Blind Estimation of Direct Sequence Spread Spectrum Signals(6)

Abstract—Self-recovering receivers for direct-sequence spreadspectrum signals with unknown spreading codes are discussed in this paper. Applications include signal interception, jamming, and low probability of intercept (LPI) communications. A multirate/m

TSATSANIS AND GIANNAKIS:BLIND ESTIMATION OF DIRECT SEQUENCE SPREAD SPECTRUM SIGNALS IN MULTIPATH

1249

(a)

(b)

(c)

(d)

Fig.6.Received and equalized symbols.will be close to 1,but we assume it is not exactly equal to

one.The correlation of the sampled system

is is a periodic function

of ,assuming that the aliasing effects

are not severe (note that

if

).Hence,an estimate of the spectral peaks

can be used to provide information

about .The Fourier

transform in (53)should be computed in the neighborhood of the “assumed”bit

rate for

some

can be estimated

as

(54)

Once

using (2),where the spreading

code was a Gold sequence of length 31[see Fig.4(a)].The chip rate signal was then modulated using a rectangular spectral

pulse

Abstract—Self-recovering receivers for direct-sequence spreadspectrum signals with unknown spreading codes are discussed in this paper. Applications include signal interception, jamming, and low probability of intercept (LPI) communications. A multirate/m

1250IEEE TRANSACTIONS ON SIGNAL PROCESSING,VOL.45,NO.5,MAY

1997

Fig.7.Performance of matched filter and ZF

receiver.

Fig.8.Bit period estimation.

The path delays

are (57)

where

(58)By sampling (57)

every

Abstract—Self-recovering receivers for direct-sequence spreadspectrum signals with unknown spreading codes are discussed in this paper. Applications include signal interception, jamming, and low probability of intercept (LPI) communications. A multirate/m

TSATSANIS AND GIANNAKIS:BLIND ESTIMATION OF DIRECT SEQUENCE SPREAD SPECTRUM SIGNALS IN MULTIPATH1251

response

).

Test Case1:The subspace method of(19)and(20)was

used to estimate the unknown impulse

response

.Fig.4(d)shows the es-

timated

was used(equivalent to two bit

periods),in this way overestimating the actual channel order

of.The overestimation can be seen in Fig.4(d),

where

bits,

SNR

the standard deviation(dashed-dotted line)of the100

runs.We observe a reasonable estimation accuracy despite the

low SNR.

Test Case2—Receiver Design:Based on the

estimated

)were implemented[using(31)and(33),

respectively].Fig.6(a)shows the transmitted BPSK

sequence

,whereas Fig.6(b)shows the received

data,which

are corrupted by ISI and additive noise.In Fig.6(c)and(d),

the estimated is shown using the matchedfilter and the

ZF structures,respectively.Both receivers manage to equalize

the data adequately,as shown in thefigures.The remaining

fluctuations at the output of the matchedfilter are due to

residual ISI,whereas those at the output of the ZF receiver

are due to noise effects.

A better picture of the performance of the two schemes

is obtained by the results of Section V.The probability of

error for the two alternatives was evaluated using(43)and

(48)and is plotted in Fig.7versus SNR.The matchedfi …… 此处隐藏：5937字，全部文档内容请下载后查看。喜欢就下载吧 ……