57,567 research outputs found
Communication systems supporting multimedia multi-user applications
Multimedia multi-user applications are becoming more and more important. Intensive research is underway on the design of protocols and protocol entities for future communication systems supporting multimedia multi-user applications. The development of a service description ensures that protocol designs actually produce the required functional behavior. The authors explain the approach to the description of a multimedia multi-user service. An example illustrates the use of the service description in the design of communication systems. Next, they present the basic requirements of multimedia and multi-user communications. A call model underlies and structures the service description. Finally, the authors describe the service in terms of service element
Multi-user Communication in Difficult Interference
The co-channel interference (CCI) is one of the major impairments in wireless
communication. CCI typically reduces the reliability of wireless communication
links, but the difficult CCI which is no more or less strong to the desired
signals destroys wireless links despite having myriad of CCI mitigation
methods. It is shown in this paper that M-QAM (Quadrature Amplitude Modulation)
or similar modulation schemes which modulate information both in in-phase and
quadrature-phase are particularly vulnerable to difficult CCI. Despite
well-known shortcomings, it is shown in this paper that M-PAM or similar
schemes that use a single dimension for modulation provides an important mean
for difficult CCI mitigation.Comment: 4 pages, 2 figs and accepted in IEEE ICASSP 2019, Brighton, U
Adaptive Modulation in Multi-user Cognitive Radio Networks over Fading Channels
In this paper, the performance of adaptive modulation in multi-user cognitive
radio networks over fading channels is analyzed. Multi-user diversity is
considered for opportunistic user selection among multiple secondary users. The
analysis is obtained for Nakagami- fading channels. Both adaptive continuous
rate and adaptive discrete rate schemes are analysed in opportunistic spectrum
access and spectrum sharing. Numerical results are obtained and depicted to
quantify the effects of multi-user fading environments on adaptive modulation
operating in cognitive radio networks
Non-atomic Games for Multi-User Systems
In this contribution, the performance of a multi-user system is analyzed in
the context of frequency selective fading channels. Using game theoretic tools,
a useful framework is provided in order to determine the optimal power
allocation when users know only their own channel (while perfect channel state
information is assumed at the base station). We consider the realistic case of
frequency selective channels for uplink CDMA. This scenario illustrates the
case of decentralized schemes, where limited information on the network is
available at the terminal. Various receivers are considered, namely the Matched
filter, the MMSE filter and the optimum filter. The goal of this paper is to
derive simple expressions for the non-cooperative Nash equilibrium as the
number of mobiles becomes large and the spreading length increases. To that end
two asymptotic methodologies are combined. The first is asymptotic random
matrix theory which allows us to obtain explicit expressions of the impact of
all other mobiles on any given tagged mobile. The second is the theory of
non-atomic games which computes good approximations of the Nash equilibrium as
the number of mobiles grows.Comment: 17 pages, 4 figures, submitted to IEEE JSAC Special Issue on ``Game
Theory in Communication Systems'
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