01158911

8/12/2019 01158911

http://slidepdf.com/reader/full/01158911 1/4

P3-11

BER Performance under Rician Fading Environments in Radio-on-Fiber

Ubiquitous Antenna Arch itecture

for R oad-to-Vehicle Wireless CDM System

S h i n TAKAHASHI Hideaki OHTSUKI K a t s u t o s h i TSUKAMOTO and Shozo KOMAKI

Department of Communications Engineering, Graduate School of Engineering, Osaka University,

Yamada-oka 2-1 Suita-shi, Osaka, 565-0871 Japan

Tel: +81-6-6879 -7717, Fax: +81-6-6879-7715, E-mail: [email protected] u.a~.~

bstract This paper evaluates the BER performance

under Rician fading environment in radio-on-fiher

ubiquitous antenna architecture for Road-to-Vehicle

wireless CDM system. As a result , the BER perfo m-

ance is improved in comparison with that of u s i n g

s i n g l e RBS w i t h o u t r a d i o transmission

s c h e m e .

1. Introduction

Many traffic problems such as traffic jams, trafficaccidents, and environmental problems according to

them have motivated extensive research in Intelligent

Transport System (ITS) technology. Road-to-Vehicle

Communication (RVC) system is one of the key tech-

nologies in ITS. Using millimeter-wave band is con-

sidered since its large available bandwidth for provid-

ing high data transmission rate of various multimedia

communication services in RVC [1] [2]. However

there are many problems in using millimeter-wave

hand. One of them is the high free-space loss. The

cellular zones, hence, must he small, such as several

O m. So, many radio base stations (RBSs) must he

needed and handovers will he frequent and handover

control will he quite complex.

Against these problems, it is suitable to use the ra-

dio-on-fiber (RoF) ubiquitous antenna architecture. In

this architecture, several RBSs are connected to one

CS by RoF links and the size of RBSs is small he-

cause each RES needs only a device to convert be-

tween optical signals and radio signals [4]. To realize

the seamless communication in this architecture, it has

been proposed the use of code division multiplexing

(CD M) radio transmission scheme, which can perform

soft handover, in [I]-[4]. his scheme, moreover, candistinguish multipath fading signals each, and then

combines divided signals using a maximum ratio

combining diversity technique, such as the Rake di-

versity reception, hence receiving characteristic will

be improved. In [3], multipath Rayleigb and Rician

fading environment was considered, but the delay

between direct wave and scattered waves in Rician

fading environment wasn’t considered. In line-of-site

communication, it can he considered birect wave and

scattered waves arrive all at once if the distance be-

tween the RBS and the MS is small, at the same time

if the distance between the RBS and the MS is larger,

it can be considered scattered waves arrive after direct

wave for some time.

253

8/12/2019 01158911


In this paper, we evaluate hit error rate (BEK) under

multipath Rayleigh and Rician fading envirnnrnents in

consideration of the delay between direct wave and

scattered waves in downlink by co mputer simulation.

2. System configuration and models

Fig. 1RoF ubiquitous ante nna architecture

Figure 1 illustrates the RoF ubiquitous antenna ar-

chitecture. In this architecture, several RBSs are con-

nected to control station (CS) by star type RoF link.

The CS equips all radio modulation and demod ulation

units, and each RBS equips only O E and E/O con-

verters.

Fig.2 show s the configuration for the downlink. Th e

CS employs QPSK modulation and direct spread

spectrum for CDM in the downlink. Then the R F SS

signals are converted into an optical intensity modu-

lated signal and transmitted to several RBSs through

RoF link. At each RBS the op tical signal is converted

into RF signal and transmitted to the mobile stations

(MSs). A M S received some RF signals propagated

through some paths from some RBSs. At the M S

modulator, sliding-carrelator despreads the received

signal, where these paths are optimally combined at

coherent Rake combiner performing maximum ratio

combining diversity. Finally. the optimal QPSK signal

is demodulated to the transmitted data.

Fig. 2 Configuration of downlink transmission

In this paper, w e consider the following three types

of channel delay profiles between a RBS and a MS:

AWGNchannel with only a direct component.

Rayleigh fading channel with multiple indirect com-

ponents.

Rician fadin g channel type A with a direct component

and scattered com ponents arriving simultaneously.

Rician fadin g channel type B with a direct component

and delayed and scattered components.

Direct com pon ent Direct com pon ent

ca tter ed , Scadcomponen t s componen t s

t

4 ype A (b) Type

Fig. 3 Delay profile in Rician fad ing channels

3. Computer simulation

We examine BER of the system by computer simu-

lations. The simulation parameters are indicated in

Table 1. We assume that in Type B Rician fading

channel the delay between scattered components and

the direct component is 16 [nsec] which corresponds

to a c hip duration.

-25 -

8/12/2019 01158911


Table. 1 Simulation parameters

F i r s t m o d u l a t i o n

S e c o n d m o d u l a t i o n DS SS

R i c e f a c t o r

Fig.4-6 show relation ship between BER and aver-

age E&o of total received signals, in Rayleigh fading

channel, Rician fading channel type A , and Rician

fading channel type B, respectively. In each simula-

tion, signals are transmitted from two RB Ss, and the

level difference between the received signals is 0 [dB]

The arrival time difference between two received sig-

nals is 0 [T,] and [T,]. By way of com pariso n, we

simulate in using single RBS with CDM and without

spread-spectrum (SS) radio transmission scheme.

Fig. 4 BER performance in Rayleigh fading channel

IL

I

0 5 10 15 20 25 3

Aveage Eb iNo Id01

Fig. 5 BER performance in Rician fading channel

type A

10

10

10m

I O

10-

0 10 15 2 25 30

Average EbiNo [dB1

Fig. 6 BER performa nce in Rician fading channel

type B

It is s e e n f r o m F i g. 4 a n d 5 that i n R a y l e i g h

a n d R i c i a n f a d i n g c h a n n e l t y p e A, t h e r e is no

difference between t h e BER p e r f o r m a n c e s i n us-

i n g s i n g le RBS w i t h C D M a n d w i t h o u t r ad io

t r a n s m i s s i o n s c h em e . In Fig .6 , how e ve r , u s ing

s i n g l e RBS w i t h C D M t r a n s m i s s i o n s c h e m e

s ho w s b e t t e r B E R p e r f o r m a n c e than w i t h o u t

radio transmission scheme. Because CDM radio

transmission scheme can suppresses the delayed scat-

t e r e d w a v e s .

I n R a y l ei g h f a d i n g c h a n n e l as s h o w n i n F i g .4 ,

using two RBSs, the BER performance of c a se ar-

r i v a l t i m e d i f f e r e n c e b e t w e e n t w o r e c e i v e d

signa ls of 2 [T ,] i s b e t t e r t h a n t h a t of c a s e n o

a r r i v a l t i m e d i f f e re n c e b e t w e e n t w o r e c e iv e d

signa ls , because it is impossible to distinguish the

multipath signals if the signals from two RBSs arrive

all at once. The BER performance of case n o a rr iv al

t i m e d i f f e r en c e b e t w e e n t w o r e c ei v e d s i g n a l s is

s a m e as that of u s i n g s i n g l e RBS w i t h CD M a n d

w i t h o u t r ad io t r a n s m i s s i o n s c h e m e .

In Rice fading channel as s h o w n in Fig.5 a n d 6

however , the BER performance of case no a rr iva l

t i m e d i f fe r e n ce b e t w e e n t w o r e c ei v e d s i g n a l s is

b e t t e r t h a n t h a t of c a s e a r r i v a l t i m e d i f fe r e n ce

be tw e e n tw o re c e ive d s igna l s o f 2 [T,], because

the SNR is more improved according to the cohe rent

-255-

8/12/2019 01158911


addition of the direct wave components than the ef-

f e c t of Ra k e d ive r s i t y in reducing the fluctu ation in

the received signal strength.

4. Conclusions

In this paper, we evaluated BER under multipath

Rayleigh and Rician fading environments in consid-

eration of the delay between direct wave and scattered

waves in downlink by computer simulation. As the

result, the BER performance in Rician fading channel

B is better than that in Rician fading channel A he-

cause CDM radio transmission scheme can suppress

the delayed scattered waves. Comparing the BER

performances that delay between received signals

from two RBSs is 0 [TJ with [TJ, former is better

in Rayleigh fading channel, and latter is better in Ri-

cian fading channel A, B. In Rayleigh fading channel,

the BER performance of c a s e a r r i v a l t i m e differ-

e n c e b e t w e e n t w o r e c e i v e d s i g n a l s o f 2 [T,] is

better than that of u s i n g s i n g le RBS w i t h o u t

r a d i o t r a n s m i s s i o n s c h e m e . In R i c e f a d i n g

c h a n n e l , the BER p e r f o r m a n c e in u s i n g t w o

R B S w i t h CDM transmission scheme is better

than tha t of using single RBS w i thou t r a d io

t r a n s m i s s i o n s c h e m e

Acknowledgment

This paper is partially supported by the

Grants-in-Aid for Scientific Research (B) No.

14350202, from the Japan Society for the Promotion

of S cience.

5. References

[I] H.Harada, K.Sato, M.Fujise. “A Feasibility Study on a

Radio-on-Fiber Based Road-to-Vehicle Communication

Systems by a Code Division Multiplexing Radio Trans-mission Scheme,” Proc.of ITST2000, pp.155-160,Oct.2000

H.Harada, K.Sato, M.Fujise, “ A Radio-on-fiber Based

Millimeter-wave Road-vehicle by a Code Division Mul-tiplexing Radio Transmission Scheme Symmetry be-tween Uplink and Downlink - ” Proc.of ITST2001,pp.47-52, Oct.2001

[3] KShimezawa, H.Harada, HShirai, M.Fujise, “An ad-

121

vanced DSRC system based on a

code-division-multiplexing based radio transmissionscheme,” Proc.of ITST200l. pp.77-82, O ct.2001

[4] K.Tsukamoto, Y.Kadota, M.Okada and S.Komaki,“Macro Diversity using Photonic Fed Ubiquitous An

tenna ArchirecNre for Road-to-Vehicle Communication,”Proc.of WPMC’99, pp.468-473, Sep. 1999.

[ ] John.G.Proakis, Digital Communications, McCraw-Hill,

1983

-256-

01158911

Documents

Transcript of 01158911