50 lines
4.1 KiB
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50 lines
4.1 KiB
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=========================
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Settings for Radio Mobile
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*Radio Mobile* is a valuable timesaving tool for network planning and modeling. The results obtained depend upon the accuracy of the settings used to generate the model. The following Radio Mobile settings have proven useful. The full AREDN |trade| forum post for these settings appears here: `Radio Mobile Settings <https://www.arednmesh.org/content/question-about-radio-mobile-link>`_
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===================== ===================
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Radio System Section Recommended Setting
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===================== ===================
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TX power (Watts) 0.25
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TX line loss (dB) 0.5
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TX antenna gain (dBi) [varies]
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RX antenna gain (dBi) [varies]
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RX line loss (dB) 0.5
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RX threshold (μV) 4
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===================== ===================
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While the radio may have a TX Power specification of 1/2 watt (27 dBm), it's more accurate to use 1/4 watt (24 dBm) for dual chain (MIMO) devices because the power is split between the vertical and horizontal domains. The TX and RX Line Loss is minimal, so you can use 1/2 dB to account for the coax jumpers. Using 4 μV for the Receive Threshold will approximate the device's receive sensitivity of -94 dB. It is usually best to underestimate the TX and RX Antenna Gain in order to obtain a more realistic model.
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When Radio Mobile completes its link analysis, it will display the Fade Margin. For a solid connection a fade margin of 15 dB or greater is needed. Anything above that will only increase the MCS rate. For example, MCS15 requires 19 dB more received signal (94 - 75) and the Ubiquiti Rocket transmit power is 5 dB lower at that same rate, so you will need a total of 24 dB (19 + 5) additional fade margin (39 dB in total) to achieve that data rate. 39 dB is a large Fade Margin and is not often achieved on a link.
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**Determining the MCS Rate**
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If you telnet to your node, the following command will indicate the MCS rate the device is running:
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``cat /sys/kernel/debug/ieee80211/phy0/netdev:wlan0/stations/*/rc_stats``
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Here is an example from an endpoint node pointing to a backbone node over 25 miles away. The *Node Status* screen indicates -73/-95/22 dB SNR.
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>>>
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type rate throughput ewma prob this prob retry this succ/attempt success attempts
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HT20/LGI MCS0 5.6 100.0 100.0 1 0( 0) 1 1
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HT20/LGI MCS1 10.5 100.0 100.0 4 0( 0) 4 4
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HT20/LGI MCS2 14.8 100.0 100.0 5 0( 0) 93 93
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HT20/LGI MCS3 18.6 97.7 100.0 5 0( 0) 1380 1416
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HT20/LGI tP MCS4 25.1 99.9 100.0 5 0( 0) 31688 33264
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HT20/LGI MCS5 8.6 25.8 100.0 0 0( 0) 175 3495
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HT20/LGI MCS6 0.0 0.0 0.0 0 0( 0) 1 3495
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HT20/LGI MCS7 0.0 0.0 0.0 0 0( 0) 0 3495
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HT20/LGI MCS8 10.5 100.0 100.0 0 0( 0) 1 1
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HT20/LGI MCS9 18.6 99.9 100.0 5 0( 0) 368 380
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HT20/LGI MCS10 25.1 99.9 100.0 5 0( 0) 37921 38776
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HT20/LGI T MCS11 30.3 99.9 100.0 5 0( 0) 439091 448760
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HT20/LGI MCS12 14.1 33.2 100.0 6 0( 0) 4482 8447
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HT20/LGI MCS13 0.0 0.0 0.0 0 0( 0) 0 3495
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HT20/LGI MCS14 0.0 0.0 0.0 0 0( 0) 0 3496
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HT20/LGI MCS15 0.0 0.0 0.0 0 0( 0) 0 3495
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The "T" in the 10th character position indicates the current MCS rate, and a "t" indicates the current fallback rate. In this case the link is running MCS11 at 30.3 Mbps.
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