ABSTRACTThe paper describes selected news in wireless computer network standards, interesting for military purposes. For completeness, some advances in WiFi (IEEE 802.11) are mentioned. The main focus is aimed at the wireless technology WiMAX, which promises easily extensible and cheap method of broadband communication both for public and military objectives. Finally, the ZigBee as a solution for special purposes is shortly discussed. INTRODUCTIONWe can see substantial progress in wireless networking (especially IEEE 802.11, i.e. Wireless LAN or WLAN) lately. The first WLAN standards were not very suitable for military purposes for several reasons, especially security [1]. The most important affairs concern speed and security improvement, but the brand new and hopeful standard 802.16 or WiMAX is being developed. It is described more closely. There are also other interesting wireless solutions, although suppose to be used in commercial environment, potentially applicable in a special military activity. The example is a ZigBee technology, which description is included in the paper. WLAN speed improvementMost today's WLANs operate at 11 Mb/s to 54 Mb/s. Even though WLANs are primarily designed as LAN devices, they can be used to provide site-to-site connectivity at distances approximately up to 40 km (line of the sight). The new standard, designated 802.11n "Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: Enhancements for Higher Effective Throughput" is under development [2], [3]. The aim is to improve the speed of WLAN up to 100 Mb/s really for users (not from physical layer point of view - compare 802.11a/g with 54 Mb/s, but in fact up to 20 Mb/s), better say to establish wide accepted international standard. Only two final proposals from more than 60 candidates rested in 2005, they are TGn Synch and WWiSE. Both use MIMO (Multiple-Input Multiple-Output) technology, i.e. several signal paths (and antennas on the transmitter/receiver site). The group TGn Synch (Atheros, Agere, Cisco, Intel, Matsushita, Mitsubishi, Nortel, Panasonic, Philips, Qualcomm, Samsung, Sony and Toshiba) proposed the first standard. Its project even assumes data throughput up to 500 Mb/s (the Orthogonal Frequency-Division Multiplexing should be used). The proposed channel bandwidth was originally 40 MHz, but it was decreased to 20 MHz from backward compatibility reason. Number of MIMO transmitters/receivers is 2/2. The WWiSE group (World Wide Spectrum Efficiency) proposed second standard, members of WWiSE are Airgo Networks, Broadcom, Conexant, France Telecom, Hughes Network Systems, Mitsubishi, Motorola, Nokia, NTT, STMicroelectronics and Texas Instruments. Their solution uses 2/2 MIMO with spatial multiplex, 20 MHz channels and aggregated speed of 130 Mb/s. The IEEE 802.11n task group meeting held in March 2005 did not fetch the winner. Instead it has decided to organize following procedure: either both groups find an acceptable compromise or already refused suggestions would be consider again. Moreover, the three proposal groups reinstated during the May meeting (TGn Sync, WWiSE and MITMOT, the last one was formerly eliminated) indicated that they have begun working together to create a single merged proposal. As a result, the task group postponed the pending down select voting process until the merged document will be ready. The 802.11n task group break up almost happened in begin of 2006 because of continuing internal controversy. Fortunately the compromise was finally adopted, but the solution was not accepted by required majority of members on next meeting in June. The reason was unsecured coexistence with existing 802.11a/b/g/h devices, which result could be mutual jamming. The different channel spacing and binding also need additional discussion. news in Security standardsSecurity in the IEEE 802.11 specification - which applies to 802.11b, 802.11a, and 802.11g - was generally taken as poor. Several vulnerabilities in the authentication, data-privacy, and message-integrity mechanisms defined in the specification were found. The following major vulnerabilities are summarized here:
Wireless attack methods can be broken up into three categories:
Security was not a big concern for early WLANs. The equipment was proprietary, expensive, and hard to find. Many WLANs used the "secret" Service Set Identifier (SSID, up to 32 ASCII characters) as a basic form of security. The IEEE enhanced Wired Equivalent Privacy (WEP) with Temporal Key Integrity Protocol (TKIP), which provides robust authentication options with 802.1x to make 802.11 based wireless LANs more secure. The IEEE also had looked for stronger encryption mechanisms and has adopted the use of the Advanced Encryption Standard (AES) to the data privacy section of the 802.11i standard, which has the following key components: Temporal Key Integrity Protocol (TKIP), Counter-Mode/CBC-MAC Protocol (CCMP), IEEE 802.1x and EAP encapsulation over LANs (EAPOL). In addition to 802.1x, some vendors support the use of layer 3 IP Security (IPSec) based VPNs over 802.3 wired LANs and 802.11 WLANs, using VPN termination devices and VPN client software installed on wireless devices. This is vital to provide cost-effective enterprise access from public spaces such as hotels and airports. New three projects that also concern security have started in 2005 [3], [4]. They are: P802.11u "Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: IEEE 802.11 Interworking with External Networks". Supplement for harmonization of collaboration between 802.11 and external networks. P802.11v "Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: IEEE 802.11 Wireless Network Management" - common interface for device management in WLAN, by centralized or distributed way on the data link layer. It also includes necessary MIB changes. P802.11w "Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: Protected Management Frames" - Extension of current MAC sublayer a few more mechanisms (data integrity support, data source authenticity, data privacy and protection against replay type attacks for selected frames. WIMAXWiMAX (Worldwide Interoperability for Microwave Access) is a Broadband Wireless Access (BWA) solution based on standards recommendations from the Institute for Electrical and Electronics Engineers (IEEE) 802.16 working group [8] and the European Telecommunications Standards Institute (ETSI). WiMAX is promoted by the WiMAX Forum; a special interest group of approximately 300 members from the manufacturing, carrier, service provider, consulting and related communities [11], [12]. WiMAX is a third generation of data transfers mobile technology for the wireless access to the wide-area data networks. It exceeds GPRS, Edge or CDMA and will probably supersede today's widely deployed WiFi technologies. The IEEE 802.16 standard was released in 2001 [12] and standardized Local Multipoint Distribution Services (LMDS). Focused on fixed wireless and designed to accommodate point-to-point and point-to-multipoint topologies, 802.16 was tuned to frequencies in the 10-66 GHz range (selected segments only!) and required LOS. This first standard got little attention. Next version, 802.16a released in 2003, was based on Multichannel Multipoint Distribution Services (MMDS) and the European HiperMAN system. This extension operates in the 2-11 GHz rang, which includes both licensed and license-exempt bands (selected segments). It is designed for both point-to-point and point-to-multipoint topologies, and usually requires LOS. 802.16d, aka 802.16-2004, the most recently released version of the standard, is a compilation and modification of previous versions and amendments 802.16a, b and c. Released in 2004 and operating in the 2-11 GHz range (again, only in a few segments), it was designed for point-to-point, point-to-multipoint and meshed topologies. 802.16-2004 operates best with line of the sight (LOS), but does not require it (NLOS). This extension of the standard includes support for indoor Customer Premises Equipment (CPE). Newer version, 802.16e, finalized in October 2005, adds hand-off capability, thereby supporting portability and mobility. Operating in the 2-11 GHz range (segments), it is designed for point-to-multipoint applications, does not require LOS. Where LOS can be achieved, WiMAX cell coverage can as much as 50 km; otherwise the typical cell radius might be in the range of 8 km. The fixed wireless standards provide for shared bandwidth up to about 70 Mb/s per Base Station (BS). The level of actual throughput depends on LOS, distance, air quality, interference and other factors that can affect signal quality. Mobile network deployments (802.16e) can be expected to provide up to 15 Mb/s of shared bandwidth within a cell radius of up to three kilometers and support mobile subscribers up to 150 km/h:
WiMAX SecurityThe 802.16 security protocol is built on enhancements to the Privacy Key Management (PKM) developed for cable modem communications. The protocol uses X.509 digital certificates with RSA encryption for authentication and key exchange. Traffic encryption mandates the use of Data Encryption Standard (DES) with 56-bit keys. WiMAX ApplicationsIssues aside, the applications for WiMAX are numerous [5], [6], including:
WiMAX drawbacksWiMAX has also its drawbacks, as well:
Today's reality - WiMAX devicesThe 802.16 set is all about the future, as no complete commercial systems are yet in operation. Intel indeed has developed the PRO/Wireless 5116 chipset [7] (former Rosendale), but its delivery was delayed (commercial availability even April 2005). Other competitors are for example Fujitsu Microelectronics (Japan), Sequans Communications (France) and Wavesat (Canada). As a rule, those chipsets doesn't contain the radio part that must be solved independently (for example Athena Semiconductors's ATS90xx). Because of 802.16 standard considerable elaborateness, the conformity of WiMAX devices should be rigorously tested. The WiMAX Forum has selected Cetecom (Spain) as a principal certification laboratory for WiMAX devices. This year, more WiMAX devices (BS, CPE) were presented on several exhibitions (WCA Symposium, 3GSMM World Congress, CTIA Wireless 2005, etc.). Producers were Siemens (SkyMax), Motorola (Canopy), Airspan (AS.MAX), BelAir Networks (WMSA), Redline Communications (AN 100), Nortel and LG Electronics, Alcatel and Alvarion. The pilot projects have prepared AT&T (USA), France Telecom (France), Deutsche Telekom (Germany), WiMAX Telecom AG (Austria, Switzerland). ZigBee / IEEE 802.15.4The ZigBee / IEEE 802.15.4 solution belongs under so called Personal Area Networks (PAN). Their basic feature is low radiated energy and consequently very long durability life (there is expectation that time of sending will take only 0.1 % of total duty cycle). That technology is intended for usage such as sensors, telemetry, vehicles, industry, medicine, household, toys, RFID etc. ZigBee devices will be cheap (the price is expected under $1). So they can be installed directly in inapproachable places like the bulb sockets, which can be subsequently easy controlled [14], [15]. On the contrary, the ZigBee based network can be relatively wide, if needed. The routing protocols are defined in that networks, particular devices can pass messages among them etc. First of all, it is necessary to mention that there are two different standards. They were born in dissimilar environments, but they complement each other. The first standard, 802.15.4 (published in 2003), solves the hardware, i.e. physical and media access control (MAC) sublayers. Next standard, ZigBee itself, has existed since 2004 and it deals more likely with software, i.e. network and application layers, security, management etc. [16]. In detail - the 802.15.4 supposes to use the following frequency bands: 868 MHz (Europe, 20 kb/s, 1 channel), 915 MHz (Americas, 40 kb/s, 10 channels) a 2,4 GHz (worldwide, 250 kb/s, 16 channels). The coverage should be 30-100 meters or more, the lifespan should be limited by the battery durability. The modulation is DSSS, communication is two-way, messages are acknowledged and the timing can be controlled by beacon. Data encryption, authorisation and recency are guaranteed during transmission. Node number in the network is 255/65535, coupling time is less than 30 ms, activation time from the stand-by mode is less than 15 ms as well as channel access time. On the contrary the ZigBee (specified by ZigBee Alliance) is concerned with topology (star, extended star, mesh), routing, enhanced security (32/64/128 bits AES); it also defines application interface. The ZigBee devices can be divided into three categories:
The ZigBee Alliance defined the certification procedure for ZigBee products conformity with standards in the begin 2006. National Technical Services, Inc and TUV Rheinland Group have been authorised as an independent validation bodies. The ZigBee technology appears to be very suitable for military use. In addition to the labelling (goods, supplies, vehicles), it can be use in the sensors for reconnaissance, watching etc. CONCLUSIONSModern wireless networks can notably change traditional military communication systems. Instead of hierarchical arrangement, they can be built on areal coverage base. The command structure can be subsequently created on higher layer. Next, we can see rapid development of commercial wireless solutions. It is very important to be in touch with them. Not only smaller countries have no enough financial means for complete production of special military communication devices. The new wireless standards, although their evolution is not straight-lined, promises brand new possibilities for military communication and information systems. Among them, especially WiMAX appears very important. BIBLIOGRAPHY[1] P. Zandl: Bezdrátové sítě WiFi, ISBN 80-7226-632-2, Computer Press, Brno, Czech Republic, 2003 [2] R. Pužmanová: Kdy bude 100 Mbit/s WiFi? [3] The Working Group for WLAN Standards: Current 802.11 WG Documents from March 2002, [4] R. Pužmanová: 802.11u,v,w a také k (RRM) [5] The Intel Library: Deploying License-Exempt WiMAX Solutions, Intel Corporation, 2005 http://www.intel.com/netcomms/technologies/wimax/306013.pdf [6] The Intel Library: Understanding Wi-Fi and WiMAX as Metro-Access Solutions, Intel Corporation, 2004 http://www.intel.com/netcomms/technologies/wimax/304471.pdf [7] Intel Product Brief: IntelR PRO/Wireless 5116 Broadband Interface, Intel Corporation, 2005 http://www.intel.com/network/connectivity/products/wireless/307327.pdf [8] Technology Intel Magazine: IEEE 802.16 WirelessMAN Specification Accelerates Wireless Broadband Access, Intel Corporation, 2003 http://www.intel.com/technology/magazine/standards/st08031.pdf [9] Intel in Communications: Orthogonal Frequency Division Multiplexing, http://www.intel.com/netcomms/technologies/wimax/303787.pdf [10] Intel in Communications: Adaptive Modulation (QPSK, QAM), [11] R. Horak: WiMAX: WLL by the Numbers, [12] The IEEE 802.16 Working Group on Broadband Wireless Access Standards: 802.16e Closing Report http://grouper.ieee.org/groups/802/16 [13] Intel Product Brief: Interaktivní terénní videokonference pro krizový management ochrany obyvatelstva, http://www.army.cz/scripts/detail.php?id=5601 [14] http://www.zigbee.org/en/index.asp [15] http://en.wikipedia.org/wiki/ZigBee |
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