Issue link: https://read.uberflip.com/i/1428383
LoRaWAN 1.0.3 Specification ©2018 LoRa™ Alliance Page 64 of 72 The authors reserve the right to change specifications without notice. In this example the network has two confirmed data frames to transmit to the end-device. The 1647 frame exchange is initiated by the end-device via a normal "unconfirmed" uplink message on 1648 channel A. The network uses the first receive window to transmit the Data0 with the bit 1649 FPending set as a confirmed data message. The device acknowledges the reception of the 1650 frame by transmitting back an empty frame with the ACK bit set on a new channel B. 1651 RECEIVE_DELAY1 seconds later, the network transmits the second frame Data1 on channel 1652 B, again using a confirmed data message but with the FPending bit cleared. The end-device 1653 acknowledges on channel C. 1654 1655 Figure 31: Downlink timing diagram for frame-pending messages, example 2 1656 In this example, the downlink frames are "unconfirmed" frames, the end-device does not need 1657 to send back and acknowledge. Receiving the Data0 unconfirmed frame with the FPending 1658 bit set the end-device sends an empty data frame. This first uplink is not received by the 1659 network. If no downlink is received during the two receive windows, the network has to wait 1660 for the next spontaneous uplink of the end-device to retry the transfer. The end-device can 1661 speed up the procedure by sending a new empty data frame. 1662 Note: An acknowledgement is never sent twice. 1663 The FPending bit, the ACK bit, and payload data can all be present in the same downlink. For 1664 example, the following frame exchange is perfectly valid. 1665 1666 1667 Figure 32: Downlink timing diagram for frame-pending messages, example 3 1668 The end-device sends a "confirmed data" uplink. The network can answer with a confirmed 1669 downlink containing Data + ACK + "Frame pending" then the exchange continues as 1670 previously described. 1671 18.4 Data-Rate Adaptation during Message Retransmissions 1672 When an end-device attempts the transmission of a "confirmed' frame toward the network it 1673 expects to receive an acknowledgement in one of the subsequent reception slot. In the 1674 absence of the acknowledgement it will try to re-transmit the same data again. This re- 1675 gateway End-point Data uplink {cu} Data0+F_P {cd} void {cu+1} ok void {cu+3} ok ok Data1+F_P {cd} void {cu+2} gateway End-point Confirmed Data uplink {cu} Confirmed Data0+F_P+ACK {cd} ACK {cu+1} Confirmed Data1+F_P {cd+1} ACK {cu+3} ok void {cu+2} Receiving a frame without the ACK bit set , server retransmits Data1 ok ok Confirmed Data1+F_P {cd+1} (diag 2)