hannel bandwidth using Most traditional radio architectures operate on a single digital filters that can be altered. While a series of band or range of frequencies. There are many applications switched analog filters could be used to change the where multiple frequencies of operations are desired. channel bandwidth in a traditional receiver, only a small These include cellular communications, government and number would be practical. Additionally, digital filters nongovernment agencies, and intelligence collection, to have the potential to implement filters not possible in the list a few. Where these situations exist, the norm is to analog domain. Lastly, digital filters can be tailored to utilize multiple radios, each designed to operate in one both adapt around interferers and compensate for specified band. A multiband radio has the ability to transmission path distortion, both features that analog operate on two or more bands either sequentially or filters are hard pressed to accomplish. simultaneously, as in the case of a base station that may be linking handsets from different bands. Multi-carrier History and evolution of software- defined radio A multi-carrier or multi-channel radio has the ability to simultaneously operate on more than one frequency at The history of SDR began in the mid-1980s. One of the a time. This may be within the same band or, in the case first major developments for SDR was the SpeakEasy, of a multiband radio, in two different bands at the same a transceiver platform designed by Hazeltine and time. Quite often, multi-carrier applies to a base station Motorola that was based on SDR technology for Rome that may be servicing many users at once, but it can also Air Force Base, New York. The SpeakEasy was designed apply to a user terminal that may be processing both to provide tactical military communications from 2 MHz voice and data on different RF carriers. to 2 GHz and to provide interoperability between the different air interface standards of the different branches Multimode of the