15.1 Beacon physical layer

3 Besides relaying messages between end-devices and network servers, all gateways

  1. participate in providing a time-synchronization mechanisms by sending beacons at regular
  2. fixed intervals configurable per network (BEACON_INTERVAL). All beacons are transmitted
  3. in radio packet implicit mode, that is, without a LoRa physical header and with no CRC being
  4. appended by the radio.

8

PHY Preamble BCNPayload
  1. The beacon Preamble begins with (a longer than default) 10 unmodulated symbols. This
  2. allows end-devices to implement a low power duty-cycled beacon search.
  3. The beacon frame length is tightly coupled to the operation of the radio Physical layer.
  4. Therefore the actual frame length might change from one region implementation to another.
  5. The changing fields are highlighted in Bold in the following sections.

15.1.1 EU 863-870MHz ISM Band

  1. The beacons are transmitted using the following settings
DR 3 Corresponds to SF9 spreading factor with
125 kHz BW
CR 1 Coding rate = 4/5
frequency 869.525 MHz This is the recommended frequency allowing
+27 dBm EIRP. Network operators may use
a different frequency as long as ETSI
compliance is achieved
16The beacon frame content is:
Size (bytes) 3 4 1 7 2
BCNPayload NetID Time CRC GwSpecific CRC

| 17 |

15.1.2 US 902-928MHz ISM Band

18 The beacons are transmitted using the following settings:
DR 10 Corresponds to SF10 spreading factor
with 500kHz bw
CR 1 Coding rate = 4/5
frequencies 923.3 to 927.5MHz Beaconing is performed on the same
with 600kHz steps channel that normal downstream traffic as
defined in the Class A specification
19 The downstream channel used for a given beacon is:
20 Channel = * ( )+
  1.  whereby beacon_time is the integer value of the 4 bytes ―Time‖ field of the beacon
  2. frame
  3.  whereby beacon_period is the periodicity of beacons , 128 seconds
  4.  whereby floor(x) designates rounding to the integer immediately inferior to x

25

©2016 LoRa™ Alliance Page 51 of 70

The authors reserve the right to change specifications without notice.

LoRaWAN Specification
1 Example: the first beacon will be transmitted on 923.3MHz , the
2 second on 923.9MHz, the 9th beacon will be on 923.3MHz again.
3
4
5
6
Beacon channel nb Frequency [MHz]
0 923.3
1 923.9
2 924.5
3 925.1
4 925.7
5 926.3
6 926.9
7 927.5

7

8

9 The beacon frame content is:

Size (bytes) 3 4 2 7 1 2
BCNPayload NetID Time CRC GwSpecific RFU CRC

10

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