mirror of https://github.com/ARMmbed/mbed-os.git
35 lines
2.6 KiB
Plaintext
35 lines
2.6 KiB
Plaintext
Frequency sub-bands in US915/AU915:
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US915/AU915 PHYs define channel structures which can support up-to 72 channels for upstream.
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First 64 channels (0-63), occupy 125 kHz and the last 8 channels (64-71) occupy 500 kHz.
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However, most of the base stations available in the market support 8 or 16 channels.
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Network acquisition can become costly if the device have no prior knowledge of active channel plan and it enables
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all 72 channels to begin with.
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LoRaWAN 1.0.2 Regional parameters specification refers to a strategy of probing a set of nine channels (8 + 1) for
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joining process. According to that strategy the device is supposed to alternatively select a channel from a set of
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8, 125 kHz channels and a 500 kHz channel.
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For example send a join request alternatively on a randomly selected channel from a set of 0-7 channels and
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channel 64 which is the first 500 kHz channel.
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Once the device has joined the network (in case of OTAA) or have sent the first uplink (in case of ABP), the network
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may send a LinkAdrReq mac command to set the channel mask to be used. Please note that these PHY layers do not
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support CFList so LinkAdrReq is the way the network tells you what channel plan to use.
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Mbed LoRaWAN stack can be configured to use a particular frequency sub-band (FSB) which means that we don't have to
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probe all sets of channels. "fsb-mask" in lorawan/mbed_lib.json is the parameter which can be used to tell the
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system which FSB or a set of FSBs to use. By default the "fsb-mask" is set to "{0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF, 0x00FF}"
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that means all channels are active, i.e., 64 125 kHz channels and 8 500 kHz channels are active. If the user wishes
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to use a custom FSB, he/she needs to set appropriate mask as the value of "fsb-mask". For example:
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If the user wishes to use the first FSB, i.e., first 8 125 kHz channels (0-7) and the first 500 kHz channel:
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"fsb-mask" = "{0x00FF, 0x0000, 0x0000, 0x0000, 0x0001}"
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Similarly, if the user wishes to use second FSB, i.e., 2nd set of 8 125 kHz channels (8-15) and the 2nd 500 kHz
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channel:
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"fsb-mask" = "{0xFF00, 0x0000, 0x0000, 0x0000, 0x0002}"
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You can also combine FSBs if your base station supports more than 8 channels. For example:
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"fsb-mask" = "{0x00FF, 0x0000, 0x0000, 0xFF00, 0x0081}"
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will mean use channels 0-7(125 kHz) + channel 64 (500 KHz) and channels 56-63 (125 kHz) + channel 71 (500 kHz).
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Please note that for Certification requirements, you need to alternate between 125 kHz and 500 kHz channels and that's
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why before joining you should not set a mask that enables only 500 kHz or only 125 kHz channels. |