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28-520: NXDN is implemented by Icom in their IDAS system and by Kenwood as NEXEDGE; both Kenwood and Icom now offer dual-standard equipment which supports the European dPMR standard. Icom and Kenwood began their collaboration in 2003. The NXDN protocol was announced in 2005, and NXDN-compatible products first appeared in 2006. The NXDN Common Air Interface (CAI) was accepted at the Study Group 5 (SG5) meeting of

56-419: A 12.5 kHz channel for example, can be allocated as voice/voice, voice/data, or data/data. As of 2012, this capability cannot be implemented in commercially available hardware on simplex or "talkaround" frequencies, but only through repeaters. Systems that use NXDN also support mixed analog FM and digital NXDN equipment, including direct radio-to-radio communications. This allows system owners to migrate to

84-482: A call to another radio whether that radio is using the same site or another site within the network. With all forms of technology it is vital that products from any manufacturer will interoperate without conflict. To ensure that this will be the case, ETSI has also developed and published a range of European standards for compliance and interoperability testing. These standards are the ETSI TS 102 587 series for dPMR446 and

112-567: A co-channel wide area network. dPMR Mode 3 can offer multichannel, multisite trunked radio networks. This ensures optimum use of spectrum and optimum density of radio traffic. Management of the radio network starts from the authentication of radios that wish to connect. Calls are set up by the infrastructure when both parties have responded to the call request ensuring optimum use of the radio resource. Calls may be diverted to other radios, landline numbers or even IP addresses. The infrastructure managing these beacon channels would be capable of placing

140-435: A common spectrum allocation by using spread-spectrum techniques. The basic NXDN channel is digital and can be either 12.5 kHz or 6.25 kHz wide. 6.25 kHz dual-channel systems can be configured to fit within a 12.5 kHz channel. This effectively doubles the spectrum efficiency compared to an analog FM system occupying a 12.5 kHz channel. The architecture of NXDN is such that two NXDN channels, within

168-503: A narrowband, digital system without replacing the entire system at once. NXDN equipment is currently FCC type-accepted for use on VHF (137-174 MHz) and UHF (406-512 MHz) bands. Data is transmitted using 4-level frequency-shift keying (FSK) modulation. NXDN uses the AMBE+2 vocoder ( codec ) for digital audio. This combination provides better weak-signal voice quality than for analog FM. For an equivalent transmitter power, NXDN

196-552: A sampling rate of 8 kHz in 20-ms frames. The audio data is usually combined with up to 7 bit/s of forward error correction data, producing a total RF bandwidth of approximately 2,250 Hz (compared to 2,700–3,000 Hz for an analogue single sideband transmission). Lost frames can be masked by using the parameters of the previous frame to fill in the gap. AMBE is used by the Inmarsat and Iridium satellite telephony systems and certain channels on XM Satellite Radio and

224-503: A schedule for transition to 6.25 kHz narrowband technology.” NXDN uses Frequency-Division Multiple Access (FDMA) technology in which different communication streams are separated by frequency and run concurrently. Time-Division Multiple Access (TDMA) systems combine the communications streams into a single stream in which information from the different streams is transmitted in interleaved time allocations or "slots." Code-Division Multiple Access (CDMA) systems allow many users to share

252-561: Is capable of voice, data and voice+data modes of operation. This means that dPMR446 can provide voice calls, text messaging ( SMS ), status and embedded data such as GPS position etc. This is the peer to peer mode of dPMR (without repeaters or infrastructure) but without the limitations of the licence-free counterpart. It can operate all typical licensed PMR frequency bands and without the RF power limits of dPMR446. As well as offering voice and data, dPMR446 Mode 1 also supports combined voice+data so it

280-672: Is dependent on the performance of the AMBE+2 voice codec used by NXDN. The AMBE family of vocoders has been subjected to comparative testing and found to be adequate for its intended uses, primarily mobile and aeronautical radio. The AMBE+2 vocoder has also been selected for use in the Motorola MOTOTRBO radio family as well as DMR systems, and Project 25 (P25) mobile radio system. The following reports and papers are descriptions of laboratory-environment evaluations of AMBE+2 and other speech vocoders. Compromises in audio quality are inherent in

308-650: Is directly applicable to any system using similar multi-band excitation coders. The NXDN Forum was formed in order to promote the NXDN protocol in North and South America. The forum's members are: DPMR dPMR or digital private mobile radio , is a common air interface for digital mobile communications. dPMR is an open, non-proprietary standard that was developed by the European Telecommunications Standards Institute (ETSI) and published under

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336-589: Is not interoperable in digital mode and therefore, must revert to analog FM mode. dPMR446 radios are licence-free products for use in the 446.0–446.2 MHz band within Europe. These are fully digital versions of PMR446 radios. dPMR446 radios comply with the ETSI TS 102 490 open standard and are limited to 500 mW RF power with fixed antennas per ECC Decision (05)12. They are ideally suited to recreational and professional users who do not need wide area coverage with base stations and repeaters. dPMR446 equipment

364-484: Is possible to embed data into a voice call or automatically append it at the end of a call. dPMR Mode 2 operations include repeaters and other infrastructure. This brings extra functionality such as analogue or digital network interfaces which can be IP based. Inclusion of repeaters and base stations means that wide area coverage is possible even more so when multiple repeaters are used. Such multiple repeaters can be managed by dynamic channel selection or they can be part of

392-596: Is represented as having a wider range and slightly better multi-path characteristics than analog FM in typical RF environments, specifically at the 12 dB SINAD threshold. The transmission bit rate is 4,800 bit/s. The following FCC emission designators apply to NXDN transmissions: The NXDN protocol provides support for the following functions. Implementation of the functions and the user-level interfaces by which they are accessed and used may vary by manufacturer. In all lossy compression schemes, trade-offs are made in voice reproduction quality in return for minimizing

420-475: Is so tight, two 6.25 kHz dPMR signals can be used next to each other within a 12.5 kHz channel without causing interference to each other or adjacent channels. Compliance with EN301 166 at 6.25 kHz for current equipment provides some measure of guarantee that interference issues will be no different with either 12.5 kHz or 25 kHz. Frequency co-coordinators in the USA have even made recommendations to

448-607: Is the speech coder for OpenSky Trunked radio systems . AMBE is used in D-STAR amateur radio digital voice communications. It has met criticism from the amateur radio community because the nature of its patent and licensing runs counter to the openness of amateur radio, as well as usage restriction for being "undisclosed digital code" under FCC rule 97.309(b) and similar national legislation. System Fusion , open specification from Yaesu , also uses AMBE codec with C4FM modulation. The NXDN digital voice and data protocol uses

476-419: The "multi-band excitation" method of speech coding, that was patented in 1997 (now expired) by founders of DVSI as "Multi-Band Excitation" (MBE). All consequent improvements known as Improved Multi-Band Excitation (IMBE), Advanced Multiband Excitation (AMBE), AMBE+ and AMBE+2 are based on this MBE method. AMBE is a codebook -based vocoder that operates at bitrates of between 2 and 9.6 kbit/s, and at

504-505: The AMBE+2 codec. Use of the AMBE standard requires a license from Digital Voice Systems, Inc. While a licensing fee is due for most codecs, DVSI does not disclose software licensing terms. Anecdotal evidence suggests that licensing fee begin from between $ 100,000 to $ 1 million. For purposes of comparison, licensing fees for use of the MP3 standard started at $ 15,000. For small-scale use and prototyping,

532-598: The AMBE+2 codec. NXDN is implemented by Icom in the IDAS system and by Kenwood as NEXEDGE. APCO Project 25 Phase 2 trunked radio systems also use the AMBE+2 codec, while older Phase 1 radios such as the Motorola XTL and XTS series use the earlier IMBE codec. Newer Phase 1 capable radios such as the APX series radios use the AMBE+2 codec, which is backwards compatible with Phase 1. Digital Mobile Radio (DMR) and Motorola's MOTOTRBO use

560-456: The ETSI TS 102 726 series for licensed dPMR Mode1, 2 and 3 products. A dPMR Memorandum of Understanding (MoU) group was created in 2007 by a group of companies who wished to support the latest digital PMR radio technology known as dPMR. The group currently includes radio and silicon manufacturers, protocol, software and systems developers. Members have agreed to work for the common aims of interoperability, compliance and success of dPMR. In 2011

588-654: The FCC about setting up new 6.25 kHz systems adjacent to existing systems, outlining parameters to avoid harmful interference. dPMR equipment complies with the relevant European standard ETSI EN 301 166 as well as the FCC emission mask applicable for operation in the US. dPMR supports several voice coding algorithms. Class A equipment is based on AMBE+2 vocoder, Class R uses RALCWI (Robust Advanced Low Complexity Waveform Interpolation) vocoder, and Class M equipment uses manufacturer specific algorithm. Equipment from these different classes

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616-610: The International Telecommunication Union Radiocommunications Sector (ITU-R) held in November 2016 and in report M.2014-3 published in February 2017 as an international digital land mobile system . The NXDN protocol and the communications products in which it is used are intended for commercial Private Land Mobile Radio (PLMR) and public safety communications systems. The technology satisfies

644-460: The U.S. Federal Communications Commission (FCC) mandate requiring all communications systems covered by Part 90 regulations to use narrowband technology by January 1, 2013. Part 90 regulations specify a bandwidth of 12.5 kHz, but the FCC “strongly urges licensees to consider migrating directly to 6.25 kHz technology rather than first adopting 12.5 kHz technology and later migrating to 6.25 kHz technology.” The FCC “will expeditiously establish

672-418: The group was renamed the dPMR Association. Advanced Multi-Band Excitation Multi-Band Excitation ( MBE ) is a series of proprietary speech coding standards developed by Digital Voice Systems, Inc. (DVSI). In 1967 Osamu Fujimura ( MIT ) showed basic advantages of the multi-band representation of speech ("An Approximation to Voice Aperiodicity", IEEE 1968). This work gave a start to development of

700-421: The only option is to purchase a dedicated hardware IC from DVSI. These ICs can be purchased for less than $ 100 in small quantities. DSP Innovations Inc. offers a software implementation of APCO P25 Phase 1 (Full-Rate) and Phase 2 (Half-Rate) codecs as well as DMR and dPMR codecs. A technology licence from DVSI is required. The patent for IMBE has expired. Codec2 is an open source alternative which uses half of

728-479: The raw bit rate of the transmission. This leads to artifacts and compromises of frequency response in reproduced speech. Encoders and other compression schemes that are highly optimized for speech are often unsuitable for non-speech audio, such as music or frequency-shift keyed data. Using an inappropriate encoder usually results in the creation of distortion and artifacts in the reproduced audio. The audio reproduction quality of IDAS and NEXEDGE communications systems

756-415: The reference ETSI TS 102 658. A simplified version of the dPMR protocol intended for licence-free applications was also published by ETSI under the reference TS 102 490. dPMR is very similar to NXDN protocol implementation by Kenwood and Icom ; both now offer dual-standard equipment (July 2013). What is significant is that dPMR achieves all this in a 6.25 kHz channel. Because the emission mask

784-511: The use of any codebook -based speech coder , particularly when used in conditions of high background noise. Incremental improvements are being made in the algorithms, which may lead to differences in performance even while the basic method remains unchanged. In the US, the Department of Commerce Public Safety Communications Research laboratory regularly reports on progress in this field. While their work specifically pertains to Project 25 radios, it

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