CONTRIBUTION AND LIMITS OF A LOSSLESS DATA

COMPRESSTION METHOD FOR PERFORMANCE

OF OPTICAL WIRELESS CHANNELS IN DIGITAL

MULTIMEDEA APPLICATIONS

K. A. Moustafa

Faculty of Computers & Information - Munofiya University - Egypt

Keywords: Digital Images Transmission (DIT), Optical Wireless Channel (OWLC).

Abstract: For the digital multimedia communication systems, the modification of the transmission rate, transmission

capacity and the bandwidth, parameters are an important for the performance of the Optical Wireless

Channel (OWLC). Multilevel-Digital pulse Interval Modulation (M-DPIM) is the most method which

contributes in the improving of these parameters. The large size of multimedia sources has been performed

the main problem for the data transmission. Thus, in this paper a lossless images compression method by

Minimizing Pixels Number of Objects (MPNO) is applied. The properties of the Digital Images

Transmission (DIT) with and without compression by using MPNO method are discussed. The compression

ratio of the MPNO method compared with other compression methods is evaluated. Transmission

Parameters Values (TPV) of the M-DPIM system with and without compressed input by using MPNO

method are computed. Finally, for special types of the DIT, the MPNO method has been satisfied good

results.

1 INTRODUCTION

Multimedia era has been rapidly moved toward

digitization, processing, storage, and transmission of

images. With the increasing popularity of Web

browsers, image transmission has become one of the

largest uses of Internet bandwidth for multimedia

communications. Thus, the digital images

transmitted are compressed as much as possible

before the bits are transmitted via the

communications and storage channels. Recently, the

increasing in numbers of digital images devices,

such as scanners, plotters and digital camera has

seen an explosion in the availability of Digital

Images Transmission (DIT) (Kamimura et al.,

1993), (Tanenbum, 2003), (Wu et al., 2003).

The OWLC (transmission and detection) offers

immunity from fading and security at the physical

level where the optical signal is typically contained

within the indoor communication environment for

the DIT. The transmission rate, transmission

capacity and the bandwidth are important parameters

for the performance of the OWLC (Smyth et al.,

1993), (Hranilovic and Kschischang, 2003). Thus,

the M-DPIM (Ghassemlooy and Aldibbiat, 2006) is

the most method which contributes in the improving

of these parameters compared with pulse position

modulation (PPM) (Audeh et al., 1996), digital pulse

interval modulation (DPIM) (Ghassemlooy et al.,

1998) and dual header pulse interval modulation

(DH-PIM) (Aldibbiat et al., 2002) But, still and all

the large size of the DIT has been performed the

main problem for the TPV. For a data compression

field, a lossless images compression method by

Minimizing Pixels Number of Objects (MPNO) is

proposed and generalized in our previous works

(Fahd et al., 2006), (Fahd et al., 2007).

In this paper we propose the contribution and

limits of the MPNO method for a Digital Images

Transmission (DIT) in the OWLC. We will apply

MPNO method in OWLC which used the M-DPIM

system. The transmission parameters values (TPV)

of the M-DPIM system with and without

compression by using MPNO method will be

computed. The compression ratio of MPNO

compared with Portable Network Graphics (PNG)

and Graphics Interchange Format (GIF)

161

A. Moustafa K. (2007).

CONTRIBUTION AND LIMITS OF A LOSSLESS DATA COMPRESSTION METHOD FOR PERFORMANCE OF OPTICAL WIRELESS CHANNELS IN

DIGITAL MULTIMEDEA APPLICATIONS.

In Proceedings of the Second International Conference on Wireless Information Networks and Systems, pages 161-165

DOI: 10.5220/0002149401610165

 SciTePress

compression methods is introduced in this work

(ISO/IEC 15948, 2003), (Version 89a (c), 1987).

The rest of the paper is organized as follows. In

Section 2, introduce overview of (PNG, GIF and M-

DPIM system). The MPNO method is introduced In

Section 3. The properties of the DIT are introduced

in Section 4. The results and discussion of the

compression ratio of the MPNO method compared

with other methods, and (the bit rate, the

transmission bandwidth requirement, transmission

capacity and the reset delay time of demodulator)

values of the DIT for the M-DPIM with and without

compression by using MPNO method for M-DPIM

system are computed in section 5. Contribution and

limits of the MPNO for the performance of the

OWLC are presented in conclusions of Section 6.

Finally, the last section presents the references.

2 PREVIOUS WORKS

2.1 PNG Compression Method

Portable Network Graphics (PNG) is one of the

modern image formats for lossless image

compression. The PNG file format supports

grayscale, indexed color, and true colours as well as

other features, such as transparency, interlacing and

gamma correction (ISO/IEC 15948, 2003).

2.2 GIF Compression Method

Graphics Interchange Format GIF offers a protocol

intended for on-line transmission and interchange of

raster graphic data. Cartoon-style images and clip-

arts are often entropy-coded using the GIF format

that supports 256 colors. However, the GIF format

may not be the most efficient way to compress

cartoon images. For example, cartoon images often

contain large areas of a uniform color. This spatial

relationship among colors has not been exploited

explicitly in the GIF compression (Version 89a (c),

1987).

2.3 The M-DPIM for OWLC System

Multilevel-Digital pulse Interval Modulation (M-

DPIM) is the most method which contributes in the

improving of the TPV of the DIT within OWLC

(Ghassemlooy and Aldibbiat, 2006). The

transmission parameters of M-DPIM modulator are:

- Bandwidth requirement normalized to NRZ-OOK

is:

(

)

(

)

(1)B

req

avb

⋅

Where:

MLR

avb

are the bit rate of DIT, average

symbol length of the modulated codeword and the

number of slots of the input data respectively.

- Transmission capacity (TC) is:

- In the M-DPIM modulator, the latch will fetch the

next input word after a delay period, which is the

duration of transmitting the present symbol. This

delay period is:

Where: Ts: is the pulse duration within the

modulator.

- For the demodulator stage of M-DPIM system, the

reset delay time of counter (RDT) is:

Figure 1: Paper structure, (a) block diagram of MPNO and

M-DIPM system, (b, c, d, e) computation points.

MPNO

Encoder

Original

DIT

(b)

Computation Point of

TPV Without

Compression

(c)

Computation Point of

(TPV & Compression

Ratio)

With Com

ression

Image Encoder

without Compression

MPNO Decoder

Original DIT

M-DPIM

Transmitter

(OWLC)

Channel

(In-Door)

M-DPIM

Receiver

(d)

Computation

Point Of

(M-DPIM)

Parameters

With and without

Compression

DIT Bit-stream

(110010110….)

M-DIPM

System

DIT Bit-stream

(110010110….)

(e)

Computation

Point of

Reset Delay

Time

With and

Without

Compression

(a)

()

(5)

1-M

R+

()

(4)2 d periodDelay

T+=

(

)

()

(3)

12B4M

req

−

(

)

(2)

1-M

)6(2

TRDT =

WINSYS 2007 - International Conference on Wireless Information Networks and Systems

162

(0, 0)

(Xpmax , Ypmax)

(a)

(b)

3 MPNO METHOD

The basic structure of this paper is illustrated in

figure1. The encoder of the MPNO method has the

following main stages: image preparation, object

extraction, object preparation, vectoring, differential

encoding, Huffman encoding, and frame building.

In image preparation: The image is converting

into 2D matrix, which consists of the pixels values

of this image.

In object extraction stage: the matrix of the

image is scanned from top to bottom and from left to

right in order to detect the starting pixel of the

object, after that the pixels of the object (PO’s) are

detected and the pattern for PO’s is generated, the

output of this process as shown in figure 2, where:

(0,0) and (Xpmax , Ypmax) are the start and end

points of the pattern of the extracted object,

respectively.

Figure 2: Object Extraction, (a) the image, (b) pattern of

PO’s of blue object.

In object preparation stage: The repetitions of the

PO’s in the horizontal, vertical and diagonal

coordinates and the intersection are removed. The

out of object preparation is encoded in encoding

stage. -The compression ratio for any type of image

compression is computed by the following formula:

Where: OSI and CSI are: Original Image Size (KB)

and Compressed Image Size (KB) respectively.

In frame building stage: the encoder has general

structure which defines the format of the total fields

in output bit-stream. The decoder part of this method

builds an exact copy for the transmitted image from

its bit-stream frame as follows. Firstly, the decoder

decompresses the objects embedded in the bit-

stream frame and secondly, it fills the pixels values

which removed by the encoder stage.

4 PROPERTIES OF DIT

We consider that Intra- frame of video film (I-frame)

can be represented by a one digital image. Then one

image must be transmitted on line in time

approximately equal to (0.033) sec, then the duration

time of the pulse which represent one bit (0 or 1) of

the transmitted bit stream (

) is:

Where: TBI is transmission bandwidth of image:

Image Size (IS) is:

Where: (HPN, VPN, NbP, IS and TBI) are: is

horizontal pixels number, vertical pixels number,

and number of bits per pixel, image size (KB)

respectively.

Then the bit rate

(

)

of DIT is:

5 DISCUSSION OF RESULTS

In this section, we evaluate and discuss the

contribution of the MPNO method for TPV of the

DIT within OWLC which used the M-DPIM stage.

The effect of image compression by using

MPNO method is shown in figures 3 and 5. By

using equation (7), the comparison between the

proposed Method (MPNO) and both GIF and PNG

methods is illustrated in Table 1. It is clear that the

image compression by this method was more active

especially for geometric-style images compared with

GIF and PNG methods

The bit rate computation computed by using

equations (8), (11). The bit rate computation of DIT

with and without MPNO Compression is shown in

Table (2). It is clear that, the MPNO method has

been introduced lower values of

()

. This

minimization of the bit will be improved the values

of both the hardware devices speed and the

transmission bandwidth which requirements for

OWLC system. Whereas, the increasing in speed of

the hardware devices is performed the main problem

for NRZ-transmission systems. By using equations

(7)100

OSI

CSI - OSI

Image of Ration Compressio ∗=

(

)

()

)9(

)(

MbTBI

(8)

TBI

0.033

()

(11)

=sb

(

)

(

)( )

()

)10(

108

)(

NbPVPNHPN

KBIS

CONTRIBUTION AND LIMITS OF A LOSSLESS DATA COMPRESSTION METHOD FOR PERFORMANCE OF

OPTICAL WIRELESS CHANNELS IN DIGITAL MULTIMEDEA APPLICATIONS

163

(1), (2), the

req

computation of DIT with and

without MPNO Compression for M-DPIM

Modulator is shown in Table 2.

The compression of

DIT by using MPNO method offers decreasing of

req

values. Related to the equations and the

discussion of reference (Ghassemlooy and Aldibbiat,

2006), the performance of M-DPIM system has been

improved by this minimization of

req

From equation (3) and Table (3), the TC value of M-

DPIM Modulator at (M = 8) is decreasing with

applied the DIT in (MPNO) encoder. By decreasing

the TC, the performance of the M-DPIM system has

been improved. Related to equation (6) and Table

(3), the RDT value is increasing with applied the

DIT in (MPNO) encoder, thus the demodulator

hardware’s speed is decreased. By the increasing of

RDT value, it is also improves a slot

synchronization in the demodulator stage for M-

DPIM system.

Figure 3: Effect of MPNO method on Image 1.

Figure 4: Effect of MPNO method on Image 2.

Figure 5: Effect of MPNO method on Image 3.

Table 1: The compression ratio comparison between

MPNO method and both GIF and PNG methods.

Compressed

Size (KB)

Compression

Ratio (%)

DIT

- bits

Images

MPNO

GIF PNG

MPNO

GIF PNG

Image 1

(443x458)

199 KB

0. 507

6.85 3.56

99.74

96.55 98.21

Image 2

(107x111)

12.7 KB

0. 499

1. 6 1. 37

96. 07

87.07 89.21

Image 3

(300x400)

118 KB

7. 8

7. 9 6. 2

93 .38

93.30 94.74

Table 2: The computations of DIT bit rate

and M-

DPIM bandwidth requirement req

with and without

MPNO encoder.

(

)

of DIT

()

MbsB

req

at ( M = 8)

DIT

8 – bits

Images

Without

MPNO

(

)

Mbs

With

MPNO

(

)

Mbs

Without

MPNO

()

Mbs

With

(MPNO)

(

)

Mbs

Image (1)

(443x458)

48. 242

0. 123

395.102

1.007

Image (2)

(107x111)

3. 078

0. 120

25. 209

0. 983

Image (3)

(300x400)

28. 606

1. 890

234. 28

15 .479

Table 3: The computations of transmission capacity (TC)

of M-DPIM modulator and (RDT) of demodulator.

of M-DPIM

at ( M = 8)

(RDT)

at ( M = 8)

DIT

– bits

Images

Without

MPNO

(

)

Mbs

With

MPNO

(

)

Mbs

Without

MPNO

()

sec

With

(MPNO)

()

sec

Image (1)

(443x458)

760.176

1.937

0.081

31.776

Image (2)

(107x111)

48.502

1. 891

1. 269

32. 57

Image (3)

(300x400)

450.760

29.781

0. 136

2. 067

Decompressed

(199 KB)

Compressed

(0.507 KB)

Original Image 1

443x458 (199 KB)

Decompressed

(12.7 KB)

Compressed

(0.499 KB)

Original Image 2

107x111 (12.7 KB)

Compressed

(7.8 KB)

Original Image 3

300x400 (118 KB)

Decompressed

(118 KB)

WINSYS 2007 - International Conference on Wireless Information Networks and Systems

164

6 CONCLUSION

The paper results show that MPNO method offers

good compression ratio compared with GIF and

PNG methods lower Bit Rate lower bandwidth

requirement, higher RDT and lower transmission

capacity of DIT for M-DPIM system compared with

no compression case. It also improves the speed of

the hardware devices of the modulator and slot

synchronization in the demodulator stage, especially

for geometric-style images which has 256 colors at

any size, but each colored object in image must be

contented only one level from the 256 levels of

colors. Finally, the MPNO method has been satisfied

good contributions for digital multimedia

applications.

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CONTRIBUTION AND LIMITS OF A LOSSLESS DATA COMPRESSTION METHOD FOR PERFORMANCE OF

OPTICAL WIRELESS CHANNELS IN DIGITAL MULTIMEDEA APPLICATIONS

165