Spectrum Handoff Process Research Articles

Spectral Efficiency Enhancement using Hybrid Pre-Coder Based Spectrum Handover Mechanism

The use of Millimeter-wave (mm-Wave) has recently immensely enhanced in various communication applications due to massive technological developments in wireless communications. Furthermore, mm-Wave consists of a high bandwidth spectrum that can handle large demands of data transmission and internet services. However, high interference is observed in previous research at the time of spectrum handover from secondary (unlicensed) users to primary (licensed) users. Thus, interference reduction by achieving high spectral efficiency and an easy spectrum handoff process with minimum delay is an important research area. Therefore, a Hybrid Pre-coder Design based Spectrum Handoff (HPDSH) Algorithm is proposed in this article to increase spectrum efficiency in Cognitive Radio Networks(CRNs) and to access the large bandwidth spectrum of mm-Wave systems to meet the high data rate demands of current cellular networks. Moreover, a HPDSH Algorithm is presented to enhance spectral efficiency and this algorithm is utilized to take handover decisions and select backup channels. Here, different scenarios and parameters are considered to evaluate the performance efficiency of the proposed HPDSH Algorithm in terms of spectral efficiency and Signal to Noise (SNR) ratio. The proposed HPDSH Algorithm is compared against precoding methods like the OMP algorithm and SIC based methods.

Analyzing Cognitive Radio Network Operation With the Mechanism of Deciding Handoff and Process of Handoff Employing Varied Distribution Models (5G)

Cognitive radio networks (CRNs) deal with sensing, decision making, sharing, and mobility. Among these aspects, spectrum mobility assumes a vital role for spectrum handoff to occur. When the spectrum handoff process is analyzed, there are call drops, spectrum handoff, and interferences with the adjacent channels. For minimizing the handoff of the spectrum's probability as well as the call drops, which involves three processes, which are followed in sequential order, results demonstrate a better QoS. In the following three processes, the first process starts with the Markov model that identifies a channel's states and selects the channel which is apt. The second process, multiple attributes decision making (MADM), methods choose one of the best possible channels among all the channels based on various metrics in the proposed hybrid method. In the third process, the spectrum handoff is analyzed through different distribution models to indicate which model is the desirable one for a handoff process such as the one with stationary users or the other with non-stationary users.

Optimization of Ant Colony for Next Generation Wireless Cognitive Networks

In this work, the spectrum handoff process carried out by secondary users according to priority classes in cognitive radio networks is proposed. The network structure design of analytical and simulation models is simulated with the RIVERBED software. Moreover, deciding on the most suitable spectrum handoff process is determined by using artificial intelligence techniques. Using multi-parameter decision-making processes is the objective of our work. Optimization of the spectrum handoff number with the help of an ant colony algorithm is the main goal of our work. By studying similar aspects of cognitive radio networks and ant colony algorithms, the number of handoffs is reduced within the most appropriate scenario.

Handoff Security Using Artificial Neural Networks in Cognitive Radio Networks

The dynamic and highly open nature of cognitive radio (CR) makes cognitive communication extremely vulnerable to various malicious activities resulting from several security threats. Although extensive efforts have been devoted to the research and development of spectrum sharing systems, security issues are not well addressed for the cognitive radio network (CRN). The sensing and dynamic access mechanism invites a number of security threats at the physical layer in the CRN. In particular, during the handoff of cognitive users (CUs), a malicious user (MU) may perform new types of attacks specific to handoff CU (HCU). In this article, we present a new type of security threat, called a cognitive user emulation attack (CUEA), which occurs during the spectrum handoff in a CRN. In CUEA, an attacker aims to block the legitimate users (i.e., HCUs) from accessing the new and unused channels by mimicking them. The problem comes from the fact that during the delay in the spectrum handoff process, when users vacate to occupy an unused channel, the MU can behave as a legitimate HCU to block the user from occupying the unused channel. Consequently, the MU can affect the data transmission process and degrade the network performance. To address this problem, we first present a detailed investigation of the security threats specific to CUs that occur during their mobility. Also, we discuss the problems for different communication networks (i.e., centralized and decentralized), where CUEA takes place with different attacking strategies. Further, we examine the challenges of CUEA in different networks by classifying them into a range of open issues. Moreover, we illustrate the need for artificial intelligence techniques for making efficient autonomous decisions to improve the network performance in terms of throughput, energy consumption, and delivery delay. We also discuss the prospective challenges of the primary user emulation attack and future research directions.

Artificial bee colony–based spectrum handoff algorithm in wireless cognitive radio networks

SummaryIn this work, we proposed a new artificial bee colony–based spectrum handoff algorithm for wireless cognitive radio systems. In our wireless cognitive radio system, primary users, secondary users, and related base stations exist in the same communication environment. For our artificial bee colony–based algorithm, secondary users that always struggle to discover an idle channel have a leading role. While honey bees work hard to find the best‐quality nectar source for foraging, secondary users try to find idle channels for making communication. In this way, secondary users are organized for different missions such as sensing and handoff similar to honey bees to minimize spectrum handoff delay by working together. In the spectrum handoff stage, some secondary users must sense the spectrum so that the interrupted secondary user may perform the spectrum handoff process. In our developed spectrum handoff algorithm, the spectrum availability characteristic is observed on the basis of the missions of the bees in the artificial bee colony algorithm with the aim of minimizing the spectrum handoff delay and maximizing probability of finding an idle channel. With the help of the algorithm that is developed using the artificial bee colony, spectrum handoff delay of secondary users is considerably decreased for different number of users without reducing probability of finding an available channel.

Energy-efficient target channel sequence design for spectrum handoffs in Cognitive radio networks

Cognitive radio is considered as an efficient way to improve the spectrum efficiency. As one of its key technologies, spectrum handoff can guarantee the transmission continuity of secondary users (SUs). In this paper, we address a new and more generalized spectrum handoff problem in cognitive radio networks (CRNs), by considering simultaneously energy efficiency, multiple spectrum handoffs and multiple channels. Furthermore, effects of the primary users' (PUs') arrival and service rate on the target channel sequence selection are also considered. In order to obtain the energy-efficient target channel sequence, we firstly analyze the energy consumption and the number of delivered bits per hertz in the spectrum handoff process, and formulate a ratio-type energy efficiency optimization problem, which can be transformed into a parametric problem by utilizing fractional programming. Then, we propose an algorithm combining dynamic programming with bisection (DPB) algorithm to solve the energy efficiency optimization problem. Our simulation results verify that the designed target channel sequence has better performance than the existing algorithms in terms of energy efficiency.

Improving spectrum handoff utilization for prioritized cognitive radio users by exploiting channel bonding with starvation mitigation

In this study, priority based non-preemptive M/G/1 queueing model of spectrum handoff scheme is proposed in Wireless Cognitive Radio Networks. Channel bonding mechanism with starvation mitigation is employed in order to improve spectrum handoff utilization for secondary users. Since spectrum handoff offers an opportunity to secondary users for continuing their communication, it is of critical significance to determine action of primary users. In the queueing model, prioritized data traffic with aging solution to starvation is exploited to meet requirements of the secondary users. In aging mechanism; when the packet of the low priority secondary user waits in the queue more than three frame times, priority of that packet is increased. Packets of secondary users are categorized into three different priority classes, i.e., urgent, real time, and non-real time where non-real time data packets have the lowest priority while urgent data packets have the highest priority. Channel bonding mechanism is described as combining two subsequent time slots if the size of the packet is bigger than one time slot. Idle time slots for channel bonding are determined using both proactive and reactive decision based spectrum handoff schemes. Before starting spectrum handoff process with proactive scheme, first of two subsequent time slot is sensed using reactive scheme. Riverbed Modeler simulation software is utilized to simulate channel bonding and aging mechanisms. Analytical results are shown to be matched with the simulation results obtained under different load and arrival rates. This study has also exposed that the throughput of secondary users could be increased significantly by employing aging solution to starvation, and channel bonding mechanisms.

Spectrum Handoff Method Based on Extenics for Cognitive Radio Sensor Networks

A spectrum handoff model and optimal channel decision method based on Extenics have been proposed in order to resolve the optimal channel decision problem of spectrum handoff in Cognitive Radio Sensor Networks. The method of matter-element Extenics is used to analyses the spectrum handoff process. The channel state through the spectrum sensing and status information of the primary users is analyzed and transformed by matter-element Extenics. Then the parameters to determine the best channel are calculated on the basis of Extenics correlation function. Finally the optimal channel is selected. The simulation results show that the proposed method can improve spectrum utilization efficiency of Cognitive Radio Sensor Networks and can reduce the interrupt probability of second users.

Evolution handoff strategy for real-time video transmission over practical cognitive radio networks

The transmission delay of real-time video packet mainly depends on the sensing time delay (short-term factor) and the entire frame transmission delay (long-term factor). Therefore, the optimization problem in the spectrum handoff process should be formulated as the combination of microscopic optimization and macroscopic optimization. In this paper, we focus on the issue of combining these two optimization models, and propose a novel Evolution Spectrum Handoff (ESH) strategy to minimize the expected transmission delay of real-time video packet. In the micro-optimized model, considering the tradeoff between Primary User's (PU's) allowable collision percentage of each channel and transmission delay of video packet, we propose a mixed integer non-linear programming scheme. The scheme is able to achieve the minimum sensing time which is termed as an optimal stopping time. In the macro-optimized model, using the optimal stopping time as reward function within the partially observable Markov decision process framework, the EHS strategy is designed to search an optimal target channel set and minimize the expected delay of packet in the long-term real-time video transmission. Meanwhile, the minimum expected transmission delay is obtained under practical cognitive radio networks' conditions, i.e., secondary user's mobility, PU's random access, imperfect sensing information, etc‥ Theoretical analysis and simulation results show that the ESH strategy can effectively reduce the transmission delay of video packet in spectrum handoff process.

Stochastic spectrum handoff protocols for partially observable cognitive radio networks

Recent studies have been conducted to indicate the ineffective usage of licensed bands due to static spectrum allocation. In order to improve spectrum utilization, cognitive radio (CR) is therefore suggested to dynamically exploit the opportunistic primary frequency spectrums. How to provide efficient spectrum handoff has been considered a crucial issue in the CR networks. Existing spectrum handoff algorithms assume that all the channels can be correctly sensed by the CR users in order to perform appropriate spectrum handoff process. However, this assumption is impractical since excessive time will be required for the CR user to sense the entire spectrum space. In this paper, the partially observable Markov decision process (POMDP) is applied to estimate the network information by partially sensing the frequency spectrums. A POMDP-based spectrum handoff (POSH) scheme is proposed to determine the optimal target channel for spectrum handoff according to the partially observable channel state information. Moreover, a POMDP-based multi-user spectrum handoff (M-POSH) protocol is proposed to exploit the POMDP policy into multi-user CR networks by distributing CR users to frequency spectrum bins opportunistically. By adopting the policies resulted from the POSH and M-POSH algorithms for target channel selection, minimal waiting time at each occurrence of spectrum handoff can be achieved which will be feasible for multimedia applications. Numerical results illustrate that the proposed spectrum handoff protocols can effectively minimize the required waiting time for spectrum handoff in the CR networks.