U.S. patent application number 12/198913 was filed with the patent office on 2009-01-01 for transmission power control method and apparatus for mobile communication system.
Invention is credited to Nobukazu Doi, Riaz Esmailzadeh, Takashi Yano.
Application Number | 20090005106 12/198913 |
Document ID | / |
Family ID | 18074792 |
Filed Date | 2009-01-01 |
United States Patent
Application |
20090005106 |
Kind Code |
A1 |
Esmailzadeh; Riaz ; et
al. |
January 1, 2009 |
TRANSMISSION POWER CONTROL METHOD AND APPARATUS FOR MOBILE
COMMUNICATION SYSTEM
Abstract
A method and apparatus for controlling the power of a signal
transmitted between a base station and a mobile terminal which
constitute a mobile communication system. At least one of the base
station and the mobile terminal has functions to compare a
predetermined reference value and a necessary transmission power
obtained as a result of transmission power control in order to
compensate for a signal intensity fluctuation occurring on a link
between the base station and the mobile terminal, temporarily
stopping the transmission if the necessary transmission power is
larger than a predetermined permissible value, and transmit the
signal if the necessary transmission power is equal to or smaller
than the predetermined permissible value.
Inventors: |
Esmailzadeh; Riaz;
(Yokosuka, JP) ; Yano; Takashi; (Tokorozwa-shi,
JP) ; Doi; Nobukazu; (Hachioji-shi, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET, SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
18074792 |
Appl. No.: |
12/198913 |
Filed: |
August 27, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
11544655 |
Oct 10, 2006 |
7421283 |
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12198913 |
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|
10376310 |
Mar 3, 2003 |
7120457 |
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11544655 |
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|
09729272 |
Dec 5, 2000 |
6546260 |
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10376310 |
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08975672 |
Nov 28, 1997 |
6175744 |
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|
09729272 |
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Current U.S.
Class: |
455/522 |
Current CPC
Class: |
H04W 52/362 20130101;
H04W 52/24 20130101 |
Class at
Publication: |
455/522 |
International
Class: |
H04B 7/00 20060101
H04B007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 27, 1996 |
JP |
08-316232 |
Claims
1. A communication system with signal fade compensation comprising
at least one mobile terminal which communicates with a base station
by radio, comprising: an antenna for receiving signals from said
base station and transmitting signals to said base station; and a
processing means for judging whether or not to transmit data to
said base station based on a condition of a channel between said
mobile terminal and said base station, wherein, if said processing
means judges not to transmit said data, said transmission of the
data is temporarily stopped.
2. A communication system according to claim 1, wherein, if said
processing means judges not to transmit said data, said
transmission of the data is stopped for at least a slot period.
3. A communication system according to claim 2, wherein said
condition of a channel includes a signal intensity of a signal
received via the channel between said mobile terminal and said base
station.
4. A communication system according to claim 1, wherein said
condition of a channel includes a signal intensity of a signal
received via the channel between said mobile terminal and said base
station.
Description
[0001] The present application is the first of two concurrently
filed continuation applications of U.S. application Ser. No.
11/544,655, fild Oct. 10, 2006, which, in turn, is a continuation
of U.S. application Ser. No. 10/376,310, filed Mar. 3, 2003 (now
U.S. Pat. No. 7,120,457), which, in turn, is a continuation of U.S.
application Ser. No. 09/729,272, filed Dec. 5, 2000 (now U.S. Pat.
No. 6,546,260), and which, in turn, is a continuation of U.S.
application Ser. No. 08/975,672, filed Nov. 28, 1997 (now U.S. Pat.
No. 6,175,744); and the entire disclosures of which are hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention generally relates to a transmission
power control method and apparatus for mobile communication system
which controls the transmission power between the base station and
mobile terminal of a mobile communication system, and particularly
to the effective technology suitable for use in the transmission
power control method and apparatus for mobile communication system
which controls the transmission power in accordance with the change
of signals received between the base station and mobile terminal of
the mobile communication system of TDD-SS (Time Division
Duplex-Spread Spectrum) and FDD (Frequency Division Duplex)
system.
[0003] There is a conventional mobile communication system for
transmitting and receiving data by radio between base stations and
mobile terminals. This mobile communication system employs
different carrier frequencies for the up link on which signals are
transmitted from a mobile terminal to the base station and for the
down link on which signals are transmitted from the base station to
the mobile terminal by the FDD.
[0004] The signal transmitted and received between the base station
and mobile terminal of this mobile communication system is
attenuated along the distance between the base station and mobile
terminal, and by obstacles present therebetween, and fluctuated by
the fading due to the interference between the direct wave and the
reflected wave, or the like.
[0005] In order to compensate the fluctuation due to the fading in
the signal transmitted and received between the base station and
the mobile terminal is dependent upon the carrier frequency, the
transmission power in the FDD mobile communication system is
controlled by closed-loop control. For example, the IS-95
specifications apply up link transmission power control of the FDD
system which controls the transmission power of the terminal. The
technique on the scheme of the FDD down link power control is
proposed in U.S. Pat. No. 5,559,790 entitled "Spread Spectrum
Communication System and Transmission Power Control Method
Therefor" invented by Yano, et al., assigned to the present
assignee and issued Sep. 24, 1996. In addition, another technique
on the information of the up link power control is proposed in a
copending U.S. patent application Ser. No. 08/690,819 entitled
"CDMA Mobile Communication System and Communication Method" by
those inventors, assigned to the present assignee and filed on Aug.
1, 1996. The disclosure of the above U.S. application, and the
continuation application, Ser. No. 08/678,656 of the above U.S.
patent, filed on Jul. 11, 1996, are incorporated in the disclosure
of this application by reference.
[0006] Whether the mobile communication system is of CDMA-FDD or
CDMA-TDD, the following problem is caused when transmission power
control is performed through the transmission path between the
mobile terminal and the base station. In other words, when the
attenuation of data in the transmission path between the base
station and a particular mobile terminal is temporarily increased,
the base station transmits signals with an extremely higher power
in accordance with the transmission power control, and thus
interferes with other mobile terminals. In addition, when the
transmission power from a mobile terminal, on the contrary, is
excessively risen, it also obstructs or interferes with other base
stations.
[0007] Moreover, in the FDD mobile communication system, since the
closed loop control is still performed in which the transmission
power on the up link is controlled by the mobile terminal in
accordance with the up link power control information obtained at
the base station, while that on the down link is controlled by the
base station in accordance with the down link power control
information attained at the mobile terminal, there is the problem
that it takes a long time to control the transmission power.
SUMMARY OF THE INVENTION
[0008] Accordingly, it is an object of the invention to provide a
transmission power control method and apparatus for the mobile
communication system, by which the transmission power can be
prevented from being wasted and from obstructing other
stations.
[0009] It is another object of the invention to provide a
transmission power control method and apparatus for the mobile
communication system, which can fast compensate for the signal
fluctuation occurring on the up link that is provided from the
mobile terminal to the base station.
[0010] It is still another object of the invention to provide a
transmission power control method and apparatus for the mobile
communication system, which can fast compensate for the signal
fluctuation caused on the down link that is provided from the base
station to the mobile terminal.
[0011] According to the concept of the present invention, there is
provided a transmission power control method and apparatus for
controlling the power of a signal transmitted between a base
station and a mobile terminal, which includes: means for detecting
a signal fluctuation occurring on a down link or up link; means for
generating power control information in order to compensate for the
signal fluctuation occurring on the up link or down link on the
basis of the detected signal fluctuation; means for compensating
for the power of the signal transmitted on the up link or down link
on the basis of the information; and means for comparing the
generated power control information and a predetermined permissible
compensated value, temporarily stopping the transmission if the
power control information is larger than a predetermined
permissible compensation value as a result of the comparison, and
compensating for the transmission power if the power control
information is equal to or smaller than the predetermined
permissible compensation value, all the above means being provided
in the base station or mobile terminal. The above idea is useful
particularly when a signal of data packets is transmitted between
the base station and the mobile terminal. In this idea, unlike the
speech service, when the transmission power of the packet is
requested to be more than a predetermined value, and when it will
be too intense to interfere with other base stations or mobile
terminals in a mobile communication system, the transmission is
temporarily stopped, and a certain time later it resumes, in which
case it has been confirmed by the inventors that the communications
are not disturbed at all.
[0012] In order to achieve the above objects, the present invention
proposes the following typical aspects.
[0013] (1) A transmission power control method for controlling the
power of a signal transmitted between the base station and the
mobile terminal which constitute a mobile communication system,
comprises the steps of detecting a signal fluctuation occurring on
a down link that is provided to transmit a signal from the base
station to the mobile terminal, generating power control
information for compensating for a signal fluctuation on an up link
on the basis of the detected signal fluctuation, compensating for
the transmission power of the signal transmitted on the up link
from the mobile terminal to the base station on the basis of the
generated power control information, and transmitting the power
control information used for compensating for the transmission
power, and transmitting the signal of which the power has been
compensated, from the mobile terminal to the base station.
[0014] In the transmission power control method for the mobile
communication system, the mobile terminal that communicates with
the base station receives a signal transmitted on a down link from
the base station to the mobile terminal, for example, a pilot
signal transmitted on a pilot channel.
[0015] Then, the mobile terminal detects a signal fluctuation, such
as the attenuation, occurring on the down link due to the fading
and distance or an obstacle along the channel.
[0016] The mobile terminal assumes that the detected signal
fluctuation in the down link similarly occurs in the up link on
which a signal is transmitted from the mobile terminal to the base
station, and generates power control information to compensate for
the signal fluctuation occurring on the up link.
[0017] Then, the mobile terminal modifies the transmission power of
the signal to be transmitted on the up link from the mobile
terminal to the base station on the basis of the generated power
control information.
[0018] In addition, the mobile terminal also transmits the power
control information used for compensating for the transmission
power from the mobile terminal to the base station.
[0019] Thus, according to the transmission power control method for
the mobile communication system, since the mobile terminal
compensates for the signal fluctuation occurring on the up link for
the transmission from the mobile terminal to the base station by
detecting the signal fluctuation occurring on the down link for the
transmission from the base station to the mobile terminal, it is
possible to fast compensate for the signal fluctuation occurring on
the up link for the transmission from the mobile terminal to the
base station.
[0020] (2) A transmission power control method for the mobile
communication system, according to the aspect (1), wherein the base
terminal that communicates with the mobile terminal has functions
to receive the power control information transmitted from the
mobile terminal to the base station, detect a signal fluctuation
occurring on the up link for the transmission from the mobile
terminal to the base station, generate power control information to
compensate for the signal fluctuation occurring on the down link on
the basis of the detected signal fluctuation and the power control
information sent from the mobile terminal, and compensate for the
transmission power of the signal to be transmitted on the down link
from the base station to the mobile terminal on the basis of the
generated power control information.
[0021] The base station receives a signal sent on the up link from
the mobile terminal to the base station, for example, a signal of
reservation packets and data packets transmitted on a reservation
channel and transmission channel.
[0022] The base station detects the signal fluctuation occurring on
the up link for the transmission from the mobile terminal to the
base station, and generate power control information to compensate
for the signal fluctuation occurring on the down link on the basis
of the detected signal fluctuation and the power control
information sent from the mobile terminal.
[0023] Then, the base station modifies the transmission power of
the signal transmitted on the down link from the base station to
the mobile terminal on the basis of the generated power control
information.
[0024] Thus, according to the transmission power control method for
the mobile communication system, since the base station detects the
signal fluctuation occurring on the up link for the transmission
from the mobile terminal to the base station, and compensates for
the signal fluctuation occurring on the down link for the
transmission from the base station to the mobile terminal, it is
possible to fast compensate for the signal fluctuation occurring on
the down link for the transmission from the base station to the
mobile terminal.
[0025] (3) A transmission power control method for the mobile
communication system, according to the aspect (1) or (2), further
comprising the steps of comparing the generated power control
information and a maximum permissible modification or compensation
value, temporarily stopping the transmission if the generated power
control information is larger than the maximum permissible
compensation value, and compensating for the transmission power if
the generated power control information is equal to or smaller than
the maximum permissible compensation value.
[0026] More specifically, the base station or the mobile terminal
compares the generated associated power control information and the
maximum permissible compensation value of the base station or the
mobile terminal, temporarily stops the transmission if the
generated power control information is larger than the maximum
permissible compensation value until the next time slot comes.
[0027] If the generated power control information is equal to or
smaller than the maximum permissible compensation value, the
transmission power is compensated on the basis of the generated
power control information.
[0028] Thus, according to the transmission power control method for
the mobile communication system, since the transmission is
temporarily stopped if the generated control information is larger
than the maximum permissible compensation value and resumes when
the power control information becomes equal to or smaller than the
maximum permissible compensation value, the transmission power can
be prevented from being wasted.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a block diagram of a mobile communication system
according to one embodiment of the invention.
[0030] FIG. 2 is a block diagram of a base station 100 of the
mobile communication system according to this embodiment.
[0031] FIG. 3 is a block diagram of a mobile terminal 110 of the
mobile communication system according to this embodiment.
[0032] FIG. 4 is a timing chart briefly showing the data
transmission in the mobile communication system according to this
embodiment.
[0033] FIG. 5 is a flowchart showing procedures of the transmission
power control by the base station 100 of the mobile communication
system according to this embodiment.
[0034] FIG. 6 is a flowchart showing procedures of the transmission
power control by the mobile terminal 110 of the mobile
communication system according to this embodiment.
[0035] FIG. 7 is a block diagram of a mobile communication system
according to another embodiment of the invention.
[0036] FIG. 8 is a flowchart showing procedures of the transmission
power control by a base station 700 of a mobile communication
system according to the above other embodiment.
[0037] FIG. 9 is a flowchart showing procedures of the transmission
power control by a mobile terminal 710 of a mobile communication
system according to the above other embodiment.
[0038] Other objects, features and advantages of the invention will
become apparent when reading the description of the following
embodiments taken in conjunction with the accompanying
drawings.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] One embodiment of the transmission power control method and
apparatus according to the invention will be described, which is
used in the mobile communication system and which controls the
transmission power when communication is made between a base
station and a mobile terminal by means of the TDD-SS system.
[0040] FIG. 1 is a block diagram showing an outline of the
construction of the mobile communication system according to this
embodiment. Referring to FIG. 1, the mobile communication system of
this embodiment has the base station 100 which includes a down link
transmission power setter 101, a down link power control
information comparator 102, a down link power control information
generator 103 and a power control information receiver 104, the
mobile terminal 110 which includes an up link transmission power
setter 111, an up link power control information comparator 112, an
up link power control information generator 113 and a power control
information transmitter 114, communication channels 120 which
include an up link 121, a down link 122 and guard times 123, and a
carrier frequency 124.
[0041] The base station 100 and the mobile terminal 110 are
connected by the up link 121 on which a signal is transmitted from
the mobile terminal 110 to the base station 100 and the down link
122 on which a signal is transmitted from the base station 100 to
the mobile terminal 110. The communication channels 120 on the
carrier frequency 124 are assigned in a time-sharing manner to the
up link 121 and down link 122 between which the guard times 123 are
provided to prevent the interference.
[0042] The down link transmission power setter 101 of the base
station 100 responds to the result from the down link power control
information comparator 102 to fix a transmission power that is to
be transmitted on the down link 122 from the base station 100.
[0043] The down link power control information comparator 102 of
the base station 100 compares whether or not the control
information of down link 122 which is generated by the down link
power control information generator 103 is larger than the maximum
permissible compensation value of the base station 100.
[0044] The down link power control information generator 103
generates power control information for the down link 122 by using
the signal information on the up link 121 and the power control
information of the down link sent from the mobile terminal 110.
[0045] Since the signal received by the base station 100 on the up
link 121 has been compensated by the mobile terminal 110, the down
link power control information generator 103 of the base station
100 computes the value of the signal on the up link 121 before
compensation by use of the power control information transmitted
from the mobile terminal 110, and generates the power control
information for the down link 122.
[0046] The power control information receiver 104 of the base
station 100 receives the power control information transmitted from
the mobile terminal 110.
[0047] The up link transmission power setter 111 of the mobile
terminal 110 determines the transmission power which the mobile
terminal 110 is to transmit on the up link 121 in accordance with
the result from the up link power control information comparator
112.
[0048] The up link power control information comparator 112 of the
mobile terminal 110 compares whether or not the control information
of the up link 121 which is generated by the up link power control
information generator 113 is larger than the maximum permissible
compensation value of the mobile terminal 110.
[0049] The up link power control information generator 113 of the
mobile terminal 110 generates the power control information of the
up link 121 by use of the signal information on the down link
122.
[0050] The power control information transmitter 114 of the mobile
terminal 110 transmits the power control information of the up link
121 set by the up link transmission power setter 111 to the base
station 100.
[0051] FIG. 2 is a block diagram showing an outline of the
construction of the base station 100 of the mobile communication
system according to this embodiment. The base station 100 further
includes a CPU 201, a memory 202, a display unit 203, an
input/output unit 204, the digital signal processor (DSP) 205, a
mobile communication exchange interface unit 206, an antenna 210, a
pilot channel modulator 211, an answering channel modulator 212, a
transmission channel modulator 213, reservation channel matched
filters 214-215, transmission channel matched filters 216-217, a
para-noise code generator (PN code generator) 218, adders 220 and
221, multipliers 230 and 231, and a TDD switch 240.
[0052] In the base station 100, a bus connects the CPU 201 that
controls the operation of the whole base station 100, the memory
202 that loads a control program for controlling the operation of
the whole base station 100, the display unit 203 that displays the
operating condition of the base station 100, the input/output unit
204 that instructs the base station 100 to operate for the
input/output process, the DSP 205 that controls the process for
communicating with the mobile terminal 110, and the mobile
communication exchange interface unit 206.
[0053] The base station 100 communicates with the mobile terminal
110 by means of TDD-SS. Between the base station 100 and the mobile
terminal 110, there are provided a pilot channel, a reservation
channel, an answering (responding) channel and a transmission
channel on the same carrier frequency 124 (see FIG. 4).
[0054] The DSP 205 of the base station 100 includes the down link
transmission power setter 101, the down link power control
information comparator 102, the down link power control information
generator 103 and the power control information receiver 104 as
described above.
[0055] In addition, the DSP 205 is connected to the pilot channel
modulator 211, the answering channel modulator 212, the
transmission channel modulator 213, the reservation channel matched
filters 214-215, the transmission channel matched filters 216-217,
the PN code generator 218, and the TDD switch 240.
[0056] The pilot channel modulator 211 of the base station 100
modulates the pilot channel for the transmission of the pilot
signal, and supplies the modulated pilot signal through the adder
220, multiplier 230 and TDD switch 240 to the antenna 210, from
which it is transmitted to the mobile terminal 110.
[0057] The answering channel modulator 212 modulates the answering
channel through which an answer or response to the reservation
packet received from the mobile terminal 110 is transmitted. The
modulated answer to the reservation packet is supplied through the
adders 220 and 221, multiplier 230 and TDD switch 240 to the
antenna 210, from which it is transmitted to the mobile terminal
110.
[0058] The transmission channel modulator 213 modulates a plurality
of transmission channels on which data packets are transmitted. The
modulated data packet is supplied through the adders 220 and 221,
multiplier 230 and TDD switch 240 to the antenna 210, from which it
is transmitted to the mobile terminal 110.
[0059] The reservation channel matched filters 214-215 receive the
reservation packets transmitted from the mobile terminal 110, and
the received reservation packets are processed by the DSP 205.
[0060] The transmission channel matched filters 216-217 receive the
data packets sent from the mobile terminal 110, and the received
data packets are processed by the DSP 205.
[0061] The PN code generator 218 generates the PN code that is used
on each of the pilot channel, reservation channel, answering
channel and transmission channel.
[0062] The TDD switch 240 responds to a TDD timing signal produced
from the DSP 205 to timely switch the up link 121 and down link
122, or to timely change over from transmission to reception or
vice versa. When the base station 100 receives the power control
information from the mobile terminal 110, it supplies the received
power control information through the reservation channel matched
filters 214-215 and transmission channel matched filters 216-217 to
the power control information receiver 104 of the DSP 205.
[0063] The power control signal fixed by the down link transmission
power setter 101 of the DSP 205 is supplied to the pilot channel
modulator 211, answering channel modulator 212 and transmission
channel modulator 213.
[0064] FIG. 3 shows in block diagram an outline of the construction
of the mobile terminal 110 of the mobile communication system
according to this embodiment. Referring to FIG. 3, the mobile
terminal 110 further has a CPU 301, a memory 302, a display unit
303, an input/output unit 304, the DSP 305, an antenna 310, a
reservation channel modulator 311, a transmission channel modulator
312, a pilot channel demodulator 313, an answering channel
demodulator 314, a transmission channel demodulator 315, a PN code
generator 316, a fading-compensating power controller 317, an adder
320, multipliers 330 and 331, and a TDD switch 340.
[0065] In the mobile terminal 110, as illustrated in FIG. 3, the
CPU 301 that controls the operation of the whole terminal is
connected to the memory 302 that loads a control program, the
display unit 303 that displays the condition of the operation, the
input/output unit 304 that makes the input/output process on the
data to transmit or have received, and the DSP 305 that controls
the process for communicating with the base station 100.
[0066] The DSP 305 of the mobile terminal 110 includes the up link
transmission power setter 111, the up link power control
information comparator 112, the up link power control information
generator 113 and the power control information transmitter 114 as
described above.
[0067] The DSP 305 is connected via a bus to the reservation
channel modulator 311, transmission channel modulator 312, pilot
channel demodulator 313, answering channel demodulator 314,
transmission channel demodulator 315, PN code generator 316,
fading-compensating power controller 317, and TDD switch 340.
[0068] The reservation channel modulator 311 modulates the
reservation channel through which a notice of reservation for a
transmission channel is sent to the base station 100, informing the
base station of having data packets to be transmitted through the
transmission channel. The transmission channel modulator 312
modulates a plurality of transmission channels on which data
packets are transmitted.
[0069] The reservation packets and data packets, which have been
modulated by the reservation channel modulator 311 and transmission
channel modulator 312, respectively, are supplied through the adder
320, multiplier 330, fading-compensating power controller 317 and
TDD switch 340 to the antenna 310, from which those packets are
transmitted from the antenna to the base station 100.
[0070] The pilot channel demodulator 313 demodulates the pilot
channel on which a pilot signal is transmitted. The signal
intensity and TDD timing of the received and demodulated pilot
signal are supplied to the DSP 305.
[0071] The answering channel demodulator 314 demodulates the
answering channel on which answering packets are transmitted. The
transmission channel demodulator 315 demodulates a plurality of
transmission channels on which data packets are transmitted.
[0072] The PN code generator 316 generates a plurality of PN codes
to be used on each of the pilot channel, reservation channel,
answering channel and transmission channel.
[0073] The fading-compensating power controller 317 controls the
transmission power on the basis of the fading information produced
from the DSP 305.
[0074] The TDD switch 340 responds to a TDD timing signal produced
from the DSP 305 to timely switch the up link 121 and down link
122, or to timely change over from transmission to reception or
vice versa.
[0075] FIG. 4 is a timing chart schematically showing the data
transmission in the mobile communication system according to this
embodiment. Referring to FIG. 4, reference numerals 401-403
represent the reservation packets, 411-413 the answering packets,
421-423 the data packets, and 431 and 432 the pilot data.
[0076] As illustrated in FIG. 4, the data that are transmitted and
received in the mobile communication system contain the reservation
packets 401-403, answering packets 411-413, data packets 421-423,
and pilot data 431 and 432.
[0077] That is, when the reservation packets 401-403 are
transmitted from the mobile terminal 110 to the base station 100,
the base station 100 sends the answering packets 411-413 to the
mobile terminal 110, and then the mobile terminal 110 transmits the
data packets 421-423 to the base station 100.
[0078] The reservation packets 401-403, answering packets 411-413,
data packets 421-423 and pilot data 431 and 432 transmitted and
received in the mobile communication system according to this
embodiment are spread in their spectra in the form of the
reservation code, answering code, up/down transmission code and
pilot code, respectively, and transmitted on both up link 121 and
down link 122 of the same carrier frequency 124.
[0079] The channels using the carrier frequency 124 are separated
as up link 121 and down link 122 in a time sharing manner. Before
the mobile terminal 110 transmits data packets 421-423 to the base
station, the reservation packets 401-403 are first transmitted on
the up link 121 from the mobile terminal 110 to the base station
100.
[0080] The base station 100 that received the reservation packets
401-403 determines a transmission channel to be assigned to the
mobile terminal 110, and then transmits the answering packets
411-413 on the down link 122 to the mobile terminal 110.
[0081] The mobile terminal 110 that received the answering packets
411-413 transmits the data packets 421-423 to the base station
100.
[0082] The pilot signal to be transmitted from the base station 100
to the mobile terminal 110 is transmitted only on the down link 122
as the pilot data 431 and 432 are assigned thereto.
[0083] FIG. 5 shows the procedure of the process for the
transmission power control in the base station 100 of the mobile
communication system according to this embodiment.
[0084] As illustrated in FIG. 5, the base station 100 makes
transmission power control so that the transmission power on the
down link 122 is determined on the basis of the power control
information sent from the mobile terminal 110 and the signal
intensity on the up link 121, and transmitted to the mobile
terminal 110.
[0085] In the base station 100, at step 501, the signal on the
reservation channel or transmission channel is received from the
reservation channel matched filters 214-215 or transmission channel
matched filters 216-217.
[0086] At step 502, the down link power control information
generator 103 of the DSP 205 of the base station 100 extracts the
intensity from the input signal on the reservation channel or
transmission channel at each bit.
[0087] At step 503, the down link power control information
generator 103 of the base station 100 estimates the fading of the
up link 121 by using the power control information of the mobile
terminal 110 received by the power control information receiver 104
and the previously received signal intensity at each bit on the
reservation channel or transmission channel.
[0088] In other words, since the signal on the up link 121 is
already compensated for by the mobile terminal 110, the received
signal intensity on the reservation channel or transmission channel
of the up link 121 is restored to the previous signal intensity
before the compensation by the mobile terminal 110 by use of the
information on the fading within the power control information
transmitted from the mobile terminal 110, and then the fading on
the up link 121 is estimated.
[0089] At step 504, the down link power control information
generator 103 of the base station 100 computes the transmission
power necessary for compensating for the fading that has been
estimated at step 503.
[0090] At step 505, the down link power control information
comparator 102 of the base station 100 compares the necessary power
computed by the down link power control information generator 103
and the maximum permissible compensation value of the transmission
power which can be compensated for by the base station 100.
[0091] At step 505, if the transmission power necessary for
compensating for the fading estimated at step 503 is larger than
the maximum permissible compensation value of the base station 100
as a result of the comparison between the necessary power computed
by the down link power control information generator 103 and the
maximum permissible compensation value of the base station 100, the
program goes to step 506.
[0092] At step 506, the base station 100 stops until the following
slot, and then the program goes back to the step 502.
[0093] At step 505, if the transmission power necessary for
compensating for the fading estimated at step 503 is equal to or
lower than the maximum permissible compensation value of the base
station 100 as a result of the comparison between the necessary
power calculated by the down link power control information
generator 103 and the maximum permissible compensation value of the
base station 100, the program goes to step 507.
[0094] At step 507, the down link transmission power setter 101 of
the base station 100 fixes the transmission power on the down link
122 according to the necessary power calculated by the down link
power control information generator 103.
[0095] FIG. 6 shows the procedure of the process for the
transmission power control in the mobile terminal 110 of the mobile
communication system according to this embodiment.
[0096] As illustrated in FIG. 6, the mobile terminal 110 makes
transmission power control so as to set the transmission power on
the up link 121 by receiving the pilot signal sent from the base
station 100, and to transmit to the base station 100 the power
control information used to control the transmission power.
[0097] In the mobile terminal 110, at step 601, the pilot signal
transmitted from the base station 100 is received by the pilot
channel demodulator 313 and fed to the DSP 305.
[0098] At step 602, the up link power control information generator
113 of the mobile terminal 110 extracts the signal intensity from
the received pilot signal.
[0099] At step 603, the up link power control information generator
113 of the mobile terminal 110 integrates the extracted signal
intensity over the particular time slot period in which the
received pilot signal is transmitted or over the particular packet
period in which the packet is sent.
[0100] At step 604, the up link power control information generator
113 of the mobile terminal 110 computes the attenuation of the
pilot signal due to the distance or the shadowing attenuation of
the pilot signal due to obstacles along the channel from the
integrated value over the slot or packet period.
[0101] At step 605, the up link power control information generator
113 of the mobile terminal 110 computes the compensation value for
use in the compensation for the attenuation calculated at step
604.
[0102] At step 606, the up link power control information generator
113 of the mobile terminal 110 estimates the fading caused in the
pilot signal from the signal intensity at each bit of the pilot
signal extracted at step 602.
[0103] At step 607, the up link power control information generator
113 of the mobile terminal 110 calculates the compensation value
for use in compensating for the fading estimated at step 606.
[0104] At step 608, the up link power control information
comparator 112 of the mobile terminal 110 compares the transmission
power necessary to compensate for the fading calculated by the up
link power control information generator 113, and the maximum
permissible compensation value of the maximum transmission power
which can be compensated for by the mobile terminal 110.
[0105] At step 608, if the transmission power necessary to
compensate for the fading estimated at step 607 is larger than the
maximum permissible compensation value of the mobile terminal 100
as a result of the comparison between the necessary power
calculated by the up link power control information generator 113
and the maximum permissible compensation value of the mobile
terminal 110, the program goes to step 609.
[0106] At step 609, the mobile terminal 110 stops until the
following slot, and then the program goes back to step 602.
[0107] At step 608, if the transmission power necessary to correct
the fading estimated at step 607 is equal to or smaller than the
maximum permissible compensation value of the mobile terminal 100
as a result of the comparison between the necessary power
calculated by the up link power control information generator 113
and the maximum permissible compensation value of the mobile
terminal 110, the program goes to step 610.
[0108] At step 610, the up link transmission power setter 111 of
the mobile terminal 110 selects a transmission power level nearest
to the necessary power calculated by the up link power control
information generator 113 from a plurality of previously set
transmission power levels.
[0109] At step 611, the up link transmission power setter 111 of
the mobile terminal 110 sets the transmission power on the up link
121 in accordance with the compensation value for use in
compensating for the distance or shadowing attenuation which was
calculated at step 605 and the transmission power level selected at
step 610.
[0110] At step 612, the up link power control information generator
113 of the mobile terminal 110 measures the ratio C/I from the
integrated value obtained when the pilot signal was integrated over
the slot or packet period at step 603.
[0111] At step 613, the power control information transmitter 114
of the mobile terminal 110 sends the information of fading set at
step 611 and the ratio C/I obtained at step 612 as power control
information to the base station 100.
[0112] Another embodiment of the mobile communication system using
FDD to which the invention is applied will be described with
reference to FIGS. 7 to 9.
[0113] Referring to FIG. 7, the FDD mobile communication system
includes a base station 700 which has a down link power control
information receiver 701, a down link transmission power setter
702, an up link power control information generator 703 and an up
link power control information transmitter 704, a mobile terminal
710 which has a down link power control information transmitter
711, a down link power control information generator 712, an up
link transmission power setter 713 and an up link power control
information receiver 714, an up link 721, a down link 722, a guard
frequency 723, an up link carrier frequency 724, and a down link
carrier frequency 725.
[0114] In this system, the base station 700 and the mobile terminal
710 are connected by the up link 721 for transmitting a signal from
the mobile terminal 710 to the base station 700, and the down link
722 for transmitting a signal from the base station 700 to the
mobile terminal 710. The up link 721 and down link 722 utilize
different carrier frequencies, or the up link carrier frequency 724
and the down link carrier frequency 725, respectively, with the
guard frequency band 723 provided between the channels in order to
prevent the interference.
[0115] When the base station 700 sends a pilot signal on the down
link 722, the mobile terminal 710 receives the pilot signal, and
causes the down link power control information generator 712 to
measure the intensity of the received pilot signal on the down link
and to thereby estimate the attenuation of the signal and fading
condition in the transmission path. Thus, it generates down link
power control information for use in controlling the transmission
power in the down link 722.
[0116] The down link power control information transmitter 711 of
the mobile terminal 710 transmits the generated down link power
control information through the up link 721 to the base station
700.
[0117] The down link power control information receiver 701 of the
base station 700 receives the down link power control information
sent from the mobile terminal 710, and supplies it to the down link
transmission power setter 702. The down link transmission power
setter 702 of the base station 700 sets the transmission power of
the down link 722 by using the received down link power control
information.
[0118] The up link power control information generator 703 of the
base station 700, when receiving the signal on the up link 721 from
the mobile terminal 710, measures the condition of fading or the
like of the signal on the up link 721, and generates up link power
control information for use in controlling the transmission power
of the up link 721. The power control information transmitter 704
of the base station 700 transmits the generated up link power
control information through the down link 722 to the mobile
terminal 710.
[0119] The up link power control information receiver 714 of the
mobile terminal 710 receives the up link power control information
sent from the base station 700, and supplies it to the up link
transmission power setter 713. The up link transmission power
setter 713 sets the transmission power of the up link 721 by using
the received up link power control information.
[0120] FIG. 8 shows the procedure of the process for the
transmission power control in the base station 700 of the mobile
communication system.
[0121] As illustrated in FIG. 8, the base station 700 makes
transmission power control so that the transmission power of the
down link 722 is set according to the down link power control
information sent from the mobile terminal 710, and that the
condition of the fading or the like on the up link 721 is measured,
thus producing up link power control information, which is
transmitted to the mobile terminal 710.
[0122] At step 801, the down link power control information
receiver 701 of the base station 700 receives the down link power
control information sent from the mobile terminal 710 through the
up link 721.
[0123] At step 802, the down link transmission power setter 702 of
the base station 700 calculates the necessary transmission power by
using the down link power control information sent from the mobile
terminal 710. At step 802A, the down link power control information
comparator 706 of the base station 700 compares the transmission
power necessary for use in compensating for the necessary power
that is generated by the down link power control information
generator 705, and the maximum permissible compensation value of
the maximum transmission power that can be compensated for in the
base station 700.
[0124] At step 802A, if the necessary transmission power calculated
on the basis of the down link power control information is larger
than the maximum permissible compensation value of the base station
700 as a result of the comparison, the program goes to step 802B
for stopping the transmission. After the transmission is stopped
until the next slot or packet period, the program goes to step 804,
where the signal from the matched filter is received. On the other
hand, if the calculated necessary transmission power is equal to or
smaller than the maximum permissible compensation value of the base
station 700, the program goes to step 803, where the transmission
power is set.
[0125] At step 803, the down link transmission power setter 702 of
the base station 700 sets the transmission power of the down link
722 by using the calculated necessary transmission power.
[0126] At step 804, the up link power control information generator
703 of the base station 700 receives the signal sent on the up link
721 from the mobile terminal 710.
[0127] At step 805, the up link power control information generator
703 of the base station 700 extracts the signal intensity at each
bit from the received signal on the up link 721.
[0128] At step 806, the up link power control information generator
703 of the base station 700 estimates the fading of the signal sent
on the up link 721 from the mobile terminal 710 on the basis of the
change of the signal intensity extracted at each bit, and generates
up link power control information.
[0129] At step 807, the up link power control information
transmitter 704 of the base station 700 transmits the up link power
control information, which the up link power control information
generator 703 has generated, through the down link 722 to the
mobile terminal 710.
[0130] FIG. 9 shows the procedure of the process for the
transmission power control in the mobile terminal 710 of the mobile
communication system according to this latter embodiment.
[0131] As illustrated in FIG. 9, the mobile terminal 710 makes
transmission power control so that the transmission power of the up
link 721 is set according to the up link power control information
sent from the base station 700, and that the condition of the
fading or the like of the signal on the down link 722 is measured,
thus generating down link power control information, which is sent
to the base station 700.
[0132] At step 901, the mobile terminal 710 receives the pilot
signal sent on the down link 722 from the base station 700. At step
902, the up link transmission power setter 713 of the mobile
terminal 710 extracts the signal intensity at each bit from the
received pilot signal.
[0133] At step 903, the up link transmission power setter 713 of
the mobile terminal 710 integrates the extracted signal intensity
over a particular time, namely, a time slot for which data is
transmitted, or a packet period for which a packet is
transmitted.
[0134] At step 904, the up link transmission power setter 713 of
the mobile terminal 710 calculates the attenuation of the pilot
signal due to the distance or the shadowing attenuation due to the
obstacles along the transmission path on the basis of the
integrated value over the slot or packet period.
[0135] At step 905, the up link power control information receiver
714 of the mobile terminal 710 extracts information of the
attenuation due to the distance or shadowing from the received up
link power control information.
[0136] At step 906, the up link transmission setter 713 of the
mobile terminal 710 computes a necessary transmission power of the
signal to be sent on the up link 721 on the basis of the
attenuation of the pilot signal due to the distance or the
attenuation of the pilot signal due to the obstacles which has been
calculated at step 904, and the information of the attenuation due
to the distance or shadowing which has been extracted at step 905.
At step 906A, the up link power control information comparator 716
of the mobile terminal 710 compares the transmission power
calculated for compensation by the up link power control
information generator with the maximum permissible compensation
value of the maximum transmission power that can be compensated for
in the mobile terminal 710. At step 906A, if the transmission power
calculates at step 906 and necessary to compensate for the
attenuation which is the result of the steps 904, 905 is larger
than the maximum permissible compensation value of the mobile
terminal 710 when the necessary power calculated by the up link
power control information generator 715 is compared with the
maximum permissible compensation value of the mobile terminal 710,
the program goes to step 906B. At step 906B, the mobile terminal
710 stops until the next slot or packet period, and then the
program goes to step 908, where the fading is estimated.
[0137] At step 906A, if the necessary power calculated by the up
link power control information generator is equal to or smaller
than the maximum permissible compensation value of the mobile
terminal 710, the program goes to step 907, where the transmission
power is set.
[0138] At step 907, the up link transmission power setter 713 of
the mobile terminal 710 sets the above-calculated transmission
power of the up link 721.
[0139] At step 908, the down link power control information
generator 712 of the mobile terminal 710 estimates the fading in
the down link 722 by using the signal intensity extracted at each
bit from the pilot signal at step 902, and the distance or
shadowing attenuation calculated at step 904.
[0140] At step 909, the down link power control information
generator 712 of the mobile terminal 710 measures the ratio C/I
(Carrier/Interference) from the integrated value that was attained
by integration over the slot or packet period of the pilot signal
at step 903.
[0141] At step 910, the down link power control information
transmitter 711 of the mobile terminal 710 transmits the
information of fading estimated at step 908 and the ratio C/I
obtained at step 909 as the down link power control information on
the up link 721.
[0142] According to the mobile communication system using FDD, as
describe above, the power control information of the up link 721
which has been obtained in the base station 700 is transmitted to
the mobile terminal 710 in order for the mobile terminal 710 to
control the transmission power of the up link 721, and the power
control information of the down link 722 which has been attained in
the mobile terminal 710 is transmitted to the base station 700 in
order for the base station 700 to control the transmission power of
the down link 722.
[0143] The maximum permissible compensation value in the above
comparing process can be dynamically set in accordance with the
condition of the communication path, for example, the velocity of
the mobile terminal. The maximum permissible compensation value
further can be set in accordance with the difference between the
data rates of the communication packets or the service quality
needed. Each of the above procedures for the transmission power
control can be implemented by a processing software configuration
using programs associated with the control procedure.
[0144] While the present invention has been specifically described
on the basis of the above embodiments, the invention is not limited
to the above embodiments, but of course, various changes and
compensations can be made on the invention without departing from
the scope of the invention.
* * * * *