NMT 900 Nordic Mobile Telephone in 900 MHz frequency band

NMT 900, which stands for Nordic Mobile Telephone 900, is a telecommunications standard used in the Nordic countries. It operates in the 900 MHz frequency band and is based on the analog technology of the first-generation mobile telephony systems.

NMT 900 was developed in the 1980s and became commercially available in the early 1990s. It was designed to provide mobile voice communication services across large geographical areas with relatively low population densities. The Nordic countries, including Denmark, Finland, Iceland, Norway, and Sweden, adopted this standard as a common platform for mobile telephony.

The choice of the 900 MHz frequency band for NMT 900 had several advantages. Firstly, the lower frequency band enabled better signal propagation over long distances and through obstacles such as buildings and vegetation. This made NMT 900 particularly suitable for providing mobile coverage in rural and sparsely populated areas. Additionally, the lower frequency band allowed for the use of larger cells, resulting in a smaller number of base stations required to provide coverage over a given area.

NMT 900 operated on a Time Division Multiple Access (TDMA) scheme, which divided the frequency band into time slots. Each time slot could accommodate a single voice call, and multiple calls could be handled simultaneously by utilizing different time slots. The TDMA scheme ensured efficient use of the available frequency resources and allowed for a high capacity of simultaneous calls within a cell.

In terms of technical specifications, NMT 900 supported a maximum output power of around 10 Watts for mobile handsets, which provided a reasonable range for communication. The system employed frequency modulation (FM) for voice transmission and had a channel bandwidth of 25 kHz. The modulation scheme, combined with error correction techniques, ensured reliable voice quality even in the presence of noise and interference.

NMT 900 offered basic voice services such as voice calls and short messaging. The system did not support advanced features like data transmission or multimedia capabilities, as it was primarily designed for voice communication. However, it laid the foundation for the subsequent development of digital mobile telephony systems that would offer enhanced functionality and data services.

The success of NMT 900 can be attributed to its regional adoption and the collaboration between the Nordic countries. By standardizing on a common platform, roaming between different networks within the region became possible, enabling seamless communication for users across borders. This increased the convenience and accessibility of mobile telephony services and facilitated economic and social integration within the Nordic countries.

However, as technology advanced and the demand for mobile services increased, NMT 900 gradually became outdated. The limitations of analog technology and the lack of support for data services made it less competitive compared to newer digital standards such as GSM (Global System for Mobile Communications). Consequently, the Nordic countries, like many other countries worldwide, transitioned to digital mobile systems, leading to the eventual discontinuation of NMT 900 networks.

In summary, NMT 900 was a mobile telephony standard operating in the 900 MHz frequency band. It provided voice communication services in the Nordic countries, offering extensive coverage in rural areas and supporting regional roaming. Despite its limitations in terms of technology and data capabilities, NMT 900 played a significant role in establishing mobile telephony in the Nordic region and paved the way for the subsequent evolution of digital mobile systems.