Annals of telecommunications /
Annales des télécommunications
Vol. 63, n°5-6, May-June 2008
Content available on SpringerLink
http://www.springerlink.com/content/120920/
Wireless
communication systems
Guest editors : Michel Terré (CNAM, Paris, France)
Bernhard Walke (RWTH Aachen University, Aachen, Germany), Luis Correia
(Instituto Superior Tecnico, Lisbon, Portugal), Alain Sibille (ENSTA, Paris,
France)
> Michel Terré, Bernhard
Walke, Luis Correia, Alain Sibille
Kumar’s, Zipf’s and other
laws: how to structure a large-scale wireless network?
>M.
Dohler (1)· T. Watteyne (2,3)· F. Valois (3)· J.-L. Lu (3)
(1)Centre Tecnologic de
Telecomunicacions de Catalunya (CTTC), Parc Mediterrani de la Tecnologia, Av. Canal
Olimpic S/N, 08860, Castelldefels, Barcelona, Spain e-mail:
mischa.dohler@cttc.es
(2)France Télécom R&D, Meylan Cedex,
38243, France
(3)ARES INRIA / CITI, INSA-Lyon, 69621, France
Abstract Networks with a very large number of nodes
are known to suffer from scalability problems, influencing throughput, delay,
and other quality-ofservice parameters. Mainly applicable to wireless sensor networks,
this paper extends prior work and aims to give some fundamental indications on
a scalable and optimum (or near-optimum) structuring approach for large-scale
wireless networks. Scalability and optimality will be defined with relation to
various performance criteria, an example of which is the throughput per node in
the network. Various laws known from different domains will be invoked to
quantify the performance of a given topology; most notably, we will make use of
the well-known Kumar’s law, as well as less-known Zipf’s and other scaling
laws. Optimum network structures are derived and discussed for a plethora of
different scenarios, facilitating knowledgeable design guidelines for these
types of networks.
Keywords
Large-scale wireless network · Asymptotic behaviour · Scaling
laws
On multicell cooperative
transmission in backhaul-constrained cellular systems
>Patrick Marsch Gerhard
Fettweis
Vodafone Chair Mobile Communications
Systems, Technische Universität Dresden, Dresden, Germany
Abstract Recent work has shown that multicell cooperative signal processing in
cellular networks can significantly increase system capacity and fairness. For example,
multicell joint transmission and joint detection can be performed to combat
intercell interference, often mentioned in the context of distributed antenna systems.
Most publications in this field assume that an infinite amount of information
can be exchanged between the cooperating base stations, neglecting the main
downside of such systems, namely, the need for an additional network backhaul.
In recent publications, we have thus proposed an optimization framework and algorithm
that applies multicell signal processing to only a carefully selected subset of
users for cellular systems with a strongly constrained backhaul. In this paper,
we consider the cellular downlink and provide a comprehensive summary and
extension of our previous and current work. We compare the performance obtained
through centralized or decentralized optimization approaches, or through
optimal or suboptimal calculation of precoding matrices, and identify
reasonable performance–complexity trade-offs. It is shown that even
low-complexity optimization approaches for cellular systems with a strongly
constrained backhaul can yield major performance improvements over conventional
systems.
Keywords Network
MIMO · Joint transmission · Beamforming · Constrained backhaul
Performance impact of
flexible power arrangement in OFDMA based cellular communication networks
>Yikang Xiang (1) Jijun Luo (1) Egon Schulz (1) Carmelita Görg (2)
(1) Nokia
Siemens Network GmbH & Co.KG, Munich, Germany
(2) ComNets, University of Bremen, Bremen, Germany
Abstract In the OFDMA-based downlink of wireless cellular communication
networks, the intercell interference would be a key performance-limiting
factor, especially for the cell edge users. To enhance the cell edge user
performance, several flexible power allocation schemes have been proposed,
e.g., the so-called soft frequency reuse scheme and the partial frequency reuse
scheme. This paper analyzes those schemes in a very realistic multicell
setting, investigates the layer 2 resource allocation algorithms that are
associated to the physical layer setting, and finally gives results of the performance
evaluation.
Keywords OFDMA · Frequency
reuse · Multicell · Power allocation
Decentralized spectrum and
radio resource management enabled by an on-demand Cognitive Pilot Channel
>O.
Sallent & R. Agustí & J. Pérez-Romero & L. Giupponi
Department
of Signal Theory and Communications, Universitat Politècnica de Catalunya
(UPC), c/ Jordi Girona, 1-3, Campus Nord UPC, D4 Building, 08034 Barcelona,
Spain
Abstract This paper presents a framework to achieve an efficient dynamic and
decentralized spectrum and radio resource usage in heterogeneous wireless
network scenarios. The envisaged technical solution follows a layered approach,
where joint radio resource management (JRRM) and advanced spectrum management
mechanisms are identified at both the intra- and inter-operator levels. The
importance of cognitive network functionalities is highlighted. An ondemand Cognitive
Pilot Channel (CPC) is proposed as radio enabler solution for decentralized
operation with decision making processes executed at the mobile terminal side. The
suitability of the proposed solution is shown by comparison with a broadcast
CPC approach. Finally, the paper presents and evaluates decentralized JRRM
algorithms both at the intra- and inter-operator levels using the proposed
framework.
Keywords Advanced
spectrum management . Joint radio resource management . Decentralized
algorithms . Cognitive Pilot Channel . Cognitive networks
Performance evaluation of
multicast MISO–OFDM systems
>Berna
Özbek (1) · Didier Le Ruyet (2) · Hajer Khanfir (2)
(1) Electrical
and Electronics Engineering Department, Izmir Institute of Technology, Urla
35430, Izmir, Turkey
(2) Electronics
and Communications Laboratory, Conservatoire National des Arts et Métiers
(CNAM), 292 rue Saint Martin, 75141, Paris, France
Abstract In this paper, we analyze the performance of multicast orthogonal
frequency division multiplexing (OFDM) systems with single and multiple
transmit antennas. We show that the resource allocation that includes the
subcarrier allocation, bit loading, and the precoding vector selection in the
multiple-input singleoutput (MISO) case is a difficult optimization problem. Consequently,
we propose suboptimal algorithms based on the maximization of the sum data rate
and the maximization of the minimum user data rate criteria. For practical
application, we consider a complete transmission chain by combining powerful
erasure codes with the proposed algorithms. Using this scheme, we guarantee
that each user receives the same amount of information to decode the same data.
Simulation results show that, for both single-input single-output (SISO)–OFDM
andMISO–OFDM cases, the proposed multicast OFDM systems achieve gains over the
worst user case algorithm.
Keywords Multicast OFDM ·
Adaptive resource allocation · Multiple transmit antennas · Precoding vector
optimization · Subcarrier and bit allocation · Erasure codes
Analytical investigation of
intersection based range-free localization
>Michel
Sortais (1) · Sven D. Hermann (2) · Adam Wolisz (2)
(1) MAP5, UMR CNRS 8145, Université
Paris Descartes, 45 rue des Saints-Pères, 75006 Paris, France e-mail:
sortais@math-info.univ-paris5.fr
(2) Telecommunications
Networks Group, Technische Universität Berlin, Einsteinufer 25, 10587 Berlin,
Germany
Abstract The localization of mobile devices is essential for the provisioning of
location-based services, e.g., to locate people facing an accident or to
provide relevant information to device users, depending on their current
whereabouts. Several localization mechanisms have been developed using
estimates of absolute distances or angles between the devices and the base
stations of the networks. These mechanisms often require expensive enhancements
of the existing base stations or mobile devices. In recent years, so-called
range-free approaches have been proposed, which limit the possible positions of
a device to the coverage areas of radio network cells, without relying on precise
distances or angles. The accuracy of the corresponding information can be
refined by computing the intersection area of all cells that cover the current
position of the device. However, the computation of this intersection area, e.g.,
by the location server of a network carrier, can be a complex task. To avoid
unnecessary workload, one would like to preestimate the possible reduction of
location uncertainty, i.e., the information gain that can be achieved. The
contribution of this paper is an analytical and numerical investigation of the
problem. Several approaches are presented for the computation of the
information gain, based on stochastic geometry and on a Monte-Carlo method. We
show that simple scaling arguments can be used to estimate the order of magnitude
of the average information gain, while more complex approximations based on
Voronoi cells lead to relatively good results.
Keywords Range-free
localization · Location information gain · Stochastic geometry · Poisson point
processes · Voronoi tessellation
Varia
Evaluating voice traffic
requirements on IEEE 802.11 ad hoc networks
>Pedro
Braconnot Velloso (1) Marcelo G.
Rubinstein (2) Otto Carlos M. B. Duarte (3)
(1) LIP6/CNRS,
Université Pierre et Marie Curie, 8, rue du Capitaine Scott, 75015 Paris,
France
(2) PEL/DETEL-FEN,
Universidade do Estado do Rio de Janeiro, R. São Fco. Xavier, 524, 20550-013
Rio de Janeiro, RJ, Brazil
(3) GTA/COPPE/Poli,
Universidade Federal do Rio de Janeiro, P.O. Box 68504, 21945-970 Rio de
Janeiro, RJ, Brazil
Abstract This paper analyzes voice transmission capacity on IEEE 802.11 ad hoc
networks by performing simulations related to delay, jitter, loss rate, and
consecutive losses. We evaluate the influence of mobility on the number of
sources transmitting voice. Another issue addressed in this paper is the effect
of node density on voice transmission. Our simulation model has allowed us to
identify the main reasons for voice degradation in ad hoc networks. Results
show that voice transmission capacity degrades with mobility and network load,
being more sensitive to high mobility due to link failures. The network
capacity can easily experience a decrease of up to 60% on the number of voice
transmissions on a multi-hop environment. We also show that node density is
also relevant when considering voice transmission on multi-hop networks.
Keywords Wireless ad hoc
networks . IEEE 802.11 . Voice transmission . Mobility
Super-quasiorthogonal
space-time trellis codes for four transmit antennas with rectangular signal
constellations
>Corneliu Eugen D. Sterian (1) · Yi Wu (2) Matthias Pätzold (2)
(1) Polytechnic University of Bucharest,
Bucharest, Romania e-mail: steriancorneliu@hotmail.com
(2) University
of Agder, Grimstad, Norway
Abstract In this paper, we present the first superquasiorthogonal space-time
trellis codes (SQOSTTCs) for systems with four transmit antennas using various types
of rectangular signal constellations to increase the spectral efficiency up to
5 bits/s/Hz. In our wireless communications system, we define an
eightdimensional (8D) signal constellation as Cartesian product of four
two-dimensional (2D) rectangular signal sets. The transmission of an 8D point
from the first antenna is achieved by transmitting four concatenated 2D points
in four consecutive channel uses. The 2D symbols transmitted from the other
three antennas are not independent but so chosen as to form, together with the
symbols transmitted from the first antenna, the entries of a 4 × 4 quasiorthogonal
transmission matrix. The union of two sets of quasiorthogonal transmission
matrices forms a so-called super-quasiorthogonal signal set. With the 4 × 4 quasiorthogonal
transmission matrices, we then label the state transitions of a trellis diagram
describing the operation of the encoder. The simulation results of the frame
error rate and the bit error rate demonstrate the excellent performance of our
proposed SQOSTTCs.
Keywords MIMO wireless
systems · Quadrature-amplitude modulation · Space-time coding · Super-quasiorthogonal
space-time codes · Transmit antenna diversity · Trellis-coded modulation