WO2013186660A1

WO2013186660A1 - Method and apparatus for communication using a scrambling scheme and a|reference signal depending both on a selected modulation type

Info

Publication number: WO2013186660A1
Application number: PCT/IB2013/054471
Authority: WO
Inventors: Karl LAMPINEN; Tommi Koivisto; Mihai Enescu; Timo Roman; Maja LONCAR; Lars Christensen; Soeren Christensen
Original assignee: Renesas Mobile Corporation
Priority date: 2012-05-31
Filing date: 2013-05-30
Publication date: 2013-12-19
Also published as: GB2502605A; GB201209744D0

Abstract

A method, apparatus and computer program product are provided for reference symbol sequence allocation. In this regard, a method is provided that comprises determining a modulation type used in a transmission of received data. In some example embodiments, the modulation type includes at least one of real valued modulation or complex valued modulation. The method of this embodiment may also include determining a scrambling sequence and demodulation reference signal sequence for use in processing of the received data based on the modulation type used in the transmission of the received data. The method of this embodiment may also include determining a channel estimate based on the demodulation reference signal sequence and descrambling the received data.

Description

METHOD AND APPARATUS FOR COMMUNICATION USING A SCRAMBLING SCHEME

AND A REFERENCE SIGNAL DEPENDING BOTH ON A SELECTED MODULATION TYPE

Technical Field

Embodiments of the present invention relate generally to communications technology and, more particularly, to example reference symbol sequence allocation

Background

Increasing network density is a trend in both network deployments and third Generation Partnership Project (3GPP) standardization efforts. The main driver for the need for increased network density includes the ever increasing communications device density and the increasing need for networks to provide better coverage and capacity. In some examples, increasing the network density through the addition of macro sites or small cells (e.g. in the context of heterogeneous network deployments) may lead to increased interference conditions and thus may result in the degradation in the quality of service.

Methods to address interference on the transmitter side, for example, include but are not limited to, coordinated multi-point -type of transmissions (CoMP). CoMP, for example, may be used to improve cell edge performance by turning interference into useful signals. Interference may also be addressed at the receiver end, for example, 3 GPP Release 11 is to include performance requirements for receivers based on linear minimum mean square error (LMMSE) estimator, also known as interference rejection combining (IRC) algorithm. Other type of receivers such as maximum likelihood (ML) detection can also take into account the interference structure. By way of a further example, 3GPP standardization may also describe, for example, single antenna interference cancellation (SAIC). The principle in SAIC, for example, is to transmit binary phase shift keying (BPSK) signals and decode these using an IQ-split receiver, hence enabling improved interference suppression. In some examples, the interference covariance information needed in an interference suppression receiver may be estimated from, for example, reference signal positions. Another method may include, subtracting the serving cell reference signal contribution from the received signal in the reference signal positions and then calculating the sample set covariance from the residual signal.

Summary

According to the invention, there is provided the method of claim 1.

Advantageously, for example, the use of real valued modulation may lead to improved interference mitigation and signal to interference and noise ratio conditions.

According to the invention, there is also provided the apparatus of claim 15. According to the invention, there is also provided the computer readable medium o f claim 30.

According to the invention, there is also provided the method of claim 31. According to the invention, there is also provided the apparatus of claim 38. According to the invention, there is also provided the computer readable medium of claim 46.

Brief Description of the Drawings

Having thus described the example embodiments of the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

Figure 1 is a schematic representation of a system having a communication device that may be configured for reference symbol sequence allocation and that may benefit from example embodiments of the present invention;

Figure 2 is a block diagram of an apparatus that may be embodied by a communication device and/or an access point in accordance with some example embodiments of the present invention;

Figure 3 is a flow chart illustrating operations performed by an example receiver in accordance with some example embodiments of the present invention; and

Figure 4 is a flow chart illustrating operations performed by an example transmitter in accordance with some example embodiments of the present invention. Detailed Description

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

As used in this application, the term "circuitry" refers to all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) to combinations of circuits and software (and/or firmware), such as (as applicable): (i) to a combination of processor(s) or (ii) to portions ofprocessor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) to circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.

This definition of "circuitry" applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term "circuitry" would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term "circuitry" would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or application specific integrated circuit for a mobile phone or a similar integrated circuit in server, a cellular network device, or other network device.

In some examples, long term evolution (LTE) specifications are configured to support complex valued constellations, such as M-quadrature amplitude modulation (M-QAM) or the like. Thus in some examples, a communication device that is equipped with 2 receive (Rx) antennas may be configured, for example, to efficiently mitigate inter-cell interference from one rank 1 complex-valued interferer signal provided the desired transmission is rank 1 complex-valued as well. However, a real valued modulation (e.g. M- level pulse amplitude modulation M-PAM) transmission may further enable the ability to increase the degrees of freedom in the receiver as the intended transmission would be configured to occupy one dimension out of four available (2 in phase (I)/quadrature (Q) branches * 2 receive (Rx) antennas). Alternatively or additionally, communication devices having a single Rx chain may also be configured, for example, to utilize real valued modulation. Real valued modulation may be configured, in some example embodiments, to enable rank 1 desired signal reception and rank 1 inter-cell interference mitigation. In a system configured to operate using complex valued modulations, a single Rx chain communication device may not be capable of efficient interference suppression. In an instance in which real valued modulations are utilized in an example system, a single Rx chain communication device may have the capability to receive a real value modulated signal and may also be configured to cancel or suppress a real valued modulated interferer.

In some example embodiments, real valued modulations may be used to adjust for and/or handle interference. For example, real valued modulations may be configured to enable degrees of freedom for receivers such as LMMSE-IRC. By way of further example and in an example LTE context, real valued modulations may be configured to enable a receiver, such as a communication device, access point and/or the like, to suppress interference from multiple interfering devices. Alternatively or additionally and in an example comprising an in-phase/quadrature (I/Q) -split receiver, a real valued transmitted signal may also be configured to be reflected in a covariance matrix of the interference constructed or estimated at the receiver side. The covariance matrix may be estimated, for example, using received real valued symbols (RS).

In further examples, a received complex signal may, for example, be represented by:

r' = H'₀x'₀ + n' (1)

Where, for example, r' represents a received signal on a sub-carrier, H', represents a spatial channel matrix on a sub-carrier for a cell i, n' represents other cell interference and noise on a sub-carrier, and Xi' represents transmitted signals on a sub- carrier for cell i. From the complex valued domain as in (1), for example, an example equivalent signal model can be expanded based on real and imaginary parts as follows:

⁼ [H_Q°₀ H ] [XQ°₀] ⁺ [n_Q' ] &

Where, for example, subscripts I and Q refer to real and imaginary signal components, respectively. In some example embodiments, a real-valued covariance matrix of a transmitted signal may assume that modulated I/Q signal branches are independent in a complex constellation:

In other examples the modulated signal may be modulated over the I branch with real-valued modulation (e.g. assuming that transmit power of the system is normalized to 1.0), the real valued covariance may include:

Γ1.0 01

C χχ,ϊ,ΡΑΜ 1 y. Q (4)

0 Q oJ

The covariance matrix of the interference is expressed, in some examples, as:

Γ _ y^Ncell

Where σ% refers to the additive white gaussian noise (AWGN) variance and / refers to the identity matrix.

In some examples, real or complex valued modulation may be also reflected in the interference due to the C_{xx i} for each cell. Increased interference suppression gain may be achieved in an instance in which neighboring cells are allocated with real valued modulation which is reflected in the C_nn in (5). In some examples, the interference covariance term C_nn is formed by adding determined interference covariance 's from the interfering cells and other (thermal) interference of the system. Traditional LMMSE estimate of the transmitted symbols can be represented, for example, as:

An example of estimating transmitted real valued modulated symbols, such as a pulse amplitude modulation (PAM), may be expressed as:

[0001] An example maximum likelihood (ML) receiver may also be constructed based on the real valued signal model as shown with reference to equation (2). In this receiver algorithm, for example, conditional probability may be maximized. This algorithm may also contain the information on the structure of the interference, i.e. C_nn, and can be used to suppress interference. The use of real or complex valued modulation in the neighboring cells is reflected in the C_nn.

Since interference is estimated, for example, from the reference symbol locations at the communications device, the estimated interference characteristics at reference symbol locations are configured to be equal to the interference characteristics of the locations of the interfering data. For example, in the case of communication device specific reference signal, such as a demodulation reference signal (DM-RS), reference symbols occupy the same positions over the time- frequency grid regardless of the cell identification or other parameters. Therefore, by way of example and as described in example embodiments herein, in order to capture correct interference characteristics for interference covariance estimation in an instance in which real-valued modulations are used for interfering PDSCH, corresponding reference symbols, such as DM-RS, are configured to be real-valued. In some example embodiments herein, real valued sequence generation for communication device specific reference signal (e.g. UE-specific reference signal as is described in 3GPP TS 36.21 1 which is incorporated by reference herein) is configured for capturing interference characteristics which are mitigated at the communication device, such as through LMMSE-IRC processing. Alternatively or additionally and by way of example, real- valued RS may be achieved using complex- valued modulation between constellation points that lie on a straight (ID) line in the constellation diagram.

In some example embodiments described herein, an RS sequence allocation and physical downlink shared channel (PDSCH) scrambling may be configured to, for example, enable efficient operation of an I/Q-split receiver. In some examples, the method, apparatus and computer program product may be further configured for use, for example, in LTE downlink by a receiver, but may also be used for uplink in an instance in which the receiver is an access point and the interference is coming from other communication devices (e.g. within other cells) as well as for other network elements that are configured to operate as a receiver. Alternatively or additionally, the method, apparatus and computer program product described herein may, for example, be used in device-to-device (D2D) communications where the receiver is a communication device and the interference may be generated by other communication devices, scenarios with downlink (DL) - uplink (UL), interference, UL-DL interference, for example in time division duplex (TDD) scenarios where different transmit direction is used in different cells, and/or the like.

Although the method, apparatus and computer program product as described herein may be implemented in a variety of different systems, one example of such a system is shown in Figure 1 , which includes a communication device (e.g., communication device 10) that is capable of communication via an access point 12, such as a base station, a macro cell, a Node B, an eNB, a coordination unit, a macro base station or other access point, with a network 14 (e.g., a core network). While the network may be configured in accordance with LTE or LTE -Advanced (LTE-A ), other networks may support the method, apparatus and computer program product of embodiments of the present invention including those configured in accordance with wideband code division multiple access (W-CDMA™), CDMA2000, global system for mobile communications (GSM™), general packet radio service (GPRS™), IEEE™ 802.1 1 standard for wireless fidelity (WiFi), wireless local access network (WLAN™) Worldwide Interoperability for Microwave Access (WiMAX™) protocols, and/or the like.

The network 14 may include a collection of various different nodes, devices or functions that may be in communication with each other via corresponding wired and/or wireless interfaces. For example, the network may include one or more cells, including access point 12 and which may serve a respective coverage area. The access point 12 may be, for example, part of one or more cellular or mobile networks or public land mobile networks (PLMNs). In turn, other devices such as processing devices (e.g., personal computers, server computers or the like) may be coupled to the communication device 10 and/or other communication devices via the network.

A communication device, such as the communication device 10 (also known as user equipment (UE), a mobile terminal or the like), may be in communication with other communication devices or other devices via the access point 12 and, in turn, the network 14. In some cases, the communication device 10 may include an antenna or a plurality of antennas for transmitting signals to and for receiving signals from an access point 12. As is described herein the communication device 10 and/or the access point 12 may take the form of a transmitter and/or receiver.

In some example embodiments, the communication device 10 may be a mobile communication device such as, for example, a mobile telephone, portable digital assistant (PDA), pager, laptop computer, STA, or any of numerous other hand held or portable communication devices, computation devices, content generation devices, content consumption devices, or combinations thereof. Other such devices that are configured to connect to the network include, but are not limited to a refrigerator, a security system, a home lighting system, and/or the like. As such, the communication device 10 may include one or more processors that may define processing circuitry and a processing system, either alone or in combination with one or more memories. The processing circuitry may utilize instructions stored in the memory to cause the communication device 10 to operate in a particular way or execute specific functionality when the instructions are executed by the one or more processors. The communication device 10 may also include communication circuitry and corresponding hardware/software to enable communication with other devices and/or the network 14.

In some example embodiments, an access point 12 may function as the transmitter and a communication device 10 may function as the receiver. However, it may be envisioned that either the access point 12 or the communication device 10 may function as the transmitter and either the access point 12 or the communication device 10 may function as the receiver. As such the terms as used herein may be used interchangeably to apply to the identified devices operating a network.

In one embodiment, for example, the communication device 10 and/or the access point 12 may be embodied as or otherwise include an apparatus 20 as generically represented by the block diagram of Figure 2. While the apparatus 20 may be employed, for example, by a communication device 10 or an access point 12, it should be noted that the components, devices or elements described below may not be mandatory and thus some may be omitted in certain embodiments. Additionally, some embodiments may include further or different components, devices or elements beyond those shown and described herein.

As shown in Figure 2, the apparatus 20 may include or otherwise be in communication with processing circuitry 22 that is configurable to perform actions in accordance with example embodiments described herein. The processing circuitry may be configured to perform data processing, application execution and/or other processing and management services according to an example embodiment of the present invention. In some embodiments, the apparatus or the processing circuitry may be embodied as a chip or chip set. In other words, the apparatus or the processing circuitry may comprise one or more physical packages (e.g., chips) including materials, components and/or wires on a structural assembly (e.g., a baseboard). The structural assembly may provide physical strength, conservation of size, and/or limitation of electrical interaction for component circuitry included thereon. The apparatus or the processing circuitry may therefore, in some cases, be configured to implement an embodiment of the present invention on a single chip or as a single "system on a chip." As such, in some cases, a chip or chipset may constitute means for performing one or more operations for providing the functionalities described herein.

In an example embodiment, the processing circuitry 22 may include a processor 24 and memory 28 that may be in communication with or otherwise control a communication interface 26 and, in some cases, a user interface 29. As such, the processing circuitry may be embodied as a circuit chip (e.g., an integrated circuit chip) configured (e.g., with hardware, software or a combination of hardware and software) to perform operations described herein. However, in some embodiments taken in the context of the communication device 10, the processing circuitry may be embodied as a portion of a mobile computing device or other mobile terminal.

The user interface 29 (if implemented) may be in communication with the processing circuitry 22 to receive an indication of a user input at the user interface and/or to provide an audible, visual, mechanical or other output to the user. As such, the user interface may include, for example, a keyboard, a mouse, a trackball, a display, a touch screen, a microphone, a speaker, and/or other input/output mechanisms. The apparatus 20 need not always include a user interface. For example, in instances in which the apparatus is embodied as an access point 12, the apparatus may not include a user interface. As such, the user interface is shown in dashed lines in Figure 2.

The communication interface 26 may include one or more interface mechanisms for enabling communication with other devices and/or networks. In some cases, the communication interface may be any means such as a device or circuitry embodied in either hardware, or a combination of hardware and software that is configured to receive and/or transmit data from/to a network 14 and/or any other device or module in communication with the processing circuitry 22, such as between the communication device 10 and the access point 12. In this regard, the communication interface may include, for example, an antenna (or multiple antennas) and supporting hardware and/or software for enabling communications with a wireless communication network and/or a communication modem or other hardware/software for supporting communication via cable, digital subscriber line (DSL), universal serial bus (USB), Ethernet or other methods.

In an example embodiment, the memory 28 may include one or more non- transitory memory devices such as, for example, volatile and/or non-volatile memory that may be either fixed or removable. The memory may be configured to store information, data, applications, instructions or the like for enabling the apparatus 20 to carry out various functions in accordance with example embodiments of the present invention. For example, the memory could be configured to buffer input data for processing by the processor 24. Additionally or alternatively, the memory could be configured to store instructions for execution by the processor. As yet another alternative, the memory may include one of a plurality of databases that may store a variety of files, contents or data sets. Among the contents of the memory, applications may be stored for execution by the processor in order to carry out the functionality associated with each respective application. In some cases, the memory may be in communication with the processor via a bus for passing information among components of the apparatus.

The processor 24 may be embodied in a number of different ways. For example, the processor may be embodied as various processing means such as one or more of a microprocessor or other processing element, a coprocessor, a controller or various other computing or processing devices including integrated circuits such as, for example, an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), or the like. In an example embodiment, the processor may be configured to execute instructions stored in the memory 28 or otherwise accessible to the processor. As such, whether configured by hardware or by a combination of hardware and software, the processor may represent an entity (e.g., physically embodied in circuitry - in the form of processing circuitry 22) capable of performing operations according to embodiments of the present invention while configured accordingly. Thus, for example, when the processor is embodied as an ASIC, FPGA or the like, the processor may be specifically configured hardware for conducting the operations described herein. Alternatively, as another example, when the processor is embodied as an executor of software instructions, the instructions may specifically configure the processor to perform the operations described herein. In some example embodiments, a transmitter, such as access point 12, may select a modulation type for a transmission of data. In other embodiments, the modulation type may be provided by a network, may be signaled by another network entity and/or the like. The scheduled modulation type may be signaled or otherwise provided by the transmitter to a receiver, such as a communication device 10. For example, an access point 12 may provide an indication of the modulation type in the downlink control information (DCI).

Multiple modulation types may be selected by the transmitter, such as access point 12, the modulation types comprising at least one of real valued and complex valued modulation. In instances in which the scheduled modulation is a real valued modulation, such as PAM, the real valued modulation is indicated in the DCI as the modulation and coding scheme (MCS). For example, the DCI is configured to contain one field on the MCS and in cases of dual codeword transmission, the DCI may be configured to contain two MCS fields or alternatively a first MCS field for a first transport block or codeword and a differential MCS field for a second transport block or codeword wherein said differential MCS field is relative the first MCS field. In some example embodiments, the DCI containing the indication of the used MCS may be transmitted either on the physical downlink control channel (PDCCH) or on the enhanced physical downlink control channel (ePDCCH).

In some example embodiments, the access point 12, may be configured, such as by the processing circuitry 22, the processor 24, the communication interface 26 or the like to schedule real valued data modulation and/or complex valued data modulation. In an instance in which real valued data modulation is scheduled on the physical downlink shared channel (PDSCH), the access point 12 or other transmitter, such as by the processing circuitry 22, the processor 24, the communication interface 26 or the like, causes real valued symbols to be transmitted in designated positions on a resource element grid. In some example embodiments, the reference symbols may be communication device specific reference signals (e.g. UE-specific reference signals). The transmitter, such as access point 12, is further configured, such as by the processing circuitry 22, the processor 24, the communication interface 26 or the like, to use real valued scrambling to scramble the data (e.g. scrambling of coded bits in each of the code words to be transmitted on the physical channel may result to real valued scrambling. Alternatively or additionally, real valued scrambling code symbols may be used to multiply the modulated symbols). The scrambled data is then modulated to create real valued modulation symbols, the real valued modulation symbols being mapped onto one or more transmission layers, such as by the processing circuitry 22, the processor 24. In an instance in which precoded reference symbols are used, the real valued symbols are precoded, such as the by the access point 12, transmitter or the like. Alternatively or additionally, precoding may be performed with either real value or complex valued precoding weights. The transmitter, such as access point 12, then causes the data to be transmitted, such as via the communication interface 26.

Alternatively or additionally, in an instance in which complex valued data modulation is scheduled, the access point 12 or other transmitter, such as by the processing circuitry 22, the processor 24, the communication interface 26 or the like, causes complex valued symbols to be transmitted in designated positions on a resource element grid in a transmission of data. In some example embodiments, the reference symbols may be communication device specific reference signals (e.g. UE- specific reference signal). The transmitter, such as the access point 12, is further configured, such as by the processing circuitry 22, the processor 24, the communication interface 26 or the like, to use complex valued scrambling to scramble the data. The scrambled data is then modulated to create complex valued modulation symbols, the complex valued modulation symbols being mapped onto one or more transmission layers, such as by the processing circuitry 22, the processor 24,. In an instance in which precoded reference symbols are used, the complex valued symbols are precoded, such as the by the access point 12, transmitter or the like. The transmitter, such as access point 12, then causes the data to be transmitted, such as via the communication interface 26.

In some example embodiments, the receiver, such as communication device 10, is configured to determine the scheduled modulation type, such as by the processing circuitry 22, the processor 24, the communication interface 26 or the like. In some example embodiments, the scheduled modulation type is indicated in the DCI. Based on the scheduled modulation type, the receiver determines a scrambling sequence and a demodulation reference symbol sequence, such as a DM-RS sequence. For example a real valued scrambling sequence and a real valued DM-RS sequence are used for descrambling and demodulation in an instance in with real valued modulation is the scheduled modulation type. In an instance in which precoding is applied to data symbols, the associated DM-RS may be configured to undergo the same precoding operation as the data symbols. The receiver, such as the communication device 10, is configured to perform DM-RS channel estimate and descrambling of PDSCH data, such as by the processing circuitry 22, the processor 24, or the like.

In some example embodiments, the communications device 10, the receiver, or the like is configured to determine, such as via the DCI, that real valued modulation type is used for transmission of the data. As such, real valued symbols, such as DM- RS, are configured to be used for determining, such as by the processing circuitry 22, the processor 24, or the like, channel estimate and interference covariance based on the real valued symbols. Furthermore, the scrambling sequence for PDSCH data and DM-RS are determined to be real valued. One example of real valued symbol scrambling sequence r _n (m) may be defined by:

Where the example pseudo-random sequence c(i) is defined by a length-31 Gold sequence, in some examples. The pseudo-random sequence generator may be for instance initialized with c_Mt =

/2j + l) - (2 + l)- 2¹⁶ + ¾_CID at the start of each subframe where X is configured by higher layers or dynamically signaled with additional bits of DCI format and nsci_D ⁼{0,l}. Above, n_s is the slot number within a radio frame.

In some example embodiments, the communications device 10, the receiver, or the like is configured to determine, such as the DCI, that a complex valued modulation type is used for transmission of the data. As such, complex valued symbols are configured to be used, and the scrambling sequence for PDSCH data and DM-RS are determined to be complex valued. As such, the receiver, such as the communications device 10 is configured to determine a channel modulation and/or an interference covariance matrix for demodulation based on the complex valued symbols. Alternatively or additionally, in some examples, complex valued modulation may be backwards compatible.

Alternatively or additionally, in an instance in which the receiver, such as the communication device 10, is configured with a suppression receiver, such as LMMSE or ML, the receiver is configured to estimate, such as by the processing circuitry 22, the processor 24, or the like an interference covariance matrix, such as, for example, as calculated in equation (5).

In some example embodiments, the scrambling and the modulation symbol set are similar for the received data as well as the DM-RS reference symbols. As such the data and RS resource elements may have similar covariance characteristics. Therefore the PDSCH interference may be determined based on the reference symbols, such as by the processing circuitry 22, the processor 24 or the like. Alternatively or additionally, in an instance in which neighboring cells are utilizing real or complex valued modulation, the modulation type may be determined in the covariance estimate by the communication device 10, the receiver or the like, thus, for example, enabling efficient interference suppression with covariance information.

Alternatively or additionally, real valued modulation and real valued scrambling may be applied to any physical channel and its associated DM-RS. By way of example, physical channels include but are not limited to PDSCH and/or ePDCCH. In some examples, the systems and methods described with respect to the PDSCH may apply to the ePDCCH. In ePDCCH, the receiver, such as the communication device 10, may determine modulation type via blind detection of the ePDCCH using different modulations. Alternatively or additionally, modulation type may be configured via higher layers, such as radio resource control signaling to the receiver. In some example embodiments, real-valued modulation via the ePDCCH is configured to include real-valued RS scrambling. For example, the scrambling sequence is determined based on the modulation type.

Figures 3 and 4 illustrate example operations performed by a method, apparatus and computer program product, such as apparatus 20 of Figure 2 in accordance with one embodiment of the present invention. It will be understood that each block of the flowcharts, and combinations of blocks in the flowcharts, may be implemented by various means, such as hardware, firmware, processor, circuitry and/or other device associated with execution of software including one or more computer program instructions. For example, one or more of the procedures described herein may be embodied by computer program instructions. In this regard, the computer program instructions which embody the procedures described herein may be stored by a memory 28 of an apparatus employing an embodiment of the present invention and executed by a processor 24 in the apparatus. As will be appreciated, any such computer program instructions may be loaded onto a computer or other programmable apparatus (e.g., hardware) to produce a machine, such that the resulting computer or other programmable apparatus provides for implementation of the functions specified in the flowcharts' block(s). These computer program instructions may also be stored in a non-transitory computer-readable storage memory that may direct a computer or other programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable storage memory produce an article of manufacture, the execution of which implements the function specified in the flowcharts' block(s). The computer program instructions may also be loaded onto a computer or other programmable apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to produce a computer- implemented process such that the instructions which execute on the computer or other programmable apparatus provide operations for implementing the functions specified in the flowcharts' block(s). As such, the operations of Figures 3 and 4, when executed, convert a computer or processing circuitry into a particular machine configured to perform an example embodiment of the present invention. Accordingly, the operations of Figures 3 and 4 define an algorithm for configuring a computer or processing circuitry 22, e.g., processor, to perform an example embodiment. In some cases, a general purpose computer may be provided with an instance of the processor which performs the algorithm of Figures 3 and 4 to transform the general purpose computer into a particular machine configured to perform an example embodiment.

Accordingly, blocks of the flowcharts support combinations of means for performing the specified functions and combinations of operations for performing the specified functions. It will also be understood that one or more blocks of the flowchart, and combinations of blocks in the flowcharts, can be implemented by special purpose hardware-based computer systems which perform the specified functions, or combinations of special purpose hardware and computer instructions.

In some embodiments, certain ones of the operations herein may be modified or further amplified as described below. Moreover, in some embodiments additional optional operations may also be included. It should be appreciated that each of the modifications, optional additions or amplifications below may be included with the operations herein either alone or in combination with any others among the features described herein.

Figure 3 is a flow chart illustrating operations performed by an example receiver, such as communications device 10, in accordance with some example embodiments of the present invention. As is shown with respect to decision operation 302, the apparatus 20 embodied, for example, by a receiver such as the communications device 10, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for determining a modulation type used in a transmission of received data. In some example embodiments, the modulation type may be a real valued modulation type or a complex valued modulation type. In some example embodiments, a scrambling sequence and demodulation reference signal sequence is determined for use in processing of the received data based on the modulation type determined with respect to decision operation 302. A channel estimate and an interference co variance matrix for demodulation may be also be determined, such as the processing circuitry 22, the processor 24 or the like, based at least in part on the reference symbols included in the transmission and in some example embodiments. The received data may then be descrambled and decoded.

In an instance in which a real valued modulation type is determined in decision operation 302, then as is shown with respect to operation 304, the apparatus 20 embodied, for example, by a receiver such as the communications device 10, may include means, such as the processing circuitry 22, the processor 24, or the like, for determining that real valued symbols are used in the scrambling sequence and the demodulation reference signal sequence. As is shown with respect to operation 306, the apparatus 20 embodied, for example, by a receiver such as the communications device 10, may include means, such as the processing circuitry 22, the processor 24, or the like, for determining a channel estimate based on the real valued symbols. As is shown with respect to operation 308, the apparatus 20 embodied, for example, by a receiver such as the communications device 10, may include means, such as the processing circuitry 22, the processor 24, or the like, for determining an interference covariance based on the real valued symbols.

As is shown with respect to operation 310, the apparatus 20 embodied, for example, by a receiver such as the communications device 10, may include means, such as the processing circuitry 22, the processor 24, or the like, for descrambling the received data based on a real valued scrambling sequence. As is shown with respect to operation 312, the apparatus 20 embodied, for example, by a receiver such as the communications device 10, may include means, such as the processing circuitry 22, the processor 24, or the like, for demodulated and decoding the received data.

In an instance in which a complex valued modulation type is determined in decision operation 302, then as is shown with respect to operation 314, the apparatus 20 embodied, for example, by a receiver such as the communications device 10, may include means, such as the processing circuitry 22, the processor 24, or the like, for determining that complex valued symbols are used in the scrambling sequence and the demodulation reference signal sequence. As is shown with respect to operation 316, the apparatus 20 embodied, for example, by a receiver such as the communications device 10, may include means, such as the processing circuitry 22, the processor 24, or the like, for determining a channel estimate based on the complex valued symbols. As is shown with respect to operation 318, the apparatus 20 embodied, for example, by a receiver such as the communications device 10, may include means, such as the processing circuitry 22, the processor 24, or the like, for determining an interference covariance based on the complex valued symbols.

As is shown with respect to operation 320, the apparatus 20 embodied, for example, by a receiver such as the communications device 10, may include means, such as the processing circuitry 22, the processor 24, or the like, for descrambling the received data based on a complex valued scrambling sequence. As is shown with respect to operation 322, the apparatus 20 embodied, for example, by a receiver such as the communications device 10, may include means, such as the processing circuitry 22, the processor 24, or the like, for demodulated and decoding the received data. Figure 4 is a flow chart illustrating operations performed by an example transmitter, such as access point 12, in accordance with some example embodiments of the present invention. As is shown with respect to decision operation 402, the apparatus 20 embodied, for example, by a transmitter such as the access point 12, may include means, such as the processing circuitry 22, the processor 24 or the like, for determining a scheduled modulation type for a transmission of data. In some example embodiments, the transmitter may be configured to determine a modulation type, in other example embodiments, the network, another network entity, or the like may determine a modulation type. In some example embodiments, a scrambling sequence may be determined based on the scheduled modulation type. The one or more reference symbols may be caused to be transmitted in designated positions on a resource element grid. In some example embodiments, the one or more reference symbols are modulated based on the scheduled modulation type in decision operation 402.

In an instance in which, a real valued modulation type is scheduled at decision operation 402, then as is shown with respect to operation 404, the apparatus 20 embodied, for example, by a transmitter such as the access point 12, may include means, such as the processing circuitry 22, the processor 24 or the like, for causing the reference symbols to be real valued symbols. As is shown with respect to operation 406, the apparatus 20 embodied, for example, by a transmitter such as the access point 12, may include means, such as the processing circuitry 22, the processor 24 or the like, for causing the data to be scrambled using real valued scrambling. As is shown with respect to operation 408, the apparatus 20 embodied, for example, by a transmitter such as the access point 12, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for causing the real valued symbols to be transmitted in designated positions on a resource element grid. As is shown with respect to operation 410, the apparatus 20 embodied, for example, by a transmitter such as the access point 12, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for causing precoding to be applied to the real valued symbols. In some example embodiments, the associated DM-RS is caused to undergo the same precoding applied to the real valued symbols. In an instance in which, a complex valued modulation type is scheduled at decision operation 402, then as is shown with respect to operation 412, the apparatus 20 embodied, for example, by a transmitter such as the access point 12, may include means, such as the processing circuitry 22, the processor 24 or the like, for causing the reference symbols to be complex valued symbols. As is shown with respect to operation 414, the apparatus 20 embodied, for example, by a transmitter such as the access point 12, may include means, such as the processing circuitry 22, the processor 24 or the like, for causing the data to be scrambled using complex valued scrambling. As is shown with respect to operation 416, the apparatus 20 embodied, for example, by a transmitter such as the access point 12, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for causing the complex valued symbols to be transmitted in designated positions on a resource element grid. As is shown with respect to operation 418, the apparatus 20 embodied, for example, by a transmitter such as the access point 12, may include means, such as the processing circuitry 22, the processor 24, the communication interface 26 or the like, for causing precoding to be applied to the complex valued symbols. In some example embodiments, the associated DM-RS is caused to undergo the same precoding applied to the complex valued symbols.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A method comprising:

determining a modulation type used in a transmission of received data, the modulation type comprising at least one of real valued modulation or complex valued modulation;

determining a scrambling sequence and demodulation reference signal sequence for use in processing of the received data based on the modulation type used in the transmission of the received data;

determining a channel estimate based on the demodulation reference signal sequence; and

descrambling the received data.

2. A method according to Claim 1, further comprising:

determining that real valued modulation is the modulation type used in the transmission of the received data; and

determining a channel estimate based on real valued symbols.

3. A method according to Claim 2, wherein the real valued symbols are used in the scrambling sequence and the demodulation reference signal sequence.

4. A method according to any one of Claims 2 or 3, wherein the received data is descrambled based on a real valued scrambling sequence and decoded.

5. A method according to any one of Claims 2 to 4, wherein the received data is demodulated based on a real valued demodulation reference signal sequence.

6. A method according to any one of Claims 2 to 5, wherein the real valued modulations are used as transmitted symbols in the transmission of the received data.

7. A method according to any one of Claims 2 to 6, further comprising:

determining an interference covariance matrix for demodulation based on the real valued symbols.

8. A method according to Claim 1, further comprising:

determining that complex modulation is the modulation type used in the transmission of the received data; and

determining a channel estimate based on complex valued symbols.

9. A method according to Claim 8, wherein the complex valued symbols are used in the scrambling sequence and demodulation reference signal sequence

10. A method according to any one of Claims 8 or 9, wherein the received data is descrambled based on a complex valued scrambling sequence and decoded.

11. A method according to any one of Claims 8 to 10, wherein the received data is demodulated based on a complex valued demodulation reference signal sequence.

12. A method according to any one of Claims 8 to 11, further comprising:

determining an interference covariance matrix for demodulation based on the complex valued symbols.

13. A method according to any one of Claims 1 to 12, wherein the modulation type is indicated in the control information.

14. A method according to any one of Claims 1 to 13, wherein the reference symbols are communication device specific reference symbols.

15. An apparatus comprising:

a processing system arranged to cause the apparatus to at least:

determine a modulation type used in a transmission of received data, the modulation type comprising at least one of real valued modulation or complex valued modulation;

determine a scrambling sequence and demodulation reference signal sequence for use in processing of the received data based on the modulation type used in the transmission of the received data;

determine a channel estimate based on the demodulation reference signal sequence; and

descramble the received data.

16. An apparatus according to Claim 15, wherein the processing system is arranged to cause the apparatus to:

determine that real valued modulation is the modulation type used in the transmission of the received data; and

determine a channel estimate based on real valued symbols.

17. An apparatus according to Claim 16, wherein the real valued symbols are used in the scrambling sequence and the demodulation reference signal sequence.

18. An apparatus according to any one of Claims 16 or 17, wherein the received data is descrambled based on a real valued scrambling sequence and decoded.

19. An apparatus according to any one of Claims 16 to 18, wherein the received data is demodulated based on a real valued demodulation reference signal sequence.

20. An apparatus according to any one of Claims 16 to 19, wherein the real valued modulations are used as transmitted symbols in the transmission of the received data.

21. An apparatus according to any one of Claims 19 to 20, wherein the processing system is arranged to cause the apparatus to:

determine an interference covariance matrix for demodulation based on the real valued symbols.

22. An apparatus according to Claim 15, wherein the processing system is arranged to cause the apparatus to:

determine that complex modulation is the modulation type used in the transmission of the received data; and

determine a channel estimate based on complex valued symbols.

23. An apparatus according to Claim 22, wherein the complex valued symbols are used in the scrambling sequence and demodulation reference signal sequence.

24. An apparatus according to any one of Claims 22 or 23, wherein the received data is descrambled based on a complex valued scrambling sequence and decoded.

25. An apparatus according to any one of Claims 22 to 24, wherein the received data is demodulated based on a complex valued demodulation reference signal sequence.

26. An apparatus according to any one of Claims 22 to 25, wherein the processing system is arranged to cause the apparatus to:

determine an interference covariance matrix for demodulation based on the complex valued symbols.

27. An apparatus according to any one of Claims 15 to 26, wherein the modulation type is indicated in the control information.

28. An apparatus according to any one of Claims 15 to 27, wherein the reference symbols are communication device specific reference symbols.

29. An apparatus according to any one of Claims 15 to 28, wherein the apparatus comprises at least one of an access point, user equipment or a communications device.

30. A computer readable medium comprising a set of instructions, which, when executed on an apparatus causes the apparatus to perform the method of any of claims 1 to 14.

31. A method comprising:

determining a scheduled modulation type for a transmission of data, wherein the modulation type comprises a real valued modulation type or a complex valued modulation type;

determining a scrambling sequence based on the modulation type; and causing one or more reference symbols to be transmitted in designated positions on a resource element grid, the one or more reference symbols modulated based on the modulation type.

32. A method according to Claim 31 , further comprising:

determining that the modulation type is a real valued modulation type;

causing the one or more reference symbols to be real valued symbols; and causing the data to be scrambled using real valued scrambling.

33. A method according to Claim 31 , further comprising:

causing the real valued symbols to be precoded, in an instance in which precoded reference symbols are used.

34. A method according to Claim 31, further comprising:

determining that the modulation type is a complex valued modulation type; causing the one or more references symbols to be complex valued symbols; and

causing the data to be scrambled using complex valued scrambling.

35. A method according to Claim 34, further comprising:

causing the complex valued symbols to be precoded, in an instance in which precoded reference symbols are used.

36. A method according to any one of Claims 31 to 35, further comprising:

causing the modulation type to be indicated in control information.

37. A method according to any one of Claims 31 to 36, wherein the one or more reference symbols are communication device specific reference signals.

38. An apparatus comprising:

a processing system arranged to cause the apparatus to at least: determine a modulation type for a transmission of data, wherein the modulation type comprises a real valued modulation type or a complex valued modulation type;

determine a scrambling sequence based on the modulation type; and cause one or more reference symbols to be transmitted in designated positions on a resource element grid, the one or more reference symbols modulated based on the modulation type.

39. An apparatus according to Claim 38, wherein the processing system is arranged to cause the apparatus to:

determine that the modulation type is a real valued modulation type;

cause the one or more reference symbols to be real valued symbols; and cause the data to be scrambled using real valued scrambling.

40. An apparatus according to Claim 39, wherein the processing system is arranged to cause the apparatus to:

cause the real valued symbols to be precoded, in an instance in which precoded reference symbols are used.

41. An apparatus according to Claim 38, wherein the processing system is arranged to cause the apparatus to:

determine that the modulation type is a complex valued modulation type; cause the one or more references symbols to be complex valued symbols; and cause the data to be scrambled using complex valued scrambling.

42. An apparatus according to Claim 41, wherein the processing system is arranged to cause the apparatus to: cause the complex valued symbols to be precoded, in an instance in which precoded reference symbols are used.

43. An apparatus according to any one of Claims 40 to 42, wherein the processing system is arranged to cause the apparatus to:

cause the modulation type to be indicated in control information.

44. An apparatus according to any one of Claims 40 to 43, wherein the one or more reference symbols are communication device specific reference signals.

45. An apparatus according to any one of Claims 38 to 44, wherein the apparatus comprises at least one of an access point, user equipment or a communications device.

46. A computer readable medium comprising a set of instructions, which, when executed on an apparatus causes the apparatus to perform the method of any of claims

31 to 37.