Avoiding exposed node problems in wireless local area networks

Abstract

A method, apparatus and computer program product for preventing occurrences of the hidden node problem are presented. A transmission request (CC-RTS) is received from a source node, the CC-RTS frame including a reservation duration value indicating the length of time needed for a transmission reservation. A timer is adjusted for the period other nodes must refrain from transmitting on the channel (NAV) equal to a duration of a transmission request / transmission response (CC-RTS / CC-CTS) handshake. When the CC-RTS has been denied, then a second CC-RTS frame is received having a reservation duration value of zero, and when the CC-RTS is accepted then the NAV is extended to remainder of the reservation duration value of the original CC-RTS frame. The CC-RTS and CC-CTS are sent at a more robust PHY mode than traffic frames.

Description

Background technique

[0001] Wireless local area networks (WLANs) have become ubiquitous. In a wireless local area network (LAN), wireless channels can be reserved for transmission of frame sequences, while using an asynchronous distributed random channel access method. In this case, both the source and destination of the transmission broadcast the reservation duration in order to establish the interference neighborhood.

[0002] According to the 802.11 Distributed Channel Access MAC protocol, neighbors are notified of the transmission using RTS / CTS frames. To establish an interference neighborhood, the source and destination of the transmission send RTS and CTS frames containing the reservation duration, respectively. A node either receives a frame to refrain from transmission, or it agrees to receive a transmission for a specified duration. In this way, transmission will be refrained from being transmitted for the duration indicated in the received CTS frame by a "hidden t...

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