The ms is the mobile subscriber equipment, which can originate and receive calls and communicate with the bts. It allows multiple groups to share the same channel at the same time by assigning each group to different code. This technique alone enhances the probabilityofdetection pod performanceof the dbs receiver. The dsss signal direct sequence spread spectrum dsss.
Analysis for a twostage acquisition scheme for directsequence spreadspectrum cdma upamanyu madhow, member, ieee, and michael b. Highperformance wireless via the merger of ci chipshaped. A general description of direct sequence spreading. But this is a very important feature for smart phones.
An overview of multicarrier cdma article pdf available in ieee communications magazine 3512. 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. Index termscdma, direct sequence, equalization, interfer ence suppression, mmse, nearfar problem, timing acquisition, training. Direct sequence cdma device and method for using the same.
The umts world is an 3g mobile system news and information provider. Using a maximum length sequence m1 of length n2m1, another sequence m2 is formed. Auto and crosscorrelation function for msequences, gold sequences, and kasamisequences. Adaptive matched filter and vector correlator for a code division multiple access cdma modem. Sequences design for ofdm and cdma systems by fei huo a thesis. A merger of dscdma with spatial division multiple access sdma highly enhances the performance of the dbs. Cdma is used for the 3g mobile communication system. We introduce a novel merger of direct sequence code division multiple access ds cdma and smart antenna arrays.
The digital data is directly coded at a much higher frequency. The performance of sequence acquisition for gold sequence based dscdma systems is studied in this paper. In direct sequence spread spectrum transmission, the user data signal is multiplied by a code sequence. Cdma2000 1xevdo evolutiondata optimized, often abbreviated as evdo or ev, is a telecommunications standard for the wireless transmission of data through radio signals, typically for broadband internet access. Correlation properties of wcdma synchronisation codes igor s.
Wcdma for umts principles introduction cdma background history key parameters code division multiple access cdma why cdma. Because this detector is nonparametric, we can decide the threshold of the detector without first having to estimate the variance of timevarying interference. Recently there has been an increasing interest in the application of the direct sequence code. In direct sequence spread spectrum dsss, the transmitter and receiver. 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. For simplicity, the spreading code sequences for the users are assumed to be random bit sequences 7 t 1. W e introduce a novel merger of direct sequence code divisio n multiple access dscdma and smart antenna arr ays. Pdf time hopping directsequence cdma for asynchronous. Manikas imperial college london ee303 communication systems an overview of fundamentals prof. In telecommunications, directsequence spread spectrum dsss is a spreadspectrum modulation technique primarily used to reduce overall signal. Comparison of the sensitivities of mccdma and mcds.
A differentially coherent pn code acquisition receiver for cdma systems mohammad h. Cdmas is listed in the worlds largest and most authoritative dictionary database of abbreviations and acronyms the free dictionary. Optimal cdma signature sequences, inverse eigenvalue. The ratio between the user symbol time and the chip time is called the spread factor. We consider the use of a sliding correlatortype structure for the acquisition scheme. Overloaded data services impact on voice calls data service not only increases the data traffic, but also occupies a lot of bandwidth on signaling channel, which. Principles of code division multiple access cdma professor a. As we combine every data symbol with a complete pn code, the ds processing gain is equal. Cdmax cdma communicator data sheet, honeywell home, resideo security americas. With regard to the ds cdma scheme, we employ carrier interferometry ds cdma cids cdma, a novel implementation of ds cdma where chips are decomposable into narrowband frequency components. Cdma network architecture consists of following elements mobile station ms.
The bts transmits and receives radio signals, realizing communication between the radio system and the mobile station. Direct sequence is the best known spread spectrum technique. Value of cdma of cdma networks and networks and to the. Generate a local pseudorandom code with a higher rate than the data to. To generate small set of kasami code, pn sequence is the fundamental sequence to start with. Direct sequence spread spectrum requires the overall channel including, where.
In code division multiple access cdma systems all users transmit in the same bandwidth. Mobile subscribers access the cdma 000 1x data network using a mobile station, such as a mobile phone, modem, a laptop with an embedded cdma 000 chip, a broadband access wireless router, or pc card on a laptop computer. These detectors are alternatives to the noncoherent detectors that have. The transmitter mixes the packets constituting a message into the digital signal stream in an order determined by a pseudorandom number sequence that is also known to the intended receiver, which uses. Pursley, fellow, ieee abstractthe problem of acquisition of synchronism is consid ered for directsequence spreadspectrum dsss codedivision multipleaccess cdma systems. Pn code acquisition using nonparametric detectors in ds. Pdf using direct sequence spread spectrum in marine. With regard to the ds cdma scheme, we employ carrier interferometry ds cdma cids cdma, a novel implementation of ds cdma where chips are decomposable into nnarrowband frequency components.
With regard to the ds cdma scheme, we employ carrier interferometry ds cdma cids cdma, a novel implementation of ds cdma where chips are decomposable into open image in new window narrowband frequency components. Walsh codes are used to identify the data for each individual transmission. The principle of spread spectrum is used to work with cdma. Cdma overview code division multiple access cellular. Analysis of multipath and fading effects on direct. Baum 3 in direct sequence code division multiple access dscdma systems, signal acquisition is nec essary before communication can commence. Whereas, cdma stands for code division multiple access, is a technology that refers to the network type. Moreover, in the design of code division multiple access cdma spreading sequence sets, it is critical that each sequence in the set has low autocorrelations and low cross. Direct sequence spreading page 2 of 16 faster moving, random sequence every. Honig, fellow, ieee abstract joint transmitterreceiver adaptation is studied for the reverse link of a direct sequencecode division multiple access system with short signature sequences. The next generation cdma technologies hsiaohwa chen national cheng kung university, taiwan bicintinnial bicbntennial. Gsm and cdma spectrum frequencies the cdma network operates in the frequency spectrum of cdma 850 mhz and 1900 mhz while the gsm network operates in the frequency spectrum of gsm 850 mhz and 1900 mhz. Acquisition performance of gold sequence based dscdma.
With re gard to the dscdma scheme, we employ carrier interferometry dscdma. Multicode code division multiple access in this section the capability of wts to transmitand receive on multiple cdma channels by the means of mccdma is discussed. Mobile stations allow mobile users to access verizon wirelesshosted services, the internet, or enterprise services. Spread signal is below the noise level and noise has no effect on the signal. The duration of an element in the code is called the chip time.
It uses multiplexing techniques including code division multiple access cdma as well as timedivision access to maximize both individual users throughput and the overall. Short pn sequences for direct sequence spread spectrum. Looking for online definition of cdmas or what cdmas stands for. Direct sequence spread spectrum an overview sciencedirect. A differentially coherent pn code acquisition receiver for. Islt 2003, yokohama, japan, june 29 july 4,2003 optimal cdma signature sequences, inverse eigenvalue problems and alternating minimization joel a. The auto and the crosscorrelation functionm sequences with length 15 gold sequences with length 31 kasami sequences with length 63figure 16. Direct sequencing cdma transmitreceive chain aruna, g. Cdmax cdma communicator data sheet, honeywell home. In this paper, we propose to use a new nonparametric noncoherent detector for pn code acquisition in dscdma systems. Cdma networks have pilot channels which carry no data but are used by the subscriber s mobile unit to acquire the system and assist in the soft handoff process.
Sousa, senior member, ieee abstract new differentially coherent detectors for acquisition of direct sequence spreadspectrum signals are introduced. Correlation properties of wcdma synchronisation codes. How does it support more than one group in the same channel. Large set orthogonal kasami codes for cdma system 34 important types of binary sequence sets because of their very low crosscorrelation. Cdma code division multiple access also called spreadspectrum and code division multiplexing, one of the competing transmission technologies for digital mobile phones. Short pn sequences for direct sequence spread spectrum radios. The sequence produced by this implementation is shown in table 1. This technique has a number of desirable features, including narrowband interference suppression and a lower required chip rate than that of a singlecarrier system. A spread spectrum information bearing signal is one whose bandwidth is much larger than what is needed to transmit data reliably. Cdma currently does not support voice and data concurrent services.
U analysis for a twostage acquisition scheme for direct. Analysis of bit error probability of directsequence cdma. Pdf highperformance wireless via the merger of ci chip. Highperformancewirelessviathemergerofci chipshapedds. Numerical approach to maximize snr for cdma systems. Signature sequence adaptation for dscdma with multipath gowri s. Using direct sequence spread spectrum in marine radio communication. The mostcommon techniques of cdma are frequencyhopped cdma or directsequence cdma. Comprehensive coverage of umts 3g news, licensing, business developments, 3g wcdma telecommunication technology, multi media mobile phones and future communications. If directsequence spreadspectrum modulation is used, then it is also necessary to synchronize to the code sequence that was used to produce the spectral.
Numerical approach to maximize snr for cdma systems hirofumi tsuda. Let i e i, i be the information bit to be transmitted by user i i 1. The current spreading sequence of 3g cdma systems is the gold code 6. Direct sequence spreading page 7 of 16 2 the shift around method is shown in figure 5. Spreading sequences used in cdma walsh code one of the 64 orthogonal bit pattern at a rate of 1. The result is sent through the channel, sampled, and the sampled signal is multiplied by the corresponding random bit. This method of acquisition is called a sliding correlator. This is the preferred method for implementing an msequence in hardware. In cdma systems, we use spreading sequences as codes to. Cdma, code division multiple access an implementation of direct sequence spread spectrum, dsss, and was used almost universally for 3g mobile communications standards as it provided an excellent format as a multiple access scheme.
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. Performance analysis of multicarrier direct sequence mc. Spreading sequences used in cdma wireless applications. Performance analysis of multicarrier directsequence mc ds cdma with fading kazi abu taher, md ruhul minhaz and s. Since acquisition of a in sequence in dscdma systems can be for. Acquisition of directsequence spreadspectrum signals.
Cdma stands for code division multiple access cdma is a direct sequence ds spread spectrum modulation technique, where in, a narrow band of less than 10 khz user information voice or data is transmitted over a wide rf bandwidth of 1. Code division multiple access cdma spread spectrum modulation informaldenition ofspreadspectrumsignal viterbi 1. Mmse interference suppression for timing acquisition and. Code division multiple access cdma, this modulated signal st. If the period of an output sequence of a nstage linear feedback shift register is p 2n 1, this sequence is called a msequence. Cdma principles spreading codes multipath radio channel and rake receiver problems to solve macro diversity and soft handover nearfar problem and power control umts general requirements fdd vs. Code acquisition in advanced cdma networks academic dissertation to be presented with the assent of the faculty of technology, university of oulu, for public discussion in raahensali auditorium l10, linnanmaa, on december 9th, 2002, at 12 noon oulun yliopisto, oulu 2002. Giunta for the academic course of digital signal processing of the third university of rome rome, may 2000. Receiver attempts to recover signals from multiple paths and combine them. A spread spectrum signal is one for which the essential fourier. Pdf this paper investigates transmission schemes for asynchronous transmitteronly wireless sensor nodes. Majumder bangladesh university of engineering and technology, bangladesh. In a cdma system, usually galois generators are used to produce msequences each of which is comprised of the sequence of period 2n1 not all0 state and a mask.