1. Project: IEEE 802.15 Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [TG4a Comment Resolution – Regulations and Framework]
Date Submitted: [March 2006]
Source: [Matt Welborn] Company [Freescale Semiconductor, Inc]
Address [8133 Leesburg Pike Vienna, VA USA]
Voice:[ ],
Re: []
Abstract: []
Purpose: [Provide framework for revision baseline draft]
Notice: This document has been prepared to assist the IEEE 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

2. Regulatory Annex - Description and Purpose
Informative:
“This annex provides informational references to and key summary of the more critical regulatory requirements, with analysis of the impact on the specifications and design of IEEE products where appropriate. Due to the great breadth and variety of worldwide regulations it is not possible to cover all nations in the available time and space.”
Our situation:
UWB regulations exist only in the US, under the FCC
Other regions may or may not have rules before 2007
Regulations will likely continue to change for years

3. Recommendation Outline rules that are settled: FCC
Acknowledge situation worldwide as changing
Brief descriptions of potential outcomes in other regions
Don’t try to guess what will happen
Describe features we have provided in TG4a to deal with this situation
Helpful to reader
Responsive to “No” comments (about 20 T & TR)

4. Relevant Features of TG4a
Multiple bands and band group definitions
Support for different rules in different regions
Regulatory restrictions
Minimum bandwidth
Performance based on low PSD
Potential for LDC operation
Potential for data rate network topology requirements
Potential for transparent per-device control of spectrum
Mechanisms to support future network-based mitigation requirements
Compliance with specific regulations is enabled by the standard, but is still the responsibility of the implementer.

5. Responses to Comments: Worldwide Regulatory Support (~10 comments)
The selected frequency plan does not follow the expected regulation in Japan and Europe which plans to allow the use of GHz without DAA. More work needs to be done on this to address expected and potential regulations in other regions outside of the US.
Response: The Committee has revised the band structure to closely align with the GHz band while reducing implementation complexity. Additionally, this has been made the default mandatory band for the lower band group.

6. Response for DAA
“This standard is likely not to be allowed for worldwide usage as it contains no provisions for operation in Asia or Europe. This system should incorporate detect and avoid measures to narrow-band incumbents.”
Response: The current proposals for mitigation requirements are still being developed by regulators and seem to depend on future spectral allocations to other systems in some regions.
The Committee has provided options to allow transparent per- device control of spectrum through pulse shaping. The Committee has also provided a basic mechanism to allow network-based mitigation under the control of the PNC.
As the specifics of mitigation requirements (such as DAA) are still TBD, the details of this mechanism are considered implementation-dependent and are thus out-of-scope for this work. Overly-restrictive requirements would increase the complexity and cost of devices and are to be avoided.

7. Geographic Awareness
“Based on the great diversity of regulations (or proposed regulations) on UWB, the TG4a implementors will have three choices:1) have multiple SKUs for different regulatory administrations, and constrain the distribution of each SKU geographically.2) ship ‘one-sized-fits-all’ devices. (As of last november, that looked like 7.25 – 9.0 GHz.)3) add simple geographic awareness, or functional equivalent, into the design as an option”
Response: The Committee has provided enough options to allow the implementation to support either (1) or (2) above – regional or global applications based on our current understanding of potential regulations worldwide.
Adding feature (3) is determined to be beyond the scope of the PAR at this time.

8. Response for LDC
“Band plan and coexistence technology such as DAA or LDC may be included in the standard because Japanese and EU Regulations request them.”
Response: The Committee has provided mandatory and option features to allow the implementation to support LDC operation. The use of shorter preambles and symbols can allow further reduced duty cycle operation.
Coordination and enforcement of a potential LDC requirement is implementation-dependent and is therefore out-of-scope for work.

9. OOB Emission Limits
The frequency plan will not meet expected regulatory requirements for GHz without DAA in Europe, Japan, and Korea.
Make the frequency plan fall within GHz with suppression to -70dBm/MHz from GHz.
Response: The OOB emission limits will likely vary in different regions and are therefore implementation dependent. Imposing unnecessarily low limits where not required would increase implementation complexity and cost.

10. Sub-GHz UWB Band Group
I know of no regulatory authority which allows UWB operation below 1 GHz. For example, per FCC rule , "Fundamental radiation from intentional radiators operating under this Section shall not be allowed in the bands MHz, MHz, MHz and MHz." The standard should not contain elements which cannot be implemented.
Response: There are many regions that have yet to create initial UWB regulations and even the US has indicated that UWB regulations will likely be relaxed based on future deployment experience. There are precedents for exceptions to the Restricted Band regulations, for example the UWB rules themselves (47 CFR 15, sub-part F).
The Committee has provided optional modes that could provide enhanced communications and ranging performance for evolving regulations or applications where commercial regulatory compliance is not essential.

11. Optional/Mandatory Bands
The channel allocations are not consistent with the PAR requirement for an "international" standard, based on the current proposals for Japan and EU.
Resolve conflicts with regulatory actions either by removing the channels which conflict, make those channels that conflict with some regulatory domains optional, amending the power limits, or other means to allow design of a a system which complies with regulatory requirements.
Response: The Committee has revised the band structure to closely align with the GHz band while reducing implementation complexity. Additionally, this has been made the default mandatory band for the lower band group.
The Committee has also provided multiple band groups for regions with large differences in UWB spectrum, as well as a 2.4 GHz ISM band group for regions with no UWB spectrum allowance.

12. TG4a Overview
Responsive to PAR: Low complexity & power with precision ranging
Regulatory flexibility: Multiple bands in different band groups tailored to expected regulations around the world
Coexistence: Low PSD + low duty cycle + multiple bands + other features
Scalable performance vs. complexity: responsive to the wide range of proposed applications

13. Baseline Mode – Low Complexity with Robust Performance in Multipath
Single UWB band centered at ~4.5 GHz
Based on MHz band spacing
Hybrid PPM+BPSK modulation
Default preamble
64 symbols of L=31 perfect ternary sequence
Data rate: nominal 850 kb/s (851 kb/s)
Concatenated code
Systematic RS + Systematic convolutional code
Very low complexity Aloha medium access control
Ideal for low duty cycle UWB waveforms
Wide bandwidth (>500 MHz) for precision ranging

14. Spectrum Usage
Provides flexibility for coexistence and regulatory compliance worldwide
4 band groups
1: 3.1 to 4.8 GHz
2: 6 to 10.6 GHz
3: 2.4 ISM band (non-UWB  requires different modulation)
4: 500 MHz
One or more designated operating frequencies within each band group
Each band group has a single mandatory band to minimize complexity while ensuring interoperability

15. Comments in “Framework”
First, here is a summary list of some of the "sub-topics" within "Framework" category (w/ # of individual comments in each)
- coexistence with other UWB (3)
- too many modes or confusing (27)
- incompleteness (10)
- number precision (3)
- operation of modes/rates (13)
- sub-GHz mode (7)
Others: (~1 each)
- ranging, PRFs, preambles, packet size, chaos mode, FFD

16. 5.2.1 Network formation Add:
Some channels have a single PHY mode defined.
Some channels have s single mandatory mode but one or mode optional modes to provide additional flexibility
Network formation always performed using mandatory mode to ensure reliable operation
    Specific mechanisms are defined in XX.YY to allow one ore more devices to use option modes after initial formation 

17. 5.3.1 PHY
List (add): 2400 CSS (Worldwide), UWB (Worldwide, varying by region)
Text: LR-WPANS can operate in multiple independent band groups. A device can implement a single band or multiple bands, but in each band implemented must support the mandatory channel to ensure interoperability for devices that share a common band group. For UWB devices, there are three independent band groups: 500 MHz, GHz and GHz. Each has a single mandatory channel and devices in each band operate independently of the other bands. Devices in the three different UWB band groups use the same bandwidths and chipping rates to simplify design and implementation, with each band having different performance, coexistence, and regulatory characteristics.  The three different UWB band groups provide flexibility to allow LR-WPAN devices flexibility to operate in different regions as the UWB regulations are defined and updated over time.
The UWB PHY also incorporates a number of optional enhancements to potentially improve performance, reduce power consumption, or enhance coexistence characteristics. These optional enhancements:
Do not compromise the existing LR-WPAN model that all devices operating in a common band group will always be able to interoperate with a single default mandatory mode
Do not raise the baseline complexity for compliant devices, but rather recognize that some applications or implementations may need enhanced performance or coexistence capabilities while still maintaining full interoperability, and
Provide the capability to UWB LR-WPAN devices to operate under a wider range of RF channel conditions while still providing robust performance and precision ranging
Reference to sections that describe enhancement options and mechanisms for managing enhanced modes while ensuring interoperability

18. 5.4 Functional Overview add: ... and ranging.
5.4.1 Superframe Structure
5.4.2 Data transfer model
add: ... or ALOHA, as appropriate...
add: ... or ALOHA, as appropriate...
add: ... or ALOHA, as appropriate...
5.4.3 Frame structure
5.4.4 Robustness
CSMA-CA Mechanism
a  ALOHA protocol for the UWB PHY
[text to be provided based on a modification of existing text in TG4a draft]

19. 5.4 Functional Overview (cont.)
Frame Acknowledgment
Data Verification
 Enhanced Robustness Features for UWB PHY
Extremely wide bandwidth characteristics (UWB) that can provide very robust performance under harsh multipath and interference conditions
Concatenated forward error correction (FEC) system to provide flexible and robust performance under harsh multipath conditions 
Optional pulse control features that can potentially improved performance under some channel conditions while providing reliable communications and precision ranging capabilities
5.4.5    Power consumption considerations
Additional power consumption features provided by the UWB PHY
Hybrid modulation that allows for very simple receiver architectures to minimize power consumption and implementation complexity ...
Optional pulse control features that can potentially allow lower power consumption under some channel conditions ...
Optional shorter symbols and preambles that can allow reduced duty cycle operation for reduced power operation or for enhanced coexistence (when conditions allow)

20. 5.7 Coexistence 5.7.1. UWB band Coexistence
 UWB bands operate in spectrum different from other PHY that use unlicensed spectrum.
 Due to these special considerations, a number of extra features have been included with the UWB PHY design to support coexistence with other other spectrum users as well as with other UWB systems.
    (1) Low PSD - compliant with regulations for UWB in different parts of the world, including low OOB emission requirements
    (2) Multiple band groups and operating frequencies within each band - allows devices the option to avoid bands that might be in use or otherwise unavailable
    (3) Optional modes to operate with shorter symbol timing to minimize emissions and channel occupancy when applications allow
    (4) Specific commands that provide a basic framework to allow higher layers to control the radio for coexistence functions and possible interference mitigation
    (5) Optional spectral control features based on pulse shaping to allow enhanced coexistence with other spectrum users  
[Reference to CA document]
MHz CSS band Coexistence
[text + Reference to CA document]

21. Modulation and FEC
Extremely low complexity architectures are supported for key applications
Hybrid design to provide scalable complexity and performance
Combined PPM and convolutional coding to support coherent and non-coherent architectures
Provides robust performance even in extreme multipath environments
Systematic FEC codes to allow flexible decoding implementation

22. Back up slides

23. There are too many preamble/PRF combinations and the longer preambles are too long. The suggested regulatory actions in EU and Japan suggest some kind of mitigation in the bands 4a occupies. The most promising mitigation suggested for low bit rate UWB devices is the "low duty cycle" option (LDC) which is also the most feasible for 4a requirements for low complexity. The longer preambles < 1ms will make it unlikely that 4a will be able to comply with reasonably expected LDC specifications; the result could severely limit potential compliance with EU and Japan regulations and/or require active detect and avoid implementation, which greatly complicate the design of the device, compromising the PAR requirement for "ultra low cost, ultra low power".

24. Pulse Shaping Pulse-based UWB technology allows the use of
Latitude in pulse shape allow implementation to optimize for different issues:
Control spectrum
Improve performance in different areas
Minimize complexity
Baseline pulse is specified
Additional optional modifications are identified
Composite pulse based on linear combination
Chirp & CS  intended to reduce cross-correlation
Phase incoherent pulse [was “chaos”]

25. Precision Ranging Precision ranging capability is provided
MAC layer support:
PHY layer support: variable preamble lengths provided to support channel estimation and multipath correction
Ranging protocols

26. Scalability Extreme multipath conditions High density deployments
Reduced PRF for operation in extreme channels
High density deployments
Multiple codes per operating band
Time dithering for piconet isolation
High processing gain for isolation
Alternate symbol rates to trade off robustness and channel duty cycle