Simultaneous adaptation using a full-duplex beacon TECHNICAL FIELD

The invention relates to the field of wireless communications, and more particularly to a communication between a base station and a user equipment device.

BACKGROUND

In the wireless communication systems between a base station (BS) or eNodeB and a plurality of user equipment (UE) devices, the provision of a channel state information (CSI) or a channel quality indicator (CQJ) is essential to select the appropriate transmission parameters for the next communication attempt.

In a frequency division duplex (FDD) scheme, the transmission towards and from the BS takes place at different frequencies. However, in environments with mobility, the channel conditions can change very quickly such that the obtained CSI can get outdated. It becomes worse when the UE devices transmit short packets sparingly over time, which is the case in machine-to-machine (M2M) communications, wireless sensor networks, Internet of Things (loT) applications, conventional cellular uplinks (ULs) sometimes and mobile satellite communications using satellites in geostationary or more distant orbits.

Several conventional solutions, taken either singly or in combination as it is the case for example in the Long Term Evolution Standard (LTE), exist to extract an updated CSI. In the CSI extraction from previous data, whenever a UE device transmits data to the BS, the latter estimates the channel quality, selects a modulation and coding scheme (MCS) based on that channel quality, and communicates through feedback the MCS to the UE device, which will then use it for its next transmission. Nevertheless, the main disadvantage of that solution lies in the delays involved in the process. Indeed, at the time when the UE device is about to transmit again, the channel conditions may have noticeably changed such that the selected MCS may not be the most suitable anymore, which may result in lower data rates or cause an outage when the data packet cannot be decoded. That is further exacerbated when the UE devices transmit sparingly over time. Moreover, that type of solution consumes resources in the feedback process, especially when the number of active UE devices is very high. In the CSI extraction from a periodic sounding, the UE devices may periodically probe the communication channel by sending a known sequence, even if they have no data to transmit. Such a process can be supported by LTE through the so-called sounding reference signals (SRS). The BS will use that known sequence to obtain updated estimations of the channel quality and feed them back to the UE device. However, that solution not only increases the signaling and the feedback overhead, but also significantly affects the network performance and the efficiency in terms of net throughput. In addition, the actual values of the sounding period might still produce outdated indicators.

Irrespectively of how the CSI is obtained, it is furthermore common to use delay

compensation techniques to try to prevent the outdating of the information, i.e., the channel aging. A standard technique may be the prediction of the state of the channel in the future based on a number of previous samples. Despite those delay compensation techniques, the outdating of the information cannot however be fully avoided. SUMMARY

It is therefore an object of the present invention to provide apparatuses, a system and methods for acquiring an updated channel state information (CSI). The object is achieved by the features of the independent claims. Further embodiments of the invention are apparent from the dependent claims, the description and the figures.

According to a first aspect, the invention relates to a base station, the base station bei adapted to receive an uplink signal in a first frequency, transmit a downlink signal in a second frequency and transmit a pilot sequence in the first frequency. Thereby, the base station can receive the uplink signal in a frequency while transmitting in the same frequency the pilot sequence, from which a valuable information related, for example, to a communication channel state can then be extracted.

According to a first implementation of the base station according to the first aspect, the pilot sequence is uninterruptedly or almost uninterruptedly transmitted in the first frequency.

Thereby, the information to be then extracted from the transmitted pilot sequence can be updated and rendered available at any time if uninterruptedly transmitted or almost at any time if almost uninterruptedly transmitted. The almost uninterrupted transmission can be defined as a repeating transmission with a sufficiently short time interval between two transmissions to be considered to be a quasi-continuous transmission.

According to a second implementation of the base station according to the first

implementation of the first aspect, the base station is adapted to apply a self-interference mitigation to the received uplink signal.

Thereby, the quality of the received uplink signal can be enhanced by minimizing the impact of any interference on itself.

The above object is also solved in accordance with a second aspect.

According to the second aspect, the invention relates to a user equipment device being adapted to transmit an uplink signal in a first frequency, receive a downlink signal in a second frequency and receive a pilot sequence in the first frequency.

Thereby, the user equipment device can transmit the uplink signal in a frequency while receiving in the same frequency the pilot sequence, from which the user equipment device can then extract a valuable information related, for example, to a communication channel state. According to a first implementation of the user equipment device according to the second aspect, the pilot sequence is uninterruptedly or almost uninterruptedly received in the first frequency. Thereby, the information to be then extracted from the received pilot sequence can be updated and rendered available at any time if uninterruptedly received or almost at any time if almost uninterruptedly received. The almost uninterrupted reception can be defined as a repeating reception with a sufficiently short time interval between two receptions to be considered to be a quasi-continuous reception.

According to a second implementation of the base station according to the second aspect or the first implementation of the second aspect, the user equipment device is adapted to obtain a channel information from the received pilot sequence. Thereby, the user equipment device can obtain a channel information from the received pilot sequence and determine its own transmission parameters using the updated information extracted from the received pilot sequence.

According to a third implementation of the user equipment device according to the second aspect or any one of the preceding implementations of the second aspect, the user equipment device is adapted to apply a self-interference mitigation to the received pilot sequence.

Thereby, the quality of the received pilot sequence can be enhanced by minimizing the impact of any interference on itself.

According to a fourth implementation of the user equipment device according to the second aspect or any one of the preceding implementations of the second aspect, the user equipment device is adapted to discriminate between the pilot sequence and a plurality of other individually transmitted pilot sequences. Thereby, the user equipment device can find the pilot sequence corresponding to its own transmission channel amongst a possible plurality of other pilot sequences. If the pilot sequences are orthogonal, the discrimination to find the corresponding pilot sequence can be carried out optimally, namely without interference.

According to a fifth implementation of the user equipment device according to the fourth implementation of the second aspect, the user equipment is adapted to obtain a quality estimation of the channel from the discriminated pilot sequence after discriminating the pilot sequences.

Thereby, the user equipment device can itself estimate the quality of the dedicated transmission channel. The user equipment device can then use the estimated quality information but also an information about a risk of colliding with other uplink signals transmitted from other UE devices in order to decide whether to transmit or not the uplink signal, which leads to avoid unnecessary transmissions and also to save power. Indeed, the user equipment can be adapted to transmit either independently of the activity of other user equipment devices according to the obtained quality estimation when the uplink signal is transmitted in a random access or dependently of the activity of other user equipment devices according to the risk of colliding with the uplink signals that are transmitted, in particular at the same time, from those other user equipment devices when the uplink signal is transmitted in a full-duplex carrier-sense multiple access. In addition, the user equipment device can be adapted to compensate for an internal delay caused inside it, which leads to reduce the transmission latency. According to a sixth implementation of the user equipment device according to the fifth implementation of the second aspect, the user equipment is adapted to select transmission parameters based on the obtained quality estimation of the channel.

Thereby, the user equipment device can itself select suitable and updated transmission parameters (e.g., an appropriate modulation and coding scheme) with a delay only due to its internal processing, which reduces the transmission latency and increases the transmission throughput. The above object is also solved in accordance with a third aspect.

According to the third aspect, the invention relates to a wireless communication system comprising at least one base station, each base station being as specified in the first aspect and the implementations of the first aspect, and at least one user equipment device, each user equipment device being as specified in the second aspect and the implementations of the second aspect, and wherein each pilot sequence is unique with respect to each base station.

The above object is also solved in accordance with a fourth aspect.

According to the fourth aspect, the invention relates to a method for communicating from a base station, the method comprising the steps of receiving an uplink signal in a first frequency, transmitting a downlink signal in a second frequency and transmitting a pilot sequence in the first frequency.

According to a first implementation of the method according to the fourth aspect, the pilot sequence is uninterruptedly or almost uninterruptedly transmitted in the first frequency.

The above object is also solved in accordance with a fifth aspect.

According to the fifth aspect, the invention relates to a method for communicating from a user equipment device, the method comprising the steps of transmitting an uplink signal in a first frequency, receiving a downlink signal in a second frequency and receiving a pilot sequence in the first frequency.

The above object is also solved in accordance with a sixth aspect. According to the sixth aspect, the invention relates to a method for communicating between a base station and a user equipment device, the method comprising the steps of applying the steps as specified in the fourth aspect and the implementation of the fourth aspect in connection with the base station and applying the steps as specified in the fifth aspect in connection with the user equipment device.

The above object is also solved in accordance with a seventh aspect.

According to the seventh aspect, the invention relates to a computer program comprising program code for performing the method according to any one of the fourth, fifth and sixth aspects and/or any one of their respective implementation forms when executed on a computer.

Thereby, the method can be performed in an automatic and repeatable manner.

The computer program can be performed by any one of the above apparatuses or devices. The apparatuses or devices can be programmably arranged to perform the computer program.

Embodiments of the invention can be implemented in hardware, software or in any combination thereof. It shall further be understood that a preferred embodiment of the invention can also be any combination of the dependent claims or above embodiments with the respective

independent claim.

These and other aspects of the invention will be apparent and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present disclosure, the invention will be explained in more detail with reference to the exemplary embodiments shown in the drawings, in which: Fig. 1 shows a block diagram of a wireless communication system according to an embodiment of the present invention; and

Fig. 2 shows a block diagram of a user equipment device according to an

embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Fig. 1 shows a block diagram of a wireless communication system 100 according to an exemplary embodiment of the invention. The wireless communication system 100 comprises at least one user equipment (UE) device and a base station (BS).

As depicted in Fig. 1, the BS communicates with three UE devices (UEl, UE2, UE3) through a communication channel. Thus, the BS receives from each of those UE devices a respective uplink signal (S1JJL, S2_UL, S3_UL), for example a data signal, in a same first frequency (f_UL). On the other hand, the BS transmits towards each of those UE devices a respective downlink signal (S1_DL, S2_DL, S3_DL), for example a data signal, in a respective second frequency (fl_DL, f2_DL, f3_DL) different from the first frequency (f_UL). In addition, as shown by the dashed line, the BS uninterruptedly or almost uninterruptedly transmits towards each of those UE devices a unique sequence already known by themselves, for example a unique pilot sequence, hereafter designated as a beacon, in the same frequency as the first frequency (f_UL) in which it receives the respective uplink signal (S1_UL, S2_UL, S3JJL). It should be noted that the almost uninterrupted transmission can be defined as a repeating transmission with a sufficiently short time interval between two transmissions to be considered to be a quasi-continuous transmission.

Due to the continuous or quasi-continuous transmission of the beacon from the BS in the same frequency as the uplink signal transmitted from the respective UE device, an interference between the beacon and the uplink signal can occur. It results therefrom that both the BS and the UE device are required to work in a full duplex (FD) mode with respect to the beacon and the uplink signal, and consequently to have self-interference mitigation capabilities. Furthermore, it should be noted that the overall network interference does not increase since the UE devices and the BS use their respective FD capabilities for the respective transmission of their uplink signal and the beacon, and not for the transmission of their respective uplink and downlink signals. In addition, the UE devices are required to contend for the respective communication channel in a non-scheduled way since the continuous transmission of the beacon in the same frequency as the received uplink signal does not allow the BS to send a scheduling information to the respective UE devices. The UE devices use their respective beacon continuously or quasi-continuously received to extract the channel state information (CSI) at any time when they wish and only with the delay of their internal processing. Thus, the UE devices with high mobility profiles and low mobility profiles can be identically served, which simplifies the overall architecture and decreases the need for complex mobility prediction and tracking techniques.

Based on the extracted CSI, the UE devices are then adapted to autonomously select their respective modulation and coding scheme (MCS). Thereby, a more suitable MCS can be selected, the transmission throughput can be increased and the transmission latency can also be reduced since fewer uplink signal retransmissions due to an inappropriate selected MCS will occur, which further contributes to increasing the system net throughput. In addition, the resources can be freed as there is no need neither for MCS feedback from the base station nor for periodic channel sounding from the UE device.

It should be noted that the invention field is not limited to a wireless communication between one BS and a plurality of UE devices, but can also be extended to a wireless communication between a plurality of BSs as individually aforementioned and a plurality of UE devices as aforementioned, each pilot sequence or beacon being unique with respect to each BS. Fig. 2 shows a block diagram 200 of a user equipment (UE) device according to an embodiment of the present invention. The block diagram 200 comprises a first unit 210, a second unit 220, a third unit 230 and a fourth unit 240. As above mentioned, the UE device is required to work in a full duplex (FD) mode, as it continuously or quasi-continuously receives a pilot sequence or a beacon from the BS in the same frequency as the BS receives the uplink signal transmitted from the UE device, and consequently required to have self-interference mitigation capabilities. So, the first unit 210 is adapted to mitigate the self-interference caused by the own transmission of the uplink signal with respect to the beacon signal received at its input. In order to perform such a mitigation, we need to know the symbols being transmitted by the uplink signal from the UE device at that same time and the well-known self-interfering channel, i.e., the channel experienced by the uplink signal between the transmission port and the reception port of the UE device. Thereby, the first unit 210 comprises a self-interfering channel estimation unit, which is adapted to receive the outgoing symbols transmitted from the UE device through an output of the fourth unit 240, and a self-interference suppression unit. Based on the received outgoing symbols, an estimation of the self-interfering channel is carried out and the estimation result is then used to control the self-interference suppression unit. If the UE device does not transmit an uplink signal, then the mitigation operation of the first unit 210 can be skipped.

An UE device can hear the beacon transmissions from a plurality of BSs. In order to estimate the quality of the communication channel between a respective BS and an UE device, the UE device is then adapted through the second unit 220 to identify the respective BS amongst the plurality of BSs and hence the respective communication channel. For this purpose, the second unit 220 receives the different beacon signals transmitted through the self- interference suppression unit of the first unit 210 and discriminates between the received beacon signals and therefore the respective communication channels. If the beacon signals are orthogonal, then there is no interference between the BSs and the discrimination can be perfectly performed. Conversely, if the beacon signals are not orthogonal and the potentially interfering BSs are close to each other or in the same neighborhood, then the UE device cannot distinguish between the channels of different BSs, which results in a "polluted", i.e., coarse, channel estimation. In another scenario, if the beacon signals are not orthogonal and the potentially interfering BSs are much farther away than the respective BS to identify, then the UE device can also distinguish between the channels of different BSs. In a further scenario ignoring the distance between the BSs, the UE device can still distinguish between the channels of different BSs provided that the beacon signals are almost orthogonal, namely non-orthogonal but with good cross-correlation properties. Afterwards, based on the discrimination result, the second unit 220 estimates the quality of the respective

communication channel using conventional channel estimation methods, e.g., a linear channel estimation based on mean squared error (MSE) minimization or an iterative turbo channel estimation.

The third unit 230 is provided in order to compensate for the internal processing delay caused by the self-interference mitigation, the channel identification and the channel quality estimation. Such a compensation can be made, for example by using the prediction of future channel states, such as the linear prediction and the Kalman filtering.

Based on the estimated quality of the respective communication channel, the UE device selects its transmission parameters, such as an appropriate modulation and coding scheme (MCS), through the fourth unit 240. Furthermore, in order to take account of unforeseen impairments, a back-off can be used, which selects slightly more robust transmission parameters than the ones selected based on the estimated quality of the respective communication channel. The back-off value can be fixed or variable depending on the success of the previous transmissions.

However, the UE device can also decide not to transmit and therefore not to use the selected transmission parameters, such as the MCS, if the estimated quality of the respective communication channel is considered too low or the UE device detects other UE devices using the medium at the same time. The first option of not transmitting may occur when a vehicle with a vehicular network goes through a tunnel, thereby leading to energy saving, or when the transmission uses a random access (RA) scheme. Using the RA scheme, the UE device can transmit independently of the activity of the other UE devices, the possible collisions being accounted for in the code domain or dealt with in any other way at the respective BS. The second option of not transmitting may occur when the UE device is capable of "listening" to the medium, for example when the transmission uses a full-duplex carrier-sense multiple access (FD-CSMA) scheme. Using the FD-CSMA scheme, the UE device can transmit dependently of the activity of the other UE devices according to the risk of colliding with the uplink signals.

In summary, the present invention relates to apparatuses and methods for transmitting from at least one user equipment (UE) device a respective uplink signal in a first frequency towards at least one base station (BS), and transmitting from the at least one base station, both a downlink signal in a second frequency different from the first frequency and a respective pilot sequence or beacon in a same frequency as the first frequency. The pilot sequence is unique with respect to each base station and uninterruptedly or almost uninterruptedly transmitted from the at least one base station. The at least one base station and the at least one user equipment device apply each a self-interference mitigation, and the pilot sequence is used by the at least one user equipment device in order to select appropriate transmission parameters to transmit. While the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. From reading the present disclosure, other modifications will be apparent to a person skilled in the art. Such modifications may involve other features which are already known in the art and which may be used instead of or in addition to features already described herein. In particular, the transmission system is not restricted to an optical transmission system.

Rather, the present invention can be applied to any wired or wireless transmission system. The receiver device of the proposed system can be implemented in discrete hardware or based on software routines for controlling signal processors at the reception side.

The invention has been described in conjunction with various embodiments herein.

However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Although the present invention has been described with reference to specific features and embodiments thereof, it is evident that various modifications and combinations can be made thereto without departing from the spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded simply as an illustration of the invention as defined by the appended claims, and are contemplated to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present invention.