Carrier Aggregation Research Articles

Determination of the level of environment comfort using ordinal scales

To determine the degree of ecological environment comfort many indicators, such as bioclimatic indicators, temperature, humidity, seismicity, bogs, the ability of the soil and waterways to cleanse itself, the presence of blood-sucking insects, are used. The scale is set for each of the indicator to compare the individual regions on the basis of a number of quantitative indicators. The generalized (integrated) measure of comfort can be used in evaluating the joint action of various factors that degrade the ecological environment in addition to conventional values or individual levels. The generalized comfort index is defined by using values or performance levels of individual comfort considering weight factors or informativity coefficients.Very often integral indicator of comfort is defined as the average ratings of certain parameters. But this definition is associated with the following disadvantages. Firstly, the scale of the integral index is discrete-verbal numerical scale and there is no way to decide at intermediate values of the integral index with different combinations of ingredients. Secondly, the scale of the integral index is conditional numerical scale, i.e. the level of comfort in scores determined arbitrarily, as some indicators show ordinal properties and are distributed only equivalence relation and order. Therefore, aggregation of such indicators in the integral index operator must be intended only for ordinal values, i.e. algebraic summation can not be used. The paper presents the ways of aggregating of the ecological environment individual comfort indicators in the integral index, due to which a decision on the general level of environmental comfort using the scale with fuzzy linguistic variables is taken.Considering the bioclimatic comfort ordinal scales in order to improve the accuracy of the generalized level of bioclimatic comfort, the use of carrier aggregation suggested - median secondary Walsh was proposed in the paper. For the final decision at various combinations of individual comfort indicators the scale with fuzzy linguistic variables is used.

LTE-Advanced Pro RF Front-End Implementations to Meet Emerging Carrier Aggregation and DL MIMO Requirements

RF front-end (RFFE) architectures and implementations are developing new ways to optimize LTE-Advanced PRO (Rel 13) multi-component carrier aggregation, advanced features to increase spectral efficiency such as higher order modulation and higher order MIMO, and the concurrent operation of all of these features together. In this article, we describe best practices for meeting the challenging coexistence, harmonic management, linearity, and efficiency performance related to the functional partitioning, optimized integration, and technology selection of the RFFE. Recent trends to improve radio performance are driving specific blocks (e.g., the low noise amplifier) into the RFFE, with associated architecture changes in both primary and diversity paths. Carrier aggregation features are supported in a number of different methods with different insertion loss, isolation, and noise figure trade-offs, and here we examine benefits of a new category of highly integrated diversity receive modules to enhance receiver sensitivity across all use cases. Movement toward higher order MIMO in the DL is compounding additional RF Rx path support and requirements, and cost-effective solutions for optimum performance trade-offs require a holistic and complete RF system view of both Tx and Rx in order to address these emerging requirements.

Testing of the Carrier Aggregation Mode for a Live LTE Base Station in Reverberation Chamber

For the first time, the carrier aggregation feature of a live fourth-generation Long-Term Evolution (4G-LTE) base station (BS) is checked, adopting a reverberation chamber as a propagating environment. For this purpose, two nonadjacent bands were chosen, i.e., 800 and 1800 MHz, and alternatively set as primary and secondary cells. The multipath conditions were tuned by adding the absorbing material inside the chamber and ranging from an empty condition with a rich multipath to a real environment such as an indoor scenario. The latter is a very interesting and popular situation as it represents one in which people use mobile phones. The multipath variation effect on the BS performance was accurately verified by introducing power compensation to account for the variation of the chamber quality factor $Q$ due to the insertion of absorbers. A complete over-the-air test was carried out by checking typical transmission quality parameters, which are of interest to manufacturers and mobile network operators. Results highlight the differences between the performance of the two bands as a function of multipath degree and signal strength.

A linear LTE‐advanced CMOS RF power amplifier with integrated phase linearizer

ABSTRACTIn this work, a linear CMOS RF power amplifier (RF PA) to support 40‐MHz BW long‐term evolution‐advanced (LTE‐A) application is developed. The AM–PM distortion of the CMOS RF PA is compensated by the proposed wideband phase linearizer, which generates asymmetric triangular current waveform to provide pre‐distorted current to the RF PA. The fabricated PA is tested with 40‐MHz BW LTE‐A signal at 0.837 GHz carrier frequency and showing 30.3% overall system power‐added efficiency (PAE) and −36.1 dBc carrier aggregation (CA) evolved universal terrestrial radio access (E‐UTRA) adjacent channel leakage ratio (ACLR) at 24 dBm output power. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1119–1122, 2017

The Useful Impact of Carrier Aggregation: A Measurement Study in South Korea for Commercial LTE-Advanced Networks

Carrier aggregation (CA) is one of the main features of the long-term evolution (LTE)-Advanced network that was introduced in Third-Generation Partnership Project (3GPP) Release 10 (Rel-10). CA was applied to commercial cellular networks in South Korea in the middle of 2013; however, the performance of CA in commercial networks has not yet been well studied. This article describes how CA technology is applied to a commercial network and how it performs. An extensive field drive test was conducted to compare CA technology performance with that of non-CA technology by using commercial evolved node B (eNB) and user equipment (UE) in a dense urban area and a suburban area. Downlink (DL) CA with two component carriers (CCs) of 30-MHz aggregated bandwidth (BW) was used in the network with one CC of 20-MHz BW at Band 7 and the other with 10-MHz BW at Band 5. The measurement results verified that the maximum DL data rate of CA reached 203 Mb/s, close to the theoretical peak bit rate of 225 Mb/s, and the average DL data rate was 76 Mb/s during the suburban drive test. As a comparison, the maximum DL data rate of single-carrier Band 7 was 141 Mb/s, and the average DL data rate was 51 Mb/s in the same area.

License assisted access-WiFi coexistence with TXOP backoff for LTE in unlicensed band

License assisted access (LAA) was proposed as a solution to the challenge of satisfying high throughput requirement in cellular network with limited licensed band. LAA uses long term evolution (LTE) carrier aggregation technique to combine licensed and unlicensed bands, specifically 5 GHz WiFi band, in order to achieve high data rates. However, LAA has several critical concerns for services provision on 5 GHz unlicensed band. In this article, an overview of the techniques concerning the coexistence of LTE and WiFi on the same unlicensed band is presented. We first present several general approaches including power control of LTE evolved Node B (eNB), carrier selection, LTE duty cycling, self clear to send (CTS) and request to send/CTS (RTS/ CTS), and listen before talk (LBT). Then, we focus on LBT techniques for LAA-WiFi coexistence and discuss how LBT based coexistence solutions can dynamically respond to the variations in network load and ensure fair coexistence in a distributed manner. Based on the LBT mechanism, we also present a fairness-aware LAA-WiFi coexisting scheme with TXOP (transmitted in a single transmission opportunity) backoff for LAA eNB. Finally, the performances of various LBT solutions for LAA-WiFi coexistence are evaluated using Markov chain analytical model.

Enhanced coverage through relay assisted carrier aggregation for cellular networks

Carrier aggregation (CA) is an important feature of next generation cellular networks to meet the growing demand for wireless broadband services from fast-growing mobile users. This also facilitates the efficient use of fragmented spectrum among users of varying data rates. However, this does bring in a number of new implementation challenges, among which energy efficiency along with ensuring coverage and capacity fairness for users becomes the fundamental challenge for such systems. This paper initially analyses the outage capacity of such systems for both intra- and inter-band CA. Then, relaying is proposed as an energy efficient technique for enhancing the capacity and coverage of such systems. In this context, the ergodic rate of a typical user is analysed for both single- and multi-flow relay assisted CA systems. Different band deployment configurations are also analysed and compared. Further, it is observed that relays can be utilised to boost the capacity of lower frequency component carriers ensuring better capacity fairness among the users.

Performance Analysis of Two Level Calendar Disc Scheduling in LTE Advanced System with Carrier Aggregation

Carrier aggregation (CA) is introduced in long term evolution advanced (LTE-A) networks for effectively utilize the wider bandwidth of up to 100 MHz, while ensuring the backward compatibility with LTE networks. So, a well-designed scheduling method is indispensable when both the type of users (LTE and LTE-A users) is present in the network. In this paper, a two level calendar disc scheduling method is proposed to satisfy the quality of service requirements of real-time users. A calendar disc is a continuous time frame of one component carrier. Initially, the level-1 scheduler, namely, the disc scheduler (DS) schedules the packets based on user type, packet type and the supported CA by the user equipment by calculating the DS metric and creates calendar discs. At the next level, level-2 scheduler called super scheduler schedules the packets in frequency domain by processing on those calendar disc created by DS. From the simulation results it is confirmed that the algorithm provides 7% increase in Total Goodput, 50% reduction in PLR, 16% reduction in delay for VoIP flows and 5% increase in Total Goodput, 88% reduction in delay for video flows when compared to the existing algorithm.

Toward Cooperation by Carrier Aggregation in Heterogeneous Networks: A Hierarchical Game Approach

This paper studies the resource-allocation problem for a heterogeneous network (HetNet) in which the spectrum owned by a macrocell operator (MCO) can be shared by both unlicensed users (UUs) and licensed users (LUs). We formulate a novel hierarchical game theoretic framework to jointly optimize the transmit powers and subband allocations of the UUs and the pricing strategies of the MCO. In our framework, an overlapping coalition formation (OCF) game has been introduced to model the cooperative behaviors of the UUs. We then integrate this OCF game into a Stackelberg game-based hierarchical framework. We prove that the core of our proposed OCF game is nonempty and introduce an optimal subband-allocation scheme for UUs. A simple distributed algorithm is proposed for UUs to autonomously form an optimal coalition formation (CF) structure. The Stackelberg equilibrium (SE) of the proposed hierarchical game is derived, and its uniqueness and optimality are proved. A distributed joint optimization algorithm is also proposed to approach the SE of the game with limited information exchanges between the MCO and the UUs.

Non-overlapping conditions to enable multi- dimensional behavioral models/dpds for multi-band or non-continuous carrier aggregation systems

To linearize the multi-band PAs/ transmitters, a serial of multi-band predistortion models based on multi-dimensional architecture have been proposed. However, most of these models work properly only for the signals whose harmonic and intermodulation products of carriers' non-overlap with the interested fundamental bands. In this paper, the non-overlapping conditions for dual-band and tri-band signals are derived and denoted in the form of closed-form expression. It can be used to verify whether a given dual-band/ multi-band signals can be linearized properly by these multi-dimensional behavioral models. Also the conditions can be used to plan the frequency spacing and maximum bandwidth of a multi-band or non-continuous carrier aggregation signal. Several dual-band and triband signals were tested on the same PA, by employing 2-D DPD and 3-D DPD behavioral models. The measurement results show that the signals which don’t satisfy the non-overlapping conditions cannot be linearized well by the multi-dimensional behavioral models which does not take the harmonic and intermodulation products of carriers' into account.

Digital Mobile Fronthaul Based on Delta–Sigma Modulation for 32 LTE Carrier Aggregation and FBMC Signals

We first experimentally demonstrated a digital mobile fronthaul (MFH) architecture using delta-sigma modulation as the new digitization interface to replace the conventional common public radio interface (CPRI). Both one-bit and two-bit delta-sigma modulations were demonstrated, and the digitized signals were transmitted over on-off keying (OOK) or 4-level pulse-amplitude-modulation (PAM4) optical intensity modulation-direct detection (IM-DD) links. 32 LTE component carriers (CCs) were digitized and transmitted over a 25-km single-λ 10-Gbaud OOK/PAM4 link, so that 32 LTE carrier aggregation (CA) specified by 3GPP release 13 can be supported. Compared with the conventional digitization interface based on CPRI, the fronthaul capacity is increased by four times. Error vector magnitude (EVM) less than 5% or 2.1% for all LTE CCs was obtained using one-bit and two-bit delta-sigma modulators, so that high-order modulations (256QAM/1024QAM) can be supported. As a waveform-agnostic digitization interface, delta-sigma modulation can digitize not only 4G-LTE but also 5G waveforms, and its 5G compatibility was verified by filter-bank-multicarrier (FBMC) signals. The tolerance to bit error ratio (BER) of the proposed delta-sigma modulation-based digital MFH was evaluated, and no significant EVM degradation was observed for BER up to 3 χ 10−5. A comparison with analog MFH reveals that the proposed digital MFH based on delta-sigma modulation can offer improved resilience against noise and nonlinear impairments, and it increases the fronthaul capacity by four times compared with the conventional CPRI-based digital MFH without significant EVM penalty.

A SURVEY OF LTE WI-FI COEXISTENCE IN UNLICENSED BANDS

With the rapid growth of mobile data, many LTE operators are interested in leveraging unlicensed bands to enhance data rates and user experience. Th is paper investigates the problem of the coexistence of LTE and Wi-Fi in 5 GHz unlicensed bands. We fi rst introduce the current rules for the 5 GHz unlicensed bands and the carrier aggregation technique. We then discuss four deployment scenarios and two LTE-unlicensed (LTE-U) coexistence scenarios. Further, we provide a feature comparison between LTE and Wi-Fi in the PHY/MAC layers, and review the coexistence methods for LTE-U and Wi-Fi without or with the Listen- Before-Talk (LBT) mechanism. Th is paper is concluded by an examination of Wi-Fi link aggregation and in-device coexistence issues.

Improving performance of mobile fronthaul architecture employing high order delta-sigma modulator with PAM-4 format.

An improved high-order delta-sigma modulator with multi-level quantizer is proposed to enable carrier aggregation of 4G-LTE signals in mobile fronthaul. Different from conventional delta-sigma modulation-based digital mobile fronthaul, a 2-bit quantizer is employed to reduce the quantization noise, which enabling the transmission via PAM-4 based IM-DD channel. Moreover, we employ the 4th-order high-pass filter (HPF) to replace the 1st-order HPF in the conventional delta-sigma modulator, resulting in a much better noise shaping performance. In the experiment, a PAM-4 based mobile fronthaul transmission of 32 aggregated 4G-LTE signals with a CPRI equivalent data rate of 39.32-Gb/s is demonstrated in a single-λ 10-Gb/s IM-DD channel. Significant improvement of 68% is achieved in the average EVM performance compared to the previous delta-sigma modulation-based digital mobile fronthaul.

Indoor user navigation for CA in LTE‐advanced

In this study, the authors tackle the problem of carrier aggregation (CA) in downlink of long-term evolution advanced (LTE-A) femtocell networks. They propose a novel approach in a new perspective: namely, user navigation, to improve the CA performance of an LTE-A system in the indoor environment. The proposed indoor user navigation (IUN) algorithm exploits the a priori knowledge of radio interferences between femtocells to build a geometric quality-of-service (QoS) map, which can be utilised to navigate users toward the locations suitable for performing CA to satisfy the QoS requirements. The simulations demonstrate the effectiveness of the proposed IUN algorithm to improve the CA performance in terms of the aggregate throughput for the LTE-A femtocell networks.

Dynamic slot-based carrier scheduling scheme for downlink multimedia traffic over LTE advanced networks with carrier aggregation

Carrier aggregation (CA) in long-term evolution advanced (LTE-A) networks is a promising tool for providing bandwidth extension for high data rate communication. In CA, the efficient scheduling of carriers has imposed a new challenge in the design of delay-sensitive carrier scheduling for mobile multimedia applications. In this paper, a new dynamic slot-based carrier scheduling scheme has been proposed for efficient resource allocation to support the quality of service (QoS) of mobile traffic over CA transmission. The key idea of this scheduling is the allocation of slots for each component carrier based on the queue state information, taking into consideration the priority based on the delay requirements of individual mobile multimedia traffic. Two different cases of the scheduler with and without priority are implemented to facilitate the performance comparison. The simulation results show that the proposed scheme provides better spectrum utilization, throughput, and delay performance than the existing scheduling scheme and improves delay-sensitive mobile traffic QoS.

Performance Analysis of Carrier Aggregation for Various Mobile Network Implementations Scenario Based on Spectrum Allocated

Carrier Aggregation (CA) is one of the Long Term Evolution Advanced (LTE-A) features that allow mobile network operators (MNO) to combine multiple component carriers (CCs) across the available spectrum to create a wider bandwidth channel for increasing the network data throughput and overall capacity. CA has a potential to enhance data rates and network performance in the downlink, uplink, or both, and it can support aggregation of frequency division duplexing (FDD) as well as time division duplexing (TDD). The technique enables the MNO to exploit fragmented spectrum allocations and can be utilized to aggregate licensed and unlicensed carrier spectrum as well.

Dual-Band Digital Predistortion Using a Single Transmitter Observation Receiver and Single Training Engine

This paper tackles the hardware complexity of a digital predistortion (DPD) system used to linearize a power amplifier (PA) driven with interband carrier aggregated (CA) signals (i.e., two component carriers with different modulation bandwidths and wide frequency separations). It focuses particularly on reducing the required bandwidth, and number of channels, of the transmitter's observation receiver (TOR) as well as the specifications of the underlying building blocks (e.g., speed of the analog-to-digital converter). A novel dualband DPD system using a single TOR was devised. The training of the DPD for each band was carried out in an alternating fashion, using a single training engine following a model-reference adaptive control approach with a recursive least squares algorithm. The proposed approach was experimentally validated by successfully linearizing a 20-W Class F Doherty PA driven with different multistandard CA signals.

Energy Management in LTE Networks

Wireless cellular networks have seen dramatic growth in number of mobile users. As a result, data requirements, and hence the base-station power consumption has increased significantly. It in turn adds to the operational expenditures and also causes global warming. The base station power consumption in long-term evolution (LTE) has, therefore, become a major challenge for vendors to stay green and profitable in competitive cellular industry. It necessitates novel methods to devise energy efficient communication in LTE. Importance of the topic has attracted huge research interests worldwide. Energy saving (ES) approaches proposed in the literature can be broadly classified in categories of energy efficient resource allocation, load balancing, carrier aggregation, and bandwidth expansion. Each of these methods has its own pros and cons leading to a tradeoff between ES and other performance metrics resulting into open research questions. This paper discusses various ES techniques for the LTE systems and critically analyses their usability through a comprehensive comparative study.

Preparing Linearity and Efficiency for 5G: Digital Predistortion for Dual-Band Doherty Power Amplifiers with Mixed-Mode Carrier Aggregation

As new wireless communication standards seek to meet the myriad demands of today's end users, the traditional RF transmitter chain is faced with an evolving set of challenges. To maximize information throughput, signal bandwidths are continuously growing. In fourth-generation longterm evolution-advanced (also called LTE-A), for example, to meet the stated goals of 1-Gb/s downlink and 500-Mb/s uplink speeds, the carrier aggregation (CA) technique was introduced, expanding the maximum transmit bandwidth up to 100 MHz [1]. With mobile traffic expected to increase by a factor of 1,000 over the next decade, future fifth-generation (5G) systems will continue to place new demands on the transmit chain [2].

Multiport Multiband Chassis-Mode Antenna Design Using Characteristic Modes

Multiport antenna architectures that are well isolated, both within and across multiple frequency bands, not only support multiple technologies such as multiple-input--multiple-output and carrier aggregation, but also ease the design of the RF front end. In this letter, the theory of characteristic modes (TCM) is applied in a systematic manner to isolate the ports operating in the same frequency band and in different frequency bands, the latter of which is a new application of TCM. Moreover, by quantifying the amount of isolation between the multiple ports via the electromagnetic isolation method, the use of TCM as a decoupling tool for multiple antenna systems is verified. A four-port chassis-mode antenna is presented that features high levels of interband and intraband decoupling in three bands, two of which are below 1 GHz. The antenna is experimentally verified, and the measured port parameters and radiation patterns are found to match well with simulations.