Receiver Initiated Channel Hopping (RICH)

Tech ID: 10183 / UC Case 2000-314-0


Medium-access control (MAC) protocols based on collision avoidance have become increasingly important over the past few years due to their simple applicability to wireless local-access networks (LANs) and ad hoc networks. In traditional collision-avoidance protocols, the transmitting node first sends a request-to-send (RTS) packet to the receiver. If the receiver receives this RTS correctly, the node responds with a clear-to-send (CTS) signal. In this system, a sender can transmit a data packet only after successfully receiving a CTS. However, to prevent data packets from colliding with other packets, the senders must sense the channel before sending the RTS. This carrier sensing or assignment of unique codes to nodes ensures that the intended receivers hear data packets without interference from hidden sources. However, this can greatly limit the applicability of these systems because the senders and receivers must find each other's codes before communicating with one another.

Technology Description

Scientists at the University of California have developed a novel group of MAC protocols called receiver-initiated channel-hopping (RICH) protocols. These are the first MAC protocols based on receiver-initiated collision-avoidance handshakes. These reliable protocols provide collision-free reception of data at the intended receivers in the presence of hidden terminals without the need for carrier sensing or unique code assignments to nodes.


  • Ad hoc networks based on commercial radios operating in unlicensed frequency bands


  • Solves the hidden-terminal problem by eliminating data packet collisions without the need to carrier sensing or code assignments
  • System performance does not depend upon the network topology

Patent Status

Country Type Number Dated Case
United States Of America Issued Patent 7,002,910 02/21/2006 2000-314


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  • Garcia-Luna-Aceves, Jose Joaquin(JJ

Other Information


Receiver, channel hopping, medium-access control, MAC, local-access networks, LAN, ad-hoc networks, transmission, collision avoidance, frequency bands, network topology, Cat3

Categorized As