Spread Spectrum Techniques: Methods, Advantages, And Applications

Spread Spectrum Technology

Discuss about the Measurement of RF System Nonlinearity.

The spread spectrum techniques are used as by the help of the spread spectrum method the signal which is generated with a particular bandwidth is spread in the frequency domain. This will result in the signal spreading over a larger bandwidth. The use of the spread spectrum techniques can be made for various other purposes. The use of the spread spectrum technology may be used for the reduction of the noise in the channel. The use of the spread spectrum method is helpful in the registering of the safe and efficient technique of communication through the various mediums (Wichman & Larson, 2017).  A large number of problem arises due to the presence of interference in a system. Due to the presence of the interference, there is a reduction in the quality of the output. The use of the spread spectrum technology also helps in the reduction of the interference in the system as a result increasing the efficiency of the system and the increasing the quality of the output of the system.

The process takes place on a bandwidth whose frequency is larger than the original information frequency which is transmitted. The basic modulation technique that is used in the spread spectrum transmission method is the frequency hopping technique. The spread spectrum is a type of method of signal structuring that uses the method of  the direct sequence, the frequency method or it may be a hybrid or the mixture of the both. The potential interference is reduced in this method (JPL Wireless Communication, 2018). The reduced interference is transferred to the receivers and in this process it is made sure that the privacy is also achieved. The spread spectrum method exist in a number of forms such as the frequency- hopping spread spectrum, direct sequence spread spectrum, the time- hopping spread spectrum, chirp spread spectrum and the combination of all these techniques. The description about two of the methods is given below that shows the contrast, use of both the techniques and how the techniques work.

Frequency hopping spread spectrum: The frequency hopping spread spectrum method is a form of the spread spectrum method. The process takes place by the help of the transmission of the radio signals among the frequency channels. The process takes place by the help of the generation of the pseudorandom sequence, which is identified by both the transmitter and the receiver (Smys, Prakash & Raj, 2015). The method can be used as a multiple access method. The use of the frequency- hopping spread spectrum may be made in the sector of the code division multiple access in the form of frequency- hopping code division multiple access.

Frequency Hopping Spread Spectrum Method

Direct Sequence spread spectrum: The method of the direct sequence spread spectrum may be used in order to reduce the signal interference in an overall manner that is present. The direct sequence spread spectrum method is a method of spread spectrum modulation technique, the spreading if which signal makes the channel of the wideband more noisy. This wideband channel occurs due to the spreading of the signal (Quyen et al., 2016). This process allows to provide greater resistance to the interference.  With the help of  this method, the message signal is made use in order to modulate the bit sequence, which is known as the PN sequence or the pseudo noise code.

The use of the radio system can be made in order to transfer the information from one telecommunication system to the other. These information are transferred or are shared in the form of signal using air as the mode of transfer (Peng et al., 2015). The radio system is a complex structure and may consist of a number of devices. The various devices that the radio system is composed of are:

• Power supply unit
• Controlling unit
• Antenna turning unit
• Filter and Multicoupler
• Power Amplifier
• Audio unit
• System Racks

The mixers can be stated as frequency mixers. The use of the frequency mixers may be made in order to create new frequencies. The creation of the new frequencies will help in the interconnection of the two or more signals. The transmission of the signal takes place from one frequency range to the other frequency range. The main working principle of the mixer lies in the fact that the mixer can identify the sum and the difference level of the frequencies and these are transmitted for the communication (Nickolas, 2015). The active mixers and the passive mixers are the two kinds of mixers that are present. The main function of the active mixers is to increase the strength of the signal while the function of the passive mixer is to decrease the strength of the signal. The active devices can increase the strength of the signal as these consist of the active devices. The use of the passive mixers may be made in instances where the output signal should have a lower strength as compared to the input. The passive mixers are designed by the use of the passive devices such as diodes. The passive mixers find a wide range of application because of the wide bandwidth that the passive mixers are having.

The unbalanced mixer other than the production of the signal allows the passage of both the input and the output signals. The unbalanced mixer has the characteristic of operating in a situation that does not have the presence of the DC bias. There is a input port for the receiving of the input signal. There is also a local oscillator which is involved in the taking of the input of the signals.

Direct Sequence Spread Spectrum Method

The use of the single balanced mixers can be made in order to handle any kind of noise or the radio frequencies. The use of the single balanced mixers can be made for the handling of the data in the local oscillator so that the noise that is present can be easily removed (RadioElectronics, 2017). The single balanced mixers have a simple structure which is easy to understand and implement.

The double balanced mixers can be stated as a type of the passive device mixer. There are a  number of advantage that the double balanced mixers are having as compared to the single balanced mixers. The advantage of the double balanced mixer may be to improve the linearity of the system (RadioElectronics, 2018). However, compromise is made on the noise of the system in the process of improvement of the linearity.

There are a number of technologies that are being used, which depends on the concept of the use of the wireless networks. Some of the advanced technologies involve:

• Li- Fi: This is the concept where the communication is made on the basis of the high speed lights. This is an advanced form of technology, which implements the idea of the high speed lights. The concept of Wi- fi can be compared to the Li- fi as both are similar concepts as both make the use of the electromagnetic wave for the carrying out of the communication or for the transfer of the information (Tsonev, Videv & Haas, 2014). As the Li- fi has the advantages of using the light for the communication process and security, there are also few weakness such as if there is unavailability of light then the communication is stopped. The other weakness is that the Li- fi has to transmit the data within a specified range.

• Zigbee: The Zigbee has a communication between the controller and the sensors and is used as personal area network. The cost of implementation of the technology is less and it also requires low power. The other strength may be more number of users can make connect to the network at the same time (Alliancen, 2015). The weakness of Zigbee involve the limited capabilities due to the low cost. The other weakness involve the dependency on the other wireless technologies for the communication to complete.

• Bluetooth: The Bluetooth device is the other device that is used as a wireless technology device. The strength of this type of device is that it is easy to understand and use and there is less chances of interfering with the other devices. The clear sight of view is also not required for the communication (Faragher & Harle, 2015). The weaknesses may involve the low transmission speed, requiring of more battery power for carrying out the data communication. The large distance communication is not supported by the Bluetooth concept.

The antenna is a device that are used for the convergence of the radio frequency into the alternating current (Ding et al., 2015). There are different types of antennas such as the Yagi- Uda antenna, Horn antenna, Cellular antenna and the Grid antenna. The antenna, which is most suitable for the future use is the cellular antenna (Malicki & Johnson, 2017). The reason why the cellular antenna would be most suitable for the future use is that this type of antenna are the easiest to configure and this type of antenna would also help in the reduction of the traffic. This type of antennas also provide more coverage area as compared to the other antennas.

References:

JPL Wireless Communication. (2018). Spread Spectrum Transmission. https://www.wirelesscommunication.nl/reference/chaptr05/cdma/cdma.htm

Nickolas, C. (2015). The Basics of Mixers . https://www.digikey.com/en/articles/techzone/2011/oct/the-basics-of-mixers

RadioElectronics. (2017). Diode Single Balanced Mixer. https://www.radio-electronics.com/info/circuits/diode_single_balanced_mixer/diode_single_balanced_mixer.php

RadioElectronics. (2018). Double Balanced Mixer Tutorial. https://www.radio-electronics.com/info/rf-technology-design/mixers/double-balanced-mixer-tutorial.php

Peng, M., Li, Y., Zhao, Z., & Wang, C. (2015). System architecture and key technologies for 5G heterogeneous cloud radio access networks. IEEE network, 29(2), 6-14.

Wichman, A. R., & Larson, L. E. (2017). Background measurement of RF system nonlinearity using spread-spectrum methods. In ARFTG Microwave Measurement Symposium (ARFTG), 2017 90th (pp. 1-4). IEEE.

Smys, S., Prakash, J. T., & Raj, J. S. (2015). Conducted Emission Reduction by Frequency Hopping Spread Spectrum Techniques. National Academy Science Letters, 38(3), 197-201.

Quyen, N. X., Duong, T. Q., Vo, N. S., Xie, Q., & Shu, L. (2016). Chaotic direct-sequence spread-spectrum with variable symbol period: A technique for enhancing physical layer security. Computer Networks, 109, 4-12.

Ding, Z., Zhong, C., Ng, D. W. K., Peng, M., Suraweera, H. A., Schober, R., & Poor, H. V. (2015). Application of smart antenna technologies in simultaneous wireless information and power transfer. IEEE Communications Magazine, 53(4), 86-93.

Malicki, J. J., & Johnson, C. A. (2017). The cilium: cellular antenna and central processing unit. Trends in cell biology, 27(2), 126-140.

Tsonev, D., Videv, S., & Haas, H. (2014). Light fidelity (Li-Fi): towards all-optical networking. In Broadband Access Communication Technologies VIII (Vol. 9007, p. 900702). International Society for Optics and Photonics.

Faragher, R., & Harle, R. (2015). Location fingerprinting with bluetooth low energy beacons. IEEE journal on Selected Areas in Communications, 33(11), 2418-2428.

Alliancen, Z. (2015). Zigbee.