#!/bin/sh
while true; do
    sleep 3300  # 55 min * 60 sec

    echo "Bouncing the wifi at `date`"

    # You might need to change en1 to something else.
    # ifconfig can tell you what network adapter to use
    networksetup -setairportpower en1 off
    sleep 2
    networksetup -setairportpower en1 on
done