Pranesh Sthapit

Smart digital door lock for the home automation

In this paper, we propose a smart digital door lock system for home automation. A digital door lock system is equipment that uses the digital information such as a secret code, semi-conductors, smart card, and finger prints as the method for authentication instead of the legacy key system. In our proposed system, a ZigBee module is embedded in digital door lock and the door lock acts as a central main controller of the overall home automation system. Technically, our proposed system is the network of sensor nodes and actuators with digital door lock as base station. A door lock system proposed here consists of RFID reader for user authentication, touch LCD, motor module for opening and closing of the door, sensor modules for detecting the condition inside the house, communication module, and control module for controlling other modules. Sensor nodes for environment sensing are deployed at appropriate places at home. Status of individual ZigBee module can be monitored and controlled by the centralized controller, digital door lock. As the door lock is the first and last thing people come across in entering and leaving the home respectively, the home automation function in digital door lock system enables user to conveniently control and monitor home environment and condition all at once before entering or leaving the house. Furthermore, it also allows users to remotely monitor the condition inside the house through Internet or any other public network. The biggest advantage of our proposed system over existing ones is that it can be easily installed when and where necessary without requirement of any infrastructures and proper planning.

Medium reservation based sensor MAC protocol for low latency and high energy efficiency

In this paper, we present a new MAC protocol satisfying with both high energy efficiency and low transmission latency at the same time over wireless sensor network, named as medium reservation preamble based MAC (MRPM). Unlike other synchronized duty cycle MACs, MRPM does not have separate time frames for SYNC and data traffics. Both traffics are integrated in a short listen period. Also, the channel contention is excluded from listen period and transferred to new period called contention period. The contention period precedes the listen period, and only transmitters wake up in this contention period and contend for medium reservation, whereas non-transmitters bypass it. These approaches enable MRPM to achieve adaptive duty cycle and quite short listen period. Moreover, MRPM uses carrier sensing information for advanced adaptive listening which makes packets to travel multiple hops away in a single sleep/listen cycle. The simulation results verify that MRPM has features of high energy efficiency and low latency.

Effects of Radio Triggered Sensor MAC Protocol over Wireless Sensor Network

In this paper, we present a new medium access control (MAC) protocol called Radio Triggered Sensor MAC (RTM) protocol that is expected for the next generation sensor network. The proposed RTM is a cross-layer MAC protocol which utilizes the passive radio sensor hardware for efficient medium access. The passive radio sensors harvest the energy from the wireless signal and energize itself. The passive radio sensor is responsible for waking up the sleeping node. The sensor nodes stay in the sleep mode with their normal communication radio turned off. In order to communicate with neighboring sensor nodes, a wake-up signal is transmitted. This wake-up signal energizes the passive radio sensors waking up the sensor nodes. After the data communication, the sensor nodes are turned off. We compared RTM with Sensor MAC (S-MAC) protocol under various duty cycles through simulation in Network Simulator (ns-2). The simulation results show that RTM is 2 times energy efficient than S-MAC (with 20% duty cycle) at message period of 3 secs and 6 times at message period of 15 secs. Also, the latency of RTM is very close to the latency of S-MAC without duty cycle. This MAC protocol showing less energy consumption and faster data delivery features will be very valuable to specific applications such as wireless body area network (WBAN) and security monitoring system.

Coordinator assisted passive discovery for mobile end devices in IEEE 802.15.4

Energy conservation has been the key focus of research in low-rate wireless personal area networks (WPANs). Several algorithms have been proposed to dynamically adjust the duty cycle of nodes in beacon-enabled WPANs. Increasing beacon interval for lowering the duty cycle of end devices decreases the probability of fast node association, when passive scan is used. Moreover, the requirement of performing coordinator discovery increases with mobility of end devices because of frequent cell changes. In this paper, we propose a scheme for facilitating prompt passive discovery of coordinator(s) by mobile end devices. Simulation analysis has shown that proposed scheme can swiftly discover the coordinator(s) irrespective of beacon interval length.

Passive Synchronization Based Energy-Efficient MAC Protocol over M2M Wireless Networks

Providing diverse quality-of-service (QoS) with ultra-low power consumption and mobility support is the most important and challenging issue in machine-to-machine (M2M) networks. In a typical beacon-enabled network, nodes need to wake up for receiving periodic beacon in order to maintain synchronization. Here, we present a new MAC protocol called passive-synchronization-based energy-efficient MAC (PSMAC) that synchronizes nodes in their sleep state by using interrupt generated from the proposed radio-triggered hardware. In order to activate the radio-triggered hardware, the synchronization frame is broadcast, but in a separate channel called synchronization channel, so that interrupts are not generated during data transmission. This synchronization frame is also used for providing the fast and energy-efficient association. Network information is embedded into the synchronization frame so that mobile nodes can learn about their neighbors just by scanning the synchronization channel. Furthermore, by positioning the beacon period after the contention access period, PSMAC provides fast and preemptive slot allocation that can handle diverse QoS requirements. We compare PSMAC with IEEE 802.15.4 and show that PSMAC has much better performance in node association time, energy efficiency, and faster data delivery at the cost of additional radio-triggered hardware and a dedicated channel.

Medium Reservation Based MAC for Delay-Sensitive Wireless Sensor Network

In this paper, we present a new MAC protocol satisfying with both high energy efficiency and low transmission latency at the same time over wireless sensor network, named as medium reservation preamble based MAC (MRPM). The proposed MRPM is a synchronized duty cycle MAC protocol. MRPM has three main features. The first feature is that MRPM does not have separate time frames for Sync and data traffics. Both traffics are integrated in a short listen period. The second feature is the novel approach of medium reservation done by a transmitter. That is, the contention period precedes the listen period, and only transmitters wake up in this contention period and contend for medium reservation, avoiding the non-transmitters from idle listening. The above-mentioned two features have made MRPM to achieve listen period of very short length, which make our protocol energy efficient. As the final feature, MRPM uses carrier sensing information for advanced adaptive listening which makes packets travel multiple hops away in a single sleep/listen cycle. We compared MRPM with S-MAC and TEEM protocols through ns-2 simulation. The simulation results show that MRPM outperforms S-MAC and TEEM at both metrics of energy efficiency and latency.

Data Fragmentation Scheme with Block ACK in Wireless Sensor Networks

Reduction of power consumption and networks life expansion are crucial for a wireless sensor network (WSN). This is typically performed by introducing low duty cycle in a sensor node. A special challenge in WSNs is transmission of a large amount of data, like images and video, that is becoming more and more required in various applications. A wireless network is very much prone to communication errors. Thus, for the efficient design, the large data messages are broken down into smaller fragments and those smaller fragments are transmitted. But this approach introduces the burden of exchanging redundant control packets increasing the energy consumption and the transmission delay. In this paper, we propose a data fragmentation scheme using a block acknowledgment (BA) mechanism to minimize the number of the control packets and delayed transmission caused by fragmentation. We implemented the proposed scheme in sensor MAC (S-MAC) and compared it with the original S-MAC through ns-2 simulation. The simulation results verify that our scheme can decrease energy consumption as well as end to end delay.

Intelligent network synchronization for energy saving in low duty cycle MAC protocols

Several MAC protocols such as S-MAC, T-MAC, DSMAC, and TEEM have exploited scheduled sleep/listen cycles to conserve energy in sensor networks. These protocols use periodic SYNC packet in their SYNC period to follow the same schedule with their neighbors. We have found that these protocols use around 40% of their listen period for SYNC period. In an average, unused SYNC periods consume more than 20% of the total energy consumption. In this paper, we analyze the periodic nature of SYNC packet and develop a new algorithm, named as intelligent network synchronization (INS), which exploits the periodic nature of SYNC packet to reduce energy consumption. The proposed INS makes nodes bypass their own SYNC period by monitoring sleep/listen cycles of their each neighbor. We evaluate INS through both mathematical analysis and simulation. These results show the achievement of up to 25% of energy saving.

Medium Reservation Preamble Based Medium Access Control for Wireless Sensor Network

In this paper, we present the new energy efficient MAC protocol for WSN, named as medium reservation preamble based MAC (MRPM). Inspired by S-MAC, the proposed MRPM is also a synchronized duty cycle MAC protocol. However, unlike S-MAC, the proposed protocol doesn’t have separate time frame for Sync and data traffics. Both traffics are integrated in a short listen period. The listen period is further shortened by excluding the channel contention from listen period and transferring it to new period called contention period. The contention period precedes the listen period, and only transmitters wake up in this contention period and contend for medium reservation, avoiding the receivers from idle listening. Now, with these features, our MRPM is much energy efficient than the conventional synchronized duty cycle MAC protocols. We compared MRPM with S-MAC and TEEM protocols through ns-2 simulation. The simulation results show that MRPM is 55% more energy efficient than S-MAC and 35 % more than TEEM.

Handover Strategies in Beacon-Enabled Mobile Sensor Network

IEEE 802.15.4 has become the de facto standard in many areas of wireless sensor network (WSN) such as body area networks, industrial automation, and healthcare domains. In many WSN applications, the sensor nodes could be mobile, and indoor communications are limited in terms of signal propagation. Therefore, a large number of access points need to be deployed to cover large areas. To maintain the sensor connectivity, sensor node should frequently change the serving access point by performing a mechanism known as a handover. We observed that the amount of time required for the association process is the key reason IEEE 802.15.4 is unable to handle the mobility. In this paper, we show what is required for node mobility support and propose three strategies for the support. First, the proactive algorithm is developed to anticipate the future link breakage. Second, a new greedy scanning technique is presented, which prevents nodes from scanning multiple channels. Third, the coordinator selection algorithm is developed which chooses the best coordinator that gives the longest connectivity time reducing the handover frequency. Experimental results have verified that our schemes work well in the mobile sensor network environment.