Definition and concept of spread spectrum

Spread Spectrum is a communication technology that disperses a signal's bandwidth over a broad spectrum of frequencies. It entails modulating the signal using a special programming to enable transmission across a wide range of frequencies. The benefits of this method include more safety, greater resistance to interference, and effective use of the available bandwidth. Wireless local area networks (WLAN), cellular networks, and military communications are just a few of the areas where Spread Spectrum provides dependable reliable wireless communication. Spread spectrum technology improves signal quality, avoids interference, and ensures dependable data transfer by spreading the signal.

 There are two types of Spread Spectrum

• Frequency Hopping Spread Spectrum (FHSS)
• Direct Sequence Spread Spectrum (DSSS)

Frequency Hopping Spread Spectrum (FHSS) is a spread spectrum technology used in wireless communication. It involves fast changing frequencies within a predetermined sequence. The signal is divided into small piceses of packets and transmitted across different frequencies, hopping from one frequency to another in a synchronized manner. FHSS provides enhanced resistance against interference, as well as improved security and privacy. By dynamically hopping frequencies, FHSS enables reliable data transmission in the presence of noise, jamming, or other sources of interference, making it suitable for applications such as wireless LANs, Bluetooth devices, and military communications.

• Frequency hopping is a spread spectrum technique that involves transmitting the signal over a random sequence of frequencies.
• That is, first transmitting at one frequency, then a second, then a third, and so on. 
• The random sequence of frequencies is computed by a pseudorandom number generator. 
• The receiver uses the same algorithm as the sender and initializes it with the same seed and hence is able to hop frequencies in sync with the transmitter to correctly receive the frame. 
Table Of Contents

Direct Sequence Spread Spectrum (DSSS)

Wireless communication systems use the spread spectrum technique known as direct sequence spread spectrum (DSSS). By multiplying the initial data signal with a high-rate pseudo-random noise (PN), often referred to as a spreading code, the signal is spread across a wider bandwidth. A binary sequence known as the spreading code serves as a "mask" for expanding the signal.

Multiple chips (signal elements with a shorter duration) of the spreading code are used in DSSS to represent each bit of the original data. A broader bandwidth transmission is the effect of this. The phrase "direct sequence" refers to the direct multiplication of the signal with the spreading code and refers to the spreading code's often significantly faster data rate compared to the original data.

•   Each bit of data is represented by multiple bits in the transmitted signal.
•   DSSS takes a user data stream and performs an XOR operation with a pseudo –random number.  
•   This pseudo random number is  called as chipping sequence. 

What are the applications of FHSS and DSSS?

FHSS 

• Wireless Local Area Networks( WLAN) FHSS is generally used in WLAN systems to give dependable and secure wireless connectivity, especially in surroundings with hindrance from other bias.
• Bluetooth Technology FHSS serves as the foundation for Bluetooth, enabling flawless communication between colorful bias similar as smartphones, tablets, and wearable bias.
• Service and Defense Systems FHSS is considerably employed in military and defense operations for secure and robust communication, effectively fighting jamming and interception attempts.

DSSS

• Wireless Communications DSSS is wider used in wireless communication systems, including WLANs, cellular networks, and satellite dispatches, due to its capability to give good and robust transmission indeed in the presence of hindrance.
• CDMA- based Systems DSSS is a core technology in Code Division Multiple Access( CDMA) systems, enabling multiple druggies to partake the same frequence band while maintaining data sequestration and minimizing hindrance.
• GPS Navigation DSSS is employed in Global Positioning System( GPS) navigation to transmit and admit accurate positioning signals, allowing for precise position shadowing and navigation.

WIRELESS LAN ( IEEE 802.11) 

•     Wireless communication is one of the fastest-growing technologies. 
•     The demand for connecting devices without the use of cables is increasing    everywhere. 
•     Wireless LANs can be found on college campuses, in office buildings, and in many public areas. 

ADVANTAGES OF WLAN /  802.11

1. Flexibility: Within radio coverage, nodes can access each other as radio waves  can penetrate even  partition walls.
2. Planning : No prior planning is required for connectivity as long as devices follow standard convention
3. Design : Allows to design and develop mobile devices.
4. Robustness : Wireless network can survive disaster. If the devices survive, communication  can still be established. 

DISADVANTAGES OF WLAN /  802.11

1. Quality of Service : Low bandwidth  (1 – 10 Mbps), higher error rates due to interference, delay due to error  correction and detection.
2. Cost : Wireless LAN adapters are  costly compared to wired adapters.
3. Proprietary Solution : Due to slow standardization process, many solution are proprietary that limit the homogeneity of operation.  
4. Restriction : Individual countries have their  own  radio spectral policies.  This restricts the development of the technology
5. Safety and Security : Wireless Radio waves may interfere with other devices.  Eg;  In a hospital, radio waves may  interfere with high-tech equipment. 

Conclusion

In conclusion, spread spectrum in WLAN plays a vital part in revolutionizing wireless connectivity. By employing ways like frequence Hopping Spread Spectrum( FHSS) and Direct Sequence Spread Spectrum( DSSS), it enhances resistance against hindrance, ensures good data transmission, and provides secure communication. Spread spectrum in WLAN enables flawless connectivity in crowded surroundings, mollifying the impact of hindrance from other bias. It optimizes bandwidth application, allowing for effective sharing of available diapason resources. With its robustness, security, and capability to overcome hindrance, spread diapason in WLAN continues to drive the advancement of wireless networking, supporting the ever- growing demand for dependable and high- performance wireless communication. 

WLAN technologies uses Spread Spectrum (SS) technology. 

• The demand for connecting devices without the use of cables is increasing    everywhere. 
•     Wireless LANs can be found on college campuses, in office buildings, and in many public areas.