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Reporting Order Control for Fast Primary Detection in Cooperative Spectrum Sensing
Gosan Noh,Hano Wang,Junho Jo,Byoung-Hoon Kim,Daesik Hong IEEE 2011 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.60 No.8
<P>Although cooperative spectrum sensing improves sensing accuracy in cognitive radio systems, additional reporting time is required to report the local test statistics until the existence of the primary user is verified, resulting in detection delay. To reduce the reporting time, we propose controlling the reporting order of the local test statistics, so that the local test statistics are reported to the fusion center in descending order of magnitude. As a result, the global test statistic at the fusion center accumulates faster than the case without reporting order control, reducing the reporting time needed to determine when the threshold for detecting the primary user has been exceeded. To do this, we propose, based on distributed access control, a combination of order identification, which finds the order of the local test statistic, and transmission probability calculation according to the identified order. Simulation results show that the proposed reporting order control significantly reduces the reporting time for detecting the primary user.</P>
Ergodic Capacity Analysis of Spectrum Sharing in the Presence of Primary Interference
Gosan Noh,Jonghyun Bang,Sungmook Lim,Daesik Hong 대한전자공학회 2015 ITC-CSCC :International Technical Conference on Ci Vol.2015 No.6
In this paper, we provide an exact capacity derivation for the ergodic capacity of the secondary user in a spectrum sharing environment. Considering the effect of the interference from the primary user, the closed-form expression for the ergodic capacity is obtained under both average and peak received-power constraints at the primary user. Numerical results show that our derived ergodic capacity perfectly matches the results from a computer simulation.
Throughput Analysis and Optimization of Sensing-Based Cognitive Radio Systems With Markovian Traffic
Gosan Noh,Jemin Lee,Hano Wang,Sungtae Kim,Sooyong Choi,Daesik Hong IEEE 2010 IEEE Transactions on Vehicular Technology VT Vol.59 No.8
<P>This paper analyzes the secondary user throughput of a sensing-based cognitive radio system with Markovian traffic. Under the Markovian traffic assumption, imperfect packet capture, which occurs upon the random arrival of primary user packets, considerably affects the secondary user throughput. Considering both the primary user packet capture and energy detection of the captured packet, we derive the secondary user throughput. Additionally, using the tradeoff between the sensing accuracy and the secondary user throughput, we solve a joint optimization dealing with both the sensing duration and the sensing period to maximize the secondary user throughput with an interference constraint for the primary user.</P>
Exact Capacity Analysis of Spectrum Sharing Systems: Average Received-Power Constraint
Gosan Noh,Sungmook Lim,Daesik Hong IEEE 2013 IEEE COMMUNICATIONS LETTERS Vol.17 No.5
<P>This letter presents an exact closed-form expression for the ergodic capacity of the secondary user in a spectrum sharing environment under an average received-power constraint, considering the effect of the interference from the primary user. Using capacity maximizing water-filling power allocation, we provide the closed-form expressions for the ergodic capacity and the average received-power assuming Rayleigh fading channels. Numerical results show that the primary user interference significantly affects the ergodic capacity of the secondary user. The obtained formulas can be used when predicting whether spectrum sharing is beneficial in a practical channel environment.</P>
Enabling Technologies toward Fully LTE-Compatible Full-Duplex Radio
Noh, Gosan,Wang, Hanho,Shin, Changyong,Kim, Seunghyeon,Jeon, Youngil,Shin, Hyunchol,Kim, Jinup,Kim, Ilgyu Institute of Electrical and Electronics Engineers 2017 IEEE communications magazine Vol.55 No.3
<P>Full-duplex radio has potential to double spectral efficiency by simultaneously transmitting and receiving signals in the same frequency band, but at the expense of additional hardware and power consumption for self-interference cancellation. Hence, the deployment of a full-duplex cellular network can be realized by employing full-duplex functionality only at an eNodeB, which is supposed to have sufficient computation and power resources, and by scheduling pairs of half-duplex UEs that are in either downlink or uplink. By doing so, fast and smooth full-duplex deployment is possible while minimally affecting the legacy UEs and the rest of the network entities. In this article, we provide technical challenges and solutions for an LTE-compatible full-duplex cellular network, featuring wideband and wide dynamic range support for RF self-interference cancellation, and robust and efficient self-interference channel estimation for digital self-interference cancellation. Based on a realistic LTE-based cellular model, our full-duplex radio design is evaluated through system-level simulations and real-world testbed experiments. Simulation results show that a significant throughput gain can be achieved by the full-duplex technique despite the existence of physical limiting factors such as path loss, fading, and other-cell interference. Testbed measurements reveal that at a bandwidth of 20 MHz, self-interference cancellation up to 37 dB is achieved in the RF domain, and most of the residual self-interference is further cancelled down to the noise floor in the subsequent digital domain.</P>
TV 화이트 스페이스에서 서로 다른 대역폭을 가진 시스템들의 공존을 위한 적응적 채널 선택 기법
노고산(Gosan Noh),방극준(Keuk-Joon Bang),홍대식(Daesik Hong) 大韓電子工學會 2012 電子工學會論文誌-TC (Telecommunications) Vol.49 No.3
본 논문에서는 TV 화이트 스페이스(TV White Space; TVWS)에서 이종 시스템 간 채널 선택 방법에 대하여 다루도록 한다. 먼저, 대상이 되는 시스템 구조에 대하여 정의한다. 그리고 정의된 시스템 구조에서 TVWS에 서로 다른 시스템들이 공존하는 경우 여러 개의 TVWS 채널들을 공존하는 시스템들이 어떻게 나누어 쓸 것인지를 정의한다. 구체적으로는 TVWS에 서로 다른 대역폭을 가지는 시스템들이 공존하는 경우 전체적으로 채널이 남는다고 하더라도 좁은 대역폭을 가지는 채널들만 남은 경우 넓은 대역폭을 가지는 기기는 채널 사용 기회가 없어져서 Blocking이 되어버린다. 그러므로 대역폭의 차이로 인하여 채널을 새로운 시스템에 할당하는데 있어서 제한이 되는 상황을 최소화시키기 위하여 TV 채널 공유 시스템에게 할당할 채널을 선택하는데 있어서 넓은 단위의 사용 가능한 채널을 최대한 남겨두고 좁은 단위의 사용 가능한 채널부터 선택하는 방법을 제안한다. 제안된 방법은 IEEE 802.19.1 시스템 구조뿐만 아니라 일반적인 용도에서 TVWS의 주파수 사용 효율을 높여준다. In this paper, we consider a channel selection method for the coexistence of heterogeneous systems in the TV white space (TVWS). First, we define the target heterogeneous system structure. Then, under the defined system structure, we discuss how the heterogeneous systems share the TVWS channels. Specifically, the heterogeneous systems having different bandwidths cannot use the TVWS channels due to the lack of wideband channels when only narrowband channels are remained. Hence, in order to minimize the blocking from the different bandwidth problem, we propose a channel selection method for the narrowband systems to firstly occupy the narrowband channels rather than the wideband channels. The proposed narrowband-first channel selection is shown to enhance the spectral efficiency of the TVWS, especially in the IEEE 802.19.1 wireless coexistence system.
인지 무선 통신 시스템에서 에너지 제한적 개방 루프 협력 센싱 기법에 대한 연구
노고산(Gosan Noh),임성묵(Sungmook Lim),왕한호(Hanho Wang) 대한전기학회 2014 전기학회논문지 P Vol.63 No.1
In cognitive radios, secondary users can use the spectrum exclusively allocated to a primary wireless system if the secondary users detect the spectrum in idle states. Because the secondary users can utilize the idle state of the spectrum, the utilization rate of the spectrum can be improved. The idle states can be detected by using secondary users" sensing schemes. However, the wireless channel environment where secondary users perform the spectrum sensing is not very friendly to secondary users because the signal-to-noise ratio of the received primary signal is very low. Hence, cooperative sensing scheme where more than one secondary user take part in the spectrum sensing is generally used in cognitive radios. In this paper, we investigate the cooperative sensing performance for machine-to-machine communication devices operated by batteries with limited energy. In general, the energy consumed for the spectrum sensing increases as the length of the sensing period and the number of cooperative sensing nodes. Accordingly, even though the total amount of the consumed energy is the same, an energy allocation methodology how to distribute the energy to the sensing period and sensing nodes can achieve the optimum sensing performance, which is numerically analyzed.