5G New Radio channel coding for messaging in Smart Grid

https://doi.org/10.1016/j.segan.2021.100495Get rights and content

Abstract

The integration of the fifth generation of mobile communications (5G) into the distribution network has the potential to empower Advanced Metering Infrastructure (AMI) and Phasor Measurement Unit (PMU) applications, thus further advancing the concept of Smart Grid (SG). This paper analyzes the compatibility of 5G-NR (New Radio) standard-recommended coding schemes: Low-Density Parity-Check (LDPC) and Polar coding with message formats for generalized AMI and PMU communication recommended by standards IEEE Std 1703 and IEEE Std C37.118.2, respectively. Two standard-defined examples of communication sessions have been considered to determine the required 5G-NR transmission channel and associated coding scheme to be used for AMI and PMU-specific messages. The corresponding simulations have been performed following the specifics and boundaries defined by communication standards for 5G, AMI, and PMUs. In the AMI use case, simulation results indicate LDPC code superiority leading to the recommendation to be used for all message formats. PMU use case results reveal the Polar code application benefits for command messaging and its potential to be used for data messaging instead of LDPC code, which would require future adjustments of PMU data message format and further research on latency issues.

Introduction

An increasing number of smart devices and the realization of the Internet of Things (IoT) vision require fast, highly reliable, and safe communication. It is expected that the 5G, the fifth generation of mobile communications, will be capable to answer adequately to a broad scope of novel applications characterized with large connection density, very high traffic intensity, and very high mobility. Compared with the 3G that is operator-centric and 4G that is service-oriented, 5G is a user-centric concept and it supports a new radio access technology called 5G-NR (New Radio) and an enhanced core network called NGC (Next Generation Core) [1], [2].

Smart grid (SG) is seen as a solution for globally increasing energy requirements by adding novel information and communication technologies (ICTs) to the traditional grid and integrating renewable sources. Highly flexible, secured, and two-way communication is crucial for the realization of SG vision in the real world. Among well-known wired and wireless communication technologies, the 5G, thanks to its performances, holds the potential to revolutionize the energy sector like nothing else before.

There are three major 5G-NR usage scenarios defined through the 3rd Generation Partnership Project (3GPP) (Fig. 1) [3]:

  • Enhanced mobile broadband (eMBB) provides greater bandwidth, higher data rates, higher data traffic, and higher mobility, hence resulting in an enhanced and seamless user experience at the end.

  • Ultra-reliable and low-latency communication (URLLC) is meant for mission-critical applications (applications that have very low-latency and extreme reliability).

  • Massive machine-type communication (mMTC) technology provides connectivity of a huge number of IoT battery-powered, low cost, and low data rate devices.

Typical devices used in a nowadays distribution systems that could be connected to the future 5G network are also shown in Fig. 1. Remote control of circuit breakers is expected to reduce time of electricity interruption. Electrical appliances could be remotely controlled by distribution system operators to implement demand side management functions. Relay protection units could benefit from mutual communication in terms of improvement of sensitivity, selectivity, and tripping time.

Among the many devices required for advanced SG operation, Smart Meters (SM) and Phasor Measurement Units (PMU) are inevitable. Advanced Metering Infrastructure (AMI) is being massively deployed in SG. AMI facilitates two-way communication between SMs and meter data management units which can be achieved using cellular technology [4]. The AMI is an ICT infrastructure that automatically gathers information to monitor, control, and calculate customers billing for further processes [5]. AMI meters shall be able to store 5-min interval data for a minimum of 45 days for four channels [6] with typical reporting rates of 1 data frame per 15 or 30 min. Since the millions of SMs are already deployed in the existing distribution systems [7] and based on the typical SM reporting rates, AMI requires mMTC technology. Effective implementation of wide-area monitoring, protection, control, and self-healing functions in SG requires PMUs [8]. Required reporting rates for PMU can be higher than 50 data frames per second for 50 Hz power systems with overall delays in the range 20–50 ms (sampling window, measurement filtering, PMU processing, and communication system delays) [9]. The number of PMUs in distribution systems is not expected to be large due to high investment costs. PMUs will be used only for the most important operating functions in SG, thus they will be installed only at the most important buses. The previous considerations of reporting rate, delay, and the number of PMUs, together with high-reliability requirements for control and protection applications, indicate the URLLC technology requirement. The key issue to be considered is a requirement of simultaneous usage of mMTC and URLLC technologies in SG. To enable simultaneous AMI and PMU applications over the same 5G communication network, both mMTC and URLLC should be supported. Network slicing is one of the most promising approaches to enable communication requirements of heterogeneous devices [10]. Smart grid 5G slice deployment involves virtualized infrastructure layers [11].

5G NR standard is being continuously developed through 3GPP with still many open questions related to mMTC and URLLC technologies. Channel coding consideration plays a very important role in future 5G technologies as it significantly affects the latency and reliability of communication systems. 5G channel coding schemes have been already tested and validated for eMBB technology. Two capacity-achieving channel coding schemes of low-density parity-check (LDPC) codes and Polar codes have been adopted for 5G where the former is for user data and the latter is for control information [12]. LDPC codes offer more flexibility in terms of a variable code rate and transport block length, and they also support high throughput. Polar codes outperform LDPC codes in error-correcting capability for short transport blocks.

Validation of 5G channel coding performance for SG-specific applications is not an easy task. The selection of proper coding scheme for applications in SG depends on standards ANSI C12.22/IEEE Std 1703 [13] and IEEE Std C37.118.2 [9], defining communication protocols for AMI and PMUs, respectively. In the previous research paper [14], LDPC and polar coding techniques have been compared on a single example of the short command message for PMU. It has been concluded that polar coding outperforms LDPC coding when considering Bit Error Rate (BER) performance. Thus, polar coding has been recommended to be used for command messaging in the SG. Therefore, previous research has been focused only on a special type of message in SG. Command messages are important only for specific remote-control applications such as turn on/off devices (circuit breakers, PMUs, etc.). Since earlier defined standards for AMI and PMUs [9], [13] already contain functional requirements for the general communication system, it is necessary to check for corresponding compliance of the 5G NR standard [3]. Besides compatibility requirements, the error-correcting capability and latency remain the main factors relevant for selecting channel coding schemes in SG-specific applications. The 5G channel coding schemes should be tested and validated on standard-based message formats and according to standard-based communication sessions for AMI and PMUs.

Hence, there are two main research objectives considered in this paper. The first one is to determine which of the 5G channel coding techniques performs better for the entire standard-based communication sessions related to PMU and AMI applications. It is mandatory to conduct research on the error correcting capabilities of 5G coding techniques prior to making decision on their selection for standard-defined messages used in AMI and PMU communication. The second research goal is to consider the compatibility between already used standards for AMI and PMU communication [9], [13] and the newly developed 5G communication standards [3], mainly in terms of message structure and length limitations. The power system industry already uses standards [9], [13] and now it is required to make research towards the transition to 5G communication.

This paper is organized as follows. Typical standard-based communication sessions for AMI and PMUs are described in Section 2. The implementation steps and the comparative analysis of LDPC and Polar coding schemes are presented in Section 3. LDPC and Polar coding schemes are tested and validated based on the BER performance for the cases of standard-based AMI and PMU message formats and different channel models. The simulation results are presented in Section 4. Section 5 gives a brief summary of the research and conclusion remarks.

Section snippets

Standard-based communication sessions for AMI and PMU

The IEEE 2030-2011 standard [15] defines the communication architecture of the SG. The communication technologies currently deployed in the power system need to be reconsidered and newly analyzed to find the possibilities of their utilization in SG. Wider coverage area, high data rates, greater bandwidth, well-established infrastructure, and low maintenance justify the use of cellular communications for information exchange among different components in the SG environment [16].

Communication

5G channel coding schemes

Since the main problem of communication is to transmit data from sender to receiver (over the physical medium that is subject to noise) in a reliable and efficient manner, correction of transmission errors or Forward Error Correction (FEC) is of immense importance. In other words, channel coding in mobile communication plays a key role in increasing the reliability of the wireless communication system. The performances of adequate channel code are flexibility, high reliability, low cost, low

AMI and PMU standard-based message formats

Transport block contents and sizes for different AMI and PMU messages can be determined according to standards [13] and [9], respectively. Messages used in typical communication sessions for SM (Fig. 2a) and PMU (Fig. 2b) have transport block sizes as given in Table 1.

Read request and read response message examples used in AMI communication session are modified according to Offset/Octet-count method for partial access to Table 23 of SM which is intended for billing purposes. Table 23 contains

Conclusion

Reliable two-way 5G-NR communication in SG-specific applications, such as AMI and PMU, is dependent on selected transmission channels and associated coding schemes. The consideration of 5G-NR communication-empowered AMI and PMU requires the research on compatibility between specific communication standards dealing with AMI and PMU, and 5G-NR communication standard. In this paper, we focus on getting the answer on BER performance of 5G coding techniques for the entire standard-based

CRediT authorship contribution statement

Mirjana Maksimović: Conceptualization, Methodology, Investigation, Software, Writing. Miodrag Forcan: Conceptualization, Methodology, Investigation, Data curation, Visualization, Writing.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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