Issue link: https://read.uberflip.com/i/1540208
Regional Parameters RP002-1.0.5 ©2022-2025 LoRa Alliance ® Page 103 of 116 The authors reserve the right to change specifications without notice. 5 Physical Layer 2090 2091 The LoRaWAN uses a physical layer to communicate with other devices. Three physical 2092 layers are currently supported through the long range (LoRa), Long-Range Frequency 2093 Hopping Spread Spectrum (LR-FHSS), and Frequency shift keying (FSK) modulations. 2094 5.1 LoRa Description 2095 5.1.1 LoRa Packet Physical Structure 2096 LoRa uplink and downlink messages use the radio packet explicit header mode, in which the 2097 LoRa physical header (PHDR) plus a header CRC (PHDR_CRC) are included. In explicit header 2098 mode, the PHDR specifies the payload length in bytes, the forward error correction rate, and 2099 the presence of an OPTIONAL CRC for the payload. The integrity of the payload is protected 2100 by a CRC for uplink messages. LoRaWAN beacons are transmitted using LoRa modulation in 2101 implicit header mode with no payload CRC. The size of the payload depends on the beacon's 2102 data rate. In implicit header mode, neither the PHDR nor PHDR_CRC are present. 2103 The PHDR, PHDR_CRC and payload CRC fields are inserted by the radio transceiver. 2104 Size 8 Symbols 4.25 Symbols 8 Symbols L bytes (from PHDR) 0 / 2 Bytes Packet Structure Preamble SyncWord PHDR PHDR_CRC PHYPayload CRC (presence defined in following sections) Table 111: LoRa PHY structure 2105 Note: Data sheets for the LoRa radio transceiver contain detailed 2106 descriptions of the LoRa radio packet implicit/explicit modes. 2107 5.1.2 LoRa Settings 2108 In order to be fully compliant with LoRaWAN, an end-device SHALL configure the LoRa 2109 physical layer as described in Table 112 and Table 113: 2110 2111 Parameter Uplink Value Downlink Value Class B Beacon Preamble size 8 symbols 10 symbols SyncWord SF12 to SF7: 0x34, SF6 to SF5: 0x12 Header type Explicit Implicit CRC presence True False Coding Rate 4/5 Spreading Factor Defined by the data rate, specified in each region Bandwidth IQ polarization Not-inverted Inverted Not-inverted Table 112: LoRa physical layer settings 2112 The LDRO parameter stands for Low Data Rate Optimizer. If set, the modulation alphabet is 2113 reduced to allow better synchronization and tracking on the receiver. Since such 2114 synchronization is more difficult on low data rates, it is enabled only on the lowest data rates. 2115 It also increases the tolerance for multipath delays from simultaneous transmissions (that gain 2116 does not depend on data rate). This parameter is not signaled in the PHDR. Therefore, it needs 2117 to be set to a constant value for each data rate. 2118 2119 2120