CWISA-102 Questions and Answers

• LoRa Modulation: LoRa (Long Range) is a proprietary wireless technology that utilizes Chirp Spread Spectrum (CSS) modulation.
• CSS Characteristics:

References

• LoRa: https://en.wikipedia.org/wiki/LoRa
• Chirp Spread Spectrum (CSS): https://en.wikipedia.org/wiki/Chirp_spread_spectrum

• OFDM vs. OFDMA:

References

• OFDM: https://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexing
• OFDMA: https://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiple_access

• IEEE's Role: The Institute of Electrical and Electronics Engineers (IEEE) is a global organization critical in developing and promoting technical standards across various fields, including wireless technologies.
• Standards Work: IEEE creates wireless technology standards like:

References

• IEEE: https://www.ieee.org/

• WWAN (Wide-Area Wireless Network): WWANs provide connectivity over extensive geographic areas, typically covering regions or even entire countries.
• Cellular Technology: WWANs often rely on cellular networks (3G, 4G, 5G) offered by mobile carriers.

References

• WWAN: https://en.wikipedia.org/wiki/Wireless_wide_area_network

• Cloud Connectivity Relies on IP: Most cloud-based services operate via the internet, which utilizes Internet Protocol (IP) at Layer 3 of the network model.
• Flexibility: Various Layer 2 technologies (Ethernet, Wi-Fi) can connect to a Layer 3 network that ultimately provides Internet access
• BLE Exception: Bluetooth Low Energy can have cloud connectivity, but often through gateways and not as a direct Layer 2 connection.
• Eliminating Incorrect Options: IPX/SPX is an outdated protocol, and cellular is only one possible way to achieve Internet access.

References:

• OSI Model: Descriptions of Network Layers, especially Layer 2 (Data Link) and Layer 3 (Network).
• Cloud Architecture: Diagrams showing how devices commonly access cloud resources through internet-based infrastructures.

• Bottom-Up Troubleshooting: The OSI model provides a structured diagnostic approach. Starting at Layer 1 ensures basic physical connectivity issues are ruled out first.
• MQTT Relies on IP: MQTT operates at a higher layer of the OSI model, relying on TCP/IP (Layers 4 and 3) for communication. Problems at the physical layer will disrupt everything built upon it.
• Checking the Fundamentals: Before investigating complex application issues (MQTT), verify cables, link lights, Wi-Fi signal strength, etc.

References:

• OSI Model: Descriptions of the seven layers, emphasizing the foundation provided by Layer 1 (Physical).
• Network Troubleshooting Guides: Resources that outline common Layer 1 problems and their symptoms.

• IP Ratings & Manufacturing: IP66 provides:
• Harsh Manufacturing Environments: IP66 is common due to dust, dirt, and potential exposure to liquids during cleaning or spills.

References

• IP Ratings: https://en.wikipedia.org/wiki/IP_Code

• PHP's Cross-Platform Nature: PHP originated for server-side web development, but also has a command-line interface (CLI) enabling its use for scripts and automation tasks.
• Other Options:

References:

• PHP (Introduction): Overviews mentioning its dual role in server-side web applications and as a general-purpose scripting language.
• PHP CLI: Documentation on the command-line interface for PHP.

• Automation for Consistency: Scripts eliminate the potential for human error during repetitive configuration tasks on multiple devices. This ensures uniformity across the wireless solution.
• Speed and Efficiency: Scripts can be much faster than manual configuration, particularly in large deployments.
• Other Benefits: While scripts might aid signal strength (e.g., optimizing settings) or enhance solution capabilities, their core value in configuration is reducing errors.

References:

• Network Automation: Benefits of using scripts for configuration management.
• Configuration Management Best Practices: Emphasize the importance of consistency and repeatability.

• LoRa: This refers to the underlying radio modulation technique using Chirp Spread Spectrum (CSS). It defines how data is physically encoded onto the wireless signal.
• LoRaWAN: This is the network protocol built on top of LoRa. It manages device communication, network topology, and aspects like security. It operates at the MAC sublayer of the Data Link layer (Layer 2) of the OSI model
• LoRa vs. LoRaWAN: Key takeaway is that LoRa is the physical layer technology, while LoRaWAN adds the networking layer for management.

References:

• LoRa Modulation: Technical explanations of Chirp Spread Spectrum (CSS).
• LoRaWAN Specification: Official documentation detailing the network architecture and MAC layer functions.
• OSI Model: Descriptions of the Data Link layer and its role in networking.

• PtMP (Point-to-Multipoint): A single access point (AP) communicates with multiple client devices. This means the AP needs to manage how the available airtime is shared among those clients.
• Airtime Fairness: Mechanisms are needed to ensure that:
• PtP (Point-to-Point): A dedicated link only has two devices, eliminating the need for complex airtime management.
• Considerations in Both: While interference, SINR, and frequency selection are important in both PtMP and PtP systems, the need for airtime management is unique to the multipoint scenario.

References:

• Wireless Network Topologies (PtP vs. PtMP): Explanations of the differences in how communication is managed in each scenario.
• TDMA (Time Division Multiple Access): A common airtime sharing method used in PtMP systems.

• Overlay vs. Integrated Monitoring:
• Overlay Advantage: Since the overlay system is separate, it doesn't add overhead or complexity to the core network, avoiding potential disruption of wireless services.

• Attenuation: Describes the progressive loss of signal strength as it travels through a medium (like air, cables, walls). It's caused by factors like absorption, distance, and obstacles.
• Other Phenomena:

References

• Attenuation: https://en.wikipedia.org/wiki/Attenuation

• HTTP's Popularity: HTTP is the foundation of the web, making it widely known and supported. Developers have extensive familiarity with its concepts (methods, headers, status codes, etc.).
• REST APIs and Webhooks: These often leverage HTTP for communication, building upon existing knowledge and tools.
• Tradeoffs:

References:

• REST APIs: Overviews of their use of HTTP, demonstrating its prevalence in API development.
• Developer Experience with HTTP: Discussions on the familiarity with and availability of HTTP libraries in various programming languages

• Perception Layer: The foundation of an IoT system, it consists of sensors and actuators that: