Smartphone Applications for Indoor Real-Time Location Systems

(RTLSs) with Bluetooth Low Energy

Naoya Arisaka

, Noritaka Mamorita

and Akihiro Takeuchi

Graduate School of Medical Sciences, Kitasato University, Sagamihara, Japan

Department of Clinical and Rehabilitation Engineering Hokkaido Institute of Technology, Sapporo, Japan

Department of Medical Informatics, School of Allied Health Sciences, Kitasato University, Sagamihara, Japan

Keywords: Bluetooth Low Energy, Real-Time Location System, Smartphone Application, iPhone.

Abstract: The benefits of Hospital real-time location systems (RTLSs) have been characterized as increasing

efficiency and reducing operational costs. We developed iPhone applications for an indoor RTLS with

Bluetooth low energy (BLE) and evaluated the system in our laboratory rooms instead of on actual hospital

wards. The applications were installed in peripherals as tags on iPhone5s, centrals as access points (5th-

generation iPod touch pads or iPhone5s) placed in rooms in a concrete building, and a monitor as a server

on an iPhone5. The centrals and monitor were connected on a wireless LAN. Each peripheral communicates

with a central by BLE, and the centrals communicate with the monitor by sockets on TCP/IP. While

individuals with iPhone5s moved around in the building, the “access events” were captured in a few ten-

second units at about 10 m from a central. The monitor showed the access events with the peripheral

identifier and location, and interactively returned messages to the peripheral. A RTLS was simply created

with only iPhone applications using Bluetooth low energy without RFID tags. This system may effectively

be used as an indoor RTLS, patient tracking, and calling system.

1 INTRODUCTION

Real-time location systems (RTLSs) are local

systems for the identification and tracking of the

location of assets in real- or near-real-time (Fisher,

2012; Kamel Boulos, 2012; Lui, 2007). Although as

an outdoor RTLS, GPS (global positioning system)

has been quite successful, it fails to repeat this

success indoors (Kamel Boulos). Hospitals are often

large institutions, and personnel often find it difficult

to locate portable equipment and individuals when

necessary. Although it is hard to believe, this is

currently an actual problem.

RTLSs have been implemented and

experimented in hospitals to track tagged items and

individuals. The systems work by having a hardware

tag placed on a piece of equipment or an individual.

Tags communicate their locations through a network

of sensors that triangulates its position. The data

from this network are then mediated by a software

interface so that users can see a graphical

representation of the locations of all the tags on the

network or can search for a particular tag to locate a

piece of equipment or an individual (Carrasco, 2010).

When staff members require assets, they log onto the

system at a workstation or on a mobile device,

identify where the closest available item or

individual is located, and go and get it or the

individual. Hospital RTLSs can be used to improve

workflow, increase efficiency, productivity, and

staff and patients’ satisfaction (Carrasco, Kamel

Boulos).

However, the choice of hospital RTLS

technology must be made very carefully (Kamel

Boulos). Hospital RTLSs incorporate various types

of hardware with software interfaces (Fisher).

Although sensing a device may employ

radiofrequency identification (RFID), Wi-Fi, ultra-

wide band, infrared, ZigBee, Bluetooth, or

ultrasound, most systems in a surveillance study of

hospital RTLSs (Fisher) were RFID based. For

degree of accuracy, newer RTLSs offer improved

tracking capabilities, yet most of the systems

continue to fail at accomplishing room-level

accuracy (Fisher).

Bluetooth is the wireless technology standard

and has been exchanging data over short distances

from fixed and mobile devices, creating personal

Arisaka N., Mamorita N. and Takeuchi A..

Smartphone Applications for Indoor Real-Time Location Systems (RTLSs) with Bluetooth Low Energy.

DOI: 10.5220/0004722800850090

In Proceedings of the International Conference on Biomedical Electronics and Devices (BIODEVICES-2014), pages 85-90

ISBN: 978-989-758-013-0

 2014 SCITEPRESS (Science and Technology Publications, Lda.)

area networks (Heydon, 2012; Lui). Bluetooth has

been managed by the Bluetooth Special Interest

Group (Bluetooth SIG, 2013) and today exists in

many products, such as smartphones, tablets, pads,

media players, high definition headsets, watches, etc.

Bluetooth is also used in healthcare to real-timely

send biomedical data, e.g., heart rate, blood pressure,

temperature, electrocardiogram, photoplethysmo-

gram, oxygen saturation, energy expenditure,

location information, etc. (Kuroda, 2013; Amano,

2012; Lee, 2012; Nakamura, 2012). The data

generated in these devices are transmitted to

personal computers or other such devices via

Bluetooth.

Newer smartphones include “Bluetooth low

energy” and move with a tag or an individual. A

Bluetooth application could be created on a

smartphone/computer without a special hardware

device. Then the smartphone could be used as a

device tag instead of a special RFID tag of the RTLS.

In theory, an application on a smartphone can

interactively communicate with an application on a

smartphone/personal computer/tablet using the

Bluetooth low energy device. Because the Bluetooth

low energy protocol is not backward compatible

with the previous “Classic Bluetooth” protocol, it is

necessary to create/revise applications to capacitate

interactive communications.

To our knowledge, there are no studies of

hospital RTLSs using smartphones and Bluetooth

low energy in the PubMed database. PCs using

Bluetooth low energy are not yet commonly used as

sensor/beacon networks. Therefore, we have

developed an indoor RTLS with interactive

communication ability by only using smartphone

applications and confirmed the system’s usability in

our laboratory rooms instead of on actual hospital

wards. We hope that this study will serve as a guide

for developers of these types of applications and

help identify potential research problems and future

products.

2 MATERIALS AND METHODS

2.1 Bluetooth Low Energy

“Classic Bluetooth” was a wireless computer

network technology and designed to unite the

separate worlds of computing and communications,

linking cell phones to laptops. Bluetooth started with

Basic Rate with maximum Physical Layer data rate

of 1 megabit per second (Heydon). Enhanced Data

Rate was added in version 2.0 of Bluetooth to

increase the Physical Layer data rates to 3 Mbps.

The data rate in version 3.0 of Bluetooth increased

up to 54 Mbps. Bluetooth low energy is a subset of

version 4.0. However, Bluetooth low energy takes a

completely different direction and is intended to

provide considerably reduced power consumption

instead of increasing the data rate, currently

available is 0.3 Mbps. It can keep a connection up

for many hours or even days. The transmission

distance of Bluetooth low energy is a maximum of

50 m (160 ft).

For programming a communication application

with Bluetooth low energy, two users are

conceptually assumed: a peripheral and a central

(Apple Inc.). The peripheral typically has its own

original data that is needed by other users/devices.

The central typically uses the data served up by a

peripheral to accomplish some task. Peripherals

broadcast some of the data they have in form of

advertising packets over the air. Centrals can scan

for peripherals that they might be interested in.

When a central discovers such a peripheral, the

central can request to connect with the peripheral

and begin exploring and interacting with that

peripheral’s data. The peripheral subsequently

responds to the central appropriately.

2.2 System Overview

The system is generally made up of three kinds of

elements, tags for each item or individual, access

points, and a monitor on LAN (Figure 1). For

hardware, iPhone5s and/or 5th-generation iPod

touch pads are used without any microcomputer in

this system. The “peripheral,” “central,” and

“monitor” applications were installed in their

respective devices. Communication between a

peripheral and a central uses Bluetooth low energy.

Communication between a central and the monitor

uses sockets on TCP/IP with Wi-Fi.

Figure 1: System overview located in our building.

BIODEVICES2014-InternationalConferenceonBiomedicalElectronicsandDevices

Figure 2 shows communication events and

messages between applications. The monitor

provides continual service as a server and is always

ready to accept any connection requests from any of

the system’s clients. When the client/central is

powered on, it is automatically registered in the

monitor.

The peripheral and central search advertising

devices (advertise on) every 10 seconds with

Bluetooth low energy. When advertising between

the devices is established, the advertise turns off

(advertise off) and an event “connect” is

automatically pops up. These devices exchange

messages between themselves such as nickname and

UUID defined on the peripheral, ID and location

name on the central. The central also sends the

connection event to a monitor.

The monitor receives the event and displays the

event on a screen with additional information and

interactively returns certain responses and/or

comments to the particular central and peripheral.

When the peripheral moves outside of an access

point, an event “disconnect” notice is transmitted to

these devices. The peripheral resumes advertising.

2.3 Application on Peripheral, Central

and Monitor

Applications for peripheral, central, and monitor

provided information, where (access point), when

(discovered and disappeared), and who

( nickname/asset/nurse, etc.) or what (device ID/data

type/data/sensor device, etc.). These applications

were delivered from common master source codes

with Objective-C, Xcode 4.6.2, on a Mac Mini (CPU

Intel Core i7, 4GB, 1600M Hz, DDR3, OS X 10.8.4,

Apple).

The most important parts were communication

routines for Bluetooth and sockets on TCP/IP. The

Core Bluetooth framework handles low-level details

from the Bluetooth 4.0 specification. In the

central/client application, classes, and the methods

used were

: CBPeripheralManager,

updateValue, CBCentralManager,

scanForPeripheralsWithService,

CBPeripheral,write, read, etc. for Bluetooth,

and

NSNetService, NSFileHandle,

NSNetSeriviceBrowser, NSNetService,

write, etc. for sockets (Figure 3). A class

NSnotificationCenter

bidirectionally transmits

events and data between a central class and client

class. The peripheral and monitor applications were

subsets of the central/client application.

Because Bluetooth low energy was designed to

send a small amount of data, up to 20 bytes at once,

the transmission routines were devised to

send/receive long string messages. Errors that

occurred while handling the smartphones were the

unintentional pressing of functions on the touch

screen in pockets or bags, which was solved by the

use of double taps (Neubert, 2010).

Figure 2: Simplified sequence.

Figure 3: Application overview.

SmartphoneApplicationsforIndoorReal-TimeLocationSystems(RTLSs)withBluetoothLowEnergy

3 STATUS REPORT

The system was evaluated in a concrete building

instead of hospital wards (Figure 1). Applications

for centrals, as access points, were installed in

iPhone5s and 5th-generation iPod touch pads. These

devices were positioned on the second floor at a

lounge and the Medical Informatics, Biomedical

Engineering, and Clinical Engineering laboratory

rooms. The distances between these access points

were each about 30 m in a direct line of sight. A

person with an iPhone5 installed with a peripheral

walked around in the building. During the test walk,

the access events and response messages were

displayed on the smartphones and they were

captured in ten-second units.

Figure 4 shows a captured screen of the monitor.

A textbox on the top of the screen was used to set

the user’s own ID and to send a message, ex. “Hello,”

to a peripheral with the button, “Send Data.” The

message, “Hello,” was shown in peripheral screen

below. When the monitor got a request to connect

from a certain client, the monitor responded, “I

request your ID,” to each client at any time. In this

case, three “location IDs” were received

Figure 4: Captured screen of monitor.

sequentially: “Biomedical Engineering Lab,”

“Medical Informatics Lab,” and “Lounge.” The

corresponding messages were displayed on the last

two lines of the monitor screen, “Nicary in Lounge”

and “Nicary left Lounge.”

Figure 5 is a screen shot of an access point with

the ID, “Lounge.” A status bar on the top shows

active icons of Wi-Fi on the left side and Bluetooth

on the right side. The upper area of the screen was

for a client, and the lower area was for a central. The

client area showed the connection sequences, such

as “Search,” “Discovered,” and “Connect to the

monitor with TCP/IP in the local domain.” The last

three lines showed the access events that were sent

to the monitor, “Connected peripheral” and

“Disconnect.” The peripheral area showed

connection sequences in the central, such as

“Discovered peripheral,” “Connected,”

“Discovered,” ”Received MYDATA,” “Send myID

and Lounge,” etc.

Figure 6 shows a screen of the peripheral with ID,

“Nicary,” set on the top textbox. The second box and

the button were used to send a message to the

monitor. The peripheral was found by a central at,

“Biomedical Engineering Lab,” indicating that an

Figure 5: Captured screen of central/client.

BIODEVICES2014-InternationalConferenceonBiomedicalElectronicsandDevices

asset being tested might be near there or in the

Biomedical Engineering laboratory. The peripheral

moved out from the access point to “Medical

Informatics” with a message, “Hello,” from the

monitor and returned a message, “Hi!” It got to the

lounge.

The operating time of the peripheral device is

bound to the battery life of the smartphone. The

power consumption of Bluetooth low energy is not

defined in the Bluetooth specifications. The battery

level can be monitored in units of 5% with certain

APIs. The battery level during the use of the

application on a peripheral was measured hourly for

about 6 h. The results were compared with the

control in which an application was not used. The

battery levels in use and under control declined

linearly from 100% to 15% of the power over a 5-h

period (Figure 7). There were no significant

differences. There were no data under 10% because

of the compulsorily smartphone shut down at battery

levels of 10% or lower.

4 DISCUSSION

An RTLS could be constructed simply with only

smartphones without PCs, RFID tags, and their

sensor network. Three kinds of applications worked

well as an RTLS with a few devices. Although

peripheral, central and monitor applications could be

designed to communicate with two or more devices,

we should confirm how many devises could operate

completely as one system.

RTLSs are usually evaluated for accuracy,

however, the accuracy should be considered

according to the requirements of the system (Lui).

We assumed a room-level accuracy. The

transmission distance of Bluetooth low energy is

approximately 50 m but insufficient for indoor

RTLSs. However, the distances to locate assets can

roughly be controlled by monitoring the RSSI

(Received Signal Strength Indicator) in an

application. In the present study, the distance was set

at approximately 10 m in a direct line of sight. That

might be adequate to locate individuals and other

assets such as respirators and intravenous pumps in a

hospital. The battery level was kept for 5h with

Bluretooth low energy, in which means that the

application can be used for a few hours during

hospital stays for outpatients.

There are no Bluetooth low energy beacons or

sensor networks in hospitals yet. Because the access

point devices, smartphones, were placed on desks in

the present study, the system lacks the reality of an

actual hospital setting. If an application with

Bluetooth low energy like our central/client was

installed in the in the hospital PCs currently in use,

they could all function as Bluetooth low energy

beacons without any other additional devices.

Current health monitoring devices with

Bluetooth low energy are used to automatically

collect data from their system’s devices and send

data to their servers on the Internet (Lee, Neubert).

However, thedevices cannot find the asset “locations”

because there are no access points in any of the

Figure 6: Captured screen of peripheral.

Figure 7: The battery levels were measured hourly in use

and no use of the application.

SmartphoneApplicationsforIndoorReal-TimeLocationSystems(RTLSs)withBluetoothLowEnergy

rooms. When such devices can automatically access

beacons, these “locations” will become important

additional information, e.g., “Sports club” or

“Massage room,” or in the case of monitoring heart

rate and body temperature, e.g., “Sauna,” “Pool,”

“Day room,” or “Greenhouse.” This relatively

simple technology will be common in hospitals

world wide in the next few years.

In future works, two computer applications for

the access point and the monitor will be developed

and implemented on Mac usually working in rooms

to function as fix access points instead of personal

iPhones.

5 CONCLUSIONS

A RTLS was simply created with smartphones

installing applications using Bluetooth low energy

without RFID tags and its sensor network.

DISCLOSURE STATEMENT

The authors declare no conflict of interest.

ACKNOWLEDGEMENTS

The authors thank Robert E. Brandt (Founder, CEO,

amd CME of MedEd Japan) for advice on the

English language in the preparation and editing of

this manuscript.

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