JP2007325082A - Wireless base facility, and its communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise a S/N ratio in a communication system such as wireless LAN or the like. <P>SOLUTION: The wireless base facility comprises a base station 110, a relay reception station 150, and a cable 9 for connecting both. The base station 110 comprises a base antenna 111 and an RF part 112 for extracting base band signals out of wireless signals. The relay reception station 150 comprises a relay antenna 151 and an RF part 152 for extracting base band signals out of the wireless signal. The base station 110 further comprises a synchronizing process part 120 which synchronizes the base band signal from the RF band 112 with that from the relay reception station 150. The synchronizing process part 120 comprises detecting parts 121a and 121b for detecting preamble completion time in each base band signal, delay devices 123a and 123b for matching phases of the base band signals according to each completion time, and an adder 125 for adding the base band signals together, of which phases match after passing the delay devices 123a and 123b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless base facility that performs wireless communication by a PHS (Personal Handyphone System) that employs a wireless local area network (LAN) or a time division multiple access (TDMA) method, and a communication method therefor.

  In recent years, wireless LANs have become widespread as one of computer communication networks, and are actively used in offices, homes, urban areas (for example, stations, airports, fast food restaurants) and the like. As is well known, in such a wireless LAN, wireless communication is performed between a base station called AP (Access Point) and a wireless communication terminal. The wireless LAN is defined in IEEE (Institute of Electrical and Electronics Engineers) 802.11 described in Non-Patent Document 1 below.

  In general, since a wireless communication terminal is movable and uses a battery as its power source, it is desired to reduce power consumption. Furthermore, it is desired that the wireless communication terminal expands the range in which communication with the AP is possible.

  In order to meet such a demand, for example, Patent Document 1 below discloses a technique in which an antenna is installed at a position distant from the AP and the antenna and the AP are connected by a cable.

Japanese Patent Laid-Open No. 2002-221385 "Wireless LAN Medium Control (MAC) and Physical Layer (PHY) Specifications" ANSI / IEEE Std 802.11, 1999 Edition

  However, in the above prior art, the signal-to-noise ratio is not so good and transmission errors are likely to occur because the signal from the wireless communication terminal is received by the antenna and attenuated in the process of being transmitted to the AP via the cable. There is a problem.

  The present invention has been made paying attention to such conventional problems, and provides a radio base facility and a communication method thereof capable of increasing the S / N ratio while reducing the power consumption of a radio communication terminal. The purpose is to provide.

The invention relating to the radio base facility for solving the above problems
Baseband signal processing means for transmitting / receiving a radio signal to / from a radio communication terminal and modulating and demodulating a baseband signal included in the radio signal is provided between the radio communication terminal and another communication terminal. In a wireless base facility that relays communications,
A base station equipped with a base antenna for transmitting and receiving radio signals to and from a wireless communication terminal;
One or more relay receiving stations equipped with a relay antenna for receiving a radio signal from a radio communication terminal;
A cable connecting between the one or more relay receiving stations and the base station;
With
One of the base station and the relay receiving station is:
One or more second baseband signal extraction means for extracting a baseband signal from a radio signal received by the relay antenna for each of the relay antennas of the one or more relay base stations;
The base station
First baseband signal extraction means for extracting a baseband signal from a radio signal received by the base antenna;
The position between each baseband signal in the baseband signal extracted by the first baseband signal extraction means and the baseband signal respectively extracted by the one or more second baseband signal extraction units. Phase difference detection means for detecting a phase difference;
Based on the phase difference detected by the phase difference detecting means, the phase of at least one of the baseband signals is shifted to eliminate the phase difference between the baseband signals. Phase adjustment means;
Synthesizing the baseband signals whose phase differences are eliminated by the phase adjusting means, and combining the baseband signals obtained by the synthesis to the baseband signal processing means;
It is characterized by having.

  Here, the relay receiving station has the relay antenna and the second baseband signal extracting means, and the cable is a baseband signal extracted by the second baseband means of the relay receiving station. Preferably, the base station and the relay receiving station are connected to each other in order to transmit the signal to the phase difference detecting means and the synthesizing means of the base station.

  Further, the phase difference detecting means grasps the end time of each preamble signal included in each baseband signal, and obtains the phase difference between the baseband signals from the end time of each preamble signal. It may be.

The above radio base facilities
First signal strength detection means for detecting the signal strength of the baseband signal extracted by the first baseband signal extraction means, and basebands extracted by the one or more second baseband signal extraction means, respectively. Second signal strength detection means for detecting the signal strength of each signal; first weight calculation means for obtaining a weight corresponding to the signal strength detected by the first signal strength detection means; and the second signal Second weight calculating means for obtaining a weight corresponding to each signal intensity detected by the intensity detecting means,
The synthesizing unit multiplies each baseband signal whose phase difference has been eliminated by the phase adjustment unit by the weight obtained for each baseband signal, and adds each baseband signal after multiplication. It may be a thing.

The invention relating to the communication method of the radio base facility for solving the above problems,
A base station having a base antenna that transmits and receives radio signals to and from the radio communication terminal, one or more relay receiving stations that have a relay antenna that receives radio signals from the radio communication terminal, and one or more base stations A wireless base facility having a cable connecting to the relay receiving station, transmitting and receiving wireless signals to and from wireless communication terminals, and modulating and demodulating baseband signals included in the wireless signals In a communication method of a wireless base facility that relays communication between the wireless communication terminal and another communication terminal through a baseband signal processing step,
A first baseband signal extraction step of extracting a baseband signal from a radio signal received by the base antenna;
A second baseband signal extracting step for extracting a baseband signal from a radio signal received by the relay antenna for each of the relay antennas of the one or more relay base stations;
Detecting a phase difference between the baseband signals in the baseband signal extracted in the first baseband signal extraction step and one or more baseband signals extracted in the second baseband signal extraction step A phase difference detection step to perform,
Based on the phase difference detected in the phase difference detection step, the phase of at least one of the baseband signals is shifted to eliminate the phase difference between the baseband signals. A phase adjustment process;
Synthesizing the baseband signals having no phase difference in the phase adjustment step, and sending the baseband signal obtained by the synthesis to the baseband signal processing step;
It is characterized by including.

  Hereinafter, various embodiments of a wireless communication system according to the present invention will be described in detail with reference to the drawings.

  First, a first embodiment of a wireless communication system will be described with reference to FIGS.

  As shown in FIG. 1, the wireless communication system according to the present embodiment includes a plurality of wireless base facilities 100 and wired communication terminals 4 connected to a LAN (Local Area Network) 3, and other wireless communication facilities via the wireless base facility 100. Wireless communication terminals 5a and 5b that communicate with the terminal are provided. The LAN 3 is connected to an IP (Internet Protocol) network 1 via a router 2. Each of the wireless communication terminals 5a and 5b is an information communication terminal having a wireless LAN communication function that operates in compliance with IEEE802.11. For example, a telephone terminal such as a wireless IP telephone, a personal computer, a PDA (Personal Digital Assistant), or the like A wireless LAN card connected to the information terminal and a wireless LAN board mounted on the information terminal.

  Each wireless base facility 100 has a wireless LAN communication function that operates in conformity with IEEE802.11 and a wired LAN communication function such as Ethernet (registered trademark) that operates in conformity with IEEE802.3. Wireless LAN communication is performed between 5a and 5b, and wired LAN communication is performed with other devices (such as the wired communication terminal 4 and the router 2) connected to the LAN 3.

  The router 2 is interposed between the LAN 3 and the IP network 1 and monitors an IP packet flowing on the LAN 3 and an IP packet obtained from the IP network 1, and IP header information (destination IP address information and port number) of the IP packet. The IP packet is routed to the IP network 1 side when it is determined that the IP packet flowing on the LAN 3 should be routed to the IP network 1 side. If it is determined that the IP packet obtained from the IP network 1 is to be routed to the LAN 3 side, it is sent to the LAN 3 side.

  The wired wireless terminal 4 is a personal computer having a wired LAN board, and is connected to the LAN 3 to transmit and receive IP packets and perform IP communication (LAN communication).

  With the above configuration, the wireless communication terminals 5a and 5b on the LAN side perform IP communication with other wireless communication terminals on the LAN side and the wired communication terminal 4 via the wireless base facility 100, and the router 2, the IP network 1, IP communication can be performed with various communication terminals connected to the IP network 1.

  The radio base facility 100 includes a base station 110 having a base antenna 111 for transmitting and receiving radio signals with the radio communication terminals 5a and 5b, and a relay antenna for receiving radio signals from the radio communication terminals 5a and 5b. And a relay receiving station 150 having 151. The base station 110 and the relay receiving station 150 are connected by a cable 9.

  In addition to the base antenna 111 described above, the base station 110 includes an RF (Radio Frequency) unit 112, a synthesis processing unit 120, a baseband unit 131, a MAC (Media Access Controller) layer processing unit 132, and a LAN interface unit. 133, a program memory unit 135, a work memory unit 136, and a communication control processing unit 137. The baseband unit 131, the MAC layer processing unit 132, and the LAN interface unit 133 are connected to the communication control processing unit 37 via the bus 139.

  The communication control processing unit 137 controls the baseband unit 131, the MAC layer processing unit 132, and the LAN interface unit 133 while using the work memory unit 136 according to the control program and setting data in the program memory unit 135.

  The LAN interface unit 133 refers to an IP header including an IP address of an IP packet received from the LAN 3, a TCP (Transmission Control Protocol) port number, or a UDP (User Datagram Protocol) port number, based on a preset rule. To route the IP packet.

  The MAC layer processing unit 132 performs conversion processing of the MAC layer of the IP packet between the data link layer of IEEE802.3 that is the Ethernet (registered trademark) standard and the data link layer of IEEE802.11 that is the wireless LAN standard. . The baseband unit 131 modulates an IP packet (digital) subjected to MAC processing for IEEE802.11 into an analog baseband signal, or demodulates an analog baseband signal to restore the original IP packet (digital). To do. The RF unit 112 defines the analog baseband signal received from the baseband unit 131 in accordance with, for example, the DS-SS (Direct Sequence Spread Spectrum) method or the FH-SS method (Frequency Hopping Spread Spectrum) in accordance with IEEE802.11. A radio signal is transmitted from the antenna 111 on the carrier radio frequency. On the contrary, the carrier radio frequency is removed from the radio signal received from the antenna 111 to restore the original analog baseband signal, which is sent to the synthesis processing unit 120.

  The relay receiving station 150 includes an RF unit 152 in addition to the relay antenna 151 described above.

  Next, detailed configurations of the RF units 112 and 152 and the synthesis processing unit 120 will be described with reference to FIG.

  The RF units 112 and 152 of the present embodiment employ a two-phase phase modulation method, and acquire and train the phase of the carrier wave from the preamble signal in the radio signal received by the antennas 111 and 151. Carrier multipliers 113 and 153 for generating analog baseband signals by multiplying the carrier waves from the carrier reproducers 113 and 153 and the radio signals received by the antennas 111 and 151, , Low pass filters (LPF) 115 and 155 for removing high frequency components from the signals from the multipliers 114 and 154.

  Here, the two-phase phase modulation method will be briefly described.

  The two-phase phase modulation method is a method using two types of carrier waves whose phases are 180 degrees different from each other.

  The baseband unit 131 converts, for example, a digital signal “1” / “0” into an analog signal + 1 / −1 at the time of transmission. In this case, the RF unit 112 multiplies the baseband signal and the wireless carrier wave by the multiplier 114 to generate a wireless signal. At this time, if the baseband signal is +1, the carrier wave as it is is multiplied by the baseband signal, and if the baseband signal is −1, the carrier wave whose phase is shifted by 180 ° is multiplied by the baseband signal.

  Further, at the time of reception, the carrier wave generation unit 113 acquires the phase of the carrier wave of the radio signal by training from the preamble in the radio signal, and gives the carrier wave of this phase to the multiplier 114. When the radio signal from the antenna 111 and the carrier wave from the carrier wave generation unit 113 are in phase, the multiplier 114 multiplies both to generate a +1 DC signal and a double harmonic. . In addition, when the radio signal from the antenna 111 and the carrier wave from the carrier wave generation unit 113 are in opposite phases, the multiplier 114 multiplies them to produce a −1 DC signal and a double harmonic. Generated. When the signal from the multiplier 114 passes through the LPF 115, the harmonic component is removed, and a baseband signal which is a DC signal of ± 1 is obtained.

  The combining processing unit 120 of the base station 100 includes a first detection unit 121a that detects the signal strength of the preamble signal in the baseband signal from the RF unit 112 and the end time of the preamble signal, and a base from the relay receiving station 150. The second detection unit 121b that detects the signal strength of the preamble signal in the band signal and the end time of the preamble signal, the signal strength detected by the first detection unit 121a, and the second detection unit 121b The gain for each baseband signal is set based on the signal strength, and the time difference between both baseband signals from the time detected by the first detector 121a and the time detected by the second detector 121b, that is, A delay amount / gain setting unit 122 that obtains a phase difference and sets a delay amount for any baseband signal, and a delay amount / gain setting The first delay unit 123a that delays the baseband signal from the RF unit 112 by the amount of delay instructed from 122, and the base from the relay receiving station 150 by the amount of delay instructed from the delay amount / gain setting unit 122 A second delay unit 123b that delays the band signal, a first amplifier 124a that amplifies the baseband signal from the first delay unit 123a by a gain instructed by the delay amount / gain setting unit 122, and a delay amount From the second amplifier 124b that amplifies the baseband signal from the second delay unit 123b by the gain instructed by the gain setting unit 122, the baseband signal from the first amplifier 124a, and the second amplifier 124b. And an adder 125 for adding the baseband signals.

  Note that the “first baseband signal extraction unit” and the “second baseband signal extraction unit” in the “claims” are the RF unit 112 and the relay reception unit of the base station 110 in the present embodiment, respectively. This corresponds to 150 RF units 152. The “phase difference detection means” includes the first and second detection units 121a and 121b in the present embodiment, and a delay amount / gain setting unit that obtains a phase difference from each time detected by the detection units 121a and 121b. 122. The “phase adjusting means” includes a delay amount / gain setting unit 122 and first and second delay units 123 a that delay each baseband signal according to the delay amount set by the delay amount / gain setting unit 122. 123b. The “first weight calculating unit” and the “second tail weight calculating unit” are configured to include a delay amount / gain setting unit 122 that calculates a gain (weight) for each baseband signal. The “synthesizing means” includes first and second amplifiers 124 a and 124 b and an adder 125.

  Next, a frame configuration of a signal on the wireless LAN will be described with reference to FIG.

  A frame on the wireless LAN includes a 12-byte fixed length preamble 11, a 4-byte fixed-length PLCP (Physical Layer Convergence Protocol) header 12, a variable-length MAC header 13, a variable-length frame body 14, and a 4-byte frame. It has a fixed length FCS (Frame Check Sequence) 15.

  Among the above frame constituent elements, the preamble 11 serves as a training signal for demodulating the received signal into the original baseband signal by the RF unit. For this reason, the preamble 11 is present at the head of the signal, and the number of bytes and their contents are fixed. Therefore, in the present embodiment, when such a characteristic of the preamble 11 is used and the signal strength of the baseband signal is detected, the signal strength of the preamble 11 portion is detected, and the phase shift between the baseband signals is detected. At the time of adjustment, the end time of the preamble for each baseband signal is detected.

  Next, the operation of the radio base facility 100 of this embodiment will be described.

  Here, suppose that the wireless communication terminal 5a in FIG. 1 transmits a wireless signal, and this wireless signal is received by the base antenna 111 of the base station 110 of the wireless base facility 100 and the relay antenna 151 of the relay receiving station 150. And

  The radio signal received by the base antenna 111 of the base station 110 is multiplied by the carrier from the carrier recovery unit 113 of the RF unit 112 by the multiplier 114 to obtain an analog baseband signal. Further, high frequency components are removed from the baseband signal by the LPF 115. The baseband signal that has passed through the LPF 115 is sent to the first detection unit 121a and the first delay unit 123a of the synthesis processing unit 120. The first detection unit 121a detects the signal strength (voltage amplitude of the signal component) of the preamble portion in the baseband signal and also detects the end time of the preamble portion. As described above with reference to FIG. 3, the method for detecting the end time of the preamble part includes a method for detecting the PLCP header part attached after the preamble, and the preamble has its number of bands and Since the contents are fixed, a method of detecting reception of the preamble and predicting the end time of the preamble part can be considered.

  On the other hand, as for the radio signal received by the relay antenna 151 of the relay receiving station 150, the baseband signal is extracted by the FR unit 152 of the relay receiving station as described above. This baseband signal is sent to the second detection unit 121b and the second delay unit 123b of the base station 110 via the cable 9 connecting the base station 110 and the relay receiving station 150. Similarly to the first detection unit 121a, the second detection unit 121b detects the signal strength of the preamble portion in the baseband signal and also detects the end time of the preamble portion. Here, the important point is that the radio signal received by the relay antenna 151 is not sent as it is to the base station 110 via the cable 9, but after extracting the baseband signal from the radio signal, the baseband signal is 9 is sent to the base station 110 via 9. This is because when the wireless signal is sent to the base station 110 via the cable 9 as it is, the frequency of the wireless signal is 2.4 GHz, which is an extremely high frequency. This is because the frequency of the baseband signal is several tens of megahertz that is much lower than the frequency of the radio signal, so that the amount of signal attenuation is small. That is, by sending a baseband signal having a low frequency through the cable 9 as in this embodiment, the signal attenuation can be suppressed and the S / N ratio can be increased.

  The delay amount / gain setting unit 122 is notified of the signal strength of each baseband signal detected by the first detection unit 121a and the second detection unit 121b and the end time of the preamble portion.

  In the delay amount / gain setting unit 122, the delay amount for each baseband signal is obtained from the preamble end time of each baseband signal detected by the first detection unit 121a and the second detection unit 121b. From the signal strength of each baseband signal detected by the first detection unit 121a and the second detection unit 121b, a gain for each baseband signal is obtained.

  When determining the delay amount for each baseband signal, the delay amount / gain setting unit 122 first uses the latest end time of the preamble end times of each baseband signal as a reference. For a baseband signal with an end time earlier than this, the difference between the end time of this baseband signal and the reference end time is used as the delay amount. The delay amount for each baseband signal obtained by the delay amount / gain setting unit 122 is notified to the corresponding delay units 123a and 123b, and the basebands transmitted from the RF units 112 and 152 by the delay units 123a and 123b. Delay the signal by the amount of delay. That is, the baseband signal received earlier than this is delayed so that the phase matches the latest received baseband signal.

  The gain for each baseband signal is a value proportional to the signal strength of each baseband signal, and when each baseband signal is added by an adder 125 described later, the strength of the baseband signal after the addition is predetermined. The value becomes a constant value. The gain for each baseband signal obtained by the delay amount / gain setting unit 122 is notified to the corresponding amplifiers 124a and 124b, and the baseband signals transmitted from the RF units 112 and 152 are transmitted by the amplifiers 124a and 124b. Amplified by the gain. The reason why the gain is set to a value proportional to the signal strength will be described later.

  The baseband signal amplified by the first amplifier 124 a and the baseband signal amplified by the second amplifier 124 b are added by the adder 125 and sent to the baseband unit 131.

  As described above, the baseband unit 131 demodulates the analog baseband signal and restores the original IP packet (digital).

  As described above, in this embodiment, the baseband signals among the radio signals received by the plurality of antennas 111 and 151 are combined to generate a new baseband signal. Can be increased.

  Here, the reason why the S / N ratio of a signal can be increased by combining a plurality of baseband signals will be described.

  In the signal handled as the baseband signal in the radio base facility 100, a noise component is mixed in addition to the baseband signal component generated by the endless communication terminal. Therefore, the noise intensity in the signal received by the base antenna 111 and the noise intensity in the signal received by the relay antenna 151 are N1 and N2, respectively, and noise components are removed from the signal received by the base antenna 111. When the intensity of the signal (original baseband signal) and the intensity of the signal obtained by removing the noise component from the signal received by the relay antenna 151 are S1 and S2, respectively, the baseband signals mixed with noise are added together. The signal strength S can be expressed as follows.

S = (S1 + N1) + (S2 + N2)
Here, for simplicity, if S1 = S2 = S0 and N1 = N2 = N0,
S = 2 ・ S0 ＋ √2 ・ N0
It becomes. That is, when S1 and S2 which are related to each other are added, the strength is doubled, and when N1 and N2 which are not related to each other is added, the strength is only √2.

  However, when signals received from three antennas are added, the intensity of the original baseband signal is tripled and the noise intensity is only √3 times.

  Therefore, the S / N ratio of the signal can be increased by combining a plurality of baseband signals.

  Next, the reason why the gain for each baseband signal is proportional to the intensity of the corresponding baseband signal will be described.

  When the two signal voltages (intensities) S1 and S2 having a correlation of 1 are multiplied by weights 1 and α, respectively, and then added together, Equation 1 is established.

Signal voltage after addition = S1 + α · S2 (Formula 1)
Therefore, the received signal power after addition is expressed by Equation 2.

Sum of received signal power = square of signal voltage after addition = (S1 + α · S2) ² (Formula 2)
On the other hand, since the noise voltages are uncorrelated with each other, the sum of the received power of the two noise voltages N1 and N2 is not the square of the voltage addition but the addition of the two noise powers, and Equation 3 is established.

Noise received power sum = N1 ² + (α · N2) ² (Equation 3)
Therefore, the ratio (S / N ratio) between the received signal and noise after addition can be expressed as shown in Equation 4.

S / N ratio = (S1 + α · S2) ² / (N1 ² + (α · N2) ² ) (Formula 4)
Here, in order to obtain α at which the S / N ratio is maximized, Equation 5 needs to be satisfied if a condition for partial differentiation with α to obtain 0 is obtained. δ represents partial differentiation.

δ (S / N ratio) / δα = −2α (S1 + α · S2) ² · N2 ² / (N1 ² + α ² · N2) ² +
+ 2S2 (S1 + α ・ S2) / (N1 ² + α ²・ N2 ² )
= 0 (Formula 5)
If this is arranged and expressed by a quadratic expression of α, Expression 6 is obtained.

S1 ・ S2 ・ N2 ²・ α ² ＋ (S1 ²・ N2 ² −S2 ²・ N1 ² ) −S1 ・ S2 ・ N1 ² = 0 (Formula 6)
When α is obtained from Equation 6, Equation 7 is established.

α = (S2 ² · N1 ² -S1 ² · N2 ² ± (S1 ² · N2 ² + S2 ² · N1 ² )) / 2S1 · S2 · N2 ² (Formula 7)
Since α is positive, Equation 8 is obtained when + is selected in the above ±.

α = S2 ・ N1 ² / S1 ・ N2 ² (Formula 8)
For simplicity, assuming that the noise level does not depend on the antenna and is constant and N1 = N2, α is the ratio of the signal voltage as shown in Equation 9, and the S / N ratio after synthesis. Is maximized.

α = S2 / S1 (Formula 9)
Therefore, in this embodiment, the voltage amplitude of the preamble portion of the baseband signal is approximated to the voltage amplitude of the signal component, and this is used as the gain of baseband signal amplification so that the S / N ratio is maximized. Yes. In addition, since the gain for each baseband signal is proportional to the intensity of the corresponding baseband signal, simply speaking, a signal considered to have a good S / N is preferentially synthesized. You can intuitively understand that the S / N ratio after synthesis is high without waiting for the explanation given above.

  As described above, in the present embodiment, the S / N ratio can be extremely increased for the following reasons.

  (1) Combining multiple baseband signals.

  (2) When combining a plurality of baseband signals, each baseband signal is amplified by an amount corresponding to the strength of the corresponding baseband signal.

  (3) When a signal is transmitted from the relay receiving station 150 to the base station 100 via the cable 9, a baseband signal having a frequency lower than that of the radio signal is transmitted to suppress the signal attenuation.

  In the present embodiment, since the antennas 111 and 151 are provided at different positions as the radio base facility, the communication range of the radio base facility can be expanded and the power consumption of the radio communication terminals 5a and 5b can be suppressed. .

  Furthermore, this embodiment is also effective as a countermeasure for the so-called hidden terminal problem. The hidden terminal problem is, for example, when there is a radio wave obstacle between two terminals, both terminals cannot recognize other terminals for their own terminals, and both terminals transmit signals to the AP almost simultaneously. The problem is that the signals from both terminals interfere and the signals from either terminal cannot be received normally.

  As shown in FIG. 4, for example, with the base station 110 as a reference, a base antenna 111 is provided on one side, a relay antenna 151 is provided on the other side, and a radio wave obstruction is provided between both antennas 111 and 151. When A is present, the wireless communication terminal 5a existing near the base antenna 111 cannot recognize the presence of the endless communication terminal 5c adjacent to the relay antenna 151. In such a case, the wireless communication terminal 5a may start to send a radio signal to the radio base facility 100 immediately after the endless communication terminal 5c starts sending a radio signal to the radio base facility 100. That is, a hidden terminal problem may occur. Therefore, by the relay antenna 151, the base antenna 111 transmits another radio communication terminal 5a from the other radio communication terminal 5a after a predetermined time from the start of reception of the radio signal from a certain radio communication terminal 5c. If the radio signal received by the base station antenna 111 is set to 0, or the RF signal received by the base station antenna 111 is discarded by the RF unit, it is hidden. The terminal problem can be solved. That is, the hidden terminal problem can be solved by canceling the gain of the wireless signal transmitted later to 0 or discarding it. The predetermined time is a time that is considered as a time lag between radio signals received by each antenna when radio signals from the same radio communication terminal are received by different antennas, and is larger than the maximum time. It's time.

  Next, a first modification of the first embodiment described above will be described with reference to FIG.

  The RF units 112 and 152 of the first embodiment employ a two-phase phase modulation method, but this modification employs a four-phase phase modulation method.

  When this four-phase phase modulation method is adopted, the RF unit 112b of the base station 110b receives the carrier wave generated by the carrier wave generating unit 113, the carrier wave reproduced by the carrier wave reproducing unit 113, and the antenna 111, as in the above-described embodiment. The first multiplier 114 that multiplies the radio signal and the first LPF 115 that removes high frequency components from the signal from the first multiplier 114, and the carrier wave reproduced by the carrier wave reproducing unit 113. A 90 ° phase shift unit 116 that advances the phase of the second phase by 90 °, a second multiplier 114b that multiplies the carrier signal and the radio signal received by the antenna 111 from the 90 ° phase shift unit 116, and the second multiplier 114b. And a second LPF 115b that removes high-frequency components from the above signal. Since the RF unit 152b of the relay receiving station 150b has the same configuration as the RF unit 112b of the base station 110b, description thereof is omitted here.

  Here, the four-phase phase modulation method will be briefly described.

  The four-phase phase modulation method is a method that uses four types of conveyance in which the phase of the carrier wave is shifted by 90 °. That is, similar to the two-phase phase modulation method, this is a method using two types of carrier waves whose phases are 180 ° different from each other and a carrier wave advanced by 90 ° with respect to each of the two types of carrier waves.

  In the baseband unit 131, for example, digital signals “11” / “10” / “01” / “00” are converted into analog signals (1 + 0i) / (0 + i) / (− 1 + 0i) / (0−i) during transmission. Convert to Here, the real number represents multiplication of the real number radio carrier wave as in the case of the two-phase phase modulation, where 1 is output as it is without changing the phase or amplitude, and −1 is the phase shifted by 180 ° and the amplitude is The signal is output as it is, and 0 means that the signal is attenuated to make the amplitude 0. Further, the imaginary number indicates that the “radio carrier wave for real number” is multiplied by a radio carrier wave having a phase advanced by 90 °. That is, “i” is output as it is without changing the phase (90 ° phase when viewed from the radio carrier for real numbers) and amplitude with respect to the radio carrier with the phase advanced by “radio carrier for real numbers” by 90 °. , -I shifts the phase by 180 [deg.] (The phase is 270 [deg.] When viewed from the radio carrier for real numbers) and outputs the amplitude as it is, and 0i attenuates the signal to make the amplitude zero.

  At the time of reception, the real number radio carrier from the carrier generation unit 113 and the radio signal received by the antenna 111 are multiplied by the first multiplier 114, and the real number radio carrier from the carrier generation unit 113 is multiplied by 90. The second multiplier 114b multiplies the radio carrier wave whose phase is advanced by 90 ° by the phase shift unit 116 and the radio signal received by the antenna 111. As a result of multiplication in any of the multipliers 114 and 114b, if the multiplied radio signal and the radio carrier are in phase or opposite phase, a DC component of 1 or -1 and a double harmonic are generated as in the case of two-phase modulation. The Further, when the phase of the multiplied radio signal and the radio carrier is 90 ° or 270 ° out of phase, a zero DC component and a double harmonic are generated. Then, the signals from the multipliers 114 and 114b pass through the corresponding LPFs 115 and 115b, so that the harmonic components are removed, and the base is a DC signal whose real part is ± 1 or 0 and whose imaginary part is ± i or 0i. A band signal is obtained.

  Next, a second modification of the first embodiment described above will be described with reference to FIG.

  In the first embodiment, one relay receiving station 150 is provided. However, in this modification, a plurality of relay receiving stations 150 and 150c are provided.

  In the present modification, the configuration of each relay receiving station 150, 150c is the same as the configuration of the relay receiving station 150 of the first embodiment. Also, the configuration of the combining processing unit 120c of the base station 110c is basically the same as that of the combining processing unit 120 of the first embodiment. However, in the case of this modification, a detector 121c, a delay unit 123c, and an amplifier 124c are added to the increased number of relay receiving stations 150c because the number of relay receiving stations has increased from that of the first embodiment.

  As described above, in this modification, the communication range of the radio base facility is further expanded and the power consumption of the radio communication terminals 5a and 5b can be further suppressed by increasing the number of relay receiving stations. In addition, although the facility of this modification is provided with the two relay receiving stations 150 and 150c, it cannot be overemphasized that many relay receiving stations may be provided.

  Next, a second embodiment of the wireless communication system will be described with reference to FIG.

  The first embodiment is an example in which the present invention is applied to a wireless LAN system, but this embodiment is an example in which the present invention is applied to a PHS (Personal Handyphone System) that employs a TDMA (Time Division Multiple Access) method. It is.

  The wireless communication system of this embodiment includes a plurality of wireless base facilities 100d and 100d that wirelessly communicate with the wireless communication terminal 5d by the TDMA method. The radio base facilities 100d and 100d are connected to each other by a PHS network 1d using an ISDN line.

  Similarly to the first embodiment, the radio base facility 100d receives a radio signal from the radio station 5d and a base station 110d having a base antenna 111 for transmitting and receiving radio signals to and from the radio communication terminal 5d. A relay receiving station 150d having a relay antenna 151d. The base station 110d and the relay receiving station 150d are connected by a cable 9. In a system that performs wireless communication using the TDMA scheme, the base station 110d of the present embodiment may be referred to as a master base station, and the relay reception station 150d of the present embodiment may be referred to as a slave base station.

  In addition to the above-described base antenna 111d, the base station 110d includes an RF unit 112d, a synthesis processing unit 120d, a baseband unit 131d, a MAC layer processing unit 132d, and a TDMA as a baseband signal from the baseband unit 131d. While decomposing the signal, the TDMA processing unit 132d converts the voice signal or the data signal into a TDMA signal as a baseband signal, and compresses and encodes the voice signal or the data signal and sends it to the TDMA processing unit 132d. An ADPCM (Adaptive Differential Pulse Code Modulation) 133d that decompresses and decodes a signal from the unit 132d, an ISDN interface unit 134d, a program memory unit 135d, a work memory unit 136d, and a communication control processing unit 137d are provided. The baseband unit 131d, the TDMA processing unit 132d, the ADPCM 133d, and the ISDN interface unit 134d are connected to the communication control processing unit 37d via the bus 39.

  The relay receiving station 150d includes an RF unit 152d in addition to the relay antenna 151d described above.

  Even in the radio base facility 100d according to the present embodiment that performs radio communication using the TDMA scheme, when the radio signal from the radio communication terminal 5d is received by the base antenna 111d and the relay antenna 151d, the base antenna 111d as in the first embodiment. The baseband signal is extracted from the radio signal received by the RF unit 112d of the base station 110d, and the baseband signal is extracted from the radio signal received by the relay antenna 151d by the RF unit 152d of the relay receiving station 150d. Each baseband signal is synthesized by the synthesis processing unit 120d in the same manner as in the first embodiment, and then sent to the baseband unit 131d. Note that the composition and operation of the composition processing unit 120d of this embodiment are basically the same as those of the composition processing unit 120 of the first embodiment.

  As described above, the same effect as that of the first embodiment can be obtained in the radio base facility 100d of the present embodiment that performs radio communication using the TDMA method. That is, also in this embodiment, the communication range of the radio base facility is expanded, the power consumption of the radio communication terminals 5a and 5b can be suppressed, and the S / N ratio can be extremely increased.

  In each of the above embodiments, after the baseband signal is extracted from the radio signal in the relay receiving stations 150, 150b, 150c, and 150d, the baseband signal is transmitted to the base stations 110, 110b, 110c, and 110d via the cable 9. Even if the baseband signal is extracted from the radio signal in the base station after the radio signal received by the relay antenna is transmitted to the base station via the cable 9, the baseband signal is synthesized. / N ratio improvement can be expected. However, from the viewpoint of suppressing signal attenuation during cable transmission, it is preferable to extract a baseband signal from a radio signal and then transmit this baseband signal to the base station via a cable as in the above embodiments. Needless to say.

  Further, in each of the embodiments described above, the intensity of the analog baseband signal is detected by the synthesis processing units 120, 120c, and 120d, but the RF units 112, 112b, 112d, 152, 152b, 152c, and 152d The signal strength of the radio signal may be detected, and the gain of each baseband signal may be obtained based on this signal strength. However, from the viewpoint of making the gain of each baseband signal proportional to the strength of the baseband signal, the signal strength of the baseband signal is detected as in this embodiment rather than detecting the signal strength of the radio signal. Is preferred.

  In the above embodiment, the analog baseband signal is synthesized. However, the analog baseband signal extracted by the RF unit is converted into a digital signal of about 10 bits, for example, and sent to the synthesis processing unit. Therefore, measurement of the end time of the preamble, measurement of signal strength, adjustment of delay time and amplification factor may be performed. As described above, when the digitized baseband signal is synthesized, the digitized baseband signal may be transmitted from the relay receiving station.

It is explanatory drawing which shows the structure of the radio | wireless communications system in 1st Embodiment which concerns on this invention. It is a functional block diagram of the RF unit and the synthesis processing unit in the first embodiment according to the present invention. It is explanatory drawing which shows the frame structure of the signal on wireless LAN. It is explanatory drawing for demonstrating the reason which can eliminate a hidden terminal problem in the radio | wireless communications system in 1st Embodiment which concerns on this invention. It is a functional block diagram of RF part as the 1st modification in a 1st embodiment concerning the present invention. It is a functional block diagram of RF part and a composition processing part as the 2nd modification in a 1st embodiment concerning the present invention. It is explanatory drawing which shows the structure of the radio | wireless communications system in 2nd Embodiment which concerns on this invention.

Explanation of symbols

1: IP network, 1d: PHS network, 3: LAN, 5a, 5b, 5d: wireless communication terminal, 9: cable, 100, 100c, 100d: no base facility, 110, 110b, 110c, 110d: base station, 111 , 111d: base antenna, 112, 112b, 112d, 152, 152b, 152c, 152d: RF unit, 120, 120c, 120d: synthesis processing unit, 121a, 121b, 121c: detection unit, 122: delay amount / gain setting unit 123a, 123b, 123c: delay unit, 124a, 124b, 124c: amplifier, 125: adder, 131, 131d: baseband unit, 150, 150b, 150c, 150d: relay receiving station, 151, 151c, 151d: relay antenna

Claims (7)

Baseband signal processing means for transmitting / receiving a radio signal to / from a radio communication terminal and modulating and demodulating a baseband signal included in the radio signal is provided between the radio communication terminal and another communication terminal. In a wireless base facility that relays communications,
A base station equipped with a base antenna for transmitting and receiving radio signals to and from a wireless communication terminal;
One or more relay receiving stations equipped with a relay antenna for receiving a radio signal from a radio communication terminal;
A cable connecting between the one or more relay receiving stations and the base station;
With
One of the base station and the relay receiving station is:
One or more second baseband signal extraction means for extracting a baseband signal from a radio signal received by the relay antenna for each of the relay antennas of the one or more relay base stations;
The base station
First baseband signal extraction means for extracting a baseband signal from a radio signal received by the base antenna;
The position between each baseband signal in the baseband signal extracted by the first baseband signal extraction means and the baseband signal respectively extracted by the one or more second baseband signal extraction units. Phase difference detection means for detecting a phase difference;
Based on the phase difference detected by the phase difference detecting means, the phase of at least one of the baseband signals is shifted to eliminate the phase difference between the baseband signals. Phase adjustment means;
Synthesizing the baseband signals whose phase differences are eliminated by the phase adjusting means, and combining the baseband signals obtained by the synthesis to the baseband signal processing means;
A radio base facility characterized by comprising: In the radio base facility according to claim 1,
The relay receiving station has the relay antenna and the second baseband signal extraction means,
The cable transmits the baseband signal extracted by the second baseband unit of the relay receiving station to the phase difference detecting unit and the combining unit of the base station, and transmits the baseband signal to the relay receiving unit. Connect with stations,
A radio base facility characterized by that. In the radio base facility according to any one of claims 1 and 2,
The phase difference detecting means grasps the end time of each preamble signal included in each baseband signal, and obtains the phase difference between the baseband signals from the end time of each preamble signal.
A radio base facility characterized by that. In the radio base facility according to any one of claims 1 to 3,
First signal strength detection means for detecting the signal strength of the baseband signal extracted by the first baseband signal extraction means;
Second signal strength detection means for detecting the signal strength of each of the baseband signals extracted by the one or more second baseband signal extraction means;
First weight calculating means for obtaining a weight according to the signal strength detected by the first signal strength detecting means;
Second weight calculating means for obtaining a weight corresponding to each signal intensity detected by the second signal intensity detecting means;
With
The synthesizing unit multiplies each baseband signal whose phase difference has been eliminated by the phase adjustment unit by the weight obtained for each baseband signal, and adds each baseband signal after multiplication.
A radio base facility characterized by that. A base station having a base antenna that transmits and receives radio signals to and from the radio communication terminal, one or more relay receiving stations that have a relay antenna that receives radio signals from the radio communication terminal, and one or more base stations A wireless base facility having a cable connecting to the relay receiving station, transmitting and receiving wireless signals to and from wireless communication terminals, and modulating and demodulating baseband signals included in the wireless signals In a communication method of a wireless base facility that relays communication between the wireless communication terminal and another communication terminal through a baseband signal processing step,
A first baseband signal extraction step of extracting a baseband signal from a radio signal received by the base antenna;
A second baseband signal extracting step for extracting a baseband signal from a radio signal received by the relay antenna for each of the relay antennas of the one or more relay base stations;
Detecting a phase difference between the baseband signals in the baseband signal extracted in the first baseband signal extraction step and one or more baseband signals extracted in the second baseband signal extraction step A phase difference detection step to perform,
Based on the phase difference detected in the phase difference detection step, the phase of at least one of the baseband signals is shifted to eliminate the phase difference between the baseband signals. A phase adjustment process;
Synthesizing the baseband signals having no phase difference in the phase adjustment step, and sending the baseband signal obtained by the synthesis to the baseband signal processing step;
A communication method for a radio base facility, comprising: The wireless base facility communication method according to claim 5,
In the phase difference detection step, the end time of each preamble signal included in each baseband signal is grasped, and the phase difference between the baseband signals is obtained from the end time of each preamble signal.
A communication method for a radio base facility. In the communication method of the radio base facility according to any one of claims 5 and 6,
A first signal strength detection step of detecting a signal strength of the baseband signal extracted in the first baseband signal step;
A second signal strength detection step of detecting signal strengths of one or more baseband signals extracted in the second baseband signal extraction step;
A first weight calculating step for obtaining a weight according to the signal strength detected in the first signal strength detecting step;
A second weight calculating step for obtaining a weight corresponding to each signal strength detected in the second signal strength detecting step;
Including
In the synthesis step, each baseband signal whose phase difference has been eliminated in the phase adjustment step is multiplied by the weight obtained for each baseband signal, and each baseband signal after multiplication is added.
A communication method for a radio base facility.

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