WO2016188553A1 - Methods and nodes in a wireless communication network - Google Patents

Abstract

A Controlling Network Node (130) and a method (500) therein, in a communication network (100), for modifying an active set (300) of Radio Links, RLs (140-1, 140-2, 140-n), where the active set of RLs (300) is to be used by a UE (120), for wireless communication with at least one network node (110-1, 110-2, 110-3) in the communication network (100). The CNN (130) comprises a processing unit (620), configured to detect a constraint of the wireless communication between the UE (120) and the network node (110-1, 110-2, 110-3); and modify the active set (300) of RLs (140-1, 140-2, 140-n), based on the detected constraint of the wireless communication.

Description

METHODS AND NODES IN A WIRELESS COMMUNICATION NETWORK

TECHNICAL FIELD

Implementations described herein generally relate to a controlling network node and a methods therein. In particular, a mechanism is herein described, for modifying an active set of radio links.

BACKGROUND

The explosion of data requirements in today^'s cellular networks impose a heavy burden in terms of bandwidth requirements both in downlink (DL) and uplink (UL). In the present con- text, the expression DL is used for the transmission path from the base station to a User Equipment (UE). The expression UL is used for the transmission path in the opposite direction i.e. from the UE to the base station.

The Universal Mobile Telecommunications System (UMTS) network, given its near ubiqui- tous presence, is in particular need of features which improve the spectral efficiency of the network. Due to the long time UMTS has existed in the market, it is especially difficult to find cost-effective solutions to achieve performance improvements in both or either UL and DL.

The most advanced features currently available often require the adoption of new and more expensive architectures or the installation of more capable hardware.

From an efficiency view point, it is desirable to introduce new mechanisms for improving efficiency of communication networks. SUMMARY

It is therefore an object to obviate at least some of the above mentioned disadvantages and to modify an active set of Radio Links (RLs) for improving communication in a wireless communication network. This and other objects are achieved by the features of the appended independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

According to a first aspect, a Controlling Network Node (CNN) is provided in a communica- tion network, for modifying an active set of RLs, where the active set of RLs is to be used by a User Equipment (UE), for wireless communication with at least one network node in the communication network. The CNN comprises a processing unit, configured to detect a constraint of the wireless communication between the UE and the network node. Also the processing unit is configured to modify the active set of RLs, based on the detected constraint of the wireless communication.

In conventional methods, the maximum active set size and the threshold levels for requesting entrance and exclusion, respectively, from the active set are fixed. This creates a problem when the capacity requirements in UL and DL are imbalanced. This results in low capacity. However, thanks to the introduction of flexible and dynamically adjustable modification of the active set of RLs, based on a detected constraint in either UL or DL, signalling resources may be allocated from UL to DL and vice versa. By the provided dynamical management of the active set size, system resources are better used and adapted to the resource demands. In a first possible implementation of the CNN according to the first aspect, the detected constraint may be an UL congestion, or a DL congestion.

By detecting an UL congestion and at the same time available DL capacity, or alternatively by detecting a DL congestion and at the same time available UL capacity, it is possible to dynamically manage resources between UL and DL. Thereby capacity of the communication network is increased, leading to an enhanced user experience by the UE user. Thus the communication within the wireless communication network is improved.

In a second possible implementation of the CNN according to the first aspect, or the first possible implementation of the first aspect, the processing unit is further configured to detect an UL congestion being the detected constraint of the wireless communication between the UE and the network node. Furthermore, the processing unit is further configured to modify the active set of RLs by increasing the number of RLs in the active set, compared to an initial number of RLs.

By adding more RLs to the active set when an UL congestion is detected, the UL capacity is increased, leading to increased capacity of the communication network.

In a third possible implementation of the CNN according to the first aspect, or any of the previous possible implementations of the first aspect, the processing unit is configured to increase the number of RLs in the active set, compared to the initial number of RLs. This may be made by controlling the maximum number of RLs allowed in the active set, increasing a 1 A threshold value, with respect to a serving cell RL strength, for transmitting a 1A report from the UE to the CNN, or increasing a 1 B threshold value, with respect to the serving cell RL strength, for transmitting a 1 B report from the UE to the CNN. By adding more RLs to the active set when an UL congestion is detected, the UL capacity is increased, leading to increased capacity of the communication network. This may be made by changing any, some or all of the enumerated limits.

In a fourth possible implementation of the CNN according to the first aspect, or any of the previous possible implementations of the first aspect, the processing unit may be further configured to detect a DL congestion being the detected constraint of the wireless communication between the UE and the at least one network node. The processing unit may be further configured to modify the active set of RLs by decreasing the number of RLs in the active set, compared to the initial number of RLs.

By reducing RLs from the active set when a DL congestion is detected, the DL capacity is increased, leading to increased capacity of the communication network.

In a fifth possible implementation of the CNN according to the first aspect, or any of the previous possible implementations of the first aspect, the processing unit is configured to decrease the number of RLs in the active set, compared to the initial number of RLs. This may be made by controlling the number of RLs in the active set, decreasing a 1 A threshold value, with respect to the serving cell RL strength, for transmitting a 1A report from the UE to the CNN, or decreasing a 1 B threshold value, with respect to the serving cell RL strength, for transmitting a 1 B report from the UE to the CNN.

By reducing RLs from the active set when a DL congestion is detected, the DL capacity is increased, leading to increased capacity of the communication network. This may be made by changing any, some or all of the enumerated limits.

In a sixth possible implementation of the CNN according to the first aspect, or any of the previous possible implementations of the first aspect, the processing unit is further configured to detect the constraint of the wireless communication between the UE and the network node by detecting an imbalance between UL and DL received signal strength in at least one RL. Further the processing unit is configured to modify the active set of RLs based on DL signal measurements made by the UE and based on UL signal measurements made by the network node. Thereby more correct signal measurements may be made, both in UL and DL.

In a seventh possible implementation of the CNN according to the first aspect, or any of the previous possible implementations of the first aspect, the processing unit is configured to send a scrambling code of the UE to a plurality of network nodes communicating with the UE. Further the processing unit is configured to instruct the network nodes to measure and report signal strength of UL pilot signals received from the UE. Also, the processing unit is further configured to receive UL signal measurements of the UE UL pilot signals, from the network nodes. In addition the processing unit is configured to modify the active set of RLs to be used by the UE, based on received UL signal measurements.

Thereby, UL pilot signal measurements by the network nodes are enabled. It is then possible to detect e.g. that another cell than the serving cell has the strongest UL signal. It is thereby possible to reduce the UL signal transmission power, in comparison with letting the serving cell control the transmission power of the UE, energy is saved by the UE. Thereby the time between battery re-charge of the UE is prolonged, which provides a longer operational time for the user of the UE. Also UL interference is reduced, as the transmission power of the UE is reduced, leading to an enhanced user experience of other UE users.

In an eighth possible implementation of the CNN according to the first aspect, or any of the previous possible implementations of the first aspect, the processing unit is configured to detect imbalance between UL and DL received signal strength in the RL when the difference between DL signal measurements made by the UE and UL signal measurements made by the network node exceeds a threshold value. Also, the processing unit is configured to increase the number of RLs in the active set, compared to the initial number of RLs when the detected constraint comprises an UL congestion; ordecrease the number of RLs in the active set, compared to an initial number of RLs when the detected constraint comprises a DL congestion.

Thereby, in case of conflicting measurement reports between UL and DL pilot signals, priority may be given to the signal measurements made by the network nodes in case the UL performance is to be improved and vice versa, priority may be given to the UE reports in case when the DL performance is to be improved.

In a ninth possible implementation of the CNN according to the first aspect, or any of the previous possible implementations of the first aspect, the CNN is distinct from the network node in the communication network. Also, the communication network is a Universal Mobile Telecommunications System (UMTS) network. Further, the CNN is a Radio Network Controller (RNC). Also the network node is a Node B. Thereby, a convenient and operationally reliable implementation form of the first aspect is enabled.

In a tenth possible implementation of the CNN according to the first aspect, or any of the previous possible implementations of the first aspect, the CNN is comprised in the network node or in the RNC in the communication network.

Thereby an alternative implementation form is enabled.

According to a second aspect, a method is provided for use in a CNN in a communication network. The method aims at modifying an active set of RLs where the active set of RLs is to be used by a UE, for wireless communication with at least one network node in the communication network. The method comprises detecting a constraint of the wireless communication between the UE and the network node. Further the method comprises modifying the active set of RLs, based on the detected constraint of the wireless communication.

In conventional methods, the maximum active set size and the threshold levels for requesting entrance and exclusion, respectively, from the active set are fixed. This creates a problem when the capacity requirements in UL and DL are imbalanced. This results in low capacity. However, thanks to the introduction of flexible and dynamically adjustable modification of the active set of RLs, based on a detected constraint in either UL or DL, signalling resources may be allocated from UL to DL and vice versa. By the provided dynamical management of the active set size, system resources are better used and adapted to the resource demands. Thus, the communication within the wireless communication network is improved.

In a first possible implementation of the method according to the second aspect, the detected constraint is an UL congestion or a DL congestion.

By detecting an UL congestion and at the same time available DL capacity, or alternatively by detecting a DL congestion and at the same time available UL capacity, it is possible to dynamically manage resources between UL and DL. Thereby capacity of the communication network is increased, leading to an enhanced user experience by the UE user. In a second possible implementation of the method according to the second aspect, or the first possible implementation of the second aspect, the detected constraint of the wireless communication between the UE and the network node comprises an UL congestion. Also, the modification of the active set comprises increasing the number of RLs in the active set, compared to an initial number of RLs.

By adding more RLs to the active set when an UL congestion is detected, the UL capacity is increased, leading to increased capacity of the communication network.

In a third possible implementation of the method according to the second aspect, or any of the previous possible implementations of the second aspect, the number of RLs in the active set is increased, compared to the initial number of RLs. The increase may be made by controlling the number of RLs in the active set, increasing a 1 A threshold value, with respect to a serving cell RL strength, for transmitting a 1 A report from the UE to the CNN, or increasing a 1 B threshold value, with respect to the serving cell RL strength, for transmitting a 1 B report from the UE to the CNN.

By adding more RLs to the active set when an UL congestion is detected, the UL capacity is increased, leading to increased capacity of the communication network. This may be made by changing any, some or all of the enumerated limits.

In a fourth possible implementation of the method according to the second aspect, or any of the previous possible implementations of the second aspect, the detected constraint of the wireless communication comprises a DL congestion. In such case, the modification of the active set comprises decreasing the number of RLs in the active set, compared to the initial number of RLs.

By reducing RLs from the active set when a DL congestion is detected, the DL capacity is increased, leading to increased capacity of the communication network.

In a fifth possible implementation of the method according to the second aspect, or any of the previous possible implementations of the second aspect, the number of RLs in the active set is decreased compared to the initial number of RLs. This may be made by controlling the number of RLs in the active set, decreasing the 1 A threshold value, with respect to the serving cell RL strength, for transmitting the 1A report from the UE to the CNN, or decreasing the 1 B threshold value, with respect to the serving cell RL strength, for transmitting the 1 B report from the UE to the CNN.

By reducing RLs from the active set when a DL congestion is detected, the DL capacity is increased, leading to increased capacity of the communication network. This may be made by changing any, some or all of the enumerated limits.

In a sixth possible implementation of the method according to the second aspect, or any of the previous possible implementations of the second aspect, the method may comprise de- tecting the constraint of the wireless communication between the UE and the network node by detecting an imbalance between UL and DL received signal strength in at least one RL. Also, the modification of the active set of RLs is based on DL signal measurements made by the UE and based on UL signal measurements made by the network node. By detecting imbalance in the communication system and allocating resources for countering the imbalance, the capacity of the communication network is increased.

In a seventh possible implementation of the method according to the second aspect, or any of the previous possible implementations of the second aspect, the method further comprises sending a scrambling code of the UE to a plurality of network nodes communicating with the UE. Also the method comprises instructing the network nodes to measure and report signal strength of UL pilot signals received from the UE. Further the method comprises receiving UL signal measurements of the UE UL pilot signals, from the network nodes. Also the method further comprises modifying the active set of RLs to be used by the UE, based on received UL signal measurements.

Thereby, UL pilot signal measurements by the network nodes are enabled. It is then possible to detect e.g. that another cell than the serving cell has the strongest UL signal. It is thereby possible to reduce the UL signal transmission power, in comparison with letting the serving cell control the transmission power of the UE, energy is saved by the UE. Thereby the time between battery re-charge of the UE is prolonged, which provides a longer operational time for the user of the UE. Also UL interference is reduced, as the transmission power of the UE is reduced, leading to an enhanced user experience of other UE users. In an eighth possible implementation of the method according to the second aspect, or any of the previous possible implementations of the second aspect, the imbalance between UL and DL received signal strength in the RL is detected when the difference between DL signal measurements made by the UE and UL signal measurements made by the network nodes exceeds a threshold value. Further, the modification of the active set comprises increasing the number of RLs in the active set, compared to the initial number of RLs when the detected constraint comprises an UL congestion; or decreasing the number of RLs in the active set, compared to an initial number of RLs when the detected constraint comprises a downlink congestion.

Thereby, in case of conflicting measurement reports between UL and DL pilot signals, priority may be given to the signal measurements made by the network nodes in case the UL per- formance is to be improved and vice versa, priority may be given to the UE reports in case when the DL performance is to be improved.

According to a third aspect, a computer program is provided, comprising a program code for performing a method according to the second aspect, or any of the previous possible imple- mentations of the second aspect, when the computer program runs on a computer.

In conventional methods, the maximum active set size and the threshold levels for requesting entrance and exclusion, respectively, from the active set are fixed. This creates a problem when the capacity requirements in UL and DL are imbalanced. This results in low capacity.

However, thanks to the introduction of flexible and dynamically adjustable modification of the active set of RLs, based on a detected constraint in either UL or DL, signalling resources may be allocated from UL to DL and vice versa. By the provided dynamical management of the active set size, system resources are better used and adapted to the resource demands. Further, the network capacity is improved without necessarily having to invest in new hardware, as a software update may implement the herein described method. Thereby, the communication within the wireless communication network is improved.

Other objects, advantages and novel features of the described aspects will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are described in more detail with reference to attached drawings, illustrating examples in which:

Figure 1 is a block diagram illustrating wireless communication according to some embodiments. is a block diagram illustrating wireless communication according to some embodiments.

is a block diagram illustrating a radio frame for wireless communication according to some embodiments.

is a block diagram illustrating received DL signal strength difference of RLs compared to a serving cell and the modification of an active set of RLs for the UE according to some embodiments.

is a block diagram illustrating received DL signal strength difference of RLs compared to a serving cell and the modification of an active set of RLs for the UE according to some embodiments, in an uplink congestion situation.

is a block diagram illustrating received DL signal strength difference of RLs compared to a serving cell and the modification of an active set of RLs for the UE according to some embodiments, in an uplink congestion situation.

is a block diagram illustrating received DL signal strength difference of RLs compared to a serving cell and the modification of an active set of RLs for the UE according to some embodiments, in an uplink congestion situation.

is a block diagram illustrating received DL signal strength difference of RLs compared to a serving cell and the modification of an active set of RLs for the UE according to some embodiments, in an uplink congestion situation.

is a block diagram depicting received DL signal strength difference of RLs compared to a serving cell and the modification of an active set of RLs for the UE according to some embodiments, in a downlink congestion situation. is a block diagram depicting received DL signal strength difference of RLs compared to a serving cell and the modification of an active set of RLs for the UE according to some embodiments, in a downlink congestion situation. is a block diagram depicting received DL signal strength difference of RLs compared to a serving cell and the modification of an active set of RLs for the UE according to some embodiments, in a downlink congestion situation. is a block diagram depicting received DL signal strength difference of RLs compared to a serving cell and the modification of an active set of RLs for the UE according to some embodiments, in a downlink congestion situation. is a flow chart illustrating a method according to an embodiment. DETAILED DESCRIPTION

Embodiments of the invention described herein are defined as a node and a method in a node, which may be put into practice in the embodiments described below. These embodiments may, however, be exemplified and realised in many different forms and are not to be limited to the examples set forth herein; rather, these illustrative examples of embodiments are provided so that this disclosure will be thorough and complete.

Still other objects and features may become apparent from the following detailed description, considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the herein disclosed embodiments, for which reference is to be made to the appended claims. Further, the drawings are not necessarily drawn to scale and, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.

Figure 1 is a schematic illustration over a wireless communication network 100 comprising a plurality of network nodes 110-1 , 110-2, 110-3, which are controlled by a Controlling Network Node (CNN) 130. Any, some or all of the network nodes 1 10-1 , 1 10-2, 1 10-3 may communicate wirelessly with a UE 120 over a Radio Link (RL) 140-1 , 140-2, 140-n, where n is an arbitrary integer in the interval 0 < n <∞.

The wireless communication network 100 may at least partly be based on radio access technologies such as, e.g., 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), LTE-Advanced, Evolved Universal Terrestrial Radio Access Network (E-UTRAN), Universal Mobile Telecommunications System (UMTS), Global System for Mobile Communications (originally: Groupe Special Mobile) (GSM)/ Enhanced Data rate for GSM Evolution (GSM/EDGE), Wideband Code Division Multiple Access (WCDMA), Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, Single-Carrier FDMA (SC-FDMA) networks, Worldwide Inter- operability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), High Speed Packet Access (HSPA) Evolved Universal Terrestrial Radio Access (E-UTRA), High-Speed Uplink Packet Access (HSUPA), High Speed Downlink Packet Access (HSDPA), Universal Terrestrial Radio Access (UTRA), GSM EDGE Radio Access Network (GERAN), 3GPP2 CDMA technologies, e.g., CDMA2000 1 x RTT and High Rate Packet Data (HRPD), Wi-Fi, or similar, just to mention some few options. The expressions "wireless communication network", "wireless communication system" and/ or "cellular telecommunication system" may within the technological context of this disclosure sometimes be utilised interchangeably. However, subsequently the wireless communication network 100 will be described as an UMTS system wherein the CNN 130 is a Radio Network Controller (RNC) and the network node 1 10-1 , 1 10-2, 1 10-3 is a Node B, or NB.

In the illustrated embodiment, the network nodes 1 10-1 , 1 10-2, 1 10-3 are represented by a radio network node or base station, such as e.g., a Radio Base Station (RBS) or Base Transceiver Station (BTS), which in some networks may be referred to as eNB, NodeB, NB or B- node, Access Point, pico base station, femto base station, beacon device, relay node, re- peater or any other network node configured for communication with the UE 120 over a wireless interface, depending, e.g., of the radio access technology and/ or terminology used.

The UE 120 may in this illustrated embodiment be represented by a mobile station also known as a mobile device, wireless terminal, mobile telephone, cellular telephone, computer tablet or laptop with wireless capability, etc.

The UE 120 in the present context may be, for example, portable, pocket-storable, handheld, computer comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/ or data, via the network nodes 1 10-1 , 1 10-2, 1 10-3 and the wireless communica- tion network 100.

The wireless communication network 100 may cover a geographical area which is divided into cell areas, with each cell area being served by a network node, such as the illustrated network nodes 1 10-1 , 1 10-2, 1 10-3.

Sometimes, the expression "cell" may be used for denoting the network node itself. However, the cell may also in normal terminology be used for the geographical area where radio coverage is provided by the network node at a base station site. Any of the network nodes 1 10-1 , 1 10-2, 1 10-3, situated on the base station site, may serve one or several cells. The network nodes 1 10-1 , 1 10-2, 1 10-3 may communicate over the air interface operating on radio frequencies with any mobile device 120 within range of the network nodes 1 10-1 , 1 10- 2, 1 10-3. The communication between each cell and the UE 120 is made over a RL 140-1 , 140-2, 140-n. It is to be noted that the illustrated network setting of three instances of the network nodes 1 10-1 , 1 10-2, 1 10-3 and one UE 120 in Figure 1 is to be regarded as a non-limiting example of an embodiment only. The wireless communication network 100 may comprise any other number and/ or combination of the discussed network nodes 1 10-1 , 1 10-2, 1 10-3 and/ or UE 120. A plurality of UEs 120 and another configuration of network nodes 1 10-1 , 1 10-2, 1 10-3 may thus be involved in some embodiments of the disclosed invention. Thus whenever "one" or "a" network nodes 1 10-1 , 1 10-2, 1 10-3 and/ or UE 120 is referred to in the present context, a plurality of the network nodes 1 10-1 , 1 10-2, 1 10-3, and/ or UE 120 may be involved, according to some embodiments.

The purpose of the illustration in Figure 1 is to provide a simplified, general overview of the wireless communication network 100 and the involved methods and nodes, such as the network nodes 1 10-1 , 1 10-2, 1 10-3, the UE 120, the CNN 130 as herein described, and the functionalities involved.

According to some embodiments, a method is provided for alleviating the severity of scenar- ios wherein the network 100 is either UL limited or DL limited but not both at the same time by shifting radio capacity from DL to UL and vice versa, depending on where such capacity is more urgently needed.

In relation to some of the disclosed embodiments, the relevant aspects of the UMTS archi- tecture are the concepts of Soft Handover (SHO) and Softer Handover (SoHO). The term handover, or handoff as it also may be referred to as, refers to the process of transferring an ongoing call or data session from one RL 140-1 , 140-2, 140-n connected to the communication network 100, to another RL 140-1 , 140-2, 140-n. A UE 120 can have an active connection to more than one cell. The set of cells which have an active connection to the UE 120 and are able to decode the signal received from the UE 120 form the active set of the UE 120. In case the cells belong to the same network node 1 10-1 , 1 10-2, 1 10-3, the received signal is soft combined and may be referred to as Softer Handover (SoHO). If the cells belong to different network nodes 1 10-1 , 1 10-2, 1 10-3, the frames may be combined after decoding (e.g. via Selection Combining) and may be referred to as Soft Handover (SHO). A new RL 140-1 , 140-2, 140-n may be added to the active set or removed from it, based on event-based measurement reports generated by the UE 120. Such measurement reports are called respectively the 1 A and 1 B events reports. The active set size is in conventional solutions limited to a max number (typically 3) to avoid excessive consumption of DL control information. The UE 120 maintains a list of cells (called the monitored set) whose pilot channel Ec/ NO is continuously measured but not strong enough to be added to the active set. It is to be noted that the monitored set of cells is different from the active set of RLs. Based on such measurement of the set of monitored cells the UE 120 can, among others, indicate to the CNN 5 130 the addition or the removal of a cell or RL to the active set.

When the UE 120 is connected to one cell, e.g. the serving cell, and the quality of another cell (as measured, for example, by the Ec/ NO) is within a fixed threshold (typically 3 dB) from the serving cell for longer than an hysteresis period, the event 1 A is reported and the proce-0 dure for adding the cell to the active set is started if the CNN 130 decides to do so, according to conventional solutions.

Similarly when the UE 120 is connected to more than one cell, and the quality of the weakest cell (as measured, for example, by the Ec/ NO) is below a fixed threshold (typically 6 dB)5 from the strongest cell (the serving cell) for longer than an hysteresis period, the event 1 B is reported and the procedure for removing the cell from the active set is started if the CNN 130 decides to do so, according to conventional solutions. Ec/ NO (received energy per chip over interference spectral density) is a measurement made e.g. on a common pilot signal such as e.g. Common Pilot Channel (CPICH) in UMTS, for observing noise and interference level0 in the network 100.

Thus, according to conventional solutions the 1 A and 1 B thresholds are fixed and the maximum active set size is fixed. This results in a lower capacity than what would be possible (in UL or DL) if the active set size would be managed dynamically. This also creates a problem5 when the capacity requirements in UL and DL are imbalanced.

In a scenario where the UL capacity is limited but not the DL capacity, it is in some embodiments possible to increase the active set size of the UE 120 and, thus, the UL spectral efficiency while consuming more DL resources used for control information (more specifically0 the control signalling of the additional RLs 140-1 , 140-2, 140-n). In this way, capacity is shifted from DL to UL by increasing the UL capacity (used for data transfer) at the expense of the DL capacity (used for control signalling).

Similarly, in case the DL capacity is limited but not UL capacity, it is possible to decrease the5 active set size of the UE 120 and, thus, the UL spectral efficiency while consuming less DL resources used for control information (specifically saving on the control resources previ- ously used for the released RLs 140-1 , 140-2, 140-n). In this way we are effectively shifting capacity from UL to DL by decreasing the RLs 140-1 , 140-2, 140-n and thus the DL capacity used for control at the expense of the UL capacity previously used for data. The CNN 130 may be comprised in an RNC in some embodiments, e.g. when implemented in an UMTS system 100, or any UMTS-related environment. However, in some other alternative embodiments, the CNN 130 may be comprised in the network node 1 10-1 , 1 10-2, 1 10-3. For enhanced clarity, any internal electronics or other components of the CNN 130, not completely indispensable for understanding the herein described embodiments have been omitted from Figure 1 .

The CNN 130 may comprise a receiving unit 610, configured to receive information from the network nodes 1 10-1 , 1 10-2, 1 10-3 over a wired or wireless interface. The received information may comprise for example signal strength measurements of DL network node signals made by the UE 120.

In addition, the CNN 130 also comprises a processing unit 620, configured to perform various computational tasks as the disclosed method, as will be explained in detail later in this disclosure.

Such processing unit 620 may comprise one or more instances of a processing circuit, i.e. a Central Processing Unit (CPU), a processor, a processing circuit, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The herein utilised expression "processing unit" may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones enumerated above. In addition, the CNN 130 also comprises a transmitter 630 configured to transmit information to the network nodes 1 10-1 , 1 10-2, 1 10-3 over a wired or wireless interface. The transmitted information may comprise e.g. control signalling to the network nodes 1 10-1 , 1 10-2, 1 10-3, or to the UE 120, via the network nodes 1 10-1 , 1 10-2, 1 10-3. Furthermore, the CNN 130 may further comprise at least one memory 640, according to some embodiments. The optional memory 640 may comprise a physical device utilised to store data or programs, i.e., sequences of instructions, on a temporary or permanent basis. According to some embodiments, the memory 640 may comprise integrated circuits comprising silicon-based transistors. Further, the memory 640 may be volatile or non-volatile.

Figure 2 illustrates schematically a wireless communication network 100 similar to, or even identical with the wireless communication network 100 depicted in Figure 1 .

The UE 120 is in a soft handover situation, or softer handover situation (depending on which cell is the serving cell). The UE 120 in the illustrated scenario has a set of active RLs 140-1 , 140-2, 140-n comprising three RLs 140-1 , 140-2, 140-n, a first RL 140-1 is connected to a serving cell of the serving node 1 10-1 , a second RL 140-2 is connected to a non-serving cell of the serving node 1 10-1 and a third RL 140-3 is connected to a non-serving cell of the non-serving node 1 10-2.

Starting from 3GPP Release 6 of UMTS, there are four types of DL dedicated physical chan- nels, the Downlink Dedicated Physical Channel (DL DPCH), the Fractional Dedicated Physical Channel (F-DPCH), the Enhanced Dedicated Channel (E-DCH) Relative Grant Channel (E-RGCH), and the E-DCH Hybrid Automatic Repeat re-Quest (ARQ) Indicator Channel (E- HICH). In the herein described embodiments, the DL DPCH is primarily discussed. The DL DPCH is a dedicated (per UE) channel which carries the DL Dedicated Physical Control Channel (DPCCH) and the DL Dedicated Physical Data Channel (DPDCH). The DL DPCCH, which carries control information, uses significant power which is therefore not available for data. Within one DL DPCH, dedicated data, generated at Layer 2 and above, are transmitted time- multiplexed with control information, such as e.g. pilot, Transport Format Combination Indicator (TFCI) and Transmit Power Control (TPC), generated at Layer 1 . The DL DPCH can thus be seen as a time multiplex of a DPDCH and a DPCCH, as shown in Figure 3, which illustrates a frame structure for DL DPCH.

The 10 ms radio frame 210 is split into 15 slots 220-0, 220-1 , ..., 220-14, each with a duration of 2560 chips. The number of bits carried per slot 220-0, 220-1 , 220-14 depends on the Spreading Factor (SF) which varies from 512 for 10 carried bits i.e., 5 Quadrature Phase Shift Keying (QPSK) symbols to 4 for 1280 carried bits (i.e., 640 QPSK symbols).

Starting from Release 5, the DPDCH and DPCCH (that compose the DPCH) carry respectively layer 3 and layer 1 control information. The SF of the DPCH is typically set to 256. User-plane data are carried on the High Speed Downlink Packet Access (HSDPA) channel. (In a typical DPCH configuration, the DPCH channel may consume about 0.5% of the total base stations power per RL 140-1 , 140-2, 140-n). According to some embodiments, in a scenario wherein the UL capacity is limited, but not DL capacity, the UL capacity may be increased by increasing the active set size by allowing inclusion of more RLs 140-1 , 140-2, 140-n. Thereby, also the consumption of DL control channel resources is increased. This particular scenario in some different variants is illustrated in Figures 4B-4E.

According to some embodiments, in a scenario wherein the DL capacity is limited, but not UL capacity, the DL capacity may be increased by decreasing the active set size by reducing the number of RLs 140-1 , 140-2, 140-n in the active set. Thus the consumption of DL control channel resources is decreased leaving more resources for data. This particular sce- nario in some different variants is illustrated in Figures 5A-5D.

The above mentioned increase in UL capacity, or alternatively in DL capacity may be performed either by modification of the maximum number of RLs 140-1 , 140-2, 140-n that can be added to the active set and/ or by modifying the standard 3GPP (25.331 ) SHO thresh- old level 1A for adding a RL 140-1 , 140-2, 140-n to the active set and/ or by modifying the standard 3GPP (25.331 ) SHO threshold level 1 B for deleting a RL 140-1 , 140-2, 140- n from the active set.

Thanks to the disclosed embodiments, a network-controlled method is provided to add/ de- lete a RL 140-1 , 140-2, 140-n to/ from the active set based on quality measure of the DPCCH channel pilot domain. The disclosed method may in some embodiments also be useful in case of UL/ DL imbalance.

Figure 4A comprises a diagram which discloses an example of signal strength measure- ments made by the UE 120, of DL pilot signals transmitted over different respective RLs 140- 1 , 140-2, 140-n. Also, the 1A and 1 B limits are visualised together with the signal strength measurements over nine RLs 140-1 , 140-2, 140-n.

Also, an active set 300 of RLs 140-1 , 140-2, 140-n is visualised. In the illustrated example, the active set 300 comprises two RLs: RL 1 and RL 4. This is only a non-limiting example. Further, at the bottom of Figure 4A is the UL/ DL transmission illustrated. All DL data is transmitted over the serving cell RL 1 while UL data is transmitted both over RL 1 and RL 4. In the DL of RL 1 and RL 4 is control information transmitted such as e.g. TPC.

5 The illustrated example in Figure 4A is used as a starting point, or reference for comparison when the subsequent Figures 4B-4E and Figures 5A-5D are discussed. But first the diagram of signal strength measurements will be further explained.

The UE 120 in this example has nine RLs 140-1 , 140-2, 140-n in its monitored set of RLs. 10 Thus the UE 120 is continuously measuring DL pilot signals over the nine RLs 140-1 , 140- 2, 140-n and compare them with the reference signal strength 330 of a DL pilot signal received over the serving cell RL 1 , and also with the 1A limit 310 and the 1 B limit 320.

In this non-limiting example, the 1A limit 310 is set to 3 dB below the reference signal strength 5 330 of the DL pilot signal received over the serving cell RL 1 . However, unlike conventional solutions, the 1A limit 310 may be dynamically adjusted to any value.

Further, in another non-limiting example, the 1 B limit 320 is set to 6 dB below the reference signal strength 330 of the DL pilot signal received over the serving cell RL 1 . However, unlike 20 conventional solutions, the 1 B limit 320 may be dynamically adjusted to any value.

Also, the active set size is limited to three RLs 140-1 , 140-2, 140-n. However, as only two RLs are fulfilling the signal strength requirements for entering the active set 300, the active set 300 is not limited by the active set size limit in this embodiment.

25

Thus, looking a bit closer at the diagram, the serving cell RL 1 has the strongest received signal strength. This may often be the case, however, any non-serving cell RL may at least temporarily have a stronger received signal strength, e.g. until a change of serving cell RL is made.

30

RL 2 in this example has a rather weak received signal strength about 10 dB below the serving cell RL strength 330.

RL 3 has a received signal strength stronger than the 1 B limit 320, i.e. the limit for being 35 excluded from the active set 300, but has not achieved the 1A limit 310. Thus RL 3 does not fulfil the requirements for inclusion into the active set 300 with the current 1A limit. RL 4 has a decreasing received signal strength trend, which currently is at approximately the same received signal strength measurement level as the previously discussed RL 3. However, as the received signal strength previously has been stronger than the 1A limit 310 for inclusion of RL 4 to the active set 300, RL 4 is included in the active set 300.

RL 5 has a received signal strength stronger than the 1 B limit 320, and also stronger than the signal strength of the above discussed RL 4. However, as RL 5 has not achieved the 1A limit 310, RL 5 does not fulfil the requirements for inclusion into the active set 300 with the current 1A limit.

RL 6 has a decreasing received signal strength trend, currently below the 1 B limit 320. RL 6 does thereby not fulfil the requirements for being included in the active set 300.

RL 7 and RL 8 have very weak received signal strengths, far below the 1A limit 310 for inclusion into the active set 300.

RL 9 has an increasing trend, almost but not quite achieving the 1A limit 310. Thus RL 9 is currently not included in the active set 300, but will probably be if the increasing trend persists.

It is to be noted that the received signal strength in this example actually is higher on RL 9, RL 5 and perhaps also RL 3, which are not comprised in the active set 300, than RL 4 which is comprised in the active set 300. This somehow also illustrates yet a weakness of the conventional solutions with fixed 1 A limit 310 and/ or fixed 1 B limit 320.

Figure 4B is illustrating the same diagram and other illustrations as illustrated in the previously described Figure 4A, in a scenario where the uplink is congested while there is free capacity in the DL. The received signal strengths of all DL signals over the RLs 140-1 , 140- 2, 140-n are identical with the situation illustrated in Figure 4A.

The depicted diagram in Figure 4B reflects the situation after a period larger than the reference period.

In this example, the 1A limit value 310 for transmitting a 1A report for requesting introduction of a RL 140-1 , 140-2, 140-n that has a received signal strength stronger than the 1A limit value 310, has been changed from -3 dB to -5 dB, as counted from the received signal strength of the serving cell RL 300. Thus the threshold for being entered into the active set 300 has been decreased. As illustrated in the diagram, RL 9 now has a stronger received signal than the 1A limit value 310. Actually, also RL 5 has a stronger received signal than the 1A limit value 310, but cannot be entered into the active set 300 due to the maximum limitation of RLs in the active set 300, which in this example has been set to 3.

Thereby, by adjusting the 1 A limit value 310 from -3 dB to -5 dB, the active set 300 is modified from comprising two RLs, namely RL 1 and RL 4, into comprising three RLs: RL 1 , RL 5 and RL 9.

The thereby achieved effect is illustrated at the bottom of Figure 4B, i.e. that UL data is transmitted over three RLs instead of the previous two RLs. In the opposite DL direction, control information is sent over three RLs (RL 1 , RL 5 and RL 9) instead of the previous two RLs (RL 1 and RL 4). Thus more resources are used in the DL in comparison with the situation illustrated in Figure 4A. However, as the presumption was that capacity was available in the DL, but there was a congestion in the UL, the UL congestion problem is solved, or at least somewhat diminished, while the additional DL control signalling does not introduce any problem as there is free capacity to use in DL.

Thereby the signalling within the communication network 100 is improved thanks to the added flexibility in allocation of signalling resources from DL to UL, and vice versa.

Figure 4C is illustrating the same diagram and other illustrations as illustrated in the previ- ously described Figure 4A and Figure 4B, but in a scenario where the uplink is congested while there are free capacity in the DL. The received signal strengths of all DL signals over the RLs 140-1 , 140-2, 140-n are identical with the situation illustrated in Figure 4A and Figure 4B. However, in this example, the 1 B limit value 320 for transmitting a 1 B report for requesting removal of a RL 140-1 , 140-2, 140-n that has a received signal strength weaker than the 1 B limit value 320, has been changed from -6 dB to -8 dB, as counted from the received signal strength of the serving cell RL 300. Thus the threshold for being removed from the active set 300 has been decreased. As illustrated in the diagram, RL 6 now has a stronger received signal than the 1 B limit value 320. Actually, also RL 9 has a stronger received signal than the 1 B limit value 320, but cannot be entered into the active set 300 since it has not passed the threshold 1 A. Actually, even if the received signal of RL 9 were to pass the threshold 1 A for a period longer than a reference period due to the maximum limitation of RLs in the active set 300, which in this example has been set to 3. Also signals received over RL 3 and RL 5 are stronger than the 1 B limit value 5 320, but as these signals have not reached the 1A limit value 310 for being introduced to the active set 300, they are not comprised in the active set 300.

Thereby, by adjusting the 1 B limit value 320 from -6 dB to -8 dB, the active set 300 is modified from comprising two RLs, namely RL 1 and RL 4, into comprising three RLs: RL 1 , RL 4 and0 RL 5, in comparison with the situation illustrated in Figure 4A.

The thereby achieved effect is illustrated at the bottom of Figure 4C, i.e. that UL data is transmitted over three RLs (RL 1 , RL 4 and RL 6) instead of the previous two RLs (RL 1 and RL 4). In the opposite DL direction, control information is sent over three RLs instead of the5 previous two RLs. Thus more resources are used in the DL in comparison with the situation illustrated in Figure 4A. However, as the presumption was that capacity was available in the DL, but there was a congestion in the UL, the UL congestion problem is solved, or at least somewhat diminished, while the additional DL control signalling does not introduce any problem as there is free capacity to use in DL.

0

Thereby the signalling within the communication network 100 is improved thanks to the added flexibility in allocation of signalling resources from DL to UL, and vice versa.

Figure 4D is illustrating the same diagram and other illustrations as illustrated in the previ-5 ously described Figure 4A, in a scenario where the uplink is congested while there is free capacity in the DL. The received signal strengths of all DL signals over the RLs 140-1 , 140- 2, 140-n are identical with the situation illustrated in Figure 4A, Figure 4B and Figure 4C, with exception for RL 5 and RL 9, which in this scenario have stronger received respective signal strengths than the 1A limit 310.

0

In this example, the maximum number of RLs 140-1 , 140-2, 140-n allowed in the active set 300 has been altered from three (in the example illustrated in Figure 4A) to four.

Thereby more RLs 140-1 , 140-2, 140-n are allowed in the active set 300. Before the5 change, the active set 300 comprised RL1 , RL 5 and RL 9. RL 4 also fulfils the requirements for being entered into the active set 300, but when the maximum number of RLs 140-1 , 140- 2, 140-n allowed in the active set 300 is limited to three, this is not possible. By changing the maximum number of RLs 140-1 , 140-2, 140-n allowed in the active set 300 to four instead, the active set 300 comprises RL 1 , RL 4, RL 5 and RL 9.

The thereby achieved effect is illustrated at the bottom of Figure 4D, i.e. that UL data is transmitted over four RLs (RL 1 , RL 4, RL 6 and RL 9) instead of the previous three RLs (RL 1 , RL 5 and RL 9). In the opposite DL direction, control information is sent over four RLs instead of the previous three RLs. Thus more resources are used in the DL in comparison with the situation before the increase of the maximum numbers of RLs in the active set 300. However, as the presumption was that capacity was available in the DL, but there was a congestion in the UL, the UL congestion problem is solved, or at least somewhat diminished, while the additional DL control signalling does not introduce any problem as there is free capacity to use in DL.

Thereby the signalling within the communication network 100 is improved thanks to the added flexibility in allocation of signalling resources from DL to UL, and vice versa.

Figure 4E is illustrating the same diagram and other illustrations as illustrated in the previously described Figure 4A, in a scenario where the uplink is congested while there is free capacity in the DL. The received signal strengths of all DL signals over the RLs 140-1 , 140- 2, 140-n are identical with the situation illustrated in Figure 4D.

In this example, the 1A limit value 310 for transmitting a 1A report for requesting introduction of a RL 140-1 , 140-2, 140-n that has a received signal strength stronger than the 1A limit value 310, has been changed from -3 dB to -5 dB, as counted from the received signal strength of the serving cell RL 300.

Further the 1 B limit value 320 for transmitting a 1 B report for requesting removal of a RL 140-1 , 140-2, 140-n that has a received signal strength weaker than the 1 B limit value 320, has been changed from -6 dB to -8 dB, as counted from the received signal strength of the serving cell RL 300.

In addition, also the maximum number of RLs 140-1 , 140-2, 140-n allowed in the active set 300 has been altered from three (in the example illustrated in Figure 1A) to six. Thereby more RLs 140-1 , 140-2, 140-n are allowed in the active set 300. Before the change, the active set 300 comprised RLI and RL 4. After the changes, the active set 300 comprises RL 1 , RL 4, RL 5, RL 6, and RL 9. The thereby achieved effect is illustrated at the bottom of Figure 4E, i.e. that UL data is transmitted over five RLs (RL 1 , RL 4, RL 5, RL 6 and RL 9) instead of the previous two RLs (RL 1 and RL 4). In the opposite DL direction, control information is sent overfive RLs instead of the previous two RLs. Thus more resources are used in the DL in comparison with the situation before the alteration of the 1A limit 310, the 1 B limit 320 and the increase of the maximum numbers of RLs in the active set 300. However, as the presumption was that capacity was available in the DL, but there was a congestion in the UL, the UL congestion problem is solved, or at least somewhat diminished, while the additional DL control signalling does not introduce any problem as there is free capacity to use in DL.

Thereby the signalling within the communication network 100 is improved thanks to the added flexibility in allocation of signalling resources from DL to UL, and vice versa. By studying Figure 4B-Figure 4E and compare them with Figure 4A, various different embodiments are illustrated where the UL quality of transmitted radio signals is enhanced, by shifting transmission resources to UL by utilising spare DL resources.

Figure 5A- Figure 5D are illustrating the opposite situation in relation to the scenarios in Figures 4B- Figure 4E, i.e. there is a congestion in DL, while having sufficient load available in UL.

Here the concept is not necessarily that the signal strength/ quality is sufficient (because usually the power control would guarantee that) but that there is spare load in UL, that is, the UL load is lower than either a target load (the target load may typically be 75%) or lower than a congestion load (the UL may typically be considered congested at 95% load). In this case it may be afforded to remove some RLs from the active set 300 of the UE 120, with the result that the UE 120 may increase the transmission power and consequently the UL load may be increased because the increased power transmitted (and therefore received), but this is OK because there are available load capacity in UL or, more generally, because the load situation is more critical in DL.

The load as herein used may be defined as:

L = (useful received power) / (total received power) = (Itot - N)/ltot To actually preserve the same performance in UL it would be required to be sure that the UE 120 has spare transmission power, so that the transmission power of the UE 120 may be increased when the active set is reduced in some embodiments. Figure 5A illustrates the same diagram and other illustrations as illustrated in the previously described Figure 4A, but in a scenario where there is a congestion in DL while having spare load (compared to a target/ congestion threshold) in the UL. The received signal strengths of all DL signals over the RLs 140-1 , 140-2, 140-n are identical with the situation illustrated in Figure 4A.

In this example, the 1A limit value 310 for transmitting a 1A report for requesting introduction of a RL 140-1 , 140-2, 140-n that has a received signal strength stronger than the 1A limit value 310, has been changed from -3 dB to -1 dB, as counted from the received signal strength of the serving cell RL 300.

Thus the threshold for being entered into the active set 300 has been increased. As illustrated in the diagram, RL 4 no longer achieve the 1A limit value 310 and thus cannot be entered into the active set 300 of RLs. Thereby, by adjusting the 1 A limit value 310 from -3 dB to -1 dB, the active set 300 is modified from comprising two RLs, namely RL 1 and RL 4, into comprising only one RLs: RL 1 .

The thereby achieved effect is illustrated at the bottom of Figure 5A (to be compared with the corresponding illustration at the bottom of Figure 4A), i.e. that UL data is transmitted over one RL instead of the previous two RLs. In the opposite DL direction, control information is also sent over one RL (i.e. RL 1 ) instead of the previous two RLs (RL 1 and RL 4). Thus less signalling resources are used in DL in comparison with the situation illustrated in Figure 4A while more resources are used for data in UL. Thereby radio capacity is saved. However, as the presumption was that spare load was available in the UL (i.e. the UL received signal strength of radio signals transmitted by the UE 120 are of sufficient strength, i.e. stronger than a defined threshold level even after the active set size is reduced and the transmission power of the UE 120 is increased), DL resources are released. Thereby the overall capacity within the communication network 100 is improved thanks to the added flexibility in allocation of signalling resources from DL to UL, and vice versa. Figure 5B illustrates the same diagram and other illustrations as illustrated in the previously described Figure 4A and also in Figure 5A, but in a scenario where there is a congestion in DL while having spare load (compared to a target/ congestion threshold) in the UL. The received signal strengths of all DL signals over the RLs 140-1 , 140-2, 140-n are identical with the situation illustrated in Figure 4A and in Figure 5A.

In this example, the 1 B limit value 320 for transmitting a 1 B report for requesting removal of a RL 140-1 , 140-2, 140-n that has a received signal strength weaker than the 1 B limit value 320, has been changed from -6 dB to -4 dB, as counted from the received signal strength of the serving cell RL 300.

Thus the threshold for being removed from the active set 300 has been increased. As illustrated in the diagram, RL 4 thus is below the 1 B limit value 320 and thus is excluded from the active set 300.

Thereby, by adjusting the 1 B limit value 320 from -6 dB to -4 dB, the active set 300 is modified from comprising two RLs, namely RL 1 and RL 4, into comprising only one RL: RL 1 , in comparison with the situation illustrated in Figure 4A. The thereby achieved effect is illustrated at the bottom of Figure 5B (to be compared with the corresponding illustration at the bottom of Figure 4A), i.e. that UL data is transmitted over one RL instead of the previous two RLs. In the opposite DL direction, control information is also sent over one RL (i.e. RL 1 ) instead of the previous two RLs (RL 1 and RL 4). Thus less resources are used for control in DL, which then become available for data transmission while more resources (in particular load, due to increased power) may be used in UL. But this is OK because there are spare load in UL, the overall capacity of the network is increased.

However, as the presumption was that the UL received signal strength of radio signals trans- mitted by the UE 120 are of sufficient strength, i.e. stronger than a defined threshold level, DL resources are released.

Thereby the signalling within the communication network 100 is improved thanks to the added flexibility in allocation of signalling resources from DL to UL, and vice versa.

Figure 5C illustrates the same diagram and other illustrations as illustrated in the previously described Figure 4A and also in Figure 5A and Figure 5B, in a scenario where there is a congestion in DL while having spare load (compared to a target/ congestion threshold) in the UL. The received signal strengths of all DL signals over the RLs 140-1 , 140-2, 140-n are identical with the situation illustrated in Figure 4A and in Figure 5A- Figure 5B. In this example, the maximum number of RLs 140-1 , 140-2, 140-n allowed in the active set 300 has been altered from 3 (in the example illustrated in Figure 4A) to 1.

Thereby less RLs 140-1 , 140-2, 140-n are allowed in the active set 300. Before the change, the active set 300 comprised RL1 and RL 4. By changing the maximum number of RLs 140-1 , 140-2, 140-n allowed in the active set 300 to one instead, the active set 300 is reduced to comprising only RL 1.

The thereby achieved effect is illustrated at the bottom of Figure 5C, i.e. that UL data is transmitted over one RLs (i.e. RL 1 ) instead of the previous two RLs (RL 1 and RL 4). In the opposite DL direction, control information is sent over one RLs instead of the previous two RLs. Thus less resources are used in the DL in comparison with the situation before the decrease of the maximum numbers of RLs in the active set 300. However, as the presumption was that the received signal strength of signals transmitted by the UE 120 was fully sufficient, i.e. exceeding a threshold limit, the UL transmission over two RLs is redundant.

Thereby the signalling within the communication network 100 is improved thanks to the added flexibility in allocation of signalling resources from DL to UL, and vice versa.

Figure 5D is illustrating the same diagram and other illustrations as illustrated in the previ- ously described Figure 4A and Figures 5A- Figures 5C, but in a scenario where the DL is congested while having spare load (compared to a target/ congestion threshold) in the UL. The received signal strengths of all DL signals over the RLs 140-1 , 140-2, 140-n are identical with the situation illustrated in Figure 4A or Figure 5A- Figure 5C. In this embodiment, the previously illustrated examples of means for reducing the active set 300 are combined.

The 1A limit value 310 for transmitting a 1A report for requesting introduction of a RL 140-1 , 140-2, 140-n that has a received signal strength stronger than the 1A limit value 310, has been changed from -3 dB to -1 dB, as counted from the received signal strength of the serving cell RL 300. Further the 1 B limit value 320 for transmitting a 1 B report for requesting removal of a RL 140-1 , 140-2, 140-n that has a received signal strength weaker than the 1 B limit value 320, has been changed from -6 dB to -4 dB, as counted from the received signal strength of the serving cell RL 300.

In addition, also the maximum number of RLs 140-1 , 140-2, 140-n allowed in the active set 300 has been altered from three (in the example illustrated in Figure 1A) to one.

Thereby less RLs 140-1 , 140-2, 140-n are allowed in the active set 300. Before the change, the active set 300 comprised RL1 and RL 4. After the changes, the active set 300 comprises only RL 1 .

The thereby achieved effect is illustrated at the bottom of Figure 5D, i.e. that UL data is transmitted over one RL (RL 1 ) instead of the previous two RLs (RL 1 and RL 4). In the opposite DL direction, control information is sent over one RL instead of the previous two RLs. Thus less resources are used in the DL in comparison with the situation before the alteration of the 1A limit 310, the 1 B limit 320 and the decrease of the maximum numbers of RLs in the active set 300. However, as the presumption was that the received signal strength of signals transmitted by the UE 120 was fully sufficient, i.e. exceeding a threshold limit, the UL transmission over two RLs is redundant.

Thereby the signalling within the communication network 100 is improved thanks to the added flexibility in allocation of signalling resources from DL to UL, and vice versa. By studying Figure 5A-Figure 5D and compare them with Figure 4A, various different embodiments are illustrated where DL resources are saved.

Figure 6 is a flow chart illustrating embodiments of a method 500 for use in a Controlling Network Node (CNN) 130 in a communication network 100, for modifying an active set 300 of RLs 140-1 , 140-2, 140-n. The active set of RLs 300 is to be used by a UE 120, for wireless communication with at least one network node 1 10-1 , 1 10-2, 1 10-3 in the communication network 100.

The network node 1 10-1 , 1 10-2, 1 10-3 may comprise a Node B (NB) in some embodiments. The UE 120 may comprise e.g. a mobile station, cell phone or similar, or a wearable computing device, mobile sensor or similar. Thus in some embodiments, the CNN 130 may be distinct from the network node 1 10-1 , 1 10-2, 1 10-3 in the communication network 100. Further, the communication network 100 may be based on e.g. 3GPP Universal Mobile Telecommunications System (UMTS) network or any similar or related communication technology concept. The CNN 130 may be a Radio Network Controller, RNC in some embodiments and the network node 1 10-1 , 1 10-2, 1 10-3 may be a Node B.

However, the CNN 130 may in some alternative embodiments be comprised in the network node 1 10-1 , 1 10-2, 1 10-3, or in the RNC in the communication network 100.

To appropriately modify the active set 300 of RLs 140-1 , 140-2, 140-n, the method 500 may comprise a number of actions 501 -505. It is however to be noted that any, some or all of the described actions 501 -505, may be performed in a somewhat different chronological order than the enumeration indicates. At least some of the actions 501 -505 may be per- formed simultaneously or even be performed in an at least partly reversed order according to different embodiments. Further, it is to be noted that some actions may be performed in a plurality of alternative manners according to different embodiments, and that some such alternative manners may be performed only within some, but not necessarily all embodiments. Further, the authentication according to at least some of the performed actions 501 -505 may be periodically repeated in some embodiments.

In Action 501 a constraint of the wireless communication between the UE 120 and the network node 1 10-1 , 1 10-2, 1 10-3 is detected. The detected constraint of the wireless communication between the UE 120 and the network node 1 10-1 , 1 10-2, 1 10-3 may be an UL congestion or a DL congestion, but not both at the same time.

The detected constraint of the wireless communication between the UE 120 and the network node 1 10-1 , 1 10-2, 1 10-3 may in some embodiments comprise detecting an imbalance between UL and DL received signal strength in at least one RL 140-1 , 140-2, 140-n.

Action 502 is comprised only in some optional embodiments. The optional action 502 comprises sending a scrambling code of the UE 120 to a plurality of network nodes 1 10-1 , 1 10- 2, 1 10-3 communicating with the UE 120. Action 503 is comprised only in some optional embodiments. The optional action 503 comprises instructing the network nodes 1 10-1 , 1 10-2, 1 10-3 to measure and report signal strength of UL pilot signals received from the UE 120.

5 Action 504 is comprised only in some optional embodiments. The optional action 504 comprises receiving UL signal measurements of the UE UL pilot signals, from the network nodes 1 10-1 , 1 10-2, 1 10-3.

Action 505 comprises modifying the active set 300 of RLs 140-1 , 140-2, 140-n, based 10 on the detected 501 constraint of the wireless communication.

The detected constraint of the wireless communication between the UE 120 and the network node 1 10-1 , 1 10-2, 1 10-3 may in some embodiments comprise an UL congestion. In those embodiments, the modification of the active set 300 may comprise increasing the number of 15 RLs 140-1 , 140-2, 140-n in the active set 300, compared to an initial number of RLs 140- 1 , 140-2, 140-n.

This may be made by increasing the number of RLs 140-1 , 140-2, 140-n in the active set 300 compared to the initial number of RLs 140-1 , 140-2, 140-n, by performing any, some

20 or all of: controlling the number of RLs 140-1 , 140-2, 140-n in the active set 300, increasing a 1A threshold value 310, with respect to a serving cell RL strength 330, for transmitting a 1A report from the UE 120 to the CNN 130 and/ or increasing a 1 B threshold value 320, with respect to the serving cell RL strength 330, for transmitting a 1 B report from the UE 120 to the CNN 130. The number of RLs 140-1 , 140-2, 140-n in the active set 300 may be

25 controlled by adjusting the maximum allowed number of RLs in the active set 300.

According to those embodiments, when the DL of the communication network 100 is experiencing congestion, e.g. measured as the load being above a reference threshold for a period longer than a reference period while the UL has available resources, the 1 A threshold 30 value 310 and the 1 B threshold value 320 are dynamically decreased as well as the value of the maximum allowed active set size.

As an example, by decreasing the 1 A and 1 B thresholds by 1 dB as a non- limiting example more restrictive requirements are imposed on the quality of the RLs 140-1 , 140-2, 140-n added to the active set 300; and, consequently, also the number of RLs 140-1 , 140-2, 35 140-n which are added to the active set 300 are decreased. In this way the DL resources used for control information are limited to the highest quality links and the saved capacity can be used for data transmission. Similarly, the maximum active set size may be decreased and RLs 140-1 , 140-2, 140-n that have the lowest quality compared to the serving cell RL may be discarded.

5

In some other embodiments, the detected 501 constraint of the wireless communication may comprise a DL congestion. In such embodiments, the modification of the active set 300 comprises decreasing the number of RLs 140-1 , 140-2, 140-n in the active set 300, compared to the initial number of RLs 140-1 , 140-2, 140-n. The number of RLs 140-1 , 140-2,

10 140-n in the active set 300 may be decreased compared to the initial number of RLs 140-1 , 140-2, 140-n, by controlling the number of RLs 140-1 , 140-2, 140-n in the active set 300; decreasing the 1A threshold value 310, with respect to the serving cell RL strength 330, for transmitting the 1A report from the UE 120 to the CNN 130; or decreasing the 1 B threshold value 320, with respect to the serving cell RL strength 330, for transmitting the 1 B report

15 from the UE 120 to the CNN 130.

According to those embodiments, when the UL of the communication network 100 is experiencing congestion, e.g. measured as the load being above a reference threshold for a period longer than a reference period while the DL has available resources, the 1 A threshold 20 value 310 and the 1 B threshold value 320 may be dynamically increased and/ or the value of the maximum allowed active set size may be increased.

As an example, by increasing the 1A and 1 B thresholds by 1 dB in comparison with the received signal strength of the serving cell RL 330, less restrictive requirements on the qual-

25 ity of the RLs 140-1 , 140-2, 140-n that can be added to the active set 300 are imposed.

Consequently, the number of RLs 140-1 , 140-2, 140-n which are added to the active set 300 are increased. In this way available capacity in DL may be utilised for controlling additional RLs 140-1 , 140-2, 140-n added to the active set 300 by a given UE 120. Similarly the maximum active set size may be increased and thereby RLs 140-1 , 140-2, 140-n that

30 contribute to the decoding of the UE's signal may be added to the active set 300.

In some embodiments, wherein the detected constraint of the wireless communication between the UE 120 and the network node 1 10-1 , 1 10-2, 1 10-3 comprises detecting 501 an imbalance between UL and DL received signal strength in at least one RL 140-1 , 140-2, 35 140-n, the modification 505 of the active set 300 of RLs 140-1 , 140-2, 140-n may be based on DL signal measurements made by the UE 120 and based on UL signal measurements made by the network node 1 10-1 , 1 10-2, 1 10-3. In previously known conventional solutions, RLs 140-1 , 140-2, 140-n are added to, and removed from the active set 300 based on the measurement reports 1 A and 1 B respectively, sent by the UE 120, but in case UL and DL path-losses are imbalanced, as it may happen e.g. in a Frequency Division Duplex (FDD) system, where the signals in UL and DL are carried on different frequency bands which may be affected differently by interference and disturbances. Thus, the report sent by the UE 120 does not necessarily reflect the UL quality of the RL 140-1 , 140-2, 140-n, so that the best forward links may not be identified. As a solution to this shortcoming according to some embodiments, RLs 140-1 , 140-2, 140-n may be added to, and/ or deleted from the active set 300 of the UE 120, based on measurements of UL signals made by at least one network node 1 10-1 , 1 10-2, 1 10-3.

Thus, according to some embodiments, the CNN 130 may send the scrambling codes of the UE 120, or a plurality of UEs such as e.g. all UEs within the network 100 to at least one network node 1 10-1 , 1 10-2, 1 10-3, such as for example all network nodes 1 10-1 , 1 10-2, 1 10- 3 in the network 100, and instruct them to detect such UEs 120.

Thereby, one, some or all of the network nodes 1 10-1 , 1 10-2, 1 10-3 each may measure UL signals from the UE 120, such as the pilot Bit Error Rate (BER) or the pilot Signal-to-lnter- ference-plus-Noise Ratio (SINR) of the UE 120 in each of its own cells and report such measures to the CNN 130, either in an event-based fashion by defining a minimum absolute threshold and a set of relative thresholds, or periodically in different embodiments. The CNN 130 may then decide to which cell to assign the role of the serving cell, and which RL 140-

1 , 140-2, 140-n to add or remove to the active set 300, based on the pilot BER or pilot SINR measurements from each RL 140-1 , 140-2, 140-n and the network nodes 1 10-1 ,

1 10-2, 1 10-3 from which the UL pilot BER or pilot SINR measurement is reported.

More specifically the CNN 130 may sort the pilot BER or pilot SINR measurements within each network node 1 10-1 , 1 10-2, 1 10-3 and select, according to some criterion, the serving cell (e.g. the cell having the lowest pilot BER or pilot SINR). Then more RLs 140-1 , 140-2, 140-n may be added, taking them first from the same network node 1 10-1 , 1 10-2, 1 10-3 of the serving cell (if their performance is within a given threshold from the serving cell) then from other network nodes 1 10-1 , 1 10-2, 1 10-3 until the maximum number of RLs 140-1 , 140-

2, 140-n per active set 300 is reached or no additional RLs 140-1 , 140-2, 140-n sat- isfying the relative requirement on the pilot BER or pilot SINR are available. The relative and absolute thresholds on the pilot BER or pilot SI NR for the addition or removal of RLs 140-1 , 140-2, 140-n can be dynamically changed depending on the UL and DL load conditions as already explained in the previous embodiment A and B. Adopting this network-controlled mode enables reduction of the frequency, i.e. periodicity of the measure- 5 ment reports 1 A and 1 B sent by the UE 120.

It is to be noted that the here utilised measurement of interference and noise ratio "SINR" may be exchanged for, such as e.g. Signal-to-Noise-plus-lnterference Ratio (SNIR), Signal- to-lnterference Ratio (SIR), Signal-to-Noise Ratio (SNR), or any similar ratio for determining 10 interference and/ or noise impact of a signal.

Further, the BER is a measurement of the number of bit errors per unit time. However, other similar measurements for determining the number of correctly received bits of a data stream over a communication channel that have been altered due to noise, interference, distortion 15 or bit synchronisation errors, may be utilised.

According to some alternative embodiments wherein action 504 has been performed, the active set 300 of RLs 140-1 , 140-2, 140-n to be used by the UE 120 may be modified 505, based on the received 504 UL signal measurements.

20

In some embodiments, wherein the imbalance between UL and DL received signal strength in the RL 140-1 , 140-2, 140-n has been detected 501 when the difference between DL signal measurements made by the UE 120 and UL signal measurements made by the network nodes 1 10-1 , 1 10-2, 1 10-3 exceeds a threshold value, the modification of the active set 25 300 may comprise increasing the number of RLs 140-1 , 140-2, 140-n in the active set 300, compared to the initial number of RLs 140-1 , 140-2, 140-n when the detected constraint comprises an UL congestion; or decreasing the number of RLs 140-1 , 140-2, 140- n in the active set 300, compared to an initial number of RLs 140-1 , 140-2, 140-n when the detected constraint comprises a DL congestion.

30

In case of conflicting measurement reports in UL and DL in some embodiments, e.g. the UE signals the addition of a RL 140-1 , 140-2, 140-n while the network node signals the removal, and vice versa the CNN 130 should give priority to the network nodes 1 10-1 , 1 10-2, 1 10-3 reports in case the UL performance is to be improved and vice versa, give priority to 35 the UE reports in case the DL performance is to be improved. The CNN 130 in the communication network 100 comprises a processing unit 620, as discussed already in conjunction with the presentation of Figure 1 and Figure 2. The processing unit 620 is configured to detect a constraint of the wireless communication between the UE 120 and the network node 1 10-1 , 1 10-2, 1 10-3. The processing unit 620 is further configured to modify the active set 300 of RLs 140-1 , 140-2, 140-n, based on the detected constraint of the wireless communication. Such constraint may be an UL congestion, or a DL congestion, but not both at the same time.

In some embodiments, the processing unit 620 may be further configured to detect an UL congestion being the detected constraint of the wireless communication between the UE 120 and the network node 1 10-1 , 1 10-2, 1 10-3. Further the processing unit 620 may be further configured to modify the active set 300 of RLs 140-1 , 140-2, 140-n by increasing the number of RLs 140-1 , 140-2, 140-n in the active set 300, compared to an initial number of RLs 140-1 , 140-2, 140-n.

The processing unit 620 may further be configured to increase the number of RLs 140-1 , 140-2, 140-n in the active set 300, compared to the initial number of RLs 140-1 , 140-2, 140-n, by controlling the number of RLs 140-1 , 140-2, 140-n in the active set 300. Also, the processing unit 620 may be configured to increase a 1 A threshold value 310, with respect to a serving cell RL strength 330, for transmitting a 1A report from the UE 120 to the CNN 130. Further the processing unit 620 may be configured to increase a 1 B threshold value 320, with respect to the serving cell RL strength 330, for transmitting a 1 B report from the UE 120 to the CNN 130. In some embodiments, the processing unit 620 may additionally be configured to detect a DL congestion being the detected constraint of the wireless communication between the UE 120 and the at least one network node 1 10-1 , 1 10-2, 1 10-3. Also, the processing unit 620 may be configured to modify the active set 300 of RLs 140-1 , 140-2, 140-n by decreasing the number of RLs 140-1 , 140-2, 140-n in the active set 300, compared to the initial number of RLs 140-1 , 140-2, 140-n.

In some embodiments, the processing unit 620 may also be configured to decrease the number of RLs 140-1 , 140-2, 140-n in the active set 300, compared to the initial number of RLs 140-1 , 140-2, 140-n by controlling the number of RLs 140-1 , 140-2, 140-n in the active set 300. The processing unit 620 may further be configured to decrease a 1 A threshold value 310, with respect to the serving cell RL strength 330, for transmitting a 1A report from the UE 120 to the CNN 130. Further the processing unit 620 may also be configured to decrease a 1 B threshold value 320, with respect to the serving cell RL strength 330, for transmitting a 1 B report from the UE 120 to the CNN 130.

Furthermore, the processing unit 620 may also be configured to detect the constraint of the 5 wireless communication between the UE 120 and the network node 1 10-1 , 1 10-2, 1 10-3 by detecting an imbalance between UL and DL received signal strength in at least one RL 140- 1 , 140-2, 140-n. In addition the processing unit 620 may be configured to modify the active set 300 of RLs 140-1 , 140-2, 140-n based on DL signal measurements made by the UE 120 and based on UL signal measurements made by the network node 1 10-1 , 1 10- 10 2, 1 10-3.

The processing unit 620 may in addition also be configured to send a scrambling code of the UE 120 to a plurality of network nodes 1 10-1 , 1 10-2, 1 10-3 communicating with the UE 120. Further the processing unit 620 may also be configured to instruct the network nodes 1 10-1 , 15 1 10-2, 1 10-3 to measure and report signal strength/ quality of uplink pilot signals received from the UE 120. The processing unit 620 may be configured to receive UL signal measurements of the UE uplink pilot signals, from the network nodes 1 10-1 , 1 10-2, 1 10-3. Additionally, the processing unit 620 may be configured to modify the active set 300 of RLs 140-1 , 140-2, 140-n to be used by the UE 120, based on received UL signal measurements.

20

Further the processing unit 620 may in some embodiments be configured to detect imbalance between UL and DL received signal strength in the RL 140-1 , 140-2, 140-n when the difference between DL signal measurements made by the UE 120 and UL signal measurements made by the network node 1 10-1 , 1 10-2, 1 10-3 exceeds a threshold value. The

25 processing unit 620 may also be configured to increase the number of RLs 140-1 , 140-2, 140-n in the active set 300, compared to the initial number of RLs 140-1 , 140-2, 140-n when the detected constraint comprises an UL congestion. Also, the processing unit 620 may be configured to decrease the number of RLs 140-1 , 140-2, 140-n in the active set 300, compared to an initial number of RLs 140-1 , 140-2, 140-n when the detected con-

30 straint comprises a DL congestion.

The processing unit 620 may thus be configured to perform the method 500 according to at least some of the described actions 501 -505.

35 The above described actions 501 -505 to be performed in the CNN 130 may be implemented through the one or more processing units 620 in the CNN 130, together with computer program product for performing at least some of the functions of the actions 501 -505. Thus a computer program comprising program code may perform a method 500 according to any, at least some, or all of the functions of the actions 501 -505 for modifying an active set 300 of RLs 140-1 , 140-2, 140-n, where the active set 300 is to be used by a UE 120, for wireless communication with at least one network node 1 10-1 , 1 10-2, 1 10-3 in the commu- nication network 100, when the computer program is loaded into the processing unit 620 of the CNN 130.

Furthermore, the method 500 according to at least some of the actions 501 -505 may be implemented in a computer program, having code means, which when run by the processing unit 620 in the CNN 130, causes the processing unit 620 to execute at least some of the actions 501 -505 of the method 500. The computer program is comprised in a computer readable medium of a computer program product. The computer readable medium may comprise essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electri- cally Erasable PROM), a hard disk drive or any other appropriate medium such as a disk or tape that may hold machine readable data in a non-transitory manner. The computer program product may furthermore be provided as computer program code on a server and downloaded to the CNN 130 remotely, e.g., over an Internet or an intranet connection. The terminology used in the description of the embodiments as illustrated in the accompanying drawings is not intended to be limiting of the described method 500; the CNN 130; the network node 1 10-1 , 1 10-2, 1 10-3 and/ or the UE 120. Various changes, substitutions and/ or alterations may be made, without departing from the invention as defined by the appended claims.

As used herein, the term "and/ or" comprises any and all combinations of one or more of the associated listed items. The term "or" as used herein, is to be interpreted as a mathematical OR, i.e., as an inclusive disjunction; not as a mathematical exclusive OR (XOR), unless expressly stated otherwise. In addition, the singular forms "a", "an" and "the" are to be inter- preted as "at least one", thus also possibly comprising a plurality of entities of the same kind, unless expressly stated otherwise. It will be further understood that the terms "includes", "comprises", "including" and/ or "comprising", specifies the presence of stated features, actions, integers, steps, operations, elements, and/ or components, but do not preclude the presence or addition of one or more other features, actions, integers, steps, operations, ele- ments, components, and/ or groups thereof. A single unit such as e.g. a processing unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/ distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms such as via Internet or other wired or wireless communication system.

Claims

1 . A Controlling Network Node, CNN (130), in a communication network (100), for modifying an active set (300) of Radio Links, RLs (140-1 , 140-2, 140-n), where the active set (300) is to be used by a User Equipment, UE (120), for wireless communication with at least one network node (1 10-1 , 1 10-2, 1 10-3) in the communication network (100), wherein the CNN (130) comprises a processing unit (620), configured to:

detect a constraint of the wireless communication between the UE (120) and the network node (1 10-1 , 1 10-2, 1 10-3); and

modify the active set (300) of RLs (140-1 , 140-2, ... , 140-n), based on the detected constraint of the wireless communication.

2. The CNN (130) according to claim 1 , wherein the detected constraint is an uplink congestion, or a downlink congestion.

3. The CNN (130) according to any of claim 1 or claim 2, wherein the processing unit (620) is further configured to:

detect an uplink congestion being the detected constraint of the wireless communication between the UE (120) and the network node (1 10-1 , 1 10-2, 1 10-3); and

modify the active set (300) of RLs (140-1 , 140-2, 140-n) by increasing the num- ber of RLs (140-1 , 140-2, 140-n) in the active set (300), compared to an initial number of RLs (140-1 , 140-2, 140-n).

4. The CNN (130) according to claim 3, wherein the processing unit (620) is configured to increase the number of RLs (140-1 , 140-2, 140-n) in the active set (300), compared to the initial number of RLs (140-1 , 140-2, 140-n), by:

controlling the number of RLs (140-1 , 140-2, 140-n) in the active set (300); increasing a 1A threshold value (310), with respect to a serving cell RL strength (330), for transmitting a 1A report from the UE (120) to the CNN (130); or

increasing a 1 B threshold value (320), with respect to the serving cell RL strength (330), for transmitting a 1 B report from the UE (120) to the CNN (130).

5. The CNN (130) according to any of claim 1 or claim 2, wherein the processing unit (620) is further configured to:

detect a downlink congestion being the detected constraint of the wireless commu- nication between the UE (120) and the at least one network node (1 10-1 , 1 10-2, 1 10-3); and modify the active set (300) of RLs (140-1 , 140-2, 140-n) by decreasing the number of RLs (140-1 , 140-2, 140-n) in the active set (300), compared to the initial number of RLs (140-1 , 140-2, 140-n).

6. The CNN (130) according to claim 5, wherein the processing unit (620) is configured to decrease the number of RLs (140-1 , 140-2, 140-n) in the active set (300), compared to the initial number of RLs (140-1 , 140-2, 140-n) by:

controlling the number of RLs (140-1 , 140-2, 140-n) in the active set (300); decreasing a 1A threshold value (310), with respect to the serving cell RL strength (330), for transmitting a 1A report from the UE (120) to the CNN (130); or

decreasing a 1 B threshold value (320), with respect to the serving cell RL strength (330), for transmitting a 1 B report from the UE (120) to the CNN (130).

7. The CNN (130) according to any of claims 1 -6, wherein the processing unit (620) is configured to:

detect the constraint of the wireless communication between the UE (120) and the network node (1 10-1 , 1 10-2, 1 10-3) by detecting an imbalance between uplink and downlink received signal strength in at least one RL (140-1 , 140-2, 140-n); and

modify the active set (300) of RLs (140-1 , 140-2, 140-n) based on downlink sig- nal measurements made by the UE (120) and based on uplink signal measurements made by the network node (1 10-1 , 1 10-2, 1 10-3).

8. The CNN (130) according to claim 7, the processing unit (620) is configured to: send a scrambling code of the UE (120) to a plurality of network nodes (1 10-1 , 1 10- 2, 1 10-3) communicating with the UE (120);

instruct the network nodes (1 10-1 , 1 10-2, 1 10-3) to measure and report signal strength of uplink pilot signals received from the UE (120);

receive uplink signal measurements of the UE uplink pilot signals, from the network nodes (1 10-1 , 1 10-2, 1 10-3); and

modify the active set (300) of RLs (140-1 , 140-2, 140-n) to be used by the UE

(120), based on received uplink signal measurements.

9. The CNN (130) according to any of claim 7 or claim 8, wherein the processing unit (620) is configured to:

detect imbalance between uplink and downlink received signal strength in the RL

(140-1 , 140-2, 140-n) when the difference between downlink signal measurements made by the UE (120) and uplink signal measurements made by the network node (1 10-1 , 1 10-2, 1 10-3) exceeds a threshold value; and

increase the number of RLs (140-1 , 140-2, 140-n) in the active set (300), compared to the initial number of RLs (140-1 , 140-2, 140-n) when the detected constraint 5 comprises an uplink congestion; or

decrease the number of RLs (140-1 , 140-2, 140-n) in the active set (300), compared to an initial number of RLs (140-1 , 140-2, 140-n) when the detected constraint comprises a downlink congestion.

10 10. The CNN (130) according to any of claims 1 -9, wherein the CNN (130) is comprised in the network node (1 10-1 , 1 10-2, 1 10-3) or in a Radio Network Controller, RNC, in the communication network (100).

1 1 . A method (500) in a Controlling Network Node, CNN (130) in a communication net- 15 work (100), for modifying an active set (300) of Radio Links, RLs (140-1 , 140-2, 140-n), where the active set (300) is to be used by a User Equipment, UE (120), for wireless communication with at least one network node (1 10-1 , 1 10-2, 1 10-3) in the communication network (100), wherein the method (500) comprises:

detecting (501 ) a constraint of the wireless communication between the UE (120) 20 and the network node (1 10-1 , 1 10-2, 1 10-3); and

modifying (505) the active set (300) of RLs (140-1 , 140-2, 140-n), based on the detected (501 ) constraint of the wireless communication.

12. A computer program comprising program code for performing a method (500) ac- 25 cording to claim 1 1 , when the computer program runs on a computer.