WO2017111809A1

WO2017111809A1 - Enhanced coverage mode for machine type communication (mtc)

Info

Publication number: WO2017111809A1
Application number: PCT/US2015/000361
Authority: WO
Inventors: Gang Xiong; Debdeep CHATTERJEE; Seunghee Han
Original assignee: Intel IP Corporation
Priority date: 2015-12-24
Filing date: 2015-12-24
Publication date: 2017-06-29

Abstract

A technology is provided to perform uplink and downlink transmission operating in an enhanced coverage mode is disclosed. A user equipment (UE) can process an indication, received from an evolved node B (eNB), for using enhanced demodulation reference signals (DMRS) structure of the UE operating in the enhanced coverage mode for MTC. The UE can determine a cyclic shift (CS) and orthogonal cover code (OCC) for the enhanced DMRS by using a mapping rule for a 3-bit cyclic shift in a downlink control information (DCI) format. The UE can transmit enhanced demodulation reference signals (DMRS) with enhanced DMRS symbols in a plurality of K DMRS positions of a subframe for a physical uplink shared channel (PUSCH) transmission, wherein K is a positive integer greater than two.

Description

ENHANCED COVERAGE MODE FOR

MACHINE TYPE COMMUNICATION (MTC)

BACKGROUND

[0001] Wireless mobile communication uses various standards and protocols to transmit data between a node (e.g., a transmission station) and a wireless device (e.g., a mobile device). Some wireless devices communicate using orthogonal frequency-division multiple access (OFDMA) in a downlink (DL) transmission and single carrier frequency division multiple access (SC-FDMA) in an uplink (UL) transmission. 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 standard (e.g., 802.16e, 802.16m), which is commonly known to industry groups as WiMAX

(Worldwide interoperability for Microwave Access), and the IEEE 802.11 standard, which is commonly known to industry groups as WiFi.

[0002] In 3GPP radio access network (RAN) LTE systems, the node can be a combination of Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node Bs (also commonly denoted as evolved Node Bs, enhanced Node Bs, eNodeBs, or eNBs) and Radio Network Controllers (RNCs), which communicates with the wireless device, known as a user equipment (UE). The downlink (DL) transmission can be a

communication from the node (e.g., eNodeB) to the wireless device (e.g., UE), and the uplink (UL) transmission can be a communication from the wireless device to the node.

[0003] In LTE, data can be transmitted from the eNB to the UE via a physical downlink shared channel (PDSCH). A physical uplink control channel (PUCCH) can be used to acknowledge that data was received. Downlink and uplink channels or transmissions can use time-division duplexing (TDD) or frequency-division duplexing (FDD).

[0004] Machine-Type Communications (MTC) is a promising and emerging to enable a ubiquitous computing environment towards the concept of the "internet of Things (IoT). Potential MTC based applications include smart metering, healthcare monitoring, remote security surveillance, intelligent transportation system, etc. These services and applications stimulate the design and development of a new type of MTC device that allows for being seamlessly integrated into current and next generation mobile broadband networks such as LTE and LTE-Advanced.

[0005] Current LTE and LTE-Advanced standards are not designed for MTC or MTC operating environments. For example, it is envisioned that a large number of MTC devices will be deployed for specific services within one cell in the near future. When such a massive number of MTC devices attempt to access and communicate with the network, the large number of devices can overwhelm the network. MTC devices can also typically operate with differences in bandwidth, power usage, and battery life relative to typical UEs such as mobile phones.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Features and advantages of the disclosure will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the disclosure; and, wherein:

[0007] FIG. 1 illustrates an LTE operation zone within a cell having an evolved node B (eNB) with two devices in accordance with an example;

[0008] FIG. 2 illustrates a mapping of a cyclic shift field in an uplink-related downlink control information (DCI) to n^_MRS^, and [1 ^^Λ(0)[ν ^Λ(1)], where np_MRS^ is cyclic shift value which is indicated in the downlink control information (DCI) for uplink grant; [W^A(0)[W^A(1)] is the orthogonal cover code (OCC) and Λ is the layer index in accordance with an example;

[0009] FIGS. 3A-3B depict a set of orthogonal cover codes (OCCs) for each value of demodulation reference signal (DMRS) sequences within a single subframe in accordance with an example;

[0010] FIG. 4 illustrates a demodulation reference signal (DMRS) symbol position with 3 DMRS symbols for a normal cyclic prefix (CP) in accordance with an example;

[0011] FIG. 5A-5C illustrates various mapping rules for cyclic shift and orthogonal cover codes (OCCs) with 3 demodulation reference signal (DMRS) symbol in accordance with an example; [0012] FIG. 6A-6B illustrates various examples of demodulation reference signal (DMRS) symbol positions with 4 DMRS symbols for a normal cyclic prefix (CP) in accordance with an example;

[0013] FIG. 7A-7C illustrates various examples of mapping rules for cyclic shift and orthogonal cover codes (OCCs) with 4 demodulation reference signal (DMRS) symbol in accordance with an example;

[0014] FIG. 8A-8C illustrates various examples of mapping of user equipment (UE)- specific reference signals (RS), antenna ports 7-10 for normal cyclic prefix (CP) in accordance with an example;

[0015] FIG. 9 illustrates a mapping of a user equipment (UE)-specific reference signals (RS), antenna ports 7-10 for normal cyclic prefix (CP) in accordance with an example;

[0016] FIG. 10-1 1 illustrate various examples of mapping additional resource elements (REs) are defined in the same OFDM symbols where a current reference signal (RS) for normal cyclic prefix (CP) is defined in accordance with an example;

[0017] FIG. 12 illustrates a mapping of additional resource elements (REs) are defined in the same OFDM symbols where a current reference signal (RS) for extended cyclic prefix (CP) is defined in accordance with an example;

[0018] FIG. 13 illustrates an orthogonal cover code (OCC) mapping of normal cyclic prefix (CP) in accordance with an example;

[0019] FIG. 14 illustrates an orthogonal cover code (OCC) mapping of extended cyclic prefix (CP) in accordance with an example;

[0020] FIG. 15 illustrates additional resource elements (RE) for an antenna port regarded as a same CDM group for applying OCC in accordance with an example;

[0021] FIG. 16 illustrates an additional example of additional resource elements (RE) for an antenna port regarded as a same CDM group for applying OCC in accordance with an example;

[0022] FIG. 17 illustrates additional resource elements (RE) for an antenna port regarded as an independent CDM group for applying OCC in accordance with an example;

[0023] FIG. 18 depicts functionality of a user equipment (UE) operable to perform uplink transmission operating in an enhanced coverage mode for machine type communication (MTC) in accordance with an example;

[0024] FIG. 19 depicts an additional example of functionality of a user equipment (UE) operable to perform downlink reception operating in an enhanced coverage mode for machine type communication (MTC) in accordance with an example;

[0025] FIG. 20 depicts an additional example of functionality of a user equipment (UE) operable to perform downlink reception operating in an enhanced coverage mode for machine type communication (MTC) in accordance with an example;

[0026] FIG. 21 illustrates a diagram of a wireless device (e.g., UE) in accordance with an example;

[0027] FIG. 22 illustrates a diagram of a node (e.g., eNB) and wireless device (e.g., UE) in accordance with an example; and

[0028] FIG. 23 illustrates a diagram of example components of a User Equipment (UE) device in accordance with an example.

[0029] Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the technology is thereby intended.

DETAILED DESCRIPTION

[0030] Before the present technology is disclosed and described, it is to be understood that this technology is not limited to the particular structures, process steps, or materials disclosed herein, but is extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular examples only and is not intended to be limiting. The same reference numerals in different drawings represent the same element. Numbers provided in flow charts and processes are provided for clarity in illustrating steps and operations and do not necessarily indicate a particular order or sequence. EXAMPLE EMBODIMENTS

[0031] An initial overview of embodiments is provided below and then specific embodiments are described in further detail later. This initial summary is intended to aid readers in understanding the more quickly but is not intended to identify key features or essential features of the nor is it intended to limit the scope of the claimed subject matter.

[0032] In one aspect, a Machine-Type Communication (MTC) enables ubiquitous computing environments towards the concept of the "Internet of Things (IoT)", such as MTC based applications including smart metering, healthcare monitoring, remote security surveillance, intelligent transportation system, and the like. In one aspect, IoT services and applications can be integrated into mobile broadband networks such as in third generation partnership project (3GPP) long term evolution (LTE) and LTE-Advanced, in order to the lower device cost, enhanced coverage and reduced power consumption by reducing transmission bandwidth for MTC system to 1.4MHz as the minimum bandwidth for LTE system. In this case, the transmission bandwidth for both control and data channels can be reduced to 1.4MHz.

[0033] However, when a large number of MTC devices are deployed for specific services within one cell and attempt to access and communicate with a network, a single MTC region with 1.4MHz bandwidth may not be sufficient. Thus, multiple MTC regions with 1. 4 MHz can be allocated by an Evolved Universal Terrestrial Radio Access Network (E- UTRAN) Node Bs (also commonly denoted as evolved Node Bs, enhanced Node Bs, eNodeBs, or eNBs).

[0034] In addition, for example, some MTC devices can be installed in basements of residential buildings and these devices can experience significantly greater penetration losses on a radio interface.

[0035] In order to provide sufficient network coverage of such MTC devices, special coverage enhancement considerations can be used for various physical channels.

Moreover, the MTCs devices can be used to improve the coverage (e.g. up to 15dB for frequency-division duplexing "FDD"). Increasing resource signal (RS) density can be used to improve the coverage (performance) by improving the channel estimation performance provided that the channel estimation performance would be a bottleneck to determine the overall performance in low SNR region, which is a target scenario in MTC. [0036] As such, in one aspect, channel estimation for uplink transmission can be improved by increasing a number of DeModulation Reference Symbols (DMRS). As a result, uplink coverage can be improved and repetition level for physical uplink shared channel (PUSCH) transmission may be reduced accordingly. It should be noted that in the case of low signal to noise ratio (SNR) or noise-limited scenarios, channel estimation can a bottleneck in term of decoding performance.

[0037] In one aspect, enhanced physical downlink control channel (EPDCCH) or a UE- specific resource signal (RS) based Transmission Mode (e.g. TM9) of physical downlink shared channel (PDSCH) can be used for MTC. The patterns for EPDCCH DMRS and PDSCH UE specific RS can be the same except for the different antenna ports and the RS density can be for EPDCCH and or UE specific RS based TM.

[0038] In one aspect, the present technology provides an uplink DMRS design for MTC user equipment (UEs) in enhanced coverage mode. In one aspect, the present technology provides for demodulation reference signals (DMRS) positions for physical uplink shared channel (PUSCH) transmission for MTC UEs operating in enhanced coverage mode. A mapping rule of a 3-bit cyclic shift field in downlink control information (DCI) format to cyclic shift and orthogonal cover code (OCC) for DM-RS generation is provided. Group hopping and cyclic shift (CS) hopping for PUSCH DM-RS with 3 or 4 symbols are also provided. In one aspect, an indication can be provided to use the enhanced DMRS structure for MTC UEs in enhanced coverage mode.

[0039] In one aspect, a technology is described to perform uplink transmission operating in an enhanced coverage mode is disclosed. In one aspect, a user equipment (UE) can receive, from an evolved node B (eNB), an indication for using an enhanced

demodulation reference signals (DMRS) structure of the UE operating in the enhanced coverage mode for MTC. The UE can determine a cyclic shift (CS) and orthogonal cover code (OCC) for the enhanced DMRS by using a mapping rule for a 3-bit cyclic shift in a downlink control information (DCI) format. The UE can transmit enhanced demodulation reference signals (DMRS) with K DMRS symbols in a plurality of DMRS positions of a subframe for a physical uplink shared channel (PUSCH) transmission, wherein is a positive integer greater than two.

[0040] It should be noted that in one aspect, enhanced DMRS can be defined according to a comparison of an existing DMRS for both downlink and uplink. For example, for downlink, a total number of resource elements (Res) allocated for DMRS is 24 (for all antenna ports). For uplink, the total number of symbols allocated for DMRS is 2 symbols. For enhanced DMRS in the downlink, the total number of DMRS can be greater than 24 for all APs. For enhanced DMRS in the uplink, the total number of symbols can be greater than 2. For example, in 3GPP LTE Rel. 12, the same 12 REs can be allocated for AP 7, 8, 11 , and 13 and the same 12 REs can be allocated for AP 9, 10, 12, and 14 for PDSCH DM-RS. However, when AP 7 is used, for instance, the RE positions on AP 9 are unused to allow FDM multiplexing of DM-RS on AP 7 and 9. Accordingly, the total number of RE used for DM-RS is 24 in the PDSCH in 3GPP Rel. 12. For PUSCH, a total of 2 symbols are used for DM-RS in 3 GPP LTE Rel. 12. An enhanced DM-RS can include more than 24 RE for PDSCH DM-RS and more than 2 symbols for PUSCH DMRS.

[0041] In yet another aspect, a technology is described to perform downlink transmission operating in an enhanced coverage mode. A user equipment (UE) can process an indication, received from an evolved node B (eNB), for using a enhanced demodulation reference signals (DMRS) structure of the UE operating in the enhanced coverage mode for MTC. The UE can receive a first reference signal (RS) for a first antenna port (AP) and a second RS for a second AP. The UE can perform channel estimation from the first AP and the second AP by assuming the first AP and the second AP are a same AP.

[0042] In yet another aspect, a technology is described to perform downlink transmission operating in an enhanced coverage mode is disclosed. A user equipment (UE) can receive a first reference signal (RS) for a first antenna port (AP) on a resource element (RE) placed in an Orthogonal Frequency Division Multiplexing (OFDM) symbol for a second RS for a second AP. The UE can process a first reference signal (RS) for a first antenna port (AP) on a resource element (RE) placed in an Orthogonal Frequency Division Multiplexing (OFDM) symbol that is different than an alternative OFDM symbol of a second RS for a second AP.

[0043] In one aspect, more than one antenna ports can be used for a RS, and the antenna ports can be assumed to be the same antenna port. In one aspect, additional resource elements (REs) can be defined in the same OFDM symbols where a current RS is defined. The additional REs can be defined in different OFDM symbols where a current RS is defined.

[0044] FIG. 1 illustrates an LTE operation zone within a cell 100 having an evolved node B (eNB) with two devices. FIG. 1 illustrates an eNB 104 that can be associated with an anchor cell, macro cell or primary cell. Also, the cell 100 can include User equipment (UE or UEs) 108, 1 10 that are in communication with the eNB 104.

[0045] The eNB 104 can be a high transmission power eNB, such as a macro eNB, for coverage and connectivity. The eNB 104 can be responsible for mobility and can also be responsible for radio resource control (RRC) signaling. User equipment (UE or UEs) 108, 1 10 can be supported by the macro eNB 104.

[0046] As shown in FIG. 1 , the UEl 108 can be located relatively close to the eNB 104 whereas the UE2 1 10 is positioned close to the cell edge. When the eNB 104 has knowledge about preferred CP lengths for both UEs 108, 1 10, it can be possible that the eNB 104 decides to employ a shorter CP for the data packet targeted for the UEl 108, and a longer CP for the data packet of the UE2 110.

[0047] FIG. 2 illustrates a mapping of a cyclic shift field in an uplink-related downlink control information (DCI) to η_{βΜΚδ λ}, and [W (0) W^x(l)], where n _{MRS X} is cyclic shift value which is indicated in the downlink control information (DCI) for uplink grant; [W^A(0)[W^A(1)] is the orthogonal cover code (OCC) and Λ is the layer index. In one aspect, Demodulation Reference Signals (DMRS) associated with transmission of physical uplink shared channel (PUSCH) can be derived from Zadoff-Chu sequences. These sequences may then be cyclically shifted and used to multiplex reference signals (RS) from different UEs within a cell. In addition, multiple mutually orthogonal reference signals can be generated by employing different cyclic shifts of ZC sequence and applying orthogonal cover code (OCC) to the two reference-signal transmissions within a subframe, such as using length-2 orthogonal cover code [1, 1] and [1,—1]. The cyclic shift for DMRS generation can be derived from a combination of a 3-bit cell specific broadcast cyclic time shift offset parameter, a 3-bit cyclic time shift offset indicated in each uplink scheduling grant and a pseudo-random cyclic shift offset obtained from the output of the length-31 Gold sequence generator. The 3-bit indication in the DCI format can also be used to derive the OCC for DM-RS generation. As illustrated in FIG. 2, a mapping of 3-bit cyclic shift field in DCI format to cyclic shift and OCC for DM-RS generation is illustrated. That is, FIG. 2 illustrates a mapping of a cyclic shift field in an uplink-related downlink control information (DCI) to ηρ_{ΜΚ5 λ}, and [W^x(0) W^x(l)]. λ can denote a layer, ηρ_{ΜΚ5 λ} can denote a cyclic shift (CS) in accordance with layers, and [W^x(0) W^x(l)] can denote a Walsh code value in accordance with layers.

[0048] That is, FIG. 2 illustrates mapping of three bits in the downlink control information (DCI) to cyclic shifts while maintaining a mapping of the three bits to DMRS. For example, if four cyclic shifts are selected, such as {0, 3, 6, 9} from the mapping table in FIG. 2, then values 000 maps to 0, 001 maps to 6, 010 maps to 3, and 1 1 1 maps to 9.

[0049] It should be noted that a demodulation reference signal (DMRS) can be transmitted in the uplink. The cyclic shift sequence (CS sequence), which is an orthogonal sequence and a Walsh sequence (orthogonal cover code, OCC) can be used as the demodulation reference signal. A cyclic shift value can be represented by "cyclic shift (CS) number "0 to 11 "." In this way, orthogonality among cyclic shift sequences can be secured.

[0050] An orthogonal sequence w^)(m) in FIG. 2 can use a cyclic shift field in the latest UL-related DCI for a transport block associated with corresponding PUSCH

transmission. A cyclic shift α_λ in a slot n_s can be given as

In this case, n_{cs A} = (n¾,_RS + n _j¾_{RS X} + n_PN(n_s))modl2 and n_PN(n_s) can be given using a pseudo-random sequence c(i) and c(i) can be cell-specific and a pseudo-random sequence generator initialized to a specific initial value (may be cell-specific) at the start of each radio frame. The nj¾,_{RS X} can be given according to a parameter cyclic shift provided by higher layers, and η_β¾_{Κ5 λ} can be given by the cyclic shift for a enhanced DMRS field in a most recent uplink-related DCI for a transport block associated with a corresponding PUSCH transmission where no_{MRS X}can be given in FIG. 2.

[0051] FIG. 3 A is a table depicting a set of orthogonal cover codes (OCCs) when the number (K) of DMRS sequences (or symbols) within a D2D discovery resource of a single subframe is three (i.e., K=3). The set of OCCs can be used for D2D discovery at the UE and UE operable to perform uplink transmission operating in an enhanced coverage mode for machine type communication (MTC). The orthogonal sequences can be based on a length-3 DFT code. The orthogonal sequences can be represented as [w(o) ... W(2)] when K=3. Each orthogonal sequence can be associated with a particular sequence index n_oc. For example, when the sequence index is 0, the orthogonal sequence is [1 1 1 ]. When the sequence index is 1 , the orthogonal sequence is 1 ε'^2π/³ e'^4ir/³. When the sequence index is 2, the orthogonal sequence is 1 e'^{4lT 3} e>^2lt/³. Therefore, an appropriate orthogonal sequence can be applied to the DMRS sequence when K=3.

[0052] FIG. 3B is a table depicting a set of orthogonal cover codes (OCCs) when the number ( ) of DMRS sequences (or symbols) within a D2D discovery resource of a single subframe is four (i.e., =4). The set of OCCs can be used for D2D discovery at the UE and UE operable to perform uplink transmission operating in an enhanced coverage mode for machine type communication (MTC).. The orthogonal sequences can be based on a length-4 Walsh-Hadamard code. The orthogonal sequences can be represented as [w(o) ... W(3)] when =4. Each orthogonal sequence can be associated with a particular sequence index n_oc. For example, when the sequence index is 0, the orthogonal sequence is [+1 +1 +1 +1]. When the sequence index is 1 , the orthogonal sequence is [+1 -1 +1 -1]. When the sequence index is 2, the orthogonal sequence is [+1 +1 -1 -1 ]. When the sequence index is 3, the orthogonal sequence is [+1 -1 -1 +1 ]. Therefore, an appropriate orthogonal sequence can be applied to the DMRS sequence when =4.

[0053] FIG. 4 illustrates a demodulation reference signal (DMRS) symbol position with 3 DMRS symbols for a normal cyclic prefix (CP) in accordance with an example. That is, FIG.4 illustrates examples of enhanced DMRS positions with 3 DM-RS symbols for normal CR In FIG. 4, additional DMRS symbol can be inserted in the last symbol of the 1 st slot (option a) or the first symbol of the 2nd slot (option b). It should be noted that different positions of this additional DM-RS symbol can be defined in the new PUSCH DM-RS symbol and for extended CP case.

[0054] With the additional DMRS symbol(s), the mapping of 3-bit cyclic shift field in DCI format to cyclic shift and OCC for DMRS generation can be updated, as illustrated in FIGS. 5A-5C. In order to minimize the specification impact and implementation cost, the cyclic shift values remain unchanged for the corresponding 3-bit cyclic shift field in DCI format. [0055] FIGS. 5A-5C illustrates various mapping rules for cyclic shift and orthogonal cover codes (OCCs) with 3 demodulation reference signal (DMRS) symbol in accordance with an example.

[0056] In one aspect, the OCC applied for the additional DMRS symbol (e.g., 3 DMRS symbols) can be the same as the one for the existing DMRS symbol within the same slot. For instance, when the additional DMRS symbol (e.g., K = 3) is inserted in the last symbol of 1 st slot, the OCC on this the additional DMRS symbol (e.g., K = 3) can be the same as the one for the 1 st DMRS symbol. Thus, according to the enhanced DMRS structure, the mapping rule can be updated as in FIG. 5A. It should be noted that only 1 layer may be used for MTC UEs with reduced bandwidth, i.e., λ = 0.

[0057] In one aspect, λ can denote a layer, n_{pMRS λ} can denote a cyclic shift (CS) in accordance with layers, and [W^x(0) W^x(l) W (2)] can denote a orthogonal cover code value in accordance with layers. For example, when the transmitted _p^_RS^ cyclic shift value of 0, 4, 2 or 6 corresponds to the 3 bit cyclic shift field in uplink-related DCI format of 000, 011 , 100, and 111, respectively, the orthogonal cover codes (e.g.,

[W^A(0) W^x(l) W^x(2)] can denote [+1 +1 +1]. When the transmitted n^_{Rs i} cyclic shift value of 6, 3, 8 or 10, corresponds to the 3 bit cyclic shift field in uplink-related DCI format of 001 , 010, 101 , 110, respectively, the orthogonal cover codes (e.g.,

[W^x(0) W^x(l) W^x(2)] can denote [+1+1-1].

[0058] As noted in FIG. 5B, a length-3 DFT code can be applied for the OCC on 3

DMRS symbol structure. FIG. 5B illustrates the example of applying length-3 DFT code for the mapping rule of cyclic shift and OCC. It should be noted that the 3-bit cyclic shift field in DCI format can be easily extended to map with other OCC using different entries of length-3 DFT code in FIG. 5B. As illustrated in FIG. 5B, when the transmitted n ,¾_{RS λ} cyclic shift value of 0, 4, 2 or 6 corresponds to the 3 bit cyclic shift field in uplink-related DCI format of 000, 011 , 100, and 1 11 , respectively, the orthogonal cover codes (e.g., [W^x(0) W^x(l) W^x(2)]) can denote [+1+1+1]. When the transmitted ⁿDMRS x ^cvc'i^{c sn}'ft value of 6 and 8, corresponds to the 3 bit cyclic shift field in uplink- related DCI format of 001 and 101 respectively, the orthogonal cover codes (e.g.,

[W^A(0) W^x(l) W^A(2)] can denote 1 e'²^³ e' ^lt/3. When the transmitted n¾_{RS X} cyclic shift value of 3 and 10, corresponds to the 3 bit cyclic shift field in uplink-related DCI format of 010 and 110 respectively, the orthogonal cover codes (e.g.,

[W^A(0) W^x(l) W^x(2)] can denote 1 e'⁴*/³ e^j27l/3.

[0059] As noted in FIG. 5C, a length-3 DFT code can be applied for the OCC on 3 DMRS symbol structure. FIG. 5B illustrates the example of applying length-3 DFT code for the mapping rule of cyclic shift and OCC. It should be noted that the 3-bit cyclic shift field in DCI format can be easily extended to map with other OCC using different entries of length-3 DFT code in FIG. 5B. As illustrated in FIG. 5B, when the transmitted ⁿDMRS x ^cy^{cnc sn}'ft value of 0, 6, 3, and 6 corresponds to the 3 bit cyclic shift field in uplink-related DCI format of 000, 001 , 010 and 111 , respectively, the orthogonal cover codes (e.g., [W^A(0) W^x(l) W^x(2)]) can denote [+1 +1+1 ]. When the transmitted ⁿDMRS x ^cvc''^{c sn}'ft value of 4 and 10, corresponds to the 3 bit cyclic shift field in uplink- related DCI format of 011 and 110 respectively, the orthogonal cover codes (e.g.,

[W^A(0) W^A(1) W^x(2)] can denote 1 e'^4lt/³ e ³. When the transmitted n£¾_{RS X} cyclic shift value of 2 and 8, corresponds to the 3 bit cyclic shift field in uplink-related DCI format of 100 and 101 respectively, the orthogonal cover codes (e.g.,

[W^A(0) W^x(l) W^A(2)] can denote 1 e'^2Tt/³ e>⁴⁷¹/³.

[0060] FIG. 6A-6B illustrates various examples of demodulation reference signal (DMRS) symbol positions with 4 DMRS symbols for a normal cyclic prefix (CP) in accordance with an example. That is, FIG.6A-6B illustrates examples of enhanced DMRS positions with 4 DM-RS symbols for normal CP.

[0061] In FIG. 6A, additional DMRS symbols (e.g., 4 DMRS symbols) can be inserted in the last symbol of the each slot (option a) or the first symbol of the each slot (option b). It should be noted that different positions of this additional DMRS symbols in the PUSCH K=4 DMRS symbol structure can be defined.

[0062] In an additional aspect, FIG. 6B illustrates additional examples of demodulation reference signal (DMRS) symbol positions with 4 DMRS symbols for a normal cyclic prefix (CP). In FIG. 6B, option (a) depicts =4 DMRS symbols can be inserted in OFDM symbol #1 and #5 for each slot; while in the option (b), =4 DMRS symbols can be inserted in OFDM symbol #2 and #4 for each slot. It should be noted that different positions of K=4 DMRS symbols in the PUSCH =4 DMRS symbol structure for extended CP case can be used.

[0063] FIG. 7A-7C illustrates various examples of mapping rules for cyclic shift and orthogonal cover codes (OCCs) with 4 demodulation reference signal (DMRS) symbol in accordance with an example. In one aspect, λ can denote a layer, ^ηρ_{Μβ5 λ} can denote a cyclic shift (CS) in accordance with layers, and [W^A(0) W^A(1) W^A(2) W^A(3)] can denote a orthogonal cover code value in accordance with layers.

[0064] As illustrated in FIG. 7A, a length-4 DFT code can be applied for the OCC on 4 DMRS symbol structure. For example, when the transmitted nj¾,_{RS X} cyclic shift value of 0, 4, 2 or 6 corresponds to the 3-bit cyclic shift field in uplink-related DCl format of 000, 01 1, 100, and 111 , respectively, the orthogonal cover codes (e.g., [W^A(0) W^A(1) W^A(2) W^A(3)]) can denote [+1+1+1+1]. When the transmitted n_p¾_RS^ cyclic shift value of 6, 3, 8 or 10, corresponds to the 3-bit cyclic shift field in uplink-related DCl format of 001 , 010, 101 , 110, respectively, the orthogonal cover codes (e.g., [W^A(0) W^A(1) W^A(2) W^A(3)]) can denote [+1+1 -1-1 ].

[0065] As noted in FIG. 7B, a length-4 DFT code can be applied for the OCC on 4 DMRS symbol structure. FIG. 7B illustrates the example of applying length-4 DFT code for the mapping rule of cyclic shift and OCC. It should be noted that the 4-bit cyclic shift field in DCl format can be easily extended to map with other OCC using different entries of length-4 DFT code in FIG. 7B.

[0066] As illustrated in FIG. 7B, when the transmitted η_ρ^_{Κ5 λ} cyclic shift value of 0 or 2 corresponds to the 3 bit cyclic shift field in uplink- related DCl format of 000 or 100, respectively, the orthogonal cover codes ((e.g., [W^A(0) W^A(1) W^A(2) W^A(3)]) can denote [+1+1+1 ]. When the transmitted n_p¾_{RS X} cyclic shift value of 6 and 8, corresponds to the 4 bit cyclic shift field in uplink-related DCl format of 001 and 101 respectively, the orthogonal cover codes ( ((e.g., [W^A(0) W^A(1) W^A(2) W^A(3)]) can denote [+1 -1 +1 -1 ]. When the transmitted η[,¾_{Κ5 λ} cyclic shift value of 3 and 10, corresponds to the 3 bit cyclic shift field in uplink-related DCl format of 010 and 1 10 respectively, the orthogonal cover codes (e.g., [W^A(0) W (1) W (2) W^A(3)]) can denote [+1+1 -1 -1]. [0067] When the transmitted η ¾_Κ5Λ cyclic shift value of 4 and 9, corresponds to the 3 bit cyclic shift field in uplink-related DCI format of 011 and 111 respectively, the orthogonal cover codes orthogonal cover codes (e.g., [W^x(0) W^x(l) W^x(2) W^x(3)]) can denote [+1 -1 -1+1]. [0068] As illustrated in FIG. 7C, when the transmitted η^,,^ cyclic shift value of 0 or 6 corresponds to the 3 bit cyclic shift field in uplink-related DCI format of 000 or 001, respectively, the orthogonal cover codes (e.g., [W^x(0) W^x(l) W^x(2) W^x(3)]) can denote [+1+1+1 ]. When the transmitted n_p^,_RS^ cyclic shift value of 3 and 6, corresponds to the 3 bit cyclic shift field in uplink-related DCI format of 010 and 1 1 1 respectively, the orthogonal cover codes ( ((e.g., [W^x(0) W^x(l) W^x(2) W^x(3)]) can denote [+1 -1+1-1 ].

(2)

When the transmitted nj^_RS^ cyclic shift value of 4 and 10, corresponds to the 3 bit cyclic shift field in uplink-related DCI format of 011 and 110 respectively, the orthogonal cover codes (e.g., [W^x(0) W^x(l) W^x(2) W^x(3)]) can denote [+1+1 -1-1].

(2)

[0069] When the transmitted n_p^,_RS^ cyclic shift value of 2 and 8, corresponds to the 3 bit cyclic shift field in uplink-related DCI format of 100 and 101 respectively, the orthogonal cover codes orthogonal cover codes (e.g., [W (0) W^x(l) W^x(2) W^x(3)]) can denote [+1-1 -1+1].

[0070] It should be noted that = DMRS symbols can be greater than 4. For example can be a positive integer that is great than or equal to 3. Moreover, in one aspect, can be a positive integer that is great than or equal to 4. In one example, similar to the DMRS positions as defined in 3GPP LTE Release 8 for PUCCH la lb transmission, OFDM symbol #3, #4 and #5 of each slot can be allocated for enhanced DMRS symbols of a PUSCH transmission. In one aspect, the number of enhanced DMRS symbols can be increased to 6.

[0071] In one aspect, group hopping and cyclic shift (CS) hopping may be used for a PUSCH enhanced DMRS structure. In one aspect, a sequence group may be determined based on cell identification information, such as cell identification (ID), and higher layer signaling for each slot. Thus, when more than one PUSCH enhanced DMRS symbol structure are present within a slot, a group-hopping mechanism can be extended to be slot- RS symbol-based and DM-RS symbol-based to maximize benefits of inter-cell interference randomization. Accordingly, in one aspect, a sequence group number u in slot n_smay be defined by a group hopping pattern f_gh(n_s) and a sequence shift pattern f_ssaccording to a formula expressible as:

u = (fgh(n_s)+ f_ss)mod 30 (1 ).

[0072] Where n_s denotes a slot; the group hopping pattern f_gh (n_s, q) can be appropriately defined depending on a number of the DMRS symbols in a slot. Moreover, regarding the hopping of cyclic shift (CS) within the PUSCH transmission, a cyclic shift α_λ in a slot n_s can be given as α_λ= 2nn_csA/12. In this case, n_cs = (n^^ + n{¾,_{RS X} + n_PN(n_s))modl2 and n_PN (n_s) can be given using a pseudo-random sequence c(i); where ⁿPN(ⁿs) denotes a cell specific cyclic shift value. c(i) can be cell-specific and a pseudorandom sequence generator initialized to a specific initial value (may be cell-specific) at the start of each radio frame. The ηρ^_{|Κ5 λ} can be given according to a parameter cyclic sift provided by higher layers, and np^_RS^ can be given by the cyclic shift for an enhanced DMRS field in a most recent uplink-related DCI for a transport block associated with a corresponding PUSCH transmission where nj_)MRS^can be given in FIG. 2.

[0073] Thus, similar to the extension of group hopping, CS hopping (CSH) can be extended as well considering multiple DM-RS symbols within a slot (e.g., a cyclic shift hopping was defined as a function of subframe index and now the cyclic shift hopping is defined as a function of a slot index . Accordingly, in one aspect, the quantity n_PN (n_s) can be re-defined as a function of slot-number within the radio frame and the enhanced DMRS symbol index q within a slot as n_PN (n_s, q) wheren_PN(n_s, q) can be appropriately defined depending on number of enhanced DMRS symbols in a slot.

[0074] In one aspect, a signal indication or "indicator" may be provided to use the enhanced DMRS symbol structure. For example, the eNB can signal an indication of to use the enhanced DMRS structure for MTC UEs operating in enhanced coverage mode.

[0075] In one aspect, when transmitting the PUSCH, MTC UEs operating in enhanced coverage mode can always use the enhanced DMRS symbol structure. This indicates that eNB can assume the enhanced DMRS symbol structure for channel estimation for MTC UEs in enhanced coverage mode.

[0076] In one aspect, when transmitting the PUSCH, MTC UEs operating in enhanced coverage mode can use the enhanced DMRS symbol structure for PUSCH transmission only when the coverage extension level exceeds a certain level (e.g., XdB, where X can be a predefined or can be configured by a higher layer eNB via either system information block (SIB) or UE-specific dedicated RRC signalling. In one example, X can equal l OdB. For MTC UEs with coverage extension level less than XdB, they will use the existing DM-RS structure for PUSCH transmission.

[0077] In an additional aspect, an indication of the use of the enhanced DMRS symbol structure can be signalled by an eNB via UE specific dedicated RRC signalling. In yet an additional aspect, an eNB can indicate the use of the enhanced DMRS symbol structure in an uplink related DCI format. In one example, 1 bit for the indication of the enhanced DMRS symbol structure can be explicitly signalled in DCI format 0 for an uplink grant. Zero padding can be performed to ensure equal payload size as the DCI format 1 A.

[0078] In another aspect, because some of the modulation and coding schemes (MCSs), such as MCS for Quadrature Amplitude Modulation (64QAM modulation), may not be used for MTC UEs in enhanced coverage mode, an eNB can signal the indication of 64QAM modulation using any unused MCSs. For example, 14 < I' CS— 28 in an uplink grant can indicate that MTC UEs in enhanced coverage mode will use this new DM-RS structure for PUSCH transmission and I_MCS = I'_MCs^— 14, where I_MCS and I'_MCs are the MCS index.

[0079] In another aspect, because MTC UEs in enhanced coverage mode can employ a maximum transmit power for uplink transmission, a transmit power control (TPC) command for scheduled PUSCH transmission in DCI format 0 may not be necessary. As such, an eNB can signal the indication of enhanced DMRS symbol structure in 1 of 2-bit TPC commands. Alternatively, the eNB can use only 1 -bit TPC command for transmit power control of the scheduled PUSCH and the other 1 bit can be used for the indication of the enhanced DMRS symbol structure.

[0080] FIGS. 8A-8C illustrates various examples of mapping of user equipment (UE)- specific reference signals (RS), antenna ports 7- 10 for normal cyclic prefix (CP) in accordance with an example. That is, FIGS. 8A-8C illustrate the resource elements used for UE-specific reference signals for normal cyclic prefix for antenna ports (AP) 7, 8, 9 and 10. In one aspect, FIG. 8A-8C illustrate the UE specific reference signals (RS) and the RS patterns can be used for EPDCCH DMRS. Replacing antenna port numbers 7 - 10 by 107 - 1 10 provides an illustration of the resource elements used for demodulation reference signals associated with EPDCCH for normal cyclic prefix.

[0081] FIG. 9 illustrates a mapping of a user equipment (UE)-specific reference signals (RS), antenna ports 7-10 for normal cyclic prefix (CP) in accordance with an example. FIG. 9 depicts the resource elements used for UE-specific reference signals for extended cyclic prefix for antenna ports 7, 8. Replacing antenna port numbers 7 - 8 by AP 107 - 108 provides an illustration of the resource elements used for demodulation reference signals associated with EPDCCH for extended cyclic prefix.

[0082] In one aspect, either AP 107 or 108 can be used for EPDCCH transmission. It is proposed to use more than one AP for EPDCCH to improve the channel estimation performance (in this example for MTC application). In one aspect, the design of FIG. 9 can also apply for PDSCH with APs 7-14. In one aspect, multiple antenna ports can be used as the same AP. Thus, a UE can perform the channel estimation from a first AP and a second AP by assuming the first AP and the second AP are regarded as the same AP.

[0083] For example, multiple AP assignments of EPDCCH for one or multiple UEs can be one of any combinations of APs. For instance, in a scenario when the number of multiple APs is 2, the following combinations of APs can include: { 107, 108}, {107, 108}, { 107, 109}, { 107, 110}, { 107, 1 11 }, { 107, 112}, { 107, 113 }, { 107, 114}, { 108, 109}, { 108, 1 10}, { 108, 111 }, { 108, 1 12}, { 108, 1 13}, { 108, 114}, ... , or { 113, 114}.

[0084] Moreover, multiple AP assignments can further be optimized by assigning the multiple APs from different CDM groups and avoiding unnecessary dispreading to distinguish the AP, and providing more efficient sampling in frequency domain, which can provide increased channel estimation performance particularly in frequency selective channel. In one aspect, current CDM groups can be:

1 ) CDM group 1 : AP 107, 108, 1 1 1 , 1 13

2) CDM group 2: AP 109, 1 10, 1 12, 1 14

[0085] Thus, for instance, when a number of multiple APs is 2, the multiple APs for an EPDCCH can be { 107, 109}, { 108, 1 10}, { 111 , 112}, { 1 13, 114}, { 107, 1 10}, { 108, 109}, etc. By the CDM group 1 and COM group 2 multiple AP assignment for an EPDCCH, the channel property/QCL assumptions can be described as, for example if the multiple APs are { 107, 109}, DMRS associated with an EPDCCH can be transmitted on AP 107 and 109. The channel over which a symbol on the AP 107 is conveyed can be inferred from the channel over which the symbol on the AP 109 is conveyed.

[0086] In one aspect, for a certain mode of EPDCCH transmission (e.g. distributed EPDCCH), an eNB can apply per-RE based precoder cycling for the two APs 107 and 109. For more efficient channel estimation, if enhanced DMRS structure is used for distributed EPDCCH, per-RE based precoder cycling should not be applied by the eNB and instead a common precoding can be applied to REs corresponding to both APs 107 and 109.That is, pre-RE based precoder cycling can mean that different REs can be applied with a different precoder. In contrast, common precoding can mean that different REs will be applied with same precoder. It should be noted that in one aspect, enhanced DMRS can be defined according to a comparison of an existing DMRS for both downlink and uplink. For example, for downlink, a total number of resource elements (Res) allocated for DMRS is 24 (for all antenna ports). For uplink, the total number of symbols allocated for DMRS is 2 symbols. For enhanced DMRS in the downlink, the total number of DMRS can be greater than 24 for all APs. For enhanced DMRS in the uplink, the total number of symbols can be greater than 2.

[0087] In one aspect, additional resource elements (REs) for RS can be defined in the same OFDM symbols where a current RS is defined. Also, additional REs to a previously defined RS pattern can be placed in the same OFDM symbols where a current RS is defined. For instance, as illustrated in FIG. 10 where AP 107/109 can be defined in k=l , 6, 11 for API 07, and k=0, 5, 10 for API 09. The OFDM symbol can be defined as 1=5, 6 in each slot. The additional REs can be defined in 1=5, 6 in each slot.

[0088] Turning now to FIG. 10-12, various examples are illustrated of mapping additional resource elements (REs) are defined in the same OFDM symbols where a current reference signal (RS) for normal cyclic prefix (CP) is defined.

[0089] FIG. 10 depicts an example of mapping additional resource elements (REs) are defined in the same OFDM symbols where a current reference signal (RS) for normal cyclic prefix (CP) (other than special subframe configuration 1, 2, 6, 7, 3, 4, 8, and 9). In one embodiment, FIG. 10 illustrates k=4, 9 for AP107 and at k=3, 8 for AP109. Any potential collision with the existing RS (e.g. cell-specific reference signals "CRS", channel state information reference signal "CSI-RS", etc.) can be avoided.

[0090] FIG. 11 depicts an example of mapping additional resource elements (REs) which are defined in the same OFDM symbols where a current reference signal (RS) for normal cyclic prefix (CP) (other than special subframe configuration 1, 2, 6, 7, 3, 4, 8, and 9). FIG. 11 prioritizes AP 107 and 109, which are used for distributed EPDCCH transmission while filling all REs in the OFDM symbols carrying an original DM RS.

[0091] FIG. 12 depicts an example of mapping additional resource elements (REs) which are defined in the same OFDM symbols where a current reference signal (RS) for extended cyclic prefix (CP) (other than special subframe configuration 1, 2, 3, 5, and 6).

[0092] In yet an additional example, Orthogonal Code Cover (OCC) mapping can be provided considering peak power randomization. In one aspect, OCC mapping is illustrated in FIG. 13. FIG. 13 illustrates an orthogonal cover code (OCC) mapping of normal cyclic prefix (CP) in accordance with an example. FIG. 13 illustrates a mapping of additional resource elements (REs) are defined in the same OFDM symbols where a current reference signal (RS) for normal cyclic prefix (CP) is defined.

[0093] For example, for the same CDM group, OCC mapping {a,b,c,d} can be reversely mapped (e.g., mirror imaging of each group of adjacent symbol pairs) in a frequency direction. For the different CDM groups, there is an offset {c, d, a, b} (i.e. offset value 2 in right circular shift) and also is reversely mapped in frequency direction. That is, the same reference signal pattern can be used for two CDM groups and length-4 Walsh Codes can be used for OCC allocation. That is, the multiplexing of reference signals within a CDM subgroup can be achieved by applying orthogonal cover codes (OCC) across the time domain. The OCC can be a set of codes which all have zero cross-correlation. Thus, two signals encoded with two different codes from the set will not interfere with one another. An example of an OCC is a Walsh code. As illustrated in FIG. 13, Walsh codes can be defined using a Walsh matrix of length N, i.e. having N columns. Each row in the Walsh matrix is one length-N Walsh code. For example, the Walsh matrix of length-4 is: W = ( 1 1 1 1 1 - 1 1 - 1 1 1 - 1 - 1 1 - 1 - 1 1 ). Each row in this matrix can form one code of length 4, i.e. the codes are [1 , 1, 1 , 1 ], [1 , -1 , 1, -1 ], [1 , 1 , -1 , -1] and [1 , -1 , -1 , 1]. These four codes are all orthogonal with respect to each other. The individual "l "s and "-l "s of each code will be referred to as "code elements" in the following. Although Walsh codes can be used throughout this disclosure to exemplify the technology, it should be understood that any OCC can be used. Reference to "applying an orthogonal cover code" or "transmitting a signal using an orthogonal cover code" can refer to one code out of a set of mutually orthogonal codes, e.g. one row from the Walsh matrix. The reference signal pattern for the first CDM group, i.e. subcarriers 1 , 6, and 11 of the first RB. A second CDM group can be used, comprising subcarriers 2, 7, and 12 of the first RB. Thus, up to eight antenna ports may be supported in this example; four in the first CDM group, and four in the second CDM group. Each antenna port can transmit one reference signal in each CDM subgroup, and the reference signal is spread across four REs in the time domain using a length-4 Walsh code.

[0094] FIG. 14 illustrates an orthogonal cover code (OCC) mapping of extended cyclic prefix (CP) in accordance with an example. The OCC mapping pattern shown in FIG 14. presents two different mechanisms, for both a normal subframe and a special subframe with Downlink Pilot Timeslot (DwPTS), when extended cyclic prefix (CP) is used.

[0095] FIG. 15 illustrates additional resource elements (RE) for an antenna port regarded as a same CDM group for applying OCC in accordance with an example. For adding additional resource elements (REs) in FIG. 15 for the peak power randomization, the new and/or additional REs for an antenna port (AP) can be regarded as the same CDM group for applying the OCC mapping. For example, CDM group 1 and 2 follow the same OCC mapping as an existing OCC mapping. CDM group 3 and 4 have the same OCC mapping as the OCC mapping of CDM group 1 and 2, respectively. CDM group 1 and 3 can be regarded the same AP. CDM group 2 and 4 can be regarded as the same AP. It should be noted that at each frequency occurrence for each CDM group (e.g., CDM groups 1 -4), reverse mapping can be applied.

[0096] FIG. 16 illustrates an additional example of additional resource elements (RE) for an antenna port regarded as a same CDM group for applying OCC in accordance with an example. The new and/or additional REs for an antenna port (AP) can be regarded as the same CDM group for applying the OCC mapping. For example, CDM group 1 and 2 follow a same or similar OCC mapping as an existing OCC mapping. CDM group 3 and 4 can have the same OCC mapping as the CDM group 1 and 2, respectively. CDM group 1 and 3 can be regarded the same AP. CDM group 2 and 4 can be regarded as the same AP.

[0097] FIG. 17 illustrates additional resource elements (RE) for an antenna port regarded as an independent CDM group for applying OCC in accordance with an example. The new and/or additional REs for an antenna port (AP) can be regarded as a different and/or independent CDM group for applying the OCC mapping. For example, different offsets (offset X in left right circular shift) between CDM groups can be applied. CDM group 2 can have an offset '2' in a right shift in reference to CDM group 1. CDM group 3 can have an offset T in a right shift in reference to CDM group 1. CDM group 4 can have an offset '3 ' in a right shift in reference to CDM group 1 . It should be noted that at each frequency occurrence for each CDM group (e.g., CDM groups 1 -4), reverse mapping can be applied.

[0098] In one aspect, additional REs can defined in the different OFDM symbols where a current RS is defined and can increase the transmit energy by allowing the transmission in a different time occurrence. In one aspect, (including pre-Rel- 13 UEs, non-MTC UEs and MTC UEs that are not in Enhanced Coverage (EC) mode) can be prohibited from being co-scheduled with UEs in EC mode for EPDCCH or PDSCH on the subframes with enhanced DM-RS structure.

[0099] In another aspect, data symbols for the EPDCCH PDSCH transmissions to legacy UEs (including pre-Rel-13 UEs, non-MTC UEs and MTC UEs that are not in Enhanced Coverage (EC) mode) corresponding to the REs on which new and/or additional DMRS that are mapped are punctured. In another aspect, the data symbols for the

EPDCCH/PDSCH transmissions to 3GPP LTE Rel-13 non-MTC UEs and 3GPP LTE Rel- 1 3 MTC UEs that are not in EC mode corresponding to the REs on the new and/or additional DMRS that are mapped are rate-matched. (The rate matching can be used to match a number of bits in transport block (TB) to the number of bits that can be transmitted in the given allocation.) This would impose a constraint that all 3GPP LTE Rel-13 UEs should be made aware of the presence of increased density DM-RS on the given subframes. Detailed options for the signaling of the use of the enhanced DM-RS structures are presented next. [00100] Moreover, in one aspect, an eNB can signal an indication of using the enhanced DMRS structure for MTC UEs in enhanced coverage mode. In one aspect, when transmitting EPDCCH or PDSCH, an eNB can always use the enhanced DMRS structure. This indicates that MTC UEs in enhanced coverage mode can use the enhanced DMRS structure for channel estimation.

[00101] In another aspect, an eNB can use the enhanced DMRS structure for EPDCCH or PDSCH transmission only when the coverage extension level for the targeted MTC UEs exceeds certain level (i.e., XdB, where X can be predefined and/or configured by a higher layer eNB via either system information block (SIB) and or a UE-specific dedicated RRC signaling. In one example, X can equal lOdB. For MTC UEs with a coverage extension level that is less than XdB, the MTC UEs can use an existing DMRS structure for channel estimation.

[00102] In one aspect, an indication of the use of the enhanced DMRS structure can be signaled by eNB via UE specific dedicated RRC signaling. In an additional aspect, an eNB can indicated the use of the enhanced DMRS structure in downlink related DCI format. In one example, 1 bit for the indication of the enhanced DMRS structure can be explicitly signaled in DCI format 1 A for downlink assignment.

[00103] In another aspect, because some of the modulation and coding schemes (MCSs), such as MCS for Quadrature Amplitude Modulation (64QAM modulation), may not be used for MTC UEs in enhanced coverage mode, an eNB can signal the indication of the enhanced DMRS structure using any unused MCSs. For example, with 14 < I'MCS≤ 28 in an uplink grant can indicate that MTC UEs in enhanced coverage mode will use this new DM-RS structure for PDSCH transmission and I_MCS = I'MCS^— 14, where 1_MCS and ' MCS ^{are tne} MCS index.

[00104] In another example, MTC UEs in enhanced coverage mode can employ a maximum transmit power for uplink transmission, and thus a transmit power control (TPC) command for PUCCH transmission in DCI format 1 A may not be necessary. In this case, an eNB may signal the indication of the enhanced DMRS structure in a 1 of 2- bit TPC command. Alternatively, an eNB can use a 1-bit TPC command for transmit power control of PUCCH transmission and another 1 bit can be used for the indication of the enhanced DMRS structure. [00105] FIG. 18 depicts functionality of a user equipment (UE) operable to perform uplink transmission operating in an enhanced coverage mode for machine type communication (MTC) in accordance with an example. FIG. 18 depicts functionality of a user equipment (UE) operable to perform uplink transmission operating in an enhanced coverage mode for machine type communication (MTC) in accordance with an example. The functionality 1800 can be implemented as a method or the functionality 1800 can be executed as instructions on a machine, where the instructions are included on at least one computer readable medium or one non-transitory machine readable storage medium. The one or more processors can be configured to process an indication, received from an evolved node B (eNB), for using enhanced demodulation reference signals (DMRS) structure of the UE operating in the enhanced coverage mode for MTC, as in block 1810.

[00106] The one or more processors can be configured to determine a cyclic shift (CS) and orthogonal cover code (OCC) for the enhanced DMRS by using a mapping rule for a 3-bit cyclic shift in a downlink control information (DCI) format, as in block 1820. The one or more processors can be configured to generate, for transmission (e.g., process for transmission), enhanced demodulation reference signals (DMRS) with K DMRS symbols in a plurality of DMRS positions of a subframe for a physical uplink shared channel (PUSCH) transmission, wherein K is a positive integer greater than two, as in block 1830.

[00107] FIG. 19 depicts an additional example of functionality of a user equipment (UE) operable to perform downlink reception operating in an enhanced coverage mode for machine type communication (MTC) in accordance with an example.

[00108] The functionality 1900 can be implemented as a method or the functionality 1900 can be executed as instructions on a machine, where the instructions are included on at least one computer readable medium or one non-transitory machine readable storage medium. The one or more processors can process and/or receive a first reference signal (RS) for a first antenna port (AP) and a second RS for a second AP, as in block 1910.

[00109] The one or more processors can perform channel estimation from the first AP and the second AP by assuming the first AP and the second AP are a same AP, as in block 1920. The one or more processors can use the first RS and the second RS for

demodulation reference signal (DMRS) of an enhanced physical downlink control channel (EPDCCH) or for a UE-specific RS of physical downlink shared channel (PDSCH), as in block 1930.

[00110] FIG. 20 depicts an additional example of functionality of a user equipment (UE) operable to perform downlink reception operating in an enhanced coverage mode for machine type communication (MTC) in accordance with an example.

[00111] The functionality 2000 can be implemented as a method or the functionality 2000 can be executed as instructions on a machine, where the instructions are included on at least one computer readable medium or one non-transitory machine readable storage medium. The one or more processors can be configured to receive a first reference signal (RS) for a first antenna port (AP) and a second RS for a second AP, as in block 2010.

[00112] The one or more processors can be configured to receive an additional reference signal (RS) for the first antenna port (AP) on the resource element (RE) placed in an Orthogonal Frequency Division Multiplexing (OFDM) symbol for the second RS for the second AP, as in block 2020. The one or more processors can be configured to an additional reference signal (RS) for the first antenna port (AP) on a resource element (RE) placed in an Orthogonal Frequency Division Multiplexing (OFDM) symbol that is different than an alternative OFDM symbol of the second RS for the second AP, as in block 2030.

[00113] FIG. 21 illustrates a diagram of a wireless device (e.g., UE) 2100 in accordance with an example. FIG. 21 provides an example illustration of the wireless device, such as a user equipment (UE), a mobile station (MS), a mobile wireless device, a mobile communication device, a tablet, a handset, or other type of wireless device. In one aspect, the wireless device can include at least one of an antenna, a touch sensitive display screen, a speaker, a microphone, a graphics processor, an application processor, a baseband processor, an internal memory, a non-volatile memory port, and combinations thereof. The wireless device can include one or more antennas configured to

communicate with a node or 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), a remote radio unit (RRU), a central processing module (CPM), or other type of wireless wide area network (WWAN) access point. The wireless device can be configured to communicate using at least one wireless communication standard including 3GPP LTE, WiMAX, High Speed Packet Access (HSPA), Bluetooth, and WiFi. The wireless device can communicate using separate antennas for each wireless communication standard or shared antennas for multiple wireless communication standards. The wireless device can communicate in a wireless local area network (WLAN), a wireless personal area network (WPAN), and/or a WWAN.

[00114] FIG. 22 illustrates a diagram 2200 of a node 2210 (e.g., eNB and/or a Serving GPRS Support Node) and wireless device (e.g., UE) in accordance with an example. The node can include a base station (BS), a Node B (NB), an evolved Node B (eNB), a baseband unit (BBU), a remote radio head (RRH), a remote radio equipment (RRE), a remote radio unit (RRU), or a central processing module (CPM). In one aspect, the node can be a Serving GPRS Support Node. The node 2210 can include a node device 2212. The node device 2212 or the node 2210 can be configured to communicate with the wireless device 2220. The node device 2212 can be configured to implement the described. The node device 2212 can include a processing module 2214 and a transceiver module 2216. In one aspect, the node device 2212 can include the transceiver module 2216 and the processing module 2214 forming a circuitry 2218 for the node 2210. In one aspect, the transceiver module 2216 and the processing module 2214 can form a circuitry of the node device 2212. The processing module 2214 can include one or more processors and memory. In one embodiment, the processing module 2222 can include one or more application processors. The transceiver module 2216 can include a transceiver and one or more processors and memory. In one embodiment, the transceiver module 2216 can include a baseband processor.

[00115] The wireless device 2220 can include a transceiver module 2224 and a processing module 2222. The processing module 2222 can include one or more processors and memory. In one embodiment, the processing module 2222 can include one or more application processors. The transceiver module 2224 can include a transceiver and one or more processors and memory. In one embodiment, the transceiver module 2224 can include a baseband processor. The wireless device 2220 can be configured to implement the described. The node 2210 and the wireless devices 2220 can also include one or more storage mediums, such as the transceiver module 2216, 2224 and/or the processing module 2214, 2222.

[00116] As used herein, the term "circuitry" can refer to, be part of, or include an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group), and/or memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable hardware components that provide the described functionality. In some aspects, the circuitry can be implemented in, or functions associated with the circuitry can be implemented by, one or more software or firmware modules. In some aspects, circuitry can include logic, at least partially operable in hardware.

[00117] FIG. 23 illustrates, for one aspect, example components of a User Equipment (UE) device 2300. In some aspects, the UE device 2300 can include application circuitry 2302, baseband circuitry 2304, Radio Frequency (RF) circuitry 2306, front-end module (FEM) circuitry 2308 and one or more antennas 2310, coupled together at least as shown.

[00118] The application circuitry 2302 can include one or more application processors. For example, the application circuitry 2302 can include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor(s) can include any combination of general-purpose processors and dedicated processors (e.g., graphics processors, application processors, etc.). The processors can be coupled with and/or can include a storage medium 2312, and can be configured to execute instructions stored in the storage medium 2312 to enable various applications and/or operating systems to run on the system.

[00119] The baseband circuitry 2304 can include circuitry such as, but not limited to, one or more single-core or multi-core processors. The baseband circuitry 2304 can include one or more baseband processors and/or control logic to process baseband signals received from a receive signal path of the RF circuitry 2306 and to generate baseband signals for a transmit signal path of the RF circuitry 2306. Baseband processing circuitry 2304 can interface with the application circuitry 2302 for generation and processing of the baseband signals and for controlling operations of the RF circuitry 2306. For example, in some aspects, the baseband circuitry 2304 can include a second generation (2G) baseband processor 2304a, third generation (3G) baseband processor 2304b, fourth generation (4G) baseband processor 2304c, and/or other baseband processors) 2304d for other existing generations, generations in development or to be developed in the future (e.g., fifth generation (5G), 6G, etc.). The baseband circuitry 2304 (e.g., one or more of baseband processors 2304a-d) can handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 2306. The radio control functions can include, but are not limited to, signal

modulation/demodulation, encoding/decoding, radio frequency shifting, etc. In some aspects, modulation/demodulation circuitry of the baseband circuitry 2304 can include Fast-Fourier Transform (FFT), precoding, and/or constellation mapping/demapping functionality. In some aspects, encoding/decoding circuitry of the baseband circuitry 2304 can include convolution, tail-biting convolution, turbo, Viterbi, and/or Low Density Parity Check (LDPC) encoder/decoder functionality. Aspects of

modulation/demodulation and encoder/decoder functionality are not limited to these examples and can include other suitable functionality in other aspects.

[00120] In some aspects, the baseband circuitry 2304 can include elements of a protocol stack such as, for example, elements of an evolved universal terrestrial radio access network (EUTRAN) protocol including, for example, physical (PHY), media access control (MAC), radio link control (RLC), packet data convergence protocol (PDCP), and/or radio resource control (RRC) elements. A central processing unit (CPU) 2304e of the baseband circuitry 2304 can be configured to run elements of the protocol stack for signaling of the PHY, MAC, RLC, PDCP and/or RRC layers. In some aspects, the baseband circuitry can include one or more audio digital signal processor(s) (DSP) 2304f. The audio DSP(s) 2304f can be include elements for compression/decompression and echo cancellation and can include other suitable processing elements in other aspects. Components of the baseband circuitry can be suitably combined in a single chip, a single chipset, or disposed on a same circuit board in some aspects. In some aspects, some or all of the constituent components of the baseband circuitry 2304 and the application circuitry 2302 can be implemented together such as, for example, on a system on a chip (SOC).

[00121] In some aspects, the baseband circuitry 2304 can provide for

communication compatible with one or more radio technologies. For example, in some aspects, the baseband circuitry 2304 can support communication with an evolved universal terrestrial radio access network (EUTRAN) and/or other wireless metropolitan area networks (WMAN), a wireless local area network (WLAN), a wireless personal area network (WPAN). Aspects in which the baseband circuitry 2304 is configured to support radio communications of more than one wireless protocol can be referred to as multi- mode baseband circuitry.

[00122] RF circuitry 2306 can enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various aspects, the RF circuitry 2306 can include switches, filters, amplifiers, etc. to facilitate the communication with the wireless network. RF circuitry 2306 can include a receive signal path which can include circuitry to down-convert RF signals received from the FEM circuitry 2308 and provide baseband signals to the baseband circuitry 2304. RF circuitry 2306 can also include a transmit signal path which can include circuitry to up-convert baseband signals provided by the baseband circuitry 2304 and provide RF output signals to the FEM circuitry 2308 for transmission.

[00123] In some aspects, the RF circuitry 2306 can include a receive signal path and a transmit signal path. The receive signal path of the RF circuitry 2306 can include mixer circuitry 2306a, amplifier circuitry 2306b and filter circuitry 2306c. The transmit signal path of the RF circuitry 2306 can include filter circuitry 2306c and mixer circuitry 2306a. RF circuitry 2306 can also include synthesizer circuitry 2306d for synthesizing a frequency for use by the mixer circuitry 2306a of the receive signal path and the transmit signal path. In some aspects, the mixer circuitry 2306a of the receive signal path can be configured to down-convert RF signals received from the FEM circuitry 2308 based on the synthesized frequency provided by synthesizer circuitry 2306d. The amplifier circuitry 2306b can be configured to amplify the down-converted signals and the filter circuitry 2306c can 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 can be provided to the baseband circuitry 2304 for further processing. In some aspects, the output baseband signals can be zero-frequency baseband signals, although this is not a constraint. In some aspects, mixer circuitry 2306a of the receive signal path can comprise passive mixers, although the scope of the aspects is not limited in this respect.

[00124] In some aspects, the mixer circuitry 2306a of the transmit signal path can be configured to up-convert input baseband signals based on the synthesized frequency provided by the synthesizer circuitry 2306d to generate RF output signals for the FEM circuitry 2308. The baseband signals can be provided by the baseband circuitry 2304 and can be filtered by filter circuitry 2306c. The filter circuitry 2306c can include a low-pass filter (LPF), although the scope of the aspects is not limited in this respect.

[00125] In some aspects, the mixer circuitry 2306a of the receive signal path and the mixer circuitry 2306a of the transmit signal path can include two or more mixers and can be arranged for quadrature downconversion and/or upconversion respectively. In some aspects, the mixer circuitry 2306a of the receive signal path and the mixer circuitry 2306a of the transmit signal path can include two or more mixers and can be arranged for image rejection (e.g., Hartley image rejection). In some aspects, the mixer circuitry 2306a of the receive signal path and the mixer circuitry 2306a can be arranged for direct

downconversion and/or direct upconversion, respectively. In some aspects, the mixer circuitry 2306a of the receive signal path and the mixer circuitry 2306a of the transmit signal path can be configured for super-heterodyne operation.

[00126] In some aspects, the output baseband signals and the input baseband signals can be analog baseband signals, although the scope of the aspects is not limited in this respect. In some alternate aspects, the output baseband signals and the input baseband signals can be digital baseband signals. In these alternate aspects, the RF circuitry 2306 can include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry and the baseband circuitry 2304 can include a digital baseband interface to communicate with the RF circuitry 2306.

[00127] In some dual-mode embodiments, a separate radio IC circuitry can be provided for processing signals for each spectrum, although the scope of the

embodiments is not limited in this respect.

[00128] In some embodiments, the synthesizer circuitry 2306d can 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 can be suitable. For example, synthesizer circuitry 2306d can be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider.

[00129] The synthesizer circuitry 2306d can be configured to synthesize an output frequency for use by the mixer circuitry 2306a of the RF circuitry 2306 based on a frequency input and a divider control input. In some embodiments, the synthesizer circuitry 2306d can be a fractional N N+l synthesizer.

[00130] In some embodiments, frequency input can be provided by a voltage controlled oscillator (VCO), although that is not a constraint. Divider control input can be provided by either the baseband circuitry 2304 or the applications processor 2302 depending on the desired output frequency. In some embodiments, a divider control input (e.g., N) can be determined from a look-up table based on a channel indicated by the applications processor 2302.

[00131] Synthesizer circuitry 2306d of the RF circuitry 2306 can include a divider, a delay-locked loop (DLL), a multiplexer and a phase accumulator. In some embodiments, the divider can be a dual modulus divider (DMD) and the phase accumulator can be a digital phase accumulator (DPA). In some embodiments, the DMD can 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 can 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 can 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.

[00132] In some embodiments, synthesizer circuitry 2306d can be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency can 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 can be a LO frequency (fLO). In some embodiments, the RF circuitry 2306 can include an IQ/polar converter.

[00133] FEM circuitry 2308 can include a receive signal path which can include circuitry configured to operate on RF signals received from one or more antennas 2310, amplify the received signals and provide the amplified versions of the received signals to the RF circuitry 2306 for further processing. FEM circuitry 2308 can also include a transmit signal path which can include circuitry configured to amplify signals for transmission provided by the RF circuitry 2306 for transmission by one or more of the one or more antennas 2310.

[00134] In some embodiments, the FEM circuitry 2308 can include a TX RX switch to switch between transmit mode and receive mode operation. The FEM circuitry can include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry can include a low-noise amplifier (LNA) to amplify received RF signals and provide the amplified received RF signals as an output (e.g., to the RF circuitry 2306). The transmit signal path of the FEM circuitry 2308 can include a power amplifier (PA) to amplify input RF signals (e.g., provided by RF circuitry 2306), and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 2310.

[00135] In some embodiments, the UE device 2300 can include additional elements such as, for example, memory/storage, display, camera, sensor, and/or input/output (I/O) interface.

Examples

[00136] The following examples pertain to specific embodiments and point out specific features, elements, or steps that can be used or otherwise combined in achieving such embodiments.

[00137] Example 1 includes an apparatus of a user equipment (UE), the UE configured to perform uplink transmission operating in an enhanced coverage mode for machine type communication (MTC), the apparatus comprising one or more processors and memory configured to: process an indication, received from an evolved node B (eNB), for using enhanced demodulation reference signals (DMRS) structure of the UE operating in the enhanced coverage mode for MTC; determine a cyclic shift (CS) and orthogonal cover code (OCC) for the enhanced DMRS by using a mapping rule for a 3-bit cyclic shift in a downlink control information (DCI) format; and generate, for transmission, enhanced demodulation reference signals (DMRS) with K DMRS symbols in a plurality of DMRS positions of a subframe for a physical uplink shared channel (PUSCH) transmission, wherein is a positive integer greater than two.

[00138] Example 2 includes the apparatus of example 1 , wherein the one or more processors are further configured to process an indication, received from the eNB, to use the enhanced DMRS for channel estimation with the UE operating in the enhanced coverage mode for the MTC, wherein the enhanced DMRS is represented in a downlink as a total number of DMRS resource elements (RE) greater than 24 for each antenna port and the enhanced DMRS is represented in an uplink as a total number of symbols greater than 2.

[00139] Example 3 includes the apparatus of example l , wherein the one or more processors are further configured to generate the enhanced DMRS in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of a first slot of the subframe of a reference signal (RS) or a first OFDM symbol of a second slot of the subframe the RS.

[00140] Example 4 includes the apparatus of example 1 or 3, wherein the one or more processors are further configured to: generate two of the enhanced DMRS either in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of each slot of a subframe of a reference signal (RS) or in a first OFDM symbol of each slot of the subframe the RS; and generate two alternative enhanced DMRS either in OFDM symbol # 1 and OFDM symbol #5 for each slot of the subframe of the RS or OFDM symbol #2 and OFDM symbol #4 for each slot of the subframe of the RS.

[00141] Example 5 includes the apparatus of example 4, wherein the one or more processors are further configured to apply an identical OCC for the two alternative DMRS and an existing DMRS within a same slot of the subframe of the RS.

[00 42] Example 6 includes the apparatus of example 1 or 5, wherein the one or more processors are further configured to apply one of a plurality of orthogonal sequences for the OCC on the enhanced DMRS, wherein the plurality of orthogonal sequences include at least a discrete Fourier transformation (DFT code) a Walsh-Hadamard sequence.

[00143] Example 7 includes the apparatus of example 6, wherein the one or more processors are further configured to apply a length-3 DFT code or a length-4 Walsh- Hadamard sequence for the OCC on the enhanced DMRS.

[00144] Example 8 includes the apparatus of example 1 or 7, wherein the one or more processors are further configured to generate patterns of the cyclic shift hopping and the group hopping based on a slot of a subframe of a reference signal (RS) or a enhanced DMRS symbol index.

[00145] Example 9 includes the apparatus of example 1 , wherein the one or more processors are further configured to use the enhanced DMRS for PUSCH transmission when a coverage extension level exceeds a predetermined level.

[00146] Example 10 includes the apparatus of example 1 or 9, wherein the one or more processors are further configured to process a notification received from an evolved node B (eNB) to use the enhanced DMRS for PUSCH transmission by the eNB via UE-specific dedicated radio resource control (RRC) signaling.

[00147] Example 1 1 includes the apparatus of example 1 or 10, wherein the one or more processors are further configured to process a notification to use the enhanced DMRS in an uplink related DCI format in an explicit signal or implicit signal.

[00148] Example 12 includes the apparatus of example 1 , wherein the apparatus includes at least one of an antenna, a touch sensitive display screen, a speaker, a microphone, a graphics processor, an application processor, a baseband processor, an internal memory, a non-volatile memory port, and combinations thereof.

[00149] Example 13 includes apparatus of a user equipment (UE), the UE configured to perform downlink reception, the apparatus comprising one or more processors and memory configured to: process a first reference signal (RS) for a first antenna port (AP) and a second RS for a second AP; perform a channel estimation from the first AP and the second AP by assuming the first AP and the second AP are a same AP; and use the first RS and the second RS for demodulation reference signal (DMRS) of an enhanced physical downlink control channel (EPDCCH) or for a UE-specific RS of physical downlink shared channel (PDSCH).

[00150] Example 14 includes the apparatus of example 13, wherein the one or more processors and memory are further configured to infer a channel over which an

Orthogonal Frequency Division Multiplexing (OFDM) symbol on the first AP is conveyed from a channel over which an alternative OFDM symbol on the second AP is conveyed.

[00151] Example 15 includes apparatus of a user equipment (UE), the UE configured to perform downlink reception, the apparatus comprising one or more processors and memory configured to: process a first reference signal (RS) for a first antenna port (AP) on a resource element (RE) placed in an Orthogonal Frequency Division Multiplexing (OFDM) symbol for a second RS for a second AP, wherein the first AP is processed from a code division multiplexing (CDM) group and the second AP is processed from an alternative CDM group; and use a enhanced demodulation reference signals (DMRS) structure of an enhanced physical downlink control channel (EPDCCH) transmission or a physical downlink shared channel (PDSCH) transmission.

[00152] Example 16 includes the apparatus of example 15, wherein the one or more processors and memory are further configured to: use an orthogonal code cover (OCC) mapping for the first AP that is identical to the second AP; allow an enhanced node B

(eNB) to use the enhanced DMRS structure of the UE operating in an enhanced coverage mode for machine type communication (MTC); use a enhanced demodulation reference signals (DMRS) structure of an enhanced physical downlink control channel (EPDCCH) transmission or a physical downlink shared channel (PDSCH) transmission when a coverage extension level exceeds a predetermined level; process a signal, received from an enhanced node B (eNB), by a UE-specific dedicated radio resource control signaling to use a enhanced demodulation reference signals (DMRS); or process a signal, received from an enhanced node B (eNB), either explicitly or implicitly in a downlink control information (DCI) format to use a enhanced demodulation reference signals (DMRS).

[00153] Example 17 includes the apparatus of example 15 or 16, wherein the one or more processors and memory are further configured to map an orthogonal code cover (OCC) mapping with mirror imaging for each group of adjacent OFDM symbol pairs in a frequency direction for a code division multiplexing (CDM).

[00154] Example 18 includes the apparatus of example 15, wherein the one or more processors and memory are further configured to use an orthogonal code cover (OCC) mapping for the first AP with an offset to the second AP.

[00155] Example 19 includes the apparatus of example 15 or 18, wherein the one or more processors and memory are further configured to reverse an orthogonal code cover (OCC) mapping from the orthogonal code vector.

[00156] Example 20 includes an apparatus of an evolved node B (eNB), the apparatus comprising one or more processors and memory configured to: process an indication, for transmission to a user equipment (UE), to indicate to the UE to use a enhanced demodulation reference signals (DMRS) structure of the UE operating in an enhanced coverage mode for machine type communication (MTC) to enable the UE to determine a cyclic shift (CS) and orthogonal cover code (OCC) for the enhanced DMRS by using a mapping rule for a 3-bit cyclic shift in a downlink control information (DCI) format; and process the enhanced DMRS, received from the UE, having DMRS symbols in a plurality of DMRS positions of a subframe for a physical uplink shared channel (PUSCH) transmission, wherein K is a positive integer greater than two.

[00157] Example 21 includes the apparatus of example 20, wherein the one or more processors are further configured to process an indication, for transmission to the UE, to use the enhanced DMRS for channel estimation with the UE operating in the enhanced coverage mode for the MTC, wherein the enhanced DMRS is represented in a downlink as a total number of DMRS resource elements (RE) greater than 24 for each antenna port and the enhanced DMRS is represented in an uplink as a total number of symbols greater than 2.

[00158] Example 22 includes the apparatus of example 20 or 21 , wherein the one or more processors are further configured to process the enhanced DMRS, received from the UE, in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of a first slot of the subframe of a reference signal (RS) or a first OFDM symbol of a second slot of the subframe the RS.

[00159] Example 23 includes the apparatus of example 20, wherein the one or more processors are further configured to: process two of the enhanced DMRS, received from the UE, either in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of each slot of a subframe of a reference signal (RS) or in a first OFDM symbol of each slot of the subframe the RS; or process two alternative enhanced DMRS, received from the UE, either in OFDM symbol #1 and OFDM symbol #5 for each slot of the subframe of the RS or OFDM symbol #2 and OFDM symbol #4 for each slot of the subframe of the RS.

[00160] Example 24 includes an apparatus of a user equipment (UE), the UE configured to perform uplink transmission operating in an enhanced coverage mode for machine type communication (MTC), the apparatus comprising one or more processors and memory configured to: process an indication, received from an evolved node B (eNB), for using enhanced demodulation reference signals (DMRS) structure of the UE operating in the enhanced coverage mode for MTC; determine a cyclic shift (CS) and orthogonal cover code (OCC) for the enhanced DMRS by using a mapping rule for a 3-bit cyclic shift in a downlink control information (DCI) format; and generate, for transmission, enhanced demodulation reference signals (DMRS) with K DMRS symbols in a plurality of DMRS positions of a subframe for a physical uplink shared channel (PUSCH) transmission, wherein K is a positive integer greater than two.

[00161] Example 25 includes the apparatus of example 24, wherein the one or more processors are further configured to process an indication, received from the eNB, to use the enhanced DMRS for channel estimation with the UE operating in the enhanced coverage mode for the MTC, wherein the enhanced DMRS is represented in a downlink as a total number of DMRS RE greater than 24 for each antenna port and the enhanced DMRS is represented in an uplink as a total number of symbols greater than 2. [00162] Example 26 includes the apparatus of example 24, wherein the one or more processors are further configured to generate the enhanced DMRS in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of a first slot of the subframe of a reference signal (RS) or a first OFDM symbol of a second slot of the subframe the RS.

[00163] Example 27 includes the apparatus of example 24, wherein the one or more processors are further configured to: generate two of the enhanced DMRS either in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of each slot of a subframe of a reference signal (RS) or in a first OFDM symbol of each slot of the subframe the RS; and generate two alternative enhanced DMRS either in OFDM symbol # 1 and OFDM symbol #5 for each slot of the subframe of the RS or OFDM symbol #2 and OFDM symbol #4 for each slot of the subframe of the RS.

[00164] Example 28 includes the apparatus of example 27, wherein the one or more processors are further configured to apply an identical OCC for the two alternative DMRS and an existing DMRS within a same slot of the subframe of the RS.

[00165] Example 29 includes the apparatus of example 24, wherein the one or more processors are further configured to apply one of a plurality of orthogonal sequences for the OCC on the enhanced DMRS, wherein the plurality of orthogonal sequences include at least a discrete Fourier transformation (DFT code) a Walsh-Hadamard sequence.

[00166] Example 30 includes the apparatus of example 29, wherein the one or more processors are further configured to apply a length-3 DFT code or a length-4 Walsh- Hadamard sequence for the OCC on the enhanced DMRS.

[00167] Example 31 includes the apparatus of example 30, wherein the one or more processors are further configured to generate patterns of the cyclic shift hopping and the group hopping based on a slot of a subframe of a reference signal (RS) or a enhanced DMRS symbol index.

[00168] Example 32 includes the apparatus of example 24, wherein the one or more processors are further configured to use the enhanced DMRS for PUSCH transmission when a coverage extension level exceeds a predetermined level.

[00169] Example 33 includes the apparatus of example 24, wherein the one or more processors are further configured to process a notification received from an evolved node B (eNB) to use the enhanced DMRS for PUSCH transmission by the eNB via UE-specific dedicated radio resource control (RRC) signaling. [00170] Example 34 includes the apparatus of example 24, wherein the one or more processors are further configured to process a notification to use the enhanced DMRS in an uplink related DCI format in an explicit signal or implicit signal.

[00171] Example 35 includes the apparatus of example 24, wherein the apparatus includes at least one of an antenna, a touch sensitive display screen, a speaker, a microphone, a graphics processor, an application processor, a baseband processor, an internal memory, a non-volatile memory port, and combinations thereof.

[00172] Example 36 includes an apparatus of a user equipment (UE), the UE configured to perform downlink reception, the apparatus comprising one or more processors and memory configured to: process a first reference signal (RS) for a first antenna port (AP) and a second RS for a second AP; perform a channel estimation from the first AP and the second AP by assuming the first AP and the second AP are a same AP; and use the first RS and the second RS for demodulation reference signal (DMRS) of an enhanced physical downlink control channel (EPDCCH) or for a UE-specific RS of physical downlink shared channel (PDSCH).

[00173] Example 37 includes the apparatus of example 36, wherein the one or more processors and memory are further configured to infer a channel over which an

[00174] Example 38 includes an apparatus of a user equipment (UE), the UE configured to perform downlink reception, the apparatus comprising one or more processors and memory configured to: process a first reference signal (RS) for a first antenna port (AP) on a resource element (RE) placed in an Orthogonal Frequency Division Multiplexing (OFDM) symbol for a second RS for a second AP, wherein the first AP is processed from a code division multiplexing (CDM) group and the second AP is processed from an alternative CDM group; and use a enhanced demodulation reference signals (DMRS) structure of an enhanced physical downlink control channel (EPDCCH) transmission or a physical downlink shared channel (PDSCH) transmission.

[00175] Example 39 includes the apparatus of example 38, wherein the one or more processors and memory are further configured to: use an orthogonal code cover (OCC) mapping for the first AP that is identical to the second AP; allow an enhanced node B (eNB) to use the enhanced DMRS structure of the UE operating in an enhanced coverage mode for machine type communication (MTC); use a enhanced demodulation reference signals (DMRS) structure of an enhanced physical downlink control channel (EPDCCH) transmission or a physical downlink shared channel (PDSCH) transmission when a coverage extension level exceeds a predetermined level; process a signal, received from an enhanced node B (eNB), by a UE-specific dedicated radio resource control signaling to use a enhanced demodulation reference signals (DMRS); or process a signal, received from an enhanced node B (eNB), either explicitly or implicitly in a downlink control information (DCI) format to use a enhanced demodulation reference signals (DMRS).

[00176] Example 40 includes the apparatus of example 38, wherein the one or more processors and memory are further configured to map an orthogonal code cover (OCC) mapping with mirror imaging for each group of adjacent OFDM symbol pairs in a frequency direction for a code division multiplexing (CDM).

[00177] Example 41 includes the apparatus of example 38, wherein the one or more processors and memory are further configured to use an orthogonal code cover (OCC) mapping for the first AP with an offset to the second AP.

[00178] Example 42 includes the apparatus of example 38, wherein the one or more processors and memory are further configured to reverse an orthogonal code cover (OCC) mapping from the orthogonal code vector.

[00179] Example 43 includes an apparatus of an evolved node B (eNB), the apparatus comprising one or more processors and memory configured to: process an indication, for transmission to a user equipment (UE), to indicate to the UE to use a enhanced demodulation reference signals (DMRS) structure of the UE operating in an enhanced coverage mode for machine type communication (MTC) to enable the UE to determine a cyclic shift (CS) and orthogonal cover code (OCC) for the enhanced DMRS by using a mapping rule for a 3-bit cyclic shift in a downlink control information (DCI) format; and process the enhanced DMRS, received from the UE, having K DMRS symbols in a plurality of DMRS positions of a subframe for a physical uplink shared channel (PUSCH) transmission, wherein K is a positive integer greater than two.

[00180] Example 44 includes the apparatus of example 43, wherein the one or more processors are further configured to process an indication, for transmission to the UE, to use the enhanced DMRS for channel estimation with the UE operating in the enhanced coverage mode for the MTC, wherein the enhanced DMRS is represented in a downlink as a total number of DMRS RE greater than 24 for each antenna port and the enhanced DMRS is represented in an uplink as a total number of symbols greater than 2.

[00181] Example 45 includes the apparatus of example 43, wherein the one or more processors are further configured to process the enhanced DMRS, received from the UE, in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of a first slot of the subframe of a reference signal (RS) or a first OFDM symbol of a second slot of the subframe the RS.

[00182] Example 46 includes the apparatus of example 43, wherein the one or more processors are further configured to: process two of the enhanced DMRS, received from the UE, either in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of each slot of a subframe of a reference signal (RS) or in a first OFDM symbol of each slot of the subframe the RS; or process two alternative enhanced DMRS, received from the UE, either in OFDM symbol #1 and OFDM symbol #5 for each slot of the subframe of the RS or OFDM symbol #2 and OFDM symbol #4 for each slot of the subframe of the RS.

[00183] Example 47 includes an apparatus of a user equipment (UE), the UE configured to perform uplink transmission operating in an enhanced coverage mode for machine type communication (MTC), the apparatus comprising one or more processors and memory configured to: process an indication, received from an evolved node B

(eNB), for using enhanced demodulation reference signals (DMRS) structure of the UE operating in the enhanced coverage mode for MTC; determine a cyclic shift (CS) and orthogonal cover code (OCC) for the enhanced DMRS by using a mapping rule for a 3-bit cyclic shift in a downlink control information (DCI) format; and generate, for transmission, enhanced demodulation reference signals (DMRS) with K DMRS symbols in a plurality of DMRS positions of a subframe for a physical uplink shared channel (PUSCH) transmission, wherein is a positive integer greater than two.

[00184] Example 48 includes the apparatus of example 47, wherein the one or more processors are further configured to: process an indication, received from the eNB, to use the enhanced DMRS for channel estimation with the UE operating in the enhanced coverage mode for the MTC, wherein the enhanced DMRS is represented in a downlink as a total number of DMRS RE greater than 24 for each antenna port and the enhanced DMRS is represented in an uplink as a total number of symbols greater than 2; generate the enhanced DMRS in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of a first slot of the subframe of a reference signal (RS) or a first OFDM symbol of a second slot of the subframe the RS; generate two of the enhanced DMRS either in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of each slot of a subframe of a reference signal (RS) or in a first OFDM symbol of each slot of the subframe the RS; or generate two alternative enhanced DMRS either in OFDM symbol #1 and OFDM symbol #5 for each slot of the subframe of the RS or OFDM symbol #2 and OFDM symbol #4 for each slot of the subframe of the RS.

[00185] Example 49 includes the apparatus of example 47 or 48, wherein the one or more processors are further configured to: apply an identical OCC for the two alternative DMRS and an existing DMRS within a same slot of the subframe of the RS; or apply one of a plurality of orthogonal sequences for the OCC on the enhanced DMRS, wherein the plurality of orthogonal sequences include at least a discrete Fourier transformation (DFT code) a Walsh-Hadamard sequence, wherein the one or more processors are further configured to apply a length-3 DFT code or a length-4 Walsh-Hadamard sequence for the OCC on the enhanced DMRS.

[00186] In Example 50, the subject matter of Example 47 or any of the Examples described herein may further include, wherein the one or more processors are further configured to: generate patterns of the cyclic shift hopping and the group hopping based on a slot of a subframe of a reference signal (RS) or a enhanced DMRS symbol index; or use the enhanced DMRS for PUSCH transmission when a coverage extension level exceeds a predetermined level.

[00187] In Example 51 , the subject matter of Example 47 or any of the Examples described herein may further include, wherein the one or more processors are further configured to process a notification received from an evolved node B (eNB) to use the enhanced DMRS for PUSCH transmission by the eNB via UE-specific dedicated radio resource control (RRC) signaling.

[00188] In Example 52, the subject matter of Example 47 or any of the Examples described herein may further include, wherein the one or more processors are further configured to: process a notification to use the enhanced DMRS in an uplink related DCI format in an explicit signal or implicit signal. [00189] In Example 53, the subject matter of Example 47 or any of the Examples described herein may further include, wherein the apparatus includes at least one of an antenna, a touch sensitive display screen, a speaker, a microphone, a graphics processor, an application processor, a baseband processor, an internal memory, a non-volatile memory port, and combinations thereof.

[00190] Example 54 includes an apparatus of a user equipment (UE), the UE configured to perform downlink reception, the apparatus comprising one or more processors and memory configured to: process a first reference signal (RS) for a first antenna port (AP) and a second RS for a second AP; perform a channel estimation from the first AP and the second AP by assuming the first AP and the second AP are a same AP; and use the first RS and the second RS for demodulation reference signal (DMRS) of an enhanced physical downlink control channel (EPDCCH) or for a UE-specific RS of physical downlink shared channel (PDSCH).

[00191] Example 55 includes the apparatus of example 54, wherein the one or more processors and memory are further configured to infer a channel over which an

[00192] Example 56 includes an apparatus of a user equipment (UE), the UE configured to perform downlink reception, the apparatus comprising one or more processors and memory configured to: process a first reference signal (RS) for a first antenna port (AP) on a resource element (RE) placed in an Orthogonal Frequency Division Multiplexing (OFDM) symbol for a second RS for a second AP, wherein the first AP is processed from a code division multiplexing (CDM) group and the second AP is processed from an alternative CDM group; and use a enhanced demodulation reference signals (DMRS) structure of an enhanced physical downlink control channel (EPDCCH) transmission or a physical downlink shared channel (PDSCH) transmission.

[00193] Example 57 includes the apparatus of example 56, wherein the one or more processors and memory are further configured to: use an orthogonal code cover (OCC) mapping for the first AP that is identical to the second AP; allow an enhanced node B

[00194] Example 58 includes the apparatus of example 56 or 57, wherein the one or more processors and memory are further configured to: map an orthogonal code cover (OCC) mapping with mirror imaging for each group of adjacent OFDM symbol pairs in a frequency direction for a code division multiplexing (CDM); or use an orthogonal code cover (OCC) mapping for the first AP with an offset to the second AP.

[00195] In Example 59, the subject matter of Example 56 or any of the Examples described herein may further include, wherein the one or more processors and memory are further configured to reverse an orthogonal code cover (OCC) mapping from the orthogonal code vector.

[00196] Example 60 includes an apparatus of an evolved node B (eNB), the apparatus comprising one or more processors and memory configured to: process an indication, for transmission to a user equipment (UE), to indicate to the UE to use a enhanced demodulation reference signals (DMRS) structure of the UE operating in an enhanced coverage mode for machine type communication (MTC) to enable the UE to determine a cyclic shift (CS) and orthogonal cover code (OCC) for the enhanced DMRS by using a mapping rule for a 3-bit cyclic shift in a downlink control information (DCI) format; and process the enhanced DMRS, received from the UE, having K DMRS symbols in a plurality of DMRS positions of a subframe for a physical uplink shared channel (PUSCH) transmission, wherein K is a positive integer greater than two.

[00197] Example 61 includes the apparatus of example 60, wherein the one or more processors are further configured to: process an indication, for transmission to the UE, to use the enhanced DMRS for channel estimation with the UE operating in the enhanced coverage mode for the MTC, wherein the enhanced DMRS is represented in a downlink as a total number of DMRS RE greater than 24 for each antenna port and the enhanced DMRS is represented in an uplink as a total number of symbols greater than 2; process the enhanced DMRS, received from the UE, in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of a first slot of the subframe of a reference signal (RS) or a first OFDM symbol of a second slot of the subframe the RS; process two of the enhanced DMRS, received from the UE, either in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of each slot of a subframe of a reference signal (RS) or in a first OFDM symbol of each slot of the subframe the RS; process two alternative enhanced DMRS, received from the UE, either in OFDM symbol #1 and OFDM symbol #5 for each slot of the subframe of the RS or OFDM symbol #2 and OFDM symbol #4 for each slot of the subframe of the RS.

[00198] Example 62 includes a device to perform uplink transmission and/or downlink reception, the device comprising: means for processing an indication, received from an evolved node B (eNB), for using enhanced demodulation reference signals (DMRS) structure of the UE operating in the enhanced coverage mode for MTC; means for determining a cyclic shift (CS) and orthogonal cover code (OCC) for the enhanced DMRS by using a mapping rule for a 3-bit cyclic shift in a downlink control information (DCI) format; and means for generating, for transmission, enhanced demodulation reference signals (DMRS) with K DMRS symbols in a plurality of DMRS positions of a subframe for a physical uplink shared channel (PUSCH) transmission, wherein K is a positive integer greater than two.

[00199] Example 63 includes the device of example 62, further comprising means for: processing an indication, received from the eNB, to use the enhanced DMRS for channel estimation with the UE operating in the enhanced coverage mode for the MTC, wherein the enhanced DMRS is represented in a downlink as a total number of DMRS RE greater than 24 for each antenna port and the enhanced DMRS is represented in an uplink as a total number of symbols greater than 2; generating the enhanced DMRS in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of a first slot of the subframe of a reference signal (RS) or a first OFDM symbol of a second slot of the subframe the RS; generating two of the enhanced DMRS either in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of each slot of a subframe of a reference signal (RS) or in a first OFDM symbol of each slot of the subframe the RS; or generating two alternative enhanced DMRS either in OFDM symbol #1 and OFDM symbol #5 for each slot of the subframe of the RS or OFDM symbol #2 and OFDM symbol #4 for each slot of the subframe of the RS.

[00200] Example 64 includes the device of example 62, further comprising means for: applying an identical OCC for the two alternative DMRS and an existing DMRS within a same slot of the subframe of the RS; or applying one of a plurality of orthogonal sequences for the OCC on the enhanced DMRS, wherein the plurality of orthogonal sequences include at least a discrete Fourier transformation (DFT code) a Walsh- Hadamard sequence, wherein the one or more processors are further configured to apply a length-3 DFT code or a length-4 Walsh-Hadamard sequence for the OCC on the enhanced DMRS.

[00201] Example 65 includes the device of example 62, further comprising means for: generating patterns of the cyclic shift hopping and the group hopping based on a slot of a subframe of a reference signal (RS) or a enhanced DMRS symbol index; or using the enhanced DMRS for PUSCH transmission when a coverage extension level exceeds a predetermined level.

[00202] Example 66 includes the device of example 62, further comprising means for processing a notification received from an evolved node B (eNB) to use the enhanced DMRS for PUSCH transmission by the eNB via UE-specific dedicated radio resource control (RRC) signaling.

[00203] Various techniques, or certain aspects or portions thereof, may take the form of program code (i.e., instructions) embodied in tangible media, such as floppy diskettes, compact disc-read-only memory (CD-ROMs), hard drives, non-transitory computer readable storage medium, or any other machine-readable storage medium wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the various techniques. Circuitry can include hardware, firmware, program code, executable code, computer instructions, and/or software. A non-transitory computer readable storage medium can be a computer readable storage medium that does not include signal. In the case of program code execution on programmable computers, the computing device may include a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device, and at least one output device. The volatile and non-volatile memory and/or storage elements may be a random-access memory (RAM), erasable programmable read only memory (EPROM), flash drive, optical drive, magnetic hard drive, solid state drive, or other medium for storing electronic data. The node and wireless device may also include a transceiver module (i.e., transceiver), a counter module (i.e., counter), a processing module (i.e., processor), and/or a clock module (i.e., clock) or timer module (i.e., timer). One or more programs that may implement or utilize the various techniques described herein may use an application programming interface (API), reusable controls, and the like. Such programs may be implemented in a high level procedural or object oriented programming language to communicate with a computer system. However, the program(s) may be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language, and combined with hardware implementations.

[00204] As used herein, the term processor can include general purpose processors, specialized processors such as VLSI, FPGAs, or other types of specialized processors, as well as base band processors used in transceivers to send, receive, and process wireless communications.

[00205] It should be understood that many of the functional units described in this specification have been labeled as modules, in order to more particularly emphasize their implementation independence. For example, a module may be implemented as a hardware circuit comprising custom very-large-scale integration (VLSI) circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like.

[00206] Modules may also be implemented in software for execution by various types of processors. An identified module of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions, which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module may not have to be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the module and achieve the stated purpose for the module.

[00207] Indeed, a module of executable code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network. The modules may be passive or active, including agents operable to perform desired functions.

[00208] Reference throughout this specification to "an example" or "exemplary" means 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, appearances of the phrases "in an example" or the word "exemplary" in various places throughout this specification are not necessarily all referring to the same embodiment.

[00209] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present technology may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as defacto equivalents of one another, but are to be considered as separate and autonomous representations of the present technology.

[00210] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of layouts, distances, network examples, etc., to provide a thorough understanding of embodiments of the technology. One skilled in the relevant art will recognize, however, that the technology can be practiced without one or more of the specific details, or with other methods, components, layouts, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the technology.

[00211] While the forgoing examples are illustrative of the principles of the present technology in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the technology. Accordingly, it is not intended that the application be limited, except as by the claims set forth below.

Claims

CLAIMS What is claimed is:

1. An apparatus of a user equipment (UE), the UE configured to perform uplink transmission operating in an enhanced coverage mode for machine type communication (MTC), the apparatus comprising one or more processors and memory configured to:

process an indication, received from an evolved node B (eNB), for using enhanced demodulation reference signals (DMRS) structure of the UE operating in the enhanced coverage mode for MTC;

determine a cyclic shift (CS) and orthogonal cover code (OCC) for the enhanced DMRS by using a mapping rule for a 3-bit cyclic shift in a downlink control information (DCI) format; and

generate, for transmission, enhanced DMRS with DMRS symbols in a plurality of DMRS positions of a subframe for a physical uplink shared channel (PUSCH) transmission, wherein K is a positive integer greater than two.

The apparatus of claim 1, wherein the one or more processors are further configured to process an indication, received from the eNB, to use the enhanced DMRS for channel estimation with the UE operating in the enhanced coverage mode for the MTC, wherein the enhanced DMRS is represented in a downlink as a total number of DMRS resource elements (RE) greater than 24 for each antenna port and the enhanced DMRS is represented in an uplink as a total number of symbols greater than 2.

The apparatus of claim 1 , wherein the one or more processors are further configured to generate the enhanced DMRS in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of a first slot of the subframe of a reference signal (RS) or a first OFDM symbol of a second slot of the subframe the RS.

4. The apparatus of claim 1 or 3, wherein the one or more processors are further configured to:

generate two of the enhanced DMRS either in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of each slot of a subframe of a reference signal (RS) or in a first OFDM symbol of each slot of the subframe the RS; and generate two alternative enhanced DMRS either in OFDM symbol #1 and OFDM symbol #5 for each slot of the subframe of the RS or OFDM symbol #2 and OFDM symbol #4 for each slot of the subframe of the RS.

5. The apparatus of claim 4, wherein the one or more processors are further configured to apply an identical OCC for the two alternative DMRS and an existing DMRS within a same slot of the subframe of the RS.

6. The apparatus of claim 1 or 5, wherein the one or more processors are further configured to apply one of a plurality of orthogonal sequences for the OCC on the enhanced DMRS, wherein the plurality of orthogonal sequences include at least a discrete Fourier transformation (DFT code) a Walsh-Hadamard sequence.

7. The apparatus of claim 6, wherein the one or more processors are further configured to apply a lehgth-3 DFT code or a length-4 Walsh-Hadamard sequence for the OCC on the enhanced DMRS.

8. The apparatus of claim 1 or 7, wherein the one or more processors are further configured to generate patterns of the cyclic shift hopping and the group hopping based on a slot of a subframe of a reference signal (RS) or an enhanced DMRS symbol index.

9. The apparatus of claim 1 , wherein the one or more processors are further configured to use the enhanced DMRS for PUSCH transmission when a coverage extension level exceeds a predetermined level.

10. The apparatus of claim 1 or 9, wherein the one or more processors are further configured to process a notification received from an evolved node B (eNB) to use the enhanced DMRS for PUSCH transmission by the eNB via UE-specific dedicated radio resource control (RRC) signaling.

1 1. The apparatus of claim 1 or 10, wherein the one or more processors are further configured to process a notification to use the enhanced DMRS in an uplink related DCI format in an explicit signal or implicit signal.

12. The apparatus of claim 1 , wherein the apparatus includes at least one of an antenna, a touch sensitive display screen, a speaker, a microphone, a graphics processor, an application processor, a baseband processor, an internal memory, a non-volatile memory port, and combinations thereof.

13. An apparatus of a user equipment (UE), the UE configured to perform

downlink reception, the apparatus comprising one or more processors and memory configured to:

process a first reference signal (RS) for a first antenna port (AP) and a second RS for a second AP;

perform a channel estimation from the first AP and the second AP by assuming the first AP and the second AP are a same AP; and

use the first RS and the second RS for demodulation reference signal (DMRS) of an enhanced physical downlink control channel (EPDCCH) or for a UE-specific RS of physical downlink shared channel (PDSCH).

14. The apparatus of claim 13, wherein the one or more processors and memory are further configured to infer a channel over which an Orthogonal Frequency Division Multiplexing (OFDM) symbol on the first AP is conveyed from a channel over which an alternative OFDM symbol on the second AP is conveyed.

15. An apparatus of a user equipment (UE), the UE configured to perform downlink reception, the apparatus comprising one or more processors and memory configured to:

process a first reference signal (RS) for a first antenna port (AP) on a resource element (RE) placed in an Orthogonal Frequency Division

Multiplexing (OFDM) symbol for a second RS for a second AP, wherein the first AP is processed from a code division multiplexing (CDM) group and the second AP is processed from an alternative CDM group; and

use a enhanced demodulation reference signals (DMRS) structure of an enhanced physical downlink control channel (EPDCCH) transmission or a physical downlink shared channel (PDSCH) transmission.

16. The apparatus of claim 15, wherein the one or more processors and memory are further configured to:

use an orthogonal code cover (OCC) mapping for the first AP that is identical to the second AP;

allow an enhanced node B (eNB) to use the enhanced DMRS structure of the UE operating in an enhanced coverage mode for machine type communication (MTC);

use a enhanced demodulation reference signals (DMRS) structure of an enhanced physical downlink control channel (EPDCCH) transmission or a physical downlink shared channel (PDSCH) transmission when a coverage extension level exceeds a predetermined level;

process a signal, received from an enhanced node B (eNB), by a UE- specific dedicated radio resource control signaling to use a enhanced

demodulation reference signals (DMRS); or

process a signal, received from an enhanced node B (eNB), either explicitly or implicitly in a downlink control information (DCI) format to use a enhanced demodulation reference signals (DMRS).

17. The apparatus of claim 1 or 16, wherein the one or more processors and memory are further configured to map an orthogonal code cover (OCC) mapping with mirror imaging for each group of adjacent OFDM symbol pairs in a frequency direction for a code division multiplexing (CDM).

18. The apparatus of claim 15, wherein the one or more processors and memory are further configured to use an orthogonal code cover (OCC) mapping for the first AP with an offset to the second AP.

19. The apparatus of claim 15 or 18, wherein the one or more processors and memory are further configured to reverse an orthogonal code cover (OCC) mapping from the orthogonal code vector.

20. An apparatus of an evolved node B (eNB), the apparatus comprising one or more processors and memory configured to:

process an indication, for transmission to a user equipment (UE), to indicate to the UE to use an enhanced demodulation reference signals (DMRS) structure of the UE operating in an enhanced coverage mode for machine type communication (MTC) to enable the UE to determine a cyclic shift (CS) and orthogonal cover code (OCC) for the enhanced DMRS by using a mapping rule for a 3-bit cyclic shift in a downlink control information (DCI) format; and

process the enhanced DMRS, received from the UE, having K DMRS symbols in a plurality of DMRS positions of a subframe for a physical uplink shared channel (PUSCH) transmission, wherein is a positive integer greater than two.

21. The apparatus of claim 20, wherein the one or more processors are further configured to process an indication, for transmission to the UE, to use the enhanced DMRS for channel estimation with the UE operating in the enhanced coverage mode for the MTC, wherein the enhanced DMRS is represented in a downlink as a total number of DMRS greater than 24 for each antenna port and the enhanced DMRS is represented in an uplink as a total number of symbols greater than 2.

22. The apparatus of claim 20 or 21 , wherein the one or more processors are further configured to process the enhanced DMRS, received from the UE, in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of a first slot of the subframe of a reference signal (RS) or a first OFDM symbol of a second slot of the subframe the RS.

23. The apparatus of claim 20, wherein the one or more processors are further configured to:

process two of the enhanced DMRS, received from the UE, either in a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of each slot of a subframe of a reference signal (RS) or in a first OFDM symbol of each slot of the subframe the RS; or

process two alternative enhanced DMRS, received from the UE, either in OFDM symbol # 1 and OFDM symbol #5 for each slot of the subframe of the RS or OFDM symbol #2 and OFDM symbol #4 for each slot of the subframe of the RS.