April, 2005 IEEE 802.15-05-0225-00-004a

IEEE P802.15

Wireless Personal Area Networks

Project / IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
Title / Draft - Proposal ideas for Ranging with non-coherent receivers
Date Submitted / [27 April 2005]
Source / [Patricia MARTIGNE]
[FT R&D]
[Meylan, FRANCE] / Voice:[ +33 4 76 76 44 03 ]
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Re: / 802.15.4a base line
Abstract / Technical issues for Ranging with non-coherent receivers
Purpose / Proposal for further detailed discussions within the non-coherent Ranging study group
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.

ISSUES FOR RANGING WITH NON-COHERENT RX

Among non-coherent Receivers, we can distinguish between energy-collection receivers and energy-detection receivers.

First category (energy-collection based) needs long integrationtime, about 50 ns, in order to catch as muchenergy as possible. This can be used for communication applications. But it does not allow for a detection of the leading edge of signals, which means that it is not relevant for accurate-ranging applications.

Second category (energy-detection based) works on the pulse element, that is with integration time of the order of around 3 ns. Associated with an efficient acquisition algorithm, it is appropriate for accurate-ranging applications.

Issue 1 :

Only energy-detection receivers are considered here for ranging.

"Energy-detection receivers need to use an efficient acquisition algorithm" means that the latter shall result in an optimal threshold which allows to detect the presence of the wanted signal when it arrives at the receiver antenna, and also, for ranging purposes, to find the time when the leading edge appeared : the threshold is updated from the position it first had when receiving the strongest path to the position allowing it to detect the leading edge (supposed to be the direct path). To make this adjustment possible to non-coherent receivers, full energy should be included in one single pulse.

Issue 2 :

Single-pulse scheme is needed for non-coherent ranging (instead of a train of pulses).

Moreover, the non-coherent receiver needs a known sequence for the acquisition process. The preamble shall be chosen in such a way that the acquisition is achieved in a limited time.

-There was a proposal for using the ternary code sequence from document 15-05-113 (Atlanta meeting, March 2005).

-Another idea would be to use a time hopping sequence, which would provide a particular time-signature allowing the acquisition algorithm to find the leading edge moment in a timely manner (reference : document 15-05-014, Monterey meeting, January 2005).

 Issue 3 :

Preamble shall be chosen with particular attention to ensure the acquisition process will be done in a timely manner. First proposals : ternary code sequence from doc 15-05-113, or a time-hopping sequence to be determined.

Still keeping in mind the need for an efficient and quick acquisition process, the OOK modulation is proposed.When receiving a '1' bit, the signal power may be twice higher according to the average power FCC limits. This higher energy is helpful for the non-coherent receiver to find the leading edge.

Also OOK is favored for its performance towards power consumption, low power consumption being one of the main objectives for TG4a in general.

 Issue 4 :

OOK is the modulation proposed for non-coherent ranging.

Draft-ProposalPage 1Patricia MARTIGNE