Vehicle wireless communications Cell design - IEEE Xplore

Nets4Cars-4

CSNDSP 2010

392

Vehicle wireless communications Cell design ' ' Tsutomu Tsuboi ,Jun Yamada , Naoki Yamauchi " Noriaki Yoshikawa

'

2

Automotive System Div. Renesas Electronics Corp. 2 Cyber Creative Institute

2-6-2, Otemachi, Chiyoda-ku, Tokyo 100-0004, Japan

Abstract-

The

purpose

of

this

paper

is

to

define

wireless

communications system and their conditions which make 1-10 Mega bit per second (Mbps) data transmission for vehicles by using

one

unique

telecommunication communication

common

systems.

systems

(Universal

Mobile

(Dedicated

Short

analysis

There

available

are

such

Telecommunications Range

among

several

several

wireless

as

3G

or

System),

Communication),

and

UMTS DSRC WiMAX

(Worldwide Interoperability for Microwave Access). There is new DSRC technology such as IEEE802.11p, so called WAVE (Wireless Access in Vehicle Environment) under development. In order to develop multi-media transmission for vehicles, more than few Mega bit per second data rate is required. In order to make communication type and conditions among different type of architectures among 3G, WAVE, and WiMAX, authors define one unique analysis based on marketing requirements conditions

with Erlang formula comparing with wireless physical conditions. It is the first time to analysis among potential different types of wireless communication systems and provides appropriate cell design

guide

line to support real-time high

speed

order to use more efficient and establish economical activities under limited wireless frequency, it is worth to study cell design for vehicle network especially in urban area because there are many potential market to use infrastructure networks combination such as WiFi, Optical fiber network, 3G and WiMAX in future. Authors have introduced existing mobile communication cell design method such as Erlang formula into DSRC cell design in the previous paperl) and explained reasonable cell size and data rate. And as results, around 300 vehicles in 200 300 m radius cell in 5.9GHz DSRC can receive 2Mbps data rate wireless communication services for each. This kind of throughput is good for multi-media communications such as video streaming. But there is no comparison among other potential wireless networks. Therefore authors use this analysis methods to other networks based on same market requirements conditions at this time.

wireless

communication for vehicles.

I. INTRODUCTION In this paper, authors provide the first wireless communication comparison for the next DRSC applications among existing networks such as 3G and potential developing new technology such as WAVE and WiMAX. Authors has alreadr describes cell design method for DSRC in previous paperl in which brings well known mobile communication ,, traffic theory "Erlang formula 2) into DSRC cell design and explains reasonable cell design for vehicular applications. And in this paper, authors expand this analysis into among potential wireless communication networks in above described. A DSRC cell design method is described in section II and showed how to define system conditions. After section II, each cell design analysis among 3G, WiMAX and WAVE, and comparison each cell design are described in section III. Then total simulation parameters comparison such as vehicle capacity in a cell and user data rate for vehicles based on several vehicle density conditions within a cell in section IV. And fmally conclusion and summary are described in section V. In terms of DSRC specification, there are several activities such as IEEE802.11p, ETSI3) (European Telecommunication Standard Institute), ARIB4) (Association of Radio Industries and Businesses) in Japan, C2C-CC (Car to Car Communication Consortium) etc. But there is not so much cell design analysis and discussion among those activities because they are more focusing on safety application between cars. In

978-1-86135-369-6/101$25.00 ©2010 IEEE

II. DSRC cell design There are two steps for DSRC cell design. First of all, it is calculated system capacity from traffic intensity with using total number of channels each wireless communication. For example, 3G wireless system supports 8Mbps accessibility in a cell. Therefore if each vehicle in cell needs to 2Mbps access, then number of channels is four as subscribe number. Once traffic intensity loss is fIXed, traffic intensity can be calculated by Erlang formula (1) for each wireless communication channel capacity or subscribe number. B = (A"/S !) /

{I

+

�(An/n!)} ---------------------(1)

B: traffic intensity loss, A: traffic intensity, S: subscribe number (number of vehicles in a cell) In case of 3G, total traffic intensity in a cell is 1.259 erl if traffic intensity loss is 3% (B=0.03) by Erlang formula (A = 1.259). And if each user can access two minutes per hour with traffic intensive communication factor 0.5 and full duplex mode, the each traffic intensity will be 1 x (2/60) x 0.5 x 112= 0.008 erl/subscriber. Then System vehicle capacity or user number of vehicle (UNV) is 1.259/0.008 = 157.38. The traffic intensity loss is based on existing mobile communication ratio. And two minutes access is defmed time which a vehicle can run between 600m ahead to an intersection and 600m after an intersection with 40 km/h velocity. Those parameters are defmed by market requirements. This process is mainly

Nets4Cars-4

I I

I

I

No. of Vehicle

I

Subscribe ratio

I I

CSNDSP 2010

393

driven from market requirements parameters which is shown in Figure 1. Therefore UNV is "Needs simulation results".

Demand No. of vehicle

case of 3G, AUNVIUNV will be 0.0013922 at 2Mbps. In order to calculate appropriate data rate with AUNVIUNV 1, user data rate becomes 19kbps in 3G condition. (Figure 4) In

=

Frequency

Radius of cell

I

User data rate

l

No. of Vehicle in cell (UNY)

feedback

I

A UNV

Needs

I

Needs simulation result (UNY)

I

UNV

=

1

Figure 3 Simulation process for DSRC cell optimization

Figure 1. System vehicle capacity calculations According to physical condition such as 800MHz, 3km cell radius under 3G conditions, physical acceptable number of vehicle should be calculated by certain vehicle density in a cell. If vehicle density of a cell is 2,000 / km2, physical vehicle capacity or acceptable number of user vehicle (AUNV) is 3 x 3 x 1t X 2,000 56,520. This process is driven by physical conditions shown in Figure 2. Therefore AUNV is "Seeds simulation results".

3G

10

kbps 1000

=

10 00

0.1

0 .01

System (DSRC, 3G, WiMax etc.) 0.00 1

User traffi c condition

0.000 1

User data rate

Figure 4. 3G cell design calculation Acceptable No. of Vehicle (AUNV)

Seeds

Seeds simulation result (AUNV)

Figure 2 Physical vehicle capacity calculations After all calculation for System vehicle capacity UNV and Physical vehicle capacity ANUV, it is compared between AUNV and UNV for checking economical conditions. If the ratio of AUNVIUNV becomes nearly "I", then this condition of DSRC cell is sufficient condition because system requirement vehicle capacity and physical vehicle capacity become equal. This process is shown in Figure 3 and it is continued to feedback user data rate until AUNVIUNV ration becomes one.

If the simulation result of AUNVIUNV is less than 1, the designed cell is not enough large to support DSRC communication among vehicles in a cell. It should be made feedback to adjust user data rate i.e. reduction of user wireless communication data rate to becomes equal than 1 or changes Wireless communication system from DSRC to others such as 3G and or WiMAX. In case of 3G wireless communication system, the conclusions of appropriate conditions are as follows; • Subscribe density: 2,000 / km2 According to some field experimental traffic vehicle measurement, vehicle density was more than 150 vehicles per 1 km, which is equivalent with 2,000 / km2 The subscribe density 2,000 / km2 data comes from Japanese vehicle traffic density data from MLIT (Ministry of Land, Infrastructure, Transport) and Tourism4) and Information Processing Society of JapanS) • Traffic intensity: 0.008 erl

Nets4Cars-4

CSNDSP 2010

394

User access is one time in a cell and two minutes communication period with traffic intensive communication factor 0.5 and full duplex mode for independent channels for transmit and receive. Therefore formula of traffic intensity for each transmits and receives is I x (2/60) xO.5x1l2= 0.008 erl • Cell size: 3km radius • Traffic intensity loss ratio: 0.03 • Appropriate each vehicle wireless access data rate becomes 9kbps and total number of vehicles is 56,520 in a cell.. In terms of Erlang formula, author uses B type. A packet is based on queue but Erlang B formula is more safety side because traffic intensity loss of queue becomes reduce from calculation result of queue model. In this paper, those above calculations are expanded into other potential vehicle wireless communication such as WAVE and, WiMAX. In next section III, comparison among each vehicle wireless communication system i.e. 3G, WiMAX, and WAVE.

author picks up 700MHz band, 2.5GHz band, and 5.9GHz. There is also 3.5GHz band available in WiMAX but it is not so much different with 2.5GHz behavior, then it is abbreviated in this paper. For WAVE, 700MHz and 5.9GHz are selected. 700MHz band is assigned in Japanese next ITS system and 5.9GHz band has been assigned in North America and Europe. There is also potential sub Giga-Hz frequency in future world wide but it is also not so much different behavior with 700MHz, so it is also abbreviated at this time. In terms of System capacity of vehicle (UNV), author use the following conditions; • Subscribe density: 2,000 / km2 • Traffic intensity: 0.008 erl for 3G, WiMAX 0.016 erl for WAVE • Cell size: in table 1 • Traffic intensity loss ratio: 0.03 Table II. System vehicle capacity (UNV) summary Access Frequenc\' 10kbps &OO�'IHz

3G

�

\ViMA)' bGHz

III. Vehicle wireless communication cell design In terms of vehicle wireless communications, author picks up the following potential communication systems. 3G mobile access could be used from vehicle to base station for vehicle network and this system has already established in several services such as taxi allocation management system but neither for safety nor high speed application such as internet access. And next potential is WiMAX but it has just started in several countries such as USA, Korea and Japan. WAVE is currently under development in world wide but specification is under evaluation and not started yet. And it is going to specified IEEE802.llp, ETSI TC-ITS (European Telecommunication Standard Institute Technical Committee ITS group) and ARIB (Association of Radio Industries and Businesses), which is described before. Main application of WAVE is safety application but it has also user service communication capability with service channels (SCHs). In table I , there are potential vehicle wireless communication systems parameters.

Table I. Potential vehicle wireless communication systems Access 3G

Frequency

Cell Rate

SOOMHz

5Mbps

700MHz WiMAX

2.5GHz

20Mbps

5.9GHz WAVE

700MHz 5.9GHz

30Mbps

In 3G network, 800MHz frequency, 3km cell radius parameter is common based on experimental value. In terms of WiMAX, there are several frequency bands. Therefore

�

WAVE

700MHz

�

20kbps

iOkbps

iOOkbps

100kbps

IMbps

2Mbps

3Mbps

1003625

4922i

1&&2i

&&7i

13125

4975

limi

35

2i4iOO

126000

4922i

23&iO

40iO

17375

6&75

3175

2i4iOO

126000

4922i

23&iO

40iO

17375

6&75

3175

l272iO

63000

246125

1192i

202i

&6&.7i

343.7i

li&.7i

191i625 9i0625

36&125

1&2iO

321&.7i

14375

600

34i

9i7&l.2i 47i313 1&406.2i

912i

160937i

71&.7i

300

1725

The summary of System vehicle capacity (UNV) will be got with Erlang formula. (Shown in Table II) For next step, it is necessary to calculate Physical vehicle capacity (AUNV), which is defined by physical parameter i.e. Cell radius and traffic density i.e. 2,000 / km 2. It is shown in Table III. Table III. Physical vehicle capacity (AUNV)

Access 3G

Irnyslcal capacity(k) Frequency Radius (km) Area(km2) @D=2 800MHz

3

28.26

56.52

700MHz

4

50.24

100.48

WiMAX 2.5GHz

1

3.14

6.28

5.9GHz

0.3

0.2826

0.5652

700MHz

0.4

0.5024

1.0048

5.9GHz

0.2

0.1256

0.2512

WAVE

After getting System vehicle capacity (UNV) and Physical vehicle capacity (AUNV), it is going to calculate the ratio of AUNV/UNV. Then appropriate user data rate should be calculated. It is shown in mail comparison graphs each wireless access. The next calculation is based on 700MHz accesses, which are WiMAX and WAVE. Then cell design calculation results are shown in figure 5.

Nets4Cars-4

CSNDSP 2010

395 700MHz

59 . 0Hz

1000

1000

100 100

10

_WiMAX

10

--.-WAVE

0 .1 0.01

10

0.00 1 --

-

10 00 kbp s

100

0.1

-----

Figure 5. 700MHz cell design calculation Figure 7. 5.9GHz cell design calculation According figure 5, an appropriate user data rate of WiMAX is 22kbps and vehicle capacity is 100,420 with 4km radius cell and appropriate user rate of WAVE is 1.2Mbps and vehicle capacity is 1,004 with 400m radius cell. In case of 2.5GHz cell design calculation, it is shown in figure 6. According to the results, an appropriate user data rate of WiMAX will be 250kbps and vehicle capacity is 6,280 with lkm radius cell and an appropriate user data rate of WAVE is 3.8Mbps with 251 with lkm cell. But 2.4/2.5GHz WAVE system is not currently considered because of ISM band for 2.4GHz.

However 5.9GHz WiMAX, it is possible to use but 5.9GHz is assigned to WAVE widely in the world and other ETC (Electric Toll Correction) system at 5.8GHz near 5.9GHz band. Therefore WiMAX 5.9GHz is not be used. As for summary in this section, wireless vehicle communication cell design comparison results are shown in table IV. Table IV. Comparison wireless access for vehicle cell design Access

Frequency

250H z

700MHz

WiMAX

250Hz

100

10

_WiMAX

.. +

10

10 00

kbp s

0 .1

0.01

Figure 6. 2.5GHz cell design calculation In terms of 5.9GHz, cell design calculation is shown in figure 7. An appropriate user data rate of WiMAX is l.3Mbps and vehicle capacity is 565 with 300m radius of cell and an appropriate user data rate is 4Mbps and vehicle capacity is 251 with 200m radius cell.

56, 520

19kbps 22k

100,480

20M bps

5.90Hz

Terminal rate

capacity

8Mbps

700MHz

WAVE

1000

Cell Rate

800MHz

30

30M bps

bjJs

Cell size 3km 4km

6,280

2 50kbps

Ikm

1,00 5

I.2Mbps

400m

25 1

4Mbps

200m

According to table IV, it is concluded as follows; • For wide range wireless communication, WiMAX access is good candidate and most suitable condition will be 2.5GHz, which each vehicle can access up to 250kbps and around 6,000 vehicles in lkm radius cell. • For next DSRC application, WAVE could be good candidate. For 700Mz, 1.2Mbps user data rate and around 1,000 vehicle with 400m radius cell. For higher data rate, 5.9GHz WAVE also would be candidate up 4Mbps but rage is relatively short such as 200m radius cell. Those more than IMbps data rate could be good for multimedia application for DRSC. Table IV is condensed urban area case and if average car density data6) is used, the results are shown in table V. Ta bl e VC ompanson Access 30 Wi MAX WAVE

Frequency 800MHz 700MHz 2. 50Hz 700MHz 5.90Hz

. I ess access wire

Cell Rate 8Mbps 20Mbps 30Mbps

capacity

Terminal rate

Cell size

14, 1 30

6 5kbps

3km

2 5,120

100kbps

4km

1, 570

2.2Mbps

Ikm

2 51

4Mkbps

400m

62

10Mbps

200m

Nets4Cars-4

CSNDSP 2010

396

IV Parameter comparison against vehicle density In previous section, comparison wireless access parameters on 500 1km2 car density in table V. In order to compare other condition between 2000 1km2 to 500 1km2 vehicle density conditions, same simulation procedure has to be done and then the comparison results among each wireless access are the followings. The each vehicle data rate comparison versus car density is shown in figure 8.

vehicles in a cell against WAVE (5.9GHz) system. On the other hand, 3G and WiMAX are good coverage for vehicle wireless communications but not so good for multimedia application. But WiMAX (2.5GHz) is good candidate for reasonable data rate with few hundred kbps and few thousands vehicles in a cell such as MAP update and VRM (Vehicle Relationships Management) service/solution, which informs a driver and/or car owner of accurate status of the vehicle conditions. V. SUMMARY

Data Rate vs Density

10000

'" 0.D -'"

----3G

�

1000 100

r--�

10

-.- WiMAX(700)

-

•

In this study, several wireless communications have been examined for the next DSRC applications. Author uses Erlang formula for the cell design simulation and achieves following conclusions. And it is effective for cell design.

---- WiMAX(2. 5)

.....

--- WAY E(700)

-

a)

--WAVE( 5.9)

I 1 .0

0. 5

1.5

2.0

k

vehicles/lon2

Figure 8. Data rate vs. vehicle density among wireless accesses b) According figure 8, WAVE is appropriate wireless access for multimedia application because data rate is more than 1Mbps. But WiMAX (700MHz) and 3G are not enough data rate for multimedia application. The next parameter is vehicle capacity versus car density, which is shown in figure 9.

1000000 iii

..c:

" > "-

0 0

z

100000 10000 1000 100

--__lIE

-

:

It is necessary to have more field test data with more real vehicles access test in future for examine parameters. ACKNOWLEDGMENTS

Capacity vs Density

�

WAVE system is good for multi-media communication for vehicles. i) WAVE (700MHz) system is good safety and multimedia application with 1.2Mbps among 1,000 vehicles in a cell ii) WAVE (5.9GHz) system is better performance for multimedia application at 4Mbps among 250 vehicles in a cell WiMAX (2.5GHz) system is good wide range DRSC with 250kbps among 6,000 vehicles in a cell. But it is not enough to support multi-media application.

•

1----3G I

10

REFERENCES

-.- WiMAX(700)

---- WiMAX(2 5)

:

--

The authors appreciate Mr.lzuru Yamada and Mr.Hiroki Ichikawa of Hitachi Communication and Information Engineering Company for developing DSRC evaluation kits.

[I]T.Tsuboi; ICUMT2009 (International Conference Ultra Modem

--- WA VE(700) --WAVE( 5 9)

I

Telecommunications) / Nets4Cars-2009International Workshop on Communication Technologies for vehicles; "Cell design for Next

0. 5

1.0

1. 5

2 .0

k vehicleslkm2

DSRC application" [2] H.Akiyama, K.Kawashima; Information Communication Traffic,

Figure 9. Capacity vs. vehicle density among wireless accesses According to figure 9, vehicle capacity in a cell of WAVE is less than 1000 because WAVE is relative short range of wireless access against broadband access such as 3G. According to those simulation results for comparison wireless access parameters against car density from 5001km2 (average car density condition) to 20001km2 (most cloudy condition such as urban area), WAVE access is fit for urban multimedia wireless access for vehicles and WAVE (700MHz) has better range and capacity for

The Telecommunications Association (ISBN 4-88549-15-4C0055) [3]ETSI Standard ES202663vl.l) [4] MLIT Ministry of Land, Infrastructure, Transport and Tourism 2007.Dec. data (http://www.pref.gifu.lg.jp/pref/sI8890/zusetu/h17/pdf/I-IO.pdf) [5]Information Processing Society of Japan; T.Haruna, T.Narita A Proposal of Density-based Vehicle-to-Vehicle Routing Protocol (lF2 April 2006) [6]Ministry of Land, Infrastructure and Transport in Japan (http://www.mlit.go.jp/jidoshaikensatorokulshogaikokulsyo04_I.ht m)