KR20110050359A - Method of broadcasting system information of neighbour base stations - Google Patents

Abstract

PURPOSE: A transmission method of the neighboring base station system information is provided to obtain system information of a neighboring station filled with corresponding segment based on system information of a corresponding reference base station. CONSTITUTION: A priority base station select a reference base station for writing a message about system information of a neighboring base station(S100). The base station configures a broadcasting message(S110). The broadcasting message includes only a system parameter using a different value with a reference base station of corresponding segments as a system information of neighboring base station. The base station broadcasts the configured neighbor base station broadcasting message(S120).

Description

Method of Broadcasting System Information of Neighbor Base Stations {Method of Broadcasting System Information of Neighbor Base Stations}

The present invention relates to wireless communication, and more particularly, to a method for transmitting system information of a neighbor base station in a mobile communication terminal and a mobile communication base station.

In order for a mobile communication terminal (hereinafter, referred to as a "terminal") to access a mobile communication base station (hereinafter, referred to as a "base station") and perform communication, the terminal should acquire system information of the base station.

However, when handing over between base stations, if system information of the target base station is acquired after the connection between the terminal and the base station is switched from the serving base station to the target base station, the service delay time until the terminal acquires the system information Will be created.

In order to prevent this, the prior art transmits the neighbor base station broadcast message (AAI-NBR-ADV) as a message containing the system information of the neighbor base station so that the terminal acquires the system information of the neighbor base station before handover.

Table 1 shows the format of a neighbor base station broadcast message used in the prior art.

Syntax Notes AAI_NBR-ADV () {   N_Cell_Type Number of neighbor cell types   N_Fragmentation Number of total fragment of NBR-ADV Cell type
Cell type of neighbor ABSs included in this fragment   Fragment Index Index of this fragment   N_ABSs Number of ABSs included in this message   For (i = 0; i <N_ABSs; i ++) {     ABS ID     ABS Index Index of this ABS     SFH encoding format 0b00: sub-packet information
0b01: delta encoding
0b10: no sub-packet information
0b11: reserved     Control bitmap     If (SFH encoding format == 0b00) {       If (Control bitmap [0] = 1) {         SFH Sub-packet 1       }       If (Control bitmap [1] = 1) {         SFH Sub-packet 2       }       If (Control bitmap [2] = 1) {         SFH Sub-packet 3       }     }     If (SFH encoding format == 0b01) {       Delta information Delta encoding with respect to the reference ABS     }   } }

As shown in Table 1, the neighbor BS broadcast message may be fragmented into several segments, and may include various types of BS information such as macro cells, micro cells, femto cells, as well as BSs of the same type. .

The system information of each neighboring base station is represented by a total of three methods as follows by a parameter called an SFH encoding format.

1) Sub-packet information: Three subpackets transmitted by SFH are selectively included in the neighbor base station broadcast message. In this case, all parameters in each sub packet are included in the neighbor base station broadcast message.

2) Delta encoding: Only different information among the system information of the serving base station or neighboring base station included in the neighboring base station broadcast message transmitting the neighboring base station broadcast message and the system information of the current neighboring base station is selectively added to the neighbor base station broadcast message. Included.

3) No sub-packet information: Does not include system information about the current base station.

In the prior art, in order to reduce the size of a neighbor BS broadcast message, a method including only a system parameter having a value different from that of a serving BS or a neighbor BS immediately before is supported.

In a scheme in which a neighbor base station broadcast message includes only system parameters having a value different from that of a serving base station, for example, if the serving base station is a macro cell and one of the neighbor base stations is a femto cell, the two base stations share values of many parameters with each other. It can be set differently. In this case, since many of the parameters of the neighbor base station, which is a femto cell, are different from those of the serving base station, which is a macro cell, many system parameters of the neighbor base station should be included in the neighbor base station broadcast message.

As described above, in a system supporting different types of neighbor base stations, the size of the neighbor base station broadcast message increases because many parameters having different values must be included.

In order to prevent this, a scheme of selectively including only system information and other parameters of a previous neighboring base station in a neighboring base station broadcast message may be used.

However, in this method, since all neighbor base stations included in the neighbor base station broadcast continuously refer to previous neighbor base stations, the process for acquiring all system parameters of one neighbor base station is complicated, and the time until acquiring the system parameters is complicated. There is a problem that takes a lot. For example, if there are four neighboring base stations A, B, C, and D, each base station is based on a neighboring previous base station, i.e., base station B is based on base station A, base station C is on base B, and The D base station should determine whether to include the system parameters based on the C base station.

Therefore, in order to determine whether to include the system parameters of the base station D, the transmitting side should acquire the system parameters of the base station C, and the system parameters of the base station B, and furthermore, the base station A in relation to the parameters of the base station C, have a lot of time. Not only does it take, but it also goes through a complicated process. In addition, in order to obtain all the system information of the base station D, the receiving side must extract all parameter values for the base station C based on the base station A and the base station B, and then extract the parameters of the base station D based on this.

That is, considering a system in which there are many adjacent femto cells around a macro cell, the process of extracting system information becomes more complicated as the number of neighbor base stations increases.

Furthermore, neighboring base station broadcast messages are fragmented when transmitted and transmitted for each segment. Therefore, it is difficult to obtain accurate system information of all neighbor base stations until all segments of the neighbor base station broadcast message previously transmitted are obtained.

In addition, fragmentation is performed for each cell type, and when a broadcast transmission cycle is changed for each fragmented segment, a time for acquiring system information of a specific neighboring base station becomes long.

This allows the handover to be performed without system information, eventually increasing the service downtime that occurs during the handover.

The present invention is to provide a method for a base station to create and transmit the system information of the neighboring base station so that the terminal can effectively use the system information of the neighboring base station irrespective of the difference in configuration requirements between neighboring base stations.

The present invention provides a method for transmitting system information of an adjacent base station from the base station.

The present invention includes the steps of dividing a fragment of a neighboring base station broadcast message into segments (fragmentation) and transmitting a neighboring base station broadcast message fragmented into segments to the terminal, the segment includes information of the reference base station selected for each segment, The system information of each neighboring base station included in the segment includes only parameters using values different from those of the reference base station.

Each segment includes information of the reference base station, and based on the system information of the reference base station, the system information of the neighboring base station described in the segment can be obtained. Therefore, even if all the segments are not received, the neighboring base station described in the received segment System information can be obtained.

In addition, in order to obtain accurate system information of each neighboring base station, since only the system information of the reference base station referenced by the neighboring base station needs to be obtained, the conventional method of acquiring all neighboring base station information previously transmitted to obtain the system information of the specific neighboring base station. Compared with the technique, the acquisition time of neighboring base station information is shortened.

By selecting a different reference base station by a specific base station type, by a specific base station group or by each individual base station, and including only system parameters using values different from the selected reference base station in the neighbor base station broadcast message, the overhead of the neighbor base station broadcast message is reduced. Can be reduced.

When several types of base stations are mixed, such as when a large number of femto cells exist around a macro cell, the effect according to the present invention is further increased.

1 is a block diagram illustrating a wireless communication system.
2 shows an example of a frame structure.
3 is a flowchart illustrating a method of transmitting neighbor base station information according to the present invention.

The following technologies include Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier-Frequency Division Multiple Access (SC-FDMA), and the like. Such as various wireless communication systems.

CDMA may be implemented with a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data rates for GSM Evolution (EDGE). OFDMA may be implemented in a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA). UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) long term evolution (LTE) is part of an Evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink.

1 is a block diagram illustrating a wireless communication system. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

Referring to FIG. 1, a wireless communication system includes a user equipment (UE) 10 and a base station 20 (BS). The terminal 10 may be fixed or mobile, and various terms such as mobile station (MS), advanced mobile station (AMS), user terminal (UT), subscriber station (SS), and wireless device (wireless device) may be used. do.

The base station 20 generally refers to a fixed station communicating with the terminal 10, and includes an advanced base station (ABS), a node-b (node-b), a base transceiver system (BTS), and an access point ( Various terms such as Access Point may be used. One or more cells exist in one base station 20.

Hereinafter, downlink (DL) means communication from the base station 20 to the terminal 10, and uplink (UL) means communication from the terminal 10 to the base station 20. In downlink, the transmitter may be part of the base station 20 or the base station 20 and the receiver may be part of the terminal 10 or the part of the terminal 10. In uplink, the transmitter may be a terminal 10 or a part constituting the terminal 10 and the receiver may be a base station 20 or a part constituting the base station 20.

For clarity, the following description focuses on IEEE 802.16m, but the technical spirit of the present invention is not limited thereto.

2 shows an example of a frame structure.

Referring to FIG. 2, a superframe includes a superframe header (SFH) and four frames (F0, F1, F2, F3), and each frame includes eight subframes (SF0). , SF1, SF2, SF3, SF4, SF5, SF6, SF7). In the case of using a superframe, the transmission period of control information that does not need to be transmitted frequently can be increased in units of superframes, thereby increasing the efficiency of transmission. In addition, data allocation and scheduling are most frequently performed in subframe units, thereby reducing delay characteristics of data transmission considering a retransmission mechanism. The size of each superframe is 20ms and the size of each frame is illustrated as 5ms, but is not limited thereto.

The superframe header may be placed at the front of the superframe, and a common control channel is assigned. The common control channel is a channel used for transmitting control information that can be commonly used by all terminals in a cell, such as information on frames or system information of a superframe.

Each subframe may be used for uplink transmission or downlink transmission. The subframe may consist of 6 or 7 OFDM symbols, but this is only an example. Time division duplexing (TDD) or frequency division duplexing (FDD) may be applied to the frame.

In TDD, each subframe is used in uplink or downlink at different times at the same frequency. That is, subframes in the TDD frame are divided into an uplink subframe and a downlink subframe in the time domain.

In FDD, each subframe is used in uplink or downlink at different frequencies at the same time. That is, subframes in the FDD frame are divided into an uplink subframe and a downlink subframe in the frequency domain. Uplink transmission and downlink transmission occupy different frequency bands and may be simultaneously performed.

3 is a flowchart illustrating a method of transmitting neighbor base station system information according to the present invention.

Referring to FIG. 3, first, a base station selects a reference base station to compose a message regarding system information of a neighboring base station (S100). An example of a message related to system information of a neighbor base station is a neighbor base station broadcast message (AAI-NBR-ADV). Hereinafter, a method of transmitting a neighbor base station broadcast message will be described as an embodiment of the present invention.

A reference base station (reference ABS) is a base station for comparison when determining whether to include a corresponding parameter of a neighboring base station in a message by comparing parameters to create system information of neighboring base stations. That is, the operation of determining whether the system parameter of the neighboring base station is a system parameter using a different value from the reference base station is performed using the reference base station information included in the neighbor base station broadcast message.

The neighbor base station broadcast message may be fragmented and transmitted to the terminal, and is generally transmitted by broadcasting. In the present invention, the neighbor base station broadcast message includes the information of the reference base station for each segment. The reference base station is also selected for each segment.

In the present invention, the reference base station information for determining whether to include the system parameters of each neighboring base station in order to encode the system information of the neighboring base station is further informed for each segment of the neighboring base station broadcast message transmitted, so that it is different from the system information of the reference base station. Only information is included in the neighbor base station broadcast message.

A method of including and using the reference base station information for each segment will be described in detail.

If each segment includes all the information of the reference base station and includes only the system parameters of the neighboring base station having a different value from the system information of the reference base station, the terminal does not receive the entire neighboring base station broadcast message, System information of the neighbor base station described in the segment may be obtained through the information of the reference base station included in the segment.

If each segment includes the indicator of the reference base station as information of the reference base station, if only the segment including the reference base station indicated by the reference base station indicator (reference ABS index) of the segment received by the terminal is received, the adjacent base station broadcast Even if the entire message is not received, the system information of the neighboring base station included in the received segment can be obtained from the system information of the reference base station included in the additionally received segment.

In addition, when the reference base station is selected from a list of neighboring base stations included in the corresponding segment, system information of the neighboring base stations included in the segment can be obtained using only the received segment without additionally receiving another segment. .

With regard to selecting a reference base station, the reference base station may be selected for a specific base station type, a specific base station group, or for each individual base station. For example, when a reference base station is selected for each specific base station type, neighboring base stations may be grouped by each type to select reference base stations for macro base stations and reference base stations for femtocells.

Of course, the reference base station may have a different value for each segment, or may select among neighboring base stations of the segment.

A broadcast message including only system parameters using values different from the reference base station of the corresponding segment as system information of the neighboring base station is configured (S110), and the neighboring base station broadcast message thus configured is broadcasted (S120).

Determining whether a system parameter using a value different from that of the reference base station is performed by using the reference base station indicator included in the neighbor base station broadcast message.

Table 2 below schematically shows a first embodiment of a method for transmitting system information of a neighbor base station proposed by the present invention. In this embodiment, a reference base station indicator (reference ABS index) is included as reference base station information in a neighbor base station broadcast message.

Syntax Notes AAI_NBR-ADV () {   N_Cell_Type Number of neighbor cell types   N_Fragmentation Number of total fragment of NBR-ADV   Cell type Cell type of neighbor ABSs included in this fragment   Fragment Index Index of this fragment   Reference ABS index the index of the reference BS for delta encoding of system information of neighbor ABSs included in this fragment   N_ABSs Number of ABSs included in this message   For (i = 0; i <N_ABSs; i ++) {     ABS ID     SFH encoding format 0b00: sub-packet information
0b01: delta encoding
0b10: no sub-packet information
0b11: reserved     Control bitmap     If (SFH encoding format == 0b00) {       If (Control bitmap [0] = 1) {         SFH Sub-packet 1       }       If (Control bitmap [1] = 1) {         SFH Sub-packet 2       }       If (Control bitmap [2] = 1) {         SFH Sub-packet 3       }     }     Else {       Delta information Delta encoding with respect to the ABS of which index is equal to Reference ABS index     }   } }

As shown in Table 2, in this embodiment, a reference base station indicator (reference ABS index) is included in each segment of a neighbor base station broadcast message, so that the specific base station indicated by the reference base station indicator for all neighbor base stations included in the currently transmitted segment. It only includes parameters that use different values based on the system information.

The reference base station indicator is included for every segment and does not have to have the same value. For example, if one segment includes only base stations supporting a macro cell and the other segment includes only base stations supporting a femto cell, each reference base station indicator represents a macro cell and a femto cell for each segment. It may have an indicator value of the base station.

As can be seen from Table 2, in this embodiment, neighboring base stations included in each segment have one common reference base station indicator.

Therefore, even if the neighboring base station broadcast message is fragmented into several segments, if only the segment including the base station indicated by the reference base station indicator can be received, all segments, i.e., all of the neighboring base stations described in the segment, are not received. System information can be obtained.

Furthermore, if the segment contains all the necessary system information of the reference base station, not just the reference base station indicator, or if the reference base station is selected from the neighbor base stations in the segment, all neighbor base station systems in the segment, even if only that segment is received. Information can be obtained.

When fragmentation is performed for each cell type of a neighbor base station or when a common system parameter is used for a specific group of base stations, a parameter using different values between the reference base station and neighbor base stations is reduced, so that the overhead of the neighbor base station broadcast message is reduced. Greatly decreases.

Table 3 below schematically shows a second embodiment of a method for transmitting system information of a neighbor base station proposed by the present invention. Also in this embodiment, a reference base station indicator (reference ABS index) is included as reference base station information in a neighbor base station broadcast message.

Syntax Notes AAI_NBR-ADV () {   N_Cell_Type Number of neighbor cell types   N_Fragmentation Number of total fragment of NBR-ADV   Cell type Cell type of neighbor ABSs included in this fragment   Fragment Index Index of this fragment   N_ABSs Number of ABSs included in this message   For (i = 0; i <N_ABSs; i ++) {     ABS ID     SFH encoding format 0b00: sub-packet information
0b01: delta encoding
0b10: no sub-packet information
0b11: reserved     Control bitmap     If (SFH encoding format == 0b00) {       If (Control bitmap [0] = 1) {         SFH Sub-packet 1       }       If (Control bitmap [1] = 1) {         SFH Sub-packet 2       }       If (Control bitmap [2] = 1) {         SFH Sub-packet 3       }     }     Else {       Reference ABS index the index of the reference BS for delta encoding of system information of this neighbor ABS       Delta information Delta encoding with respect to the ABS of which index is equal to Reference ABS index     }   } }

As can be seen from Table 3, in this embodiment, a reference base station is selected for each neighboring base station to determine whether to include system parameters based on different base stations for each neighboring base station, and the reference base station indicator is included in the neighbor base station broadcast message. .

Each neighboring base station can have the reference base station selected as the most suitable for itself by selecting a reference base station having the most parameters using the same value. Therefore, the size of the entire neighbor base station broadcast message is optimized.

In order to obtain the system information of a specific neighboring base station, all the segments of the neighboring base station broadcast message, that is, even if the entire base station broadcast message is not received, only the segment of the neighbor base station broadcast message including the reference base station indicator for the neighboring base station is received. System information of a neighbor base station can be obtained.

Table 4 below schematically shows a third embodiment of a method for transmitting system information of a neighbor base station proposed by the present invention. The information of the reference base station is also included in the form of an index.

Syntax Notes AAI_NBR-ADV () {   N_Cell_Type Number of neighbor cell types   N_Fragmentation Number of total fragment of NBR-ADV   Cell type Cell type of neighbor ABSs included in this fragment   Fragment Index Index of this fragment   N_ABSs Number of ABSs included in this message   For (i = 0; i <N_ABSs; i ++) {     ABS ID     Reference ABS index If this is set to 0xFF, then there is no reference ABS for SFH encoding. Therefore, all SFH information of this ABS shall be included in this message     Control bitmap     If (Reference ABS index == 0xFF) {       If (Control bitmap [0] = 1) {         SFH Sub-packet 1       }       If (Control bitmap [1] = 1) {         SFH Sub-packet 2       }       If (Control bitmap [2] = 1) {         SFH Sub-packet 3       }     }     Else {       Delta information Delta encoding with respect to the ABS of which index is equal to Reference ABS index     }   } }

In this embodiment, information on how to include system information of each neighboring base station in the neighboring base station broadcast message is indicated using a specific value of the reference base station indicator.

Each neighboring base station includes a reference base station indicator for reference, and if the value is 0xFF, it means that there is no base station to refer to. Since there is no base station to refer to, it is not possible to indicate whether a parameter is omitted, so system information of a neighbor base station is represented by parameters of an SFH encoding format.

If the values of system parameters between neighboring base stations do not differ significantly, most of them operate to include only system parameters having different values based on a specific base station in order to reduce the size of the neighbor base station broadcast message.

In this case, only the addition of the reference base station indicator can perform operations when the SFH encoding format and the reference base station indicator are added, which is advantageous in terms of overhead.

According to the configuration of the present invention, the neighboring base station broadcast message is selected because a different reference base station is selected for a specific base station type, a specific base station group, or each individual base station, and only the system parameters using values different from the selected reference base station are included in the neighbor base station broadcast message. This can reduce the overhead of the message.

In addition, in order to obtain accurate system information of each neighboring base station, since only the system information of a reference base station referenced by the neighboring base station needs to be acquired, all conventional neighboring base station information obtained in order to acquire system information of a specific neighboring base station is acquired. Compared with the technique, the acquisition time of neighboring base station information is shortened.

Unlike macro cells, femto cells are densely installed because of their small cell coverage, and if the neighboring base station cells to be transmitted have a plurality of femto cells mixed around the macro cell, the number of transmissions is increased due to the densely installed femto cells. It's possible. Therefore, in the conventional technology of acquiring information of all neighboring base stations previously transmitted in order to obtain system information of neighboring base stations, when multiple femto cells are mixed around a macro cell, the time-saving effect of obtaining system information according to the present invention is reduced. Becomes bigger.

Although the neighboring base station broadcast message is described as an example of a message regarding the system information of the neighboring base station for easy description, in the present invention, the message about the system information of the neighboring base station is not limited to the neighboring base station broadcast message (AAI-NBR-AVD). And may be applied to various information messages including system information of neighboring base stations.

In addition, the message about the system information of the adjacent base station is generally transmitted by broadcasting, but the message transmission method of the present invention is not limited thereto and may be performed by various transmission methods.

Claims (1)

A method for transmitting system information of a neighbor base station from a base station,
Fragmenting a neighbor base station broadcast message into segments; And
Transmitting the neighbor base station broadcast message fragmented into segments to a terminal;
The segment includes information of the reference base station selected for each segment,
The system information of each neighboring base station included in the segment includes only a parameter using a value different from the system information of the reference base station.

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