COMP4336/9336代写、Mobile Data Networking代做、代写Java/Python，c/c++程序语言

日期：2019-07-30 10:04

Assignment for COMP4336/9336 Mobile Data Networking

Semester 2, 2019 (Individual Assignment)

Due: 11:59pm Thursday 01 August 2019

Weighting: 20%

Title: Device-to-device Communication over Audio

Background and Motivation

Most mobile devices include a speaker and a microphone. This creates an opportunity to enable

device-to-device (D2D) communication over audio that would work for almost 100% of the available

devices in the market. Audio-based D2D would also enable any other devices with a speaker, such as

a TV, FM radio, musical instruments, alarm systems, and so on to communicate directly with a

personal mobile device without having to configure WiFi or Bluetooth connections. Audio-based

D2D can also provide a more efficient and ubiquitous alternative to NFC-based communication used

for a growing volume of mobile payment transactions and other emerging services. Tech giants have

already started exploring the potentials of audio-based D2D giving rise to new developments such as

Google Tone, an extension of Chrome that lets nearby devices to share URLs over inaudible sound

frequencies.

Learning objectives

Upon completing this assignment, students will:

1. Gain insight to audio-based data communication applicable to current mobile devices,

2. Master the access to speaker and microphone in mobile devices, and

3. Learn how to design and implement a basic audio-based data transmitter and receiver for

personal mobile devices

Assignment Tasks

Task 1 Single Tone Detection [3 marks]

In this task, the transmitting device, such as a laptop, will continuously transmit a single sinusoidal

tone with a given frequency using the built-in speaker and a receiving device, such as a mobile phone,

will detect the frequency. Upon tone detection, the receiver may do some simple tasks, such as

displaying the value of the frequency detected, to confirm that it is working correctly. The

transmitting device may implement a very simple interface for the user to generate a single tone with

a given frequency, such as a text input for the user to specify the frequency (tone) to be transmitted.

This should work for both lower frequencies (audible) and higher frequencies (less audible or even

inaudible).

? Mahbub Hassan 2019

Knowledge of conventional digital signal processing (DSP), which employs Fast Fourier Transform

to analyse all frequencies in the entire spectrum, is NOT required to complete this task. You are

instead encouraged to implement a very simple method, the Goertzel algorithm, which can detect the

presence of a single tone with only a few lines of code. There are many sites on the Internet offering

tutorial and even codes for Goertzel algorithm (you need to do some search). You are free to use any

such codes to complete your task, but you need to acknowledge the source of the code and any

modifications you have done to the original code to make it work for your case.

[Note that Goertzel algorithm is not explained in the lectures, but its study and implementation on

your own is an essential part of this assignment and learning. Your tutor may provide some basic

help regarding tone generation etc., you are also allowed to discuss these topics on the Moodle

forum.]

Task 2 Extension of Single Tone Detection [3 marks]

Extend your transmitter code so it allows the user to input any digit between 1-9 and let the receiver

display the digit. For this, you will need to hardcode different frequencies to different digits. You

may have to play around with different frequencies until it works properly (Hint: if the frequencies

are too close to each other, Goertzel algorithm may not work properly).

You should demonstrate two versions, audible and inaudible (less audible). For the inaudible version,

finding 9 high frequencies for your speaker/microphone that are completely inaudible may be

difficult. You are, therefore, allowed to go down the frequency range at the price of making them

slightly audible. Try to be as much inaudible as possible and report the maximum frequency range

that works for your hardware.

Task 3 Dual Tone Detection [4 marks]

In the previous tasks, you generated a single tone using a single sinusoidal frequency. Find out how

you can combine two distinct frequencies in the same sine wave, so each signal actually carries two

frequencies. Addition of multiple frequencies in the same signal makes the communication more

robust to noise. Do the following

(a) Extend your code from Task 2 to implement the traditional Dual Tone Multiple Frequency

(DTMF) still used in many touch-tone handsets. Select the standard frequencies of DTMF

system (see Table 1), so it sounds like touch tone handsets.

(b) Then explore the possibility of implementing DTMF in the inaudible band and report the

capability of your hardware in terms of the frequency range that works. Note that all you have

to do for this is to try and observe different combinations of high frequencies (as shown in

Table 1, standard DTMF uses audible frequencies).

Mahbub Hassan 2019

Table 1 DTMF frequencies (in Hz) for digits 1-9. For example, you need to transmit frequencies 697 Hz along

with frequency 1209 Hz simultaneously to represent the digit 1.

1209 1336 1477

697 1 2 3

770 4 5 6

852 7 8 9

Task 4 Packetized Data Communication with Audio Tones [6 marks]

In Tasks 1-3, you have implemented and demonstrated the capability of a commercial mobile device

to detect audio tones using its built-in microphone. In this task, you will develop a basic data

communication system that can use this capability to transmit a small packet of few bits, which may

represent a short URL, a short text message, a credit card number, and so on. To implement packetized

communication, you will need to refresh your basic networking prerequisite knowledge of a number

of concepts including preamble detection and modulation.

Your implemented system will work as follows. The transmitter will allow the user to input a single

word or a multi-digit number. It will then transmit a series of bits representing the letters or digits of

the word/number (you could consider the ASCII standard) and the receiver will be required to detect

all those bits received in sequence, recognise the corresponding letters/digits, and display the

transmitted word/number.

While it appears a simple extension from previous tasks, the main challenge lies in synchronizing the

receiver with the transmitter so each bit interval is detected correctly. That’s where the preamble

comes in. There are many different choices for designing the preamble of a packet. You are free to

design your own preamble. The only objective is to make it work for your audio-based

communication.

For modulating a ‘1’ and a ‘0’ bit on the audio tone (carrier signal), there are many options. You are

required to implement only the most basic and simplest modulations, such as either binary amplitude

shift keying (BASK) or binary frequency shift keying (BFSK). For BASK, you can simply use a zero

amplitude, i.e., no transmission, and a positive amplitude, i.e., a transmission, also known as ONOFF

keying (OOK). For BFSK, you can choose to use two different frequencies for data transmission,

one representing a ‘1’ and the other a ‘0’. You are free to choose any other modulation techniques

that you feel comfortable with.

Task 5 Error correction [4 marks]

Audio communication may be affected by noise corrupting your data transmission. In this task, you

will implement some basic error correction, such as Hamming code, Parity code, etc. that will allow

the receiver to detect whether the received data is the same as the transmitted data. You may then

decide to discard any incorrectly received packet and only display correctly received packet at the

receiver. Mahbub Hassan 2019

Some Interesting Links

Android microphone API

https://developer.android.com/reference/android/media/MediaRecorder.AudioSource

Hidden acoustic communication with smartphones

https://cse.buffalo.edu/~lusu/papers/MobiCom2016.pdf

Google’s ultrasonic networking

http://smus.com/ultrasonic-networking/

http://www.theverge.com/2014/6/26/5846726/chromecast-will-use-ultrasonic-sounds-to-connect-nearby-devices

Assignment Submission and Marking

For this assignment, you will NOT have to submit your code, but you will upload in Moodle a pdf

report explaining how you solved your tasks, what design choices you have made and why, by the

assignment due date (11:59pm Thursday 01 August 2019) and demonstrate your working project in

Week 11. Demo slots and venue will be posted on Moodle later.

In the report, you have to provide the main code fragment (up to 30 lines) of the last task you

complete. For example, you should provide the main code of task 3 if you finish the first three tasks.

Based on that, we only assess tasks 1-3 during the demo, even though you complete more tasks after

the due. Each task will be assessed based on both the report and the demo, which contribute 20% and

80% respectively.

Late penalty at the rate of 10% per day late will apply if the report is submitted after 11:59pm

Thursday 01 August 2019.

The End (We hope you enjoy doing this assignment)