AUSPI Presentation To TRAI On Spectrum Response To COAI

 

Telecom Regulatory Authority of India Presentation on behalf of the Association of Unified Telecom Service Providers of India  –   – Response to Nokia’s Paper on Interference Issues –   –  ITU-B3 1900 Band and ITU Band 1: 1920-1980/2110-2170 MHz

Dr Y S Rao Contribution by QUALCOMM & Lucent

13 October 2004

New Delhi

 

EXECUTIVE SUMMARY

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Synopsis of AUSPI’s stand  stand  

Present allocation in 800 MHz for CDMA – CDMA – Not  Not sufficient for multiple operators.

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Internationally allocation for large operators varies from 10+10MHz to 20+20 MHz (average allocation 15+15 MHz). CDMA operators need additional allocation in other bands to grow their networks.

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Globally, CDMA systems work in 800 MHz and 1900 MHz, with the exception of Korea  –  Korean PCS is unique and is not used anywhere else in the  – world.

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 AUSPI has proposed service neutral plan plan of 800 MHz and 1900 MHz for CDMA and 900 MHz and 1800 MHz for GSM in line with international standards. AUSPI Proprietary

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Main points of NOKIA’s presentation  presentation  

GSM is opposed to 1900 MHz allocation for use by CDMA Operators  –  It overlaps with WARC’92 recommended IMT-2000 Band of 1920 – 1980 MHz paired with 2110-2170 MHz

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Even a small allocation 10+10 MHz for unacceptable CDMA2000 operation in the USPCSofBand USPCS will cause cause una cceptable interference to a WCDMA system in the WARC’92 IMT-2000 IMT-2000 band   Adequate protection of the WCDMA uplink uplink will require: □

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Very high rejection filters at every CDMA2000 and WCDMA Base Station Guard bands greater than 5 MHz Site to site coordination 15% additional IMT-2000 sites to account for lost coverage Several thousand Euros added per site to pay for all this AUSPI Proprietary

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Main points of NOKIA’s presentation –  –  contd…   contd… 

There is no incentive for a CDMA2000 operator to invest in filters □

Experience of “mixed” CDMA/GSM in 800/900 MHz in India/Asia show that that CDMA operators neglect neglect additional additional filtering

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Operators do not coordinate in practice  Adequate protecti protection on of the CDM CDMA A downlink(UE) Interferenc Interference e from IMT-2000/ WCDMA User Equipment and USPCS CDMA UE is not possible □

This will result in a USPCS CDMA capacity loss up to 35%

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Our General Response GSM opposition is unjustified: □

WARC-2000 has recommended recommended different bands for IMTIMT 2000/3G allowing flexibility for the administration to choose any band from:   

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806 –   960 MHz, 806 – 1710 – 1710  –1885 1885 MHz, 2500 –2690 MHz.

ITU-R recommendation No. M.1036.2 identified different paired frequency arrangements for IMT-2000   A1&A2 

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B1 to B6

3GPP has already standardised DCS1800 for 3G/UMTS [No. TS25.105(Rel-5)] and has already been requested to quickly standardise 900 MHz for for the same AUSPI Proprietary

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Our General Response – Response –  contd… contd…   

Notwithstanding its position to have the USPCS band allocated for CDMA operators, AUSPI now responds responds to Nokia Nokia interference issues with a mixed band plan of USPCS and

the WARC IMT-2000   As per the ERC-101 Report, there are three methods to study interference between two adjacent frequency bands: □

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Minimum Coupling Loss (MCL) Enhanced – Minimum Enhanced –  Minimum Coupling Loss (E- MCL) Monte Carlo Method

Method used by Nokia is MCL □

 As per the ERC-101 Report, the MCL MCL method evaluates evaluates the worst case scenario and gives spectrally inefficient results AUSPI Proprietary

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TECHNICAL RESPONSE

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Clarification on band allocations near 2 GHz (ITU Definitio Definitions) ns) 

Nokia states on page 3: “even the allocation of as little as 10 MHz for PCS CDMA within 1900-1910/1980-1990 MHz will severely interfere the uplink portion (1920 - 1980 MHz) of the ITU-R globally harmonized IMT- 2000 2 GHz band”.   band”.

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We believe this is confusing the technical discussion since IMT-2000(3G) IMT -2000(3G) systems can be deployed in both of these bands. In ITU-R M.1036-2 the ITU has stated that the following 3 bands (in addition to others-i.e. 1710-1770 MHz/ 2110-2170 MHz) are equally valid bands for IMT-2000 and that administrations can implement all or parts of these frequency arrangements for IMT-2000 services in the 2 GHz region. It is up to the Administrations of each country to decide which which arrangement, or mix of arrangements best suits its own needs. needs. ITU band 1, commonly termed the “UMTS” “UMT S” band  band   1920-1980/ 2110 -2170 MHz ITU band 2, commonly termed the “DCS“DCS -1800” band  band   1710-1785/18 1710-1785/1805-1880 05-1880 MHz □

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ITU band 3, commonly termed the “USPCS” “USPC S” band  band   1850-1910/ 1930 -1990 MHz 9

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Existing band allocations near 2 GHz (ITU Definitio Definitions) ns) 

We also note that each Standards Organization, eg 3GPP and and 3GPP2, 3GPP2, refer to these bands bands by other designations

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To avoid confusion in this presentation, we will refer to these bands by their ITU designations, as shown on the previous chart

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The next chart shows these bands as defined by the ITU. □

Red lines indicate mobile transmit bands

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Blue  lines indicate BTS transmit bands Blue

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Green line indicates DECT assigned bands in India

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Existing ITU Band allocations near 2 GHz 1700

1750

1800

1850

1900

1950

2000

2050

2100

2150

2200

0

1

1

UMTS

2

2

DCS-1800

3

3

USPCS

4

4

DECT

5

1920-1980/2110-2170

1710-1785/1805-1880

1850-1910/1930-1990

1880-1900/-

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Frequency allocation arrangement addressed by NOKIA 1700

1750

1800

1850

1900

1950

2000

2050

2100

2150

2200

0

1

1

UMTS

2

2

DCS-1800

3

3

USPCS

4

4

DECT

5

1920-1980/2110-2170

1710-1785/1805-1880

1900-1910/1980-1990

1880-1900/-

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NOKIA’s claims on a mixed band plan  plan  

Nokia claim page 3: … allocation of even 10 MHz from the USPCS (ITU B3) band will essentially block the IMT-2000 IMT-2000 evolution…  evolution…  □

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The previous figure shows the allocation arrangement addressed by Nokia

Our response: □

Normal design practice for this arrangement will place the last WCDMA carrier 2.5MHz below the 1980 MHz boundary and the first f irst CDMA 2000 carrier 1.25MHz above the 1980 MHz boundary. This arrangement places these carriers 3.75 MHz apart, and provides an inherent guard band of 1.2 MHz 1.2 MHz = 3.75 – 3.75 –(3.84+1.25)/2 (3.84+1.25)/2

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 Additional guard band can be obtained obtained without “essentially blocking” IMT- 2000 evolution  Dropping 1 CDMA 2000 carrier gains 1.25 MHz  Dropping 1 WCDMA carrier gains 5 MHz  Reducing the WCDMA channel spacing to 4.8 MHz gains 2 MHz These inherent easilydesigns increased guard the requirement on and any filter needed tobands assurereduce interference is not an issue

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NOKIA concern number 1 – 1 – CDMA2000  CDMA2000 BTS TX Emissions to WCDMA BTS RX 

Nokia claim on pages 3 and 4: “-13dBm/MHz limit for CDMA BS does not consider mixed band plan.” CDMA BS will transmit unfiltered spurious emissions and wideband wideband noise across the uplink portion of the ITU-B1 band

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Our response: □

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Nokia assumes the worst case noise density from a CDMA2000 BTS of  – 13dBm/MHz  –  13dBm/MHz (or -73dBm/Hz)*, but commercial c ommercial BTS typically perform better, as much as 22dB better. Given that a significant number of Base Stations have been deployed, it would seem reasonable to use real data rather than worst case limits The specification says nothing about whether a mixed band plan will work. We believe it is possible possible to have a mixed band plan such that operators get a fair and equitable opportunity to offer IMT-2000 IMT -2000 services as soon as possibleIf a mixed plan is anticipated, more appropriate emissions can be specified. The entire ITU-B1 band is not affected equally. Only the first WCDMA carrier below 1980 MHz is an issue.

* Note: this is a specification from an early version standard, which has been recently changed to -30dBm/30KHz -30dBm/30KHz ( or -75dBm/Hz)

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Interference issues with mixed band plan – plan  – Emissions contd…  contd…  

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Nokia claim page 4: Nokia quotes Lucent as saying 77dB of filtering at the CDMA 2000 BTS may be required to solve the BTS BT S to BTS noise interference issue. This supports an overall Isolation target of 107dB, as derived by Lucent. Nokia also concludes that the only way to prevent interference from spurious emissions coming from CDMA 2000 BTS transmitters in the ITU-B3 band into WCDMA BTS receivers in the ITU-B1 band is to install additional filters in all ITUB3 stations. Ourbase comments: □

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The requirement for 77 dB of filtering arises from Nokia’s assumption that 30dB of antenna isolation is all that can be obtained. But this limit only applies to systems sharing the same antenna, and over 50dB of isolation can be obtained in both collocated and non collocated arrangements that do not share an antenna.  A more reasonable approach, approach, stated by Lucent, is to assume a filter with 60dB rejection. Then the required antenna isolation is 47dB, well within standard practice. It is not the case that expensive technical modifications of infrastructure must occur to permit the use of some s ome of the PCS and ITU-B1 IT U-B1 frequency bands. We will later show the only modification required is to add filters. We further believe that 60dB filter rejection is the maximum required and will show that it can be obtained in real, commercially available designs.

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Interference issues with mixed band plan – plan  – Emissions contd…  Our comments, contd…   In computing the -107 dB isolation requirement, Lucent used a worst case Minimum Coupling Loss (MCL) analysis procedure with CDMA 2000 emissions at -73dBm/Hz, plus assuming ass uming this interference arrived at the WCDMA BTS receiver 10dB below the noise floor, estimated at -170 dBm/Hz. ( i.e. festablish rom a 4dB noise receiver). This worst case analysis serves well to from limits onfigure the interference issue. Even in this worst case condition we believe that coexistence is achievable. However, ERC report 101 [1] states s tates that the minimum coupling method yields pessimistic results when compared to real world results, and recommends a procedure procedure if more more accurate Monte-Carlo Monte-Carlo simulations are not available. One particular comment stands out: The degradation should be estimated with the desired signal at 3dB above the minimum sensitivity. In line with with these guidelines, guidelines, we we believe a 1dB degradation in noise noise figure as more reasonable reasonable for CDMA systems, and which is actually more more severe than that recommended by ERC-101. This sets the allowable interference density at -176 dBm/Hz □

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Interference issues with mixed band plan – plan  – Emissions continued Our comments, contd…  

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Given an allowable allowable interference density of -176dBm/Hz -176dBm/Hz at the ITUB1 BTS receiver, and a specified emission density or – or – 75dBm/Hz  75dBm/Hz from the CDMA 2000 transmitter, the required isolation is 101 dB, not 107dB If the emission density is at a more typical level, level, as much as 22 dB below the specified specified level, the the required isolation is 79 dB, far less than the worst case estimates Based on these values, we would consider a reasonable isolation requirement to be not more than 90 dB, which could be met with a 50 dB filter and 40 dB of antenna coupling loss In any case, the reduction in required isolation can be used to reduce the required antenna coupling loss, the filter rejection loss, or the guard band

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Interference issues with mixed band plan – plan  – General 

Nokia claim on page 5: use of mitigation techniques will not work because there is no incentive incentive for the perspective perspective PCS CDMA operator operator in 19001910/1980-1990 1910/1980-19 90 MHz to invest and and to provide the necessary additional filtering. Severe interference has been observed in the 800 MHz band, where a similar boundary condition occurs.

Our response: 

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Nokia fails to consider that the t he ITU-B1 band can be shared** between WCDMA and CDMA 2000. CDMA 2000 may well end up on both sides of the 1980 boundary. To avoid interference later, the boundary problem must be addressed now It is also not true t rue that in case of CDMA 2000/GSM band plans in 800/900 MHz bands the operators have neglected the needtofor filters It isinaIndia fact that CDMA filters have been provided solve the 850MHz issue In addition there was a resolution between the operators to take the necessary steps and to the best of our knowledge there are no significant interference issues between between CDMA and GSM GSM in 800/900 800/900 MHz bands  □

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Notwithstanding its position to have the ITU-B3 band allocated for CDMA operators, **  AUSPI is responding to Nokia’s interference issues concerning concerning a mixed band plan  plan 

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Interference issues with mixed band plan – plan  – Blocking 

Nokia claim page 6: Use of mitigation techniques, if imposed upon the operators, are not viable due to large site coordination distance, large guard bands, high cost and need for additional sites due to degradation. 114dB of total isolation will will be required, and and sites will need need to be 300 Meters apart even when 60dB of filtering is added at WCDMA receivers

Our response: typical data we believe believe 114 dB isolation is not   After reviewing typical required for the ITU-B3 to ITU-B1 blocking interference condition  In computing this number Lucent again used a worst case analysis procedure  

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First, Lucent assumed CDMA2000 power of 46.8dBm (for three carriers). We aagree with thistransmitted assumption Lucent then computed the allowable blocking level at the WCDMA receiver at -66.8dBm at the receiver input from the WCDMA ACS specification The difference of these numbers is 113.6 dB, rounded to the isolation requirement of 114dB

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Interference issues with mixed band plan – plan  – Blocking contd… contd…   Our response continued: 

 Actual blocking measurements have been performed performed in generic programs with cooperative partner FDD vendors and indirectly as part of co-siting tests on ITU-B1 operators’ FDD networks. These experiments were performed on six different FDD vendors equipment and across all TDD channels in the core ITUB1 bands. These measurements have been averaged to protect confidentiality and are summarised below. Note these are considerably higher than the default specification of -55 dBm.  At 5 MHz offset the interfering interfering signal was –37dBm, 18 dB larger than the specified level of -55dBm, and about 30 dB larger than the worst case calculated level of – of –66.8 66.8 dBm. Interfering channel (TDD signal)

Interfering signal level for 1dB noise rise in 1922 MHz FDD UL

1900-1905 MHz

-9dBm

1905-1910 MHz

-17dBm

1910-1915 MHz

-27dBm

1915-1920 MHz

-37dBm

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Interference issues with mixed band plan – plan  – Blocking contd…  contd…  Our response continued:   As before, after reviewing this analysis, we believe this is too severe when using the worst case minimum coupling loss (MCL) method of computing system coexistence 

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Given a transmitted power of of 46.8dBm three CDMAreceiver carriers,for and aspecified blocking level -55dBmfrom at the WCDMA a 5MHz offset, the computed isolation is 101.8dB, not 114dB Given a transmitted power of 46.8dBm from three CDMA carriers, and a typical blocking level of -37dBm at the WCDMA receiver for a 5MHz offset, the computed isolation is 83.8dB, far less than the worst case 114dB  As before, we would would consider a reasonable reasonable isolation requirement requirement to be not more than 90 dB, which could be met with a 50 dB filter and 40 dB of antenna coupling loss In any case, the reduction in required isolation can be used to reduce the required antenna coupling loss, the filter rejection loss, or the guard band

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Interference issues with mixed band plan – plan  – Blocking contd…  contd…  

Nokia claim page 6: Use of mitigation techniques, if imposed upon the operators, are not viable due to large site coordination distance, large guard bands, high cost and need for additional sites due to degradation. 54 dB of antenna isolation will be required, and sites will need to be 300 Meters apart even when 60dB of filtering is added at WCDMA receivers. (This is to t o meet the 114 dB total isolation requirement)

Our response continued: 

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Site coordination distances: We do not agree with Nokia’s N okia’s conclusion that a 300 meter minimum site-site distance is needed when 54dB of isolation is desired. In line 6 of their table on page 6, we see Nokia has listed 54dB as the available antenna isolation. Since the Free Space loss at 300 Meters at 1980 MHz is 88dB (as shown in the next chart) this means that Nokia has assumed BTS antenna gains of 17dB each and that they are directed exactly at each other. Nokia also neglected any cable losses in their their analysis It is recommended ( ERC-101) that 10 dB antenna gains be used when determining interference. Using these values reduces the free space loss requirement to 74dB and the site to site spacing to about 75 Meters  Analytical and measured data ( see later charts) show that 54 dB total isolation is also quite possible possible when antennas antennas are mounted mounted on the same mast

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Free Space loss model for BTS to BTS interference calculations Free Space Transmission Loss vs Distance (Assumes Isotropic A Antennas) ntennas) 1980 MHz

15 15.0 .0 Met Meter er BTS BTS

15 15.0 .0 M Met eter er

-50

-60

-70

-80

   ) -90    B    d    (    s    s    o    L -100

-110

-120

-130

-140 0. 01

0. 10

Distance (Km)

1 .0 0

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coupling for antennas  Antenna coupling antennas mounted on a common mast (a) Broadside Configuration C onfiguration 0

(b) Colinear Configuration

0

Measured

-10

Predicted

   )    B-20    d    (   g-30   n    i    l   p-40   u   o    C-50

Predicted

   )    B-20    d    (   g -30   n    i    l   p -40   u   o    C-50

Measured

-10

-60

-60

-70

-70

0 0

20

40

60

80

100

120

140

160

20

40

60

80

100

120

140

160

Separation Distance (inches)

Separation Separa tion Distance (inches) 

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The above data may be found in “prediction “pr ediction of Mutual Coupling between Base Station Antenna  Arrays, RAWCON 2002 conference paper. These measurements are comparable to the following table found in contribution UK WP8F WP(04)026, which was aimed at solving the boundary problem between TDD and FDD bands in Europe. The data applies equally well in the case here

Antenna configuration 

Coupling loss 

Dual antennas in the same radome  

30dB 

Default separation on the same mast 1m 

55-65dB 

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Interference issues with mixed band plan – plan  – Filter Characteristi Characteristics cs 

Nokia claim page 7: Lucent proposal that interference problems can be mitigated by providing providing 2.25 MHz guard guard band and 60 dB dB additional filtering at the CDMA BS and WCDMA BS is not practical

Our response:  Considering the blocks at the band edges will most likely be 5 or 10MHz wide, it is quite possible to design filters that can provide 60 dB rejection in a very small frequency range from the band edge edge  The next chart shows the measured response of a “low cost” BTS filter that can meet the objections from Nokia given a 5 MHz allocation at the edge edge of of the band 

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This filter has 60 dB of rejection within 1 MHz from the band edge, coupled with less than 0.75 dB of insertion loss. It will easily support 3 CDMA2000 carriers or 1 WCDMA carrier If the edge band allocations at 1980 MHz were 5MHz each, using this filter would result in the need for NO added guard band If this filter replaced the existing filters, rather than added to the existing filter, there would be essentially no loss in coverage

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Suitable filter for 1980 band edge isolation for 5MHz allocations

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Interference issues with mixed band plan – plan  – Filter Issue (repeated) 

Nokia claim page 7: Lucent proposal that interference problems can be mitigated by providing 2.25 MHz guard band and 60 60 dB additional filtering at the CDMA BS and WCDMA BS is not practical:

Our response:  The next chart shows the simulated response of a “low cost” BTS filter that can meet the objections from Nokia given a 10 MHz MHz allocation at the edge of the band  This filter has 60 dB of rejection 2.5 MHz from the band edge, coupled with less than 0.5 dB of insertion loss in the desired band □

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This implies that some emissions would pass through and additional means for isolation are required

Some options were discussed earlier, and using the Lucent suggestion of having 4.8MHz spacing between WCDMA carriers is enough to solve this problem with no loss in the total number of carriers in either band

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Suitable filter for 1980 band edge isolation for 10 MHz allocations

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BTS to BTS interference issues –  Summary issues – Summary  

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Using minimum coupling loss methods to establish Isolation requirements leads to overly pessimistic results, not representative of the real world. Using specified performance performance values for transmitters and receivers receivers to establish Isolation requirements also leads to overly pessimistic results, since they are not representative of the actual equipment equipment performance. performance. We believe 90 dB isolation is adequate to meet the BTS to BTS interference conditions for both the emission and blocking issues. But that up to 114 dB can be met with a combination c ombination of filters and antenna isolation if needed in extreme cases. 60 dB rejection filters are available 50 dB of antenna isolation is quite possible with good practice, for collocated and non-collocated systems. Only 30 dB is possible for systems that share the same antenna. 50 dB of antenna isolation can be achieved with site to site spacing of 30 Meters. 40 dB of antenna isolation can be achieved with site to site spacing of 10 Meters. If the edge band allocations at 1980 MHz were 5MHz each, filters are available which would result in the need for NO added guard band.

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Interference issues: IMT-2000 handset to the PCS CDMA handset, Monte-Carlo method 

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Nokia claim on page 9: mixed plan will result in interference between the IMT-2000 handset to the PCS CDMA CDMA handset when they are in close proximity to each other Lucent has provided TRAI with the results of a Monte-Carlo method to estimate the issue of mobile station interference interference □

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We will not repeat that presentation here, but do restate exactly the results:

Under the assumed conditions, CDMA downlink capacity degradation is