Objective. One of the main problems in e -health environments for developing an accurate multiuser identification is in the large number of patients, especially with itinerant medical devices and elderly people. This paper aims to contribute with two approaches to be included in ISO/IEEE 11073 family of standards as a standardized procedure for multiuser identification that can be used for a large variety of medical devices, regardless of their brand or model. From this contribution and to validate it, this work proposes a standardized e-health solution , including multiuser identification, implementing it in real health environments for elderly people , and evaluating their usability, interoperability , and adoption in daily living. Materials and Methods. This works implements the internationally recommended Personal Health Devices ISO/IEEE 11073 standards as a multiplatform environment (Windows / Linux / Mac OS) and fulfils the paradigms of scalability, modularity, portability, maintainability , and robustness. The standard e -health solution has been implemented in 26 health environments in several cities in Spain (Madrid, Barcelona, Sevilla, Zaragoza, etc.) , consisting of 118 health professionals, 319 senior patients , and 18 technical profession als. Results. The proposed multiuser identification reduces the human error rate (from 13.3% to less than 5 %) with positive evaluation: almost 70% of users are satisfied , with usability and time savings that are more than 50% in all the groups (nursing, me dicine , and caregiving) and environments (residences, health centres, and hospitals). Discussion. The use of e -health solutions within multiuser identification , as it is proposed through two standard-compliant approaches , permits advanced services and dat a analysis for a large variety of medical devices, regardless of their brand or model. Conclusion. This paper contributes an open interoperable e -health solution as alternative to the closed and commercial solutions and enables third -party developers to work collaboratively and extend the already implemented features , owing to the design based on plugins, value -added services , and multiple transport technologies and protocols. KEYWORDS e-health solution; elderly people; interoperability; ISO/IEEE 11073 standard; multiuser identification; wireless technologies. I. INTRODUCTION A ke y advantage of the application of e -health in health environments , such as hospital services, health centres, and residences for the elderly , is the improvement in healthcare quality owing to the reduction of human errors and time consumption caused by manual data acquisition and entry (patient identification, vital signs, samples, etc.) [1]. Recent studies [2] have show n that the most frequent errors in patient misidentification are due to missing wristbands (34%), incorrect charts or notes in files (20%), administrative issues (19%), and incorrect labelling (14%). Although a full elimination of such problems may not be possible, services based on e -health systems approach an error rate close to zero by employing automatized devices for data collection , instant communication with the centralized dat abase, and accurate information of their measurements, samples , or treatments [3]. In this multiuser context, the contribution of e-health solutions is especially useful for the correct identification of elderly people: follow -up of chronic diseases, digital management of residences, assistive technology, etc. [ 4]. Nowadays, patient identification is confirmed using several methods [5], [6] such as personal health card s, Radio Frequency IDentification (RFID) tags, or bracelet s with barcode s. There are several devices available in the market that can read the identification of the pati ent, including Patient Monitor M indray VS600 [7] and Philips SureSign family [8], among others. It is also noteworthy the initiative Health Level 7 (HL7): a set of standards to facilitate the electronic exchange of clinical information that uses a formal Unified Modelling Language (UML) notation and an Extensible Markup Language (XML) metalanguage. Within HL7, Fast Healt hcare Interoperability Resource (HL7 FHIR) is the specific standard for health care data exchange [9]. However, personal health devices pr esent a disadvantage because they are not completely plug -and-play , so they require standardized procedures to ensur e interoperability in communications [10]. In this conte xt, Personal Connected Health Alliance (PCH Alliance) is the main initiative in the world concerning patient/consumer -cent red health, wellnes s, and disease prevention [11]. Among the standards recognized by the global community (within PCH Alliance ), the international recommendation for interoperable communication among medical devices is ISO/IEEE 11073 [12]. ISO/IEEE 11073 includes several families of standards: Point -of-Care (PoC), focused on using wireless communication technologies for medical devices that exchange vital signs through information technology (IT) infrastructure; Service-oriented Device Connectivity (SDC), focused on defin ing an architecture for service -oriented distributed PoC medical devices and medical IT systems over web services; and Personal Health Device (PHD) , focused on evolving PoC and SDC with specif ic features for patient -centred environments . This PHD family is the object of this work due to its innovative functionalities of real-time monitoring, plug -and-play services and wearable technologies [13]. However, ISO/IEEE 11073 -PHD is not optimized for handling a large number of users, such as hospital services, health centres, or residences for the elderly, which is the focus of this paper. Ther efore, the adaptation o f ISO/IEEE 11073 -PHD for these e -health environments requires new approaches that ensure interoperability between medical devices, facilitate the transmission of i nformation safely , and ensure the reliability of communication , independently of brand or mode . Furthermore , the user -friendliness of these standard-compliant e - health solutions and their non-intrusiveness in the lives of patients are required acceptance criterion to verify adherence to the provided services and their adoption in daily livi ng [14]. Moreover, evaluation, not only from a technological scope but a usability and cost -effectiveness perspective, is a key element for the success of these contributions [15]. preprint · Wireless Standard-compliant e -Health Solution for Elderly People with Multiuser Identification 2 This pape r aims to c ontribute with two approaches to be included in ISO/IEEE 11073 family of standards as a standardized procedure for multi user identification (see Section II ) that is implemented in a wireless e -health solution (see Section I II). Section IV presents the results of the technical validation and user evaluation to assess its suitability for elderly people in multiuser environments. II. MULTIUSER IDENTIFICATION As previous ly mentioned , a key problem in standard -compliant e-health solutions is conducting unique identification in an environment with a large number of users and wireless medical devices that are carried by staff from room to roo m to take measurements from different patients . To solve this, it is necessary to ensure that the measurements taken with a medical device (with its identifier, Device ID) are safely associated with the patient identifier (Patient ID) to avoid errors and confusion . Because the internationally recommended standard s do not implement user identification systems, this paper proposes two approaches to build an ISO/IEEE 11073- compliant procedure for a standardized multi user identification . The first approach is to add an accessory th at the healthcare professional can use to identify the patient and associate the measurement device identifier (Device ID) with the Patient ID so that the information can be sent and sto red safely in an Electronic Health Record (EHR) server, as shown in Fi g. 1. This method is not fully compatible with ISO/IEEE 11073 but integrat es nonstandard medical devices by sending the P atient ID and Device ID using a nonstandard protocol and sending the measured data using an ISO/IEEE 11073- compliant protocol. Thus, with this first approach, the stages of identifying the patient and sending the information are designed to verify that the measured data is associated with the correct Patient ID, reducing the possibility of confusion and corruption of information . The steps are identified in Fig. 1 with parenthesis . First, the healthcare professional reads the tag of the patient and the tag of the medical device (agent) and connects to a mobile computing device acting as coordinator (manager) (1). Then, the agent se nds the patient identification data and checks whether the patient exists (2). Next, the professional takes the measurement, and the agent sends the data to the manager (3). To verify that the tags initially read are correct, the professional reads the tag of the patient and the tag of the device again (4), and the manager checks whether the new ID sent is the same as that sent in stage one (5) and, if it is the same, an acknowledgment is sent before disconnecting the device (6). This method verifie s that the measured data is associated with the correct Device ID and Patient ID. In this case, a n external Check Device ID (a n RFID wearable device) that can identify the medical device and the patient is necessary. Thus, the healthcare professional taking a mea surement would perform the following steps : first, read the tag of the patient with the RFID wearable device; second, read the label of the device; and third, take the measurement ( SpO 2, glucose level, blood pressure, etc .). Finally, the professional would read the tag of the patient again and the Device ID to confirm that the data acquired has been associated with the correct Patient ID. ID Check Device Medical Device / Agent Coordinator/Manager EHR Server Association Request Association Response (Connected) Data (System-ID | Patient-ID) Check (Patient_ID) DataResponse (Patient-ID) DataResponse (Patient-ID) Association Request Association Response Confirmed Event Report (Data) Acknowledgment (OK )Association Release Request Association Release Response Check Data RequestData (System-ID | Patient-ID) DataResponse (Patient-ID)Data (System-ID | Patient-ID) Compare (System-ID | Patient-ID)Acknowledgment (OK ) Association Release Request Association Release ResponseData ( System-ID, Patient-ID, measure, etc.)Must be check the ID of the Patient and the Medical Device Compare the first read of Patient-ID and System-ID with the Second Acknowledgment (OK )Read tags and connect (1) Check System -ID and Patient -ID (2) MD Send Data (3) Read tags again and send Ids (4) Check new Ids are de same than before (5) Release connection and Send data to EHR server (6) Fig. 1. Patient ID identification w ith an external Check Device ID preprint · Wireless Standard-compliant e -Health Solution for Elderly People with Multiuser Identification 3 The second approach is fully compatible with ISO/IEEE 11073, using a device that can read the Patient ID label, represented in Fig. 2, with the steps identified in parenthesis . The procedure can be conducted as follows: the medical device reads the RFID tag and stores the information within the Patient ID, inside its PM -Segment. When it connects to the server (1) and sends the unique Device ID, which is mandatory in ISO/IEEE 11073- compliant medical devices, the server queries the database to determine if the medical device is itinerant (2). If it is, the server requires sending the patient data (PM -sec-Person -ID in ISO/IEEE 11073- PHD) to the medical device (3). It later sends the measurement data (4), disconnects the medical device (5), and sends the data to the EHR Server (6). This method permits using the identification of the patient in itinerant devices , instead of the traditional method used on ISO/IEEE 11073, where a device is linked to a patient , and the system uses the unique Device ID for identifying the patient. Medical Device / Agent Coordinator /Manager EHR Server AssocRequest (System -ID, Dev-Configuration, etc.) AssocResponse (Accepted, DataProtoID, etc.) Check: SystemID, ConfigID Manager recognizes the System-ID and Dev-Configuration-ID Data (Response | Confirmed Event Report, etc.)Check if System is itinerant, if not go to step 4 (TRX) Data (System-ID) DataResponse (Itinerant) Check: ItinerantData (Invoke | Event Report, etc.) Data(Invoke | ConfirmedAction, obj-handle, MDC_ACT_SEG_TRIG_XFER, MDC_ ATTR_PM_SEG_PERSON_ID) Data(Response | Confirmed Action, obj-handle, MDC_ACT_SEG_TRIG_XFER, TrigSegmDataXferRsp) Data(Invoke | CfmEventReport, MDC_NOTI_SEGMENT_DATA, SegmentDataEvent) Data(Response | CfmEventReport, MDC_NOTI_SEGMENT_DATA, SegmentDataResult)Loop until all segment data transfered Data (Invoke | Confirmed Action, obj-handle MDC_ACT_SEG_CLEAR, MDC_ATTR_ PM_SEG_PERSON _ID) Data (Response | Confirmed Action, obj-handle MDC_ACT_SEG_CLEAR)Clear PM-Seg-Person-Id Association Release Request Association Release Response Data (System-ID, Patient-ID,measure ,etc.) Acknowledgment (OK )START Request Patient ID(Person-ID in 11073 PHD) END Resquest Patient IDConfirmed Event Report (data) Acknowledgment (OK )Connect (1) Check if itinerant (2) Send patient data (3) Send medical measurement data (4) Release (5) Send Data to Server (6) Fig. 2. Patient ID transmission when the RFID reader is included in the medical device preprint · Wireless Standard-compliant e -Health Solution for Elderly People with Multiuser Identification 4 III. MATERIALS AND METHODS The design criteria to respond to the challenges raised above include three key elements: wireless interoperability , security, and usability follow ing the ETSI Guide 202 487 guidelines [16]. The propose d ISO/IEEE 11073 -PHD architecture fulfils the paradigms of scalability, modularity, portability, maintainability , and robustness following a modularized architecture (detailed in Fig. 3) with three conceptual layers (Technology, Communications , and Application) , within two -harmonization shim layers (Transport and Protocol). The Application layer (upper area shown in Fig. 3 ) provides a us er interface to manage the state of the medical devices and other value -added services , such as events, notifications, messages , through the Protocol Harmonization layer. The Communication Layer (middle area shown in Fig. 3 ) implements the three -level ISO/IEE E 11073- PHD stack : Device Specializations ( ISO/IEEE 11073- 104zz), Optimized Exchange Protocol ( ISO/IEEE 11073- 20601) , and Transport Communications Protocols through the Transport Harmonization layer. The Technology Layer (lower area shown in Fig. 3 ) integrates several wireless technologies , such as Bluetooth (Health Device Profile, HDP), Near Field Communications (NFC PHD class) , and ZigBee (Health Care Profile, HCP), among others wired technologies such as USB (PHD class). As an example of the layer interaction workflow in a real operation, Fig. 4 details the connection procedure between an agent and a manager followin g ISO/IEEE 11073- PHD over Bluetooth HDP. This example shows the transitions between each architecture layer (in white colour ) and each harmonization layer (in grey colour ), within the state changes applied through the ISO/IEEE 11073 Communication Model. Thus, a manager is initially in a Disconnected state, where it does not process any data , only connection events. Then, when a connection event (Event.Connection) occurs, the manager moves to an Unassociated state. From this state, if the manager receives a message event (Associating Request) from the agent, both move to an Associating state, and after receiving the appro priate ISO/IEEE 11073- PHD configuration (SendingConfig) , if needed by the manager, they proceed to the Operating state to start exchanging medical data. Fig. 3. Proposed ISO/IEEE 11073 architecture based on a three- layer model (Technology, Communications , and Application within Transport and Protocol harmonization shim layers) includi ng the wireless protocol stacks COMMUNICATIONS LAYER APPLICATION LAYERUser Interface and other value -added services PROTOCOL HARMONIZATION LAYER 1073 -104zz Device Specializations-10404 Pulse Oximeter -10404 Pulse Oximeter -10404 Pulse Oximeter -10404 Pulse Oximeter -10404 Pulse Oximeter -10404 Pulse Oximeter -10404 Pulse Oximeter -10404 Pulse Oximeter -10404 Pulse Oximeter -10404 Pulse Oximeter -10404 Pulse Oximeter -10404 Pulse Oximeter -10404 Pulse Oximeter 1073 -20601 Optimized Exchange Protocol TRANSPORT HARMONIZATION LAYER Bluetooth HDProfileNFC PHD classZigBee HCProfileUSB PHD classASN.1Medical Device System (MDS) Service Model Finite State Machine (FSM)Communications ModelDomain Information Model (DIM) APDUs MDER BT moduleHCIGAP L2CAPSDPDIMCAP TECHNOLOGY LAYER preprint · Wireless Standard-compliant e -Health Solution for Elderly People with Multiuser Identification 5 Fig 4. Connection procedure between an agent and a manager following the ISO/IEEE 11073 -PHD standard over Bluetooth HDP Application Layer AssociatingISO/IEEE 11073 agent Protocol Harmonization Layer Event Connection Notification Communication LayerGUI 11073 -104zz Device Specialization 11073 -20601 Optimized Exchange Protocol Transport Harmonization Layer Transport Connect Indication Notification Technology LayerBluetooth HDP MDS Disconnected Technology LayerBluetooth HDP Transport Harmonization Layer Transport Connect Request Notification Communication Layer11073 -20601 Optimized Exchange Protocol Unassociated Transport Harmonization Layer Associating Request Notification Technology LayerBluetooth HDPMedical Data TransmissionOperatingOperatingISO/IEEE 11073 manager Bluetooth HDP 11073 -20601 11073 -104zzTransport Harmonization Layer GUIProtocol Harmonization Layer11073 -104zz 11073 -20601 Bluetooth HDPTransport Harmonization Layer Bluetooth HDP 11073 -20601 11073 -104zzTransport Harmonization Layer GUIProtocol Harmonization Layer11073 -104zz 11073 -20601 Bluetooth HDPTransport Harmonization Layer Configuring preprint · Wireless Standard-compliant e -Health Solution for Elderly People with Multiuser Identification 6 The proposed e -health solution was implemented in 26 health environments in several cities in Spain (Madrid, Barcelona, Sevilla, Zaragoza, etc.) , consisting of 118 health professionals, 319 senior patients , and 18 technical professionals with th is distribution : • 13 residences for the elderly . The participants were: - 67 health professionals in medicine, nursing, therapeutic care, physiotherapy, and psychology, among other specialities (45 women and 22 men aged between 29 and 59 years). - 183 seniors (105 women and 79 men) aged between 62 and 87 years. - 9 technical professionals such as residence staff . • 8 health centres . The participants were: - 34 health professionals of primary health specialities (21 women and 13 men aged between 35 and 61 years). - 74 seniors (43 men and 31 women) aged between 63 and 85 years. - 4 technical professionals of the health centres . • 5 hospital services. The participants were: - 17 health professionals in internal medicine, chronic diseases, etc. (11 men and 6 women aged between 41 and 58 years). - 62 seniors (35 women and 27 men) aged between 6 5 and 8 3 years. - 5 technical professionals of the hospitals . The evaluation was planned as a pilot study , where all of the participants were volunteers , who signed informed consent . All data of the participants and their interaction with the e -health solution were confidential and protected fulfilling the European Union EU 2016/679 General Data Protection Regulation (GDPR). The e-health solution contained all the technological elements detailed in this article (see Fig. 5): PCH Alliance -certified devices (AND UA- 767PBT -Ci blood pressure monitor [ 17], AND UC - 351PBT -Ci weighing scale [ 18] and NONIN 3150 WristOx2 pulse oximeter [ 19]) with wireless (Bluetooth HDP) technologies , multi user identificati on using RFID technologies , and standard e -health service s (as ISO/IEEE 11073 manager) implemented using tablet devices . When the e -health solution was installed in every health environment , a short training session ( 20 min) was performed, and all participants were using the service daily for 15 days. In all these scenarios, the evaluation methodology was performed using a QUIS questionnaire to assess not only the subjective satisfaction of the users but specific aspects of the human -computer interaction . All participants responded to the QUIS questionnaire. QUIS is an instrument developed by the Human -Computer Interaction Lab at the University of Maryland and internationally validated as an evaluatio n tool [20]. Version 7.0 incl udes a demographic questionnaire , questions regarding the technical knowledge of the user, a measure of overall system satisfaction along a 6-point scale , and measures of specific interface factors on a 9 -point scale. Furthermore, several ad-hoc questions were added to record specific information about the e-health solution using a 5-choice scale (more suitable for the elderly): “very much”, “much”, “indiff erent”, “little” and “very little” : - “Having the e -health solution in your work routine , could you perform your daily activities in complete normalcy?” - “Do you find the size and weight of the different elements of the e -health solution adequate?” - “Do y ou find battery life adequate?” - “Is it easy to correctly use medical devices ?” - “Is it easy to correctly use multiuser identificatio n tags?” - “If you have been moving with the e -health solution , do you find range coverage adequate?” ... among other specific que stions a bout medical devices, multi user identification, etc. Fig 5. ISO/IEEE 11073 -PHD e -health solution with PCHAlliance -certified devices over Bluetooth HDP and multi user identification through RFID technologies preprint · Wireless Standard-compliant e -Health Solution for Elderly People with Multiuser Identification 7 IV. RESULTS From a technical point of view, the propos ed ISO/IEEE 11073 -PHD architecture has been implemented as the multiplatform environment (Windows / Linux / Mac OS) , and their conformance s have been validated using the official Toshiba Bluetooth stack, certified by P CH Alliance . For verification of the standard communication (following the connection procedure detai led in Fig. 4 ), all connection attempts were captured for two weeks in the 26 health environments of the pilot study. For each case (in rows), Table I shows the success ratio (%) for every first attempt, second attempt, and the following attempts. The communication works correctly (on overage) 9 7.9% of the time (9 5.1% on the first attempt and 3 .0% on the second attempt) and only 1 .9% (on overage) of the connectio ns require more than 2 attempts . Because the results are equivalent regardless of health environments, hereafter, graphics are presented as average values of all health environments (indicating the particular deviations) . Regarding the verification of accuracy in the multi user identification , follow ing the ID transmission procedure detailed in Fig. 2, Table II shows different situations with one (1dev), two (2dev), three (3dev) , or four (4dev) medical devices and one (1mng) or two (2mng) managers i n the same coverage area. Before the pilot study, the daily routine showed th at 13.3% of human errors were due to manual data acquisition, in correct treatments , and inaccurate patient identification . The l ower rows (with 1 manager) show that errors due to the incorrect selection of other devices previously connected (in the ‘C’ row ) increase from 1.3 % (2dev) to 1 .9% (3dev). With only 1 device , there is no error because the previous device is always the same. Thus , errors due to no device being detected (in the ‘A’ row) are proportionally decrease d to the number of devices. Adding another manager (2mng) reduces the errors that are caused by missing a manager ( on average, from 1.0 ± 0.1 (1mng) to 0 .7 ± 0.1 (2mng), in the ‘B’ row ) but increases connection errors ( on average, from 1.3 ± 0.3 (1mng) to 1.9 ± 0 .5 (2mng) , in the ‘D’ row ) because of interference between managers . Adding more devices (with 2mng), connection errors (in the ‘D’ row) proportionally in crease ( regarding 1mng) by approximately 0.2% , and errors due to incorrect selection of previous devices (in the ‘C’ row ) slightly increase from 0.9% (2dev) and 1.6% (3dev) to 2.1% (4dev). T hese results show that the method proposed in this paper does not have significant errors or malfunctions (in all cases, malfunction errors are around 0.5– 0.6% , in the ‘E’ row ), and the method improves the accuracy in the multi user identification by reducing the error rate to 4.9% on average (less than 5 %). Table I. Success ratio (%) of standard communication Connection R01 R02 R03 R04 R05 R06 R07 R08 R09 R10 R11 R12 R13 1st attempt 95.6 96.0 95.6 95.3 95.1 94.1 94.3 95.8 94.8 95.2 95.3 95.2 95.7 2nd attempt 3.0 3.9 2.7 3.1 2.6 4.0 2.4 3.3 2.4 3.7 2.1 3.6 2.4 next attempt s 1.4 0.1 1.7 1.6 2.3 1.9 3.3 0.9 2.8 1.1 2.6 1.2 1.9 (a) Residences for the elderly: R01 to R13 Connection HC1 HC2 HC3 HC4 HC5 HC6 HC7 HC8 HS1 HS2 HS3 HS4 HS5 1st attempt 95.6 95.3 95.1 96.0 94.6 95.2 94.8 95.3 94.5 94.3 94.5 95.3 94.4 2nd attempt 2.2 2.8 3.1 3.3 2.3 3.3 3.0 2.3 3.1 3.7 3.4 3.1 4.0 next attempts 2.2 1.9 1.8 0.7 3.1 1.5 2.2 2.4 2.4 2.0 2.1 1.6 1.6 (b) Health Centres (HC1 to HC8) and Hospital Services (HS1 to HS5) Table II. Success ratio (%) of multiuser identification mean 1dev 1mng 2dev 1mng 3dev 1mng 1dev 2mng 2dev 2mng 3dev 2mng 4dev 2mng Success 95.1% 95.8% 95.2% 95.1% 95.3% 95.2% 95.2% 94.3% Errors 4.9% 4.2% 4.8% 4.9% 4.7% 4.8% 4.8% 5.7% A. no device 0.7% 1.3% 0.7% 0.4% 1.1% 0.6% 0.3% 0.8% B. no manager 0.9% 0.9% 1.0% 1.1% 0.6% 0.7% 0.8% 1.0% C. previous device 1.1% 0.0% 1.3% 1.9% 0.0% 0.9% 1.6% 2.1% D. connection errors 1.6% 1.6% 1.2% 1.0% 2.4% 1.9% 1.4% 1.2% E. malfunctions 0.6% 0.4% 0.6% 0.5% 0.6% 0.7% 0.7% 0.6% preprint · Wireless Standard-compliant e -Health Solution for Elderly People with Multiuser Identification 8 A summary of usability and acceptance of users , follo wing the first section of the QUIS questionnaire , is detailed in Table III. The general impression (terrible -wonderful axis) is really good (8.2 ± 0.7), practically all users rated the system higher or equal to 8 points. Results of ease (difficult -easy) of use and learn ing show that more than 75% of users find the solution easy to use (7 .6 ± 0.8) and even easier to learn (7 .9 ± 1 .3). Regarding the question s about whether the solution is stimulating (or dull) and flexible (or rigid), answers show that both ratings are acceptable, 5.7 ± 1.6 and 6.1 ± 1.9 , respectively . To analyse the power of the solution , questions were asked to rate the perceived speed and reliability, and the answers reveal an adequate power (7. 1 ± 1.4). Finally, almost 70% of users were satisfied with the solution , independently of their age, sex, educational level , and technological knowledge . To check the consistency of the questionnaires, Table IV details multiple results . More than 90% of users find the graphics and colours with much or very much adequacy. For the majority of users, the information format and the user identification seem “indifferent” and demonstrate the technology transparency as a positive point of the solution . Similarly , there is no clear preference between tablet s and smartphone s, although their p