Future generation cellular networks are expected to provide ubiquitous broadband access to a continuously growing number of mobile users. In this context, LTE systems represent an important milestone towards the so called 4G cellular networks. A key feature of LTE is the adoption of advanced Radio Resource Management procedures in order to increase the system performance up to the Shannon limit. Packet scheduling mechanisms, in particular, play a fundamental role, because they are responsible for choosing, with fine time and frequency resolutions, how to distribute radio resources among different stations, taking into account channel condition and QoS requirements. This goal should be accomplished by providing, at the same time, an optimal trade-off between spectral efficiency and fairness. In this context, this paper provides an overview on the key issues that arise in the design of a resource allocation algorithm for LTE networks. It is intended for a wide range of readers as it covers the topic from basics to advanced aspects. The downlink channel under frequency division duplex configuration is considered as object of our study, but most of the considerations are valid for other configurations as well. Moreover, a survey on the most recent techniques is reported, including a classification of the different approaches presented in literature. Performance comparisons of the most well-known schemes, with particular focus on QoS provisioning capabilities, are also provided for complementing the described concepts. Thus, this survey would be useful for readers interested in learning the basic concepts before going into the details of a particular scheduling strategy, as well as for researchers aiming at deepening more specific aspects.

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Downlink Packet Scheduling in LTE Cellular Networks: Key Design Issues and a Survey

Review: A survey of active and passive indoor localisation systems

Facilitating Cooperation for Wireless Systems Cooperative Communications: Hardware, Channel & PHY focuses on issues pertaining to the PHY layer of wireless communication networks, offering a rigorous taxonomy of this dispersed field, along with a range of application scenarios for cooperative and distributed schemes, demonstrating how these techniques can be employed. The authors discuss hardware, complexity and power consumption issues, which are vital for understanding what can be realized at the PHY layer, showing how wireless channel models differ from more traditional models, and highlighting the reliance of PHY algorithm performance on the underlying channel models. Numerous transparent and regenerative relaying protocols are described in detail for a variety of transparent and regenerative cooperative schemes. Key Features: Introduces background, concepts, applications, milestones and thorough taxonomy Identifies the potential in this emerging technology applied to e.g. LTE/WiMAX, WSN Discusses latest wireless channel models for transparent and regenerative protocols Addresses the fundamentals as well as latest emerging PHY protocols Introduces transparent distributed STBC, STTC, multiplexing and beamforming protocols Quantifies regenerative distributed space-time, channel and network coding protocols Explores system optimization, such as distributed power allocation and relay selection Introduces and compares analog and digital hardware architectures Quantifies complexity, memory and power consumption of 3G UMTS & 4G LTE/WiMAX relay Highlights future research challenges within the cooperative communications field This book is an invaluable guide for professionals and researchers in communications fields. It will also be of interest to graduates of communications and electronic engineering courses. It forms part of an entire series dedicated to cooperative wireless systems.

Cooperative Communications: Hardware, Channel and PHY

Due to their numerous advantages, communications over multicarrier schemes constitute an appealing approach for broadband wireless systems. Especially, the strong penetration of orthogonal frequency division multiplexing (OFDM) into the communications standards has triggered heavy investigation on multicarrier systems, leading to re-consideration of different approaches as an alternative to OFDM. The goal of the present survey is not only to provide a unified review of waveform design options for multicarrier schemes, but also to pave the way for the evolution of the multicarrier schemes from the current state of the art to future technologies. In particular, a generalized framework on multicarrier schemes is presented, based on what to transmit, i.e., symbols, how to transmit, i.e., filters, and where/when to transmit, i.e., lattice. Capitalizing on this framework, different variations of orthogonal, bi-orthogonal, and non-orthogonal multicarrier schemes are discussed. In addition, filter designs for various multicarrier systems are reviewed considering four different design perspectives: energy concentration, rapid decay, spectrum nulling, and channel/hardware characteristics. Subsequently, evaluation tools which may be used to compare different filters in multicarrier schemes are studied. Finally, multicarrier schemes are evaluated from the perspective of practical implementation aspects, such as lattice adaptation, equalization, synchronization, multiple antennas, and hardware impairments.

A Survey on Multicarrier Communications: Prototype Filters, Lattice Structures, and Implementation Aspects

A survey on bio-inspired networking

The ever-increasing growth of user demand, the limitations of the third generation of wireless mobile communication systems, and the emergence of new mobile broadband technologies on the market have brought researchers and industries to a thorough reflection on the fourth generation. Many prophetic visions have appeared in the literature presenting 4G as the ultimate boundary of wireless mobile communication without any limit to its potential, but in practical terms not giving any design rules and thus any definition of it. In this article we give a pragmatic definition of 4G derived from a new user-centric methodology that considers the user as the "cornerstone" of the design. In this way, we devise fundamental user scenarios that implicitly reveal the key features of 4G, which are then expressed explicitly in a new framework - the "user-centric" system - that describes the various level of interdependency among them. This approach consequently contributes to the identification of the real technical step-up of 4G with respect to 3G. Finally, an example of a potential 4G application is also given in order to demonstrate the validity of the overall methodology

Defining 4G technology from the users perspective

Single-carrier frequency division multiple access (SC-FDMA) has been selected as the uplink access scheme in the UTRA Long Term Evolution (LTE) due to its low peak-to-average power ratio properties compared to orthogonal frequency division multiple access. Nevertheless, in order to achieve such a benefit, it requires a localized allocation of the resource blocks, which naturally imposes a severe constraint on the scheduler design. In this paper, three new channel-aware scheduling algorithms for SC-FDMA are proposed and evaluated in both local and wide area scenarios. Whereas the first maximum expansion (FME) and the recursive maximum expansion (RME) are relative simple solutions to the above-mentioned problem, the minimum area-difference to the envelope (MADE) is a more computational expensive approach, which, on the other hand, performs closer to the optimal combinatorial solution. Simulation results show that adopting a proportional fair metric all the proposed algorithms quickly reach a high level of data-rate fairness. At the same time, they definitely outperform the round-robin scheduling in terms of cell spectral efficiency with gains up to 68.8% in wide area environments.

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Channel-aware scheduling algorithms for SC-FDMA in LTE uplink

The system requirements for IMT-A are currently being specified by the ITU. Target peak data rates of 1 Gb/s in local areas and 100 Mb/s in wide areas are expected to be provided by means of advanced MIMO antenna configurations and very high spectrum allocations (on the order of 100 MHz). For the downlink, OFDMA is unanimously considered the most appropriate technique for achieving high spectral efficiency. For the uplink, the LTE of the 3GPP, for example, employs SCFDMA due to its low PAPR properties compared to OFDMA. For future IMT-A systems, the decision on the most appropriate uplink access scheme is still an open issue, as many benefits can be obtained by exploiting the flexible frequency granularity of OFDMA. In this article we discuss the suitability of using OFDMA or SC-FDMA in the uplink for local area high-data-rate scenarios by considering as target performance metrics the PAPR and multiuser diversity gain. Also, new bandwidth configurations have been proposed to cope with the 100 MHz spectrum allocation. In particular, the PAPR analysis shows that a localized (not distributed) allocation of the resource blocks (RBs) in the frequency domain shall be employed for SC-FDMA in order to keep its advantages over OFDMA in terms of PAPR reduction. Furthermore, from the multiuser diversity gain evaluation emerges the fact that the impact of different RB sizes and bandwidth configurations is low, given the propagation characteristics of the assumed local area environment. For full bandwidth usage, OFDMA only outperforms SC-FDMA when the number of frequency multiplexed users is low. As the spectrum load decreases, instead, OFDMA outperforms SC-FDMA also for a high number of frequency multiplexed users, due to its more flexible resource allocation. In this contex different channel-aware scheduling algorithms have been proposed due to the resource allocation differences between the two blocks chemes.

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OFDMA vs. SC-FDMA: performance comparison in local area imt-a scenarios

This book presents the most recent state of the art in mobile positioning and tracking techniques. This book discusses mobile positioning solutions applied on top of current wireless communication networks. In addition, the authors introduce advanced and novel topics such as localization in heterogeneous and cooperative networks, providing a unified treatment of the topic for researchers and industry professionals alike. Furthermore, the book focuses on application areas of positioning, basics of wireless communications for positioning, data fusion and filtering techniques, fundamentals of tracking, error mitigation techniques, positioning systems and technologies, and cooperative mobile positioning systems. Key Features: Covers the state of the art of satellite- and terrestrial-based positioning systems, spanning from outdoor to indoor environments and from wide area networks to short-range networks Discusses a whole range of topics related to mobile positioning: from fundamentals of positioning to the description of a wide spectrum of mobility models for tracking, from details on data fusion and filtering techniques to error mitigation techniques (including aspects of signal processing) Provides a solid bridge between research and industry envisaging a potential implementation of the presented solutions Fills the gap between positioning and communication systems, showing how features of communication systems can be used for positioning purposes and how the retrieved location information can be used to enhance the performance of wireless networks. Includes an accompanying website This book will be a valuable guide for advanced students studying related courses. Professionals and practitioners in the field of positioning and mobile technologies, and software and service developers will also find this book of interest.

Mobile Positioning and Tracking: From Conventional to Cooperative Techniques

In this paper, we exploit the concept of cooperative localization by utilizing the additional information obtained from short-range links to enhance the location estimation accuracy in forthcoming cellular systems. Simulations for a hybrid WiMAX/Wi-Fi system are carried out considering an outdoor environment, where time difference of arrival (TDOA) and received signal strength (RSS) measurements are combined thanks to advanced data fusion techniques. Results show that the proposed system allows to meet the federal Communications Commission (FCC) requirements and overcome the ever changing channel conditions.

Simone Frattasi

Papers

Defining 4G technology from the users perspective

Channel-aware scheduling algorithms for SC-FDMA in LTE uplink

OFDMA vs. SC-FDMA: performance comparison in local area imt-a scenarios

Mobile Positioning and Tracking: From Conventional to Cooperative Techniques

Cooperative Positioning Techniques for Mobile Localization in 4G Cellular Networks