broadband wlan at millimeter waves arounds 60ghz

8/6/2019 Broadband WLAN at Millimeter Waves Arounds 60GHZ

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Naftall (lull) HerscovlclAnTeg

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ChrlstosChr is todou louDepartmentof Electrical andComp uter EngineeringUniversityof New MexicoAlbuquerque, NM 87131-1356 USA

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Broadband Wireless Local-Area Networksat Millimeter Waves Around 60 GHz

Andreas G. Siamarou

University of Cyprus, Department of PhysicsPO Box 20537, Nicosia, CY-1678, Cyprus

Abstract

During the past few years, research covering propagation, channel characterization, and wireless system performance hasyield a substantial knowledge of the 60 GHz channel. Th e unlicensed 60 GHz frequency band presents many attractive prop-erties for wireless communications. This paper addresses some wideband propagation characteristics for broadband wireless

LAN s (BWLANs). Important system-design characteristics, from m easured resuits obtained from tw o wideband 60 GHz LOSradio links, are presented. Measurements were undertaken using the swept-frequency channel-sounding method. Analysisfrom the complex frequency responses in a worst-case scenario has yielded a lower-coherence-bandwidth value of 5 MHz.Minimum and maximum coherence bandwidths, obtained with a directional-horn transmitting antenna and an omnidirec-

tional receiving antenna, were 1.10 MHz and 105.33 MHz, respectively. It was observed that the coherence bandwidth fluctu-ated significantly with the location of the receiver with respect to the base station. These results can be use d for the modelingand design of future BWLANs.

Keywords: Local area networks; broadband communications; land mobile radio data communication; millimeter wavepropagation: millimeter wave communication; communication channels; land mobile radio propagation factors: millimeter wavemeasurements; multimedia com munication

1. Introduction

roadband wireless LANs (BWLANs), earmarked for futureB ideband wireless services in the 60 CHz band, are envisagedwith data-transmission rates up to 150 Mbis [1-13]. The 60GH z

band i s o f much interest, since this i s the hand in which massive

amounts of spectral space ( 5 GHz) have been allocated worldw idefor dense wireless loca l communications [ 2 ] . In addition, the6 0 G H r front-end technology i s emerging rapidly. There ar e a

number of multimedia applications for short-range conimunica-

tions. Indoor applications are likely to include wireless access to

local-area networks, the successfu l implementation of which

IEEE Antennosond Propogotlon Mogozine. Vol. 45, No. I , February 2003

requires a detailed knowledge of radio-propaga tion modes inside

buildings. I t i s o f great importance to determine exactly whatinformation i s required from the measurements and their conse-

quent applications. Essentially, measurements should he capableofproviding information pertinent to both accurate channelmodeling(i.e., simulation), and the implementation of radio systems an d

networks. This paper deals with experimental resu l ts conducted at

62.4 GH z from measured responses taken in two indoor environ-ments o f a university building to characterize the channels' fre-

qucnc y-cone lation function. Section 2 outlines some services,

applications, and characteristics of broadband wireless systems.Section 3 explains the measurement setup, th e environment, and

17 7

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the procedure used for the experiments. The last section presents

the concluding remarks and future work.

Communication

Infrastructure

Configurations

2. Services, Applications and

Characteristics ofBroadband Wireless Systems

The system concepts of a WLAN (wide-area local network),such as HIPERLA N, and of a broadband cellular system, such as a

BWLAN, are different: they are directed toward services andapplications that differ in many aspects. A comparison of several

systems conceming two of the key features (mobility and data rate)

is shown in Figure 1 [3], where it is clear that no overlap exists

between the two approaches. The differences are more salient

when o ther parameters are compared (Table 1 [3]).

for asynchronous services 64 kbis up to

2.048 Mhis for time-hounded services

Connectionless, Connectionless and connection-oriented

No, only HIPERLA N nodes with functions

for transmittins: and receiving, an d

optionally for forwarding, bridging, and

intemetworkin:: units

Standalo ne, ad.-hoc netwo rking, integration

or MAC-level bridging with other LANs,

150 Mbis

Yes, cellular system consisting of mobile

stations, base stations comprising

transceivers, controller, and interworking

Stand-alone, integration with B-ISDN,

interworking with other networksintemetworkinRwith other networks

3 .60 GHz Broadband Wireless LANEnvironment and Measurement Setup

3.1 Transmitter

M obility U p t o 3 6 k "

Coveraee Locallv "unlimited" due to forwardine of

converted (mixed) to a 62 .4 GH z carrier, prior to transmission. Th e

phase-locked oscillator (PLO) can be either synthesized from a

I0 0 MHz intemal oven-controlled crystal, or from an extemal ref-

erence. The up-converter has an IF bandwidth from dc to 6 GHz,

and can also be used as a modulator. The output of the up-

converter consists of two sidebands at a level approximately 6-

7 dB below the swept-IF signal level. The upper sideband, with

frequencies between 63.4 GHz and 64.4 GHz, is passed through afilter. The bandpass filter, with pass-hand specified at 63.4 GHz

an d 65 .4 GHz, also suppresses the lower sideband between

60 .4 GHz and 61.4 GHz.

Up to 100 kmih

"Unlimited" due to cellular infrastructure

Figure 2 shows the block diagram of this system [14]. At thetransmitter, the synthesized output of a vector network analyzer

(VNA HP8714C) is step-swept between 1-2 GHz. This is then up-

Channel Access

Frequency Bands

Duplexing

Roquiwd Dah Rate

Fi g u r e 1. A compar i son of mobi l ity and da ta ra tes for severa l

systems.

up to 800 m at 1 Mbis

FDMA ITDMA, variable data packets (up to

24322 bit), no kame structure, contention

mode with priority symbols)

5.15-5.30 GHz

17.1-17.3 GH z

1 frequency TDD

1 frequency

FDMA ITDMA, frame structure with fixed

time slots and transmission bursts (356

39.5-40.5an d 42.5-43.5 GH z

62.0-63.0an d 65.0-66.0 G H z

2 frequencies FDD, up to 4 carriers in

Ta b l e 1. A compar i son of HIPER LAN and B WLA N character i st i cs .

H I P E R L A N B W L A N

Public and private system

Mobile and w ireless extension to or

replacement of fixed B-ISDNIndoor and outdoor, all IBC services and

LANs

computer

ServicesiData Rates

I I1 active nodes

1 Up to 50 m at :!0 Mbis and

1 and handover

1 Up to I km, epending on antenna andange

I parallelI 40 to 150 Mbishysical Channel Access

Modulation 1 OMSK I 4- and 16-OQAM

1 23.5 Mbis

178 IEEE Antennos ond Propogailon Mogodne, Vol. 45. NO. 1. Februov 2003



F ig u re 2. T h e 62.4 GHz channel-sound ing system fo r 4G

BWLANs.

F ig u re 3. Th e mil l imeter-wave band omnid irect ional an tenna.

3.2 Receiver

At the receiver, a 62.4 GHz phase-locked o scillator is synthe-

sized from the same 100 MHz oven-controlled crystal by connect-

ing a 50 m Sucoflex flexible coaxial cable (very low loss: 0.23-

0.73 dBIm) from the transmitter to the receiver. The 1-2 GHz sig-

nal is coheren tly detected, amplified by an LN A (low-noise ampli-

fier), with bandwidth of 900-2000 MHz and 32 dB gain. It then is

fed hack through a second 50 m Sucoflex flexible coaxial cable tothe receiving port of the vector network analyzer, to measure the

channel's transfer function. The channel-sounding system was

calibrated in an anecho ic chamber.

3.3 Antennas

Two antenna configurations were used in the measurements.

Two stand ard horns were used at the transmitter and receiver in the

first configuration. In the second configuration, a standard homand an omnidirectional antenna were used as transmitting and

receiving antennas, respectively. The standard horn, with a gain of

10 dBi, had 3 dB beamwidths of 69" an d 55' in the E and H p lanes,

respectively. The o mnidirectional antenna had 6 dBi of gain, and

full azimuth coverage with a 6 . Y E-plane (elevation) heamwidth

[15]. It consisted of two reflector plates supported by a hollow

plastic cylinder, as shown in Figure 3.

3.4 Environment and Analysis of

Measured Results

Frequency-response measurements were obtained in two

indoor line-of-sight (LOS) channels. The first environment com-

prised a comidor (41 OO x 1 Y 1 x 2.68 m; see Figure 4), located onthe second floor comdor of a four-story building. The corridor had

window s in alcoves, a fixed metallic heater, wooden doo rs to vari-

ous rooms, and plasterboard sidewalls covered with a thin metalsheet. The floor was covered with vinyl plastic tiles, and the ceil-

ing was covered with polystyrene tiles to which neon lamps were

attached over the length of the corridor. The above scenario is con-

sidered to be the worst-case sc enario for a typical60 GHz system.

The second environment (12.80 x 6.92 x 2.60 m) was a lec-

ture room, with thick walls made of bricks and concrete blocks,

and with a carpeted floor and a ceiling made of polystyrene tiles.

Cubic-shaped electric metallic heaters and windows were present

on one wall. There was also a metallic fire door with two white

boards. Th e tables and chairs were arranged in order to simulate an

office environment. Two measurement links were set up, one with

the room empty and ano ther with furniture.

In the corridor, the transmitter was mounted on a box and leftstationary at one end. The receiver was displac ed to different loca-

F ig u re 4a. T h e l e c t u re r o o m 60 GHz broadband wireless LA N

env ironment .

F ig u re 4 b . T h e co r r id o r 6 0 G H z b ro ad b an d w i re l e s s LA Nenv ironment .

IEEE Antennas and PfopagationMagozine. Vol. 45 . NO. , February 2003 I79



Fi g u r e 5. Th e frequency-correlat ion funct ions obtained in the

c o r r i d o r . Cu r v e a ( the upper, thicker l ine on the lef t) is for a

separa t ion of 1.5 m (probe), curve b ( the l ighter , ce ntral l ine) is

for a separa t ion of 18.09 m, an d curv e c ( the lower l ine) is for a

separa t ion of 37.80 m.

Hom-Hom

Hom-Omni

Furniture

Empty

Co r r i d o r

Room

lions along the center line of the corridor, thus varying its positionfrom the transmitter. Both the transmitting and receiving antennas

were placed 1.70 m abov e the floor, pointing in each other's direc-

tion.

Figure 5 shows the frequency-correlation functions (FCF)

obtained for three transmitter-receiver distances. Curve a (referred

to as the probe signal) was taken at 1.5 m, which emulates the cali-

bration geometly and could be assumed to have negligible mnlti-

path contributions. Curves h and c correspond to the freq,uency-

correlation functions obtained at 18.09 m and 37.8 m, respectively.

Th e degradation with respect to the prob e signal (1.50 m) of the

frequency-correlation functions corresponding to 18.09 m an d37.80 m of transmit-receive terminal distances can be seen in Fig-

ur e 5 .

A rapid decrease of the frequency-correlation function with

respect to the frequency separation and, also, as the receivermoved away from the base station, wer e observed. The decr,:ase of

the frequency-correlation function was not monotonic, and this

was due to the presence of multipath echoes in the mm-wave radio

channel. The 90th percentile of th e coherence bandwidth at a cor-

relation level of 0.9 for the corridor values stayed below 38 MHz.

The minimum and maximum Bo,, coherence bandwidths, obtained

with a directional-hom transmitting antenna and an omnidirec-

tional receiving antenna, w ere 1.10 MH z and 105.3 MHz, respec-

tively (Table 2). The coherence-bandwidth function for the 0.9 cor-

relation level as a function of the receiver position for the corridor

is shown in Figure 6. It can be observed that the coherence band-

width was highly variable with changes in the location of the

receiver w ith respect to the base station [16, 171. Strictly speaking,

the highly fluctuating coherence bandwidth means that the :system

designer can only rely on the lower values of this param'zter in

such an environment. From Figure 6, this is about 5 MHz.

~

M i u M a x S/D M e a n 90%

1.3 84.5 16.0 14.1 38.0

1.1 105.3 16.4 11.5 31.5

5.8 75.6 21.5 31.3 62.8

6.8 82.6 23.3 23.3 72.0

4. Conclusions and Future work

The huge amount o f transmission capacity required for

broadband wireless LANs can only be accommodated in the

180 I1

Table 2. Th e stat ist ics of the coherence-bandwidth funct ion f or

th e 0.9 correlat ion level for the corrido r an d the room, for the

cases investigated.

" . . 10 5 10 15 20 25 30 35 40

Disiancs from the Bare stelion jmj

Figure 6. Th e c o h e r e n c e b a n d wi d th for th e 0.9 correlat io n level

as a funct ion of the receiver posi t ion in th e corridor, showing a

lower value of abo ut 5 MHz.

60 GHz frequency band. T he mm-wave bands are of special inter-

est for indoor applications, because of the potential for frequency

reuse. There is a massive amount of spectral space allocated

worldwide for dense wireless local communications. It is

extremely important to determine exactly what information is

required from the measurements, and what are the applications.Measurements should be capable of providing information pert-

nent to both accurate channel modeling, and to the design evalua-

tion of radio services. The 90th percentile of the coherence band-

width at a correlation level of 0.9 for the corridor values stayed

helow 38M Hz . The minimnm and maximum coherence

bandwidths obtained with a directional-horn transmitting antenna

and an omn idirectional receiving antenna were 1.10 MH z and

105.33 MHz, respectively. T he lower coherence bandw idth valueobtained in a worst-case 60 GH r scenario was 5 MHz. It was

observed that the coherence bandwidth fluctuated significantly

with the location of the receiver with respect to the base station.

The reasons for the fluctuations were shown to he due to the pres-

ence or absence of frequency selectivity in the channel response,

which varied significantly with small displacements in the position

of the receiver. The measurement results presented in this papercan be used to refine the existing 6 0 GH z channel models, and to

assist in the development of new models.

Future research work is recommended in the following direc-

tions:

Performance ev aluation of 60 GHz indoor radio channels, to

include data transmission and BE R measurements. Thisevaluation can be based on directly measurement results.

Th e application o f various diversity, equalization, modula-

FEE Antennas an d Propagation Magazine. Vol. 45, O. I , February 2003



tion, and coding techniques for widehand 60 GHz m ulti-path channels represents a challenging area for future

research.

Deterministic modeling using ray-tracing of 60 GHz indoor

radio channels.

a Statistical propagation modeling might he considered, based

on an extensive measurement data pool.

Indoor-outdoor m obile characterization in various 60 GHz

environments, to include second-order channel statistics,

e.g., Doppler spectra, angles of arrival, and average fadestatistics.

Determination of an asynchronous transfer method, tailoredto handle broadb and information traffic in a wireless LAN.

Items such as transfer mode, duplex method, error control,multi-access control, and OFDM cou ld be investigated.

Biological effects on human tissues and SAR in the human

operators exposed to 60 GHz EM radiation in environments

likely to occur in W LAN applications.

Design of low-cost antenna solutions operating at 60 GHz.

Charting out everything that should be done to pave the way

towards affordable high-voltage production of 60 GHz

front-end MMlCs.

5. References

1. J. V. Femando, L. M. Correia, and J. M. Brazio, “Frequency

Reuse and System Capacity in Mobile Broadband Systems: Com-

parison between 40 and 60 GHz Bands,” Wireless Personal C om-

munications, 19 , 2001, pp. 1-24.

2. P. F. M Smulders, “Exploiting the 60 GHz Band for Local

Wireless Multimedia Access: Prospects and Future Directions,”

IEEE Communications Maguzirre,39 , January 2002, pp. 140-147.

3 . L. M. Correia and R. Prasad, “An Overview of Wireless Broad-

band Communications,” IEEE Communications Magazine, 34, 1,

January 1997, pp. 28-33.

4. L. Femandes and L. M. Correia, “Project R2067-MBS,” Pro-

ceedings ofth e Joint COST 227031 Workshop on Mobile Commu-

nications, September 1993, pp. 156-171

5 . R. Prasad and L. M. Correia, “Wireless Broadband Multimedia

Communications,” International Workshop on Telecommunica-

tions Systems, Saha Alam, Malaysia, May 1997, pp. 1-15.

6. P. F. M Smulders, Broadband Wireless LANs: A Feasibiliry

Study, PhD thesis, Eindhoven University cf Technology, TheNetherlands, 1995, ISBN 90-386-0100-X.

7. Jay E. Padgett, Christoph G. Gunther, and Takeshi Hattori,

“Overview of Wireless Personal Communications,” IEEE Commu-

nications Magazine, 33, 1, January 1995, pp. 28-41.

8. Jose J. G. Femades, Peter A. Watson, and Jose C. Neves,

“Wireless LANs: Physical Properties of Infra-Red Systems vs.

Mmw Systems,” IEEE Communications Magazine, 32 , 8, August1994, pp. 68-73.

9. Walter Honcharenko, Jan P. Kruys, David Y. Lee, and Nitin J.Shah, ”Broadband Wireless Access,” IEEE CommunicationsMagazine, 35, , January 1997, pp. 20-26.

10.J . Mikkonen et al., “Emerging Wireless Broadband Networks,”

IEEE Communications Magazine, February 1 998, pp. 1 12-117.

11. Euro. R adiocommu. Comm ., “Frequency Range 29.7 MHz to

105 GHz and Associated European Table of Frequency Alloca-

tions and Utilisations,” ECR rep. 25, February 1998,http://www.ero.dk

12 . D. S. Polydorou, P. G . Babalis, and C. N. Capsalis, “StatisticalCharacterization of Fading in LO S Wireless Channels with a Finite

Number of Dominant Paths. Application in Millimeter Frequen-

cies,” International Journal o Inpared and Millimerer W aves, 20,3, March 1999, pp. 461-472.

13. Zhimin Zhou, “Spatial and Temporal CM Equalization for

Broadband Wireless Indoor Networks at Millimeter Waves,”

International Journal of Infrared and Millimeter Waves, 22 , 2,February 2001, pp. 255-263.

14. A. G. Siamarou, “Wireless Local Area Radio Networks: Wide-hand Characterisation and Measurements at 62.4 GHz,“ PhD the-

sis, University of Glamorgan, United Kingdom, June, 2001.

1 5 . H. B. Abdullah, “Microwave and Millimeter-Wave Omnidi-

rectional Antennas in the Azimuth Plane for Mobile Communica-

tions,” PhD dissertation, University of Bath, UK 1994.

16.A. G . Siamarou and M. 0.AI-Nuaimi, “Widehand Propagation

Measurements for future .Millimetre 60 GHz Wireless LANs,”

Nectronics Letters, 38 , 16, August 2002, pp. 918-920, ISSN 0013-

5194.

17. M. 0. AI-Nuaimi and A. G. Siamarou, “Coherence Bandwidth

Characterization and Estimation for Indoor Rician Multipath

Wireless Channels Using Measurements at 62.4 GHz,” IEE Pro-

ceedings on Microwaves, Antennas and Propacation, 149, 3 , June

2002,pp. 181-187, ISSN 1350-2417

Andreas G. Siamarou was bom in Trikomo, Famagusta,

Cyprus on October 30, 1972. He received the Diploma of Techni-cian Engineer form the Higher Technical Institute (HTI), Nicosia,

Cyprus, in Electrical Engineering in July, 199 3, and a B Eng(Hons)in Electronics and Communication Engineering (First Class) from

the University of Glamorgan, Wales, United Kingdom in June,1998. From 1998-2001, he was a research assistant, working

towards a Ph D degree at the same university, in the area of broad-

hand wireless communications. He currently is a Research Scien-tist in the Department of Physics, University of Cyprus, Cyprus.

His research interests include modeling, measurements, and char-

acterization of indoor and outdoor fixed and mobile wireless com-

munications systems, mitigation techniques for multipath cancel-

lation, and high-speed network s. %

IEEE Antennas on d Propagallon Mogozine. Vol. 45. No. 1. February 2003 181

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broadband wlan at millimeter waves arounds 60ghz

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