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TC23-00017 The LoRa Alliance © 2019 3 of the parameters present in the LinkAdrReq command. An end-device SHOULD accept the channel mask controls present in LinkADRReq even when the ADR bit is not set. When the downlink ADR bit is set, it informs the end-device that the Network Server is in a position to send ADR commands. The device MAY independently set/unset the uplink ADR bit. When the downlink ADR bit is unset, it signals the end-device that due to rapid changes of the radio channel, the network temporarily cannot estimate the best data rate. In that case the device has the choice to either • Uunset the ADR uplink bit, and control its uplink data rate, transmit power and channel plan following its own strategy. This SHOULD be the typical strategy for a mobile end- device. • Ignore it (keep the uplink ADR bit set) and apply the normal ADR backoff algorithm in the absence of downlinks. This SHOULD be the typical strategy for a stationary end- device[DK1]. The ADR bit MAY may be set and unset by the end-device or the Network on demand. However, whenever possible, the ADR scheme should SHOULD be enabled to increase the battery life of the end-device and maximize the network capacity. Note: Even mobile end-devices are actually immobile most of the time. So depending on its state of mobility, an end-device can request the network to optimize its data rate using the uplink ADR bit. Default Tx Power is the maximum transmission power allowed for the device considering device capabilities and regional regulatory constraints. The dDevice shall use this power level, until the network asks for lessattempts to change the power level, throughby using the LinkADRReq MAC command. If an end-device wishes to check for connectivity loss or if an end-device's whose data rate is optimized by the network to use a data rate higher than its lowest availabledefault data rate, or a TXPower lower than its default TXPower, the end deviceit periodically needs to validate that the network still receives the uplink frames. Each time the uplink frame counter is incremented (for each new uplink frame, repeated transmissions do not increase the frame counter), the device increments an ADR_ACK_CNT counter. After ADR_ACK_LIMIT uplinks (ADR_ACK_CNT >= ADR_ACK_LIMIT) without receiving any a class A downlink response, itthe end device sets the ADR acknowledgment request bit (ADRACKReq) on uplink transmissions. The network is required to respond with a downlink frame within the next ADR_ACK_DELAY frames,. aAny received class A downlink frame received following an uplink frame resets the ADR_ACK_CNT counter., uUpon receipt reception of any class A downlink the end-device MUST clear the ADRACKReq bit. The downlink ACK bit does not need to be set as any response class A downlink frame received byduring the receive slot of the end-device indicates that the gateway network has still received the uplinks from this device. If no reply class A downlink frame is received within the next ADR_ACK_DELAY uplinks (i.e., after a total of ADR_ACK_LIMIT + ADR_ACK_DELAY transmitted frames), the end-device MAY MUST try to regain connectivity by first stepping up setting the transmit power to the default power if possible then switching to the next lower data rate that provides a longer radio range. The end-device will MUST further lower its data rate step by step every time ADR_ACK_DELAY are transmittedis reached. Once the device has completed the ADR backoff algorithmreached the lowest data rate without receiving a class A downlink frame, it MUST re-enable all default uplink frequency channels and reset nbTrans to its default value of 1. The ADRACKReq SHALL not be set if the device uses its lowest available data rate because in that case no action can be taken to improve the link range.[GR2]

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