U.S. patent application number 12/070945 was filed with the patent office on 2008-08-14 for power control method and device.
This patent application is currently assigned to Nokia Corporation. Invention is credited to Mika Raitola.
Application Number | 20080194285 12/070945 |
Document ID | / |
Family ID | 8167349 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080194285 |
Kind Code |
A1 |
Raitola; Mika |
August 14, 2008 |
Power control method and device
Abstract
The present invention proposes a method for controlling a power
used for transmitting data between a terminal device (TD) and a
transceiver device (BTS) of a communication system, said method
comprising the steps of monitoring (S2) during a predetermined time
unit the power used in a transmission between said terminal device
(TD) and said transceiver device (BTS), requesting (S3) an increase
or a decrease of the power used in the transmission by using a
specific information element (TPC) for each predetermined time
unit, storing (S4) a predetermined number (w) of said specific
information elements (TPC), calculating (S5, S6) a first value and
a second value concerning the power of transmission during said
predetermined number (w) of said specific information elements
(TPC), and deciding (S7) by using the first value and the second
value concerning the power calculated in said calculating step (S5,
S6), whether the first value concerning the power is greater than a
sum of the second value concerning the power and a predetermined
level (L). The present invention also proposes a corresponding
device.
Inventors: |
Raitola; Mika; (Masala,
FI) |
Correspondence
Address: |
HARRINGTON & SMITH, PC
4 RESEARCH DRIVE
SHELTON
CT
06484-6212
US
|
Assignee: |
Nokia Corporation
|
Family ID: |
8167349 |
Appl. No.: |
12/070945 |
Filed: |
February 21, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10018584 |
Feb 4, 2002 |
7336629 |
|
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PCT/EP99/04495 |
Jun 29, 1999 |
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12070945 |
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Current U.S.
Class: |
455/522 |
Current CPC
Class: |
H04W 52/221
20130101 |
Class at
Publication: |
455/522 |
International
Class: |
H04Q 7/20 20060101
H04Q007/20; H04B 7/00 20060101 H04B007/00 |
Claims
1-18. (canceled)
19. A method, comprising: receiving a request to change
transmission power between a terminal device and a transceiver
device, the change indicated by a specific information element in
each of predetermined time units, calculating a power raise
requested for the transmission power during a predetermined number
of said time units, calculating an average received power of
transmission during the predetermined number of said time units,
determining whether the calculated power raise is greater than a
sum of the calculated average received power and a predetermined
level, and controlling the transmission power on the basis of the
determination.
20. The method according to claim 19, wherein the predetermined
time unit is a timeslot.
21. The method according to claim 19, wherein the predetermined
time unit is a frame composed of a plurality of timeslots.
22. The method according to claim 19, wherein a value of each one
of said specific information elements in each predetermined time
unit is one of -1 indicating a request for a decrease of power and
+1 indicating a request for an increase of power.
23. The method according to claim 19, further comprising: if the
determination is positive, inhibiting an increase of the power used
in the transmission even if an increase is requested, and if the
determination is negative, allowing an increase in the power used
in the transmission when an increase is requested.
24. The method of claim 19, where the method is performed by at
least one of said transceiver device and said terminal device.
25. The method of claim 19, where the method is performed in a
downlink direction.
26. The method of claim 19, where the method is performed in an
uplink direction.
27. An apparatus comprising: a receiver configurable to receive a
request to change transmission power between a terminal device and
a transceiver device, the change indicated by a specific
information element in each of predetermined time units, a
calculating device configurable to calculate a power raise
requested for the transmission power during a predetermined number
of said time units, the calculating device further configured to
calculate an average received power of transmission during the
predetermined number of said time units, a deciding device
configured to determine whether the calculated power raise is
greater than a sum of the calculated average received power and a
predetermined level, and an output device configured to control the
transmission power on the basis of the determination.
28. The apparatus according to claim 27, wherein the predetermined
time unit is a timeslot.
29. The apparatus according to claim 27, wherein the predetermined
time unit is a frame composed of a plurality of timeslots.
30. The apparatus according to claim 27, wherein a value of each
one of said specific information elements used in each
predetermined time unit is one of -1 indicating a request for a
decrease of power and +1 indicating a request for an increase of
power.
31. The apparatus according to claim 27, where in response to the
deciding device determining, the output means further configured
to: if the determination is positive, inhibit an increase of the
power used in the transmission even if an increase is requested,
and if the determination is negative, allow an increase in the
power used in the transmission when an increase is requested.
32. The apparatus of claim 27 embodied in at least one of the
transceiver device and the terminal device.
33. The apparatus of claim 27, where power used in a downlink
transmission is controlled.
34. The apparatus of claim 27, where power used in an uplink
transmission is controlled.
35. A storing means embodying software executable by a device to
perform operations comprising: receiving a request to change
transmission power between a terminal device and a transceiver
device, the change indicated by a specific information element in
each of predetermined time units, calculating a power raise
requested for the power used in the transmission during a
predetermined number of said time units, calculating an average
received transmission power during a predetermined number of said
time units, determining whether the calculated power raise is
greater than a sum of the calculated average received power and a
predetermined level, and controlling the transmission power on the
basis of the determination.
36. A method, comprising: receiving a request indicating a
determined change of power used in a transmission between a
terminal device and a transceiver device, the request comprising a
specific information element in each of predetermined time units,
calculating from the information element a power raise requested
for the power used in the transmission during a predetermined
number of said time units, calculating an average received power of
transmission during the predetermined number of said time units,
determining whether the calculated power is greater than a sum of
the calculated average received power and a predetermined level,
and controlling the power used in the transmission between the
terminal device and the transceiver device on the basis of the
determination.
37. The method according to claim 36, wherein the predetermined
time unit is a timeslot.
38. The method according to claim 36, wherein the predetermined
time unit is a frame composed of a plurality of timeslots.
39. The method according to claim 36, wherein a value of each one
of said specific information elements used in each predetermined
time unit is one of -1 indicating a request for a decrease of power
and +1 indicating a request for an increase of power.
40. The method according to claim 36, further comprising: if the
determination is positive, inhibiting an increase of the power used
in the transmission even if an increase is requested, and if the
determination is negative, allowing an increase in the power used
in the transmission when an increase is requested.
41. The method of claim 36, where the method is performed by at
least one of said transceiver device and said terminal device.
42. The method of claim 36, where the method is performed in a
downlink direction.
43. The method of claim 36, where the method is performed in an
uplink direction.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation of and claims priority to U.S. patent
application Ser. No. 10/018,584, which is a national stage entry
from International Application PCT/EP99/04495 filed on Jun. 29,
1999.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for controlling a
power used for transmitting data between a terminal device and a
transceiver device of a communication system and also to a
corresponding device. In particular, the present invention is
directed to a power control method and corresponding device used in
Code Division Multiple Access (CDMA) systems.
BACKGROUND OF THE INVENTION
[0003] In recent years, mobile radio telecommunication systems have
widely spread. Such mobile radio telecommunication systems (for
example GSM, 3rd generation system such as the Universal Mobile
Telecommunications System (UMTS) and others) operate with different
data transmission methods. Such a data transmission method is for
example a Code Division Multiple Access (CDMA) method. Said CDMA
method is further developed into a Wideband Code Division Multiple
Access (WCDMA) method (or Broadband CDMA) using a greater frequency
band for example to be used in 3rd generation communication systems
like the UMTS.
[0004] In both CDMA and WCDMA methods, the basic operating
principle is similar. Data to be transmitted between terminal
devices such as mobile stations via a communication network
comprising several network elements such as transceiver devices
such as base transceiver stations, mobile switching centers and the
like is multiplied with a unique code allocated to each connection.
Said code has a higher frequency than the data which results in a
wide transmission bandwidth in comparison with the original data
bandwidth. This process is also known as spreading.
[0005] On a receiving side knowing the respective code, the
transmitted signal is decoded and the recovered data is processed
further. This process is also known as despreading.
[0006] For a correct recovery of the data from the transmitted
signal a major condition is that the received signals have a
(nearly) constant and equal strength. Since in a mobile
telecommunication system, for example due to a movement of the
terminal devices, widely different signal strengths may be received
when transmitting always with the same transmission power,
interference between different terminal devices transmitting at the
same time may occur. Therefore, an accurate power control in uplink
(terminal device to transceiver station) and downlink (transceiver
station to terminal device) is required.
[0007] In third generation CDMA systems (e. g. cdma2000, WCDMA)
fast power control is used both in uplink and downlink. Here, the
decoding performance is optimal when the received signal power is
as constant as possible. This is required especially when the
service delay is limited (for example in speech communication) and
a fading may cause errors. The fast power control is able to follow
even fast fadings.
[0008] On the other hand, the downlink transmission capacity is
maximized when the transmitted power is minimized, i. e. the
generated interference is as low as possible. However, fast power
control aims that the received power is constant. This means that
the transmitted power varies greatly, which increases the
transmitted power average. Also, the variation of transmitted power
causes power spikes which are harmful for system load control.
SUMMARY OF THE INVENTION
[0009] Consequently, it is an object of the present invention to
provide an improved method and a corresponding device for
controlling a power used for transmitting data between a terminal
device and a transceiver device of a communication system.
[0010] According to the present invention, this object is achieved
by a method for controlling a power used for transmitting data
between a terminal device and a transceiver device of a
communication system, said method comprising the steps of
monitoring during a predetermined time unit the power used in a
transmission between said terminal device and said transceiver
device, requesting an increase or a decrease of the power used in
the transmission by using a specific information element for each
predetermined time unit, storing a predetermined number of said
specific information elements, calculating a first value and a
second value concerning the power of transmission during said
predetermined number of said specific information elements, and
deciding by using the first value and the second value concerning
the power calculated in said calculating step, whether the first
value concerning the power is greater than a sum of the second
value concerning the power and a predetermined level.
[0011] Furthermore, the present invention proposes a device for
controlling a power used for transmitting data between a terminal
device and a transceiver device of a communication system, said
device comprising monitoring means for monitoring during a
predetermined time unit the power used in a transmission between
said terminal device and said transceiver device, requesting means
for requesting an increase or a decrease of the power used in the
transmission by using a specific information element for each
predetermined time unit, storing means for storing a predetermined
number of said specific information elements, calculating means for
calculating a first value and a second value concerning the power
of transmission during said predetermined number of said specific
information elements, and deciding means for deciding by using the
first value and the second value concerning the power calculated by
said calculating means, whether the first value concerning the
power is greater than a sum of the second value concerning the
power and a predetermined level.
[0012] Advantageous further developments of the present invention
are as set out in the respective dependent claims.
[0013] According to the present invention, the proposed method
and/or device are easy to implement since only small changes to
present systems are necessary.
[0014] Furthermore, for example a downlink power control according
to the present invention is able to maximize the decoding
performance by following fading as well as possible and also to
minimize the interference caused to the other terminal devices. It
is possible to follow even fast fading as in the fast power
control, but if the requested power raise within a predetermined
time is to high a corresponding high increase of the transmission
power is prevented. Moreover, excessively high power spikes are
inhibited and therefore the performance of the system load control
can be improved.
[0015] Preferred embodiments of the invention are described herein
below in detail by way of example with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows a flowchart illustrating the method according
to the present invention.
[0017] FIG. 2 shows a block circuit diagram illustrating an
embodiment of the device according to the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0018] In the following, as a first example, the above mentioned
downlink case is described.
[0019] With reference to FIG. 1, a power control method according
to the present invention is illustrated in the flowchart.
[0020] In step S1, the power control is started, for example when a
packet data communication connection is established between two
terminal devices TD via a communication network (i. e. via at least
one base transceiver station BTS). During the communication, the
signal strength (i. e. the transmission power) from the base
transceiver station BTS is frequently monitored in each timeslot by
the terminal device TD (step S2). If necessary, i. e. when the
signal strength changes above or below a predetermined value, in
step S3, the terminal device TD requests an increase or decrease of
the transmission power of the base transceiver station,
respectively.
[0021] This request is represented by specific information elements
or commands which are known as so-called transfer power control
bits TPC. Said TPC bits have a value of +1 if an increase of power
by a predetermined level is requested and a value of -1 if a
decrease of power by a predetermined level is requested. For each
time unit, one TPC bit is sent. Said time unit is for example one
timeslot or a frame consisting of a plurality of timeslots.
[0022] In step S4, the base transceiver station BTS receives said
TPC bits sent for each time unit. Furthermore, a predetermined
number w of said TPC bits, i. e. TPC bits of a predetermined number
w of subsequent time units are stored. When reaching the
predetermined number w, in step S5, a power raise during the recent
w time units is calculated. This power raise can be determined for
example by summing the TPC bits. Then, in step S6, also an received
average power of transmission (e. g. indicated in dB) is calculated
during said w time units by using the TPC bits. The calculation of
the average power can be performed, for example, as follows: In the
beginning of a calculation period, the power (i. e. the signal
strength) has an value of e. g. 10 dBm. When in the calculation
period TPC bits -1, +1, +1, +1 are sent, the average power is
calculated by average
power=((10-1)+(10-1+1)+(10-1+1+1)++(10-1+1+1+1))/4=42/4 [dBm].
[0023] In step S7, it is decided by using said calculated power
raise and average power of transmission during the w time units,
whether the power raise is higher than a sum of the average power
and a predetermined level L. Said predetermined level L is given
for example in dB.
[0024] If the decision in step S7 is positive, i. e. the power
raise for said w time units is at least L dB higher than the
average power, a increase of the transmission power is inhibited
(step S8). That means, the transmission power used by the base
transceiver station BTS to the terminal device TD is kept constant
or is even decreased, even if an increase was requested.
[0025] On the other hand, if the decision in step S7 is negative,
i. e. the power raise during said w time units is not L dB higher
than the average power, a power raise is allowed, i. e. the
transmission power can be increased (or decreased) by the base
transceiver station (step S9) as requested. The transmission power
sent by the base transceiver station is increased (or decreased)
according to the sum of all TPC bits received during all w time
units (e. g. +3). Optionally, the transmission power may only be
increased (or decreased) according to the most recent requested
power raise (i. e. only the last received TPC bit, for example +1,
is taken into account). The decision, in which way of the above
described cases the power is changed, may be depending on the
respective application.
[0026] In step S10, the power control method is restarted.
[0027] With reference to FIG. 2, a device adapted to perform a
power control method according to the present invention is
described below.
[0028] When the communication between terminal devices TD via at
least one base transceiver station BTS (and probably other network
elements) starts, the received signal strength (i. e. the
transmission power used for the communication) is monitored
frequently and periodically at each time unit by a monitoring means
10. A requesting means 20 requests an increase or a decrease of the
transmission power used by the base transceiver station BTS
depending on results of said monitoring means 10. For this purpose
a TPC bit having a value of +1 or -1 is sent each timeslot as
command data from the terminal device TD to the base transceiver
station BTS.
[0029] Said TPC bits are received by a receiving means 30, for
example at the base transceiver station, to be stored in a storing
means 40. Said storing means 40 is adapted to store at least a
predetermined number w of TPC bits (TPC bits of w time units or
timeslots). When the predetermined number w of TPC bits is reached,
a calculating means 50 calculates the power raise and the average
power using the stored TPC bits during said w time units as
described above.
[0030] In a deciding means 60 it is decided whether the calculated
power raise is greater than the sum of the average power and the
predetermined level L.
[0031] Depending on the result of said deciding means 60 an output
means 70 outputs a power change signal which inhibit a transmission
power change by the base transceiver station BTS in the case that
the power raise is at least L dB higher than the average power. On
the other hand, in the case that the power raise is not L dB higher
than the average power, a power change signal is output to allow a
increase (or decrease) of power by the base transceiver station BTS
as requested.
[0032] A proposal for parameters w and L are w=16 . . . 64 and L=1
dB . . . 3 dB. However, other parameter values can be used
depending on for example user specific or connection type specific
specifications.
[0033] By using the above described downlink power control it is
possible to reach of several dB in comparison to the conventional
power control. The reached gain depends also on the connection
type, e. g. outdoor to indoor channel, single path channel etc. In
case that there are only few multipaths, the gain is the highest.
It is possible to reach a 20% gain in capacity in comparison to the
previous known methods in the system level.
[0034] As a second embodiment, the above described method and
device can also be used in uplink direction, i. e. in power control
for signaling from the terminal device TD to the base transceiver
station BTS. In this case, the signal strength from the terminal
device TD is monitored by the base transceiver station. The further
steps of storing, calculating, comparing/deciding and outputting
(steps S4 to S9) and the corresponding means 30 to 70 may then be
implemented also in the base transceiver station BTS or in the
terminal device TD. In case of the uplink power control, the method
for example is based on received signal to interference ratio (SIR)
values which represent the difference between a, wanted" signal and
an interfering signal.
[0035] It is to be noted that the present invention can be
implemented as hardware and/or software in the terminal device
and/or the base transceiver station. The present invention can be
used preferably in WCDMA systems during a packet data
communication, but also in any other CDMA system (for example
IS-95, cdma2000 etc.) during any data communication (speech, packet
data and the like).
[0036] Furthermore, the calculation (and therefore the decision
whether to allow or to prevent a power raise) can be done timeslot
per timeslot. Alternatively, it is also possible to use more
timeslots or time units (i. e. TPC bits) for the calculation of the
power raise and the average power.
[0037] The present invention proposes a method for controlling a
power used for transmitting data between a terminal device TD and a
transceiver device BTS of a communication system, said method
comprising the steps of monitoring S2 during a predetermined time
unit the power used in a transmission between said terminal device
TD and said transceiver device BTS, requesting S3 an increase or a
decrease of the power used in the transmission by using a specific
information element TPC for each predetermined time unit, storing
S4 a predetermined number w of said specific information elements
TPC, calculating S5, S6 a first value and a second value concerning
the power of transmission during said predetermined number w of
said specific information elements TPC, and deciding S7 by using
the first value and the second value concerning the power
calculated in said calculating step S5, S6, whether the first value
concerning the power is greater than a sum of the second value
concerning the power and a predetermined level L. The present
invention also proposes a corresponding device.
[0038] It should be understood that the above description and
accompanying figures are merely intended to illustrate the present
invention by way of example only. The preferred embodiments of the
present invention may thus vary within the scope of the attached
claims.
* * * * *