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

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Compromise for UWB Interoperability – MAC Overview] Date Submitted: [20 February, 2004] Source: [Matt Welborn] Company [Motorola, Inc] Address [8133 Leesburg Pike] Voice:[703-269-3000], FAX: [703-249-3092], E-Mail:[mwelborn@xtremespectrum.com] Re: [IEEE 802.15.3a Call For Intent to Present for Ad-Hoc Meeting] Abstract: [This document provides an overview of a proposed Common Signaling Mode that would allow the inter-operation or MB-OFDM and DS-UWB devices.] Purpose: [Promote further discussion and compromise activities to advance the development of the TG3a Higher rate PHY standard.] 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. Welborn, Motorola

2. MB-OFDM & DS-UWB Interoperability • Past TG3a deliberations have focused on choosing one solution of the two remaining – either MB-OFDM or DS-UWB • Another solution is to choose both: • The 802.15.3 MAC is a TDMA MAC and uses central control to assign time slots for use by individual devices • This TDMA behavior can serve as the basis for the two fundamentally different classes of UWB devices to interoperate while using the 15.3 MAC • Once a device is assigned a timeslot, that slot can be used for either MB-OFDM or DS-UWB transmissions, as the device chooses • The basic mechanism needed to make this work is a “common language” or common signaling mode (CSM) that allows MB-OFDM and DS-USB devices to communicate at some basic level to allow time slot request and allocations Welborn, Motorola

3. MB-OFDM & DS-UWB Interoperability • CSM would be used for beacon in default mode • Also for control frames between dissimilar class devices • CSM could also be used for data exchange in assigned time slots between different class devices • CSM needs to be of sufficient data rate to cause minimal impact to superframe overhead Beacon (CSM) MB-OFDM Slot DS-UWB Slot CSM Slot Super-frame Welborn, Motorola

4. Overhead of a Slower Beacon for Superframe Beacon Preamble Beacon Payload SIFS Other Traffic Total Beacon Overhead Total Superframe Duration (65 ms) • Assume a “heavily loaded” piconet: 100 information elements in beacon • “Fast” 15.3a beacon overhead with 100 IEs (e.g. CTAs) @ 55 Mbps • (15 us preamble + 107 us payload + 10 us SIFS) / 65 ms = 0.2 % • CSM beacon overhead, assume 100 IEs (e.g. CTAs) @ 9.2 Mbps • (50 us preamble + 643 us payload + 10 us SIFS) / 65 ms = 1.1 % • Overhead (as a percent) would be higher for a shorter superframe duration • Conclusion: Slower beacon bit rates provide acceptable increase in beacon overhead (Too slow? at 1 Mbps, overhead grows to ~10%) Welborn, Motorola

5. MB-OFDM & DS-UWB Interoperability Data traffic Using MB-OFDM MB-OFDM Device • Beacons (some or all) broadcast using CSM • New device association using CSM in association MCTA • Other MCTA control traffic using CSM or negotiated higher rates DS-UWB Device MB-OFDM Device CSM Existing piconet Association using CSM DS-UWB PNC DS-UWB DS-UWB Device Welborn, Motorola

6. Other MAC Issues • CSM simply becomes a required data rate “mode” for both classes of TG3a devices • Higher data rates (110, 200 Mbps) are also required, but can be implemented in device for either MB-OFDM or DS-UWB (or both) • PNC records DEV capabilities during association • Supported data rates using MB-OFDM or DS-UWB or both • Also announced to other DEVs in piconet • CSM used for beacon and control traffic when required • Used for MCTA traffic between dissimilar devices • Similar devices (DEV/PNC pair) negotiate CSM or native mode for MCTA • CSM can also be used for data traffic between dissimilar devices during assigned CTAs • CSM enables establishment & control of child or neighbor piconet if segregated operation in desired Welborn, Motorola

7. Conclusions • The creation of a common signaling mode will allow co-existence and interoperability between DS-UWB and MB-OFDM devices • Minimum useful data rate for 15.3 MAC-based interoperability is ~10 Mbps • A Common Signaling Mode is described that: • Provides interoperability in a shared piconet environment • Prevents coexistence problems for two different UWB PHYs • Can achieve desired data rates and provide robust performance • Requires minimal additional complexity in MB-OFDM & DS-UWB • See additional details on PHY waveform for CSM in companion document 802.15-04/081r1 (or latest revision) Welborn, Motorola