114 JOURNAL OF EMERGING TECHNOLOGIES IN WEB INTELLIGENCE, VOL. 2, NO. 2, MAY 2010prevents transitions <strong>of</strong> system states from q1 to q4. Asdiscussed above <strong>in</strong> average case transition from q1 to q4is only possible if made <strong>in</strong> .0005 seconds. Suchmechanism can be based on detect<strong>in</strong>g system callsequence required for this transition. If any suchsequence is detected it should delay (approximately .0005execution <strong>of</strong> these system calls so that before the systemstate will change from q2 or q3 to state q4, transitionfrom q1 or q2 to state q1(<strong>in</strong>itial healthy state) took place.This mechanism can be implemented by chang<strong>in</strong>goperat<strong>in</strong>g system kernel.IX. CONCLUSIONIn this paper, we propose a new time stamp<strong>in</strong>g basedapproach to check <strong>in</strong>tegrity <strong>of</strong> log files <strong>of</strong> HIDS. Thisapproach can be comb<strong>in</strong>ed with Detection and AutoRecovery based architecture to Protect Host Based IDS.As discussed <strong>in</strong> section 4, unlike other approaches ourapproach does not use virtual mach<strong>in</strong>e and hence doesnot affect system performance adversely.Our mechanism ensures that HIDS process alwayslive (cannot be killed by adversary) and the <strong>in</strong>formationrelated to HIDS can never be updated by any adversary.This architecture also ensures the <strong>in</strong>tegrity <strong>of</strong> frequentlyupdated log files <strong>of</strong> HIDS.REFERENCESFigure-4: DFA represent<strong>in</strong>g sequence <strong>of</strong> steps to disable ourarchitecture.Issue <strong>of</strong> authorization and <strong>in</strong>tegrity <strong>of</strong> genu<strong>in</strong>eupdates <strong>of</strong> HIDS <strong>in</strong>formation is another important issueto be addressed. In this approach, we did not consider anytechnique to authorize <strong>of</strong> update. Because IDS’srules/signature database requires frequent updates,<strong>in</strong>clusion <strong>of</strong> a strong authorization mechanism would berequired.[1] A. Abraham, C. Grosan and C.M. Vide. EvolutionaryDesign <strong>of</strong> Intrusion Detection Programs. International<strong>Journal</strong> <strong>of</strong> Network Security, Vol. 4, No. 3, 2007.[2] M Laureano, C Maziero, E Jamhour, Protect<strong>in</strong>g hostbased<strong>in</strong>trusion detectors through virtual mach<strong>in</strong>es-Computer Networks- Elsevier, 2007.[3] P. Chen, B. Noble, When Virtual Is Better Than Real,Workshop on Hot Topics <strong>in</strong> Operat<strong>in</strong>g Systems, 2001.[4] T. Garf<strong>in</strong>kel, M. Rosenblum, A virtual mach<strong>in</strong>e<strong>in</strong>trospection based architecture for <strong>in</strong>trusion detection,ISOC Network and Distributed System SecuritySymposium (2003).[5] S. Axelsson. Research <strong>in</strong> <strong>in</strong>trusion detection systems: Asurvey. Technical report, Chalmers University <strong>of</strong>Technology, 1999.[6] G. Dunlap, S. K<strong>in</strong>g, S. C<strong>in</strong>ar, M. Basrai, P. Chen, ReVirt:Enabl<strong>in</strong>g Intrusion Analysis through Virtual-Mach<strong>in</strong>eLogg<strong>in</strong>g and Replay, USENIX Symposium on Operat<strong>in</strong>gSystems Design and Implementation, 2002.[7] Sur<strong>in</strong>der S<strong>in</strong>gh khurana, Ms. Divya Bansal, Pr<strong>of</strong>. SanjeevS<strong>of</strong>at “Detection and Auto Recovery Approach to ProtectHost Based IDS” 2009 IEEE International AdvanceComput<strong>in</strong>g Conference (IACC 2009)© 2010 ACADEMY PUBLISHER
JOURNAL OF EMERGING TECHNOLOGIES IN WEB INTELLIGENCE, VOL. 2, NO. 2, MAY 2010 115S<strong>of</strong>tware RadioVarun SharmaInfosys <strong>Technologies</strong> Limited, Chandigarh, IndiaEmail: Varun_sharma15@<strong>in</strong>fosys.comYadv<strong>in</strong>der S<strong>in</strong>gh MannInfosys <strong>Technologies</strong> Limited, Chandigarh, IndiaEmail: Yadv<strong>in</strong>derS_Mann@<strong>in</strong>fosys.comAbstract— This paper aims to provide an overview onrapidly grow<strong>in</strong>g technology <strong>in</strong> the radio doma<strong>in</strong> whichovercomes the drawbacks suffered by the conventionalanalog radio. This is the age <strong>of</strong> S<strong>of</strong>tware radio – thetechnology which tries to transform the hardware radiotransceivers <strong>in</strong>to smart programmable devices which can fit<strong>in</strong>to various devices available <strong>in</strong> today’s rapidly evolv<strong>in</strong>gwireless communication <strong>in</strong>dustry. This new technology hassome or the entire physical layer functions s<strong>of</strong>tware def<strong>in</strong>ed.All <strong>of</strong> the waveform process<strong>in</strong>g, <strong>in</strong>clud<strong>in</strong>g the physical layer,<strong>of</strong> a wireless device moves <strong>in</strong>to the s<strong>of</strong>tware. An idealS<strong>of</strong>tware Radio provides improved device flexibility,s<strong>of</strong>tware portability, and reduced development costs. Thispaper tries to get <strong>in</strong>to the details <strong>of</strong> all this. It takes onethrough a brief history <strong>of</strong> conventional radios, analyzes thedrawbacks and then focuses on the S<strong>of</strong>tware radio <strong>in</strong>overcom<strong>in</strong>g these short com<strong>in</strong>gs.I. HISTORYRadio, as anyone would perceive, is a device that canwirelessly transmit or receive signals <strong>in</strong> the radi<strong>of</strong>requency (RF) part <strong>of</strong> the electromagnetic spectrum. J.CMaxwell postulated the theory <strong>of</strong> electromagnetic wavepropagation which was confirmed by H Hertz. Theseelectromagnetic waves travel through space eitherdirectly, or have their path altered by reflection,refraction or diffraction. When EM Waves come <strong>in</strong>contact with a conductor; they get converted to anelectrical energy, radio or micro wave depend<strong>in</strong>g on itswavelength. Radio waves can carry <strong>in</strong>formation byvary<strong>in</strong>g a comb<strong>in</strong>ation <strong>of</strong> the amplitude, frequency andphase <strong>of</strong> the wave with<strong>in</strong> a frequency band. Nikola Teslaand Guglielmo Marconi <strong>in</strong>vented devices that used radiowaves for communication.Earlier, radio systems relied entirely on the energycollected by an antenna to produce signals for theoperator. Radios became more useful after the <strong>in</strong>vention<strong>of</strong> electronic devices such as the vacuum tube and laterthe transistor, which made it possible to amplify weaksignals.Today most <strong>of</strong> our gadgets conta<strong>in</strong> a radio system <strong>in</strong> it.From a cell phone to television , a walkie-talkie <strong>in</strong> a toy,space vehicles, cell phones or Satellite phones,Audio/Video broadcast<strong>in</strong>g, Navigation Systems, RADARand many other applications. Traditional Radios werebuilt only for a particular frequency range, modulationtype, and output power. “Figure 1. shows a typicaltraditional radio receiver.The RF signal is converted to Intermediate Frequency(IF) us<strong>in</strong>g a programmable local oscillator. The IF signalis a fixed frequency and the IF signal is then amplifiedand filtered before feed<strong>in</strong>g it to demodulator. Each k<strong>in</strong>d<strong>of</strong> radio will have its own type <strong>of</strong> demodulator to extractthe audio data for play<strong>in</strong>g it on speaker. These radioswould require hardware changes to modify thesefundamental characteristics like frequency range,modulation type etc. Moreover, with the advancement <strong>of</strong>technology, new communication standards keep com<strong>in</strong>gand are used to varied degree <strong>in</strong> different countries e.g.CDMA, GSM EDGE, 3G, etc. The Conventional radioscannot cope with these advances, due to compatibilityissues. Hence, there was a need for dynamicallyconfigurable radios which could be used for variousapplications by simply re-configur<strong>in</strong>g the s<strong>of</strong>twarerunn<strong>in</strong>g <strong>in</strong> them. They can also be made to comply withthe various communication standards, just by chang<strong>in</strong>gthe implemented protocol. This is the world <strong>of</strong> S<strong>of</strong>twareRadio.Figure 1. Block Diagram <strong>of</strong> a Traditional Radio Receiver© 2010 ACADEMY PUBLISHERdoi:10.4304/jetwi.2.2.115-121