This thread has been locked.
If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.
Part Number: CC1352P
I am running a PER test between our device and a Launchpad. Our device is the TX and the Launchpad is the RX. The distance between the devices is about 110m in a field. The PHY setting is the standard 20dBm, 200kbps PHY from the preset list in SmartRF Studio, on channel 902.4MHz.
I suspect the BER should be lower than I'm seeing in these conditions with what seems like pretty strong SNR (27dB). Do you agree, and do you have any suggestions of possible debug methods?
I would have expected PER close to 0 % (no loss) based on the description. Are you sure about the PER and BER numbers you have measured, I would have expeted a high PER and a high BER and the other way around.
What I would try is:
- Different location (same distance between RX and TX)
- DIfferent time (see if you see a difference based on the time you do the test)
- Try different channels
- You can also try shorter packets to see how this impacts.
I would suspec that you have some noise that causes bit errors.
We are glad that we were able to resolve this issue, and will now proceed to close this thread.
If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.
In reply to TER:
This is Wilson working on the same platform
May I know for far distance communication limit on 50kbps data rate, as we measured the noise floor could not be that low as the conducted sensitivity level around -109dBm, which means SNR may be <0dB?
In reply to Wilson Chen80:
Sensitivity is measured conducted and in an environment with a minimum of external noise. In the field, radio noise will be on the air. This noise will both be location and time dependent. Some locations will have more noise, urban environment will have more noise than in the middle of nowhere. The noise will also increase if something is sending etc.
Understanding you are saying the noise of SNR as Arthur's mentioning point. But it would be good to know how low the SNR that for 50kbps and 200kbps can receive the packet successfully regardless of audio application concern (latency)
Normal communication receiver system would consider below, and TI would know the Minimum Eb/No or C/N requirement
The required SNR for 50 and 200 kBps is about 7.
my opinion, 0,23% BER is a really bad value at your reporoted RSSI, escpecially if you use (G)FSK or even OOK (two state modulation schmemes->should have high noise imunity).
The problem might be caused by an (narrow band) interferer / intererence and not by gaussian white noise. White noise should enter in the picture when we near to the sensstivity level.
BER, PER, BLER formulas are valid in presence of white noise only. Because, wihite noise governed by the nature and not a man-made phenomenon. White noise can be controlled relative easily by filters, transmission speed etc due to its flat spectrum, noise power depends on the bandwidth (of sensing Network): Pn=k*T*B. white noise insatenteous amplitude has Gaussian distribution: mean=0 (no DC content), power is the variance (square of std deviation=sigma, std dev corresponds to RMS voltage: within RMS values the 63% of amplitude (samples), amplitudes > RMS are even rare, if detection thershold >6*sigma->no erronous bit detection (below 1ppm)).
If antenna can be detached you may apply wired link between the parts (be careful: do not overdrive receiver input- 20..30dB attenuator pad recommended and minimum TX level) to exlude a possible interferer.
- maybe distorted baseband signal the rootcause : when too narrow band (IF) filter used and after reshaping demodulated signal, timming problem can occur (similary when you pass UART/RS232 transmission trough a slow optocpupler)- check frequency offset, crystal circuitry and AFC: the IF signal is not at the centre of bandpass filter, check PLL settings at TX, RX side- on board EMC issue pls check grounding and CPU interface. It is worth to use ferrite beads on data line.- Is supply voltage clean? Enough low impedance (properly bypassed)? You may switch it by the CPU. Pls check wheter MOSFET can enough open when ON (enough small Vgsth and Rdson)
Thank you TER for the answer to my SNR question
We doubt using TI EVK to detect environment receive noise floor is limited use for reference during our test in the field
Q1: Since from the path loss equation: = 2010 + 1010 + − 28, whereas Lfn number might not be easy to involve the multi-path environment (multi-reflections) so as the RSSI could be widely ranging for the receiver, at different test duration/time, right?
Q2: There are coarse two kinds of noise for sensitivity noise floor or NF, one is AWGN @ 900MHz at environment measured by TI EVK that is accountable while the other is human made LTE eNodeB band 8 (925~960MHz) that cannot be directly taken account into
Correct me if wrong.
For some reason the equation did not show as wanted, correct again for Q1 equation:
Path loss (dB) = 20* LOG (f) + 10n *LOG(d) + Lfn − 28; Lfn is a factor varying with the environment of the channel
The white noise can come in to the picture even enough above the sensitivity level (calculated for given Bps) in this case:
the FSK demodulator (I assume this is the modulation scheme) cannot develop enough output signal swing (which is the function of FM signal frequency deviaton - its gain expressed in [V/kHz] ) resulting the detected signal just exceeds the data comparator threshold but leaving no enough margin-> noise can influence the data recovery.
-> Thus the frequency deviation setting may be improper at the TX side.
In reply to Joseph82:
Q1: The environment will be both place and time dependent meaning that you can get different results if you test the exact same place at different times. We did some tests this summer and we saw that the noise floor changed at least 10 dB from one day to another.
Q2: LTE is one known noise source. But at some locations it's a lot of RF devices that generate background noise. This doesn't have to be a signal that uses the same channel that you are operating on. Since all devices have phase noise energy could be bleeding into the used channel. It's a lot of radio traffic out there meaning that some bands are crowded and hence the noisefloor increases.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.