Multiple Component Carriers Research Articles

Downlink Radio Resource Management Through CoMP and Carrier Aggregation for LTE-Advanced Network

Long Term Evolution-Advanced (LTE-A) offers several new technologies to improve the performance of the user. However, poor received signal and interference from adjacent cells in the cell-edge area can reduce the efficiency of using individual technology. Therefore, the cell-edge users have lower throughput compared to the other users in the cell and LTE-A standard. An efficient downlink radio resource management scheme is proposed in this paper by combining the coordinated multipoint transmission and reception technique along with carrier aggregation technique to achieve higher throughput for the cell-edge user and better overall performance. The proposed method jointly transmits multiple component carriers to the cell-edge user from different cells to increase the bandwidth, strengthen the received signal, and reduce the interference while it satisfies several constraints. Modified largest weighted delay first packet scheduling algorithm is deployed for resource allocation, which takes into account the delay parameters, the probability of packet loss, and data rates of the user. The obtained system-level simulation results show that the proposed method significantly enhances the throughput performances, spectral efficiency, and fairness index, compared with the existing conventional methods.

Bandwidth‐switchable cellular CMOS RF receiver front‐end for intra‐band carrier aggregation

AbstractA bandwidth‐switchable cellular complementary metal‐oxide‐semiconductor radio frequency receiver front‐end design employing a current‐reusing technique is presented in a 65‐nm RF CMOS technology. The proposed single‐ended receiver front‐end can fully support both narrowband and wideband multiple‐channel RF signals for up to three intraband carrier aggregations with high performance and low direct current consumption. To achieve different bandwidth‐handling capability, a narrowband‐ and a wideband‐switchable low noise amplifier is provided to realize appropriate matching conditions and transconductance, while maintaining high performance in multiple component carrier (CC) modes. The design operates at frequency bands of 700‐2700 MHz with 1.2 V. The design achieves conversion gains of more than 40 and 46 dB and noise figures (NFs) of less than 4.9 and 3.5 dB in wideband and narrowband modes, respectively. NF degradation in multiple CC modes is less than 0.5 dB for both bandwidth conditions.

Optimization a Scheduling Algorithm of CA in LTE ADV

Long-Term Advancement Progressed (LTE-ADV) is the advancement of the long-term evolution, which created via 3GPP. LTE-ADV aims to offer a transmission bandwidth of (100) MHz by using Carrier Aggregation (CA) to aggregate LTE-ADV carriers. To increase the data capacity of the system and resource allocation converts a very good tool. LTE-Advanced multiple Component Carriers (CCs) becomes a difficult optimization problem. In the paper proposes a new scheduling algorithm and compares with a different scheduling traditional algorithms that are proportional fair and round robin in the CA, in order to find the best scheduler that provides high-quality throughput and improves fairness. It i also evaluates mapping model types are Mutual Information Effective SINR Mapping (MIESM) and Exponential Effective SINR Mapping (EESM). The results show that the throughput in the proposed algorithm with MIESM outperforms from others mapping and scheduling.

Energy Efficient Power Allocation for Carrier Aggregation in Heterogeneous Networks: Partial Feedback and Circuit Power Consumption

The energy-efficient power allocation for carrier aggregation (CA) in heterogeneous networks (HetNets) is studied in this paper. We assume that multiple component carriers belong to HetNets and, thus, inter-band CA is considered, where both full and partial feedback scenarios are investigated. For the latter, we consider quantized channel state information at the transmitter and the corresponding power allocation policies are derived. Next, we derive energy-efficient optimal power allocation policies by assuming circuit power consumption for the transmitter that account for the multiple radio frequency (RF) chains required to support massive inter-band CA. The resulting algorithms are then used in order to investigate the relation between optimal energy efficiency (EE) and design parameters such as the number of frequency bands, antennas and feedback allocation through controlling the quantized information. A greedy optimization algorithm is also introduced to jointly optimize the aforementioned parameters. By carrying out simulations, it is observed that the achievable EE gains for massive CA in HetNets is further limited by either the number of feedback bits or the increase in RF circuits power consumption.

On Channel Selection for Carrier Aggregation Systems

In this paper, the problem of sub-channel selection for carrier aggregation (CA) systems is examined. CA enables the achievement of high data rate links via simultaneous transmissions over multiple component carriers. A CA system usually occupies only a limited number of sub-channels $M$ of these components due to limitations on the maximum permitted number of sub-channels per system. From an information theoretic point of view, a CA system should detect and employ the $M$ -best sub-channels out of the $N$ available ones. To that end, such a system probes a subset of sub-channels during each coherence time via pilot transmission. Then, for the best $M$ sub-channels, one-bit feedback information is transmitted in order to prohibit the transmission through sub-channels with gain below a threshold. The aim is to derive tractable forms via employing the extreme value theory for the sum rate (lower bound on ergodic capacity) achieved by the system under Rayleigh fading and then, to optimize jointly the training length and power, the number of the probed sub-channels (probing bandwidth size) and the feedback threshold such that the sum rate is maximized by considering the sub-channel estimation error. The accuracy of the theoretical analysis is verified by numerical results.

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. This paper analyzes the performance gains and complexity level that arises from the aggregation of three inter-band component carriers (3CC) as compared to the aggregation of 2CC using a Vienna LTE System Level simulator. The results show a considerable growth in the average cell throughput when 3CC aggregations are implemented over the 2CC aggregation, at the expense of reduction in the fairness index. The reduction in the fairness index implies that, the scheduler has an increased task in resource allocations due to the added component carrier. Compensating for such decrease in the fairness index could result into scheduler design complexity. The proposed scheme can be adopted in combining various component carriers, to increase the bandwidth and hence the data rates.

An Improved Radio Resource Management with Carrier Aggregation in LTE Advanced

Long term evolution-advanced (LTE-A) system introduces carrier aggregation (CA) technique to improve the user throughput by aggregating multiple component carriers (CCs). Previous research works related to downlink radio resource allocation with carrier aggregation have not considered the delay factor and the error probability. Therefore, the previous methods are unable to provide better quality of service (QoS) compared to the LTE-A standard. This paper considers the radio resource management problem by zooming into the head of line delay, probability of packet loss, and the delay threshold for different types of data. In doing this, several constraints are imposed following the specifications of LTE-A system. Hence, an improved method is developed in this study to enhance the system throughput and to maintain the computational complexity. Extensive simulations were carried out with other well-known methods to verify the overall performance of the proposed method. The result obtained indicates that the proposed method outperforms the previous methods in the measurement of average user throughput, average cell throughput, fairness index, and spectral efficiency.

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.

A Novel Algorithm for Efficient Downlink Packet Scheduling for Multiple-Component-Carrier Cellular Systems

The simultaneous aggregation of multiple component carriers (CCs) for use by a base station constitutes one of the more promising strategies for providing substantially enhanced bandwidths for packet transmissions in 4th and 5th generation cellular systems. To the best of our knowledge, however, few previous studies have undertaken a thorough investigation of various performance aspects of the use of a simple yet effective packet scheduling algorithm in which multiple CCs are aggregated for transmission in such systems. Consequently, the present study presents an efficient packet scheduling algorithm designed on the basis of the proportional fair criterion for use in multiple-CC systems for downlink transmission. The proposed algorithm includes a focus on providing simultaneous transmission support for both real-time (RT) and non-RT traffic. This algorithm can, when applied with sufficiently efficient designs, provide adequate utilization of spectrum resources for the purposes of transmissions, while also improving energy efficiency to some extent. According to simulation results, the performance of the proposed algorithm in terms of system throughput, mean delay, and fairness constitute substantial improvements over those of an algorithm in which the CCs are used independently instead of being aggregated.

FBMC in Next-Generation Mobile Fronthaul Networks With Centralized Pre-Equalization

In this letter, we proposed a centralized pre-equalization mechanism in a fiber-wireless integrated mobile fronthaul system to compensate the channel degradation among multiple component carriers (CCs) with reduced complexity and cost at user terminals. Orthogonal frequency division multiplexing and filter-bank multicarrier (FBMC) with and without frequency-domain pre-equalization are compared in a 50-GHz radio-over-fiber testbed. In comparison, FBMC with the proposed pre-equalization performs better because asynchronous up-link CCs can be quasi-seamlessly aggregated without interference, which enables baseband-unit (BBU) pool to precisely estimate the channel quality and perform pre-equalization for multiple bands with high spectral efficiency. Bidirectional transmission experiments are conducted with two independent asynchronous user terminals controlled by one BBU pool. An error vector magnitude of <6% is obtained with 1.1-GHz 5-CC carrier aggregation over 25-km standard single-mode fiber and 1.2-m wireless channel.

A Novel Power-Saving Transmission Scheme for Multiple-Component-Carrier Cellular Systems

As mobile data traffic levels have increased exponentially, resulting in rising energy costs in recent years, the demand for and development of green communication technologies has resulted in various energy-saving designs for cellular systems. At the same time, recent technological advances have allowed multiple component carriers (CCs) to be simultaneously utilized in a base station (BS), a development that has made the energy consumption of BSs a matter of increasing concern. To help address this concern, herein we propose a novel scheme aimed at efficiently minimizing the power consumption of BS transceivers during transmission, while still ensuring good service quality and fairness for users. Specifically, the scheme utilizes the dynamic activation/deactivation of CCs during data transmission to increase power usage efficiency. To test its effectiveness, the proposed scheme was applied to a model consisting of a BS with orthogonal frequency division multiple access-based CCs in a downlink transmission environment. The results indicated that, given periods of relatively light traffic loads, the total power consumption of the proposed scheme is significantly lower than that of schemes in which all the CCs of a BS are constantly activated, suggesting the scheme’s potential for reducing both energy costs and carbon dioxide emissions.

Low-Complexity and Low-Feedback-Rate Channel Allocation in CA MIMO Systems with Heterogeneous Channel Feedback

In this paper, we propose a low complexity and low-feedback-rate channel allocation for carrier aggregation (CA) MIMO systems as an application to heterogeneous networks (HetNets) with multiple component carriers (CCs) and users. The proposed channel allocation technique relies on the heterogeneous channel feedback concept due to the heterogeneous channel statistics of the different CCs. We apply the heterogeneous channel feedback, where the channel feedback granularity is provided using best- $M$ selected feedback strategy. The precoding matrix indicator (PMI) and rank indicator (RI) are designed with a low complexity so that the PMI/RI reports are calculated more efficiently per CC and user. This approach reduces the complexity significantly in a multiuser and multichannel scenario. Next, we deal with the low-feedback rate and thus devise a channel allocation problem. The problem on one hand provides the minimization of the feedback overhead and, on the other hand, it guarantees the quality-of-service request of each user for a specific target throughput. The problem is considered as a channel assignment problem; thus, the Hungarian method is first used. Next, a low complexity solution is devised using the stable matching algorithm. A complexity analysis and evaluation among the original and the proposed approach for the low-complexity and the low-feedback-rate channel allocation is carried out. This comparison reveals the benefits of the proposed solution for CA MIMO system in HetNets. The proposed approach can be considered as a proposal to the future massive CA, i.e., up to 32 CCs.

A Filter-Bank Transceiver Architecture for Massive Non-Contiguous Carrier Aggregation

Current application of carrier aggregation (CA), a key enabling technology for wideband communications over fragmented spectrum, is limited to only a small number of component carriers (CCs). However, wireless broadband connectivity of future networks requires the exploitation of multiple, contiguous, and non-contiguous CCs (NC-CCs). By considering a large number of aggregated NC-CCs, the concept of massive non-contiguous CA (NC-CA) is realized, which offers the highest flexibility in spectrum aggregation. In order to fully exploit the system-level benefits of massive NC-CA, transceivers capable of efficiently accommodating parallel transmissions over all of the available NC-CCs are required. This is a challenging task in which current NC-CA transceiver architectures, including the straightforward parallel chains implementation, fail to accomplish, as they suffer from scalability and efficiency issues. Focusing on the digital baseband processing part of the transceiver, this paper proposes an efficient filter-bank transceiver architecture able to accommodate a large number of NC-CCs with a small complexity increase compared with the ideal case of the transceiver operating on a single CC with the same aggregate bandwidth. Specification of this new architecture is cast as a filter design problem with minimal assumptions on transmitted waveform format, channel statistics, and decoding scheme, allowing for universally applicable designs. Both heuristic and optimal design methodologies are provided, the latter obtained using the notion of capacity mean square error as an appropriate performance/design metric. The performance of the proposed architecture is evaluated analytically, and a case study where it is applied for OFDM transmissions is provided.

Energy-Efficient Resource Allocation for LTE-A Networks

Energy-efficient resource allocation can significantly reduce power consumption of network and, consequently, operating expenses. In this letter, we study the energy efficiency of long-term evolution (LTE) networks with carrier aggregation, where user equipments are able to utilize multiple component carriers simultaneously. Furthermore, an LTE-compliant optimal resource block allocation algorithm to maximize throughput while minimizing energy consumption is proposed. Single-cell multi-user simulation results show that the proposed algorithm offers significant gains in terms of cell throughput and energy consumption over the state-of-the-art solutions.

Energy-Efficient Transmissions for Green Base Stations With a Novel Carrier Activation Algorithm: A System-Level Perspective

A base station (BS) that enables multiple component carriers (CCs) to be jointly utilized for data transmissions is one of the most advanced cellular systems. This kind of BS aims to cope with the amazingly fast-growing demand from various users. However, such a BS is the most energy-intensive part of a cellular network because the activation of its additional CCs consumes a large amount of energy, which, in turn, causes environmental problems and higher costs for cellular operators. Consequently, how to efficiently save energy when using a multi-CC BS is an increasingly critical concern in the deployment of green cellular networks. This paper builds a practical framework for studying energy-efficient transmissions for a multi-CC BS from a system-level perspective involving both radio resource allocation and CC activation/deactivation, while also presenting several new transmission schemes for use in the multi-CC BS. In these schemes, a novel energy-saving algorithm for activating/deactivating CCs is combined with different radio resource allocation approaches, respectively. Simulation results demonstrate that these schemes have much better energy-saving performance than that of the conventional one. Furthermore, comparisons among the presented schemes are detailed.

Radio resource management for uplink carrier aggregation in LTE-Advanced

This paper investigates the uplink resource allocation problem in the context of Long-Term Evolution (LTE)-Advanced systems with carrier aggregation (CA) and dual-cluster scheduling. On one hand, these Rel’10 functionalities can increase the available transmission bandwidth and scheduling flexibility in uplink. On the other hand, they will introduce additional power back-off for the power amplifier in the user equipment (UE) with non-contiguous resource allocation. Taking into account that the uplink is inherently limited by the maximum transmission power of the UE, the assignment of uplink CA and/or dual cluster transmission for LTE-Advanced UEs has to be careful. A pathloss-threshold-based component carrier (CC) and cluster configuration algorithm is proposed to determine whether an LTE-Advanced UE should be configured with multiple CCs and/or dual cluster scheduling. An extended bandwidth-expansion-based packet scheduling algorithm is proposed for dual-cluster transmission, which tightly couples the bandwidth allocation and packet scheduling together to exploit the frequency domain diversity with low complexity. Simulation results show that with proper differentiation between power-limited and non-power-limited UEs, Rel’10 CA with dual-cluster scheduling can maintain similar coverage performance as in Rel'8 case while achieving substantial gains in median and peak user throughputs. Moreover, the proposed CC assignment algorithm achieves higher user throughput as compared to blindly assigning all UEs on all available CCs.

Novel Cellular System Design using Standalone and Centralized mmWave-based Multi-Spot Beam Structure

This paper presents new mmWave-based cellular system as one of means to achieve the capacity requirement of 5G mobile communications. The base station of new system covers its service area with spot beams formed by many beamforming antennas, and one beam can be composed of multiple frequency allocation beam component carriers in which one broadband bandwidth is divided into multiple sub-bands at the millimeter frequency. The best feature of new cellular architecture is the multi-layered FA dynamic cell configuration and it means that one or more beam component carrier(s) can be grouped and then operated as one cell. The effect of this dynamic cell configuration is to avoid interference among cells via the association among multi-layered FAs and to imitate pseudo-small cells and pseudo-macro cell like 3GPP small cell enhancement architecture (user equipment in small cell enhancement architecture can use coverage layer (macro cell(s)) for mobility robustness and capacity layer (small cells) for capacity offering). In this paper, we design new system, its basic operation and evaluate its capacity to confirm the possibility as an alternative of 5G mobile communications.

Admission Control and Scheduling Algorithm for Multi-carrier Systems

LTE-Advanced aims to provide a transmission bandwidth of 100 MHz by using carrier aggregation to aggregate LTE Rel. 8 carriers. In order to increase the system capacity, resource allocation becomes a very good tool, and, in the context of the existence of multiple component carriers in LTE-Advanced becomes a complex optimization problem. This paper proposes a Multi-Carrier Scheduling Algorithm that takes into account the user's QoS requirements and also targets the maximization of the user throughput. The algorithm is evaluated in a scenario with both macro and femto base stations (i.e. a HetNet scenario) that respects the 3GPP specifications. Numerical results show that this algorithm has better performances than the traditional round robin and proportionally fair resource scheduling algorithms.

Multispectrum Signal Transmitters: Advances in Broadband High-Efficiency Power Amplifiers for Carrier Aggregated Signals

The growing demand for broadband mobile access drives the deployment of sophisticated and increasingly spectrum-efficient modulation techniques and access technologies resulting in communication signals with highly varying envelopes and increasing peakto-average power ratios (PAPRs). These communication signals call for advanced transmitter architectures and design techniques. This is particularly the case for the constituent radio frequency (RF) power amplifiers (PAs), which are required to amplify communication signals efficiently while maintaining signal quality and minimizing out-of-band emissions in adjacent channels. The Doherty [1] technique has been successfully applied to develop highly efficient solid-state PAs for wireless communication applications. Benefiting from recent advancements in laterally diffused metal oxide semiconductors (LDMOSs), and taking advantage of the advent of gallium nitride (GaN) technology, Doherty PA (DPA) demonstrators with average drain efficiencies approaching 50% were reported in [2]-[4]. Unfortunately, the underlying narrow bandwidth of these demonstrators currently restricts their use to infrastructure supporting third-generation (3G) wireless networks. Communication signals required by the 3G Partnership Project (3GPP) specifications for long-term evolution (LTE) will have to utilize carrier aggregation to meet the need for transmission bandwidth. Carrier aggregation refers to the use of more than one spectrum portion to deploy multiple component carriers to yield aggregated channels of wider transmission bandwidth (up to 100 MHz). Figure 1 illustrates the three carrier aggregation scenarios that are envisaged: 1) intraband contiguous carrier aggregation (contiguous component carriers aggregated in the same operating band), 2) intraband noncontiguous carrier aggregation (noncontiguous carriers aggregated in the same operating band), and 3) interband carrier aggregation (carrier aggregation of component carriers in different operating bands that may be contiguous or noncontiguous within each band).

An Efficient Downlink Radio Resource Allocation with Carrier Aggregation in LTE-Advanced Networks

In long term evolution-advanced (LTE-A) networks, the carrier aggregation technique is incorporated for user equipments (UEs) to simultaneously aggregate multiple component carriers (CCs) for achieving higher transmission rate. Many research works for LTE-A systems with carrier aggregation configuration have concentrated on the radio resource management problem for downlink transmission, including mainly CC assignment and packet scheduling. Most previous studies have not considered that the assigned CCs in each UE can be changed. Furthermore, they also have not considered the modulation and coding scheme constraint, as specified in LTE-A standards. Therefore, their proposed schemes may limit the radio resource usage and are not compatible with LTE-A systems. In this paper, we assume that the scheduler can reassign CCs to each UE at each transmission time interval and formulate the downlink radio resource scheduling problem under the modulation and coding scheme constraint, which is proved to be NP-hard. Then, a novel greedy-based scheme is proposed to maximize the system throughput while maintaining proportional fairness of radio resource allocation among all UEs. We show that this scheme can guarantee at least half of the performance of the optimal solution. Simulation results show that our proposed scheme outperforms the schemes in previous studies.