SOFTWARE DEFINED RADIO IN WIRELESS AD-HOC NETWORK Ajay Kr. Sigh 1, G. Sigh 2 ad D. S. Chauha 2 1 Departmet of Computer Sciece ad Egieerig Jaypee Uiversity of Iformatio Techology, Sola -173 215, Idia 2 Departmet of Electroics ad Commuicatio Egieerig Jaypee Uiversity of Iformatio Techology, Sola -173 215, Idia E-mail: ajay41274@yahoo.com ad drghashyam.sigh@yahoo.com ABSTRACT The parameters of commuicatio i ad-hoc etwork such as the distace betwee odes ad chael characteristics chages frequetly with the positio of the user. For efficiet use of such a commuicatio systems, we ca chage software specificatio rather tha chagig ay hardware (such as chip), because chage of hardware is difficult ad cost effective as compared to that of software. O such way software defied radio (SDR) is simple ad ecoomically beeficial. I this paper, we are usig cocept of M-ary phase shift keyig (MPSK) techique for adaptive detectio. Implemetatio of MPSK adaptive detectio is performed by usig software programmig of MPSK modulatio ad it ca be reprogrammed accordig to the requiremet. Use of radio sigal makes this etwork more reliable ad flexible because of its property. 1. INTRODUCTION Software Defied Radio (SDR) reduces the burde of chagig the hardware so frequetly. A radio is used i wireless commuicatios device i which the physical ad lik layer fuctios are implemeted i software. This eables a sigle wireless device to be reprogrammed to use differet modulatio, codig, ad access protocols. The mai advatage of software is its flexibility such that i ca be programmed for emergig stadards. It also ca be dyamically updated with ew software without ay chage i hardware ad ifrastructure. Rapid deploymet is aother importat feature of the software radio. I wireless applicatios where differet stadards might be deployed, user s roamig ca be a big issue i existig platform. Most software radio research to date has bee drive by the iteroperability problems preset i commercial ad military wireless systems [1, 2]. I commercial systems, the multitude of differet cellular stadards ihibits uiversal roamig ad ew stadards are deployed slowly sice it requires istallig ew base statio hardware ad distributig ew hadsets to users. Similarly, the varyig operatioal requiremets of the differet braches of the military require differet radios ad hiders the coordiatio of joit operatios. Software radio also provides the flexibility to adapt dyamically. The ideal software radio iteroperates with ay commuicatios service i its RF preselector bad ad A/D badwidth. By ruig a differet algorithm, the software radio istatly recofigures itself to the appropriate sigal format. This opes iterestig possibilities for expaded radio services. A future software radio might autoomously select the best trasmissio mode (Persoal Commuicatio Network, Mobile Cellular Network, etc), sed probig sigals to establish a lik, explore commuicatios protocols with the remote ed ad adapt to the remote sigal format. It could select the mode for lowest cost, service availability or best sigal quality. The software radio recofigures itself o the fly to support the required services [3]. 2. ARCHITECTURE OF SDR This sigal travelig from trasmittig atea will be collected at receivig atea the to radio frequecy (RF) from RF to dow coverter. Atea RF sig Atea Dow Cover sio IF sig Aalog to Fig. 1.Commoly used SDR receiver. Software cotrolled RF Frot Ed Aalog to SDR sig SDR sig Fig. 2. Advace SDR receiver with software-cotrolled frot ed.
After that passes through aalog to digital coverter (ADC) i order to get digital sigal which is to be fed i digital sigal processig (DSP) ad ultimately the sigal passes to computer CPU s frot ed for further processig as show i Figure 1. Sigal comig from atea is passed i software cotrolled RF Frot ed the to ADC ultimately the sigal passes to computer CPU for further processig as show i Figure 2. 3. APPLICATION AREA OF SDR SDR ca be used as a part of cogitive radio [4] ad i wireless commuicatio system i which either etwork or wireless ode chages its trasmissio or receptio parameters to commuicate efficietly avoidig iterferece with licesed or ulicesed users. This alteratio of parameters is based o the active moitorig of several factors i the exteral ad iteral radio eviromet, such as radio frequecy spectrum, user behavior ad etwork state. 3.1 FPGA Field-Programmable Gate Arrays (FPGA) have formed the basis for high-performace ad affordable computig systems. FPGA- based logic simulators ca emulate complex logic desigs at clock speeds of several orders of magitude faster tha eve accelerated software simulators, while FPGA-based prototypig systems provide great flexibility i rapid prototypig ad system verificatio. However, besides FPGA pi limitatio, existig FPGA-based systems [5] also meet the problem of improvig the routability of itercoect etworks i the architecture desig. FPGA related systems ad products have draw great attetios from egieers ad desigers. FPGA based systems ca provide ovel, high-performace, ad affordable approaches to rapid prototypig, logic emulators, ad dyamically recofigurable subsystems, because FPGA approach allows flexibility, fast time-to-market, customizability ad just-itime productio. These systems ca ru several orders of magitude faster tha software eve with. 3.2 JTRS Joit Tactical Radio System (JTRS) ofte proouced "jitters" is plaed as the ext-geeratio voice-ad-data radio for use by the U.S. military i field operatios. Lauched with a Missio Needs Statemet ad a subsequet requiremets documet (which has bee revised several times), JTRS [6] is a software-defied radio that will work with may existig military ad civilia radios. It icludes itegrated ecryptio ad Widebad Networkig Software to create mobile ad hoc etworks. The fuctioality ad expadability of the Joit Tactical Radio System are built upo the Software Commuicatios Architecture (SCA), a ope-architecture framework that tells desigers how hardware ad software are to operate i harmoy. It govers the structure ad operatio of the JTRS, eablig programmable radios to load waveforms, ru applicatios, ad be etworked ito a itegrated system. A Core Framework, providig a stadard operatig eviromet, must be implemeted o every hardware set. Iteroperability amog radio sets is icreased because the same waveform software ca be easily ported to all radios. 3.3 GPP Geeral purpose processor (GPP) [7] is a macro-processor that is ot tied to, or itegrated with, a particular laguage or piece of software. I its simplest form, a macro processor is a program that copies a stream of text from oe place to aother, makig some kid of systematic set of replacemets as it does so. Macro processors are ofte embedded i other programs (for example, may assembler programs icorporate a macro processor ad the C-laguage madate the presece of a preprocessor which icorporates some crude macro processig facilities). However, macro processors may also be stad aloe programs, which mea that it is easy to use them for processig ay kid of text at all. Geeral purpose macro processors ca be used for may tasks; they have bee used for laguage expasio (defiig ew laguage costructs that ca be expressed i terms of existig laguage compoets), for systematic textual replacemets that require some kid of decisio makig (where a global edit would be isufficiet), ad for textual reformattig (e.g. coditioal extractio of material from a HTML file). 3.4 ASIC A applicatio-specific itegrated circuit (ASIC) It is a itegrated circuit (IC) customized for a particular use, rather tha iteded for geeral-purpose use. For example, a chip desiged solely to ru a cell phoe is a ASIC. I cotrast, the 7400 series ad 4000 series itegrated circuits are logic buildig blocks that ca be wired together for use i may differet applicatios. Itermediate betwee ASICs [8] ad stadard products are applicatio specific stadard products (ASSPs). As feature sizes have shruk ad desig tools improved over the years, the maximum complexity (ad hece fuctioality) possible i a ASIC has grow from 5,000 gates to over 100 millio. Moder ASICs ofte iclude etire 32-bit processors, memory blocks icludig ROM, RAM, EEPROM, Flash ad other large buildig blocks. Such a ASIC is ofte termed a SoC (system-o-a-chip). Desigers of digital ASICs use a hardware descriptio laguage (HDL), such as Verilog or VHDL, to describe the fuctioality of ASICs.
4. M-ARY PSK DIGITAL MODULATION I the digital commuicatio systems M-ary [9] phase shift keyig (MPSK) the characteristics of MPSK ad detectio are described as follows. MPSK carrier phase have M values, usually it chooses M = 2 where is positive iteger, the phase value ofte are at same iterval 2Πi θ i = + ϕ (1) M where i = 0,1,2,, M -1, M = 2 Ad ϕ is the iitial phase. Here we are goig to cosider rectagle evelops MPSK, modulated sigal i time-domai is expressed as:- T s =10, N=100 2Es Ζ MPSK( t) = rect ( t T s) cos[ ωc t + θ( )] (2) Ts where Ts is the symbol duratio, Es is the uit symbol s sigal eergy, θ ( ) is the carrier phase at t = Ts ad rect is rectagle fuctio. Value is give as:- 1, 0 t Ts rect() t = (3) 0, Others θ ( ) θ i Where i = 0,1,2,, M -1 Derived from formula { } (1). If iitial phase ϕ =0, the Ζ MPSK() t = arect( t Ts) cosωct brectt ( Ts) siωct where a b = = 2Es cos θ ( ) Ts 2Es si θ ( ) Ts From (4), we ca say that MPSK sigal may be orthogoal. The above equatio reveals that the MPSK sigal may use two orthogoal carrier sigals to realize the coheret detectio. Whe T s equals to 10 ad (o of iteratio) N equals to 100 our graph have greater time iterval, where N is the umber of terms, as show i Figure 3. Whe we icrease T s to 60 ad N to 300 our graph compresses ad teds to orthogoal. We will get close to ideal (orthogoal) if we will icrease T s ad N as show i Figure 4. (4) Fig. 3. MPSK modulatio. T s =60, N=300 Fig. 4. Left shiftig of gap ad compressio of sigal. 5. CONCLUSION With the use of SDR, we ca chage the parameter of Adhoc etwork by usig M-ary PSK modulatio techique. Just by chagig software, we achieve the desired output. Hece it reduces the task to a great extet. I cotiuous phase rate modulatio, we ca idetify them for each phase rate properties. These ca be implemeted by software radio. These are ivolved i may specific problems such as differetial ecodig MPSK ad filter before modulatio. We eed to differetiate them accordig to their ew properties as phase. These cocepts will be used to develop adaptive software usig various applicatios.
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