CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of US Provisional Application No.

62/401,716 (P109638Z) filed September 29, 2016. Said Application No. 62/401,716 is hereby incorporated herein by reference in its entirety.

BACKGROUND

[0002] In the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) standards such LTE Release 11 to LTE Release 13, multiple enhancements of a user equipment (UE) advanced receiver for the interference-limited environments were introduced, including but not limited to linear minimum mean square error interference rejection combining (LMMSE-IRC), cell-specific reference signals interference mitigation (CRS-IM), single-user multiple-input multiple-output (SU-MIMO) interference mitigation (IM), network-assisted interference cancellation and suppression (NAICS), and other advanced receivers. The substantial part of the respective 3GPP work was dedicated to the introduction of the CRS Interference Mitigation (CRS- IM), which was done in the scope of the Release 11 Further Enhanced Inter-Cell Interference Coordination (FelCIC) Work Item (WI) and Release 12 and Release 13 CRS-IM Study Item (SI) and WI. The purpose of the introduced CRS-IM functionality is to specify the receiver mechanisms to mitigate the dominant CRS interference from the neighboring cells, which may become a limiting factor for the downlink (DL) performance in the FelCIC almost blank subframes (ABS) subframes in the heterogeneous networks (HetNet) deployments and also for the generic synchronous homogeneous and heterogeneous deployments with the partial downlink resource utilization. In particular, the 3GPP studies have shown that using regular receivers (LMMSE-IRC) for handling the CRS interference may result in substantial performance degradation especially for the scenarios with partial interference cell loading.

[0003] As the result of the 3 GPP work in LTE Release 11 through Release 13, multiple

CRS-IM UE demodulation performance requirements were defined covering some typical LTE operation scenarios. The test coverage, however, is rather limited and only a subset of the important operation scenarios is addressed. CRS-IM requirements may be introduced for the case of the network deployments using two CRS antenna ports (APs) only, meanwhile the UE behavior for the case of four CRS antenna ports (APs) deployments is undefined. CRS-IM requirements are defined for the case using the same number of CRS APs in the serving and interference cells, while in the heterogeneous networks different cells may use different CRS configurations, for example four CRS APs for the Macro cell and two CRS APs for the Small cells. CRS-IM requirements are specified for the UEs equipped with two receive antennas only, while the UEs with four receive antennas, which are emerging in the market, may also benefit from the CRS-IM. As a result, in Release 14 a new WI on the CRS-IM and SU-MIMO IM receiver enhancements has been recently approved.

DESCRIPTION OF THE DRAWING FIGURES

[0004] Claimed subject matter is particularly pointed out and distinctly claimed in the concluding portion of the specification. However, such subject matter may be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0005] FIG. 1 is a diagram of a network illustrating four cell-specific reference signal

(CRS) antenna ports and a mix of two and four CRS antenna ports in accordance with one or more embodiments;

[0006] FIG. 2 is a diagram of a non-colliding CRS scenario with four CRS antenna ports in the serving cell and the interference cells in accordance with one or more embodiments;

[0007] FIG. 3 is a diagram of four and two, and two and four, CRS antenna ports mix scenarios with non-colliding CRS patterns in accordance with one or more embodiments;

[0008] FIG. 4 is a diagram of four and two, and two and four, CRS antenna ports mix scenarios with colliding CRS patterns;

[0009] FIG. 5 is a diagram of four CRS antenna ports CRS-IM simulation results in accordance with one or more embodiments;

[00010] FIG. 6 is a diagram of example components of a device in accordance with some embodiments; and

[00011 ] FIG. 7 is a diagram of example interfaces of baseband circuitry in accordance with one or more embodiments.

[00012] It will be appreciated that for simplicity and/or clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, if considered appropriate, reference numerals have been repeated among the figures to indicate corresponding and/or analogous elements.

DETAILED DESCRIPTION

[00013] In the following detailed description, numerous specific details are set forth to provide a thorough understanding of claimed subject matter. It will, however, be understood by those skilled in the art that claimed subject matter may be practiced without these specific details. In other instances, well-known methods, procedures, components and/or circuits have not been described in detail. [00014] Referring now to FIG. 1, a diagram of a network illustrating four cell-specific reference signal (CRS) antenna ports and a mix of two and four CRS antenna ports in accordance with one or more embodiments will be discussed. In the network 100 of FIG. 1 macro cell 110 may communicate with a macro cell user equipment (UE) 112 using four cell-specific reference signal (CRS) antenna ports (APs), and macro cell 116 may communicate with macro cell UE 118 using four CRS APs. Macro cell 116 may be an interferer for communications between macro cell 110 and macro cell UE 112. Similarly, small cell 120 may communicate with small cell UE 122 using two CRS APs. In such an environment, macro cell 116 may be an interferer for communications between small cell 120 and small cell UE 122, and small cell 120 may be an interferer for communications between macro cell 116 and macro cell UE 118.

[00015] Deployments of cells using four CRS APs may be utilized to enable high peak data rate transmissions using the CRS-based transmission modes and are expected to get more attraction with the introduction of the UEs having four receive antennas (4RX UEs). Meanwhile, UEs capable of two CRS APs interference mitigation (IM) may not be capable to perform CRS- IM for four CRS APs. Therefore, in the Release 14 CRS-IM WI it is planned to introduce the respective requirements to check proper UE implementation and ensure robust and efficient UE operation. In the meanwhile, four CRS APs CRS-IM may have high implementation complexity. Therefore, methods for CRS-IM complexity reduction are discussed herein.

[00016] In heterogenous network (HetNet) deployments, the macro cell and small cell may have different characteristics, and the number of transmit antennas and CRS APs at the macro cells may be larger comparing to the small cells. For instance, a mix of two CRS APs and four CRS APs in the neighboring cells may be a common situation, for example four CRS APs at the macro cell 116 and two CRS APs in small cell 120 as shown in FIG. 1. Reduced complexity CRS-IM for four CRS APs is shown in and described with respect to FIG. 2, below. CRS-IM and Interference whitening for scenarios with mix of two CRS APs and four CRS APs in the serving cell and interfering cells is shown in and described with respect to FIG. 3, below.

[00017] Referring now to FIG. 2, a diagram of a non-colliding CRS scenario with four CRS antenna ports in the serving cell and the interference cells in accordance with one or more embodiments will be discussed. In one particular embodiment, reduced complexity CRS-IM for four CRS APs may address inter-cell interference arising in LTE networks wherein neighboring cells have non-colliding CRS patterns and the interference cell has four CRS APs. The term non- colliding CRS scenario may refer to the situation when serving cells and interference cells have non-overlapping CRS REs patterns which may happen when the cells have different cell identifiers (IDs), for example, mod(Cell ID 1, 3)≠ mod(Cell ID 2,3). FIG. 2 illustrates an example of the LTE signal structure for one physical resource block (PRB) pair for the serving cell and the interference cell for the Normal cyclic prefix (CP) case under assumption that the control region occupies single orthogonal frequency-division multiplexing (OFDM) symbol, and both cells have CRS-based physical downlink shared channel (PDSCH) transmission modes (TMs), and no other signals are present such as demodulation reference signals (DMRS), channel state information reference signals (CSI-RS), and so on. Both cells in the example of FIG. 2 have four CRS APs. It may be observed that serving cell data in the PDSCH and control resource elements (REs) may experience interference from the neighboring cell CRS REs. This scenario is substantially similar to the scenario considered in the LTE Release 11 through Release 13 work with the exception that the interference cell has four CRS APs, while in the previous releases the requirements are introduced for the case of two CRS APs.

[00018] Thus, FIG. 2 shows the structures of a serving cell signal 210 and an interference cell signal 212 arranged so that the four CRS signals 214 of the serving cell signal 210 do not interfere with four CRS signals 214 of the interference cell signal 212 and vice versa. The control region resource elements (REs) 216 are shown for the physical downlink control channel (PDCCH), the physical control format indicator channel (PCFICH), and the physical hybrid automatic repeat request (ARQ) indicator channel (PHICH). The serving cell physical downlink shared channel (PDSCH) signals 218 are shown for the serving cell signal 210, and the interferer PDSCH signals 220 are shown for the interference cell signal 212. It should be noted that the term interference cell signal may refer to a signal from a neighboring cell that has the potential to interfere with the cell signal from a particular serving cell, although interference from the interference cell with the present cell, and interference from the present serving cell with the interference cell, may be mitigated using the embodiments described herein, and the scope of the claimed subject matter is not limited in this respect. Using the structure of the serving cell signal 210 and the interference cell signal 212 shown in FIG. 2 may mitigate, reduce, or eliminate the interference from the CRS signals among neighboring cells, and the scope of the claimed subject matter is not limited in this respect.

[00019] FIG. 2 shows an embodiment for CRS-IM wherein the two cells, the serving cell and the neighboring potential interference cell, both may utilize four CRS APs for PDSCH transmission. In one or more embodiments, the possible set of conventional CRS-IM algorithms may be described that typically may be considered for CRS-IM implementation for the case of two CRS APs. For CRS interference cancellation (CRS-IC), the main idea is to explicitly cancel the reconstructed interference CRS signal from the total receive signal prior to the useful signal demodulation. The following operations may be considered: interference cell channel estimation on the CRS REs, interference CRS signal reconstruction, cancellation of the reconstructed interference CRS signal from the total receive signals, and useful signal demodulation. For CRS whitening (CRS-WF), the UE estimates the interference plus noise covariance matrix corresponding to the CRS interference and applies different pre-whitening, referred to as interference rejection combining for the REs with interference from the CRS REs and data REs. Different approaches for the interference plus noise covariance matrix estimation may be utilized, for example based on interferer channel estimation, or based on subtraction of the serving cell data signal covariance matrix from the total receive signal covariance matrix on the CRS REs and others. For CRS power scaling (CRS-PS), the signals on the REs affected by the CRS interference may be power scaled in order to reduce the negative impact from the CRS interference. In some cases, the power scaling coefficient may be set equal to zero which results in the puncturing of signals on the REs affected by the CRS interference. Typically, the CRS-IC method provides the best performance followed by the CRS-WF approach. The CRS-PS approach typically has reduced performance.

[00020] For the non-colliding CRS-IM in the scenarios with four CRS APs, several factors may be considered. First, the CRS-IC and CRS-WF complexity may substantially increase as compared to the case of four CRS APs, especially for the case of using four receive antennas (4RX). Second, in the case of four CRS APs with non-colliding CRS patterns, the number of data REs with CRS interference may be increased as compared to the case of two CRS APs, although a larger portion of interference may come from the CRS APs 0 and 1 as compared to the CRS APs 2 and 3. A comparison of the two cases is shown in Table 1, below.

[00021 ] In order to reduce the CRS-IM complexity for handling non-colliding CRS interference in the case of using four CRS APs, it may be possible to use different CRS-IM algorithms for handling interference from different CRS APs. For example, different methods may be applied to handle interference from CRS APs 0-1 and from CRS APs 2-3. The basic principle is that a more complex and efficient algorithm may be applied for handling CRS APs 0- 1 interference, and a less complex approach may be applied for handling CRS APs 2-3. In particular, the following processing methods may be utilized as shown in Table 2, below.

Table 2 - Multi-algorithm methods to implement CRS-IM for different CRS APs

[00022] In some embodiments, the same multi-algorithm approach may be used for handling different subsets of CRS APs. For example, one algorithm may be applied for handling CRS AP 0, and another algorithm for other ports, or one algorithm for ports 0-2 and another algorithm for port 3, and so on. The approaches described herein also may be applicable for the case where UE handles interference from more than one dominant interference cell. In such an arrangement, the embodiment describe above may be generalized for the case of multi-cell interference mitigation. For example, different CRS-IM algorithms may be utilized for handling different subsets of CRS APs from different interference cells, for example a first method may be applied for CRS APs 0-1 from cell #1, a second method may be applied for CRS APs 0-1 from cell #2, and a third method may be applied for CRS APs 2-3 from Cells #1 and #2, although the scope of the claimed subject matter is not limited in this respect.

[00023] Referring now to FIG. 3, a diagram of four and two, and two and four, CRS antenna ports mix scenarios with non-colliding CRS patterns in accordance with one or more embodiments will be discussed. The embodiment shown in FIG. 3 may utilize CRS-IM and interference whitening for scenarios having a mix of two CRS APs and four CRS APs in the serving cell and the interference cell. In such an embodiment, the inter-cell interference scenario arising in the LTE networks may be addressed for the case where neighboring cells have a different number of CRS APs. For example, the serving cell may have two CRS APs and the interference cell, the neighboring cell, may have four CRS APs, or vice versa. For such scenarios, the interference environment is different compared to the case of using the same number of CRS APs in both the neighboring cells as shown for example in FIG. 2. For scenarios with a mix of two CRS APs and four CRS APs, the following terms may be utilized. Non-colliding CRS may refer to a scenario wherein the serving cell and the interference, or neighboring cell, have non-overlapping CRS REs patterns for APs 0-1. Such a scenario may occur when cells have different cell IDs, for example where mod(Cell ID 1, 3)≠ mod(Cell ID 2,3). Colliding CRS may refer to a scenario wherein the serving cell and the interference cell, or the neighboring cell, have overlapping CRS REs patterns for APs 0-1. Such a scenario may occur when cells have the same cell IDs, for example where mod(Cell ID 1, 3) = mod(Cell ID 2,3). FIG. 3 illustrate an example of the LTE signal structures for one PRB pair for the non-colliding CRS scenario when Cell #1 has four CRS APs and Cell #2 has two CRS APs, wherein the Cell #1 signal 310 and the Cell #2 signal 312 are shown. Cell #1 signal 310 may include CRS signals 314 for four CRS APs, and further may show control region REs 316 and REs 318 with CRS interference, and Cell #1 PDSCH signals 320. Cell #2 signal 312 may include CRS signals 314 for two CRS APs, and further may show control region REs 316 and REs 318 with CRS interference, and Cell #2 PDSCH signals 322.

[00024] Referring now to FIG. 4, a diagram of four and two, and two and four, CRS antenna ports mix scenarios with colliding CRS patterns will be discussed. FIG. 4 illustrates an example of the LTE signal structure for the colliding CRS scenario wherein Cell #1 has four CRS APs and Cell #2 has two CRS APs. The illustrations are provided for a Normal cyclic prefix (CP) case under an assumption that the control region occupies a single OFDM symbol, both cells have CRS- based PDSCH transmission modes (TMs), and no other signals are present, for example demodulation reference signals (DMRS), channel state information reference signals (CSI-RS), and so on.

[00025] For the non-colliding CRS scenarios with a mix of two CRS APs and four CRS APs, the regular non-colliding CRS-IM framework may be applied, and no enhancements may be needed. The UE may attempt to mitigate CRS interference on the REs corresponding to the CRS of the neighboring cell. Colliding CRS scenarios with two CRS APs in the serving cell and four CRS APs in the interference cell may be characterized by the following interference environment shown in FIG. 4. The serving cell, Cell #2, has two CRS APs, and the interferer cell, Cell #1, has four CRS APs with colliding CRS patterns. As an example, the serving cell, Cell #1 may have cell ID 0 and the interference cell, Cell # 2, may have cell ID 6. The CRS APs 0-1 of the interference cell may cause interference to the CRS APs 0-1 of the serving cell. The CRS APs 2- 3 of the interference cell may cause interference to the data and control channel REs of the serving cell.

[00026] In such a scenario, the CRS of the interference cell may provide interference to both data REs and CRS REs of the serving cell. The CRS-IM framework for this scenario may include colliding CRS-IM for CRS APs 0- 1 and non-colliding CRS-IM for CRS APs 2-3.

[00027] The colliding CRS scenario with four CRS APs in the serving cell and two CRS APs in the interference cell may be characterized by the following interference environment as shown in FIG. 4. The serving cell, Cell #1, has four CRS APs, and interferer cell, Cell #2, has two CRS APs with colliding CRS patterns. For example, the serving sell may have cell ID 0, and the interference cell may have cell ID 6. The CRS APs 0-1 of the interference cell may cause interference to the CRS APs 0- 1 of the serving cell. Data REs of the serving cell may experience interference from data REs of the interference cell. The CRS APs 2-3 of the serving cell may experience interference from the data REs of the interference cells.

[00028] In the example shown in FIG. 4, the Cell #1 signal 410 may include CRS signals 414 for four CRS APs, and the Cell #2 signal 412 may include CRS signals 414 for two CRS APs. Cell #1 signal 410 and Cell #2 signal 412 may include control region REs 416 and REs 418 with CRS interference. Cell #1 signal 410 includes Cell #1 PDSCH signals 420, and Cell # signal 412 includes Cell #2 PDSCH signals 422.

[00029] Typical UE receiver structures may rely on the estimates of the receive signal interference plus noise covariance matrices (RI+N) to apply interference suppression, for example linear minimum mean square error interference rejection combining (LMMSE-IRC) receivers, or reduced-complexity maximum likelihood (R-ML) receivers with interference pre-whitening. For the CRS-based TMs, it is assumed that RI+N may be estimated on the CRS REs of the serving cell after subtraction of the reconstructed CRS signals of the serving cell. For the DMRS-based TMs, RI+N may be estimated on the DMRS REs after subtraction of the reconstructed useful signal DMRS signals.

[00030] For the particular scenario in which the RI+N is estimated on the CRS REs of the serving cell, the interference estimate may be mismatched with the actual interference observed on the data REs. Therefore, in order to obtain an actual interference data signal estimate, estimation of the RI+N may be performed on only the CRS APs 2-3 of the serving cell without using CRS APs 0-1.

[00031 ] Although the embodiments discussed herein are directed to physical downlink shared channel (PDSCH) receiver enhancements, similar concepts also may be applied to UE receivers for other downlink physical channels including but not limited to physical downlink control channel (PDCCH), physical hybrid automatic repeat request (ARQ) indicator channel (PHICH), physical broadcast channel (PBCH), or enhanced physical downlink control channel (EPDCCH), and so on, and the scope of the claimed subject matter is not limited in this respect. Furthermore, the embodiments discussed herein are applicable for both CRS-based TMs and DMRS-based TMs. The embodiment of FIG. 2 may be extended for the case of two CRS APs wherein different methods may be applied for handling interference on CRS APs 0-1, and embodiments of FIG. 3 and FIG. 4 may be extended for the case of a mix of one or two CRS APs and one or 4 CRS APs, and the scope of the claimed subject matter is not limited in these respects. The example embodiments are provided herein for the Normal CP case similarly may be applied for the Extended CP case, and the embodiments herein also may be applicable to the case wherein the UE handles interference from more than one dominant interfering cells, and the scope of the claimed subject matter is not limited in these respects.

[00032] Referring now to FIG. 5, a diagram of four CRS antenna ports CRS-IM simulation results in accordance with one or more embodiments will be discussed. In FIG. 5 the simulation results illustrate the CRS-IM performance for the scenarios with four CRS APs in the serving and interference cells. The simulation results are provided for different receiver types as follows. Receiver #1 uses full complexity four port CRS-IC processing. Receiver #2 uses reduced complexity CRS-IM processing wherein CRS-IC is used for CRS APs 0-1 interference and regular data LMMSE-IRC is used for handling CRS APs 2-3 interference. Receiver #3 uses reduced complexity CRS-IM processing wherein CRS-IC is used for CRS APs 0-1 interference and CRS- PS (power scaling) is used for handling CRS APs 2-3 interference. Transmission mode 9 (TM9) with modulation and coding scheme (MCS) #9 is shown in graph 510, and TM9 and MCS #14 is shown in graph 512. LMMSE-IRC results with no CRS-IM is shown on plot 514, CRS-IM Receiver #1 is shown on plot 516, CRS-IM Receiver #2 is shown on plot 518, and CRS-IM Receiver #3 is shown on plot 520. The simulation results of FIG. 5 indicate that a reduced complexity algorithm approach as shown in and described in the embodiment of FIG. 2 for Receiver #3 allows reaching the performance of the full complexity CRS-IC receiver while promising noticeable complexity reduction.

[00033] FIG. 6 illustrates example components of a device 600 in accordance with some embodiments. Device 600 may tangibly embody at least some components of macro cell 110, macro cell UE 112, macro cell 116, macro cell UE 118, small cell 120, or small cell UE 122 of FIG. 1, which may include more components or fewer components than device 600, and the scope of the claimed subject matter is not limited in this respect. In some embodiments, the device 600 may include application circuitry 602, baseband circuitry 604, Radio Frequency (RF) circuitry 606, front-end module (FEM) circuitry 608, one or more antennas 610, and power management circuitry (PMC) 612 coupled together at least as shown. The components of the illustrated device 600 may be included in a UE or a RAN node. In some embodiments, the device 600 may include less elements (e.g., a RAN node may not utilize application circuitry 602, and instead include a processor/controller to process IP data received from an EPC). In some embodiments, the device 600 may include additional elements such as, for example, memory/storage, display, camera, sensor, or input/output (I/O) interface. In other embodiments, the components described below may be included in more than one device (e.g., said circuitries may be separately included in more than one device for Cloud-RAN (C-RAN) implementations).

[00034] The application circuitry 602 may include one or more application processors. For example, the application circuitry 602 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor(s) may include any combination of general-purpose processors and dedicated processors (e.g., graphics processors, application processors, etc.). The processors may be coupled with or may include memory/storage and may be configured to execute instructions stored in the memory/storage to enable various applications or operating systems to run on the device 600. In some embodiments, processors of application circuitry 602 may process IP data packets received from an EPC.

[00035] The baseband circuitry 604 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The baseband circuitry 604 may include one or more baseband processors or control logic to process baseband signals received from a receive signal path of the RF circuitry 606 and to generate baseband signals for a transmit signal path of the RF circuitry 606. Baseband processing circuity 604 may interface with the application circuitry 602 for generation and processing of the baseband signals and for controlling operations of the RF circuitry 606. For example, in some embodiments, the baseband circuitry 604 may include a third generation (3G) baseband processor 604 A, a fourth generation (4G) baseband processor 604B, a fifth generation (5G) baseband processor 604C, or other baseband processor(s) 604D for other existing generations, generations in development or to be developed in the future (e.g., second generation (2G), si6h generation (6G), etc.). The baseband circuitry 604 (e.g., one or more of baseband processors 604A-D) may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 606. In other embodiments, some or all of the functionality of baseband processors 604A-D may be included in modules stored in the memory 604G and executed via a Central Processing Unit (CPU) 604E. The radio control functions may include, but are not limited to, signal modulation/demodulation, encoding/decoding, radio frequency shifting, etc. In some embodiments, modulation/demodulation circuitry of the baseband circuitry 604 may include Fast-Fourier Transform (FFT), precoding, or constellation mapping/demapping functionality. In some embodiments, encoding/decoding circuitry of the baseband circuitry 604 may include convolution, tail-biting convolution, turbo, Viterbi, or Low Density Parity Check (LDPC) encoder/decoder functionality. Embodiments of modulation/demodulation and encoder/decoder functionality are not limited to these examples and may include other suitable functionality in other embodiments.

[00036] In some embodiments, the baseband circuitry 604 may include one or more audio digital signal processor(s) (DSP) 604F. The audio DSP(s) 604F may be include elements for compression/decompression and echo cancellation and may include other suitable processing elements in other embodiments. Components of the baseband circuitry may be suitably combined in a single chip, a single chipset, or disposed on a same circuit board in some embodiments. In some embodiments, some or all of the constituent components of the baseband circuitry 604 and the application circuitry 602 may be implemented together such as, for example, on a system on a chip (SOC).

[00037] In some embodiments, the baseband circuitry 604 may provide for communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry 604 may support communication with an evolved universal terrestrial radio access network (EUTRAN) or other wireless metropolitan area networks (WMAN), a wireless local area network (WLAN), a wireless personal area network (WPAN). Embodiments in which the baseband circuitry 604 is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry.

[00038] RF circuitry 606 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry 606 may include switches, filters, amplifiers, etc. to facilitate the communication with the wireless network. RF circuitry 606 may include a receive signal path which may include circuitry to down-convert RF signals received from the FEM circuitry 608 and provide baseband signals to the baseband circuitry 604. RF circuitry 606 may also include a transmit signal path which may include circuitry to up-convert baseband signals provided by the baseband circuitry 604 and provide RF output signals to the FEM circuitry 608 for transmission.

[00039] In some embodiments, the receive signal path of the RF circuitry 606 may include mixer circuitry 606a, amplifier circuitry 606b and filter circuitry 606c. In some embodiments, the transmit signal path of the RF circuitry 606 may include filter circuitry 606c and mixer circuitry 606a. RF circuitry 606 may also include synthesizer circuitry 606d for synthesizing a frequency for use by the mixer circuitry 606a of the receive signal path and the transmit signal path. In some embodiments, the mixer circuitry 606a of the receive signal path may be configured to down- convert RF signals received from the FEM circuitry 608 based on the synthesized frequency provided by synthesizer circuitry 606d. The amplifier circuitry 606b may be configured to amplify the down-converted signals and the filter circuitry 606c may be a low-pass filter (LPF) or band- pass filter (BPF) configured to remove unwanted signals from the down-converted signals to generate output baseband signals. Output baseband signals may be provided to the baseband circuitry 604 for further processing. In some embodiments, the output baseband signals may be zero-frequency baseband signals, although this is not a requirement. In some embodiments, mixer circuitry 606a of the receive signal path may comprise passive mixers, although the scope of the embodiments is not limited in this respect.

[00040] In some embodiments, the mixer circuitry 606a of the transmit signal path may be configured to up-convert input baseband signals based on the synthesized frequency provided by the synthesizer circuitry 606d to generate RF output signals for the FEM circuitry 608. The baseband signals may be provided by the baseband circuitry 604 and may be filtered by filter circuitry 606c.

[00041 ] In some embodiments, the mixer circuitry 606a of the receive signal path and the mixer circuitry 606a of the transmit signal path may include two or more mixers and may be arranged for quadrature downconversion and upconversion, respectively. In some embodiments, the mixer circuitry 606a of the receive signal path and the mixer circuitry 606a of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g., Hartley image rejection). In some embodiments, the mixer circuitry 606a of the receive signal path and the mixer circuitry 606a may be arranged for direct downconversion and direct upconversion, respectively. In some embodiments, the mixer circuitry 606a of the receive signal path and the mixer circuitry 606a of the transmit signal path may be configured for super-heterodyne operation.

[00042] In some embodiments, the output baseband signals and the input baseband signals may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternate embodiments, the output baseband signals and the input baseband signals may be digital baseband signals. In these alternate embodiments, the RF circuitry 606 may include analog-to-digital converter (ADC) and digital-to- analog converter (DAC) circuitry and the baseband circuitry 604 may include a digital baseband interface to communicate with the RF circuitry 606.

[00043] In some dual-mode embodiments, a separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the embodiments is not limited in this respect. In some embodiments, the synthesizer circuitry 606d may be a fractional-N synthesizer or a fractional N/N+l synthesizer, although the scope of the embodiments is not limited in this respect as other types of frequency synthesizers may be suitable. For example, synthesizer circuitry 606d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider. [00044] The synthesizer circuitry 606d may be configured to synthesize an output frequency for use by the mixer circuitry 606a of the RF circuitry 606 based on a frequency input and a divider control input. In some embodiments, the synthesizer circuitry 606d may be a fractional N/N+l synthesizer.

[00045] In some embodiments, frequency input may be provided by a voltage controlled oscillator (VCO), although that is not a requirement. Divider control input may be provided by either the baseband circuitry 604 or the applications processor 602 depending on the desired output frequency. In some embodiments, a divider control input (e.g., N) may be determined from a lookup table based on a channel indicated by the applications processor 602.

[00046] Synthesizer circuitry 606d of the RF circuitry 606 may include a divider, a delay- locked loop (DLL), a multiplexer and a phase accumulator. In some embodiments, the divider may be a dual modulus divider (DMD) and the phase accumulator may be a digital phase accumulator (DP A). In some embodiments, the DMD may be configured to divide the input signal by either N or N+l (e.g., based on a carry out) to provide a fractional division ratio. In some example embodiments, the DLL may include a set of cascaded, tunable, delay elements, a phase detector, a charge pump and a D-type flip-flop. In these embodiments, the delay elements may be configured to break a VCO period up into Nd equal packets of phase, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle.

[00047] In some embodiments, synthesizer circuitry 606d may be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency may be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with quadrature generator and divider circuitry to generate multiple signals at the carrier frequency with multiple different phases with respect to each other. In some embodiments, the output frequency may be a LO frequency (fLO). In some embodiments, the RF circuitry 606 may include an IQ/polar converter.

[00048] FEM circuitry 608 may include a receive signal path which may include circuitry configured to operate on RF signals received from one or more antennas 610, amplify the received signals and provide the amplified versions of the received signals to the RF circuitry 606 for further processing. FEM circuitry 608 may also include a transmit signal path which may include circuitry configured to amplify signals for transmission provided by the RF circuitry 606 for transmission by one or more of the one or more antennas 610. In various embodiments, the amplification through the transmit or receive signal paths may be done solely in the RF circuitry 606, solely in the FEM 608, or in both the RF circuitry 606 and the FEM 608. [00049] In some embodiments, the FEM circuitry 608 may include a TX/RX switch to switch between transmit mode and receive mode operation. The FEM circuitry may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry may include an LNA to amplify received RF signals and provide the amplified received RF signals as an output (e.g., to the RF circuitry 606). The transmit signal path of the FEM circuitry 608 may include a power amplifier (PA) to amplify input RF signals (e.g., provided by RF circuitry 606), and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 610).

[00050] In some embodiments, the PMC 612 may manage power provided to the baseband circuitry 604. In particular, the PMC 612 may control power-source selection, voltage scaling, battery charging, or DC-to-DC conversion. The PMC 612 may often be included when the device

600 is capable of being powered by a battery, for example, when the device is included in a UE.

The PMC 612 may increase the power conversion efficiency while providing desirable implementation size and heat dissipation characteristics.

[00051 ] While FIG. 6 shows the PMC 612 coupled only with the baseband circuitry 604. In other embodiments, however, the PMC 6 12 may be additionally or alternatively coupled with, and perform similar power management operations for, other components such as, but not limited to, application circuitry 602, RF circuitry 606, or FEM 608.

[00052] In some embodiments, the PMC 612 may control, or otherwise be part of, various power saving mechanisms of the device 600. For example, if the device 600 is in an RRC_Connected state, where it is still connected to the RAN node as it expects to receive traffic shortly, then it may enter a state known as Discontinuous Reception Mode (DRX) after a period of inactivity. During this state, the device 600 may power down for brief intervals of time and thus save power.

[00053] If there is no data traffic activity for an extended period of time, then the device 600 may transition off to an RRC_Idle state, where it disconnects from the network and does not perform operations such as channel quality feedback, handover, etc. The device 600 goes into a very low power state and it performs paging where again it periodically wakes up to listen to the network and then powers down again. The device 600 may not receive data in this state, in order to receive data, it must transition back to RRC_Connected state.

[00054] An additional power saving mode may allow a device to be unavailable to the network for periods longer than a paging interval (ranging from seconds to a few hours). During this time, the device is totally unreachable to the network and may power down completely. Any data sent during this time incurs a large delay and it is assumed the delay is acceptable. [00055] Processors of the application circuitry 602 and processors of the baseband circuitry 604 may be used to execute elements of one or more instances of a protocol stack. For example, processors of the baseband circuitry 604, alone or in combination, may be used execute Layer 3, Layer 2, or Layer 1 functionality, while processors of the application circuitry 604 may utilize data (e.g., packet data) received from these layers and further execute Layer 4 functionality (e.g., transmission communication protocol (TCP) and user datagram protocol (UDP) layers). As referred to herein, Layer 3 may comprise a radio resource control (RRC) layer, described in further detail below. As referred to herein, Layer 2 may comprise a medium access control (MAC) layer, a radio link control (RLC) layer, and a packet data convergence protocol (PDCP) layer, described in further detail below. As referred to herein, Layer 1 may comprise a physical (PHY) layer of a UE/RAN node, described in further detail below.

[00056] FIG. 7 illustrates example interfaces of baseband circuitry in accordance with some embodiments. As discussed above, the baseband circuitry 604 of FIG.6 may comprise processors 604A-604E and a memory 604G utilized by said processors. Each of the processors 604A-604E may include a memory interface, 704A-704E, respectively, to send/receive data to/from the memory 604G.

[00057] The baseband circuitry 604 may further include one or more interfaces to communicatively couple to other circuitries/devices, such as a memory interface 712 (e.g., an interface to send/receive data to/from memory external to the baseband circuitry 604), an application circuitry interface 714 (e.g., an interface to send/receive data to/from the application circuitry 602 of FIG. 6), an RF circuitry interface 716 (e.g., an interface to send/receive data to/from RF circuitry 606 of FIG. 6), a wireless hardware connectivity interface 718 (e.g., an interface to send/receive data to/from Near Field Communication (NFC) components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components), and a power management interface 720 (e.g., an interface to send/receive power or control signals to/from the PMC 612.

[00058] The following are example implementations of the subject matter described herein. It should be noted that any of the examples and the variations thereof described herein may be used in any permutation or combination of any other one or more examples or variations, although the scope of the claimed subject matter is not limited in these respects.

[00059] In example one, an apparatus of a user equipment (UE) comprises one or more baseband processors to apply interference mitigation to cell-specific reference signals (CRS) from an interference cell using a first interference mitigation operation on a first subset of interference CRS antenna ports (APs), and using a second interference mitigation operation on a second subset of the interference CRS APs, wherein the one or more baseband processors are to perform channel estimation using the CRS signals from the interference cell, and a memory to store channel estimation information. Example two may include the subject matter of example one or any of the examples described herein, wherein the interference cell CRS signal positions do not completely overlap with the serving cell signal CRS positions. Example three may include the subject matter of example one or any of the examples described herein, wherein a number of the interference cell CRS APs is four. Example four may include the subject matter of example one or any of the examples described herein, wherein the first interference mitigation operation comprises CRS interference cancellation (CRS-IC) for CRS APs 0-1, and wherein the second interference mitigation operation comprises CRS interference whitening (CRS-WF) for CRS APs 2-3. Example five may include the subject matter of example one or any of the examples described herein, wherein the first interference mitigation operation comprises CRS interference cancellation (CRS-IC) for CRS APs 0-1, and the second interference mitigation operation comprises CRS interference power scaling (CRS-PS) for CRS APs 2-3. Example six may include the subject matter of example one or any of the examples described herein, wherein the first interference mitigation operation comprises CRS interference whitening (CRS-WF) for CRS APs 0-1, and the second interference mitigation operation comprises CRS interference power scaling (CRS-PS) for CRS APs 2-3. Example seven may include the subject matter of example one or any of the examples described herein, wherein the first interference mitigation operation comprises any CRS interference mitigation operation for CRS APs 0-1, and the second interference mitigation operation comprises normal data processing for CRS APs 2-3.

[00060] In example eight, an apparatus of a user equipment (UE) comprises one or more baseband processors to apply receive signal interference and noise covariance matrix estimation using cell-specific reference signals (CRS) from a serving cell which are overlapped with data signals of interference cell, wherein the one or more baseband processors are to perform channel estimation using the CRS signals from the serving cell, and a memory to store channel estimation information. Example nine may include the subject matter of example eight or any of the examples described herein, wherein a number of the serving cell CRS APs is four and a number of the interference cell CRS APs is two. Example ten may include the subject matter of example eight or any of the examples described herein, wherein the interference cell CRS signal positions partially overlap with the serving cell signal CRS positions.

[00061 ] In example eleven, one or more machine-readable media have instructions stored thereon that, if executed by an apparatus of a user equipment (UE), results in applying a first interference mitigation operation to a first subset of cell-specific reference signals (CRS) antenna ports (APs) from an interference cell, applying a second interference mitigation operation to a second subset of the CRS APs from the interference cell, performing channel estimation using CRS signals from the interference cell, and storing channel estimation information. Example twelve may include the subject matter of example eleven or any of the examples described herein, wherein the interference cell CRS signals positions do not completely overlap with the serving cell signal CRS positions. Example thirteen may include the subject matter of example eleven or any of the examples described herein, wherein a number of the interference cell CRS APs is four. Example fourteen may include the subject matter of example eleven or any of the examples described herein, wherein the first interference mitigation operation comprises CRS interference cancellation (CRS-IC) for CRS APs 0-1, and wherein the second interference mitigation operation comprises CRS interference whitening (CRS-WF) for CRS APs 2-3. Example fifteen may include the subject matter of example eleven or any of the examples described herein, wherein the first interference mitigation operation comprises CRS interference cancellation (CRS-IC) for CRS APs 0-1, and the second interference mitigation operation comprises CRS interference power scaling (CRS-PS) for CRS APs 2-3. Example sixteen may include the subject matter of example eleven or any of the examples described herein, wherein the first interference mitigation operation comprises CRS interference whitening (CRS-WF) for CRS APs 0-1, and the second mitigation operation comprises CRS interference power scaling (CRS-PS) for CRS APs 2-3. Example seventeen may include the subject matter of example eleven or any of the examples described herein, wherein the first interference mitigation operation comprises any CRS interference mitigation operation for CRS APs 0-1, and the second interference mitigation operation comprises normal data processing for CRS APs 2-3.

[00062] In example eighteen, one or more machine-readable media have instructions stored thereon that, if executed by an apparatus of a user equipment (UE), results in applying receive signal interference and noise covariance matrix estimation using cell-specific reference signals (CRS) from a serving cell which are overlapped with data signals of interference cell, performing channel estimation using the CRS signals from the serving cell, and storing channel estimation information. Example nineteen may include the subject matter of example eighteen or any of the examples described herein, wherein a number of the serving cell CRS APs is four and a number of the interference cell CRS APs is two. Example may include the subject matter of example eighteen or any of the examples described herein, wherein the interference cell CRS signals positions partially overlap with the serving cell signal CRS positions.

[00063] In example twenty-one, an apparatus of a user equipment (UE) comprises means for applying a first interference mitigation operation to a first subset of cell- specific reference signals (CRS) antenna ports (APs) from an interference cell, means for applying a second interference mitigation operation to a second subset of the CRS APs from the interference cell, means for performing channel estimation using CRS signals from the interference cell, and means for storing channel estimation information. Example twenty-two may include the subject matter of example twenty-one or any of the examples described herein, wherein the interference cell CRS signals positions do not completely overlap with the serving cell signal CRS positions. Example twenty-three may include the subject matter of example twenty-one or any of the examples described herein, wherein a number of the interference cell CRS APs is four. Example twenty- four may include the subject matter of example twenty-one or any of the examples described herein, wherein the first interference mitigation apparatus operation comprises CRS interference cancellation (CRS-IC) for CRS APs 0-1, and wherein the second interference mitigation operation comprises CRS interference whitening (CRS-WF) for CRS APs 2-3. Example twenty-five may include the subject matter of example twenty-one or any of the examples described herein, wherein the first interference mitigation operation comprises CRS interference cancellation (CRS-IC) for CRS APs 0-1, and the second interference mitigation operation comprises CRS interference power scaling (CRS-PS) for CRS APs 2-3. Example twenty-six may include the subject matter of example twenty-one or any of the examples described herein, wherein the first interference mitigation operation comprises CRS interference whitening (CRS-WF) for CRS APs 0-1, and the second mitigation operation comprises CRS interference power scaling (CRS-PS) for CRS APs 2- 3. Example twenty-seven may include the subject matter of example twenty-one or any of the examples described herein, wherein the first interference mitigation operation comprises any CRS interference mitigation operation for CRS APs 0-1, and the second interference mitigation operation comprises normal data processing for CRS APs 2-3.

[00064] In example twenty-eight, an apparatus of a user equipment (UE) comprises means for applying receive signal interference and noise covariance matrix estimation using cell-specific reference signals (CRS) from a serving cell which are overlapped with data signals of interference cell, means for performing channel estimation using the CRS signals from the serving cell, and means for storing channel estimation information. Example twenty-nine may include the subject matter of example twenty-eight or any of the examples described herein, wherein a number of the serving cell CRS antenna ports (APs) is four and a number of the interference cell CRS APs is two. Example thirty may include the subject matter of example twenty-eight or any of the examples described herein, wherein the interference cell CRS signals positions partially overlap with the serving cell signal CRS positions. In example thirty-one, machine-readable storage includes machine -readable instructions, when executed, to realize an apparatus as claimed in any preceding claim.

[00065] In the description herein and/or claims, the terms coupled and/or connected, along with their derivatives, may be used. In particular embodiments, connected may be used to indicate that two or more elements are in direct physical and/or electrical contact with each other. Coupled may mean that two or more elements are in direct physical and/or electrical contact. Coupled, however, may also mean that two or more elements may not be in direct contact with each other, but yet may still cooperate and/or interact with each other. For example, "coupled" may mean that two or more elements do not contact each other but are indirectly joined together via another element or intermediate elements. Finally, the terms "on," "overlying," and "over" may be used in the following description and claims. "On," "overlying," and "over" may be used to indicate that two or more elements are in direct physical contact with each other. It should be noted, however, that "over" may also mean that two or more elements are not in direct contact with each other. For example, "over" may mean that one element is above another element but not contact each other and may have another element or elements in between the two elements. Furthermore, the term "and/or" may mean "and", it may mean "or", it may mean "exclusive-or", it may mean "one", it may mean "some, but not all", it may mean "neither", and/or it may mean "both", although the scope of claimed subject matter is not limited in this respect. In the description herein and/or claims, the terms "comprise" and "include," along with their derivatives, may be used and are intended as synonyms for each other.

[00066] Although the claimed subject matter has been described with a certain degree of particularity, it should be recognized that elements thereof may be altered by persons skilled in the art without departing from the spirit and/or scope of claimed subject matter. It is believed that the subject matter pertaining to CRS interference mitigation framework for scenarios with four and mix of two and four CRS antenna ports and many of its attendant utilities will be understood by the forgoing description, and it will be apparent that various changes may be made in the form, construction and/or arrangement of the components thereof without departing from the scope and/or spirit of the claimed subject matter or without sacrificing all of its material advantages, the form herein before described being merely an explanatory embodiment thereof, and/or further without providing substantial change thereto. It is the intention of the claims to encompass and/or include such changes.