1,951 research outputs found
Subcarrier and Power Allocation for LDS-OFDM System
Low Density Signature-Orthogonal Frequency Division Multiplexing (LDS-OFDM) has been introduced recently as an efficient multiple access technique. In this paper, we focus on the subcarrier and power allocation scheme for uplink LDS-OFDM system. Since the resource allocation problem is not convex due to the discrete nature of subcarrier allocation, the complexity of finding the optimal solutions is extremely high. We propose a heuristic subcarrier and power allocation algorithm to maximize the weighted sum-rate. The simulation results show that the proposed algorithm can significantly increase the spectral efficiency of the system. Furthermore, it is shown that LDS-OFDM system can achieve an outage probability much less than that for OFDMA system
Advanced Access Schemes for Future Broadband Wireless Networks
International audienc
Fairness Evaluation in Cooperative Hybrid Cellular Systems
Many method has been applied previously to improve the fairness of a wireless communication system. In this paper, we propose using hybrid schemes, where more than one transmission scheme are used in one system, to achieve this objective. These schemes consist of cooperative transmission schemes, maximal ratio transmission and interference alignment, and non-cooperative schemes, orthogonal and non-orthogonal schemes used alongside and in combinations in the same system to improve the fairness. We provide different weight calculation methods to vary the output of the fairness problem. We show the solution of the radio resource allocation problem for the transmission schemes used. Finally, simulation results is provided to show fairness achieved, in terms of Jain's fairness index, by applying the hybrid schemes proposed and the different weight calculation methods at different inter-site distances
Maximizing Energy Efficiency in Multiple Access Channels by Exploiting Packet Dropping and Transmitter Buffering
Quality of service (QoS) for a network is characterized in terms of various
parameters specifying packet delay and loss tolerance requirements for the
application. The unpredictable nature of the wireless channel demands for
application of certain mechanisms to meet the QoS requirements. Traditionally,
medium access control (MAC) and network layers perform these tasks. However,
these mechanisms do not take (fading) channel conditions into account. In this
paper, we investigate the problem using cross layer techniques where
information flow and joint optimization of higher and physical layer is
permitted. We propose a scheduling scheme to optimize the energy consumption of
a multiuser multi-access system such that QoS constraints in terms of packet
loss are fulfilled while the system is able to maximize the advantages emerging
from multiuser diversity. Specifically, this work focuses on modeling and
analyzing the effects of packet buffering capabilities of the transmitter on
the system energy for a packet loss tolerant application. We discuss low
complexity schemes which show comparable performance to the proposed scheme.
The numerical evaluation reveals useful insights about the coupling effects of
different QoS parameters on the system energy consumption and validates our
analytical results.Comment: in IEEE trans. Wireless communications, 201
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