Transmission of uplink sounding reference signal

Abstract

Provided are methods for transmission of a sounding reference signal (srs) being independent of or separated from an uplink channel. The method may include receiving ue-specific configuration information including an uplink reference signal identity from the first transmission/reception point, determining the second transmission/reception point indicated by the uplink reference signal identity included in the received ue-specific configuration information as an uplink channel reception entity, transmitting the uplink channel to the determined second transmission/reception point, using the uplink reference signal identity, generating an srs, using the physical cell identity of the first transmission/reception point, determining the first transmission/reception point as an srs reception entity, and transmitting the generated srs to the determined first transmission/reception point indicated by the physical cell identity.

Description

CROSS REFERENCE TO PRIOR APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2012-0062278 (filed on Jun. 11, 2012), Korean Patent Application No. 10-2012-0096443 (filed on Aug. 31, 2012), and Korean Patent Application No. 10-2012-0141262 (filed on Dec. 6, 2012), which are hereby incorporated by reference in their entirety.

BACKGROUND

The present an exemplaryinventioninventioninventioninventionan exemplaryinventionEmbodiment 1
r_u,v^{(α{tilde over (p)})}(n)=e^{jα{tilde over (p)}n}r_u,v(n)  [Formula 2]

where, r_u,v^{(α{tilde over (p)})}(n) denotes a reference signal (RS) sequence, α_{{tilde over (p)}} denotes a cyclic shift (CS), r_u,v(n) denotes a base sequence, 0≤n<M_sc^RS, M_sc^RS=mN_sc^RB, 1≤m≤N_RB^{max, UL}, and M_sc^RS is the number of subcarriers assigned for UL RS sequence in the frequency domain.

Base sequences may be differently generated according to the sequence group number u, the base sequence number v within the group, and a sequence length n.

In a sequence group hopping, 30 sequence groups may be hopped per slot regardless of the number of resource blocks (RBs) assigned to user equipment.

More specifically, the sequence group number u in slot n_s may be defined by a group hopping pattern f_gh(n_s) and a sequence-shift pattern f_ss, according to Formula 3 below.
u=(f_gh(n_s)+f_ss)mod 30  [Formula 3]

The sequence group hopping pattern f_gh(n_s) may be the same for PUCCH and PUSCH. However, the sequence-shift pattern f_ss may be different for PUCCH and PUSCH.

The group-hopping pattern f_gh(n_s) may be given by Formula 4 below for PUSCH and PUCCH.

$\begin{array}{cc}{f}_{\mathrm{gh}}\left(n_s\right)=\{\begin{array}{cc}0& \mathrm{if}\mathrm{group}\mathrm{hopping}\mathrm{is}\mathrm{disabled}\\ \left(\sum _{i=0}^{7}c\left(8n_s+i\right)·2^i\right)\mathrm{mod}30& \mathrm{if}\mathrm{group}\mathrm{hopping}\mathrm{is}\mathrm{enabled}\end{array}& \left[\mathrm{Formula}4\right]\end{array}$

In Formula 4, c(i) denotes a pseudo-random sequence. When user equipment 120 receives n_ID^SRS for an SRS transmission from eNB 110, the pseudo-random sequence c(i) may be initialized using a UE-specific parameter n_ID^SRS_ID in each radio frame. More specifically, the pseudo-random sequence may be initialized with

$c_{\mathrm{init}}=\lfloor \frac{n_{\mathrm{ID}}^{\mathrm{SRS}}}{30}\rfloor .$

Definition of the sequence-shift pattern f_ss may be different between PUCCH, PUSCH and SRS. For an SRS, the sequence-shift pattern f_ss^SRS may be given by f_ss^SRS=n_ID^SRS mod 30.

Sequence hopping may be applied for reference signals of length 6 RBs or larger (M_sc^RS≥6N_sc^RB). For reference-signals of length less than 6 RBs (M_sc^RS<6N_sc^RB), the base sequence number v within the base sequence group may be given by v=0.

For reference-signals of length 6 RBs or larger (M_sc^RS6N_sc^RB), the base sequence number v within the base sequence group in slot n_s may be defined by Formula 5 below.

$\begin{array}{cc}v=\{\begin{array}{cc}c\left(n_s\right)& \begin{array}{c}\mathrm{if}\mathrm{group}\mathrm{hopping}\mathrm{is}\mathrm{disabled}\\ \mathrm{and}\mathrm{sequence}\mathrm{hopping}\mathrm{is}\mathrm{enabled}\end{array}\\ 0& \mathrm{otherwise}\end{array}& \left[\mathrm{Formula}5\right]\end{array}$

In Formula 5, c(i) denotes a pseudo-random sequence. The pseudo-random sequence may be initialized with

$c_{\mathrm{init}}=\lfloor \frac{n_{\mathrm{ID}}^{\mathrm{SRS}}}{30}\rfloor ·2^5+\left(n_{\mathrm{ID}}^{\mathrm{SRS}}+{\Delta }_{\mathrm{ss}}\right)\mathrm{mod}30$
in each radio frame.

The cyclic shift α_{{tilde over (p)}} may be differently generated for each user equipment and for each antenna port, according to Formula 6 below.

$\begin{array}{cc}{\alpha }_{\tilde{p}}=2\pi \frac{n_{\mathrm{SRS}}^{\mathrm{cs},\tilde{p}}}{8}& \left[\mathrm{Formula}6\right]\end{array}$ $n_{\mathrm{SRS}}^{\mathrm{cs},\tilde{p}}=\left(n_{\mathrm{SRS}}^{\mathrm{cs}}+\frac{8\tilde{p}}{N_{\mathrm{ap}}}\right)\mathrm{mod}8$ $\tilde{p}\in \left\{0,1,\dots ,N_{\mathrm{ap}}-1\right\}$

In Formula 6, n_SRS^CS used to calculate the cyclic shift α_{{tilde over (p)}} a may be transmitted by higher-layer signaling (e.g., RRC). For example, in case of n_SRS^CS, a total of 8 values (e.g., n_SRS^CS={0, 1, 2, 3, 4, 5, 6, 7}) for each user equipment may be transmitted. Cyclic shift α_{{tilde over (p)}} for each antenna port may be determined based on the transmitted n_SRS^CS as described in Formula 6. {tilde over (p)} denotes an antenna port number index, and N_ap denotes the number of antenna ports used for an SRS transmission.

An SRS sequence may be generated according to Formula 1 using the base sequence of Formula 2 and the cyclic shift (CS) α_{{tilde over (p)}} of Formula 6. Such SRS sequence generation procedure may be performed in OFDM modulator 2010 shown in FIG. 20. At step S430, user equipment 120 may assign radio resources for SRS transmission, and transmit the generated SRS (e.g., an SRS generated at step S420) through the assigned radio resources, to a transmission/reception point (e.g., RRH 112) indicated by n_ID^SRS.

A UE-specific parameter indicating an uplink reference signal identity may indicate the same reference signal identity for a periodic SRS and an aperiodic SRS.

In this case, sequence group numbers and base sequence numbers for the periodic SRS and the aperiodic SRS may be determined as the same value. However, the sequence group numbers and the base sequence numbers for the periodic or aperiodic SRS may be determined independently from a sequence group number and a base sequence number for PUCCH and PUSCH.

That is, an SRS sequence may be determined independently from PUCCH and PUSCH. Accordingly, a TDD system may independently measure a downlink channel quality of a serving transmission/reception point and a downlink channel quality of a different transmission/reception point. Herein, the TDD system may use an uplink channel quality measurement and a channel reciprocity for the serving transmission/reception point and the different transmission/reception point. Furthermore, the SRS transmission method may allow for recognition of a location or a geometry of user equipment, using an SRS. Accordingly, in the case that the user equipment is located on edge of a cell or at the center of the cell, it may be possible to improve data throughput for a downlink by using a UE-specific downlink transmission method.

Meanwhile, sequence group numbers and base sequence numbers used for a periodic SRS and an periodic SRS may be assigned independently from each other, through RRC parameters. In at least one embodiment, indication information for corresponding base sequence numbers and sequence group numbers may be included in PDCCH transmitted dynamically. Alternatively, base sequence numbers and sequence group numbers used for a periodic SRS and an periodic SRS may be dynamically indicated through a RRC parameter (e.g., a parameter having a length of 1 bit) predefined by RRC signaling.

Accordingly, an SRS sequence may be generated independently from PUCCH and PUSCH. Furthermore, user equipment may transmit an SRS to a serving transmission/reception point or a different transmission/reception point. Therefore, a transmission/reception point (e.g., a base station) received the SRS may flexibly perform a scheduling procedure.

For a periodic SRS and an aperiodic SRS, a transmission to a serving transmission/reception point and a transmission to a different transmission/reception point (i.e., a transmission/reception point other than the serving transmission/reception point) may be independently performed.

In an SRS transmission method, a UE-specific parameter indicating an SRS identity may indicate different reference signal identities for a periodic SRS and an aperiodic SRS.

In this case, a sequence group number and a base sequence number for the periodic SRS may be determined independently form a sequence group number and a base sequence numbers for the aperiodic SRS. Furthermore, the sequence group numbers and the base sequence numbers for the periodic and aperiodic SRSs may be determined independently from a sequence group number and a base sequence number for PUCCH and PUSCH.

For example, in Formula 1 to Formula 6, an SRS may be generated using a periodic SRS identity n_ID^SRS, and the generated SRS may be transmitted to a transmission/reception point indicated by the periodic SRS identity n_ID^SRS. Meanwhile, an SRS may be generated using an aperiodic SRS identity n_ID^SRS′ being independent of a periodic SRS identity n_ID^SRS. The generated SRS may be transmitted to a transmission/reception point indicated by the aperiodic SRS identity n n_ID^SRS′. Herein, the periodic SRS identity n_ID^SRS and the aperiodic SRS identity n_ID^SRS′ may independently indicate a corresponding transmission/reception point for SRS transmission. Furthermore, the periodic SRS identity n_ID^SRS and/or the aperiodic SRS identity n_ID^SRS′ may not necessarily indicate a serving transmission/reception point. Accordingly, the periodic SRS identity n_ID^SRS and/or the aperiodic SRS identity n_ID^SRS′ may indicate a certain transmission/reception points (e.g., eNB 110) other than the serving transmission/reception point.

That is, an SRS sequence may be determined independently from PUCCH and PUSCH. Furthermore, sequences for a periodic SRS and an aperiodic SRS may be independently determined from each other. Accordingly, a TDD system may independently measure a downlink channel quality of a serving transmission/reception point and a downlink channel quality of a different transmission/reception point. Herein, the TDD system may use an uplink channel quality measurement and a channel reciprocity for the serving transmission/reception point and the different transmission/reception point.

Furthermore, the SRS transmission method may allow for recognition of a location or a geometry of user equipment, using an SRS. Accordingly, in the case that user equipment is located on edge of a cell or at the center of the cell, it may be possible to improve data throughput for a downlink by using a UE-specific downlink transmission method.

FIG. 21 illustrates a position of a symbol carrying an SRS. FIG. 22 illustrates a non-frequency hopping SRS and a frequency hopping SRS.

Referring to FIG. 21 and FIG. 22, an SRS may be transmitted by the last symbol of a subframe. In the frequency domain, SRS transmissions should cover the frequency band that is of interest for a frequency-domain scheduling. As illustrated in FIG. 22(a), a sufficiently wideband SRS transmission may be performed such that channel quality of an entire frequency band of interest can be estimated with a single SRS transmission. As illustrated in FIG. 22(b), a sequence of SRS transmissions may jointly cover the entire frequency band of interest, by transmitting a narrowband SRS using hopping in the frequency domain.

As described above, when an SRS is mapped to resource elements, SC-FDMA symbols may be generated by a SC-FDMA generator (not shown in FIG. 20). SRS signals corresponding to the generated SC-FDMA symbols may be transmitted to a corresponding transmission/reception point.

Specific subframes carrying SRSs may be periodically or aperiodically determined. For example, “cell-specific sub-frames for SRS transmission” (hereinafter, referred to as “cell-specific SRS subframes”) may be configured or defined as shown in Table Embodiment 1inventioninventioninvention disclosure. Therefore, the embodiments disclosed in the present invention are intended to illustrate the technical idea of the present invention, and the scope of the present invention is not limited by the embodiment. The scope of the present invention disclosure shall be construed on the basis of the accompanying claims in such a manner that all of the technical ideas included within the scope equivalent to the claims belong to the present invention disclosure.

Claims

1. A method of transmitting an uplink sounding reference signal (srs) in user equipment (ue) in a coordinated multi-point transmission/reception system (CoMP system), the method comprising:

receiving, by the user equipment, ue-specific configuration information including an uplink reference signal identity associated with an uplink channel, from a first transmission/reception point of a plurality of different transmission/reception points, wherein the uplink reference signal identity is independent of a physical cell identity of the first transmission/reception point and indicates a second transmission/reception point as a reception entity of the uplink channel; and

performing, by the user equipment, an independent transmission of the uplink channel and an srs to different transmission/reception points, using the uplink reference signal identity or the physical cell identity according to a type of an uplink transmission,

wherein when the type of the uplink transmission is an uplink channel transmission,

the performing includes:

obtaining the uplink reference signal identity from the received ue-specific configuration information;

determining the second transmission/reception point indicated by the uplink reference signal identity, as an uplink channel reception entity, wherein the second transmission/reception point is different from the first transmission/reception point; and

transmitting, by the user equipment, the uplink channel to the determined second transmission/reception point, using the uplink reference signal identity;

wherein when the type of the uplink transmission is an srs transmission,

the performing includes:

generating, by the user equipment, an srs independent of the uplink channel, using the physical cell identity of the first transmission/reception point;

determining the first transmission/reception point which has transmitted the ue-specific configuration information to the user equipment, as an srs reception entity; and

transmitting, by the user equipment, the generated srs to the determined first transmission/reception point;

wherein:

the srs includes at least one of a periodic srs and an aperiodic srs,

the generating an srs includes generating both the periodic srs and the aperiodic srs using the physical cell identity of the first transmission/reception point, and

the transmitting the generated srs includes transmitting one of the periodic srs and the aperiodic srs to the first transmission/reception point indicated by the physical cell identity;

wherein the uplink channel is at least one of a physical uplink shared channel and a physical uplink control channel; and

wherein the receiving ue-specific configuration information includes receiving, from the first transmission/reception point, the ue-specific configuration information including the uplink reference signal identity, either through a ue-specific parameter, or dynamically through at least one of a physical downlink control channel (PDCCH) and an enhanced physical downlink control channel (EPDCCH).

2. The method of claim 1, wherein:

the generating an srs includes generating one of the periodic srs and the aperiodic srs using the physical cell identity of the first transmission/reception point, and the other srs using the uplink reference signal identity; and

the transmitting the generated srs includes transmitting one of the periodic srs and the aperiodic srs to the first transmission/reception point, and the other srs to the second transmission/reception point indicated by the uplink reference signal identity.

3. User equipment in a coordinated multi-point transmission/reception system (CoMP system), the user equipment comprising:

a receiver configured to receive ue-specific configuration information including an uplink reference signal identity associated with an uplink channel, from a first transmission/reception point of a plurality of different transmission/reception points, wherein the uplink reference signal identity is independent of a physical cell identity of the first transmission/reception point and indicates a second transmission/reception point as a reception entity of the uplink channel; and

a transmitter configured to perform an independent transmission of the uplink channel and a sounding reference signal (srs) to different transmission/reception points, using the uplink reference signal identity or the physical cell identity according to whether a type of an uplink transmission is an uplink channel transmission or an srs transmission,

wherein the transmitter includes:

an uplink channel transmission unit configured to obtain the uplink reference signal identity from the received ue-specific configuration information; to determine the second transmission/reception point indicated by the uplink reference signal identity, as an uplink channel reception entity; and to transmit the uplink channel to the determined second transmission/reception point, using the uplink reference signal identity, wherein the second transmission/reception point is different from the first transmission/reception point;

an srs generating unit configured to generate an srs being independent of the uplink channel, using the physical cell identity of the first transmission/reception point; and

an srs transmitting unit configured to determine the first transmission/reception point which has transmitted the ue-specific configuration information to the user equipment, as an srs reception entity, and to transmit the generated srs to the determined first transmission/reception point;

wherein:

the srs includes at least one of a periodic srs and an aperiodic srs,

the srs generating unit is configured to generate both the periodic srs and the aperiodic srs using the physical cell identity of the first transmission/reception point, and

the srs transmitting unit is configured to transmit one of the periodic srs and the aperiodic srs to the first transmission/reception point indicated by the physical cell identity;

wherein the uplink channel is at least one of a physical uplink shared channel and a physical uplink control channel; and

wherein the receiver is configured to receive, from the first transmission/reception point, the ue-specific configuration information including the uplink reference signal identity, either through a ue-specific parameter, or dynamically through at least one of a physical downlink control channel (PDCCH) and an enhanced physical downlink control channel (EPDCCH).

4. The user equipment of claim 3, wherein:

the srs generating unit is configured to generate one of the periodic srs and the aperiodic srs using the physical cell identity of the first transmission/reception point, and to generate the other srs using the uplink reference signal identity; and

the srs transmitting unit is configured to transmit one of the periodic srs and the aperiodic srs to the first transmission/reception point, and to transmit the other srs to the second transmission/reception point indicated by the uplink reference signal identity.

5. A method of transmitting an uplink sounding reference signal (srs) in user equipment (ue) in a coordinated multi-point transmission/reception system (CoMP system), the method comprising:

receiving, by the user equipment, ue-specific configuration information including a sounding reference signal (srs) identity from a first transmission/reception point of a plurality of different transmission/reception points, wherein the srs identity is independently determined to be distinguished from an uplink reference signal identity for an uplink channel and indicates a second transmission/reception point as a reception entity of an srs; and

performing, by the user equipment, an independent transmission of the uplink channel and the srs to different transmission/reception points, using the uplink reference signal identity or the srs identity according to a type of an uplink transmission,

wherein when the type of the uplink transmission is an srs transmission,

the performing includes:

obtaining, by the user equipment, the srs identity from the received ue-specific configuration information;

generating, by the user equipment, an srs using the srs identity;

determining the second transmission/reception point ue-specifically indicated by the srs identity, as an srs reception entity, wherein the second transmission/reception point is different from the first transmission/reception point which has transmitted the ue-specific configuration information to the user equipment; and

transmitting, by the user equipment, the generated srs to the determined second transmission/reception point;

wherein the srs includes at least one of a periodic srs and an aperiodic srs;

wherein the generating an srs includes generating both the periodic srs and the aperiodic srs using the srs identity; and

wherein the receiving ue-specific configuration information includes receiving, from the first transmission/reception point, the ue-specific configuration information including the srs identity, either through a ue-specific parameter, or dynamically through at least one of a physical downlink control channel (PDCCH) and an enhanced physical downlink control channel (EPDCCH).

6. The method of claim 5, wherein:

the ue-specific configuration information includes a same reference signal identity for the periodic srs and the aperiodic srs.

7. The method of claim 5, wherein:

the ue-specific configuration information includes a different reference signal identity for each of the periodic srs and the aperiodic srs.

8. The method of claim 5, wherein:

the generating an srs includes generating one of the periodic srs and the aperiodic srs using the srs identity, and the other srs using a physical cell identity of the first transmission/reception point; and

the transmitting the generated srs includes transmitting one of the periodic srs and the aperiodic srs to the second transmission/reception point indicated by the srs identity, and the other srs to the first transmission/reception point.

9. A method of transmitting an uplink sounding reference signal (srs) in user equipment (ue) in a coordinated multi-point transmission/reception system (CoMP system) including a first transmission/reception point and a second transmission/reception point, the method comprising:

receiving, by the user equipment, ue-specific configuration information including an uplink reference signal identity which is an independent identity distinguished from a physical cell identity of the first transmission/reception point and indicates the second transmission/reception point as a reception entity of the uplink channel from the first transmission/reception point through either a ue-specific parameter or dynamically through at least one of a physical downlink control channel (PDCCH) and an enhanced physical downlink control channel (EPDCCH);

determining, by the user equipment, the second transmission/reception point indicated by the uplink reference signal identity included in the received ue-specific configuration information as an uplink channel reception entity, and transmitting the uplink channel to the determined second transmission/reception point, using the uplink reference signal identity; and

generating, by the user equipment, both a periodic srs and an aperiodic srs, using the physical cell identity of the first transmission/reception point, determining the first transmission/reception point as an srs reception entity, and transmitting the generated periodic srs and aperiodic srs to the determined first transmission/reception point indicated by the physical cell identity through the uplink channels.

10. The method of claim 9, wherein the second transmission/reception point is different from the first transmission/reception point.

11. The method of the claim 9, wherein the uplink channel includes a PUCCH and a PUSCH.

12. User equipment in a coordinated multi-point transmission/reception system (CoMP system) including a first transmission/reception point and a second transmission/reception point, the user equipment comprising:

a receiver configured to receive ue-specific configuration information including an uplink reference signal identity which is an independent identify distinguished from of a physical cell identity of the first transmission/reception point and indicates the second transmission/reception point as a reception entity of the uplink channel from the first transmission/reception point through either a ue-specific parameter or dynamically through at least one of a physical downlink control channel (PDCCH) and an enhanced physical downlink control channel (EPDCCH); and

a transmitter configured to determine the second transmission/reception point indicated by the uplink reference signal identity included in the received ue-specific configuration information as an uplink channel reception entity and transmit the uplink channel to the determined second transmission/reception point, using the uplink reference signal identity, and generate both a periodic srs and an aperiodic srs, using the physical cell identity of the first transmission/reception point, determine the first transmission/reception point as an srs reception entity and transmit the generated periodic srs and aperiodic srs to the determined first transmission/reception point indicated by the physical cell identity through the uplink channel.

13. The user equipment of claim 12, wherein the second transmission/reception point is different from the first transmission/reception point.

14. The user equipment of claim 13, wherein the uplink channel includes a PUCCH and a PUSCH.

15. A method of transmitting an uplink sounding reference signal (srs) in user equipment (ue) in a coordinated multi-point transmission/reception system (CoMP system), the method comprising:

receiving, by the user equipment, ue-specific configuration information including a sounding reference signal (srs) identity from a first transmission/reception point among a plurality of different transmission/reception points, wherein the srs identity is independently determined to be distinguished from an uplink reference signal identity for an uplink channel and indicates a second transmission/reception point as a reception entity of an srs; and

performing, by the user equipment, an independent transmission of the uplink channel and the srs to different transmission/reception points, using the uplink reference signal identity or the srs identity according to a type of an uplink transmission,

wherein when the type of the uplink transmission is an srs transmission, the performing includes:

generating, by the user equipment, an srs using the srs identity included in the received ue-specific configuration information;

determining the second transmission/reception point ue-specifically indicated by the srs identity, as an srs reception entity, wherein the second transmission/reception point is different from the first transmission/reception point which has transmitted the ue-specific configuration information to the user equipment; and

transmitting, by the user equipment, the generated srs to the determined second transmission/reception point;

wherein the srs includes a periodic srs and an aperiodic srs;

wherein the generating an srs includes generating both the periodic srs and the aperiodic srs using the srs identity; and

wherein the receiving ue-specific configuration information includes receiving, from the first transmission/reception point, the ue-specific configuration information including the srs identity, either through a ue-specific parameter, or dynamically through at least one of a physical downlink control channel (PDCCH) and an enhanced physical downlink control channel (EPDCCH).

16. The method of claim 15, wherein:

the ue-specific configuration information includes the sounding reference signal identity which is the same for the periodic srs and the aperiodic srs.

17. The method of claim 15, wherein:

the ue-specific configuration information includes the sounding reference signal identity which is different for the periodic srs and the aperiodic srs.