When streaming data from a router to the Gateway device, as when metering data is downloaded from an energy meter, the Router device will continuously receive data on the UART. Data will be transmitted along the established hop-path from the Router to the gateway. At every hop, there will be a short delay for handshaking and re-transmission of the packet. The typical delay per hop for packets with full payload contents, with default configuration settings, is approximately 100ms. Due to the mechanisms that handle Listen Before Talk (LBT), handshaking and re-transmission, the time is an average estimate. Time between two payload packets is on average two hop-periods, as a new packet may not be transmitted until the previous packet has travelled some distance from the originating Router. This means the maximum download speed is going to be approximately 200ms (three hops) per packet. With a maximum payload size of 120 bytes, the typical download speed will be 120/0.2 = 600 bytes/second (4800 bps). Except when downloading from a Router device that is linked directly to the Gateway device, number of hops will have little effect on download time. Routers that connect directly to the Gateway will however have shorter download time, as the packets are only travelling a single hop and are not redistributed after the first hop. Given above conditions, a typical download time for 2kbytes of data will be 1024*2/ 600 = 3.4 seconds when data is hopping in a network with reliable connections. For connections directly to a Gateway device, the download speed will be closer to 1k Bytes/second. For networks with poor connectivity, download times may be longer, due to retransmissions of packets.
Last Update: February 12, 2018