In addition to a structure of a conventional CDMA/TDD radio communication system, a base station includes a pilot signal generating circuit for generating a pilot signal that has a constant transmission power level and is known in mobile units and a pilot channel spreading circuit for transmitting the pilot signal to the mobile units through a transmission line. Each of the mobile units includes a pilot signal reception level measuring circuit for measuring reception power of the received pilot signal and a transmission power control circuit for controlling transmission power of a power amplification circuit based on the measured reception power of the received pilot signal.
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0. 46. A code division multiple access/time division duplex base station comprising:
means for generating a pilot signal which has a constant transmission power level and which has contents that are previously known in a mobile unit; and means for transmitting said pilot signal in a burst manner through at least one spreading channel.
0. 40. A code division multiple access/time division duplex mobile unit comprising:
means for determining a reception power of a pilot signal which is transmitted from a base station at a constant level and a reception power of a data signal which is transmitted from said base station; and means for controlling transmission power based on said determined reception power of said pilot signal and said determined reception power of said data signal.
0. 49. A code division multiple access/time division duplex radio communication method between a base station and a mobile unit comprising the steps of:
transmitting, in said base station, a data signal and a pilot signal through at least one spreading channel, said pilot signal having a constant transmission power level; and controlling, in said mobile unit, transmission power based on a reception power of said pilot signal and a reception power of said data signal transmitted from said base station.
0. 37. A code division multiple access/time division duplex radio communication system comprising a base station and, a mobile unit, wherein:
said base station comprises means for transmitting a data signal and a pilot signal, which has a constant transmission power level, to said mobile unit through at least one spreading channel; and said mobile unit comprises means for controlling transmission power based on a reception power of said pilot signal and a reception power of said data signal transmitted to said mobile unit.
0. 50. A code division multiple access/time division duplex radio communication method between a base station and a mobile unit, comprising the steps of:
transmitting, in said base station, a pilot signal through at least one spreading channel, said pilot signal having a constant transmission power level; and controlling, in said mobile unit, transmission power based on a reception power of said pilot signal and a quality of received data, said quality being determined by measuring an error rate comprising at least one of a bit error rate and a frame error rate.
0. 38. A code division multiple access/time division duplex radio communication system comprising a base station and a mobile unit, wherein:
said base station comprises means for transmitting a pilot signal, which has a constant transmission power level, to said mobile unit through at least one spreading channel; and said mobile unit comprises means for controlling transmission power based on (i) a reception power of said pilot signal and (ii) a quality of received data, said quality being determined by measuring an error rate comprising at least one of a bit error rate and a frame error rate.
0. 51. A code division multiple access/time division duplex radio communication method between a base station and a mobile unit, comprising the steps of:
transmitting, in said base station, a data signal and a pilot signal through at least one spreading channel, said pilot signal having a constant transmission power level; and controlling, in said mobile unit, transmission power based on a reception power of said pilot signal, a reception power of said data signal transmitted from said base station, and a quality of received data, said quality being determined by measuring an error rate comprising at least one of a bit error rate and a frame error rate.
0. 41. A code division multiple access/time division duplex mobile unit comprising:
means for determining a reception power of a pilot signal which is transmitted from a base station at a constant level, a reception power of a data signal which is transmitted from said base station, and a quality of received data transmitted from said base station, said quality being determined by measuring an error rate comprising at least one of a bit error rate and a frame error rate; and means for controlling transmission power based on said determined reception power of said pilot signal, said determined reception power of said data signal, and said determined quality of said received data.
0. 39. A code division multiple access/time division duplex radio communication system comprising a base station and a mobile unit, wherein:
said base station comprises means for transmitting a data signal and a pilot signal, which has a constant transmission power level, to said mobile unit through at least one spreading channel; and said mobile unit comprises means for controlling transmission power based on (i) a reception power of said pilot signal, (ii) a reception power of said data signal transmitted to said mobile unit and (iii) a quality of received data, said quality being determined by measuring an error rate comprising at least one of a bit error rate and a frame error rate.
1. A code-division multiple access/time division duplex radio communication system comprising a base station and one or more mobile units, wherein:
said base station comprises: pilot signal generating means for generating a pilot signal which has a constant transmission power level and which has contents that are previously known in said one or more mobile units; pilot signal spreading means for spreading said pilot signal in accordance with spreading codes to generate a spread pilot signal; and pilot signal transmitting means for transmitting said spread pilot signal in a bursting manner to said one or more mobile units; and each of said mobile units comprises: pilot signal despreading means for despreading said spread pilot signal to obtain said pilot signal; pilot signal level measuring means for measuring a reception power of said pilot signal obtained by said despreading means; and transmission power control means for controlling a transmission power based on the measured reception power of said pilot signal obtained by said despreading means.
0. 2. A radio communication system according to
0. 3. A radio communication system according to
0. 4. A radio communication system according to
phase detecting means for obtaining a phase of a carrier wave by the spread pilot signal transmitted from said base station; and despreading means for demodulating data utilizing an output of said phase detecting means.
0. 5. A radio communication system according to
a local oscillator; frequency offset detecting means for obtaining an offset of a carrier frequency in said local oscillator based on the spread pilot signal transmitted from said base station; and frequency adjusting means for adjusting a frequency of the local oscillator using an output of said frequency offset detecting means.
0. 6. A radio communication according to
synchronization acquisition means for acquiring synchronization of the spreading codes by the spread pilot signal transmitted from said base station; synchronization holding means for holding synchronization of the spreading codes by the spread pilot signal transmitted from said base station; phase detection means for obtaining a phase of a carrier wave by the spread pilot signal transmitted from said base station; despreading means for demodulating data utilizing an output of said phase detection means; frequency offset detection means for obtaining an offset of a carrier frequency in a local oscillator of said mobile unit based on the spread pilot signal transmitted from said base station; and frequency adjusting means for adjusting a frequency of the local oscillator of said mobile unit using an output of said frequency offset detection means.
0. 7. A radio communication system according to any one of
0. 8. A radio communication system according to any of
0. 9. A radio communication system according to
0. 10. A radio communication system according to
each of said mobile units further comprises data signal level measuring means for measuring a reception power of a data signal transmitted thereto; and said transmission power control means controls the transmission power based on outputs of said pilot signal level measuring means and said data signal level measuring means.
0. 11. A radio communication system according to
synchronization acquisition means for acquiring synchronization of the spreading codes by the spread pilot signal transmitted from said base station; synchronization holding means for holding synchronization of the spreading codes by the spread pilot signal transmitted from said base station; phase detection means for obtaining a phase of a carrier wave by the spread pilot signal transmitted from said base station; despreading means for demodulating data utilizing an output of said phase detection means; a local oscillator; frequency offset detection means for obtaining an offset of a carrier frequency in said local oscillator based on the spread pilot signal transmitted from said base station; and frequency adjusting means for adjusting a frequency of the local oscillator using an output of said frequency offset detection means.
0. 12. A radio communication system according to
0. 13. A radio communication system according to
each of said mobile units further comprises data quality measuring means for measuring a quality of received data; and said transmission power control means controls the transmission power based on outputs of said pilot signal level measuring means and said data quality measuring means.
0. 14. A radio communication system according to
synchronization acquisition means for acquiring synchronization of said spreading codes by the spread pilot signal transmitted from said base station; synchronization holding means for holding synchronization of said spreading codes by the spread pilot signal transmitted from said base station; phase detection means for obtaining a phase of a carrier wave by the spread pilot signal transmitted from said base station; despreading means for demodulating data utilizing an output of said phase detection means; a local oscillator; frequency offset detection means for obtaining an offset of a carrier frequency in said local oscillator based on the spread pilot signal transmitted from said base station; and frequency adjusting means for adjusting a frequency of the local oscillator using an output of said frequency offset detection means.
0. 15. A radio communication system according to
0. 16. A radio communication system according to
each of said mobile units further comprises data signal level measuring means for measuring a reception power of a data signal transmitted thereto and data quality measuring means for measuring a quality of received data; and said transmission power control means controls the transmission power based on outputs of said pilot signal level measuring means, said data signal level measuring means and said data quality measuring means.
0. 17. A radio communication system according to
synchronization acquisition means for acquiring synchronization of said spreading codes by the spread pilot signal transmitted from said base station; synchronization holding means for holding synchronization of said spreading codes by the spread pilot signal transmitted from said base station; phase detection means for obtaining a phase of a carrier wave by the spread pilot signal transmitted from said base station; despreading means for demodulating data utilizing an output of said phase detection means; a local oscillator; frequency offset detection means for obtaining an offset of a carrier frequency in said local oscillator based on the spread pilot signal transmitted from said base station; and frequency adjusting means for adjusting a frequency of the local oscillator using an output of said frequency offset detection means.
0. 18. A radio communication system according to
0. 19. A radio communication system according to
said base station further comprises single tone transmission means for transmitting a single tone having a constant transmission power level and a single frequency to said mobile units; each of said mobile units further comprises single tone level measuring means for measuring a reception power of said single tone; and said transmission power control means controls the transmission power based on outputs of said pilot signal level measuring means and said single tone level measuring means.
0. 20. A radio communication system according to
0. 21. A radio communication system according to
0. 22. A radio communication system according to
phase detection means for obtaining a phase of a carrier wave by the spread pilot signal transmitted from said base station; and despreading means for demodulating data utilizing an output of said phase detection means.
0. 23. A radio communication system according to
a local oscillator; frequency offset detection means for obtaining an offset of a carrier frequency in said local oscillator based on the spread pilot signal transmitted from said base station; and frequency adjusting means for adjusting a frequency of the local oscillator using an output of said frequency offset detection means.
0. 24. A radio communication system according to
synchronization acquisition means for acquiring synchronization of the spreading codes by the spread pilot signal transmitted from said base station; synchronization holding means for holding synchronization of the spreading codes by the spread pilot transmitted from said base station; phase detection means for obtaining a phase of a carrier wave by the spread pilot signal transmitted from said base station; despreading means for demodulating data utilizing an output of said phase detection means; a local oscillator; frequency offset detection means for obtaining an offset of a carrier frequency in said local oscillator based on the spread pilot signal transmitted from said base station; and frequency adjusting means for adjusting a frequency of the local oscillator using an output of said frequency offset detection means.
0. 25. A radio communication system according to any one of
0. 26. A radio communication system according to any of
0. 27. A radio communication system according to
0. 28. A radio communication system according to
said base station further comprises single tone transmission means for transmitting a single tone having a constant transmission power level and a single frequency to said mobile units; each of said mobile units further comprises single tone level measuring means for measuring a reception power of said single tone; and said transmission power control means controls the transmission power based on outputs of said pilot signal level measuring means, said data signal level measuring means and said single tone level measuring means.
0. 29. A radio communication system according to
synchronization acquisition means for acquiring synchronization of said spreading codes by the spread pilot signal transmitted from said base station; synchronization holding means for holding synchronization of said spreading codes by the spread pilot signal transmitted from said base station; phase detection means for obtaining a phase of a carrier wave by the pilot signal transmitted from said base station; despreading means for demodulating data utilizing an output of said phase detection means; a local oscillator; frequency offset detection means for obtaining an offset of a carrier frequency in said local oscillator based on the spread pilot signal transmitted from said base station; and frequency adjusting means for adjusting a frequency of the local oscillator using an output of said frequency offset detection means.
0. 30. A radio communication system according to
0. 31. A radio communication system according to
said base station further comprises single tone transmission means for transmitting a single tone having a constant transmission power level and a single frequency to said mobile units; each of said mobile units further comprises single tone level measuring means for measuring a reception power of said single tone; and said transmission power control means controls the transmission power based on outputs of said pilot signal level measuring means, said data quality measuring means and said single tone level measuring means.
0. 32. A radio communication system according to
synchronization acquisition means for acquiring synchronization of the spreading codes by the spread pilot signal transmitted from said base station; synchronization holding means for holding synchronization of said spreading codes by the spread pilot signal transmitted from said base station; phase detection means for obtaining a phase of a carrier wave by the spread pilot signal transmitted from said base station; despreading means for demodulating data utilizing an output of said phase detection means; a local oscillator; frequency offset detection means for obtaining an offset of a carrier frequency in said local oscillator based on the spread pilot signal transmitted from said base station; and frequency adjusting means for adjusting a frequency of the local oscillator using an output of said frequency offset detection means.
0. 33. A radio communication system according to
0. 34. A radio communication system according to
said base station further comprises single tone transmission means for transmitting a single tone having a constant transmission power level and a single frequency to said mobile units; each of said mobile units further comprises single tone level measuring means for measuring a reception power of said single tone; and said transmission power control means controls the transmission power based on outputs of said pilot signal level measuring means, said data single level measuring means, said data quality measuring means and said single tone level measuring means.
0. 35. A radio communication system according to
synchronization acquisition means for acquiring synchronization of said spreading codes by the spread pilot signal transmitted from said base station; synchronization holding means for holding synchronization of said spreading codes by the spread pilot signal transmitted from said base station; phase detection means for obtaining a phase of a carrier wave by the spread pilot signal transmitted from said base station; despreading means for demodulating data utilizing an output of said phase detection means; a local oscillator; frequency offset detection means for obtaining an offset of a carrier frequency in said local oscillator based on the spread pilot signal transmitted from said base station; and frequency adjusting means for adjusting a frequency of the local oscillator using an output of said frequency offset detection means.
0. 36. A CDMA/TDD radio communication system according to
0. 42. A mobile unit according to
0. 43. A mobile unit according to
0. 44. A mobile unit according to
phase detecting means for obtaining a phase of a carrier wave by said pilot signal transmitted from said base station; and despreading means for demodulating data utilizing an output of said phase detecting means.
0. 45. A mobile unit according to
frequency offset detecting means for obtaining an offset of a carrier frequency in a local oscillator of said mobile unit by said pilot signal transmitted from said base station; and frequency adjusting means for adjusting a frequency of said local oscillator of said mobile unit using an output of said frequency offset detecting means.
0. 47. A base station according to
0. 48. A base station according to
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1. Field of the Invention
The present invention relates to a CDMA/TDD radio communication system.
2. Description of the Related Art
Demand for land mobile communication devices such as car telephones and portable telephones is increasing remarkably, and a frequency effective utilization technique for securing larger subscriber capacity in a limited frequency band have become important in recent years. A code-division multiple access (CDMA) system attracts attention as one of multiple access systems for frequency effective utilization. In the CDMA system, when a signal level from a mobile unit near a base station is high in a reverse link from the mobile unit to the base station, such a near-far problem that a signal from another mobile unit become unreceivable is generated. Thus, it is required to control transmission power of the mobile unit so that the base station receives the signal from any mobile unit at the same level.
On the other hand, since propagation conditions both for transmission and reception are the same in a time division duplex (TDD) system in which transmission and reception are performed in the same frequency band, when the propagation condition on one side is known, the propagation condition on the other side can be known. With this, it is possible to measure the reception power at the mobile unit and to control the transmission power of the mobile unit based on the measured value.
Transmission power control techniques in a conventional CDMA/TDD radio communication system will be described hereinafter with reference to FIG. 1. In
Next, the operation of the conventional example described above will be explained. In the base station 1, the first transmitted data 11 are spread by means of the data channel spreading circuit 3. The spread signal is transmitted to the mobile unit 2 through the transmission line 5 after being added to the spread signals of other channels. The signal received by the mobile unit 2 is despread in the data channel despreading circuit 6 to obtain the second received data 13. In the data signal reception level measuring circuit 7, the reception level is measured with the second received data 13. In the transmission power control circuit 8, attenuation in the transmission line 5 is estimated based on the measured value of the reception level to determine the transmission power when the mobile unit 2 spreads the second transmitted data 14 by the spreading circuit 9 and transmits those data after amplification in the power amplification circuit 10. The data transmitted from the mobile unit 2 through the transmission line 5 are despread by the despreading circuit 4 in the base station 1 to obtain the first received data 12. When the power level of the first transmitted data 11 transmitted from the base station 1 is constant, it is possible to obtain the attenuation of the transmission line 5 accurately, so that it is possible to control the transmission power of the mobile unit 2 accurately.
In the conventional transmission power control techniques described above, however, it is impossible to obtain the attenuation of the transmission line 5 accurately and to control the transmission power accurately when the transmission power level of the first transmitted data 11 changes. Further, the attenuations of the transmission line 5 estimated in respective mobile units 2 are different due to the fact that the contents of the transmission data transmitted from the base station 1 to respective mobile units 2 are different from one another and separate spreading codes are used, respectively, and the transmission power of respective mobile units 2 is determined based on the estimated attenuation of the transmission line 5. Thus, the power arriving at the base station 1 from respective mobile units 2 becomes uneven.
The present invention is to solve the above-mentioned conventional problems and has for its object to provide a CDMA/TDD radio communication system capable of controlling transmission power with high precision.
In order to achieve the above-mentioned object, according to the present invention, there is provided, in the base station, a circuit for transmitting a pilot signal that has a constant power level and is known in respective mobile units, and highly precise transmission power control is made based on this pilot signal in respective mobile units.
According to the present invention, it becomes possible to control transmission power accurately and to solve such a problem that communication becomes impossible due to a near-far problem.
The First Embodiment
A first embodiment of the present invention will be described hereinafter with reference to FIG. 2. In
The operation of the CDMA/TDD radio communication system structured as described above will be described with reference to
Further, since the pilot signal is known in the mobile unit 200, it is possible to perform the synchronization acquisition and synchronization holding of the spread signal by the synchronization acquisition circuit 21 and the synchronization holding circuit 22, the phase detection of the carrier wave by the phase detecting circuit 23, the detection of frequency offset in the local oscillator by the frequency offset detecting circuit 34, and the adjustment for compensating for the shift of the carrier frequency attendant upon Doppler effect from the detected frequency offset by means of the local oscillator frequency adjusting circuit 25 by using the received pilot signal.
Furthermore, in the base station 100, it is possible that the pilot signal transmission level setting circuit 17 lowers a relative level of the interference from the other spreading channels in the received pilot signal by making the transmission power level of the pilot signal higher than any one of the signal levels of the other spreading channels. With this, it is possible to improve the precision of the transmission power control, the synchronization acquisition, the synchronization holding, the phase detection, the frequency offset detection and the local oscillator frequency adjustment which are described previously.
Further, an optional data sequence is assumed for a pilot signal generated by the pilot signal generating circuit 15 of the base station 100, but the pilot signal may be formed of a data sequence of all "1's" or "0's". In this case, the circuit configurations of the pilot signal generating circuit 15, the pilot signal reception level measuring circuit 19, the synchronization acquisition circuit 21, the synchronization holding circuit 22, the phase detecting circuit 23, the frequency offset detecting circuit 24 and the local oscillator frequency adjusting circuit 25 become simple, so that it is possible to curtail the circuit scale.
As described above, according to the embodiment described above, it is possible to estimate the attenuation of the transmission line 5 accurately because the transmission power of the pilot signal transmitted from the base station 100 toward respective mobile units 200 is constant and the pilot signal is known in the respective mobile units 200, and, even when Rayleigh fading is generated with the movement of the mobile unit 200 and the attenuation of the transmission line 5 changes suddenly, such matters can be followed by the pilot signal.
The Second Embodiment
A second embodiment of the present invention will be described hereinafter with reference to FIG. 4. In
The operation of the CDMA/TDD radio communication system thus structured will be described with reference to
On the other hand, a single tone 132 such as shown in
Further, since the pilot signal is known in the mobile unit 1200, it is possible to perform the synchronization acquisition and synchronization holding of the spread signal by the synchronization acquisition circuit 121 and the synchronization holding circuit 122, the detection of the phase of the carrier wave by the phase detecting circuit 123, the detection of frequency offset in the local oscillator by the frequency offset detecting circuit 124, and the adjustment for compensating for the shift of the carrier frequency attendant upon the Doppler effect from the frequency offset detected by the local oscillator frequency adjusting circuit 125 using the received pilot signal.
Furthermore, in the base station 1100, the pilot signal transmission level setting circuit 117 can lower the relative level of interference by another spreading channel in the received pilot signal by making the transmission power level of the pilot signal higher than the signal level of other spreading channels. With this, it is possible to improve precision of the transmission power control, the synchronization acquisition, the synchronization holding, the phase detection, the frequency offset detection and the local oscillator frequency adjustment described above.
Further, although an optional data sequence is assumed for the pilot signal generated by the pilot signal generating circuit 115 of the base station 1100, the pilot signal may also be formed of the data sequence of all "1's" or "0's". In this case, the circuit configurations of the pilot signal generating circuit 115, the pilot signal reception level measuring circuit 119, the synchronization acquisition circuit 121, the synchronization holding circuit 122, the phase detecting circuit 123, the frequency offset detecting circuit 124 and the local oscillator frequency adjusting circuit 125 become simple, so that it is possible to curtail the circuit scale.
As described above, according to the second embodiment, it is possible to estimate the attenuation of the transmission line 5 accurately because the transmission power level of the pilot signal transmitted from the base station 1100 toward respective mobile units 1200 is constant and the pilot signal is known in the mobile units 1200, and, even when Rayleigh fading is generated and the attenuation of the transmission line 5 is changed suddenly attendant upon movement of the mobile unit 1200, such matters can be followed by the pilot signal. Further, since the single tone having a constant transmission power level and a single frequency is always transmitted from the base station 1100 toward the respective mobile units 1200, respective mobile units 1200 are able to monitor the state of the transmission line 5 also in the time slot for performing transmission and to follow a sudden state change of the transmission line such as shadowing.
Watanabe, Masatoshi, Miya, Kazuyuki, Kato, Osamu, Nakano, Takayuki
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