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We consider an underlay cognitive radio network, in which the cognitive users (also referred to as secondary users (SUs)) are allowed to access the licensed spectrum simultaneously with the primary users (PUs). Specifically we solve a beamforming and power allocation problem in the downlink with mixed quality-of-service (QoS) requirements where a set of SUs are required to achieve a specific signal-to-interference...
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...
This paper studies a spectrum sharing scenario between an uplink cognitive relay network (CRN) and some nearby low power ad-hoc networks. In particular, the dynamic resource allocation of the CRN is analyzed, which aims to minimize the average interfering time with the ad-hoc networks subject to a minimal average uplink throughput constraint. A long term average rate formula is considered, which is...
Isolation and performance are critical issues for virtual networking. In this paper, we consider the use of Xen virtualization platform for building software-based virtual routers. We propose a network monitor for Xen to increase the isolation and the performance on packet forwarding. The network monitor controls the use of shared resources and punishes misbehaving virtual routers, guaranteeing an...
Nodes in most cooperative networks are powered by batteries and some of which are even non-rechargeable. Therefore, power allocation schemes must be developed to save the transmit power and improve the life-time of the system. In this context, we present a novel power allocation scheme for multiple relay nodes that results in efficient cooperative communication. Considering channel path loss, the...
In an opportunistic spectrum access based cognitive radio network, the secondary user (SU) does not transmit when the primary user (PU) is detected to be present. If the SU detects that the PU is inactive during a sensing period, it is usually assumed that the SU will transmit its data at peak power in the following data transmission frame. However, when the PU is detected to be inactive, the PU may...
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...
This paper presents an evolution framework of resource allocation by infection among secondary users (SUs) in an OFDMA-based cognitive radio cellular networks. Each primary user (PU) sells his extra sub-channels to SUs in his sensing range to achieve the highest payoff and each SU may come across another in his sensing range to make infection. Two different infection processes among SUs, the infection...
Support of non-contiguous frequency resource allocation (FRA) based on clustered discrete Fourier transform-spread orthogonal frequency division multiplexing (clustered DFT-S-OFDM) is considered a key element of LTE-Advanced uplink to enhance the spectrum efficiency via an enhanced frequency domain scheduling. However, reduction of out-of-band emissions due to multiple clusters is a critical issue...
Providing physical-layer security for mobile users in future broadband wireless networks is of both theoretical and practical importance. In this paper, we formulate an analytical framework for resource allocation in a downlink OFDMA-based broadband network with coexistence of secure users (SU) and normal users (NU). The problem is formulated as joint power and subcarrier allocation with the objective...
In this paper, we focus on joint subchannel and power allocation for layered multicast streams in OFDMA cellular networks, where the multicast stream is composed of a basic layer and an enhancement layer. Our goal is to maximize the system total throughput with a total power constraint and a minimum rate requirement. A low-complexity allocation algorithm is proposed, which combined a cost-based subchannel...
The emerging WiMAX technology (IEEE 802.16) is a fourth generation standard for low-cost, high-speed and long range wireless communications for a large variety of civilian and military applications. IEEE 802.16j has introduced the concept of mesh network model and a special type of node called Relay Station (RS) for traffic relay for Subscriber Stations (SSs). A WiMAX mesh network is able to provide...
Uplink resource allocation with intercell interference mitigation in LTE networks is investigated. A non-cooperative probabilistic interference avoidance scheme and a pricing-based cooperative power control scheme are proposed. A scheduling algorithm is presented and used with the proposed interference mitigation schemes. In the absence of power control, scheduling with the probabilistic interference...
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...
This paper proposes an adaptive fractional frequency reuse (FFR) resource allocation scheme for downlink transmission of OFDMA cellular networks. Resource allocation is localized in the sense that in each region system resources are assigned based on local traffic demand. Furthermore, the allocated resources in each region adapt to changes in the environment (i.e. channel gains and number/mobility...
In this paper, we study the cooperative network coding problem in relay-assisted wireless access networks. In such a network, each mobile station can choose different transmission schemes: directly transmitting to the base station, pure relaying by a relay station, or via cooperative network coding. We analyze the impact of the different schemes on the network throughput. We find the performance of...
This paper investigates the user and channel diversity in OFDMA wireless systems with network coding. In particular, the paper introduces an adaptive resource allocation scheme to minimize the total transmit power while maintaining a required end-to-end BER. The proposed adaptive sub-carrier allocation scheme de-couples the bit loading of the network coded OFDMA system into three independent bit loadings...
This paper studies training-based transmissions over multiple-input multiple-output (MIMO) fading channels in the presence of jamming. Each transmission block consists of a training phase and a data transmission phase. From an information-theoretic viewpoint, we formulate a max-min problem on the energy allocation between the two phases. The legitimate user of the channel aims to design a robust energy...
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