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A major challenge in wireless sensor networks (WSN) is that spatially distributed nodes need to achieve a global task in a completely decentralised manner. Motivated by the fact that optimisation problems in WSNs can often be formulated as Markov random field (MRF) energy minimisation, a general MRF-based framework for the design of distributed WSN algorithms was proposed recently. Building upon this...
In OFDMA-based Cognitive Radio (CR) systems, how to deal with the time-varying nature of avaliliable spectrum resources has become a hotspot and challenging problem in resource allocation. Traditional resource allocation algorithm can not guarantee proportional rates among non-real-time CR user (CRU) because the number of available subchannels is smaller than the number of CRUs in some OFDM symbol...
The resource allocation in cognitive radio networks is one of the key issues to improve the spectrum efficiency. In most previous work, only one type of the secondary user (SU) network architecture is considered, i.e., it is always assumed that all SUs are centralized, or all are distributed. However, in heterogeneous cognitive radio networks, which takes both the centralized and distributed architectures...
We consider the allocation of spectral and power resources every subframe (1~ms) on the uplink of the Long Term Evolution (LTE) wideband orthogonal frequency division multiple access (OFDMA) cellular network. System bandwidth is divided into multiple sub-bands. The fractional power control to manage interference is allowed to be a function of the sub-band. Moreover, the channel gains from the base-station...
The performance of an OFDM system can be improved by performing per-subcarrier antenna selection, which facilitates the exploitation of frequency and spatial diversity in the wireless channel. In this paper, we extend the concept of per-subcarrier antenna selection to a multiuser cognitive radio environment and present a practical subcarrier and antenna selection algorithm that exploits the multiuser,...
With the rapid advance in the technology area of data storage, storage capacities have increased substantially while the price has been dropping fast. Motivated by this trend, it has been proposed in the Cache-and-Forward architecture that storage is incorporated into each intermediate CNF router. Content can be cached at CNF routers when they flow through the network, and therefore, routers can serve...
In this paper, we propose centralized and distributed power allocation algorithms for a multi-user, multi relay cellular network using decode-and-forward (DF) cooperation strategy taking channel uncertainty into account. The objective is to minimize the total uplink power of the network taking each user's target data rate as the quality of service (QoS) constraint under imperfect channel state information...
Recently, cognitive radio has become a hot spot, in which secondary users could use the frequency bands when primary users are absent. Hence, the detection of primary users' presence plays an important role in cognitive radio networks. In this paper, a cognitive radio network with multiple licensed users is considered. Secondary users cooperatively detect the presence of primary users using energy...
In this paper, we investigate the optimal packet scheduling problem in a two-user multiple access communication system, where the transmitters are able to harvest energy from the nature. Under a deterministic system setting, we assume that the energy harvesting times and harvested energy amounts are known before the transmission starts. For the packet arrivals, we assume that packets have already...
The cooperative information aggregation (CIA) scheme for distributed estimation was proposed in our past research considering the realistic wireless sensor network (WSN) environments. In the existing CIA scheme, a multi-bit quantizer is applied at all nodes, however, each node only transmits one predetermined bit of its quantized observation to the fusion center (FC) to economize the energy expense...
In this paper we propose framework for energy efficient (margin adaptive, MA) resource allocation in multiuser SC-FDMA under synchronous HARQ constraints. Resource allocation is formulated as a two-stage problem where resources are allocated in both time and frequency. To limit the impact of retransmissions on the time-frequency problem segmentation, we propose use of a block scheduling interval that...
In this paper, we investigate the optimal precoding scheme for relay networks with finite-alphabet constraints. We show that the previous work utilizing various design criteria to maximize either the diversity or the transmission rate with the Gaussian inputs assumption may lead to significant loss for a practical system with finite constellation set constraint. A linear precoding scheme is proposed...
In this paper, we consider a two-way asymmetric relaying channel with unmatched traffics from two sources. Aiming at maximizing the sum rate under a minimum rate constraint, we address the optimization problem (in terms of time and power allocation) for two decode-and-forward (DF) strategies, namely, the decode-and-forward with joint modulation (DF-JM) and the decode-and-forward with network-superposition...
Distributed spatial diversity systems, such as multi-relay and multi-user networks, have drawn significant attention from the research community. However, their feasibility in a practical environment remains an open concern. Most notably, how to optimize cooperation between multiple users with individual interests and how practical systems issues can erode diversity gains. Whilst existing information...
The main objectives of a self-organizing network (SON) technology are autonomous network deployment, network performance optimization and real-time adaptation to environmental changes. There are three functionalities in SON, such as self-configuration, self-optimization and self-healing. In this paper, we focus on the self-healing issue with respect to abrupt network faults. In order to solve this...
By supporting advanced multimedia applications and multitasking, recent Smartphone operation systems offer great flexibility to the users but make these devices even more difficult to serve. Now, operators of cellular networks face a situation where many applications and services generate highly heterogeneous and bursty traffic patterns. To cope with this challenge, we introduce Context-Aware Resource...
We consider one of the latest feature included in the Release 9 of the GSM/EDGE standard: the Orthogonal Sub Channel (OSC) transmission scheme. OSC aims at doubling the cell capacity by multiplexing two co-cell users on the same radio resource. In this work we deal with the challenge of finding the optimum pairing strategy among co-cell OSC users exploiting the Adaptive QPSK (AQPSK) modulation in...
We address the problem of designing efficient resource allocation schemes for an OFDMA based multiuser cooperative communication system that uses amplify and forward relaying. With a two-phase relaying protocol, we assume that both source and the relay have fixed power constraints and that the source employs a selective relaying mechanism. That is, the source adaptively decides on which frequency...
We study a cooperative communication system consisting of two users in half duplex mode communicating with one destination over additive white Gaussian noise (AWGN). Cooperation is performed between the two users by partial decode-forward relaying over 3 time slots with variable duration. During the first two slots, each user alternatively transmits and partially decodes while during the last time...
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