Скачать или смотреть Mobile Systems – Design & Energy Efficiency | Chapter 18 – Software Architecture in Practice (4th)

This detailed architectural analysis of mobile systems, which encompass ubiquitous devices like smartphones, vehicles, and robots that lack permanent, continuous power, outlines five critical characteristics that software architects must manage differently than fixed systems. Energy management is paramount, focusing on finite power sources like batteries or fuel-powered generators. Architectural concerns involve implementing tactics for monitoring the power source (often utilizing a Battery Management System or BMS), throttling energy usage (such as reducing display brightness, lowering processor clock rates, or decreasing sensor reading frequency), and ensuring graceful tolerance for power loss, allowing systems to restart quickly and resume operation while preserving data integrity and consistency in permanent storage. Network connectivity requires architects to navigate the wide variety of wireless protocols spanning distances from Near Field Communication (NFC) up to cellular and satellite communication. Key design considerations include supporting only essential communication interfaces to conserve power, enabling seamless transitions between different networks (e.g., Wi-Fi to cellular), dynamically selecting the appropriate protocol based on factors like bandwidth and cost, and designing for inherent challenges like intermittent connectivity or total loss of signal while maintaining data integrity. Furthermore, mobile platforms rely heavily on sensors and actuators to interact with and perceive their environment. The system must create an accurate representation of the external environment, achieved through a sensor stack that handles crucial functions like reading raw data, smoothing data (using techniques such as moving averages or Kalman filters), converting readings into a common format, and performing sensor fusion—intelligently combining inputs from diverse sensors (e.g., radar, lidar, thermal imagers) to recognize complex objects like pedestrians. Architects must also plan for degraded operation should a sensor fail. Addressing resource constraints requires balancing the contribution of a resource against its physical properties like volume, weight, and cost, considering safety, thermal limits, and environmental exposure. Critical decisions include assigning software tasks to specific Electronic Control Units (ECUs) within larger systems, leveraging specialized processors and criticality factors, and deciding which functions can be offloaded to the cloud to utilize greater storage and processing power. Finally, the life cycle of mobile systems presents unique issues, often starting with hardware selection that constrains subsequent software design. Testing is complicated by the need to verify display layouts across many devices, simulate network transitions, and ensure state preservation upon unexpected shutdown. Deploying updates requires strategies for maintaining data consistency (often via the cloud), ensuring updates only occur when safe, supporting partial system deployment, and planning for long-term extendability and retrofitting of components. Comprehensive, offloaded logging is vital for incident investigation and usage analysis.


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