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Vrishab’s Status Report for 04/10/2021

Real-Time Signal Processing

In the previous weeks, we have been collecting data on one machine, a Windows surface pro, and processing it on another, a new Macbook Pro. The reason being that the driver software was not supported on mac, but we knew that our Windows computer did not have the processing power to handle our signals in real time. The data was manually transferred using a USB stick which was clearly a stopgap solution. This week Enock and I implemented a server on that processes data — transferred over UDP — from the Windows machine in real time. The addition of this server to our signal processing pipeline has greatly increased the speed at which we can capture data and debug, and it is an integral part of our final design.

Debugging Signal Capture

In attempting to correlate the data collected from two antennas, I noticed that there were some inconsistencies in our results. Sometimes, the correlations looked reasonable, and other times less so. Through extensive testing, we discovered that one of the outputs from our downconverter board was corrupted. We have a spare downconverter which performed perfectly after replacement.

Progress Since Last Week

I have made a lot of progress on the correlation code since last week. That, in addition to the UDP server, has enabled fast (<<1sec) delay calculations between the two signals.

Tasks for Next Week

I will be working with Enock and Txanton on adding two additional RTL SDRs to our system. I will also be implementing angle of arrival estimation, which is a simple equation that will be added to our code.

 

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Vrishab’s Status Report for 04/03/2021

Signal Synchronization

Quite a lot of progress was made on signal synchronization this week. I was able to achieve coherent signal capture between two RTL SDRs, which was partially completed last week, but the captured signals were too weak. To correct this issue, I incorporated a bandpass filter into our signal capture pipeline and moved testing locations. The combination of these two resulted in a much stronger captured signal which we could correlate between the two receivers.

System Integration and WiFi Signal Capture

Working with Enock and Txanton, we have completed our integration of all the hardware in order to capture WiFi signals using our SDRs. Using my phone hotspot as a WiFi source, we were able to capture the signals from my phone with the SDR and produce a spectrogram of the results.

Progress Since Last Week

We have completed the integration of all our hardware and have captured WiFi signals; this was a major hurdle in our design process that we have now overcome. We are ready to begin our beamforming implementation.

Plans for Next Week

We are going to implement the beamforming algorithm as a separate offline script. Doing the processing offline will render the code easier to write and debug. We can transfer the code to C (using cython/numba or equivalent) to facilitate real-time processing.

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Txanton’s Status Report for 04/03/2021

This week we made some large breakthroughs. Initially we were planning on using an Arduino since we had many available to us and they are relatively easy to program. The only challenge with this is they use 5V logic and the Voltage Controlled Oscillator we are using uses 3V3 logic levels meaning we need to convert them. We attempted to use the Sparkfun Logic Level Converters however the method of switching they use were not fast enough to support the slowest SPI speed of the Arduino. My team members considered using a Raspberry Pi since it uses 3V3 logic levels so I wrote a quick Python script to configure the VCO in case they did end up using the Rasberry Pi. Due to accessibility issues my team members ended up not using the Raspberry Pi but had a Ti MSP430 available to them which uses 3V3 logic levels so we attempted to use that. It looked promising since there was an IDE called Energia which used Arduino libraries to program it so the code I wrote this week should work. Unfortunately we had some issues setting up the development environment for that chip and none of us had experience with the platform so we moved on. My team members were able to borrow an STM32 Nucleo board, a platform with which I am very familiar with, so I rewrote the program to set the VCO registers for this microcontroller and we were able to get it to working and use it with our downmixer.

I spent a lot of time this week writing the code to program the VCO (for multiple microcontrollers) and next week I will start on the heatmap and webcam capture code.

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Vrishab’s Status Report for 03/27/2021

Signal Capture Pipeline Design Changes

Since there was no status report last week due to the midsemester break, we have made some considerable progress — as well as some significant changes — to our beamforming architecture. Based on the feedback from our presentation two weeks ago, we have decided against fabricating our own PCB to convert analog signals from the WiFi antennas to digital signals that we can process. Instead, we will be using an array of cheap SDRs (~$25 each) to capture the downconverted signals and convert them into digital signals. The downconversion will now be done using commodity downconverters, which we have already purchased and are en route.

My role was largely in organizing these changes. I also used two SDRs which we borrowed from Dr. Swarun Kumar to perform beamforming on radio signals in the FM band, which will be close to the intermittent frequency of the boards we ordered. Enock and I also met with one of Dr. Kumar’s graduate students, Atul Bansal, to further discuss possible modifications beamformer implementation, such as synchronization schemes, and to receive feedback on our implementation .

Design Report

As a group, we spent a considerable amount of time writing our design report. My contribution to this was the signal processing portions as well as miscellaneous contributions to the introduction, architechture overview, risk management, etc.

Progress Since Last Report

We have finalized our implementation and have ordered parts. We have a working beamformer implementation for signals in the FM band.

Plans for Next Week

Once our parts arrive we will begin integration and testing. Since the ordered parts are development boards, which are designed to be plug-and-play, we should be able to begin testing without delay.

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Txanton’s Status Report for 03/27/2021

This week I finalized the last few products that we needed to order. After some careful consideration I found the downmixing evaluation board that we plan on using, it features dual channel interfaces meaning we can connect two antennas to it, and it also is 50 Ohm impedance matched meaning we don’t need any additional hardware to prevent reflections on the signal line. We also found some WiFi antennas that seemed relatively directional without sacrificing field of view too much so that we can get sufficient overlap to get meaningful information from each antenna. The last product we ordered were the SMA cables needed to to connect all of these devices. By using these cables we are able to space out the antennas accordingly so that we can perform beamforming.

We also spent some time this week on administrative tasks as we needed to organize our task breakdown in order to make sure we are able to complete everything on time. By making a more detailed breakdown of tasks we will be able to stay more focused and not spend as much time trying to decide what to work on next. This upcoming week we hope to start receiving components so that we can start testing with the actual parts that we will be using. This will allow us to start working on solving any problems that may arise when we start combining these modules.

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Team Status Report for 03/13/2021

Presentation

Our team spent a considerable amount of time early in the week creating the presentation slide deck. Some considerable effort went into creating some of the animations and visuals to accompany the technical content of our presentation. In particular, we provided an artist’s rendition of our final product, a series of animated beamformer signal response plots, and a block diagram of our product. (We note that the feedback from one of the instructors stated that we stole our block diagram from somewhere without crediting its source — this could not be further from the truth, as we created the diagram ourselves.)  We also chose Vrishab as our presenter and helped him dry-run the presentation.

Downconversion

We had a lengthy discussion with Shaun Stevens who is Dr. Kim’s graduate student. During our meeting, Shaun helped us flesh out the downconversion process and provided feedback on other aspects of our implementation.

With his help, we have now identified the specific channel of 2.4GHz WiFi that we are going to work with — channel 6 — which has a bandwidth of 22MHz. Thus, after downconversion, our A/D converter need only sample at the nyquist rate of (22/2)MHz upper frequency * 2 = 22MHz. We have selected the specific ADC that will accomplish this task.

Progress Since Last Week

We now have identified all of the components that are needed to implement our system from the antenna array through the FPGA. We have also identified the critical components for our downconverter, which we were not aware we needed as of last week.

Plans for Next Week

We will begin PCB layout next week and plan to meet with Dr. Carley for feedback on our layout once complete. We plan to send out our schematics to have our PCB fabricated at the end of next week.

 

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Vrishab’s Status Report for 03/13/2021

Presentation

This week, I presented our project progress in our Section C presentations. This took some considerable effort, both in terms of designing the slide deck and performing dry runs of the presentation beforehand. The feedback from the presentation was useful and will help clarify some of the portions of our design review in the coming weeks.

Meeting with Shaun Stevens (Dr. Kim’s Grad Student)

We met with Shaun to discuss the specifics of our antenna design and signal processing pipeline implementation. He gave us some extremely valuable feedback, which has changed some aspects of our design. We are now going to be downconverting the collected WiFi signals from 2.4 GHz to baseband, and we will then sample the downconverted signal at a correspondingly lower rate. Performing these steps will require a voltage-controlled oscillator, the make and model of which we have already identified. Adding the oscillator to our system has incurred a slight delay in our progress, but has actually had the effect of speeding development since we won’t have to sample the signal at 4.8 GHz (which was something that we had planned on taking a week to figure out).

Progress Since Last Week

Last week we stated that we would begin on the PCB design. Txanton has been heavily focused on this, and we are on track to finish the layout and meet with Dr. Carley for review within the coming week. I have been aiding in some aspects of the PCB design, specifically with the selection of some of the components.

Plans for Next Week

We plan to have the PCB layout completed and will meet with Dr. Carley to verify that our design will work. We will then send the specs out to have our board fabricated and shipped back.

 

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Txanton’s Status Report for 03/13/2021

This week we had design presentation’s which took up some of the time we had planned for this week. Outside of the design presentations I mostly spent this week finalizing the components we plan to use for our RF Front-End circuit. During this time we had a meeting with a CMU Graduate student who is doing research in this area so that we could discuss some of our plans with him to help ensure some of our assumptions were correct. This graduate student was also a valuable resource for helping learn about some other techniques for sampling such as I/Q Demodulation which may be useful in getting information from the radio signals.

Now that we have most of the components selected I plan on drafting the schematic and then scheduling a meeting with Professor Carley, since he does research on RF Circuitry, in order to review the schematic and again helps us identify some possible flaws we may have made so that we can finally go ahead and order our PCB’s. Regarding the schedule I believe that I am slightly behind on the PCB design but do not foresee it taking up too much of our slack so I still believe that our project is on pace.

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Txanton’s Status Report for 03/06/2021

This I was doing research into what components we need in order to get meaningful data from the antenna’s. In our weekly meeting it was brought to our attention that there was likely additional circuitry needed in between the antenna’s and our ADC. Since specific information was not immediately available to us about this I did some research in order to try and figure this out.

During this research one thing I found out is that we will likely need to use an amplifier to boost the signal. I was not aware that RF signals were as low power as they are so in order to avoid noise and get a higher Signal to Noise Ratio (SNR) we will need to use an amplifier, this will also amplify noise, however it should be to a lesser effect. I also found that some circuits make use of a bandpass filter in order to help get rid of some of this noise and smooth the signal, this is something I will keep in mind as we start to design our circuit.

I was unable to find too much more detail however I will keep looking and earlier in the week we reached out to a graduate student at CMU doing similar research and hopefully they will be able to give some additional insight into some of the challenges.

This next week I will continue to search for circuitry related to antenna’s and will continue doing research so that we can get started on the design of our PCB as soon as possible, since we will not only have to create the PCB but also wait for it to be fabricated and shipped, and then also wait for the components that will be going on it to be shipped as well. In order to minimize the impact of this delay I will try and make sure we can order both parts and the PCB as soon as possible.

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Team Status Report for 02/27/2021

This week we spent a lot of time watching our peers present their own projects which helped us to get a good idea of how other groups were approaching their own challenges and try to find ways we can adapt that to our own.

We did not get as much done this week as we would have liked due to the project presentations, however we still were able to get a solid start on our requirements. Since we decided on cylindrical antenna’s we started to try and address the challenge of how to make sure they stay in a consistent arrangement with proper angles between each antenna. Our solution for this was a 3D printed rigid body in order to keep all of the antenna’s in place. We also did research on different digital beamforming algorithms so that we may start comparing and contrasting them to see if they meet our near real-time constraints and their difficulty in implementation.

Going forward, we plan to focus our attention towards the antenna’s and the PCB that all of the antenna’s will connect to. By focusing on this it will allow us to get prepared to start ordering components so that we may start working on our physical implementation and start prototyping as soon as possible. We will also start organizing our information regarding DSP algorithms so that we can get an idea of how we will implement them. We will also need to make a decision regarding whether or not we will use a Software Defined Radio, such as GNU Radio, or if we will use a FPGA instead as they both have benefits and drawbacks.