Hello Wideband/UWB Gurus, how to measure "energy samples" from Energy Detector?

Hello Wideband/UWB Gurus, how to measure "energy samples" from Energy Detector?

(Under a vehicle's belly, ) I attach a sensors (which act like a Tx) to the vehicle's tires- one sensor for each tire. As the vehicle moves, tire revolves and makes a circular "region". I have a dedicated receiver (Rx) somewhere in the middle from all (multiple-- thinking 18 wheeler, etc.) tires!

Multipath and NLOS are expected.

Question:
(1) Is the channel between the Tx and Rx time varying when the vehicle is moving?
(2) Do I have to consider fading?
(3) As the tire moves, the position of the Tx moves along the circular region. Do I need to consider doppler?
(4) I want to use Energy Detector (for non-coherence detection) to detect the UWB signals. Google tells me "energy samples" are received form the energy detector. but how does one collect "energy samples"?
(5) I want to measure and store a signal metric (like that "energy samples") and store in a database, tagging the name of the region as well. Basically, "region" here means tire.
(6) Furthermore, I want to use ray tracing to simulate this kind of environment. DO I need to define/assume some kind of channel model? Indoor UWB Channel model? S-V, etc?

Please provide me some hints. Does anyone know one or two (or more) books that talks about these topics?

Thank you.

Re: Hello Wideband/UWB Gurus, how to measure "energy samples" from Energy Detector?

I don't understand what you mean by "Energy Detector". What are you trying to accomplish? If you just want to sense the tyre's position or rotation, you could use fixed sensors connected to a central point with cable or optical fiber.

Re: Hello Wideband/UWB Gurus, how to measure "energy samples" from Energy Detector?

x201s said:

(Under a vehicle's belly, ) I attach a sensors (which act like a Tx) to the vehicle's tires- one sensor for each tire.
Question:
(1) Is the channel between the Tx and Rx time varying when the vehicle is moving?
(2) Do I have to consider fading?
(3) As the tire moves, the position of the Tx moves along the circular region. Do I need to consider doppler?

Thank you.

Click to expand...

1 and 2 are yes. the Tx is moving, also there will be some variability in the road and nearby surrounding objects which will cause time varying multipath.
3 Each Tx will have a constantly changing velocity vector. The portion of that vector that is directly toward or away from the Rx will cause doppler shift.

Re: Hello Wideband/UWB Gurus, how to measure "energy samples" from Energy Detector?

First, the energy detector:
I don't know anything about it myself (yet)-- I decided to use this because literature say that it is less complex and thus good for an application in my mind.

Found the following through Google.
(a) For low system complexity and power consumption, we focus on the noncoherent reception of PPM signals, which is akin to GML detection. The symbol decision is based on
finding the pulse position that contains the maximum energy. Source: **broken link removed**

(b) For non-coherent receivers, the data is decoded by comparing the total energy in the two different burst slots. The window size for the energy collection
is adjusted by the transmitted burst duration plus the channel spread. Source: **broken link removed**

See? They both talk about "energy". Back to my question (4), how does one measure energy in this context?

To answer your question what I am trying to do: I want to attach air/inflation pressure sensor in a tire wheel (don't know if it is feasible and people would want to do that, but right now I am concerned with its signal processing aspect), and when low inflation is sensed, some kind of signal (UWB-PPM? or OOK?) will be sent to a receiver. I want to record signals from many (hundreds? thousands?) different position of the wheel as it rotates. Say, rotate a few cm and measure/record signal from there, rotate another few cm, etc. In the training phase, I will also record the tire id. this will be done for each tire of the vehicle. Later in the localization phase, a signal originating from some unknown tire will be compared with the database and the low pressure tire will be identified. That's the idea I am after. Just identifying a "region" (a tire) is sufficient for this kind of problem.

Not only I have to figure out how I measure "energy", I also need to implement the wave propagation part with ray tracing.

Thank you for your interest.

---------- Post added at 01:38 ---------- Previous post was at 01:22 ----------

pstuckey:
Thank you for the comments.
I am taking con-coherent approach (no need to know channel information) to reduce complexity, so may be I should have asked: can I neglect (2) and (3) when two "regions" (=tires) are so closely placed? (5 cm?)
If by neglecting (2) and (3) results in the application's accuracy to less than 5cm (for example), then I will have to consider (2) and (3).

I admit that I am learning as I am asking.. I am sorry and I ask for your and other reader's understanding.
With or without (2) and (3), ray tracing still looks formidable to me.

Re: Hello Wideband/UWB Gurus, how to measure "energy samples" from Energy Detector?

Tire-pressure monitoring systems are already fairly widely used. Perhaps you could get some ideas for your project by looking at existing commercial solutions.

Re: Hello Wideband/UWB Gurus, how to measure "energy samples" from Energy Detector?

I know that the TPMS have been here for a while. But I haven't found any systems that use UWB.
FSK: 434
**broken link removed**
ASK: 315, 433, 868MHz carriers
https://www.sensorland.com/HowPage040.html

I have not been able to find more than basic information like frequency and modulation. They don't talk about fading, Doppler, multipath.

I am not trying to develop and sell anything now, and (I think) it need not be sell-able -- except, the TPMS with UWB should have some novelty in it because it is for my graduation thesis!
I also know that several papers have been written about some combination of UWB and TPMS, but not the the way I am describing my problem and/solution.

So back to "energy detector".. how does one detect "energy"?

Or, let's put it this way: if you were to solve this as I formulated, how would you do it?

Re: Hello Wideband/UWB Gurus, how to measure "energy samples" from Energy Detector?

Hi X201s,

As far as I have read, the energy detection of a signal in a receiver is achieved by passing the signal through a square-law device, followed by an integrator and a sampler.
Also, it seems that to increase SNR the samples can be averaged over N symbols (it is assumed that only one pulse is used per symbol for simplicity).

I advice you to take a look to the book "Ultra-wideband Positioning Systems. Theoretical limits, ranging algorithms and protocols", specifically to section 5.3.3 "Energy Detection Receiver", also, there are some references that might be useful.

Hope it helps,

--E

Re: Hello Wideband/UWB Gurus, how to measure "energy samples" from Energy Detector?

OxEthan: thank you. I will check that book.
The energy detector seems to measure amplitude.. but what do I know.
Actually, I also found a propagation model just for this kind of situation. Here: https://publik.tuwien.ac.at/files/PubDat_186175.pdf
One problem is that the authors proposed that model for narrow band. I want to use their model for wide band and ultra-wide band for that matter.
I suspect something must be changed to adapt that narrow and model to suit my purpose. Do you have any suggestion?
Thanks again.

Re: Hello Wideband/UWB Gurus, how to measure "energy samples" from Energy Detector?

Hi x201s,

What I sent you is related for localization purposes with UWB, which is my topic of research for now. However, I think questions related with it may also be applied to your topic. I do not know much channel modeling it for now. But there is also some work done available for UWB channels for the IEEE 802.15.4a. Maybe, along with the aforementioned book, you can take some ideas from here:

https://www.ieee802.org/15/pub/04/15-04-0662-02-004a-channel-model-final-report-r1.pdf
If you search with google Im pretty sure you can find the channel models in matlab (even there is some code in the report I have referenced).

--E

Re: Hello Wideband/UWB Gurus, how to measure "energy samples" from Energy Detector?

Hi OxEthan:
I think IEEE 802.15.4a channel model is not applicable in my case. I think the channel model in my last post is the best fit...
I just don't know how to code that channel model into Matlab or C or C++, Python.. etc.