WO2015036012A1

WO2015036012A1 - Method and node in a wireless communication system

Info

Publication number: WO2015036012A1
Application number: PCT/EP2013/068730
Authority: WO
Inventors: Mats Hogberg; Bjorn Sihlbom
Original assignee: Huawei Technologies Co.,Ltd.
Priority date: 2013-09-10
Filing date: 2013-09-10
Publication date: 2015-03-19

Abstract

Wireless communication system (100) and method (600) in a wireless communication system (100) comprising a radio network node (110) and a resource management node (130), for adapting coverage of the radio network node (110) to variations in traffic load within a cell (140) served by the radio network node (110). The radio network node (110) comprises a plurality of antenna elements (210-1, 210-2, 210-n), forming a multiple antenna array (210) which is configured for MlMO transmission. The method (600) comprises determining (601) traffic related information within the cell (140) and/or from one or several adjacent cells (145), that are adjacent to the cell (140). The method (600) also comprises storing (602) the determined (601) traffic related information in a data base (150), together with a time stamp. Additionally, the method (600) further comprises establishing (603) a cell traffic pattern by analysing the stored (602) traffic related information and detecting traffic variations in time within the cell (140). Furthermore the method (600) additionally comprises calculating (604) a downlink pre-coder, based on the established (603) cell traffic pattern together with a traffic intensity estimation, hand over rate and/or dropped connections statistics from the adjacent cells (145). Also, the method (600) further comprises adapting (605) coverage of the radio network node (110) according to the downlink pre-coder.

Description

METHOD AND NODE IN A WIRELESS COMMUNICATION SYSTEM

TECHNICAL FIELD

Implementations described herein generally relate to a wireless communication system and method in a wireless communication system. In particular is herein described a mechanism for adapting coverage of a radio network node, configured for a Multiple-Input and Multiple- Output (MIMO transmission, in the wireless communication system.

BACKGROUND

A User Equipment (UE), also known as a mobile station, wireless terminal and/ or mobile terminal is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system or a wireless communication network. The communication may be made, e.g., between UEs, between a UE and a wire connected telephone and/ or between a UE and a server via a Radio Access Network (RAN) and possibly one or more core networks. The wireless communication may comprise various communication services such as voice, messaging, packet data, video, broadcast, etc.

The UE may further be referred to as mobile telephone, cellular telephone, computer tablet or laptop with wireless capability, etc. The UE in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/ or data, via the radio access network, with another entity, such as another UE or a server. The wireless communication system covers a geographical area which is divided into cell areas, with each cell area being served by a radio network node, or base station, e.g., a Radio Base Station (RBS) or Base Transceiver Station (BTS), which in some networks may be referred to as "eNB", "eNodeB", "NodeB" or "B node", depending on the technology and/ or terminology used.

Sometimes, the expression "cell" may be used for denoting the radio network node itself. However, the cell may also in normal terminology be used for the geographical area where radio coverage is provided by the radio network node at a base station site. One radio network node, situated on the base station site, may serve one or several cells. The radio net- work nodes may communicate over the air interface operating on radio frequencies with any UE within range of the respective radio network node. In some radio access networks, several radio network nodes may be connected, e.g., by landlines or microwave, to a Radio Network Controller (RNC), e.g., in Universal Mobile Telecommunications System (UMTS). The RNC, also sometimes termed Base Station Controller (BSC), e.g., in GSM, may supervise and coordinate various activities of the plural radio network nodes connected thereto. GSM is an abbreviation for Global System for Mobile Communications (originally: Groupe Special Mobile).

In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) radio network nodes, which may be referred to as eNodeBs or eNBs, may be connected to a gateway, e.g., a radio access gateway, to one or more core networks.

In the present context, the expressions downlink, downstream link or forward link may be used for the transmission path from the radio network node to the UE. The expression up- link, upstream link or reverse link may be used for the transmission path in the opposite direction, i.e., from the UE to the radio network node.

Beyond 3G mobile communication systems, such as e.g., 3GPP LTE, offer high data rate in the downlink by employing multiple antenna systems utilising Multiple-Input and Multiple- Output (MIMO).

Antenna arrays with large number of elements enable the increase in capacity by utilising spatial beam forming and spatial multiplexing. The benefit of these large arrays is the ability to spatially resolve and separate received and transmitted signals with very high resolu- tion.

Both single user MI MO with many layers and multi user MIMO will increase the network performance and system capacity. Especially in the uplink, the radio network node receiver will have the new freedom of spatial diversity to handle interference and increase the Sig- nal Interference Noise Ratio (SINR). One challenge with a radio network node that uses a large antenna array and many transceivers are to transmit the Down Link (DL) reference signals, or pilot signals; and the broadcast channel and common control channel for wanted coverage area. The reference signals and the broadcast channel and common control channel are used by the UE uses to detect (cell search) and connect (cell selection) to the radio network node. These signals and channels define the coverage area, or cell, for the radio network node. In a radio network node that uses a single column antenna with one or few transceivers the coverage is defined by the antenna column pattern and the power of the cell defining signals and channels.

The radio network node according to prior art are often equipped with a sector antenna that consists of several dual polarized antenna element placed in one column separated with a certain distance in wavelengths and combined to form a antenna pattern for azimuth and elevation cuts, as illustrated in Figure 1A and Figure 1 B, respectively. The sector antenna usually are equipped with a Remote Electrical Tilt (RET) function that can change the phase offset between each antenna element in the antenna array column so that the eleva- tion beam can be down tilted according to the horizontal plane. The azimuth and elevation antenna pattern are equal for all signals and channels that the base band and transceiver are transmitting and will form the coverage of the cell. An example of cell coverage is illustrated in Figure 1 C, depicting cell pattern for a sector antenna placed 32 m above ground level with electrical down tilt of 8 degrees.

As the traffic load within a cell may vary over time in different parts of the cell, it may be desired to also adapt the traffic capacity within the cell. One option may be to add micro nodes, pico nodes etc. in order to cover hotspots. However, such solution requires added hardware, which adds costs but also complexity to the system.

Changing direction of the antenna of the radio network node may be another option; however it is difficult to know what the traffic pattern within the cell looks like. The radio network node according to prior art has the possibility to change the direction of the elevation antenna beam and therefore change the down link coverage. The degrees of freedom to op- timise the down link cell coverage are then limited to steer the elevation beam.

A change of direction may be made e.g. by blind estimation. However, if the estimation is wrong, or the traffic pattern change over time due to structural changes in the landscape within the cell (new buildings, new roads, new use of old buildings etc.) the traffic capacity within the cell may decline and become even worse than in case the antenna direction is not changed at all.

Thus it appears that further development is required for improving cell coverage of a Ml MO radio network node. SUMMARY

It is therefore an object to obviate at least some of the above mentioned disadvantages and to improve the performance in a wireless communication system. 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 method is provided in a wireless communication system com- prising a radio network node and a resource management node. The method aims at adapting coverage of the radio network node to variations in traffic load within a cell, served by the radio network node. The radio network node comprises a plurality of antenna elements, forming a multiple antenna array which is configured for Multiple Input Multiple Output (Ml MO) transmission. The method comprises determining traffic related information within the cell and/ or from one or several adjacent cells, that are adjacent to the cell. Further, the method also comprises storing the determined traffic related information in a data base, together with a time stamp. In addition, the method furthermore comprises establishing a cell traffic pattern by analysing the stored traffic related information and detecting traffic variations in time within the cell. Also, in addition, the method comprises calculating a downlink pre-coder, based on the established cell traffic pattern together with a traffic intensity estimation, hand over rate and/ or dropped connections statistics from the adjacent cells. The method in addition comprises adapting coverage of the radio network node according to the downlink pre-coder. In a first possible implementation of the method according to the first aspect, the determined traffic related information comprises Direction of Arrival (DoA) and a device ID for a user equipment accessing the cell.

In a second possible implementation of the method according to the first possible imple- mentation, the determination of DoA for the user equipment accessing the cell comprises receiving wireless signals from the user equipment, selecting a subset of signals received from the user equipment having a received signal strength exceeding a predetermined threshold value, and determining DoA for the selected signals. In some possible implementations, average DoA value may be determined for minimizing data.

In a third possible implementation of the method according to the first aspect or any possible previous implementation, the traffic related information comprises a detected hand over failure, a direction indication of the detected hand over failure, a detected lost UE connection, a direction indication of such detected lost UE connection, detected interference from traffic within the cell and/ or the adjacent cell, a direction indication of such detected interference from traffic within the cell and/ or the adjacent cells. In some such possible imple- mentations, device ID may be associated and transmitted for enabling identification of the UE in question on the network side.

In a fourth possible implementation of the method according to the first aspect, or any possible previous implementation, the multiple antenna array the traffic intensity estimation and/ or a direction indication of the traffic intensity estimation, based on the traffic related information, such that a hot spot is detectable.

In a fifth possible implementation of the method according to the first aspect, or any possible previous implementation, the downlink pre-coder is time-varied based on traffic infor- mation such as DoA, time stamp and traffic intensity. This possible implementation may be made internally within the radio network node.

In a sixth possible implementation of the method according to the first aspect, or any possible previous implementation, the actions of storing the determined traffic related informa- tion in the data base, together with a time stamp and establishing the cell traffic pattern by analysing the stored traffic related information and detecting traffic variations in time within the cell are performed within the resource management node. This possible implementation may be enabled in the resource management node, based on information received from the radio network node.

In a seventh possible implementation of the method according to the first aspect, or any possible previous implementation, the actions of determining traffic related information within the cell and/ or the adjacent cell; calculating a downlink pre-coder, based on the established cell traffic pattern; and adapting coverage of the radio network node according to the downlink pre-coder are performed within the radio network node.

In an eighth possible implementation of the method according to the first aspect, or any possible previous implementation, the radio network node comprises an evolved NodeB (eNodeB), wherein the resource management node comprises a radio resource manage- ment node (RRM) and wherein the wireless communication network is based on 3rd Generation Partnership Project Long Term Evolution (3GPP LTE). According to a second aspect, a wireless communication system comprising a radio network node and a resource management node is provided for adapting coverage of the radio network node to variations in traffic load within a cell served by the radio network node. The radio network node comprises a plurality of antenna elements, forming a multiple an- tenna array which is configured for MIMO transmission. The wireless communication system comprises a processor within the radio network node, configured for determining traffic related information within the cell and/ or from one or several adjacent cells that are adjacent to the cell, and also configured for calculating a downlink pre-coder, based on the established cell traffic pattern together with a traffic intensity estimation, hand over rate and/ or dropped connections statistics from one or several adjacent cells, and in addition configured for adapting coverage of the radio network node according to the downlink pre-coder. Additionally, the wireless communication system comprises a processor within the resource management node, configured for storing the determined traffic related information in a data base, together with a time stamp, and also configured for establishing a cell traffic pattern by analysing the stored traffic related information and detecting traffic variations in time within the cell.

In a first possible implementation of the wireless communication system according to the second aspect, the radio network node comprises a receiver, configured for receiving wire- less signals from the user equipment.

In a second possible implementation of the wireless communication system according to the second aspect or the first possible implementation of the second aspect, the radio network node comprises an evolved NodeB (eNodeB), and wherein the resource manage- ment node comprises a radio resource management node (RRM); and wherein the wireless communication network is based on 3rd Generation Partnership Project Long Term Evolution (3GPP LTE).

According to a third aspect, a computer program is provided, comprising program code for performing a method according to the first aspect, or any possible implementation of the first aspect, for adapting coverage of a radio network node to variations in traffic load within a cell served by the radio network node, when the computer program is loaded into a processor of the radio network node, and a processor within the resource management node, respectively.

According to a fourth aspect, a computer program product is provided, comprising a computer readable storage medium storing program code thereon for in a wireless communica- tion system for adapting coverage of the radio network node to variations in traffic load within a cell served by the radio network node. The program code comprising instructions for executing a method, comprising determining traffic related information within the cell and/ or from one or several adjacent cells, that are adjacent to the cell. The method also comprises storing the determined traffic related information in a data base, together with a time stamp. Also, the method comprises establishing a cell traffic pattern by analysing the stored traffic related information and detecting traffic variations in time within the cell. In addition the method also comprises calculating a downlink pre-coder, based on the established cell traffic pattern together with a traffic intensity estimation, hand over rate and/ or dropped connections statistics from the adjacent cells. Furthermore, the method comprises adapting coverage of the radio network node according to the downlink pre-coder.

The prior art radio network node has limited, or no possibility to collect information of areas or direction were the traffic intensity is high or areas were problem with frequent handovers or dropped cell is small. Also time dependent traffic is difficult to adapt the down link cell coverage for. This problem is solved by the implementations herein described.

The above described aspects and their implementations differ from the prior art solutions in that a new capability of estimating DOA for traffic load and interference within the cell is provided. Also, a new capability to design a downlink cell pre-coder to improve network performance and be able to adapt the cell coverage to time variation in traffic load. Further, the above capability is useful for both FDD and TDD systems.

According to some implementations, the radio network node comprising many transceivers and a large antenna array, the downlink coverage is created by combing each antenna element signal to form an antenna pattern that is possible to be optimised according to the radio environment, neighbouring cell interference and network parameters as throughput, drop rate and hand over rate. Applicable standards such as 3GPP; procedures and its interfaces are supported. The radio network node comprising many transceivers and a large antenna array, has the capability of spatial pre-filter to detect Direction of Arrival (DOA) and design a downlink pre-coder for the downlink cell signals and channels to adapt to the spatial nature of the traffic load and interference. The downlink cell pre-coder can be updated so that time variant traffic load over day, over the week, over the month or over the year may be made. Thereby an improved performance within the wireless communication sys- tern is provided. Other objects, advantages and novel features of the aspects of the invention 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 in which:

Figure 1A is a diagram illustrating a possible azimuth pattern of a radio network node sector antenna according to prior art.

Figure 1 B is a diagram illustrating a possible elevation pattern of a radio network node sector antenna according to prior art.

Figure 1 C is a block diagram illustrating a cell pattern for a sector antenna according to prior art.

Figure 2 is a block diagram illustrating a wireless communication system according to some embodiments of the invention.

Figure 3 is a block diagram illustrating a radio network node architecture according to an embodiment of the invention.

Figure 4 is a block diagram illustrating a radio network node architecture according to an embodiment of the invention.

Figure 5A is a combined flow chart and signalling scheme, illustrating an embodiment of the invention.

Figure 5B is a block diagram, illustrating an embodiment of the invention.

Figure 5C is a block diagram, illustrating an embodiment of the invention.

Figure 6 is a flow chart illustrating a method in a radio network node according to an embodiment of the invention.

Figure 7A is a block diagram illustrating a wireless communication system architecture according to an embodiment of the invention.

Figure 7B is a block diagram illustrating a wireless communication system architecture according to an embodiment of the invention. DETAILED DESCRIPTION

Embodiments of the invention described herein are defined as a wireless communication system and a method in a wireless communication system, 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 descrip- tion, 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 2 is a schematic illustration over a wireless communication system 100 comprising a radio network node 110 communicating with a User Equipment (UE) 120, situated within a cell 140, served by the radio network node 1 10.

The wireless communication system 100 may at least partly be based on radio access technologies such as, e.g., 3GPP 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)/ En- hanced 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 Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), High Speed Packet Access (HSPA) Evolved Universal Terrestrial Radio Access (E-UTRA), Universal Terrestrial Radio Access (UTRA), GSM EDGE Radio Access Network (GERAN), 3GPP2 CDMA technologies, e.g., CDMA2000 1x RTT and High Rate Packet Data (HRPD), 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 some- times be utilised interchangeably. The wireless communication system 100 may be configured to operate according to the Time Division Duplex (TDD) and/ or the Frequency Division Duplex (FDD) principle, according to different embodiments. TDD is an application of time-division multiplexing to separate uplink and downlink signals in time, possibly with a Guard Period (GP) situated in the time domain between the uplink and downlink signalling. FDD means that the transmitter and receiver operate at different carrier frequencies. Further, the wireless communication system 100 and the radio network node 1 10 may be configurable for Ml MO, Multi-MI MO, massive Ml MO and/ or Antenna Array System (AAS), according to different embodiments.

The radio network node 1 10 is connected to a resource management node 130, which in turn may be connected to a data base 150.

The purpose of the illustration in Figure 2 is to provide a simplified, general overview of the wireless communication system 100 and the involved methods and nodes, such as the radio network node 1 10, the resource management node 130 and user equipment 120 herein described, and the functionalities involved. The method and wireless communication system 100 will subsequently, as a non-limiting example, be described in a 3GPP LTE/ LTE-Advanced environment, but the embodiments of the disclosed method and wireless communication system 100 may be based on another access technology such as, e.g., any of the above already enumerated. Thus, although embodiments of the invention may be described based on, and using the lingo of, 3GPP LTE systems, it is by no means limited to 3GPP LTE.

The illustrated wireless communication system 100 comprises the radio network node 1 10, which may send radio signals to be received by the user equipment 120.

It is to be noted that the illustrated network setting of one radio network node 1 10 and one user equipment 120 in Figure 2 is to be regarded as a non-limiting example of an embodiment only. The wireless communication system 100 may comprise any other number and/ or combination of radio network nodes 1 10 and/ or user equipment 120. A plurality of user equipment 120 and another configuration of radio network nodes 1 10 may thus be involved in some embodiments of the disclosed invention. Thus whenever "one" or "a/ an" user equipment 120 and/ or radio network node 1 10 is referred to in the present context, a plurality of user equipment 120 and/ or radio network nodes 1 10 may be involved, according to some embodiments. The radio network node 1 10 may according to some embodiments be configured for downlink transmission and may be referred to, respectively, as e.g., a base station, NodeB, evolved Node Bs (eNB, or eNode B), base transceiver station, Access Point Base Station, base station router, Radio Base Station (RBS), micro base station, pico base station, femto base station, Home eNodeB, sensor, beacon device, relay node, repeater or any other network node configured for communication with the user equipment 120 over a wireless interface, depending, e.g., of the radio access technology and/ or terminology used.

The user equipment 120 may correspondingly be represented by, e.g. a wireless communication terminal, a mobile cellular phone, a Personal Digital Assistant (PDA), a wireless platform, a mobile station, a tablet computer, a portable communication device, a laptop, a computer, a wireless terminal acting as a relay, a relay node, a mobile relay, a Customer Premises Equipment (CPE), a Fixed Wireless Access (FWA) nodes or any other kind of device configured to communicate wirelessly with the radio network node 1 10, according to different embodiments and different vocabulary.

The illustrated wireless communication system 100 also comprises the resource management node 130, which may be represented by a Radio Resource Management (RRM) node, according to some embodiments. Some embodiments of the invention defines a method where downlink coverage of the radio network node 1 10 will be defined by areas or directions where traffic intensity is high; time dependent traffic load; areas or directions where interference from any other neighbour cell is high; and/ or Information from the resource management node 130/ data base 150 of hand over and drop rate.

For the Radio Access Network (RAN) the interaction with the radio network node 1 10, that have the capability to report time and direction dependent traffic load and areas with high interference from other cells network performance, will give the possibility for the resource management node 130 to dynamic optimize, or at least improve, the RAN performance by configure the downlink coverage of the radio network node 1 10. Figure 3 discloses an embodiment of the radio network node 1 10 in the wireless communication system 100. The radio network node 1 10 comprises, or is connectable to, a Multiple Antenna Array 210, which is configurable for Ml MO. The Multiple Antenna Array 210 comprises a plurality of antenna elements 210-1 , 210-2, 210-n. The antenna elements 210-1 , 210-2, 210-n may sometimes also be referred to as Active Antenna Modules (AAM), where the AAM may comprise a Radio Frequency (RF) transceiver and antenna element.

According to an embodiment of the invention, the radio network node 1 10 and the multiple antenna array 210 may be configured as vertical single column, providing Elevation beam forming capability. Also, the radio network node 1 10 and the multiple antenna array 210 may be configured for providing Azimuth beam forming capability by means of a horizontal single row, planar or conformal. In addition, the radio network node 1 10 and the multiple antenna array 210 may be configured for both elevation and azimuth beam forming capa- bility by means of a 2D array with several rows and columns, planar or conformal.

The radio network node 1 10 comprises several transceivers. Each transceiver can be mapped to one or several antenna elements 210-1 , 210-2, 210-n. Uplink signals transmitted by the user equipment 120 may be received at different Direction of Arrivals (DoA) φ1 , φ2, ..., φη at each respective antenna element 210-1 , 210-2, 210-n comprised in the multiple antenna array 210. The mapping determines the resolution of the antenna beam pointing in both elevation and azimuth and Direction of Arrival resolution.

Direction of Arrival (DoA) may denote the direction from which a propagating radio wave arrives at the multiple antenna array 210. In some embodiments, an associated technique of beamforming may be utilised for estimating the signal from a given direction.

Angle of Arrival (AoA) measurement is an alternative measurement related to DoA, for determining the direction of propagation of a radio-frequency wave incident on the multiple antenna array 210. AoA determines the direction by measuring the Time Difference of Arrival (TDOA) at individual antenna elements 210-1 , 210-2, 210-n of the multiple antenna array 210. From these delays the AoA may be calculated. The alternative measurement of AoA may sometimes be utilised instead of, or together with DoA, according to some embodiments.

The function spatial pre-filter according to some embodiments, may use the uplink antenna streams from the transceivers uplink part to detect DoA φ1 , φ2, ..., φη for the strongest path from the user equipment 120. These DoA φ1 , φ2, ..., φη may be used to determine and select the direction that is useful for transmission in downlink transmissions. In this application the DoA φ1 , φ2, ..., φη may be used by the resource management node 130 to collect information of traffic intensity, in which area/ direction and how it varies with time of 5 day or weekdays. Also information of interference direction for each cell and areas/ direction with Hand Over (HO); drop rate problems can be detected. This information can be used to optimise, or improve, the network performance by changing the downlink cell 140 for the radio network node 1 10 that have the capability of spatial pre-filter and downlink cell beam forming.

10

Figure 4 illustrates a many element architecture of a radio network node 1 10 having a logical interface to the resource management node 130.

The spatial pre-filter detect the strongest signal path for the connected user equipment 15 120. For each user equipment 120, the strongest DoA φ1 , φ2, ..., φη, signal strength and interference level will be used for both the resource management node 130 and for the user equipment specific downlink pre-coder algorithm. The DoA estimation may be valid for both FDD and TDD systems as long as it is within the coherence bandwidth of the radio environment.

20

The radio network node 1 10 comprises a number of functionalities, such as e.g. a Digital Processing Unit (DPU) 320, with base band. Further, the Digital Processing Unit 320 may be connected to the resource management node 130. Also, the radio network node 1 10 comprises a pre-filter design functionality 330, configured for designing a downlink pre- 25 filter. The radio network node 1 10 also comprises a receiver pre-filter functionality 340. The radio network node 1 10 further may comprise a transmission beamforming cell coverage functionality 350. The enumerated functionalities 330, 340, 350 may be connectable to the array antenna elements modules 210, comprising modulation/ demodulation, power amplifiers and low noise amplifiers, for example.

30

The resource management node 130 may use the information from the radio network node 1 10, and also from other, neighbouring radio network nodes with the spatial pre-filter and downlink cell optimization capability and optimize the RAN performance. This can be done to compensate for non perfect site and time dependent traffic. The radio network node 1 10 35 may design a downlink pre-coder based on the information from the resource management node 130. The downlink pre-coder for the cell 140 may send downlink cell signals and channels in the direction where the traffic intensity is high and interference to other cells is low, acceptable or decreased.

Figure 5A illustrates an example of a combined signalling scheme and flow chart, accord- ing to an embodiment.

The radio network node 1 10 may establish and map an initial downlink cell pattern, by determining traffic related information within the cell 140. The radio network node 1 10 may collect data of traffic, direction of arrival φ1 , φ2, ..., φη, detected interference from other neighbouring cells etc. This collected information may be sent to the resource management node 130, which may store and process the received traffic data. The resource management node 130, which may comprise or be connectable to a data base 150, may store the received traffic data associated with time and/ or geographic area of the user equipment 120, within the cell 140. Based on the collected information, the resource management node 130 may configure a downlink cell pattern for the radio network node 1 10. This may be made by establishing a cell traffic pattern by analysing the stored traffic related information and detecting traffic variations in time within the cell 140.

This information, i.e. the established cell traffic pattern, may be provided to the radio net- work node 1 10, which may calculate a downlink pre-coder, based on data from the resource management node 130 for downlink cell pattern. Thereby, a downlink pre-coder may be calculated, based on the established cell traffic pattern together with a traffic intensity estimation, hand over rate and/ or dropped connections statistics from the adjacent cells and adapting coverage of the radio network node 1 10 according to the downlink pre- coder.

Figure 5B illustrates an overview of an embodiment of the invention, and the contextual environment wherein the invention may be implemented. The radio network node 1 10 which is serving the cell 140 and the resource management node 130 have through the previously described method located a first hotspot 410, at a first time interval t1 , and a second hotspot 420 at a second time interval t2, in the illustrated non limiting example.

For example, the first hotspot 410 may comprise e.g. an office building or similar, with high traffic during office hours 8-17, but very small traffic during evenings and weekends. The second hotspot 420 may be e.g. a pub/ restaurant area with little traffic during daytime but high traffic during evenings and weekends. Thereby, thanks to the discovered hotspots 410, 420 and the time dependency of the hot- spots 410, 420, it is possible to redirect the cell coverage within the cell 140 served by the radio network node 1 10. Thus a dynamic cell adaptation is enabled thanks to embodiments of the invention, which improve service of user equipment 120 within the cell 140.

The cell 140 is surrounded by a number of neighbour cells 145, which may be served by the same radio network node 1 10 as the cell 140, or by another, neighbour radio network node 115. The radio network nodes 1 10, 1 15 are connected to the resource management node 130, which thereby may receive and collect information concerning interference of radio traffic between cells 140, 145, lost connections during hand over between cell borders, hand over rate etc.

The collected radio traffic information may be stored within a database 150, where it may be retrieved by the resource management node 130 and assist in configuring a downlink cell pattern for the cell 140, according to some embodiments.

Figure 5C is depicting the radio network node 1 10 which is serving the cell 140 and the two time dependent hot spots previously discussed and illustrated in Figure 5B. In this illustrative example, the transmission direction of the multiple antenna array 210 of the radio network node 1 10 may be altered between a first setting 510, in order to cover the first hotspot 410 during a first time interval, and a second setting 520, in order to cover a second hotspot 420 during a second time interval, in the illustrated non limiting example. Thereby, the performance within the wireless communication system 100 may be improved, or even optimised due to time dependent traffic load and traffic intensity by adaption of the downlink cell coverage to the traffic and interference spatial nature.

Figure 6 is a flow chart illustrating embodiments of a method 600 in a wireless communica- tion system 100 comprising a radio network node 1 10 and a resource management node 130. The method 600 is configured for adapting coverage of the radio network node 1 10 to variations in traffic load such as e.g. hotspots 410, 420 within a cell 140 served by the radio network node 1 10. The variations may be in real time, in short time perspective such as over the day, and/ or log term perspective such as variations over seasons of the year. The radio network node 1 10 comprises a plurality of antenna elements 210-1 , 210-2, 210-n, forming a multiple antenna array 210 which is configured for Multiple Input Multiple Output (MIMO) transmission. The radio network node 1 10 may comprise an evolved NodeB (eNodeB). The resource management node 130 may comprise a radio resource management node (RRM) and the wireless communication network 100 may be based on 3rd Generation Partnership Project 5 Long Term Evolution (3GPP LTE). Further, the wireless communication system 100 may be based on FDD or TDD in different embodiments.

To appropriately adapting coverage of the radio network node 1 10 to variations in traffic load, the method 600 may comprise a number of actions 601 -605.

10

It is however to be noted that any, some or all of the described actions 601 -605, may be performed in a somewhat different chronological order than the enumeration indicates, be performed simultaneously or even be performed in a completely reversed order according to different embodiments. Further, it is to be noted that some actions may be performed in 15 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. The method 600 may comprise the following actions:

Action 601

20 Traffic related information within the cell 140 and/ or from one or several adjacent cells 145, which are adjacent to the cell 140 is determined.

The determined 601 traffic related information may comprise direction of Arrival (DoA) and/ or a device ID for a User Equipment (UE) 120 accessing the cell 140, according to some 25 embodiments.

Such determination of DoA for the user equipment 120 accessing the cell 140 may comprise: receiving wireless signals from the user equipment 120, selecting a subset of signals received from the user equipment 120 having a received signal strength exceeding a pre- 30 determined threshold value, and determining DoA for the selected signals.

The traffic related information may comprise e.g. a detected hand over failure, a direction indication of the detected hand over failure, a detected lost UE connection, a direction indication of such detected lost UE connection, detected interference from traffic within the cell 35 140 and/ or the adjacent cell 145, a direction indication of such detected interference from traffic within the cell 140 and/ or the adjacent cells 145. The action of determining traffic related information within the cell 140 and/ or the adjacent cell 145 may be performed within the radio network node 1 10.

Action 602

The determined 601 traffic related information is stored in a data base 150, together with a time stamp.

The action of storing the determined 601 traffic related information in the data base 150, together with a time stamp may be performed within the resource management node 130, according to some embodiments.

According to some embodiments, the traffic related information may be transmitted to the resource management node 130, which may store the traffic related information in the data base 150.

Action 603

A cell traffic pattern is established by analysing the stored 602 traffic related information and detecting traffic variations in time within the cell 140. The temporal traffic variations within the cell 140 may be in short term, over the day and/ or long term over the year.

The cell traffic pattern may comprise traffic intensity estimation and/ or a direction indication of the traffic intensity estimation, based on the traffic related information, such that a hot spot 410, 420 may be detectable, according to some embodiments. The action of establishing the cell traffic pattern by analysing the stored traffic related information and detecting traffic variations in time within the cell 140 may be performed within the resource management node 130.

Action 604

A downlink pre-coder is calculated, based on the established 603 cell traffic pattern together with a traffic intensity estimation, hand over rate and/ or dropped connections statistics from the adjacent cells 145.

The downlink pre-coder may be time-varied in some embodiments.

The action of calculating a downlink pre-coder, based on the established cell traffic pattern may be performed within the radio network node 1 10. Action 605

The coverage of the radio network node 1 10 is adapted according to the downlink pre- coder.

5

The action of adapting coverage of the radio network node 1 10 according to the downlink pre-coder may be performed within the radio network node 1 10.

The purpose of action 605 may be to adapt the cell coverage for the traffic load continu- 10 ously, according to some embodiments, which is symbolically illustrated with a loop back to action 601.

Figure 7A illustrates an embodiment of a wireless communication system 100 comprising a radio network node 1 10 and a resource management node 130. The wireless communi- 15 cation system 100 is configured for performing at least some of the previously described method actions 601 -605, for adapting coverage of the radio network node 1 10 to variations in traffic load within a cell 140 served by the radio network node 1 10.

The radio network node 1 10 comprises a plurality of antenna elements 210-1 , 210-2, 20 210-n, forming a multiple antenna array 210, or AAM, which is configured for Multiple Input Multiple Output (MIMO) transmission.

The radio network node 1 10 may comprise an evolved NodeB (eNodeB). The resource management node 130 may comprise a radio resource management node (RRM) and the 25 wireless communication network 100 may be based on 3rd Generation Partnership Project Long Term Evolution (3GPP LTE). Further, the wireless communication system 100 may be based on FDD or TDD in different embodiments.

The wireless communication system 100 comprises a processor 720 in the radio network 30 node 1 10. The processor 720 is configured for determining traffic related information within the cell 140 and/ or from one or several adjacent cells 145 that are adjacent to the cell 140. The processor 720 is also configured for calculating a downlink pre-coder, based on the established cell traffic pattern together with a traffic intensity estimation, hand over rate and/ or dropped connections statistics from one or several adjacent cells 145. In addition, 35 the processor 720 is further configured for adapting coverage of the radio network node 1 10 according to the downlink pre-coder. The processor 720 may be configured for determining Direction of Arrival (DoA) and/ or a device ID for a User Equipment (UE) 120 accessing the cell 140, according to some embodiments. Further, the processor 720 may be configured for determining DoA for the user equipment 120 accessing the cell 140 by receiving wireless signals from the user equip- ment 120, selecting a subset of signals received from the user equipment 120 having a received signal strength exceeding a predetermined threshold value, and determining DoA for the selected signals, according to some embodiments.

Furthermore, the processor 720 may also be configured for detecting hand over failure, a direction indication of the detected hand over failure, a detected lost UE connection, a direction indication of such detected lost UE connection, detected interference from traffic within the cell 140 and/ or the adjacent cell 145, a direction indication of such detected interference from traffic within the cell 140 and/ or the adjacent cells 145, according to some embodiments.

The processor 720 may also be configured for calculating a time-varied downlink pre-coder in some embodiments.

Such processor 720 may comprise one or more instances of a processing circuit, i.e. a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The herein utilised expression "processor" 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.

Further, the wireless communication system 100 also comprises a processor 820 within the resource management node 130, configured for storing the determined traffic related information in a data base 150, together with a time stamp. The processor 820 is also configured for establishing a cell traffic pattern by analysing the stored traffic related informa- tion and detecting traffic variations in time within the cell 140.

The processor 820 may additionally be configured for storing traffic related information received from the radio network node 1 10, together with a time stamp in some embodiments. Also, the processor 820 may further be configured for detecting a hot spot 410, 420 within the cell 140, based on the cell traffic pattern which may comprise traffic intensity estimation and/ or a direction indication of the traffic intensity estimation. Further, the processor 820 may also be configured for analysing the stored traffic related information and detecting traffic variations in time within the cell 140.

Such processor 820 may comprise one or more instances of a processing circuit, i.e. a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The herein utilised expression "processor" 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.

The wireless communication system 100 may in some embodiments comprise a receiver 710 in the radio network node 1 10 configured for receiving wireless signals from the user equipment 120 or any other entity configured for wireless communication over a wireless interface according to some embodiments.

The wireless communication system 100 may in some embodiments also comprise a data base 150 configured for storing collected traffic information, related to e.g. traffic intensity, hand over, dropping rate, together with a time stamp and an area or direction indication. The data base 150 may be connectable for the resource management node 130.

In addition, the wireless communication system 100 may further comprise a transmitter 730 in the radio network node 1 10. The transmitter 730 may be configured for transmitting wireless signals to the user equipment 120, via the multiple antenna array 210. In addition according to some embodiments, the wireless communication system 100 may in some embodiments also comprise at least one memory 725 in the radio network node 1 10. The optional memory 725 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 725 may comprise integrated circuits comprising silicon- based transistors. Further, the memory 725 may be volatile or non-volatile.

Figure 7B illustrates an alternative embodiment of a wireless communication system 100 comprising a radio network node 1 10 and a resource management node 130, similar to the embodiment illustrated in Figure 7A. The wireless communication system 100 is configured for performing at least some of the previously described method actions 601 -605, for adapting coverage of the radio network node 1 10 to variations in traffic load within a cell 140 served by the radio network node 1 10. The radio network node 1 10 comprises a plurality of antenna elements 210-1 , 210-2, 210-n, forming a multiple antenna array 210, or AAM, which is configured for Multiple Input Multiple Output (MIMO) transmission.

The radio network node 1 10 may comprise an evolved NodeB (eNodeB). The resource management node 130 may comprise a radio resource management node (RRM) and the wireless communication network 100 may be based on 3rd Generation Partnership Project Long Term Evolution (3GPP LTE). Further, the wireless communication system 100 may be based on FDD or TDD in different embodiments.

The wireless communication system 100 comprises a determining unit 722 within the radio network node 1 10, configured for determining traffic related information within the cell 140 and/ or from one or several adjacent cells 145, which are adjacent to the cell 140.

In addition, the wireless communication system 100 comprises a calculating unit 724 within the radio network node 1 10, configured for calculating a downlink pre-coder, based on the established cell traffic pattern together with a traffic intensity estimation, hand over rate and/ or dropped connections statistics from the adjacent cells 145.

Also, the wireless communication system 100 comprises an adapting unit 726 within the radio network node 1 10, configured for adapting the coverage of the radio network node 1 10 according to the downlink pre-coder. The enumerated units, the determining unit 722, the calculating unit 724 and/ or adapting unit 726 may be comprised within a processor 720 in the radio network node 1 10.

Furthermore, the wireless communication system 100 comprises a storing unit 822 within the resource management node 130, configured for storing traffic related information in the data base 150, together with a time stamp.

Also, the wireless communication system 100 comprises an establishing unit 824 within the resource management node 130, configured for establishing a cell traffic pattern by analysing the stored traffic related information and detecting traffic variations in time within the cell 140. The storing unit 822 and the establishing unit 824 may be comprised within a processor 820 in the resource management node 130.

The actions 601 -605 to be performed in the wireless communication system 100 may be 5 implemented through the one or more processing circuits 720, 820 in the radio network node 1 10 and the resource management node 130 together with computer program product for performing the functions of the actions 601 -605.

Thus a computer program comprising program code for performing the method 600 ac- 10 cording to any of actions 601 -605, for adapting coverage of a radio network node 1 10 to variations in traffic load within a cell 140 served by the radio network node 1 10, when the computer program is loaded into a processor 720 of the radio network node 1 10, and a processor 820 within the resource management node 130, respectively.

15 Thereby a computer program product may comprise a computer readable storage medium storing program code thereon for use by a wireless communication system 100 for adapting coverage of the radio network node 1 10 to variations in traffic load within a cell 140 served by the radio network node 1 10. The program code comprises instructions for executing a method 600 comprising determining 601 traffic related information within the cell

20 140 and/ or from one or several adjacent cells 145, that are adjacent to the cell 140. The method 600 also comprises storing 602 the determined 601 traffic related information in a data base 150, together with a time stamp. Further, the method 600 additionally comprises establishing 603 a cell traffic pattern by analysing the stored 602 traffic related information and detecting traffic variations in time within the cell 140. The method 600 may also in ad-

25 dition comprise calculating 604 a downlink pre-coder, based on the established 603 cell traffic pattern together with a traffic intensity estimation, hand over rate and/ or dropped connections statistics from the adjacent cells 145. Furthermore, the method 600 in addition may also comprise adapting 605 coverage of the radio network node 1 10 according to the downlink pre-coder.

30

The computer program product mentioned above may be provided for instance in the form of a data carrier carrying computer program code for performing at least some of the actions 601 -605 according to some embodiments when being loaded into the respective processors 720, 820. The data carrier may be, e.g., a hard disk, a CD ROM disc, a mem- 35 ory stick, an optical storage device, a magnetic storage device 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 pro- gram code on a server and downloaded to the radio network node 1 10 and the resource management node 130 remotely, e.g., over an Internet or an intranet connection.

The terminology used in the description of the embodiments as illustrated in the accompa- nying drawings is not intended to be limiting of the described method 600 and/ or wireless communication system 100. 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. In addition, the singular forms "a", "an" and "the" are to be interpreted 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 pre- elude the presence or addition of one or more other features, actions, integers, steps, operations, elements, components, and/ or groups thereof. A single unit such as e.g. a processor 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 method (600) in a wireless communication system (100) comprising a radio network node (1 10) and a resource management node (130), for adapting coverage of the radio network node (1 10) to variations in traffic load within a cell (140) served by the radio network node (1 10), which radio network node (1 10) comprises a plurality of antenna elements (210-1 , 210-2, 210-n), forming a multiple antenna array (210) which is configured for Multiple Input Multiple Output, MIMO, transmission, the method (600) comprising:

determining (601 ) traffic related information within the cell (140) and/ or from one or several adjacent cells (145), that are adjacent to the cell (140);

storing (602) the determined (601 ) traffic related information in a data base (150), together with a time stamp;

establishing (603) a cell traffic pattern by analysing the stored (602) traffic related information and detecting traffic variations in time within the cell (140);

calculating (604) a downlink pre-coder, based on the established (603) cell traffic pattern together with a traffic intensity estimation, hand over rate and/ or dropped connections statistics from the adjacent cells (145); and

adapting (605) coverage of the radio network node (1 10) according to the downlink pre-coder.

2. The method (600) according to claim 1 , wherein the determined (601 ) traffic related information comprises Direction of Arrival, DoA, and a device ID for a user equipment, UE, (120) accessing the cell (140).

3. The method (600) according to claim 2, wherein the determination of DoA for the UE (120) accessing the cell (140) comprises:

receiving wireless signals from the user equipment (120);

selecting a subset of signals received from the user equipment (120) having a received signal strength exceeding a predetermined threshold value;

determining DoA for the selected signals.

4. The method (600) according to any of claims 1-3, wherein the traffic related information comprises a detected hand over failure, a direction indication of the detected hand over failure, a detected lost UE connection, a direction indication of such detected lost UE connection, detected interference from traffic within the cell (140) and/ or the adjacent cell (145), a direction indication of such detected interference from traffic within the cell (140) and/ or the adjacent cells (145).

5. The method (600) according to any of claims 1-4, wherein the cell traffic pattern comprises traffic intensity estimation and/ or a direction indication of the traffic intensity estimation, based on the traffic related information, such that a hot spot 410, 420 is detectable.

6. The method (600) according to any of claims 1 -5, wherein the downlink pre-coder is time-varied.

7. The method (600) according to any of claims 1 -6, wherein the actions of storing (602) the determined (601 ) traffic related information in the data base (150), together with a time stamp and establishing (603) the cell traffic pattern by analysing the stored traffic related information and detecting traffic variations in time within the cell (140) are performed within the resource management node (130).

8. The method (600) according to any of claims 1-7, wherein the actions of determining (601 ) traffic related information within the cell (140) and/ or the adjacent cell (145); calculating (604) a downlink pre-coder, based on the established cell traffic pattern; and adapting (605) coverage of the radio network node (1 10) according to the downlink pre- coder are performed within the radio network node (1 10).

9. The method (600) according to any of claims 1-8, wherein the radio network node (1 10) comprises an evolved NodeB, eNodeB; wherein the resource management node (130) comprises a radio resource management node, RRM; and wherein the wireless communication network (100) is based on 3rd Generation Partnership Project Long Term Evolution, 3GPP LTE.

10. A wireless communication system (100) comprising a radio network node (1 10) and a resource management node (130), for adapting coverage of the radio network node (1 10) to variations in traffic load within a cell (140) served by the radio network node (1 10), which radio network node (1 10) comprises a plurality of antenna elements (210-1 , 210-2, 210-n), forming a multiple antenna array (210) which is configured for Multiple Input Multiple Output, MIMO, transmission, the wireless communication system (100) comprising:

a processor (720) within the radio network node (1 10), configured for determining traffic related information within the cell (140) and/ or from one or several adjacent cells (145) that are adjacent to the cell (140), and also configured for calculating a downlink pre- coder, based on the established cell traffic pattern together with a traffic intensity estima- tion, hand over rate and/ or dropped connections statistics from one or several adjacent cells (145), and in addition configured for adapting coverage of the radio network node (1 10) according to the downlink pre-coder; and

a processor (820) within the resource management node (130), configured for 5 storing the determined traffic related information in a data base (150), together with a time stamp, and also configured for establishing a cell traffic pattern by analysing the stored traffic related information and detecting traffic variations in time within the cell (140).

1 1. The wireless communication system (100) according to claim 10, wherein the ra- 10 dio network node (1 10) comprises a receiver (710), configured for receiving wireless signals from the user equipment (120).

12. The wireless communication system (100) according to any of claims 10-1 1 , wherein the radio network node (1 10) comprises an evolved NodeB, eNodeB; wherein the

15 resource management node (130) comprises a radio resource management node, RRM; and wherein the wireless communication network (100) is based on 3rd Generation Partnership Project Long Term Evolution, 3GPP LTE.

13. A computer program comprising program code for performing a method (600) ac- 20 cording to any of claims 1-9, for adapting coverage of a radio network node (1 10) to variations in traffic load within a cell (140) served by the radio network node (1 10), when the computer program is loaded into a processor (720) of the radio network node (1 10), and a processor (820) within the resource management node (130), respectively.

25 14. A computer program product comprising a computer readable storage medium storing program code thereon for use in a wireless communication system (100) for adapting coverage of the radio network node (1 10) to variations in traffic load within a cell (140) served by the radio network node (1 10), wherein the program code comprising instructions for executing a method (600) comprising:

30 determining (601 ) traffic related information within the cell (140) and/ or from one or several adjacent cells (145), that are adjacent to the cell (140);

establishing (603) a cell traffic pattern by analysing the stored (602) traffic related

35 information and detecting traffic variations in time within the cell (140); calculating (604) a downlink pre-coder, based on the established (603) cell traffic pattern together with a traffic intensity estimation, hand over rate and/ or dropped connections statistics from the adjacent cells (145); and