Performance analysis of a dsequence based direct sequence cdma system s. Covers both direct sequence and fast hopping methods. Generate a local pseudorandom code with a higher rate than the data to. May 05, 2010 code division multiple access introduction cont. Performance analysis for optimization of cdma 20001x cellular mobile radio network ifeagwu e. The rayleigh distribution has a probability density function pdf given by prr a. This technology makes optimal use of available bandwidth and is based on spread spectrum technology. As we combine every data symbol with a complete pn code, the ds processing gain is equal.
To access a sequence from a database, enter the usa here. The digital matched filter dmf is a most powerful device that maximizes the synchronization systems performance. Direct sequencing cdma transmitreceive chain aruna, g. Code division multiple access or cdma has its roots in wwii era spread spectrum technology. Performance analysis of multicarrier direct sequence mc. Direct sequence spreading page 7 of 16 2 the shift around method is shown in figure 5. The algorithm is suitable for both synchronous and asynchronous multiple access directsequence codedivi. Baum 3 in direct sequence code division multiple access ds cdma systems, signal acquisition is nec essary before communication can commence. The ratio between the user symbol time and the chip time is called the spread factor. Giannakis, fellow, ieee, and ananthram swami, senior member, ieee abstract we compare single user digital multicarrier spread spectrum mcss modulation with direct sequence ds ss. Matlab, simulink building a dircet sequence spread spectrum model. Figure 1 a binary information signal to modulate this signal, we would multiply this sequence with a.
Scheduling and hybrid scheduling used to combine benefits of. These two technologies differ in the way calls and data travel over the mobile phone networks. Fhcdma is the repetitive switching of frequency at the time of radio transmission. Recently there has been an increasing interest in the application of the direct sequence code division multiple access cdma technique as a radio interface to provide multimedia services for. Department of electronics and communication enginerring, government college of technology, coimbatore 641025, india abstract this paper presents an analysis of multipath and fading effects on a dscdma system direct sequencecode division multiple access system. Performance analysis for optimization of cdma 20001x. Introduction in communication systems an attractive approach for economical, spectral efficient, and high quality digital cellular and personal communication services is the use of direct sequence code division multiple access ds cdma technique 1. Code division multiple access cdma is a sort of multiplexing that facilitates various signals to occupy a single transmission channel.
Cdma networks have pilot channels which carry no data but are used by the subscribers mobile unit to acquire the system and assist in the soft handoff process. Be sure to sequence by your unique keys and build the application. Analysis of multipath and fading effects on direct sequencing. With regard to the ds cdma scheme, we employ carrier interferometry ds cdma cids. The direct sequence process ds is probably the most well known and the most applied spread spectrum technology. Short pn sequences for direct sequence spread spectrum. Direct sequence spread spectrum dsss direct sequence spread spectrum dsss is the most common version of spread spectrum in use today, due to its simplicity and ease of implementation. Performance analysis of multicarrier direct sequence mc ds. How does it support more than one group in the same channel. To upload a sequence from your local computer, select it here. The bandwidth of the coded data signal is chosen to be much larger than the bandwidth of the original data signal, that is, the encoding process enlarges spreads the spectrum of the data signal. We introduce a novel merger of direct sequence code division multiple access dscdma and smart antenna arrays. Pdf highperformance wireless via the merger of ci chip. Pdf the performance and some of the implementation aspects of a practical mobile.
Performance analysis of multicarrier directsequence mc ds cdma with fading kazi abu taher, md ruhul minhaz and s. Introduction i n directsequence codedivision multiple access dscdma, each users symbols are spread by a userspecific code, which expands the bandwidth compared with the data rate 18, 19, 23. There are two main types of codes used in cdma, pn sequence codes and walsh codes. Highperformance wireless via the merger of ci chipshaped. Ci introduces families of orthogonal polyphase codes that can be used for channel coding, spreading, andor multiple access. Cdma is a spread spectrum technique where multiple users to access the system at the same example in a cell, and of course on the same frequency. Direct sequence is the best known spread spectrum technique.
Performance analysis for optimization of cdma 20001x cellular. An evaluation of direct sequence cdma for future mobile communication. Additionally, the transmission security afforded by long pn sequences in the waveform is important as is the ability to do code division multiple access cdma. What is frequency hopping code division multiple access fh. Figure 1 a binary information signal to modulate this signal, we would multiply this sequence with a sinusoid and its spectrum would look like as in figure 2. Dsss direct sequence spread spectrum i xor of the signal with pseudorandom number code sequence many chips per bit e. The mostcommon techniques of cdma are frequencyhopped cdma or directsequence cdma. Cdma can be implemented in several ways, two of which are frequency hopping and direct sequencing. When allslices are occupied in the system no additional wireless terminal can be accommodated. Dsss systems as proposed for the unlicensed ism band use a form of ds that. The sequence produced by this implementation is shown in table 1.
Cdma is the short form of code division multiple access. Kak the performance of a d sequence based direct sequence cdma system over an additive white gaussian noise awgn channel is analyzed. Pdf walshlike nonlinear phase orthogonal codes for direct. It allows multiple groups to share the same channel at the same time by assigning each group to different code. Ovsf is used in wcdmaumts, and is an implementation of directsequence spread spectrumcdma directsequence spread spectrumdscdma. This method has been adopted by qualcomm in designing their wireless communications network as well as by the infopad project here at uc berkeley. Introduction i n direct sequence codedivision multiple access ds cdma, each users symbols are spread by a userspecific code, which expands the bandwidth compared with the data rate 18, 19, 23. In second and third generation wireless communication a protocol named cdma came into existence. It might perhaps fit into one of those articles, if it necessarily has to be merged. Next, build a retrieval application, choosing the merge data to pdf template. May 04, 20 when allslices are occupied in the system no additional wireless terminal can be accommodated.
The bandwidth of the data signal is now multiplied by a factor n ds. Digital multicarrier spread spectrum versus direct sequence. The signal st occupies a bandwidth w that depends on the modulation scheme used. To spread spectrum, we simply multiply st by a high frequency chip waveform ct that has bandwidth nw, where n is said to be the. Performance analysis of a dsequence based direct sequence. Direct sequence cdma device and method for using the same. Majumder bangladesh university of engineering and technology, bangladesh. The digital data is directly coded at a much higher frequency. Wideband directsequence cdma this report contained in this annex was prepared during the evaluation work of smg2 as a possible basis for the utra standard.
Setting up rules is done after selecting recipients for the mail merge, and after inserting merge fields in the document go to mailings rule, and choose a rule based on the descriptions below. Matlab, simulink building a dircet sequence spread spectrum. Direct sequence spread spectrum dsss consider the complex baseband signal st x n smnt nts 1 where mk 2 f0. Ds cdma direct sequence code division multiple access is a multiple access scheme based on dsss, by spreading the signals fromto different users with different codes. The code is generated pseudorandomly, the receiver knows how to generate the same code, and correlates the received signal with that code to extract the data. Cdma, dsss, bpsk, pn code, states started in octoddfs. Analysis of a direct sequence bpsk cdma system analysis of a direct sequence bpsk cdma system objective. Direct sequence spread spectrum, also known as direct sequence code division multiple access ds cdma, is one of two approaches to spread spectrum modulation for digital signal transmission over the airwaves.
Here, the data signal is multiplied by a pseudo random code pn code pseudo noise code, which has similar characteristics as noise does. Ber performances of size 31 nearorthogonal gold, size 32 w alsh. Ratio and equal gain diversity combining in direct sequence cdma future. The duration of an element in the code is called the chip time. Frequency hopping code division multiple access fhcdma is a basic modulation technique used in spread spectrum signal transmission. Ovsf is used in wcdmaumts, and is an implementation of direct sequence spread spectrum cdma direct sequence spread spectrumds cdma. Spreading codes for direct sequence cdma and wideband cdma. Direct sequence spread spectrum, also known as direct sequence code division multiple access dscdma, is one of two approaches to spread spectrum modulation for digital signal transmission over the airwaves.
Directsequence protocols, such as dscdma, are provided with ci to greatly improve performance and reduce transceiver complexity. Index termscdma, direct sequence, equalization, interfer ence suppression. Baum 3 in direct sequence code division multiple access dscdma systems, signal acquisition is nec essary before communication can commence. Direct sequence spread spectrum is the technique used in todays most powerful cellular communications technology, code division multiple access. For example, youre sending out the same invitation for a quarterly meeting. This technique has a number of desirable features, including narrowband interference suppression and a lower required chip rate than that of a singlecarrier system. Multiple access capability is also provided by code division multiple access cdma. In direct sequence spread spectrum transmission, the user data signal is multiplied by a code sequence. Boutros, member, ieee abstract a new joint detection method based on sphere packing lattice decoding is presented in this paper. Spreadspectrum ss communications technology was first described on paper by an actress and a. Introduction in communication systems an attractive approach for economical, spectral efficient, and high quality digital cellular and personal communication services is the use of direct sequence code division multiple access dscdma technique 1. The receiver, knowing the code sequence of the user, decodes the received signal and recovers the original data.
Basic note on spread spectrum cdma signals 3 figure 1. Pdf walsh codes are perfectly orthogonal binary antipodal block codes that found their use in. Direct sequence spread spectrum systems merge their input data with a fast spreading sequence and transmit a wideband signal. An air interface based on directsequence cdma and operation at a wide bandwidth gives the opportunity to design a system with properties fulfilling the thirdgeneration requirements. The results indicate a superior performance for this system over a pn sequence based cdma system when. Spread spectrum, cdma and gps university of california.
What is direct sequence spread spectrum dsss or direct. Short pn sequences for direct sequence spread spectrum radios. The most important aspect in the cdma receiver is pn sequence synchronization. It spreads information using codes that are unique to the mobile station in all the cdma cellular. Direct sequence spread spectrum for resistance to jamming and multipath shengli zhou, student member, ieee, georgios b. Be sure to select all tables and fields that you would possibly wish to utilize in your pdf merge. Code division multiple access cdma the concept of signal spreading and its uses in communications lets take a stright forward binary signal of symbol rate 2. Hybrid acquisition of direct sequence cdma signals 1 venugopal v. The spreading factor is the ratio of the chips umts 3. With regard to the dscdma scheme, we employ carrier interferometry dscdma cidsc. One can, of course, combine the above access methods. This helps to reduce the strength of electronic warfare, that is, the.
Your data source doesnt store the meeting dates, and the meeting date. In 1985, the fcc allocated three frequency bands to spread spectrum communications. A direct sequence spread spectrum signal is one in which the amplitude of an already modulated signal is. This is the preferred method for implementing an msequence in hardware. Pdf using direct sequence spread spectrum in marine radio. Therefore, discriminate the users on the reverse link i. Performance analysis of a d sequence based direct sequence cdma system s. Fh cdma is the repetitive switching of frequency at the time of radio transmission. Kak the performance of a dsequence based direct sequence cdma system over an additive white gaussian noise awgn channel is analyzed. International journal of recent technology and engineering. Note that the output sequence shown here is the reverse of the one in table 1. Receiver attempts to recover signals from multiple paths and combine them.
Us20090110033a1 multicarrier sublayer for direct sequence. Code division multiple access cdma user 1 time frequency users share bandwidth by using code sequences that are orthogonal to each other some second generation systems use cdma most of third generation systems use cdma user 2 user n code. We introduce a novel merger of direct sequence code division multiple access ds cdma and smart antenna arrays. Mmse interference suppression for timing acquisition and. Code division multiple access code division multiple access cdmacdma zm lti l i th b d b h imultiple users occupying the same band by having different codes is known as a cdma code division multiple access system let w spread bandwidth in hz r1tr 1t b date rate data signal bandwidth in hz date rate data signal bandwidth in hz.
The technology is commonly used in ultrahighfrequency uhf cellular telephone systems, bands ranging between the 800mhz and 1. Frequency hopping code division multiple access fh cdma is a basic modulation technique used in spread spectrum signal transmission. It is the technique by which same frequency and time interval is used by mobile subscribers base stations by way of unique digital codes. Direct sequence spread spectrum cdma is a direct sequence spread spectrum system. Improved performance over secondgeneration systems, including. Communication and cdma code division multiple access. Pdf an evaluation of direct sequence cdma for future mobile.
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