Translation: IEEE 802.15.4z Standard. What awaits us in the future?

Hello, Habr! I present to you the translation of the article "IEEE P802.15. Wireless Personal Area Networks . "



<sup>Article translation: mentor.ieee.org/802.15/documents?is_dcn=coexistence%20document&is_group=004z

File:
09-Apr-2019 ET
Coexistence Document 15.4z
Benjamin A. Rolfe (BCA / UWBA / NXP / et al)
15-18- 0523-05-004z-coexistence-document-15-4z.docx</sup>

In February 2019, the non-profit organization UWB Alliance was created . The alliance includes such companies as: Apple, Hyundai, Kia, Zebra, Decawave, Alteros, Novelda, Ubisense and others.

In order to coordinate work to promote and improve the technology for transmitting radio signals in an ultra-wide band (UWB or UWB). Within this organization, a working group was created to develop the IEEE 802.15.4z standard.

Good afternoon. My name is Eugene, I work for RealTrac Technologies. I propose to your court a translation of the report on the work of the IEEE 802.15.4z standard development group, and I will also be happy to answer questions about the current situation with ultra-wideband technologies, development paths and applications.

Introduction

This document provides a brief compatibility analysis that was performed to evaluate the performance of systems using 802.15.4-2015 HRP and LRP PHY as amended by P802.15.4z with respect to other 802 wireless standards that may operate in the same range. .

1. Terminology

The terms used in this document have the following meanings:

“basic standard” means the standard 802.15.4-2015 and all amendments approved at the time of preparation of this document.

“802.15.4” means the basic standard.

“This amendment” means amendment P802.15.4z: Amendment of the Standard for Low Speed ​​Wireless Networks: Enhanced High Speed ​​Pulses (HRP), Low Speed ​​Pulses (LRP), UWB in the physical environment (PHYs) and related frequency range determination methods.

2. Overview

Systems based on 802.15.4 UWB are widely used around the world. The initial version of 802.15.4a-2007 included the HRP UWB PHY in the standard, and the LRP UWB PHY was added to 802.15.4f-2010. The P802.5.4z amendment applies to both UWB PHY and new and existing applications. Current UWB systems operate worldwide at very low power spectral densities. This document provides an analysis of compatibility with other 802 standard wireless systems, including older versions of 802.15.4 and current 802.11 systems.

There are many sources of UWB compatibility information. The method used in this document is to summarize the results regarding compatibility between 802 wireless systems capable of operating in the same frequency ranges. References to CAD 802.15.4a [8] and 802.15.4f [9] and studies [10] [11] describe the compatibility of UWB PHY with the following systems:

• 802.15.4 PHY operating in overlapping frequency bands
• 802.16 operating in the range from 3.4 to 3.8 GHz
• 802.11 OFDM operating in the 5GHz and 6GHz bands.

All over the world, UWB systems transmit with very low power, usually limited by the limits of power spectral density (PSD), consistent with spurious and / or unintentional electromagnetic emissions established for unintentional emitters. For example, in the United States, as well as in many parts of Asia and Europe, the PSD limit is -41.3 dBm.

2.1 Overview of UWB 802.15.4z

2.1.1 Frequency ranges considered

Figure 1 shows the 802.15.4 UWB channel plans defined in the basic standard and supplemented by this amendment. The 802.15.4z amendment defines new devices with extended range capabilities that work in terms of high-speed channels; no changes to devices operating on low-speed channel plans are included in this amendment.


Figure 1: Spectral Graphics

This amendment extends the LRP channel plan, as shown in the figure, with the addition of channel definitions to the upper range of the UWB. This amendment does not change the HRP channel plan. The highlighted “Globally Accessible UWB Spectrum” illustrates the channels in terms of UWB channels that are available in all regulatory domains that support LRP and HRP devices as defined in the basic standard and this amendment. Other channels are available in a more limited number of regulatory domains.

2.1.2 Relevant 802 standards

Table 1 lists other 802 standards that may operate in overlapping ranges. This information is taken from Appendix E to [5] and [6].

Table 1: Other Thematic Wireless Standards 802


Note that most WLAN applications use a channel spacing of 20 to 80 MHz. The analysis referred to in this document mainly relates to channel spacing of 5 to 160 MHz.

2.1.3 LRP PHY

This amendment extends LRP PHY to support the following features:

• New PHY packet formats
  The frame duration is likely to be shorter - less exposure and less exposure.
  
  Fewer pulses and shorter packet lengths
  More reliable under
  PSD interference conditions and the peak level is the same as the previous UWB
  Energy levels remained unchanged
  Less time and energy required for packet transmission
  
• New modulation and PRF
  
  No change in impact
  May be more noise immunity
  

2.1.4 HRP

This amendment adds the following characteristics to HRP PHY:

• New modulation and PRF
  
  Does not use BPM The
  peak of PRF has not changed The
  average value of PRF can change, but is equal to the same energy within the standard limits
  New codes allow data to be transmitted at a higher PRF speed, fewer frames will lead to a reduction in frame transmission time
  Increased data transfer rate has led to lower costs.
  
• Adding additional preamble codes
• Impact on
  
  legacy HRP form New codes ignored by older devices
  Compatible PHY modes for interacting with legacy devices
  
• More reliable transmission
  
  Better control of instantaneous peak power
  Reduces the number of relayings required
  

2.1.5 MAC Improvements and Their Impact on Compatibility

The new MAC features added by this amendment use the existing MAC features to ensure compatibility with legacy 802.15.4 devices, as well as to preserve the tested compatibility features provided by the standard.
The MAC is supplemented by this amendment with the provisions used in measuring distance in a transmission medium as follows:

• Broadcast / Multicast: Broadcast scheduling and multicast communication
• New information elements for transmitting information used to measure the distance of exchange of relevant information
• MAC features for distance measurement monitoring with improved integrity checking
• Changes in SAP MAC to support new ranking and data sharing tools

The channel access methods used to evaluate the channel status and start transmitting data are not changed by these additional MAC functions. The impact on compatibility is minimal.

2.2 Overview of compatibility mechanisms in 802.15.4

The compatibility mechanisms in clause 802.15.4 are described in [8] and [9]. Compatibility is also enhanced by the inherent 802.15.4 short duty cycle, thanks to the MAC architecture, as explained in [13].

MAC changes made to this amendment will have a minimal impact on compatibility:

• New scheduling capabilities are similar and compatible with existing channel access control mechanisms (CSMA-CA)
• New features retain compatibility in terms of load reduction, efficient duty cycle and access control to channels, as described in [8]

UWB PHYs operate at very low power, typically at or below the limits of background electromagnetic emissions. This typically limits the impact of UWB emitters on other systems.

2.3 Compatibility Analysis Methodology

The compatibility studies referred to in this document are generally carried out in accordance with the methodology described in [12] and considering each system both as a subject and an object of influence. In this document, a compatibility analysis has been reviewed for its compliance with current 802 standards, and here we present relevant findings. 802 wireless standards are changing, so more research has been conducted and disseminated specifically evaluating interoperability between 802.15.4 UWB and 802.11 systems. The findings of these studies are presented in this paper.

The compatibility studies [10] and [11] cited in this paper use the Monte Carlo simulation technique to evaluate potential impacts when sharing the spectrum.

3. Different systems with the same frequency bands

This clause presents compatibility factors with other 802 systems that operate in the same frequency ranges. In this clause, by various, they mean different from the IR-UWB operating in accordance with the 802.15.4 LRP or HRP PHY specifications.

3.1 802.11 Compatibility

As described in detail in Appendix E to [5] and [6], 802.11 systems can operate in different ranges, as shown in Table 1, with channel spacing from 5 MHz to 160 MHz. 802.11 WLAN devices can operate with relatively high EIIRP power of up to 1000 mW (30 dBm) in some regions. UWB devices operate with an average EIRP limited to - 41.3 dBm / MHz. 802.15.4 UWB devices use a nominal bandwidth of 500 MHz or higher.

Studies [10] and [11] present simulation results illustrating the effects of 802.11 systems operating near 802.15.4 UWB-based systems. The study examines various deployment scenarios and operating conditions.

3.1.1 Impact of WLAN on 802.15.4 UWB

The results for the scenarios described in [10] and [11] illustrate potential impacts. The WGSE PT45 study [10] considers both single interference and total interference using simulation methods in combination with active signal measurement data. The results show that interference from an 802.11 wireless LAN up to 946 meters results in a sensitivity loss of more than 3 dB in UWB communications and location tracking systems. For sounding, the corresponding distance is 212 meters. A total assessment of interference during Monte Carlo simulation shows that with a WLAN duty cycle of 1.97%, the probability of a decrease in sensitivity to UWB communications and location tracking devices is more than 3 dB and ranges from 5 to 15%.

For sensors, the probability of a decrease in sensitivity of more than 3 dB is from 3 to 6%. In [11] using modeling methods, additional configurations and scenarios are investigated. Studies show significant effects on both communication and range / location. This study also includes mitigation recommendations to improve interoperability.

3.1.2 Impact of 802.15.4 UWB on 802.11 WLAN

UWB devices operate with an average EIRP of -41 dBm / MHz, the signal attenuation required to limit the loss of sensitivity of a UWB 802.11 device by 3 dB is shown in the table below.

Table 2: Calculation of the Interference Threshold for an 802.11 System


In the worst case, the signal attenuation model at the control distance d0 = 1m.

In the 6 GHz band, it is 48 dB, based on the Friis equation.

Using this model, the required diversity for signal attenuation of 67 dB is less than 9 m. Please note that this is the worst case scenario since screening effects and indirect visibility areas are not taken into account; they will further reduce the required diversity.
To illustrate, the following table shows the attenuation of the signal at the reference distance d0, as well as the minimum required separation distances, for example, frequencies from 3 GHz to 6 GHz:

Table 3 Reference for path loss

3.2 802.15.4 Compatible Systems

RCC PHYs can operate in ranges as shown in Table 1. Apparently, RCC PHYs will not be operated in close proximity to UWB systems. RCC is mainly used outdoors and near railway lines.

3.3 Other Considered 802 Wireless Systems

Link [8] describes in detail the compatibility properties between systems based on 802.15.4 UWB and 802.16. The results show that the PER value falls below 1% at a spacing distance of 1 m, and when the spacing distance is> 6.9 m, the effect on 802.16 from the UWB LRP signal becomes negligible.

The results show that when using the 802.16 system as a source of interference and the HRP UWB system as an object of influence, the indicator falls below 1% at a separation distance of 44 m and at a separation distance of more than 140 m it becomes insignificant.

The signal structure, bandwidth, and power spectral density of the LRP symbol is quite similar to the HRP signal, so the results for LRP should be similar to those shown in Ref. [8].

4. 802.15.4 UWB system

This provision describes the compatibility situation for this amendment and existing 802.15.4 UWB systems.

4.1 HRP

The old 802.15.4a HRP and the new 802.15.4z HRP modes use preamble sequences to synchronize and measure distances. Both sequence standards are designed to be more reliable under interference conditions. Sequences in both standards will have very low correlation with sequences in another standard. Inter-standard interference between preambles will be almost identical to intra-standard interference. Both standards use a bandwidth of 500 MHz. Both use a 128 ns symbol for operation at ~ 7 Mbps and a 32 ns symbol for operation at ~ 30 Mbps. 802.15.4z HRP uses higher PRF values ​​than 802.15.4z HRP. Auto-adjustment of transmit power may vary slightly due to peak spectrum limitations. Nonetheless,

4.2 LRP

Changes to this amendment depend on the same channel access method and are expected to have the same impact as the availability of additional obsolete LRP devices in the field of radio influence. The compatibility mechanisms described in [9] are identical. Fiberglass systems are expected to operate at a very low duty cycle.

5. Conclusion

The UWB systems described in this amendment will have minimal or no impact on other 802 wireless systems operating in the field of radio influence. Low signal power and low duty cycle reduce the impact of interference from the UWB signal on systems other than UWB. In particular, the impact on other systems based on 802.15.4 and 802.11 in the same sphere of radio influence is usually not detected.

When working in the same field of radio influence as legacy UWB 802.15.4 systems, the impact of systems operating in accordance with this amendment is equal to or less than the effect of additional legacy devices. Adding preambles and STS reduces the impact on legacy UWBs, as they do not recognize signals in legacy systems and are thus below noise level.

As an object of interference, the UWB systems described in this amendment will be compatible with traditional UWB systems, since the signals from them will be recognized and properly processed. In the presence of 802.11-based systems operating in close proximity, significant impact on the UWB system is expected due to the use of higher power. The degree of impact is most dependent on the operating cycle of the system (s) 802.11. Physical separation reduces exposure.

Thanks for attention. If you have questions about UWB technology and its current stage of development, I am ready to answer your questions in the comments.