JP4129092B2 - OFDM transmission / reception device, radio communication base station device, and OFDM transmission / reception method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an OFDM transmission / reception apparatus , a radio communication base station apparatus, and an OFDM transmission / reception method that perform communication using an OFDM (Orthogonal Frequency Division Multiplexing; hereinafter referred to as OFDM) system that performs communication using a plurality of subcarriers.
[0002]
[Prior art]
In the conventional OFDM transmission / reception apparatus, the frequency band is allocated according to the purpose of use and the type of wireless communication for each use, for example, television broadcasting, mobile phone, FM radio broadcasting, etc. For example, wireless communications with different modulation schemes do not interfere with each other.
[0003]
In particular, the power of non-public wireless communication that is arbitrarily performed, such as communication used by the general public, such as mobile phones and wireless LANs, does not interfere with public wireless communication such as television broadcasting and AM radio broadcasting. The use frequency band is determined in consideration of
[0004]
[Problems to be solved by the invention]
However, in the conventional system, there is a problem that the frequency utilization efficiency may be poor such that a certain frequency band has insufficient capacity and another certain band has a margin.
[0005]
Also, using one frequency band for a plurality of types of wireless communication may affect each other's communication because the modulation schemes in each wireless communication are different.
[0006]
In particular, when the non-public system uses the frequency band originally assigned to the public system, it is important to prevent the public system from being damaged by the use of the non-public system.
[0007]
The present invention has been made in view of the above points, and an OFDM transmission / reception apparatus that uses the same frequency band for a plurality of types of wireless communication with different modulation schemes and prioritizes highly public communication in the use An object of the present invention is to provide a radio communication base station apparatus and an OFDM transmission / reception method .
[0008]
[Means for Solving the Problems]
The gist of the present invention is to synchronize all devices performing wireless communication in a plurality of types of wireless communication with different modulation schemes assigned to the same frequency band, and use the same frequency band in a time-sharing manner. This is to assign public wireless communication to each divided slot with priority over non-public wireless communication.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
OFDM transmitting and receiving apparatus according to a first aspect of the present invention, the OFDM transmitting and receiving means for performing frequency generating means for generating a plurality of different frequencies, the communication using a plurality of frequencies generated as the carrier wave, use of the OFDM transmitting and receiving means Control information to the other station using only the carrier of the specific frequency selected by the selection means, operating the selection means prior to communication between the selection means for selecting the carrier to be used and the other station adopting a different communication method And a control means for transmitting.
[0010]
According to this configuration, communication can be performed between communication methods adopting an orthogonal modulation method even when the communication methods are different. For example, a base station that performs multi-carrier communication can communicate with a base station that performs single-carrier communication.
[0011]
OFDM transmitting and receiving apparatus according to a second aspect of the present invention, in a first aspect, the control means, the selecting means to select a carrier having a center frequency band frequency near the frequency band used in the other stations To reduce the number of carrier waves used by the OFDM transmission / reception means .
[0012]
According to this configuration, communication can be performed in the vicinity of the center frequency of the used frequency of other stations, so that communication quality is improved.
[0013]
In the OFDM transmitter / receiver according to the third aspect of the present invention, in the first aspect, the control means selects a pair of carriers having a frequency closest to a center frequency band of a frequency band used by the other station. The selection means is operated to reduce the number of carriers used by the OFDM transmission / reception means .
[0014]
According to this configuration, stable transmission / reception is possible. That is, since the subcarriers normally used in the OFDM system are even numbers, the circuit operation is stabilized if a pair of carriers close to the center frequency is used.
[0015]
OFDM transmitting and receiving apparatus according to a fourth aspect of the present invention, in the third one of aspects from the first, said control means activates said selection means only when sending an access channel inserts a frame sync signal The number of carrier waves used by the OFDM transmission / reception means is reduced.
[0016]
With this configuration, since frame synchronization can be established simultaneously with detection of symbol synchronization of the access channel, synchronization can be established efficiently.
[0017]
OFDM transmitting and receiving apparatus according to a fifth aspect of the present invention, in the fourth one of aspects from the first connection request signal receiving means for receiving a connection request signal including information on the number of carriers and a communication application from said other station comprising a said control means, in accordance with the contents of the connection request signal, and to determine the carrier number of the OFDM transmitting and receiving means are used.
[0018]
According to this configuration, it is possible to select an optimal carrier wave according to the communication method of the other station according to the content of the received connection request signal.
[0019]
OFDM transmitting and receiving apparatus according to a sixth aspect of the present invention, in the fifth aspect, the configuration comprises assignment means for assigning the wireless communication with the other station is the empty slot of the user channel connection request signal source, the It was.
[0020]
According to this configuration, since a plurality of types of wireless communication are divided in a time division manner, wireless communication with different modulation schemes can coexist in one frequency band.
[0021]
The OFDM transmitter / receiver according to a seventh aspect of the present invention is the OFDM transmitter / receiver according to the sixth aspect, wherein the allocating means is a traffic monitoring unit that monitors a congestion degree of wireless communication with other stations than the other station, and the congestion degree and the connection a determination unit from a priority of the information regarding the communication application in the request signal to determine the number of slots to be allocated to the other station, and the slot number variable unit for changing the number of slots allocated to said other station in response to an output of the determining unit, The structure which has is taken.
[0022]
According to this configuration, when there is a request from the base station that performs non-public communication to the base station that performs public communication using the public frequency band, Since slots can be allocated so that public communication is prioritized, it is possible to eliminate obstacles to public communication while increasing the usable bandwidth of non-public communication.
[0023]
The radio communication base station apparatus according to the eighth aspect of the present invention comprises a connection request signal transmitting means for transmitting a connection request signal including information relating to the number of carriers and communication use, and any one of claims 5 to 7. A configuration is adopted in which wireless communication is performed with a base station apparatus having the OFDM transmission / reception apparatus according to the aspect .
[0024]
According to this configuration, since the non-public communication can use the public frequency band in a non-priority manner, it is possible to increase the usable bandwidth of the non-public communication while eliminating the obstacle to the public communication. it can.
[0025]
OFDM transmitting and receiving method according to a ninth aspect of the present invention includes a frequency generating step of generating a plurality of different frequencies, the OFDM transmitting and receiving step that performs communication using a plurality of frequencies generated as the carrier wave, use of the OFDM transmitting and receiving step Control information to the other station using only the carrier wave of the specific frequency selected in the selection step by operating the selection step prior to communication with the other station adopting a different communication method And a control step for transmitting.
[0026]
With this configuration, communication can be performed between communication methods adopting an orthogonal modulation method even when the communication methods are different. For example, a base station that performs multi-carrier communication can communicate with a base station that performs single-carrier communication.
[0027]
OFDM transmitting and receiving method according to a tenth aspect of the present invention, in the ninth aspect, the control step, the selection step to select a carrier having a frequency of the center frequency band near the frequency band used in the other stations To reduce the number of carriers used in the OFDM transmission and reception process .
[0028]
According to this configuration, communication can be performed in the vicinity of the center frequency of the used frequency of other stations, so that communication quality is improved.
[0029]
OFDM transmitting and receiving method according to an eleventh aspect of the present invention, in the ninth aspect, the control step, to select a pair of carrier waves having a frequency closest to the center frequency band of the frequency band used in the other stations The selection step is operated to reduce the number of carriers used in the OFDM transmission / reception step .
[0030]
According to this configuration, stable transmission / reception is possible. That is, since the subcarriers normally used in the OFDM system are even numbers, the circuit operation is stabilized if a pair of carriers close to the center frequency is used.
[0031]
OFDM transmitting and receiving method according to the twelfth aspect of the present invention is the eleventh one aspect of the ninth, the control step activates said selecting step only when sending an access channel inserts a frame sync signal The number of carriers used in the OFDM transmission / reception process is reduced.
[0032]
With this configuration, since frame synchronization can be established simultaneously with detection of symbol synchronization of the access channel, synchronization can be established efficiently.
[0033]
OFDM transmitting and receiving method according to the thirteenth aspect of the present invention is the twelfth one aspect of the ninth connection request signal reception step of receiving a connection request signal including information on the number of carriers and a communication application from said other station the a, the control step, depending on the content of the connection request signal, and to determine the carrier number of the OFDM transmitting and receiving process is used.
[0034]
According to this configuration, it is possible to select an optimal carrier wave according to the communication method of the other station according to the content of the received connection request signal.
[0035]
OFDM transmitting and receiving method according to a fourteenth aspect of the present invention, first the thirteenth aspect, that comprises the assignment process, assigning the radio communication with the other station is the empty slot of the user channel connection request signal source I made it.
[0036]
According to this configuration, since a plurality of types of wireless communication are divided in a time division manner, wireless communication with different modulation schemes can coexist in one frequency band.
[0037]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0038]
In this embodiment, public communication is performed by multi-carrier communication, for example, Orthogonal Frequency Division Multiplexing (hereinafter referred to as OFDM), and the frequency band originally assigned to this public system is changed. Non-public communication performed by single carrier communication interrupts and uses non-priority.
[0039]
Hereinafter, the radio communication system according to the present embodiment will be described with reference to FIGS. FIG. 1 is a schematic diagram showing a frequency spectrum in a radio communication system according to an embodiment of the present invention.
[0040]
FIG. 1 (a) shows the frequency spectrum used in the wireless communication of the spread spectrum system, FIG. 1 (b) shows the single carrier system, and FIG. 1 (c) shows the multi-carrier system such as OFDM. Represents each. Currently, a method of dividing and using the 5 GHz frequency band in a form as shown in the figure is proposed as the OFDM method.
[0041]
As shown in the figure, since different frequency bands are assigned to different communication methods, for example, single carrier communication can only be transmitted / received by one carrier in transmission / reception. Cannot receive even if is sent.
[0042]
Therefore, in this state, non-public communication using the single carrier method cannot receive synchronization signals sent from public communication using the multi-carrier method, and cannot synchronize with the public system.
[0043]
Therefore, in the present embodiment, the number of carriers is reduced, that is, the access channel is transmitted using only two subcarriers as shown in FIG. 1D, and a non-public system using a single carrier scheme is used. Base station equipment can receive this access channel and synchronize with the public system.
[0044]
The process of reducing the number of carrier waves will be described with reference to FIG. FIG. 2 is a schematic block diagram of the OFDM transmitter / receiver.
[0045]
The input symbol sequence is divided by the S / P converter 201 according to the number of subcarriers, and subcarriers of different frequencies generated by the oscillator 202 are multiplied by the multipliers 203 and 204 to obtain a low-speed symbol sequence. This low-speed symbol string is transmitted through a band filter 210 after being multiplied by a carrier wave generated by a carrier wave oscillator 209 by a multiplier 208 via a selection circuit 205, a parallel-serial converter 206, and an LPF (low-pass filter) 207.
[0046]
Each frame is composed of an access slot, a control slot, a message slot, and the like. Normally, communication is performed using all subcarriers at all times. However, in the present invention, as described above, the access channel is received in order to be synchronized with the public system. In this transmission period, transmission is performed using only a part of the subcarriers.
[0047]
Any subcarrier may be selected, but if a subcarrier near the center frequency of a frequency band used in another assumed communication method is used, communication quality and accuracy are improved.
[0048]
Specifically, for example, when communicating with another station adopting the single carrier scheme shown in FIG. 1B, all sub-stations used for one communication of the normal OFDM scheme as shown in FIG. Of the carriers, two subcarriers located near the center frequency may be used.
[0049]
As described above, the method for selecting only a specific subcarrier may be to operate only the modulator using the specific subcarrier or to select only the output.
[0050]
In the OFDM base station transmission apparatus shown in FIG. 2, the selection circuit 205 selects only a signal using a specific subcarrier.
[0051]
Next, a reception signal demodulation method performed by a single-carrier receiving apparatus that receives a signal as shown in FIG. Assuming that a rotating signal vector having an amplitude A ₀ is received using a subcarrier having a frequency ω, the in-phase component (Ir) and the quadrature component (Qr) of the received signal are respectively
Ir (τ) = A ₀ (cosωτ + cosθ)
Qr (τ) = jA ₀ (sin ωτ−sin θ)
It can be expressed as cos θ and sin θ are phase shift amounts of the respective components.
[0052]
Further, the frequency characteristic of the received signal can be expressed by power that is an envelope of a vector, as shown in the following equation.
Power = | Ir (nT) + Qr (nT) | ²
= {A ₀ (cosωτ + cosθ) + jA ₀ (sinωτ−sinθ)}
× {A ₀ (cos ωτ + cos θ) −jA ₀ (sin ωτ−sin θ)}
= {A ₀ (cos ωτ + cos θ)} ² + {A ₀ (sin ωτ−sin θ)} ²
= A ₀ ² {cos2ωτ + 2cosωτcosθ + cos2θ}
+ A ₀ ² {sin2ωτ + 2sinωτsinθ + sin2θ}
= A ₀ ² {cos2ωτ + sin2ωτ + cos2θ + sin2θ}
+ A ₀ ² {cosωτcosθ-2sinωτsinθ}
[0053]
As is apparent from the above equation, the second term is the fundamental frequency, whereas the first term has all the frequency components doubled, indicating that the second harmonic has been generated. Therefore, by filtering the received signal composed of the fundamental frequency and the second harmonic and removing the fundamental frequency, the second harmonic is stably extracted, and the extracted second harmonic is further divided by a frequency divider. By returning to the fundamental frequency, the carrier can be reproduced.
[0054]
Therefore, in all other communication systems adopting the orthogonal modulation system, carrier recovery can be performed by providing means for squaring the received wave transmitted from the OFDM base station transmitter.
[0055]
By using this regenerated carrier as a local signal in quadrature detection, a signal transmitted from the OFDM base station transmitter can be normally received and demodulated data can be obtained, and symbol synchronization can be achieved. By inserting the frequency information of the carrier wave used in the access channel, control channel, and data channel into the downlink signal transmitted from the OFDM base station transmitter, other stations that receive this receive more accurate reception. Can be done.
[0056]
Note that the sampling signal for A / D conversion, the transfer clock, and the like can be appropriately adjusted according to the reproduced carrier.
[0057]
Next, a procedure when non-public communication interrupts the public frequency band will be described with reference to FIGS. 3 to 5 are schematic diagrams showing a schematic configuration of a radio frame in the radio communication system according to the embodiment of the present invention.
[0058]
FIG. 3 shows a frame configuration of a public communication base station and a non-public communication base station that is out of synchronization with the public base station. The horizontal axis is time.
[0059]
When a non-public base station monitors the frequency band and recognizes that it is a public communication band, when communicating using the free capacity of that frequency band, it sends a connection request signal to the public base station. To do.
[0060]
The connection request signal includes information that the source is a non-public base station and that the single carrier method is used.
[0061]
The public base station that has received such a connection request signal transmits an access channel in which a frame synchronization signal is placed on two subcarriers as shown in FIG.
[0062]
As shown in FIG. 3, one frame includes an access slot 301, a control slot, and a message slot. The non-public base station that is not synchronized with the public base station receives the access slot 301 containing the frame synchronization signal, performs symbol synchronization based on the received signal by the above-described method, Establish synchronization.
[0063]
However, since the OFDM signal is offset by the subcarrier frequency, in a non-public communication reception system that performs quadrature modulation / demodulation, when receiving signals from the two subcarriers and performing quadrature detection, the baseband signal is Causes constellation rotation on the IQ plane. Therefore, in the present embodiment, the public base station apparatus differentially encodes the frame synchronization signal in advance.
[0064]
In this way, the non-public base station can synchronize to obtain information on the frame start position and frame period of the public base station.
[0065]
FIG. 4 shows a frame configuration in a state where a non-public base station that wishes to interrupt has established synchronization with the public base station.
The public base station transmits, to a synchronized non-public base station, a signal indicating whether this band is available and how many slots are allocated if possible.
[0066]
Here, three slots, that is, slots 7 to 9 among the message slots of the public base station, are assigned to the non-public assignment slot 401.
[0067]
FIG. 5 shows a state in which the non-public base station to which the non-public assignment slot 301 is assigned performs non-public wireless communication using the band.
[0068]
Here, a state is shown in which one non-public communication terminal A to C is allocated to three non-public system allocation slots 401 and wireless communication is performed. As shown in the figure, slots 7 to 9 are used for the downlink in the nth frame, and are used for the uplink in the (n + 1) th frame.
[0069]
Note that when allocating the non-public system allocation slot, the public base station allocates the maximum available slots for non-public system so as to enhance the convenience of non-public communication. However, since the use for public communication is given priority, the traffic and demand for public communication are always monitored, and the number of non-public allocation slots 301 is increased or decreased as necessary.
[0070]
Further, in the above-described embodiment, non-public modulation / demodulation schemes such as a single carrier orthogonal modulation / demodulation scheme, a direct spread modulation / demodulation scheme, a chirp modulation / demodulation scheme, and a pulse position modulation / demodulation scheme can be considered.
[0071]
【The invention's effect】
As described above, according to the present invention, it is possible to use the same frequency band for a plurality of types of wireless communication with different modulation schemes, and to give priority to public communication with high publicity when using the same frequency band.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a frequency spectrum in an OFDM transceiver apparatus according to an embodiment of the present invention. FIG. 2 is a schematic block diagram of the OFDM transceiver apparatus according to the embodiment. FIG. 4 is a schematic diagram showing a schematic configuration of a radio frame in the OFDM transceiver apparatus according to the embodiment. FIG. 4 is a schematic diagram showing a schematic configuration of a radio frame in the OFDM transceiver apparatus according to the embodiment. Schematic diagram showing the schematic configuration of a radio frame in the Internet [Explanation of symbols]
201 Frequency generation means 204 Selection circuit 301 Access slot 401 Non-public allocation slot

Claims (14)

Taking a frequency generating means for generating a plurality of different frequencies, the OFDM transmitting and receiving means for communicating using a plurality of frequencies generated as the carrier wave, means for selecting a carrier for use of the OFDM transmitting and receiving means, a different communication scheme Control means for operating the selection means prior to communication with another station and transmitting control information to the other station using only a carrier having a specific frequency selected by the selection means , OFDM transmitting and receiving apparatus. Wherein said control means includes a wherein a carrier having a center frequency band frequency near the frequency band used for other stations to operate the selection means to select, the OFDM transmitting and receiving means reduces the number of carriers to be used The OFDM transmitting / receiving apparatus according to claim 1. The control means operates said selection means to select a pair of carrier waves having a frequency closest to the center frequency band of the frequency band used in the other stations, reducing the number of carriers used by the OFDM transmitting and receiving means The OFDM transmission / reception apparatus according to claim 1. Wherein, only when sending an access channel inserts a frame sync signal to operate said selection means, of claims 1 to 3, characterized in that to reduce the number of carriers that the OFDM transmitting and receiving means is used The OFDM transmission / reception apparatus in any one. Comprises a connection request signal receiving means for receiving from the other station a connection request signal including information on the number of carriers and communication applications, the control means in accordance with the content of the connection request signal, the OFDM transmitting and receiving means is used The OFDM transmission / reception apparatus according to claim 1, wherein the number of carrier waves is determined. 6. The OFDM transmission / reception apparatus according to claim 5, further comprising allocating means for allocating an empty slot of the user channel to wireless communication with the other station that is a connection request signal source. The assignment means includes a traffic monitoring unit for monitoring a congestion degree of the radio communication with other than the other stations, the number of slots to be allocated to the other station and a priority of the information regarding the communication applications of the congestion degree and the connecting request signal 7. The OFDM transmission / reception apparatus according to claim 6, further comprising: a determination unit that determines the number of slots, and a slot number variable unit that changes a number of slots allocated to the other station according to an output of the determination unit.   8. A connection request signal transmitting means for transmitting a connection request signal including information on the number of carriers and communication usage is provided, and wireless communication is performed with a base station apparatus having the OFDM transmitting / receiving apparatus according to claim 5. A wireless communication base station apparatus. A frequency generation process for generating a plurality of different frequencies, an OFDM transmission / reception process in which communication is performed using the generated plurality of frequencies as carrier waves, and a selection process for selecting a carrier wave used in the OFDM transmission / reception process are employed. A control step of operating the selection step prior to communication with another station and transmitting control information to the other station using only a carrier having a specific frequency selected in the selection step. OFDM transmission / reception method. Wherein the control step includes a wherein a carrier having a center frequency band frequency near the frequency band used for other stations to operate the selection process to select, the OFDM transmitting and receiving process reduces the number of carriers to be used The OFDM transmission / reception method according to claim 9. The control process is that the to select a pair of carrier waves having a frequency closest to the center frequency band of the frequency band used for other stations to operate the selection process, the OFDM transmitting and receiving process reduces the number of carriers to be used The OFDM transmission / reception method according to claim 9. Wherein the control step is only during transmission of the access channel inserts a frame sync signal to operate the selection process, according to claim 11 claim 9, characterized in that to reduce the number of carriers used the OFDM transmitting and receiving step The OFDM transmission / reception method according to any one of the above. A connection request signal reception step of a connection request signal including information on the number of carriers and communication applications received from the other station, the control step, depending on the content of the connection request signal, the OFDM transmitting and receiving process is used The OFDM transmission / reception method according to any one of claims 9 to 12, wherein the number of carriers is determined. OFDM transmitting and receiving method according to claim 13, characterized by comprising allocation step of allocating a free slot in the user channel to the wireless communication with the other station is a connection request signal source, a.

Images