IEEE 802.11 requires nodes competing for access to the channel to wait for a "backoff" interval, randomly selected from a specified range, before initiating a transmission. Selfish nodes may wait for smaller backoff intervals than well-behaved nodes, thereby obtaining an unfair advantage. IEEE802.11要求节点等待一个随机时间间隔之后再竞争访问信道,如果某些节点等待一个较小的时间间隔,那么对其他普通节点来说,这是不公平的。