Module07_-_deck_1

WLAN Design Concepts

Overview

Provider: WILEY, SYBEXThis module covers various critical aspects of WLAN (Wireless Local Area Network) design that ensure optimal performance and reliability in different environmental scenarios.

Key Topics

• Coverage Design

• Received Signal Strength (RSSI)

• Signal-to-Noise Ratio (SNR)

• Dynamic Rate Switching

• Transmit Power

• Roaming Strategies

• Channel Design (2.4 GHz & 5 GHz)

• Capacity Design

• Airtime Consumption

Important Metrics

• Minimum Recommended RSSI of -70 dBm: This threshold is essential for maintaining reliable connectivity in WLAN environments. Values above -70 dBm indicate the ability to maintain high data rates and quality connections, which is critical for applications like video streaming and online gaming.

• Importance of Maintaining High SNR: A higher Signal-to-Noise Ratio reduces the likelihood of data corruption, leading to more reliable performance and improved user experiences. This is particularly vital for VoWiFi (Voice over Wi-Fi) applications where voice quality is paramount.

Coverage Design

• Received Signal Strength: The quality of connectivity is significantly influenced by the RSSI, which measures the power level received from the access point.

  • -70 dBm: Indicates adequate conditions for high data rate connectivity.

  • -65 dBm: This level is particularly suitable for applications requiring VoWiFi, emphasizing strong signals for voice communications.

Received Sensitivity for Data Rates (2.4 GHz):

Signal-to-Noise Ratio (SNR)

• Importance of SNR: A critical metric for ensuring the integrity of data transmissions. Low SNR leads to data corruption issues that can severely affect network performance.

• Recommended SNR Values:

  • 20 dB: Minimum for standard data transmissions

  • 25 dB: Preferred for VoWiFi applications

  • 29 dB: Required for 256 QAM, facilitating faster data rates

  • 35 dB: Required for 1024 QAM, applicable in high-capacity scenarios

Example Calculations:

If the received signal is -70 dBm and the ambient noise floor is -95 dBm, the calculated SNR is 25 dB, creating a healthy environment for VoWiFi applications.

Roaming Design

• Roaming Considerations: Clients autonomously make roaming decisions based on evaluated thresholds of signal strength and SNR to ensure seamless connectivity across different Wi-Fi coverage areas.

  • Notably, Apple devices offer detailed documentation regarding specific roaming thresholds to optimize network performance.

• Fast Secure Roaming (FSR): Essential for VoWiFi, enabling quick transitions between access points without dropping connections. It is crucial during high-demand scenarios. The 802.11r protocol facilitates expedited BSS transitions, significantly improving roaming efficiency.

Channel Design

• 2.4 GHz Channel Design:The 2.4 GHz band has only three non-overlapping channels (1, 6, 11). Proper channel selection is critical to avoid Adjacent Channel Interference (ACI), which can degrade network performance and user experiences.

• 5 GHz Channel Design:The 5 GHz band offers a broader range of channels, significantly reducing interference issues compared to the 2.4 GHz band. Channels should be spaced at least two apart and provide adequate physical separation to mitigate Co-Channel Interference (CCI).

Capacity Design

• High Density:Defined by the number of users/devices in a specific geographical area. Environments may be categorized into

  • High Density (HD)

  • Very High Density (VHD)

  • Ultra High DensityEach category requires tailored planning and design approaches to accommodate the varying demands for network resources.

Data Needs by Application:

• Email/Web browsing: 500 Kbps – 1 Mbps

• HD video streaming: 2 Mbps – 5 MbpsUnderstanding client capabilities and application data needs is essential for optimizing overall network performance, as not all clients exhibit the same hardware specifications and capacity.

Airtime Consumption

• The RF medium operates on a half-duplex basis, meaning only one device can transmit at any given moment. This necessity for careful management of network resources is crucial for optimal performance.

• The presence of multiple SSIDs in a WLAN can increase management overhead, adversely affecting performance. Best practices recommend limiting the number of SSIDs to a maximum of 3-4 to optimize airtime utilization and efficiency.

Antenna Design

• Indoor Antennas:Utilizing directional patch antennas can yield optimized RF performance, particularly in structured environments such as warehouses and venues requiring high-density coverage.

• Stadium Design:Environments characterized by ultra-high density commonly benefit from MIMO (Multiple Input Multiple Output) patch antennas. Integrating predictive modeling tools can significantly enhance both Wi-Fi and cellular service in such challenging settings.