Patent Application
20140219125
The present invention relates to a wireless communication system, a communication method, a communication device and a base-station device.
A cellular system divides an area to provide wireless communication services into a plurality of zones (cells) around base stations and performs transmission and reception of radio signals between each base station and a plurality of terminals existing in a cell covered by the base station. In recent years, there is a growing need for expansion of an area in which it is possible to provide high-speed/high-quality wireless services, and there is a growing demand for the improvement of performance in a low throughput area in a cellular system in the related art.
For example, there are two following techniques suggested up to the present time for such a demand. One is to provide wireless communication services in a smaller cell by adding base stations in a low throughput area in a system, changing the arrangement of cells in the related art, using more base stations as described in PTL 1. This method is generally called “cell-splitting”. The other is to improve the throughput on the cell edge by establishing cooperation with a plurality of base stations that cover a plurality of cells through a control station with respect to a cell edge area with large intercell interference and solving the intercell interference as described in PTL 2. This method is called “CoMP (Coordinated Multi-Point Operation)”, and standardization in LTE (Long Term Evolution)-Advanced is discussed by 3GPP (the 3rd Generation Partnership Project) as described in NPTL 1.
In the two above-mentioned techniques aimed at the improvement of the performance in the low throughput area for the expansion of a high-communication-speed/high-communication-quality area, there are the following problems.
First, since an increase in the number of cells and addition of base stations according to the cell-splitting cause a change in the system configuration, a case is considered where a disadvantageous influence on the stability of network management is caused in addition to the construction cost. Further, interference in a cell edge area becomes remarkable due to the increase in the number of cells.
When the cell edge area is set as a new cell, there is a case where the control load increases in the system due to an increase of the cell and the lack of resources for control information become a problem.
Moreover, since there is a case where the coordinated multi-point operation for interference measures in the cell edge area influences all base stations associated with processing for the cell edge area and it is not possible to flexibly use the communication resources of each base station and the processing performance, there is a problem where excessive communication resources and processing performance are wasted for the interference measures in the cell edge area and the system efficiency degrades.
Taking into account the above points, it is one object of the present invention to provide a wireless communication system, communication method, and communication device that have a mechanism to establish both the stability of network management and the efficiency of interference measures in a cellular system, a mobile communication system, or a portable phone system, and so on.
Moreover, it is another object of the present invention to improve the use efficiency of resources of cells while maintaining a system load in the expansion of a high-communication-speed/high-communication-quality area.
The above-mentioned problem can be solved by a system of fixed-cell support base-station devices, which conform to a cell concept in the related art and have functions of physical layer processing and higher layer processing, and an unfixed-area support base-station device which is not limited to the cell concept and has a physical layer processing function.
The unfixed-area support base-station device can be configured so as to have an interface that performs data transmission with the fixed-cell support base-station device. The unfixed-area support base-station device can be configured so as to take a partial role of the plurality of fixed-cell support base-station devices and perform physical layer signal processing for a low throughput area.
Here, it is possible to make a configuration such that network management of the higher layer is performed on the premise of the fixed-cell ID and control information of the fixed-cell support base-station device.
Moreover, in the unfixed-area support base-station device, it can be formed so as to have a feature that the cell ID is not assigned from the network management side of the higher layer.
According to one aspect of the present invention, a wireless base-station device is provided. The wireless base-station device has a feature that a registered cell is not added, that is, content of a neighbor list to record a cell is not changed in a higher-layer network management station in a cellular system, and an unfixed-cell support base-station device performs signal processing of a physical layer for a terminal in a low throughput area, selects an arbitrary antenna group (single antenna or multiple antennas) from antennas or antenna group linked to a fixed-cell support base station and transmits it together with a transmission signal of the fixed-cell support base station. The unfixed-cell support base-station device includes an interface which performs signal exchange with the fixed-cell support base station, a physical layer signal processing controller and a physical layer signal processing unit based on data analyzed by the fixed-cell support base station. The physical layer signal processing controller determines whether the unfixed-cell support base-station device needs to perform the physical layer signal processing, and generates control information used for the physical layer signal processing. The physical layer signal processing unit creates a transmission signal over radio RF resources (antenna group) of multiple fixed cells.
Moreover, a centralized wireless base-station device can be configured such that the fixed-cell support base-station device and the unfixed-area support base-station device are collectively arranged in one place.
According to another aspect of the present invention, there is provided a wireless communication system including: a first base station for fixed-cell support connected with one or multiple first antennas; a second base station for fixed-cell support connected with one or multiple second antennas; and a communication device for unfixed-area support which performs transmission or reception of a signal with the first base station and the second base station and creates scheduling information and antenna mapping information, in which: the first base station transmits a first reference signal to a terminal during a service; the first base station receives first channel information and/or first communication quality information between the one or multiple first antennas and the terminal, which are calculated by the terminal using the received first reference signal, from the terminal; the first base station transmits identification information of the second base station that covers another cell in which the terminal is located, to the terminal, based on the first channel information and/or the first communication quality information, in a case where reception signal intensity or a ratio of a reception signal to an interference signal is equal to or less than a threshold defined in advance; the first base station receives second channel information between the one or multiple second antennas and the terminal, which is calculated by the terminal using a second reference signal received from the second base station specified by the identification information, from the terminal; the first base station transmits a support request including identification information of the terminal, identification information of the first base station, the identification information of the second base station, the first and second channel information, and transmission signal to the terminal, to the communication device; the communication device selects an antenna combination with highest communication quality or higher communication quality than a threshold defined in advance, from the one or multiple first antennas and the one or multiple second antennas, based on the support request, creates scheduling information and antenna mapping information of a time frequency resource, and transmits an instruction signal including the scheduling information, the antenna mapping information, and the transmission signal to the terminal, to the first base station and the second base station; and the first base station and the second base station each multiplex and map the transmission signal to the terminal and other transmission signals according to the scheduling information and the antenna mapping information, based on the instruction signal, and perform transmission from each antenna included in the selected antenna combination.
Moreover, according to another aspect of the present invention, there is provided a communication method in a wireless communication system, the wireless communication system including: a first base station for fixed-cell support connected with one or multiple antennas; a second base station for fixed-cell support connected with one or multiple second antennas; and a communication device for unfixed-area support which performs transmission or reception of a signal with the first base station and the second base station and creates scheduling information and antenna mapping information, in which: the first base station transmits a first reference signal to a terminal during a service; the first base station receives first channel information and/or first communication quality information between the one or multiple first antennas and the terminal, which are calculated by the terminal using the received first reference signal, from the terminal; the first base station transmits identification information of the second base station that covers another cell in which the terminal is located, to the terminal, based on the first channel information and/or the first communication quality information, in a case where reception signal intensity or a ratio of a reception signal to an interference signal is equal to or less than a threshold defined in advance; the first base station receives second channel information between the one or multiple second antennas and the terminal, which is calculated by the terminal using a second reference signal received from the second base station specified by the identification information, from the terminal; the first base station transmits a support request including identification information of the terminal, identification information of the first base station, the identification information of the second base station, the first and second channel information, and a transmission signal to the terminal, to the communication device; the communication device selects an antenna combination with highest communication quality or higher communication quality than a threshold defined in advance, from the one or multiple first antennas and the one or multiple second antennas, based on the support request, creates scheduling information and antenna mapping information of a time frequency resource, and transmits an instruction signal including the scheduling information, the antenna mapping information, and the transmission signal to the terminal, to the first base station and the second base station; and the first base station and the second base station each multiplex and map the transmission signal to the terminal and other transmission signals according to the scheduling information and the antenna mapping information, based on the instruction signal, and perform transmission from each antenna included in the selected antenna combination.
Further, according to another aspect of the present invention, there is provided a communication device in a wireless communication system including: a first base station for fixed-cell support connected with one or multiple antennas; a second base station for fixed-cell support connected with one or multiple second antennas; and a communication device for unfixed-area support which performs transmission or reception of a signal with the first base station and the second base station and creates scheduling information and antenna mapping information, in which: the first base station transmits a first reference signal to a terminal during a service; the first base station receives first channel information and/or first communication quality information between the one or multiple first antennas and the terminal, which are calculated by the terminal using the received first reference signal, from the terminal; the first base station transmits identification information of the second base station that covers another cell in which the terminal is located, to the terminal, based on the first channel information and/or the first communication quality information, in a case where reception signal intensity or a ratio of a reception signal to an interference signal is equal to or less than a threshold defined in advance; the first base station receives second channel information between the one or multiple second antennas and the terminal, which is calculated by the terminal using a second reference signal received from the second base station specified by the identification information, from the terminal; the first base station transmits a support request including identification information of the terminal, identification information of the first base station, the identification information of the second base station, the first and second channel information and a transmission signal to the terminal, to the communication device; and when the communication device receives a support request from the first base station, the communication device selects an antenna combination with highest communication quality or higher communication quality than a threshold defined in advance, from the one or multiple first antennas and the one or multiple second antennas, based on the support request, creates scheduling information and antenna mapping information of a time frequency resource, transmits an instruction signal including the scheduling information, the antenna mapping information, and the transmission signal to the terminal, to the first base station and the second base station, and causes the first base station and the second base station to multiplex and map the transmission signal to the terminal and other transmission signals according to the scheduling information and the antenna mapping information, based on the instruction signal, and perform transmission from each antenna included in the selected antenna combination.
Moreover, according to another aspect of the present invention, there is provided a base-station device in a wireless communication system, the base-station device including: a first base station unit for fixed-cell support connected with one or multiple antennas; a second base station unit for fixed-cell support connected with one or multiple second antennas; a communication unit for unfixed-area support which performs transmission or reception of a signal with the first base station unit and the second base station unit and creates scheduling information and antenna mapping information; and a signal synthesis unit which synthesizes transmission signals from the first base station unit, the second base station unit and the communication unit, in which the first base station unit transmits a first reference signal to a terminal during a service; the first base station unit receives first channel information and/or first communication quality information between the one or multiple first antennas and the terminal, which are calculated by the terminal using the received first reference signal, from the terminal; the first base station unit transmits identification information of the second base station unit that covers another cell in which the terminal is located, to the terminal, based on the first channel information and/or the first communication quality information, in a case where reception signal intensity or a ratio of a reception signal to an interference signal is equal to or less than a threshold defined in advance; the first base station unit receives second channel information between the one or multiple second antennas and the terminal, which is calculated by the terminal using a second reference signal received from the second base station specified by the identification information, from the terminal; the first base station unit transmits a support request including identification information of the terminal, identification information of the first base station, the identification information of the second base station, the first and second channel information and a transmission signal to the terminal, to the communication unit; the communication unit selects an antenna combination with highest communication quality or higher communication quality than a threshold defined in advance, from the one or multiple first antennas and the one or multiple second antennas, based on the support request, creates scheduling information and antenna mapping information of a time frequency resource, maps the transmission signal to the terminal according to the scheduling information and the antenna mapping information and performs transmission to the transmission signal synthesis unit; and the transmission signal synthesis unit multiplexes and maps the transmission signal from the communication unit to the terminal and other transmission signals from the first base station unit and the second base station unit, and performs transmission from each antenna included in the selected antenna combination.
According to another aspect of the present invention, there is provided a wireless communication system including base stations and a terminal, in which each of the base stations are classified into a fixed-cell support base station and an unfixed-area support base station.
According to another aspect of the present invention, an unfixed-area base station is a wireless base-station device in which a covered area is not limited as a cell and is registered as a cell on a network management side of a higher layer and which has a wireless baseband processing function.
According to another aspect of the present invention, the unfixed-area support base station is a wireless communication device which takes a partial role of the plurality of fixed-cell support base-station devices, uses control information of the plurality of fixed-cell support base stations, selects an arbitrary antenna group (single antenna or multiple antennas) from antennas or antenna group linked to the plurality of fixed-cell support base stations, and transmits it together with a transmission signal of each fixed-cell support base station.
According to another aspect of the present invention, the unfixed-area support base station is a wireless base-station device including an interface which performs signal exchange with a fixed-cell support base station, a physical layer signal processing controller and a physical layer signal processing unit which perform processing based on data analyzed by the fixed-cell support base station, in which: the physical layer signal processing controller determines whether the unfixed-cell support base-station device needs to perform physical layer signal processing, and generates control information used for physical layer signal processing; and the physical layer signal process ing unit creates a transmission signal over radio RF resources (antenna group) of multiple fixed cells.
Moreover, it is possible to provide a wireless communication system in which a fixed-cell support base station and an unfixed-cell support base station exist in a radio service area at the same time. Moreover, the wireless communication system can be characterized in sharing a radio RF resource and performing wireless baseband processing in the fixed-cell support base station or the unfixed-cell support base station according to the state of reception quality.
According to another aspect of the present invention, the unfixed-area support base station is a wireless communication device including: a fixed-cell state monitoring unit which monitors quality information of a fixed cell and determines whether there is a necessity for unfixed-area formation; a control information for unfixed-area signal formation acquisition unit which selects antenna is included in an unfixed area and in which fixed cell the antenna is included, based on control information of a fixed cell, and acquires control information such as channel information; and an unfixed-area signal creation unit which creates a transmission signal and performs interference measure to reduce an influence from the transmission signal to the fixed cell.
Moreover, the unfixed-area support base station may decide whether to select all antennas connected to a fixed cell base station or select part of them. The unfixed-area support base station may decide whether to use all communication resources of a fixed-cell base station or use part of them.
According to another aspect of the present invention, the unfixed-area support base station is a wireless base station including: means for taking a partial role of the plurality of fixed-cell support base-station devices; means for using control information of a fixed-cell support base station; means for selecting an arbitrary antenna group (single antenna or multiple antennas) from antennas or antenna group linked to the fixed-cell support base station; and means for performing transmission together with a transmission signal of the fixed-cell support base station.
According to another aspect of the present invention, the unfixed-area support base station is a wireless base-station device including: an interface device which performs signal exchange with a fixed-cell support base station; a physical layer signal processing controller and a physical layer signal processing device which perform processing based on data analyzed by the fixed-cell support base station; a device which determines whether an unfixed-cell support base-station device needs to perform physical layer signal processing; a device which generates control information used for physical layer signal processing; and a device which creates a transmission signal over radio RF resources (antenna group) of multiple fixed cells.
According to the present invention, it is possible to maintain the stability of network management without increasing the number of cells, establish both the cell-splitting effect and flexible interference measures, and efficiently realize the expansion of a high-communication-speed/high-communication-quality area.
Moreover, according to the present invention, a support area is not limited by the processing performance of a device and it is possible to freely adapt it according to the demand.
In the following, a wireless communication system, wireless communication device, and wireless communication method according to an embodiment of the present invention are described in detail with reference to the drawings.
The first embodiment of the present invention is described with reference to
An unfixed-area support base station 400 illustrated in
The fixed-cell support base stations 510 and 520 provide wireless communication services to terminals in cells managed by them through their antennas. The base stations 510 and 520 periodically broadcast synchronization signals and system information. Downlink (from the base stations to the terminal) synchronization is established using the received synchronization signals after a terminal 511 is powered on, and, moreover, the terminal 511 decides a serving base station from the received signals of the different base stations according to a standard such as the reception intensity, and acquires a cell ID (S201). The present embodiment premises that the serving base station of the terminal 511 is the base station 510, as one example without loss of generality. Further, the terminal 511 creates a random access preamble based on the system information broadcast by the base station 510 (S203) and transmits it to the base station 510. The base station 510 creates an instruction for transmission timing adjustment of the terminal on the basis of the random access preamble of the terminal 511, performs uplink (from the terminal to the base station) resource assignment (S205) and transmits a random access response to the terminal 511. The terminal 511 adjusts the transmit timing according to the random access response and notifies a terminal identifier to the base station 511 by the use of an uplink resource. By this means, the initial connection with access to the cellular system in the terminal 511 is enabled, and it is possible to receive services from the base station.
For transmission and reception of radio service data, the base station 510 transmits a reference signal generated based on the cell ID. The terminal 511 compares the received reference signal and the previously received reference signal, performs channel information estimation between each antenna of the base station 510 and the terminal 511, and provisionally calculates (or calculates) the communication quality (S209). The terminal 511 feeds back channel information and the communication quality information to the base station 510. The base station 510 decides whether to support transmission to the terminal 511 by oneself, based on the fed-back channel information and communication quality information (S211). For example, the base station 510 can make this decision when the power ratio of the received signal to interference, the SINR, the SN ratio or the intensity of the received signal is equal to or less than a threshold defined in advance. When deciding to support it by oneself, the base station 510 continues communication with the terminal 511 by itself. On the other hand, when deciding not to support it by oneself (when deciding to perform coordinated multi-point operation), the base station 510 transmits adjacent base station information (adjacent cell information) to the terminal 511 and notifies the adjacent cell ID and/or the adjacent base station ID, and so on. The terminal 511 acquires the adjacent cell ID and/or the adjacent base station ID, and so on (S213). In the present embodiment, as one example, it is assumed that a base station that covers the adjacent cell is the base station 520. Using the reference signal transmitted by the base station 520, the terminal 511 performs channel information estimation between each antenna of the base station 520 and the terminal 511 (S215), and reports it to the base station 510. Moreover, the base station 510 transmits a support request illustrated in
In response to the support request, the base station 500 performs unfixed-area support processing by the use of that information (S217; see the flowchart described below for details). In this processing, the base station 500 selects an antenna combination in which it is possible to acquire the highest communication quality or higher communication quality than a threshold defined in advance, from arbitrary antenna combinations among the antennas of the base stations 510 and 520, and performs scheduling and antenna mapping according to the selected antenna combination. According to the result of such unfixed-area support processing, the base station 500 transmits an instruction signal illustrated in
Next, on the premise of the selected antenna combination, the base station 500 decides scheduling (assignment of time frequency resources) and communication scheme of the terminal (S107). Further, according to this decision, the base station 500 performs baseband processing on transmission data to the terminal 511 and generates a transmission signal (S109). Mapping information on each antenna and the transmission signal is created together with the generated transmission signal (S111), and the scheduling and communication scheme information of the terminal 511 are transmitted to a related fixed-cell support base station together (S113). Here, it shifts to step S103 in a case where there is an unprocessed support request (S115), and the base station 500 does not operate in a case where there is no unprocessed support request (S115).
The present invention is applicable to a centralized base station in which a plurality of base-station devices is arranged in one place. As the second embodiment, an example is described where a plurality of fixed-cell support base-station devices and an unfixed-area support base-station device are collectively arranged in one centralized base station. Here, the fixed-cell support base-station devices and the unfixed-area support base-station device are respectively realized by a BBU (baseband unit). The base stations are centralized in one place and the antennas of each cell are arranged in the cell in a decentralized manner by RRH (Remote Radio Head).
According to the present embodiment, it is possible to maintain the stability of network management without increasing the number of cells, establish both the cell-splitting effect and flexible interference measures, and efficiently realize the expansion of a high-communication-speed/high-communication-quality area.
The present invention is applicable to various wireless communication systems such as a cellular system, a mobile communication system, and a portable phone system. Moreover, as a terminal, various radio terminals besides a mobile terminal are applicable.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-203592 | Sep 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2012/071757 | 8/29/2012 | WO | 00 | 4/9/2014 |
