HK1079632B - Method and system for load balancing, load control device, accesss piont and subscriber terminal - Google Patents

Description

Load balancing method, system, load control equipment, access point and user terminal

Technical Field

The present invention relates to a load balancing method in a wireless communication network, a corresponding system, a load control device, a corresponding access point for a wireless communication network, a corresponding network element for a wireless communication network, a corresponding user terminal for a wireless communication network, and a computer program product for implementing a load balancing method in a wireless communication network.

Background

In recent years, wireless communication networks, for example for data and/or voice transmission, have become increasingly important. An example of such a wireless communication network is a Wireless Local Area Network (WLAN) independent of radio frequencies or the like (infrared or the like) used for this network. In such WLANs, user terminals such as personal computers, telecommunication devices, mobile phones, personal digital assistants, etc. are able to perform communication with each other or with corresponding user terminals of other networks (e.g. wired LANs, WLANs, fixed or mobile telecommunication networks, etc.) via corresponding communication protocols.

The general architecture of a WLAN is well known and will only be briefly described. The elements of a WLAN are a user terminal and an Access Point (AP) with which the user terminal communicates via a wireless communication interface, e.g. a radio or infrared based interface. An access point covers a specific area, which is hereinafter referred to as a cell. The size of the cell may depend on the environment, network company specifications, number of associated users, etc. The AP is adapted to control the communication of the user terminals within this cell, e.g. by allocating frequency channels, establishing connections for the user terminals, forwarding data to destination terminals, etc. The user terminal is typically associated with an access point, which is hereinafter referred to as the serving AP. Further, a distribution network to which the access points are connected is provided. Through the distribution network, communication connections between different APS or external networks, e.g. fixed networks, mobile telecommunication networks (e.g. GSM, UMTS, etc.), can be established for the user terminal. In the case of a mobile user terminal, there are cases where the user terminal leaves the cell of its serving AP. In this case, roaming is performed. Roaming means that the user terminal searches for an available AP whose connection quality is better than a predetermined threshold or the like, and switches the connection to this other available AP, which becomes the serving AP. The decision whether to perform roaming is made, for example, based on signal strength measurements or the like.

WLANs are implemented according to a particular standard. One of these standards is, for example, the IEEE (institute of electrical and electronics engineers) 802.11 standard or a corresponding extension thereof, for example the IEEE802.11 h standard, which is well known to those skilled in the art.

In the IEEE802.11 standard, MAC (MAC: medium access control) and PHY (physical layer) protocols are specifically defined. For example, using MAC protocols to allow interoperability between compatible physical layers, to reduce the probability of collisions between different user terminals, etc. In addition, the IEEE802.11 MAC protocol specifies beacon frames that are transmitted by the access point at regular intervals to allow stations to monitor for the presence of the access point. The IEEE802.11 MAC protocol also provides a set of management frames, including probe request frames sent by the user terminal followed by probe response frames sent by available access points, allowing the user terminal to actively scan to determine if there is an access point operating on a certain channel frequency and to show the user terminal the parameter settings being used by the access point. In addition, a MAC address is provided which is used as an identification element for the corresponding WLAN element.

According to the prior art, roaming of a user terminal from one AP to another AP is enabled according to specific structural settings in a wireless communication network. According to these configuration settings, the user terminal determines whether or not the latest reception quality is sufficient based on the communication reception quality measurement. If not, the user terminal may initiate a well-known roaming procedure.

However, according to this conventional roaming procedure, the load conditions in the wireless communication network are not taken into account in the roaming decision. In other words, the user terminal may switch to an AP in which the load conditions are such that the quality of the communication connection does not meet requirements, or is associated therewith. Thus, in conventional wireless communication networks, there is no load balancing between the respective APs.

In document EP 1156623 a1, a wireless LAN is described in which a roaming procedure is added to a load balancing function. To balance the load within the WLAN, the user terminal receives load information from the access point relating to the load status of the access point. The user terminal may then choose to establish a communication connection with one of the access points by using a cost function in which the received load information is taken into account.

However, in certain situations, a problem may arise in that the load-based roaming procedure is not performed in an advantageous manner. In a cellular type environment, the customer may be "hesitant" in selecting the correct cell based on conventional measurement information. It may then happen that the user terminal has measurement information that causes the cell, i.e. the serving AP, to change very easily or frequently. In particular, in the middle of a transmission, this results in undesired application pauses, for example pauses in data transmission or the like. Typically, roaming in a WLAN cell takes some time when changing from a serving AP to a neighboring AP. In other words, the effect of such easy roaming is a "stopped" application, which does not continue until signaling has been performed in the roaming state. In particular, when a user terminal is located in a densely used wireless network environment (i.e., a plurality of user terminals are communicating in respective cells), there is a so-called "round-trip handover" effect. In other words, it is decided quite frequently to change the service access of the user terminal even so that the same 2 APs participate in roaming.

Disclosure of Invention

It is therefore an object of the present invention to enable improved load balancing in a wireless communication network.

This object is for example achieved by a method for load balancing in a wireless communication network comprising: at least one user terminal for establishing and performing a wireless communication connection in the wireless communication network; a plurality of access points for controlling the wireless communication connection of the at least one user terminal and exchanging information with the at least one user terminal, wherein one of the plurality of access points is associated with the at least one user terminal; and a load control device, located outside the user terminal, for processing information relating to load in the wireless communication network and instructing the user terminal to roam from the associated one of the plurality of access points to another one of the plurality of access points, the method comprising the steps of: receiving in the user terminal access point status information determined in the plurality of access points, determining communication status information relating to the plurality of access points, and processing the received access point status information and the communication status information to obtain roaming support information; in the load control device, the roaming support information is processed by an access point related load based roaming analysis using a handover algorithm, and depending on the result of the access point related load based roaming analysis, it is decided whether to associate the user terminal with another one of the plurality of access points, and if so, roaming of the user terminal to the another one of the plurality of access points in the wireless communication network is initiated.

Furthermore, this object is for example achieved by a system for load balancing in a wireless communication network comprising: at least one user terminal for establishing and performing a wireless communication connection in the wireless communication network; and a plurality of access points for controlling the wireless communication connection of the at least one user terminal and exchanging information with the at least one user terminal, wherein one of the plurality of access points is associated with the at least one user terminal, the system comprising: access point load status monitoring means, located within each of the plurality of access points, for measuring the transmission load of the access point and transmitting access point status information; roaming support means within said user terminal for receiving said access point status information from said plurality of access points, determining communication status information relating to said plurality of access points, processing said received access point status information and said communication status information to obtain and transmit roaming support information; and a load control device, located outside the user terminal, for processing the roaming support information by an access point related load based roaming analysis using a handover algorithm, deciding whether to associate the user terminal with another one of the plurality of access points according to a result of the access point related load based roaming analysis, and initiating roaming of the user terminal from the associated access point to the another one of the plurality of access points in the wireless communication network.

Furthermore, this object is achieved by a load control device for load balancing in a wireless communication network comprising: at least one user terminal for establishing and performing a wireless communication connection in the wireless communication network; and a plurality of access points for controlling the wireless communication connection of the at least one user terminal and exchanging information with the at least one user terminal, wherein one of the plurality of access points is associated with the at least one user terminal, wherein the load control device is located outside the user terminal and is configured to process roaming support information received from a user terminal obtained by the user terminal from access point status information of the plurality of access points by access point related load based roaming analysis using a handover algorithm, deciding whether to associate the user terminal with another access point of the plurality of access points based on a result of the access point-related load based roaming analysis, and initiating roaming of the user terminal from the associated access point to the another one of the plurality of access points in the wireless communication network.

Further, this object is achieved by an access point for use in a wireless communication network comprising at least one user terminal for establishing and performing a wireless communication connection in the wireless communication network, and a plurality of other access points for controlling the wireless communication connection of the at least one user terminal and exchanging information with the at least one user terminal, wherein the access point comprises: access point load status monitoring means for measuring a transmission load of the access point and transmitting access point status information; and a load control device as described above.

Furthermore, this object is achieved by a network element for use in a wireless communication network comprising: at least one user terminal for establishing and performing a wireless communication connection in the wireless communication network; and a plurality of access points for controlling the wireless communication connection of the at least one user terminal and exchanging information with the at least one user terminal, wherein one of the plurality of access points is associated with the at least one user terminal, wherein the network element is separate from and connected to the plurality of access points and comprises a load control device as described above.

Further, this object is achieved by a user terminal for use in a wireless communication network comprising a plurality of access points for controlling said wireless communication connection of said at least one user terminal and exchanging information with said at least one user terminal, wherein one of said plurality of access points is associated with said at least one user terminal, said user terminal comprising: roaming support means for receiving said access point status information from said plurality of access points, determining communication status information relating to said plurality of access points, and processing said received access point status information and said communication status information to obtain roaming support information and sending said roaming support information to a load control device as described above, wherein said user terminal performs roaming from said associated access point to another one of said plurality of access points in said wireless communication network in response to an instruction from said load control device, wherein said another one of said plurality of access points is indicated in said instruction from said load control device.

This object is furthermore achieved by a computer program product for a data processing device, comprising software code portions for the steps of the load balancing method as defined above, when said product is run on said data processing device.

Further advantageous developments of the invention are set forth in the respective dependent claims.

The invention is particularly useful for balancing load conditions in a wireless communication network in such a way that a user terminal can perform roaming to another AP for better data throughput even if signal strength conditions do not require such a change of serving AP. Thus, the AP capacity available to the user terminal is utilized in an improved manner. Furthermore, the so-called round-trip handover effect during the roaming process of the user terminal can be suppressed.

The load balancing of the present invention can be used, for example, in WLAN environments (e.g., the environment of the IEEE802.11 standard) and extensions thereof (e.g., IEEE802.11 h).

The access point status information may include an access point identification element, e.g., a MAC address, and an access point load status indication determined for each access point indicating a load condition of the access point.

The communication state information determined in the user terminal may for example comprise a received signal strength indication, RSSI, indicating the received signal strength of the communication between the access point and said user terminal. Further, a carrier-to-interference ratio, C/I, for each access point may be determined for the communication state information. In addition, a terminal transmit power state may be determined for the communication state information.

Roaming support information can be obtained in the user terminal by processing the received access point state information and communication state information. It may comprise statistics (tables or lists) of access point related communication states and load information derived or measured from received access point state information, such as RSSI statistics, C/I statistics, load state information, AP/client transmit power state statistics, etc., which are assigned to the respective access points by the access point identification unit.

The roaming support information may be processed using a handover algorithm in a roaming analysis based on access point related loading. Thus, load and connection quality conditions are calculated for the connections between the user terminal and the available access points from the roaming support information. Thus, an optimal access point associated with the user terminal can be determined based on the respective load and connection quality conditions.

Furthermore, roaming analysis based on access point related load, e.g. processing parameters used in handover algorithms derived from roaming support information, may be weighted differently. For example, parameters related to connection quality conditions are given priority over parameters related to load conditions. Thus, operator specific roaming and load balancing settings are further improved.

The load control function may be provided at different locations. For example, the access point may include a load control function. Alternatively, the load control may be located in a specific network element separate from the access point, wherein this network element is connected to the access point in the wireless communication network.

As a further improvement, the access point internal monitoring information determined in the access point can be used for load control. For example, by comparing the access point identification elements in the roaming support information, the load control function determines the access points available to the user terminal and selects only the access point internal monitoring information of such available access points. Load control then processes the roaming support information and the selected access point internal monitoring information by enhanced roaming analysis based on access point related load. A decision is made whether to associate the user terminal with another access point based on the results of the enhanced roaming analysis based on the access point associated load. If so, roaming of the user terminal to this other access point in the wireless communication network is initiated.

The access point determined access point internal monitoring information includes, for example, retransmission rates to the associated user terminals, backoff windows and/or net allocation vectors (net allocation vectors) of the access point. By this, external interference statistics can be taken into account in an enhanced roaming analysis based on access point related load, which improves roaming and load balancing decisions in a wireless communication network.

Similar to the access point related load based roaming analysis defined above, in the access point related load based enhanced roaming analysis process, parameters used therein and derived from the roaming support information and the selected access point internal monitoring information may be weighted differently. Thus, operator specific roaming and load balancing settings are further improved.

Preferred embodiments of the present invention are described in more detail below with reference to the accompanying drawings.

Drawings

Fig. 1 shows a schematic diagram of a WLAN network according to a first embodiment of the invention.

Fig. 2 shows a block circuit diagram of a load balancing system according to a first embodiment.

Fig. 3 shows a flow chart of a load balancing method according to a first embodiment.

Fig. 4 shows a schematic diagram of a WLAN network according to a second embodiment of the invention.

Fig. 5 shows a block circuit diagram of a load balancing system according to a second embodiment.

Fig. 6 and 7 show a flow chart of a load balancing method according to a second embodiment.

Detailed Description

A first embodiment of the invention is described below with reference to fig. 1, 2 and 3.

Referring to fig. 1, a wireless communication network, e.g., a WLAN, includes several access points AP1, AP2, AP3 as communication control units. Further, in the illustrated example, a backbone network is provided that acts as a distribution network connecting the APs to each other and to external destination points, such as other WLANs or fixed networks. To connect the AP to the backbone network, a well-known input/output (I/O) interface is used.

Each AP defines a cell of a particular size (as indicated by the circle around the AP). The user terminals T1, T2, T3 within the network may be associated (connected) with an AP (serving AP) in whose cell the user terminals are located. In the present example, as initial conditions, the user terminal T1 is associated with AP1, T2 is associated with AP2, and T3 is associated with AP 3.

Regardless of its specific type (e.g., personal computer, mobile phone, etc.), the user terminal includes several means (not shown) known to those skilled in the art as required by its communication functionality. Such means are, for example, a processor for executing instructions and processing data of a communication connection (e.g. transmission content and signaling-related data), memory means (e.g. ROM, RAM, EEPROM, etc.) for storing instructions and data and serving as a working area for the processor or the like, input means (e.g. floppy disks, CD-ROMs, EEPROMs, etc.) for inputting data and instructions by software, user interface means (e.g. screens, keyboards, microphones, communication headsets, etc.) for providing monitoring and operating possibilities for a user, and network interface means (e.g. and wireless interface means, antennas, etc.) for establishing a communication connection under the control of the processor. These means can be integrated in one device (for example in the case of a mobile phone) or in several devices forming a user terminal (for example in the case of a personal computer).

Similarly, the access point includes several devices (not shown) known to those skilled in the art as needed for its communication functions. Such means are for example processors for executing instructions and processing data for communication connections (e.g. transmitting forwarding and signaling related data), memory means (e.g. ROM, RAM, EEPROM, etc.) for storing instructions and data and acting as a working area for the processor, etc., input means (e.g. floppy disks, CD-ROMs, EEPROMs, etc.) for entering data and instructions by software, user interface means (e.g. screens, keyboards, microphones, communication headsets, etc.) for providing monitoring and operating possibilities for a user, network interface means (e.g. and wireless interface means, antennas, etc.) for establishing communication connections with a user terminal under control of the processor, distributed network interface means for communicating with other APs under control of the processor via a backbone network, etc. In addition to the dedicated communication connection with the associated user terminal, the AP is adapted to send signalling data within its cell, thereby allowing determination of connection quality information relating to this AP. This may be performed by beacon frames that are transmitted permanently or at specific intervals.

In the WLAN of fig. 1, the user terminal receives this signaling data from those APs to which the cell it is located belongs. This means that T1 receives signaling data from AP1, AP2, AP3, T2 receives signaling data from AP1, AP2, T3 receives signaling data from AP1, AP 3. On the other hand, the user terminal transmits data to its corresponding serving AP. The signalling data may be used to determine the connection quality status of the user terminal, i.e. there is an AP providing better communication conditions in addition to the current serving AP. In this case the user terminal initiates a roaming procedure for association with other APs as is known in the art and described for example in connection with the corresponding standard of the wireless communication network.

In addition to this "normal" roaming procedure, according to the present embodiment, a further function is provided of initiating a roaming procedure, i.e. performing load balancing, depending on the load conditions in the WLAN. To this end, the signaling data includes load information determined in the AP in relation to an identification unit identifying the transmitting AP.

Roaming based on load balancing functionality is described in more detail with reference to fig. 2 and 3.

In fig. 2, a block circuit diagram of a load balancing system in a WLAN according to a first embodiment is shown. In fig. 3, a flow chart illustrating a method of load balancing in a wireless communication network is shown.

For simplicity, only one user terminal T1 is illustrated in fig. 2, where the user terminal T1 is to be load balanced, i.e. roaming decision. However, the process described below may be applied in parallel to multiple user terminals.

According to fig. 2, the APs comprise access point load status monitoring means (APLSM)11, 12, 13 adapted to determine the transmission load in the respective AP1, AP2 and AP 3. Furthermore, a load control device (LC)21, 22, 23 is comprised in the AP, which is adapted to perform a load based roaming analysis involving access point specific information and to initiate a roaming procedure for the user terminal. The load control device 21 is activated (as indicated by the dashed boxes of LCs 22 and 23) for user terminal T1 associated with AP1 (i.e. its AP is the serving AP). The user terminal T1, on the other hand, comprises roaming support means 30 adapted to process data and generate information, which data and information are used in connection with load balancing.

The transmission load condition may be determined in the AP as follows. The AP knows the number of relevant clients, e.g. by checking a list of identification elements stored for the relevant user terminals, e.g. their respective MAC addresses. In addition, simultaneous transmissions of related user terminals are monitored. The transmission-based estimation can have a certain timing window, where the window is observed over a certain period of transmitted samples. This is used as an indication of the transmission load, for example in the form of "send sample ═ transmission load". This can be averaged and used as a parameter for the load information.

The AP transmits the load information, for example, in the form of AP status information (APST), which may be included in a beacon frame transmitted by the AP. This means that all user terminals within range of the AP can receive this load information by means of signalling information periodically transmitted from the AP. The APST also contains an information element (e.g., MAC address) of the transmitting AP to allow load information to be distributed to the corresponding AP. Also, in case of, for example, 802.11h WLAN, Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC) information may be included in signaling information (APST) from the AP.

The user terminal may perform a measurement of the quality of the communication connection during the silent period. In this example, the roaming support apparatus 30 of the user terminal T1 receives the APST from the AP1, the AP2 and the AP3 through the wireless communication interface (step S10 in fig. 3). The roaming support apparatus 30 performs a process on the received information to generate roaming support information (RSUP, step S20 in fig. 3). For example, in this process, statistics (or a table or list) of the load conditions of the available (i.e., received) APs are formed. Furthermore, for all available APs, Received Signal Strength Indication (RSSI) measurements, well known to those skilled in the art, are performed in the user terminal, e.g. by means of its processor. RSSI measurements and load information determinations are assigned to the received APs by their MAC addresses and statistical information (tables or lists) thereof is formed.

In addition, the user terminal T1 may calculate a carrier-to-interference ratio (C/I) of the communication connection between each client (i.e., the user terminal T1) and the available AP (i.e., each cell) based on the received signaling information. The C/I can be used as an indication of the connection quality with a particular AP.

As optional further information, the terminal transmit power status can be determined at the user terminal side. This is useful in the case of static power control. However, in the IEEE802.11 h based network, the AP of the user terminal is used to control the transmission power, i.e., in the case where a transmission power stepping state is available.

Furthermore, the APST may include load information indicating the load status of the user terminal itself. This means that the user terminal measures the amount of transmitted data, e.g. in a predetermined time period, and forms corresponding statistical information.

The roaming support means 30 may collect and determine these pieces of information (APST) for a predetermined period of time and form roaming support information RSUP based on these collected pieces of information. For this purpose, the information and the processing results can be stored in a corresponding memory of the user terminal. However, there may be other criteria for stopping the formation of RSUP, such as an instruction from the user, an indication from the serving AP, and so on.

When the formation of the RSUP is completed (e.g., after a predetermined time period), the roaming support apparatus 30 transmits the RSUP to the load control device 21 of the serving AP1, i.e., the serving AP1, through the interface means of the user terminal T1 (step S30 in fig. 3). The load control device 21 processes the received RSUP to perform a roaming analysis based on the AP-related load (step S40 in fig. 3).

Specifically, the load control device 21 determines an AP suitable as a candidate for roaming of the user terminal T1, i.e., an AP providing sufficient signal strength, from the RSSI list contained in the RSUP. For example, the RSSI must reach a predetermined threshold. From the load information relating to the available APs, the load control device 21 is able to directly determine the capacity that the respective available AP has. The load control device may include dynamically adjustable thresholds for each AP of the WLAN indicating an "overload" condition. This means that it can be determined how many simultaneous users are allowed and to what extent the throughput of the AP can be reduced. When the transmit power state is included in the RSUP, it may be determined whether the available APs, i.e., their cells, are "equal" cells. This means that it can be determined whether the user terminal transmit power is at an appropriate level for the respective AP to receive the transmission. It should be noted that the transmit power of different cells may be different depending on the network planning, and further, the C/I statistics contained in RSUP can be used to determine the signal quality of the cell.

All information contained in RSUP is related to the AP by means of an information element (MAC address). Thus, the communication and load conditions of each of AP1, AP2, and AP3 can be determined with certainty.

The AP-related load based roaming analysis performed in the load control device 21 uses, for example, a handover algorithm whose parameters are derived from RSUP information (i.e. e.g. RSSI, C/I, load information, transmit power state). The processor of the (serving) AP may be used for the calculation of the handover algorithm. The structure of such a handover algorithm is manufacturer dependent and depends, for example, on the network structure, the setting of minimum signaling requirements, etc. The handover algorithm for the AP-related load based roaming analysis according to the present example is similar to algorithms commonly used and known by those skilled in the art. It should be noted that existing and future handover algorithms can easily be adapted by the person skilled in the art such that the proposed concept of load balancing functionality (i.e. roaming analysis based on AP related load) can be implemented. Those skilled in the art understand how to use the derived parameters within these manufacturer-specific switching algorithms so that the desired results are obtained.

Furthermore, the parameters derived from RSUP information may be weighted differently. This means that different status information, e.g. RSSI, C/I, load information, etc., can be divided. For example, parameters related to load information may be weighted higher (with higher priority) than parameters related to C/I, especially when the AP is determined to be "overloaded". Thus, a "back door" in the roaming decision can be used to force roaming to an AP even if the signal quality is not sufficient under normal circumstances. In addition, the weights can be flexibly set, for example, according to the overall transmission conditions. For example, when the load condition of the AP is important (the transmission load is higher than the predetermined threshold), the load control device 21 provides the parameters relating to the load information with higher priority than the case of low transmission load. Thus, criteria for roaming decision can be flexibly set.

It should be noted that the above-mentioned weighting is only an example and may be adjusted by the operator according to his choice.

Alternatively, to calculate the handover algorithm, the load control device 21 may use load information received directly from the serving AP load information. Thus, in the AP-related load based roaming analysis, most of the current load information can be used at least for the serving AP.

According to the result of the handover algorithm, the load control apparatus 21 decides whether or not to initiate a roaming procedure for the user terminal T1 (step S50 in fig. 3). This means that the load control device determines whether an AP is available for the user terminal T1, which provides sufficient communication connection quality and has a lower transmission load than the currently serving AP 1. If not ("no"), the serving AP1 continues to hold and the load balancing process is repeated.

On the other hand, when the load control device 21 determines that there is a "better" AP, a roaming procedure is initiated. For this purpose, the load control device 21 determines the target AP through a roaming analysis based on the AP-related load according to the MAC address contained in the RSUP. Next, an instruction (roaming) indicating that roaming to the determined new AP (for example, AP2) is to be performed is transmitted to the user terminal T1 through the serving AP1 (step S60 in fig. 3). Upon receiving this roaming instruction, the user terminal T1 performs roaming to the indicated AP2 in a known manner (step S70 in fig. 3). Thereafter, the load balancing process is repeated in conjunction with the load control device 22 of the AP2 as the new serving AP.

Next, as an exemplary case, a load balancing process according to the first embodiment is described with reference to fig. 1.

The user terminals T2 and T3 receive signaling information from 2 APs, and the user terminal T1 receives signaling information from all 3 APs. The user terminal sends its RSUP to its corresponding serving AP. The load control device of the respective AP processes this RSUP and makes a decision on the roaming of the user terminal in a centralized manner. The following situation may arise, for example, when using C/I statistics. When it is determined that the AP1 is "overloaded". T1 measures AP1, AP2 and AP3 and forms a statistical measurement database in the form of RSUP. Analysis of the measurements indicated that the AP2 loading was low due to the overload of the AP 1. Thus, as a preliminary result, the AP2 can be used as a target AP for roaming. In this example, however, the AP2 has a too dense, i.e., unclean, channel. The C/I statistics indicate that the adjacent C/I criteria are not satisfied. On the other hand, analysis showed that AP3 was also overloaded. The roaming option is then to use the "unclean" channel in the AP 2.

The load balancing function can be implemented, for example, by means of software code portions which are loaded into the respective network element (user terminal, access point) by means of its reading means and its memory. The access point is able to receive additional information RSUP from the user terminal and forward it towards the load control device.

A second embodiment is described below with reference to fig. 4 to 7.

It should be noted that certain means, functions and procedures of the second embodiment are similar to the corresponding means, functions and procedures of the first embodiment. And thus a detailed description thereof will be omitted.

Fig. 4 shows a wireless communication network, e.g. a WLAN, comprising several access points AP1, AP2, AP3 as communication control units, and a backbone network acting as a distribution network connecting the APs to each other and to external destination points, e.g. other WLANs or fixed networks. Furthermore, a separate network element 100 is provided, which comprises a load control device (LC) 110. The discrete network element 100 is connected to an access point through a backbone network to exchange data.

User terminals T1, T2, T3 located within the cell defined by the access points AP1, AP2, AP3 may be associated (connected) with an AP (serving AP). In the present example, as initial conditions, the user terminal T1 is associated with AP1, T2 is associated with AP2, and T3 is associated with AP 3.

The basic elements of the user terminal and the access point are similar to those described in the first embodiment. The separate network element 100 may have an access point like structure and comprise (not shown) at least a processor, memory means, input means, reading means, interface means, etc.

In the WLAN of fig. 4, the user terminal receives signaling data from those APs to which the cell in which it is located belongs. This means that T1 receives signaling data from AP1, AP2, AP3, T2 receives signaling data from AP1, AP2, T3 receives signaling data from AP1, AP 3. The signalling data may be used to determine the connection quality status of the user terminal, i.e. there is an AP providing better communication conditions in addition to the current serving AP. The signaling data includes load information determined in the AP in relation to an identification unit identifying the transmitting AP.

On the other hand, the user terminal sends data to its corresponding serving AP according to the received signaling data. The AP forwards this data to the network element 100. Furthermore, the AP is adapted to send separate monitoring information to the network element 100.

The network unit 100 processes data forwarded from the user terminal and may transmit the processing result to the user terminal through the backbone network and the serving AP.

Roaming based on load balancing functionality is described in more detail with reference to fig. 5 to 7.

In fig. 5, a block circuit diagram of a load balancing system in a WLAN according to a second embodiment is shown. In fig. 6 and 7, flow diagrams illustrating a method of load balancing in a wireless communication network are shown.

For simplicity, only one user terminal T1 is illustrated in fig. 5, where the user terminal T1 will be load balanced, i.e. roaming decision. However, the process described below may be applied in parallel to multiple user terminals.

According to fig. 5, the APs comprise access point load status monitoring means (APLSM)111, 112, 113 adapted to determine the transmission load in the respective AP1, AP2 and AP 3. Furthermore, the access point comprises access point internal monitoring means (APIM)211, 212, 213 which are adapted to measure external interference to form statistical information thereof and to send the statistical information directly to the load control device 110, for example in the form of access point internal monitoring information (APIM). External interference from an AP may be caused by another AP in the network, another non-WLAN system, such as a bluetooth client/AP, etc. This external interference may be determined, for example, based on measurements of the retransmission rate of the AP, monitoring results of the backoff window of each user terminal associated with the respective AP, determination of a list of Net Allocation Vectors (NAVs) of possible hidden user terminals, etc. This means that the APIM contains information concerning the external interference of the AP itself, which cannot be determined by measurements in the user terminal T1. Of course, an APIM can be identified as belonging to a particular AP, for example by including the MAC address of that AP.

The user terminal T1, on the other hand, comprises roaming support means 110 adapted to process data and generate information, which data and information are used in connection with load balancing.

Furthermore, the network element 100 comprises a load control device 110 adapted to perform a load-based enhanced roaming analysis involving the access point specific information and to initiate a roaming procedure for the user terminal. The load control device 110 located in the separate network element 100 is responsible for all APs connected to it and supports load balancing (in this example, AP1, AP2, AP 3).

As described in connection with the first embodiment, the transmission load condition may be determined in the AP by the APLSM 111, 112, 113 and transmitted to the roaming support apparatus 300 of the in-range user terminal T1 by means of the load information contained in the access point status information (APST). The APST also contains an information element (e.g., MAC address) of the transmitting AP to allow load information to be distributed to the corresponding AP.

Also, in case of, for example, 802.11h WLAN, Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC) information may be included in signaling information (APST) from the AP.

The user terminal T1 may perform the measurement of the quality of the communication connection during the silent period. In this example, the roaming support apparatus 300 of the user terminal T1 receives the APST from the AP1, the AP2 and the AP3 (step S110 in fig. 6). The roaming support apparatus 300 performs a process on the received information to generate roaming support information (step S120 in fig. 6). For example, in this process, statistics (or lists) of the load conditions of the available (i.e., received) APs, Received Signal Strength Indication (RSSI) measurements, and the like are formed. The received AP is assigned RSSI measurements and load information determinations by the AP's MAC address.

In addition, statistical information related to a carrier-to-interference ratio (C/I), a terminal transmission power state, and load information indicating a load state of the user terminal itself may be formed in the roaming support apparatus 300.

The roaming support apparatus 300 may collect and determine such information for a predetermined time period and form roaming support information RSUP according to such collected information. For this purpose, the information and the processing results can be stored in a corresponding memory of the user terminal. However, there may be other criteria for stopping the formation of RSUP, such as an instruction from the user, an indication from the serving AP, and so on.

When the formation of the RSUP is completed (e.g., after a predetermined time period), the roaming support apparatus 300 transmits the RSUP to the load control device 110 of the network element 100 through the serving AP1 and the backbone network (step S130 in fig. 6). It should be noted that for simplicity the data exchange between the user terminal T1 and the network element 100 is shown in a direct manner in fig. 5. However, in practice, the transmission between them is performed through the serving AP and the backbone network of the user terminal.

Thus, steps S110, S120 and S130 are similar to steps S10, S20 and S30 of the first embodiment, except that the information is sent to the load control device 110 in the separate network element 100.

In parallel with the APST and RSUP related measurements, the access point internal monitoring means 211, 212, 213 of AP1, AP2 and AP3, respectively, determine information relating to external interference and transmit the corresponding APIM to the load control device 110 (step S140 in fig. 6). Preferably, the determination and transmission of the APIM in the AP is performed in correspondence (synchronization) with the determination and transmission of the RSUP in the user terminal, for example, according to a predetermined time period.

The load control device 110 then determines and selects those APIMs that are sent from the APs available to the user terminal T1. This can be achieved, for example, by comparing the MAC addresses contained in RSUP and APIM so that only APIM of those APs which are also received by the user terminal T1 are considered for further processing (step S150 in fig. 6).

The load control device 110 now processes the RSUP from the user terminal T1 and the selected APIM from the access points AP1, AP2, AP3 to perform an enhanced roaming analysis based on the AP-related load (step S160 in fig. 6).

Specifically, the load control device 110 determines an AP suitable as a candidate for roaming of the user terminal T1, i.e., an AP providing sufficient signal strength, from the RSSI list contained in the RSUP. For example, the RSSI must reach a predetermined threshold. From the load information relating to the available APs, the load control device 110 is able to directly determine the capacity that the respective available AP has. The load control device may include dynamically adjustable thresholds for each AP of the WLAN indicating an "overload" condition. This "overload" threshold may be sent directly from the AP, for example, by the APIM. When the transmit power state is included in the RSUP, it may be determined whether the available APs, i.e., their cells, are "equal" cells. In addition, the C/I statistics contained in RSUP can be used to determine the signal quality of the cell. All information contained in RSUP is related to the AP by means of an information element (MAC address). Thus, the communication and load conditions of each of AP1, AP2, and AP3 can be determined with certainty. In addition, the load control device 110 determines whether the AP is affected by external interference (which may affect the connection quality of the user terminal) based on the APIM.

The enhanced roaming analysis performed in the load control device 110 based on AP-related load, for example, uses a modified handover algorithm whose parameters are derived from RSUP information (i.e., such as RSSI, C/I, load information, transmit power state) and APIM information (i.e., such as retransmission rate, backoff window, etc.). The processor of the (serving) AP may be used to modify the calculation of the handover algorithm. The structure of such a handover algorithm is manufacturer dependent and depends, for example, on the network structure, the setting of minimum signaling requirements, etc. The handover algorithm for enhanced roaming analysis based on AP related load according to the present example is similar to algorithms commonly used and known by those skilled in the art. It should be noted that existing and future handover algorithms can easily be adapted by the person skilled in the art such that the proposed concept of load balancing functionality (i.e. enhanced roaming analysis based on AP related load) can be implemented. Those skilled in the art understand how to use the derived parameters within these manufacturer-specific switching algorithms so that the desired results are obtained.

In addition, parameters derived from RSUP information and APIM information may be weighted differently. This means that different status information and/or interference information, e.g. RSSI, C/I, load information, retransmission rate, etc., can be divided. For example, parameters related to load information may be weighted higher (with higher priority) than parameters related to C/I, especially when the AP is determined to be "overloaded". On the other hand, parameters relating to external interference are weighted higher than parameters relating to received signal strength. Thus, a "back door" in the roaming decision can be used to force roaming to an AP even if the signal quality is not sufficient under normal circumstances. In addition, the weights can be flexibly set, for example, according to the overall transmission conditions. For example, when the load condition of the AP is important (the transmission load is higher than the predetermined threshold), the load control device 110 provides the parameters related to the load information with higher priority than the case of low transmission load. Thus, criteria for roaming decision can be flexibly set.

It should be noted that the above-mentioned weighting is only an example and may be adjusted by the operator according to his choice.

Based on the result of the handover algorithm, the load control device 110 decides whether or not to initiate a roaming procedure for the user terminal T1 (step S170 in fig. 7). This means that the load control device 110 determines whether an AP is available for the user terminal T1, which provides sufficient communication connection quality and has a lower transmission load than the currently serving AP 1. If not ("no"), the serving AP1 continues to hold and the load balancing process is repeated.

On the other hand, when the load control device 110 determines that a "better" AP exists, a roaming procedure is initiated. To this end, the load control device 110 determines a target AP through an enhanced roaming analysis based on AP-related loads according to the MAC address included in the RSUP and the APIM. Next, an instruction (roaming) indicating that roaming to the determined new AP (for example, AP2) is to be performed is transmitted to the user terminal T1 through the serving AP1 (step S180 in fig. 7). Upon receiving this roaming instruction, the user terminal T1 performs roaming to the indicated AP2 in a known manner (step S190 in fig. 7). Thereafter, the load balancing process is repeated in conjunction with the new serving AP2 and the load control device 110 of the network element 100.

Next, as an exemplary situation, a load balancing process according to the first embodiment is described with reference to fig. 4.

The user terminals T2 and T3 receive signaling information from 2 APs, and the user terminal T1 receives signaling information from all 3 APs. The user terminal sends its RSUP to its corresponding serving AP. The serving AP forwards the RSUP to the load control device 110 in the separate network element 100. In addition, the AP transmits an APIM to the load control device 110. When a roaming decision is to be made for the user terminal T1, the load control device 110 selects all received APIMs for further processing. The load control device 110 processes RSUP and APIM and makes decisions on roaming of user terminals in a centralized manner. For example, there may be a situation where AP1 is determined to be "overloaded" and the enhanced measurement analysis indicates that AP2 and AP3 are under load. Both AP2 and AP3 have sufficient C/I. In addition, AP2 has better RSSI statistics than AP 3. However, from the APIM, it is known that the AP2 is affected by external interference. Thus, the load control device 110 decides that the user terminal T1 must perform roaming to the AP 3.

The load balancing function can be implemented, for example, by means of software code portions which are loaded into the respective network element (user terminal, access point, network element) by means of its reading means and its memory. The access point is able to receive additional information RSUP from the user terminal and forward it towards the load control device.

Due to the implementation of the load control device in a fixed network element (AP or a separate network element), more complex processing methods (e.g. handover algorithms) and larger memory capacities can be used than the rather limited capabilities of the (mobile) user terminal.

It should be noted that features of one of the above embodiments are applicable in other embodiments as well. For example, the load control device in the first embodiment may be located in a separate network element connected to the AP via the backbone network. Further, in the second embodiment, the load control device may be located in each AP. The AP is then adapted to receive APIM from other APs.

Furthermore, although the above description relates to a WLAN, the invention is also applicable to other wireless network types, such as mobile telecommunications networks and the like.

It is possible to implement a load balancing function in existing systems even if there are network elements (user terminals, access points) that do not support the load balancing function. In this case, those network elements whose stations are described in the IEEE802.11 standard that do not understand the information relating to load balancing can ignore this information and perform normal roaming procedures that are not based on load information.

As mentioned above, the measurements of the user terminals are handled in a centralized manner by using a load balancing function in the access point (i.e. the serving access point) or in a separate network element connected to the access point of the wireless communication network.

The load balancing function is then able to take into account load information from a plurality of access points, as well as from a plurality of user terminals. This means that load balancing can be improved, since the decision as to whether the user terminal has to roam is made on the basis of the expanded set of information. For example, the load balancing function can take into account "future" events that may occur when another user terminal changes APs so that more capacity is available in the current AP. By making the decision in the AP side load control device or in the separate network element side load control device (both monitoring the whole wireless communication network), undesired round-trip switching effects can be reduced. The load control is performed in a more "timed" based manner, i.e. there will be a somewhat longer analysis period in the handover (roaming) decision. This also represents support in situations where complex measurements and handover algorithms are not possible for the user terminal. Thus, the transmission load over the entire wireless communication network is balanced.

As described above, for load balancing in a wireless communication network comprising at least one user terminal T1, T2, T3 and a plurality of access points AP1, AP2, AP3, a load control device 21,110 is used, which is located outside the user terminal, wherein the load control device is adapted to process information related to the load in the wireless communication network and to instruct the user terminal to roam from a relevant access point to another one of the plurality of access points. Receiving access point status information APST, S10, S110 determined among the plurality of access points, and determining communication status information related to the plurality of access points S20, S120.

The user terminal processes these information into roaming support information RSUP, S20, S120, and then processes the roaming support information in the load control device through roaming analysis based on access point related load S40, S160. Hereby, the load control device decides whether to relate the user terminal to another one of the plurality of access points S50, S170.

It is to be understood that the foregoing description and drawings are only illustrative of the invention. The preferred embodiments of the invention may vary within the scope of the attached claims.

Claims (42)

1. A method for load balancing in a wireless communication network, the wireless communication network comprising:

at least one user terminal (T1, T2, T3) for establishing and performing a wireless communication connection in the wireless communication network;

a plurality of access points (AP1, AP2, AP3) for controlling the wireless communication connection of the at least one user terminal and exchanging information with the at least one user terminal, wherein one of the plurality of access points is associated with the at least one user terminal; and

a load control device (21; 110) located outside the user terminal for processing information related to the load in the wireless communication network and instructing the user terminal to roam from the associated one of the plurality of access points to another one of the plurality of access points,

the method comprises the following steps:

receiving in the user terminal access point status information APST determined among the plurality of access points (S10; S110), determining communication status information related to the plurality of access points (S20; S120), and processing (S20; S120) the received access point status information and the communication status information to obtain roaming support information RSUP;

in the load control device, the roaming support information is processed (S40; S160) by an access point related load based roaming analysis using a handover algorithm, and depending on the result of the access point related load based roaming analysis, it is decided (S50; S170) whether to relate the user terminal to another one of the plurality of access points, and if so, then

Roaming of the user terminal to the other one of the plurality of access points in the wireless communication network is initiated (S60; S180).

2. The method according to claim 1, wherein the access point status information APST comprises an access point identification element and an access point load status indication determined in the respective access point.

3. The method according to claim 1 or 2, wherein in the step of determining communication state information, a received signal strength indication, RSSI, indicating received signal strengths of the plurality of access points is determined.

4. A method according to claim 1 or 2, wherein in the step of determining communication status information, the carrier to interference ratio, C/I, of each access point is determined.

5. The method of claim 1 or 2, wherein in the step of determining communication state information, a terminal transmission power state is determined.

6. The method according to claim 1 or 2, wherein said roaming support information RSUP obtained in said step of processing said received access point status information and said communication status information comprises statistical information of access point related communication status and load information derived from said received access point status information.

7. Method according to claim 1 or 2, wherein in the step of processing the roaming support information in the load control device by roaming analysis based on access point related loads, a handover algorithm is used to calculate load and connection quality conditions of the plurality of access points from the roaming support information and to determine an optimal access point related to the user terminal.

8. The method according to claim 1 or 2, wherein in said access point related load based roaming analysis, different weighting is applied to the processing parameters used in said access point related load based roaming analysis, which are derived from said roaming support information RSUP.

9. Method according to claim 1 or 2, wherein the load control device (21) is located in at least one of the plurality of access points.

10. A method according to claim 1 or 2, wherein the load control device (110) is located in a network element (100) separate from the plurality of access points, the network element being connected to the plurality of access points in the wireless communication network.

11. The method of claim 10, further comprising the step of:

transmitting (S140) access point internal monitoring information, APIM, from the plurality of access points to the load control device (110) in the network element;

determining (S150), in the load control device, access points available to the user terminal and selecting access point internal monitoring information of the available access points;

in the load control device, the roaming support information RSUP and the selected access point internal monitoring information APIM are processed (S160) by an enhanced roaming analysis based on access point related load, and depending on the result of the enhanced roaming analysis based on access point related load, it is decided (S170) whether to correlate the user terminal with another access point of the plurality of access points, and if so, whether to correlate the user terminal with the other access point of the plurality of access points

Initiating (S180) roaming of the user terminal to the other one of the plurality of access points in the wireless communication network.

12. The method according to claim 11, wherein the access point internal monitoring information APIM comprises, for a respective one of the plurality of access points, at least one of: retransmission rates to the relevant user terminals, backoff windows for the relevant user terminals and possible net allocation vectors for hidden user terminals.

13. The method of claim 11, wherein processing parameters used in the enhanced access point related load based roaming analysis and derived from the roaming support information and the selected access point internal monitoring information are weighted differently in the enhanced access point related load based roaming analysis.

14. A system for load balancing in a wireless communication network, the wireless communication network comprising:

at least one user terminal (T1, T2, T3) for establishing and performing a wireless communication connection in the wireless communication network; and

a plurality of access points (AP1, AP2, AP3) for controlling the wireless communication connection of the at least one user terminal and exchanging information with the at least one user terminal, wherein one of the plurality of access points is associated with the at least one user terminal,

the system comprises:

access point load status monitoring means (11, 12, 13; 111, 112, 113) located within each of said plurality of access points for measuring the transmission load of the access point and for transmitting access point status information APST;

roaming support means (30; 300) located within the user terminal for receiving the access point status information from the plurality of access points, determining communication status information relating to the plurality of access points, and processing the received access point status information and the communication status information to obtain and transmit roaming support information; and

load control means (21; 110) located outside the user terminal for processing the roaming support information by an access point related load based roaming analysis using a handover algorithm, deciding whether to associate the user terminal with another one of the plurality of access points based on a result of the access point related load based roaming analysis, and initiating roaming of the user terminal from the associated access point to the another one of the plurality of access points in the wireless communication network.

15. The system according to claim 14, wherein said access point status information APST comprises an access point identification element and an access point load status indication determined in the respective access point.

16. The system according to claim 14 or 15, wherein the roaming support device is configured for determining a received signal strength indication, RSSI, indicative of received signal strengths of the plurality of access points.

17. A system according to claim 14 or 15, wherein the roaming support means is configured to determine the carrier-to-interference ratio for each access point.

18. A system according to claim 14 or 15, wherein said roaming support means is configured to determine a terminal transmit power state.

19. The system according to claim 14 or 15, wherein said roaming support information obtained in and transmitted from said roaming support means comprises statistical information of access point related communication status and load information derived from said received access point status information.

20. The system according to claim 14 or 15, wherein said load control device is configured for processing said roaming support information in said access point related load based roaming analysis using a handover algorithm, for calculating load and connection quality conditions of said plurality of access points from said roaming support information, and for determining an optimal access point related to said user terminal.

21. System according to claim 14 or 15, wherein said load control device is configured for differently weighting processing parameters used in said access point related load based roaming analysis, derived from said roaming support information.

22. System according to claim 14 or 15, wherein the load control device (21) is located in at least one of the plurality of access points.

23. The system according to claim 14 or 15, wherein the load control device (110) is located in a network element (100) separate from the plurality of access points, the network element being connected to the plurality of access points in the wireless communication network.

24. The system of claim 21, further comprising:

access point internal monitoring means (211, 212, 213) located within each of said plurality of access points for determining access point internal monitoring information APIM and transmitting said access point internal monitoring information to said load control device,

wherein the load control device (110) is configured to determine access points available to the user terminal from the access point internal monitoring information and to select access point internal monitoring information of the available access points, to process the roaming support information and the selected access point internal monitoring information by an enhanced access point related load based roaming analysis, to decide whether to associate the user terminal with another one of the plurality of access points from a result of the enhanced access point related load based roaming analysis, and to initiate roaming of the user terminal to the another one of the plurality of access points in the wireless communication network.

25. The system of claim 24, wherein the access point internal monitoring information comprises, for a respective one of the plurality of access points, at least one of: retransmission rates to the relevant user terminals, backoff windows for the relevant user terminals and possible net allocation vectors for hidden user terminals.

26. The system according to claim 24, wherein said load control device is configured for differently weighting processing parameters used in said enhanced access point related load based roaming analysis, derived from said roaming support information and said selected access point internal monitoring information.

27. A load control device (21; 110) for load balancing in a wireless communication network, the wireless communication network comprising:

at least one user terminal (T1, T2, T3) for establishing and performing a wireless communication connection in the wireless communication network; and

a plurality of access points (AP1, AP2, AP3) for controlling the wireless communication connection of the at least one user terminal and exchanging information with the at least one user terminal, wherein one of the plurality of access points is associated with the at least one user terminal,

wherein the load control device is located outside the user terminal, is configured to process roaming support information received from a user terminal, obtained by the user terminal from access point status information APST of the plurality of access points, by access point related load based roaming analysis using a handover algorithm, to decide whether to associate the user terminal with another one of the plurality of access points, based on a result of the access point related load based roaming analysis, and to initiate roaming of the user terminal from the associated access point to the another one of the plurality of access points in the wireless communication network.

28. Load control device according to claim 27, wherein the access point status information comprises an access point identification element and an access point load status indication determined in the respective access point.

29. Load control device according to claim 27 or 28, wherein the roaming support information comprises at least a received signal strength indication indicating received signal strengths of the plurality of access points.

30. Load control device according to claim 27 or 28, wherein said roaming support information comprises at least a carrier-to-interference ratio of each access point.

31. Load control device according to claim 27 or 28, wherein said roaming support information comprises at least a terminal transmit power status.

32. Load control device according to claim 27 or 28, wherein said roaming support information comprises access point related communication status and load information statistics derived from said received access point status information.

33. Load control device according to claim 27 or 28, wherein said load control device is configured for processing said roaming support information in said access point related load based roaming analysis using a handover algorithm, for calculating load and connection quality conditions of said plurality of access points from said roaming support information, and for determining an optimal access point related to said user terminal.

34. Load control device according to claim 27 or 28, wherein the load control device is configured for differently weighting the processing parameters used in the access point related load based roaming analysis, derived from the roaming support information.

35. Load control device according to claim 27 or 28, wherein said load control device (21) is located in at least one of said plurality of access points.

36. A load control device according to claim 27 or 28, wherein said load control device (110) is located in a network element (100) separate from said plurality of access points, said network element being connected to said plurality of access points in said wireless communication network.

37. Load control device according to claim 36, wherein the load control device (110) is configured to receive access point internal monitoring information APIM of the plurality of access points, to determine from the access point internal monitoring information access points available to the user terminal, and to select access point internal monitoring information of the available access points, to process the roaming support information and the selected access point internal monitoring information by an enhanced access point related load based roaming analysis, to decide whether to associate the user terminal with another one of the plurality of access points according to the result of the enhanced access point related load based roaming analysis, and to initiate roaming of the user terminal to the another one of the plurality of access points in the wireless communication network.

38. The load control device of claim 37, wherein the access point internal monitoring information comprises, for a respective one of the plurality of access points, at least one of: retransmission rate to the associated user terminal, backoff window and net allocation vector.

39. Load control device according to claim 37, wherein the load control device is configured for differently weighting processing parameters used in the enhanced access point related load based roaming analysis, derived from the roaming support information and the selected access point internal monitoring information.

40. An access point (AP1, AP2, AP3) for use in a wireless communication network, the wireless communication network comprising at least one user terminal (T1, T2, T3) for establishing and performing a wireless communication connection in the wireless communication network, and a plurality of other access points for controlling the wireless communication connection of the at least one user terminal and exchanging information with the at least one user terminal,

wherein the access point comprises:

access point load status monitoring means (11, 12, 13) for measuring the transmission load of the access point and transmitting access point status information; and

a load control device (21) according to any of claims 27 to 35.

41. A network element (100) for use in a wireless communication network, the wireless communication network comprising:

at least one user terminal (T1, T2, T3) for establishing and performing a wireless communication connection in the wireless communication network; and

a plurality of access points (AP1, AP2, AP3) for controlling the wireless communication connection of the at least one user terminal and exchanging information with the at least one user terminal, wherein one of the plurality of access points is associated with the at least one user terminal,

wherein the network element (100) is separate from and connected to the plurality of access points and comprises a load control device (21) according to any of claims 27 to 35 and 36 to 39.

42. A user terminal (T1, T2, T3) for use in a wireless communication network, said wireless communication network comprising a plurality of access points (AP1, AP2, AP3) for controlling said wireless communication connection of said at least one user terminal and exchanging information with said at least one user terminal, wherein one of said plurality of access points is associated with said at least one user terminal,

the user terminal includes:

roaming support means (30; 300) for receiving the access point status information APST from the plurality of access points, determining communication status information relating to the plurality of access points, and processing the received access point status information and the communication status information to obtain roaming support information RSUP and sending the roaming support information to a load control device (21; 110) according to any one of claims 27 to 39,

wherein the user terminal performs roaming from the associated access point to another one of the plurality of access points in the wireless communication network in response to an instruction from the load control device, wherein the another one of the plurality of access points is indicated in the instruction from the load control device.