System search method and mobile terminal performing the same

A mobile terminal and system search method for the same are provided. The present invention enables a rapid system search with minimized battery consumption after a system loss. The system search method, using a search parameter specifying a first search time S0 and search periods (Do+S1) of a wait time Do and search time S1, includes performing, when the mobile terminal experiences a system loss, an initial system search to search for a system to use for the first search time S0 and increasing, when a system to use is found during the first search time S0, the first search time S0 to reset the search parameter.

PRIORITY

This application claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Jul. 12, 2007 and assigned Serial No. 2007-0070150, the entire disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a system search method in a communication system. More particularly, the present invention relates to a mobile terminal and method for performing a system search that minimizes battery consumption after a system loss.

2. Description of the Related Art

In general, to establish a communication channel, a mobile terminal selects a base station of a mobile communication system for synchronization, and acquires system information from the selected base station. The mobile terminal notifies the base station of its location and registration information using the acquired system information, establishes the communication channel and receives call-related services.

Here, the term “system” refers to a communications infrastructure that is managed by a mobile network operator to provide mobile communication services to mobile terminals. The system may use analog technology, digital cellular technology, Personal Communications Service (PCS) technology and the like.

When a system loss occurs, owing to a loss or failure of the communication channel with a base station, a mobile terminal performs a system search according to a preset system search parameter. That is, the mobile terminal attempts to reestablish the same or another communication channel with a base station by searching for a system. According to the preset system search parameter, the mobile terminal performs an initial system search for a first search time period. If no system is found during the first search time period, the mobile terminal transitions to a power-saving mode (e.g. sleep mode) and then performs a system search for a second search time period. The second search time period corresponds to a preset search period composed of the duration of the power-saving mode and the duration of the system search. This second search time period may be repeated if necessary.

According to a conventional search parameter, the first search time is set to be longer than the second search time. Hence, even if no system is found during the first search time, battery power is still rapidly consumed. Alternatively, if the first search time is set to be shorter, battery power can be saved. However, the system search is more likely to be unsuccessful, and service quality of the mobile communication system can be degraded.

SUMMARY OF THE INVENTION

An aspect of the present invention is to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide a mobile terminal and system search method for the same that enable rapid system search with minimized battery consumption after a system loss.

In accordance with an aspect of the present invention, a system search method for a mobile terminal according to a search parameter specifying a first search time S0and search periods (Do+S1) of a wait time Doand search time S1is provided. The method includes performing, when the mobile terminal experiences a system loss, an initial system search to search for a system for the first search time S0, increasing, when a system is found during the first search time S0, the first search time S0and resetting the search parameter.

In accordance with another aspect of the present invention, a mobile terminal is provided. The mobile terminal includes a wireless communication unit for attempting to connect to a mobile communication system and for receiving system information from a connected mobile communication system, a storage unit for storing a search parameter specifying a first search time S0and search periods (Do+S1) of a wait time Doand search time S1, a search section for performing, upon occurrence of system loss, an initial system search to search for a system for the first search time S0through the wireless communication unit and a first resetter for increasing, when a system to use is found during the first search time S0, the first search time S0to reset the search parameter.

In accordance with an aspect of the present invention, after a temporary system loss occurs owing to unfavorable conditions of a mobile communication network, the first search time is increased and the wait time is reduced, thereby enabling rapid system recovery with minimized battery consumption.

In addition, when no system is found during the first search time owing to unfavorable conditions of a mobile communication network, the first search time is reduced and the wait time is increased, thereby enabling rapid system recovery with minimized battery consumption.

Thus, according to a success or a failure of the system search during the first search time, the first search time or the wait time is adjusted to enable rapid system recovery with minimized battery consumption.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the following description, the expression max {A1, A2} produces the larger one of A1and A2, and the expression min {B1, B2} produces the smaller one of B1and B2.

FIG. 1is a block diagram illustrating interactions between a mobile terminal and a mobile communication system in accordance with an exemplary embodiment of the present invention.

Referring toFIG. 1, a mobile terminal10according to an exemplary embodiment of the present invention is connected to a mobile communication system20through a mobile communication network30.

The mobile communication system20divides its entire service area into smaller service regions known as cells, which are managed by corresponding base stations. These base stations are then centrally managed by Mobile Switching Centers (MSC) to enable subscribers to make a call while traveling between cells.

The mobile terminal10obtains system information through interactions with a base station of the mobile communication system20, and sends its location and registration information to the mobile communication system20using the obtained system information to receive call-related services. That is, the mobile terminal10establishes a communication channel with the mobile communication system20through a base station.

According to an exemplary implementation, when a system loss occurs owing to failure of the communication channel with the base station, the mobile terminal10performs a system search to search for the mobile communication system20and to reestablish the communication channel or establish a new communication channel. The system search is performed according to a system search parameter preset at the mobile terminal10. A default system search parameter is installed in the mobile terminal10during the manufacturing process.

The search parameter is given by a combination of search times Siand wait times Di(wherein i is a nonnegative integer). As illustrated inFIG. 2, the search parameter includes a first search time S0and repeating search periods, where each search period (Di+Si+1) is the sum of a wait time Diand search time Si+1. That is, if the mobile communication system20is found during the k+1thsearch time Sk, the time required for system search Tscan be given by Equation 1.

In an exemplary implementation, search times Siand wait times Disatisfy the condition given by Equation 2. Of course, this is merely an example and the search and wait times can be varied from each other.
S0>D0>S1,S1=S2=S3= . . . =Si+1,D0=D1=D2= . . . =Di[Equation 2]

In an exemplary implementation, the mobile terminal10alters the system search parameter according to the results of a system search performed after a system loss.

A system loss may occur for any of several reasons. For example, system loss may occur when conditions of the mobile communication network30temporarily deteriorate in an area where the mobile terminal10is located. Alternatively, system loss may occur when the mobile terminal10is located at a shadow area where signals from the mobile communication network30are not readily received. Of course, system loss also occurs when the mobile terminal10is powered off.

If a system loss occurs due to temporary deterioration of communication conditions, there is a high probability that a system search will succeed during the first search time S0. In this case, it is preferable to increase the first search time S0to more rapidly reestablish the channel with the mobile communication system. That is, because of the high probability that the system search will be successful since the deterioration is only temporary, the first search time is extended to avoid entering the wait period. Since the wait period is not entered, the positive search results are achieved more rapidly.

On the other hand, if a system loss occurs due to difficulty of signal reception, such as may occur when the mobile terminal is located in a shadow area, it is unlikely that a system search will succeed during the first search time S0and it is highly probable that a system search is performed irrespective of the search parameter. In this case, it is preferable to decrease the first search time S0for saving battery power.

FIG. 3is a block diagram illustrating a mobile terminal according to an exemplary embodiment of the present invention.

Referring toFIG. 3, a mobile terminal10according to an exemplary embodiment of the present invention is described in more detail. The mobile terminal10includes a control unit11, an input unit12, a storage unit13, a wireless communication unit14, a display unit15, and a battery16.

The control unit11controls the overall operation of the mobile terminal10. In an exemplary implementation, the control unit11performs a system search after failure of a communication channel with the mobile communication system20, and resets the search parameter depending upon the search result.

The input unit12provides a plurality of keys for manipulation of the mobile terminal10, and sends a selection signal associated with a key selection of the user to the control unit11. The input unit12may include a keypad, a touchpad, a pointing device, a touch screen and the like for input.

The storage unit13stores programs necessary for operation and control of the mobile terminal10. The storage unit13also stores data generated from execution of the programs. In particular, the storage unit13stores executable programs for performing a system search and for resetting the search parameter according to the search result. The storage unit13stores system information13areceived from the mobile communication system20, and the search parameter13b.

The wireless communication unit14performs a series of operations related to wireless communication such as the sending and receiving of signals to and from the mobile communication system20. When performing a system search according to the search parameter, the wireless communication unit14attempts to connect to a mobile communication system20and obtains system information from the connected mobile communication system20. In particular, after a system loss, the wireless communication unit14performs a system search according to the search parameter to find a mobile communication system20and establish or reestablish a communication channel for connection.

The display unit15displays various menus associated with functions executed by the mobile terminal10as well as information stored in the storage unit13. The display unit15may include a panel of a liquid crystal display device and a touch screen. Use of a touch screen enables the display unit15to act simultaneously as a display device and an input device.

The battery16supplies necessary power to the elements of the mobile terminal10.

In more detail, the control unit11includes a search section11afor performing a system search according to the search parameter13b, and first and second resetters11band11cto adjust the search parameter according to the search result. The first and second resetters11band11cupdate the search parameter13bstored in the storage unit13with an adjusted version.

When a system loss occurs, the search section11aperforms a system search according to the current search parameter13bstored in the storage unit13. If the system search is successful, the search section11areceives system information13afrom the found mobile communication system20and stores the received system information13ain the storage unit13. The system information13ais received as part of system parameters from a base station of the mobile communication system20. The system parameters include information on channels, location, System IDentification (SID), and Network IDentification (NID). The system information13aincludes data for SID and NID.

When the system search is successful during the first search time S0, the first resetter11badjusts the search parameter. Specifically, the first resetter11bincreases the first search time S0. For example, the first resetter11bincreases the first search time S0by a preset duration Scto an extent not longer than a maximum search time Smax. In addition, the first resetter11bdecreases wait times Di. For example, the first resetter11bdecreases wait times Diby a preset duration Dcto an extent not shorter than a minimum wait time Dmin. When the system search during the first search time S0(k=0) is successful, the adjusted search parameter can be given by Equation 3.
i=k+1,S0=min{S0+Sc,Smax},Di=max{Di−Dc,Dmin}  [Equation 3]

In Equation 3, the wait times Diare the same and Di=D0.

The reason for adjusting the search parameter by the first resetter11bmay be described as follows. A successful system search during the first search time S0may indicate that the system loss is temporary. Hence, as explained above, to increase the probability of a successful system search as well as achieve the success more rapidly, the first search time S0is increased and the wait times Diare decreased. Further, to cope with a possible error in this adjustment or with an abrupt change of communication conditions, the first resetter11bincreases the first search time S0and decreases the wait times Diin a stepwise manner.

The second resetter11cadjusts the search parameter when the system search during the first search time S0fails. That is, the second resetter11cdecreases the first search time S0so that the first search time S0rapidly converges to the minimum search time Smin. For example, if the mobile communication system20is found during the k+1thsearch time Sk, the second resetter11cadjusts the first search time S0using Equation 4.
i=k+1,S0=max{S0−α·k·Sc,Smin}(α: constant)  [Equation 4]

The adjusted first search time S0is a function that is proportional to k with a slope of −α·Sc, and has a minimum of Smin. Alternatively, the adjusted first search time S0may be set to a function proportional to kn(n: natural number greater than or equal to 1), in which case the adjusted first search time S0more rapidly converges to the minimum search time Sminwith increasing n and fixed α·Sc.

In addition, the second resetter11cincreases the wait time Diso that it rapidly converges to the maximum wait time Dmax. For example, if the mobile communication system20is found during the k+1thsearch time Sk, the second resetter11cadjusts the wait time Diusing Equation 5.
i=k+1,Di=min{Di+α·k·Dc,Dmax}(α: constant)  [Equation 5]

The adjusted wait time Diis a function that is proportional to k with a slope of α·Sc, and has a maximum of Dmax. Alternatively, the adjusted wait time Dimay be set to a function proportional to kn(n: natural number greater than or equal to 1), in which case the adjusted wait time Dimore rapidly converges to the maximum wait time Dmaxwith increasing n and fixed α·Sc.

The reason for adjusting the search parameter by the second resetter11cmay be described as follows. Failure of the system search during the first search time S0may indicate that the mobile terminal10is in a shadow area where signals from the mobile communication system20are not readily received. In this case, increasing the first search time S0or decreasing the wait time Dimay not contribute towards increasing the probability of a successful system search. Instead, an increased first search time S0may simply cause an increase in battery power consumption without an increased probability of a successful system search during that time. Hence, the second resetter11cadjusts the search parameter so that the first search time S0and the wait time Dirapidly converge to the minimum search time Sminand maximum wait time Dmaxrespectively.

Referring toFIGS. 1 to 4, an exemplary system search method of the mobile terminal10is described. A system search method according to an exemplary embodiment of the present invention is performed when the mobile terminal10fails in a system search upon power up or when a system loss occurs during a communication service.

FIG. 4is a flowchart illustrating a system search method according to an exemplary embodiment of the present invention.

Referring toFIG. 4, the mobile terminal10sets the search parameter to satisfy Equation 2 in step S51. The search parameter may be a default version set during the manufacturing process or an updated version of the default version.

The control unit11determines whether a system loss occurs in step S53. That is, the control unit11determines whether communication with the mobile communication system20is interrupted or the communication channel is otherwise disturbed.

If system loss has occurred, the search section11aperforms an initial system search according to the set search parameter in step S55.

The search section11adetermines the result of the initial system search in step S57.

If no system is found, the search section11adetermines whether the first search time S0has expired in step S59. If the first search time S0has not expired, the search section11arepeats steps S55and S57. That is, the initial system search is repeated until expiration of the first search time S0.

If a system is found within the first search time S0, the first resetter11badjusts the first search time S0and the wait time Diusing Equation 3 in step S61. That is, the first search time S0is increased by a preset duration Scto an extent not longer than the maximum search time Smax, and the wait time Diis decreased by a preset duration Dcto an extent not shorter than the minimum wait time Dmin.

The first resetter11bupdates the search parameter13bstored in the storage unit13using the adjusted search times and wait times. If a system is found, the search section11areceives system information13afrom the found mobile communication system20and stores the received system information13ain the storage unit13.

If the first search time S0has expired at step S59(i.e. no system is found within the first search time S0), the search section11atransitions to the power-saving mode and performs a system search according to search periods (Di+Si+1) in step S63. The search section11arepeats waiting and searching while performing the system search.

The search section11adetermines whether a system is found in step S65. If no system is found, the search section11areturns to step S63.

If a system is found during the k+1thsearch time Sk, the second resetter11cadjusts the first search time S0using Equation 4, and the wait time Diusing Equation 5 in step S67. That is, the first search time S0is reduced so as to rapidly converge to the minimum search time Smin, and the wait time Diis increased so as to rapidly converge to the maximum wait time Dmax.

The second resetter11cupdates the search parameter13bstored in the storage unit13using the adjusted search times and wait times. If a system is found, the search section11areceives system information13afrom the found mobile communication system20and stores the received system information13ain the storage unit13.

The control unit11repeats steps S53to S67until a termination request is issued in step S69. As described above, when a system loss occurs, the control unit11performs a system search according to the updated search parameter. The search parameter is readjusted according to the search result of the system search to achieve success more rapidly as well as saving on battery power.

Although exemplary embodiments of the present invention have been described in detail hereinabove, it should be understood that many variations and modifications of the basic inventive concept herein described, which may appear to those skilled in the art, will still fall within the spirit and scope of the exemplary embodiments of the present invention as defined in the appended claims and their equivalents.