Hong Seong Park

Maximum allowable delay bounds of networked control systems

This paper proposes a new method to obtain a maximum allowable delay bound for a scheduling of networked control systems. The proposed method is formulated in terms of linear matrix inequalities and can give a much less conservative delay bound than the existing methods. A network scheduling method is presented based on the delay obtained through the proposed method, the bandwidth of a network is allocated to each node and the sampling period of each sensor and controller is determined. The presented method can handle three types of data (periodic data, sporadic data, and message) and guarantees real-time transmission of periodic and sporadic data, and minimum network utilization for non-real time message.

A scheduling method for network-based control systems

This paper presents a scheduling method for network-based control systems with three types of data (periodic data, sporadic data, and messages). As a basic parameter for the scheduling method for network-based control systems, a maximum allowable delay bound is used,which guarantees stability of network-based control systems and is derived from characteristics of the given plant using the presented theorems. The presented scheduling method for network-based control systems can adjust the sampling period as small as possible, allocate the bandwidth of the network for three types of data, and exchange the transmission orders of data for sensors and actuators. In addition, the presented scheduling method guarantees real-time transmission of sporadic and periodic data, and minimum utilization for nonreal-time messages. The proposed method is shown to be useful by examples.

Packet Error Rate Analysis of ZigBee Under WLAN and Bluetooth Interferences

In this paper, the performance of IEEE 802.15.4 ZigBee under the interference of IEEE 802.11b wireless local area network (WLAN) and/or Bluetooth is evaluated using an analytic model for the coexistence among ZigBee, WLAN, and Bluetooth. The packet error rate (PER) is evaluated, where the PER is obtained from the bit error rate (BER) and the collision time. The BER is obtained from the signal-to-interference-plus-noise ratio (SINR). Finally, the analytic results are validated by simulations.

Packet Error Rate Analysis of IEEE 802.11b under IEEE 802.15.4 Interference

This paper presents an interference model of IEEE 802.11b wireless local area network (WLAN) affected by IEEE 802.15.4 wireless personal area network (WPAN). The packet error rate (PER) of the IEEE 802.11b under the interference of the IEEE 802.15.4 is analyzed, and is obtained by the bit error rate (BER) and the collision time. The safe distance ratio can be obtained from the PER. Further, this paper suggests a packet length to reduce the effect of the IEEE 802.15.4 interference and obtain a maximum throughput of the IEEE 802.11b. The analytic results are validated using the simulation

Mutual interference analysis of IEEE 802.15.4 and IEEE 802.11b

IEEE 802.15.4 and IEEE 802.11b, operating in the 2.4GHz unlicensed industrial scientific medical (ISM) frequency band, may lead to signal interference and result in significant performance degradation when devices are collocated in the same environment. The main goal of this paper is to evaluate the effect of mutual interference on the performance of IEEE 802.15.4 and IEEE 802.11b systems. An analytic model for interference between IEEE 802.15.4 and IEEE 802.11b is suggested. The packet error rate (PER), transmission delay, and throughput are evaluated for IEEE 802.15.4 and IEEE 802.11b. The power spectral density of the IEEE 802.11b is considered in order to determine in-band interference power of the IEEE 802.11b to the IEEE 802.15.4. The simulation results by OPNET are shown to validate the numerical analysis.

An Enhanced CSMA-CA Algorithm for IEEE 802.15.4 LR-WPANs

Two mechanisms are proposed to enhance throughput and energy efficiency of IEEE 802.15.4 CSMA-CA. The first one is an enhanced collision resolution (ECR) mechanism that adjusts the backoff exponent (BE) based on both consecutive clear channel assessment (CCA) busy results and a packet transmission. The second one is an enhanced backoff (EB) mechanism that shifts the range of backoff counters by utilizing the CCA outcome. The simulation results demonstrate that the proposed mechanisms significantly enhance both throughput and energy efficiency of IEEE 802.15.4

EHRP: Enhanced hierarchical routing protocol for zigbee mesh networks ee

This letter proposes the enhanced hierarchical routing protocol (EHRP) for ZigBee mesh networks. The EHRP finds the shortest hierarchical path based on the ZigBee hierarchical addressing scheme. The EHRP provides efficient and reliable routing paths. In addition, the EHRP is completely compatible with ZigBee v.1.0 standard. Simulation results demonstrate that the EHRP reduces routing overhead and route discovery delay of ZigBee mesh networks significantly compared with the hierarchical routing protocol (HRP) defined in ZigBee v1.0.

Stability and a scheduling method for network-based control systems

This paper presents network-induced maximum allowable delay bounds for stability of network-based control systems and a scheduling method for network-based control systems by using these bounds. The maximum allowable delay bounds for stability of network-based control systems are obtained using the Lyapunov theorem. Also a scheduling method considering three kinds of data (periodic, real-time asynchronous, and nonreal-time asynchronous data) is presented, which allocates the bandwidth of a network for each node and determines the sampling time of each sensor and controller. This method also guarantees the real-time transmission of the real-time synchronous data and periodic data, and the transmission of the nonreal-time asynchronous data. To show usefulness of the proposed method, the proposed method is tested in two types of network protocols such as the token control and the central control.

Lecture notes in computer science: packet error rate analysis of IEEE 802.15.4 under IEEE 802.11b interference

In this paper, the packet error rate (PER) of IEEE 802.15.4 low rate wireless personal area network (WPAN) under the interference of IEEE 802.11b wireless local area network (WLAN) is analyzed. The PER is obtained from the bit error rate (BER) and the collision time. The BER is obtained from signal to noise and interference ratio. The power spectral density of the IEEE 802.11b is considered in order to determine in-band interference power of the IEEE 802.11b to the IEEE 802.15.4. The simulation results are shown to validate the numerical analysis.

Aggregation Time Control Algorithm for Time constrained Data Delivery in Wireless Sensor Networks

This paper proposes and evaluates a new aggregation algorithm in wireless sensor networks with time constraint. In the proposed algorithm, each aggregation node controls its aggregation time in order to aggregate and transfer data from child nodes within a given deadline of the sink node. The objective of the algorithm is to deliver the time constrained data within time bound while reducing the energy consumption resulted from the number of transmissions. Based on the aggregation tree, the proposed algorithm considers the number of the child nodes to determine the aggregation time. The performance of the proposed algorithm is evaluated using both the miss ratio and the aggregation gain