NXDN

Last updated
IDAS Radio IC-F3162DT ICOM IC-F3162dt.jpg
IDAS Radio IC-F3162DT

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.

Contents

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]

NEXEDGE NXDN Hand Portable NEXEDGE NXDN.jpg
NEXEDGE NXDN Hand Portable

History

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.

The following FCC emission designators apply to NXDN transmissions: [9]

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.

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 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. [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]

See also

Related Research Articles

<span class="mw-page-title-main">Packet radio</span> Form of amateur radio data communications using the AX25 protocol

In digital radio, packet radio is the application of packet switching techniques to digital radio communications. Packet radio uses a packet switching protocol as opposed to circuit switching or message switching protocols to transmit digital data via a radio communication link.

Speech coding is an application of data compression to digital audio signals containing speech. Speech coding uses speech-specific parameter estimation using audio signal processing techniques to model the speech signal, combined with generic data compression algorithms to represent the resulting modeled parameters in a compact bitstream.

<span class="mw-page-title-main">Vocoder</span> Voice encryption, transformation, and synthesis device

A vocoder is a category of speech coding that analyzes and synthesizes the human voice signal for audio data compression, multiplexing, voice encryption or voice transformation.

Narrowband signals are signals that occupy a narrow range of frequencies or that have a small fractional bandwidth. In the audio spectrum, narrowband sounds are sounds that occupy a narrow range of frequencies. In telephony, narrowband is usually considered to cover frequencies 300–3400 Hz, i.e. the voiceband.

<span class="mw-page-title-main">Digital Radio Mondiale</span> Digital radio broadcasting standard

Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting—particularly shortwave—and FM broadcasting. DRM is more spectrally efficient than AM and FM, allowing more stations, at higher quality, into a given amount of bandwidth, using xHE-AAC audio coding format. Various other MPEG-4 codecs and Opus are also compatible, but the standard now specifies xHE-AAC.

Terrestrial Trunked Radio, a European standard for a trunked radio system, is a professional mobile radio and two-way transceiver specification. TETRA was specifically designed for use by government agencies, emergency services, for public safety networks, rail transport staff for train radios, transport services and the military. TETRA is the European version of trunked radio, similar to Project 25.

The International Telecommunication Union uses an internationally agreed system for classifying radio frequency signals. Each type of radio emission is classified according to its bandwidth, method of modulation, nature of the modulating signal, and type of information transmitted on the carrier signal. It is based on characteristics of the signal, not on the transmitter used.

IS-54 and IS-136 are second-generation (2G) mobile phone systems, known as Digital AMPS (D-AMPS), and most often referred to as TDMA, are a further development of the North American 1G mobile system Advanced Mobile Phone System (AMPS). It was once prevalent throughout the Americas, particularly in the United States and Canada since the first commercial network was deployed in 1993. D-AMPS is considered end-of-life, and existing networks have mostly been replaced by GSM/GPRS or CDMA2000 technologies.

<span class="mw-page-title-main">HD Radio</span> Digital radio broadcast technology

HD Radio (HDR) is a trademark for an in-band on-channel (IBOC) digital radio broadcast technology. HD radio generally simulcasts an existing analog radio station in digital format with less noise and with additional text information. HD Radio is used primarily by AM and FM radio stations in the United States, U.S. Virgin Islands, Canada, Mexico and the Philippines, with a few implementations outside North America.

<span class="mw-page-title-main">Project 25</span> Set of Telecommunications Standards

Project 25 is a suite of standards for interoperable digital two-way radio products. P25 was developed by public safety professionals in North America and has gained acceptance for public safety, security, public service, and commercial applications worldwide. P25 radios are a direct replacement for analog UHF radios, adding the ability to transfer data as well as voice for more natural implementations of encryption and text messaging. P25 radios are commonly implemented by dispatch organizations, such as police, fire, ambulance and emergency rescue service, using vehicle-mounted radios combined with repeaters and handheld walkie-talkie use.

<span class="mw-page-title-main">Icom Incorporated</span> Radio equipment manufacturer

Icom Inc. is a Japanese manufacturer of radio transmitting and receiving equipment, founded in 1954 by Tokuzo Inoue with the company's original name being "Inoue". Its products now include equipment for radio amateurs, pilots, maritime applications, land mobile professional applications and radio scanner enthusiasts.

<span class="mw-page-title-main">Secure voice</span> Encrypted voice communication

Secure voice is a term in cryptography for the encryption of voice communication over a range of communication types such as radio, telephone or IP.

D-STAR is a digital voice and data protocol specification for amateur radio. The system was developed in the late 1990s by the Japan Amateur Radio League and uses minimum-shift keying in its packet-based standard. There are other digital modes that have been adapted for use by amateurs, but D-STAR was the first that was designed specifically for amateur radio.

MPT 1327 is an industry standard for trunked radio communications networks.

Multi-Band Excitation (MBE) is a series of proprietary speech coding standards developed by Digital Voice Systems, Inc. (DVSI).

Digital mobile radio (DMR) is a digital radio standard for voice and data transmission in non-public radio networks. It was created by the European Telecommunications Standards Institute (ETSI), and is designed to be low-cost and easy to use. DMR, along with P25 phase II and NXDN are the main competitor technologies in achieving 6.25 kHz equivalent bandwidth using the proprietary AMBE+2 vocoder. DMR and P25 II both use two-slot TDMA in a 12.5 kHz channel, while NXDN uses discrete 6.25 kHz channels using frequency division and TETRA uses a four-slot TDMA in a 25 kHz channel.

<span class="mw-page-title-main">Digital private mobile radio</span> Type of digital radio service

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 the reference ETSI TS 102 658.

<span class="mw-page-title-main">M17 (amateur radio)</span> Open source amateur radio mode

M17 is a digital radio modulation mode developed by Wojciech Kaczmarski et al. M17 is primarily designed for voice communications on the VHF amateur radio bands, and above. The project received a grant from the Amateur Radio Digital Communications in 2021 and 2022. The protocol has been integrated into several hardware and software projects. In 2021, Kaczmarski received the ARRL Technical Innovation Award for developing an open-source digital radio communication protocol, leading to further advancements in amateur radio.

References

  1. "Icom Inc. Global". Archived from the original on 2009-01-23. Retrieved 2009-01-22.
  2. "Walkie Talkies | NEXEDGE | PMR446 | Ham Radio • Kenwood Comms".
  3. "Icom Inc. Global". Archived from the original on 2012-04-04. Retrieved 2012-02-11.
  4. "Walkie Talkies | NEXEDGE | PMR446 | Ham Radio • Kenwood Comms".
  5. "The history of NXDN™". NXDN-Forum. Retrieved May 21, 2016.
  6. "Private Land Mobile Radio Services". 17 May 2016. Archived from the original on 22 February 2009. Retrieved 22 January 2009.
  7. "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.
  8. "New Vocoder Delivers Highest-Quality Available at 2.0 – 9.6 kbps". Archived from the original on 2009-02-07. Retrieved 2009-01-22.
  9. "Emission Designator - the RadioReference Wiki".
  10. 1 2 3 NXDN Technical Specifications, TS 1-D Version 1.3. JVC KENWOOD Corporation and Icom Incorporated. 2007–2012. pp. 6, 9.
  11. Redding, Christopher (May 2001). "Voice Quality Assessment of Vocoders in Tandem Configuration" (PDF). NTIA Report 01-386.
  12. 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.
  13. "Project 25 Vocoder Evaluation Mean Opinion Score Test". Tia TSB-102.babe.
  14. "Welcome to the PSCR Program". 3 March 2016.
  15. "Who are our members?". nxdn-forum.com. Retrieved 2022-08-04.