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In addition to wireless network resources that specify the cost to build connections, service performance highly affects the design of IIoT networks. Several service measures are identified to indicate the level of service satisfaction (while ensuring QoS), and they are extensively utilized in formulating wireless design. Service performance factors that form a set of basic metrics are data throughput, delay, coverage, and scalability.

1 Data throughput: Service requirements are specified by several data rate metrics such as real-time throughput, aggregated throughput, raw data rate, good throughput (goodput), peak and minimum throughput, average throughput, and instantaneous data rate. Throughput is the key indicator for high-performance services such as autonomous driving and robot-assisted surgery.

2 Delay: It specifies the latency over the communication link and is composed of the transmission delay, queuing delay, and jitter. As a service indicator, delay defines the speed of data delivery across networks and verifies the timeline for data packets transmission. This is an essentially important metric for mission-critical industrial applications such as real-time control and safety that are featured by stringent latency requirements.

3 Coverage: It is defined as the wireless network range that connectivity is provided for services. Generally, the worst-case channel for all terminals in the coverage area is considered as the performance metric of wireless network.

4 Scalability: It stands for the number of nodes that could be connected to the wireless network. Given that there are various IIoT services with different levels of scalability, this performance metric is highly associated with the traffic load of network.

Generally, the combination of multiple indicators forms a composite service metric in wireless systems, and the selected indicators are optimized for the given service requirements.