A Proactive Dynamic Spectrum Access Method against both Erroneous Spectrum Sensing and Asynchronous Inter-Channel Spectrum Sensing

( Junrong Gu ),( Sung Jeen Jang ),( Jae Moung Kim ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.1

Most of the current frequency hopping (FH) based dynamic spectrum access (DSA) methods concern a reactive channel access scheme with synchronous inter-channel spectrum sensing, i.e., FH is reactively triggered by the primary user (PU)`s return reported by spectrum sensing, and the PU channel to be switched to is assumed precisely just sensed or ready to be sensed, as if the inter-channel spectrum sensing moments are synchronous. However, the inter-channel spectrum sensing moments are more likely to be asynchronous, which risks PU suffering more interference. Moreover, the spectrum sensing is usually erroneous, which renders the problem more complex. To address this problem, we propose a proactive FH based DSA method against both erroneous spectrum sensing and asynchronous inter-channel spectrum sensing (moments). We term it as proactive DSA. The optimal FH sequence is obtained by dynamic programming. The complexity is also analyzed. Finally, the simulation results confirm the effectiveness of the proposed method.

Optimal Power Allocation in an 'Off' Spectrum Sensing Interval for Cognitive Radio

Junrong Gu,Wha Sook Jeon IEEE 2013 IEEE COMMUNICATIONS LETTERS Vol.17 No.10

<P>Most of the current works about cognitive radio favor a constant power allocation policy during an 'off' spectrum sensing interval, which is the time between two spectrum sensing activities when the outcome of the first spectrum sensing indicates 'off'. However, according to our work, this policy becomes suboptimal with respect to bit error rate minimization, when the traffics of primary user follow an alternating renewal process. Therefore, under this scenario, we suggest the optimal power allocation policy, by solving a convex optimization problem on power allocation of secondary user. Our results provide meaningful insight into the design of transmitting schemes for cognitive radio.</P>

Spectrum Sensing by Exploiting the Similarity of PDFs of Two Time-Adjacent Detected Data Sets with Cross Entropy

GU, Junrong,LIU, Wenlong,JANG, Sung Jeen,KIM, Jae Moung 'Institute of Electronics, Information and Communi 2011 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.eb94 No.12

Side Lobe Suppression Based on Optimized Phase Rotation Sequence

GU, Junrong,HWANG, Jae Ho,HAN, Ning,KIM, Jae Moung The Institute of Electronics, Information and Comm 2010 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.93 No.2

<P>This paper proposes an optimized phase rotation sequence method for side lobe suppression by complementing and regulating the side lobe suppression sequence set. The sequence set is efficiently enhanced through the quadratically constrained least square model. The theoretical suppression performance of our method is discussed. Furthermore, our scheme is also suitable for cognitive radio, which is analyzed in the simulation part. The simulation results confirm the effectiveness of our schemes.</P>

Proactive Frequency-Hopping Dynamic Spectrum Access Against Asynchronous Interchannel Spectrum Sensing

Junrong Gu,Wha Sook Jeon,Jae Moung Kim IEEE 2013 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.62 No.8

<P>In the frequency-hopping-based dynamic spectrum access (FH-DSA) methods, both reactive and proactive channel switching (CS) schemes are widely adopted. However, when they are coupled with asynchronous interchannel spectrum sensing (moments), there are at least two drawbacks in these CS schemes, i.e., producing more interference to a primary user (PU) and fewer throughputs to a secondary user (SU). Therefore, to overcome these two drawbacks, we propose a proactive FH-DSA method against asynchronous interchannel spectrum sensing with reduced interference to the PU, while enhancing the SU throughput by eliminating the spectrum sensing time overhead during CS. The optimal FH policy is obtained by formulating proactive FH-DSA in the dynamic programming framework. Furthermore, we derive the theoretical average interference and the bound of average delay under the proposed FH-DSA. Based on them, while considering the tradeoff between exploration and exploitation, and the practical requirements for interference and throughput, we propose one extension which proactively takes FH subject to an interference constraint to further reduce interference. The complexity of the proposed schemes is also analyzed. Finally, simulation results show the performance improvement of the proposed schemes.</P>

An Improved Entropy Based Sensing by Exploring Phase Information

Haowei Lee(이호위),Junrong Gu(구준롱),SungHwan Sohn(손성환),SungJeen Jang(장성진),JaeMoung Kim(김재명) 한국통신학회 2010 韓國通信學會論文誌 Vol.35 No.9a

In this paper, we present a new sensing method based on phase entropy. Entropy is a measurement which quantifies the information content contained in a signal. For the PSK modulation, the information is encoded in the phase of the transmitted signal. By focusing on phase, more information is collected during sensing, which suggests a superior performance. The sensing based on Phase entropy is not limited to PSK signal. We generalize it to PAM signal as well. It is more advantageous to detect the phase. The simulation results have confirmed the excellent performance of this novel sensing algorithm.

Asynchronous Cooperative Spectrum Sensing Scheme on Primary Users with Fast “On/Off” State Variations in Spectrum Sensing Windows

Jingying Jin(김정영),Junrong Gu(구준룡),Jae Moung Kim(김재명) 한국통신학회 2013 韓國通信學會論文誌 Vol.25 No.8

Cognitive Radio has attracted intensive interests of the researchers, recently. The data rate always increases in the emerging technologies. The increased data rate poses mainly two challenges for spectrum sensing. One is that the state of primary user (PU) is fast and alternatively varying between “on/off” in a spectrum sensing window. The other is that the asynchronicity among the reports in a cooperative spectrum sensing setting becomes more apparent. Both of them would deteriorate the spectrum sensing performance. Thus, we propose an asynchronous cooperative spectrum sensing method to cope with these two challenges. A likelihood ratio test based spectrum sensing is developed for a single cooperator. The likelihood ratio is obtained in the setting of fast varying PU state. The likelihood ratio test is uniformly powerful according to the Neyman-pearson lemma. Furthermore, the asynchronicity among the cooperators are studied. Two sets of fusion weights are discussed for the asynchronous time among cooperators. One is designed based on the condition probability of the PU state variation and the other one is designed based on the queueing theory. The simulation results are provided with different fusion methods. The performance improvements are demonstrated.

An Improved DSA Strategy based on Triple-States Reward Function

타사미아(Tasmia Ahmed),구준롱(Junrong Gu),장성진(Sung Jeen Jang),김재명(Jae Moung Kim) 大韓電子工學會 2010 電子工學會論文誌-TC (Telecommunications) Vol.47 No.11

본 논문은 보상함수 수정을 통해 보다 완벽한 DSA(Dynamic Spectrum Access)를 수행하는 새로운 방법을 제시하였다. POMDP(Partially Observable Markov Decision Process)는 미래의 스펙트럼 상태를 예측하는데 사용되는 알고리즘으로서, 그 중 보상함수는 스펙트럼을 예측하는데 있어 가장 중요한 부분이다. 그러나 보상함수는 Busy 및 Idle의 두 가지 상태만 갖고 있기 때문에 채널에서 충돌이 발생하게 되면 보상함수는 Busy를 반환함으로써 2차 사용자의 성능을 감소시키게 된다. 따라서 본 논문에서는 기존의 Busy를 Busy 및 Collision 의 두 상태로 구분하였고, 이렇게 추가된 Collision 상태를 통해 2차 사용자의 채널 접근 기회를 보다 향상시킴으로서 데이터 전송율을 증대시킬 수 있도록 하였다. 또한 본 논문은 새로운 알고리즘의 신뢰도 벡터를 수학적으로 분석하였다. 마지막으로 시뮬레이션 결과를 통해 개선된 보상함수의 성능을 검증하고, 이를 통해 새로운 알고리즘이 CR 네트워크에서 2차 사용자의 성능을 향상시킬 수 있음을 보인다. In this paper, we present a new method to complete Dynamic Spectrum Access by modifying the reward function. Partially Observable Markov Decision Process (POMDP) is an eligible algorithm to predict the upcoming spectrum opportunity. In POMDP, Reward function is the last portion and very important for prediction. However, the Reward function has only two states (Busy and Idle). When collision happens in the channel, reward function indicates busy state which is responsible for the throughput decreasing of secondary user. In this paper, we focus the difference between busy and collision state. We have proposed a new algorithm for reward function that indicates an additional state of collision which brings better communication opportunity for secondary users. Secondary users properly utilize opportunities to access Primary User channels for efficient data transmission with the help of the new reward function. We have derived mathematical belief vector of the new algorithm as well. Simulation results have corroborated the superior performance of improved reward function. The new algorithm has increased the throughput for secondary user in cognitive radio network.

Optimal Sensing Strategy Against Collision With Primary User in Cognitive Radio Systems

Jeon, Wha Sook,Gu, Junrong,Jeong, Dong Geun IEEE 2015 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.64 No.3

<P>The cognitive radio (CR) system needs to optimally set the sensing period and sensing time, to efficiently utilize the channel while protecting a primary user (PU). The optimal sensing period for maximizing the effective throughput of the CR system depends on not only the on/off pattern of the PU and the sensing error probabilities but also the size of a data packet, the transmission rate, and the forward error correction capability. In this paper, we mathematically derive the optimal sensing period while taking all of these factors into account. On the basis of this optimal period, we design the sensing strategy under which the CR user has the breaks for sensing during a data packet transmission. With the proposed sensing strategy, the CR system can protect the PU very well while achieving the high effective throughput.</P>

Dynamic Spectrum Load Balancing for Cognitive Radio in Frequency Domain and Time Domain

Juan Chen,손성환,Junrong Gu,김재명 한국ITS학회 2009 한국ITS학회논문지 Vol.8 No.3

As a solution to spectrum under-utilization problem, Cognitive radio (CR) introduces a dynamic spectrum access technology. In the area, one of the most important problems is how secondary users (SUs) should choose between the available channels, which means how to achieve load balancing between channels. We consider spectrum load balancing problem for CR system in frequency domain and especially in time domain. Our objective is to balance the load among the channels and balance the occupied time length of slots for a fixed channel dynamically in order to obtain a user-optimal solution. In frequency domain, we refer to Dynamic Noncooperative Scheme with Communication (DNCOOPC) used in distributed system and a distributed Dynamic Spectrum Load Balancing algorithm (DSLB) is formed based on DNCOOPC. In time domain, Spectrum Load Balancing method with QoS support is proposed based on Dynamic Feed Back theory and Hash Table (SLBDH). The performance of DSLB and SLBDH are evaluated. In frequency domain, DSLB is more efficient compared with existing Compare_And_Balance (CAB) algorithm and gets more throughput compared with Spectrum Load Balancing (SLB) algorithm. Also, DSLB is a fair scheme for all devices. In time domain, SLBDH is an efficient and precise solution compared with Spectrum Load Smoothing (SLS) method.