Folks:
I’ve been reading many questions about real range between an anchor and a tag or anchor initialization anchor.
I tested in an outdoor environment the maximum possible range between an anchor and a gateway and I found 34m. I’m using 6.8 Mbps default data rate. No parameters change.
The point is: Using the free space calculator and considering the following technical aspects:
Tx power = -17dBm
antenna gain = -1 dBi ( the average antenna gain according to documentation)
freq. = 6.5 GHz
distance = 33m
gives a received power of -98 dBm, which is the anchor sensitivy for a packet error rate of 10% (dwm datahseet ver 20.9 pag. 11) . Increasing the distance above 34m I loose the connection.
So, for my understanding , I’m trying to extend this range to at least 50m using 6.8 Mbps.
Is there a possibility to do it ?
According to documentation, Smart Power is enabled by default. It increases the power in a very short period less than 1ms. I’m using all default configurations. So, if it increases the power, shouldn’t I see a longer range between the anchor and gateway in normal operation?
DWm 1000 user manual, item 2.5.5, page 23, “Default Configurations that should be modified”. My point is: why they are not already set and secondly, if I change these parameters, will they affect the range or may affect sensitivy ?
I was trying to do something similar, get as much range as possible at 6.8 Mbps. From my own experience getting over 50 m at 6.8 Mbps ends up being very tricky unless you start playing with directional antennas. There are some settings you can play with to try to get a little bit more range (preamble size and detection settings, SFD pattern etc…) and they give you a tiny bit more range but not a huge amount.
In the end I found only two ways to reliably get over 50 a) Ignore the rules and crank the power up. b) Drop the data rate to 850 kbps.
For a commercial product b) is your only realistic option. For an R&D project that you don’t plan to sell option a) is normally the simplest way to go. Just don’t tell anyone I told you that
There are two power limits in the regulations, the peak power and the average power over a 1 ms period. For systems sending large packets the average power is often the limit and so that is where the power limits are normally set. Which means if you only send a very short packet and only send 1 packet every ms then you can dial the power up a bit. How much depends on the packet size.
What smart power does is automatically apply this power boost based on the packet length. It is assumed that you have set the power levels correctly to allow for things like ensuring you don’t violate the peak power limit and such that if you do send two packets within 1 ms you still stay under the average limit since smart power only allows for the current packet.
It’s really only of use if you are sending variable size packets. If the packet size and rate are fixed it’s simpler to just set the power at the correct level.
If you are using decawave firmware then it should already be doing this for you. They aren’t set correctly because when they made the chip design they had to specify the power up defaults to build into the chip. They didn’t know exactly what the correct settings would be since they didn’t have a chip to test them on and so had to make some educated guesses. Those guesses turned out to be wrong for some of the registers.
They could update the chip design to fix this but that is expensive and simply not worth it given the firmware is probably going to set those values anyway depending on the operating mode.
Andy. Thanks for your answer but I still have questions :
So you recommend to change to 850 Kbps , but in reallity if you calculate free space, considering that the sensitivity difference for 110 Kbps, range is improved slightly in few meters (-101 dBm for 850K , -102 dBm for 110L @ 1%). So the point is: Are there parameters that I can modify in order to exchange range to 50 m but keeping 6.8Mbps ? You told that there are quite a few. Can you tell me exactly what are they?
We cannot increase the power because next step is to submit to our regulatory for certification. We plan to use it for customers.
I’ m using the default parameters, I’ m not changing the packet size. Just using as is. So , I thought that smart power would increase it in a " smart " way.
Going back to the question 3, you are saying that all the parameters come correctly set from factory and there’s nothing much to do ?
We plan changing the antenna and use LNA to increase range. There’s a company in netherlands which is using a horn antenna . They say that range goes till 1Km but I believe that they may use as a bridge , pehaps.
In general at 6.8 Mbps the data portion of the packet is the weak link so there isn’t a lot you can do to improve things, all of the things you can change are to do with detecting the start of a frame not decoding the data payload. That said if you have line of sight you can play with the LDE_CFG1 register to set the threshold levels. You can play with the SFD type and length and the preamble length. And you can also play with OPS_SEL in the OTP_STAT register.
And a PRF of 64MHz seems to work better than 16 MHz.
I did some testing with these and got a very slight improvement in range, it would sometimes work at 50m but not reliably. I’m using a custom antenna not the default one.
In the end I went to 850 kbps and a 16 bit SFD to get the range I needed, that got me around 50% more range. I then trimmed my two way ranging packets to the bone to keep the transmit times down.
3 & 4) That depends entirely on the firmware you are using. I wrote everything from scratch so I’m not familiar with the decawave firmware but it will be setting reasonable defaults for general use. You may be able to improve them for your specific use.
An LNA or high gain antenna on the transmit doesn’t help. The regulatory limits are for transmitted power in the direction of peak gain. If you have an external amplifier then you have to decrease the decawave power. Same if you have antenna gain. You may gain a little due to lower signal distortion (the on chip amplifier isn’t going to be as good as a good external one) but not a lot.
A better antenna and amplifier can however help on the receive side. Assuming you can live with the power consumption and directional antenna.
