KR20100115004A - A handoff access method and device based on random access channel - Google Patents

Abstract

PURPOSE: A method and a device for connecting handover based on a random connection channel are provided to not start the same handover connection message to the same time slot in the same random connection sub channel in a situation where the assignment of a specific code in a terminal which requires a handover connection in a wireless interface, thereby avoiding a collision between handoff access messages. CONSTITUTION: A target BS(Base Station) transmits a handoff response message to a source BS(S704). A mobile terminal checks a random number of specific codes in a handoff command message after receiving handoff command message. The mobile terminal selects a specific code and random access sub channel corresponding to the specific code(S706). The target BS starts a handoff access process in the mobile terminal and the random access sub channel(S708).

Description

A handoff access method and device based on random access channel

The present invention relates to the field of communications, and more particularly, to a method and apparatus for handoff access based on a random access channel.

As shown in FIG. 1, a cellular wireless communication system mainly includes a terminal, a wireless access network, and a core network.

In a cellular wireless communication system, the terminal needs to send a message of random access through one uplink public channel before starting communication with the network.

This public channel is called a random access channel.

The primary purpose of random access is to occupy limited radio channel resources in a competing manner and sometimes to obtain uplink synchronization information.

The uplink synchronization information is used when the terminal determines when to send an uplink signal, so that the uplink signal falls within the signal reception time window of the base station receiver.

In a cellular wireless communication system, channels are divided through various available multiple access technologies such as code division, frequency division, and time division, and the minimum unit of each channel in the time domain is a frame.

A random access frame or a combination of frames is called a random access time slot, and random access time slots of the same channel constitute a random access subchannel in a manner.

In FIG. 2, nine channels are configured with three frequency carriers and three channel codes, and for example, channels are configured with No. 2 frequency carriers and No. 2 channel codes.

In each of the six frames of the channel, one frame is used as a random access time slot, and the time interval between random access time slots is 5 frames, and one random access subchannel is configured in the channel.

Since a random access subchannel is also assigned to a channel composed of a number 1 frequency carrier and a number 1 channel code, there are two random access subchannels in the cell.

The data rate of the message itself is very low to ensure the effective coverage of the original random access message. In other words, the information bits that can be contained are limited. For example, in the Long Term Evolution (LTE) system currently discussed in the 3GPP (3rd Generation Mobile Partnership Project), any time slot consisting of an asynchronous single frame (1 ms) loads information that does not exceed 10 bits. can do.

The information bits in such random access messages are generally indicated by sequence numbers of feature codes with high self correlation. In one random access time slot, the wireless access network can distinguish random access messages containing different feature codes.

Therefore, a collision occurs only when two random access messages including the same feature code are simultaneously received in the same random access time slot. Due to the collision, the wireless access network cannot distinguish between individual terminals, that is, the effect is the same as that of receiving a connection request from only one terminal from the wireless access network.

Under these circumstances, it is necessary to ensure successful connection of one terminal between the terminal and the radio access network through an additional conflict resolution mechanism.

The failed terminal is again connected to the wireless network through the contention scheme. Sometimes, due to the collision, a connection failure of all the collided terminals may be brought.

The initial connection process starting from the idle state as described above is one cause of the random access process. Another important cause is the handoff access procedure between base stations.

In the communication process between the terminal and the network, when the terminal moves between different cells, it is necessary to maintain the communication by switching radio channels. If the target cell and the source cell are located in different base stations, the handoff-enabled method prepares the radio channel resources in the handoff preparation phase first and accesses the radio channel already allocated by the target base station through the source base station. Notify the terminal to do so. This approach is very effective for systems based on dedicated radio channel resources, for example GSM (Global Mobile Communication Systems).

However, in a wireless communication system based on a shared channel, for example, LTE, the handoff scheme increases the complexity of the system and lowers the utilization rate of radio channel resources. This is because the source base station must take control of the time difference with the target base station in the step of starting the handoff so that the terminal can notify the start time reasonable to access the target base station. In addition, it is difficult to control the exact time difference, and the wireless access network must obtain the time difference by using a relatively complicated mechanism. In addition, the transmission time of the message in the wireless access network or the wireless interface is indeterminate, and it is very difficult to leave shared radio channel resources at the target base station. It may miss connection time or cause unexpected delays. Therefore, in general, extra radio channel resources are left to ensure a smooth handoff, thereby lowering the utilization of radio resources. Therefore, in general, a handoff scheme that does not leave radio channel resources is used. That is, the terminal obtains radio channel resources through a competitive random access scheme in the target base station. With the development of cellular wireless communication system technology, the time required for the random access procedure is very short, for example, about 20 ms in the LTE system.

When a terminal in communication moves between cellular networks, it is necessary to ensure continuity of communication through means of handoff and the like. In general, other channels except the public channel use a shared channel mechanism and arrange uplink radio resources in a wireless access network.

The delay in which the terminal is connected to the wireless access network through the random access scheme is very important even for all connection causes. Relatively, however, there is a greater demand for delay in access handoff in cellular wireless communication systems, i.e., time delay in handoff interruption. When the terminal moves between cellular, the most important and most direct cause of the handoff is that the signal of the original serving cell has already fallen into a dangerous state. If the radio channel is not immediately switched to a cell with a good signal, the communication quality of the terminal will be drastically lowered, even if the call is cut off and interrupted. In terms of the terminal, even the same delay is very different from starting in the idle or inactive state and starting in the work activity state. The terminal is more sensitive to the latter. The delay of the random access procedure is mainly caused by the above-mentioned "collision" phenomenon. This is because only one terminal can be connected to the wireless network due to a collision. This is because all terminals in collision may fail. This is because the delay has already occurred even if the failed terminal is connected again. Due to the importance of the handoff connection, a method of eliminating the collision probability when the terminal switches the connection is needed.

Accordingly, there is a need for a handoff connection solution for a cellular wireless communication system that can solve the above problem.

It is an object of the present invention to provide a method and apparatus for handoff access based on a random access channel in order to solve the problem of not distinguishing the importance of handoff access in the related art.

One aspect of the present invention provides a method of handoff connection based on a random access channel used for handoff connection of a mobile terminal in a cellular mobile communication system, the method comprising the steps of: a, The source base station sends a handoff request message to the target base station requesting to switch the mobile terminal it is providing service to the target base station, step b, the target base station sends a handoff response message to the source base station, and the source base station The mobile station sends the content of the handoff response message included in the handoff command to the mobile station, wherein the handoff command message includes the sequence number of the pre-signed feature code assigned to the mobile station by the target base station and the random access of the pre-signed feature code. Sub-channels are included and feature codes left in advance are handed off Is a random access feature code left for the mobile terminal only, step c, after receiving the handoff command message, the mobile terminal checks the sequence number of the remaining feature code included in the handoff command message, In step d, the target base station starts the handoff access procedure in the mobile station and the random access subchannel.

Another aspect of the present invention provides a handoff access apparatus based on a random access channel used for handoff access of a mobile terminal in a cellular mobile communication system, the apparatus comprising: providing a source base station with its own service. A handoff claim module for sending a handoff request message to the target base station, the target base station sending a handoff response message to the source base station, wherein the source base station sends a handoff response message to the target base station; A handoff response module for sending a handoff command to the mobile terminal, wherein the handoff command message includes a sequence number of a pre-signed feature code assigned to the mobile terminal by the target base station and a pre-signed feature code; Random access subchannels are included and left ahead The long feature code is some random access feature code left in advance for the mobile terminal to be handoffed and identifies the sequence number of the feature code left in the handoff command message after the mobile terminal receives the handoff command message. A subchannel selection module for selecting a random access subchannel in which a feature code left in advance and a feature code left in advance are located, and a handoff access for causing a target base station to start a process of handoff access in a random access subchannel with a mobile terminal. Contains modules

Through the above technical solution, the present invention realizes the following effects:

According to the method according to the present invention, even when the terminal requesting the handoff connection at any time in the air interface is assigned a feature code, the terminal does not start the same handoff connection message in the same time slot of the same random access subchannel. Conflicts between handoff access messages are avoided and duplication can be avoided when the handoff access messages verify the identity of the terminal on the radio access network side.

Referring to the drawings below, the present invention will be described in detail in combination with the embodiments.

The present invention provides a method and apparatus for handoff access based on a random access channel.

3 is a handoff flowchart for assigning a feature code left in advance for a handoff connection by a cellular mobile communication system.

The handoff process is described below:

In step S302, the terminal sends a measurement report including the measurement information of the neighbor cell to the source base station providing the service.

The source base station analyzes the measurement report sent from the terminal and combines it with the radio resource management information placed in the terminal to determine whether to switch the terminal from the coverage of the base station.

If you decide to switch from the source base station, select the target base station to switch to.

In step S304, the source base station broadcasts a handoff request message including a context related to the terminal stored in the source base station to the target base station.

In step S306, the target base station allocates a temporary identification number to the terminal after preserving the context.

The target base station also allocates the feature code previously left in the terminal.

The handoff response message sent to the source base station includes the sequence number of the feature code left in advance and information on the random access subchannel where the feature code is located.

This information corresponds to the temporary identification number assigned to the terminal.

In step S308, the source base station sends a handoff command message including the sequence number of the pre-remained feature code allocated to the terminal through the air interface, the random access subchannel information where the feature code is located, and the temporary identification number of the terminal.

In step S310, after receiving the handoff command message, the terminal sends a random access message in the random access subchannel specified in the message and uses the left feature code specified in the random access message.

In step S312, after receiving the random access message, the target base station determines that the feature code used in the message is a handoff connection without collision if the feature code is left in advance. The identification of the terminal is then confirmed based on the sequence number of the feature code and the information of the random access subchannel that received the random access message. Then, feedback information, such as uplink synchronization information and uplink radio channel resources, is fed back to the terminal through the handoff access response message.

In step S314, the terminal sends a handoff completion message after receiving the handoff access response message.

The LTE system currently discussed in this field is a typical cellular wireless communication system.

As shown in FIG. 4, the system is composed of a terminal, a base station and a core network, and whether there is a logical or physical connection between the base stations is determined according to the network demand for mobility management.

All base stations are connected to the core network. A radio access network is formed with all base stations connected to the core network, and uplink / downlink radio resource management is based on the idea of all channel sharing and is controlled by the base station.

The Long Term Evolution (LTE) system configures a channel in the frequency domain. As shown in FIG. 5, four frequency bands constitute four channels.

Frames used for random access on a channel are called random access time slots, and random access time slots having fixed intervals on one channel constitute a random access subchannel.

The terminal sends a random access message in the uplink random access subchannel when switching between the initial access, uplink synchronization, uplink resource request, or the base station. Information bits loaded in the message are indicated by sequence numbers of highly correlated feature codes. do.

First embodiment

In one LTE system, if there are two random access subchannels in one cell, the time slot has a 10 ms time interval, and 64 feature codes (that is, 6 information bits are displayed) within one time slot, a 1 second random access opportunity In total, 2x100x64, or 12,800.

The time that the LTE system completes one handoff, that is, the time from the assignment of the feature code left in advance until the terminal is switched to the target base station is 50 ms.

The percentage of handoff connections in the cell is 37.5%, leaving a total of 24 feature codes.

When busy, there are 3000 terminals in the cell, and the number of random access starts every second, of which 12 are handoff access claims.

If the law of arrival of random access matches the Poisson distribution, the collision occurrence probability seen from all terminal angles at random access is 0.25% unless the feature code is left in advance. Among them, a handoff terminal is included.

If 24 feature codes are left in advance, there are 20 random access claims per second, 40 feature codes are shared, and the probability of collision is also 0.25%.

However, 12 handoff access claims can use the 24 feature codes left in advance and no conflicts will occur. In other words, the probability of collision is 0%.

Second embodiment

In the present embodiment, cell 1 of the target base station has two random access subchannels, and each subchannel has 64 feature codes, of which 40 to 63 feature codes are reserved for handoff.

As shown in FIG. 6, the handoff process of the feature code left in advance includes the following steps:

In step S602, the terminal A performs measurement on the neighboring cell based on the measurement control information sent from the base station, and then sends the measurement result to the base station providing the service, that is, the source base station through the measurement report.

In step S604, the source base station determines to switch terminal A to cell 1 of the target base station and sends a handoff request message including the context of the source base station terminal to the target base station.

In step S606, the target base station allocates a 16-bit temporary identification number to the terminal A, the value of which is ox6382, and allocates a feature code left in advance of the first random access subchannel of cell 1, the sequence number of which is 45, The temporary identification number, the pre-assigned feature code to be assigned, and the random access subchannel to be located are individually corresponded.

Thereafter, the target base station sends a handoff response message including the temporary identification number of the terminal A, the sequence number 45 of the feature code, and the information of the first random access subchannel.

Step S608, the source base station transmits the temporary identification number received in the handoff response message, the feature code sequence number, the information of the first random access subchannel of the cell 1, and the target base station through the handoff command on the air interface. Other related descriptive information is sent to the terminal A.

In step S610, the terminal A sends a random access message in the first random access subchannel of the cell 1 of the target base station after receiving the handoff command message, and edits the feature code having sequence number 45 in the message.

Step S612, the target base station determines that the terminal is performing a handoff connection based on the sequence number of the received feature code, and then based on the first random access subchannel information located with sequence number 45 of the feature code. To the terminal A with the temporary identification number ox6382.

The target base station then sends a handoff access response message including synchronization information and uplink resource information from the logical dedicated channel to the terminal A.

Sending of messages can also use HARO technology to improve the safety of sending messages.

In step S614, the terminal A sends a handoff completion message after receiving the handoff access response message.

From the above description it can be seen that according to the present invention the following effects can be obtained:

According to the method according to the present invention, even if the terminal requesting the handoff connection at any time in the air interface is assigned a feature code, the terminal does not start the same handoff connection message in the same time slot in the same random access subchannel. Conflicts between handoff access messages can be avoided, and handoff access messages can be avoided to have duplexity when verifying the identity of the terminal on the radio access network side.

It will be appreciated by those skilled in the art that each module or step of the present invention may be realized through a general computing device, may be concentrated in one computing device, or may be distributed in a network composed of a plurality of computing devices.

In addition, each module or each step of the present invention may be realized through a program code that can be executed by the computing device.

Therefore, each module or each step may be stored in a memory device and executed by a calculation device, or may be manufactured as an integrated circuit module, or a plurality of modules or steps may be manufactured as a single integrated circuit module.

As described above, the present invention is not limited to any specific combination of hardware and software.

In addition, if the technical personnel in the field that can bring a change in the embodiment is clear and does not exceed the protection scope of the present invention.

The description is not intended to limit the invention to the preferred embodiments of the invention.

Those skilled in the art can bring various developments and changes to the present invention.

All the number, equivalent replacement, improvement, etc. which are performed in the situation which does not deviate from the mind and principle of this invention are all within the protection scope of this invention.

7 is a flow chart of a handoff access method based on a random access channel according to the present invention, comprising the following steps:

 In step S702, a handoff request message is sent from the source base station to the target base station to request that the mobile terminal providing the service switch to the target base station.

In step S704, when the target base station sends the handoff to the source base station, the source base station sends the content of the handoff response message included in the handoff command to the mobile terminal, wherein the handoff command message is sent from the target base station to the mobile terminal. The random access subchannel including the sequence number of the pre-signed feature code and the pre-signed feature code is included, and the pre-signed feature code is some random access feature code that is left in advance for use only by the mobile terminal of the handoff connection. .

In step S706, the mobile terminal checks the sequence number of the feature code left in the handoff command message after receiving the handoff command message and selects a random access subchannel in which the feature code left and the feature code left in advance are located. do.

In step S708, the target base station starts the process of handoff access in the random access subchannel with the mobile terminal.

Step S704 may also include a step of including a temporary identification number assigned to the mobile terminal in the handoff command message.

The temporary identification number corresponds to the subchannel where the feature code left in advance and the feature code left in advance correspond.

Step S706 may also include specifying that the mobile terminal sends a random access message using the feature code previously left in the random access subchannel.

In addition, the step S708 confirms that the mobile terminal starts from the mobile terminal based on the feature code left in advance by the target base station, and checks the temporary identity number based on the feature code and the random access subchannel left in advance. And sending the handoff access response message only to the mobile terminal corresponding to the number.

In addition, the handoff connection response message may be transmitted on a downlink logical dedicated channel or may be transmitted on a logical dedicated channel using a mixed automatic retransmission request technique.

Step S708 may also include sending a handoff complete message after receiving the handoff access response message at the mobile terminal.

8 is a block diagram of a handoff access device 800 based on a random access channel according to the present invention.

The handoff connection device is:

A handoff billing module 802 for causing a source base station to send a handoff request message to the target base station, requesting to switch the mobile terminal it is providing to the target base station;

A handoff response module 804 for causing the target base station to send a handoff response message to the source base station, and the source base station to send the contents of the handoff response message included in the handoff command to the mobile terminal; The off command message includes the sequence number of the pre-signed feature code assigned to the mobile station by the target base station and the random access subchannel information where the pre-signed feature code is located. Some random access feature codes you left for

After the mobile terminal receives the handoff command message, the mobile station confirms that the handoff command message includes the sequence number of the feature code left in advance, and selects a random access subchannel in which the feature code left in advance and the feature code left in advance are located. A sub channel selection module 806,

And a handoff connection module 808 for causing the target base station to begin the process of handoff connection in the random access subchannel with the mobile terminal.

In addition, the handoff response module 804 may include a temporary identification number corresponding to the random access subchannel where the target base station has assigned to the mobile terminal in the handoff command message and the feature code left in advance and the feature code left in advance. You can also

In addition, the subchannel selection module 806 may allow the mobile terminal to send a random access message using a feature code left in the random access subchannel.

In addition, the handoff connection module 808 checks the handoff connection initiated by the mobile terminal based on the feature code left by the target base station in advance and checks the temporary identification number based on the feature code and the random access subchannel left in advance. A handoff access response message may be sent only to the mobile terminal corresponding to the identification number.

The handoff connection module 808 may also cause the handoff connection response message to be sent on the downlink logical dedicated channel or on the logical dedicated channel using mixed automatic retransmission billing techniques.

The handoff connection module 808 may also cause the mobile terminal to send a handoff complete message after receiving the handoff connection response message.

Hereinafter, an embodiment according to the present invention will be described in detail.

The wireless access network of the cellular wireless communication system of the present invention distinguishes handoff connection and other random access by the following method:

1, the feature code left in advance is some random access feature code left in advance only for the mobile terminal to handoff access,

2, since the feature code in the random access message secretly explains the cause of the connection, that is, if the feature code in any one of the random access messages is the feature code left in advance, the cause of the connection is a handoff connection.

If there are a plurality of random access subchannels in a cell, the feature code may also be left in advance in the plurality of random access subchannels. The feature code left in advance should be assigned to the accessing terminal and the random access subchannel in which the feature code is located should be specified. This is to prevent a collision caused by access to the same random access subchannel to which a terminal allocated with the same pre-existing feature code. The information of the feature code left in one or more random access subchannels as described above is called the information left in advance of the feature code.

As shown in Fig. 9, part A indicates that all causes of random access to one random access subchannel in one cell share all feature codes, and the possibility of terminal collision conforms to the time slot ALOHA law. If the arrival of a random connection conforms to the Poisson Law, then from the angle of the terminal, the probability of collision when starting a random connection is:

Ps = 1-e-G.

Ps is the probability of collision when the terminal is randomly connected

G is the random access charge quantity that can be received on average for each random access opportunity.

One random access opportunity means an opportunity to start one random access procedure using one feature code in one random access time slot. The number of random access opportunities within one second of a cell

Nro = Nf × 1000 / T × Ns

Nro is the number of random access opportunities

Nf is the number of random access subchannels in the cell

T is the time interval between random access time slots and the unit is milliseconds (ms)

Ns is the total number of feature codes in one random access time slot.

As shown in Fig. 9, part B indicates that some feature codes therein are left in advance and become feature codes left in advance. At the same time, random connections having the same ratio for random connections, that is, handoff connections are also distinguished. The handoff connection shares all the feature code left in advance. However, other random access shares code that is not left over. This is because the same ratio of random access quantity (Nf) and feature code quantity (Ns) were separated and did not change compared to before the separation of the random access quantity G, which is averagely acceptable for each remaining random access opportunity, according to the time slot ALOHA theory. Based on this, the collision probability of the remaining random access does not change.

However, in the handoff connection, the feature code left in advance is assigned by the wireless access network, so that a certain management method can be used to ensure that a collision does not occur between terminals connected to the handoff.

Other features and advantages of the present invention will be described in detail in the following description section and will be more clearly understood through the description, or will be learned by practice of the invention. The objects and other advantages of the present invention can be realized and obtained through structures particularly pointed out in the written description, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings described herein are intended to further understand the present invention and are a part of the present invention, and the embodiments and descriptions thereof described are for interpreting the present invention and not to unduly limit the present invention.

1 is a structural diagram of a conventional cellular wireless communication system,

2 is a guide diagram of a conventional random access subchannel and a time slot,

3 is a flowchart of a handoff using a feature code left by a cellular wireless communication system according to an embodiment of the present invention;

4 is a structural guide diagram of an LTE system,

5 is a guide diagram of a random access subchannel and a time slot of an LTE system,

6 is a flowchart of a handoff using a feature code left by an LTE system according to an embodiment of the present invention.

7 is a flowchart of a handoff access method based on a random access channel according to the present invention;

8 is a block diagram of a handoff access device based on a random access channel according to the present invention;

9 is a guide diagram leaving a feature code of an embodiment according to the present invention in advance.

<Description of the symbols for the main parts of the drawings>

800: handoff connection device 802: handoff charging module

804: Handoff Response Module 806: Subchannel Selection Module

808: Handoff Connection Module

Claims (8)

A handoff access method based on a random access channel used for handoff access of a mobile terminal in a cellular mobile communication system, Sending, by the source base station, a handoff request message to the target base station requesting to switch the mobile terminal providing the service to the target base station; Sending, by the target base station, a handoff response message to the source base station, and the source base station sending contents of a handoff response message included in a handoff command to the mobile terminal; The handoff command message includes a sequence number of a preliminary feature code assigned to the mobile terminal by the target base station and a random access subchannel in which the prestored feature code is located, and the preloaded feature code is a handoff access. Some random access feature codes left in advance for only the mobile terminal, After receiving the handoff command message, the mobile station checks the sequence number of the preliminary feature code included in the handoff command message and selects a random access subchannel in which the prestored feature code and the preloaded feature code are located. Selecting step c, And the target base station (d) starts a handoff access procedure in the random access subchannel with the mobile terminal. According to claim 1, wherein step b, And a temporary identification number assigned to the mobile terminal in correspondence with the sub-channel in which the previously left feature code and the previously left feature code are located and included in the handoff command message. The method of claim 1, wherein the step c, Designating, by the mobile terminal, to send a random access message using the feature code left in the random access subchannel. The method of claim 3, wherein In step d, the target base station confirms that the mobile terminal starts from the mobile terminal based on the feature code left in advance, and confirms the temporary identity number based on the feature code and the random access subchannel. And sending a handoff access response message only to the mobile terminal corresponding to the temporary identification number. The method of claim 4, wherein And transmitting the handoff access response message in a downlink logical dedicated channel or in a logical dedicated channel using a mixed automatic retransmission charging technique. The method of claim 4, wherein The step d includes the step of sending a handoff complete message after receiving the handoff access response message in the mobile terminal. A handoff access device based on a random access channel used for handoff access of a mobile terminal in a cellular mobile communication system, A handoff billing module for causing a source base station to send a handoff request message to the target base station, claiming to switch the mobile terminal it is providing to the target base station; A handoff response module for causing the target base station to send a handoff response message to the source base station, wherein the source base station sends the contents of the handoff response message included in the handoff command to the mobile terminal, wherein the handoff The off command message includes a sequence number of the pre-remained feature code assigned to the mobile terminal by the target base station and a random access subchannel in which the pre-remained feature code is located, and the pre-received feature code is a mobile terminal to which handoff is connected. Some random access feature code left for After the mobile terminal receives the handoff command message, the mobile station confirms that the handoff command message includes the sequence number of the feature code that has been left in advance. A sub-channel selection module for selecting And a handoff access module for causing the target base station to initiate a handoff access procedure in the random access subchannel with the mobile terminal. The method of claim 7, wherein And the handoff connection module transmits the handoff connection response message on a downlink logical dedicated channel or on a logical dedicated channel using a mixed automatic retransmission charging technique.

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