What factor severely limits the range of systems operating in the 60GHz band?
60GHz Absorption:The 60GHz band experiences significant signal attenuation due to absorption by oxygen molecules in the atmosphere. This severely restricts the usable range of wireless systems operating in this frequency.
Why Other Options Don't Apply:
Atmospheric Scattering:Impacts longer wavelength transmissions, less significant at 60GHz.
Solar Radiation:Can cause interference on some frequencies, but not a primary range limitation at 60GHz.
Rain Fade:Primarily affects higher frequencies (above 10GHz), but its impact is less severe than oxygen absorption at 60GHz.
References:
60GHz Propagation Characteristics:Technical papers discussing oxygen absorption and its influence on range limitations.
Millimeter-wave (mmWave) Communication:Overviews highlighting the challenges and short-range applications of 60GHz systems.
What consideration is found in PtMP systems that is not found in PtP systems?
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:
Each client gets a fair chance to communicate
High-priority traffic isn't starved by low-priority traffic
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):References 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.
As an RF signal propagates it becomes weaker as it gets farther away from the transmitter. What concept is described?
The concept described isFree Space Path Loss (FSPL). FSPL refers to the reduction in power density of an electromagnetic wave as it propagates through a clear, unobstructed path in free space. This weakening of the signal is due to the spreading of the wavefront as it travels, causing the power to be distributed over a larger area. The FSPL can be calculated using the Friis Transmission Equation, which shows that the received power decreases with the square of the distance from the transmitter. This concept is fundamental to understanding the behavior of RF signals in various communication systems, including wireless IoT, where the signal strength at the receiver is a critical factor for reliable data transmission.
What is the primary difference between LoRa and LoRaWAN
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.
What user authentication method is commonly used in guest Wi-Fi networks in the hospitality industry?
Captive Portals for Guest Access:These are web pages that intercept users' requests before granting full internet access. They often require agreeing to terms, entering basic information, or viewing ads.
Hospitality Fit:Captive portals are simple to deploy, require minimal user setup, and provide control for the hospitality provider (e.g., usage limits).
Why Other Options Are Less Common:
NTLM:Microsoft authentication, mainly for corporate networks, too complex for casual guest use.
Kerberos:Complex authentication for enterprise, overkill for guest Wi-Fi
SIM Cards:Used in cellular devices, not for general Wi-Fi access.
References:
Captive Portals:References of how they work and their use cases.
Guest Wi-Fi in Hospitality:Best practices highlight the prevalence of captive portals in this industry.
