RU2793108C2 - Integrated mobility in access network and in transport network - Google Patents

Abstract

FIELD: wireless communication.

SUBSTANCE: subnetwork of a mobile communication system contains a macro-cell base station and a set of small cell base stations, each of which has either a direct connection to the macro-cell base station or a connection to the macro-cell base station via one or several other small cell base stations. The macro-cell base station is made with the possibility of setting of UE device having RRC connection to the macro-cell base station, using information about suitable small cell base stations, for provision of UE device with a possibility of autonomous switching between small cell base stations. The macro-cell base station is made with the possibility of setting of small cell base stations.

EFFECT: provision of UE switching between small cell base stations.

14 cl, 9 dwg, 4 tbl

Description

Technical field

The present invention relates to a method for managing a mobile communication network in which user devices can switch from one communication cell to another.

State of the art

Known cellular mobile communication networks include a core network (CN, Core Network) and one or more radio access networks (RAN, Radio Access Network). The CN network performs, among other things, the functions of authenticating and authorizing users and devices, managing and monitoring the quality of service (QoS, Quality of Service), providing access to various data networks and routing data between RANs and data networks. As a rule, the CN network does not depend on radio access technology (RAT, Radio Access Technology), i.e. performs only functions that are not related to a specific RAT technology or RAN network.

Each RAN performs functions that provide user devices (UE, User Equipment) with wireless radio access to the core network. Some of these features are specific to RAT technology such as UMTS, LTE, or 5G New Radio (NR). The RAN consists of several macro cell base stations with a particular RAT technology (NB, eNB, gNB) and may additionally contain a number of small cell base stations (SC, Small Cell) with the same or different RAT technology.

UEs registered with the CN may have a current connection with the RAN and with the CN, i. e. be in connected mode, or may not be connected, i.e. be in standby or inactive mode. Typically, connected mode UEs are controlled by a single base station, herein referred to as a serving base station or a serving cell. The serving base station uses a Radio Resource Control (RRC) protocol to establish an RRC protocol context at the UE and at the base station. The context of the RRC protocol includes the radio capabilities of the UE, the current setup of bearers with the appropriate QoS, the multiplexing of services or applications on those bearers and the multiplexing of those bearers in physical resources, the allocated resources, and the measurements to be performed by the UE, and triggers and content for reporting on such measurements. The measurement configuration includes an indication of the neighbor cells to be measured, which neighbor cells may use the same RAT and the same frequency as the control base station, the same RAT and a different frequency, or a different RAT.

When the measurement reports received by the serving base station indicate that the neighboring cell has better communication conditions than the serving cell, the base station may perform a handover procedure in which it prepares the selected target cell for handover and instructs the device UE to handover to this target cell. During preparation, the target cell receives an RRC protocol context from the serving cell, so communication between the UE and the target cell can typically continue from the state it was in the serving cell.

US20110143738A1 describes Autonomous Search Functions (ASFs) that change functionality based on external inputs, optimizing the search strategy for the current environment. Mobile devices use the ASF functions in the LTE network to scan the frequency band for information broadcast by cells. The information broadcast by the cells of the UTRA (Universal Terrestrial Radio Access) system and the E-UTRA (Evolved Universal Terrestrial Radio Access) system may contain the identifier of the closed subscriber group (CSG, Closed Subscriber Group) of the cell; information specifying supported protocols; information identifying the supported radio access technology (RAT) and the rating of the cell on its frequency, as well as other information identifying the cell and how to connect to it. The mobile device may use the detected cell information to initiate cell proximity detection messages to perform handover or to prevent handover. When a mobile device connected to a UTRA or E-UTRA base station enters or leaves proximity to another cell, the network may initiate handover messages between the current base station of the mobile device and the base station of the discovered cell.

US9717110 presents wireless communication methods between first and second wireless communication devices, wherein the first device sends a chirp signal to second devices in a mesh network during a first wake-up period common to the first and second devices. The first device receives the keep-alive signal and connection setting information from a certain wireless relay device among the second devices during the first wake-up period, and the connection setting information contains resource allocation information. In addition, the downlink call may be transmitted to the first device along with connection setup information.

US20170055192A1 describes a UE-centric mobility mechanism in which the UE performs connected mode cell reselection when using the extended DRX function, i. when the UE does not receive data for an extended period of time. The reselection criteria is received from the source cell in the RRC connected state, and the UE decides either to apply network mobility controls or to autonomously reselect the cell by the UE, depending on the conditions, such as extended DRX. When autonomous reselection by the UE and signaling is required in the target cell, the RRC recovery procedure is used by the UE to establish a connection with the target cell. As a result, the target cell obtains a UE device context from the source cell, similar to establishing or resuming an RRC connection from idle mode.

Document EP2879440A1 describes a method for controlling a small cell base station in a system containing small cell base stations controlled by a macro cell base station. The small cells take measurements and the information is transmitted to the base station of the macro cell.

WO2017028808A1 discusses an on-line cell reselection method in which a UE can perform cell reselection without handover signaling. Document EP3125640A1 describes a bearer control procedure where a UE has dual bearer type connection capability between a primary cell group and a secondary cell group. WO2015065010A1 describes a method for performing dual connectivity in a heterogeneous network including, for example, a macro cell base station and small cell base stations.

Wireless repeaters are known from the LTE network. These are base stations that are wirelessly connected to the core network through the so-called donor base stations (DeNBs). For UEs served by a wireless relay, such a relay looks like a normal base station controlling the UE, i.e. an RRC connection is established between the relay and the UE. With respect to the DeNB, the wireless relay acts like the UE, but the radio resources used for communication between the UE and the relay are controlled by the DeNB or to some extent by the CN.

Dual or multiple connection mechanisms are known from LTE and NR networks, in which one UE has an RRC connection and an active radio link with a serving cell, in this case called the primary cell, and in addition one or more active radio links with secondary cells. honeycombs. The primary cell controls the UE as well as the secondary cells with respect to their association with the UE. A base station constituting a secondary cell for a UE may control other UEs in parallel as a primary or serving cell. The addition and removal of secondary cells for the UE is entirely under the control of the primary cell.

To migrate from LTE to new 5G NR technologies, dual connection is introduced with a UE having a primary cell providing an LTE connection and secondary cells providing a 5G NR connection, or vice versa. In this case, the secondary cells also have an RRC connection with the UE with the corresponding secondary RAT, but the primary cell still controls the connections, including the addition and removal of secondary cells.

For a single UE, the serving base station is typically the only or primary access point to the core network. In other words, the exchange of control messages with the core network, the so-called NAS (Non-Access Stratum) signaling, is routed to the core network via this base station. In addition, user data is transmitted via the serving cell, except for some dual connection scenarios in which multiple access points of the CN are used to transmit user data. If the CN needs to initiate signaling or data transmission to the UE, it requests signaling or data transmission from the serving base station.

Recently, the 3GPP consortium has begun to investigate the application of 5G NR radio access technology for wireless backhaul links commonly used for small cells (SCs). The aim of this study is to provide low-cost and low-effort deployment of SC cells by wirelessly connecting SC cells to a control base station, the so-called Next Generation Donor Node B (DgNB). These studies include multi-hop scenarios where an SC connects to another SC over a wireless link and the last SC on that route provides a direct link to the DgNB.

The new multi-hop wireless RAN may use different architectures in terms of which node, i.e. which base station manages such a multi-hop RAN and UEs connected thereto. Each solution has its own advantages and disadvantages.

Like known wireless repeaters in an LTE network, each base station (small cell SC) in a multi-hop RAN can act as a complete base station with respect to a served UE or a served cell SC. However, for its transport channel, such a SC cell will act similarly to a UE served by a next hop SC cell or a DgNB station (for the uppermost SC cell). The disadvantages of this solution are that each handover of UEs between SCs requires a context transfer between SCs over the hierarchical RAN. Since security keys for encryption and integrity protection are established between the serving base station and the UE, the SCs must be built accordingly, i.e. located in an inaccessible place or protected by a casing that protects the security keys from being read. This greatly increases the cost of such a SC cell. In addition, no node manages the multi-hop network on its own, so each SC needs knowledge of the surrounding neighbor cells in order to correctly set up measurements in the served UEs. This makes it difficult to set up such wireless SCs and may require intervention in the operation and maintenance system for each newly set up SC. Another drawback is that for the CN, each SC in this architecture will be a serving RAN for the UE, i. each handover of a UE between small cells will require an update of the corresponding CN.

An alternative approach is to terminate each RRC connection at the DgNB station, i.e. all UEs and SCs with a wireless transport network through the RAN set up an RRC connection with a DgNB station, which in turn manages all devices within the RAN. This makes it easy to set up SCs that are fully configurable by the DgNB. Since, in this case, security is configured when each device interacts with the DgNB station, the issue of securing the served devices is removed from the SCs, and the cost of the SC and its installation can be reduced.

However, this alternative architecture introduces a delay in establishing a connection between the devices and the base station serving them, which in this case is the DgNB station, and this contradicts the requirement that the serving base station perform some functions very quickly and quickly transmit the resulting settings to the served devices. One example of such low latency procedures is the communication of measurement results and the resulting handover decision.

The present invention overcomes the disadvantage of multi-hop RAN based on DgNBs and makes this architecture the most advantageous solution for implementing SCs.

Disclosure of invention

The present invention implements a subnetwork of a mobile communication system comprising a first base station (macro cell base station) and a plurality of second base stations (small cell base stations), where the plurality of second base stations wirelessly communicate with the first base station. Every second base station maintains either a direct connection to the first base station or a connection to the first base station via one or more other second base stations. The first base station is configured to configure a UE having an RRC connection with the first base station using information about suitable second base stations (i.e., second base station candidates) to enable the UE to autonomously switch between the second base stations. The first base station is configured to configure the second base stations using the configuration information of the second base stations, allowing the second base stations to transmit data to the UE and receive data from the UE, and to multiplex and route data to and from the UE.

The invention also implements a corresponding UE device, a small cell base station, and a method for managing a mobile communication network.

Brief description of the drawings

Hereinafter, by way of example only, preferred embodiments of the invention are described with reference to the accompanying drawings.

In FIG. 1 is a layout diagram of a multi-hop wireless transport network.

In FIG. 2A, 2B and 2C show the layers of the protocol stack.

In FIG. 3 is a diagram of a subnet.

In FIG. 4 is a message passing diagram.

In FIG. 5 shows an additional message passing scheme.

In FIG. 6 is a diagram of another subnet.

In FIG. 7 is a message passing diagram.

In FIG. 8 shows a diagram of another subnet.

In FIG. 9 is a message passing diagram for the subnet of FIG. 8.

Implementation of the invention

In FIG. 1 shows an example of a multi-hop wireless transport RAN with a 5G New Radio (NR) Donor Base Station (DgNB) connected to a CN. The DgNB station manages a subnetwork of several cascaded wirelessly connected small cell base stations. Each small cell base station has one wireless transport channel with another small cell base station or DgNB station, as well as any (including zero) number of access channels to other small cell base stations or UEs.

The DgNB station has access channels 1 and 5 to small cells SC2.1 and SC2.2, respectively.

The small cell base station SC2.1 has access channels 2 and 4 to small cells SC3.1 and SC3.2, respectively. In addition, the small cell SC2.1 provides an access channel to the device UE3. Small cell SC2.2 has access channels to small cell SC3.3 and to UE5.

Small cell SC3.1 provides NR network connection to two devices UE1 and UE2, and small cell SC3.2 provides NR network connection to UE4 through respective access channels.

In accordance with the present invention, all small cells and UEs in this example have an active connection to the RAN and through the RAN to the CN, which can then provide connections to various data networks (not shown). UE1, UE2 and UE4 establish an RRC connection with a DgNB station on a first communication channel, eg channel 3, and a first small cell connected via a wireless transport channel, eg channel 2, to a second small cell. The second small cell is connected wirelessly, eg, on channel 1, to the DgNB station. UE3 and UE5 also have an RRC connection with the DgNB station through a direct connection to small cells connected to the DgNB station via a wireless channel.

All radio links in the uplink (UL, Uplink) and downlink (DL, Downlink) have their own transmitter identification, i.e. the receiving base station in all previous cellular radio systems can distinguish between data received from different transmitters, and the devices also know which base station they are receiving from.

In accordance with the present invention, all small cells in this example have an RRC connection with a DgNB station, either over a forward wireless transport channel or over a wireless transport channel with another small cell.

The small cell base stations in this new architecture are similar to layer 2 relays. They do not control or configure the UE's access to the RAN. Both are performed by the DgNB station. They provide radio resources over the access channel to the served UEs and served small cells according to their configuration received from the DgNB. In the downlink, they decode the data received on the wireless transport channel and recover the segmented data packets, and then segment and encode these packets for forwarding on the wireless access channel to the next small cell base station or UE. In the uplink, the small cell base stations decode the data received on the access channel and recover the segmented data packets, and then segment and encode these packets for forwarding over the wireless transport channel to the next small cell base station or DgNB station.

In order to ensure the quality of QoS in the entire described multi-hop network, it is necessary to distinguish between different transmission channels from different UEs in each small cell. Only then can the small cells apply the priority for the channel and for the UE and provide resource allocation. As a result, in air interfaces between two small cells or between a small cell and a DgNB station, for each data packet, it is required to specify the source UE and the transmission channel. In other words, small cells must be able to distinguish data packets from one transmission channel of the UE from data packets from another transmission channel of the same UE. In addition, they must be able to distinguish data packets from one transmission channel of a UE from data packets from a transmission channel of another UE.

The radio interface, for example, in the wireless transport channel, in any case provides information about the source device transmitting data in the uplink, i.e. about the device on the other side of the span. In addition, the air interface provides the identification of the transmission channel for this hop, but on each subsequent hop, the source device data and information about the transmission channel are lost.

In accordance with the present invention, a small cell multiplexes all data received from previous hop transmission channels having the same or similar QoS, generally from different source devices, into one next hop transmission channel with the corresponding QoS. The data thus multiplexed is transmitted over the air interface between two small cells. An indication of the source device and the original transmission channel is included in or added to the data packets. This information is used in the receiver when making the next decision about data multiplexing in the next hop transmission channels. This allows each small cell base station to forward packets according to their individual QoS and priority.

Transmission channels are also indicated in the existing radio interface, for example, in the LTE system, by indicating the logical channel identifier (LogCh-ID, Logical Channel Identification) in the header of the MAC address of the data packet. Here, the LogCh-ID is unique within only one RRC connection between the UE and the serving base station. Other devices may use the same LogCh-ID to indicate their transmission channels. To uniquely identify the sender of a packet, the base stations use the UE's internal device identifiers at the physical layer.

In the present invention, packet processing in a concatenated network of small cell base stations requires an identification combining a UE identification and a transmission channel identification. In this sense, the term "bearer" is used for any data streams with a common or similar QoS quality and priority. In existing radio access networks, the term "transmission channel" is also commonly used. In the rest of this invention, this term is used without loss of generality. Like the LogCh-ID, the joint indication of the source UEs and transmission channels is called the Global Logical Channel Identity (GLogCh-ID), which is then used in the multi-hop network on each hop.

The GLogCh-ID is unique for each transmission channel of each UE served on the subnet. A UE can always be identified by a GLogCh-ID if, for example, this identifier consists of two parts - a UE device identifier unique to a UE on a given subnet and a LogCh-ID unique to a transmission channel of a single UE, similar to the LogCh-ID used in the existing protocol stack. Alternatively, the GLogCh-ID does not contain separate identifiers for the UE and the bearer.

The DgNB station participates in the multiplexing control. It configures all small cells using the GLogCh-ID and the appropriate QoS and priorities of the devices they are configured to work with, to actually or potentially act as a router, or to provide an access channel.

To simplify the description, the following will focus on only a few of the nodes shown in FIGS. 1, namely at UE1s, stations SC3.1, SC2.1, links 3, 2 and 1, as well as at the DgNB station.

In FIG. 2A, 2B and 2C show the protocol stack layers predominantly used in the involved nodes and based on the layers of the NR air interface protocol stack proposed here.

In FIG. 2A shows a protocol stack for establishing and maintaining an RRC connection between a UE1 and a DgNB (control plane) via small cells SC3.1 and SC2.1. An RRC connection is established between the UE1 and the DgNB, with the RRC protocol peers located at the UE and the DgNB. A security association is also established for these two entities, and the PDCP protocol layer uses this security association (ie the corresponding pre-shared keys) to encrypt and protect the integrity of the RRC messages. Sub-PDCP protocols, i.e. the radio link control protocol (RLC, Radio Link Control), the medium access control protocol (MAC, Medium Access Control), and the physical layer protocol (PHY) refer to the actual radio link. Therefore, they are present in every node involved, and each hop is established by the respective counterparty protocols on each side of the hop.

For each hop between network nodes, i.e. between two small cells or between a small cell and a DgNB station, a received packet multiplexing function is required for the next hop transmission channel and to indicate the GLogCh-ID introduced in the present invention. To do this, the protocol stack of each of these hops contains, in addition to the known functions of the RLC, MAC and physical layers, a relay function that transfers the GLogCh-ID identifier to the header field of the transmitted packets and, based on the setting by the DgNB station, decides on the transmission channels of the next hop, in which packets should be multiplexed. This relay function may be performed at the RLC layer as an optional function with an additional RLC header field. Alternatively, the inter-hop protocol stack may include an additional extended PDCP layer for this function. In FIG. 2A shows another alternate function at an additional protocol layer called Relaying Protocol (RP) without loss of generality.

Similarly, in FIG. 2B shows the corresponding protocol stack for transferring user data from UE1 to the DgNB. The Service Data Stream Multiplexing Protocol (SDAP) recently introduced for 5G NR and the PDCP protocol for encryption, integrity protection and compression of control data are present in the UE1 device and the DgNB station. As before, protocols below PDCP, i.e. radio link control (RLC), medium access control (MAC) and physical layer (PHY) protocols, refer to the actual radio link and hence are present in every participating node. The newly introduced relay function with GLogCh-ID and multiplexing is also shown as a relay protocol (RP) with alternatives as described above.

In FIG. 2B shows a protocol stack for establishing and maintaining an RRC connection between a small cell SC3.1 and a DgNB station. The RRC and PDCP protocol counterparties are in the SC3.1 cell and in the DgNB station, respectively; RLC, MAC and PHY protocols are inter-hop. The relay function, for example at the RP protocol level, is required only on the second hop of this connection, i.e. from SC2.1 cell to DgNB station. The protocol stack for establishing and maintaining an RRC connection between a SC2.1 cell and a DgNB station, not shown in either figure, is very similar to that shown in FIG. 2B, but with a direct peer of each protocol stack layer between SC2.1 and the DgNB.

According to the architecture described above, one aspect of the present invention is to set up a DgNB station for small cells for possible handover. The setting is performed so that the UE can autonomously switch the connection from the current source small cell to the connection to one of the suitable target small cells based on the criteria configured by the DgNB, but without informing the measurement results related to the source and target cells, and without base station commands to perform handover.

The UE tunes in to a set of suitable small cells, i. e. cell IDs, frequency resources and radio parameters. This configuration may include additional information such as access mode to the target cell, for example, over a random access channel (RACH) or by direct resource request over an uplink control channel. In addition, this configuration contains cell switching criteria, such as: a threshold below which the current performance of the source cell must fall to consider cell switching; thresholds for comparing characteristics of source and target cells; the duration during which the received signal strength in the target cell must be higher by a threshold amount than in the source cell, or other criteria. If these criteria are met, the UE switches to the target cell immediately.

The above list of potential target cells differs significantly from the well-known neighbor cell list, which contains cells for performing measurements and transmitting their results to the serving cell according to certain criteria, so that the serving cell can decide to prepare a handover and instruct the UE to perform handover. In this case, the configuration of the currently applied neighbor list and the corresponding measurement and informing setting, as well as quality indicators can coexist with the present invention for candidate target cells that are not under the control of the DgNB station serving this UE.

In addition, the candidate cell list and autonomous cell switching are significantly different from cell selection after radio link failure in the serving cell, since the latter requires the UE to enter the idle state, i.e. set a new RRC context for the selected cell.

The setting of suitable small cells is not only performed at the UE. The DgNB station also sets up suitable small target cells to ensure that data transmission via the target cell is started immediately after cell switching.

The DgNB station sets up suitable target cells using all the information necessary for transmitting and receiving data, as well as for multiplexing and routing data (control data and user data) to and from the UE. In other words, the following is configured in suitable small cells:

- MAC layer configuration containing:

- information about the existing signaling and data transmission channels installed in the UE;

- multiplexing information for multiplexing data channels in transport channels or in physical resources;

- priority information, such as the priority of one UE's transmission channels relative to each other and/or the priority of a UE relative to other UEs or small cells served by the same small cell;

- physical layer configuration, containing:

- UE device identifier (UE-Id), such as C-RNTI, known from the LTE system, with which the UE device can identify itself when accessing the target cell;

- UE radio capabilities and radio parameters;

- one or more global logical channel identifiers (GLogCh-ID) to be transmitted along with the data received from the UE in order to ensure proper multiplexing on the next hops;

- routing information for transporting downlink information to and/or uplink from the UE.

The DgNB station sets up the above information in the appropriate small cell configuration, i.e. small cells that can be directly accessed by the UE through an air connection. In addition, the DgNB station tunes all small cells that are on the route between any of the eligible target small cells and the DgNB station. In these small cells for routing that do not have an air interface with the UE, the following is configured:

- GLogCh-IDs used to identify data with different QoS quality and/or priority (ie data from different channels) sent by or addressed to the UE;

- relevant QoS quality and/or priority information;

- routing information for transporting downlink information to and/or uplink from the UE.

In general, it can be said that all small cells potentially involved in the UE's data routing are configured by telling them the information necessary to forward data packets to or from the UE according to the packet's individual QoS requirements. The small cells that can be used to serve the UE's radio bearer are further informed of the UE's device ID, as well as the physical layer and MAC layer parameters for setting up and maintaining the radio bearer.

The UE switching to the target cell requests uplink resources from the target cell using its UE-Id. The target cell may identify the UE based on the predetermined UE-Id and provide the available resources according to the transmission channel, multiplexing, and priority information. Resources are requested by the UE to transmit user data or control data such as application data or RRC messages, which also indicates to the target small cell base station that the UE has switched cells.

Ideally, the UE restarts its RLC and MAC layer node and no further context transmission from the original small cell is required. Depending on the desired QoS of the transmission channels, lost packets may be retransmitted at the PDCP layer between the UE and the DgNB. Since the UE has a security association with the DgNB, all data is encrypted and its integrity is optionally protected, so there is no need for the target small cell to perform any security setup procedures with the UE.

In order to provide fast subnet route switching and direct downlink traffic to a new small cell, once the UE is served by the small cell, the small cell informs the higher layer small cell that the UE is currently served by this target small cell. This procedure is repeated by all small cells upward in the hierarchical level until a base station is reached that is part of both the old and the new route. This base station may be referred to as a common base station and may be either a small cell or a DgNB station. The common base station immediately starts routing the downlink packets along the new route to the target small cell. For a small cell, the condition for informing the small cell of the next hop about the service of the UE may be that the UE indicates its UE-ID in the resource request. A preferred alternative is for the small cell to receive the first data packet, for example, containing an RRC message from the UE to the DgNB. This packet, transmitted on a new route, indicates a route switch to any small cell located on the way to the common base station. In other words, the first uplink burst serves as an indicator for the additional small cells that the UE has arrived. An alternative is for small cells to have peer-to-peer signaling, eg through their transport network's MAC layer or through the new SC-SC protocol.

As previously described, one useful aspect of the new station-oriented DgNB architecture is that transmission security is provided between the UE and the DgNB so that the UE and the small cells do not need to perform additional protection procedures that delay cell switching. One disadvantage of not having a security association between a UE and any small cell is the possibility of security attacks by rogue UEs that simply access the small cell with a fake UE-Id or the real UE-Id of the rogue device, inject false data into the uplink and forward data related to the UE to the new small cell, which allows the data to be moved away from the real small cell serving the corresponding UE.

The use of integrity protection prevents a rogue UE from successfully injecting erroneous data into the data stream. In addition, the encryption ensures that the data cannot be read by a rogue UE. However, denial-of-service attacks are possible because a redirect to a new target cell initiated by a rogue UE prevents data from reaching the desired target UE.

To prevent such attacks, the common base station must temporarily duplicate the downlink packets along the new and old routes. In addition, it must accept uplink packets coming from both routes to be forwarded on the same route above the common base station in the hierarchical system. Any duplicated packets must be filtered at the DgNB station using PDCP layer sequence numbers or integrity protections.

Finally, the UE itself must inform the DgNB that it has switched to another serving cell in an RRC message generated by the UE, of course, with security, i.e. its receipt informs the DgNB station to switch to another cell. The affected small cells may additionally inform the DgNB station via their RRC or similar protocol of the changes that have occurred. In response, the DgNB station informs the affected small cells of the switch to another route, i.e. small cells lower in the hierarchy than the common base station on the old route can be informed to stop routing data to and from the UE, the common base station is informed to stop duplicating packets and use only the new route, and the UE and small cells receive information about new small cells that can be used for autonomous handover in the future.

A common base station can only apply duplication of packets for a limited time. It may start a timer that stops when a new route is confirmed by the DgNB. If the specified time elapses before receiving such an acknowledgment, the DgNB station may stop duplicating packets and return to the old route, assuming that the new route has failed.

In connection with the autonomous cell switching according to the present invention described here, data transmission through the UE and the core network continues until the DgNB station is informed of the cell switching or informs the small cells accordingly, while the data delay is minimal. Thus, the present invention eliminates the delay introduced by multi-hop radio subnetworks.

In the downlink, the new route will be used only after the common base station receives the route switching information. Between the cell switch by the UE and the transmission of the first downlink packets on the new route to the target small cell, some packets may be delivered to the downlink on the old route. To reduce the probability of packet loss or the number of lost packets, the UE, depending on its capabilities, may continue to receive packets from the source small cell until the first packet enters the downlink in the target small cell. The reset at the RLC, MAC and PHY layers at the UE will only occur when the first downlink packet arrives at the new cell.

If the UE is using a communication service that requires very reliable data transmission, redundant data transmission may be useful to avoid packet loss. The newly introduced architecture of the present invention can be successfully used in this case as well. The UE may have multiple serving small cells and use the appropriate target small cell setting to provide autonomous mobility. The UE may use the mechanisms described to autonomously switch one of the small cells while keeping the rest of the redundant channels intact. The rest of the redundant channels can only be switched after acknowledgment of the uplink and downlink transmission through the autonomously selected target small cell, for example, when the first packet arrives on the downlink or when the corresponding RRC message is received from the DgNB station on the downlink. Redundant transmission may be a transmission channel QoS setting used permanently for a particular transmission channel, or a feature used temporarily only during the described small cell switching to prevent packet loss.

The present invention can also be used to implement dual connectivity in which one UE is connected in parallel to different base stations. The UE may be connected to at least two small cells managed by the same DgNB and may use autonomous switching techniques to select the best cells. Alternatively, the UE may be connected to the first base station and to the small cell managed according to the present invention by the DgNB, without the first base station being controlled by the DgNB. The best small cell is then selected by an autonomous switching method, with the first base station remaining the same or replaced using existing handover procedures.

Yet another alternative architecture, shown in FIG. 1 is a UE with at least two parallel connections to the same DgNB station, one through a direct air interface and the other through a small cell with a wireless transport network as described here. In this case, the control signals can be transmitted on a direct link with the DgNB station, and the UE is configured to autonomously select the best small cell for the parallel connection. However, the main goal of autonomous cell switching, which is to eliminate the control signaling delay when informing about the results of measurements and performing handover, implemented by the multi-hop architecture of cascaded small cells, is not achieved in this case.

Another embodiment of the present invention is the use of multiple small cells to organize multiple transmission channels with one UE, in which the optimal small cell is selected by the UE for different radio channels. Some small cells can be optimized for certain tasks, while other tasks can be solved only to a limited extent or not at all. For example, some small cells are designed for low latency applications but do not provide high data rates. Such small cells may transmit information about their properties to enable UEs to take this information into account when selecting new small cells, or the special properties of small cells may be contained in the suitable cell configuration from the DgNB. The autonomous cell switching described hereinafter is performed by the UE for only a portion of the transmission channels configured or to be configured by the UE. These mechanisms are applied as described above, and the GLogCh-ID of the uplink packets allows the common base station to apply downlink route adaptation only to the corresponding transmission channels. In addition, the route acknowledgment received later from the DgNB confirms the new route for some of the transmission channels of the UE while the remaining transmission channels still use the old route. This use case of the present invention is especially useful for the new types of data traffic "ultra-low latency" (ULL, Ultra Low Latency), "ultra-reliability" (URL, Ultra Reliability) and "massive Internet of Things" (MIoT, Massive Internet of Things) of the developed 5G network , which may be used on some UE transmission channels, while other channels may be used for normal broadband traffic. An example implementation could be a small cell base station with low latency within the UE's coverage area directly connected to the DgNB station, bypassing multiple wireless hops of the transport network of alternative small cell base stations within the UE's coverage area. A low latency small cell base station provides only limited bandwidth or only connectionless data transmission, while other small cell base stations implement other services within a more efficient but slower multi-hop wireless transport network.

The mechanisms described above allow autonomous switching of a serving cell for UEs. The new architecture shown in Fig. 1 is based on a wireless transport network for small cell base stations involved. The wireless transport network between small cells is based on the same radio interface (or similar) as the radio interface between the UE and the small cell. Therefore, the original mechanisms of the present invention can also be applied to the wireless transport network itself.

A small cell base station, such as SC3.1 station, served by another small cell base station, SC2.1 station, can be configured to possibly autonomously switch to a suitable small cell, such as SC2.2 cell. Routing and multiplexing information and radio and identification information are prepared for the suitable small cell so that the small cell SC2.2 can take over the service of the small cell SC3.1 after cell switching. Therefore, all of the mechanisms described above can be used, such as route switching, packet duplication, and final route announcement by the DgNB using layer 3 signaling. transmissions routed by SC3.1 originating from other devices such as UE1 and UE2 are already associated with the GLogCh-ID. Assuming that the small cell does not generate any user data, only the signaling radio bearers for establishing and maintaining the RRC connection between the SC3.1 small cell and the DgNB station should be identified using GLogCh-IDs, and should be associated with QoS information. and/or priority in a suitable SC2.2 small cell.

The application of the present invention to a wireless transport network allows flexible dynamic configuration of the transport network. However, since it is assumed that small cells are not mobile, the number of small cells suitable for automatic cell switching in this case may be much less than the number of UEs (typically mobile). Such a switching option may be a countermeasure against the effects of dynamic shadowing between two small cells or against failure of the small cells. However, mobile small cells can benefit from the described network architecture and mechanisms, similar to UEs.

Preparing a candidate small cell as a wireless transport network for another small cell after autonomous cell switching requires that the candidate small cell be aware of all current and potential transmission channels served or routed by the source small cell. This means that if the wireless backhaul network is larger and has a deeper hierarchy than the network in the example of FIG. 1, and the small cell routing traffic covers several dozen other small cells, each of which is associated with several UEs, the volume of configuration information for preparing each small cell for autonomous switching greatly increases. Configuration tuning and updating requires very high wireless network bandwidth and computing resources in the DgNB station and in small cells.

An alternative would be to provide an identical overall configuration for all small cells of the wireless transport network, i. e. when the configuration of each small cell contains complete information about the served channels and devices, for example, all GLogCh-IDs, corresponding priorities and QoS. The configuration information may be broadcast from the DgNB station, i. e. the complete configuration is once reported by the DgNB station to all small cells directly connected to the DgNB station, and these small cells, after receiving the configuration information, store and apply this configuration, and forward the information to all subsequent small cells that are served on the forward channel. The same mechanism can be applied to a configuration update that only transfers changes to the saved full configuration. The broadcast mechanism requires that a shared security key be available in all involved small cells to protect integrity to ensure that the configuration information is correct. Security can be provided either with a symmetric key transmitted via dedicated Layer 3 signaling by the DgNB to each small cell, or with an asymmetric key pair of the DgNB whose public key is pre-set or broadcast as a certificate verified by the receiving small cells.

The described broadcast prepares each small cell for a possible cell handoff for all UEs and small cells. The possible configuration of the devices switching to suitable small cells should ensure that the handover is still under the control of the DgNB station. In addition, multicast transmission can be used, i. e. broadcasting various configuration messages addressed to the small cell group. This reduces the number of single configuration messages in larger subnets of multi-hop wireless transport networks.

It should be noted that what is stated in the description of the present invention does not interfere with the security of the wireless transport connection of the base station of a small cell, for example, using a secure tunnel, such as an IPSec tunnel, to prevent eavesdropping and manipulation of data at this level. This option is not further described in this invention, since it does not affect the inventive step and advantages of the present invention, but is simply an embodiment of it.

In FIG. 3 shows a simplified architecture comprising a DgNB station, three small cell base stations SC2, SC3.1 and SC3.2, and a UE. The UE has an access channel to a small cell base station SC3.1. Small cells SC3.1 and SC3.2 have wireless transport links with a small cell base station SC2 that has a wireless transport link with a DgNB station. The DgNB station is connected to the operator's core network.

In the message passing diagram shown in FIG. 4 shows the exchange of messages and data in the subnetwork shown in FIG. 3. As a prerequisite, shown as a single block without detail, it is assumed that according to the basic architecture of this invention, all small cell base stations and the UE have an RRC connection with a DgNB.

In the initial state shown in Fig. 4, the UE performs ongoing uplink (UL) and downlink (DL) data transmission. For this purpose, the small cells SC3.1 and SC2 are configured in accordance with the present invention so that they can provide QoS for the transmission channels to which the UE is currently configured. The UE has an assigned UE device identifier, such as C-RNTI according to the LTE standard, which is used by the UE in uplink transmission to indicate the source of the data. This condition may be met by scrambling the uplink messages with the UE's device identifier, or simply by transmitting the identifier or portions thereof as part of the data. The UE device ID is also used by the serving small cell for downlink data transmission when accessing the resources used for data transmission to the UE. Scrambling or other techniques may also be used to transmit the UE device identifier or portions thereof in downlink resource allocation. According to the present invention, the small cell base station SC3.1 is configured by the C-RNTI of the UE. In addition, the UE may be given dedicated small cell resources in the time and/or frequency domain to request uplink transmission scheduling from the SC3.1 small cell base station. Other radio parameters regarding radio features supported or preferred by the UE may also be configured similar to known radio standards such as LTE or 5G NR.

The UE can have three radio channels for signaling and four radio channels for data transmission, for a total of seven radio channels with the corresponding QoS parameters as shown in Table 1. The corresponding information is configured in the UE and in the SC3.1 small cell base station, which is currently serves the UE.

Table 1

LogCh-ID Radio channel type Relative Priority GLogCh ID 1 SRB0 1 65 2 SRB1 1 66 3 SRB2 4 67 4 DRB1 Quality as far as possible 6 68 5 DRB2 SIP (Session Initiation Protocol) signaling 3 69 6 DRB3 Voice over IP (Voice over IP) 2 70 7 DRB4 Video Streaming 5 71

The SC3.1 small cell base station has a wireless transport channel with the SC2 small cell base station, which can have eight configurable radio channels - three signaling radio channels for establishing and maintaining its own RRC connection with the DgNB station, and five radio channels for forwarding or relaying data with different QoS . Table 2 shows an example of wireless transport channels configured for SC3.1 stations in SC3.1 and SC2. Only the three signaling radio bearers from the SC3.1 station are assigned a global logical channel identifier, since all forwarded or relayed data is expected to already contain a GLogCh-ID according to its origin and transmission channel.

table 2

LogCh-ID Radio channel type Relative Priority GLogCh ID 1 SRB0 1 101 2 SRB1 1 102 3 SRB2 4 103 4 DRB1 Quality as far as possible 6 - 5 DRB2 SIP Signaling 3 - 6 DRB3 Voice VoIP 2 - 7 DRB4 Video Streaming 5 - 8 DRB5 Video calling 2 -

Similarly, the SC3.2 small cell information can be configured in SC3.2 and SC2 stations according to Table 3:

Table 3

LogCh-ID Radio channel type Relative Priority GLogCh ID 1 SRB0 1 104 2 SRB1 1 105 3 SRB2 4 106 4 DRB1 Quality as far as possible 6 - 5 DRB2 SIP Signaling 3 - 6 DRB3 Voice VoIP 2 - 7 DRB4 Video Streaming 5 - 8 DRB5 Video calling 2 -

According to the present invention, the SC2 small cell base station configuration contains information about devices that are served or potentially served by the SC2 small cell, such as GLogCh-ID, QoS quality, and priority information, which information may differ from that contained in serviced devices. For example, the priority information in the SC2 small cell base station may consider that the SC2 small cell base station's own high priority signaling radio bearers have a higher priority than similar channels forwarded or relayed by the SC2 cell. In addition, the high priority radio bearers for signaling small cell base stations served by SC2, such as SC3.1 and SC3.2, may have a higher priority than the radio bearers for signaling UEs. Such an example of data pertaining to the UE and small cell base stations SC3.1 and SC3.2 configured by the DgNB in SC2 is shown in Table 4. In addition, the small cell base station SC2 is configured with its own signaling radio bearers and data like base stations SC3.1 and SC3.2 in tables 2 and 3.

Table 4

GLogCh ID Relative Priority Radio channel type Routing 65 3 High priority signaling SC3.1 66 3 High priority signaling SC3.1 67 6 Low priority signaling SC3.1 68 8 Quality as far as possible SC3.1 69 5 SIP signaling SC3.1 70 4 VoIP voice communication SC3.1 71 7 streaming video SC3.1 101 2 High priority signaling 102 2 High priority signaling 103 5 Low priority signaling 104 2 High priority signaling 105 2 High priority signaling 106 5 Low priority signaling

According to the present invention, the small cell base station SC3.1 receives data from the UE over any radio channel. It can be assumed that user data packets arrive via all radio data transmission channels, i.e. DRB1, DRB2, DRB3 and DRB4. The small cell base station SC3.1 receives the packets, decodes and demultiplexes them, and reconstructs the segmented packets as original user data packets. In most cases, these are IP packets from the respective applications. In other examples, where packets are received on signaling radio bearers SRB0, SRB1, or SRB2, these packets may not be IP packets, but RRC messages from the RRC layer of the UE. The SC3.1 station, based on the radio channel on which the packet was received, and based on the setting by the DgNB station, determines the global logical channel identifier GLogCh-ID for each user data packet and adds it to the data packet before forwarding this packet over the wireless transport network to the base station small cell SC2. In other words, for packets received from the UE over the DRB1 data radio bearer, GLogCh-ID = 68 is added before data is sent over the wireless transport network. and 71, respectively. Such an addition may be in accordance with any suitable protocol, for example, any of the existing protocols in the 5G NR protocol stack or a new protocol, which in the example of FIG. 2 is called Relay Protocol (RP). Packet forwarding is performed according to the configuration setting by the DgNB station, i.e. in accordance with the configuration data of Table 2. In this table, for each radio channel of the UE, the relative priority of data processing is set, taking into account the transmission order of packets multiplexed into the same resources. Higher priority, i.e. lower integer values of the relative priority parameter serve as a condition for priority transmission, and packets with a lower priority are transmitted only if there are no higher priority packets waiting to be transmitted. In addition, in Table 2, for each of the radio bearers of the UE, radio bearer type information, which can also be referred to as quality of service (QoS), indicating the nature of the service for which the data is used, is given. The radio bearer type may be used by the small cell base station to select one of five small cell base station data radio bearers DRB4-DRB8 for forwarding the data packet. The same principle applies to data packets received by the small cell base station SC3.1 from the UE on one of the signaling radio bearers SRB0, SRB1 or SRB2 with the corresponding higher priority, different QoS quality or radio bearer type and with the GLogCh-ID, having a value of 65, 66 or 67, respectively.

A small cell base station SC2 receiving a data packet from a small cell base station SC3.1 on any of the radio channels DRB1, DRB2, DRB3, DRB4, or DRB5 in the wireless transport channel of the SC3.1 cell must decode and demultiplex the packets, recover segmented packets, and determine added GLogCh-ID. It looks for the GLogCh-ID as configured by the DgNB station. In the example shown, searching for a packet from a UE with LogCh-ID = 68 results in SC2 forwarding it according to best effort QoS and relative priority 8. The small cell base station SC2 has no information about UE device and does not need to associate GLogCh-ID = 68 with a specific device. However, it obtains enough information to decide to forward the packet with the appropriate QoS and priority, and by forwarding the GLogCh-ID along with the received data packet, it provides enough information for subsequent small cells to make a forwarding decision, and for the DgNB station to determine if this packet belongs to a particular UE. If the small cell base station SC2 has configured a transmission channel to the DgNB station corresponding to data transmission with "as far as possible" quality, then this channel is used and the data is multiplexed into available resources according to priority 8.

The DgNB station has information about the distribution of GLogCh-IDs allocated to UE devices and the corresponding radio channels of UE devices in the subnet controlled by the DgNB station, therefore, after successfully receiving the packet, the DgNB station can correctly determine the PDCP and / or RRC layer object to which it is addressed by the GLogCh-ID identifier. this package.

The uplink data transmission from the UE to the DgNB via a multi-hop subnet has been described above. For the downlink, the same principles may apply, ie. to all data packets transmitted to the base station of a small cell, for example, station SC2, the DgNB station adds a GLogCh-ID. The small cell base station SC2 determines the GLogCh-ID, looks up the appropriate QoS and priority, and forwards the data packets with the LogCh-ID. In order for the small cell base station to be able to determine the route, i. e. to which of the served devices the data packet should be directed, the DgNB station sets up routing information in small cells for devices that are not served by them on the access channel. In this example, it is the small cell base station SC2, and the routing setting is shown as an example in the "Routing" column of Table 4.

In this table, all radio bearers directed to and from the UE are routed through the small cell base station SC3.1. The routing information may be provided as a next hop address or a device name in the next hop, the latter shown in Table 4. Alternatively, the routing information may be provided as a next hop index, which is an index pointer to a predetermined table.

Table 4 does not contain routing information for the SC3.1 and SC3.2 small cell base station radio bearers, since both of these small cell base stations are served on the access channel by SC2, so the GLogCh-ID of any packet corresponds to the access channel radio bearer and, therefore, end device.

As shown in FIG. 4, the above description basically explains, firstly, the preliminary assumption of the established RRC connection of each UE and the small cell base station with the DgNB station, as shown in the drawing in the upper block. Secondly, the two-way communication between the UE or other devices and the DgNB has been described above, which is simply shown in the drawing by the double-headed arrows.

According to the present invention, a DgNB station tunes UEs using candidate cell information, which in this embodiment contains information about a cell within the coverage area of a small cell base station SC3.2. This information may contain information about resources, such as the bandwidth or the average frequency of the bandwidth of the candidate cell. This information may also include a cell identifier, such as a physical cell identifier, encoded in the synchronization signals broadcast in the cell to enable cell identification based on the synchronization signals. In addition, this information may contain a UE device identifier used by the UE when accessing a suitable cell. In this embodiment, it is assumed that the UE device identifier, such as C-RNTI, does not change in autonomous cell switching. For random access or other access methods to a suitable data restricted cell, both the UE and the cell may be configured with a short UE device identifier in addition to or instead of the C-RNTI.

In addition, the suitable small cell SC3.2 is configured so that it can serve the UE after the UE switches autonomously to another cell. For this purpose, the UE device identifier, in this embodiment, the C-RNTI and/or short UE device identifier, as well as additional information necessary for servicing the UE device, is included in the SC3.2 cell configuration. For example, the radio capabilities of the UE are indicated in terms of the MAC layer and the physical layer.

In addition, in the small cell base station SC3.2, the information according to Table 1 currently present in the UE and in the small cell base station SC3.1 is also configured to serve the UE. This information allows the SC3.2 to multiplex the downlink data to the corresponding radio channels and forward the uplink data with the appropriate QoS and priority by adding the correct GLogCh-ID as explained above with respect to the base station of the small cell SC3.1.

The small cell base station SC3.2 broadcasts the timing and reference signals, as well as system information received by the UE, and the measurement results of the suitable SC3.2 cell characteristics are determined, used by the UE to decide on a possible cell switch. The information transmitted by the SC3.2 cell is shown in the drawing with a dashed line, since this is just an example and any other condition can be used in the implementation of the present invention to make the decision of the UE to switch cells. The system information may contain load information allowing the UE to determine whether the quality of service expected in SC3.2 is better than the current quality of service in SC3.1.

According to this embodiment, the UE decides autonomous cell switching and requests resources from the base station of the suitable small cell SC3.2. This can be done by randomly accessing a suitable small cell with a short UE device ID that was provided during setup. The UE may, in the first random access message, request resources to send a longer second message on the provided resources. Alternatively, if random access is not required, eg for performance reasons, the UE may directly use the physical uplink control channel to request uplink resources using the C-RNTI.

During this procedure, downlink data transmission through the small cell base station SC3.1 can continue. Depending on the radio capability of the UE, it may be able to successfully receive data from SC3.1 and acknowledge in the uplink after starting uplink data transmission to SC3.2. This variant is shown in dashed lines in Fig. 4.

The candidate small cell SC3.2 may respond to the request for uplink resources by granting uplink resources, which, upon receipt by the UE, allows the candidate small cell SC3.2 to become a new serving small cell. The UE compiles the first uplink data packets, for example, from the user data packets or from the uplink RRC message, and transmits them to the small cell base station SC3.2. These packets are received and then mapping of the configured radio bearers to the radio bearers of the wireless transport link is performed as described in relation to forwarding uplink packets to the SC3.1 small cell base station, including adding the GLogCh-ID to the corresponding communication protocol.

According to the present invention, once the uplink data packets from the UE are received by the small cell base station SC2 and recognized by the LogCh-ID, duplication of the downlink data packets to the UE of the same channel recognized by the same LogCh-ID is started. Duplication in this case means that these downlink packets are transmitted by the small cell base station along the old route, i.e. to the small cell base station SC3.1 in this embodiment of the invention and, in addition, they are copied to the new path on which the first uplink packets were received, i. e. to a small cell base station SC3.2.

If the GLogCh-ID is constructed to identify all transmission channels belonging to one UE, then the principle of temporary copying of downlink data packets in a small cell base station can be applied to all transmission channels of a UE after receiving the first uplink data packet. If the GLogCh-ID does not distinguish between UEs, downlink copying may only apply to bidirectional links for which uplink packets have been received. In this case, the UE may be allowed to send empty uplink packets for transmission channels that currently have no data to send on the uplink to speed up the use of the new downlink route for all channels. These empty packets may have zero length user data, i.e. may contain only a small header, or may be otherwise marked to exclude them from the data stream in the radio access subnet.

Reception of the first downlink burst by the UE through the new SC3.2 small cell base station, first grant of the uplink, or successful receipt of the uplink burst acknowledgment by the new small cell base station may trigger the UE to inform the DgNB of successful cell switching in an RRC message, for example in the path switch info message. Reception of this message by the DgNB may cause the DgNB to inform all involved small cells of the route switching, i. a request is sent to the small cell base station SC2 to advertise a new route to the UE, a request is sent to the small cell base station SC3.2 to act as a serving small cell, and the cell SC3.1 is configured to remove the UE device context or to be used in as a suitable small cell for future cell switching back to the old cell.

If the small cell base station SC2 copied the downlink packets for only a portion of the UE's transmission channels, the DgNB may initiate advertisement of this route for all the UE's transmission channels.

Next, the downlink data transmission for all transmission channels of the UE is routed to the new small cell base station. After that, the DgNB station can perform a new setup of the UE by providing new suitable small cells.

In FIG. 5 shows a variant of the previous embodiment based on the same subnetwork architecture as shown in FIG. 3. The preconditions for RRC connections of the UE and all small cell base stations with the DgNB station and setting of small cell base stations SC3.1 and SC2 using GLogCh-IDs and routing information are the same as in the previous embodiment.

In this embodiment, according to a new aspect of this invention, the small cell base station SC3.1 is configured to inform the DgNB if the connection with the UE is lost. The small cell SC3.1 informs the DgNB of the loss of connection with the UE by transmitting the identification of the UE, or informs the loss of the connection of the served bearers by transmitting the list of GLogCh-IDs with which the connection is lost. Any such information may be sent to the DgNB station as a bearer loss notification.

As shown in FIG. 5, at some point in time, the UE and the small cell base station SC3.1 detect a loss of connection, for example, due to a radio link failure due to the UE leaving the cell, due to UE antenna shadowing, and the like. The UE must immediately start buffering uplink data because the link is unavailable for transmission. This is no different from the current implementation of UE devices. According to the present invention, the small cell base station SC3.1 informs the DgNB station that the connection with the UE has been lost, after which the DgNB station starts buffering downlink data. The DgNB station may also start a timer which, after a set time, starts an implicit release of the RRC connection with the UE. In this embodiment, it is assumed that the timer has not expired and the RRC connection is maintained.

The UE performs an autonomous cell handover to a suitable small cell, in this embodiment, to an SC3.2 cell, and transmits on the uplink, preferably as the first uplink burst, an RRC message informing the DgNB of the route handoff. The RRC layer reconfigures the involved small cells SC2, SC3.1 and SC3.2 to a new route to and from the UE, and starts transmission of buffered downlink data before continuing normal transmission of new downlink data. The UE may start transmitting uplink data immediately after autonomous cell switching.

Another embodiment of the invention is described below. This variant is a modification of a part of the previous embodiments of the invention with the architecture according to FIG. 6. Compared to the architecture shown in FIG. 3, the depicted subnet has one more hierarchy level. This variant is provided to show the useful aspect of the present invention for larger subnets.

If all five small cell base stations of a subnetwork are configured to actually or potentially serve a UE, then the small cell base station customization according to the two previous embodiments consumes significant radio resources on the wireless access links. An alternative is shown in Fig. 7. The DgNB broadcasts a small cell reconfiguration message containing small cell routing preparation information, i. e. GLogCh-IDs and corresponding QoS, priority and routing information. Broadcasting in this case means disseminating information to all directly connected small cell base stations of a subnetwork in order to save and apply the configuration, as well as sending this information in parallel by each small cell base station to subsequent directly connected small cell base stations via an access channel.

According to FIG. 7, all small cell base stations that have received the reconfiguration message forward the message after checking its integrity, for example, by checking the integrity based on a certificate stored in each small cell base station and received from the network operator. After checking the integrity, the configuration is saved and applied in further work.

This efficient subnet configuration distribution mechanism can be combined with the basic steps of the present invention described by way of example for the first two embodiments of the invention.

Any reconfiguration of a UE or a subnetwork small cell base station that adds, removes, or significantly reconfigures a signaling or data link will subsequently cause a small cell reconfiguration message to be broadcast containing the updated GLogCh-ID, priority, QoS, and/or routing information so that all small cell base stations are ready to serve this UE after autonomous cell switching. If the efficient broadcast mechanism according to the third embodiment of the invention is not used, any such reconfiguration of the UE or the small cell base station results in the need to individually reconfigure all involved small cell base stations.

The fourth embodiment of the invention is based on the architecture shown in FIG. 8, similar to the architecture of FIG. 3, except that the small cell base station SC3.2 is directly connected to the DgNB station. The SC3.2 station can be optimized for low latency, limited bandwidth communications.

The UE may be running multiple applications assuming a QoS that does not require low communication latency. In addition, the UE has one application that occasionally generates data packets requiring low latency transmission (ULL data), which typically generates a limited amount of downlink traffic, such as one network layer acknowledgment.

In FIG. 9 shows the sequence of messages according to this embodiment of the invention. It is assumed that the UE is connected to the small cell base station SC3.1 and has an RRC connection with the DgNB station similar to the first embodiment of the invention. The UE is set to at least one SC3.2 suitable for ULL data transmission. This cell is not considered when setting up autonomous cell switching, as in other embodiments of the invention, but is considered when autonomously selecting a cell for transmitting ULL data. The small cell base station SC3.2 is configured as a suitable cell, but this setting may be limited to support only ULL data radio bearers, for example, with one GLogCh-ID, and UE radio bearers without signaling.

At some point, the ULL data is generated by the corresponding application, the UE selects a suitable SC3.2 cell to transmit it, and requests resources for uplink transmission, while the uplink and downlink transmission through the SC3.1 small cell base station continues for other applications, i.e. other radio channels, or for RRC layer signaling. After receiving the grant, the UE transmits ULL data in the uplink, which is forwarded according to the small cell configuration to the DgNB. The resulting downlink data is processed similarly: routed and received from SC3.2 at the UE. Further, the UE may inform the DgNB to transmit data to the newly selected small cell base station SC3.2, and the DgNB may reconfigure the small cell base station and confirm the new route. These steps are described here as optional and shown in FIG. 9 with dashed lines, since for a single data transmission any involvement of the DgNB station other than data routing can be excluded.

Specific aspects of the invention can be summarized as follows.

The base station manages a radio access subnetwork comprising at least one UE and multiple cascaded small cell base stations, where at least one UE and multiple cascaded small cell base stations have an RRC connection with the base station.

Several cascaded small cell base stations comprise:

- multiple base stations of small cells, each of which has a wireless transport channel with another base station of a small cell;

at least one small cell base station having a wireless transport channel with the base station;

- several base stations of small cells, each of which has a wireless access channel to other base stations of small cells; And

at least one small cell base station having a wireless access channel to at least one UE.

The base station sets up the UE using the suitable small cell information, comprising identification information of at least one suitable small cell within the coverage area of one of the plurality of cascaded small cell base stations for autonomous cell switching, and at least one condition for performing autonomous switching hundred

The base station configures at least one small cell base station as suitable for establishing a wireless access channel to at least one UE after autonomous switching by the UE, wherein setting the suitable small cell base station includes setting:

- identification of the UE used by the UE when accessing a suitable small cell;

- one or more transmission channel identifiers identifying one or more transmission channels of the UE; And

- forwarding processing information of the identifiers of one or more transmission channels, wherein the forwarding processing information comprises quality of service parameters and/or priority information and/or routing information for forwarding to or from the UE the data packets received by the appropriate base small cell station.

The base station receives information about the cell switch performed by the UE autonomously (the execution of the cell switch is not initiated by the station).

The base station is capable, upon receiving the information of cell switching performed by the UE autonomously, setting up the UE by indicating the updated information of the suitable small cell, and also confirming, after receiving the information of the cell switching performed by the UE autonomously, the route switching in the small cell base stations, involved in routing data to or from the UE.

The base station manages a radio access subnetwork comprising at least one UE and several cascaded small cell base stations, where at least one UE and several cascaded small cell base stations have an RRC connection with the base station, and several cascaded base stations small cells include:

- several small cell base stations having a wireless transport channel with another small cell base station;

at least one small cell base station having a wireless transport channel with the base station;

- several small cell base stations having a wireless access channel to other small cell base stations; And

at least one small cell base station having a wireless access channel to at least one UE.

The base station sets up the UE using the suitable small cell information, comprising identification information of at least one suitable small cell within the coverage area of one of the plurality of cascaded small cell base stations for autonomous cell switching, and at least one condition for performing autonomous switching hundred

The base station configures at least one small cell base station to route data of one or one of the plurality of UEs, the configuration including:

- one or more transmission channel identifiers identifying one or more transmission channels of the UE;

- Forward processing information for each of one or more bearer identifiers, wherein the forward processing information comprises quality of service parameters and/or priority information and/or routing information for routing downlink data packets received over the wireless transport. channel to the UE, and the routing information comprises at least one first path for routing downlink data packets to the UE and at least one alternate path for routing downlink data packets to the UE after autonomous cell switching by the UE.

The base station confirms the route switching to the small cell base station in response to receiving information on one of the alternative paths in cell switching performed by the UE autonomously.

The acknowledgment by the base station of the route switch to the base station of a small cell contains a request to stop duplicating the transmission of data packets along the first route.

Setting up at least one small cell base station for routing data of one of the UEs includes reporting the same configuration information to all small cell base stations having an access channel to the base station, for setting up the small cell base stations, and for forwarding the configuration information by the small cell base stations cells to other small cell base stations, and configuration information integrity protection is provided, which allows the small cell base stations to check the integrity of the configuration data.

The UE device for performing autonomous cell switching has a wireless access channel to the first small cell base station, an RRC connection with the macro cell base station controlling the first small cell base station and the UE, receives from the macro cell base station UE device identification information and suitable small cell information , containing identification information of at least one suitable small cell and at least one condition for performing autonomous cell switching.

Based on the measurement results of signal characteristics received from the candidate small cell and at least one condition for performing autonomous cell switching, the UE autonomously decides to switch to the candidate small cell and requests uplink resources for data transmission from the candidate small cell using the identification UE device information.

The UE autonomously decides to switch cells without receiving a message triggering a switch to a suitable small cell and without informing the first base station of the small cell of the cell switch. The UE performs cell switching while data transmission to and/or from the first base station of the small cell is ongoing.

The UE may be configured such that, after successfully performing a cell switch, it informs the base station of the cell switch in an RRC message sent via the switched small cell, wherein the cell switch is considered successful after receiving from the switched small cell a permission to granting an uplink resource or a downlink data packet.

After receiving from the base station information about the measurement results of the characteristics of the neighboring cell containing the identification information of at least one cell not controlled by the base station, and when measuring (in parallel, but in fact never simultaneously) the characteristics of the received signals of suitable small cells based on the identification information at least one suitable small cell to decide whether to perform autonomous cell switching, the UE may perform neighbor cell measurements according to the neighbor cell measurement information.

The UE may report the neighbor cell measurements to the base station of the macro cell according to the neighbor cell measurement information regardless of autonomous cell switching.

A small cell base station controlled by a base station having a wireless transport channel with another small cell base station controlled by the base station receives from the macro cell base station a UE device identification information comprising:

- a UE device identifier identifying a UE device that is not currently served by a small cell base station;

- one or more radio bearer identifiers uniquely identifying (within the subnet controlled by the base station) one or more radio bearers of the identified UE; And

forwarding processing information associated with identifiers of one or more radio bearers, wherein the forwarding processing information contains quality of service information and/or priority information and/or routing information.

Small cell base station:

- receives from the UE an uplink resource request containing a UE device identifier;

- identifies the UE device based on the respective UE device identifiers received from the UE device and from the base station of the macro cell;

- provides uplink resources to the identified UE without additional communication with the macro cell base station with respect to this UE; And

- receives an uplink data packet over a radio channel from a UE, determines a radio bearer identifier uniquely identifying a radio bearer of a UE, and forwards this data packet along with the determined radio bearer identifier to another small cell base station over a wireless transport channel according to the forwarding processing information .

A small cell base station controlled by a base station having a wireless transport channel (with another base station) and having wireless access channels to at least two additional small cell base stations controlled by the base station receives from the base station:

- one or more bearer identifiers, each of which identifies one or more bearers of a particular UE,

forwarding processing information associated with one or more identified transmission channels, wherein the forwarding processing information comprises quality of service information and/or priority information and/or routing information for routing downlink data packets received over the wireless transport channel to a specific UE, and the routing information comprises at least first and second paths for routing downlink data packets to a specific UE.

The small cell base station, when transmitting all downlink data packets identified by the channel ID, whose route to a specific UE is to follow the first route contained in the routing information, in response to receiving at least one uplink data packet from a specific UE on the second route (access channel) contained in the routing information, starts transmitting all downlink data packets identified by the channel ID to be directed to the specific UE on the second route.

The small cell base station may be arranged such that the start of transmission of all downlink data packets identified by the channel identifier to be directed to a particular UE via the second route includes transmission of copies of all downlink data packets identified by the channel identifier, which are should be directed to a specific UE, also on the first route contained in the routing information.

The small cell base station stops transmitting copies of all downlink data packets identified by the channel ID to be directed to a specific UE via the first route contained in the routing information after receiving an acknowledgment message from the macro cell base station over the handover-acknowledge wireless transport channel route.

Claims (24)

1. A mobile communication system with a subnet comprising a macro cell base station and a plurality of small cell base stations having wireless communication with the macro cell base station, wherein each small cell base station is either directly connected to the macro cell base station or connected to the macro cell base station via one or more other small cell base stations, and the macro cell base station is configured to: - setting a user equipment (UE) having a Radio Resource Control (RRC) connection with a macro cell base station using information about suitable small cell base stations to enable the UE to autonomously switch between small cell base stations, and - settings of small cell base stations using small cell base station configuration information comprising a UE device identifier identifying a UE configured by a macro cell base station using suitable small cell base station information related to small cell base stations, and one or more radio bearer identifiers uniquely identifying one or more radio bearers of the UE, wherein the small cell base station configuration information allows the small cell base stations to receive data from the UE over a radio bearer, determine a radio bearer identifier uniquely identifying a radio bearer, and forward the data along with the determined radio bearer identifier . 2. The system of claim 1, wherein the information about the suitable small cell base station comprises information selected from a list containing small cell base station identifiers, small cell base station frequency resources, small cell base station radio parameters, small cell base station access mode, cells and switching criteria of the small cell base station. 3. The system according to claim 1 or 2, wherein the configuration information of the small cell base station comprises information selected from a list containing medium access control (MAC) configuration elements, physical layer configuration elements, a global logical channel identifier transmitted for macro cell base station along with data received from the UE and routing information for transporting uplink information from the UE and/or downlink to the UE. 4. The system according to any one of the preceding claims, wherein the coverage of the base stations of the small cells is less than the coverage of the base station of the macro cell. 5. The system of claim 4, wherein the small cell base stations form a small cell network with some small cell base stations having a direct connection to the first base station and other small cell base stations having an indirect connection to the first base station through one or several small cell base stations. 6. The system according to claim 5, wherein each small cell base station is configured to multiplex data received from different radio channels into one transmission channel directed to the macro cell base station, wherein the multiplexing depends on the QoS setting of the received data radio channel, and the pointer of the source radio channel is added to the transmitted data packets. 7. The system as claimed in any one of the preceding claims, wherein the macro cell base station is configured to communicate a UE's device identifier to those of the small cell base stations that may participate in routing transmission of data packets from the UE to the macro cell base station, and the identifier is used by the UE. to request radio resources from base stations of small cells. 8. The system according to any one of the preceding claims, wherein the macro cell base station is configured to report to the small cell base stations information about all radio channels and devices served by the subnet, indicating radio priorities and quality of service settings. 9. The system according to any one of the preceding claims, wherein the configuration information of the small cell base station comprises routing information for routing downlink packets received on the wireless transport channel to the UE, the routing information comprising at least one first path for routing downlink data packets to the UE; and at least one alternate path for routing downlink data packets to the UE after autonomous cell switching by the UE. 10. The system of claim. 9, wherein the macro cell base station is configured to confirm a route switch from the first small cell base station to the second small cell base station in response to receiving cell switching information performed by the UE on one of at least two alternative routes. 11. The system of claim 9 or 10, wherein the small cell base station configuration information is used to report the same configuration information to all small cell base stations having a direct connection with the macro cell base station, to configure the small cell base stations, and to be forwarded by the base stations small cell base stations of this configuration information to other small cell base stations, while protecting the integrity of the configuration information, which allows the small cell base stations to check the integrity of the configuration data. 12. A user equipment (UE) configured to autonomously switch cells in a subnet of a mobile communication system comprising a macro cell base station and a plurality of small cell base stations that the UE can switch between, wherein the UE is configured to receive a macro cell from the base station with which it has a radio resource control connection, UE device identification information, and suitable cell information containing identification information and at least one autonomous switching initiation condition between the first small cell base station and the second small cell base station, and in addition, the UE is capable of requesting uplink resources from the candidate cell for data transmission using the identification information of the UE device, and transmitting uplink data over the air using the uplink resources received from the candidate cell, wherein using the UE identification information allows the candidate cell to determine the identifier radio bearer uniquely identifying the radio bearer, and forward the data packet along with the determined radio bearer identifier to another small cell base station over the wireless transport channel. 13. A small cell base station controlled by a macro cell base station, configured to receive user equipment (UE) information from the macro cell base station, comprising: - a UE device identifier identifying a UE device currently not served by a small cell base station; - one or more radio bearer identifiers uniquely identifying one or more radio bearers of the identified UE; - forwarding processing information associated with the identifiers of one or more radio channels and containing quality of service information and/or priority information and/or routing information, wherein the base station of a small cell is configured to: - receiving from the UE an uplink resource request containing the identifier of the UE; - identifying the UE device based on the UE device identifier received from the UE device and from the macro cell base station; - granting uplink resources to the identified UE without further communication with the macro cell base station with respect to that UE; And - receiving an uplink data packet over a radio channel from a UE, determining a radio bearer identifier uniquely identifying a radio channel of the UE, and forwarding this data packet along with the determined radio bearer identifier to another small cell base station over a wireless transport channel according to forwarding processing information . 14. A method for managing a mobile communication network comprising at least one macro cell base station and a plurality of small cell base stations wirelessly connected to the macro cell base station, including allowing a UE to establish a connection with the macro cell base station via a first of the small cell base stations. cells to autonomously switch the connection so that it passes through the second of the small cell base stations by assigning a local unique identifier to the connection and reporting this local unique identifier to a plurality of small cell base stations over a wireless transport channel, the UE transmitting the local unique identifier of the second of small cell base stations during autonomous handover, and the local unique identifier is unique to the macro cell base station and to the plurality of small cell base stations and identifies the data flow of the UE on the wireless transport channel.

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