The question states that all mesh nodes are properly configured, which rules out software or settings-related issues like security mismatches or incorrect mesh IDs. The problem is a failure to connect, which in a wireless network with correct configuration, most commonly points to a physical layer (Layer 1) issue. Inadequate signal strength (RSSI) or a poor signal-to-noise ratio (SNR) due to excessive distance or physical obstructions are the primary causes of link failure. Repositioning the faulty nodes to be closer to other nodes or to establish a better line-of-sight directly addresses this fundamental RF connectivity requirement, allowing for a stable mesh link to be formed.

A. Place the faulty mesh nodes in their own mesh network

This action isolates the nodes rather than integrating them, defeating the purpose of a single, unified mesh network. It is a workaround, not a solution to the connectivity problem.

C. Change the output power settings only on the faulty mesh nodes

This may create an asymmetric link where one node can "shout" but not "hear" replies. Effective communication requires a stable, two-way connection, which this action does not guarantee.

D. Change the security settings on the faulty mesh nodes

The prompt states all nodes are "properly configured." Changing security on some nodes would create a mismatch, actively preventing them from authenticating and connecting to the existing mesh.

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1. CWNP, "CWISA-102 Certified Wireless IoT Solutions Administrator Official Study Guide," 1st ed., 2021: Chapter 6, "The IoT RF Spectrum," discusses the principles of RF behavior, including signal attenuation due to distance and obstructions. While not specific to mesh troubleshooting, it establishes the foundational concept that physical placement is critical for signal reception, stating, "As the signal propagates from the antenna, it is attenuated by a variety of factors... The most significant factor is free space path loss (FSPL)..." This directly supports that moving a node (changing its path) is a valid troubleshooting step for connectivity.

2. Kurose, J. F., & Ross, K. W., "Computer Networking: A Top-Down Approach," 8th ed., Pearson, 2021: In Chapter 7.2, "Wireless Links and Network Characteristics," the text explains that signal strength decreases as the distance between sender and receiver increases. It also details how multipath propagation and interference from objects can degrade signal quality. This core networking principle confirms that moving a device is a primary method to overcome poor signal quality. (Specific reference: Section 7.2.1, "CDMA," and surrounding discussions on signal-to-noise ratio).

3. Akyildiz, I. F., & Wang, X., "A survey on wireless mesh networks," IEEE Communications Magazine, vol. 43, no. 9, pp. S23-S30, Sept. 2005, doi: 10.1109/MCOM.2005.1509968: This peer-reviewed article emphasizes the importance of network topology and node placement. Section III, "ROUTING IN WMNs," implicitly relies on the existence of stable links between nodes, which are a function of the physical RF environment. The survey discusses how connectivity is a prerequisite for routing, and connectivity is determined by factors like distance and interference, which are addressed by node placement.

Free Space Path Loss (FSPL) is the fundamental concept that describes the reduction in signal strength, or attenuation, of an electromagnetic wave as it propagates through a line-of-sight path in free space. This loss is not due to absorption by a medium but rather the geometric spreading of the wave's energy over a larger area as it travels away from the transmitter. According to the inverse-square law, the power density of the signal decreases proportionally to the square of the distance from the source. Therefore, as an RF signal gets farther from the transmitter, it becomes weaker.

B. RF latency: This refers to the time delay a signal experiences while propagating from the transmitter to the receiver, not the loss of signal strength.

C. Beamwidth: This is an antenna characteristic that defines the angle of the main lobe of its radiation pattern, describing the signal's directivity, not its attenuation over distance.

D. Diffraction: This is a propagation phenomenon where RF waves bend around the edges of an obstacle, which is different from the general signal weakening in open space.

1. Rappaport, T. S. (2002). Wireless Communications: Principles and Practice (2nd ed.). Prentice Hall. In Chapter 4, "Mobile Radio Propagation: Large-Scale Path Loss," Section 4.2, "Free Space Propagation Model," it is stated: "The free space power received by a receiver antenna... is directly proportional to the square of the wavelength and inversely proportional to the square of the T-R separation distance." (p. 101). This inverse relationship with the square of the distance is the definition of FSPL.

2. MIT OpenCourseWare. (2012). 6.02 Introduction to EECS II: Digital Communication Systems, Fall 2012. Lecture 15 Notes, "Wireless Communication." Section 15.2, "Path Loss," explains that received power (PR) is proportional to 1/d², where 'd' is the distance. This section explicitly defines path loss as the signal attenuation due to distance.

3. Ling, S. J., Sanny, J., & Moebs, W. (2016). University Physics Volume 1. OpenStax. In Chapter 16, "Waves," Section 16.8, "Energy and Power of a Wave," the text explains that for a spherical wave, "The intensity is therefore proportional to 1/r²," where 'r' is the distance from the source. This inverse-square law is the physical principle underlying Free Space Path Loss.

PHP (PHP: Hypertext Preprocessor) is a versatile, general-purpose scripting language. While it is most famous for server-side web development where scripts are processed by a web server to generate dynamic content, it also includes a powerful Command Line Interface (CLI). The PHP CLI allows scripts to be executed directly from a terminal or command prompt, making it suitable for a wide range of tasks outside of a web context, such as automation, data processing, and system administration scripts. This dual capability is a key feature of the language.

A. PHP is a cross-platform language, officially supported on various operating systems, including Linux, Windows, macOS, and others, not just Linux.

B. The PHP Command Line Interface (CLI) SAPI (Server Application Programming Interface) is specifically designed for running scripts outside of a web server.

C. PHP's primary and most widespread use is for server-side scripting in web applications, where it is processed by a web server.

1. The PHP Group, PHP Manual, "What is PHP?". "PHP is a popular general-purpose scripting language that is especially suited to web development. [...] But PHP can do much more. There are three main areas where PHP scripts are used. - Server-side scripting. [...] - Command line scripting. [...] - Writing desktop applications." This section explicitly states the main uses, including both server-side (web) and command-line scripting.

Source: https://www.php.net/manual/en/intro-whatis.php

2. The PHP Group, PHP Manual, "Using PHP from the command line". "PHP is not only for creating web pages. Since PHP 4.3.0, PHP has a new SAPI type named CLI, which stands for Command Line Interface. As the name implies, this SAPI type main focus is on developing shell (or desktop) applications with PHP." This document details the existence and purpose of the CLI, confirming its use beyond web applications.

Source: https://www.php.net/manual/en/features.commandline.php

Cloud-based wireless solutions require on-premises network devices, such as access points and switches, to communicate with a management platform hosted on the internet. This communication is fundamentally based on the Internet Protocol (IP), which operates at Layer 3 of the OSI model. Therefore, any network that can assign an IP address to the device and provide a routed path to the public internet will enable connectivity to the cloud controller. This is not limited to a single type of connection like cellular; it can be any standard internet backhaul, including wired Ethernet (DSL, cable, fiber), cellular, or satellite, as long as it provides Layer 3 IP routing.

A. BLE (Bluetooth Low Energy) is a Layer 2 protocol for short-range, low-power communication and is not used for backhaul connectivity to the internet.

C. IPX/SPX is a legacy, non-routable protocol suite that has been superseded by TCP/IP and is not used on the modern internet.

D. While cellular is a valid method for internet access, it is not the exclusive method; wired Ethernet connections are more common for fixed infrastructure.

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1. CWNP. (2021). CWISA-102: Certified Wireless IoT Solutions Administrator Official Study Guide. Syngress.

Page 318, Chapter 10, "Cloud-Based WLAN Architecture": The text states, "The APs connect to the cloud-based controller through the Internet." This establishes that internet connectivity is the medium.

Page 36, Chapter 2, "IoT Fundamentals": The guide explains the TCP/IP model, where the Internet layer (Layer 3) is responsible for "addressing and routing of datagrams across networks," which is the fundamental mechanism for all internet communication.

2. Cisco Meraki. (n.d.). Upstream Firewall Rules for Cloud Connectivity. Cisco Meraki Documentation.

Section "Meraki Cloud Communication": The documentation specifies that Meraki devices (a cloud-based solution) "must be able to communicate with the Meraki Cloud... This is done via a secure tunnel over the Internet." It then lists required IP addresses and ports, confirming the reliance on standard Layer 3 IP connectivity to the internet.

3. Kurose, J. F., & Ross, K. W. (2021). Computer Networking: A Top-Down Approach (8th ed.). Pearson.

Chapter 4, "The Network Layer: Data Plane": This chapter details the function of the network layer (Layer 3) and the Internet Protocol (IP) as the core components enabling global connectivity between hosts across disparate networks, which is the foundational principle for any device connecting to a cloud service.

A wireless transceiver is a device that combines a radio transmitter and a radio receiver into a single unit. The fundamental component responsible for this function is the radio. The radio hardware handles the modulation of data onto a carrier wave for transmission and the demodulation of an incoming carrier wave to extract data for reception. While other components like memory and I/O are essential for a functional device, the radio is the specific, primary component that implements the wireless transceiver capability. Without the radio, the device cannot send or receive wireless signals.

A. GPIO pins are General Purpose Input/Output pins used for digital signaling and interfacing with other components, not for implementing the core radio frequency (RF) functions of a transceiver.

B. SRAM (Static Random-Access Memory) is volatile memory used by the processor for temporary data storage during operation. It does not perform wireless communication.

C. Flash memory is non-volatile storage for firmware and application code. It is essential for the device's program but is not the radio transceiver itself.

1. CWNP, "CWISA-102 Certified Wireless IoT Solutions Administrator Official Study Guide," 1st ed., 2021.

Chapter 2: The Things of IoT, Section: IoT Device Hardware. This chapter details the core components of an IoT device. It explicitly identifies the "radio" or "wireless module" as the component responsible for wireless communication, distinct from the microcontroller, memory (SRAM/Flash), and I/O interfaces (like GPIO).

2. Espressif Systems, "ESP32-S3 Series Datasheet," Version 1.3, 2023.

Section 2.1: Block Diagram, Page 13. The official block diagram for this popular wireless System on a Chip (SoC) clearly shows a dedicated "Wi-Fi & Bluetooth LE RF" block. This block, the radio transceiver, is shown as a separate, primary component from the CPU cores, SRAM, ROM (used for bootloader, analogous to Flash for user code), and GPIO matrix.

3. Asghari, H., & Scaglione, A. (2015). "Introduction to Networked Control Systems." Cornell University.

Chapter 7: Wireless Communication for NCS, Section 7.1: Wireless Transceiver Architecture, Page 135. This university courseware material presents a generic wireless transceiver block diagram. The core "RF Front-End" (the radio) is shown as the essential block that interfaces with the antenna and handles signal transmission and reception, separate from the digital baseband processing and microcontroller units.