Thursday, March 23, 2023

LTE for Defense Applications

Asish Jain, Application Engineer, Keysight Technologies India Pvt. Ltd.

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Since ancient times most of the communication technologies first found their ways into defense applications. The research and development in communication technologies has had distinct differentiation in terms of defense use and commercial use. Technologies for defense use have been covert until their inventors and governments thought to make them available for public use. On the other hand, commercial use technologies had a difficult time making inroads into the defense sector due to their open architecture, standardization, security concerns, etc. However, this environment is rapidly changing with the adoption of commercial wireless communication technologies across the globe. The sheer size of user base and the overall impact of modern technology motivates researchers to improve the existing wireless communication technologies to meet and exceed the growing demands of users. In less than 25 years, advancements in cellular technologies have grown data rates from a few tens of kbps to a Gbps. Commercial off-the-shelf (COTS) products have become a familiar name in the defense industry resulting in benefits like shorter development cycles, ready availability, lower cost and ease of technology refresh. Earlier roadblocks like standardization and open architecture have become advantages as they allow defense R&D to benefit from best practices of the commercial industry and make appropriate technology modifications to suit the needs of defense applications.

Wireless communication for defense applications

Due to the complexity and diversity of defense requirements, there are numerous types of communication systems required. Communications systems as traditional as high-frequency (HF) two-way radios to more elaborate systems such as satellite communications (SATCOM), RADAR and airborne early warning and control (AEW&C) systems are being used. With new technologies in place, current warfare is now being termed as network centric warfare wherein a robustly networked defense force improves information sharing which enhances the quality of information and shared situational awareness. This shared situational awareness enables collaboration and self-synchronization, and enhances sustainability and speed of command. All of these dramatically increase mission effectiveness. In network centric warfare, both speed of information sharing and quality of information form an integral part of the information domain and this is where a choice of communication technology plays an important role. Commercial cellular communication technologies like GSM and WCDMA were limited in terms of data rates, bandwidths, IP connectivity etc. These limitations are being addressed by continuous enhancements in the 4th generation of cellular technology; LTE. In release 12 of 3GPP LTE standards, enhancements specific to public safety and mission critical applications were identified and these have taken shape in the latest release 14 of 3GPP LTE standards.

What makes LTE relevant?

LTE offers multiple deployment bandwidths:1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz, which makes it a flexible choice depending on the application. LTE being an all IP technology offers high level of security as desired for defense applications. One of the most important aspects of LTE in this regards is OFDM and OFDMA. Orthogonal frequency division multiplexing (OFDM) has been the backbone of current commercial wireless systems because it delivers high data throughput in real-world environments, along with spectral efficiency and link flexibility. OFDM’s low symbol rate and multicarrier structure, combined with coding and forward error correction, allow it to operate effectively in channel conditions degraded by interference, jamming, and frequency selective fading.

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Because of its multicarrier structure, OFDM is readily extendable to simultaneous multiple-access capability by mapping subcarriers to users in a scheme called orthogonal frequency division multiple access (OFDMA). This multiple access approach is especially attractive because multiple users can be supported in a flexible fashion with only minor changes in the air interface. In addition, Multiple-Input Multiple-Output (MIMO) techniques can be used with OFDM and OFDMA systems to further improve data throughput in the presence of multipath environments.

These underlying benefits of LTE makes it attractive for flexible deployment in defense applications, both terrestrial and marine. One of the important elements of network centric warfare is video streaming for improved situational awareness. Defense users could potentially take advantage of sophisticated existing hardware and software solutions that offer proven commercial performance in different physical environments from wide open terrain to complex obstructed urban environments. COTS solutions can be configured to meet many different commercial requirements in terms of number of users, required average and peak data rates, cell sizes and configurations, and overall coverage areas.

They not only include network infrastructure but a range of handsets and terminals that implement sophisticated roaming features that can comprise automatic switching to nearby LAN resources when available. This is a powerful benefit when optimizing the use of valuable metropolitan area network (MAN) resources. While these technologies were not designed with defense applications in mind, particularly in the areas of security and resistance to jamming, they are designed to handle environments with interference and competing spectral users. They could potentially serve as a base layer, to which additional layers for security and robustness or redundancy may be added.



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