Implementation of Embedded Testbeds Using USRP and GNU-Radio for Performance Measurement and Analysis of PPS and PCO-Based Time Synchronizations

Implementation of Embedded Testbeds Using USRP and GNU-Radio for Performance Measurement and Analysis of PPS and PCO-Based Time Synchronizations

Hyun Jae Park, Cheol-woong Lee, Taeyoung Shin, Byeong-hee Roh, Soo Bum Park, Jungwook Choi
Copyright: © 2021 |Pages: 11
DOI: 10.4018/IJITN.2021010103
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Abstract

In wireless networks, time synchronization is one of the key functions for the MAC and the physical layer because it is important to accurately transmit data by maintaining the order and consistency of transmission between nodes. The time synchronization can be divided into centralized and distributed methods and there are many synchronization schemes. However, there are little testbeds for comparing and analyzing various time synchronization schemes in a real environment. Most papers analyze the proposed time synchronization algorithm by simulation, and some testbeds are also configured for the proposed scheme only. In this paper, the authors build embedded testbeds using USRP and GNU-Radio. The two typical methods of the centralized and decentralized time synchronizations, PPS, and PCO-based schemes, respectively, are implemented on the testbeds and their performances are measured and analyzed in the real environment.
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PPS-based Centralized Time Synchronization

PPS (Pulse Per Second)-based time synchronization is a scheme in which one or more reference nodes generates a pulse to all the nodes with every predetermined period. The receiving nodes detect the valid signal and perform time synchronization.

Figure 1 shows an example of PPS-based time synchronization. Let Sthreshold be the threshold of the reference signal which the receiving nodes recognize the signal and the Tp be the predetermined period of the reference signal. The reference node generates a reference signal its power exceeding Sthreshold with every Tp, which is the predetermined period of the reference signal. Then the other three receiving nodes detect the valid signal using Sthreshold and perform time synchronization at the detection point.

Figure 1.

Example of an PPS-based time synchronization

IJITN.2021010103.f01
Figure 2.

Illustration of the interaction between two PCOs

IJITN.2021010103.f02
Figure 3.

Simplified block diagram of USRP-based SDR system

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