WO2014089782A1

WO2014089782A1 - Design and signaling for enhanced srs

Info

Publication number: WO2014089782A1
Application number: PCT/CN2012/086453
Authority: WO
Inventors: Erlin Zeng; Pengfei Sun; Shuang TAN
Original assignee: Broadcom Corporation
Priority date: 2012-12-12
Filing date: 2012-12-12
Publication date: 2014-06-19

Abstract

It is provided a method, comprising reserving a first resource element at a predefined first time for transmitting a sounding reference signal; checking if a reservation instruction is received; reserving, based on the reservation instruction, a second resource element at a second time for transmitting the sounding reference signal; and undoing, upon receipt of the reservation instruction, the reserving of the first resource element.

Description

DESIGN AND SIGNALING FOR ENHANCED SRS

Field of the invention The present invention relates in particular but not only to uplink (UL) OFDMA, which is a potential feature targeted on local area scenario in LTE Rel-12. More specifically, this invention is related to an enhanced SRS design and related control signaling which is particularly useful in UL OFDMA. Background of the invention

Abbreviations

3GPP 3^rd Generation Partnership Project

TS Technical Specification

SRS Sounding Reference Signal

eSRS enhanced SRS

LTE™ Long Term Evolution

DCI Downlink Control Information

DFT Discrete Fourier Transformation

DM RS Demodulation RS

HARQ Hybrid Adaptive Repeat and Request

FDMA Frequency Division Multiple Access

OFDMA Orthogonal Frequency Division Multiple Access

PAPR Peak-to-Average Power Ratio

PRB Physical Resource Blocks

PUCCH Physical Uplink Control Channel

PUSCH Physical Uplink Shared Channel

RE Resource Element

RI Rank Indicator

RS Reference Signal

UCI Uplink Control Information

UL Uplink

MCS Modulation and Coding Scheme

CSI Channel State Indicator OCC Orthogonal Cover Code

UE User Equipment

NB NodeB

eNB evolved NB

BW Bandwidth

SF Subframe

UTRA Universal Terrestrial Radio Access

UTRAN UTRA Network

E-UTRA Evolved UTRA

E-UTRAN Evolved UTRAN

SI Study Item

There is a study item proposal for physical layer enhancements in local area scenario [1] .

In LTE Rel-11, SC-FDMA is used for uplink transmission, where the property of low Peak-to-Average Power Ratio (PAPR) needs to be kept in order to fully utilize UE's power amplifier capability. UL OFDMA can be used in local area scenario, where PAPR is no longer a limiting factor. Furthermore, the typical channel fading in local area scenario varies slowly due to low mobility, and it is more flat in the frequency domain compared with the case of macro cell scenario.

In a conventional LTE system (e.g., LTE release 8/9/10/11), the SRS overhead is 6 REs per PRB per port [2] . This means, the SRS signal will occupy every other subcarrier (which if referred to as "Comb" operation) in the entire bandwidth that is assigned to SRS transmission.

Conventionally, SRS and PUSCH multiplexing is as follows: In section 5.3.4 of [2], it is specified that PUSCH will not use the last OFDM symbol in the subframe, if that symbol is used for SRS transmission of the same UE, or is configured in the cell for other UE's possible SRS transmission.

Fig. 1 shows a PRB according to the prior art. In the frequency domain, the PRB comprises 12 subcarriers, and in the time domain, it comprises 1 subframe comprising 2 slots, each having 7 resource elements (RE) on which a symbol may be transmitted. Thus, a PRB comprises 12*2*7 = 168 REs.

As indicated in Fig. 1, the SRS symbols of the SRS signal are transmitted from the UE to the e B in the last RE of the subframe, on every second subcarrier. Once a UE recognizes that the subframe is a SRS subframe on which SRS may be transmitted, it does not transmit PUSCH on the last symbol no matter if there is a SRS transmission. There are 6 REs used for each SRS signal in each PRB. Some related technical aspects are listed here. A new SRS design is desired in release 12 for overhead reduction and more flexibility in resource mapping. SRS design in the current LTE system is related to our new design, but our design is different and is targeted on solving the issues of the current SRS. In [3] it is proposed to use DM RS for sounding. The problem with this design is that it impacts uplink scheduling from a cell perspective, as the scheduler needs to ensure the DM RS sounding for one UE is not interfering another UE that may use the same (or partial same) set of PRBs for PUSCH transmissions. Furthermore, the RS overhead with DM RS pattern-based SRS is still high (i.e., 24 REs per PRB according to current DM RS specification). Furthermore, RS overhead reduction based on such design is difficult, again due to the consideration of multiple user multiplexing in the uplink transmissions.

References

[1] RP-121403 New SI proposal : Small Cell Enhancements for E-UTRA and E- UTRAIM - Physical-layer Aspects

[2] 3GPP TS 36.211, vll.0.0, section 5.5.3

[3] Rl-100263, Channel Sounding Capacity Improvements Summary of the invention

It is an object of the present invention to improve the prior art. In particular, it is an object to reduce the reference signal overhead, thus improving spectrum efficiency in the local area scenario.

According to a first aspect of the invention, there is provided an apparatus, comprising at least one processor, at least one memory including computer program code, and the at least one processor, with the at least one memory and the computer program code, being arranged to cause the apparatus to at least perform: reserving a first resource element at a predefined first time for transmitting a sounding reference signal; checking if a reservation instruction is received; reserving, based on the reservation instruction, a second resource element at a second time for transmitting the sounding reference signal; and undoing, upon receipt of the reservation instruction, the reserving of the first resource element. According to a second aspect of the invention, there is provided an apparatus, comprising first reserving means adapted to reserve a first resource element at a predefined first time for transmitting a sounding reference signal; checking means adapted to check if a reservation instruction is received; second reserving means adapted to reserve, based on the reservation instruction, a second resource element at a second time for transmitting the sounding reference signal; and undoing means adapted to undo, upon receipt of the reservation instruction, the reserving of the first resource element.

According to a third aspect of the inventioin, there is provided a terminal, comprising an apparatus according to any of the first and second aspects, and at least one controller configured to control a transmitting of the sounding reference signal.

According to a fourth aspect of the invention, there is provided an apparatus, comprising at least one processor, at least one memory including computer program code, and the at least one processor, with the at least one memory and the computer program code, being arranged to cause the apparatus to at least perform : receiving a sounding reference signal on a first resource element at a predefined first time; providing a reservation instruction for reserving a second resource element at a second time for transmitting the sounding reference signal; inhibiting the receiving of the sounding reference signal on the first resource element; and receiving the sounding reference signal on the second resource element.

According to a fifth aspect of the invention, there is provided an apparatus, comprising first receiving means adapted to receive a sounding reference signal on a first resource element at a predefined first time; providing measns adapted to provide a reservation instruction for reserving a second resource element at a second time for transmitting the sounding reference signal; inhibiting means adapted to inhibit the receiving of the sounding reference signal on the first resource element; and second receiving means adapted to receive the sounding reference signal on the second resource element. According to a sixth aspect of the invention, there is provided a cell, comprising an apparatus according to any of the fourth and fifth aspects; and at least one controller for controlling a receiving of the sounding reference signal.

According to a seventh aspect of the invention, there is provided a method, comprising reserving a first resource element at a predefined first time for transmitting a sounding reference signal; checking if a reservation instruction is received; reserving, based on the reservation instruction, a second resource element at a second time for transmitting the sounding reference signal; and undoing, upon receipt of the reservation instruction, the reserving of the first resource element.

According to an eighth aspect of the invention, there is provided amethod, comprising : receiving a sounding reference signal on a first resource element at a predefined first time; providing a reservation instruction for reserving a second resource element at a second time for transmitting the sounding reference signal; inhibiting the receiving of the sounding reference signal on the first resource element; and receiving the sounding reference signal on the second resource element. Each of the methods of the seventh and eighth aspects may be a method of controlling a sounding reference signal.

According to a ninth aspect of the invention, there is provided a computer program product comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out the method according to any one of the seventh and eighth aspects. The computer program product may be embodied as a computer-readable medium.

According to some embodiments of the invention, for example at least the following advantages are achieved:

Reference signal overhead is reduced and spectrum efficiency is improved. This advantage may be particularly relevant in the local area scenario. The interference of SRS to PUSCH is addressed and solved. Interference of SRS of different ceils is mitigated.

It is to be understood that any of the above modifications can be applied singly or in combination to the respective aspects to which they refer, unless they are explicitly stated as excluding alternatives.

Brief description of the drawings

Further details, features, objects, and advantages are apparent from the following detailed description of the preferred embodiments of the present invention which is to be taken in conjunction with the appended drawings, wherein

Fig. 1 shows a PRB comprising a SRS signal according to the prior art; Fig. 2 shows a PRB comprising a SRS signal according to an embodiment of the invention;

Fig. 3 shows a number of PRBs in the frequency-time-domain with joint eSRS and D RS transmission according to an embodiment of the invention; Fig. 4 shows a PRB of two different UEs. Left column : according to the prior art; Middle and right columns: according to embodiments of the invention; Fig. 5 shows a time domain multiplexing of eSRS triggering and CSI feedback request according to an embodiment of the invention;

Fig. 6 shows an apparatus according to an embodiment of the invention; Fig. 7 shows a method according to an embodiment of the invention;

Fig. 8 shows an apparatus according to an embodiment of the invention; and

Fig. 9 shows a method according to an embodiment of the invention.

Detailed description of certain embodiments

Herein below, certain embodiments of the present invention are described in detail with reference to the accompanying drawings, wherein the features of the embodiments can be freely combined with each other unless otherwise described. However, it is to be expressly understood that the description of certain embodiments is given for by way of example only, and that it is by no way intended to be understood as limiting the invention to the disclosed details. Moreover, it is to be understood that the apparatus is configured to perform the corresponding method, although in some cases only the apparatus or only the method are described.

The above mentioned high SRS overhead of 6 Res per PRB per port is not efficient in the local area scenario due to the channel properties discussed above. Furthermore, the conventional SRS and PUSCH multiplexing is not efficient in the local area scenario. Taking into account the above channel fading properties of the local area scenario, according to embodiments of the invention the reference signal overhead is reduced further in the local area scenario. Hence, an enhanced SRS design (eSRS) and related signaling is provided.

Based on the eSRS, according to some embodiments of the invention, one or more of the following additional improvements are provided:

• eSRS and DM RS are applied for sounding purpose;

· A signaling is introduced for indicating whether or not PUSCH rate matching around the enhanced SRS REs should take place, to avoid interference between SRS and PUSCH; and

• A signaling design for determination of a SRS trigger without PUSCH transmission from the same UE in the subframe (named enhanced SRS-only uplink transmissions) is provided.

Enhanced SRS (eSRS) according to some embodiments of the invention uses a spare pattern, which has an overhead of N_eSRS REs per PRB per antenna port. The PUSCH transmissions of the same or a different UE are mapped round these N_eSRS REs in the corresponding PRBs. Each of the following parameters of eSRS may be either predefined or configured or adjusted via higher layer signaling or via physical layer signaling :

• N_ eSRS,

- The bandwidth BW_eSRS,

■ The number of antenna port Nport_eSRS, and

■ eSRS resource index of each port.

Namely, according to some embodiments, some of the parameters may be predefined and some may be configured or adjusted.

In local area scenario, the sounding may not require so dense REs as according to the prior art due to the relatively flat channel (slowly varying channel fading). Instead, according to some embodiments or the invention, a more flexible allocation of the SRS signal is provided. In some embodiments of the invention, multiple cells may coordinate their SRS allocation to manage inter-cell interference. For example, one cell A may share its own eSRS parameters to a neighboring cell B, which makes it possible for the neighboring cell B to avoid creating interference to the corresponding eSRS resources in cell A. Or with such assistant information, cell B may schedule its own eSRS resources differently to avoid interference from cell A.

Fig. 2 shows a PRB according to an embodiment of the invention. More in detail, in Fig. 2, an eSRS resource allocation according to an embodiment of the invention is illustrated. The resources of one cell (cell 1) are marked in slant lines, the resources of another cell (cell 2) are marked in vertical lines. The resources of eSRS for the two cells are separated in the time and frequency domain. Compared to the prior art, the separation may be achieved more easily because the eSRS design is not restricted to the last symbol, in particular if OFDMA is introduced, which has no restriction of the single carrier property. Thus, the interference between eSRS of the two cells is easily reduced.

In addition, the eSRS according to some embodiments of the invention allows flexible resource allocation. Thus, cell 2 could configure more resources than cell 1 due to heavier sounding demand. This flexibility reduces the unnecessary waste of resources due to the conventional SRS.

According to some embodiments of the invention, rules to enable using joint eSRS and DMRS transmission for sounding purpose are defined. The rules may allow muting eSRS in the frequency resources where DMRS is transmitted to benefit from dense reference signals of DMRS and reducing eSRS overhead.

Since eSRS is not restricted to the last symbol of a subframe, eNB may be supposed to perform sounding in any symbol of the subframe. If the UE may has simultaneous PUSCH and eSRS transmission, the DM RS, which is used at the base station for demodulating PUSCH, provides a much more dense reference signal than the eSRS, which is better for sounding purpose. Accordingly, according to some embodiments of the invention, eNB implicitly or explicitly controls the UE to mute the eSRS at all subcarriers which comprise a PRB where DM RS is transmitted.

Fig. 3 shows how the sounding is performed based on combined DM RS and eSRS according to an embodiment of the invention. Note that each square in Fig. 3 indicates a PRB instead of a RE. Thus, the bandwidth difference of PUSCH and configured eSRS BW is shown. Namely, the bandwidth of eSRS may be larger than that of DM RS, which has the same bandwidth as the PUSCH. On the subcarriers that are allocated for PUSCH with DM RS (marked with vertical lines), the eSRS will not be transmitted. These "muted" PRBs are marked with horizontal lines. The REs of the corresponding PRBs may be used for PUSCH transmission. At a frequency outside of the PUSCH transmission, eSRS (marked in black) is transmitted. Note that eSRS and DM RS may be transmitted at different times. In the embodiment of Fig. 3, eSRS is transmitted 1 PRB prior to DM RS.

UE may evaluate on its own, based on predefined rules, whether or not to mute the eSRS, or it may receive a corresponding signaling from eNB. Such a predefined rule may be e.g. if a subcarrier is allocated to PUSCH, it is checked if eSRS is allocated to a PRB comprising this subcarrier. If yes, eSRS is muted in this PRB. Otherwise, eSRS is transmitted in the PRB.

According to some embodiments of the invention, a new indication field (e.g. "fl") is provided to the uplink grant DCI to indicate whether the PUSCH needs to be rate matched around a set of eSRS resources.

The defined set S_eSRS of eSRS resources shall typically contain all the eSRS resources used by all the UEs in the cell in a given time period. For different uplink subframes, the set S„eSRS can be configured to be the same or to be different.

In some embodiments of the invention, the new field has one bit. Exemp!arily, it is defined so that: - If fl = 0, PUSCH shall not rate match around any allocated eSRS resources within S_eSRS, even if the scheduled PRB set of PUSCH overlaps or partially overlaps with S_eSRS.

- If fl = 1, PUSCH shall rate match around eSRS if there is any overlapping between scheduled PRB set and S_eSRS.

With such signaling, the network can decide not to trigger any eSRS in a uplink subframe, and thus all the resources can be used by PUSCH for better spectrum efficiency. This is in particular advantageous if the S_eSRS resources are configured via higher layer signaling.

For the multiplexing of eSRS and PUSCH of the same user in the uplink subframe, explicit eSRS triggering filed can be added to the uplink grant DCI format. In this case, as UE is aware of the planned transmission of its own eSRS, even in case fl = 0, UE may still at least rate match its own PUSCH transmissions around the assigned eSRS resources.

Fig. 4 illustrates the difference of the eSRS resource allocation according to some embodiments of the invention to that of conventional SRS resource allocation considering the PUSCH transmission. Each of the blocks shows a PRB with its 168 REs, represented as squares.

On the top of the left column, the resource utilization of a UE#A that transmits PUSCH (white squares) with the corresponding DM RS (squares marked with slant lines) and with conventional SRS (black squares) is shown. At the bottom of the left column, resource utilization of another UE#B transmitting PUSCH only is demonstrated. As it is shown by the squares with cross marks at the end of each subframe, many resources are wasted due to the legacy SRS design. This waste is significantly reduced by the eSRS design according to some embodiments of the invention. As shown on top of the middle column, UE #A transmitting eSRS does not waste any resources in the frequency (subcarrier) with PUSCH and eSRS transmission. On the bottom of the middle column, resource utilization of UE#B is shown. UE #B avoids using the configured eSRS resource because another UE (UE #A) is transmitting eSRS on that resource (indicated to UE#B by signaling fl = l from the network).

On the bottom of the right column, resource utilization of UE#C is shown. Via the indication of fl=0, UE#C knows that no other UE is transmitting eSRS. Hence, UE #C uses the eSRS resources for PUSCH transmission. In each of the resource utilizations shown in Fig. 4, instead of PUSCH, PUCCH may be transmitted in some or all of the corresponding REs.

In summary, the eSRS signaling design according to some embodiments of the invention allows a much higher spectrum efficiency by reducing the wasted RE of legacy SRS design. Namely, the signaling allows UEs, either with eSRS transmission (UE#A) or without eSRS transmission (UE #B, UE #C) but whose PUSCH overlaps the configured eSRS BW, to maximize the utilization of resources. According to some embodiments of the invention, in the uplink grant DCI format it is foreseen to indicate that a specific grant is to schedule an enhanced SRS- only PUSCH which comprises eSRS only. In this case, no uplink data or uplink control information will be transmitted in the subframe, and the spare DCI bits such as resource allocation field can be used to indicate resources for SRS . In this way, the eSRS parameters are adjusted by physical layer signaling dynamically, which is more flexible compared with higher layer signaling.

The indication may be explicit by one or more bit(s) dedicated to the indication and/or by using one or multiple predefined combinations of MCS field and CSI request field. One example of using a predefined combination of MCS and CSI request field is the following : In a current DCI format, there are 5 bits MCS field I_MCS and 2 bits CSI request field I_CSI. In the example, if I_MCS = 29 and I_CSI = 0, UE determines that in the subframe there is no data or aperiodic CSI to transmit. If eSRS-only trigger is determined, some fields (e.g. those related to data transmission and aperiodic CSI transmission; hereinafter in general called spare fields) are not required. According to some embodiment of the invention, the spare field(s) such as resource allocation filed, cyclic shift for DM RS and OCC index are used to adjust eSRS parameters.

For example, for the case of uplink bandwidth of 20Mhz (100 PRBs) the resource allocation field is 13 bits, and the DM RS and OCC index field is 3 bits. One simple example of eSRS resource scheduling is to reuse the resource allocation filed to adjust the PRBs to transmit eSRS, and use the DM RS and OCC index filed to indicate one out of 4 combinations of predefined !M_eSRS and Nport_SRS.

In the local area scenario, the channel fading changes slowly, so neither eSRS nor CSI feedback needs to be transmitted frequently. In this case, it is possible that network uses proper scheduling to multiplex eSRS triggering and CSI request in the time domain.

One example of such time multiplexing according to embodiments of the invention is shown in Figure 5. The boxes in Figure 5 are subframes. In the example, there are 10 subframes in the radio frame. In this example, UE receives a request to transmit PUSCH and CSI feedback in UL subframe #7 from the special subframe #1, and requires to transmit eSRS in UL subframe #8 from the DL subframe #4. If eSRS is triggered in this way, eSRS and PUSCH/CSI may not be multiplexed in the same UL subframe.

Fig, 6 shows an apparatus according to an embodiment of the invention. The apparatus may be a terminal such as a UE or a part thereo. Fig. 7 shows a method according to an embodiment of the invention. The apparatus according to Fig. 6 may perform the method of Fig. 7 but is not limited to this method. The method of Fig. 7 may be performed by the apparatus of Fig. 6 but is not limited to being performed by this apparatus. The apparatus comprises at least one processor 10 and at least one memory 20. The at least one memory 20 includes computer program code, and the at least one processor 10, with the at least one memory 20 and the computer program code is arranged to cause the apparatus to reserve (S10) a first resource element at a predefined first time for transmitting a sounding reference signal. For example, as according to conventional LTE specifications, the last resource element of a subframe may be reserved for SRS transmission.

In step S20, the apparatus checks if a reservation instruction is received. This means, that eSRS resource utilization should be applied.

Based on the receipt of the reservation instruction, a second resource element is reserved (S30) for transmitting the sounding reference signal. This second resource element is at a second time, which may be different from the predefined first time. Also, upon receipt of the reservation instruction, the reserving of the first resource element is undone (S40). That is, the first resource element may be used for other purposes than SRS transmission such as PUSCH transmission. Steps S30 and S40 may be performed simultaneously or in an arbitrary sequence.

Fig. 8 shows an apparatus according to an embodiment of the invention. The apparatus may be a base station such as a NodeB or eNodeB or a part thereof. Fig. 9 shows a method according to an embodiment of the invention. The apparatus according to Fig. 8 may perform the method of Fig. 9 but is not limited to this method. The method of Fig. 9 may be performed by the apparatus of Fig. 8 but is not limited to being performed by this apparatus.

The apparatus comprises at least one processor 110 and at least one memory 120. The at least one memory 120 includes computer program code, and the at least one processor 110, with the at least one memory 120 and the computer program code is arranged to cause the apparatus to receive (S110) a sounding reference signal on a first resource element at a predefined first time. For example, as according to conventional LTE specifications, the last resource element of a subframe may be reserved for SRS reception. According to step S120, the apparatus provides a reservation instruction for reserving a second resource element at a second time for transmitting the sounding reference signal. This means, that eSRS resource utilization should be applied. The second time may be different from the predefined first time.

Then, according to step S130, the apparatus inhibits the receiving of the sounding reference signal on the first resource element and, according to step S140, receives the sounding reference signal on the second resource element. Steps S130 and S140 may be performed simultaneously or in an arbitrary sequence.

Embodiments of the invention are described with respect to a local area scenario. However, embodiments of the invention may be employed in other scenarios, too, in particular where a lower density of SRS symbols is acceptable.

Embodiments of the invention are described with respect to OFDMA. However, embodiments of the invention do not require OFDMA, in particular if a lower density of SRS symbols is acceptable. For example, embodiments of the invention may be employed in a FDMA local area scenario.

Embodiments of the invention are described based on an LTE system but embodiments of the invention may be applied to other radio access technologies such as LTE-A, WiFi, WLAN, UMTS, HSPA, if sounding reference signals may be employed. Even more, embodiments of the invention may be employed in wireline transmission systems, too, if sounding reference signals may be used.

A terminal may be a machine type device, a user equipment, a mobile phone, a laptop, a smartphone, a tablet PC, or any other device that may attach to a mobile network. A base station may be a NodeB, an eNodeB or any other base station of a radio network.

If not otherwise stated or otherwise made clear from the context, the statement that two entities are different means that they are differently addressed in their respective network. It does not necessarily mean that they are based on different hardware. That is, each of the entities described in the present description may be based on a different hardware, or some or all of the entities may be based on the same hardware.

According to the above description, it should thus be apparent that exemplary embodiments of the present invention provide, for example a receiver such as an iterative receiver, or a component thereof, an apparatus such as a terminal or a base station embodying the same, a method for controlling and/or operating the same, and computer program(s) controlling and/or operating the same as well as mediums carrying such computer program(s) and forming computer program product(s).

According to exemplarily embodiments of the present invention, a system may comprise any conceivable combination of the thus depicted devices/apparatuses and other network elements, which are configured to cooperate with any one of them.

In general, it is to be noted that respective functional blocks or elements according to above-described aspects can be implemented by any known means, either in hardware and/or software/firmware, respectively, if it is only adapted to perform the described functions of the respective parts. The mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device.

Generally, any structural means such as a processor or other circuitry may refer to one or more of the following : (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) combinations of circuits and software (and/or firmware), such as (as applicable): (i) a combination of processor(s) or (ii) portions of processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present. Also, it may also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware, any integrated circuit, or the like.

Generally, any procedural step or functionality is suitable to be implemented as software/firmware or by hardware without changing the idea of the present invention. Such software may be software code independent and can be specified using any known or future developed programming language, such as e.g. Java, C++, C, and Assembler, as long as the functionality defined by the method steps is preserved. Such hardware may be hardware type independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconductor), CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL (Transistor-Transistor Logic), etc., using for example ASIC (Application Specific IC (Integrated Circuit)) components, FPGA (Field-programmable Gate Arrays) components, CPLD (Complex Programmable Logic Device) components or DSP (Digital Signal Processor) components. A device/apparatus may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device/apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor. A device may be regarded as a device/apparatus or as an assembly of more than one device/apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for example. Apparatuses and/or means or parts thereof can be implemented as individual devices, but this does not exclude that they may be implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved. Such and similar principles are to be considered as known to a skilled person. Software in the sense of the present description comprises software code as such comprising code means or portions or a computer program or a computer program product for performing the respective functions, as well as software (or a computer program or a computer program product) embodied on a tangible medium such as a computer-readable (storage) medium having stored thereon a respective data structure or code means/portions or embodied in a signal or in a chip, potentially during processing thereof.

The present invention also covers any conceivable combination of method steps and operations described above, and any conceivable combination of nodes, apparatuses, modules or elements described above, as long as the above- described concepts of methodology and structural arrangement are applicable.

It is to be understood that what is described above is what is presently considered the preferred embodiments of the present invention. However, it should be noted that the description of the preferred embodiments is given by way of example only and that various modifications may be made without departing from the scope of the invention as defined by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. An apparatus, comprising

at least one processor,

at least one memory including computer program code, and

the at least one processor, with the at least one memory and the computer program code, being arranged to cause the apparatus to at least perform :

reserving a first resource element at a predefined first time for transmitting a sounding reference signal;

checking if a reservation instruction is received;

reserving, based on the reservation instruction, a second resource element at a second time for transmitting the sounding reference signal; and

undoing, upon receipt of the reservation instruction, the reserving of the first resource element.

2. The apparatus according to claim 1, wherein the predefined first time is a last symbol of a subframe.

3. The apparatus according to any of claims 1 to 2, wherein the at least one processor is additionally arranged to perform:

checking if an undoing instruction is received;

undoing the reserving of the second resource element upon receipt of the undoing ^"instruction.

4. The apparatus according to any of claims 1 to 3, wherein the at least one processor is additionally arranged to perform :

checking if a demodulation reference signal is transmitted in a physical resource block comprising a subcarrier of the second resource element; and

undoing the reserving of the second resource element if the demodulation reference signal is transmitted in the physical resource block.

5. The apparatus according to any of claims 1 to 4, wherein the at least one processor is additionally arranged to perform : determining if a physical resource block scheduled for an uplink shared channel overlaps with the second resource element; and

rate matching an uplink signal to be transmitted on the uplink shared channel such that the uplink signal is not transmitted on the second resource element.

6. The apparatus according to claim 5, wherein the at least one processor is additionally arranged to perform:

checking if a rate matching denial instruction is received; and

adapting or inhibiting the rate matching upon receipt of the rate matching denial instruction such that the uplink signal is transmitted on the second resource element; and

inhibiting transmitting the sounding reference signal on the second resource element.

7. The apparatus according to claim 6, wherein the at least one processor is additionally arranged to perform :

checking if a rate matching instruction is received;

rate matching the uplink signal upon receipt of the rate matching denial instruction such that the uplink signal is not transmitted on the second resource element; and

neglecting the inhibiting of the transmitting of the sounding reference signal on the second resource element.

8. The apparatus according to any of claims 1 to 7, wherein the at least one processor is additionally arranged to perform :

checking if an oniy-indication is received in a grant of an uplink subframe; inhibiting, upon receipt of the only-indication, to transmit at least one of data and a channel state indicator in the uplink subframe;

evaluating the grant for adjustment information for transmitting the sounding reference signal;

reserving a third resource element for the transmitting of the sounding reference signal based on the adjustment information.

9. The apparatus according to claim 8, wherein the at least one processor is additionally arranged to perform:

evaluating a modulation and coding scheme field and a channel state information field of the received grant;

deciding if the modulation and coding scheme field and the channel state information field have a predetermined value combination; wherein

it is positively checked that the only-indication is received if the modulation and coding scheme field and the channel state information field have the predetermined value combination.

10. A terminal, comprising

an apparatus according to any of claims 1 to 9, and

at least one controller configured to control a transmitting of the sounding reference signal.

11. An apparatus, comprising

at least one processor,

at least one memory including computer program code, and

receiving a sounding reference signal on a first resource element at a predefined first time;

providing a reservation instruction for reserving a second resource element at a second time for transmitting the sounding reference signal;

inhibiting the receiving of the sounding reference signal on the first resource element; and

receiving the sounding reference signal on the second resource element.

12. The apparatus according to claim 11, wherein the predefined first time is a last symbol of a subframe.

13. The apparatus according to any of claims 11 to 12, wherein the at least one processor is additionally arranged to perform : coordinating with a base station device such that the second resource element is separated from a foreign resource element in at least one of a frequency and a time, wherein the foreign resource element is indicated by the base station device to be reserved for transmitting a sounding reference signal to the base station device.

14. The apparatus according to any of claims 11 to 131, wherein the at least one processor is additionally arranged to perform :

providing an undoing instruction for undoing the reserving of the second resource element;

inhibiting the receiving of the sounding reference signal on the second resource element.

15. The apparatus according to any of claims 11 to 141, wherein the at least one processor is additionally arranged to perform:

inhibiting the receiving of the sounding reference signal on the second resource element if the demodulation reference signal is transmitted in the physical resource block.

16. The apparatus according to any of claims 11 to 15, wherein the at least one processor is additionally arranged to perform:

determining if a physical resource block scheduled for an uplink shared channel overlaps with the second resource element; and

demodulating an uplink signal received on the uplink shared channel taking into account that the received uplink signal is rate-matched such that the uplink signal is not transmitted on the second resource element.

17. The apparatus according to claim 16, wherein the at least one processor is additionally arranged to perform:

providing a rate matching denial instruction for denying rate matching of the uplink signal around the second resource element;

18. The apparatus according to claim 17, wherein the at least one processor is additionally arranged to perform :

providing, to a user equipment, a rate matching instruction for rate matching of the uplink signal around the second resource element;

triggering the user element to transmit the sounding reference signal on the second resource element.

19. The apparatus according to any of claims 11 to 18, wherein the at least one processor is additionally arranged to perform :

providing an only-indication in a grant of an uplink subframe;

inhibiting receiving at least one of data and a channel state indicator in the uplink subframe;

providing an adjustment information for transmitting the sounding reference signal in the grant;

receiving the sounding reference signal in a third resource element corresponding to the adjustment information.

20. The apparatus according to claim 19, wherein the at least one processor is additionally arranged to perform :

providing the only-indication by setting a predetermined value combination of the modulation and coding scheme field and the channel state information field in the grant.

21. Cell, comprising

an apparatus according to any of claims 11 to 20; and

at least one controller for controlling a receiving of the sounding reference signal.

22. A method, comprising:

checking if a reservation instruction is received; reserving, based on the reservation instruction, a second resource element at a second time for transmitting the sounding reference signal; and

23. The method according to claim 22, wherein the predefined first time is a last symbol of a subframe.

24. The method according to any of claims 22 to 23, additionally comprising : checking if an undoing instruction is received;

undoing the reserving of the second resource element upon receipt of the undoing instruction.

25. The method according to any of claims 22 to 24, additionally comprising : checking if a demodulation reference signal is transmitted in a physical resource block comprising a subcarrier of the second resource element; and

26. The method according to any of claims 22 to 25, additionally comprising : determining if a physical resource block scheduled for an uplink shared channel overlaps with the second resource element; and

27. The method according to claim 26, additionally comprising:

checking if a rate matching denial instruction is received; and

28. The method according to claim 27, additionally comprising :

checking if a rate matching instruction is received;

29. The method according to any of claims 22 to 28, additionally comprising : checking if an only-indication is received in a grant of an uplink subframe; inhibiting, upon receipt of the only-indication, to transmit at least one of data and a channel state indicator in the uplink subframe;

30. The method according to claim 29, additionally comprising :

31. A method, comprising :

receiving the sounding reference signal on the second resource element.

32. The method according to claim 31, wherein the predefined first time is a last symbol of a subframe.

33. The method according to any of claims 31 to 32, additionally comprising: coordinating with a base station device such that the second resource element is separated from a foreign resource element in at least one of a frequency and a time, wherein the foreign resource element is indicated by the base station device to be reserved for transmitting a sounding reference signal to the base station device.

34. The method according to any of claims 31 to 33, additionally comprising : providing an undoing instruction for undoing the reserving of the second resource element;

35. The method according to any of claims 31 to 34, additionally comprising : checking if a demodulation reference signal is transmitted in a physical resource block comprising a subcarrier of the second resource element; and

36. The method according to any of claims 31 to 35, additionally comprising: determining if a physical resource block scheduled for an uplink shared channel overlaps with the second resource element; and

37. The method according to claim 36, additionally comprising:

providing a rate matching denial instruction for denying rate matching of the uplink signal around the second resource element; inhibiting transmitting the sounding reference signal on the second resource element.

38. The method according to claim 37, additionally comprising :

39. The method according to any of claims 31 to 38, additionally comprising : providing an only-indication in a grant of an uplink subframe;

40. The method according to claim 39, additionally comprising :

41. A computer program product comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out the method according to any one of method claims 22 to 40.

42. The computer program product according to claim 41, embodied as a computer-readable medium.