What do the terms Link Capacity and Link Quality mean?
Link Capacity and Link Quality are two important terms used by ePMP devices to convey the status of the wireless connection between two radios. Understanding what these terms represent empowers operators to make decisions on how to increase the stability and speed of their networks.
Link Quality: This defines the physical Packet Error Rate (PER) in the uplink direction by percentage. Link Quality is based on the link’s current operating MCS (Modulation and Coding Scheme, or rate-adapt mechanism) and average ARQ (Automatic Repeat re-Quest) retries. If there are no ARQ retries, then the Link Quality reported is 100%. As ARQ retries increase (usually due to interference) the Link Quality percentage reported by the device is reduced. In other words, if Link Quality is low, it is probable that radio interference is causing the device to resend signaling to achieve successful delivery. Consider running a spectrum analysis on site or using the ePMP eDetect tool (via the device web management interface) to profile interference levels that may be reducing Link Quality.
The background color on the web management interface corresponds to a percentage range. Blue is between 80% and 100%. Green is between 50% and 80%. Yellow is between 30% and 50%. Red is between 0% and 30%.
Link Capacity is based on the current operating MCS (rate-adapt) level of throughput compared to the theoretical throughput of the highest MCS level (MCS15). This value is based on the link budget of the wireless connection (a measurement of the signaling from the transmitter through the cabling, air, etc. to the receiver). For example, an SM closer to the AP may exhibit a higher Link Capacity than an SM far away from the AP because the signaling is stronger at the closer SM, resulting in a greater Link Capacity. Operators may check antenna alignment/positioning and transmitter output power levels to maximize the Link Capacity of an ePMP wireless connection.
The background color on the web management interface corresponds to a percentage range. Blue is between 80% and 100%. Green is between 50% and 80%. Yellow is between 30% and 50%. Red is between 0% and 30%.