Frequency hopping pattern and arrangement for sounding reference signal

Abstract

A method, an apparatus, and a computer program that includes forming frequency hopping position of the sounding reference signal is based on a hopping pattern. The hopping pattern of the sounding reference signal is configured to utilize a tree assignment for a frequency allocation of the sounding reference signal and to support at least one frequency band branch per layer. The hopping pattern of the sounding reference signal is also configured to provide consecutive sounding reference signals on widely separated frequency allocations.

Description

REFERENCE TO RELATED APPLICATIONS

This application
where:

• n_l,orig is the reference value of allocation index for tree layer l. In other words, it gives the allocation index value for a common reference frame & subframe number+subframe offset from dedicated RRC signaling,

$\begin{array}{cc}{F}_{l,t}=N_l/2\lfloor \frac{t\mathrm{mod}\prod _{l^{\prime }=0}^l{N}_{l^{\prime }}}{\prod _{l^{\prime }=0}^{l-1}{N}_{l^{\prime }}}\rfloor +\lfloor \frac{t\mathrm{mod}\prod _{l^{\prime }=0}^l{N}_{l^{\prime }}}{2\prod _{l^{\prime }=0}^{l-1}{N}_{l^{\prime }}}\rfloor \mathrm{if}{N}_l\mathrm{even};& \left(\mathrm{Eq}.3\right)\end{array}$

$\begin{array}{cc}{F}_{l,t}=\lfloor N_l/2\rfloor \lfloor t/\prod _{l^{\prime }=0}^{l-1}{N}_{l^{\prime }}\rfloor \mathrm{if}{N}_l\mathrm{odd}& \left(\mathrm{Eq}.4\right)\end{array}$

• where N_l is the number new branches per a branch on the assignment tree layer l. For example, on an OVSF code tree, N_l=2.
• t is the time index for the SRS, and is relative on common reference frame & subframe number and it is function of current frame number, subframe number, SRS subframe offset and SRS period. Essentially it is a running index of SRS occurrences relative to a common time reference, obtaining values {0, 1, 2, . . . }. For example, t may be given, e.g, as t=[10×(frame number−reference frame number)+subframe number−reference subframe number−subframe offset]/SRS period.

In one embodiment, F_l,t can be simplified as indicated below:

$\begin{array}{cc}{F}_{l,t}=N_l/2\lfloor \frac{t\mathrm{mod}{2}^{l-1}{N}_l}{2^{l-1}}\rfloor +\lfloor \frac{t\mathrm{mod}{2}^{l-1}{N}_l}{2^l}\rfloor \mathrm{if}{N}_l\mathrm{even}& \left(\mathrm{Eq}.5\right)\end{array}$
F_l,t=└N_l/2┘└t/2^l−1┘  (Eq. 6)
if N_l odd

FIG. 8 illustrates a method 800 for forming a hopping SRS. After calculation of SRS position, UE 120 checks if SRS overlaps the bandwidth not supporting the SRS transmission (i.e., current PUCCH region broadcasted by eNB) in step 810. Typically, UE 120 may perform the truncation autonomously without additional UE 120 specific signalling. The length of the SRS hopping pattern is given by number of branches on the tree layer corresponding to the allocated SRS bandwidth as given below in equation 7.
Π_l=0^LSRSN_l.  (Eq. 7)
Alternatively, frequency hopping may be applied only to some tree layers. As an example, frequency hopping may be applied to tree layers l_min and but may not be applied to tree layers from 0 to l_min−1. As a result, the proposed frequency hopping pattern can be defined by (Eq. 1) where:
F_l,t=0  (Eq. 8)
if l<l_min;
If l is equal to or larger than l_min,

$\begin{array}{cc}{F}_{l.t}=N_l/2\lfloor \frac{t\mathrm{mod}\prod _{l^{\prime }=l_{\min }-1}^l{N}_{l^{\prime }}}{\prod _{l^{\prime }=l_{\min }-1}^{l-1}{N}_{l^{\prime }}}\rfloor +\lfloor \frac{t\mathrm{mod}\prod _{l^{\prime }=l_{\min }-1}^l{N}_{l^{\prime }}}{2\prod _{l^{\prime }=l_{\min }-1}^{l-1}{N}_{l^{\prime }}}\rfloor & \left(\mathrm{Eq}.9\right)\end{array}$

$\begin{array}{cc}{F}_{l,t}=\lfloor N_l/2\rfloor \lfloor t/\prod _{l^{\prime }=l_{\min }-1}^{l-1}{N}_{l^{\prime }}\rfloor \mathrm{if}{N}_l\mathrm{odd}.& \left(\mathrm{Eq}.10\right)\end{array}$
Differing from previous notation, N_lmin−1=1 in (Eq. 9) and (Eq. 10) regardless of the number of new branches on tree layer l_min−1.

Continuing with FIG. 8, if the SRS overlaps, SRS may be truncated towards the maximum allowed SRS BW in step 820. For example, FIG. 7B illustrates an exemplary SRS arrangement 750 with dynamically changing PUCCH region, in which the SRS has been truncated to adjust for the PUCCH region. If truncation is not possible, SRS transmission is dropped in step 830.

Alternatively, eNB 110 may facilitate for PUCCH region changes by broadcasting the SRS tree structure parameters (e.g. number of layers, N_l, and associated SRS bandwidths). When PUCCH region or, alternatively, allowed SRS region changes, the broadcasted SRS tree structure parameters are changed. In another embodiment, at the change of broadcasted SRS tree structure parameters, the existing SRS allocations are autonomously mapped in UE 120 and eNB 110 onto allocations on the current SRS tree according to predefined allocation re-mapping rules. The number of SRS allocations may be reduced in the SRS tree reconfiguration. In that case, certain UEs 120 identified by the predefined allocation re-mapping rules will autonomously stop their SRS transmissions until they receive new UE 120 specific SRS configuration via higher layer signaling. The hopping pattern is always defined according the currently broadcasted SRS tree and, thus, covering the whole SRS region currently allowed. This embodiment allows for reconfiguration of SRS tree with minimal UE 120 specific signaling. It should be appreciated that the presented SRS allocation re-mapping can be applied for SRS allocations with and without frequency hopping.

As a result, the hopping SRS forming method 800 illustrated in FIG. 8 may utilize a tree assignment for SRS frequency allocation and may support multiple frequency band branches per tree layer. Also, the hopping SRS forming method 800 illustrated in FIG. 8 provides consecutive SRS signals on widely separated frequency allocations, thus, maximizing frequency diversity in consecutive CQI measurements. Furthermore, the hopping SRS forming method 800 illustrated in FIG. 8 may prevent frequency hopping SRS from puncturing the PUCCH (persistent PUSCH) region. The hopping SRS forming method 800 illustrated in FIG. 8 may further allow minimization of the signalling burden related to frequency hopping SRS: frequency hopping can be made cell-specific parameter which only requires one bit from the system information block (SIB) message.

It should be appreciated that the SRS may be scheduled with or without frequency hopping. For example, referring to FIG. 1, the selection between frequency hopping and non-hopping SRS may be specific to a cell 101 and is then broadcasted to all of the UEs 120 within the cell 101. Alternatively, the hopping/non-hopping selection may be specific to each UE 120, and may be configured with dedicated radio resource controller (RRC) 111. The separation of frequency hopping and non-hopping SRS is then implemented at the node B 110 (or enhanced node B, eNB). For example, the hopping and non-hopping SRS can be separated with a repetition factor (RPF) comb or with subframe offsets.

For example, as illustrated in FIG. 9, an exemplary transmission block 900 includes frequency hopping SRS and non-hopping SRS that are multiplexed into same SRS symbol (or SC-FDMA symbol) when the period of non-hopping SRS is longer than the one of hopping SRS.

With frequency hopping SRS, multiple SRS periods may potentially cause additional restrictions on the SRS configurations. Typically, all frequency hopping SRS preferably have the same period on each particular SRS symbol and comb combination. For example, 2 ms and 5 ms periods can be used simultaneously for frequency hopping SRS in a cell if they are allocated on different combs.

Similarly, configuration of a one shot SRS is relatively straightforward by adapting previous techniques, whereby the SRS can be configured either with or without frequency hopping.

Referring again to FIG. 1, a cell may include multiple antennas 112 to provide antenna diversity. Transmission antenna diversity can be a closed loop transmission, wherein up-link channel information is fed back from a mobile station. With closed loop antenna selection, the transmitting antennas typically alternate between consecutive SRS transmissions. Similarly, the transmitting antennas would also typically alternate in the case of frequency hopping SRS. However, in order to transmit the same frequency from both antennas, consecutive SRSs are preferably transmitted from the same antenna only once in the same frequency hopping period. For example, the first SRS of the hopping period may be transmitted from the same antenna as the last SRS of the hopping period.

Referring now to FIG. 4, a process flow diagram 400 in accordance with some embodiments is now presented. In particular, the flow diagram 400 illustrates the interaction between a node B 110 and a UE 120. The UE 120 may receive RRC signaling 440, which is SRS configuration signaling. The UE 120 uses data from the RRC signaling 440 to create an uplink message 460 to the node B 110 including a SRS allocated as disclosed herein. The node B 110 may then respond with the UL scheduling grant signaled via DL 470, such as a PDCCH, in reply to the request by the UE 120 in the uplink message 460. In response to the UL scheduling grant in the UL message 460, the UE 120 may forward to the node B 110 UL data transmission 480 for which the link adaptation/scheduling decisions have been performed based on transmitted SRS.

Referring now to FIG. 2, a UE 120 in accordance with certain embodiments is now provided. The UE 120 includes a processor 210 configured to access stored data in a storage device 230 to form an uplink message that includes the SRS. The storage device 230 may store, for example, data related to the DM RS and SRS signals, a desired maximum cyclic shift separation, and details to support a tree-based band assignment. Similarly, the storage device 230 may store data as needed for the processor 220 to determine sufficient bandwidth to reserve for PUCCH and Persistent PUSCH and the corresponding desired DFT and RPF sizes for the SRS band and bandwidth allocation. This information stored in the storage 230 may be provided, for example, by a user interface 210 or is received from an outside source via a receiver 250. The processor 220 may then form the uplink message that includes the SRS on allocated band with allocated bandwidth and forward this uplink message to a transmitter 240 for transmission to an outside device, such as a node B.

As described above, the SRS transmission should not “puncture” the PUCCH region or otherwise attempt to transmit over a RB reserved for the PUCCH. Similarly, it is possible to configure the PUCCH bandwidth-parameter in such a way that the SRS is not overlapping with the (majority of) persistent PUSCH allocations. Accordingly, one embodiment relates to fulfilling this requirement that the SRS transmission should not puncture the PUCCH regions even in cases in which the PUCCH bandwidth (BW), including persistent PUSCH, varies dynamically.

As depicted in FIG. 10, each of the UE 120 in a cell may include a processor 1011, memory 1012, and input and output devices 1013-1014. The source 1010 may further include software 1015 and related hardware 1016 to perform the functions related to forming and transmitting an appropriate SRS message, as disclosed in the some embodiments. For example, the source 120 may receive and store configuration criteria for the SRS to be transmitted, access the memory and form the SRS messages using the stored parameters, and then remove the stored parameters from memory after receiving confirmation that the transmitted SRS message was received by the base station 110. Thus, the processing of the SRS messages to be transmitted may be performed, as needed by circuitry in the hardware 1016 or software 1015.

Likewise, the Node B 110 may include a processor 1021, memory 1022, and input and output devices 1023-1024. The base station (e.g. node 110) may further include software 1025 and related hardware 1026 for performing the functions related to the receiving and decoding of the transmitted SRS signals, as disclosed in the present application. Also, the Node B 110 may include logic in the hardware 1026 or the software 1025 to form a configuration message defining the criteria for the SRS message for a particular node B 110 or for all of the node Bs 110 in a cell.

A computer program embodied on a computer-readable medium, a compute-readable medium encoded with a computer program, or similar language may be embodied as a tangible data storage device storing computer software programs configured to control a processor, digital processing device, central processing unit (CPU), or the like, to perform one or more operations or execute one or more software instructions. A tangible data storage device may be embodied as a volatile memory device or a nonvolatile memory device, and/or a combination of a volatile memory device and a nonvolatile memory device. Accordingly, some of the embodiments provide for a computer-readable medium encoded with a computer program, where the computer program is configured to perform operations.

It should be noted that reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the embodiments described above should be or are in any single embodiment. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment described above. Thus, discussion of the features and advantages, and similar language, throughout this specification may, but do not necessarily, refer to the same embodiment.

Furthermore, the described features, advantages, and characteristics of the invention may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the invention can be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments.

Claims

1. A method, comprising:

forming, by a processor user equipment, a frequency hopping position of the a sounding reference signal based on a hopping pattern;

configuring, at the user equipment, the hopping pattern of the sounding reference signal to utilize a tree assignment for a frequency allocation of the sounding reference signal and to support at least one frequency band branch per layer;

configuring, at the user equipment, the hopping pattern of the sounding reference signal to provide consecutive sounding reference signals on widely separated frequency allocations;

defining, at the user equipment, a frequency-domain starting position for a hopping sounding reference signal based on a similar equation as the sounding reference signal without frequency hopping; and

defining, at the user equipment, the hopping pattern in terms of n_l for tree layers 1 and above:

n_l=F_l,t+n_l,orig mod N_l, where n_l,orig is a reference value of an allocation index for tree layer 1 l,

where N_l is a number of new branches per a branch on an assignment tree layer 1 l, where t is a time index for the sounding reference signal and is relative on a common reference frame and subframe number and is a function of the current frame number, the subframe number and a sounding reference signal period, n_l is the sounding reference signal frequency position index on tree layer 1 l, and F_l,t is a sounding reference signal position.

2. The method according to claim 1, further comprising:

defining a frequency-domain starting position of k₀ by

3. The method according to claim 1, further comprising:

defining F_l,t as

4. The method according to claim 1, further comprising:

defining the frequency hopping of sounding reference signal only for tree layers 1 l_min and above; and

defining the hopping pattern in terms of n_l for tree layers 1 l_min and above:

n_l=F_l,t+n_l,origmod N_l, where n_l,orig is a reference value of an allocation index for tree layer 1 l,

where N_l is a number of new branches per a branch on an assignment tree layer 1 l, where t is a time index for the sounding reference signal and is relative on a common reference frame and subframe number and is a function of the current frame number, the subframe number and a sounding reference signal period.

5. The method according to claim 4, further comprising:

defining F_l,t as F_l,t=0 when 1 l<1 l_min;

defining F_l,t as

6. The method according to claim 1, further comprising:

receiving a selection between the a frequency hopping and the a non-frequency hopping sounding reference signal,

wherein the sounding reference signal is configured with the frequency hopping or without the frequency hopping,

wherein the selection of the frequency hopping and the non-frequency hopping sounding reference signal is specific to a user equipment or to all user equipments within a cell.

7. The method according to claim 1, further comprising:

receiving a radio resource control signal from an apparatus, the radio resource control signal is a sounding reference signal configuration signalling;

transmitting an uplink message to the apparatus including an allocated sounding reference signal based on data in the radio resource control signal.

8. An apparatus, comprising: a processor configured to process frequency hopping position of the sounding reference signal based on a hopping pattern, wherein the hopping pattern of the sounding reference signal is configured to utilize a tree assignment for a frequency allocation of the sounding reference signal and to support at least one frequency band branch per layer, to provide consecutive sounding reference signals on widely separated frequency allocations, to define a frequency-domain starting position for a hopping sounding reference signal based on a similar equation as the sounding reference signal without frequency hopping, and to define the hopping pattern in terms of n_l for tree layers 1 and above: n_l=F_l,t+n_l,origmod N_l, where n_l,orig is a reference value of an allocation index for tree layer l, where N_l is a number of new branches per a branch on an assignment tree layer l, where t is a time index for the sounding reference signal and is relative on a common reference frame and subframe number and is a function of the current frame number, the subframe number and a sounding reference signal period, n_l is the sounding reference signal frequency position index on tree layer l and F_l,t is a sounding reference signal position.

9. The apparatus according to claim 8, wherein the processor is further configured to define a frequency-domain starting position of k₀ by

10. The apparatus according to claim 8, wherein the processor is further configured to

define F_l,t as

11. The apparatus according to claim 8, wherein the processor is further configured to

define the frequency hopping of sounding reference signal only for tree layers l_min and above; and

define the hopping pattern in terms of n_l for tree layers l_min and above:

12. The apparatus according to claim 11, wherein the processor is further configured to

define F_l,t as F_l,t=0 when l<l_min;

define F_l,t as

13. The apparatus according to claim 8, further comprising:

a receiver configured to receive a selection between the frequency hopping and the non-frequency hopping sounding reference signal,

wherein the sounding reference signal is configured with the frequency hopping or without the frequency hopping,

wherein the selection of the frequency hopping and the non-frequency hopping sounding reference signal is specific to a user equipment or to all user equipments within a cell.

14. The apparatus according to claim 8, further comprising:

a receiver configured to receive a receiving a radio resource control signal from another apparatus, the radio resource control signal is a sounding reference signal configuration signalling;

a transmitter configured to transmit an uplink message to the other apparatus including an allocated sounding reference signal based on data in the radio resource control signal.

15. A non-transitory computer-readable medium including a computer program, wherein the computer program is configured to control a processor to perform a method, comprising:

forming a frequency hopping position of the a sounding reference signal based on a hopping pattern;

configuring the hopping pattern of the sounding reference signal to utilize a tree assignment for a frequency allocation of the sounding reference signal and to support at least one frequency band branch per layer;

configuring the hopping pattern of the sounding reference signal to provide consecutive sounding reference signals on widely separated frequency allocations;

defining a frequency-domain starting position for a hopping sounding reference signal based on a similar equation as the sounding reference signal without frequency hopping; and

defining the hopping pattern in terms of n_l for tree layers 1 and above:

n_l=F_l,t+n_l,orig mod N_l, where n_l,orig is a reference value of an allocation index for tree layer 1 l,

where N_l is a number of new branches per a branch on an assignment tree layer 1 l, where t is a time index for the sounding reference signal and is relative on a common reference frame and subframe number and is a function of the current frame number, the subframe number and a sounding reference signal period, n₁ n_l is the sounding reference signal frequency position index on tree layer 1 l and F_l,t is a sounding reference signal position.

16. An apparatus, comprising: forming means for forming a frequency hopping position of the sounding reference signal based on a hopping pattern; configuring means for configuring the hopping pattern of the sounding reference signal to utilize a tree assignment for a frequency allocation of the sounding reference signal, to support at least one frequency band branch per layer, and to provide consecutive sounding reference signals on widely separated frequency allocations; defining means for defining a frequency-domain starting position for a hopping sounding reference signal based on a similar equation as the sounding reference signal without frequency hopping and for defining the hopping pattern in terms of n_l for tree layers 1 and above: n₁=F_l,t+n_l,origmod N_l, where n_l,orig is a reference value of an allocation index for tree layer l, where N_l is a number of new branches per a branch on an assignment tree layer l, where t is a time index for the sounding reference signal and is relative on a common reference frame and subframe number and is a function of the current frame number, the subframe number and a sounding reference signal period, n_l is the sounding reference signal frequency position index on tree layer l and F_l,t is a sounding reference signal position.

17. A method, comprising:

forming, by a processor user equipment, a frequency hopping position of the a sounding reference signal based on a hopping pattern;

configuring, at the user equipment, the hopping pattern of the sounding reference signal to utilize a tree assignment for a frequency allocation of the sounding reference signal and to support at least one frequency band branch per layer;

configuring, at the user equipment, the hopping pattern of the sounding reference signal to provide consecutive sounding reference signals on widely separated frequency allocations;

defining, at the user equipment, a frequency-domain starting position for a hopping sounding reference signal based on a similar equation as the sounding reference signal without frequency hopping;

defining, at the user equipment, the hopping pattern in terms of n_l for tree layers 1 and above:

n_l=F_l,t+n_l,origmod N_l, where n_l,orig is a reference value of an allocation index for tree layer 1 l,

where N_l is a number of new branches per a branch on an assignment tree layer 1 l, where t is a time index for the sounding reference signal and is relative on a common reference frame and subframe number and is a function of the current frame number, the subframe number and a sounding reference signal period, n_l is the sounding reference signal frequency position index on tree layer 1 l, and F_l,t is a sounding reference signal position;

receiving, at the user equipment, a radio resource control signal from an apparatus, the radio resource control signal is a sounding reference signal configuration signalling; and

transmitting, at the user equipment, an uplink message to the apparatus including an allocated sounding reference signal based on data in the radio resource control signal.

18. An apparatus, comprising: a processor configured to process frequency hopping position of the sounding reference signal based on a hopping pattern, wherein the hopping pattern of the sounding reference signal is configured to utilize a tree assignment for a frequency allocation of the sounding reference signal and to support at least one frequency band branch per layer, to provide consecutive sounding reference signals on widely separated frequency allocations, to define a frequency-domain starting position for a hopping sounding reference signal based on a similar equation as the sounding reference signal without frequency hopping, and to define the hopping pattern in terms of n_l for tree layers 1 and above: n₁=F_1,t+n_l,origmod N_l, where n_l,orig is a reference value of an allocation index for tree layer l, where N_l is a number of new branches per a branch on an assignment tree layer l, where t is a time index for the sounding reference signal and is relative on a common reference frame and subframe number and is a function of the current frame number, the subframe number and a sounding reference signal period, n_l is the sounding reference signal frequency position index on tree layer l, and F_l,t is a sounding reference signal position; a receiver configured to receive a receiving a radio resource control signal from another apparatus, the radio resource control signal is a sounding reference signal configuration signalling; and a transmitter configured to transmit an uplink message to the other apparatus including an allocated sounding reference signal based on data in the radio resource control signal.