Internet DRAFT - draft-ietf-lpwan-overview
draft-ietf-lpwan-overview
lpwan S. Farrell, Ed.
Internet-Draft Trinity College Dublin
Intended status: Informational February 7, 2018
Expires: August 11, 2018
LPWAN Overview
draft-ietf-lpwan-overview-10
Abstract
Low Power Wide Area Networks (LPWAN) are wireless technologies with
characteristics such as large coverage areas, low bandwidth, possibly
very small packet and application layer data sizes and long battery
life operation. This memo is an informational overview of the set of
LPWAN technologies being considered in the IETF and of the gaps that
exist between the needs of those technologies and the goal of running
IP in LPWANs.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on August 11, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
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include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. LPWAN Technologies . . . . . . . . . . . . . . . . . . . . . 3
2.1. LoRaWAN . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.1. Provenance and Documents . . . . . . . . . . . . . . 4
2.1.2. Characteristics . . . . . . . . . . . . . . . . . . . 4
2.2. Narrowband IoT (NB-IoT) . . . . . . . . . . . . . . . . . 11
2.2.1. Provenance and Documents . . . . . . . . . . . . . . 11
2.2.2. Characteristics . . . . . . . . . . . . . . . . . . . 11
2.3. SIGFOX . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.1. Provenance and Documents . . . . . . . . . . . . . . 15
2.3.2. Characteristics . . . . . . . . . . . . . . . . . . . 16
2.4. Wi-SUN Alliance Field Area Network (FAN) . . . . . . . . 20
2.4.1. Provenance and Documents . . . . . . . . . . . . . . 20
2.4.2. Characteristics . . . . . . . . . . . . . . . . . . . 21
3. Generic Terminology . . . . . . . . . . . . . . . . . . . . . 24
4. Gap Analysis . . . . . . . . . . . . . . . . . . . . . . . . 25
4.1. Naive application of IPv6 . . . . . . . . . . . . . . . . 26
4.2. 6LoWPAN . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.2.1. Header Compression . . . . . . . . . . . . . . . . . 27
4.2.2. Address Autoconfiguration . . . . . . . . . . . . . . 27
4.2.3. Fragmentation . . . . . . . . . . . . . . . . . . . . 27
4.2.4. Neighbor Discovery . . . . . . . . . . . . . . . . . 28
4.3. 6lo . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.4. 6tisch . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.5. RoHC . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.6. ROLL . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.7. CoAP . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.8. Mobility . . . . . . . . . . . . . . . . . . . . . . . . 30
4.9. DNS and LPWAN . . . . . . . . . . . . . . . . . . . . . . 31
5. Security Considerations . . . . . . . . . . . . . . . . . . . 31
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 32
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 35
9. Informative References . . . . . . . . . . . . . . . . . . . 35
Appendix A. Changes . . . . . . . . . . . . . . . . . . . . . . 41
A.1. From -00 to -01 . . . . . . . . . . . . . . . . . . . . . 41
A.2. From -01 to -02 . . . . . . . . . . . . . . . . . . . . . 41
A.3. From -02 to -03 . . . . . . . . . . . . . . . . . . . . . 41
A.4. From -03 to -04 . . . . . . . . . . . . . . . . . . . . . 42
A.5. From -04 to -05 . . . . . . . . . . . . . . . . . . . . . 42
A.6. From -05 to -06 . . . . . . . . . . . . . . . . . . . . . 42
A.7. From -06 to -07 . . . . . . . . . . . . . . . . . . . . . 42
A.8. From -07 to -08 . . . . . . . . . . . . . . . . . . . . . 42
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A.9. From -08 to -09 . . . . . . . . . . . . . . . . . . . . . 43
A.10. From -09 to -10 . . . . . . . . . . . . . . . . . . . . . 43
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 43
1. Introduction
This document provides background material and an overview of the
technologies being considered in the IETF's Low Power Wide-Area
Networking (LPWAN) working group. We also provide a gap analysis
between the needs of these technologies and currently available IETF
specifications.
Most technologies in this space aim for similar goals of supporting
large numbers of very low-cost, low-throughput devices with very-low
power consumption, so that even battery-powered devices can be
deployed for years. LPWAN devices also tend to be constrained in
their use of bandwidth, for example with limited frequencies being
allowed to be used within limited duty-cycles (usually expressed as a
percentage of time per-hour that the device is allowed to transmit.)
And as the name implies, coverage of large areas is also a common
goal. So, by and large, the different technologies aim for
deployment in very similar circumstances.
What mainly distinguishes LPWANs from other constrained networks is
that in LPWANs the balancing act related to power consumption/battery
life, cost and bandwidth tends to prioritise doing better with
respect to power and cost and we are more willing to live with
extremely low bandwidth and constrained duty-cycles when making the
various trade-offs required, in order to get the multiple-kilometre
radio links implied by the "wide area" aspect of the LPWAN term.
Existing pilot deployments have shown huge potential and created much
industrial interest in these technologies. As of today, essentially
no LPWAN end-devices (other than for Wi-SUN) have IP capabilities.
Connecting LPWANs to the Internet would provide significant benefits
to these networks in terms of interoperability, application
deployment, and management, among others. The goal of the IETF LPWAN
working group is to, where necessary, adapt IETF-defined protocols,
addressing schemes and naming to this particular constrained
environment.
This document is largely the work of the people listed in Section 7.
2. LPWAN Technologies
This section provides an overview of the set of LPWAN technologies
that are being considered in the LPWAN working group. The text for
each was mainly contributed by proponents of each technology.
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Note that this text is not intended to be normative in any sense, but
simply to help the reader in finding the relevant layer 2
specifications and in understanding how those integrate with IETF-
defined technologies. Similarly, there is no attempt here to set out
the pros and cons of the relevant technologies.
Note that some of the technology-specific drafts referenced below may
have been updated since publication of this document.
2.1. LoRaWAN
2.1.1. Provenance and Documents
LoRaWAN is an ISM-based wireless technology for long-range low-power
low-data-rate applications developed by the LoRa Alliance, a
membership consortium. <https://www.lora-alliance.org/> This draft
is based on version 1.0.2 [LoRaSpec] of the LoRa specification. That
specification is publicly available and has already seen several
deployments across the globe.
2.1.2. Characteristics
LoRaWAN aims to support end-devices operating on a single battery for
an extended period of time (e.g., 10 years or more), extended
coverage through 155 dB maximum coupling loss, and reliable and
efficient file download (as needed for remote software/firmware
upgrade).
LoRaWAN networks are typically organized in a star-of-stars topology
in which gateways relay messages between end-devices and a central
"network server" in the backend. Gateways are connected to the
network server via IP links while end-devices use single-hop LoRaWAN
communication that can be received at one or more gateways.
Communication is generally bi-directional; uplink communication from
end-devices to the network server is favored in terms of overall
bandwidth availability.
Figure 1 shows the entities involved in a LoRaWAN network.
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+----------+
|End-device| * * *
+----------+ * +---------+
* | Gateway +---+
+----------+ * +---------+ | +---------+
|End-device| * * * +---+ Network +--- Application
+----------+ * | | Server |
* +---------+ | +---------+
+----------+ * | Gateway +---+
|End-device| * * * * +---------+
+----------+
Key: * LoRaWAN Radio
+---+ IP connectivity
Figure 1: LoRaWAN architecture
o End-device: a LoRa client device, sometimes called a mote.
Communicates with gateways.
o Gateway: a radio on the infrastructure-side, sometimes called a
concentrator or base-station. Communicates with end-devices and,
via IP, with a network server.
o Network Server: The Network Server (NS) terminates the LoRaWAN MAC
layer for the end-devices connected to the network. It is the
center of the star topology.
o Join Server: The Join Server (JS) is a server on the Internet side
of an NS that processes join requests from an end-devices.
o Uplink message: refers to communications from an end-device to a
network server or application via one or more gateways.
o Downlink message: refers to communications from a network server
or application via one gateway to a single end-device or a group
of end-devices (considering multicasting).
o Application: refers to application layer code both on the end-
device and running "behind" the network server. For LoRaWAN,
there will generally only be one application running on most end-
devices. Interfaces between the network server and application
are not further described here.
In LoRaWAN networks, end-device transmissions may be received at
multiple gateways, so during nominal operation a network server may
see multiple instances of the same uplink message from an end-device.
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The LoRaWAN network infrastructure manages the data rate and RF
output power for each end-device individually by means of an adaptive
data rate (ADR) scheme. End-devices may transmit on any channel
allowed by local regulation at any time.
LoRaWAN radios make use of industrial, scientific and medical (ISM)
bands, for example, 433MHz and 868MHz within the European Union and
915MHz in the Americas.
The end-device changes channel in a pseudo-random fashion for every
transmission to help make the system more robust to interference and/
or to conform to local regulations.
Figure 2 below shows that after a transmission slot a Class A device
turns on its receiver for two short receive windows that are offset
from the end of the transmission window. End-devices can only
transmit a subsequent uplink frame after the end of the associated
receive windows. When a device joins a LoRaWAN network, there are
similar timeouts on parts of that process.
|----------------------------| |--------| |--------|
| Tx | | Rx | | Rx |
|----------------------------| |--------| |--------|
|---------|
Rx delay 1
|------------------------|
Rx delay 2
Figure 2: LoRaWAN Class A transmission and reception window
Given the different regional requirements the detailed specification
for the LoRaWAN physical layer (taking up more than 30 pages of the
specification) is not reproduced here. Instead and mainly to
illustrate the kinds of issue encountered, in Table 1 we present some
of the default settings for one ISM band (without fully explaining
those here) and in Table 2 we describe maxima and minima for some
parameters of interest to those defining ways to use IETF protocols
over the LoRaWAN MAC layer.
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+------------------------+------------------------------------------+
| Parameters | Default Value |
+------------------------+------------------------------------------+
| Rx delay 1 | 1 s |
| | |
| Rx delay 2 | 2 s (must be RECEIVE_DELAY1 + 1s) |
| | |
| join delay 1 | 5 s |
| | |
| join delay 2 | 6 s |
| | |
| 868MHz Default | 3 (868.1,868.2,868.3), data rate: |
| channels | 0.3-50kbps |
+------------------------+------------------------------------------+
Table 1: Default settings for EU 868MHz band
+-----------------------------------------------+--------+----------+
| Parameter/Notes | Min | Max |
+-----------------------------------------------+--------+----------+
| Duty Cycle: some but not all ISM bands impose | 1% | no-limit |
| a limit in terms of how often an end-device | | |
| can transmit. In some cases LoRaWAN is more | | |
| restrictive in an attempt to avoid | | |
| congestion. | | |
| | | |
| EU 868MHz band data rate/frame-size | 250 | 50000 |
| | bits/s | bits/s : |
| | : 59 | 250 |
| | octets | octets |
| | | |
| US 915MHz band data rate/frame-size | 980 | 21900 |
| | bits/s | bits/s : |
| | : 19 | 250 |
| | octets | octets |
+-----------------------------------------------+--------+----------+
Table 2: Minima and Maxima for various LoRaWAN Parameters
Note that in the case of the smallest frame size (19 octets), 8
octets are required for LoRa MAC layer headers leaving only 11 octets
for payload (including MAC layer options). However, those settings
do not apply for the join procedure - end-devices are required to use
a channel and data rate that can send the 23-byte Join-request
message for the join procedure.
Uplink and downlink higher layer data is carried in a MACPayload.
There is a concept of "ports" (an optional 8-bit value) to handle
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different applications on an end-device. Port zero is reserved for
LoRaWAN specific messaging, such as the configuration of the end
device's network parameters (available channels, data rates, ADR
parameters, RX1/2 delay, etc.).
In addition to carrying higher layer PDUs there are Join-Request and
Join-Response (aka Join-Accept) messages for handling network access.
And so-called "MAC commands" (see below) up to 15 bytes long can be
piggybacked in an options field ("FOpts").
There are a number of MAC commands for link and device status
checking, ADR and duty-cycle negotiation, managing the RX windows and
radio channel settings. For example, the link check response message
allows the network server (in response to a request from an end-
device) to inform an end-device about the signal attenuation seen
most recently at a gateway, and to also tell the end-device how many
gateways received the corresponding link request MAC command.
Some MAC commands are initiated by the network server. For example,
one command allows the network server to ask an end-device to reduce
its duty-cycle to only use a proportion of the maximum allowed in a
region. Another allows the network server to query the end-device's
power status with the response from the end-device specifying whether
it has an external power source or is battery powered (in which case
a relative battery level is also sent to the network server).
In order to operate nominally on a LoRaWAN network, a device needs a
32-bit device address, that is assigned when the device "joins" the
network (see below for the join procedure) or that is pre-provisioned
into the device. In case of roaming devices, the device address is
assigned based on the 24-bit network identifier (NetID) that is
allocated to the network by the LoRa Alliance. Non-roaming devices
can be assigned device addresses by the network without relying on a
LoRa Alliance-assigned NetID.
End-devices are assumed to work with one or a quite limited number of
applications, identified by a 64-bit AppEUI, which is assumed to be a
registered IEEE EUI64 value. In addition, a device needs to have two
symmetric session keys, one for protecting network artifacts
(port=0), the NwkSKey, and another for protecting application layer
traffic, the AppSKey. Both keys are used for 128-bit AES
cryptographic operations. So, one option is for an end-device to
have all of the above, plus channel information, somehow
(pre-)provisioned, in which case the end-device can simply start
transmitting. This is achievable in many cases via out-of-band means
given the nature of LoRaWAN networks. Table 3 summarizes these
values.
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+---------+---------------------------------------------------------+
| Value | Description |
+---------+---------------------------------------------------------+
| DevAddr | DevAddr (32-bits) = device-specific network address |
| | generated from the NetID |
| | |
| AppEUI | IEEE EUI64 corresponding to the join server for an |
| | application |
| | |
| NwkSKey | 128-bit network session key used with AES-CMAC |
| | |
| AppSKey | 128-bit application session key used with AES-CTR |
| | |
| AppKey | 128-bit application session key used with AES-ECB |
+---------+---------------------------------------------------------+
Table 3: Values required for nominal operation
As an alternative, end-devices can use the LoRaWAN join procedure
with a join server behind the NS in order to setup some of these
values and dynamically gain access to the network. To use the join
procedure, an end-device must still know the AppEUI, and in addition,
a different (long-term) symmetric key that is bound to the AppEUI -
this is the application key (AppKey), and is distinct from the
application session key (AppSKey). The AppKey is required to be
specific to the device, that is, each end-device should have a
different AppKey value. And finally, the end-device also needs a
long-term identifier for itself, syntactically also an EUI-64, and
known as the device EUI or DevEUI. Table 4 summarizes these values.
+---------+----------------------------------------------------+
| Value | Description |
+---------+----------------------------------------------------+
| DevEUI | IEEE EUI64 naming the device |
| | |
| AppEUI | IEEE EUI64 naming the application |
| | |
| AppKey | 128-bit long term application key for use with AES |
+---------+----------------------------------------------------+
Table 4: Values required for join procedure
The join procedure involves a special exchange where the end-device
asserts the AppEUI and DevEUI (integrity protected with the long-term
AppKey, but not encrypted) in a Join-request uplink message. This is
then routed to the network server which interacts with an entity that
knows that AppKey to verify the Join-request. All going well, a
Join-accept downlink message is returned from the network server to
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the end-device that specifies the 24-bit NetID, 32-bit DevAddr and
channel information and from which the AppSKey and NwkSKey can be
derived based on knowledge of the AppKey. This provides the end-
device with all the values listed in Table 3.
All payloads are encrypted and have data integrity. MAC commands,
when sent as a payload (port zero), are therefore protected. MAC
commands piggy-backed as frame options ("FOpts") are however sent in
clear. Any MAC commands sent as frame options and not only as
payload, are visible to a passive attacker but are not malleable for
an active attacker due to the use of the Message Integrity Check
(MIC) described below.
For LoRaWAN version 1.0.x, the NWkSkey session key is used to provide
data integrity between the end-device and the network server. The
AppSKey is used to provide data confidentiality between the end-
device and network server, or to the application "behind" the network
server, depending on the implementation of the network.
All MAC layer messages have an outer 32-bit MIC calculated using AES-
CMAC calculated over the ciphertext payload and other headers and
using the NwkSkey. Payloads are encrypted using AES-128, with a
counter-mode derived from IEEE 802.15.4 using the AppSKey. Gateways
are not expected to be provided with the AppSKey or NwkSKey, all of
the infrastructure-side cryptography happens in (or "behind") the
network server. When session keys are derived from the AppKey as a
result of the join procedure the Join-accept message payload is
specially handled.
The long-term AppKey is directly used to protect the Join-accept
message content, but the function used is not an AES-encrypt
operation, but rather an AES-decrypt operation. The justification is
that this means that the end-device only needs to implement the AES-
encrypt operation. (The counter mode variant used for payload
decryption means the end-device doesn't need an AES-decrypt
primitive.)
The Join-accept plaintext is always less than 16 bytes long, so
electronic code book (ECB) mode is used for protecting Join-accept
messages. The Join-accept contains an AppNonce (a 24 bit value) that
is recovered on the end-device along with the other Join-accept
content (e.g. DevAddr) using the AES-encrypt operation. Once the
Join-accept payload is available to the end-device the session keys
are derived from the AppKey, AppNonce and other values, again using
an ECB mode AES-encrypt operation, with the plaintext input being a
maximum of 16 octets.
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2.2. Narrowband IoT (NB-IoT)
2.2.1. Provenance and Documents
Narrowband Internet of Things (NB-IoT) is developed and standardized
by 3GPP. The standardization of NB-IoT was finalized with 3GPP
Release 13 in June 2016, and further enhancements for NB-IoT are
specified in 3GPP Release 14 in 2017, for example in the form of
multicast support. Further features and improvements will be
developed in the following releases, but NB-IoT has been ready to be
deployed since 2016, and is rather simple to deploy especially in the
existing LTE networks with a software upgrade in the operator's base
stations. For more information of what has been specified for NB-
IoT, 3GPP specification 36.300 [TGPP36300] provides an overview and
overall description of the E-UTRAN radio interface protocol
architecture, while specifications 36.321 [TGPP36321], 36.322
[TGPP36322], 36.323 [TGPP36323] and 36.331 [TGPP36331] give more
detailed description of MAC, Radio Link Control (RLC), Packet Data
Convergence Protocol (PDCP) and Radio Resource Control (RRC) protocol
layers, respectively. Note that the description below assumes
familiarity with numerous 3GPP terms.
For a general overview of NB-IoT, see [nbiot-ov].
2.2.2. Characteristics
Specific targets for NB-IoT include: Less than US$5 module cost,
extended coverage of 164 dB maximum coupling loss, battery life of
over 10 years, ~55000 devices per cell and uplink reporting latency
of less than 10 seconds.
NB-IoT supports Half Duplex FDD operation mode with 60 kbps peak rate
in uplink and 30 kbps peak rate in downlink, and a maximum
transmission unit (MTU) size of 1600 bytes limited by PDCP layer (see
Figure 4 for the protocol structure), which is the highest layer in
the user plane, as explained later. Any packet size up to the said
MTU size can be passed to the NB-IoT stack from higher layers,
segmentation of the packet is performed in the RLC layer, which can
segment the data to transmission blocks with size as small as 16
bits. As the name suggests, NB-IoT uses narrowbands with bandwidth
of 180 kHz in both downlink and uplink. The multiple access scheme
used in the downlink is OFDMA with 15 kHz sub-carrier spacing. In
uplink, SC-FDMA single tone with either 15kHz or 3.75 kHz tone
spacing is used, or optionally multi-tone SC- FDMA can be used with
15 kHz tone spacing.
NB-IoT can be deployed in three ways. In-band deployment means that
the narrowband is deployed inside the LTE band and radio resources
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are flexibly shared between NB-IoT and normal LTE carrier. In Guard-
band deployment the narrowband uses the unused resource blocks
between two adjacent LTE carriers. Standalone deployment is also
supported, where the narrowband can be located alone in dedicated
spectrum, which makes it possible for example to reframe a GSM
carrier at 850/900 MHz for NB-IoT. All three deployment modes are
used in licensed frequency bands. The maximum transmission power is
either 20 or 23 dBm for uplink transmissions, while for downlink
transmission the eNodeB may use higher transmission power, up to 46
dBm depending on the deployment.
A maximum coupling loss (MCL) target for NB-IoT coverage enhancements
defined by 3GPP is 164 dB. With this MCL, the performance of NB-IoT
in downlink varies between 200 bps and 2-3 kbps, depending on the
deployment mode. Stand-alone operation may achieve the highest data
rates, up to few kbps, while in-band and guard-band operations may
reach several hundreds of bps. NB-IoT may even operate with MCL
higher than 170 dB with very low bit rates.
For signaling optimization, two options are introduced in addition to
legacy LTE RRC connection setup; mandatory Data-over-NAS (Control
Plane optimization, solution 2 in [TGPP23720]) and optional RRC
Suspend/Resume (User Plane optimization, solution 18 in [TGPP23720]).
In the control plane optimization the data is sent over Non-Access
Stratum, directly to/from Mobility Management Entity (MME) (see
Figure 3 for the network architecture) in the core network to the
User Equipment (UE) without interaction from the base station. This
means there are no Access Stratum security or header compression
provided by the PDCP layer in the eNodeB, as the Access Stratum is
bypassed, and only limited RRC procedures. RoHC based header
compression may still optionally be provided and terminated in MME.
The RRC Suspend/Resume procedures reduce the signaling overhead
required for UE state transition from RRC Idle to RRC Connected mode
compared to legacy LTE operation in order to have quicker user plane
transaction with the network and return to RRC Idle mode faster.
In order to prolong device battery life, both power-saving mode (PSM)
and extended DRX (eDRX) are available to NB-IoT. With eDRX the RRC
Connected mode DRX cycle is up to 10.24 seconds and in RRC Idle the
eDRX cycle can be up to 3 hours. In PSM the device is in a deep
sleep state and only wakes up for uplink reporting, after which there
is a window, configured by the network, during which the device
receiver is open for downlink connectivity, of for periodical "keep-
alive" signaling (PSM uses periodic TAU signaling with additional
reception window for downlink reachability).
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Since NB-IoT operates in licensed spectrum, it has no channel access
restrictions allowing up to a 100% duty-cycle.
3GPP access security is specified in [TGPP33203].
+--+
|UE| \ +------+ +------+
+--+ \ | MME |------| HSS |
\ / +------+ +------+
+--+ \+--------+ / |
|UE| ----| eNodeB |- |
+--+ /+--------+ \ |
/ \ +--------+
/ \| | +------+ Service PDN
+--+ / | S-GW |----| P-GW |---- e.g. Internet
|UE| | | +------+
+--+ +--------+
Figure 3: 3GPP network architecture
Figure 3 shows the 3GPP network architecture, which applies to NB-
IoT. Mobility Management Entity (MME) is responsible for handling
the mobility of the UE. MME tasks include tracking and paging UEs,
session management, choosing the Serving gateway for the UE during
initial attachment and authenticating the user. At MME, the Non-
Access Stratum (NAS) signaling from the UE is terminated.
Serving Gateway (S-GW) routes and forwards the user data packets
through the access network and acts as a mobility anchor for UEs
during handover between base stations known as eNodeBs and also
during handovers between NB-IoT and other 3GPP technologies.
Packet Data Network Gateway (P-GW) works as an interface between 3GPP
network and external networks.
The Home Subscriber Server (HSS) contains user-related and
subscription- related information. It is a database, which performs
mobility management, session establishment support, user
authentication and access authorization.
E-UTRAN consists of components of a single type, eNodeB. eNodeB is a
base station, which controls the UEs in one or several cells.
The 3GPP radio protocol architecture is illustrated in Figure 4.
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+---------+ +---------+
| NAS |----|-----------------------------|----| NAS |
+---------+ | +---------+---------+ | +---------+
| RRC |----|----| RRC | S1-AP |----|----| S1-AP |
+---------+ | +---------+---------+ | +---------+
| PDCP |----|----| PDCP | SCTP |----|----| SCTP |
+---------+ | +---------+---------+ | +---------+
| RLC |----|----| RLC | IP |----|----| IP |
+---------+ | +---------+---------+ | +---------+
| MAC |----|----| MAC | L2 |----|----| L2 |
+---------+ | +---------+---------+ | +---------+
| PHY |----|----| PHY | PHY |----|----| PHY |
+---------+ +---------+---------+ +---------+
LTE-Uu S1-MME
UE eNodeB MME
Figure 4: 3GPP radio protocol architecture for control plane
Control plane protocol stack
The radio protocol architecture of NB-IoT (and LTE) is separated into
control plane and user plane. The control plane consists of
protocols which control the radio access bearers and the connection
between the UE and the network. The highest layer of control plane
is called Non-Access Stratum (NAS), which conveys the radio signaling
between the UE and the Evolved Packet Core (EPC), passing
transparently through the radio network. NAS responsible for
authentication, security control, mobility management and bearer
management.
Access Stratum (AS) is the functional layer below NAS, and in the
control plane it consists of Radio Resource Control protocol (RRC)
[TGPP36331], which handles connection establishment and release
functions, broadcast of system information, radio bearer
establishment, reconfiguration and release. RRC configures the user
and control planes according to the network status. There exists two
RRC states, RRC_Idle or RRC_Connected, and RRC entity controls the
switching between these states. In RRC_Idle, the network knows that
the UE is present in the network and the UE can be reached in case of
incoming call/downlink data. In this state, the UE monitors paging,
performs cell measurements and cell selection and acquires system
information. Also the UE can receive broadcast and multicast data,
but it is not expected to transmit or receive unicast data. In
RRC_Connected the UE has a connection to the eNodeB, the network
knows the UE location on the cell level and the UE may receive and
transmit unicast data. An RRC connection is established when the UE
is expected to be active in the network, to transmit or receive data.
The RRC connection is released, switching back to RRC_Idle, when
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there is no more traffic in order to preserve UE battery life and
radio resources. However, a new feature was introduced for NB-IoT,
as mentioned earlier, which allows data to be transmitted from the
MME directly to the UE transparently to the eNodeB, thus bypassing AS
functions.
Packet Data Convergence Protocol's (PDCP) [TGPP36323] main services
in control plane are transfer of control plane data, ciphering and
integrity protection.
Radio Link Control protocol (RLC) [TGPP36322] performs transfer of
upper layer PDUs and optionally error correction with Automatic
Repeat reQuest (ARQ), concatenation, segmentation, and reassembly of
RLC SDUs, in-sequence delivery of upper layer PDUs, duplicate
detection, RLC SDU discard, RLC-re-establishment and protocol error
detection and recovery.
Medium Access Control protocol (MAC) [TGPP36321] provides mapping
between logical channels and transport channels, multiplexing of MAC
SDUs, scheduling information reporting, error correction with HARQ,
priority handling and transport format selection.
Physical layer [TGPP36201] provides data transport services to higher
layers. These include error detection and indication to higher
layers, FEC encoding, HARQ soft-combining, rate matching and mapping
of the transport channels onto physical channels, power weighting and
modulation of physical channels, frequency and time synchronization
and radio characteristics measurements.
User plane is responsible for transferring the user data through the
Access Stratum. It interfaces with IP and the highest layer of user
plane is PDCP, which in user plane performs header compression using
Robust Header Compression (RoHC), transfer of user plane data between
eNodeB and UE, ciphering and integrity protection. Similar to
control plane, lower layers in user plane include RLC, MAC and
physical layer performing the same tasks as in control plane.
2.3. SIGFOX
2.3.1. Provenance and Documents
The SIGFOX LPWAN is in line with the terminology and specifications
being defined by ETSI [etsi_unb]. As of today, SIGFOX's network has
been fully deployed in 12 countries, with ongoing deployments on 26
other countries, giving in total a geography of 2 million square
kilometers, containing 512 million people.
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2.3.2. Characteristics
SIGFOX LPWAN autonomous battery-operated devices send only a few
bytes per day, week or month, in principle allowing them to remain on
a single battery for up to 10-15 years. Hence, the system is
designed as to allow devices to last several years, sometimes even
buried underground.
Since the radio protocol is connection-less and optimized for uplink
communications, the capacity of a SIGFOX base station depends on the
number of messages generated by devices, and not on the actual number
of devices. Likewise, the battery life of devices depends on the
number of messages generated by the device. Depending on the use
case, devices can vary from sending less than one message per device
per day, to dozens of messages per device per day.
The coverage of the cell depends on the link budget and on the type
of deployment (urban, rural, etc.). The radio interface is compliant
with the following regulations:
Spectrum allocation in the USA [fcc_ref]
Spectrum allocation in Europe [etsi_ref]
Spectrum allocation in Japan [arib_ref]
The SIGFOX radio interface is also compliant with the local
regulations of the following countries: Australia, Brazil, Canada,
Kenya, Lebanon, Mauritius, Mexico, New Zealand, Oman, Peru,
Singapore, South Africa, South Korea, and Thailand.
The radio interface is based on Ultra Narrow Band (UNB)
communications, which allow an increased transmission range by
spending a limited amount of energy at the device. Moreover, UNB
allows a large number of devices to coexist in a given cell without
significantly increasing the spectrum interference.
Both uplink and downlink are supported, although the system is
optimized for uplink communications. Due to spectrum optimizations,
different uplink and downlink frames and time synchronization methods
are needed.
The main radio characteristics of the UNB uplink transmission are:
o Channelization mask: 100 Hz / 600 Hz (depending on the region)
o Uplink baud rate: 100 baud / 600 baud (depending on the region)
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o Modulation scheme: DBPSK
o Uplink transmission power: compliant with local regulation
o Link budget: 155 dB (or better)
o Central frequency accuracy: not relevant, provided there is no
significant frequency drift within an uplink packet transmission
For example, in Europe the UNB uplink frequency band is limited to
868.00 to 868.60 MHz, with a maximum output power of 25 mW and a duty
cycle of 1%.
The format of the uplink frame is the following:
+--------+--------+--------+------------------+-------------+-----+
|Preamble| Frame | Dev ID | Payload |Msg Auth Code| FCS |
| | Sync | | | | |
+--------+--------+--------+------------------+-------------+-----+
Figure 5: Uplink Frame Format
The uplink frame is composed of the following fields:
o Preamble: 19 bits
o Frame sync and header: 29 bits
o Device ID: 32 bits
o Payload: 0-96 bits
o Authentication: 16-40 bits
o Frame check sequence: 16 bits (CRC)
The main radio characteristics of the UNB downlink transmission are:
o Channelization mask: 1.5 kHz
o Downlink baud rate: 600 baud
o Modulation scheme: GFSK
o Downlink transmission power: 500 mW / 4W (depending on the region)
o Link budget: 153 dB (or better)
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o Central frequency accuracy: the center frequency of downlink
transmission is set by the network according to the corresponding
uplink transmission
For example, in Europe the UNB downlink frequency band is limited to
869.40 to 869.65 MHz, with a maximum output power of 500 mW with 10%
duty cycle.
The format of the downlink frame is the following:
+------------+-----+---------+------------------+-------------+-----+
| Preamble |Frame| ECC | Payload |Msg Auth Code| FCS |
| |Sync | | | | |
+------------+-----+---------+------------------+-------------+-----+
Figure 6: Downlink Frame Format
The downlink frame is composed of the following fields:
o Preamble: 91 bits
o Frame sync and header: 13 bits
o Error Correcting Code (ECC): 32 bits
o Payload: 0-64 bits
o Authentication: 16 bits
o Frame check sequence: 8 bits (CRC)
The radio interface is optimized for uplink transmissions, which are
asynchronous. Downlink communications are achieved by devices
querying the network for available data.
A device willing to receive downlink messages opens a fixed window
for reception after sending an uplink transmission. The delay and
duration of this window have fixed values. The network transmits the
downlink message for a given device during the reception window, and
the network also selects the base station (BS) for transmitting the
corresponding downlink message.
Uplink and downlink transmissions are unbalanced due to the
regulatory constraints on ISM bands. Under the strictest
regulations, the system can allow a maximum of 140 uplink messages
and 4 downlink messages per device per day. These restrictions can
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be slightly relaxed depending on system conditions and the specific
regulatory domain of operation.
+---+
|DEV| * +------+
+---+ * | RA |
* +------+
+---+ * |
|DEV| * * * * |
+---+ * +----+ |
* | BS | \ +--------+
+---+ * +----+ \ | |
DA -----|DEV| * * * | SC |----- NA
+---+ * / | |
* +----+ / +--------+
+---+ * | BS |/
|DEV| * * * * +----+
+---+ *
*
+---+ *
|DEV| * *
+---+
Figure 7: SIGFOX network architecture
Figure 7 depicts the different elements of the SIGFOX network
architecture.
SIGFOX has a "one-contract one-network" model allowing devices to
connect in any country, without any need or notion of either roaming
or handover.
The architecture consists of a single cloud-based core network, which
allows global connectivity with minimal impact on the end device and
radio access network. The core network elements are the Service
Center (SC) and the Registration Authority (RA). The SC is in charge
of the data connectivity between the Base Station (BS) and the
Internet, as well as the control and management of the BSs and End
Points. The RA is in charge of the End Point network access
authorization.
The radio access network is comprised of several BSs connected
directly to the SC. Each BS performs complex L1/L2 functions,
leaving some L2 and L3 functionalities to the SC.
The Devices (DEVs) or End Points (EPs) are the objects that
communicate application data between local device applications (DAs)
and network applications (NAs).
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Devices (or EPs) can be static or nomadic, as they associate with the
SC and they do not attach to any specific BS. Hence, they can
communicate with the SC through one or multiple BSs.
Due to constraints in the complexity of the Device, it is assumed
that Devices host only one or very few device applications, which
most of the time communicate each to a single network application at
a time.
The radio protocol authenticates and ensures the integrity of each
message. This is achieved by using a unique device ID and an AES-128
based message authentication code, ensuring that the message has been
generated and sent by the device with the ID claimed in the message.
Application data can be encrypted at the application level or not,
depending on the criticality of the use case, to provide a balance
between cost and effort vs. risk. AES-128 in counter mode is used
for encryption. Cryptographic keys are independent for each device.
These keys are associated with the device ID and separate integrity
and confidentiality keys are pre-provisioned. A confidentiality key
is only provisioned if confidentiality is to be used. At the time of
writing the algorithms and keying details for this are not published.
2.4. Wi-SUN Alliance Field Area Network (FAN)
Text here is via personal communication from Bob Heile
(bheile@ieee.org) and was authored by Bob and Sum Chin Sean. Duffy
(paduffy@cisco.com) also provided additional comments/input on this
section.
2.4.1. Provenance and Documents
The Wi-SUN Alliance <https://www.wi-sun.org/> is an industry alliance
for smart city, smart grid, smart utility, and a broad set of general
IoT applications. The Wi-SUN Alliance Field Area Network (FAN)
profile is open standards based (primarily on IETF and IEEE802
standards) and was developed to address applications like smart
municipality/city infrastructure monitoring and management, electric
vehicle (EV) infrastructure, advanced metering infrastructure (AMI),
distribution automation (DA), supervisory control and data
acquisition (SCADA) protection/management, distributed generation
monitoring and management, and many more IoT applications.
Additionally, the Alliance has created a certification program to
promote global multi-vendor interoperability.
The FAN profile is specified within ANSI/TIA as an extension of work
previously done on Smart Utility Networks. [ANSI-4957-000]. Updates
to those specifications intended to be published in 2017 will contain
details of the FAN profile. A current snapshot of the work to
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produce that profile is presented in [wisun-pressie1]
[wisun-pressie2] .
2.4.2. Characteristics
The FAN profile is an IPv6 wireless mesh network with support for
enterprise level security. The frequency hopping wireless mesh
topology aims to offer superior network robustness, reliability due
to high redundancy, good scalability due to the flexible mesh
configuration and good resilience to interference. Very low power
modes are in development permitting long term battery operation of
network nodes.
The following list contains some overall characteristics of Wi-SUN
that are relevant to LPWAN applications.
o Coverage: The range of Wi-SUN FAN is typically 2 -- 3 km in line
of sight, matching the needs of neighborhood area networks, campus
area networks, or corporate area networks. The range can also be
extended via multi-hop networking.
o High bandwidth, low link latency: Wi-SUN supports relatively high
bandwidth, i.e. up to 300 kbps [FANTPS], enables remote update and
upgrade of devices so that they can handle new applications,
extending their working life. Wi-SUN supports LPWAN IoT
applications that require on-demand control by providing low link
latency (0.02s) and bi-directional communication.
o Low power consumption: FAN devices draw less than 2 uA when
resting and only 8 mA when listening. Such devices can maintain a
long lifetime even if they are frequently listening. For
instance, suppose the device transmits data for 10 ms once every
10 s; theoretically, a battery of 1000 mAh can last more than 10
years.
o Scalability: Tens of millions Wi-SUN FAN devices have been
deployed in urban, suburban and rural environments, including
deployments with more than 1 million devices.
A FAN contains one or more networks. Within a network, nodes assume
one of three operational roles. First, each network contains a
Border Router providing Wide Area Network (WAN) connectivity to the
network. The Border Router maintains source routing tables for all
nodes within its network, provides node authentication and key
management services, and disseminates network-wide information such
as broadcast schedules. Secondly, Router nodes, which provide upward
and downward packet forwarding (within a network). A Router also
provides services for relaying security and address management
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protocols. Lastly, Leaf nodes provide minimum capabilities:
discovering and joining a network, send/receive IPv6 packets, etc. A
low power network may contain a mesh topology with Routers at the
edges that construct a star topology with Leaf nodes.
The FAN profile is based on various open standards developed by the
IETF (including [RFC0768], [RFC2460], [RFC4443] and [RFC6282]),
IEEE802 (including [IEEE-802-15-4] and [IEEE-802-15-9]) and ANSI/TIA
[ANSI-4957-210] for low power and lossy networks.
The FAN profile specification provides an application-independent
IPv6-based transport service. There are two possible methods for
establishing the IPv6 packet routing: Routing Protocol for Low-Power
and Lossy Networks (RPL) at the Network layer is mandatory, and
Multi-Hop Delivery Service (MHDS) is optional at the Data Link layer.
Table 5 provides an overview of the FAN network stack.
The Transport service is based on User Datagram Protocol (UDP)
defined in RFC768 or Transmission Control Protocol (TCP) defined in
RFC793.
The Network service is provided by IPv6 as defined in RFC2460 with
6LoWPAN adaptation as defined in RFC4944 and RFC6282. ICMPv6, as
defined in RFC4443, is used for the control plane during information
exchange.
The Data Link service provides both control/management of the
Physical layer and data transfer/management services to the Network
layer. These services are divided into Media Access Control (MAC)
and Logical Link Control (LLC) sub-layers. The LLC sub-layer
provides a protocol dispatch service which supports 6LoWPAN and an
optional MAC sub-layer mesh service. The MAC sub-layer is
constructed using data structures defined in IEEE802.15.4-2015.
Multiple modes of frequency hopping are defined. The entire MAC
payload is encapsulated in an IEEE802.15.9 Information Element to
enable LLC protocol dispatch between upper layer 6LoWPAN processing,
MAC sublayer mesh processing, etc. These areas will be expanded once
IEEE802.15.12 is completed.
The PHY service is derived from a sub-set of the SUN FSK
specification in IEEE802.15.4-2015. The 2-FSK modulation schemes,
with channel spacing range from 200 to 600 kHz, are defined to
provide data rates from 50 to 300 kbps, with Forward Error Coding
(FEC) as an optional feature. Towards enabling ultra-low-power
applications, the PHY layer design is also extendable to low energy
and critical infrastructure monitoring networks.
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+----------------------+--------------------------------------------+
| Layer | Description |
+----------------------+--------------------------------------------+
| IPv6 protocol suite | TCP/UDP |
| | |
| | 6LoWPAN Adaptation + Header Compression |
| | |
| | DHCPv6 for IP address management. |
| | |
| | Routing using RPL. |
| | |
| | ICMPv6. |
| | |
| | Unicast and Multicast forwarding. |
| | |
| MAC based on IEEE | Frequency hopping |
| 802.15.4e + IE | |
| extensions | |
| | |
| | Discovery and Join |
| | |
| | Protocol Dispatch (IEEE 802.15.9) |
| | |
| | Several Frame Exchange patterns |
| | |
| | Optional Mesh Under routing (ANSI |
| | 4957.210). |
| | |
| PHY based on | Various data rates and regions |
| 802.15.4g | |
| | |
| Security | 802.1X/EAP-TLS/PKI Authentication. |
| | TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 |
| | required for EAP-TLS. |
| | |
| | 802.11i Group Key Management |
| | |
| | Frame security is implemented as AES-CCM* |
| | as specified in IEEE 802.15.4 |
| | |
| | Optional ETSI-TS-102-887-2 Node 2 Node Key |
| | Management |
+----------------------+--------------------------------------------+
Table 5: Wi-SUN Stack Overview
The FAN security supports Data Link layer network access control,
mutual authentication, and establishment of a secure pairwise link
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between a FAN node and its Border Router, which is implemented with
an adaptation of IEEE802.1X and EAP-TLS as described in [RFC5216]
using secure device identity as described in IEEE802.1AR.
Certificate formats are based upon [RFC5280]. A secure group link
between a Border Router and a set of FAN nodes is established using
an adaptation of the IEEE802.11 Four-Way Handshake. A set of 4 group
keys are maintained within the network, one of which is the current
transmit key. Secure node to node links are supported between one-
hop FAN neighbors using an adaptation of ETSI-TS-102-887-2. FAN
nodes implement Frame Security as specified in IEEE802.15.4-2015.
3. Generic Terminology
LPWAN technologies, such as those discussed above, have similar
architectures but different terminology. We can identify different
types of entities in a typical LPWAN network:
o End-Devices are the devices or the "things" (e.g. sensors,
actuators, etc.); they are named differently in each technology
(End Device, User Equipment or End Point). There can be a high
density of end devices per radio gateway.
o The Radio Gateway, which is the end point of the constrained link.
It is known as: Gateway, Evolved Node B or Base station.
o The Network Gateway or Router is the interconnection node between
the Radio Gateway and the Internet. It is known as: Network
Server, Serving GW or Service Center.
o LPWAN-AAA Server, which controls the user authentication, the
applications. It is known as: Join-Server, Home Subscriber Server
or Registration Authority. (We use the term LPWAN-AAA server
because we're not assuming that this entity speaks RADIUS or
Diameter as many/most AAA servers do, but equally we don't want to
rule that out, as the functionality will be similar.
o At last we have the Application Server, known also as Packet Data
Node Gateway or Network Application.
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+---------------------------------------------------------------------+
| Function/ | | | | | |
|Technology | LORAWAN | NB-IOT | SIGFOX | Wi-SUN | IETF |
+-----------+-----------+-----------+------------+--------+-----------+
| Sensor, | | | | | |
|Actuator, | End | User | End | Leaf | Device |
|device, | Device | Equipment | Point | Node | (Dev) |
| object | | | | | |
+-----------+-----------+-----------+------------+--------+-----------+
|Transceiver| | Evolved | Base | Router | RADIO |
| Antenna | Gateway | Node B | Station | Node | Gateway |
+-----------+-----------+-----------+------------+--------+-----------+
| Server | Network | PDN GW/ | Service | Border | Network |
| | Server | SCEF | Center | Router | Gateway |
| | | | | | (NGW) |
+-----------+-----------+-----------+------------+--------+-----------+
| Security | Join | Home |Registration|Authent.| LPWAN- |
| Server | Server | Subscriber| Authority | Server | AAA |
| | | Server | | | SERVER |
+-----------+-----------+-----------+------------+--------+-----------+
|Application|Application|Application| Network |Appli- |Application|
| | Server | Server | Application| cation | (App) |
+---------------------------------------------------------------------+
Figure 8: LPWAN Architecture Terminology
+------+
() () () | |LPWAN-|
() () () () / \ +---------+ | AAA |
() () () () () () / \========| /\ |====|Server| +-----------+
() () () | | <--|--> | +------+ |APPLICATION|
() () () () / \============| v |==============| (App) |
() () () / \ +---------+ +-----------+
Dev Radio Gateways NGW
Figure 9: LPWAN Architecture
In addition to the names of entities, LPWANs are also subject to
possibly regional frequency band regulations. Those may include
restrictions on the duty-cycle, for example requiring that hosts only
transmit for a certain percentage of each hour.
4. Gap Analysis
This section considers some of the gaps between current LPWAN
technologies and the goals of the LPWAN working group. Many of the
generic considerations described in [RFC7452] will also apply in
LPWANs, as end-devices can also be considered as a subclass of (so-
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called) "smart objects." In addition, LPWAN device implementers will
also need to consider the issues relating to firmware updates
described in [RFC8240].
4.1. Naive application of IPv6
IPv6 [RFC8200] has been designed to allocate addresses to all the
nodes connected to the Internet. Nevertheless, the header overhead
of at least 40 bytes introduced by the protocol is incompatible with
LPWAN constraints. If IPv6 with no further optimization were used,
several LPWAN frames could be needed just to carry the IP header.
Another problem arises from IPv6 MTU requirements, which require the
layer below to support at least 1280 byte packets [RFC2460].
IPv6 has a configuration protocol - neighbor discovery protocol,
(NDP) [RFC4861]). For a node to learn network parameters NDP
generates regular traffic with a relatively large message size that
does not fit LPWAN constraints.
In some LPWAN technologies, layer two multicast is not supported. In
that case, if the network topology is a star, the solution and
considerations of section 3.2.5 of [RFC7668] may be applied.
Other key protocols such as DHCPv6 [RFC3315], IPsec [RFC4301] and TLS
[RFC5246] have similarly problematic properties in this context.
Each of those require relatively frequent round-trips between the
host and some other host on the network. In the case of
cryptographic protocols such as IPsec and TLS, in addition to the
round-trips required for secure session establishment, cryptographic
operations can require padding and addition of authenticators that
are problematic when considering LPWAN lower layers. Note that mains
powered Wi-SUN mesh router nodes will typically be more resource
capable than the other LPWAN techs discussed. This can enable use of
more "chatty" protocols for some aspects of Wi-SUN.
4.2. 6LoWPAN
Several technologies that exhibit significant constraints in various
dimensions have exploited the 6LoWPAN suite of specifications
[RFC4944], [RFC6282], [RFC6775] to support IPv6
[I-D.hong-6lo-use-cases]. However, the constraints of LPWANs, often
more extreme than those typical of technologies that have (re)used
6LoWPAN, constitute a challenge for the 6LoWPAN suite in order to
enable IPv6 over LPWAN. LPWANs are characterized by device
constraints (in terms of processing capacity, memory, and energy
availability), and specially, link constraints, such as:
o tiny layer two payload size (from ~10 to ~100 bytes),
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o very low bit rate (from ~10 bit/s to ~100 kbit/s), and
o in some specific technologies, further message rate constraints
(e.g. between ~0.1 message/minute and ~1 message/minute) due to
regional regulations that limit the duty cycle.
4.2.1. Header Compression
6LoWPAN header compression reduces IPv6 (and UDP) header overhead by
eliding header fields when they can be derived from the link layer,
and by assuming that some of the header fields will frequently carry
expected values. 6LoWPAN provides both stateless and stateful header
compression. In the latter, all nodes of a 6LoWPAN are assumed to
share compression context. In the best case, the IPv6 header for
link-local communication can be reduced to only 2 bytes. For global
communication, the IPv6 header may be compressed down to 3 bytes in
the most extreme case. However, in more practical situations, the
smallest IPv6 header size may be 11 bytes (one address prefix
compressed) or 19 bytes (both source and destination prefixes
compressed). These headers are large considering the link layer
payload size of LPWAN technologies, and in some cases are even bigger
than the LPWAN PDUs. 6LoWPAN has been initially designed for IEEE
802.15.4 networks with a frame size up to 127 bytes and a throughput
of up to 250 kb/s, which may or may not be duty-cycled.
4.2.2. Address Autoconfiguration
Traditionally, Interface Identifiers (IIDs) have been derived from
link layer identifiers [RFC4944] . This allows optimizations such as
header compression. Nevertheless, recent guidance has given advice
on the fact that, due to privacy concerns, 6LoWPAN devices should not
be configured to embed their link layer addresses in the IID by
default. [RFC8065] provides guidance on better methods for
generating IIDs.
4.2.3. Fragmentation
As stated above, IPv6 requires the layer below to support an MTU of
1280 bytes [RFC2460]. Therefore, given the low maximum payload size
of LPWAN technologies, fragmentation is needed.
If a layer of an LPWAN technology supports fragmentation, proper
analysis has to be carried out to decide whether the fragmentation
functionality provided by the lower layer or fragmentation at the
adaptation layer should be used. Otherwise, fragmentation
functionality shall be used at the adaptation layer.
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6LoWPAN defined a fragmentation mechanism and a fragmentation header
to support the transmission of IPv6 packets over IEEE 802.15.4
networks [RFC4944]. While the 6LoWPAN fragmentation header is
appropriate for IEEE 802.15.4-2003 (which has a frame payload size of
81-102 bytes), it is not suitable for several LPWAN technologies,
many of which have a maximum payload size that is one order of
magnitude below that of IEEE 802.15.4-2003. The overhead of the
6LoWPAN fragmentation header is high, considering the reduced payload
size of LPWAN technologies and the limited energy availability of the
devices using such technologies. Furthermore, its datagram offset
field is expressed in increments of eight octets. In some LPWAN
technologies, the 6LoWPAN fragmentation header plus eight octets from
the original datagram exceeds the available space in the layer two
payload. In addition, the MTU in the LPWAN networks could be
variable which implies a variable fragmentation solution.
4.2.4. Neighbor Discovery
6LoWPAN Neighbor Discovery [RFC6775] defined optimizations to IPv6
Neighbor Discovery [RFC4861], in order to adapt functionality of the
latter for networks of devices using IEEE 802.15.4 or similar
technologies. The optimizations comprise host-initiated interactions
to allow for sleeping hosts, replacement of multicast-based address
resolution for hosts by an address registration mechanism, multihop
extensions for prefix distribution and duplicate address detection
(note that these are not needed in a star topology network), and
support for 6LoWPAN header compression.
6LoWPAN Neighbor Discovery may be used in not so severely constrained
LPWAN networks. The relative overhead incurred will depend on the
LPWAN technology used (and on its configuration, if appropriate). In
certain LPWAN setups (with a maximum payload size above ~60 bytes,
and duty-cycle-free or equivalent operation), an RS/RA/NS/NA exchange
may be completed in a few seconds, without incurring packet
fragmentation.
In other LPWANs (with a maximum payload size of ~10 bytes, and a
message rate of ~0.1 message/minute), the same exchange may take
hours or even days, leading to severe fragmentation and consuming a
significant amount of the available network resources. 6LoWPAN
Neighbor Discovery behavior may be tuned through the use of
appropriate values for the default Router Lifetime, the Valid
Lifetime in the PIOs, and the Valid Lifetime in the 6LoWPAN Context
Option (6CO), as well as the address Registration Lifetime. However,
for the latter LPWANs mentioned above, 6LoWPAN Neighbor Discovery is
not suitable.
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4.3. 6lo
The 6lo WG has been reusing and adapting 6LoWPAN to enable IPv6
support over link layer technologies such as Bluetooth Low Energy
(BTLE), ITU-T G.9959, DECT-ULE, MS/TP-RS485, NFC IEEE 802.11ah. (See
<https://tools.ietf.org/wg/6lo> for details.) These technologies are
similar in several aspects to IEEE 802.15.4, which was the original
6LoWPAN target technology.
6lo has mostly used the subset of 6LoWPAN techniques best suited for
each lower layer technology, and has provided additional
optimizations for technologies where the star topology is used, such
as BTLE or DECT-ULE.
The main constraint in these networks comes from the nature of the
devices (constrained devices), whereas in LPWANs it is the network
itself that imposes the most stringent constraints.
4.4. 6tisch
The 6tisch solution is dedicated to mesh networks that operate using
802.15.4e MAC with a deterministic slotted channel. The time slot
channel (TSCH) can help to reduce collisions and to enable a better
balance over the channels. It improves the battery life by avoiding
the idle listening time for the return channel.
A key element of 6tisch is the use of synchronization to enable
determinism. TSCH and 6TiSCH may provide a standard scheduling
function. The LPWAN networks probably will not support
synchronization like the one used in 6tisch.
4.5. RoHC
Robust header compression (RoHC) is a header compression mechanism
[RFC3095] developed for multimedia flows in a point to point channel.
RoHC uses 3 levels of compression, each level having its own header
format. In the first level, RoHC sends 52 bytes of header, in the
second level the header could be from 34 to 15 bytes and in the third
level header size could be from 7 to 2 bytes. The level of
compression is managed by a sequence number, which varies in size
from 2 bytes to 4 bits in the minimal compression. SN compression is
done with an algorithm called W-LSB (Window- Least Significant Bits).
This window has a 4-bit size representing 15 packets, so every 15
packets RoHC needs to slide the window in order to receive the
correct sequence number, and sliding the window implies a reduction
of the level of compression. When packets are lost or errored, the
decompressor loses context and drops packets until a bigger header is
sent with more complete information. To estimate the performance of
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RoHC, an average header size is used. This average depends on the
transmission conditions, but most of the time is between 3 and 4
bytes.
RoHC has not been adapted specifically to the constrained hosts and
networks of LPWANs: it does not take into account energy limitations
nor the transmission rate, and RoHC context is synchronised during
transmission, which does not allow better compression.
4.6. ROLL
Most technologies considered by the lpwan WG are based on a star
topology, which eliminates the need for routing at that layer.
Future work may address additional use-cases that may require
adaptation of existing routing protocols or the definition of new
ones. As of the time of writing, work similar to that done in the
ROLL WG and other routing protocols are out of scope of the LPWAN WG.
4.7. CoAP
CoAP [RFC7252] provides a RESTful framework for applications intended
to run on constrained IP networks. It may be necessary to adapt CoAP
or related protocols to take into account for the extreme duty cycles
and the potentially extremely limited throughput of LPWANs.
For example, some of the timers in CoAP may need to be redefined.
Taking into account CoAP acknowledgments may allow the reduction of
L2 acknowledgments. On the other hand, the current work in progress
in the CoRE WG where the COMI/CoOL network management interface
which, uses Structured Identifiers (SID) to reduce payload size over
CoAP may prove to be a good solution for the LPWAN technologies. The
overhead is reduced by adding a dictionary which matches a URI to a
small identifier and a compact mapping of the YANG model into the
CBOR binary representation.
4.8. Mobility
LPWAN nodes can be mobile. However, LPWAN mobility is different from
the one specified for Mobile IP. LPWAN implies sporadic traffic and
will rarely be used for high-frequency, real-time communications.
The applications do not generate a flow, they need to save energy and
most of the time the node will be down.
In addition, LPWAN mobility may mostly apply to groups of devices,
that represent a network in which case mobility is more a concern for
the gateway than the devices. NEMO [RFC3963] Mobility or other
mobile gateway solutions (such as a gateway with an LTE uplink) may
be used in the case where some end-devices belonging to the same
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network gateway move from one point to another such that they are not
aware of being mobile.
4.9. DNS and LPWAN
The Domain Name System (DNS) DNS [RFC1035], enables applications to
name things with a globally resolvable name. Many protocols use the
DNS to identify hosts, for example applications using CoAP.
The DNS query/answer protocol as a pre-cursor to other communication
within the time-to-live (TTL) of a DNS answer is clearly problematic
in an LPWAN, say where only one round-trip per hour can be used, and
with a TTL that is less than 3600. It is currently unclear whether
and how DNS-like functionality might be provided in LPWANs.
5. Security Considerations
Most LPWAN technologies integrate some authentication or encryption
mechanisms that were defined outside the IETF. The working group may
need to do work to integrate these mechanisms to unify management. A
standardized Authentication, Accounting, and Authorization (AAA)
infrastructure [RFC2904] may offer a scalable solution for some of
the security and management issues for LPWANs. AAA offers
centralized management that may be of use in LPWANs, for example
[I-D.garcia-dime-diameter-lorawan] and
[I-D.garcia-radext-radius-lorawan] suggest possible security
processes for a LoRaWAN network. Similar mechanisms may be useful to
explore for other LPWAN technologies.
Some applications using LPWANs may raise few or no privacy
considerations. For example, temperature sensors in a large office
building may not raise privacy issues. However, the same sensors, if
deployed in a home environment and especially if triggered due to
human presence, can raise significant privacy issues - if an end-
device emits (an encrypted) packet every time someone enters a room
in a home, then that traffic is privacy sensitive. And the more that
the existence of that traffic is visible to network entities, the
more privacy sensitivities arise. At this point, it is not clear
whether there are workable mitigations for problems like this - in a
more typical network, one would consider defining padding mechanisms
and allowing for cover traffic. In some LPWANs, those mechanisms may
not be feasible. Nonetheless, the privacy challenges do exist and
can be real and so some solutions will be needed. Note that many
aspects of solutions in this space may not be visible in IETF
specifications, but can be e.g. implementation or deployment
specific.
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Another challenge for LPWANs will be how to handle key management and
associated protocols. In a more traditional network (e.g. the web),
servers can "staple" Online Certificate Status Protocol (OCSP)
responses in order to allow browsers to check revocation status for
presented certificates. [RFC6961] While the stapling approach is
likely something that would help in an LPWAN, as it avoids an RTT,
certificates and OCSP responses are bulky items and will prove
challenging to handle in LPWANs with bounded bandwidth.
6. IANA Considerations
There are no IANA considerations related to this memo.
7. Contributors
[[RFC editor: Please fix names below for I18N.]]
As stated above this document is mainly a collection of content
developed by the full set of contributors listed below. The main
input documents and their authors were:
o Text for Section 2.1 was provided by Alper Yegin and Stephen
Farrell in [I-D.farrell-lpwan-lora-overview].
o Text for Section 2.2 was provided by Antti Ratilainen in
[I-D.ratilainen-lpwan-nb-iot].
o Text for Section 2.3 was provided by Juan Carlos Zuniga and Benoit
Ponsard in [I-D.zuniga-lpwan-sigfox-system-description].
o Text for Section 2.4 was provided via personal communication from
Bob Heile (bheile@ieee.org) and was authored by Bob and Sum Chin
Sean. There is no Internet draft for that at present.
o Text for Section 4 was provided by Ana Minabiru, Carles Gomez,
Laurent Toutain, Josep Paradells and Jon Crowcroft in
[I-D.minaburo-lpwan-gap-analysis]. Additional text from that
draft is also used elsewhere above.
The full list of contributors are:
Jon Crowcroft
University of Cambridge
JJ Thomson Avenue
Cambridge, CB3 0FD
United Kingdom
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Email: jon.crowcroft@cl.cam.ac.uk
Carles Gomez
UPC/i2CAT
C/Esteve Terradas, 7
Castelldefels 08860
Spain
Email: carlesgo@entel.upc.edu
Bob Heile
Wi-Sun Alliance
11 Robert Toner Blvd, Suite 5-301
North Attleboro, MA 02763
USA
Phone: +1-781-929-4832
Email: bheile@ieee.org
Ana Minaburo
Acklio
2bis rue de la Chataigneraie
35510 Cesson-Sevigne Cedex
France
Email: ana@ackl.io
Josep PAradells
UPC/i2CAT
C/Jordi Girona, 1-3
Barcelona 08034
Spain
Email: josep.paradells@entel.upc.edu
Charles E. Perkins
Futurewei
2330 Central Expressway
Santa Clara 95050
Unites States
Email: charliep@computer.org
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Benoit Ponsard
SIGFOX
425 rue Jean Rostand
Labege 31670
France
Email: Benoit.Ponsard@sigfox.com
URI: http://www.sigfox.com/
Antti Ratilainen
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: antti.ratilainen@ericsson.com
Chin-Sean SUM
Wi-Sun Alliance
20, Science Park Rd
Singapore 117674
Phone: +65 6771 1011
Email: sum@wi-sun.org
Laurent Toutain
Institut MINES TELECOM ; TELECOM Bretagne
2 rue de la Chataigneraie
CS 17607
35576 Cesson-Sevigne Cedex
France
Email: Laurent.Toutain@telecom-bretagne.eu
Alper Yegin
Actility
Paris, Paris
FR
Email: alper.yegin@actility.com
Juan Carlos Zuniga
SIGFOX
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425 rue Jean Rostand
Labege 31670
France
Email: JuanCarlos.Zuniga@sigfox.com
URI: http://www.sigfox.com/
8. Acknowledgments
Thanks to all those listed in Section 7 for the excellent text.
Errors in the handling of that are solely the editor's fault.
[[RFC editor: Please fix names below for I18N, at least Mirja's does
need fixing.]]
In addition to the contributors above, thanks are due to (in
alphabetical order): Abdussalam Baryun, Andy Malis, Arun
(arun@acklio.com), Behcet SariKaya, Dan Garcia Carrillo, Jiazi Yi,
Mirja Kuehlewind, Paul Duffy, Russ Housley, Samita Chakrabarti, Thad
Guidry, Warren Kumari, for comments.
Alexander Pelov and Pascal Thubert were the LPWAN WG chairs while
this document was developed.
Stephen Farrell's work on this memo was supported by Pervasive
Nation, the Science Foundation Ireland's CONNECT centre national IoT
network. <https://connectcentre.ie/pervasive-nation/>
9. Informative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980, <https://www.rfc-
editor.org/info/rfc768>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <https://www.rfc-editor.org/info/rfc2460>.
[RFC2904] Vollbrecht, J., Calhoun, P., Farrell, S., Gommans, L.,
Gross, G., de Bruijn, B., de Laat, C., Holdrege, M., and
D. Spence, "AAA Authorization Framework", RFC 2904,
DOI 10.17487/RFC2904, August 2000, <https://www.rfc-
editor.org/info/rfc2904>.
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[RFC3095] Bormann, C., Burmeister, C., Degermark, M., Fukushima, H.,
Hannu, H., Jonsson, L-E., Hakenberg, R., Koren, T., Le,
K., Liu, Z., Martensson, A., Miyazaki, A., Svanbro, K.,
Wiebke, T., Yoshimura, T., and H. Zheng, "RObust Header
Compression (ROHC): Framework and four profiles: RTP, UDP,
ESP, and uncompressed", RFC 3095, DOI 10.17487/RFC3095,
July 2001, <https://www.rfc-editor.org/info/rfc3095>.
[RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
C., and M. Carney, "Dynamic Host Configuration Protocol
for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
2003, <https://www.rfc-editor.org/info/rfc3315>.
[RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
Thubert, "Network Mobility (NEMO) Basic Support Protocol",
RFC 3963, DOI 10.17487/RFC3963, January 2005,
<https://www.rfc-editor.org/info/rfc3963>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/info/rfc4443>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007, <https://www.rfc-
editor.org/info/rfc4861>.
[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
<https://www.rfc-editor.org/info/rfc4944>.
[RFC5216] Simon, D., Aboba, B., and R. Hurst, "The EAP-TLS
Authentication Protocol", RFC 5216, DOI 10.17487/RFC5216,
March 2008, <https://www.rfc-editor.org/info/rfc5216>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008, <https://www.rfc-
editor.org/info/rfc5246>.
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[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
DOI 10.17487/RFC6282, September 2011, <https://www.rfc-
editor.org/info/rfc6282>.
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012,
<https://www.rfc-editor.org/info/rfc6775>.
[RFC6961] Pettersen, Y., "The Transport Layer Security (TLS)
Multiple Certificate Status Request Extension", RFC 6961,
DOI 10.17487/RFC6961, June 2013, <https://www.rfc-
editor.org/info/rfc6961>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014, <https://www.rfc-
editor.org/info/rfc7252>.
[RFC7452] Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson,
"Architectural Considerations in Smart Object Networking",
RFC 7452, DOI 10.17487/RFC7452, March 2015,
<https://www.rfc-editor.org/info/rfc7452>.
[RFC7668] Nieminen, J., Savolainen, T., Isomaki, M., Patil, B.,
Shelby, Z., and C. Gomez, "IPv6 over BLUETOOTH(R) Low
Energy", RFC 7668, DOI 10.17487/RFC7668, October 2015,
<https://www.rfc-editor.org/info/rfc7668>.
[RFC8065] Thaler, D., "Privacy Considerations for IPv6 Adaptation-
Layer Mechanisms", RFC 8065, DOI 10.17487/RFC8065,
February 2017, <https://www.rfc-editor.org/info/rfc8065>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017, <https://www.rfc-
editor.org/info/rfc8200>.
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[RFC8240] Tschofenig, H. and S. Farrell, "Report from the Internet
of Things Software Update (IoTSU) Workshop 2016",
RFC 8240, DOI 10.17487/RFC8240, September 2017,
<https://www.rfc-editor.org/info/rfc8240>.
[I-D.farrell-lpwan-lora-overview]
Farrell, S. and A. Yegin, "LoRaWAN Overview", draft-
farrell-lpwan-lora-overview-01 (work in progress), October
2016.
[I-D.minaburo-lpwan-gap-analysis]
Minaburo, A., Gomez, C., Toutain, L., Paradells, J., and
J. Crowcroft, "LPWAN Survey and GAP Analysis", draft-
minaburo-lpwan-gap-analysis-02 (work in progress), October
2016.
[I-D.zuniga-lpwan-sigfox-system-description]
Zuniga, J. and B. PONSARD, "SIGFOX System Description",
draft-zuniga-lpwan-sigfox-system-description-04 (work in
progress), December 2017.
[I-D.ratilainen-lpwan-nb-iot]
Ratilainen, A., "NB-IoT characteristics", draft-
ratilainen-lpwan-nb-iot-00 (work in progress), July 2016.
[I-D.garcia-dime-diameter-lorawan]
Garcia, D., Lopez, R., Kandasamy, A., and A. Pelov,
"LoRaWAN Authentication in Diameter", draft-garcia-dime-
diameter-lorawan-00 (work in progress), May 2016.
[I-D.garcia-radext-radius-lorawan]
Garcia, D., Lopez, R., Kandasamy, A., and A. Pelov,
"LoRaWAN Authentication in RADIUS", draft-garcia-radext-
radius-lorawan-03 (work in progress), May 2017.
[I-D.hong-6lo-use-cases]
Hong, Y. and C. Gomez, "IPv6 over Constrained Node
Networks(6lo) Applicability & Use cases", draft-hong-6lo-
use-cases-03 (work in progress), October 2016.
[TGPP36300]
3GPP, "TS 36.300 v13.4.0 Evolved Universal Terrestrial
Radio Access (E-UTRA) and Evolved Universal Terrestrial
Radio Access Network (E-UTRAN); Overall description; Stage
2", 2016,
<http://www.3gpp.org/ftp/Specs/2016-09/Rel-14/36_series/>.
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[TGPP36321]
3GPP, "TS 36.321 v13.2.0 Evolved Universal Terrestrial
Radio Access (E-UTRA); Medium Access Control (MAC)
protocol specification", 2016.
[TGPP36322]
3GPP, "TS 36.322 v13.2.0 Evolved Universal Terrestrial
Radio Access (E-UTRA); Radio Link Control (RLC) protocol
specification", 2016.
[TGPP36323]
3GPP, "TS 36.323 v13.2.0 Evolved Universal Terrestrial
Radio Access (E-UTRA); Packet Data Convergence Protocol
(PDCP) specification (Not yet available)", 2016.
[TGPP36331]
3GPP, "TS 36.331 v13.2.0 Evolved Universal Terrestrial
Radio Access (E-UTRA); Radio Resource Control (RRC);
Protocol specification", 2016.
[TGPP36201]
3GPP, "TS 36.201 v13.2.0 - Evolved Universal Terrestrial
Radio Access (E-UTRA); LTE physical layer; General
description", 2016.
[TGPP23720]
3GPP, "TR 23.720 v13.0.0 - Study on architecture
enhancements for Cellular Internet of Things", 2016.
[TGPP33203]
3GPP, "TS 33.203 v13.1.0 - 3G security; Access security
for IP-based services", 2016.
[fcc_ref] "FCC CFR 47 Part 15.247 Telecommunication Radio Frequency
Devices - Operation within the bands 902-928 MHz,
2400-2483.5 MHz, and 5725-5850 MHz.", June 2016.
[etsi_ref]
"ETSI EN 300-220 (Parts 1 and 2): 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", May 2016.
[arib_ref]
"ARIB STD-T108 (Version 1.0): 920MHz-Band Telemeter,
Telecontrol and data transmission radio equipment.",
February 2012.
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[LoRaSpec]
LoRa Alliance, "LoRaWAN Specification Version V1.0.2",
July 2016, <http://portal.lora-
alliance.org/DesktopModules/Inventures_Document/
FileDownload.aspx?ContentID=1398>.
[ANSI-4957-000]
ANSI, TIA-4957.000, "Architecture Overview for the Smart
Utility Network", May 2013, <https://global.ihs.com/
doc_detail.cfm?%26rid=TIA%26item_s_key=00606368>.
[ANSI-4957-210]
ANSI, TIA-4957.210, "Multi-Hop Delivery Specification of a
Data Link Sub-Layer", May 2013, <https://global.ihs.com/
doc_detail.cfm?%26csf=TIA%26item_s_key=00601800>.
[wisun-pressie1]
Phil Beecher, Chair, Wi-SUN Alliance, "Wi-SUN Alliance
Overview", March 2017, <http://indiasmartgrid.org/event201
7/10-03-2017/4.%20Roundtable%20on%20Communication%20and%20
Cyber%20Security/1.%20Phil%20Beecher.pdf>.
[wisun-pressie2]
Bob Heile, Director of Standards, Wi-SUN Alliance, "IETF97
Wi-SUN Alliance Field Area Network (FAN) Overview",
November 2016,
<https://www.ietf.org/proceedings/97/slides/slides-97-
lpwan-35-wi-sun-presentation-00.pdf>.
[IEEE-802-15-4]
"IEEE Standard for Low-Rate Wireless Personal Area
Networks (WPANs)", IEEE Standard 802.15.4, 2015,
<https://standards.ieee.org/findstds/
standard/802.15.4-2015.html>.
[IEEE-802-15-9]
"IEEE Recommended Practice for Transport of Key Management
Protocol (KMP) Datagrams", IEEE Standard 802.15.9, 2016,
<https://standards.ieee.org/findstds/
standard/802.15.9-2016.html>.
[etsi_unb]
"ETSI TR 103 435 System Reference document (SRdoc); Short
Range Devices (SRD); Technical characteristics for Ultra
Narrow Band (UNB) SRDs operating in the UHF spectrum below
1 GHz", February 2017.
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[nbiot-ov]
Beyene, Yihenew Dagne, et al., "NB-IoT technology overview
and experience from cloud-RAN implementation", IEEE
Wireless Communications 24,3 (2017): 26-32, June 2017.
Appendix A. Changes
[[RFC editor: Please remove this before publication]]
A.1. From -00 to -01
o WG have stated they want this to be an RFC.
o WG clearly want to keep the RF details.
o Various changes made to remove/resolve a number of editorial notes
from -00 (in some cases as per suggestions from Ana Minaburo)
o Merged PR's: #1...
o Rejected PR's: #2 (change was made to .txt not .xml but was
replicated manually by editor)
o Github repo is at: https://github.com/sftcd/lpwan-ov
A.2. From -01 to -02
o WG seem to agree with editor suggestions in slides 13-24 of the
presentation on this topic given at IETF98 (See:
https://www.ietf.org/proceedings/98/slides/slides-98-lpwan-
aggregated-slides-07.pdf)
o Got new text wrt Wi-SUN via email from Paul Duffy and merged that
in
o Reflected list discussion wrt terminology and "end-device"
o Merged PR's: #3...
A.3. From -02 to -03
o Editorial changes and typo fixes thanks to Fred Baker running
something called Grammerly and sending me it's report.
o Merged PR's: #4, #6, #7...
o Editor did an editing pass on the lot.
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A.4. From -03 to -04
o Picked up a PR that had been wrongly applied that expands UE
o Editorial changes wrt LoRa suggested by Alper
o Editorial changes wrt SIGFOX provided by Juan-Carlos
A.5. From -04 to -05
o Handled Russ Housley's WGLC review.
o Handled Alper Yegin's WGLC review.
A.6. From -05 to -06
o More Alper comments:-)
o Added some more detail about sigfox security.
o Added Wi-SUN changes from Charlie Perkins
A.7. From -06 to -07
Yet more Alper comments:-)
Comments from Behcet Sarikaya
A.8. From -07 to -08
various typos
Last call and directorate comments from Abdussalam Baryun (AB) and
Andy Malis
20180118 IESG ballot comments from Warren: nits handled, two
possible bits of text still needed.
Some more AB comments handled. Still need to check over 7452 and
8240 to see if issues from those need to be discussed here.
Corrected "no IP capabilities - Wi-SUN devices do v6 (thanks Paul
Duffy:-)
Mirja's AD ballot comments handled.
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Added a sentence in intro trying to say what's "special" about
LPWAN compared to other constrained networks. (As suggested by
Warren.)
Added text @ start of gap analysis referring to RFCs 7252 and
8240, as suggested by a few folks (AB, Warren, Mirja)
Added nbiot-ov reference for those who'd like a more polished
presentation of NB-IoT
A.9. From -08 to -09
Changes due to IoT-DIR review from Samita Chakrabarti: fixed error
on max rate between tables 1 and 2; s/eNb/eNodeB/; fixed
references to hong-6lo-use-cases; added RFC8065 reference
A.10. From -09 to -10
Added Charlie Perkins as contributor - was supposed to have been
done ages ago - editor forgot;-)
Author's Address
Stephen Farrell (editor)
Trinity College Dublin
Dublin 2
Ireland
Phone: +353-1-896-2354
Email: stephen.farrell@cs.tcd.ie
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