Skip to main content

Downlink LoRaWAN® multicast packets

This topic describes reference information about downlink LoRaWAN® multicast packets.

Multicast​

Multicast allows a group of devices to receive the same downlink packet at the same time by transmitting it only once by the base station. It offers significant downlink capacity gain and optimizes the usage of the radio resources.

A multicast group is composed of LoRaWAN® devices implementing:

  • A regular unicast ABP or OTAA device, associated with a first set of {DevEUI, DevAddr, NwkSKey, AppSKey} for ABP and {DevEUI, AppKey} for OTAA

  • A virtual ABP device of Class B or C, associated with another set of {DevEUI, DevAddr, NwkSKey, AppSKey} pre-shared by all members of the multicast group.

Multicast downlink packets are represented with a special multicast flag .

In the expandable panel, the class of the multicast group is indicated: Multicast class C.

The same downlink multicast packet may be transmitted displayed several times in Wireless Logger. This happens when the initial transmission of the downlink multicast packet was not successful on all the base stations involved in the multicast session. In this case, the LRC reattempts to transmit again the downlink packet to via the base station that reported transmission failure on the previous attempt. The maximum number of LRC attempts is configured in the multicast connectivity plan associated with the subscriber's multicast group. By default, it is set to 3 transmissions.

Example This downlink multicast packet has been transmitted more than once by the LRC. Notice the downlink frame counters 10774 and 10775:

See Downlink metadata columns and Downlink expandable panel.

Multicast summary report​

For each downlink multicast packet, Wireless Logger displays a multicast summary report. The purpose of this report is to give the effective radio frequency transmission status of the downlink multicast packet.

Note Effective radio frequency transmission only ensures that the downlink packet has effectively been transmitted by an LRR base station. It does not guarantee that the device has received it.

An example of multicast summary report is provided below, it is represented by the symbol.

In this example, the multicast transmission was successful on the two base stations participating to the multicast session.

In case of transmission failure on one or several LRR base stations, either after the first transmission attempt by the LRC or after the maximum number of transmission attempts, the multicast summary report provides the distribution of LRR failure delivery causes.

Transmission status shows multicast downlink transmission status:

Transmission statusExplanation
PARTIALSome LRRs failed to transmit the downlink packet. Another attempt will be made to transmit the packet to theses LRRs.
SUCCESSAll LRRs successfully transmitted the downlink packet.
ABORTEDSome LRRs failed to transmit the downlink. No more attempt will be made to transmit the packet to theses LRRs (maximum number of attempts already reached).
Cause valueCategory name
AxTransmission slot busy
- (A0) Radio stopped
- (A1) Downlink radio stopped
- (A2) Ping slot not available (Class B multicast only)
- (A3) Radio busy
- (A4) Listen before talk
- (A5) Radio board error
BxReceived too late for ping slot
- (B0) Too late for ping slot
DxDuty cycle or gateway constraint
- (D0) Duty cycle constraint detected by LRR
- (DA) Duty cycle constraint detected by LRC
- (DB) Max dwell time constraint detected by the LRC
- (DC) No GPS-synchronized LRR detected by the LRC (Class B multicast only)
- (DD) No LRR connected detected by the LRC
- (DF) Wrong NetID
ExFrame expired before transmitting
- (E0) Max delay for Class C - 60 seconds

Example In the following multicast summary report, we can see that a transmission slot has been twice busy (A3) while the failure causes of the gateway constraint have occurred 7 times (D0) and 3 times (DC).

Last updated on