Indu Shakya

Kathmandu

Software radio is technology that replaces hardware completely, if not most. It means that by using software radio we are freed of hardware modifications to the devices. The concept of software radio was coined by a Swedish scientist Joseph Mitola in 1991. It is an enabling technology that let users access multitude of wireless networks from a single device without requiring any hardware modifications.

The functions of hardware are introduced as independent programmes with several process-specific software modules. We can implement the single device to any wireless network terminal by simply loading and executing the specific software modules.

The aim of Software Radio is move the ADC (Analog to Digital Converter) and DAC (Digital to Analog Converter). However, this is not feasible due to very high frequency of analog RF signals and current ADC/DAC technologies cannot sample signals in such a high frequency. So, some sort of frequency down/up conversion is required that signals might be sampled from analog to digital domain and vice versa. Once we have successfully sampled the signals into digital form, all the subsequent signal processing can be done completely on software using very high speed DSP (Digital Signal Processor). General Purpose Processors (Intel, Motorola) are also the possibilities, which means that we can perform signal-processing tasks using off the shelf PC with the aid of Real Time Operating Systems (Linux). With software programming we can create modules that work as modulator, demodulator, channel encoder/decoder, framing/deframing, byte/bit extractor etc. If the device is to be used as 3G terminals then software modules of 3G network processes are loaded. When there is a presence of Wireless LAN Access Point the device will load software modules of Wireless LAN processes. The switching between different networks become instant and seamless as software running in background is loaded in the matter of milliseconds.

With the software radio we can turn our device into Intelligent Wireless terminal capable of switching to any wireless networks. The design of Software radio is also future proof.