Long Term Evolution Downlink Transmission Research Articles

Exponentially weighted proportional fair scheduling algorithm for the OFDMA system

This study aims to propose an exponentially weighted proportional fair (EWPF) scheduling algorithm for orthogonal frequency division multiple access (OFDMA) system for long-term evolution downlink transmission. The proposed algorithm improves the system performance in the user-perceived throughput (UPT) by adding exponential weights to different types of services. The UPT employed to measure the system capability is novel and customer oriented; it reflects the experiences of users in an efficient manner and determines whether the users scheduling is reasonable. The EWPF algorithm is compared with two other schedulers, and our simulation results showed that the EWPF can increase the overall UPT and can maintain the fairness for prioritizing the transmission of some types of traffic.

Comparative Study of Packet Scheduling Algorithm in LTE Network

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.

LTE and WiFi co-existence in 5 GHz unlicensed band

Since the future mobile networks will require significantly higher data throughput, and the Long-Term Evolution (LTE) licensed bands are already occupied, the frequency band extension and the data rate increase may be achieved by using some of the available unlicensed bands. The most appropriate unlicensed band for this purpose lies in 5 GHz frequency range. However, this unlicensed band is already occupied by WiFi networks and a special attention has to be paid to coordinate these two different networks in the shared spectrum usage. Therefore, this paper considers the shared access co-existence in 5 GHz unlicensed band between uncoordinated LTE and WiFi networks. More precisely, it considers the influence of the LTE downlink transmission on the performance of the WiFi networks. The experimental results show that the LTE significantly degrades the WiFi network performance, which means that some of the coordination algorithms have to be employed.

Resource allocation algorithm for LTE networks using fuzzy based adaptive priority and effective bandwidth estimation

In this paper, we propose a scheme to allocate resource blocks for the Long Term Evolution (LTE) downlink based on the estimation of the effective bandwidths of traffic flows, where users’ priorities are adaptively computed using fuzzy logic. The effective bandwidth of each user traffic flow that is estimated through the parameters of the adaptive β-Multifractal Wavelet Mode modeling, is used to attain their quality of service (QoS) parameters. The proposed allocation scheme aims to guarantee the QoS parameters of users respecting the constraints of modulation and code schemes (modulation and coding scheme) of the LTE downlink transmission. The proposed algorithm considers the average channel quality and the adaptive estimation of effective bandwidth to decide about the scheduling of available radio resources. The efficiency of the proposed scheme is verified through simulations and compared to other algorithms in the literature in terms of parameters such as: system throughput, required data rate not provided, fairness index, data loss rate and network delay.

Improved MLWDF scheduler for LTE downlink transmission

ABSTRACTIn long-term evolution (LTE) downlink transmission, modified least weighted delay first (MLWDF) scheduler is a quality of service (QoS) aware scheduling scheme for real-time (RT) services. Nevertheless, MLWDF performs below optimal among the trade-off between strict delay and loss restraints of RT and non-RT traffic flows, respectively. This is further worsened with the implementation of hybrid automatic retransmission request (HARQ). As these restraints grow unabated with increasing number of user demands, the performance of MLWDF further reduces. In order to ameliorate this situation, there is a need to directly incorporate the variations in user demands and HARQ implementation as parameters to the MLWDF scheduler. In this work, an improvement to the MLWDF scheduler is proposed. The improvement entails adding two novel parameters that characterise user demand and HARQ implementation. The scheduler was tested using varying three classes of service in QoS class identifiers (QCIs) table standardised by Third Generation Partnership Project for LTE network to characterise different services. It was also tested on the basis of packet prioritisation. The proposed scheduler was simulated with LTE-SIM simulator and compared with the MLWDF and proportional fairness schedulers. In terms of delay, throughput and packet loss ratio; the proposed scheduler increased overall system performance.

Buffer-aware adaptive resource allocation scheme in LTE transmission systems

Dynamic resource allocation scheme is a key component of 3GPP long-term evolution (LTE) for satisfying quality-of-service (QoS) requirement as well as improving the system throughput. In this paper, a buffer-aware adaptive resource allocation scheme for LTE downlink transmission is proposed for improving the overall system throughput while guaranteeing the statistic QoS and keeping certain fairness among users. Specifically, the priorities of the users’ data queues in the base station are ranked by their remaining life time or their queue overflow probability which is estimated by applying large deviation principle. An online measurement based algorithm which requires no statistical knowledge of the network conditions uses the queue priorities to dynamically allocate the resource blocks (RBs) for avoiding buffer overflow and providing statistic QoS guarantee. The simulation results show that the proposed algorithm improves the throughput and fairness while considerably reducing the average bit loss rate.

Comparative Study of Downlink Packet Scheduling for LTE Networks

Scheduling is the method of dynamically allocating radio resources to user equipment based on scheduling algorithms involved in the long term evolution (LTE) base station. Several algorithms have been proposed by network researchers as the realization of scheduling algorithm which explains an open issue in LTE standard to be able to meet the quality of service requirements for different applications. In this paper, we evaluate the performance of six scheduling algorithms suggested for LTE downlink transmission. The analysis is inspected for a multicellular with interference scenario for real-time and non-real-time traffic.

Protection Ratio and Antenna Separation for DVB—T/LTE Coexistence Issues

This paper concerns the analysis of adjacent channel interference of the 3GPP Long Term Evolution (LTE) E-UTRA (Evolved Universal Terrestrial Radio Access) mobile systems into Digital Video Broadcasting - Terrestrial (DVB-T) systems. The simulated performance of both systems allows us to define recommendations for minimizing the interference effects. The subjective quality of the received TV signal has been evaluated experimentally in terms of picture failure (PF). We also investigated the importance of the selection of suitable Spectral Emission Masks (SEMs) of the LTE downlink transmission. Results show that, by using the ECC 148 SEM, both the protection ratio and the minimum distance between LTE towers and DVB-T receivers can be significantly decreased.

Two Dimensional Signal Spreading in UMTS LTE: Exploiting Time-Frequency Diversity to Increase Throughput

This paper proposes a two-dimensional spreading method in UMTS Long Term Evolution (LTE). Such a method brings additional time-frequency diversity which is beneficial in terms of the ability to decode transmitted data at the receiver site under multipath fading. Additional diversity is provided due to the fact that chips of transmitted signals are spread using a Walsh-Hadamard spreading sequence over several subcarriers as well as over several time-slots simultaneously. A comparison with state-of-the-art LTE downlink transmission is provided. To enable reproducibility and to increase credibility of our results, an open source Vienna LTE simulator is utilized. LTE transmissions with the proposed 2D spreading are tested on several channel models. Simulations show that apart from an Additive White Gaussian Noise channel model, this 2D spreading based method outperforms the throughput performance of standard LTE. At high Signal to Noise Ratio (SNR), the throughput increase in most channel models is higher than 10 %.

Wavelet-based downlink scheduling and resource allocation for long-term evolution cellular systems

This study proposes the use of wavelet transform in long-term evolution (LTE) cellular systems. Mathematical expressions are derived to represent data rate in LTE downlink transmission based on Wavelet and Fourier Transforms. Furthermore, a comparison between these two systems is provided. Simulation results show the proposed orthogonal wavelet division multiplexing (OWDM) approach outperforms the traditional orthogonal frequency division multiplexing-based systems. The data rate can also be increased by the amount of CyclicPrefix/SymbolTime%, as there is no need for a channel prefix in an OWDM-based system.