Project: IEEE P802.15 Working Group for Wireless Personal Area Networks        (WPANs)
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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [CCA of UWB channel] Date Submitted: [November, 2005] Source: [Bin Zhen, Huan-Bang Li, Yihong Qi, Ryuji Kohno, Company: National Institute of Information and Communications Technology ]

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Project ieee p802 15 working group for wireless personal area networks wpans 4196463

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

Submission Title: [CCA of UWB channel]

Date Submitted: [November, 2005]

Source: [Bin Zhen, Huan-Bang Li, Yihong Qi, Ryuji Kohno, Company: National Institute of Information and Communications Technology ]

Contact: Bin Zhen

Voice:+81 46 847 5445, E-Mail: [email protected]]

Abstract: [To enable CSMA in the 15.4a network ]

Purpose: [MAC]

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.


Cca of uwb channel

CCA of UWB channel

Bin Zhen, Huan-Bang Li, Yihong Qi and Ryuji Kohno


Motivations

Motivations

  • Although 4a nodes are low duty cycle, the network load is not light. Traffic in sensor network is usually burst style.

    • Inactive period

    • Pending data from coordinator to multiple nodes

    • An event is usually sensed and reported by multiple sensors

  • The UWB spectrum mask of EU and Japan requests interference mitigation technology, e.g. DAA.

  • To follow the architecture of 15.4


Basic ideas

Basic ideas

  • Because of low radiation power, sparse and short nature of UWB pulse, CCA of UWB channel is difficult.

  • Frame preamble is of some regular structure. But the data portion is pretty random.

    • Data portion is hard to be sensed

  • To enable CCA at any time, we must introduce regular structure to the whole UWB frame

    • Superimposed preamble


Cca using preamble

CCA using preamble

  • After multipath channel, the periodicity of preamble still remains.

    • This enables time average processing without synchronization

  • Spreading gain of preamble pluses another benefit


Cca using preamble cont

CCA using preamble (cont.)

Original spectrum

Polluted spectrum after channel

Real experimental data:

30.875MHz PRF, 31 bit ternary code, 20GHz ADC

Taiyo-yuden UWB antenna


Cca using preamble cont1

CCA using preamble (cont.)

Preamble chip buried

in the noise

Preamble chip

after processing

Noise background

Cable connected

Indoor channel, 10 meters


Superimposed preamble

Superimposed preamble

  • Continue preamble using spread code S1 during data portion which using other orthogonal spread codes

    • CDMA style multiplexing

  • Whenever performing carrier sense using spread code S1, preamble can be sensed

Ternary code S2

Ternary code S3

Ternary code S1

Header

Payload

Channel

Preamble

+

Preamble

Ternary code S1

Total frame duration


Reference protocols

Reference protocols

  • Pure ALOHA

  • Preamble-only CSMA

    • Assume only the frame preamble can be sensed. The data part is sensed as free channel.

  • FSK-style CSMA

    • Continue to sense the media until preamble is found or the end of packet duration

  • All-frame CSMA

    • Idea case where all frame can be sensed as CCA in narrow-band system


Performance analysis

6

preamble-only

preamble-only

all-frame

5

0.25

all-frame

FSK

FSK

aloha

aloha

4

0.2

superimposed

superimposed

power/good-transmission

3

normalized payload throughput

0.15

2

0.1

1

0.05

0

0

-1

0

10

10

-1

0

10

10

offered load

offered load

Performance analysis

0.5ms preamble, Tcs=0.032ms, 1Mbps, 32 bytes data

CS spends the same power as transmission

No CS error


Normalized performance

3.5

1

preamble-only

all-frame

3

FSK

0.8

aloha

2.5

superimposed

0.6

normalized payload throughput

normalized power/good transmission

2

preamble-only

0.4

1.5

all-frame

FSK

0.2

aloha

1

superimposed

0.5

0

-1

-1

0

0

10

10

10

10

offered load

Normalized performance

  • After inserting preamble into payload portion, network payload throughput increases

  • Even in light network load, ALOHA and preamble-only CSMA spends more power than superimposed CSMA


Performance with cca error

6

all-frame

all-frame

5

0.25

aloha

aloha

superimposed

superimposed

superimposed

4

superimposed

0.2

power/good-transmission

3

normalized payload throughput

0.15

2

0.1

1

0.05

0

0

-1

0

10

10

-1

0

10

10

offered load

offered load

Performance with CCA error

CCA probability= 0.8

CCA probability= 0.95

CCA probability= 0.95

CCA probability= 0.8

  • With only 80% detection probability, the maximal through is doubled compared with that of ALOHA


Conclusions

Conclusions

  • Pure ALOHA gives worst performance. It only works when offered load is less then 0.2.

    • Only sensing the frame preamble is not enough

    • Performance of FSK style CSMA is poor

  • Sensing the whole UWB packet is possible by adding regular structure

    • Superimposed preamble

    • Even with CCA error, network performance is still better than ALOHA

  • Benefits

    • PHY layer implementation

    • Good throughput and low power consumption in heavy network load.


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