Optimizing power consumption of a base station
Field of the invention
The invention relates to the field of mobile telecommunication, more specifically to
optimizing power consumption of a base station in a mobile telecommunication network.
Background and related art
A state of the art base station consumes a maximum power for a maximum traffic
load in the respective cell. Such a base station is optimized for the maximum traffic
load in the respective cell and consumes more than 50% of the maximum power
even when no data is transmitted or received by the base station. The base station
is operated inefficiently in times of low traffic loads in the respective cell, because a
lower traffic load does not lead to a significantly lower power consumption of the
base station. In other words, the ratio of consumed power per transmitted data bit
increases significantly for relatively low traffic loads.
Summary
It is an object of the invention to provide an improved method of communication in a
mobile telecommunication network, an improved base station apparatus, and an
improved computer-readable storage medium.
This object is achieved by the method, the base station apparatus, and the computer-
readable storage medium according to the independent claims. Embodiments
of the invention are given in the dependent claims.
The invention relates to a method of communicating in a cell of a mobile telecom
munication network. A resource of the transmission medium is divided into a plurality
of resource blocks. Each resource block is defined by a time period and a frequency
interval within a time-frequency continuum. The resource blocks are used
for scheduling data transmissions in said telecommunication network.
In other words, when data transmissions are scheduled on resource blocks the time
and the frequency interval for the data transmissions is determined by the resource
blocks.
An amplifier amplifies signals, which are transmitted by the base station. The load of
the amplifier in a time period mainly depends on the number of resource blocks that
are scheduled for this time period. It is to be noted that only a part of the resource
blocks is used for scheduling data transmissions on them. Some resource blocks
may be only used for transmitting pilots. The output load also comprises resource
blocks, which are only used for transmitting pilots and not for transmitting data..
A traffic load is measured in the cell and subsequently it is determined, if the traffic
load is lower than a first traffic load threshold. A maximum used output load of an
amplifier of the base station is decreased, if the traffic load is lower than the first traf¬
fic load threshold. The maximum used output load of the amplifier is limited by the
number of resource blocks, on which data transmissions are scheduled.
The maximum used output load of the amplifier may be decreased by scheduling
data transmissions only on a subset of resource blocks and/or by decreasing a
power level of user data at an input of the amplifier in some or all of the scheduled
resource blocks.
If the traffic load is lower than the first traffic load threshold, an operation point of the
amplifier of the base station of the cell is adjusted. The operation point of the ampli¬
fier is defined by the signal power level of the signals at the input of the amplifier
and the signal output level at the output of the amplifier. Decreasing the maximum
used output load of the amplifier results in decreasing the input voltage at the input
of the power amplifier and decreasing the maximum output voltage at the output of
the amplifier. In other words, the operation point of the amplifier would automatically
be set to lower input and output signal levels. This means that the operation point is
located further away from a saturation value for a relatively low maximum used out¬
put load than for a higher maximum used output load.
Adjusting the operation point may be described herein also as decreasing the saturation
point of the amplifier. In other words, if the traffic load is lower than the first
traffic load threshold, the saturation point of the power amplifier is decreased. De¬
creasing the saturation point may for example be performed by decreasing the bias
voltage of the amplifier and/or by switching off a subset of amplifier components or
stages, when the amplifier comprises a plurality of amplifier components or stages.
Hence, adjusting the operation point of the amplifier could also be referred to as ad¬
justing the saturation value of the amplifier.
It is also determined, if the traffic load is higher than a second traffic load threshold.
If so, the maximum used output load of the amplifier of the base station is increased
and the operation point of the amplifier is consequently adjusted. Adjusting the op¬
eration point of the amplifier is performed correspondingly to the above described
adjustment, when the traffic load is higher than the second traffic load threshold.
Preferably, the operation point of the amplifier is set to a higher value by increasing
the bias voltage and/or by switching on amplifier components or stages of the ampli¬
fier, when the traffic load is higher than the second traffic load threshold.
It is to be noted that the first and the second traffic load threshold may be changed
dynamically. Thus, the thresholds do not need to be constant over the time. The first
and the second traffic load threshold may also be the same value. Preferably, the
second traffic load threshold is a higher value than the first traffic load threshold.
According to embodiments of the invention adjusting the operation point is per¬
formed by decreasing the bias voltage of the amplifier, if the traffic load is lower than
the first traffic load threshold. Adjusting the operation point is performed by increas¬
ing the bias voltage of the amplifier, if the traffic load is higher than the second traffic
load threshold.
According to embodiments of the invention the amplifier comprises a plurality of
amplifier components or stages. Adjusting the operation point may be performed by
switching off a subset of amplifier components or stages if the traffic load is lower
than the first traffic load threshold. If the traffic load is higher than the second traffic
load threshold, adjusting the operation point may be performed by switching on said
amplifier components or stages.
According to embodiments of the invention decreasing the output load of the ampli¬
fier is performed by determining a first subset of resource blocks. All resource
blocks of the first subset are also comprised by the plurality of resource blocks. In
other words, the plurality of resource blocks is the maximum number of resource
blocks and the subset of resource blocks may be less or equal to the maximum of
the resource blocks. Data transmissions are scheduled only on the first subset of
resource blocks, if the traffic load is lower than the first traffic load threshold. In other
words, not every resource block is used for scheduling data transmissions. Only the
first subset is used for scheduling data transmissions. It is to be noted that resource
blocks may also be used for transmitting pilots. These resource blocks do not form
part of the first subset.
The subset of resource blocks may be dynamically determined. This means that the
number of resource blocks in the first subset may vary over time also when the traf¬
fic load does not vary. In other words, the subset of resource blocks may be
changed, although the traffic load does not pass the first traffic load threshold. This
allows the scheduler to select for each time period a subset of resource blocks with
good transmission performance and to avoid using resource blocks with poor
transmission performance.
Increasing the output load of the amplifier is performed by determining a second
subset of resource blocks. All resource blocks of the second subset are also comprised
by the plurality of resource blocks. The second subset comprises more re¬
source blocks than the first subset. If the traffic load is higher than the second traffic
load threshold, data transmissions are scheduled only on the second subset of re¬
source blocks. In other words, when the traffic load exceeds the second traffic load
threshold, more resource blocks are used for scheduling data transmissions than in
the case when the traffic load is lower than the first traffic load threshold. The sec¬
ond subset of resource blocks may also vary in time, although the traffic load may
always be higher than the second traffic load threshold.
According to embodiments of the invention decreasing the output load of the ampli¬
fier is performed by decreasing a power level of user data at an input of the amplifier
in some or all of the scheduled resource blocks. A modulation encoding scheme
being used for transmitting said resource blocks may be changed. In other words,
when the power level of user data at the input of the amplifier is decreased a lower
modulation encoding scheme is used for transmitting said resource blocks. A lower
modulation encoding scheme means that data transmissions become more robust
against interferences and noise. Hence, a lower modulation encoding scheme can
compensate for the decreased power level. Increasing the output load of the ampli¬
fier is performed by increasing the power level of user data at the input of the amplifier
in some or all of the scheduled resource blocks. In this case the modulation en¬
coding scheme has also changed. Preferably a higher modulation encoding scheme
is then used for transmitting said resource blocks. A higher modulation encoding
scheme results in a higher data rate for the data transmission.
According to embodiments of the invention the method comprises a timer. The timer
defines a time. The timer is started directly after having decreased or increased the
output load of the amplifier. A further increasing or decreasing of the output load is
disabled during the time defined by the timer. In other words, the timer avoids
switching too fast between different output loads of the amplifier.
According to embodiments of the invention a time schedule is used for predetermin¬
ing a development of the traffic load. The development of the traffic load is used for
determining, if the maximum used output load of the amplifier and/or the operation
point of the amplifier is adjusted. For example, on a Monday morning between 5 and
8 a.m. a traffic load above the second traffic load is expected and this sets an in¬
creasing of the maximum used output load of the amplifier. The time schedule can
for example define times and/or days with higher and/or lower traffic loads. Hence,
using the time schedule for predetermining the development of the traffic oad
means that the traffic load is determined for a future time period by using the time
schedule.
The time schedule may be fixed or the time schedule may be changed dynamically.
For dynamically changing the time schedule, results of measured traffic loads are
stored in the base station. The time schedule is then generated or changed by using
these results. For example the results show that on a Friday afternoon between 5
p.m. and 6 p.m. the traffic load always decreases by 20%. If the time schedule
would predict a decreasing of only 10%, the time schedule is changed by using the
measurement results.
According to embodiments of the invention the determination if the traffic load is
lower than the first traffic load threshold or higher than the second traffic load
threshold is triggered by the traffic load. In other words, when the traffic load passes
by the first or the second traffic load threshold, the determination is triggered. An¬
other approach could be to determine the traffic load regularly. The time intervals for
the determination may be periodical or depending on the time schedule.
According to embodiments of the invention the method further comprises adjusting
at least one signal processing part of the base station after decreasing or increasing
the output load of the amplifier. The at least one signal processing part processes
signals before the signals are transmitted by the base station. The signal processing
part may for example be executing clipping algorithm in the digital signal condition¬
ing part of the transceiver, processing hardware for baseband processing, and/or
signal processing hardware in the digital signal processing circuit.
According to embodiments of the invention data is scheduled to be transmitted at a
later point of time after measuring the traffic load, if the traffic load in the cell would
be higher than the second traffic load threshold, when said data would be transmitted
directly, and if the traffic load in the cell is lower than the second traffic load
threshold when said data is transmitted at the later point of time. In other words, the
scheduler reduces the traffic load by delaying data transmissions. This may be ad¬
vantageous for avoiding increasing the maximum used output load of the amplifier.
According to embodiments of the invention the amplifier is switched off, when no
data transmissions are scheduled. It is to be noted that in this case the data trans¬
missions are to be understood as comprising user data and control data.
According to embodiments of the invention pilots, synchronization information,
and/or a control channel are transmitted from the base station only for the currently
used subset of resource blocks. For example if only the first subset of resource
blocks is used, no pilots are transmitted for the rest of the resource blocks not be¬
longing to the first subset of resource blocks.
According to embodiments of the invention the base station transmits a signal to a
neighboring base station or a central network entity of the mobile telecommunication
network. The neighboring base station is comprised by a neighboring cell. The sig¬
nal is indicative of information about the subset of resource blocks currently being
used by the base station. The neighboring base station or the central network entity
uses this information for determining a further subset of resource blocks for schedul¬
ing data transmissions in the neighboring cell. In other words, by transmitting said
signals the base stations of the mobile telecommunication network determine in a
centralized or decentralized manner the use of which subsets of resource blocks in
which cell is most advantageous. In the decentralized manner the central network
entity manages exchanging of the signals and determining the subsets for each cell.
In another aspect the invention relates to a base station apparatus, wherein the
base station apparatus is located in a cell of a mobile telecommunication network.
The base station apparatus comprises an amplifier for amplifying signals and an¬
tenna means for transmitting the amplified signals and for receiving signals. The
base station apparatus further comprises a processor, which is adapted for execut¬
ing program instructions stored on a storage medium.
The processor is adapted for determining, if the traffic load is lower than a first traffic
load threshold. Means for decreasing a maximum used output load of the amplifier
of the base station may be implemented by the processor. It is to be noted that the
means for decreasing the maximum used output load decrease the maximum used
output oad of the amplifier, if the traffic load is lower than the first traffic load
threshold. The amplifier amplifies the signals being transmitted by the base station.
The base station apparatus further comprises means for adjusting an operation
point of the amplifier of the base station, if the traffic load is lower than the first traffic
load threshold. The base station further comprises means for determining, if the traf¬
fic load is higher than a second traffic load threshold and means for increasing the
maximum used output load of the amplifier, if the traffic load is higher than the sec¬
ond traffic load threshold. Furthermore, the base station apparatus comprises
means for adjusting the operation point of the amplifier, if the traffic load is higher
than the second traffic load threshold.
In yet another aspect the invention relates to a computer-readable storage medium
comprising instructions that when executed by a base station apparatus cause the
base station apparatus to perform a method of communicating in a cell of a mobile
telecommunication network. At least one resource is divided into a plurality of re¬
source blocks. The resource blocks are used for scheduling data transmissions in
said telecommunication network. The method comprises measuring a traffic load in
the cell, determining, if the traffic load is lower than a first traffic load threshold, decreasing
a maximum used output load of an amplifier of the base station, if the t raf
fic load is lower than the first traffic load threshold. The amplifier amplifies signals
being transmitted by the base station.
An operation point of the amplifier is adjusted, if the traffic load is lower than the first
traffic load threshold. Further it is determined, if the traffic load is higher than a sec¬
ond traffic load threshold. The maximum used output load of the amplifier of the
base station is increased, if the traffic oad is higher than the second traffic load
threshold. The operation point of the amplifier is adjusted, if the traffic load is higher
than the second traffic load threshold.
Brief description of the drawings
In the following embodiments of the invention are explained in greater detail, by way
of example only, making reference to the drawings in which:
is a schematic view of characteristic curves of a base station amplifier
Fig. 2 is a schematic view of resource blocks,
is a schematic view of a subset of resource blocks being used for
scheduling data transmissions over a time of 10 succeeding resource
blocks,
Fig. 4 is a schematic view of a subset of resource blocks with resource
blocks varying over time,
is a block diagram of a base station apparatus according to embodi¬
ments of the invention, and
is a flow diagram of a method according to embodiments of the inven
tion.
Detailed description
Like numbered elements in these Figs are either identical elements or perform the
same function. Elements which have been discussed previously will not necessarily
be discussed in later Figs, if the function is identical.
Fig. 1 is a schematic view of characteristic curves of a base station amplifier. Each
diagram consists of a characteristic curve and a corresponding traffic load diagram
of the traffic load in the respective cell. Fig. 1a shows the characteristic curve for a
state of the art amplifier in a cell with a relatively high traffic load. Fig. 1b illustrates
the characteristic curve of the state of the art amplifier in a cell with a relatively low
traffic load. The higher the traffic load the higher is the operation point of the ampli¬
fier. In other words, for higher traffic loads the operation point is located nearer to a
saturation point 100 of the amplifier. Fig. a shows the characteristic curve of an
amplifier and the operation point 102 in a cell with a relatively high traffic load. The
maximum used operation point 112 of the amplifier lies for a high traffic load near
the saturation value 100. For a relatively low traffic load depicted in Fig. 1 , the op¬
eration point 104 of the amplifier is located at a lower point of the characteristic
curve, further away from the saturation point. This means that the amplifier con¬
sumes more power than necessary for sufficiently amplifying the signals.
Figs. 1c and 1d show the operation points 106 and 108 of the power amplifier oper¬
ated with adjustment of the saturation power level according to embodiments of the
invention. For a relatively high traffic load as depicted in Fig. 1c no difference can be
seen to Fig. 1a. But in Fig. 1d the amplifier is operated with a lower saturation power
level and the maximum used operation point 118 of the amplifier lies close to the
adjusted saturation point 101 in case of a low traffic load. This means that the power
consumption of the amplifier is reduced, because it is operated more efficiently than
in Fig 1c.
Adjusting the operation point may for example be performed by reducing the num¬
ber of resource blocks used for scheduling data transmission and reducing the bias
voltage of the amplifier. By reducing the number of resource blocks used for sched¬
uling data transmissions, the maximum used output load of the amplifier is de¬
creased. And by reducing the bias voltage of the amplifier, the saturation point of the
amplifier is decreased, which results - as can be seen in Fig. 1d - in an approach of
the saturation value 101 towards the operation point 108 and the maximum used
operation point 118.
According to embodiments of the invention a maximum cell output power should be
adapted to the traffic load allowing for a reconfiguration of the amplifier. The motiva¬
tion is that the scheduler of a base station can be configured to utilize only a fraction
of the resource elements so that it is assured that the power amplifier output is sig¬
nificantly lower than the maximum output. In this case the amplifier can be reconfig¬
ured such it operates much more efficiently. Such reconfiguration comprises e.g. the
power supply of the power amplifier which can use lower bias voltage, so that less
DC input power is consumed, and an adaptation of the clipping threshold in the digi¬
tal signal conditioning part of the transceiver. Estimations show that for typical daily
load profiles up to 30% power saving can be expected on daily average.
The scheduler predicts the required maximum capacity for the near future, e.g. from
typical daily traffic patterns and/or from the traffic that was served in the latest sec¬
onds or minutes. Also the number of connected mobile devices such as mobile
phones, PDAs, and/or mobile computers or the requested number of services by the
connected mobile devices can be used for the estimation. Within the predicted ca¬
pacity range the scheduler is still free to select the best resource elements from the
full cell bandwidth. When at a later time the prediction for the near future changes,
the operation point of the amplifier is adapted. The transition of the amplifier opera¬
tion point can be smoothed out over several seconds to allow digital signal processing
algorithms to adapt with minimum signal distortion.
Each resource element is still transmitted with the same spectral power density so
the coverage area and link quality of the cell is not impacted. The method does not
require modifications in the mobile device.
Fig. 2 is a schematic view of a plurality of resource blocks 202 in a downlink channel
according to the 3GPP Long Term Evolution (LTE) standard. Each resource blocks
comprise a plurality of resource elements 200. The resource elements are defined
by a period of time 204 and a frequency interval 206. Consequently, a physical resource
block is also defined by a larger period of time and a larger frequency inter¬
val. For example if a resource block 202 comprises 168 resource elements and
each resource element is defined by a period of time 204 of 0.07ms and a frequency
interval 206 of 5kHz, the resource block 200 is defined by a time of 1ms and a fre¬
quency interval of 180kHz.
Fig. 3 is a schematic view of a plurality of resource blocks 202. It is to be noted that
only a subset 300 of resource blocks is used for scheduling data transmissions. Two
other subsets 302 and 304 are not used for scheduling data transmission. In Fig. 3
only one third of the frequency interval is used. This results in the fact that the power
amplifier can be operated with only one third of the maximum transmission power.
Also pilots 306 of the subsets 302 and 304 not being used for scheduling data
transmissions are suppressed. This may be optionally performed for saving more
power.
Fig. 4 is a schematic view of a subset 400 of resource blocks, which varies over
time. Over the whole time only one third of the resource blocks is used for schedul¬
ing. This means the subset 400 of resource blocks always comprises one third of
the plurality of resource blocks, but not always the same frequency interval is used
for scheduling data transmissions. This may be advantageous for opportunistic re¬
source allocation, because the scheduler can still use the full scheduling diversity. In
this case all pilots need to be sent. Interferences with neighboring cells may be re¬
duced by this subset of resource blocks varying in time.
For example the base station may measure the average traffic load of the last 5
minutes and estimates the required capacity in the next 15 minutes. When e.g. 50%
of the capacity is enough to serve the ongoing traffic, the scheduler limits the num¬
ber of resource blocks that may be scheduled in one subframe to 50% of the maxi¬
mum. This limits the maximum amplifier output and thus allows reducing the bias
voltage and potentially also the peak to average power ratio (PAPR) of the power
amplifier for the next 15 minutes. This will reduce the 3dB compression point of the
amplifier characteristic but due to the known limit of output power the bias voltage
can be safely selected so that no saturation of output signal occurs. An example
scenario for a macro cell is given in the following table, using typical output power
for LTE macro cells with standardized bandwidth. These output powers apply also
for a 20 MHz cell with limited scheduling within the full bandwidth, because the
power amplifier performance does not significantly depend on the distribution of the
scheduled resource blocks within the bandwidth.
Bandwidth Number of Re¬ Relative capac¬ Cell output
source Blocks ity to 20MHz power
per subframe bandwidth
1.4 MHz 6 6% 3 dBm
3 MHz 15 15% 40 dBm
5 MHz 25 25% 43 dBm
10 MHz 50 50% 46 dBm
15 MHz 75 75% 48 dBm
20 MHz 100 100% 49 dBm
For example a cell operating at 20 MHz will require 49dBm of radio frequency output
power at full average oad (e.g. in busy hours). During night times with only 5% of
load the scheduler may be limited to a maximum of 6 resource blocks per subframe.
In this case the maximum average output power is only 37dBm and thus the saturation
power level may be reduced by as much as 12dB. The saturation power is
mainly given by the DC power supply voltage of the power amplifier, which in turn
drives a bias current. Lowering the saturation power level thus lowers the DC power
consumption of the power amplifier. Additionally, for lower capacity utilization the
PAPR may be lower so that the new saturation level can be chosen with lower
backoff, i.e. closer to the average power level given in the above table. This enables
even higher power savings than the table suggests.
Other embodiments may use other time scales for adaptation, in the range of sec
onds to hours.
Further embodiments may use additional power saving methods utilizing the limited
capacity utilization of the scheduler. For example, lower data scheduling reduces
the calculation effort of base band processing, so the base band processing hard¬
ware may be operated in a power save mode, e.g. by reducing the clock rate or
switching off some parts of parallel processing circuits. Also other parts of the base
station can benefit from the reduced resource utilization. A control interface can be
used between the scheduler and those software and hardware components to trig¬
ger their switching of energy saving modes.
According to embodiments of the invention the base station uses a time schedule of
the traffic behavior of the cells and configures accordingly the periods with defined
capacity limitations of the scheduler. The following table shows an example of the
capacity limit and the output power limit for working days and weekend in 5 steps
each:
Hour Working day Weekend
0h - 5h 15% and 40 dBm 6% and 37 dBm
5h - 8h 15% and 43 dBm 15% and 40 dBm
8h - 12h 50% and 46 dBm 25% and 43 dBm
12h - 18h 100% arid 49 dBm 50% and 46 dBm
18h - 24h 50% and 46 dBm 50% and 46 dBm
There are 2 possibilities for the initiation of such a modification either by a central¬
ized approach, where the Operating and Maintenance Network (O&M) signals the
new configuration in terms of capacity limitations and output power towards the concerned
cell as well as to their neighbor cells, or by a decentralized approach, where
the base station is responsible for the new settings by using appropriate selfoptimization
algorithms. In the latter case the configured values will be exchanged
over the 3GPP X2 interface to concerned neighbor cells, which need the information
for the configuration of the Allowed MeasBandwidth, which is specified in 3GPP TS
36.331 .
According to embodiments of the invention the adaptation of capacity is combined
with switching off the power amplifier during fractions of a millisecond when actually
no resource element is scheduled. In this case the scheduler could aggregate
scheduled resource elements as much as possible within the capacity limitation to
create as many time intervals as possible where no data or reference signals are to
be transmitted .
According to embodiments of the invention the scheduler communicates the limitation
of resource scheduling to one or several neighbouring cells. These cells can
coordinate which elements are scheduled to reduce interference. For example in a
situation with 50% load cell 1 could use all even resource blocks and cell 2 all odd
blocks. Both cells save energy according to this invention. At the same time the in¬
terference between the cells is drastically reduced. The lower interference level can
be leveraged to transmit at a higher modulation scheme, which further reduces the
load level and yields more saving potential by further capacity limitation of the
scheduler.
In yet another embodiment the scheduler triggers changes of the used capacity not
only to the DC power supply of the power amplifier (to change the bias voltage) but
also to the digital signal processing. This may allow reducing transient effects in the
signal quality and speed up the adaptation of the digital signal processing. For example
the thresholds of the clipping algorithm can be adapted synchronously to the
upcoming change of power amplifier operation point. This requires implementation
specific changes in the control interfaces of the base station hardware and might
require modification of standardized equipment or interfaces.
Further pilots of subcarriers not belonging to the center band and thus not to the
subcarriers foreseen to schedule data to mobile devices might be suppressed to¬
gether with some adaptation of cell individual offsets used for mobility measure¬
ments by the mobile devices. As an alternative a special offset parameter could be
introduced. This would allow saving pilot transmission power overhead for cases
were cells are empty or nearly empty.
Fig. 5 is a block diagram of a base station apparatus 500. The base station apparatus
comprises a digital storage 502, an amplifier 506, an antenna 508, and a proc¬
essor 5 10. Program instructions 504 are stored in digital storage 502.
In operation, the amplifier 506 amplifies signals, which are subsequently transmitted
via antenna 508. The processor 510 is adapted for executing program instructions
504. The processor 5 10 is further adapted for scheduling data transmissions on re¬
source blocks. The program instructions 504 executed by the processor 5 10 cause
the base station apparatus 500 to measure or calculate a traffic load in the cell (not
depicted) served by the base station apparatus 500.
The processor 510 is further adapted for determining, if the traffic load is lower than
a first traffic load threshold or higher than a second traffic load threshold. A maxi¬
mum used output load of the amplifier 506 is decreased, if the traffic load is lower
than the first traffic load threshold. The maximum used output load of the amplifier
506 is increased, if the traffic load is higher than the second traffic load threshold. n
both cases, the operation point of the amplifier 506 is subsequently adjusted for o p
timizing power consumption of the base station apparatus 500.
Fig. 6 is a flow diagram of a method according to embodiments of the invention. In a
first step S 1 a traffic load in the cell is measured or calculated. Then, in step S2, it is
determined if the traffic oad is lower than a first traffic load threshold or higher than
a second traffic load threshold.
If the traffic load is lower than the first traffic load threshold, the method proceeds to
step S3 of Fig. 6. Step S3 comprises decreasing a maximum used output load of the
amplifier of the base station. This may for example be performed by scheduling data
transmissions only on a subset of resource blocks and/or by decreasing a power
level of user data at an input of the amplifier in some or all of the scheduled re¬
source blocks.
If the traffic load is higher than the second traffic load threshold, the method goes
from step S2 to step S5. Step S5 comprises increasing the maximum used output
load. This may be performed correspondingly to step S3 by scheduling data trans¬
missions on more resource blocks and/or by increasing the power level of user data
at the input of the amplifier. In other words, performing step S5 has the opposite
effect of performing step S3.
In both cases, the operation point of the amplifier is adjusted in step S4. This may
for example be performed by decreasing the bias voltage of the amplifier, if step S3
has been performed previously, or by increasing the bias voltage, if step S5 has
been performed previously.
List of Reference Numerals
100 saturation value
102 operation point
104 operation point
106 operation point
108 operation point
112 maximum used operation point
114 maximum used operation point
116 maximum used operation point
118 maximum used operation point
200 resource element
202 resource blocks
204 time
206 frequency interval
300 subset of resource blocks
302 subset of resource blocks
304 subset of resource blocks
306 pilots
400 subset of resource blocks
500 base station
502 digital storage
504 program instructions
506 amplifier
508 antenna
510 processor
C l a i s
1. A method of communicating in a cell of a mobile telecommunication
network, wherein a resource is divided into a plurality of resource blocks
(202), each resource block being defined by a time period (204) and a
frequency interval (206), wherein the resource blocks (202) are used for
scheduling data transmissions in said telecommunication network, wherein
the method comprises the following steps:
- measuring (S1 ) a traffic load in the cell;
- determining (S2), if the traffic load is lower than a first traffic load
threshold;
- decreasing (S3) a maximum used output load of an amplifier (506)
of the base station, if the traffic load is lower than the first traffic load
threshold, wherein the amplifier (506) amplifies signals being
transmitted by the base station;
- adjusting (S4) an operation point (102; 104; 106; 108; 112; 114;
116; 118; 124) of the amplifier (506), if the traffic load is lower than
the first traffic load threshold;
- determining (S2), if the traffic load is higher than a second traffic
load threshold;
- increasing (S5) the maximum used output load of the amplifier (506)
of the base station, if the traffic load is higher than the second traffic
load threshold; and
- adjusting (S4) the operation point ( 102; 104; 106; 108; 112; 114;
116; 118; 124) of the amplifier (506), if the traffic load is higher than
the second traffic load threshold;
- defining a time by a timer, wherein the timer is started directly after
having decreased or increased the output load of the amplifier (506),
and wherein a further increasing or decreasing of the output load is
disabled during the time defined by the timer.
2 . Method according to claim , wherein adjusting the operation point ( 102;
104; 106; 108; 112; 114; 116; 118; 124) is performed by decreasing the
bias voltage of the amplifier (506), if the traffic load is lower than the first
traffic load threshold, and wherein adjusting the operation point (102; 104;
106; 108; 112; 14; 1 6; 118; 124) is performed by increasing the bias
voltage of the amplifier (506), if the traffic load is higher than the second
traffic load threshold.
3. Method according to claim 1, wherein the amplifier (506) comprises a
plurality of amplifier components, wherein adjusting the operation point
(102; 104; 106; 108; 112; 114; 116; 118; 124) is performed by switching off
a subset of amplifier components, if the traffic load is lower than the first
traffic load threshold, and wherein adjusting the operation point (102; 104;
106; 108; 112; 114; 116; 118; 124) is performed by switching on said
amplifier components, if the traffic load is higher than the second traffic
load threshold.
4. Method according to any one of the preceding claims, wherein decreasing
the output load of the amplifier (506) is performed by
- determining a first subset (300; 400) of resource blocks, wherein all
resource blocks of the first subset (300; 400) are also comprised by
the plurality of resource blocks (202);
- scheduling data transmissions only on the first subset (300; 400) of
resource blocks, if the traffic load is lower than the first traffic load
threshold;
and wherein increasing the output load of the amplifier (506) is performed by
- determining a second subset of resource blocks, wherein all
resource blocks of the second subset are also comprised by the
plurality of resource blocks (202), and wherein the second subset
comprises more resource blocks than the first subset;
- scheduling data transmissions only on the second subset of
resource blocks, if the traffic load is higher than the second traffic
load threshold.
5. Method according to any one of the preceding claims, wherein decreasing
the output load of the amplifier (506) is performed by
- decreasing a power level of user data at an input of the amplifier
(506) in some or all of the scheduled resource blocks and changing
a modulation and coding scheme being used for transmitting said
resource blocks;
and wherein increasing the output load of the amplifier (506) is performed by
- increasing the power level of user data at the input of the amplifier
(506) in some or all of the scheduled resource blocks and changing
the modulation and coding scheme being used for transmitting said
resource blocks.
6. Method according to any one of the preceding claims, wherein a time
schedule is used for predetermining a development of the traffic load, and
wherein the development of the traffic load is used for determining if the
maximum used output load of the amplifier (506) and/or the operation point
(102; 104; 106; 108; 112; 114; 116; 118; 124) of the amplifier (506) is
adjusted.
7. Method according to any one of the preceding claims, wherein the
determination, if the traffic load is lower than the first traffic load threshold
or higher than the second traffic load threshold, is triggered by the traffic
load.
8. Method according to any one of the preceding claims, wherein the method
further comprises adjusting at least one signal processing part of the base
station after decreasing or increasing the output load of the amplifier (506),
wherein the at least one signal processing part processes signals before
the signals are transmitted by the base station.
9. Method according to any one of the preceding claims, wherein data is
scheduled to be transmitted at a later point of time after measuring the
traffic load, if the traffic load in the cell would be higher than the second
traffic load threshold, when said data would be transmitted directly, and if
the traffic load in the cell is lower than the second traffic load threshold,
when said data is transmitted at the later point of time.
10. Method according to any one of the preceding claims, wherein the amplifier
(506) is switched off, when no data transmissions are scheduled.
11.Method according to any one of the preceding claims, wherein pilots,
synchronization information, and/or a control channel are transmitted from
the base station only for the currently used subset of resource blocks.
12. Method according to any one of the preceding claims, wherein the base
station transmits a signal to a neighbouring base station or a central
network entity of the mobile telecommunication network, the neighbouring
base station being comprised by a neighbouring cell, wherein the signal is
indicative of information about the subset of resource blocks currently
being used by the base station, and wherein the neighbouring base station
or the central network entity uses this information for determining a further
subset of resource blocks for scheduling data transmissions in the
neighbouring cell.
13.A base station apparatus (500), the base station apparatus being located in
a cell of a mobile telecommunication network, wherein the base station
apparatus comprises:
- an amplifier (506) for amplifying signals;
- antenna means (508) for transmitting the amplified signals and for
receiving signals;
- means (51 0) for determining, if the traffic load is lower than a first
traffic load threshold;
- means (51 0) for decreasing a maximum used output load of the
amplifier (506) of the base station, if the traffic load is lower than the
first traffic load threshold;
- means (510) for adjusting an operation point (102; 104; 106; 108;
1 2 ; 114; 116; 118; 124) of the amplifier (506), if the traffic load is
lower than the first traffic load threshold;
- means (51 0) for determining, if the traffic load is higher than a
second traffic load threshold;
- means (51 0) for increasing the maximum used output load of the
amplifier (506), if the traffic load is higher than the second traffic load
threshold;
- means (510) for adjusting the operation point (102; 104; 106; 108;
112; 1 4; 116; 118; 124) of the amplifier (506), if the traffic load is
higher than the second traffic load threshold; and
- a timer, the timer defining a time, wherein the timer is started directly
after having decreased or increased the output load of the amplifier
(506), and wherein a further increasing or decreasing of the output
load is disabled during the time defined by the timer.
14.A computer-readable storage medium (502) comprising instructions (504)
that when executed by a base station apparatus (500) cause the base
station apparatus to perform a method of communicating in a cell of a
mobile telecommunication network, wherein at least one resource is
divided into a plurality of resource blocks (202), the resource blocks (202)
being used for scheduling data transmissions in said telecommunication
network, wherein the method comprises the following steps:
- measuring a traffic load in the cell;
- determining, if the traffic load is lower than a first traffic oad
threshold;
- decreasing a maximum used output load of an amplifier (506) of the
base station, if the traffic load is lower than the first traffic load
threshold, wherein the amplifier (506) amplifies signals being
transmitted by the base station;
- adjusting an operation point (102; 04; 106; 108; 112; 114; 116;
118; 124) of the amplifier (506), if the traffic load is lower than the
first traffic load threshold;
- determining, if the traffic load is higher than a second traffic load
threshold;
- increasing the maximum used output load of the amplifier (506) of
the base station, if the traffic load is higher than the second traffic
load threshold;
- adjusting the operation point (102; 104; 106; 108; 112; 114; 116;
118; 24) of the amplifier (506), if the traffic load is higher than the
second traffic load threshold; and
- defining a time by a timer, wherein the timer is started directly after
having decreased or increased the output load of the amplifier (506),
and wherein a further increasing or decreasing of the output load is
disabled during the time defined by the timer.