WO2015036014A1

WO2015036014A1 - Dynamic dagc update rate

Info

Publication number: WO2015036014A1
Application number: PCT/EP2013/068753
Authority: WO
Inventors: Magnus Nilsson; Anders Lamm; Marc MJÖGEMAN
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2013-09-10
Filing date: 2013-09-10
Publication date: 2015-03-19

Abstract

The embodiments herein relate to a method in a first network node (201) for handling power changes in data traffic. When power of the data traffic is increasing compared to previous traffic, the first network node (201) performs digital automatic gain control of the data traffic using at least one of a first update rate and a first step size. When the power of the data traffic is decreasing compared to the previous traffic, the first network node (201) performs digital automatic gain control of the data traffic using at least one of a second update rate and a second step size. The first update rate is different from the second update rate and the first step size is different from the second step size, or the first update rate is different from the second update rate, or the first step size is different from the second step size.

Description

DYNAMIC DAGC UPDATE RATE

TECHNICAL FIELD

5

Embodiments herein relate generally to a first network node and a method in the first network node. More particularly the embodiments herein relate to handling power changes in data traffic received from a second network node in a communications network.

o

BACKGROUND

In a typical communications network a wireless device, communicates via a Radio Access 5 Network (RAN) to one or more Core Networks (CNs). The communications network may also be referred to as e.g. a wireless communications network, a wireless

communications system, a communications network, a communications system, a network or a system. 0 The wireless device may be a device by which a subscriber may access services offered by an operator's network and services outside the operator's network to which the operator's radio access network and core network provide access, e.g. access to the Internet. The wireless device may be any device, mobile or stationary, enabled to communicate over a radio channel in the communications network, for instance but not5 limited to e.g. user equipment, terminal, mobile station, mobile phone, smart phone, sensors, meters, vehicles, household appliances, medical appliances, media players, cameras, Machine to Machine (M2M) device or any type of consumer electronic, for instance but not limited to television, radio, lighting arrangements, tablet computer, laptop or Personal Computer (PC). The device may be portable, pocket storable, hand0 held, computer comprised, or vehicle mounted devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another wireless device or a server.

The wireless devices are enabled to communicate wirelessly within the communications5 network. The communication may be performed e.g. between two wireless devices, between a wireless device and a regular telephone and/or between the wireless devices and a server via the radio access network and possibly one or more core networks and possibly the Internet.

5 The radio access network covers a geographical area which may be divided into cell areas, with each cell area being served by a network node such as a base station. In some radio access networks, the base station is also called Radio Base Station (RBS), evolved NodeB (eNB), NodeB or B node. A cell may be described as a geographical area where radio coverage is provided by the base station at a base station site. The base o station communicates with the wireless devices within range of the base station.

AGC is an acronym for Automatic Gain Control or Automatic Gain controller. The AGC may be found in any device or system where wide amplitude variations in an output signal may lead to a loss of information or to an unacceptable performance of the system/device. 5 This way, saturation of various circuit blocks in the device or system may be avoided. The role of the AGC is to automatically adjust the gain of an input signal in order to provide a relatively constant output amplitude. This means that units following the AGC require less dynamic ranges. AGC may also be described as an adaptive system where the average output signal level is fed back to adjust the gain to an appropriate level for a range of input0 signal levels. For example, without the AGC the sound emitted from an Amplitude

Modulation (AM) radio receiver would vary to an extreme extent from a weak to a strong signal. The AGC effectively reduces the volume if the signal is strong and raises it when it is weaker. 5 AGCs are widely applied in digital communication systems and are in such scenarios referred to as DAGC. DAGC is an acronym for Digital Automatic Gain Control or Digital Automatic Gain Controller. Quantization and DAGC may be commonly used in at least one network node of the communications network in order to reduce the bandwidth of an input signal to e.g. save transmission capacity as well as power used for signal

0 processing of the signal. The DAGC performs continuous adjustments in a network

node's gain in order to maintain a relative constant output signal. Quantization is a procedure of constraining something from a continuous set of values to a relatively small discrete set, i.e. the process of mapping a large set of input values to a smaller set - such as rounding values to some unit of precision. A device that performs quantization is5 called a quantizer. One purpose of a DAGC is to scale the input signal so that the information of the quantized signal is maximized even though the amplitude and thus the power of the signal changes.

5

A scale factor of the DAGC is updated as the signal level changes. In general, a scale factor is a number which scales, or is multiplied to, some quantity. The update rate of the scale factor is the frequency of possible changes of the scale factor. The update rate may also be referred to as a frequency. A step size is the magnitude by which the scale factor o may be changed during an update. Thus, the combination of update rate and step size will determine how well the DAGC may preserve the information of the signal and thus in the end the overall performance of the communications network.

Figure 1 illustrates an embodiment of a DAGCs functionality with an update rate and step 5 size in order to preserve information of a quantized signal. The x-axis of Figure 1

represents time and the y-axis of Figure 1 represents the amplitude of the signal. The update rate is along the x-axis and the steps size is along the y-axis. The continuous line in Figure 1 represents the continuous incoming signal. The vertical lines in Figure 1 represents the window/range which the digital automatic gain controlled signal should be0 within.

During the circumstances that the input signal does not change power rapidly, the DACG may be designed to change the scale factor slowly. Such relatively slow changing power was a typical pattern during the initial phase of the Wideband Code Division Multiple5 Access (WCDMA) communications network technology, when most variations were due to admittance of Release '99 (R99) wireless devices. The advantage with a design choice of having a slowly changing DAGC scale factor is that the signal processing after the quantization may be simplified without knowledge of the DAGC scale factor. 0 In current standard design, a constant update rate in the DAGC is applied. For e.g.

(W)CDMA communications networks this update rate is optimized to get sufficient good performance with many Low Data Rate (LDR) services such as e.g. voice or other LDR types. A LDR service may be explained to be a service which does not substantially affect other services in the network.

5 In a communications network with rapid changing power levels, a fast update rate is needed to avoid saturation in the DAGC. Adopting a fast update rate without the DACG scale factor used in baseband, will give degraded performance due to estimation errors. Saturation in the DAGC may be described as when the power of the received data traffic 5 exceeds a certain level, i.e. that the limit of the power has been reached. The level may be referred to as maximum of dynamic range. The level/limit may be fixed by the design of the DAGC. The term baseband mentioned above may describe signals and systems whose range of frequencies is measured from close to 0 hertz to a cut-off frequency (a maximum bandwidth or highest signal frequency). Baseband may sometimes be used as o a noun for a band of frequencies starting close to zero. In other embodiments, a

baseband processor may be described as a chip in wireless devices that performs signal processing and implements the wireless device's real-time radio transmission operations.

With the current standard, a fixed update rate and fixed step size is used in the DAGC 5 tracking. The DAGC tracks the incoming continuous signal with the same fixed update rate and step size when the power of the received data traffic is both increasing and decreasing. The current standard is a trade-off between up- and down-ramping and may provide discontinuity problems. 0 A problem of the current standard may be that in general a slow DAGC is desired, but it still needs to be fast enough to avoid saturation.

SUMMARY

5

An objective of embodiments herein is therefore to provide improved DAGC in a communications network.

According to a first aspect, the object is achieved by a method in a first network node for0 handling power changes in data traffic received from a second network node in a

communications network. When power of the received data traffic is increasing compared to power of previous received data traffic, the first network node performs digital automatic gain control of the received data traffic using at least one of a first update rate and a first step size. When the power of the received data traffic is decreasing compared to the5 power of the previous received data traffic, the first network node performs digital automatic gain control of the received data traffic using at least one of a second update rate and a second step size. The first update rate is different from the second update rate and the first step size is different from the second step size, or the first update rate is different from the second update rate, or the first step size is different from the second 5 step size.

According to a second aspect, the object is achieved by a first network node for handling power changes in data traffic received from the second network node in the

communications network. The first network node comprises a DAGC. When power of the o received data traffic is increasing compared to power of previous received data traffic, the DAGC is adapted to perform digital automatic gain control of the received data traffic using at least one of a first update rate and a first step size. When the power of the received data traffic is decreasing compared to power of previous received data traffic, the DAGC is adapted to perform digital automatic gain control of the received data traffic 5 using at least one of a second update rate and a second step size. The first update rate is different from the second update rate and the first step size is different from the second step size, or the first update rate is different from the second update rate, or the first step size is different from the second step size. 0 Since the first updated rate is different from the second update rate and the first step size is different from the second step size, or the first update rate is different from the second update rate, or the first step size is different from the second step size, it may be possible for the first network node to adjust fast to large power increases and to adjust slow to smaller power changes. The update rate and step size is dynamic, i.e. they are not fixed.5 This decreases the probability for saturation in the DAGC and it also decreases the

probability of estimation errors, which provides improved DAGC in the communications network.

Embodiments herein afford many advantages, of which a non-exhaustive list of examples0 follows:

One advantage of the embodiments herein may be that a DAGC with different update rates and step sizes may improve network performance and stability for communications networks with mixed services. Mixed services are a mix of both high and low data rate5 services. Another advantage of the embodiments herein may be that as the DAGC adjusts fast to large power increases, but adjusts slow to smaller power changes, the probability for saturation may be decreased and the probability of estimation errors due to an 5 uncompensated DAGC scale factor may also be decreased. This may improve the

performance of a high data rate wireless device.

The low data rate wireless device may also benefit from the embodiments herein. o A further advantage of the embodiments herein may be that they may improve the

spectral efficiency of network nodes which simultaneously transmits information with different traffic profiles.

The embodiments herein are not limited to the features and advantages mentioned 5 above. A person skilled in the art will recognize additional features and advantages upon reading the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

0

The embodiments herein will now be further described in more detail in the following detailed description by reference to the appended drawings illustrating the embodiments and in which: 5 Fig. 1 is a graph illustrating a DAGCs functionality with update rate and step size.

Fig. 2 is a schematic block diagram illustrating embodiments of a

communications network. 0 Fig. 3 is a signaling diagram illustrating embodiments of a method in a

communications network.

Fig. 4 shows graphs illustrating embodiments of a DAGCs functionality with

update rate and step size.

5 Fig. 5 is a schematic block diagram illustrating embodiments of a method in a DAGC.

Fig. 6 is a schematic block diagram illustrating embodiments of a simulation

scenario.

Fig. 7 is a graph illustrating HDR service performance.

Fig. 8 is a graph illustrating LDR service performance.

Fig. 9 is a flow chart illustrating embodiments of a method in a first network node.

Fig. 10 is a schematic block diagram illustrating embodiments of a first network node.

The drawings are not necessarily to scale and the dimensions of certain features may have been exaggerated for the sake of clarity. Emphasis is instead placed upon illustrating the principle of the embodiments herein.

DETAILED DESCRIPTION

Today's industrial standard solution for quantization and DAGC limits the overall capacity of a communications network. The reason is that different applications such as for example a file upload, a web browser or a speech call has significant different traffic profiles. In order to increase the capacity of the communications network, as many as possible of all different traffic profiles should have a good performance in terms of e.g. resource consumption of energy per transmitted information bit. To achieve this, the efficiency of each network node needs to be improved. The embodiments herein provide a method which improves the spectral efficiency of network nodes which simultaneously transmit information with different traffic profiles. Spectral efficiency may also be referred to as spectrum efficiency and bandwidth efficiency and may be measured in bit/s/Hz.

The embodiments herein combine the usage of a slow DAGC with a possibility of fast changes only if a risk of saturation is detected. By limiting the case when the DAGC is fast, the need of using a DAGC scale factor in baseband may be minimized. The gain with avoiding saturation by applying a fast DAGC outperforms the alternative of always having a slow DAGC, still not using the scale factor in baseband.

5 Figure 2 depicts a communications network 200 in which embodiments herein may be implemented. The communications network 200 may in some embodiments apply to one or more radio access technologies such as for example Long Term Evolution (LTE), LTE Advanced, WCDMA, Global System for Mobile Communications (GSM), Worldwide Interoperability for Microwave Access (WiMax), WiFi, or any other Third Generation o Partnership Project (3GPP) radio access technology, or other radio access technologies such as Wireless Local Area Network (WLAN).

The communications network 200 comprises a first network node 201 communicating with a second network node 203 over a communications link 205. In some 5 embodiments, the first network node 201 is a wireless device and the second network node 203 is a base station. In other embodiments, the first network node 201 is a base station and the second network node 203 is a wireless device. A wireless device is served by a base station. 0 The communications network 200 may cover a geographical area which is divided into cell areas. Each cell area is served by a base station. The base station may be referred to as e.g. eNB, eNodeB, NodeB, B node, RBS or Base Transceiver Station (BTS), depending on the technology and terminology used. 5 A wireless device may be a device by which a subscriber may access services offered by an operator's network and services outside an operator's network to which the operator's radio access network and core network provide access, e.g. access to the Internet. The wireless device may be any device, mobile or stationary, enabled to communicate over a radio channel in the communications network, for instance but not limited to e.g. user0 equipment, terminal, mobile station mobile phone, smart phone, sensors, meters, vehicles, household appliances, medical appliances, media players, cameras, M2M device or any type of consumer electronic, for instance but not limited to television, radio, lighting arrangements, tablet computer, laptop or PC. The wireless device may be portable, pocket storable, hand held, computer comprised, or vehicle mounted devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another wireless device or a server.

It should be noted that the communication link 205 between the first network node 201 and the second network node 203 may be of any suitable kind. The link may use any suitable protocol depending on type and level of layer (e.g. as indicated by the Open

Systems Interconnection (OSI) model) as understood by the person skilled in the art.

The method for handling power changes in data traffic received from a second network node 203 in a communications network 200 according to some embodiments will now be described with reference to the signaling diagram depicted in Figure 3 with reference to Figure 4 illustrating embodiments of an uplink data traffic load scenario. The top graph in Figure 4 illustrates an example uplink traffic load scenario. Alternative A in Figure 4 illustrates the current industry setting. Alternatives B and C illustrates the embodiments herein. The method comprises the following steps, which steps may as well be carried out in another suitable order than described below:

Step 301

The second network node 203 transmits data traffic to the first network node 201 . The data traffic may be related to e.g. voice or data. The data traffic may be UpLink (UL) or DownLink (DL) data traffic depending on whether the second network node 203 is a base station or a wireless device and whether the first network node 201 is a base station or a wireless device. UL is in the direction from a wireless device to a base station and DL is in the direction from the base station to a wireless device.

Step 302

The first network node 201 receives the data traffic from the second network node and estimates the traffic load, i.e. the power of the data traffic received in step 301 . Step 303

The first network node 201 determines whether the power of the received data traffic has changed, i.e. whether it has increased or decreased compared to previous received data traffic which was received by the first network node 201 power before step 301 . An example of the change in power may be as seen in the top graph of figure 4. The power has increased from time t1 to time 2 and decreased from time t3 to time t4. Step 304a

If the power of the received data traffic has increased when receiving the data traffic in step 301 , the first network node 201 performs digital automatic gain control of the received data traffic using least one of a first update rate and a first step size. Another criterion for using at least one of the first update rate and the first step size may be that the power change is positive, i.e. above zero, and above a positive threshold. Using other words, that the increase is of a certain size, e.g. that the change is a fast power increase. Step 304b

If the power of the received data traffic has decreased when receiving the data traffic in step 302, the first network node 201 performs digital automatic gain control of the received data traffic using at least one of a second update rate and a second step size. Another criterion for using at least one of the second update rate and the second step size may be that the power change is negative and larger than a negative threshold, i.e. that the decrease is of a certain size.

The update rate and steps sizes are as follows:

• The first update rate is different from the second update rate and the first step size is different from the second step size, or

• The first update rate is different from the second update rate, or

• The first step size is different from the second step size.

The output of steps 304a or 304b of figure 3 is a scaled and quantized output signal , i.e. a signal to which at least one of the first update rate and first step size applied or to which at least one of the second update rate and the second step size is applied.

Steps 304a and 304b above may be exemplified in alternatives B and C in Figure 4. In alternative B, the DAGC of the first network node 201 tracks the received data traffic with a fast update rate when the power increases and tracks the received data traffic with a slow update rate when the power decreases. In alternative B, the step size is the same when the power increase and decreases the update rate is faster r when the power increases than when the power decreases. In alternative C, the DAGC of the first network node 201 tracks the received data traffic with a fast update rate and a large step size when the power increases and with a slow update rate and a small step size when the power decreases. Figure 4 will be described in more detail below.

The digital automatic gain control is dynamic in that the first updated rate is different from 5 the second update rate and that the first step size is different from the second step size or that the first update rate is different from the second update rate, or that the first step size is different from the second step size. Using other words, the digital automatic gain

control is dynamic in that it is adapted to adjust fast to a large power change o With the current standard, a fixed update rate and fixed step size was used in the DAGC tracking, i.e. static, as seen in alternative A in Figure 4. In alternative A, the fixed update rate and the fixed step size is exemplified to be of medium speed. The DAGC tracks the incoming data traffic with the same update rate and step size regardless of whether the power increases or decreases. The same update rate and steps size is used when the power of the received 5 data traffic is increasing and when it is decreasing. The current standard in alternative A is a trade-off between up- and down-ramping.

According to the embodiments herein exemplified in alternatives B and C of figure 4 the update rate and/or the step size are flexible. Alternative B exemplifies a setting where the step size is0 fixed but the update rate is faster for increasing received power from data traffic. The update rate is slower for decreasing received power. Alternative C exemplifies a setting the step size is larger and the update rate is faster for increasing received power and where the step size is smaller and the update rate is slower for decreasing received power. Further alternatives not shown in figure 4 are also possible such as keeping the update rate fixed and changing the step5 size differently for increasing and decreasing received power respectively.

A fast update rate is used when there is a rapid changing power level in order to avoid saturation in the DAGC. Saturation may lower the performance of the first network node 201 . In general, saturation may occur when the data traffic received by the first network0 node 201 exceeds a maximum level, or the output of the first network node 201 exceeds a maximum output level. Saturation may result in distortion components that may degrade performance. Hence, it may be desirable to perform DAGC in a manner to obtain good performance, i.e. to avoid saturation. The automatic gain control in steps 304a and 304b will now be described in more detail with reference to Figure 5. Figure 5 is a schematic block diagram illustrating

embodiments of a method in a DAGC 1001 comprised in the first network node 201 . The DAGC 1001 has an update rate K that depends on the power change. The update rate K determines how often the DAGC 1001 should be updated and the step size determines how much a scale factor a may change each update. The update rate K may also be referred to as a sample rate. In the embodiments herein, the update rate and step size are different depending on the power change of the received data traffic. K is a positive integer larger than zero.

The data traffic received by the DAGC 1001 of the first network node 201 may be In- phase Quadrature (IQ) data. Power estimation 501 is performed on the received data traffic in order to determine the power of the data traffic received in step 301 in figure 3. The power estimation 501 corresponds to step 302 of figure 3. The output of the power estimation 501 is referred to as Pk. The k in Pk is a sample index and it is is not related to the update rate K. At least one of the update rate K and steps size is chosen by evaluating the difference between the estimated input power Pk and the corresponding power level of previously chosen scale factor in box 502 in figure 5. Box 502 of figure 5 corresponds to steps 304a and 304b of figure 3. A scale factor calculation 503 is performed based on at least one of the power estimate Pk, the update rate K and the step size. The calculated scale factor is referred to as a. The scale factor a is mapped to a corresponding power level in box 504. The corresponding power level is referred to as P(a) and is the by DAGC estimated signal power based on previously estimated Pk and different constraints in the DAGC, power change of the data traffic which takes place when the first network node 201 receives data traffic from the second network node 203. The mapping of the chosen scale factor to the corresponding power level may be calculated as Pk- P(a) or as Pk-Pk-1 . The P(a) is used when choosing at least one of the update rate K and the step size in box 502. The received data traffic is scaled with the scale factor a and quantized in box 505 which provides an output signal which is the scaled and quantized IQ signal to be further processed.

A general example of the algorithm to choose the step size and update rate in box 502 in figure 5 and steps 304a and 304b in figure 3 may be follows:

If (Pk - P(a) > Thresholdpos1 ) set K = K_Fast1

stepsize = Stepsize_Large1

else lf( Thresholdpos1 >=(Pk - P(a)) > Thresholdpos2) set K = K_Fast2

stepsize = Stepsize_Large2

else If (Thresholdpos2 >=(Pk - P(a)) > Thresholdpos3) set K = K_Fast3

stepsize = Stepsize_Large3

else If (ThresholdposN >=(Pk - P(a)) >0)

set K = K FastN

stepsize = Stepsize_LargeN else If (0 >=(Pk - P(a)) > Thresholdnegl ) set K = K_Slow1

stepsize = Stepsize_Small1

else If (Thresholdnegl >=(Pk - P(a)) > Thresholdneg2 ) set K = K_Slow2

stepsize = Stepsize_Small2 else If (ThresholdnegM >=(Pk - set K = K_SlowM stepsize = Stepsize_SmallM

Where

Thresholdposl > Thresholdpos2 > Thresholdpos3 > .... > ThresholdposN > 0 0 > Thresholdnegl > Thresholdneg2 > Thresholdneg3 > >ThresholdnegM

K FastN is an update rate which is faster than K SLowM. Stepsize_LargeN is a step size which is larger than Stepsize_SmallM. ThreholdposN is a positive threshold and

ThresholdnegM is a negative threshold. N and M are positive integers. The

ThresholdposN and the ThresholdnegM may be predetermined or they may be dynamically assigned and changed when necessary. In some embodiments, Pk-Pk-1 may be used instead of Pk-P(a) in the algorithm above.

A simulation scenario with a pulsed High Data Rate (HDR) service and a continuous transmitting Low Data Rate (LDR) service will now be described with reference to Figure 6. The HDR service is shown in the top of figure 6 and the LDR service is shown in the bottom of figure 6. The x-axis of figure 6 represents the time measured in milliseconds (ms) and the y-axis of figure 6 represents the transmission (Tx) power. The LDR service may be voice and the HDR service may be data. The HDR service is transmitting an Enhanced Dedicated Channel (E-DCH) in 14 Transmission Time Intervals (TTIs) (seen as the high boxes in figure 6) and is silent for 10 TTIs (seen as the low boxes in figure 6) while the Dedicated Physical Control CHannel (DPCCH) is still transmitted continuously. The E-DCH transmission is repeated periodically. Each TTI is 2ms. The LDR service transmits the Dedicated Channel (DCH) continuously and the TTI is 20ms. E-DCH is a transport channel used in the 3G technologies. The E-DCH improves capacity and data throughput and reduces the delays in dedicated channels in the uplink. The E-DCH may be configured simultaneously with one or more DCHs. A DCH may be uplink or downlink 5 and is used to transfer data to a particular wireless device. Each wireless device has its own DCH in each direction.

Figure 7 shows the performance of a scenario where the HDR service is transmitting data discontinuously according to the pattern of figure 6. The x-axis of Figure 7 represents the o Ec/NO and the y-axis represents the Block Error Rate (BLER). Ec/NO is the chip energy divided by thermal noise. Figure 8 shows the performance of the LDR service for the simulation scenario in figure 6. The x-axis of Figure 8 represents the Ec/NO and the y- axis represents the BLER. The continuous line in figures 7 and 8 with legend mixed DAGC represents the performance by having a DAGC with different update rate and step 5 size, as described previously. The dotted line in figures 7 and 8 with legend slow DAGC represents the performance by having a fixed update rate and step size where the update rate is slow compared to the fixed update rate represented by the continuous line with a circle with legend fast DAGC. As may be seen from Figures 7 and 8, the mixed update rate illustrated with the continuous line provides the best overall performance since both0 the HDR and the LDR services achieve good performance.

The method described above will now be described seen from the perspective of the first network node 201 . Figure 9 is a flowchart describing the present method in the first network node 201 for handling power changes in data traffic received from a second5 network node 203 in a communications network 200. In some embodiments, the first network node 201 is a base station and the second network node 203 is a wireless device. In some embodiments, the first network node 201 is a wireless device and the second network node 203 is a base station. The method comprises the following steps to be performed by the first network node 201 :

0

Step 901

This step corresponds to step 304a in figure 3 and to steps 502 and 503 in figure 5.

When power of the received data traffic is increasing compared to power of previous received data traffic, the first network node 201 performs digital automatic gain control of5 the received data traffic using at least one of a first update rate and a first step size. In some embodiments, the power of the received data traffic is increasing when a power change is positive and larger than a positive threshold.

5 The power change may be determined by subtracting the power of the previous received data traffic from the power of the current received data traffic.

Step 902

This step corresponds to step 304b in figure 3 and to step 502 and 503 in figure 5. When o the power of the received data traffic is decreasing compared to the power of the previous received data traffic, the first network node 201 performs digital automatic gain control of the received data traffic using at least one of a second update rate and a second step size. The first updated rate is different from the second update rate and the first step size is different from the second step size, or the first update rate is different from the second5 update rate, or the first step size is different from the second step size.

In some embodiments, the power of the received data traffic is decreasing when the power change is negative and larger than a negative threshold. 0 In some embodiments,

- the first update rate is faster, i.e. larger, than the second update rate and the first step size is larger than the second step size; or

- the first update rate is faster, i.e. larger, than the second update rate; or

- the first step size is larger than the second step size; or

5 - the first update rate is slower, i.e. smaller, than the second update rate and the first step size is smaller than the second step size; or

- the first update rate is slower, i.e. smaller, than the second update rate; or

- the first step size is smaller than the second step size. 0 In some embodiments, the first update rate is slower, i.e. smaller than the second update rate. In some embodiments, the first step size is smaller than the second step size.

To perform the method steps shown in figure 9 for handling power changes in data traffic received from a second network node 203 in a communications network 200, the first5 network node 201 comprises an arrangement as shown in Figure 10. The first network node 201 comprises a DAGC 1001 . The DAGC 1001 is adapted to, when power of the received data traffic is increasing compared to power of previous received data traffic, perform digital automatic gain control of the received data traffic 5 using at least one of a first update rate and a first step size. The DAGC 1001 is further adapted to, when the power of the received data traffic is decreasing compared to power of previous received data traffic, perform digital automatic gain control of the received data traffic using at least one of a second update rate and a second step size. The first updated rate is different from the second update rate and the first step size is different o from the second step size, or the first update rate is different from the second update rate, or the first step size is different from the second step size.

In some embodiments, the power of the received data traffic is increasing when a power change is positive and larger than a positive threshold, and the power of the received data 5 traffic is decreasing when the power change is negative and larger than a negative

threshold.

In some embodiments, the power change is determined by subtracting the power of the previous received data traffic from the power of the current received data traffic.

0

In some embodiments,

- the first update rate is faster, i.e. larger, than the second update rate; or5 - the first step size is larger than the second step size; or

- the first update rate is slower, i.e. smaller, than the second update rate and the first step size is smaller than the second step size; or

- the first step size is smaller than the second step size.

0

As mentioned above, the first network node may be a base station and the second network node may be a wireless device, or the first network node 201 is a wireless device and the second network node 203 is a base station. The first network node 201 may comprise a receiver 1003 adapted to receive data traffic from e.g. the second network node 203 and other nodes in the communications network 200.

5 The first network node 201 may comprise a transmitter 1005 which is adapted to transmit data traffic to other nodes in the communications network 200 such as the second network node 203.

Those skilled in the art will appreciate that the DAGC 1001 , the receiver 1003 and the o transmitter 1005 described above may refer to a combination of analog and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in a memory, that when executed by the one or more processors such as the processor 1010 perform as described below. 5 The first network node 201 may further comprise a memory 1008 comprising one or more memory units. The memory 1008 is arranged to be used to store data, received data streams, power level measurements, power changes (increase and/or decrease), current and previous received data traffic, first and second step size, first and second update rate, threshold values, information indicating saturation, scale factor, output signal, time0 periods, configurations, schedulings, and applications to perform the methods herein when being executed in the first network node 201 .

The present mechanism for handling power changes in data traffic received from a second network node 203 in a communications network may be implemented through one5 or more processors, such as a processor 1010 in the first network node 201 depicted in Figure 10, together with computer program code for performing the functions of the embodiments herein. The processor may be for example a Digital Signal Processor (DSP), Application Specific Integrated Circuit (ASIC) processor, Field-Programmable Gate Array (FPGA) processor or microprocessor. The program code mentioned above may0 also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the first network node 201 . One such carrier may be in the form of a CD ROM disc or the memory 1008. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on5 a server and downloaded to the first network node 201 . The embodiments herein are not limited to the above described embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the embodiments, which is 5 defined by the appending claims.

It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components, but does not preclude the presence or addition of one or more other o features, integers, steps, components or groups thereof. It should also be noted that the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements. The term "configured to" used herein may also be referred to as "arranged to" or "adapted to". 5 It should also be emphasised that the steps of the methods defined in the appended claims may, without departing from the embodiments herein, be performed in another order than the order in which they appear in the claims.

Claims

1 . A method in a first network node (201 ) for handling power changes in data traffic received from a second network node (203) in a communications network (200), the

5 method comprising:

when power of the received data traffic is increasing compared to power of previous received data traffic, performing (303a, 502, 503, 901 ) digital automatic gain control of the received data traffic using at least one of a first update rate and a first step size; and

o when the power of the received data traffic is decreasing compared to the power of the previous received data traffic, performing (303b, 502, 503, 902) digital automatic gain control of the received data traffic using at least one of a second update rate and a second step size;

wherein the first update rate is different from the second update rate and the first step size 5 is different from the second step size, or

wherein the first update rate is different from the second update rate, or

wherein the first step size is different from the second step size.

2. The method according to claim 1 , wherein the power of the received data traffic is0 increasing when a power change is positive and larger than a positive threshold, and wherein the power of the received data traffic is decreasing when the power change is negative and larger than a negative threshold.

3. The method according to claim 2, wherein the power change is determined by

5 subtracting the power of the previous received data traffic from the power of the current received data traffic.

4. The method according to any one of claims 1 -3, wherein the first update rate is faster than the second update rate and the first step size is larger than the second step size; or0 wherein the first update rate is faster than the second update rate; or

wherein the first step size is larger than the second step size; or

wherein the first update rate is slower than the second update rate and the first step size is smaller than the second step size; or

wherein the first update rate is slower than the second update rate; or

5 wherein the first step size is smaller than the second step size.

5. The method according to any one of claims 1 -4, wherein the first network node (201 ) is a base station and the second network node (203) is a wireless device; or

wherein the first network node (201 ) is a wireless device and the second network node 5 (203) is a base station.

6. A first network node (201 ) for handling power changes in data traffic received from a second network node (203) in a communications network (200), the first network node (201 ) comprising:

o a Digital Automatic Gain Controller, DAGC, (1001 ) adapted to:

when power of the received data traffic is increasing compared to power of previous received data traffic, performing digital automatic gain control of the received data traffic using at least one of a first update rate and a first step size; and

5 when the power of the received data traffic is decreasing compared to power of previous received data traffic, performing digital automatic gain control of the received data traffic using at least one of a second update rate and a second step size;

wherein the first update rate is different from the second update rate, and

0 the first step size is different from the second step size, or

wherein the first update rate is different from the second update rate, or

wherein the first step size is different from the second step size.

7. The first network node (201 ) according to claim 6, wherein the power of the received5 data traffic is increasing when an power change is positive and larger than a positive threshold, and

wherein the power of the received data traffic is decreasing when the power change is negative and larger than a negative threshold. 0 8. The first network node (201 ) according to claim 7, wherein the power change is determined by subtracting the power of the previous received data traffic from the power of the current received data traffic.

9. The first network node (201 ) according to any one of claims 7-9, wherein the first update rate is faster than the second update rate and the first step size is larger than the second step size; or

wherein the first update rate is faster than the second update rate; or

5 wherein the first step size is larger than the second step size; or

wherein the first update rate is slower than the second update rate and

the first step size is smaller than the second step size; or

wherein the first update rate is slower than the second update rate; or

wherein the first step size is smaller than the second step size.

o

10. The first network node (201 ) according to any one of claims 6-9, wherein the first network node (201 ) is a base station and the second network node (203) is a wireless device; or