Journal of Emerging Technologies in Web Intelligence Contents

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120 JOURNAL OF EMERGING TECHNOLOGIES IN WEB INTELLIGENCE, VOL. 2, NO. 2, MAY 2010Now the modulated signal is contained in the form ofenvelope of full wave rectified signal and can berecovered by applying a low pass filter to remove thecarrier frequency. “Error! Reference source notfound.shows the output of a first order Infinite ImpulseResponse (IIR) filter. The equation of filter used is:Yn = 0.997*Yn-1 + 0.003*Xn.In (4) above,Xn is new input sample (RectSignal),Yn-1 is previous output sample,Yn is new output sample (demodulated signal).Figure 10. Demodulated signal after low pass filterV. SOFTWARE RADIO AS A SOLUTION TO CONVENTIONALANALOG RADIOSA Software Radio in contrast to a traditional Radioruns on a generic hardware platform to perform all themodulation/demodulation, frequency selection, filteringetc in digital domain as also explained above in theexample. It can perform role of a cordless phone, cellphone, internet access tool, a GPS receiver etc. all in one.This is possible by changing the software used forprocessing. Hence, there is no limitation of any particularfrequency range, modulation type, and output power in aSoftware Radio. All these flexibilities of software radiooffer advantages which can be broadly classified as:A. Frequency-AgileThe software programmable processing allows it tooperate in the entire radio waves frequency bands.B. Easy to plug n playIt is a radio into which multiple contractors could plugparts and software.C. Global MobilityIt caters to the model as it is flexible to support most ofthe communications standards like CDMA, GSM, IS-136etc.D. Inter-operabilityIt can be made to inter-operate with different wirelessprotocols, incorporate new services, and upgrade to newstandards etc by simply downloading a new program (or anewer version of the software) or by change of selectionfrom the user interface.E. Compact and Power EfficientDue to reduced number of components used inSoftware Radio, its size is reduced resulting in ease ofmanufacturing. Also less hardware results in less powerconsumption.(4)F. Quality of ServiceAs Software Radio is Software dependent; hence agreater quality of service is delivered consistently.VI. APPLICATIONS OF SOFTWARE RADIOThe ultimate goal of Software Radio is to provide asingle radio trans-receiver which can play the roles ofcordless telephone, cell phone, wireless fax, wireless e-mail system, pager, wireless videoconferencing unit,wireless Web browser, Global Positioning System (GPS)unit, and other functions still in the realm of sciencefiction, operable from any location on the surface of theearth, and perhaps in space as well. Few of theapplications of software Radio has been coveredhenceforth and shows the variety of functionality towhich it can cater to.A. Pacemakers and Implantable Cardiac DefibrillatorsWirelessly reprogrammable and implantable medicaldevices (IMDs) such as pacemakers, implantablecardioverter defibrillators (ICDs), neurostimulators, andimplantable drug pumps use embedded computers andradios to monitor chronic disorders and treat patients withautomatic therapies. For instance, an ICD that senses arapid heartbeat can administer an electrical shock alsoknown as the software radio attacks to restore a normalheart rhythm, then later reports this event to a health carepractitioner who uses a commercial device programmerwith wireless capabilities to extract data from the ICD ormodify its settings without surgery. Clinical trials haveshown that these devices significantly improve survivalrates in certain populations. [4]B. Smart sensorsSoftware Radios can be implemented as smart sensorsto determine the amount of various particles present inatmosphere, hence useful for pollution check, weatherforecast etc. When used as Bio-sensor with configurablesoftware, it can be used in study of complex anatomy.C. One Cell phone for many standardsIt is highly inconvenient for a regular inter countrytraveler to change his mobile connection forcommunication due to network issues. For example,3GPP UMTS is popular in European nations, whileC/TDMA standards are widely used across North andSouth America. So, every time one travels through acountry he has to have the country specific cellularphone. But with the coming of Software radio, it can be athing of past as the Software Radio can adapt to change inthe local air interface by a simple software change. Allthe base stations and terminals using Software Radioarchitecture can support multiple air interfaces duringperiods of transition and be easily upgraded.D. Cost Effective Up gradation of a Cellular BaseStationThe growth in radio technology is in-step with thedemand of today’s customer, but is the business ready?The customer may have asked for audio files in his© 2010 ACADEMY PUBLISHER
JOURNAL OF EMERGING TECHNOLOGIES IN WEB INTELLIGENCE, VOL. 2, NO. 2, MAY 2010 121cellular services yesterday, but today they look for videostreams in their phone and tomorrow they might ask forlive data feed. The cellular industry cannot afford to losebusiness by not making such changes. Software Radiohelps to save them millions by easy upgrades in software.There is no need for investment in the hardware, savingthem both money and time. It is also a boon forcustomers as they don’t need to purchase newer handsetsfor newer technology. Just as any individual or businesscan update a software program used on a PC, by usingSoftware Radio technology, any cellular providers canupgrade software easily and quickly to make changes ontheir systems. As a result, the cost for cellular phoneservice can continue to be decreased for consumers;while the providers can see higher margins for the servicethey provide.E. Usability in EmergencyAs the software radio is compact and easilydeployable, it can be useful for temporary coverageduring emergencies and special events. A software radiocan be programmed and mounted onto a vehicle anddriven to the site of a natural disaster to bring incommunications where they may have been damaged andto support multiple standards.F. High Definition TV ApplicationsSoftware Radios are finding significant applications inthe conversion of both analog and digital transmissions toHDTV, an upcoming broadcast technology.VII. CHALLENGES & LIMITATIONSSoftware radio technology alters traditional radios inthree ways namely moving A/D closer to antenna,substitute hardware with software processing andfacilitating transition from dedicated to general-purposehardware. This decreases the number of hardwarecomponents resulting in high degree of extensibility for awide range of features. This will also eliminate theredundant hardware as found in dual band phones etc.There are several technological challenges faced inSoftware Radio today, like the usage of faster A/Dconverters, requirement for less power consumption,implementing smart antennas and making the overallradio more cost effective. ADCs which can digitize thehigh range signal are very expensive. They also increasethe level of SFDR (spurious free dynamic range). Hence,the signal received are down converted from RF signaland digitized at IF range via ADCs before sending thedata to DSPs. To overcome this limitation, more researchand development would be required to build lessexpensive ADCs covering more dynamic range andsupporting greater sampling rates. For FPGAs, interval toreprogram FPGA’s limits its usability.The authenticity and security of downloaded softwareis another area of concern. There is a need for a globallyrecognized regulatory body which can control theseprocesses. Certification from bodies like FederalCommunications Commission (FCC) is another hurdle.FCC certification process presumes that any software thatis bundled with the hardware be certified as a unit. Butsoftware radio being programmable at any time poseschallenges in certification. A new certification procedurehas been created. Software changes which can affectradio frequency, power and modulation are subject tomore streamlined process. However, FCC does not certifyany changes by third party software vendors. Allmodifications are the responsibility of the originalmanufacturer whose original hardware/software radiobundle was certified. This requires that all theindependent vendors need to work via equipmentmanufacturers. Hence, certifying software radios pose asignificant challenge because of cumbersome certificationprocesses, especially for domains like aerospace anddefense which require testing for all possible scenarioswhere software may misbehave.VIII. FUTURE OF SOFTWARE RADIOUltimate aim of software radio would be to move ADCand DAC just next to Antenna and doing everything insoftware. Currently, the cost of high frequency ADCs andspecialized hardware for digital signal processing are fewof the factors limiting the application of software radiosto high end use only. As the technology advances, thecosts will come down and processing power of generalpurpose computing platforms will increase. Once theprocessing power crosses the threshold required forperforming necessary radio functions, broaderapplications and scales of economy will come into placeand we will see software radios being used in our day today use gadgets. How soon it can happen is still an openquestion but software radio is likely to be an importanttechnology in the years to come.REFERENCES[1] Jeffrey H. Reed, “Software Radio”.[2] J Mitola, "The Software Radio", IEEE NationalTelesystems Conference, 1992 - Digital Object Identifier10.1109/NTC.1992.267870.[3] Ulrich L. Rohde, "Digital HF Radio: A Sampling ofTechniques”, Ham Radio Magazine, April, 1985.[4] http://www.secure-medicine.org/icd-study/icd-study.pdf[5] “A Software-Defined Radio for the Masses, Part 1- 4”,Gerald Youngblood, AC5OG[6] http://www.sdrforum.org/[7] http://rfdesign.com/mag/radio_fast_hot_data/index.html[8] http://www.dspguide.com/© 2010 ACADEMY PUBLISHER
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