Selected Papers

Mesh-type Broadband Fixed WirelessAccess System
Daisei Uchida†, Makoto Sugita, Ichihiko Toyoda,
and Takeo Atsugi
Abstract
The mesh-type fixed wireless access (FWA) system, which uses directional antennas and forms a wireless mesh network, is an attractive way of providing broadband services because it offers significantly
enhanced frequency utilization efficiency and makes service area expansion easy. This paper outlines themesh-type broadband FWA system and evaluates by computer simulation its frequency utilization efficiency under free-space loss propagation conditions and user station accommodation rates in Shinjuku
ward, Tokyo. Results are compared with conventional point-to-multipoint FWA systems.

1. Introduction
The demand for broadband access to the Internet isincreasing along with the rapid deployment of Internet technologies and services for broadband. Fixedwireless access (FWA) systems are expected to play
an important role in deploying high-speed Internet
access services rapidly to supplement ADSL (asymmetric digital subscriber line) systems and FTTH
(fiber to the home) systems. Point-to-multipoint (PMP) systems [1] and point-to-point (P-P) systems [2]that use the quasi-millimeter and millimeter bands
are now in commercial use. If we consider that such
FWA systems offer broadband services to many users
who are deployed widely, the following problems
must be considered. In P-MP systems, the total interference power cannot be sufficiently reduced because
the base stations must use wide-beam antennas.
Accordingly, their frequency utilization efficiency is
too low. In both systems, each user station can be only
one hop from the base station, so some hops are quite
long. Therefore, the user stations and base stations
need large high-power amplifiers and high-gain
antennas, which raises the costs. In the P-P system,
each base station needs as many antennas as the num† NTT Network Innovation Laboratories
Yokosuka-shi, 239-0847 Japan
E-mail: uchida.daisei@lab.ntt.co.jp

44

ber of user stations accommodated.
To solve these problems, the mesh-type broadband
FWA system (hereafter, shortened to mesh system)has been proposed [3], [4]. It can use directional
antennas to greatly reduce the interference and transmission power. In addition, the stations should bemuch cheaper and the services areas should be easier
to expand, because signals are relayed in a hop-byhop manner, which shortens the distances between
stations. Its frequency utilization efficiency has been
evaluated under autonomous distributed control [5],[6]. These evaluated efficiencies reflect the degradation caused by non-optimum channel assignment followed by autonomous distributed control in which
each station selects its own channels based on radio
statements made in a limited area surrounding the station. Therefore, the theoretical frequency utilization
efficiency that this system can offer was not clarified
in these studies. Moreover, although its routing methods for selecting appropriate paths and traffic sharing
methods have been studied to enhance the frequency
utilization efficiency [7], [8], the effect on service
area expansion has not been quantitatively evaluated.
In this paper, therefore, we focus on the theoreticalfrequency utilization efficiency and user stationaccommodation rate of a mesh system and evaluate
them by computer simulation in comparison with PMP systems. We evaluated the frequency utilization
efficiency under optimum channel assignment to
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Selected Papers

obtain the theoretical value, and line-of-sight (LOS)
rate based on three-dimensional geographical information to obtain the accommodation rate. The simulation results show that its frequency utilization efficiency is 4.5 to 6 times higher under free-space loss
propagation and the distance between stations toachieve an accommodation rate of 95% in Shinjuku
ward is 55% less than in conventional P-MP systems.
2. Mesh-type broadband FWA system
Figure 1 shows a typical mesh system. It consistsof route stations and user stations. The route stations
are connected to the wired backbone network. The
user stations are connected to the route stations
and/or other user stations to relay signals by wirelesstransmission. A user station is classified as either a“relay station” or an “end station”, according to its
role. In addition, a “channel” and “path” are defined
between the stations. Figure 2 illustrates these definitions. A “relay station” is a user station that transmits
and receives not only its own signals, but also thoseof other user stations to relay them. An “end station”
is a user station at the edge of the wireless network; ithandles only its own signals. A “path” is the connection between stations and a “channel” is a line set up
in the path, as shown in Fig. 2. All stations use direc-

tional antennas and they are connected on a point-topoint basis.
As indicated in Fig. 1, the mesh system offers several advantages. For example, because user stations
can pass information to other user stations, the inherent problem of non-line-of-sight (NLOS) transmission in the P-MP system is resolved. Therefore, themesh system is expected to expand service areas
more than a P-MP system. In addition, the short distance between user stations eliminates the need forlarge high-power amplifiers and large antennas inuser stations, resulting in cheaper stations. Furthermore, the use of directional antennas reduces theinterference power from other channels. Therefore,
the mesh system is expected to offer high frequency
utilization efficiency when many user stations arewidely deployed.
3. Simulation evaluation of performances ofmesh systems
3.1 Frequency utilization efficiency of meshsystems
To focus on the theoretical frequency utilization
efficiency that a mesh system can offer, which is considered to be its potential one, we evaluated its frequency utilization efficiency under optimum channel
Route station
Internet network

User station
Due tolong range
Public network

WTW
T

Due to shadowing

User station

User station
Due toshadowing

WT
W
T

Fiber
WT
W
T
P-P access within short range
WT: wireless terminal

Fig. 1. Mesh-type broadband FWA system.

Vol. 2 No. 1 Jan. 200445

Selected Papers

Wired backbone
network
Channels
Channels

Path

Path
Path
ChannelRelay station
Route station

User station
End station

Fig. 2. Definitions in mesh systems.

assignment assuming central control.
(1) Calculation steps
We assume that each user station wants services
with a guaranteed bit rate, so each path between aroute station and a user station in the mesh systemneeds an additional channel to relay information froma route station to a user station. Carrier waves areadded as relay channels in this evaluation. On theother hand, in the P-MP system, a carrier is allocatedto a sector, where we assume that the bandwidth of
the assigned carrier equals the bandwidth per user
multiplied by the number of user stations. Figure 3
shows the number of channels and carriers in both
systems. Under this assumption, we conducted computer simulations to evaluate the frequency utilization
efficiency on downlinks (paths from the route stations
to the user stations) for the mesh and P-MP systems
as follows.
1. C/I (desired carrier-to-interference power ratio)
values of all channels on downlinks were calculated.
2. The “offered C/I” for each user station wasderived from the calculated C/Is. It is defined as
the minimum C/I in all channels assigned for auser station because it impacts the transmission
rate between a route station and the user stationin tree-type wireless networks (described in thenext section).
46

3. The “95%-guaranteed C/I” was derived fromthe offered C/I. It is defined as the lowest 5% of
the offered C/I values of all user stations, and itmeans the C/I that guarantees to connect 95%
of all user stations to the route stations.
4. In order to sensitively reflect the C/Is in the frequency utilization efficiency, we assume thatthe system has a link adaptation function that
can adaptively change the transmission rateaccording to the radio transmission quality. We
used the HiSWANa [9] or HIPERLAN Type 2[10] standard as an example of a link adaptation
model. Table 1 shows the required C/Ns (carrier-to-noise ratios) for each transmission rate of
HiSWANa, where the transmission quality
threshold was set to a packet error rate (PER) of
0.1. The 95%-guaranteed C/I was converted
into frequency utilization efficiency based on
the required C/Ns. Assuming that the interference level was much larger than the noise level,
the required C/N was converted into therequired C/I, and the 95%-guaranteed C/I wasused to determine the transmission rate. Finally, the frequency utilization efficiency wasderived from the transmission rate [11].
(2) Simulation models
All the simulation models used to evaluate the frequency utilization efficiencies were the same as the
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1ch

3ch

1ch

6ch
6ch
6ch

1ch

2ch

6ch

1ch=1 carrier
6ch

2ch

3ch

1ch

6ch
1ch

6ch
6ch
8 directional antennas

1ch(a) Mesh system

Route station
User station

Its bandwidth is 12
times larger than thatof mesh system.

12ch
1 carrier (TDM)

1 carrier (TDM)

4 sector antennas

1 carrier (TDM)

1 carrier (TDM)(b) P-MP system

Fig. 3. The number of channels and carriers.
Table 1. Required C/N to achieve PER of 0.1 for HiSWANa or HIPERLAN Type 2.
(bandwidth: 18 MHz, temperature: 300 K, noise figure: 10 dB, margin: 4 dB)
PHY mode

Modulation

Coding rate

0

BPSK

1/2

1

BPSK

2

QPSK

Transmission
Receiverate (Mbit/s) sensitivity (dBm)

RequiredC/N (dB)

6

–85

3

3/4

9

–83

5

1/2

12

–81

7

3

QPSK

3/4

18

–79

9

4

16QAM

9/16

27

–75

13

5

16QAM

3/4

36

–73

15

6

64QAM

3/4

54

–68

20

ones described in ref. [11]. We considered that theroute stations formed cell configurations to accommodate as many widely deployed user stations as
possible.
Figure 4 shows the cell configuration and user station sites in each cell. The cell configuration is basedon squares and a route station is placed at the centerof each cell. The simulation target is 6 × 6 cells. The
Vol. 2 No. 1 Jan. 2004

frequency utilization efficiency was evaluated only
for the central 2 × 2 cells, which suffer interference
from the surrounding cells. Each cell is divided into 7
× 7 lattice boxes and a user station is randomly placedin each of the 48 lattice boxes other than the central
one.
Figure 5 shows route construction in the mesh system. We assumed a tree-type wireless network, in47

Selected Papers: Route station: Evaluated cells

1 cell(a) Model of cell configuration: Route station: User station: Path direction

Fig. 5. Model for route construction in mesh systems.

Half power beamwidth: 10°
Sidelobe attenuation: –25 (dB)0
: Route station: Lattice box: User station(b) User station in a cellFig. 4. Model of cell configuration and user station sites
in a cell.

which each user station was connected to the route
station in its cell by 1, 2, or 3 hops. The routes in thetree-type wireless networks were designed as shownin Fig. 5, where the points representing the user stations were replaced by lattice points (the centers of
the lattice boxes), so that each path accommodated
almost the same number of user stations.
In a mesh system, each route station has 8 antennas
and each user station has 1, 2, or 3 antennas. They are
directional antennas with beamwidth of 5, 10, 20, or
30°. In the P-MP system, each route station (called abase station in conventional FWA systems) has four
sector antennas whose beamwidth is 90° and eachuser station has the same directional antenna as in themesh system. Figure 6 shows the antenna patterns,
where D(θ) is the antenna gain function of angle θ,48–5Relative power (dB)

: Lattice point

–10

–15

–20

–25

–30
–30

–20

–10

0

–10

–20

–30

Angle (degrees)D(θ) =

cosΘH(θ) (–θα ≤ θ ≤ θα)αB(θ < –θα, θα < θ)ΘH

αB = cos (θα), ΘH = log10[2 – {cos(θH/2)}]

Fig. 6. Antenna pattern.

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Selected Papers

θH is half power beamwidth, and αB is the sidelobe
attenuation level, when the half power beamwidth is
10° and the sidelobe attenuation level is –25 dB.
In the P-MP system, the carrier assignment is optimized by the cluster assignment mechanism. One
carrier is allocated per sector and the cluster size isfour. So the total number of carriers is 4.
In the mesh system, the carrier assignment is optimized by a simulated annealing algorithm [11], [13].
This algorithm produces carrier assignment in themesh system with the lowest sum of the I/C (interference-to-desired carrier power ratio) in all channels.
Moreover, we assumed free-space propagation in
calculating the path loss, no adjacent channel interference, and a constant load in all channels. We
assumed that the desired signal level was the same forall user stations. The above simulation parameters are
summarized in Table 2.
(3) Simulation results
Figure 7 shows the 95%-guaranteed C/I as a function of antenna half power beamwidth for sidelobe
attenuation levels of –15 dB and –25 dB; the numberof carriers was 16, 24, and 48 in mesh systems. As
shown in Fig. 7, the mesh system offered 12 to 20 dB
higher 95%-guaranteed C/I than the P-MP system athalf power beamwidth of 5°. Moreover, decreasing
the antenna half power beamwidth increased the
95%-guaranteed C/I. From here onwards, we clarify
that the channel capacity is improved by using directional antennas. Figure 8 shows the frequency uti-

lization efficiency as a function of the number of carriers for sidelobe attenuation levels of –15 dB and–25 dB, and the half power beamwidth of 5°. As
shown in Fig. 8, when the number of carriers was lessthan 11, the mesh system offered lower frequency utilization efficiency than the P-MP system. Note thatthe maximum number of transmitting and receiving
channels used by a user station was 11 in this meshtopology model; this degradation occurred because
the maximum number of channels per user station
exceeded the number of carriers. This means thatsome transmitting and receiving channels at a user
station shared the same carrier, so the interference
power in the channels could not be reduced sufficiently by using directional antennas. As a result, theC/I of those channels degraded significantly. Therefore, the number of carriers must exceed the maximum number of transmitting and receiving channels
used by a user station if mesh systems are to offer sufficient frequency utilization efficiency. In contrast,
when the number of carriers was 12 or more, themesh system offered 4.5 to 6 times higher frequency
utilization efficiency than the P-MP system. For thisnumber of carriers, when the antenna sidelobe attenuation level was –15 dB, the frequency utilization
efficiency of the mesh system improved with thenumber of carriers. In contrast, when the antennasidelobe attenuation level was –25 dB, increasing thenumber of carriers decreased the frequency utilization efficiency. When the antenna sidelobe attenua-

Table 2. Simulation parameters.
Value

Parameter

Cell

Mesh systems
Square model

Number6 × 6 cells(Evaluated cells: 2 × 2 cells in the center)

Point
Number in a cell

User station

Random point in each lattice box
48 (3 hops)

Average interval between
user stations
Route station

Half power
beamwidth

P-MP systems

Configuration

User station48
1/7 × cell Length
90° (4 sector area)

5, 10, 20, 30°

Sidelobe attenuation (s)5,10, 20, 30°–15, –25 (dB)

Number of carriers (f)6, 10, 12, 16, 24, 48

4Method of carrier assignment

Simulated annealing

Cluster assignment mechanism

Access scheme

Point-to-point

TDM(Number of user stations
accommodated in a sector area: 12)

Bandwidth per carrier

18 (MHz)

Propagation modelVol. 2 No. 1 Jan. 2004

18 × 12 (MHz)Free-space-loss

49

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35

95% guaranteed C/I (dB)Mesh (f = 16/s = –25 (dB))
Mesh (f = 24/s = –25 (dB))
Mesh (f = 48/s = –25 (dB))
P-MP (s = –25 (dB))

Mesh (f = 16/s = –15 (dB))
Mesh (f = 24/s = –15 (dB))
Mesh (f = 48/s = –15 (dB))
P-MP (s = –15 (dB))

30

25
20 dB
20

15

12 dB

10

5

0

0

5

10

15

20

25

30

35

Half power beamwidth (degrees)Fig. 7. 95% guaranteed C/I.
7

Frequency utilization efficiency (bit/s/Hz/cell)

Beamwidth = 5°

Mesh (s = –15 (dB))
Mesh (s = –25 (dB))
P-MP (s = –15 (dB))
P-MP (s = –25 (dB))

65

4
6 times
32

4.5 times

1

0

0

8

16

24
Number of carriers

32

40

48

Fig. 8. Frequency utilization efficiency.

tion level was –15 dB, the 95%-guaranteed C/I wasmuch lower than the required C/I for the maximum
transmission rate in HiSWANa (called “saturation
C/I” hereafter). Therefore, when the number of carriers was small, the decrease in transmission ratecaused by the interference power was larger than the
improvement in frequency utilization efficiency.
On the other hand, when the antenna sidelobe atten50

uation level was –25 dB, the 95%-guaranteed C/I wasclose to the saturation C/I even when the number ofcarriers was small. Therefore, the improvement waslarger than the decrease. Accordingly, the optimum
number of carriers in terms of maximizing the frequency utilization efficiency depends on the antennasidelobe attenuation level.

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3.2 User station accommodation rate in meshsystems
Next, we evaluated the rate of accommodating user
station in mesh systems compared with that of the PMP system by a LOS simulator [14]. For a mesh system, the accommodation rate means the number ofuser stations that can be connected to route stations,either directly or via relay channels, divided by the
total number of user stations, which are widely
deployed. For a P-MP system, on the other hand, thisrate refers only to direct connections (i.e., it excludes
relaying). The simulator can evaluate LOS rates
reflecting real geographical conditions. Specifically,
it can judge whether or not there is a physical line ofsight between any two points in the real world, taking
into account buildings, based on three-dimensional
geographical information such as land elevations anddata about buildings. Moreover, it also forms treetype wireless networks with the minimum total hop
numbers and distances between the stations based on
all the evaluated line-of-sight statements.
(1) Simulation conditions
The simulation conditions used to evaluate the user
station accommodation rates are described below.
1. The evaluated area was Shinjuku Ward inTokyo.
2. Route stations were placed as follows. First, theevaluated area was divided into 15 hexagons
with centers 1500 m apart. Then, a circle ofradius 750 m with its center coinciding withthat of the hexagon was drawn in each hexagon,
and one point was randomly selected in eachcircle. Finally, one route station was placed at
the top of the highest building in each circle
whose center point is the selected point andradius is 300 m. Moreover, the antennas of theroute stations were set at 15 m high from thetops of the buildings. The number of route stations was 15.
3. User stations were placed as follows. First, theevaluated area was divided into 208 hexagons
with centers 400 m apart. Then, a circle ofradius 200 m with its center coinciding withthat of the hexagon was drawn in each hexagon,
and one point was randomly selected in eachcircle. Finally, one user station was placed at
the top of the highest building in each circle
whose center point is the selected point andradius is 50 m. Moreover, the antennas of user
stations were set at 1 m high from the top of thebuildings. Therefore, the total number of user
stations was 208. Though user station locations
Vol. 2 No. 1 Jan. 2004

are not limited in a real system, we used thissimple model as an example of user station
placement used in the physical LOS calculation
for the first step of evaluating the accommodation rate. Note that this placement is appropriate only for stations acting as relays.
4. When a given station could not see the whole ofanother antenna in the LOS simulator, we
judged the path between the two stations to be
non-LOS, where the shape of each antenna wasassumed to be square.
5. Tree-type wireless networks were automatically formed based on all the evaluated line-ofsight statements according to the above
process.
Figure 9 shows examples of results obtained with
the LOS simulator for the 23 wards of Tokyo.
(2) Simulation results
Table 3 shows accommodation rates (AR) in the PMP system as a function of the maximum range (MR)defined to be the longest distance within which user
stations can be connected to the route stations. Table
3 also shows i) the number of user stations that areoutside circles having a radius of MR from the centers of any route station divided by the total numberof user stations (hereafter denoted OMR: outside
maximum range rate) and ii) the number of user stations that are inside such circles and the centers ofsome route stations, but are non-LOS from them
divided by the total number of user stations (hereafter
denoted IMR-NLOS). Figure 10 shows the definitions of MR, OMR, IMR-NLOS, and AR. As shownin Table 3, only 30% of user stations can be accommodated in an P-MP system when MR is 500 m, but
the accommodation rate is about 90% when MR is1400 m. However, about 7% of user stations within
MR are non-LOS from some route stations. To
achieve an accommodation rate of over 95%, MR
must be more than 1800 m.
Figure 11 shows accommodation rates in a meshsystem as a function of the maximum hop numbers,
for the maximum range of 400, 500, 600, 700, and
800 m. When there is only one hop, the evaluated system corresponds to the P-MP system. When there are
multiple hops, the accommodation rate is defined as
the rate of user stations that can connect to a route station either directly or in a hop-by-hop manner. As
shown in Fig. 11, when MR is 500 m, a mesh systemwith three hops achieves an accommodation rate ofabout 73%, which is about 2.4 times larger than thatof a P-MP system. Though further increasing the hop
number improves the accommodation rate, above51

Selected Papers

Results of judging whether or not two points are physically in lineof sight

Tree-type wireless networks are automatically formed based on
all the line-of-sight statements

Red lines: non line-of-sightBlue lines: line-of-sight

Fig. 9. Examples of results obtained with the LOS simulator.

Non-line-of-sightNot
connected

Connected

IMR-NLOSMR
OMR: Route station MR: Range of route station: User station OMR: Ratio of user stations that are outside any range
IMR-NLOS: Ratio of user stations that are within some ranges and are NLOS with a route stationin the ranges
AR: Ratio of user stations that can connect to a route station (1-OMR-IMR-NLOS)

Fig. 10. Definitions of rates in P-MP system.

four hops the improvement is slight and it saturates atabout 84%. Increasing MR also improves the accommodation rate. A mesh system with three hops
achieves an accommodation rate of 95% when MR is
800 m, which is 55% shorter than that of a P-MP system for the same accommodation rate.

Table 3. Accommodation rate of user stations in
P-MP systems.
MR (m)OMR (%)

IMR-NLOS (%)

AR (%)

500

43.96

25.12

30.92

1000

9.07

11.22

79.71

1200

4.35

8.69

86.96

4. Conclusion

1400

1.99

7.19

90.82

1600

0.97

6.76

92.27

We are studying a mesh-type broadband FWA system composed of user stations and route stations connected to the wired backbone network. To assess its
advantages, we evaluated its frequency utilization

1800

0

5.31

94.69

52

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Selected Papers

References

Accommodation rate of user stations

1
0.9

[1]

0.8
0.7
0.6
0.5
MR = 400 m
MR = 500 m
MR = 600 m
MR = 700 m
MR = 800 m

0.4
0.3
0.2
0.1
0

0

2

4
6
Hop numbers

810Fig. 11. Accommodation rate of user stations in meshsystems.

efficiency under optimum channel assignment in afree-space loss propagation condition and its accommodation rate of user stations in Shinjuku ward basedon the real geographical conditions by computer simulation. The results show that it significantly
improves frequency utilization efficiency and reduces
the maximum distance needed between stations toachieve an accommodation rate of 95% comparedwith a P-MP FWA system. Therefore, the mesh-type
FWA system is more promising than the conventional P-MP FWA system for implementing broadband
services. It is also attractive as the entrance radio network for next-generation cellular systems because it
will provide more bandwidth, so more base stations
can be deployed.

Vol. 2 No. 1 Jan. 2004

“FWA PP system using quasi-millimeter wave and millimeter wave
frequency,” ARIB (Association of Radio Industries and Businesses)
in Japan, STD-T58, 1999.
[2] “FWA P-MP system using quasi-millimeter wave and millimeterwave frequency,” ARIB in Japan, STD-T59, 1999.
[3] T. Atsugi and M. Umehira, “Proposal of a Broadband FWA System
employing Mesh Network Topology,” IEICE, B-5-211, Fall 2001.
[4] S. Nomoto, Y. Kishi, S. Konishi, O. Maeshima, S. Watanabe, and T.
Kato, “A Proposal of MM-Wave Adaptive Wireless Network with
Mesh Topology for Broadband, High-Capacity FWA Systems,”
IEICE, B-5-270, Spring 2001.
[5] S. Konishi, Y. Kishi, and S. Nomoto, “Consideration on duplex
modes and resource allocation algorithms for MP-MP BFWA networks carrying asymmetric traffic,” WCNC2002, Vol. 2, pp. 774779, Mar. 2002.
[6] K. Ebata and H. Furukawa, “A Study of Number of Directional
Antennas and Required Bandwidth for Wireless Base Node Repeater
Network,” IEICE, RCS2001-94, Jul. 2001.
[7] N. Harada, J. Sangianmwong, K. Tsukamoto, S. Komaki, E. Okamoto, and H. Ogawa, “A Consideration on Routing Method Based on
Packet Traffic for Millimeter-Wave Broadband Wireless Access Systems,” IEICE, B-5-330, Spring 2002.
[8] Y. Kishi, K. Tabata, S. Konishi, and S. Nomoto, “A proposal of an
Adaptive Channel Allocation and Traffic Engineering Algorithm in
Multi-hop Mesh Networks for Broadband Fixed Wireless Access,”
WCNC2003, Vol. 2, pp. 1043-1048, Mar. 2002.
[9] Low Power Data Communication Systems Broadband Mobile AccessCommunication System Type a (HiSWANa),” ARIB in Japan, STDT70, 2000.
[10] “Broadband Radio Access Networks (BRAN); HIPERLAN Type 2;
Physical layer,” ETSI TS 101 475 V1.1.1, Apr. 2000.
[11] D. Uchida, T. Atsugi, and M. Umehira, “Frequency Utilization Efficiency Improvement in Mesh Type Broadband FWA System using
Directional Antenna,” Wireless 2002, Vol. 1, pp. 30-37, Jul. 2002.
[12] D. Uchida, T. Sugiyama, and M. Umehira, “Effect of Enhancement
Channel Capacity Mesh Type Broadband FWA Systems by Using
Link Adaptation,” IEICE, RCS2002-105, Jul. 2002.
[13] S. Kirkpatrick, C. D. Gelatt Jr., and M. P. Vecchi, “Optimization by
Simulated Annealing,” Science 220, No. 4598, pp. 671-680, May
1983.
[14] M. Sugita, I. Toyoda, T. Atsugi, and M. Umehira, “Accommodation
Rate Evaluation of Base Station in the Wireless Entrance Networks
Using the LOS Simulator,” IEICE, B-5-254, Mar. 2003.

53

Selected Papers

Daisei Uchida
Member, Wireless Systems Research Group,
Wireless Systems Innovation Laboratory, NTT
Network Innovation Laboratories.
He received the B.S. and M.S. degrees inapplied physics from Tokyo Institute of Technology, Tokyo, in 1994 and 1997, respectively.
Since joining NTT in 1997, he has worked on theaccess scheme for satellite systems, the radio
channel assignment and tree topology of PHSbased local positioning and information systems
to form wireless multi-hop networks
autonomously, and the radio channel assignment
and transmission power control for mesh-type
broadband FWA systems. He is currently
engaged in R&D of modulation-demodulation
schemes for SDM-COFDM systems. He is amember of the Institute of Electronics, Information and Communication Engineers (IEICE). He
received the Young Engineer Award from IEICE
in 2001.

Makoto Sugita
Assistant manager, Research & Development
Planning Department, NTT DoCoMo.
He received the B.S. and M.S. degrees in mathematics from Kyoto University, Kyoto in 1991
and 1993, respectively. Since joining NTT in
1993, he has been engaged in R&D of wirelesssecurity and next-generation wireless access. He
is currently working for NTT DoCoMo,
researching and evaluating cryptosystems usedin electronic government in the Information
Technology and Promotion Agency. He is amember of IEICE.

54

Ichihiko Toyoda
Senior Research Engineer, Wireless Systems
Innovation Laboratory, NTT Network Innovation Laboratories.
He received the B.E., M.E., and Dr. Eng.
degrees in communication engineering from
Osaka University, Osaka in 1985, 1987, and1990, respectively. In 1990, he joined NTT
Radio Communication Systems Laboratories,
Kanagawa, Japan, where he was engaged indevelopmental research based on electromagnetic analysis for three-dimensional (3-D) and uniplanar MMICs. From 1994 to 1996, he was withNTT Electronics Technology Corporation,
Kanagawa, Japan, where he was engaged in thedevelopment of wireless communication equipment and MMICs. From 1996 to 1997, he waswith NTT Wireless Systems Laboratories, Kanagawa, Japan, where he conducted
R&D on highly integrated multifunctional MMICs, high-frequency Si MMICs, and
MMIC design software based on 3-D masterslice MMIC technology. From 1997 to
2001, he was engaged in developing ultrahigh-speed digital ICs and MMICs for
optical and wireless communication systems as Engineering Director of IC Design
at NTT Electronics Corporation, Kanagawa, Japan. His current interests concern
millimeter- and quasi-millimeter-wave high-speed wireless access systems and theirapplications. He is a member of IEICE and IEEE. He received the 1993 Young
Engineer Award presented by IEICE, the Japan Microwave Prize presented at the
1994 Asia-Pacific Microwave Conference in Tokyo, and the 18th Telecom System
Technology Award from the Telecommunications Advancement Foundation.

Takeo Atsugi
Senior Engineer, Wireless Systems Technology Department, Wireless Communications Division, Access Networks Business Headquarters,
NTT Advanced Technology Corporation.
He received the B.E. degree from Niigata University, Niigata in 1979. He has been with NTT
Electrical Communication Laboratories since
1979, working on R&D of TDMA synchronization, forward error correction and transmission
power control schemes for satellite communications, and switching systems for mobile satellite
communications, TDMA satellite communications, personal handy-phone systems (PHS), andmesh-type broadband FWA systems. He moved
to NTT Advanced Technology Corporation in
Oct. 2002. He is currently engaged in the development of various wireless systems. He is amember of IEEE and IEICE.

NTT Technical Review