964 A Survey of Competency Management Software Information Systems Hartman, A., & Sifonis, J. (2000). Net ready. Strategies for success in the e-conomy. McGraw- Hill. Kamara, J. M., Anumbad, C. J., & Carrillo, P. M. (2002). A clever approach to selecting a knowledge management system. International Journal of Project Management, 20(3), 205-211. Levy-Leboyer, C. (1997). Gestión de las com- petencias. Cómo analizarlas, cómo evaluarlas, cómo desarrollarlas, ediciones gestión 2000. Barcelona: SA. Lindgren, R. (2005). Adopting competence sys- tems in fast growing knowledge intensive orga- nizations. Journal of Information & Knowledge Management, 4, 1-13. Lindgren, R., & Stenmark, D. (2002). Designing competence systems: Towards interest-activated technology. Scandinavian Journal of Information Systems, 14, 19-35. Means, G., & Schneider, D. (2000). Meta-capi- talism. The e-business revolution and the design of companies. Nordstrom, A. K., & Ridderstrale, J. (2000). Funky business. Talent makes capital dance. Stockholm, Sweden: Book House Publishing.and Markets in the XXI century. Pricewaterhouse Coopers, Deusto Ediciones. Rollett, H. (2003). Knowledge management processes and technologies. Boston: Kluver Academic Publishers. Sagi-Vela, L. (2004). Gestión por competencias. El reto compartido del crecimiento personal y de la organización. Madrid: ESIC Editorial, Pozuelo de Alarcón. The Hay Group. (1996). Las competencias: Clave p a r a u n a g e s t i ó n i n t e g r a d a d e l o s r e c u r s o s h u m a - nos. Bilbao, Spain: Ediciones Deusto SA. This work was previously published in Competencies in Organizational E-Learning: Concepts and Tools, edited by M. Sicilia, pp. 41-82, copyright 2007 by Information Science Publishing (an imprint of IGI Global). 965 Copyright © 2009, IGI Global, distributing in print or electronic forms without written permission of IGI Global is prohibited. Chapter 3.18 A Brief Overview of Wireless Systems and Standards Sundar G. Sankaran Atheros Communications, USA ABSTRACT This chapter provides a brief overview of wireless systems and standards. The evolution of wireless systems from voice-centric circuit-switched sys- tems to data-centric packet-switched systems is G LVF XV V HG 7KH¿UV W DQG VH FRQG JH QH U DW LRQ ZLU H - less systems were designed primarily for voice service. The data rate supported by these systems is very limited. The 2.5G systems were developed WRUHWUR¿WVHFRQGJHQHUDWLRQV\VWHPVWRVXSSRUW higher data rate applications. The third-generation systems are designed to meet the demands of the Internet era. A wide range of IP-based services is provided using these systems. IEEE 802.16 standard-based systems, commonly referred to as WiMAX, are being proposed as an alterna- tive to third-generation systems for carrying data WUDI¿F3RSXODUZLUHOHVV/$1DQGZLUHOHVV3$1 standards are also discussed. INTRODUCTION Wireless systems have been around for over a cen- tury. Guglielmo Marconi successfully transmitted Morse code from Cornwall, England to St-John’s, Canada in 1901. The wireless technology has come a long way since then. The proliferation of Internet in every aspect of life resulted in rapid convergence of computing and communication industries fueling an explosive growth of wireless communication in the mid-1990s. Now, mobile computing—the use of a portable computing de- vice capable of wireless networking—is a reality. For example, today’s PDAs and cell phones have WKHFDSDELOLW\IRU,QWHUQHWVXU¿QJ&RQVHTXHQWO\ one can use the PDAs and cell phones to do ev- HU\WKLQJIURPVWRFNWUDGLQJWR¿QGLQJ GULYLQJ directions. WiFi enabled laptops allow the users to connect to Internet from WiFi hotspots, which are becoming ubiquitous. Emerging standards such as WiMAX aim to provide high-speed wire- less data access from anywhere at anytime. This 966 A Brief Overview of Wireless Systems and Standards chapter describes various wireless standards that have made mobile computing a reality. FIRST- AND SECOND-GENERATION CELLULAR SYSTEMS 7KH¿UVWJHQHUDWLRQFHOOXODUV\VWHPVGHYHORSHGLQ the late 1970s, use analog modulation techniques. These systems are designed primarily to carry analog speech. Very low-rate data transmission is possible in these systems. The advance mobile phone service (AMPS) system, developed by $77%HOO/DEVLVDQH[DPSOHRI¿UVWJHQHUD- tion wireless systems. A good fraction of cellular systems currently deployed around the world are based on AMPS. For example, AMPS is still being used in some rural parts of the U.S. Starting in the early 1990s, wireless operators started deploying second-generation cellular sys- tems that use digital modulation (Yacoub, 2001). The second-generation systems use advanced digital-signal-processing algorithms to process signals. The transition to digital from analog allowed the second-generation cellular systems to offer higher capacity 1 WKDQWKH¿UVWJHQHUDWLRQ analog systems. The second-generation systems offer services such as text messaging, also known as short message service (SMS), and circuit switched data (CSD), in addition to legacy voice service. Some of the popular second-generation cellular systems include global system mobile (GSM), interim standard 136 (IS-136), and interim standard 95 (IS-95). The GSM system (Mouly, 1992) was originally designed and deployed in Europe to solve the fragmentation problems 2 of WKH¿UVWFHOOXODUV\VWHPVLQ(XURSH1RZ*60 is the most widely deployed wireless system in the world, with deployments in Europe, Asia, Australia, South America, and some parts of the U.S. IS-136, the American counterpart of GSM, LVDGLJLWDOHYROXWLRQRIWKH¿UVWJHQHUDWLRQ$036 system. It is often, albeit imprecisely, referred to as the TDMA standard since it uses time division multiple access (TDMA) air interface. However, it should be noted that many other standards, including GSM, use TDMA. The IS-136 systems are widely deployed in North America. IS-95, pioneered by Qualcomm, is the popular second- generation system based on code division multiple access (CDMA). It is also known as cdmaOne. These systems are in wide use in North America, South Korea, India, and China. The second-generation cellular systems were rolled out before the dawn of the Internet era. &RQVHTXHQWO\WKHVHV\VWHPVDUHQRWHI¿FLHQWLQ carrying data: these systems transfer data with F L UF X LW V ZLW FK L Q J ZK L FK LVQ RW D VH I ¿F LH Q WD V SD F NH W switching, used by systems of later generation. Furthermore, the data rate provided by these sys- tems is very limited. For example, GSM systems provide a maximum data rate of 14.4 kbps. EVOLUTION FROM SECOND GENERATION TO 2.5G New 2.5G technologies were developed in an HIIRUWWRUHWUR¿WWKHVHFRQGJHQHUDWLRQV\VWHPV to be able to support the higher data rates that are required by modern Internet applications. These technologies enable cellular service pro- viders to support features such as Web browsing, e-mail, mobile commerce (m-commerce), and location-based mobile services using existing second-generation infrastructure, with minimal hardware and software upgrades to base stations and handsets. The popular 2.5G systems include high speed circuit switched data (HSCSD), general packet radio service (GPRS), and enhanced data rates for GSM evolution (EDGE) (Halonen, Romero, & Melero, 2003). HSCSD is a 2.5G upgrade to GSM. It needs just a software upgrade at the base stations. With this upgrade, the maximum data rate per user can be increased to 57.6 kbps. However, the data transfer is still done with circuit switching. 967 A Brief Overview of Wireless Systems and Standards GPRS is a 2.5G upgrade to both GSM and IS-136. These systems use packet switching and provide access to the Internet at a maximum data rate of 171.2 kbps. EDGE is a more advanced upgrade, requiring addition of new hardware and software at the existing base stations, to both GSM and IS- 136. The EDGE systems can provide a maximum per user data rate of 384 kbps. 3 The cellular systems belonging to 2.5G and above support a new Web browsing format lan- guage called wireless application protocol (WAP). This language was designed to meet the challenges of Web browsing from a wireless handset, which usually has small displays and limited memory. The wireless devices usually run WAP-based microbrowsers. These browsers allow the users to access the Web using one hand without requir- ing a keyboard. THIRD-GENERATION CELLULAR SYSTEMS The third-generation cellular systems (Mandyam & Lai, 2002) aim to provide a wide range of Inter- net protocol (IP) based services, along with voice and data services, using a single handset, whether GULYLQJ ZDONLQJ RU VWDQGLQJ VWLOO LQ DQ RI¿FH setting. The key attributes of third-generation systems include 144 kbps or higher data rate in KLJKPRELOLW\YHKLFXODUWUDI¿FNESVIRUSH- GHVWULDQWUDI¿F0ESVRUKLJKHUIRULQGRRUWUDI¿F and capability to determine geographic position of mobiles and report it to both the network and the mobile terminal. Some of the third-generation wireless standards include CDMA2000 and uni- versal mobile telecommunication system (UMTS, also known as W-CDMA) (3GPP2 Web site, n.d.; UMTS Forum Web site, n.d.). CDMA2000 is the 3G evolution of IS-95, while W-CDMA is the 3G evolution of GSM and IS-136. The CDMA2000 family of standards includes CDMA2000 1xRTT (also known as 1xRTT), CDMA2000 1xEV-DO (often referred to as EV- DO), and CDMA2000 1xEV-DV (also known as EV-DV). The 1xRTT (short for single-carrier radio transmission technology) systems provide data rates up to 144 kbps, while the latest generation of EV-DO (short for evolution data optimized) systems are capable of providing data rates up to 3.1 Mbps. 1xRTT and EV-DO have been rolled out in the U.S. by Verizon and Sprint. The EV- DV (short for evolution data voice) supports both voice and data users simultaneously. Due to lack of interest by carriers, the EV-DV development is currently on hold. UMTS is the European and Japanese counter- part of CDMA2000. The UMTS system has been deployed in Japan by NTT DoCoMo. An evolution of UMTS known as high speed downlink packet Figure 1. Evolution of wireless standards AMPS GSM IS-136 IS-95 HSCSD GPRS EDGE WCDMA CDMA-2000 1G 2G 2.5G 3G WiMAX WiBro 4G 968 A Brief Overview of Wireless Systems and Standards access (HSDPA) has been rolled out in the U.S. by Cingular. WIRELESS LOCAL AREA NETWORKS Wireless local area networks (WLAN) are rapidly UHSODFLQJ ZLUHV ZLWKLQKRPHV DQGRI¿FHV7KH most common wireless LANs are based on the IEEE 802.11 standard (Gast, 2005; Wi-Fi Web sit e, n.d.). T he y are c om mon ly referre d t o as Wi Fi networks. The phenomenal growth of Internet combined with increased use of portable, laptop computers also contributed to the rapid acceptance of WLANs. Some of the other factors that can be attributed to their widespread adaptation are their low cost and the ease of installation. They can be easily deployed by individuals within buildings without a license (since these devices usually operate in license-free band). The original 802.11 standard, adopted in 1997, provided data rates up to 2 Mbps. Higher data rate enhancements to 802.11, commonly referred to as 802.11a, 802.11b, and 802.11g, emerged later. The 802.11b system operates in the 2.4 GHz band and provides data rates up to 11 Mbps. One of the drawbacks of 802.11b is its limited capacity due to the limited bandwidth availability in the 2.4 GHz band. This capacity limitation restricted the use RI:/$1VLQRI¿FHHQYLURQPHQWVZKHUHKLJKHU capacity is usually needed. Furthermore, the 2.4 *+]LVDOUHDG\³FURZGHG´ZLWKRWKHUGHYLFHVVXFK as cordless phones, Bluetooth, and microwaves. These drawbacks were mitigated with the emer- gence of 802.11a devices, which operate in the 5 GHz band and provide data rates up to 54 Mbps. The wider bandwidth available in the 5 GHz band DOORZVXVLQJDEDVHG:/$1VLQRI¿FH environments. The 802.11g standard, adopted in 2003, provides data rates up to 54 Mbps in the 2.4 GHz band. The emerging 802.11n standard promises data rates up to 600 Mbps. The 802.11n draft compliant products are expected to reach the market in the second half of 2006. WiFi has proven to be a way of providing reliable in-building wireless access. The cellular phone manufacturers are launching dual mode GSM/WiFi devices that can make and receive calls on both cellular network and enterprise WLAN. The European counterpart of WiFi is Hiper- LAN (short for high performance radio local area network), standardized by European Telecommu- nications Standards Institute (ETSI). HiperLANs have similar physical layer as Wi-Fi and are used FKLHÀ\LQ(XURSH WIRELESS METROPOLITAN AREA NETWORK Wireless metropolitan area networks (WMAN) aim to provide always on broadband access to Internet at anytime from anywhere. The most successful wireless MAN technology is based on the IEEE 802.16 standard, which is often referred to as WiMAX networks (Ohrtman, 2005; WiMAX Forum Web site, n.d.). WiMAX is an alternative to third-generation cellular systems to provide broadband connections over long distances, and it is considered to be a fourth-generation technology. While the third-generation systems support both circuit and packet switching, the fourth-genera- tion systems support packet switching only. The ¿UVWJHQHUDWLRQ:L0$;SURGXFWVDUHH[SHFWHG to support data rates up to 40 Mbps per channel at vehicular speeds. High performance radio metropolitan area network (HiperMAN) is the European alternative WR:L0$;.RUHDDGRSWHGDÀDYRURI:L0$; known as wireless broadband (WiBro) as its wireless MAN standard. 969 A Brief Overview of Wireless Systems and Standards WIRELESS PERSONAL AREA NETWORKS Wireless personal area networks (WPANs) are designed to replace the wires that connect devices to one another (such as printer cables, headphone cables, cables that run from personal computers to mouse, cables that run from set-top boxes). Bluetooth (Bluetooth Web site, n.d.) is the most widely embraced WPAN standard. It operates in the 2.4 GHz unlicensed band and provides short-range communication within a nominal range of 10 meters. Many laptops and cell phones currently support Bluetooth connections. Some car manufacturers, including Acura and BMW, are installing Bluetooth in cars. The latest Blue- tooth devices consume extremely low power and provide reliable communication at data rates up to 2.1 Mbps. ZigBee (ZigBee Web site, n.d.) is another competing technology for wireless PAN. ZigBee devices are expected to be cheaper and simpler than Bluetooth devices. The target applications for ZigBee include general-purpose, inexpensive, self-organizing mesh network that can be shared by medical devices, smoke and intruder alarms, and building and home automation. CONCLUSION The wireless revolution is just beginning. The FRQÀXHQFHRIFRPPXQLFDWLRQDQGFRPSXWLQJ has created many new applications for wireless systems. The throughput, capacity, and range of wireless systems are constantly being improved. This chapter summarized the evolution that has happened over the last 2 decades. 7KH¿UVWDQGVHFRQGJHQHUDWLRQV\VWHPVZHUH primarily designed for voice applications. The *V\VWHPVZHUHGHVLJQHGWREHUHWUR¿WWR* systems to support data. The third-generation systems were designed to support both voice and data, while the evolving fourth-generation systems are being designed to support primar- ily data. The WLAN system based on WiFi has seen tremendous growth and success over the last 5 years. REFERENCES Bluetooth Web site. (n.d.). Retrieved February, 2006 from http://www.bluetooth.com Gast, M. (2005). 802.11 Wireless networks: The GH¿QLWLYH JXLGH (2 nd ed.). Sebastapol: O’Reilly Media, Inc. Halonen, T., Romero J., & Melero J. (2003). GSM, GPRS, and EDGE performance: Evolution towards 3G/UMTS. West Sussex: John Wiley & Sons. Mandyam, G., & Lai J. (2002). Third generation CDMA systems for enhanced data services. San Diego: Academic Press. Mouly, M., & Pautet, M. (1992). The GSM system for mobile communications. Palaiseau: Telecom Publishing. Ohrtman, F. (2005). WiMAX handbook. New York: McGraw Hill Professional. 3GPP2 Web site. (n.d.). Retrieved February 2006 from http://www.3gpp2.org UMTS-Forum Web site. (n.d.). Retrieved February 2006 from http://www.umts-forum.org Wi-Fi Web site. (n.d.). Retrieved February 2006 from KWWSZL¿RUg WiMAX FORUM Web site. (n.d.). Retrieved Fe- bruary 2006 from http://www.wimaxforum.org Yacoub, M. (2001). Wireless technology: Pro- tocols, standards, and techniques. Boca Raton: CRC Press. 970 A Brief Overview of Wireless Systems and Standards ZigBee Web site. (n.d.). Retrieved February 2006 from http://www.zigbee.org ENDNOTES 1 Capacity is the number of active users that can be supported at the same time. 2 Before GSM deployment, different parts of Europe used different cellular standards and it was not possible to use the same handset everywhere. 3 This is the maximum data rate per GSM channel. By combining many GSM channels together, it is possible to achieve data rates up to several megabits per second. 971 A Brief Overview of Wireless Systems and Standards APPENDIX: GLOSSARY 1xRTT Single Carrier Radio Transmission Technology AMPS Advance Mobile Phone Service CDMA Code Division Multiple Access CSD Circuit Switched Data EDGE Enhanced Data Rates for GSM Evolution EV-DO Evolution Data Optimized EV-DV Evolution Data Voice GPRS General Packet Data Service GSM Global System Mobile HiperLAN High Performance Radio Local Area Network HSCSD High Speed Circuit Switched Data HSDPA High Speed Downlink Packet Access IP Internet Protocol IS-136 Interim Standard 136 IS-95 Interim Standard 95 PSD Packet Switched Data SMS Short Message Service TDMA Time Division Multiple Access UMTS Universal Mobile Telecommunication System WAP Wireless Application Protocol WAP Wireless Application Protocol WiFi Wireless Fidelity WiMAX Worldwide Interoperability for Microwave Access WiBRO Wireless Broadband WLAN Wireless Local Area Network WPAN Wireless Personal Area Network WMAN Wireless Metropolitan Area Network This work was previously published in E-Business Process Management: Technologies and Solutions, edited by J. Sounder- pandan and T. Sinha, pp. 148-154, copyright 2007 by IGI Publishing (an imprint of IGI Global). 972 Copyright © 2009, IGI Global, distributing in print or electronic forms without written permission of IGI Global is prohibited. Chapter 3.19 Wireless Networks Based on WiFi and Related Technologies Rajendra V. Boppana University of Texas at San Antonio, USA Suresh Chalasani University of Wisconsin-Parkside, USA ABSTRACT Multihop wireless networks based on WiFi tech- QRORJ\RIIHUÀH[LEOHDQGLQH[SHQVLYHQHWZRUNLQJ possibilities. Applications of multihop wireless networks range from personal networks within consumer homes to citywide departmental net- works to wide-area vehicular ad hoc networks. In this chapter, we focus on multihop ad hoc net- works with communication among user devices and access points, where available, without the restriction that the user devices need to be within WKHUDGLRUDQJHRIDFFHVVSRLQWV:H¿UVWGHVFULEH pure WiFi networks and their limitations. Next we discuss mixed networks based on WiFi and other wired and wireless technologies to provide robust city-scale networks. This chapter also explores security issues and vulnerabilities of wireless networks. An emerging application of WiFi ad hoc networks-5),'UDGLRIUHTXHQF\LGHQWL¿FD- tion) networks based on the WiFi technology for warehouses and large retail stores-is presented. This chapter also presents another emerging ap- plication of WiFi-based networks: vehicular ad hoc networks for automobiles. INTRODUCTION Cellular and :L)LZLUHOHVV¿GHOLW\DUHFXUUHQWO\ the most popular and actively pursued wireless technologies for consumer and business use. A cellular network consists of several base sta- tions, each covering a small geographical region. Together the base stations cover a wide region such as a city. To be useful, the entire region of interest must be covered without gaps by these base stations. This requires billions of dollars of investment in network infrastructure consisting of wireless spectrum and base stations. An en- tirely different type of wireless network is made possible by the ZLUHOHVV¿GHOLW\:L)LWHFKQRO- 973 Wireless Networks Based on WiFi and Related Technologies ogy. This technology (based on the IEEE 802.11 standard (IEEE Computer Society LAN/MAN Standards Committee, 1999)) enables wireless communication on an ad hoc basis. In the simplest FRQ¿JXUDWLRQDZLUHOHVVDFFHVVSRLQWGHQRWHG hotspot) can be used to share an Internet connec- tion among several tens of users in a small area such as a conference room or a coffee shop. The network connectivity is limited to the radio range (about 50 meters) of the hotspots, and communi- cation among users must go through the access point. Such networks, called wireless local area networks (WLANs), are already extensively used by businesses and academic campuses. In this chapter, we focus on multihop ad hoc networks with communication among user devices and ac- cess points, where available, without the restriction that the user devices need to be within the radio range of access points. The WiFi technology is inexpensive due to two factors: (a) the use of free, unlicensed radio spectrum at 2.4 GHz and 5.8 GHz bands obviates heavy investment in private, dedicated radio spectrum, and (b) the widespread use of WiFi equipped PDAs, laptops, and even phones SURYLGHVVLJQL¿FDQWEXVLQHVVRSSRUWXQLWLHVDQG MXVWL¿FDWLRQIRUGHSOR\LQJDGKRF:L)LQHWZRUNV Since all WiFi devices must comply with the IEEE standard, WiFi products from multiple vendors can be mixed and matched for seamless opera- tion. This has driven the cost of individual WiFi devices low, which in turn, made deployment of WiFi-based networks covering medium to large areas an attractive and, even necessary, business investment. In this chapter, we describe various trends in the design and deployment of wireless networks based on WiFi and other technologies (Gast, 2005; Macker & Corson, 1998; Murthy & Manoj, 2004). The rest of the chapter is organized as IROORZV7KHVHFWLRQ³$G+RF:LUHOHVV1HW- works” describes pure WiFi networks and their O L P LW D W LR QV ³0L [ HG :LU HOH VV1HW ZRU N V´ GH V F U LE H V mixed networks based on WiFi and other wired and wireless technologies to provide robust city- VFDOHQHWZRUNV³6HFXULW\LQ:LUHOHVV1HWZRUNV´ describes security issues and vulnerabilities of ZLUHOHVVQHWZRUNV³5),':LUHOHVV1HWZRUNV´ describes an emerging application of WiFi ad KRFQHWZRUNV5),'UDGLRIUHTXHQF\LGHQWL¿FD- tion) networks based on the WiFi technology for ZDUHKRXVHV DQG ODUJH UHWDLO VWRUHV ³9HKLFXODU Ad Hoc Networks” describes another emerging application of WiFi-based networks: vehicular ad KRFQHWZRUNVIRUDXWRPRELOHV7KH³6XPPDU\´ section summarizes the chapter. AD HOC WIRELESS NETWORKS An ad hoc wireless network is an impromptu network formed by several wireless devices, such as PDAs, laptops, and phones, without relying on an existing network infrastructure (Perkins, 2000). These devices (denoted as nodes) may be mobile and use a common wireless technology such as WiFi. To facilitate communication among the nodes that are not directly in the radio range of one another, the other nodes act as intermedi- ate routers, just like routers in the Internet. Such networks are useful in military combat situations, where a group of soldiers must be connected to exchange information, or in emergency rescue operations, where there is no network infra- structure or the existing infrastructure has been destroyed. Because of frequent topology changes due to node mobility and due to wireless inter- ference, the existing networking software used for the Internet is not suitable for these ad hoc networks. Consequently, extensive research on routing protocols and transport protocols has been conducted to make ad hoc networks suitable for general-purpose use. 5RXWLQJSURWRFROVDUHEURDGO\FODVVL¿HGLQWR proactive and reactive protocols. A proactive protocol keeps track of all possible routes within the ad hoc network, and disseminates routing information with others, periodically, or when- . KLJKPRELOLWYHKLFXODUWUDI¿FNESVIRUSH- GHVWULDQWUDI¿F0ESVRUKLJKHUIRULQGRRUWUDI¿F and capability to determine geographic position of mobiles and report it to both the network and the mobile terminal. Some of the third-generation wireless standards include CDMA2000 and. minimal hardware and software upgrades to base stations and handsets. The popular 2.5G systems include high speed circuit switched data (HSCSD), general packet radio service (GPRS), and enhanced. switching. 967 A Brief Overview of Wireless Systems and Standards GPRS is a 2.5G upgrade to both GSM and IS-136. These systems use packet switching and provide access to the Internet at a maximum