JP3097808B2 - Communication device and method, and communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication apparatus, a communication method, and a communication system for performing frequency division multiple access (FDMA) transmission. More specifically, the present invention relates to a communication device that receives a carrier wave transmitted from another base station during communication or measures the level thereof, a communication system that performs communication between a plurality of base stations and a mobile station, and a communication method. .

[0002]

2. Description of the Related Art Conventional mobile communication services such as mobile telephones and car telephones have provided analog transmission services. On the other hand, the service of the digital communication system which has been recently implemented adopts TDMA (time division multiple access system) in which a plurality of users are temporally multiplexed and transmitted on one carrier frequency as a radio access system. I have. In this method, the timing at which one user receives a signal is within a slot in a certain time range within one frame.
The current mobile communication system has a cellular configuration, and a mobile station needs a function of determining a cell to which the mobile station belongs.
For this purpose, it is necessary to measure reception levels of signals from a plurality of base stations. Also, when a user of another cell uses the same frequency as the frequency currently used for communication, the interference level from this user increases. When the interference level exceeds a required SIR (signal to interference ratio), the channel is switched to a channel of another frequency. Therefore, the mobile station
During communication, it is necessary to detect the level of a carrier (carrier) for monitoring the peripheral zone specified by the base station.

In TDMA transmission, for example, as shown in FIG. 1, a reception level can be detected within this time by using an empty slot (level detection slot) other than a reception slot and a transmission slot. During this empty slot, the frequency of the frequency synthesizer is adjusted to the designated carrier for level monitoring, level detection is performed within this time, and a plurality of detected sample values are averaged to obtain a received signal level. As described above, in the TDMA, the reception signal level of the carrier signal different from the communication carrier in the reception slot can be detected by one receiver by using the empty slot. However, SCPC / FDMA (Single Channel) in which one carrier channel is used by one user.
Per Carrier / Frequency Div
In the multi-access (i.e., multiple-access) mode, when a communication state is entered, two-sequence receiving units are required as shown in FIG. 2 to detect different carrier signal levels in order to perform communication in the signal stripping mode. That is, the received signal from the input terminal 11 is divided into two by the hybrid 12 and supplied to the band pass filters (BPF) 13 and 14. The outputs of the BPFs 13 and 14 are respectively
At 16, the signals are frequency-mixed with the local signals of the frequency synthesizers 17 and 18, and frequency-converted outputs are taken out by band-pass filters (BPF) 19 and 21, respectively. BPF1
9 and 21 are output from an automatic gain amplifier (AGC) 2 respectively.
The signals are amplified by 2 and 23 and detected by I and Q channel baseband signals by quadrature detection circuits 24 and 25, respectively. The I and Q baseband signals from the quadrature detection circuit 24 are converted into digital signals by A / D converters 26 and 27, respectively, supplied to a demodulation circuit 28, and demodulated. Similarly, the I and Q baseband signals from the quadrature detection circuit 25 are converted into digital signals by A / D converters 29 and 31, respectively.
The signal is supplied to the demodulation circuit 32 and demodulated. The outputs of the band-pass filters 19 and 21 are branched and supplied to level detection circuits 33 and 34, respectively, where the reception levels are detected.

[0004]

In the TDMA transmission system, the level of another channel can be measured during idle time when a signal of a reception channel is not transmitted. On the other hand, a receiver using the conventional FDMA transmission method cannot measure a received signal level of a channel having a frequency other than the carrier frequency during a call. In order to monitor the level of the peripheral zone during a call for channel switching, two series of receiving units are required, and the circuit scale of the receiving circuit of the mobile station has almost doubled. In this respect, the FDMA system is disadvantageous compared to the TDMA system.

[0005] In a conventional wireless communication apparatus, the frequency of a carrier is switched by a frequency synthesizer in the RF frequency band.
For this reason, information contained in carriers of different frequencies cannot be transmitted or received in duplicate. In order to perform transmission and reception using a plurality of carriers, a conventional FDMA wireless device needs to include two transmission units and two reception units.

Mobile stations are strictly required to have light weight and low power consumption. In these respects, having two transmission units and two reception units is a great disadvantage. Therefore, an object of the present invention is to provide a communication device and a communication method capable of detecting a level of a carrier signal of a channel different from a channel during a call without having two transmission units and two reception units. Still another object of the present invention is to provide a communication apparatus and a communication method capable of simultaneously transmitting and receiving signals on a plurality of channels without providing two transmission units and two reception units.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a down-converting circuit for converting a frequency of a received input signal of an FDMA into an intermediate frequency, and converting the intermediate frequency into an I / O signal. A quadrature detection circuit for converting the baseband signal into a digital signal, an A / D converter for converting the baseband signal into a digital signal, and converting the digital signal into two carrier frequencies included in the received input signal. And a first and a second frequency conversion circuit for converting the signals into two signals having a center frequency of zero.

According to a second aspect of the present invention, there is provided a down conversion circuit for converting a frequency of a received input signal of an FDMA into an intermediate frequency, a quadrature detection circuit for converting the intermediate frequency into baseband signals of I and Q channels, A / D conversion means for converting a baseband signal into a digital signal, a memory for storing the digital signal, and a signal read from the memory, which is converted into a center frequency corresponding to each of two carrier frequencies included in the received signal. A frequency conversion circuit for converting two zero signals by time division is provided.

A third aspect of the present invention is the communication apparatus according to the first or second aspect, wherein the demodulation circuit demodulates one of the two signals and detects the level of the other of the two signals. And a level detecting means.

A fourth aspect of the present invention is the communication device according to the first or second aspect, wherein the first demodulation circuit demodulates one of the two signals and the other of the two signals. And a second demodulation circuit.

According to a fifth aspect of the present invention, there is provided a modulation circuit for digitally modulating information to be transmitted at each of a plurality of carrier frequencies to generate a plurality of modulation signals, and an addition circuit for digitally adding outputs of the plurality of modulation circuits. A circuit, a D / A converter for D / A converting the output added by the adding circuit, a converting circuit for converting the output of the D / A converter to a high frequency, and transmitting the output converted by the converting circuit. Transmission means.

According to a sixth aspect of the present invention, in the communication device according to the fifth aspect, the modulation circuit digitally modulates the information to each of the plurality of carrier frequencies in a time-division manner. I do.

[0013] According to a seventh aspect of the present invention, there is provided a communication system comprising a mobile station, a plurality of base stations communicating with the mobile station by the FDMA method, and a control station connected to the plurality of base stations. Wherein the mobile station comprises
The communication device according to the, transmitting information to the plurality of base stations simultaneously, the plurality of base stations has means for receiving information transmitted from the mobile station, the control station And a means for combining information received by the plurality of base stations.

[0014] The invention according to claim 8 is a communication system comprising a mobile station, a plurality of base stations communicating with the mobile station by the FDMA method, and a control station connected to the plurality of base stations. Wherein the control station comprises:
The communication device according to the, to transmit information to be transmitted to the mobile station to the plurality of base stations, each of the plurality of base stations has means for transmitting the information to the mobile station,
The mobile station has a communication device according to claim 4, means for simultaneously receiving the information from the plurality of base stations, and means for combining information received from the plurality of base stations. I do.

According to a ninth aspect of the present invention, a received input signal of the FDMA system is frequency-converted into an intermediate frequency, the intermediate frequency is converted into baseband signals of I and Q channels, and the baseband signal is converted into a digital signal. A / D conversion,
The digital signal is included in the received input signal 2
It is characterized in that it is converted into two signals having a center frequency of zero corresponding to each of the two carrier frequencies.

According to a tenth aspect of the present invention, the received input signal of the FDMA system is frequency-converted into an intermediate frequency, and the intermediate frequency is converted into baseband signals of I and Q channels.
A / D converting the baseband signal into a digital signal, storing the digital signal in a memory, and converting the signal read from the memory into a center frequency zero corresponding to each of two carrier frequencies included in the received signal. It is characterized in that it is converted into two signals by time division.

According to an eleventh aspect of the present invention, in the communication method according to the ninth or tenth aspect, one of the two signals is further demodulated and the level of the other is detected.

According to a twelfth aspect of the present invention, in the communication method according to the ninth or tenth aspect, the two signals are further demodulated.

According to a thirteenth aspect of the present invention, a plurality of modulated signals are generated by digitally modulating information to be transmitted at each of a plurality of carrier frequencies, the plurality of modulated signals are digitally added, and the added output is output. D / A conversion is performed, the D / A converted signal is converted to a high frequency, and the converted signal is transmitted.

According to a fourteenth aspect of the present invention, in the communication method according to the thirteenth aspect, the modulation signal is generated by digitally modulating the information in a time division manner to each of the plurality of carrier frequencies. It is characterized by performing.

According to a fifteenth aspect of the present invention, there is provided a communication system comprising a mobile station, a plurality of base stations communicating with the mobile station by the FDMA method, and a control station connected to the plurality of base stations. The mobile station, according to the communication method according to claim 13 or 14,
Transmitting information to the plurality of base stations simultaneously, the plurality of base stations receiving information transmitted from the mobile station, and the control station receiving information received by the plurality of base stations; A demodulation and synthesis are performed by the communication method according to the twelfth aspect.

According to a sixteenth aspect of the present invention, there is provided a communication system comprising a mobile station, a plurality of base stations communicating with the mobile station by the FDMA method, and a control station connected to the plurality of base stations. The communication method according to claim 13, wherein the control station is a communication method according to claim 13 or 14,
The information to be transmitted to the mobile station is transmitted to the plurality of base stations, each of the plurality of base stations transmits the information to the mobile station, and the mobile station transmits the information from the plurality of base stations. Are simultaneously received, demodulated and combined by the communication method according to claim 12.

[0023]

According to the present invention, a received input signal of the FDMA system is frequency-converted into an intermediate frequency, further converted into baseband signals of I and Q channels, and converted into a digital signal by A / D conversion.
It is converted into two signals having a center frequency of zero corresponding to each of the two carrier frequencies included in the received input signal. The digitally converted signal may be temporarily stored in a memory, and the signal read from the memory may be time-divisionally converted into two signals having a center frequency of zero corresponding to each of two carrier frequencies included in the received signal. This allows
One of the two signals can be demodulated to detect the level of the other, or the two signals can be demodulated together.

The information to be transmitted is digitally modulated at each of a plurality of carrier frequencies to generate a plurality of modulated signals, which are digitally added, D / A converted, and D / A converted.
The A-converted signal is converted to a high frequency and transmitted. The modulation signal may be generated by digitally modulating information into each of a plurality of carrier frequencies in a time division manner.

Further, according to the present invention, in an uplink channel, a mobile station simultaneously transmits to a plurality of base stations, a plurality of base stations receive information transmitted from the mobile station, and a plurality of base stations receive information. Are synthesized by the control station. In the downlink channel, the control station transmits information to be transmitted to the mobile station to a plurality of base stations, each of the plurality of base stations transmits information to the mobile station, and the mobile station simultaneously transmits information from the plurality of base stations. Receive and combine the received information.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 3 shows an embodiment of the present invention. Parts corresponding to those in FIG. 2 are denoted by the same reference numerals. The received input signal is supplied to the BPF 13 without being divided into two, and is frequency-mixed by the mixer 15 with the fixed frequency local signal from the fixed oscillator 41. Thus, the input high-frequency signal is frequency-converted into an intermediate-frequency signal while being multiplexed on the frequency axis. That is, the mixer 15 and the band-pass filter 19 constitute a down-conversion circuit. The intermediate frequency signal is AGC
At 22, the signal is linearly amplified to a required signal level, and further, at a quadrature detection circuit 24, quadrature detection is performed on I and Q channels, for example, using a frequency at one end of the entire band as a local signal. The detection outputs are offset from each other by a frequency corresponding to each carrier signal of the original plurality of input high-frequency signals.

The detection outputs of the I and Q channels are A
The signal is converted into a digital signal by the / D converters 26 and 27, and the frequency is converted by the frequency conversion circuits 43 and 44 to be included in the input high-frequency signal. Signals corresponding to the two target channels are output as signals having a center frequency of zero, and supplied to the demodulation circuit 28 and the level detection circuit 45, respectively. In the frequency conversion circuit 43, a channel for communication is converted into I and Q baseband signals having a center frequency of zero. When the level of the designated carrier in the peripheral zone is detected, the designated carrier is converted into I,
The signals are converted into Q baseband signals, and the sum I ² + Q ² of the squares of the amplitudes of these I and Q baseband signals is calculated by the level detection circuit 45.

The frequency conversion circuit 43 is configured, for example, as shown in FIG. That is, the A / D converters 26 and 27
Signal from the _{cos [φ n ± 2πΔf i t} ], sin [φ
_n ± _{2πΔf i} t] Each of the local signal generator 45,4
6 from the digital local signal cos (± 2πΔf _i
t), are respectively multiplied by the multiplier 47, 48 and sin (± 2πΔf _i t). The multiplied outputs are supplied to a frequency correction circuit 53 through low-pass filters 51 and 52, respectively. As shown in FIG. 3, the local oscillator 41 is a fixed oscillator, and the local signal generators 45 and 46 also change the local signal frequency for channel selection. Quasi-synchronous quadrature detection is performed without following the frequency. Therefore, the quadrature detection output contains a frequency error and a fixed phase error. These errors are corrected by the frequency correction circuit 53 by digital processing.

The frequency conversion by digital processing may be constituted by a frequency conversion filter described in Japanese Patent Application No. 4-199018. For example, as shown in FIG. 4B, a low-pass signal is previously removed by a low-pass filter for the frequency-offset component after the quadrature detection (FIG. 4B).
a). Then, by sampling at this center frequency corresponding to each offset frequency, a folded signal component having a center frequency of zero is generated (FIG. 4B), and finally this component is extracted by a low-pass filter (FIG. 4 (B)). B) c). In this configuration, the same filter can be configured by changing the sampling frequency according to the frequency of each channel.

(Embodiment 2) FIG. 5 shows a hardware block configuration of a communication apparatus in this embodiment. Parts corresponding to those in FIG. 3 are denoted by the same reference numerals. In the present invention, the outputs of the A / D converters 26 and 27 are temporarily stored in the memory circuit 55,
The data is read out at twice the writing speed and supplied to the frequency conversion circuit 56. The frequency conversion circuit 56 performs the same processing as the frequency conversion circuit 43 in FIG. 3 in synchronization with the even-numbered read clock of the memory circuit 55, and synchronizes with the odd-numbered read clock in the memory circuit 55.
Perform the same processing as. The output of the frequency conversion circuit 56 is supplied to the demodulation circuit 28 and the level detection circuit 45. The demodulation circuit 28 performs demodulation processing in synchronization with the even-numbered read clock of the memory circuit 55, and the level detection circuit 45 performs level detection processing in synchronization with the odd-numbered read clock.

(Embodiment 3) FIG. 6 shows an embodiment in which the present invention is applied to a mobile station receiver that performs CDMA transmission having a plurality of carrier signals. Parts corresponding to those in FIG. 3 are denoted by the same reference numerals. The received spread signals having different carrier frequencies are first converted into baseband signals having a center frequency of zero by the frequency conversion circuits 43 and 44. Thereafter, the signals are inversely converted into narrowband signals by the correlation detectors 57 and 58 using spreading codes corresponding to the received signals. In FIG. 6, a two-series baseband processing circuit is described. However, as described in the second embodiment, if the data is temporarily stored in a memory and time-division processing is performed using a high-speed clock, the number of circuits after the frequency conversion circuit is reduced. Baseband processing for 1 channel
It can also be performed by a series baseband circuit.

(Embodiment 4) FIG. 7 shows a system configuration of a network system using the communication device of the present invention. The mobile station 140 moves from the zone of the base station 120 to another base station 1
When moving to zone 30, handover (channel switching) is performed. Since a carrier is switched at the time of handover, a momentary interruption has conventionally occurred. In order to perform a handover without an instantaneous interruption, a plurality of base stations 120, 1
30 to the same mobile station 140 with respective carriers f1,
A method of transmitting the same information by f2 and combining the same information transmitted on each carrier by the mobile station 140 is considered. In the uplink channel, base stations 120 and 130 receive radio waves transmitted from the same mobile station 140 and control station 110 combines the information.

According to the communication apparatus and the communication method described in the first to third embodiments, it is possible to perform frequency conversion on carrier waves of a plurality of frequencies without providing two receiving circuits. In the first to third embodiments, one of the plurality of carrier waves is demodulated and the other is detected in level, but in the present embodiment, a demodulation circuit is provided in place of the level detection circuit 45 shown in FIGS. Thus, the control station 110 and the mobile station 140 can demodulate a plurality of carriers without providing two receiving circuits. Further, as described in the third embodiment, even when the baseband processing for several channels is performed by a single-series baseband circuit in the receiving circuit of FIG. 6, demodulation is performed instead of the level detection circuit 45 of FIG. By providing the circuit, demodulation for a plurality of carrier waves can be performed similarly.

As a method of synthesizing signals transmitted from a plurality of base stations, maximum ratio combining in which weighting and addition are performed according to the levels of received signals can be used. Thereby, the greatest diversity effect can be obtained, and the communication quality can be improved.

In the uplink channel, mobile station 140
Transmits the same information to the base stations 120 and 130 using a plurality of carriers. In the transmission circuit, a modulation circuit is provided in place of the demodulation circuit used in the reception circuit, and a D / A converter is provided in place of the A / D converters 26 and 27. The digital signals output from the plurality of frequency conversion circuits 43 and 44 are added and input to a D / A converter. As described in the second embodiment, a single frequency conversion circuit 56 may be used to perform frequency conversion on a plurality of carriers in a time-division manner, and may add the two frequency-converted digital signals. In order to synchronize the two carrier signals output in a time-division manner, a memory circuit 55 may be provided as in the second embodiment, and the signals stored in the memory may be added.

Signals of different carrier waves transmitted from mobile station 140 are received by a plurality of base stations 120 and 130, and diversity combining is performed by control station 110. As a result, communication quality in the uplink channel can be improved.

[0038]

As described above, according to the present invention, only a small number of circuits are added to the conventional FDMA transmission radio, and two receiving systems are not provided, and a channel of a carrier frequency other than during communication is not provided. Level can be detected.

Further, according to the communication apparatus of the present invention, transmission and reception can be simultaneously performed on a plurality of channels without providing two transmission circuits and two reception circuits.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a transmission frame in TDMA transmission.

FIG. 2 is a hardware block diagram of a receiving circuit of a conventional FDMA mobile station.

FIG. 3 is a hardware block diagram of a receiving circuit of the communication device of the present invention in the first embodiment.

FIG. 4A is a circuit diagram showing an example of frequency conversion circuits 43 and 44, and FIG. 4B is an explanatory diagram showing a frequency conversion method.

FIG. 5 is a hardware block diagram of a receiving circuit of the communication device according to the second embodiment of the present invention.

FIG. 6 is a hardware block diagram of a receiving circuit of the communication device according to the third embodiment of the present invention.

FIG. 7 is an explanatory diagram illustrating handover between carrier waves having different frequencies.

[Explanation of symbols]

11 Input Terminal for Received Signal 12 HYB (Hybrid) 13, 14, 19, 21 BPF (Band Pass Filter) 15, 16 Multiplier 17, 18 Frequency Synthesizer 22, 23 AGC (Automatic Gain Amplifier) 24, 25 Quadrature Detection Circuit 26 , 27, 29, 31 A / D converter 28, 32 Demodulation circuit 33, 34 Level detection circuit

────────────────────────────────────────────────── (5) References JP-A-4-271624 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 7/24-7/26 102 H04Q 7 / 00-7/38

Claims (16)

(57) [Claims] A down-conversion circuit for converting the frequency of a received input signal of an FDMA into an intermediate frequency; a quadrature detection circuit for converting the intermediate frequency into baseband signals of I and Q channels; A / to convert
D conversion means, and the digital signal included in the received input signal
A communication device comprising: first and second frequency conversion circuits for converting two signals having a center frequency of zero corresponding to each of two carrier frequencies. 2. A down-conversion circuit for frequency-converting a received input signal of FDMA to an intermediate frequency; a quadrature detection circuit for converting the intermediate frequency to I- and Q-channel baseband signals; A / to convert
D conversion means, a memory for storing the digital signal, and a signal read from the memory, which is time-divisionally converted into two signals having a center frequency of zero corresponding to each of two carrier frequencies included in the received signal. And a frequency conversion circuit. 3. The communication device according to claim 1, further comprising: a demodulation circuit that demodulates one of the two signals; and a level detection unit that detects a level of the other of the two signals. A communication device, comprising: 4. The communication device according to claim 1, wherein the first demodulation circuit demodulates one of the two signals, and the second demodulation circuit demodulates the other of the two signals. A communication device, further comprising: 5. A modulation circuit for digitally modulating information to be transmitted at each of a plurality of carrier frequencies to generate a plurality of modulation signals; an addition circuit for digitally adding outputs of the plurality of modulation circuits; D for D / A conversion of the added output
A communication device, comprising: an A / A converter; a conversion circuit that converts an output of the D / A converter to a high frequency; and a transmission unit that transmits an output converted by the conversion circuit. 6. The communication device according to claim 5, wherein the modulation circuit digitally modulates the information in a time-division manner to each of the plurality of carrier frequencies. 7. A mobile station, and FDMA for the mobile station.
A communication system comprising: a plurality of base stations performing communication in a system; and a control station connected to the plurality of base stations, wherein the mobile station includes the communication device according to claim 5 or 6, The communication device according to claim 4, wherein the plurality of base stations have means for simultaneously transmitting information to the plurality of base stations, and the plurality of base stations have means for receiving information transmitted from the mobile station. And means for combining information received by the plurality of base stations. 8. A mobile station, and FDMA for the mobile station.
A communication system comprising: a plurality of base stations performing communication in a system; and a control station connected to the plurality of base stations, wherein the control station includes the communication device according to claim 5 or 6, The mobile station transmits information to be transmitted to the plurality of base stations, and each of the plurality of base stations includes a unit configured to transmit the information to the mobile station. A communication system comprising: the communication device according to claim 1; means for simultaneously receiving the information from the plurality of base stations; and means for combining information received from the plurality of base stations. 9. A frequency-converted reception signal of an FDMA system to an intermediate frequency, the intermediate frequency is converted to baseband signals of I and Q channels, and the baseband signal is A / D-converted to a digital signal. A digital signal is included in the received input signal.
A communication method comprising converting two signals having a center frequency of zero corresponding to each of two carrier frequencies. 10. A frequency-converted reception input signal of the FDMA system to an intermediate frequency, the intermediate frequency is converted to baseband signals of I and Q channels, and the baseband signal is A / D converted to a digital signal. A digital signal is stored in a memory, and a signal read from the memory is time-divisionally converted into two signals having a center frequency of zero corresponding to each of two carrier frequencies included in the received signal. Communication method. 11. The communication method according to claim 9, further comprising demodulating one of the two signals and detecting the level of the other. 12. The communication method according to claim 9 or 10, further comprising demodulating the two signals. 13. Digitally modulating information to be transmitted at each of a plurality of carrier frequencies to generate a plurality of modulation signals, digitally adding the plurality of modulation signals, and D / A-converting the added output; A communication method comprising: converting an A / A converted signal to a high frequency; and transmitting the converted signal. 14. The communication method according to claim 13, wherein the generation of the modulation signal is performed by digitally modulating the information in a time division manner to each of the plurality of carrier frequencies. Method. 15. A mobile station and an FDM for the mobile station.
A communication method applied to a communication system including a plurality of base stations that perform communication in the A system and a control station connected to the plurality of base stations, wherein the mobile station is the mobile station according to claim 13 or 14. According to the communication method, the information is transmitted to the plurality of base stations simultaneously, the plurality of base stations receive information transmitted from the mobile station, and the control station receives the plurality of base stations. A communication method, comprising: receiving the received information, demodulating the information by the communication method according to claim 12, and combining the demodulated information. 16. A mobile station and an FDM for the mobile station.
A communication method applied to a communication system including a plurality of base stations that perform communication according to the A method and a control station connected to the plurality of base stations, wherein the control station is the communication device according to claim 13 or 14. Transmitting the information to be transmitted to the mobile station to the plurality of base stations, each of the plurality of base stations transmits the information to the mobile station, A communication method comprising: simultaneously receiving the information from a base station; and demodulating and combining the information by the communication method according to claim 12.