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The spectrum sharing has recently passed into a mainstream Cognitive Radio (CR) strategy. We investigate the core issue in this strategy: interference mitigation at Primary Receiver (PR).We propose a linear precoder design which aims at alleviating the interference caused by Secondary User (SU) from the source for Orthogonal Space-Time Block Coding (OSTBC) based CR. We resort to Minimum Variance (MV)...
In this work we compare full-duplex (FD) and half-duplex (HD) relaying in terms of outage probability and throughput. We consider a practical FD relay model where the loop interference between transmitted and received signals is taken into account. We analyze two modes for FD transmission, block Markov encoding and multi-hop transmission without interference cancellation, and two different modes for...
As the regulation in wireless communications is moving toward a more flexible and efficient way of managing radio spectrum, it is envisaged that multiple small-sized cellular networks owned by different operators, e.g., facility owners or local operators, will operate in close vicinity on shared spectrum. In this environment, the networks may compete for their own utilities in a selfish manner with...
This paper studies the achievable performance of a single-antenna spectrum-sharing system. Due to limited cooperation between secondary users (SUs) and primary users (PUs), perfect channel state information (CSI) related to the PUs is hard to obtain for the SUs. Therefore, we assume the secondary transmitter and receiver have only statistical CSI from the secondary transmitter to the primary receiver...
In this paper a spectrum sharing scheme is proposed to maximize the successful transmission probability of a single-hop cognitive network coexisting with a random primary network. Both cognitive and primary networks exhibit randomness in topologies and endure imperfect wireless channel conditions. For a given primary outage probability bound, the maximum secondary transmit power is determined and...
We consider spectrum sharing in a cognitive radio network where a secondary user co-exists with an ARQ-based primary user. A spectrum sharing protocol is proposed where the secondary user switches between cooperation and access modes. In the cooperation mode, the secondary system serves as a relay to assist the primary transmission, and in return accumulates credits. The credits allow the secondary...
Cognitive users need to be capable of utilizing wireless spectrum without causing harmful interference to primary users. In this paper, we consider a multi-antenna cognitive radio system with multiple secondary data streams subject to individual signal-to-noise-ratio (SNR) constraints. With cognitive beamforming, the secondary transmitter attempts to nullify the interference received at the primary...
Cognitive relaying is a promising technique to improve spectrum utilization in mobile networks. In this paper, we consider a scenario in which a secondary transmitter communicates with a secondary receiver by the help of a secondary relay. The secondary user should adjust its transmission power in order to not cause any harmful interference to the multiple primary users operating in the licensed spectrum...
We consider an underlay cognitive radio system consisting of a secondary transmitter (ST), K secondary receivers (SRs) and a primary receiver (PR). Data transmission is granted to the ST under the constraint that the generated peak interference to the PR is below a predetermined interference temperature level. Assuming that the ST can adaptively adjust its transmit power according to the fading state...
In this paper we address the problem of Weighted Sum Rate (WSR) maximization for a K-user Multiple-Input Single-Output (MISO) cognitive Interference Channel (IFC) with linear transmit beamforming (BF) vectors in an underlay cognitive radio setting. We consider a set of L single-antenna Primary receivers to which the cognitive system can causes a limited amount of interference. We thus propose an iterative...
In this paper, we propose a novel approach for cooperative systems performance optimization. We are interested on the uplink CDMA communications, known to be both intra-cell and inter-cell interference limited. More precisely, we define a multi-access interference (MAI) cost that reliably quantifies the additional interference generated by a relayed communication to the whole cellular system. For...
This paper addresses bounds on the transmission capacities of two coexisting wireless networks (a primary and a secondary network), where each with multiple antennas shares the same spectrum and operates in the same geographic region. In the two coexisting network, the secondary (SR) network limits its interference to the primary (PR) network by carefully controlling its active transmitter density...
In this paper we propose a general model to estimate the maximum allowed transmit power of a secondary node based on the measured signal from the primary transmitter that is willing to share its downlink spectrum. The transmit power should satisfy primary constraints related to the minimum required Signal to Interference and Noise Ratio (SINR) of its users. The model can be used by secondary nodes...
The multi-user multi-relay system is investigated in this paper. Multi-user precoding is utilized at the source node to mitigate the interference among data streams. Since the transmitting power of relay nodes is constrained independently, the interference among data streams can not be completely mitigated at the destination nodes. An energy-efficient relaying scheme is proposed at relay nodes to...
A relay station (RS)-based cellular system deployment is considered, where multiple base stations (BS) cooperate in the BS-RS in-band transmission for the downlink. With the joint optimization of the resources allocated to the wireless backhaul and to the RS-MS access, it is possible to exploit the benefits of networked-MIMO along with combating the pathloss and shadowing effects, and thus obtain...
Relayed transmission is a promising technique to increase coverage and achievable capacity of the communication systems. A cognitive OFDM-based decode-and-forward (DF) cooperative relay network is considered in this paper. The objective of the problem is to maximize the capacity of the cognitive radio (CR) system while guaranteeing that the interference introduced to the primary system is below the...
This paper studies multiple relay selection schemes in two-hop cognitive relay networks to maximize the signal-to-noise ratio (SNR) of the secondary receiver. We first formulate the relay selection as a nonlinear integral programming, and then propose two suboptimal methods, greedy scheme and hybrid scheme. Based on the sorted efficiency function, the greedy scheme selects the secondary relay nodes...
We consider a cooperative cognitive radio system, where a secondary user may relay data for the primary user. Under the half-duplex assumption and packet collision model, the primary and secondary instantaneous data rates are derived, as a function of the power allocation factor by the secondary user to relay the primary user's data. We study the optimal power allocation to maximize the secondary...
Cognitive radio technology enables the coexistence of Primary (PUs) and Secondary Users (SUs) in the same spectrum. In this work, it is assumed that the PU implements a retransmission-based error control technique (ARQ). This creates an inherent redundancy in the interference created by primary transmissions to the SU. We investigate secondary transmission policies that take advantage of this redundancy...
Characterizing the topology and therefore fundamental limits is a must to establish effective end-to-end cognitive radio networking (CRN). However, there lacks complete understanding of the relationship among connectivity, interference, latency and other system parameters of the CRN. To clarify this complication, by employing tools from both percolation theory and stochastic geometry, we thus provide...
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