Join a wireless network vs Establish WDS

What is difference between "joining" wireless network and "establishing" a WDS?

When an AirPort Express Base Station (AX) "joins" a wireless network, it is no longer performing as a router, but as a wireless client instead. You would primarily use this configuration if you only want to share a USB printer and/or for iTunes streaming.

When the AX is configured with another AirPort in a WDS, the AX would be used to extend the wireless range of that other AirPort.

Can I have one express join extreme's wireless network and have the other two expess establish a WDS?

Yes, however, with two of the AXs extending the AirPort Extreme Base Station's (AEBS) wireless network, the joining AX would be joining the now extended network.

In WDS, is this correct "extreme" -> "express (main)" -> "express(remote)"?

There are actually two types of WDS that the AirPorts can support. The older 802.11g AirPorts can only support the "static" version, and the 802.11n AirPorts can support both the static and newer "dynamic" versions of WDS.

So, depending on which versions your AirPorts are, it would be possible to configure the AEBS as the main, one of the AXs as a relay, and another AX as a remote.

And if I want to extend more I would add anther "express(relay)", right?

The older static WDS allows for: main > relay > remote. You can have up to four relays connected to the main, and up to four remotes connected to each relay.

Can I log on wirelessly to "express(relay"? Or, only remote and main has wifi connection function?

All base stations in a WDS (main, relay, or remote) can be configured to support wireless clients.

And, does placing the express horizontal or vertically affect the range? Which is better?

Not really, Either orientation would provide a similar antenna pattern in an open area.

I have the newer version of Airport extreme and express.

So, I have decided to set up the WDS network. However, I dont see the WDS tab in the Airport Extreme menu.

In order for the WDS option to appear in the AirPort Utility for the newer 802.11n base stations, you just need to hold down the Option key on your Mac before making a selection.

How do I set up the Extreme with Express under the WDS network? (Extreme <via join wireless network> express (main) <via WDS> express (relay or remote))?

OR

(Extreme <via WDS> express (main) <via WDS> express (relay or remote))?

o Extreme: WDS main
o Express #1: WDS relay
o Express #2: WDS remote

Here are the basic steps to configuring for a static WDS with the newer 802.11n AirPorts:

AEBSn - WDS Setup
(Note: To facilitate the WDS set up, temporarily connect the remote (& relay) base station(s) to the AEBSn by Ethernet during the set up phase, and then, relocate it to the desired location when complete. Also, jot down the AirPort IDs (MAC addresses) for each of the base stations to be used in the WDS. The AirPort ID and is printed on the label on the bottom/side of the base station.)

Main Base Station Setup - AEBSn
o Click the AirPort status menu in the menu bar and choose the wireless network created by the base station you want to set up as the main base station.
o Open AirPort Utility (located in the Utilities folder in the Applications folder on a Macintosh computer, or in Start > All Programs > AirPort on a computer using Windows).
o Select the main base station, and then, choose Manual Setup from the Base
Station menu.
o Enter the base station password if necessary. If the base station is using the default password of public, you will not be prompted for a password.
o Click Wireless in the toolbar, and then, choose “Participate in a WDS network” from the Wireless Mode pop-up menu. Note: You will need to hold down the Option key in order to get this option on the AEBSn, 802.11n AirPort Express Base Station (AXn), or Time Capsule (TC).
o Click WDS and then, choose “WDS main” from the WDS Mode pop-up menu.
o Select the “Allow wireless clients” checkbox if you want client computer to connect to this base station.
o Click the Add "+" button and enter the AirPort ID of the base station you want to connect to this base station.
o Click Update to send the new settings to the base stations in the WDS.

Remote Base Station Setup - AX#2
o Open AirPort Utility; select the remote base station, and then, choose Manual Setup from the Base Station menu.
o Enter the base station password, if necessary.
o Enter the same network password as the main base station, if necessary.
o Click AirPort in the toolbar, and then, click Wireless. Choose “Participate in a WDS network” from the Wireless Mode pop-up menu, and then, choose the same channel as the main base station from the Channel pop-up menu.
o Click WDS and choose “WDS remote” 0from the pop-up menu.
o Enter the AirPort ID of the main base station in the WDS Main field.
o Click Update to transfer the settings to the base station.

Relay Base Station Setup - AX#1
o Open AirPort Utility; select the relay base station, and then, choose Manual Setup from the Base Station menu.
o Enter the same network password as the main base station, if necessary.
o Click AirPort in the toolbar, and then, click Wireless. Choose “Participate in a WDS network” from the Wireless Mode pop-up menu, and then, choose the same channel as the main base station from the Channel pop-up menu.
o Click WDS and choose “WDS relay” from the WDS Mode pop-up menu.
o Enter the AirPort ID of the main base station in the Main AirPort ID field.
o Click the Add "+" button and enter the AirPort ID of the remote base station this relay base station will connect to.
o Click Update to transfer the new WDS settings to the relay and remote base stations.

(ref: Pages 42-46 of " Designing AirPort Networks.)