Link Resource Adaptation for Multiantenna Bit-Interleaved Coded Multicarrier Systems

n/

Cross-layer link adaptation for goodput optimization in MIMO BIC-OFDM systems

This work proposes a novel cross-layer link performance prediction (LPP) model and link adaptation (LA) strategy for soft-decoded multiple-input multiple-output (MIMO) bit-interleaved coded orthogonal frequency division multiplexing (BIC-OFDM) systems employing hybrid automatic repeat request (HARQ) protocols. The derived LPP, exploiting the concept of effective signal-to-noise ratio mapping (ESM) to model system performance over frequency-selective channels, does not only account for the actual channel state information at the transmitter and the adoption of practical modulation and coding schemes (MCSs), but also for the effect of the HARQ mechanism with bit-level combining at the receiver. Such method, named aggregated ESM, or αESM for short, exhibits an accurate performance prediction combined with a closed-form solution, enabling a flexible LA strategy, that selects at every protocol round the MCS maximizing the expected goodput (EGP), i.e., the number of correctly received bits per unit of time. The analytical expression of the EGP is derived capitalizing on the αESM and resorting to the renewal theory. Simulation results carried out in realistic wireless scenarios corroborate our theoretical claims and show the performance gain obtained by the proposed αESM-based LA strategy when compared with the best LA algorithms proposed so far for the same kind of systems

GOODPUT BASED ADAPTIVE MODULATION AND CODING ALGORITHM FOR BIC-OFDM SYSTEMS

WiMAX IEEE 802.16m standard description and implementation of simulation software. SISO and MIMO techniques(open loop and closed loop) implementation and resultis validation. A novel physical abstraction and Link layer prediction for 802.16m MIMO BIC-OFDM system based on goodput maximization: Effective SNR mapping, with low complexity but same performance or even better compared with MIESM, called novel kESM. Theoretical derivation of novel kESM physical abstraction technique, comparison between kESM and MI-ESM / EESM. Goodput oriented adaptive modulation and coding algorithm for BIC-OFDM wireless system based on above-mentioned abstraction. Theoretical derivation and dissertation. Simulations of 802.16m WiMAX system using C++ and C++ with IT++ libraries(used in NEWCOMM++ project). Various graphic rapresentation for different modulation and coding schemas, dissertation abuot visual and practical results

Resource allocation software algorithms for AMC-OFDM systems

PhD ThesisIn recent years, adaptive modulation and coding (AMC) technologies, resource allocation strategies and user scheduling for single-cell downlink orthogonal frequency division multiplexing (OFDM) and orthogonal frequency division multiple access (OFDMA) systems have been widely researched in order to ensure that capacity and throughput are maximised. In terms of AMC technologies, the correlation between the channel coefficients corresponding to the transmitted sub-carriers has not been considered yet. In the literature of resource allocation and user scheduling, either channel coding is not considered or only a fixed code rate is specified. Consequently, with a fixed number of data sub-carriers for each user, all these criteria restrict the flexibility of exploiting the available channel capacity, which reflects negatively on system throughput. At the same time, the presented scheduling algorithms so far managed the data of each user regardless the fair services of all users. The philosophy of this thesis is to maximise the average system throughput by proposing novel AMC, resource allocation and user scheduling strategies for OFDM and OFDMA systems based on developed software engineering life cycle models. These models have been designed to guarantee the scalability, extendibility and portability of the proposed strategies. This thesis presents an AMC strategy that divides the transmitted frame into sub-channels with an equal number of sub-carriers and selects different modulation and coding schemes (MCSs) amongst them rather than considering the same MCS for the entire frame. This strategy has been combined with a pilot adjustment scheme that reduces the pilots used for channel estimation in each sub-channel depending on the measured coherence bandwidth, signal to noise ratio (SNR), and SNR fluctuation values. The reduced pilots are replaced with additional data sub-carriers in order to improve the throughput. Additionally, a novel resource allocation strategy has been introduced in order to maximise the system throughput by distributing the users, transmission power and information bit streams over the employed sub-channels. The introduced method utilises the proposed AMC strategy in combination with pilot adjustment scheme to tackle the problem of channel capacity exploiting efficiently. It presents the throughput as a new cost function in terms of spectral efficiency and bit-error rate (BER), in which both convolutional coding rates and modulation order can be varied. The investigated throughput maximisation problem has been solved by producing two approaches. Firstly, optimised approach that solves the adopted problem optimally using the well known Lagrange multipliers method. This approach requires a huge search processes to achieve the optimal allocation of the resources, which yields a high computational complexity. To overcome the complexity issue, the second approach decouples the considered maximisation problem into two sub-problems based on the decomposition method on the cost of performance particularly for low SNR values. The proposed resource allocation strategy has been developed to work with multi-input-multi-output (MIMO) based AMC-OFDMA systems. In this project, two MIMO transmission criteria are considered, i.e. traditional and eigen-mode. In contrast, a user scheduling algorithm combined with the proposed resource allocation and AMC strategies is presented. The user scheduling algorithm aims to maximize the average system throughput by arranging the users in distinct queues according to their priorities and selecting the best user of each queue individually in order to guarantee a fair user service amongst different priority levels. When the involved users are scheduled, the scheduled users have been passed to the resource allocation to implement the distribution of the available resources. The proposed strategies have been tested over different international telecommunication union (ITU) channel profiles. The obtained simulation results show the superior performance of the introduced approaches in comparison with the related conventional methods. Furthermore, the gradually improvement in the throughput performance of the AMC-OFDM/ODMA system throughout the combination of the proposed strategies is clearly explained.Ministry of Higher Education and Scientific Research/IRAQ

D13.3 Overall assessment of selected techniques on energy- and bandwidth-efficient communications

Deliverable D13.3 del projecte europeu NEWCOM#The report presents the outcome of the Joint Research Activities (JRA) of WP1.3 in the last year of the Newcom# project. The activities focus on the investigation of bandwidth and energy efficient techniques for current and emerging wireless systems. The JRAs are categorized in three Tasks: (i) the first deals with techniques for power efficiency and minimization at the transceiver and network level; (ii) the second deals with the handling of interference by appropriate low interference transmission techniques; (iii) the third is concentrated on Radio Resource Management (RRM) and Interference Management (IM) in selected scenarios, including HetNets and multi-tier networks.Peer ReviewedPostprint (published version

Pattern Diversity Characterization of Reconfigurable Antenna Arrays for Next Generation Wireless Systems

The use of multi-antenna technology in wireless radio communications has attracted tremendous attention due to its potential to increase data rates without requiring additional bandwidth and transmission power. This has been driven by the burgeoning demand for high data rates and the need for instantaneous and ubiquitous access to information. It is therefore no surprise that current and future generation wireless standards such as LTE and WiMAX have adopted the use of adaptive multi-antenna systems also known as adaptive Multiple Input and Multiple Output (MIMO) as their de facto transmission technology. In this thesis work, we focus on the design of a smart wireless antenna system, and the study of relevant techniques that enable us to reap the benefits of their deployment in small wireless devices with MIMO capability. Specifically, we employ a new class of adaptive antenna systems known as Reconfigurable Antenna Systems (RAS) for portable devices. These antennas are capable of dynamically changing their electrical and radiation characteristics to suit the conditions of the wireless channel. The changing radiation patterns lead to pattern diversity gains that improve system performance. This is in contrast to conventional non-reconfigurable arrays which depend on signal processing techniques such as antenna grouping and beamforming to achieve performance gains. However, despite the demonstrable system-level performance benefits of RAS in adaptive MIMO, few of these antennas have been adopted and integrated in state-of-the-art wireless standards. Their usage has been partly inhibited by the prohibitive costs of implementation and operation in a real wireless infrastructure. As part of this thesis research effort we attempt to integrate these new antennas into a cost-effective real wireless MIMO testbed for use in current generation technologies. The solution integration is carried-out through the use of readily available software-defined radio frameworks. We first design, analyze and characterize the pattern diversity in RAS antenna arrays that resonate at frequencies suitable for 4G applications. We then study the benefits of pattern diversity obtained from RAS arrays over conventional space diversity approaches such as antenna grouping and beamforming. This dissertation also presents low-complexity adaptive physical layer models and algorithms to exploit the benefits of RAS array integration in MIMO wireless systems. We implement these algorithms in software-defined radio frameworks, experimentally test, and benchmark them against other established approaches in literature. And finally, integrate and test these RAS array design prototypes as part of the MIMO wireless system that leverages a state-of-the-art wireless base station and mobile terminals.Ph.D., Electrical Engineering -- Drexel University, 201

Wideband CMOS Data Converters for Linear and Efficient mmWave Transmitters

With continuously increasing demands for wireless connectivity, higher\ua0carrier frequencies and wider bandwidths are explored. To overcome a limited transmit power at these higher carrier frequencies, multiple\ua0input multiple output (MIMO) systems, with a large number of transmitters\ua0and antennas, are used to direct the transmitted power towards\ua0the user. With a large transmitter count, each individual transmitter\ua0needs to be small and allow for tight integration with digital circuits. In\ua0addition, modern communication standards require linear transmitters,\ua0making linearity an important factor in the transmitter design.In this thesis, radio frequency digital-to-analog converter (RF-DAC)-based transmitters are explored. They shift the transition from digital\ua0to analog closer to the antennas, performing both digital-to-analog\ua0conversion and up-conversion in a single block. To reduce the need for\ua0computationally costly digital predistortion (DPD), a linear and wellbehaved\ua0RF-DAC transfer characteristic is desirable. The combination\ua0of non-overlapping local oscillator (LO) signals and an expanding segmented\ua0non-linear RF-DAC scaling is evaluated as a way to linearize\ua0the transmitter. This linearization concept has been studied both for\ua0the linearization of the RF-DAC itself and for the joint linearization of\ua0the cascaded RF-DAC-based modulator and power amplifier (PA) combination.\ua0To adapt the linearization, observation receivers are needed.\ua0In these, high-speed analog-to-digital converters (ADCs) have a central\ua0role. A high-speed ADC has been designed and evaluated to understand\ua0how concepts used to increase the sample rate affect the dynamic performance