Streamlining Compact Frame Encoding for Improved Software Parsing
Enhance the software parsing efficiency of compact frame encoding within the IEEE P802.15.4 working group by proposing a modified approach that simplifies specification and allows for sequential parsing without complex branching based on message IDs. The submission by Billy Verso of Qorvo aims to streamline decoding for commonly used compact frames, offering insights on omitting Message IDs and introducing a presence field per Compact Frame ID for future extensibility.
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May 2025 doc.: <15-25-xxxx-00-04ab> Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [A modified Compact frame encoding.] Date Submitted: [12th May 2025] Source: [Billy Verso, ] Company [Qorvo, Inc.] Address [ ] E-Mail:[billy.verso (at) qorvo.com] Re: [Proposals for TG4ab next generation UWB project] Abstract: [Proposed reworking of Compact frame encoding to streamline software parsing upon reception.] Purpose: [To promote further discussion on potential improvements to the IEEE 802.15.4ab amendment.] 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. Billy Verso (Qorvo) Submission Slide 1
May 2025 doc.: <15-25-xxxx-00-04ab> Introduction / motivation During a discussion about the Compact frame decoding, it was commented to me by a software designer that the frame encoding did not lead to streamlined software decode: Each combination of Compact Frame ID + Message Control ID needs different handling, i.e., for any particular Compact Frame ID, the various encodings with different Message Control ID can have common fields but at different offsets in the frame. There is no easy parsing rule to allow field extraction, each one is different. Result, it needs a big (ugly) nested switch statement with a separate handling for each case . I offered to comment on this during D02 ballot to propose a modified encoding. Hence, we have comment #534 and this submission. Index 534 (Billy) page 111 clause 10.39.11.3 line 1 Comment The compact frame encoding does not lend itself to streamlined message parsing because each Compact Frame ID and Message ID is a separate message with different layout. Before it is too late let's consider whether it could/should be improved. Proposed Change Consider whether there is a better way. (I plan to prepare a submission with some suggestions to help the group in this consideration.) Billy Verso (Qorvo) Submission Slide 2
May 2025 doc.: <15-25-xxxx-00-04ab> Modified compact frame encoding proposal Reasons to modify the encoding: Simpler specification: only one description for each Compact Frame ID Allow for easier parsing in software code, so parsing can be done sequentially, without any need to follow different paths based on the message ID sub-field Basic idea: Message ID is omitted which saves one byte for some frames Saved byte is reused for a presence field Presence field is defined per Compact Frame ID (instead of one global definition) The presence field can allow for expansion as required and future extension Billy Verso (Qorvo) Submission Slide 3
May 2025 doc.: <15-25-xxxx-00-04ab> The following slides examine what could be done to streamline the software decoding of the compact frames that are most used, i.e., the ones used during active ranging rounds. We can look at a doing this for all the other frames, if the group thinks this modified approach is worth adopting. NB: The encoding modifications that follow are just examples to explain the approach proposed. These can be reworked if the group decides to progress this idea. Billy Verso (Qorvo) Submission Slide 4
May 2025 doc.: <15-25-xxxx-00-04ab> One-to-one poll compact frame Current encoding: Message control 0x00 => Same size (zero-padded), i.e., has Poll Control = 0x00, Presence = 0x00, Pad = 0x00 Message control 0x01 => One octet smaller (-1 for message ID) Presence bitmap Modified encoding: Billy Verso (Qorvo) Submission Slide 5
May 2025 doc.: <15-25-xxxx-00-04ab> One-to-one response compact frame Current encoding: Message control 0x00 => Same size (zero-padded), i.e., has Presence = 0x00, Pad = 0x00, 0x00, 0x00, 0x00, 0x00. Message control 0x01 => One octet smaller (-1 for message ID) Presence bitmap Bit Meaning 0, 1 Channel Map present / type 2 Management PHY config present 3 Management MAC config present Modified encoding: 4 Ranging PHY config present 5 MMS Number of Fragments present 0/16/40/48 0/8/16/24/32 6 Response Status present 7 Extension / reserved for future Billy Verso (Qorvo) Submission Slide 6
May 2025 doc.: <15-25-xxxx-00-04ab> One-to-one initiator report Current encoding: Modified encoding: Presence bitmap Bit Meaning 0 Round-Trip Time present 1 Reply Time present 2-6 Reserved 7 Extension / reserved for future Frame size remains same (presence field added instead of message ID) Billy Verso (Qorvo) Submission Slide 7
May 2025 doc.: <15-25-xxxx-00-04ab> One-to-one responder report Current encoding: Modified encoding: Presence bitmap Bit Meaning 0, 1 Channel Map present / type 2 Management PHY config present 3 Management MAC config present 4 Ranging PHY config present 5 MMS Number of Fragments present 6 Round trip time present Frame size remains same (presence field added instead of message ID) 7 Extension / reserved for future Billy Verso (Qorvo) Submission Slide 8
May 2025 doc.: <15-25-xxxx-00-04ab> Conclusion, summary of modified frame encoding proposal Software parsing of received frames is made easier: Only a single flow per Compact Frame ID Message ID is replaced by an expandable presence bitmap. Presence bitmap is defined per compact frame ID instead of using a single global definition Saves one byte for some frames, (maybe two bytes saved in some cases) Billy Verso (Qorvo) Submission Slide 9
May 2025 doc.: <15-25-xxxx-00-04ab> Possible way(s) forward Index 534 (Billy) page 111 clause 10.39.11.3 line 1 Comment The compact frame encoding does not lend itself to streamlined message parsing because each Compact Frame ID and Message ID is a separate message with different layout. Before it is too late let's consider whether it could/should be improved. Proposed Change Consider whether there is a better way. (I plan to prepare a submission with some suggestions to help the group in this consideration.) Path (A) Path (B) If the group thinks there is merit in doing this If the group, especially those who were the main contributors to the current scheme, are against making any such change, then there is little point in trying to develop this idea any further. And those who were the main contributors to defining the current scheme are prepared to assist in the work of defining and agreeing a modified encoding. In that case, we can resolve the comment as Rejected , with a reason like: The group is satisfied with the current encoding . Then, we can leave Comment Index #534 open to cover that work. Billy Verso (Qorvo) Submission Slide 10
May 2025 doc.: <15-25-xxxx-00-04ab> The End Billy Verso (Qorvo) Submission Slide 11
