Zero-Roaming DAP

What Is a Zero-Roaming DAP?

The zero-roaming distributed access point (DAP) is a critical element in the zero-roaming distributed Wi-Fi solution. It works in conjunction with optical radio units (ORUs) and antenna units (AUs) to establish a WLAN that features zero roaming, wide coverage, and tri-network isolation (intranet, extranet, and IoT) with integrated deployment. These characteristics make the zero-roaming distributed Wi-Fi solution suitable for dense-room scenarios.

Why Do We Need a DAP?

In dense-room environments, frequent Wi-Fi roaming occurs when stations (STAs) move between multiple rooms, leading to potential packet loss and service interruptions. For instance, in a hospital ward, medical personnel often face these issues when moving between wards. Doctors use tablets for patient information (like high-definition medical imaging), and nurses use barcode scanners for medication management. In such scenarios, frequent roaming between access points (APs) causes packet loss, affecting medical care efficiency. A DAP eliminates this issue by ensuring that STAs do not roam when moving between rooms, thus addressing in-roaming packet loss.

Additionally, a DAP can reduce network construction and operational costs. When separate intranet, extranet, and IoT deployments are required, costs are high and management becomes complex. A DAP allows the combination of radio signals from the intranet, extranet, and IoT, significantly reducing costs. Even though the antennas are shared, the DAP ensures data isolation across the three networks, maintaining security.

How Is the DAP Networking Implemented?

In the zero-roaming distributed Wi-Fi architecture, DAPs work alongside ORUs and AUs, with the DAP centrally managing these components. ORUs and AUs function as plug-and-play antennas with long-distance coverage capabilities, operating after simple cable connections without additional configurations. They extend the DAP's signals to multiple rooms, providing extensive intranet Wi-Fi coverage.

1. 1. DAP: Forwards data, processes radio signals, and manages ORUs. It supports both Fit and Fat modes. In Fit mode, it is centrally managed by the intranet WAC. It connects to ORUs for remote signal transmission and can also connect to extranet APs and IoT base stations, converting radio signals to optical signals.

2. 2. ORU: Amplifies radio signals over distances up to 500 meters, connecting to the DAP via ultra-long hybrid cables.

3. 3. AU: Transmits and receives signals, directly connecting to ORUs through RF feeders.

Users can deploy the intranet, extranet, and IoT based on site requirements:

Extranet: Uses a traditional WAC + Fit AP architecture. The extranet WAC manages extranet APs, which connect to the DAP through RF feeders and share antennas with the DAP, providing the same Wi-Fi coverage as the intranet.

How Does a DAP Implement Zero Roaming?

In traditional roaming, a STA disconnects from one AP and re-authenticates with another, causing service interruptions. In the zero-roaming distributed Wi-Fi solution, the DAP, along with its ORUs and AUs, acts as a single AP with multiple antennas. STAs remain connected to the same AP across the DAP's coverage, eliminating the need to switch channels or roam, thus preventing packet loss and service interruptions.

When a STA moves beyond the DAP's coverage, minimal packet loss may occur during the transition to another AP. For example, if a DAP covers each floor, roaming still happens when a STA moves between floors.

Differences Between Zero-Roaming Distributed and Agile Distributed Wi-Fi Networks

Both zero-roaming and agile distributed Wi-Fi solutions provide wide-range WLAN coverage for dense-room scenarios, but they differ in several ways:

• Roaming: Zero-roaming ensures no roaming during movement, preventing packet loss. Agile distributed Wi-Fi involves roaming between RUs, potentially causing some packet loss.

• Capacity: Zero-roaming is suitable for services without high capacity needs, whereas agile distributed Wi-Fi supports high-capacity requirements.

• Network Isolation: Zero-roaming uses physical isolation for intranet and extranet data via separate forwarding by a DAP and extranet AP. Agile distributed Wi-Fi employs logical isolation, using different VAPs.

How Does a DAP Work?

On a zero-roaming distributed Wi-Fi network, the DAP converts information into digital signals through source coding, then into radio waves using channel coding and modulation. ORUs amplify these signals for long-distance transmission, and AUs transmit and receive the signals, extending coverage.

1. Source Coding: Converts raw information into compressed digital signals without distortion.

2. Channel Coding: Detects and corrects errors, enhancing transmission reliability.

3. Modulation: Converts digital signals into radio waves by superimposing them on high-frequency signals, enabling transmission over antennas.

4. Air Interface: The invisible interface for wireless communication.

5. Channel: The path for transmitting information, defined by 802.11 standards.