• Title, Summary, Keyword: Wireless connectivity

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Connectivity Analysis of Cognitive Radio Ad-hoc Networks with Shadow Fading

  • Dung, Le The;An, Beongku
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.9 no.9
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    • pp.3335-3356
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    • 2015
  • In this paper, we analyze the connectivity of cognitive radio ad-hoc networks in a log-normal shadow fading environment. Considering secondary user and primary user's locations and primary user's active state are randomly distributed according to a homogeneous Poisson process and taking into account the spectrum sensing efficiency of secondary user, we derive mathematical models to investigate the connectivity of cognitive radio ad-hoc networks in three aspects and compare with the connectivity of ad-hoc networks. First, from the viewpoint of a secondary user, we study the communication probability of that secondary user. Second, we examine the possibility that two secondary users can establish a direct communication link between them. Finally, we extend to the case of finding the probability that two arbitrary secondary users can communicate via multi-hop path. We verify the correctness of our analytical approach by comparing with simulations. The numerical results show that in cognitive radio ad-hoc networks, high fading variance helps to remarkably improve connectivity behavior in the same condition of secondary user's density and primary user's average active rate. Furthermore, the impact of shadowing on wireless connection probability dominates that of primary user's average active rate. Finally, the spectrum sensing efficiency of secondary user significantly impacts the connectivity features. The analysis in this paper provides an efficient way for system designers to characterize and optimize the connectivity of cognitive radio ad-hoc networks in practical wireless environment.

A Simple but Efficient Scheme for Reliable Connectivity and High Performance in Ad-hoc Wireless Networks

  • Tak, Sung-Woo
    • Journal of information and communication convergence engineering
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    • v.10 no.2
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    • pp.141-148
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    • 2012
  • This paper presents a simple but efficient scheme incorporating a reputation-based approach and a cross-layer approach, called the SIM scheme, for maintaining reliable connectivity and high performance in ad-hoc wireless networks. The SIM scheme incorporates the following two things: an ad-hoc routing scheme with a reputation-based approach exploiting the game theory concept based on an evolutionarily stable strategy, and a cross-layer approach between the network layer and the transport layer employing a reputation-based approach.

Localized Algorithm to Improve Connectivity and Topological Resilience of Multi-hop Wireless Networks

  • Kim, Tae-Hoon;Tipper, David;Krishnamurthy, Prashant
    • Journal of information and communication convergence engineering
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    • v.11 no.2
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    • pp.69-81
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    • 2013
  • Maintaining connectivity is essential in multi-hop wireless networks since the network topology cannot be pre-determined due to mobility and environmental effects. To maintain the connectivity, a critical point in the network topology should be identified where the critical point is the link or node that partitions the network when it fails. In this paper, we propose a new critical point identification algorithm and also present numerical results that compare the critical points of the network and H-hop sub-network illustrating how effectively sub-network information can detect the network-wide critical points. Then, we propose two localized topological control resilient schemes that can be applied to both global and local H-hop sub-network critical points to improve the network connectivity and the network resilience. Numerical studies to evaluate the proposed schemes under node and link failure network conditions show that our proposed resilient schemes increase the probability of the network being connected in variety of link and node failure conditions.

Optimal Frame Aggregation Level for Connectivity-Based Multipolling Protocol in IEEE 802.11 Wireless LANs (IEEE 802.11 무선랜에서 연결정보 기반의 멀티폴링 프로토콜을 위한 최적의 프레임 애그리게이션 레벨)

  • Choi, Woo-Yong
    • Journal of Korean Institute of Industrial Engineers
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    • v.40 no.5
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    • pp.520-525
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    • 2014
  • When the PCF (Point Coordinated Function) MAC protocol is combined with the frame aggregation method to enhance the MAC performance in IEEE 802.11 wireless LANs, the formulae for the optimal frame aggregation level for best PCF MAC performance were derived in our previous study. We extend the formulae for the PCF protocol to derive the optimal frame aggregation level for the connectivity-based multipolling MAC protocol in IEEE 802.11 wireless LANs. By simulations, we compare the performances of IEEE 802.11 wireless LANs with the optimal and random frame aggregation levels. Compared with the random frame aggregation level, the optimal frame aggregation level significantly improves the performance of IEEE 802.11 wireless LANs.

Architectures and Connection Probabilities forWireless Ad Hoc and Hybrid Communication Networks

  • Chen, Jeng-Hong;Lindsey, William C.
    • Journal of Communications and Networks
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    • v.4 no.3
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    • pp.161-169
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    • 2002
  • Ad hoc wireless networks involving large populations of scattered communication nodes will play a key role in the development of low power, high capacity, interactive, multimedia communication networks. Such networks must support arbitrary network connections and provide coverage anywhere and anytime. This paper partitions such arbitrarily connected network architectures into three distinct groups, identifies the associated dual network architectures and counts the number of network architectures assuming there exist N network nodes. Connectivity between network nodes is characterized as a random event. Defining the link availability P as the probability that two arbitrary network nodes in an ad hoc network are directly connected, the network connection probability $ \integral_n$(p) that any two network nodes will be directly or indirectly connected is derived. The network connection probability $ \integral_n$(p) is evaluated and graphically demonstrated as a function of p and N. It is shown that ad hoc wireless networks containing a large number of network nodes possesses the same network connectivity performance as does a fixed network, i.e., for p>0, $lim_{N\to\infty} Integral_n(p)$ = 1. Furthermore, by cooperating with fixed networks, the ad hoc network connection probability is used to derive the global network connection probability for hybrid networks. These probabilities serve to characterize network connectivity performance for users of wireless ad hoc and hybrid networks, e.g., IEEE 802.11, IEEE 802.15, IEEE 1394-95, ETSI BRAN HIPERLAN, Bluetooth, wireless ATM and the world wide web (WWW).

Tighter Throughput Lower Bounds of Connectivity-Based Reliable Multicast MAC Protocol for IEEE 802.11 Wireless LANs (IEEE 802.11 무선랜에서 연결정보 기반의 신뢰성 있는 멀티캐스트 MAC 프로토콜을 위한 쓰루풋의 하한 유도)

  • Choi, Woo-Yong
    • Journal of Korean Institute of Industrial Engineers
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    • v.38 no.4
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    • pp.285-288
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    • 2012
  • The connectivity-based reliable multicast MAC protocol was proposed for IEEE 802.11 wireless LANs and the formulae for the lower bounds of the multicast downlink throughput and the uplink throughput of the connectivity-based reliable multicast MAC protocol were derived in our previous study. We provide the tighter throughput lower bounds of the connectivity-based reliable multicast MAC protocol than the lower bounds presented in our previous study.

A Rate Separating Multi-Channel Protocol for Improving Channel Diversity and Node Connectivity in IEEE 802.11 Mesh Networks (IEEE 802.11 메쉬 네트워크에서 채널 다양성과 노드 연결성 향상을 위한 레이트 분할 멀티 채널 프로토콜)

  • Kim, Sok-Hyong;Suh, Young-Joo;Kwon, Dong-Hee
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.12A
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    • pp.1152-1159
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    • 2010
  • Wireless Mesh Networks (WMNs) provides Internet accesses to users by forming backbone networks via wireless links. A key problem of WMN is network capacity. For this, multi-channel and multi-rate functions of IEEE 802.11 can be utilized. Depending on channel assignments, multi-channel determines node connectivity and channel diversity. Also, in IEEE 802.11 multi-rate networks, the rate anomaly problem occurs, the phenomenon that low-rate links degrades the performance of high-rate links. In this paper, we propose rate separating multi-channel (RSMC) protocols that improves the node connectivity and channel diversity, and mitigates the rate anomaly problem. RSMC increases the channel diversity by forming tree-based WMNs and decreases the rate anomaly by separating different rate links on the tree via channels. In addition, it uses network connectivity (NC) algorithm to increase the node connectivity. Through simulations, we demonstrate that the RSMC shows improved performance than existing multi-channel protocols in terms of aggregate throughput, node connectivity, channel diversity.

The Asymptotic Throughput and Connectivity of Cognitive Radio Networks with Directional Transmission

  • Wei, Zhiqing;Feng, Zhiyong;Zhang, Qixun;Li, Wei;Gulliver, T. Aaron
    • Journal of Communications and Networks
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    • v.16 no.2
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    • pp.227-237
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    • 2014
  • Throughput scaling laws for two coexisting ad hoc networks with m primary users (PUs) and n secondary users (SUs) randomly distributed in an unit area have been widely studied. Early work showed that the secondary network performs as well as stand-alone networks, namely, the per-node throughput of the secondary networks is ${\Theta}(1/\sqrt{n{\log}n})$. In this paper, we show that by exploiting directional spectrum opportunities in secondary network, the throughput of secondary network can be improved. If the beamwidth of secondary transmitter (TX)'s main lobe is ${\delta}=o(1/{\log}n)$, SUs can achieve a per-node throughput of ${\Theta}(1/\sqrt{n{\log}n})$ for directional transmission and omni reception (DTOR), which is ${\Theta}({\log}n)$ times higher than the throughput with-out directional transmission. On the contrary, if ${\delta}={\omega}(1/{\log}n)$, the throughput gain of SUs is $2{\pi}/{\delta}$ for DTOR compared with the throughput without directional antennas. Similarly, we have derived the throughput for other cases of directional transmission. The connectivity is another critical metric to evaluate the performance of random ad hoc networks. The relation between the number of SUs n and the number of PUs m is assumed to be $n=m^{\beta}$. We show that with the HDP-VDP routing scheme, which is widely employed in the analysis of throughput scaling laws of ad hoc networks, the connectivity of a single SU can be guaranteed when ${\beta}$ > 1, and the connectivity of a single secondary path can be guaranteed when ${\beta}$ > 2. While circumventing routing can improve the connectivity of cognitive radio ad hoc network, we verify that the connectivity of a single SU as well as a single secondary path can be guaranteed when ${\beta}$ > 1. Thus, to achieve the connectivity of secondary networks, the density of SUs should be (asymptotically) bigger than that of PUs.

Improved Connectivity-Based Reliable Multicast MAC Protocol for IEEE 802.11 Wireless LANs (IEEE 802.11 무선랜에서 신뢰성 있는 멀티캐스트 전송을 위한 연결정보 기반의 효율적인 MAC 프로토콜)

  • Choi, Woo-Yong
    • Journal of Korean Institute of Industrial Engineers
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    • v.36 no.2
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    • pp.94-100
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    • 2010
  • The reliable multicast MAC (Medium Access Control) protocol is needed to guarantee the recipients' nonerroneous reception of the multicast data frames, which can be transmitted by the AP (Access Point) in infrastructure mode IEEE 802.11 wireless LANs. Enhancing the BMMM (Batch Mode Multicast MAC) protocol, in the literature, the connectivity-based reliable multicast MAC protocol was proposed to reduce the RAK (Request for ACKnowledgement) frame transmissions and enhance the multicast MAC performance. However, the number of necessary RAK frame transmissions increases as the number of multicast recipients increases. To alleviate the problem of the larger number of RAK frame transmissions with the larger number of multicast recipients, we propose the clustering algorithm for partitioning the recipients into a small number of clusters, so that the recipients are connected each other within the same clusters. Numerical examples are presented to show the reliable multicast MAC performance improvement by the clustering algorithm.

Connectivity-Based Distributed Localization in Wireless Sensor Network (무선 센서 네트워크에서 연결성 정보만을 이용하여 노드 위치를 추정하는 분산 알고리즘)

  • Kwon Oh-Heum;Song Ha-Joo;Kim Sook-Yeon
    • The KIPS Transactions:PartC
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    • v.12C no.4
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    • pp.525-534
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    • 2005
  • We present several distributed algorithms for localizing nodes of a wireless sensor network. Our algorithms determine locations of nodes based on the connectivity between nodes. The basic idea behind our algorithms is to estimate distances between nearby nodes by counting their common neighbors. We analyze the performance of our algorithms experimentally. The results of experiments show that our algorithms achieve performance improvements upon the existing algorithms