WO2024133930A1

WO2024133930A1 - Papr reduction in ofdm uplink

Info

Publication number: WO2024133930A1
Application number: PCT/EP2023/087725
Authority: WO
Inventors: Martin Warwick Beale; Samuel Asangbeng Atungsiri; Shin Horng Wong
Original assignee: Sony Group Corporation; Sony Europe B.V.
Priority date: 2022-12-23
Filing date: 2023-12-22
Publication date: 2024-06-27

Abstract

Methods, communications devices, infrastructure equipment and circuitry are disclosed which allow for reduction of signal distortion in an OFDM waveform to be used for an uplink transmission. A first OFDM waveform is generated by a communications device using a first channel processing chain having a particular level of signal distortion. The communications device then generates a modified OFDM waveform by modifying the channel processing chain as compared to the first channel processing chain. The modifications to the channel processing chain result in the modified OFDM waveform having a level of signal distortion that is different to the first OFDM waveform. The modifications to the channel processing chain may be indicated by the communications device to the receiving base station, or the base station may transmit a set of possible (predetermined) modifications to the channel processing chain to the communications device.

Description

PAPR REDUCTION IN OFDM UPLINK

The present application claims the Paris Convention priority of European patent application EP22216462.6, filed 23 December 2022, the contents of which are hereby incorporated by reference.

BACKGROUND

Field of the Disclosure

The present disclosure relates to wireless telecommunications, apparatuses and methods.

Description of the Related Art

The “background” description provided is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in the background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present disclosure.

Recent generation mobile telecommunication systems, such as those based on the 3^rd Generation Partnership Project (3GPP (RTM)) defined Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE) and 5G New Radio (NR) architectures, are able to support a wider range of services than simple voice and messaging services offered by previous generations of mobile telecommunication systems. For example, with the improved radio interface and enhanced data rates provided by LTE and NR systems, a user can experience high data rate applications such as mobile video streaming and mobile video conferencing that would previously only have been available via a fixed line data connection.

In addition to supporting these kinds of more sophisticated services and devices, it is also proposed for newer generation mobile telecommunication systems such as NR to support less complex services and devices which make use of the reliable and wide ranging coverage of newer generation mobile telecommunication systems without necessarily needing to rely on the high data rates available in such systems. For example, a less complex device may be a tiny device equipped with sensors and a small battery capacity. Such a less complex device needs to transmit the sensor data at a typically infrequent and/or low data rate.

The demand to deploy such networks is therefore strong and there is a desire to improve the coverage area and flexibility of these networks. It is also desirable to make efficient use of network resources and battery capacity and to reduce signalling overheads.

SUMMARY

The present disclosure is defined by the claims.

According to a first aspect, there is provided a method of operating a communications device configured to transmit signals to and/or receive signals from an infrastructure equipment via a wireless access interface provided by a wireless communications network, the wireless communications network comprising at least the infrastructure equipment. The method comprises: performing channel processing for a transport block to be transmitted in an uplink transmission to create a first set of modulation symbols mapped to physical resource elements, wherein performing the channel processing includes applying one or more channel processing chains to the transport block; performing orthogonal frequency-division multiplexing (OFDM) modulation to the first set of modulation symbols to generate a first OFDM waveform to be transmitted for the uplink transmission; modifying the channel processing chain for the transport block to generate one or more modified OFDM waveforms; determining an OFDM waveform of one or more modified OFDM waveforms to be transmitted; and transmitting the determined modified OFDM waveform.

According to a second aspect, there is provided a method of operating an infrastructure equipment configured to transmit signals to and/or receive signals from a communication device via a wireless access interface provided by a wireless communications network, the wireless communications network comprising at least the infrastructure equipment. The method comprises: receiving, from a communications device, an uplink transmission, wherein the uplink transmission uses a particular OFDM waveform of a plurality of OFDM waveforms, wherein each OFDM waveform of the plurality of OFDM waveforms is generated by a different channel processing chain. The method may further comprise: receiving, from the communications device, an indication of one or more modifications to the channel processing chain for generating the particular OFDM waveform; and/or transmitting, for receipt by the communications device, a set of possible modifications to the channel processing chain for generating the plurality of OFDM waveforms, wherein the channel processing chain for generating the particular OFDM waveform includes one or more of the set of possible modifications.

Respective aspects and features of the present disclosure are defined in the appended claims.

It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the present technology. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments and advantages of the present disclosure are explained with reference to the following detailed description taken in conjunction with the accompanying drawings, wherein:

Figure 1 schematically represents some elements of an LTE-type wireless telecommunications system.

Figure 2 schematically represents some elements of an NR-type wireless telecommunications system.

Figure 3 schematically represents some components of the wireless telecommunications system shown in Fig. 2 in more detail.

Figure 4 illustrates a method for physical uplink shared channel (PLISCH) transport channel processing.

Figure 5 illustrates a method for PLISCH physical channel processing.

Figure 6 illustrates a process of mapping modulation symbols to physical resources for an uplink transmission.

Figure 7 illustrates a process of mapping modulation symbols to physical resources for an uplink transmission according to an example teaching of the disclosure.

Figures 8A and 8B illustrate a process of mapping modulation symbols to physical resources for an uplink transmission according to an example teaching of the disclosure.

Figures 9A and 9B illustrate a process of mapping modulation symbols to physical resources for an uplink transmission according to an example teaching of the disclosure. Figure 10 illustrates a process of rotating modulation symbols for an uplink transmission according to an example teaching of the disclosure.

Figure 11 illustrates a flow diagram of an example method for a communications device according to the present disclosure.

Figure 12 illustrates a flow diagram of an example method for an infrastructure equipment according to the present disclosure.

Figure 13 illustrates a flow diagram of an example method for an infrastructure equipment according to the present disclosure.

Like reference numerals designate identical or corresponding parts throughout the drawings.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Long Term Evolution (LTE) Wireless Communications System

Fig. 1 provides a schematic diagram illustrating some basic functionality of a mobile telecommunications network / system 6 operating generally in accordance with LTE principles, but which may also support other radio access technologies, and which may be adapted to implement embodiments of the disclosure as described herein. Various elements of Fig. 1 and certain aspects of their respective modes of operation are well-known and defined in the relevant standards administered by the 3GPP body, and also described in many books on the subject, for example, Holma, H. and Toskala, A [1], It will be appreciated that operational aspects of the telecommunications networks discussed herein which are not specifically described (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be implemented in accordance with any known techniques, for example according to the relevant standards and known proposed modifications and additions to the relevant standards.

The network 6 includes a plurality of base stations 1 connected to a core network 2. Each base station provides a coverage area 3 (i.e. a cell) within which data can be communicated to and from communications devices 4.

Although each base station 1 is shown in Fig. 1 as a single entity, the skilled person will appreciate that some of the functions of the base station may be carried out by disparate, inter-connected elements, such as antennas (or antennae), remote radio heads, amplifiers, etc. Collectively, one or more base stations may form a radio access network.

Data is transmitted from base stations 1 to communications devices 4 within their respective coverage areas 3 via a radio downlink (DL). Data is transmitted from communications devices 4 to the base stations 1 via a radio uplink (UL). The core network 2 routes data to and from the communications devices 4 via the respective base stations 1 and provides functions such as authentication, mobility management, charging and so on. A communications device may also be referred to as a mobile station, user equipment (UE), user terminal, mobile radio, terminal device and so forth.

Services provided by the core network 2 may include connectivity to the internet or to external telephony services. The core network 2 may further track the location of the communications devices 4 so that it can efficiently contact (i.e. page) the communications devices 4 for transmitting downlink data towards the communications devices 4.

A base station, which is an example of network infrastructure equipment, may also be referred to as a transceiver station, nodeB, e-nodeB, eNB, g-nodeB, gNB and so forth (note g-nodeB and gNB are related to 5G New Radio - see below). In this regard different terminology is often associated with different generations of wireless telecommunications systems for elements providing broadly comparable functionality. However, certain embodiments of the disclosure may be equally implemented in different generations of wireless telecommunications systems, and for simplicity certain terminology may be used regardless of the underlying network architecture. That is to say, the use of a specific term in relation to certain example implementations is not intended to indicate these implementations are limited to a certain generation of network that may be most associated with that particular terminology.

In the present disclosure, any apparatus (e.g. communications device, infrastructure equipment and the like) which transmits and/or receives wireless telecommunications signals in any of the exemplified wireless telecommunication networks I systems may be referred to generally as a wireless telecommunications apparatus.

5G New Radio (NR) Wireless Communications System

An example configuration of a wireless communications network which uses some of the terminology proposed for NR is shown in Fig. 2. In Fig. 2 a plurality of transmission and reception points (TRPs) 10 are connected to distributed control units (Dlls) 41 , 42 by a connection interface represented as a line 16. Each of the TRPs 10 is arranged to transmit and receive signals via a wireless access interface within a radio frequency bandwidth available to the wireless communications network. Thus, within a range for performing radio communications via the wireless access interface, each of the TRPs 10, forms a cell of the wireless communications network as represented by a circle 12. As such, wireless communications devices 14 which are within a radio communications range provided by the cells 12 can transmit and receive signals to and from the TRPs 10 via the wireless access interface. Each of the distributed units 41 , 42 are connected to a central unit (CU) 40 (which may be referred to as a controlling node) via an interface 46. The central unit 40 is then connected to a core network 20 which may contain all other functions required for communicating data to and from the wireless communications devices and the core network 20. The core network 20 may be connected to other networks 25.

The elements of the wireless access network shown in Fig. 2 may operate in a similar way to corresponding elements of an LTE network as described with regard to the example of Fig. 1. It will be appreciated that operational aspects of the telecommunications network represented in Fig. 2 and of other networks discussed herein in accordance with embodiments of the disclosure which are not specifically described (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be implemented in accordance with any known techniques, for example according to currently used approaches for implementing such operational aspects of wireless telecommunications systems, e.g. in accordance with the relevant standards.

The TRPs 10 of Fig. 2 may in part have a corresponding functionality to a base station or eNodeB of an LTE network. Similarly, the communications devices 14 may have a functionality corresponding to the UE devices 4 known for operation with an LTE network. It will be appreciated, therefore, that operational aspects of an NR network (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be different to those known from LTE or other known mobile telecommunications standards. However, it will also be appreciated that each of the core network component, base stations and communications devices of an NR network will be functionally similar to, respectively, the core network component, base stations and communications devices of an LTE wireless communications network. In terms of broad top-level functionality, the core network 20 connected to the NR telecommunications system represented in Fig. 2 may be broadly considered to correspond with the core network 2 represented in Fig. 1 , and the central unit 40 and associated Dlls 41 , 42 I TRPs 10 may be broadly considered to provide functionality corresponding to the base stations 1 of Fig. 1. The term network infrastructure equipment I access node may be used to encompass these elements and more conventional base station type elements of wireless telecommunications systems. Depending on the application at hand the responsibility for scheduling transmissions which are scheduled on the radio interface between the respective distributed units and the communications devices may lie with the CU 40, Dlls 41 , 42 and/or TRPs 10. Communications devices 14 are represented in Fig. 2 within the coverage area of respective communication cells 12. These communications devices 14 may thus exchange signalling with the CU 40 via the TRP 10 associated with their respective communication cells 12.

It will further be appreciated that Fig. 2 represents merely one example of a proposed architecture for an NR-based telecommunications system in which approaches in accordance with the principles described herein may be adopted, and the functionality disclosed herein may also be applied in respect of wireless telecommunications systems having different architectures.

Thus certain embodiments of the disclosure as discussed herein may be implemented in wireless telecommunication systems I networks according to various different architectures, such as the example architectures shown in Figs. 1 and 2. It will thus be appreciated the specific wireless telecommunications architecture in any given implementation is not of primary significance to the principles described herein. In this regard, certain embodiments of the disclosure may be described generally in the context of communications between network infrastructure equipment I access nodes and a communications device, wherein the specific nature of the network infrastructure equipment I access node and the communications device will depend on the network infrastructure for the implementation at hand. For example, in some scenarios the network infrastructure equipment I access node may comprise a base station, such as an LTE-type base station 1 as shown in Fig. 1 which is adapted to provide functionality in accordance with the principles described herein, and in other examples the network infrastructure equipment may comprise a CU 40, DU 41 , 42 and I or TRP 10 of the kind shown in Fig. 2 which is adapted to provide functionality in accordance with the principles described.

A more detailed diagram of some of the components of the network shown in Fig. 2 is provided by Fig. 3. In Fig. 3, a TRP 10 as shown in Fig. 2 comprises, as a simplified representation, a wireless transmitter 30, a wireless receiver 32 and a controller or controlling processor 34 which is configured to control the transmitter 30 and the receiver 32 to transmit radio signals to and receive radio signals from one or more UEs 14 within a cell 12 formed by the TRP 10. As shown in Fig. 3, an example UE 14 is shown to include a corresponding wireless transmitter 49, wireless receiver 48 and a controller or controlling processor 44 which is configured to control the transmitter 49 to transmit signals representing uplink data to the wireless communications network via the wireless access interface formed by the TRP 10 and the receiver 48 to receive downlink data as signals transmitted by the transmitter 30.

The transmitters 30, 49 and the receivers 32, 48 (as well as other transmitters, receivers and transceivers described in relation to examples and embodiments of the present disclosure) may include radio frequency filters and amplifiers as well as signal processing components and devices in order to transmit and receive radio signals in accordance, for example, with the 5G/NR standard. The controllers 34, 44 (as well as other controllers described in relation to examples and embodiments of the present disclosure) may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc., configured to carry out instructions which are stored on a computer readable medium, such as a non-volatile memory. The processing steps described herein may be carried out by, for example, a microprocessor in conjunction with a random access memory, operating according to instructions stored on a computer readable medium.

As shown in Fig. 3, the TRP 10 also includes a network interface 50 which connects to the DU 42 via a physical interface 16. The network interface 50 therefore provides a communication link for data and signalling traffic from the TRP 10 via the DU 42 and the CU 40 to the core network 20.

The interface 46 between the DU 42 and the CU 40 is known as the F1 interface which can be a physical or a logical interface. The F1 interface 46 between CU and DU may operate in accordance with specifications 3GPP TS 38.470 and 3GPP TS 38.473 and, for example, may be formed from a fibre optic or other wired high bandwidth connection. In one example, the connection 16 from the TRP 10 to the DU 42 is fibre optic. The connection between a TRP 10 and the core network 20 can be generally referred to as a backhaul, which comprises the interface 16 from the network interface 50 of the TRP 10 to the DU 42 and the F1 interface 46 from the DU 42 to the CU 40.

In the following examples, the coupling loss (CL) between a UE (e.g. a UE 14) and a gNB (which is an example of a TRP 10) is considered. The CL depends largely on the distance between the UE and gNB but also on any obstacles such as buildings, traffic, foliage, etc. that happen to be located in the line of sight between the UE and gNB. The CL may also be influenced by propagation conditions such as fading due to precipitation and Doppler spread due to UE mobility. On the DL (downlink), coverage can be improved by transmitting more power from the gNB. In the UL (uplink), the UE can also increase transmit power. However, the more power a UE transmits, the faster its battery will be drained. Therefore, if a UE is to transmit more power in coverage-limited situations, there is a desire for this to be done as efficiently as possible in order to reduce the drain on the UE battery.

PUSCH channel processing and mapping

In order to generate an OFDM waveform for a transport block (i.e. data to be included in an uplink transmission), a process called PUSCH channel processing is carried out. In particular, a PUSCH channel processing chain is followed, where various processing is performed on the transport block in order to generate the OFDM waveform. This channel processing chain may be logically divided into two sections: a PUSCH transport channel processing chain and a PUSCH physical channel processing chain. While the distinction between these two processing chains is not clear, it is generally considered that functional blocks specified in TS38.212 [2] are concerned with transport channel processing while those functional blocks specified in TS38.211 [3] are concerned with physical channel processing. Examples of these two processing chains are shown in Figures 4 and 5 respectively, which are generally known and understood by the skilled person.

Figure 4 illustrates an example of a transport channel processing chain 400, as reproduced from [4], A transport block 410 is input to the transport channel processing chain 400. At step 420, a cyclic redundancy check (CRC) is attached to the transport block, and at step 430 a low-density parity-check (LDPC) base graph is selected. At step 440, code block segmentation and code block CRC attachment are performed, and at step 450 channel coding is performed.

At step 460, a rate matching step is performed. The rate matching step consists of two constituent steps: bit selection and bit interleaving. In the bit selection function, the output bits of the channel coding step are fed into a circular memory buffer. The number of physical bits in the allocation, Np_hy_aiioc, are calculated, based on the allocated physical resources. The number of bits read out of the circular memory buffer, N_RM_out, is equal to the number of physical bits in the allocation: NRM_out = N_Phy_aiioc- The starting point from which bits are read out from the circular buffer depends on the RV (redundancy version) applied. There are 4 possible RVs and the RV that the UE should apply may be signalled in a PLISCH allocation, or otherwise known to both the UE and gNB. By varying the RV, different sets of systematic and parity bits are chosen for actual transmission as physical channel bits. The chosen bits are then fed into a bit interleaver. The number of rows in the interleaver is based on the modulation order applied, for example, the bit interleaver consists of 4 rows when 16QAM is used. Bits are read into the bit interleaver row-by-row and are read out column-by-column. If the bit interleaver consists of Ni_nt_rows, bits are read into the interleaver in the row order 1 , 2, . . . . Nint_ rows-

At step 470, code block concatenation is performed, and at step 480 data and control multiplexing is performed. At step 490, the process may continue towards the remaining channel processing (i.e. physical channel processing), as exemplified in Figure 5.

Figure 5 illustrates an example of a physical channel processing chain 500, as reproduced from [4], The output 490 of the transport channel processing chain 400 is used as input 510 for the physical channel processing chain 500. The physical channel processing chain produces a set of modulation symbols from the physical channel bits of the transport block, maps said modulation symbols to physical resource blocks, and generates an OFDM waveform, as will be described below. Modulation symbols are complex-valued symbols which are mapped to physical resource elements (i.e. physical resources) to allow an OFDM waveform to be generated.

At step 520, a scrambling process is performed where a scrambling sequence is applied to the transport block (i.e. scrambling is applied to the physical channel bits associated with the transport block that are input to the physical channel processing chain 500). The scrambling sequence is chosen from a plurality of different scrambling sequences. At step 530, a modulation step is performed on the physical channel bits, whereby a mapping between bit sequences and modulation symbols is applied. For example, as explained in [3], in the case of QPSK modulation, pairs of bits, b(2i b(2i +i) , are mapped to complex-value modulation symbols d(i) according to Equation (1):

However, other modulation schemes exist and may be alternatively used. At step 540, layer mapping is performed, whereby a mapping between modulation symbols and multiple in multiple out (MIMO) layers is applied. The layer mapping process is described in section 6.3.1.3 of TS38.211 [3], In particular, in the layer mapping step 540, the modulation symbols are assigned to layers in a round-robin fashion. The different layers are then further processed on a layer-by-layer basis, i.e. each layer is processed as a parallel stream.

At step 550, a transform precoding step is performed, and at step 560 a precoding step is performed. At step 570, the modulation symbols are mapped to particular physical resources (i.e. physical resource elements). This process is explained in section 6.3.1.6 of [3], In this process, modulation symbols are mapped to resource elements first in order of subcarrier/tone (i.e. from low frequency to high frequency) and then in order of OFDM symbol. This is illustrated in Figure 6. Figure 6 illustrates a plurality of ODFM symbols 610 of a slot arranged in time order, where OFDM symbol 610a occurs earlier in time than OFDM symbol 610b, OFDM symbol 610b occurs earlier in time than OFDM symbol 610c, and so on for all OFDM symbols 610 in the slot. In the present example, there are fourteen OFDM symbols 610 in the slot, meaning the OFDM symbols are labelled OFDM symbols 610a-n.

Each OFDM symbol 610 includes one or more physical resource blocks (PRBs) 620, containing a plurality of subcarriers. In the example of Figure 6, each OFDM symbol includes two PRBs 620a and 620b, each containing 12 subcarriers/tones to which modulation symbols 630 may be mapped, however the exact values may vary based on the implementation. Figure 6 also shows a plurality of groups of modulation symbols 630 arranged in (i.e. mapped to) the PRBs 620 of the OFDM symbols 610. In Figure 6, the various different shadings for the modulation symbols 630a-n each indicate a group of modulation symbols corresponding to a PRB (i.e. a group of 12 modulation symbols, as a PRB includes 12 subcarriers/tones). As shown by the arrows in Figure 6, the modulation symbols 630 are sequentially mapped to subcarriers starting with the lowest frequency subcarrier of the first OFDM symbol 610a to the highest frequency subcarrier of the first OFDM symbol 610a. After all subcarriers of the first OFDM symbol 610a have a mapped modulation symbol 630, the same process occurs for the second OFDM symbol 610b, and then sequentially for all remaining OFDM symbols of the slot. As such, the modulation symbols 630 are mapped to resource elements first in order of subcarrier, and then in order of OFDM symbol 610.

After step 570 where modulation symbols are mapped to resource blocks, the method of Figure 5 proceeds to step 580 of generating the OFDM waveform. Here an inverse fast Fourier transform (IFFT) function is applied to the set of tones/subcarriers to which the modulation symbols have been mapped to generate the OFDM waveform. The application of the IFFT function may generate a CP-OFDM (Cyclic Prefix - Orthogonal Frequency Division Multiplexing) or DFT-S-OFDM (Discrete Fourier Transform - Spread - Orthogonal Frequency Division Multiplexing) waveform. Subsequent steps 590, including e.g. digital to analogue conversion, may then result in the transmission of the uplink signal by the UE.

NR Operation with CP-OFDM UL waveform

3GPP Release 17 (Rel-17) NR-capable UEs support both CP-OFDM and DFT-S-OFDM as UL transmission waveforms. In normal use, the gNB selects the waveform to be used for UL transmissions and informs the UE via SIB1 (System Information Block 1) (for Message 3 (Msg3) of the initial access procedure) and semi-statically via RRC (Radio Resource Control) signalling (for both dynamic and configured grant PUSCH (Physical Uplink Shared Channel) transmissions).

DFT-S-OFDM is similar to single carrier waveforms in having a lower peak-to-average power ratio (PAPR) than the multi-carrier CP-OFDM waveform. A transmitter using DFT-S-OFDM can therefore operate its output power amplifier at its non-linear characteristic region without fear of excessive waveform clipping because of the low PAPR nature of DFT-S-OFDM that produces a low Adjacent Channel Leakage Power Ratio (ACLR). Further, because of its lower ACLR, the UE can operate with a lower maximum power reduction (MPR) factor than a UE transmitting CP-OFDM. This means that a UE transmitting DFT-S-OFDM in the UL is allowed to transmit more power (for example, in some cases as much as 1.5dB) than a UE using CP- OFDM. The use of DFT-S-OFDM therefore allows a given UE to achieve a higher maximum output power for its class very efficiently whilst saving battery power. Furthermore, as DFT-S- OFDM does not support MIMO (multiple-input and multiple-output), cross spatial interference is reduced, meaning that for the same UE transmit power, DFT-S-OFDM can have significantly more coverage than CP-OFDM.

On the other hand, in Rel-17, the number of constellations allowed for use with DFT-S-OFDM is limited. This results in limited support for high-capacity services. Furthermore, DFT-S-OFDM is only specified for one-layer operation and so cannot operate with MIMO. This limits system capacity.

CP-OFDM is a multi-carrier modulation scheme and so suffers from a higher PAPR. A higher PAPR signal is characterized by occasional peaks that are significantly higher than the normal (e.g. average) amplitude of the signal. When such peak amplitudes go through a transmit power amplifier of a UE, the amplifier limits the rapid excursion resulting in clipping the peak thereby degrading the error vector magnitude (EVM) of the signal and producing spills of interference into adjacent channels to cause adjacent channel interference (ACI). ACI decreases the ACLR of the channel concerned.

It is therefore desirable for a level of distortion (e.g. PAPR or EVM) reduction to be achieved for CP-OFDM so the benefits of CP-OFDM can be enjoyed in coverage extension (e.g. by allowing UE transmit power amplifier(s) to transmit more power to increase coverage) without unduly draining the UE battery. It is also desirable, for example, to allow a UE with CP-OFDM configured as its UL waveform and needing to increase its coverage (for example, because it is about to fall out of acceptable coverage) to apply distortion reduction for either all UL transmissions or only those that are out of coverage (noting that higher data rate UL transmissions might be out of coverage while lower data rate UL transmissions might be in coverage).

PAPR (i.e. distortion) reduction can reduce the amplitude of such peaks by limiting the amount and rate of amplitude excursions that create such peaks. The peaks in a multi-carrier modulated signal arise when a number of the subcarriers that comprise the signal cohere in such a manner that their individual contributions to the amplitude of a given time domain sample of the OFDM symbol waveform combine constructively. If such a constructive combination between subcarriers is reduced, then the amplitude of the peak will also be reduced.

A known way of doing this, for example in broadcast systems such as that described in [5], is called tone reservation and entails excluding the amplitude contributions of some of the contributing subcarriers from the signal altogether. In tone reservation, a fraction of tones allocated to a UE will be reserved for the UE to use in shaping its output OFDM symbol waveform to reduce the amplitudes of any peaks of the waveform. No data is transmitted on these tones. If such reserved tones match the OFDM subcarriers that contribute a high proportion of the amplitude contributions that cohere to create the peaks, this allows the peak(s) to be reduced. Apart from muting subcarriers, tone reservation can also be done by loading the reserved tones with calculated complex samples. Complex samples are complex values that are not indicative of information to be transmitted but, rather, are determined to help depress the amplitude excursions that create the peaks.

A benefit of tone reservation is that it is performed just prior to OFDM waveform generation. In order to iterate over different tone reservation patterns, a fixed set of mapped resource blocks can be used and tones can be reserved on that fixed set. The iterations only require the generation of OFDM waveforms rather than the re-processing of the whole physical channel and/or transport channel processing chain. A drawback of tone reservation is that the signal contains tones that do not carry any data. These unused tones are a waste of spectrum (if tones are zero-ed) or both spectrum and power (if tones are transmitted with PAPR- reducing complex samples). Accordingly, the present inventors have identified an approach for reducing PAPR without wasting spectrum.

Transport and physical channel processing chain adaptation According to the present invention, the channel processing chain for a PLISCH can be adapted, e.g. by varying one or more parameters, in order to reduce the level of distortion (referred to hereinafter as PAPR, however other measures of distortion, such as EVM, may be used) of a signal to be transmitted. That is, when it is determined that the PAPR for a signal to be transmitted is above a predetermined threshold, the channel processing for a transport block may be re-performed with a modified channel processing chain. This may result in a signal with reduced PAPR which can then be transmitted. The channel processing chain may be modified by modifying one or more parameters in the transport channel processing chain and/or the physical channel processing chain. Furthermore, the modification of the channel processing chain may occur in cases where the PAPR of the original OFDM waveform has not been measured).

A measurement, such as PAPR, may be indicative of the amount of distortion that would be created once the signal (i.e. OFDM waveform) is transmitted by the UE’s power amplifier and antenna. According to UE implementation, the relationship between the measurement and the amount of distortion may differ. For example, a UE with a highly linear power amplifier may create a small amount of distortion based on a signal with a high PAPR, whereas a UE with a non-linear or saturating power amplifier may create a larger amount of distortion based on a signal with a lower PAPR. Hence, the predetermined threshold at which an alternative channel processing chain is chosen may be determined by the UE, for example by taking into account known aspects of the UE implementation.

According to the present invention, a UE identifies a transport block to be transmitted in a first uplink transmission. This transport block may be similar to the transport block 410 discussed in relation to Figure 4. The UE performs channel processing for the transport block to be transmitted in the first uplink transmission to create a first set of modulation symbols mapped to physical resource elements. The channel processing may be similar to the channel processing discussed in relation to Figure 4 and/or Figure 5, and may include applying one or more channel processing chains (such as the transport channel processing chain 400 of Figure 4 or the physical channel processing chain 500 of Figure 5) to the transport block. The UE then performs OFDM modulation to the first set of modulation symbols to generate a first OFDM waveform to be transmitted for the first uplink transmission. This process may correspond to step 580 of Figure 5.

After generating the first OFDM waveform, the UE measures the PAPR for the first OFDM waveform. If the UE determines that the PAPR for the first OFDM waveform is above a predetermined threshold, the UE, in response, re-performs some or all of the channel processing with a modified channel processing chain in order to generate one or more modified OFDM waveforms. The channel processing chain may be modified by varying one or more parameters of the channel processing chain as compared to the original channel processing chain. After generating the one or more modified OFDM waveforms, the UE determines an OFDM waveform to be transmitted. For example, if multiple modified OFDM waveforms are generated, the UE may measure the PAPR for the modified OFDM waveforms and transmit the OFDM waveform with the lowest PAPR. Alternatively, the UE may generate only one modified OFDM waveform, and the UE may determine that it will transmit the modified OFDM waveform without measuring the PAPR of the modified OFDM waveform, or may measure the PAPR of the modified OFDM waveform and transmit either the first OFDM waveform or the modified OFDM waveform, based on which of the waveforms has the lowest PAPR.

The modifications to the channel processing chain may be determined by the UE and indicated to the gNB, for example via signalling within an uplink control information (UCI) transmitted on a physical uplink control channel (PLICCH) or a physical uplink shared channel (PLISCH), via the use of a particular a demodulation reference signal (DM RS) sequence used in the uplink transmission, or via the use of a particular a cyclic shift applied to the DMRS sequence used in the uplink transmission. In addition or alternatively, the gNB may signal a set of one or more possible modifications that the UE may make to the channel processing chain. For example, the gNB may indicate a possible alternative mapping for mapping modulations symbols to resource elements, or any of the other possible modifications discussed herein. The set of possible modifications may be signalled to the UE either via dedicated signalling, or via other signalling such as a system information block (SIB) carrying system information (SI). The gNB may blind decode the receive uplink transmission according to any (i.e. none, one, or more) of the set of possible modifications (e.g. if the number of possible modifications is comparatively small). Alternatively, the UE may signal to the UE which (if any) of the set of possible modifications the UE has applied in generating the modified signal. The UE may apply one or more of the set of possible modifications. The gNB may also signal an indication of the signal distortion (i.e. PAPR) threshold to the UE, however the threshold may be UE- specific.

According to an example teaching of the disclosure, a UE may modify the mapping of the modulation symbols to the physical resource elements in order to reduce PAPR. In other words, the UE may modify the manner in which step 570 of the physical channel processing chain 500 is performed when re-performing channel processing for the transport block. For example, a parameter may be changed that modifies the OFDM symbols to which particular modulation symbols are mapped. This example is illustrated in Figure 7, where different sets of modulation symbols 630 are swapped with one another across different OFDM symbols 610.

In particular, in Figure 7 the set of modulation symbols 630b, which were mapped to the second PRB 620b of the first OFDM symbol 610a in Figure 6, are swapped with the set of modulation symbols 630c, which were mapped to the first PRB 620a of the second OFDM symbol 610b in Figure 6. This swap is indicated by the double-pointed arrow between modulation symbols 630b and 630c. In Figure 7, only the first two OFDM symbols 610a and 610b are shown for ease explanation, however it should be appreciated that this process may be repeated for further sets of neighbouring (i.e. adjacent) OFDM symbols, such that modulation symbols in the third OFDM symbol 610c may be swapped with modulation symbols in the fourth OFDM symbol (not shown), and so on for some or all of the remaining OFDM symbols 610 of the slot. In Figure 6, an entire PRB 620 of modulation symbols is swapped between OFDM symbols, however in other examples the quantity of modulation symbols swapped may vary. For example, one or more tones/subcarriers of modulation symbols may be swapped between OFDM symbols, or one or multiple PRBs may be swapped between OFDM symbols.

In other words, a set of modulation symbols (i.e. a subset of the total modulation symbols produced during the channel processing) are swapped with another set of modulation symbols (as compared with the original mapping) in a different OFDM symbol when mapping the modulation symbols to the physical resources (i.e. swapping subsets of modulations symbols between different OFDM symbols). As such, if the combination of particular sets of modulation symbols (e.g. modulation symbols 630a and 630b) results in a high PAPR, the re-mapping of the modulation in this way results in a different combination of tones, which may reduce the PAPR of the modified OFDM waveform.

In Figure 6, when PRBs are swapped between OFDM symbols, the frequency location of the PRBs is changed, however the PAPR lowering effect can also be achieved when the frequency location of the PRBs is unchanged during the swap. For example, referring to Figure 6, the set of modulation symbols 630b in the second PRB 620b of the first OFDM symbol 610a may be swapped with the set of modulation symbols 630d in the second PRB 620b of the second OFDM symbol 610b. Swapping a set of modulation symbols at the same frequency location between OFDM symbols will lead to different total set of tones being combined in the OFDM waveform generation process, leading to OFDM waveforms with different PAPRs. In the original example of Figure 6, a first OFDM waveform for the first OFDM symbol 610a is generated from the sets of modulation symbols 630a and 630b. In the modified example under discussion, a second OFDM waveform for the first OFDM symbol 610a is generated for the sets of modulation symbols 630a and 630d. The PAPR of these first and second OFDM waveforms may be different and selection of the OFDM waveform with the lowest PAPR will lead to a coverage improvement.

Alternatively or in addition to swapping sets (or subsets) of modulation symbols across different OFDM symbols, the sets of modulation symbols may be mapped using a circular (i.e. cyclical) buffer, whereby the location at which the modulation symbols are read out of the circular buffer is shifted relative to the location at which the modulation symbols are written into the circular buffer; this amounts to a rotation of the circular buffer. The amount of rotation of the circular buffer is a parameter that may be varied in order to change the mapping of the modulation symbols to the physical resources.

This example is illustrated in Figures 8A and 8B. Figure 8A illustrates the first two OFDM symbols 610a and 610b of Figure 6, where all like reference symbols indicate identical elements. In addition, the example of Figure 8A includes a circular buffer 810. The circular buffer 810 includes a write-in pointer 820 and a read-out pointer 830, however in Figure 8A the write-in pointer 820 and read-out pointer 830 have the same location/value, and as such only one line is shown in the buffer 810. As the write-in pointer 820 and read-out pointer 830 have the same location/value, there is no rotation of the circular buffer, and as such the modulation symbols are written into and read out of the circular buffer at the same location, meaning the modulation symbols 630 are mapped to the resource elements in the same manner as shown in Figure 6.

In contrast, in Figure 8B, the read-out pointer 830 does not have the same location/value as the write-in pointer 820 (i.e. the read-out pointer 830 is rotated in the circular buffer relative to the write-in pointer 820). In other words, the modulation symbols are written into and read out of the circular buffer at different locations. This creates a shift in the mapping of the modulation symbols relative to the mapping shown in Figure 8A. In particular, in Figure 8B a shift of 3 modulation symbols/subcarriers/tones is applied. Accordingly, the modulation symbols are mapped to the resource elements with a shift of three modulation symbols. Therefore, when mapping the modulation symbols 630 to the resource elements, the first three modulation symbols are skipped and inserted after a full rotation of the buffer. This creates a difference in mapping of modulation symbols, as can be seen by comparing Figures 8A and 8B. As such, in this example, applying a cyclical buffer to a stream of the first set of modulation symbols during mapping of a first set of modulation symbols to the physical resource elements alters the location (i.e. the mapping) of the first set of modulation symbols within the physical resource elements. This different mapping can lead to a different combination of tones which may reduce the PAPR of the OFDM waveform.

Alternatively or in addition to the above examples, the mapping of a group of modulation symbols may be swapped with that of another group of modulation symbols within the same OFDM symbol. This example is shown in Figures 9A and 9B. Figure 9A illustrates the first two OFDM symbols 610a and 610b of Figure 6, where all like reference symbols indicate identical elements. In Figure 9A, the modulation symbols 630 are mapped to the resource elements in the same manner as Figure 6. However, in Figure 9B, modulation symbols 630a are swapped with modulation symbols 630b, and modulation symbols 630c are swapped with modulation symbols 630d, as indicated by the double-pointed arrows. In other words, the example of Figures 9A and 9B includes swapping subsets of the first set of modulation symbols within the same OFDM symbol. In this example, although the same sets of modulation symbols 630a and 630b are transmitted together within the same OFDM symbol 610a, applying the respective modulations to different tones/subcarriers in Figure 9B will lead to a different OFDM waveform for Figure 9B, as opposed to Figure 9A, which may lead to a lower PAPR. In Figures 9A and 9B, an entire PRB 620 of modulation symbols is swapped within the same OFDM symbol, however in other examples the quantity of modulation symbols swapped may vary. For example, one or more tones/subcarriers of modulation symbols may be swapped within the same OFDM symbol, or one or multiple PRBs may be swapped within the same OFDM symbol.

While the aforementioned examples involve modifying a mapping of the modulation symbols to resource elements, other modifications to the channel processing chains are possible (in addition or as an alternative to the aforementioned examples), which lead to different OFDM waveforms, and hence provide the possibility of reduced PAPR. For example, a modulation of the modulation symbols may itself be rotated with or without altering the mapping of the modulation symbols. This is illustrated in Figure 10 which shows two versions of the same OFDM symbol 1010. In a first version 1010a of the OFDM symbol, a PRB 1020 includes 12 tones/subcarriers, where a first set of modulation symbols 1030a and a second set of modulation symbols 1030b are mapped to the tones/subcarriers. Only a single PRB 1020 is shown in Figure 10, however the OFDM symbol 1010 may include one or more PRBs 1020.

The modulation symbols 1030 mapped to the OFDM symbol 1010 each have an applied modulation having a particular rotation 1040a. The rotation 1040a is indicated by the icons next to the modulation symbols, which show four quadrants (indicating four possible orthogonal rotations), and a mark in a particular quadrant indicating the rotation of that particular modulation symbol. The icons hence represent constellation points within a modulation scheme, such that the constellation points of the modulation scheme for the modulation symbols may be rotated within the present example. In Figure 10, the constellation points belong to a QPSK modulation scheme, but this technique is also applicable to other modulation schemes. When re-processing the processing channel chains, the modulation rotation 1040b of some or all of the OFDM symbols 1030 in the second version 1010b of the OFDM symbol may be rotated relative to the first version 1010a of the OFDM symbol. For example, as shown in Figure 10, the set of modulation symbols 1030b may be rotated (e.g. by 90 degrees), while the set of modulation symbols 1030a may not be rotated. By rotating the modulation of various sets of modulation symbols, a different set of tones is included within the resultant OFDM waveform, which may result in a waveform with reduced PAPR.

In examples, different sets of modulation symbols may be rotated by different amounts (e.g. a set of modulation symbols may be rotated by 90 degrees, while another set of modulation symbols may be rotated by 180 degrees. In addition, the modulation rotation may be applied to an entire PRB, multiple PRBs, a subset of tones in a PRB, or one or more individual tones. Furthermore, the modulation rotation may not necessarily be a multiple of 90 degrees, as in the examples above. Instead, the modulation rotation may be a multiple of any known amount. That is, as a receiver of the uplink transmission may know the amount of modulation rotation that has been applied (e.g. via signalling from the UE or by blind decoding according to one or more predetermined modulation rotations), the receiver can de-rotate the symbol in order to decode it. While the above examples relate to modifying a mapping of the modulation symbols to resource elements or modifying a modulation rotation of mapped modulation symbols, any other portion of the channel processing chain may be additionally or alternatively modified in order to generate a different OFDM waveform, which may have a lower PAPR. For example, the layer mapping of step 540 of Figure 5 may be modified, where the mapping between modulation symbols and MIMO layers is altered, such that in an alternate mapping a different set of modulation symbols is mapped to each MIMO layer. As described above, in current systems, modulation symbols are mapped to MIMO layers in a round-robin fashion, such that (for a four MIMO layer transmission) the first modulation symbol is mapped to the first layer, the second modulation symbol is mapped to the second layer, and so on for all modulation symbols. In a modified mapping, according to this example, the order of mapping modulation symbols may be changed relative to the original mapping, for example, the first modulation symbol may be mapped to the second MIMO layer, the second modulation symbol m mapped to the first MIMO layer, the third modulation symbol may be mapped to the fourth MIMO layer etc.

Additionally or alternatively, step 530 of Figure 5 may be altered, whereby the mapping between bit sequences and modulation symbols is altered. For example, instead of using Equation (1) for mapping pairs of bits to the modulation symbols for QPSK modulation, a different mapping may be used, such as that of Equation (2) below:

Additionally or alternatively, step 520 of Figure 5 may be altered, such that a different scrambling sequence can be applied. This would lead to a different set of physical channel bits being produced, which would lead to different modulation symbols being created. This would then lead to a different signal after OFDM generation, where this signal will have a different PAPR.

Additionally or alternatively, step 460 of Figure 4 may be altered, where a different rate matching process may be applied. For example, the UE can decide to transmit with a different redundancy version to the one that it was originally scheduled to use (i.e. that used for the original OFDM waveform). The different redundancy version will lead to a different set of parity and systematic bits being transmitted and hence a different set of physical channel bits being transmitted. The different physical channel bits will lead to different modulation symbols being mapped and hence to a different waveform being generated. As discussed above, the redundancy version to be used may be created by writing systematic and physical bits into a circular buffer and reading them out from a different location. Different read-out locations are defined for creating the different redundancy versions. In this example, an offset may be added to the read-out location. This will lead to different physical channel bit sequences and hence different sets of modulation symbols. Furthermore, different interleavers within the rate matching function may be used, which will lead to different sequences of physical channel bits and hence different modulation symbol streams. As an example, methods of modifying the interleaver in the rate matching function include: inserting bits into the interleaver row-by-row but not in sequential order. For example, instead to inserting bits into the interleaver in the order of rows 1 ,2,3,4, bits are inserted into rows in the order 2,1 ,4,3. Alternatively, bits may be inserted into the interleaver in inverse row order. For example, instead to inserting bits into the interleaver in the order of rows 1 ,2, 3, 4, bits are inserted into rows in the order 4,3,2, 1. Additionally or alternatively, bits may be read out of the interleaver in a different column order. For example, instead of reading bits out in the column order 1 ,2, 3, 4, bits are read out in the order 2, 1 ,4, 3. Alternatively, bits may be read out of the interleaver in inverse column order. In other words, bits are read out of the interleaver from the last column to the first column. Accordingly, the rate matching step 460 of Figure 4 may be modified in a number of different ways, which may be combined with one another in a number of ways. Furthermore, while not described in detail, it should be appreciated that any other step of the channel processing chains of Figures 4 and 5 may be modified, as this will lead to a different OFDM waveform, which will have a different PAPR to the original OFDM waveform, and any combination of the methods can be implemented, e.g. rotation of the constellation (as in Fig 10) can be combined with alternate modulation symbol to RE mapping (such as in Fig 7, 8 or 9), for which the PAPR was determined to be above a predetermined threshold. The threshold may be determined by the UE based on a number of factors (e.g. a battery level, or environmental conditions). For example, the UE may set the threshold to be higher when the battery level is higher, as the UE has a greater ability to increase transmission power (and therefore overcome the issues caused by high PAPR) when the battery level is high. The threshold may also be signalled to the UE by a gNB (i.e. infrastructure equipment) in substantially any manner, or the threshold may be defined in the specifications, such that the UE does not require any explicit signalling from a gNB in relation to the threshold.

When modifying the channel processing chains in response to detecting a high PAPR for a first OFDM waveform, modified OFDM waveforms are produced. Any number of OFDM waveforms may be produced. For example, the UE may perform multiple different modifications to the channel processing chains to generate multiple modified OFDM waveforms. Each of these OFDM waveforms will have a different PAPR. As such, the UE may measure the PAPR for the modified OFDM waveforms and select an OFDM waveform (of the modified OFDM waveforms, and optionally the original OFDM waveform) having the lowest PAPR to transmit.

In some examples, each of the modified OFDM waveforms may be generated in response to determining that a previous modified OFDM waveform has a PAPR below a particular threshold. For example, the UE may initially generate only a single modified OFDM waveform, and, if the PAPR of this modified OFDM waveform is below a particular threshold, transmit the modified OFDM waveform. However, if the UE determines that the PAPR of the modified OFDM waveform is above a particular threshold (e.g. the same threshold as for the original OFDM waveform, or the PAPR level of the original OFDM waveform), the UE may generate a further modified OFDM waveform by modifying the channel processing chain in a different manner. The UE may then selectively transmit the further modified OFDM waveform based on whether the PAPR for the further modified OFDM waveform is above a particular threshold. The process of generating a modified OFDM waveform and selectively transmitting said OFDM waveform based on a measured PAPR level, may, for example, continue until an OFDM waveform with an acceptable PAPR is generated, or until a predetermined number of OFDM waveforms have been generated, where a particular OFDM is chosen (e.g. the OFDM waveform with the lowest PAPR) for transmission.

In one example, the UE determines the PAPR for a plurality of modified OFDM waveforms and selects the waveform with the lowest PAPR. The UE then determines the difference (or headroom), PpAPR_headmom, between the PAPR of this selected waveform and a PAPR threshold, PpAPRjh shoid- PpAPRjhreshoid may be indicative of the PAPR at which unacceptable clipping/distortion occurs. The UE then changes its transmit power by the amount P PAPR_headroom , subject to a maximum transmission limitation. For example, if the PAPR of the selected waveform is less than the threshold, such that PpAPR_headmom is positive, the UE may transmit at an increased power thus directly increasing coverage.

Alternatively, only a single modified OFDM waveform may be generated. The UE may then measure the PAPR of the modified OFDM waveform and select the OFDM waveform (of the modified OFDM waveform and the original OFDM waveform) having the lowest PAPR to transmit. Alternatively, the UE may generate only one modified OFDM waveform and may not measure the PAPR of the modified waveform, but nonetheless transmit the modified OFDM waveform. This example recognises that the PAPR of the original OFDM waveform is unacceptably high (above the threshold), and as such that, even though the PAPR of the modified OFDM waveform is unknown, transmitting the modified OFDM waveform is not disadvantageous. In particular, if the PAPR of the modified OFDM is lower than the PAPR of the original OFDM waveform, then the uplink transmission is transmitted with lower PAPR, which is advantageous for reasons discussed above. Alternatively, if the PAPR of the modified OFDM is higher than the PAPR of the original OFDM waveform, then an OFDM waveform with an unacceptable PAPR level is transmitted, which would have been the case if the original OFDM waveform was transmitted. As such, transmitting the OFDM waveform with higher PAPR is not particularly disadvantageous, as both OFDM waveforms have unacceptably high PAPRs. However, in this scenario, the amount of re-processing of the channel processing chains is reduced as only one modified OFDM waveform is generated, and no additional PAPR measurements are performed.

As mentioned above, the manner in which the channel processing chain is modified when generating the modified OFDM waveform may be signalled to the gNB (i.e. infrastructure equipment). These modifications may be signalled in any number of ways. For example, the modifications may signalled via use of a different demodulation reference signal (DM RS) sequence for the transmission, or use a particular cyclic shift in the DMRS sequence. Furthermore, the modifications may be signalled within an uplink control information (UCI) carried on a physical uplink control channel (PLICCH) or multiplexed into a PLISCH. A PLICCH is expected to be robust and not susceptible to error due to PAPR issues. A number of predetermined modifications to the channel processing chain may exist, and as such it may be possible for the UE to signal the modifications made using a comparatively small number of bits of information. Moreover, the modifications described above may be applied on a perOFDM symbol and/or per-PRB basis, which may also be indicated in the signalling to the gNB. Furthermore, in some cases a fixed number of the modifications (e.g. modulation rotations) to the channel processing chains may be predetermined. As such, if, for example, the number of predetermined modification options is small, the UE may not need to signal the modifications to the gNB, such that the gNB may attempt to blind decode the uplink transmission based on one or more of the predetermined modifications.

Furthermore, the gNB may signal a set of permitted modifications to the UE, for example in configuration signalling (i.e. as part of a connection process between the UE and the gNB) or system information (SI). For example, referring to Figure 10, the gNB may signal the permitted modulation rotations. Referring to Figure 9, the gNB may signal the manner in which PRBs may be swapped. When the rate-matching function is adapted, the set of possible offsets to be applied to the circular memory buffer when redundancy versions are chosen may be signalled by the gNB to the UE. The benefits of signalling the set of permitted modifications to the UE are that the signalling from the UE to the gNB to indicate which modification has been applied can be minimised and that the decoding complexity at the gNB can be constrained (the gNB only has to be able to decode from the set of permitted modifications rather than having to be able to decode any possible modification).

While the above description of the invention has focussed on describing the invention with respect to uplink transmissions from the UE to the gNB, it will be appreciated that the teachings are also applicable for downlink transmissions from the gNB to the UE. Network energy saving is increasingly important in order to reduce network energy consumption for both environmental and financial reasons. Hence, there is a desire to operate base stations efficiently. One method of improving base station (gNB) efficiency is hence to operate the base station power amplifier close to saturation and to take steps to deal with or minimise the associated distortion. Hence, it is advantageous to choose a transport and I or physical channel mapping scheme for downlink transmissions, according to embodiments of this invention, that leads to low PAPR (or EVM) and hence low distortion.

Figure 11 illustrates a flow diagram of an example method 1100 for a communications device according to the present disclosure. At step S1100, the communications device performs channel processing for a transport block to be transmitted in an uplink transmission, wherein performing the channel processing includes applying one or more channel processing chains to the transport block. At step S1120, the communications device performs OFDM modulation to the first set of modulation symbols to generate a first OFDM waveform to be transmitted for the uplink transmission. In some cases, performing OFDM modulation may be considered to be part of the channel processing chain, or performing OFDM modulation may be considered to be separate from the channel processing chain. At step S1130, the communications device modifies the channel processing chain for the transport block to generate one or more modified OFDM waveforms. In other words, the communications device re-performs some or all of the channel processing chain, but modifies one or more parameters of the channel processing chain in order to generate one or more OFDM waveform for the transport block that is different to the original OFDM waveform. At step S1140, the communications device determines an OFDM waveform of one or more modified OFDM waveforms to be transmitted and at step S1150 transmits the determined modified OFDM waveform to the infrastructure equipment.

Figure 12 illustrates a flow diagram of an example method 1200 for an infrastructure equipment according to the present disclosure. At step 1210, the infrastructure equipment receives, from a communications device, an uplink transmission, wherein the uplink transmission uses a particular OFDM waveform of a plurality of OFDM waveforms, wherein each OFDM waveform of the plurality of OFDM waveforms is generated by a different channel processing chain. At step 1220, the infrastructure equipment receives, from the communications device, an indication of one or more modifications to the channel processing chain for generating the particular OFDM waveform. While Figure 12 illustrates step S1220 as being performed after step 1210, it should be appreciated that step 1220 may alternatively be performed before step 1210 or concurrently with step 1210. For example, the infrastructure equipment may receive a UCI from the communications device indicating the modifications before or after the uplink transmission is received. Alternatively, an indication of the modifications may be included in a DMRS sequence or a cyclic shift applied to the DMRS sequence for the uplink transmission.

Figure 13 illustrates a flow diagram of an example method 1300 for an infrastructure equipment according to the present disclosure. At step 1310, the infrastructure equipment transmits, for receipt by the communications device, a set of possible modifications to the channel processing chain for generating the plurality of OFDM waveforms, wherein the channel processing chain for generating the particular OFDM waveform includes one or more of the set of possible modifications. The possible modifications may include one or more modifications and may, for example, be transmitted in dedicated signalling to the communications device, or in an SIB. The infrastructure may, in some cases, additionally receive an indication of which (if any) of the set of possible modification have been applied to the channel processing chain when generating the OFDM waveform for the uplink transmission. The UE may also apply one or more of the set of possible modifications.

Accordingly, from one perspective there has been disclosed methods, communications devices, infrastructure equipment and circuitry which allow for reduction of signal distortion in an OFDM waveform to be used for an uplink transmission. A first OFDM waveform is generated by a communications device using a first channel processing chain having a particular level of signal distortion. The communications device then generates a modified OFDM waveform by modifying the channel processing chain as compared to the first channel processing chain. The modifications to the channel processing chain result in the modified OFDM waveform having a level of signal distortion that is different to the first OFDM waveform. The modifications to the channel processing chain may be indicated by the communications device to the receiving base station, or the base station may transmit a set of possible (predetermined) modifications to the channel processing chain to the communications device.

Further examples of feature combinations taught by the present disclosure are set out in the following numbered clauses:

1. A method of operating a communications device configured to transmit signals to and/or receive signals from an infrastructure equipment via a wireless access interface provided by a wireless communications network, the wireless communications network comprising at least the infrastructure equipment, the method comprising: performing channel processing for a transport block to be transmitted in an uplink transmission to create a first set of modulation symbols mapped to physical resource elements, wherein performing the channel processing includes applying one or more channel processing chains to the transport block; performing orthogonal frequency-division multiplexing (OFDM) modulation to the first set of modulation symbols to generate a first OFDM waveform to be transmitted for the uplink transmission; modifying the channel processing chain for the transport block to generate one or more modified OFDM waveforms; determining an OFDM waveform of one or more modified OFDM waveforms to be transmitted; and transmitting the determined modified OFDM waveform.

2. The method according to clause 1 , further comprising: measuring a level of distortion for the first OFDM waveform; and determining that the level of distortion for the first OFDM waveform is above a predetermined threshold; wherein modifying the channel processing chain is performed in response to determining that the level of distortion for the first OFDM waveform is above a predetermined threshold.

3. The method according to clause 2, wherein the level of distortion is one or more of: a peak-to-average power ratio (PAPR); or an error vector magnitude (EVM).

4. The method according to clause 2 or clause 3, further comprising measuring a level of distortion for the one or more modified OFDM waveforms; and wherein determining the OFDM waveform of one or more modified OFDM waveforms to be transmitted is based on the measurement of the level of distortion for the one or more modified OFDM waveforms.

5. The method according to clause 4, further comprising: determining a distortion headroom amount, the distortion headroom amount being a difference between the level of distortion of the determined modified OFDM waveform and the predetermined threshold; and determining a transmission power of the determined OFDM waveform based on the distortion headroom amount.

6. The method according to any preceding clause, wherein the channel processing includes one or both of transport channel processing and physical channel processing.

7. The method according to any preceding clause, further comprising: transmitting an indication of the modification to channel processing chain.

8. The method according to clause 7, wherein the modification is indicated by one or more of: a demodulation reference signal (DMRS) sequence used for the uplink transmission; a cyclic shift applied to the DMRS sequence used for the uplink transmission; or signalling within an uplink control information (UCI) transmitted on a physical uplink control channel (PLICCH) or a physical uplink shared channel.

9. The method according to any preceding clause, wherein modifying the channel processing comprises modifying a mapping of the first set of modulation symbols to the physical resource elements.

10. The method according to clause 9, wherein modifying a mapping of the first set of modulation symbols to the physical resource elements comprises swapping subsets of the first set of modulation symbols between different OFDM symbols.

11. The method according to clause 9 or clause 10, wherein modifying a mapping of the first set of modulation symbols to the physical resource elements comprises swapping subsets of the first set of modulation symbols within the same OFDM symbol.

12. The method according to any of clauses 9-11 , wherein modifying a mapping of the first set of modulation symbols to the physical resource elements comprises applying a cyclical buffer to a stream of the first set of modulation symbols during mapping of the first set of modulation symbols to the physical resource elements to alter the location of the first set of modulation symbols within the physical resource elements.

13. The method according to any of clauses 9-12, wherein modifying the channel processing comprises rotating a modulation of a subset of modulation symbols mapped to a particular OFDM symbol.

14. The method according to clause 13, wherein rotating the modulation of the subset of modulation symbols mapped to the particular OFDM symbol comprises rotating the modulation of all modulation symbols mapped to a particular physical resource block.

15. The method according to clause 13 or clause 14, wherein rotating the modulation of the subset of modulation symbols mapped to the particular OFDM symbol comprises rotating a first group of modulation symbols by a first amount, and rotating a second group of modulation symbols by a second amount.

16. The method according to clause 15, wherein the first and second groups of modulation symbols correspond to different tones allocated to the communications device.

17. The method according to clause 15, wherein the first and second groups of modulation symbols correspond to different physical resource blocks.

18. The method according to any of clauses 13-17, wherein rotating a modulation of a subset of modulation symbols mapped to a particular OFDM symbol comprises rotating the modulation by a multiple of 90 degrees.

19. The method according to any of clauses 13-17, wherein rotating a modulation of a subset of modulation symbols mapped to a particular OFDM symbol comprises rotating the modulation by an amount other than 90 degrees.

20. The method according to any preceding clause, wherein modifying the channel processing chain for the transport block comprises modifying a mapping between modulation symbols and multiple in multiple out (MIMO) layers.

21. The method according to any preceding clause, wherein modifying the channel processing chain for the transport block comprises modifying a mapping between bit sequences and modulation symbols.

22. The method according to any preceding clause, wherein modifying the channel processing chain for the transport block comprises using a different scrambling sequence in generating the one or more modified OFDM waveforms than a scrambling sequence used in generating the first OFDM waveform.

23. The method according to any preceding clause, wherein modifying the channel processing chain for the transport block comprises using a different redundancy version in generating the one or more modified OFDM waveforms than a redundancy version used in generating the first OFDM waveform.

24. The method according to any preceding clause, wherein modifying the channel processing chain for the transport block comprises applying an offset to a redundancy version used in generating the first OFDM waveform when generating the one or more modified OFDM waveforms.

25. The method according to any preceding clause, wherein modifying the channel processing chain for the transport block comprises using a different interleaver in generating the one or more modified OFDM waveforms than an interleaver used in generating the first OFDM waveform.

26. The method according to any preceding clause, wherein the channel processing chain for the transport block is modified in a predetermined manner to generate a single modified OFDM waveform; and wherein the modified OFDM waveform is transmitted in response to determining that a level of distortion for the first OFDM waveform is above a predetermined threshold.

27. The method according to any preceding clause, wherein the uplink transmission is a physical uplink shared channel (PLISCH) transmission. 28. The method according to any preceding clause, further comprising: receiving, from the infrastructure equipment, one or more predetermined modifications to the channel processing chain for use by the communications device in generating the one or more modified OFDM waveforms.

29. A communications device comprising: a transceiver configured to transmit signals to and/or to receive signals from an infrastructure equipment of a wireless communications network via a wireless radio interface provided by the wireless communications network, and a controller configured in combination with the transceiver to: perform channel processing for a transport block to be transmitted in an uplink transmission to create a first set of modulation symbols mapped to physical resource elements, wherein performing the channel processing includes applying one or more channel processing chains to the transport block; perform orthogonal frequency-division multiplexing (OFDM) modulation to the first set of modulation symbols to generate a first OFDM waveform to be transmitted for the uplink transmission; modify the channel processing chain for the transport block to generate one or more modified OFDM waveforms; determine an OFDM waveform of one or more modified OFDM waveforms to be transmitted; and transmit the determined modified OFDM waveform.

30. Circuitry for a communications device, the circuitry comprising: transceiver circuitry configured to transmit signals to and/or to receive signals from an infrastructure equipment of a wireless communications network via a wireless radio interface provided by the wireless communications network, and controller circuitry configured in combination with the transceiver circuitry to: perform channel processing for a transport block to be transmitted in an uplink transmission to create a first set of modulation symbols mapped to physical resource elements, wherein performing the channel processing includes applying one or more channel processing chains to the transport block; perform orthogonal frequency-division multiplexing (OFDM) modulation to the first set of modulation symbols to generate a first OFDM waveform to be transmitted for the uplink transmission; modify the channel processing chain for the transport block to generate one or more modified OFDM waveforms; determine an OFDM waveform of one or more modified OFDM waveforms to be transmitted; and transmit the determined modified OFDM waveform.

31 . A method of operating an infrastructure equipment configured to transmit signals to and/or receive signals from a communication device via a wireless access interface provided by a wireless communications network, the wireless communications network comprising at least the infrastructure equipment, the method comprising: receiving, from a communications device, an uplink transmission, wherein the uplink transmission uses a particular OFDM waveform of a plurality of OFDM waveforms, wherein each OFDM waveform of the plurality of OFDM waveforms is generated by a different channel processing chain.

32. The method according to clause 31 , further comprising: receiving, from the communications device, an indication of one or more modifications to the channel processing chain for generating the particular OFDM waveform.

33. The method according to clause 32, wherein the one or more modifications are indicated by one or more of: a demodulation reference signal (DMRS) sequence used in the uplink transmission; a cyclic shift applied to the DMRS sequence used in the uplink transmission; or signalling within an uplink control information (UCI) transmitted on a physical uplink control channel (PLICCH) or a physical uplink shared channel.

34. The method according to any of clauses 31-33, further comprising: transmitting, for receipt by the communications device, a set of possible modifications to the channel processing chain for generating the plurality of OFDM waveforms, wherein the channel processing chain for generating the particular OFDM waveform includes one or more of the set of possible modifications.

35. The method according to clause 34, wherein the indication of the one or more modifications is included in one or more of: a system information block (SIB) transmission, or configuration signalling transmitted to the communications device as part of a connection process between the infrastructure equipment and the communications device.

36. The method according to any of clauses 31-35, further comprising: transmitting, for receipt by the communications device, an indication of a predetermined threshold of an acceptable level of signal distortion for an OFDM waveform.

37. The method according to any of clauses 31-36, wherein the channel processing chain includes one or both of a transport channel processing chain and physical channel processing chain.

38. The method according to any of clauses 31-37, wherein the different channel processing chains include different mappings of a first set of modulation symbols to physical resource elements.

39. The method according to clause 38, wherein the different mappings include swapping subsets of the first set of modulation symbols between different OFDM symbols.

40. The method according to clause 38 or 39, wherein the different mappings include swapping subsets of the first set of modulation symbols within the same OFDM symbols.

41 . The method according to any of clauses 38-40, wherein the different mappings include applying a cyclical buffer to a stream of the first set of modulation symbols during mapping of the first set of modulation symbols to the physical resource elements to alter the location of the first set of modulation symbols within the physical resource elements.

42. The method according to any of clauses 31-41 , wherein the different channel processing chains include different rotations of a modulation of a subset of modulation symbols mapped to a particular OFDM symbol.

43. The method according to clause 42, wherein rotating the modulation of the subset of modulation symbols mapped to the particular OFDM symbol comprises rotating the modulation of all modulation symbols mapped to a particular physical resource block.

44. The method according to clause 42 or 43, wherein rotating the modulation of the subset of modulation symbols mapped to the particular OFDM symbol comprises rotating a first group of modulation symbols by a first amount, and rotating a second group of modulation symbols by a second amount.

45. The method according to clause 44, wherein the first and second groups of modulation symbols correspond to different tones allocated to the communications device.

46. The method according to clause 44, wherein the first and second groups of modulation symbols correspond to different physical resource blocks.

47. The method according to any of clauses 42-46, wherein rotating a modulation of a subset of modulation symbols mapped to a particular OFDM symbol comprises rotating the modulation by a multiple of 90 degrees.

48. The method according to any of clauses 42-46, wherein rotating a modulation of a subset of modulation symbols mapped to a particular OFDM symbol comprises rotating the modulation by an amount other than 90 degrees.

49. The method according to any of clauses 31-48, wherein the different channel processing chains include different mappings between modulation symbols and multiple in multiple out (MIMO) layers.

50. The method according to any of clauses 31-49, wherein the different channel processing chains include different mappings between bit sequences and modulation symbols.

51. The method according to any of clauses 31-50, wherein the different channel processing chains include different scrambling sequences for generating the OFDM waveforms.

52. The method according to any of clauses 31-51 , wherein the different channel processing chains include different redundancy versions for generating OFDM waveforms.

53. The method according to any of clauses 31-52, wherein the different channel processing chains include different offsets to a redundancy version used in generating the OFDM waveforms.

54. The method according to any of clauses 31-53, wherein the different channel processing chains include different interleavers for generating the OFDM waveforms.

55. The method according to any of clauses 31-54, wherein the uplink transmission is a physical uplink shared channel (PLISCH) transmission.

56. An infrastructure equipment comprising: a transceiver configured to transmit signals to and/or to receive signals from a communications device via a wireless radio interface provided by the infrastructure equipment, and a controller configured in combination with the transceiver to: receive, from a communications device, an uplink transmission, wherein the uplink transmission uses a particular OFDM waveform of a plurality of OFDM waveforms, wherein each OFDM waveform of the plurality of OFDM waveforms is generated by a different channel processing chain.

57. Circuitry for an infrastructure equipment, the circuitry comprising: transceiver circuitry configured to transmit signals to and/or to receive signals from a communications device via a wireless radio interface provided by the infrastructure equipment, and controller circuitry configured in combination with the transceiver circuitry to: receive, from a communications device, an uplink transmission, wherein the uplink transmission uses a particular OFDM waveform of a plurality of OFDM waveforms, wherein each OFDM waveform of the plurality of OFDM waveforms is generated by a different channel processing chain.

REFERENCES

[1] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based radio access”, John Wiley and Sons, 2009.

[2] TS38.212, V17.3.0, 3GPP

[3] TS38.211 , V17.3.0, 3GPP

[4] “5G New Radio in Bullets”; Johnson, Chris; 2019; ISBN: 9781081444594

[5] EN302755, “Digital Video Broadcasting (DVB): Frame structure, channel coding and modulation for a second generation digital terrestrial television broadcasting system (DVB- 72)”, 2008.

Claims

2. The method according to claim 1 , further comprising: measuring a level of distortion for the first OFDM waveform; and determining that the level of distortion for the first OFDM waveform is above a predetermined threshold; wherein modifying the channel processing chain is performed in response to determining that the level of distortion for the first OFDM waveform is above a predetermined threshold.

3. The method according to claim 2, wherein the level of distortion is one or more of: a peak-to-average power ratio (PAPR); or an error vector magnitude (EVM).

4. The method according to claim 2, further comprising measuring a level of distortion for the one or more modified OFDM waveforms; and wherein determining the OFDM waveform of one or more modified OFDM waveforms to be transmitted is based on the measurement of the level of distortion for the one or more modified OFDM waveforms.

5. The method according to claim 4, further comprising: determining a distortion headroom amount, the distortion headroom amount being a difference between the level of distortion of the determined modified OFDM waveform and the predetermined threshold; and determining a transmission power of the determined OFDM waveform based on the distortion headroom amount.

6. The method according to claim 1 , wherein the channel processing includes one or both of transport channel processing and physical channel processing.

7. The method according to claim 1 , further comprising: transmitting an indication of the modification to channel processing chain.

8. The method according to claim 7, wherein the modification is indicated by one or more of: a demodulation reference signal (DMRS) sequence used for the uplink transmission; a cyclic shift applied to the DMRS sequence used for the uplink transmission; or signalling within an uplink control information (UCI) transmitted on a physical uplink control channel (PLICCH) or a physical uplink shared channel (PLISCH).

9. The method according to claim 1 , wherein modifying the channel processing comprises modifying a mapping of the first set of modulation symbols to the physical resource elements.

10. The method according to claim 9, wherein modifying a mapping of the first set of modulation symbols to the physical resource elements comprises swapping subsets of the first set of modulation symbols between different OFDM symbols.

11. The method according to claim 9, wherein modifying a mapping of the first set of modulation symbols to the physical resource elements comprises swapping subsets of the first set of modulation symbols within the same OFDM symbol.

12. The method according to claim 9, wherein modifying a mapping of the first set of modulation symbols to the physical resource elements comprises applying a cyclical buffer to a stream of the first set of modulation symbols during mapping of the first set of modulation symbols to the physical resource elements to alter the location of the first set of modulation symbols within the physical resource elements.

13. The method according to claim 9, wherein modifying the channel processing comprises rotating a modulation of a subset of modulation symbols mapped to a particular OFDM symbol.

14. The method according to claim 13, wherein rotating the modulation of the subset of modulation symbols mapped to the particular OFDM symbol comprises rotating the modulation of all modulation symbols mapped to a particular physical resource block.

15. The method according to claim 13, wherein rotating the modulation of the subset of modulation symbols mapped to the particular OFDM symbol comprises rotating a first group of modulation symbols by a first amount, and rotating a second group of modulation symbols by a second amount.

16. The method according to claim 15, wherein the first and second groups of modulation symbols correspond to different tones allocated to the communications device.

17. The method according to claim 15, wherein the first and second groups of modulation symbols correspond to different physical resource blocks.

18. The method according to claim 13, wherein rotating a modulation of a subset of modulation symbols mapped to a particular OFDM symbol comprises rotating the modulation by a multiple of 90 degrees.

19. The method according to claim 13, wherein rotating a modulation of a subset of modulation symbols mapped to a particular OFDM symbol comprises rotating the modulation by an amount other than 90 degrees.

20. The method according to claim 1 , wherein modifying the channel processing chain for the transport block comprises modifying a mapping between modulation symbols and multiple in multiple out (MIMO) layers.

21. The method according to claim 1 , wherein modifying the channel processing chain for the transport block comprises modifying a mapping between bit sequences and modulation symbols.

22. The method according to claim 1 , wherein modifying the channel processing chain for the transport block comprises using a different scrambling sequence in generating the one or more modified OFDM waveforms than a scrambling sequence used in generating the first OFDM waveform.

23. The method according to claim 1 , wherein modifying the channel processing chain for the transport block comprises using a different redundancy version in generating the one or more modified OFDM waveforms than a redundancy version used in generating the first OFDM waveform.

24. The method according to claim 1 , wherein modifying the channel processing chain for the transport block comprises applying an offset to a redundancy version used in generating the first OFDM waveform when generating the one or more modified OFDM waveforms.

25. The method according to claim 1 , wherein modifying the channel processing chain for the transport block comprises using a different interleaver in generating the one or more modified OFDM waveforms than an interleaver used in generating the first OFDM waveform.

26. The method according to claim 1 , wherein the channel processing chain for the transport block is modified in a predetermined manner to generate a single modified OFDM waveform; and wherein the modified OFDM waveform is transmitted in response to determining that a level of distortion for the first OFDM waveform is above a predetermined threshold.

27. The method according to claim 1, wherein the uplink transmission is a physical uplink shared channel (PLISCH) transmission.

28. The method according to claim 1 , further comprising: receiving, from the infrastructure equipment, one or more predetermined modifications to the channel processing chain for use by the communications device in generating the one or more modified OFDM waveforms.

31. A method of operating an infrastructure equipment configured to transmit signals to and/or receive signals from a communication device via a wireless access interface provided by a wireless communications network, the wireless communications network comprising at least the infrastructure equipment, the method comprising: receiving, from a communications device, an uplink transmission, wherein the uplink transmission uses a particular OFDM waveform of a plurality of OFDM waveforms, wherein each OFDM waveform of the plurality of OFDM waveforms is generated by a different channel processing chain.

32. The method according to claim 31, further comprising: receiving, from the communications device, an indication of one or more modifications to the channel processing chain for generating the particular OFDM waveform.

33. The method according to claim 32, wherein the one or more modifications are indicated by one or more of: a demodulation reference signal (DMRS) sequence used in the uplink transmission; a cyclic shift applied to the DMRS sequence used in the uplink transmission; or signalling within an uplink control information (UCI) transmitted on a physical uplink control channel (PLICCH) or a physical uplink shared channel (PLISCH).

34. The method according to claim 31, further comprising: transmitting, for receipt by the communications device, a set of possible modifications to the channel processing chain for generating the plurality of OFDM waveforms, wherein the channel processing chain for generating the particular OFDM waveform includes one or more of the set of possible modifications.

35. The method according to claim 34, wherein the indication of the one or more modifications is included in one or more of: a system information block (SIB) transmission, or configuration signalling transmitted to the communications device as part of a connection process between the infrastructure equipment and the communications device.

36. The method according to claim 31, further comprising: transmitting, for receipt by the communications device, an indication of a predetermined threshold of an acceptable level of signal distortion for an OFDM waveform.

37. The method according to claim 31, wherein the channel processing chain includes one or both of a transport channel processing chain and physical channel processing chain.

38. The method according to claim 31, wherein the different channel processing chains include different mappings of a first set of modulation symbols to physical resource elements.

39. The method according to claim 38, wherein the different mappings include swapping subsets of the first set of modulation symbols between different OFDM symbols.

40. The method according to claim 38, wherein the different mappings include swapping subsets of the first set of modulation symbols within the same OFDM symbols.

41. The method according to claim 38, wherein the different mappings include applying a cyclical buffer to a stream of the first set of modulation symbols during mapping of the first set of modulation symbols to the physical resource elements to alter the location of the first set of modulation symbols within the physical resource elements.

42. The method according to claim 31, wherein the different channel processing chains include different rotations of a modulation of a subset of modulation symbols mapped to a particular OFDM symbol.

43. The method according to claim 42, wherein rotating the modulation of the subset of modulation symbols mapped to the particular OFDM symbol comprises rotating the modulation of all modulation symbols mapped to a particular physical resource block.

44. The method according to claim 42, wherein rotating the modulation of the subset of modulation symbols mapped to the particular OFDM symbol comprises rotating a first group of modulation symbols by a first amount, and rotating a second group of modulation symbols by a second amount.

45. The method according to claim 44, wherein the first and second groups of modulation symbols correspond to different tones allocated to the communications device.

46. The method according to claim 44, wherein the first and second groups of modulation symbols correspond to different physical resource blocks.

47. The method according to claim 42, wherein rotating a modulation of a subset of modulation symbols mapped to a particular OFDM symbol comprises rotating the modulation by a multiple of 90 degrees.

48. The method according to claim 42, wherein rotating a modulation of a subset of modulation symbols mapped to a particular OFDM symbol comprises rotating the modulation by an amount other than 90 degrees.

49. The method according to claim 31, wherein the different channel processing chains include different mappings between modulation symbols and multiple in multiple out (MIMO) layers.

50. The method according to claim 31, wherein the different channel processing chains include different mappings between bit sequences and modulation symbols.

51. The method according to claim 31, wherein the different channel processing chains include different scrambling sequences for generating the OFDM waveforms.

52. The method according to claim 31, wherein the different channel processing chains include different redundancy versions for generating OFDM waveforms.

53. The method according to claim 31, wherein the different channel processing chains include different offsets to a redundancy version used in generating the OFDM waveforms.

54. The method according to claim 31, wherein the different channel processing chains include different interleavers for generating the OFDM waveforms.

55. The method according to claim 31, wherein the uplink transmission is a physical uplink shared channel (PLISCH) transmission.