• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권3호
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• pp.911-923
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• 2014

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.

• Journal of Communications and Networks
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• 제14권1호
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• pp.51-62
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• 2012

The exponential growth in wireless services has resulted in an overly crowded spectrum. The current state of spectrum allocation indicates that most usable frequencies have already been occupied. This makes one pessimistic about the feasibility of integrating emerging wireless services such as large-scale sensor networks into the existing communication infrastructure. Cognitive radio is an emerging dynamic spectrum access technology that can be used for flexibly and efficiently achieving open spectrum sharing. Cognitive radio is an intelligent wireless communication system that is aware of its radio environment and that is capable of adapting its operation to statistical variations of the radio frequency. In ad hoc cognitive radio networks, a common control channel (CCC) is usually used for supporting transmission coordination and spectrum-related information exchange. Determining a CCC in distributed networks is a challenging research issue because the spectrum availability at each ad hoc node is quite different and dynamic due to the interference between and coexistence of primary users. In this paper, we propose a novel CCC selection protocol that is implemented in a distributed way according to the appearance patterns of primary systems and connectivity among nodes. The proposed protocol minimizes the possibility of CCC disruption by primary user activities and maximizes node connectivity when the control channel is set up. It also facilitates adaptive recovery of the control channel when the primary user is detected on that channel.

• Journal of information and communication convergence engineering
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• 제7권3호
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• pp.241-246
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• 2009

Advances in mobile and wireless networking technologies have enabled mobile ad hoc networks applicable to a wide range of areas. Many cases of even such ad hoc networks demand to be accessible to the global network. Owing to be diversified in features depending on applications, however, some those networks may consist of devices or nodes which do not facilitate all the same transport protocols. This results in unreachable situations of establishing ad hoc network: such as non-existence of all required access points, faults or contention in a path of particular protocol communication. Interworking between different transport protocols can alleviate such problems. This paper proposes an interworking scheme to improve data transport performance and network accessibility, especially in such a mobile ad hoc network that is applicable to data communications among ships or user's convenient u-health services. Modeling and simulation analysis are used to verify the improvement.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2003년도 춘계종합학술대회
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• pp.213-217
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• 2003

Ad-Hoc망은 어떠한 집중화된 관리 혹은 표준 지원 서비스의 도움 없이 임시 네트워크를 형성시킨 무선 이동 호스트들의 집합으로서 고정된 라우터 없이 이동 호스트들이 라우터로 동작하므로 기존의 라우팅 프로토콜 알고리즘들은 효율적일 수 없다. Ad-Hoc망의 프로토콜은 크게 Table-Driven 경로 선정 알고리즘과 On-Demand 경로선정 알고리즘으로 나눌 수 있고 이론적인 면에서는 On-Demand 경로설정 방식의 절차가 더 효율적인 방식으로 제시되고 있다. 본 논문에서는 On-Demand Ad-Hoc망에서 AODV, DSR 라우팅 프로토콜의 노드 당 처리율을 시뮬레이션을 통해 분석하였다.

• 한국멀티미디어학회논문지
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• 제13권6호
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• pp.849-864
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• 2010

This paper proposes a multipath routing protocol called cross-layer multipath AODV (CM-AODV) for wireless ad hoc networks, which selects multiple routes on demand based on the signal-to-interference plus noise ratio (SINR) measured at the physical layer. Note that AODV (Ad hoc On-demand Distance Vector) is one of the most popular routing protocols for mobile ad hoc networks. Each time a route request (RREQ) message is forwarded hop by hop, each forwarding node updates the route quality which is defined as the minimum SINR of serialized links in a route and is contained in the RREQ header. While achieving robust packet delivery, the proposed CM-AODV is amenable to immediate implementation using existing technology by neither defining additional packet types nor increasing packet length. Compared to the conventional multipath version of AODV (which is called AOMDV), CM-AODV assigns the construction of multiple paths to the destination node and makes it algorithmically simple, resulting in the improved performance of packet delivery and the less overhead incurred at intermediate nodes. Our performance study shows that CM-AODV significantly outperforms AOMDV in terms of packet delivery ratio and average end-to-end delay, and results in less routing overhead.

• ETRI Journal
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• 제38권5호
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• pp.922-933
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• 2016

IP header compression schemes offer a valuable measure for bandwidth preservation. Such schemes have been practically implemented in infrastructure-based IP networks for point-to-point links. However, minimal research and practical implementation efforts have been conducted in the direction of an IP header compression strategy that can meet the peculiar requirements of multi-hop ad hoc wireless networks. In this paper, we present a practically implemented multi-hop IP header compression scheme using the Robust Header Compression (ROHC) protocol suite. The scheme runs on a novel identifier (ID) based networking architecture, known as an ID-based ad hoc network (IDHOCNET). IDHOCNET additionally solves a number of bottlenecks of pure IP-based ad hoc networks that have emerged owing to IP address auto-configuration service, distributed naming and name resolution, and the role of an IP address as an identifier at the application layer. The proposed scheme was tested on a multi-hop test bed. The results show that the implemented scheme has better gain and requires only O (1) ROHC contexts.

• 한국전자파학회논문지
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• 제23권5호
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• pp.632-639
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• 2012

Ad-hoc 네트워크는 음영 지역, 재난 지역, 전쟁 시와 같은 통신 인프라가 구축되기 어려운 상황에서 유용하게 사용될 수 있다. 그러나 음성 및 데이터 서비스 등과 같은 무선 서비스의 제공을 위해 많은 양의 네트워크 용량이 필요하게 되지만, 기존의 제한된 주파수 자원에 따른 주파수 부족 상황 및 주파수 자원 정책의 규제에 따라 원활한 주파수 사용이 어려운 상황이다. 이에 따라 높은 주파수 활용을 제공하는 인지 무선 시스템을 ad-hoc 네트워크에 적용하여 보다 다양하고 확장된 네트워크 서비스를 제공할 수 있다. 하지만 기존 스펙트럼 센싱에 있어 임계치가 정적으로 작용하므로 detection probability가 낮게 검출되는 단점이 있다. 이러한 점을 보완하여 신호들의 detection probability를 향상시키기 위해 adaptive threshold를 이용할 것이다. 본 논문에서는 동적인 임계치를 이용하여 수신 신호의 power에 따라 임계치가 변화하여 신호들의 detection probability를 향상시키는 센싱 성능을 보여 준다.

• 대한임베디드공학회논문지
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• 제2권3호
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• pp.155-163
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• 2007

In Ad Hoc Networks, a connection breaks due to the irregular movement of mobile nodes and the inherent characteristics of the wireless medium such as the interference and the multi-path fading. AODV, a typical on-demand routing protocol in Ad Hoc networks, uses Destination sequence numbering for loop-free, but it may cause RREQ broadcast storm problem. This paper proposes AODV_ods that does not need destination sequence number, in routing message and routing table without routing loop. To show the effectiveness of the proposed scheme, we performed extensive simulation with NS-2. The simulation results show that the proposed ADOV_ods efficiently uses wireless bandwidth compare to the original AODV. Finally AODV ods reduces the routing overhead, end to end delay and increases the overall packet delivery ratio.

• 한국정보통신학회논문지
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• 제5권7호
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• pp.1250-1256
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• 2001

본 논문에서는 Ad Hoc 무선 LAN에서의 자원 관리방식을 제안하였다. 이 방식은 분산적인 자원 관리방식과 직교주파수분할 다중화-부호분할 다중화(Orthogonal Frequency Division Multiplexing-Code Division Multiple Access, OFDM-CDMA) 기술을 결합하여 QoS를 보장하는 멀티미디어 서비스를 지원한다. 이 방식에 대하여 호 거절률(Blocking Rate)과 QoS 손실확률(QoS Loss Probability)의 관점에서 성능을 분석하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1839-1842
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• 2002

Ad hoc networks are characterized by multi- hop wireless connectivity, frequently changing network topology and the need for efficient dynamic routing protocols. In this paper, we proposed a new technique to adjust the zone radius by concentrating the changes of network traffic in a particular direction, which we refer to as AZRP. We demonstrate that even though ZRP and AZRP share a similar hybrid routing behavior, the differences in the protocol mechanics can lead to significant performance differentials. We discuss the algorithm and report on the performance of AZRP scheme, and compare it to the ZRP routing protocol. Our results indicate clearly that AZRP outperforms ZRP by reducing significantly the number of route query messages. And thereby increases the efficiency of the network load.