Demonstrating cdma, frequency hopping, and other wireless techniques with pspice. Code sequences for frequency hopping cdma contributed by jack glas, lucent in wireless compute networks or wireless lans with many terminals, slow frequency hopping is applied to reduce the problems due to the nearfar effect. We will now concentrate on the most popular technique. Baseband frequency hopping vs synthesized frequency hopping. Spectral plots illustrate directsequence spreadspectrum dsss and frequency hopping spreadspectrum fhss methods. Frequency hoping spread spectrum channel sequence dictated by spreading code receiver, hopping between frequencies in synchronization with transmitter, picks up message advantages oeavesdroppers hear only unintelligible blips oattempts to jam signal on one frequency succeed only at knocking out a few bits. In figure 11 the transmission process oftwo wireless terminals is given. Theoretical equations are given to allow performance estimates.
The frequency hopping helps to improve interference diversity and frequency diversity. In this paper, the suitability of slow frequency hopping code division mul tiple access sfhcdma is characterised, for application in third generation wireless communications. How many frequency hopping modes in gsm posted on 28 december, 2012 the requirement that the bcch trx must transmit continuously in all the time slots sets strict limitations on how the frequency hopping can be realized in a cell. Code division multiple access or cdma has its roots in wwii era spread spectrum technology. Direct sequence ds direct sequence code division multiple access ds cdma is a technique to multiplex users by different codes.
Frequency hopping spread spectrum security improvement with. Cdma channel numbers and corresponding frequencies for band 16 class 9 and. Cdma can be implemented in several ways, two of which are frequency hopping and direct sequencing. We collected most searched pages list related with frequency hopping in gsm ppt and more about it. However, if eavesdroppers can obtain 42 bits of plaintextciphertext pairs, the longcode mask can be. It compares baseband frequency hopping vs synthesized frequency hopping and mentions difference between baseband frequency hopping and synthesized frequency hopping.
The data is burst is hopped over the frames by utilising code sequences. In recent years growing demand on available radio spectrum, as the fundamental shared resource of wireless communication. Frequency hopping spread spectrum fhss direct sequence. Chapter 7 multiple division techniques outline frequency division multiple access fdma time division multiple access tdma code division multiple access cdma comparison of fdma, tdma, and cdma walsh codes nearfar problem types of interferences analog and digital signals basic modulation techniques amplitude modulation am frequency modulation fm. Frequency hopping spread spectrum fhss and direct sequence spread spectrum dsss. The advantage is that the signal sees a different channel and a different set of interfering signals during each hop. Important encoding method for wireless communications. Cdma is altering the face of cellular and pcs communication by.
In order to properly receive the signal, the receiver must be set to the same hopping code and listen to the incoming signal at the right time and correct frequency. Pdf frequencyhopping versus interference cancellation. Directsequence ds, frequencyhopping fh, timehopping th and multicarrier cdma mccdma. Other discussions in these pages show why this is true. On the contrary, it is crucial to the very high spectral efficiency that is the hallmark of cdma. Code division multiple access an overview sciencedirect. Pdf passive optical fast frequencyhop cdma communications. We present a multirate optical fast frequency hopping cdma offhcdma system architecture using fiber bragg gratings fbgs. Signal broadcast over seemingly random series of frequencies. Frequency hopping code division multiple access fh cdma is a basic modulation technique used in spread spectrum signal transmission. Timeslot allocations among different users in a tdma system. Cdma channel number to cdma frequency assignment 14 correspondence for band class 9233 15 table 2. Investigations of the wireless channel indicate that frequency hopping mitigates the poorpropagation characteristics associated with low mobilitycommon to fixed wireless applications. In this paper, the suitability of slow frequencyhopping code division multiple access sfhcdma isevaluated for wireless local access applications.
An improved method and apparatus for optical and radio frequency implementation of a fast frequency hopping spread spectrum communication for code division multiple access systems is disclosed. Frequency hopping spread spectrum fhss is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. Pdf this paper proposes an allfiber fast optical frequencyhop code division multiple access ffhcdma for highbandwidth communications. Frequencyhopping spread spectrum fhss is a method of transmitting radio signals by. Each terminal following the principal of frequency hopping hopsto another frequency slice at the beginning of a new slot. Pdf frequency hopping cdma for flexible third generation. Fcc id qzcwwic3ev electric meter with multiband cdma and. Also, this chapter investigates the effect of the values of frequency reuse factor n on the system capacity of the cellular frequency hopping system. The number of frequencies to hop over is limited to 63, which is the maximum number of frequencies in the mobile allocation ma list covered in section 1. The application of frequency hopping cdma for future. This paper addresses the problem of realtime multimedia transmission in fiberoptic networks using code division multiple access cdma. Code division multiple access cdma i the cdma standard was originally designed by qualcomm in the u.
Cdma technology has been dominated by a technique exploiting direct sequence ds spread spectrum. Frequency hopping spread spectrum a pseudonoise sequence pn t generated at the modulator is used in conjunction with an mary fsk modulation to shift the carrier frequency of the fsk signal pseudorandomly, at the hopping rate r h. Multirate optical fast frequency hopping cdma system using. Frequency hopping is mechanism in which the system changes the frequency uplink and downlink during transmission at regular intervals. Frequency hopping code division multiple access fhcdma is a basic modulation technique used in spread spectrum signal transmission. Direct sequence ds direct sequence code division multiple access dscdma is a technique to multiplex users by different codes. Synthesized hopping is illustrated in below figure. Frequency hopping is the repeated switching of frequencies during radio transmission so as to minimize the effectiveness of unauthorized interception or jamming of telecommunications, also known as, the frequencyhopping code division multiple accesses fhcdma scholtz, 1982.
It is also possible to make use of combinations of them. Us20040208624a1 fast frequency hopping spread spectrum for. To keep the necessary bandwidth within limits and the frequency synthesizers realizable, the fhsequencelength n fh is mostly kept small. In this technique, the same bandwidth is used by different users. In a system where a pool of cdma users share a channel characterized by a number of f. In the synthesized frequency hopping all the trxs except the bcch trx change their frequency for every tdma frame according to the hopping sequence. Therefore, frequency hopping is a very important technology for reducing gsm system interference and improving frequency reuse ratio. Wwic3ev electric meter with multiband cdma and frequency. Pdf evaluation board for frequency hoppingcdma systems. Frequency hopping spread spectrum fhss has found a number of applications in cellular systems, wireless local loop, and wireless local area networks. The precise order in which the break occurs is determined by a hopping table generated by using a pseudorandom code sequence. Directsequence ds, frequency hopping fh, time hopping th and multicarrier cdma mc cdma.
By transmitting the message energy over a bandwidth much wider than the minimum required, spread spectrum modulation techniques present two major advantages. Band class specification for cdma2000 spread spectrum. Frequency hopping versus interference cancellation for td cdma. Frequency hopping code division multiple access for wireless. Code division multiple access cdma is a multiple access technology where the users are separated by unique orthogonal codes, which means that all users can use the same frequency and transmit at the same time. Direct sequence direct sequence is the best known spread spectrum. Chapter 7 multiple division techniques outline frequency division multiple access fdma time division multiple access tdma code division multiple access cdma comparison of fdma, tdma, and cdma walsh codes nearfar problem types of interferences analog and digital signals basic modulation techniques amplitude modulation am. In addition, we argue that, in multimedia applications, different services have different quality of service qos requirements. Following are the two types of spread spectrum techniques. Cdma with interfering signal session 2632 demonstrating cdma, frequency hopping, and other wireless techniques with pspice andrew rusek, barbara oakley department of electrical and systems engineering oakland university, rochester, michigan 48309 abstract. They are synthesized frequency hopping and baseband frequency hopping.
This helps to reduce the strength of electronic warfare, that is, the. Frequency hopping is an old technique introduced firstly in military transmission system to ensure the secrecy of communications and combat jamming. Frequency hopping technology frequency hopping is a spread spectrum in which the propagation takes place by hopping in frequency over a wide band. An introduction to spreadspectrum communications tutorial. Frequency hopping code division multiple access for. To illuminate this property we take a frequency hopping system as an example. The method avoids the frequency hopping synthesizer requirements in the transmitter as well as in the receiver. Receiver, hopping between frequencies in synchronization with. For adaptive frequency hopping in the unlicensed bands pdf. Spread spectrum northeastern university college of. The net effect is to maintain a single logical channel if. Mceliece california institute of technology, 11 681, pasadena, ca 91125 abstract this paper compares the performances of direct sequence.
A comparison of cdma and frequency hopping in a cellular. Electric meter with multiband cdma and frequency hopping transmitters users manual 1 details for fcc id qzcwwic3ev made by elster solutions, llc. May 04, 20 to illuminate this property we take a frequency hopping system as an example. Keywords frequency hopping cdma multipath fading channels. Frequency hopping spread spectrum security improvement.
Fcc id application submitted by elster solutions, llc for electric meter with multiband cdma and frequency hopping transmitters for fcc id qzcwwic3ev qzc wwic3ev user manual, frequency, reports, images and more. In fhss, which stands for frequency hopping spread spectrum, rf carrier frequency is changed according to the pseudorandom sequenceprs or pn sequence. Us20040208624a1 fast frequency hopping spread spectrum. Pdf demonstrating cdma, frequency hopping, and other. Frequency hopping with contributions by jack glas, lucent. Frequency hopping code division multiple access fhcdma. The data is divided into frames, that itself are divided into time intervals.
A comparison of cdma and frequency hopping in a cellular environment michael i. There is no fundamental theoretical barrier to the effectiveness of spreadspectrum communications. The transmitted signal occupies a number of frequencies in time, each for a period of time t h 1r. Demonstrating cdma, frequency hopping, and other wireless. Pdf mechanisms based on frequency hopping have been widely used in many applications such as the personal communications services.
Cdmacode division multiple access cdma access to the air is determined by a key or code figure 10. Hopping rate is a function of the speed information. Frequency hopping with contributions by jack glas, lucent in frequency hopping systems, the transmitter changes the carrier frequency according to a certain hopping pattern. In 1985, the fcc allocated three frequency bands to spread spectrum communications.
Pdf frequencyhopping versus interference cancellation for. According to gsm standard recommendations, slow frequency hopping can be used in gsm communication system. Frequencyhopped generalized mccdma for multipath and interference suppression y shengli zhou, georgios b. This pn sequence is known to both transmitter and receiver and hence help demodulatedecode the information. Frequency hopping refers to the regular hopping of carrier frequency within certain range. Fh cdma is the repetitive switching of frequency at the time of radio transmission. Cdma preferred set of frequency assignments for band class 8232 table 2. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. From the beginning it was designed to be resistant to noise, interference, jamming, and unauthorized detection. Fhcdma is the repetitive switching of frequency at the time of radio transmission. Frequency hopping cdma for flexible third generation wireless networks conference paper pdf available december 1997 with 27 reads how we measure reads. There are two types of frequency hopping based on use of rf carrier frequencies for the rf transceivers for burst transmission in gsm. Direct sequence spread spectrum techniques spread spectrum technology was first introduced about 50 years ago by the military as a way of sending secure communications. Moreover, specifically the security of the frequency hopping code division multiple access fh cdma sys tem mainly relies on the longcode generator that con sists of a 42bit longcode mask generated by a 42bit lfsrs.
Moreover, specifically the security of the frequency hopping code division multiple access fhcdma sys tem mainly relies on the longcode generator that con sists of a 42bit longcode mask generated by a 42bit lfsrs. In cdma, every channel uses the full available spectrum. The signal is spread by changing the frequency over the transmitted time of the signal. Frequency hoping spread spectrum channel sequence dictated by spreading code receiver, hopping between frequencies in synchronization with transmitter, picks up message advantages oeavesdroppers hear only unintelligible blips oattempts to jam signal on. Instead of directphase shift modulation of a digital sequence onto the rf carrier, as in dscdma, the sequence is used to frequency hop the carrier. There exist different techniques to spread a signal.
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