Primary and secondary nodes are synergistic, that is to say, the primary node sends messages to the control node S while the secondary node sends messages by virtue of primary nodes at the same time.
Hence, a household that has specified fishing as their primary occupation, and farming as their secondary occupation, will be represented by a link going from the primary node (representing fishing) to the secondary node (representing farming).
The primary node measures blood pressure, while the secondary node measures blood oxygen.
To this end, the authors propose a concurrent access MAC (CA-MAC) protocol, which does not require any CCC and limits the waiting time for the secondary nodes by allowing parallel channel access by multiple communication pairs within the same time slot.
We modeled the occupancy of the licensed channel by the primary network as a Markov process, and the secondary nodes opportunistically accessed the channel with the ALOHA protocol.
Considering a CR network, a secondary network is overlaid with a primary network, i.e., the secondary nodes could be allowed to occupy the channel when it is not used by primary nodes.
The cost of data transfer from the secondary nodes to the primary node should be at a minimum.
If the ACK returned by the high-priority node is not received, the forwarding process of the high-priority node is repeated by the secondary priority node to forward the packet.
(3) After receiving the messages sent by secondary nodes A, B encrypts the encrypted message ({A,B,Na}_{K_{textit {as}}}) and identifier A, random Nb with pre-shared key Kbs, along with plain text identifier B, and sends them to the control node S. (4) After receiving Message 3, S decrypts the message and verifies it.
Supposing slotted ALOHA multiple access is adopted by secondary nodes, we derive the closed-form expression of the local delay by modeling the channel occupied by primary nodes as continuous-time Markov on-off process.
