Weilian Su

Wireless sensor networks: a survey

This paper describes the concept of sensor networks which has been made viable by the convergence of micro-electro-mechanical systems technology, wireless communications and digital electronics. First, the sensing tasks and the potential sensor networks applications are explored, and a review of factors influencing the design of sensor networks is provided. Then, the communication architecture for sensor networks is outlined, and the algorithms and protocols developed for each layer in the literature are explored. Open research issues for the realization of sensor networks are also discussed.

A survey on sensor networks

The advancement in wireless communications and electronics has enabled the development of low-cost sensor networks. The sensor networks can be used for various application areas (e.g., health, military, home). For different application areas, there are different technical issues that researchers are currently resolving. The current state of the art of sensor networks is captured in this article, where solutions are discussed under their related protocol stack layer sections. This article also points out the open research issues and intends to spark new interests and developments in this field.

Time-diffusion synchronization protocol for wireless sensor networks

In the near future, small intelligent devices will be deployed in homes, plantations, oceans, rivers, streets, and highways to monitor the environment. These devices require time synchronization, so voice and video data from different sensor nodes can be fused and displayed in a meaningful way at the sink. Instead of time synchronization between just the sender and receiver or within a local group of sensor nodes, some applications require the sensor nodes to maintain a similar time within a certain tolerance throughout the lifetime of the network. The Time-Diffusion Synchronization Protocol (TDP) is proposed as a network-wide time synchronization protocol. It allows the sensor network to reach an equilibrium time and maintains a small time deviation tolerance from the equilibrium time. In addition, it is analytically shown that the TDP enables time in the network to converge. Also, simulations are performed to validate the effectiveness of TDP in synchronizing the time throughout the network and balancing the energy consumed by the sensor nodes.

InterPlaNetary internet: state-of-the-art and research challenges

The developments in the space technologies are enabling the realization of deep space scientific missions such as Mars exploration. InterPlaNetary (IPN) Internet is expected to be the next step in the design and development of deep space networks as the Internet of the deep space planetary networks. However, there exist significant challenges to be addressed for the realization of this objective. Many researchers and several international organizations are currently engaged in defining and addressing these challenges and developing the required technologies for the realization of the InterPlaNetary Internet. In this paper, the current status of the research efforts to realize the InterPlaNetary Internet objective is captured. The communication architecture is presented, and the challenges posed by the several aspects of the InterPlaNetary Internet are introduced. The existing algorithms and protocols developed for each layer and the other related work are explored, and their shortcomings are pointed out along with the open research issues for the realization of the InterPlaNetary Internet. The objective of this survey is to motivate the researchers around the world to tackle these challenging problems and help to realize the InterPlaNetary Internet.

Multiple RFID Tags Access Algorithm

One of the main problems that affect the data integrity of passive RFID systems is the collision between the tags. A popular anticollision algorithm which dominates the standards in HF and UHF passive RFID systems is framed slotted Aloha (FSA) and some variations of FSA. Throughput and average time delay of the RFID system which determines the performance/efficiency of the system are reduced rapidly when the number of tags inside the interrogation zone is increased. Using larger frame sizes is not always the solution. This paper discusses and compares the existing protocols, and proposes a variation of FSA, called progressing scanning (PS) algorithm. The PS algorithm divides the tags in the interrogation zone into smaller groups and gives the reader the ability to communicate with each of them. For performance analysis, the PS algorithm was evaluated with the parameters of a typical passive RFID system at 2.5 GHz. The results showed that the PS algorithm can improve the efficiency of the RFID system and provide a reliable solution for cases with a high density of tags in the area (over 800 tags).

The state of the art in interplanetary Internet

Developments in space technologies are enabling the realization of deep space scientific missions such as Mars exploration. Interplanetary (IPN) Internet is expected to be the next step in the design and development of deep space networks as the Internet in the space. However, there are significant challenges to be addressed for the realization of this objective. This article captures the current state of the art and open research challenges, and intends to motivate researchers around the world to tackle these challenging problems and help realize the IPN Internet.

Channel propagation characteristics of wireless MICAz sensor nodes

Wireless sensor nodes are envisioned to be deployed in the urban and indoor environments. With the advancement of technologies, such as nano-wires and molecular circuits, sensor nodes will become small, cheap and power efficient. At present, many researchers are implementing and developing protocols with MICAz motes. Thus, it is important to understand the propagation characteristics of the MICAz motes. Antenna patterns and interferences are measured. In addition, software models of the mote and environment are created with the CST Microwave Studio and Rhino; afterwards, they are feed into Urbana and are simulated. The simulated and measured results are compared, thus, validating the correctness of models, which are later used to simulate the urban and indoor environments in Urbana.

Communication protocols for sensor networks

This chapter describes about the challenges and essence of designing communication protocols for wireless sensor networks. The sensor nodes are densely deployed and collaboratively work together to provide higher quality sensing in time and space as compared to traditional stationary sensors. The applications of these sensor nodes as well as the issues in the transport, network, datalink, and physical layers are discussed. For applications that require precise timing, different types of timing techniques are explored.

Overview of Communication Protocols for Sensor Networks

© 2005 by Taylor & Francis Group, LLC. As the technology for wireless communications advances and the cost of manufacturing a sensor node continues to decrease, a low-cost but yet powerful sensor network may be deployed for various applications that can be envisioned for daily life. Although each sensor node may seem to be much less capable than a traditional stationary sensor, a collective effort of the sensor nodes may provide sensing capabilities in space and time that surpass the stationary sensor.

The jitter time-stamp approach for clock recovery of real-time variable bit-rate traffic

When multimedia streams arrive at the receiver, their temporal relationships may be distorted due to jitter. Assuming the media stream is packetized, the jitter is then the packets arrival time deviation from its expected arrival time. There are various ways to reduce jitter, which include synchronization at the application layer, or synchronization at the asynchronous transfer mode (ATM) adaptation layer (AAL). The new source rate recovery scheme called jitter time-stamp (JTS) provides synchronization at the ATM adaptation layer 2 (AAL2) which is used to carry variable bit-rate traffic such as compressed voice and video. JTS is implemented, and experiments have shown that it is able to recover the source rate.