Narrow band power line communication over low-voltage mains―Part 31:Narrow band orthogonal frequency division multiplexing power line―Communication physical layer specification
National Standards Technical Committee Electrical Measuring Instruments (SAC/TC 104) is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
GB/T 31983 consists of the following parts under the general title Narrow Band Power Line Communication over Low-voltage Mains:
——Part 11: 3kHz to 500kHz Frequency Bands and Classifications, Limits of Output Level and Electromagnetic Disturbances;
——Part 21: Immunity Requirements for Communication Equipment and System of 3kHz to 500kHz Frequency Bands;
——Part 31: Narrow Band Orthogonal Frequency Division Multiplexing Power Line - Communication Physical Layer Specification;
——Part 32: Narrow Band Orthogonal Frequency Division Multiplexing Power Line Communication - Data Link Layer Specification
This is Part 31 of GB/T 31983.
This part is developed in accordance with the rules given in GB/T 1.1-2009.
Attention is drawn to the possibility that some of the elements of this standard may be the subject of patent rights. The issuing body of this document shall not be held responsible for identifying any or all such patent rights.
This part was proposed by China Machinery Industry Federation.
This part is under the jurisdiction of National Standards Technical Committee Electrical Measuring Instruments (SAC/TC 104).
Introduction
Along with the rapid development of Smart Grid and IOTIPS, improvement of network and communication technology according to new demand is urgent. Power grid is a vast network connecting various electric equipment and terminals, and the data transmission and network connection between various electric equipment and terminals by utilizing power line can be realized without rewiring. Developed countries and International Standardization Organization promote communication technology and standardization with power line as medium and have successively launched standards such as ITU.g.9901/2/3/4 and IEEE 1901.2. This standard series are prepared in combination with national conditions of China against this background.
This specification of physical layer protocol supports the special frequency band of 3~500kHz, and is applicable to the data transmission and communication of data equipment through indoor or outdoor low-voltage AC distribution line or DC transmission line. This specification of physical layer protocol is based on orthogonal frequency division multiplexing (OFDM) technology and allows for specific center frequency and bandwith defined by specific application system.
Data link layer protocol may be defined based on this specification of physical layer protocol. This specification of physical layer protocol is not limited to any particular application layer protocol of narrow band power line communication, and it is applicable to various application systems of narrow band power line communication over low-voltage mains, including (but not limited to) electric energy meter automatic meter reading (AMR), AMI/AMM, smart home control, street lamp control, building intelligence, electric vehicle charge control, etc.
Narrow Band Power Line Communication over Low-voltage Mains
Part 31: Narrow Band Orthogonal Frequency Division Multiplexing Power Line - Communication Physical Layer Specification
1 Scope
This part of GB/T 31983 specifies the physical layer protocol specification of narrow band power line communication (PLC) over low-voltage mains based on orthogonal frequency division multiplexing (OFDM) technology, including physical layer protocol data unit format (PPDU), channel coding, interleaving, OFDM modulation, physical layer signal frame generation and continuous transmission modes and power-frequency synchronous zero-crossing time slot transmission mode, etc.
This part is applicable to the data transmission and communication of 3~500kHz frequency band through indoor or outdoor low-voltage AC distribution line or DC transmission line. A complete PLC system composed of multiple communication nodes which is established on low-voltage distribution network based on physical layer protocol specification of this part also includes data link layer (DLL, which is composed of medium access control sublayer MAC and logical link control sublayer LLC) and applications related to specific application situations. Typical application situations of narrow band power line communication over low-voltage mains includes electric energy meter automatic meter reading (AMR), AMI/AMM, smart home control, street lamp control, intelligent building, four-meter automatic reading and other applications of Smart Grid, e.g. electric vehicle charge control.
This part is also applicable to medium-voltage power line communication and urban-rural long-distance power line communication.
2 Normative References
The following referenced document is indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 31983.11-2015 Narrow Band Power Line Communication over Low-voltage Mains - Part 11: 3kHz~500kHz Frequency Bands and Classifications, Limits of Output Level and Electromagnetic Disturbances
3 Terms, Definitions, Symbols and Abbreviations
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
power line communication
the communication or control realized between data terminals by transmission with power line as physical medium through modulating information data to appropriate carrier frequency
3.1.2
power line carrier communication
i.e. power line communication
3.1.3
narrow band power line communication
the power line communication with carrier frequency at frequency band of 3~500kHz
3.1.4
power line communication over low-voltage mains
the power line communication with low-voltage distribution line as medium
3.1.5
power line communication lower layer protocol
power line communication lower layer protocol includes physical layer and data link layer (composed of medium access control sublayer and logical link control sublayer)
3.1.6
application of power line communication
specific application system of power line communication established on power line communication lower layer protocol, which is provided with determined service function and application layer protocol
3.2 Symbols
For the purposes of this document, the following symbols and codes apply.
b——the width of bit group loaded to subcarrier.
DL——the length factor of data carried by payload.
G——the number of subcarrier groups.
LMPDU——the number of MPDU bytes to be transmitted in MAC layer.
m——the number of lines of interleaver.
MOFDM——the number of OFDM at maximum single-frame payload.
N——the sampling number of IFFT.
NCP——the sampling number of cyclic prefixes.
n——the number of OFDM symbols.
3.3 Abbreviations
For the purposes of this document, the abbreviations specified in Table 1 apply.
Table 1 Abbreviations
AI Application Interface
AMI Advanced Metering Infrastructure
AMR Automatic Meter Reading
AMM Advanced Metering Management
APP Application
APS Application Support Layer
ASG Active Subcarrier Group
BPSK Binary Phase Shift Keying
CENELEC European Committee for Electrotechnical Standardization
CRC Cyclic Redundancy Check
CSMA/CA Carrier Sense Multiple Access with Collision Avoidance
CP Cyclic Prefix
DID Domain Identification
DLL Data Link Layer
DM Domain Master Node
DSC Data Subcarrier
FCI Frame Control Information
FEC Forward Error Correction
FFT Fast Fourier Transform
FSC Forbidden Subcarrier
FT Frame Type
GI Guard Interval
HCS Header Check Sum
HEM Home Energy Management
IBSC In-band Subcarrier
IEC International Electrotechnical Committee
IEEE Institute of Electrical and Electronics Engineers
IFFT Inverse Fast Fourier Transform
ITU International Telecommunications Union
LSB Least Significant Bit
LLC Logical Link Control
MAC Medium Access Control
MDI Media Dependent Interface
MPDU MAC Protocol Data Unit
MSB Most Significant Bit
MSC Masked Subcarrier
MSG Masked Subcarrier Group
OBSC Out-of-band Subcarrier
OFDM Orthogonal Frequency Division Multiplexing
OSI Open System Interconnection
PHY Physical Layer
PSC Pilot Subcarrier
PLC Power Line Communication
PMI Physical Media Independent Interface
PN Pseudo-random Noise Sequence
PSDU PHY Service Data Unit
QPSK Quaternary Phase Shift Keying
QAM Quaternary Amplitude Modulation
RS Reed-Solomon Code
TM Tone Map
TN Terminal Node
USC Usable Subcarrier
4 Network Model
4.1 PLC Domain
PLC domain refers to a power line communication category established on low-voltage distribution network, which is provided with the following characteristics:
a) A PLC domain includes a domain management node (DM) and multiple terminal equipment nodes (TN). DM, which is composed of networking management and routing management, etc., is responsible for managing terminal equipment nodes in domain. Each node has a medium access control (MAC) address which must be unique in a domain.
b) A low-voltage distribution network may have multiple PLC domains, and each domain has a domain identification (DID) which must be unique in a low-voltage distribution network. The classification of these domains is logical other than physical, and adjacent domains may be partially overlapped. Therefore, a node in certain domain may "hear" a node in another domain in physical layer. Certain measures, including wave trap isolation, domain identification, access mechanism of time domain or frequency domain multiplexing channel, etc., shall be taken to eliminate or reduce the effect of inter-domain crosstalk on PLC communication.
c) PLC domain may be an "incompletely connected" domain, i.e. point to point communication between two nodes in domain cannot be realized in physical layer due to causes such as channel noise, interference and signal attenuation. Therefore, communication between nodes in domain may make use of relay forwarding by other nodes.
4.2 Reference Model
4.2.1 General
PLC domain protocol reference model and its corresponding relationship with OSI reference model are shown in Figure 1. This model includes physical layer (PHY), medium access control sublayer (MAC), logical link control sublayer (LLC), application support layer (APS) and application (APP). PHY layer, MAC sublayer and LLC sublayer constitute a lower layer protocol independent of specific application, providing service for application through APS layer and application interface (AI). In actual system, application corresponds to a specific application situation and application protocol, e.g. AMR, home energy management (HEM), etc.
Figure 1 PLC Reference Model
4.2.2 Main function and service of each layer
APS layer provides adaptation function for application protocol data to pass through DLL layer for transmission. Application interface (AI) is defined by specific application situation, generally including physical or logical interface and interaction protocol. Application submits to-be-transmitted data and receives data through AI. APS conducts data transmitting and receiving by data link layer service.
LLC sublayer and MAC sublayer constitute data link layer (DLL). DLL provides terminal-terminal data link for application. LLC sublayer is responsible for establishing, managing and controlling network route, including node relay forwarding control. MAC sublayer is responsible for the access control of medium shared by power line, including carrier sense multiple access with collision avoidance (CSMA/CA) algorithm, so as to avoid transmission collision.
Physical layer is responsible for MAC sublayer data channel coding, OFDM modulation, PHY signal frame generation and coupling of signal to power line for transmission. In receiving direction, physical layer will carry out demodulation and decoding for signal frame received from power line, recover data link layer data and submit it to MAC sublayer.
Medium independent PHY interface (PMI) is a PHY service interface independent of specific physical medium. PMI is a functional interface defined in service primitive, including PHY data and management service.
Physical layer is connected with physical medium through medium dependent interface (MDI); MDI depends on specific physical medium and includes electrical index requirements of signal as well as the coupling and connection specifications of signal and physical medium.
Moreover, physical layer, MAC sublayer, LLC sublayer and APS layer provide management service respectively through managing primitive PHY-MGMT, MAC-MGMT, LLC-MGMT and APS-MGMT.
4.2.3 PHY service
See Table 2 and Table 3 for data service and management service independent of specific physical medium which are provided by physical layer through PMI.
Table 2 PHY Data Service
Data service Direction Description
PHY-DATA.req DLL -> PHY DLL requests PHY to transmit MPDU
PHY-DATA.cnf PHY -> DLL PHY returns the previous PHY-DATA.req implementation result (transmitting success, transmitting failure, receiving terminal positive acknowledgement, receiving terminal negative acknowledgment, acknowledge timeout, etc.)
PHY-DATA.ind PHY -> DLL PHY transmits the received frame to MAC layer
PHY-ACK.req DLL -> PHY DLL requests PHY to transmit ACK frame
PHY-ACK.ind PHY->DLL PHY transmits the received acknowledgement frame contents to MAC layer
Table 3 PHY Management Service
Management service Direction Description
PHY-MGMT.req -> PHY Management request
PHY-MGMT.cnf PHY -> PHY returns the previous PHY-MGMT.req implementation result
PHY-MGMT.ind PHY -> PHY transmits indication relevant with physical layer management
PHY-MGMT.res -> PHY Response to PHY-MGMG.ind (local)
5 PHY Coding and Modulation
5.1 General
This physical layer is based on the narrow band OFDM technology covering 3~500kHz frequency band, and supports the continuous transmission mode or power-frequency synchronous zero-crossing time slot transmission mode of PHY signal frame.
5.2 Block Diagram for Physical Layer
Block diagram for PHY transmitting terminal is detailed in Figure 2.
Transmitting terminal completes the transformation from the input data bits to power line transmission signals. The input to-be-transmitted data bits, after bit scrambling, RS coding, convolutional coding, puncturing, bit repeating and interleaving, are subject to constellation mapping from bits to symbols; the mapped data, together with pilot data, are subject to OFDM symbol modulation with cyclic prefix insertion, windowing and overlapping, thus forming the frame part of data. The data frame part is multiplexed with preamble and frame header to form signal transmitting frame and is finally injected into power line through analog front end for transmission.
Foreword i
Introduction ii
1 Scope
2 Normative References
3 Terms, Definitions, Symbols and Abbreviations
4 Network Model
4.1 PLC Domain
4.2 Reference Model
5 PHY Coding and Modulation
5.1 General
5.2 Block Diagram for Physical Layer
5.3 Data Preprocessing
5.4 PHY Frame Format
5.5 Subcarrier
5.6 Channel Coding
5.7 OFDM Modulation
6 Signal Transmission Mode of Physical Layer
6.1 General
6.2 Continuous Transmission Mode
6.3 Power-frequency Synchronous Zero-crossing Time Slot Transmission Mode
7 PHY Service
7.1 General
7.2 Data Service
7.3 PHY Management Service
7.4 Physical Constant and Attribute
8 Requirements of Electrical Index
Annex A (Normative) Structures of CRC-5 and CRC
Annex B (Normative) Frequency Plan
Annex C (Normative) Bit Scrambling Structure
Annex D (Normative) Structure of Convolutional Coder
Annex E (Normative) Structure Diagram of Pseudo-random Sequence PNb(k) Generator
Bibliography
