1. Submission Title: [Preamble length and packet efficiency for TG4a]
November 2005
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Preamble length and packet efficiency for TG4a]
Date Submitted: [16-Nov-2005]
Source: [Laurent Ouvry]
Company [CEA-Leti]
Address [17 rue des Martyrs Grenoble]
Voice:[ ], FAX: [ ],
E−Mail:
Re: [ a.]
Abstract: [Show the resulting “packet efficiency” for different options of bit rates, preamble lengths, packet length, PRF and propose a short preamble length]
Purpose: [To promote discussion in a.]
Notice: This document has been prepared to assist the IEEE P 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 P
L. Ouvry — CEA-Leti

2. Objective Determine impact of : on “packet efficiency”
November 2005
Objective
Determine impact of :
Preamble length
PSDU length
Bit rate
Mean PRF
on “packet efficiency”
Propose a shorter preamble length value adapted to higher bit rates communications
L. Ouvry — CEA-Leti

3. Assumptions « Packet efficiency » definition there is :
November 2005
Assumptions
« Packet efficiency » definition there is :
PSDU length / (PSDU length + Preamble length)
This is an upper bound value
PHR length is set to 0
FEC is taken into account (PSDU length calculated with PD-SAP bit rates)
Preamble
Header
Payload (PSDU)
L. Ouvry — CEA-Leti

4. Mean PRF 15.875 MHz, PSDU 32 octets
November 2005
Mean PRF MHz, PSDU 32 octets
Acceptable
Too low
In black : highest values
In red : proposal
L. Ouvry — CEA-Leti

5. Mean PRF 3.96875 MHz, PSDU 127 octets
November 2005
Mean PRF MHz, PSDU 127 octets
Acceptable
Too low
In black : highest values
In red : proposal
L. Ouvry — CEA-Leti

6. Mean PRF 15.875 MHz, PSDU 127 octets
November 2005
Mean PRF MHz, PSDU 127 octets
Very Good
Still Too low
Here is the proposal
In black : highest values
As a comparison, efficiency is > 95%
with the maximum PSDU length
In red : proposal
L. Ouvry — CEA-Leti

7. November 2005
Conclusions
With the existing preamble length, the packet efficiency is not satisfactory, especially for :
For optional higher bit rates even with the longest packets
For low PRF with medium packet size at mandatory bit rate
The existing preamble lengths are 64, 256, 1024, 4096 expressed in code duration
The proposed fifth preamble length is 16 code durations (resp 16 us and 64 us with 16 and 4 MHz PRF)
This proposal is also good to reduce duty cycle
L. Ouvry — CEA-Leti