01-03-2013, 10:14 AM
Software Defined Radio (SDR) Block Diagram
Software Defined.ppt (Size: 3.83 MB / Downloads: 28)
INTRODUCTION
This report provides an assessment of the SDR technology as it applies to the public safety community. Although the military community has realized many benefits from recent advances in SDR technology, the land mobile radio (LMR) equipment vendors have yet to use SDR technology. This report presents an overview of the SDR marketplace, the potential risks and benefits of implementing SDR technology on LMR subscriber terminal equipment for use by the public safety community, and analysis on recent rulings and guidelines published by the Federal Communication Commission (FCC) that will influence the continuing development of SDR technology.
Background
LMR networks provide wireless communications for local, state, and federal public safety communities. The existing LMR networks are based on a wide range of technologies. Typically, most LMR networks operate across disparate frequency bands and multiple technologies, introducing interoperability challenges. The advancements of intelligent network (IN) technology have allowed for the possibility to distribute computing to all network elements (rather than processing from a centralized location). The application of IN-based technology will likely result in a fundamental shift of network topology from existing disparate LMR architectures to more flexible interoperable architectures. The distribution of processing in the IN environment will occur across all network elements, including subscriber equipment. This intelligent subscriber equipment will be made possible by SDR technology.
SOFTWARE DEFINED RADIO TECHNOLOGY
This section provides a brief overview on software defined radio technology and introduces SDR subscriber equipment.
Definition of SDR
An SDR device (e.g., portables and mobiles) allows users to change transmitter and receiver characteristics such as modulation type, wideband and narrowband operations, radiated power, and air interfaces by making software changes without any hardware alternation. Traditional LMR devices are based on specialized hardware such as transistors and integrated circuits. In more modern LMR radios, digital signal processor (DSP) chips are used for analog-to-digital and digital-to-analog conversion of the radio transmissions. A DSP chip is a real-time digital signal processor that can alter its functionality by executing different software algorithms.
Recent advances in DSP chip design and fabrication will allow for more advanced DSP chips able to support multiple functions. This is due to continuous improvement in manufacturing techniques for creating chip components at extremely small sizes (fractions of a micron), therefore producing DSP chips with more built-in functionality. SDR devices will take advantage of these advanced DSP chips to have multiple functionalities such as supporting multiple access technologies (e.g., operate on different radio technologies). SDR devices are envisioned to interoperate with existing and evolving LMR systems by switching modes and also are capable of operating in multiple public safety frequency bands.