users’ channels. The allocation of these resources determines the quality of service (QoS) provided by the system to each user. Since different users experience different channels, this scheme does not only exploit the frequency diversity of the channel, but also the inherent multiuser diversity of the system. In multiuser transmission schemes, like OFDMA, the information-theoretic system performance is usually characterized by the capacity region. It is defined as the set of rates 6

This paper study the performance of an orthogonal frequency division multiple access (OFDMA) system under fractional load based in long term evolution (LTE) downlink. Fractional load is defined by a situation where only a fraction of the bandwidth is used for transmission due to lack of traffic. This type of situation should result in a global increase of signal to interference and noise ratio (SINR) conditions in the network. We propose different methods integrating the transmission pattern selection to the packet scheduling functionality of the enode-B depending only on the channel quality indicator (CQI) reports from the user equipments. Fractional load handling is operated without inter eNode-B coordination. We conclude that the system can operate under fractional load conditions if the CQI is calculated with wideband interference. Further gain can be obtained if the CQI is calculated with local interference, however, in that case, it is necessary to inject a certain time correlation in the transmission patterns due to reporting delay.

Orthogonal Frequency Division Multiple Access (OFDMA) gains increasing attention for broadband, high data rate fixed/mobile communications. As the basic modulation technique in OFDMA is orthogonal frequency division multiplexing (OFDM), it is severely affected by carrier frequency offset (CFO). The CFO causes loss of orthogonality among the subcarriers. In this paper, we propose a method for joint estimation of CFO and cell ID. Cell ID represents the number of the preamble selected by the base station in the downlink. The proposed method is based on the preamble suggested for OFDMA mode of WMAN where the preamble is loaded on every third subcarrier. The proposed method is an extension of Schimdl and Coxpsilas method. We also propose a method for estimation of CP length. Van de Beekpsilas method is adapted for the estimation of CP length in OFDMA mode of WMAN. Simulations are conducted for AWGN and frequency selective channels to demonstrate the performance of the proposed methods.

Performance analysis of colour coded multiple access (CCMA) orthogonal frequency division multiplexing (OFDM) visible light communication (VLC) System is discussed in this paper. First, characteristics of optical OFDM are studied. Second, CCMA is achieved using three laser diodes (LD): red, green and blue LDs. Finally, OFDM-modulated signals are optically modulated with red, green and blue LDs (RGB LDs). Then these three optical signals are combined together to form white light which illuminates as well as provides high-speed data transmission. The performance of the proposed CCMA OFDM VLC system is studied using constellation diagrams, signals and spectrum comparisons. The system is simulated for the data rate of 10 Gbps.

Orthogonal multiple access (MA) techniques harmonize the access of multiple users to the network, thus preventing the collision of transmissions from different users. Preserving the orthogonality between transmissions can be achieved in the frequency domain MA, time domain MA, and code domain MA techniques that have been used in 2G and 3G. A more robust technique, known as orthogonal frequency division MA, combines time and frequency domains and was incorporated to LTE (Long Term Evolution). For 5G New Radio, the adoption of Orthogonal Frequency Division Multiplexing (OFDM)‐based MA implies significant differences related, among others, to the fact that NR supports different numerologies according to the selected subcarrier spacing.

At present, Long-Term Evolution (LTE) is the most popular Internet access technology because of its robust wireless connectivity that can support data, voice, video and messaging traffic. This advantage has significantly increased the number of users availing themselves of these services through various devices. Such an increase in the number of users has also increased network traffic. Thus, scheduling algorithms are needed to prioritize and distribute available resources among users to improve system performance. Researchers have proposed several algorithms that focus on meeting the Quality of Service requirement for different applications. The current study evaluates the performance of four scheduling algorithms for LTE downlink transmission, namely, proportional fair, exponential PF, exponential rule and log-rule algorithms, in a certain scenario. The performance of these algorithms was evaluated using an LTE-Sim simulator. Simulation results show that the log-rule algorithm outperforms other packet scheduling algorithms in terms of delay, throughput and packet loss ratio when serving Voice-over-Internet Protocol packet data service on the LTE network.

The Long Term Evolution (LTE) standards are generated by the Third Generation Partnership Project (3GPP) for the Fourth Generation (4G) wireless communication systems. The Fourth Generation (4G) wireless communication standards use new physical layer signaling techniques in their physical layer. Single Carrier Frequency Division Multiple Access (SC-FDMA) and Orthogonal Frequency Division Multiple Access (OFDMA) are the two major signaling techniques used in LTE. OFDMA is used in the downlink of the Fourth Generation (4G) wireless communication systems for its high spectral efficiency and SC-FDMA is used in the uplink of the Fourth Generation (4G) wireless communication systems for its high power efficiency. The main objective of this paper is to design and implement the reliable and energy efficient architecture for LTE uplink system using FPGA. IFDMA is the most energy efficient subcarrier mapping scheme of SC-FDMA multiple access scheme. In IFDMA, the data symbols subcarrier mapping is not one to one instead each subcarrier carries a part from each data symbol transmitted at that time instant. The reason for the selection of IFDMA subcarrier mapping along with SC-FDMA multiple access scheme for LTE uplink comes mainly from its advantage to provide a low peak to average power ratio (PAPR) for the transmitted waveform. This results in less power consumption in the mobile station during uplink transmission. The reliability of the system is improved using interleaving process by avoiding packet loss. Convolution codes are less complex and are used to provide error free transmission. The enhancement of energy efficiency is done using the convolution coded IFDMA. The chosen energy efficient architecture must be more power efficient and support high data rates, which is the main requirement for the mobile user. The proposed reliable and energy efficient architecture for LTE uplink system is implemented using Xilinx system generator tool.

OFDM (Orthogonal Frequency Division Multiplexing) is one of the famous technologies that supports very high data rate. It is one of the best techniques to overcome adverse effects of multipath spread. OFDMA (Orthogonal Frequency Division Multiple Access) is an extension of OFDM. It permits many users to transmit simultaneously on the different subcarriers per OFDM symbol. This paper deals with how the resources like bandwidth, power, subcarrier and bit allocations can be done efficiently to improve the spectral efficiency and to achieve the maximum system capacity. Allocating the total available power and maintaining fairness among users is a difficult task. It is necessary to maintain tradeoff between system capacity, computational complexity and fairness. Several optimization techniques are used to minimize the overall transmit power of a multiuser OFDM system. This paper surveys different resource allocation algorithms developed for the downlink of multiuser OFDM systems.

In this paper, we propose fairness-oriented packet scheduling (PS) schemes with power-efficient control mechanism for future packet radio systems. In general, the radio resource management functionality plays an important role in new OFDMA based networks. The control of the network resource division among the users is performed by packet scheduling functionality based on maximizing cell coverage and capacity satisfying, and certain quality of service requirements. Moreover, multiantenna transmit-receive schemes provide additional flexibility to packet scheduler functionality. In order to mitigate inter-cell and co-channel interference problems in OFDMA cellular networks soft frequency reuse with different power masks patterns is used. Stemming from the earlier enhanced proportional fair scheduler studies for single-input multiple-output (SIMO) and multiple-input multipleoutput (MIMO) systems, we extend the development of efficient packet scheduling algorithms by adding transmit power considerations in the overall priority metrics calculations and scheduling decisions. Furthermore, we evaluate the proposed scheduling schemes by simulating practical orthogonal frequency division multiple access (OFDMA) based packet radio system in terms of throughput, coverage and fairness distribution among users. As a concrete example, under reduced overall transmit power constraint and unequal power distribution for different sub-bands, we demonstrate that by using the proposed power-aware multi-user scheduling schemes, significant coverage and fairness improvements in the order of 70% and 20%, respectively, can be obtained, at the expense of average throughput loss of only 15%.

This chapter presents a brief overview of the OFDMA technique used in 4G WiMAX (Worldwide Interoperability for Microwave Access) and 4G LTE (Long-Term Evolution) cellular system. It is shown that OFDMA is an extension of FDMA, where each frequency band is placed at the null of the adjacent frequency band. This is governed by the well-known “Fourier transform,” so that adjacent frequency bands are orthogonal to each other. OFDMA is a full-duplex communication system. The communication link is maintained in both directions in the time domain known as time division duplex (TDD). Numerous illustrations are used to bring students up to date in key concepts, underlying principles, and practical applications of “Fourier transform,” spectrum, and orthogonal properties of spectrum, leading to OFDMA. Construction of OFDMA channels from the FCC-allocated band is presented to illustrate the concept.

We consider the allocation of spectral and power resources every subframe (1~ms) on the uplink of the Long Term Evolution (LTE) wideband orthogonal frequency division multiple access (OFDMA) cellular network. System bandwidth is divided into multiple sub-bands. The fractional power control to manage interference is allowed to be a function of the sub-band. Moreover, the channel gains from the base-station to the mobiles (user equipment (UE) in LTE) can vary with the sub-band. The power and spectral resources are to be allocated among different UEs in a cell based on channel conditions, desired fairness/QoS, and constraints on power due to interference and power limitation at a UE. For $N$ UEs and $M$ sub-bands, we exploit the structure of the underlying optimization problem to obtain an $O(NM)$ algorithm for optimal resource allocation when a UE can be allocated resources in a non-contiguous manner in frequency. To implement this in an OFDMA system, we delineate a simple control signalling structure where the UE computes in $O(M)$ time a waterfilling solution every subframe it is assigned resources. When the allocation is restricted to contiguous allocation in frequency due to single carrier constraint in LTE, we convert the solution computed above in $O(NM)$ time into a feasible solution. For typical network scenarios, the solution thus computed is numerically shown to be very close to the optimal solution with no restrictions.

Packet scheduler plays the central role in determining the overall performance of the 3GPP long-term evolution (LTE) based on packet-switching operation. In this paper, a novel minimum transmit power-based (MP) packet-scheduling algorithm is proposed that can achieve power-efficient transmission to the UEs while providing both system throughput gain and fairness improvement. The proposed algorithm is based on a new scheduling metric focusing on the ratio of the transmit power per bit and allocates the physical resource block (PRB) to the UE that requires the least ratio of the transmit power per bit. Through computer simulation, the performance of the proposed MP packet-scheduling algorithm is compared with the conventional packet-scheduling algorithms by two primary criteria: fairness and throughput. The simulation results show that the proposed algorithm outperforms the conventional algorithms in terms of the fairness and throughput.