Performance Analysis of Opportunistic Spectrum Access Protocol for Multi-Channel Cognitive Radio Networks

김경재,곽경섭,최봉대 한국통신학회 2013 Journal of communications and networks Vol.15 No.1

Cognitive radio (CR) has emerged as one of effective methods to enhance the utilization of existing radio spectrum. Main principle of CR is that secondary users (SUs) are allowed to use the spectrum unused by primary users (PUs) without interfering PU’s transmissions. In this paper, PUs operate on a slot-by-slot basis and SUs try to exploit the slots unused by PUs. We propose OSA protocols in the single channel and we propose an opportunistic spectrum access (OSA) protocols in the multi-channel cognitive radio networks with one control channel and several licensed channels where a slot is divided into contention phase and transmission phase. A slot is divided into reporting phase, contention phase and transmission phase. The reporting phase plays a role of finding idle channels unused by PUs and the contention phase plays a role of selecting a SU who will send packets in the data transmission phase. One SU is selected by carrier sense multiple access / collision avoidance (CSMA/CA) with request to send / clear to send (RTS/CTS) mechanism on control channel and the SU is allowed to occupy all remaining part of all idle channels during the current slot. For mathematical analysis, first we deal with the singlechannel case and we model the proposed OSA media access control (MAC) protocol by three-dimensional discrete time Markov chain (DTMC) whose one-step transition probabilitymatrix has a special structure so as to apply the censored Markov chain method to obtain the steady state distribution.We obtain the throughput and the distribution of access delay. Next we deal with the multi-channel case and obtain the throughput and the distribution of access delay by using results of single-channel case. In numerical results,our mathematical analysis is verified by simulations and we give numerical results on throughput and access delay of the proposed MAC protocol. Finally, we find the maximum allowable number of SUs satisfying the requirements on throughput and access delay.

Performance Analysis of Opportunistic Spectrum Access Protocol for Multi-Channel Cognitive Radio Networks

Kim, Kyung Jae,Kwak, Kyung Sup,Choi, Bong Dae The Korea Institute of Information and Commucation 2013 Journal of communications and networks Vol.15 No.1

Cognitive radio (CR) has emerged as one of effective methods to enhance the utilization of existing radio spectrum. Main principle of CR is that secondary users (SUs) are allowed to use the spectrum unused by primary users (PUs) without interfering PU's transmissions. In this paper, PUs operate on a slot-by-slot basis and SUs try to exploit the slots unused by PUs. We propose OSA protocols in the single channel and we propose an opportunistic spectrum access (OSA) protocols in the multi-channel cognitive radio networks with one control channel and several licensed channels where a slot is divided into contention phase and transmission phase. A slot is divided into reporting phase, contention phase and transmission phase. The reporting phase plays a role of finding idle channels unused by PUs and the contention phase plays a role of selecting a SU who will send packets in the data transmission phase. One SU is selected by carrier sense multiple access / collision avoidance (CSMA/CA) with request to send / clear to send (RTS/CTS) mechanism on control channel and the SU is allowed to occupy all remaining part of all idle channels during the current slot. For mathematical analysis, first we deal with the single-channel case and we model the proposed OSA media access control (MAC) protocol by three-dimensional discrete time Markov chain (DTMC) whose one-step transition probability matrix has a special structure so as to apply the censored Markov chain method to obtain the steady state distribution.We obtain the throughput and the distribution of access delay. Next we deal with the multi-channel case and obtain the throughput and the distribution of access delay by using results of single-channel case. In numerical results, our mathematical analysis is verified by simulations and we give numerical results on throughput and access delay of the proposed MAC protocol. Finally, we find the maximum allowable number of SUs satisfying the requirements on throughput and access delay.

클러스터 OFDM에 기초한 기회적 다중채널 알로하 인지무선의 스펙트럼 이용

최상호 한국정보과학회 2012 정보과학회논문지 : 정보통신 Vol.39 No.4

센서 네트워크와 같은 저비용 저부하 애드 혹 무선 시스템에 응용을 타깃으로 한 클러스터 OFDM에 기초한 기회적 다중채널 알로하 인지무선(COCR) 방안을 제안한다. 기회적 채널 선택 기반의 COCR을 설계하며, 완전 스펙트럼 센싱 혹은 불완전 스펙트럼 센싱하에 스펙트럼 이용률을 이론적 및 수치적인 접근을 통해 분석한다. 시뮬레이션을 통해 제안방식의 스펙트럼 이용률 P가 기존의 랜덤 채널 선택 기반의 OMC-CSMA CR 방식에 비해 특별히 낮은 제공 부하(G ≤1.3)에서 탁월함을 보여준다. COCR의 최대 스펙트럼 이용률 Pmax (= 0.8)는 기존 OMC-CSMA CR 방식의 약 90%이고 기존 OMC-ALOHA CR 방식의 약 230%이다. We present a clustered-OFDM-based opportunistic-multichannel-ALOHA cognitive radio (COCR) for low-cost low-load ad-hoc-based wireless systems like sensor networks. We implement COCR on the basis of opportunistic channel selection and analyze its spectrum efficiency, analytically as well as numerically, under the perfect or imperfect spectrum sensing. Via simulation, we show that the proposed scheme is superior to conventional opportunistic-multichannel-CSMA CR (OMC-CSMA CR) with random channel selection in terms of spectrum utilization ratio P, especially at a small offered-load (G≤1.3). The maximum spectrum utilization ratioPmax (= max{P}) of COCR is 0.8, about 90% of that of conventional OMC-CSMA CR and about 230% of that of conventional opportunistic-multichannel-ALOHA CR (OMC-ALOHA CR).

Channel Statistical MAC Protocol for Cognitive Radio

Xiang, Gao,Zhu, Wenmin,Park, Hyung-Kun The Korea Institute of Information and Commucation 2010 Journal of information and communication convergen Vol.8 No.1

opportunistic spectrum access (OSA) allows unlicensed users to share licensed spectrum in space and time with no or little interference to primary users, with bring new research challenges in MAC design. We propose a cognitive MAC protocol using statistical channel information and selecting appropriate idle channel for transmission. The protocol based on the CSMA/CA, exploits statistics of spectrum usage for decision making on channel access. Idle channel availability, spectrum hole sufficiency and available channel condition will be included in algorithm statistical information. The model include the control channel and data channel, the transmitter negotiates with receiver on transmission parameters through control channel, statistical decision results (successful rate of transmission) from exchanged transmission parameters of control channel should pass the threshold and decide the data transmission with spectrum hole on data channel. A dynamical sensing range as a important parameter introduced to maintain the our protocol performance. The proposed protocol's simulation will show that proposed protocol does improve the throughput performance via traditional opportunistic spectrum access MAC protocol.

Channel Prediction-Based Channel Allocation Scheme for Multichannel Cognitive Radio Networks

Lee, Juhyeon,Park, Hyung-Kun The Korea Institute of Information and Commucation 2014 Journal of communications and networks Vol.16 No.2

Cognitive radio (CR) has been proposed to solve the spectrum utilization problem by dynamically exploiting the unused spectrum. In CR networks, a spectrum selection scheme is an important process to efficiently exploit the spectrum holes, and an efficient channel allocation scheme must be designed to minimize interference to the primary network as well as to achieve better spectrum utilization. In this paper, we propose a multichannel selection algorithm that uses spectrum hole prediction to limit the interference to the primary network and to exploit channel characteristics in order to enhance channel utilization. The proposed scheme considers both the interference length and the channel capacity to limit the interference to primary users and to enhance system performance. By using the proposed scheme, channel utilization is improved whereas the system limits the collision rate of the CR packets.

Opportunistic Spectrum Access Based on a Constrained Multi-Armed Bandit Formulation

Ai, Jing,Abouzeid, Alhussein A. The Korea Institute of Information and Commucation 2009 Journal of communications and networks Vol.11 No.2

Tracking and exploiting instantaneous spectrum opportunities are fundamental challenges in opportunistic spectrum access (OSA) in presence of the bursty traffic of primary users and the limited spectrum sensing capability of secondary users. In order to take advantage of the history of spectrum sensing and access decisions, a sequential decision framework is widely used to design optimal policies. However, many existing schemes, based on a partially observed Markov decision process (POMDP) framework, reveal that optimal policies are non-stationary in nature which renders them difficult to calculate and implement. Therefore, this work pursues stationary OSA policies, which are thereby efficient yet low-complexity, while still incorporating many practical factors, such as spectrum sensing errors and a priori unknown statistical spectrum knowledge. First, with an approximation on channel evolution, OSA is formulated in a multi-armed bandit (MAB) framework. As a result, the optimal policy is specified by the wellknown Gittins index rule, where the channel with the largest Gittins index is always selected. Then, closed-form formulas are derived for the Gittins indices with tunable approximation, and the design of a reinforcement learning algorithm is presented for calculating the Gittins indices, depending on whether the Markovian channel parameters are available a priori or not. Finally, the superiority of the scheme is presented via extensive experiments compared to other existing schemes in terms of the quality of policies and optimality.

Opportunistic Spectrum Access with Dynamic Users: Directional Graphical Game and Stochastic Learning

( Yuli Zhang ),( Yuhua Xu ),( Qihui Wu ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.12

This paper investigates the channel selection problem with dynamic users and the asymmetric interference relation in distributed opportunistic spectrum access systems. Since users transmitting data are based on their traffic demands, they dynamically compete for the channel occupation. Moreover, the heterogeneous interference range leads to asymmetric interference relation. The dynamic users and asymmetric interference relation bring about new challenges such as dynamic random systems and poor fairness. In this article, we will focus on maximizing the tradeoff between the achievable utility and access cost of each user, formulate the channel selection problem as a directional graphical game and prove it as an exact potential game presenting at least one pure Nash equilibrium point. We show that the best NE point maximizes both the personal and system utility, and employ the stochastic learning approach algorithm for achieving the best NE point. Simulation results show that the algorithm converges, presents near-optimal performance and good fairness, and the directional graphical model improves the systems throughput performance in different asymmetric level systems.

Opportunistic Spectrum Access Based on a Constrained Multi-Armed Bandit Formulation

Jing Ai,Alhussein A. Abouzeid 한국통신학회 2009 Journal of communications and networks Vol.11 No.2

Tracking and exploiting instantaneous spectrum opportunities are fundamental challenges in opportunistic spectrum access (OSA) in presence of the bursty traffic of primary users and the limited spectrum sensing capability of secondary users. In order to take advantage of the history of spectrum sensing and access decisions, a sequential decision framework is widely used to design optimal policies. However, many existing schemes, based on a partially observed Markov decision process (POMDP) framework, reveal that optimal policies are non-stationary in nature which renders them difficult to calculate and implement. Therefore, this work pursues stationary OSA policies, which are thereby efficient yet low-complexity, while still incorporating many practical factors, such as spectrum sensing errors and a priori unknown statistical spectrum knowledge. First, with an approximation on channel evolution, OSA is formulated in a multi-armed bandit (MAB) framework. As a result, the optimal policy is specified by the wellknown Gittins index rule, where the channel with the largest Gittins index is always selected. Then, closed-form formulas are derived for the Gittins indices with tunable approximation, and the design of a reinforcement learning algorithm is presented for calculating the Gittins indices, depending on whether the Markovian channel parameters are available a priori or not. Finally, the superiority of the scheme is presented via extensive experiments compared to other existing schemes in terms of the quality of policies and optimality.

Opportunistic Spectrum Access with Discrete Feedback in Unknown and Dynamic Environment:A Multi-agent Learning Approach

( Zhan Gao ),( Junhong Chen ),( Yuhua Xu ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.10

This article investigates the problem of opportunistic spectrum access in dynamic environment, in which the signal-to-noise ratio (SNR) is time-varying. Different from existing work on continuous feedback, we consider more practical scenarios in which the transmitter receives an Acknowledgment (ACK) if the received SNR is larger than the required threshold, and otherwise a Non-Acknowledgment (NACK). That is, the feedback is discrete. Several applications with different threshold values are also considered in this work. The channel selection problem is formulated as a non-cooperative game, and subsequently it is proved to be a potential game, which has at least one pure strategy Nash equilibrium. Following this, a multi-agent Q-learning algorithm is proposed to converge to Nash equilibria of the game. Furthermore, opportunistic spectrum access with multiple discrete feedbacks is also investigated. Finally, the simulation results verify that the proposed multi-agent Q-learning algorithm is applicable to both situations with binary feedback and multiple discrete feedbacks.

Joint Opportunistic Spectrum Access and Optimal Power Allocation Strategies for Full Duplex Single Secondary User MIMO Cognitive Radio Network

( Wenjing Yue ),( Yapeng Ren ),( Zhen Yang ),( Zhi Chen ),( Qingmin Meng ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.10

This paper introduces a full duplex single secondary user multiple-input multiple-output (FD-SSU-MIMO) cognitive radio network, where secondary user (SU) opportunistically accesses the authorized spectrum unoccupied by primary user (PU) and transmits data based on FD-MIMO mode. Then we study the network achievable average sum-rate maximization problem under sum transmit power budget constraint at SU communication nodes. In order to solve the trade-off problem between SU`s sensing time and data transmission time based on opportunistic spectrum access (OSA) and the power allocation problem based on FD-MIMO transmit mode, we propose a simple trisection algorithm to obtain the optimal sensing time and apply an alternating optimization (AO) algorithm to tackle the FD-MIMO based network achievable sum-rate maximization problem. Simulation results show that our proposed sensing time optimization and AO-based optimal power allocation strategies obtain a higher achievable average sum-rate than sequential convex approximations for matrix-variable programming (SCAMP)-based power allocation for the FD transmission mode, as well as equal power allocation for the half duplex (HD) transmission mode.