第 489 回電波研連 F 分科会
開催日：2004 年 11 月 19 日

市街地伝搬路における支配的な散乱物体の特定
ゴレイシ ミール†

潤一†

高田

今井

哲朗††

† 東京工業大学 〒 152–8550 東京目黒区大岡山 2–12–1–S6–4†† NTT ドコモ R&D センタ 〒 239–8536 神奈川県横須賀市光の丘 3–5
E-mail: †{mir,takada}@ap.ide.titech.ac.jp, ††imai@mlab.yrp.nttdocomo.ac.jp

キーワード

散乱，都市モバイルチャネル，指向性アンテナ

Investigating Dominant Scatterers in Urban Mobile Propagation Channel
Mir GHORAISHI† , Junichi TAKADA† , and Tetsuro IMAI††† Tokyo Institute of Technology, 2-12-1-S6-4, Ookayama, Meguroku, Tokyo, 152-8550 Japan†† R&D Center, NTT DoCoMo Inc., 3-5, Hikarino-oka, Yokosuka-shi, Kanagawa, 239-8536, Japan
E-mail: †{mir,takada}@ap.ide.titech.ac.jp, ††imai@mlab.yrp.nttdocomo.ac.jp
Abstract The data obtained from a series of wideband directional measurements performed in an urban area in a
microcell scenario is analyzed. We try to estimate the dominant scatterer objects in the propagation channel comparing
the data obtained from experiment and accurate map of the area which includes all present objects. Results show that
all metallic objects in the transmitter and receiver vicinity have a significant impact on the propagation channel.
Key words scatterer, urban mobile channel, directive antenna

1. Introduction

then to identify the dominant scatterers in such an environment.
To this end we have accomplished a series of measurements in

Recent researches on mobile radio channels has revealed thata typical urban area in a small microcell scenario. The trans-

the received waves approach from finite distinct directions withmitter and receiver were in a line-of-sight (LOS) configurationdifferent delays to the receiver. This is because the scatterers

with equal height of 3 meters from the ground. The results show

are not usually distributed uniformly throughout the whole cov-that most metallic objects within a distance of 200 meters fromerage area, but rather occur in clusters [1], [4], [7], [8]. Mea-transmitter and receiver can be identified as an important scat-

surement analyses in urban macrocell environment show thatterer.

there are a few strong scatterers delivering a significant fraction of received power. In small macrocellular environments

2. Test Equipment

the scatterers are basically building edges, walls and roof edges

The block diagram of the system is shown in Fig.1. Anten-[5], [6], [9]. On the other hand some measurements assisting

nas were mounted on the roof-tops at both transmitter and re-with high resolution data processing uncovers that in the smaller

ceiver. The transmitter employed an omnidirectional sleeve an-cells, some objects other than buildings have been involved intenna, and at the receiver a patch array as a directive antenna

the scattering of the received waves [3], [2]. In most of thesewas used to detect the scatterers. Both transmitter and receiverresults, a significant amount of the received energy have beenantennas were rotated, for different purposes. The transmitterdelivered by one bounce scattered waves.

antenna was rotated with a diameter of 0.5 meters and constant

The aim of this work is first to confirm the clusterized nature

rotation speed of 5 rpm to create dynamic uncorrelated fading.

of the receiving waves in the urban microcellular channel andThis was done to average the multipath interference within the—1—

Figure 1 System Block Diagram.

Table 1 Parameters used in experiments.
fc

Tx

3.35 GHz

SignalBPSK with PN-9 SequencePower

35 dBmAntennaSleeve (2.2 dBi)

Antenna Height

3m

Antenna Rotation

5 rpm free run

Antenna Rotation Diame-

50 cm

ter
Patch Array (15 dBi)
Antenna10◦ beamwidths in Azimuth and Elevation

Rx

Antenna Height

3m

Antenna Rotation

3◦ step (120 point for fullazimuth)Antenna Rotation Diame-

60 cm
Figure 2 Measuement site viewed from Rx location. Up: North, Be-

terlow: South.
Tx-Rx Separation

60 m

beam. At the receiver the measurement was accomplished in

3. Measurement Siteevery 3◦ rotation of the directive antenna with vertical and hor-

Fig. 3 shows the map of the measurement site, an urban areaizontal beamwidths of 10◦ . The transmitter and receiver anten-

near Kannai station in Yokohama. The transmitter and receivernas were both mounted at a height of 3 meters on the top of thewere located 60 meters apart in a line-of-sight configuration.

different cars. At the transmitter a PN-9 sequence of 50 Mcps,

The street width was 26 meters and both transmitter and re-corresponding to a path resolution of 6 meters, was being trans-

ceiver were located 5.5 meters from walls of the same side. Sur-mitted. At the receiver, the signal was received for every 3◦

rounding buildings had an average height of 20 meters. Just inof the direction. The correlator output the instantaneous power

between Tx and Rx, a road with 13 meters width was crossing

delay spectrum. By averaging 978 delay spectra for each ofso that there was no buildings to satisfy the specular reflection

the directions, the power delay profile was produced. By using

condition. The measurements were accomplished during mid-these directional power delay profiles, we are able to identify

nights with a very low traffic in the street. Fig. 2 shows thethe clusters of received power in delay-azimuth domain. Table

north and south views of the measurement site taken from the

1 shows the parameters used in the experiments.

receiver location.

—2—

Figure 3 Measurement site.

Figure 4 The received power distribution assuming single bounce.

4. Identification of Scattering Objects
Precise maps of the area including surrounding buildings andobjects are prepared. Assuming the single bounce, ellipticalzoning of the scatterers in the delay domain is possible. Therefore, the map can be digitized into the delay-DoA grids, as
shown in Fig. 3, where for the sake of visibility only selected
grids are sketched. Using these grids the scatterers can be identified on the map. Fig. 4 shows the the distribution of clusters,
assuming the single bounce. A number of different visible objects could be identified as sources of scattering by this method.
Some other clusters, such as those inside the building zones,
could not be identified as the scatterers, considering the heightof the buildings. They shall be the multiply scattered components. Fig. 5 shows the power angular profiles before and after

Figure 5 Power angular profiles before and after the extraction of
LOS, identified scatterers and all clusters.

the extraction of identified scattering components. Note thatLOS component has been removed in advance to clarify howtion for each scatterer can be found in Table 2. The last columnmuch of the power of the scattered waves has been identified.

of this table shows the excess loss for each scatterer, which is

In Fig 6 seven areas can be recognized in which the identi-

calculated taking into account the free space loss for scatteredfied scatterers have delivered a significant amount of received

waves. In the following we will try to inspect the characteristics

power. Signal scattering in each of these areas has been causedof the scatterers in each of the sets.

by one or a set of scatterer objects. The distribution of the scat-

Set A. In the scatterers set A we have observed a number ofterers of each set in the experiment environment is shown in

different objects carrying a considerable amount of the received

Fig. 7. The description, rough dimensions and power contribu-

power. Direction of arrival for the received signals corresponding to this set are between 0◦ and 40◦ . The objects are located—3—rivals of the scattered waves from these objects are within 180◦
to 200◦ and their distance to the receiver antenna are relatively
short. The radar pole and traffic sign are very close to the receiver antenna and therefore deliver a big amount of scattered
power to the receiver.
Set F. This set has only one object that is a metallic handle very
close to the receiver antenna and at with a direction of arrival of231◦ . It seems that it has a very strong effect because the object
is located just 1 meter far from the receiver antenna.
Set G. This set is also including only one object that is a signboard attached to the street’s wall in a distance of 6 meters fromthe receiver antenna with a direction of arrival equal to 249◦ .
Figure 6 Identified scatterer sets.

In addition to these scatterers, a number of received cluster
waves have been detected which we have not been able to as-along the street at the north of both transmitter and receiver (insign any visible object to them. This can be due to multi re-a more distant location to receiver compared to transmitter) andflection effect. Table 3 also shows the residual powers. It is

up to 160 meters far from receiver antenna. The objects areobservable that 19% of the received power were scattered bystreet lights, traffic lights and signs, signboards and a big metal-

these identified scatterers.

lic object laid on the ground in front of one of the buildings.
The contribution of each object to the received power depends
to the object size, its angle toward transmitter and receiver antennas and its distances to them. The strongest scattered waves
are arriving from a traffic light-sign close to the transmitter, astore signboard and the big metallic object on the ground whichis also relatively close to the transmitter. In addition to signals
scattered from these objects some other clusters are also identified but we have not been able to designate any visible object tothem. This is because they are possibly multi reflected received
paths or from a moving object.
Set B. This set includes only one scatterer with a direction of arrival equal to 72◦ . However because the scatterer is very close
to both receiver and transmitter it has a big impact on the receiving power. The object is a metallic plate attached to theside walk lattice.
Set C. This set includes a street light, a traffic light and a traffic sign. With direction of arrivals equal to 123◦ and 126◦

Figure 7 The distribution of identified scatterers.

these scatterers have the most powerful influence on the received power. This is due to their close distance to the receiverantenna.
Set D. This set consists of multiple objects with directions of arrival from 150◦ to 180◦ . These scatterer objects are signboards,
street lights, traffic lights and traffic signs. The strongest scattered component among this set is one scattered by a big signboard above the rooftop of a building.
Set E. The three objects composing this set are a street radarpole, a traffic sign and traffic light poles. The direction of ar-

5. Discussion
The results of section 4. makes it clear that the objects as
small as 40 × 40 cm2 traffic signs are a potential source of significant scattering in the urban microcell propagation channel.
It also reveals that every traffic light and street light up to a distance of 200 meters from receiver or transmitter has a significant
scattering impact in the received power. Every metallic object
in the area seems to be involved in scattering transmitted signals—4—

to the receiver. The strength of any object’s effect depends to its
material, its size and shape, its surface angle to wavefront, itsdistance to the transmitter and receiver antenna and the overall
structural configuration of the environment and the distributionof the objects in the microcell. Assuming single bounce wewere able to identify a number of scatterer objects. The contirbution of these objects to the received non-line-of-sight signals
is 19% of the power. A larger amount of received signals werearriving in clusters, however we were not able to identify theirscattering objects probably due to the one bounce assumption.
These unidentified clusters deliver 56% of the received power.

439-448 April 2000.
[6] J. Laurila, K. Kalliola, M. Toeltsch,K. Hugl, P. Vainikainen, E.
Bonek, ”Wideband 3D characterization of mobile radio channels
in urban environment,” Antennas and Propagation, IEEE Transactions on, Volume: 50 Issue: 2, pp.233-243, Feb. 2002.
[7] U. Martin, ”Spatio-temporal Radio Channel Characteristics in
Urban Macrocells”, IEE Proceedings in Radar, Sonar and Navigation, vol. 145, no. 1, pp. 42-49, February 1998.
[8] Y. Oda, T. Taga, ”Clustering of Local Scattered Multipath Components in Urban Mobile Environments,” Proceedings of 55th
IEEE Vehicular Technology Conference (VTC Spring 2002),
vol. 1, pp. 11-15, May 2002.
[9] L. Vuokko, P. Vainikainen, J. Takada, ”Clusterization of
Measured DoA Data in an Urban Macrocellular Environment,” COST273 7th Meeting of the Management Committee,
TD(03)122, May 2003.

6. Acknowledgement
The authors would like to thank NTT DoCoMo Inc. for its
support to this project. Particularly we are grateful to Mr. Shinji
Miyazaki for setting up the measurements.
References[1] H. Asplund, A.F. Molisch, M. Steinbauer, N.B. Mehta, ”Clustering of scatterers in mobile radio channels-evaluation andmodeling in the COST259 directional channel model,” Proceedings of IEEE International Conference on Communications(ICC2002),Vol.2, pp.901-905, April 2002.
[2] E. Bonek, H. Hofstetter, C.F. Mecklenbrauker, M. Steinbauer,”Double-Directional Superresolution Radio Channel Measurements,” Proceedings of 39th Allerton Conference, Allerton,
USA, Oct. 2001.
[3] B.H. Fleury, X. Yin; K.G. Rohbrandt, P. Jourdan, A. Stucki,”Performance of a high-resolution scheme for joint estimationof delay and bidirection dispersion in the radio channel,” Proceedings of the Vehicular Technology Conference (VTC Spring2002), Vol.1, pp.522-526, May 2002.
[4] J. Fuhl, J-P. Rossi, E. Bonek, ”High-resolution 3D Direction-OfArrival determination for urban mobile radio,” IEEE Trans. on
Antennas and Propagation, Vol 45, pp.672-683, April 1997.
[5] K. Kalliola, H. Laitinen, L.I. Vaskelainen, P. Vainikainen, ”Realtime 3-D spatial-temporal dual-polarized measurement of wideband radio channel at mobile station,” Instrumentation and Measurement, IEEE Transactions on , Volume: 49 Issue: 2 , pp.

Table 3 Composition of the total received power.
Total Received Power-50.2 dB

Power of LOS component-51.4 dB

Power of identified scatterers component-63.4 dB

Power of residual component (Contributed to the identi- -57.1 dB
fied scatterers)
Ratio of the identified scattered power over the total scat-

19%

tered power
Power of all clusters component-58.8 dB

Power of residual component (Contributed to all clusters) -59.8 dB
Ratio of the clusters power over the total scattered power

56%

—5—

Table 2 Identified scattering objects.
Set

No

Object Description

Rough Dimensions (m2 )Contributed Excess Loss
Loss (dB)(dB)

1Store signboard

4×1

80.1

18.3

2

Traffic sign and light and its pole

0.6 × 0.6, 0.35 × 1, 6 × 0.3

81.3

14.8

3

Street light pole

7 × 0.3

82.4

20.4

4

Traffic light and its pole

0.35 × 1, 6 × 0.3

83.3

21.5

5

A big metallic object on the ground

5 × 1.2

83.8

19.5

6

Traffic sign ×2(0.5 × 0.4) × 2

84.6

21.5

7

Signboard

0.8 × 0.8

85

23.6

8

Traffic light pole

6 × 0.3

85.5

24.3

9

Street light pole

7 × 0.3

86.1

24.9

10

Traffic sign and light and its pole

0.4 × 0.4, 0.25 × 0.5, 6 × 0.3

86.9

20.4

11

Traffic sign pole

8 × 0.4

88.4

26.4

12

Traffic light pole

6 × 0.3

88.4

23.3

13

Traffic sign

0.6 × 0.8

89.9

21.4

14

Traffic sign

0.5 × 0.5

93.3

25.1

15

Traffic sign

0.4 × 0.4

96

28.5

16

Traffic sign × 2(0.5 × 0.5) × 2

99.9

29.5

17

Signboard (relatively far)6 × 0.8

101.4

26.2

18

Street light pole

7 × 0.3

103.3

33.4

19

Signboard (relatively far)6 × 0.8

104.6

29.6

1

A metallic plate attached to the sidewalk

0.6 × 1

85.2

23.4

1

Street light pole

7 × 0.3

86.2

22.7

2

Traffic light pole

6 × 0.3

99.4

34.9

3

Traffic sign

0.5 × 0.5

100.6

36.0

1

Over roof signboard

3 × 1.2

90.5

18.4

2

Street radar pole

5 × 0.3

94.1

26.7

3

Big traffic board

1.6 × 1.8

94.4

26.9

4

Traffic sign and light and its pole

0.5 × 0.5, 0.35 × 1, 6 × 0.3

94.6

28.9

5

Traffic sign

0.5 × 0.5

95.4

28.8

6

Signboard

3×1

96.2

25.7

7

Street light pole

7 × 0.3

96.5

27.2

8

Traffic sign ×3(0.5 × 0.5) × 2, 0.4 × 0.4

99.5

27.7

9

Traffic light and its pole

0.35 × 1, 6 × 0.3

100.4

31.2

10

Store signboard

0.6 × 2.5

101.4

30.2

1

Street radar pole and traffic sign

5 × 3, 0.4 × 0.4

89.4

27.6

2

Traffic light pole

6 × 0.3

93.6

31.0

3

Traffic light pole

6 × 0.3

98.6

33.1

F

1

Metallic bar

1 × 0.1

90

29.3

G

1

Signboard

4 × 0.4

92.2

30.8

A

B

C

D

E

—6—