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DSP Innovations Inc. → SPR Vocoders 600-1200 bps Allow To Achieve The Impossible

The development of digital voice (DV) technology has had a significant impact on High Frequency (HF) voice communications. The secure features of DV in combination with the benefits of modern digital signal processing (i.e. equalization, narrow-band interference suppression, FEC, interleaving, etc) have provided users with some great advantages when communicating over challenging HF links. It becomes feasible due to very low bit rate (VLBR) vocoders such as MELPe operated on 1200 and 600 bps bit rate.

These vocoders operate very long superframe, combining a few adjacent speech frames of the MELPe 2400 bps vocoder and using different encoding schemes for each combination of these frames. It allows to provide high compression rate, keeping satisfactory speech quality. However, all other characteristics suffer very much though they are not less important than speech quality.

Major problem is very low robustness to channel errors:

Usage of different encoding schemes for each combination of frames reduces robustness catastrophically because even single error may change encoding scheme and distort complete superframe. Because of this problem an operation of the vocoder becomes impossible in extreme conditions when channel has a low signal to noise ratio (SNR), limiting significantly communication range or area coverage.

Moreover, there are other important limitations: Big time delay, because of big superframe, complicates normal conversation, especially when the talking is intensive (e.g. in extreme conditions). Also, these vocoders require a lot of computing resources and memory.

In contrast to these vocoders, SPR Vocoders, developed by DSP Innovations, Inc., are free of all these disadvantages. Innovative Sinusoidal Pulsed Representation (SPR) model, used in SPR vocoders, allows to operate a short superframe and the same encoded method for all frames, providing superior characteristics of these vocoders in comparison with MELPe.

What concrete advantages has HF-radio gotten, using SPR vocoder?

1. Major advantage is approximately two times higher robustness in noisy channel, that is equal to a double gain of SNR or transmitter power. For example, speech quality of the SPR 600 bps vocoder in channel with BER = 2% is approximately equal to speech quality of the MELPe 600 bps vocoder in channel with BER = 1%. The gain in 1% of BER is equal to 2-3 dB gain of SNR (it is depends on modulation type) that is equal up to double gain in transmitter power. In other words, HF-radio with SPR 600 bps vocoder provides the same communication quality at twice lower transmitter power! Or much more area coverage at the same transmitter power!

What does it give? It is:

• reliable communication even when it was impossible earlier,
• great economy of power consumption in transmission mode,
• decrease in value and cost of equipment

Other advantages also are very important:

2. Very low computing complexity. Approximately three times lower than MELPe. It allows to decrease power consumption in a receive mode, increasing significantly a life time of battery, that is very important for mobile radio.

3. Low time delay. Time delay is 60ms for 1200 bps and 100 ms for 600 bps bit rate, that makes conversation more comfortable and easy.

4. Low needs of memory. Memory usage is many times lower. It allows to decrease additionally a cost of equipment.

In addition, technical characteristics of HF-radio may be improved more, thanks to wide and fine-gradation line of SPR vocoders from DSP Innovations. For example, SPR Robust 800 bps vocoder has additional redundancy increasing more robustness of the SPR Classic 600 bps vocoder, providing more unique possibilities of the updated HF-radio.

DSP Innovations, Inc. (DSPINI) was founded in 2007, having united the best Russian scientists, software engineers and hardware designers who have great experience in DSP and development of various telecommunication equipment. The mainstream is speech technologies and voice communication: innovative methods of speech coding, speech enhancement (noise and echo cancelling, spectrum equalization, etc.), advanced methods of \"source-channel coding\".

DSP Innovations, Inc. (www.dspini.com) is supplier of DSP-software and engineering services. Proprietary “royalty-free” and standard vocoders from DSPINI have superior characteristics, operate in range from 300 bps up to 64 kbps bit rates and are used in: Secure Voice, Software Defined Radio, Wireless, VoIP, Voice Storage, etc. Having great experience in development of math intensive algorithms and software, in hardware design, production, testing and exploitation of various radio and telecommunication equipment, DSPINI’s team uses strong background to provide to each customer the most advantageous solution.

DSP Innovations Inc. DSP Innovations, Inc. (DSPINI) was founded in 2007, having united the best Russian scientists, software engineers and hardware designers who have great experience in DSP and development of various telecommunication equipment. The mainstream is speech technologies and voice communication: innovative methods of speech coding, speech enhancement (noise and echo cancelling, spectrum equalization, etc.), advanced methods of "source-channel coding". DSP Innovations is supplier of DSP-software and engineering services. Proprietary “royalty-free” and standard vocoders from DSPINI have superior characteristics, operate in range from 300 bps up to 64 kbps bit rates and are used in: Secure Voice, Software Defined Radio, Wireless, VoIP, Voice Storage, etc. Having great experience in development of math intensive algorithms and software, in hardware design, production, testing and exploitation of various radio and telecommunication equipment, DSPINI’s team uses strong background to provide to each customer the most advantageous solution. www.dspini.com • Контактная информация

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