Abstract: One feature provides a method for a client node to establish a session key with a group node by obtaining an epoch identity value associated with a current epoch, wherein obtaining the epoch identity value includes one of computing the epoch identity value based on a node real time or negotiating the epoch identity value with the group node, computing a restricted key using a shared secret key, the epoch identity value, and a group node identity associated with the group node, and executing a session key establishment protocol with the group node to derive the session key using the restricted key as a master key in the session key establishment protocol. The session key may be established between the group node and the client node even though communications between the group node and the central node is only intermittently available during the current epoch.

Abstract: One feature provides a method for a client node to establish a session key with a group node by obtaining an epoch identity value associated with a current epoch, wherein obtaining the epoch identity value includes one of computing the epoch identity value based on a node real time or negotiating the epoch identity value with the group node, computing a restricted key using a shared secret key, the epoch identity value, and a group node identity associated with the group node, and executing a session key establishment protocol with the group node to derive the session key using the restricted key as a master key in the session key establishment protocol. The session key may be established between the group node and the client node even though communications between the group node and the central node is only intermittently available during the current epoch.

Abstract: A method for wireless communication is disclosed, the method including transmitting a plurality of preambles; and detecting an acknowledgement to one of the preambles during the transmission of another one of the preambles. An apparatus for performing the method is also disclosed.

Abstract: An apparatus is disclosed having a receiver configured to communicate, by a first apparatus, with a second apparatus in a first mode; determine side information by the first apparatus based on the communication during the first mode; and store the side information by the first apparatus for communication in a second mode with the second apparatus, wherein the first and second modes of communication have different date rates. A method for wireless communications is also disclosed.