G.H RAISONI COLLEGE OF ENGINEERING (An Autonomous Institute Under UGC act 1956 & affiliated to R.T.M. Nagpur

University)Department Of Electronics & Telecommunication Engineering,

Session 2015-16

Presentation On “Spread Spectrum Communication”

For TAE-2 of Subject Wireless Sensor Network

Submitted By:- AMIT V. LUTEM.Tech III Sem.

(Communication Engg.) Roll No. 13

Communication System

•In telecommunication, a communications system is a collection of individual communications networks, transmission systems, relay stations, tributary stations, and data terminal equipment usually capable of interconnection and interoperation to form an integrated whole.

•The components of a communications system serve a common purpose, are technically compatible, use common procedures, respond to controls, and operate in union.

• In general words the communication can be defined as the process of connection between two systems with the use of medium may be wired or wireless depending on the type of system

•The approach to these communication are also different for different systems.

Spread Spectrum Communication

• In wireless Sensor Network Spread-spectrum Communication techniques are methods by which a signal is generated with a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth.

• These techniques are used for a variety of reasons including the establishment of secure communications, increasing resistance to natural interference, noise and jamming, to prevent detection etc.

• This is a technique in which a communication signal is transmitted on a bandwidth considerably larger than the frequency content of the original information.

• Frequency hopping is a basic modulation technique used in spread spectrum signal communication.

• Spread-spectrum communications is a signal structuring technique that employs direct sequence, frequency hopping, or a hybrid of these, which can be used for multiple access and multiple functions.

• This technique decreases the potential interference to other receivers while achieving privacy.

• There are two Spread Spectrum Communication techniques: 1] Frequency Hopping Spread Spectrum (FHSS) 2] Direct Sequence Spread Spectrum (DSSS)

• A few spread-spectrum circuits employ continuous frequency variation, which is an analog scheme.

Frequency Hopping Spread Spectrum (FHSS)

• FHSS is used to broadcast the signals over seemingly random series of frequencies.

• Receiver of FHSS hops between frequencies in sync with transmitter.

• In FHSS jamming on one frequency affects only a few bits.

• FHSS typically carriers 2k frequencies forming 2k channels.

• Channel spacing corresponds with bandwidth of input

• Each channel used for fixed interval300 ms in IEEE 802.11.Some number of bits transmitted using some encoding scheme

Fig.1: Frequency Hopping Spread Spectrum System Transmitter

Fig.2: Frequency Hopping Spread Spectrum System Receiver

Fig.3: Functioning of FHSS

Direct Sequence Spread Spectrum (DSSS)

• In DSSS each bit represented by multiple bits using spreading code.

• DSSS spreads signal across wider frequency band in proportion to number of bits used. 10 bit spreading code spreads signal across 10 times bandwidth of 1 bit code.

• The method of performing the DSSS is combine input with spreading code using XOR. Input bit 1 inverts spreading code bit. Input zero bit doesn’t alter spreading code bit. Data rate equal to original spreading code.

• The functioning of DSSS is somewhat similar with FHSS.

Fig.4: Direct Sequence Spread Spectrum Transmitter

Fig.5: Direct Sequence Spread Spectrum Receiver

Fig.6: DSSS example

Advantages of Spread Spectrum Communication

• The SS Communications are widely used today for Military, Industrial, Avionics, Scientific, and Civil uses.

• It is used in Jam-resistant communication systems.

• It is useful in multiple access communications wherein many users communicate over a shared channel like CDMA system.

• Spread Spectrum Communications is often used in high resolution ranging. It is possible to locate an object with good accuracy using SS techniques.

• Long-range wireless phones and wireless sensors for home and industry

APPLICATIONS

• Cellular/PCS base station interconnect

• Private networks

• Railroads and transportation

• Utilities like electricity, oil, gas and water

• Disaster recovery and special event PSTN extensions

• Videoconferencing

CONCLUSION

• It can be seen that the Spread Spectrum Communication has an important place in the various communication systems with various features.

• The spread spectrum communication has an advantage of multiple user in single system with multiple channels at a same time.

• It is not only used in the industrial systems but can also be implemented this communication system in the household or general use.

• Being a simple but at the same time its effectiveness, places this communication type at the most of the reliable communication system.

THANK YOU…!!!!!!