A Distributed Medium Access Control Protocol for Cognitive Radio Ad Hoc Networks

( Gyanendra Prasad Joshi ),( Sung Won Kim ),( Changsu Kim ),( Seung Yeob Nam ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.1

We propose a distributed medium access control protocol for cognitive radio networks to opportunistically utilize multiple channels. Under the proposed protocol, cognitive radio nodes forecast and rank channel availability observing primary users` activities on the channels for a period of time by time series analyzing using smoothing models for seasonal data by Winters` method. The proposed approach protects primary users, mitigates channel access delay, and increases network performance. We analyze the optimal time to sense channels to avoid conflict with the primary users. We simulate and compare the proposed protocol with the existing protocol. The results show that the proposed approach utilizes channels more efficiently.

Analysis of Channel Access Delay in CR-MAC Protocol for Ad Hoc Cognitive Radio Wireless Sensor Networks without a Common Control Channel

( Gyanendra Prasad Joshi ),( Seung Yeob Nam ),( Srijana Acharya ),( Sung Won Kim ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.3

Ad hoc cognitive radio wireless sensor networks allow secondary wireless sensor nodes to recognize spectrum opportunities and transmit data. Most existing protocols proposed for ad hoc cognitive radio wireless sensor networks require a dedicated common control channel. Allocating one channel just for control packet exchange is a waste of resources for channel-constrained networks. There are very few protocols that do not rely on a common control channel and that exchange channel-negotiation control packets during a pre-allocated time on the data channels. This, however, can require a substantial amount of time to access the channel when an incumbent is present on the channel, where the nodes are intended to negotiate for the data channel. This study examined channel access delay on cognitive radio wireless sensor networks that have no dedicated common control channel.

Void Less Geo-Routing for Wireless Sensor Networks

Gyanendra Prasad Joshi,Chae-Woo Lee 대한전기학회 2007 정보 및 제어 심포지엄 논문집 Vol.2007 No.4

Void Less Geo-Routing for Wireless Sensor Networks

Gyanendra Prasad Joshi,Chae-Woo Lee 대한전기학회 2007 대한전기학회 학술대회 논문집 Vol.2007 No.4

Geographic wireless sensor networks use position information for Greedy routing. Greedy routing works well in dense network where as in sparse network it may fail and require the use of recovery algorithms. Recovery algorithms help the packet to get out of the communication void. However, these algorithms are generally costlier for resource constrained position based wireless sensor type networks. In the present work, we propose a Void Avoidance Algorithm (VAA): a novel idea based on virtual distance upgrading that allows wireless sensor nodes to remove all stuck nodes by transforming the routing graph and forward packet using greedy routing only without recovery algorithm. In VAA, the stuck node upgrades distance unless it finds next hop node which is closer to the destination than itself. VAA guarantees the packet delivery if there is a topologically valid path exists. NS-2 is used to evaluate the performance and correctness of VAA and compared the performance with GPSR. Simulation results show that our proposed algorithm achieves higher delivery ratio, lower energy consumption and efficient path.

위치기반 무선 센서 네트워크를 위한 보이드(void) 회피 라우팅 프로토콜

Gyanendra Prasad Joshi,제갈찬(Chan Jaegal),이채우(Chae-woo Lee) 대한전자공학회 2008 電子工學會論文誌-TC (Telecommunications) Vol.45 No.10

위치 기반의 라우팅 기법을 사용하는 센서 네트워크에서는 구현이 간단한 그리디(greedy) 라우팅이 흔히 사용된다. 그리디 라우팅은 센서 노드의 밀도가 높은 곳에는 잘 동작하지만 그렇지 않은 곳에서는 라우팅이 실패할 가능성이 크다. 그리디 라우팅 실패 시에는 패킷을 보이드(void)로부터 빠져나오게 하는 별도의 회복(recovery) 알고리즘이 필요하고 이러한 추가적인 알고리즘은 패킷의 송수신 양과 센서의 에너지 소비량을 증가시키는 문제를 발생시킨다. 여기서 언급한 보이드란 전송할 패킷을 가진 노드가 자신보다 목적지 노드에 더 가까운 이웃 노드를 찾지 못하여 그리디 포워딩으로 더 이상 패킷을 전송하지 못하는 지역을 의미한다. 따라서 본 논문은 보이드로 인한 라우팅 문제점들을 개선하기 위해 VODUA(Virtually Ordered Distance Upgrade Algorithm)라는 효율적인 라우팅 알고리즘을 제안한다. VODUA에서는 연결 정보를 나타내는 라우팅 그래프를 노드끼리 서로 교환하고, 패킷 전송이 불가능한 노드인 stuck 노드가 발생하면 거리 비용(DC)을 사용하여 네트워크 내의 stuck 노드를 제거한다. 본 논문에서는 거리 비용을 증가시켜 stuck 노드의 패킷이 보이드를 회피하여 원하는 목적지 노드까지 성공적으로 전송할 수 있도록 하는 새로운 방식의 라우팅 알고리즘을 설명한다. 또한 회복 알고리즘과 같은 추가적인 알고리즘 없이도 패킷이 전송 가능 한 경로를 가질 수 있도록 설계하여 기존의 라우팅 기법보다 더 빠르고 적은 에너지 소모를 통해 라우팅 한다. 그리고 VODUA에서는 각각의 노드들이 네트워크 전체가 아닌 한 홉(hop) 이내에서 라우팅하고 토폴로지 상태정보를 사용하지 않기 때문에 노드의 실패(failure)나 토폴로지 변화에 적응이 빠르다. 시뮬레이션 결과는 VODUA가 짧은 전송 지연 시간을 통하여 신속하게 패킷을 전송할 수 있음을 보인다. 또한 GPSR과 DUA에 대해 더 적은 홉 수를 가지는 경로로 패킷이 전송 가능함을 보인다. Greedy routing which is easy to apply to geographic wireless sensor networks is frequently used. Greedy routing works well in dense networks whereas in sparse networks it may fail. When greedy routing fails, it needs a recovery algorithm to get out of the communication void. However, additional recovery algorithm causes problems that increase both the amount of packet transmission and energy consumption. Communication void is a condition where all neighbor nodes are further away from the destination than the node currently holding a packet, and it therefore cannot forward a packet using greedy forwarding. Therefore we propose a VODUA(Virtually Ordered Distance Upgrade Algorithm) as a novel idea to improve and solve the problem of void. In VODUA, nodes exchange routing graphs that indicate information of connection among the nodes and if there exist a stuck node that cannot forward packets, it is terminated using Distance Cost(DC). In this study, we indicate that packets reach successfully their destination while avoiding void through upgrading of DC. We designed the VODUA algorithm to find valid routes through faster delivery and less energy consumption without requirement for an additional recovery algorithm. Moreover, by using VODUA, a network can be adapted rapidly to node's failure or topological change. This is because the algorithm utilizes information of single hop instead of topological information of entire network. Simulation results show that VODUA can deliver packets from source node to destination with shorter time and less hops than other pre-existing algorithms like GPSR and DUA.

White-light generation using a remote-phosphor-coated diffusing surface excited by the high-brightness

Gyanendra Singh,Dalip Singh Mehta 한국정보디스플레이학회 2014 Journal of information display Vol.15 No.2

White-light generation by cerium-doped yttrium aluminum garnet inorganic phosphor, which was used to coat a diffusingpolyethylene terephthalate (PET) substrate excited by a blue light-emitting diode (LED) is reported. The diffused PETsubstrate was used to scatter the directional light of the blue LED at a large angle while the phosphor layer was used toconvert the blue light to white light through the downconversion mechanism. The diffuser is color-tunable, which can beachieved by varying the phosphor concentration and the thickness of the coating material. The Commission Internationalde l’Eclairage (CIE) coordinates and the correlated color temperature for the white-light emission were calculated, and theresults are reported herein. It was found that the white-light source had the CIE coordinates (0.33, 0.34) and had a broadspectrum profile.

Rendezvous Issues in AD Hoc Cognitive Radio Networks

( Gyanendra Prasad Joshi ),( Seung Yeob Nam ),( Sung Won Kim ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.11

Rendezvous is a process of two or more cognitive radio nodes gathering on the same channel at the same time for a negotiation to establish data communications. This paper discusses rendezvous issues in cognitive radio networks. It details why rendezvous is an issue in cognitive radio networks and how rendezvous works. It classifies channel access methods, and details sequence-based channel-hopping methods. It surveys existing works on blind rendezvous and compares the proposed algorithms in terms of the maximum time to rendezvous. This paper discusses the properties that an efficient channel-hopping rendezvous algorithm should have and illustrates common issues in the existing rendezvous methods. It also explains open research issues in the rendezvous area.

Diamond Face Grinding of WC-Co Composite with Spark Assistance: Experimental Study and Parameter Optimization

Gyanendra Kumar Singh,Vinod Yadava,Raghuvir Kumar 한국정밀공학회 2010 International Journal of Precision Engineering and Vol.11 No.4

Electro-discharge machining (EDM) characteristics of tungsten carbide-cobalt composite are accompanied by a number of problems such as the presence of resolidified layer, large tool wear rate and thermal cracks. Use of combination of conventional grinding and EDM (a new hybrid feature) has potential to overcome these problems. This article presents the face grinding of tungsten carbide-cobalt composite (WC-Co) with electrical spark discharge incorporated within face of wheel and flat surface of cylindrical workpiece. A face grinding setup for electro- discharge diamond grinding (EDDG) process is developed. The effect of input parameters such as wheel speed, current, pulse on-time and duty factor on output parameters such as material removal rate (MRR), wheel wear rate (WWR) and average surface roughness (ASR), are investigated. The present study shows that MRR increases with increase in current and wheel speed while it decreases with increase in pulse on-time for higher pulse on-time (above 100 μs). The most significant factor has been found as wheel speed affecting the robustness of electro- discharge diamond face grinding (EDDFG) process.

Decentralized Predictive MAC Protocol for Ad Hoc Cognitive Radio Networks

Joshi, Gyanendra Prasad,Nam, Seung Yeob,Kim, Sung Won Springer-Verlag 2014 WIRELESS PERSONAL COMMUNICATIONS Vol.74 No.2

Routing Layer Solution for Mitigating Frequent Channel Switching in Ad Hoc Cognitive Radio Networks

Joshi, Gyanendra Prasad,Sung Won Kim,Seung Yeob Nam IEEE 2015 IEEE communications letters Vol.19 No.11

<P>This letter analytically shows the requirements of cross-layer-based routing in ad hoc cognitive radio networks. This work estimates the number of channel switching in various scenarios and analyzes how non-cross-layer-based protocols suffer from delay. We suggest a route selection method to mitigate the frequent channel switching.</P>