Feature: Communications
LTE for specialised applications By Edward Young, Senior Vice President and General Manager at CommAgility
Image: Tomas Anton Escobar for Unsplash T
oday, more and more wireless applications require fast, reliable, secure communications, in a growing range of applications that include
satellite communications, aviation, high- speed rail and private networks. While other technologies such as
Wi-Fi are readily available and aff ordable to install, across many applications the underlying technology and protocols do not provide the necessary capability, speed, reliability and security. To meet these requirements, many designers are looking to long-term evolution (LTE) based networks.
LTE LTE is a standard for wireless broadband, developed by the 3GPP group, which is commonly considered 4G technology. It has become the standard of choice for a wide range of specialised networks previously built on proprietary networking technologies. T ese applications typically use their own dedicated, private wireless network, instead of relying on one of the mobile networks we all use for our smartphones. By using their own private network, connectivity can be provided where the public networks don’t reach, so performance and coverage can be
guaranteed. T e network can also be customised to provide features or capabilities beyond the LTE standard. For these private networks, LTE off ers
spectral effi ciency and a well-defi ned architecture, as well as low latency, fast speeds and high reliability. By basing these networks on well-defi ned global standards, developers can apply expertise, technology and protocols from the commercial world. Looking ahead, 5G is another
standards-based option that is becoming increasingly popular for such specalised applications. Building a private network with
LTE involves developing a radio access network (RAN) that wirelessly connects base stations (oſt en called small cells, access points or eNodeB) and mobile devices known as user equipment (UE). T e base stations then use LTE ‘core’ soſt ware, providing a link to the backhaul network. T e soſt ware that manages the RAN includes a physical layer (PHY) and a protocol stack. In a standard OSI network model, the PHY is layer 1 (L1), whilst the protocol stack is L2/L3.
LTE benefi ts Before network designers can capitalise on the benefi ts of LTE, they must fi rst address the technical challenges of its system requirements. While LTE provides an
56 December 2021/January/2022
www.electronicsworld.co.uk
excellent basis for a solution, specialised applications normally cannot use the LTE standard without modifi cations. Private networks oſt en require diff erent performance and capabilities than those in the specifi cations, in areas such as coverage, power, propagation delay and Doppler shiſt . For example, in an aviation application
where LTE is being used to communicate between an aircraſt and a base station on the ground, the system must be able to handle the time delays due to the distances involved. With an altitude over 10,000 metres, these are longer than those supported by the LTE standard. T e aircraſt ’s high speed, typically cruising at over 900km/h, also means the frequency shiſt of the signals due to the Doppler eff ect is greater than that specifi ed in the standard, which again requires customisation of the soſt ware being used. In terms of hardware, a typical system
will run on a system-on-chip (SoC), such as Texas Instruments’s Keystone II TCI6630K2L, a low-power baseband solution with an integrated digital radio front end (DRFE). T e TCI6630K2L includes two Arm Cortex-A15 RISC cores and four TMS320C66x DSP cores with fi xed- and fl oating-point processing. T is enables it to provide the processing performance needed for LTE applications, whilst keeping power consumption low.
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