JP5376333B2 - Wireless communication system - Google Patents

Description

  The present invention relates to a wireless communication system that uses, for example, OFDMA (Orthogonal Frequency Division Multiple Access) -TDD (Time Division Duplex) communication method, and more particularly to direct communication between mobile station devices (hereinafter referred to as direct communication between mobile stations). It is related with the radio | wireless communications system which implement | achieves communication.

  For example, in an Orthogonal Division Multiplexing (OFDM) scheme, a data sequence to be transmitted is divided into a plurality of pieces and transmitted in parallel using a plurality of subcarriers. Therefore, in this method, even under frequency selective fading, since it can be regarded as flat fading with each subcarrier, the influence of distortion due to multipath can be reduced. Also, by inserting a signal called CP (Cyclic Prefix), the influence of intersymbol interference can be removed, and high-speed and high-quality data transmission is possible.

The OFDMA scheme is a multiple access scheme based on the OFDM scheme. Multiple access is shared by a plurality of users, and a specific subcarrier and a specific symbol are adaptively allocated to each user, thereby performing multiple access. Is realized.
In a multi-user system based on OFDM, it is common to apply multiple access based on OFDMA to manage all channel assignments in the downlink and uplink directions with a base station apparatus.
In general, the direction from the base station apparatus to the mobile station apparatus is the downlink direction, and the direction from the mobile station apparatus to the base station apparatus is the uplink direction.

FIG. 4 shows a frame configuration example of the OFDMA-TDD communication system according to the conventional example when the duplex system is the TDD system. The horizontal direction represents the OFDM symbol direction (time direction), and the vertical direction represents the subcarrier direction (frequency direction).
The frame of this example includes a downlink synchronization signal 11 area, a downlink control area 12, and a downlink data area 13 as downlink subframe areas, and an uplink control area 14, An upstream data area 101 is provided.

  The downlink subframe always starts with a downlink synchronization signal 11 (also called a preamble), and the mobile station apparatus detects the downlink synchronization signal 11 and performs frame synchronization pull-in. Next, the mobile station apparatus outputs a time / frequency synchronization signal in the uplink control region 14, and the base station apparatus determines the time lag in transmission timing and the transmission frequency of the mobile station apparatus from the time / frequency synchronization signal. The shift is detected, and the time correction amount and the frequency correction amount are output in the downlink control region 12 to the mobile station apparatus. Then, the mobile station apparatus corrects a transmission timing shift and a transmission frequency shift based on the received time correction amount and the frequency correction amount, thereby establishing synchronization and causing no interference to other users. In this state, a transmission signal can be output.

  When the mobile station apparatus completes the connection with the base station apparatus in this way, the base station apparatus sets the allocation of the downlink data area 13 and the uplink data area 101 to the user for each frame, and Information is output from the downlink control area 12 and transmission data is output from the downlink data area 13 based on the allocation. Then, based on the allocation information received in the downlink control area 12, the mobile station apparatus receives data addressed to itself in the downlink data area 13, and outputs transmission data in the uplink data area 101 based on the allocation. To do.

  As described above, in the frame configuration according to the conventional example, data transmission from the base station apparatus to the mobile station apparatus is performed in the downlink data area 13, and data transmission from the mobile station apparatus to the base station apparatus is performed in the uplink data area 101. This realizes data communication between the base station apparatus and the mobile station apparatus.

JP 2007-053579 A

  However, in the OFDMA-TDD communication method according to the conventional example as described above, the downlink direction is limited to communication from the base station apparatus to the mobile station apparatus, and the uplink direction is limited to communication from the mobile station apparatus to the base station apparatus. Therefore, the mobile station devices cannot directly communicate (direct communication between mobile stations) without going through the base station device.

  Therefore, in the OFDMA-TDD radio system according to the conventional example described above, a specific subcarrier is assigned as a dedicated channel for direct communication between mobile stations, and the mobile station uses the dedicated channel in a state independent of the base station apparatus. Inter-direct communication can be considered, but when signals are transmitted asynchronously to the base station device, interference between OFDM symbols occurs. Furthermore, if there is an offset in the transmission frequency of the mobile station device, inter-carrier interference occurs. As a result, there is a problem that the communication quality is greatly deteriorated.

The present invention has been made in view of such conventional circumstances. For example, it is an object of the present invention to provide a radio communication system capable of effectively realizing direct communication between mobile stations in an OFDMA-TDD communication system. And
As a specific example, an object of the present invention is to provide a wireless communication system capable of realizing direct communication between mobile stations without degradation of communication quality in an OFDMA-TDD communication system.

In order to achieve the above object, in the present invention, an OFDMA-TDD communication wireless communication system having a base station apparatus and a plurality of mobile station apparatuses has the following configuration.
That is, in the base station apparatus, when the mobile station apparatus communicates only with the base station apparatus for the upstream data area included in the radio frame, all of the upstream data area is moved. When a request for direct communication between the mobile station apparatus is received from the mobile station apparatus, a part of the uplink data area is moved. Control is performed so as to be allocated as a communication area (synchronization signal area) for synchronization between station apparatuses and a communication area (direct communication area between mobile stations) for direct communication between mobile station apparatuses.

  In the mobile station apparatus, the request transmission means transmits a request for performing direct communication between the mobile station apparatuses to the base station apparatus without going through the base station apparatus. When the indirect synchronization signal transmission means can directly synchronize with the base station apparatus (for example, in an area where direct communication with the base station apparatus is possible) The mobile station apparatus synchronizes an indirect synchronization signal, which is a signal for other mobile station apparatuses to synchronize indirectly with the base station apparatus, based on the synchronization state. When it is impossible to directly synchronize with the base station apparatus (for example, directly communicate with the base station apparatus) Based on the state of synchronization, receiving an indirect synchronization signal transmitted from another mobile station device and indirectly synchronizing with the base station device. And other mobile station devices are indirectly synchronized with the base station device. Indirect synchronization signal is a signal for taking transmitted using communication area for synchronization between the mobile station device. As a communication area for direct communication means to perform direct communication between the mobile station devices by the base station device based on a synchronization state taken directly or indirectly with the base station device Direct communication between mobile station apparatuses is performed using the allocated communication area.

  Accordingly, not only for mobile station devices that are directly synchronized with the base station device, but also for mobile station devices that are relayed by other mobile station devices and indirectly secured with the base station device, the inter-mobile station direct Thus, direct communication between mobile stations can be effectively realized in the OFDMA-TDD communication system. For example, in the OFDMA-TDD communication system, communication quality is not deteriorated. In addition, direct communication between mobile stations can be realized.

Here, various numbers may be used as the number of base station apparatuses and the number of mobile station apparatuses included in the wireless communication system.
In the mobile station device, a request for performing direct communication between the mobile station devices is transmitted in response to an operation by an operator (person), for example.
Various radio frames may be used. For example, a radio frame obtained by adding the improvements according to the present invention to those generally used in the OFDMA-TDD communication scheme is used. .

  Also, in the base station apparatus, various methods may be used as a method for determining the case where all mobile station apparatuses communicate only with the base station apparatus. For example, the mobile station apparatus moves from any mobile station apparatus. A method for determining a case where a request for performing direct communication between station apparatuses is not received as a corresponding case, and even if such a request is received from one or more mobile station apparatuses, all requests are subsequently received. A method can be used in which a case where the mobile station apparatus is withdrawn (for example, all mobile station apparatuses that have issued a request have shifted to another mode) are applicable, or the base station apparatus is under the control of its own apparatus. It is also possible to use a method of storing and managing in a memory whether or not each mobile station apparatus is in a mode for performing direct communication between mobile station apparatuses, and determining based on the management contents.

In addition, various aspects may be used as some aspects of the communication area for synchronizing between mobile station apparatuses and the uplink data area allocated as a communication area for performing direct communication between mobile station apparatuses. . Further, a part of the uplink data area may be set in advance in the base station apparatus and each mobile station apparatus and stored in the memory, or may be stored in the memory from the base station apparatus during operation or the like. May be notified.
In addition, for example, the entire uplink data area is used for communication between the mobile station apparatus and the base station apparatus, or a part of the uplink data area is synchronized between the mobile station apparatuses between the communication area and the mobile station apparatus. The allocation as a communication area for performing direct communication is, for example, notified from the base station apparatus to the corresponding mobile station apparatus (for example, all mobile station apparatuses may always be notified).

In the wireless communication system according to the present invention, the following configuration can be taken as an example of the configuration.
That is, the direct communication means provided in the mobile station apparatus narrows one or both of the time direction and the frequency direction in a preset manner according to the reliability of synchronization with the base station apparatus. It has a function of using the communication area for direct communication between mobile station apparatuses.

  Therefore, it is used for direct communication between mobile station apparatuses when the reliability of synchronization between the mobile station apparatus and the base station apparatus is low (for example, when indirect synchronization is established instead of direct synchronization). By narrowing the communication area to be used, for example, interference with a signal included in the communication area used for communication between the base station apparatus and the mobile station apparatus can be prevented.

Here, depending on the reliability of synchronization between the mobile station apparatus and the base station apparatus, one or both of the time direction and the frequency direction of the communication area used for direct communication between the mobile station apparatuses (preset communication) Various modes may be used as a mode of narrowing (rather than the region).
In addition, the communication area used for direct communication between mobile station apparatuses is preferably narrowed in both the time direction and the frequency direction, for example, but only one of them may be narrowed.
In addition, it is not always necessary to narrow the communication area used for direct communication between mobile station apparatuses. For example, direct synchronization is established between the mobile station apparatus and the base station apparatus. In such a case, a mode in which the communication area used for direct communication between mobile station apparatuses is not narrowed may be used.

Furthermore, in the wireless communication system according to the present invention, the following configuration can be taken as an example of the configuration.
That is, the indirect synchronization signal transmission means provided in the mobile station apparatus transmits an indirect synchronization signal including information corresponding to the number of times relayed by the mobile station apparatus. The direct communication means provided in the mobile station apparatus synchronizes indirectly with the base station apparatus as a preset mode according to the reliability of synchronization with the base station apparatus. For this reason, a mode is used in which the width to be narrowed in one or both of the time direction and the frequency direction of the communication region is increased as the number of relays identified by the indirect synchronization signal used for this purpose increases.

Accordingly, the communication area used for direct communication between the mobile station devices can be narrowed according to the number of other mobile station devices relayed when the mobile station device is indirectly synchronized with the base station device.
Here, as the information according to the number of times relayed by the mobile station device included in the indirect synchronization signal, various information may be used, for example, information on the number of times itself may be used, or Other information may be used.

  As described above, according to the wireless communication system according to the present invention, for example, direct communication between mobile stations can be effectively realized in the OFDMA-TDD communication system.

It is a figure which shows the structural example of the flame | frame of the OFDMA-TDD communication system which concerns on one Example of this invention. It is a figure which shows the structural example of the radio | wireless communications system which concerns on one Example of this invention. (A)-(c) is a figure which shows the usage example of the channel at the time of the direct communication between the mobile stations of the OFDMA-TDD communication system which concerns on one Example of this invention. It is a figure which shows the structural example of the flame | frame of the OFDMA-TDD communication system which concerns on a prior art example.

Embodiments according to the present invention will be described with reference to the drawings.
For example, when the duplex method is the TDD method, a part of the uplink channel is allocated for direct communication between mobile stations, so that the mobile station device and other mobile station devices can be connected without going through the base station device. It is possible to communicate directly between.

FIG. 1 shows an example of a frame structure of an OFDMA-TDD communication system according to an embodiment of the present invention. The horizontal direction represents the OFDM symbol direction (time direction), and the vertical direction represents the subcarrier direction (frequency direction).
The frame of this example includes a downlink synchronization signal 11 area, a downlink control area 12, and a downlink data area 13 as downlink subframe areas, and an uplink control area 14, An uplink data area 15, a synchronization signal area 21, and a direct communication area 22 between mobile stations are provided.

The downlink synchronization signal 11 is used for the mobile station apparatus to achieve frame synchronization with the base station apparatus.
The downlink control area 12 is used for sending a control signal from the base station apparatus to the mobile station apparatus.
The downlink data area 13 is used for sending data from the base station apparatus to the mobile station apparatus.
The uplink control area 14 is used for sending a control signal from the mobile station apparatus to the base station apparatus.
The uplink data area 15 is used for transmitting data from the mobile station apparatus to the base station apparatus.

The synchronization signal area 21 is a synchronization signal for a mobile station device that exists outside the area (communication area) of the base station device to indirectly perform frame synchronization with the base station device. It is used for transmission from other mobile station apparatuses existing outside.
The inter-mobile station direct communication area 22 is used for transmitting data when mobile station apparatuses perform direct communication without going through a base station apparatus. Here, as two or more mobile station apparatuses that perform direct communication between mobile stations, for example, one or more (or all of them) may be mobile station apparatuses that indirectly establish frame synchronization with the base station apparatus. There may be.

In this example, for example, the synchronization signal area 21 and the direct communication area 22 between mobile stations are included in the upstream data area 15, and when these areas 21 and 22 are not allocated, the same as the upstream data area 15. Be treated.
In this example, the synchronization signal area 21 and the direct communication area 22 between mobile stations are considered to be included in the uplink data area 15, and as another way of understanding, these areas 15, 21, and 22 are separated. Although it can be regarded as a region, it is substantially the same in any way.
Here, for convenience of explanation, in FIG. 1, the same parts 11 to 14 as those shown in FIG.

FIG. 2 shows a configuration example of a wireless communication system according to an embodiment of the present invention.
The wireless communication system of this example includes a base station device and a plurality of mobile station devices (for example, mobile station devices A to E). The number of devices may be various.
The base station apparatus performs downlink / uplink channel assignment processing and wireless communication with mobile station apparatuses existing in the area, and each mobile station apparatus wirelessly communicates with the base station apparatus. Processing and processing for directly communicating with other mobile station devices are performed.
Here, FIG. 2 shows an example of the arrangement of mobile station apparatuses during direct communication between mobile stations in the OFDMA-TDD communication system of this example.

FIGS. 3A to 3C show examples of channel use during direct communication between mobile stations in the OFDMA-TDD communication system of this example.
With reference to FIGS. 1 to 3, an example of operations up to direct communication between mobile stations and operation during direct communication between mobile stations in the wireless communication system of this example will be described.
The process until mobile station apparatus A and mobile station apparatus B existing in the area of the base station apparatus are connected to the base station apparatus, for example, is the same as in the OFDMA-TDD communication scheme according to the prior art. The detailed process is omitted.

First, the outline | summary of operation | movement of the base station apparatus and mobile station apparatus AE in this example is demonstrated.
When all the mobile station devices communicate with only the base station device for the uplink data region 15 included in the radio frame, the base station device has the mobile station device and the base station device all of the uplink data region 15 Assign to be used for communication with. That is, in this case, the synchronization signal area 21 and the direct communication area 22 between mobile stations are not allocated and are handled in the same manner as the uplink data area 15.
In addition, when the base station apparatus receives a request for performing direct communication between the mobile station apparatuses from the mobile station apparatus, communication for performing direct communication between the mobile station apparatuses for a part of the uplink data area 15 As areas (in this example, the synchronization signal area 21 and the direct communication area 22 between mobile stations) are allocated.

When the mobile station device communicates with another mobile station device or the like via the base station device (when it is in the base station communication mode), for example, the mobile station device performs the same as in the conventional technique.
Further, the mobile station apparatus performs direct communication between the mobile station apparatuses without going through the base station apparatus (in the case of the direct communication mode between mobile stations), and directly synchronizes the radio frame with the base station apparatus. (In this example, when the mobile station apparatus is within the area of the base station apparatus), a request for direct communication between the mobile station apparatuses is transmitted to the base station apparatus, and the base station apparatus A process of directly establishing synchronization of the radio frame with the station apparatus is performed, and a synchronization signal for synchronizing the radio frame with another mobile station apparatus is generated in the synchronization signal area 21 based on the synchronization state of the radio frame. Perform output relay processing. Here, in the mobile station apparatus that has already established the synchronization of the radio frame directly with the base station apparatus, the process of further establishing the synchronization may not be performed.

  Further, the mobile station apparatus performs direct communication between the mobile station apparatuses without going through the base station apparatus (in the case of the direct communication mode between mobile stations), and directly synchronizes the radio frame with the base station apparatus. When it cannot be taken (in this example, when it is outside the area of the base station apparatus), it receives the synchronization signal output from the other mobile station apparatus in the synchronization signal area 21 and receives the synchronization signal. The radio frame synchronization process is performed indirectly with the base station apparatus, and a synchronization signal for synchronizing the radio frame with another mobile station apparatus based on the synchronization state of the radio frame. The relay processing output at 21 is performed.

Next, a specific example will be described.
In this example, mobile station apparatuses A to E are in the state of direct communication between mobile stations, and the base station apparatus allocates synchronization signal area 21 and direct communication area 22 between mobile stations to uplink data area 15. To do.
In the example of FIG. 2, the mobile station device A and the mobile station device B are in a state in which synchronization is established directly with the base station device, and as shown in FIG. 3A, the mobile station device A and the mobile station device B outputs a synchronization signal (first synchronization signal) every frame at the head symbol of the synchronization signal area 21.
Here, the first synchronization signal is composed of a code division multiple access (CDMA) code as in the case of the ranging code, and can be received separately even when a plurality of synchronization signals overlap.
Further, in this example, the synchronization signal region 21 has a time direction from the synchronization signal (here, the first synchronization signal) so as not to interfere with adjacent channels even if there is a timing offset or a frequency offset. A wide area is secured in both directions in the frequency direction.

  Next, the mobile station apparatus C existing at a position where it can receive the radio signal from the mobile station apparatus A receives the first synchronization signal output from the mobile station apparatus A and indirectly receives the base station. The apparatus establishes rough synchronization with the apparatus, but is delayed in the time direction by the propagation delay between the mobile station apparatus A and the mobile station apparatus C and appears to be shifted in the frequency direction due to the frequency offset of the mobile station apparatus C. It appears that the first synchronization signal is received at the receiving position as shown in b).

  Similarly, the mobile station apparatus D existing at a position where it can receive the radio signal from the mobile station apparatus B receives the first synchronization signal output from the mobile station apparatus B and indirectly receives the base station. The apparatus establishes rough synchronization with the apparatus, but appears delayed in the time direction by the propagation delay between the mobile station apparatus B and the mobile station apparatus D and shifted in the frequency direction due to the frequency offset of the mobile station apparatus D. It appears that the first synchronization signal is received at the receiving position as shown in b).

  Thereafter, the mobile station device C and the mobile station device D output a synchronization signal (second synchronization signal) with the first symbol of the synchronization signal region 21 every frame, but the mobile station device C communicates with the mobile station device A. Since the output is delayed by the propagation delay, the mobile station apparatus D outputs the delay by the propagation delay with respect to the mobile station apparatus B, and since both have a frequency offset, the first symbol in the synchronization signal area 21 is the first symbol. Even if it is intended to output the second synchronization signal, as shown in FIG. 3B, it is shifted backward in time by the propagation delay and further shifted in the frequency direction.

Here, in this example, as the synchronization signal region 21, a region for a plurality of OFDM symbols is secured in consideration of the above-described propagation delay, and further, frequency synchronization is considered at both ends in the frequency direction in consideration of the frequency offset. Since the unused subcarriers are secured, the synchronization signal does not interfere with adjacent channels.
Similarly to the first synchronization signal, the second synchronization signal is composed of a CDMA code, and can be received separately even when a plurality of synchronization signals overlap.

  Next, the mobile station apparatus E existing at a position where it can receive the radio signal from the mobile station apparatus C receives the second synchronization signal output from the mobile station apparatus C, and indirectly receives the base station. Coarse synchronization is established with the apparatus, but in the time direction by an amount that is the sum of the propagation delay between the mobile station apparatus A and the mobile station apparatus C and the propagation delay between the mobile station apparatus C and the mobile station apparatus E. Since it appears delayed and shifted in the frequency direction due to the frequency offset of the mobile station apparatus E, it appears that the second synchronization signal is received at the reception position as shown in FIG.

  Thereafter, the mobile station apparatus E outputs a synchronization signal (third synchronization signal) every frame at the first symbol of the synchronization signal area 21, but the mobile station apparatus E propagates from the mobile station apparatus A via the mobile station apparatus C. Since the output is delayed by the delay amount and there is a frequency offset, even if the third synchronization signal is intended to be output at the first symbol of the synchronization signal region 21, as shown in FIG. The output is shifted backward in time and further shifted in the frequency direction.

Here, in this example, as the synchronization signal region 21, a region for a plurality of OFDM symbols is secured in consideration of the above-described propagation delay, and further, frequency synchronization is considered at both ends in the frequency direction in consideration of the frequency offset. Since the unused subcarriers are secured, the synchronization signal does not interfere with adjacent channels.
Similarly to the first and second synchronization signals, the third synchronization signal is composed of a CDMA code so that even when a plurality of synchronization signals overlap, they can be received separately. Yes.

  At this point, for example, when attention is paid to the mobile station device C, both the first synchronization signal transmitted from the mobile station device A and the third synchronization signal transmitted from the mobile station device E are received. In this case, synchronization with a small error is established by selecting the first synchronization signal with higher reliability. In this way, in this example, a plurality of types of synchronization signals are used properly so that it is possible to determine how many mobile station apparatuses have established coarse synchronization with the base station apparatus. The reliability of synchronization of each mobile station apparatus can be clearly distinguished depending on whether a signal is received.

  As an example, information such as a count value (for example, a value m) of the number of relays is included in the m-th synchronization signal (m is an integer of 1 or more) according to the number of relays. Then, when a mobile station apparatus outside the area of the base station apparatus receives a plurality of synchronization signals, synchronization with the base station apparatus is indirectly performed using a synchronization signal with a smaller number of relays. .

Next, when the mobile station apparatus D and the mobile station apparatus E that have established rough synchronization with the base station apparatus perform direct communication between the mobile stations using the inter-mobile station direct communication area 22 without going through the base station apparatus. To do.
Here, in this example, as direct communication between mobile stations, it is assumed that one user occupies and uses the direct communication area 22 between mobile stations like PressTalk, and individual areas are allocated to a plurality of users. Such control is not considered.

  Since the mobile station apparatus D has received the first synchronization signal and has established a rough synchronization with the base station apparatus, the synchronization shift is larger in both the time direction and the frequency direction than the mobile station apparatus B. ing. Therefore, in this example, as shown in FIG. 3B, the entire area of the direct communication area 22 between mobile stations is not used, but the areas not used for transmission at the rear part in the time direction and at both ends in the frequency direction are used. Provide effects equivalent to guard time and guard band. Thereby, in this example, even if there is a shift in the time direction or the frequency direction due to coarse synchronization with the base station apparatus by the first synchronization signal, data can be transmitted without causing interference to the adjacent channel.

  Further, since the mobile station apparatus E has received the second synchronization signal and has established coarse synchronization with the base station apparatus, the error in the time direction and the frequency direction is further increased as compared with the mobile station apparatus D. There is a possibility. Therefore, in this example, as shown in FIG. 3C, in the direct communication area 22 between mobile stations, the area not used for transmission at the rear part in the time direction and at both ends in the frequency direction is further expanded than the mobile station apparatus D. The effect equivalent to the guard time and the guard band is further increased. Thereby, in this example, even if there is a shift in the time direction or the frequency direction due to rough synchronization with the base station apparatus by the second synchronization signal, data can be transmitted without causing interference to the adjacent channel.

  In addition, since the mobile station apparatus A or the mobile station apparatus B establishes direct synchronization with the base station apparatus when performing direct communication between mobile stations, as shown in FIG. Communication can be performed using the entire direct communication area 22.

  On the other hand, in the mobile station apparatus on the receiving side in the direct communication between mobile stations, it is necessary to recognize in which area of the direct communication area 22 between the mobile stations the transmitting mobile station apparatus transmits data. . Therefore, in this example, a modulation scheme, an error correction scheme, and a number of used subcarriers (number of used subchannels) are included in a region that is always transmitted in the direct communication region 22 between mobile stations (a region that is set as such). , Mapping information consisting of the number of used OFDM symbols, etc. is embedded on the transmitting side with a known modulation scheme, known error correction scheme, known subcarrier number (known subchannel number), known OFDM symbol number, and on the receiving side By demodulating and decoding this, the remaining received data is correctly demodulated and decoded. Note that these pieces of known information are set and stored in advance in each mobile station device, for example.

Next, the transition between the state in which the base station apparatus does not assign the synchronization signal area 21 and the direct communication area 22 between mobile stations to the uplink data area 15 and the state in which it is assigned will be described.
In this example, it is assumed that all the mobile station devices connected to the base station device communicate with the base station device (hereinafter also referred to as base station communication) as an initial state, and the mobile station device A and the mobile station are in that state. After the device B shifts to the mobile station direct communication mode and performs direct communication between the mobile stations between the mobile station device D and the mobile station device E, the mobile station device A and the mobile station device B are normally connected again. A sequence for returning to the base station communication mode will be described.
It is assumed that each of the mobile station devices C to E is in the direct communication mode at a timing before performing direct communication.

  In the initial state, since there is no mobile station apparatus that performs direct communication between mobile stations in the communication area of the base station apparatus, the synchronization signal area 21 and the direct communication area 22 between mobile stations are the uplink data area 15. Is assigned to the user as a part of (that is, treated as the uplink data area 15). In this case, the frame configuration of this example is equivalent to the frame configuration according to the conventional example shown in FIG.

From this state, the mobile station apparatus A issues a direct inter-mobile station communication request to the base station apparatus using the uplink control area 14 in order to shift to the inter-mobile station direct communication mode.
Here, the direct communication request between mobile stations is a signal for notifying the base station apparatus from the mobile station apparatus that the mobile station direct communication mode is to be shifted. At this time, if a radio frame area used for direct communication between mobile stations is not secured, an area securing process is performed in response to this request.

  That is, the base station apparatus receives a request for direct communication between mobile stations from the mobile station apparatus A, secures the synchronization signal area 21 and the direct communication area 22 between mobile stations only for direct communication between mobile stations, and performs base station communication. Only the uplink data area 15 (area not including the synchronization signal area 21 and the direct communication area 22 between mobile stations) is allocated to other mobile station apparatuses. Further, the base station apparatus returns a direct communication request response between mobile stations to the mobile station apparatus A using the downlink control area 12, and further outputs an inter-mobile station direct communication permission to the mobile station apparatus A in each subsequent frame. To do.

Here, the direct communication request response between mobile stations is a signal for notifying the mobile station apparatus from the base station apparatus that the request from the mobile station apparatus has been correctly processed. With this notification, the mobile station apparatus shifts to the direct communication mode between mobile stations.
The mobile station direct communication permission is a signal for confirming that the mobile station apparatus can correctly receive the transmission signal from the base station apparatus (in a synchronized state). Sent.
Note that the information related to the area reserved for direct communication between mobile stations (for example, information on whether or not the area is reserved, and in which area is reserved) uses the downlink control area 12. Then, every frame is transmitted from the base station apparatus to the mobile station apparatus in the direct communication mode between mobile stations.

Next, the mobile station apparatus B also issues a direct inter-mobile station communication request to the base station apparatus using the uplink control area 14 in order to shift to the inter-mobile station direct communication mode.
The base station apparatus receives a request for direct communication between mobile stations from the mobile station apparatus B, but a new area since the synchronization signal area 21 and the direct communication area 22 between mobile stations are already reserved exclusively for direct communication between mobile stations. The mobile station apparatus B returns a direct communication request response between mobile stations to the mobile station apparatus B using the downlink control area 12, and the mobile station apparatus B uses the downlink control area 12 in subsequent frames. Output direct communication permission every frame.

  At this stage, the mobile station apparatus A, the mobile station apparatus B, and the mobile station apparatuses C to E existing outside the area of the base station apparatus (in the inter-mobile station direct communication mode) existing in the area of the base station apparatus The mobile station direct communication area 22 can be shared between the two mobile station apparatuses, and for example, voice communication or data communication by press talk can be performed without going through the base station apparatus. Here, it is assumed that the synchronization signal area 21 is used and the mobile station apparatuses C to E are indirectly synchronized with the base station apparatus.

Thereafter, for example, the mobile station apparatus B issues a base station communication request to the base station apparatus using the uplink control region 14 in order to shift to the base station communication mode.
Upon receiving the base station communication request from the mobile station device B, the base station device cancels the direct communication mode between the mobile stations of the mobile station device B, and uses the downlink control area 12 to communicate with the mobile station device B. Returns a request response. Then, the mobile station apparatus B receiving this base station communication request response shifts to the base station communication mode, and in the subsequent frames, the uplink data area 15 (at this stage, the synchronization signal area 21 and the inter-mobile station direct communication area 22). Area that does not contain).

Thereafter, for example, the mobile station apparatus A also issues a base station communication request to the base station apparatus using the uplink control region 14 in order to shift to the base station communication mode.
Upon receiving the base station communication request from the mobile station device A, the base station device cancels the direct communication mode between the mobile stations of the mobile station device A, and uses the downlink control area 12 to communicate with the mobile station device A. Returns a request response. At this time, since there is no mobile station apparatus that performs direct communication between mobile stations in the area of the base station apparatus, the base station apparatus sets the synchronization signal area 21 and the direct communication area 22 between mobile stations in the uplink data area 15. Reserving as part (opening of the synchronization signal area 21 and the direct communication area 22 between mobile stations).
Then, the mobile station apparatus A that has received the base station communication request response shifts to the base station communication mode, and in the subsequent frames, the uplink data area 15 (an area including the synchronization signal area 21 and the direct communication area 22 between the mobile stations) Will be assigned.

  Thus, in the frame configuration of this example, only when there is a mobile station apparatus that performs direct communication between mobile stations in the area of the base station apparatus, a part of the uplink data area 15 is an area dedicated to direct communication between mobile stations ( The synchronization signal area 21 and the direct communication area 22) between the mobile stations are secured, and in all other cases, the entire uplink data area 15 is secured in the base station communication, so that the reduction in transmission efficiency is suppressed and the direct communication between the mobile stations is performed. Can be realized. In addition, since the mobile station apparatus maintains synchronization directly or indirectly with the base station apparatus even in the inter-mobile station direct communication mode, it does not cause inter-symbol interference or inter-carrier interference (or It is possible to realize direct communication between mobile stations by reducing it.

Here, in this example, one-to-one communication between a certain mobile station device and another mobile station device has been described as an example. However, for example, one-to-many communication may be performed and secured. How to use the area for direct communication may be variously used depending on the mode of the system.
As an example, a mode in which a certain terminal device (for example, a mobile station device or another communication device) communicates with all of the mobile station devices in the direct communication mode between mobile stations can be used in one-to-many manner. As an example, it is possible to use a mode in which a plurality of mobile station apparatuses are grouped in advance and communication is performed with a mobile station apparatus in a direct communication mode between mobile stations in a specific group.

Further, for example, information that a certain mobile station apparatus has shifted to the direct communication mode between mobile stations, or an area for direct communication between mobile stations (synchronization signal area 21 and direct communication area 22 between mobile stations) ) Can be used in such a manner that information such as information is secured from the base station apparatus to another mobile station apparatus. In this case, the mobile station apparatus that has received such notification performs, for example, a determination to shift to the direct communication mode between mobile stations based on the information.
In addition, since it is not always necessary for another mobile station device to grasp information that a certain mobile station device has already shifted to the direct communication mode between mobile stations, a mode in which such information is not reported is used. May be.

  As described above, in the wireless communication system of the present example, the mobile station apparatus that has established synchronization with the base station apparatus within the area of the base station apparatus outputs the synchronization signal (first synchronization signal), and The mobile station apparatus existing outside the area of the station apparatus receives the synchronization signal (first synchronization signal) and indirectly establishes synchronization with the base station apparatus, and thus indirectly the base station The mobile station apparatus that has established synchronization with the apparatus outputs a new synchronization signal (second synchronization signal), and another mobile station apparatus that exists outside the area of the base station apparatus receives the new synchronization signal (second synchronization signal). 2) and indirectly establishes synchronization with the base station apparatus, and thereafter, the base station apparatus indirectly transmits to another mobile station apparatus that exists outside the area of the base station apparatus. By establishing synchronization with the mobile station devices (e.g. Chikyoku device indirectly mobile station apparatus to each other establishing the synchronization can include a) is carried out between mobile station direct communication without passing through the base station apparatus.

Thus, in the wireless communication system of this example, after the mobile station apparatus that exists outside the area of the base station apparatus establishes coarse synchronization indirectly with the base station apparatus using the synchronization signal region 21, the mobile station apparatus By using the inter-direct communication area 22, it is possible to directly communicate with other mobile station devices existing within or outside the area of the base station device without going through the base station device.
Also, in this example, when the mobile station device establishes frame synchronization with the base station device, a plurality of types of synchronization signals are selectively used to distinguish how many mobile station devices have established frame synchronization. To do.

  In this example, the communication area (direct communication area 22 between mobile stations) used by the mobile station apparatus that performs direct communication between mobile stations is used for communication between the base station apparatus and the mobile station apparatus, for example. Depending on the reliability of the frame synchronization with the base station apparatus (in this example, the number of relays) so as not to cause interference with signals included in the communication area, both the time direction and the frequency direction (as other configuration examples) Communication may be performed using a communication area (transmission signal) for direct communication in which any one of them may be narrowed.

As a specific example, as the reliability of synchronization with the base station device becomes lower (in this example, the number of relays increases), the region used in the direct communication region 22 between mobile stations is set in the time direction and the frequency direction. In order to achieve direct communication between mobile stations without degrading the communication quality, while ensuring the communication capacity according to the reliability of synchronization, by narrowing both of them (other configuration examples may be either) be able to.
Here, in this example, the synchronization signal for the mobile station device to synchronize the radio frame with another mobile station device includes different information depending on the number of times relayed by the mobile station device, and the mobile station device In the station apparatus, as the number of relays identified based on this information increases, the width to be narrowed in both the time direction and the frequency direction (which may be either one as another configuration example) is increased.

  Thus, in the wireless communication system of this example, a part of the uplink data area 15 is secured in the direct communication area 22 between mobile stations, and the mobile station apparatus existing outside the area of the base station apparatus is indirectly The area used in the direct communication area 22 between mobile stations is synchronized with the base station apparatus and the reliability of synchronization with the base station apparatus becomes lower (both in the time direction and in the frequency direction) By narrowing at the same time, direct communication between mobile stations can be realized without degrading communication quality while ensuring communication capacity according to the reliability of synchronization with the base station apparatus.

In the radio communication system of the present example, the base station apparatus uses a communication area (synchronization signal area) for synchronizing the uplink data area 15 included in the radio frame as shown in FIG. 1 between the mobile station apparatuses. 21 and a function for controlling switching between a state in which a communication area (direct communication area between mobile stations) 22 for direct communication between the mobile station apparatus and an assigned state is not assigned constitutes a frame area control means.
Further, in the wireless communication system of this example, the mobile station apparatus includes a request transmission means with a function of transmitting a request for performing direct communication between the mobile station apparatuses to the base station apparatus. 21 is used to transmit an indirect synchronization signal (in this example, a first synchronization signal, a second synchronization signal, or a third synchronization signal), and an indirect synchronization signal transmission unit is configured between mobile stations. A direct communication means is configured by the function of performing direct communication. Moreover, in the mobile station apparatus of this example, as shown in FIGS. 3A to 3C, it is used in the direct communication area 22 between mobile stations according to the reliability of synchronization with the base station apparatus. Narrowing the area to be performed is performed.

Here, the configuration of the system and apparatus according to the present invention is not necessarily limited to the configuration described above, and various configurations may be used. The present invention can also be provided as, for example, a method or method for executing the processing according to the present invention, a program for realizing such a method or method, or a recording medium for recording the program. It is also possible to provide various systems and devices.
The application field of the present invention is not necessarily limited to the above-described fields, and the present invention can be applied to various fields.
In addition, as various processes performed in the system and apparatus according to the present invention, for example, the processor executes a control program stored in a ROM (Read Only Memory) in hardware resources including a processor and a memory. A controlled configuration may be used, and for example, each functional unit for executing the processing may be configured as an independent hardware circuit.
The present invention can also be understood as a computer-readable recording medium such as a floppy (registered trademark) disk or a CD (Compact Disc) -ROM storing the control program, and the program (itself). The processing according to the present invention can be performed by inputting the program from the recording medium to the computer and causing the processor to execute the program.

  11. Downlink synchronization signal, 12. Downlink control area, 13. Downlink data area, 14. Uplink control area, 15, 101 Uplink data area, 21 Sync signal area, 22. Between mobile stations Direct communication area,

Claims (2)

In a radio communication system of an OFDMA-TDD communication system having a base station apparatus and a plurality of mobile station apparatuses,
When all the mobile station devices communicate only with the base station device with respect to the uplink data region included in the radio frame, the base station device has all the uplink data regions with the mobile station device and the base station device. In order to synchronize a part of the uplink data area between the mobile station apparatuses when a request for direct communication between the mobile station apparatuses is received from the mobile station apparatus. Frame area control means for controlling to be assigned as a communication area for direct communication between the communication area and the mobile station device,
The mobile station apparatus transmits a request for performing direct communication between the mobile station apparatuses without going through the base station apparatus to the base station apparatus;
When it is possible to directly synchronize with the base station apparatus, another mobile station apparatus indirectly synchronizes with the base station apparatus based on the synchronization state When an indirect synchronization signal, which is a signal, is transmitted using a communication area for synchronization between the mobile station apparatuses, and it is impossible to directly synchronize with the base station apparatus Receiving an indirect synchronization signal transmitted from another mobile station device and indirectly synchronizing with the base station device, and the other mobile station device communicates with the base station device based on the synchronization state. An indirect synchronization signal transmitting means for transmitting an indirect synchronization signal that is a signal for indirectly synchronizing between the mobile station devices using a communication region for synchronization,
Communication area allocated as a communication area for performing direct communication between the mobile station apparatuses by the base station apparatus based on a synchronization state directly or indirectly taken with the base station apparatus Using direct communication means for performing direct communication between mobile station devices,
The direct communication means provided in the mobile station apparatus is a communication area in which one or both of the time direction and the frequency direction is narrowed in a preset manner according to the reliability of synchronization with the base station apparatus. Is used for direct communication between mobile station apparatuses. In a radio communication system of an OFDMA-TDD communication system having a base station apparatus and a plurality of mobile station apparatuses,
When all the mobile station devices communicate only with the base station device with respect to the uplink data region included in the radio frame, the base station device has all the uplink data regions with the mobile station device and the base station device. In order to synchronize a part of the uplink data area between the mobile station apparatuses when a request for direct communication between the mobile station apparatuses is received from the mobile station apparatus. Frame area control means for controlling to be assigned as a communication area for direct communication between the communication area and the mobile station device,
The mobile station apparatus transmits a request for performing direct communication between the mobile station apparatuses without going through the base station apparatus to the base station apparatus;
When it is possible to directly synchronize with the base station apparatus, another mobile station apparatus indirectly synchronizes with the base station apparatus based on the synchronization state When an indirect synchronization signal, which is a signal, is transmitted using a communication area for synchronization between the mobile station apparatuses, and it is impossible to directly synchronize with the base station apparatus Receiving an indirect synchronization signal transmitted from another mobile station device and indirectly synchronizing with the base station device, and the other mobile station device communicates with the base station device based on the synchronization state. An indirect synchronization signal transmitting means for transmitting an indirect synchronization signal that is a signal for indirectly synchronizing between the mobile station devices using a communication region for synchronization,
Communication area allocated as a communication area for performing direct communication between the mobile station apparatuses by the base station apparatus based on a synchronization state directly or indirectly taken with the base station apparatus Using direct communication means for performing direct communication between mobile station devices,
The indirect synchronization signal transmitting means provided in the mobile station device transmits an indirect synchronization signal including information according to the number of times relayed by the mobile station device,
The direct communication means provided in the mobile station apparatus synchronizes indirectly with the base station apparatus as a preset mode according to the reliability of synchronization with the base station apparatus. A wireless communication system characterized by using a mode in which the width that is narrowed in one or both of the time direction and the frequency direction of the communication region is increased as the number of relays identified by the indirect synchronization signal used for this purpose increases.

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