1. CDMA WIRELESS DATA TRANSMITTER By Vijay kumar kintali B.tech 7 th semester Regd no:0701222065

2. CONTENTS  NEED FOR WIRED DATA TRANSMITTER  LIMITATION OF WIRED DATA TRANSMITTER  EVOLUTION OF WIRELESS DATA TRANSMITTER  CDMA TECHNIQUE  SPREAD SPECTRUM TECHNIQUE  SIGNAL MODULATION TECHNIQUES  MULTIPLE ACCESS METHODS  ADVANTAGES DISADVANTAGES AND FUTURE SCOPE  APPLICATIONS  CONCLUSION

3. NEED FOR WIRED DATA TRANSMITTER  For the past decade the state of technology for machine health monitoring has been continuously improving.  Majority of monitoring systems employed at the factory floor still require maintenance engineers to manually collect data and analyze them off-line.  Most of these systems require wired connections for data acquisition and transmission.

4. LIMITATION OF WIRED DATA TRANSMITTER  Low accessibility  Complex hardware  Space consuming  Power consuming

5. EVOLUTION OF WIRELESS DATA TRANSMITTER  To overcome the restrictions of wired data connection wireless data transmission for embedded sensing and machine condition monitoring has been developed.  Most of these systems operate on batteries and transmit data over a short distance to a data logging station nearby.  A challenging issue in wireless data transmission is to design for low power, less circuitry complexity, and high reliability.  The paper deals with wireless data transmitter employing code division multiple access schemes.

6. CDMA TECHNIQUE  CDMA stands for CODE DIVISION MULTIPLE ACCESS.  Developed by US company –QUALACOMM.  Digital technology for delivering mobile telephone services.  Uses spread-spectrum techniques.  CDMA doesn’t design a specific frequency to each user neither it is time-shared.

7. SPREAD SPECTRUM TECHNIQUE

8. SIGNAL MODULATION TECHNIQUES:  Amplitude Shift Keying(ASK) The ASK technique modulates the data by assigning each symbol a different amplitude level, e.g.: two levels for binary data.  Frequency Shift Keying(FSK) This technique employs different frequencies for different symbols transmitted.  PHASE SHIFT KEYING(PSK) Here, the carrier wave by itself represent a symbol, whereas all other symbols are defined by phase shift from the phase of carrier.

9. MULTIPLE ACCESS METHODS : In order to accommodate multiple transmitters with one data receiver and achieve design flexibility and extensibility a multiple data access scheme needs to be implemented. Three design options were considered:  Frequency division multiple access[FDMA] In FDMA, each transmitter has a frequency exclusively assigned to it. This enables transmitter to send data at any time regardless of other transmitters. The frequency ranges can be transmitted simultaneously and should be non-overlapping. Contd

10. Time Division Multiple Access [TDMA]  A single carrier frequency can be used by several transmitters, if it is ensured that at no time more than one transmitter sends data simultaneously.  Accordingly, each transmitter is assigned a time slot for signal transmission.  The time slots need to be synchronized between all the transmitters in the system.  This requires that for each transmitter, a separate receiver is implemented, and the receiver must be ON at all times, increasing the power consumption of the circuitry. contd

11. Code Division Multiple Access [CDMA]  CDMA is based on coding theory and uses sequences of numbers called chips.  Here the bandwidth of shared through code, the stations use different codes to achieve multiple access.  To generate chip sequences we use Walsh tables it uses two basic rules w 1= [ +1] w 2N= WNWN WNWN WNWN WNWN

12. Bit 0 silent 0 +1 [-1 -1 -1 -1] [+1 +1 +1 +1][+1 -1 +1 -1] [+1 -1 -1 +1][+1 +1 -1 -1] [0 0 0 0][+1 -1 -1 +1] [-1 +1 -1 +1] [-1 -1 -3 +1] DATA Data bit 0 - 1Data bit 1 +1 Silence 0

13. Data Transmitter based on CDMA technique

14. Flow-chart for data transmission sequence

15. ADVANTAGES  Power tuning  Voice quality  User density  Cost at a suitable level i.e., less cost  Wireless increases utility and accessibility  Software implementation allows further modification  Increased mobility and scalability: more portable, half the size of credit card.

16. DISADVANTAGES  WCDMA has higher data speed than CDMA  It reported initial difficulty in market introduction.  Reducing clock frequency and transmission speed for reduced power consumption will lead to a prolonged transmission time. FUTURE SCOPE  Can be used in mobile communication with a speed up to 2mbps for voice, video data and image transmission with WCDMA.

17. APPLICATIONS  Machine health monitoring to machine components  Design of a wide range of electronic instruments such as data loggers, data acquisition cards, hand- held metering devices  Systems that are difficult to access or not suitable for wired sensor data acquisition.  A rice sized chip called Verichip embedded in body,made of biocompatible materials, stores entire medical history of implantee.

18. Conclusion CDMA transmitter demonstrates the feasibility of employing a sophisticated transmission scheme in an embedded sensor for machine health monitoring. Focusing on constraints and power efficiency during the design phase.

19. References:  www.google.com  www.TECHONLINE.com  www.wikipedia.com  Halsall.F,’ “ Wireless Local Area Networks”, Data communications, Computer networks and open systems.  Robert. X. Gao, Philipp Hunerberg- design of a CDMA-Based wireless Data Transmitter for Embedded serving

20. Thank you

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