Abstract:
Provided is a power saving method for a mobile terminal, of a WiBro communication system, particularly for a standby mode. A power saving method for a mobile terminal having a modem for communicating with a base station and a host for controlling the modem, includes starting, at the mobile terminal, a timer if a resource withdrawal is determined through a negotiation with the base station; turning off power to the modem; determining whether the timer has expired; and turning on the power to the modem.

Description:
PRIORITY 
       [0001]    This application claims priority under 35 U.S.C. § 119 to an application entitled “Power Saving Method For Mobile Terminal” filed in the Korean Intellectual Property Office on Oct. 12, 2006 and assigned Serial No. 2006-0099353, the contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a Wireless Broadband (WiBro) mobile communication system and, in particular, to a power saving method for a mobile terminal of the WiBro communication system. 
         [0004]    2. Description of the Related Art 
         [0005]    The technological advancements and rising usage of mobile communication have dramatically influenced people&#39;s everyday life. As a result of these technological advancements, mobile communication devices are becoming ever more popular and widely accepted for data communications as well as for conventional voice communications, and user requirements for various convenient services and high speed data transmission increase. 
         [0006]    Wireless Broadband (WiBro) is a wireless broadband Internet technology developed for satisfying user&#39;s demands for wireless voice and data communication while on the move. WiBro provides the user with voice and data connectivity anytime and anywhere even on the move. 
         [0007]    WiBro operates in the 2.3 GHz bandwidth and covers about 1 Km range. WiBro supports high-speed data service in an indoor and outdoor stationary and pedestrian-speed and mobile environment of below 60 Km/h. WiBro also provides high speed and reliable Internet service at a low cost relative to other communication networks. 
         [0008]    A mobile terminal provides for transition between different modes (i.e., active, sleep, and idle modes). In the active mode, the mobile terminal transmits and receives packets to and from a base station. The sleep mode is intended to minimize power consumption of the mobile terminal by pre-negotiated periods of absence from the base station air interface. The idle mode allows the mobile terminal to become periodically available for downlink broadcast traffic so as to conserve power and operational resources. 
         [0009]    The mobile terminal typically spends a large majority of its time in the idle and sleep modes and the power consumption during a standby mode including the idle and sleep modes has a major impact on efficient power management for the overall standby and active modes. That is, power conservation in the standby mode is an important issue for efficient power management. 
         [0010]    Since most WiBro terminals are mobile terminals, high power consumption in the standby mode reduces the standby and communication time, resulting in reduction of user satisfaction. 
         [0011]      FIG. 1  is a message flow diagram illustrating an operation of a conventional mobile terminal in a standby mode. 
         [0012]    Referring to  FIG. 1 , if a modem  120  of the mobile phone receives a Deregistration Request message (Dreg_Req) from a host  110  of a mobile phone in step S 101 , the modem  120  transmits the Deregistration Request message (Dreg_Req) to a base station  130  in step S 103 . Upon receiving the Deregistration Request message (Dreg_Req), the base station  130  transmits a Deregistration Confirmation message (Dreg_Cmd) to the mobile phone in response to the Deregistration Request message (Dreg_Req) in step S 105 . 
         [0013]    Upon receiving the Deregistration Confirmation message (Dreg_Cmd), in step S 107  the modem  120  transmits a Deregistration ACKnowledgement message (Dreg_ACK) to the host  110 . 
         [0014]    If the Deregistration ACKnowledgement message (Dreg_ACK) is received, the host  110  transmits a channel state request message (Air_State_Req) to the modem  120  in step S 109 . 
         [0015]    In response to the channel state request message (Air_State_Req), the modem  120  collects channel state information in step S 111  and then transmits a channel state response message (Air_State_Resp) containing the collected channel state information to the host  110  in step S 113 . The mobile terminal checks the channel state by repeating the steps S 109  to S 113  in the standby mode. 
         [0016]    As described above, the host  110  and the modem  120  of the mobile terminal are turned on in the standby mode, resulting in power consumption. 
         [0017]    Particularly, the WiBro mobile terminal operates in different modes according to settings configured by a user or by the mobile terminal itself in a service zone. The WiBro mobile terminal checks a WiBro service availability and types of services in a current location by monitoring the channel state in the standby mode. The WiBro mobile terminal can be implemented with another network modem chip in addition to a WiBro modem chip for supporting various network services. Since most WiBro terminals are battery-powered mobile terminals, low standby power consumption is a significant factor for determining the performance of a mobile terminal. 
         [0018]    However, since the conventional WiBro mobile terminal must maintain channel synchronization, power consumption for obtaining the channel state is required even in the standby mode. Accordingly, there can be room for further saving the power in the standby mode. 
       SUMMARY OF THE INVENTION 
       [0019]    The present invention has been made in an effort to solve the above problems, and it is an aspect of the present invention to provide a power saving method of a mobile terminal that is capable of reducing power consumption in a standby mode. 
         [0020]    It is another aspect of the present invention to provide a power saving method of a mobile terminal that is capable of reducing power consumption in a standby mode by turning off physical layer elements except when periodic channel state collection times. 
         [0021]    It is still another aspect of the present invention to provide a power saving method of a mobile terminal that is capable of reducing power consumption in a standby mode by turning off the terminal&#39;s power after channel synchronization until an event occurs. 
         [0022]    It is yet still another aspect of the present invention to provide a power saving method of a mobile terminal that is capable of reducing power consumption in a standby mode by controlling standby-to-active mode transition at one of a host and modem. 
         [0023]    In accordance with an aspect of the present invention, there is provided a power saving method for a mobile terminal having a modem for communicating with a base station and a host for controlling the modem. The power saving method includes starting, at the mobile terminal, a timer if a resource withdrawal is determined through a negotiation with the base station; turning off a power of the modem; determining whether the timer has expired; and turning on the power of the modem. 
         [0024]    Preferably, the timer is managed by the host or by the modem. 
         [0025]    Preferably, the power saving method further includes transmitting a deregistration request message to the base station for withdrawing the resources; receiving a deregistration confirmation message in response to the deregistration request message; and determining the resource withdrawal if the deregistration confirmation message is received. 
         [0026]    In accordance with another aspect of the present invention, there is provided a power saving method for a mobile terminal having a modem for communicating with a base station and a host for controlling the modem. The power saving method includes transmitting a standby request message from the host to the modem if a resource withdrawal is determined; turning off, at the modem, power to the modem and transmitting a standby response message to the host upon receiving the standby request message; starting, at the host, a timer upon receiving the standby response message; transmitting a synchronization request message to the modem if the timer expires; and turning on, at the modem, the power to the modem upon receiving the synchronization request message. 
         [0027]    Preferably, the power saving method further includes performing, at the modem, synchronization with the base station after turning on the power; measuring a Received Signal Strength Indicator and Carrier-to-Interference and Noise Ratio; and transmitting the Received Signal Strength Indicator and Carrier-to-Interference and Noise Ratio to the host. 
         [0028]    Preferably, the power saving method further includes transmitting, at the mobile terminal, a deregistration request message to the base station for withdrawing the resources; receiving a deregistration confirmation message in response to the deregistration request message; and determining the resource withdrawal if the deregistration confirmation message is received. 
         [0029]    In accordance with yet another aspect of the present invention, there is provided a power saving method for a mobile terminal having a modem for communicating with a base station and a host for controlling the modem. The power saving method includes transmitting, at the host, a standby request message to the modem if a resource withdrawal is determined; turning off, at the modem, power to the modem, upon receiving the standby request message, transmitting a standby response message to the host, and starting a timer; turning on, at the modem, the power to the modem if the timer expires; collecting channel state information; and transmitting the collected channel state information to the host. 
         [0030]    Preferably, the standby request message includes a channel state report time interval. 
         [0031]    Preferably, the channel state information includes a Received Signal Strength Indicator and Carrier-to-Interference and Noise Ratio. 
         [0032]    Preferably, the timer is set on the basis of the channel state report time interval. 
         [0033]    Preferably, the power saving method further includes transmitting a deregistration request message to the base station for withdrawing the resources; receiving a deregistration confirmation message in response to the deregistration request message; and determining the resource withdrawal if the deregistration confirmation message is received. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description in conjunction with the accompanying drawings, in which: 
           [0035]      FIG. 1  is a message flow diagram illustrating an operation of a conventional mobile terminal in a standby mode; 
           [0036]      FIG. 2  is a block diagram illustrating a configuration of a mobile terminal employing a power saving method according to an embodiment of the present invention; 
           [0037]      FIG. 3  is a message flow diagram illustrating an operation of a mobile terminal in a standby mode of power saving method according to a first embodiment of the present invention; and 
           [0038]      FIG. 4  is a message flow diagram illustrating an operation of a mobile terminal in a standby mode of a power saving method according to a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0039]    Exemplary embodiments of the present invention are described with reference to the accompanying drawings in detail. The same reference numbers are used throughout the drawings to refer to the same or like parts. Detailed descriptions of well-known functions and structures incorporated herein may be omitted to avoid obscuring the subject matter of the present invention. 
         [0040]    The standby mode power saving method of the present invention is described in association with a mobile terminal equipped with a WiBro modem as an example. However, the present invention is not limited to the WiBro mobile terminal, but, can be adapted to mobile devices such as a digital broadcasting receiver, Personal Digital Assistant (PDA), Smartphone, International Mobile Telecommunication 2000 (IMT-2000) terminal, Code Division Multiple Access (CDMA) terminal, Global System for Mobile communication (GSM) terminal, Universal Mobile Telecommunications System (UMTS) terminal, and Wireless Local Area Network (WLAN) terminal, powered by battery. 
         [0041]    The power saving method of the present invention enables a mobile terminal to conserve battery power by blocking power supply to physical elements in a standby mode except when periodic times at which the mobile terminal should wake up for collecting channel states. That is, the mobile terminal shuts down the power right after obtaining the synchronization with the base station until a wakeup event occurs in the standby mode, thereby reducing power consumption. Thus, the host or the modem performs the state transition from the standby mode to the active mode. 
         [0042]      FIG. 2  is a block diagram illustrating a configuration of a mobile terminal employing a power saving method according to an aspect of the present invention. In this aspect of the present invention, the mobile terminal is provided with a WiBro module. 
         [0043]    Referring to  FIG. 2 , the mobile terminal  200  includes a host  210  and a modem  220 . The host  210  includes a WiBro Connection Manager (WCM)  211  and a WiBro device driver  213 , and the modem  220  includes a modem host interface  221  and a modem control module  223 . 
         [0044]    The WCM  211  is a host application, and the WiBro device driver  213  is embodied in software for transferring a control packet generated by the WCM  211  to the modem  220 . 
         [0045]    The modem host interface  221  analyzes the control packet received from the WiBro device driver  213  and forwards transmission data and control signals obtained by the analysis result to the modem control module  223 . The modem control module  223  performs an internal control in accordance with the control signal or transmits the transmission data to the base station. 
         [0046]    If a service release request is input by a user while receiving WiBro service, the WCM  211  generates a Deregistration Request (Dreg-Req) message. The Dreg-Req message is transmitted to the base station through the WiBro device driver  213 , modem host interface  221 , and modem control module  223 . If a Deregistration Confirmation (Dreg-Cmd) is received in response to the Dreg-Req message, the mobile terminal enters the standby mode. 
         [0047]    In the standby mode, the conventional mobile terminal maintains operations of the WCM  211  and modem  220  for obtaining channel state information, and the operations of the WCM  211  and modem  220  in standby mode consume power. Such standby mode power consumption continues until the mobile phone operation is terminated with the WiBro system. 
         [0048]    In this embodiment, the mobile terminal blocks the power supply to the physical layer elements except at periodic time points at which the mobile terminal collects the channel states in the standby mode. 
         [0049]      FIG. 3  is a message flow diagram illustrating an operation of a mobile terminal in a standby mode of a power saving method according to an embodiment of the present invention. In this embodiment, a host  311  of the mobile terminal  310  performs the standby mode power management. 
         [0050]    The standby mode power saving method according to this is performed upon a modem  313  of the mobile terminal  310  receiving a Deregistration Confirmation (Dreg_Cmd) message from a base station  320  in step S 35  in response to a Deregistration Request (Dreg_Req) message sent by the host  311  to the modem  313  in step S 31  and forwarded therefrom to the base station  320  in step S 33 . 
         [0051]    Referring to  FIG. 3 , when the Dreg_Cmd message is received from the base station  320 , the modem  313  of the mobile terminal  310  outputs a Deregistration Response (Dreg_Resp) message to the host  311  in step S 301 . 
         [0052]    Upon receiving the Dreg_Resp message from the modem  313 , the host  311  generates a Standby Request (Standby_Req) message and transfers it to the modem  313  in step S 303 . The Standby_Req message is a request message for the modem  313  to enter the standby mode. 
         [0053]    The modem  313  then determines whether to enter the standby mode. If the modem  313  determines that the standby mode entry is possible, the modem  313  shuts off the power to physical layer elements in step S 305  and transmits a Standby Response (Standby_Resp) message to the host  311  in step S 307 . 
         [0054]    Then in step S 309 , the host  311  starts a timer and waits for the timer to expire. When the timer expires, the host  311  generates a Synchronization Request (Sync_Req) message and transfers the Sync_Req message to the modem  313  in step S 311 . 
         [0055]    In step S 313 , upon receiving the Sync_Req message, the modem  313  performs synchronization with the base station and collects information on a Received Signal Strength Indicator (RSSI) and Carrier-to-Interference and Noise Ratio (CINR) in step S 315 . 
         [0056]    If the synchronization is successfully performed and the RSSI and CINR are collected, the modem  313  outputs a Synchronization Response (Sync_Resp) message containing the CINR to the host  311  in step S 317 . The RSSI and CINR can be collected after the synchronization is successfully performed. If synchronization failed in a predetermined time, the modem  313  determines that the mobile terminal  310  is out of the WiBro service area and enters an out of service mode. 
         [0057]    If the Sync-Resp message is received, the host  311  outputs a Channel State Request (Air_State_Req) message to the modem  313  in step S 319 . In step S 321 , the modem  313  collects channel states and in step S 323  transfers a Channel State Response (Air_State_Resp) containing the channel states to the host  311 . 
         [0058]    Upon receiving the Air_State_Resp message, the host  311  transmits a Standby Request (Standby_Req) message to the modem  313  such that the modem  313  enters the standby mode in step S 303 . That is, the host  311  checks the state of the modem  313  and requests the channel state information, if the modem  313  is in a normal state. According to the channel state information received from the modem  313  at step S 323 , the host  311  may enable the modem to enter the standby mode. For the process of entering the standby mode and steps thereafter, the steps S 303  to S 323  are repeated. 
         [0059]    As described above, in this embodiment of the present invention, the host starts the timer upon receiving the standby mode response messages from the modem and requests to collect the channel state information when the timer expires. Before the timer expires, the modem and other physical layer elements are turned off so as to conserve the power in the standby mode. 
         [0060]      FIG. 4  is a message flow diagram illustrating an operation of a mobile terminal in a standby mode of a power saving method according to a second embodiment of the present invention. In this embodiment, the standby mode power management is performed by a modem  413  of a mobile terminal  410 . 
         [0061]    The standby mode power saving method is performed upon the modem  413  of the mobile terminal  410  receiving a Deregistration Confirmation (Dreg_Cmd) message from the base station  420  in response to a Deregistration Request (Dreg_Req) sent by a host  411  to the modem  413  in step S 41  and forwarded therefrom to the base station  420  in step S 43 . 
         [0062]    Referring to  FIG. 4 , when the Dreg_Cmd message is received from the base station  420 , the modem  413  of the mobile terminal  410  outputs a Deregistration Response (Dreg_Resp) message to the host  411  of the mobile terminal  410  in step S 401 . 
         [0063]    Upon receiving the Dreg_Resp message from the modem  413 , the host  411  transfers a Standby Request (Standby_Req) message to the modem  413  in step S 403 . The Standby_Req message contains information on a channel state report time interval such that the modem  413  sleeps and wakes up on the basis of the channel state report time interval. That is, the modem  413  determines whether to enter the standby mode, and turns off the power if it is determined that the standby mode entry is possible in step S 404 . 
         [0064]    At the same time, in step S 405  the modem transmits a Standby Response (Standby_Resp) message to the host  411  in response to the Standby_Req message, and also starts a timer set on the basis of the channel state report time interval in step S 407 . While the timer operates, the modem  413  minimizes the power consumed in the physical layer elements. 
         [0065]    In step S 409 , the modem  413  determines whether the timer has expired and performs synchronization with the base station in step S 411  when the timer expires. Next, if the synchronization is successfully performed, in step S 413  the modem  413  collects the RSSI and CINR and transmits a Channel State Response (Air_State_Resp) message containing the RSSI and CINR to the host  411  in step S 415 . If the synchronization fails within a predetermined time duration, the modem  413  determines that the mobile terminal  410  is out of the WiBro service area and enters an out of service mode. 
         [0066]    Upon receiving the Air_State_Resp message, the host  411  transmits a Standby_Request so as to repeat the steps S 403  to S 415 . 
         [0067]    As described above, in this embodiment of the present invention, the modem starts the timer on the basis of the channel state report, the interval contained in the Standby Request message received from the host and wakes up only when the timer expires for collecting the channel state information in the standby mode, thereby efficiently managing the power consumption in the standby mode. 
         [0068]    As described above, the power saving method for a mobile terminal enables physical layer elements including a modem to sleep for most standby mode duration and only wake up at preset times for collecting channel state information, resulting in reduction of power consumption in the standby mode. 
         [0069]    Although exemplary embodiments of the present invention have been described in detail herein-above, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the present art will still fall within the spirit and scope of the present invention, as defined in the appended claims.