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In [1], a new frame structure is introduced to improve throughput and spectrum sensing capabilities compared to conventional cognitive radio (CR) systems that use the frame structure with a periodic sensing. However, even though employing two levels of power only for primary users (PUs) can be considered for CR systems, it may not be practical as the PUs often transmit with multiple levels of power...
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...
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...
Cognitive Radio is utilized to exploit the existing wireless spectrum opportunistically, in which way to alleviate the spectrum shortage problem. It is of fundamental importance in cognitive radio adhoc networks for users to meet on a common channel via rendezvous and thereby establish communication links. In this paper, we investigate the probability analytic model to discuss the problem of rendezvous...
The secrecy transmission performance of cognitive radio ad hoc networks is investigated in this paper. The existing work on secrecy capacity of cognitive radio networks focus on order sense results like scaling laws, however, these results only give asymptotic predictions without an exact expression. In order to overcome this limitation, we propose a new method to derive the closed-form expression...
In this paper, lattice network coding (LNC) is studied in the multiple-antenna (MA) two-way relay channel (TWRC), where each user has a single antenna and the relay has multiple antennas. We propose two relay computation schemes for the MA TWRC with nested lattice codes, namely the receive antenna selection (RAS) scheme and the receive antenna combining (RAC) scheme. In the RAS scheme, the relay calculates...
In this paper, a novel opportunistic protocol is proposed for the two-way relaying systems with direct link. Unlike the existing protocols, the proposed protocol opportunistically exploits analog network coding and the direct link. The proposed protocol switches its strategies to support two traffic flows simultaneously or support only one traffic flow based on instantaneous channel conditions. An...
We consider the fairness in cooperative data exchange (CDE) problem among a set of wireless clients. In this system, each client initially obtains a subset of the packets. They exchange packets in order to reconstruct the entire packet set. We study the problem of how to find a transmission strategy that distributes the communication load most evenly in all strategies that have the same sum-rate (the...
In this paper, we propose a signal transmission model for multi-group multi-way (MGMW) relaying which allows complete information exchange among users belonging to different user groups, with applications such as file sharing among users separated by large distances. We achieve this through the use of multi-stage non-regenerative relay stations (RSs). The groups of multiple users are connected to...
This paper proposes a new TDMA-based cooperative MAC scheme for a two-hop relay network in which there are several helpers besides a default relay node. Here, a helper has lower obligation than the default relay to help packet forwarding. The proposed method is developed from the existing CR-TDMA scheme, and named as opportunistic CR-TDMA or OCR-TDMA. We derive the throughput performance of CR-TDMA...
This paper introduces a new contention window (CW) adaptation algorithm to reduce the collision level in an IEEE802.11 based network with the main objective of maximizing energy efficiency while maintaining required Quality of Service (QoS) performance. The main concept of the proposed algorithm is to dynamically adjust the contention window size according to the network load condition, which represents...
Named Data Networking (NDN) as a promising future network architecture has been attracted a lot of attention. In NDN, to keep fairness between flows and avoid congestion, one of the most important issues is the traffic control. Although some works have been done to solve the traffic control problem by controlling the sending/forwarding of Interest, to the best of our knowledge, the cooperation between...
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