11%2e Phs 2dumts and Gsm 2dumts Interference

7/27/2019 11%2e Phs 2dumts and Gsm 2dumts Interference

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PHS-UMTS and GSM-UMTSInterference Analysis

November 2003


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Nortel Networks Confidential and Proprietary

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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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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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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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)



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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


Lucent RBS2000/6 Hybr id

Lucent RBS2000/ 12 Hybrid

Rx/ Tx Rx/Tx ou Rx



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


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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11%2e Phs 2dumts and Gsm 2dumts Interference