The Power Control feature in Zigbee Sub-Ghz
Per the description (5.14.5 Power Control) in Zigbee smart energy specification, the Smart Energy device should support power control feature. The power control feature works only on Sub-GHz interface and not on the 2.4 GHz interface. In this KBA, I will introduce what is function of power control and how it works in EmberZnet.
What is the function of power control?
The function of power control is to optimize the transmission power on each Sub-GHz link. The sleepy end device and its parent will use an optimized TX power after negotiation.
How it works?
First, the initial power level negotiation occurring during the joining process, which ensures that the optimum signal level (defined as 20dB above the sensitivity limit) is maintained at the receiver for good reception. The functional description of initial power negotiation occurring when using an EBR and EB during initial joining is explained below.
After the initial power control negotiation, the TX power values used for the link remain unchanged until the below network layer communication finished.
Second, when the end device joined to network, it will send out End Device Timeout Request to its parent and its parent sends back End Device Timeout Response which includes the info whether it supports Power Negotiation or not. If its parent supports Power Negotiation feature, the end device shall generate a Link Power Delta request as a unicast to its parent, then periodically wake up and send a Link Power Delta request later.
The Link Power Delta request interval can be configurated in “Zigbee stack library” plugin, the default value is 300 seconds.
Upon receipt of a Link Power Delta Request, the parent will set the new optimized TX power and then send out a Link Power Delta Response to the end device. When the end device receives the Link Power Delta Response, it will set the new optimized TX power. Till here, the power of the link between end device and parent is optimized.
Its parent receipts the EBR and extracts the TX power IE, then calculates what power is necessary to overcome this path loss. After that, the new TX power and the end device's EUI64 will be stored in parent’s power entry.
Is it mac layer responsibility to do this extraction from the TX power IE, calculation of path loss and adding the new TX power to the table ? or this would be done on upper layers ?
Hi Ahmed Khaled,
it is already handled by stack, so the APP layer doesn't need to handle it.