Appropriate Integration of Wake-up Receivers in Simulations Tools

based on Real Experiments

Amina Whichi

1,2 a

, Robert Fromm

1 b

, Ahmed Fakhfakh

and Faouzi Derbel

1 c

Faculty of Engineering, Leipzig University of Applied Sciences (HTWK), Leipzig, Germany

Laboratory of Signals, Systems, Artiﬁcial Intelligence and Networks (SM@RTs),

Digital Research Center of Sfax (CRNS), Tunisia

Keywords:

Internet of Things (IoT), Wireless Sensor Network (WSN), Wake-up Receiver (WuRx), Ultra-Low Power

(ULP), OMNeT++, INET, Performance Evaluation.

Abstract:

Wireless Sensor Networks (WSNs) are an emerging and promising approach to Internet of Things (IoT).

However, energy consumption is regarded as one of the most critical problems in WSNs due to the devices’

limits.To address this problem, an ultra-low-power radio receiver known as a wake-up receiver (WuRx) is used

to handle idle listening while the main radio is turned off. Since simulators for performance prediction have

become almost indispensable in the design and management of new hardware equipment and components, we

will present in this paper the design of a wake-up receiver module, that could be a solution to the energy con-

sumption’s challenge, in OMNeT++ and compare it to experimental results, focusing on energy performance

and reliability factors.

1 INTRODUCTION

Wireless sensor networks (WSNs) have piqued the in-

terest of the scientiﬁc community in the last decade

and in the coming years, allowing us to realize

their numerous applications in disciplines such as

medicine, military, the environment, and academics.

WSNs are made up of hundreds, if not thousands, of

sensor nodes that are powered by batteries with lim-

ited energy (Cheour et al., 2013a), processing, stor-

age, and transmission capabilities. The sensor node’s

energy supply is limited, and the radio consumes a

signiﬁcant amount of the node’s energy (Nithyanandh

et al., 2017) and (Shabbir et al., 2017). When there is

no communication, the ideal approach in sensor net-

works is to put the radio into sleep mode to save en-

ergy. There are two primary groups in these works:

Duty-Cycling Media Access Control(MAC) protocols

(Shabbir et al., 2017) and wake-up receivers (Sadok

et al., 2016) and (Marinkovic and Popovici, 2011).

Duty-cycling is a simple method for conserving re-

sources and extending the overall network lifespan.

For a set period of time, the node will turn off its

transceiver, only to wake up periodically to determine

https://orcid.org/0000-0001-5168-683X

https://orcid.org/0000-0002-2905-0648

https://orcid.org/0000-0002-7038-8157

whether or not to receive the message. The goal of

this strategy is to reduce idle listening and, as a result,

power consumption when communicating with nodes.

Different MAC protocols have also been proposed for

this approach. Most provide the basic parameter of

duty-cycle, which speciﬁes the percentage of time a

node stays asleep and does not communicate.

Existing MAC protocols can be classiﬁed as syn-

chronous or asynchronous duty-cycling. The coordi-

nation of wake-up periods between neighboring nodes

is implied by synchronous duty-cycling. This enables

message exchange in agreed-upon time slots with no

additional interaction for each message. Coordina-

tion, on the other hand, usually implies a constant

overhead even when no messages are exchanged, also

this type of duty-cycling can present difﬁculty when

it comes to the synchronization. This coordination is

not used by asynchronous duty-cycling, which nego-

tiates medium access only when messages are to be

exchanged. In receiver initiated (RI) asynchronous

duty-cycling, nodes wake up from deep sleep on a

regular basis to check the radio medium. However,

in some cases this category of duty-cycling might

present a low reliability in some applications for ex-

ample the tracking and localization (Guidara et al.,

2019) , where the reference node can be unaware

about the presence of the target.

Whichi, A., Fromm, R., Fakhfakh, A. and Derbel, F.

Appropriate Integration of Wake-up Receivers in Simulations Tools based on Real Experiments.

DOI: 10.5220/0011012500003118

In Proceedings of the 11th International Conference on Sensor Networks (SENSORNETS 2022), pages 275-280

ISBN: 978-989-758-551-7; ISSN: 2184-4380

275

To overcome these short-comes, the wake-up ra-

dios that are triggered by events propose a solution to

the problem of idle listening. Wake-up radios previ-

ously published are characterized by low-power and

low-sensitivity (Sadok et al., 2016) and (Marinkovic

and Popovici, 2011). The WuRx uses far less power

than the main transceiver and only sends an inter-

rupt when a packet with a user-deﬁned address is re-

ceived. Embedding such a device allows for better

event-triggered applications where real-time behavior

and a longer lifetime are required. To evaluate the

new design where the WuRx is integrated for a WSN,

numerous trials with various representative scenarios

are required. Furthermore, in order to generate statis-

tically signiﬁcant ﬁndings, these tests should ideally

be repeated numerous times. Performing these stud-

ies in the real world takes a lot of effort and money.

As a result,a simulator should be used to test this pro-

posed design(Halkes and Langendoen, 2014). Sim-

ulators are a low-cost and quick approach to run a

large number of experiments with various typologies

and parameter settings(Cheour et al., 2013b).In other

words, Simulators can be utilized in research exper-

iments to get more ﬁne-grained results than similar

real-world investigations(Dwivedi et al., 2011). One

issue with simulators is that it is difﬁcult to demon-

strate that a simulation experiment matches a similar

real-world experiment. The goal of this contribution

is to look at how well simulation ﬁndings for the wake

up receiver module and the difference between simu-

lation and real-world results will be highlighted due

to different attenuation (Ketata et al., 2020) with the

help of experimental result.

2 RELATED WORK

Studies on wake-up receivers consist mainly of two

parts: Hardware development for low-power wake-

up circuitry and software development for networking

protocols that utilize wake-up receivers. The func-

tioning principles of the wake up receiver technolo-

gies proposed in the literature or available on the mar-

ket vary. The Wake up receiver concepts can be di-

vided into two types based on their energy sources:

passive wake up receivers, in which the wake up cir-

cuitry is triggered by an external energy source, and

active wake up receivers, in which the internal battery

is used to power the wake up receiver.

2.1 Hardware Development

There are commercialized wake-up receivers that can

use an active wake-up receiver to achieve low energy

consumption. For example, there is a three-channel

wake-up receiver on the market. It features three

types of power management: sleep, standby, and re-

ceive. Many of the channels are turned off in sleep

mode. In the receive mode, the channel’s correla-

tor is working and the channel scans the input signal

waveform for a correct wake-up pattern. After an ad-

justable timeout duration, the channel returns to its

standby mode if no feedback.

The current values presented in table 1 are for all

cases where there are three channels enabled.

Table 1: The current consumption of different WuRx in the

market [3].

Operating states Regulator on Regulator off

= 3 V V

= 2.4V

Sleep current 0.8 µA 0.3 µA

Standby current 7.0 µA 6.5 µA

Receiving current 7.2 µA 6.8 µA

There are further proposals for hardware based

on the super-regenerative principle (Joehl et al.,

2001). A second lower-frequency oscillator is used by

super-generative receivers to supply a single lower-

frequency oscillator. Six orders of magnitude for sys-

tem circuit proﬁts. This second oscillation interrupts

occasionally, the primary radio frequency (RF) oscil-

lation, which enables the steady buildup of the RF sig-

nal. Therefore, they make active wake-up receivers

that are very low-power. A prior study by Joehl et al.

(Joehl et al., 2001) presents an implementation of a

super-regenerative transceiver that consumes 3.6 mW

for a receiver sensitivity of −105 dBm, and the emit-

ter current consumption is 6 mA for 0 dBm output

power. Recently, a super-regenerative transceiver that

consumes 400 µW on reception and 1.6 mW on trans-

mission is proposed for wireless sensor networks by

(Otis et al., 2005). Also another study done by (Sadok

et al., 2016) presents a novel architecture to enhance

the WuRx sensitivity to be −60 dBm while consum-

ing 2.53 µA in channel monitoring and it is also able

to decode a 16 bit wake-up pattern.

2.2 Software Development

Although wake-up receivers offer numerous advan-

tages and are academically used in wireless sensor

networks, there are few media access control (MAC)

or routing protocols that support their use, and the

majority of available protocols are limited to simu-

lations. The current wake-up receiver protocols like

E2RMAC (Vivek et al., 2007), WUR MAC (Guidara

et al., 2019) , RTWAC [9] and GWRMAC (Karvonen

et al., 2014) support single hop contact only. Com-

pared to synchronous or asynchronous MAC proto-

EWSN-IoT 2022 - Special Session on Energy-Aware Wireless Sensor Networks for IoT

276

cols, these protocols indicate superior energy needs,

yet their efﬁciency is only focused on simulation data.

In (Miller and Vaidya, 2005) a loop using preamble

based synchronization between the transmitter and

the receiver is used. A triggered wake-up is often

speciﬁed, in addition to wake-up with preamble mes-

saging, in which each node wakes up once at dura-

tion T . In order to minimize the overall energy con-

sumption, the authors attempt to optimize the T val-

ues based on the given packet arrival rate. Since the

wake-up delay increases the data packets end-to-end

delay, a range of protocols are proposed to reduce

the wake-up delay experienced. One such protocol

is Latency Reduced Energy Efﬁcient MAC (LEEM)

and it is a reservation hop. head scheme (Dhanaraj

et al., 2005). The concept is to reserve the next

hop’s channel, that is, to wake-up the next hop in ad-

vance of the destination. To support broadcasting and

dedicated messages, each node in Radio Triggered

Wake-up with Addressing Capabilities (RTWAC) has

a unique and shared wake-up address. However, the

sole purpose of wake-up messages is to initiate an

event occurrence, such as a sensor reading at the re-

ceiver node. Data communication is realized by a

more common Carrier Sense Multiple Access with

Collision Avoidance (CSMA/CA) MAC protocol that

is not further speciﬁed, using the main radio. wake-up

receivers may be used as used in (Shah and Rabaey,

2002). Since it suggests a routing protocol. The ba-

sic MAC protocol is speciﬁed for sending on a ra-

dio station, a wake-up signal. The channel access is

CSMA/CA. The use of a similar approach is in (Shah

and Rabaey, 2002), where a MAC protocol incorpo-

rating CSMA and code-division is introduced by the

authors for multiple access (CDMA). A summary of

seven separate WuRx implementations was compiled

by (Marinkovic and Popovici, 2011). Their usage was

however, not in the area of WSNs, but in the region of

networks for Wireless Body Area (WBANs).

3 SIMULATION’S

ENVIRONMENT AND RESULTS

In order to get a better understanding for the power-

hungry processes inside each sensor node and to

prove the effectiveness of the WuRx-based commu-

nication, network simulations will be run. For verify-

ing, managing, and predicting the behavior of WSNs

in a controlled and reproducible environment, net-

work simulation is used as a powerful evaluation

methodology since it is featured by the ease of imple-

mentation, low cost and scalability. for this work, the

simulation tool that chosen is OMNeT++. this sim-

ulator supports multiple radio interfaces and multiple

channels and offers an easy access to change the phys-

ical layer properties which in our case was needed to

add the new WuRx interface. for the evaluation of

the new added module, we comapred it to two duty

cycling mac protocols X-MAC and B-MAC that are

predeﬁned in OMNeT++. in Table 2 , the different

power states values and the used parameters are pre-

sented.

Table 2: Simulation Parameter Set.

Approach Parameter Value

Carrier Frequency 868 MHz

Preamble Duration 0

Wake-Up Header Bit Length 0

Radio Antenna Type Isotropic

Bitrate 8000 bps

Modulation FSK

Protocol CsmaCa

Acknowledgements False

Receiving Power 7.5 µW

Carrier Frequency 868 MHz

Antenna Type Isotropic

Data Radio Transmitter Power 24 mW

Protocol CsmaCa

Acknowledgments True

3.1 WuRx Architecture in OMNeT++

Figure 1: New proposed model of the wake-up based node

in OMNeT++.

A new model was built and implemented into the node

structure in order to investigate the WuRx behavior

in our nodes. To put it in other words, the INET

node structure was kept with the exception of modi-

fying the wireless interface by adding a second one to

include the WuRx-necessary components and a con-

troller to manage communication between the data

Appropriate Integration of Wake-up Receivers in Simulations Tools based on Real Experiments

277

link layer, physical layer (both of which are regarded

as one in this work), and network layer. Figure 1 de-

picts the node’s new planned architecture. This model

is based on the research published in (Whichi et al.,

2021) . Basically, when evaluating WuRx nodes, the

main radio is managed by a Transceiver Controller

module, depicted as Control block in 1 which allows

the application to monitor and control the status of the

transceiver as is done in WuRx platforms

3.2 Simulation Results

Figure 2: Residual energy capacity in different scenarios.

Based on (Whichi et al., 2021), the scenario is a sim-

ple peer to peer communication where the main goal

was to compare the performance of the added mod-

ule with LPL protocols. to get a more reliable results

a physical environment was added to the network. At

the end of simulations, the WuRx module showed bet-

ter results on both aspects power consumption and re-

liability(number of received packets). compared to X-

MAc, the WuRx module consumed 37 % less power.

as in the case of the B-MAc protocol, the WuRx con-

sumed 90 % less energy. However, these results only

show the performance of the new structure with the

simulation environment and in order to evaluate the

module properly the same scenario should be con-

ducted using a WuRx hardware design. The following

section presents a set of experimental measurement

done using a BJT WuRx design done within our lab-

oratory.

4 EXPERIMENTAL

ENVIRONMENT AND RESULTS

The experimental measurements will be built up using

two sensor node ultilizing the MSP430G2553 where

one node is a transmitter and the other will just re-

ceive. The MSP430 is a series of ultra-low-power

mixed-signal microcontrollers. I also used a WuRx

implementation developed by (Fromm et al., 2021).

Figure 3: Building blocks of the WuRx-based sensor node.

The used WuRx implementation can be divided

into multiple building blocks. Figure 3 depicts the cir-

cuit’s block diagram. The antenna receives the trans-

mitted electromagnetic waves. They have a low am-

plitude, a high noise ﬁgure, and are usually affected

due interferences, reﬂection and diffractions. A band-

pass ﬁlter is typically used to pass only signals in the

appropriate frequency bands. However, in-band inter-

ferences between different systems operating in the

same environment are to be expected. The 868 MHz

band is employed in the proposed circuit by select-

ing an appropriate surface acoustic wave (SAW) ﬁlter.

This ﬁlter’s input and output impedances are typically

50 Ω (Fromm et al., 2021).

The experimental results were carried out inside

a laboratory.the measurements were carried using an

msp430G2553. To be able to measure the current the

following set up was set: A 1 Ω resistor was integrated

in the cable that was connected to our oscilloscope.

For the power we used a 3 V lithium battery.

4.1 Experimental Results

4.1.1 Experimental Results from WuRx

Figure 6 shows the graph of the current while receiv-

ing the wake-up packet. It is in the order of 12 µA,

based on the data sheet, which explains why the graph

is noisy.

Table 3: Comparison of currents while tranmission and

reception from datasheet, experiments and simulation for

Wupt only.

Results Transmitting Receiving

current current

Datasheet 21 mA 12 µA

Experimental 25 mA 12.57 mA

Simulation 23.1 mA 9.9 µA

In table 3 we present the comparison between

the simulation, Data sheet and experimental measure-

ments of the WuRx. These measurements intend to

evaluate the performance of the added module in OM-

NeT++. Due to the low value of the receiving current,

an ampliﬁer was used in order to be able to detect

EWSN-IoT 2022 - Special Session on Energy-Aware Wireless Sensor Networks for IoT

278

the signal. As shown in the table, both the receiving

and transmitted current is approximately the same as

the data sheet and experimental measurements. The

difference could be explained by the Various physi-

cal environment factors, such as scattering, reﬂection,

or diffraction, that can inﬂuence radio transmission

in conventional wireless communication systems. In

addition to that the transmitted signal could reach

the receiving antenna through Many paths (also see

known as multi-path propagation) as a result of some

obstacles that obstruct the Line-Of-Sight (LOS) path

as well as reﬂections from the physical environment.

These multi path components have different terms of

time delay and amplitude attenuation and phase shift

data (Liyanage et al., 2018). Though OMNeT++ has

a physical environment module that is implemented in

the different scenarios , the difference between simu-

lation and hardware still exists since it does not con-

tain all the attenuation that could be found in reality.

4.1.2 Experimental Results for the Node

This section presents our measurements using the

same set up mentioned in the previous section but

with a10 Ω resistor.

Figure 4: Current signal of the transmitter.

This ﬁgure 4 shows the current of the transmit-

ter during the 4 different states. The wake up packet

(Wupt) transmission, the active state, the Data trans-

mission state and the reception of the acknowledge-

ment. The current in the Wupt transmission is around

14 mA. This value could be explained by the fact

that during the transmission, the WuRx uses the OOK

modulation. Since the life cycle is 50 % we can

conclude that the value of the current should be (21

mA +7 mA )/2=14mA , where 21 mA is the current

while transmitting in +11 dBm and 7 mA is the cur-

rent while transmitting in -7 dBm. In the same graph

while it is ampliﬁed, a false detection of a Wupt can

be seen.

Figure 5: Current signal of the Receiver.

Figure 6: Detection of WuPt using an ampliﬁer.

In ﬁgure 5 the signal of the Receiver and its differ-

ent states were shown.the ﬁrst state is the data recep-

tion and it is of 10 mA value and the second state is

the transmission of the acknowledgement state and it

is of 17 mA. Figure 6 is the same ﬁgure but using the

ampliﬁer in order to detect the reception of the Wupt

that is in the order of 12 µA.

Figure 7: Bar chart with the different power consumption in

different states.

The ﬁgure 7 shows the different states in all the

different environments and the power consumption.

It can be seen that even between data sheet and exper-

imental results there is a deviation due to the different

Appropriate Integration of Wake-up Receivers in Simulations Tools based on Real Experiments

279

set ups where the measurements were done and dif-

ferent conditions. Also, the performance of the added

module in the simulation has a merge of error of 9

%.This could be explained by the lack of attenuation

and interference that occurs when carrying the exper-

imental measurements.

5 CONCLUSIONS AND FUTURE

WORK

In this work, an evaluation of a WuRx model in a sim-

ulation tool is presented. In order to have a full com-

prehension of the model performance, both the simu-

lation and experimental set ups were done under the

same conditions and using the same power parame-

ters and same message length at a carrier frequency of

868 MHz. Upon comparison of the results, the simu-

lation’s WuRx model showed a small divergence from

the results shown using the MSP430G2553. This

could be explained by the fact that in general the sim-

ulations, even with introducing environment models,

are still working without taking consideration of the

material quality, other machines interference, cables’

interference. To improve the results of the simula-

tion, a new model of a CPU will be built in order to

be able to introduce different parameters of different

boards. Also new environmental modules will be im-

plemented to ensure precise results.

ACKNOWLEDGEMENTS

This research was performed at Leipzig University of

Applied Science (HTWK). The authors would like

to thank the German Academic Exchange Service

(DAAD) and the European Social Fund for the ﬁnan-

cial support and their encouragement.

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