KR100483511B1 - Decision method of search window size of mobile terminal in hanoff - Google Patents

Abstract

The present invention relates to a mobile communication system, and in particular, to determine the size of the search window at the time of handoff of the mobile terminal as the largest value. The method of determining the search window size of the mobile terminal at the time of handoff according to the present invention, Receiving a PSMM transmitted from the mobile terminal, checking whether a drop pilot exists, and comparing window size values of active pilots except the drop pilot if the drop pilot exists; And comparing the search window size of the ad pilot in the case where the largest search window size and the ad pilot exist as a result of the comparison, and determining a large value as the search window size and transmitting it to the terminal.

Preferably, after receiving the PSMM from the mobile terminal, the search window size value of the active pilot is compared with the search window size value of the pilot to be added, and a large value is determined as the search window size and transmitted to the terminal.

Description

Decision method of search window size of mobile terminal in hanoff}

In the mobile communication system, a search window size transmitted to the terminal to ensure the call quality of the mobile terminal during the handoff that guarantees the mobility of the terminal among the call processing functions of the mobile communication switch using the CDMA technology, in particular, It relates to a method for determining.

In general, when a handoff event occurs in a call terminal, a call control processor (CCP) determines a handoff type (ADD, DROP or SWAP) and instructs the handoff to be performed. A new search window size value is transmitted to the terminal through a Handoff Direction Message (HDM) and an In Traffic System Parameter Message (ITSPM). The call quality is maintained.

The handoff procedure in the mobile communication system is shown in FIG. 1. 1 illustrates a method of determining a search window size value in HDM and ITSPM transmission according to the present invention.

Referring to FIG. 1, when a call is established, the terminal continuously checks the base station pilot strength belonging to its neighbor, and when the base station pilot strength is one of the handoff information equal to or greater than a predetermined value (T_ADD), a PSMM (Pilot Strength Measurement Message) ) Is transmitted through the ongoing call channel (SBP / SVC) of the current call (PSMM_S2C) and transmitted to the system (CCP).

Here, the SBP (Selector Bank Processor) is a board that has a processor that controls several SVC boards, and the SVC (Selector Vocoder Card) is a physical resource that is mounted on the control station to receive voice calls (vocoder ( vocoder) exists. In addition, SVCS means that there are a plurality of SVCs, HSVCS means that there are a plurality of HSVCs, and HSVC processes only packet data calls, not voice calls, and is mounted in a control station (BSC), where physical resources exist. It is a board.

The system (CCP) receiving the PSMM uses a handoff type (ADD) using pilot strengths of base stations reported by a UE included in a corresponding message, pilot offset information of each base station, and neighbor base station and sector information that it currently has. , DROP or SWAP).

A handoff type add (ADD) state is a state in which a terminal moves from a serving base station to add another target base station, and a drop (DROP) state is a state in which a terminal moves from a previous base station to a serving base station and receives a target base station. When the mobile station is removed, the previous base station is removed. The swap state is a state where the ad state and the drop state are simultaneously performed.

Then, when the strength of the pilot is large enough and the pilot offset value from the terminal is compared with the information between the base stations of the system, it is determined as the soft handoff add state when the sector of another base station in the same control station is different from the base station to which the current call is set. The resource allocation request message I_HoffReq_C2B is transmitted to the base station to be ADDed. Then, the target base station notifies the TC (Traffic Channel) that the soft handoff is made with the TC resources occupied by the base station and gives a command (tc_mob_asgn) to prepare and receives a response (tc_asgn_ack).

In addition, the target base station in which the radio resource allocation is normally performed at the same frequency and the same frame offset reports the corresponding resource information to the call control processor (CCP) (I_HoffAsgn_B2C), and the call control processor receives the corresponding message and checks the information. Send it to SVCS / HSVCS.

In the case of the soft ADD (HoffAsgn_C2S), the SVCS / HSVCS sets a call channel and a link newly assigned to the target base station. At this time, the SBP / SVC transmits a message (tc_soft_ho_progress) indicating that handoff is in progress to a serving traffic channel, which is one of call path elements, and receives a response (vs_ack_ctrl). A procedure for synchronizing the newly added traffic channel with the vocoder in the SVC (HSVC) is performed (Time Sync). Thereafter, the message received from the call control processor is transmitted to the terminal through the newly established call channel in addition to the existing call channel (s) using the EHDM / UHDM (Extended / Universal Handoff Direction Message).

The SBP / SVC transmits a null frame to tune to a new channel by a terminal receiving an HDM on the traffic channel of the target base station, and informs that the traffic channel of the target base station has received it (vs_mob_acq_ctl). In response to this, the received response is processed (tc_ack_ctrl). The target base station also reports to the target base station BSP that the traffic channel TC has received null traffic (sel_lk_on).

Upon receiving the EHDM / UHDM message, the UE registers the Pilot PN included in the message in its Active Set and transmits the information to the system using the HCM (Handoff Completion Message) to the call channel in use. (HoffCmpl_S2C).

The system then requests a message requesting various parameters and information required for handoff to the call control processor of the target base station and receives necessary information in response thereto (CfgReq_C2C, NbrCfgRep_C2C). The call control processor transmits an In-Traffic System Parameter Message (ITSPM) and a neighbor list update message (Neighbor List Update Message) to the terminal (InTraffic_C2S, NbrLstUpd_C2S).

In this way, soft handoff is performed for the base station to be added.

Here, the method of determining the search window size when the HDM (EHDM, UHDM) is transmitted to the terminal is as follows.

In case of a handoff due to the ad situation, the search window size is determined by transmitting the search window size of the pilot to be added to the terminal.

In case of a handoff in a drop and swap situation, the search window size of the most active pilot is transmitted when the reference pilot of the call control processor is dropped, and the reference pilot is searched when the reference pilot of the call control processor is not dropped. Send the window size.

The search window size is determined at the time of ITSPM transmission to the terminal. This is transmitted when the handoff is normally completed, and the optimal value is determined by comparing the search window values of the active pilots.

However, the search window size is a size that the UE searches for receiving a pilot signal transmitted from the base station. In fact, the search window size is a value obtained by changing the range (interval) of the PN chip to search and distinguishing it by an index. Say. If the value of the search window size is large, more pilot signals can be found because the range of the PN chip to be searched is increased, while the search time of the terminal is increased, which may affect battery life. There are disadvantages.

Also, in determining the search window size during HDM transmission, as shown in FIG. 2 during handoff in the ADD situation. 2 is a flowchart illustrating a problem that may occur when a handoff is performed by an ad of a conventional base station. After the call control processor receives the PSMM transmitted from the mobile station, if the activated search window (srch_win_a) of the pilot to be added is smaller than the existing value, the terminal operates with the activated search window (srch_win_a) received through the HDM. If the UE normally receives the ITSPM at the time of the handoff completion, it operates with the normal search window size value (Srch_win_a, n, r = 10,11,11), but if the UE does not receive the ITSPM, the small size search is performed. Due to operating with a window value, a call drop may occur due to an increase in the frame error rate (FER).

In FIG. 2, if the reference pilots are 10 (a), 11 (n), and 11 (r), a means an active pilot, n means a neighbor pilot, and r means a remaining pilot. Therefore, when the PSMM is received from the mobile terminal and the activated search window srch_win_7 of the pilot to be added is smaller than the existing reference pilot 10, the terminal operates with the activated search window srch_win_7 received through the EHDM and handoffs. If the terminal normally receives the ITSPM at the completion time, the terminal operates with a normal search window size value (S201 to S205). However, when the ITSPM is not normally received at the completion of the handoff, since a small search window value (srch_win_a, n, r = 7,11,11) is operated, call drop may occur due to an increase in the FER. (S206-S208).

In addition, as shown in Figure 3 during the handoff in the drop and swap situation.

3 is a flowchart illustrating a problem that may occur when a handoff is caused by a drop and a swap of a conventional base station.

When the call control processor receives the PSMM from the mobile terminal (S301), the terminal when the activated search window (srch_win_a) value of the reference pilot (ref. Pilot = 7) is smaller than that of the other active pilot (10). Is operated with a small active search window (srch_win_a = 7) received through the EHDM (S302). If the UE normally receives the ITSPM at the completion of the handoff, the normal search window size value (Srch_win_a, n, r = 10,11,10), but if it does not receive ITSPM, it operates as small search window value (Srch_win_a, n, r = 7,11,10). Call Drop) may occur (S303 ~ S305).

In the case of a drop of an active pilot other than the reference PN (Ref PN), if the activated search window (srch_win_a) value of the reference PN is smaller than other active pilots, the FER increases and the possibility of call disconnection increases.

In addition, in the case of the drop of the reference PN, the pilot having the strongest strength among the remaining active sets is selected as the reference PN (Ref PN), and its activated search window srch_win_a is lowered through the EHDM. At this time, if the activated search window (srch_win_a) of the strongest pilot is smaller than other active pilots, there is a problem in that FER increases and call disconnection increases.

The present invention has been made to solve the above problem, and when there is a change in active pilots at the time of handoff completion, a larger value is determined as the window search size and transmitted to the terminal compared to the existing value to fit the changed case. In addition, the present invention provides a method of determining a search window size of a mobile terminal at the time of a handoff, which allows the handoff database of the call control processor to be updated and managed every time when the handoff is completed. The present invention does not determine the search parameter value of a specific pilot according to the handoff type when transmitting all the handoff direction messages (HDM), but considers the ad handoff, drop handoff, and swap handoff situations at the completion of the handoff. Between search windows of the mobile terminal during handoff to determine the optimal search parameter value Its purpose is to provide a method for determining the risk.

In order to achieve the above object, a method of determining a search window size of a mobile terminal during handoff according to the present invention includes:

Receiving a PSMM transmitted from the mobile terminal, checking whether a drop pilot exists, and comparing window size values of active pilots except the drop pilot if the drop pilot exists;

And comparing the search window size value of the ad pilot with the largest search window size and the ad pilot, and determining a large value as the search window size and transmitting the larger value to the terminal.

Preferably, when the mobile terminal is handed off, the search window size value is compared with the search window size value of the pilot to be added, and a large value is determined as the search window size and transmitted to the terminal.

Preferably, the determined search window size value is transmitted to the corresponding terminal through the EHDM and UHDM.

A method of determining a search window size of a mobile terminal during handoff according to the present invention as described above will be described with reference to the accompanying drawings.

First, in general, when the protocol revision of the terminal (protocol revision) is more than '6' 95C (3G) UHDM is used, and in the case of 95A / B (2G) terminal less than '6' EHDM is used.

In the case of the 95C terminal, since the UHDM includes all the search parameter values, the UHDM determines the optimal search parameter value in the UHDM and descends the terminal to the terminal.

When all HDM (EHDM / UHDM) transmissions are performed, the optimal search parameter value is determined in consideration of the situation when the handoff is completed, not a method of determining the search window parameter value of a specific pilot according to the handoff type.

The algorithm to be performed for each handoff type will be described.

First, in a handoff in an ad situation, the mobile terminal compares the search window size value of the pilot to be added with the existing search window size value before performing the handoff, and compares the value of the pilot search window size value of the pilot with the mobile terminal. The size of the search window is determined and transmitted to the terminal through the EHDM (or UHDM).

In addition, during a handoff in a drop situation, the call control processor receiving the pilot strengths of the base stations due to the movement of the mobile terminal compares the search window size values of the remaining active pilots except the drop pilot, and compares the largest search window. The size is compared with the existing search window size value before the handoff is performed (before the drop), and a large value is determined as the search window size and transmitted to the terminal through the EHDM (or UHDM).

The handoff in the swap situation is automatically determined by the search window size due to the ad and drop cases.

4 is a flowchart illustrating a method for determining a search window size of a mobile terminal during handoff according to an exemplary embodiment of the present invention.

First, it will be described under the condition that the search window size value before performing the handoff is the same as the previous search window size value due to the movement of the mobile terminal.

The call control processor receives the PSMM from the mobile terminal (S401), recognizes the handoff occurrence and confirms whether a drop pilot exists (S402), and if the drop pilot exists, activates the active pilots except the drop pilot. The largest value of the search window size is determined (S403).

Thereafter, when the drop pilot does not exist or after the largest search window size value is determined among the active pilots, it is checked whether the ad pilot exists (S404). As a result of the check, if the ad pilot exists, the search window size value of the ad pilot is compared with the determined search window size value when the drop pilot exists, and a large value is determined as the search window size of the mobile terminal, and the EHDM (or UHDM) is determined. If the ad pilot exists, the search window size value of the ad pilot is compared with the existing search window size value before handoff when the drop pilot is not present. The search window size of the mobile terminal is determined (S405).

In the case of using the EHDM, various parameters including the search window size are lowered together through the ITSPM at the end of the handoff. Since some parameters cannot be supplied with EHDM messages, they are finally given through ITSPM.

In addition, when using UHDM, since all parameter information necessary for handoff is included, there is no need to lower ITSPM separately. Therefore, the search window size value is also lowered through the UHDM at the time of progress rather than completion.

As such, the call control processor updates and manages pilot information in the handoff database in the call control processor at the time when the handoff proceeds and completes, and changes the environment when there are changes in the active pilots at the time of performing the new handoff. The larger value is determined by comparing with the existing value to determine the search window size value.

 According to the method of determining a search window size of a mobile terminal during handoff according to the present invention, the terminal transmits an optimal search window size value to the terminal at an optimal time according to the movement of the mobile terminal in order to improve call quality of the mobile terminal. By improving the handoff success rate and reducing the possibility of truncation, an improvement in call quality can be expected. In addition, when all handoff direction messages (HDM) are transmitted, a search parameter value of a specific pilot according to the handoff type is determined. Rather, it is possible to determine an optimal search parameter value in consideration of ad handoff, drop handoff, and swap handoff situations when the handoff is completed.

1 is a flow chart showing a conventional soft handoff processing method.

Figure 2 is a flow chart showing a problem that may occur when the handoff by the add of the conventional base station.

3 is a flow chart illustrating a problem that may occur during handoff due to drop and swap of a conventional base station.

4 is a flowchart illustrating a method for determining a search window size transmitted to a mobile terminal during handoff according to the present invention.

Claims (3)

A method for determining a search window size value delivered according to a handoff of a mobile terminal, When the mobile terminal completes the handoff, after checking whether the drop pilot exists, and if the drop pilot exists, comparing the window size values of the active pilots except the drop pilot to determine a large value as the window size. ; Confirming whether the ad pilot exists; Comparing the search window size value of the ad pilot with the determined search window size value of the active pilot if the ad pilot exists, and as a result, determining a search window size having a large window size and transmitting the search window size to the terminal; A method for determining the search window size of a mobile terminal during handoff. The method of claim 1, When the handoff of the mobile terminal is completed, when the drop file does not exist, the search window size value of the existing active pilot before handoff and the search window size value of the pilot to be added are compared. The search window size determination method of a mobile terminal in handoff, characterized in that the value is determined as a search window size and transmitted to the terminal. The method according to claim 1 or 2, The determined search window size value is transmitted to a corresponding terminal through an Extended Handoff Direction Message (EHDM) or a Universal Handoff Direction Message (UHDM) .