CN110350951B

CN110350951B - Uplink signaling for coordinated multipoint communications

Info

Publication number: CN110350951B
Application number: CN201910608365.5A
Authority: CN
Inventors: R·M·本德林; A·埃克本扬; R·陈
Original assignee: Texas Instruments Inc
Current assignee: Texas Instruments Inc
Priority date: 2012-08-03
Filing date: 2013-08-02
Publication date: 2023-11-24
Anticipated expiration: 2033-08-02
Also published as: WO2014022773A1; CN104521156B; JP2015527845A; JP7116274B2; JP6352913B2; JP6616455B2; CN110350951A; CN104521156A; JP2018164279A; JP2020039152A

Abstract

The present application relates to uplink signaling for coordinated multipoint communications. A method of operating a wireless communication system is disclosed (fig. 6). The method includes receiving a Virtual Cell Identification (VCID) parameter from a remote transmitter (600). In response to the VCID, base Sequence Index (BSI) and Cyclic Shift Hopping (CSH) parameters are determined (604, 606). A pseudo-random sequence is selected in response to BSI and CSH (610, 612). A reference signal is generated using the selected pseudo-random sequence (614).

Description

Uplink signaling for coordinated multipoint communications

The present application is a divisional application of chinese patent application 201380041227.4 entitled "uplink signaling for coordinated multipoint communication" filed on 2013, 08 and 02.

Technical Field

The present application relates to wireless communication systems, and more particularly, to uplink signaling of control information in a coordinated multipoint (CoMP) communication system.

Background

Conventional cellular communication systems operate in a point-to-point single cell transmission manner, in which user terminals or devices (UEs) are uniquely connected to and served by a single cellular base station (eNB or eNodeB) at a given time. An example of such a system is 3GPP long term evolution (LTE release 8). Advanced cellular systems aim to further improve data rates and performance by employing multipoint-to-point or coordinated multipoint (CoMP) communications, where multiple base stations can cooperatively design downlink transmissions to serve a UE simultaneously. An example of such a system is the 3GPP LTE-advanced system (release 10 and beyond). This greatly increases the signal strength received at the UE by transmitting the same signal from different base stations to each UE. This is particularly beneficial for cell edge UEs observing strong interference from neighboring base stations. With CoMP, interference from neighboring base stations becomes a useful signal, and thus, reception quality is significantly improved. Thus, if multiple nearby cells are working cooperatively, the UE in CoMP communication mode will be served much better.

Fig. 1 illustrates an exemplary wireless communication network 100. An exemplary telecommunications network includes base stations 101, 102, and 103, although in operation, the telecommunications network must include more base stations. Each of base stations 101, 102, and 103 (enbs) are operable over respective coverage areas 104, 105, and 106. The coverage area of each base station is further divided into cells. In the illustrated network, the coverage area of each base station is divided into three cells. A handset or other User Equipment (UE) 109 is shown in cell a 108. Cell a 108 is within coverage area 104 of base station 101. Base station 101 transmits signals to UE 109 and receives transmissions from UE 109. As UE 109 moves out of cell a 108 and into cell B107, UE 109 may be handed off to base station 102. Because UE 109 is synchronized with base station 101, UE 109 can employ non-synchronized random access to initiate a handoff to base station 102. UE 109 can also employ non-synchronized random access to request allocation of uplink 111 time or frequency or code resources. If the UE 109 has data ready for transmission, which may be traffic data, measurement reports, or tracking area updates, the UE 109 can transmit a random access signal on the uplink 111. The random access signal informs the base station 101 that the UE 109 requires uplink resources to transmit the UE's data. Base station 101 responds by transmitting a message to UE 109 via downlink 110 containing parameters and possibly timing error corrections that allocate resources for UE 109 uplink transmissions. After receiving the resource allocation and possibly timing advance message transmitted by base station 101 on downlink 110, UE 109 optionally adjusts its transmission timing and transmits data on uplink 111 using the allocated resources during a predetermined time interval. Base station 101 configures UE 109 for periodic uplink Sounding Reference Signal (SRS) transmission. The base station 101 estimates uplink Channel Quality Information (CQI) from the SRS transmission.

Uplink (UL) coordinated multipoint (CoMP) communications require coordination between multiple network nodes to help improve reception by UEs. This involves efficient resource utilization and avoidance of high inter-cell interference. In particular, heterogeneous deployments of small cells controlled by low power nodes, such as pico (pico) enbs and Radio Remote Heads (RRHs), are deployed within macro cells, such as 108. In a coordinated multipoint (CoMP) wireless communication system, a UE receives signals from a plurality of base stations (enbs). These base stations may be macro enbs, pico enbs, femto enbs, or other suitable Transmission Points (TPs). For each UE, a plurality of channel state information reference signal (CSI-RS) resources are configured based on which UE is capable of measuring downlink channel state information. Each CSI-RS resource can be associated with a base station, a Remote Radio Head (RRH), or a distributed antenna through the E-UTRAN. The UE then transmits to the eNB over an OFDM frame using allocated Physical Resource Blocks (PRBs) on the Uplink (UL).

Referring now to fig. 2, a block diagram of a prior art heterogeneous wireless communication system is provided. The system includes macro cells a and B separated by a cell boundary 200. Cell a is controlled by macro eNB 202 and includes pico cell 204 controlled by pico eNB 206. Cell B includes pico cell 222 controlled by pico eNB 228 in communication 226 with pico UE 224. Pico eNB 206 provides services to UEs within area 204, such as pico UE 208. Pico eNB 206 communicates with pico UE 208 over data and control channels 210. Cell a also includes macro UE 214 in direct communication with macro eNB 202 via data and control channel 218. Introducing pico eNB 206 within macro cell a provides cell or region splitting gain due to additional cells being established within the same geographic region. Heterogeneous deployments can be further categorized into shared or unique Physical Cell Identification (PCID) scenarios. Referring to fig. 2, in a shared PCID scenario, both macro eNB 202 and pico eNB 206 share the same PCID. Thus, DL transmissions from two base stations to a UE can be made to appear as a single transmission from a distributed antenna system. Alternatively, pico eNB 206 may have a different unique PCID than macro eNB 202. These two cases create different interference environments.

An uplink reference signal from the UE to the eNB is used to estimate uplink channel state information. These reference signals include control channel Reference Signals (RSs), traffic channel demodulation reference signals (DMRSs), and Sounding Reference Signals (SRS). In LTE, the control channel and the traffic channel are referred to as a Physical Uplink Control Channel (PUCCH) and a Physical Uplink Shared Channel (PUSCH), respectively. Orthogonality of reference signals within a cell is maintained by using different cyclic shifts from a base sequence. The uplink reference signal within a communication system is typically modulated with a constant amplitude zero auto-correlation (CAZAC) sequence or a pseudo-random noise (PN) sequence. However, the different base sequences are not orthogonal and require good network planning to achieve low cross-correlation between neighboring cells. Inter-cell interference is mitigated by interference randomization techniques such as cell-specific base sequence hopping and cyclic shift hopping patterns. Moreover, different problems arise depending on whether all cells within a CoMP communication system have a unique cell ID or share the same cell ID.

In prior art heterogeneous wireless communication systems, inter-cell interference increases significantly due to short inter-site or inter-point distances. For UL cell selection, the UE preferably selects the cell with the lowest path loss in terms of reduced UL interference. For example, macro UE 214 transmits uplink data and control and also receives downlink control information over wireless connection 218 with macro eNB 202. However, communication link 212 between macro UE 214 and pico eNB 206 has less path loss than communication link 218. Thus, macro UE 214 generates significant UL interference 212 to pico eNB 206 in an attempt to maintain acceptable link quality for eNB 202. Significant interference to pico eNB 228 may also be generated when macro UE 214 is close to cell border 200. For the case of sharing PCIDs, all enbs within a macrocell effectively form a super cell comprising a distributed antenna system with a single PCID. Thus, there is little or no inter-cell interference because the transmitted reference signal is a cyclic shift of the same base sequence. On the other hand, no region splitting gain can be obtained, thereby utilizing multiple deployed enbs in the same geographic region. For the unique PCID case, macro UE 214 may generate unacceptable UL interference to pico eNB 206. Conversely, pico eNB 206 degrades DL reception for macro UE 214. Thus, it is desirable for macro UE 214 to be configured to transmit to pico eNB 206 to reduce interference and also conserve battery life by reducing its UL transmit power. Thus, a tradeoff can be observed between increasing network capacity and mitigating the resulting increase in inter-cell or inter-point interference.

While the above approach provides a stable improvement over wireless communications, the inventors of the present application recognize that further improvements in the transmission of UL control information are still possible. The preferred embodiments described below are therefore directed to this and improvements over the prior art.

Disclosure of Invention

In a preferred embodiment of the present application, a method of operating a wireless communication system is disclosed, the method comprising: an identification parameter (ID) is received from a remote transmitter. In response to the received ID, a Base Sequence Index (BSI) and a Cyclic Shift Hopping (CSH) sequence are determined. A first pseudo-random sequence is determined in response to the BSI. In response to the CSH, a subsequent pseudo-random sequence is selected. The method also includes receiving a set of dedicated parameters from a remote transmitter to determine a time/frequency region for transmitting uplink control information or a sounding reference signal.

Drawings

Fig. 1 is a block diagram of a prior art wireless communication system;

fig. 2 is a block diagram of a heterogeneous deployment of a prior art wireless communication system, showing a macro cell and two pico cells;

fig. 3 is a block diagram of a wireless communication system of the present application showing a macrocell with reduced inter-point interference and a picocell deployed within a macrocell area;

fig. 4 is a block diagram illustrating logical resource block allocation of macro and pico cells as in fig. 3;

fig. 5 shows a flowchart of sequence selection of a Sounding Reference Signal (SRS) and a PUCCH Reference Signal (RS);

fig. 6 shows a flow chart of determining a mapping of PUCCH resources to logical resource blocks based on cell-specific or UE-specific PUCCH parameters; and

fig. 7 is a flow chart of inter-eNB signaling of a UE-specific configuration to determine PUCCH and SRS transmission parameters.

Detailed Description

Inter-channel interference is a significant problem in the uplink control channel of LTE wireless communication systems.

The following abbreviations are used throughout the relevant specification.

BLER: block error Rate

BSI base sequence index

CQI channel quality indicator

CRS cell-specific reference signals

CRC cyclic redundancy check

CSH cyclic shift hopping

CSI channel State information

CSI-RS channel state information reference signal

DCI downlink control indicator

DL downlink

DMRS demodulation reference symbols or UE-specific reference symbols

DPS dynamic Point selection

eNB E-UTRAN node B or base station

Enhanced Physical Downlink Control Channel (EPDCCH)

E-UTRAN evolved universal terrestrial radio access network

HARQ-ACK hybrid automatic repeat request-acknowledgement

IRC interference rejection combining

JT: joint transmission

LTE Long term evolution

MIMO: multiple input multiple output

MRC maximum ratio combination

PCFICH physical control Format indicator channel

PCID physical cell identification

PDCCH physical downlink control channel

PDSCH physical downlink shared channel

PMI precoding matrix indicator

PRB physical resource Block

PUCCH physical uplink control channel

PUSCH physical uplink shared channel

QAM quadrature amplitude modulation

RI rank indicator

RNTI radio network temporary indicator

RRC: radio resource control

SNR signal to noise ratio

SRS sounding reference signal

TPC: transmit power control

UE (user equipment)

Uplink

UpPTS uplink pilot time slot

VCID virtual cell identifier

Embodiments of the present application are directed to enhancing uplink control transmissions on PUCCH and sounding reference signal transmissions in CoMP communication systems. Methods for dividing uplink control regions between cells to minimize inter-cell interference are described. UEs approaching the cell boundary may generate severe UL interference in the neighboring cells due to transmission of non-orthogonal PUCCH reference signal base sequences in the neighboring cells, the severity of the interference being proportional to the difference in path loss between the UE to the desired eNB and the UE to the neighboring enbs. Here, the path loss is a decrease in power density or signal attenuation when an electromagnetic wave propagates. Referring to fig. 3, in accordance with one embodiment of the present application, pico eNB 206 measures received interference (due in part to macro UE 214) with each cell having a unique physical cell ID. Pico eNB 206 informs macro eNB 202 on backhaul link 216 if UL interference is greater than a predetermined threshold. One logical interface over which such inter-eNB signaling occurs is the X2 interface. Macro eNB 202 then instructs macro UE 214 to employ the PCID of pico cell 206 when initializing a pseudo random sequence generator to generate BSI and CSH sequences for PUCCH transmission. Macro UE 214 is now considered a CoMP UE, where intra-cell orthogonality between UE 214 and pico UE 208 is achieved and interference 212 (fig. 2) is eliminated. However, one problem with this approach is that UE 214 determines the resource block allocation for uplink control transmission based on the PUCCH parameters of its serving cell (macro eNB 202). This may result in PUCCH resource allocation collision between CoMP UEs and legacy UEs when transmitting channel state information reports, scheduling requests, and HARQ-ACK feedback. One solution to this problem is to split the uplink control transmissions from CoMP UEs and legacy UEs into different RBs. This partitioning must be carefully managed to avoid increasing PUCCH overhead.

In an alternative embodiment of the present application, where all cells in the CoMP cooperating set share a common PCID, PUCCH region splitting gain is achieved by configuring the UE to transmit to the nearest eNB. Here, there is a trade-off between increasing inter-point interference and region PUCCH capacity. According to the present embodiment, UE clusters that are relatively close to each other and spatially isolated from other clusters are assigned unique IDs for initializing pseudo random sequence generators for PUCCH reference signals and sounding reference signals. The new set created by these UE clusters can be referred to as virtual cells and the dedicated IDs are the corresponding Virtual Cell IDs (VCIDs).

Other example uses of this virtual cell concept are possible. An alternative embodiment is described below with reference to fig. 3. eNB 202 configures macrocell a with pcid=123, pico eNB 206 configures its pico cell with pcid=231, and pico eNB 228 configures its pico cell with pcid=55. Under the control of eNB 202, an entirely new virtual cell can be configured with VCID n by UE 214 _ID =500.

Dynamic PUCCH resource allocation is quite different from semi-static PUCCH resource allocation. Here, the dynamic PUCCH resource allocation is determined according to DL scheduling assignment transmitted on PDCCH or EPDCCH. The present application calculates a single parameter m to map PUCCH Resource Blocks (RBs) of both legacy UEs and CoMP UEs using existing parameters from LTE release 8-10. The concept taught by the present application is a method of configuring UE-specific semi-static and dynamic PUCCH regions, wherein the former determines a semi-static region for transmitting CSI reports, scheduling requests and HARQ-ACK feedback caused by semi-persistent scheduling, and the latter determines a region for dynamic HARQ-ACK feedback.

Referring now to fig. 4, there is a block diagram illustrating a logical resource block allocation m for a macro cell and a pico cell as in fig. 3. The parameter m increases in the indicated vertical direction. Fig. 4 illustrates a case of Resource Block (RB) allocation in which a macro UE is virtually transmitted to a pico eNB. Virtual transmission refers to a macro UE configured as a CoMP UE to transmit uplink control information to a pico eNB. The logical RB mapping of the macro UE configuration is shown on the left side of fig. 4. Each RB contains a PUCCH resource group, wherein the number of resources in the RB depends on the transmission type of the PUCCH. Blocks 400 through 406 represent PUSCH, dynamic PUCCH format 1a/1b, semi-static PUCCH region of PUCCH format 1/1a/1b, and semi-static PUCCH region of PUCCH format 2/2a/2b, respectively. The number of RBs allocated to the PUCCH format 2/2a/2b region is defined by N ⁽²⁾ _RB，m Represented, while the starting offset of the dynamic PUCCH region is represented by N ⁽¹⁾ _PUCCH，m And (3) representing. Logical RB mapping of pico UE configuration is shown on the right, where semi-static and dynamic PUCCH regions have similar definitions. Block 410 represents PUSCH, block 414 represents dynamic PUCCH format 1a/1b region, block 416 represents semi-static PUCCH format 1/1a/1b region and block 418 represents semi-static PUCCH format 2/2a/2b region. LTE release 8-10 defines PUCCH resource mapping to resource block m. These earlier versions of UE are based on parameter N ⁽²⁾ _RB And N ⁽¹⁾ _PUCCH The starting offset of the dynamic PUCCH region is determined.

The CoMP UEs in the macro cell can be configured to transmit UL control information in the CoMP dynamic PUCCH region depicted by block 412 of fig. 4. Thus, coMP uplink control transmissions to the pico eNB do not collide with the pico cell's inherent uplink control transmissions. However, if CoMP UEs are provided only with a representation denoted N ⁽¹⁾ _PUCCH，UE If it should use the CSI field parameter N of the macro as indicated by vertical arrow 420 ⁽²⁾ _RB，m As an initial offset. In this case, dynamic PUCCH transmission of CoMP UE will be slightly smaller than that of the picoOther dynamic PUCCH resources in the region or even PUSCH transmission collisions. Collisions may also occur if mixed RBs exist, with one RB containing PUCCH resources for both HARQ-ACK feedback and CSI reporting. Thus, according to an embodiment of the present application, both dynamic PUCCH offset and CSI region parameters are provided to the UE.

Referring now to fig. 5, a flow chart is shown how a UE determines a mapping of PUCCH resources to logical resource blocks. The UE receives the RRC message 500. If N is detected in message 500 ⁽¹⁾ _PUCCH，UE And N ⁽²⁾ _RB，UE The UE determines a PUCCH resource to RB mapping 504 based on the detected parameters. Otherwise, if the RRC message 500 does not contain one or more dedicated PUCCH mapping parameters, the UE is based on the common parameter N of the serving cell ⁽¹⁾ _PUCCH And N ⁽²⁾ _RB The PUCCH resource to RB mapping is determined as shown in 506.

In another embodiment of the present application, a special ID, n, is utilized _ID The UE is configured with the dedicated ID for generating a Base Sequence Index (BSI) and a Cyclic Shift Hopping (CSH) sequence of all PUCCH formats. The UE uses PCID or n _ID Initializing a pseudo-random sequence generator. A binary flag signal is signaled to the UE to indicate whether the UE applies the PCID of the serving cell or the application specific ID to generate BSI and CSH sequences. The UE is further configured with a UE-specific parameter N ⁽¹⁾ _PUCCH，UE And N ⁽²⁾ _RB，UE To determine a starting offset of the dynamic PUCCH region.

Referring now to fig. 6, a flowchart of how a UE generates a reference signal for PUCCH or SRS transmission is shown. The UE monitors the RRC message 600. The UE determines in 602 whether the detected RRC message contains a dedicated PUCCH or SRS ID, n _ID . If n is present _ID Then the UE uses n _ID A pseudo-random number generator 604 for the base sequence set, sequence, and cyclic shift hopping sequence is initialized. Otherwise, if n is not detected in the RRC message _ID The UE initializes the pseudo-random sequence generator for the base sequence group, sequence, and cyclic shift hopping sequence with the PCID 606 of its serving cell. If block 608 determines thatPUCCH is to be transmitted, then in block 610 the UE selects sequence 0 from the PUCCH sequence group and corresponds to slot n _S Is used for cyclic shift of (a). Otherwise, if block 608 determines that SRS is to be transmitted, the UE selects a sequence group and a cyclic shift corresponding to the slot and corresponding SRS SC-FDMA symbol(s) within the slot at 612. In block 614, the UE generates an appropriate reference signal using the selected sequence.

CoMP enhancement can also be extended to SRS transmission within the CoMP coordination area. For the shared PCID case, this enables SRS capacity to be increased but at the cost of increased inter-cell interference. Therefore, as the number of serving UEs in the CoMP coordination area increases, ensuring sufficient SRS capacity and maintaining reasonable SRS overhead per cell becomes a major issue. By configuring UEs aggregated around a reception point to have virtual cell IDs for SRS transmission to the desired reception point, region splitting gain can be achieved. As VCIDs are introduced for SRS transmission, the present application also describes a new mechanism for improving SRS operation in heterogeneous deployments. One case is more UEs transmitting to the macro eNB than to the pico eNB. Therefore, applying the same cell-specific SRS subframe configuration on both the macro cell and the pico cell unfairly sacrifices PUSCH transmission efficiency in the pico cell due to PUSCH rate matching in the cell-specific SRS subframes. For decoupled data and control, different but related problems arise, where the UE receives PDCCH from one eNB but transmits PUSCH to a different eNB. Thus, if the SRS subframe configurations between two cells are different, it is necessary to determine which of these configurations the UE should take.

One embodiment of the present application is a dedicated UE-specific ID configured for SRS transmission. The UE determines a base sequence group and a sequence hopping pattern from the signaled SRS ID.

Another embodiment of the present application is to further configure the UE with dedicated SRS parameters. For example, a macro UE can be configured with cell-specific SRS parameters of a pico cell to transmit SRS to a pico eNB. The UE can be configured with dedicated parameters for SRS subframe configuration, SRS bandwidth configuration, and parameters for enabling/disabling simultaneous SRS and HARQ-ACK transmission. For a TDD system, the UE can be further configured with parameters defining a maximum uplink pilot time slot (UpPTS) region.

Both open loop and closed loop UL power control are closely related to CoMP operation. This is because the wireless network may configure one set of transmission points for the DL of the UE and one different set of reception points for the UL of the UE. Referring back to fig. 3, for example, UE 214 may be configured to send UL transmissions to pico eNB 206 to minimize interference. However, UE 214 may still be configured to receive DL transmissions from macro eNB 202. The problem of power control occurs when the path loss between UE 214 and pico eNB 206 is significantly different from the path loss between UE 214 and macro eNB 202. The UE may be UL power controlled such that reception at the pico eNB is below a desired threshold. Macro eNB 202 may, however, still monitor UL transmissions from UE 214 for radio resource management functions or for use in the DL of a TDD system in which channel interactivity (reciprocity) between UL and DL can be exploited. Thus, a power reduction that only meets the receive threshold at the pico eNB may degrade the reception at the macro eNB. This problem typically occurs when the Transmission Point (TP) and the Reception Point (RP) of the UE are not collocated. One solution to this problem is to provide separate power control loops for UL and DL. The first power control loop can be used for PUSCH, PUCCH, and SRS transmissions to a nearby eNB. The second power control loop is used to ensure reliable reception at a second eNB having a larger path loss to the UE than the first eNB. However, this creates other problems, such as backward compatibility with legacy systems. For example, a new mechanism is needed for the eNB to signal independent Transmit Power Control (TPC) commands to the UE. SRS power control for LTE release 10 is given by equation [1 ].

Here, P _CMAX，c (i) Is the configured maximum transmit power of subframe i of serving cell c. P (P) _{SRS_offset, c} (m) is the higher layer half of m=0 and m=1 for serving cell cStatically configured 4-bit parameters. Here, m is a trigger type that triggers SRS transmission. M is M _SRS，c (i) Is the bandwidth of SRS transmission in the subframe of serving cell c. The current power control adjustment state for subframe i of serving cell c is f _c (i)。P _{O_PUSCH，c} (j) And alpha _c (j) The PUSCH reference power spectral density and fractional (fractional) power control parameters for serving cell c, respectively. Here, j indicates the type of PUSCH transmission, i.e. in response to semi-persistent, dynamic or random access response grants. PL (PL) _c Is the downlink pathloss estimate calculated by the UE for serving cell c.

Another embodiment of the present application solves the above-described power control problem and maintains backward compatibility with minimal impact on existing specifications. According to the present embodiment, the UE is configured by higher layer signaling to transmit with offset P _{SRS_offset} (1) Is used for UL transmission. UE configured by higher layer signaling to transmit with offset P _{SRS_offset} (2) Is used for DL transmission. The power control parameters replace the single power control parameters, respectively, and correspond to UL power and DL power, respectively.

Methods of signaling two or more power control commands to a UE are described. The UE can be configured for aperiodic SRS transmission using a dedicated power control command in a set of power control signals transmitted on the PDCCH in a Downlink Control Information (DCI) format. The UE can be configured by RRC signaling, wherein the locations of the two or more indexes in the bitmap contain transmit power control commands to the plurality of UEs. One TPC index indicates TPC commands for the first power control loop and the other TPC index indicates TPC commands for the second power control loop. Each TPC index can indicate either a 1 or 2 bit TPC command. For example, in LTE release 10 systems, a 2-bit command is transmitted in DCI format 3 and a 1-bit command is transmitted in DCI format 3A. When the CRC of the DCI format is scrambled by the PUCCH RNTI, one TPC index can indicate a TPC command for the PUCCH, and another TPC index can indicate a TPC command for the aperiodic SRS transmission. As a separate implementation, a set of one or more indices can be used to indicate different SRS TPC commands to the UE. The main idea is to configure the UE with multiple indices in a set of power control DCIs to indicate TPC commands for different power control loops, without excluding other variations.

The prior art for CoMP operation focuses mainly on cases where inter-eNB signaling in CoMP coordination areas occurs on an ideal backhaul link characterized by ultra-high throughput and ultra-low delays on the order of less than 1-2 milliseconds. Embodiments of the present application are also designed to operate in deployments where the delay in inter-eNB signaling is on the order of at least tens of milliseconds. The base station may request neighboring base stations to transmit their PUCCH configuration through backhaul signaling (using, for example, the X2 signaling protocol). Alternatively, the base station can signal the PUCCH configuration of a cell to one or more target cells controlled by other base stations via an X2 logical interface under its control. At a minimum, dynamic PUCCH offset parameters are indicated in PUCCH information elements signaled on the backhaul link. In addition, the number of RBs allocated for transmitting CSI reports can be indicated to allow neighboring eNBs to accurately determine HARQ-ACK regions for cells controlled by different eNBs. Other parameters may optionally be signaled including the number of PUCCH format 1/1a/1b resources that can be assigned in one RB, the number of cyclic shifts reserved for transmitting HARQ-ACKs, and the scheduling request in the resource block for hybrid transmission of HARQ-ACK scheduling request and CSI.

In a different embodiment of the application, the PUCCH configuration or some elements of this configuration can be signaled by the first base station when requested by the second base station. In an alternative embodiment, the first base station may transmit a preferred PUCCH configuration for the neighboring cell to the second base station under the control of the second base station.

For SRS transmission, the first base station may indicate the SRS subframe configuration and SRS bandwidth configuration of the cell to the second base station controlling the neighboring cell via, for example, an X2 interface under its control. The second base station may consider this information when configuring the cell-specific SRS configuration of the neighboring cell and the dedicated SRS configuration of the cell edge UE in that cell. For example, referring to fig. 3, enb 202 can configure macro cell a to have a 5ms period and a 0 subframe offset for a cell-specific SRS subframe. Upon receiving this information, pico eNB 206 can configure the pico cell with the same 5ms period but with a different subframe offset to avoid inter-cell interference. In addition, for a TDD system, parameters defining the maximum UpPTS region can be signaled over a backhaul link (such as an X2 interface).

Referring now to fig. 7, an exemplary flow chart depicting inter-eNB signaling capable of network operation in a heterogeneous network deployment is shown. The eNB 702 controlling the cell serving the UE 700 transmits a request for cell-specific PUCCH and/or SRS configuration of the neighboring cell under the control of the eNB 704. The request message 708 is transmitted over the backhaul link using the X2 signaling protocol. The eNB 704 sends a reply message 710 acknowledging the previous request and also transmits the requested PUCCH or SRS configuration over the backhaul link. The eNB 702 decides 712 whether the UE should be configured to transmit PUCCH and/or SRS to the eNB 704 based on the information received from the eNB 704 and the UE measurement report 706. If the decision is affirmative, the eNB 702 transmits an RRC configuration message 714 to the UE 700 with dedicated PUCCH or SRS parameters that match the PUCCH or SRS configuration of the eNB 704. For PUCCH transmission, UE 700 determines 716 an RB mapping and transmits required uplink control information 718 on PUCCH. For aperiodic SRS request 720 for eNB 704, the ue transmits SRS 722 to eNB 704. Based on the UE measurement report 706, the enb may alternatively determine at 712 that the UE 700 should continue using the cell common PUCCH or SRS configuration. In this case, blocks 716, 718, 720, and 722 are performed according to the cell common configuration of eNB 702.

Still further, although several examples have been provided, those skilled in the art will recognize that various modifications, substitutions, or changes may be made to the described embodiments and still fall within the scope of the application as defined by the following claims. Other combinations will be apparent to those skilled in the art from which the present specification can be derived.

Claims

1. A method of operating a wireless communication device, the method comprising:

receiving a signal from a base station;

selecting a cell-specific parameter when the signal is in a first state, or selecting a user-specific parameter when the signal is in a second state, wherein the user-specific parameter is a virtual cell identification parameter;

initializing a first pseudo-random sequence generator for generating a base sequence using the virtual cell identification parameter;

initializing a second pseudo-random sequence generator for generating a cyclic shift hopping sequence using the virtual cell identification parameter;

generating an uplink reference signal in response to the selected parameter; and

the uplink reference signal generated from the base sequence and the cyclic shift hopping sequence is transmitted.

2. A method of operating a wireless communication device, comprising:

receiving a signal from a base station;

determining a physical uplink control channel, PUCCH, or sounding reference signal, SRS, ID, n _ID Whether or not present in the signal;

when n is _ID When present in the signal, n is used _ID Initializing a pseudo-random number generator for the base sequence set, the sequence, and the cyclic shift hopping sequence;

when n is _ID Initializing a pseudo-random number generator for a base sequence group, sequence and cyclic shift hopping sequence with a physical cell identity, PCID, associated with the base station when not present in the signal;

selecting a cell-specific parameter when the signal is in a first state, or selecting a user-specific parameter when the signal is in a second state; and

an uplink reference signal is generated in response to the selected parameter.