WO2012060503A1

WO2012060503A1 - Shared repeater and mobile communication system

Info

Publication number: WO2012060503A1
Application number: PCT/KR2010/008135
Authority: WO
Inventors: 이용훈; 오영석; 유희정; 성영철; 류근영; 조동호
Original assignee: 한국과학기술원
Priority date: 2010-11-01
Filing date: 2010-11-17
Publication date: 2012-05-10
Also published as: KR101197613B1; KR20120047326A

Abstract

The present invention relates to a shared repeater for repeating communication between a mobile communication terminal and a base station in a mobile communication system, and to a mobile communication system including the shared repeater. By installing the shared repeater for repeating the communication between each base of the station and corresponding mobile communication terminals at the cell boundaries of the base stations, the problem of cell interference which occurs on the mobile communication terminal at the cell boundary can be minimized. As a result, the quality of communication for users located at the cell boundary can be guaranteed, and total cell capacity can also be significantly increased. Representative drawing: figure 3

Description

Shared repeater and mobile communication system

The present invention relates to a mobile communication system including a shared repeater and a shared repeater for relaying communication between a mobile communication terminal and a base station in a mobile communication system.

Recently, a mobile communication terminal such as a mobile phone or a smart phone has been widely used for acquiring various information through various aspects of communication, including making a voice call while users move. In such a communication, not only the quality of a voice call but also a video call requiring a high data transfer amount and a communication quality in a data communication are more important.

In such a mobile communication system, each base station provides a service to mobile terminals in its cell and installs a base station so that the boundary areas of each cell overlap each other, so that when a user moves between cells, the mobile communication is performed at the cell boundary. The service of the terminal is to be made smoothly.

However, as shown in FIG. 1, mobile communication terminals located at cell boundaries are subjected to inter-cell interference by signals of other adjacent base stations, thereby making it difficult to guarantee communication quality.

Therefore, there is a need for an interference management technique for ensuring communication quality of a mobile communication terminal located at a cell boundary and increasing overall system capacity. To this end, when a communication between a mobile communication terminal located at a cell boundary and a base station is established, each base station allocates different resources such as time, frequency, or code to the mobile communication terminals, which is generated due to a signal from an adjacent base station. Cell interference was effectively removed. However, this method has a disadvantage in that the cell capacity is reduced by the number of orthogonal resources.

In order to solve this problem, in recent years, an interference alignment technique (IA) and a capacity increasing technique for maximizing the maximum signal-to-interference noise ratio (Max-SINR) so that the interference signals exist only in a limited interference space, etc. In this paper, these techniques can improve the transmission rate in a multi-user interference channel.

In addition, the existing repeater has been used to solve the shadow area problem of the cellular system or to expand the coverage of the base station, and in recent years, multiple base stations and the shared repeater are wirelessly connected so that the neighboring cell interference is zero-forced at the shared repeater. A technique for eliminating by zero-forcing has also been proposed. In this technique, since the shared repeater and the base stations are wirelessly connected, the shared repeater becomes a half-duplex form, and thus cell capacity is halved. In addition, since multi-user multi input multi output (MIMO) signal processing, such as ZF, must be performed, the implementation of a shared repeater is not only complicated, but also has a constraint of satisfying a condition for the number of antennas.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and an object thereof is to provide a technique for minimizing cell interference which may be caused by a signal of an adjacent base station at a cell boundary.

In one aspect of the present invention, a shared repeater includes: at least one base station communication unit provided to perform communication with a plurality of adjacent base stations; A terminal communication unit provided to perform communication with the mobile communication terminal; An amplifying unit for amplifying a signal received through the at least one base station communication unit and outputting the signal to the terminal communication unit, and amplifying the signal received through the terminal communication unit and outputting the signal to the base station communication unit; And at least one base station communication unit, terminal communication unit, and amplifying unit to transmit the received signal to any one of a plurality of base stations when a signal is received from the mobile communication terminal, and to transmit the received signal to the mobile communication terminal when a signal is received from the base station. A control unit for controlling; Characterized in that it comprises a.

In this case, the control unit combines the signals received from a plurality of base stations or mobile communication terminal into a single signal and outputs the signal to the one or more base station communication unit or the terminal communication unit.

In addition, when a signal is received from a mobile communication terminal located at a cell boundary, the controller transmits the signal to any one of base stations corresponding to a cell to which the mobile communication terminal belongs.

And the base station communication unit is characterized in that the communication is made through the communication using a plurality of base stations or optical communication or microwave.

The control unit may control the at least one base station communication unit to perform multi-user signal processing on the signals received at the mobile communication terminal.

In this case, the multi-user signal processing is characterized in that at least one of multi-user decoding (MUD) or receive zero-forcing (ZF).

On the other hand, in order to achieve this object, in one aspect of the present invention, a mobile communication system includes: a plurality of base stations connected to a mobile communication network; A mobile communication terminal connected to a mobile communication network through communication with any one of the plurality of base stations; And a shared repeater located at cell boundaries of the plurality of base stations, communicating with the plurality of base stations, and relaying communication between the mobile communication terminal and the plurality of base stations. Characterized in that it comprises a.

At this time, the shared repeater is characterized in that the communication with the plurality of base stations using optical communication or microwave.

When the shared repeater receives a signal from a mobile communication terminal located at a cell boundary, the shared repeater transmits the received signal to any one of the plurality of base stations, and any one of the plurality of base stations receiving the signal transmits the signal. The communication with the communication terminal is characterized in that the control is made only through the shared repeater.

In addition, the base station in communication with the shared repeater of the plurality of base stations when the mobile terminal performs MUD (Multi-user Decoding), the mobile communication terminal to control the transmission rate or multiplex so that the signal can be recovered without error The signal is transmitted to the shared repeater through user signal processing.

And any one of a plurality of base stations for receiving a signal from the mobile communication terminal is characterized in that to perform a multi-user signal processing to obtain its own signal.

The multi-user signal processing may be any one or more of multi-user decoding (MUD) and received zero-forcing (ZF).

In addition, when performing multi-user decoding (MUD) at any one of a plurality of base stations receiving a signal from the mobile communication terminal, the mobile communication terminal may recover a signal without error at any one of the plurality of base stations. It is characterized by controlling the transmission rate so that.

At this time, the mobile communication terminal is characterized by generating a precoder of the mobile communication terminal to control the transmission rate so that the total capacity of the signal when the signal is transmitted to the shared repeater side.

The shared repeater may be configured with a mobile communication terminal adjacent to a cell boundary of the base station during downlink communication in which a signal is transmitted from a base station to a mobile communication terminal.

As described above, the present invention provides a shared repeater that communicates with a plurality of base stations at a cell boundary between base stations, thereby minimizing problems caused by cell interference in a mobile communication terminal located at a cell boundary. It is possible for the users located to guarantee the communication quality of the mobile communication terminal, and further increase the cell capacity of the entire mobile communication system.

In addition, by communicating through a shared repeater, when uplink communication is performed from the mobile communication terminal side to the base station side, a channel between the mobile communication terminals located at the cell boundary and the base stations is multiplexed in the existing interference channel. When the channel is changed to a multiple access channel and downlink communication is performed, the existing interference channel is changed to a broadcast channel. Also, mobile terminals located at a cell boundary communicate with a shared relay that is closer than a base station. As a result, a target signal-to-noise ratio can be obtained with a smaller transmission power than when directly communicating with a base station, thereby increasing battery efficiency of mobile communication terminals, and reducing the amount of adjacent cell interference generated by high transmission power. By reducing, there is an effect that the network capacity can be increased.

1 is a diagram illustrating communication between a mobile communication terminal and a base station in a conventional base station cell boundary.

2 is a block diagram showing a shared repeater of the present invention.

FIG. 3 is a diagram illustrating communication between a mobile communication terminal and a base station at a base station cell boundary of the present invention.

4 is a diagram illustrating the coverage of the shared repeater of the present invention.

FIG. 5 is a simulation result when a mobile communication terminal has a uniform distribution in a shaded area and the number of antennas of a mobile communication terminal, a shared repeater, and a base station is one in the present invention.

6 is a simulation result when the mobile communication terminal has a uniform distribution in the shaded area, and the number of antennas of the mobile communication terminal, the shared repeater, and the base station is two.

7 is a diagram illustrating a mobile terminal through a shared repeater 100 located at a cell boundary of the present invention.

* Description of the sign *

100: shared repeater

110: base station communication unit 120: terminal communication unit

130: amplification unit 140: control unit

200: base station 300: mobile communication terminal

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings, and the well-known technical parts will be omitted or compressed for brevity of description.

The shared repeater 100 of the present invention includes a base station communication unit 110, a terminal communication unit 120, an amplifier 130, and a controller 140, which are described with reference to FIGS. 2 to 7. Will be explained.

The base station communication unit 110 is in communication with the base station 200 installed in the vicinity of the shared repeater 100, the base station communication unit 110 at this time is made of the communication using each base station 200 and the optical cable or microwave Communication is made through a reliable link.

The terminal communication unit 120 communicates with a plurality of mobile communication terminals 300 adjacent to the shared repeater 100 during the up / down link communication.

The amplification unit 130 amplifies the signal received from the terminal communication unit 120 and outputs the signal to the base station communication unit 110, and amplifies the signal received from the base station communication unit 110 to output the terminal communication unit 120. To perform. That is, the amplifier 130 amplifies and outputs each received signal in uplink communication or downlink communication.

In other words, in the case of uplink communication, a signal from the mobile communication terminal 300 is received by the terminal communication unit 120 and then transmitted to the base station 200 through the base station communication unit 110 via the amplifier 130. In the case of downlink communication, a signal from the base station 200 is received by the base station communication unit 110 and then transmitted to the mobile communication terminal 300 through the terminal communication unit 120 via the amplifier 130.

In this case, the control unit 140 combines signals from the plurality of base stations 200 or the plurality of mobile communication terminals 300 into one, and the other roles are transmitted after the conventional amplification (AF: Amplify-and-Forward). Is the same as the repeaters.

3 is a diagram of a plurality of mobile communication terminals located at a cell boundary between a plurality of adjacent base stations 200 connected to a plurality of adjacent base stations 200 by a reliable link such as communication using an optical cable or a microwave. In this case, communication with the 300 is performed, wherein each base station 200 and each mobile communication terminal 300 have channel information (CSI: channel state) between the shared repeater 100 and all mobile communication terminals 300. share information).

That is, in the uplink communication in which a signal is transmitted from the mobile communication terminal 300 to the base station 200, the interference by the adjacent cell is not received by the base station 200 from the multi-user decoding (MUD) or the received zero-forcing (ZF). It is possible to solve using multi-user signal processing such as, or to solve using the transmission ZF in the mobile communication terminal 300, the downlink that the signal is transmitted from the base station 200 to the mobile communication terminal 300 side In communication, interference by an adjacent cell may be solved by using multi-user signal processing such as MUD or receiving ZF in the mobile communication terminal 300 or transmitting ZF in the base station 200.

In order to explain this, in an embodiment of the present invention, it will be described in more detail below, assuming that the number of the base station 200 is three. Of course, the number of the base station 200 can be expanded as needed, and the base station 200, the mobile communication terminal 300 and the shared repeater 100 is described as an example that is composed of a plurality of antennas, In this case, the number of antennas of the base station 200, the mobile communication terminal 300, and the shared repeater 100 may not be identical.

1) Embodiment in Up-Link Communication

The mobile communication terminal 300 located at a cell boundary transmits data to any one of the plurality of base stations 200 through the shared relay 100 without directly communicating with the base station 200 of the cell to which the cell belongs. The signal received from the shared repeater 100 may be represented as shown in [Equation 1]. At this time, since the shared repeater 100 and each base station 200 is connected by a reliable link, Equation 1 may be regarded as the same as the signal received from each base station 200.

Equation 1

here,

Is

Following the distribution of

Data of the second terminal (at this time,

Can be applied even if the control is not generated by the Gaussian Codebook or when power control is performed for each symbol sent).

Is

Transmission power of the second terminal,

Is

sign

Precoder of the second terminal, in which case,

Is,

Is

The channel between the second terminal and the shared repeater 100,

Is

Additive White Gaussian Noise (AWGN) following the distribution of.

The shared repeater 100 transmits a signal received from the mobile communication terminal 300 to the corresponding base stations 200 connected by a reliable link, and the base station 200 decodes the received signal. When the base station 200 performs the MUD, each mobile communication terminal 300 controls the transmission rate so that each base station 200 can perform the MUD without error.

When the number of antennas of the base station 200 satisfies the constraint of the number of antennas capable of receiving ZF (the number of antennas of the base station 200 ≥ the sum of the number of antennas of the mobile communication terminal 300 located at the cell boundary), each base station ( In step 200), a reception ZF is performed.

In addition, when the MUD is performed by the base station 200, since the shared repeater 100 and the plurality of base stations 200 are connected by a reliable link, the total capacity of the system is determined by the shared repeater 100. It is equal to the total capacity when it is assumed to run. Here, a multiple access channel (MAC) is formed between each of the terminals and the shared repeater 100, and in each mobile communication terminal 300 in order for the base station 200 to restore data of the corresponding terminal without error. It is necessary to control the transmission rate as shown in [Equation 2].

Equation 2

here

Is

The rate of the second terminal,

Is

Wow

Mutual information between them. Under the inequality condition of Equation 2, a precoder value of each mobile communication terminal 300 that maximizes the sum rate of cell boundary terminals is obtained through Equation 3.

Equation 3

subject to

and inequalities in [Equation 2]

Since the mobile communication terminals 300 located at the cell boundary are close to the shared repeater 100 located at the cell boundary, the target signal-to-noise ratio (target) is reduced with a smaller transmission power than when directly communicating with the corresponding base station 200. Signal-to-Noise Ratio (SNR) can be obtained.

Table 1

Cell structure	Hexagonal grid, 3-cell
BS, MS pair	3 pairs
Tx, Rx distribution	Uniform distribution
Cell radius	1000 m
Cell edge radius	50 ~ 200m
BS (RS) -to-MS Propagation loss	128.1 + 37.6 log 10 (R) 128.1 + 28.8 log 10 (R), Rinkilometers
Shadowing, Fading model	Log Normal stdev 8 dB, Rayleigh fading
Carrier frequency
	2 GHz
Bandwidth
	10 MHz
Tx power (BS, RS / MS)	24/16 dBm
BS / RS Antenna gain	10 dBi
MS Antenna gain	0 dBi
Thermal noise density	-174 dBm / Hz
Noise figure	9 dB

4 and Table 1 are simulation environments used for performance verification when the present invention is applied to a cellular communication system. In FIG. 4, one cell is selected from each cell in a shaded area of the cell to be serviced through the shared repeater 100, and the mobile communication terminal 300 is uniformly distributed in the shaded area. Assume that we have Figures 5 and 6 show this in a given environment

(SISO: Single Input Single Output) and

Results of the simulation of one case (MIMO).

As can be seen in Figures 5 and 6, in the system using the shared repeater 100 of the cell boundary, when the cell size is 1000m and the cell boundary distance is 50m, the mobile communication terminal 300 at the cell boundary is It can be seen that there is a performance gain of more than 10 times compared to a conventional system (Comventional Scheme), a TDMA (Time Division Multiple Access) based system, an IA based system, and a Max-SINR based system that directly communicate with the base stations 200.

The IA-based system guarantees maximum performance when the SNR is high in the multi-user interference channel. However, in this simulation environment, the mobile communication terminal 300 at the cell boundary is located in a low SNR region, and exhibits similar performance. The Max-SINR based system shows higher performance than existing systems, but this value is much smaller than the value using the shared repeater 100. The reason is that the distance between the shared repeater 100 and the mobile communication terminal 300 at the cell boundary is very close, so if the same power is used in the mobile communication terminal 300 at the cell boundary, the multiple access channel having a very high SNR Because it is formed. If the target capacity is determined, since the target capacity can be obtained with lower battery power, battery power of the mobile communication terminals 300 located at the cell boundary can be saved.

In addition, in order to obtain higher cell capacity, more shared repeaters 100 may be installed as needed. The shared repeater 100 installed at the cell boundary is not only cheaper in terms of cost than when the small base station 200 is installed, but also merely transmits the received signal to the corresponding base station 200 through a reliable link such as an optical cable. Therefore, unlike when installing the small base station 200 has the advantage that does not cause another cell boundary problem or handover problem. Therefore, the method of installing the small base station 200 instead of the shared repeater 100 increases the overhead and complexity of the system compared to the method of using the shared repeater 100, and thus the shared repeater 100 as in the present invention. ) Is more effective.

2) Embodiment in Down-Link Communication

The base stations 200 do not communicate directly with the mobile communication terminals 300 located at their cell boundaries, but transmit data corresponding to the shared relay 100 through a reliable link. The signal received from the shared repeater 100 may be represented as shown in [Equation 4].

Equation 4

here

Is

Following the distribution of

Data of the second base station 200 (in this case,

Is also applicable when the power is not generated by the Gaussian Codebook or when power control is performed for each symbol sent).

Is

The transmission power of the second base station 200,

Is

sign

Is the precoder of the base station 200,

Is,

Is

The channel between the base station 200 and the shared repeater 100,

Is

Additive White Gaussian Noise (AWGN) following the distribution of.

The shared repeater 100 distributes the received signal to each mobile communication terminal 300. Since the shared repeater 100 and each base station 200 are connected by a reliable link, when performing the MUD in each mobile communication terminal 300, each base station 200, each mobile communication terminal 300 in a distribution channel Performs rate control to enable MUD without error.

When the number of antennas of the base station 200 satisfies the constraint of the number of antennas capable of transmitting ZF (the number of antennas of the base station 200 ≥ the sum of the number of antennas of the mobile communication terminals 300 located at the cell boundary), each base station ( In step 200, a transmission ZF may be performed. In this case, cooperative communication for sharing transmission data between the base stations 200 is required. In addition, when cooperation with the base station 200 is made, DPC (Dirty Paper Coding), CMHP (Cover-van der Meulen-Hajek-Pursley), etc. may be applied in addition to the transmission ZF.

3) Mobile communication terminal selection protocol using shared repeater

FIG. 7 is a diagram illustrating a mobile terminal 300 supporting mobility through a shared repeater 100 located at a cell boundary, and moves from a cell position (a) to another cell position (e). If there is a mobile communication terminal 300, the mobile communication terminal 300 at the position of (a) currently has its own signal-to-interference noise ratio (SINR) 200a). If this value is large enough, the mobile communication terminal 300 at the position of (a) will communicate directly with the first base station 200a to which it belongs.

However, as the mobile communication terminal 300 moves to the cell boundary (the mobile communication terminal 300 moves from the position of (a) to the position of (b)), the SINR becomes lower and this value is larger than the first threshold. If low, the first base station 200a may reduce the communication quality of the mobile communication terminal 300, so a candidate set capable of communicating the mobile communication terminal 300 using the shared repeater 100 may be a candidate set. Classify as) In this case, the mobile terminal 300 still communicates directly with the first base station 200a to which it belongs.

However, when the mobile communication terminal 300 moves to the position of (c) so that the SINR is very low due to the neighboring cell interference and thus lower than the second threshold, the mobile communication terminal 300 is located in the positions of (a) and (b). In the first base station (200a) when the communication was made to the mobile terminal 300 is classified as an active set (Active Set), the communication with the mobile communication terminal 300 using the shared repeater 100 Communicate The mobile communication terminal 300 classified as an activity set feeds back SINRs with the first and

second base stations

200a and 200b to both the first and

second base stations

200a and 200b forming the cell boundary, respectively. do. In this case, the SINR with the first base station 200a is referred to as the first SINR, and the SINR with the second base station 200b is referred to as the second SINR.

When the mobile communication terminal 300 moves to the position of (d) and moves to a cell of another base station 200b, when the first SINR <2 SINR is exceeded and the second SINR exceeds the second threshold, the position of (d) is reached. The located mobile communication terminal 300 is again classified as a candidate set, directly communicates with the second base station 200b, and feeds back SINR only to the second base station 200b.

In this way, if the mobile communication terminal 300 moves to the position of (e) and completely moves out of the cell boundary, and the SINR of the mobile communication terminal 300 exceeds the first threshold, it is released from the candidate set and continues to the second base station. Communicate with 200b.

As described above, the detailed description of the present invention has been made by the embodiments with reference to the accompanying drawings. However, since the above-described embodiments have only been described with reference to preferred examples of the present invention, the present invention is limited to the above embodiments. It should not be understood that the scope of the present invention is to be understood by the claims and equivalent concepts described below.

Claims

One or more base station communication units provided to perform communication with a plurality of adjacent base stations;

A terminal communication unit provided to perform communication with the mobile communication terminal;

An amplifying unit for amplifying a signal received through the at least one base station communication unit and outputting the signal to the terminal communication unit, and amplifying the signal received through the terminal communication unit and outputting the signal to the base station communication unit; And

Control the one or more base station communication unit, terminal communication unit and amplification unit to transmit the received signal to any one of a plurality of base stations when the signal is received from the mobile communication terminal, and to transmit the received signal to the mobile communication terminal when the signal is received from the base station A control unit; Characterized in that it comprises

Shared repeater.
The method of claim 1,

The control unit combines the signals received from a plurality of base stations or mobile communication terminal into a single signal and outputs the signal to the one or more base station communication unit or terminal communication unit

Shared repeater.
The method of claim 1,

When the control unit receives a signal from a mobile communication terminal located at a cell boundary, the controller transmits the signal to any one of base stations corresponding to a cell to which the mobile communication terminal belongs.

Shared repeater.
The method of claim 1,

The base station communication unit is characterized in that the communication with a plurality of base stations through the communication using optical or microwave

Shared repeater.
The method of claim 1,

The control unit controls the at least one base station communication unit to perform the multi-user signal processing in the plurality of base stations for the signal received from the mobile communication terminal side

Shared repeater.
The method of claim 5,

The multi-user signal processing may be any one or more of multi-user decoding (MUD) or receive zero-forcing (ZF).

Shared repeater.
A plurality of base stations connected to a mobile communication network;

A mobile communication terminal connected to a mobile communication network through communication with any one of the plurality of base stations; And

A shared repeater located at a cell boundary of the plurality of base stations, communicating with the plurality of base stations, and relaying communication between the mobile communication terminal and the plurality of base stations; Characterized in that it comprises

Mobile communication system.
The method of claim 7, wherein

The shared repeater is characterized in that the communication with the plurality of base stations using optical communication or microwave

Mobile communication system.
The method of claim 7, wherein

When the shared repeater receives a signal from a mobile communication terminal located at a cell boundary, the shared repeater transmits the received signal to any one of the plurality of base stations.

Any one of the plurality of base stations receiving the signal controls communication with the mobile communication terminal transmitting the signal only through the shared repeater.

Mobile communication system.
The method of claim 7, wherein

The base station communicating with the shared repeater among the plurality of base stations controls the data rate or multi-user signal so that the mobile communication terminal can recover the signal without error when MUD (Multi-user Decoding) is performed in the mobile communication terminal. Transmitting the signal to the shared repeater side through the process

Mobile communication system.
The method of claim 7, wherein

Any one of a plurality of base stations receiving a signal from the mobile communication terminal side performs a multi-user signal processing to obtain its own signal

Mobile communication system.
The method of claim 11,

The multi-user signal processing may be any one or more of multi-user decoding (MUD) or receive zero-forcing (ZF).

Mobile communication systems.
The method of claim 7, wherein

When performing MUD (Multi-user Decoding) in any one of a plurality of base stations receiving a signal from the mobile communication terminal side,

The mobile communication terminal controls the data rate so that any one of the plurality of base stations can recover a signal without error.

Mobile communication system.
The method of claim 13,

The mobile communication terminal controls the data rate by generating a precoder of the mobile communication terminal so that the total capacity of the signal is maximum when the signal is transmitted to the shared repeater side.

Mobile communication system.
The method of claim 7, wherein

The shared repeater may be configured with a mobile communication terminal adjacent to a cell boundary of the base station during downlink communication in which a signal is transmitted from a base station to a mobile communication terminal.

Mobile communication system.