The throughput test is performed using unicast iPerf. Figure 5-11 shows the throughput of different PHYs, using the maximize responsiveness network configuration. The test is carried out by sending 1200-byte payload packets for 60 seconds between one router node, connected to a border router, as shown in Figure 5-12.

The results for each different PHY in the one router node throughput test can be seen in Figure 5-11.

Figure 5-11 shows the measured results showing increased throughput for higher data rates as expected. The throughput test is also repeated with large network configuration using the same configuration as the join tests for a given data rate to study impact of throughput for one pair of devices from number of hops and other neighboring devices and is shown in Figure 5-12.

After a full join of the network shown above, the throughput on each hop is tested by selecting three different router nodes from this hop and sending 1200-byte payload packets for 60 seconds between the border router and each node. This increases the maximum throughput until the packet error rate is greater than 2%. The test is repeated for every hop (1-5) and network configuration (maximize responsiveness, balanced mode, maximize scalability). The results are outlined in Figure 5-13.

The throughput test is performed using unicast iPerf-based traffic, which injects back-to-back UDP packets into the network. In the default TI Wi-SUN configuration, broadcast dwell time and broadcast interval are set to 250ms and 1s, respectively, implying that only 75% of airtime is available for unicast traffic. Considering the 50kbps data rate, this implies a maximum possible network capacity for unicast traffic as 37.5kbps.

For the maximize scalability configuration, which has the least control overhead and leaves most of the available bandwidth to data throughput, the result throughput is approximately 24kbps. This is 65% of network capacity, as expected for a CSMA based network.

For the maximize responsiveness configuration, a data throughput of approximately 12kbps (approximately 33% of available capability) implies that the remaining 32% , which were available in the maximize scalability configuration, is taken over by additional network control traffic.

As the number of hops increases, spatial diversity helps increase maximum parallel transmissions compared to total number of hops needed to cross for a given packet.

The frequency hopping scheme in the Wi-SUN stack utilizes the network spectrum in a multihop scenario. Theoretically, if everything else is good and the throughput of a one hop network is X, then the throughput of a 2 hop network is ½X (only 1 parallel transmission to cross 2 hops). The throughput of a 3 hop network is also ½X (can be either 1 or 2 parallel link transmissions to cross 3 hops). Similarly, the throughput for 4 hop network and 5 hop network is also ½X.

In the maximize scalability configuration, where most of the network capacity is used for application throughput, this pattern is more apparent. For the maximize responsiveness and balanced mode configurations, the application throughput does not show significant proportional loss for higher hops since the protocol overhead from all nodes in network dominates the overall traffic which scales with additional hops. Throughput tests with other data rates are expected to show similar trends depending on available network capacity.