Detail of GB/T 20851.1-2019

Introduction of GB/T 20851.1-2019

Codeofchina.com 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 20851 comprises the following parts under the general title Electronic toll collection - dedicated short range communication: —— Part 1: Physical layer; —— Part 2: Data link layer; —— Part 3: Application layer; —— Part 4: Equipment application; —— Part 5: Test methods of the main parameters in physical layer. This is part 1 of GB/T 20851. This part is developed in accordance with the rules given in GB/T 1.1-2009. This part replaces GB/T 20851.1-2007 Electronic toll collection - Dedicated short range communication - Part 1: Physical layer. In addition to editorial changes, the following main technical changes have been made with respect to GB/T 20851.1-2007: —— the technical requirements are modified for downlink, the contents of "downlink" are moved into the "technical requirements for downlink" (see clause 6 of this standard; 5.2 of Edition 2007); —— the requirements are added for downlink antenna side lobe level, antenna front-to-back ratio, 14 kHz square wave wake-up signal accuracy, OBU maximum input signal power, OBU cochannel interference rejection ratio, OBU adjacent channel interference rejection ratio, OBU blocking interference rejection ratio and other indicators (see clause 6 of this standard); —— the requirements are modified for downlink modulation factor, OBU reception bandwidth, preamble and other indicators (see clause 6 of this standard; 5.2 of Edition 2007); —— the technical requirements are modified for uplink, the contents of "uplink" are moved into the "technical requirements for uplink" (see clause 7 of this standard; 5.3 of Edition 2007); —— the requirements are added for the uplink RSU maximum input signal power, RSU cochannel interference rejection ratio, RSU adjacent channel interference rejection ratio, RSU blocking interference rejection ratio, RSU reception bandwidth and other indicators (see clause 7 of this standard); —— the requirements are modified for the uplink adjacent channel leakage power ratio, modulation factor, bit clock accuracy, preamble and other indicators (see clause 7 of this standard; 5.3 of Edition 2007); This part was proposed by and is under the jurisdiction of the National Technical Committee 268 on Intelligent Transportation Systems of Standardization Administration of China. The previous edition replaced by this part is as follows: —— GB/T 20851.1-2007. Electronic toll collection - Dedicated short range communication - Part 1: Physical layer 1 Scope This part of GB/T 20851 specifies the basic requirements of the physical layers used for dedicated short range communication of electronic toll collection and technical requirements for the downlink and uplink. This part is applicable to electronic toll collection system for highways and urban roads, and may be used as a reference for fields of automated vehicle identification, vehicle access control system, etc. 2 Normative references The following referenced documents are 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 9410-2008 General specification for antennas used in the mobile communications GB/T 13622-2012 Terminology for radio regulation GB/T 14733.7-2008 Terminology for telecommunication - Oscillations, signals and related devices GB/T 14733.9-2008 Terminology for telecommunication - Radio wave propagation GB/T 20839-2007 Intelligent transport systems - General terminology 3 Terms and definitions For the purposes of this document, the terms and definitions given in GB/T 9410-2008, GB/T 13622-2012, GB/T 14733.7-2008, GB/T 14733.9-2008, and GB/T 20839-2007 and the following apply. 3.1 wakeup the process by which an on-board unit (OBU) transits from a dormant state to an operating state 3.2 preamble the presignal of the physical layer frame information which is independent from the link layer and may be a modulated or unmodulated carrier 3.3 post-amble The postsignal of the physical layer frame information which is independent from the link layer and may be a modulated or unmodulated carrier 4 Symbols and abbreviations 4.1 Symbols For the purposes of this document, the following symbols apply. dBm: the ratio of power to 1 mW. RSU1: transmitting antenna of roadside unit. RSUr: receiving antenna of roadside unit. 4.2 Abbreviations For the purposes of this document, the following abbreviations apply. ASK: Amplitude Shift Keying BER: Bit Error Rate e.i.r.p: Equivalent Isotropically Radiated Power ETC: Electronic Toll Collection FSK: Frequency Shift Keying OBU: On Board Unit RSU: Roadside Unit XPD: Cross Polarization Discrimination 5 General requirements The physical layer includes uplink and downlink, and each link shall meet the corresponding technical requirements. Physical layer links involve two categories of requirements: Categories A and B. Category A shall be applicable to ETC applications. Category B may also support high rate data transfer applications on the basis of being applicable to ETC applications. The requirements for carrier frequency, e.i.r.p and spurious emission shall conform to the regulations of relevant competent departments. Refer to the Notice on the use of 5.8 GHz frequency band for regulations on frequency band management. 6 Technical requirements for downlink The technical requirements for downlink are shown in Table 1. Table 1 Technical requirements for downlink S.N. Parameters Category A Category B 1 Carrier frequency Channel 1 5.830 GHz 5.830 GHz Channel 2 5.840 GHz 5.840 GHz 2 Occupied bandwidth ≤5 MHz ≤5 MHz 3 Frequency tolerance ±10×10-6 ±5×10-6 4 e.i.r.p ≤ + 33 dBm ≤ + 33 dBm 5 Spurious emission 30 MHz ~ 1,000 MHz ≤ -36 dBm/100 kHz ≤ -36 dBm/100 kHz 2,400.0 MHz ~ 2,483.5 MHZ ≤ -40 dBm/1 MHz ≤ -40 dBm/1 MHz 3,400 MHz ~ 3,530 MHZ ≤ -40 dBm/1 MHz ≤ -40 dBm/1 MHz 5,725 MHz ~ 5,850 MHZa ≤ -33 dBm/100 kHz ≤ -33 dBm/100 kHz Others 1 GHz ~ 20 GHz ≤ -30 dBm/1 MHz ≤ -30 dBm/1 MHz 6 Adjacent channel leakage power ratio ≤ -30 dB ≤ -30 dB 7 Half power lobe width of antenna Horizontal plane < 38° < 38° Vertical plane < 45° < 45° 8 Antenna side lobe level < -20 dB < -20 dB 9 Antenna front-to-back ratio > +25 dB > +25 dB 10 Antenna polarization Right-handed circular polarization Right-handed circular polarization 11 XPD Maximum gain direction RSUt ≥ 15 dB RSUt ≥ 15 dB -3 dB area RSUt ≥ 10 dB RSUt ≥ 10 dB 12 Modulation mode ASK FSK 13 Modulation factor/ modulation error Modulation factor: 0.7~0.9 Modulation error: -200 kHz~+200 kHz 14 Frequency offset — ± 512 kHz 15 Encoding mode FM0 MANCHESTER 16 Bit rate 256 kbit/s 1 Mbit/s 17 Bit clock accuracy ± 100×10-6 ± 20×10-6 18 OBU wakeup methodb 15 ~ 17 periods of 14 kHz square wave 15 ~ 17 periods of 14 kHz square wave 19 14 kHz square wave wakeup signal accuracy ± 0.5 kHz ± 0.5 kHz 20 OBU wakeup time < 5 ms < 5 ms 21 OBU wakeup sensitivity ≤ -40 dBm ≤ -40 dBm 22 OBU receiving sensitivity ≤ -50 dBmc ≤ -70 dBm 23 OBU maximum input signal power ≥ -20 dBm ≥ -20 dBm 24 OBU cochannel interference rejection ratio < + 15 dB < + 15 dB 25 OBU adjacent channel interference rejection ratio < + 15 dB < + 15 dB 26 OBU blocking interference rejection ratio < - 10 dB < - 10 dB 27 OBU reception bandwidth Maximum: 5.825 GHz~5.845 GHz, minimum: 5.8285 GHz~5.8315 GHz, 5.8385 GHz~5.8415 GHz Maximum: 5.825 GHz~5.845 GHz, minimum: 5.8285 GHz~5.8315 GHz, 5.8385 GHz~5.8415 GHz 28 BER Within 10 × 10-6 Within 1 × 10-6 29 Preambled 16-bit "1" plus 16-bit "0" 16-bit "1" plus 16-bit "0" 30 Post-amble 1~8 bits 1~8 bits a It corresponds to emission on a frequency, or frequencies, which are outside the 2.5 times the carrier channel bandwidth. b The RSU is required to transmit this waveform; the OBU may choose to be wakeup by this waveform or by normal communication frame signals. c The OBU receiving sensitivity shall be greater than the wakeup sensitivity by over 5 dB. d The time interval between the end of the 14 kHz square wave wakeup signal and the start of the preamble shall not be greater than 72 μs. 7 Technical requirements for uplink

Contents of GB/T 20851.1-2019

Foreword III 1 Scope 2 Normative references 3 Terms and definitions 4 Symbols and abbreviations 5 General requirements 6 Technical requirements for downlink 7 Technical requirements for uplink Bibliography