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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [ How Energy Detector handles Inter-Pulse Interference? ]

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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [ How Energy Detector handles Inter-Pulse Interference? ] Date Submitted: [12 May 2005] Source: [Francois Chin, Lei Zhongding, Yuen-Sam Kwok, Xiaoming Peng]

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slide1

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Submission Title: [How Energy Detector handles Inter-Pulse Interference?]

Date Submitted: [12 May 2005]

Source: [Francois Chin, Lei Zhongding, Yuen-Sam Kwok, Xiaoming Peng]

Company: [Institute for Infocomm Research, Singapore]

Address: [21 Heng Mui Keng Terrace, Singapore 119613]

Voice: [65-68745687] FAX: [65-67744990] E-Mail: [[email protected]]

Re: []

Abstract: [Presents signaling options to achieve precision ranging with both coherent and non-coherent receivers]

Purpose: [To discuss which signal waveform would be the most feasible in terms of performance and implementation trade-offs]

Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.

Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.

Francois Chin (I2R)

objectives
Objectives
  • CMOS technology imposes max PR interval limit
  • Inter-pulse interference expected
  • Important for energy detector to handle inter-pulse interference in order to function in various multipath channels

Francois Chin (I2R)

slide3

Ternary Signaling - Synchronisation with Energy Detector

Pulse Repetition Interval ~ 30ns

1

2

3

4

5

6

7

8

30

31

…………………………

Non-inverted pulses are blue,

Inverted pulses are green.

Synchronisation / Ranging

preamble = Binary Base

Sequence repeated

For K times…

……………

……………

.................

Symbol Interval ~940ns

Symbol Interval ~940ns

Francois Chin (I2R)

how energy detector despread

Soft output

RAKE combiner

Noncoherent detection of OOK

Soft

Despread

LPF /

integrator

BPF

( )2

ADC

Sample Rate 1/Tc

{1,-1} Binary Sequence

Figure 1. The block diagram of energy detection receiver using soft despreader and RAKE combiner

How Energy Detector despread?

Ternary Seq [+ - - 0 0 0 + - 0 + + + 0 + 0 - 0 0 0 0 + 0 0 - 0 - + 0 0 - - ]

After Square Law

& Integration in PRI

Unipolar M-Seq [+ + + 0 0 0 + + 0 + + + 0 + 0 + 0 0 0 0 + 0 0 + 0 + + 0 0 + + ]

Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + ]

Francois Chin (I2R)

slide5

Synchronisation with Energy Detector in AWGN

Before Depreader – Unipolar M-Seq [+ + + 0 0 0 + + 0 + + + 0 + 0 + 0 0 0 0 + 0 0 + 0 + + 0 0 + + ] repeated 4x

Despread Sequence – Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + ]

Francois Chin (I2R)

how energy detector handle inter pulse interference
How Energy Detector handle inter- pulse interference?

Pulse Repetition Interval ~ 30ns

d5

d1

d2

d3

d4

d6

d7

Ternary signaling

Non-inverted pulses are blue,

Inverted pulses are red.

PRI

T8

T6

T5

T7

T1

T2

T3

T4

Let’s zoom into the channel details

PRI

T1

T2

T3

T4

Francois Chin (I2R)

energy integration in pri

= complex channel samples @ 500MHz

Energy Integration in PRI

@ TX

Ternary codes

Multipath Channel

d5

d1

d2

d3

d4

d6

d7

Pulse Repetition Interval 30ns

PRI

T1

T2

T3

T4

@ RX (assume noiseless case)

Received signal matrix

(PRI/column)

Take the 3rd PRI as example

Francois Chin (I2R)

energy integration in pri8
Energy Integration in PRI

(some noise due

to cross terms)

After square-law device at 3rd PRI

Apply integration over PRI = Column Sum

The soft ADC value for 3rd PRI:

Each PRI contains partial energy from previous pulses

More noise due

to cross terms

Multipath energy spread each PRI

Francois Chin (I2R)

energy detector sees an equivalent unipolar sequence after integration in pri
Energy Detector Sees An Equivalent Unipolar Sequence after integration in PRI

Pulse Repetition Interval ~ 30ns

d5

d1

d2

d3

d4

d6

d7

Ternary signaling

Non-inverted pulses are blue,

Inverted pulses are red.

After

Square Law

& Integration

in PRI

cj=dj2

Sequence become Unipolar

e1

e2

e3

c5

c1

c2

c3

c4

c6

c7

More Noise due

to cross terms

+

PRI

T1

T2

T3

T4

integrator Output is a convolution of the equivalent Unipolar Sequence with a PRI-spaced

tap-delay-line channel, each tap comprising multipath energy within a correponding PRI

Francois Chin (I2R)

in multipath channels

Soft output

e1

e1

e2

e2

e3

e3

RAKE combiner

Noncoherent detection of OOK

Soft

Despread

PRI

PRI

LPF /

integrator

BPF

( )2

ADC

T1

T1

T2

T2

T3

T3

T4

T4

Sample Rate 1/Tc

{1,-1} Binary Sequence

Figure 1. The block diagram of energy detection receiver using soft despreader and RAKE combiner

In Multipath Channels …

Ternary Seq [+ - - 0 0 0 + - 0 + + + 0 + 0 –

0 0 0 0 + 0 0 - 0 - + 0 0 - - ]

Unipolar M-Seq [+ + + 0 0 0 + + 0 + + + 0 + 0 +

0 0 0 0 + 0 0 + 0 + + 0 0 + + ]

Despread Sequence = Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + ]

Francois Chin (I2R)

sliding correlator output @ pri

e1

e2

e3

PRI

T1

T2

T3

T4

Sliding Correlator Output @ PRI ….

Synchronisation in Multipath Channels

Equivalent to

Simple RAKE combining at the despreader output

(in fact, simple summation across despreader output)

can be used to collect energy across PRI

Francois Chin (I2R)

slide12

Summary

  • Square Law / Envelope Detector effectively convert a ternary sequence to a Unipolar Sequence
  • Energy integration in PRI converts the multipath channels into a PRI-spaced tap-delay-line channel , each tap comprising multipath energy within a correponding PRI
  • Energy collector / integrator Output is a convolution of the equivalent Unipolar Sequence with the PRI-spaced tap-delay-line channel
  • Simple RAKE combining at the despreader output (in fact, simple summation across despreader output, no need RAKE coefficients) can be used to collect energy across PRI
  • Energy Detector can handle inter-pulse interference just as normal direct sequence spread spectrum systems

Francois Chin (I2R)

slide13

Appendix

Francois Chin (I2R)

slide14

Ternary – Bipolar – Unipolar Conversion

Ternary

± → +

0 → -

Bipolar

This is in fact m-Sequences!

+ → +

- → 0

Unipolar

Francois Chin (I2R)

slide15

Properties of M-Sequence

Transmit – Unipolar M-Seq [+ + + 0 0 0 + + 0 + + + 0 + 0 + 0 0 0 0 + 0 0 + 0 + + 0 0 + + ] repeated 4x

Receive – Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + ]

ZERO

autocorrelation

Francois Chin (I2R)

slide16

Properties of M-Sequence

Transmit – Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + ] repeated 4x

Receive – Unipolar M-Seq [+ + + 0 0 0 + + 0 + + + 0 + 0 + 0 0 0 0 + 0 0 + 0 + + 0 0 + + ]

ZERO

autocorrelation

Francois Chin (I2R)

slide17

Properties of M-Sequence

Transmit – Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + + ] repeated 4x

Receive – Bipolar M-Seq [+ + + - - - + + - + + + - + - + - - - - + - - + - + + - - + +]

HIGH peak

LOW

autocorrelation

Francois Chin (I2R)

slide19

Synchronisation Preamble

  • M-sequences has excellent autocorrelation properties
  • Synchronisation / Ranging Preamble is constructed by repeating the base sequence
    • Common Signaling (Mode 1)
      • Ternary for e.g. Beacon Packet
    • Receiver-specific signaling (Mode 2)
      • Ternary for Energy Detector
      • Bipolar for Coherent and Differential Chip Detectors
  • Long preamble for distant nodes is constructed by further symbol repetition

Francois Chin (I2R)

slide20

Ranging:

Code Sequences for different Receiver

Criteria/Target – ZERO autocorrelation sidelobes for best leading edge detection

Francois Chin (I2R)

slide21

Communication:

Code Sequences for different Receiver

Criteria/Target – Max SNR and min inter-sequence interference after despreading

Francois Chin (I2R)

slide22

Snychronisation:

Code Sequences for different Receiver

Criteria/Target – balance max post-despreading SNR and low auto-correlation sidelobes

Francois Chin (I2R)

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