JP2007043332A - Cellular mobile communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that high-speed data communication becomes difficult in a cellular mobile communication system due to a decrease in communication quality due to an increase in attenuation of a desired signal and an increase in the amount of interference signal at a point away from a base station A cellular mobile communication system is provided.
A mobile station M transmits data x, y, and z together via a traffic channel using an OFDM signal at a point where radio wave attenuation is small, such as a point D, and has a maximum communication speed. The data is communicated with. On the other hand, when the mobile station M moves from the point D to the point E, it is far from any of the base stations A, B, and C. Therefore, the data x, y, and z are divided into three to prevent interference. By using a spread OFDM signal having a high level, the coherency is increased, and data x, y, z are transmitted almost simultaneously from the three base stations A, B, C to realize high-speed data transmission equivalently.
[Selection] Figure 1

Description

  The present invention relates to a cellular mobile communication system using a cellular system that performs single frequency repetition, and more particularly, to a cellular mobile communication system that achieves higher communication speed even when communication conditions such as large interference are not good.

  Conventionally, a cellular system in which a service area is divided into a limited area (cell) and base stations are arranged to communicate with mobile stations in the cell has been used as a communication system for mobile phones. In a second generation mobile communication system based on FDMA / TDMA (Frequency Division Multiple Access / Time Division Multiple Access) technology, a method of changing the frequency allocated by the cell so that the signals of adjacent cells do not interfere with each other is used. On the other hand, in the third generation mobile communication system based on CDMA (Code Division Multiple Access) technology, it is possible to use the same frequency in adjacent cells due to interference resistance obtained by spread spectrum.

  In the fourth generation mobile communication system, demand for higher-speed data communication is expected, and it is promising to use OFDM (Orthogonal Frequency Division Multiplexing) technology capable of high-speed data transmission using a broadband signal in a mobile communication environment. Is being viewed. However, since OFDM has a problem of low interference resistance when used in a system that uses the same frequency in adjacent cells, a communication system having higher interference resistance by combining OFDM technology and CDMA technology. Has been proposed.

  As the above methods, there are spread OFDM (Orthogonal Frequency Division Multiplexing) and MC-CDMA (Multi-Carrier Code Division Multiple Access) methods. These are based on OFDM technology and incorporate the idea of spread spectrum and code multiplexing.

  As described above, the spread spectrum and code multiplexing techniques are combined with the OFDM technique, and the method of allocating to a plurality of subcarriers and OFDM symbols is defined as spread OFDM. Hereinafter, the operation of the OFDM and spread OFDM transceivers will be briefly described. To do.

  First, operations of the OFDM transmitter and receiver will be described.

  FIG. 29 is a block diagram of a transceiver using the OFDM scheme. FIG. 29A is a block diagram of the transmitter, and FIG. 29B is a block diagram of the receiver.

  The number of transmission data symbols in one frame is Nf = Ns × Nc.

  Here, Nc is the number of subcarriers, and Ns is the number of OFDM symbols. In addition to this, a pilot symbol for channel estimation is usually included, but is omitted here.

  The transmission symbols are parallelized for each Nc symbol by a serial / parallel converter (hereinafter referred to as “S / P” (Serial / Parallel)) 500, and the parallel transmission symbols become subcarrier components. Inverse FFT is performed by an inverse fast Fourier transform unit (hereinafter referred to as “IFFT (Inverse Fast Fourier Transform)”) 501, and parallel / serial conversion unit (hereinafter referred to as “P / S” (hereinafter referred to as “Parallel / Serial”)) 502. Converted to a time signal sequence.

  Note that the processing unit of IFFT processing (the same applies to FFT processing described later) is one OFDM symbol.

  In “AddGI” block 503, a guard interval (hereinafter referred to as GI) is added for each OFDM symbol.

  FIG. 30 illustrates an arrangement relationship between the OFDM symbol and the GI.

  As shown in FIG. 30, GI is data in which a signal behind the OFDM symbol is inserted before the OFDM symbol. By this GI, it is possible to prevent interference due to a delayed wave in the wireless communication path.

  FIG. 31 is a diagram showing an arrangement of transmission symbols in a transmission signal within one frame in OFDM.

  In the example shown in FIG. 31, one frame is composed of Ns OFDM symbols, and the transmission symbols are sequentially arranged in the frequency direction in the OFDM symbols.

  In the receiver that receives the transmission signal, the “Remove GI” block 504 cuts out an OFDM symbol, that is, an FFT processing unit under the control of the timing detector 505, and the cut out OFDM symbol is converted into an S / P converter. After being transformed by 506, a fast Fourier transform unit (hereinafter referred to as “FFT (Fast Fourier Transform)”) 507 performs FFT processing to extract each subcarrier component. Thereafter, P / S conversion is performed by P / S 508 to obtain a symbol string in the same order as the symbol arrangement of the transmission frame.

  Next, the concept of the spread OFDM method will be briefly described.

  In the spread OFDM scheme, the same transmission symbol is arranged over a plurality of subcarriers or a plurality of OFDM symbols as shown in FIG. 32 in order to perform frequency domain or time domain spreading. In FIG. 32 (a), the spreading factor in the frequency domain is 4, and the same data symbol is transmitted on four subcarriers. In FIG. 32B, both the frequency domain and time domain spreading factors are 2, and the same data symbol is transmitted using two subcarriers and two OFDM symbols. In these examples, since spreading with a spreading factor of 4 is performed, the transmission rate of transmission symbols is reduced to ¼.

  Thus, the spread OFDM scheme is a scheme that is resistant to interference at the expense of the transmission rate of transmission symbols.

  FIG. 33 is a block diagram of a spread OFDM transceiver that performs frequency domain spreading. FIG. 33 (a) is a block diagram of the transmitter, and FIG. 33 (b) is a block diagram of the receiver.

  In FIG. 33, the spreading factor of frequency domain spreading is SF. The number of transmission symbols in one frame is 1 / SF compared to OFDM.

  In the transmitter shown in FIG. 33 (a), the frequency domain spreading processing unit 600 performs frequency domain spreading on the symbols parallelized for each Nc / SF symbol by the S / P block 500, and each subcarrier component. It becomes. This frequency domain spreading is performed by copying one symbol to SF subcarrier components and multiplying by a spreading code. Further, IFFT 501 and P / S conversion 502 are performed to form a time signal sequence. In the “AddGI” block 503, a guard interval (hereinafter referred to as “GI”) is added for each OFDM symbol.

  Compared with the OFDM transmitter shown in FIG. 29A, the configuration is the same except that a spreading processing unit 600 that performs frequency domain spreading is inserted before IFFT 501.

  On the other hand, the receiver shown in FIG. 33 (b) has the same configuration except that a frequency domain despreading processing unit 601 for despreading the detected carrier component is inserted after the FFT 507. Through the P / S converter 508 in the final processing stage, a symbol string in the same order as the symbol arrangement of the transmission frame is obtained.

  Hereinafter, a conventional example or a currently proposed cellular mobile communication system using OFDM and a spread OFDM system capable of high-speed data transmission using a broadband signal in the mobile communication environment described above will be described.

  As a fourth generation cellular mobile communication system, OFDM-based SCS-MC-CDMA system (see “Non-Patent Document 1”) and OFDM-based VSF-OFCDM (Variable Spreading Factor-Othogonal Frequency and Code Division) A “Multiplexing” method (see “Non-Patent Document 2”) has been proposed. In the SCS-MC-CDMA system, a control channel and a communication channel are arranged on different subcarriers on the frequency axis. On the other hand, the VSF-OFCDM system is a method of multiplexing a communication channel spread in the time domain and a control channel spread in both the time and frequency areas using orthogonal codes.

  Further, in the fourth generation cellular mobile communication system, as a means for obtaining resistance to noise and other interference signals and ensuring communication quality, transmission for performing data communication with higher power to a user at a point with high attenuation Instead of power control, adaptive modulation and coding schemes have been proposed.

  The adaptive modulation and coding scheme described above increases the maximum communication speed by using multi-level modulation and a high coding rate error correction code for a user at a location that is close to the base station, that is, has a small attenuation. This is a method of ensuring communication quality by reducing the communication speed by reducing the modulation multi-level number and the coding rate for a user who has a large attenuation such as a boundary and a large interference.

  Further, a technique for mutually using the OFDM system and the MC-CDMA system and solving the drawbacks of the respective communication systems is disclosed in Patent Document 1 ("JP 2004-158901 A"). In the cellular mobile communication system, switching between the OFDM scheme and the MC-CDMA scheme is performed in units of transmission slots depending on the channel state between the mobile terminal and the base station.

Further, as a means for ensuring communication quality in the cellular mobile communication system using the OFDM system, the propagation delay difference to the mobile station is the distance I obtained by multiplying the above-described GI time T _GI and the radio wave propagation speed C. The base station arrangement or time _TGI is set so as not to be larger than the distance D between the base stations, and a plurality of base stations perform transmission in synchronization, thereby mitigating interference between channels and improving communication quality. Non-Patent Document 3 discloses an SC (Synchronous Coherent) -OFDM technique that enables interference mitigation demodulation such as MMSE (Minimum Mean Square Error) diversity demodulation.
JP 2004-158901 A Nagata et al., "A Study on Common Control Channel Synchronization in SCS-MC-CDMA System", 2004 IEICE General Conference B-5-81 Kishiyama et al., "Outdoor Experiment Results of Adaptive Modulation / Demodulation and Channel Coding in Downlink VSF-OFCDM Broadband Wireless Access", 2004 IEICE General Conference B-5-94 Kevin L. Baum, “Synchronous Coherent Orthogonal Frequency Division Multiplexing System, Method, Software and Device” VTC '99 pp 2222-2226, 1998.

  However, in the above-described conventional example using the OFDM and the spread OFDM method capable of high-speed data transmission using a wideband signal in the mobile communication environment described above, both of the users are at a point where attenuation is large and interference is large. However, there is a problem in that the maximum communication speed cannot be increased because a system that prioritizes ensuring communication quality is used at the expense of data communication speed.

  Therefore, the present invention has been proposed in order to solve the above-described problems. In a cellular mobile communication system, the communication quality is improved by increasing the attenuation amount of the desired signal and increasing the interference signal amount at a point away from the base station. An object of the present invention is to provide a cellular mobile communication system that solves the problem that high-speed data communication becomes difficult due to a decrease.

  In order to achieve the above object, the present invention adopts the following configuration and has the following features.

  The cellular mobile communication system according to the present invention is a cellular mobile communication system in which a mobile station can receive radio signals from a plurality of nearby base stations substantially simultaneously, and transmits a predetermined amount of communication data at a substantially maximum communication speed. A base station having a first communication mode and a second communication mode for transmitting communication data obtained by increasing communication quality instead of reducing communication speed and dividing the predetermined communication data amount at a certain ratio A transmitter, a receiver of a mobile station that can receive transmission data in the first communication mode and the second communication mode, and a case where the transmission data from a network including the Internet is transmitted to the mobile station A base station controller that performs radio resource control of the entire system including how much data amount is allocated to which base station among the plurality of base stations; The first communication mode is a mode in which communication is performed between a transmitter of one base station and a receiver of the mobile station among the plurality of base stations, while the second communication mode Is a mode used when the communication environment condition is not good compared to the communication environment condition using the first communication mode, from a plurality of base stations near the mobile station selected by the base station controller In a mode in which the mobile station receiver receives the divided communication data transmitted by the base station controller at substantially the same time and communicates while ensuring a predetermined communication speed compared to the substantially maximum communication speed. It is characterized by being.

  Further, in the cellular mobile communication system according to the present invention, the transmitter of the base station may further reduce the communication speed as in the second communication mode without dividing the predetermined communication data amount. Third communication which is a mode in which communication quality is improved and communication is performed between a transmitter of one base station and a receiver of the mobile station among the plurality of base stations, as in the first communication mode. Mode, and transmits transmission data to the receiver of the mobile station by the third communication mode, and the receiver of the mobile station receives transmission data transmitted by the third communication mode. It is characterized by doing.

  In the cellular mobile communication system according to the present invention, the mobile station includes base station selection means for automatically selecting a plurality of base stations near the mobile station, and the base station selection means includes a plurality of base stations. Measure the reception level of each radio signal from the base station, select a predetermined number of base stations based on the measured reception level, and select the reception level or a parameter indicating the channel quality corresponding to the reception level. Transmission to the base station controller via one or a plurality of base stations.

Further, in the cellular mobile communication system according to the present invention, the base station controller comprises base station selection means capable of automatically selecting a plurality of base stations in the vicinity of the mobile station,
The base station selection means receives selection information including the reception level or a parameter indicating the channel quality corresponding to the reception level from the mobile station via the base station, and based on the selection information, It is characterized by making a selection.

  Further, in the cellular mobile communication system according to the present invention, is the communication condition between the transmitter of the base station and the receiver of the mobile station good after the base station controller selects the base station? If the communication condition is determined to be good, the first communication mode is selected and communication is performed between the base station and the mobile station in the first communication mode. On the other hand, it is determined that the communication conditions are not good, and the third communication mode is selected according to the amount of communication traffic in the cell and the communication service quality provided to each mobile station, and the selected base station Communication is performed between the mobile station and the mobile station.

  Further, in the cellular mobile communication system according to the present invention, a communication mode for performing high-speed data communication using a wideband signal including an OFDM signal, wherein the second or third communication mode includes a wideband OFDM signal. This is a communication mode in which communication is performed using a signal having high interference resistance.

  The cellular mobile communication system according to the present invention is a communication mode for performing high-speed data communication using a wideband signal including an OFDM signal having a high modulation multi-level number or a high coding rate. The communication mode is a communication mode in which communication is performed using a signal having a wide band and high interference resistance, including an OFDM signal having a low modulation multi-level number or a low coding rate.

  In addition, the cellular mobile communication system according to the present invention, when using a spread OFDM signal in the second or third communication mode, orthogonal subcarriers having a frequency separated from each other by a predetermined interval for a plurality of identical data. And the spread OFDM signal is transmitted, and the frequency diversity reception is performed by receiving the signal that has passed through the communication path having different characteristics, thereby improving the interference resistance.

  Also, in the cellular mobile communication system according to the present invention, each of the plurality of base stations has an identification number so as to be able to receive signals of the base stations separately and simultaneously receive them, and is located in the vicinity of each base station The base stations are grouped so that they do not have the same base station identification number, and the receivers of the mobile stations receive a plurality of base stations having different base station identification numbers almost simultaneously.

  As described above, according to the cellular mobile communication system of the present invention, the first communication mode in which a predetermined communication data amount is transmitted at the maximum communication speed and the predetermined communication data amount are divided. Instead of lowering the communication speed only, the transmitter of the base station having the second communication mode for performing transmission with improved communication quality, the first communication mode, and the second communication mode can be received. By configuring the receiver of the mobile station, it is possible to increase the operation rate of the base station and increase the communication speed according to the communication state.

  In addition, according to the cellular mobile communication system of the present invention, the third communication that performs transmission without increasing the communication data amount by reducing the communication speed as in the second communication mode to improve the communication quality. By providing a mode, communication with one base station is possible even when the communication environment conditions are not good, so that resources of the base station can be effectively used according to the communication state.

  In addition, it is possible to achieve high communication quality such as assigning orthogonal subcarriers having a frequency separated by a fixed interval to a plurality of identical data, performing multicarrier transmission, and improving interference resistance.

  Hereinafter, an embodiment of a cellular mobile communication system according to the present invention will be described in detail with reference to the accompanying drawings.

  1 to 33 show an example of an embodiment of a cellular mobile communication system according to the present invention. In the drawings, the same reference numerals denote the same parts.

  First, the basic concept of the cellular mobile communication system according to the present invention will be described below with reference to FIGS.

  FIG. 1 is a system conceptual diagram for explaining the basic concept of a cellular mobile communication system according to the present invention.

  As shown in FIG. 1, in a cellular mobile communication system that divides a service into regions (cells) of a limited range and arranges each base station and communicates with a mobile station, three representative cells 10 , 11 and 12, base stations A, B, and C are respectively arranged.

  Also, when the mobile station M is in the vicinity point D of the cell 10 (base station A) and when the mobile station M moves and there is a point E in the boundary region 13 where the three cells 10, 11, and 12 overlap. Shows an example of data communication.

  FIG. 2 is a network configuration diagram showing connections between the base station controller 14, traffic data between base stations, and control information.

As shown in FIG. 2, the base station controller 14 is a device that controls radio resources. For example, the base station controller 14 is connected to the core network 15 connected to the Internet 16 and each base station. When transmitting transmission data to the mobile station M, the base station (in this case, the base stations A, B, C) of the plurality of base stations to which the radio channel is assigned, Radio resource control of the entire system is performed such as how to allocate which of the transmission data to each base station.
The communication line connected to the base controller 14 is not limited to the Internet 16 and may be a dedicated communication line such as a LAN network.

  In addition, as shown in FIG. 1, in the present embodiment, a case where one base station controller 14 exists in the system is shown, but in a larger scale system, a plurality of base station controllers each include a plurality of base station controllers. It will be connected to the base station. A system configuration in which the functions of the base station controller related to the present invention are provided in each base station is also possible. That is, a configuration in which a plurality of base stations directly exchange information and determine a base station and a communication mode for transmitting to the mobile station M is also conceivable.

  Here, normally, at a point such as the point D where the attenuation of the radio wave is small and high interference resistance is not required, for example, an OFDM signal is used between the base station A and the mobile station M (hereinafter referred to as OFDM or spreading). Data communication is performed at the maximum communication speed in this communication method, which will be described using an OFDM signal. In this case, the base station controller 14 transmits all data x, y, z to the base station A and transmits the data. The base station A that has received the data collectively transmits the data x, y, and z to the mobile station M via a traffic channel described later. This communication mode is referred to as a first communication mode.

  On the other hand, when the mobile station M moves from the point D to the point E, the point E in the boundary region 13 is far from any of the base stations A, B, and C, and the radio waves are attenuated or interfered. large. Therefore, the mobile station M is required to have high interference resistance in order to increase the data communication speed.

  In order to satisfy this requirement, data x, y, z is divided into three, and data x, y, z is assigned to each base station A, B, C, so that the data transmission amount of one base station is 3 Decrease by a factor. The base station controller 14 transmits data x to the base station A, data y to the base station B, and data z to the base station C, thereby reducing the data allocation amount per base station. . By reducing the amount of data transmission, for example, by using a spread OFDM signal that is resistant to interference and improving interference resistance, data x, y, and z can be received from three base stations A, B, and C almost simultaneously. Are transmitted at the same time and received at the mobile station M almost simultaneously, so that communication parameters are selected so that the communication speed is as equal as possible to the communication speed of the first communication mode, and data at a predetermined speed is selected. Transmission can be realized. This communication mode is referred to as a second communication mode.

  Furthermore, when the mobile station M is in a poor communication environment such as the point E, when many other mobile stations are communicating at the same time, or there is a mobile station with a higher priority. In some cases, many radio resources cannot be allocated to the mobile station M. In such a case, for example, the mobile station M communicates only with the base station A and, like the second communication mode, uses a spread OFDM signal that is resistant to interference to increase interference resistance, Increase communication reliability and ensure communication quality. This communication mode is referred to as a third communication mode.

  Here, when the first, second, and third communication modes described above are executed, a base station selection method and a transition method from an arbitrary communication mode to another communication mode will be briefly described.

  The necessity of each communication mode is as described above. However, as shown in FIG. 1, the positional relationship between the neighboring base station and the mobile station M, the change of the communication environment state, or each cell It is necessary to perform an appropriate communication mode transition, that is, mode selection, according to changes in traffic quality and communication quality required for communication with the mobile station M and other mobile stations. For example, the mode transition from the first communication mode to the second communication mode or the third communication mode is performed when the currently selected base station A (in the first communication mode, only the base station A is selected). The reception signal level of the pilot (which will be described later) is always detected, and when the communication environment conditions change, the communication mode transition may be performed when the reception signal level becomes lower than a predetermined reception power level. Alternatively, when the interference level is measured together with the received signal level of the base station A, and a desired signal power to interference signal power ratio (SIR) is calculated, and the SIR falls below a predetermined level. The communication mode may be shifted.

When the transition to the second communication mode is performed, the currently selected base station A is reviewed again, and the base station A ′, base station selection means of the mobile station M or the base station controller 14 or a combination thereof is used. In the case of selecting B ′, C ′ and shifting to the third communication mode, it is necessary to review the currently selected base station A and select the base station A ′.
As a method for selecting the base stations A ′, B ′, and C ′, for example, when the base station selection unit of the mobile station M performs selection, pilot signals from a plurality of peripheral base stations are always used as described later. A base station A ′, B ′, C ′ that receives and has a predetermined reception power level or higher is selected. The base stations A ′, B ′, and C ′ may be selected in consideration of information at the stage of selecting the base station A.

  Note that control channel data, which will be described later, has a smaller amount of data than a traffic channel, but at the same time requires high reliability. Therefore, using a spread OFDM signal that has been spread in the frequency domain or in the time domain (or in both areas), it provides high interference resistance and further suppresses interference between base stations. And transmitted from each of the base stations A, B, and C.

  In the second and third communication modes, as will be described later, frequency diversity can be performed by using orthogonal subcarriers that are separated by a fixed interval and obtaining a plurality of channels. Can be higher.

  Next, the basic concept of the above-described cellular mobile communication system according to the present invention will be described in more detail.

  The basic concept of performing parallel transmission, which is the second communication mode using the above three base stations A, B, and C, is outlined, but this basic concept enables high-speed transmission by parallel transmission. It uses MIMO (Multiple Input Multiple Output) technology and OFDM technology that is strong against multipath.

  Normally, parallel transmission by MIMO is performed using a multi-antenna, but in this embodiment, multi-input is realized by parallel transmission from a plurality of base stations.

  In OFDM, if the delayed wave is within the GI range, intersymbol interference due to multipath can be suppressed.

  In the case of parallel transmission by MIMO using a normal multi-antenna, the antennas of the transmitting base station are almost at the same position, so the propagation delay difference does not need to be considered in particular compared to the delay due to multi-path. In this case, since transmission from a plurality of base stations is performed almost simultaneously, it is desirable that the difference in propagation delay from the base station to the mobile station does not become larger than GI.

  In addition, it is difficult for a mobile station to include a plurality of antennas in order to improve portability.

  Therefore, in order to solve this problem, in this embodiment, a spread OFDM signal that performs frequency domain spreading is used instead of the OFDM signal. That is, a plurality of channels having different propagation path characteristics can be obtained by assigning signals to subcarriers with different frequencies after spreading in the frequency domain. This realizes multi-output.

  FIG. 3 is a diagram illustrating an arrangement of base stations in a plurality of cells.

  Base station identification numbers from # 0 to # 3 are assigned to each base station (the position of the base station is indicated by a symbol “+”). Base stations with the same base station identification number are arranged so as not to be adjacent to each other, and the mobile station distinguishes and simultaneously receives signals of base stations with different base station identification numbers.

  FIG. 4 is a diagram for explaining OFDM GI.

It is desirable that D> T _GI × C so that a signal from a base station that may receive simultaneously or a base station that may cause large interference is not received beyond the _GI . Here, the GI length is T _GI seconds, and the distance between adjacent base stations is D meters. C is the propagation speed of radio waves.

  Next, signal configurations of pilot channels, control channels, and traffic channels for realizing high-speed parallel transmission based on the basic concept of the above-described cellular mobile communication system according to the present invention will be described.

  FIG. 5 is a configuration diagram on the time and frequency axes of each channel signal used in the cellular mobile communication system according to the present invention.

  Each base station (represented by base stations A, B, and C in FIG. 5) has a traffic channel for transmitting data such as voice and image to the mobile station M, and control information including destination information of the traffic channel data. Each channel signal is transmitted almost simultaneously using a control channel for transmitting and the like and a pilot channel for performing channel estimation (including measurement of reception power level of each base station).

  As shown in FIG. 5, for example, since the pilot signals are transmitted from the base stations A, B, and C almost simultaneously, it is necessary to receive the signals separately on the mobile station M side without causing interference. Therefore, a pilot signal from each base station is transmitted using an orthogonal code corresponding to a base station identification number (shown in Formula 1) described later. Further, the control channel signal and the traffic signal are also devised so that the mobile station M can easily separate the control channel signal and the traffic signal as described later.

  The pilot channel is time multiplexed. That is, as shown in FIG. 5, the pilot signal is transmitted using different OFDM symbols in terms of time between time 0 and Np at the beginning of the frame. On the other hand, the control channel signal and traffic channel signal are transmitted after time Np.

  In this embodiment, the control channel signal is generated as a spread OFDM signal subjected to frequency domain spreading. After frequency spreading, it is scrambled with a scramble code. This scramble code is a common code for the control channel.

  The traffic channel is scrambled using a different random sequence for each base station, and is non-orthogonal signal multiplexed with the control channel signal.

Pilot symbols are also scrambled with the same random sequence as the traffic channel, but interference between base stations is suppressed by using a pilot pattern that is orthogonal to the pilot signals of different base station numbers in the time direction. To do.
The pilot signal is arranged at the front end of the frame, but it is also possible to arrange the pilot signal separately before, after or in the middle of the frame. Alternatively, only some of the Nc subcarriers may be used. For traffic channel signals and control channel signals, only control signals may be transmitted when there is no traffic signal. By assigning traffic signals and control signals to different OFDM symbols or different subcarriers. It is also possible to eliminate mutual interference.
As shown above, the base channel for selecting a plurality of base stations can be obtained by multiplexing the signal configurations of the pilot channel, the control channel, and the traffic channel while minimizing interference between the base stations as much as possible. Basic data configuration for high-speed data transmission between the base station and mobile station according to the communication environment conditions that are the objectives of this system, making it easy to identify stations and improving signal transmission efficiency It becomes.

  Next, based on each channel configuration described above, the configuration and operation of each of the transmitter of the base station and the receiver of the mobile station will be described in detail with reference to a block diagram.

  FIG. 6 is a block diagram of the transmitter of the base station, and FIG. 10 is a block diagram of the receiver of the mobile terminal (mobile station).

  As shown in FIG. 6, the base station transmitter 17 receives control information including information for selecting a communication mode from the base station controller 14 (shown in FIG. 1), generates control channel data, and performs communication. A control unit 20 that generates control signals such as mode switching, a control channel buffer unit 18 that temporarily buffers the generated control channel data, a control channel symbol generation unit 21 that generates control channel symbols, and traffic channel data A traffic channel buffer unit 19 for temporarily buffering, a traffic channel symbol generating unit 22 for generating traffic channel symbols by inputting traffic channel data, a pilot channel signal generating unit 23 for generating pilot signals, and a control signal Control channel signal generator 24 to A traffic channel signal generation unit 25 that generates a traffic signal, a control signal generated by the control channel signal generation unit 24, and a traffic signal generated by the traffic channel signal generation unit 25 are combined to generate a combined signal. After the pilot signal generated from the start of the frame is completed, the combiner 26, a switch 27 for switching to the combined signal, and an antenna 28 for transmitting the combined signal or pilot signal are provided.

On the other hand, as shown in FIG. 10, the mobile station receiver 39 includes an antenna 40 that receives a control channel signal or a control channel signal and a traffic channel signal combined signal or pilot signal transmitted from the transmission unit of the base station, A pilot channel signal processing unit 41 that generates pilot symbols from the received pilot signal, a control channel signal processing unit 42 that extracts control channel symbols from the received control channel signal, and control channel data from the extracted control channel symbols A control channel data reproducing unit 44 for extracting traffic channel signal processing unit 43 for extracting a traffic channel symbol from the received traffic channel signal, and a traffic channel data extracting unit for extracting traffic channel data from the extracted traffic channel symbol. And click the channel data reproduction unit 45, furthermore, is configured to include a general control unit 46 for generating a communication mode switching control signal to be input to the traffic channel signal processing unit (control channel information), the. The overall control unit 46 further includes base station selection means for measuring the received signal level from a plurality of base stations from the received signal and selecting a base station that makes an access request.
The control channel information is generated from control information including communication mode selection information transmitted from the base station controller.

  First, in the base station transmitter and mobile station receiver configured as described above, FIG. 7 is a block diagram of the pilot channel signal generation unit 23 of the transmitter and FIG. A pilot channel signal processing unit corresponding to one base station in the pilot channel signal processing unit 41 will be described with reference to the block diagram 11 of FIG.

  FIG. 7 is a block diagram of pilot channel signal generation unit 23 in the transmitter of the base station.

  FIG. 11 is a block diagram showing a pilot channel signal processing unit corresponding to one base station in the pilot channel signal processing unit 41 in the receiver of the mobile station.

  Each subcarrier component of the pilot symbol is denoted by p (i, j).

  Here, i is a time-direction index and takes a value from 0 to Np-1. j is an index in the frequency direction and takes a value from 0 to Nc-1.

As shown in FIG. 7, in generating a pilot signal, an orthogonal code orthogonal between base stations having different base station numbers is copied by a copy unit 30, and this orthogonal code and base station are copied by a pilot scrambling code multiplier 31. Multiply by the station-specific scramble code and frequency spread. Here, base station identification numbers # 0 to # 3 are used corresponding to FIG. 3, and the number of pilot symbols Np is four.
Hereinafter, the embodiment will be described assuming that four base station identification numbers are used. However, more base station identification numbers can be used, and the scope of the present invention is four base station identification numbers. It is not limited to the case of using. When a larger number of base station identification numbers are used, the following formulas and the like need to be modified. However, those skilled in the art can easily perform these modifications based on the principle of the present invention. it can.

A scramble code specific to the base station l is represented by x ₀ ^(l) , x ₁ ^(l) ,..., X _Nc-1 ^(l) .

Further, the base station identification number corresponding to the base station l is represented by n (l). The orthogonal code of length 4 corresponding to the base station identification number n (l) is represented by w ₀ ^{(n (l))} , w ₁ ^{(n (l))} , w ₂ ^{(n (l))} , w ₃ ^{(n ( l))} . At this time, the pilot symbol component p ^(l) (i, j) is expressed by the following equation.

Here, for x ^(l) , for example, a part of the Maximum Length Sequence (m series) whose period is longer than Nc may be allocated to different base stations. In addition, w ^{(n (l))} may assign each orthogonal row of the Hadamard sequence to each base station identification number.
The pilot signal components of the base stations 0, 1 and 2 obtained with such a configuration are as shown in FIGS.
Further, p ^(l) (i, j) does not necessarily need to be configured by the equation shown in Equation 1, and satisfies the relationship of the following equation for base stations l and l ′ having different base station identification numbers. If so, different signals may be used.

When signals are received from a plurality of base stations (l = 0, 1,..., M−1), the receiver of the mobile station receives a reception signal represented by the following equation.

  The h (l, j) is a channel gain in subcarrier j between the base station l and the mobile station.

  Further, the channel gain is assumed to have a small variation in the time direction, and the index in the time direction is omitted.

The channel estimation signal generation unit 50 of the pilot channel signal processing unit 41 of the receiver 39 multiplies the reception signal r (i, j) by the complex conjugate of the pilot symbols of the base station as shown in the following equation. By doing so, an estimated value of the channel gain can be calculated. This estimated channel gain is expressed by the following equation.

  In the above equation, in the equation described in the second line, Σ means that the base station identification number is the sum of the components of the base station equal to the base station l ′ for which the channel gain estimation value is to be calculated. is doing.

  The reason for this development is that pilot signals of base stations with different base station identification numbers can be eliminated by the orthogonality of pilot symbols.

  The equation in the third row is described separately for the base station signal component to be calculated and the base station components having the same base station identification number but different base station numbers.

  The second term becomes smaller because different base stations with the same base station identification number are far from each other and the amount of attenuation increases. Furthermore, in order to obtain highly accurate channel gain information, it is possible to average a plurality of adjacent subcarrier components.

  Next, in the transmitter of the base station and the receiver of the mobile station, FIG. 8 is a block diagram of the control channel signal generation unit 24 of the transmitter and the control of the receiver for the generation of the control channel signal and the generation of the control channel symbol. The channel signal processing unit 42 will be described with reference to a block diagram 12 showing a control channel signal processing unit corresponding to one base station.

  FIG. 8 is a block diagram of the control channel signal generation unit 24 in the transmitter of the base station.

  FIG. 12 is a block diagram showing a control channel signal processing unit corresponding to one base station among the control channel signal processing units 42 in the receiver of the mobile station.

  As shown in FIG. 8, the control signal frequency spreading unit 32 scrambles the control channel symbol with the following control channel scrambling code.

The control channel scramble code z ^(l) is obtained by using the control channel common codes y ₀ , y ₁ ,..., Y _Nc-1 and the aforementioned x ^(l) , w ^{(n (l))} . It becomes like the following formula.

Here, jmod4 means a remainder obtained by dividing j by 4, and means a maximum integer not exceeding x. A control channel symbol transmits one symbol on four consecutive subcarriers. That is, when the control channel symbol before scramble is represented by c ^(l) (i, j), the following equation is obtained.

このような構成で得られた基地局０，１，２の制御チャネル信号成分はそれぞれ図１７、１８、１９のようになる。 Here, j = 0, 1,... N _c −1, i = 0, 1,... N _d −1, and i = 0 for the first OFDM symbol including the control channel symbol It is defined as
A control channel signal generated from the control channel scramble code shown in Equation 5 and the control channel symbol shown in Equation 6 is expressed by the following equation.

The control channel signal components of the base stations 0, 1, and 2 obtained with such a configuration are as shown in FIGS.

Further, the control channel scramble code z ^(l) does not necessarily need to be constituted by the equation 4 and satisfies the relationship of the following equation for the base stations l and l ′ having different base station identification numbers. Different codes may be used as long as they are different. There is no need to use a fixed pattern in the time direction.

  The control signal shown above transmitted from the transmitter 19 of the base station is received by the receiver 39 of the mobile station, and further corresponds to one base station in the control channel signal processing unit 42 as shown in FIG. The control channel signal processing unit extracts control channel symbols.

  Hereinafter, a procedure for extracting control channel symbols will be described.

The received signal received by the mobile station receiver 39 from a plurality of base stations (l = 0, 1,... M−1) is expressed by the following equation.

First, the control channel symbol despreading unit 51 of the receiver 39 outputs a signal represented by the following formula by multiplying the complex conjugate of the common code y.

であるので、隣接するサブキャリアのチャネルゲインが下記の式に示すように、

further,

Therefore, as shown in the following equation, the channel gain of adjacent subcarriers is

Assuming that they are almost equal, a received signal in which signals from a plurality of base stations are mixed can be converted into four signals having different base station identification numbers as shown in the following equation.

However, j is a multiple of 4. That is, by multiplying the above equation 8 by the orthogonal code w _j ^{n (l)} of length 4 corresponding to the base station identification number n (l), the control channel signal of the adjacent base station is separated and the base station identification This means that control channel signals of base stations having different numbers can be received simultaneously and extracted separately.

Furthermore, the control channel symbol c ^(l) (i, j) of each base station can be extracted by performing despreading by multiplying the channel gain obtained from the pilot signal by a specific scramble code.

An expression showing the extraction process of the control channel symbol is shown below.

Here, G is a channel gain after synthesis, and I is an interference signal component. In the above equation, since the estimated channel gain is used as the weight, G≈ | h (l, j) | ² , but a different weight can be obtained from the estimated channel gain. For example, in an environment where the delay dispersion of the communication channel is large and the frequency selectivity is strong, the assumption of Equation 9 is not satisfied, and the interference signal component I may be large. In such a case, interference and noise can be suppressed by using a weight based on the MMSE (Minimum Mean Square Error) standard.
In this way, by receiving control information of a plurality of base stations having different base station identification numbers, the receiver 39 of the mobile station receives data included in the traffic channel signal received simultaneously with the control channel signal. It is possible to determine whether the data is transmitted from which base station.

  Next, FIG. 9 which is a block diagram of the traffic channel signal generation unit 25 of the transmitter and the traffic channel of the receiver for the generation of traffic channel signals and the generation of traffic symbols in the transmitter of the base station and the receiver of the mobile station The signal processing unit 43 will be described with reference to a block diagram 13 showing a traffic channel signal processing unit corresponding to one base station.

  When the mobile station M is located at the point D near the base station A, as described above, the communication mode is the first communication mode, and only the base station A is selected. That is, the switches (SW A, SW B) shown in FIG. 9 are respectively brought down by the control signal from the control unit 20, and the traffic channel symbol is input to the lower traffic channel signal generation unit. Then, one-to-one communication is performed between the base station A and the mobile station M, and the data of the traffic channel is transmitted at the maximum speed. Therefore, the OFDM signal is used as it is as shown in FIG. In FIG. 9, the switching of the communication mode is indicated by SW, but it is logical only and does not necessarily mean actual hardware.

The traffic channel signal at this time is

It becomes. That is, the traffic channel signal uses scrambling codes x ₀ ^(l) , x ₁ ^(l) ,... X _Nc-1 ^(l) specific to the base station 1 by the traffic scrambling code multiplier 34. And scrambled.

In addition, each subcarrier component d ^(l) (i, j) of the OFDM symbol is expressed by the following equation with respect to the transmission symbol s (k).

j = 0, 1,... N _c -1, i = 0, 1,... N _d −1, l are numbers of specific base stations.
The traffic channel signal components of the base stations 0, 1, and 2 obtained with such a configuration are as shown in FIGS.
Further, although x ^(l) is used as the traffic channel scramble code, it is not always necessary to use the same code as the pilot channel scramble code, and an arbitrary pattern different depending on the base station may be used. Absent.

Here, in order to make the scramble code used for the traffic channel signal different from the scramble code for the control channel, the signals of both channels become independent signals. Therefore, as shown in the channel configuration diagram shown in FIG. 5, the traffic channel signal and the control channel signal are combined by the combiner 26 and transmitted. This synthesized signal is expressed by the following equation.

  The synthesized signal obtained by synthesizing the received traffic channel signal and the control channel signal is separated by the control channel signal processing unit 42 and the traffic channel signal processing unit 43 independently of each other to control each selected base station. Channel symbols and traffic channel symbols are recovered. The procedure for reproducing the control channel symbol from the separated control channel signal is as described above.

  On the other hand, a procedure for reproducing traffic symbols in the first communication mode will be described below.

The switches (SW C, SW D) shown in FIG. 13 fall down on the basis of the control channel information from the overall control unit 46, and the traffic channel symbols are input to the traffic channel signal processing unit on the lower side. In the traffic channel symbol recovery unit 52b of the processing unit 43, the traffic signal is simply a complex of scramble codes x ₀ ^(l) , x ₁ ^(l) ,... X _Nc-1 ^(l) specific to the base station l. After multiplying the conjugate conjugate and the complex conjugate of the estimated channel gain, it is transmitted to the P / S converter 508b as it is. As a result, the traffic channel symbol is reproduced.

  Next, the mobile station M moves from the position D to the point E (point E shown in FIG. 3) where the communication environment condition is not good, and the traffic channel signal when the communication in the second communication mode described above is started. Generation and reproduction and generation and reproduction of traffic channel symbols will be described.

  When the mobile station M is in an environment such as the point E, the mobile station M at the point E is away from the base station, so that the signal attenuation is large and the interference signal power is large. If it is transmitted at the same strength, it cannot be received well at point E.

  Therefore, the base stations A, B, and C transmit different traffic data to the mobile station. That is, Nc symbols in the entire frequency direction are divided into 1/3 and transmitted by each base station. One base station can transmit one symbol by spreading it into three identical symbols.

This makes it possible to use a spread OFDM signal that is resistant to interference, and improve communication quality. Here, the switches (SW A, SW B) shown in FIG. 9 are each turned upward by the control signal from the control unit 20, and the traffic channel symbol is the traffic signal frequency spreading unit of the upper traffic channel signal generation unit 25. The same three data symbols are transmitted using three subcarriers. However, without using adjacent subcarriers, data symbols are transmitted using subcarriers whose frequencies are separated by Nc / 3 times the subcarrier interval. This can be expressed as an equation:

It becomes.
Here, j = 0,1, ····, N c / 3-1, i = 0,1, ····, N d -1,

l = 0, 1, 2.
The traffic channel signal components of the base stations 0, 1 and 2 obtained in such a configuration are as shown in FIGS.

In the receiver of the portable terminal, the switches (SW C, SW D) shown in FIG. 13 are respectively tilted upward by the control channel information from the overall control unit 46, and the traffic channel signal is processed by the upper traffic channel signal processing. As shown in the traffic channel symbol despreading unit 52a in FIG. 13, the signal components of three subcarriers separated by N _c / 3 times the subcarrier interval are synthesized, demodulated, and traffic Channel symbols are played back. Thus, since the frequency diversity effect can be obtained, it is possible to improve the communication quality by averaging the fluctuation of the subcarrier level.

  Also, the data transmission rate per station is 1/3 as described above, but the same transmission rate as that at the point D at the mobile station M at the point E by receiving signals from the three base stations almost simultaneously. Can be realized.

  Note that since the control channel signal and the traffic channel signal are transmitted almost simultaneously by the combined signal, the two channel signals may interfere with each other. In this case, it is possible to first demodulate the control channel, cancel the control channel signal component from the combined signal, and then demodulate the traffic signal. Thereby, the communication quality of a traffic channel signal can be improved.

  Here, in the traffic channel signal generation unit 25 shown in FIG. 9 and the traffic signal processing unit 43 shown in FIG. 13, the third communication mode in which communication is performed between the transmitter of one base station and the mobile terminal described above is as follows. It is implemented using the upper block that implements the two communication modes. Since only 1/3 of the entire symbol is processed in this block, the time for processing the entire data requires three times the processing time. For this reason, the data transmission rate is reduced to 1/3.

  Next, in the mobile communication system between the base station and mobile station described above, FIG. This will be described below with reference to flowcharts 27 and 28.

FIG. 26 is a flowchart showing a procedure when one base station is selected by the base station selection means in the receiver of the mobile station M, and the first communication mode is selected by the base station controller.
FIG. 27 is a flowchart showing a procedure when a plurality of base stations are selected by the base station selection means in the receiver of the mobile station M and the second communication mode is selected by the base station controller.
Further, FIG. 28 is a flowchart showing a procedure when a plurality of base stations are selected by the base station selection means in the receiver of the mobile station M and the third communication mode is selected by the base station controller.

The operations of the base station controller, base station, and mobile station will be described below based on these flowcharts.
In this flowchart, the case where the base station is selected by the base station selection means of the mobile station will be described. However, when the base station controller selects the base station, the final selection right of the base station moves to the base station controller side. The execution flow is almost the same as the above flow, and the description is omitted.

  First, a description will be given based on the flowchart of FIG.

  The pilot channel signal processing unit 41 receives pilot signals from neighboring base stations (step S100). Then, the pilot channel signal processing unit 41 measures the reception signal level of each surrounding base station (step S101).

  Next, the base station selection means of the overall control unit 46 determines the received signal level of the base station measured in step S101 from among a plurality of base stations having the same base station identification number (# 0 to # 3). Among them, the base station having the maximum received signal level is selected for each base station identification number, for example, four base stations are selected (step S102).

  Next, a base station having a level lower than a predetermined dB from the base station having the maximum received signal level is excluded (step S103). Further, if there are more than 3 selected base stations, the minimum reception level is excluded. (Step S104). In the present embodiment (FIG. 26), an example is shown in which the mobile station M is at a point close to the base station A, and therefore only the base station A is selected here.

  Next, in step S105, an access request is transmitted to the selected base station A. Then, data such as information on the selected base station A and communication quality parameters are transmitted to the base station A.

Receiving the access request, the base station A transmits an access request from the mobile station M to the base station controller 14 and transmits the information of the selected base station A and the communication quality parameter (step S106).
When receiving an access request from the base station A, the base station controller 14 transmits an access permission to the base station A, determines the communication mode to the first communication mode, and transmits control information and traffic data. (Step S107).

  Next, the base station A that has received access permission from the base station controller generates a frame that includes a combined signal of the control channel signal and the traffic channel signal, and transmits the frame to the mobile station A (step S108). Then, the receiver of the mobile station M demodulates the control channel signal from the selected base station A (step S109).

  Further, whether or not there is an error in the decoded control channel data is determined by a CRC (Cyclic-Redundancy-Check) code or the like (step S110), and if it can be received without error (step S110; Yes), the traffic channel signal Whether the information addressed to the local station is included is determined based on the received control information (step S111). If the information addressed to the local station is included (step S111; Yes), the traffic channel of the base station A Is demodulated and decoded (step S112).

  If there is an error in the received control channel data in step S110 (step S110; No), or if it is found in step S111 that information addressed to the own station is not included (step S111; No). Does not perform subsequent processing on the traffic channel signal of the base station A (step S113).

  Here, the control channel of the reception candidate base station is received, error detection is performed with a CRC code or the like, and if there is no error (step S110; Yes), a control channel signal replica is generated and canceled from the received signal, A method of demodulating the traffic channel of the base station signal may be taken.

  In addition to the method based on the received signal level, a criterion for selecting base stations may be a method of ordering based on the propagation loss of the wireless communication path. Further, in order to use the distance from the base station as a reference, an ordering method based on the received signal timing and the propagation delay amount may be considered.

Next, a case where there are two selected stations and a case where the communication mode is the second and third communication modes will be described with reference to FIGS.
Steps S100 to S104 are the same processing as the flow shown in FIG. However, since the present embodiment (FIGS. 27 and 28) shows an example in which the mobile station M is near the boundary between the base stations A and B, the base stations A and B are selected here. In step S104, when the base stations A and B whose reception level difference is within a predetermined range are selected, the mobile station M transmits an access request to the base stations A and B, and each is selected. Information and respective communication quality parameters are transmitted (step S200).

  When receiving the access request, the base station A transmits an access request from the mobile station M to the base station controller, and also transmits a communication quality parameter of the base station A (step S201). Similarly, when the base station B accepts the access request, it transmits an access request from the mobile station M to the base station controller, and also transmits a communication quality parameter of the base station B (step S202).

  The base station controller that has received the access request from the base stations A and B determines whether there is a margin in the traffic volume of each cell of the base stations A and B (step S203). When there is a margin in traffic (step S203; Yes), the access permission is transmitted to the base stations A and B, and the base station controller sets the communication mode to the second communication mode. The control information and traffic data are transmitted in response to (step S204).

  The base stations A and B that have accepted the access permission generate frames to the mobile station M and transmit them almost simultaneously (steps S205 and S206).

  Next, the receiver of the mobile station M receives the control channel signals from the selected base stations A and B almost simultaneously and demodulates them (step S207). The receiver of the mobile station M determines whether or not the control channel data can be received without error for each of the base stations A and B (step S208), and if it can be received without error (step S208; Yes). Then, it is determined whether the information addressed to the own station is included in the control channel data (step S209). If the information addressed to the own station is included (step S209; Yes), the traffic channel is demodulated and decoded. This is performed (step S210).

  If there is an error in reception in step S208 (step S208; No), and if no information addressed to the own station is included in step S209 (step S209; No), the traffic channel signal is demodulated. Without processing (step S211), only the signal of the base station that has been found to contain information addressed to itself is processed.

  Next, in step S203, when the determination condition is not satisfied (step S203; No), the processing shifts to the processing of (A) shown in FIG. With two base stations A and B selected, either base station A or B with good communication conditions is selected. Here, it is assumed that the base station A is selected. The base station controller sets the communication mode to the third communication mode, issues access permission to the base station A, and transmits control information and traffic data (step S220).

  The base station A that has accepted the access permission generates a frame and transmits it to the mobile station M (step S221).

  At this time, the mobile station M does not have information that the mode 3 is selected and data is transmitted from the base station A. Therefore, the mobile station M operates so as to receive the signals of both the base stations A and B that transmitted the access request. The receiver of the mobile station M receives and demodulates the control channel signals of the base stations A and B (step S222). It is determined whether or not the demodulated control channel data of the base station A or B can be received without error (step S223). When the demodulated control channel data can be received without error (step S223; Yes), the control channel data is addressed to the own station. It is determined whether information is included (step S224), and when information addressed to itself is included (step S224; Yes), the base station traffic channel is demodulated and decoded (step S210). .

  If there is an error in reception in step S223 (step S223; No), and if no information addressed to the own station is included in step S224 (step S224; No), the subsequent traffic channel signal is received. Is not performed (step S226).

  As described above, it is possible to automatically execute selection of an appropriate base station and selection of a communication mode according to the communication environment state.

  Note that the cellular mobile communication system according to the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

It is a system conceptual diagram explaining the basic concept of the cellular mobile communication system which concerns on this invention. It is a network block diagram which shows the connection of the traffic data and control information between the base station controller 14 and each base station. It is a figure which shows arrangement | positioning of the base station in a some cell. It is a figure explaining GI of OFDM. It is a block diagram in the time and frequency axis of each channel signal used for the cellular mobile communication system which concerns on this invention. It is a block diagram of the transmitter of a base station. It is a block diagram of the pilot channel signal generation part 23 in the transmitter of a base station. It is a block diagram of the control channel signal generation part 24 in the transmitter of a base station. It is a block diagram of the traffic channel signal generation part 25 in the transmitter of a base station. It is a block diagram of the receiver of a mobile station. It is a block diagram which shows the pilot channel signal processing part corresponding to one base station among the pilot channel signal processing parts 41 in the receiver of a mobile station. It is a block diagram which shows the control channel signal processing part corresponding to one base station among the control channel signal processing parts 42 in the receiver of a mobile station. It is a block diagram which shows the traffic channel signal processing part corresponding to one base station among the traffic channel signal processing parts 43 in the receiver of a mobile station. It is the figure which showed the pilot signal component of the base station 0 in tabular form. It is the figure which showed the pilot signal component of the base station 1 in tabular form. It is the figure which showed the pilot signal component of the base station 2 in tabular form. It is the figure which showed the control channel signal component of the base station 0 in tabular form. It is the figure which showed the control channel signal component of the base station 1 in tabular form. It is the figure which showed the control channel signal component of the base station 2 in tabular form. It is the figure which showed the traffic channel signal component of the base station 0 corresponding to a 1st communication mode in tabular form. It is the figure which showed the traffic channel signal component of the base station 1 corresponding to a 1st communication mode in tabular form. It is the figure which showed the traffic channel signal component of the base station 2 corresponding to a 1st communication mode in tabular form. It is the figure which showed the traffic channel signal component of the base station 0 corresponding to a 2nd communication mode in tabular form. It is the figure which showed the traffic channel signal component of the base station 1 corresponding to a 2nd communication mode in tabular form. It is the figure which showed the traffic channel signal component of the base station 2 corresponding to a 2nd communication mode in tabular form. 7 is a flowchart showing a procedure when one base station is selected by a base station selection unit of a receiver in a mobile station M and a first communication mode is selected by a base station controller. 10 is a flowchart illustrating a procedure when a plurality of base stations are selected by a base station selection unit of a receiver in a mobile station M and a second communication mode is selected by a base station controller. 10 is a flowchart illustrating a procedure when a plurality of base stations are selected by a base station selection unit of a receiver in a mobile station M and a third communication mode is selected by a base station controller. It is a block diagram of the transmitter / receiver using the OFDM system. (A) is a block diagram of a transmitter, and (b) is a block diagram of a receiver. It is an arrangement relationship between an OFDM symbol and a GI. It is the figure which showed arrangement | positioning of the transmission symbol in the transmission signal in 1 frame of OFDM system. It is the figure which showed arrangement | positioning of the transmission symbol in the transmission signal in 1 flame | frame of a spread OFDM system. (A) is a figure which shows that the spreading factor of a frequency domain is 4, and the same data symbol is transmitted with four subcarriers. (B) is a figure which shows that the spreading factor of a frequency domain and a time domain is 2, and the same data symbol is transmitted by two subcarriers and two OFDM symbols. It is a block diagram of a transmitter / receiver of a spread OFDM system that performs frequency domain spreading. (A) is a block diagram of a transmitter, and (b) is a block diagram of a receiver.

Explanation of symbols

10, 11, 12 Cell 13 Boundary area 14 Base station controller 15 Core network 16 Internet 17 Base station transmitter 18 Control channel data buffer unit 19 Traffic channel data buffer unit 20 Control unit 21 Control channel symbol generation unit 22 Traffic channel symbol generation Unit 23 Pilot channel signal generating unit 24 Control channel signal generating unit 25 Traffic channel signal generating unit 26 Combining unit 27 Switching unit 28 Antenna 30 Copying unit (copyer)
31 pilot scramble code multiplier 32 control signal frequency spreader 33 traffic signal frequency spreader 34 traffic scramble code multiplier 39 mobile station receiver 40 antenna 41 pilot channel signal processor 42 control channel signal processor 43 traffic channel signal Processing unit 44 Control channel data recovery unit 45 Traffic channel data recovery unit 46 Overall control unit 50 Channel estimation signal generation unit 51 Control channel symbol despreading unit 52a Traffic channel symbol despreading unit 52b Traffic channel symbol recovery units 500, 500a, 500b S / P converter 501, 501a, 501b IFFT
502, 502a, 502b P / S converters 503, 503a, 503b AddGI
504 RemoveGI
505 Timing detectors 506, 506a, 506b S / P converters 507, 507a, 507b FFT
508, 508a, 508b P / S converter 600 Frequency domain spreading unit 601 Frequency domain despreading unit

Claims (9)

A cellular mobile communication system in which a mobile station can receive radio signals from a plurality of nearby base stations substantially simultaneously,
A first communication mode in which a predetermined communication data amount is transmitted at a substantially maximum communication speed, and communication data in which the predetermined communication data amount is divided at a certain ratio by increasing communication quality instead of decreasing the communication speed. A base station transmitter having a second communication mode for transmitting
A receiver of a mobile station capable of receiving transmission data according to the first communication mode and the second communication mode;
A communication means for performing communication with the outside, and when transmitting the transmission data obtained by the communication means to the mobile station, to which base station of the plurality of base stations, how much A base station controller that performs radio resource control of the entire system including whether to distribute the amount of data of
With
The first communication mode is a mode in which communication is performed between a transmitter of one base station and a receiver of the mobile station among the plurality of base stations, while the second communication mode is a communication mode. This mode is used when the environmental condition is not good compared to the communication environmental condition using the first communication mode, and is transmitted from a plurality of base stations near the mobile station selected by the base station controller. The mobile station receiver receives the divided communication data by the base station controller at substantially the same time, and communicates while ensuring a predetermined communication speed compared to the substantially maximum communication speed. A cellular mobile communication system. Further, the transmitter of the base station increases the communication quality instead of reducing the communication speed similarly to the second communication mode without dividing the predetermined communication data amount, Similarly, among the plurality of base stations, a third communication mode which is a mode for communicating between a transmitter of one base station and a receiver of the mobile station is provided, and the third communication mode , Transmit transmission data to the mobile station receiver,
The cellular mobile communication system according to claim 1, wherein the receiver of the mobile station receives transmission data transmitted in the third communication mode. The mobile station comprises base station selection means for automatically selecting a plurality of base stations near the mobile station,
The base station selection means measures the reception level of radio signals from a plurality of base stations, selects a predetermined number of base stations based on the measured reception level, and sets the reception level or the reception level. 3. The cellular device according to claim 1, wherein a parameter indicating the corresponding channel quality is transmitted to the base station controller via one or more of the selected base stations. Mobile communication system. The base station controller comprises base station selection means capable of automatically selecting a plurality of base stations near the mobile station,
The base station selection means receives selection information including the reception level or a parameter indicating the channel quality corresponding to the reception level from the mobile station via the base station, and based on the selection information, The cellular mobile communication system according to claim 3, wherein selection is performed. The base station controller, after executing the selection of the base station, determines whether or not the communication conditions between the transmitter of the base station and the receiver of the mobile station are good, and the communication conditions are good If it is determined that there is, select the first communication mode, and perform communication in the first communication mode between the base station and the mobile station,
On the other hand, it is determined that the communication condition is not good, and the third communication mode is selected according to the amount of communication traffic in the cell and the communication service quality provided to each mobile station, and the selected base station and The cellular mobile communication system according to claim 3 or 4, wherein communication is performed between the mobile stations.   The first communication mode is a communication mode for performing high-speed data communication using a wideband signal including an OFDM signal, and the second or third communication mode is a wideband signal including a spread OFDM signal. The cellular mobile communication system according to any one of claims 1 to 5, wherein the cellular mobile communication system is a communication mode in which communication is performed using a signal having high interference resistance.   The first communication mode is a communication mode for performing high-speed data communication using a wideband signal including an OFDM signal with a high modulation multi-level number or a high coding rate, and the second or third communication mode is 6. The communication mode according to claim 1, wherein the communication mode is a broadband signal including a low modulation multi-level number or a low coding rate OFDM signal and performing communication using a signal having high interference resistance. A cellular mobile communication system according to any one of the preceding claims.   When using a spread OFDM signal in the second or third communication mode, assigning orthogonal subcarriers of a frequency separated by a fixed interval to a plurality of identical data, and transmitting the spread OFDM signal, 7. The cellular mobile communication system according to claim 6, wherein interference resistance is further improved by receiving frequency diversity reception by receiving signals through communication paths having different characteristics. Each of the plurality of base stations has an identification number so that the signals of the base stations can be distinguished and received simultaneously, so that base stations located in the vicinity of each base station do not have the same base station identification number. 9. The receiver according to claim 1, wherein a receiver of the mobile station receives a plurality of base stations that are grouped and have different base station identification numbers at substantially the same time. 9. Cellular mobile communication system.

Images