Modern communications hinge on software design

An Ask the Expert feature with Anna Squires, Etherstack

Modern wireless communications rely on ever more extensive software to improve interoperability, security, data rates and spectral efficiency. Indeed, as radio technology evolves from analogue to digital, software has surpassed hardware as the most complex element in a radio device.

“It is therefore urgent that software is designed correctly to derive maximum value from this investment and to capitalise properly on the benefits of software-based systems”
-Anna Squires, Etherstack

The investment made by radio manufacturers in software has consequently increased dramatically. It will continue to do so. It is therefore urgent that software is designed correctly to derive maximum value from this investment and to capitalise properly on the benefits of software based systems.

The evolution of the ETSI TETRA standards from Release 1 to Release 2 highlights the importance of investing carefully in protocol software development. The first generation of TETRA radios to reach the market are now approaching end of life and users are anticipating the advanced features and higher data rates offered by TEDS and TETRA Release 2. However, many manufacturers are struggling to maintain their original TETRA protocol code and are finding that they can’t upgrade it or port it to next-generation processors and hardware platforms.

In order to offer a new Release 2 radio, these manufacturers are faced with two options. They can discard their existing code and begin again, with the attendant risk that the lifespan of the new software is also limited by its portability and maintainability. Or they can try and shoehorn their existing code from one processor or platform directly to another – investing additional money and time to extend the life of software that will still need to be abandoned at some point. Manufacturers can even find their choice of hardware for a next-generation platform severely constrained by legacy software that is 10 years old.

Commercial radio protocol stack software is extremely complex. It involves both signal-in-space and software co-ordination intelligence, as well as a carefully managed relationship between hardware and software to ensure that the code can be upgraded and reused on new platforms as technology evolves. Radio software design therefore needs to aim to maximise software portability, upgradability and performance – whilst minimising development costs.

Completely decoupling protocol stack development and maintenance from a specific platform, operating system and user interface is key to this, as is using correct design practice and tools and procedures geared towards embedded hardware at each of the specification, design, implementation, integration and maintenance phases.

However, most radio protocol stack developments today still involve cobbling together software design techniques and tools from other fields and different vendors, rather than offering an integrated approach geared for modern radio platforms. While commercial development tools are becoming more available, radio protocol stack development has yet to become a truly specialist enterprise within the wireless industries.

Adherence to standards also remains an important consideration for radio software design. Interoperability is a hot topic in communications, and digital standards are central to digital interoperability. The benefit of standards-based software is illustrated by comparing the digital Professional Mobile Radio (PMR) industries in Europe and North America. The European ETSI TETRA Release 1 air interface standard is well defined, firmly enforced and widely adopted, encouraging independent handheld manufacturers to the market and driving down the cost of equipment. By contrast, in North America digital PMR radios have tended to use proprietary air interfaces only loosely based on APCO P25, the North American equivalent to TETRA, due to less stringent regulation and enforcement. However this has encouraged standardisation of the P25 network interfaces and as a consequence, multi-vendor options in the network and even solutions for air interface interoperability via the network look set to flourish. In each case, where standards have been followed communications flexibility has markedly improved.

Anna Squires joined Etherstack as an engineer in 1999. In recent years, Squires has led defence Software Defined Radio (SDR) development projects with the company. She is now Etherstack's Product Development Director and is also responsible for Etherstack's Software Defined Radio strategy.