Issue editor: Hanna Bogucka
The opening issue of the Advances in Electronics and Telecommunications will collect original and unpublished research contributions in the area of modern radio communications. It will include the special issue collecting papers from the distinguished researchers of the Network of Excellence in Wireless Communications NEWCOM++, the leading European network in this area.
Kostas Stamatiou, John G. Proakis and James R. Zeidler
We consider a network of transmitters, each with a receiver at a fixed distance, and locations
drawn independently according to a homogeneous Poisson Point Process (PPP).
The transmitters and the receivers are equipped with multiple antennas.
Under a channel model that includes Rayleigh fading and path-loss, and an outage model for packet successes, we examine the performance of various spatial multiplexing techniques, namely zero-forcing (ZF), ZF with successive interference cancellation (ZF-SIC or VBLAST) and DBLAST. In each case, we determine the number of streams that maximizes the transmission capacity, defined as the maximum network throughput per unit area such that a constraint on the outage probability is satisfied. Numerical results showcase the benefit of DBLAST over ZF and VBLAST in terms of the transmission capacity. In all cases, the transmission capacity scales linearly in the number of antennas.
Sergio Benedetto and Luis M. Correia
This paper summarises the 1st NEWCOM++ Vision Book. In it, the community of NEWCOM++ researchers, shaped under the common ground of a mainly academic network of excellence, has tried to distil their scientific wisdom into a number of areas characterised by the common denominator of wireless communications, by identifying the medium-long term research tendencies/problems, describing the tools to face them and providing a relatively large number of references for the interested reader. The identified areas and the researchers involved in their redaction reflect the intersection of the major topics in wireless communications with those that are deeply investigated in NEWCOM++. They are preceded by an original description of the main trends in user/society needs and the degree of fulfilment that ongoing and future wireless communications standards will more likely help achieving.
Miguel López-Benítez and Fernando Casadevall
Most of the spectrum occupancy measurement campaigns that have been performed to the date in the context of cognitive radio are based on measurements in outdoor high points such as building roofs, balconies and towers. Although these measurement scenarios enable a more accurate estimation of the primary transmitters’ spectral activity, they may not be representative of the spectrum occupancy perceived by a cognitive radio user in many other interesting practical situations where users are not placed in a static high point. In this context, this work presents the results obtained in a spectrum measurement campaign performed over a rich diversity of measurement scenarios of practical interest. The considered scenarios include not only high points but also indoor environments as well as outdoor locations at the ground level in open areas and between buildings. The variety of considered measurement scenarios provides a broader view and understanding of dynamic spectrum occupancy under different practical scenarios of interest. The impact of considering various locations on the spectral activity perceived by a cognitive radio user is determined, analyzed and quantified. Moreover, a theoretical model for the occupancy levels observed at different locations is developed and verified with the obtained results.
Cristina Ciochina, Hikmet Sari
The controversial debate on OFDM vs. single–carrier (SC) transmission started back in the 1980s at the time of the European Digital Audio Broadcasting (DAB) and Digital Video Broadcasting (DVB) projects. The same debate took place in wireless communications a decade later, and OFDM transmission with TDMA was adopted in the IEEE 802.11a specifications for wireless local area networks (WiFi) and by the WiMAX Forum for fixed WiMAX systems. Later, orthogonal frequency-division multiple access (OFDMA) was adopted by the WiMAX Forum for mobile WiMAX systems and more recently by the 3GPP for the downlink of Long Term Evolution (LTE) systems. In contrast, single-carrier FDMA was adopted for the uplink of LTE. In this overview paper, we will review these historic developments and give some recent results on OFDMA and Single-Carrier FDMA.
Romain Couillet, Andrea Ancora and Mérouane Debbah
In this paper, we revisit the philosophical foundations of the field of channel estimation. Our main intention is to come up with a partial answer to the question: ``given some available sensed signals, how should cognitive radios ideally perform channel estimation?''. We specifically introduce a general framework to provide optimal channel estimates under any prior knowledge at the sensing device. Our discussion is articulated as a top-down approach, introducing successively (i) a discussion on the philosophical foundations of channel estimation as a simplification means for the general problem of wireless detection, (ii) an information theoretically optimal approach to channel detection assuming the sensing device has infinite memory, and (iii) a derived optimal approach when limited memory size is accounted for. The key mathematical tools used in this discussion emerge from Bayesian probability theory and are known as the maximum entropy principle and the minimum update principle. Derivations are carried out for the particular case of channel estimation in orthogonal frequency division multiplexing (OFDM) systems. While some theoretical results will be proven to match already known techniques, such as Kalman filters, another set of novel results will be shown by simulations to perform better than known channel estimation schemes.
Alberto Perotti, Piotr Remlein, Sergio Benedetto
This work is devoted to the study of adaptive coded modulations
for wireless channels impaired by the
effects of the nonlinear radio-frequency devices typically
found in user-grade electronic equipments.
The structure and properties of continuous-phase, constant-envelope
modulations such as CPM will be reviewed in a semi-tutorial fashion
and coded modulation schemes will be proposed.
Multiuser systems employing such schemes will be considered. Suitable
coded-modulation schemes will be designed and their performance will
Erdal Panayirci, Hakan Dogan, Hakan A. Cirpan
In this paper, we present an efficient iterative receiver structure of tractable complexity for joint
multiuser detection and multichannel estimation (JDE) of direct-sequence code-division multiple-access systems operating in the presence of time-varying flat fading channel. The time-varying channel is assumed to be modeled according to a piece-wise constant channel. The scheme results from an application of the expectation-maximization (EM) algorithm. The resulting EM-JDE receiver updates the data bit sequences in parallel while the channel parameters are updated in parallel. The EM algorithm provides a set of free parameters, called weight coefficients, which can be selected to optimize its performance.
An optimality criterion is defined and analytical expressions for the corresponding optimized weight coefficients are given. MonteCarlo simulations of a synchronous scenario show that the proposed JDE receiver have excellent multiuser efficiency and are robust against errors in the estimation of the channel parameters. Moreover, very short training sequences are required for the JDE schemes to converge.
Christophe MOY, Mickaël RAULET
The design of Software Defined Radio (SDR) equipments (terminals, base stations, etc.) is still very challenging. We propose here a design methodology for ultra-fast prototyping on heterogeneous platforms made of GPPs (General Purpose Processors), DSPs (Digital Signal Processors) and FPGAs (Field Programmable Gate Array). Lying on a component-based approach, the methodology mainly aims at automating as much as possible the design from an algorithmic validation to a multi-processing heterogeneous implementation. The proposed methodology is based on the SynDEx CAD design approach, which was originally dedicated to multi-GPPs networks. We show how this was changed so that it is made appropriate with an embedded context of DSP. The implication of FPGAs is then addressed and integrated in the design approach with very little restrictions. Apart from a manual HW/SW partitioning, all other operations may be kept automatic in a heterogeneous processing context. The targeted granularity of the components, which are to be assembled in the design flow, is roughly the same size as that of a FFT, a filter or a Viterbi decoder for instance. The re-use of third party or pre-developed IPs is a basis for this design approach. Thanks to the proposed design methodology it is possible to port “ultra” fast a radio application over several platforms. In addition, the proposed design methodology is not restricted to SDR equipment design, and can be useful for any real-time embedded heterogeneous design in a prototyping context.
Giacomo Bacci, Marco Luise
This paper is concerned with the general issue of game-theoretic techniques applied to the problem of resource allocation in wireless communication networks. Specifically, its first part is devoted to a tutorial explanation of game theory in the context of CDMA wireless networking, whilst the second part focuses on the particular issue of allocating power resources to optimize the receiver performance in terms of spreading code acquisition. The problem of initial signal acquisition is formulated as a noncooperative game in which each transmitter-receiver pair in the network seeks to maximize a specifically chosen utility function. For the problem at hand, the most significant utility function is represented by the ratio of the probability of signal detection to the transmitted energy per bit, and the game each receiver plays consists in setting its own transmit power and detection threshold, under a constraint on the maximum probability of spurious code locks. This formulation of the game captures the tradeoff between obtaining good code acquisition performance and saving as much energy as possible. Using the techniques introduced with the "toy examples'' in the first part of the paper, the Nash solution of the proposed game is investigated and found. Closed-form expressions for the optimal transmit power and detection threshold at the Nash equilibrium are derived, and they are compared with simulation results for a decentralized resource control algorithm.
Roberto Verdone, Flavio Fabbri
Network opportunism in wireless systems aims at jointly exploiting the resources
of separate networks. So far, small emphasis to this paradigm has been given in the
literature related to Wireless Sensor Networks (WSNs). This paper first describes a
vision on the evolution of WSNs towards the application of this concept. Then, a way
to allow exchange of information related to the available resources among networks,
is formalised. Finally, the concept is exemplified by considering a specific type of
application scenario and resource sharing approach: a vehicular network where pairs
of mobile nodes exchange packets by exploiting a store-carry-forward mechanism. This
scenario allows the introduction of the concept of Sociability Based Routing.
Andreas Zalonis, Natalia Miliou, Ioannis Dagres, Andreas Polydoros, Hanna Bogucka
This paper presents a review of techniques proposed in the literature that target the best use of resources available in a wireless communication system. These are referred to as Adaptive Modulation and Coding (AMC) techniques. A brief overview of fundamental communication limits, in particular channel capacity, is also provided in order to establish the limits for any adaptation algorithm. Furthermore, an appropriately chosen example is presented in order to demonstrate the usefulness of accurate performance modeling in the AMC design. Finally, challenges and future problems are mentioned.
Dominique Noguet, Guido Masera, Venkatesh Ramakrishnan, Marc Belleville, Dominique Morche, Gerd Asheid
Wireless communication system design has been a booming topic since the shift into the digital era in the 1990s. In the same period of time, microelectronic technologies have reach new paradigm points as they were going deeper into the submicron area. This paper gives an overview of theses emerging constraints and enablers, looking through the specific angle of how much this may impact future wireless system design. To this end, the paper analyzes the major requirements from modern digital communication systems, the way it is foreseen to evolve, and how it can be mapped onto the microelectronic roadmap.
Giovanni Emanuele Corazza, Alessandro Vanelli-Coralli, and Raffaella Pedone
In this paper, we take a broad view on the Information Society and on the Information and Communication Technologies which constitute its technical and, in a sense, social infrastructure. We discuss the fact that today the needs of human beings are strongly influenced by technology, which has become a need in itself. We propose an analysis of how the Industrial Society has left the scene in favor
of the Information Society, based on two meta-trends identified as Personalization and Distribution.
Using an original biological metaphor, we describe ”The DNA of ICT Evolution”, which uses the two meta-trends as filaments and ten trends as bases: ideal performance, ubiquity, flexibility, complexity, cognitivity, opportunism, cooperation, security, miniaturization, convergence. We then move on to a social analysis of the impact of the Information Society on nations and individuals, describing the
Information Divide, composed by the Digital Divide and the Psychological Divide. We conclude the paper by arguing that a new skill will be needed by individuals to cope with all the above, which is the skill of disciplined creative thinking.