ETSI TR 103 245 V1.1.1 (2014-11)

Electromagnetic compatibility and Radio spectrum Matters (ERM); System Reference document (SRdoc); Technical characteristics and spectrum requirements of wideband SRDs with advanced spectrum sharing capability for operation in the UHF 870 - 876 MHz and 915 - 921 MHz frequency bands

DTR/ERM-TG28-511

General Information

• Status: Published
• Publication Date: 19-Nov-2014
• Technical Committee: ERM TG28 - ERM Generic SRD's
• Current Stage: 12 - Completion
• Due Date: 28-Nov-2014
• Completion Date: 20-Nov-2014

Standards Content (Sample)

TECHNICAL REPORT
Electromagnetic compatibility
and Radio spectrum Matters (ERM);
System Reference document (SRdoc);
Technical characteristics and spectrum requirements of
wideband SRDs with advanced spectrum sharing capability for
operation in the UHF 870 - 876 MHz and 915 - 921 MHz
frequency bands
2 ETSI TR 103 245 V1.1.1 (2014-11)

Reference
DTR/ERM-TG28-511
Keywords
AFA, CSMA, IoT, M2M, SRDoc
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ETSI
3 ETSI TR 103 245 V1.1.1 (2014-11)
Contents
Intellectual Property Rights . 4
Foreword . 4
Modal verbs terminology . 4
Introduction . 4
1 Scope . 5
2 References . 5
2.1 Normative references . 5
2.2 Informative references . 5
3 Definitions and abbreviations . 6
3.1 Definitions . 6
3.2 Abbreviations . 7
4 Comments on the System Reference Document . 8
4.1 Statements by ETSI Members . 8
5 Executive summary . 8
6 Market information. 9
7 Technical characteristics . 9
7.1 Description of IEEE 802.11ah as an Example Technology for Wideband SRDs . 10
7.1.1 IEEE 802.11ah PHY . 11
7.1.2 IEEE 802.11ah MAC . 11
7.1.3 Transmitter and Receiver Specifications . 12
7.1.3.1 Transmit power levels . 12
7.2 Advanced Spectrum Sharing Capabilities . 14
7.2.1 PHY Layer CCA . 15
7.2.2 MAC Layer EDCA . 15
8 Justification of Spectrum Request . 17
9 Regulations . 18
9.1 Overview of Current UHF 870 - 876 MHz and 915 - 921 MHz Spectrum Regulations . 18
9.1.1 Regulations for SRD-designated sub-bands in 863 - 870 MHz . 19
9.1.2 Spectrum Access Techniques for SRDs. 19
9.2 Limitations of Spectrum Regulations for Wideband SRDs . 20
9.3 Proposed Changes and Benefits . 21
9.3.1 Detailed Changes to Regulatory Text . 22
10 Conclusions . 24
Annex A: Detailed Market Information . 25
A.1 Overall Connected Devices Market . 25
A.2 European Home and Building Automation Market . 25
A.3 Wearable Technologies Market . 27
History . 29

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4 ETSI TR 103 245 V1.1.1 (2014-11)

Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://ipr.etsi.org).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Report (TR) has been produced by ETSI Technical Committee Electromagnetic compatibility and Radio
spectrum Matters (ERM).
The present document includes necessary information to support the co-operation under the MoU between ETSI and the
Electronic Communications Committee (ECC) of the European Conference of Postal and Telecommunications
Administrations (CEPT).
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "may not", "need", "need not", "will",
"will not", "can" and "cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms
for the expression of provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Introduction
Wideband SRDs are a subset of the broader SRD family that can enable further market growth for divers applications
including Internet of Things, Machine-to-Machine communications, smart home/building automation and 'wearables'.
This can be achieved in particular through advanced characteristics of these devices such as higher data rates, improved
power usage, and efficient spectrum utilization. Therefore, Wideband SRD's are expected to grow rapidly over the
foreseeable future for mass market applications. Based on these expected growth rates and currently limited available
frequency bands, there is an essential need for additional spectrum for Wideband SRDs to accommodate the anticipated
market growth. The present document requests modifications to the regulatory rules of the UHF 870 - 876 MHz and
915 - 921 MHz frequency bands to enable the operation of Wideband SRDs with advanced spectrum sharing
capabilities in these bands.
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5 ETSI TR 103 245 V1.1.1 (2014-11)
1 Scope
The present document applies to the potential future usage of Wideband SRDs with advanced spectrum sharing
capabilities in the UHF 870 - 876 MHz and 915 - 921 MHz frequency bands. In particular, it:
• Gives an SRD market overview and explains the development and emergence of new Wideband SRD
technologies.
• Describes technical characteristics of Wideband SRDs, including advanced spectrum sharing capabilities, as
they relate to the usage of the UHF 870 - 876 MHz and 915 - 921 MHz spectrum.
• Details the requested regulatory changes to allow for efficient use of Wideband SRDs.
The present document is intended to include all necessary information required by the Electronic Communications
Committee (ECC) under the MoU between ETSI and the ECC.
2 References
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guarantee
their long term validity.
2.1 Normative references
The following referenced documents are necessary for the application of the present document.
Not applicable.
2.2 Informative references
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] CEPT ECC ERC Recommendation 70-03: "Relating to the Use of Short Range Devices (SRD)",
07 February 2014.
[i.2] ABI Research, "Short Range Wireless and Cellular ICs Enabling the Connected World of
Tomorrow", July 2013 (PT-1027).
[i.3] ABI Research Report "Home Automation Systems", May 5, 2014 (MD-HAS-1047).
[i.4] IHS, "Wearable Technology - World", October 2013.
[i.5] IEEE P802.11ah / Draft 2.0 June 2014. "Part II: Wireless LAN Medium Access Control (MAC)
and Physical (PHY) Layer Specifications. Amendment 6: Sub 1 GHz License Exempt Operation".
[i.6] ETSI EN 300 220-1 (V2.4.1) (2012-01): "Electromagnetic compatibility and Radio spectrum
Matters (ERM); Short Range Devices (SRD); Radio equipment to be used in the 25 MHz to
1 000 MHz frequency range with power levels ranging up to 500 mW; Part 1: Technical
characteristics and test methods".
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6 ETSI TR 103 245 V1.1.1 (2014-11)
[i.7] ETSI EN 300 328 (V1.8.1) (2012-04): "Electromagnetic compatibility and Radio spectrum
Matters (ERM); Wideband transmission systems; Data transmission equipment operating in the
2,4 GHz ISM band and using wide band modulation techniques; Harmonized EN covering the
essential requirements of article 3.2 of the R&TTE Directive".
[i.8] ETSI EN 303 204 (V1.1.0): "Electromagnetic compatibility and Radio spectrum Matters (ERM);
Network Based Short Range Devices (SRD); Radio equipment to be used in the 870 MHz to
876 MHz frequency range with power levels ranging up to 500 mW".
[i.9] CEPT ECC Report 200: "Co-existence studies for proposed SRD and RFID applications in the
frequency band 870-876 MHz and 915-921 MHz", September 2013.
[i.10] CEPT ECC Report 189: "Future Spectrum Demand for Short Range Devices in the UHF
Frequency Bands".
[i.11] CEPT ECC Report 181: "Improving Spectrum Efficiency in the SRD Bands", September 2012.
[i.12] ETSI TR 103 055 (V1.1.1) (2011-09): "Electromagnetic compatibility and Radio spectrum Matters
(ERM); System Reference document (SRdoc): Spectrum Requirements for Short Range Device,
Metropolitan Mesh Machine Networks (M3N) and Smart Metering (SM) applications".
[i.13] ETSI TR 102 649-2 (V1.3.1) (2012-08): "Electromagnetic compatibility and Radio spectrum
Matters (ERM); Technical characteristics of Short Range Devices (SRD) and RFID in the UHF
Band; System Reference Document for Radio Frequency Identification (RFID) and SRD
equipment; Part 2: Additional spectrum requirements for UHF RFID, non-specific SRDs and
specific SRDs".
[i.14] IEEE 802.11: "IEEE Standard for Information technology --Telecommunications and information
exchange between systems Local and metropolitan area networks--Specific requirements
Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY)
Specifications".
[i.15] IEEE 802.11n: "IEEE Standard for Information technology -- Local and metropolitan area
networks -- Specific requirements -- Part 11: Wireless LAN Medium Access Control (MAC)and
Physical Layer (PHY) Specifications Amendment 5: Enhancements for Higher Throughput".
[i.16] IEEE 802.11ac: "IEEE Standard for Information technology -- Telecommunications and
information exchange between systems - Local and metropolitan area networks -- Specific
requirements -- Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY)
Specifications -- Amendment 4: Enhancements for Very High Throughput for Operation in Bands
below 6 GHz".
[i.17] ABI Research Report "Commercial Building Automation", March 19, 2013. (MD-CBA-102).
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
channel: small frequency sub-band within the operating frequency band into which a Radio Signal fits
duty cycle: for the purposes of the ERC Recommendation 70-03 [i.1], the duty cycle is defined as the ratio, expressed
as a percentage, of the maximum transmitter "on" time on one carrier frequency, relative to a one hour period
NOTE: For frequency agile devices the duty cycle limit applies to the total transmission.
Listen Before Talk (LBT): action taken by a device to detect an unoccupied channel prior to transmitting
frequency agility: ability of a device to selectively change its frequency sub-band of operation within the larger
operating frequency band
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7 ETSI TR 103 245 V1.1.1 (2014-11)
Non-specific Short Range Devices (SRDs): SRDs that do not necessarily fit under the specific applications outlined in
ERC/REC 70-03 [i.1], Annexes 2 to 13
Short Range Devices (SRDs): radio devices which provide either unidirectional or bi-directional communication and
which have low capability of causing interference to other radio equipment
NOTE: SRDs use either integral, dedicated or external antennas and all modes of modulation can be permitted
subject to relevant standards. SRDs are normally "license exempt".
Specific Short Range Devices (SRDs): SRDs that are used in specific applications (e.g. Applications of
ERC/REC 70-03 [i.1], Annexes 2 to 13)
Wideband SRDs: SRD devices that use wideband modulation techniques with channel bandwidths larger than 600 kHz
(which current regulations for UHF 870 - 876 MHz and 915 - 921 MHz already specify) and up to 1 MHz
NOTE: This definition is for the purpose of notational simplicity and clarity in the context of drafting the present
document and does not claim a consensus on global definition for Wideband SRDs.
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AC Access Category
ACK Acknowledgement
AFA Adaptive Frequency Agility/Autonomous Frequency Assignment
AP Acces-Point
BPSK Binary Phase Shift Keying
BSS Basic Service Set
CA Collision Avoidance
CAGR Compound Annual Growth Rate
CCA Clear Channel Assessment
CEPT Commission Européenne des Postes et Télécommunications
CSMA Carrier Sense Multiple Access
CW Contention Window
DCF Distributed Coordination Function
DIFS DCF Interframe Spacing
DSSS Direct Sequence Spread Spectrum
e.r.p/e.i.r.p. effective radiated power/effective isotropic radiated power
ECC Electronic Communications Committee of the CEPT
EDCA Enhanced Distributed Channel Access
ER-GSM Extended Railways GSM
FFT Fast Fourier Transform
FHSS Frequency Hopping Spread Spectrum
GSM-R Global System for Mobile communication for Railway application
HVAC Heating, Ventilation and Air Conditioning
IoT Internet of Things
IP Internet Protocol
ISM Industrial Scientific and Medical
LBT Listen-Before-Talk
M2M Machine-to-Machine communication
MAC Medium Access Layer
OBSS Other Basic Service Set
OFDM Orthogonal Frequency Division Multiplexing
PER Packet Error Rate
PHY Physical Layer
PSD Power Spectral Density
QAM Quadrature Amplitude Modulation
QPSK Quadrature Phase Shift Keying
RAW Restricted Access Window
RFID Radio Frequency Identification
SIFS Short Interframe Spacing
SRD Short-Range Device
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8 ETSI TR 103 245 V1.1.1 (2014-11)
SST Sub-band Selective Transmission
STA Station
TWT Target Wake Time
TXOP Transmit Opportunity
UHF Ultra-High Frequency
4 Comments on the System Reference Document
The statements in clause 4.1 have been recorded.
4.1 Statements by ETSI Members
BWMi statement concerning the utilization in Germany of the UHF frequency bands 870 - 876 MHz and
915 - 921 MHz.
In Germany a designation of the frequency bands 870 - 876 MHz and 915 - 921 MHz for wideband SRD applications as
described in this SRdoc is not foreseen due to incumbent German military and GSM-R usage.
5 Executive summary
The present document proposes modifications to the regulatory rules of the SRDs [i.1] in Sub-1 GHz frequency ranges,
to be considered with the aim of helping market introduction and proliferation of Wideband SRDs in the overall context
of ongoing strategic re-alignment of SRD uses and allowing new bands and applications, e.g. in 870 - 876 MHz and
915 - 921 MHz frequency bands. Current usage rules [i.1] governing maximum allowable transmit bandwidth and duty
cycle will not allow even basic SRD Wideband deployments and therefore these parameters need to be reviewed by
taking into account the information given in the present document. In return, Wideband SRDs will implement advanced
spectrum sharing techniques such as more sophisticated LBT and AFA procedures to ensure coexistence and balance
the changes to spectrum usage. These changes will ultimately lead to SRD systems that are capable of more data rates to
support the needs of various SRD applications and allow more efficient and fair utilization of the spectrum.
The present document first presents market data and predictions for the growth of the "Internet of Things" (IoT) and in a
broader sense Machine-to-Machine (M2M) communications market in Europe and worldwide. The technologies for IoT
are also evolving to address the ever emerging market needs and use cases and one direction is towards Wideband SRD
systems such as (but not limited to) those based on IEEE 802.11ah [i.5]. Based on expected growth rates and currently
limited available frequency bands, there is an essential need for new spectrum designations for these types of Wideband
SRDs to support IoT deployments.
The IEEE 802.11ah [i.5] is an example technology for Wideband SRDs that allows for a wide-range of data rates
through the use of OFDM modulation and has built-in mechanisms for efficient spectrum sharing. The present
document describes its salient technical characteristics and features such as LBT based on CSMA-CA and AFA using
Sub-channel Selective Transmissions.
Based on the market data and the technical requirements for deployment of IEEE 802.11ah [i.5] (and other Wideband
SRD-type systems), spectrum designation is being requested. For Wideband SRDs to be efficiently deployed in the
UHF 870 - 876 MHz and 915 - 921 MHz frequency bands and to specifically support more sensor-type network use
cases, the following changes to spectrum regulations need to be considered:
- Creation of sub-band definitions between 870 - 875,8 MHz and 915,2 - 920,80 MHz for Wideband SRDs.
- Increase of Maximum Transmission Bandwidth from 600 kHz to 1 MHz.
- Inclusion of IEEE 802.11 [i.14] CSMA-CA as a compliant method of LBT within 870 - 876 MHz and
915 - 921 MHz, with the minimum CCA interval times and timing parameters defined to align with
IEEE 802.11ah [i.5] values.
- Relaxation of Maximum Duty Cycle for AP-type devices implementing LBT+AFA from 1 % to 10 %, and for
non-AP devices using LBT+AFA from 1 % to 2,8 %.
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9 ETSI TR 103 245 V1.1.1 (2014-11)
6 Market information
Markets that stand to benefit from Wideband SRD's are expected to grow rapidly over the foreseeable future. For
example ABI Research is projecting that globally installed base of wirelessly connected devices will grow from over 10
billion units in 2013 to over 30 billion units in 2020 [i.2]. The market for smart home/building automation, IoT/M2M,
and "Wearables" is expected to grow at a very rapid pace. For example, according to ABI Research [i.3], the market for
new installs of Home Automation systems in Europe is expected to grow by 40 % (CAGR) between 2014 and 2019 to
7,3 million in 2019. The market for wirelessly enabled building automation devices installed in Europe is expected to
grow at a rate of 19 % (CAGR) between 2014 and 2018 to 6,9 million new installs in 2018 [i.17]. The unit shipment
volume market for the emerging market of "Wearable" technology in Europe is projected to be around 70 million units
in 2018 according to IHS [i.4]. This market (e.g. for smartwatches, fitness trackers, etc.) is projected to have a high
wireless connectivity attach rate (over 60 %).
Additional relevant market data is given in annex A of the present document. Wideband SRDs are expected to become
the key enablers for new deployments and applications in the above sectors. Examples of benefits of Wideband SRD
enabled devices include increased energy efficiency in homes/buildings, medical/fitness applications to help reduce
medical expenses, remote elderly care, security/surveillance cameras, etc.
Another example of the market momentum towards the adoption of Wideband SRD technology is that the Wi-Fi
Alliance (a global, non-profit industry association of more than 600 leading companies devoted to seamless
interoperability) is working on the development of an industry interoperability program for devices that implement the
IEEE 802.11ah [i.5] standard under development.
The key advantages of using Wideband SRDs for wireless connectivity are:
• Provide higher data rates for IoT and similar data-rich applications.
• Enable IP networking for security and scalability.
• Open up new use cases for low power, battery operated, wireless sensors.
• Enables the use of one network in a home or building with enough capacity and features to support a variety of
integrated sensor type services and applications.
The expected high growth in the number of deployed Wideband SRDs drives the need for an increase in overall
network capacity. It is expected that the exiting 7 MHz of spectrum available for SRDs in the 863 - 870 MHz band will
be quickly exhausted. A complicating factor here is that usage of the 863 - 870 MHz spectrum is constrained by the 3 %
duty cycle limitation for all devices using this spectrum even with advanced spectrum sharing techniques like
LBT/AFA.
Additional spectrum for Wideband SRDs in the 870 - 876 MHz and 915 - 921 MHz bands will be required to
accommodate the anticipated market growth for IoE, M2M and "Wearable" devices. Applications and devices in these
high growth markets increasingly require higher data rates than SRDs that have been historically deployed in these
spectrum bands. For example Wideband SRDs are needed to support IP networking, to offer more robust security and to
enable more sophisticated IP based applications (like for smartgrid networking). In order to enable networks, which
could scale up to meet the anticipated demand, more advanced spectrum sharing techniques and the ability to use wider
channel bandwidths will be needed for these bands.
One additional consideration, which may apply, is that the IoE market will likely serve as an engine for technology
innovation and economic growth in the foreseeable future. The availability of larger amounts of Sub-1 GHz spectrum
with fewer spectrum usage limitations in key markets like the USA, South Korea, Japan, Australia and possibly China
may put the competitive advantage of EU member countries at risk.
7 Technical characteristics
This clause will describe the technical details of Wideband SRDs and specifically cover the future IEEE 802.11ah
system (currently in drafting process, expected completion of standard specification by early 2015 [i.5]), focusing on
the PHY/MAC characteristics and notably its advanced spectrum sharing capabilities, which are relevant to operation
and coexistence in the UHF 870 - 876 MHz and 915 - 921 MHz bands.
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10 ETSI TR 103 245 V1.1.1 (2014-11)
The term Wideband SRD is used to describe devices using technologies and protocols that have larger operation
bandwidths (e.g. ≥ 1 MHz) than most current SRDs on the market. These Wideband SRDs will also generally have
higher supported data rates as a consequence of the wider operation bandwidths.
7.1 Description of IEEE 802.11ah as an Example Technology
for Wideband SRDs
Like other IEEE 802.11-based systems, the IEEE 802.11ah [i.5] system is based on a network topology consisting of
Access Points (APs) and stations (STAs). The APs act as nodes that the STAs are associated with, and APs can
generally be expected to serve large numbers of STAs in IEEE 802.11ah [i.5]. An AP and the STA(s) associated to it
comprise a Basic Service Set (BSS) and BSSs are set up with an operating channel bandwidth around a carrier
frequency from a set of valid carrier frequencies, which are determined by regulations in the region of operation. An
overall network can consist of multiple BSSs of different coverage radiuses spread over a geographical area, with
individual BSSs overlapping or partially overlapping the frequencies and channel(s) of other BSSs (OBSS), see
Figure 1 for an illustrative example.
BSS on Channel “B”
Station
BSS on Channel “A”
Station
Station
Station
Access Point
Station Station
Access Point
Station
Station
Station
Station
Access Point
Station
BSS on Channel “A”
Figure 1: An illustrative example of a IEEE 802.11ah [i.5] network consisting of multiple BSSs
An AP is responsible for broadcasting management frames (e.g. beacon frames) to be received by the STAs in its BSS.
These management frames contain operational parameters and information necessary for the STAs to operate and
remain synchronized within the BSS.
Similar to other IEEE 802.11-based systems [i.14], APs are responsible for setting up associations with STAs entering
the BSS, and additionally serve data traffic to STAs on the downlink and respond with ACKs for incoming uplink
traffic. Because of the APs role in the BSS, they will generally need to transmit more frequently than an individual STA
would.
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11 ETSI TR 103 245 V1.1.1 (2014-11)
The IEEE 802.11ah [i.5] system is designed with rules for channel access but does not have specific limitations on
transmit duty cycles for individual devices. Because the system was defined to work globally across regions with
differing limitations, APs and STAs will adhere to the regulatory rules within the region of its operation. Regulatory
rules for the operation of Wideband SRDs (including IEEE 802.11ah [i.5] systems) in the UHF 870 - 876 MHz and
915 - 921 MHz spectrum are addressed in clause 9. Such rules will have to be established based on the findings of
co-existence studies to be performed within CEPT, i.e. an extension and evolution of the scenarios and analysis
considered in ECC Report 200.
7.1.1 IEEE 802.11ah PHY
The IEEE 802.11ah [i.5] system has an OFDM-based PHY designed for operation at sub-1 GHz carrier frequencies.
The primary design goals included multiple interoperable operation bandwidth modes, and support for a wide range of
data rates.
The supported operation bandwidths in the overall IEEE 802.11ah [i.5] system are 1, 2, 4, 8, and 16 MHz and the
OFDM tone spacing across the different bandwidth modes is a constant 31,25 kHz. OFDM symbols for 1, 2, 4, 8 and
16 MHz transmissions are based on 32, 64, 128, 256, and 512-pt FFTs, respectively. OFDM symbols will have a guard
interval duration (i.e. cyclic prefix) of 8 us or 4 us, and a single OFDM symbol will have a duration of 40 us or 36 us,
depending on the guard interval duration used. In IEEE 802.11ah [i.5], transmissions are frame-based, with each frame
consisting of multiple OFDM symbols.
However during the design, the system was specifically optimized in the lower bandwidth modes to support lower data
rates and longer ranges that would be useful for power limited (e.g. battery operated sensors) SRDs operating in
sub-1 GHz bands. Standalone operation of the lowest bandwidth mode (of 1 MHz) is envisaged for IEEE 802.11ah [i.5]
within the UHF 870 - 876 MHz and 915 - 921 MHz bands, and is the focus of the remainder of the technical
characteristics description.
The maximum duration of a single IEEE 802.11ah [i.5] frame on the medium is determined by the maximum payload
capable of being signalled in the control field of the preamble. For example, in 1 MHz operation the longest possible
single frame can be 27,92 ms. The duration of a total transmission can be longer however if MAC protocols for
aggregated PHY frame transmissions are used. These transmissions fit within Transmit Opportunity (TXOP) duration
allocated for that device, which is determined at channel access. Channel access in IEEE 802.11ah [i.5] is controlled by
the procedure described in clause 7.1.3.
In practice however, the maximum duration of a transmission or of a TXOP is regulated by the Listen-Before-Talk
(LBT) rules defined for the spectrum in the region of operation. Specifically, the LBT rules define parameters such as
the maximum "on-time" that will set the limits on the allowable TXOP durations in IEEE 802.11ah [i.5]. The LBT rules
for the UHF 870 - 876 MHz and 915 - 921 MHz bands will be discussed in clause 9.
7.1.2 IEEE 802.11ah MAC
The IEEE 802.11ah [i.5] MAC layer was designed by inheriting many of the protocols from existing IEEE 802.11
systems (i.e. IEEE 802.11n [i.15] and IEEE 802.11ac [i.16]) and then augmenting or modifying aspects to specifically
address long-range and sensor-network use cases. Some of the other design goals included low-power usage and
support for large numbers of users across multiple overlapping networks.
One such new feature in IEEE 802.11ah [i.5] is Sub-band Selective Transmission (SST), which is a type of Adaptive
Frequency Agility (AFA) scheme that allows devices to rapidly select and switch to the channels on which they
transmit, between transmissions. From the perspective of the transmitting device, this scheme allows for coordination
between it and the intended receiver to select the most favourable channel amongst a larger set on which to transmit.
The "best" channel here can be determined based on measurement to take into consideration short-term fading
conditions and/or interference levels from other sources.
For example, a single AP may be serving many sensor-type devices using 1 MHz operation bandwidth. If there is a total
of 8 MHz of spectrum available, the sensor-type STA devices can select the most favourable 1 MHz sub-channel
contained in the wider 8 MHz to transmit and receive. From the perspective of the sensor device, it can potentially
improve its link conditions from taking advantage of the available fading diversity over the wider bandwidth and
therefore ultimately improve its throughput and power usage. The overall system impact within a network is that
transmissions can potentially be more evenly distributed across the available spectrum, and that channel occupancy time
for individual channels can be reduced.
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12 ETSI TR 103 245 V1.1.1 (2014-11)
Another feature in IEEE 802.11ah [i.5] which is of particular interest to sensor device networks is support for defining
Restricted Access Windows (RAW). The AP can set up a RAW in which during certain intervals of time, specific
classes of devices (e.g. sensors) in the BSS are given exclusive access to the medium. This allows for some degree of
coordination and improvement of medium usage efficiency for coexisting traffic types within a BSS, such as between
sensor devices with lower data rates and other devices with higher data rate needs. Oftentimes RAW usage is paired
with the Target-Wake-Time feature of IEEE 802.11ah [i.5], which was designed to specifically coordinate power-save
and sleep modes across battery-operated sensor devices. Both the set-up and usage of RAW and TWT are coordinated
through beacon management frames from the APs to the STAs in their BSSs.
7.1.3 Transmitter and Receiver Specifications
The transmitter and receiver specifications and requirements for the IEEE 802.11ah system are defined in the IEEE
802.11ah specification document [i.5]. In addition to the requirements described in Sections 24.3.16 S1G (sub-1 GHz)
transmit specification and 24.3.17 S1G receiver specification, any IEEE 802.11ah device also meets the regulatory
requirements (e.g. transmit spectrum masks, max e.r.p.) of the regulatory region in which it operates. For the reader's
convenience, the transmitter and receiver specifications for Transmit Spectrum Mask, Receiver Minimum Sensitivity,
and Adjacent/Non-Adjacent channel rejection from that document are summarized in this subsection, as they will be of
relevance during future compatibility analysis for Wideband SRDs.
7.1.3.1 Transmit power levels
The maximum transmit power levels for STA and AP are based upon regulations established by regional and national
regulatory administrations. Annex D of the IEEE 802.11ah specification [i.5] summarizes these parameters for
802.11ah operation as they stand currently in various defined regulatory domains, and will change to reflect any
evolution of existing regulations. As is also stated in the IEEE 802.11ah specification [i.5], operation in countries within
the defined regulatory domains may be subject to additional or alternative national regulations, some of which may
supersede those described in the specification. The proposed maximum transmit power levels for the 870 - 876 MHz
and 915 - 921 MHz bands within CEPT countries are described in the table of clause 9.3.1.
7.1.3.2 Transmit Spectrum Mask
For 1 MHz transmissions in IEEE 802.11ah [i.5], the transmit spectral mask will have a 0dBr (dB relative to the
maximum spectral density of the signal) bandwidth of 0,9 MHz, or in other words from -0,45 to +0,45 MHz around the
transmission's center frequency. At further offsets from the center frequency, the requirements are: -20 dBr at ±0,6 MHz
offsets, -28 dBr at ±1 MHz offsets, and -40 dBr at ±1,5 MHz offsets and greater. For the regions in between the ±0,45,
±0,6, ±1, and ±1,5 MHz offsets, the spectrum mask is defined to be a linear interpolation (in dB domain) of the defined
values at those offsets.
Additionally, the transmit spectrum does not exceed the maximum of the transmit spectrum mask and -40 dBm/MHz at
any frequency offset. An illustration of the described transmit spectrum mask, when the -40 dBr spectrum level is
greater than -40 dBm/MHz, is shown in Figure 2.
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13 ETSI TR 103 245 V1.1.1 (2014-11)

Figure 2: IEEE 802.11ah [i.5] 1 MHz Transmit Spectrum Mask
7.1.3.3 Receiver Minimum Input Sensitivity
In the IEEE 802.11ah specification [i.5], the Receiver Minimum Input Sensitivity is defined as the input power level
(measured at a single receive antenna) where the device successfully receive a packet with greater than 90 % reliability
(i.e. packet error rate less than 10 %). The sensitivity level is defined for 256-byte packets and is rate-dependent and
bandwidth mode dependent.
For 1 MHz mode of operation, and for the lowest defined rate (150 kbps), the minimum sensitivity is -98 dBm. Table 1
lists the defined minimum sensitivity levels for each of the available data rates in 1 MHz mode of operation for
IEEE 802.11ah [i.5].
Table 1: Receiver Minimum Input Level Sensitivity
Modulation Code Rate Data Rate Minimum Sensitivity,
(Kbps) 1 MHz frame, 256 bytes
(dBm)
BPSK 1/4 (1/2 with 2x rep.) 150,0 -98
BPSK 1/2 300,0 -95
QPSK 1/2 600,0 -92
QPSK 3/4 900,0 -90
16-QAM 1/2 1 200,0 -87
16-QAM 3/4 1 800,0 -83
64-QAM 2/3 2 400,0 -79
64-QAM 3/4 2 700,0 -78
64-QAM 5/6 3 000,0 -77
256-QAM 3/4 3 600,0 -72
256-QAM 5/6 4 000,0 -70
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14 ETSI TR 103 245 V1.1.1 (2014-11)
7.1.3.4 Adjacent and Nonadjacent channel rejection
The adjacent and nonadjacent channel rejection requirements in the IEEE 802.11ah specification [i.5] define how
resistant a receiver should be to blocker signals in nearby bands. For the 1 MHz case in IEEE 802.11ah [i.5], the
Adjacent channel rejection requirement is tested by placing a 1 MHz blocker signal adjacent to the 1 MHz desired
signal being tested (where the center frequency of the blocker signal is 1 MHz away from the center frequency of the
desired signal being tested). The signal being tested is sent at each of its available rates (256 byte payload) and is set
such that its received power is 3 dB above the minimum input sensitivity for that rate (e.g. -95 dBm for the lowest rate
in 1 MHz). The blocker signal's power is varied until a > 10 % PER is observed for the signal of interest. The adjacent
channel rejection requirement is the relative amount (in dB) the blocker signal that exceeds the desired signal's power
before the PER threshold is crossed.
The nonadjacent channel rejection test follows the same procedure except the blocker signals are now placed at center
frequencies of 2 MHz and greater away from the center frequency of the desired signal being tested. The criteria for
satisfying the requirement are the same as that for the adjacent channel rejection test.
The test states that the blocker signal is to be an OFDM signal that is unsynchronized to the desired signal within the
1 MHz band being tested. The minimum required adjacent and nonadjacent channel rejection levels are listed in
Table 2.
Table 2: Minimum Required Adjacent and Nonadjacent Channel Rejection Levels
Modulation Code Rate Data Rate Adjacent Channel Non-Adjacent Channel
(Kbps) Rejection (dB) Rejection (dB)
BPSK 1/4 (1/2 with 2x 150,0 19 35
rep.)
BPSK 1/2 300,0 16 32
QPSK 1/2 600,0 13 29
QPSK 3/4 900,0 11 27
16-QAM 1/2 1 200,0 8 24
16-QAM 3/4 1 800,0 4 20
64-QAM 2/3 2 400,0 0 16
64-QAM 3/4 2 700,0 -1 15
64-QAM 5/6 3 000,0 -2 14
256-QAM 3/4 3 600,0 -7 9
256-QAM 5/6 4 000,0 -9 7
7.2 Advanced Spectrum Sharing Capabilities
The IEEE 802.11ah [i.5] system employs a Distributed Coordination Function (DCF) for enabling spectrum sharing and
allowing for contending devices to fairly contend for and transmit on the medium. The procedure, which is inherited
from prior IEEE 802.11 systems, is based on a Carrier Sense Multiple Access protocol with collision avoidance
(CSMA-CA) that all devices are required to follow prior to transmitting. This procedure allows for a distributed control
of channel access across devices and across BSSs that aims to reduce collisions between transmissions while allowing
for fairness in transmit opportunities. Additionally, the CSMA-CA protocol accounts for coexistence and spectrum
sharing with non-IEEE 802.11ah [i.5] technologies through the use of Energy Detection-based deferral. This procedure
detects for all transmissions on the medium independent of transmission pattern, modulation type, etc., based on
measured received energy.
The IEEE 802.11ah [i.5] CSMA-CA is based on a slotted timeline, where the PHY provides channel "busy" or "idle"
indications to the MAC once every 52 us (definition of a slot in IEEE 802.11ah [i.5]) based on a Clear Channel
Assessment (CCA) procedure. The MAC layer will use these indications from the PHY to drive its countdown/backoff
procedure, which is also operating in units of slots. A device is permitted to transmit only once the MAC
countdown/backoff procedure is completed. The duration for which the device is granted channel access is termed a
Transmit Opportunity, or TXOP.
In principle, CSMA-CA is a sophisticated and dynamic Listen-Before-Talk procedure that before transmitting detects if
the medium "busy" and only attempts transmissions after the medium has been "idle" for a set amount of time. Like any
other LBT-type protocol, the issue of Hidden Node problem might need to be considered for CSMA-CA during CEPT
coexistence studies.
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15 ETSI TR 103 245 V1.1.1 (2014-11)
7.2.1 PHY Layer CCA
As part of the CSMA-CA process, the PHY layer is responsible for performing the CCA: monitoring the contended
channel of interest for ongoing traffic or interference and declaring to the MAC whether the channel (i.e. medium) can
be considered "busy" or "idle". The conditions for declaring "busy" and "idle" are dependent on checking for both
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