In a broadband wireless access (BWA) communication system (herein indicates the Institute of Electrical and Electronics Engineers (IEEE) 802.16e communication system), a terminal sends a DREG-REQ message to a base station to enter an idle mode.
FIG. 1 depicts general idle mode entrance and entrance failure. A terminal 100 includes a modem 105 and a host 110. While a message is transmitted through the modem 105, it is illustrated that the terminal 100 transmits the message to ease the understanding.
When there is no uplink/downlink data traffic over a certain time (hereafter, referred to as a Tidletime) after a call connection, the terminal 100 enters an idle mode by signaling with a base station 120 so as to avoid power consumption.
To enter the idle mode, the terminal 100 sends an idle mode request message (hereafter, referred to as a DREG-REQ message) in step a), and starts a timer T45 in step b) to receive an idle mode approval message (hereafter, referred to as a DREG-CMD message) from the base station 120 in response to the DREG-REQ message in step b).
When receiving the DREG-CMD message from the base station 120 before the timer T45 expires in step c), the terminal 100 stops the timer T45 in step d) and enters the idle mode in steps e) and f).
When receiving no DREG-CMD message before the timer T45 expires in step g), the terminal 100 retransmits the DREG-REQ message in step h).
When the number of the retransmissions exceeds the number of allowed retransmissions of the idle mode request message (hereafter, referred to as a DREG request retry count) in step i), the terminal 100 commences the initial call connection in step j). Here, the default value of the DREG request retry count is 3.
When the terminal 100 travels in a shadow area, the deteriorated channel condition may cause an increase of the number of the retransmissions of the DREG-REQ message. As a result, the number of the retransmissions of the DREG-REQ message is liable to exceed the DREG request retry count.
In this situation, the terminal 100 can not enter the idle mode but merely repeats the initial call connection because of the failure to enter the idle mode. In addition, the power consumption is increased.