Integrated Ieee 802.11/Wlan and Ieee 802.16/Wimax Networks

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WIRELESS TECHNOLOGIES FOR E-HEALTHCARE

WIRELESS TELEMEDICINE SERVICES OVER INTEGRATED IEEE 802.11/WLAN AND IEEE 802.16/WIMAX NETWORKS

YAN ZHANG AND NIRWAN ANSARI, NEW JERSEY INSTITUTE OF TECHNOLOGY HIROSHI TSUNODA, TOHOKU INSTITUTE OF TECHNOLOGY

ABSTRACT Wireless communications overcomes most geographical, temporal, and organizational barriers Wireless telemedicine, also referred to as to the transfer of medical data and records. nic mobile health, which capitalizes on advances of In order to provide ubiquitous availability of wireless technologies to deliver health care and multimedia services and applications, wireless and exchange medical knowledge anywhere and any mobile technologies are evolving towards integra- BS2 time, overcomes most of geographical, temporal, tion of heterogeneous access networks such as and even organizational barriers to facilitate wireless personal area networks (WPANs), wire- remote diagnosis and monitoring, and transfer of less local area networks (WLANs), wireless WiMAX core networ medical data and records. In this article we metropolitan area networks (WMANs) as well as investigate the application of integrated IEEE third-generation (3G) and beyond 3G cellular 802.16/WiMAX and IEEE 802.11/WLAN broad- networks. A hybrid network based on IEEE band wireless access technologies along with the 802.11/WLANs and IEEE 802.16/WiMAX is a Internet related protocol issues for telemedicine services. strong contender since both technologies are We first review IEEE 802.11/WLAN and IEEE designed to provide ubiquitous low cost, high- 802.16/WiMAX technologies, and make a com- speed data rates, quality of service (QoS) provi- parison between IEEE 802.11/WLAN and IEEE sioning, and broadband wireless Internet access. .11e WLAN1 802.16/WiMAX. Then some open research issues IEEE 802.11/WLAN is the standard to provide Dual in the integrated IEEE 802.16/WiMAX and moderate- to high-speed data communications in gateway IEEE 802.11/WLAN networks are discussed, a short range generally within a building. The especially regarding QoS support, radio resource IEEE 802.16/WiMAX is the standard to provide The authors management, scheduling and connection admis- broadband wireless services requiring high-rate sion control schemes, as well as handover and transmission and strict QoS requirements in both investigate the mobility management. Finally, applications and indoor and outdoor environments. Furthermore, application of deployment scenarios of integrated IEEE IEEE 802.16/WiMAX network is a promising 802.16/WiMAX and IEEE 802.11/WLAN for solution to provide backhaul support for IEEE integrated IEEE telemedicine services are further deliberated. 802.11/WLAN hotspots. WiMAX has recently been implemented for telemedicine functionali- 802.16/WiMAX and INTRODUCTION ties [1]. The integrated network of IEEE 802.11/WLAN and IEEE 802.16/WiMAX can IEEE 802.11/ WLAN By deploying telecommunications technologies bring a synergetic improvement to the to deliver health care and share medical knowl- telemedicine services on coverage, data rates, and broadband wireless edge over a distance, telemedicine aims at pro- QoS provisioning to mobile users. There have access technologies viding expert-based medical care to any place been some ongoing projects related to mobile and at any time health care is needed. When the healthcare services using WLAN/WiMAX net- along with the first telemedicine services were provided, work such as Mobile Taiwan (M-Taiwan) [2] and telemedicine applications were implemented WiMAX Extension to Isolated Research Data related protocol over wired communications technologies such as (WEIRD) networks [3]. The major goal of M- plain old telephone network (POTN) and inte- Taiwan is to build a standard-compliant environ- issues for grated services digital network (ISDN). Howev- ment as the foundation for lifestyle applications er, recent developments in telemedicine resulting such as M-Service, M-Learning, and M-Life. In telemedicine from wireless advances are promoting wireless order to deliver such applications, WiMAX is services. telemedicine, also referred to as m-health or expected to be the preferred technology. WEIRD mobile health. Normally, wireless telemedicine aims to support novel applications, such as fire systems consist of wearable/implantable medical prevention, environmental monitoring, and tele- devices and wireless communications networks. medicine via WiMAX. Fourtest beds deployed in

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Europe have been used to implement, test, and • Integrated services provided by the large net- The most validate the technical solutions developed within work capacity of WiMAX enabling fully func- the WEIRD project. Various advanced medical tional telemedicine services such as various fundamental applications such as remote follow-up, remote types of diagnostics, physical monitoring, diagnosis, intervention on non-transportable pharmaceutical and drug dosage management difference between patients, remote monitoring, remote assistance, services, good quality conversational commu- and medical e-learning are expected to be nications between a physician and a patient, WLAN and WiMAX is improved by using WiMAX. and consultation among medical specialists The remainder of this article is organized as • Medium access control (MAC) layer security that they are follows. First, we briefly review WLAN and features of WiMAX providing access control designed for totally WiMAX technologies. Afterward, a comparison and encryption functions for wireless between IEEE 802.11/WLAN and IEEE 802.16/ telemedicine services different applications. WiMAX is presented. A general telemedicine • QoS framework defined in 802.16e enabling system architecture and telemedicine QoS efficient and reliable transmission of medical WLAN is the requirements are introduced. Then some data research open issues in the integrated IEEE standard to provide 802.16/WiMAX and IEEE 802.11/WLAN net- COMPARISON BETWEEN WLAN AND WIMAX works are discussed, especially on QoS support, The most fundamental difference between moderate to high- radio resource management, scheduling and con- WLAN and WiMAX is that they are designed speed data nection admission control schemes, as well as for totally different applications. WLAN is the handover and mobility management. Finally, standard to provide moderate- to high-speed communications in a application and deployment scenarios of inte- data communications within a short range, gen- grated IEEE 802.16/WiMAX and IEEE erally within a building. On the other hand, short range; WiMAX 802.11/WLAN for telemedicine services are dis- WiMAX is the standard to provide Internet cussed and illustrated. access over a long range outdoor environment. is the standard to Besides the obvious difference in transmis- provide Internet WLAN AND WIMAX OVERVIEW sion range, there are a number of improvements in the radio link technology that distinguish access over a long WLAN OVERVIEW WiMAX from WLAN. WLAN standards describe four radio link interfaces that operate range outdoor WLANs are commonly used in their 802.11a, in the 2.4 GHz or 5 GHz unlicensed radio bands. 802.11b, and 802.11g versions to provide wireless WiMAX standards include a much wider range environment. connectivity in home, office, and some commer- of potential implementations to address the cial establishments; they are also widely deployed requirements of carriers around the world. All in telemedicine systems. Since the early 1990s, WLAN implementations use unlicensed frequen- the industrial, scientific, and medical bands, 2.4 cy bands, but WiMAX can operate in either GHz and 5 GHz, have been made available for licensed or unlicensed spectrum. A detailed WLAN, among which the 802.11b and 802.11g comparison of WiMAX and WLAN technologies protocols are the most popular. IEEE 802.11b is summarized in Table 1. operates in the 2.4 GHz band and accommo- dates data rates of up to 11 Mb/s, whereas 802.11g, based on prthogonal frequency-division WLAN AND WMAN: BASIC INTEGRATION multiplexing (OFDM), operates in the same ISSUES band and provides data rates of up to 54 Mb/s. IEEE 802.11a also specifies an OFDM scheme, An integrated WiMAX and WLAN network can which is not backward compatible with the origi- be used to extend the coverage area of a WLAN nal 802.11b. It operates in the 5 GHz band with and augment the availability of e-healthcare ser- data rates of up to 54 Mb/s within 10 m, drop- vice using mobile wireless systems. However, to ping to about 6 Mb/s at a distance of 100 m. realize integrated WiMAX and WLAN networks IEEE 802.11 WLANs are most suitable for for e-healthcare service, many challenging prob- local telemedicine services, IEEE 802.11e can be lems such as QoS support, radio resource man- used for transmitting sensitive medical data with agement, scheduling, connection admission QoS support, and IEEE 802.11i provides securi- control, and handover management have to be ty support as an amendment to the original addressed. A taxonomy of related works is out- IEEE 802.11 standard by specifying security lined in Table 2, and the major contributions of mechanisms for WLANs. However, WLANs corresponding work on tackling various issues have limitations in terms of mobility and cover- are highlighted in Table 3. age area. QOS SUPPORT WIMAX OVERVIEW QoS support is vital in integrated WiMAX and IEEE 802.16/WiMAX is a good last-mile wire- WLAN for e-healthcare service because various less access solution that provides baseline fea- types of time-sensitive data should be communi- tures for flexibility in spectrum to be used all cated in such a service. For example, real-time over the world. Advantages of using WiMAX for communications and large enough bandwidth is wireless telemedicine applications over WLAN- required for transmitting high-resolution digital based systems can be summarized as follows: videos and images in mobile robotic systems. • Broadband wireless access in both fixed and Providing QoS in the integrated IEEE mobile environments 802.16/WiMAX and IEEE 802.11/WLAN net- • High bandwidth to reduce transmission delay work is a challenging issue. The need for effi- of quality images significantly cient interworking between IEEE 802.16/

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Channel Bandwidth Standard Network Band Bit rate Radio technique bandwidth efficiency

802.11 LAN < 100 m 2.4 GHz 1 or 2 Mb/s 20 MHz 2.7 Mb/s/Hz FHSS or DSSS

802.11a LAN < 100 m 5 GHz 6–54 Mb/s 20 MHz 2.7 Mb/s/Hz OFDM (64-channel)

High-rate LAN 11 Mb/s (fallback 802.11b 2.4 GHz 25 MHz 0.44 Mb/s/Hz DSSS and CCK < 100 m 5.5, 2, or 1 Mb/s)

802.11g LAN 2.4 GHz Up to 22 Mb/s 20 MHz 2.7 Mb/s/Hz OFDM (64-channel)

32–134 Mb/s (28 802.16 MAN, 1–3 mi 10–66 GHz 20, 25, 28 MHz 5 Mb/s/Hz QPSK, 16QAM, 64 QAM MHz channel)

256-subcarrier ODFM using ≤ 70 or 100 Mb/s Adjustable 802.16a MAN, 3–5 mi 2–11 GHz 5 Mb/s/Hz QPSK, 16-QAM, 64-QAM, (20 MHz channel) 1.25–20 MHz and 256-QAM

802.16e MAN, 1–3 mi < 6 GHz Up to 15 Mb/s 5 MHz 5 Mb/s/Hz Same as 802.16a

Table 1. Comparison of WiMAX and WLAN technologies.

to voice, video, best effort, and background traffic, respectively. The priorities are achieved by QoS QoS architecture [4] differentiating the contention window (CW) size and arbitration interframe space (AIFS) time. Therefore, higher-priority ACs have smaller Game-theory-based radio Admission CWs and shorter AIFSs. The EDCA mechanism resource management [5] control [5] can only provide relative differentiation among Radio resource service categories, but not absolute guarantees management and on throughput and delay performance, and it admission control Capacity analysis and radio resource management may thus starve lower-priority flows. HCCA pro- evaluation [6] vides QoS service by using signaling, scheduling and admission control. It defines a superframe Traffic rerouting containing a contention-free period followed by Scheduling BS assisted [7] enabled [8] a contention period. During the contention-free period, only nodes which are polled by the AP are eligible to transmit for a burst period assigned by the AP. IEEE 802.11e defines eight Trigger design [9] Security [10] traffic categories (TCs): TC6 and TC7 for voice, Handover TC4 and TC5 for video, TC0 and TC3 for best effort, as well as TC1 and TC2 for background Movement [11] Performance [12] information. When a new TC starts, the node needs to send a service request to the AP providing its traffic specifications so that the AP will Table 2. A taxonomy of related works in WLAN and WiMAX heterogeneous perform admission control to decide whether to networks. allow the new flow for service. In the delivery of medical data, some type of data such as real-time medical video streaming WiMAX and IEEE 802.11/WLAN arises in requires strict QoS support. In order to support order to support QoS for delay-sensitive and such requirements, the extension of the standard bandwidth-intensive applications. 802.11e EDCF scheme, referred to as medical IEEE 802.11e employs a channel access func- channel-adaptive fair allocation, has been pro- tion, hybrid coordination function (HCF), to posed [13]. support QoS provisioning in IEEE Different from IEEE 802.11/WLAN, IEEE 802.11/WLAN networks. HCF uses both a con- 802.16/WiMAX was designed from the begin- tention-based channel access method, enhanced ning with QoS in mind and defines five different distributed channel access (EDCA), for con- types of services for different types of traffic tention-based transfer, and a controlled channel flows as follows: access, referred to as HCF controlled channel • Unsolicited grant service (UGS) supports con- access (HCCA), for contention-free transfer. stant bit rate traffic, such as voice over IP EDCA and HCCA provide QoS support over (VoIP). existing distributed coordination function and • Real-time polling service (rtPS) supports real- point coordination function schemes, respective- time service flows which generate variable size ly. EDCA defines four access categories (ACs): data packets on a periodic basis (e.g., MPEG AC_VO with highest priority, AC_VI, AC_BE, video). This scheme can guarantee QoS ser- and AC_BK with lowest priority corresponding vice to meet delay requirements.

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Components Key contribution

QoS architecture [4] An architecture to provide end-to-end QoS in integrated WLAN/WiMAX networks

A Hierarchical Model for Radio Resource A game-theoretic model-based hierarchical bandwidth management and admission Management and Admission Control [5] control framework for Iintegrated IEEE 802.16/802.11 wireless networks.

A probabilistic resource reservation scheme for WLAN to WiMAX handover traffic, to Resource Reservation for Handover Traffic [6] reduce the dropping probability of handover calls.

A quantitative evaluation of the system capacity with QoS for VoIP to verify the effec- Capacity Analysis and Evaluation [6] tiveness of integrating WiMAX and WLAN networks.

ABS assisted adaptive scheduling mechanism implemented at the CPE to provide QoS BS Assisted Scheduling [7] guarantees.

A scheduling algorithm to reduce WiMAX users’ delay by rerouting traffic through Traffic Rerouting [8] lightly loaded WLAN APs.

A user centric algorithm by combining a trigger to continuously maintain connections Handover Trigger Design [9] and another one to maximize user throughput.

A MIH-based secure handover mechanism by adopting symmetric cryptography and Secure Handover [10] asymmetric cryptography to provide security protections.

A movement-aware handover avoiding frequent handovers between two base sta- Movement-Aware Handover [11] tions.

A handover algorithm that seeks to optimize a combined cost function involving the Handover Performance Optimization [12] battery lifetime of mobile nodes and load balancing over the APs/BSs.

Table 3. Key contributions of related works in WLAN and WiMAX heterogeneous networks.

• Extended real-time polling service (ertPS) is a the WLAN APs and standalone subscriber sta- new scheduling algorithm for VoIP services tions (SSs), but also the relay connections from with variable data rates and silence suppres- other base stations (BSs) at a WiMAX BS. With- sion. out these scheduling and control techniques, we • Non-real-time polling service (nrtPS) is cannot provide e-healthcare service for a huge designed to support non real-time service number of mobile users. flows that require variable size data grant A hierarchical bandwidth management and burst types on a regular basis, such as high admission control framework [5] was proposed bandwidth FTP. for integrated IEEE 802.16/802.11 wireless net- • Best effort (BE) supports services that do not works. Specifically, a two-level game-theoretic provide QoS guarantees (e.g., Web and email hierarchical model for radio resource allocation traffic). was implemented. At the first level, a bargaining From the analysis of the differences in the game between the set of standalone IEEE 802.16 QoS frameworks of both technologies, the inte- SSs and the WLAN APs is formulated to deter- gration of WLAN and WiMAX has to take into mine the optimal burst size for WMAN and account a QoS mapping procedure. Gakhar et al. WLAN connections. At the second level, con- [4] proposed an architecture to provide end-to- nections corresponding to different service types end QoS in an integrated 802.16/802.11 network. in the standalone IEEE 802.16 SSs establish a This proposal strives to map the QoS require- coalition to share the allocated bandwidth based ments of an application originated in an IEEE on the results of the bargaining game. For stand- 802.11e network to those of a serving WiMAX alone SS connections, the admission control network, and to ensure the transfer of data hav- scheme was devised based on the total utility of ing appropriate QoS backward compatible with services. For WLAN connections, admission those in the IEEE 802.11e network. control based on a non-cooperative game between the corresponding WLAN AP and the RADIO RESOURCE MANAGEMENT, SCHEDULING, WMAN BS is formulated to determine whether a new WLAN connection can be accepted or AND CONNECTION ADMISSION CONTROL not. The admission control problem can be for- Efficient radio resource management, scheduling mulated as a general sum game between these and connection admission control are still open two networks. issues in WiMAX networks, and therefore, they To demonstrate the effectiveness of integrat- are also crucial in integrated WiMAX and ing WiMAX and WLAN networks, a quantita- WLAN wireless networks. In such an integrated tive evaluation on the system capacity with QoS network, radio resources need to be allocated by provisioning of an integrated WiMAX and considering not only the local connections from WLAN for VoIP was reported in [6]. A proba-

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proposes a unified solution for providing seamless handover across heterogeneous networks. 802.11r 802.16e This framework provides universal link triggers VCC/IMS UMA I-WLAN LTE/SAE IEEE to facilitate handover phases, and can be used in 3GPP/3GPP2 conjunction with various mobility management IEEE 802.21 protocols for different layers and network archi- (MIH - Media tectures. Table 3 highlights key contributions of independent handover) some recent work [9–12] on handover management in integrated WLAN and WiMAX networks. Dai et al. [9] proposed a new user-centric handover algorithm that combines a trigger to continuously maintain the connection, and MIP SIP HIP FMIP NETLMM mSCTP MIPSHOP DNA another one to maximize the user throughput by taking into account link quality and cell load. IETF The IEEE 802.21 draft standard has not defined security mechanisms. Sun et al. [10] pro- Figure 1. Relationship of different handover standards proposed by different posed a secure handover mechanism that adopts standardization organizations (IETF, 3GPP, IEEE). symmetric cryptography and asymmetric cryptography to provide security protections during the vertical handover process. bilistic resource reservation scheme for WLAN Lee et al. [11] proposed a movement-aware to WiMAX handover traffic was proposed. This vertical handover algorithm between WLAN and scheme takes blocking probability of new calls mobile WiMAX for seamless ubiquitous access. into consideration to reduce the dropping proba- The proposed handover algorithm exploits move- bility of handover calls. ment patterns, adjusts the dwell time adaptively, A BS assisted adaptive scheduling mechanism and predicts the residual time in the cell of target [7] was proposed to be implemented at the cus- BS to avoid unnecessary handovers in the inte- tomer premises equipment to provide QoS guar- grated WLAN and mobile WiMAX networks. antees for real-time traffic and a buffer bound Lee et al. [12] proposed a generalized vertical for non-real-time traffic over the backhaul net- handover decision algorithm that optimizes work. Another scheduling algorithm [8] was pro- handover performance by using a combined cost posed to reduce WiMAX users’ delay by function involving the battery lifetime of the rerouting traffic through lightly loaded WLAN mobile nodes and load balancing over APs/BSs. APs. An enhanced algorithm for the case when the ad Although several solutions have been pro- hoc mobile nodes that form vehicular ad hoc posed for radio resource management, traffic networks (VANETs)/MANETs are included in scheduling, and connection admission control for heterogeneous networks was further proposed. integrated WiMAX and WLAN networks, per- This enhanced algorithm allows proxy nodes to formance comparison and applicability of vari- provide connectivity to the nearest AP or BS for ous schemes for telemedicine require further ad hoc mobile nodes (MNs) to share transit studies. loads, with the goal of balancing their consump- tion of battery power. HANDOVER/MOBILITY MANAGEMENT Handover management is one of the most challenging issues to be solved for seamless integra- WLAN AND WIMAX HETEROGENEOUS tion of wireless networks and providing NETWORK DEPLOYMENT SCENARIOS FOR continuous e-healthcare service for mobile users. For instance, the communication between a hos- TELEMEDICINE SERVICES pital and an ambulance must not be disconnect- This section presents some envisioned futuristic ed for pre-hospital care in spite of the movement scenarios that take advantage of integrated of the ambulance. Handover and mobility man- WiMAX and IEEE 802.11/WLAN networks for agement enable the moving ambulance to main- telemedicine services. Figure 2 shows a high- tain communication to the hospital. level system model based on the integrated Standardization organizations such as the Third WiMAX and WLAN wireless network for a Generation Partnership Project (3GPP), Internet telemedicine network connecting hospitals, clin- Engineering Task Force (IETF), and IEEE have ics, drugstores, mobile ambulances, a patient proposed different and, in some cases, comple- information management database, mobile spe- mentary approaches to the design of architec- cialists, and patients at home as well as mobile tures and protocols that enable seamless patients. Single-mode (SM) MNs equipped with handover in heterogeneous networks. Some one interface, dual-mode (DM) MNs, dual-mode important handover standards are illustrated in WLAN APs, and WiMAX BSs are potential Fig. 1. IETF protocols require optimizations and components of this heterogeneous wireless net- standardized triggers to provide seamless hand- work. The scenarios described in Fig. 2 elicit the over; they lack standardized transport layer trig- benefits and illustrate some issues in integrated gers. On the other hand, 3GPP solutions are not WLAN and WiMAX networks. The hybrid sys- flexible, and the proposed architecture is cellu- tem can be divided into five subnetworks: body lar-operator-dependent. Furthermore, 3GPP’s area networks (BANs), home care network/tele- solution for providing seamless handover is not homecare, intranet of a healthcare provider, yet well defined in current releases. IEEE 802.21 including a hospital, a clinic, and a drug store, a

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In the integrated WiMAX and WLAN networks, patients WiMAX client may reside at home BAN3 Drug Clinic store for remote patient Ambulance 1 monitoring through BS2 3G network either by connecting

Hospital WiMAX core network BS3 directly to WiMAX

3G BS 3G client BS equipped with BAN4 Internet WiMAX client

Home3 like Home2, or BS1 Home2 connecting to WLAN 802.11e WLAN1 Dual 802.11e WLAN2 dual mode APs gateway 1 Dual gateway 2 like Home 1. Home1

Dual mode PDA BAN2 client BAN1

Figure 2. IEEE 802.11e/WiFi and 802.16e/WiMAX based wireless telemedicine network.

network between the patient home and the tal services: WiMAX is a more practical and healthcare provider, and a mobile telemedicine cost-effective solution for hospital intranet network for mobile patients and health service deployment due to the relatively larger coverage providers. A wireless heterogeneous network of area of WiMAX networks than that of WLAN WLAN, WiMAX, and 3G cellular networks APs. The deployment of a WiMAX network in a (dashed lines) is also shown in Fig. 2. hospital will reduce operation and maintenance The integrated WiMAX and WLAN wireless costs, while offering full mobility support for telemedicine networks can be deployed in the patients and medical staff. following scenarios. Clinics and drugstores: In contrast to a hos- BANs: The BAN is a particularly appealing pital, WLAN APs can likely provide enough cov- solution to provide information about the health erage for clinics and drugstores. Therefore, dual status of a patient in medical environments such mode WLAN APs can be deployed at clinics and as hospitals or medical centers. The integrated drugstores to communicate with healthcare cen- 802.16/802.11 wireless-network-based tele- ters through WiMAX interfaces and to provide medicine system can also provide medical ser- local wireless coverage through WLAN inter- vices for BANs through SM (BAN2 and BAN3) faces. or DM (BAN1) mobile clients. The mobility of Wireless video telephony: A number of BAN2 is limited within WLAN2 due to only one telemedicine applications are based on the trans- WLAN interface being equipped with the client. mission of medical video, such as remote medi- Home care network/TeleHomeCare: Home cal action systems, patient remote care is a growing field in health care and is a tele-monitoring facilities, and transmission of promising solution to the medical problems of medical videos for educational purposes. High- modern society [14]. The population census indi- quality videos/images are required to ensure cates an increasing trend of the senior popula- proper diagnosis and/or assessment. Video trans- tion. Furthermore, modern life is becoming missions over a WiMAX network have proved to more stressful than ever; therefore, prolonged be an effective and efficient platform in provid- treatment is becoming more necessary. Home ing proper video content delivery [1]. care via treatments in the patient’s house with VoIP services: WiMAX can also be used for the assistance of the family reduces the need to VoIP services. Telephone bills can be drastically transport patients between homes and hospitals. reduced as a result of the use of VoIP for com- In the integrated WiMAX and WLAN networks, munications among hospitals. patients may reside at home for remote patient monitoring through either connecting directly to MOBILE TELEMEDICINE SYSTEMS a WiMAX BS equipped with a WiMAX client Mobile telemedicine systems can be deployed like Home2, or connecting to WLAN dual-mode for emergency telemedicine services, mobile APs like Home 1. patient monitoring, and mobile health service Intranet of a healthcare provider/intra-hospi- provider.

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Delgorge et al., “A Tele-Operated Mobile Ultrasound also enhance pre-hospital care in an ambulance. Scanner Using a Lightweight Robot,” IEEE Trans. Info. Ambulance crews can access the medical infor- Tech. Biomed., vol. 53, no. 4, Mar. 2005, pp. 50–58. mation database in a hospital and retrieve the required medical information of patients through BIOGRAPHIES YAN ZHANG received her B.E. and M.E. degrees in electrical WiMAX networks. Combination of video engineering from Shandong University, Jinan, Shandong, streaming and robotics systems will allow a doc- China, in 2001 and 2004, respectively. Since January 2008 tor in a hospital to perform the required inspec- she has been working toward a Ph.D. degree in the Depart- tion and diagnosis until the ambulance arrives at ment of Electrical and Computer Engineering, New Jersey Institute of Technology (NJIT), Newark. Her research inter- the hospital. ests include wireless networking, mobile computing, and network security. CONCLUSION NIRWAN ANSARI [F] ([email protected]) received his B.S.E.E., M.S.E.E., and Ph.D. from NJIT, University of Michigan, and The application of integrated WiMAX and Purdue University, respectively. He is a professor of ECE at WLAN broadband wireless access technologies NJIT. His current research focuses on various aspects of for telemedicine services and the related proto- broadband networks and multimedia communications. He col issues have been discussed in this article. An has contributed 350 technical publications. He is a Senior Technical Editor of IEEE Communications Magazine, and also overview of WLAN and WiMAX networks has serves on the Advisory/Editorial Board of five other journals. been provided, followed by a comparison of He is an IEEE Communications Society Distinguished Lecturer. WLAN and WiMAX. Open research issues related to QoS support, radio resource management, HIROSHI TSUNODA [M] received his M.S. and Ph.D degrees from the Graduate School of Information Sciences, Tohoku scheduling, and connection admission control, as University, Japan, in 2002 and 2005, respectively. From well as handover management in the WLAN and April 2005 to March 2008 he was an assistant professor in WiMAX heterogeneous networks have been dis- the Graduate School of Information Sciences, Tohoku Uni- cussed. Finally, potential applications and versity. He is now a lecturer in the Department of Informa- tion Communication Engineering, Tohoku Institute of deployment scenarios of WLAN and WiMAX Technology. His research interests include satellite network- heterogeneous networks for telemedicine ser- ing, wireless mobile networking, and network security. He vices are discussed and elicited. is a member of the IEICE and IPSJ.

36 IEEE Wireless Communications • February 2010

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