HK1250111B - Carrier measurements for multi-carrier devices - Google Patents

Description

Carrier measurements for multi-carrier devices

Background Art

Wireless mobile communication technology uses various standards and protocols to transmit data between nodes (e.g., transmission stations) and wireless devices (e.g., mobile devices). Some wireless devices use orthogonal frequency division multiple access (OFDMA) in downlink (DL) transmissions and single-carrier frequency division multiple access (SC-FDMA) in uplink (UL) transmissions to communicate. Standards and protocols that use orthogonal frequency division multiplexing (OFDM) for signal transmission include: the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE), the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standards (e.g., 802.16e, 802.16m) (commonly known in the industry as Worldwide Interoperability for Microwave Access (WiMAX)), and the IEEE 802.11 standard (commonly known in the industry as WiFi).

In a 3GPP radio access network (RAN) LTE system, a node may be a combination of an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (also commonly referred to as an evolved Node B, enhanced Node B, eNodeB, or eNB) and a radio network controller (RNC) that communicates with wireless devices, referred to as user equipment (UE). Downlink (DL) transmissions may be communications from a node (e.g., an eNodeB) to a wireless device (e.g., a UE), and uplink (UL) transmissions may be communications from a wireless device to a node.

In a homogeneous network, a node (also referred to as a macro node) can provide basic wireless coverage for wireless devices in a cell. A cell can be an area where a wireless device can operate to communicate with a macro node. Heterogeneous networks (HetNets) can be used to handle the increased traffic load on macro nodes due to the increased use and functionality of wireless devices. A HetNet can include a layer of planned high-power macro nodes (or macro eNBs) overlaid with a layer of lower-power nodes (small eNBs, micro eNBs, pico eNBs, femto eNBs, or home eNBs [HeNBs]) that can be deployed within the coverage area (cell) of the macro node in a poorly planned or even completely uncoordinated manner. Lower-power nodes (LPNs) can generally be referred to as "low-power nodes," small nodes, or small cells.

In LTE, data can be sent from the eNodeB to the UE via the Physical Downlink Shared Channel (PDSCH). Receipt of data can be acknowledged using the Physical Uplink Control Channel (PUCCH). Downlink and uplink channels or transmissions can use either Time Division Duplex (TDD) or Frequency Division Duplex (FDD).

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the present disclosure will be apparent from the following detailed description taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the present disclosure; and wherein:

1 is a flow diagram depicting signaling between a user equipment (UE) and network elements that enables the UE to perform carrier measurements in a wireless network according to an example;

FIG2 shows a table of measurement values that may be transmitted from a user equipment (UE) to a network element to indicate selected carriers for which the UE to start or stop performing carrier measurements, according to an example;

3 illustrates a table of a physical uplink control channel (PUCCH) format that may be used by a user equipment (UE) to transmit a handover notification to a network element according to an example;

FIG4 illustrates a carrier measurement and data reception pattern for a user equipment (UE) according to an example;

FIG5 illustrates a multi-carrier measurement and data reception pattern for a user equipment (UE) configured for carrier aggregation (CA) according to an example;

FIG6 illustrates a multi-carrier measurement and data reception pattern for a user equipment (UE) configured for carrier aggregation (CA) according to an example;

7 illustrates functionality of a user equipment (UE) operable to perform carrier measurements in a wireless network according to an example;

FIG8 depicts functionality of a radio base station operable to assist a user equipment (UE) in performing carrier measurements in a wireless network according to an example;

9 depicts a flow diagram of at least one non-transitory machine-readable storage medium having instructions embodied thereon for performing carrier measurements at a user equipment (UE) according to an example; and

FIG10 shows a diagram of a wireless device (eg, UE) according to an example.

Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same, but it will be understood that no limitation of the scope of the technology is intended thereby.

DETAILED DESCRIPTION

Before disclosing and describing the present technology, it should be understood that the technology is not limited to the specific structures or materials disclosed herein, but is extended to equivalents thereof as will be recognized by those skilled in the relevant art. It should also be understood that the terminology employed herein is used only for the purpose of describing specific examples and is not intended to be limiting. The same reference numerals in different figures represent the same elements. The numbers provided in the flow charts and processes are provided to clearly illustrate the actions and operations and do not necessarily indicate a particular order or sequence.

Example Embodiments

The following provides an initial overview of the technology embodiments, and then describes specific technology embodiments in more detail later. This initial overview is intended to help readers understand the technology more quickly, but is not intended to identify the key features or essential features of the technology, nor is it intended to limit the scope of the claimed subject matter.

Techniques for enabling a user equipment (UE) to perform carrier measurements in a wireless network are described. The UE may be configured for carrier aggregation (CA) and to receive data from one or more carriers simultaneously. In other words, the UE may support multiple radio frequency (RF) chains or receive (Rx) chains, i.e., the UE may receive data on multiple frequencies simultaneously. Based on a defined periodicity, the UE may stop receiving data on one carrier or more than one carrier and instead perform carrier measurements on multiple different carriers (e.g., cells with different frequencies). The carrier measurements may include inter-carrier measurements or intra-carrier measurements. After the UE completes performing the carrier measurements, the UE may continue to receive data on the one carrier.

The UE may receive one or more switching parameters indicating possible switching opportunities for the UE from a network element. The possible switching opportunities may indicate a subframe during which the UE is able to switch the radio frequency (RF) to another carrier frequency (or frequencies) so that the UE can start performing carrier measurements and/or stop performing carrier measurements. The UE may select one of the upcoming switching opportunities and send a switching notification to the network element indicating that the upcoming switching is selected by the UE. If the next switching opportunity is selected by the UE, the switching notification may be "1". The switching notification may be transmitted together with a measurement value indicating the selected carrier for which the UE will start performing carrier measurements after the switching opportunity occurs and/or the selected carrier for which the UE will stop performing carrier measurements after the switching opportunity occurs. Thus, when the switching opportunity occurs, the UE may switch to another carrier (e.g., RF chain or receive path) or may activate a carrier that is not currently in use in order to perform carrier measurements.

A general description of carrier measurements for a multi-carrier capable device is presented. A multi-carrier capable device may be a user equipment (UE) configured for carrier aggregation (CA). To support mobility scenarios, the UE may perform carrier measurements, which may include intra-frequency measurements and inter-frequency measurements. Carrier aggregation, introduced in 3GPP LTE Release 10, introduces degrees of freedom that can potentially be used to improve carrier measurement performance, although such potential has not yet been exploited. On the other hand, carrier aggregation introduces other features that require increasing the list of cells to be measured by the UE, which may increase the number of measurements to be performed at the UE.

One feature that can be used to improve performance is LTE gapless measurement, regardless of the increase in the number of measurements to be performed at a UE configured for carrier aggregation. LTE gapless measurement was introduced in 3GPP LTE Release 8 as an optional feature. Based on capability signaling from the UE to the network, the UE can signal the network whether the UE requires a measurement gap to perform measurements on a specific frequency band. The UE can signal the network whether it can perform measurements without gaps in a certain frequency band combination. In other words, with gapless measurement, the UE can continue to receive data even when measurements are being performed. In theory, since no measurement gap is required, the network can not configure any measurement gap for the frequency band combination indicated by the UE. By not configuring the measurement gap, the UE can handle measurement requests flexibly and throughput can be improved.

However, to date, no commercially available equipment on the market is capable of performing LTE gapless measurements without being restricted to a specific frequency band or frequency band combination, because gapless measurements would require two independent modems (e.g., baseband and RF) within a single device. Therefore, in most cases, the network is forced to configure at least a minimum amount of measurement gaps. Even if the available receive paths in the modem support some gapless measurements, switching these available receive paths to the desired center frequency will cause interference to the primary serving cell (e.g., PCell interruption). These interruptions may be unknown to the network because the device does not signal the network when these interruptions occur. In addition, these interruptions may degrade network performance due to the interfered transmission time intervals (TTIs) and the loss of some hybrid automatic repeat request (HARQ) processes. If interruptions are unavoidable, the network is interested in knowing when these interferences will occur so that the network can adjust its scheduling.

In previous solutions, the UE can perform carrier measurements according to a measurement gap pattern, which can indicate a set of consecutive subframes within a predefined time period during which the UE performs carrier measurements for a selected cell. The carrier measurements can include inter-frequency and inter-radio access technology (RAT) measurements. The selected cell can be within a group of cells, where each cell in the group operates at a separate frequency layer and is measured using a specific measurement gap pattern. In one example, more than one cell on the same frequency can be measured, in which case measurement samples can be recorded during these gaps and then processed offline using several assumptions for the cells. The carrier measurement for the selected cell can be a reference signal received power (RSRP) measurement or a reference signal received quality (RSRQ) measurement. Therefore, the UE can perform carrier measurements for the selected cells within the group of cells (each operating at a different frequency layer) according to the measurement gap pattern. The group of cells for which the UE performs carrier measurements can be used for carrier aggregation or data offloading.

In previous solutions, the measurement process for devices performing LTE measurements using measurement gaps was network-centric. In other words, the UE had minimal flexibility in deciding when to perform measurements or how long to perform measurements based on internal system states or power consumption considerations. The defined time period during which the UE performs carrier measurements on a selected cell may be referred to as a Measurement Gap Repetition Period (MGRP). The MGRP may be 40 milliseconds (ms) or 80 ms. One subframe may correspond to 1 ms, so 40 ms corresponds to 40 subframes and 80 ms corresponds to 80 subframes. Therefore, the UE may periodically perform carrier measurements on the selected cell every 40 or 80 ms, as directed by the network. The MGRP may vary based on the purpose of the carrier measurement. For example, if the purpose is for cell identification, the UE may perform carrier measurements on a first cell every 40 subframes. The time period during which the UE performs carrier measurements may be determined by the network. On the other hand, if the purpose is for cell measurement, the UE may perform carrier measurements on a second cell every 80 subframes. The selected cells within the group of cells may include macrocells, microcells, picocells, or femtocells.

In one example, the UE may switch to a different frequency (i.e., a frequency different from the serving cell frequency) for 6 ms every 40 ms to perform carrier measurements. In other words, the UE may spend 6 ms every 40 ms at a different frequency (e.g., frequency 1). Alternatively, the UE may spend 6 ms every 80 ms in another frequency in order to perform carrier measurements. When the UE measures an LTE carrier (e.g., frequency 1), the UE may capture the primary synchronization signal (PSS) and the secondary synchronization signal (SSS) in a 6 ms long interval because the PSS and SSS are repeated every 5 ms. In addition, the 6 ms long measurement interval includes sufficient cell-specific reference symbols for channel estimation. The 6 ms long measurement interval includes a margin for the UE to tune to a different LTE carrier (e.g., frequency 1) and back to the serving LTE carrier (e.g., frequency 0).

As an example, a UE may be served by a cell operating at a defined frequency (e.g., frequency 0), but the UE may periodically monitor the channel quality of other cells operating at other frequency layers. When the UE monitors the channel quality of another cell, the UE switches its frequency to match the cell for which carrier measurements are performed (i.e., the UE may tune its receiver or oscillator to a different carrier frequency). For example, in order to perform carrier measurements for another cell operating at frequency 1, the UE must temporarily switch its own default frequency (e.g., frequency 0) to frequency 1. When the UE completes carrier measurements for other cells, the UE may return to the default frequency (e.g., frequency 0) or switch to another frequency associated with another cell (e.g., frequency 2) in order to perform additional carrier measurements. In one example, the other cells may be adjacent to the UE and/or used by the UE in certain circumstances (e.g., for data offloading). The channel quality measured by the UE may include reference signal received power (RSRP) measurements and/or reference signal received quality (RSRQ) measurements. RSRP and RSRQ measurements may indicate signal strength from other cells operating at other frequency layers.

Carrier measurements can be facilitated by configuring pauses in uplink and downlink data transmission on at least one carrier and allowing the UE to perform carrier measurements on the at least one carrier during the pause periods. Such pauses or intervals in transmission are called measurement gaps. During measurement gaps, the UE does not transmit any data on the carrier used to perform carrier measurements, nor does the UE transmit sounding reference signals (SRS), CQI/PMI/RI, and HARQ feedback.

In previous solutions, regardless of the availability of two or more receive chains for CA-capable UEs, the UE was not provided with the flexibility to determine when and how often to perform carrier measurements, which could compromise performance and power consumption. In one example, this potential remains untapped due to insufficient signaling support for higher-order carrier aggregation (e.g., 3-downlink (DL) CA). If a UE is configured for 3DL CA, the UE can have three receive paths simultaneously. The first receive path can be mapped to the primary cell (PCell), the second receive path can be mapped to the first secondary cell (SCell1), and the third receive path can be mapped to the second secondary cell (SCell2).

With the primary cell (PCell) and the first secondary cell (SCell1) active, the UE can signal that a certain number of frequency bands can be measured in parallel using a third receive chain. Depending on whether SCell1 has been activated on the same component or an alternative component, "uninterrupted" measurements using the third receive chain may or may not result in undesirable PCell interruption. To avoid undesirable PCell interruption, all receive chains can remain active. However, this is only possible when the frequency bands to be measured are known in advance, and this configuration also leads to an unacceptable increase in power consumption.

The opportunities for gapless inter-frequency (or inter-RAT) measurements may be relatively small. Given a certain band combination, if the single band to be measured is not included in the list of bands ready for gapless measurement, a measurement gap is required, i.e., the number of actual gapless measurement opportunities may be relatively small. In addition, when only some bands can be measured without gaps under certain carrier combination conditions, there is no signaling support. If CA is combined with LTE-LTE Dual Card Dual Active (DSDA) or LTE-LTE Dual Card Dual Standby (DSDS), the network is able to support gapless measurements, but the relevant receive chain may be in use and may be unavailable. As explained in further detail below, these problems can be alleviated if the measurement gap processing is device-centric rather than network-centric.

The technology described herein provides a device-centric configuration and implementation of measurement intervals in a multi-carrier capable UE. Instead of the network determining a certain measurement time period and interval length for the UE (e.g., 6ms out of every 80ms), the network can provide a switching opportunity to the UE via signaling from the network to the UE. For example, the network can indicate to the UE that a switching opportunity occurs every four subframes. In other words, the UE can decide (as opposed to the network) whether the UE should use the switching opportunity to start or stop performing carrier measurements. The UE can notify the network which switching opportunities the UE plans to use via signaling from the UE to the network. In addition, the UE can notify the network of specific items that will be measured by the UE after the switching opportunity occurs, where the receive chain can be mapped to a PCell or one or more SCells. Alternatively, the UE can decide not to use the switching opportunity, in which case the UE does not send any signaling to the network.

The technology described herein provides a device-centric approach to performing carrier measurements that can allow the UE to optimally manage its available resources and determine the ideal balance between measurements and throughput performance. The network-centric approach can leverage the flexibility of CA-capable devices. Specifically, when the number of active carriers for the UE is less than the number of available receive paths, these available receive paths can be used to perform measurements instead of remaining idle. For example, if the UE has three RF chains and two RF chains are receiving data (from the PCell and SCell) and the third RF chain is idle, the third RF chain can be used to perform measurements for one or more cells. Due to the judicious use of switching opportunities and the newly defined communication protocol between the UE and the network, the impact on the PCell can be minimized. In addition, the network can be notified of possible interruptions and be able to schedule around them.

Regarding performance, the novel signaling described herein enables the UE to determine which handover opportunity to use, or whether a particular handover opportunity should not be used. Based on the UE's ability to select which handover opportunities to use, the UE can freely configure the required measurement interval with the desired measurement frequency. As a result, performance standards associated with more heterogeneous network structures (i.e., HetNet, small cells, Home eNodeBs) can be met.

In an exemplary deployment scenario, macro coverage must be ensured, and at the same time, multiple small cells need to be measured to enable offloading where possible. The measurement requirements for coverage and offloading are typically quite different. For small cell discovery, measurements will be performed relatively frequently compared to coverage-based handovers, and these measurements can be considered a background activity. Furthermore, latency requirements for cell offloading can be more relaxed than for measurements for macro coverage.

The techniques described herein have the flexibility to provide sufficient intervals for small cell discovery and, at the same time, enable delay-sensitive coverage measurements for handover when the UE reaches the edge of coverage.

As an example, the frequencies of a given layer (e.g., small cell layer) or 3 to 4 cells will be monitored. There may be two PSS/SSS detection attempts and six measurement intervals (or sampling opportunities), which yields a total of eight 6ms intervals for appropriate performance accuracy. In past solutions, for a single frequency, this measurement process could be ready after 7×40+6ms=286ms or 7×80+6ms=566ms. These intervals become even larger if the number of carriers or cells per carrier/layer increases, which is typically the case with the introduction of carrier aggregation and the deployment of heterogeneous networks.

In contrast, the techniques described herein may allow measurements to be distributed over more RF chains and performed in parallel, which may reduce the aforementioned interval to 8×6ms=48ms+2 short intervals of 1ms, to achieve a controlled interruption of PCell reception of a total of 50ms per layer/frequency in this specific example, which results in a speed improvement of approximately 83%. Depending on whether the UE is a 2CA UE or a 3CA UE, and whether only the PCell is active or the SCell is also received, additional configurations with improved performance are possible (with different resulting durations). In this solution, the 6ms measurement interval may be replaced by a short interval of 1ms (if LTE backward compatibility is desired). Alternatively, based on the 5G frame structure with reduced latency, the 6ms measurement interval may be replaced by a short interval of even less than 1ms. The short intervals may be used to turn on/off other available reception paths, while measurements for a certain frequency layer are ongoing in the time interval between the two short intervals, where the duration of the interval may depend on the number of cells to be monitored.

FIG1 illustrates a signaling flow between a user equipment (UE) 110 and a network element 120 that enables the UE 110 to perform carrier measurements in a wireless network. The network element 120 may include a radio base station, an evolved Node B (eNB), a mobility management entity (MME), a remote radio head (RRH), a relay node, a femto base station (or femto node), a pico base station (or pico node), or other suitable nodes in a wireless network. The UE 110 may be configured to support carrier aggregation (CA). In carrier aggregation, the UE 110 may receive signals from multiple frequency bands or cells simultaneously. Carrier aggregation may be used to increase bandwidth, thereby increasing bit rate. In other words, the UE 110 may support simultaneous reception of two or more carriers in a contiguous intra-band CA configuration or an inter-band CA configuration (i.e., the UE 110 may receive data at different RF frequencies).

For coverage or offloading purposes, UE 110 may perform carrier measurements for selected cells in a wireless network. Each selected cell may operate at a different frequency layer. Carrier measurements may be on different frequency bands or in the same frequency band. If they are on the same frequency band and the two different carriers to be measured are not too far apart (e.g., limited to within 20 MHz), both carriers may be measured without retuning. Inter-frequency measurements may be performed when UE 110 tunes its local oscillator to different frequencies, and UE 110 measures different frequencies. For example, UE 110 may receive data on frequency 1 (F1) and then measure frequency 2 (F2), where F2 is different from F1. Intra-frequency measurements may be performed while UE 110 stays on the same frequency. For example, UE 110 may perform intra-frequency measurements on the same frequency but for cells with different IDs.

In one example, UE 110 may perform carrier measurements on potential cells that may be used for handover purposes. Based on various parameters of the cell indicated by the carrier measurements (e.g., the cell's signal-to-noise ratio (SNR)), UE 110 may decide which cell should be the target cell during handover. The other cell may operate on a different frequency or frequency band. UE 110 may perform measurements based on a list of frequencies and frequency bands received at UE 110 from higher layers. To perform carrier measurements, UE 110 may tune its oscillator to a different frequency and measure that specific frequency.

In one example, the carrier measurements performed at UE 110 may be mobility measurements or secondary cell measurements. Carrier measurements may include intra-RAT measurements, which may occur when UE 110 searches for a Global System for Mobile Communications (GSM) or 3G/4G/5G cell as UE 110's LTE coverage ends. Furthermore, carrier measurements may be used for other measurement purposes in 5G networks. For example, carrier measurements may be used to detect interference in autonomous networks, device-to-device (D2D) networks, detect violations of shared spectrum access, and the like.

Since UE 110 is configured for carrier aggregation, the carriers for which the UE performs carrier measurements may include a primary cell and multiple secondary cells (e.g., four secondary cells). As a non-limiting example, UE 110 may be connected to a primary cell (PCell), a first secondary cell (SCell1), and a second secondary cell (SCell2) via carrier aggregation. UE 110 may receive data on PCell and SCell1 and perform carrier measurements using SCell2. As another example, UE 110 may receive data on PCell and perform carrier measurements on SCell1 and SCell2.

Network element 120 may send one or more handover parameters to UE 110. The handover parameters may indicate possible handover opportunities for UE 110, where the possible handover opportunities may be subframes during which UE 110 can switch to one or more carriers to start or stop performing carrier measurements. As an alternative to subframes, handover opportunities may occur at certain frames or time slots. In other words, at handover opportunities, UE 110 may switch RF chains or receive paths to perform carrier measurements. For example, during a particular handover opportunity, UE 110 may start performing carrier measurements for selected cell(s) on PCell, SCell1, and/or SCell2. At another handover opportunity, UE 110 may stop performing carrier measurements for selected cell(s) on PCell, SCell1, and/or SCell2. Thus, UE 110 may ultimately decide when and how often to perform carrier measurements, as opposed to the previous solution where network element 120 instructs UE 110 when and how often to perform carrier measurements. Based on this flexibility, UE 110 may determine whether to use specific switching opportunities or not to use specific switching opportunities in order to optimize performance and power consumption at UE 110 .

To inform UE 110 of possible handover opportunities, network element 120 may send handover parameters to UE 110. The handover parameters may indicate a time period and an offset relative to the system frame number, thereby indicating when the possible handover opportunities will occur. The handover parameters sent from network element 120 to UE 110 may include a measurement interval period, which may indicate the period or frequency at which possible handover opportunities will occur. The measurement interval period may range from 4 subframes to 127 subframes. The handover parameters sent from network element 120 to UE 110 may include a measurement interval offset, which may indicate an offset relative to the system frame number. The measurement interval offset may range from 0 subframes to 126 subframes. Based on the measurement interval period and the measurement interval offset, network element 120 may inform UE 110 where handover notifications will occur and how often they will repeat. As a non-limiting example, network element 120 may inform UE 110 that handover notifications will occur every four subframes, starting with subframe number 1 of frame 1.

In one example, the handover parameters sent from network element 120 to UE 110 may include a measurement advance, which may indicate how many subframes in advance UE 110 should notify network element 120 of a particular handover opportunity. The measurement advance may range from 8 subframes to 80 subframes for a number of reasons. For example, if there is a large downstream or upstream traffic involved with guaranteed quality of service (QoS) bit rates, the network scheduler may require additional time to compensate for the increased load. In this case, network element 120 may set one or more carriers being used by UE 110 to "not ready for scheduling." Scheduling is the process by which network element 120 decides which UEs should be given resources to transmit or receive data. Therefore, a pre-notification or measurement advance of at least 8 ms before the next handover opportunity is desirable to allow network element 120 an opportunity to reject the UE's indicated handover opportunity (at least temporarily) until scheduling congestion has been alleviated. In another example, the measurement advance can be between 8 subframes and 80 subframes to allow service-oriented and/or configuration-oriented notification ranges in the presence of Voice over LTE (VoLTE) discontinuous reception (DRX) and/or semi-persistent scheduling (SPS) modes. Both the switching opportunity and the notification range apply to DRX and/or SPS modes. In this case, it may be desirable to have switching opportunities every 20ms or 40ms and an early warning or measurement advance of up to 80ms.

In one configuration, handover parameters (i.e., measurement interval period, measurement interval offset, and measurement advance) can be programmed in a semi-static manner. For example, when UE 110 enters the coverage area of a cell in a wireless network, the handover parameters can be defined and communicated to UE 110. In one example, network element 120 can send one or more handover parameters indicating possible handover opportunities to UE 110 via radio resource control (RRC) signaling. Based on the handover parameters, UE 110 can know when a handover opportunity is available.

In one example, UE 110 may use a switching opportunity to switch to a receive path that is not currently being used for data reception in order to use the receive path to perform carrier measurements for one or more carriers. Even though UE 110 may be configured for carrier aggregation, UE 110 may not always receive data on multiple receive chains. There may be times when UE 110 receives data on a single carrier (or a single receive path) such that other carriers or receive paths are unused or idle. Therefore, UE 110 may use the unused receive path(s) to perform carrier measurements. Typically, for very specific band combinations, only three or four different carriers supported by UE 110 may be used at the same time.

As a non-limiting example, UE 110 may be connected to a primary cell (PCell) and a secondary cell (SCell1). UE 110 may receive data on the PCell but not on SCell1. In other words, the receive path associated with SCell1 is not currently being used for data reception. Therefore, for offloading purposes, UE 110 may use SCell1 to perform carrier measurements for multiple other cells. For example, while UE 110 is receiving data on the PCell, UE 110 may use another receive path associated with SCell1 to perform carrier measurements (e.g., frequency measurements) for f2, f3, and f4.

In one configuration, UE 110 may send a handover notification to network element 120 that indicates an upcoming handover opportunity selected by the UE. In other words, UE 110 may notify network element 120 that UE 110 plans to use the next handover opportunity to perform carrier measurements. For example, the handover notification may be "1" to indicate that UE 110 plans to use the next handover opportunity. As previously described, UE 110 may send the handover notification approximately 8 subframes before the selected handover opportunity occurs. In one configuration, UE 110 may send the handover notification to network element 120 via radio resource control (RRC) signaling. In an alternative configuration, UE 110 may send the handover notification to network element 120 using a medium access control (MAC) control element (CE) in the uplink, or by sending the handover notification on the PHY layer.

In one configuration, the handover notification transmitted from UE 110 to network element 120 may be sent in conjunction with a measurement value indicating the selected carriers for which the UE will begin performing carrier measurements after the handover opportunity occurs. Furthermore, the measurement value may indicate the selected carriers for which the UE will stop performing carrier measurements after the handover opportunity occurs. The measurement value may also be referred to as a measurement bitmap. Based on the measurement value, network element 120 may understand how UE 110 is using handover opportunities (i.e., which cell(s) the UE plans to measure or stop measuring after the handover opportunity occurs). FIG2 provides a specific example of the measurement value.

In one configuration, the handover notification can be sent from UE 110 to network element 120 via RRC signaling. In this case, the measurement advance may be greater than 8 ms due to RRC reconfiguration delay. In an alternative configuration, UE 110 can send the handover notification to network element 120 via a medium access control (MAC) control element (CE). If the handover notification is sent using a MAC CE, there is no need to allow for RRC reconfiguration delay, and network element 120 can react within the minimum UE-to-eNB communication delay of 4 ms. Therefore, in this case, the measurement advance can be less than 8 ms.

In one configuration, in order for the UE 110 to inform the network element 120 about the use of each switching opportunity (i.e., via measurements), the UE 110 may send a set of Nca bits to the network element 120, wherein the Nca bits include measurements describing the UE's use of the next switching opportunity. In one example, Nca may refer to the number of carriers supported by the UE 110. For example, if the UE 110 supports 3-CA, then Nca may be equal to 3. In addition, each bit may be set to "1" or "0" based on the measurements. FIG2 provides a specific example of the Nca bits and the corresponding measurements. If the next switching opportunity will not be used by the UE 110, then the UE 110 does not need to signal the network element 120 anything about the switching opportunity.

In one example, the signaling of the handover notification from UE 110 to network element 120 is not semi-static, but rather dynamically determined by UE 110. Therefore, if an uplink (UL) grant is available, UE 110 may signal the handover notification via a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH). Specifically, the handover notification may be sent in conjunction with measurement values using a newly defined PUCCH format or using the PUSCH.

In one example, if an UL grant is available, all control UL information can be sent from UE 110 on PUSCH instead of PUCCH. Similarly, additional Nca bits (e.g., 5 Nca bits) including measurement values can be mapped to PUSCH and sent in the uplink. If the measurement values are sent to network element 120 on PUSCH, an additional valid bit is needed to indicate that the Nca=5 bits reserved in PUSCH are valid. Alternatively, the Nca bits including the measurement values can be sent to network element 120 using a newly defined PUCCH format. In one example, the valid bit in the newly defined PUCCH format or PUSCH is only set when UE 110 sends measurement values to network element 120, and is only set in those subframes corresponding to the switching opportunities indicated by network element 120.

In one configuration, UE 110 may send a handover notification to network element 120, and in response, network element 120 may send a reject message to UE 110. In other words, network element 120 may prohibit UE 110 from using the indicated handover opportunity to switch carriers in order to start or stop performing carrier measurements. In other words, the reject message may indicate that UE 110 is prohibited from switching carriers when the indicated handover opportunity occurs due to scheduling congestion. Network element 120 may send the reject message to UE 110 due to scheduling congestion (or other types of congestion) in the wireless network. Network element 120 may send the reject message to UE 110 via a medium access control (MAC) control element (CE) or by sending the handover notification at the PHY layer.

After a period of time, network element 120 may detect when network congestion has decreased. Network element 120 may send a notification to UE 110 indicating that network congestion has decreased and that UE 110 is now permitted to send a handover notification to network element 120. Network element 120 may send the notification using an additional MAC CE, by sending a notification on the PHY layer, or through RRC signaling. Based on the notification UE 110 receives from network element 120, UE 110 may send an additional handover notification to network element 120. In other words, UE 110 may send another handover notification to network element 120 only after UE 110 receives a notification indicating that UE 110 is permitted to once again restart a handover opportunity.

Figure 2 shows an exemplary table of measurement values that can be transmitted from a user equipment (UE) to a network element to indicate the selected carriers for which the UE will start or stop performing carrier measurements after a handover opportunity occurs. The measurement values can be combined with a handover notification and can be sent from the UE to the eNB. The UE can plan to perform carrier measurements indicated in the measurement values corresponding to the indicated handover opportunity (e.g., 8 subframes after the UE sends the handover notification to the network element). The measurement values can also be referred to as a measurement bitmap. In one configuration, the UE can be a 3CA UE, which means that the UE is configured for carrier aggregation (CA) and can be connected to up to three carriers simultaneously. For example, the UE can be connected to a primary cell (PCell), a first secondary cell (SCell1), and a second secondary cell (SCell2). Alternatively, the UE can be connected to less than three carriers simultaneously; in the specific case of intra-band contiguous carrier aggregation, the UE can also be connected to more than three carriers.

As shown in Figure 2, a measurement value of 0 may indicate stopping measurement on any active path for SCell2, SCell1, and PCell. A measurement value of 0 may be transmitted using three Nca bits of "0," "0," and "0." A measurement value of 1 may indicate starting measurement only on PCell. A measurement value of 1 may be transmitted using three Nca bits of "0," "0," and "1." A measurement value of 2 may indicate starting measurement only on SCell1 and stopping measurement on SCell2 (if active). A measurement value of 2 may be transmitted using three Nca bits of "0," "1," and "0." A measurement value of 4 may indicate starting measurement only on SCell2 and stopping measurement on SCell1 (if active). A measurement value of 4 may be transmitted using three Nca bits of "1," "0," and "0." A measurement value of 6 may indicate starting measurement on SCell1 and SCell2. A measurement value of 6 may be transmitted using three Nca bits of "1," "1," and "0." A measurement value of 7 may indicate starting measurement on PCell, SCell1, and SCell2. The measurement value 7 can be transmitted using three Nca bits of "1", "1" and "1".

Figure 3 shows an exemplary table of physical uplink control channel (PUCCH) formats that can be used by a user equipment (UE) to transmit a handover notification to a network element such as an evolved Node B (eNB). The handover notification can be combined with a measurement value that indicates the selected carrier for which the UE will start performing carrier measurements after the handover opportunity occurs and/or the selected carrier for which the UE will stop performing carrier measurements after the handover opportunity occurs. In one example, the measurement value can be five bits (i.e., Nca=5), which indicates that the UE supports simultaneous connection to five separate carriers (e.g., a primary cell and up to four secondary cells) via carrier aggregation.

In one example, the UE may use PUCCH format 1c to send measurement values to a network element. PUCCH format 1c may be a total of 7 bits. In addition to hybrid automatic repeat request (HARQ) acknowledgment (ACK) and scheduling requests, PUCCH format 1c may also be used to send measurement values (or measurement bitmaps). In another example, the UE may use PUCCH format 2c to send measurement values to a network element. PUCCH format 2c may be a total of 27 bits. In addition to channel state information (CSI) and HARQ-ACK, PUCCH format 2c may also be used to send measurement values (or measurement bitmaps). In yet another example, the UE may use PUCCH format 3a to send measurement values to a network element. PUCCH format 3a may be a total of 53 bits. In addition to CSI, HARQ-ACK and scheduling requests, PUCCH format 3a may also be used to send measurement values (or measurement bitmaps).

Figure 4 shows an exemplary carrier measurement and data reception pattern for a user equipment (UE). The network can provide the UE with a switching opportunity in the form of a short interval. As an example, a radio base station or an evolved node B (eNB) can provide a switching notification to the UE. The switching opportunity can occur every X subframes and have a duration of Y milliseconds, where X and Y are integers. These short intervals enable the UE to turn on or off certain receiving paths (or RF chains). Although interference may occur during the switching opportunity, the network can know the interference in advance and schedule accordingly. In one example, the network can configure the switching opportunity via radio resource control (RRC) signaling. As previously described, the network can configure the switching opportunity by sending various parameters (e.g., measurement interval time period, measurement interval offset, and measurement advance) to the UE.

In the example shown in Figure 4, the UE can be a 1-CA UE. In other words, the UE can have a single receive path (i.e., RX path 1). The UE can be connected to a single carrier, for example, a primary cell (PCell), and receive data from the single carrier. The switching opportunity can occur every four subframes (or 4ms) and have a duration of 1 subframe (or 1ms). Therefore, the network can configure a repetition time period of 4 subframes. In addition, the network can configure an offset of 1 subframe because the first switching subframe occurs in subframe #1 of frame #0. As long as these switching opportunities are not used by the UE, continuous PCell reception can be maintained (i.e., there are no gaps in the transmission).

If the UE expects to perform an RF handover (i.e., switch to a different carrier or RF chain) in order to perform carrier measurements, the UE may send a handover notification to the network indicating the upcoming handover opportunity that the UE plans to use to perform carrier measurements. The UE may notify the network in advance of when the handover opportunity will occur based on the measurement advance previously received from the network. In other words, the UE may send an early warning to the network indicating the handover opportunity selected by the UE. The network may have previously configured a measurement advance (e.g., 8 subframes) based on the constraints of the network scheduler. As an example, if the UE sends a handover notification to the network, the UE may plan to use a handover opportunity that occurs approximately 8 subframes later in time than the subframe used to send the handover notification. During the subframes in which the UE is switching carriers or RF chains (i.e., at the handover opportunity), the network does not schedule any downlink (DL) traffic to the UE.

In one example, the measurement advance or warning time is large enough to allow the network to stop scheduling the UE several subframes in advance, which can avoid damage to the hybrid automatic repeat request (HARQ) process around the switching subframe. As shown in Figure 4, DL subframes in which no DL traffic can be scheduled due to damage to the HARQ process may occur between switching opportunities (for example, approximately every 8 subframes). In one example, if the UE is scheduled to receive DL data in subframe n, the UE can send ACK or NACK in the uplink in subframe (n+4) so that the base station knows that the UE has correctly decoded the DL data. As shown in Figure 4, if the network knows that the UE will use the switching opportunity in frame #0, subframe #9, the UE cannot send ACK/NACK information in the uplink in that subframe. Therefore, in frame #0, subframe #5, the network may not schedule DL data to the UE because the ACK/NACK information cannot be sent to the network.

In one example, the UE has a single receive path available (i.e., a single receive path mapped to the PCell), so when performing carrier measurements, the UE will have to interrupt any DL traffic on the receive path. The UE may adhere to a measurement advance time (or warning time) of 8 subframes. In other words, the UE will indicate any switching activity to the network at least 8 subframes before performing the switching activity. In addition to instructing the UE which switching opportunities to use, the UE may also inform the network how the UE plans to use the switching opportunities. For example, the UE may send a measurement value or a measurement bitmap to the network that indicates which carrier measurements will be performed after the switching opportunity occurs. This indication allows the network to determine whether to interrupt the UE's DL data on a particular receive path during the measurement period, because the UE (rather than the network) decides how many internal receive chains the UE performs measurements on and how long the measurements will be performed. This is in contrast to previous solutions where the network specifies the carrier measurements to be performed at the UE.

As shown in Figure 4, the UE can receive data on a receive path (e.g., a receive path mapped to a PCell). In subframe #1 of frame #0, the UE can send a switching notification to the network along with a measurement value of 1. The measurement value 1 can indicate that the UE will start performing measurements on the receive path at the next possible switching opportunity. The next possible switching opportunity coincides with the measurement advance, so in this case, the switching opportunity occurs 8 subframes later. At the switching opportunity (i.e., subframe #9 of frame #0), the UE switches to another carrier frequency, at which time the UE can start performing inter-frequency measurements at the first frequency (F1). For example, F1 can be associated with the first cell. The UE does not receive data during the switching opportunity. The UE can use the PCell receive chain to perform measurements. Based on the measurement advance of 8 subframes, the UE can send measurement values to the network 8 subframes before the UE starts switching the RF to the first frequency (F1).

The UE may spend 4 subframes performing measurements on F1. The UE may measure a second frequency (F2) after completing the measurements on F1. F2 may be associated with a second cell. In this case, the UE may perform measurements on F2 without switching RFs. Therefore, the UE does not indicate any handover activity to the network. The UE may spend 4 subframes performing measurements on F2.

When the measurement for F1 is completed, the UE may send another handover notification along with a measurement value of 1 to the network. The measurement value of 1 may indicate that, in 8 subframes, the UE plans to use the upcoming handover opportunity to start measurements on the PCell. The measurement may correspond to a third frequency (F3). F3 may be associated with a third cell. In this example, in order to measure F3, the UE needs to switch RF at the handover time, so the handover activity is indicated to the network before performing measurements for F3. After the UE measures F3, no additional measurement tasks are scheduled at the UE. The UE may send another handover notification along with a measurement value of 0, which indicates that the UE wishes to stop performing measurements on any active path. At this point, the network may continue to schedule DL data for the UE on the receive path. However, the UE may have to wait for a period of time until the next available handover opportunity (during which no measurement activity is performed) in order to continue receiving DL data on the receive path. The UE may switch back to receiving DL data on the receive path approximately 8 subframes after sending the measurement value 0 to the network.

Figure 5 shows an exemplary carrier measurement and data reception pattern for a user equipment (UE) configured for carrier aggregation (CA). In this example, the UE can be a 3-CA UE. In other words, the UE can be connected to a first receive path (i.e., RX path 1), a second receive path (i.e., RX path 2), and a third receive path (i.e., RX path 3). In one example, the first receive path can be mapped to the primary cell (PCell), the second receive path can be mapped to the first secondary cell (SCell1), and the third receive path can be mapped to the second secondary cell (SCell2). The UE can receive data on the first receive path (which is mapped to the PCell) and perform SCell1 and SCell2 secondary cell measurements. The switching opportunity can occur every four subframes (or 4ms) and have a duration of 1 subframe (or 1ms).

The UE can determine whether downlink data on the first receive path is interrupted for the duration of measurements performed on the second and third receive paths. In this case, the UE can determine to perform measurements on the second and third receive paths without interrupting data reception on the first receive path (i.e., PCell data reception) during the measurements. Therefore, the UE can continuously receive downlink data on the PCell, except for switching timings and subframes that coincide with HARQ process corruption.

The UE may send a handover notification to the network (e.g., a radio base station) along with a measurement value of 6, indicating that the UE plans to start performing measurements on the second receive path (corresponding to SCell1) and the third receive path (corresponding to SCell2) in parallel. The UE may start performing measurements 8 subframes after sending the handover notification. The UE may perform measurements on the first frequency (F1) and the third frequency (F3) in parallel, where F1 is associated with the first cell and F3 is associated with the third cell. The UE may measure F1 on the second receive path (corresponding to SCell1), and the UE may measure F3 on the third receive path (corresponding to SCell2). After measuring F1 and F3, the UE may switch RF to measure the second frequency (F2) on the second receive path (corresponding to SCell1), where F2 is associated with the second cell. Before measuring F2, the UE may send a measurement value of 2, indicating that the UE plans to start performing F2 measurements on the second receive path (corresponding to SCell1), and that the UE plans to stop performing F1 measurements on the second receive path (corresponding to SCell1) (if the path is active).

In this example, it is assumed that the fourth frequency (F4) cannot be measured in parallel with F2 due to front-end limitations. F4 may be associated with the fourth cell. Therefore, after measuring F2 on the second reception path (which corresponds to SCell1), the UE switches its RF so that the UE can measure F4 on the third reception path (which corresponds to SCell2). Before measuring F4, the UE may send a measurement value of 4, which indicates that the UE plans to start performing measurements on the third reception path for F4 (i.e., the UE plans to start measuring F4), and that the UE plans to stop performing measurements on the second path for F2 (if active) (i.e., the UE plans to stop measuring F2). After the UE measures F4, the UE may send a measurement value of 0 (8ms before the next switching opportunity) to indicate that the UE has completed performing the measurement (i.e., the UE plans to stop performing measurements on any active path).

Figure 6 shows an exemplary carrier measurement and data reception pattern for a user equipment (UE) configured for carrier aggregation (CA). In this example, the UE can be a 3-CA UE. In other words, the UE can be connected to a first receive path (i.e., RX path 1), a second receive path (i.e., RX path 2), and a third receive path (i.e., RX path 3). In one example, the first receive path can be mapped to the primary cell (PCell), the second receive path can be mapped to the first secondary cell (SCell1), and the third receive path can be mapped to the second secondary cell (SCell2). Therefore, the UE can be connected to the PCell and SCell1, while the third receive path is "idle" and not connected to any SCell. Alternatively, the UE is connected to the PCell and two secondary cells, but there is currently no data reception on the receive path bound to SCell2. In both cases, the "idle" (one or more) receive paths can be used to perform carrier measurements. The switching opportunity can occur every four subframes (or 4ms) and have a duration of 1 subframe (or 1ms).

In this example, the UE can receive DL data on a first receive path (corresponding to PCell) and a second receive path (corresponding to SCell1). The UE can send a handover notification together with a measurement value of 4 to the network, indicating that the UE plans to start performing measurements on the third receive path (or SCell2) and stop performing measurements on the second receive path (or SCell1) (if active). However, in this case, the receive path for SCell1 did not perform measurements when the handover notification was sent to the network. Therefore, the UE can perform measurements on the first frequency (F1). After F1 is measured, the UE can switch RF at the next possible handover opportunity and then perform measurements on the second frequency (F2). After F2 is measured, the UE can switch RF at the next possible handover opportunity and then perform measurements on the third frequency (F3). F1, F2 and F3 can be associated with the first cell, the second cell and the third cell, respectively. The UE can perform all measurements for F1, F2 and F3 on the receive path bound for SCell2. The UE can also send a measurement value of 4 to the network before starting measurements on F2 and F3.

In this example, the fourth frequency (F4) associated with the fourth cell cannot be measured in combination with data reception on SCell1 (e.g., due to front-end limitations). Therefore, the UE needs to measure F4 on the receive path used for SCell1. Before the UE performs measurements for F4, the UE may signal the network to interrupt data reception on the second receive path (or SCell1) during frame #2. For example, the UE may send a measurement value of 2, which indicates that the UE plans to start performing measurements on the receive path currently bound to SCell1 (i.e., the UE plans to start measuring F4), and the UE plans to stop performing measurements on the receive path currently bound to SCell2 (if active) (i.e., the UE plans to stop measuring F3). The UE may perform measurements for F4 on the receive path used for SCell1, and then signal the network to continue DL traffic on the receive path bound to SCell1 by sending a measurement value of 0 to the network.

As previously explained, the measurement value can consist of N bits, where N is an integer. Each bit can be "1" or "0", where "1" indicates that a particular component carrier (e.g., PCell or SCellx) is used for measurement and "0" indicates that a particular component carrier is not used for measurement. If the Nth bit is set to 0, the network may or may not schedule DL traffic on that particular DL carrier. In one example, the measurement value can be transmitted to the network in the UL in conjunction with a handover notification. The handover notification can be "0" or "1" to indicate whether the next possible handover opportunity will be used by the UE. In some cases, the UE may only send a handover notification "1". In other words, if the UE does not plan to use the upcoming handover opportunity, the UE does not have to send a message to the network.

Another example provides functionality 700 of a user equipment (UE) operable to perform carrier measurements in a wireless network, as shown in the flowchart of FIG7 . The functionality may be implemented as a method, or the functionality may be executed as instructions on a machine, wherein the instructions are included on at least one computer-readable medium or a non-transitory machine-readable storage medium. The UE may include one or more processors configured to receive one or more handover parameters from a network element, the one or more handover parameters indicating possible handover opportunities for the UE, wherein the UE is configured to switch a radio frequency (RF) to another carrier frequency during the possible handover opportunities to start performing carrier measurements or stop performing carrier measurements, as in block 710. The UE may include one or more processors configured to send a handover notification to the network element, the handover notification indicating an upcoming handover opportunity selected by the UE, wherein the handover notification is sent in conjunction with a measurement value indicating one or more of: a selected carrier for which the UE will start performing carrier measurements after the handover opportunity occurs, or a selected carrier for which the UE will stop performing carrier measurements after the handover opportunity occurs, as in block 720.

In one example, the one or more handover parameters received from the network element include a measurement interval period, a measurement interval offset, or a measurement advance parameter. In one example, the one or more processors are configured to receive the one or more handover parameters indicating possible handover opportunities from the network element via radio resource control (RRC) signaling. In one example, the one or more processors are configured to receive the one or more handover parameters indicating possible handover opportunities from the network element when the UE enters a coverage area of a cell in the wireless network.

In one example, the one or more processors are configured to send the handover notification from the UE to the network element using a medium access control (MAC) control element (CE) in an uplink. In one example, the one or more processors are configured to send the handover notification from the UE to the network element via radio resource control (RRC) signaling. In one example, the one or more processors are configured to send the handover notification from the UE to the network element in an uplink using a defined physical uplink control channel (PUCCH) format or a physical uplink shared channel (PUSCH).

In one example, the carrier measurement includes an inter-carrier measurement or an intra-carrier measurement. In one example, the UE is configured for carrier aggregation, and the UE performs carrier measurements for carriers on at least one and possibly multiple receive paths. In one example, the UE uses a switching opportunity to switch to a receive path that is not currently used for data reception, so as to perform carrier measurements for one or more carriers using the receive path.

In one example, the one or more processors are further configured to: in response to a handover notification sent from the UE to the network element, receive a rejection message from the network element via a medium access control (MAC) control element (CE), wherein the rejection message prohibits the UE from using the handover opportunity indicated in the handover notification, wherein the rejection message is received at the UE during scheduling congestion at the network element. In one example, the one or more processors are further configured to: receive a notification from the network element after the scheduling congestion has decreased, indicating that the UE is allowed to select the handover opportunity; and send additional handover notifications to the network element.

Another example provides functionality 800 of a radio base station operable to assist a user equipment (UE) in performing carrier measurements in a wireless network, as shown in the flowchart of FIG8 . The functionality may be implemented as a method, or the functionality may be executed as instructions on a machine, wherein the instructions are included on at least one computer-readable medium or a non-transitory machine-readable storage medium. The radio base station may include one or more processors configured to send one or more handover parameters to a UE, the one or more handover parameters indicating possible handover opportunities for the UE, wherein the UE is configured to switch a radio frequency (RF) to another carrier frequency during the possible handover opportunities in order to start performing carrier measurements or stop performing carrier measurements, as in block 810. The radio base station may include one or more processors configured to receive a handover notification from the UE, the handover notification indicating an upcoming handover opportunity selected by the UE, wherein the handover notification is received in conjunction with a measurement value indicating one or more of: a selected carrier for which the UE will start performing carrier measurements after the handover opportunity occurs, or a selected carrier for which the UE will stop performing carrier measurements after the handover opportunity occurs, as in block 820.

In one example, the one or more processors are further configured to: send a rejection message to the UE, indicating that the UE is prohibited from switching between carriers when a switching opportunity occurs due to scheduling congestion, wherein the rejection message is sent to the UE via a medium access control (MAC) control element (CE); and send an additional message to the UE via an additional MAC CE when network congestion has decreased and the UE is now allowed to send a switching notification to the radio base station.

In one example, the one or more processors are configured to send one or more handover parameters indicating possible handover opportunities to the UE via radio resource control (RRC) signaling. In one example, the one or more processors are configured to send the one or more handover parameters indicating possible handover opportunities to the UE when the UE enters a coverage area of a cell in the wireless network.

In one example, the one or more processors are configured to receive the handover notification from the UE via a medium access control (MAC) control element (CE). In one example, the one or more processors are configured to receive the handover notification from the UE via radio resource control (RRC) signaling. In one example, the one or more processors are configured to receive the handover notification from the UE via a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH).

Another example provides functionality 900 of at least one non-transitory machine-readable storage medium having instructions embodied thereon for performing carrier measurements at a user equipment (UE). When executed, the instructions may cause the UE to receive, using at least one processor of the UE, one or more handover parameters from a network element, the one or more handover parameters indicating possible handover opportunities for the UE, wherein the UE is configured to switch radio frequency (RF) to another carrier frequency during the possible handover opportunities in order to start performing carrier measurements or stop performing carrier measurements, as in block 910. When executed, the instructions may cause the UE to send, using at least one processor of the UE, a handover notification to the network element, the handover notification indicating an upcoming handover opportunity selected by the UE, wherein the handover notification is sent in conjunction with a measurement value indicating one or more of: a selected carrier for which the UE will start performing carrier measurements after the handover opportunity occurs, or a selected carrier for which the UE will stop performing carrier measurements after the handover opportunity occurs, as in block 920.

In one configuration, the at least one non-transitory machine-readable storage medium may include instructions that, when executed by at least one processor of the UE, perform the following operations: receive one or more handover parameters from a network element via radio resource control (RRC) signaling, the one or more handover parameters indicating possible handover opportunities, wherein the one or more handover parameters include a measurement interval time period, a measurement interval offset, or a measurement advance parameter.

In one configuration, the at least one non-transitory machine-readable storage medium may include instructions that, when executed by at least one processor of a UE, perform the following operations: sending a handover notification to a network element using a medium access control (MAC) control element (CE) or via radio resource control (RRC) signaling. In one example, the UE uses the handover opportunity to switch to a receive path not currently used for data reception in order to perform carrier measurements for one or more carriers using the receive path.

Figure 10 provides an example diagram of a wireless device, such as a user equipment (UE), a mobile station (MS), a mobile wireless device, a mobile communication device, a tablet, a mobile phone, or other types of wireless devices. The wireless device may include one or more antennas configured to communicate with: a node, a macro node, a low power node (LPN), or a transmission station such as a base station (BS), an evolved Node B (eNB), a baseband unit (BBU), a remote radio head (RRH), a remote radio equipment (RRE), a relay station (RS), a radio equipment (RE), or other types of wireless wide area network (WWAN) access points. The wireless device may be configured to communicate using at least one wireless communication standard, including 3GP LTE, WiMAX, high speed packet access (HSPA), Bluetooth, and WiFi. The wireless device may communicate using a separate antenna for each wireless communication standard or a shared antenna for multiple wireless communication standards. The wireless device may communicate in a wireless local area network (WLAN), a wireless personal area network (WPAN), and/or a WWAN.

FIG10 also provides an illustration of a microphone and one or more speakers that can be used for audio input and output from the wireless device. The display screen can be a liquid crystal display (LCD) screen or other type of display screen, such as an organic light emitting diode (OLED) display. The display screen can be configured as a touch screen. The touch screen can use capacitive, resistive, or other types of touch screen technology. An application processor and a graphics processor can be coupled to internal memory to provide processing and display capabilities. A non-volatile memory port can also be used to provide data input/output options to the user. A non-volatile memory port can also be used to expand the storage capacity of the wireless device. A keyboard can be integrated with the wireless device or wirelessly connected to the wireless device to provide additional user input. A touch screen can also be used to provide a virtual keyboard.

Various technologies or aspects or portions thereof may take the form of program codes (i.e., instructions) embodied in tangible media, such as floppy disks, CD-ROMs, hard drives, non-transitory computer-readable storage media, or any other machine-readable storage media, wherein when the program code is loaded into a machine (e.g., a computer) and executed by the machine, the machine becomes a device for implementing the various technologies. Circuits may include hardware, firmware, program codes, executable code, computer instructions, and/or software. Non-transitory computer-readable storage media may be computer-readable storage media that do not include signals. When the program code is executed on a programmable computer, the computing device may include a processor, a storage medium (including volatile and non-volatile memory and/or storage elements) that can be read by the processor, at least one input device, and at least one output device. Volatile and non-volatile memory and/or storage elements may be RAM, EPROM, flash drives, optical drives, magnetic hard drives, solid-state drives, or other media for storing electronic data. Nodes and wireless devices may also include transceiver modules, counter modules, processing modules, and/or clock modules or timer modules. One or more programs that can implement or utilize the various techniques described herein can use application programming interfaces (APIs), reusable controls, and the like. Such programs can be implemented in high-level procedural or object-oriented programming languages to communicate with a computer system. However, if desired, the program(s) can be implemented in assembly or machine language. In any case, the language can be a compiled or parsed language and combined with a hardware implementation.

As used herein, the term processor may include general purpose processors, special purpose processors (eg, VLSI, FPGA, or other types of special purpose processors), and baseband processors used in a transceiver to transmit, receive, and process wireless communications.

It should be understood that many of the functional units described in this specification have been labeled as modules in order to more specifically emphasize their implementation independence. For example, a module can be implemented as a hardware circuit comprising custom VLSI circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module can also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, etc.

In one example, multiple hardware circuits or multiple processors can be used to implement the functional units described in this specification. For example, a first hardware circuit or a first processor can be used to perform processing operations, and a second hardware circuit or a second processor (e.g., a transceiver or a baseband processor) can be used to communicate with other entities. The first hardware circuit and the second hardware circuit can be integrated into a single hardware circuit, or alternatively, the first hardware circuit and the second hardware circuit can be separate hardware circuits.

Module can also be realized in software for various types of processor execution.Identified executable code module can for example comprise one or more physical or logical blocks of computer instructions, for example, they can be organized as objects, processes, or functions.Yet the executable file of identified module does not need to be physically located together, but can comprise different instructions stored in different locations, and when being logically connected together, these instructions comprise module and realize the described purpose of module.

In fact, the module of executable code can be a single instruction or many instructions, and can even be distributed on several different code segments, in different programs and across several memory devices.Similarly, operational data can be identified and illustrated in this article in module, and can embody or be organized in the data structure of any appropriate type in any appropriate form.Operational data can be collected as a single data set or can be distributed on the different locations that comprise different storage devices, and can only exist as the electronic signal on system or network at least in part.Module can be passive or active, comprises the agent that can be operated to perform desired function.

References throughout this specification to "an example" indicate that a particular feature, structure, or characteristic described in connection with the example is included in at least one embodiment of the present technology. Thus, the appearances of the phrase "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.

As used herein, for convenience, multiple items, structural elements, constituent elements, and/or materials can be presented in a public list. However, these lists should be understood as each member in the list being individually identified as a separate and unique member. Therefore, there is no separate member in the list, only based on their appearance in the public group and without contrary instructions, but should be understood as the actual equivalent of any other member in the same list. In addition, the various embodiments and examples of the present technology can be quoted together with the alternatives of its various components herein. It is understood that such embodiments, examples and alternatives are not understood as actual equivalents to each other, but will be considered as the independent and autonomous representation of the present technology.

In addition, described features, structures or characteristics can be combined in one or more embodiments in any appropriate manner. In the following description, many specific details (e.g., examples of layout, distance, network examples, etc.) are provided to provide a thorough understanding of the embodiments of the present technology. However, those skilled in the relevant art will recognize that it is possible to implement the present technology without one or more of these specific details or by utilizing other methods, components, layouts, etc. In other cases, known structures, materials or operations are not shown or described in detail to avoid blurring the aspects of the present technology.

Although the above examples are illustrative of the principles of the present technology in one or more specific applications, it will be apparent to those skilled in the art that many modifications may be made in details of form, use, and implementation without exercising inventive power and without departing from the principles and concepts of the present technology. Therefore, the present technology is not intended to be limited except as set forth in the claims below.

Claims (26)

1. An apparatus operable to perform carrier measurement in a wireless network, the apparatus comprising circuitry configured to: The UE receives one or more handover parameters from a network element, the one or more handover parameters indicating a possible handover timing for the UE, wherein the UE is configured to switch radio frequency (RF) to another carrier frequency during the possible handover timing to initiate or cease carrier measurement. The one or more handover parameters include a measurement interval time period, a measurement interval offset, and a measurement advance parameter, the measurement interval time period indicating the period of the possible handover timing, the measurement interval offset indicating an offset relative to a system frame number, and the measurement advance parameter defining the number of subframes the UE notifies the network element in advance of the upcoming handover timing; and A handover notification is sent to the network element, the handover notification indicating that an upcoming handover opportunity is selected by the UE from the possible handover opportunities, wherein the handover notification is sent in conjunction with a measurement value indicating one or more of the following: the carrier selected by the UE for which it will begin performing carrier measurements after the handover opportunity occurs, or the carrier selected by the UE for which it will stop performing carrier measurements after the handover opportunity occurs. 2. The apparatus of claim 1, wherein the circuitry is configured to receive, via Radio Resource Control (RRC) signaling, the one or more handover parameters indicating the possible handover timing from the network element. 3. The apparatus of claim 1, wherein the circuit is configured to receive, from the network element, one or more handover parameters indicating the possible handover timing when the UE enters the coverage area of a cell in the wireless network. 4. The apparatus of claim 1, wherein the circuitry is configured to use a Media Access Control (MAC) control element (CE) in the uplink to send the handover notification from the UE to the network element. 5. The apparatus of claim 1, wherein the circuitry is configured to send the handover notification from the UE to the network element via Radio Resource Control (RRC) signaling. 6. The apparatus of claim 1, wherein the circuitry is configured to send the handover notification from the UE to the network element in the uplink using a defined Physical Uplink Control Channel (PUCCH) format or Physical Uplink Shared Channel (PUSCH). 7. The apparatus of claim 1, wherein the carrier measurement includes inter-carrier measurement or intra-carrier measurement. 8. The apparatus of claim 1, wherein the UE is configured for carrier aggregation, and the carrier for which the UE performs the carrier measurement includes a primary cell and a plurality of secondary cells. 9. The apparatus of claim 1, wherein the UE uses the handover timing to switch to a reception path not currently used for data reception, so as to use that reception path to perform carrier measurements for one or more carriers. 10. The apparatus of claim 1, wherein the circuitry is further configured to: receive a rejection message from the network element via a media access control (MAC) control element (CE) in response to the handover notification sent from the UE to the network element, wherein the rejection message prohibits the UE from using the handover timing indicated in the handover notification, wherein the rejection message is received at the UE during scheduling congestion at the network element. 11. The apparatus of claim 10, wherein the circuit is further configured to: After the scheduling congestion has decreased, a notification is received from the network element indicating that the UE is permitted to select a handover timing; and Send additional handover notifications to the network elements. 12. An apparatus for a radio base station operable to assist a user equipment (UE) in performing carrier measurements in a wireless network, the apparatus comprising one or more processors configured to: One or more handover parameters are sent to the UE, indicating possible handover timings for the UE, wherein the UE is configured to switch radio frequency (RF) to another carrier frequency during the possible handover timing to initiate or cease carrier measurement. The one or more handover parameters include a measurement interval period, a measurement interval offset, and a measurement advance parameter. The measurement interval period indicates the period of the possible handover timing, the measurement interval offset indicates an offset relative to a system frame number, and the measurement advance parameter defines the number of subframes the UE notifies network elements in advance of the upcoming handover timing. The UE receives a handover notification indicating an upcoming handover opportunity selected by the UE from the possible handover opportunities, wherein the handover notification is received in conjunction with a measurement indicating one or more of the following: a carrier selected by the UE for which it will begin performing carrier measurements after the handover opportunity occurs, or a carrier selected by the UE for which it will stop performing carrier measurements after the handover opportunity occurs. 13. The apparatus of claim 12, wherein the one or more processors are further configured to: A rejection message is sent to the UE, indicating that the UE is prohibited from handover between carriers when the handover opportunity occurs due to scheduling congestion, wherein the rejection message is sent to the UE via a Media Access Control (MAC) element (CE); and When network congestion has decreased and the UE is now permitted to send a handover notification to the radio base station, an additional message is sent to the UE via an additional MAC CE. 14. The apparatus of claim 12, wherein the one or more processors are configured to send the one or more handover parameters indicating the possible handover timing to the UE via Radio Resource Control (RRC) signaling. 15. The apparatus of claim 12, wherein the one or more processors are configured to send the one or more handover parameters indicating the possible handover timing to the UE when the UE enters the coverage area of a cell in the wireless network. 16. The apparatus of claim 12, wherein the one or more processors are configured to receive the handover notification from the UE via a Media Access Control (MAC) control element (CE). 17. The apparatus of claim 12, wherein the one or more processors are configured to receive the handover notification from the UE via Radio Resource Control (RRC) signaling. 18. The apparatus of claim 12, wherein the one or more processors are configured to receive the handover notification from the UE via a Physical Uplink Control Channel (PUCCH) or a Physical Uplink Shared Channel (PUSCH). 19. At least one non-transitory machine-readable storage medium having instructions embodied thereon for performing carrier measurement at a user equipment (UE), the instructions, when executed, performing the following operations: The UE uses at least one processor to receive one or more handover parameters from a network element, the one or more handover parameters indicating a possible handover timing for the UE, wherein the UE is configured to switch radio frequency (RF) to another carrier frequency during the possible handover timing to initiate or cease carrier measurement. The one or more handover parameters include a measurement interval time period, a measurement interval offset, and a measurement advance parameter, the measurement interval time period indicating the period of the possible handover timing, the measurement interval offset indicating an offset relative to a system frame number, and the measurement advance parameter defining the number of subframes the UE notifies the network element in advance of the upcoming handover timing; and The UE uses at least one processor to send a handover notification to the network element, the handover notification indicating that an upcoming handover timing is selected by the UE from the possible handover timings, wherein the handover notification is sent in conjunction with a measurement indicating one or more of the following: a carrier selected by the UE for which it will begin performing carrier measurements after the handover timing occurs, or a carrier selected by the UE for which it will stop performing carrier measurements after the handover timing occurs. 20. The at least one non-transitory machine-readable storage medium of claim 19, further comprising instructions that, when executed by the at least one processor of the local UE, perform the following operations: receiving, via radio resource control (RRC) signaling, the one or more handover parameters indicating the possible handover timing from the network element. 21. The at least one non-transitory machine-readable storage medium of claim 19, further comprising instructions that, when executed by the at least one processor of a local UE, perform the following operations: send the handover notification to the network element using a Media Access Control (MAC) control element (CE) or via Radio Resource Control (RRC) signaling. 22. The at least one non-transitory machine-readable storage medium of claim 19, wherein the UE uses the handover timing to switch to a receive path not currently used for data reception so as to use that receive path to perform carrier measurements for one or more carriers. 23. A user equipment (UE) operable to perform carrier measurement, comprising: A means for receiving one or more handover parameters from a network element, the one or more handover parameters indicating a possible handover timing for the UE, wherein the UE is configured to switch radio frequency (RF) to another carrier frequency during the possible handover timing to initiate or cease carrier measurement, the one or more handover parameters including a measurement interval time period, a measurement interval offset, and a measurement advance parameter, the measurement interval time period indicating the period of the possible handover timing, the measurement interval offset indicating an offset relative to a system frame number, and the measurement advance parameter defining the number of subframes by which the UE notifies the network element in advance of the upcoming handover timing; and A means for sending a handover notification to the network element, the handover notification indicating an upcoming handover timing selected by the UE from the possible handover timings, wherein the handover notification is sent in conjunction with a measurement indicating one or more of the following: a carrier selected by the UE for which it will begin performing carrier measurements after the handover timing occurs, or a carrier selected by the UE for which it will stop performing carrier measurements after the handover timing occurs. 24. The UE of claim 23, further comprising: means for receiving, via radio resource control (RRC) signaling, the one or more handover parameters indicating the possible handover timing from the network element, wherein the one or more handover parameters include a measurement interval time period, a measurement interval offset, or a measurement advance parameter. 25. The UE of claim 23, further comprising: means for sending the handover notification to the network element using a Media Access Control (MAC) control element (CE) or via Radio Resource Control (RRC) signaling. 26. The UE of claim 23, wherein the UE uses the handover timing to switch to a reception path not currently used for data reception, so as to use the reception path to perform carrier measurements for one or more carriers.