JP5356430B2 - Wireless communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio system that realizes public wireless access when multiple base stations of wireless home networks of general homes cooperate with one another. <P>SOLUTION: In a wireless communication system in which a plurality of base stations each connect with a first terminal station via a first wireless system, and allow the first terminal station under control of each base station to communicate with a network side via a control station, the plurality of base stations comprises: synchronization means for establishing clock synchronization or timing synchronization with each other; and second wireless system connection means for connecting with a second terminal station via a second wireless system different from the first wireless system. The control station comprises second wireless system base station control means which groups several base stations whose installation locations are close among the plurality of base stations, combines each second wireless system connection means of the grouped several base stations, and realizes a function as a base station of performing communication with the second terminal station, which enables communication between the second terminal station and the network side via the second wireless system. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  According to the present invention, a plurality of base stations belonging to a first radio system existing in a wide range are partly used to form a base station of a second radio system different from the first radio system. The present invention relates to a wireless communication system that performs communication. In particular, the first wireless system is a wireless home network connected to a core network such as the Internet via a wired line such as an optical fiber or ADSL, and a base station belonging to the first wireless system is a base station of the wireless home network. The present invention relates to a wireless communication system that forms a base station of a second wireless system by utilizing a part of the functions of the plurality of base stations.

  In recent years, communication systems using radio have rapidly spread. This is due to the fact that mobile phones have been widely used in the past, and in recent years it has become possible to realize high-speed wireless access such as wireless LAN and WiMAX (Worldwide interoperability for microwave access). Many of these use the microwave band, which is a relatively low frequency preferable in terms of communication conditions, and can stably communicate even when the base station and the terminal station are in an out-of-line environment.

  For example, taking WiMAX as an example, unlike a wireless LAN that does not require a license, transmission of large power is possible by using a frequency band that requires a license, and the area covered by one base station is several kilometers in radius. It also extends. Conversely, however, since a large number of users share a finite frequency resource in a very wide area, the average throughput per user decreases as the service spreads. In general, in order to improve the throughput per unit area with respect to a predetermined bandwidth, each service area is narrowed, individual cells are made into microcells, and a radio packet collision avoidance technique with carrier sense or a plurality of them are used. It is preferable to reuse the same frequency channel at a remote location, such as performing frequency repetition on the channel.

  In the case of a wireless LAN that does not require a license, the explosive spread in recent years has led to a reduction in the prices of base stations and terminal devices, and various communication companies provide public wireless LAN services at a very low cost. However, these are limited to users who have a basic contract with a mobile line such as an optical line or a mobile phone provided separately by each telecommunications company, and the available locations are such as station premises and airports. It is limited to places for collecting customers such as public facilities, hotels, and coffee shops. There is a fee-based but inexpensive wireless service that does not involve another basic contract with these carriers, but the service areas are discretely scattered except in the central area where the population is particularly dense. The service is not available in other areas.

  As an approach to solve the factors that hinder the expansion of the service area, a user who has provided an environment that can be connected to the Internet at home uses a wireless LAN base station (usually called an AP (Access Point)). The volunteer network is constructed by installing and opening this base station to neighboring users. In particular, in the service based on “Fon” shown in Non-Patent Document 1, other users' APs are used free of charge in return for the user opening their home AP. In this way, by providing APs installed at home for free or inexpensively, the network expands in a self-propagating manner.

FIG. 10 shows a configuration example of the wireless communication system described in Non-Patent Document 1.
In FIG. 10, 101 is a base station, 102-1 and 102-2 are terminal stations, 103 is a network, 104 is a user's home, 105 is a router, and 106 is a wired line such as an optical fiber. The base station 101 in the user's home 104 is connected to the network 103 via a router 105 and a wired line 106 such as an optical fiber. The base station 101 communicates with the terminal station 102-1 in the home via a wireless line. Accordingly, the terminal station 102-1 can connect to the network 103 via the base station 101 and acquire necessary information from the Internet. Basically, the base station 101 installed in the user's home 104 is installed to communicate with the terminal station 102-1 in the user's home, but the radio waves transmitted by the base station 101 are outdoors. Therefore, the outdoor terminal station 102-2 can also communicate with the base station 101.

  Here, although not shown in the figure, the user of the terminal station 102-2 has similarly installed a base station at home, and the base station is a terminal station of another user, for example, the terminal station 102 in the figure. -1 can also communicate via a wireless line and access the Internet. In this way, a large number of users open mutual base stations, so the installation location of the base station or access point is limited, and the public wireless LAN service with a narrow usable area is relatively wider. It can be used in the area.

  FIG. 11 shows a configuration example of the distributed antenna system described in Non-Patent Document 2. This distributed antenna system has a configuration in which a plurality of remote base stations perform transmission in cooperation.

  In FIG. 11, 111-1 to 111-3 are individual cells performing cooperative communication, 112-1 to 112-3 are remote base stations of each cell, 113-1 to 113-6 are terminal stations, and 114 is A control station 115 represents a wired transmission line such as an optical fiber. The remote base stations 112-1 to 112-3 in the cells 111-1 to 111-3 communicate with the terminal stations 113-1 to 113-6 using the same frequency channel. The control station 114 controls the remote base stations 112-1 to 112-3 via a wired transmission path 115 such as an optical fiber. Since the communication is performed using the same frequency, each of the terminal stations 113-1 to 113-6 can receive signals from a plurality of remote base stations 113-1 to 113-3. For example, the terminal station 113-4 can improve the communication characteristics by receiving signals from all the remote base stations 112-1 to 112-3. In particular, if the channel information of the remote base station 112-1 and the terminal station 113-4, the remote base station 112-2 and the terminal station 113-4, and the remote base station 112-3 and the terminal station 113-4 are known, respectively. For example, when the remote base stations 112-1 to 112-3 transmit signals to the terminal station 113-4, transmission weights are transmitted on the transmission side so that the received signals are in-phase combined at the terminal station 113-4. Communication characteristics can be improved by performing multiplication. The control of the signal processing for the in-phase synthesis is all performed by the control station 114, and the remote base stations 112-1 to 112-3 operate according to the instruction of the control station 114.

  In the distributed antenna system, the characteristics are improved by making the best use of such effects. What is characteristic here is that, for example, the remote base station 112-1 operates under the control of the control station 114, but can operate without the other remote base stations 112-2 to 112-3. As a function, the remote base station 112-1 and the control station 114 are combined to provide all the functions.

"How much Fon can I use?", Nikkei Communication June 15, 2007 issue Daiki Matsuda et al., "A Study on Channel Capacity of Distributed Antenna System Using Maximum Ratio Transmission", IEICE RCS2007-196, pp.61-66, March 2008

  The radio communication system shown in FIG. 10 opens a base station installed in each user's home to terminal devices of an unspecified number of users in addition to the terminal devices in the user's home, and communicates with each other. The point which was able to do is characteristic. However, the problem here is that when radio waves from a base station installed indoors leak out outdoors, there is a loss of radio waves when passing through walls and windows. This value largely depends on the material of the house walls and windows, but a loss of at least 10 dB, usually about 20 dB is expected. If there is a propagation loss in free space, that is, a propagation loss proportional to the square of the distance, the loss of 20 dB means that the serviceable area radius becomes 1/10. Even if the propagation loss is proportional to the cube of the distance, the serviceable area radius is approximately 1/5 from the loss of 20 dB.

  Originally, in the case of wireless LAN devices that are assumed to be used indoors, the transmission power is generally not so high, including the background of the use of inexpensive and low-linearity transmission amplifiers. The area that can be covered is small. In general, when the base station is installed at a high place and the terminal station and the base station have a clear positional relationship, communication can be performed stably even if they are about 100 m apart. If it cannot be secured, the distance that can be communicated rapidly is limited. In the case of the wireless communication system of FIG. 10, since the passage loss of the wall of the house further narrows the area area, as a result, communication is not possible unless it is close to the user's house that can be used.

  In recent years, the broadband environment provided by optical fiber is rapidly expanding, but the percentage of subscribers who are actually building a broadband environment is about 30%. The penetration rate is hard to say. In order to improve broadband penetration in such a situation, it is necessary to create a foundation for providing inexpensive Internet access. For this purpose, for example, a cover of a wireless communication system as described in Non-Patent Document 1 is required. There is a need for technology to expand the area.

  In the present invention, a plurality of base stations belonging to the first radio system utilize a part of the functions, and form a base station of a second radio system different from the first radio system under the control station. An object of the present invention is to provide a radio communication system in which the plurality of base stations can communicate with a terminal station via a second radio system in cooperation.

According to a first aspect of the present invention, there is provided a wireless communication system including a control station connected to a network and a plurality of base stations connected to the control station via a wired or wireless communication line. In a wireless communication system in which a first terminal station connected to a first terminal station via one wireless system and a first terminal station under each base station can communicate with a network side via a control station, a plurality of base stations Comprises a synchronization means for clock synchronization or timing synchronization with each other, and a second wireless system connection means for connecting to the second terminal station via a second wireless system different from the first wireless system, Groups a plurality of base stations that are close to each other among the plurality of base stations, combines the second wireless system connection means of the grouped base stations, and communicates with the second terminal station A second radio system base station control means for realizing a function as Chikyoku, via a second radio system, a configuration that enables communication between the second terminal station and the network side, the The second radio system is configured to communicate by an orthogonal frequency division multiplexing (OFDM) modulation scheme or an orthogonal frequency division multiple access (OFDMA) scheme, and the second radio system base station control means of the control station Divides and assigns all subcarriers used for communication to each grouped base station, indicates the subcarrier assigned to each base station, and transmits a downlink signal transmitted on the subcarrier to each base station. The uplink signal received by the transmitting terminal and the second radio system received by each grouped base station and transmitted by the second terminal station And a second wireless system connection unit of the plurality of base stations receives the downlink signal transmitted from the transmission unit of the control station, and receives a subcarrier assigned to each base station. A downlink transmission means for transferring to the second terminal station, and an uplink reception means for receiving the uplink signal transmitted from the second terminal station and transferring it to the control station.

A wireless communication system according to a second aspect of the present invention includes a control station connected to a network and a plurality of base stations connected to the control station via a wired or wireless communication line. In a wireless communication system in which a first terminal station connected to a first terminal station via one wireless system and a first terminal station under each base station can communicate with a network side via a control station, a plurality of base stations Comprises a synchronization means for clock synchronization or timing synchronization with each other, and a second wireless system connection means for connecting to the second terminal station via a second wireless system different from the first wireless system, Groups a plurality of base stations that are close to each other among the plurality of base stations, combines the second wireless system connection means of the grouped base stations, and communicates with the second terminal station A second radio system base station control means for realizing a function as Chikyoku, via a second radio system, a configuration that enables communication between the second terminal station and the network side, the 2 is configured to communicate by an orthogonal frequency division multiplexing (OFDM) modulation scheme or an orthogonal frequency division multiple access (OFDMA) scheme, and the second radio system base station control means of the control station Receiving a transmission means for transmitting a downlink signal transmitted via the second wireless system to the station, and an uplink signal of the second wireless system received by each grouped base station; Receiving means for reproducing the transmitted uplink signal, wherein the second radio system connecting means of the plurality of base stations receives the downlink signal transmitted from the transmitting means of the control station. By using the OFDM symbol of the downlink signal as a unit, the base station grouped in the signal area excluding the guard interval gives the downlink signal by adding a guard interval to a signal having a cyclic delay amount different from each other. A downlink transmission means for generating and transferring to the second terminal station; and an uplink reception means for receiving the uplink signal transmitted from the second terminal station and transferring the uplink signal to the control station.

According to a third aspect of the present invention, there is provided a wireless communication system including a control station connected to a network and a plurality of base stations connected to the control station via a wired or wireless communication line. In a wireless communication system in which a first terminal station connected to a first terminal station via one wireless system and a first terminal station under each base station can communicate with a network side via a control station, a plurality of base stations Comprises a synchronization means for clock synchronization or timing synchronization with each other, and a second wireless system connection means for connecting to the second terminal station via a second wireless system different from the first wireless system, Groups a plurality of base stations that are close to each other among the plurality of base stations, combines the second wireless system connection means of the grouped base stations, and communicates with the second terminal station A second radio system base station control means for realizing a function as Chikyoku, via a second radio system, a configuration that enables communication between the second terminal station and the network side, the The second radio system is configured to be able to perform MIMO transmission that spatially multiplexes a plurality of signal sequences, and the second radio system base station control means of the control station transmits a plurality of downlink signals to be transmitted to the second terminal station. A transmission unit that divides the signal sequence, assigns a plurality of signal sequences to each base station, and transmits each of the allocated signal sequences to each grouped base station; and a second unit received by each grouped base station Receiving means for receiving the uplink signal of the radio system and reproducing the uplink signal transmitted by the second terminal station, the second radio system connection means of the plurality of base stations from the transmitting means of the control station A downlink transmitting means for receiving each signal sequence of the received downlink signal and transferring it to the second terminal station; and an uplink for receiving the uplink signal transmitted from the second terminal station and transferring it to the control station Link receiving means.

In the radio communication system of the first or second invention, the frequency channel used by the first radio system and the second radio system is the same frequency channel or an adjacent frequency channel, and performs OFDM and OFDMA FFT and IFFT processing. The means to be implemented is shared by the first radio system and the second radio system.

According to a fourth aspect of the present invention, there is provided a wireless communication system including a control station connected to a network and a plurality of base stations connected to the control station via a wired or wireless communication line. In a wireless communication system in which a first terminal station connected to a first terminal station via one wireless system and a first terminal station under each base station can communicate with a network side via a control station, a plurality of base stations Comprises a synchronization means for clock synchronization or timing synchronization with each other, and a second wireless system connection means for connecting to the second terminal station via a second wireless system different from the first wireless system, Groups a plurality of base stations that are close to each other among the plurality of base stations, combines the second wireless system connection means of the grouped base stations, and communicates with the second terminal station A second radio system base station control means for realizing a function as Chikyoku, via a second radio system, a configuration that enables communication between the second terminal station and the network side, the The first wireless system is a wireless system that realizes a home wireless home network that can be connected to the Internet via a wired or wireless communication line, and the second wireless system is a wireless system that realizes public wireless access. is there.

  The wireless communication system of the present invention can open a base station installed in each user's home to terminal devices of an unspecified number of users outside the user's home and communicate with each other. In general, when the radio waves of base stations installed indoors leak to the outside, there is a loss of radio waves when passing through walls and windows, especially at the terminal station side in the downlink. The reception power is greatly reduced, and as a result, the communication quality is greatly deteriorated. Finally, it was difficult to achieve stable communication over a wide range. As a result, stable communication can be realized over a wide range. At this time, the functions of each base station device do not need to implement all of the functions necessary for communication with the terminal device outside the user's home, but by installing only a part thereof, the individual base station devices The functional load that should be provided can be reduced. Further, channel information between each base station apparatus and the terminal station is not always necessary, and the above effect can be achieved with simple control.

It is a figure which shows the structural example of the radio | wireless communications system in Example 1 of this invention. It is a figure which shows the outline | summary of the 1st radio system and 2nd radio system in Example 1 of this invention. It is a figure which shows the example of the downlink signal of the 2nd radio | wireless system in Example 1 of this invention. It is a figure which shows the example of the downlink signal of the 2nd radio | wireless system in Example 2 of this invention. It is a figure which shows the structural example of the radio | wireless communications system in Example 3 of this invention. It is a figure which shows the structural example of the radio | wireless communications system in Example 4 of this invention. It is a figure which shows the structural example of the radio | wireless communications system in Example 5 of this invention. It is a figure which shows the structural example of the radio | wireless communications system in Example 6 of this invention. It is a figure which shows the operation example of the radio | wireless communications system in Example 6 of this invention. It is a figure which shows the structural example of the conventional radio | wireless communications system. It is a figure which shows the structural example of the conventional distributed antenna system.

FIG. 1 shows a configuration example of a wireless communication system according to the first embodiment of the present invention.
In FIG. 1, 1 is a control station, 2 is a wired or wireless line such as an optical fiber, 3-1 to 3-3 are base station apparatuses, and 4-1 to 4-3 are transmission / reception units corresponding to the first wireless system. A first wireless unit that performs processing, 5-1 to 5-3 are first BB (baseband) processing units that perform baseband processing corresponding to the first wireless system, and 6-1 to 6-3 are IFs (interfaces). Sections 7-1 to 7-3 are a second BB processing section (# 1) to a second BB processing section (# 3) and 8-1 to 8-8 that perform partial processing of baseband processing corresponding to the second wireless system. -3 is a second radio unit that performs transmission / reception processing corresponding to the second radio system, 9-1 to 9-3 are control units, and 10-1a to 10-3a are antennas that transmit and receive signals of the first radio system. 10-1b to 10-3b are antennas for transmitting and receiving signals of the second wireless system. Na, 11-1 to 11-3 is a terminal station of the first wireless system (first terminal station), 12 denotes a terminal station of the second wireless system (second terminal station).

  The control station 1 is connected to each of the base station devices 3-1 to 3-3 via the wired line 2, and is also connected to a network such as the Internet. For example, when data is input from the network side to the control station 1 with respect to the first terminal station 11-1, the control station 1 connects to the IF unit 6-1 of the base station apparatus 3-1 via the wired line 2. Transfer the data. The IF unit 6-1 terminates the data, recognizes the data addressed to the first terminal station 11-1 from the information attached to the data, etc., performs baseband signal processing in the first BB processing unit 5-1, The 1 radio section 4-1 converts it to a radio signal and transmits it as a radio signal from the antenna 10-1a. The transmitted signal is received by the first terminal station 11-1, and necessary signal processing is performed.

  Conversely, the signal transmitted from the first terminal station 11-1 is received by the antenna 10-1a, and this is subjected to radio signal processing by the first radio unit 10-1a to be converted into a baseband digital signal. The first BB processing unit 5-1 performs baseband signal processing to extract data. The IF unit 6-1 performs predetermined signal processing for transferring this data to the control station 1, transfers the data to the control station 1 via the wired line 2, and the control station 1 transfers the data to the network side as necessary. To do.

  The above process is the same in the other base station apparatuses 3-2 to 3-3 and the first terminal stations 11-2 to 11-3. In general, each of the base station devices 3-1 to 3-3 is installed in a user's house, and each establishes a first wireless system (wireless home network) with the first terminal stations 11-1 to 11-3. , In which closed communication is performed.

  On the other hand, the 2nd terminal station 12 outside each user's house constitutes the 2nd radio system between each base station apparatus 3-1 to 3-3, and the 1st terminal station 11-1 to 11-11. -3 and perform communication concurrently. However, the second BB processing unit (# 1) 7-1 to the second BB processing unit (# 3) 7-3 included in each of the base station devices 3-1 to 3-3 are each independently the base of the second radio system. The entire band processing (described later) is not performed, and only a part of the function is performed. Therefore, when data is input to the control station 1 from the network side addressed to the second terminal station 12, the control station 1 processes the signal as appropriate (described later), and each signal subjected to separate processing is wired. The data is transferred to the IF units 6-1 to 6-3 of the base station apparatuses 3-1 to 3-3 via the line 2. When the IF units 6-1 to 6-3 recognize that the signals are addressed to the second terminal station 12, the signals are sent to the second BB processing unit (# 1) 7-1 to the second BB processing unit (# 3) 7- Forward to 3.

  For example, the second BB processing unit (# 1) 7-1 of the base station device 3-1 performs part of the signal processing of the baseband signal processing of the second wireless system assigned to the own station. Similarly, the second BB processing unit (# 2) 7-2 of the base station device 3-2 performs a part of signal processing different from the base station device 3-1 of the baseband signal processing of the second wireless system. . Similarly, the second BB processing unit (# 3) 7-3 of the base station device 3-3 is a partial signal different from the base station devices 3-1 to 3-2 of the baseband signal processing of the second wireless system. Perform the process. The baseband signal processing here is, for example, signal modulation processing, interleaving, error correction coding, and modulation processing for each subcarrier when applying OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme. In addition, the processing includes all or some of various processing such as IFFT processing, guard interval insertion, IFFT processing, digital / analog conversion, and the like. Then, when the signal processing in the control station 1 and each of the base station devices 3-1 to 3-3 is aggregated, the entire baseband signal processing of the second radio system is configured. The signals processed in this way are transmitted as radio signals from the antennas 10-1b to 10-3b to the second terminal station 12 via the second radio units 8-1 to 8-3. The second terminal station 12 combines the signals transmitted from the base station apparatuses 3-1 to 3-3, performs baseband signal processing, and restores the data transmitted from the control station 1.

  On the other hand, signals transmitted from the second terminal station 12 are received by the antennas 10-1b to 10-3b, and converted into baseband digital signals by radio signal processing in the second radio units 8-1 to 8-3. The corresponding baseband signal processing is performed in the second BB processing unit (# 1) 7-1 to the second BB processing unit (# 3) 7-3. However, not all of the baseband signal processing of the received signal of each base station apparatus 3-1 to 3-3 is necessarily performed here, and the minimum necessary functions such as timing detection for the received signal, out-of-band signal A part or a combination of a series of processes such as suppression filter processing, guard interval removal and FFT processing in the OFDM modulation system is performed, and the control station 1 having the remaining functions performs the remaining signal processing. In such a case, the IF units 6-1 to 6-3 perform predetermined signal processing for transferring intermediate processing data processed halfway to the control station 1, and via the wired line 2 The data is transferred to the control station 1, and the control station 1 performs the remaining signal processing, performs predetermined signal processing for extracting data, and transfers this to the network side as necessary.

  The series of processes described above is controlled by the control units 9-1 to 9-3 common to the first wireless system and the second wireless system, and the timing adjustment between the respective functions and mutual data input / output are performed. Etc. are managed. Further, as described above, the IF units 6-1 to 6-3 and the control station 1 perform various communications such as Internet protocol and packet processing such as Ethernet (registered trademark) in order to communicate with a network or an external device. Signal processing may be included. Similarly, although not shown in FIG. 1, network devices such as routers are installed between the base station apparatuses 3-1 to 3-3 and the control station 1 as shown in FIG. Such signal processing may be realized in a network device. However, since the description here focuses on the processing of radio signals, details of various signal processing such as Internet protocol and packet processing such as Ethernet in the upper layer are omitted here. In addition, the control station 1 performs high communication quality by performing, for example, maximum ratio combining processing on the uplink signals of the second wireless system collected from the base station devices 3-1 to 3-3. The signal processing is performed.

  The second terminal station 12 may be a mobile terminal that accompanies movement, or may be a semi-fixed installation type terminal device that is used in a user's house. In this case, if the second terminal station 12 is registered in advance, the information about the location is known, and a combination (group) of the base station apparatuses 3-1 to 3-3 that performs signal processing in cooperation with each other is known. Select at control station 1. Here, it is possible to select a combination of different base station apparatuses for each second terminal station, or to divide the area and select a base station apparatus that cooperates for each area, and exists in that area. All the terminal stations of the second wireless system may communicate with a common combination of base station apparatuses.

  In the description of FIG. 1, the second terminal station 12 has been described as being outside the user's home. However, the second terminal station 12 may be a general mobile terminal. May be in the user's home. In general, in order to efficiently execute various controls, it is preferable that the location of the second terminal station 12 is clear, and the configuration shown in FIG. 2 is a typical operation mode.

FIG. 2 shows an overview of the first radio system and the second radio system according to the first embodiment of the present invention.
2, the same numbers as those in FIG. 1 indicate the same functions. Further, 51-1 to 51-3 are user houses having base station apparatuses 3-1 to 3-3, 52 is a user house having the second terminal station 12, and 53-1 to 53-3 are optical terminal apparatuses and routers. 54 represents a network connected to the control unit 1. The base station devices 3-1 to 3-3 in the user homes 51-1 to 51-3 pass through the routers 53-1 to 53-3 and the control station 1 via the wired line 2 such as an optical fiber. And further connected to the network 54. The base station devices 3-1 to 3-3 communicate with the first terminal stations 11-1 to 11-3 in the home via the first wireless system.

  At the same time, the base station devices 3-1 to 3-3 communicate with the second terminal station 12 in the user home 52 that does not have the base station device using the second wireless system. In user homes 51-1 to 51-3 having base station apparatuses 3-1 to 3-3, routers and the like 53-1 to 53- that manage the routing of the first terminal stations 11-1 to 11-3, etc. However, the second terminal station 12 is not managed by the routers 53-1 to 53-3, and the control station 1 or the network 54 has a function of managing the routing of the second terminal station 12. Have. This is the same as in the prior art, in which the routing management of the routers 53-1 to 53-3 is provided in the network 54.

FIG. 3 shows an example of a downlink signal of the second radio system in the first embodiment of the present invention.
In FIG. 3, 30 is a conventional base station apparatus, 3-1 to 3-3 are base station apparatuses of the first embodiment shown in FIGS. 1 and 2, and 32 is a downlink signal transmitted from the conventional base station apparatus 30. Reference numerals 33-1 to 33-3 denote downlink signals respectively transmitted from the base station apparatuses 3-1 to 3-3 according to the first embodiment.

  For example, it is assumed that the first and second wireless systems use an OFDM modulation scheme or a frequency orthogonal division multiple access (OFDMA). In this case, each base station apparatus transmits a signal at a predetermined symbol period on the time axis. Further, each transmission signal is divided into a plurality of signals called subcarriers on the frequency axis, and a signal is assigned to each of the frequency direction and time direction. The blocks indicated by thick solid lines 32 and 33-1 to 33-3 shown in FIG. 3 represent signals actually transmitted in units of subcarriers. On the other hand, blocks indicated by broken lines 33-1 to 33-3 represent signals that are not actually used for transmission.

  If the system employs the OFDM modulation scheme, the conventional base station apparatus 30 performs communication using all subcarriers on the frequency axis. On the time axis, if the data to be transmitted cannot be accommodated in one symbol, a signal is transmitted over a plurality of symbols. In the case of OFDMA, broadcast information addressed to a plurality of terminal stations is transmitted at the beginning of the frame, and the terminal station is instructed to allocate a band on the time axis and frequency axis. In the payload area that accommodates the data following the broadcast information, a predetermined frequency subcarrier may be extracted in a limited manner, and signal transmission may be performed. However, at least when broadcast information is transmitted, the signal is transmitted over the entire bandwidth. Send. Thus, when transmitting a signal over the entire band, signal transmission is performed by equally distributing the transmission power unique to the apparatus to each subcarrier.

  On the other hand, in the base station apparatuses 3-1 to 3-3 of the first embodiment, the functions are shared and signals are transmitted. Here, although an example in the case of using 12 subcarriers in 12 blocks in the frequency direction is shown, the base station apparatus 3-1 has four higher ranks, the base station apparatus 3-2 has four succeeding base stations, The station apparatus 3-3 performs transmission by sharing the following four subcarriers. As a point, if the whole signal is synthesized, it becomes the same signal as the signal 32 transmitted by the conventional base station apparatus 30, but the function is shared by each base station apparatus and the signal is transmitted. Is different. That is, when each base station apparatus transmits subcarriers in a shared manner, the same power as when each base station apparatus transmits a signal over the entire band is transmitted concentrated on the allocated subcarriers. .

  In this case, compared with the conventional base station apparatus 30, the total transmission power of the three base station apparatuses 3-1 to 3-3 of the first embodiment is tripled. Expected to be obtained. Furthermore, regarding subcarrier signals of blocks indicated by thick solid lines 33-1 to 33-3, the power of each subcarrier transmitted by each base station apparatus is compared with the case of transmitting all subcarrier signals. Therefore, it is expected that very stable communication can be performed particularly with respect to subcarriers transmitted by the base station closest to the terminal station among the base station apparatuses 3-1 to 3-3 of the first embodiment. Is done. In normal wireless communication, error correction encoding processing is performed on a wireless signal, so that a signal combined with these highly reliable signals is temporarily received from the base station apparatus 3-3 of the first embodiment. Even if the reception level of the received signal is relatively weak, it is possible to compensate for the code error by error correction.

  In addition, as an example in which a plurality of base station apparatuses perform transmission in a coordinated manner as described above, the example of the distributed antenna system of Non-Patent Document 2 has been described above. However, in this distributed antenna system, all base station apparatuses are all While transmitting signals, the signals are transmitted by multiplying each signal by a transmission weight that is a predetermined coefficient. As a result, in the terminal station on the receiving side, it is possible to adjust so that the signals from the respective base station apparatuses are synthesized with the same phase. Alternatively, when a technique called multi-user MIMO (Multiple Input Multiple Output) is used in combination, a signal from a plurality of base station apparatuses can be received by a terminal station having a desired signal, but other terminals The station can adjust so that the signal is suppressed and cannot be received (that is, it does not cause interference). However, in order to perform such coordinated transmission, channel information between each base station apparatus and the terminal station needs to be known, and a channel feedback mechanism for that purpose is necessary, for example, the terminal station side In order to synthesize the signals from the base station devices in the same phase, complicated processing such as frequency and phase synchronization is required. In particular, when there is a frequency error between the base station apparatuses, even if the transmission weight of the same phase combination can be obtained once by channel feedback, the phase relationship of the result of combining the signals from the base station apparatuses is time Therefore, the phase relationship condition is immediately lost, and the operation of the distributed antenna system becomes unstable.

  On the other hand, in the first embodiment of the present invention, since the processing is simplified, it is not necessary to calculate the transmission weight, and thus the processing such as channel feedback and strict frequency synchronization as described above is not required.

  In FIG. 3, the allocation to each base station apparatus is arranged so as to be continuous subcarriers, but it is also possible to shuffle and make uniform within the entire band. Further, a common modulation scheme may be used for each subcarrier, or different modulation schemes may be used. At this time, for example, a high transmission rate may be assigned when communicating with a base station apparatus physically close to the terminal station, and a low transmission rate modulation method may be fixedly assigned to a distant base station apparatus, or fading may be performed. If there is a time variation due to the above, different modulation schemes may be used for each subcarrier even in the same base station. Further, in subcarrier allocation of each base station apparatus, subcarriers that can be communicated under good conditions may be selected in consideration of time variation, and subcarriers allocated at any time may be dynamically optimized.

  By the way, in the structure of Example 1, in order to ensure the orthogonality between the subcarriers which each base station apparatus 3-1 to 3-3 transmits separately, mutual frequency error by the synchronization of the clock of each base station apparatus Must be below a predetermined level. Similarly, it is necessary to synchronize the signal transmission timing. In order to achieve these synchronizations and suppress mutual frequency errors, some synchronization means is indispensable between the base station apparatuses 3-1 to 3-3 and the control station 1. For example, there is a method in which each of the base station apparatuses 3-1 to 3-3 and the control station 1 receives the absolute time and high-precision clock supply using GPS (Global Positioning System), which will be described separately. The same applies to other embodiments in which the synchronization means described below is not specified.

FIG. 4 shows an example of a downlink signal of the second radio system according to the second embodiment of the present invention.
In the second embodiment, an example in which cyclic shift delay diversity is used in the second wireless system using the OFDM or OFDMA of the first embodiment shown in FIG. 1 will be described.

  In FIG. 4, a conventional radio base station 30 transmits OFDM symbols 34-1 and 34-2 from two antennas # 1 and # 2, respectively. Here, as an example, an example is shown in which each OFDM symbol is divided into five parts, and the head thereof is a guard interval region. That is, the OFDM symbol 34-1 has a configuration in which the last signal d is added as a guard interval to the transmission signal a, b, c, d excluding the guard interval. On the other hand, the OFDM symbol 34-2 generates the transmission signals b, c, d, a by shifting the signals a, b, c, d of the OFDM symbol 34-1 by ¼ period, and the last signal a Is added as a guard interval at the beginning. The same applies to the following OFDM symbols 35-1 and 35-2 and OFDM symbols 36-1 and 36-2.

  The base station apparatuses 31-1, 31-2, and 31-3 according to the second embodiment generate and transmit signals obtained by shifting the signals transmitted from the plurality of antennas by the conventional radio base station 30 by different delay amounts. To do. That is, the OFDM symbol 37-1 transmitted by the base station apparatus 31-1 has a configuration in which the last signal d is added as a guard interval to the transmission signals a, b, c, and d. The OFDM symbol 37-2 transmitted by the base station apparatus 31-2 generates transmission signals b, c, d, a by shifting the signals a, b, c, d of the OFDM symbol 37-1 by ¼ period. The last signal a is added to the head as a guard interval. The OFDM symbol 37-3 transmitted by the base station apparatus 31-3 generates transmission signals c, d, a, b by shifting the signals b, c, d, a of the OFDM symbol 37-2 by ¼ period. The last signal b is added as a guard interval to the head. The same applies to the following OFDM symbols 38-1 to 38-3 and OFDM symbols 39-1 to 39-3. This transmission signal shift process is performed in each of the base station apparatuses 31-1, 31-2, and 31-3 according to the control of the control station 1 shown in FIG.

  In general, when the number of antennas that transmit signals with a constant transmission power is increased, the effect of expanding coverage can be expected by increasing the total transmission power. However, if the signals from each antenna are combined in opposite phases, the reception level is reversed. Decreases and has an adverse effect. Cyclic shift delay diversity has the effect of randomizing the phase relationship of signal combining when viewed for each subcarrier, and can reduce the risk that most subcarriers are unlucky and combined in opposite phase at a certain terminal. And stable communication can be provided. Also, with cyclic shift delay diversity, the greater the distance between antennas or the greater the number of antennas, the higher the randomness of the reception level for each subcarrier on the frequency axis, and the average reception level for all subcarriers. There is a tendency to suppress the spread of distribution. In the configuration in which a plurality of base station apparatuses share and perform cyclic shift delay diversity as in the present embodiment, each base station apparatus has a configuration in which the distance between the antennas is increased in one conventional base station apparatus. It is physically separated, and more stable communication can be expected.

FIG. 5 shows a configuration example of a wireless communication system according to the third embodiment of the present invention.
In FIG. 5, the difference from the first embodiment shown in FIG. 1 is that the second terminal station 12 that performs one-to-one SISO (Single Input Single Output) communication with the base station apparatuses 3-1 to 3-3. Instead, the second terminal station 13 including a plurality of antennas that perform MIMO transmission with the base station apparatuses 3-1 to 3-3 is used.

  Normally, a base station apparatus for performing MIMO transmission needs to have a plurality of antennas, but in the case of a user house base station apparatus, it is not always possible to assume a high-function base station apparatus. As a countermeasure in that case, the base station apparatuses 3-1 to 3-3 may share one antenna for each MIMO transmission to realize the MIMO transmission as a whole. In this case, the second BB processing units 7-1 to 7-3 perform signal processing for each MIMO stream to be transmitted.

  In the above description, MIMO transmission generally uses (1) a space time block code (STBC) to improve transmission speed by multiplexing a plurality of streams of signals in space as spatial multiplexing transmission. There are usage methods such as improving channel gain by encoding, (3) performing antenna directivity control of single stream transmission by phased array-like control, and MIMO transmission here is (1) ( The control of 2) is intended, and advanced control similar to that of the distributed antenna system such as channel feedback is required, and the use method of (3) in which communication itself can be established with only one base station apparatus is not included. Note that (1) and (2) differ from the prior art in that the overall functions required for MIMO transmission are divided and the individual functions are distributed to each base station apparatus.

  With such a configuration, the sum of the power transmitted by each base station becomes the power that is actually transmitted to the wireless medium, so that the coverage can be expanded. Also, when multiplexing by MIMO, the correlation tends to decrease as the distance between antennas increases, so the probability that the multiplexed signals can be separated increases. Therefore, since MIMO is performed by signals transmitted from different base stations, higher communication quality than the conventional configuration can be obtained. In the case where MIMO is performed by four base stations based on the realization of the same transmission rate (for example, 24 Mbps) as compared with the conventional technique in which a single stream signal is transmitted by one base station. In other words, since one base station only needs to transmit at a transmission rate of 6 Mbps, a lower modulation scheme or the like can be used, and as a result, coverage is expanded.

  FIG. 6 shows a configuration example of a wireless communication system according to the fourth embodiment of the present invention. As described above, the present embodiment shows a method for synchronizing the base station apparatuses 3-1 to 3-3 and the control station 1 and suppressing the mutual frequency error. Here, an example applied to the configuration of the first embodiment is shown, but the same applies to other embodiments.

  In FIG. 6, the difference from the first embodiment shown in FIG. 1 is that GPS 14-1 to 14-3 are installed in each of the base station devices 3-1 to 3-3, and the control station 1 is similarly GPS 14-4. Are connected to receive common clock and timing information. Here, a common clock is supplied from the GPS 14-1 to 14-3 to the control units 9-1 to 9-3, and various baseband processes of the second BB processing units 7-1 to 7-3 are based on this clock. Synchronization (including analog / digital conversion and digital / analog conversion processing) and local signals used for signal processing such as frequency conversion in the second radio units 8-1 to 8-3 can be achieved.

  Similarly, the transmission / reception timing can be synchronized by receiving information on the absolute time from the GPS 14-1 to 14-3. At this time, the control station 1 is also provided with the GPS 14-4, so that the timing synchronization between the base station apparatuses 3-1 to 3-3 and the control station 1 is achieved, and information regarding the transmission timing of the transmission data is controlled. By notifying from the station 1, the timing can be aligned. However, the control here does not necessarily require an explicit timing instruction, but rules such as how to synchronize the frame period, symbol period, etc. used for communication with the absolute time (for example, the fractional part in seconds) It is also possible to correspond at the time when becomes zero coincides with the boundary of each cycle.

  Note that the same control may be synchronized through a wired line such as an optical fiber connected to the network, in addition to using the GPS. Alternatively, the radio waves of another wireless system may be received and synchronized with the system.

  Each base station apparatus in a distributed antenna system requires strict timing and frequency synchronization, but the accuracy required in the present invention is greatly relaxed. For example, when OFDM or OFDMA is used, if the timing error is smaller than the guard interval length with respect to timing, it is absorbed by the propagation delay difference due to multipath, and there is no practical problem. Also, if the frequency error is small compared to the frequency interval of each subcarrier, there is almost no influence on the separation processing for each subcarrier by FFT processing. Therefore, by synchronizing the clock and timing with GPS or other means, the wireless communication system of the present invention can be made to function stably.

FIG. 7 shows a configuration example of a wireless communication system according to the fifth embodiment of the present invention.
In FIG. 7, the difference from the first embodiment shown in FIG. 1 is that the second baseband processing units 7-1 to 7-3 are converted into A / D (analog / digital) -D / A (digital / analog) conversion processing units. The configuration is replaced with 15-1 to 15-3. In the first embodiment, in the communication with the terminal station 12 of the second wireless system, the second BB processing units 7-1 to 7-3 include all or a part of various baseband processes. On the other hand, when the processing is simplified, the control station 1 performs the processing, encapsulates the sampling data used in the D / A conversion, and transfers the data to each of the base station devices 3-1 to 3-3. 6-1 to 6-3 through A / D-D / A processing units 15-1 to 15-3, where D / A conversion is performed and second radio units 8-1 to 8-3. Signal transmission may be performed via the antennas 10-1b to 10-3b.

  In the above embodiment, it is assumed that the first wireless system and the second wireless system are basically different standards, for example, different frequency bands such as the 2.4 GHz band and the 5 GHz band. The first wireless unit 4 related to the second wireless system and the second wireless unit 8 related to the second wireless system are physically separated. As an advantage, even if the first wireless unit 4 is transmitting a signal, the second wireless unit 8 is allowed to receive the signal at the same time. This is because the filters arranged in the first radio unit 4 and the second radio unit 8 suppress out-of-band signals and can be operated without mutual interference in subsequent signal processing. .

  However, if the first radio system and the second radio system do not need to operate independently from each other, the same frequency band is used, and the antenna, radio unit, and even the baseband processing unit are shared with each other. It is also possible to do. In this case, the first wireless system and the second wireless system may follow a common standard or may be different.

FIG. 8 shows a configuration example of a wireless communication system according to the sixth embodiment of the present invention.
In FIG. 8, the difference from the first embodiment shown in FIG. 1 is that the first wireless unit 4-1 to 4-3 and the second wireless unit 8-1 to 8-3 in FIG. 1 to 19-3, antennas 20-1 to 20-3 that share the antennas 10-1a to 10-3a and the antennas 10-1b to 10-3b in FIG. 1, and the first BB processing unit 17-1 As a part of the functions of ˜17-3, the second BB processing units 18-1 to 18-3 are included.

FIG. 9 shows an operation example of the wireless communication system according to the sixth embodiment of the present invention.
Here, both the first radio system and the second radio system are assumed to be radio systems using OFDM or OFDMA, the frequency is shown on the horizontal axis, and the usage status of subcarriers in each radio system is illustrated. The left half of the whole shows the use band of the first radio system, and the right half shows the use band of the second radio system. Each use band is in a relationship of adjacent channels, and a guard band is arranged in order to avoid mutual inter-channel interference.

  In the first radio system, signal transmission of all subcarriers except the guard band is performed by one base station apparatus. On the other hand, in the second radio system, for example, as shown in the figure, one base station apparatus transmits only a part of all subcarriers assigned to the second radio system, and the other base station apparatus transmits the remaining subcarriers. Send carrier. In the example of this figure, when performing FFT processing and IFFT processing in baseband processing in OFDM or OFDMA, it is possible to perform each in a batch. For example, in the first radio system and the second radio system as a whole, if the number of points at the time of performing FFT / IFFT is doubled, the signals of the respective channels are maintained while maintaining the subcarrier orthogonal relationship on the frequency axis. Processing such as signal separation can be performed. Specifically, if the first radio system and the second radio system are based on a wireless LAN standard such as IEEE802.11a / b / g / n, respectively, a 64-point FFT (64 subcarriers are assumed as a whole) However, in actuality, only 52 subcarriers are used. If 128-point FFT is performed by halving the sampling interval and doubling the number of points, FFT / IFFT signal processing can be performed for both channels at the same time, and the orthogonality between channels is maintained. It is possible.

  Assuming such processing, as shown in FIG. 8, the second BB processing units 18-1 to 18-3 implement signal processing related to the first wireless system as the first BB processing units 17-1 to 17-3. The radio units 19-1 to 19-3 can simultaneously transmit or receive adjacent channels together. In this case, since one cannot transmit while the other is transmitting, there are some restrictions on use, but there is an advantage that the circuit scale can be greatly reduced.

  In addition, although the example in which each base station apparatus shares and communicates with the whole subcarrier as shown in the above-mentioned Example 1 was shown in FIG. 9, 2nd Example, 3rd Example In the same manner, the same discussion can be made when each base station apparatus transmits signals of all subcarriers.

1 Control station 2 Wired line (or wireless line)
3-1 to 3-3 Base station apparatus 4-1 to 4-3 First wireless unit 5-1 to 5-3 First BB processing unit 6-1 to 6-3 IF unit 7-1 Second BB processing unit (# 1)
7-2 Second BB processing section (# 2)
7-3 Second BB processing section (# 3)
8-1 to 8-3 Second radio unit 9-1 to 9-3 Control unit 10-1a to 10-3a Antenna 10-1b to 10-3b Antenna 11-1 to 11-3 Terminal of first radio system Station (first terminal station)
12 Terminal station of second radio system (second terminal station)
13 Second terminal station having a plurality of antennas 14-1 to 14-4 GPS
15-1 to 15-3 A / D-D / A conversion processing unit 16-1 to 16-3 control unit 17-1 to 17-3 first BB processing unit 18-1 to 18-3 second BB processing unit 19- 1-19-3 Radio unit 20-1-20-3 Antenna

Claims (5)

A control station connected to the network, and a plurality of base stations connected to the control station via a wired or wireless communication line, and each of the plurality of base stations includes a first radio system via a first wireless system. In a wireless communication system that connects to a terminal station and enables the first terminal station under each base station to communicate with the network side via the control station ,
The plurality of base stations are connected to a second radio system connection unit via a second radio system different from the first radio system and a synchronization unit that synchronizes clocks or timings with each other. And
The control station groups a plurality of base stations that are close to each other among the plurality of base stations, combines the second radio system connection means of the grouped base stations, and the second terminal station A second radio system base station control means for realizing a function as a base station that communicates with
A configuration that enables communication between the second terminal station and the network side via the second wireless system;
The second wireless system is configured to communicate in an orthogonal frequency division multiplexing (OFDM) modulation scheme or an orthogonal frequency division multiple access (OFDMA) scheme,
The second radio system base station control means of the control station,
All the subcarriers used for communication by the second radio system are divided and assigned to the grouped base stations, the subcarriers assigned to the base stations are indicated, and downlink signals transmitted by the subcarriers are transmitted. Transmitting means for transmitting to each base station,
Receiving means for receiving the uplink signal of the second radio system received by each of the grouped base stations and reproducing the uplink signal transmitted by the second terminal station;
The second wireless system connection means of the plurality of base stations is
A downlink transmission unit that receives a downlink signal transmitted from the transmission unit of the control station and transfers the downlink signal to the second terminal station using a subcarrier assigned to each base station;
A radio communication system, comprising: an uplink reception unit that receives an uplink signal transmitted from the second terminal station and transfers the uplink signal to the control station. A control station connected to the network, and a plurality of base stations connected to the control station via a wired or wireless communication line, and each of the plurality of base stations includes a first radio system via a first wireless system. In a wireless communication system that connects to a terminal station and enables the first terminal station under each base station to communicate with the network side via the control station ,
The plurality of base stations are connected to a second radio system connection unit via a second radio system different from the first radio system and a synchronization unit that synchronizes clocks or timings with each other. And
The control station groups a plurality of base stations that are close to each other among the plurality of base stations, combines the second radio system connection means of the grouped base stations, and the second terminal station A second radio system base station control means for realizing a function as a base station that communicates with
A configuration that enables communication between the second terminal station and the network side via the second wireless system;
The second wireless system is configured to communicate in an orthogonal frequency division multiplexing (OFDM) modulation scheme or an orthogonal frequency division multiple access (OFDMA) scheme,
The second radio system base station control means of the control station,
Transmitting means for transmitting a downlink signal transmitted via the second radio system to each of the grouped base stations;
Receiving means for receiving the uplink signal of the second radio system received by each of the grouped base stations and reproducing the uplink signal transmitted by the second terminal station;
The second wireless system connection means of the plurality of base stations is
The downlink signal transmitted from the transmission means of the control station is received, and cyclic delay amounts different from each other in each of the base stations grouped in the signal region excluding the guard interval in units of OFDM symbols of the downlink signal. A downlink transmission means for generating a downlink signal by assigning a guard interval to a signal given a cyclic delay, and transferring the downlink signal to the second terminal station;
A radio communication system, comprising: an uplink reception unit that receives an uplink signal transmitted from the second terminal station and transfers the uplink signal to the control station. A control station connected to the network, and a plurality of base stations connected to the control station via a wired or wireless communication line, and each of the plurality of base stations includes a first radio system via a first wireless system. In a wireless communication system that connects to a terminal station and enables the first terminal station under each base station to communicate with the network side via the control station ,
The plurality of base stations are connected to a second radio system connection unit via a second radio system different from the first radio system and a synchronization unit that synchronizes clocks or timings with each other. And
The control station groups a plurality of base stations that are close to each other among the plurality of base stations, combines the second radio system connection means of the grouped base stations, and the second terminal station A second radio system base station control means for realizing a function as a base station that communicates with
A configuration that enables communication between the second terminal station and the network side via the second wireless system;
The second wireless system is configured to be capable of MIMO (Multiple Input Multiple Output) transmission that spatially multiplexes a plurality of signal sequences,
The second radio system base station control means of the control station,
A downlink signal to be transmitted to the second terminal station is divided into a plurality of signal sequences, a plurality of signal sequences are assigned to each base station, and each assigned signal sequence is transmitted to each grouped base station. A transmission means;
Receiving means for receiving the uplink signal of the second radio system received by each of the grouped base stations and reproducing the uplink signal transmitted by the second terminal station;
The second wireless system connection means of the plurality of base stations is
Downlink transmission means for receiving each signal sequence of the downlink signal transmitted from the transmission means of the control station and transferring it to the second terminal station;
A radio communication system, comprising: an uplink reception unit that receives an uplink signal transmitted from the second terminal station and transfers the uplink signal to the control station. The wireless communication system according to claim 1 or 2 ,
The frequency channels used by the first radio system and the second radio system are the same frequency channel or adjacent frequency channels, and means for performing FFT or IFFT processing of OFDM or OFDMA is provided on the first radio system and A wireless communication system characterized by being shared by the second wireless system. A control station connected to the network, and a plurality of base stations connected to the control station via a wired or wireless communication line, and each of the plurality of base stations includes a first radio system via a first wireless system. In a wireless communication system that connects to a terminal station and enables the first terminal station under each base station to communicate with the network side via the control station ,
The plurality of base stations are connected to a second radio system connection unit via a second radio system different from the first radio system and a synchronization unit that synchronizes clocks or timings with each other. And
The control station groups a plurality of base stations that are close to each other among the plurality of base stations, combines the second radio system connection means of the grouped base stations, and the second terminal station A second radio system base station control means for realizing a function as a base station that communicates with
A configuration that enables communication between the second terminal station and the network side via the second wireless system;
The first wireless system is a wireless system that realizes a general home wireless home network that can be connected to the Internet via a wired or wireless communication line,
The wireless communication system, wherein the second wireless system is a wireless system for realizing public wireless access.

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