Low-Rate UWB Communication Systems Based on Chaotic Modulations

Wideband Wireless Communications Laboratory, Xiamen University

Low-Rate UWB Communication Systems Based on Chaotic Modulations

Lin Wang1, Wei Kai Xu1, Guanrong Chen2

1.Dept. of Communication Engineering,

Xiamen University, China

2.Dept. of Electronics Engineering, CityU of HK, China

27/07/2010


42-2

Contents Background System design of UWB based chaos

modulations Rapid timing synchronization for FM-DCSK

UWB User cooperation DCSK communication system Ongoing work Conclusions


42-3

Contents

Background System design of UWB based chaos




42-4

Background Basic idea of UWB

Communications in a frequency band already occupied (Coexistence)

Making frequency re-use possible by limiting the PSD of Equivalent Isotropically Radiated Power (EIRP)

UWB radio regulation Federal Communications Commission (FCC, USA) determined onl

y the maximum emission limit and minimum bandwidth Method for access to UWB frequency band has not yet been fixed

Note: UWB regulations say nothing about the type of carrier and technique used to generate UWB carrier. So Any kind of carriers, including chaotic signals, may be used; any kind of modulation scheme may be used


42-5

Background

UWB frequency band Frequency band allocated to handheld UWB devices: 3.1

GHz to 10.6 GHz

Define: UWB transmitter is an intentional radiator that, at any time instant fractional bandwidth Or, UWB bandwidth 500 MHz, regardless of the

fractional bandwidth

2( ) /( ) 20%H L H LBW f f f f


42-6

Background FCC limits on radiated UWB signal

To avoid interference caused in the existing narrowband systems, not the radiated power but the PSD of EIRP is limited

Definition of Equivalent Isotropically Radiated Power (EIRP)= (power supplied to the antenna) *(antenna gain)

ERIP limits in two ways: Peak level of the emissions contained within a 50-MHz bandwidth centere

d on the frequency at which the highest radiated emission occurs should not exceed 0 dBm EIRP

Average radiated emissions shall not exceed -41.3 dBm EIRP when measured using a resolution bandwidth of 1 MHz over the frequency band of 3.1 GHz to 10.6 GHz

Note: Low-data rate (less than 350 kbit/s) UWB systems are peak power limited, while high-data rate ones are average power limited


42-7

Background Carrier types of UWB

Impulse radio, such as Gaussian pulse Sine waveform, MB-OFDM, FM-UWB etc. Chaotic waveform

Modulation schemes Pulse-Amplitude Modulation (PAM), pulse carrier Pulse-Polarity Modulation (PPoM), pulse carrier On-Off Keying modulation (OOK), arbitrary carrier Pulse-Position Modulation (PPM), arbitrary carrier Transmitted-Reference Modulation (TR), arbitrary carrier


42-8

Background TR Modulation: Binary information is mapped into two wavelets,

the first chips serves as a reference, the second one carries the information

Tf

Ts Tg

guard interval

reference chips

information chips

Modulation: • Bit “1” : Second chips is equal to the delayed reference one • Bit “0” : Second chips is equal to the inverted and delayed reference one

Where: Tg >Tch Delay between thereference and information bearing chipsNote: Wavelet may be either a fixed(impulse radio) or a chaotic waveform

Note: FM-DCSK/DCSK is a TR modulation based on chaotic carrier.

RMS delay of channel


42-9

Background Applications of low-rate UWB

Sensor networks, wireless networking devices of embedded system, smart houses, offices and mall etc.

Categories of low-rate UWB Data-rate: typically around 1Mbps LR-WPAN: covers personal operational area, short range from 10-

30m LR-WLAN: coverage up to 100m

IEEE Standards about low-rate UWB Existing: IEEE 802.15.4 Standard, used by ZigBee alliance Alternative UWB(2007): IEEE 802.15.4a Standard WPAN low rat

e alternative PHY


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42-11

System model of FM-DCSK UWB

Re ( ) ( / 2)fTz r t r t T dt

UWB Chaos Pulse Generator

FM Modulator

Delay T/2

-1

K

Binary information to be transmitted

Channel

DelayTf/2

Threshold Decision

estimated bit

TT

T

f

f

dt2

2

Transmitter

Receiver

reference chips

Tf

Ts Tg

guard interval

information chips

Signal structure

Noncoherent detect: observation signal is

Where is integration duration.T


42-12

Analysis and Optimization of System Performance (1)

In the absence of ISI, the receive signal as

)()]2

()([2

)( tnT

tagtgE

tr fb

Suppose a data symbol a = 1 is transmitted, the output of the detector is

dtT

trtrRzT f )

2()(

0

4321

00

0

2

0

2

0

22

222

2

T fTb

T fbT

b

Tb

dtT

tntnRdttntgRE

dtT

tntgRE

dttgE

dttgE

z

Where:ζ1 is the signal energy captured in the integration, ζ2 and ζ3 are the signal-noise cross terms, and ζ4 is the noise-noise cross term.

Above three cross terms can be approximated as independent Gaussian random variables. And their distributions are respectively as below:

)

4,0(~,

2

00

32

dttgENN

T

b ),0(~ 204 BTNN


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Analysis and Optimization of System Performance (2)

Then the bit error rate (BER) probability can be written as

dttgENBTN

dttgEQ

P

yPP

T

b

T

b

e

2

0020

22

0

4321

24

)(

0

0

According to expression of BER, the optimization of integration time Topt is equivalent to the maximization:

dttgENBTN

dttgET

T

b

T

b

Topt 2

0020

22

0

24

)(maxarg

Note: above expression can not only prove that the existence of the optimal integration interval Topt, but also show that the optimal value depends on Eb, N0, B and g(t).


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Simulation results(1)

10 11 12 13 14 15 16 17 18 19 2010

-5

10-4

10-3

10-2

10-1

100

Eb/N0 [dB]

BE

R

CM1

Tg = 7.5ns

Tg = 22.5ns

Tg = 47.5ns

Tg = 97.5ns

Tg =197.5ns

10 11 12 13 14 15 16 17 18 19 2010

-7

10-6

10-5

10-4

10-3

10-2

10-1

100

Eb/N0 [dB]

BE

R

CM4

Tg = 7.5ns

Tg = 22.5ns

Tg = 47.5ns

Tg = 97.5ns

Tg =197.5ns

Performance of the fixed integration interval UWB-FM-DCSK system, when the guard interval length Tg is 7.5, 22.5, 47.5, 97.5 and 197.5ns, with the integration interval is Tf/2 and the chip duration Ts is 2.5ns Left: CM1 Right: CM4.

Remark: 1.When semi-bit Tf/2 duration integration interval is used, the BER performance is obviously affected by guard interval Tg. Larger Tg, lower BER. 2. On the other hand, since the integration interval is equal to Tf /2, increasing of Tf means more noise energy captured whereas signal energy almost unchanged, so the BERis deteriorated when Tg great than a threshold.


42-15


BER as a function of the integration interval, with Eb/N0 increases from

10dB to 18dB in CM1and CM2. Tg is set as 197.5ns and Ts is 2.5ns.

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

x 10-7

10-4

10-3

10-2

10-1

100

CM1

T [s]

BE

R

10dB11dB12dB13dB14dB15dB16dB17dB18dB

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

x 10-7

10-4

10-3

10-2

10-1

100

T [s]

BE

R

CM2

10dB11dB12dB13dB14dB15dB16dB17dB18dB

Remark: the BER of the proposed system as a function of the integration interval T (from 0 to Tf/2 with the stepping 4ns) in different Eb/N0 condition and different channel mode. And there exists an optimum integration interval when BER is minimized corresponding to each Eb/N0.


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10 11 12 13 14 15 16 17 18 19 202010

-4

10-2

100

Eb/N0 [dB]

BE

R

10 11 12 13 14 15 16 17 18 19 202010

-4

10-2

100

Eb/N0 [dB]

BE

R

CM2 T = Topt

CM2 T = Tf/2

CM1 T = Topt

CM1 T = Tf/2

10 11 12 13 14 15 16 17 18 19 2010

-6

10-4

10-2

100

Eb/N0 [dB]

BE

R

10 11 12 13 14 15 16 17 18 19 2010

-8

10-6

10-4

10-2

100

Eb/N0 [dB]

BE

R

CM3 T = Topt

CM3 T = Tf/2

CM4 T = Topt

CM4 T = Tf/2

Performance comparison between the non-optimal integration interval scheme and the presented

optimization scheme of CM1, CM2, CM3 and CM4, Tf is set as 400ns and Ts is 2.5ns

Remark: BER performance of the presented optimization method outperforms the scheme when the integration interval keeps a fixed value of Tf/2 about 2.2dB in CM1, CM3 and CM4 while about 1.2dB in CM2, because of much channel delay in CM2 than others.


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Improved DCSK/FM-DCSK Scheme

Problem of TR-UWB receiver (including DCSK/FM-DCSK) All digital implementation: extremely high power consumption due

to needing GHz A/D converter.

Analog implementation RF front-end: a RF delay line is required, which is extremely difficult to implement in CMOS. Especially, long delay implementation, such as several decades ns.

How to solve this problem? Design an alterative DCSK transceiver which eliminates the RF

delay line.


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An alterative DCSK scheme: CS-DCSK(1)

Code-shifted DCSK (CS-DCSK) Both the reference and information bearing wavelets are sent in the same time slot.

The two wavelets are separated by Walsh codes instead of time delay. The diagram of transmitter and receiver as follows,

Walsh functiongenerator

Chaotic signalgenerator

1,Iw

2,Iw

NIw ,

)(tsb

b

cT cT

Walsh functiongenerator

2,Rw

NRw ,

1,Rw

Transmittedinformation

dtcs NTT

0

)(~ tr)(tr Z b

A

B

1

, 10

( )N

R k ck

w rect t kT

1

, 10

( )N

I k ck

w rect t kT

Transmitter

Receiver

1 1

, 1 , 10 0

( ) ( ) ( ),N N

b R k c I k c s ck k

s t w c t kT b w c t kT T NT

Transmitted signal:

1 ( 1)

, 1 , 10

( ). ( )c

c

N k T

R k I kkTk

Z w r t w r t dt

Observation signal:


42-19

An alterative DCSK scheme: CS-DCSK(2)

,. ,.R Iw and w,. ,.R Iw and wWhere are Walsh code sequences, they are orthogonality.

can be any two rows which are taken from Walsh code matrix. Such as Walsh code matrix1 1 1 1

1 1 1 1

1 1 1 1

1 1 1 1

W

,.Rw

,.IwProperties of CS-DCSK: ● eliminates the delay circuit at receiver. ● the reference and information bearing wavelets are transmitted in the same time slot using Walsh code sequences. ● the reference and information bearing wavelets are orthogonality, which can beproven as follows,

1 1

, 1 , 10 00

2 2 2,1 ,1 ,2 ,2 , 1 , 1

0

,1 ,1 ,2 ,2 , 1 , 1

0

( ) ( )

( ) ( ) ( 1)

02 2

s c

s c

T NT N N

R k c I k ck k

T NT

R I R I c R N I N c

Tb bR I R I R N I N

w c t kT b w c t kT dt

b w w c t w w c t T w w c t N T dt

E Eb w w w w w w b

N N

R Iw w


42-20

BER performance analysis of CS-DCSK

According to Gaussian Approximation (GA) method, the BER is computed as

2

2 2 20 0

1 1Pr 0 1 Pr 0 1

2 2

11

2 2 var 1

21

2 2 2 var 4

k

k k

BER Z b Z b

E Z berfc

Z b

N E xerfc

N x N N E x N N

If the Logistic map is used, we have

2 1

2kE x 2 1var

8kx

So, BER of CS-DCSK can be approx.

12 2 2 2

0 0

2 2 2 2

12 2

0 02

2 2 var 41

2 4

4 21 1

2 2

k k

k

b b

N x N N E x N NBER erfc

N E x

N N Nerfc

N E E

BER performances of the CS-DCSK over AWGN for

theoretical results (solid lines), and simulated results

Remark: The BER performance isfunction of spread-spectrum factor. It is similar to traditional DCSK modulation.


42-21

CS-DCSK performance over multipath fading channels

Performance comparisons of CS-DCSK and DCSK over Rayleigh fading channel conditioned with

different spread factor. Left: Channel I: PDP: [0.4 0.4 0.2] Right: Channel II, PDP: [0.6 0.3 0.1]

Remark: The BER performances of the CS-DCSK have almost same with that of DCSK except for small SF. It is illustrated thatthe CS-DCSK is a competitive alterative scheme of DCSK.


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modulations Rapid timing synchronization for FM-

DCSK UWB User cooperation DCSK communication system Ongoing work Conclusions


42-23

Problem of present non-coherent UWB synchronization algorithm

● Timing synchronization is a major challenge for the implementation of non-coherent UWB receivers.

● Present non-coherent UWB timing synchronization algorithm: the operation of correlation between two neighboring symbols and the operation of picking the peak from a large amount of correlation values.

● Problem: Above algorithm operation is not available for the FM-DCSK UWB system for two reasons: first, a chaotic waveform varies from symbol to symbol, even if the samebit is transmitted repeatedly, which is the main difference between the FM-DCSK UWB and the conventional non-coherent TR UWB; second, noise-like chaotic signals have low values of inter-symbol correlation. Thus, a new timing synchronization algorithm with rapidity and low complexity is required for the FM-DCSK UWB communication system.


42-24

Rapid timing synchronization algorithm for FM-DCSK UWB receiver(1)

Algorithm basic idea: takes advantage of the excellent correlation characteristic of chaotic signals, finish timing synchronization based on intra-symbol correlation operation.

Algorithm step: ■Step 0: Divide the interval into N parts uniformly, and take the beginning point of each part as the integral starting point. Thus, within one symbol observation interval, N integral results are obtained:

ˆ ˆ[ , ]T

ˆ4

T

r t

/ 2r t T

ˆ2

T

3ˆ

4

T

T TI

kth bit (k+1)th bit

(0)0S (0)

1S (0)2S (0)

3S

ˆ /(0)

ˆ /( ) ( / 2) , 0,1, 1.

IiT N T

i iT NS r t r t T dt i N

Where ,define: [ , / 2]I wT T T (0)arg max , 0,1, 1.ii

I S i N

Then update according to

ˆ ˆ / , .mod N I T N T

Example for Divide the interval

into 4 parts

ˆ ˆ[ , ]T


42-25

Rapid timing synchronization algorithm for FM-DCSK UWB receiver(2)

ˆ ˆ[ / , / ]T N T N

2 / .T N

After step 0, the target interval, in which lies, can be determined in whose length is

Step q: (q>0)Through step q-1, it is known that lies in the interval , which is then uniformly divided into two sub-intervals, namely and . The purpose of this step is to determine in which sub-interval lies, and the determination is based on formulas given below:

1 1ˆ ˆ[ / (2 ), / (2 )]q qT N T N 1ˆ ˆ[ / (2 ), ]qT N 1ˆ ˆ[ , / (2 )]qT N

ˆ 1( ) 2

ˆ 12

( ) ( / 2) , 0,1j

Iq

j

q

TT

q NTj

N

S r t r t T dt j

1

1

ˆ ˆ, , 02

ˆ ˆ, , 1.2

q

q

Tif J

N

Tif J

N

( )arg max , 0,1.qj

j

J S j

ˆ , 02ˆ

ˆ , 1.2

q

q

Tif J

NT

if JN

Update

Where:


42-26

Rapid timing synchronization algorithm for FM-DCSK UWB receiver(3)Algorithm stop condition: define synchronization resolution ,so needing number of steps that maximum timing error is less than or equal to the resolution

.2 resq

TT

N

So, 2log .res

Tq

NT

Define, 2log ,propres

Tq

NT

Thus, If the algorithm ends; otherwise update q = q + 1,and repeat step q.

,propq q

.resT


42-27

Numerical and simulated results(1)Comparison between the Proposed Algorithm and the Conventional Algorithm

10-10

10-9

10-8

100

101

102

103

104

Tres (s)

requ

ired

num

ber

of s

teps

q prop

q ref

Required number of steps vs. (T = 200ns, N = 4).

resT

In the terms of proposed algorithm andreference algorithm, the number stepsfor given synchronization solution is

2log ,propres

Tq

NT

Proposed:

Reference: / ( ) .ref f resq T N T

Remark: the time complexity of the reference algorithm is , whereas the counterpart in the new algorithm here is only

(1/ )resO T

2(log (1/ )).resO T


42-28

Numerical and simulated results(2)Timing performance under different N

15 20 25 300

10

20

30

40

50

60

70

80

90

Eb/N0 (dB)

(a)

tim

ing p

robabili

ty (

%)

N=2

N=4N=8

15 20 25 300

5

10

15

20

25

30

35

Eb/N0 (dB)

(b)

avera

ge t

imin

g e

rror

(ns)

N=2

N=4N=8

ET

LT

AT

LT

ET

Comparison among (a) timing probabilities, (b) average timing errors vs. Eb/N0 under different values of N over CM1

Where:earlier timing (ET):

later timing (LT):

accurate timing (AT):

ˆ resT

ˆ resT

ˆ [ , ]res resT T

Remark: Since the BER performance is highly sensitive to LT but less sensitive to ET, it is clear that the larger the probability of LT, the worse the BER performance. Here, occurrence probabilities of ET is great than LT. Thus, the average BER performance is good.


42-29



UWB User cooperation DCSK

communication system Ongoing work Conclusions


42-30

Motivation There are two fundamental aspects of wireless communication that

make the problem challenging and interesting. First is the phenomenon of fading: the time-variation of the channel

strengths due to the small-scale effect of multipath fading Second is the phenomenon of interference: such as, inter-user inference,

inter-symbol inference (ISI) that is introduced by multipath channel.

So, how to deal with fading and with interference is central to the design of wireless communication systems. Diversity – an effective method to mitigate channel fading

As an alterative spread-spectrum technology, DCSK/FM-DCSK has superior capability in terms of anti-interference over multipath fading channels. For improving performance of DCSK, space diversity is a promising

technology. Such as, multiple antenna, user cooperative diversity, etc.


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Cooperative communications can provide transmit diversity for most wireless networks.

Since one user’s signals can be relayed by other users’ independent fading paths to the destination, in cooperative communications, terminals share others’ antennas to achieve transmit diversity.

This approach achieves spatial diversity through all partners’ antennas, which enhances the ability of combating fading in wireless communication systems. Such as WSN, WPAN and WBAN, which are complicated applications requesting low-cost, low power and various demands of QoS. (VMIMO)

User Cooperative Diversity (Combating fading)


42-32

Frequency modulated differential chaos shift keying (DCSK/FM-DCSK) is a joint modulation and spread spectrum technique.

The noise performance of DCSK/FM-DCSK is superior to most conventional modulation schemes in multi-path channel environment. In particular, frequency-modulated differential chaos shift keying (DCSK/FM-DCSK) technique offers robustness against multi-path interference and channel imperfections.

DCSK/FM-DCSK demonstrates itself as a promising modulation technique for many low-cost and low-complexity wireless transmission applications, such as wireless sensor networks (WSN) and low-data-rate wireless personal or body area networks (WPAN, WBAN).

Thus, combination of user cooperative diversity and DCSK/FM-DCSK is an efficient scheme to anti-fading and anti-interference (ISI).

DCSK/FM-DCSK (Combating multi-path interference)


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DCSK user cooperative system based on Walsh codes

Data of U1 Data of U2

Data of U2 Data of U1

Base station

U1

U2

U1

U2

Base station

)(/)( 11 tXtY

)(/)( 22 tXtY

2,1H 1,2H0,2H

0,1H

)(0 tY

0,1H

0,2H

)(2,1 tX

)(1,2 tX

(a) Odd period, transmit selfdata

(b) Even period, relay thedata of partner’ s

)(0 tY

Model of user cooperative communication systems

User 1

User 2

(a) Conventional cooperation

(b) Space-time cooperation

Cooperation period

Antenna of user #

21, ww

21, ww

43, ww

43, ww

21, ww

21, ww

43, ww

43, ww

21, wwUser 1

User 2

21, ww

43, ww

Antenna ofuser # Cooperation period

21, ww 21, ww

43, ww

43 , ww 21, ww

43, ww 43 , ww 21, ww

43, ww

User 1 data

User 2 data

Cooperation protocol of the

two-user DCSK-CC system

Walsh codes are used as multi-access codes for two users. At odd slot, user 1 and user 2 transmit self information to partner and destination, respectively, at even slot, user 1 and user 2 relay partner’s information to destination. According to transmit self information

or not at even slot, there are two user cooperative diversity protocol: conventional cooperation and space-time cooperation.


42-34

Simulated results(1) –Comparisons between DCSK cooperative system and CDMA cooperative system

BEP performance comparisons of the DCSK cooperation system and the CDMA cooperative system with different distance ratio , here all distances are normalized by the distance

Spread-spectrum factor is 32 (left) and 64 (right). Spread code of CDMA is Golden sequence, CDMA system with conventional receiver, simulation environment is multipath fading channel with PDP of [0.4 0.4 0.2].

: :SD SR RDd d dSDd

Remark: The BEP curves indicate that the performance of the DCSK cooperative system with a steeper slope is more sensitive to noise than the CDMA cooperative system at high values of SNR. The DCSK cooperative system is more effective at high SNR, especially in near-far scenarios, such as user distance ratio 1:1:0.5 and 1:0.8:0.4.


42-35

Simulated results(2)-Performance comparisons between conventional cooperation and space-time cooperation

BEP performance of conventional cooperation protocol and space-time cooperation protocol, spread spectrum is 32 (left) and 64 (right).

Remark: Unlike the user cooperative communication systems based on traditional digital modulations, the performance of the space-time cooperative system is not better than that of the conventional cooperative system in the DCSK cooperative system at all times.


42-36

Simulated results(3) Performances under different chaotic maps

BEP performances of DCSK cooperative system when logistic map, cubic map and Bernoulli-shift map are used, respectively, spread-spectrumfactor is 32

21 1 2k kx x

31 4 3k k kx x x

1

1.2 1 0

1.2 1 0k k

kk k

x when xx

x when x

Logistic map:

Cubic map:

Bernoulli-shift map:

Remark: It is found that the chaotic sequences generated by the Bernoulli-shift map produce higher BEP, while the BEPs for the system using the cubic map and the logistic map are the same. There are similar results in conventional multiuser DCSK systems


42-37

Properties of user cooperative DCSK communication system In near-far scenarios, the performance of DCSK user cooperative

system is better than that of CDMA user cooperative system with conventional receiver.

The conventional cooperation is a better cooperation protocol than the space-time cooperation in DCSK cooperative system.

There are similar performance results with DCSK under different

chaotic maps.

Consequently, the DCSK cooperative system can be expected applicable to energy-constrained and low-cost wireless networks with simple cooperation protocols


42-38





42-39

Ongoing work To boost the application of chaos-based UWB

communications, chaotic signal generators working directly in the microwave frequency region is developing.

Chaos-based communications are used in traffic (ITS)

Network coding and cross-layer design of DCSK/FM-DCSK based network.


42-40

Conclusions In meddle & low-data rate systems where the low power

consumption and low price are crucial, only non-coherent receivers can be used. DCSK/FM-DCSK is best choice in chaos modulations.

The rapid timing synchronization algorithm based chaotic signal property is efficient and robust in FM-DCSK UWB non-coherent receiver.

An alterative simplified DCSK (CS-DCSK) scheme is more promising in low-cost application scenarios.

There are many space to optimize multi-user communication system based on DCSK/FM-DCSK modulation.


42-41

References G. Kolumbán, M. P. Kennedy, G. Kis, and Z. Jákó, “FM-DCSK: a novel method for chaotic communications,” in P

roc. IEEE ISCAS, May, 1998, vol.4, pp. 477-480. F.C.M. Lau and C.K. Tse, Chaos-based Digital Communication Systems:Operating Principles, Analysis Methods, a

nd Performance Evaluation, (Springer-Verlag, Berlin), 2003. Y. Xia, C. K. Tse, and F. C. M. Lau, “Performance of differential chaos-shift-keying digital communication systems

over a multipath fading channel with delay spread,” IEEE Trans. Circuits Syst. II, Exp. Briefs, vol. 51, pp. 680-684, Dec. 2004.

G. Kolumbán, “UWB technology: Chaotic communications versus noncoherent impulse radio,” in Proc. ECCTD, Sept., 2005, vol. 2, pp. II/79-II/82.

C. C. Chong and S. K. Yong, “UWB direct chaotic communication technology for low-rate WPAN applications,” IEEE Trans. Vehicular Technology, vol. 57, pp. 1527-1536, Mar. 2008.

X. Min, W. K. Xu, L. Wang, and G. R. Chen, “Promising performance of a frequency-modulated differential chaos shift keying ultra-wideband system under indoor environments,” IET Commun., vol. 4, pp125-134, Jan. 2010.

Shaoyan Chen, Lin Wang and Guanrong Chen “Data-Aided Timing Synchronization for FM-DCSK UWB Communication Systems”, IEEE Trans. Industrial Electronics, vol.57, May 2010.

Jing Xu, Weikai Xu, Lin Wang and Guanrong Chen, “Design and Simulation of a Cooperative Communication System Based on DCSK/FM-DCSK,” in Proc. IEEE ISCAS, Paris, France, May 2010

W. K. Xu, L. Wang and G. R. Chen, “Performance of DCSK Cooperative Communication Systems over Multipath Fading Channels,” IEEE Trans. Circuits and Systems-I, be accepted.

W. K. Xu, L. Wang and G. Kolumban, “A Novel Differential Chaos Shift Keying Scheme,” International Journal of Bifurcation and Chaos, under review in the second round.


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Thank you!

Low-Rate UWB Communication Systems Based on Chaotic Modulations

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