BeomSeok Kim

A novel priority-based channel access algorithm for contention-based MAC protocol in WBANs

Wireless body area networks (WBANs) which is standardized by IEEE 802.15 TG6 support communication service with in/on/around body. Similar to wireless sensor network (WSN) environment, devices of WBAN may be densely deployed. Compared with WSN, however, WBAN operates in a centralized manner, and thus, contention complexity on contention-based phase of WBAN may be larger than WSN. In this paper, we propose a novel channel access algorithm for contention based MAC protocol in WBANs. The proposed algorithm classifies the contention-based access phase into 4-levels by the priority of packet that is defined in WBAN draft document, and divides the contention-based access phase into sub-period by calculated offset. Extensive simulation results show that the proposed algorithm achieves low complexity such as reduced collisions, low power consumption, and high channel utilization compared with the IEEE 802.15.6 baseline MAC protocol.

An AHP-Based Flexible Relay Node Selection Scheme for WBANs

A Wireless body area network (WBAN) is a communication network that provides both medical and consumer electronics services by using sensors in/on/around a human body. In general, a WBAN environment suffers from frequent link loss due to interferences among sensors scattered over a body. In addition, the channel condition can frequently change by postural body movement, which increases packet drops, retransmissions, and eventually power consumption. This paper presents an Analytical Hierarchy Process (AHP)-based flexible relay node selection scheme that considers a multitude of decision factors, such as average SNR, remaining energy ratio, and traffic load. Moreover, the proposed scheme can adaptively satisfy the requirements of WBAN in various scenarios. Our simulation study shows that the proposed method provides high communication reliability and low power consumption.

An AHP-Based Interface and Channel Selection for Multi-channel MAC Protocol in IoT Ecosystem

Recently, the significance of internet of things (IoT) is rapidly growing in the next generation of information and communication technology due to rapid advances in wireless communication technologies which have triggered the development of low-power, reliable and miniaturized devices. These advances lead to the creation of IoT ecosystem that enables development of various services. Especially, there are a number of attempts to apply communication technology of IoT in the field of healthcare services which deals with medical applications such as a remote medical treatment. In IoT-based healthcare system, in general, a number of medical devices are densely deployed in narrow area. Therefore, they are exposed to signal interference among them which causes significant performance degradation. In this paper, we present an Analytical Hierarchy Process (AHP)-based network interface and channel selection algorithm for multi-channel MAC protocols in IoT ecosystem that take into account a multitude of decision factors, such as expected channel condition, latency and frame reception ratio. The proposed scheme can provide flexibility for various requirements of different medical services through performing AHP. In particular, the proposed scheme considers IoT-based healthcare system because it is the most complex scenario of fundamental IoT applications. To evaluate the performance of the proposed algorithm, we perform extensive simulations, and the simulation study shows that the proposed algorithm provides low latency and high reliability.

ACESS: Adaptive Channel Estimation and Selection Scheme for Coexistence Mitigation in WBANs

A Wireless Body Area Networks (WBAN) is a communication network that provides both medical and consumer electronics (CE) services by using sensor devices in, on, or around a human body. To provide reliable communication with low power consumption for in-body communication, the IEEE 802.15.6 provides Medical Implant Communication Service (MICS) band and defines its communication policy. However, MICS band communication suffer from the coexistence problem, which causes significant performance degradation due to high-density deployment and network-level mobility of WBANs. In addition, existing coexistence mitigation schemes in IEEE 802.15.6 do not consider the MICS band. To overcome the coexistence problem, numerous studies have been conducted for multi-channel usage in WBANs, but they just include simple channel selection schemes which do not provide reliable channel selection. This paper proposes an Adaptive Channel Estimation and Selection Scheme (ACESS) for coexistence mitigation in WBANs. The proposed method maintains a history table and predicts the conditions of available channels based on two-state Markov chain with an exponentially controlled channel history, which can control the sensitivity of prediction. Our simulation study show that the proposed scheme can improve communication performance in terms of Packet Reception Ratio (PRR) under coexistence environments with multiple WBANs.

A distributed multi-coloring algorithm for coexistence mitigation in WBANs

A Wireless Body Area Network (WBAN) which consists of wireless sensors in/on/around human body requires high reliability for medical data. The coexistence problem which occurs when multiple-WBANs occupy the same channel at the same time declines the performance of the network. It is an important issue because this problem causes the collision of data among WBANs. For that reason, the IEEE 802.15.6 which was established for WBAN standardization defined guidelines to solve this problem, but these guidelines did not provide detailed methods. To solve this problem, there are also a few related works by using graph coloring algorithm as a general theory to assign limited resources but they cannot satisfy the requirements of WBAN. In this paper, we propose a distributed multi-coloring algorithm to mitigate coexistence problems among WBANs. The proposed algorithm shows short transmission-cycle per WBAN through multiple coloring with a color sequence and the efficiency of the proposed scheme is verified by the numerical results which outperform existing works in multiple WBANs environment.

A partitioning scheme to guarantee minimum execution time for multiple applications in sensor network nodes

Due to rapid development of embedded system technologies, miniaturization of low-power sensor nodes becomes possible. Based on these improvements of sensor nodes, several sensor applications can run on a single sensor hardware and all of the applications in sensor network should be guaranteed the real-time requirements and independence. To satisfy these requirements, the virtualization concept was proposed. However, the virtualization cannot be applied to sensor nodes because it requires powerful computing resources. To solve this problem, the partitioning scheme which is categorized into temporal partitioning and spatial partitioning has been proposed. In this paper, we design and implement temporal partitioning scheme for sensor nodes and validate that our implementation guarantees minimum execution time of each partition.

Adaptive route discovery for wireless sensor networks

A wireless sensor network is composed of a sink node and numerous sensor nodes. Typically, the sink node issues commands and sensor nodes generate traffic for the commands. The commands can be broadcasted or unicasted according to application services. In the wireless sensor network, routes for data transmission can be set by broadcasting a control packet from the sink node. Among tiny sensor nodes the broadcasting for the route discovery is performed efficiently because the sensor nodes have insufficient resources and the broadcasting can spend large amount of energy. This paper proposes an adaptive route discovery scheme for wireless sensor networks. The proposed method determines a node that rebroadcasts the control packet from the sink node. By the rebroadcast nodes, a routing tree toward the sink node is constructed. The node selection is performed by distributed manner considering nodes status (i.e., residual energy and connectivity).

DF(Dynamic and Flexible)-MAC : A Flexible MAC Protocol for WBAN

Wireless body area network(WBAN) provide communication service in the vicinity of the body. Since WBANs utilize both MICS frequency band for implant medical applications and ISM frequency band for medical and consumer electronics(CE) applications. Therefore, MAC protocols in WBAN should be designed considering flexibility between medical and CE applications. In this paper, we identify the requirements of WBAN MAC protocols and propose a WBAN MAC protocol which satisfies the requirements. In other to provide transmission flexibility for various applications. we present the dynamic CFP allocation and opportunity period. Extensive simulation result show that the proposed protocol achieves improved throughput and latency in WEAN environment cimpared with IEEE 802.15.4.