1,721,125 research outputs found
Efficient simulation of frame and bit error rate in wireless systems with convolutional codes and correlated fading channels
No full textThis paper proposes an efficient semi-analytical simulation method for the evaluation of convolutional code performance over fading channels. The major emphasis is placed on frame transmission over correlated fading channels attracting great attention in wireless communications. The simulation method exploits the analytical evaluation of suitable bounds for frame and bit error probability conditioned to the fading process samples. The most general bound is an upper bound obtained by adapting a well-known hound for the AWGN channel to the fading channel. A second simple approximated (lower) bound is also introduced to allow the construction of a very efficient estimator for frame and hit error probability. The efficiency of the proposed method with respect to the usual simulation is investigated and the results prove the possibility of an accurate and fast evaluation in the region of low error probabilities
Evaluation of frame and bit error probabilities for convolutional codes on fading channels
No full textTechniques for radio network optimization
No full textPacket-switching communication is gaining an ever increasing relevance for
wireless networks. On one hand, releasing radio resources to single communication
units, i.e. the packets, is much more efficient than releasing
resources to entire connection; on the other hand, IP is becoming the predominant
technology in the backbone network for integration and transport
of heterogeneous multimedia and data traffic. Two important radio resource
optimization problem have to be considered, within this framework, for the
design of MAC and RRM functionalities in a wireless packet network. The
first problem is to look for the best way (as a tradeoff between capacity and
complexity) to dynamically assign radio resources to a set of users having
packets to transmit. The second problem is to look for the best way (as a
tradeoff among capacity, user satisfaction, fairness and complexity) to schedule
packet transmission in time over the available radio resources for a set of
users with one or more packet traffic sources with possible QoS constraint
Outage probability evaluation for systems employing linear block codes on independent channels
No full textOutage probability for systems employing such codes jointly with interleaving, frequency hopping or selection diversity, is evaluated. A unified formal description and a new evaluation algorithm have been developed and applied. In order to check their applicability to some microcellular systems, the behavior of such techniques is investigated in the presence of Rice/Rayleigh flat fading and co-channel interference. Their convenience is determined by taking into account the tradeoff between performance and spectrum efficiency
Linear Wireless Networks with Variable Length and Density: Scaling Laws and Design Considerations
No full textIn this paper we consider linear wireless networks
with variable number of nodes. We first derive a basic cut-set
bound for transport capacity of this class of networks highlighting
the functional dependence on both node density and network
length. After, we investigate how transport throughput scales with
respect to node density δ in a wireless network with multihop
communication. While in linear multihop networks without
fading transport throughput does not increase by increasing node
density, i.e. it scales as δ0 with a gap with respect to capacity
bounds, we show that a capacity increase up to log δ is achieved
in the presence of fading by using, instead of a simple nearestneighbor
communication, suitable algorithms that adaptively
schedule source-destination links in the networks. Finally, we
compare multihop schemes with schemes based on distributed
MIMO communication by discussing the relevant differences and
showing that, despite the latter strategy is able to asymptotically
achieve scaling law bound approaching δ, multihop schemes
appear better in terms of capacity in a significant range of values
of δ and when the network becomes extende
Adaptive Resource Allocation with Proportional Rate Constraints for Uplink SC-FDMA Systems
No full textIn this work we address the problem of ergodic
sum-rate maximization under proportional rate constraints for
the uplink of single-carrier frequency division multiple access
(SC-FDMA) systems. Finding optimal solution generally requires
high computational complexity, because SC-FDMA imposes the
contiguous allocation of the available frequency resources. To
reduce complexity we propose a novel sub-optimal algorithmic
solution, based on Lagrangian relaxation of the rate constraints,
which exploits a simple but effective estimation of the average
number of the resources to allocate in order to reduce the search
space. The complexity of the resulting algorithm increases only
linearly with the number of users and the number of resources,
while the performance gap to optimal solution is limited to the
10% of the sum-rate
High-speed indoor wireless COFDM systems at 60 GHz: performance and design criteria
No full textWith the aim of defining system design criteria, the performance of a high-speed indoor wireless communication system using COFDM and working at 60 GHz is analyzed. An actual propagation environment, which has been characterized by means of a ray-tracing technique, is considered for the analysis. Suitable algorithms are introduced to evaluate the performance in this environment. The effects of antenna sectorization, OFDM clustering, frequency diversity and code choices are investigated and discussed. Moreover, a definition of coverage is proposed and discussed. The feasibility of a COFDM system for 155 Mbit/s ATM transmission with transmitter power of 10 dBm and an 80% coverage of the NLOS points in the scenario considered is shown in the results
Effects of Spreading Code on the Performance of CDMA Picocellular Systems with Rake Receivers
No full textBy exploiting analytical and semianalytical methodologies, performance of DS-CDMA system for picocellular applications, including multipath propagation channels and a RAKE receiver, is evaluated. The system performance is defined in terms of both the mean bit error probability and outage probability, taking the exact evaluation of spreading codes correlation into account. The spreading sequences investigated include some well known two-level sequences and multilevel sequences with complex mapping. By varying the spreading codes and propagation channel conditions, the following aspects have been considered in the numerical results: a comparison of RAKE receivers and simple correlator receivers, the trade-off between receiving taps number and performance, the degradation effects due to not ideal spreading code correlation, and a comparison between binary and multilevel sequence
Performance evaluation method and comparison of local radio systems on selective fading channels
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