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In this paper, we study a multi-level power allocation scheme for SUs in cognitive radio systems that uses a new frame structure to improve overall throughput of the system. The scheme is different from the conventional strategies in that the PU can now transmit with multiple levels of power rather than a constant level of power, which seems to be more realistic and practical. Our proposed strategy...
Recently, the demand for faster and more reliable data transmission has brought up complex communications systems. As a result, it has become more difficult to carry out closed-form solutions that can provide insight about performance levels. In this paper, different from the existing research, we study a cognitive radio system that employs hybrid-automatic-repeat-request (HARQ) protocols under quality-of-service...
Cognitive cellular networks can enable opportunistic network access but their effectiveness relies on adaptive handoff algorithms. However, in cognitive radio networks the usufructuary rights of a secondary user are rescinded due to the unanticipated appearance of a primary user causing potential service disruption. In order to provide uninterrupted service to a cognitive cellular user, we propose...
In this paper, a new spectrum sensing (SS) method, called maximum-to-mean energy detector (MMED), is proposed. Considering a wireless communication system with many angles of arrival (AoA), the suggested method is based on beamforming and the ratio of the maximum energy to the mean one of the received signal. The proposal is totally blind and it does not require the knowledge of the signal, the channel...
To maximize spectrum access opportunities for white space devices, incorporating real-time spectrum sensing with geolocation database is a promising approach to enhance detection resolution. Advanced spectrum sensing techniques are needed to quickly and accurately identify spectrum occupancy over a wide frequency range. However, the stringent requirements from the wideband signal acquisition and processing...
Device to device (D2D) communication is essential in Internet of things (IoT). Cognitive radio (CR)-enabled device is a promising technique to address D2D communications. Among all the functions supported in IoT, priority-based spectrum access is less investigated yet urgently desired in IoT. An important operation to achieve this capacity is channel hopping (CH) based rendezvous which allows two...
State-of-the-art sensing methods mostly exploit spectrum holes (SHs) in conventional frequency, time, and geography dimensions, which can hardly satisfy the increasing throughput demand of CR networks. Meanwhile, the rapid development of multi-antenna technology makes the terminal obtain the angle recognition capability. Motivated by this, this paper analyzes SHs from the angle/space domain and design...
We consider a single channel energy harvesting cognitive radio system, where the joint optimization of spectrum sensing, channel probing and transmission power control is considered with the goal to maximize the throughput. We model this control problem as a two-stage continuous-state Markov decision process with one stage for sensing and probing control, and the other for transmission power control...
For cooperative cognitive radio networks (CR-Nets), spectrum sensing is a key technology to detect spectrum holes which are inadequacy exploited by primary communication system. This paper presents an adaptive spectrum sensing based on multiple measurement vectors. In the proposed method, by using this structure, cognitive user can use less number of measurements that achieve spectrum holes detection...
This paper proposes a channel allocation scheme for Wide-Area Low-Rate Wireless Personal Area Networks (LR-WPAN) based on a cooperative centralized spectrum sensing approach. We refer here to a three-tiers LR-WPAN architecture, where we can distinguish the sensor devices level, the Child-coordinators level and, finally, the super LR-WPAN coordinator level. In the proposed scheme, channels allocation...
With the growing number of connected devices (e.g. smartphones, sensors, actuators and cameras) in 5G, the massive Internet of Thing (IoT) is expected to address a wide range of characteristics and demands, with more radio-frequency (RF) bands to support multiple frequency transmission by 2020. Separate antennas and RF chips may be required for widely separated frequency bands. The development of...
To overcome the hidden terminal problem a secondary user (SU) may encounter, cooperative spectrum sensing (CSS) is proposed and gained much attention in the last decades. However, due to the selfish nature, SUs may not cooperate unconditionally as most previous works have assumed. Therefore, how to stimulate SUs to play cooperatively is an important issue. In this paper, we propose a reputation-based...
Cooperative sensing enables secondary users to combine individual sensing results in order to attain sensing accuracies beyond those achieved by consumer RF devices. However, due to sensing costs, secondary users may prefer not to cooperate to the sensing task, leading to higher false alarm probability. In this paper, we study how information about the presence of cooperators affects the dynamics...
Usually energy-detection based spectrum sensing techniques for Cognitive Radios need, as preliminary operation, the spectrum segmentation in smaller sub-bands, in order to apply test statistic over each sub-band rather than over the entire span, resulting in a sensitivity and selectivity improvement of the output. Despite uniform subdivision is the easiest way, the problem resides on the optimal sub-band...
Military wireless networks are used for exchange of constantly growing amount of data. The result is an increasing number of radio networks and required bandwidth both in civilian and military ones. It also causes a lot of interferences so coexistence between networks becomes a demand, because there is a lot of different sources of various interferences. Our radio systems are the mainly a source of...
Cognitive radio (CR) is the key technology that provides to use frequency spectrum effectively. Spectrum sensing, a critical function of CR, detects spectrum holes. Energy based detection (ED) is the most preferred spectrum sensing technique by researchers because it only requires the energy of received signals. The sensing performance of the ED is mainly based on the wireless communication channel...
Priority queue-based techniques improve spectrum efficiency by allocating the underutilized spectral bands (holes) of primary users to secondary users in Cognitive Radio Networks (CRN). This article proposes a Distributed Precedence Queuing scheme for Efficient Spectrum Management (DPQESM) in CRNs. The proposed method classifies the available channels into periodic and aperiodic based on the state...
In a cognitive radio network (CRN), a premise for two nodes to communicate is having a rendezvous which means that they switch to the same channel simultaneously. Most existing channel hopping solutions for the rendezvous problem is for a homogeneous CRN where nodes have the same type of cognitive radio and thus can sense the same spectrum. In reality, nodes have different types of cognitive radios...
Human and animal societies exhibit complex cognitive and social processes of coordination, cooperation, and competition among their members. Among other functions, these processes can facilitate fairer sharing of resources among community members and enhance individual survival outcomes. In this work, three bio-socially inspired models for secondary users of spectrum in cognitive radio networks are...
Cognitive radio has been regarded as a technology that guarantees a significant increase in spectrum utilization efficiency. Depending on this technology; spectrum management, spectrum sensing and spectrum handoff have emerged. In cognitive radio networks, how the frequency channels are to be assigned between users is at the top of the newsworthy topics. In addition, it is also the current topic to...
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