JULY - 2023AEROSPACEDEFENSEREVIEW.COM9The IMA Core System (Figure 4) can be defined as a set of standardised modules communicating across a unified digital network. The IMA Core System processes inputs that are received from the platform's low and high bandwidth sensors. It can be viewed as a single entity comprising many integrated processing resources which can be used to construct any avionics system regardless of size and complexity. Multiple systems can be architected and overlaid on the partitioned platform resources to form a highly integrated system with full isolation and independence of each individual system. Nevertheless, the digital bus interconnecting AU with RU entails a certain bandwidth and processing power that is usually not available in generic IMA Core Systems. In fact, IMA lacks adequate bandwidth to enable low latency data exchanges with the Antenna Unit. Hence, integration may only happen with an upgrade of IMAs.A solution to turn IMA suitable for high demanding quality of service and class of service requirements of future radio systems requires to move "down" the RU-AU "cutting point", mentioned before, which has some drawbacks: the Antenna Unit becomes more complex and has to embed its own dedicated digital signal processing hardware, bigger in size, and dissipating more heat. Conversely, a lower throughput is required at the level of the digital bus interface and the Radio Unit will then have a simplified design. Proof of ConceptValidation of using IMA to sustain Radio Unit functions could be based on two initial waveforms such as the L-Band Digital Aeronautical Communications System (LDACS) and the SESAR-defined solution for Inmarsat-based SATCOM designated as IRIS. The physical layers of LDACS and IRIS are well defined in ICAO standards and recommended practices (SARPS) as well as in several other standards such as EUROCAE ED-262 (Technical Standard of Aviation Profiles for ATN/IPS) and RTCA DO-379 (Internet Protocol Suite Profiles).For an end-to-end QoS/performance measurement, several levels of interfacing must be considered (Figure 5) but the focus must be placed on those between RF front-ends and the SDR platforms (AU-RU digital RF interface). The complete AU-RU interface definition must cover layers 1 and 2, including the selection of the physical cabling (copper or optical) and protocols which determine data formats. The selection of AU-RU interfaces relies on trade-offs between the throughput and round-trip-time, characteristic of each waveform, and its channel bandwidth and the availability of low latency interfaces. Protocol options include Avionics Full Duplex Switched Ethernet (AFDX) which is already used in aviation context and supports data throughputs up to 1 Gbps.The final validation plan must offer a methodology to determine the performance levels that the AU-RU exchanges can reach with the RU integrated in IMA, considering transmission delay, BER/SNR, dynamic range and packet loss on the basis of a set up that emulates processing units, interfaces, cabling and smart antennae. Fig. 4 ­ The IMA Core System Fig. 3 ­ SDR Cutting PointTHE IMA CORE SYSTEM PROCESSES INPUTS THAT ARE RECEIVED FROM THE PLATFORM'S LOW AND HIGH BANDWIDTH SENSORS. IT CAN BE VIEWED AS A SINGLE ENTITY COMPRISING MANY INTEGRATED PROCESSING RESOURCES WHICH CAN BE USED TO CONSTRUCT ANY AVIONICS SYSTEM REGARDLESS OF SIZE AND COMPLEXITY Fig. 5 ­ SDR Interfacing
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