How many messages can be received by a single 16 channel gateway at the same time ?
In theory, 16 …
But each channel can receive different data rates at same time. So if we have d0 to d5, is it correct to say that we can receive
6 x 16 = 96 messages ???
Each channel can scan for preambles (the transmission before the actual data) at all data rates, but can only handle one frequency / data-rate combination for reception at a time. As soon as the preamble is heard, a channel is setup to receive the message.
So, it can hear a possible 96 signals but can only receive 16 messages.
Barely more than an 8 channel gateway can, since TTN only uses 8 channels.
In theory if you doubled up the receivers on them, you might luck out and occasional get a packet caught by one that was missed by the other.
But in the realm of TTN’s 8 channel a network, a 16 channel gateway simply isn’t worth the money - get another 8 channel gateway and put it somewhere else.
Granted someone did recently claim that they did a custom setup on an alternate sub-band for the second concentrator, and that the TTN servers happened to map the uplinks to corresponding downlink channels. But that’s not something that should be counted on, since it’s outside the design parameters… The TTN servers would also end up instructing nodes to only use the official 8 channels, so you’d have to hack their response to that, too…
Does things enterprise stack also uses 8 channels only ?
Hi @abhishek2101, the frequency plans that are supported by the TTI v3 enterprise stack - including the number of channels - are listed at:
The TTI v3 information is based on the github config yml file repository at:
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Below is what I got from the semtech website. Can anybody clarify this.
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Data Collisions and Spreading Factor Orthogonality
With LoRa, packets using different spreading factors are orthogonal, meaning that they are invisible to each other: as mentioned earlier, they simply appear as noise to one another. Therefore, two packets that arrive at the same time on the same receive channel at different spreading factors will not collide and, both will be demodulated by the gateway modem chip. However, two packets with the same spreading factor arriving at the same time on the same channel might result in a collision. However if one of the two packets is stronger by six dB, it will survive.
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If two (or more) devices send on the same frequency with different SF at the same time, they will not interfere with each others signal and will be processed.
If two (or more) devices send on the same frequency with the same SF at the same time, they will likely interfere with each others signal, unless one is much much stronger than the other.
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It’s a little more complicated than that.
One issue is that not all spreading factor / bandwidth combinations are actually orthogonal. For example, SF9BW500 and SF7BW125 have chirps with the the same “slope” so they readily interfere with each other. Granted, because available concentrators have 8 125 KHz IF’s and only one 500 KHz IF, nodes mostly use 125 KHz so this kind of combination is not all that likely in current LoRaWAN usage, though there is typically a wide channel configured between two narrow ones…
Another is that the chirps are only orthogonal when the difference in signal strength is not too extreme. In my experience, a node with a few dozen meters of a gateway can interfere with the reception of more distant nodes, even when they are on entirely other frequencies as well as spreading factors.
The OP was asking for a simplification / re-work of the Semtech wording but useful info for those who want detail.