TW201605263A - Method of performing cell selection in wireless communication system - Google Patents

Abstract

If a serving cell which the user equipment is currently camping on is barred from cell selection/reselection by the network, the user equipment is configured to search a suitable cell and/or an acceptable cell. Therefore, the user equipment can camp on another suitable cell or another acceptable cell more easily, thereby improving communication quality.

Description

Method for performing base station selection in a wireless communication system

The present invention relates to a method of performing base station selection in a wireless communication system, and more particularly to a method of performing base station selection in a wireless communication system when the service base station is blocked.

The 3rd Generation (3G) network system developed by the 3rd Generation Partnership Project (3GPP) includes the universal mobile telecommunications system (UMTS) and the global mobile communication system. The global system for mobile communications edge radio access network (GERAN) is characterized by providing high spectrum utilization efficiency, high coverage, high quality and high rate of multimedia data transmission. The universal terrestrial radio access network (UTRAN) in the universal mobile telecommunication system can be regarded as a wireless access network, in which the network side includes a plurality of base stations (Node-B, NB), To communicate with a plurality of user equipment (UE) at the user end. In addition, in order to improve the general mobile telecommunications system, 3GPP further develops a 4th Generation (4G) long term evolution (LTE) system to meet the increasing demands of users. The Long Term Evolution (LTE) system is considered to provide a new wireless interface and wireless network architecture that provides high data transfer rates, low latency, packet optimization, and improved system capacity and coverage, including a number of evolved base stations (evolved Nodes). -B, eNB) An evolved universal terrestrial radio access network (E-UTRAN), which is used to communicate with the UE on the one hand and non-access layer on the other hand (non- The access stratum (NAS) controls the core network (CN) for communication, and the core network includes a servo gateway and a mobility management entity (MME).

According to the 3GPP specifications, after selecting a public land mobile network identity (PLMN), the user equipment can perform a cell selection procedure and a cell reselection procedure to use. Related network services. The purpose of the base station selection procedure is to allow the user equipment to camp on a serving base, and to receive system information and establish radio resource control (RRC) connections from the PLMN. Access the network through the control channel, and receive/reply paging messages. The purpose of the base station reselection procedure is to allow the user device to switch to a target cell that is better camped on other signals.

The 3GPP specification defines different types of base stations based on the services that the base station can provide, such as a suitable base cell, an acceptable base cell, a barred cell, and a reserved cell. Wait. The user device can know the type of the base station through the status information in the system information block type 3 (SIB3) or the system information block type 4 (SIB4), which is blocked. The base station and the reserved base station prohibit any user equipment from camping on it, so the base station selection procedure can only be performed for the appropriate base station and the acceptable base station. However, although the user equipment station previously selected by the user equipment in the base station selection procedure may be allowed to perform base station selection/base station Re-selection procedure, but when the user equipment resides in the service base station, the network may set the service base station to prohibit base station selection/base station reselection for specific reasons, after which other user devices will not be able to reside. At the service base station. The existing 3GPP specifications have not defined the corresponding operation of the user equipment for the situation where the base station in the camp is changed from the appropriate base station or the acceptable base station to the blocked base station or the reserved base station, and thus the user equipment may not be able to execute. The base station selection process is instead camped on other suitable base stations or acceptable base stations, which in turn affects communication quality.

The present invention provides a method of performing a base station selection in a wireless communication system. The wireless communication system includes a user device and a plurality of base stations. The method includes a user device camping on a particular base station of the plurality of base stations; and when determining that the particular base station is not prohibited from performing the base station selection or a base station reselection while camping on the particular base station, The user device evaluates whether a suitable base station can be found in the plurality of base stations; and when the evaluation can find the suitable base station, the user device resides at the suitable base station.

The present invention further provides a method of performing a base station selection in a wireless communication system. The wireless communication system includes a user device and a plurality of base stations. The method includes a user device camping on a particular base station of the plurality of base stations; and when determining that the particular base station is not prohibited from performing the base station selection or a base station reselection while camping on the particular base station, The user device evaluates whether an acceptable base station can be found in the plurality of base stations; and when the evaluation can find the acceptable base station, the user device resides at the acceptable base station.

110~180‧‧‧Steps

1 and 2 are flowcharts showing a method of performing base station selection in a wireless communication system according to an embodiment of the present invention.

3 and 4 are diagrams showing states of execution of a base station selection procedure in a wireless communication system in accordance with an embodiment of the present invention.

For a wireless communication system including a user device and a plurality of base stations, the present invention can provide a method of performing base station selection. Each base station can be one NB in a UTRAN, one eNB in an EUTRAN, or a base station in other types of networks. The user device may include a mobile phone, a personal digital assistant (PDA), a handheld computer, a tablet computer, a nettop computer, a laptop computer, or other wireless device. Device for communication function. However, the types of base stations and user devices do not limit the scope of the present invention.

1 is a flow chart of a method for performing base station selection in a wireless communication system according to an embodiment of the present invention, which includes the following steps.

Step 110: The user equipment performs a base station selection procedure to select a specific base station as a service base station; and step 120 is performed.

Step 120: The user equipment resides at the service base station and receives system information from the service base station; and step 130 is performed.

Step 130: The user device determines, according to the system information, whether the serving base station is prohibited from performing base station selection or base station reselection; if yes, step 140 is performed; if not, step 180 is performed.

Step 140: The user device evaluates whether a suitable base station can be searched; if yes, step 150 is performed; if not, step 160 is performed.

Step 150: The user device executes the base station selection procedure to camp on the appropriate base station; step 180 is performed.

Step 160: The user device evaluates whether an acceptable base station can be searched; if yes, step 170 is performed; if not, step 160 is performed.

Step 170: The user equipment executes the base station selection procedure to camp on the acceptable base station; step 180 is performed.

Step 180: The user device performs other operations.

According to the current 3GPP specifications (eg TS 36.304), the base station selection procedure consists of two phases: the selected target base station and the selected service base station. In the first phase of the selected target base station, the user device selects the target base station based on the PLMN identification list owned by the user, the base station information of the memory, or the scanned list of neighboring base stations. If the base station that matches the PLMN identification list owned by the user is not found, or if no smart card is inserted, the user device selects the target base station according to the strength of the signal. After the target base station is selected, the user device begins to receive and process system information received from the target base station. The system information includes _Q rxlevmeas, threshold _{Q qualmeas, Q rxlevmin, Q qualmin} , Q rxlevminoffset, Q qualminoffset and P _compensation parameters and _{Thresh serving, LowQ, Thresh Serving,} LowP, Thresh X, LowQ and Thresh _{X, LowQ} the like, using The device can calculate parameters such as Srxlev and Squal and learn the relevant cell selection criteria/cell reselection criteria. Srxlev represents a base station selecting a cell selection RX level value, and Squal represents a cell selection quality value. Q _rxlevmeas represents a measured cell RX level value or a reference signal receiving power (RSRP). Q _qualmeas represents a measured cell quality value or a reference signal receiving quality (RSRQ). Q _rxlevmin represents a minimum required RX level in the cell. Q _qualmin represents a minimum required quality level in the cell. Q _{rxlevminoffset} represents one of the offset values included in the Srxlev evaluation when searching for higher priority PLMNs. Q _{qualminoffset} represents one of the offset values included in the Squal evaluation when searching for higher priority PLMNs. P _compensation is (P _{EMAX -} P _PowerClass ) and the larger of 0, where P _EMAX represents the maximum transmit power available to the user device and P _PowerClass represents the maximum RF output power of the user device. Thresh _{Serving, LowQ} and Thresh _{Serving, LowP} represent the low threshold used in the service frequency in the re-election evaluation. Thresh _{X, LowQ} and Thresh _{X, LowP} represent the critical values used when re-electing lower priority rates.

The units of Srxlev and Squal are decibels (dB), which are defined by the following formulas (1) and (2), respectively.

Srxlev = Q _rxlevmeas - (Q _rxlevmin + Q _{rxlevminoffset} ) - P _compensation ... (1).

Squal=Q _qualmeas -(Q _qualmin +Q _{qualminoffset} )...(2).

In the second phase of the selected service base station, the user equipment determines whether the target base station is a suitable base station based on the base station selection criteria learned from the system information provided by the target base station. The base station selection criterion is determined by using the signal receiving threshold (such as Srxlev and/or Squal) and status information indicated in the target base station system information. Equation (3) shows the base station selection criterion S1 under the frequency division duplex (FDD) architecture. Equation (4) shows the base station selection criteria under the time division duplex (TDD) architecture. S2.

S1: Srxlev>0 and Squal>0...(3).

S2: Srxlev>0...(4).

In step 110, if a specific base station is selected in the first phase, it is determined in the second phase that the signal strength of the specific base station is greater than the signal reception threshold (eg, satisfies the base station selection criterion S1 or S2), and the state of the specific base station The information display is not prohibited for base station selection or base station reselection. At this time, the user equipment will select a specific base station as the service base station.

In step 120, the user device resides at the serving base station and continuously receives system information from the serving base station, and then learns the base station selection criteria and frequency list to perform base station selection evaluation accordingly.

As previously mentioned, although the user device may be allowed to perform base station selection/base station reselection at a particular base station previously selected as the serving base station in step 110, but while the user device resides in the serving base station The network may change the status information of a specific base station for a specific reason. For example, the status information in the SIB3 or SIB4 broadcast by the first base station includes "Cell Barred", "Cell reserved for operator use", and "Extended reservation". Information element (IE) such as Cell reservation on extension. When the network allows a specific base station to operate normally, the above information element can be set to an "not barred" state; when the network side does not want any user device to reside on a specific base station, the above information element can be set. It is "barred".

In step 130, if the user device determines, according to the system information, that the serving base station is not prohibited from performing base station selection or base station reselection, then other operations are performed in step 180, such as performing a base defined in the current 3GPP specifications. Desk selection assessment and base station re-election assessment. Once the user device determines, according to the system information, that the service base station is prohibited from performing base station selection or base station reselection, step 140 is performed.

As mentioned earlier, the 3GPP specification defines different types of base stations based on the services that the base station can provide, such as suitable base stations, acceptable base stations, blocked base stations, and reserved base stations. A user device that installs a valid smart card can use normal service when camping on a suitable base station. The user device can only use restricted services when camping on an acceptable base station. The user device cannot reside on the blocked base station and the reserved base station. In step 140, the user device evaluates whether a suitable base station can be found.

According to the 3GPP specifications, the user equipment can use two base station selection criteria: initial cell selection or stored information cell selection. In the initial base station selection evaluation, the user equipment does not need to know in advance which RF channel is an evolved universal terrestrial global radio access carrier (E-UTRA carrier), but directly scans all radio frequencies in the E-UTRA band according to its own capabilities. aisle. For each carrier frequency, the user device only determines the base station with the strongest signal as the appropriate base station. In the storage information base station selection evaluation, the user equipment needs to know the storage information of the specific carrier frequency from the previously received measurement control information element or the previously detected base station, and first attempts to synchronize with the specific carrier frequency. In the embodiment of the present invention, the user device may perform an initial base station selection evaluation, a storage information base station selection evaluation, or perform a storage in sequence in step 140. The information base station selects an assessment and an initial base station selection assessment to search for a suitable base station.

If a suitable base station can be found in step 140, the user device will perform a base station selection procedure to camp on the appropriate base station in step 150, and then perform other operations in step 180, such as performing a base station as defined in the current 3GPP specifications. Select assessment and base station re-election assessment.

If a suitable base station cannot be found in step 140, the user device will then evaluate in step 160 whether an acceptable base station can be found. In an embodiment of the invention, the user device may perform an initial base station selection assessment or a stored information base station selection assessment in step 160 to search for acceptable base stations.

If an acceptable base station can be searched for in step 160, the user device performs a base station selection procedure to reside at the acceptable base station at step 170, and then performs other operations at step 180, such as performing as defined in the current 3GPP specifications. Base station selection assessment and base station re-election assessment.

2 is a flow chart of a method for executing a base station selection procedure in a wireless communication system according to an embodiment of the present invention, which includes the following steps.

Step 110: The user equipment performs a base station selection procedure to select a specific base station as a service base station; and step 120 is performed.

Step 120: The user device resides at the service base station and from the service base The station receives the system information; step 130 is performed.

Step 130: The user device determines, according to the system information, whether the service base station is prohibited from performing base station selection or base station reselection; if yes, step 160 is performed; if not, step 180 is performed.

Step 160: The user device evaluates whether an acceptable base station can be searched; if yes, step 170 is performed; if not, step 160 is performed.

Step 170: The user equipment executes the base station selection procedure to camp on the acceptable base station; step 180 is performed.

Step 180: The user device performs other operations.

The embodiment shown in Fig. 2 is similar to the first one, except that when it is determined in step 130 that the serving base station has been prohibited from performing base station selection or base station reselection, the method shown in Fig. 1 attempts to search for a suitable one. The base station and the base station can be accepted, and the method shown in Figure 2 will only attempt to search for acceptable base stations.

3 and 4 are diagrams showing states of execution of a base station selection procedure in a wireless communication system in accordance with an embodiment of the present invention. Figure 3 is a state diagram for the method shown in Figure 1, in which once the user device selects a new PLMN or the service base station is prohibited from performing base station selection/base station reselection, it will enter the "base station selection evaluation". Status, such as performing an initial base station selection or storing information base station selection. Figure 4 is a state diagram for the method shown in Figure 2, in which once the user device is not inserted into the smart card or the service base station is prohibited from performing base station selection/base station reselection, it will enter the "base station selection evaluation". State, for example, to perform any base station selection.

In the method for performing the base station selection according to the present invention, when the user device resides in the service base station, if the network terminal sets the service base station to be prohibited for a specific reason For base station selection/base station reselection, the user device will search for a suitable base station and/or an acceptable base station. Therefore, the present invention can make the user device residing on the blocked base station easier to relocate to another suitable target base station or an acceptable target base station, thereby improving communication quality.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

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Claims (7)

A method of performing cell selection in a wireless communication system, the wireless communication system including a user device and a plurality of base stations, the method comprising: a user device residing in the plurality of base stations a specific base station; the user device evaluates in the plurality of base stations when it is determined that the particular base station is not prohibited from performing the base station selection or a cell reselection while camping on the specific base station Whether a suitable suitable cell can be found; and when the evaluation can find the suitable base station, the user device resides at the appropriate base station. The method of claim 1, further comprising: receiving, during the camping at the specific base station, the user device receiving system information from the specific base station; the user device determining, according to the status information indicated by the system information Whether the particular base station is prohibited from performing the base station selection or the base station reselection. The method of claim 2, wherein the status information comprises a "Cell Barred" information element defined in a 3rd Generation Partnership Project (3GPP) specification ( Information element (IE), a "Cello reserved for operator use" information element, and a "Cell reservation on extension" information element; When the "blocked base station" information element, the "base station reserved for the operator" information element and one of the "extended reserved base station" information elements are set to a "barred" state, The user equipment determines that the specific base station is prohibited from performing the base station selection or the base station reselection; and when the "blocked base station" information component, the "reserved base station" information component of the operator, and the " When the extended base station information element is set to an "not barred" state, the user device determines that the particular base station is not prohibited from performing the base station selection or the base station reselection. The method of claim 1, further comprising: when the evaluation fails to find the suitable base station, the user device evaluates whether an acceptable base station can be found in the plurality of base stations; When the evaluation can find the acceptable base station, the user device resides at the acceptable base station. A method of performing cell selection in a wireless communication system, the wireless communication system including a user device and a plurality of base stations, the method comprising: a user device residing in the plurality of base stations a specific base station; the user device evaluates in the plurality of base stations when it is determined that the particular base station is not prohibited from performing the base station selection or a cell reselection while camping on the specific base station Whether an acceptable base cell can be searched; and when the evaluation can find the acceptable base station, the user device resides at the acceptable base station. The method of claim 5, further comprising: receiving, during the camping at the particular base station, the user device receiving system information from the specific base station; the user device determining, according to the status information indicated by the system information Whether the particular base station is prohibited from performing the base station selection or the base station reselection. The method of claim 6, wherein the status information comprises a "Cell Barred" information element defined in a 3rd Generation Partnership Project (3GPP) specification ( Information element, IE), a "Cello reserved for operator use" information element, and a "Cell reservation on extension" information element; when the "blocked base" The user device determines that the information component, the "base station reserved for the operator" information element, and one of the "extended reserved base station" information elements are set to a "barred" state. The specific base station is prohibited from making the base station selection or the base station reselection; and the "blocked base station" information component, the "reserved base station for the operator" information component and the "extended base station" When the information element is set to an "not barred" state, the user device determines that the specific base station is not prohibited from performing the base station selection or the base station reselection. .