Multi-mode Analogue/Digital PMR/LMR Processing
The traditional analogue PMR industry is finally going digital. The word ‘Digital’ is seen in the market place as meaning advanced and better than Analogue, which is questionable, however digital does present a number of advantages for the user, operator and in the area of spectrum management.
Data capability is a major benefit to the end user, opening up completely new application areas
more synonymous with the mobile phone market, such as texting and gaming.
Operators, benefit by potentially doubling their end user capability and therefore revenue chain,
with their same channel allocation.
Spectrally, digital PMR is at least twice as efficient as analogue, offering 6.25kHz channel
bandwidth per communication, as opposed to 12.5kHz or even 25kHz in the legacy analogue systems.
In forthcoming years, we will see digital PMR (dPMR) systems being installed worldwide, gradually displacing
existing analogue systems.
In the short to medium term there is a clear requirement for multi-mode (analogue/digital) radios
to be developed. This will simplify the introduction of digital radios in the market place by
providing users with key benefits such as data capability on digital systems and for legacy analogue
systems: full backward compatibility.
The multi-mode (analogue/digital) radio approach has benefits for the radio manufacturer: a single
radio platform design capable of supplying both analogue and digital PMR market needs.
Two distinct methodologies exist to enable the narrowband PMR market to go digital:
- Time Division Multiple Access (TDMA) and,
- Frequency Division Multiple Access (FDMA)
Here we focus on the FDMA route as it is generally considered to have a number of benefits over the more complex and more costly TDMA route.
Radio Platforms are the Answer
CML's CMX7141 Digital PMR (dPMR) Processor IC is ideally placed to meet the specific requirements of both
new and emerging digital PMR radio systems and dual-mode digital/analogue two-way radio platforms.
Built on CML’s proprietary FirmASIC® technology the CMX7141 encompasses the elements required for the implementation of a digital radio’s air interface physical and data link layers.
The Vocoder is also completely managed and controlled by the CMX7141 enabling a small, low power host microcontroller to be utilised for overall radio operation.
Vocoder Management and Control
The CMX7141 completely manages and controls the external Vocoder function
therefore, provides the most efficient data routing through the digital PMR/LMR Air Interfaced
Layers thus, keeping the overall system power consumption to an absolute minimum.
The Vocoder connectivity by default is designed to work with
CML’s low bit rate RALCWI vocoder chips, CMX608/CMX618, but can also be configured to work with third party Vocoders.
Function Image™ is the Key to Flexibility
The Function Image™ concept is the key to a multi-mode radio platform. A Function Image™ is a small
data file that is uploaded to the CMX7141 during power-up.
The Function Image™ configures on-chip subsystems to provide the operation and functionality for a
specific application. Two methods of uploading the Function Image™ into the CMX7141 are available,
as depicted below.
- Method 1 - The Function Image™ is loaded into and retained within the Host’s Flash memory.
During CMX7141 initialisation, the Function Image™ is uploaded into the device via the host and C-BUS. - Method 2 - The Function Image™ is loaded directly into the optional serial Flash attached
to the CMX7141.
The Function Image™ is then automatically uploaded into the CMX7141 during power, without Host intervention.
The CMX7141 multi-mode digital PMR/LMR processor chip is perfectly positioned to fulfil the needs of an SDR platform. A single radio hardware design can to be reconfigured to meet the needs of a conventional analogue two-way radio, currently defined digital PMR/LMR systems and adapt to meet the requirements of the emerging digital specifications.
This is all achievable due to the flexibility of the Function Image™ concept.
Uploading a different CMX7141 Function Image™ completely changes the devices operation and function.
Function images are available to support both analogue digital PMR/LMR systems with an evolving roadmap
to support new emerging digital PRM/LMR systems.
Please visit the CMX7141 ‘My CML Technical Portal’ page on the CML website for the latest information.
If you are interested in more information concerning support for a digital PMR/LMR system mention on the roadmap, please contact your local CML representative.
Common to all Function Images and operating modes for the CMX7141:
- Low power 3.3V operation
- Small footprint packaging – 48 pin LQFP and VQFN
- Auxiliary ADCs (4 mux inputs)
- Auxiliary DACs (4 outputs)
- Two auxiliary system clock outputs
- Optional serial Flash memory
- Progress powersave operating modes
- Analogue two-way radio – this is an emulation of the CMX7041 providing:
- Concurrent audio, signalling and data operations
- Complete audio processing including scrambler option
- Sub-audio signalling – CTCSS, DSC and XTCSS
- Audio-band signalling – Selcall, DTMF
- FFSK/MSK data modem with packet and free format modes
- Marine VHF operations – DSC, NOAA WAT and SAME
- Three analogue signal inputs
- Single and two-point modulation drivers
- Digital PMR – dPMR
- Conforming to ETSI TS 102 490 and EN 301 166 specifications
- Air Interface physical layer (layer 1)
- Air Interface data link layer (layer 2)
- 4FSK Modem
- Soft decision decoding
- Automatic Frame Sync Detection (AFSD)
-
Vocoder connectivity
- Management and control
- Data transport
- CMX7141 Digital PMR/LMR Processor
- CMX608 Half-duplex RALCWI Vocoder
- CMX618 Half-duplex RALCWI Vocoder with Audio Codec
- CMX638 Full-duplex RALCWI Vocoder with Audio Codec
- CMX981 Advanced Digital Radio Baseband Processor
- CMX980A Digital Radio Baseband Processor
- CMX998 Cartesian Feed-back Loop Transmitter
CML is keen to work with radio manufacturers to support new and emerging digital PMR/LMR systems with the development of a specific Function Image™.
Standard, semi-custom and full custom Function Image™ possibilities exist.
Further details concerning the availability of Function Images for the CMX7141 can be found at ‘My CML Technical Portal’ on CML’s website www.cmlmicro.com. If you would like to discuss your specific digital PMR/LMR requirements in more detail, please contact your local CML representative.
© 2008 CML Microcircuits