Enhancement of Uplink Achievable Rate and Power Allocation in LTE-Advanced Network System (original) (raw)
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Uplink and Downlink of LTE-Release 10 in Cellular Communications
International Journal of Informatics and Communication Technology (IJ-ICT), 2012
In LTE-Advanced, orthogonal frequency division multiple access (OFDMA) has been selected as the multiple access scheme for downlink and singlecarrier frequency division multiple access (SC-FDMA) for uplink. OFDM is an attractive modulation technique in a cellular environment to combat frequency selective fading channels with a relatively low-complexity receiver. However, OFDM requires an expensive and inherently inefficient power amplifier in the transmitter due to the high peak-to-average power ratio (PAPR) of the multicarrier signal. This paper, presents the main components of LTE-Advanced including the all the details of Uplink (SC-FDMA) and Downlink (OFDMA). Also this paper clarifies the main reasons of using SC-FDMA in uplink and using OFDMA in downlink only, in order to obtain flexible mobile communication technology.
LTE Uplink Transmission Scheme
The Long Term Evolution (LTE) standard requires an uplink transmission rate of up to 86 Mbps. In order to support such a high data rate and avoid the high Peak-to-Average Power Ratio (PAPR) disadvantage in Orthogonal-FDMA, Single Carrier Frequency Division Multiple Access(SC-FDMA) is used in the uplink communication in LTE cellular systems. In this paper an overview of LTE and the LTE uplink transmissions is given, especially the SC-FDMA technique. Additionally results from a PAPR analysis, comparing OFDMA and SC-FDMA using different subcarrier mapping schemes, are presented. Finally an adaptive hybrid subcarrier mapping scheme, a combination of localized and distributed mapping schemes, is proposed as a technique for reaching good transmission performance with low PAPR.
An Enhanced Energy Efficient Multiple Access Scheme for a High Data Rate LTE Uplink System
The Long Term Evolution (LTE) standards are provided by the Third Generation Partnership Project (3GPP) for the fourth generation (4G) wireless communication systems. LTE standard provides a very high spectral efficiency, bandwidth, data rate and coverage. The LTE uplink mobile devices are powered by battery, which is a fixed-power resource. The limited power resource for the battery-powered wireless devices is a huge obstacle for further development of more sophisticated devices. Researchers have focused on increasing the capacity of the mobile battery. However, the slow development in battery capacities cannot catch up with the speed of evolution in LTE technologies and mobile devices. Hence we need to augment the present LTE uplink system as more energy efficient. In LTE uplink communication better peak power characteristic is necessary for better power efficiency in mobile terminals. Multiple access schemes used in LTE will attain to drain the foremost energy from the battery. Single Carrier Frequency Division Multiple Access (SC–FDMA) and Orthogonal Division Multiple Access (OFDMA) are the two major multiple access techniques used in LTE. The main objective of this paper is to analyze and find a more energy efficient multiple access scheme for the high data rate LTE uplink system.
Wireless Networks, 2015
Resource allocation in Long Term Evaluation (LTE) uplink is challenging because of two reasons: (1) it requires contiguous resource block allocation and (2) high complexity due to per user based power allocation among resource blocks. This paper presents a low complexity, optimal power resource allocation scheme for LTE uplink. We propose Virtual Cluster-based Proportional Fairness scheme that exploits the link adaptation information available at MAC layer to form virtual clusters. The distributed proportional fair scheduler ensures a minimum throughput for all users in the coverage area by assigning contiguous resource blocks, proportional to the throughput and the number of users in a particular cluster or group. Then, it allocates power to each resource block through water-filling algorithm which gives 20.2 % increase in average user throughout compared to equal power allocation. Simulations have been performed using practical scenarios of uniformly distributed users in Rician fading environment. Mathematical framework has been devised for network planning to get the best possible fairness with promising level of quality of service.
Performance Comparison of OFDMA and SCFDMA in LTE Systems
2014
Single carrier frequency division multiple access (SCFDMA) is adopted for the uplink transmission of Long Term Evolution (LTE). SCFDMA is modified form of OFDMA which uses discrete Fourier transform (DFT) spreading before OFDMA modulation. LTE uses SCFDMA scheme for the uplink transmissions due to its lower peak to average power ratio (PAPR) and orthogonal frequency division multiplexing access (OFDMA) in downlink. In this paper we analyze PAPR using pulse shaping and without pulse shaping filters. Simulation results show that SCFDMA has lower PAPR than OFDMA. SCFDMA has 10 dB PAPR improvement than standard OFDMA without using pulse shaping filter .With pulsed shaping filter PAPR of SCFDMA is improved by 7db than standard OFDMA.
Review of resource allocation techniques in downlink LTE
Long Term Evolution (LTE), by third generation project partnership (3GPP) is one of the radio access technologies used for delivering broadband mobile services. It is mainly influenced by high data rates, minimum delay and the capacity due to scalable bandwidth and its flexibility. The downlink LTE employs orthogonal frequency division multiple access (OFDMA) as a multiple access technique. The conventional resource allocation method in OFDMA employed different modulation and coding scheme (MCS) on allocated subcarriers to achieve good throughput. But, in the downlink LTE, all scheduling blocks at a given transmission time interval (TTI) to user must adopt same MCS and these brings about constraints in the system and as a result degrade system performance. This paper reviewed several resource allocation schemes for throughput maximization in LTE downlink. In each of the schemes considered, the suboptimal solution shows a significant performance improvement compared to the optimal solution. A quality of service (QoS) guaranteed RB allocation achieves high throughput compared to other schemes considered in this article.
Power Analysis of LTE System for Uplink Scenario
There is a constant need to minimize power consumption at user equipment (UE) of wireless communication devices. In this paper we carry out the total power consumed at the handset for Long Term Evolution (LTE) systems. In uplink transmission, Single Carrier-Frequency Division Multiple Access (SC-FDMA) has been adopted as a transmission technology by 3GPP community people instead of Orthogonal Frequency Division Multiple Access (OFDMA) used for downlink transmission technology. SC-FDMA is categorized into Localized FDMA (LFDMA) and Interleaved FDMA (IFDMA). Here, we present the power analysis of LTE system for uplink scenario. We have taken three power components namely radio, circuit and computation power. The total power consumption has been compared between IFDMA and LFDMA transmission technology at a fixed bit error rate (BER) of . We have studied the effect of varying the number of Resource Blocks (RBs) on the total power consumed. We demonstrate through our simulation that at smaller number of RBs (16, 32) LFDMA performances is better as compared to IFDMA in terms of total power consumption.
Performance analysis of Resource allocation techniques in Downlink LTE
Long Term Evolution (LTE), by third generation project partnership (3GPP) is one of the radio access technologies used for delivering broadband mobile services. It is mainly influenced by high data rates, minimum delay and the capacity due to scalable bandwidth and its flexibility. The downlink LTE employs orthogonal frequency division multiple access (OFDMA) as a multiple access technique. The conventional resource allocation method in OFDMA employed different modulation and coding scheme (MCS) on allocated subcarriers to achieve good throughput. But, in the downlink LTE, all scheduling blocks at a given transmission time interval (TTI) to user must adopt same MCS and these brings about constraints in the system and as a result degrade system performance. This paper reviewed several resource allocation schemes for performance analysis in downlink direction for LTE systems. In each of the schemes considered, the suboptimal solution showed a significant performance improvement compared to the optimal solution. A quality of service (QoS) guaranteed resource block(RB) allocation achieved high throughput compared to other schemes considered in this article.
A REVIEW OF RESOURCE ALLOCATION TECHNIQUES FOR THROUGHPUT MAXIMIZATION IN DOWNLINK LTE
Long Term Evolution (LTE), by third generation project partnership (3GPP) is one of the radio access technologies used for delivering broadband mobile services. It is mainly influenced by high data rates, minimum delay and the capacity due to scalable bandwidth and its flexibility. The downlink LTE employs orthogonal frequency division multiple access (OFDMA) as a multiple access technique. The conventional resource allocation method in OFDMA employed different modulation and coding scheme (MCS) on allocated subcarriers to achieve good throughput. But, in the downlink LTE, all scheduling blocks at a given transmission time interval (TTI) to user must adopt same MCS and these brings about constraints in the system and as a result degrade system performance. This paper reviewed several resource allocation schemes for throughput maximization in LTE downlink. In each of the schemes considered, the sub-optimal solution shows a significant performance improvement compared to the optimal solution. A quality of service (QoS) guaranteed RB allocation achieves high throughput compared to other schemes considered in this article.