802.11ah LPWA Interworking - POSTECHdpnm.postech.ac.kr/netsoft2016/workshops/workshop3/802...2 Introduction LoRaWAN, IEEE 802.11ah Problem Definition and Existing Work 802.11ah –LoRaWAN

802.11ah LPWA InterworkingSoft5G, IEEE NetSoft, 2016

Mukesh Taneja

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Introduction

LoRaWAN, IEEE 802.11ah

Problem Definition and Existing Work

802.11ah – LoRaWAN Interworking: Proposals

Summary and Future Work

Agenda

Soft5G, IEEE NetSoft 2016

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Low data rate

High density of sensors

Low power

Multiple years of device operation on a single AA battery (assuming hourly reading from sensors

Wide area coverage

500 m and above

Limited mobility

Low cost networks, ….

LPWA Networks for IoT Applications

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LoRaWAN™

Weightless

3GPP NB-IoT, ….

SigFox

IEEE 802.11ah

….

Multiple LPWA (or similar) Technologies

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https://www.lora-alliance.org/

https://www.lora-alliance.org/What-Is-LoRa/Technology

https://www.lora-alliance.org/What-Is-LoRa/LoRaWAN-White-Papers

Note: Using LoRaWAN instead of LoRaWAN™ and LoRa instead of LoRa® in these slides.

Use LoRa Alliance website for exact information.

LoRaWAN

https://www.lora-alliance.org/

https://www.lora-alliance.org/What-Is-LoRa/Technology

https://www.lora-alliance.org/What-Is-LoRa/LoRaWAN-White-Papers

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LoRa GWLoRa GW

LoRa GW

LoRa Network

Server

(Cloud)

Tools / APIs /

Applications

LoRa end-devices

LoRaWAN Network

Architecture – A Simplified

View

Repeater

Note: Check LoRa Alliance website for exact information

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Class A Device – A Simplified View

LoRa

end-device

LoRa GW

Time

Ref: Adapted from https://www.lora-alliance.org/What-Is-LoRa/Technology


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Class B

Class B device opens extra (scheduled) receive windows in addition to two receive windows as opened by class A device

Requires time-synchronized beacons from GW

Gives more opportunities to send downlink data to sensor device

Class C

Always “on” device

LoRa - Class B or C Device


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Current WiFi

Contention based access

Performance limitations with high number of devices

Short range

802.11ah

Sub 1GHz

Range ~ 1 km

Support for large number of devices per AP

Low power operation

158 Kbps – 78 Mbps

IEEE 802.11ah


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Traffic Indicator Map (TIM) with current WiFi

AP indicates to end-device that it has data pending for it.

Enhanced..

Delivery TIM beacon

802.11ah

Scheduled (TIM devices)

Unscheduled operation (non-TIM devices)

IEEE 802.11ah (Contd.)


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Scheduled operation

Devices are divided into multiple groups

Devices can access medium only during specific Restricted Access Window (RAW) assigned to that block (or group) of devices

Unscheduled operation

802.11ah Operation


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802.11ah - Scheduled and Un-scheduled mode of operation


Ref: Adapted from

IEEE802.11ah. Refer to

spec for exact information

Problem Definition and SolutionDisclaimer: Opinions presented here are author’s own opinions.

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802.11ah and

LoRa LoRa only 802.11ah and

LoRa

802.11ah only

802.11ah and

LoRa coverageLoRa coverage

802.11ah and

LoRa coverage

802.11ah

coverage

802.11ah and LoRa device LoRa (only) device 802.11ah (only) device

A (Smart City) scenario considered in this paper


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A device could be operating in class A of LoRaWAN (type of) network. It may be receiving more frequent UL or DL data than usual and may want to switch to class B or C of LoRaWAN network.

Similarly, an 802.11ah device could be operating as a non-TIM station and its UL/DL communication behavior may change due to some events. It may need a different class to meet its communication requirements.

What is a good approach in such scenarios?

Problem I


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A device may want to change its class of operation due to more frequent UL / DL communication and may also be mobile at the same time.

New mode that this device wants may not be feasible (or desirable) in the new area where this device is moving.

Mobility management? Access network selection?

Problem II


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Consider an end device d, that is operating as LoRa class A device.

It tries to communicate more UL / DL data than what it is allowed to do.

Class AB:

Gives it more DL opportunities but not enough UL opportunities.

Class AC:

Network could be already supporting high number of class C devices

Device may have higher communication requirements than class A and class B but may not have sufficient data for it to require to move to class C

May also increase power consumption of this device more than what was needed to support its new communication requirements

Solution (Proposal) – Problem I


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If this device supports multimode 802.11ah-LoRaWAN functionality, we may want to switch this device from LoRaWAN Class A to a suitable class in 802.11ah.

No suitable class supported in 802.11ah for some scenarios

Defining operation for a new class in 802.11ah for some such scenarios

802.11ah Hybrid Mode

HybridMode-I and HybridMode - II

Solution (Proposal) – Problem I (Contd.)


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AP (knows that device d is operating in hybrid mode)

DL data

for device d

AP tries to

communicate

data to device

d. It buffers

this if it

can’t get

access to

channel

Beacon

includes

TIM IE

for device

d

TIM (RAW) Non-TIM

(PRAW or TWT)Unscheduled

- If any pending DL data at AP for this device after

RAW: device can get that during unscheduled and

PRAW / TWT periods and need not wait for next

RAW in the next DTIM beacon interval.

Beacon Beacon

TIM (RAW) Unscheduled

HybridMode device d

can continue to access

medium in the intervals

assigned for other blocks

or groups as well (as per

operator defined policies)

802.11ah – Hybrid Mode (as proposed in this paper)

End-device


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Enhanced Association Request

AP - supports TIM (RAW), non-TIM(PRAW), unscheduled and Hybrid Mode

Association Response

Device (station) x

With an indicator

that device is asking

to operate in 802.11ah

hybrid mode.

AP grants request for hybrid mode by

device x. Assigns a special AID, aidh, to

keep track that it is a hybrid mode device.

AP - supports TIM (RAW), non-TIM(PRAW), unscheduled and Hybrid Mode

Mode Change Request Mode Change Response

Device (station) x

Device asking to change mode

From TIM to HybridMode-I or

HybridMode-II

Device asking to switch to 802.11ah Hybrid Mode


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Introducing Access Network / Mode Selection and Resource Management (ANMSRM) module in 802.11ah – LPWA networks

ANDSF (used for LTE-WLAN interworking) could be enhanced

Helps to decide access network (e.g. LoRa or 802.11ah) and device class

Aids in improving resource utilization in these networks

Allows operator to implement various policies

ANMSRM


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802.11ah - LoRaWAN

end devices

802.11ah AP

LoRaWAN GWLoRaWAN GW

LoRaWAN Network

Server

802.11ah AP

WLC

ANMSRM

Module

1. Device d, working in LoRaWAN

Class A (or B) asks to allow switchover

to LoRaWAN class C

d

4. ANMSRM analyzes performance of device d,

other network nodes and end devices.

5. Asks device d to move to 802.11ah hybrid mode.

6. Device d evaluates and accepts the

response. It starts communication with

802.11ah AP using “hybrid” mode.

2a

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3. Sends request

to ANMSRM after doing

an initial assessment

2b

2a. LoRaWAN performance reports

2b. 802.11ah performance

reports

(via enhanced MAC or CoAP)

3

2a


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Solicited mode

For example, device may ask to move from LoRa Class A to Class B but the ANMSRM module may decide to move this to 802.11ah TIM (RAW)

Unsolicited mode

ANMSRM to consider performance reports dynamically and take decisions regarding access network and class of each device

Dynamically change durations of RAW, PRAW and unscheduled modes for 802.11ah network. Specify the DTIM beacon interval from where this change will be operational in the network.

ANMSRM (Contd.)


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Can also ask an end-device to join different RAT / class at the initial access time itself.

For example, if an end device tries to access 802.11ah network in TIM (RAW) mode, the ANMSRM module may ask the 802.11ah AP to indicate to end device in association response to use LoRaWAN Class B.

Suitable MAC layer objects can be added to convey such messages to end device.

ANMSRM (Contd.)


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We could have a device that sends small amount of data sporadically but may need to send lot of data on detection of certain events.

There could also be need to communicate high amount of data during software upgrade or configuration management.

Also, for delay sensitive applications, network may want to send some packets sooner than what is allowed by LoRaWAN or 802.11ah classes.

Aggregation (for dual mode devices)

802.11ah – LoRaWAN Aggregation


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802.11ah - LoRaWAN

end devices

802.11ah AP

x y

LoRaWAN GW

LoRaWAN Network Server

DL: Pkt1, Pkt2, Pkt3,

Pkt4, Pkt5, …..

DL: Pkt1, Pkt2,

Pkt4, ….

DL:

Pkt3, Pkt5, ….WLC

Aggregator Node

Aggregator node could be

a separate node or co-located

with WLC, 802.11ah AP or LoRa NS

UL802.11ah – LoRa Network Aggregation Architecture

DL Pkt k could correspond to application

layer protocol command (such as for

CoAP / UDP) or IP packet or MAC packet


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DTIM

Block1

DTIM

Block1

Block2 Block m

RAWm

Block2 Block m

RAWm

DTIM

Block1

DTIM beacon interval n

802.11ah AP

For buffered packets:

Aggregation module to

LoRaWAN NS

to end-device x(m)

802.11ah - LoRaWAN end device x(m)

802.11ah AP device x(m)

a b c d e

Send

via

802.11ah

Ack for successfully transmitted packets:

LoRaWAN NS Aggregation Module

Send via

LoRaWAN

Time

DL Aggregation


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802.11ah AP

(with aggregation module) LoRaWAN NS 802.11ah-LoRaWAN device x(m)

(802.11ah TIM, Block m)

a

RAWm

b

c

DTIM Beacon (from 802.11ah AP)

d

eRAWm

802.11ah AP sends DL packets to device x(m) belonging to block m.

802.11ah AP also asks device x(m) to activate LoRaWAN RAT with class C

Pending

DL packets for

device x(m)=Yes

Some packets (based on certain policies)

are sent from AP to LoRaWAN NS

NS 802.11ah AP: status of DL

packets for device x(m)

LoRaWAN NS sends these packets to device x(m)

LoRaWAN NS device x(m)

Status of DL packets

802.11ah AP device x(m)

LoRaWAN NS device x(m)

DL Aggregation for 802.11ah TIM mode device when LoRa Class C is activated


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Mobility for LoRaWAN Class B device

Idle mode mobility management for LoRa device

Mobility Management


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LoRaWAN Network

Server

LoRaWAN

GW a1

GW a2 GW a3 GW a5 GW a6 GW a7

Class B

device m

Class B

device mClass B

device m

UL

DL periodic slots for Class B device

No or limited collision(s) during these DL

slots as LoRaWAN NS can allocate these after

running a suitable resource allocation method

Higher chances of collision during these DL

slots as the device moves (as it could be an area where

there are already many devices of type B or C present)

GW a4

Location:

Loc1Loc2 Loc3

Mobility Management for LoRaWAN

Class B device

Soft5G,

IEEE NetSoft 2016

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LoRaWAN NS needs to detect that this device m is mobile.

Monitor the LoRa GWs through which it is getting UL data from device m.

If device is equipped with GPS, it can send information about its location.

LoRaWAN NS: Can it can keep providing expected service?

If there are several contending devices, it is indicated to ANMSRM

This module picks up dual mode devices and evaluates to see if some of these can be provided service with a suitable 802.11ah mode.

For example, it may move a Class B LoRaWAN device to 802.11ah with TIM (RAW) mode.

Mobility Management – Class B Device (Contd.)


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802.11ah module of

802.11ah-LoRaWAN end-device

Device moves

from location A to

B in idle mode.

802.11ah AP

(location A)

802.11ah AP

(location B)

Enhanced Association Request

(with id of LoRaWAN device, id of LoRaWAN

NS with which is communicated the last time,

optionally location coordinates of end device

if available and other parameters)

LoRaWAN Network

Server

If association successful – indicate

movement of end device,

provide location coordinates of

802.11ah AP (location B)

Association Response (success)LoRaWAN NS to use above to help identify

LoRaWAN GWs that can communicate

with that end-device and use this for

resource management

Idle Mode

Mobility

Management


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Summary

A framework that helps to decide suitable access technology and class of operation for dual mode 802.11ah – LoRaWAN devices.

New hybrid mode of operation for 802.11ah devices that can be used for “802.11ah-LoRaWAN” as well as “802.11ah only” networks.

Aggregation for 802.11ah – LoRaWAN type of networks.

Mobility management

Future work

Summary and Future Work


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Documents

802.11ah LPWA Interworking - POSTECHdpnm.postech.ac.kr/netsoft2016/workshops/workshop3/802...2 Introduction LoRaWAN, IEEE 802.11ah Problem Definition and Existing Work 802.11ah –LoRaWAN