Chapter 1 What’s New for FortiOS 5.0 : Wireless : Wireless client load balancing for high-density deployments
  
Wireless client load balancing for high-density deployments
Wireless load balancing allows your wireless network to distribute wireless traffic more efficiently among wireless access points and available frequency bands. FortiGate wireless controllers support the following types of client load balancing:
Access Point Hand-off - the wireless controller signals a client to switch to another access point.
Frequency Hand-off - the wireless controller monitors the usage of 2.4GHz and 5GHz bands, and signals clients to switch to the lesser-used frequency.
Load balancing is not applied to roaming clients.