15.2 Beacon frame content

1. The beacon payload BCNPayload consists of a network common part and a gateway-
2. specific part.

14

15 The network common part contains a network identifier NetID to uniquely identify the

1. network for which the beacon is sent, and a timestamp Time in seconds since 00:00:00
2. Coordinated Universal Time (UTC), 1 January 1970. The integrity of the beacon‘s network
3. common part is protected by an 8 or 16 bits CRC depending on PHY layer parameters. The
4. CRC-16 is computed on the NetID+Time fields as defined in the IEEE 802.15.4-2003 section
5. 7.2.1.8. When an 8 bits CRC is required then the 8 LSBs of the computed CRC-16 are used.
6. For example: This is a valid EU868 beacon frame:

22 AA BB CC | 00 00 02 CC | 7E | 00 | 01 20 00 | 00 81 03 | DE 55

23 Bytes are transmitted left to right. The corresponding field values are: 24

25 The CRC-16 of the NetID+Time fields is 0xC87E but only the 8LSBs are used in that case 26

27 The seven LSB of the NetID are called NwkID and match the seven MSB of the short 28 address of an end-device. Neighboring or overlapping networks must have different 29 NwkIDs.

©2016 LoRa™ Alliance Page 52 of 70

The authors reserve the right to change specifications without notice.

LoRaWAN Specification

1. The gateway specific part provides additional information regarding the gateway sending a
2. beacon and therefore may differ for each gateway. The RFU field when applicable (region
3. specific) should be equal to 0. The optional part is protected by a CRC-16 computed on the
4. GwSpecific+RFU fields. The CRC-16 definition is the same as for the mandatory part.
5. For example: This is a valid US900 beacon:

1. Listening and synchronizing to the network common part is sufficient to operate a stationary
2. end-device in Class B mode. A mobile end-device should also demodulate the gateway
3. specific part of the beacon to be able to signal to the network server whenever he is moving
4. from one cell to another.