Patent Application
20250038940
The present invention relates to a method to process, at a base station, uplink frequency areas in a cross division duplex (XDD) context.
The invention also pertains to a base station implementing said method.
For 3GPP Release 18, discussions started related to Cross Division Duplex (XDD) for Time Division Duplex (TDD) and, more generally, discussions started related to the evolution of duplex operation for NR, with the example areas of deployment scenarios, including duplex mode and interference management. Thus XDD, simultaneously operating UL and DL on the same TDD carrier but on different frequency, is one of the fields to be further investigated for Release 18.
Major New Radio (NR) bands, e.g. all frequencies in 3.5 GHz or 6 GHz range, are TDD spectrum. It means that uplink (UL) and downlink (DL) happen in the same band and are separated by defining certain slot for UL or DL as depicted in
The slot configuration period thus defines a DL-UL transmission periodicity including downlink only slots D, uplink only slots U and flexible slots F, D/L and F/U. The second line on
UE specific information to the slot configuration is necessary to help the network adjust DL/UL pattern based on the UE needs. Due to this adjacent DL or UL regions defined, there is a certain delay for the overall UEs concerning individual HARQ feedback. HARQ feedback needs to have a certain minimum time but may be delayed until timeslot in the right direction occurs. This leads to additional delays for some devices depending on the overall configuration.
Depending on the desired traffic, a configuration providing more DL or UL opportunities can be chosen. However the DL and UL form consecutive areas as UL/DL switching in the UE takes correspondingly time. It however allows to get rid of the duplex filter which in FDD is used to separate UL and DL frequencies.
The table below shows the provided latency calculation.
It shows that TDD latency is longer than comparable FDD latency. Thus subframe/slot switching increase the overhead and, giving that many 5G bands are TDD, means unpaired frequency bands, this is a general drawback which would be overcome if UL and DL would exist in parallel.
Thus the biggest drawback when looking at the TDD spectrum is the delay caused by the subsequent UL/DL usage change. So an RTT-loop DL-assignment/UL-sending/DL-acknowledgement takes correspondingly time, and becomes even longer when considering that also HARQ retransmissions may be needed. As a consequence, XDD-evolution is intended in Release 18.
So XDD, or full-duplex in TDD band, as depicted in
XDD as depicted in
Such a solution significantly reduces the latency also in TDD bands. However, as evoked above, it also brings new challenges and rules for assignment of the XDD usage and interference scenarios. Especially the area where adjacent base stations could operate on the same frequency chunk in different directions leads to base-station to base-station interference. Typically one base station is transmitting at high power to its served UEs in a direction whether the other base station is trying to receive at minimum sensitivity in said frequency chunks signals from its UEs and hence leads to the above-mentioned base-station to base station interference. The receiving base station experiences in said range also the emissions of the neighbor base stations as interference for the wanted UE signals.
This invention especially deals with interference scenarios arising at the base station for the case that different gNBs use the available spectrum differently. Operators already pointed to the fact that the UL/DL sharing between different gNodeBs should be supported to be different as they may have different traffic needs and to allow for flexibility. Some devices will do more DL, for example software, transmission of films data, while other devices are UL centric, for example video surveillance. Other devices may rather have equal demands on DL and UL, for example real-time gaming. In 3GPP for Release 18 Subband Full-duplex option (SBFD) for TDD bands is thus considered. Operators expressed the clear intention to have individual UL/DL split in each base station which leads to the interference scenarios including BS cross link interference.
As a consequence, it should be possible to configure the frequency chunks being used for UL and DL differently for neighboring base stations, and having a certain flexibility in changing said assignment on a longer time base. However, when supporting different traffic directions in different base stations in different directions, this leads to the field of interference.
Typically, one base station tries to receive at minimum sensitivity in a certain frequency area while another base-station being a few kilometers away transmits at maximum power on the same frequency chunks. In many such conditions, the base stations will be in loss of signal, meaning that the second base station signal arrives with a significant power at the other receiving base station and hence there is the interference situation for the receiving base station.
Thus a base station supporting larger RX area (UL) will face corresponding interference at the UL sides, used by the neighbor cell as DL. It means that in this area the neighbor cell DL is received in conjunction with the desired UE UL traffic.
This invention especially focuses on the cross-link interference between the base stations. As depicted in
According to the prior art, such interferences can be prevented by doing synchronized SXDD for avoiding such interference scenarios. Another solution would be to act with less power in the respective frequency chunks. It could be alternative solutions but they have clear efficiency drawback as all base stations would have to apply a same UL/DL split, irrespective of the individual traffic needs in said cell. Also the impacted frequency chunks would be limited in their usage to avoid interference to neighbors. Those frequency chunks would then be used only in a certain direction or with less power to minimize interference.
In parallel, UE cross-cell interference is so far known and solved by the UE doing neighbor cell measurements and, having the knowledge of neighbor SS-blocks, especially PSS and SSS sequence, the UE is hence able to subtract said SS blocks signals from its receiving sequence. This method is UE centric and solves interferences only on the UE side, such receivers are called interference cancelation receivers. It means that, receiving information on neighbor cells while doing neighbor cell measurements, they hence subtract those to achieve a better signal to noise ratio while receiving their wanted signal.
Further alternative and advantageous solutions would, accordingly, be desirable in the art.
The present invention aims at mitigate base station cross interference. It is here noted that network assisted base station cross interference was so far never an issue addressed and hence no further methods than synchronization were deployed as related solution.
The present invention is defined, in its broadest sense, as a method to dynamically process, at a base station, uplink frequency areas in a cross division duplex (XDD) context, said method comprising the steps of:
The invention thus provides signalling between cellular entities related to signal in downlink that can be subtracted. The base station which causes accordingly cross link interference provides additional information on the usage/content of said frequency chunk which will cause the interference. Contrarily to any interference correction known in the prior art, the base station does not perform measurements but only subtract content according to the additional information as provided by the other base station. The base stations not only exchange information on their applied UL/DL ratio but also information on cell specific signals that are used in the interference frequency area.
Additional information on content of the interference frequency area enables the base station to know the content sent by the other base station in the interference frequency area and not to consider it among received signal. Typically a mathematical signal cancellation can then be performed. With the invention is provided additional information on the usage/content of said frequency chunk which will cause the interference which enables such a cancellation. The interfered base station can perform XDD interference suppression. The information exchange enables to eliminate BS crosslink interference.
Advantageously, the additional information on content of the interference frequency area enabling the base station to know the content sent by the other base station in the interference frequency area, the step of processing signals received in the interference frequency area comprises subtracting such content in the interference frequency area.
This is advantageous for the base station to simply subtract a content in the interference frequency area, content that it knows or has means to know it.
In an embodiment, said content sent by the neighboring base station in the interference frequency area includes repetitive constant signals.
This is advantageous as it places cell specific information that does not change, which is preferable to simplify the cancellation of the interfering signals in the interference frequency area. Advantageously such information are not individually ciphered for privacy and security reasons but refer to cell specific information. Hence the information stays constant over time and only needs to be provided once.
Advantageously, the additional information includes, at least once, the repetitive constant signals in order for the base station to be able to subtract it from the received signals in the interference frequency area.
This content is here directly provided in the additional information.
The nature of the content can also be designated in the additional information as far as the base station already received this content once and can retrieve it or as far as the base station knows this content.
It is thus particularly adapted to signals and information which can be provided once to the neighbour cell or that are known also by to the neighbour cell. It is then accordingly subtracted from the received signal to eliminate the BS-cross interference and only the UE signal from its own UE sending in UL remains.
Advantageously, the repetitive constant signals are common between the two base stations
This can typically be synchronization signals, a part of them being also common for all base stations and thus easy to subtract by the base station. The SS-blocks are indeed the simplest and most straightforward content that can be introduced in the interference frequency signal.
Thus, according to an embodiment, repetitive constant signals are chosen among the followings:
The invention is thus typically based on exchanging information on System Information provided via neighbour cells and related update information when needed, thus enabling coordination for deployment of those information in a specific interference frequency area.
In further embodiment, said content of the interference frequency area includes temporary signals.
In such embodiment, it is useful that the base station received at least once the temporary signals in the additional information exchanged according to the invention.
Typically, temporary signals are on demand system information.
The interference frequency area is thus used preferably by the base station having the largest downlink frequency area to transmit on demand system information to the UE.
Advantageously, additional information includes respective signaling when on demand system information is activated or deactivated or MBMS broadcast.
This enables to provide information about the occurrence of temporary signals or about their changes.
The invention allows flexibility compared to a static approach and also avoids the usage of such overlapping bands with reduced power and hence reduced efficiency. The base station is informed on cell specific signals that can be cancelled in the signals received in the interference frequency area.
This method allows to eliminate the cross-BS interference to a large extend without causing heavy signaling flow on the N2 interface, i.e. the interface between base stations as defined within 3GPP between the base stations. Said information exchange may be performed in special standardized containers for intra-base station interference synchronization and notification. Said information exchange may also be performed or enhanced by proprietary signaling which is also of importance in case the base stations are from the same vendor, i.e. having enhanced means for intra-vendor interference avoidance between base stations.
According to an embodiment, information about UL/DL split from another base station having larger downlink frequency area comprises an indication that the uplink frequency area is deviated and indication on the side on which it is deviated.
The information exchange is related to a certain pre-configuration indicating area/side in what direction UL/DL from the pre-configuration is deviated.
Advantageously, an uplink border, being a UL/DL switching frequency, is provided in addition to the information about UL/DL split.
With this information, the base stations can co-ordinate at least one border to match and localize the interference. The base station that implements the method of the invention is thus aware in which area UL, respectively areas DL, is used.
According to an advantageous embodiment, a general uplink border, being a UL/DL switching frequency, is signaled by a network entity for all involved base stations to apply same frequency for UL/DL switching for all base stations operating on said frequency.
Thus the present invention in addition considers the alignment of at least one frequency border where UL/DL switching is done, as it is beneficial to focus the interference affected frequencies to one frequency area only. Said alignment is advantageously done by a network entity providing said one switching border to all base stations for localizing the interference in one frequency area. And hence all above information exchange can be referred to said area. It also eases the exchange and update of information in case that the UL/DL allocation of a base station changes. Indeed, with this embodiment, for all base station directly, only one frequency region would be affected. It is clearly advantageous compared to a scenario where the UL is centered in the inner frequency range and where two lateral frequency areas would experience new interference situations compared to the one fixed side UL/DL switching approach.
According to another advantageous embodiment, a maximum allowed UL/DL ratio, in which the base station can decide on the UL or DL allocation of frequency resources, is signaled by a network entity.
In accordance to the alignment of the first UL/DL switching border, also the maximum allowed UL/DL ratio or the frequency bandwidth which is allowed to be used for either UL or DL is advantageously signaled by a network entity to the base station. This has the advantage that not only one of the boarders is aligned but also that a base station can evaluate which could be the maximum affected region for base station interference. Hence, it can take first preventive measures on avoiding being impacted by cross-base station interference. Even with boarders not synchronized still would be of value, because you known what you can allocate, and also what others could allocate in opposite direction, hence what is the critical area/areas.
Advantageously the method further comprises a step of receiving at a medium access control of the base station, the respective information on UL/DL synchronized switching frequency and the respective maximum allowed UL/DL ratio which can be used for UL or DL, also by other base stations, and a step, for the medium access control, of performing resources allocation avoiding said frequency area for delay critical and high QoS sessions.
It means that the information on centralized UL/DL switching point and maximum allowed UL/DL ratio or frequency area for allocation in either direction, and thus an amount of spectrum which can be used for UL or DL also by other base stations is made aware to the base station medium access control and the medium access control (MAC) performs resource allocation in accordance.
This can thus be done without receiving any information from its neighbor cells, as the base station can evaluate the maximum impacted frequency area. In that frequency area it can place especially non-critical communication to avoid any impacts on delay critical information exchange with user equipments. This can result in placing the UL of delay critical communication in other frequency areas than the frequency area which may be used for DL by surrounding base stations. Hence regardless of the neighbor cell autonomous UL/DL allocation, base station cross interference can only occur in said frequency area which is either allowed for UL or DL depending on the base station traffic needs. Any further coordination for this area is independent of the benefit of knowing which may be the base station cross interference affected frequency range and has a value of its own.
In addition based on this information a base station vendor could add internal means between the base station for interference minimization or mitigation. Indeed vendors may not have specified what they need to do but rather only what is the impacted area and the invention is advantageous in such a situation.
At least it would be possible to schedule delay critical or delay sensitive application with respective 5G QoS outside of this potential base station cross interference region and to allocate this region preferably for less-delay critical services such as background downloads or best effort services. It means that availability of such information is especially suitable for the medium access control (MAC) to consider such information for scheduling purposes.
The present invention also relates to a base station adapted to dynamically process uplink frequency areas in a cross division duplex (XDD) context according to the method of one of preceding claims, said base station comprising:
To the accomplishment of the foregoing and related ends, one or more embodiments comprise the features hereinafter fully described and particularly pointed out in the claims.
The following description and the annexed drawings set forth in detail certain illustrative aspects and are indicative of but a few of the various ways in which the principles of the embodiments may be employed. Other advantages and novel features will become apparent from the following detailed description when considered in conjunction with the drawings and the disclosed embodiments are intended to include all such aspects and their equivalents.
For a more complete understanding of the invention, the invention will now be described in detail with reference to the accompanying drawing. The detailed description will illustrate and describe what is considered as a preferred embodiment of the invention. It should of course be understood that various modifications and changes in form or detail could readily be made without departing from the scope of the invention. It is therefore intended that the invention may not be limited to the exact form and detail shown and described herein, nor to anything less than the whole of the invention disclosed herein and as claimed hereinafter. The same elements have been designated with the same references in the different drawings. For clarity, only those elements and steps which are useful to the understanding of the present invention have been shown in the drawings and will be described.
This exchange of information between base stations enables them to know used UL/DL split and where the deviation occurs from pre-configuration. Such a pre-configuration is shown on
The base station gNB1 has then the possibility to send information on usage of impacted area US_IF. Thus, the base station gNB2 receives such an information in a step S3. According to a preferred embodiment of the invention, this information includes SS-block and SIBs periodicity and timing.
More generally, it is advantageous that information on usage of impacted area US_IF includes signals and information, which can be provided once to the neighbor cell or are known also by to the neighbor cell. This is then simple to accordingly subtract them from the received signal to eliminate the BS-cross interference. Then only the UE signal from its own UE sending in UL remains.
It means that said signals are transferred once to the neighbor base station including respective used RNTI and later on only related maintenance information is transferred. One a priori known signal is the PSS, means the primary synchronization sequence, which is identical for all base station. For other a priori known signals such as SSS or area SIBs only respective coding/X-RNTI and maintenance information needs to be provided.
The a priori knowledge can be assumed when both base stations belong to the same area and a certain area specific SIB is provided, hence the content of said SIB is the same and a priori known by all base stations of said area. If the respective used encoding/X-RNTI used for said transmission is also made available for the neighbor base station and information when said information is provided/activated with which periodicity, the base station can eliminate it mathematically in its time and frequency grid to avoid BS cross-interference from said transmissions. In the simplest situation, the base stations are synchronized, i.e. have the same timing and hence only the applied timing needs to be provided to the neighbor cell for elimination otherwise timing difference needs to be evaluated in addition.
Then, in a step S4, the base station gNB2 subtracts signals related to the information provided by the base station gNB1 at appropriate time mathematically from received context. It thus improves UL reception of its user equipments (UE) around. According to this embodiment, the base station gNB2 removes constant interferer signal.
According to an advantageous embodiment, the base station gNB1 also sends Information AC_IF on activation of an area SIB, frequency periodicity and timing, advantageously with a start/stop information. Thus in a step S5, the base station gNB2 receives this activation information AC_IF. The base station gNB2 in then enabled to subtract related signals at appropriate time mathematically from received context. It further improves UL reception of its UEs. This embodiment enables the base station gNB2 to remove momentary interferer signal in a step S6.
Then advantageously, for maintenance, the base station gNB1 also provides information CH_IF on content change or scheduling change of a SIB in the frequency chunk that is concerned by interferences. Thus in a step S7, the base station gNB2 receives this maintenance information CH_IF. The base station gNB2 is then enabled to perform maintenance of the interference processing.
It is here noted that the UL/DL unbalance between the cells may change, however here the change is rather on a longer time basis and related information is also exchanged to adapt the above mentioned mechanism. Also no cross-interference occurs in case all base stations are adopted to same UL/DL ratio.
The
As illustrated by
This is particularly adapted in case of only moderate deviation, i.e. in the order of 5 or 10 or 20 MHz which relates to the SS-block width. The smaller UL is not anymore placed by the base station gNB2 centered in the total frequency area. It rather adapt to one of the UL/DL cross synchronized borders SB of the neighbor cell, i.e. locate the cross-interference region only to one side. This is what is shown on
In this case, to achieve the alignment of the interference to one frequency area, one of the corresponding frequency where switching of UL to DL is performed is here a fixed switching frequency SB signaled by one network entity to all base stations. Hence all interference is allocated to one frequency area which is illustrated by a dotted area. So one of the boundaries is fixed signaled by one network entity and hence all base station have this one fixed switching frequency SB.
In its resulting downlink area, the base station gNB1 sends typically system information SIB as shown on
The base station that implement the method of the invention is informed on cell specific signals i.e. SS-blocks and System Information, BCH provisioning of on demand SIB or subset 0 which are provided in the cross-link interference area. Once information provided, only activation or deactivation of the on-demand SIBs or other changes need to be indicated. Signaling constantly the entire signal transmitted in said region is from traffic perspective not a suitable method but information on SIBs, i.e. knowing their content and X-RNTI leads to the situation that only once said information needs to be transferred and only upon changes new content information needs to be provided. When the content remains unchanged only activation and deactivation of SIBs on demand needs to be signaled by the interferer base station to neighboring base stations. Thus, here, gNB 2 knows the timing and additional information of the transmitted SS-block of gNB1 and can eliminate it accordingly in its UL time/frequency grid.
The invention thus allows full flexible usage by the XDD intra-MNO/Intra-frequency overlapping frequency chunks by assigning common cell information preferably to these regions so that the signal can be made known to the neighbor base station once including periodicity and used X-RNTI, i.e. Common Identity. Then it is only needed to provide continuously the information in case when on demand BCH information is activated in said area on which relation to the present SS-blocks, i.e. timing, in said area respectively the subcarriers used.
In the above detailed description, reference is made to the accompanying drawings that show, by way of illustration, 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. The above detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, appropriately interpreted.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21306775.4 | Dec 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/085647 | 12/13/2022 | WO |
