- Q. Is NEXEDGE® compatible with other companies' products or systems?
- A. Yes. The NXDN™ protocol used by NEXEDGE® is compatible with other companies' products that conform to the mandatory features and standard optional features specified by the NXDN™ Forum. Details will be provided on a future Forum website.
- Q. Is NEXEDGE® compatible with P25?
- A. No. The NEXEDGE® radio system uses the NXDN™ protocol, whereas P25 radio systems use the TIA102 standard. Since these systems use different protocols they cannot communicate with each other. Kenwood has its own range of P25-compatible radio equipment.
- Q. Is NEXEDGE® compatible with TETRA?
- A. No. TETRA is a TDMA radio system, standardized by ETSI.
- Q. As regards NEXEDGE® making effective use of current analog systems, specifically what components are of use?
- A. You can use power amps, combiners and other equipment that form part of analog systems. Moreover, NEXEDGE® radios have a digital mode and an analog mode, so it is possible to gradually convert systems currently in use from analog to digital. Also, absolutely no special peripheral equipment is required for 6.25kHz operation; standard LMR facilities can be used as they are.
- Q. We currently use another trunked system. Can we connect a NEXEDGE® trunked site to it?
- A. No. It is not possible to directly connect a NEXEDGE® site to an analog trunked site (e.g. LTR® or PassPort).
- Q. Does Mixed Mode work in trunked mode?
- A. No. Mixed mode is available only for "conventional" operation (analog conventional & NEXEDGE® conventional).
- Q. What people do you recommend the NEXEDGE® system for?
- A. We recommend it to people with the following sorts of needs and issues.
- "Our present equipment suffers from a rasping kind of noise on the edges of the communications area."
- "We want to extend the range a little, but we are hesitating because of the cost of installing repeaters."
- "With our present equipment, competitors can eavesdrop on our communications and there are leaks of important information. We could prevent this with scramblers, but it's expensive."
- "We want to send GPS positional information simultaneous with voice, and sometimes we want to send long data message instead of voice, but right now we have neither of these capabilities."
- "We currently use LTR® Trunked, but we only have about 200 IDs, which is inconvenient."
- "We are operating a multisite system, but running costs are high because we have to use leased lines to connect the different sites."
- "We are running a system as an SMR operator, but too much time is spent in managing IDs and accounting. We want something simpler."
- "We want to make the right choices now so that we will not be faced with additional costs if and when we are compelled to transition to 6.25kHz in the future."
- Q. How is it that both FM and NEXEDGE® units can share the same RF channel?
- A. With conventional operations using 12.5kHz channels, NEXEDGE® radios can be used in either analog or digital modes. However, since the frequency is the same, a choice must be made between analog and digital. For example, if someone transmits in analog mode, the receiving unit will switch automatically to analog. Similarly, for digital mode transmissions the receiving unit will switch to digital and receive by decoding the digital voice signal.
- Q. How is it that both voice and data be transmitted simultaneously on the same channel?
- A. With analog communications, it is not possible to transmit voice and data simultaneously, but this can be done using digital mode. This is because with digital technology the voice signal is also converted into a digital signal for transmission; in other words, both voice and data can be converted into a digital signal and sent together. At the receiving end, the voice and data are separated and individually decoded.
- Q. How far exactly does NEXEDGE® coverage extend?
- A. It is not possible to precisely compare coverage area since it varies depending on the conditions for radio wave propagation. When comparing the coverage areas of a NEXEDGE® system and an analog system, typically the following is true:
4800bps > 9600bps H ≈ Narrow FM
When using a NEXEDGE® multisite system, the system service area increases according to the number of sites.
- Q. Can the system be used during a power failure?
- A. Connecting UPS (uninterruptible power supply) units to your system will enable you to continue operation for a limited time without mains power. A radio can be used for as long as the battery charge lasts.
- Q. Are any NEXEDGE® systems actually in operation yet?
- A. Yes. In the North American market NEXEDGE® systems have already been adopted for use in hotels and factories, and by SMR operators, among others.
- Q. Is NXDN™ an "open standard"?
- A. NXDN™ is supported by the NXDN™ Forum, which is comprised of many companies including a radio manufacturer and a tester manufacturer. They have announced that they will open the NXDN™ technical specification in 2Q 2012.
- Q. Is NXDN™ a proven technology?
- A. Yes. We have invested several years and significant resources in the development of NXDN™. NXDN™ specifications have been verified both theoretically, using computer simulations, and also practically in countless field tests using NEXEDGE® prototypes.
- Q. Why did JVC KENWOOD develop NXDN™?
- A. When a public body decides on standard technical specifications, as is the case with APCO and TETRA, compatible equipment from different manufacturers can be used together. However, in the case of digital radios for business applications, the process of deciding on standard technical specifications has been held up and so equipment from one manufacturer will not be compatible with another brand. Yet it was necessary to prepare for the anticipated FFC requirement for Part 90 licensees to migrate to 6.25kHz narrowband technology. So that the business user would not be at a disadvantage, we engaged in joint research and developed a standard protocol for digital communications.
- Q. What are the most significant benefits of using the NXDN™ protocol?
- A. The following are especially noteworthy:
NXDN™ offers clear digital voice communications with little or no noise. Thanks to digital modulation, a high degree of confidentiality is available. Current FM analog equipment (power amps, combiners, etc.) can continue to be used. Since voice and data can be transmitted at the same time, even without a reserved frequency it is easy to add data to radio communications. You can be sure of coverage that is equivalent to or better than that of an analog system.
- Q. Is NXDN™ (digital) robust when it comes to interference?
- A. Switching to digital does not mean that one can solve the RF-based interference suffered by today's systems. Adjacent and co-channel interference will sound different when using digital equipment, but digital technology in itself will not solve historic interference issues.
- Q. What sort of systems use FDMA?
- A. The FDMA access method has been employed in many LMR trunked systems such as LTR®, SmartNet, and MPT. Project 25 Phase I for digital public safety radio also uses an FDMA access method.
- Q. What are the benefits of FDMA?
- A. In order to satisfy the spectrum efficiency requirement for one voice path per 6.25kHz bandwidth, one can employ the 2-slot TDMA (12.5kHz channel) method, but FDMA is superior for large zones and for direct communications between radios. FDMA is also simpler than TDMA when it comes to servicing and maintenance. Basically with the 2-slot TDMA method, in direct mode operations only one of the slots can be used for communications, so 6.25kHz frequency efficiency is not achieved (it requires complex control). With TDMA the guard time required between slots to prevent data collision reduces the coverage area and the effective data rate per slot; FDMA is not subject to such limitations.
- Q. What is OCXO and when do I need to use it?
- A. The radio laws in each country require a degree of stability in the frequencies used for transmission. For example, for UHF transmissions the FCC in the United States and Canada's IC require a frequency stability of ±0.5ppm for a base station operating with 6.25kHz-wide channels. An OCXO unit is necessary to ensure this high degree of frequency stability.
- LTR® is a registered trademark of E.F. Johnson Company.