til the next MMC. These allocations are used for data Chapter Ten communication within the cluster, with the direction and use of each MS-CTA being specified in the preceding MMC. As shown in Figure 10-6, although the MAC layer media access slots which support the channel will be discontinuous in time, the MMCs effectively pull these slots together into a contiguous channel for communication within the cluster. To ensure strict compliance with the MAC layer requirements, such as beaconing and distributed control, a wireless USB host is required to implement the full WiMedia MAC protocol. Other devices are only required to implement the wireless USB protocol that operates within the wireless USB channel. Wireless USB defines mechanisms to ensure that a host is aware of and respects the DRP reservations of any possible hidden neighbours of devices in its cluster. Three device classes are defined, as shown in Table 10-11, with different levels of "awareness" of the full MAC protocol. Directed beaconing devices have the capability to capture control protocol information transmitted by devices that are not part of the cluster and to transmit this back to the host via the wireless USB channel. This enables the host to periodically check for the presence of devices complying with the WiMedia MAC that are outside its range, and to ensure that MAC Super frame N-1 Super frame N Super frame N+1 DRP messages Reserved MASs Next MMC Next MMC Next MMC Transaction group 1 Transaction group 2 Transaction group n Figure 10-6: Wireless USB Channel within MAC Layer Superframes Wireless PAN Standards Table 10-11: Wireless USB Device Classes Device class Description Self-beaconing devices These devices comply fully with MAC level protocols and do all related beaconing. Directed beaconing devices These devices perform beaconing and other MAC functions under the direction of the wireless USB host device. Non-beaconing devices These devices have reduced transmit power and receiver sensitivity and can only operate in close proximity to th