Contents

Mobile Technology in Term of generation. Spectrum Allocation and N/W Architecture Approaches to 3G Radio Network Planning Link Budget What is CPICH,Ec and Ec/Io Handover Scrambling Code Planning Neighbour List Site Selection Criteria

Cellular Generations Mobile Technology in terms of generations 1st Generation or 1G 2nd Generation or 2G 2.5G 3rd Generation or 3G 4th Generation 0r 4G

Data rate

Progress of data rates with time and generation

time

Future of 3G

Projection

Spectrum Allocations 3GPP rel41920 60MHz FDDUplink

1980

2010 2025

2110 60MHz

2170

2200

TDD

SATELLITE TDDUplink

FDDDownlink

SATELLITEDownlink

Duplex 190 MHz 3G(WCDMA) 2GHz frequency band for Europe and APAC Frequency MHz1850 1910 60MHz FDDUplink

1930 60MHz FDD

1990

Downlink

Duplex 80 MHz 3G(WCDMA 1900) for U.S

UMTS Network ArchitectureInternet TCP/IP)

GPRS GSM/WCDMA mobile RAN RNCPS Core Network

3G SGSN GGSN

Circuit Switched Core Network

SRR

USIM card GSM/WCDMA (Node B) mobile MSC MGW (Node B) WCDM A mobile

HLR

(PSTN/ISDN) IN SCP

RNC

CBC

Scrambling Codes & CPICH

CPICH

The Common Pilot Channel (CPICH) is broadcast from every cell It carries no information and can be thought of as a beacon constantly transmitting the Scrambling Code of the cell It is this Beacon that is used by the phone for its cell measurements for network acquisition and handover purposes (Ec, Ec/Io). Beacon: A signaling or guiding device, such as a lighthouse, located on a coast. A radiotransmitter that emits a characteristic guidance signal.

Comments Majority of the measurements are based on CPICH. Thumb rule is that, if UE cant see the CPICH, it cant see the cell. Initial optimisation is purely based on the CPICH measurements. In the Downlink, WCDMA cells are identified by their SC. Its like a BCCH in GSM but the difference is in using same frequency.

Concepts of RSCP and Ec/No Three Important Terms RSCP (Received signal code power) Ec/Io ( Energy per chip/ Noise density) Eb/No (Energy per bit/Noise density)

Total Received Power Io

Io

In a WCDMA network the User Equipment (UE) receives signals from many cells Io* = No = The sum total of all of these signals (dBm)

Received Power of a CPICH

Ec1

Ec2

Using the properties of SCs the UE is able to extract the respective CPICH levels from the sites received RSCP = The Received Power of a Particular CPICH (dBm) Ec = Energy per Chip

The CPICH Quality (Ec/Io)

Ec1

Ec2

From the previous two measures we can calculate a signal quality for each CPICH (SC) received Ec/Io = Ec - Io (dB) Eb/No = Ec/Io+ Processing Gain

Handover Types Intra-Frequency Handovers Softer Handover

Handover between sectors of the same Node B (handled by BTS) MS simultaneously connected to multiple cells (from different Node Bs) Arises when inter-RNC SHO is not possible (Iur not supported or Iur congestion) Decision procedure is the same as SHO (MEHO and RNC controlled)

Soft Handover Hard Handover

Inter-Frequency Handover Can be intra-RAN, intra-RNC, inter-RNC

Inter-RAT HandoverHandovers between GSM and WCDMA (NEHO)

MEHO- Mobile evaluated handover NEHO- Network evaluated handover

Handovers in WCDMA - Softer HO Softer handover occurs between sectors of the same site

Handovers in WCDMA - Soft HO Soft handover occurs between sectors of the different sites

For both softer and soft it is the Ec/Io levels used to determine whether a cell should be added or removed from the active set

Handovers - Inter frequency HO Inter frequency handover occurs between two WCDMA carriers Will be used once operator deploys its second carrier, for microcell layer or capacity purposes

Handovers - Inter system HO Inter system handover occurs between 3G and 2G sites As with all handovers, accurate adjacencies will be required

3G

2G

UMTS CELL PLANNING

UMTS & GSM Network PlanningGSM900/1800: 3G(W CDMA):

Approaches to 3G Radio Network Planning

There are two approaches to 3G radio network planning:

Path loss based 3G simulation based.

Approaches to 3G Radio Network Planning The path loss based approach: is relatively simple and is the most commonly adopted approach. makes use of software tools which are relatively mature and results which are easy to interpret. makes use of maximum allowed path loss figures resulting from 3G link budgets. generates plots and statistics for 3G coverage, best server areas and C/I analysis. The 3G simulation based approach: is more complex and time consuming. is often used for focused 3G system investigations rather than wide area radio network planning. uses software tools which are less mature and results which are more difficult to interpret. makes use of 3G parameter assumptions and a 3G traffic profile. generates plots and statistics for coverage, capacity, soft handover, intercell interference, uplink load and downlink transmit power.

3G Simulation based Approach The 3G simulation based approach to radio network planning requires the use of a 3G radio network planning tool. The majority of 3G radio network planning tools, including NetAct Planner make use of Monte Carlo simulations. Monte Carlo simulations are static simulation. This means that system performance is evaluated by considering many independent instants (snap shots) in time. In the case of static simulations, the population of UE are re-distributed across the simulation area for every simulation snap shot. For each snap shot the uplink and downlink transmit power requirements are computed based upon link loss, C/I requirement and the level of interference. UE which are not able to achieve their C/I requirements are categorized as being in outage. Outage may also be caused by factors such as inadequate baseband processing resources or reaching the maximum allowed increase in uplink interference. By considering a large number of instants in the time the simulation is able to provide an indication of the probability of certain events occurring, e.g. the probability that a UE will be able to establish a connection at a specific location. The simulation is also able to provide an indication of average performance metrics such as cell throughput and downlink transmit power.

3G Simulation based ApproachInput

Output

3G site candidates with their physical configuration (antenna type, antenna height, antenna tilt ,antenna azimuth, feeder type and feeder length) propagation model digital terrain map 3G parameter assumptions 3G traffic profile

service coverage system capacity soft handover overhead Intercell interference uplink and downlink transmit powers uplink and downlink interference floors connection establishment failure mechanisms

Simplified Network Planning FlowchartInitial network dimensioning CW Measurement Create nominal plan Define search ring Identify site options Site selection Site acquisition Detailed site design Site construction

Link Budget OverviewSoft handover gain, antenna gain

Noise figure Body loss Cable losses Building Penetration loss

Max Allowed Path Loss (L)

= Tx Signal + All Gains Other Losses Rx Sensitivity

Link Budget Uplink Service Link Budget Downlink Service Link Budget Downlink CPICH(A step towards validating link budgets is to validate whether the uplink service, downlink service or CPICH is the limiting link.)

Service Type Uplink bit rate

Nokia Specific No UE dependant UE dependant No UE dependant No No Yes No No No Yes No Yes No No No Yes Yes No No No No Yes Yes

Speech 12.2 21.0 0.0 3.0 18.0 3.84 25.0 4.4 50 3.0 -108.0 3.0 -102.0 -122.6 18.5 2.0 2.0 1.8 2.0 12.0 90 10 7.8 -121.5 139.5

CS Data 64 21.0 2.0 0.0 23.0 3.84 17.8 2.0 50 3.0 -108.0 3.0 -102.0 -117.8 18.5 2.0 2.0 1.8 2.0 12.0 90 10 7.8 -116.7 139.7

PS Data 64 21.0 2.0 0.0 23.0 3.84 17.8 2.0 50 3.0 -108.0 3.0 -102.0 -117.8 18.5 2.0 2.0 1.8 2.0 12.0 90 10 7.8 -116.7 139.7 kbps dBm dBi dB dBm Mcps dB dB % dB dBm dB dBm dBm dBi dB dB dB dB dB % dB dB dBm dB

Uplink Link Budget

Maximum transmit power Terminal antenna gain Body loss Transmit EIRP Chip rate Processing gain Required Eb/N0 Target uplink load Rise over thermal noise Thermal noise power Receiver noise figure Interference floor Receiver sensitivity Node B antenna gain Cable loss Benefit of using MHA/TMA Fast fading margin Soft handover gain Building penetration loss Indoor location probability Indoor standard deviation Slow fading margin Isotropic power required Allowed propagation loss

Path loss = Tx signal + all gains - losses - ( SNR + Noise)Bit rateTotal TX power available TX antenna gain Body loss TX EIRP per traffic channel RX antenna gain RX cable and connector losses Receiver noise figure Thermal noise density Cell loading oise rise due to interference Total effect of noise Information rate Effective required Eb/ o RX sensitivity Soft Handoff Gain Fast fading Margin Log normal fade margin In-building penetration loss (urban) Maximum path loss urban

bit/sdBm dBi dB dBm dBi dB dB dBm/Hz % dB dBm/Hz dBHz dB dBm dB dB dB dB dB

6400021 2 0 23 18 3 3 -174 70 5.23 -171 48.06 2.54 -115.40 4.5 2.5 11.6 20 123.80

a b c d e=b+c-d f g h j k l=10*log10(1/(1-(k/100))) m=h+j n=db(a) o p=l+m+n+o+correction factor q r s t pl=e+f+q-g-p-r-s-t

Service Type

Nokia Specific

Speech

CS Data

PS Data

Downlink Link Budget

Downlink bit rate Maximum transmit power Cable loss MHA insertion loss Node B antenna gain Transmit EIRP Processing gain Required Eb/N0 Target loading Rise over thermal noise Thermal noise power Receiver noise figure Interference floor Receiver sensitivity Terminal antenna gain Body loss Fast fading margin Soft handover gain MDC gain Building penetration loss Indoor location probability Indoor standard deviation Slow fading margin Isotropic power required Allowed propagation loss

No Yes No Yes No Yes No UE dependant No No No UE dependant No UE dependant UE dependant No UE dependant UE dependant UE dependant No No No No Yes Yes

12.2 34.2 2.0 0.5 18.5 50.2 25.0 7.9 80 7.0 -108.0 8.0 -93.0 -110.1 0.0 3.0 0.0 2.0 1.2 12.0 90 10 7.8 -90.5 140.7

64 37.2 2.0 0.5 18.5 53.2 17.8 5.3 80 7.0 -108.0 8.0 -93.0 -105.5 2.0 0.0 0.0 2.0 1.2 12.0 90 10 7.8 -90.9 144.1

64 37.2 2.0 0.5 18.5 53.2 17.8 5.0 80 7.0 -108.0 8.0 -93.0 -105.8 2.0 0.0 0.0 2.0 1.2 12.0 90 10 7.8 -91.2 144.4

128 40.0 2.0 0.5 18.5 56.0 14.8 4.7 80 7.0 -108.0 8.0 -93.0 -103.1 2.0 0.0 0.0 2.0 1.2 12.0 90 10 7.8 -88.5 144.5

384 40.0 2.0 0.5 18.5 56.0 10.0 4.8 80 7.0 -108.0 8.0 -93.0 -98.2 2.0 0.0 0.0 2.0 1.2 12.0 90 10 7.8 -83.6 139.6

kbps dBm dB dB dBi dBm dB dB % dB dBm dB dBm dBm dBi dB dB dB dB dB % dB dB dBm dB

Downlink CPICHService Type Nokia Specific CPICH

Maximum transmit power Cable loss MHA insertion loss Node B antenna gain Transmit EIRP Required Ec/I0 Target loading Rise over thermal noise Thermal noise power Receiver noise figure Interference floor Receiver sensitivity Terminal antenna gain Body loss Fast fading margin Building penetration loss Indoor location probability Indoor standard deviation Slow fading margin Isotropic power required Allowed propagation loss

Yes No Yes No Yes UE dependant No No No UE dependant No UE dependant UE dependant No No No No No No Yes Yes

33.0 2.0 0.5 18.5 49.0 -15 80 7.0 -108.0 8.0 -93.0 -108.0 0.0 3.0 0.0 12.0 90 10 7.8 -85.2 134.2

dBm dB dBi dBi dBm dB % dB dBm dB dBm dBm dBi dB dB dB % dB dB dBm dB

Service Type

Speech

CS Data

PS Data

Bit rate Uplink allowed propagation loss (original)

12.2 139.5

64 139.7

64 139.7

128 -

384 -

kbps dB

Downlink allowed propagation loss CPICH allowed propagation loss

140.7

144.1

144.4 134.2

144.5

139.6

dB dB

Scrambling Code Planning The 512 downlink primary scrambling codes are organized into 64 groups of 8. Each cell within the radio network plan should be assigned a primary scrambling code. Scrambling code planning strategies can be defined that maximize the number of neighbors belonging to the same code group or that maximize the number of neighbors belonging to different code groups. The difference between the two strategies has not been quantified in the field but is likely to be dependant upon the UE implementation.

Neighbor List

Maximum NBR list for Nokia is 46 Intra-Frequency Cells (ADJS) - 32 Inter-Frequency Cells (ADJI) - 32 Inter-System Cells (ADJG) 32(If an operator has both GSM900 and DCS1800 networks then it is possible to define inter-system neighbors only for the GSM900 layer or only for the DCS1800 layer.)

Site Selection Criteria

Site Selection Criteria

Proper site location determines usefulness of itscells

Sites are expensive Sites are long-term investments Site acquisition is a slow process Hundreds/thousands of sites needed per networkBase station sites are valuable longlong-term assets for the operator

How do I assess a site option? Each site needs to be assessed on several grounds. Radio Transmission Access Power Planning

Ideally every site option reported by the surveyor would pass in each of the areas listed above.

Bad GSM Sites In GSM, there were two types of bad sites. Donkeys - Low sites which provide very little coverage. Donkeys carry so little traffic that they often never pay for themselves. Boomers - High sites which propagate much further than is needed. A boomer will cause localised interference and prevent capacity being added to some other sites in the area.

Small Donkey site

Large Boomer site

Bad UMTS Sites Good radio engineering practice doesnt change much for UMTS. It just becomes more important.

In UMTS A Donkey will never pay for itself. A Boomer will reduce the range and capacity of surrounding sites.

Two major factors determine whether a site is considered good, a Donkey or a Boomer, They are: Site location. Antenna height.

Other parameters can be used in an attempt to control booming sites but it is far better to avoid building them in the first place.

Importance of Controlling 'Little i' WCDMA is an interference-limited network. I.e. capacity of the network is directly linked to how interference is maintained/controlled. From the Radio Network Planning point of view, the "little i" - other-to-own cell interference- is the only thing that can really be influenced by the Planner during the site selection and planning stage. WCDMA RF planning is all about having good dominance in the desired coverage area. Unlike in GSM, that there is no frequency plan to "play" with in order to minimise the effects of bad sites. Uplink Load EquationLUL ! (1 pw _rise i )

Downlink Load Equation

1 W k !1 1 Eb R v N k k o k K

LDL !

K

k !1

(Eb / No)k ?1 Ek i A vk (W / R)k

Importance of Controlling 'Little i'BTS TX power MS TX power Ec/Io BTS Eb/No MS Eb/No 43 dBm170

128 kbpsi= i= i= i= i= i= i= i= 0.2 0.2 0.4 0.4 0.6 0.6 0.8 0.8

21 dBm

1.5 5.5

aximum propagation loss (dB)

-16.5 dB

165

160

Other to own cell 0.2, 0.4, 0.6, interference ratio i 0.8 Orthogonality Channel profile MS speed MS/BTS NF Antenna gain 0.6 ITU Vehicular A, 3 km/h 3 km/h 8 dB / 4 dB 16 dBi

155

150

145

RESULT: Doubling of the "little i" will cause throughput to decrease to 70% of the original value

Planners have to select the sites diligently so that the other-to-own cell interference ratio is MINIMIZED by planning clear dominance areas during site selection / planning phase.

140

0

500

1000

1500

L throughput in kbps

i = Coverage Overlap Some overlap is required to allow soft handover to occur Need to control amount of interference since the network capacity is directly related to it. Soft handover helps to reduce interference. (Soft HO Gain) Too much overlap: Increases interference to other cells --> reduce capacity Increases Soft Handover overhead --> reduce capacity

Bad Site Location Avoid hill-top locations for BS sites (same for GSM) uncontrolled interference interleaved coverage no sharp dominance areas awkward Soft/Hard HO behaviours BUT: good location for microwave links ! (TNP jurisdiction)uncontrolled, strong interferences

wanted cell boundary

interleaved coverage areas: weak own signal, strong foreign signal

Good Site Location Prefer sites off the hill-tops use hills/high rise buildings to separate cells contiguous coverage area well defined dominance areas needs only low antenna heights if sites are slightly elevated above valley bottom

wanted cell boundary

Characteristics of a good siteIt has good clearance, no obstacles around, and it overlooks the surrounding rooftops. This site will give good macro coverage. Bad site; blocked by neighbour building

Characteristics of a good siteUplink Load Equationk 1

Downlink Load EquationK k !1

L !

( / )k ?1 Ek i A vk (W / )k

1

L

(1

ris i )

K

1 W k

k

vk

BAD: In a urban/dense urban area, too high a site is a bad site since it will introduce too much interference to other sites in the network (remember the little i) while for a rural area it's a good site.

Examples of Bad Sites

Typical mess! => GSM1800 antennas with space div. between CDMA (IS-95) antennas and pointing directly at the high building

GSM1800 and GSM900 antennas are too close => Not enough isolation => Intermodulation and spurious emission. These situations can easily be avoided!! Time consuming and costly to fix.

Examples of Bad SitesLittle i, Little i, Little i !!!

Arghhh note how far you can see roughly 10km = TOO FAR. There is a river as well, so interference is enormous. Site distance is about 700meters in this phase!! Site was good in phase 1 when distance between sites was 4km!

Well shit happens who could have known that they were going to build this high building one year after installation ? Planners should have anticipated this during initial site surveys!

Examples of Bad Sites

The TX/RX and Rx div antennas are not pointing in the same direction! Installation problem.

Is this installation OK? The satellite dish is in near field of the GSM900 antennas -> some effects for sure. Definite interference to satellite system. But could not be tested because the satellite system was not in use! Avoid installing antennas in close proximity to other objects since its radiation pattern will be altered.

Examples of GOOD Sites

Enough space between the two Tx/Rx and Rx Div., AND pointing in the same direction! Site survey point of view: Provides clear dominance to the desired coverage area.

Summary of Site Selection Guidelines The objective is to select a site location which covers the desired area but keeps emissions to a minimum. The site should be located as close to the traffic source as possible. The closer the site is to the traffic, the less output power will be required by the user equipment and node B. This will minimize the noise affecting other users on both the serving cell as well as other nearby cells.

The antenna height selected will depend largely on the type of environment in which the site is to be located. Eg Dense Urban, Urban, Suburban, Rural. The key factor to be considered is how well can the emissions be controlled.

Summary of Site Selection Guidelines You can "feel" the site only if you are there! If one or more of these characteristics are not fulfilled by the examined site, the Field Planner should REJECT the site and choose another site Be flexible, even creative! Try to think of all the possible implementation solutions that the site could support: different pole heights, split poles for different sectors, etc. Always check neighbouring sites, to be sure your chosen candidate is "fitting" well into the surrounding, e.g. for coverage, SHO zones,etc.

Using Existing Cellular Sites Most UMTS networks will be built around an existing GSM network. Many GSM networks were built around existing analogue sites. In the early days of analogue cellular sites were often located to give maximum coverage. No thought was given to capacity issues. Despite causing problems in high capacity networks, many of these high sites are still in operation today. Most cellular networks contain these nightmare sites. When rolling out UMTS around an existing network it is vital to avoid these sites.

UMTS Configurations Most vendors support the same basic configurations. Omni 3 sector 6 sector Each vendor supports their own variations on these configurations. Some require similar amounts of equipment to a GSM BTS. Some increase the number of antennas on a site. The configuration can be affected by the wide variety of UMTS antennas.

Co-locating a Node B at a GSM site Isolation requirements between UMTS and GSM systems can be derived from UMTS and GSM specifications. In many cases equipment performance will exceed the requirements in the specifications. Each vendor should be able to provide information which can be used to improve the isolation requirements. The isolation requirements will affect Choice of antenna configuration Filtering at both the GSM and UMTS sites. Isolation is the attenuation from the output port of a transmitter to the input port of the receiver.

Interference Issues Wideband Noise - unwanted emissions from modulation process and non-linearity of transmitter Spurious Emissions - Harmonic, Parasitic, Inter-modulation products Blocking - Transmitter carriers from another system Inter-modulation Products - Spurious emission, specifications consider this in particular Active: non-linearities of active components - can be filtered out by BTS Passive: non-linearities of passive components - cannot be filtered out by BTS

Other EMC problems - feeders, antennas, transceivers and receivers

Interference Issues Nonlinear system transfer function can be expressed as a series expansion

x

Sy

y = a0 + a1x + a2x2 + a3x3 + ...

In the case of one input frequency, vin = cos [1t, output will consist of harmonics, m[1 Fundamental (m = 1) frequency is the desired one. If m > 1, there are higher order harmonics in output => harmonic distortion. Can be generated both inside an offender or a victim system.

In the case of two input frequencies, vin = cos [1t + cos [2t , output will consist of harmonics m[1 + n[2, where n and m are positive or negative integers. Intermodulation is the process of generating an output signal containing frequency components not present in the input signal. Called intermodulation distortion (IMD). Most harmful are 3rd order (|m| + |n| = 3) products. Can be generated both inside an offender or a victim system.

Interference from Other System GSM spurious emissions and intermodulation results of GSM 1800 interfere WCDMA receiver sensitivity WCDMA spurious emissions interfere GSM receiver sensitivity GSM transmitter blocks WCDMA receiver WCDMA transmitter blocks GSM receiver

GSM 1800 UL1710-1785 MHz

GSM 1800 DL1805-1880 MHz 40 MHz

UMTS UL1920-1980 MHz

UMTS DL2110-2170 MHz

M Distortionfrom GSM1800 DL to WCDMA UL GSM1800 IM3 (3rd order intermodulation) products hits into the WCDMA FDD UL RX band if: 1862.6 e f2 e 1879.8 MHz 1805.2 e f1 e 1839.6 MHz For active elements IM products levels are higher than IM products produced by passive components Typical IM3 suppression values for power amplifiers are -30 -50 dBc depending on frequency spacing and offset Typical values for passive elements are -100 -160 dBc

fIM3 = 2f2 - f1

f1

f2 X dBc fIM3

GSM1800 UL

GSM1800 DL

WCDMA UL

WCDMA DL

1710 - 1785 MHz 1805 - 1880 MHz MHz 1920 - 1980 MHz 2110 - 2170 MHz 40

Harmonic distortion Harmonic distortion can be a problem in the case of co-siting of GSM900 and WCDMA. GSM900 DL frequencies are 935 - 960 MHz and second harmonics may fall into the WCDMA TDD band and into the lower end of the FDD band.

2nd harmonics fGSM = 950 - 960 MHz ... GSM900 935 - 960 MHz

2nd harmonics can be filtered out at the output of GSM900 BTS.

WCDMA WCDMA FDD TDD 1920 - 1980 f 1900 -1920 MHz

Isolation RequirementsGSM 900 GSM 1800 UMT1920 1980 MHz 2110 2170 MHz Receiving band 890 915 MHz 1710 1785 MHz (UL) Transmitting band 935 960 MHz 1805 1880 MHz (DL)

For example - To prevent UMT BT blocking: with transmit power = 43 dBm Max level of interfering signal for blocking = -15 dBm in UMT

Isolation required = 58 dBm

1805 MHz 1710 MHz 1785 MHz

1880 MHz 1920 MHz

2110 MHz 1980 MHz

2170 MHz

G M 1800 Rx

G M 1800 Tx

UMT Rx

UMT Rx

Achieving Isolation RequirementsGSM

Isolation can be provided in a variety of different ways. By antenna selection and positioning. By filtering out the interfering signal. By using diplexers and triplexers with shared feeder and multiband antennas.UMTS

GSMFilter

UMTS GSM

Diplexer

UMTS

Co-siting - Antenna Installations Difficult to calculate isolation between two antennas and measurements are required. Best configurations - antennas pointing in different directions or where there is vertical separation between antennas The following configurations will should all give 30dB isolation.

d d 90 d 120 d 180 d

d

d = 0.3 - 0.5 m

d=1-3m

d = 0.5 - 2 m

Site sharing with third party systems Some UMTS sites might be colocated with other non GSM operators. PMR (Private mobile radios) Minimum separation Broadcast Navigation UMTS antennas

Some of these systems use older equipment which might be more vulnerable to EMC issues. Need to define minimum antenna separations between systems Better to avoid sites used for safety critical applications.

Other systems

Antenna installation issues: Clearance angle

h (m e te rs ) C le a r a n c e a n g le (m e te rs )

Rules of thumb: h u d/2, d < 10 m h u d/3, 10 < d < 20 m h u d/4, d > 30 m

Side view

Antenna d (meters)

Top view

Antenna installation Safety margin of 15r between the reflecting surface and the 3 dB lobe

d h a s to b e > 3 .2 m