RU2567545C1 - Radio communication system, base station, relay station and radio communication method - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: relay station (20) performs wireless communication with a base station (10), and a mobile station (30) performs wireless communication with the base station (10) or the relay station (20). The relay station (20) limits reception of a radio signal from the base station (10) when clocking, wherein the radio signal is transmitted to the mobile station (30). The relay station (20) transmits a message #1 on random access to the base station (10). The base station (10) transmits a message #2 when clocking, which is defined based on whether the source of the message #1 is the relay station (20). The relay station (20) receives the message #2 from the base station (10).

EFFECT: smooth random access using a relay station.

4 cl, 30 dwg

Description

FIELD OF TECHNOLOGY

The embodiments described below relate to a radio communication system, a base station, a relay station, and a radio communication method.

BACKGROUND

Currently, radio communication systems, such as a cellular telephone system and radio MAN (regional wireless network), are widely used. In order to achieve further acceleration and high-capacity radio communications, a lively discussion is ongoing about the next generation radio technology. For example, 3GPP (3rd Generation Partnership Project), which is one of the international standardization organizations, offers a standard called LTE (long-term development project) and a standard called LTE-A (advanced long-term development project), which is the development of LTE ( see, for example, non-patent literature 1).

In a radio communication system including a base station and a mobile station, a relay station that relays radio communications may be provided between the base station and the mobile station. By providing a relay station, an area (blind spot) is covered in which radio communication is hindered by blocking radio wave propagation caused by buildings, the range of a cell covered by a base station is expanded, and communication throughput is improved.

However, in a relay station, interference (which may be referred to as intrinsic interference) may occur between the transmission signal of its own station and the reception signal. Assume, for example, that the frequency range used between the base station and the relay station and the frequency range used between the relay station and the mobile station overlap with each other. In this case, the radio signal transmitted to the mobile station enters the receiver of the relay station, and as a result, the radio signal may not be correctly received from the base station. To cope with this problem, it was proposed that the relay station be controlled in such a way that radio signal reception from the base station and radio signal transmission to the mobile station are not performed at the same time (see, for example, section 9.3 from non-patent literature 2).

Another radio communication system including a base station and a mobile station may provide a configuration in which a random access procedure from a mobile station to a base station is defined. With random access, the mobile station gains access to the base station without having a specially assigned radio resource through the base station (see, for example, section 10.1.5 from non-patent literature 3).

As a random access preamble (which may be referred to as Msg 1 (Message 1)), for example, a mobile station transmits to a base station a signal sequence selected from among a plurality of candidates using a predetermined random access channel. Upon receiving Msg 1, the base station transmits a random access response (which may be referred to as Msg 2 (Message 2)) as a response. It should be noted that at this time, the base station does not recognize the original message transmission device Msg 1. Upon receiving the Msg 2, the mobile station transmits a message (which may be referred to as Msg 3 (Message 3)) to the base station, including the identifier of its own station. Upon receiving the Msg 3, the base station transmits a message (which may be referred to as Msg 4 (Message 4)) to the mobile station as a response.

Here, the interval until the base station sends back the Msg 2 message from receiving Msg 1 and the interval until the base station sends back the Msg 4 from receiving the Msg 3 message are not fixed, and preferably remain within a predetermined allowable range . Based on this flexibility, the base station can schedule and efficiently transmit Msg 2 and Msg 4. While the base station can transmit Msg 2 or Msg 4, the mobile station monitors the radio signal from the base station and detects Msg 2 or Msg 4 (see for example, section 5.1 of non-patent literature 6).

List of references

Non-Patent Literature

NPTL1: 3rd Generation Partnership Project, "Requirements for further advancements for Evolved Universal Terrestrial Radio Access (E-UTRA)", 3GPP TR 36.913 V8.0.1, 2009-03.

NPTL2: 3rd Generation Partnership Project, "Feasibility study for Further advancements for E-UTRA", 3GPP TR 36.912 V9.0.0, 2009-09.

NPTL3: 3rd Generation Partnership Project, "Evolved Universal Terrestrial Radio Access Network (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description", 3GPP TS 36.300 V9.3.0, 2010-03.

NPTL4: 3rd Generation Partnership Project, "Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification", 3GPP TS 36.331 V9.2.0, 2010-03.

NPTL5: 3rd Generation Partnership Project, "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation", 3GPP TS 36.211 V9.1.0, 2010-03.

NPTL6: 3rd Generation Partnership Project, "Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC) protocol specification", 3GPP TS 36.321 V9.3.0, 2010-06.

NPTL7: 3rd Generation Partnership Project, "Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Link Control (RLC) protocol specification", 3GPP TS 36.322 V9.2.0, 2010-06.

SUMMARY OF THE INVENTION

Technical problem

Let us turn to a radio communication system, which includes a base station, a relay station and a mobile station, and in which the relay station performs random access to the base station. At this time, a problem arises in how the base station and the relay station preferably perform a random access procedure. In particular, in conventional random access, the timing at which the base station can send a message back varies. If the message is sent back during timing, in which the relay station transmits a radio signal to the mobile station, the relay station may not correctly receive the message due to internal interference.

In view of the foregoing, it is an object of the present invention to provide a radio communication system in which random access by a relay station is smooth, a base station, a relay station and a radio communication method.

Solution

In order to solve the above problem, a radio communication system is provided that includes a base station; a relay station that wirelessly communicates with a base station; and a mobile station that wirelessly communicates with a base or relay station, wherein: the relay station includes: a first radio communication unit that transmits a first random access message to the base station and which receives a radio signal including a second message from the base station about random access; and a first controller that restricts the reception of the radio signal from the base station during clocking, in which the radio signal is transmitted to the mobile station; and the base station includes: a second radio communication unit that receives a first message and transmits a second message; and a second controller that controls the timing of the transmission of the second message, based on whether the transmission source of the received first message is a relay station.

Further, in order to solve the above problem, a radio communication system is provided that includes a base station; mobile station; and a relay station that wirelessly communicates with the base station and the mobile station, wherein: the base station includes a first radio communication unit that receives a first random access message and which transmits a second random access message within a period of a predetermined duration after receiving the first message; and the relay station includes: a second radio communication unit that transmits the first message to the base station and receives the second message from the base station, and a controller that restricts the transmission of the radio signal to the mobile station at least during the period from the beginning of the period with a predetermined duration after transmitting the first message until receiving the second message.

Further, in order to solve the above problem, a radio communication method used in a system that includes a base station, a relay station and a mobile station and in which the relay station wirelessly communicates with the base station and in which the mobile station wirelessly communicates with the base or a relay station, the radio communication method comprising: allowing the relay station to limit the reception of the radio signal from the base station during clocking, in which the radio signal transmitted to the mobile station; allowing the relay station to transmit the first random access message to the base station; allowing the base station to transmit a second random access message on timing, which is determined based on whether the transmission source of the first message is a relay station; and allowing the relay station to receive a second message from the base station.

Advantageous Results of the Invention

According to the above radio communication system, base station, relay station, and radio communication method, random access by the relay station is smooth.

The above and other objects, features, and advantages of this invention will become apparent from the following detailed description of the presently preferred embodiment of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] FIG. 1 illustrates a radio communication system according to a first embodiment.

[FIG. 2] FIG. 2 illustrates a radio communication system according to a second embodiment.

[FIG. 3] FIG. 3 illustrates an example of a structure of a radio frame.

[FIG. 4] FIG. 4 illustrates an example of the use of a radio resource.

[FIG. 5] FIG. 5 is a sequence diagram illustrating an example random access procedure.

[FIG. 6] FIG. 6 is a block diagram illustrating a base station.

[FIG. 7] FIG. 7 is a block diagram illustrating a relay station.

[FIG. 8] FIG. 8 is a block diagram illustrating a mobile station.

[FIG. 9] FIG. 9 is a flowchart illustrating an operation of a base station according to a second embodiment.

[FIG. 10] FIG. 10 is a flowchart illustrating an operation of a relay station according to a second embodiment.

[FIG. 11] FIG. 11 is a flowchart illustrating an operation of a mobile station according to a second embodiment.

[FIG. 12] FIG. 12 illustrates an example of random access according to a second embodiment.

[FIG. 13] FIG. 13 is a flowchart illustrating an operation of a base station according to a third embodiment.

[FIG. 14] FIG. 14 is a flowchart illustrating an operation of a relay station according to a third embodiment.

[FIG. 15] FIG. 15 is a flowchart illustrating an operation of a mobile station according to a third embodiment.

[FIG. 16] FIG. 16 illustrates an example of random access according to a third embodiment.

[FIG. 17] FIG. 17 illustrates another example of random access according to a third embodiment.

[FIG. 18] FIG. 18 is a flowchart illustrating an operation of a base station according to a fourth embodiment.

[FIG. 19] FIG. 19 is a flowchart illustrating an operation of a relay station according to a fourth embodiment.

[FIG. 20] FIG. 20 illustrates an example of random access according to a fourth embodiment.

[FIG. 21] FIG. 21 illustrates another example of random access according to a fourth embodiment.

[FIG. 22] FIG. 22 is a flowchart illustrating an operation of a base station according to a fifth embodiment.

[FIG. 23] FIG. 23 is a flowchart illustrating an operation of a relay station according to a fifth embodiment.

[FIG. 24] FIG. 24 illustrates an example of random access according to a fifth embodiment.

[FIG. 25] FIG. 25 is a flowchart illustrating an operation of a base station according to a sixth embodiment.

[FIG. 26] FIG. 26 is a flowchart illustrating an operation of a relay station according to a sixth embodiment.

[FIG. 27] FIG. 27 illustrates an example of random access according to a sixth embodiment.

[FIG. 28] FIG. 28 is a flowchart illustrating an operation of a base station according to a seventh embodiment.

[FIG. 29] FIG. 29 is a flowchart illustrating an operation of a relay station according to a seventh embodiment.

[FIG. 30] FIG. 30 illustrates an example of random access according to a seventh embodiment.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention are described below in detail with reference to the accompanying drawings, in which like reference numerals refer to like elements throughout.

(First Embodiment)

FIG. 1 illustrates a radio communication system according to a first embodiment. The radio communication system according to the first embodiment includes a base station 10, a relay station 20 and a mobile station 30. Examples of the mobile station 30 include a cell phone and a personal digital assistant. The relay station 20 may be a mobile radio relay station or a stationary radio relay station. The mobile station 30 wirelessly communicates with the base station 10 or the relay station 20. The relay station 20 performs random access (RA) to the base station 10 and establishes a connection, thereby transmitting data between the base station 10 and the mobile station 30.

The base station 10 includes a radio communication unit 11 and a controller 12. The radio communication unit 11 receives a first random access message (message # 1) and transmits a second random access message (message # 2). Examples of message # 1 include Msg 1 and Msg 3, and examples of message # 2 include Msg 2 and Msg 4. Controller 12 determines whether the transmission source of message # 1 received by radio unit 11 is a relay station 20. Based on whether the transmission source is a relay station 20, the controller 12 then controls the timing at which the radio communication unit 11 transmits message # 2.

The relay station 20 includes a radio communication unit 21 and a controller 22. The radio communication unit 21 wirelessly communicates with the base station 10. During random access, the radio communication unit 21 transmits message # 1 to the base station 10 and receives message # 2 from the base station 10. The controller 22 controls the clocking of the radio so that internal interference does not occur between the radio signal received from the base station 10 and the radio signal transmitted to the mobile station 30. Specifically, in the timing at which the radio signal is transmitted I am to the mobile station 30, the radio communication unit 21 restricts the reception of the radio signal from the base station 10 (for example, stops the reception circuit). The radio signal transmitted to the mobile station 30 by the relay station 20 includes an RS (Reference signal) used to measure the quality of communication through the mobile station 30.

Here, in the case where the message # 1 is an Msg 1 message, examples of the method for determining the transmission source of the message # 1 through the controller 12 include a method based on the signal sequence included in the message # 1 and a timing based method when which received message # 1. In the first method, a signal sequence for a relay station and a signal sequence for a mobile station are prepared, and the radio communication unit 21 generates a message # 1 by using a signal sequence for a relay station. In the case where another relay station is present in the radio communication system, the relay station 20 may use a signal sequence for the relay station shared with this other relay station. In the latter method, the RACH (random access channel) for the relay station and the RACH for the mobile station are configured separately, and the radio communication unit 21 transmits message # 1 through the RACH for the relay station.

In the case where the transmission source of message # 1 is a relay station 20 (or another relay station), or a mobile station 30 (or another mobile station), the controller 12 then changes the algorithm to determine the transmission timing of message # 2. In the first case, the controller 12 selects the timing at which the relay station 20 does not limit the reception of the radio signal. On timing, in which data is able to be transmitted from the base station 10 to the relay station 20, for example, when some agreements have been reached between both stations, the controller 12 selects the timing according to these agreements. On the other hand, in the latter case, the controller 12 performs scheduling and selects an arbitrary clock within an acceptable period.

According to the proposed radio communication system of the first embodiment, the relay station 20 restricts the reception of the radio signal from the base station 10 at a clock in which the radio signal is transmitted to the mobile station 30. The relay station 20 further transmits a message # 1 to the base station 10. The base station 10 determines whether whether the transmission source of message # 1 is relay station 20, and transmits message # 2 at a timing determined according to the determination results. Relay station 20 receives message # 2 from base station 10.

As a result, the radio communication system smoothly performs random access from the relay station 20 to the base station 10. In particular, the relay station 20 restricts reception so that internal interference does not occur between the radio signal received from the base station 10 and the radio signal transmitted to the mobile station 30. When the transmission source of message # 1 is not a mobile station 30, but a relay station 20, the base station 10 determines the transmission timing of message # 2, taking into account the limitations of the reception timing of the relay translational station 20. Therefore, the radio communication system suppresses the possibility that the relay station 20 can not receive the message # 2 in the normal way.

In the second to seventh embodiments, described below, an example of a radio communication system including a base station, a relay station, and a mobile station in accordance with LTE or LTE-A is included.

(Second Embodiment)

FIG. 2 illustrates a radio communication system according to a second embodiment. The radio communication system according to the second embodiment includes a base station 100, relay stations 200 and 200a, and mobile stations 300 and 300a. In the following description, we will mainly assume that the mobile station 300 transmits data with the base station 100 using the relay station 200, and the mobile station 300a directly transmits data with the base station 100.

Base station 100 is a radio communication device that wirelessly communicates with relay stations 200 and 200a, and a mobile station 300a. Base station 100 is connected to a host station (not illustrated) via a wired line. The base station 100 receives data from the host station, and transmits it to the relay stations 200 and 200a, and the mobile station 300a via a downlink (DL). On the other hand, through the uplink (UL), the base station 100 receives data from the relay stations 200 and 200a, and the mobile station 300a, and transmits them to the host station.

Relay station 200 is a radio communication device that transmits data transmissions between base station 100 and mobile station 300. Through DL, relay station 200 receives data from base station 100 and transmits them to mobile station 300. On the other hand, through UL, relay station 200 receives data from to the mobile station 300 and transmits them to the base station 100. In a similar manner, the relay station 200a also transmits data transmissions. The relay stations 200 and 200a may be mobile radio relay stations or fixed radio relay stations.

Here, the relay stations 200 and 200a correspond to a so-called Type 1 relay station. In particular, the relay stations 200 and 200a perform protocol processing up to layer 3, and behave with respect to the mobile stations 300 and 300a in the same manner as in the base station 100. From the mobile stations 300 and 300a, the cell, in addition to provided by the base station 100, is considered to be provided by relay stations 200 and 200a. The frequency range used for radio communication between the base station and the relay station, at least in part, overlaps with the frequency range used for radio communication between the relay station and the mobile station.

Mobile stations 300 and 300a are radio terminal devices that communicate with base station 100. Mobile stations 300 and 300a communicate with base station 100 through relay stations 200 and 200a. Examples of mobile stations 300 and 300a include a cell phone and a personal digital assistant device. Via DL, the mobile station 300 receives data from the relay station 200. Via UL, on the other hand, the mobile station 300 transmits data to the relay station 200.

For radio communication over DL, OFDMA (orthogonal frequency division multiple access) is used, and for radio communication over UL, SC-FDMA (frequency division multiple access, single-carrier access) is used. Further, a base station can be called a BS (base station) relay the station can be called RN (relay node) or RTS (relay station), and the mobile station can be called MS (mobile station), or UE (user Equipment).

FIG. 3 illustrates an example of a structure of a radio frame. Using each of the DL and UL, a radio frame, as illustrated in FIG. 3 is transmitted and received between the base station and the relay station, as well as between the relay station and the mobile station. In the second embodiment, FDD (frequency division duplexed transmission) is used as a duplex transmission system. It should be noted that TDD (time division duplex) can be used.

A 10 ms wide radio frame includes ten subframes (subframes # 0- # 9) with a width of 1 ms. Each subframe includes two slots (a slot in the first half and a slot in the second half) with a width of 0.5 ms. Data or control signal scheduling is performed in units of subframes. The radio resource of a subframe is segmented in the frequency direction or in the time direction for control. The smallest unit in the frequency direction is the subcarrier, and the smallest unit in the time direction is the symbol. The number of characters included in the subframe may vary depending on the type of subframes.

FIG. 4 illustrates an example of the use of radio resources. A communication channel is provided in the DL subframe and the UL subframe transmitted and received by the relay stations 200 and 200a.

In the DL subframe, several characters (one to three characters) of the header are the area for control, and the remaining characters are the area for data. In the control area, a PDCCH (Physical Downlink Control Channel) is provided in order to transmit a physical control signal. In the data area, a PBCH (Physical Broadcast Channel) is provided for transmitting broadcast information and an R-PDCCH (Physical Relay Downlink Control Channel) for transmitting control data regarding the relay. In the UL subframe, a PRACH (Physical Random Access Channel) is provided in order to transmit a random access preamble.

In the DL subframe, a reference signal, which is a pilot signal, is transmitted in both of the control and data areas. While DL data transmission is not performed, a reference signal is transmitted. The mobile station 300 measures a reception power level or radio quality by using a reference signal.

Here, the relay stations 200 and 200a receive data from the base station 100 and configure a subframe (DL reverse transmission) that does not carry data to the slave mobile station. Signals in which transmission is stopped also include a reference signal. It should be noted that in the control area of the relay stations 200 and 200a, it is allowed to receive data from the base station 100 and transmit data to the slave mobile station at the same time. In other words, the relay stations 200 and 200a may stop transmitting data in both of the control and data areas, or only in the data area.

For example, the DL reverse transmission is configured such that the DL subframe of the relay stations 200 and 200a can be an MBSFN subframe (networks with a single frequency of a multicast multimedia broadcast service). The MBSFN subframe is a subframe in which the base station 100 typically performs MBSFN transmission. MBSFN transmission is used when multiple transmitting stations jointly transmit data of the same content at the same timing by using the same modulation and frequency scheme. In a second embodiment, in a radio communication system including relay stations 200 and 200a, an MBSFN subframe is used to configure a DL reverse transmission subframe of relay stations 200 and 200a. Using this process, as illustrated in FIG. 4, for example, since the relay stations 200 and 200a do not transmit a reference signal in the data area in the MBSFN subframe, internal interference does not occur even if the relay stations 200 and 200a receive data in this area.

The relay stations 200 and 200a also transmit data to the base station 100 and configure a subframe (UL reverse transmission) in which data is not received from the slave mobile station. The timing for DL reverse transmission and the timing for UL reverse transmission may be the same or different from each other.

Relay stations 200 and 200a configured with UL reverse transmission do not give data permissions (UL grant) before a predetermined time (for example, four subframes) from UL reverse transmission. As a result, the slave mobile stations do not transmit data in the UL reverse transmission. Further, the relay stations 200 and 200a do not transmit data to the slave mobile stations before a predetermined time from the UL reverse transmission. As a result, the slave mobile stations do not transmit ACK (acknowledgment) / NACK (negative acknowledgment) in the UL reverse transmission.

It should be noted that the relay stations 200 and 200a control the timing at which the slave mobile stations transmit data, as described above. Therefore, even in each subframe, except for a predetermined UL reverse transmission, the relay stations 200 and 200a can stop receiving data from the slave mobile station and transmit data to the base station 100 by scheduling.

In addition, the timing for the reverse transmission was agreed between the base station 100 and the relay stations 200 and 200a. The relay stations 200 and 200a may determine the timing and notify the base station 100 of the timing. Or, alternatively, the base station 100 may determine the timing and notify the relay stations 200 and 200a of the timing. The timing for the reverse transmission may be different between the relay stations 200 and 200a. The relay stations 200 and 200a broadcast information indicating clocking for the reverse transmission. The mobile station 300 recognizes the timing based on broadcast information received from the relay station 200.

FIG. 5 is a sequence diagram illustrating an example random access procedure. Here, the mobile station 300a performs random access to the base station 100.

The random access procedure illustrated in FIG. 5 includes the following steps.

(Step S1) The mobile station 300a selects one signal sequence from among candidates from a plurality of signal sequences and transmits it as a random access preamble (Msg 1) using PRACH. The random access preamble can then be referred to simply as the preamble.

(Step S2) After the detection of Msg 1, the base station 100 transmits a random access response (Msg 2). Msg 2 transmit within a predetermined period. More specifically, the base station 100 transmits Msg 2 within a period A of parts of subframes counted after three subframes from the subframe in which Msg 1 is received. The value of A is previously set to any of 2, 3, 4, 5, 6, 7, 8, and 10.

(Step S3) Within the period in which Msg 2 can be transmitted, the mobile station 300a monitors the received signal from the base station 100. After detecting the Msg 2, the mobile station 300a transmits a message (Msg 3) called a scheduled transmission to the base station 100. In Msg 3, the identifier of the mobile station 300a is included.

(Step S4) The base station 100 receives the Msg 3 from the mobile station 300a and transmits a message called “Contest Resolution” (Msg 4) to the mobile station 300a. Msg 4 is transmitted within a predetermined period. More specifically, the base station 100 transmits Msg 4 within B parts of subframes counted from the subframe in which Msg 3 is received. The value of B is preset to any of 8, 16, 24, 32, 40, 48, 56, and 64. B within the period in which Msg 4 can be transmitted, the mobile station 300a monitors the received signal from the base station 100.

Meanwhile, the method (RA trigger) by which random access is performed includes the following.

(1) An abnormality is detected in the connection between the base station 100 and the mobile station 300a. This connection abnormality includes the case where the T310 timer is disabled, as described in previous non-patent literature 4, and the case of failure of the retransmission control of the data in the RLC layer (radio link control).

(2) The mobile station 300a receives the handover start instruction from the base station as a handover source, and accesses the base station as a handover destination.

(3) Mobile station 300a fails to access base station 100 by using a scheduling request scheme. A scheduling request scheme is an access scheme in which a mobile station 300a transmits a scheduling request to a base station 100 by using a radio resource for control data and receives a radio resource distribution for data transmission.

(4) The mobile station 300a fails to transmit data to the base station 100 by using the contention-based uplink transmission method. The contention-based uplink transmission method is a method in which a mobile station 300a transmits data to a base station 100 by using a radio resource shared by a plurality of mobile stations. Failure in data transmission may be caused by contention (conflict). The competition-based uplink transmission method is described, for example, in a collection of articles on 3GPP (R2-093812, "Contention based uplink transmission").

(5) Mobile station 300a fails in security authentication.

(6) The mobile station 300a fails to reconfigure the radio resource, namely, reconfigure the RRC (Radio Resource Control) connection. The reconfiguration of the RRC connection is described, for example, in section 5.3.5.5 of the previous non-patent literature 4.

Even during random access from relay stations 200 and 200a to base station 100, Msg 1-Msg 4 are transmitted in the same manner as in random access from mobile station 300a to base station 100. It should be noted that in the case of relay stations 200 and 200a , the transmission timing of Msg 2 and Msg 4 is different from the timing of mobile station 300a.

FIG. 6 is a block diagram illustrating a base station. Base station 100 includes a radio communication unit 110, a wired communication unit 120, a data processing unit 130, and a controller 140.

The radio communication unit 110 is a radio interface that wirelessly communicates with the relay stations 200 and 200a, and the mobile station 300a. The radio communication unit 110 performs signal processing, including demodulating and decoding the received radio signal, and extracts data and a control signal. The radio communication unit 110 further detects a preamble transmitted using PRACH. The radio communication unit 110 supplies the data to be transmitted to the host station to the data processing unit 130. On the other hand, the radio communication unit 110 receives data from the data processing unit 130 and generates a control signal based on an instruction from the controller 140. The radio communication unit 110 then performs signal processing including encoding and modulation for the data and the control signal, and outputs a radio signal.

The wired communication unit 120 is a communication interface that performs wired communication with a host station. The wired communication unit 120 receives data addressed to the mobile stations 300 and 300a from the host station and feeds it to the data processing unit 130. On the other hand, the wired communication unit 120 converts the data received from the data processing unit 130 into a wired network packet form and transmits them to the host station.

The data processing unit 130 receives the data to be transmitted to the host station from the radio communication unit 110 and provides them to the wire communication unit 120. On the other hand, the data processing unit 130 receives data addressed to the mobile stations 300 and 300a from the wire communication unit 120, and maps the data to the radio frame under the control of the controller 140, thereby supplying them to the radio communication unit 110.

A controller 140 controls the processes of the radio communication unit 110, the wire communication unit 120, and the data processing unit 130. The controller 140 has a data plane block 150 and a control plane block 160. A data plane unit 150 controls the transmission and reception of data between its own station and any of the relay stations 200 and 200a and the mobile station 300a. The control plane block 160 controls the transmission and reception of the control signal between its own station and any of the relay stations 200 and 200a and the mobile station 300a.

Namely, the control plane unit 160 receives a control signal extracted by the radio communication unit 110, and performs communication control according to the control signal. The control plane unit 160 further notifies the radio communication unit 110 of the transmitted control signal. The control plane unit 160 has a preamble control unit 161, an RA slot control unit 162, and a reverse gear controller 163.

The preamble control unit 161 controls candidates for preambles used for random access. When the preamble for the relay station and the preamble for the mobile station are distinguished, the preamble control unit 161 determines whether the preamble detected by the radio communication unit 110 is one for the relay station or one for the mobile station.

The RA slot control unit 162 controls the slot (RA slot) in which the PRACH is configured. When the RA slot for the relay station and the RA slot for the mobile station are distinguished, the RA slot control unit 162 determines whether the slot in which the preamble is detected by the radio communication unit 110 is one for the relay station or one for the mobile station. Further, the RA slot control unit 162 can dynamically configure the RA slot according to the conditions of occurrence of the RA trigger or the configuration status of the DL reverse transmission of relay stations 200 and 200a.

The reverse transmission controller 163 controls the reverse transmissions of the relay stations 200 and 200a, and controls the timing of the transmission and reception of the radio signal. When the random access source is a relay station, the reverse transmission controller 163 refers to the DL reverse transmission configuration status of the relay stations 200 and 200a, and determines the timing for transmitting Msg 2 or Msg 4.

FIG. 7 is a block diagram illustrating a relay station. The relay station 200 includes radio blocks 210 and 220, a scheduler 230, and a controller 240. The relay station 200a is also deployed using the same block structure as that of the relay station 200.

The radio communication unit 210 is a radio interface that wirelessly communicates with the base station 100. The radio communication unit 210 performs signal processing, including demodulating and decoding the received radio signal, and extracts data or a control signal. The radiocommunication unit 210 supplies the data addressed to the mobile station 300 to the scheduler 230. On the other hand, the radiocommunication unit 210 receives data from the scheduler 230 and generates a control signal or preamble based on instructions from the controller 240. The radiocommunication unit 210 then performs signal processing, including encoding and modulation, and outputs a radio signal.

The radio communication unit 220 is a radio interface that wirelessly communicates with the mobile station 300. The radio communication unit 220 performs signal processing, including demodulating and decoding the received radio signal, and extracts data or a control signal. The radio communication unit 220 supplies the data to be transmitted to the base station 100 to the scheduler 230. On the other hand, the radio communication unit 220 receives data from the scheduler 230 and generates a control signal or a reference signal based on instructions from the controller 240. The radio communication unit 220 then performs signal processing, including coding and modulation, and outputs a radio signal.

The scheduler 230 schedules the transmission of data from the base station 100 to the mobile station 300 and the transmission of data from the mobile station 300 to the base station 100. Namely, the scheduler 230 maps the data addressed to the mobile station 300 received from the radio communication unit 210 to the DL radio frame and provides it to the radio communication unit 220. On the other hand, the scheduler 230 maps the data addressed to the base station 100 obtained from the radio communication unit 220 to the UL radio frame and feeds it to the radio communication unit 210.

The controller 240 controls the processes of the radio communication units 210 and 220 and the scheduler 230. The controller 240 has a data plane block 250 and a control plane block 260.

The data plane block 250 controls the transmission and reception of data between its own station and any of the base station 100 and the mobile station 300. The data plane block 250 has a scheduler controller 251. The scheduler controller 251 controls the method for scheduling the scheduler 230.

The control plane block 260 controls the transmission and reception of a control signal between its own station and any of the base station 100 and the mobile station 300. In particular, the control plane block 260 receives a control signal extracted by the radio communication units 210 and 220, and performs communication control according to the control signal . The control plane unit 260 further notifies the radio communication units 210 and 220 of the transmitted control signal. The control plane unit 260 has a preamble control unit 261, an RA transmission control unit 262, and a reverse transmission controller 263.

The preamble control unit 261 controls the candidates of the preambles used in random access, and selects the preamble used in the Msg 1 during random access to the base station 100. When the preamble for the relay station and the preamble for the mobile station are distinguished, the preamble control unit 261 selects the preamble for the relay station.

The RA transmission control unit 262 captures the RA slot and selects the RA slot used to transmit Msg 1 during random access to the base station 100. When the RA slot for the relay station and the RA slot for the mobile station are distinguished, the RA transmission control unit 262 selects the RA slot for relay station.

A reverse transmission controller 263 controls the reverse transmission of its own station and controls the timing of the transmission and reception of the radio signal. In particular, at least in the area for DL reverse transmission data, the reverse transmission controller 263 does not transmit data or a reference signal to the mobile station 300. In addition to the reverse transmission used in normal data transmission, the reverse transmission controller 263 may configure a temporary reverse transmission during random access.

FIG. 8 is a block diagram illustrating a mobile station. The mobile station 300 includes a radio communication unit 310, a data processing unit 320, and a controller 330. The mobile station 300a is also deployed using the same block structure as that of the mobile station 300.

The radio communication unit 310 is a radio interface that wirelessly communicates with the relay station 200 or the base station 100. The radio communication unit 310 performs signal processing, including demodulating and decoding the received radio signal, and extracts data or a control signal. The radio communication unit 310 supplies the extracted data to the data processing unit 320. On the other hand, the radio communication unit 310 receives data from the data processing unit 320 and generates a control signal based on an instruction from the controller 330. The radio communication unit 310 then performs signal processing, including coding and modulation, and outputs a radio signal.

The data processing unit 320 generates data to be transmitted to the relay station 200 or the base station 100 and supplies them to the radio communication unit 310. On the other hand, the data processing unit 320 receives data addressed to its own station from the radio communication unit 310 and performs the process according to the data type.

A controller 330 controls the processes of the radio communication unit 310 and the data processing unit 320. The controller 330 has a data plane block 340 and a control plane block 350. A data plane block 340 controls the transmission and reception of radio data. The control plane unit 350 controls the transmission and reception of the radio signal. The control plane unit 350 has a preamble control unit 351 and an RA slot control unit 352.

The preamble control unit 351 manages the candidates for the preambles used in random access and selects the preamble used in the Msg 1 during random access to the relay station 200 or the base station 100. When the preamble for the relay station and the preamble for the mobile station are distinguished, the preamble control unit 351 selects the preamble for the mobile station.

The RA slot control unit 352 captures the RA slot and selects the RA slot used to transmit Msg 1 during random access to the relay station 200 or the base station 100. When the RA slot for the relay station and the RA slot for the mobile station are distinguished, the slot control unit 352 RA selects the RA slot for the mobile station.

Regarding random access, the processes performed by the base station 100, the relay station 200, and the mobile station 300 (or the mobile station 300a) should be described below. In a second embodiment, the base station 100 determines, based on the preamble used, whether the transmission source Msg 1 is a relay station or a mobile station.

FIG. 9 is a flowchart illustrating a process of a base station according to a second embodiment. The process illustrated in FIG. 9 includes the following steps:

(Step S111) The radio communication unit 110 receives the preamble (Msg 1) using PRACH. At this time, the Msg 1 transmission source was not specifically identified.

(Step S112) The preamble control unit 161 determines whether the received preamble is a preamble for a relay station. If so, the process proceeds to step S113. Otherwise, the process proceeds to step S114.

(Step S113) The reverse transmission controller 163 selects the DL reverse transmission of each of the relay stations 200 and 200a within the period in which Msg 2 is transmitted (namely, the period within parts of subframes after three subframes from the subframe in which Msg 1 is received). The process then proceeds to step S115.

(Step S114) The control plane block 160 performs scheduling and selects an arbitrary subframe within the period in which Msg 2 is transmitted.

(Step S115) The radio communication unit 110 transmits the Msg 2 using the PDCCH or R-PDCCH of the subframe selected in step S113 or S114. In the case where a plurality of subframes are selected in step S113 when the timing of the DL reverse transmissions is different between the relay stations 200 and 200a, the radio communication unit 110 transmits Msg 2 in each subframe. The reason is that whether any of the relay stations 200 and 200a Msg 1 transmits while receiving Msg 1, is not identified.

(Step S116) The radio communication unit 110 receives the Msg 3.

(Step S117) The control plane block 160 determines the transmission source Msg 3. The transmission source Msg 3 is determined by using the identifier included in Msg 3. If the transmission source is a relay station, the process proceeds to step S118. If the transmission source is not a relay station, the process proceeds to step S119. Here, the transmission source is assumed to be a relay station 200.

(Step S118) The reverse transmission controller 163 selects the DL reverse transmission of the relay station 200 within a period (namely, a period within B parts of subframes counted from a subframe in which Msg 3 is received) in which Msg 4 is transmitted. The process then proceeds to to step S120. Since the Msg 3 transmission source is specifically identified at the time of receiving the Msg 3, the reverse transmission controller 163 does not need to select a DL reverse transmission of the relay station 200a.

(Step S119) The control plane block 160 performs scheduling and selects an arbitrary subframe within the period in which Msg 4 is transmitted.

(Step S120) The radio communication unit 110 transmits the Msg 4 using the PDCCH or R-PDCCH of the subframe selected in step S118 or S119.

FIG. 10 is a flowchart illustrating a process of a relay station according to a second embodiment. The process illustrated in FIG. 10 includes the following steps:

(Step S121) The radio communication unit 210 receives the broadcast information using the PBCH from the base station 100. Information regarding the timing of the RA slot is included in this broadcast information. The RA slot may be a shared relay station and a mobile station. RA transmission control unit 262 selects the UL reverse transmission slot RA. It should be noted that when the reception of radio signals from the mobile station 300 can be stopped, the RA transmission control unit 262 can select the RA slot, with the exception of the RA slot in the UL reverse transmission.

(Step S122) From among the preamble candidates, the preamble control unit 261 selects a preamble for the relay station. The preamble for the relay station may be shared between the relay stations 200 and 200a. The radio communication unit 210 transmits the selected preamble by using the RA slot selected in step S121.

(Step S123) The reverse transmission controller 263 restricts the transmission of the radio signal (including the reference signal) to the mobile station 300 by using DL reverse transmission. When the Msg 2 message is transmitted using the PDCCH, the reverse transmission controller 263 stops signal transmission in both of the control and data areas. When Msg 2 is transmitted using the R-PDCCH, the reverse transmission controller 263 stops signal transmission in at least the data area.

(Step S124) The radiocommunication unit 210 receives the Msg 2 from the base station 100 using the DL reverse link PDCCH or R-PDCCH.

(Step S125) The radio communication unit 210 transmits the Msg 3 to the base station 100. Preferably, the radio communication unit 210 transmits the Msg 3 to the base station 100 using the UL reverse transmission.

(Step S126) The reverse transmission controller 263 restricts the transmission of the radio signal (including the reference signal) to the mobile station 300 via DL reverse transmission. When Msg 4 is transmitted using the PDCCH, the reverse transmission controller 263 stops signal transmission in both of the control and data areas. When Msg 4 is transmitted using the R-PDCCH, the reverse transmission controller 263 stops signal transmission in at least the data area.

(Step S127) The radiocommunication unit 210 receives the Msg 4 from the base station 100 using a PDCCH or DL reverse transmission R-PDCCH. Using the above steps, the radio communication unit 210 completes the random access procedure from the relay station 200 to the base station 100.

FIG. 11 is a flowchart illustrating an operation of a mobile station according to a second embodiment. Assume that the mobile station 300 performs random access to the relay station 200 or the base station 100. The process illustrated in FIG. 11 includes the following steps:

(Step S131) The radio communication unit 310 receives the broadcast information using the PBCH from the relay station 200 or the base station 100. Information regarding the timing of the RA slot is included in this broadcast information. The RA slot control unit 352 selects one RA slot.

(Step S132) The preamble control unit 351 selects one preamble for the mobile station from among the preamble candidates. The radio communication unit 310 transmits the selected preamble through the RA slot selected in step S131.

(Step S133) The radio communication unit 310 monitors the PDCCH within a period (namely, a period of A parts of subframes after three subframes from the subframe in which Msg 1 is transmitted), in which Msg 2 is transmitted, and receives Msg 2 from the relay station 200 or the base station 100. It should be noted that the radio communication unit 310 receives Msg 2 in a subframe except for the subframe in the DL reverse transmission.

(Step S134) The radio communication unit 310 transmits the Msg 3 to the relay station 200 or the base station 100. The radio communication unit 310 transmits the Msg 3 to the relay station 200 in a subframe except for the subframe in the UL reverse transmission.

(Step S135) The radio communication unit 310 monitors the PDCCH within a period (namely, a period of B parts of subframes counted from a subframe in which Msg 3 is transmitted) in which Msg 4 is transmitted, and receives Msg 4 from the relay station 200 or the base station 100. It should be noted that the radio communication unit 310 receives the Msg 4 from the relay station 200 in a subframe with the exception of the subframe in the DL reverse transmission.

(Step S136) Using the process up to step S135, the radio communication unit 310 completes the random access procedure from its own station to the relay station 200 or the base station 100. Then, the radio communication unit 310 performs data transfer between its own station and any relay station 200 and the base station 100. It should be noted that when connected to the relay station 200, the mobile station 300 performs data transmission in the subframe except for the subframe in the reverse transmission.

FIG. 12 illustrates an example of random access according to a second embodiment. The message flow illustrated in FIG. 12 includes the following steps:

(Step S11) The relay station 200 transmits Msg 1 to the base station 100 using the UL reverse transmission. The preamble, which is to be transmitted as Msg 1, is the preamble for the relay station. Based on this preamble, the base station 100 recognizes that the transmission source Msg 1 is a relay station 200.

(Step S12) The base station 100 transmits the Msg 2 using the DL reverse transmission R-PDCCH of the relay station 200 within the period in which the Msg 2 is transmitted. When a signal, such as a reference signal, is not transmitted in the data area, the relay station 200 receives Msg 2.

(Step S13) The base station 100 transmits the Msg 2 using the DL reverse transmission of the relay station 200a within the period in which the Msg 2 is transmitted. It should be noted that since the relay station 200a did not transmit the Msg 1, it ignores the Msg 2 received from base station 100.

(Step S14) The relay station 200 transmits the Msg 2 to the base station 100 using the UL reverse transmission. Based on the identifier included in the Msg 3, the base station 100 recognizes that the transmission source of the Msg 3 is a relay station 200.

(Step S15) The base station 100 transmits the Msg 2 using the DL reverse transmission R-PDCCH of the relay station 200 within the period in which the Msg 4 is transmitted. When a signal, such as a reference signal, is not transmitted in the data area, the relay station 200 receives Msg 4.

In the proposed radio communication system of the second embodiment, the base station 100 is configured to determine based on the preamble adopted as Msg 1 whether the transmission source Msg 1 is a relay station or a mobile station. In the case where the transmission source is a relay station, the base station 100 then controls the transmission timing so that the transmission source can receive Msg 2 through the existing DL reverse transmission. In the case where the source of the Msg 3 transmission is the relay station 200, the base station 100 further controls the transmission timing so that the relay station 200 can receive the Msg 4 via the existing DL reverse transmission. According to a second embodiment, the radio communication system suppresses the internal interference of the relay station 200 and smoothly performs random access from the relay station 200 to the base station 100.

(Third Embodiment)

A third embodiment is described below. Since the third embodiment shares some elements with the preceding second embodiment, the following description will focus on their distinctive elements, omitting explanations of similar elements. The third embodiment differs from the second embodiment in a method for determining whether the transmission source Msg 1 is a relay station or a mobile station.

The radio communication system according to the third embodiment is deployed by using the same device configuration as that of the second embodiment illustrated in FIG. 2. Next, the base station, the relay station, and the mobile station according to the third embodiment are deployed using the same block configurations as those of the second embodiment illustrated in FIG. 6-8. Hereinafter, a third embodiment is described with reference to the same reference signs, as illustrated in FIG. 6-8.

FIG. 13 is a flowchart illustrating a process of a base station according to a third embodiment. The process illustrated in FIG. 13 includes the following steps:

(Step S211) The RA slot control unit 162 configures the individual RA slots for the relay station and the mobile station. Through the PBCH, the radio communication unit 110 transmits information indicating the timing of the RA slots for the mobile station and the relay station as broadcast information. It should be noted that the radio communication unit 110 may transmit information indicating the timing of the RA slot for the relay station as individual control data to the relay stations 200 and 200a.

As described in previous non-patent literature 5, normal information indicating clocking of the RA slot is transmitted as a parameter (PRACH configuration index) in the broadcast information. Suppose, for example, that information indicating the timing of an RA slot for a relay station is inserted as a new parameter in the broadcast information for transmission. The RA slot for the relay station can be set to a low frequency, such as once every 40 ms.

(Step S212) The radio communication unit 110 receives the preamble using PRACH.

(Step S213) The RA slot control unit 162 determines whether a preamble is received through the RA slot for the relay station or the mobile station. If the preamble is received through the RA slot for the relay station, the process proceeds to step S214. If the preamble is received through the RA slot for the mobile station, the process proceeds to step S215.

(Step S214) The reverse transmission controller 163 selects each DL reverse transmission of the relay stations 200 and 200a within the period in which Msg 2 is transmitted. The process then proceeds to step S216.

(Step S215) The control plane block 160 performs scheduling and selects an arbitrary subframe within the period in which Msg 2 is transmitted.

(Step S216) The radio communication unit 110 transmits the Msg 2 using the PDCCH or R-PDCCH of the subframe selected in step S214 or S215. When the timing of DL reverse transmissions is different between relay stations 200 and 200a, the radio communication unit 110 transmits Msg 2 through each DL reverse transmission.

(Step S217) The radio communication unit 110 receives the Msg 3.

(Step S218) The control plane block 160 determines the transmission source Msg 3. If the transmission source is a relay station, the process proceeds to step S219. If the transmission source is not a relay station, the process proceeds to step S220. Here, the transmission source is assumed to be a relay station 200.

(Step S219) The reverse transmission controller 163 selects the DL reverse transmission of the relay station 200 within the period in which the Msg 4 is transmitted. The process then proceeds to step S221. The reverse gear controller 163 does not have to select a DL reverse gear of the relay station 200a.

(Step S220) The control plane block 160 performs scheduling and selects an arbitrary subframe within the period in which Msg 4 is transmitted.

(Step S221) The radio communication unit 110 transmits the Msg 4 using the PDCCH or R-PDCCH of the subframe selected in step S219 or S220.

FIG. 14 is a flowchart illustrating an operation of a relay station according to a third embodiment. The process illustrated in FIG. 14 includes the following steps.

(Step S231) Through the PBCH, the radio communication unit 210 receives broadcast information from the base station 100. Information indicating the timing of the RA slot for the relay station is included in the broadcast information.

(Step S232) The RA transmission control unit 262 selects an RA slot for the relay station. The RA transmission control unit 262 preferably selects an RA slot for the relay station provided in the UL reverse transmission.

(Step S233) The preamble control unit 261 selects one preamble from among the preamble candidates. Preamble candidates are shared between relay stations 200 and 200a or mobile stations 300 and 300a. The radio communication unit 210 transmits the selected preamble through the RA slot selected in step S232.

(Step S234) The reverse transmission controller 263 restricts the transmission of the radio signal (including the reference signal) to the mobile station 300 by using DL reverse transmission.

(Step S235) The radio communication unit 210 receives the Msg 2 from the base station 100 using a PDCCH or an R-PDCCH subframe in the DL reverse transmission.

(Step S236) The radio communication unit 210 transmits the Msg 3 to the base station 100. Preferably, the radio communication unit 210 transmits the Msg 3 to the base station 100 using the UL reverse transmission.

(Step S237) The reverse transmission controller 263 restricts the transmission of the radio signal (including the reference signal) to the mobile station 300 by using DL reverse transmission.

(Step S238) The radio communication unit 210 receives the Msg 4 from the base station 100 using a PDCCH or an R-PDCCH subframe in the DL reverse transmission.

FIG. 15 is a flowchart illustrating an operation of a mobile station according to a third embodiment. Here, the mobile station 300 is assumed to perform random access to the relay station 200 or the base station 100. The process illustrated in FIG. 15 includes the following steps.

(Step S241) The radio communication unit 310 receives broadcast information from the relay station 200 or the base station 100 using the PBCH. The broadcast information includes information indicating the timing of the RA slot for the mobile station. An RA slot control unit 352 selects an RA slot for the mobile station.

(Step S242) The preamble control unit 351 selects one preamble from among the preamble candidates. Preamble candidates are shared between relay stations 200 and 200a or mobile stations 300 and 300a. The radio communication unit 310 transmits the selected preamble through the RA slot selected in step S241.

(Step S243) The radio communication unit 310 monitors the PVCCH within the period in which the Msg 2 is transmitted and receives the Msg 2 from the relay station 200 or the base station 100. It should be noted that the radio communication unit 310 receives the Msg 2 from the relay station 200 using the subframe as except for a subframe in DL reverse gear.

(Step S244) The radio communication unit 310 transmits the Msg 3 to the relay station 200 or the base station 100. The radio communication unit 310 transmits the Msg 3 to the relay station 200 using a subframe except for a subframe in the UL reverse transmission.

(Step S245) The radio communication unit 310 monitors the PDCCH within the period in which the Msg 4 is transmitted, and receives the Msg 4 from the relay station 200 or the base station 100. It should be noted that the radio communication unit 310 receives the Msg 4 from the relay station 200 using the subframe for except for a subframe in DL reverse gear.

(Step S246) The radio communication unit 310 transmits data between its own station and any of the relay station 200 and the base station 100. It should be noted that when connected to the relay station 200, the radio communication unit 310 performs data transmission using the subframe except for the subframe in the reverse transmission.

FIG. 16 illustrates an example of random access according to a third embodiment. The message flow illustrated in FIG. 16 includes the following steps.

(Step S21) The relay station 200 transmits the Msg 1 to the base station 100 through the RA slot for the relay station of the UL reverse transmission subframe. The preamble transmitted as Msg 1 may be a shared relay station and a mobile station. Based on the timing of the reception of the preamble, the base station 100 recognizes that the transmission source Msg 1 is a relay station 200.

(Step S22) The base station 100 transmits the Msg 1 using the DL reverse transmission R-PDCCH of the relay station 200 within the period in which the Msg 2 is transmitted. When a signal, such as a reference signal, is not transmitted in the data area, the relay station 200 receives Msg 2.

(Step S23) The base station 100 transmits the Msg 2 by using the DL reverse transmission of the relay station 200a within the period in which the Msg 2 is transmitted.

(Step S24) The relay station 200 transmits the Msg 2 to the base station 100 using the UL reverse transmission. Based on the identifier included in the Msg 3, the base station 100 recognizes that the transmission source of the Msg 3 is a relay station 200.

(Step S25) The base station 100 transmits the Msg 2 using the DL reverse transmission R-PDCCH of the relay station 200 within the period in which the Msg 4 is transmitted. When a signal, such as a reference signal, is not transmitted in the data area, the relay station 200 receives Msg 4.

Meanwhile, the base station 100 does not always have to configure the RA slot for the relay station. In particular, the base station 100 may configure the RA slot after detecting the RA trigger on the relay stations 200 and 200a.

FIG. 17 illustrates another example of random access according to a third embodiment. The base station 100 does not assign a radio resource to the PRACH for the relay station in a normal situation. On the other hand, when the RA trigger is detected and determining that any of the relay stations 200 and 200a can perform random access, the base station 100 assigns a radio resource to the PRACH for the relay station. At this time, by using a timer, the base station 100 may limit the period in which the radio resource is assigned. Relay stations 200 and 200a transmit Msg 1 within this period. As can be seen from the above description, when the relay stations 200 and 200a do not perform random access, the base station 100 assigns the radio resource of the RA slot used for the relay station to an arbitrary channel except PRACH, thereby effectively using the radio resource.

According to a third embodiment, the proposed radio communication system allows the base station 100 to determine, based on the clock at which Msg 1 is received, whether the transmission source Msg 1 is a relay station or a mobile station. When the transmission source is a relay station, the base station 100 then controls the timing of the transmission so that the relay station can receive Msg 2 via the existing DL reverse transmission. When the source of the Msg 3 transmission is the relay station 200, the base station 100 further controls the transmission timing so that the relay station 200 can receive the Msg 4 through the existing DL reverse transmission. According to a third embodiment, the radio communication system suppresses the internal interference of the relay station 200 and smoothly performs random access from the relay station 200 to the base station 100.

(Fourth Embodiment)

A fourth embodiment is described below. Since the fourth embodiment shares some elements with the preceding second and third embodiments, the following description will focus on their distinctive elements, omitting explanations of similar elements. The fourth embodiment differs from the second and third embodiments by the timing in which Msg 2 or 4 is transmitted.

The radio communication system according to the fourth embodiment is deployed by using the same device configuration as that of the second embodiment illustrated in FIG. 2. Next, the base station, the relay station, and the mobile station according to the fourth embodiment are deployed by using the same block configurations as those of the second embodiment illustrated in FIG. 6-8. Hereinafter, the fourth embodiment will be described with reference to the same reference numerals as illustrated in FIG. 6-8.

FIG. 18 is a flowchart illustrating an operation of a base station according to a fourth embodiment. Since the processes of steps S311, S312, S314-S317, S319 and S320 illustrated in FIG. 18 are the same as those of steps S111, S112, S114 to S117, S119 and S120 illustrated in FIG. 9, the description will not be repeated.

(Step S313) The reverse gear controller 163 selects the default DL reverse gear within the period in which Msg 2 is transmitted. The default reverse gear is a reverse gear that is not valid in a normal situation, but automatically becomes valid during random access. The default reverse feed timing, for example, is mutually configured between relay stations 200 and 200a. The default retransmission timing of the relay stations 200 and 200a is pre-configured between their own stations and the base station 100, and is configured, for example, by the telecommunications operator during the deployment of the relay stations 200 and 200a.

(Step S318) The reverse transmission controller 163 selects a default DL reverse transmission within the period in which the Msg 4 is transmitted.

FIG. 19 is a flowchart illustrating an operation of a relay station according to a fourth embodiment. The process illustrated in FIG. 19 includes the following steps.

(Step S321) The control plane block 260 determines whether to detect a RA trigger. If so, the process advances to step S322. Otherwise, the control plane block 260 repeats the process of step S321.

(Step S322) In addition to the existing reverse gear, the reverse gear controller 263 makes the default reverse gear with a predetermined timing effective.

(Step S323) The RA transmission control unit 262 selects the RA slot of the default UL reverse subframe. It should be noted that by stopping the reception of the radio signal from the mobile station 300, the RA transmission control unit 262 can select the RA slot except for such a default reverse transmission by UL.

(Step S324) From among the preamble candidates, the preamble control unit 261 selects a preamble for the relay station. The radio communication unit 210 transmits the selected preamble through the RA slot selected in step S323.

(Step S325) In addition to the DL reverse transmission, the reverse transmission controller 263 restricts the transmission of the radio signal to the mobile station 300 via the default DL reverse transmission.

(Step S326) The radiocommunication unit 210 receives the Msg 2 from the base station 100 using the default DL backhaul PDCCH or R-PDCCH.

(Step S327) The radio communication unit 210 transmits the Msg 3 to the base station 100. Preferably, the radio communication unit 210 transmits the Msg 3 to the base station 100 via the default UL reverse transmission.

(Step S328) In addition to the DL reverse transmission, the reverse transmission controller 263 restricts the transmission of the radio signal to the mobile station 300 via the default DL reverse transmission.

(Step S329) The radio communication unit 210 receives the Msg 4 from the base station 100 using the default DL PDCCH or R-PDCCH reverse transmission.

FIG. 20 illustrates an example of random access according to a fourth embodiment. The message flow illustrated in FIG. 20 includes the following steps.

(Step S31) The relay station 200 transmits the Msg 1 to the base station 100 through the default reverse transmission by UL. The preamble to be transmitted is the preamble for the relay station. Based on the preamble, the base station 100 recognizes that the transmission source of the Msg 1 is a relay station.

(Step S32) The base station 100 transmits the Msg 2 using the default DL reverse transmission R-PDCCH within the period in which the Msg 2 is transmitted. The base station 100 does not need to transmit the Msg 2 through each DL reverse transmission of the relay stations 200 and 200a. When a signal, such as a reference signal, is not transmitted in the data area, the relay station 200 receives Msg 2. When the reverse transmission authenticity is confirmed by default, the relay station 200a receives Msg 2, whereas when the default reverse transmission authentication is not confirmed, the relay station 200a does not receive Msg 2.

(Step S33) The relay station 200 transmits the Msg 2 to the base station 100 via the default UL reverse transmission. Based on the identifier included in the Msg 3, the base station 100 recognizes that the transmission source of the Msg 3 is a relay station 200.

(Step S34) The base station 100 transmits the Msg 2 using the default DL reverse transmission R-PDCCH within the period in which the Msg 4 is transmitted. When a signal, such as a reference signal, is not transmitted in the data area, the relay station 200 receives the Msg four.

In the foregoing description, whether the transmission source Msg 1 is a relay station is determined by using the method according to the second embodiment. Further, the determination can be made by using the method according to the third embodiment.

FIG. 21 illustrates another example of random access according to a fourth embodiment. The message flow illustrated in FIG. 21 includes the following steps.

(Step S35) The relay station 200 transmits the Msg 1 to the base station 100 through the RA slot for the relay station of the default UL reverse transmission subframe. Based on the timing of receiving the preamble, the base station 100 recognizes that the transmission source of the Msg 1 is a relay station. After detecting the RA trigger, the base station 100 can make the RA slot for the relay station reliable.

(Step S36) The base station 100 transmits the Msg 1 using the default DL reverse transmission R-PDCCH within the period in which the Msg 2 is transmitted. When a signal, such as a reference signal, is not transmitted in the data area, the relay station 200 receives the Msg 2.

(Step S37) The relay station 200 transmits Msg 1 to the base station 100 via the default UL reverse transmission. Based on the identifier included in the Msg 3, the base station 100 recognizes that the transmission source of the Msg 3 is a relay station 200.

(Step S38) The base station 100 transmits the Msg 1 using the default DL reverse transmission R-PDCCH within the period in which the Msg 4 is transmitted. When a signal, such as a reference signal, is not transmitted in the data area, the relay station 200 receives the Msg four.

In the fourth embodiment, in the same manner as in the second and third embodiments, the proposed radio communication system smoothly performs random access from the relay station 200 to the base station 100. Further, in the fourth embodiment, the radio communication system makes a common transmission timing of Msg 2 and Msg 4 , and simplifies random access control. The moment when the transmission timing has been made general, in particular is checked for authenticity in the case of random access involved in a handover.

(Fifth Embodiment)

A fifth embodiment is described below. Since the fifth embodiment shares some elements with the preceding second and third embodiments, the following description will focus on their distinctive elements, omitting explanations of similar elements. The fifth embodiment is different from the second and third embodiments by a subframe in which an RA slot is configured.

The radio communication system according to the fifth embodiment is deployed by using the same device configuration as that of the second embodiment illustrated in FIG. 2. Next, the base station, the relay station, and the mobile station according to the fifth embodiment are deployed using the same block configurations as those of the second embodiment illustrated in FIG. 6-8. Hereinafter, the fifth embodiment will be described with reference to the reference numerals as illustrated in FIG. 6-8.

FIG. 22 is a flowchart illustrating an operation of a base station according to a fifth embodiment. Since the processes of steps S412, S413, and S415-S421 illustrated in FIG. 22 are the same as such of steps S212, S213, and S215-S221 illustrated in FIG. 13, the description will not be repeated.

(Step S411) The RA slot control unit 162 configures the RA slot for the relay station in the subframe before the k parts of the subframes (e.g., three subframes) from the reverse transmission DL of the relay stations 200 and 200a. When the timing of DL reverse transmissions is different between relay stations 200 and 200a, the RA slot control unit 162 configures the RA slot for the relay station in front of k portions of subframes from each DL reverse transmission.

(Step S414) The reverse transmission controller 163 selects the DL reverse transmission after k parts of the subframes from which the Msg 1 is received. It should be noted that when there are circumstances that Msg 2 cannot be transmitted from the subframe after k parts of the subframes from the above subframe the reverse transfer controller 163 may select another DL reverse transmission after k parts of the subframes or later from the above subframe within the period in which the Msg 2 is transmitted.

FIG. 23 is a flowchart illustrating a process of a relay station according to a fifth embodiment. Since the processes of steps S432, S433, and S435-S437 illustrated in FIG. 23 are the same as those of steps S233, S234, and S236-S238 illustrated in FIG. 14, the description will not be repeated.

(Step S431) The RA transmission control unit 262 selects the RA slot of the subframe before k parts of the subframes (e.g., three subframes) from the DL reverse transmission as the RA slot for the relay station. When the subframe of the selected RA slot is not a UL reverse transmission subframe, the reverse transmission controller 263 controls that data is not received from the mobile station 300 using this subframe.

(Step S434) The radio communication unit 210 starts monitoring the PDCCH or R-PDCCH from the DL reverse subframe after k parts of the subframes from the subframe in which Msg 1 is transmitted. Msg 2 is expected to be received using the DL reverse transmission. It should be noted that when Msg 2 is not received using DL reverse transmission, the radio communication unit 210 monitors the PDCCH or R-PDCCH from the DL reverse transmission subframe after the above subframes or later.

FIG. 24 illustrates an example of random access according to a fifth embodiment. The message flow illustrated in FIG. 24 includes the following steps.

(Step S41) The relay station 200 transmits Msg 1 to the base station 100 through the slot RA of the subframe before three subframes from the DL reverse transmission subframe. Based on the timing of receiving the preamble, the base station 100 recognizes that the transmission source of the Msg 1 is a relay station.

(Step S42) The base station 100 transmits Msg 2 using the R-PDCCH of the DL reverse subframe after three subframes from the subframe in which Msg 1 is received. When a signal, such as a reference signal, is not transmitted in the data area, the relay station 200 receives Msg 2.

(Step S43) The relay station 200 transmits the Msg 2 to the base station 100 using the UL reverse transmission. Based on the identifier included in the Msg 3, the base station 100 recognizes that the transmission source of the Msg 3 is a relay station 200.

(Step S44) The base station 100 transmits the Msg 2 using the DL reverse transmission R-PDCCH of the DL relay station 200 within the period in which the Msg 4 is transmitted. When a signal, such as a reference signal, is not transmitted in the data area, the relay station 200 receives Msg 4.

In the foregoing description, whether the transmission source Msg 1 is a relay station is determined by using the method according to the third embodiment; can also be determined by using the method according to the second embodiment.

In the fifth embodiment, in the same manner as in the second and third embodiments, the proposed radio communication system smoothly performs random access from the relay station 200 to the base station 100. Further, in the fifth embodiment, the relay station 200 smoothly starts random access, even if the slot RA is not provided in UL reverse gear. In addition, the relay station 200 preferably monitors the reception signal after a predetermined time after the transmission of Msg 1, thereby simplifying control.

(Sixth Embodiment)

A sixth embodiment is described below. Since the sixth embodiment shares some of the elements with the preceding second and third embodiments, the following description will focus on their distinctive elements, omitting explanations of similar elements. In a sixth embodiment, Msg 2 and Msg 4 are also transmitted using a subframe except for a subframe in the reverse transmission of the DL relay station.

The radio communication system according to the sixth embodiment is deployed by using the same device configuration as that of the second embodiment illustrated in FIG. 2. Next, the base station, the relay station, and the mobile station according to the sixth embodiment are deployed using the same block configurations as those of the second embodiment illustrated in FIG. 6-8. Hereinafter, a sixth embodiment is described with reference to reference numerals, which is illustrated in FIG. 6-8.

FIG. 25 is a flowchart illustrating an operation of a base station according to a sixth embodiment. Since the processes of steps S511, S512, S514-S517, S519 and S520 are illustrated in FIG. 25 are the same as those of steps S111, S112, S114 to S117, S119, and S120 illustrated in FIG. 9, the description will not be repeated.

(Step S513) The reverse transmission controller 163 selects a subframe after m parts of the subframes from the subframe in which Msg 1 is received. The symbol m indicates a predetermined value of the base station 100 and the relay stations 200 and 200a, and is set, for example, to three.

(Step S518) The reverse transmission controller 163 selects a subframe after n parts of the subframes from the subframe in which Msg 3 is received. The symbol n indicates a predetermined value of the base station 100 and the relay stations 200 and 200a, and is set, for example, to eight.

FIG. 26 is a flowchart illustrating an operation of a relay station according to a sixth embodiment. Since the processes of steps S521, S522, and S525 illustrated in FIG. 26 are the same as such of steps S121, S122, and S125 illustrated in FIG. 10, the description will not be repeated.

(Step S523) The reverse transmission controller 263 restricts the transmission of the radio signal (including the reference signal) to the mobile station 300 using the subframe after m parts of the subframes from the subframe in which Msg 1 is transmitted. When the Msg 2 is transmitted using the PDCCH, the reverse transmission controller 263 stops transmitting signal in both of the areas for control and data. When Msg 2 is transmitted using the R-PDCCH, the reverse transmission controller 263 stops signal transmission in at least the data area.

(Step S524) The radio communication unit 210 receives the Msg 2 from the base station 100 using a PDCCH or R-PDCCH subframe after m parts of subframes from the above subframe.

(Step S526) The reverse transmission controller 263 restricts the transmission of the radio signal (including the reference signal) to the mobile station 300 using the subframe after n parts of the subframes from the subframe in which the Msg 3 is transmitted. When the Msg 4 is transmitted using the PDCCH, the reverse transmission controller 263 stops the transmission signal in both of the areas for control and data. When Msg 4 is transmitted using the R-PDCCH, the reverse transmission controller 263 stops signal transmission in at least the data area.

(Step S527) The radio communication unit 210 receives the Msg 4 from the base station 100 using a PDCCH or an R-PDCCH subframe after n parts of subframes from the aforementioned subframe.

FIG. 27 illustrates an example of random access according to a sixth embodiment. The message flow illustrated in FIG. 27 includes the following steps.

(Step S51) The relay station 200 transmits the Msg 1 to the base station 100 by using the preamble for this relay station. Based on the preamble, the base station 100 recognizes that the transmission source of the Msg 1 is a relay station.

(Step S52) The base station 100 transmits the Msg 2 using the R-PDCCH subframe after three subframes from the subframe in which the Msg 1 is received. Using the subframe after three subframes of the subframe in which Msg 1 is transmitted, the relay station 200 controls a signal, such as a reference signal that should not be transmitted in the data area, thus receiving Msg 2.

(Step S53) The relay station 200 transmits the Msg 2 to the base station 100. Based on the identifier included in the Msg 3, the base station 100 recognizes that the transmission source of the Msg 3 is the relay station 200.

(Step S54) Using the R-PDCCH, the subframe after eight subframes from the subframe in which the Msg 3 is received, the base station 100 transmits the Msg 4. Using the subframe after eight subframes from the subframe in which the Msg 3 is transmitted, the relay station 200 controls the signal, such as a reference signal that should not be transmitted in the data area, thus receiving Msg 4.

In the foregoing description, whether the transmission source Msg 1 is a relay station is determined by using the method according to the second embodiment; further, may be determined by using the method according to the third embodiment.

In the sixth embodiment, in the same manner as in the second and third embodiments, the proposed radio communication system smoothly performs random access from the relay station 200 to the base station 100. In the sixth embodiment, since the interval between Msg 1 and Msg 2, as well as the interval between Msg 3 and Msg 4 is fixed, the radio communication system simplifies random access control in the relay station 200. On the other hand, with respect to random access from the mobile station 300a to the base station 100, since the intervals are not tanovleny, radio communication system provides scheduling flexibility.

(Seventh Embodiment)

A seventh embodiment is described below. Since the seventh embodiment shares some elements with the preceding second embodiment, the following description will focus on their distinctive elements, omitting explanations of such elements. In the preceding second to sixth embodiments, the timing of the transmission of Msg 2 or Msg 4 is changed based on the fact that the transmission source of the Msg 1 or Msg 3 is a relay station or a mobile station. Compared with the above, in the seventh embodiment, even if the base station does not distinguish that the transmission source is a relay station or a mobile station, the radio communication system performs random access.

The radio communication system according to the seventh embodiment is deployed by using the same device configuration as that of the second embodiment illustrated in FIG. 2. Next, the base station, the relay station, and the mobile station according to the seventh embodiment are deployed using the same block configurations as those of the second embodiment illustrated in FIG. 6-8. Hereinafter, the seventh embodiment is described with reference to reference numerals, such as those illustrated in FIG. 6-8.

FIG. 28 is a flowchart illustrating an operation of a base station according to a seventh embodiment. The process illustrated in FIG. 28 includes the following steps.

(Step S611) The radio communication unit 110 receives the preamble (Msg 1) using PRACH. At this time, the Msg 1 transmission source was not specifically identified.

(Step S612) The control plane block 160 performs scheduling, and selects an arbitrary subframe within the period in which Msg 2 is transmitted.

(Step S613) The radio communication unit 110 transmits the Msg 2 using the PDCCH or R-PDCCH of the subframe selected in step S612.

(Step S614) The radio communication unit 110 receives Msg 3. Here, the transmission source is assumed to be a relay station 200.

(Step S615) The control plane block 160 performs scheduling and selects an arbitrary subframe within the period in which Msg 4 is transmitted.

(Step S616) The radio communication unit 110 transmits the Msg 4 using the PDCCH or R-PDCCH of the subframe selected in step S615.

FIG. 29 is a flowchart illustrating an operation of a relay station according to a seventh embodiment. The process illustrated in FIG. 29 includes the following steps.

(Step S621) The radio communication unit 210 receives broadcast information from the base station 100 using the PBCH. The broadcast information includes information regarding the timing of the RA slot. RA transmission control unit 262 selects one RA slot. The postback controller 263 controls data that should not be received from the mobile station 300 using a subframe on which an RA slot is provided.

(Step S622) The preamble control unit 261 selects one preamble from among the preamble candidates. The radio communication unit 210 transmits the selected preamble using the RA slot selected in step S621.

(Step S623) The reverse transmission controller 263 restricts the transmission of the radio signal (including the reference signal) to the mobile station 300 until it receives Msg 2 from the beginning of the period in which Msg 2 can be received. When the Msg 2 is transmitted using PDCCH, the controller 263 reverse transmission stops signal transmission in both of the control and data areas. When Msg 2 is transmitted using the R-PDCCH, the reverse transmission controller 263 stops signal transmission in at least the data area.

(Step S624) The radio communication unit 210 receives the Msg 2 from the base station 100 using a PDCCH or R-PDCCH.

(Step S625) The transmit reverse transmission controller 263 re-starts transmitting the radio signal (including the reference signal) to the mobile station 300.

(Step S626) The radio communication unit 210 transmits the Msg 3 to the base station 100.

(Step S627) The reverse transmission controller 263 restricts the transmission of the radio signal (including the reference signal) to the mobile station 300 until it receives Msg 4 from the beginning of the period in which Msg 4 can be received. When the Msg 2 is transmitted using the PDCCH, the controller 263 reverse transmission stops signal transmission in both of the control and data areas. When Msg 2 is transmitted using the R-PDCCH, the reverse transmission controller 263 stops signal transmission in at least the data area.

(Step S628) The radio communication unit 210 receives the Msg 2 from the base station 100 using a PDCCH or R-PDCCH.

(Step S629) The reverse transmission controller 263 re-starts transmitting the radio signal (including the reference signal) to the mobile station 300.

FIG. 30 illustrates an example of random access according to a seventh embodiment. The message flow illustrated in FIG. 30 includes the following steps.

(Step S61) The relay station 200 transmits Msg 1 to the base station 100.

(Step S62) The base station 100 performs scheduling and transmits Msg 2 using the R-PDCCH of any subframe within the period in which the Msg 2 is transmitted. Using the subframe after three subframes or later from the subframe in which Msg 1 is transmitted, the relay station 200 controls a signal, such as a reference signal, which should not be transmitted in the data area, thereby receiving Msg 2.

(Step S63) The relay station 200 transmits the Msg 3 to the base station 100. Based on the identifier included in the Msg 3, the base station 100 recognizes that the transmission source of the Msg 3 is the relay station 200.

(Step S64) The base station 100 performs scheduling and transmits Msg 4 using the R-PDCCH of any subframe within the period in which Msg 4 is transmitted. Using the subframe or later in which Msg 3 is transmitted, the relay station 200 controls the signal such as a reference signal that should not be transmitted in the data area, thus receiving Msg 4.

In a seventh embodiment, the proposed radio communication system suppresses the internal interference of the relay station 200 and smoothly performs random access from the relay station 200 to the base station 100. Further, the base station 100 does not distinguish between random access by the relay station 200 and random access through the mobile station 300a, and therefore, it preferably performs the general procedure. As a result, the radio communication system simplifies random access control.

The foregoing discussion is presented only as illustrative of the principles of the present invention. Further, since numerous modifications and changes will be apparent to those skilled in the art, it is not desirable to limit the invention to the exact structure and uses shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims. and their equivalents.

List of Reference Items

10 Base station

20 Relay station

11, 21 Radio communication unit

22 Controller

30 Mobile station.

Claims (4)

1. A radio communication system comprising:
base station
a relay station that wirelessly communicates with a base station; and
a mobile station that wirelessly communicates with a base station or a relay station, wherein:
Relay station includes:
a first radio communication unit that transmits a first random access message to a base station and which receives a radio signal from a base station including a second random access message, and
The base station includes:
a second radio communication unit that receives the first message and transmits the second message; and
a controller that controls the timing of the transmission of the second message based on whether the transmission source of the received first message is a relay station,
the controller restricts the transmission of radio signals from the base station to the relay station in the subframes of the relay station, which are not configured as subframes of a network with a single frequency of the multicast multimedia broadcasting service (MBSFN). 2. A base station used in a system including a mobile station and a relay station that restricts the reception of a radio signal within a partial period and for receiving random access from a relay station or
a mobile station, the base station comprising:
a radio communication unit that receives a first random access message and transmits a second random access message; and
a controller that controls the timing of the transmission of the second message based on whether the transmission source of the received first message is a relay station,
the controller restricts the transmission of radio signals from the base station to the relay station in the subframes of the relay station, which are not configured as subframes of a network with a single frequency of the multicast multimedia broadcasting service (MBSFN). 3. A relay station used in a system including a base station and a mobile station, the relay station comprising:
a radio communication unit that transmits a first random access message to a base station and receives a second random access message from a base station,
wherein, when the first message is transmitted by using a signal sequence indicating that the transmission source is a relay station, or when clocked indicating that the transmission source is a relay station, the radio communication unit receives a second message from the base station,
however, the transmission of radio signals from the base station to the relay station is limited in the subframes of the relay station, which are not configured as
subframes of a network with a single frequency of the service multicast broadcast multimedia information (MBSFN). 4. A radio communication method used in a system that includes a base station, a relay station and a mobile station, and in which the relay station wirelessly communicates with the base station, and in which the mobile station wirelessly communicates with the base station or relay station, the method Radiocommunication contains:
a relay station transmitting a first random access message to a base station;
transmitting, by the base station, a second random access message at a timing that is determined based on whether the transmission source of the first message is a relay station; and
receiving, by the relay station, a second message from the base station,
however, the transmission of radio signals from the base station to the relay station is limited to subframes of the relay station, which are not configured as subframes of a network with a single frequency of the multicast multimedia broadcasting service (MBSFN).

Images