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The Complete Encryption Solution
Encryption is not just a radio terminal option, but a system function. While the majority of encryption hardware is fitted in the terminal, the whole system performance plays its part.


A System Not a Product
Encryption places another whole level of control over a radio system’s audio and keying systems and virtually all system components can have an effect. Further, some features advertised by a module supplier may not be compatible with some radios, or configurations of radios. The combination of radio terminals, base unit and encryption module configurations is immense, especially with all the programmable features in software.


Encryption Extent
Customer requirements will determine whether all or part of a system’s audio paths are encrypted. The two main configuration types are end-to-end encrypt and radio path encrypt.


Base / Repeater Component
Encryption extent and other issues are part of the base / repeater aspects of the system design. In some systems there will be no encryption products in the base station units, others there will be.


PMR / Trunking
Both PMR and Trunking systems have a requirement for and can be configured for encryption. However, the keying and audio paths are controlled differently, and need separate consideration.


Uniqueness
Each radio system that requires encryption and has some user specified requirements will be unique. This means each needs its own design. A system design is a set of documents describing exactly how it functions, what hardware and software is required to achieve that, and how it is to be tested in production and for user acceptance.


System Management
In large fleets, the process of managing the encryption unit codes, handling lost units, changing settings of units, etc can become a major task. There are two key issues:
  • Initial set up of the units in the portables, mobiles and base units
  • Ongoing maintenance of these units

Some aspects can be done with Over-The-Air-Reprogramming (OTAR) while the unit is still in the radio, by sending codes to it over the radio channel. This avoids the time consuming return-to-base, disassembly, connecting programming equipment to the unit, and radio reassembly.

Where supported by the unit, this allows such features as:

  • remote disabling of a stolen radio
  • remote open mic operation of a unit in an emergency or if stolen
  • changing of code sets in use for a whole fleet
  • changing of unit behaviour (eg enabling a feature such as alert tones)
  • moving units to different group codes

Note that these capabilities that give great flexibility of capability are also what makes every system different, and require attention in the system design stage.

The OTAR can be driven from an unencrypted mobile, portable or via the base station. This would be decided as part of the system design.