11%2e phs 2dumts and gsm 2dumts interference
TRANSCRIPT
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PHS-UMTS and GSM-UMTSInterference Analysis
November 2003
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Outline
Interference Overview
Co-located Base Stations
Analysis
PHS to UMTS, UMTS to PHS GSM to UMTS, UMTS to GSM
Solutions
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Interference Overview
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Many Technologies Share theRadio Spectrum
UMTS & GSM (FDD) have separate downlink and uplink allocations
PHS (TDD) has one allocation for both downlink and uplink
BTS Transmitting BTS Receiving
Tx Rx
GSM: 930 960 MHz
DCS: 1850 1880 MHz
UMTS: 2110 2170 MHz
GSM: 880 915 MHz
DCS: 1755 1785 MHz
UMTS: 1920 1980 MHz
PHS: 1900 1915
Potential for
Interference
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Tx-Channel
In Tx-Band
Out Tx-Band Out Tx-Band
Rx-Channel
Out Rx-BandIn Rx-Band
Out Rx-Band
Interference Basics
Transmitters radiate signals In-channel
In-band
Out-of-band
In-channel signals areintentional, all others areunintentional
The performance of thereceiver is evaluated
In-channel
In-band
Out-of-band
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Interference Basics
A receiver can be affected by Wideband noise
Spurious emissions
Inter-modulation products
Generated by the transmitter Generated by the receiver due to nearby transmissions
Normal transmitted carriers of near transmitters (blocking)
Consequences
Receiver de-sensitization (in-channel) Receiver blocking (out-of-band)
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Spurious Emissions & Inter-modulations Example
Tx-Channel
In Tx-Band
Out Tx-Band Out Tx-Band
Rx-Channel
Out Rx-Band In Rx-Band Out Rx-Band
System A
System B
Out-of-band transmissions
from system A fall inside the
receive channel for system B
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Blocking Example
Tx-Channel
In Tx-BandOut Tx-Band Out Tx-Band
In-channel transmissions fromsystem A fall outside the
receive band for system B
Rx-Channel
Out Rx-Band In Rx-Band Out Rx-Band
System A
System B
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Considerations and Goals of theInterference Analysis
Spurious Emissions andIntermodulations Analysis
Blocking Analysis
Required isolation
between UMTS other
technology to meetdesensitization target
Antenna performance BTS performance
Isolation =
Path Loss
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Interference Scenarios
Recall that eachnode has a transmitter and a receiver Number of possible interference scenarios is large
Scenarios BTS to BTS: DL to UL interference
Mobile to mobile: UL to DL interference
One system BTS to other system mobile: DL to DL interference
One system mobile to other system BTS: UL to UL interference
Recall that technologies generate mutual interference Each of these scenarios has two directions, e.g., UMTS to PHS,
and PHS to UMTS
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Base Station to Base Station,Mobile to Mobile
Coverage Impact
to Victim System
Mobile to mobile interference
Mobile is far from its own base station
Low downlink power headroom available
Interference generated by other systemsmobile reduces victim mobiles coverage
Receiver desensitization!
Base station to base station interference
Base stations are co-located
High base station transmit power
Interference generated by one base station
reduces other base stations coverage
Receiver desensitization!
Coverage Impact
to Victim Mobile
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Downlink Impacts to CDMA-basedSystems
These examples have shown coverage lossas a result ofdownlink interference
However, with CDMA-based systems such as UMTS, theimpact of downlink interference is actually capaci ty los s
With CDMA, downlink interference raises the averagepower per radio bearer (PRB) which reduces capacity (N)
VSPUP
PPPN
RB
blockingoverhead
max
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Our Focus is Co-located BaseStations
Mobile to mobile interference
Cant prevent mobiles from getting too near one another
Mobile-base station interference
Same operator: Can minimize this phenomenon through co-location
Different operator: Cant prevent mobiles from approaching otheroperators base stations
Base station to base station (co-location) interference
Our focus today
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Co-located Base Stations
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Co-located Base Stations
Emissions from one base station can desensitize the other This results in cell shrinkage on the victim system
The goal is to determine the required isolation betweenbase station which results in acceptable desensitization
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Co-located Base Stations
The amount of desensitization which is acceptable is anengineering decision, not a hard rule
A higher threshold results in more sites but less cost per site
A lower threshold results in more equipment (e.g., filters) and
design challenges at the cell site, but fewer sites
We choose 0.8 dB desensitization
Big differences between requirements in the technicalspecifications and actual equipment performance
Real equipment is usually much betterthan spec. We try to consider both
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Relevant Co-location Scenarios
PHS (UMTS) transmitter to UMTS (PHS) receiver
GSM (UMTS) transmitter to UMTS (GSM) receiver
We consider all sources of interference
Wideband noise Spurious emissions
Intermodulations
Blocking
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Analysis
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PHS Base Station to UMTS Base Station
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Calculating the MaximumInterference Level in the UMTSReceive Band
Base station noise floor -174.0 + 10*log10(3,840,000) + 3.3 = -104.9 dBm
Base station noise floor with interference -104.9 + 0.8 = -104.1 dBm
Difference between noise floors with and withoutinterference
39.3 32.7 = 6.6 fW = -112 dBm
So maximum strength for any interferer is -112 dBm
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PHS to UMTS Wideband Noise
Recall UMTS uplink: 1920-1980 MHz
PHS downlink: 1900-1915 MHz
PHS wideband emissions specifications are vague Only coverwithin 948 kHz of the carrier frequency
However, PHS likely generates insignificant widebandnoise in the UMTS receiver
5 MHz
Separation
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PHS to UMTS SpuriousEmissions
Again the PHS emissions specifications are vague Specification requires less than 2.5 W outside of the PHS band
(no bandwidth specified)
We assume 5 MHz; the specification is effectively -56 dBm/5 MHz
This implies that 56 dB of isolation between PHS and UMTSare required
Reference points are the base station antenna ports
Cannot be achieved through antenna separation alone
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PHS to UMTS Intermodulations
The PHS specifications do not explicitly specifyintermodulation limits
We assume they are included in the spurious emissionsrequirements
This again implies 56 dB of isolation between PHS andUMTS are required
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PHS to UMTS Blocking
UMTS TS 25.104 specifies a blocking tolerance of -40 dBmin the PHS band (1900-1915 MHz)
We assume a PHS base station transmit power of 13 dBm
This implies that 53 dB of isolation between PHS and UMTSare required
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UMTS Base Station to PHS Base Station
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Calculating the MaximumInterference Level in the PHSReceive Band
Base station noise floor -174.0 + 10*log10(300,000) + 4.0 = -115.2 dBm
Base station noise floor with interference -115.2 + 0.8 = -114.4 dBm
Difference between noise floors with and withoutinterference
3.6 3.0 = 0.6 fW = -122 dBm
So maximum strength for any interferer is -122 dBm
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UMTS to PHS Wideband Noise
Similar to PHS transmitter in UMTS receiver
The UMTS transmitter generates insignificant widebandnoise in the PHS receive band
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UMTS to PHS SpuriousEmissions
UMTS TS 25.104 specifies spurious emissions of98 dBmover 100 kHz
Effectively -93.2 dBm/300 kHz
We assume a PHS base station noise figure of 4 dB
This implies that 29 dB of isolation between UMTS and PHSare required
Achieved easily through antenna separation
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UMTS to PHS IntermodulationProducts
The requirement is the same as for spurious emissions
The same isolation is required (29 dB)
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UMTS to PHS Blocking
No PHS specifications available
S S f S
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PHS-UMTS Interference Summary
The most constraining form of interference is spuriousemissions from PHS to UMTS Requires 56 dB of isolation
However
We have been forced to interpret the vague PHS specifications;our interpretation could be pessimistic
Regardless, real PHS equipment probably performs much better
Isolation can be realized throughAntenna separation (free space loss): at least 32 dB
Antenna gain patterns, especially if separation is verticalAntenna cable losses: about 5 dB
Filtering on the PHS base station: up to 19 dB, depending
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GSM Base Station to UMTS Base Station
GSM t UMTS Wid b d N i
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GSM to UMTS Wideband Noise
Frequency separation between the GSM 900/1800 band andthe UMTS band is large
GSM 900/1800 generates insignificant wideband noise inthe UMTS receiver
GSM t UMTS S i
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GSM to UMTS SpuriousEmissions
Prior to GSM R99, GSM 05.05 limits on spurious emissionsin the UMTS band were very loose
Originally -30 dBm/3 MHz, tightened to -96 dBm/100 kHz
For pre-R99: 83 dB of isolation between UMTS and GSM
are requiredAgain, very difficult to achieve through antenna separation alone
For post-R99: only 32 dB of isolation required Easy to achieve through antenna separation
GSM t UMTS I t d l ti
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GSM to UMTS Intermodulations
GSM 05.05 recommends that intermodulations should notexceed spurious emissions
If interfering signal is 30 dB less than the desired signal
Since the requirement is the same as for spurious
emissions, we need the same isolation (83 dB or 32 dB)
GSM to UMTS Blocking
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GSM to UMTS Blocking
UMTS TS 25.104 specifies a blocking tolerance in the GSMtransmit band of +16 dBm
Only 27 dB of isolation are required
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UMTS BTS to GSM BTS
UMTS to GSM Wideband Noise
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UMTS to GSM Wideband Noise
Similar to GSM transmitter in UMTS receiver
The UMTS transmitter generates insignificant widebandnoise in the GSM receive band
UMTS to GSM Spurious
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UMTS to GSM SpuriousEmissions
UMTS TS 25.104 specifies spurious emissions of98 dBmover 100 kHz
29 dB of isolation between the UMTS antenna port and theGSM antenna port are required
Easy to achieve
UMTS to GSM Intermodulation
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UMTS to GSM IntermodulationProducts
Since the requirement is the same as for spuriousemissions, we need the same isolation (29 dB)
UMTS to GSM Blocking
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UMTS to GSM Blocking
GSM 05.05 recommendations on out-of-band blocking are GSM 900: 8 dBm
GSM 1800: 0 dBm
We assume a UMTS transmit power of 45 dBm
Isolation requirements are thus GSM 900: 37 dB
GSM 1800: 45 dB
GSM-UMTS Interference Summary
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GSM-UMTS Interference Summary
The most constraining forms of interference are Spurious emissions from pre-R99 GSM to UMTS: requires 83 dB
of isolation
Blocking from UMTS to GSM: requires up to 45 dB of isolation
However, real equipment performs much better Only need 32-42 dB of isolation between the GSM transmitter and
UMTS receiver (not 83 dB)
Only need 0-3 dB of isolation between the UMTS transmitter andGSM receiver (not 45 dB)
GSM-UMTS Interference Summary
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GSM-UMTS Interference Summary
Isolation relatively easy to realize
Antenna separation (free space loss) provides 32 dB ofloss if distance is at least 1 meter
Antenna gain patterns can provide significant loss,especially if separation is vertical
Antenna cable losses can provide about 5 dB
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Solutions
Strategies
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Strategies
Deployment methods Co-location of technologies (base stations) to minimize mobile-
base station mutual interference
Physically separated antennas
Vertical separation provides the most isolation
Additional hardware Transmit filtering to address wideband noise, spurious emissions
Receive filtering to address blocking, some intermodulations
Method
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Wideband
Noise
Spurious
emissionsIntermodulations
Blocking
Co-location Solutions
BTS Radio
Performance Filter /Diplexer /
Triplexer
BTS Antenna
Antenna Decoupling
Antenna Isolation
Method
Co-located Site Configuration
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Co located Site ConfigurationExample
Antenna separation Vertical (preferred)
Horizontal
External filter(s)
On the transmitter to reducespurious emissions andwideband noise
On the receiver to reduceblocking
System A BTS
System B
BTS
Antenna
Separation
Examples of Antenna Configurations
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p g
Rx/ Tx Rx/Tx ou Rx
Ericsson RBS200 c/ duplexEricsson RBS2202Lucent RBS2000/ 6 HybridLucent RBS2000/ 12 Hybrid
Rx/Tx Rx/Tx
UMTS
Rx/ Tx Rx/Tx ou Rx
Ericsson RBS200 c/ duplexEricsson RBS2202
Lucent RBS2000/6 Hybr idLucent RBS2000/12 Hybr id
Tm
a
Tm
a
Tm
a
Tm
a
Tm
a
Tm
a
GSM 900 GSM 900Rx/Tx Rx/Tx
UMTS
Rx/ Tx Rx/Tx ou Rx
Ericsson RBS200 c/ duplexEricsson RBS2202
Lucent RBS2000/6 Hybr id
Lucent RBS2000/ 12 Hybrid
Rx/ Tx Rx/Tx ou Rx
Ericsson RBS200 c/ duplexEricsson RBS2202
Lucent RBS2000/6 Hybr id
Lucent RBS2000/ 12 Hybrid
Tm
a
Tm
a
Tm
a
Tm
a
Tm
a
Tm
a
GSM 900 GSM 900
Rx/Tx Rx/Tx
UMTS
Rx/Tx Rx/Tx
1800
Tm
a
Tm
a
Rx/ Tx Rx/Tx ou Rx
Ericsson RBS200 c/dupl exEricsson RBS2202Lucent RBS2000/6 HybridLucent RBS2000/12 Hybrid
Rx/ Tx Rx/Tx ou Rx
Ericsson RBS200 c/dup lexEricsson RBS2202Lucent RBS2000/6 HybridLucent RBS2000/12 Hybrid
Rx/Tx Rx/Tx
1800
Tm
a
Tm
a
Tm
a
Tm
aTm
a
Tm
a
Tm
a
Tm
a
GSM 900GSM 900GSM 1800 GSM 1800
Rx/Tx Rx/Txou Rx
Ericsson RBS200 c/ duplex
Ericsson RBS2202Lucent RBS2000/6 Hybr idLucent RBS2000/12 Hybr id
Rx/Tx Rx/Tx
1800
Tm
a
Tm
a
Tm
a
Tm
a
Rx/Tx Rx/Tx
UMTS
Rx/Tx Rx/Tx
1800
Rx/Tx Rx/TxouRx
Ericsson RBS200 c/ duplex
Ericsson RBS2202Lucent RBS2000/6 Hybr id
Lucent RBS2000/12 Hybr id
Tm
a
Tm
a
Tm
a
Tm
a
Tm
a
Tm
a
GSM 900 GSM 900
GSM 1800 GSM 1800
Conclusions
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UMTS co-location with PHS and GSM is a commercialnecessity
Mutual interference between UMTS and other systemsmust be addressed
Particularly UMTS-PHS and UMTS-GSM
Solutions do exist: Both deployment strategies andhardware can be used to reduce impacts of interference
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