Low Power, Accurate Time Synchronization MAC Protocol for Real-Time Wireless Data Acquisition

Park

Wireless Communications and Mobile Computing

et al. 2017

Generally, various traffic requirements in wireless sensor network are mostly dependent on specific application types, that is, eventdriven, continuous, and query-driven types. In these applications, real-time delivery is one of the important research challenges. However, due to harsh networking environment around a node, many researchers usually take different approach from conventional networks. In order to discuss and analyze the advantage or disadvantage of these approaches, some comprehensive survey literatures were published; however they are either out of date or compiled for communication protocols on single layer. Based on this deficiency, in this paper, we present the up-to-date research approaches and discuss the important features related to real-time communications in wireless sensor networks. As for grouping, we categorize the approaches into hard, soft, and firm real-time model. Furthermore, in all these categories, research has been focused on MAC and scheduling and routing according to research area or objective in second level. Finally, the article also suggests potential directions for future research in the field.

Section: Soft Real-time Communications In Wsnmentioning

confidence: 99%

A Survey on Real-Time Communications in Wireless Sensor Networks

Park

Wireless Communications and Mobile Computing

et al. 2017

“…In the scattered communicating network every node having each clock has a value that differs from real time (International Atomic Time (TAI) is being the best representation); no clock is perfect [21]. A quartz-based electronic clock maintains a consistent inaccuracy, but keeps imperfect time.…”

Section: Clock Drift or Clock Skewmentioning

confidence: 99%

“…In this work of the accurate clock synchronization in scattered network also overcome the problem of clock drift or clock skew. All the computer systems in the network are generally synchronized to a standard time called Coordinated Universal Time (UTC) where UTC is the primary time standard by which the world regulates time and clocks [21]- [24]. The clock supports basically three types of clocks that are-1.…”

Section: Clock Drift or Clock Skewmentioning

confidence: 99%

Performance Analysis of DTSA in Distributed Network

Masne¹,

Shrawankar²

2013

IJCA

In a distributed system, synchronization of time is an important functionality for supporting real-time scenario like online banking applications, database queries and real time applications etc. A clock synchronization is necessary to measure the duration of activities that start on one node and terminate on another one. Although the some of the existing algorithms for time synchronization depend on sending and receiving messages from different system. Scheduling such task sets with time constraints requires timing information to be accurate. Synchronizing these clocks allows services in higher layers to assume a global time within certain bounds of accuracy. The system clocks of different nodes are not works on same clock time. Usually, there is an offset between the times, so accuracy is not achieved. The clock time collection interval, in which clock time of remote nodes are collected and corrected with global time, which determines the period of the correction of the local clocks. Such a decomposition can reduce delay and achieve accuracy in network.The paper presented in approach towards Delay Tolerant Synchronization Algorithm (DTSA) which is combination of Network Time Protocol (NTP) and Delay Tolerant Protocol (DTP) which synchronizes nodes in a network with Global Time Server (GTS) using NTP. Simulation results show that the DTSA reduces delay and achieve accuracy in scattered network.

“…This forbids its use in very sparsely distributed systems, as well as in wireless or highly mobile systems where latency-balanced transmission is impractical or impossible [115].…”

Section: Synchronization Over Data Linksmentioning

confidence: 99%

“…In [115] and [118], the methods for synchronization through timing messages are divided into three categories, depending on the basic messaging step that they rely on: sender-to-receiver methods, receiver-to-receiver methods, and one-way messaging methods. The first one involves the exchange of timing messages between two nodes which then proceed to synchronize their time references to each other.…”

Section: Synchronization Over Data Linksmentioning

confidence: 99%

Development of a data acquisition architecture with distributed synchronization for a Positron Emission Tomography system with integrated front-end.

Varea¹,

Ramón²

Positron Emission Tomography (PET) is a non-invasive nuclear medical imaging modality that makes it possible to observe the distribution of metabolic substances within a patient's body after marking them with radioactive isotopes and arranging an annular scanner around him in order to detect their decays. The main applications of this technique are the detection and tracing of tumors in cancer patients and metabolic studies with small animals.The Electronic Design for Nuclear Applications (EDNA) research group within the Instituto de Instrumentación para Imagen Molecular (I3M) has been involved in the study of high performance PET systems and maintains a small experimental setup with two detector modules. This thesis is framed within the necessity of developing a new data acquisition system (DAQ) for the aforementioned setup that corrects the drawbacks of the existing one. The main objective is to define a DAQ architecture that is completely scalable, modular, and guarantees the mobility and the possibility of reusing its components, so that it admits any extension of modification of the setup and it is possible to export it directly to the configurations used by other groups or experiments. At the same time, this architecture should be compatible with the best possible resolutions attainable at the present instead of imposing artificial limits on system performance. In particular, the new DAQ system should outperform the previous one.As a first step, a general study of DAQ architectures is carried out in the context of experimental setups for PET and other high energy physics applications. On one hand, the conclusion is reached that the desired specifications require early digitization of detector signals, exclusively digital communication between modules, and the absence of a centralized trigger. On the other hand, the necessity of a very precise distributed synchronization scheme between modules becomes apparent, with errors in the order of 100 ps, and operating directly over the data links. A study of the existing methods reveals their severe limitations in terms of achievable precision. A theoretical analysis of the situation is carried out with the goal of overcoming them, and a new synchronization algorithm is proposed that is able to reach the desired resolution while getting rid of the restrictions on clock iii alignment that are imposed by virtually all usual schemes. Since the measurement of clock phase difference plays a crucial role in the proposed algorithm, extensions to the existing methods are defined and analyzed that improve them significantly. The proposed scheme for synchronism is validated using commercial evaluation boards.Taking the proposed synchronization method as a starting point, a DAQ architecture for PET is defined that is composed of two types of module (acquisition and concentration) whose replication makes it possible to arrange a hierarchic system of arbitrary size, and circuit boards are designed and commissioned that implement a realization of the architecture for the...