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LoRaWAN® Regional Parameters RP002-1.0.4 ©2022 LoRa Alliance ® Page 89 of 101 The authors reserve the right to change specifications without notice. 4 Physical Layer 1796 1797 The LoRaWAN uses a physical layer to communicate with other devices. Three physical 1798 layers are currently supported through the long range (LoRa), Long-Range Frequency 1799 Hopping Spread Spectrum (LR-FHSS), and Frequency shift keying (FSK) modulations. 1800 4.1 LoRa Description 1801 4.1.1 LoRa Packet Physical Structure 1802 LoRa messages use the radio packet explicit header mode, in which the LoRa physical header 1803 (PHDR) plus a header CRC (PHDR_CRC) are included. 36 In explicit header mode, the PHDR 1804 specifies the payload length in bytes, the forward error correction rate, and the presence of an 1805 OPTIONAL CRC for the payload. The integrity of the payload is protected by a CRC for uplink 1806 messages. LoRaWAN beacons are transmitted using LoRa modulation in implicit header 1807 mode with no payload CRC. The size of the payload depends on the beacon's data rate. In 1808 implicit header mode, neither the PHDR nor PHDR_CRC are present. 1809 The PHDR , PHDR_CRC and payload CRC fields are inserted by the radio transceiver. 1810 PHY: 1811 Size 8 Symbols 4.25 Symbols 8 Symbols L bytes (from PHDR) 2 Bytes Packet Structure Preamble Synchronization Word PHDR PHDR_CRC PHYPayload CRC (uplink only) Table 97: LoRa PHY structure 1812 4.1.2 LoRa Settings 1813 In order to be fully compliant with LoRaWAN, an end-device SHALL configure the LoRa 1814 physical layer as described in Table 98 and Table 99: 1815 1816 Parameter Uplink Value Downlink Value Class B Beacon Preamble size 8 symbols 10 symbols SyncWord 0x34 (Public) 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 98: LoRa physical layer settings 1817 The LDRO parameter stands for Low Data Rate Optimizer. If set, the modulation alphabet is 1818 reduced to allow better synchronization and tracking on the receiver. Since such 1819 synchronization is more difficult on low data rates, it is enabled only on the lowest data rates. 1820 It also increases the tolerance for multipath delays from simultaneous transmissions (that gain 1821 does not depend on data rate). This parameter is not signaled in the PHDR. Therefore, it needs 1822 to be set to a constant value for each data rate. 1823 1824 36 See the LoRa radio transceiver datasheet for a description of LoRa radio packet implicit/explicit modes.

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