24-01-2010, 02:34 PM
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Whatâ„¢s the Software Defined Radio
Software Defined Radio (SDR) refers to the technology wherein software
modules running on a generic hardware platform consisting of DSPs and
general purpose microprocessors are used to implement radio functions
such as generation of transmitted signal (modulation) at transmitter
and tuning/detection of received radio signal (demodulation) at
receiver.¦a radio that includes a transmitter in
which the operationg parameters of the
transmitter, including the frequency range,
modulation type or maximum radiated or
conducted output power can be altered by
making a change in software without
making any hardware changes
-FCC definition
FCC, federal communications commission
2. Motivation of SDR
Commercial wireless communication industry is currently facing problems
due to constant evolution of link-layer protocol standards (2.5G, 3G,
and 4G)
existence of incompatible wireless network technologies in different
countries inhibiting deployment of global roaming facilities
problems in rolling-out new services/features due to wide-spread
presence of legacy subscriber handsets.
Continuous transition from analog to digital
software defines waveforms
analog signal processing is replaced with DSP
Evolving technologies
NMT >> GSM >> UMTS >> ???
infrastructure upgrades
Multimode devices
4G devices
legacy devices
same device for different networks
Reusable devices
devices can be upgraded
software update
Increasing DSP capabilities
computational power increases
power consumption decreases
Money
Concept
Software replaces hardware as much as
possible
reduces costs
increases versability
Equipment/infrastructure â„¢recyclingâ„¢
by software updates
Anything is possible
within the current limits
Applications
Military
real-time flexibility
secure
Commercial
international connectivity
Civilian
portable command for crisis management
Bluetooth, WLAN, GPS, Radar, WCDMA, GPRS, GSM,
PCS, DECT, AM, FM, etc.
Features
Reconfigurability
co-existence of multiple software modules
implementing different standards
dynamic configuration both in terminals and in
infrastructure equipment
future-proof, multi-service, multi-mode, multiband,
multi-standard terminals and
infrastructure equipment
Ubiquitous Connectivity
if the terminal is incompatible with the network
technology, an appropriate software module is
installed (over-the-air)
the infrastructure equipment can adjust to the
legacy terminals
Interoperability
SDR facilitates implementation of open
architecture radio systems
End-users can use third-party applications
seamlessly
SDR, software defined radio
Programmability
Hardware radio
no software changes
Software controlled radio
in PDR, BB operations and page link layer
protocols are implemented in software.
Software defined radio
SDR system is one in which the BB
processing as well as DDC/DUC modules are
programmable. PDR, programmable digital radio
DDC/DUC, digital BB, baseband down/up converter
Ideal software radio
programmability is extended to the RF section
Ultimate software radio
in a single chip, no external antenna and no
restrictions on operating frequency
intended for comparison purposes only
Typical Components of SDR
Analog Radio Frequency (RF) receiver/transmitter in the 200 MHz to
multi-gigahertz range.
High-speed A/D and D/A converters to digitize a wide portion of the
spectrum at 25 to 210 Msamples/sec.
High-speed front-end signal processing including Digital Down
Conversion (DDC) consisting of one or more chains of mix + filter +
decimate or up conversion.
Protocol-specific processing such as Wideband Code Division Multiple
Access (W-CDMA) or OFDM, including spreading/de-spreading, frequency-
hop-and chip-rate recovery, code/decode functions, including
modulation/demodulation, carrier and symbol rate recovery, and channel
interleaving/de-interleaving.
Data communications interface with carrier networks and backbone for
data I/O and command-and-control processing, usually handled by general
purpose ARM or PowerPC processors and Real-Time Operating System
(RTOS).
