Patent Description:
<FIG> is a schematic representation of an example of a network infrastructure, such as a wireless communication network or wireless communication system, including a plurality of base stations eNB<NUM> to eNB<NUM>, each serving a specific area surrounding the base station schematically represented by the respective cells <NUM><NUM> to <NUM><NUM>. The base stations are provided to serve users within a cell. A user may be a stationary device or a mobile device. Further, the wireless communication system may be accessed by loT devices which connect to a base station or to a user. IoT devices may include physical devices, vehicles, buildings and other items having embedded therein electronics, software, sensors, actuators, or the like as well as network connectivity that enable these devices to collect and exchange data across an existing network infrastructure. <FIG> shows an exemplary view of only five cells, however, the wireless communication system may include more such cells. <FIG> shows two users UE1 and UE2, also referred to as user equipment (UE), that are in cell <NUM><NUM> and that are served by base station eNB<NUM>. Another user UE<NUM> is shown in cell <NUM><NUM> which is served by base station eNB<NUM>. The arrows <NUM><NUM>, <NUM><NUM> and <NUM><NUM> schematically represent uplink/downlink connections for transmitting data from a user UE<NUM>, UE<NUM> and UE<NUM> to the base stations eNB<NUM>, eNB<NUM> or for transmitting data from the base stations eNB<NUM>, eNB<NUM> to the users UE<NUM>, UE<NUM>, UE<NUM>. Further, <FIG> shows two loT devices <NUM><NUM> and <NUM><NUM> in cell <NUM><NUM>, which may be stationary or mobile devices. The loT device <NUM><NUM> accesses the wireless communication system via the base station eNB<NUM> to receive and transmit data as schematically represented by arrow <NUM><NUM>. The IoT device <NUM><NUM> accesses the wireless communication system via the user UE<NUM> as is schematically represented by arrow <NUM><NUM>.

The wireless communication system may be any single-tone or multicarrier system based on frequency-division multiplexing, like the orthogonal frequency-division multiplexing (OFDM) system, the orthogonal frequency-division multiple access (OFDMA) system defined by the LTE standard, or any other IFFT-based signal with or without CP, e.g. DFT-s-OFDM. Other waveforms, like non-orthogonal waveforms for multiple access, e.g. filterbank multicarrier (FBMC), generalized frequency division multiplexing (GFDM) or universal filtered multi carrier (UFMC), may be used.

For data transmission a physical resource grid may be uses, as defined, e.g., by the LTE standard. The physical resource grid may comprise a set of resource elements to which various physical channels and physical signals are mapped. For example, in accordance with the LTE standard, the physical channels may include the physical downlink shared channel (PDSCH) carrying user specific data, also referred to as downlink payload data, the physical broadcast channel (PBCH) carrying for example the master information block, the physical downlink control channel (PDCCH) carrying for example the downlink control information (DCI), etc. The physical signals may comprise reference signals (RS), synchronization signals and the like. The LTE resource grid comprises a <NUM> milliseconds frame in the time domain having a given bandwidth in the frequency domain. The frame has <NUM> subframes of <NUM> millisecond length, and each subframe includes two slots of <NUM> or <NUM> OFDM symbols depending on the cyclic prefix (CP) length. The PDCCH may be defined by a pre-defined number of OFDM symbols per slot. For example, the resource elements of the first three symbols may be mapped to the PDCCH, i.e., the size of the PDCCH is limited. Consequently, the number of also limits how many DCIs is limited that may be carried in one subframe. This may, in turn, limit the number of UEs which may receive an allocation for the subframe when using dynamic scheduling.

<FIG> shows an example of a LTE OFDMA-based subframe with two antenna ports for different selected Tx antenna ports. The subframe includes two resource blocks (RB) each made up of one slot of the subframe and <NUM> subcarriers in the frequency domain. The subcarriers in the frequency domain are shown as subcarrier <NUM> to subcarrier <NUM>, and in the time domain, each slot includes <NUM> OFDM symbols, e.g. in the slot <NUM> OFDM symbols <NUM> to <NUM> and in slot <NUM> OFDM symbols <NUM> to <NUM>. A resource element is made up of one symbol in the time domain and one subcarrier in the frequency domain. The white boxes <NUM> represent resource elements allocated to the PDSCH carrying the payload or user data, also referred to a payload region. The resource elements for the physical control channels (carrying non-payload or non-user data), also referred to the control region, are represented by the hatched boxes <NUM>. In accordance with examples, resource elements <NUM> may be allocated to the PDCCH, to the physical control format indicator channel (PCFICH), and to the physical hybrid ARQ indicator channel (PHICH). The cross-hatched boxes <NUM> represent resource elements which are allocated to the RS that may be used for the channel estimation. The black boxes <NUM> represent unused resources in the current antenna port that may correspond to RSs in another antenna port.

The resource elements <NUM>, <NUM>, <NUM> allocated to the physical control channels and to the physical reference signals are not evenly distributed over time. More specifically, in slot <NUM> of the subframe the resource elements associated with the symbol <NUM> and the symbol <NUM> are allocated to the physical control channels or to the physical reference signals, no resource elements in the symbols <NUM> and <NUM> are allocated to payload data. The resource elements associated with symbol <NUM> in slot <NUM> as well as the resource elements associated with symbols <NUM> and <NUM> in slot <NUM> of the subframe are allocated in part to the physical control channels or to the physical reference signals. The white resource elements shown in <FIG> may carry symbols associated with payload data or user data and in the slot <NUM> for symbols <NUM>, <NUM>, <NUM> and <NUM>, all resource elements <NUM> may be allocated to payload data, while less resource elements <NUM> are allocated to payload data in symbol <NUM> of slot <NUM>, and no resource element is allocated to payload data in symbols <NUM> and <NUM>. In slot <NUM> the resource elements associated with symbols <NUM>, <NUM>, <NUM>, <NUM> and <NUM> are all allocated to payload data, while for symbols <NUM> and <NUM> less resource elements are allocated to payload data.

The duration of the subframe is <NUM> millisecond, and in accordance with the LTE standard, the TTI is <NUM> millisecond. When transmitting data using the resource grid structure shown in <FIG>, the receiver, for example the mobile terminal or mobile user, receives the resource elements depicted in <FIG> in <NUM> millisecond. The information contained or defined by the resource elements may be processed, and for each transmission, i.e., for each TTI having the <NUM> millisecond length, a constant number of payload data is received. The transmission scheme leads to an end-to-end latency of more than <NUM> millisecond, as the receiver first receives a transmission having a duration of <NUM> millisecond and then, once the transmission is completed, processes the control information to see whether some data has been sent to the receiver, and in case it is true, the receiver decodes the data channel of a length of <NUM> millisecond. Thus, the duration of the transmission and the processing time add up to a period exceeding <NUM> millisecond.

As explained above, the PDCCH is defined by a pre-defined number of OFDM symbols, i.e., there the size the PDCCH is limited which, consequently, also limits how many DCIs may be carried in one subframe having a length of <NUM> millisecond. This may, in turn, limit the number of UEs which may receive an allocation for the subframe when using dynamic scheduling. To support more allocations, without increasing the size of the PDCCH, semi-persistent scheduling (SPS) may be used. When using SPS, the UE is pre-configured by the transmitter or base station with a SPS C-RNTI (radio network temporary identifier), also be referred to as an allocation ID, and a periodicity. Once pre-configured, the UE may receive a further message defining an allocation for a downlink and/or uplink transmission of data on the basis of the associated SPS C-RNTI. This allocation will repeat according to the pre-configured periodicity (SPS interval). In other words, once allocated, the resources may be repeatedly used for receiving/transmitting data by the UE without the need to perform scheduling in each subframe. In case the radio link conditions change, the base station may provide to the UE a resource allocation message for re-allocating resources.

The SPS scheme is described, for example, in references [<NUM>] and [<NUM>]. SPS is a combination of persistent and dynamic scheduling. The persistent scheduling is used for the allocation of periodic resources intended for a transmission of transport blocks, and the dynamic scheduling is used for potentially needed incremental redundancy, i.e. hybrid automatic repeat request (HARQ) retransmissions. SPS allows for the reduction of control information overhead that originates, for example, from signaling the downlink (DL) and uplink (UL) resource allocation patterns at times where a connection needs to transfer data. SPS may be used both for the DL and UL of both FDD (frequency division duplexing) and TDD (time division duplexing). Reference [<NUM>] describes the initial configuration and the following activation/release of SPS. The base station may configure the UE to perform SPS at any time. Typically, this is done at the time of the dedicated bearer establishment for the service by RRC (radio resource control). The SPS may be configured/re-configured by RRC at any time using a configuration message that is also referred to as "SPS-Config". The SPS-Config message may include the SPS C-RNTI as well as configuration information for the downlink and for the uplink. The configuration message does not allow a UE to start the SPS, rather, the base station serving the UE has to explicitly activate SPS so as to allow the UE to use SPS grants/assignments.

Once the UE has received the SPS-Config message including the SPS C-RNTI associated with the UE, the UE may be configured by higher layers to decode the PDCCH with CRC (cyclic redundancy check) scrambled by the SPS C-RNTI in every subframe, as the eNB may activate/release SPS at any time using a DCI message. A SPS activation/release message is validated by the UE as is explained in detail in reference [<NUM>].

After a valid activation, the UE decodes the PDCCH for CRC scrambled by the SPS C-RNTI to check for SPS-validated DCI control information in every SPS subframe, i.e., in every subframe as defined by the SPS interval, the UE looks for information regarding possible changes, e.g. changes in the assigned resources, in the transmission mode, the MCS (modulation and coding scheme) or the like. The assignment of the resource blocks within the subframe is subject to the choice of the base station, and in case the UE does not receive any SPS-validated DCI, the resource block assignment and the other transmission parameters, like transmission mode and MCS, remain as currently configured, thereby avoiding a control signaling overhead.

SPS is used for services with periodic resource demands, and different applications may require different arrival times of transport blocks which may be configured by the SPS interval parameters. For example, Voice over IP (VoIP) is an application where data arrives in periodic bursts of <NUM> milliseconds. Beyond that, as mentioned above, there are mission-critical and latency-constrained communications services; for example, URLLC (ultra reliable low latency communication) services, such as in machine-type communication and in vehicular communication, which require pre-configured resources in shorter periods of time; for example, in periods of below <NUM> milliseconds down to the micro-second level and below. Applying SPS to such applications or services leads to the least possible signaling overhead when compared to frequent dynamic configuration updates, and embodiments of the present invention address SPS for such latency-constrained applications.

Further, for the aforementioned latency-constrained applications, but also for conventional applications, respective services and higher OSI layers, such as on the Application Layer, as well as rate-controlled protocols on the Network Layer (for example, TCP), may gain performance in terms of network throughput, adaption latency or RTT (round trip time) reduction if SPS may be directly influenced and/or adapted by the application, service or protocol.

<FIG> shows an example of a conventional SPS configuration provided by RRC (see reference [<NUM>]). The configuration parameters "semi-persistentschedintervalDL" and "semi-persistentschedintervalUL" are based on a <NUM>-bit field indicating an enumeration of <NUM> different modes for the SPS intervals, also referred to as SPS periods. From the <NUM> configurable modes, there is a selection of <NUM> predefined periods which are labeled sfN for a scheduling period of N subframes, with N ≥ <NUM>. Further, <NUM> dynamically adjustable periods labeled spareX are provided. The base station provides the user equipment with an additional SPS-Config mode, using, for example, an RRC connection set up message, an RRC connection reconfiguration message or an RRC connection re-establishment message, as is outlined in reference [<NUM>]. The general dependency of the intervals or periods on the basis of multiples of a subframe, as defined in reference [<NUM>], i.e., the dependency on several milliseconds, is also valid for the spareX configurations; however, when using the spareX configuration, the SPS period may be lowered down to a minimum of <NUM> subframe (<NUM> millisecond).

Thus, SPS may be used to reduce the control overhead for periodic transmissions. SPS may be for use cases such as voice over LTE, however, SPS is applicable to many more use cases which go together with different requirements as they may be encountered, e.g., in V2X (vehicle to everything) or V2V (vehicle to vehicle) scenarios. Such specific use cases may require more complex SPS configurations, including nested SPS configurations. For example, V2V and V2X scenarios involve a high speed movement of the use equipment so that cell handovers may happen quite frequently. Currently, all SPS configurations are lost on handover, i.e., when a user equipment moves from one cell to another cell of the wireless communication network so as to be no longer served by the currently responsible source base station but by a new target base station which is also referred to as a handover, the SPS configuration currently implemented in the UE is no longer maintained. This requires that the SPS configuration in the UE has to be reconfigured with the new or target base station.

In certain scenarios, such as the above mentioned V2X or V2V scenarios, the user equipment may be configured with more than one SPS configuration. For example, up to eight SPS configurations may be implemented in a user equipment in a V2X or a V2V scenario. Independent of the loss of the SPS configurations at handover, when configuring the user equipment in a scenario with multiple SPS configurations, additional control messages are needed, such as the above mentioned DCI messages. For each of the SPS configurations one DCI message is needed to activate the respective SPS configuration and another DCI message is needed to initially allocate resources for the SPS configuration or to re-allocate resources for the respective SPS configuration in case the channel quality changes. Thus, the increase in the number of SPS configurations with which a user equipment may be configured goes together with a corresponding increase in the number of control messages.

<CIT> describes a method and an apparatus for performing a handover in an evolved universal terrestrial radio access network, E-UTRAN. A wireless transmit/receive unit, WTRU, sends a measurement report to a source evolved Node B, eNB, and receives a handover command from the source eNB. The WTRU initiates reception and processing of a primary broadcast channel, P-BCH, at the target cell after receiving the handover command. The WTRU then sends a random access preamble to the target eNB, receives a random access response from the target eNB, and sends a handover complete message to the target eNB. The reception and processing of the P-BCH may be initiated immediately after receiving the handover command or after sending the handover complete message. The WTRU may apply default configuration or source cell configuration in the target cell until a target cell SFN and/or P-BCH information are acquired.

<CIT> describes a method for establishing multiple radio connections by a user equipment, UE. The method includes receiving a first physical downlink control channel, PDCCH, that includes a first cyclic redundancy check, CRC, scrambled by a first cell radio network temporary identifier, C-RNTI, in a primary radio connection. The method also includes decoding the first PDCCH. The method also includes receiving a second PDCCH that includes a second CRC scrambled by a second C-RNTI in a secondary radio connection. The method also includes decoding the second PDCCH.

<CIT> describes a learning-based determination of semi-persistent scheduling of a data-packet flow wireless communication. A packetized data flow served to a wireless terminal is fully scheduled for an initial period of time in order to collect statistics associated with scheduled packet sizes, S, and inter-packet times, T. An analysis of a cumulative distribution of {S, T} pairs indicates whether a characteristic packet size and size dispersion are associated with the cumulative distribution. Inter-time intervals associated with the characteristic size and dispersion complete a transport format. The semi-persistent scheduling is utilized for the packetized flow when a characteristic transport format can be extracted or learned from the accumulated statistics. The extracted transport formats can be employed to optimize scheduling efficiency upon a handover.

In accordance with a first aspect, it is an object of the present invention to provide an approach avoiding SPS reconfigurations within a UE after a handover and allowing for a continuous SPS even in case of a handover.

The dependent claims specify the preferred embodiments of the invention.

In the following, embodiments of the invention are described with particular reference to <FIG> and <FIG>. The other embodiments and examples of the disclosure are provided for illustrative purposes to support a better understanding of the invention.

Embodiments of the present invention are now described in further detail with reference to the accompanying drawings, in which:.

In the following, preferred embodiments of the present invention are described in further detail with reference to the enclosed drawings in which elements having the same or similar function are referenced by the same reference signs.

Embodiments of a first aspect covered by the claimed invention will now be described. In accordance with the first aspect, the present invention provides for continuous or non-interrupted SPS of the user equipment after a handover.

<FIG> shows a part of a wireless communication network similar to the one described above with reference to <FIG>. Three cells <NUM><NUM> to <NUM><NUM> are shown. Each cell <NUM><NUM> to <NUM><NUM> includes a base station eNB<NUM> to eNB<NUM>. The core network <NUM> of the wireless communication network is schematically represented which includes the mobile management entity (MME) <NUM>. The base stations eNB<NUM> to eNB<NUM> are connected to the core network <NUM> via the S1 interface. Further, the base stations eNB<NUM> to eNB<NUM> are directly connected with each other via the X2 interface. The UE is a mobile terminal provided in an automobile. In other embodiments, the UE may by any kind of vehicular device. The UE includes an antenna ANTUE to receive/transmit a radio signal <NUM>. Each of the base stations eNB<NUM> to eNB<NUM> includes a respective antenna ANTeNB1 to ANTeNB3 to receive/transmit the radio signal <NUM>. The UE is initially located in the cell <NUM><NUM>, also referred to as the source cell. The base station eNB<NUM> associated with the source cell <NUM><NUM> serves the UE, i.e., the UE is connected to the wireless communication network via the base station eNB<NUM> to receive/transmit data in a downlink/uplink connection. The UE may be within an automobile or may be part of the automobile. The UE is assumed to travel at a high speed and as the UE travels it will eventually leave the source cell <NUM><NUM>. In accordance with its moving trajectory <NUM>, the UE will reach the cell <NUM><NUM>, also referred to as the target cell. When moving from the source cell <NUM><NUM> to the target cell <NUM><NUM>, a handover will be performed so that the UE will be served by the target base station eNB<NUM> of the target cell <NUM><NUM> following the handover. As the UE keeps on moving in accordance with the moving trajectory <NUM>, it will eventually leave the cell <NUM><NUM> which is now the source cell and enter into the new target cell <NUM><NUM> so that another handover occurs and the UE, following the handover, will be served by the base station eNB<NUM>. An example of a handover procedure and the respective messages exchanged between the UE, the source base station, the target base station and the MME <NUM> as well as the serving gateway is described in reference [<NUM>]. The handover may be triggered by the core network, e.g. the MME <NUM>, or it may be triggered by the UE.

The UE is configured with SPS. Currently SPS is cell-based, i.e., the UE will be configured by the base station eNB<NUM> with SPS. The base station eNB<NUM> issues one or more control messages, such as DCI messages to activate SPS and to allocate resources in accordance with the SPS configuration. SPS will be carried out as long as the UE is within the cell <NUM><NUM>. After the handover and once the UE reached the target cell <NUM><NUM> to be served by the base station eNB<NUM>, the UE is newly configured with SPS in the target cell <NUM><NUM>. Also a new identifier for SPS control signaling, like the SPS C-RNTI in a LTE system, may be issued by the target base station eNB<NUM>. RNTI in general is an identifier for SPS control signaling which may be named differently in other environments. For example, in a V2X environment a new RNTI may be provided for up to eight SPS configurations.

In accordance with the present invention, newly configuring the UE with SPS following a handover is avoided. The UE, when moving from the source cell <NUM><NUM> to the target cell <NUM><NUM>, e.g., when performing a handover, maintains the SPS. In accordance with embodiments, it is only necessary to re-activate the SPS by an activation signal from the target base station eNB<NUM> without the need to provide a complete and new configuration of the UE by the target base station. In accordance with embodiments also a new identifier for SPS control signaling, like the SPS C-RNTI, is issued.

In accordance with further embodiments of the present invention, to maintain SPS the SPS configuration that was used, for example by the source base station eNB<NUM> to configure the UE with SPS, is forwarded to the target base station eNB<NUM> upon the handover. For example, the X2 interface may be used to pass the SPS configuration from the source base station eNB<NUM> to the target base station eNB<NUM>. In other embodiments, the SPS configuration may be passed from the source base station eNB<NUM> to the target base station eNB<NUM> via the core network using the S1 interfaces of the respective base stations. In yet other embodiments, the UE may directly transmit the SPS configurations during the handover procedure to the target eNB<NUM>. No new configuration or reconfiguration of the SPS is needed following the handover of the UE from the source cell <NUM><NUM> to the target cell <NUM><NUM>, which is then the new source cell. The UE maintains the SPS configuration and the target base station eNB<NUM> receives the SPS configuration implemented in the UE and continues with the SPS on the basis of the received SPS configuration. In accordance with embodiments, an activation signal may be sent out by the target base station eNB<NUM> to indicate to the UE that SPS is continued.

In accordance with other embodiments, the activation may occur responsive to a resource assignment for SPS by the target base station.

In accordance with embodiments, in addition to passing the SPS configuration to the target base station eNB<NUM>, the target base station may update the SPS C-RNTI and inform the UE accordingly, for example in a situation in which the SPS C-RNTI has been used in the source cell <NUM><NUM> is occupied, blocked or otherwise used in the target cell <NUM><NUM>.

In <FIG>, the UE is either within the automobile or is part of the automobile. In accordance with other embodiments, the UE may be another kind of mobile terminal, for example a handheld device or a sensor operating in accordance with the NB-IOT standard. The sensor may be part of the automobile or it may be part of another moving entity such as a high speed train. The user of the UE may be a passenger within the vehicle travelling on a highway or the user may be a passenger in a high speed train or an airplane. In such scenarios, the UE will experience frequent handovers and, in accordance with the inventive approach, any reconfiguration of the SPS is avoided, as the UE maintains the one or more current SPS configurations, which are transferred by the source base station to the target base station via the X2 interface or via the S1 interface. In accordance with embodiments, the SN status transfer message may be used to transfer the SPS configuration(s). An example of a data structure including the SPS configuration has been described above with reference to <FIG>.

<FIG> shows that a base station is provided for one cell. However, a base station may also be provided for a plurality of cells as is schematically shown in <FIG> shows a scenario similar to the one in <FIG> except that base station eNB<NUM> is provided for a plurality of cells, namely cells <NUM><NUM>, <NUM><NUM> and <NUM><NUM>. A UE within one of cells <NUM><NUM>, <NUM><NUM> and <NUM><NUM> will connect to the network via base station eNB<NUM>. When the UE moves, e.g., from the cell <NUM><NUM> to the cell <NUM><NUM> a handover will take place. Also in such a scenario, SPS needs to be newly configured when a handover occurs, despite the fact that the base station does not change. Newly configuring the UE with SPS following the handover is avoided. The UE, when moving from the source cell <NUM><NUM> to the target cell <NUM><NUM>, i.e., when performing a handover, maintains the SPS. Since the base station eNB<NUM> is aware of the SPS configuration, no transfer of the SPS configuration occurs in this scenario. In this embodiment only a new identifier for SPS control signaling, like the SPS C-RNTI, is issued following the handover.

In accordance with further embodiments, transferring the SPS configuration from the source cell or the source base station to the target cell or target base station further includes signaling the time of the next expected SPS packet to the target base station so as to allow the target base station to continue with the SPS with the correct timing. For example, the time to the next SPS interval may be signaled towards the target base station. In accordance with other embodiments, the period of the SPS interval which has already been used up so far is signaled to the target base station or the start of the next SPS interval is signaled as an absolute time, for example on the basis of the radio frame, the subframe number, the slot number or the TTI (Transmission Time Interval) number. In accordance with embodiments, the time of the next expected SPS packet is signaled to the target base station either by the user equipment or by the source base station. <FIG> is a schematic representation showing how the SPS synchronization is kept during handover in accordance with an embodiment. <FIG> illustrates a downlink situation in which a user equipment is initially served by a source base station and data <NUM> from higher layers in the network is to be transmitted to the user equipment. The user equipment is configured with SPS having a periodicity or SPS interval <NUM>. For example, when data <NUM><NUM> is received at the source base station, at a time t<NUM>, the data <NUM><NUM> is transmitted from the base station to the user equipment on the scheduled resources. At a later time, further data <NUM><NUM> may be received at the base station which is transmitted to the user equipment at t<NUM>. The time difference between t<NUM> and t<NUM> is the SPS interval <NUM>. <FIG> schematically represents the handover at <NUM>, and following the handover <NUM>, the user equipment is no longer served by the source base station but is now served by the target base station. The target base station receives information about the SPS configuration of the UE and about the time to the next expected SPS packet so that data <NUM><NUM> for the user equipment is transmitted by the target base station at the time t<NUM>. Further data <NUM><NUM> may be transmitted from the target base station to the user equipment at the time t<NUM>. The respective times t<NUM> to t<NUM> are separated by the SPS interval <NUM> which is defined in the SPS configuration of the user equipment. The SPS interval is kept also after the handover as the time to the next SPS transmission t<NUM> is signaled to the target base station either by the user equipment or by the source base station. This process is transparent for the higher layers of the system so that a continuous SPS even in case of a handover is enabled.

In accordance with further embodiments, the UE may inform the target base station about the SPS configuration and the SPS C-RNTI using an uplink control or data channel and the source base station may send an indication of the UE or a list of UEs to the target base station indicating if specific information will be included in the control or data channel. For example, when the X2 interface or the handover context transfer is not available, the UE informs the target eNB on their SPS configuration through the UL control or data channel. The UE may use RRC signaling to transmit its SPS configuration and/or the time to the next SPS occurrence to the target eNB after the handover with the request to continue the same SPS configuration. This request may be acknowledged by the target eNB by directly activating the SPS via DCI or via RRC signaling.

In accordance with further embodiments, when the handover occurs, in the handover region, a dual connectivity of the UE may be provided. The UE may be connected to the source and target base stations which may help leverage a reconfiguration duration for time critical applications. SPS configuration updates may be triggered by the target base station through the X2 interface, for example for signaling the new SPS C-RNTI to the UE, and the source base station may act as the transmitter of the update message. In other words, the dual connectivity mode, in which the UE maintains dual connectivity to the source and target base stations, allows handling a situation in which the SPS C-RNTI of the source cell cannot be used in the target cell, and the target base station may already generate an update of the SPS configuration indicating also the C-RNTI to be used. The update is then performed by the source base station by transmitting the updated SPS configuration to the UE being in the handover region.

As mentioned above, in accordance with embodiments, in a situation in which the target cell <NUM><NUM> in <FIG> does not allow using the same SPS C-RNTI as used by the source cell <NUM><NUM>, for example because the SPS C-RNTI is used for another UE in the target cell, either the source base station or the target base station may update the SPS C-RNTI for the UE, for example using RRC (radio resource control) signaling. This signaling may include a RRC connection reconfiguration message that is issued by the source base station eNB<NUM> to reconfigure the UE so that the SPS C-RNTI, upon the handover, is updated with the new SPS C-RNTI to be used in the target cell. In accordance with other embodiments, the SPS C-RNTI may be updated by the target base station, also by an RRC signaling, once the handover is completed.

In <FIG>, it has been assumed that all base stations are macro base stations of the wireless communication network. However, in accordance with other embodiments, the respective base stations may all be small cell base stations, such as femto base stations, being deployed within a macro cell of the wireless communication network. In accordance with other embodiments, the base stations may include macro cell base stations and small cell base stations.

In accordance with other embodiments, the inventive approach may also be applied to UEs which are not moving at a high speed, i.e., the inventive approach may also be applied to UEs which experience a handover less frequently than a fast moving UE. Thus, the inventive approach is not limited to fast travelling UEs.

In accordance with embodiments, the SPS C-RNTI for the UE may be updated using an RRC (radio resource control) signaling. This signaling may include a RRC connection reconfiguration message that is issued by the source base station to reconfigure the UE so that the SPS C-RNTI, upon the handover, is updated with the new SPS C-RNTI to be used in the target cell. In accordance with other embodiments, the SPS C-RNTI may be updated by the target base station, also by an RRC signaling, once the handover is completed. <FIG> shows an embodiment of a modified RRC message used to update the SPS C-RNTI in accordance with embodiments of the present invention. When compared to the SPS-configuration message depicted in <FIG>, the RRC message to update the SPS C-RNTI is extended to include the entry "newSemiPersistSchedC-RNTI" <NUM>, the entry "oldSemiPersistSchedC-RNTI" <NUM>, the entry "update NULL" <NUM> and the entry "update NULL" <NUM>. The RRC message as depicted in <FIG> may be used by the source base station which may request a SPS-C-RNTI to be used in the target cell from the target base station, for example via the X2 interface. Prior to the handover or reconnection of the UE to the target cell, the update message may be issued. The source base station generates the update message and includes into entry <NUM> the new SPS C-RNTI received from the target base station, while the currently used SPS C-RNTI of the source base station is still indicated at entry <NUM> so that, despite the receipt of the update, as the entries <NUM> and <NUM> are still indicated as "null", the UE continues to use the old or source SPS C-RNTI. Once the handover is completed, the target base station may update the configuration by changing the entry <NUM> and <NUM> so that it is indicated that now the new SPS C-RNTI for the target cell <NUM> is to be used. The SPS update message as indicated in <FIG> may be based on the SPS-Config RRC message as it is described in reference [<NUM>]. <FIG> shows at <NUM> schematically an embodiment in accordance with which the above described information about the time to the next SPS is included in the SPS configuration.

In accordance with other embodiments of the present invention, the UE which maintains its SPS configuration may be reactivated following a handover by the target base station. The initial SPS configuration may be modified to include a "Keep on Handover" flag which, when activated, causes the UE to wait for a certain time after the handover for a reactivation of SPS by the target base station and, in case no reactivation is received, the SPS is suspended. The reactivation may be a signal from the target base station which may include a new SPS C-RNTI. In case no new SPS C-RNTI is included, the currently used SPS C-RNTI is considered to be still valid and the UE keeps using this SPS C-RNTI. This may be done by a corresponding RRC signaling to change the SPS C-RNTI or directly by a DCS activation with the old RNTI or a new one, if assigned by the source eNB. When the SPS is not reactivated within this certain time, the UE releases its SPS configuration. <FIG> shows an embodiment of a modified SPS configuration message, more specifically a portion of the SPS configuration message for the downlink and for the uplink is shown including the additional entries <NUM> and <NUM> defining the Keep on Handover flag.

In the following, a second aspect that is not covered by the claimed invention, will be described in further detail. It is noted that the second aspect described in the following can be used in combination with the first aspect described above or it may be used independent of the first aspect. In accordance with the second aspect, the signaling of control messages is reduced by providing a single control message or DCI message to the user equipment which is configured with SPS for the activation of a resource allocation of one or more SPS configurations, or for activating a plurality of SPS configurations, or for addressing a group of SPS configurations by a single DCI message. Instead of using separate DCI messages for activating the SPS in the user equipment and for the resource allocation or for reconfiguring the resource allocation in case of changing channel properties, initially, when the SPS is to be started, the user equipment receives a single DCI message which causes SPS to be activated and which may also include the resource allocation information. The second aspect may also be used together with the above described first aspect providing for a continuous SPS in case of a handover.

In the following, examples of the second aspect will be described in further detail. <FIG> shows a schematic representation of a SPS DCI message <NUM> including a number of fields for controlling the UE being configured with SPS using a single SPS configuration. In the example of <FIG>, the DCI message <NUM> includes information about the modulation and coding scheme <NUM><NUM>, information about the resources <NUM><NUM> to be allocated for the respective SPS configuration for which the DCI message is provided, and information <NUM><NUM> which causes the SPS in the UE to be activated. Thus, one or a single DCI message <NUM> is used to activate the SPS in the user equipment and to allocate resources for the SPS configuration. Thus, in accordance with the example described with reference to <FIG>, signaling overhead for sending a plurality of DCI control messages, namely separate DCI control messages to activate and allocate resources is avoided as the activation and resource allocation is done in a single DCI message.

<FIG> shows a further example of the second aspect in accordance with which it is assumed that a user equipment is scheduled with SPS using a plurality of different SPS configurations, as it might be implemented in V2X or V2V scenarios. For example, plural SPS configurations may be used dependent on the kind of data to be transmitted so as to meet requirements of transmission intervals which may be different for data from different entities, for example, data regarding specific information about the state of the vehicle may require to be transmitted less frequently than position information about the vehicle. Also the size of the data to be transmitted may be different. For the different kinds of data to be transmitted or to be received at the user equipment, different SPS intervals and, therefore, different SPS configurations, may be implemented at the user equipment. Also a different number of resources may be required for the transmission. To reduce signaling overhead in such a scenario, in accordance with the embodiment depicted in <FIG> the SPS DCI message <NUM> is provided. It is assumed that the SPS DCI message <NUM> is for a user equipment being configured with SPS using eight different SPS configurations. The SPS DCI message <NUM> includes information 202i which causes SPS configurations to be activated upon receipt of the DCI message at the user equipment. The SPS DCI message <NUM> may be used to activate all of the SPS configurations or it may be used to activate a subset or a group of the SPS configurations. In the latter case, the SPS DCI message <NUM> includes the optional information <NUM><NUM> identifying those SPS configurations or a group of SPS configurations (see also the example described below with reference to <FIG>) to be activated upon receipt of the DCI message at the user equipment. The SPS configurations or the group SPS configurations may have associated therewith respective identifiers, also referred to as SPS-IDs, and for those SPS configurations to be activated, the field <NUM><NUM> includes the corresponding SPS-IDs. When only activating the SPS configurations no additional information concerning the modulation and coding scheme may be needed. Thus, in accordance with the example of <FIG>, only one DCI message or a single DCI message is used to activate all or a subset of the SPS configurations with which a user equipment may be configured, thereby reducing the signaling overhead to a single DCI message rather than sending up to eight different DCI messages for activating each of the SPS configurations individually. The DCI message <NUM> does not cause any resource allocation, this may be done by a separate DCI message sent at a later time. This later DCI message may be an individual message for each of the SPS configurations or it may be a combined SPS DCI indicating the resources for all or the subset of activated SPS configurations with which the user equipment is configured.

<FIG> shows an example of a DCI message to allocate resources to all or a subset of SPS configurations <NUM> to <NUM> that may be used in a user equipment configured with SPS. The SPS DCI message <NUM> is provided which includes information <NUM><NUM> about the modulation and coding scheme. The SPS DCI message <NUM> includes information <NUM><NUM> about resources to be allocated for the SPS configurations, e.g., dependent on the data size defined by the SPS configuration. The SPS DCI message <NUM> may be used to allocate the resources for all of the SPS configurations or it may be used to allocate the resources for a subset or a group of the SPS configurations. In the latter case, the SPS DCI message <NUM> includes the optional information <NUM><NUM> identifying those SPS configurations or a group of SPS configurations (see also the example described below with reference to <FIG>) for which resources are to be allocated upon receipt of the DCI message at the user equipment. The SPS configurations or the group SPS configurations may have associated therewith respective identifiers, also referred to as SPS-IDs, and for those SPS configurations for which resources are to be allocated, the field <NUM><NUM> includes the corresponding SPS-IDs. In the example of <FIG>, it is assumed that up to eight SPS configurations are configured in the UE, and the DCI message <NUM> signals in field <NUM><NUM> for all or each addressed SPS configuration the respective resources to be allocated. For example, a first set of resources or resource elements may be assigned to the SPS configuration <NUM>, and the following resource elements are allocated to SPS configurations <NUM> to <NUM>. This is schematically represented on the right hand side of <FIG> showing the subframe and the DCI message <NUM><NUM> that is transmitted in the PDCCH and includes the resource information <NUM><NUM> which, as is schematically indicated in the subframe, points to the respective resource elements. Thus, in accordance with the example of <FIG>, one DCI message or a single DCI message is used to allocate the resources for all or a subset of the SPS configurations <NUM> to <NUM>.

<FIG> shows another example of the second aspect in accordance with which it is assumed, again, that the user equipment is configured with SPS using up to eight SPS configurations <NUM> to <NUM> and each of the SPS configurations includes a specific SPS interval and a specific data size. The example of <FIG> combines the above described examples of <FIG> and <FIG> in that the DCI message <NUM> activates and allocates resources for all or a subset of the SPS configurations <NUM> to <NUM>. The DCI message <NUM> includes the information about the modulation and coding scheme <NUM><NUM> to be used and, as necessary, further control information. The SPS DCI message <NUM> includes information <NUM><NUM> which causes SPS configurations to be activated upon receipt of the DCI message at the user equipment, and information <NUM><NUM> about resources to be allocated for the SPS configurations, e.g., dependent on the data size defined by the SPS configuration. The SPS DCI message <NUM> may be used to activate and allocate the and resources for all of the SPS configurations or it may be used to activate and allocate the resources for a subset or a group of the SPS configurations. In the latter case, the SPS DCI message <NUM> includes the optional information <NUM><NUM> identifying those SPS configurations or a group of SPS configurations (see also the example described below with reference to <FIG>) to be activated and for which resources are to be allocated upon receipt of the DCI message at the user equipment. The SPS configurations or the group SPS configurations may have associated therewith respective identifiers, also referred to as SPS-IDs, and for those SPS configurations which are activated and for which resources are allocated, the field <NUM><NUM> includes the corresponding SPS-IDs. Thus, in the example of <FIG>, one DCI message or a single DCI message is used to activate and allocate resources for one or more of the SPS configurations <NUM> to <NUM>. As described above with reference to <FIG>, the DCI is transmitted in the PDCCH of the subframe and the resource allocation is schematically represented at <NUM><NUM> in the right hand side of <FIG>.

The above described examples of the second aspect are not limited to user equipments operated in V2V or V2X scenarios but may apply to any kind of user equipment including one or more SPS configurations to be used.

The examples described above reference to <FIG> allow for a significant reduction of control message signaling thereby reducing the control message signaling overhead. The above described approach regarding the use of one DCI message for activating and/or allocating resources for one or more SPS configurations may be used either for the downlink configuration or for the uplink configuration. In accordance with further examples, a single DCI message may be used for configuring the resources and activating the SPS for both the uplink and downlink transmission of data.

<FIG> shows an example for assigning resources for several SPS configurations using one DCI message, as has been described above with reference to <FIG> or <FIG>. Three SPS configurations SPS <NUM> to SPS <NUM> having different SPS time intervals t1 to t3 and different data sizes x1 to x3 are shown. Further, each SPS configuration has associated therewith an identifier ID i1, i2, i3. The DCI message <NUM>, <NUM> indicates at <NUM><NUM> or <NUM><NUM> the resources or a block of resources to be used for all SPS configurations. The block of resources to be assigned is schematically represented in <FIG> at <NUM>. The block <NUM> of resources may be formed by a plurality of resource elements of a subframe which may be continuous in time/frequency, or may be separate from each other. In other words, a continuous block of resource elements may be provided or a non-continuous block of resource elements may be provided, The resource elements of the respective block are allocated to the respective SPS configurations by the DCI message. In the example of <FIG>, the single DCI message <NUM>, <NUM> assigns the resources for all SPS configurations SPS<NUM> to SPS<NUM> and, in case there are more SPS configurations also for the additional SPS configurations. The resources or the resource block <NUM> is split using the data size of each SPS configuration by assigning the resources from the first to the last configuration according to the identifier associated with the respective SPS configuration. Thus, as is shown in <FIG>, a first set of resources or resource elements is allocated to the SPS configuration <NUM> having the identifier i1, and subsequent resource elements are allocated to the SPS configuration having the identifier i2. In accordance with other examples, the resource elements in the block <NUM> may be allocated in a different way, for example, the first resource elements may be assigned to one of the second or third SPS configurations, or resource elements which are non-continuous may be assigned to the same SPS configuration, for example, the SPS configuration having the ID i1 may have a first set of resource elements at the beginning of the block <NUM> assigned thereto, and a further number of resource elements from another part of the block <NUM> which is non-continuous with the first block. The one or single DCI may be used to allocate or change resources for several configurations at once by allocating the amount of resources necessary for transmitting all configurations simultaneously, by defining the resources of resource block <NUM> and then causing an allocation of the resources from the block <NUM> at the user equipment in accordance with the respective configurations as described above.

<FIG> illustrates another example of the second aspect providing for a dynamic assignment of resources to respective SPS configurations. <FIG>, in a similar way to <FIG>, shows three SPS configurations SPS1 to SPS3 having different SPS intervals, different data sizes and different IDs. On the right side of <FIG>, the maximum resources to be assigned by a single DCI, such as DCI message <NUM>, <NUM> described above with reference to <FIG> and <FIG>, are shown as resource block <NUM>. The resource block <NUM> may define a continuous or non-continuous number of resource elements to be allocated to the SPS configurations. When sending a DCI message to allocate resources, it may be determined that at the time t<NUM> all three SPS configurations are used by the UE, and the resources provided by block <NUM> are distributed among the SPS configurations in accordance with the respective data sizes. At time t<NUM>, it may be determined that currently only the first SPS configuration is used so that not all of the allocated resources of the block <NUM> are needed for the SPS configurations. As is shown at time t<NUM> only the resources for SPS configuration <NUM> are allocated, and the other resources of block <NUM> remain free. In accordance with examples, these free resource elements may be scheduled otherwise. For example, the free resource elements may be used by the same UE for non SPS traffic, or may be used by a different UE. At time t<NUM>, it is determined that the UE uses the second SPS configuration in addition to the first SPS configuration, and the DCI now also allocates the resources for the second SPS configuration. The number of free resources is smaller than at time t<NUM>. The situation at time t<NUM> corresponds to the one at time t<NUM>, and the situation at time t<NUM> corresponds to the situation at time t<NUM>.

Thus, in accordance with the example of <FIG>, the resources that may be needed for the SPS configuration are allocated at the very beginning for each SPS occurrence, however, the number of resources actually used at a specific time is determined dependent on how many SPS configurations are currently scheduled and dependent on the size or data used by the respective SPS configuration in the UE.

Another example of the second aspect will now be described with reference to <FIG>. A number of SPS configurations are combined into a group. <FIG> shows in the upper part an example in which a UE may be configured with four SPS configurations SPS1 to SPS4, each having assigned a SPS ID. The SPS configurations may be controlled in accordance with the DCI messages described above with reference to <FIG>. In accordance with the example of <FIG>, all of SPS configurations or a subset of SPS configurations are combined into a group. <FIG> shows a group having assigned thereto an ID which is used to address, within the DCI message, all members of the group, which includes SPS configurations SPS1, SPS3 and SPS4 as indicated by the respective IDs. When a DCI message is sent indicating ID5, all SPS configurations SPS1, SPS3 and SPS4 will be addressed, e.g., to be changed or modified. For example, when indicating in the respective ID fields <NUM><NUM>, <NUM><NUM> and <NUM><NUM> of the DCI messages <NUM>, <NUM>, <NUM> the group ID, all SPS configurations in this group will be addressed. By using one or a single DCI message, groups of SPS configurations may be switched. For example, several SPS configurations may be changed using a single DCI message. Further, SPS configurations may be added or removed semi-statically from the group, and the DCI message having the corresponding group ID will change all the configurations in the group. In accordance with examples, adding/removing a SPS configuration to/from a group is caused not by a DCI message, but a further control message may be used that is received at the UE. For example, a RRC message may be used. In accordance with other examples, an implicit removal from a group may occur, when a SPS configuration (currently belonging to a group) is reconfigured on its own with a DCI.

Embodiments of the present invention may be implemented in a wireless communication system as depicted in <FIG> including base stations and UEs, like mobile terminals or loT devices. <FIG> is a schematic representation of a wireless communication system for communicating information between a base station BS and a UE. The base station BS includes one or more antennas ANTBS or an antenna array having a plurality of antenna elements. The UE includes one or more antennas ANTUE. As is indicated by the arrow <NUM> signals are communicated between the base station BS and the UE via a wireless communication link, like a radio link. The wireless communication system may operate in accordance with the techniques of the first aspect and the second aspect described herein.

For example, in accordance with the first aspect the UE is served by the base station BS which in this scenario is a source base station of a source cell of the wireless communication network. The wireless communication network includes a plurality of cells, and each cell has a base station. The UE receives via the one or more antennas ANTUE a radio signal including a SPS configuration message from the base station so that the UE is configured with semi-persistent scheduling in accordance with the SPS configuration provided by the source base station. The UE will maintain SPS when moving from the source cell to a target cell of the wireless communication network. The UE includes a signal processor <NUM> to process the SPS configuration message and to maintain SPS after moving from the source cell to the target cell, e.g., following a handover. The base station BS, when operating as the source base station, serves the UE located in the source cell, and configures the UE with SPS in accordance with the SPS configuration. The base station BS comprises a signal processor <NUM> to generate a radio signal to transmit the SPS configuration to a target base station associated with a target cell, when the user equipment moves from the source cell to the target cell of the wireless communication network. The base station BS, when operating as the target base station, receives the SPS configuration from the source base station currently serving the UE configured with SPS in accordance with the SPS configuration. The SPS configuration is received when the UE moves from the source cell to the target cell. The base station BS comprises a signal processor <NUM> to process a received radio signal to obtain the SPS configuration transmitted by the source base station. Further, the signal processor <NUM> generates a radio signal to serve the UE located in the target cell using SPS in accordance with the received SPS configuration.

For example, in accordance with an example of the second aspect, the user equipment UE is configured with SPS in accordance with a SPS configuration. The UE receives via the one or more antennas ANTUE a radio signal, which includes a control message. The UE includes a signal processor <NUM> to process the radio signal to obtain the control message which signals an activation of the SPS configuration and which signals resources to be allocated for the SPS configuration. The base station BS configures the UE with SPS in accordance with the SPS configuration, e.g., by generating a SPS configuration message using the signal processor <NUM> and sending the SPS configuration message to the UE via the one or more antennas ANTBS. Further, the base station generates and transmits a radio signal to the UE, which includes a control message. The control message signals an activation of the SPS configuration and signals resources to be allocated for the SPS configuration.

In accordance with another example of the second aspect, the user equipment UE is configured with SPS in accordance with a plurality of SPS configurations. The UE receives via the one or more antennas ANTUE a radio signal, which includes a control message. The UE includes a signal processor <NUM> to process the radio signal to obtain the control message which signals an activation of the plurality of SPS configurations. The control message may also signal resources to be allocated for the plurality of SPS configurations. The base station BS configures the UE with SPS in accordance with the plurality of SPS configurations, e.g., by generating one or more SPS configuration messages using the signal processor <NUM> and sending the one or more SPS configuration messages to the UE via the one or more antennas ANTBS. Further, the generates and transmits a radio signal to the UE, which includes a control message. The control message signals an activation of the plurality of SPS configurations. The control message may also signal resources to be allocated for the plurality of SPS configurations.

In accordance with yet another example of the second aspect, the user equipment UE is configured with SPS in accordance with one or more groups of SPS configurations, a group of SPS configurations including two or more SPS configurations. The UE receives via the one or more antennas ANTUE a radio signal, which includes a control message. The UE includes a signal processor <NUM> to process the radio signal to obtain the control message which addresses the SPS configurations of one or more of the groups of SPS configurations. The base station BS configures the UE with SPS in accordance with one or more groups of SPS configurations, a group of SPS configurations including two or more SPS configurations, e.g., by generating one or more SPS configuration messages using the signal processor <NUM> and sending the one or more SPS configuration messages to the UE via the one or more antennas ANTBS. Further, the generates and transmits a radio signal to the UE, which includes a control message. The control message addresses the SPS configurations of one or more of the groups of SPS configurations.

Depending on certain implementation requirements, embodiments of the invention may be implemented in hardware or in software. The implementation may be performed using a digital storage medium, for example cloud storage, a floppy disk, a DVD, a Blue-Ray, a CD, a ROM, a PROM, an EPROM, an EEPROM or a FLASH memory, having electronically readable control signals stored thereon, which cooperate (or are capable of cooperating) with a programmable computer system such that the respective method is performed.

Claim 1:
A user equipment (UE), wherein
the user equipment (UE) is configured to be served by a source base station (eNB<NUM>) of
a source cell (<NUM>) of a wireless communication network, and the user equipment (UE) is configured with semi-persistent scheduling, SPS, in accordance with a SPS configuration provided by the source base station (eNB<NUM>),
the user equipment (UE) is configured to transmit the SPS configuration to a target base station (eNB<NUM>), when the user equipment (UE) moves from the source cell (<NUM><NUM>) to the target cell (<NUM><NUM>);
the user equipment (UE) is configured to maintain the SPS when moving from the source cell (<NUM><NUM>) to the target cell (<NUM><NUM>);
characterised in that
the user equipment (UE) is configured to signal a time of a next SPS packet to a target base station (eNB<NUM>) when the user equipment (UE) moves from the source cell (<NUM><NUM>) to the target cell (<NUM><NUM>), wherein the time of a next SPS packet is signaled as a time of a next SPS interval or as an absolute time, or as a period of a SPS interval which has already been used up so far; and
the user equipment (UE) is configured to receive the next SPS packet from the target base station (eNB<NUM>) at the signaled time of the next SPS packet.