Wireless Distribution System (WDS) Explained

A Wireless Distribution System (WDS) allows wireless access points (APs) to interconnect wirelessly. This enables you to expand a wireless network without needing a wired backbone to link the APs. This article will explain the core concepts of WDS and provide a basic configuration example using pseudo-code to demonstrate the underlying principles.

Fundamental Concepts / Prerequisites

To understand WDS, you should have a basic grasp of the following:

• Wireless Networks (Wi-Fi): Familiarity with the basic principles of how Wi-Fi works (e.g., SSIDs, channels, encryption).
• MAC Addresses: Understanding the concept of MAC addresses as unique identifiers for network devices.
• IP Addressing: Basic knowledge of IP addresses and subnet masks.
• Routing (Basic): The concept of directing network traffic between different networks or devices.

WDS relies on the APs knowing the MAC addresses of each other. It also uses a "bridging" function, where the AP forwards traffic between wired and wireless clients.

Core Implementation/Solution: WDS Configuration (Pseudo-Code)

This example demonstrates the basic configuration steps required on each Access Point (AP) in a WDS setup. This is a simplified representation using pseudo-code.

// AP1 Configuration (Main AP, connected to the internet)

AP1.SSID = "MyNetwork"
AP1.Channel = 6
AP1.SecurityMode = "WPA2-PSK"
AP1.Password = "MySecurePassword"
AP1.WDSMode = "Enable"
AP1.WDSBridgeMAC = AP2.MACAddress // MAC address of AP2

// AP2 Configuration (Extender AP)

AP2.SSID = "MyNetwork"  // Must match AP1's SSID
AP2.Channel = 6          // Must match AP1's channel
AP2.SecurityMode = "WPA2-PSK" // Must match AP1's security
AP2.Password = "MySecurePassword" // Must match AP1's password
AP2.WDSMode = "Enable"
AP2.WDSBridgeMAC = AP1.MACAddress // MAC address of AP1

// AP1 acts as a "root" or main access point,
// AP2 acts as a "repeater" or extender

// In a more complex setup, you might have multiple APs in a chain or star topology.
// Each AP would need to know the MAC addresses of the APs it's bridging to.

Code Explanation

The pseudo-code demonstrates the fundamental configuration steps. Let's break it down:

AP1 Configuration:

• AP1.SSID = "MyNetwork": Sets the Service Set Identifier (SSID), which is the name of the wireless network.
• AP1.Channel = 6: Sets the wireless channel to use (e.g., channel 6). All APs in the WDS must use the same channel.
• AP1.SecurityMode = "WPA2-PSK": Configures the security mode (e.g., WPA2-PSK with a pre-shared key). All APs must use the same security protocol and password.
• AP1.Password = "MySecurePassword": Sets the password for the wireless network.
• AP1.WDSMode = "Enable": Enables WDS mode on the access point.
• AP1.WDSBridgeMAC = AP2.MACAddress: Specifies the MAC address of the other access point(s) it will communicate with in the WDS. This is crucial for establishing the bridge.

AP2 Configuration:

• The SSID, channel, security mode, and password must match AP1's configuration. This ensures that wireless clients can roam seamlessly between the APs.
• AP2.WDSMode = "Enable": Enables WDS mode on AP2.
• AP2.WDSBridgeMAC = AP1.MACAddress: Specifies the MAC address of AP1, allowing AP2 to connect back to the root AP.

The key to WDS is the WDSBridgeMAC setting. This tells each AP which other AP to connect to and bridge traffic with.

Complexity Analysis

The configuration of WDS itself doesn't have a significant time or space complexity in the traditional algorithmic sense. The time complexity to configure an AP is O(1) – a fixed number of operations regardless of the network size. However, the *performance* of the network *using* WDS does have complexities to consider:

• Time Complexity (Network Performance): WDS introduces overhead. Every packet has to be transmitted wirelessly between the APs. This can significantly reduce the overall throughput compared to a wired network. The performance impact can depend on many factors, including distance between APs, interference, and the number of hops in the WDS topology. A single hop will halve the available bandwidth.
• Space Complexity (Configuration): The space complexity is O(N), where N is the number of WDS links that need to be configured on each AP. In simpler setups (e.g., a star topology with one main AP), N might be small and effectively constant. However, in mesh networks with many links, N can be more significant.

Alternative Approaches

An alternative approach to extending a wireless network is to use a mesh network. Mesh networks are more intelligent than WDS. They often use dynamic routing protocols to automatically determine the best path for data to travel, which can improve performance and reliability. Mesh networks are also self-healing, meaning that if one AP fails, the network can automatically re-route traffic. However, mesh networks are generally more complex to set up and manage than WDS.

Another alternative would be using Powerline adapters to create a "wired" backhaul. Then use each device as a separate access point with the same SSID to allow clients to roam.

Conclusion

WDS provides a relatively simple way to extend a wireless network without running Ethernet cables. However, it comes with a performance penalty due to the wireless backhaul. Carefully consider the trade-offs between ease of setup and network performance before implementing WDS. Mesh networks offer a more robust and scalable solution but at the cost of increased complexity.