JP2020039152A - Uplink signaling for cooperative multipoint communication - Google Patents

Abstract

To allow UL control information transmission for cooperative multipoint communication to be further improved.SOLUTION: A method for operating a wireless communication system includes receiving a virtual cell identification (VCID) parameter (600) from a remote transmitter, and determining a base sequence index (BSI) and a cyclic shift hopping (CSH) parameter (604, 606) from the received VCID. A pseudo-random sequence is selected in response to the BSI and CSH (610, 612). An appropriate reference signal is generated using the selected pseudo-random sequence (614).SELECTED DRAWING: Figure 6

Description

  This embodiment relates to a wireless communication system, and more specifically, to uplink signaling of control information in a Cooperative Multipoint (CoMP) communication system.

  Conventional cellular communication systems operate with a point-to-point single cell transmission scheme. In this scheme, a user terminal or equipment (UE) is uniquely connected to and served by one cellular base station (eNB or eNodeB) at a given time. An example of such a system is 3GPP Long Term Evolution (LTE Release 8). Modern cellular systems employ data points by employing multipoint or coordinated multi-point (CoMP) communication, in which multiple base stations can cooperatively design downlink transmissions to serve UEs simultaneously. And to further improve performance. An example of such a system is the 3GPP LTE Advanced System (Release 10 or later). This is greatly improved in that the received signal strength at the UE is transmitted by transmitting the same signal to each UE from different base stations. This is especially beneficial for cell edge UEs that experience strong interference from neighboring base stations. In CoMP, interference from nearby base stations becomes a useful signal, and thus the reception quality is greatly improved. Thus, a UE in CoMP communication mode will receive much better service if several nearby cells work together.

  FIG. 1 shows an example of a wireless telecommunications network 100. Although the telecommunications network shown includes base stations 101, 102, and 103, in operation the telecommunications network needs to include more base stations. Base stations 101, 102, and 103 (eNB) are operable over corresponding coverage areas 104, 105, and 106, respectively. The coverage area of each base station is further divided into cells. In the network shown, the coverage area of each base station is divided into three cells. Cell A 108 shows a handset or other user equipment (UE) 109. Cell A 108 is within coverage area 104 of base station 101. The base station 101 transmits to the UE 109 and receives the transmission from the UE 109. As UE 109 moves out of cell A 108 and enters cell B 107, UE 109 may be handed over to base station 102. Since UE 109 is synchronized with base station 101, UE 109 may use asynchronous random access to initiate a handover to base station 102. UE 109 may also use asynchronous random access to request an allocation of uplink 111 time or frequency or code resources. If UE 109 has data ready for transmission, which may be, for example, traffic data, measurement reports, or tracking area update information, UE 109 may transmit a random access signal on uplink 111. This random access signal informs base station 101 that UE 109 has requested the uplink resource to transmit UE data. The base station 101 responds by sending a message containing parameters of the resources allocated to the UE 109 uplink transmission, along with possible timing error corrections, to the UE 109 via the downlink 110. After receiving the resource allocation and possible timing advance messages transmitted by the base station 101 on the downlink 110, the UE 109 optionally adjusts its transmission timing to reduce the allocated resources for a predetermined time interval. The data is transmitted on the uplink 111 to be used. Base station 101 establishes UE 109 for periodic uplink sounding reference signal (SRS) transmission. Base station 101 estimates uplink channel quality information (CQI) from SRS transmissions.

  Uplink (UL) Cooperative Multipoint (CoMP) communication requires coordination between multiple network nodes to facilitate improved reception from UEs. This involves efficient resource utilization and avoidance of high inter-cell interference. In particular, a non-uniform arrangement of small cells controlled by low power nodes, such as pico eNBs and Remote Radio Heads (RRH), is placed in macro cells, such as 108. In a coordinated multi-point (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, multiple channel state information reference signal (CSI-RS) resources are configured based on which UEs can measure downlink channel state information. Each CSI-RS resource may be associated with a base station, a Remote Radio Head (RRH), or a distributed antenna by E-UTRAN. The UE then transmits to the eNB in an OFDM frame using the assigned physical resource block (PRB) in the uplink (UL).

  Referring now to FIG. 2, there is a diagram of a prior art heterogeneous wireless communication system. The system includes macro cells A and B cells 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 serves UEs such as pico UE 208 in region 204. Pico eNB 206 communicates with pico UE 208 via data and control channel 210. Cell A further includes a macro UE 214, which communicates directly with the macro eNB 202 via a data and control channel 218. The introduction of pico eNB 206 in macrocell A provides cell or area split gain due to the creation of additional cells in the same geographic area. Non-uniform placement may also be categorized as a shared or unique Physical Cell Identity (PCID) scenario. Referring to FIG. 2, in the shared PCID scenario, both the macro eNB 202 and the pico eNB 206 share the same PCID. Thus, DL transmissions from both base stations to the UE may be made such that a single transmission appears from the distributed antenna system. Alternatively, pico eNB 206 may have a unique PCID different from macro eNB 202. These two scenarios result in 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 a control channel reference signal (RS), a traffic channel demodulation reference signal (DMRS), and a sounding reference signal (SRS). In LTE, the control and traffic channels are known as the physical uplink control channel (PUCCH) and the physical uplink shared channel (PUSCH), respectively. The orthogonality of the reference signal in the cell is maintained by using a cyclic shift different from the base sequence. Uplink reference signals in communication systems are typically modulated with a constant amplitude zero autocorrelation (CAZAC) sequence or a pseudo-random noise (PN) sequence. However, different base sequences require good network planning to achieve low cross-correlation between neighboring cells, rather than orthogonal. Inter-cell interference is mitigated by interference randomization techniques such as cell-specific base sequence hopping and cyclic shift hopping patterns. Also, different problems arise depending on whether all cells in the CoMP communication system have a unique cell ID or share the same cell ID.

  In prior art heterogeneous wireless communication systems, short inter-site or point-to-point distances significantly increase inter-cell interference. In UL cell selection, it is better for the UE to select the cell with the lowest path loss in terms of reducing UL interference. For example, macro UE 214 transmits uplink data and control, and receives downlink control information on wireless connection 218 with macro eNB 202. However, the communication link 212 between the macro UE 214 and the pico eNB 206 has a shorter path loss than the communication link 218. As such, macro UE 214 attempts to maintain acceptable link quality with macro eNB 202 while generating significant UL interference 212 to pico eNB 206. When macro UE 214 is near cell boundary 200, macro UE 214 may also generate significant interference 220 for pico eNB 228. In a shared PCID scenario, all eNBs in a macrocell effectively form a supercell including a distributed antenna system thanks to a single PCID. Thus, there is little or no inter-cell interference since the transmitted reference signal is a cyclic shift of the same base sequence. On the other hand, an area split gain for using a plurality of deployed eNBs in the same geographical area cannot be obtained. In a unique PCID scenario, macro UE 214 may generate unacceptable UL interference for pico eNB 206. Conversely, the pico eNB 206 degrades the DL reception of the macro UE 214. Accordingly, it is desirable that the macro UE 214 be configured to transmit to the pico eNB 206 to reduce interference, and to conserve battery life by reducing its UL transmit power. Thus, it can be seen that there is a trade-off between increasing network capacity and mitigating the resulting increase in inter-cell or point-to-point interference.

  Although the preceding approaches provide steady improvement in wireless communication, the present inventors have recognized that further improvements in UL control information transmission are possible. Accordingly, the preferred embodiments described hereinafter are directed not only to this but also to improvements over the prior art.

  In a preferred embodiment of the present invention, a method for operating a wireless communication system is disclosed. The method includes receiving an identification parameter (ID) from a remote transmitter. In response to the received ID, a base sequence index (BSI) and a cyclic shift hopping (CSH) sequence are determined. In response to the BSI, a first pseudo-random sequence is determined. A subsequent pseudo-random sequence is selected in response to the CSH. The method further includes receiving a set of dedicated parameters from a remote transmitter to determine a time / frequency domain for transmitting uplink control information or a sounding reference signal.

FIG. 1 is a diagram of a prior art wireless communication system.

FIG. 1 is a diagram of a non-uniform arrangement of a prior art wireless communication system showing a macrocell and two picocells.

FIG. 2 is a diagram of a wireless communication system of the present invention showing macro cells and pico cells located within a macro cell area with reduced point-to-point interference.

FIG. 4 is a block diagram illustrating logical resource block allocation for macro cells and pico cells as in FIG.

5 is a flowchart illustrating sequence selection for a sounding reference signal (SRS) and a PUCCH reference signal (RS).

FIG. 7 is a flowchart illustrating PUCCH resource mapping to a logical resource block based on cell-specific or UE-specific PUCCH parameters.

It is a flowchart of the signaling between eNBs for determining UE specific structure of PUCCH and SRS transmission parameters.

  In an uplink control channel of an LTE wireless communication system, inter-channel interference is a major problem.

The following abbreviations may be used herein.
BLER: Block error rate BSI: Base sequence index CQI: Channel quality indicator CRS: Cell specific reference signal CRC: Cyclic redundancy check CSH: Cyclic shift hopping CSI: Channel state information CSI-RS: Channel state information reference signal DCI: Down Link Control Indicator DL: Downlink DMRS: Demodulation Reference Symbol or UE Specific Reference Symbol DPS: Dynamic Point Selection eNB: E-UTRAN Node B or Base Station EPDCCH: Enhanced Physical Downlink Control Channel E-UTRAN: Evolved Universal Terrestrial Radio Access Network HARQ-ACK: Hybrid Auto Repeat Request Acknowledge IRC: Interference Suppression Combination JT: Joint Transmission LT : Long Term Evolution MIMO: Multiple Input Multiple Output MRC: MRC 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: Transmission power control UE: User equipment UL: Uplink UpPTS: Uplink pilot time slot VCID: Virtual cell identifier

  Embodiments of the present invention are directed to improving uplink control transmission on PUCCH and sounding reference signal transmission in a CoMP communication system. The present invention describes a method for partitioning an uplink control region between cells such that inter-cell interference is minimized. A UE that is close to a cell boundary may generate severe UL interference in a neighboring cell due to transmission of a non-orthogonal PUCCH reference signal base sequence in the neighboring cell. The severity of the interference is proportional to the difference in path loss between the UE to the intended eNB and the UE to a nearby eNB. Here, path loss is a reduction in power density or signal attenuation with respect to electromagnetic wave propagation. Referring to FIG. 3, in accordance with one embodiment of the present invention for the case where each cell has a unique physical cell ID, pico eNB 206 measures received interference partially due to macro UE 214. If the UL interference is greater than a predetermined threshold, the pico eNB 206 informs the macro eNB 202 on the backhaul link 216. One logical interface in which such inter-eNB signaling is performed is the X2 interface. Subsequently, macro eNB 202 instructs macro UE 214 to employ the PCID of pico cell 206 when initializing the pseudo-random sequence generator to generate BSI and CSH sequences for PUCCH transmission. Macro UE 214 is here considered a CoMP UE, where inter-cell orthogonality between UE 214 and pico UE 208 is achieved and interference 212 (FIG. 2) is eliminated. However, one problem with this method is that UE 214 determines its resource block assignment for uplink control transmission based on the (macro eNB 202) PUCCH parameters of the cell it serves. This can be a PUCCH resource allocation collision between the CoMP UE and the legacy UE when transmitting the channel state information report, the scheduling request, and the HARQ-ACK feedback. One solution to this problem is to partition uplink control transmissions from CoMP UE and legacy UE into different RBs. This partition needs to be carefully managed to avoid increasing the PUCCH overhead.

  In an alternative embodiment of the present invention where all cells in the CoMP coordination set share a common PCID, PUCCH area split gain is achieved by configuring the UE to transmit to the nearest eNB. Here, there is a trade-off between increasing point-to-point interference and area PUCCH capacity. According to this embodiment, a cluster of UEs that are relatively close to each other and spatially isolated from other clusters have unique IDs to initialize a pseudo-random sequence generator for the PUCCH reference signal and the sounding reference signal. Assigned. The new set created by these UE clusters may be considered as a virtual cell, and this dedicated ID is the corresponding virtual cell ID (VCID).

  Other example applications of this concept of a virtual cell are possible. Referring to FIG. 3, an alternative embodiment is as follows. The eNB 202 configures the macro cell A with PCID = 123, the pico eNB 206 configures the pico cell with PCID = 231, and the pico eNB 228 configures the pico cell with PCID = 55. By configuring UE 214 with VCIDnID = 500, an entirely new virtual cell under the control of eNB 202 may be created.

  Dynamic PUCCH resource allocation is significantly different from semi-static PUCCH resource allocation. Here, the dynamic PUCCH resource allocation is determined from the DL scheduling assignment sent on the PDCCH or EPDCCH. The present invention uses existing parameters from LTE releases 8 to 10 to compute a single parameter m to map PUCCH resource blocks (RBs) for both legacy and CoMP UEs. The concept taught by the present invention is a method of configuring UE specific semi-static and dynamic PUCCH regions, the former comprising CSI reports, scheduling requests, and HARQ-ACKs due to semi-persistent scheduling. The latter determines a region for dynamic HARQ-ACK feedback, while determining a semi-static region to send feedback.

  Referring now to FIG. 4, there is a diagram illustrating a logical resource block assignment m for macro cells and pico cells as in FIG. The parameter m increases in the vertical direction as shown. FIG. 4 illustrates a case of resource block (RB) allocation in which a macro UE is virtually transmitted to a pico eNB. By virtual transmission, we mean that the macro UE is configured as a CoMP UE for transmitting uplink control information to the pico eNB. The logical RB map for the macro UE configuration is shown on the left of FIG. Each RB includes a group of PUCCH resources, and the number of resources in the RB depends on the type of PUCCH transmission. Blocks 400 to 406 represent a PUSCH, a dynamic PUCCH format 1a / 1b, a semi-static PUCCH region for the PUCCH format 1 / 1a / 1b, and a semi-static PUCCH region for the PUCCH format 2 / 2a / 2b, respectively. The number of RBs allocated to the PUCCH format 2 / 2a / 2b region is denoted by N (2) RB, m, while the starting offset for the dynamic PUCCH region is denoted by N (1) PUCCH, m. The logical RB map for pico UE configuration is shown to the right with similar definitions for semi-static and dynamic PUCCH regions. Block 410 represents the PUSCH, block 414 represents the dynamic PUCCH format 1a / 1b area, block 416 represents the semi-static PUCCH format 1 / 1a / 1b area, and block 418 represents the semi-static PUCCH format 2 / 2a2b area. LTE Releases 8 to 10 define PUCCH resource mapping for resource block m. The UEs of these previous releases determine the starting offset of the dynamic PUCCH region based on the parameters N (2) RB and N (1) PUCCH.

  A CoMP UE in a macro cell may be configured to transmit UL control information in a CoMP dynamic PUCCH region indicated by block 412 in FIG. Thus, the CoMP uplink control transmission to the pico eNB does not collide with the original pico cell uplink control transmission. However, if the CoMP UE only has a new dedicated dynamic PUCCH offset parameter, denoted as N (1) PUCCH, UE, the CoMP UE may use the macro CSI region parameter N as the initial offset as shown by the vertical arrow 420. (2) RB, m can be used. In this case, the CoMP UE's dynamic PUCCH transmission may collide with other dynamic PUCCH resources or even with the PUSCH transmission in pico cells. There may also be collisions when there is a mixed RB where one RB includes PUCCH resources for both HARQ-ACK feedback and CSI reporting. Therefore, according to an embodiment of the present invention, both the dynamic PUCCH offset and the CSI region parameters are provided to the UE.

  Referring now to FIG. 5, a flowchart is shown to illustrate how the UE determines the mapping of PUCCH resources to logical resource blocks. The UE receives the RRC message 500. If one or more dedicated PUCCH parameters from N (1) PUCCH, UE and N (2) RB, UE are detected in message 500, the UE may perform PUCCH resource to RB based on the detected parameters. Determine 504 the mapping. Otherwise, if the RRC message 500 does not include one or more dedicated PUCCH mapping parameters, the UE may, as at 506, use the common parameters of the N (1) PUCCH and N (2) RB serving cells. The PUCCH resource to RB mapping is determined based on the PUCCH resource to RB mapping.

  In another embodiment of the present invention, the UE is configured with a dedicated ID nID, which generates both the base sequence index (BSI) and the cyclic shift hopping (CSH) sequence for all PUCCH formats Used to The UE initializes the pseudo-random sequence generator using either the PCID or the nID. To generate the BSI and CSH sequences, a binary flag is signaled to the UE to indicate whether the UE applies the serving cell's PCID or dedicated ID. The UE is further configured with dedicated UE specific parameters N (1) PUCCH, UE and N (2) RB, UE to determine the starting offset of the dynamic PUCCH region.

  Referring now to FIG. 6, a flowchart is shown to illustrate how a UE generates a reference signal for PUCCH or SRS transmission. The UE monitors 600 for the RRC message. The UE may determine at 602 whether the detected RRC message includes a dedicated PUCCH or SRS ID nID. If the nID is present, the UE initializes 604 a pseudo-random number generator with the nID for the base sequence group, sequence and cyclic shift hopping sequence. Otherwise, if no nID is detected in the RRC message, the UE initializes a pseudo-random sequence generator with the PCID 606 of the cell it serves for base sequence group, sequence and cyclic shift hopping sequence. If block 608 determines that a PUCCH is to be transmitted, the UE selects a sequence 0 from the PUCCH sequence group and cyclic shift corresponding to time slot nS at block 610. Otherwise, if block 608 determines that an SRS should be transmitted, the UE may, at 612, sequence corresponding to the time slot and a corresponding SRS SC-FDMA symbol in the time slot. Select group and cyclic shift. At block 614, the UE generates an appropriate reference signal using the selected sequence.

  CoMP enhancement can be further extended to SRS transmission in CoMP coordination areas. In a shared PCID scenario, this allows for increased SRS capacity, but at the expense of increased inter-cell interference. Thus, ensuring adequate SRS capacity while maintaining reasonable SRS overhead per cell becomes a major issue as the number of served UEs increases within a CoMP coordination area. Area split gain may be achieved by configuring UEs gathered around a receiving point with a virtual cell ID for SRS transmission to the desired receiving point. As a result of introducing VCID for SRS transmission, the present invention also describes a new mechanism for improving SRS operation in non-uniform deployments. One case is when more UEs are transmitting to the macro eNB than to the pico eNB. Therefore, applying the same cell-specific SRS subframe configuration across macro and pico cells disproportionately disadvantages PUSCH transmission efficiency in pico cells due to PUSCH rate matching in cell-specific SRS subframes. Another related problem arises for separating data and control, in which the UE receives the PDCCH from one eNB but transmits the PUSCH to a different eNB. Therefore, if the SRS subframe configuration is different between the two cells, it needs to be determined which of these configurations should be adopted by the UE.

  One embodiment of the present invention is a configuration of a dedicated UE specific ID 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 invention is that the UE is further configured with dedicated SRS parameters. For example, a macro UE may be configured with a cell-specific SRS parameter of a pico cell to transmit an SRS to a pico eNB. The UE may be configured with dedicated parameters for SRS subframe configuration, SRS bandwidth configuration, and parameters for enabling / disabling simultaneous SRS and HARQ-ACK transmission. In a TDD system, the UE may be further configured with parameters that define 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 UE's DL and a different set of reception points for the UE's UL. Referring again to FIG. 3, for example, UE 214 may be configured to send a UL transmission to pico eNB 206 to minimize interference. However, UE 214 may still be configured to receive DL transmissions from macro eNB 202. Power control issues arise 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. However, macro eNB 202 may still monitor UL transmissions from UE 214 for radio resource management functions or for use in the DL in a TDD system where channel reciprocity between the UL and the DL may be used. . Therefore, reducing the power only to satisfy the reception threshold in the pico eNB can degrade the reception in the macro eNB. This problem typically occurs when the transmission point (TP) and the reception point (RP) for 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 may be used for PUSCH, PUCCH, and SRS transmissions to nearby eNBs. The second power control loop is used to ensure reliable reception at the second eNB, which has a larger path loss to the UE than the first eNB. However, this raises other issues, such as backward compatibility with legacy systems. For example, a new mechanism is needed in the eNB to signal independent transmit power control (TPC) commands to the UE. SRS power control for LTE Release 10 is obtained by equation [1].
Here, PCMAX, c (i) is the maximum transmission power of the subframe i for serving the cell c. PSRS_OFFSET, c (m) is a 4-bit parameter semi-statically configured by higher layers at m = 0 and m = 1 to service cell c. Here, m is a trigger type for inducing SRS transmission. MSRS, c (i) is the bandwidth of SRS transmission in subframe i for serving cell c. The current power control adjustment state of subframe i for serving cell c is fc (i). P0_PUSCH, c (j) and αc (j) are the PUSCH reference power spectral density and the fractional power control parameters, respectively, for serving cell c. Here, j indicates the type of PUSCH transmission, ie, respond to semi-persistent, dynamic, or random access response grant. PLc is a downlink path loss estimate calculated by the UE for serving cell c.

  Another embodiment of the present invention solves the power control problem described above and maintains backward compatibility with minimal impact on existing specifications. According to this embodiment, the UE is configured with higher layer signaling to transmit an aperiodic SRS with offset PSRS_OFFSET (1) for UL transmission. The UE is configured with higher layer signaling to transmit an aperiodic SRS with offset PSRS_OFFSET (2) for DL transmission. The power control parameters are individually substituted for a single power control parameter and correspond to UL and DL power, respectively.

  The present invention describes a method for signaling two or more power control commands to a UE. The UE may be configured for aperiodic SRS transmission using a dedicated power control command in a group power control signal transmitted on the PDCCH in a downlink control information (DCI) format. A UE may be configured with RRC signaling with two or more index positions in a bitmap that includes transmit power control commands to multiple UEs. One TPC index indicates a TPC command for a first power control loop, and another TPC index indicates a TPC command for a second power control loop. Each TPC index may indicate a 1 or 2 bit TPC instruction. For example, in an LTE Release 10 system, a 2-bit instruction is transmitted in DCI format 3, and a 1-bit instruction is transmitted in DCI format 3A. When the DCI format CRC is scrambled by the PUCCH RNTI, one TPC index may indicate a TPC command for PUCCH and another TPC index indicates a TPC command for aperiodic SRS transmission. Can be. As a separate example, one or more sets of indices may be used to indicate different SRS TPC commands to the UE. Other variants are not excluded and the main concept is that the UE is configured with multiple indices in group power control DCI to indicate TPC commands for different power control loops.

  The prior art for CoMP operation is mainly based on ideal backhaul links where inter-eNB signaling in CoMP coordination areas is characterized by very high throughput and very low latency of less than approximately 1-2 ms. Target scenarios that occur. This embodiment of the invention is also designed to work in deployments where the latency in inter-eNB signaling is at least approximately tens of milliseconds. A base station may request that neighboring base stations transmit their PUCCH configurations via backhaul signaling (eg, using the X2 signaling protocol). Alternatively, the base station may signal, via an X2 logical interface, the PUCCH configuration of the cell under its control to one or more target cells controlled by other base stations. At least the dynamic PUCCH offset parameter is indicated in the PUCCH information element signaled on the backhaul link. Also, the number of RBs allocated to send CSI reports may be indicated to allow neighboring eNBs to accurately determine the HARQ-ACK region for cells controlled by different eNBs. . Number of PUCCH format 1 / 1a / 1b resources that can be assigned in one RB, number of cyclic shifts reserved for transmitting HARQ-ACK, and resources used for mixed transmission of HARQ-ACK scheduling request and CSI Other parameters may optionally be signaled, including scheduling requests in blocks.

  In different embodiments of the invention, the PUCCH configuration or some of the components of this configuration may be signaled by the first base station when requested by the second base station. In an alternative embodiment, a first base station may carry a preferred PUCCH configuration for neighboring cells under the control of a second base station to a second base station.

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

  Referring now to FIG. 7, an exemplary flowchart illustrating inter-eNB signaling to enable network operation in a non-uniform network deployment is shown. An eNB 702 that controls a cell serving the UE 700 sends a request for a cell-specific PUCCH and / or SRS configuration of a neighboring cell under the control of the eNB 704. A request message 708 is sent over the backhaul link using the X2 signaling protocol. The eNB 704 sends a reply message 710 acknowledging the previous request and also sends the requested PUCCH or SRS configuration over the backhaul link. The eNB 702 makes a decision 712 based on the received information from the eNB 704 and based on the UE measurement report 706 whether the UE should be configured to send the PUCCH and / or SRS to the eNB 704. If this determination is affirmative, eNB 702 sends an RRC configuration message 714 to UE 700 along with a dedicated PUCCH or SRS parameter that matches the eNB 704 PUCCH or SRS configuration. For PUCCH transmission, UE 700 determines RB mapping at 716 and transmits 718 the required uplink control information on PUCCH. In an aperiodic SRS request 720 targeting eNB 704, the UE sends 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 to use the cell-common PUCCH or SRS configuration. In this case, blocks 716, 718, 720, and 722 may be made according to the cell common configuration of eNB 702.

  Also, while many such examples have been provided, those skilled in the art will appreciate that the described implementation may be practiced without departing from the scope of the invention as defined in the claims set forth below. It should be understood that various changes, substitutions, or alterations can be made to the examples. Other combinations will be apparent to one of skill in the art to which this description may be referred.

Claims (20)

A method of operating a wireless communication system, comprising:
Receiving a signal from a base station;
Selecting a cell specific parameter in response to a first state of the signal;
Selecting a user specific parameter in response to a second state of the signal; and transmitting an uplink reference signal in response to the selected parameter;
Including, methods. The method of claim 1, wherein
The method, wherein the user specific parameter is a virtual cell identification parameter. 3. The method according to claim 2, wherein
Initializing a first pseudo-random sequence generator to generate a base sequence with the virtual cell identification parameters;
Initializing a second pseudo-random sequence generator to generate a cyclic shift hopping sequence with the virtual cell identification parameter; and calculating the uplink reference signal generated from the base sequence and the cyclic shift hopping sequence. Sending,
Including, methods. The method of claim 1, wherein
The method, wherein the cell-specific parameters are common to cells served by the base station. The method of claim 1, wherein
A method comprising transmitting the reference signal on a physical uplink control channel (PUCCH). The method of claim 1, wherein
The method, wherein the reference signal is a sounding reference signal (SRS). The method of claim 1, wherein
Configuring user equipment with dedicated user-specific uplink control resource allocation parameters to determine an uplink control region for transmitting a channel state information report; and scheduling and hybrid auto repeat request (HARQ) acknowledgment reports. Determining the uplink control region to transmit
Including, methods. The method of claim 1, wherein
A method comprising determining resource blocks for transmitting uplink control information on an uplink control channel. 9. The method according to claim 8, wherein
The method, wherein the uplink control information is one of a hybrid automatic repeat request acknowledgment (HARQ-ACK), a channel state information report, and a scheduling request. The method according to claim 9, wherein
The method wherein the HARQ-ACK is responsive to one of a previous control signal scheduling downlink data transmission and a semi-persistently scheduled downlink data transmission. The method of claim 1, wherein
A method comprising constructing a user equipment with dedicated sounding reference signal (SRS) resource allocation parameters to determine a time-frequency resource for transmitting a sounding reference signal. The method according to claim 11, wherein
The SRS resource allocation parameter is used to transmit an SRS bandwidth configuration, an SRS subframe configuration, a hybrid auto-repeat request acknowledgment and an instruction as to whether simultaneous transmission of an SRS is permitted in a subframe, and a random access preamble. The method comprises one or more of a number of resources assigned to the system. A method of operating a wireless communication system, comprising:
Transmitting uplink control information from a second base station to a first base station; and for user equipment (UE) in a cell served by the first base station in response to the uplink control information. Determining the uplink control resources of the
Including, methods. 14. The method according to claim 13, wherein
The first base station requests uplink control configuration parameters for the physical uplink control channel (PUCCH) region of a cell served by the second base station; Transmitting the requested uplink control configuration parameters, and wherein the first base station determines a dedicated uplink control region for the UE. 14. The method according to claim 13, wherein
The method, wherein the second base station sends a preferred target PUCCH resource configuration to the first base station to determine a PUCCH region in a cell controlled by the first base station. 14. The method according to claim 13, wherein
The method, wherein the uplink control information is transmitted on an X2 logical interface. A method of operating a wireless communication system, comprising:
Transmitting at least two uplink transmission power control commands from the network to the user equipment;
Receiving a first uplink transmit power control command to transmit uplink control information and / or a sounding reference signal to a first base station;
Receiving a second uplink transmit power control command to transmit a sounding reference signal to a second base station;
Including the method 18. The method according to claim 17, wherein
Determining at least two indices in the group power control command received in the detected downlink control information format,
The first index indicates a transmission power control command for transmitting the uplink control information and / or the sounding reference signal to the first base station;
The second index indicates a transmission power control command for transmitting the sounding reference signal to the second base station;
Including, methods. 18. The method according to claim 17, wherein
Requesting by a first base station a cell common sounding reference signal (SRS) configuration of a cell controlled by a second base station; and transmitting the cell common SRS configuration to the first base station by the second base station. Transmitting by the station;
Including, methods. 20. The method according to claim 19, wherein
The method, wherein the SRS configuration includes one of an SRS bandwidth configuration, an SRS subframe configuration, and a parameter that defines a maximum uplink region of a subframe in a time division duplex (TDD) system.