BR112016024941B1 - USER DEVICE AND CORRESPONDING METHOD - Google Patents

Abstract

USER DEVICE, ACCESS NODE DEVICE, CENTRAL NETWORK CONTROLLER AND CORRESPONDING METHODS. The present invention relates to a user device, an access node device and a central network controller. The user device (10) comprises a transceiver (11) configured to synchronize with a radio communication network (20); said transceiver (11) is further configured to broadcast an indication signal comprising at least one reference signal to one or more access node devices (30) of said radio communication network (20). The access node device (30) comprises a transceiver (31) configured to receive a broadcast indication signal from a user device (10) synchronized with said radio communication network (20); and further a processor (32) configured to derive information from said received broadcast indication signal and use said derived information in a network procedure of said radio communication network (20). Furthermore, the present invention also relates to corresponding methods, a computer program and a computer program product.

Description

FIELD OF TECHNIQUE

[001] The present invention relates to a user device and corresponding network devices for wireless communication. Furthermore, the present invention also relates to corresponding methods, a computer program and a computer program product.

BACKGROUND

[002] In conventional systems, the Random Access (RA) procedure is the first procedure in which the radio network of a wireless communication system knows that a User Device (DU) is trying to establish a connection to the network. At this stage the DU does not have any resources or channels available to inform the network of its desire to connect, so it will send its request over a shared medium. There may be many other DUs in the same area sending the same request, in which case there is also a possibility of collisions between requests coming from different DUs. Such an RA procedure is called a contention based RA procedure. After a successful RA procedure, the DU has the ability to initiate data transmissions with the Access Node (NA) connected. The RA procedure for Long Term Evolution (LTE) is mainly specified in 3GPP TS 36.321 and TS 36.213.

[003] LTE uses the RA procedure for a DU (or User Equipment, EU, in LTE) to make a connection to an NA of the radio network and to obtain the timing advance for the Uplink (UL). Additionally, the RA handles collisions that can occur when two or more DUs are trying to make a connection at the same time. In conventional systems, after each transfer decision, the DU establishes a connection to the new NA through the RA procedure. The RA is initiated with a DU preamble message. If the NA can successfully decode the preamble, it sends the RA response to the DU, which contains the UL timing advance, a temporary value of the Cell Radio Network Temporary Identifier (C-RNTI) and a UL grant for Msg3 (the 3GPP term for the first scheduled UL transmission in the contention-based RA procedure), which is to be used for Radio Resource Control (RRC) connection establishment.

[004] Another aspect is the mobility of a DU that is already in the connected state. In existing legacy systems, transfer decisions are based on measurements made by DUs during periods of time called measurement gaps. Measurement gap locations are specified by network-specified parameters. Currently, for example, in LTE systems, the mobility and procedural issues of AR are solved for large cells, where the BUs are not constantly making automatic changes from one cell to another. Therefore, in LTE, the DU looks at the macrocell NAs and decides which ones provide the best signal. However, when a transfer takes place, the DU is required to establish a connection to the new NA through the RA procedure.

SUMMARY

[005] An objective of the present solution is to provide a solution that mitigates or solves the disadvantages and problems of conventional solutions.

[006] According to a first aspect of the invention, the aforementioned objects and other objects are achieved with a user device comprising a transceiver configured to synchronize with a radio communication network; said transceiver is further configured to broadcast an indication signal comprising at least one reference signal to one or more access node devices of said radio communication network.

[007] According to a second aspect of the invention, the aforementioned objects and other objects are achieved with an access node device for a radio communication network, said access node device comprising: a transceiver configured to receive a broadcast indication signal from a user device synchronized with said radio communication network; and a processor configured to derive information from said received broadcast indication signal and to use said derived information in a network procedure of said radio communication network.

[008] According to a third aspect of the invention, the aforementioned objects and other objects are achieved with a central network controller for a radio communication network, said central network controller comprising: a transceiver configured to receive, from from at least one access node device of said radio communication network, information derived from an indication signal originally broadcast by a user device; a processor configured to, based on information received from said at least one access node device, decide which access node device (or access node devices) of said radio communication network will connect to said device and gathering connection configuration information indicating at least one access node device of said radio communication network to which said user device will establish a connection; and wherein said transceiver is further configured to forward said connection setup information to at least one access node device that will establish a connection to said user device.

[009] According to a fourth aspect of the invention, the aforementioned objects and other objects are achieved by a method in a user device comprising the steps of: synchronizing with a radio communication network; and broadcasting an indication signal comprising at least one reference signal to one or more access node devices of the radio communication network.

[010] According to a fifth aspect of the invention, the aforementioned objects and other objects are achieved by a method in an access node device for a radio communication network, the method comprising the steps of: receiving a signal broadcast indication from a user device synchronized with said radio communication network; deriving information from said received broadcast indication signal; and using said derived information in a network procedure of said radio communication network.

[011] According to a sixth aspect of the invention, the aforementioned objectives and other objectives are achieved by a method in a central network controller for a radio communication network, the method comprising the steps of: receiving, from from a plurality of access node devices of said radio communication network, information derived from an indication signal originally broadcast by a user device; deciding, based on information received from the at least one access node device, which access node device will connect to said user device; gathering connection configuration information indicating at least one access node device of said radio communication network to which said user device will establish a connection; and forwarding said connection configuration information to at least one access node device that will establish a connection to said user device.

[012] The present invention also relates to a computer program, distinguished by code means, which, when executed by processing means, cause said processing means to execute any method according to the present invention. Furthermore, the invention also relates to a computer program product comprising a computer readable medium and said computer program mentioned, wherein said computer program is included in the computer readable medium, and comprises one or more from the group: ROM (Read Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically EPROM) and hard disk drive.

[013] A reference signal is a signal whose content is perfectly known to both the sender and the intended receiver of a communication link end. Therefore, the reference signal can, for example, be used to determine channel coefficients, which can be used for multiple purposes, including channel equalization, precoding, positioning, signal quality estimation, modulation and scheme selection. coding, etc. With the reference signal DU positioning is also possible.

[014] The present solution has at least the following advantages over conventional solutions.

[015] Reduced power consumption in the DU since the network instead of the DU can handle problems related to mobility and channel quality by measuring the present indication signal.

[016] Allowing a more agile RA procedure since the network can instantly measure the DU and channel location during the RA procedure and decide the NA(s) for the DU. The present solution therefore also implies improved DU positioning and DU transfer prediction due to the indication signal.

[017] Furthermore, enhanced mobility control is possible as the network can monitor the DU and direct data traffic through the nearest NA(s) to the DU. It also means simplified DU signaling and processing by hiding automatic DU changes.

[018] The embodiments of the present invention also enable updated CSI techniques for CoMP and Multiple Inputs and Multiple Outputs of Multiple Users in all neighboring NAs in Time Division Duplex (TDD) systems, including interference estimates.

[019] Furthermore, the embodiments of the present invention also enable more accurate interference coordination since each possible link is well known due to the fact that each NA can receive indications from all DUs within the indication range. Therefore, interference can be coordinated, which improves spectral efficiency. This is an important aspect for dense networks.

[020] According to an implementation form of the first aspect, said indication signal further comprises identity information of said user device. When the indication signal comprises identity information, the user device can be identified when the indication signal is not programmed. For example, when the user device is transmitting contention-based mode indication signals as in the RA procedure. Another aspect is that when the user device is sending indication signals, rarely just for mobility tracking purposes, the user device can also be identified after the user device has moved to another area.

[021] According to an implementation form of the first aspect, said indication signal additionally comprises one or more information elements in the group comprising: capability of said user device, transmission power level of said indication signal, power voltage gap for said indication signal, channel status information associated with said indication signal, and service provider identity for said user device. By including the capability information in the indication signal, the network can know whether it can support the user device or not, for example, in the RA procedure. Indication signals could also be used to pass power level and power voltage gap information if the indication transmission power is dynamically controlled. If the network needs CSI information from the downlink channel, then the indication could pass CSI information. The point with this type of indication in the TDD system is to get rid of reporting CSI information. For example, if the user's device sends CSI reports, the network may have the ability to estimate interference leakage experienced by the user from neighboring access nodes.

[022] According to an implementation form of the first aspect, said user device is configured to: when not connected to any of the access node devices of said radio communication network include identity information of said device within said indication signal and transmitting said indication signal as part of a random access procedure; and when connected to at least one access node device of said radio communication network optimizing the inclusion of said identity information in said indication signal. When the user's device is not known over the network, some identifier is needed. However, when the user device is connected and programmed, the identifier would consume all physical resources and is therefore omitted.

[023] According to an implementation form of the first aspect, said transceiver is further configured to broadcast said indication signal using a dedicated broadcast channel of said radio communication network. With the use of a dedicated broadcast channel all access nodes in a coordinated area can receive the indication signals, without the need to scan all available channels.

[024] According to an implementation form of the first aspect, said transceiver is further configured to: receive an indication response signal that includes connection configuration information, and establish a connection with (at least one access node of) said radio communication network based on said connection configuration information. In this way, the connection to the user's device can be made. The indication response signal may be transmitted from the access node to which the transceiver will connect or may be transmitted by another access node of said radio communication network.

[025] According to this form of implementation, said transceiver is further configured to: receive an indication control signal that includes indication transmission interval control information, and broadcast indication signals in accordance with said indication information indication transmission interval control. In this way, the indication signaling can be optimized to, for example, reduce overhead.

[026] According to an implementation form of the first aspect, said indication signals additionally comprise sound reference signals.

[027] According to an implementation form of the second aspect, said network procedure comprises at least one of a random access procedure, a joint procedure for assigning a service access node device to said user device, a channel estimation procedure, a radio resource management procedure, or mobility control procedure of said user device. In this way, the information in the indication signal can advantageously be used in different network procedures.

[028] According to an implementation form of the second aspect, said transceiver is further configured to transmit an indication control signal to said user device, said indication control signal comprises transmission interval control information of indication. In this way, the indication signaling can be optimized, for example, to reduce the signaling overhead.

[029] According to an implementation form of the second aspect, said transceiver is further configured to forward said derived information to one or more additional access node devices of said radio communication network, and to receive additional derived information said indication signal from one or more additional access node devices of said radio communication network; and said processor is configured to, based on the derived information and the received information, decide which of the access node devices of said radio communication network will connect to said user device. In this way, coordinated network procedures can be performed in a distributed manner, such as coordinated beamforming, resource scheduling, and interference control.

[030] According to an implementation form, said transceiver is further configured to forward said derived information to a central network controller, and to receive connection configuration information from a central network controller, whereby the connection configuration information indicates at least one access node device of said radio communication network to which said user device will establish a connection. In this way, coordinated network procedures can be performed centrally, such as coordinated beamforming, resource scheduling, and interference control.

[031] According to an implementation form of the second aspect, said transceiver is further configured to transmit an indication response signal to said user device, said indication response signal comprises connection configuration information indicating at least at least one access node device of said radio communication network to which said user device will establish a connection.

[032] It should be understood that the present methods may be modified, mutatis mutandis, to fully correspond to all embodiments of the present transmitting device and receiving device.

[033] It should be noted that additional applications and advantages of the invention will be evident from the detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS

[034] The attached drawings are intended to clarify and explain the different embodiments of the present invention, in which: - Figure 1 shows a user device according to an embodiment of the present invention; - Figure 2 shows a method on a user device according to an embodiment of the present invention; - Figure 3 shows an access node device according to an embodiment of the present invention; - Figure 4 shows a method on an access node device according to an embodiment of the present invention; - Figure 5 illustrates a user device that broadcasts indication signals in a wireless communication system and how a plurality of NAs receive the indication signal; - Figure 6 shows a central network controller according to an embodiment of the present invention; - Figure 7 shows a method in a central network controller according to an embodiment of the present invention; - Figure 8 illustrates an example of indication signaling in the NA mesh network; - Figure 9 illustrates an example of indication signaling with a central network controller; - Figure 10 illustrates another example of indication signaling in the NA mesh network; - Figure 11 illustrates an example of indication signaling with a central network controller; and - Figure 12 shows performance results of embodiments of the present invention.

DETAILED DESCRIPTION

[035] In the future, the deployment of dense cell phone network will be a key aspect to increase network capacity and data rates. As legacy wireless cellular network systems are relying on DU (user device) measurements in mobility issues, the DU must constantly measure its own cells and neighboring cells so that the DU can choose the best cell candidates. service and report measurements to the network. Due to the fact that the NA cannot transmit or receive data during the measurement gap this is not effective and measurement during measurement gaps placed in Discontinuous Receive Idle Time (DRX) consumes power. Additionally, the processes of heavy transfers and connection establishment consume time and resources of frequency and energy.

[036] It is also expected that the DUs are simultaneously served by multiple NAs, instead of a single NA. It is therefore much more efficient and sometimes even necessary for the network to have complete control over which NAs should serve a particular DU. In such scenarios it would be computationally demanding and inefficient for the DUs to keep track of all NAs and provide measurement results to the network. Therefore, the concept of a transfer must be rethought to maintain seamless mobility, even for high-speed DUs. Furthermore, in dense implementations with inter-NA distances less than 100 meters, the UL/DL timing difference is not significant and could be handled with cyclic prefix only. Therefore, there is no need for the DU to get the initial UL timing advance through the RA procedure as it is currently done in LTE after each handover.

[037] Therefore, the embodiments of the present invention allow DU-centric control, instead of cell-centric or conventional network-centric control of the radio network. One goal is to shift the mobility control burden from the DUs to the radio network. In this way, the DUs reduce power consumption and the network is able to serve the DUs as best as possible without extra signaling to perform DU measurements or control information for the DU to handle cell changes. This means that the DU need not be aware of the “cell”, or rather the NA or NAs serving the DU. In a DU-centric approach with Multiple Users Multiple Inputs and Multiple Outputs (MU-MIMO) the cell concept becomes unnecessary.

[038] A user device (DU) in this disclosure should mean any communication device that is arranged to connect to a wireless communication system for communication. Examples of such devices are mobile phones, smart phones, tablet-type computers, laptop-type computers, etc.

[039] As mentioned above, the proposed solution makes the procedure for RA and DU mobility in, for example, dense small cell implementation networks more agile. There is no need for DUs to perform network measurements for transfer purposes, and no RA procedures are required after each transfer - only during initial connection establishment to the network. Although connected to the network, the DU only needs to know the time at which it is expected to transmit, and by receiving the present indication signals from the DU at designated times the network takes care of the necessary service parameters. The proposed concept is very useful in TDD systems, since it enables the use of channel reciprocity to estimate the Downlink (DL) Channel State Information (CSI) (corresponding to the channel quality) based on the signals no UL indication and no explicit CSI feedback is required. However, it should be noted that embodiments of the present invention are not limited to TDD systems.

[040] The antecedents of the embodiments of the present invention were found in the ineffectiveness of conventional techniques to manipulate connection establishment and DU mobility in wireless cellular telephony networks. Conventional technologies are designed for very large radius cells where the DU is typically not performing automatic changes. However, in future systems, densification of cellular networks is a key aspect to provide high data rates and to handle an increasing number of DUs in densely populated areas such as urban areas. In such radio networks it has been found by the inventors that it is more effective for the network to be aware of the DUs and not of each individual DU trying to decide which of the - potentially overlapping - NA or networks the DU should use according to conventional solutions. . Therefore, the embodiments of the present invention provide, among other things, more effective techniques for connection establishment and mobility control compared to conventional solutions.

[041] The present DU-centric wireless networking concept relies on network-controlled mobility and connection establishment. This is based on the indication signals broadcast by a DU, from which a possible network controller and/or NAs (neighbours) on the network can measure the DU location and select the best serving NA or a set of multiple NAs. of service for a particular DU. Additionally, inter-NA interference could be coordinated by a central network controller, which would know the position, signal quality, and expected transfer of network DUs. Alternatively, NAs could share information between neighboring NAs and coordinate DU mobility without a superior controlling entity in a distributed fashion.

[042] Embodiments of the present invention depend on various broadcast indication signals, which are not dedicated to a specific receiver NA. Indication signals are broadcast by DUs to enable DU-centric network control. The indication signal can therefore, according to one embodiment, be broadcast on a dedicated broadcast channel of the radio communication network. Additionally, the indication signal may also comprise control data for other network aspect like scheduling request, etc.

[043] Figure 1 shows a DU 10, according to an embodiment of the present invention. The DU 10 comprises a transceiver 11 configured to synchronize with a radio communication network 20 (shown in Figure 5). The transceiver 11 is further configured to broadcast an indication signal comprising at least one reference signal to one or more access node devices 30 of the radio communication network 20. In Figure 1, the DU comprises an antenna unit of transmission (Tx) which is used for indication signal transmissions.

[044] Figure 2 illustrates a flowchart for a corresponding method in a DU 10. This method comprises the steps of: • 100 Synchronize with a radio communication network; and • 110 Broadcasting an indication signal comprising at least one reference signal to one or more access node devices of the radio communication network.

[045] Furthermore, Figure 3 shows an NA 30 according to an embodiment of the present invention. The NA 30 comprises a transceiver 31 configured to receive a broadcast indication signal from a user device 10 synchronized with a radio communication network 20. The NA further comprises a processor 32 configured to derive information from the signal. received broadcast indication and for using the derived information in a network procedure of the radio communication network 20. The NA 30 also comprises, in this example, a receiving antenna unit (Rx) for receiving indication signals from one or more more DUs. An NA is a radio network device through which the DU can access the network. Therefore, the NA is part of the network and has the roles and capabilities to provide such a connection. It can, for example, be a base station, a radio head unit, etc.

[046] The network procedure may be at least one of a random access procedure, a joint procedure for assigning a service NA device to user device 10, a channel estimation procedure, a network resource management procedure radio, or mobility control procedure of said user device 10.

[047] Figure 4 illustrates a flowchart for a corresponding method in the NA 30 according to an embodiment of the present invention. The present method comprises the steps of: • 300 Receiving a broadcast indication signal from a user device synchronized with said radio communication network; • 310 Deriving information from said received broadcast indication signal; and • 320 Using said derived information in a networking procedure of said radio communication network.

[048] Figure 5 shows how a DU 10 broadcasts indication signals in a wireless communication system that includes a radio network 20 for one or more NAs of the radio network that have communication interfaces between different network devices. The DU 10 broadcasts the indication signal, for example, on a dedicated indication broadcast channel. The NAs 30a, 30b, 30c receive the indication signal in that case and use the information in the indication signal for any suitable network procedure. Furthermore, in Figure 5 a central network controller 40 is part of the radio network 20. The NAs 30a, 30b, 30c can forward information in the indication signal to the central network controller 40 which can assign one or more NAs to the DU selecting NAs, determining connection configuration information, and signaling connection configuration information to the selected NAs. The selected NA may, upon receipt of connection configuration information, initiate relevant network procedure(s).

[049] However, if the network procedure is RA there should be at least some temporary identifier in the indication signal, which means that the indication signal additionally comprises DU identity information according to a modality.

[050] Once the DU is connected to the radio network, the indication signals can be programmed (by the network) and then only a specific reference signal message is sufficient to carry out measurements and monitor the system's DUs. Furthermore, the indication signal may comprise Audio Reference Signals (SRSs) as reference signals, for example, when such modality is used with legacy LTE.

[051] Furthermore, when the DU is in connected mode (or in some other mode where the user is identified) there may be, for example, programmed indications that use only certain subcarriers so the DUs can be located and programmed effectively in the spatial domain, and, for example, another indication signal sent by programming candidates using full band and some subband. By receiving and measuring these broader indications the NAs 30 or the central network controller 40 can further optimize dynamic programming decisions and accurately calculate precoders for, for example, MU-MIMO or CoMP transmissions.

[052] According to one embodiment, the DU is configured to: when not connected to any of the access node devices, include DU identity information in the indication signal and transmit the indication signal as part of a procedure of AR; and when connected to at least one NA device omitting the inclusion of said identity information in said indication signal.

[053] For example, after a DU has synchronized with the network and received the necessary system information, the DU initiates connection establishment by sending an “RA indication message” on a network specified random access channel . The frequencies and time allocations for that RA channel are obtained from the system information received before the RA procedure starts. For Random Access Channel (RACH), for example, a certain full-band time slot could be used so that the network can measure and estimate bandwidth usage effectiveness of the full system of the DU. Simultaneously, the network can update the CSI on all cooperating NAs within range.

[054] The indication signal for RA may contain an individual DU Identity (ID), possibly also DU capabilities and a reference signal or it could just contain a generated preamble sequence and the reference signal (but the indication is not addressed to a given NA, i.e. it is free of a destination address).

[055] Alternatively, the indication signal for RA could also include an address or identification of the Service Provider (SP) associated with the DU. This could allow the SP to reach the UN for DL traffic. When a NA detects an indication signal for RA, it can forward information derived from the indication signal to a central network controller (connected to all NAs in a given area), which waits a short period of time to detect if other NAs received the same indication signal for RA and forwarded the information to the central controller. After that, the central controller can select the best service cell (covered by one NA) or a set of multiple service cells (covered by a plurality of NAs) for the DU, for example in the case of CoMP, based on the reference signal measurements provided by the NAs. Afterwards, an NA is selected to send the acknowledgments (as an indication response signal) to the DU. Such an indication response signal may, but does not necessarily, indicate yet another NA to which the DU will establish a connection. The NA sending such an indication response signal need not necessarily be one of the NAs to which the UN will connect, but it can be.

[056] Accordingly, embodiments of the present invention also relate to a core network controller 40 for a radio communication network 20. With reference to Figure 6, the core network controller 40 comprises a transceiver 41 configured to receive, the from at least one access node device 30 of the radio communication network 20, information derived from an indication signal originally broadcast by a user device 10. The central network controller 40 further includes a processor 42 configured to, with based on information received from the at least one access node device 30, decide which access node device will connect to the user device 10, and gather connection configuration information that indicates at least one access node device of the radio communication network 20 to which the user device 10 will establish a connection. Additionally, the transceiver 41 is also configured to forward the connection setup information to at least one access node device 30 that will establish a connection to the user device 10.

[057] Figure 7 illustrates a flowchart for a method in the central network controller 40. The present method comprises the steps of: • 400 Receiving, from a plurality of access node devices of said radio communication network, information derived from an indication signal originally broadcast by a user device; • 410 Decide, based on information received from the at least one access node device, which access node device will connect to said user device; • 415 Gather connection configuration information indicating at least one access node device of said radio communication network to which said user device will establish a connection; • 420 Forward said connection configuration information to at least one access node device which will establish a connection to said user device.

[058] According to additional embodiments, for example, in a CoMP scenario the transceiver can forward the connection configuration information to a plurality of access node devices that will establish a connection to the user device 10.

[059] As mentioned above, Figure 5 also shows how NAs forward information delivered from received indication signals to a central network controller 40 which, after proper processing, forwards connection configuration information to at least one access node which will establish a connection to the user device 10. The present NA is therefore further configured to receive the connection configuration information and connect to the DU according to the connection configuration information.

[060] Optionally, the confirmation could be transmitted in CoMP mode from all the NAs that received the RA indication with sufficient signal quality to allow the channel estimation.

[061] Another solution is to use a more distributed approach (in which no central controller is involved) in which the NAs could jointly decide, among neighboring NAs, which among them is the best to serve each DU. Note that the acknowledgment in this case need not be sent immediately upon receipt of an indication signal, but rather in a later time window set aside for that purpose. This allows the decision on the service NA to be made centrally or distributed.

[062] In addition, during the RA, the DU can i) use measurements based on the network reference signal to approximate an adequate transmit power, ii) use fixed power for RA indication signals, iii) use a power boost until a response is received. Therefore, this information can be included in this indication sign.

[063] Additionally, the DU may include transmit power level or power voltage slack information in an indication signal for more accurate network-driven transmit power control, for example, via the acknowledgment/response messages from NA. To avoid collisions, a random feedback time can be used if the indication response signal is not received in time. The indication response signal sent from the NA(s) to the DU could contain allocation for the RRC connection request, or the network could transmit the RRC connection configuration without separate request with the use of RRC resources. specific frequencies/time.

[064] When the RRC connection is established, the DU could start sending Sound Reference Signal (SRS) indications (or any other suitable reference signals) to the radio network at specific frequency/time intervals. SRS indications are network-programmed and will contain the pilot signal, from which the network can estimate DU channel conditions. In addition, to obtain more efficient bandwidth usage, frequency hopping or pseudo-orthogonal codes could be used for SRS indications. However, in very dense networks with only a few DUs per NA, it could be beneficial to use the full operating bandwidth for indication transmissions at certain time intervals for accurate channel measurements. On the other hand, while accompanying mobile handover in idle mode, or if multiple DUs need to be programmed for the same indication period, in addition, multiple access through, for example, OFDMA combined with frequency hopping could be used.

[065] SRS indications could be received and forwarded to the central controller by all NAs in the receiving range. The central controller could have the ability to program the SRS indications so that collisions do not occur between nearby DUs. Based on the indication information received from multiple NAs, the central controller can then measure the UN uplink signal quality, position, predict UN transfer, predict interference from DL to other UNs and choose the appropriate DL/UL cooperation modes for the NAs accordingly.

[066] The position estimate can be based, for example, on trilateration using available information (signal strength, arrival time, etc.). DU transfer can be predicted, for example, based on position history, or estimated velocities of the observed Doppler shift in the received indication signals. Intercell interference can be estimated based on the fact that NAs can estimate the CSI for each DU from the SRS indications. This allows them (or the central controller) to assess how much interference (leakage) the DL transmissions cause to DUs that are not being served by the particular NAs. Therefore, the central controller can orient the NA antennas, perform handoff decisions, intercell interference coordination, and forward transmitted data to the correct NAs. Alternatively, a mesh approach (without a central controller) could be used and the NAs could handle the UN mobility issues by communicating with neighboring NAs.

[067] The interval of the indication signals broadcast by the DU can be dynamic and controlled by the radio network according to a modality. Therefore, the present NA can be further configured to transmit an indication control signal to the user device 10, which includes indication transmission interval control information. The DU 10 receives the indication control signal and broadcasts indication signals in accordance with said indication transmission interval control information comprised in the received indication control signal.

[068] Therefore, a more frequent indication transmission interval could be assigned to DUs with high mobility. On the other hand, stationary DUs such as infrastructure-related sensors (eg power meters, etc.) would not need to be transmitting indication intervals as frequently. Furthermore, different types of indication signals with different intervals could be used, for example between idle and connected modes, i.e. related to discontinuous transmission cycle of DUs.

[069] By receiving and measuring indication signals broadcast by DUs from the system, the radio network can form a dynamic map based on the locations of DUs and experienced interference, which can be used for link adaptation and therefore reducing the need for the DU to measure and report the measurement to the radio network.

[070] Figures 8 to 11 illustrate examples of how DU indication messages can be used in dense small cell implementation. The examples in Figures 8 and 9, show the use case where the RA indication includes at least a unique DU ID and the DU capabilities like supported frequency bands, supported communication protocols, etc.

[071] When a DU without an established RRC connection initiates connection establishment, the DU starts sending indication signals to the RA, which uses frequencies and time resources dedicated to random access transmissions. The DU can obtain RA resource slots, for example, by obtaining blocks of system information transmitted by NAs periodically. Once one or multiple NAs discover the DU, the RRC connection can be established. The DU with RRC connection can then start sending the reference signal indications on allocated frequencies and time resources so that the NAs can follow the DU and measure channel conditions for it. In Figures 8 and 10, the NAs are a mesh-like network. In Figures 9 and 11, the radio network is controlled by a central control entity.

[072] In Figure 8, the DU 10 broadcasts an RA indication signal that is received by one or more NAs 30. In F8:1 the DU waits for the RA indication response and retransmits an indication after the feedback time if no response is received. In F8:2 a NA is assigned to take the DU context and establish a connection with the DU. At F8:3 the DU 10 has dedicated RRC parameters and the DU 10 can start sending SRS indications. At F8:4 DU 10 transmits periodic SRS indications according to dedicated RRC parameters or indication allocation grants interspersed with data transmissions. At F8:5 neighboring NAs share load results and SRS indication measurements. The transfer can be requested by an NA that can serve the DU 10 better.

[073] In Figure 9, the DU 10 broadcasts an RA indication signal that is received by one or more NAs 30. In F9:1 the DU 10 waits for the RA indication response and retransmits an indication after a feedback time if no response is received. In F9:2 each NA 30 that received the indication forwards RA indication information to a central network controller 40. The information may contain parameters such as, for example, reception time, signal level, SP ID, DU ID , etc. At F9:3 the controller waits if any other NA obtained the same indication with better signal quality and the response crosses the NA with the best hypercell. In F9:4 a NA is assigned to take context from the DU and establish a connection with the DU 10. In F9:5 the DU 10 transmits periodic SRS indications according to dedicated RRC parameters or interleaved indication allocation grants with data transmissions. At F9:6 each NA forwards SRS indication information to the controller 40. At F9:7 the controller 40 collects indications from the NAs and makes mobility decisions for the DU based on the SRS indication measurements. As an example, the controller 40 can initiate a handoff of the DU 10 from one NA to another based on the SRS indication measurements.

[074] In Figure 10, the DU 10 broadcasts an RA indication signal that is received by one or more NAs 30. In F10:1 the DU waits for the RA indication response (which may include the DU ID, the RRC connection request, etc.) and retransmits an indication after a feedback time if no response is received. In F10:2 a NA is assigned to take the context of the DU and establish a connection with the DU. In F10:3 the DU 10 has dedicated RRC parameters and the DU 10 can start sending SRS indications. In F10:4 the DU transmits periodic SRS indications according to dedicated RRC parameters or indication allocation grants interspersed with data transmissions. In F10:5 neighboring NAs share SRS indication load and measurement results. The transfer can be requested by an NA that can serve the DU 10 better.

[075] In Figure 11, the DU 10 broadcasts an RA indication signal that is received by one or more NAs 30. In F11:1, the DU 10 waits for the RA indication response and retransmits an indication after a feedback time if no response is received. At F11:2 each NA forwards RA indication information to controller 40. The information may contain parameters such as, for example, reception time, signal level, SP ID, UN ID, etc. At F11:3 the controller waits if any other NA has obtained the same indication with better signal quality and a response crosses the NA with better hypercell. In F11:4 a NA is assigned to take the context of the DU and establish a connection with the DU. At F11:5 the DU has dedicated RRC parameters and the DU can start sending SRS indications. In F11:6 the DU transmits periodic SRS indications according to dedicated RRC parameters or indication allocation grants interspersed with data transmissions. In F11:7 each NA forwards SRS indication to the controller. At F11:8 the controller collects indications from the NAs and makes mobility decisions for the DU based on the SRS indication measurements.

[076] In Figures 8 and 9, the DU uses indication signals for RA, including the necessary DU information so that the network can identify the DU.

[077] In the examples in Figures 10 and 11, the case of the DU in which the indication signal for RA includes at least the RA preamble sequence that includes a randomly generated UN identifier is illustrated. The functional differences between the examples in Figures 8 to 11 are in the RRC connection establishment. In Figures 8 and 9, the DUs have predefined identifiers and, therefore, collisions, in which the same NA receives two or more preambles with the same identifier, should be impossible. If the random preamble sequence is randomly selected it is possible that two DUs end up using the same identifier. Therefore, in Figures 9 and 10 the preamble collision cases are taken into account. For example, if two DUs end up sending an RRC connection request at the same time, only one of them will get the response. The other will start an RA procedure from the beginning after a random feedback time.

[078] In Figures 8 and 10, the DUs are sending more RA preamble-like indication signals from LTE to RA. Once a NA discovers a DU trying to establish an RRC connection, the NA begins a handshaking process so that the unique identifier can be assigned to the DU and the RRC connection can be established. In Figures 9 and 11, the separate controller node 40 receives indication information and makes decisions about the serving NA or multiple serving NAs for the radio network.

[079] In what follows, a comparison of power consumption between LTE and the proposed solution was calculated. It is assumed that an LTE DU (or rather a UE in LTE technology) is reporting its CSI/PMI/RI in PUCCH every 10ms during active time only, and the measurement gap interval is 40 ms. The assumption is that measurement gaps would be placed in the DRX downtime if possible. DRX Active Time is set to 1ms, so a 1ms DRX cycle means receiving constant DL. For a network that would use indications for channel estimation and BU mobility, a DU would, in this example, send a total of 10 μs indication every 1 ms during Active Time and 10 μ s indication every 100 ms during Opportunity to DRX (i.e. the possibility of DU for suspension). The results are shown in Figure 12.

[080] It can be seen from Figure 12 that although TX consumes more power than RX, the indication could actually consume a very small amount of power compared to using frequent CSI measurement and reporting gap. This is due to the relatively low duty cycle. During constant receive, power consumption is equal with these parameters.

[081] Embodiments of the present invention are intended for Radio Access Techniques (RATs) of close implementation, but can also be used in future releases of legacy systems such as LTE. Additionally, for LTE, a similar new type of handoffs feature could be introduced, which would allow the radio network to handle the mobility of the DU between cells without the UN being aware of the automatic changes. The reason is that LTE requires EU reporting and measurements and the transfer procedure has too much signaling and delay in this system. It is generally stated that with LTE only stationary EUs can be served with small cells. However, in future communication systems agile mobility support should also be enabled for dense small cell implementations, or no longer form traditional cells, just control areas or so-called “hypercells”.

[082] As described above, the present indication signal may contain various information elements (such as DU ID, DU capacity information, TX power level or power voltage gap, CSI, reference signal, etc.) required by the network and there can be various types of indications for various purposes such as AR, idle mode and connected mode, active time and opportunity for DRX time, for example. The indication transmission interval could be controlled by the network dynamically so that high mobility DUs send indications more frequently to provide more accurate location information to the network. If the DU is not moving or the DU is in idle mode, the DU could output signals more frequently to optimize spectrum usage and power consumption.

[083] It is also noted that all arrangements of this DU, NA and core network controller have corresponding methods that are part of this solution.

[084] In addition, any method according to an embodiment of the present invention can be implemented in a computer program, having code means, which when executed by processor means, cause the processing means to execute the steps of the method . The computer program is included on a computer-readable medium of a computer program product. The computer-readable medium may comprise essentially any memory such as a ROM (Read Only Memory), a PROM (Programmable Read Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.

[085] Furthermore, it is understood by the skilled person that the present devices comprise the necessary communication capabilities in the form of, for example, functions, means, units, elements, etc., to realize the present solution. Examples of other means, units, elements, and functions are: processors, memory, transceivers, control logic, encoders, decoders, mapping units, multipliers, decision units, selection units, switches, interleavers, deinterleavers, modulators, demodulators , inputs, outputs, antennas, amplifiers, RX unit, TX unit, DSPs, MSDs, TCM encoder, TCM decoder, interfaces, communication protocols, etc. that are arranged properly together.

[086] Specifically, the processors of the present devices may comprise, for example, one or more instances of 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 can interpret and execute instructions. The term "processor" can therefore represent a set of processing circuits comprising a plurality of processing circuits, such as, for example, any, some or all of those mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing data comprising temporary data storage and device control functions such as call processing control, user interface control, or the like. .

[087] Finally, it should be understood that the present invention is not limited to the embodiments described above, but also refers to and incorporates all embodiments within the scope of the appended independent claims.

Claims (6)

1. User device (10) characterized in that it comprises a transceiver (11) configured to synchronize with a radio communication network (20); said transceiver (11) is further configured to broadcast an indication signal comprising at least one reference signal to one or more access node devices (30) of said radio communication network (20), wherein said user device (10) is configured to: when not connected to any of the access node devices (30) of said radio communication network (20) include identity information of said user device (10) in said indication sign; and when connected to at least one access node device (30) of said radio communication network (20) omitting the inclusion of said identity information in said indication signal. 2. User device (10), according to claim 1, characterized in that said indication signal additionally comprises one or more information elements in the group comprising: capabilities of said user device (10), level transmission power of said indication signal, voltage power gap for said indication signal, channel status information associated with said indication signal, and service provider identity for said user device (10). 3. User device (10) according to any one of claims 1 or 2, characterized in that said transceiver (11) is additionally configured to broadcast said indication signal using a dedicated broadcast channel of said radio communication network (20). 4. User device (10), according to any one of claims 1 to 3, characterized in that said transceiver (11) is additionally configured to: receive an indication response signal that includes connection configuration information , and establishing a connection with said radio communication network (20) based on said connection configuration information. 5. User device (10) according to claim 4, characterized in that said transceiver (11) is further configured to: receive an indication control signal that includes indication transmission interval control information , and broadcasting the indication signals in accordance with said indication transmission interval control information. 6. Method in a user device (10) characterized in that it comprises the steps of: synchronizing (100) with a radio communication network (20); and broadcasting (110) an indication signal comprising at least one reference signal to one or more access node devices (30) of said radio communication network (20); when not connected to any of the access node devices (30) of said radio communication network (20), including identification information of said user device (10) within said indication signal; and when connected to at least one access node device (30) of said radio communication network (20), omitting inclusion of said identity information within said indication signal.