Hi Alex,
You can use an AP for WDS with no WLSM (Module):) Have a look
Configuring WDS, Fast Secure Roaming, and Radio Management
Understanding WDS
When you configure Wireless Domain Services on your network, access points on your wireless LAN use the WDS device (either an access point or a switch configured as the WDS device) to provide fast, secure roaming for client devices and to participate in radio management. If you use a switch as the WDS device, the switch must be equipped with a Wireless LAN Services Module (WLSM). An access point configured as the WDS device supports up to 60 participating access points. A WLSM-equipped switch supports up to 300 participating access points.
Fast, secure roaming provides rapid reauthentication when a client device roams from one access point to another, preventing delays in voice and other time-sensitive applications.
Access points participating in radio management forward information about the radio environment (such as possible rogue access points and client associations and disassociations) to the WDS device. The WDS device aggregates the information and forwards it to a wireless LAN solution engine (WLSE) device on your network.
Role of the WDS Device
The WDS device performs several tasks on your wireless LAN:
Advertises its WDS capability and participates in electing the best WDS device for your wireless LAN. When you configure your wireless LAN for WDS, you set up one device as the main WDS candidate and one or more additional devices as backup WDS candidates. If the main WDS device goes off line, one of the backup WDS devices takes its place.
Authenticates all access points in the subnet and establishes a secure communication channel with each of them.
Collects radio data from access points in the subnet, aggregates the data, and forwards it to the WLSE device on your network.
Registers all client devices in the subnet, establishes session keys for them, and caches their security credentials. When a client roams to another access point, the WDS device forwards the client's security credentials to the new access point.
Participating Access Points Supported by WDS Devices
Access point that also serves client devices
30AP's
Access point with radio interfaces disabled
60AP's
WLSM-equipped switch
300AP's
Role of Access Points Using the WDS Device
The access points on your wireless LAN interact with the WDS device in these activities:
Discover and track the current WDS device and relay WDS advertisements to the wireless LAN.
Authenticate with the WDS device and establish a secure communication channel to the WDS device.
Register associated client devices with the WDS device.
Report radio data to the WDS device.
From this good doc;
http://www.cisco.com/en/US/products/hw/wireless/ps4570/products_configuration_guide_chapter09186a0080341d2d.html#wp1035881
Wireless Domain Services Configuration
http://www.cisco.com/en/US/products/hw/wireless/ps4570/products_configuration_example09186a00801c951f.shtml
Wireless Domain Services FAQ
http://www.cisco.com/en/US/tech/tk722/tk809/technologies_q_and_a_item09186a00804d4421.shtml
Hope this helps!
Rob
