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There are number of ways in which the Software Defined Radio has been defined. The SDR forum, which in collaboration with IEEE has defined Software Radio as: - "Radio in which some or the entire Physical Layer is Software Defined ". A radio is a device that wirelessly transmits or receives signals in the Radio Frequency (RF). It is a part of electromagnetic spectrum which allows the transfer of information. In the current world radio frequencies to access wireless is in every device like cell phones, computers, car door openers, vehicles, and televisions. The basic
Characteristics of, radio the, Digital Signal Processing which is flexible and reconfigurable functional block, a software radio is radio in which the receiver digitization is performed at some downstream from the antenna. This type of digitization is basically performed after the wideband filtering, low noise amplification and down conversion to a lower frequency n subsequent stage. The reverse of this is performed at the transmitter digitization. Because of the rapid pace in development of technology the 'SDR' will sooner progress to 'SR', where digitization is at or nearer to antenna and all the processing for radio is performed by software at high-speed Digital Signal Processing element.
1.2 SDR Evolution:
This is the generic description of the stages in SDR Evolution where there is a key transition stage in the metamorphosis of SDR to SR . The core technology that is been included in this evolution is the digital signal processing, Analog to Digital and Digital to Analog conversion capabilities, DSP advances, algorithms, memory advances, and the basic need of the fundamental building blocks required for the digitization and the manipulations of the radio signals in the digital space and any translation of necessary translation of frequency in analog environment are been included during this transition .
Stage 1: For example if we consider the simplified example of a commercial wireless terminal, this stage is basically single mode and single band handset. This figure represents ANY single mode like AMPS, CDMA, TDMA, GSM, etc and single frequency band like 850, 900, 1800, 1900 etc. This stage is considered to be the basic traditional product implementation. imgd005.jpg
Figure1: SDR Evolution Stage 1.
Stage 2: Similarly in this stage Quadruple-mode and Quadruple-band handsets are used. This figure represents ANY Quadruple-mode, traditional-design, multiband, multimode handsets like AMPS, CDMA, TDMA, GSM and Quadruple-frequency band like 800, 900, 1800, 1900 MHz img004.jpg
Figure2: SDR Evolution Stage 2
Stage 3: This is the first revolutionary stage which retains the conventional approach to the current complex part in the FR front end and back end is applied by the SDR solution, it makes some sense in the near term. In this stage Analog to Digital and Digital to Analog and signal processing chips have been introduced and these chips have the capability to process the IF and baseband processing. yhttjutj.jpg
Figure3: SDR Evolution Stage 3
Stage 4: The last stage is the future product which might be considered as the ultimate evolution as the technology is evolving in A/D capabilities. The modes are analog and Software Radio Engine with frequency bands of are between 850-2000 MHzimg003.jpg
Figure4: SDR Evolution Stage 4
Adaptive Intelligent Software Radio:
Adaptive Intelligent Software Radio (AI-SR) is a radio that is capable of adapting operational environment with achieving high performance and spectral efficiency. The basic concept of this kind of radio is to adapt the environment by automatically adopting its operational mode. There are basic need of adopting to its environment automatically such as, artificial intelligence, computational power to process adaptive intelligence algorithms in real time and as well as it needs real-time data from mobile network interface, radio-frequency bands available, user needs, applications, minimum performance requirement which might be subscriber as well application dependent, air interface protocol, propagation environment and SDR platform capabilities. An AI-SR is also a radio which is capable of all functionalities in a SR as well as can adapt to its operational environment for enhanced spectral efficiency and improved spectrum Management. Figure 5 illustrates the technological evolution of AI-SR from SDR. The transition from SDR to SR is possible with the introduction of efficient signal processing techniques along with adroit faster memory chips and signal processors technologies. This enables the transition of digitization of a radio to move from the baseband signal section all the way to IF and RF sections, making SR as a reality. Intelligent network algorithms are required for transition of such an AI-SR system. Figure 5: Evolution of SDR-SR-AISR Untitled.jpg
Digital Radio, Multiband and Multimode:
A Digital Radio is a radio in which the signal is digitized at some levels between the Antenna and the input/output devices. These are the application specific integrated circuits where the signal processing takes place after the A/D conversion which is performed by special purpose, such radios are not called SDR.
Multiband refers to operating in the multiple frequency bands of the spectrum for a handset or base station. Multimode refers to the operation of a handset or a base station in multiple modes like multiple air interface standards, multiple access techniques, etc. Multimode and Multiband, these capabilities can be implemented by using a varity of hardware and software techniques. This can even be implemented by SDR. As we know that SBR can be applicable to many differing marcketplace for wireless. There are 3 major application universes consideration for the implementation of SBR,
Comercial Wireless (ex: Cell phones, landlines, PCS, etc ).
Civil Government(ex: for public safety, local state, etc).
As we know that as the technology went on growing new concepts where discovered because of rapid adoption of artificial intelligence, automatic operations, etc they then introduced Cognitive Radio. Cognitive radio is a radio that where the internal sate and the environment are known to the communication system, such as location and the utilization of RF frequency spectrum at its location. The predefined objectives of the system are used to make decisions about the operations behavior of the System. Cognitive radio was defined by many for the utilization of Software Defined Radio, Adaptive System, and many other technologies to robotically (without human intervention) achieve the desired objective or to adjust its behavior. It is difficult to the end-users to make optimal use of frequency spectrum available and wireless networks with a common set of radio hardware. But this will reduce the cost to the end-user as it will allow the end-users to communicate from anywhere with anyone and in whichever manner is appropriate.SDR Related Technologies
Figure 6: Relationship between associated wireless technologies .
Intelligent radio is a cognitive radio but it is capable of machine learning. Intelligent Radio help Cognitive radio to improve in ways it adapts to the change in the performance and the environment to serve its end users in better ways to its needs and efficient way.
Architectural perception for SDR:
The Radio Implementer Plane: The basic architecture of radio device can be divided into two parts whether it is terminal or base station. They are:
Radio Front End- This is the radio frequency aspects.
Radio Back End- This is a signal processing.
Traditionally this division of the architecture leads to the artificial implementation of hardware as the foremost element of front end and the h/w integration with s/w as the back end. As technology advances these assignment of h/w and s/w will change, as the s/w becomes the dominant driver and the h/w becoming the supporting role. As it has been known that a large portion of complexity of commercial wireless devices today is in RF need to cover multiple frequency bands. As the additional accommodation of frequency bands and modes the front end and back end considerations are very complex in them and are one of relative complexity in wireless devise.
The Network operator Plane:
Wireless networks are static and only voice and limited amount of data can be received or transmitted. These devices are fixed at their capabilities and configuration at each end. Hence SDR is taking the pledge to change these static networks into dynamically adaptive systems.
In the forth coming years wireless network is going to be a combined integration of 2G, 2.5G, and 3G with a good proliferation of the new standard changes in current standards and the new standards which are already underdevelopment. Each standard essentially needs to put new systems into places before the consumers can use it and the wireless carrier can begin making money. The constant evolution of existing standards can be best seen GSM. In GSM it is been told that once in 12-15 months of period a new network overlap is scheduled to be added in the GSM Standards. Examples of the variations are Adaptive Multirate Codec (AMC), 14.4 kbps data services, GPRS among either.
Figure7: Generalized Functional Architecture 
Since a single adaption network can meet the potential evolution of SBR base-station and handsets with currently existing standards and with adapting to the new standards, the creation of multiple overlay networks for each new standards may no longer be needed or at the very least reduced.
Benefits of SDR:
SDR can be benefit many of the users because of it wide range of adoption. 
For Radio Equipment Manufacturers and System Integrators, SDR Enables:
Implementation of a common architecture for a family of radio "products", allowing new products to be introduced into the market.
Software to be recycle across radio "products", plummeting development
For Radio Service Providers, SDR Enables:
New features and capabilities to be combined to existing infrastructure without requiring major new capital expenditures and allowing service providers to quasi-future proof their networks.
The utilization of a common radio platform for multiple markets will significantly reducing logistical support and operating expenditures.
For End Users - from business travelers to soldiers, SDR technology aims to:
Reduce costs in providing end-users with access to ubiquitous wireless communications - enabling them to communicate with whomever, whenever and wherever they need.
Future Direction in SDR:
If we go on discussing about the future direction on SDR there are plenty and huge developments going on under development. As a result we will pick one of the market which is focusing on the future development on the SDR Mobile Handset (MD). European Telecommunications Standards Institute (ETSI) RSS has identified an SDR architecture approach for mobile device (MD) as a basis for future development in SDR Standards . They have identified general architectural requirements such as interface requirements, operational requirements and capability requirements. Some of these are been stated below:
The Capability Requirements are :
Multiradio Configuration Capability.
Multiradio Operation Capability.
Multiradio resource sharing Capability.
The Interface Requirements are :
Unified Radio application interface.
Radio Programming Interface.
Interface to the reconfigurable RF Transceiver.
SDR rate of Adoption:
A research by SDR Forum commissioned a number of reports in 2006 to evaluate the rate of Adoption of SDR technology in various markets. These analyses resulted in the fact that in certain markets "SDR is moving beyond the innovators and early adopters" as defined by Geoffery Moore in "Crossing the Chasm", into the early majority phase defining the mainstream market.
The true fact about adopting the technology is not because of the innovation or the visualization but because of the ability to successfully solve the problem in the specific market. The majority of these adoptions are found in defense application, cellular infrastructure systems are increasingly deploying programmable processing devices to create common platform and multiband-multiprotocol base station that can support multiple infrastructure standards. These cellular handsets are increasingly using system on chip (SoC) devices with embedded programmable "DSP Cores" to process the baseband signals/modem processing.
There is another market that is adopting this technology which is the Seattleite "Modem" in the commercial and defense market for processing frequency and baseband signal processing. Usually these systems do not markets as SDR's, they usually utilize and benefit from these technologies to solve the market problems such as time to market in supporting new and evolving air interface standards, cost of development, cost of upgrades and maintenance, cost of production, or problems related with network interoperability.
AS SDR offers many compelling benefits to Radio System designers, though there are many challenges that remain unanswered on how effectively to implement and manage flexibility in a wireless system. Software radio platforms helps the researchers and developers the ability to develop their applications in advance of designing customized hardware. As this rapid pace of development in technology low cost platforms are now possible though few are generally available. Even though SDR technology has evolved more slowly than expected some years ago, there are now many positive signs of getting this technology into aware and use it, the clearest ones being in the form of SDR products entering the market. Several major initiatives, at national and cooperative levels between nations and the industry are cobblestoned the way for SDR. In this article, we provided an overview of multi-core architectures for future SDR platforms and their mapping flows. First, we motivated the need for scalable and reconfigurable heterogeneous multi-core SDR platforms driven by technology constraints, user demands, and business aspects. Then we had a look at the benefits of SDR how is it beneficial to the end-users, manufacturers, and the service providers. Then we gave an overview of the future requirements of the SDR considering the Mobile Device architecture as a base for it. Then finally we conclude saying the use of SDR technology helps in predicting to replace many of the traditional methods of implementing transmitters and receivers while offering a wide range of adaptability, multi-functionality encompassing modes of operation, re-configurability, radio frequency bands, air interfaces, and waveform.