Wireless Access Technologies: IEEE. 802.22/WRAN and IEEE 802.16/WiMAX. Roberto Magana-Rodriguez, Salvador Villarreal-Reyes*, Alejandro Galaviz-.
Telemedicine Services over Rural Broadband Wireless Access Technologies: IEEE 802.22/WRAN and IEEE 802.16/WiMAX Roberto Magana-Rodriguez, Salvador Villarreal-Reyes*, Alejandro GalavizMosqueda, Raul Rivera-Rodriguez and Roberto Conte-Galvan CICESE Research Center, Electronics and Telecommunications, Ensenada, México {rmagana,svillar,agalaviz,rrivera,conte}@cicese.edu.mx
Abstract. Telemedicine services represent restrictive applications mostly dedicated to consultation, diagnosis and monitoring of patients through their biomedical signals by health specialists. Since wireless telemedicine services depend on technological infrastructure, rural area coverage has been considered an important challenge, and the Institute of Electrical and Electronics Engineers (IEEE) 802.16/WiMAX standard has been used to provide broadband wireless access (BWA) because of its MAC and PHY characteristics. However, the switch-off of the analog terrestrial network presents the opportunity of delivering high data rates over large coverage areas by means of TV white spaces (TVWS) technology using cognitive radio capabilities. Hence, at the end of 2011 the IEEE Working Group for Wireless Regional Area Networks (WRAN) released the first TVWS standard named 802.22. Within this standard bandwidth availability depends on the geographical location of the base station (BS) and the customer premise equipment (CPE).Therefore, a model to evaluate the suitability of IEEE 802.22 and WiMAX for the deployment of rural telemedicine networks is proposed. The model considers specific traffic profiles based on the telemedicine services that will be offered over the rural wireless telemedicine network. The evaluation presented in this chapter is performed by calculating the number of telemedicine services that IEEE 802.22/WRAN and IEEE 802.16/WiMAX networks can support considering the available bandwidth and the telemedicine traffic profiles requirements. Frame preambles and a MAC/PHY overhead factor per active connection are considered within the analysis. Furthermore an example based on the state of Chiapas, Mexico, is presented as a case of study for the deployment of wireless rural telemedicine networks based on the IEEE 802.16/WiMAX and IEEE 802.22/WRAN standards.
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1 Introduction Traditionally, medical practice services are based on patient consultation, diagnosis and follow-up scheme. These services involve several methods and specific medical instruments that require the patient presence to treat multiple health conditions. In this context, recent technological advances not only have provided health professionals with new methods and instruments to assist them in the evaluation and decision making process, but also have provided them with new communication methods that allow reaching patients located in remote sites. This method of reaching and interacting with patients through communication technologies is known as Telemedicine. Telemedicine involves the use of information and communications technologies (ICT) to deliver medical information related to health services from one location to another [1]. Thus, telemedicine implies the distribution of medical services, traditionally offered in a face-to-face consultation, by means of telecommunications technologies [2]. The use of ICT for clinical activities has been increasing in recent years, as a consequence of the rapid development that has provided diverse technological solutions (e.g. mobile telephony, voice over IP (VoIP), video streaming, digital imaging, etc) that can be used for the delivery of health services. The medical services offered by telemedicine can be classified as: teleconsulting, telemonitoring, telediagnosis, teleeducation and medical database access [3]. Furthermore, according to [4] telemedicine applications include: initial patient evaluations, triage decisions, surgical follow-up, routine consultation or second opinion (primary care encounters), medical imaging, public health, preventive medicine and patient education. There are three main factors to consider when planning a telemedicine deployment: the medical application scenario, the medical services requirements, and the ICT infrastructure. In fact, when the telemedicine deployment considers the use of already available telecommunications infrastructure, the kind of telemedicine services that can be offered will be limited by the capacity of the network (or networks) connecting the sites. As a consequence of this, the variety and number of telemedicine services offered in urban areas are larger than those offered in rural areas. Currently there exists an unequal distribution of medical services between urban and rural areas, [5]. In fact, providing traditional medical services in rural regions faces several challenges such as: mobility issues, poor technological infrastructure, large travelling times and natural geographical barriers among others, [6]. Thus, the use of telemedicine (which includes mHealth) represents an opportunity to provide rural regions with health services that otherwise would not be available. Rural telemedicine implies the use and/or deployment of telecommunication networks to deliver medical services in underserved, isolated and sparsely populated areas. In this matter, long range broadband wireless access (BWA)
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technologies present a feasible solution for the implementation of telemedicine and mHealth services in rural areas.
1.1 Metropolitan and Rural Area Broadband Wireless Access Technologies The exponential growth of wireless networks has been a key factor in the development of mHealth technologies. Wireless networks can be categorized according to their maximum coverage area into: wireless local area networks (WLANs), wireless wide area networks (WWANs), wireless metropolitan area networks (WMANs) and wireless regional area networks (WRANs). WWANs and WLANs are the most widely adopted technologies and are able to deliver peak data rates in excess of 100 Mbps (e.g. LTE and IEEE 802.11n), [7]. However, the coverage area of WWANs and WLANs may restrict its use as a standalone solution for the implementation of rural telemedicine and mHealth services. Thus, the use of WMANs and WRANs seems to be more suitable for the deployment of rural telemedicine and mHealth solutions, as it will be discussed throughout the chapter. In the next paragraphs two BWA technologies suitable for rural scenarios are introduced. The Institute of Electrical and Electronics Engineers (IEEE) 802.16 task group has been developing a family of standards for WMANs since 2001, which resulted in the IEEE 802.16 standards family, [8, p. 16]. Similar to the WiFi Alliance with the IEEE 802.11 family of standards, the Worldwide Interoperability for Microwave Access (WiMAX) forum released a certification based on IEEE 802.16 standards for WMANs. The certification aim is to guarantee technological interoperability between different IEEE 802.16 equipment vendors. With the release of the IEEE 802.16m standard in 2011 (known as mobile WiMAX release 2), the IEEE 802.16 family of standards included both fixed and high-speed mobile wireless services. The IEEE 802.16/WiMAX standard provides coverage ranges of up to 50 kilometers for line-of-sight (LOS) and up to 24 kilometers for non-line-ofsight (NLOS) transmissions. Therefore it is considered a suitable technology to cover rural areas and a feasible solution to serve as a backbone network over a backhaul infrastructure. In contrast to fixed WiMAX, the IEEE 802.16m standard supports mobility and is fully capable of serving dense urban areas with a coverage ranging from 5 to 15 kilometers for NLOS transmissions. This version of the standard provides peak data rates of up to 70 Mbps, [9]. Through the adoption of quality of service (QoS) and scheduling mechanisms, WiMAX is able to support time constrained transmissions such as: multimedia streaming, real time surveillance, VoIP, and multimedia conferencing, [10]. As previously mentioned, the WRANs represent another alternative to enable BWA in rural areas. A recent trend for the implementation of WRANs is the use of cognitive radio networks (CRN) technology. The aim of a cognitive radio net-
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work is to be able to transmit in unused frequency bands commonly assigned to other technologies or services on a non-interference basis. This is achieved by means of active spectrum sensing, such that when a frequency band is found to be free the CRN will use this band to transmit information. The active sensing must be kept while exchanging information within the CRN, such that when transmissions from primary users are found the CRN will cease its transmissions releasing the frequency band. The analog switch-off towards the migration from analog to digital television broadcasts, presented an opportunity for the development of WRAN solutions operating over frequency bands previously used by analog TV transmissions. These frequency bands are commonly referred as TV white spaces (TVWS). Thus, because of the notice of proposed rule making (NPRM) issued by the United States Federal Communications Commission (FCC) regarding unlicensed operation in TV broadcast bands (i.e. TVWS), the IEEE formed the 802.22 working group to develop the first cognitive radio WRAN standard. As a result, the IEEE 802.22 standard was released in 2011, [11, p. 22]. The IEEE 802.22 standard supports fixed and mobile stations considering both LOS and NLOS transmissions with the aim of providing BWA to suburban and rural areas. This standard provides a maximum transmission range of up to 100 kilometers delivering peak data rates of up to 22.69 Mbps per channel. Therefore the IEEE 802.22 standard doubles the coverage range of similar BWA technologies such as IEEE 802.16/WiMAX. A major contribution of the IEEE 802.22 standard is the inclusion of cognitive radio capabilities, which enable IEEE 802.22 networks to operate as secondary users in TVWS frequency bands. Thus, according to the FCC rules, the IEEE 802.22 transceivers must actively perform spectrum sensing to avoid or stop using frequency bands found to be occupied by transmissions from primary users, particularly digital/analog TV transmissions and Part 74 broadcast auxiliary services (i.e. wireless microphones). Both technologies, IEEE 802.16/WiMAX and IEEE 802.22/WRAN, aim to offer wireless data services for fixed and mobile users comparable to those offered by wireline networks. Thus, both standards can be considered as emerging long range BWA technologies, [6].
1.2 Telemedicine Services over Metropolitan and Rural Area Broadband Wireless Access Technologies A basic telemedicine deployment generally involves data acquisition from patients, transmission, processing and, depending on the offered services, remote storage. To be effective, any telemedicine solution must consider the QoS and bandwidth requirements for the different telemedicine services included within the deployment. Thus, in order to be a suitable alternative for the implementation of rural telemedicine networks, a particular BWA technology must be able to satisfy the QoS, bandwidth and transmission range requirements of the network. In this
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chapter the feasibility of using the IEEE 802.22/WRAN and IEEE 802.16/WiMAX standards to deliver rural telemedicine services is studied. It has been shown that the IEEE 802.16/WiMAX standard presents a viable solution for the deployment of telemedicine and mHealth services, [12]–[29]. The proposed mHealth applications cover different scenarios and can be categorized as: accident, clinical care and home care, [12], [13]. In [14] and [15] the authors implemented a telecommunications backbone from a local clinic to a hospital using WiMAX. The network aim was to support a medical information system (MIS). The MIS provided remote locations with telemedicine services such as: expertise sharing between physicians; remote consultations; access to laboratory analysis and tests results for physicians; access to a medical scientific website; and an appointment scheduling application for patients. An integrated system using a heterogeneous network architecture with WiMAX and WLANs was proposed in [16]. The aim of the system was to deliver mHealth services such as: patient monitoring, medical data access, emergency and pre-hospital care. In a different perspective, [17] introduces a mapping from multiple mHealth services parameters to mobile QoS variables in WiMAX. In contrast, [18] proposes a particular WiMAX dynamic subframe allocation for the support of mHealth services. Both proposals aim to enable telemedicine services under clinical care, home care and emergency scenarios. The development of telediagnosis services for ambulances has received particular attention, because of its potential for improving the survival rate of patients in emergency situations. Typically, an emergency scenario requires providing realtime communications capabilities in order to support the transmission of biomedical signals, voice and/or video, all of them in real time. Providing these capabilities will enable the provisioning of services such as: pre-hospital care, remote assistance, second opinion to paramedics, etc. Different telemedicine and mHealth emergency systems such as WiMAX extensions for remote and isolated research data networks (WEIRD), [19], [20], Emergence Wi-Medicine (EWM), [21], and Focused Assessment with Sonography for Trauma using Tele-echography (FASTele), [22], have been developed as integral systems based in WiMAX technologies. The WEIRD project includes applications for remote diagnosis, monitoring and follow-up in general telemedicine scenarios,. EWM tries to improve hospital admission times through enhanced videoconferencing services. This is achieved by modifying the maximum video bit rates over a WiMAX platform, [21]. The FASTele project uses WiMAX technology to provide a wireless link between an ambulance and a hospital. This link is used by a physician located in the hospital to remotely control a portable and attachable tele-echography robot system, [22]. Other proposals focus in modifications to the IEEE 802.16/WiMAX standard in order to transmit high quality video images from ultrasound devices in emergency situations, [23]–[25]. In [23] a cross-layer approach based on region of interest (ROI) algorithms and resource allocation mechanisms are used to guarantee QoS parameters in the transmission of ultrasound video data. Another approaches consider the use of H.264/advanced video coding (AVC), [24, p. 264], or
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high-efficiency video coding (HEVC) standards, [25], to enable the transmission of high resolution ultrasound video with quality comparable to the in-hospital examination standards. Another telemedicine and mHealth area that has drawn a lot of attention is the development of telemonitoring systems for home care scenarios. These systems look to transmit the patient’s biomedical signals to enable health specialists to evaluate his/her health status. In this context, WiMAX and IEEE 802.22 can fulfill the requirements specified in [26] to enable extra-BAN communication for mHealth applications. For example, in [27] a telemonitoring system framework based on WiMAX technology for chronic hypertension patients is proposed. Although all the previously mentioned projects show that WiMAX is viable technology to implement telemedicine and mHealth services, its coverage range below 50 kilometers may represent a drawback for its deployment in certain rural scenarios. In fact, deployment of telemedicine services in scarcely populated areas with urban centers separated by long distances may require the use of broadband satellite communications (BSC), leaving the use of WiMAX as a wireless last mile solution, [28]. However, a drawback with a BSC solution is the operational cost. Therefore, an alternative solution could be the deployment of wireless telemedicine networks based on the IEEE 802.22 standard. Theoretically this standard could double the coverage range offered by WiMAX. The IEEE 802.22 standard defines a CRN technology that uses an opportunistic spectrum access scheme. Consequently, QoS provisioning as required by telemedicine and mHealth networks may present a major challenge. Nevertheless, in [29] it was shown that, by designing resource allocation methods for urgent and periodic traffic profiles, the CRNs are a suitable technology for wireless telemedicine implementations. A performance evaluation of both, the IEEE 802.22/WRAN and the IEEE 802.16/WiMAX standards, is carried out in this chapter in order to assess its suitability to provide rural telemedicine services. Thus, Section 2 provides an overview of both standards. Section 3 introduces a wireless telemedicine model for rural areas. Performance evaluation results obtained using this telemedicine model are provided in Section 4. Finally, the conclusions are presented in Section 5.
2 IEEE 802.22/WRAN and IEEE 802.16/ WiMAX Standards Overview An overview of the physical (PHY) and medium access control (MAC) layers of the IEEE 802.22/WRAN and IEEE 802.16/WiMAX standards is provided in this section. The section ends with a summary of the main parameters that must be considered for the deployment of rural telemedicine networks using these technologies.
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2.1 IEEE 802.22/WRAN The IEEE 802.22 air interface includes 50 channels from 54-698 MHz in USA and Canada. A total of 60 channels with 6 MHz bandwidth from 47-862 MHz are considered for Western Europe. Additionally, for other countries in Africa, Asia and the Pacific bandwidths of 7 MHz or 8 MHz per channel are contemplated. A single air interface based on 2048 carriers orthogonal frequency-division multiple access (OFDMA) is used to provide a reliable link for NLOS operation in a single time-domain duplex (TDD) mode. Because different channel delays must be supported, four different lengths of cyclic prefix defined as 1/4, 1/8, 1/16 and 1/32 are considered. The standard includes an adaptive modulation and coding (AMC) scheme defined by the PHY layer description. The AMC considers the quality variations in the wireless link (caused by fading, interference, etc.) to provide enhanced data rates between a base station (BS) and a customer premise equipment (CPE). Therefore, the use of quaternary phase shift keying (QPSK), 16-quadrature amplitude modulation (16-QAM) and 64-quadrature amplitude modulation (64QAM), with four coding rates (1/2, 2/3, 3/4, 5/6) for each OFDMA subcarrier are considered in IEEE 802.22 to provide robustness over time variable wireless links. The MAC layer includes cognitive capabilities for a reliable protection of primary users (PUs) in TVWS frequency bands and to enable self-coexistence between IEEE 802.22 networks located nearby. The frequency bands used by an IEEE 802.22 cell will depend on the TV channels availability which is inherent to the geolocation of both the BS and CPE. Additionally, the use of frequency bands by the BS and the CPE will be restricted by Part 74 device broadcast transmissions (i.e. narrowband primary users -NPU- like wireless microphones). Therefore, the cognitive capabilities of IEEE 802.22 networks rely on their capacity to detect the primary users (PUs – TV transmissions and NPUs) over all the possible operational channels. Thus, the CPE and the BS will be forced to stop any transmission in channels where PUs are detected. In case a CPE detects a PU it will notify the BS via an urgent coexistence situation (UGS) message. Then, an incumbent detection recovery protocol (IDRP) will be performed such that the BS will reallocate the CPE transmissions to a backup channel. In case the BS detects a PU, it will run the IDRP to reallocate all the transmissions from the CPEs that were using the channel where the PU was found. The IEEE 802.22 standard includes a normal operational mode, where one WRAN cell transmits over an entire channel using all the available frames merged into a superframe. Additionally, a self-coexistence operational mode is considered in the standard. This operation mode aims to coordinate transmissions from multiple WRAN cells by assigning one or several frames to one particular WRAN. The self-coexistence mode uses a coexistence beacon protocol (CBP) operated by BSs detecting concurrent transmissions from other WRANs. The CBP protocol requires broadcasting a packet containing BS identifiers through a dedicated self-
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coexistence window (SCW). This facilitates network discovery, coordination and spectrum sharing. The IEEE 802.22 systems use a connection-oriented protocol to exchange information between the BS and the CPEs. This protocol allows the CPEs to request particular bandwidth allocations from the BS in a dynamic fashion. However, as granting all the bandwidth allocations requests from different CPEs may consume all the available system resources, the BSs must decide how to assign resources to a particular CPE. There is not a pre-defined way to perform this, leaving the resource allocation scheduling as an open issue. Commonly, the scheduling algorithms look to provide a certain degree of fairness regarding resource allocation to CPEs. However, in the case of telemedicine networks an “unfair” scheduling algorithm that prioritizes the traffic generated by telemedicine and mHealth applications may be required. In addition to cognitive radio capabilities, the IEEE 802.22 MAC layer includes geolocation operations, channel database access and spectrum sensing initialization. These functionalities are needed for synchronization, ranging, capacity negotiation, registration and connection setup authorization processes. The BSs and the CPEs use satellite-based geolocation technology to perform two main tasks: synchronization with other WRAN networks through a global time source; and verification of unused TV channels on the region by referring to an up-to-date database. Nevertheless, regardless of the channel status (used or unused) registered in the database, the spectrum sensing function must be performed by both the CPEs and BSs. The IEEE 802.22 standard provides three types of QoS schemes: unsolicited grant service (UGS), polling service (PS) and best-effort service (BE). These schemes support constant bit rate (CBR) and variable bit rate (VBR) traffic to enable real and non-real time transmissions. The UGS service is designed to carry CBR traffic where fixed-size data packets are transmitted periodically. Thus, the BS will reserve the required resources (if available) to support CBR traffic transmissions from the CPE with the aim of reducing the negative effects of delay and jitter. The PS service offers two service subtypes supporting two kinds of VBR traffic: real-time and no real-time. These service subtypes are called real-time polling service (rtPS) and non-realtime polling service (nrtPS). The rtPS service supports the transmission of real-time data streams by dynamically assigning system resources based on the QoS requirements. Contrary to rtPS, the nrtPS service just assigns a minimum bandwidth that can be used for the transmission of no realtime data streams. Lastly, the BE service does not guarantee any QoS, since its bandwidth allocation depends on the policies used for the other service types. Because of the QoS schemes included in the IEEE 802.22/WRAN standard, it seems to be a viable technology for the deployment of wireless telemedicine networks. Nevertheless, an open research issue for the implementation of IEEE 802.22/WRAN telemedicine networks is how to deal with possible throughput drops caused by sporadic PU transmissions (detected by either the BS or the CPEs).
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2.2 IEEE 802.16/WiMAX The air interface of IEEE 802.16/WiMAX operates at unlicensed spectrum between the 2-11 GHz frequency range or licensed spectrum between the 10-66 GHz frequency range. For NLOS scenarios IEEE 802.16/WiMAX supports two different air interfaces at the PHY layer: OFDM and OFDMA, [30], [31]. Furthermore, the IEEE 802.16e includes a scalable OFDMA (S-OFDMA) air interface. The standard supports channel bandwidths ranging from 1.5 MHz to 20 MHz. Additionally, it considers the use of adaptive modulation and coding (AMC). Thus, the modulation and coding schemes employed in each OFDM subcarrier are set based on a link quality indicator. The standard includes a connection oriented MAC layer definition to support different types of QoS. Hence, the MAC protocol considers an unidirectional connection for all transmissions between BS and mobile station (MS), [32]. The standard defines two medium access schemes: time division duplex (TDD) and frequency division duplex (FDD). In both cases, bandwidth for QoS connections can be requested. Because the BS performs the network management, it assigns the bandwidth reservation and transmission opportunities for each MS. However, each MS can dynamically request bandwidth from the BS by using a bandwidth-request (BWR) protocol data unit (PDU) in a contention or contention-free mode (e.g. polling). Additionally, IEEE 802.16e defines different BWR protocols such as: unsolicited request, poll-me bit, piggybacking, bandwidth stealing, codeword over quality indicator channel (CQICH) and code division multiple access (CDMA) code-based BWR. Similar to the IEEE 802.22/WRAN standard, there are different scheduling service types in IEEE 802.16/WiMAX, namely: unsolicited grant service (UGS), extended real-time polling service (ertPS), real-time polling service, non real-time polling service, and best-effort service. Each of these service types has its own QoS parameters like minimum throughput requirement and delay/jitter constraints.
2.3 IEEE 802.22/WRAN and IEEE 802.16/WiMAX Main Characteristics Comparison A comparison of the main characteristics of the IEEE 802.22/WRAN and IEEE 802.16/WiMAX standards is presented in Table 1. Although both standards show some similarities at the PHY and MAC layers (e.g. the use of OFDMA, ACM, QoS types of services), the bandwidth allocations, transmission ranges, and MAC frame sizes are different. As previously mentioned, IEEE 802.22/WRAN networks operate as secondary users in TVWS frequency bands. Operation in these bands within the United States is unlicensed as far as there is not interference to PUs. The rules to use
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TVWS channels are still under review worldwide. However, other countries such as Mexico, the European Community, South Africa, and China among others are considering to follow the United States TVWS regulation model. Therefore, it is fair to assume that IEEE 802.22/WRAN networks potentially have 60 unlicensed channels to operate worldwide. In contrast, most of the operating frequencies considered in the IEEE 802.16/WiMAX standard are licensed, except by the 2.4 GHz and 5.8 GHz frequency bands which are already used by other wireless technologies (e.g. WiFi, ZigBee, Bluetooth). Because of IEEE 802.16/WiMAX operates at frequencies above 2 GHz, the propagation characteristics limit its maximum transmission range to 50 kilometers for LOS and to approximately 24 kilometers for NLOS. In comparison, the IEEE 802.22/WRAN standard operating bands are allocated below 900 MHz. Therefore the maximum transmission range of IEEE 802.22/WRAN doubles the range offered by IEEE 802.16/WiMAX, reaching up to 100 kilometers for LOS and up to 33 kilometers for NLOS transmissions. Table 1 Comparison between IEEE 802.16 and IEEE 802.22 System parameters
IEEE 802.16/WiMAX
IEEE 802.22/WRAN
Frequency band
2-10 GHz
54-862 MHz
Channel bandwidth
≥ 5 MHz
6, 7, 8 MHz
Transmission rate
10-40 Mbps
23-31 Mbps
Cell radius
Up to 50 kms.
Up to 100 kms.
Multiple access
TDMA or OFDMA
OFDMA
MAC frame size
5 ms
10 ms
Another difference between the IEEE 802.16/WiMAX and IEEE 802.22/WRAN standards relies on their maximum data rates. The IEEE 802.16e standard is fully capable of achieving a maximum data rate of up to 40 Mbps. In comparison the IEEE 802.22 standard supports up to 31 Mbps using a 64-QAM modulation scheme, [11, p. 22], [33]. However, IEEE 802.22 achieves this data rate using a bandwidth channel of only 8 MHz instead of the 20 MHz required by the IEEE 802.16e standard. The maximum data rate is only achieved when the distance between the BS and the user (MS in WiMAX and CPE in IEEE 802.22/WRAN) is relatively short, such that 64-QAM can be used without incurring in an unacceptable bit error rate (BER). Thus, in order to further compare the capabilities offered by the IEEE 802.22/WRAN and IEEE 802.16/WiMAX standards, the Fig. 1 shows a graphical representation of the modulation scheme used for a given coverage area in a typical deployment scenario. Since the coverage range of IEEE 802.22 is larger than that of IEEE 802.16, the overlapping between IEEE 802.22 QPSK and IEEE 802.16 is minimal. In contrast it can be seen that the areas covered by IEEE 802.22 16-QAM and IEEE 802.16 QPSK are similar (they are almost completely overlapped). Furthermore, the area corresponding to IEEE 802.22 64-QAM com-
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pletely covers the area corresponding to IEEE 802.16 64-QAM and a significant portion of the area corresponding to IEEE 802.16 16-QAM. This means that the range achieved with IEEE 802.22 for QPSK, 16-QAM, and 64-QAM is larger than that achieved with WiMAX. Fig. 1 Modulation schemes used for a given coverage range for typical IEEE 802.22/WRAN and IEEE 802.16/WiMAX deployments.
Although the previous discussion could lead to a preliminary conclusion regarding the suitability of IEEE 802.16/WiMAX and IEEE 802.22/WRAN for the deployment of rural telemedicine networks, it is necessary to define a wireless telemedicine model for rural regions before reaching any conclusion. Thus, in the following section such model is proposed in order to assess the capabilities offered by each technology to allocate rural telemedicine services.
3 Wireless Telemedicine Model One of the main challenges in rural telemedicine is mobility, [34]. Since health specialists are often concentrated in main urban centers, rural patients may be exposed to long traveling times in order to be attended. This condition may represent a major effort for post-operative, re-convalescing and elderly patients, [35]. There-
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fore, wireless rural telemedicine presents an alternative solution not only to reduce travel time issues, but also to extend health services by offering health care specialist consultation in situ. A rural telemedicine model must take into account the health issues prevalent among the rural population and their particular needs. Thus the telemedicine services offered should focus in attending critical health issues prevalent on the rural population, which may be different to those found in large urban centers. Another aspect that must be considered is the technological infrastructure found in the place where the rural telemedicine solution will be implemented. For example, [36] presents a study of the economic impact of rural hospitals in the United States, where it was assumed that the telemedicine sites had wired connectivity. Such assumption may not be used to perform a similar study for developing countries, as most rural clinics may not have wired connectivity. In fact, there are several examples in the literature, [34]–[50], that propose the deployment of wireless rural telemedicine solutions to offer medical services to the rural population in developing countries. Deploying a rural wireless telemedicine network based on IEEE 802.16/WiMAX and IEEE 802.22/WRAN may offer advantages where there are not wired solutions available. Thus, the rural telemedicine model proposed in this chapter for the evaluation of IEEE 802.16/WiMAX and IEEE 802.22/WRAN will be based in previous efforts for the deployment of wireless rural telemedicine services.
3.1 Telemedicine Services As mentioned before, from a general perspective telemedicine services comprise teleconsulting, telediagnosis, telemonitoring, medical database access (MDBA) and teleducation, [3]. The inclusion of one or all services in a telemedicine model depends on the application scenario. For instance, because of the large technological and health infrastructure available in countries like Germany and the United States, rural telemedicine services focusing on home monitoring have been proposed, e.g. [37], [38]. Differently, in developing countries, (e.g. Malaysia and Bangladesh) rural telemedicine is mainly focused on interconnecting rural clinics with main hospitals. This, in order to assist local physicians remotely by extending health specialist services through telediagnosis and teleconsulting, [39], [40]. A few examples of different rural telemedicine efforts around the world are listed in Table 2. In this table the differences and similarities between telemedicine services offered by different projects can be observed.
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Table 2 Rural telemedicine services offered by different projects around the world Ref.
Country
Telediagnosis
[41]–[43]
China Local Physician collects data and communicates with health specialist for diagnosis purposes
[34], [35], [44]–[46]
India
[40], [50]
MDBA
Health specialist The consulting is Available to The local physi- The storage based their diagno- performed be- postgraduate cian is in charge of collected sis on collected da- tween local phy- students, dis- to perform the data are ta and described sician and heal trict hospital monitoring based available their recommenda- specialist only to doctors, para- on scheduled ap- for local tions to local phy- discuss the pa- medical work- pointments to up- and remote sicians tient file infor- ers and hospi- date the patients locations mation tal file from the administrator hospital dato improve patabase tient care skills
[47], [48] Africa Local Physician collects data and communicates with health specialist for diagnosis purposes
[49]
Teleconsulting Teleeducation Telemonitoring
The patient con- Academic and Patients monitor- The storage sulting is a health training meet- ing is performed of collected specialist deci- ings are by local physi- data are sion based on a scheduled be- cians based available performed diag- tween local scheduled apfor local nosis meeting to and remote lo- pointments for and remote review the col- cations follow-up and da- locations lecting data ta collections from the purposes hospital database
The local physi- Training of cian can choose local physito perform a con- cians to imsultation with a prove their local hospital consulting specialist or a medical skills tertiary hospital specialist
Patients monitor- The access ing is performed to a medical by local physi- database cians for follow- available up monitoring lo- for local cally sending physicians basic information allows them to remote hospitalto identify and prevent particular diseases
Indonesia Local Physician collects data and update the patient record file for diagnosis purposes
The consultation awaits the update of patient record profile with health specialist recommendations
Patients monitoring is performed by local physicians for followup monitoring updating the information to remote hospital
The storage of collected data are available for local and remote locations from the hospital database
Latin America
The consultation update of patient record profile is performed between physician
Patients monitoring is performed by local physicians for followup monitoring
The storage of collected data are available for local
14 and health specialist
updating the in- and remote formation to re- locations mote hospital from the hospital database
3.2 Telemedicine Traffic Profile The definition of a traffic profile for a telemedicine network depends on the services to be offered and the technological infrastructure available. For instance, the International MedioNet of China (IMNC) network is based on Internet access through plain old telephone service (POTS) to enable rural telemedicine consultation services, [41]. In the matter of technological infrastructure, connection availability towards the deployment of a telemedicine network may limit the medical services that can be offered. In other words, a telemedicine model designed to offer diagnosis services using high definition video (with a minimal bandwidth requirement of 400 Kbps connection) may require QoS provisioning that a modem connection over a POTS network (with a bandwidth of 56 Kbps) cannot offer. The definition of a traffic profile for rural telemedicine should not be based only on the telemedicine applications, but also on the particular health requirements of the rural population. Therefore, it is difficult to define a general telemedicine traffic profile for rural areas. Thus, a few examples of the traffic profiles used in different rural telemedicine projects are presented in Table 3. Note that most projects include VoIP services even though the used link offered different connection bandwidths (e.g. 1 Mbps ADSL in [42] vs. 128 kbps ISDN in [51]). Table 3 Rural telemedicine traffic profiles in different projects around the world Country
Ref.
Applications
China
[42]
VoIP Conferencing Real Time Streaming
Traffic Profiles Constant Bit Rate
HTTP
Non Real Time Streaming
FTP
Variable Bit Rate
Available Bandwidth
ADSL Connection up to 1 Mbps.
E-mail [43]
ECG Signal up. 5-12 lead
Store and Forward Non-Real Time Streaming Constant or Variable Bit Rate
India
[35]
VoIP Conferencing Real Time Streaming Constant Bit Rate Web based Medical Non Real Time Streaming
Bluetooth up to 1 Mbps 3G Mobile Technology ADSL Connection up to 512 Kbps.
15 Application System Variable Bit Rate [44]
HTTP
Non Real Time Streaming Variable Bit Rate
ECG
Store and Forward
Blood Pressure
Non-Real Time Streaming
Heart Rate
Constant or Variable Bit Rate
Bluetooth up to 1 Mbps 3G Mobile Technology
Breathing Rate Body Temperature Blood Glucose Cholesterol Oximeter [34]
VoIP Conferencing Real Time Streaming Constant Bit Rate Web based Medical Non Real Time Streaming Application System Variable Bit Rate
[45]
VoIP Conferencing Real Time Streaming Constant Bit Rate Mobile X-Ray
Store and Forward
Portable Ultrasound Non-Real Time Streaming Scanner Constant or Variable Bit Rate ECG
Connection up to 512 Kbps.
CDMA 2000 Mobile Technology Link Aggregation up to 220 Kbps.
Ophthalmoscope Retinoscope Digital Microscope [46], [51]
VoIP Conferencing Real Time Streaming Constant Bit Rate High Definition Im- Store and Forward ages via E-mail Non-Real Time Streaming ECG Constant or Variable Bit Rate
ISDN up to 128 Kbps
3.3 Rural Telemedicine Model As mentioned before, the telemedicine services offered in a rural telemedicine network depend on the rural population requirements. Based on the examples introduced in the previous sections, the rural telemedicine model proposed in this chapter includes the following services: 1) Teleconsulting has two cases: physician-specialist and patient-specialist. The first one is performed between a local physician and a remote specialist. Its aim is to discuss the patient record in order to obtain recommendations. In the second one a videoconference is set up to perform the
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patient’s physical check required by the remote specialist for follow up purposes. 2) Telediagnosis has two cases: ambulance-clinic and clinic-hospital diagnosis. In the first one a local physician obtains patient-collected data and emits its recommendations to paramedics, while setting up pre-hospital treatment. In clinic-hospital diagnosis the local clinic physician collects the patient’s data and sends the information to the health specialist located in a hospital. The local physician can receive the specialist recommendations and instructions in real time or after a waiting time. 3) In Telemonitoring a local nurse or physician collect biomedical data from patients (e.g. blood pressure, ECG, EEG, etc.) and send it to a remote database for follow-up and patient record update purposes. 4) Teleeducation is based on scheduled meetings between clinic physicians and the hospital specialist medical board for training purposes. In this service, access to remote hospital medical databases is provided to local clinic physicians in order to perform consultations of the patient records. The traffic profile for the offered telemedicine services described in the proposed model is shown in Table 4. In order to define the data rates the information reported in, [12], [24], [52] was considered. The traffic profile was defined considering average values, as the required uplink (UL) and downlink (DL) data rates differ from one medical specialty to another. Table 4 Rural telemedicine model traffic profile, applications and services
The number of fixed and mobile wireless connections needed in a rural wireless telemedicine deployment varies with the proximity of the populations to the local clinics. Thus, when there is a relatively large number of rural settlements in a given area, the number of required services may also be large. Hence, in order to evaluate the suitability of IEEE 802.16/WiMAX and IEEE 802.22/WRAN to deploy rural telemedicine networks in this kind of scenario a case of study based on the state of Chiapas, Mexico, will be presented. In Mexico more than 37% of states or provinces have over 30% of rural population. The most drastic case is represent by Chiapas state which has 51% of rural population, [53]. Also Chiapas has the maximum poverty index in Mexico, reaching over 74%, [54]. Therefore, Chiapas is a representative example where people needs primary and extended medical services, including consultation by health specialists. At least 30 municipalities are located within a radio of 50 km from the capital city of Chiapas (including the touristic city of San Cristobal de la Casas),
17
and 15 of them can be classified as rural. Based on these conditions, the generic rural wireless telemedicine network architecture that will be used for the evaluation of IEEE 802.16/WiMAX and IEEE 802.22/WRAN capabilities is shown in Fig. 2. The network includes a 50 km backhaul link between points A and B. Additionally other link distances are: 22 km (A to C), 17 km (A to D), 18 km (A to E), 24 km (A to F), 14 km (A to G) and 60 km (A to H). Fig. 2 Generic rural wireless telemedicine network architecture
By using the rural telemedicine model and the generic rural wireless telemedicine network architecture, the number of active services that can be supported by the IEEE 802.16/WiMAX and IEEE 802.22/WRAN standards will be calculated. The number of services will be limited by bandwidth and QoS requirements. Therefore, the system resources for the telemedicine services must be reserved by means of resource scheduling algorithms. In IEEE 802.16/WiMAX the use of scheduling algorithms towards QoS provisioning has been widely studied in [9], [12], [55]. Nevertheless, from the bandwidth availability point of view, an evaluation using a throughput metric can be performed. Thus, in the following section the system capacity in terms of the number of telemedicine services supported will be calculated using the maximum throughput.
4 System Performance Evaluation As mentioned in Section 1.3, the IEEE 802.16/WiMAX standard has shown its suitability to enable rural telemedicine networks around the world. However, the
18
IEEE 802.22/WRAN standard, as an emerging technology, represents an alternative for the deployment of rural telemedicine networks because of its capability to operate through TVWS channels with ranges of up to 100 kilometers. Therefore, in order to establish the bandwidth availability per channel towards the deployment of rural wireless telemedicine networks, an evaluation based on maximum throughput is presented in this section for the IEEE 802.16/WiMAX and IEEE 802.22/WRAN standards.
4.1 Throughput Performance Calculation The performance evaluation of a system based on throughput requires finding the maximum data rate achieved considering parameters such as modulation, frame overhead, and system reserved resources, among others. The calculation presented in this section was performed with the system parameters shown in Table 5. Table 5 System parameters for the evaluation of IEEE 802.16/WiMAX and IEEE 802.22/WRAN System parameters
IEEE 802.16/WiMAX
IEEE 802.22/WRAN
Bandwidth channel
5 MHz
6 MHz
Sampling frequency
5.6 MHz
6.856 MHz
NFFT
512
2048
Frame duration (ms)
5
10
Cyclic prefix
1/8
1/8
Modulation
QPSK, 16-QAM, 64-QAM
QPSK, 16-QAM, 64-QAM
Coding rate
1/2, 2/3, 3/4, 5/6
1/2, 2/3, 3/4, 5/6
Symbol time (ms)
102.9
336.05
TTG/RTG (ms)
105.71 / 60
209.88 / 305.86
Symbols per frame
48
30
The IEEE 802.16e standard calculation is based on the Partially Used SubCarrier (PUSC) scheme in order to obtain the maximum data rate, [56]. Different to 802.16e, the IEEE 802.22 standard defines a fixed number of subchannels available for any link according to a bandwidth request protocol.
4.2 Data Bandwidth Allocation Data bandwidth allocation in IEEE 802.16e and IEEE 802.22 depends on system parameters such as: channel bandwidth, coding and modulation schemes, number
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of OFDM subcarriers, etc. Four mandatory overhead symbols corresponding to downlink/uplink (DL/UL) MAPs messages, frame preamble and TTG/RTG are considered in both cases for throughput calculation. Using these considerations and the parameters shown in Table 5, the peak throughput results for both technologies are reported in Table 6. It is important to note that these results are consistent with the values presented in the standards definitions, [8], [11]. The system performance evaluation presented in this section uses the rural telemedicine model introduced in the Section 3.3. In this context, IEEE 802.16/WiMAX technology offers connectivity up to 50 km for LOS and up to 24 km for NLOS. Under similar conditions IEEE 802.22/WRAN is able to offer a maximum transmission range of 100 km in LOS and 65 km in NLOS. However, these transmission ranges are reached under ideal conditions. Therefore, in order to better assess the suitability of both technologies for the deployment of rural telemedicine networks, the propagation model introduced in [57] is used to adjust the maximum transmission ranges as follows: For IEEE 802.16/WiMAX it is assumed that a range of: 24 km is achieved with QPSK-3/4; 11 km is reached with 16-QAM-3/4; and 6 km is achieved with 64-QAM-3/4. For IEEE 802.22/WRAN it is assumed that a range of: 65 km is achieved with QPSK-3/4; 32 km is reached with 16-QAM-2/3; and 9 km is achieved with 64-QAM-3/4. Regarding the relationship between modulation-coding and maximum transmission ranges, from Fig. 2 it can be observed that point F is located at the boundary where IEEE 802.16/WiMAX can offer QPSK-3/4. Nevertheless, in the same point IEEE 802.22/WRAN is able to offer 16-QAM-2/3. Furthermore, IEEE 802.22/WRAN is able to offer QPSK-3/4 coverage for point H, which is not reached by WiMAX. Table 6 Peak throughput comparisons between IEEE 802.22 and IEEE 802.16e Modulation scheme
Coding rate
IEEE 802.16/WiMAX (Mbps)
IEEE 802.22/WRAN (Mbps)
QPSK
1/2
5.56
4.54
2/3
-
4.99
3/4
8.34
5.62
5/6
-
6.24
1/2
11.12
7.49
2/3
-
9.98
3/4
16.68
11.23
5/6
-
12.48
1/2
16.68
11.23
2/3
22.25
14.98
3/4
25.03
16.85
5/6
27.81
18.72
16-QAM
64-QAM
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Because both technologies can operate in TDD mode, flexible UL and DL data bandwidth allocations can be used as far as at least 10% of the available data bandwidth is reserved for both the DL and the UL. Therefore, in order to evaluate the system performance for asymmetric DL/UL data bandwidth allocations, increments/decrements of 10% for the DL/UL will be used. A total of 15 municipalities from the case of study introduced in Section 3.3 are considered for the evaluation of the capacities offered by IEEE 802.16/WiMAX and IEEE 802.22/WRAN for rural telemedicine deployments. Thus, a maximum of 15 rural locations are used to calculate the number of active telemedicine services that can be offered for each DL/UL data bandwidth allocation. Additionally, it will be assumed that the users are located within the major overlapping area shown in Fig. 1. Hence, QPSK-3/4 transmissions will be available for WiMAX and 16-QAM-2/3 transmission will be available for IEEE 802.22/WRAN. The data throughput is affected by the MAC and PHY layers overhead, which is a function of the number of active users in the network. No overhead reduction methods are considered for the analysis. Therefore, the MAC/PHY overhead will be comprised by the DL/UL MAP, the information elements (IE) formats, and ranging and bandwidth requests. Because of the similarities in MAC and PHY layers between IEEE 802.22/WRAN and IEEE 802.16e, the overhead percentage calculation method proposed in [58] will be used for both technologies. The calculated overhead percentage factors are shown in Table 7. Table 7 MAC and PHY layers overhead percentage for IEEE 802.22/WRAN and IEEE 802.16e Number of active users
IEEE 802.16e (%)
IEEE 802.22 (%)
1
32.91
30.24
2
34.97
33.60
3
37.03
36.96
4
39.09
40.32
5
41.14
43.68
6
43.20
47.04
7
45.26
50.40
8
47.31
53.76
9
49.37
57.12
10
51.43
60.48
11
53.49
63.84
12
55.54
67.20
13
57.60
70.56
14
59.66
73.92
15
61.71
77.28
21
As previously mentioned, data throughput will be affected by the overhead percentage factor. For example, although IEEE 802.16e QPSK-3/4 peak data rate is 8.34 Mbps and IEEE 802.22/WRAN 16-QAM-2/3 peak data rate is 9.98 Mbps (see Table 6), when two users are active within the network the throughputs are 5.42 Mbps and 6.63 Mbps respectively. This reduction in the data rates is due to the 34.97% and 33.60% overhead percentage factors of IEEE 802.16e and IEEE 802.22/WRAN respectively (see Table 7). Therefore, if an ambulance service with telediagnosis requires 1,517 Kbps for the UL and 425 Kbps for the DL, then a maximum of two ambulance services can be enabled for this modulation scheme. Following the procedure described before, it is possible to calculate the number of telemedicine services that can be enabled for a given DL/UL data bandwidth allocation. Thus, by using the model introduced in Section 3.3 and the information provided in Tables 4, 6 and 7, the number of telemedicine services that can be enabled for a given DL/UL data bandwidth allocation is shown in Fig. 3. Fig. 3 Data Bandwidth allocation comparative between the IEEE 802.16e and the IEEE 802.22 standards for different telemedicine services. a) Telediagnosis, b) Teleconsulting, c) Telemonitoring, d) Teleeducation.
Fig. 3a shows that a maximum of 2 active ambulances transmitting telediagnosis services can be supported by IEEE 802.16/WiMAX. Similarly, a maximum of 3 active ambulances can be connected when using IEEE 802.22/WRAN. Both technologies achieved a maximum of 4 active clinic-hospital connections transmitting telediagnosis services. Fig. 3b shows that the IEEE 802.16/WiMAX standard can support up to 13 active physician-specialist connections transmitting teleconsulting services. In contrast, the maximum number of ac-
22
tive physician-specialist connections achieved with IEEE 802.22/WRAN is 12. Considering patient-specialist teleconsulting services, the IEEE 802.22/WRAN standard is able to allocate up to 6 active connections, but the IEEE 802.16/WiMAX standard supports a maximum of 5. Similar to telediagnosis, an asymmetric DL/UL data bandwidth allocation was considered for telemonitoring services. Nonetheless, telemonitoring only sends traffic through the upstream link. Therefore, the number of allocated telemonitoring services rises when the UL available data rate is increased as shonw in Fig. 3c. Both technologies show a similar behavior in the number of supported telemonitoring services, with a maximum of 11 connections. Note that when the maximum number of active services supported is relatively low, IEEE 802.22/WRAN can support up to one additional connection compared to IEEE 802.16/WiMAX. However, when the maximum number of active services supported is large this behavior is inverted. The reason for this is that the overhead percentage factor of IEEE 802.22/WRAN is below that offered by IEEE 802.16/WiMAX when the number of active users is less than 4 (see Table 7). As mentioned before, IEEE 802.16/WiMAX has been widely used to deploy telemedicine networks in several countries. For this reason, it is not surprising that Fig. 3 confirms the capability of WiMAX to support different telemedicine services. Furthermore, from Fig. 3 it can also be observed that IEEE 802.22 provides similar capabilities to those offered by IEEE 802.16/WiMAX. Therefore, it can be concluded that IEEE 802.22 presents a feasible solution for the implementation of rural telemedicine networks.
4.3 Telemedicine Services over BWA technologies in Mexico The deployment of WiMAX technology in Mexico has mainly focused on education services. Since 2008, the Corporación Universitaria para el Desarrollo de Internet (CUDI) has developed several WiMAX projects. For instance, the proposal named “Proyecto WiMAX Jalisco” is related to the transmission of voice and data, interconnecting universities to extend the technological infrastructure in the Jalisco state. As detailed in [59], the IEEE 802.22 standard is a suitable technology for the deployment of wireless rural networks in locations where the population density is below 60 inhabitants/Km2. However, to the best of our knowledge, no WRAN project has been proposed in Mexico yet. This despite that near 50% of Mexican cities fulfill this requirement [53]. In Mexico, the regulation of the TVWS channels has been delayed. However, the objective of this proposal is to evaluate the suitability of using IEEE 802.22/WRAN technology to deliver telemedicine services in rural areas, this despite the status of the TVWS channels regulations.
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5 Case Studies Case 1. In this chapter has been exhibited the throughput performance of IEEE 802.22/WRAN standard for all available modulation and coding schemes based on 1/8 cyclic prefix mode. However, a total of four cyclic prefixes modes are included in the IEEE 802.22/WRAN PHY layer definition. Hence, calculate the maximum data rate over one channel offered by the IEEE 802.22 for all available cyclic prefixes using the same system parameters considered in this chapter to observe the throughput capacity relation with the maximum system capacity. Case 2. In section 4 a performance evaluation of telemedicine services bandwidth allocation capacity for IEEE 802.22/WRAN and IEEE 802.16/WiMAX standards based on the Chiapas example with a maximum of 16 municipalities included has been presented. However teleconsulting and telediagnosis have two sides (clinic/patient and clinic/ambulance traffic profiles respectively) that has been studied independently. Hence, calculate the maximum number of teleconsulting and telediagnosis services overall traffic profiles (including the two sides on each case) that can be allocated in the IEEE 802.22/WRAN and IEEE 802.16/WiMAX for each UL/DL scheme based on QPSK-3/4 and 16-QAM-2/3 modulation-coding modes respectively.
6 IEEE 802.16/WiMAX and IEEE 802.22/WRAN technologies future direction Even though IEEE 802.16/WiMAX has been widely deployed to enable rural telemedicine applications, there are still important open research issues around this scenario that must be addressed, such as: end-to-end security and QoS for telemedicine traffic. Considering that medical information from patients is transmitted over wireless links, end-to-end security is an important issue as data confidentiality must be observed overall the wireless telemedicine network. In this regard not only engineering issues must be addressed, but also legislative issues. Since telemedicine traffic profiles may define asymmetric traffic flows (i.e. telediagnosis), the study QoS provisioning techniques is needed to properly implement wireless telemedicine services. The IEEE 802.16 standard has been constantly updated to adjust its competencies considering the emerging needs. Hence, the following updates should consider using TVWS channels for its operation and include scheduling techniques to add QoS capabilities. Because spectrum license fees may represent an additional cost in the deployment of wireless rural telemedicine networks, IEEE 802.22 may present an alternative solution for the implementation of such networks. Nevertheless, the analog switch-off to enable TVWS channels worldwide is planned to finish at the end of 2020. Therefore the deployment of IEEE 802.22/WRAN technol-
24
ogy will depend on the portion of TVWS channels regulated as unlicensed according to each country normativity. Since IEEE 802.22 include cognitive radio capabilities the study of primary users detection techniques should be developed. Similarly, coexistence engineering issues should be addressed to guarantee nointerference operation between IEEE 802.22 networks located nearby. In future, the deployment of IEEE 802.16 and IEEE 802.22 networks will enable the implementation of mHealth applications for underserved areas. Over this assumption, highly populated continents (i.e. Africa and Asia) with large rural regions can greatly benefit with the deployment of wireless rural telemedicine networks.
7 Conclusions In this chapter, a wireless telemedicine solution for the delivery of telemedicine services over rural regions has been proposed. In order to assess the suitability of IEEE 802.16/WiMAX and IEEE 802.22/WRAN for the implementation of rural telemedicine networks, a rural telemedicine model that includes traffic profile descriptions and a deployment scenario was introduced. The traffic profile descriptions were telediagnosis, teleconsunting, telemonitoring and teleeducation services. The system performance evaluation was carried out considering asymmetric data bandwidth allocations for the UL and DL of both technologies. By considering the overhead percentage factor, the maximum number of active telemedicine services was calculated for each standard. The presented results showed that the IEEE 802.22/WRAN standard is fully capable of supporting telediagnosis, teleconsulting, telemonitoring and teleeducation services in rural deployments. Moreover, the IEEE 802.22/WRAN and IEEE 802.16/WiMAX standards showed similar performance regarding the maximum number of active telemedicine services. Consequently, it can be concluded that IEEE 802.22/WRAN presents a viable solution for the implementation of wireless rural telemedicine networks. The rural telemedicine model used in this chapter included a deployment scenario where the situation of the state of Chiapas, Mexico was used as an example. The aim was to assess the potential benefits that the deployment of wireless rural telemedicine networks can offer. Based on the results presented in this chapter, it can be said that it is feasible to deploy wireless rural telemedicine networks within Mexico by using IEEE 802.22/WRAN technology. Considering that IEEE 802.22/WRAN has the potential to operate in unlicensed TVWS channels, and its maximum transmission range doubles the one offered by IEEE 802.16e/WiMAX, then the deployment of IEEE 802.22/WRAN rural telemedicine networks has the potential to offer lower operating and implementation costs compared to WiMAX or another rural connectivity solutions (e.g. BSC). As nearly 50% of Mexican rural regions may present favorable conditions for the deployment of IEEE
25
802.22/WRAN networks, its utilization for telemedicine applications can improve the provisioning of healthcare services in Mexico.
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9 Keywords WRAN, WiMAX, telemedicine, TVWS, BWA, rural wireless networks
10 Questions and Answers Question 1. Because health specialists tend to concentrate in the main cities. What are some types of patients that may be benefit with the deployment of rural telemedicine networks based on mobility issues? Answer 1. Post-operative, re-convalescing and elderly patients
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Question 2. The IEEE 802.16/WiMAX technology has been leading the deployment of rural telemedicine. What is the major benefit offered by the IEEE 802.22/WRAN technology based on its TVWS operating channels compared to the IEEE 802.16/WiMAX standard? Answer 2. The IEEE 802.22/WRAN offers a maximum transmission range up to 100 kms compared to the IEEE 802.16/WiMAX maximum transmission range up to 50 kms. Question 3. In Section 2 has been established through a coverage radio overlapping that different modulation schemes can be delivered in the same location considering IEEE 802.16/WiMAX or IEEE 802.22/WRAN standards. What are the IEEE 802.22 WRAN modulation schemes offered overall IEEE 802.16/WiMAX standard considering QPSK, 16-QAM and 64-QAM schemes? Answer 3. Within the 64-QAM modulation coverage radius based on IEEE 802.16/WiMAX there is no different modulation scheme from the IEEE802.22/WRAN standard. Within the 16-QAM modulation coverage radius based on IEEE 802.16/WiMAX a 16-QAM and 64-QAM modulation schemes are offered by the IEEE802.22/WRAN standard. Within the QPSK modulation coverage radius based on IEEE 802.16/WiMAX a QPSK and 16-QAM modulation schemes are offered by the IEEE802.22/WRAN standard. Question 4. Based on the proposed wireless telemedicine model. What are the telemedicine services with asymmetric traffic profile considered into the bandwidth allocation capacity evaluation? Answer 4. Telemonitoring and Telediagnosis.
