What Is a Zero-Roaming DAP?

Why Do We Need a DAP?

In a dense-room scenario, when STAs move between multiple rooms, Wi-Fi roaming frequently occurs, which may easily cause packet loss or even service interruption. The ward area of a hospital is a typical dense-room scenario. Medical personnel often encounter the preceding issues when moving between wards. For example, doctors use tablets to query patient information (such as HD medical imaging) during mobile ward rounds, and nurses use barcode scanners for outbound and confirmation of medicines during bedside care. In these typical scenarios, tablets and barcode scanners frequently roam between APs, causing in-roaming packet loss and compromising medical care efficiency. This is where the DAP comes in. It is the core of a zero-roaming distributed Wi-Fi network. Such a network ensures that STAs do not roam when moving between rooms, therefore addressing the in-roaming packet loss issue.

In addition, a DAP can also reduce network construction and O&M costs. When the intranet, extranet, and IoT need to be deployed independently, the network construction cost is high and the O&M is difficult. In addition to forwarding intranet data, a DAP helps combine radio signals of the extranet and IoT. After an extranet AP and IoT base stations are directly connected to the DAP, the three networks can share the same antennas, which greatly reduces costs. During signal combination, the DAP does not process extranet or IoT data using the CPU. Therefore, even if antennas are shared, data on the three networks is still isolated from each other, thereby ensuring network security.

How Is the DAP Networking Implemented?

In the zero-roaming distributed Wi-Fi network architecture, a DAP, ORUs, and AUs are typically used together, and the DAP centrally manages ORUs and AUs. The ORUs and AUs can be considered as a set of plug-and-play antennas with long-distance coverage capabilities. They can work after cable connection is complete, without the need of additional configurations. They extend signals from the DAP to multiple rooms, thereby delivering large-scale intranet Wi-Fi coverage.

• DAP: forwards data, processes radio signals, manages ORUs, and so on. A DAP supports both the Fit and Fat mode. When working in Fit mode, a DAP can be centrally managed by the intranet WAC. In the downlink direction, the DAP connects to ORUs to implement remote signal transmission. Additionally, the DAP can connect to an extranet AP and IoT base stations and provide radio-optical signal conversion capabilities.
• ORU: amplifies radio signals at a distance of 500 m by connecting to a DAP through an ultra-long hybrid cable.
• AU: transmits and receives signals and directly connects to an ORU through an RF feeder.

Users can deploy the extranet and IoT together with the intranet based on site requirements.

• Extranet: The traditional WAC + Fit AP networking architecture is used, where an extranet WAC is used to manage and control extranet APs. After directly connecting to the DAP through an RF feeder, an extranet AP shares antennas with the DAP to deliver the same extranet Wi-Fi coverage as the intranet.
• IoT: IoT base stations are deployed to provide IoT services. A DAP can connect to a maximum of four IoT base stations operating on the 2.4 GHz frequency band and two IoT base stations operating on the 433 MHz frequency band. After IoT base stations are directly connected to the DAP through RF feeders, the DAP converts IoT signals into optical signals and transmits the optical signals to ORUs. Then, 2.4 GHz IoT base stations can directly share the antennas with the DAP, and 433 MHz antennas need to be independently deployed on the ORUs for 433 MHz IoT base stations.

How Does a DAP Implement Zero Roaming?

In the conventional roaming handover process, a STA needs to disconnect from the associated AP and then complete the authentication process again on a new AP. This process takes a period of time, which is the roaming handover time required by a STA. Service packet loss may occur during the roaming handover duration, and long roaming handover duration will affect user experience negatively.

In the zero-roaming distributed Wi-Fi solution, a DAP as well as its ORUs and AUs can be considered as an AP with 64 antennas. In the entire coverage of the DAP, STAs are always associated with the same AP, without the need to switch channels or roam between APs. This addresses the packet loss and service interruption issues caused by roaming handover.

When a STA moves beyond the coverage of the DAP, a small number of packets may be lost when the STA roams from the DAP to another AP. For example, if a DAP deployed on each floor provides the signal coverage for its own floor, roaming still occurs when a STA moves between floors.

What Are the Differences Between Zero-Roaming Distributed and Agile Distributed Wi-Fi Networks?

Similar to the zero-roaming distributed Wi-Fi solution, the agile distributed Wi-Fi solution provides a wide-range WLAN coverage based on the distributed architecture for dense-room scenarios. An agile distributed Wi-Fi solution consists of the central AP and remote units (RUs).

• Central AP: is also known as the agile distributed AP. It implements the data forwarding function and also provides functions similar to a WAC to centrally manage and coordinate RUs, such as STA going online, configuration delivery, and STA roaming between RUs.
• RU: serves as a remote RF module for a central AP. RUs are used to receive and transmit 802.11 packets over the air interface.

Products Related to the Zero-Roaming Distributed Wi-Fi Solution

Huawei launched the zero-roaming distributed Wi-Fi solution in 2023. Related devices include:

• DAP: AirEngine 9700D-S
• ORU: AirEngine 5760-11DH
• AU: 27014400 indoor 2.4 GHz & 5 GHz single-polarized omnidirectional antenna
• Extranet AP that can connect to the DAP: AirEngine 6761-21E