AH-MAC: Adaptive Hierarchical MAC Protocol for Low-Rate Wireless Sensor Network Applications

Algorithm 1

Cluster head join algorithm.

() procedure start_scan()

()  best_parent_addr = 0XFFFF; min_dfs = 255; scan_timer = ON

()  wake_after(0)                                ⊳ wakeup now

()  start_scan_timer(0, SCAN_LENGTH)    ⊳ scan_timer starts now and will fire after SCAN_LENGTH

() end procedure

() procedure recv_beacon(src, dfs, accept)

()  if scan_timer then

()   if (dfs < min_dfs & accept) then                   ⊳ replace current parent

()     min_dfs = dfs

()    best_parent_addr = src

()   end if

()   if (my_parent_addr == best_parent_addr) then      ⊳ restore synchronization with last parent

()    stop_scan_timer()

()    scan_timer = OFF

()   end if

() end if

() if scan_timer then

()   return

() end if

() if (not associated) then

()   sleep_after(slot_time)

()   wake_after()

()   send_associate_request_packet()

() else if (data available) then

()   sleep_after(slot_time)

()   wake_after(my_slot slot_time)             ⊳ wake up in my slot to start my frame

()   try_send_data()

(28) else

()   sleep_after(0)

()   wake_after(my_slot slot_time)

() end if

() end procedure

() procedure scan_handler()                    ⊳ called when scan timer is fired

() if (best_parent_addr < 0XFFFF) then

()   my_parent_addr = best_parent_addr

()   my_dfs = min_dfs + 1

()   scan_timer = OFF

() else

()   sleep_after(0)

()   start_scan_timer(random delay, SCAN_LENGTH)

() end if

() return

() end procedure