direct+sequence+spread+spectrum

... động với FHSS Ví dụ Direct Sequence Spread Spectrum Transmitter Direct Sequence Spread Spectrum Transmitter Direct Sequence Spread Spectrum Using BPSK Example Approximate Spectrum of DSSS Signal ... mã PN gồm k chíp mã tương ứng với từ tần số Trải phổ dãy trực tiếp Direct Sequence Spread Spectrum    Direct Sequence Spread Spectrum (DSSS) Sử dụng mã trải phổ băng rộng để điều chế tín hiệu ... (Frequency Hopping Spread Spectrum FHSS): Hệ thống trải phổ cách nhảy tần số sóng mang tập lớn tần số, mẫu nhảy tần giả ngẫu nhiên Trải phổ dãy trực tiếp (Direct Sequence Spread Spectrum DSSS):...

Ngày tải lên: 13/09/2012, 11:16

... Reserved 18 Direct Sequence Spread Spectrum q Spread spectrum increases the bandwidth of the signal compared to narrow band by spreading the signal q There are two major types of spread spectrum ... Narrowband vs Spread Spectrum Narrowband (High Peak Power) Power Spread Spectrum (Low Peak Power) Frequency February 2005 Copyright 2005 All Rights Reserved Narrow Band vs Spread Spectrum q Narrow ... two spread spectrum techniques to be used in the licensed free Industrial, Scientific, Medical (ISM) band, 2.4 GHz, thus 802.11 and 802.11b Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence...

Ngày tải lên: 13/09/2012, 11:16

... 1.3 Spread Spectrum Techniques 1.3.1 Direct Sequence Code Division Multiple Access 1.3.2 Advantages and Drawbacks of DS-CDMA 1.3.3 Applications of Spread Spectrum 1.4 Multi-Carrier Spread Spectrum ... spreading code length is smaller or equal to the number of sub-carriers Nc , a single data symbol is not spread in the frequency direction, instead it is spread in the time direction Spread spectrum ... Bs before spreading Signal bandwidth B after spreading Frequency Figure 1-9 Power spectral density after direct sequence spreading There are many application fields for spreading the spectrum [13]:...

Ngày tải lên: 02/03/2013, 16:58

Ngày tải lên: 29/09/2013, 20:20

... requiring spread spectrum modulation: DSSS (Direct Sequence Spread Spectrum) and FHSS (Frequency Hopping Spread Spectrum) Only the RF transmission has significant presence in the market DSSS FHSS Spreading ... IQ-modulator Then they are spread with ‘ different’pilot sequences on the I and Q channels This pilot sequence or Short Code sequence has a length of 15 chips A ‘ PN-offset’in the pilot sequences is assigned ... hops/s or a channel dwell time of less than 400 ms DE NAYER (ir J Meel) IWT HOBU-fonds Spread Spectrum Spectrum The spectrum of the transmitted signals determines the network packing DSSS FHSS 11 Msps...

Ngày tải lên: 13/12/2013, 00:15

... Direct- Sequence Systems with PSK Quadriphase Direct- Sequence Systems 6.3 Wideband Direct- Sequence Systems Multicarrier Direct- Sequence System Single-Carrier Direct- Sequence System Multicarrier DS/CDMA ... DS/CDMA Orthogonal Sequences Sequences with Small Cross-Correlations Symbol Error Probability Complex-Valued Quaternary Sequences 6.2 Systems with Random Spreading Sequences Direct- Sequence Systems ... 18 21 25 27 37 39 40 41 42 52 53 Direct- Sequence Systems 2.1 Definitions and Concepts 2.2 Spreading Sequences and Waveforms Random Binary Sequence Shift-Register Sequences Periodic Autocorrelations...

Ngày tải lên: 20/01/2014, 06:20

Ngày tải lên: 19/02/2014, 14:20

... Further, spread- spectrum signals are harder to Fig 2: Generation of the direct- sequence spread- spectrum signal (spreading) Fig 3: At the receiving end, the spreadspectrum signal is despread to ... pseudo-random chip sequence Generation of the direct- sequence spread- spectrum signal (spreading) is shown in Fig The narrow-band signal and the spread- spectrum signal both use the same amount of ... spread- spectrum signal In this case, the narrow-band signal’s power density is ten times higher than the spread- spectrum signal, assuming the spread ratio as ‘10.’ At the receiving end, the spreadspectrum...

Ngày tải lên: 08/06/2014, 20:17

... the Fourier domain which spreads the power spectrum of the original signal x (hence the name spread spectrum ), while preserving its norm Equivalently, this spread spectrum phenomenon acts on ... the spread spectrum technique as discussed in Section 2.5 Let us also acknowledge that spread spectrum techniques are very popular in telecommunications For example, one can cite the direct sequence ... sensing bases, which for a Fourier sensing basis relates to a spread of the original signal spectrum by the modulation (hence the name spread spectrum ) The approach is also efficient as sensing matrices...

Ngày tải lên: 20/06/2014, 20:20

... p(t − jTf − nTc ) (1) j=−∞ n=0 where c(k) ∈ {1, −1} denotes the nth chip of the kth n user’s spreading sequence; Eb is the average bit energy; (k) dj ∈ {1, −1} is the jth message bit of the kth ... Page 11 of 11 11 AR Forouzan, M Nasiri-Kenari, JA Salehi, Performance analysis of timehopping spread- spectrum multiple-access systems: uncoded and coded schemes IEEE Trans Wirel Commun 1(4), 671–681 ... doi:10.1109/TCOMM.2004.836424 13 B Hu, NC Beaulieu, Accurate performance evaluation of time-hopping and direct- sequence UWB systems in multiuser interference IEEE Trans Commun 53(6), 1053–1062 (2005) doi:10.1109/TCOMM.2005.849792...

Ngày tải lên: 20/06/2014, 22:20

... the proposed spread spectrum sequence is depicted in Figure EURASIP Journal on Information Security Spectrum sequence (group ID) ··· Group Group Spectrum sequence (user ID) Spectrum sequence (user ... coefficients are After performing IDCT on the sequence, it is multiplied by a PN sequence to generate a specific spread spectrum sequence Then, the spread spectrum sequence assigned to the ith user is ... fingerprint sequence is a DCT basic vector modulated by a PN sequence So, a base conversion is performed to a set of PN sequences to generate new spread spectrum sequences For convenience, the sequence...

Ngày tải lên: 21/06/2014, 05:20

... the Fourier domain which spreads the power spectrum of the original signal x (hence the name spread spectrum ), while preserving its norm Equivalently, this spread spectrum phenomenon acts on ... the spread spectrum technique as discussed in Section 2.5 Let us also acknowledge that spread spectrum techniques are very popular in telecommunications For example, one can cite the direct sequence ... sensing bases, which for a Fourier sensing basis relates to a spread of the original signal spectrum by the modulation (hence the name spread spectrum ) The approach is also efficient as sensing matrices...

Ngày tải lên: 21/06/2014, 17:20

... efficiency in [13] Hybrid spread spectrum (SS), where a direct- sequence modulated signal is frequency hopped, is an attractive choice DS/FH waveform has been used in fixed spectrum systems but it ... of an industrial R/C system using a hybrid DS/FH spread spectrum technique,” in Proceedings of the 2nd IEEE International Symposium on Spread Spectrum Techniques and Applications, pp 179–182, ... partial-band jammer to a spread spectrum signal The received power EURASIP Journal on Advances in Signal Processing of the jth partial-band interferer, with transmit power y2, j , after despreading is given...

Ngày tải lên: 21/06/2014, 19:20

... will consider a simpler class of solutions, exploiting some inherent collusion resistance in spreadspectrum watermarking We focus on the solution suggested in [2] si N i=1 (1) The Euclidean norm ... w(u) , r This is sometimes used, but more often some kind of normalisation is recommended 2.1 Spread- spectrum fingerprinting 2.2.1 The general decoder We view the copyrighted file as a signal x = ... preprocessor assuming two peaks, and Preproc(2) is the preprocessor assuming a single peak 2.3 Spread spectrum collusion attacks The collusion attack is mounted by a collusion of pirates, each of...

Ngày tải lên: 22/06/2014, 00:20

... in direct sequence spread spectrum communications,” IEEE Transactions on Signal Processing, vol 49, no 4, pp 851–863, 2001 [12] A Bultan and A N Akansu, “A novel time-frequency exciser in spread ... vol 33, no 14, pp 1189–1190, 1997 [2] A Ranheim, “Narrowband interference rejection in directsequence spread- spectrum system using time-frequency decomposition,” IEE Proceedings: Communications, ... received signal r is first synchronized and correlated with the same spreading signal p To estimate bk , we use the PN sequence pk to despread rk , and integrate the result to generate the test statistic...

Ngày tải lên: 22/06/2014, 19:20

... [1; P] 4.1 Time spreading In the case of 1D time spreading Lt = L, the system would then be an multicarrier direct sequence code division multiple access (MC-DS-CDMA) system if the spreading component ... multicarrier modulation and spread spectrum In the general case, the data symbols are spread in time and frequency, and OFDM modulation is applied over the chips of the spreading codes, as presented ... Symbols spread onto pavement p (2D spreading) Kp Spread symbols L f ,p Lp Lt,p Distribution of the code chips within the time-frequency grid Figure 1: Schematic representation of the 2D-spreading...

Ngày tải lên: 22/06/2014, 19:20

... s p (t) is called a direct- sequence (DS) spreadspectrum signal The despreading operation is accomplished by multiplying s p (t) by a synchronous version of the spreading sequence: = x(t) · b(t), ... binary sequences for spread spectrum multiplexing (Corresp.),” IEEE Trans Inform Theory, vol 13, no 4, pp 619–621, 1967 [18] R C Dixon, “Gold code sequence generators (see Appendix 7),” in Spread Spectrum ... against the sequence length, N The chip rate was 0.5 Mchip/s In the referred conditions, the aliasing begins at a sequence period length around 250 New PN Even Balanced Sequences For Spread- Spectrum...

Ngày tải lên: 23/06/2014, 00:20

... generates a random sequence of 1’s and −1’s The generated binary sequence is spread by a pseudorandom m -sequence by multiplying each information bit by this sequence in the DS spreading block Next, ... described model were run with the following parameters: the spreading factor/processing gain of the spread spectrum system was g p = 127 and the spread signal was oversampled by The filter bank was an ... techniques in spread spectrum communications,” Proceedings of the IEEE, vol 76, no 6, pp 657–671, 1988 [3] F Hsu and A Giordano, “Digital whitening techniques for improving spread spectrum communications...

Ngày tải lên: 23/06/2014, 01:20

... TYPES OF SPREAD SPECTRUM MODULATION The two most common types of spread spectrum modulation are direct- sequence and frequencyhop spread spectrum (FHSS) A binary direct- sequence spread spectrum ... to explain several features of a spread spectrum modulation system The type of spread spectrum system shown in Fig is known as binary direct sequence (DS) spread spectrum modulation, because a ... two generic spread spectrum modulation techniques—QPSK spreading and frequency-hop spread spectrum book Mobk087 August 3, 2007 13:15 FUNDAMENTALS OF SPREAD SPECTRUM MODULATION 11 SPREADING CODES...

Ngày tải lên: 27/06/2014, 09:20

... to explain several features of a spread spectrum modulation system The type of spread spectrum system shown in Fig is known as binary direct sequence (DS) spread spectrum modulation, because a ... of spread spectrum systems in the presence of other users For more complete treatments of spread spectrum, the reader is referred to [1, 2, 3] KEYWORDS Code acquisition, Code tracking, Direct sequence, ... modulation techniques, the principal forms of spread spectrum modulation are described One of the most important components of a spread spectrum system is the spreading code, and several types and their...

Ngày tải lên: 07/08/2014, 21:20