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| United States Patent | 5257283 |
| Link to this page | http://www.wikipatents.com/5257283.html |
| Inventor(s) | Gilhousen; Klein S. (San Diego, CA);
Padovani; Roberto (San Diego, CA);
Wheatley, III; Charles E. (Del Mar, CA) |
| Abstract | A power control system for a cellular mobile telephone system in which
system users communicate information signals between one another via at
least one cell site using code division multiple access spread spectrum
communication signals. The power control system controls transmission
signal power for each cellular mobile telephone in the cellular mobile
telephone system wherein each cellular mobile telephone has an antenna,
transmitter and receiver and each cell-site also has an antenna,
transmitter and receiver. Cell-site transmitted signal power is measured
as received at the mobile unit. Transmitter power is adjusted at the
mobile unit in an opposite manner with respect to increases and decreases
in received signal power. A power control feedback scheme may also be
utilized. At the cell-site communicating with the mobile unit, the mobile
unit transmitted power is measured as received at the cell-site. A command
signal is generated at the cell-site and transmitted to the mobile unit
for further adjusting mobile unit transmitter power corresponding to
deviations in the cell site received signal power. The feedback scheme is
used to further adjust the mobile unit transmitter power so as to arrive
at the cell-site at a desired power level. |
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Title Information  |
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Drawing from US Patent 5257283 |
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Spread spectrum transmitter power control method and system |
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| Publication Date |
October 26, 1993 |
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| Filing Date |
August 23, 1991 |
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| Parent Case |
This is a continuation of application Ser. No. 07/433,031, filed Nov. 7,
1989, now |
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Title Information  |
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References  |
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| *references marked with an asterisk below are user-added references |
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U.S. References |
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| | Reference | Relevancy | Comments | Reference | Relevancy | Comments | 4901307 Gilhousen 370/320 Feb,1990 |      Your vote accepted [0 after 0 votes] | | 4870698 Katsuyama 455/522 Sep,1989 |      Your vote accepted [0 after 0 votes] | | 4868795 McDavid 367/77 Sep,1989 |      Your vote accepted [0 after 0 votes] | | 4811421 Havel 455/69 Mar,1989 |      Your vote accepted [0 after 0 votes] | | 4777653 Bonnerot 455/69 Oct,1988 |      Your vote accepted [0 after 0 votes] | | 4765753 Schmidt 370/332 Aug,1988 |      Your vote accepted [0 after 0 votes] | | 4672658 Kavehrad 455/555 Jun,1987 |      Your vote accepted [0 after 0 votes] | | 4641322 Hasegawa 375/145 Feb,1987 |      Your vote accepted [0 after 0 votes] | | 4613990 Halpern 455/522 Sep,1986 |      Your vote accepted [0 after 0 votes] | | 4580262 Naylor 714/708 Apr,1986 |      Your vote accepted [0 after 0 votes] | | 4495648 Giger 455/73 Jan,1985 |      Your vote accepted [0 after 0 votes] | | 4225976 Osborne 455/226.3 Sep,1980 |      Your vote accepted [0 after 0 votes] | | 4222115 Cooper 375/130 Sep,1980 |      Your vote accepted [0 after 0 votes] | | 4193031 Cooper 370/330 Mar,1980 |      Your vote accepted [0 after 0 votes] | | 4123718 Lampert 375/345 Oct,1978 |      Your vote accepted [0 after 0 votes] | | 4112257 Frost 455/437 Sep,1978 |      Your vote accepted [0 after 0 votes] | | 3925782 Anderl 455/507 Dec,1975 |      Your vote accepted [0 after 0 votes] | | | | | |
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Market Review  |
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Technical Review  |
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Claims  |
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We claim:
1. A method for controlling transmission power of a first transceiver in
communicating information signals of a first user using spread spectrum
communication signals within a first frequency band to a second
transceiver, and said first transceiver is further for extracting
information signals of a second user communicated to said first
transceiver by said second transceiver also using spread spectrum
communication signals in a second frequency band, said method comprising
the steps of:
determining combined signal power of all signals received by said first
transceiver within said second frequency band;
controlling signal power of said first transceiver transmitted spread
spectrum communication signals in inverse proportion to variations in said
determined combined signal power; and
controlling signal power of said first transceiver transmitted spread
spectrum communication signals in inverse proportion to variations in
signal power of first transceiver transmitted spread spectrum
communication signals as received by said second transceiver.
2. The method of claim 1 wherein said step of determining combined signal
power comprises the steps of:
measuring combined signal power of all signals received by said first
transceiver within said second frequency band; and
generating a corresponding measurement indication; and wherein said step of
controlling signal power of said first transceiver transmitted spread
spectrum communication signals in inverse proportion to variations in said
determined combined signal power comprises the steps of:
comparing said measurement indication with a predetermined power level so
as to provide a corresponding comparison result; and
adjusting signal power of said first transceiver transmitted spread
spectrum communication signals in response to said comparison result.
3. The method of claim 2 wherein said step of controlling signal power of
said first transceiver transmitted spread spectrum communication signals
in inverse proportion to variations in signal power of first transceiver
transmitted spread spectrum communication signals received by said second
transceiver comprises the steps of:
measuring signal power of first transceiver transmitted spread spectrum
communication signals as received by said second transceiver;
generating power adjustment commands in accordance with deviations in said
measured signal power with respect to a desired reception power level;
inserting said power adjustment commands in said second transceiver
transmitted spread spectrum communication signals to said first
transceiver; and
adjusting signal power of said first transceiver transmitted spread
spectrum communication signals in accordance with said power adjustment
commands as received by said first transceiver.
4. The method of claim 1 wherein said step of controlling signal power of
said first transceiver transmitted spread spectrum communication signals
in inverse proportion to variations in signal power of first transceiver
transmitted spread spectrum communication signals as received by said
second transceiver comprises the steps of:
measuring signal power of first transceiver transmitted spread spectrum
communication signals received by said second transceiver;
generating power adjustment commands in accordance with deviations in said
measured signal power with respect to a desired reception power level;
inserting said power adjustment commands in said second transceiver
transmitted spread spectrum communication signals to said first
transceiver; and
adjusting signal power of said first transceiver transmitted spread
spectrum communication signals in accordance with said power adjustment
commands as received by said first transceiver.
5. The method of claim 4 further comprising the step of controlling signal
power of said second transceiver transmitted spread spectrum communication
signals in inverse proportion to variations of a measured ratio, of signal
power of second transceiver transmitted spread spectrum communication
signals as received by said first transceiver to a signal power of
interfering signals, with respect to a desired ratio.
6. The method of claim 5 wherein said step of controlling signal power of
said second transceiver transmitted spread spectrum communication signals
comprises the steps of:
measuring signal power of all signals received by said first transceiver
within said second predetermined frequency band;
measuring signal power of said second transceiver transmitted spread
spectrum communication signals as received by said first transceiver;
comparing said measured signal power of said second transceiver transmitted
spread spectrum communication signals received by said first transceiver
with said measured signal power of said all signals received by said first
transceiver so as to provide a signal-to-interference ratio value;
generating power adjustment requests in accordance with deviations in said
signal-to-interference ratio value with respect to a desired
signal-to-interference ratio value;
inserting said power adjustment requests in said first transceiver
transmitted spread spectrum communication signals; and
adjusting signal power of said second transceiver transmitted spread
spectrum communication signals in correspondence with said power
adjustment requests as received by said second transceiver in said first
transceiver transmitted spread spectrum communication signals.
7. In a remote station transceiver having a receiver for receiving a base
station transmitted outbound spread spectrum signals wherein one of said
outbound spread spectrum signals contains first user information and for
demodulating said one outbound spread spectrum signal to provide said
first user information to a first user, and a transmitter for transmitting
to said base station an inbound spread spectrum signal containing second
user information, said transceiver having a power control system for
controlling at said transceiver the transmission signal power of said
inbound spread spectrum signal wherein the signal power of said inbound
spread spectrum signal as received at said base station is maintained
about a predetermined average signal power level, and wherein said base
station measures the signal power of said inbound spread spectrum signal
as received at said base station, generates power adjustment commands
according to variations in said measured signal power of said inbound
spread spectrum signal with respect to said predetermined average signal
power level and transmits said power adjustment commands in said one
outbound spread spectrum signal, said power control system comprising:
control processor means coupled to said receiver for receiving from said
receiver said power adjustment commands in said one outbound spread
spectrum signal, accumulating values corresponding to said power
adjustment commands with respect to a predetermined first power level
value, and generating a corresponding first power level control signal,
said control processor means further for generating a power level set
signal;
automatic gain control means coupled to said receiver for measuring signal
power of all of said outbound spread spectrum signals received by said
receiver, and providing a corresponding power measurement signal;
comparator means for receiving and comparing said power measurement signal
and said power level set signal, and providing a corresponding second
power level control signal; and
amplification means coupled to said transmitter for receiving said first
and second power level control signals and amplifying said inbound spread
spectrum signal at a gain level determined by said first and second power
level control signals.
8. The transceiver of claim 7 wherein said power control system
amplification means comprises:
first amplifier means for, receiving said first power level control signal
and amplifying said inbound spread spectrum signal at a first gain
determined by said first power level control signal; and
second amplifier means for receiving said second power level control signal
and said first amplifier means amplified inbound spread spectrum signal,
and amplifying said first amplifier means amplified inbound spread
spectrum signal at a second gain determined by said second power level
control signal.
9. In the transceiver of claim 8 wherein an increase in measured outbound
spread spectrum signal power corresponds to an increase in said second
power control level signal with said second amplifier means responsive
thereto for decreasing said second gain, and a decrease in measured
outbound spread spectrum signal power corresponds to a decrease in said
second power control level signal with said second amplifier means
responsive thereto for increasing said second gain.
10. In the transceiver of claim 9, said receiver having an analog portion
and a digital receiver portion, said automatic gain control means coupled
to said analog receiver portion with said signal power of said received
outbound spread spectrum signals being measured as wideband signal power,
and said digital receiver portion coupled to said control processor with
said digital receiver portion extracting said power adjustment commands
from said one outbound spread spectrum signal, wherein each power
adjustment command affects a change in said first power level control
signal with said first amplifier means responsive to each change in said
first power level control signal so as to provide a corresponding change
in said first gain.
11. In the transceiver of claim 10 wherein each change in said first gain
corresponds to a predetermined dB gain change in transmission signal power
of said inbound spread spectrum signal.
12. In the transceiver of claim 7 wherein in said power control system
measured increases and decreases in signal power respectively correspond
to decreases and increases in said gain level.
13. In the transceiver of claim 7 wherein said base station transmits said
outbound spread spectrum signals in a first predetermined frequency band
and said transceiver transmits inbound spread spectrum signal in a second
predetermined frequency band.
14. In the transceiver of claim 7 said receiver having an analog receiver
portion and a digital receiver portion, said automatic gain control means
coupled to said analog receiver portion with said signal power of said
received outbound spread spectrum signals being measured as wideband
signal power, and said digital receiver portion coupled to said control
processor with said digital receiver portion extracting said power
adjustment commands from said one outbound spread spectrum signal.
15. In the transceiver of claim 7 wherein said power control system further
comprises filter means for non-linearly limiting a rate of change in said
second power level control signal so as to provide a rate of change in
increases of said second power level control signal that is greater than a
rate of change in decreases in said second power level control signal.
16. A system for controlling transmission power of a first transceiver in
transmitting spread spectrum communication signals, to a second
transceiver such that said first transceiver transmitted signals are
maintained at a predetermined power level as received at said second
transceiver, said second transceiver also transmitting spread spectrum
communication signals to said first transceiver, said system comprising:
first power control means for determining combined signal power of second
transceiver transmitted spread spectrum communication signals received by
said first transceiver and controlling signal power of said first
transceiver transmitted spread spectrum communication signals in inverse
proportion to variations in said determined combined signal power; and
second power control means for further controlling signal power of said
first transceiver transmitted spread spectrum communication signals in
inverse proportion to variations in signal power of first transceiver
transmitted spread spectrum communication signals received by said second
transceiver.
17. The system of claim 16 wherein said first power control means provides
increases in signal power at a rate less than decreases in signal power.
18. The system of claim 16 wherein said first power control means provides
increases in signal power at a rate less than said second power control
means provides decreases in signal power.
19. The system of claim 16 wherein said open loop power control means
compensates for variations in channel conditions affecting signal power in
a second transceiver to first transceiver communication channel.
20. The system of claim 16 wherein said second power control means
compensates for variations in channel conditions affecting signal power in
a first transceiver to second transceiver communication channel.
21. The system of claim 16 wherein said first power control means
comprises:
means for measuring combined signal power of all second transceiver
transmitted spread spectrum communication signals received by said first
transceiver; and
means for adjusting signal power, of said first transceiver transmitted
spread spectrum communication signals, in inverse proportion to deviations
in said first transceiver measured signal power with respect to a
predetermined reference power level.
22. The system of claim 21 wherein said second power control means
comprises:
means for measuring signal power of first transceiver transmitted spread
spectrum communication signals received by said second transceiver;
means for generating power adjustment commands in accordance with
deviations in said second transceiver measured signal power with respect
to a desired reception power level;
means for inserting said power adjustment commands in said second
transceiver transmitted spread spectrum communication signals; and
means for further adjusting signal power of said first transceiver
transmitted spread spectrum communication signals in accordance with said
power adjustment commands as received by said first transceiver.
23. The system of claim 22 wherein said means for measuring combined signal
power of all second transceiver transmitted spread spectrum communication
signals received by said first transceiver measures wideband signal power,
and said means for measuring signal power of first transceiver transmitted
spread spectrum communication signals received by said second transceiver
digitally measures narrowband signal power.
24. The system of claim 16 wherein said second power control means
comprises:
means for measuring signal power of first transceiver transmitted spread
spectrum communication signals received by said second transceiver;
means for generating power adjustment commands in accordance with
deviations in said second transceiver measured signal power with respect
to a desired reception power level;
means for inserting said power adjustment commands in said second
transceiver transmitted spread spectrum communication signals; and
means for adjusting signal power of said first transceiver transmitted
spread spectrum communication signals in accordance with said power
adjustment commands as received by said first transceiver.
25. The system of claim 16 further comprising third power control means for
controlling signal power of said second transceiver transmitted spread
spectrum communication signals in inverse proportion to variations of a
measured ratio, of signal power of second transceiver transmitted spread
spectrum communication signals received by said first transceiver to a
signal power of interfering signals, with respect to a desired ratio.
26. The system of claim 25 wherein said third power control means
comprises:
means for, measuring signal power of all signals received by said first
transceiver, measuring signal power of said second transceiver transmitted
spread spectrum communication signals as received by said first
transceiver, comparing said measured signal power of said second
transceiver transmitted spread spectrum communication signals received by
said first transceiver with said measured signal power of said all signals
received by said first transceiver so as to provide a
signal-to-interference ratio value, generating power adjustment requests
in accordance with to deviations in said signal-to-interference ratio
value with respect to a desired predetermined signal-to-interference ratio
value, and inserting said power adjustment requests in said first
transceiver transmitted spread spectrum communication signals; and
means for adjusting signal power of said second transceiver transmitted
spread spectrum communication signals in correspondence with said power
adjustment requests as received by said second transceiver in said first
transceiver transmitted spread spectrum communication signals.
27. A system for controlling the transmission power of a first remote
transceiver of a plurality of remote transceivers, wherein each remote
transceiver is for transmitting a spread spectrum communication signal to
a base transceiver within a first predetermined frequency band, said base
transceiver also transmitting a spread spectrum communication signal to at
least said first remote transceiver within a second predetermined
frequency band, said system comprising:
first power control means for determining combined signal power of said
base transceiver transmitted spread spectrum communication signal and
other signals within said second predetermined frequency band as received
at said first transceiver, detecting variations in said first power
control means determined signal power with respect to a first
predetermined transmit power level, and adjusting signal power of said
first transceiver transmitted spread spectrum communication signal in
response to said first power control means detected variations; and
second power control means for determining signal power of said first
transceiver transmitted spread spectrum communication signal as received
at said second transceiver, detecting variations in said second power
control means determined signal power with respect to a second
predetermined transmit power level, adjusting signal power of said first
transceiver transmitted spread spectrum communication signal in response
to said second power control means detected variations.
28. The system of claim 27 wherein said first power control means
comprises:
automatic gain control means for measuring wideband signal power of said
base transceiver transmitted spread spectrum communication signal and
other signals within said second predetermined frequency band as received
at said first remote transceiver, and providing a corresponding first
power measurement signal;
comparator means for receiving and comparing said first power measurement
signal with a first power level signal representative of said first
predetermined transmit power level, and providing a corresponding first
power level control signal; and
amplification means for receiving said first power level control signal and
amplifying said first remote transceiver transmitted spread spectrum
communication signal at a gain level determined by said first power level
control signal.
29. The system of claim 28 wherein said second power control means
comprises:
second power measurement means for measuring signal power of said first
transceiver transmitted spread spectrum communication signal as received
by said second transceiver, and providing a corresponding second power
measurement signal;
second comparator means for receiving and comparing said second power
measurement signal with a second power level signal representative of said
second predetermined transmit power level, and providing a corresponding
second power level control signal;
power command generator means for receiving said corresponding second power
level control signal, generating power adjustment commands in response to
said second power level control signal, and providing said power
adjustment commands in said base transceiver transmitted spread spectrum
communication signal to said first remote transceiver;
processing means responsive to said power adjustment commands extracted
from said base transceiver transmitted spread spectrum communication
signal as received at said first remote transceiver for providing a
corresponding third power level control signal; and
said amplification means further for receiving said third power level
control signal and further amplifying said first remote transceiver
transmitted spread spectrum communication signal at a gain level
determined by said third power level control signal.
30. The system of claim 27 wherein said second power control means
comprises:
first power measurement means for measuring signal power of said first
remote transceiver transmitted spread spectrum communication signal as
received by said base transceiver, and providing a corresponding power
level control signal;
first comparator means for receiving and comparing said power measurement
signal with a power level signal representative of said second
predetermined transmit power level, and providing a corresponding first
power control signal; and
power command generator means for receiving said corresponding first power
level control signal, generating power adjustment commands in response to
said first power level control signal, and providing said power adjustment
commands in said base transceiver transmitted spread spectrum
communication signal to said first remote transceiver;
processing means responsive to said power adjustment commands extracted
from said base transceiver transmitted spread spectrum communication
signal as received at said first remote transceiver for providing a
corresponding second power level control signal; and
amplification means for receiving said second power level control signal
and amplifying said first remote transceiver transmitted spread spectrum
communication signal at a gain level determined by said second power level
control signal. |
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Claims  |
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Description  |
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BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to cellular mobile telephone systems. More
specifically, the present invention relates to a novel and improved method
and apparatus for controlling transmitter power in a code division
multiple access (CDMA) cellular mobile telephone system.
II. Description of the Related Art
The use of code division multiple access (CDMA) modulation techniques is
one of several techniques for facilitating communications in which a large
number of system users are present. Although other techniques such as time
division multiple access (TDMA), frequency division multiple access (FDMA)
and AM modulation schemes such as amplitude companded single sideband
(ACSSB) are known, CDMA has significant advantages over these other
techniques. The use of CDMA techniques in a multiple access communication
system is disclosed in U.S. patent application Ser. No. 06/921,261, filed
Oct. 17, 1986, entitled "SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION
SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS", now U.S. Pat. No.
4,901,307 assigned to the assignee of the present invention, the
disclosure thereof incorporated by reference.
In the just mentioned patent, a multiple access technique is disclosed
where a large number of mobile telephone system users each having a
transceiver communicate through satellite repeaters or terrestrial base
stations (also known as cell-sites stations, or for short cell-sites)
using code division multiple access (CDMA) spread spectrum communication
signals. In using CDMA communications, the frequency spectrum can be
reused multiple times thus permitting an increase in system user capacity.
The use of CDMA results in a much higher spectral efficiency than can be
achieved using other multiple access techniques. In a CDMA system,
increases in system capacity may be realized by controlling the
transmitter power of each mobile user so as to reduce interference to
other system users.
In the satellite application of the CDMA communication techniques, the
mobile unit transceiver measures the power level of a signal received via
a satellite repeater. Using this power measurement, along with knowledge
of the satellite transponder downlink transmit power level and the
sensitivity of the mobile unit receiver, the mobile unit transceiver can
estimate the path loss of the channel between the mobile unit and the
satellite. The mobile unit transceiver then determines the appropriate
transmitter power to be used for signal transmissions between the mobile
unit and the satellite, taking into account the path loss measurement, the
transmitted data rate and the satellite receiver sensitivity.
The signals transmitted by the mobile unit to the satellite are relayed by
the satellite to a Hub control system earth station. The Hub measures the
received signal power from signals transmitted by each active mobile unit
transceiver. The Hub then determines the deviation in the received power
level from that which is necessary to maintain the desired communications.
Preferably the desired power level is a minimum power level necessary to
maintain quality communications so as to result in a reduction in system
interference.
The Hub then transmits a power control command signal to each mobile user
so as to adjust or "fine tune" the transmit power of the mobile unit. This
command signal is used by the mobile unit to change the transmit power
level closer to a minimum level required to maintain the desired
communications. As channel conditions change, typically due to motion of
the mobile unit, both the mobile unit receiver power measurement and the
power control feedback from the Hub continually readjust the transmit
power level so as to maintain a proper power level. The power control
feedback from the Hub is generally quite slow due to round trip delays
through the satellite requiring approximately 1/2 of a second of
propagation time.
One important difference between satellite or terrestrial base stations
systems are the relative distances separating the mobile units and the
satellite or cell-site. Another important different in the satellite
versus the terrestrial system is the type of fading that occurs in these
channels. Thus, these differences require various refinements in the
approach to system power control for the terrestrial system.
In the satellite/mobile unit channel, i.e. the satellite channel, the
satellite repeaters are normally located in a geosynchronous earth orbit.
As such, the mobile units are all at approximately the same distance from
the satellite repeaters and therefore experience nearly the same
propagation loss. Furthermore, the satellite channel has a propagation
loss characteristic that follows approximately the inverse square law,
i.e. the propagation loss is inversely proportional to the square of the
distance between the mobile unit and the satellite repeater in use.
Accordingly, in the satellite channel the variation in path loss due to
distance variation is typically on the order of only 1-2 dB.
In contrast to the satellite channel, the terrestrial/mobile unit channel,
i.e. the terrestrial channel, the distance between the mobile units and
the cell sites can vary considerably. For example, one mobile unit may be
located at a distance of five miles from the cell site while another
mobile unit may be located only a few feet away. The variation in distance
may exceed a factor of one hundred to one. The terrestrial channel
experiences a propagation loss characteristic as did the satellite
channel. However, in the terrestrial channel the propagation loss
characteristic corr | | |