HIPERSIM: A Sense Range Distinctive Simulation Environment for HiperLAN Systems

This paper presents the simulator “HIPERSIM” which was developed and used to examine the behavior of HIPERLAN (Type 1). HIPERSIM simulates the HIPERLAN network under various conditions, assuming that the communication range and the sense range (signal detection range) of a node are different. In a wireless LAN, like HIPERLAN, the medium access protocol, the hidden nodes, the packet forwarding and the power saving mechanism are important issues that significantly affect the overall performance. The intention is to provide a HIPERLAN specialized tool (HIPERSIM) which can simulate most of the features of this WLAN protocol, in order to examine the performance of HIPER-LAN. The main focus is to simulate the channel access mechanism accurately, so as to examine the effectiveness of the EY-NPMA protocol, and underline its advantages and the elements that need improvement. Also, in HIPERSIM, there is emphasis on the “hidden nodes” issue. More specifically, we distinguish between the communication range and the signal detection range of a node, since this is a characteristic of the wireless nature and it affects the network operation. The simulation results show that EY-NPMA is effective and suitable for WLANs. Probably there could be some improvement in order to avert the collisions close to the receiver. © 2003, SAGE Publications. All rights reserved

An Occupancy Based Cyber-Physical System Design for Intelligent Building Automation

Cyber-physical system (CPS) includes the class of Intelligent Building Automation System (IBAS) which increasingly utilizes advanced technologies for long term stability, economy, longevity, and user comfort. However, there are diverse issues associated with wireless interconnection of the sensors, controllers, and power consuming physical end devices. In this paper, a novel architecture of CPS for wireless networked IBAS with priority-based access mechanism is proposed for zones in a large building with dynamically varying occupancy. Priority status of zones based on occupancy is determined using fuzzy inference engine. Nondominated Sorting Genetic Algorithm-II (NSGA-II) is used to solve the optimization problem involving conflicting demands of minimizing total energy consumption and maximizing occupant comfort levels in building. An algorithm is proposed for power scheduling in sensor nodes to reduce their energy consumption. Wi-Fi with Elimination-Yield Nonpreemptive Multiple Access (EY-NPMA) scheme is used for assigning priority among nodes for wireless channel access. Controller design techniques are also proposed for ensuring the stability of the closed loop control of IBAS in the presence of packet dropouts due to unreliable network links