JP5435574B2 - Distributed RoF-MIMO antenna system and cell forming method - Google Patents

Description

  The present invention relates to a distributed RoF-MIMO that increases radio frequency utilization efficiency by distributing radio antennas covering a radio area in an optical radio hybrid access network that transmits and receives radio signals via an optical fiber transmission line and a radio transmission line. The present invention relates to an antenna system and a cell forming method.

  As a technology for realizing long-distance and high-speed transmission paths between a central station (CS) and a base station (BS) in wireless communication, wireless signals are superimposed on optical signals, There is a RoF (Radio on Fiber) technology for transmitting an optical fiber while preserving the format of a radio signal.

FIG. 1 shows an outline of a RoF system (Non-Patent Document 1).
In FIG. 1, in the downstream direction from the CS to the BS, the CS modulates the optical carrier with the modulated radio signal and transmits the modulated optical carrier to the BS via the optical fiber transmission line 101. The BS receives the optical signal, demodulates the radio signal, and wirelessly transmits the signal from the antenna to the terminal. In the uplink direction from the BS to the CS, the BS modulates the optical carrier wave with the radio signal received by the antenna, and transmits it to the CS via the optical fiber transmission line 101. The CS receives the optical signal and demodulates and extracts the radio signal. By using such RoF technology, the signal processing units can be concentrated on the CS, so that the BS configuration can be simplified and the scalability of the network is improved.

  As an economical optical access network, there is a point-to-multipoint passive optical network (PON) in which an optical fiber transmission line is shared by a plurality of users.

FIG. 2 shows an overview of the PON system.
In FIG. 2, in the PON system, one optical subscriber line terminator (OLT: Optical Line Terminal) has a plurality of optical network terminators (ONUs), optical fiber transmission lines 101, and 1 to n (n is This is a network that performs 1-to-n communication via an optical coupler 102 of an integer of 2 or more. Communication between the OLT and each ONU is performed by a time division multiplexing (TDM) method.

  Moreover, there exists WDM (Wavelength Division Multiplexing) -PON as one of the implementation forms of PON (nonpatent literature 2). The WDM-PON system uses an optical multiplexer / demultiplexer (WDM filter) instead of the optical coupler 102, and realizes communication between the OLT and each ONU by assigning different use wavelengths for each ONU. Further, the ONU can be made colorless by providing a light source capable of selecting a wavelength, or by providing an optical modulator that modulates continuous light supplied from the OLT side, and turning the modulated light back. Operation becomes possible.

  On the other hand, improvement in frequency utilization efficiency of radio waves in wireless communication is an important issue, and MIMO that increases the transmission capacity of wireless communication by spatial multiplexing using a plurality of transmission / reception antennas each of a BS and a terminal (MT: Mobile Terminal) (Multiple Input Multiple Output) technology. In a MIMO radio system, if the distance between a plurality of transmission / reception antennas is increased, the correlation of multipath fading of a plurality of radio channels between BS and MT is reduced, so that a so-called rich scattering environment can be easily generated and the MIMO is facilitated. It is known that the spatial multiplexing effect can be enhanced and the transmission capacity of the wireless transmission path can be increased.

  In this MIMO wireless system, if radio signals transmitted and received by multiple BS antennas are transmitted using RoF, the BS required for MIMO can be simplified, and demodulation and signal processing of complex MIMO signals are processed collectively by CS. Furthermore, it becomes easy to disperse the BS antennas by RoF. Further, by realizing a distributed RoF-MIMO antenna system in which one MIMO cell is formed between a plurality of BSs, it is possible to further increase the radio transmission capacity and improve the frequency utilization efficiency.

FIG. 3 shows an outline of a distributed RoF-MIMO antenna system (Non-Patent Documents 3 and 4).
In FIG. 3, CS and a plurality of BSs are connected via an optical fiber transmission 101 and an optical coupler 102 having a star bus configuration. BSs on each optical fiber transmission line are sequentially connected via optical couplers (not shown). Here, four antennas are arranged in one BS, and a MIMO space surrounded by four antennas distributed and arranged in four BSs is defined as a “cell”. The relationship between the antennas 1 to 4 of each BS and the antennas 1 to 4 surrounding the cell is as shown in FIG. The CS-BS connection form, the number of BS antennas, and the cell shape are arbitrary.

  In the conventional distributed RoF-MIMO antenna system, multiplexing of optical signals transmitted / received between CS and a plurality of BSs (BS multiplexing) and multiplexing of radio signals transmitted / received by a plurality of antennas installed in the BS are performed. (Antenna multiplexing) is performed by TDM (Time Division Multiplexing). The terminal in the cell communicates wirelessly with the antennas 1 to 4 surrounding the cell, and is connected to the CS via the four BSs that accommodate the antennas 1 to 4 surrounding the cell. Is called. Since such a distributed RoF-MIMO antenna system can perform complicated MIMO processing in a concentrated manner by CS, it is possible to simplify the BS.

  In addition, when further increasing the frequency utilization efficiency, or when a radio access system using a radio wave format that uses a higher frequency than the 2 GHz band currently used in 3G mobile phones and WiMAX appears, a radio cell covered by one BS It is desirable that the size of the cell is small, and a micro cell configuration and a configuration of a pico cell and a femto cell having a smaller size are required. At this time, it becomes an issue to efficiently and economically secure an optical fiber entrance line connecting a huge number of BSs and the core network. In such a case, the distributed RoF-MIMO antenna system requires many optical fiber entrance lines connecting many BSs and CSs, and this can also be realized by performing RoF transmission with PON.

Hiroyo Ogawa, “Microwave and Millimeter-Wave Fiber Optic Technologies for Subcarrier Transmission Systems,” IEICE Transactions on Communications, Vol.E76-B, No.9, pp.1078-1090, September 1993 Katsumi Iwatsuki, Jun-ichi Kani, “Applications and Technical Issues of Wavelength-Division Multiplexing Passive Optical Networks with Colorless Optical Network Units,” IEEE / OSA Transactions on Optical Communications and Networking, Vol.1, No.4, pp.C17- C24, September 2009. Shutai Okamura, Minoru Okada, Katsutoshi Tsukamoto, Shozo Komaki, “Investigation of RoF Link Noise Influence in Ubiquitous Antenna System,” IEICE Transactions on Electronics, Vol.E80-C, No.8, pp.1527-1535, August 2003 Takuya Yamakami, Takeshi Higashino, Katsutoshi Tsukamoto, and Shozo Komaki, “An Experimental Investigation of Applying MIMO to RoF Ubiquitous Antenna System”, Proc.of 2008 IEEE Topical Meeting on MWP / APMP2008, pp.201-204, September 2008

  The conventional distributed RoF-MIMO antenna system is based on the TDM-PON system, and the processing speed increases in proportion to the number of BSs accommodated, and the number of BSs can be increased economically and efficiently. could not. Further, a distributed RoF-MIMO antenna system using a WDM-PON system has been realized, and the configurations of CS and BS for improving frequency utilization efficiency and radio transmission capacity, and further, the arrangement of BSs have not been clarified.

  In the distributed RoF-MIMO antenna system using a WDM-PON system, the present invention realizes a BS arrangement that enhances the spatial multiplexing effect of MIMO, and allocates resources to cells dynamically corresponding to traffic distribution and terminal distribution It is an object to provide a distributed RoF-MIMO antenna system and a cell formation method capable of improving the wireless transmission capacity and the frequency utilization efficiency of radio waves by MIMO with an economical and simple BS.

The first invention is a space in which one central station (CS) is connected to a plurality of base stations (BS) via optical fiber transmission lines and is surrounded by a plurality of antennas distributed and installed in the plurality of BSs. Distributed RoF-MIMO which forms one cell, performs radio communication with a radio terminal in each cell using MIMO technology, and further performs optical communication between one CS and a plurality of BSs using RoF technology In an antenna system, a WDM transmission is performed by assigning different wavelengths to each BS between a CS and a plurality of BSs. The BS transmits a MIMO signal to be transmitted / received via a plurality of antennas installed in the BS. time division multiplexing, comprising a multiplexing and demultiplexing means for transmitting and receiving superimposed on optical signals of wavelengths assigned to the BS, CS is the MIMO signals transmitted and received via a plurality of antennas that surround the cell Means for management, between the multiplexing and demultiplexing means BS, by selecting the BS with its antenna forming a cell by selecting the wavelength of the optical signals and time slots to set the shape of the cell BS antenna selection means Is provided.

  In the distributed RoF-MIMO antenna system of the first invention, the BS antenna selection means dynamically selects a BS for setting the cell shape and its antenna, and forms a cell of an arbitrary shape and an arbitrary size. It is. The BS antenna selection means is configured to form a cell having a shape and size corresponding to the number of terminals in the cell and the requested traffic, and to provide necessary radio resources for each cell.

The second invention is a space in which one central station (CS) is connected to a plurality of base stations (BS) through optical fiber transmission lines and surrounded by a plurality of antennas distributed and installed in the plurality of BSs. Distributed RoF-MIMO which forms one cell, performs radio communication with a radio terminal in each cell using MIMO technology, and further performs optical communication between one CS and a plurality of BSs using RoF technology In the antenna system cell formation method, a WDM transmission is performed by assigning different wavelengths for each BS between the CS and a plurality of BSs. The BS is a multiplexing / demultiplexing unit, and a plurality of BSs are installed in the BS. MI through the antenna time division multiplexing MIMO signals for transmission and reception, and transmitting and receiving superimposed on optical signals of wavelengths assigned to the BS, CS is sent and received via a plurality of antennas that surround the cell Means for processing the O signals, the BS antenna selection means disposed between the multiplexing and demultiplexing means BS, by selecting the BS with its antenna forming a cell by selecting the wavelength of the optical signal and a time slot Set the cell shape.

  In the cell formation method of the distributed RoF-MIMO antenna system of the second invention, the BS antenna selection means dynamically selects the BS for setting the cell shape and its antenna, and the cell having an arbitrary shape and an arbitrary size. Form. The BS antenna selection unit forms cells having a shape and size corresponding to the number of terminals in the cell and the requested traffic, and provides necessary radio resources for each cell.

  In the present invention, the WDM-PON and RoF are combined to form an entrance line that connects the CS and the BS, and a plurality of antennas that form a plurality of cells are installed in the BS. The spatial multiplexing effect can be enhanced. In the downlink, the BS and the antenna for distributing the MIMO signal are selected by the BS antenna selection means of the CS so that the MIMO spatial multiplexing effect is enhanced. The uplink can similarly process the MIMO signal transmitted from the MT and arriving via the selected BS and antenna. Further, by utilizing the high degree of freedom of BS arrangement realized by RoF, the BS and the antenna are selected so as to increase the spatial multiplexing effect of MIMO, thereby controlling the multipath environment between BS and MT. Can do.

  As described above, in the distributed RoF-MIMO antenna system of the present invention, the BS and the antenna are selected so as to enhance the spatial multiplexing effect of MIMO, and resource allocation to cells dynamically adapted to the traffic distribution and the terminal distribution is realized. It is possible to increase the wireless transmission capacity by MIMO and the frequency utilization efficiency of radio waves with an economical and simple BS.

It is a figure explaining the outline | summary of a RoF system. It is a figure explaining the outline | summary of a PON system. It is a figure explaining the outline | summary of the conventional distributed type RoF-MIMO antenna system. It is a figure which shows the cell structural example 1 of the distributed RoF-MIMO antenna system of this invention. It is a figure which shows the structural example of the optical modulation / demodulation and antenna multiplexing / separation part 13 and BS22 in a downlink. It is a figure which shows the structural example of the optical modulation / demodulation and antenna multiplexing / separation part 13 and BS22 in an uplink. It is a figure which shows the cell structural example 2 of the distributed type RoF-MIMO antenna system of this invention. It is a figure which shows the cell structural example 3 of the distributed type RoF-MIMO antenna system of this invention. It is a figure which shows the cell structural example 4 of the distributed type RoF-MIMO antenna system of this invention. It is a figure which shows the cell structural example 5 of the distributed type RoF-MIMO antenna system of this invention. 10 is a diagram illustrating a configuration example of a CS in a cell configuration example 5. FIG.

(Cell configuration example 1)
FIG. 4 shows a cell configuration example 1 of the distributed RoF-MIMO antenna system of the present invention.
Here, a different wavelength is assigned to each BS arranged in a lattice pattern, and a WDM-PON is configured with the CS using the wavelength assigned to each BS. That is, the downstream signal obtained by wavelength-multiplexing the optical signal addressed to each BS from the CS is demultiplexed to each optical fiber transmission line by the optical multiplexer / demultiplexer 15, and further assigned to each BS connected to each optical fiber transmission line. Wavelength is demultiplexed. Further, the uplink signals transmitted from each BS are wavelength-multiplexed on the optical fiber transmission line, further wavelength-multiplexed by the optical multiplexer / demultiplexer 15 and transmitted to the CS.

  Each BS has four antennas 1 to 4 here, and a MIMO signal transmitted / received via each antenna is transmitted by being superimposed on an optical signal having a wavelength assigned to each BS. Multiplexing of four MIMO signals transmitted and received by one BS can be realized by frequency multiplexing (subcarrier multiplexing, SCM) in the electric domain when radio frequency channels used in each cell are different. Further, when each cell uses the same radio frequency channel, it can be realized by time division multiplexing (TDM) or code division multiplexing (CDM) in the electrical domain.

  In FIG. 4, paying attention to the four BS22, BS32, BS33, and BS23 surrounding the cell A, MIMO communication is performed with a terminal in the cell A by the antenna 4 of the BS22, the antenna 1 of the BS32, the antenna 2 of the BS33, and the antenna 3 of the BS23. An example is shown. That is, the MIMO signal transmitted / received between the CS and the terminal in the cell A is transmitted via the BS 22, BS 32, BS 33, BS 23 that respectively accommodate the four antennas 1 to 4 surrounding the cell A. Also, four MIMO signals transmitted between the CS and one BS are transmitted / received via four antennas corresponding to four different cells around the BS. In this way, by distributing and arranging the antennas of the MIMO system in different BSs, it is possible to suppress the correlation that occurs in multipath fading between MT and BS.

  The CS includes an RF modulation / demodulation / MIMO processing unit 11 corresponding to each cell, a BS antenna selection unit 12, an optical modulation / demodulation / antenna multiplexing / demultiplexing unit (Tx / Rx) 13 and an optical multiplexer / demultiplexer 14 corresponding to each BS. The

  The RF modulation / demodulation / MIMO processing unit 11 is configured to process MIMO signals transmitted and received via the antennas 1 to 4 of the four BSs surrounding each cell. Here, an example of processing a MIMO signal transmitted / received via the antenna 4 of the BS 22 surrounding the cell A, the antenna 1 of the BS 32, the antenna 2 of the BS 33, and the antenna 3 of the BS 23 is shown.

  The optical modulation / demodulation / antenna multiplexing / demultiplexing unit 13 is configured to transmit / receive optical signals of wavelengths assigned to the respective BSs and further multiplex / demultiplex MIMO signals transmitted / received by the antennas 1 to 4 of the respective BSs. Here, an example corresponding to BS22, BS32, BS33, BS23 surrounding cell A is shown. For example, when the wavelength assigned to the BS 22 is λ (BS 22), the optical modulation / demodulation / antenna multiplexing / demultiplexing unit 13 corresponding to the BS 22 transmits and receives an optical signal of the wavelength λ (BS 22), and the antennas 1 to 4 of the BS 22 Multiplex / separate MIMO signals transmitted and received via

  The BS antenna selection unit 12 is configured to connect an RF modulation / demodulation / MIMO processing unit 11 that processes a MIMO signal corresponding to each cell and an optical modulation / demodulation / antenna multiplexing / separation unit 13 corresponding to each BS. Here, an example is shown in which a MIMO signal corresponding to cell A is connected so as to be transmitted and received through antenna 4 of BS 22, antenna 1 of BS 32, antenna 2 of BS 33, and antenna 3 of BS 23.

(Configuration example of optical modulation / demodulation / antenna multiplexing / separating unit 13 and BS 22)
FIG. 5 shows a configuration example of the optical modulation / demodulation / antenna multiplexing / demultiplexing unit 13 and BS 22 in the downlink. Here, a one-cell repetitive cell configuration in which the radio frequency channel used in each cell is the same frequency f1 is assumed.

  In FIG. 5, the optical modulation / demodulation / antenna multiplexing / demultiplexing unit 13 corresponding to the BS 22 inputs the MIMO signal transmitted from the antennas 1 to 4 of the BS 22 to the surrounding four cells to the TDM processing unit and assigns the four time slots. Antenna multiplexing is performed and input to the optical modulator MOD to modulate an optical carrier wave having a wavelength λ (BS22) corresponding to BS22. This optical signal is wavelength-multiplexed with the optical signal to the other BS by the optical multiplexer / demultiplexer 14, and transmitted to each BS via the optical fiber transmission line. The BS 22 inputs the optical signal demultiplexed by the optical multiplexer / demultiplexer 15, further demultiplexes the optical signal having the wavelength λ (BS 22) assigned by the optical multiplexer / demultiplexer 16, and inputs the demultiplexed optical signal to the light receiving device PD. Electrically converted and returned to the RF band TDM signal. The TDM signal is input to the TDM processing unit, separated into MIMO signals for each antenna, transmitted from the antennas 1 to 4 to the corresponding cells via the bandpass filter BPF, and received by terminals in each cell. .

  Although an example in which TDM is used as a multiplexing method of four MIMO signals transmitted to one BS is shown here, CDM can be used instead of TDM. In addition, when a different frequency channel is used for each cell, SCM can be used.

FIG. 6 shows a configuration example of the BS 22 and the optical modulation / demodulation / antenna multiplexing / demultiplexing unit 13 in the uplink.
In FIG. 6, MIMO signals transmitted from terminals existing in each of the four cells around BS 22 are received by antennas 1 to 4, input to a TDM processing unit via a bandpass filter BPF, and antenna-multiplexed TDM signals. Is input to the optical modulator MOD and modulates the optical carrier wave having the wavelength λ (BS22). This optical signal is wavelength-multiplexed with the optical signals of other BSs by the optical multiplexer / demultiplexers 16 and 15 and transmitted to the CS. In CS, an optical signal having a wavelength λ (BS22) is separated by an optical multiplexer / demultiplexer 14 and input to an optical modulation / demodulation / antenna multiplexing / demultiplexing unit 13 corresponding to BS22, and photoelectric conversion is performed by a photodetector PD to perform a TDM processing unit. And is separated into cell-corresponding MIMO signals.

  Although antenna multiplexing using TDM is used here, CDM can be used instead of TDM. In addition, when a different frequency channel is used for each cell, SCM can be used.

(Cell configuration example 2)
FIG. 7 shows a cell configuration example 2 of the distributed RoF-MIMO antenna system of the present invention.
In FIG. 7, cell configuration example 2 shows a cell configured by three antennas, with the cell shape surrounded by the antennas of each BS being a triangle. One BS includes six antennas for transmitting and receiving MIMO signals to and from surrounding cells. For example, the cell B is formed by the antenna 5 of the BS 22, the antenna 1 of the BS 32, and the antenna 3 of the BS 33.

  The CS RF modulation / demodulation / MIMO processing unit 11 corresponding to the cell B processes the MIMO signal transmitted and received by the antenna 22 of the BS 22, the antenna 1 of the BS 32, and the antenna 3 of the BS 33 surrounding the cell B. The MIMO signal is transmitted via the optical modulation / demodulation / antenna multiplexing / demultiplexing unit 13 corresponding to BS22, BS32, and BS33 while being superimposed on the corresponding optical signal.

(Cell configuration example 3)
FIG. 8 shows a cell configuration example 3 of the distributed RoF-MIMO antenna system of the present invention.
In FIG. 8, the cell configuration example 3 shows a cell configured by six antennas with the cell shape surrounded by the antennas of each BS being a hexagon. One BS includes three antennas for transmitting and receiving MIMO signals to surrounding cells. For example, cell C is formed by antenna 3 of BS13, antenna 3 of BS22, antenna 1 of BS32, antenna 1 of BS43, antenna 2 of BS33, and antenna 2 of BS23.

  The RF modulation / demodulation / MIMO processing unit 11 of the CS corresponding to the cell C includes the antenna 3 of the BS 13 surrounding the cell C, the antenna 3 of the BS 22, the antenna 1 of the BS 32, the antenna 1 of the BS 43, the antenna 2 of the BS 33, and the antenna 2 of the BS 23. Processes MIMO signals to be transmitted and received. This MIMO signal is transmitted via the optical modulation / demodulation / antenna multiplexing / demultiplexing unit 13 corresponding to BS13, BS22, BS32, BS43, BS33, BS23 and superimposed on the optical signal of the corresponding wavelength.

(Cell configuration example 4)
FIG. 9 shows a cell configuration example 4 of the distributed RoF-MIMO antenna system of the present invention.
In FIG. 9, in the cell configuration example 3, one BS includes six antennas for transmitting and receiving MIMO signals to and from surrounding cells, and by selecting an antenna that transmits and receives MIMO signals for each BS, each BS An example in which the cell shape surrounded by the antenna is a square, a triangle, or a hexagon is shown. For example, the cell A is a quadrangle formed by the antenna 6 of the BS 21, the antenna 1 of the BS 31, the antenna 3 of the BS 32, and the antenna 4 of the BS 22. Cell B is a triangle formed by antenna 5 of BS 32, antenna 1 of BS 42, and antenna 3 of BS 43. Cell C is a hexagon formed by antenna 5 of BS13, antenna 6 of BS22, antenna 1 of BS32, antenna 2 of BS43, antenna 3 of BS33, and antenna 4 of BS23. For example, between CS and BS 32, a MIMO signal transmitted / received via cell A and antenna 3, a MIMO signal transmitted / received via cell B and antenna 5, and a MIMO signal transmitted / received via cell C and antenna 1 Are multiplexed.

  In the cell configuration examples 1 to 4 described above, the number of antennas included in each BS and the shape of the cell surrounded by the antennas of each BS are determined in advance, and the BS antenna selection unit 12 of the CS accordingly responds to the cell-compatible RF. The modulation / demodulation / MIMO processing unit 11 is connected to the antenna port of the optical modulation / demodulation / antenna multiplexing / separation unit 13 corresponding to each BS.

  Next, a cell configuration example corresponding to a case where the number of terminals in a cell and requested traffic are different and required radio resources are different for each cell will be described.

(Cell configuration example 5)
FIG. 10 shows a cell configuration example 5 of the distributed RoF-MIMO antenna system of the present invention.
In FIG. 10, one BS includes four antennas for transmitting and receiving MIMO signals to and from surrounding cells, but only antennas for transmitting and receiving MIMO signals are described here. The cell 11 is surrounded by the antenna 4 of the BS 11. The cell 23 is surrounded by the antenna 4 of the BS 23, the antenna 1 of the BS 43, the antenna 2 of the BS 45, and the antenna 3 of the BS 25. The cell 13 is surrounded by the antenna 4 of the BS 13, the antenna 1 of the BS 23, the antenna 2 of the BS 24, and the antenna 3 of the BS 14. The cell 32 is surrounded by the antenna 4 of the BS 32, the antenna 1 of the BS 42, the antenna 2 of the BS 43, and the antenna 3 of the BS 33.

  Here, it is assumed that terminals and requested traffic are concentrated in the cells 13 and 32, the number of terminals and requested traffic are small in the cells 11 and 23, and there are no terminals in the other cells. At this time, the transmission capacity meeting the requirements is achieved by performing MIMO transmission / reception in the small cells with respect to the cells 13 and 32. On the other hand, in the cells 11 and 23, a cell that is four times as large is configured to further disperse the antenna, thereby enhancing the spatial multiplexing effect of MIMO and transmitting terminals and BSs so that the required transmission capacity is at an acceptable level. Select a wireless system with low power or high reception sensitivity but low information transmission speed on the wireless link. As a result, it is possible to improve resistance to interference from adjacent cells and reduce the interference level to adjacent cells.

  Further, when the antenna installed in the BS is not communicating with the terminal, a part or all of the device functions related to the antenna are suspended. Furthermore, when all four antennas installed in the BS are not communicating with the terminal, some or all of the device functions related to the BS are suspended. As a result, it is possible to improve the radio frequency utilization efficiency, reduce the power consumption of the BS, reduce the power consumption of the optical transmission, and effectively use the wavelengths when the number of WDM wavelengths is limited. Moreover, the complexity of the inter-cell handover process of the mobile terminal can be reduced by increasing the cell size.

  Such a cell size change or BS pause is omitted in FIG. 10, but in the BS antenna selection unit 12 shown in FIGS. 4, 7, and 8, RF modulation / demodulation processing corresponding to each cell is performed. This can be handled by dynamically switching the connection between the unit 11 and the antenna port of the optical modulation / demodulation / antenna multiplexing / demultiplexing unit 13 corresponding to each BS. This BS antenna selection unit 12 is controlled by a BS antenna selection signal derived in advance from information on terminal distribution and requested traffic, and in the downlink, an optical modulator connected to a predetermined antenna of a BS that is a transmission destination of a MIMO signal This can be realized by a cross-connect switch that switches the route so that the signal is input to. In the uplink, the four MIMO signals received from the terminals in the cell by the antennas of the predetermined four BSs are input to the predetermined RF modulation / demodulation / MIMO processing unit 11 as a group subjected to MIMO signal processing. The antenna selection unit 12 switches the paths of four MIMO signals reproduced from the optical signal.

FIG. 11 shows an example of CS configuration in cell configuration example 5.
In FIG. 11, the MIMO signal transmitted to the cell 11 is transmitted from the RF modulation / demodulation / MIMO processing unit 11 corresponding to the cell 11 through the BS antenna selection unit 12 to the antenna 1 of the BS 31, the antenna 2 of the BS 33, the antenna 3 of the BS 13, Each signal is input to the corresponding antenna port of the optical modulation / demodulation / antenna multiplexing / demultiplexing unit (Tx / Rx) 13 corresponding to the BS so as to be transmitted from the antenna 4 of the BS 11. The MIMO signal transmitted to the cell 13 is transmitted from the RF modulation / demodulation / MIMO processing unit 11 corresponding to the cell 13 through the BS antenna selection unit 12 to the antenna 1 of the BS 23, the antenna 2 of the BS 24, the antenna 3 of the BS 14, and the antenna 4 of the BS 13 Are transmitted to the corresponding antenna ports of the optical modulation / demodulation / antenna multiplexing / demultiplexing unit (Tx / Rx) 13 corresponding to each BS. The same applies to the MIMO signal transmitted to the cell 23 and the MIMO signal transmitted to the cell 32.

  The BS optical modulation / demodulation / antenna multiplexing / separating unit (Tx / Rx) 13 antenna-multiplexes the MIMO signal input to each antenna port, and superimposes each of the MIMO signals on the wavelength corresponding to the BS to transmit to each BS. The same applies to the uplink.

  In the embodiment described above, the configuration of the distributed RoF-MIMO antenna system in the BS and the square cell shape arranged in a lattice shape and the case where the antenna multiplexing on the same BS is realized by electric multiplexing by TDM have been described. It is apparent that other arbitrary BS arrangements and cell shapes can be configured according to the same principle by changing the number of multiplexing and the number of devices in accordance with the number of BS antennas. The antenna multiplexing can also be applied to other multiplexing schemes such as electrical multiplexing using TDM or FDM, or optical multiplexing using TDM, CDM, or FDM (WDM).

11 RF modulation / demodulation / MIMO processing unit 12 BS antenna selection unit 13 Optical modulation / demodulation / antenna multiplexing / separation unit (Tx / Rx)
14, 15, 16 Optical multiplexer / demultiplexer CS Central Station
BS Base Station

Claims (6)

One central station (CS) is connected to a plurality of base stations (BS) via optical fiber transmission lines, and forms one cell in a space surrounded by a plurality of antennas distributed and installed in a plurality of BSs. , Wireless communication with wireless terminals in each cell using MIMO (Multiple Input Multiple Output) technology, and optical communication using RoF (Radio-on-Fiber) technology between one CS and multiple BSs In a distributed RoF-MIMO antenna system that performs
Between the CS and the plurality of BSs, WDM (Wavelength Division Multiplexing) transmission is performed by assigning different wavelengths for each BS,
The BS is
A multiplexing / demultiplexing unit that time-division-multiplexes MIMO signals to be transmitted / received via a plurality of antennas installed in the BS, and transmits / receives the signals superimposed on an optical signal having a wavelength assigned to the BS,
The CS is
The cell is formed by selecting a wavelength and a time slot of an optical signal between a means for processing a MIMO signal transmitted / received via a plurality of antennas surrounding the cell and the multiplexing / demultiplexing means of the BS. A distributed RoF-MIMO antenna system comprising BS antenna selection means for selecting a BS and its antenna and setting the shape of the cell. The distributed RoF-MIMO antenna system according to claim 1,
The BS antenna selection means is configured to dynamically select the BS for setting the shape of the cell and its antenna to form a cell of an arbitrary shape and an arbitrary size. MIMO antenna system. The distributed RoF-MIMO antenna system according to claim 2,
The BS antenna selection means is configured to form a cell having a shape and size corresponding to the number of terminals in the cell and the requested traffic, and to provide necessary radio resources for each cell. -MIMO antenna system. One central station (CS) is connected to a plurality of base stations (BS) via optical fiber transmission lines, and forms one cell in a space surrounded by a plurality of antennas distributed and installed in a plurality of BSs. , Wireless communication with wireless terminals in each cell using MIMO (Multiple Input Multiple Output) technology, and optical communication using RoF (Radio-on-Fiber) technology between one CS and multiple BSs In a cell formation method of a distributed RoF-MIMO antenna system for performing
Between the CS and the plurality of BSs, WDM (Wavelength Division Multiplexing) transmission is performed by assigning different wavelengths for each BS,
The BS is
A multiplexing / demultiplexing unit time-division-multiplexes a MIMO signal to be transmitted / received via a plurality of antennas installed in the BS, and transmits / receives the signal superimposed on an optical signal having a wavelength assigned to the BS,
The CS is
The wavelength and time slot of an optical signal are selected by means of BS antenna selection means arranged between a means for processing a MIMO signal transmitted / received via a plurality of antennas surrounding the cell and the multiplexing / demultiplexing means of the BS cell formation method of distributed RoF-MIMO antenna system, characterized by setting the shape of BS and the cell select that antenna forming the cell by. In the cell formation method of the distributed RoF-MIMO antenna system according to claim 4,
The BS antenna selection means dynamically selects the BS for setting the shape of the cell and its antenna, and forms a cell of an arbitrary shape and an arbitrary size. A distributed RoF-MIMO antenna system comprising: Cell forming method. In the cell formation method of the distributed RoF-MIMO antenna system according to claim 5,
The BS antenna selection unit forms a cell having a shape and a size corresponding to the number of terminals in the cell and the requested traffic, and provides a necessary radio resource for each cell. Distributed RoF-MIMO antenna System cell forming method.

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