Number Of Member Nodes Research Articles

A Security-Enhanced Cluster Size Adjustment Scheme for Cognitive Radio Networks

Cognitive radio network (CRN) is the next generation wireless network that allows unlicensed users [secondary users (SUs)] to explore and use the underutilised licensed channels (white spaces) owned by licensed users (primary users). The purpose is to increase the spectrum utilization for enhanced network performance. Clustering segregates SUs in a CRN into logical groups (clusters) with each consisting of a leader (cluster head) and member nodes. A budget-based cluster size adjustment scheme is applied to enable each cluster to adjust its number of member nodes in its cluster based on the availability of white spaces in order to improve network scalability. However, cluster size adjustment is prone to attacks by malicious SUs that launch random and intelligent attacks. Hence, we incorporate an artificial intelligence approach called reinforcement learning (RL) into a trust model to countermeasure the random and intelligent attacks. The simulation results show that RL-based trust model increases the utilization of white spaces and cluster size to improve network scalability and enhance network performance despite the presence of RL-based intelligent attacks.

BEST-MAC: Bitmap-Assisted Efficient and Scalable TDMA-Based WSN MAC Protocol for Smart Cities

Smart cities have been envisioned during the last decade. Moreover, various projects have been initiated to bring this concept into reality. Smart city is basically an emergence of the existing and new Information and Communications Technologies (ICT) to make our living standard more safe and digitized. Wireless communications, such as sensors, actuators, intelligent transportation systems, and smart grids, have played a vital role in the dissemination of information under the given circumstances. Similarly, it is hard to declare any city as a smart city without taking benefits from wireless sensor networks (WSNs). However, with new requirements and delay sensitive applications, the existing WSN requires significant alterations at several layers. In this paper, a new time division multiple access (TDMA)-based medium access control (MAC) protocol, called bitmap-assisted efficient and scalable TDMA-based MAC (BEST-MAC), is proposed for adaptive traffic in hierarchical WSNs that can be deployed in the smart cities. BEST-MAC is specifically designed to improve the quality control of such smart cities applications, where diverse traffic is required and loss or delay in data traffic is unacceptable. The main contributions of BEST-MAC include: 1) it uses small size time slots; 2) the number of those time slots is more than the number of member nodes; 3) knapsack algorithm is used to schedule time slots; and 4) short node address (1 B) is proposed to identify the member nodes. First two contributions of BEST-MAC handle adaptive traffic loads of all members in an efficient manner. The knapsack algorithm not only reduces the job completion time of a node but also minimizes the average packet delay with better link utilization. The short node address reduces the control overhead that improves the energy efficiency. The simulation results verify that the proposed BEST-MAC transmits more data with less delay and energy consumption compared with the existing MAC protocols.

모바일 WSN을 위한 에너지 효율적인 경로배정 프로토콜

In this paper, we propose routing protocol for mobile wireless sensor networks with a mobile sink in cluster configuration. The proposed protocol extends LEACH-ME by introducing a mobile sink. The mobile sink moves to the cluster head with the highest number of member nodes to collect sensed data from cluster heads within its vicinity, which results in reducing energy consumption in forwarding packets to the sink. The simulation results show that the proposed protocol outperform LEACH-ME in terms of energy efficiency.

Enhanced TDMA based MAC protocol for adaptive data control in wireless sensor networks

In this paper, we propose an adaptive time division multiple access based medium access control (MAC) protocol, called bitmap-assisted shortest job first based MAC (BS-MAC), for hierarchical wireless sensor networks (WSNs). The main contribution of BS-MAC is that: (a) It uses small size time slots. (b) The number of those time slots is more than the number of member nodes. (c) Shortest job first (SJF) algorithm to schedule time slots. (d) Short node address (1 byte) to identify members nodes. First two contributions of BS-MAC handle adaptive traffic loads of all members in an efficient manner. The SJF algorithm reduces node's job completion time and to minimize the average packet delay of nodes. The short node address reduces the control overhead and makes the proposed scheme an energy efficient. The simulation results verify that the proposed BS-MAC transmits more data with less delay and energy consumption compared to the existing MAC protocols.

WCVALEACH: Weight and Coverage Based Energy Efficient Advanced Leach Algorithm

Designing a protocol stack for wireless sensor network (WSN) is a challenging task due to energy, computational, communication and storage constraints. Energy spent for communication between sensor nodes dominates the energy spent for the computation [1]. Multi -hop short range communication between wireless sensor nodes is energy efficient compared to single -hop long range communication. Hierarchical clustering is one of the possible solutions to save energy of wireless sensor nodes. LEACH [16], Advanced LEACH (ALEACH)[14] and Weight based energy efficient Advanced LEACH (WALEACH) [20] are energy efficient hierarchical clustering routing protocols. In this paper we presented Weight and Coverage based Advanced LEACH routing protocol- WCVALEACH. WCVALEACH selectsCluster Head by assigning importance (weight) to different parameters used to select Cluster Head. It also creates the non -overlapped cluster regions to cover more number of member nodes. Both of these approaches makes WCVALEACH routing protocol energy efficient and improves life time of a wireless sensor network. Simulation results shown here verify that WCVALEACH not only improves network life time compared to ALEACH, LEACH and WALEACH algorithms but Packet Reception Rate (PRR) too.

A Democratic Head Election Strategy for Clustering in Wireless Sensor Network

In recent years a lot of work has been done on Wireless Sensor Network (WSN) as it find its application in many applications including environmental monitoring and military field surveillance. In these applications tiny sensor nodes are deployed across the application regions. Data gathered by the sensor nodes are periodically collected by the base stations. As the nodes are deployed and left unattended for a long time it becomes quite difficult to recharge the node batteries. Several WSN applications require only an aggregate value to be reported to the base station. In this case sensors in different regions of the field can collaborate to aggregate their data and provide more accurate reports about their local regions. This type of data aggregation can reduce the communication overhead in the network and can increase the network life time. In order to support data aggregation through efficient network organization, nodes can be partitioned into a number of small groups called clusters. Each cluster has a coordinator, referred to as cluster head and a number of member nodes. The member nodes report their data to the respective Cluster Heads (CHs). The CHs aggregate the data and send them to the central base station through other CHs. This process improves the network lifetime which is an important metric to evaluate the network performance. In this type of system the challenging issue is to selection of CHs in each cluster along with the cluster head rotation to increase network life time and to reduce the communication overhead among the nodes in a WSN. In our work we have proposed an election algorithm to select the CHs in a democratic fashion by the nodes in the network. The performance of the proposed algorithm has been successfully demonstrated by the simulation of the proposed system.

정적 애드혹 네트워크 멀티캐스트에서 지연 시간과 에너지 소비의 트레이드오프를 위한 적응 오버레이 트리

무선 애드혹 네트워크에서의 멀티캐스팅은 그룹 내 여러 노드의 협력을 필요로 하는 많은 응용 분야에 기본적인 기능이다. 일반적인 접근 방법은 오버레이 트리를 구성하고 멀티캐스트 패킷을 트리 상의 여러 수신 노드에게 전달하는 것이다. 본 논문에서는 정적 노드로 구성된 무선 애드혹 네트워크에서 지연 시간 및 에너지를 고려하는 멀티캐스트를 위한 적응 오버레이 트리(AOT)를 제안한다. 트레이드오프(tradeoff) 함수를 정의하고 AOT 생성을 위한 새로운 알고리즘을 고안한다. 보통 지연 시간과 에너지 소비에 대한 요구 사항은 응용 분야의 종류에 따라 다르다. 트레이드오프 함수에서 파라미터를 조절함으로써, 서로 다른 종류의 응용분야에 따라 다른 AOT를 적응적으로 선택할 수 있게 된다. 각 AOT는 O(ke) 시간에 생성된다. 여기서, e는 네트워크 내의 무선 링크의 수이고 k는 멀티캐스트 그룹 내의 멤버 노드의 수이다. 시뮬레이션 결과에 의하면, AOT는 가장 빠른 트리(지연 시간이 가장 중요한 설계 요소인 경우)와 가장 에너지 효율적인 트리(에너지 소비가 일차적인 관심사인 경우) 사이의 트레이드오프를 적응적으로 제공한다. 즉, 네트워크 운용 환경에 따라 여러 AOT 중의 하나를 적절하게 선택할 수 있게 해준다. Multicasting is fundamental to many ad hoc network applications requiring collaboration of multiple nodes in a group. A general approach is to construct an overlay tree and to deliver a multicast packet to multiple receivers over the tree. This paper proposes adaptive overlay trees (AOTs) on wireless ad hoc networks of static nodes for delay- and energy-efficient multicast. A tradeoff function is derived, and an algorithm for AOT construction is developed. Note here that the requirements of delay and energy consumption may vary with different classes of applications. By adjusting parameters in the tradeoff function, different AOTs can be adaptively chosen for different classes of applications. An AOT is constructed in O(ke) time where e is the number of wireless links in a network and k is the number of member nodes in a multicast group. The simulation study shows that AOT adaptively provides tradeoffs between the fastest multicast (which is the choice if delay is the most important factor) and the most energy efficient multicast (which is used when energy consumption is the primary concern). In other words, one of AOTs can be appropriately chosen in accordance with the operation requirement.

Four-ary tree-based barrier synchronization for 2D meshes without nonmember involvement

This paper proposes a Barrier Tree for Meshes (BTM) to minimize the barrier synchronization latency for two-dimensional (2D) meshes. The proposed BTM scheme has two distinguishing features. First, the synchronization tree is 4-ary. The synchronization latency of the BTM scheme is asymptotically /spl theta/(log/sub 4/ n), while that of the fastest scheme reported in the literature is bounded between /spl Omega/(log/sub 3/ n) and /spl theta/(n/sup 1/2/), where n is the number of member nodes. Second, nonmember nodes are neither involved in the construction of a BTM nor actively participate in the synchronization operations, which avoids interference among different process groups during synchronization. This not only results in low setup overhead, but also reduces the synchronization latency. The low setup overhead is particularly effective for the dynamic process model provided in MPI-2. Extensive simulation study shows that, for up to 64/spl times/64 meshes, the BTM scheme results in about 40/spl sim/70 percent shorter synchronization latency and is more scalable than conventional schemes.