Concept

The software-defined radio (SDR) concept envisages dynamic waveform reconfigurations. This requires software and hardware support and computing resource management, in particular. ALOE supports partial or total reconfigurations of the transceiver digital signal processing chain (waveform) while facilitating the deployment of waveforms on heterogeneous and distributed hardware resources. The main attributes and functionalities of ALOE are:

• Flexibility – be able to trade implementation efficiency against flexibility. An efficient implementation makes best use of the available computing resources (low resource overhead), whereas a flexible solution allows for dynamic reconfigurations at the cost of some resource overhead.

• Execution control – coordinate execution across the entire distributed computing system.

• Abstractions – hide platform details and heterogeneity from radio applications, enabling portability.

• Data packet oriented messaging – packet-oriented instead of processor or device-specific communication mechanisms.

• Parameter control – runtime signal (parameter or variable) management.

• Resource monitoring – computing system/environment awareness.

• Computing resource management – efficiently manage the distributed and limited computing resources.

Layers

ALOE assumes that object interfaces are unknown at design time. This enables dynamically composing and recomposing processing chains at execution time while integrating the objects that assemble the desired waveform. The figure illustrates this. It shows the ALOE layers. The hardware layer typically consists of several processors or processing elements (PEs), which are physically interconnected. The ALOE Layer abstracts the hardware platform, providing a homogeneous execution environment, the ALOE platform, to applications. The abstract application layer models a radio application or waveform by means of the task graph. It abstracts the waveform modules, providing information about the involved tasks (modules or objects), their precedence constraints and data flow requirements. The real application layer uses the services or functionalities provided by the ALOE layer for assembling the complete waveform and distributing its modules among the available hardware resources.

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