NXDN stands for Next Generation Digital Narrowband, and is an open standard for public land mobile radio systems; that is, systems of two-way radios (transceivers) for bidirectional person-to-person voice communication. It was developed jointly by Icom Incorporated and Kenwood Corporation as an advanced digital system using FSK modulation that supports encrypted transmission and data as well as voice transmission. Like other land mobile systems, NXDN systems use the VHF and UHF frequency bands. It is also used as a niche mode in amateur radio.
IDAS Radio IC-F3162DT
NXDN is implemented by Icom in their IDAS system [1] and by Kenwood as NEXEDGE;[2] both Kenwood and Icom now offer dual-standard equipment which supports the European dPMR standard.[3][4]
Icom and Kenwood began their collaboration in 2003. The NXDN protocol was announced in 2005, and NXDN-compatible products first appeared in 2006.[5]
The NXDN Common Air Interface (CAI) was accepted at the Study Group 5 (SG5) meeting of 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.
Applications
The NXDN protocol and the communications products in which it is used are intended for commercial Private Land Mobile Radio (PLMR) [6] and public safety communications systems. The technology satisfies 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 a schedule for transition to 6.25 kHz narrowband technology.” [7]
Technical characteristics
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 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 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 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.[8] This combination provides better weak-signal voice quality than for analog FM. For an equivalent transmitter power, NXDN 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.
8K30F1W 12.5 kHz single channel digital voice and data
4K00F1E 6.25 kHz single channel digital voice
4K00F1D 6.25 kHz single channel digital data
4K00F1W 6.25 kHz single channel digital voice and data
4K00F2D 6.25 kHz single channel analog CW ID
Application functions
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.
Paging & status reporting: radio-to-radio and dispatch-to-radio
User aliases: 65,545 different group IDs and user IDs
Man-down and emergency call
Remote radio management functions: stun/kill/revive and monitor
Over-the-air programming
Over-the-air alias
Interface to third-party applications for: paging to radio, GPS location, taxi data terminals, in-building tracking
Audio quality
In all lossy compression schemes, trade-offs are made in voice reproduction quality in return for minimizing 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 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 Hytera's DMR systems, and the Project 25 (P25) mobile radio system. The following reports and papers are descriptions of laboratory-environment evaluations of AMBE+2 and other speech vocoders.[11][12][13]
Compromises in audio quality are inherent in 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 is directly applicable to any system using similar multi-band excitation coders.[14][failed verification]
NXDN Forum
The NXDN Forum was formed in order to promote the NXDN protocol in North and South America. The forum's members are:[15]
^"Who are our members?". nxdn-forum.com. Retrieved 2022-08-04.
External links
Comparison of FDMA and TDMA Systems
NDXN Standard
August 27, 2023
nxdn, stands, next, generation, digital, narrowband, open, standard, public, land, mobile, radio, systems, that, systems, radios, transceivers, bidirectional, person, person, voice, communication, developed, jointly, icom, incorporated, kenwood, corporation, a. NXDN stands for Next Generation Digital Narrowband and is an open standard for public land mobile radio systems that is systems of two way radios transceivers for bidirectional person to person voice communication It was developed jointly by Icom Incorporated and Kenwood Corporation as an advanced digital system using FSK modulation that supports encrypted transmission and data as well as voice transmission Like other land mobile systems NXDN systems use the VHF and UHF frequency bands It is also used as a niche mode in amateur radio IDAS Radio IC F3162DTNXDN is implemented by Icom in their IDAS system 1 and by Kenwood as NEXEDGE 2 both Kenwood and Icom now offer dual standard equipment which supports the European dPMR standard 3 4 NEXEDGE NXDN Hand PortableContents 1 History 2 Applications 3 Technical characteristics 4 Application functions 5 Audio quality 6 NXDN Forum 7 See also 8 References 9 External linksHistory EditIcom and Kenwood began their collaboration in 2003 The NXDN protocol was announced in 2005 and NXDN compatible products first appeared in 2006 5 The NXDN Common Air Interface CAI was accepted at the Study Group 5 SG5 meeting of 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 Applications EditThe NXDN protocol and the communications products in which it is used are intended for commercial Private Land Mobile Radio PLMR 6 and public safety communications systems The technology satisfies 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 a schedule for transition to 6 25 kHz narrowband technology 7 Technical characteristics EditNXDN 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 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 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 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 8 This combination provides better weak signal voice quality than for analog FM For an equivalent transmitter power NXDN 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 9 8K30F1E 12 5 kHz single channel digital voice 8K30F1D 12 5 kHz single channel digital data 8K30F1W 12 5 kHz single channel digital voice and data 4K00F1E 6 25 kHz single channel digital voice 4K00F1D 6 25 kHz single channel digital data 4K00F1W 6 25 kHz single channel digital voice and data 4K00F2D 6 25 kHz single channel analog CW IDApplication functions EditThe 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 Encryption Scramble encryption A pseudorandom binary sequence created by combining an exclusive or bitwise operation on the audio or data stream and a linear feedback shift register with a feedback polynomial of x 15 x 1 displaystyle x 15 x 1 which has a 32 767 bit repeat period yielding 32 767 possible encryption keys except all zero 10 DES Encryption 64 bit block encryption cipher operating in OFB mode using a 56 bit key expressed in 64 bits with parity bits 10 AES Encryption 128 bit block encryption cipher operating in OFB mode using a 256 bit key 10 Paging amp status reporting radio to radio and dispatch to radio User aliases 65 545 different group IDs and user IDs Man down and emergency call Remote radio management functions stun kill revive and monitor Over the air programming Over the air alias Interface to third party applications for paging to radio GPS location taxi data terminals in building trackingAudio quality EditIn all lossy compression schemes trade offs are made in voice reproduction quality in return for minimizing 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 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 Hytera s DMR systems and the Project 25 P25 mobile radio system The following reports and papers are descriptions of laboratory environment evaluations of AMBE 2 and other speech vocoders 11 12 13 Compromises in audio quality are inherent in 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 is directly applicable to any system using similar multi band excitation coders 14 failed verification NXDN Forum EditThe NXDN Forum was formed in order to promote the NXDN protocol in North and South America The forum s members are 15 CML Microcircuits Freedom Communication Technology Hytera Communications Icom Incorporated InterTalk Critical Information Systems Kenwood Corporation Ritron Inc Trident Micro Systems which was bought by Motorola Solutions in December 2014 Remota Tecnologia em ComunicacaoSee also EditDigital private mobile radio Digital mobile radio Terrestrial Trunked RadioReferences Edit Icom Inc Global a href Template Cite web html title Template Cite web cite web a CS1 maint url status link dead link Walkie Talkies NEXEDGE PMR446 Ham Radio Kenwood Comms Icom Inc Global a href Template Cite web html title Template Cite web cite web a CS1 maint url status link dead link Walkie Talkies NEXEDGE PMR446 Ham Radio Kenwood Comms The history of NXDN NXDN Forum Retrieved May 21 2016 Private Land Mobile Radio Services 17 May 2016 In the Matter of Implementation of Sections 309 j and 337 of the Communications Act of 1934 as Amended THIRD MEMORANDUM OPINION AND ORDER THIRD FURTHER NOTICE OF PROPOSED RULE MAKING AND ORDER PDF Archived from the original PDF on 2013 07 24 Retrieved 2009 01 22 New Vocoder Delivers Highest Quality Available at 2 0 9 6 kbps Archived from the original on 2009 02 07 Retrieved 2009 01 22 Emission Designator the RadioReference Wiki a b c NXDN Technical Specifications TS 1 D Version 1 3 JVC KENWOOD Corporation and Icom Incorporated 2007 2012 pp 6 9 Redding Christopher May 2001 Voice Quality Assessment of Vocoders in Tandem Configuration PDF NTIA Report 01 386 Campos Neto S F 1996 Performance assessment of 4 8 kbit S AMBE coding under aeronautical environmental conditions 1996 IEEE International Conference on Acoustics Speech and Signal Processing Conference Proceedings Vol ICASSP 96 Vol 1 Conference Proceedings pp 499 502 doi 10 1109 ICASSP 1996 541142 ISBN 0 7803 3192 3 S2CID 9223464 Project 25 Vocoder Evaluation Mean Opinion Score Test Tia TSB 102 babe Welcome to the PSCR Program 3 March 2016 Who are our members nxdn forum com Retrieved 2022 08 04 External links EditComparison of FDMA and TDMA Systems NDXN Standard Retrieved from https en wikipedia org w index php title NXDN amp oldid 1166917383, wikipedia, wiki, book, books, library,
