Method for power optimized data transmission in wireless cellular networks - Patents.com

Abstract

To provide a method for performing data transmission from a first user equipment to a base station of a cellular network which the first user equipment is camping on under coverage extension conditions.SOLUTION: A method includes: a step in which a first user equipment UE1 is communicatively connected to at least one second user equipment UE2 via a device-to-device (D2D) communication channel, and for data transmission of at least one data packet DP, the first user equipment transmits the at least one data packet to the at least one second user equipment via the D2D channel; and a step of instructing the at least one second user equipment to transmit at least one data packet time-synchronized with first transmission to a base station BS.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for data transmission from a user equipment in a cellular network.The invention also relates to a user equipment using said method.

[0002] The invention further relates to a method for operating a base station The invention also relates to a base station using said method. [Background technology]

[0003] In the field of wireless communications, cellular networks are evolving further to diversify communication methods in particular to cover a wide range of communication use cases. This represents the latest challenge that the so-called Internet of Things (IoT) poses for network operators. These challenges apply in particular to low functionality and substantially lower cost user end devices.

[0004] These pose challenges when you want minimal service with low power consumption in adverse conditions, and of course the service has to be cheap.

[0005] One such use case is improved reliable data transmission for a user equipment in a group of user equipment operating in the field, at least some of which are able to communicate with each other via device-to-device communication such as the PC5 / sidelink channels introduced in LTE.

[0006] Such user equipment is often stationary and operates particularly in areas with poor network coverage.

[0007] Now, in such a situation, the user equipment communicates in coverage extension mode, i.e. the receiver, specifically the base station, can repeat the transmission many times until it accumulates enough signal strength to decode the transmission. This coverage extension can improve the coverage condition by up to 15-18 dB, but the accumulation over time is quite non-linear: 2 repetitions can get you roughly 3 dB, but to get 18 dB, up to 2048 repetitions are needed.

[0008] However, the need to repeat the transmission 100 or more times obviously leads to delays in data transmission: when multiple user equipments of a group want to transmit data, they may have to wait until the data is transmitted, and during this transmission time the corresponding cellular network resources are blocked for all other user equipments.

[0009] Furthermore, this transmission method increases the power consumption of the user equipment, which in the case of battery operated user equipment may result in reduced battery life.

[0010] Currently, such groups are known to have one user equipment receiving transmissions from other user equipment of the group via a sidelink and transmitting data to the cellular network, the drawback being that this one user equipment consumes much more battery power than the other user equipment.

[0011] As a result, it needs to be equipped with additional resources to fulfill the role of "aggregator" user equipment. Indeed, after installation, especially after fixed installation, another user equipment may be working in better coverage conditions but may not have enough battery power. Thus, the aggregator user equipment assumes the role but in worse coverage conditions, resulting in very slow and inflexible data transmission, especially when extended coverage transmission is required. Summary of the Invention [Problem to be solved by the invention]

[0012] The object of the present invention is therefore to overcome the above mentioned drawbacks and to propose a solution for an improved flexible data transmission procedure for a group of user equipments operating in poor coverage conditions of a cellular network.

[0013] Therefore, further advantageous solutions would be desirable in the art. [Means for solving the problem]

[0014] Therefore, according to a first aspect of the invention, a method for data transmission from a first user equipment to a base station is proposed as claimed in claim 1. According to a second aspect of the invention, a user equipment is further proposed as claimed in claim 8. According to a third aspect of the invention, a method for operating a base station is proposed as claimed in claim 10. A fourth aspect of the invention relates to a base station as claimed in claim 14.

[0015] According to a first aspect of the present invention, there is provided a method for data transmission from a first user equipment to a base station of a cellular network to which the first user equipment is camped under coverage extension conditions, the method comprising the steps of: the first user equipment being communicatively connected to at least one second user equipment via a device-to-device communication channel; For data transmission of at least one data packet, the method comprises: - transmitting at least one data packet to at least one second user equipment via a device-to-device communication channel; - instructing at least one second user equipment to transmit at least one data packet time-synchronised with the first transmission to the base station.

[0016] The method of the present invention relates to user equipment operable with a base station of a cellular network for wireless communication, in particular user equipment implementing 4G (LTE), 5G (New Radio) and higher wireless technology standards.

[0017] Indeed, the extended coverage mode allows the user equipment to be capable of operating in poor coverage conditions, i.e. extended coverage conditions.

[0018] As part of the 3GPP Release 13 specification, the so-called Coverage Extension (CE) mode was introduced. It solves the reception / coverage problem by enabling communication in which the same data packet is received multiple times repeatedly in order to gather enough power for the receiver to reliably read the data packet. A prerequisite for this is that the base station supports CE user equipment. The extended coverage support is performed up to a certain coverage extension limit, which is also indicated by the base station, i.e. corresponds to the maximum number of repetitions and resources that the base station will spend in order for the user to obtain a certain coverage extension depth.

[0019] It is obvious that the power consumption increases with the number of repetitions for transmitting a data packet. On the other hand, some Machine Type Communication (MTC) or Internet of Things (IoT) applications, such as metering devices, pre-specify a certain power consumption budget that is difficult to adhere to under poor coverage conditions.

[0020] Here, the method of the invention concerns the situation of at least two user equipments operating in close proximity. In particular, the method is applicable to a larger group of user equipments installed by the same operator, although this is not essential. The known device-to-device communication channel defined in LTE / New Radio allows the user equipments to exchange data impartially via the serving base station, especially when operating with extended coverage.

[0021] Therefore, the method of the invention proposes that for data transmission from a first user equipment to a base station when operating in coverage extension conditions, at least one second user equipment is involved in the communication session.

[0022] To do so, the user equipment takes the step of transmitting at least one data packet to at least one second user equipment when it intends to transmit at least one data packet to the base station.

[0023] The user equipment also instructs at least one second user equipment to transmit at least one data packet to the base station in a time-synchronized manner with the first user equipment's own data transmission to the base station.

[0024] Time-synchronized means that all transmitted bits of the various streams arrive at a time lower than the sampling rate, so that the decision-making unit of the base station gets all the positive energies of the various streams of the same sample. The decision-making unit accumulates the energies and decides whether enough energy is available for decoding. Such an approach can be performed in parallel by several user equipments, and in a more advanced stage, a group of such user equipments can specifically repeat the transmission of a data package so that the signal can accumulate over time at the base station receiver. Since the multiple parallel repeated transmissions are not very time-spread, the nonlinear collisions are much lower as if one user equipment transmitted said package for a longer duration. The accumulation benefit is higher with lower nonlinear collisions. The combined multi-device transmission produces many advantages for avoiding adverse effects and occupying scarce network resources for a very short time. The first and at least one second user equipment then transmit data packets according to a time-synchronized schedule.

[0025] Preferably, the exchange and transmission of additional data packets occurs in a similar manner.

[0026] Preferably, the first user device does not differ from the at least one second user device in terms of hardware equipment, and any user device of the group that is located sufficiently close may be equally positioned to act as the first user device.

[0027] Sufficient proximity in this sense means as close as the smallest time unit Ts (time segment) defined in LTE. The precise definition of Ts is: Ts = 1 / (15000 x 2048) seconds, which is just over 32 nanoseconds. This is equal to 9.6 meters, taking into account the speed of light.

[0028] If we make a different calculation considering the LTE maximum bandwidth of 20 MHz bandwidth with FFT size of 2048, the sampling rate is 30.72 MHz and any signal arriving with an offset smaller than this sampling rate will not be recognized as different but will be considered the same. Even with a smaller bandwidth, the sampling rate is a corresponding fraction with fewer subcarriers.

[0029] The symbol period is the inverse of the subcarrier spacing. Therefore, for LTE, where the subcarrier spacing is 15KHz, the symbol length is 1 / (15KHz). 2048 time samples from the IFFT module fit into a symbol period of 1 / (15KHz). Therefore, the sampling frequency is (15KHz*2048) for 20MHz.

[0030] Similarly, by varying the number of subcarriers, sampling frequencies for other bandwidths will be obtained. However, considering the specific application case of connected automobiles, where the user equipment may be distributed inside the automobile to overcome the outdoor / indoor attenuation of the automobile for the user equipment, the above distance and accuracy requirements are easily and well achievable.

[0031] In more advanced approaches, the signals of various user equipments, i.e. multiple user equipments forming an organized transmit diversity radiation, may be perceived as different, and the receiver may use feedback, such as MIMO based on Alamouti codes, to adjust the timing in a learning phase that may be generated once and used accordingly for future transmissions. Such techniques are well known, for example Alamouti.

[0032] However, here there is preferably one user equipment forming an uplink (UL) transmission that is coordinated / synchronised by many user equipments.

[0033] Preferably, that user equipment of the group acts as the first user equipment from which data is to be transmitted, for example if a metering device performs a measurement and is to transmit the measurement value it acts as the first user equipment.

[0034] This makes the inventive solution very flexible, as the balance of power consumption is achieved automatically: power consumption remains linear with the amount of data the user equipment is to generate and transmit.

[0035] Instead of repeatedly transmitting the same data packet by one user equipment, the method of the present invention significantly reduces the time for transmitting the data packet in the extended coverage and also reduces the power consumption of one user equipment, especially when it is operating in worse coverage conditions than most other user equipments of the involved group.

[0036] To initiate such a group transmission, the coordinating user equipment negotiates with the serving base station and allocates the corresponding resources, indicating that this is a joint transmission. The resources provided in the above approach are sufficient in the future for the user equipment to have enough time to coordinate transmissions with other user equipments, i.e. to provide the associated timing and sequences used.

[0037] Preferably, before doing so some preliminary steps are to be taken.

[0038] According to a preferred embodiment, it is proposed that prior to transmitting at least one data packet, the first user equipment determines at least one second user equipment with which it can communicate via a device-to-device communication channel.

[0039] Preferably, before setting up the time synchronized communication, the first user device determines which other user devices are in the vicinity.

[0040] Preferably, this step is performed once, especially for fixed installations or otherwise fixed installations. For example, if more than one user device is installed in a car, it is advantageous in the initialization step to determine which user devices are in close proximity. This is performed especially by one user device. Preferably, each of the user devices performs this step.

[0041] However, if another user device is placed in the vicinity of the first user device, it is advantageous to perform the steps of this embodiment at least from time to time in order to discover this.

[0042] The determining step in particular comprises exchanging signals via a direct communication link, i.e. a sidelink, between the user equipments. The first user equipment acting as a coordinating or master user equipment can use the PSBCH physical sidelink broadcast channel or the PSSCH physical sidelink shared data channel. In general, sufficient means are known from TS 23.303 for reliable communication via the sidelink and for assessing the proximity of other user equipments.

[0043] As opposed to a pure information transmission of the master user equipment to other user equipments in its vicinity, the information exchange in the UL is a joint transmission of the user equipments, not only by the first, i.e. the master user equipment. Once the master user equipment has negotiated with the base station regarding the timing and format of the UL transmission and provided this information to at least one second user equipment in its vicinity, a joint transmission of in particular previously exchanged data packets (between the user equipments) is performed, resulting in the initiation of transmission and the format provided by the base station and distributed by the master user equipment among the second user equipments.

[0044] In another advantageous embodiment, a method is proposed comprising a step in which a first user equipment, prior to transmitting at least one data packet to a base station, negotiates with the base station timing conditions for the transmission of said at least one data packet and shares said timing conditions with at least one second user equipment via a device-to-device communication channel.

[0045] In this embodiment, it is proposed that the first user equipment exchanges information related to the envisaged distributed data transmission with the serving base station. This step is preferably performed after the previous embodiment has been carried out, i.e. when it is known, for example from a previous data transmission, how many, in particular which, second user equipments will be involved in the data transmission.

[0046] In particular, the negotiating step includes an exchange of messages regarding the user equipment's anticipated data transmission and the base station's available resources and timing constraints, and an exchange of at least one of the user equipment and base station's approval of the timing conditions.

[0047] The timing condition relates to the start of data transmission and has a direct impact on said time synchronization of data transmissions from the first and at least one second user equipment.

[0048] This step ensures that the at least one second user equipment does not have to take additional steps as overhead with respect to data transmission of the at least one data packet, which is advantageous when the amount of data to be transmitted is small, especially when the advantage gained in terms of power saving may be overcompensated by such separate signaling effort for setting up the data connection.

[0049] According to the proposed embodiment, it is the responsibility of the first user equipment to set up the data transmission session accordingly and, as a consequence, to take the effort to get everything in order before at least one second user equipment assists in transmitting data packets to the base station.

[0050] According to another preferred embodiment it is proposed that the first and at least one second user equipment maintain a common group identifier, said group identifier being used as part of negotiation with the base station and said group identifier being included in said at least one data packet.

[0051] The group identifier is transmitted or is known in advance by the base station. In contrast to existing multi-device group identifiers, said group identifiers modify the corresponding procedures when used for organized transmission. This means in particular that the data allocation from the base station for the group is made at a later time than for the single user equipment, when information on the timing to transmit from the master user equipment negotiating with the base station needs to be shared with one or more other user equipment of the group. That is, in LTE, the uplink allocation is 4 frames later, which is sufficient for UE processing with normal single-UE transmission. This is not sufficient for organized transmission, and therefore the received data needs to be distributed to the other UEs via PC5, which requires additional processing time and needs to be taken into account during negotiation. This is especially true when the other user equipments are informed sequentially via the sidelink from the master user equipment. Preferably, the user equipment is able to establish more than one sidelink connection at once and thus distributes the timing information to the other user equipments at least partly in parallel.

[0052] This embodiment is particularly useful when a user equipment of the same group wishes to transmit information, ie take over the role of master, and re-obtain the same conditions previously negotiated for the group.

[0053] According to this embodiment, mastership within a group can change, or even when the same user equipment holds mastership, it is ensured that the group identifier can be used to obtain corresponding services from the base station as a group, while each user equipment can also hold an individual identifier for any other communication purposes.

[0054] It is also useful that a second user equipment receiving a request from a first user equipment having the role of master can reject this request, especially if the second user equipment is already active in a certain number of groups. Preferably, the user equipment can work for one master user equipment, and as a result, all further requests are rejected.

[0055] Thus, the group identifier also helps the second user equipment to decide whether to reject additional transmissions: if the second user equipment is already active in a group, it will continue to transmit data packets when mastership changes among other group members.

[0056] However, there is still a risk that time-synchronized measurements may not result in sufficiently synchronized data packets being transmitted and the base station may not be able to aggregate the received signal sufficiently to decode the data packets, especially when multiple data packets are transmitted, and for later transmitted packages synchronization may be lost, especially when many user equipments are involved.

[0057] Therefore, according to another preferred embodiment, if at least one of the first and second user equipments receives an indication of synchronization imbalance from the base station, the method comprises the steps of: - indicating to at least one second user equipment to stop data transmission; - implementing corresponding synchronization improvements; - renegotiating the timing conditions of said transmissions with a base station; - sharing said timing conditions with at least one second user equipment via a device-to-device communication channel; - continuing the transmission according to the new timing conditions; A method is proposed which includes:

[0058] This embodiment is triggered by an indication of a synchronization imbalance received at the first or at least one second user equipment from the base station, which is in particular provided by a message from the base station to each user equipment.

[0059] Preferably, such an indication is sent to the first user equipment, which can then take steps to resolve the situation, which is the master user equipment of the current communication session.

[0060] However, the instruction may also be received by one of the second user devices, in which case it is proposed to present the instruction to the user device via the established device-to-device communication so as to take the necessary steps.

[0061] The necessary steps include transmitting a command to at least one second user device over the device-to-device communication channel to stop transmitting data, i.e. to cease transmission for the time being, so that the first user device likewise stops transmitting data.

[0062] The first user equipment is then supposed to perform synchronization improvement measures, if applicable. Preferably, this step includes checking whether at least one of the second user equipments does not provide sufficient synchronization stability. This may take into account previously occurring imbalance situations, especially if advantageously caused by the same user equipment.

[0063] It may then be advantageous to remove that user equipment from the group of the second user equipment and continue transmitting.

[0064] Furthermore, a time synchronization arrangement between the user devices is preferably performed.

[0065] If remedial measures are implemented, the first user equipment renegotiates the timing conditions with the base station and distributes the timing conditions among the second user equipment via the device-to-device communication channel, and ultimately continues transmitting data packets with the first and at least one second user equipment involved according to the new negotiated timing conditions and taking into account the remedial measures.

[0066] According to another preferred embodiment, the timing condition comprises repeating transmission of the data packets for at least a portion of the first and at least one second user equipment in relation to applicable extended coverage conditions.

[0067] According to this embodiment, an optimization is introduced when it is found that the repetitions required to securely transmit a data packet to the base station do not match the available number of first and second user equipments involved.

[0068] If 10 iterations are required and 10 user devices are available, then the transmission will have a high probability of success.

[0069] If 10 iterations are required and more than 10 user equipments are available, then preferably only 10 of the available user equipments are involved in the transmission of data packets to the base station. This is particularly advantageous if one of the 10 base stations is not reliable enough, for example in terms of synchronization stability. In this case it can be replaced.

[0070] Power budgets discourage using as many user devices as available when there is no need to.

[0071] Preferably, user equipments with worse coverage conditions, eg the highest CE levels, are avoided.

[0072] If 10 repetitions are required and only 6 user equipments are available, then according to a preferred embodiment it is assumed that 4 of the 6 user equipments transmit the data packet twice, which is among other things part of the time synchronization.

[0073] For simplicity and to avoid organizational overhead, it may be advantageous to have every user equipment transmit twice, i.e. as many times as necessary to ensure that there are enough repetitions available at the base station to decode the data packet.

[0074] However, preferably, as many iterations as necessary are performed.

[0075] This means that some user equipments may perform at least one more transmission of a data packet than other user equipments of the group of user equipments involved. Preferably, user equipments with better coverage conditions perform more repeated transmissions than those with worse coverage conditions.

[0076] The proposed inventive method also has an element of data security associated with it, since the user equipment does not need to be known to each other and may be owned by different subscribers.

[0077] Therefore, in another advantageous embodiment it is proposed that the first user device holds at least one content package and the method comprises a step of encrypting the at least one content package prior to transmitting the at least one data packet and distributing the result of the encryption to the at least one data packet.

[0078] The encryption performed in the first user device or an application communicatively connected thereto ensures that the second user device does not have the opportunity to evaluate what data is transmitted with the aid of at least one second user device, which significantly increases the number of user devices that can be used safely.

[0079] Prior to such data transmission, keys or certificates need to be exchanged for the base station, i.e. the targeted remote server, preferably the data transmission is set up without the involvement of other user equipment, which may take some time as possibly a general extended coverage data transmission needs to take place.

[0080] If this step occurs, the encrypted content package may be shared as a data packet with at least one second user device for transmission to the user device.

[0081] According to a second aspect of the present invention, there is provided a user equipment for operating in a cellular network by one of a plurality of base stations of the cellular network, comprising: a second user device configured to camp on the base station under coverage extension conditions and communicatively coupled to at least one second user device via a device-to-device communication channel; For data transmission of at least one data packet, a user equipment: - transmitting at least one data packet to at least one second user equipment via a device-to-device communication channel; - instructing at least one second user equipment to transmit at least one data packet time-synchronised with a first data transmission from the first user equipment to the base station; A user equipment configured as above is proposed.

[0082] The user equipment provides several components for conducting wireless communication: It comprises at least processing circuitry for executing operational software, in particular that implementing the method of the first aspect of the invention.

[0083] Additionally, the user equipment includes transmit and receive circuitry coupled to at least one antenna, typically a transceiver, for transmitting wireless communication signals to and from a base station of the cellular network.

[0084] Furthermore, a memory unit is preferably included in the user equipment for volatile and / or permanent storage of executable software, configuration data and data measured, for example prior to receiving a transmission from a serving base station.

[0085] The second aspect of the invention shares the advantages of the first aspect of the invention.

[0086] According to a third aspect of the invention, there is provided a method for a base station of a cellular network adapted to communicate in simultaneous reception mode with a plurality of user equipments, the method comprising: - receiving, from at least two user equipments, transmissions relating to the same data packet of each of the at least two user equipments; - combining the received transmission signals; - decoding the combined signal if the combination of the signals results in a sufficiently decodable signal; A method is proposed which includes:

[0087] This aspect of the invention relates to a base station being the counterpart on the air interface to a user equipment according to the second aspect of the invention in order to reach the problem posed, and it is therefore expected that the base station will also support the user equipment in its efforts to solve the problem posed.

[0088] The base station is one of multiple base stations in a cellular network and is configured to implement 4G or 5G technology standards, where the base station is commonly referred to as an eNodeB for 4G and a gNodeB for 5G.

[0089] Additionally, the base station is capable of operating in an extended coverage mode at least in the uplink.

[0090] As a result, the base station is able to store received signals within a technologically predetermined time distance or jitter.

[0091] According to the method, the base station, after negotiating with a first user equipment according to the second aspect of the present invention, receives timing condition transmissions from at least two user equipments and combines the received signals until they can be decoded.

[0092] The base station in particular comprises a decision-making unit for obtaining energy from the various streams provided, preferably in the middle of the chip, and accumulating the energy to receive sufficient energy for decoding.

[0093] This method may need to be repeated at least once to obtain sufficient power for successful decoding of data packets transmitted in multiple transmissions.

[0094] In a preferred embodiment it is further proposed to receive, prior to receiving the transmission signal, a request for negotiation of timing conditions of data transmission from one of the at least two user equipments and to transmit to said user equipment an indication of the timing conditions of transmission as part of the negotiation.

[0095] This embodiment relates to a preliminary step of setting up said data transmission session, as part of which it is envisaged that the base station receives an organised communication session request, preferably by presenting a message containing an indication related to a group identifier.

[0096] The base station then keeps track of the available resources and adds the additional time it can handle to the timing requirements.

[0097] These timing terms will be negotiated as part of the negotiation process.

[0098] Typically, both the user equipment and the base station provide a preferred time schedule, or at least some of the cornerstones upon which decisions regarding timing conditions and / or resource allocation are based.

[0099] Typically, the final decision is made at the base station side, so as to have a one-time view of the available resources.

[0100] In another preferred embodiment it is further proposed, upon detection of a group identifier in a request for negotiation of timing conditions, to allocate resources for uplink transmissions at a later time than in a request containing an identifier individually valid for the requesting user equipment.

[0101] According to this embodiment, it is proposed that the base station detects an indication related to a group identifier in the request from the user equipment.

[0102] In this case, the base station preferably knows that the request relates to an organized data transmission session, and therefore it is necessary on the part of the user equipment to request additional time for cooperation with the other, i.e. second, user equipment, which needs to be taken into account by the base station.

[0103] The amount of additional time is preferably indicated by the user equipment, for example based on a previously executed coordination task with a second user equipment. Preferably, the number of user equipments used for the expected data packet transmission influences the required additional time. As this is typically only known to the master user equipment, it is preferably considered as a step of negotiating timing conditions.

[0104] If only identifiers indicative of individual user equipment are detected by the base station, then such additional time is not required.

[0105] Therefore, as part of the negotiation, this timing delay is added to the timing requirements of the user equipment.

[0106] According to a fourth aspect of the invention, there is provided a base station of a cellular network adapted for communicating in simultaneous reception mode with a plurality of user equipments, the base station comprising: receiving, from at least two user equipments, transmissions relating to the same data packet of each of the at least two user equipments; - combining the received transmitted signals; - Decode the combined signal if the combination of the signals results in a sufficiently decodable signal. A base station configured as follows is proposed.

[0107] The fourth aspect of the invention shares the advantages of the third aspect.

[0108] As will be seen, the present invention advantageously solves the problems presented and proposes an innovative way of avoiding power-intensive data transmissions of user equipment operating in poor coverage conditions and making use of other nearby user equipment. [Brief description of the drawings]

[0109] The following description and the accompanying drawings set forth in detail certain illustrative aspects, but which illustrate only a few of the various ways in which the principles of the embodiments can be employed. Features and advantages of the invention will appear upon reading the following description and the accompanying drawings of advantageous embodiments, given by way of illustrative and not limiting example.

[0110] [Figure 1] FIG. 2 illustrates an embodiment of a group of user equipment of the type to which the present invention can be applied. [Diagram 2] FIG. 2 illustrates data transmission of a user equipment to which the present invention is applied in a coverage extension condition according to the prior art; [Diagram 3] FIG. 2 illustrates the transmission of data packets as a first exemplary embodiment of the present invention. [Figure 4] FIG. 2 illustrates the transmission of data packets in a deeper coverage extension condition as a second exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0111] FIG. 1 shows diagrammatically as an embodiment a first user equipment UE1 of the type to which the present invention applies, together with two further user equipments UE2, UE3 arranged as a user equipment group.

[0112] The user equipment of said group are in this particular exemplary embodiment installed in a motor vehicle CA, for example as different mobile units.

[0113] Each user equipment comprises a transmitting and receiving circuit, in particular a transceiver, and may utilize one or more antennas. Preferably, the antennas are provided by the vehicle in this example and are in particular shared between at least two user equipments. The different user equipments in the vehicle may be eCall boxes, parts of an entertainment unit and, for example, mobile phones. For illustrative purposes only, the different user equipments are shown as if they were mobile phones.

[0114] Furthermore, the user equipment comprises processing circuitry such as a CPU for executing software, in particular protocol stack software, for performing standard compliant communication tasks, including communication over the air interface with at least one base station BS of the cellular network CN.

[0115] The base station BS implements at least one wireless cellular communication standard, in particular 3G (UMTS / CDMA), 4G (LTE), 5G (New Radio NR) or higher. To that end, the base station BS comprises transmission and reception means, in particular antennas and transceivers. Furthermore, the base station BS provides access to cellular network components, in particular the Radio Access Network and / or indirectly the Core Network.

[0116] Furthermore, the user equipments UE1, UE2, UE3 are adapted to perform device-to-device D2D communication between the user equipments without involving a base station, in particular by means of PC5 / sidelink or ProSe functionality standardized for 4G and beyond, which allows for signal exchange between the user equipments and has advantages, in particular in terms of power consumption, compared to signaling via the base station BS.

[0117] The user equipments UE1, UE2, UE3 are configured to operate with the base station in extended coverage mode CE to overcome poor coverage conditions, so that the serving base station needs to be able to serve the user equipments in extended coverage mode as well.

[0118] Cell area 1 CEA1 indicates an area in which user equipment operating in normal coverage mode can camp on the base station BS without serious service degradation, while cell area 2 CEA2 indicates an area in which user equipment operating in extended coverage mode can be served by the base station BS.

[0119] Since the coverage extension level or number of repetitions is mainly governed by the coverage conditions, specifically the distance from the base station, obstacles, etc., the user equipment may provide different coverage extension levels to cars parked outside the coverage area or in a parking lot. Therefore, which user equipment has better coverage conditions than the other user equipment is based on how the car is parked. In the exemplary embodiment of FIG. 1, the user equipment UE3 is located closer to the base station BS than the other user equipments UE1, UE2. In this situation, it is preferable for the user equipment UE3 to transmit a signal to the base station, rather than the other two user equipments.

[0120] Alternatively, the user device may generate information such as gas usage, total mileage, or confirmation of availability of maintenance events, map updates, etc.

[0121] In FIG. 2, the transmission of data packets DP from a user equipment UE1 to a base station BS in extended coverage mode CE, as known from the prior art, is shown diagrammatically on a time bar.

[0122] It can be seen that the data packets are transmitted to the base station BS many times in succession without any changes. It is clear that this results in a significant decrease in the data transfer rate. The more times a data packet needs to be repeated, the longer it takes to transmit one data packet, and the less amount of data packets that can be transmitted in a given time.

[0123] This is attempted to be overcome by the method of the present invention, an exemplary embodiment of which is shown in figure 3. Here, a group of user equipments UE1 to UE5 are located in close proximity and camped on the same base station BS.

[0124] The user equipments are interconnected by device-to-device connections D2D, in particular PC5 / sidelink, via which a user equipment wishing to transmit a data packet DP can share the data packet with other user equipments UE2-UE5 before transmitting the data packet.

[0125] In this example, data packets are transmitted over these connections from UE1 to UE2, from UE2 to UE3, etc. This is not necessarily the only way of switching, instead one user equipment UE1 may transmit data packets DP to two or more other user equipments UE2, UE3, which is preferably configured according to the local topology of connections between the user equipments of the group.

[0126] If the user equipment is part of a motor vehicle, a device-to-device connection may be established between some of the user equipment in any way, and even a wired connection between the user equipment is considered by the present invention, especially in this context.

[0127] Therefore, such established connections are preferably chosen to be distributed before transmitting data packets to the base station BS.

[0128] It is also necessary to instruct the user equipments about the synchronization of the transmission of data packets, so that all involved user equipments are in a position to transmit time-synchronised data packets DP to the base station BS.

[0129] Obviously, this significantly reduces the time to transmit a data packet to an extended coverage area.

[0130] If the number of user equipments does not satisfy the number of repetitions required to successfully transmit the data packet to the base station, then further repetitions are required. However, with five user equipments as shown here, it is clear that the data packet is transmitted five times faster than if only one user equipment were to transmit the data packet under the same conditions. This is true regardless of whether five repetitions or 500 repetitions are required.

[0131] It is further preferred that, as shown in FIG. 4, not all user equipment transmits data packets as frequently as other user equipment of the same group of user equipment.

[0132] This is shown in this example where 7 repetitions are required to successfully transmit a data packet to the base station BS. When only 5 user equipments are available, it is advantageous to transmit as many times as actually required. This helps to save power for user equipments UE2, UE3, UE4 that do not need to make a second transmission.

[0133] The selection of which user equipment transmits and which does not in such a situation is determined in particular by battery power, coverage conditions or reliability in terms of synchronization stability.

[0134] In the foregoing detailed description, reference is made to the accompanying drawings, which show, by way of example, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that various embodiments of the invention, although different, are not necessarily mutually exclusive. For example, a particular feature, structure, or characteristic described herein in connection with one embodiment may be implemented in another embodiment without departing from the scope of the invention. In addition, it should be understood that the location or arrangement of individual elements within each disclosed embodiment may be modified without departing from the scope of the invention. Therefore, the foregoing detailed description should not be taken in a limiting sense, and the scope of the invention is defined solely by the appended claims, appropriately interpreted, along with the full range of equivalents to which the claims are entitled.

Claims

1. A method for transmitting data from a first user equipment (UE1) to a base station (BS) of a cellular network (CN) on which the first user equipment is camped under a coverage extension (CE) mode, comprising: The first user equipment (UE1) is communicatively connected to at least one second user equipment (UE2) operating in the coverage extension (CE) mode via a device-to-device communication channel (D2D); For the first user equipment (UE1) to repeatedly transmit at least one data packet (DP), the method comprises: - transmitting said at least one data packet (DP) to said at least one second user equipment (UE2) via said device-to-device communication channel (D2D); instructing said at least one second user equipment (UE2) to transmit said at least one data packet (DP) in time synchronization with a first data transmission of said first user equipment (UE1) to said base station (BS), The first data transmission transmits the at least one data packet (DP) to the base station (BS); When at least one of the first and second user equipments (UE1, UE2) receives an indication of synchronization imbalance from the base station (BS), the method further comprises the steps of: - indicating to said at least one second user equipment (UE2) to stop data transmission; - implementing corresponding synchronization improvements; - renegotiating with the base station (BS) the timing conditions of said transmissions; - sharing said timing conditions with said at least one second user equipment (UE2) via said device-to-device communication channel (D2D); - continuing the transmission according to the new timing conditions; The method includes:

2. 2. The method of claim 1, comprising, prior to transmitting the at least one data packet (DP), a step in which the first user equipment (UE1) determines the at least one second user equipment (UE2) that is capable of communicating via the device-to-device communication channel (D2D).

3. Prior to transmitting the at least one data packet (DP) to the base station (BS), the method further comprises the step of: the first user equipment (UE1) negotiating with the base station (BS) a timing condition for the transmission of the at least one data packet (DP); 2. The method of claim 1, comprising the step of sharing said timing condition with said at least one second user equipment (UE2) via said device-to-device communication channel (D2D).

4. 4. The method of claim 3, wherein the first and the at least one second user equipment (UE1, UE2) maintain a common group identifier, the group identifier being used as part of a negotiation with the base station (BS), and the group identifier being included in the at least one data packet (DP).

5. 4. The method of claim 3, wherein the timing condition includes repeating transmission of the data packets (DP) for at least a portion of the first and at least one second user equipment (UE1, UE2) in relation to an applicable coverage extension (CE) mode.

6. The first user equipment (UE1) holds at least one content package; Prior to transmitting the at least one data packet (DP), the method further comprises: - encrypting said at least one content package, The method according to claim 1 , further comprising a step of distributing the result of the encryption to said at least one data packet (DP).

7. A user equipment (UE1) operating in a cellular network (CN) and one of a plurality of base stations (BS) of the cellular network (CN), A second user equipment (UE2) configured to camp on the base station (BS) under a coverage extension (CE) mode and communicatively connected to at least one second user equipment (UE2) operating in the coverage extension (CE) mode via a device-to-device communication channel (D2D); For repeated transmission of at least one data packet (DP), the user equipment (UE1) - transmitting said at least one data packet (DP) to said at least one second user equipment (UE2) via said device-to-device communication channel (D2D), - configured to instruct said at least one second user equipment (UE2) to transmit said at least one data packet (DP) in time synchronization with a first data transmission of said user equipment (UE1) to said base station (BS), said first data transmission transmitting said at least one data packet (DP) to said base station (BS); When at least one of the first and second user equipments (UE1, UE2) receives an indication of synchronization imbalance from the base station (BS), the method further comprises the steps of: - indicating to the at least one second user equipment (UE2) to stop data transmission, - implementing corresponding synchronization improvements; - renegotiating the timing conditions of said transmissions with said base station (BS), - sharing said timing conditions with said at least one second user equipment (UE2) via said device-to-device communication channel (D2D), -Continue transmitting according to the new timing conditions A user equipment (UE1) configured as follows.

8. Prior to transmitting the at least one data packet (DP) to the base station (BS), negotiating with the base station (BS) timing conditions for the transmission of the at least one data packet (DP); Sharing said timing conditions with said at least one second user equipment (UE2) via said device-to-device communication channel (D2D). A user equipment (UE1) according to claim 7, configured to:

9. A method for a base station (BS) of a cellular network (CN) configured to communicate in a simultaneous reception mode with at least two user equipments (UE1, UE2), comprising: - one user equipment (UE1) of the at least two user equipments (UE1, UE2) is camped on the base station (BS) under a coverage extension (CE) mode, The one user equipment (UE1) is communicatively connected to at least one other user equipment (UE2) operating in a coverage extension (CE) mode via a device-to-device communication channel (D2D) and repeatedly transmits at least one data packet (DP), the method comprising: - receiving at the base station from at least two user equipments (UE1, UE2) repeated transmissions relating to the same data packet (DP) of each of said at least two user equipments (UE1, UE2); - said one user equipment (UE1) instructing said at least one other user equipment (UE2) to transmit said at least one data packet (DP) in time synchronization with a first data transmission of said one user equipment (UE1) to said base station (BS); - receiving said at least one data packet (DP) at said base station (BS) for said first data transmission; - combining the received repeated transmission signals; - decoding said combined signal if said combination results in a sufficiently decodable signal; when detecting a synchronization imbalance between the transmission signals from the at least two user equipments (UE1, UE2), - transmitting an imbalance indication message to at least one of said at least two user equipments (UE1, UE2), When at least one of the first and second user equipments (UE1, UE2) receives an indication of synchronization imbalance from the base station (BS), the method further comprises the steps of: - indicating to said at least one second user equipment (UE2) to stop data transmission; - implementing corresponding synchronization improvements; - renegotiating with the base station (BS) the timing conditions of said transmissions; - sharing said timing conditions with said at least one second user equipment (UE2) via said device-to-device communication channel (D2D); - continuing the transmission according to the new timing conditions; The method includes:

10. receiving, prior to receiving the repeated transmission signal, from one of the at least two user equipments (UE1, UE2) a request for negotiation of timing conditions for data transmission; and transmitting to said user equipment (UE1) an indication of said timing conditions of said transmission as part of said negotiation.

11. 11. The method of claim 10, further comprising the step of allocating resources for uplink transmissions at a later time than a request containing an identifier that is individually valid for the requesting user equipment (UE1) when detecting a group identifier in a request for negotiation of timing conditions.

12. A base station (BS) of a cellular network (CN) configured to communicate in a simultaneous reception mode with a plurality of user equipments (UE1, UE2), - one user equipment (UE1) of the plurality of user equipments (UE1, UE2) is camped on the base station (BS) in a spread coverage (CE) mode, The one user equipment (UE1) is communicatively connected to the other user equipment (UE2) operating in a coverage extension (CE) mode via a device-to-device communication channel (D2D), and repeatedly transmits at least one data packet (DP); The one user equipment (UE1) instructs the other user equipment (UE2) to transmit the at least one data packet (DP) in time synchronization with a first data transmission of the one user equipment (UE1) to the base station (BS), and the base station receiving from said plurality of user equipments (UE1, UE2) repeated transmissions relating to the same data packet (DP) of each of said plurality of user equipments (UE1, UE2); combining the received repeated transmission signals; - Decode the combined signal if the combination results in a sufficiently decodable signal. It is configured as follows: and further configured to transmit an imbalance indication message to at least one of the plurality of user equipments (UE1, UE2) upon detecting an imbalance in synchronization between the repeated transmission signals from the plurality of user equipments (UE1, UE2); When at least one of the first and second user equipments (UE1, UE2) receives an indication of synchronization imbalance from the base station (BS), the first user equipment (UE1) - stopping data transmission to said at least one second user equipment (UE2), - implementing corresponding synchronization improvements; - renegotiating the timing conditions of said transmissions with said base station (BS), - sharing said timing conditions with said at least one second user equipment (UE2) via said device-to-device communication channel (D2D), - A Base Station (BS) configured to continue transmission according to the new timing conditions.

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