Proactive Spectrum Handoff Research Articles

An Improved Proactive Handoff Scheme (IPHS) for Target Channel Selection in Cognitive Radio Network

In recent years, one of the challenges of spectrum allocation and utilization was fixed spectrum allocation which lead to spectrum scarcity and underutilization. In an attempt to address this challenge, Cognitive Radio Network (CRN) which uses Dynamic Spectrum Access (DSA) was proposed. It allows licensed users’ or Primary Users’ (PUs) spectrum to be shared with unlicensed users or Secondary Users (SUs). DSA could be achieved by developing an effective channel selection scheme for SUs spectrum handoff. Selecting an appropriate channel for the SUs to continue their interrupted transmission is a challenging task. Several researchers have used different techniques such as Novel Proactive Handoff Scheme (NPHS) to enhance accurate channel selection for spectrum handoff by considering only channel occupancy. These techniques still suffer some set back like high number of spectrum handoff and delay in channel selection. This paper presents an Improved Proactive Spectrum Handoff Scheme (IPHS) for accurate target channel selection in CRN. The improvement is achieved by considering channel signal quality in addition to channel occupancy as a criteria for the selection of a backup channel for spectrum handoff. Simulation results showed that the IPHS reduced the number of spectrum handoff by 15% and 26% as compared to NPHS and IEEE 802.11 scheme respectively. The average delay was also reduced by 13% and 35% as compared to NPHS and IEEE 802.11 scheme respectively.

Intelligent Process of Spectrum Handoff in Cognitive Radio Network

Spectrum handoff is a crucial function of Cognitive Radio (CR) which is the change of operating frequency. The main problem in spectrum handoff is the time taken in the searching, selection, and switching to a new available channel which can cause a significant amount of delay during spectrum handoff. This research aims to minimize the delay that occurs during spectrum handoff. A Proactive Fuzzy-Based Backup Channel Selection Scheme (PFBBCSS) was proposed where the Secondary User (SU) gathers backup channels in advance before the return of the Primary User (PU), then fuzzy logic would be used for the selection of the best channel out of the available backup channels. The proposed scheme was simulated and evaluated using the MATLAB Simulation tool and the result was compared with a Pure Proactive Spectrum Handoff Scheme. Results showed, in terms of throughput and efficient time utilization under a varying number of licensed channels, that the proposed scheme performed better, making it a good mechanism to be used for handoff decisions by the Secondary User (SU).

Spectrum handoff analysis for multiple secondary users in cognitive radio networks

<p>The cognitive radio network permits secondary users to reach unused spectrum of primary users. In this paper, a mixed preemptive/non-preemptive resume priority M/G/1 queuing model is proposed for characterizing multiple handoff delay and to minimize the extended data delivery time of secondary users that has experienced multiple spectrum handoff during its transmission. The proposed queuing model supports delay-sensitive secondary user applications. The secondary users’ traffic is classified into two priority classes, the highest priority class for delay sensitive services and the lowest priority class for delay insensitive services. Furthermore, the proposed model assigns higher priority for the interrupted secondary users over uninterrupted secondary users for each class of secondary users in order to minimize the handoff delays for secondary users that experience multiple interruptions. Analytical formulas for the average extended data delivery time are derived for two different proactive spectrum handoff strategies (always stay and always change strategies) for both classes of secondary users. Simulation of proposed system model was performed to validate the analytical results and a good agreement was obtained. The performance of the suggested model is assessed and compared with other spectrum handoff models. Numerical results illustrate that the proposed system model outperforms existing models and can reduce the extended data delivery time for the secondary users.</p>

Analysis of Spectrum Handoff delay using Finite Queuing model in Cognitive Radio Networks

Spectrum handoff is an inevitable phenomenon to exploit dynamic spectrum access in cognitive radio networks (CRNs) for better spectrum utilisation. When a licensed or primary user reclaims its operating channel, the cognitive user has to initiate a suitable handoff procedure for successful completion of its ongoing transmission. This paper analyses the prioritised proactive spectrum handoff decision for a finite capacity cognitive radio network using preemptive resume priority (PRP) M/G/1/K queuing model. Cumulative handoff delay (CHD) and total service time (TST) are taken to investigate the performance of the handoff strategies. We establish an analytical model of cumulative handoff delay and total service time of proactive switching spectrum handoff for the proposed finite length queuing network. The impact of queue length on performance measuring metrics such as CHD and TST in terms of arrival rate of primary users and mobility factor of spectrum holes are presented extensively.

A novel proactive handoff scheme with CR receiver based target channel selection for cognitive radio network

Spectrum handoff in cognitive radio networks (CRN) enables the cognitive radio (CR) users to guarantee the desired QoS of the primary users. The handoff schemes grant an efficient exploitation of the available spectrum holes in the network. In the presented work, a novel proactive spectrum handoff scheme is made for ad hoc network scenario. Here, a network coordination schemes for unlicensed users is incorporated first. In our proposed framework, unlicensed users coordinate with each other using a Common Control Channel (CCC). Primary user free channel lists (PCL’s) are shared among CR users before actual data transmission to achieve better CR node coordination as well as to share information of nearby scenario. The PCL history stored at each CR transmitter (CRTx) node is used to make channel switching policies and to let unlicensed users vacate a channel before a licensed user utilizes it to avoid unwanted interference. Moreover, the node channel matrix created for the scenario helps to improve the performance further. The improvement is achieved through taking PCL history of CRRx into count. So, a novel proactive approach is developed here which uses the PCL history of both CRTx and CRRx. Simulation results show that proposed novel proactive spectrum handoff outperforms the reactive spectrum handoff approach in terms of higher throughput and fewer collisions to licensed users. Furthermore, a distributed channel selection can achieve higher packet delivery rate compared with existing channel selection schemes.

Analysis of handoff delay for proactive spectrum handoff scheme with PRP M/G/1/K queuing system in cognitive radio networks

Spectrum handoff has a negative impact on the performance of cognitive users (CUs) in terms of handoff delay in cognitive radio (CR) networks. In this study, a pre-emptive resume priority (PRP) M/G/1/K queuing network model is proposed with a finite number of allowable interruptions for proactive decision spectrum handoff scheme in order to minimise the cumulative handoff delay (CHD) and total service time (TST) for CUs. The CHD and TST for different proactive decision handoff schemes: non-switching spectrum handoff, switching spectrum handoff, and random spectrum handoff are modeled under the proposed PRP M/G/1/K queuing network model. Comprehensive results of CHD and TST are obtained to compare the performances of the proactive decision handoff schemes under the proposed PRP M/G/1/K queuing network model. This study also presents an analytical framework to examine the effect of primary users activity and buffer size on spectrum handoff delay performance with a finite number of allowable interruptions in a CR network. Thereafter, the optimal buffer size (K) is estimated for the proposed PRP M/G/1/K queuing network model, which gives performance similar to the infinite buffer size PRP M/G/1 queuing model with negligible (<1%) error.

A distributed spectrum handoff MSRV protocol for the cognitive radio ad hoc networks

Cognitive radio technology provides opportunistic wireless spectrums access for the secondary users (SUs) while primary users (PUs) are dormant. By emergence of a PU in the cognitive radio networks, SUs are required to vacant the channel by using spectrum handoff approaches to avoid any collision. Providing an efficient and flexible coordination protocol for spectrum handoff is a challenging step. In this paper, we propose a novel proactive spectrum handoff protocol called multiple-single rendezvous (MSRV) protocol which uses multiple rendezvous (MRV) and single rendezvous (SRV) coordination policy to provide a higher throughput and context adaptability. MRV coordination policy has the advantage of negotiating in different channels simultaneously and avoid single control channel congestion. On the other hand, in order to share the PUs’ channel usage history information between the SUs for predicting channels’ availability, it is necessary to utilize a SRV coordination scheme. The proposed MSRV protocol improves the average throughput of the SUs and decreases the average service time comparing to the other existing proactive spectrum handoff protocols. Moreover, MSRV protocol gives priority to the handoff SUs which decreases service times. It is an crucial property for the delay sensitive applications. Our proposed protocol achieves 20% throughput and 13.7% average service time improvement in 1.25 and 10 (pkts/s) PUs’ traffic load compared to the SRV proactive spectrum handoff protocol proposed by Mehrnoush et al., respectively.

A proactive spectrum handoff scheme with efficient spectrum utilisation for cognitive radio ad hoc networks

This paper proposes a proactive spectrum handoff scheme for cognitive radio (CR) ad hoc networks by exploiting the efficient utilisation of the available wireless spectrum by CR. The novelty of this spectrum handoff scheme is that it is able to use the available free channels which are idle for one complete CR packet transmission as well as idle for less than one packet transmission. This has been done by channel scheduling and packet fragmentation to reduce unusable channels. In this scheme, spectrum sensing is done during packet transmission. The main contribution of the proposed spectrum handoff scheme is that it outperforms the existing proactive and reactive spectrum handoff schemes in terms of reduced CR average service time, improved throughput, and improved spectrum utilisation under the different primary user (PU) arrival rates. It is also analysed that the proposed spectrum handoff scheme is best suited scheme in heavy PU traffic arrival rates.

A proactive spectrum handoff scheme with efficient spectrum utilisation for cognitive radio ad hoc networks

This paper proposes a proactive spectrum handoff scheme for cognitive radio (CR) ad hoc networks by exploiting the efficient utilisation of the available wireless spectrum by CR. The novelty of this spectrum handoff scheme is that it is able to use the available free channels which are idle for one complete CR packet transmission as well as idle for less than one packet transmission. This has been done by channel scheduling and packet fragmentation to reduce unusable channels. In this scheme, spectrum sensing is done during packet transmission. The main contribution of the proposed spectrum handoff scheme is that it outperforms the existing proactive and reactive spectrum handoff schemes in terms of reduced CR average service time, improved throughput, and improved spectrum utilisation under the different primary user (PU) arrival rates. It is also analysed that the proposed spectrum handoff scheme is best suited scheme in heavy PU traffic arrival rates.

Delay-Constrained Optimal Transmission With Proactive Spectrum Handoff in Cognitive Radio Networks

In this paper, we investigate the transmission strategy for cognitive radios (CRs), which opportunistically operate on various primary users’ channels with the aid of proactive spectrum handoff. In particular, a secondary user (SU) in the CR network proactively predicts the future spectrum status and decides whether to keep idle, or stay in the current channel, or switch to a new channel to resume its transmission. A problem of completing a target data packet size of $\mathcal {V}$ bits within a predefined deadline $D$ time slots is formulated as a discrete-time Markov decision process, in which the SU aims at minimizing its expected total cost, i.e., transmission cost, handoff cost, and overtime penalty. We solve the problem using dynamic programming, and propose a general optimal transmission with the proactive spectrum handoff (OTPH) algorithm whose complexity is $2\times |\mathcal {V}|\times D$ . Furthermore, we prove that for a convex penalty function, the optimal handoff-aided transmission exhibits a threshold structure. A monotone OTPH algorithm with a complexity of ${\max }(|\mathcal {V}|,D)$ is used in this case. Simulation results verify that our proposed scheme achieves both the minimal total cost and the highest data transmission efficiency as compared with the traditional always staying and always changing schemes.

Traffic‐Adaptive Proactive Spectrum Handoff Strategy for Graded Secondary Users in Cognitive Radio Networks

In order to meet different delay requirements of various communication services in Cognitive radio (CR) networks, Secondary users (SUs) are divided into two classes according to the priority of accessing to spectrum in this paper. Based on the proactive spectrum handoff scheme, the Preemptive resume priority (PRP) M/G/1 queueing is used to characterize multiple spectrum handoffs under two different spectrum handoff strategies. The traffic-adaptive spectrum handoff strategy is proposed for graded SUs so as to minimize the average cumulative handoff delay. Simulation results not only verify that our theoretical analysis is valid, but also show that the strategy we proposed can reduce the average cumulative handoff delay evidently. The effect of service rate on the proposed spectrum switching point and the admissible access region are provided.

Proactive spectrum handoff protocol for cognitive radio ad hoc network and analytical evaluation

Spectrum handoff in cognitive radio technology has been emerged as a new method for improving performance of the cognitive radio networks. The authors propose a proactive spectrum handoff protocol based on a single rendezvous (SRV) coordination scheme without common control channel. This protocol utilises a multi-user greedy channel selection method to select the best channel based on minimum service time for the secondary users to achieve a higher aggregate throughput. The authors proposed a novel theoretical analysis to evaluate the aggregate throughput of the secondary users in the proposed protocol. It uses Markov Chain to model the distributed channel selection scheme. The simulation results show the proposed protocol increases the throughput up to 38.7% in comparison with the study by Song and Xie, for 12 secondary users in the network with transmission rates of primary and secondary users equal to 5 (pkt/s) and 500 (pkt/s), respectively.

Learning System for Proactive Pre-emptive Unified Spectrum Handoff (PRO-PUSH) in Cognitive Radio Mobile Ad Hoc Networks

The aim of this study is to introduce a conceptual framework for the new approach Intelligent Proactive Pre-emptive Unified Spectrum Handoff (IP PRO-PUSH) algorithm is presented, which is a highly potential intelligent technology to intelligently address the spectrum scarcity challenges in Cognitive Radio Mobile Ad hoc Networks (CR-MANETs). The fact that spectrum is a limited natural resource poses technology challenge to ensure the available frequency is used efficiently and able to cope with new services which definitely requires more bandwidth in the future. However, over the past years, traditional approaches to spectrum management have been challenged by new insights into actual use of spectrum. In order to improve the utilization of the overall radio spectrum, the Cognitive Radio (CR) is a useful solution to this low utilization of the radio spectrum. The variation in spectrum band is called spectrum mobility. The objective of the current study is to investigate the Intelligent-Based (IB) cognitive radio learning for IP Pro-PUSH and local routing based on spectrum mobility in mobile Cognitive Radio Ad hoc Networks (CR-MANET) along with a conceptual framework and its connections.

Analytical modeling for spectrum handoff decision in cognitive radio networks

Cognitive Radio (CR) is an emerging technology used to significantly improve the efficiency of spectrum utilization. Although some spectrum bands in the primary user’s licensed spectrum are intensively used, most of the spectrum bands remain underutilized. The introduction of open spectrum and dynamic spectrum access lets the secondary (unlicensed) users, supported by cognitive radios; opportunistically utilize the unused spectrum bands. However, if a primary user returns to a band occupied by a secondary user, the occupied spectrum band is vacated immediately by handing off the secondary user’s call to another idle spectrum band. Multiple spectrum handoffs can severely degrade quality of service (QoS) for the interrupted users. To avoid multiple handoffs, when a licensed primary user appears at the engaged licensed band utilized by a secondary user, an effective spectrum handoff procedure should be initiated to maintain a required level of QoS for secondary users. In other words, it enables the channel clearing while searching for target vacant channel(s) for completing unfinished transmission. This paper proposes prioritized proactive spectrum handoff decision schemes to reduce the handoff delay and the total service time. The proposed schemes have been modeled using a preemptive resume priority (PRP) M/G/1 queue to give a high priority to interrupted users to resume their transmission ahead of any other uninterrupted secondary user. The performance of proposed handoff schemes has been evaluated and compared against the existing spectrum handoff schemes. Experimental results show that the schemes developed here outperform the existing schemes in terms of average handoff delay and total service time under various traffic arrival rates as well as service rates.

ProSpect: A Proactive Spectrum Handoff Framework for Cognitive Radio Ad Hoc Networks without Common Control Channel

Cognitive Radio (CR) technology is a promising solution to enhance the spectrum utilization by enabling unlicensed users to exploit the spectrum in an opportunistic manner. Since unlicensed users are temporary visitors to the licensed spectrum, they are required to vacate the spectrum when a licensed user reclaims it. Due to the randomness of the appearance of licensed users, disruptions to both licensed and unlicensed communications are often difficult to prevent, which may lead to low throughput of both licensed and unlicensed communications. In this paper, a proactive spectrum handoff framework for CR ad hoc networks, ProSpect, is proposed to address these concerns. In the proposed framework, Channel-Switching (CW) policies and a proactive spectrum handoff protocol are proposed to let unlicensed users vacate a channel before a licensed user utilizes it to avoid unwanted interference. Network coordination schemes for unlicensed users are also incorporated into the spectrum handoff protocol design. Moreover, a distributed channel selection scheme to eliminate collisions among unlicensed users in a multiuser spectrum handoff scenario is proposed. In our proposed framework, unlicensed users coordinate with each other without using a Common Control Channel (CCC), which is highly adaptable in a spectrum-varying environment. We compare our proposed proactive spectrum handoff protocol with a reactive spectrum handoff protocol, under which unlicensed users switch channels after collisions with licensed transmissions occur. Simulation results show that our proactive spectrum handoff outperforms the reactive spectrum handoff approach in terms of higher throughput and fewer collisions to licensed users. Furthermore, our distributed channel selection can achieve higher packet delivery rate in a multiuser spectrum handoff scenario, compared with existing channel selection schemes.