Introduction and Problem specification: Man, powered by his imagination and inquisitive character, has wondered the mechanisms of Nature since time infinite. This quest for the truth, the ways in which his surrounding works, has led to many a scientific discoveries and innovations. Since the art of making fire and creating handcrafted tools, our civilization has come a long way. Science and Technology are making advances at an amazing rate. Communications is one area where Technology has undergone a rapid transformation. A century ago, telegraphs were regarded as luxuries and one of the few modes of communication with the rest of the world.
Today, the scene appears to be quite different. From telephones and telexes to Internet, e-mail and mobiles, technology has connected the whole world into a global village. One of the most interesting things about communication is that it makes use of a radio -- an extremely sophisticated radio. The telephone was invented by Alexander Graham Bell in 1876, and wireless communication can trace its roots to the invention of the radio by Nikolai Tesla in the 1880's (formally presented in 1894 by a young Italian named Guglielmo Marconi) . It was only natural that these two great technologies would eventually be combined. But now the problem was that even if a particular system were designed it would not be much appreciated if the maintaining of the system were not possible.
The same happened to the usage of radio that were specifically designed for a particular application and then it had to be re-designed again due to changes in technology. It was creating a big problem as both time and money were being wasted. Here is where the Software Radio comes into picture . This paper systematically comes first with the problems of the conventional radio, then dealing with the design issues of the software radio. After the design issue the right platform is decided by comparing the existing technologies.
The main purpose of Software Radio can be understood when it is compared to a conventional hardware radio. Let us see the functional block diagram of a receiver  that makes use of different blocks as shown in the figure. Fig: Block Diagram of a Receiver The signals received by the antenna are passed through Band Pass Filters and then making use of mixers and local oscillators the transmitted frequencies is converted to intermediate frequencies. If much lower frequencies are to be attained then the number of mixers and oscillators has to be increased. Then the Analogue to Digital converter samples the analog data to get a digital output that is then processed by the Digital Signal processor. The components from the Band Pass filter to ADC are all analog components.
The main problems here are the limited signal processing capability and also the limitations of analog components due to thermal variations, ageing effects, manufacturing inconsistency and involvement of intense testing. One solution is to implement them by defining in software. Maximizing the number of functions handled digitally allows the radio to take advantage of the flexibility of the digital signal processing circuit. Thus the paradigm for the design of a Software Designed Radio can be seen as to minimize the number of analog components uncompromisingly. Thus in this paper there is a problem about hardware radio specified and its solution is given by defining the Software Radio, but then it is not easy to design a software radio without having prior knowledge of the constraints in it. I have tried to come out with these design issues after doing an in depth survey that would let the designer know on which aspects he has to work on.
So effectively this paper deals with a problem and its solution, then the problem in the solution to the previous one with an idea which is given as below. Design Issues of a Software Radio: Though the Radio Frequency design is the most important aspect in the designing of a software radio there are other aspects that have to be taken care of too.  - Digital generation of signals: Many signals will now be generated digitally in receivers and transmitters and this gives the designer more flexibility to design the waveforms needed. - Analog to digital conversion: while designing the analog to digital converter great care has to be taken regarding the resolution and sampling rate as it may affect the system. - Digital signal processing techniques for demodulation and synchronization: This part of the software radio is very important, as there is technology upgrades in this module every small time interval. With high signal processing capabilities available it has become much easier to design the software radio.
- Advanced processing techniques for range extension and interference rejection: The availability of high speed signal processing capabilities facilitates the use of advanced techniques such as adaptive equalization, adaptive error correction, interference rejection, and smart antennas, which may previously have been too complex to implement in commercial radios. These algorithms offer the system designer new tradeoffs between performance and complexity. - New power management strategies: Power management is of utmost importance given that the transmitting power is more as the distance between two communicating nodes are large. So the design must support smart Sleep conditions in order to save the power and increase the lifetime of the system. - Need for understanding of network considerations: A normal radio is nothing but a mere pipeline for transmitting data, but a software radio is much smarter as it has to check the network conditions and adapt to the different situations. So the software Radio must be designed keeping in mind all the possible cases that tend to be complex.
No universal algorithm can be developed as the traffic is highly dynamic and without any regular pattern. - Security issues: The main advantage of a Software radio implementation is that the system can be maintained and upgraded making use of software downloads. But care must be taken that appropriate software must be downloaded and it must be to the correct system too or else sensitive data may be in the hands of unwanted people. So authentication and verification are of utmost importance. The download on the software radio and Internet can be compared as follows.  Different platforms for Software Defined Radio: The platforms for a software-defined radio can be basically divided into three Application Specific Integrated Circuits (ASIC), Digital Signal Processors and Field Programmable Gate Arrays (FPGA).
Each of them has its own advantages and disadvantages in terms of performance and overhead and depending on the application requirement one of the following standards are chosen.    Pros and Cons of the different platforms: FPGA: Pros - Re-configurability enables performing computational tasks at will. - Higher flexibility for adaptive coding for multimedia requirements such as bandwidth availability, quality of service requirements and channel characteristics. - Rapid Prototyping and design iterations.
- Certain function implementations result in decrease of die size. - Parallel processing. FPGA: Cons - Hardware is not ASIC and can lead to non-optimized performance and density. - Reconfiguration time is longer than compared to loading the software. - High power consumption during reconfiguration. DSP: Pros - It is simpler and less expensive - Gets 30% less expensive every year - Can compensate a variety of errors - Software is easier to upgrade than hardware - Deterministic timing DSP: Cons - DSP techniques are limited to signals with relatively low bandwidths.
- The need for an ADC and DAC makes DSP uneconomical for simple applications (e.g. simple filters) ASIC: Pros - Benefits of customized hardware at low costs - Re-configurable and the hardware can be used for different purposes. ASIC: Cons - Lower performance for complex functionality. - Fixed number of gates per chip which may not be sufficient to implement bigger and complex logic. Major companies doing research work at the moment: IBM WIPRO INTEL XILINX ALTERA CISCO INFOSYS MICROCHIP Apart from these there are about 500 companies in 90 different countries which are spending about a few thousand billions on the development of the software radio which serves many applications and with enhanced features. Conclusion: It can thus be concluded that if a Software Radio has to be designed, care must be taken while doing it. With many companies, provided that it follows the correct designing steps apart from investing and doing research work in full thrust, it may not be surprising if we see all applications making use of software radio with near ideal characteristics.
Thus an ideal Software radio block diagram can be viewed as follows wherein all the block functionalities are designed using software.  Fig: An ideal software Radio Block Diagram
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