阅读说明：本技术 一种lte系统软切换机制 (LTE system soft handover mechanism ) 是由 钱骅 许哲 吴龙波 丁俊涛 刘俊龙 于 2019-10-12 设计创作，主要内容包括：一种LTE系统软切换机制,在使用部分频率复用规划小区频率的情况下,用户设备UE在小区之间通过软切换机制实现基站切换。本发明用户设备UE在切换过程中始终只与一个基站BS连接,既不会有硬切换机制那样的中断期,也没有现有软切换机制的连接重叠期,因此一方面降低了UE在切换过程中的数据传输时延,另一方面不会给终端处理能力及设备器件带来压力,不会重复占用资源。(Under the condition of using partial frequency reuse planning cell frequency, User Equipment (UE) realizes base station switching between cells through a soft switching mechanism. The user equipment UE of the invention is always connected with only one base station BS in the switching process, and has no interruption period like a hard switching mechanism and no connection overlapping period of the existing soft switching mechanism, thereby reducing the data transmission delay of the UE in the switching process, bringing no pressure to the terminal processing capacity and equipment devices and avoiding repeatedly occupying resources.)

1. A soft switching mechanism of LTE system is characterized in that under the condition of using partial frequency reuse planning cell frequency, user equipment UE realizes base station switching between cells through the soft switching mechanism.

2. The soft handover mechanism of LTE system as claimed in claim 1, wherein the UE establishes connection with the source base station and performs uplink and downlink data transmission, and when the UE is located at the edge of the cell of the source base station, the inter-cell base station handover is implemented by the following steps:

1) a source base station sends a switching request command to UE;

2) after receiving the switching request command, the UE keeps the connection with the source base station and simultaneously executes random access to the target base station;

3) the target base station sends a random access success notice to the UE;

4) the UE sends a switching completion command to the target base station and disconnects the connection with the source base station;

5) after receiving the switching completion command, the target base station establishes connection with the UE and performs uplink and downlink data transmission;

6) and when the target base station establishes connection with the UE, the target base station forwards a switching completion command to the source base station, the source base station is disconnected from the UE, and the switching is finished.

Technical Field

The invention belongs to the technical field of communication, relates to a method for switching a communication terminal in a cellular network, and provides a soft switching mechanism of an LTE (Long term evolution) system.

Background

The existing handover mode of LTE (Long Term Evolution) is hard handover, that is, UE (user equipment) disconnects from a source BS (Base Station) first and then establishes a connection with a target BS, so that there is a time period during handover, during which the UE is not connected to either the source BS or the target BS and cannot receive and transmit data, thereby increasing data transmission delay.

The soft handover means that the UE establishes a connection with the target BS first, and then disconnects the connection with the source BS, and the connection from the UE to the BS is maintained all the time in the handover process, thereby reducing the data transmission delay in the handover process.

Partial Frequency reuse (ffr) (frame Frequency reuse) is a technology proposed to solve interference between cell edge users, that is, different frequencies are used in different areas of a cell, for example, 7 cells shown in fig. 1, the same Frequency F0 is used in the center portion of each cell, frequencies such as F1, F2, and F3 are used in the edge portion of a cell, for example, Frequency F1 is used in cell 1, Frequency F2 is used in cells 2, 4, and 6, and Frequency F3, F0, F1, F2, and F3 are used in cells 3, 5, and 7, for example, as shown in fig. 2.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the hard handover mode currently used in the LTE network may cause data transmission delay, and a soft handover scheme suitable for LTE needs to be provided.

The technical scheme of the invention is as follows: under the condition of using partial frequency reuse planning cell frequency, User Equipment (UE) realizes base station switching between cells through a soft switching mechanism.

The method comprises the following steps that connection is established between User Equipment (UE) and a source base station, uplink and downlink data transmission is carried out, and when the UE is positioned at the edge of a cell of the source base station, base station switching among the cells is realized through the following steps:

1) a source base station sends a switching request command to UE;

2) after receiving the switching request command, the UE keeps the connection with the source base station and simultaneously executes random access to the target base station;

3) the target base station sends a random access success notice to the UE;

4) the UE sends a switching completion command to the target base station and disconnects the connection with the source base station;

5) the target base station receives the switching completion command, establishes connection with the UE and transmits uplink and downlink data;

6) and when the target base station establishes connection with the UE, forwarding a switching completion command to the source base station, disconnecting the source base station from the UE, and ending the switching.

The LTE belongs to a pure data network, the same frequency networking and other technologies are adopted, and if the conventional soft handover technology is adopted, the frequency bands used by a source BS and a target BS are the same, so that the coordinated scheduling of time-frequency resources used by UE in handover is difficult to realize, and a soft handover mechanism is not used in the conventional LTE. The invention designs a soft switching mechanism by utilizing a partial frequency multiplexing technology, when UE needs to switch a base station, switching notification is carried out among the UE, a target BS and a source BS through a switching completion command, so that the UE is respectively connected to the source BS and the target BS by using different frequency bands in the switching process, and on the premise of not changing a BS scheduling mechanism, a data link is ensured not to be interrupted all the time in the switching process, so that the data transmission delay in the switching process is reduced compared with that in hard switching; the invention reduces the data transmission delay of UE in the switching process, does not bring pressure to the terminal and base station processing capacity and equipment devices, does not introduce the problem of coordinating and scheduling resources of a source BS and a target BS, and is a low-complexity soft switching mechanism.

Drawings

Fig. 1 is a schematic diagram of the principle of partial frequency reuse.

Fig. 2 is an exemplary diagram of frequency division for partial frequency reuse.

Fig. 3 is a schematic diagram of a user equipment handover in the case of a partial frequency reuse plan cell frequency.

Fig. 4 is a schematic diagram of a handover process of a UE according to the present invention.

Fig. 5 is a schematic diagram of a handover procedure of a source BS according to the present invention.

Fig. 6 is a schematic diagram of a handover procedure of a target BS according to the present invention.

FIG. 7 is a schematic diagram of a handover mechanism according to the present invention.

Detailed Description

The existing LTE handover is hard handover, and there is a time period during the handover, during which the UE is not connected to either the source BS or the target BS and cannot receive and transmit data, thereby increasing data transmission delay. The invention designs the soft switching mechanism by utilizing the partial frequency multiplexing technology, so that the data transmission time delay of the UE in the switching process is reduced.

In the case of using the partial frequency reuse plan cell frequency, if the UE performs handover at the cell edge, the frequency bands of the adjacent cells do not overlap, as shown in fig. 3. On the basis, the invention analyzes and discovers that the soft handover of the UE between the cells can be realized by designing a new method, thereby reducing the problem of data transmission delay caused by hard handover.

The invention discloses a soft switching mechanism of an LTE system, which realizes base station switching between cells by User Equipment (UE) through the soft switching mechanism under the condition of using partial frequency reuse planning cell frequency. As shown in fig. 7, the UE establishes a connection with the source base station, and performs uplink and downlink data transmission, and when the UE is located at the edge of the cell of the source base station, the base station switching between the cells is implemented through the following steps:

1) when User Equipment (UE) is connected with a source base station (thread 0 in the figure), the source base station sends a switching request command (thread 1 in the figure) to the UE;

2) after receiving the switching request command, the UE keeps the connection with the source base station and executes random access to the target base station (thread 2 in the figure);

3) the target base station sends a random access success notification to the UE (line 3 in the figure);

4) the UE sends a switching completion command (thread 4 in the figure) to the target base station and disconnects the connection with the source base station;

5) the target base station receives the switching completion command, establishes connection with the UE and transmits uplink and downlink data (thread 5 in the figure);

6) when the target base station establishes connection with the UE, the target base station forwards a switching completion command (thread 6 in the figure) to the source base station, the source base station disconnects the connection with the UE, and the switching is finished.

For the user equipment UE, the handover procedure is as shown in fig. 4:

a) after receiving the handover request command from the source BS, the UE maintains the connection with the source BS and continues to perform uplink and downlink data transmission and reception with the source BS.

b) The UE performs random access to the target BS.

c) And after the random access is successful, the UE sends a switching completion command to the target base station.

d) Stopping data transceiving with the source BS, disconnecting the connection with the source BS, and ending the handover.

For the source base station, the handover procedure is shown in fig. 5:

a) and sending a switching request command to the UE.

b) And continuing to receive and transmit uplink and downlink data with the UE, and waiting for a switching completion command sent by the target base station on an interface between the base stations.

c) And after receiving the switching completion command, stopping receiving and transmitting the uplink and downlink data with the UE, and ending the switching.

For the target base station, the handover procedure is shown in fig. 6:

a) and accepting the random access of the UE.

b) And waiting for a handover completion command sent by the UE.

c) And after receiving the switching completion command, scheduling the UE to execute uplink and downlink data transceiving with the UE, and forwarding the switching completion command to the source BS through the interface between the base stations.

The invention realizes that the UE always keeps the connection with the BS in the switching process, reduces the data transmission time delay in the switching process compared with the hard switching process, and simultaneously has low complexity of the whole mechanism and easy realization.