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DWT-IDWT Based Barcode Modulation Method for


G. G. Rathod

Department of Electronics Engineering

Amrutvahini College of Engineering,

Sangamner, India.

[email protected]

V. S. Ubale

Department of Electronics Engineering

Amrutvahini College of Engineering,

Sangamner, India.

[email protected]

Abstract' There are several wireless data transmission techniques in which barcodes are of great relevance. In this new approach 2D barcode is forward and its performance is compared to other standard methods for example exploiting the low-pass characteristic of a camera phone channel and is presented as a means of facilitating wireless optical communication with mobile phones. In this method, orthogonal frequency-division multiplexing (OFDM) modulation is used together with differential phase shift keying (DPSK) over adjacent frequency domain elements. The aim is to study and establish a system that is proven tolerant to camera movements, picture blur, and light leakage within neighboring pixels of an LCD,          

Keywords'2D barcode, OFDM, DPSK, LCD.


 Orthogonal Frequency Division Multiplexing (OFDM) is a parallel transmission scheme, where a high-rate serial data stream is split into a set of low-rate sub streams each of which is modulated on a separate subcarrier based on Frequency Division Multiplexing (FDM) technique.  In a usual parallel data system, the total signal frequency band is divided into non-overlapping frequency sub-channels. Each sub-channel is modulated with a separate symbol and then the sub-channels are frequency multiplexed. It is good to avoid spectral overlap of channels to eliminate inter-channel interference. However, this leads to inefficient use of the available spectrum. The bandwidth inefficiency, the ideas proposed where to use parallel data and FDM with overlapping sub-channels in which each carrying a signaling rate in frequency to avoid the use of

Figure 1. Block diagram of OFDM system model.

high speed equalization and to combat impulsive noise and multipath distortion, as well as to fully use the available bandwidth.

The block diagram of the base band OFDM system model is shown in Figure 1. The input binary information b(n) is first grouped and the signals can be mapped according to the modulation by using signal mapper and represented by x(n). The mapped signals are then converted into parallel blocks p x (n) for efficient high data rate communication. The data in the frequency domain are transformed into time domain using an Inverse Discrete Fourier Transform (IDFT) and denoted as xp (k). The receiver performs the reverse operation of the transmitter by using an FFT to analyze the signal in the frequency domain.

  After IDFT, the Cyclic Prefix (CP) extension of guard interval is inserted between two consecutive blocks, the OFDM symbol includes the binary input information along with the cyclic prefix signal pg x(k) . The signals can be converted from parallel form to serial form with the help of Parallel to Serial (P/S) converter and it is represented as g x (k). The transmitted signal x(n) passes through the frequency selective time varying channel with the effect of additive noise. At the receiver end once again serial transmission of signal is converted in parallel form and guard time is removed.

The received signal is sent to DFT block for converting time domain signals in to frequency domain. The received signals are extracted using damper and the binary information is recovered in the receiver. Figure 1.4 shows the time domain representation of an OFDM system. The CPT represents the cyclic prefix duration and Tis the OFDM symbol duration.

One- and two-dimensional barcodes have become very popular in past years and are widely used to identify products as well as services. Recently, 2D barcodes, like QR codes, are also used to optically transfer a dedicated hyperlink. All 2D barcodes share one major limitation: the storage capacity. To   overcome that, time can be introduced as a third dimension. Instead of one, a sequence of barcodes is used to transfer a larger amount of data. The main goal of the present work was to design, implement, and especially evaluate the entire workflow for such a QR code-based, three-dimensional (3D) transmission system on the receiver side, such as a Smartphone, being able to from a sender, represented by a screen. The steps comprise the capturing of the 3D barcode, the recognition and reading of the sequence of 2D barcodes, and the final retrieval of the original content. Furthermore, adversarial conditions had to be identified, tested, and documented in detail. The prototype achieves a theoretical throughput of 12,288 Bytes for 30 seconds transmission intervals, which results in approximately 3,280 bit/s. Future work may focus on increasing the throughput of the system as well as the transmission reliability by applying error detection and correction techniques.

Demand for high data rate communication system leads to design of OFDM architecture which offers high data rate up to 100mbps. Introduction of blur in digital images has become a major concern area in the data transfer and usage of orthogonal subcarriers from OFDM has successfully handled the problem of image contamination. Orthogonal frequency division multiplexing scheme utilizes the low pass filter in efficient way to ensure the transfer of low frequency bits in uncontaminated way and only requirement needed is high phase coherency which helps in detect data bits in accurate and reliable way. A detailed explanation with well-defined modification is presented in this paper based on above study and the proposed idea mainly relies on equipped modulation scheme along with LCD camera [9] movements which is used in capturing the single frame and the acquired images are perceived in better way. DPSK modulation scheme is literally called as heart of the proposed work and adjacent frequencies phase differences leads to DPSK modulation. DPSK modulation usage comes into implementation when data is inscribed in phase differences based on the required movement tolerance. Finally, DPSK-OFDM termed as DPSK method in entire project till end. Generally, phase differences in data transfer results in phase distortion may affect the relative neighboring components in negligible way and usage of DPSK modulation handle the distortion situation in better way which paves way for transmission even in high LCD vicinity and in camera relative motion. A related figure composed of LCD camera movements along with communication standards is shown in figure 1 and the mechanism presented above successfully eliminates the unnecessary channel estimation requirements which results in low processing power. Transmission information from the transmission end at maximum level is a concerned area especially from a single image and in order to meet the criteria, maximum data must be extracted from the single which is followed by increasing the data rate of the consecutive frames for decoding purpose. Extraction of the information depends on the LCD display design while in some cases it depends on the receiver end camera respectively.

Figure 2. Block diagram of DPSK Modulation Demodulation.


A. Finding the relevant patterns

Modulation/demodulation is considered as heart of the modern-day communication system which is offering high data rates to various indoor and outdoor applications by international communication standards. Extraction of inscribed information from respective barcode modulation is highly affected by power distortions. Standard finder pattern used for QR code is 1:1:3: 1:1.

B. Similarities of Barcode and Wireless RF Channel

To simplify, each 2D image is transformed into a 1D row vector which contains all the pixels in the 2D image. Each row may be considered a time domain signal with Pulse Amplitude Modulation (zeros are black pixels and ones are white pixels). Let us consider capturing an image of this row in a band limited channel with a combination of camera focus problems, light leakage from white to black pixels and resolution limitations, among others. In addition, the resulting image will also have high ISI because the camera moves along a multipath channel during image capture and mixes up the image of several neighboring pixels. In order to address these issues within a time domain radio signal, OFDM method is employed to essentially divide the channel into multiple orthogonal low bandwidth channels, and the low rate data is sent into these channels in parallel. Thus, for 1D data, the inverse Fourier transform is used for to display the data instead of using the PAM modulated process, where Hermitian symmetry conditions should be met to have real-valued outputs. The result is that most artifacts will only affect the high frequency components, leaving the low frequency components intact for data transmission. This idea may be expanded to apply to 2D signals, to meet the requirement for transferring the entire image atone. Instead of a 1D inverse Fourier transform, the 2Dversion is used in such a manner as to confine the effect of artifacts acting on two axes only to high frequency components. The study will discuss the exact modulation scheme.

C. DPSK Against OFDM

Figure 3. Block Diagram of DPSK-OFDM approach.

Transmission of data through wireless condition will be possible due to dependable modulation schemes. To conventional approaches, different modulation schemes along OFDM were actualized among them as none camwood attain low density of simplicity. In this proposed work DPSK-OFDM modulation plan is executed for finer transmission of data starting with transmitter end of the recipient end. That transmission about data through DPSK OFDM approach is indicated to Emulating figure 4.  Here that particular input made may be 'TEXT'. The encoding transform aides help to accomplishing secured QR code for consistent transmission. Encoding and deciphering for QR code may be attained by Zxing open join hotspot. Cyclic addition is used to prevent those inter-carrier-interference (ICI) over OFDM framework [7] utilizing its actual and fanciful parts of the components. The sign of the actual part determines those to start of first bit and sign of the nonexistent segments determines those second bit.

In wireless communication system, to expand information data rate orthogonal recurrence division multiplexing (OFDM) may be utilized which employments inverse fast Fourier transform at those transmitter will modulate a high bit rate indicator onto a number of carriers. The issue with this strategy may be that it obliges a greater amount complex IFFT core. Again this, we could utilization discrete wavelet transform that will produce low level computational multifaceted nature. Wavelet transform will be the a large portion suiting for utilize on AWGN channel and also measures the execution as far as bit error rate (BER) and signal to noise ratio (SNR). It increments the spectral effectiveness. Also abatements the bit error rate as contrast with Fourier transfrom and we get the better execution.


The suggested technique has been assessed and done by using MATLAB R2015b simulation tool. Those adjusted encrypted QR code obtained and transformed form phone by catching the picture. This caught picture might have been effectively decoded and decrypted will get those genuine information. Fig indicates the encrypted adjusted QR code. This QR code is shown on the phone Furthermore is transmitted to an alternate telephone catching those picture.  Fig. 4. Indicates the information exchange eventually catching those QR code. Indicates the caught QR code. On decoding and decrypting this captured QR code, the unique data is retrieved.

Figure 4. Transmitting data towards mobile phone.

Figure 5. Compare Elapsed time.


Systems Previous System New System

Elapsed Time Required 1.641066 Seconds 0.235176



Present 2D barcodes utilize PAM Similarly as the favored regulation strategy [2]. Should think about them for the recommended modulator Furthermore demodulator, both frameworks need aid actualized clinched alongside MATLAB.

A basic PAM modulator which interprets bits in to light and dim pixels about a picture may be contrasted with the recommended DPSK-OFDM strategy which employments described algorithm modulation and demodulation. Also, the enactment of QPSK-OFDM is fundamentally same as 4-QAM (Quadrature Am- plitude Modulation) OFDM used in PixNet [5], is likened to the planned DPSK-OFDM system. The main parameters that are considered include: noise and clip ratio; low pass filtering; Camera movement

For investigation of impact for each from these parameters, initially irregular information stream is adjusted and modulated to shown picture utilizing the algorithm under test. Then a regulated distortion may be applied to the picture before passing it to receiver. That bit stream in the decoder is contrasted and compared with the information of random stream. This procedure will be repeater a few times utilizing different random processes.

Figure 6. Transmitting data of the system

Figure 7. low pass filtering output of BER performance.

Figure 8. Encrypted Modulated QR code.

Figure 9. Captured QR code.

Fig 5 : Received data


A data can be securely transferred from one mobile device to another by first encrypting it and then converting the data into barcodes. This is then transferred to another device by capturing the image of the barcode. This data transfer uses visual light communication, thus reducing the possibilities of NFC attacks. In order to avoid motion blur distortions, the data is stored in phase difference of adjacent elements. The data transfer rate can be increased by increasing the bits per symbol from current 2 bits per symbol constellation. Also elapsed time required for this system is less as compare to another system and bit error rates is reduced.


[1] N. J. Woodland and B. Silver, 'Classifying apparatus and method', U.S. Patent 2 612 994,Oct. 7, 1952.

[2] Information Technology Automatic Identification and Data Capture Techniques QR Code 2005 Bar Code Symbology Specification,ISO/IEC 18004:2006, 2006.

[3] H.Katoand K .Tan, Pervasive 2d barcodes for camera phone applications,Pervasive Comput.,vol. 6, no. 4, pp. 76-85, Oct. 2007.

[4] X. Liu, D. Doermann, and H. Li,Vcode-pervasive data transfer using video barcode, IEEE Trans.Multimedia,vol. 10, no. 3, pp. 361-371,Apr. 2008.

[5] S. D. Perli, N. Ahmed, and D. Katabi, 'Pixnet: Interference-freewireless links using LCD-camera pairs', in Proc. MobiCom, 2010, pp.137148.

[6] J. Memeti, F. Santos, M. Waldburger, and B. Stiller, 'Data transferusing a camera and a three-dimensional code', Praxis der Informationsverarbeitung und Kommunikation, vol. 36, no. 1, pp. 31-37, 2013.

[7] C. Pei, Z. Zhang, and S. Zhang, Softoc: Real-time projector-wallcamera communication system,in Proc. ICCE, Jan. 2013, pp. 100-101.

[8] S. Kuzdeba, A. M. Wyglinski, and B. Hombs, 'Prototype implementation of a visual communication system employing video imagery' Proc. CCNC, 2013, pp. 184-189.

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