TECHNICAL FIELD

Implementations described herein generally relate to a network access unit and a method in a network access unit. In particular is herein described a mechanism for selecting signal path between a user equipment and a radio network node in a heterogeneous wireless communication network.

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 network, sometimes also referred to as a cellular radio system. 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 network 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 network 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 plu- ral 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. LTE is based on the GSM/EDGE and UMTS/HSPA network technologies, increasing the capacity and speed using a different radio interface together with core network improvements.

LTE-Advanced, i.e. LTE Releasel O and later releases are set to provide higher bitrates in a cost efficient way and, at the same time, completely fulfil the requirements set by International Telecommunication Union (ITU) for the International Mobile Telecommunications (IMT)-Advanced, also referred to as 4G.

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 uplink, 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.

Figure 1A illustrates an overview of the LTE system architecture. The high-level network architecture of LTE is comprised of following three main components: the UE, Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) and Evolved Packet Core (EPC). EPC is the core network.

The Home Subscriber Server (HSS) component has been carried forward from UMTS and GSM and is a central database that contains information about all the network operator's subscribers.

The Packet Data Network (PDN) Gateway (P-GW) communicates with the outside world i.e. PDN, using SGi interface. Each packet data network is identified by an Access Point Name (APN). The P-GW has the same role as the GPRS Support Node (GGSN) and the Serving GPRS Support Node (SGSN) within UMTS and GSM. The Serving Gateway (S-GW) acts as a router, and forwards data between the base station and the P-GW.

The Mobility Management Entity (MME) controls the high-level operation of the mobile by means of signalling messages and the HSS.

The Policy Control and Charging Rules Function (PCRF) is a component which is not shown in the above diagram but it is responsible for policy control decision-making, as well as for controlling the flow-based charging functionalities in the Policy Control Enforcement Function (PCEF), which resides in the P-GW.

Each eNB, or radio network node, connects with the EPC by means of the S1 interface and it can also be connected to nearby eNB's by the X2 interface, which is mainly used for signalling and packet forwarding during handover. The interface between the serving gateway and PDN gateway is known as S5/S8. This has two slightly different implementations, namely S5 if the two devices are in the same network, and S8 if they are in different networks.

Figure 1 B illustrates a heterogeneous network (Hetnet) comprising two radio network nodes, a relay node (RN), a Wi-Fi Access Point (AP). As illustrated, a UE which desires to attach to the network usually has multiple possible paths for doing so.

In such heterogeneous network, connection may e.g. be made with the radio network node directly, or via forwarding by the relay node (RN), the access point, or a neighbour radio network node. A prior art method of cell selection is based on the Reference Signal Received Power (RSRP), also known as Received Signal Strength Indication (RSSI) and/ or Received Channel Power Indicator (RCPI), assuming the wireless channel propagation models of downlink and uplink are identical. In this scheme, UEs are associated with the node from which the strongest downlink power is received.

The basic principle comprises the following steps:

(a) each network node sends a pilot signal,

(b) the UE measures the received pilot signal strength, RSRP, from the serving network node and from neighbouring network nodes and/ or relay nodes,

(c) the UE reports back to the serving network node the result of the measurements, and (d) the serving network node decides whether the UE should attach to the radio network node, the relay node, the access point, or the neighbour radio network node.

Typically, the UE is instructed to connect to the network node emitting the highest received pilot power, however an offset or threshold value may be added for avoiding frequent hand over of UEs at a cell border (ping-pong effect).

A problem with this approach is that it is based on the assumption that the channel propagation models of downlink and uplink are identical, which may not be the case. For exam- pie, the noise, which is inevitably added to the transmitted signal, may be generated by several disturbing influences such as thermal noise and other electronic noise from receiver input circuits or by interference from radiated electromagnetic noise picked up by the receiver's antenna. Generally, the undesired noise may be divided into a power dependent part (f(P)) which is a function of the transmission power (P), and a constant part (c):

noise = f(P) + c

As the transmission power of the radio network node is very high in comparison with the rather small transmission power of the UE, the constant noise part may be a neglectable part of the overall added noise for the downlink transmission, while it may be a dominating part of the uplink transmission, and vice versa. Thus, a path that gives an acceptable Signal to Interference plus Noise Ratio (SINR) in the downlink may be rather noisy in the uplink, or possibly vice versa. Instead of SINR, any similar measurement may be utilised such as e.g. Signal to Noise Ratio (SNR or S/N), Signal to Interference Ratio (SIR), Signal to Noise plus Interference Ratio (SNIR), Signal, Noise and Distortion ratio (SINAD), Signal-to- Quantization-Noise Ratio (SQNR), or any similar measurement or ratio related to a comparison of the power level of a desired signal with the level of undesired background noise.

Another problem with the prior art connection mechanism is that in a heterogeneous network, the serving radio network node is not aware of all possible connection options. For example, the serving radio network node may not be aware of any Wi-Fi access point, to which the UE has access. That may be solved by letting the user/ UE select the Wi-Fi connection. However, the UE may have even less information about possible alternative connection paths. Also, the user may have limited technical skill/ interest, just desiring to acquire an as good network connection as possible. Further, the serving radio network node may not know the reception quality in the uplink of other nodes in the network. Further, the prior art connection mechanism is putting emphasis on throughput of the network, while the UE may have a greater interest in saving transmission energy and thereby extending the time interval between battery reload. It appears that there is room for improvement for a method of accessing a UE to a heterogeneous network.

SUMMARY

It is therefore an object to obviate at least some of the above mentioned disadvantages and to improve the performance of a user equipment (UE) in a heterogeneous wireless communication network.

This and other objects are achieved by the features of the appended independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

According to a first aspect, a method is provided, for use in a network access unit, for selecting signal path between a user equipment and a radio network node in a heterogeneous wireless communication network. The heterogeneous wireless communication network also comprises a relay node and the network access unit, beside the radio network node. The method comprises receiving an access request from the user equipment. Also, the method comprises determining communication performance metrics for transmitting data between the user equipment and the radio network node. Furthermore, the method additionally comprises determining alternative connection paths between the user equipment and the radio network node. The method further comprises selecting connection path between the user equipment and the radio network node, based on the determined communication performance metrics.

In a first possible implementation of the method according to the first aspect, the selection of connection path also comprises selection of a cooperative relaying scheme for transmitting data packets between the user equipment and the radio network node.

In a second possible implementation of the method according to the first aspect, or the first possible implementation of the method according to the first aspect, the determination of communication performance metrics for transmitting data between the user equipment and the radio network node is performed independently in the uplink and the downlink. Further, the selection of connection path between the user equipment and the radio network node is performed independently in the uplink and the downlink.

In a third possible implementation of the method according to the first aspect, or any of the earlier described implementations, the method also comprises collecting signal measurement reports related to the determined alternative connection paths between the user equipment and the radio network node, and wherein the selection of connection path is based on the determined communication performance metrics and also on the collected signal measurement reports.

In a fourth possible implementation of the method according to the first aspect, or according to the third possible implementation of the method according to the first aspect, the signal measurement reports are collected from the user equipment, from the relay node and radio network node, respectively, comprised in the heterogeneous wireless communi- cation network.

In a fifth possible implementation of the method according to the first aspect, the method further comprises determining information related to a geographical location of the user equipment and wherein the connection path is selected by requesting a reference to the connection path from a data base, using the determined information related to the geographical location of the user equipment. Further, the data base comprises a network layout map and stored empirical information comprising distribution patterns for connection paths associated with different UE locations. In a sixth possible implementation of the method according to the fifth possible implementation of the first aspect, the information related to the geographical location of the user equipment comprises geographical coordinates measured by the user equipment, a signal fingerprint of signal measurements measured by the user equipment, and/ or a direction and distance estimation to the user equipment, made by the radio network node.

In a seventh possible implementation of the method according to the first aspect, or any of the earlier described implementations, the communication performance metrics for transmitting data between the user equipment and the radio network node comprises any of e.g. energy saving preference, Quality of Service (QoS) and/ or system throughput.

In an eighth possible implementation of the method according to the first aspect according to any of the third, fourth, fifth, sixth and/ or seventh possible implementation, the coopera- tive relaying scheme for transmitting data packets between the user equipment and the radio network node comprises relaying, diversity combination by multi-path, multi-hop and/ or network coding. In a ninth possible implementation of the method according to the first aspect, or any of the earlier described implementations, the heterogeneous wireless communication network comprises a Mobility Management Entity (MME) in which the network access unit is co- located. In a tenth possible implementation of the method according to the first aspect, or any of the earlier described implementations, the network access unit periodically re-perform any, some or all of the previously described actions, thereby enabling a re-selection of connection path between the user equipment and the radio network node, due to mobility of the user equipment.

According to a second aspect, a network access unit is provided, configured for selecting signal path between a user equipment and a radio network node in a heterogeneous wireless communication network. The heterogeneous wireless communication network also comprises a relay node and the network access unit. The network access unit comprises a receiver, configured for receiving an access request from the user equipment. Also, the network access unit comprises a processor, configured for determining communication performance metrics for transmitting data between the user equipment and the radio network node and also configured for determining alternative connection paths between the user equipment and the radio network node, and in addition also configured for selecting connection path between the user equipment and the radio network node, based on the determined communication performance metrics.

According to a first possible implementation of the second aspect, the processor is configured for selecting connection path by selection of a cooperative relaying scheme for trans- mitting data packets between the user equipment and the radio network node.

According to a second possible implementation of the second aspect, or the first possible implementation of the second aspect, the processor is also configured for determining communication performance metrics for transmitting data between the user equipment and the radio network node independently in the uplink and the downlink, and also configured for selecting connection path between the user equipment and the radio network node independently in the uplink and the downlink. According to a third possible implementation of the second aspect, or the first or second possible implementation of the second aspect, the processor is further configured for collecting signal measurement reports related to the determined alternative connection paths between the user equipment and the radio network node, and wherein the processor is configured for selecting connection path based on the determined communication performance metrics and also on the collected signal measurement reports.

According to a fourth possible implementation of the second aspect according to the third possible implementation, the processor is further configured for collecting the signal measurement reports from the user equipment, from the relay node and radio network node, respectively, comprised in the heterogeneous wireless communication network.

According to a fifth possible implementation of the second aspect, the processor is further configured for determining information related to a geographical location of the user equipment. Also, the processor further is configured for selecting the connection path by requesting a reference to the connection path from a data base, using the determined information related to the geographical location of the user equipment. Such data base may comprise e.g. a network layout map and/ or stored empirical information comprising com- munication performance metrics and/ or preferred configurations for different distribution patterns for connection paths associated with different UE locations.

According to a sixth possible implementation of the second aspect, according to the fifth possible implementation, the information related to the geographical location of the user equipment comprises e.g. geographical coordinates measured by the user equipment, a signal fingerprint of signal measurements measured by the user equipment, and/ or a direction and distance estimation to the user equipment, made by the radio network node.

According to a seventh possible implementation of the second aspect according to any of the previously described possible implementations thereof, the communication performance metrics for transmitting data between the user equipment and the radio network node comprises any of e.g. energy saving preference, Quality of Service (QoS) and/ or system throughput. According to an eighth possible implementation of the second aspect according to any of the previously described possible implementations thereof, the cooperative relaying scheme for transmitting data packets between the user equipment and the radio network node comprises e.g. any of relaying, diversity combination by multi-path, multi-hop and/ or network coding.

According to a ninth possible implementation of the second aspect according to any of the previously described possible implementations thereof, the heterogeneous wireless communication network comprises a Mobility Management Entity (MME) in which the network access unit is co-located.

According to a tenth possible implementation of the second aspect according to any of the previously described possible implementations thereof, the heterogeneous wireless communication network is based on 3rd Generation Partnership Project Long Term Evolution (3GPP LTE), wherein the radio network node comprises an evolved NodeB (eNodeB) and/ or wherein the relay node comprises any of e.g. an LTE relay, a micro node, a Pico base station, a Wi-Fi access point, a Femto node, a Visual Light Communication (VLC) unit or similar entity with a transmission power not exceeding the transmission power of the radio network node.

According to a third aspect, a computer program comprising program code is provided, for performing a method according to any of the first aspect, in a network access unit, for se- lecting signal path between a user equipment and a radio network node in a heterogeneous wireless communication network, also comprising a relay node and the network access unit, when the computer program is loaded into a processor of the network access unit according to the second aspect. According to a fourth aspect, a computer program product is provided, comprising a computer readable storage medium storing program code thereon for use by a network access unit, for selecting signal path between a user equipment and a radio network node in a heterogeneous wireless communication network. The heterogeneous wireless communication network comprises a relay node and the network access unit. The program code com- prising instructions for executing a method comprising receiving an access request from the user equipment. Further, the method also comprises determining communication performance metrics for transmitting data between the user equipment and the radio network node. Additionally, the method furthermore comprises determining alternative connection paths between the user equipment and the radio network node. The method also com- prises selecting connection path between the user equipment and the radio network node, based on the determined communication performance metrics. By selecting cooperative relaying schemes between user equipment and radio network node based on some criteria, such as e.g., best QoS or energy saving, and also enabling selection of best path of downlink and uplink, respectively, for UE access, it is possible to improve system performance, as optimisation according to selected criteria may be made separately in each direction, by a network function provided with information about the channel conditions for multiple available paths. Thereby an improved performance within the wireless communication network 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, illustrating examples of embodiments of the invention in which:

Figure 1A is a block diagram illustrating a wireless communication network according to prior art.

Figure 1 B is a block diagram illustrating a wireless communication network according to prior art.

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

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

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

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

Figure 3 is a signalling scheme illustrating an embodiment of the invention.

Figure 4 is a flow chart illustrating a method in a radio network node according to an embodiment of the invention.

Figure 5A is a block diagram illustrating a radio network node architecture according to an embodiment of the invention.

Figure 5B is a block diagram illustrating a radio network node architecture according to an embodiment of the invention. DETAILED DESCRIPTION

Embodiments of the invention described herein are defined as a network access unit and a method in a network access unit, which may be put into practice in the embodiments de- scribed below. These embodiments may, however, be exemplified and realised in many different forms and are not to be limited to the examples set forth herein; rather, these illustrative examples of embodiments are provided so that this disclosure will be thorough and complete. Still other objects and features may become apparent from the following detailed description, considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the herein disclosed embodiments, for which reference is to be made to the appended claims. Further, the drawings are not necessarily drawn to scale and, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.

Figure 2A is a schematic illustration over a wireless communication network 100 comprising a radio network node 110, a relay node 130 and a User Equipment (UE) 120. The radio network node 1 10 is connected with a network access unit 140, which in turn is connected to a database 150.

The enumerated entities 1 10, 120, 130, 140 and 150 comprised in the wireless communication network 100 may be configured for wireless and/ or wired communication of signals, data and/ or data packets; expressions which in the present context may be utilised interchangeably, even if the formal definition may be different between them.

The wireless communication network 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)/ Enhanced Data rate for GSM Evolution (GSM/EDGE), Wideband Code Division Multiple Access (WCDMA), Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, Single-Carrier FDMA (SC-FDMA) networks, Worldwide 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 network 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 network 100 is a heterogeneous wireless communication network, i.e. comprises network nodes having different transmission power capacity.

The purpose of the illustration in Figure 2A is to provide a simplified, general overview of the wireless communication network 100 and the involved methods and nodes, such as the radio network node 1 10, relay node 130 and user equipment 120 herein described, and the functionalities involved. The methods, radio network node 1 10, relay node 130 and user equipment 120 will subsequently, as a non-limiting example, be described in a 3GPP LTE/ LTE-Advanced environment, but the embodiments of the disclosed methods, radio network node 1 10, relay node 130 and user equipment 120 may operate in a wireless communication network 100 based on another access technology such as, e.g., any of the above already enumerated. Thus, although the embodiments of the invention are described based on, and using the lingo of, 3GPP LTE systems, it is by no means limited to 3GPP LTE. It is to be noted that the illustrated network setting of one radio network node 1 10, one relay node 130 and one user equipment 120 in Figure 2A is to be regarded as a non-limiting example of an embodiment only. The wireless communication network 100 may comprise any other number and/ or combination of radio network nodes 1 10, relay nodes 130 and/ or user equipment 120. A plurality of user equipment 120 and another configuration of radio network nodes 1 10 and/ or relay nodes 130 may thus be involved in some embodiments of the disclosed invention. Thus whenever "one" or "a/ an" user equipment 120, radio network node 1 10 and/ or relay node 130 is referred to in the present context, a plurality of user equipment 120, radio network node 1 10 and/ or relay node 130 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), macro base station, 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 relay node 130 may according to some embodiments be referred to, respectively, as e.g., 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.

In the illustrated wireless communication network 100, different cooperative schemes have been selected for downlink and uplink separately. The cooperative schemes may be relay- ing, diversity combination by multi path, multi-hop, Network Coding (NC) etc.

Assuming the selections of cooperative schemes for downlink and uplink are based on the same criteria, e.g., channel quality, a number of embodiments are illustrated in Figures 2A-2D.

In the embodiment illustrated in Figure 2A, the radio network node 1 10 transmits signals/ data directly to the user equipment 120 over a downlink path 160-1. For uplink, the relaying scheme is selected, i.e., the user equipment 120 transmits signals to the radio network node 1 10 via forwarding by the relay node 130 over an uplink path 160-2.

In this illustrated example, the channel quality of a direct downlink connection over the downlink path 160-1 is superior to that of the relaying downlink via the relay node 130. At the same time, the uplink connection over the uplink path 160-2, via the relay node 130 may have better channel quality than an alternative direct uplink connection to the radio network node 1 10. Thus, according to some embodiments, the connection path leading to the best channel quality in the uplink and downlink, respectively, may be selected according to some embodiments. However, in some embodiments, the downlink path 160-1 may be selected in the downlink for achieving the best downlink channel quality in terms of SINR while the uplink path 160-2 may be selected in the uplink for reducing the transmission power of the user equipment 120, thereby prolonging the battery operative time between battery loading.

The path selections of downlink and uplink may be based on different criteria. Downlink: the channel quality of the direct link may be better than that of relaying link. Path selection of downlink may be based on throughput, while the path selection of uplink may be based on energy saving for the user equipment 120.

Further, in some embodiments, the direct connection is selected in the downlink in the meaning that the channel quality of the direct link is better than that of the relaying link. For the uplink, the relaying scheme may be selected, even though the channel quality of relaying link is worse than that of the direct link. As the user equipment 120 is closer to the relay node 130, the relaying link saves energy for the user equipment 120.

The selection of connection paths in uplink and downlink may be made by the network ac- cess unit 140, using data stored at the database 150, which will be further explained and discussed in connection with the presentation of Figure 3 and Figure 4.

Figure 2B is a schematic illustration over a wireless communication network 100 similar to the wireless communication network 100 illustrated in Figure 2A. However, the illustrated wireless communication network 100 comprises a radio network node 1 10, a first relay node 130-1 , a second relay node 130-2 and a User Equipment (UE) 120. The radio net- work node 1 10 is connected with a network access unit 140, which in turn is connected to a database 150.

In the embodiment illustrated in Figure 2B, the radio network node 1 10 transmits signals to the user equipment 120 via the first relay node 130-1 over a downlink path 160-1. Further, for the uplink, a cooperative relaying scheme may be selected. Thus, uplink signals may be transmitted both via a direct link to the radio network node 1 10, and via the second relay node 130-2 over an uplink path 160-2. These uplink signals may then be combined at the radio network node 1 10.

Cooperative relaying scheme, which sometimes may be referred to as a cooperative diversity is a cooperative multiple antenna technique for improving or maximising total network channel capacities for any given set of bandwidths which exploits user diversity by decoding the combined signal of the relayed signal and the direct signal in wireless multi-hop networks. A conventional single hop system uses direct transmission where a receiver decodes the information only based on the direct signal while regarding the relayed signal as interference, whereas the cooperative diversity considers the other signal as contribution. That is, cooperative diversity decodes the information from the combination of two signals. Hence, it can be seen that cooperative diversity is an antenna diversity that uses distrib- uted antennas belonging to each node in a wireless network. User cooperation is thus another definition of cooperative diversity. User cooperation considers an additional fact that each user relays the other user's signal while cooperative diversity can be also achieved by multi-hop relay networking systems. In this illustrated example, the channel quality of the relaying downlink via the first relay node 130-1 may be better than a direct downlink connection. At the same time, the uplink connection over the uplink path 160-2, via the second relay node 130-2 cooperatively working with a direct uplink connection may have better channel quality than any possible alternative connection path to the radio network node 1 10.

However, in some embodiments, the uplink path 160-2 may be selected in the uplink for reducing the transmission power of the user equipment 120, thereby prolonging the battery operative time between battery loading. Figure 2C is a schematic illustration over a wireless communication network 100 similar to the wireless communication network 100 illustrated in Figure 2A and Figure 2B. However, the illustrated wireless communication network 100 comprises a radio network node 1 10, a first relay node 130-1 , a second relay node 130-2 and a User Equipment (UE) 120. The radio network node 1 10 is connected with a network access unit 140, which in turn is connected to a database 150. For downlink, the radio network node 1 10 transmits signals to the user equipment 120 by relaying via the first relay node 130-1. For uplink, a multi-hop relaying scheme is selected, i.e., the user equipment 120 transmit signals to the radio network node 1 10 by a two hops relaying via firstly the second relay node 130-2 and also the first relay node 130-1. Again, the selection of transmission paths in downlink and uplink respectively may be selected based on a channel quality estimation in the respective link direction, or in order to reduce transmission power of the user equipment 120.

Figure 2D is a schematic illustration over a wireless communication network 100 similar to the wireless communication network 100 illustrated in Figure 2A, Figure 2B and/ or Figure 2C. However, the illustrated wireless communication network 100 comprises a radio network node 1 10, a relay node 130, a first User Equipment (UE) 120-1 and a second user equipment 120-2. The radio network node 1 10 is connected with a network access unit 140, which in turn is connected to a database 150.

According to some embodiments, for the downlink, the radio network node 1 10 may transmit signals to the first user equipment 120-1 and the second user equipment 120-2 via the direct link 160-1 , 160-2, respectively. For the uplink, a network coding scheme may be selected, such that the first user equipment 120-1 and the second user equipment 120-2 firstly may send signals to the relay node 130, which may perform an Exclusive -Or (XOR)- operation or some other encoding operation, for example a linear combination in a Galois field, on the received signals before forwarding to the radio network node 1 10.

Figure 3 illustrates an example of a signalling scheme during implementation of an em- bodiment of the invention.

A challenge that has to be overcome in order to select the respective path and cooperative scheme in current systems 100 is that there is no existing, single network entity that has all the required information to determine the best paths for both uplink and downlink. Since the performance depends on multiple radio channels, it may be somewhat problematic to rely on any of the existing network nodes such as the radio network node 1 10, to take the decision. The solution is to add a function at network side, Network Access Function (NAF), which calculates the performance of each cooperative scheme and selects the best scheme according to predetermined rules, such as e.g. best channel quality, highest throughput, best SINR and/ or lowest required signalling power. The NAF makes decisions of cooperative scheme selection for the user equipment 120 based on input such as chan- nel state reports for uplink and downlink of different channels, transmission power of different nodes, Quality of Service (QoS) and energy saving preferences. For current direct transmission between the user equipment 120 and the radio network node 1 10 it may be sufficient to select the radio channel with the highest SINR to achieve the highest throughput, but when relays 130 and cooperative schemes are considered the mapping becomes more complex. The NAF may utilise models that characterise the different schemes based on measurements and estimates of multiple radio channels to calculate the expected performance of different schemes, and selects the best ones for uplink and for downlink.

For higher computational efficiency and practical deployment a static selection function may be preferred, according to some embodiments.

Path selection may depend on the network layout and geographical distribution of user equipment 120 in the cell of the radio network node 1 10. The NAF may look up the local database 150, such as e.g. a Network Environment State Database (NESD) or similar, to check if the distribution of user equipment 120 follows some typical patterns.

The database 150, or NESD, may maintain a network layout map and empirical information comprising typical distribution patterns for cooperative schemes according to some embodiments.

For the implementation, the NAF may be implemented in a Network Access Unit 140 and the NESD may be implemented in a database 150, connectable for the Network Access Unit 140. However, according to some embodiments, the NAF and/ or the Network Access Unit 140 may be co-located within a network management node such as MME 170. Alter- natively, the NAF and/ or the Network Access Unit 140 may be co-located within the radio network node 1 10, according to some embodiments.

According to the illustrated embodiment, the user equipment 120 may request to access the network by sending access request to the MME 170 which may forward the access request message to the Network Access Unit (NAU) 140, to determine the best cooperative scheme to access. In some embodiments, location information related to the location of the user equipment 120 may be comprised in the access request message. In such case, the Network Access Unit 140 may request the database 150 to check if the geographical distribution or channel measurement distribution of user equipment 120 and surrounding network follows some cooperative scheme pattern in the local database 150, or else a location service to obtain location of the user equipment 120 will be triggered by Network Access Unit 140.

After looking up the local database 150, the best cooperative scheme for the user equipment 120 may be determined. In the illustrated example, the best cooperative scheme may comprise relaying on uplink via one relay node 130 and transmitting directly from the radio network node 1 10 to the user equipment 120 on the downlink.

The NESD database 150 may respond the Network Access Unit 140 with the cooperative scheme and associated relay node ID to the Network Access Unit 140. The Network Access Unit 140 may forward the access instruction to the radio network node 1 10 where the user equipment 120 is initially connected. The Network Access Unit 140 may calculate the best cooperative scheme locally by itself if the distribution of UE and interference impact of surrounding network does not follow any empirical pattern in the NESD database 150, in some embodiments. The user equipment may then access network and transmit data according to the instruction received from the network.

In the dynamic case, where the network map, i.e. the empirical pattern in the NESD database 150 cannot give an answer about the best access schemes, the calculation of the best schemes requires measurement data from multiple wireless channels. The NAF in the Network Access Unit 140 may collect these measurements from the relevant network nodes, e.g. relay nodes 130 and radio network nodes 1 10. The collection of measurements may also require that additional measurements are configured by other nodes such as e.g. radio network nodes 1 10. Such additional measurements may be triggered by requests from the Network Access Unit 140, which may require such measurements from involved nodes.

In order to estimate the SINR, the uplink received power from the user equipment 120 when it is scheduled may be measured, together with possible interference from other UEs. In this case the NAF would need to indicate which user equipment 120 is involved in the measurement, and get the radio network nodes 1 10 and relay nodes 130 to synchronize the measurements with the transmissions from the right user equipment 120 according to some embodiments. The NAF can then estimate the channel quality of the specific radio channel, and use it as input to calculate the performance of alternative (cooperative) transmission schemes. Further, the NAF and the Network Access Unit 140 may have knowledge, or being able to extract such knowledge from the database 150 of other access technology access points available within a certain cell, and/ or for certain user equipment 120, such as e.g. a Wi-Fi access point or visual light communication.

Thereby, thanks to embodiments herein, the best channels according to predetermined criteria may be selected for uplink and for downlink, exploiting the characteristics of wireless channel more fully. Further, by selecting channel and/ or cooperative scheme on the network side, or at least mainly on the network side, energy is saved at the user equipment 120. Thus battery lifetime of the user equipment 120 does not have to suffer when implementing the method.

Different links and/ or cooperative schemes may be selected for downlink and uplink re- spectively, thereby improving performance for both links, according to predetermined criteria.

Figure 4 is a flow chart illustrating embodiments of a method 400 for use in a network access unit 140. The method 400, which may be referred to as a network access function, aims at selecting signal path between a User Equipment (UE) 120 and a radio network node 1 10 in a heterogeneous wireless communication network 100 (Hetnet). The heterogeneous wireless communication network 100 also comprises a relay node 130 and the network access unit 140. Further, the heterogeneous wireless communication network 100 in addition may comprise other network nodes and access points relating to different ac- cess technologies.

The heterogeneous wireless communication network 100 may be based on 3GPP LTE. Further, the heterogeneous wireless communication system 100 may be based on FDD or TDD in different embodiments. The radio network node 1 10 may comprise an eNodeB ac- cording to some embodiments. Further, the heterogeneous wireless communication network 100 may comprise a Mobility Management Entity (MME) in which the network access unit 140 is co-located.

To appropriately select signal path between the user equipment 120 and the radio network node 1 10, the method 400 may comprise a number of actions 401 -406. It is however to be noted that any, some or all of the described actions 401 -406, 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. Some actions such as e.g. action 404 and action 405 may be performed within some, but not necessarily all embodiments. Further, it is to be noted that some actions may be performed in a plurality of alternative manners according to different embodiments, and that some such alternative manners may be performed only within some, but not necessarily all embodiments. The network access unit 140 may in some embodiments periodically re-perform any, some or all of actions 402-406, thereby enabling a re-selection of connection path 160 between the user equipment 120 and the radio network node 1 10, due to mobility of the user equipment 120 according to some embodiments. The method 400 may comprise the following actions:

Action 401

An access request is received from the user equipment 120.

The received access request may trigger measurements of communication performance metrics according to some embodiments.

Action 402

Communication performance metrics for transmitting data between the user equipment 120 and the radio network node 1 10 are determined.

The determination of communication performance metrics for transmitting data between the user equipment 120 and the radio network node 1 10 may be performed independently in the uplink and the downlink. The communication performance metrics for transmitting data between the user equipment 120 and the radio network node 1 10 may comprise e.g. energy saving preference, Quality of Service (QoS), system throughput or other similar communication performance metrics, according to some embodiments. It thereby becomes possible to optimise the uplink connection for one performance metrics such as e.g. saving transmission energy. The downlink connection, which may be made from another node such as the radio network node 1 10, may be optimised by means of system throughput, in some embodiments. Thereby, a communication improvement is achieved within the heterogeneous wireless communication system 100.

Action 403

5 Alternative connection paths 160 between the user equipment 120 and the radio network node 1 10 are determined.

The alternative connection paths 160 may pass other nodes such as relay nodes 130, other radio network nodes 1 10, other access points such as a Wi-Fi access point, or an- 10 other user equipment forwarding or relaying wireless signals. Thereby, the best alternative connection path may be selected, which may render a communication improvement within the heterogeneous wireless communication system 100.

Action 404

15 This action may be performed within some, but not all possible embodiments described herein.

The signal measurement reports related to the determined 403 alternative connection paths 160 between the user equipment 120 and the radio network node 1 10 may be col- 20 lected.

The signal measurement reports may be collected from the user equipment 120, from the relay node 130 and radio network node 1 10, respectively, comprised in the heterogeneous wireless communication network 100. Thereby, it is possible for the network access unit 25 140 to achieve the signal measurement reports from the enumerated involved nodes.

Action 405

This action may be performed within some, but not all possible embodiments described herein.

30

Information related to a geographical location of the user equipment 120 may be determined.

Such information related to the geographical location of the user equipment 120 comprises 35 geographical coordinates measured by the user equipment 120, a signal fingerprint of signal measurements measured by the user equipment 120, and/ or a direction and distance estimation to the user equipment 120, made by the radio network node 1 10. However, ac- cording to some embodiments, the information related to the geographical location of the user equipment 120 may comprise coordinates measured by Global Positioning System (GPS) or other similar system based on satellite signalling. Action 406

Connection path 160 between the user equipment 120 and the radio network node 1 10 is selected, based on the determined 402 communication performance metrics.

The selection of connection path 160 also comprises selection of a cooperative relaying scheme for transmitting data packets between the user equipment 120 and the radio network node 1 10.

The selection of connection path 160 between the user equipment 120 and the radio network node 1 10 may be performed independently in the uplink and the downlink.

According to some embodiments, the selection of connection path 160 may be based on the determined 402 communication performance metrics and also on the collected 404 signal measurement reports. Further, according to some embodiments, wherein the connection path 160 may be selected by requesting a reference to the connection path 160 from a data base 150, using the determined 405 information related to the geographical location of the user equipment 120, wherein the data base 150 comprises a network layout map and stored empirical information comprising distribution patterns for connection paths 160 associated with differ- ent locations of the user equipment 120.

Additionally, the optional cooperative relaying scheme for transmitting data packets between the user equipment 120 and the radio network node 1 10 comprises relaying, diversity combination by multi-path, multi-hop and/ or network coding.

Figure 5A illustrates an embodiment of a network access unit 140, configured for selecting signal path between a user equipment 120 and a radio network node 1 10 in a heterogeneous wireless communication network 100, also comprising a relay node 130 and the network access unit 140. Such heterogeneous wireless communication network 100 may comprise a plurality of other nodes with various transmission power capacity and/ or using different access technologies, such as e.g. various relay nodes, micro nodes, pico nodes, femto nodes, Wi-Fi access point, an LTE relay, a Visual Light Communication (VLC) unit or similar element.

The heterogeneous wireless communication network 100 may be based on 3rd Generation Partnership Project Long Term Evolution (3GPP LTE). The radio network node 1 10 may according to some embodiments comprise an evolved NodeB (eNodeB). The relay node 130 may comprise any of a micro node, a Pico base station, a Wi-Fi access point, a Femto node, an LTE relay, a Visual Light Communication (VLC) unit or similar entity with a transmission power not exceeding the transmission power of the radio network node 1 10.

The heterogeneous wireless communication network 100 may comprise a Mobility Management Entity (MME) in which the network access unit 140 is co-located according to some embodiments. The network access unit 140 is configured for performing the method 400 according to any, some, all, or at least one of the enumerated actions 401 -406, according to some embodiments.

For enhanced clarity, any internal electronics or other components of the network access unit 140, not completely indispensable for understanding the herein described embodiments has been omitted from Figure 5A.

The network access unit 140 comprises a receiver 510, configured for receiving an access request from the user equipment 120.

Further, the network access unit 140 comprises a processor 520, configured for determining communication performance metrics for transmitting data between the user equipment 120 and the radio network node 1 10 and also configured for determining alternative connection paths 160 between the user equipment 120 and the radio network node 1 10, and in addition also configured for selecting connection path 160 between the user equipment 120 and the radio network node 1 10, based on the determined communication performance metrics.

The processor 520 may be configured for selecting connection path 160 by selection of a cooperative relaying scheme for transmitting data packets between the user equipment 120 and the radio network node 1 10, according to some embodiments. Such cooperative relaying scheme for transmitting data packets between the user equipment 120 and the radio network node 1 10 may comprise e.g. relaying, diversity combination by multi-path, multi-hop and/ or network coding or similar. Additionally, the processor 520 also may be configured for determining communication performance metrics for transmitting data between the user equipment 120 and the radio network node 1 10 independently in the uplink and the downlink in some embodiments, and also possibly configured for selecting connection path 160 between the user equipment 120 and the radio network node 1 10 independently in the uplink and the downlink.

Such communication performance metrics for transmitting data between the user equipment 120 and the radio network node 1 10 may comprise e.g. energy saving preference, Quality of Service (QoS) system throughput in some embodiments. The processor 520 may furthermore be configured, in some embodiments, for collecting signal measurement reports related to the determined alternative connection paths 160 between the user equipment 120 and the radio network node 1 10. Additionally, the processor 520 may be configured for selecting connection path 160 based on the determined communication performance metrics and also on the collected signal measurement reports in some embodiments.

The processor 520 may further be configured for collecting the signal measurement reports from the user equipment 120, from the relay node 130 and/ or the radio network node 1 10, respectively, comprised in the heterogeneous wireless communication network 100.

According to some further optional embodiments, the processor 520 may be further configured for determining information related to a geographical location of the user equipment 120. Optionally the processor 520 may be further configured for selecting the connection path 160 by requesting a reference to the connection path 160 from a data base 150, using the determined information related to the geographical location of the user equipment 120, wherein the data base 150 may comprise a network layout map and stored empirical information comprising distribution patterns for connection paths 160 associated with different UE locations; in some embodiments. Such information related to the geographical location of the user equipment 120 may comprise e.g. geographical coordinates measured by the user equipment 120, a signal fingerprint of signal measurements measured by the user equipment 120, and/ or a direction and distance estimation to the user equipment 120, made by the radio network node 1 10 according to different embodiments.

Such processor 520 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 network access unit 140 may in some embodiments comprise a transmitter 530, configured for transmitting the signal, to be received by the radio network node 1 10 and/ or the database 150. In further addition, the network access unit 140 may comprise at least one memory 525, according to some embodiments. The optional memory 525 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 525 may comprise integrated circuits comprising silicon-based transistors. Further, the memory 525 may be vola- tile or non-volatile.

Figure 5B illustrates an embodiment of a network access unit 140, configured for selecting signal path between a user equipment 120 and a radio network node 1 10 in a heterogeneous wireless communication network 100, similar to the embodiment illustrated in Figure 5A.

The heterogeneous wireless communication network 100 may be based on 3rd Generation Partnership Project Long Term Evolution (3GPP LTE). The radio network node 1 10 comprises an evolved NodeB (eNodeB). The relay node 130 may comprise any of a micro node, a Pico base station, a Wi-Fi access point, a Femto node, an LTE relay, a Visual Light Communication (VLC) unit or similar entity with a transmission power not exceeding the transmission power of the radio network node 1 10.

The heterogeneous wireless communication network 100 may comprise a Mobility Management Entity (MME) in which the network access unit 140 is co-located. In the illustrated alternative embodiment, the network access unit 140 and/ or the processor 520 comprised in the network access unit may comprise a determining unit 522, a selecting unit 526 and/ or possibly, according to some embodiments, a collecting unit 524.

5 The determining unit 522 may be configured for determining communication performance metrics for transmitting data between the user equipment 120 and the radio network node 1 10. However, the determining unit 522 may also be configured for determining alternative connection paths 160 between the user equipment 120 and the radio network node 1 10. The determining unit 522 may be configured for determining communication performance 10 metrics for transmitting data between the user equipment 120 and the radio network node 1 10 independently in the uplink and the downlink, in some embodiments. Furthermore, the determining unit 522 may also be configured for determining information related to a geographical location of the user equipment 120.

15 The selecting unit 526 may be configured for selecting connection path 160 between the user equipment 120 and the radio network node 1 10, based on the determined communication performance metrics. In some embodiments, the selecting unit 526 may be configured for selecting connection path 160 by selection of a cooperative relaying scheme for transmitting data packets between the user equipment 120 and the radio network node

20 1 10. Also, the selecting connection path 160 between the user equipment 120 and the radio network node 1 10 independently in the uplink and the downlink in some embodiments. Additionally, the selecting unit 526 may be configured for selecting connection path 160 based on the determined communication performance metrics and also on the collected signal measurement reports in some embodiments. Furthermore, the selecting unit 526

25 may be configured for selecting the connection path 160 by requesting a reference to the connection path 160 from a data base 150, using the determined information related to the geographical location of the user equipment 120. Such data base 150 may comprise a network layout map and stored empirical information comprising distribution patterns for connection paths 160 associated with different UE locations. In addition, such information

30 related to the geographical location of the user equipment 120 comprises geographical coordinates measured by the user equipment 120, a signal fingerprint of signal measurements measured by the user equipment 120, and/ or a direction and distance estimation to the user equipment 120, made by the radio network node 1 10.

35 The discussed cooperative relaying scheme for transmitting data packets between the user equipment 120 and the radio network node 1 10 may comprise e.g. relaying, diversity combination by multi-path, multi-hop and/ or network coding. The optional collecting unit 524 may be configured for collecting signal measurement reports related to the determined alternative connection paths 160 between the user equipment 120 and the radio network node 1 10. Such collecting unit 524 may further be config- ured for collecting the signal measurement reports from the user equipment 120, from the relay node 130 and radio network node 1 10, respectively, comprised in the heterogeneous wireless communication network 100.

At least a sub-set of the previously described actions 401 -406 to be performed in the net- work access unit 140 may be implemented through the one or more processing circuits 520 in the network access unit 140, together with a computer program product for performing the functions of at least some of the actions 401-406. Thus a computer program product, comprising instructions for performing the actions 401-406 may select signal path between a user equipment 120 and a radio network node 1 10 in a heterogeneous wireless commu- nication network 100, also comprising a relay node 130 and the network access unit 140, when the computer program is loaded into a processor 520 of the network access unit 140.

Thereby a computer program product may comprise a computer readable storage medium storing program code thereon for use by the network access unit 140, for selecting signal path between a user equipment 120 and a radio network node 1 10 in a heterogeneous wireless communication network 100. The heterogeneous wireless communication network 100 may also comprise a relay node 130 and the network access unit 140. The program code comprising instructions for executing the above described method 400 may comprise receiving 401 an access request from the user equipment 120. Also, the program code may comprise determining 402 communication performance metrics for transmitting data between the user equipment 120 and the radio network node 1 10. Further, the program code may also comprise determining 403 alternative connection paths 160 between the user equipment 120 and the radio network node 1 10. In addition, the program code furthermore also may comprise selecting 406 connection path 160 between the user equip- ment 120 and the radio network node 1 10, based on the determined 402 communication performance metrics.

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 ac- tions 401 -406 according to some embodiments when being loaded into the processor 520. The data carrier may be, e.g., a hard disk, a CD ROM disc, a memory 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 program code on a server and downloaded to the radio network node 1 10 remotely, e.g., over an Internet or an intranet connection.

The terminology used in the description of the embodiments as illustrated in the accompanying drawings is not intended to be limiting of the described method 400, network access unit 140 and/ or heterogeneous wireless communication network 100. Various changes, substitutions and/ or alterations may be made, without departing from the invention as de- fined 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 preclude 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 proc- essor 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 distrib- uted in other forms such as via Internet or other wired or wireless communication system.