Generation Partnership Project Long Research Articles

A glance at FD-MIMO technologies for LTE

Multiple-input multiple-output (MIMO) wireless communication technology, in which multiple antennas are jointly used for data transmission and/or reception, has been identified as a key approach to achieve the unprecedented data throughput in some advanced wireless systems such as Third Generation Partnership Project Long Term Evolution-Advanced (3GPP LTE-A) and IEEE 802.11ad. In classic MIMO-related research and development, antenna arrays consisting of only two, four, or eight logical antenna ports (for baseband processing) are usually considered due to complexity and cost issues. For instance, 3GPP LTE-A can support up to eight antenna ports for downlink transmission since Release 10. Recently, a new paradigm dubbed massive MIMO [1] has emerged, and it promises tremendous benefits by using a very large number of antenna ports for downlink data transmission. In particular, high array gains can be attained by narrow beams generated via massive MIMO, which potentially boosts the link quality for the targeted receiver and reduces interference to the other nearby users. Moreover, multi-user MIMO (MU-MIMO) can be applied in a more efficient manner with a large antenna array, as more users can be jointly served in the same radio resource through spatial division.

Power headroom report-based uplink power control in 3GPP LTE-A HetNet

In a 3rd Generation Partnership Project Long Term Evolution-Advanced (3GPP LTE-A) uplink, user equipment (UE) has a maximum transmission power limit defined by the UE power class. Generally, the cell edge UE has a higher probability to be constrained by the maximum transmission power level owing to the compensation of the large pathloss. When the UE transmission power is constrained by the maximum level, allocating a higher number of physical resource blocks (PRBs) than the UE power capability can afford will reduce the transmission power to be allocated per PRB, resulting in inefficient use of power resources. To avoid this power inefficiency, the uplink transmission power can be controlled according to the number of PRBs allocated using the power headroom report-based power efficient resource allocation (PHR-PERA) scheme proposed in this paper. Furthermore, adaptive open-loop power control (OL-PC) based on the signal-to-interference-plus-noise ratio (SINR) and the uplink interference is used to improve the cell capacity. By the uplink power control employing the proposed PHR-PERA scheme, the macro and femto UE throughputs were increased by 49.9 and 5 %, respectively, compared to the case of conventional fractional power control (FPC). Additional gains of 21.9 and 4.8 % for macro and femto UE throughputs, respectively, were achieved by adaptive OL-PC. The performance of fast closed-loop power control (CL-PC) based on the received SINR is also evaluated in this paper. The simulation results demonstrate that CL-PC supports OL-PC by compensating the fading effect for the UE uplink SINR to meet the target SINR.

Alleviating Interference through Cognitive Radio for LTE-Advanced Network

In the LTE-Advanced network, some femtocells are deployed within a macroecell for improving throughput of indoor user equipments (UEs), which are referred to as femtocell UEs (FUEs). Cross-tier interference is an important issue in this deployment, which may significantly impact signal quality between Macrocell Base Stations (MBSs) and Macrocell User Equipments (MUEs), especially for MUEs near the femtocell. To relieve this problem, the Third Generation Partnership Project Long Term Evolution-Advanced (3GPP LTE-Advanced) de<br /> fined the cognitive radio enhanced femtocell to coordinate interference for LTE-Advanced Network. Cognitive radio femtocells have the ability to sense radio environment to obtain radio parameters. In this paper, we investigated the performance of existing schemes based on fractional frequency reuse. Therefore, we proposed a scheme with cognitive radio technology to improve the performance of fractional fre-quency reuse scheme. Simulation results showed that our scheme can effectively enhance average downlink throughput of FUEs as well as the total downlink throughput in LTE-Advanced Networks.

Analysis of Quality of Services in LTE and Mobile WiMAX

Third Generation Partnership Project Long Term Evolution (3GPP LTE) and Worldwide Interoperability for Microwave Access (WiMAX) face challenges in providing Quality of Services (QoS). In this Paper, the Quality of Services of Mobile WiMAX and 3GPP LTE are analyzed and compared. We analyze the LTE and WiMAX performances in downlink employing an analytical approach for estimating the Quality of Services based on its parameters including delay and bit error rate (BER). Our proposed approach consists of two steps. The physical layer is simulated using the finite state Markov channel (FSMC) model to calculate the bit error rate. Then, the data link layer is simulated employing the effective bandwidth model for both constant and variable rate traffics. Our analysis demonstrates that WiMAX provides better QoS in low average signal to noise ratio (SNR). However, by increasing the average signal to noise ratio, both technologies provide almost the same QoS.

Two Novel Decoding Algorithms for Turbo Codes Based on Taylor Series in 3GPP LTE System

This paper proposes two novel methods to simply Logarithmic Maximum a posteriori (Log-MAP) algorithm for turbo codes in the Third Generation Partnership Project Long Term Evolution (3GPP LTE). Firstly, we exploit a new function to replace the logarithmic term in the Jacobian logarithmic function based on Taylor series, which has the best approximated accuracy compared with the existing methods. With this method, we get algorithm I. Secondly, to further simplify the complexity, we propose a new piece-wise ladder function to approximate the logarithmic term according to algorithm I. In this way, we obtain algorithm II. Simulation results show that the performance of the algorithm I is most close to the optimal algorithm. Algorithm II owns the complexity which is similar to the MAX-Log-MAP algorithm, meanwhile it can offer 0.37-0.4db performance gains than MAX-Log-MAP algorithm. DOI : http://dx.doi.org/10.11591/telkomnika.v12i5.2547

Joint precoding selection diversity with limited feedback

Coordinated multiple-point transmission (CoMP) is one of important techniques for the reduction of inter-cluster interference. Three major schemes have been presented for CoMP-joint processing transmission (CoMP-JPT) under limited-feedback environments: global, local, and single-frequency network precoding methods. However, most previous studies have demonstrated effectiveness only in specific environments without presenting numerical analyses. In this paper, we verify the characteristics of each precoding scheme based on zero-forcing beamforming (ZFBF) with semi-orthogonal user selection (SUS) by exploiting numerical analysis. In addition, we propose a selection algorithm that achieves the diversity of the precoding schemes based on limited feedback according to the downlink channel status of cellular systems. In addition, for the 3rd Generation Partnership Project Long Term Evolution-Advanced (3GPP LTE-Advanced), a network protocol that is required to adapt the CoMP-JPT scheme is implemented. Through simulations, we demonstrate that the proposed system can effectively improve the quality of service for cell-edge users while guaranteeing fairness compared to the conventional precoding schemes.

Path Loss Models for LTE and LTE-A Relay Stations

Relaying technology is an essential part of 3GPP LTE-Advanced (3 rd Generation Partnership Project Long Term Evolution - Advanced). This paper evaluates the path loss encountered on the backhaul link of relaying systems. The evaluation is based on an extensive measurements performed in 1900 MHz frequency band. The validity of different propagation models for multiple relay antenna heights is examined. The results of the analysis reveal that the applicability of commonly advocated models for relaying environment is still questionable. Some modifications of the original forms of the discussed models are introduced to make their predictions more reliable. With the proposed modifications, the analyzed models show good agreement with measurements. The prediction error is smaller than 0.37 dB, on average, and the accuracy ranges from 2.23 to 6.40 dB.

이기종 네트워크에서 클러스터 코디네이터 노드 기반의 셀간 간섭 관리 방법

차세대 이동통신 시스템 규격으로서 3GPP LTE-Advanced (Third Generation Partnership Project Long Term Evolution-Advanced)는 급격하게 증가하는 무선 데이터 트래픽 요구를 해결하기 위해 펨토 셀 혹은 피코 셀과 같은 소형 기지국 및 단말과 단말 사이에 근거리 통신을 수행하는 D2D (Device-to-Device) 통신 방식을 도입하였다. 대형 기지국인 매크로 셀과 소형 기지국인 펨토 셀과 피코 셀 그리고 D2D 통신이 한 개의 셀 내에 혼재하면서 생기는 다양한 간섭 상황이 정리되었으며, 이를 해결하기 위해서 다양한 주제 범위에서 연구가 되었다. 따라서 본 논문에서는 이러한 HetNet (Heterogeneous Network)에서 매크로 셀과 타 기종 네트워크 사이의 간섭을 관리하고 주파수 효율성을 높일 수 있는 간섭회피 방법을 제시한다. 본 논문에서 고려하는 CCN (Cluster Coordinator Node)의 도움을 받는 셀간 간섭회피 방법은 하나의 MeNB (Macro enhanced Node-B)와 다수 소형 셀들이 공존하는 HetNet 환경에서 다수 소형 셀들을 하나의 CCN이 관리하는 구조를 고려한다. HetNet에서 셀간 간섭관리를 위한 구체적인 방법으로 본 논문에서는 CCN 영역 내에 사용자들의 간섭회피를 위한 자원할당 방법을 제안하고, 이들 성능을 시스템 레벨 모의시험을 통해 검증하였다. 3GPP LTE-Advanced (Third Generation Partnership Project Long Term Evolution-Advanced) as a next generation mobile communication standard introduced small base stations such as femto cells or pico cells, and D2D (Device-to-Device) communications between mobiles in the proximity in order to satisfy the needs of rapidly growing wireless data traffic. A diverse range of topics has been studied to solve various interference situations which may occur within a single cell. In particular, an introduction of a small base station along with D2D communication raises important issues of how to increase the channel capacity and frequency efficiency in HetNets (Heterogeneous Networks). To this end, we propose in this paper methods to manage the interference between the macro cell and other small cells in the HetNet to improve the frequency efficiency. The proposed CCN (Cluster Coordinator Node)-assisted ICI (Inter-Cell Interference) avoidance methods exploit the CCN to control the interference in HetNet comprising of an MeNB (Macro enhanced Node-B) and a large number of small cells. A CCN which is located at the center of a number of small cells serves to avoid the interference between macro cell and small cells. We propose methods of resource allocation to avoid ICI for user equipments within the CCN coverage, and evaluate their performance through system-level computer simulations.

LTE networking: extending the reach for sensors in mHealth applications

ABSTRACTSensor and electronic‐health networks are widely utilized at home and in industry/research applications. In a local sense, a sensor‐to‐sensor network can have a range of a few meters to a couple of hundred meters (ZigBee Pro can extend this range up to 2000 m). With the deployment of mobile technology in the healthcare space (mobile‐Health ‘m‐Health’) and using cellular coverage, the range can virtually be unbounded. However, supporting bounded delay (end‐to‐end delay), class of service, and quality of service for critical sensor‐mHealth applications may become challenging. This challenge can be alarmingly extended when thousands of users run their sensor‐mHealth applications simultaneously and depend on limited coverage of the cell tower to transmit their health‐related data across. In this paper we will discuss how the 3rd Generation Partnership Project–Long Term Evolution networks can address such aggregation issues, and discuss the challenges and provide recommendations.Copyright © 2013 John Wiley & Sons, Ltd.

Adaptive call admission control in 3GPP LTE networks

SUMMARYIn this article, we propose new methods to reduce the handoff blocking probability in the 3rd Generation Partnership Project Long Term Evolution wireless networks. This reduction is based on an adaptive call admission control scheme that provides QoS guarantees and gives the priority of handoff call over new call in admission. The performance results of the proposed schemes are compared with other competing methods using simulation analysis. Simulation results show the major impact on the performance of the 3rd Generation Partnership Project Long Term Evolution network, which is reflected in increased resource utilization ratio to (99%) and in the ability in satisfying the requirements of QoS in terms of call blocking probability (less than 0.0628 for Voice over IP service) and dropping probability rate (less than 0.0558).Copyright © 2012 John Wiley & Sons, Ltd.

Self‐optimization of random access channel in 3rd Generation Partnership Project Long Term Evolution

ABSTRACTThe long term evolution (LTE) is being designed to enhance third generation radio access technologies, and it represents a major step towards high‐performance mobile data networks that are fully optimized for packet‐switched connections. In an initial access, the LTE user equipment executes the random access (RA) procedure while searching for serving base station and initiating services. For a good cell coverage to be obtained, feasible uplink data rate and low delays in, for example, call setup, the optimal random access channel (RACH) performance is essential. Although manual tuning of procedures can be very costly, it is important to design self‐organizing network (SON) algorithms that optimize procedures such as RA. In this paper, a mathematical framework for the RACH modeling in LTE technology is presented on the basis of probability theory and statistics. A self‐optimization algorithm for RACH preamble sequence allocation and preamble split is then examined using the deduced mathematical framework and system‐level simulations. Performance analysis is semi‐analytical: First, RACH performance results are produced using analytical model, and second, outputs are fed into a dynamic LTE network simulator. Results show that the proposed optimization approach clearly improves uplink performance and ensures a certain success rate at the first RA attempt so that shorter handover durations and call setup delays can be achieved. Copyright © 2011 John Wiley & Sons, Ltd.

A Wideband Noise Cancelling Low Noise Amplifier for 3GPP LTE Standard

This paper presents the design of a wideband low noise amplifier (LNA) for the 3GPP LTE (3rd Generation Partnership Project Long Term Evolution) standard. The proposed LNA uses a common gate topology with a noise cancellation technique for wideband (0.7 to 2.7GHz) and low noise operation. The capacitive cross coupling technique is adopted for the common gate amplifier. Consequently input matching is achieved with lower transconductance, thereby reducing the power consumption and noise contribution. The LNA is designed in a 0.18µm process and the simulations show lower than -10dB input return loss (S11), and 2.4∼2.6dB noise figure (NF) over the entire operating band (0.7∼2.7GHz) while drawing 9mA from a 1.8V supply.

PAPR in 3rd Generation Partnership Project Long Term Evolution: An Overview to Find the Impact

Third Generation Partnership Project Long Term Evolution (3GPP LTE) has adopted orthogonal frequency division multiple access (OFDMA) as the downlink and single-carrier frequency division multiple access (SC-FDMA) as the uplink for the multiple access scheme. SC-FDMA is adopted in the uplink due to its low peak-to-average-power ratio (PAPR). To reduce the PAPR in OFDMA, several techniques have been used in the literature. Many researches are still going on to find the impact of different parameters on PAPR in SC-FDMA. To further reduce the PAPR in SC-FDMA, techniques used to reduce the PAPR in OFDMA can be a potential choice. In this paper, we investigate some existing papers and find the opportunity to build a platform for further reduction in the PAPR in SC-FDMA environment.

Reconfigurable Turbo Decoder With Parallel Architecture for 3GPP LTE System

This brief presents a parallel architecture for the turbo decoder using the quadratic permutation polynomial interleaver. The supported block size ranges from 40 to 6144 with an increment of 8, and thus, it includes 188 sizes in the 3rd Generation Partnership Project Long Term Evolution standard. The proposed design can allow one, two, four, or eight soft-in/soft-out decoders to process each block with configurable iterations. To support all data transmissions in the parallel design, a multistage network with low complexity is also utilized. Moreover, a robust path metric initialization is given to improve the performance loss in small blocks and high parallelism. After fabrication in the 90-nm process, the 2.1-mm2 chip can achieve 130 Mb/s with 219 mW for the size-6144 block and eight iterations.

Efficient Implementation of a Pseudorandom Sequence Generator for High-Speed Data Communications

A conventional pseudorandom sequence generator creates only 1 bit of data per clock cycle. Therefore, it may cause a delay in data communications. In this paper, we propose an efficient implementation method for a pseudorandom sequence generator with parallel outputs. By virtue of the simple matrix multiplications, we derive a well-organized recursive formula and realize a pseudorandom sequence generator with multiple outputs. Experimental results show that, although the total area of the proposed scheme is 3% to 13% larger than that of the existing scheme, our parallel architecture improves the throughput by 2, 4, and 6 times compared with the existing scheme based on a single output. In addition, we apply our approach to a 2×2 multiple input/multiple output (MIMO) detector targeting the 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) system. Therefore, the throughput of the MIMO detector is significantly enhanced by parallel processing of data communications.

PAPR in 3rdGeneration Partnership Project Long Term Evolution: An Overview to Find the Impact

AbstractThird Generation Partnership Project Long Term Evolution (3GPP LTE) has adopted orthogonal frequency division multiple access (OFDMA) as the downlink and single-carrier frequency division multiple access (SC-FDMA) as the uplink for the multiple access scheme. SC-FDMA is adopted in the uplink due to its low peak-to-average-power ratio (PAPR). To reduce the PAPR in OFDMA, several techniques have been used in the literature. Many researches are still going on to find the impact of different parameters on PAPR in SC-FDMA. To further reduce the PAPR in SC-FDMA, techniques used to reduce the PAPR in OFDMA can be a potential choice. In this paper, we investigate some existing papers and find the opportunity to build a platform for further reduction in the PAPR in SC-FDMA environment.

DFT 확산 방식의 OFDM 통신 시스템에서 위상잡음과 직교 불균형 보상

DFT(Discrete Fourier Transform) 확산 방식의 OFDM(Orthogonal Frequency Division Multiplexing) 통신 시스템은 PAPR(Peak-to-Average Power Ratio) 저감에 매우 효과적인 시스템이며, 3GPP LTE(<TEX>$3^{rd}$</TEX> Generation Partnership Project Long Term Evolution)의 상향 링크에 SC-FDMA(Single Carrier-Frequency Division Multiple Access)에 사용된다. SC-FDMA는 일반적으로 OFDM 시스템보다 위상잡음과 직교 불균형으로 인한 ICI(Inter-Carrier Interference)에서 더 성능 열화가 발생하며, 등화기에 심각한 영향을 미친다. 그러므로 본 논문에서는 상향 링크에서 신호 전송 시 발생하는 위상잡음과 직교 불균형(IQ Imbalance: In-phase/Quadrature Imbalance), 그리고 전력 증폭기(HPA: High Power Amplifier)의 백-오프 특성에 따른 영향을 분석하고, ICI 성분을 제거할 수 있는 효과적인 등화 알고리듬을 제시한다. 제안된 등화기는 FDE(Frequency Domain Equalizer) 방식을 기반으로 설계하였으며, 기존의 PNS(Phase Noise Suppression) 알고리듬을 FDE에 사용될 수 있도록 수정하고 개선하여 위상 잡음과 직교 불균형으로 인한 ICI를 보상한다. 시뮬레이션 결과를 통하여 back-off 5.5 dB 상태에서 위상 잡음 <TEX>$0.06\;rad^2$</TEX>, 위상 에러 5도, 진폭 에러 0.005인 경우, 위상 잡음과 직교 불균형을 보상하여 SNR=14 dB 정도에서 <TEX>$BER=10^{-4}$</TEX>의 성능을 만족할 수 있다. DFT-spread OFDM(Discrete Fourier Transform-Spread Orthogonal Frequency Division Multiplexing) is very effective for solving the PAPR(Peak-to-Average Power Ratio) problem. Therefore, the SC-FDMA(Single Carrier-Frequency Division Multiple Access) which is basically same to the DFT spread OFDM was adopted as the uplink standard of the 3GPP LTE (<TEX>$3^{rd}$</TEX> Generation Partnership Project Long Term Evolution). Unlike the ordinary OFDM system, the SC-FDMA using DFT spreading method is vulnerable to the ICI(Inter-Carrier Interference) problem caused by the phase noise and IQ(In-phase/Quadrature) imbalance and effected FDE(Frequency Domain Equalizer). In this paper, the ICI effects from the phase noise and IQ imbalance which can be problems in uplink transmission are analyzed according the back-off level of HPA. Next, we propose the equalizer algorithm to remove the ICI effects. This proposed equalizer based on the FDE can be considered as up-graded and improved version of PNS(Phase Noise Suppression) algorithm. This proposed equalizer effectively compensates the ICI resulting from the phase noise and IQ imbalance. Finally, through the computer simulation, it can be shown that about SNR=14 dB is required for the <TEX>$BER=10^{-4}$</TEX> after ICI compensation when the back-off is 4.5 dB, <TEX>$\varepsilon=0.005$</TEX>, <TEX>$\phi=5^{\circ}$</TEX>, and <TEX>$pn=0.06\;rad^2$</TEX>.