High Rate - Ultra Wide Band (UWB)Background

Ecma/GA/2005/038

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Promise of a UWB Physical Layer

Data rates:• Scalable data rates from 55 Mb/s to 480 Mb/s.• 110 Mb/s at 10 meters in realistic multi-path environments.• 200 Mb/s at greater than 4 meters in realistic multi-path environments.• 480 Mb/s at 2 meters in realistic multi-path environments.

Low cost solutions.

Low power PHY solutions:

Integrated CMOS solution Single chip solutions Small form factors.

Coexistence with current and future devices.

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Overview of Multi-band OFDM

Central Idea #1:

• Divide the spectrum into bands that are 528 MHz wide.

Advantages:

• Transmitter and receiver process smaller bandwidth signals.

• Instantaneous processing BW = 528 MHz.

f3432MHz

3960MHz

4488MHz

5016MHz

5544MHz

6072MHz

6600MHz

7128MHz

7656MHz

8184MHz

8712MHz

9240MHz

9768MHz

Band #1

Band #2

Band #3

Band #4

Band #5

Band #6

Band #7

Band #8

Band#9

Band #10

Band #11

Band #12

Band #13

10296MHz

Band #14

Band Group #1 Band Group #2 Band Group #3 Band Group #4 Band Group #5

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Exploiting the Band Plan

Exploit range of band group’s to separate applications:

Longer Range Apps Use BG #1 and #2

f3432MHz

3960MHz

4488MHz

5016MHz

5544MHz

6072MHz

Band #1

Band #2

Band #3

Band #4

Band #5

Band #6

Band Group #1 Band Group #2

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Exploiting the Band Plan

Exploit range of band group’s to separate applications:

` Shorter Range Apps Use BG #3 and #4

f3432MHz

3960MHz

4488MHz

5016MHz

5544MHz

6072MHz

6600MHz

7128MHz

7656MHz

8184MHz

8712MHz

9240MHz

9768MHz

Band #7

Band #8

Band#9

Band #10

Band #11

Band #12

10296MHz

Band Group #3 Band Group #4

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Overview of Multi-band OFDM

Central Idea #2:

• Interleave OFDM symbols across all bands.

Advantages:

• Exploits frequency diversity.

• Provide robustness against multi-path / interference.

• Same transmit power as if the entire band is used.

TimeFreq (MHz)

3168

3696

4752

4224

Band # 1

Band # 2

Band # 3

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Transmitter Architecture

Block Diagram:

Architecture is similar to that of a conventional/proven OFDM system.

Major Differences:

1. Time-Frequency kernel specifies the frequency for next OFDM symbol.

2. Constellation size is limited to QPSK (limits size of IFFT/FFT, DAC/ADC).

3. For rates less than 80 Mb/s, the input to the IFFT is conjugate symmetric.• Need to only implement the “I” portion of TX analog chain. • As a result, only half the analog die size of a full “I/Q” transmitter is needed.

4. Zero-padded prefix instead of cyclic prefix.

ScramblerInputData FEC Interleaver Mapper IFFT DAC

exp(j2fct)

Time-FrequencyKernel

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Conclusions

Inherent robustness to multi-path in all expected environments.

Excellent robustness to U-NII and other generic narrowband interference.

Ability to comply with worldwide regulations:

• Channels and tones can be turned on/off dynamically to comply with changing regulations.

• Can arbitrarily shape spectrum because the tones resolution is ~4 MHz.

Example: Radio-astronomy bands in Japan.

• Only need to zero out a few tones in order to protect these services.

Channel #1 Typical OFDM waveform Channel #1 Waveform with J apaneseradioastronomical bands protected.

3260 -3267 MHz3332 - 3339 MHz3345.8 -3352.5 MHz

-f

-f

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