Implementation of embedded bluetooth data broadcast system

IJRET: International Journal of Research in Engineering and Technology ISSN: 2319-1163
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Volume: 01 Issue: 03 | Nov-2012, Available @ http://www.ijret.org 368
IMPLEMENTATION OF EMBEDDED BLUETOOTH DATA BROADCAST
SYSTEM
K.Hanuja1
, A. Rajaiah 2
, V. Jyothi3
1
Associate Professor, Department Of ECE, Abhinav Hi-tech College Of Engg, Hyderabad, India.khanuja@gmail.com
2
Associate Professor, Department Of ECE, JBREC College Of Engg , Hyderabad, India.,
3
Assistant Professor, Department of ECE, JBREC College of Engg, Hyderabad, India, jyothinaik@gmail.com
Abstract
Enhance Data Rate (EDR) in Bluetooth 2.0 specifications provide condition for Bluetooth multi-point communication. Aiming at
application requirements of Bluetooth technique in wireless communication, Embedded Bluetooth Information Broadcast System
(EBIBS) based on ARM9 microprocessor S3C2440 was designed and implemented. The system runs on ARM-Linux operation system
and achieves single point transmission, multi-point transmission and information update based on Bluetooth 2.0 specifications. BlueZ
protocol stacks and object exchange (OBEX) were utilized to complete multi-point transmission. Device driver technique was used to
switch core functions and retransmission mechanism to ensure reliability of information broadcast. The system has been verified at
broad-level and practical application. The result was also provided.
Index Terms: ARM, Bluetooth, embedded, information broadcast
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1. INTRODUCTION
Bluetooth is an open standard for wireless data and voice
communication. As a short-range wireless communications
technology standard, Bluetooth technology has been widely
applied in wireless communication field as personal
communications devices, wireless network communication and
various transmission systems for its advantages of low cost, low
power, small size and etc. The intelligent and multimedia trend
integrates embedded computer system and wireless
communication application has become increasingly clear, both
wide-area mobile communications and short-range
communication technology have played a pivotal role in
information society. Embedded Bluetooth application that
integrates embedded technology and Bluetooth communication
is one of development directions currently and future.
Traditional Bluetooth communication based on 1.0 specification
only supports unicast.
As Bluetooth technology develops, the Bluetooth 2.0
specifications add EDR technique to improve throughput of
Bluetooth data transmission and provide condition for multicast
communication. In the current data communication researches
about Bluetooth 2.0 specifications, the general Bluetooth data
communication system and wireless intelligent home gateway
are based on unicast not considering information broadcast
functions. According to 2.0 specification and combining with
TDD technique, the paper implemented Bluetooth information
broadcast system and completed multipoint transmission and
network communication among Bluetooth devices.
Information broadcast and information update with Bluetooth
provides broad development space for advertisement and other
industries related to information publish The paper is organized
as follows. In section 2, we give system functions as well as
software and hardware architecture. The specific implement of
information broadcast function is conducted in section 3.
Section 4 introduces implement of information update. The test
on information broadcast and information update is carried out
in section 5 and section 6 concludes our work.
2. Device FUNCTIONS, ARCHITECTURE
2.1 Device Overall Framework
The designed EBIBS mainly complete two functions, namely
information broadcast and information update .The information
broadcast completes the task that sends information to multiple
Bluetooth devices around EBIBS at the same time, mainly
including information unicast and multicast. Information update
achieves network communication between EBIBS and PC. It
completes seamless connections between Bluetooth and TCP/IP.
Users are permitted to access file system via FTP, so the EBIBS
can timely update information based on user requirement, which
greatly improve system operability. The architecture of EBIBS
is shown in Fig. 1. In addition, user interaction interface was
designed. The USB host in interface improves system scalability
and portability.

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Fig-1.EBIBS architecture
2.2 Device Hardware Framework
The EBIBS is based on ARM hardware development platform
and uses Samsung S3C2440 as core processor. The micro-
processor constitutes core embedded system with 64MB
SDRAM and 64M Flash. It runs ARM-Linux-2.6.12core
operation system, where Bluetooth bus-system is configured to
provide driver for USE Bluetooth adapter. As core
communication component, Bluetooth adapter connects to USB
device interface. LED and key constitute hardware part of user
interaction interface. The system is easy to extend function and
migration system. Developers can download operation system
core and upper applications to SDRAM or Flash via USB Host
interface and debug applications with RS-232 serial port.
2.3 Device. Software Framework
Software framework can be divided into two main modules,
namely information broadcast module and information update
module. The information broadcast module can be further
divided into three sub-modules: information management
module, device query module and information transform
module. Information management module is responsible for
sorting information so that user can send it in specific order. The
device query module uses Service Discovery Protocol (SDP) to
obtain information of surrounding Bluetooth devices service and
automatically filter remote device with object push service as
discovery objects. As core module, information transform
module complete information broadcasting. LED driver and key
driver are added into system to provide low level software
support for user interaction functions. The software framework
of EBIBS is shown in Fig. 2.
Fig-2. Device software framework
Information broadcast module and information update module
are designed according to official Bluetooth protocol BlueZ and
OBEX, where BlueZ includes two parts of core library bluez-
libs and bluez-utils utility. The latter provide developers with
tools support for upper-level applications.OBEX protocol is
realized by OpenOBEX application function library. Therefore,
the design firstly implements migration from BlueZ and
OpenOBEX to ARM9 hardware platform system and then
achieves other functions. LED and key driver are designed
according to embedded character-driven technology.
3. DATA BROADCAST IMPLEMENT
3.3 Unicast Implement
As information unicast basis of information broadcast, it is also
the core of design. The system firstly complete file transmission
process in single point mode. The process is based on OBEX
protocol and uses OPENOBEX function library achieves object
push on some remote device. OPENOBEX function library
completes session layer operation and corresponding object
model description of OBEX protocol. Fig. 3 shows complete
process of object push.
(1) OBEX-INIT() function is used to initiate OBEX
entity,including initiate transform type, socket description,
maximum size of send packet and maximum size of receive
packet and then return a entity handle.
(2)Store target Bluetooth device address, object push service
channel number and information file name to corresponding
local variables.
(3)Call BtOBEX_TransportConnect() function establish
transmission connection. The function firstly initiate
transmission attributes of local and remote OBEX entities and
then call socket () system function to create local socket. The
bind () function is used to bind socket and process and connect()
function is used to connect local device socket and remote
socket. Finally return connect () system call. If the return value
is 0, it indicates the connection is successful.

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(4)Broadcast system send connect request to remote device. It
firstly call OBEX-Object New () function to create a send
request object and then call OBEX-Client () to write request into
local device, and then send it out. At this moment, broadcast
system calls OBEX-Handle Input () function to wait fro
response signal of remote device. The function call select () and
register socket between broadcast system and remote device so
that system can listen to events on the socket. After remote
device responds, the function will read and process received
data, otherwise the function will block. If returned event
variable is OBEX_RSP_SUCCESS, it says that remote device
respond successfully.
(5)Send file object to remote device. Firstly,
build_object_from_file () function is used to create file object.
The function will access related file information about file
content, size and send the Object out. Then it waits for response
from remote device.
Fig-3. Object push protocol implements process
(6)Send disconnect request to remote device. As same to send
connect request, after remote device successfully respond, it
disconnects .With the above process, system completes once file
object transmission with object device. In case of information
broadcast, the process is called recycled to complete file
transmission.
After all transmission tasks completed, information transmission
parent process firstly determine whether all child process has
exited. If so, enter into next round transmission, otherwise it will
block operation and wait for other child process to exit. Each
child-process will then create information push child-process.
The process call object push function to complete transmission
to some device. In the process to waiting for push, child-process
query user key signal and respond.
In the waiting period, retransmission mechanism is initiated to
determine reason of child-process exiting. If the reason is file
transmission complete or user deny, send next information. If
the connect is failed to establish for Bluetooth channel
competition, re-initiate connect and the number should be no
more than 5 times. In order to avoid frequently send information
to same remote device, the system set transmission time interval
of 10min in particularly. If system detects some device in 10min
for the second time, it cancels transmission to the device. If it
found the device after time interval, re-send information to the
device.
3.2. Multicast Implement
Fig-4. Multicast transmission flow
Multicast transmission uses TDD and EDR technologies in
Bluetooth protocol to implement information transmission from
system to multiple Bluetooth devices. Meanwhile, multiple
process technique is used to reasonably manage multiple
transmission processes, so that the information can be sent to
remote device effectively and promptly. The TDD technique is
used so that multiple devices can share a physical channel. Data
is packet and sent in time division multiplexing manner. The
EDR technology increases transmission bandwidth and
transmission rate of Bluetooth data so as to improve information
multicast transmission efficiency. The multicast transmission
process is shown in Fig. 4
Firstly, information transmission parent process creates child
processes whose number is equal to that of Bluetooth devices.
Each sub-process independently undertake task that send
information to Bluetooth device so that information can be
broadcasted to multiple devices.

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4. DATA UPDATE IMPLEMENT
Information update function uses PAN technique to establish
network communication between broadcast system and PC
based on TCP/IP. In the Bluetooth network ,the client is called
PAN or PANU, while server provides two kinds of
services(Network Access Point) NAP and (Group Network)GN.
In EBIBS, NAP is used for networking. There are only two
devices in the network, namely PC and broadcast system. The
role of PC is PANU and system is NAP, which acts as server.
Firstly, the system is in listening state. At this moment,
Bluetooth software in PC is used to query NAP service of
EBIBS and networking request is broadcasted. After system has
listened connection request, it responds. After successful
networking, broadcast system will automatically assign IP to PC
and set its own address. If the IP of PC is set in same network
segment with broadcast system, PC can immediately
communicate with system via TCP/IP and update information in
broadcast system through FTP.
5. RESULT AND ANALYSIS
5.1. File Unicast Test
Take Bluetooth broadcast system as sender and mobile phone
with Bluetooth service as receiver. Five times of file
transmission were carried on a phone and file transmission time
was recorded to compute average transmission rate. The result is
shown in Table 1. All received image can be normally showed
in the phone. Result shows that unicast performance is stable in
case of different size and different format. The maximum rate is
up to 19.7KBps, which can meet general Bluetooth
communication requirements.
Table-1.File Unicast Test Results
5.2. File Multicast Test
The experiment is mainly used to test connect reliability and file
transmission time.
(1) Compare connect success ratio before and after adding
retransmission mechanism to show the importance of
retransmission mechanism on improving reliability of multicast.
The method to compute connection success rate is as follows:
Connection success rate = number of successful connections
/(information number in each group�number of device) �
100%.
Firstly, we tested connect success rate between test system and
remote device before retransmission mechanism was
added.Taking mobile phone as receiver client, the result is
shown in Fig. 5. The results show that the connection success
rate is only 53.33%, which cannot meet actual needs. Added
retransmission mechanism, connect success rate is up to 100%
in all cases. The connection reliability is significantly improved
to meet practical application needs.
(2) Test multicast transmission time to illustrate role of TDD in
practical transmission. Broadcast system sent a 200KB JPEG
format image to all phones and number of phones increase from
1 to 5. The test result is shown in Fig. 6. Received image can all
be normally showed on 5 phones, which indicates multicast
transmission is stable and reliable and there is no packet loss.
As phone number increases, transmission time also increase,
which indicates that TDD reasonably packet data and
transmission is reliable. In case of 5 phones, the average
transmission rate is about 58.8KBps, which has been greatly
improved compared with average transmission rate of unicast.
Chart-1: Test results of connection success rate
Chart-2: Test results of File transmission time

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CONCLUSIONS
The paper implemented BlueZ protocol stack and OpenOBEX
function library based on ARM-Linux with ARM hardware
platform. The information broadcast and update function was
achieved based on Bluetooth 2.0 protocol. The focus is on
information unicast and multicast. The EBIBS is low cost, high
reliability, real-time and can be flexibly extended. It also has
good portability and interactive features. The program can be
applied to variety municipal and public place propaganda
system combining with multimedia technologies. It can also be
used form publish of commercial advertisements, which has a
good prospect.
REFERENCES
[1] ZOU Y. and CHEN C.: MCU system software in video
conference network, International Conference on
Communication Technology Proceedings, Beijing: ICCT, 1996,
pp. 173-177.
[2] CHAUDHRY J., MURAWWAT S. and SALEEMI F.:
Power optimized secure Bluetooth communication, IEEE
International Multitopic Conference, 2008, Karachi: INMIC, pp.
182-188.
[3] GU Jian-feng, XIAO Yi and ZHANG Hai-xia: Bluetooth
Communication Based on ARM, Mechanical Engineering &
Automation, vol. 162, 2010, pp. 127-129.
[4] MAN S., YANG H. X., PENG Y. and WANG X. S.: Design
of embedded wireless smart home gateway based on ARM9,
Journal of Computer Applications, vol. 30, 2010, pp. 2541-
2544.
[5] Samsung Corporation, S3C2440A 32-bit RISC
microprocessor user's manual, http: / /www. samsung. com.
BIOGRAPHIES:
K. Hanuja .M.Tech (ECE).She is
currently working as Assoc Prof. in
Department of Electronics &
Communication and Engineering in
Abhinav Hi-Tech College Of Engineering.
She has guided more than 10 projects to
final year B.E/B.Tech students with good
industry and teaching experience. Her area of interest in
Electronics is Digital Communication, Embedded systems.
A. Rajaiah, M.Tech (ECE) He is currently
working as Prof in of Department in
Electronics & Communication Engineering
in JBREC . He has guided more than 15
projects to final year B.E/B.Tech /M.Tech
students and his area of interest in
Embedded Systems, Signal Processing.

Implementation of embedded bluetooth data broadcast system

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