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1 Nortel Confidential Information WiMAX Trial Guard Band / Interference Analysis Sept. 05, 2007
1 Nortel Confidential Information
WiMAX Trial Guard Band / Interference Analysis
Sept. 05, 2007
2 Nortel Confidential Information
Introduction
> WiMAX systems are highly flexible, it can have different channel bandwidths from 1.25Mhz to 20Mhz, and can be deployed in may different frequency bands, from 700Mhz to 6Ghz.
> No new spectrum has been allocated for WiMAX
> WiMAX may have to be deployed in the existing spectrum allocated along with TV and FWA systems
> An analysis is needed to understand GB system requirements for non-coexistence/coexistence of WiMAX, TV, and FWA systems in the same frequency band
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Spectrum Allocations
CF= 2578Mhz
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WiMAX and TV Carriers
1Mhz10 MHz
Guard
B
and
1Mhz
WiMAX CarrierWiMAX Carrier TV CarrierTV Carrier
Guard
B
and
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Filter Characteristics in WiMAX BTS
> In any BTS, there are two sets of filters: one set in the TX path and one set in the RX path
> In each of the TX path and RX path, there are also two kinds of Band-Pass filters
1. RX path• BPF in the RF band (Wide band RF filter)• RX IF Channel filter2. TX path• BPF in the RF band (Wide band RF filter)• TX channel filter
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Filters in WiMAX System (BTS or MS)
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BPF in the RX/TX band
33Mhz Pass bandwidth, 25dB rejection at an offset of 15Mhz, and 60dB at 20Mhz
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BTS TX channel filter
BBPD Performance WithModified SINC Comp Filters
-60
-50
-40
-30
-20
-10
0
10
20
-30000000 -20000000 -10000000 0 10000000 20000000 30000000
Freq Offset (Hz)
dB
noPreD
BBPD
Sinc Comp1
Sinc Comp2
Sinc Comp3
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MS TX Channel filter
35dB @ 1MHz & 100KHz VBW = 25dB @ 1MHz & 1MHz VBW
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Path Loss
Propagation Loss Vs Distance
70.0
80.0
90.0
100.0
110.0
120.0
130.0
140.0
150.0
160.0
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Distance (m)
Pro
paga
tion
Loss
(dB
)
Free Space, 2600 MHz Mexico City Suburban Flat, 2600 MHz Suburban Hilly, 2600 MHz
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TV BTS TX Interfering with WiMAX BTS RX@ 1MHz offset
TVA -28dBc @ 1Mhz Offset and -60dBc @ 3Mhz Offset
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TV BTS TX Interfering with WiMAX BTS RX@ 3MHz offset
TVA -60dBc @ 3Mhz Offset
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Summary for TV BTS TX interference WiMAX BTS RX
> TV BTS TX Interfering WiMAX BTS RX:• Theoretical calculations show that additional 38 dB isolation is
required, with 1MHz GB and 5Km distance. • Theoretical calculations show that additional 6 dB isolation is
required, with 3MHz GB and 5Km distance.
> Recommendations• Take down an additional TV channel for duration of trial (GB)• Select WiMAX sector facing away from the TV broadcast to
minimize impact on WiMAX BTS• Require additional dB isolation for TV TX cavity filter
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TV TX Interfering with WiMAX PCMCIA RX@ 1MHz offset
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TV TX Interfering with WiMAX PCMCIA RX@ 3MHz offset
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Summary for TV TX Interfering with WiMAX PCMCIA RX
> TV TX Interfering WiMAX BTS RX:• Further away TV station no issue (2.9Km)
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WiMAX BTS TX Interfering with TV RX@ 1MHz offset
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WiMAX BTS TX Interfering with TV RX@ 3MHz offset
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Summary for WiMAX BTS TX Interfering with TV RX
> WiMAX BTS TX Interfering with TV RX:• With 20dB rejection filter and 300m further away no issue• With 40dB rejection filter and 80m further away no issue
> Recommendations:• Execute the tech trial test cases during maintenance window to
minimize impacted• Custom 10Mhz BP filter
20 Nortel Confidential Information
WiMAX PCMCIA TX Interfering with TV RX
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Summary for WiMAX PCMCIA TX Interfering with TV RX
> WiMAX PCMCIA TX Interfering TV RX:• Theoretical calculations show there will be no impact on the TV
receiver at 1.5Km or further away from the WiMAX PCMCIA, with 1Mhz GB.
> Recommendations:• Execute the tech trial test cases during maintenance window to
minimize impacted
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Trial Site Coverage by RSSI
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Trial Site Coverage by C/N