Bluetooth Based Smart Sensor Networks

1. INTRODUCTION
Portable and Secure Wireless Bluetooth Sensor System has been designed and its performance has been evaluated. The sensor system is light weight and has interoperability with Personal Area Network (PAN) and the architecture has been implemented by adopting an FPGA and a Bluetooth Module. The analysis of design shows its capability of continuous transmission of analog signals and a high rate of security level. As low sampling rates, the adopted solution offers low power consumption and lower battery capacity can be adopted and sensor weight can be minimized. With higher sampling rates, the Wireless Sensor System is equipped with FGMA which offers best architecture solution and high performance. So Wireless Bluetooth Sensor system can be widely adopted in critical applications like Detecting Vital Signs in Patients having serious pathologies A technology which requires no introduction and is being used constantly in Mobile Phones, Computers, Tablet PC’S, TV’S, Gaming Consoles and much more for transferring the data from one device to another. Bluetooth Wireless technology is becoming very popular to replace existing short range wired technology with short-range Wireless technology to enable new types of applications. With the increase in use of Bluetooth Technology, Various Researches and Manufactures are closely working to use this technology in completely different environments such as in Medical sector to improve the life quality and to reduce the cost incurred by hospitals in treating patients. A new concept called PAN (Personal Area Network) is evolving along with Bluetooth Technology. A PAN consists of a limited number of units interconnected to form a network and to exchange information among the connected nodes. Bluetooth acts a local connection interface between different personal units like Mobile Phones, PDA’s, Keyboard, Mouse, Gaming Consoles and much more. Bluetooth is a true enabling technology for the PAN Vision. The units are typically consumer devices which are used by different manufactures in different ways. So in order to have better interoperability between the personal devices, the security level has to be set up by the user. The Bluetooth technology has been designed in such a intelligent manner which enables even a ordinary user to maintain a good security level to protect the data and communication links in operation. With the help of PAN Technology, users can access their data wirelessly between different devices, work on them and store them in an Information System or in Electronic Personal Record.
2. REVIEW OF LITERATURE
Bluetooth technology was invented in 1994 by engineers at Ericsson, a Swedish company. In 1998, a group of companies agreed to work together using Bluetooth technology as a way to connect their products. These companies formed the Bluetooth Special Interest Group (SIG), an organization devoted to maintaining the technology. This means that no single company “owns” Bluetooth technology, but that many members of the Bluetooth SIG work together to develop Bluetooth technology.
2.1. DISCOVERY OF THE SMART SENSOR NODES Smart sensor node discovery is the first procedure that is executed upon the gateway installation. It goals to discover all sensor nodes in the area and to build a list of sensor’s characteristics and network topology. Afterwards, it is executed periodically to facilitate addition of new or removal of the existing sensors. The following algorithm is proposed.
When the gateway is initialized, it performs bluetooth inquiry procedure. When the blue tooth device is discovered, the major and minor
device classes are checked. These parameters are set by each smart node to define type of the device and type of the attached sensors. Service class field can be used to give some additional description of offered services. if discovered device is not smart node it is discarded. Otherwise service database of the discovered smart node is searched for sensor services. As currently there is no specific sensor profile, then database is searched for the serial port profile connection parameters. Once connection strings is obtained from the device.
2.2. BLUETOOTH SENSOR ARCHITECTURE
The Bluetooth Sensor Architecture consists of seven client modules and one master module for System Control. The main component of Bluetooth Architecture is FPGA which is shown in diagram 1. FPGA allows the device to be programmed, debugged and reconfigured after it is soldered onto a printed circuit board which reduces the possibility of lead damage and electrostatic discharge exposures.

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Fig1.FPGA-The Main Component of Module

The signals are generated by biomedical sensors for monitoring critical parameters such as Vital signs in patients. It has been realized in Wireless Sensor Architecture using one Analog/Digital Convertor (ADC) and two processors sharing the Bluetooth stack. A 24-bit multiplex sigma-delta converter converts the analogue input signal with 0-5Volt range. The sampling rate is 500 Hz on each of two channels. The digital signals are transmitted to a remote acquisition master sensor via Bluetooth (PAN 1540) The FPGA controls the acquisition from the sigma-delta converter and, as soon as an AD conversion has been made saves that particular value in the FPGA internal RAM memory.
3.BLUETOOTH
Blue tooth operates in the unlicensed ISM band at 2.4 GHZ frequency band and use frequency hopping spread spectrum technique. A typical Blue tooth device has a range of about 10 meters and can be extended to 100meters. Communication channels support total bandwidth of 1 Mb / sec. A single connection supports a maximum asymmetric data transfer rate of 721 KBPS maximum of three channels.
In Bluetooth, a Piconet is a collection of up to 8 devices that frequency hop together. Each Piconet has one master usually a device that initiated establishment of the Piconet, and up to 7 slave devices. Master’s Blue tooth address is used for definition of the frequency hopping sequence. Slave devices use the master’s clock to synchronize their clocks to be able to hop simultaneously.
When a device wants to establish a Pico net it has to perform inquiry to discover other Blue tooth devices in the range. Inquiry procedure is defined in such a way to ensure that two devices will after some time, visit the same frequency same time when that happens, required information is exchanged and devices can use paging procedure to establish connection.
Jump from pioneer to another depending upon the channel When more than 7 devices needs to communicate, there are two options. The first one is to put one or more devices into the park state. Blue tooth defines three low power modes sniff, hold and park. When a device is in the park mode then it disassociates from and Piconet, but still maintains timing synchronization with it. The master of the Piconet periodically broadcasts beacons (Warning) to invite the slave to rejoin the Piconet or to allow the slave to request to rejoin. The slave can rejoin the Piconet only if there are less than seven slaves already in the Piconet. If not so, the master has to ‘park’ one of the active slaves first. All these actions cause delay and for some applications it can be unacceptable for eg: process control applications, that requires immediate response from the command centre (central control room).
Scatternet consists of several Pico nets connected by devices participating in multiple Pico net. These devices can be slaves in all Pico nets or master in one Pico net and slave in other Piconets. Using scatternets higher throughput is available and multi-hop connections between devices in different Pico nets are possible. i.e., The unit can communicate in one Pico net at time so they parameter.

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Fig.2. Master and slave

4.A SCATTERNET

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Fig.3. BLUE TOOTH BASED SENSOR NETWORK

The main challenge in front of Blue tooth developers now is to prove interoperability between different manufactures’ devices and to provide numerous interesting applications. One of such applications is wireless sensor networks.
Wireless sensor networks comprise number of small devices equipped with a sensing unit, microprocessors, and wireless communication interface and power source.
1. An important feature of wireless sensor networks is collaboration of network nodes during the task execution.
2. Another specific characteristics of wireless sensor network is Data-centric nature.
As deployment of smart sensor nodes is not planned in advance and positions of nodes in the field are not determined, it could happen that some sensor nodes end in such positions that they either cannot perform required measurement or the error probability is high. For that a redundant number of smart nodes is deployed in this field. These nodes then communicate, collaborate and share data, thus ensuring better results.
Smart sensor nodes scattered in the field, collect data and send it to users via “gateway” using multiple hop routes.

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Fig.4. wireless communication is used.

It provides functions like discovery of smart sensor nodes, generic methods of sending and receiving data to and from sensors, routing.
5.GATEWAY LOGIC
1 It controls gateway interfaces and data flow to and from sensor network.
2 It provides an abstraction level that describes the existing sensors and their characteristics.

3 It provides functions for uniform access to sensors regardless of their type, location or N/W topology, inject queries and tasks and collect replies.
Communication With Users Gateway communications with users or other sensor networks over the Internet, WAN, Satellite or some shortage communication technology. From the user point of view, quering and tasking are two main services provided by wireless sensor networks. Queries are used when user requires only the current value of the observed phenomenon. Tasking is a more complex operation and is used when a phenomenon has to be observed over a large period of time.Both queries and tasks of time to the network by the gateway which also collects replies and forwards them to users.
6.SENSOR NETWORK IMPLEMENTATION
The main goal of our implementation was to build a hardware platform and generic software solutions that can serve as the basis and a test bed for the research of wireless sensor network protocols.
Implemented sensor network consists of several smart sensor nodes and a gateway. Each smart node can have several sensors and is equipped with a microcontroller and a bluetooth radio module. Gate way and smart nodes are members of the Piconet and hence maximum seven smart nodes can exist simultaneously in the network.
For example, a pressur pressure sensor is implemented, as bluetooth node in a following way.
The sensor is connected to the bluetooth node and consists of the pressure sensing element, smart signal-conditioning circuitry including calibration and temperature compensation, and the Transducer Electronic Data Sheet (TEDS). These features are built directly into the sensor micro controller used for node communication control plus memory for TEDS configuration information.

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Fig.5. Model of Smart Sensor

7. SMART SENSOR NODE ARCHITECTURE
The architecture shown in figure can easily be developed for specific sensor configurations such as thermocouples, strain gauges, and other sensor technologies and can include sensor signal conditioning as well as communications functions.

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Fig.6. A Bluetooth Wireless Smart Sensor Network Node

Conditioned along sensor signal is digitized and digital data is then processed using stored TEDS data. The pressure sensor node collects data from multiple sensors and transmits the data via bluetooth wireless communications in the 2.4 GHZ base band to a network hub or other internet appliance such as a computer.
The node can supply excitation to each sensor, or external sensor power can be supplied. Up to eight channels are available on each node for analog inputs as well as digital output. The sensor signal is digitized with 16-bit A/D resolution for transmission along with the TEDS for each sensor. This allows each channel to identify itself to the host system. The node can operate from either an external power supply or an attached battery. The maximum transmission distance is 10 meters with an optional capability to 100 meters.
The IEEE 1451 family of standards are used for definition of functional boundaries and interfaces that are necessary to enable smart transducer to be easily connected to a variety of networks. The standards define the protocol and functions that give the transducer interchangeability in networked system, with this information a host
microcomputer recognized a pressure sensor, a temperature sensor, or another sensor type along with the measurement range and scaling information based on the information contained in the TEDS data. With blue tooth technology, small transceiver modules can be built into a wide range of products including sensor systems, allowing fast and secure transmission of data within a given radius (Usually up to 10m).
A blue tooth module consists primarily of three functional blocks – an analog 2.4 GHz., Blue tooth RF transceiver unit, and a support unit for link management and host controller interface functions.
The host controller has a hardware digital signal processing part- the Link Controller (LC), a CPU core, and it interfaces to the host environment. The link controller consists of hardware and software parts that perform blue tooth based band processing, and physical layer protocols. The link controller performs low-level digital-signal processing to establish connections, assemble or disassemble, packets, control frequency hopping, correct errors and encrypt data.

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Fig7. Bluetooth module Hardware Architecture

The CPU core allows the blue tooth module to handle inquiries and filter page request without involving the host device. The host controller can be programmed to answer certain page messages and authenticate remote links. The link manager(LM) software runs on the CPU core. The LM discovers other remote LMs and communicates with them via the link manager protocol (LMP) to perform its service provider role using the services of the underlying LC. The link manager is a software function that uses the services of the link controller to perform link setup, authentication, link configuration, and other protocols. Depending on the implementation, the link controller and link manager functions may not reside in the same processor.
Another function component is of course, the antenna, which may be integrated on the PCB or come as a standalone item. A fully implemented blue tooth module also incorporates higher-level software protocols, which govern the functionality and interoperability with other modules.
Gate way plays the role of the Piconet’s master in the sensor network. It controls establishments of the network, gathers information about the existing smart sensor nodes and sensor attached to them and provides access to them.

8.FUNCTIONS OF GATEWAY:-
 Communication with sensor networks: Shortage Wireless Communication ; Discovery of smart sensor nodes
 Gateway Logic: Controlling Gateway interface and data flow ; Providing uniform access to sensors
 Communication with users: Communication over Internet, WAN, Satellite, etc.

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Fig.8. Communication with users

9. ADVANTAGES

Ease of installation –no wires needed.

Automatic Connection- doesn’t require too many buttons to be clicked

Inexpensive

Low Energy requirements

Less interference –Frequency Hop technique

Inexpensive instruments (even a normal camcorder can be used)

Needs a lot of time for matching the vehicles in the videos

High probability of human error in matching the data
9.1. MORE ADVANTAGES

Information Processing

Control center

Information Processing According to the method mentioned above, practicetests show that the sensor nodes work at Sleep status for more than 99% of the time and have little communication operation. Meanwhile, CSR Bluetooth module consumes as low as only 15 μA at Sleep status while as high as mA

level when working at other work modes.
Thus, this trigger method based on information change and SCM environment or extraordinary conditions, such as seabed medical experiment, etc.

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Fig.9. Information processing flow

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Fig.10.Control Center Structure

As shown in Figure , the module of the control centerconnects with the access point via public network to receive, analyze and process information, and to feed back control information to the access point for
monitoring sensor nodes. The control center is also responsible for displaying relevant information andcompiling database.

9. DISADVANTAGES
More opportunities for attack –No physical security is available in wireless. One can Track people’s movements .
Battery Wastage – Battery is wasted if Bluetooth is enabled for long hours.
Connection can be very slow sometimes
Blue-Jacking and Blue bugging.
9.1. SOME MORE DISADVANTAGES
TCP/IP was designed to primarily be used by computers and not small sensor and actuator nodes. Sensor nodes, with very limited memory and processing resources, may not always be capable of using memory oncoming protocols such as TCP. Below are the most significant drawbacks and issues concerning TCP/IP in sensor networking applications.
Code overhead: Implementations of TCP/IP have shown that it is possible to use IP with only 6.3 kB of added code space, and less than 1 kB of RAM on an 8- bit microcontroller platform . This may of course be a substantial part of the total resources available on the low-end microcontrollers often found on motes. More complex software also increases the processing load on the sensor node, thus increasing the power consumption as well.
Communication overhead: Communication overhead is defined as the number of bytes (or percent) that the communication system adds to the payload when transmitting a packet. If a single byte is transmitted using TCP, the actual packet size will be 41 bytes, consisting of a 20 byte IP header followed by a 20 byte TCP header.This will result in a packet where less than 3 percent is useful data and the remaining 97% is overhead. One solution to this problem is data aggregation, where as much sensor data as possible is sent as a single packet, thus reducing the overhead. However, the end-to-end delay will increase. Another solution is to apply header compression techniques . TCP has also been shown to be ill-suited for wireless networks , with bandwidth limitation.

10. APPLICATIONS
The features described above ensure a wide range of applications for
sensor networks. Some of the possible scenarios are given below:
• Health monitoring – Wireless sensor networks can be used in various ways to improve or enhance health care services. Monitoring of patients, health diagnostics, drug administration in hospitals, telemonitoring of human physiological data and tracking and monitoring doctors and patients inside a hospital are some of the possible scenarios Various sensors (blood pressure, heart monitoring, etc.) can be attached to the patient’s body to collect
physiological data that can be either stored locally (on a PDA or home PC) or forwarded directly to the hospital server or to the doctor in charge. There are several advantages of such monitoring: it is more comfortable for patients, doctors can have 24 hours access to patients and can better understand the patient’s condition and last, but not the least, incurred expenses are much less than when such tests are done in hospitals. Wearable sensors can also be used to track patients and doctors in the hospital or to monitor and detect behavior and health condition of elderly persons and children.
• Environmental monitoring – Fire detection, water pollution monitoring, tracking movements of birds, animals or insects, detection of chemical and biological agents are some of the examples of environmental applications of wireless sensor networks For example, numerous smart sensor nodes with temperature sensors on board can be dropped from an airplane over a remote forest. After successful landing, these devices will self-organize the network and will monitor temperature profile in the forest. As soon as the fire starts, that information along with the location of fire is transferred to the command centre that can act before the fire spreads to cover a large area.
• Military and security – The initial push towards wireless sensor network research came from military agencies. Military applications are various and vary from monitoring soldiers in the field, to tracking vehicles or enemy movement. Sensors attached to soldiers, vehicles and equipment can gather information about their condition and location to help planning activities on the battlefield. In case of nuclear or biological attacks, sensor fields can gather valuable information about the intensity, radiation.
1. Test Vehicle Technique (Floating Car):
This common technique consists of hiring someone to drive a vehicle along a preselected route and measure the elapsed time and distance traversed. It is possible to equip the vehicles to automate measurement and recording.
2. Electronic distance-measuring instruments (DMIs):
The integration of an electronic DMI with the floating car technique provides an easier and safer way to collect detailed travel time information (compared to traditional floating car method). In the DMI technology, the sensor is attached to the probe vehicle’s transmission. The DMI receives consecutive pulses from the vehicle transmission while the vehicle is moving. A DMI typically can provide instantaneous speeds up to every 0.5 second intervals. This detailed travel time information can be downloaded to a portable computer in an easy-to-use data format.
The major advantages of electronic DMIs include:
• Improvement in cost-effectiveness and safety of data collection over the
test vehicle method
• Easier data processing than test vehicle technique due to automatic recording of travel times to portable computer
• Detailed travel time and delay information that can be used for identification of bottlenecks and areas of extensive delay
• Providing acceleration and deceleration details that can be a valuable source of input data for fuel consumption and mobile source emissions analysis.
Some of the disadvantages of electronic DMIs include:
• Floating car technique is still somewhat labor-intensive and is usually limited to a few measurements per day per staff member
• Travel time is only as accurate as the driver’s judgment of traffic conditions
• Floating car technique on arterial streets may not measure the delay of cross street traffic turning onto the study route
3. License plate matching:
License plate matching was used as early as the 1950s for travel time studies but it was mainly used for tracking or identifying vehicles in origin-destination travel surveys. Early license plate matching methods relied on observers to note the license plates of passing vehicles at certain locations and record the corresponding times on paper or into a tape recorder. License plates were manually matched later in the office, and travel times were computed. Recent advances in digital technology have substantially improved the accuracy of this technique. The major advantages of license plate matching include:
• Providing large sample sizes during data collection period
• Providing representative estimate of travel times through random sampling
• Providing travel times at small time intervals, giving a speed profile for the study section throughout the peak period
• Resulting in lower costs per travel time run than the floating car method
• Providing useful data for OD studies
Some of the disadvantages of the license plate matching technique are:
• Data quality concerns from incorrectly reading or mismatching license plates
• Only overall travel times (no stopped delay) are collected
• Less practical for high speed traffic or long roadway sections with low percentage of through-traffic
• High initial cost for equipment purchase
• Potential public disapproval because of privacy concerns
4. Cellular phone tracking:
Some cities have a dedicated number of cellular phone users to report their position at designated checkpoints, allowing a traffic operations center to estimate travel times on the basis of several cellular phone reports. Cellular phones in use can also be tracked using geolocation techniques.
Based on the limited test information, cellular phone tracking has the following
• Minimal cost involved with providing the vehicles with the instrument
because of the current popularity of cellular phones

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Fig.11. Steering Wheel

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Fig.12. Keyboard

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Fig.13. Mouse

11. CONCLUSION
Bluetooth represents a great chance for sensor-networked architecture. This architecture heralds wireless future for home and also for industrial implementation. With a blue tooth RF link, users only need to bring the devices with in range, and the devices will automatically link up and exchange information.
Thus implementation of blue tooth technology for sensor networks not only cuts wiring cost but also integrates the industrial environment to smarter environment.
Today, with a broader specifications and a renewed concentration on interoperability, manufacturers are ready to forge ahead and take blue tooth products to the market place. Embedded design can incorporate the blue tooth wireless technology into a range of new products to meet the growing demand for connected information appliances
11.1.FUTURE TASKS
❖ Future work is aimed to develop and design a blue tooth-enabled data concentrator for data acquisition and analysis.
 One topic that needs to be investigated is to seamlessly integrate the time scheduling mechanism into a standard Service Discovery Protocol, preferably zeroconf . This approach will enable users on the Internet as well as in the local network to both receive and set the duty cycle of sensor nodes. The usage of GPS based time synchronization is another way of obtaining correct time, and finally the precision of (S)NTP over high delay radio links (GPRS, UMTS),

must be further investigated. The usage of synchronous Bluetooth data packets (SCO) with low delay and jitter may be used to decrease the clock error between nodes. A mechanism for a sensor node to cache the time schedules of other nodes in its vicinity may also prove useful.

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