Bih-Hwang Lee

Analysis of superframe adjustment and beacon transmission for IEEE 802.15.4 cluster tree networks

Wireless sensor networks based on the IEEE 802.15.4 standard are able to achieve low-power transmissions in the low-rate and short-distance wireless personal area network (PAN). A cluster tree network consists of several clusters; each cluster has a coordinator, known as cluster coordinator, and several device nodes. In the cluster tree topology of IEEE 802.15.4, a PAN coordinator periodically transmits beacon frames to its coordinator nodes as well as a coordinator node periodically transmit beacon frames to their device nodes. The main challenge in the cluster tree network is the collisions between beacons or even between beacon and data frames, which degrades the network performance. In order to decrease collisions, this article proposes the superframe adjustment and beacon transmission scheme (SABTS) by assigning the accurate values of beacon order and superframe order for the PAN coordinator, cluster coordinators, and device nodes, and deciding the precise time for the beacon transmission of PAN and coordinator nodes. A Markov chain model for the cluster tree network is developed with taking into account packet retransmission, acknowledgement, and defer transmission. Both analytical and simulation results show that SABTS performs better than IEEE 802.15.4 standard in terms of the probability of successful transmission, network goodput, and energy consumption.

Wireless body area network for monitoring body temperature, heart beat and oxygen in blood

Wireless body area network (WBAN) is a term used to describe a network of sensor devices connected wirelessly for communication on, in and near the body to obtain physiological data from sensor devices. This paper explain the implementation of WBAN for monitoring body temperature, heart beat rate and oxygen saturation in blood. We develop the sensor reads physiological data to the desktop application, then will read the printout of the series and create a visual in the tables and graphs, as well as storing the data into a database and displayed via a website in the form of reports that can be accessed remotely. We analyze the data received from sensor nodes to server receiver with a variety of different distances 10, 20, 30, 40, and 50 meters. The experiment results show that the physiological data can be accessed through ZigBee wirelessly in short distance which suitable for WBAN.

High sensitivity wake-up radio using spreading codes: design, evaluation, and applications

Most of the published wake-up radios propose low energy design at the expense of reduced radio range, which means that they require an increased deployment density of sensor networks. In this article, we introduce a design of a high sensitivity 916.5 MHz wake-up radio using low data rate and forward error correction (FEC). It improves the sensitivity, up to -122 dBm at a data rate 370 bit/s. It achieves up to 13 dB of coding gain with symbol error rate (SER) 10-2, and up to 4 times the range of the data radio, rendering it more suitable to sensor networks. Our design can receive wake-up signal reliably from any IEEE 802.15.4 transmitter and achieves a low packet error rate (PER) 0.0159 at SNR 4 dB. Furthermore, our design encodes the node ID into a wake-up signal to avoid waking up the undesired nodes.

Monitoring system of patient position based on wireless body area sensor network

Wireless body area sensor network (WBASN) implements realtime health monitoring by outfitting patients with wireless vital sign sensors. This paper presents an aplication that can assist doctors/nurses to monitor any changes in the position of the patient; they do not need to see the patient directly. They can monitor the patient position at other room of the patient. This aplication can shows any changes in the patients position in realtime.

Study on superframe adjustment for cluster tree in wireless sensor networks

The personal area network (PAN) coordinator periodically transmits beacon frames to coordinator nodes as well as the coordinator nodes periodically transmit beacon frames to device nodes in the cluster tree topology of IEEE 802.15.4. The challenge in cluster tree network is the collisions between beacons or even between beacon and data frames, which degrades the network performance. In order to improve the collisions, this paper proposes the superframe adjustment and beacon transmission scheme (SABTS) by assigning the accurate values of beacon order and superframe order for PAN coordinator, cluster coordinators and device nodes, and deciding the precise time for beacon transmission of PAN and coordinator nodes. A Markov chain model for cluster tree network is developed with taking into account packet retransmission, acknowledgement, and defer transmission. Both analytical and simulation results present that SABTS performs better than IEEE 802.15.4 standard in terms of the probability of successful transmission, network goodput, and energy consumption.

Portable electrocardiogram sensor monitoring system based on Body Area Network

Nowadays, the use of Electrocardiogram (ECG) as a detection tool of the condition of human heartbeat is still considered difficult. So, the idea of implementing this sensor is to enhance the quality of service and to minimize the cost of using and maintaining by determining the best way in implementing and monitoring ECG sensor. This research proposes a novel approach to observe the condition of human heartbeat using ECG sensor with e-Health sensor and Raspberry Pi, mini single-board computer with robust capability, which acts as central processing unit. Those hardware sets were assembled to collect ECG voltage signals in human body. The signals are transmitted into the device and the data are stored in MySQL database for long-term monitoring access. The experimental results show effectiveness of this approach as it is successfully fulfill the idea of Body Area Network (BAN).

Study on multi-channel deterministic access for wireless mesh LAN

IEEE802.11s draft proposes a new medium access control function-mesh deterministic access (MDA), which is mainly used for single-channel wireless mesh local area network (LAN). To provide high performance and network capacity for wireless mesh LAN, this paper develops an algorithm for MDA to work well on multi-channel wireless mesh LAN. To completely avoid the collisions between control packets and data packets, the interval of the meshed delivery traffic indication message is first divided into contention period and data transmission period. We define a neighbor MP status table for MPs to support multi-channel environment. The mechanism for reserving MDA opportunity (MDAOP) uses the four-way-handshaking mode to reduce hidden node problem. We propose a multi-channel MDA (MMDA) algorithm to improve the overall performance of wireless mesh LAN in multi-channel environment.

Study on multi-channel mesh deterministic access for wireless mesh LAN

IEEE802.11s draft proposes a new medium access control (MAC) function-mesh deterministic access (MDA), which is mainly used for single-channel wireless mesh local area network (LAN). In single-channel environment, collisions between control packets and data packets may occur very often. In order to provide higher performance and network capacity for wireless mesh LAN, this article develops an algorithm for MDA to work well on multi-channel wireless mesh LAN. To reduce the hardware requirements in design, a mesh point (MP) only equips single transceiver to support multi-channel environment. To completely avoid the collision between control packets and data packets, the interval of the meshed delivery traffic indication message is first divided into contention period and data transmission period. We newly define a neighbor MP status table for MPs to support multi-channel environment. The mechanism of reserving MDA opportunity (MDAOP) adopts the four-way-handshaking mode to reduce hidden node problem; we propose channel load first random fit and multi-channel best fit mechanisms to select MDAOP. We also propose a multi-channel MDA (MMDA) algorithm to improve the overall performance of wireless mesh LAN in multi-channel environment. The theoretical analysis gives the upper limit of the throughput for MMDA. The simulation experiments clearly show the results in multi-channel wireless mesh LAN environment that MMDA performs better than the enhanced distributed channel access in throughput, average waiting time, and packet drop ratio both in the saturated and non-saturated mode.

A dynamic adjustable contention period mechanism and adaptive backoff process to improve the performance for multichannel mesh deterministic access in wireless mesh LAN

IEEE802.11s draft proposes a new medium access control function-mesh deterministic access (MDA), which is mainly used for single-channel wireless mesh local area network (LAN). In single-channel environment, collisions between control packets and data packets may occur very often. To completely avoid the collision between control packets and data packets, the mesh delivery traffic indication message (DTIM) interval is first divided into contention period and data transmission period. To reduce the hardware requirements in design, we require a mesh point (MP) only equips a single transceiver to support multichannel environment. To provide higher performance and network capacity than the original MDA for wireless mesh LAN, we proposed a multichannel MDA (MMDA) algorithm. However, the MMDA algorithm may suffer from the resource waste problem when wireless mesh LAN is at heavy-loading situation, so this paper proposes a dynamic adjustable contention period (DACP) mechanism to solve this problem. In addition, we use an adaptive backoff process (ABP) to improve the fairness of the MMDA algorithm. The theoretical analysis gives the upper limit of the throughput for the DACP mechanism. The simulation experiments clearly show the results in multichannel wireless mesh LAN environment that the proposed scheme performs better than the MMDA algorithm and the enhanced distributed channel access (EDCA) in throughput, average waiting time, and packet drop ratio.

A wireless network simulator based on design patterns for WiMAX and LTE

To study wireless network, a network simulator always is an important tool for researchers to evaluate their theories. If a selected simulator inherently has poor architecture, the maintenance, will become more difficult in the future. To increase the flexibility of a simulators architecture, the use of design patterns as the norms of system architecture design is suggested in this paper. We propose a network simulator architecture, named as CCGns, which is a discrete-event virtual network simulator and follows the IEEE 802.16-2009 standard. The main contribution of CCGns is to propose five aspects: a scalable MAC messages management and processing architecture, an applicable for multi-hop relay network architecture, a two-stage minimum variance bandwidth allocation algorithm, a comparable compound factors-based common scheduler operating interface architecture, and an exchangeable frame structure architecture for WiMAX and LTE. In the aspect of expanding module function, we show the simulation results of using uniform, random, or round-robin scheduling to allocate bandwidth resource. We try to replace the WiMAX frame structure with LTE frame structure, and demonstrate the system performance of the relay network architecture for WiMAX and LTE protocol. We hope this study will benefit researchers who need to implement their network simulators.