1. <doc.: IEEE 802.15-doc>
<month year>
<doc.: IEEE doc>
September 2010
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Harmonization of HARQ text]
Date Submitted: [15th of September 2010]
Source: [ Marco Hernandez, et. al.]
Company: [NICT, et. al.]
Address: [3-4 Hikarino-oka, Yokosuka, , Japan]
Voice:[ ], Fax: [ ], []
Re: [ MAC-UWB meeting]
Abstract: [Some proposed resolutions in sub-clause 10 depend on the MAC sub-clause. Thus, UWB sub- group addresses the MAC sub-group for discussion]
Purpose: [Material for discussion]
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
Marco, NICT, et.al.
<author>, <company>

2. September 2010
Introduction
The HARQ mechanism requires the interaction between UWB PHY and MAC during the retransmission process. Such interaction shall be set up by H0 and H1 in the PHR (see 10.8).
Such interaction between UWB PHY and MAC represents when error detection at the MAC level and/or error correction at the UWB PHY level fail, starting a process of retransmissions. Otherwise, transmission of a packet is completed and ACK is sent at the MAC level.
Marco, NICT, et.al.

3. September 2010
Introduction
a) In the initial stage, a packet or MPDU shall be used to construct the PSDU (see 10.7), but the output of encoder BCH(126,63) shall separate systematic bits (D) and parity bits (P). Systematic bits shall be used to finish the PSDU construction and both systematic bits and parity bits shall be stored. In other words, the MPDU is transmitted.
D=MPDU=MAC header+MAC frame+FCS [MAC]
D+P=BCH(D) [PHY]
Send D [PHY]
Marco, NICT, et.al.

4. September 2010
Introduction
b) If such transmitted packet is detected in error by the frame check sequence (FCS) at the MAC level, such packet is not discarded but rather stored for posterior use (V<--D ). Upon No ACK at the transmitter, the parity bits (P) previously stored shall be passed to UWB PHY for PSDU construction without BCH(126,63) encoding. In other words, parity bits of the previous MPDU are transmitted.
Problem: P does not have FCS.
Marco, NICT, et.al.

5. Solution 1) D and P use FCS at MAC level D=MAC header+MAC frame [MAC]
September 2010
Solution 1) D and P use FCS at MAC level
D=MAC header+MAC frame [MAC]
D+P=BCH(D) [PHY]
D+FCS and P+FCS [MAC]
Transmission of D+FCS or P+FCS [PHY]
Marco, NICT, et.al.

6. September 2010
Introduction
Solution 2) FCS’ at PHY level is used for P or another FCS’ at MAC level is used for P
D=MPDU=MAC header+MAC frame+FCS [MAC]
D+P=BCH(D) [PHY]
P+FCS’ [MAC] or [PHY]
Transmissions of D or P+FCS’
Marco, NICT, et.al.

7. September 2010
Introduction
The information bits (D) are recovered by either inversion of the received parity bits (P) or BCH(126,23) decoding with the stored information bits (D) and received parity bits (P).
c) However, if BCH(126,23) decoding fails, the information bits are discarded and its parity bits are stored instead (V<-P). Upon No ACK at the transmitter, the information bits (D) previously stored at RX shall be passed to the UWB PHY for PSDU construction without BCH(126,63) encoding. In other words, the MPDU is retransmitted.
Marco, NICT, et.al.

8. September 2010
Introduction
d) If such retransmitted packet (D) is detected in error by the FCS at the MAC level, BCH(126,23) decoding is applied with the received information bits (D) and its stored parity bits (P) at the UWB PHY level.
e) If BCH(126,23) decoding fails and the maximum number of retransmissions has not been reached, the parity bits are discarded, the information bits are stored instead (V<-D) and the process repeats.
Marco, NICT, et.al.

9. September 2010
PHR iteration
When HARQ is enabled, the fields (H0, H1) in the PHR shall be set to (1, 0). In case of unsuccessful reception (No Ack), the process of retransmissions controlled by (H0, H1) shall follow the algorithmic flow illustrated in Table 62.
Marco, NICT, et.al.