EA043384B1 - MEASURING CHANNEL STATE INFORMATION WHEN IMPROVING COVERAGE IN THE LTE SYSTEM - Google Patents

Description

Cross references to related applications

This patent application claims priority to US Patent Application No. 14/997665 to Chen et al., entitled CSI Measurement Under Coverage Enhancements In LTE, filed January 18, 2016; and US Provisional Patent Application No. 62/110304 to Chen et al., entitled CSI Measurement Under Coverage Enhancements In LTE, filed January 30, 2015, each of which is assigned to the assignee hereof.

Field of technology

The present disclosure, for example, relates to wireless communication systems and, more particularly, to determining channel state information (CSI) data when an uplink grant is received over more than one subframe.

Description of the Prior Art

Wireless communication systems have been widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast and so on. These systems may be multiple access systems capable of communicating with multiple users by sharing available system resources (eg, time, frequency, and power). Examples of such multiple access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems.

As an example, a multiple access wireless communication system may include a number of base stations, each of which simultaneously supports communications for multiple communications devices, also known as user equipment (UE). The base station may communicate with user equipment instances on downlink channels (eg, for transmissions from the base station to the user equipment) and on uplink channels (eg, for transmissions from the user equipment to the base station).

In some cases, the user equipment may report CSI data to the base station on the uplink. The CSI data may be based on a CSI measurement made using a CSI reference subframe. In many cases, the CSI reference subframe coincides with the subframe on which the uplink grant is transmitted from the base station to the user equipment. However, under some circumstances, uplink grant may be transmitted to the user equipment over more than one subframe. Procedures for determining CSI data may be useful when the uplink grant is received over multiple subframes.

The essence of the invention

The user equipment (UE) may be configured to report channel state information (CSI) data to the base station. The CSI data may be reported periodically or in response to a request received from the base station (eg, in an aperiodic manner). The reported CSI data may be determined by the user equipment using one or more CSI reference subframes. In cases where the user equipment receives an uplink grant on multiple subframes (eg, as in a coverage enhancement situation), the user equipment may determine which subframe or subframes to use as the CSI reference subframes. Under some circumstances, the user equipment may use the last subframe of an uplink grant Transmission Time Interval (TTI) group as the reference CSI subframe. Under some circumstances, a user equipment may use two or more uplink grant TTI subframes as reference CSI subframes. When multiple CSI reference subframes are used, the user equipment may average the CSI measurements across each of the multiple CSI reference subframes to determine the CSI data to be reported. When an uplink grant is received over multiple subframes and multiple subbands, the CSI reference subframes used by the user equipment may include TTI group subframes that are on any of the subbands.

In a first set of illustrative embodiments, a method for wireless communication is disclosed. The method may include receiving an uplink grant in a plurality of subframes comprising a group of TTIs. The method may also include identifying, based at least in part on the TTI group configuration, one or more subframes as CSI reference subframes to be used for CSI measurement. When CSI reference subframes have been identified, the method may include performing a CSI measurement of the CSI reference subframes and transmitting CSI data based at least in part on the CSI measurement.

In a second set of illustrative embodiments, a device for wireless communication is disclosed. The apparatus may include means for receiving an uplink grant

- 1 043384 in a plurality of subframes containing a group of TTIs. The apparatus may also include means for identifying, based at least in part on the configuration of the TTI group, one or more subframes as CSI reference subframes to be used for CSI measurement. In addition, the apparatus may also include means for performing a CSI measurement of the CSI reference subframes and means for transmitting CSI data based at least in part on the CSI measurement.

In a third set of illustrative embodiments, a device for wireless communication may be disclosed. The device may include a processor, a memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to receive an uplink grant in a plurality of subframes containing a group of TTIs. The instructions may also be executable by the processor to identify, at least in part based on the TTI group configuration, one or more subframes as CSI reference subframes to be used for CSI measurement. In addition, the instructions may be executable by the processor to perform a CSI measurement of CSI reference subframes and transmit CSI data based at least in part on the CSI measurement.

In a fourth set of illustrative embodiments, a non-transitory computer-readable medium storing computer-executable code for wireless communications may be disclosed. The code may be executed by a processor to receive an uplink grant in a plurality of subframes containing a group of TTIs. Code may also be executed by a processor to identify, at least in part based on the TTI group configuration, one or more subframes as CSI reference subframes to be used for CSI measurement. In addition, code may be executed by a processor to perform a CSI measurement of the CSI reference subframes and transmit CSI data based at least in part on the CSI measurement.

Aspects of various example embodiments may include identifying the last usable subframe of a group of TTIs as a reference CSI subframe. Other aspects may include identifying two or more suitable subframes in a group of TTIs as CSI reference subframes. As an example, all subframes in a group of TTIs may be identified as CSI reference subframes. Additional aspects of various illustrative embodiments may include identifying the most recent usable subframe that is at least a predetermined number of subframes earlier than the subframe used to transmit the CSI data, wherein the gap between the most recent usable subframe and the subframe used for CSI data transmission, includes at least one subframe that does not carry an uplink grant.

In some aspects, the configuration of a group of TTIs is such that a group of TTIs can be received on a single subband. In additional aspects, a physical downlink shared channel (PDSCH) group may be received on a first subband and an uplink grant may be received on a second subband. Alternatively, the configuration of the TTI interval group is such that the TTI interval group may be received as two or more subgroups of TTI intervals over corresponding two or more subbands.

In situations where a group of TTIs is received as two or more subgroups of TTIs across corresponding two or more subbands, aspects of the disclosure may include identifying the last usable subframe of the last subgroup of TTIs as a reference CSI subframe. Aspects of the disclosure may also include identifying the last valid subframe of each of the subsets of TTIs as CSI reference subframes and averaging the CSI measurements made on each of the CSI reference subframes. Aspects of the disclosure may also include identifying two or more suitable subframes in two or more subsets of TTIs as CSI reference subframes and averaging the CSI measurements made on each of the CSI reference subframes. Aspects of the disclosure may also include identifying all subframes in two or more subsets of TTIs as CSI reference subframes and averaging the CSI measurements made on each of the CSI reference subframes. In addition, aspects of the disclosure may include identifying the most recent usable subframe that is at least a predetermined number of subframes earlier than the subframe used for transmitting the CSI data, wherein the gap between the most recent usable subframe and the subframe used for transmitting CSI data includes at least one subframe that does not carry an uplink grant.

In some aspects, transmitting CSI data based at least in part on a CSI measurement may include transmitting periodic CSI (P-CSI) data based in part on a P-CSI configuration that includes a periodicity or offset for transmitting P data. -CSI, and modification of the P-CSI configuration based on the size of the uplink transmission grouping associated with the uplink grant. In other aspects, CSI based data transmission

- 2 043384 at least partly on CSI measurement, may include aperiodic data transmission

CSI (A-CSI) is based in part on the A-CSI configuration, which identifies a scheme for identifying CSI reference subframes to be used for CSI measurement.

Some aspects may further include receiving a non-zero power (NZP) CSI reference signal (CSI-RS) to measure a channel across multiple subframes of a group of TTIs. Other aspects may further include receiving a group interference measurement resource (IMR) to measure interference across multiple subframes of a group of TTIs.

In some aspects, it is determined that the identified CSI reference subframes are suitable. This can be done by determining that the CSI reference subframes are on subbands on which the PDSCH group is received. This may also be done by excluding at least one of a multicast single frequency network (MBSFN) subframe, a special downlink short-leg subframe, a subframe associated with another set of CSI subframes, or a subframe of another subband. This may further be done by determining that the CSI reference subframes are on subbands that should be used during narrowband operations.

In some aspects, a group of TTIs may be adopted in accordance with a coverage improvement technique. In other aspects, a group of TTIs may be received in a machine communication (MTC) user equipment.

The foregoing has outlined the features and technical advantages of the examples in accordance with the disclosure in order that the following detailed description may be better understood. Additional features and advantages will be described below. The disclosed concept and specific examples may be used as a basis for modifications or designs of other structures to achieve the same objectives of the present disclosure. Such equivalent construction does not depart from the scope of the appended claims. The characteristics of the concepts disclosed herein, both their organization and their manner of operation, together with their associated advantages, will be better understood from the following description taken in conjunction with the accompanying figures. Each of the figures is provided for purposes of illustration and description only and not as a definition of the limitations of the claims.

Brief description of drawings

Further understanding of the nature and advantages of the present disclosure may be gained by reference to the following drawings. In the accompanying figures, similar components or features may have the same reference marks. In addition, different components of the same type can be distinguished by adding a dash after the reference mark and a second mark that distinguishes among similar components. If only the first reference mark is used in the description, the description applies to any of the similar components having the same reference mark, regardless of the second reference mark.

Fig. 1 shows a block diagram of a wireless communication system in accordance with various aspects of the present disclosure.

Fig. 2 shows a flowchart for transmitting channel state information (CSI) in accordance with various aspects of the present disclosure.

Fig. 3A and 3B show exemplary timelines for CSI reporting in accordance with various aspects of the present disclosure.

Fig. 4 shows a timeline for a CSI message using different CSI reference subframes in accordance with various aspects of the present disclosure.

Fig. 5 shows an exemplary timeline for receiving uplink grants across multiple subframes and subbands in accordance with various aspects of the present disclosure.

Fig. 6 shows a timeline for CSI reporting using different CSI reference subframes and subbands in accordance with various aspects of the present disclosure.

Fig. 7 shows a block diagram of a device configured for use in wireless communications, in accordance with various aspects of the present disclosure.

Fig. 8 shows a block diagram of a device configured for use in wireless communications, in accordance with various aspects of the present disclosure.

Fig. 9 shows a block diagram of a wireless communication system in accordance with various aspects of the present disclosure.

Fig. 10 shows a block diagram of an apparatus for use in wireless communications in accordance with various aspects of the present disclosure.

Fig. 11 shows a block diagram of a base station for use in wireless communications in accordance with various aspects of the present disclosure.

Fig. 12 shows a block diagram of a multiple input/multiple output communication system in accordance with various aspects of the present disclosure.

Fig. 13-15 are flowcharts showing illustrative methods.

- 3 043384 wireless communications in accordance with various aspects of the present disclosure.

Detailed description

A base station may communicate with a user equipment (UE) by receiving uplink transmissions from the user equipment and sending downlink transmissions to the user equipment. Under some circumstances, the base station may select a downlink transmission configuration based on the downlink channel condition. The downlink channel condition may be reported by the user equipment to the base station in the form of channel state information (CSI) data. Downlink conditions may be determined based on measurements taken on the downlink during a particular downlink subframe, which may be referred to as a CSI reference subframe. The user equipment may report CSI data to the base station periodically or in response to specific requests from the base station (eg, in an aperiodic manner). Both periodic CSI data (P-CSI) and aperiodic CSI data (A-CSI) can be generated by the user equipment based on specific CSI reference subframes. The user equipment may identify one or more subframes for use as CSI reference subframes. However, most usefully, the identified CSI reference subframes may coincide with the downlink channels on which the base station is to perform downlink transmissions. For example, the identified CSI reference subframes may correspond to those used to transmit uplink grant from the base station.

However, under some circumstances, uplink grant may be transmitted from the base station to the user equipment over more than one subframe. Under other circumstances, the uplink grant may be transmitted from the base station to the user equipment over multiple subframes and across multiple subbands. In one example, these circumstances may arise when a base station communicates with user equipment instances that have limited communication options. As an example, a base station may operate in a coverage improvement situation. Coverage enhancement operations typically involve methods to increase communication efficiency with devices operating under certain limitations. These restrictions may include remote locations, power limitations, reception capabilities, and the like. Operations to improve coverage may include repeating transmissions within subframes, repeating transmissions across different subframes, increasing power, beamforming, spatial multiplexing, and the like. Coverage enhancement operations may also include grouping transmissions across multiple subframes and/or multiple subbands. Coverage enhancement operations can also be used for machine communications (MTC) applications or user equipment.

MTC communications and/or machine-to-machine (M2M) communications may refer to data communication technologies that allow devices to communicate with each other or a base station without human intervention. For example, MTC communications may refer to communications from devices that integrate sensors or measuring instruments to measure or collect information and relay that information to a central server or application program that can use the information or provide information to people interacting with the program or application. In many cases, MTC devices have limited power. For example, MTC devices may have limited power or may be placed in locations that are difficult to access wirelessly. Examples of applications for MTS devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, medical monitoring, wildlife monitoring, weather and geological event monitoring, vehicle fleet tracking and management, remote detection for security purposes, management physical access and transaction-based business.

Thus, in situations where coverage is improved, for example, during communication between a base station and an MTS user equipment, the base station may use grouping, for example, to improve communication between the base station and an MTS user equipment. The base station may also request CSI data from the user equipment. The user equipment, however, may need to identify one or more CSI reference subframes in order to generate CSI data. Since a base station may use multiple subframes and/or subbands to communicate with a user equipment, CSI reference subframes identified by the user equipment may usefully correspond to some of the subframes and/or subbands being used (eg, during uplink grant transmission).

Thus, as will be described in more detail below, the user equipment may use the last subframe of an uplink grant Transmission Time Interval (TTI) group as a reference CSI subframe. Under some circumstances, a user equipment may use two or more uplink grant TTI subframes as CSI reference subframes. When multiple CSI reference subframes are used, the user

- 4 043384 The equipment may average the CSI measurement over each of several CSI reference subframes to determine the CSI data to report. When an uplink grant is received over multiple subframes and multiple subbands, the CSI reference subframes used by the user equipment may include TTI group subframes that are in any of the subbands.

The following description provides examples and does not limit the scope, applicability or examples set forth in the claims. Changes may be made to the functions and configurations of the described elements without departing from the scope of the disclosure. Various examples may omit, replace, or add various procedures or components as needed. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. In addition, the functions described with respect to some examples may be combined in other examples.

Fig. 1 illustrates an example of a wireless communication system 100 in accordance with various aspects of the disclosure. Wireless communication system 100 includes base stations 105, user equipment instances 115, and a core network 130. The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. Base stations 105 communicate with the core network 130 via communication backbones 132 (eg, S1, etc.) and may configure and schedule radio communications with user equipment instances 115 or may operate under the control of a base station controller (not shown). In various examples, base stations 105 may communicate either directly or indirectly (eg, through the core network 130) with each other over communication backbones 134 (eg, X1, etc.), which may be wired or wireless links.

Base stations 105 may communicate wirelessly with instances of user equipment 115 through one or more base station antennas. Each of the base station sites 105 may provide communications coverage for a corresponding geographic coverage area 110. In some examples, base stations 105 may be referred to as a base transceiver station, radio base station, access point, radio transceiver, NodeB, enhanced NodeB (eNB), home NodeB, home eNodeB, or other suitable terms. The geographic coverage area 110 for the base station 105 may be divided into sectors that make up only a portion of the coverage area (not shown). The wireless communication system 100 may include base stations 105 of different types (eg, macro cell and/or small cell base stations). There may be overlapping geographic coverage areas 110 for different technologies.

In some examples, the wireless communication system 100 is a Long Term Evolution (LTE) or LTE-Advanced Technology (LTE-A) network. In LTE/LTE-A networks, the term eNB may typically be used to describe base stations 105, while the term user equipment may typically be used to describe user equipment instances 115. The wireless communication system 100 may be a heterogeneous LTE/LTE-A network , in which different types of eNBs provide coverage for different geographic regions. For example, each eNB or base station 105 may provide communications coverage for a macro cell, for a small cell, and/or for other types of cells. The term cell is a 3GPP term that can be used to describe a base station, a carrier or component carrier related to a base station, or a coverage area (eg, sector, etc.) of a carrier or base station depending on the context.

A macro cell typically covers a relatively large geographic area (eg, a radius of several kilometers) and can allow unrestricted access to user equipment instances with service subscriptions from a network service provider. A small cell is a base station that is less powerful than a macro cell and can operate in the same or different (eg, licensed, unlicensed, etc.) frequency range as the macro cell. Small cells may include pico cells, femto cells, and micro cells according to various examples. A picocell can cover a relatively smaller geographic area and can allow unrestricted access to user equipment instances with service subscriptions from a network service provider. A femtocell may also cover a relatively small geographic area (eg, a home) and may provide limited access to UE instances associated with the femtocell (eg, UE instances in a closed subscriber group (CSG), UE instances for home users, etc. .). An eNB for a macro cell may be referred to as a macro eNB. A small cell eNB may be referred to as a small cell eNB, pico eNB, femto eNB, or home eNB. The eNB may support one or more (eg, two, three, four, etc.) cells (eg, component carriers).

The wireless communication system 100 may support synchronous or asynchronous operation. For synchronous operation, the base stations may have similar frame timing, and

- 5 043384 transmissions from different base stations can be approximately aligned in time. For asynchronous operation, the base stations may have different frame timing alignments, and transmissions from different base stations may not be time aligned. The techniques described in this document can be used for either synchronous or asynchronous operations.

Communication networks that may provide some of the various disclosed examples may be packet networks that operate in accordance with a multi-layer protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer may be based on the IP protocol. The radio link control (RLC) layer can perform segmentation and reassembly of packets to enable communication over logical channels. The media access control (MAC) layer can perform priority management and multiplexing of logical channels into transport channels. The MAC layer can also use Hybrid Automatic Retransmission Request (ARQ) (HARQ) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the radio resource control (RRC) protocol layer may provide for the establishment, configuration, and maintenance of an RRC connection between user equipment 115 and base stations 105 or core network 130 supporting radio bearers for user plane data. At the physical layer (PHY), transport channels can be mapped to physical channels.

Instances of user equipment 115 are dispersed throughout the wireless communication system 100, and each user equipment 115 may be fixed or mobile. User equipment 115 may also include or be referred to by those skilled in the art as a mobile station, subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, telephone, user agent, mobile client, client, or some other suitable term. The user equipment 115 may be a cellular telephone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop, a cordless telephone, a wireless local link (WLL), and the like. The user equipment can communicate with various types of base stations and network equipment, including macro eNBs, small cell eNBs, relay base stations, and the like.

In some examples, UE instances 115 may be low-cost UEs or MTC UEs and may be classified as Category 0 in the LTE/LTE-A network. Category 0 user equipment instances may be limited due to various power limitations or design simplifications. For example, Category 0 user equipment may be limited to reduced peak data rates. As one example, a Category 0 user equipment may have a limit of 1000 bits per transport block. Category 0 user equipment may be limited to rank 1 transmissions, which means that the user equipment can only participate in one transmission at a time. Category 0 user equipment may be limited by the number of antennas configured for use by the user equipment. For example, a Category 0 user equipment may have only one antenna. If a Category 0 user equipment is configured for half-duplex operation, it may also have relaxed handoff timing coordination requirements (eg, Tx to Rx, or Receive to Transmit). For example, a non-Category 0 user equipment may have a 20 µs handover timing requirement, while a Category 0 user equipment may have a 1 ms handover timing requirement.

However, user equipment instances 115—either Category 0 or non-Category 0—can monitor downlink control channels, including tracking wideband control channels, the Physical Downlink Control Channel (PDCCH), and the enhanced Physical Downlink Control Channel (EPDCCH) for example. In addition, enhanced MTC (eMTS) user equipment instances may be able to handle narrowband operations over a wider system bandwidth (eg, 1.4/3/5/10/15/20 MHz bandwidth). For example, an eMTS user equipment may be able to operate at a bandwidth of 1.4 MHz (eg, a bandwidth that is 6 resource blocks (RB) wide). Support for eMTS user equipment instances may include coverage improvements resulting in signal enhancements of up to 15 dB.

Thus, instances of user equipment 115 may include both category 0 user equipment (such as MTC and eMTS user equipment) and non-category 0 user equipment. User equipment 115 may also include other categories of user equipment.

Communication links 125 shown in wireless communication system 100 may include wireless transmissions

- 6 043384 uplink transmissions from user equipment 115 to base station 105 and/or downlink transmissions from base station 105 to user equipment 115. Downlink transmissions may also be referred to as forward link transmissions, while downlink transmissions uplink transmissions may also be referred to as reverse link transmissions. Each communication link 125 may include one or more carriers, where each carrier may be a signal composed of multiple subcarriers (eg, waveform signals of different frequencies) modulated in accordance with the various wireless technologies described above. Each modulated signal may be sent on a separate subcarrier and may carry control information (eg, reference signals, control channels, etc.), overhead information, user data, etc. Links 125 may communicate bidirectionally using frequency division duplex (FDD) (eg, using paired spectrum resources) or time division duplex (TDD) operations (eg, using unpaired spectrum resources). Frame structures for FDD (eg frame structure type 1) and TDD (frame structure type 2) can be defined.

In some embodiments of system 100, base stations 105 and/or user equipment instances 115 may include multiple antennas to utilize antenna diversity schemes to improve the quality and reliability of communications between base stations 105 and user equipment instances 115. Additionally or alternatively, the base stations 105 and/or user equipment instances 115 may use multiple-input multiple-output (MIMO) techniques that can take advantage of multipath environments to transmit multiple spatial layers carrying the same or different encoded data.

The wireless communication system 100 may support multiple cells or carriers, a feature that may be referred to as carrier aggregation (CA) or multicarrier operation. The carrier may also be referred to as component carrier (CC), layer, channel, etc. The terms carrier, component carrier, cell, and channel may be used interchangeably herein. User equipment 115 may be configured with multiple downlink component carriers and one or more uplink component carriers for carrier aggregation. Carrier aggregation can be used with FDD and TDD component carriers.

The wireless communication system 100 may support CSI data transmission from user equipment instances 115 to base stations 105. Non-category 0 user equipment instances may support both P-CSI data transmission and A-CSI data transmission. Category 0 user equipment instances may also support at least one of P-CSI data transmission and A-CSI data transmission. Thus, instances of user equipment 115 may be configured to transmit CSI feedback information based on a plurality of subframes. In some examples, such as during enhanced inter-cell interference coordination (eICIC) or enhanced interference cancellation and traffic adaptation (eIMTA), user equipment 115 may be configured with two sets of subframes, resulting in CSI data being reported separately for the two sets of subframes.

Fig. 2 shows a CSI transmission flowchart 200 in accordance with various aspects of the present disclosure. In fig. 2, communication occurs between base station 105-a and user equipment 115-a. The base station 105-a may be an example of the base stations 105 illustrated in FIG. 1. The user equipment 115-a may be an example of the instances of the user equipment 115 illustrated in FIG. 1. Thus, the user equipment 115-a may be an MTS user equipment, a category 0 user equipment, a non-category 0 user equipment, etc.

In flowchart 200, base station 105-a transmits uplink grant 205 to user equipment 115-a. Uplink grant 205 may be included in a PDCCH or in some cases in a physical downlink shared channel (PDSCH). Uplink grant 205 may be transmitted over more than one subframe and may include a group of TTIs that includes multiple subframes. In some embodiments, a group of TTIs may be divided into two or more subgroups of TTIs and may be transmitted across multiple subbands. The transmission of uplink grant 205 over more than one subframe and/or subband may be the result of a coverage improvement operation and may be beneficial to user equipment 115-a when, for example, user equipment 115-a is an MTS user equipment.

Upon receiving uplink grant 205, user equipment 115-a may perform a CSI measurement at step 210 to determine CSI data 215 to transmit to base station 105-a. Typical CSI measurement techniques are described with reference to FIG. 3A and 3B below. In each scenario, user equipment 115-a identifies a CSI reference subframe to use

- 7 043384 take it for measurement. Typically, the CSI reference subframe occurs 4 ms before the message subframe (ie, the subframe used to transmit CSI data from user equipment 115a to base station 105a). In A-CSI feedback information, the reference subframe CSI is typically the same subframe in which the uplink grant is transmitted (i.e., the uplink grant that schedules transmission of the corresponding physical uplink shared channel (PUSCH) ).

The CSI reference subframe may include either a cell-specific reference signal (CRS) or a CSI reference signal (CSI-RS). The CRS signal or the CSI-RS signal may be used to assist user equipment 115-a in channel measurement and in generating CSI data. Likewise, the CSI reference subframe may also include an interference measurement resource (IMR). The CRS signal and IMR resource may be used to assist user equipment 115-a in measuring interference.

Some subframes, however, may not be suitable for measurement or for use as CSI reference subframes. For example, special subframes that have a short downlink pilot time slot (DwPTS) may not be long enough to include a CRS signal and therefore may not be suitable as CSI reference subframes. In addition, the Multicast Broadcast Single Frequency Network (MBSFN) subframe may not include a CRS signal, and thus may not be suitable as a CSI reference subframe. In certain cases, two or more sets of CSI subframes may be configured. It is expected that the plurality of downlink subframes associated with each plurality of CSI subframes may have different interference characteristics. To be a suitable reference CSI subframe, the downlink subframe may be in the same set of subframes as the corresponding reported set of CSI subframes. As another example, if an IMR resource is used to measure interference for CSI reporting, a suitable downlink subframe for measuring CSI may also comprise an IMR resource.

Although a single CSI reference subframe is required for CSI measurement, user equipment 115-a can typically use multiple subframes for CSI measurement to improve message accuracy and reliability. Measurements taken across multiple CSI reference subframes may be averaged, for example, to provide an overall CSI measurement.

Fig. 3A shows an exemplary timeline 300-a for a CSI message in accordance with various aspects of the present disclosure. Timeline 300-a includes a downlink timeline 305 and an uplink timeline 310. Downlink timeline 305 illustrates the relative timing of transmissions from a base station, such as base stations 105 in FIG. 1 or 2, while uplink timeline 310 illustrates the relative timing of transmissions from user equipment, such as user equipment instances 115 in FIG. 1 or 2. Downlink timeline 305 and uplink timeline 310 are divided into subframes 315.

Timeline 300 illustrates an example of a P-CSI message. As stated above, a typical CSI message occurs 4 ms after the presence of a CSI reference subframe. This takes place on the 300-a timeline. On timeline 300-a, P-CSI message subframe 325-a occurs 4 subframes after the corresponding reference CSI subframe 320-a. Similarly, the P-CSI message subframe 325-b occurs 4 subframes after the corresponding reference CSI subframe 320-b. Subframes 315 on timeline 300-a may be approximately 1 ms in duration. Although not shown, if the subframe 4 ms before the CSI message subframe is an unusable subframe (eg, the subframe is an uplink subframe in a TDD configuration), the reference CSI subframe for the CSI message subframe may be the most recent usable downlink subframe 5 ms before. or earlier before the CSI message subframe.

More generally, P-CSI message subframe 325 may use as a reference CSI subframe 320 a subframe 315 that is n subframes before P-CSI message subframe 325, where n is an integer that is typically equal to or greater than four. The integer n may sometimes be referred to as n{CSI, Ref}.

Fig. 3B shows an exemplary timeline 300-b for a CSI message in accordance with various aspects of the present disclosure. Timeline 300-b includes a downlink timeline 355 and an uplink timeline 360. Downlink timeline 355 illustrates the relative timing of transmissions from a base station, such as base stations 105 in FIG. 1 or 2, while uplink timeline 360 illustrates the relative timing of transmissions from user equipment, such as user equipment instances 115 in FIG. 1 or 2. Downlink timeline 355 and uplink timeline 360 are divided into subframes 315.

Timeline 300-b illustrates an example A-CSI message. As stated above, a typical A-CSI message subframe uses as a reference CSI subframe a subframe 315 in which the corresponding uplink grant is transmitted. So on the 300-b sub timeline

- 8 043384 A-CSI message frame 370-a includes transmission of a PUSCH channel enabled by uplink grant 365-a, a subframe of which is also used as a reference CSI subframe for A-CSI message subframe 370-a. Likewise, A-CSI message subframe 370-b includes transmission of a PUSCH enabled by uplink grant 365-b, a subframe of which is also used as a reference CSI subframe for A-CSI message subframe 370-b.

Although the examples shown in FIGS. 3A and 3B may be sufficient when the uplink grant is carried in a single subframe, additional options for identifying the CSI reference subframe may be useful when the uplink grant is carried over multiple subframes, as may occur during a coverage enhancement situation. as described above with respect to FIG. 1. During coverage enhancement, an uplink grant scheduling PUSCH transmission may be transmitted using multiple downlink subframes. In addition, PDSCH transmission (including uplink and downlink grants) may hop across different subbands. As an example, each subband may be subject to a limitation of 6 bandwidth resource blocks, and a hop sequence may be preset for each channel. However, the result is that the uplink grant can be transmitted over multiple subframes and/or subbands. The feedback CSI in these situations can be adjusted to accurately reflect channel and interference measurements on the subframes and subbands used for uplink grants.

When determining which subframes and subbands to use as CSI reference subframes, the following factors may be considered. First, multicast PDSCH transmissions for the same transmission block may hop across different subbands, and such hops may be predetermined. As a result, the CSI message is preferably based on measurements made on the subbands hopped by the PDSCH. Second, if there is a grouping of TTIs for uplink grant transmission, the CSI message is preferably based on one or more subframes of the plurality of subframes in which the uplink grant was transmitted. And third, the subframe selected as the CSI reference subframe must also be a valid CSI reference subframe.

The CSI reference subframe may be suitable for CSI measurement, for example, if it may include a CRS signal. Thus, DwPTS subframes and MBSFN subframes may not be suitable CSI reference subframes. The reference CSI subframe may also be suitable for CSI measurement if it is in the same set of subframes used for uplink grant transmission. In addition, for instances of MTS user equipment, the subband can act as an additional factor. For example, if the MTC user equipment is tuned to a subband that is different from the subband for which the CSI is intended to be reported, then the subframe is not suitable for CSI measurement.

Thus, the selection of a CSI reference subframe may depend on whether uplink grant is transmitted over multiple subframes, whether uplink grant is transmitted over multiple subframes and subbands, and whether individual subframes are suitable for CSI measurement.

One aspect of the disclosure addresses the selection of a CSI reference subframe when uplink grant is transmitted over multiple subframes but on a single subband (ie, in a non-subband hopping situation).

In this situation, the P-CSI message may operate as outlined above with respect to FIG. 3A. Thus, the P-CSI message subframe can be selected in accordance with the P-CSI configuration (eg, determining the periodicity and offset of the P-CSI message subframe). The reference CSI subframe can then be selected a predetermined number of subframes n before the P-CSI message subframe. In the example, n may be equal to four or more subframes. The selected CSI reference subframe must also be suitable for CSI measurements. Thus, if a subframe that is n subframes before a P-CSI message subframe is not suitable for CSI measurement, then subframe n+1 (a subframe that is n+1 subframes before a P-CSI message subframe) can be considered and used , if it is suitable.

The A-CSI message is illustrated in FIG. 4. Fig. 4 illustrates a timeline 400 for a CSI message using different CSI reference subframes in accordance with various aspects of the present disclosure. Timeline 400 includes a downlink timeline 405 and an uplink timeline 410. Downlink timeline 405 illustrates the relative timing of transmissions from a base station, such as base stations 105 in FIG. 1 or 2, while uplink timeline 410 illustrates the relative timing of transmissions from user equipment, such as user equipment instances 115 in FIG. 1 or 2. Downlink timeline 405 and uplink timeline 410 are divided into subframes 315.

Downlink timeline 405 includes uplink grant 415

- 9 043384 communication, which includes a group of TTIs that span multiple subframes 315. In the example of FIG. 4, uplink grant 415 spans eight subframes 315. Uplink grant 415 may operate to schedule PUSCH transmission 435, illustrated in uplink timeline 410. The scheduled PUSCH transmission 435 is illustrated as being scheduled for eight subframes 315 and may include an A-CSI message. In the example in FIG. 4, there is a gap of eight subframes 315 between uplink grant 415 and PUSCH transmission 435. In practice, the lengths of uplink grant 415, PUSCH transmission 435, or the gap between uplink grant 415 and PUSCH transmission 435 may vary.

The A-CSI message included in PUSCH transmission 435 may be based on CSI measurements made relative to one or more reference CSI subframes. In fig. 4, three different alternatives are illustrated for potential CSI reference subframes. In the first alternative 420, the last usable subframe 315 from a group of TTIs for uplink grant 415 may be used as a reference CSI subframe. Although the subframe 315 identified by the first alternative 420 does represent one subframe used by the uplink grant 415, the first alternative 420 will not result in the selection of a reference CSI subframe that represents all subframes 315 used by the uplink grant 415. Although not shown, a single reference subframe for CSI measurement may be defined in another subframe. As an example, the first usable subframe of a TTI group for uplink grant 415 may be used as a reference CSI subframe.

A second alternative to 425 may address this issue. In a second alternative 425, two or more subframes 315 in the entire plurality of subframes of the TTI group carrying uplink grant 415 may be used as CSI reference subframes. Two or more subframes 315 used in second alternative 425 may be required to be usable for CSI measurement. Under some circumstances, all eligible subframes 315 in a plurality of subframes 315 from a group of TTIs carrying uplink grant 415 may be used for CSI measurement. When two or more subframes 315 are used to measure CSI, the CSI measurements may be averaged to provide a single CSI data for inclusion in PUSCH transmission 435. Alternatively, individual reports corresponding to individual CSI reference subframes may also be transmitted with PUSCH transmission 435.

A third alternative 430 may involve using the technique illustrated in FIG. 3B. In a third alternative 430, the most recent usable subframe or subframes that are 4 ms or earlier than PUSCH transmission 435 may be used as the CSI reference subframe. Thus, on timeline 400, subframe 315 illustrated in third alternative 430 is four subframes before the start of PUSCH transmission 435. In this third alternative 430, the gap between the identified suitable CSI reference subframe and the PUSCH transmission 435 may include at least one subframe that does not carry an uplink grant 415. In the third alternative 430, the identified CSI reference subframe may or may not correspond to the subframe 315 in which the uplink grant 415 was transmitted.

Although the CSI reference subframes identified through the first alternative 420 and the third alternative 430 may require the least amount of processing in the user equipment 115, potentially the most accurate CSI measurement may result from the use of the second alternative 425.

Under some circumstances, transmission of the PDSCH may be repeated on the first subband while the uplink grant may be repeated or grouped on a second subband that is different from the first subband. In this case, the uplink resolution may still be on a single subband, and any of the first alternative 420, second alternative 425, or third alternative 430 illustrated in FIG. 4 can be applied to the A-CSI message. However, in this situation, the subband used for the CSI measurement (corresponding to the subband on which the uplink grant is transmitted) may not be aligned with the subband for which the next PDSCH may be transmitted. However, this situation may be under the control of base station 105, which may select different subbands to transmit uplink grants to obtain feedback CSI for different subbands. Additionally or separately, base station 105 may use P-CSI to obtain CSI measurements of different subbands to determine a preferred subband for PDSCH transmissions.

Another aspect of the disclosure addresses the selection of a CSI reference subframe when uplink grant is transmitted across multiple subframes and across multiple subbands (ie, in a subband hopping situation). This situation is illustrated in FIG. 5.

Fig. 5 shows an exemplary timeline 500 for receiving an uplink grant across multiple subframes and subbands in accordance with various aspects of the present invention.

- 10 043384th disclosure. Timeline 500 includes a downlink timeline 505 and an uplink timeline 510. Downlink timeline 505 illustrates the relative timing of transmissions from a base station, such as base stations 105 in FIG. 1 or 2, while uplink timeline 510 illustrates the relative timing of transmissions from user equipment, such as user equipment instances 115 in FIG. 1 or 2. Downlink timeline 505 and uplink timeline 510 are divided into subframes 315. Downlink timeline 505 is also divided into multiple subbands 515. In the example of FIG. 5, downlink timeline 505 includes subband 515-a, subband 515-b, subband 515-c, and subband 515-d. Any number of subbands 515 may be included in the downlink timeline 505.

The uplink grant transmitted on the downlink timeline 505 may include a TTI group that is divided into two or more TTI subgroups 520. In the example in FIG. 5, the first TTI subset 520-a is illustrated as occupying four subframes 315 on subband 515-a. The second subset of TTIs 520-b is illustrated as occupying four subframes 315 on subband 515-c. Thus, in this example, the uplink grant uses eight subframes 315 over two subsets 520 of TTIs, each of which has four subframes 315. The uplink grant may operate to schedule PUSCH transmission 525, illustrated in uplink timeline 510 . Scheduled PUSCH transmission 525 is illustrated as being scheduled for eight subframes 315 and may include an A-CSI message. In the example in FIG. 5, there is a gap of four subframes 315 between the second TTI subset 520-b and the PUSCH transmission 525. In practice, the lengths and numbers of TTI subsets 520, subbands 515 occupied by TTI subsets 520, the length of the PUSCH transmission 525, and the gap between the second (or last) TTI subset 520-b and the PUSCH transmission 525 may vary.

Splitting the uplink grant across multiple subbands 515 can help improve frequency diversity for transmissions specifically targeted to, for example, MTC UE instances. However, the base station may also benefit from selective scheduling of frequencies or subbands, although the base station is not required to do so. Thus, if a base station intends to use frequency selective scheduling, the base station will benefit from receiving a CSI message reflecting CSI measurements made on specific subbands 515. In this situation, CSI reference subframes may be identified in the same manner as described with respect to FIG. . 4 for the A-CSI message and with respect to FIG. 3A for the P-CSI message, except that the subframes to be used as reference CSI subframes may be located on subbands determined by the base station (since the base station intends to use frequency selective scheduling based on CSI measurements of different subbands).

However, when the base station does not intend to use frequency selective scheduling, CSI measurements, for example, can be taken and averaged over multiple subbands. Additional examples and alternatives are described below.

Even when subband hopping is present, the P-CSI message can operate as outlined above with respect to FIG. 3A. Thus, the P-CSI message subframe can be selected according to the P-CSI configuration (eg, the periodicity and offset of the P-CSI message subframe, and the inclusion of the subband for evaluation). A reference CSI subframe on the identified subband can then be selected a predetermined number of subframes n before the P-CSI message subframe. In the example, n may be equal to four or more subframes. The selected CSI reference subframe must also be suitable for CSI measurements. Thus, if a subframe that is n subframes before the P-CSI message subframe is not suitable for CSI measurement, then subframe n+1 (the subframe that is n+1 subframes before the P-CSI message subframe) can be considered and be used if suitable. The subband for which the CSI is reported is in this case the same as the measured subband. Alternatively, multiple CSI reference subframes spanning multiple subbands may be defined such that the P-CSI message reflects the average channel quality over multiple subbands.

The A-CSI message for a situation in which subband hopping occurs is illustrated in FIG. 6. Fig. 6 illustrates a timeline 600 for a CSI message using different CSI reference subframes in accordance with various aspects of the present disclosure. Timeline 600 includes a downlink timeline 605 and an uplink timeline 610. Downlink timeline 605 illustrates the relative timing of transmissions from a base station, such as base stations 105 in FIG. 1 or 2, while uplink timeline 610 illustrates the relative timing of transmissions from user equipment, such as user equipment instances

- 11 043384 vania 115 in Fig. 1 or 2. Downlink timeline 605 and uplink timeline 610 are divided into subframes 315. Downlink timeline 605 is also divided across multiple subbands 615. In the example of FIG. 6, downlink timeline 605 includes subband 615-a, subband 615-b, subband 615-c, and subband 615-d. Any number of subbands 615 may be included in the downlink timeline 605.

The uplink grant transmitted on the downlink timeline 605 may include a TTI group that is divided into two or more TTI subgroups 620. In the example in FIG. 6, the first subset 620-a of TTIs is illustrated as occupying four subframes 315 on subband 615-a. The second subset 620-b of TTIs is illustrated as occupying four subframes 315 on subband 615-c. Thus, in this example, the uplink grant uses eight subframes 315 across two subsets 620 of TTIs, each of which has four subframes 315. The uplink grant may operate to schedule PUSCH transmission 645, illustrated in uplink timeline 610 . Scheduled PUSCH transmission 645 is illustrated as being scheduled for eight subframes 315 and may include an A-CSI message. In the example in FIG. 6, there is a gap of four subframes 315 between the second TTI subset 620-b and the PUSCH transmission 645. In practice, the lengths and numbers of TTI subsets 620, subbands 615 occupied by TTI subsets 620, the length of the PUSCH transmission 645, and the gap between the second (or last) TTI subset 620-b and the PUSCH transmission 645 may vary.

The A-CSI message included in PUSCH transmission 645 may be based on CSI measurements made relative to one or more reference CSI subframes. In fig. 6 illustrates four different alternatives for potential CSI reference subframes. In the first alternative 625, the last usable subframe 315 of the second (or last) TTI subset 620-b may be used as a reference CSI subframe. If the identified CSI reference subframe is not suitable for CSI measurements, the next earlier subframe on the subband may be selected until a suitable subframe is identified. Although the subframe 315 identified by the first alternative 625 does represent one subframe used by the uplink grant, the first alternative 625 will not result in the selection of a reference CSI subframe that represents all subframes 315 used by the uplink grant. In addition, the first alternative 625 results in the use of a CSI reference subframe that represents only one subband on which the uplink grant is transmitted. Although not shown, two or more usable subframes may be used in the second (or last) TTI subset 620-b for CSI measurement. Although not shown, a single reference subframe for the CSI measurement may be defined in another subframe or in another subgroup. As an example, the first usable subframe of the second (or last) subset 620-b of uplink grant TTIs may be used as a reference CSI subframe. As another example, the first usable subframe of the first uplink grant TTI subset 620-a may be used as a reference CSI subframe.

The second alternative 630 improves on the first alternative 625. In the second alternative 630, the last usable subframe 315 from each of the first TTI subset 620-a and the second TTI subset 620-b may be used as reference CSI subframes. When two or more subframes 315 are used to measure CSI, the CSI measurements may be averaged to provide a single CSI data for inclusion in PUSCH transmission 645. Alternatively, individual reports corresponding to individual CSI reference subframes and subbands may also be transmitted with PUSCH transmission 645. As with each of the alternatives described herein, the identified subframes must also be suitable for CSI measurements. If one of the identified CSI reference subframes is not suitable for CSI measurements, the next earlier subframe on the subband may be selected until a suitable subframe is identified.

In a third alternative 635, two or more subframes 315 in the entire plurality of subframes of a TTI group carrying uplink permission, including the first TTI subset 620-a and the second TTI subset 620-b, may be used as reference CSI subframes. Two or more subframes 315 used in third alternative 635 may be required to be usable for CSI measurement. Under some circumstances, all eligible subframes 315 in a plurality of subframes 315 of the combined TTI subsets 620 carrying uplink permission may be used for CSI measurement. As described above, when two or more subframes 315 are used to measure CSI, the CSI measurements may be averaged to provide a single CSI data for inclusion in PUSCH transmission 645. Alternatively, individual reports corresponding to individual CSI reference subframes may also be transmitted with PUSCH transmission 645.

A fourth alternative 640 may involve using the technique illustrated

- 12 043384 noah in fig. 3B. In a fourth alternative 640, the most recent usable subframe that is 4 ms or earlier than PUSCH transmission 645 may be used as the CSI reference subframe. The subband for which the CSI is reported is in this case the same as the measured subband. Thus, on timeline 600, subframe 315 illustrated in fourth alternative 640 is four subframes before the start of PUSCH transmission 654. In this fourth alternative 640, the gap between the identified usable CSI reference subframe and PUSCH transmission 645 may include at least one subframe that does not carry an uplink grant.

Although the CSI reference subframes identified through the first alternative 625 and the fourth alternative 640 may require the least amount of processing in the user equipment 115, potentially more accurate CSI measurements may result from the use of the second alternative 630 or the third alternative 635.

The alternatives identified with respect to FIGS. 3A, 3B, 4 and 6 may be used in identifying suitable CSI reference subframes for either P-CSI or A-CSI reporting. In particular, when the CSI message is based on the CRS signal, the alternatives identified above may be sufficient to handle situations in which uplink transmission occurs over multiple subframes and/or subbands. However, when the CSI message is based on the CSI-RS signal, additional considerations may be warranted. These may include a guarantee that the non-zero power (NZP) CSI-RS signal is also grouped for channel measurements. The NZP CSI-RS group signal may be grouped along with the intended PDSCH operation. In addition, an IMR resource may be resolved in multiple subframes to support interference measurements across multiple subframes.

The alternatives identified above can be defined in the CSI configuration. For example, the A-CSI configuration may identify one or more of the alternatives described with respect to FIG. 3B, 4 or 6, for identifying a CSI reference subframe and for determining CSI data. The A-CSI configuration may be located in the user equipment 115. In an embodiment, the A-CSI configuration may be received by the user equipment 115 from the base station 105.

The P-CSI configuration can identify periodicity, offset, etc. for CSI measurements. In one embodiment, the P-CSI configuration may depend on the size of the uplink transmission grouping used by the user equipment 115. For example, if uplink grouping is not used, the user equipment 115 may use a default P-CSI configuration or an existing P-CSI configuration. CSI having a certain periodicity and/or offset. However, if uplink grouping is used, user equipment 115 may use, for example, an indexed P-CSI configuration. Thus, for a given constellation size, a P-CSI configuration can be determined. A first uplink constellation size may trigger use of a first defined P-CSI configuration, while a second uplink constellation size may trigger use of a second defined P-CSI configuration. As a specific example, a grouping size of eight for uplink transmissions may trigger a P-CSI configuration that specifies that P-CSI is transmitted every eight groups, and the offset may be determined in terms of the grouping granularity.

As an alternative configuration, P-CSI can be used regardless of the size of the uplink transmission constellation.

Additionally or separately, the minimum gap between the last usable subframe for CSI measurement and the corresponding CSI report (P-CSI, A-CSI, or both) may be greater than 4 ms. As an example, the minimum interval may be defined as 6 ms. Compared to 4 ms, the larger minimum gap provides a longer time for the MTC user equipment to process the measurement signal for the CSI message, and therefore reduces the processing requirement at the MTC user equipment. Additionally, the minimum gap may be a function of the grouping length. As an example, if the TTI binning length is 1, a minimum interval of 6 ms may be specified. If the TTI binning length is 8, a minimum interval of 10 ms can be specified.

Fig. 7 shows a block diagram 700 of an apparatus 705 for use in wireless communications in accordance with various aspects of the present disclosure. Device 705 may be an example of one or more aspects of user equipment 115 described with reference to FIG. 1 or 2 having the functionality described with respect to FIG. 3A, 3B or 4-6. Device 705 may include a UE receiver module 710, a UE CSI module 715, and/or a UE transmitter module 720. Device 705 may also be or include a processor (not shown). Each of these modules can communicate with each other.

The components of device 705 may be individually or collectively implemented using one or more application specific integrated circuits (ASICs) adapted to perform

- 13 043384 some or all applicable functions in the hardware. Alternatively, the functions may be performed by one or more other processors (or cores) on one or more integrated circuits. Other examples may use other types of integrated circuits (eg, structured ASICs, field programmable gate arrays (FPGAs), and other semi-custom integrated circuits) that can be programmed by any method known in the art. The functions of each module may also be implemented in whole or in part using instructions embodied in memory formatted for execution by general-purpose processors or specialized processors.

The user equipment receiver module 710 may receive information such as packets, user data, and/or control information related to various information channels (eg, control channels, data channels, etc.). The user equipment receiver module 710 may be configured to receive uplink group grants, for example, in a coverage enhanced environment. Uplink group grants may include groups of TTIs that are transmitted over multiple subframes and/or multiple subbands. The PDSCH transmission may also be received using the user equipment receiver module 710. Additionally, in certain aspects, a P-CSI configuration or an A-CSI configuration may be received via the user equipment receiver module 710. The received information may be transmitted to the user equipment CSI module 715 and other components of the device 705.

The user equipment CSI module 715 may be used by the device 705 to measure and report CSI data to the base station. In particular, user equipment CSI module 715 may be used in circumstances where device 705 receives an uplink grant across multiple subframes and/or subbands and CSI data needs to be determined. UE CSI module 715 may be used to recognize the configuration of received uplink grant TTI groups and determine whether the received TTI groups are distributed over multiple subframes or subbands. Based on the determined configuration, user equipment CSI module 715 may be used to identify one or more subframes for use as CSI reference subframes. The user equipment CSI module 715 may also be used to perform a CSI measurement using one or more identified CSI reference subframes. The resulting CSI data may be transmitted to the user equipment transmitter module 720 for transmission to the base station.

The user equipment transmitter module 720 may transmit one or more signals received from other components of the device 705. The user equipment transmitter module 720 may transmit CSI data to the base station in conjunction with the operations of the user equipment CSI module 715. In some examples, the user equipment transmitter module 720 may be combined with the user equipment receiver module 710 in a transceiver module.

Fig. 8 shows a block diagram 800 of a device 705-a for use in wireless communications in accordance with various examples. Device 705-a may be an example of one or more aspects of user equipment 115 described with reference to FIG. 1 or 2, performing the functions described in relation to FIG. 3A, 3B or 4-6. It may also be an example of the device 705 described with reference to FIG. 7. The device 705-a may include a UE receiver module 710-a, a UE CSI module 715-a, and/or a UE transmitter module 720-a, which may be examples of corresponding modules of the device 705. Device 705-a may also include a processor (not shown). Each of these components may have a connection with each other. The user equipment CSI module 715-a may include a TTI slot group configuration module 805, a CSI reference subframe identification module 810, or a CSI measurement module 815. The UE receiver module 710-a and the UE transmitter module 720-a may perform the functions of the UE receiver module 710 and the UE transmitter module 720 in FIG. 7 respectively.

A TTI group configuration module 805 may be used by device 705-a to determine the configuration of one or more TTI groups included in an uplink grant transmission received by device 705-a. For example, in a coverage improvement situation, device 705-a may receive an uplink grant across multiple subframes and/or subbands. An uplink grant that is transmitted over multiple subframes may include a group of TTIs that spans multiple subframes. An uplink grant that is carried over multiple subframes and subbands may include one or more subsets of TTIs, each of which spans multiple subframes, and each of which is carried on different subbands. TTI group configuration module 805 may be used by device 705-a to determine a specific inter group configuration.

- 14 043384 shaft TTI received with uplink permission.

The CSI reference subframe identification module 810 may be used by the device 705-a to identify one or more CSI reference subframes based on the TTI slot group configuration identified by the TTI slot group configuration module 805. Thus, for example, CSI reference subframe identification module 810 may include a CSI configuration that determines which of the alternatives described above with respect to FIG. 3A, 3B, 4 or 6 should be used when defining the CSI reference subframe. The CSI reference subframe identification module 810 may include multiple CSI configurations, which may be selected based on the TTI group configuration and based on whether a P-CSI message or an ACSI message is used. In one example, CSI reference subframe identification module 810 may select to use the last valid subframe of a group of TTIs or a subset of TTIs as the CSI reference subframe. In another example, CSI reference subframe identification module 810 may select to use the last valid subframe of each of several subgroups of TTIs as CSI reference subframes. Multiple subframes, including all eligible subframes in a group of TTIs or across multiple subgroups of TTIs, may be used as CSI reference subframes. In addition, subframes that occur a specified number of subframes before the CSI message may also be identified as CSI reference subframes. Finally, the identification of CSI reference subframes by the CSI reference subframe identification module may depend on the configuration of the TTI interval identified by the TTI slot group configuration module, and may also depend on the CSI configuration.

The CSI measurement module 815 may be used by the device 705-a to measure the CSI on the subframe or subframes identified as CSI reference subframes by the CSI reference subframe identification module 810. CSI measurements can also be performed according to the CSI configuration. Thus, if the CSI configuration has determined that CSI measurements should be made for multiple reference CSI subframes and then averaged together, CSI measurement module 815 will be used to perform CSI measurements and average the measurements together. Thus, CSI measurement module 815 may perform CSI measurements, average CSI measurements (when determined by the CSI configuration), and may provide transmission of one or more CSI data (eg, using user equipment transmitter module 720a).

Fig. 9 shows a system 900 for use in wireless communications in accordance with various examples. System 900 may include user equipment 115-b, which may be an example of user equipment instances 115 in FIG. 1 or 2, including the functions described with respect to FIG. 3A, 3B or 4-6. User equipment 115b may also be an example of one or more aspects of devices 705 in FIG. 7 and 8.

User equipment 115-b may typically include components for bidirectional voice and data transmission, including components for transmitting communications and components for receiving communications. UE 115-b may include UE antenna(s) 940, UE transceiver module 935, UE processor module 905, and UE memory 915 (including software (SW) 920), each of which may directly or indirectly communicate with each other (eg, through one or more buses 945). The user equipment transceiver module 935 may be configured to communicate bidirectionally through the user equipment antenna(s) 940 and/or one or more wired or wireless communication links with one or more networks, as described above. For example, user equipment transceiver module 935 may be configured to communicate bidirectionally with base stations 105 with reference to FIG. 1-6. UE transceiver module 935 may include a modem configured to modulate packets and provide modulated packets to UE antenna(s) 940 for transmission, and demodulate packets received from UE antenna(s) 940. Although user equipment 115-b may include a single UE antenna 940, user equipment 115-b may have multiple UE antennas 940 capable of transmitting and/or receiving multiple wireless transmissions in parallel. The user equipment transceiver module 935 may be capable of communicating in parallel with one or more base stations 105 via multiple component carriers.

The user equipment 115-b may include a user equipment CSI module 715-b that may perform the functions described above for the user equipment CSI modules 715 of device 705 in FIG. 7 and 8. User equipment 115-b may also include a CSI measurement averaging module 925 or a CSI configuration module 930. The CSI measurement averaging module 925 may be a module separate from the CSI measurement module 815 or included in the CSI measurement module 815 (FIG. 8) and may be used to average the CSI measurements already received prior to transmitting the CSI data to the base station. The CSI configuration module 930 can

- 15 043384 be used to store the CSI configuration, which can then be used by either the CSI reference subframe identification module 810 or the CSI measurement module 815 (FIG. 8) to determine the CSI configuration. The stored CSI configuration may specify a scheme for determining CSI reference subframes (used by CSI reference subframe identification module 810). The stored CSI configuration may also specify whether one or more CSI measurements should be taken, and whether the measurements should be averaged (used by CSI measurement module 815). The saved CSI configurations may include saved A-CSI configurations and saved PCSI configurations. In the case of stored P-CSI configurations, multiple configurations may be stored corresponding to different constellation sizes that may be used in uplink transmissions.

The user equipment memory 915 may include random access memory (RAM) and read only memory (ROM). The user equipment memory 915 may store computer-readable, computer-executable software/firmware code 920 containing instructions that are configured, when executed, to cause the user equipment processor module 905 to perform various functions described herein (e.g., perform CSI measurements on identified CSI reference subframes when user equipment 115-b has received uplink group grants). Alternatively, the computer-readable computer-executable software/firmware code 920 may not be directly executable by the user equipment processor module 905, but may be configured to cause the computer (eg, when compiled and executed) to perform the functions described herein. The user equipment processor module 905 may include an intelligent hardware device, such as a central processing unit (CPU), a microcontroller, an application specific integrated circuit (ASIC), etc.

Fig. 10 shows a block diagram 1000 of an apparatus 1005 for use in wireless communications in accordance with various aspects of the present disclosure. In some examples, device 1005 may be an example of aspects of one or more base stations 105 described with reference to FIGS. 1 or 2, and having the functionality described with respect to FIG. 3-6. In some examples, device 1005 may be part of or include an LTE/LTE-A eNB and/or an LTE/LTE-A base station. Device 1005 may also be a processor. The device 1005 may include a base station receiver module 1010, a base station CSI module 1015, and/or a base station transmitter module 1020. Each of these modules can communicate with each other.

The components of device 1005 may be individually or collectively implemented using one or more application specific integrated circuits (ASICs) adapted to perform some or all of the applicable functions in hardware. Alternatively, the functions may be performed by one or more other processors (or cores) on one or more integrated circuits. Other examples may use other types of integrated circuits (eg, structured ASICs, field programmable gate arrays (FPGAs), and other semi-custom integrated circuits) that can be programmed by any method known in the art. The functions of each module may also be implemented in whole or in part using instructions embodied in memory formatted for execution by general-purpose processors or specialized processors.

In some examples, the base station receiver module 1010 may include at least one radio frequency (RF) receiver, such as an RF receiver configured to receive CSI data transmitted by a user equipment. The base station receiver component 1010 may be used to receive various types of data and/or control signals (i.e., transmissions) over one or more links of a wireless communication system, such as one or more links of the wireless communication system 100 described with reference to fig. 1-6.

In some examples, base station transmitter module 1020 may include at least one RF transmitter, such as at least one RF transmitter configured to transmit uplink grant across multiple subframes or subbands. The base station transmitter module 1020 may also be configured to communicate a CSI configuration to a user equipment, thereby allowing the user equipment to use one or more CSI configurations when determining CSI data. Base station transmitter module 1020 may be used to transmit various types of data and/or control signals (i.e., transmission) over one or more links of a wireless communication system, such as one or more links of wireless communication system 100 described with reference to fig. 1-6.

In some examples, the base station CSI module 1015 may be configured to generate one or more CSI configurations to be used by the user equipment. CSI configurations may include different P-CSI configurations defining periodicity and offset, for example, as a function of constellation size. CSI configurations may include different A-CSI configurations identifying different options for identifying CSI reference subframes and different options for measuring CSI data. A CSI configuration may correspond to a configuration index that is known or communicated to the user equipment.

Fig. 11 shows a block diagram 1100 of a base station 105-b (eg, a base station that is part of an eNB or an entire eNB) for use in wireless communications in accordance with various aspects of the present disclosure. In some examples, base station 105-b may be an example of aspects of one or more base stations 105 described with reference to FIG. 1 or 2 having the functionality described with reference to FIG. 3A, 3B, or 4-6, and/or aspects of one or more devices 1005 when configured as a base station, as described with reference to FIG. 10. Base station 105-b may be configured to implement or provide at least some of the features and functions of the base station and/or device described with reference to FIG. 1-6.

Base station 105-b may include a base station processor module 1110, a base station memory module 1120, at least one base station transceiver module (represented by base station transceiver module(s) 1150), at least one base station antenna (represented by base station antenna(s) 1155) and/or base station CSI module 1015-a. The base station 105-b may also include one or more base station communication modules 1130 and/or a network communication module 1140. Each of these modules may communicate directly or indirectly with each other over one or more buses 1135.

The base station memory module 1120 may include random access memory (RAM) and/or read only memory (ROM). The base station memory module 1120 may store computer-readable, computer-executable software/firmware code 1125 containing instructions that, when executed, cause the base station processor module 1110 to perform various functions described herein related to wireless communications ( for example, generation and/or transfer of CSI configurations, etc.). Alternatively, the computer-readable computer executable software/firmware code 1125 may not be directly executable by the base station processor module 1110, but may be configured to cause the base station 1105 (eg, when compiled and executed) to perform various functions described in this document.

The base station processor module 1110 may include an intelligent hardware device, such as a central processing unit, a microcontroller, an application specific integrated circuit (ASIC), etc. The base station processing module 1110 may process information received through the base station transceiver module(s) 1150, the base station communication module 1130, and/or the network communication module 1140. Base station processing module 1110 may also process information to be sent to transceiver module(s) 1150 for transmission via antenna(s) 1155, base station communications module 1130 for transmission to one or more other base stations 105-c and 105-d, and/or network communications module 1140 for transmission to core network 1145, which may be an example of one or more aspects of core network 130 described with reference to FIG. 1. Base station processor module 1110 may control, alone or in connection with base station CSI module 1015a, various aspects of CSI configuration generation and transmission.

Base station transceiver module(s) 1150 may include a modem configured to modulate packets and provide modulated packets to base station antenna(s) 1155 for transmission, and demodulate packets received from base station antenna(s) 1155. Base station transceiver module(s) 1150 may, in some examples, be implemented as one or more base station transmitter modules and one or more separate base station receiver modules. Base station transceiver module(s) 1150 may support communications in a first radio frequency spectrum band and/or a second radio frequency spectrum band. Base station transceiver module(s) 1150 may be configured to communicate bidirectionally via antenna(s) 1155 with one or more user equipment instances or devices, such as one or more user equipment instances 115 described with reference to FIG. 1, 2, or 9. Base station 105-b may, for example, include multiple base station antennas 1155 (eg, an antenna array). The base station 105-b may communicate with the core network 1145 through the network communication module 1140. The base station 105-b can also communicate with other base stations, such as the base stations 105-c and 105-d, using the base station communication module 1130.

The base station CSI module 1015-a may be configured to perform and/or control some or all of the features and/or functions described with reference to FIG. 3A, 3B, 4-6 or 10 related to CSI configurations. The base station CSI module 1015-a or portions of the base station CSI module 1015-a may include a processor, and/or some or all of the functions of the base station CSI module 1015-a may be performed by the base station processor module 1110 and/ or in connection with the base station processor module 1110. In some examples, the base station CSI module 1015-a may be an example of the base station CSI module 1015 described with reference to FIG. 10.

Fig. 12 is a block diagram of a multiple-input multiple-output (MIMO) communications system 1200 including a base station 105-c and a user equipment 115-c. The MIMO communication system 1200 may illustrate aspects of the wireless communication system 100 shown in FIG. 1-6. Base station 105 may be equipped with antennas 1234-a-1234-x, and user equipment 115-c may be equipped with antennas 1252-a-1252-n. In MIMO communication system 1200, base station 105 can send data over multiple communication links simultaneously. Each link may be referred to as a layer, and the rank of the link may indicate the number of layers used for communication. For example, in a 2x2 MIMO communication system in which the base station 105-e transmits two layers, the link rank between the base station 105-e and the user equipment 115-c is two.

At base station 105, transmit processor 1220 may receive data from a data source. Transmit processor 1220 may process the data. Transmit processor 1220 may also generate control symbols and/or reference symbols. MIMO transmit (Tx) processor 1230 may perform spatial processing (eg, precoding) on data symbols, control symbols, and/or reference symbols as appropriate, and may provide output symbol streams to transmit modulators 1232-a-1232-x. Each modulator 1232 may process a corresponding output symbol stream (eg, for orthogonal frequency division multiplexing (OFDM), etc.) to obtain an output sample stream. Each modulator 1232 may further process (eg, analogize, amplify, filter, and upconvert) the output sample stream to produce a downlink signal. In one example, downlink signals from modulators 1232-a-1232-x may be transmitted through antennas 1234-a-1234-x, respectively.

At user equipment 115-c, user equipment antennas 1252-a-1252-n may receive downlink signals from base station 105-c and may provide received signals to demodulators 1254-a-1254-n, respectively. Each demodulator 1254 may process (eg, filter, amplify, down-convert, and digitize) a corresponding received signal to obtain input samples. Each demodulator 1254 may further process the input samples (eg, for OFDM multiplexing, etc.) to obtain received symbols. The MIMO sensor 1256 may receive received symbols from all demodulators 1254-a-1254-n, perform MIMO detection on the received symbols as appropriate, and provide the detected symbols. Receive processor 1258 may process (e.g., demodulate, deinterleave, and decode) the detected symbols to provide decoded data to user equipment 115-c for data output and provide decoded control information to processor 1280 or memory 1282.

The processor 1280 may, in some cases, execute stored instructions to create instances of one or more user equipment CSI modules 715-c. UE CSI module 715-c may be an example of aspects of UE CSI module 715 described with reference to FIG. 7, 8 or 9.

On the uplink in user equipment 115-c, a transmit processor 1264 may receive and process data from a data source. Transmission processor 1264 may also generate reference symbols for the reference signal. Symbols from transmit processor 1264 may be pre-encoded by MIMO transmit processor 1266 as appropriate, further processed by demodulators 1254-a-1254-l (eg, for single carrier FDMA (SC-FDMA), etc.) and transmitted to the base station 105 in accordance with the transmission parameters received from the base station 105. At base station 105, uplink signals from user equipment 115-c may be received by antennas 1234, processed by demodulators 1232, detected by MIMO sensor 1236 as appropriate, and further processed by receive processor 1238. Receive processor 1238 may provide decoded data for output to processor 1240 and/or memory 1242. Processor 1240 may in some cases execute stored instructions to instantiate one or more base station CSI modules 1015-b. Base station CSI module 1015-b may be an example of aspects of base station CSI module 1015 described with reference to FIG. 10 or 11.

The user equipment components 115-c may be individually or collectively implemented using one or more application specific integrated circuits (ASICs) adapted to perform some or all of the applicable functions in hardware. Each of these modules may be means for performing one or more functions related to the operation of the MIMO communication system 1200. Likewise, the components of the base station 105 may be individually or collectively implemented using one or more application specific integrated circuits (ASICs) adapted to perform some or all of the applicable functions in hardware. Each of these components may be means for performing one or more functions related to the operation of the MIMO communication system 1200.

Fig. 13 is a flowchart illustrating an example of a method 1300 for wireless communications in accordance with various aspects of the present disclosure. For clarity, method 1300 is described below with reference to aspects of one or more instances of user equipment 115 described with reference to FIG. 1, 2, or 9, and/or aspects of one or more devices 705 described with reference to FIG. 7 or 8. In some examples, the user equipment may execute one or more sets of codes to control functional elements of the user equipment to perform the functions described below. Additionally or alternatively, the user equipment may perform one or more of the functions described below using specialized hardware.

At step 1305, method 1300 may include identifying, at least in part based on the TTI group configuration, one or more subframes as CSI reference subframes to be used for CSI measurement. Subframes may be identified in accordance with one of the alternatives described above with respect to FIG. 3A, 3B, 4 or 6. A group of TTIs may be received with uplink permission in a plurality of subframes containing the group of TTIs. A group of TTIs may cover multiple subframes and may also be split across multiple subbands (in the form of two or more TTI subgroups). An uplink group grant may be received in accordance with a coverage enhancement technique. The receiving user equipment may be, for example, an MTS user equipment. The operations at step 1305 may be performed using the CSI reference subframe identification module 810 described with reference to FIG. 8.

At 1310, method 1300 may include performing CSI measurements of CSI reference subframes. CSI measurements can be performed according to a CSI configuration such as a P-CSI configuration or an A-CSI configuration. In some cases, the CSI measurement may include averaging CSI measurements taken across multiple CSI reference subframes. The operations at step 1310 may be performed using the information measurement module 815 described with reference to FIG. 8, and/or CSI measurement averaging module 925 or CSI configuration module 930, described with reference to FIG. 9.

At step 1315, method 1300 may include transmitting CSI data based at least in part on a CSI measurement. The CSI data may be transmitted to the base station and may be transmitted according to the CSI configuration. The operations at step 1315 may be performed using the user equipment CSI module 715 and/or the user equipment transmitter module 720, described with reference to FIG. 7 or 8.

Thus, method 1300 can provide wireless communication. It should be noted that method 1300 is just one implementation, and that the operations of method 1300 may be reordered or otherwise modified so that other implementations are possible.

Fig. 14 is a flowchart illustrating an example of a method 1400 for wireless communications in accordance with various aspects of the present disclosure. For clarity, method 1400 is described below with reference to aspects of one or more instances of user equipment 115 described with reference to FIG. 1, 2, or 9, and/or aspects of one or more devices 705 described with reference to FIG. 7 or 8. In some examples, the user equipment may execute one or more sets of codes to control functional elements of the user equipment to perform the functions described below. Additionally or alternatively, the user equipment may perform one or more of the functions described below using specialized hardware.

At steps 1410, 1415, or 1420, method 1400 may include various alternatives for identifying, at least in part based on the TTI group configuration, one or more subframes as CSI reference subframes to be used for CSI measurement.

For example, at step 1410, method 1400 may include identifying the last valid subframe of a TTI group as a reference CSI subframe. The subframe may be identified in accordance with the first alternative 420 described with respect to FIG. 4. A subframe may be considered eligible if there is no configuration of multiple CSI subframes, or if the subframe is not a special short DwPTS subframe or an MBSFN subframe, for example. The operations at step 1410 may be performed using the CSI reference subframe identification module 810 described with reference to FIG. 8.

At step 1415, method 1400 may include identifying two or more suitable subframes in a group of TTIs as CSI reference subframes. Subframes may be identified in accordance with the second alternative 425 described with respect to FIG. 4. Subframes may be considered eligible if there is no configuration of multiple CSI subframes, or if the subframes are not special short DwPTS subframes or MBSFN subframes, for example. For some

- 19 043384 circumstances, all eligible subframes of a TTI group may be identified as CSI reference subframes. The operations at step 1415 may be performed using the CSI reference subframe identification module 810 described with reference to FIG. 8.

At step 1420, method 1400 may include identifying the most recent usable subframe that is at least a predetermined number of subframes earlier than the subframe used for transmitting the CSI data, wherein the gap between the most recent usable subframe and the subframe used for CSI data transmission includes at least one subframe that does not carry an uplink grant. The subframe may be identified in accordance with the third alternative 430 described with respect to FIG. 4. A subframe may be considered eligible if there is no configuration of multiple CSI subframes, or if the subframe is not a special short DwPTS subframe or an MBSFN subframe, for example. The operations at step 1420 may be performed using the CSI reference subframe identification module 810 described with reference to FIG. 8.

At step 1425, method 1400 may include performing a CSI measurement of the CSI reference subframes. CSI measurements can be performed in accordance with a CSI configuration, such as an A-CSI configuration. The operations at step 1425 may be performed using the CSI measurement module 815 described with reference to FIG. 8, and/or the CSI configuration module 930 described with reference to FIG. 9.

At step 1430, method 1400 may include averaging CSI measurements made on each of the CSI reference subframes before transmitting the CSI data. The operations at block 1430 cannot be used in situations where only one CSI reference subframe has been identified (as may be the case if either block 1410 or 1420 was used). In addition, the operations at step 1430 cannot be used if multiple CSI entries are to be transmitted to the base station based on multiple subframes included in a group of TTIs. However, when the operations in step 1430 are used, they may be performed using the CSI measurement module 815 described with reference to FIG. 8, and/or the CSI measurement averaging module 925 described with reference to FIG. 9.

Thus, method 1400 can provide wireless communication. It should be noted that method 1400 is just one implementation and that the operations of method 1400 may be reordered or otherwise modified so that other implementations are possible.

Fig. 15 is a flowchart illustrating an example of a method 1500 for wireless communications in accordance with various aspects of the present disclosure. For clarity, method 1500 is described below with reference to aspects of one or more instances of user equipment 115 described with reference to FIG. 1, 2, or 9, and/or aspects of one or more devices 705 described with reference to FIG. 7 or 8. In some examples, the user equipment may execute one or more sets of codes to control functional elements of the user equipment to perform the functions described below. Additionally or alternatively, the user equipment may perform one or more of the functions described below using specialized hardware.

At steps 1510, 1520, 1530, or 1540, method 1500 may include various alternatives for identifying, at least in part, based on the configuration of a group of TTIs, one or more subframes as CSI reference subframes to be used for CSI measurement.

For example, at step 1510, method 1500 may include identifying the last usable subframe of the last subset of TTIs as a reference CSI subframe. The subframe may be identified in accordance with the first alternative 625 described with respect to FIG. 6. A subframe may be considered eligible if there is no configuration of multiple CSI subframes, or if the subframe is not a special short DwPTS subframe or an MBSFN subframe, for example. The operations at step 1510 may be performed using the CSI reference subframe identification module 810 described with reference to FIG. 8.

At step 1520, method 1500 may include identifying the last usable subframe of each of the subsets of TTIs as a reference CSI subframe. Subframes may be identified in accordance with the second alternative 630 described with respect to FIG. 6. Subframes may be considered eligible if there is no configuration of multiple CSI subframes, or if the subframes are not special short DwPTS subframes or MBSFN subframes, for example. The operations at step 1520 may be performed using the CSI reference subframe identification module 810 described with reference to FIG. 8.

At step 1530, method 1500 may include identifying two or more suitable subframes in two or more TTI interval subsets as CSI reference subframes. Subframes may be identified in accordance with the third alternative 635 described with respect to FIG. 6. Subframes may be considered eligible if there is no configuration of multiple CSI subframes, or if the subframes are not special short DwPTS subframes or MBSFN subframes, for example. Under some circumstances, all eligible subframes of two or more TTI subsets may be identified as CSI reference subframes. The operations at step 1530 may be performed using the CSI reference subframe identification module 810 described with reference to FIG. 8.

At step 1540, method 1500 may include identifying the most recent usable subframe that is at least a predetermined number of subframes earlier than the subframe used for transmitting the CSI data, wherein the gap between the most recent usable subframe and the subframe used for CSI data transmission includes at least one subframe that does not carry an uplink grant. The subframe may be identified in accordance with the fourth alternative 640 described with respect to FIG. 6. A subframe may be considered eligible if there is no configuration of multiple CSI subframes, or if the subframe is not a special short DwPTS subframe or an MBSFN subframe, for example. The operations at step 1540 may be performed using the CSI reference subframe identification module 810 described with reference to FIG. 8.

At step 1545, method 1500 may include performing a CSI measurement of the CSI reference subframes. CSI measurements can be performed in accordance with a CSI configuration, such as an A-CSI configuration. The operations at step 1545 may be performed using the CSI measurement module 815 described with reference to FIG. 8, and/or the CSI configuration module 930 described with reference to FIG. 9.

At step 1550, method 1500 may include averaging CSI measurements made on each of the CSI reference subframes before transmitting the CSI data. The operations at block 1550 cannot be used in situations where only one CSI reference subframe has been identified (as may be the case if either block 1510 or 1540 was used). In addition, the operations at step 1550 cannot be used if multiple CSI entries are to be transmitted to the base station based on multiple subframes included in a group of TTIs. However, when the operations in step 1550 are used, they may be performed using the CSI measurement module 815 described with reference to FIG. 8, and/or the CSI measurement averaging module 925 described with reference to FIG. 9.

Thus, method 1500 can provide wireless communication. It should be noted that method 1500 is just one implementation, and that the operations of method 1500 may be reordered or otherwise modified so that other implementations are possible.

In some examples, aspects from two or more methods 1300, 1400, or 1500 may be combined. It should be noted that methods 1300, 1400, and 1500 are only illustrative implementations, and that the operations of methods 1300, 1400, and 1500 may be rearranged or otherwise modified so that other implementations are possible.

The techniques described here can be used for various wireless communication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other systems. The terms system and network are often used interchangeably. The CDMA system can implement wireless technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 technology covers IS-2000, IS-95 and IS-856 standards. The O and A editions of the IS-2000 standard are commonly referred to as CDMA2000 1X, 1X, etc. Standard 856 (TIA-856) is commonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD), etc. UTRA technology includes wideband CDMA (WCDMA) and other modifications of CDMA. The TDMA system may implement wireless technology such as Global System for Mobile Communications (GSM). OFDMA system can implement wireless technology such as Ultra Mobile Band (UMB), Enhanced UTRA Access (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM™, etc. . UTRA and E-UTRA technologies are part of the Universal Mobile Telecommunications System (UMTS). Long Term Evolution Project Technology (3GPP LTE) and LTE Advanced (LTE-A) are new releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM technologies are described in documents from an organization called the Third Generation Partnership Project (3GPP). CDMA2000 and UMB technologies are described in documents from an organization called the Third Generation Partnership Project 2 (3GPP2). The techniques described herein can be used for the systems and wireless technologies mentioned above, as well as other systems and wireless technologies that include cellular communications (eg, LTE) over unlicensed and/or shared bandwidth. However, the LTE/LTE-A system is described above for purposes of example, and much of the above description uses LTE terminology, although the techniques are applicable outside of LTE/LTE-A applications.

The foregoing detailed description, together with the accompanying drawings, describes examples, but does not represent the only examples that may be implemented or that fall within the scope of the claims. The terms example and illustrative as used in this specification mean serving as an example, instance, or illustration and not in preference to or advantage over other examples. The detailed description includes specific details in order to provide an understanding of the techniques described. However, these techniques can be carried out without these specific details. In some cases, known structures and devices are shown in block diagram form to avoid making it difficult to understand the concepts described.

- 21 043384 examples.

Information and signals may be represented using any of a variety of different technologies and techniques. For example, the data, instructions, commands, information, signals, bits, symbols and chips that may be referenced throughout the foregoing description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

The various illustrative blocks and components described in connection with the disclosure herein may be implemented or implemented using a general purpose processor, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate array (FPGA), or other a programmable logic device, discrete logic gate or transistor logic device, discrete hardware component, or any combination thereof, configured to perform the functions described herein. The general purpose processor may be a microprocessor, but alternatively the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a digital signal processor (DSP) and a microprocessor, multiple microprocessors, one or more microprocessors together with a digital signal processor (DSP) core, or any other such configuration.

The functions described herein may be implemented in hardware, software, processor execution, firmware, or any combination thereof. If the functions are implemented in software executable by the processor, they may be stored on a computer-readable medium or transmitted over a computer-readable medium as one or more instructions or code. Other examples and implementations are within the scope and spirit of the disclosure and appended claims. For example, due to the nature of software, the functions described above may be implemented using software executed by a processor, hardware, firmware, a wired connection, or a combination of any thereof. Features that implement functions can also be physically located in different positions, including distributed in such a way that parts of the functions are implemented in different physical locations. As used herein, including in the claims, the term and/or, when used in a list of two or more items, means that any of the items listed may be used alone or any combination of two or more items listed may be used. For example, if a set is described as containing components A, B, and/or C, the set may only contain A; only in; only with; A and B in combination; A and C in combination; B and C in combination; or A, B and C in combination. Additionally, as used herein, including in the claims, the term or, when used in a list of items (for example, in a list of items preceded by a phrase such as at least one of or one or more), indicates a disjunctive a list whereby, for example, the list at least one of A, B or C means A, or B, or C, or AB, or AC or BC, or ABC (i.e., A, and B, and C) .

Computer-readable media includes both non-volatile computer storage media and communications media, including any media that allows a computer program to be transmitted from one location to another. A non-volatile storage medium can be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and without limitation, nonvolatile computer-readable media may include random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), compact disc ROM (CD) -ROM) or other optical disk storage devices, magnetic disk storage devices or other magnetic storage devices, or any other medium that can be used to carry or store a desired medium of program code in the form of instructions or data structures and that can be accessed by a computer special or general purpose or special or general purpose processor. In addition, any connection is properly called a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair cable, digital subscriber line (DSL), or wireless technology such as infrared, radio waves, and microwaves, then the coaxial cable fiber optic cable, twisted pair, DSL or wireless technologies such as infrared, radio waves and microwaves are included in the definition of media. The term disk as used includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, with discs typically reproducing data magnetically or optically using a laser. Combinations of the above are also included within the scope of the term computer-readable medium.

The previous description of the disclosure is provided to provide one skilled in the art

-

Claims (11)

the ability to make or use the disclosure. Various modifications to the disclosure will be apparent to those skilled in the art, and the general principles set forth herein may be applied to other variations without departing from the spirit or scope. Accordingly, the disclosure should not be limited to the examples and exemplars described herein, but should be given the widest scope consistent with the principles and novel features disclosed herein. CLAIM 1. A method for performing wireless communications, comprising identifying, based at least in part on a group transmission time interval (TTI) configuration, one or more suitable subframes as reference channel state information (CSI) subframes to be used for measurement. CSI, wherein the configuration of the TTI group is such that the TTI group is taken as two or more TTI subgroups over respective two or more subbands; determining that the CSI reference subframes are suitable by determining that the CSI reference subframes are on subbands on which a physical downlink shared channel (PDSCH) group is received; id identifies the last usable subframe from the last TTI subgroup as the reference CSI subframe; performing a CSI measurement for said CSI reference subframes; and transmitting CSI data based at least in part on said CSI measurement. 2. The method of claim 1, wherein identifying one or more subframes as CSI reference subframes comprises identifying the last valid subframe in each of the TTI subgroups as CSI reference subframes. 3. The method of claim 2, further comprising averaging the CSI measurements made on each of the CSI reference subframes. 4. The method of claim 1, wherein identifying said one or more subframes as CSI reference subframes comprises identifying two or more suitable subframes in said two or more TTI subsets as CSI reference subframes. 5. The method of claim 4, further comprising averaging the CSI measurements made on each of the CSI reference subframes. 6. The method of claim 1, wherein identifying said one or more subframes as CSI reference subframes comprises identifying all of the subframes in two or more TTI subgroups as CSI reference subframes. 7. The method of claim 6, further comprising averaging the CSI measurements made on each of the CSI reference subframes. 8. The method of claim 1, wherein identifying said one or more subframes as CSI reference subframes comprises identifying the most recently usable subframe that is at least a predetermined number of subframes earlier than the subframe used for transmitting CSI data, wherein the gap between the most recently usable subframe and the subframe used for transmitting the CSI data includes at least one subframe that does not carry an uplink grant. 9. The method of claim 1, wherein transmitting CSI data based at least in part on a CSI measurement comprises transmitting periodic CSI (P-CSI) data based in part on a P-CSI configuration that includes: itself the periodicity or offset for P-CSI data transmission; or transmitting aperiodic CSI (A-CSI) data based in part on an A-CSI configuration that identifies a circuit for identifying CSI reference subframes to be used for CSI measurement. 10. The method of claim 1, further comprising receiving at least one of a non-zero power (NZP) CSI reference signal (CSI-RS) for channel measurement or a group interference measurement resource (IMR) for multi-interference measurement subframes of the TTI group. 11. The method of claim 1, wherein identifying one or more subframes as CSI reference subframes comprises determining that the CSI reference subframes are suitable by determining that the CSI reference subframes are on subbands on which a physical channel group is received downlink control (PDCCH); or determining that the CSI reference subframes are suitable by eliminating at least one of a Multicast Broadcast Single Frequency Network (MBSFN) subframe, a dedicated downlink short-leg subframe, a subframe associated with another set of CSI subframes, or a subframe of another subband; or determining that the CSI reference subframes are suitable by determining that -