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Recently, security problems in massive multiple-input multiple-output (MIMO) network draw more and more attention. In this paper, a security problem for a multi-pair massive MIMO two-way amplify-and-forward (AF) relay network is considered, where multiple users exchange confidential messages via a common relay equipped with large number of antennas. We propose an optimal power allocation scheme that...
When a cognitive radio network shares the spectrum with a primary network, the harmful interference to the primary users is one of the most important concerns. In this paper, we propose a new cognitive scheme which has two cognitive sub-networks sharing the same relay station, considering the interference to the primary user. We study the Weighted Rate Balance problem with the constraint of the transmit...
In cognitive radio (CR) systems, we often use jamming schemes to improve the physical-layer security in the presence of passive eavesdroppers. However, it also needs additional signal sources to transmit artificial noise. In this paper, we investigate the multiple-input single-output (MISO) cognitive radio system where two secondary links secure each other's communication. Each secondary transmitter...
Distributed beamforming is an energy-efficient wireless communication technique that allows cooperative nodes to transmit a common message to a receiver. This paper investigates carrier synchronization for distributed beamforming in large-scale wireless networks. In order to pursue less timeslots for synchronization, we present a time-slotted round-trip carrier synchronization protocol exploiting...
In this paper, we propose a filter-and-forward (FF)beamforming strategy in the secondary relays for the one-way cognitive relay network with frequency selective fading channels. Our aim is to optimize the beamforming coefficients and the secondary transmitted power to maximize the SINR at the secondary destination, while satisfying the interference constraint on the primary network and the total relays'...
This paper investigates the cooperative beamforming in the amplify-and-forward-based cognitive relay network. Beamforming coefficients are designed to maximize the sum rate of the secondary users with a total transmit power constraint of the relays and an interference power constraint at the primary receiver. The sum rate maximization problem is firstly solved by characterizing the achievable rate...
While a cognitive radio network sharing the spectrum with a primary network, one of the major concerns is that harmful interference to the primary users should be avoided. In this paper, we propose three low-complexity algorithms for distributed beamforming in cognitive radio networks which opportunistically select a subset of cognitive source nodes whose phases may be compensated, so that the received...
Distributed beamforming (DBF) is a cooperative technology that several nodes transmit a common message to a receiver efficiently. The key to DBF is to ensure every node's signal adds coherently at the receiver by synchronizing node's carrier phase. In this paper, we present a closed-loop deterministic phase synchronization algorithm in order to pursue less synchronization time, less feedback information,...
This paper studies the cognitive one-way relay network which is composed of a pair of primary transmitter and receiver. A two-step one-way amplify-and-forward (AF) relaying scheme is used by the primary network who utilizes the cognitive radio (CR) terminals as its relay nodes. Simultaneously, the cognitive information is transmitted by multiple CR terminals to the CR base station. In the first phase...
In this paper we investigate the cooperative beamforming in cognitive radio network (CRN) composed of a primary network (PN) and a secondary network (SN). In the SN, the transmitter has to communicate with the receiver with the help of the hybrid relays which use cooperative beamforming to retransmit data. The relays will select amplify-and-forward (AF) or decode-and-forward (DF) according to the...
This paper presents an interference suppression scheme for multiuser downlink transmission in severe frequency-selective fading environments. Frequency-domain transmit beamforming and pre-equalization based on single-carrier frequency-domain equalization (SC-FDE) technique are employed to cancel co-channel interference (CCI) and to suppress intersymbol interference (ISI) with relatively low complexity...
A new blind beamforming algorithm to fast track mobile nodes is proposed in this paper. The relationship between the direction of the nodes and the weight vector of the beamforming algorithm is deduced. Utilizing the continuity of the nodes' trail in ad hoc network, the new method could initially estimate the direction of the nodes at the following moments from those obtained from the previous beamforming...
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