Communications Systems

Communications systems are intrinsic to our heritage as providers of bespoke solutions.

We will adapt your existing network for new markets or inputs, configure technology for a specific desired use or design new applications entirely.

Key Skills

  • Development of bespoke high level/system design communication networks
  • Self-organising multi-hop networks using directional antennas
  • Concept and development of IoT smart city solutions
  • Vehicle communications and telemetry, such as stolen vehicle recovery transceivers, fleet monitoring networks, and parking sensors
  • In-field wireless medical telemetry for hospital-based patient monitoring
  • PCB troubleshooting with testing and laboratory capabilities
  • Transferable experience and knowledge in communications systems across market verticals including, Defence, Security, Aerospace, IoT and Consumer
  • Low data rate low power wide-area network (LPWAN) solutions
  • High volume and low volume specialised products
  • Innovative and cost-effective consulting with real-world application
  • Adapting existing systems for new markets
  • Secure communications links to bespoke base stations
  • Rapid prototyping of candidate technologies, such as optics, sensors and radio

Richard Emmerson

Senior Consultant, Communications Systems

“There is a wide availability of standards-based radio modules and integrated circuits. This makes adding wireless connectivity a seemingly less daunting task for many hardware developers. Unfortunately, adding this technology without proper experience of radio design can often lead to costly mistakes and programme delays. For systems incorporating multiple radio standards, the risk is even greater.

Plextek has built its business on communications technology, and we offer design support throughout the product lifecycle. This might include specifying the most suitable radio standard or designing a bespoke system through to product approvals and manufacturing.”

richard emmerson headshot

Benefits of a Proprietary Solution

As a product or systems developer, the modern marketplace offers a plethora of off-the-shelf technologies that can be exploited in order to turn a new system or concept into a real business venture. This is particularly true of market sectors such as connected devices and the ‘Internet of Things’. In this instance, multiple vendors offer technology for integration into other people’s designs (such as modules) or turnkey solutions for those that do not wish to develop the solutions themselves. The opposite approach to developing all the technology is the older business model but it has clear benefits for larger players in these new markets.

Some benefits of using COTS technology / IP blocks include:

  • Low up-front development cost
  • Established levels of functionality and performance
  • Can come pre-type approved (for radio comms)

However, there are some downsides to using such COTS technologies:

  • IP blocks often closed and owned by the 3rd party vendor
  • Royalty payments (can be integrated into the module cost)
  • Obsolescence issues should a 3rd party vendor update its technology or disappear altogether
  • Not always optimum performance for your application

Opting to embark on a proprietary system development with an experienced partner, like ourselves, will inevitably involve a higher up-front cost and we make no bones about this. However, one should take a moment consider the bigger picture and long-term economics:

  • Technology optimised for the problem at hand (leading to better performance and/or battery life)
  • Full client ownership of the design (hardware and software)
  • Easier management of obsolescence
  • No royalty payments
  • No network fees or data costs (depends on the system)


This has brought continued success for our larger clients, such as Tracker UK and Telensa. Their ownership of the technology has led to far greater control during the lifespan of their system or network, minimising running costs and therefore improving long-term revenue.

Our heritage of delivering such solutions and aptitude in all the technical disciplines required, especially radio circuit and protocol design, guarantees this.

Developing a Custom Point-to-point Link Protocol

Custom point to point system, communications

A recent requirement from one of our clients was a point-to-point system in which the radio links are subject to severe shadow fading and multipath Rayleigh fading. Each link was to act as a substitute for an Ethernet wire, providing over 100 Mbps of throughput under good conditions and, more importantly, high availability low-rate communications under poor conditions.

An early decision was to treat the Ethernet replacement requirement literally. This meant that the user data transported by each link would consist of Ethernet frames, and the control data exchanged between endpoints would only be used for managing the link itself. Higher layer control and configuration for the client’s network would be transported as IP data and could, therefore, be secured with established security solutions. The result was that the protocol to be developed would only need to define a Physical and Medium Access Control layer.

After careful consideration, Orthogonal Frequency-Division Multiplexing (OFDM) was chosen because of its flexibility. Under good conditions, the RF channel can be packed with a large number of sub-channels, each modulated with a high order modulation, e.g. 256 QAM. Under poor conditions, the transmit power can be concentrated in just a few sub-channels and the modulation order can be dropped to 4 QAM.

Extensive simulations were carried out to confirm the suitability of the choice given OFDM’s two principal disadvantages: its susceptibility to receiver frequency errors and the need for highly linear signal chains, particularly in the transmitter. The simulations included power amplifier models and synthesizer phase noise models, as well as models of the fading environment.

The Medium Access Control layer imposed a Time Division Multiplexing structure on the transmitted signal that was designed to simplify the implementation of the client’s receivers while ensuring the system’s ability to support a range of propagation conditions. High-end throughput was sacrificed to this end, but a peak throughput of over 130 Mbps was nevertheless achieved.

Convolutional codes were used for forward error correction, and adaptive link control adjusted the number of active sub-channels, the modulation, and the code rate so that a wide range of throughputs could be supported, ensuring that the high availability requirement could be met.

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