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We consider a cognitive radio system in which primary user stores packets in a queue for transmission. For proper functioning of primary system, the cognitive user must ensure that primary queue remains stable. We show that such a queue stability constraint can be converted to an equivalent interference constraint on cognitive user's transmission. Under this constraint, we propose a power allocation...
In this paper, the issue of energy-aware competitive resource allocation in an amplify-and-forward (AF) relay-assisted multiple-antenna interference network is considered. A non-cooperative game-theoretic approach is taken and the EE of each communication link is defined as the ratio of the achievable rate over the consumed power. The proposed resource allocation algorithm jointly allocates the relay...
In this paper, we study the problems of power allocation in a multi-user relay-assisted wireless network. From the perspective of game theory, we formulate and analyze this power allocation problem as a power trading game by considering users as bidders and the relay as an auctioneer. Aiming at solving this problem where each bidder has a private budget limit, we apply an adaptive clinching auction...
In this paper, we study the problem of power control in a wireless ad hoc system. We consider multiple links of two hops relating source to destination. We propose to use a utility function corresponding to an approximation of the capacity of each link at high Signal to Interference plus Noise Ratio (SINR). We study analytically the problem of maximizing the sum utilities. We assume that users adjust...
This work aims to apply a new dynamic frequency reuse scheme based on fractional frequency reuse (FFR) in Cloud-RAN structure. FFR is one of the most efficient schemes to mitigate the inter-cell interference in OFDM system, while strict FFR in traditional cellular system is still facing some problems such as the inefficient use of spectrum. Cloud-RAN is a new network structure comprised of baseband...
This paper deals with the problem of sum rate maximization for a multiuser orthogonal frequency-division multiple access channel with secrecy rate constraints. We consider the case of a multiple-antenna base station (BS) and several single-antenna downlink receivers; a single secure user, a single eavesdropper and several normal users (without secrecy requirements). The eavesdropper intends to wiretap...
This paper studies secure layered video transmission in a multiuser multiple-input single-output (MISO) beamforming downlink communication system. The power allocation algorithm design is formulated as a non-convex optimization problem for minimizing the total transmit power while guaranteeing a minimum received signal-to-interference-plus-noise ratio (SINR) at the desired receiver. In particular,...
In this paper, power allocation between training and data symbols is investigated to maximize energy efficiency (EE) for multicell systems using coordinated beamforming (CBF). We formulate the EE optimization problem under a minimum rate requirement as a multi-variable non-quasiconcave fractional program. Based on an approximation of the ergodic rate, we transform the problem into a jointly quasiconcave...
Careful planning of wireless networks is essential to provide reliable communication, especially that microwave links are frequently chosen to interconnect access points within networks. The optimization of such networks belongs to the frequency assignment problems and focuses on setting polarization of the links or allocating the channels in a frequency duplex to reduce or eliminate the interference...
A high spectral efficiency cooperative communication system is proposed in this paper. The concept of signal space diversity (SSD) is utilized to double the spectral efficiency of opportunistic cooperative communication networks. SSD rotates the transmitted symbols by a certain angle at the source, before transmission, such that each in-phase and quadrature component of the rotated symbol contains...
In this paper we propose an energy efficient cognitive radio system. Our design considers an underlaying resource allocation combined with soft sensing information to achieve a sub-optimum energy efficient system. The sub-optimality is achieved by optimizing over a channel inversion power policy instead of considering a water-filling power policy. We consider an Energy per Goodbit (EPG) metric to...
In this paper, we investigate the impact of using outdated channel state information for incremental opportunistic relay selection in a spectrum sharing cognitive network. In our work, we present the outage performance of two schemes where the power allocation is based on the instantaneous outdated channel state information and the statistical knowledge of the interference links, referred to as CSI-based...
We propose a coordinated multicell beamformer design method based on the signal-to-interference-plus-noise ratios (SINRs) balancing technique within the context of mixed quality of services (QoS). Instead of attaining an overall balance of SINRs to all users in all cells, the proposed algorithm allows a specific subset of users in each cells to achieve certain target SINRs while the SINRs of the remaining...
This paper deals with the optimization of the multiuser (MU) pilot design for orthogonal-frequency-division-multiple-access (OFDMA) systems perturbed by the I/Q imbalance (IQI) impairment. For the frequency-selective Rayleigh propagation channels, the proposed approach exploits the decoupled direct and image channels, and the knowledge of the effective channel statistics to realize dual linear-minimum-mean-square-error...
We consider a spectrum sharing protocol in which a secondary system can operate on the same spectrum with a primary user. In the protocol, the secondary system helps the primary system achieve its target rate by acting as a relay for the primary system. As a reward, the remaining subcarriers can be used for the secondary transmission. In order to alleviate the disadvantages of amplify-and-forward...
In this paper, we consider both channel state uncertainty and harvested energy state uncertainty for a source-relay-destination communication link where the source and the relay are equipped with hybrid energy sources. Taking into account these uncertainties is of important for practical energy harvesting (EH) communication. While channel state uncertainties also affect conventional communication...
To combat the bottleneck effect in the relay channels, this paper proposes a simple power-control algorithm for decode-and-forward cooperative networks with opportunistic relay selection. Taking advantage of the existing channel state information, which is a by-product during the process of relay selection, an optimal power allocation factor can be easily figured out. This factor is quantized into...
In this work, we investigate the robust energy-efficient transmission for the cognitive uplink wireless system. Precisely, we propose an optimization framework for maximizing the sum energy efficiency while taking into account the uncertainty of the channel between the primary and secondary users. Here, we assume that the base station has multiple antennas and employs a zero-forcing receive filter...
Recently, substantial attention has been paid to improve the spectral efficiency of communication setups using different spectrum sharing techniques. This paper studies the throughput of spectrum sharing channels utilizing hybrid automatic repeat request (HARQ) protocols. Considering different HARQ schemes, the unlicensed user throughput is obtained under an outage probability constraint for the licensed...
A low-complexity design of multi-antenna relay processing is proposed for two-way relay networks with asymmetric data flows. The proposed scheme adopts three-phase (3P) analog network coding (ANC) which allows orthogonal transmission of two communicating nodes to overcome some disadvantages of two-phase (2P) ANC protocols. For the 3P ANC, we propose antenna selection at the relay to exploit the diversity...
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