GB2547041A

GB2547041A - Uplink peak average power ratio reduction

Info

Publication number: GB2547041A
Application number: GB1602163.6A
Authority: GB
Inventors: Liu Guang
Original assignee: TCL Communication Ltd
Current assignee: TCL Communication Ltd
Priority date: 2016-02-05
Filing date: 2016-02-05
Publication date: 2017-08-09
Also published as: GB201602163D0; WO2017133469A1

Abstract

A transmitter estimates the uplink peak-to-average power ratio (PAPR) of signals output from a plurality of signal processing branches, and selects the branch with reduced or minimal PAPR for transmission. The branch may be the first to have reached a PAPR threshold. Each branch may have a different scrambling or interleaving scheme with an identifying index value that can then be transmitted to a receiver for use in decoding the signal. The index may be transmitted as a control signal waveform. The PAPR of output when combined with the waveform representing the index may be reduced. The transmitted signal may be an OFDM signal, with the index being a PUCCH waveform within, on the distal ends, or as guard bands outside the OFDM signal. The index waveform may be punctured into the OFDM signal or be encoded within OFDM reference symbols. The PAPR may be minimised for at least a symbol or for every subframe. The PAPR minimisation may be applied to a multi-carrier transmitter in which each branch is associated with a different centre carrier, the combination of branches being compared for PAPR. A receiver may blind decode scrambled or interleaved signals.

Description

UPLINK PEAK AVERAGE POWER RATIO REDUCTION TECHNICAL FIELD

[001] Embodiments of the present invention generally relate wireless apparatus for wireless communication systems using unlicensed spectrum and in particular to methods and wireless apparatus for reducing peak average power ratio (PAPR) for uplink (UL) transmissions in such wireless communication systems.

BACKGROUND

[002] Wireless communication systems and networks, such as the third-generation (3G) of mobile telephone standards and technology are well known. Such 3G standards and technology have been developed by the 3G Partnership Project (3GPP). The 3rd generation of wireless communications has generally been developed to support macro-cell mobile phone communications. Such macro cells utilise high power base stations (NodeBs) to communicate with wireless communication units within a relatively large geographical coverage area.

[003] Typically, wireless communication units, or User Equipment (UEs) as they are often referred to, communicate with a Core Network (CN) of the 3G wireless communication network via a Radio Network Subsystem (RNS). A wireless communication network typically comprises a plurality of radio network subsystems, each radio network subsystem comprising one or more cells to which UEs may attach, and thereby connect to the network. Each macro-cellular RNS further comprises a controller, in a form of a Radio Network Controller (RNC), operably coupled to the one or more NodeBs. Communications systems and networks have developed towards a broadband and mobile system. The 3rd Generation Partnership Project has developed a Long Term Evolution (LTE) solution, namely, an Evolved Universal Mobile Telecommunication System Territorial Radio Access Network, (E-UTRAN), for a mobile access network, and a System Architecture Evolution (SAE) solution, namely, an Evolved Packet Core (EPC), for a mobile core network. A macrocell in an LTE system is supported by a base station known as an eNodeB or eNB (evolved Node B).

[004] Current wireless communication networks operate using licensed radio spectrum in which multiple accesses to the communications resources of the licensed radio spectrum is strictly controlled. Each user of the network is essentially provided a “slice” of the spectrum using a variety of multiple access techniques such as, by way of example only but not limited to, frequency division multiplexing, time division multiplexing, code division multiplexing, and space division multiplexing or a combination of one or more of these techniques. Even with a combination of these techniques, with the popularity of mobile telecommunications, the capacity of current and future telecommunications networks is still very limited, especially when using licensed radio spectrum.

[005] The use of unlicensed radio spectrum is being opened up for network operators in order to increase or supplement the capacity of their wireless communication networks. For example, a communication network based on the Long Term Evolution (LTE)/LTE advanced standards have been an enhanced downlink that uses a mechanism called Licensed-Assisted-Access (LAA) to operate on unlicensed spectrum such as, by way of example but is not limited to, the 5GHz Wi-Fi radio spectrum, which may increase the downlink capacity of current networks operating in the licensed radio spectrum. This enables the operation of a telecommunication network based on LTE in the 5GHz unlicensed spectrum for low power secondary cells based on regional regulatory power limits using carrier aggregation.

[006] Nevertheless, network operators are not allowed to have unfettered access or use of unlicensed spectrum because they must share the unlicensed spectrum with other wireless devices such as, by way of example only but not limited to, Wi-Fi access points and terminals, medical devices, utilities meters, wireless machine-to-machine devices, Internet-of-things devices. Thus, a compromise has been struck between network operators and the governing bodies of the radio spectrum in relation to the use of unlicensed spectrum. Network operators must comply with various telecommunications regulations in order to make use of the unlicensed spectrum.

[007] Currently there are two main regulations in sections 4.3 and 4.4 of the ETSI EN 301 893 V1.7.2 (2014-07) “Broadband Radio Access Networks (BRAN); 5 GHz high performance RLAN; Harmonized EN covering the essential requirements of article 3.2 of the R&TTE Directive” draft standard that each uplink (UL) wireless communication unit should comply with for the UL when using the unlicensed spectrum. The first regulation, in section 4.3 ETSI EN 301 893 V1.7.2 (2014-07), the output signal of each wireless communication unit must be able to occupy at least 80% of the whole bandwidth. Even when only 2 RBs are allocated to one terminal, they must be located with enough distance in between, e.g., one RB at the left end and the other on the right end of the system bandwidth, while they could be located anywhere next to each other currently.

[008] The second regulation, in section 4.4 ETSI EN 301 893 V1.7.2 (2014-07), describes the power density per MFIz is limited to a certain level measured in dBm (e.g., 10dBm), this means even only one RB (180KFIz) needs to be sent and the UE cannot use full power (e.g., 23dBm). To explore more power, it is expected to distribute the subcarriers in frequency in a way that they are mapped into as many “MFIz” as possible.

[009] Although the following description describes, by way of example only but is not limited to, the use of Orthogonal Frequency-Division Multiple Access (OFDMA), single-carrier and multi-carrier transmitters/receivers based on OFDM and other carrier formats, it is to be appreciated by the skilled person that the following description may be applied, not only to OFDMA or other related systems, but also to other communication systems, receivers and transmitters, such as, by way of example only but is not limited to, Code Division Multiple Access (CDMA) systems, time division multiple access (TDMA) systems, any other Frequency Division Multiple Access (FDMA) systems, or Space Division Multiple Access (SDMA) systems, or any other suitable communication system or combinations thereof.

[010] Orthogonal Frequency-Division Multiple Access (OFDMA) is a multi-user access method using an orthogonal frequency-division multiplexing (OFDM) digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual users or UEs. OFDMA is typically used in the downlink of LTE communication systems because the eNB(s) have control in granting multiple access to each UE served by that eNB. However, rather than using OFDMA for UL communications in LTE, single carrier-FDMA has certain advantages for UL communications. Most notably is the lower peak-to-average power ratio (PAPR), which can greatly benefit the design of wireless communication units in terms of transmit power efficiency and reduced cost of the transmit power amplifier. It has been adopted as the UL multiple access scheme in 3GPP LTE or Evolved UTRA (E-UTRA).

[011] The peak-to-average power ratio (PAPR) is the peak amplitude squared (giving the peak power) divided by the average power. The PAPR for a signal X may be given as: PAPR=jXPEAKj2 / E{X(n).*conj(X(n))}, where X(n) are the samples of the signal X, conj(.) is the conjugate function, and E{.} is the expectation function calculating the average. PAPR values are typically given in dB.

[012] Typically, OFDMA has a high PAPR value and in theory, it is a linear function of the number of subcarriers. It is acceptable for downlink communications to have a high PAPR, because the transmit circuitry (e.g. linear amplifiers etc.) of eNBs are robust and powerful enough to handle a high PAPR. However, high PAPR become problematic for UL communications because wireless communication units or UEs have severe design and power constraints such that their transmit circuitry (e.g. linear amplifiers etc.) are more sensitive than eNB(s) in both cost and power consumption. For this reason, single carrier-FDMA is used on the LTE UL, where the terminal front end design is only capable of handling comparatively low PAPR values. This is achieved by mapping the subcarriers in the frequency domain such that they are equally separated.

[013] The transmit power amplifier has a limited linear range and input signals exceed this range will experience more distortion. PAPR describes the power range of a signal and a high PAPR will force the amplifier to have a large backoff (reduce the output power) in order to ensure linear amplification of the signal. Additionally, high PAPR requires high resolution for the receiver analogue-to-digital (A/D) converter and places a complexity and power burden on a receiver front end at both eNB and UE. The receiver front-end of eNBs are required to be very sensitive to the considerably weaker UL signals transmitted by UEs.

[014] There are several different subcarrier mapping methods or transmission techniques that are being used or are being proposed for use with the LTE UL, which currently uses SC-FDMA. Figure 1a illustrates three of the mappings for a block of contiguous subcarriers, where for each mapping a square in figure 1a represents a subcarrier. The first mapping is the so-called Localized Frequency Division Multiple Access (LFDMA) in which all subcarriers are allocated to each wireless communication device are continuously allocated in a contiguous subblock of subcarriers. This is currently being used for LTE UL communications.

[015] The second proposed mapping is the so-called Interleaved FDMA (IFDMA) in which each of the subcarriers allocated to a wireless communication device are separated by a predetermined number of subcarriers (e.g. equal separation) and each other wireless communication unit or UE is interleaved together on the unused subcarriers.

[016] The third proposed mapping is a so-called block-lFDMA technique, which is a combination of LFDMA and IFDMA. In block-lFDMA, each wireless communication unit or UE is allocated a set of subcarriers in which each set contains two or more subsets (or groups) of subcarriers (also called subcarrier sets) that may have a size of X subcarriers, where X>=2 and X is an integer. Each subset or group of subcarriers is a continuously allocated or contiguous block of X subcarriers. That is, there is no separation between the subcarriers. Each of the two or more groups of subcarriers are separated by a number of Y subcarriers, where Y>=aXfor a>=1 and a is an integer. In some cases, a may be the number of users or UEs capable of using block-lFDMA.

[017] Figure 1 b shows a graph of the probability that the PAPR is greater than a reference PAPR (PAPRO) (e.g. Pr(PAPR>PAPRO)) vs PAPRO for a PAPR simulation of a communication system using LFDMA and block-lFDMA. As shown in figure 1b, the x-axis is PAPRO is a reference PAPR value and the y-axis is the probability that the variable PAPRs are greater than the reference PAPRO (e.g. Pr(PAPR>PAPRO)). The solid curve on left of figure 1b is when the communication system uses LFDMA over 20 resource blocks (RBs). The dashed curve on the right of figure 1b is when the communication system uses block-lFDMA over 20 RBs, which are mapped with a frequency gap equal to 4 RB width between every 2 adjacent RBs as illustrated in figure 1a. A group of subcarriers continuously allocated or that are contiguous may also be called a cluster and obviously, in this case it can be said that there are 20 clusters. It has also been observed by simulation that the more clusters there are, the higher PAPR the output signals for transmission have.

[018] As shown on the graph, for LFDMA (solid curve) the probability that a PAPR will be greater than 8dB is about 10"4 for 1 cluster or group of 20RBs when continuously allocated i.e. when allocated as a contiguous block. As can be seen, for block-lFMDA, there are about a 2dB degradation (e.g. a 2dB increase in PAPRO) at the same 10'4 probability. It is clear that block-lFDMA mapping does not have the property of single carrier FDMA (SC-FDMA), which uses L-FDMA mapping, and the PAPR of the output signal is significantly increased, which can be problematic for UL communications.

[019] Due to the above two regulation requirements being placed on the LAA UL i.e. each wireless communication unit is required to use 80% of the total frequency bandwidth for each block of 20MFIz with power constraints per MHz bandwidth, LFDMA is being seen as an unattractive mapping technique when a small number of RBs are allocated to one UE. Given these regulations, the LAA UL is evolving into an enhanced LAA UL in which the UL subcarriers are expected to be mapped onto subcarriers unevenly separated apart due to these two regulation requirements, which it seems may be satisfied by the possible use of block-lFDMA or IFDMA or combinations thereof. Each frame of L RBs may have a large number of subcarriers (e.g. for L=100, with each RB having 12 contiguous subcarrier, there will be 1200 subcarriers). Thus, one wireless communication unit at a cell edge using block-lFDMA or IFDMA with nonidentical gaps may inadvertently use a larger PAPR than a wireless communication unit closer to the cell center using LFDMA and thus overload its linear transmit amplifier. It is also a known problem that the PAPR for IFDMA and block-lFDMA are worse than for the current LFDMA techniques. There is a desire for a PAPR reduction scheme and UL control signalling for block-lFDMA and IFDMA mappings when used for the enhanced LAA UL that achieve the a reduced PAPR.

SUMMARY

[020] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[021] The invention relates to methods and apparatus for efficient reduction in peak average power ratio (PAPR) for wireless communication unit transmitters/receivers when used in the UL of wireless communication systems over unlicensed radio spectrum, where, by way of example only but not limited to, Space DMA, CDMA, TDMA, FDMA such as L-FDMA, block-lFDMA and/or IFDMA based mappings may be used. PAPR may also be reduced for UL transmissions in which multiple sets of modulated data are scrambled or interleaved with different types of scrambling or interleaving, and selecting a set of scrambled or interleaved modulated data bits that minimise an estimated PAPR for use in the UL transmission.

[022] For example, PAPR may be reduced for UL transmissions using, by way of example only but is not limited to, a single carrier and/or multiple carrier type transmitter structures in which multiple sets of modulated data are scrambled or interleaved with different types of scrambling or interleaving, and selecting a set of scrambled or interleaved modulated data bits that minimise an estimated PAPR for transmitting from the SC or MC transmitter.

[023] According to a first aspect of the invention, there is provided a transmitter apparatus for uplink peak average power ratio, PAPR, reduction in a wireless communications system, comprising: a plurality of signal processing branches coupled to a PAPR checker and a transmitter, wherein the PAPR checker is configured to: estimate the PAPR of baseband communication signals output from the corresponding signal processing branches; select the signal processing branch associated with an output baseband communication signal that has a reduced or minimal PAPR compared with other signal processing branches; and send the baseband communication signal output from the selected signal processing branch to the transmitter for uplink transmission.

[024] Optionally, the PAPR checker is configured to select the signal processing branch in which the PAPR checker detects the estimated PAPR of the corresponding output baseband communication signal is minimised over all the output baseband communication signals on the remaining signal processing branches.

[025] As an option, the PAPR checker is configured to select the signal processing branch in which the PAPR checker first detects the estimated PAPR of the corresponding output baseband communication signal to have reached a predetermined PAPR threshold.

[026] As another option, when the PAPR checker detects that all of the estimated PAPRs of the corresponding output baseband communication signals are above the predetermined PAPR threshold, then the PAPR checker is configured to select the signal processing branch in which the PAPR checker detects the estimated PAPR of the corresponding output baseband communication signal is minimised over all the output baseband communication signals on the remaining signal processing branches.

[027] Optionally, the signal processing branches are configured to receive a plurality of modulation symbols, wherein the plurality of modulation symbols are the same for each signal processing branch, and each signal processing branch further comprises: a scrambler or interleaving module coupled to an communication signal generator for outputting the baseband communication signal, wherein the scrambler or interleaving module is configured to scramble or interleave the modulation symbols prior to input to the communication signal generator.

[028] As an option, the scrambler or interleaving module of each signal processing branch, uses a different scrambling scheme or a different interleaving scheme to the other signal processing branches.

[029] Optionally, each signal processing branch is associated with an index value for identifying the scrambling scheme or interleaving scheme used to scramble or interleave the modulated symbols.

[030] As an option, the PAPR checker is configured to use the index value to identify which signal processing branch has been selected and to send the baseband communication signal of the selected signalling branch to the transmitter for transmission based on the index value.

[031] As another option, the transmitter further includes a selector with the selection inputs of the selector coupled to the output of the signal processing branches, an output of the selector coupled to the transmitter, and a control input of the selector coupled to a control output of PAPR checker, wherein the PAPR checker outputs the index value to the control input of the selector for sending the baseband communication signal output from the selected signal processing branch to the transmitter.

[032] As an option, each output baseband communication signal comprises one or more baseband communication symbols, and the PAPR checker is configured to: select the signal processing branch for every one or more baseband communciation symbols that have a reduced or minimal PAPR compared with one or more baseband communication symbols associated with other signal processing branches.

[033] As another option, the one or more baseband communication symbols for each output baseband communication signal comprises a subframe of a plurality of baseband communication symbols, and the PAPR checker is configured to: select the signal processing branch for every subframe of baseband communication symbols that have a reduced or minimal PAPR compared with the subframes of baseband communication symbols associated with other signal processing branches.

[034] Optionally, the index value associated with the selected signal processing branch is transmitted to a receiver apparatus for use in descrambling or deinterleaving a received transmitted baseband communication signal output from the selected signal processing branch.

[035] As an option, the transmitter includes a waveform generator is configured to generate a control signal waveform comprising data representative of the index value associated with the corresponding signal processing branch.

[036] Optionally, the PAPR checker is further configured to: combine each output baseband communication signal with the control waveform associated with the corresponding signal processing branch; estimate the PAPR of each combined output baseband communication signal and corresponding control signal waveform; and select the signal processing branch associated with a combined output baseband communication signal and corresponding control signal waveform that has a reduced or minimal PAPR compared with other signal processing branches.

[037] As an option, the baseband communication signal is an OFDM signal and the control signal waveform is a physical uplink control channel, PUCCH, waveform. Optionally, the PUCCH waveform is transmitted in a control channel bandwidth in the vicinity of the distal ends of carrier frequency or system bandwidth associated with the OFDM signal selected for transmission. As another option, the PUCCH waveform is transmitted in a control channel bandwidth within the carrier frequency or system bandwidth associated with the OFDM signal selected for transmission. Optionally, the PUCCH waveform is transmitted in a control channel bandwidth outside the carrier frequency or system bandwidth associated with the OFDM signal selected for transmission. As another option, the control channel bandwidth outside the carrier frequency or system bandwidth is one or more guard band(s) associated with the OFDM signal selected for transmission.

[038] Optionally, the baseband communication signal is an OFDM signal, the communication signal generator is an OFDM signal generator within the signal processing branch associated with the index value, wherein the OFDM signal generator is further configured to: puncture one or more resource elements associated with data OFDM symbols; and insert the control signal waveform or data representative of the index value into the one or more resource elements, wherein a receiver apparatus receiving the punctured OFDM signal transmission retrieves the index value from the associated resource elements for identifying the descrambling or deinterleaving scheme to retrieve the original modulation symbols.

[039] As an option, the baseband communication signal is an OFDM signal, the communication signal generator is an OFDM signal generator of the signal processing branch associated with the index value, and the OFDM signal comprises two or more resource blocks, wherein each resource block comprises a block of reference symbols, and the OFDM signal generator of the signal processing branch associated with the index value is further configured to: encode the index value within the reference symbols of two or more of the resource blocks, wherein a receiver apparatus receiving a selected OFDM signal transmission detects and decodes the index value from the associated reference symbols for identifying the descrambling or deinterleaving scheme to retrieve the original modulation symbols.

[040] As an option, the transmitter apparatus is a multi-carrier, MC, transmitter apparatus associated with two or more center carrier, CC, frequency bandwidths, and the plurality of signal processing branches comprises two or more subsets of signal processing branches, wherein each signal processing branch outputs a baseband communication signal, and each subset of signal processing branches associated with each of the CC frequency bandwidths, in which each subset of signal processing branches is coupled to the PAPR checker and the transmitter, wherein the transmitter is a MC transmitter and wherein, each signal processing branch from each subset of signal processing branches is combined with signal processing branches from different other subsets of signal processing branches to form multiple combined signal processing branches, wherein each combined signal processing branch outputs a combined baseband communication signal for input to the PAPR checker.

[041] The PAPR checker may be further configured to: estimate the PAPR of each combined baseband communciation signal associated with each of the multiple combined signal processing branches; select a set of multiple combined signal processing branches in which the combined estimated PAPR of the corresponding baseband communication signals is reduced or minimised compared with the combined estimated PAPR for other sets of multiple combined signal processing branches, wherein each set of multiple combined signal processing branches includes signal processing branches associated with all of the CC frequency bandwidths; and send the baseband communication signal outputs associated with the signal processing branches of the selected set of multiple combined signal processing branches to the MC transmitter for uplink transmission.

[042] As an option, each of the multiple combined signal processing branches is associated with an index value for identifying the scrambling schemes or interleaving schemes used to scramble or interleave the modulated symbols associated with the multiple combined signal processing branches. Optionally, the PAPR checker is configured to use the index values to identify which multiple combined signal processing branches have been selected and to send the baseband communication signals of the selected signalling branches to the transmitter for transmission based on the index values.

[043] Optionally, the transmitter apparatus as claimed in any preceding claim wherein the transmitter apparatus is a multi-carrier (MC) transmitter apparatus associated with two or more center carrier (CC) frequency bandwidths, and the plurality of signal processing branches comprises two or more subsets of signal processing branches, wherein each signal processing branch outputs a baseband communication signal, and each subset of signal processing branches associated with each of the CC frequency bandwidths, in which each subset of signal processing branches is coupled to the PAPR checker and the transmitter, wherein the transmitter is a MC transmitter and wherein each signal processing branch from each subset of signal processing branches is combined with signal processing branches from different other subsets of signal processing branches to form multiple combined signal processing branches, wherein each combined signal processing branch outputs a combined baseband communication signal for input to the PAPR checker.

[044] As an option, the PAPR checker is further configured to: estimate the PAPR of each of the combined baseband communication signals associated with each of the multiple combined signal processing branches; select a combined signal processing branch associated with a combined baseband communciation signal that has an estimated PAPR that is reduced or minimised compared with the estimated PAPR of other combined baseband communciation signals output from other combined signal processing branches, wherein each combined signal processing branch includes signal processing branches that are each associated with a different CC frequency bandwidth and include signal processing branches from all of the CC frequency bandwidths; and send the baseband communication signal outputs associated with the signal processing branches of the selected combined signal processing branch to the MC transmitter for uplink transmission.

[045] As an option, each of the combined signal processing branches is associated with an index value for identifying the scrambling schemes or interleaving schemes used to scramble or interleave the modulated symbols associated with the combined signal processing branch.

[046] Optionally, the PAPR checker is configured to use the index values to identify which combined signal processing branch has been selected and to send the baseband communication signals associated with the selected combined signal processing branch to the transmitter for transmission based on the index values. Optionally, a waveform generator configured to generate a control signal waveform comprising data representative of the index value associated with the corresponding multiple combined of signal processing branches.

[047] As an option, the PAPR checker is further configured to: combine each output baseband communication signals of the multiple combined signal processing branches with the control waveform associated with the corresponding multiple combined signal processing branches; estimate the PAPR of each combined output baseband communication signals and corresponding control signal waveform associated with each of the multiple combined signal processing branches; and select a combined signal processing branch in which the estimated PAPR of the corresponding combined baseband communication signals and control waveform is reduced or minimised compared with other combined signal processing branches.

[048] As an option, a waveform generator configured to generate a control signal waveform comprising data representative of the index value associated with the corresponding multiple combined of signal processing branches. Optionally, the PAPR checker is further configured to: combine each output baseband communication signals of the multiple combined signal processing branches with the control waveform associated with the corresponding multiple combined signal processing branches; estimate the PAPR of each combined output baseband communication signals and corresponding control signal waveform associated with each of the multiple combined signal processing branches; and select a set of multiple combined signal processing branches in which the combined estimated PAPR of the corresponding combined baseband communication signals and control waveform is reduced or minimised compared with other sets of multiple combined signal processing branches, wherein each set of multiple combined signal processing branches includes signal processing branches associated with all of the CC frequency bandwidths.

[049] According to a second aspect of the invention, there is provided a multicarrier (MC) transmitter apparatus for uplink PAPR reduction in a wireless communications system, wherein the MC transmitter apparatus is associated with two or more center carrier (CC) frequency bandwidths, the MC transmitter apparatus comprising: a plurality of signal processing branches including two or more subsets of signal processing branches, wherein each signal processing branch outputs a baseband communication signal, and each subset of signal processing branches associated with each of the CC frequency bandwidths, in which each subset of signal processing branches is coupled to the PAPR checker and an MC transmitter, and wherein each signal processing branch from each subset of signal processing branches is combined with signal processing branches from different other subsets of signal processing branches to form multiple combined signal processing branches, wherein each combined signal processing branch outputs a combined baseband communication signal for input to the PAPR checker.

[050] The PAPR checker is further configured to: estimate the PAPR of each of the combined baseband communication signals associated with each of the multiple combined signal processing branches; select a combined signal processing branch associated with a combined baseband communciation signal that has an estimated PAPR that is reduced or minimised compared with the estimated PAPR of other combined baseband communciation signals output from other combined signal processing branches, wherein each combined signal processing branch includes signal processing branches that are each associated with a different CC frequency bandwidth and include signal processing branches from all of the CC frequency bandwidths; and send the baseband communication signal outputs associated with the signal processing branches of the selected combined signal processing branch to the MC transmitter for uplink transmission.

[051] According to a third aspect of the invention, there is provided a receiver apparatus for receiving an uplink communication signal from a transmitter apparatus in a wireless communications system, wherein the uplink communciation signal is associated with a particular signal processing branch of the transmitter apparatus that uses a particular scrambling scheme or interleaving scheme for scrambling or interleaving modulation symbols prior to processing the scrambled or interleaved modulation symbols into a baseband communication signal for transmission with a reduced or minimised PAPR, and wherein the receiver apparatus has a set of scrambling or interleaving schemes including the particular scrambling or interleaving scheme used by the transmitter apparatus, the receiver apparatus further comprising: a receiver unit for receiving the uplink communciation signal transmitted from a transmitter apparatus; a demodulator unit configured to demodulate the uplink communication signal into a scrambled or interleaved set of modulation symbols; a blind decoding unit configured to: select a candidate scrambling or interleaving scheme from the set of scrambling or interleaving schemes; decode the scrambled or interleaved set of modulation symbols; perform a cyclic redundancy check on the decoded modulation symbols, and when the cyclic redundancy check passes, output the decoded modulation symbols and proceed to decode any remaining scrambled or interleaved modulation symbols using the candidate scrambling or interleaving scheme whilst performing the CRC check, when the CRC check fails, select another candidate scrambling or interleaving scheme from the set of interleaving schemes to decode and perform the CRC check on the scrambled or interleaved modulation symbols using the other candidate scrambling or interleaving scheme.

[052] According to a fourth aspect of the invention, there is provided a receiver apparatus for receiving an uplink communication signal from a transmitter apparatus in a wireless communication communications system, wherein the uplink communciation signal is associated with a particular signal processing branch of the transmitter apparatus that uses a particular scrambling scheme or interleaving scheme for scrambling or interleaving modulation symbols prior to processing the scrambled or interleaved modulation symbols into a baseband communication signal for transmission with a reduced or minimised PAPR, and wherein the uplink communication signal includes a control signal identifying the particular scrambling scheme or interleaving scheme, wherein the receiver apparatus has a set of scrambling or interleaving schemes including the particular scrambling or interleaving scheme used by the transmitter apparatus, the receiver apparatus further comprising: a receiver unit for receiving the uplink communication signal transmitted from a transmitter apparatus; a control detection unit for detecting the control signal identifying the particular scrambling or interleaving scheme; a demodulator unit configured to demodulate the uplink communication signal into a scrambled or interleaved set of modulation symbols; and a decoding unit for decoding the scrambled or interleaved modulation symbols using the identified particular scrambling or interleaving scheme.

[053] Optionally, wherein the uplink communication signal is an uplink OFDM signal and the control signal is a physical uplink control channel (PUCCH) waveform identifying the particular scrambling or interleaving scheme and the control detection unit detects the PUCCH waveform. As an option, the receiver and control unit are configured to detect the PUCCH waveform is located in a control channel bandwidth in the vicinity of the distal ends of carrier frequency or system bandwidth associated with the received OFDM signal. As another option, receiver and control unit are configured to detect the PUCCH waveform located in a control channel bandwidth outside the carrier frequency or system bandwidth associated with the OFDM signal. Optionally, the control channel bandwidth outside the carrier frequency or system bandwidth is one or more guard band(s) associated with the OFDM signal.

[054] As an option, each signal processing branch of the transmitter apparatus is associated with an index value for identifying the particular scrambling scheme or interleaving scheme used to scramble or interleave the modulated symbols, wherein the control signal comprises data representative of the index value for use by the control detection unit in identifying the particular scrambling scheme or interleaving scheme.

[055] Optionally, at the transmitter apparatus an OFDM signal generator of the signal processing branch associated with the index value is further configured to puncture one or more resource elements associated with data OFDM symbols and transmit the baseband communication signal at the output of the OFDM generator as an uplink OFDM signal transmission, and insert the control signal waveform or data representative of the index value into the one or more resource elements, wherein: the receiver unit is further configured to receive the punctured OFDM signal transmission; and the control detection unit is further configured to retrieve the index value from the associated resource elements for identifying the descrambling or deinterleaving scheme for retrieving the original modulation symbols.

[056] As an option, the received uplink communication signal is a received OFDM signal that comprises two or more resource blocks, wherein each resource block comprises a block of reference symbols, and at the transmitter an OFDM signal generator of the signal processing branch associated with the index value encoded the index value within the reference symbols of two or more of the resource blocks and transmit the baseband communication signal at the output of the OFDM generator as an uplink OFDM signal transmission, wherein: the receiver unit is configured to receive the OFDM signal transmission; and the control detection unit is further configured to detect the encoded index value within the reference symbols; the decoding unit uses the index value from the associated reference symbols for identifying the descrambling or deinterleaving scheme to retrieve the original modulation symbols.

[057] According to another aspect of the invention, there is provided a method for uplink PAPR reduction in a wireless communications system, the method, performed by a transmitter apparatus comprising a plurality of signal processing branches coupled a transmitter, the method comprising: estimating the PAPR of baseband communication signals output from the corresponding signal processing branches; selecting the signal processing branch associated with an output baseband communication signal that has a reduced or minimal PAPR compared with other signal processing branches; and sending the baseband communication signal output from the selected signal processing branch to the transmitter for uplink transmission.

[058] According to a further aspect of the invention, there is provided a method for uplink PAPR reduction in a wireless communications system, the method performed by a multi-carrier (MC) transmitter apparatus associated with two or more center carrier (CC) frequency bandwidths, the MC transmitter apparatus comprising: a plurality of signal processing branches including two or more subsets of signal processing branches, wherein each signal processing branch outputs a baseband communication signal, and each subset of signal processing branches associated with each of the CC frequency bandwidths, in which each subset of signal processing branches is coupled to an MC transmitter, and wherein each signal processing branch from each subset of signal processing branches is combined with signal processing branches from different other subsets of signal processing branches to form multiple combined signal processing branches, wherein each combined signal processing branch outputs a combined baseband communication signal, the method comprising: estimating the PAPR of each combined baseband communication signal associated with each of the multiple combined signal processing branches; selecting a set of multiple combined signal processing branches in which the combined estimated PAPR of the corresponding combined baseband communication signals is reduced or minimised compared with the combined estimated PAPR for other sets of multiple combined signal processing branches, wherein each set of multiple combined signal processing branches includes signal processing branches associated with all of the CC frequency bandwidths; and sending the baseband communication signal outputs associated with the signal processing branches of the selected set of multiple combined signal processing branches to the MC transmitter for uplink transmission.

[059] According to a further aspect of the invention, there is provided a method for receiving an uplink communication signal from a transmitter apparatus in a wireless communications system, wherein the uplink communication signal is associated with a particular signal processing branch of the transmitter apparatus that uses a particular scrambling scheme or interleaving scheme for scrambling or interleaving modulation symbols prior to processing the scrambled or interleaved modulation symbols to output a baseband communication signal for transmission as the uplink communication signal with a reduced or minimised PAPR, the method comprising: receiving the uplink communication signal transmitted from a transmitter apparatus; demodulating the uplink communication signal into a scrambled or interleaved set of modulation symbols; blind decoding the scrambled or interleaved set of modulation symbols by: selecting a candidate scrambling or interleaving scheme from a set of scrambling or interleaving schemes including the particular scrambling or interleaving scheme used by the transmitter apparatus; decoding the scrambled or interleaved set of modulation symbols; performing a cyclic redundancy check on the decoded modulation symbols; when the cyclic redundancy check passes, outputting the decoded modulation symbols, and proceeding to decode any remaining scrambled or interleaved modulation symbols using the candidate scrambling or interleaving scheme whilst performing the CRC check; when the CRC check fails, selecting another candidate scrambling or interleaving scheme from the set of interleaving schemes and performing the steps of decoding and performing the CRC check on the scrambled or interleaved modulation symbols using the other candidate scrambling or interleaving scheme.

[060] According to another aspect of the invention, there is provided a method for receiving an uplink communication signal from a transmitter apparatus in a wireless communications system, wherein the uplink communication signal is associated with a particular signal processing branch of the transmitter apparatus that uses a particular scrambling scheme or interleaving scheme for scrambling or interleaving modulation symbols prior to processing the scrambled or interleaved modulation symbols as a baseband communication signal for transmission as an uplink communication signal with a reduced or minimised PAPR, and wherein the uplink communication signal includes a control signal identifying the particular scrambling scheme or interleaving scheme, the method further comprising: receiving the uplink communication signal transmitted from a transmitter apparatus; detecting the control signal identifying the particular scrambling or interleaving scheme from a set of scrambling or interleaving schemes including the particular scrambling or interleaving scheme; demodulating the uplink communication signal into a scrambled or interleaved set of modulation symbols; and decoding the scrambled or interleaved modulation symbols using the identified particular scrambling or interleaving scheme.

[061] According to yet another aspect of the invention, there is provided a non-transitory computer-readable medium comprising program code stored thereon, which when executed on a processor, causes the processor to perform a method according to various aspects of the invention, and/or as described herein for transmitting a communication signal with reduced or minimised PAPR.

[062] According to yet another aspect of the invention, there is provided a non-transitory computer readable medium comprising program code stored thereon, which when executed on a processor, causes the processor to perform a method according to various aspects of the invention, and/or as described herein for receiving a communication signal with reduced or minimised PAPR.

[063] According to yet further aspects of the invention, there is provided a UE apparatus comprising a transmitter apparatus according to a first aspect of the invention, a second aspect of the invention, or other aspects of the invention as related to a transmitter apparatus and/or as described herein.

[064] According to a further aspect of the invention, there is provided a UE apparatus comprising a processor, a storage unit and a communications interface, wherein the processor unit, storage unit, and communications interface are configured to perform the functions associated with the transmitter apparatus according to a first aspect of the invention, a second aspect of the invention, or other aspects of the invention as related to a transmitter apparatus and/or as described herein.

[065] According to another aspect of the invention, there is provided a UE apparatus comprising a processor, a storage unit and a communications interface, wherein the processor unit, storage unit, and communications interface are configured to perform a method according to a first aspect of the invention, a second aspect of the invention, or other aspects of the invention as related to a transmitter apparatus and/or as described herein.

[066] According to an aspect of the invention, there is provided a base station apparatus comprising a receiver apparatus as described a third aspect of the invention, a fourth aspect of the invention, or other aspects of the invention related to a receiver apparatus and/or as described herein.

[067] According to another aspect of the invention there is provided a base station apparatus comprising a processor, a storage unit and a communications interface, wherein the processor unit, storage unit, communications interface are configured to perform the functions associated with the receiver apparatus according to a third aspect of the invention, a fourth aspect of the invention, or other aspects of the invention related to a receiver apparatus and/or as described herein.

[068] According to yet further aspects of the invention, there is provided a base station apparatus comprising a processor, a storage unit and a communications interface, wherein the processor unit, storage unit, communications interface are configured to perform the method according to a third aspect of the invention, a fourth aspect of the invention, or other aspects of the invention related to methods, functions of a receiver apparatus for performing the invention and/or as described herein.

[069] According to a further aspect of the invention, there is provided a telecommunications network comprising a plurality of UEs, a plurality of base stations, each base station including an apparatus according to the second aspect of the invention or as described herein, wherein each base station serves one or more of the plurality of UE.

[070] These and other aspects, features and advantages of the invention will be apparent from, and elucidated with reference to, the examples and/or embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

[071] Embodiments of the invention will be described, by way of example, with reference to the following drawings, in which: [072] Figure 1a is a schematic diagram of subcarrier arrangements for L-FDMA, IFDMA and block-lFDMA mappings in accordance with embodiment(s) of the invention; [073] Figure 1b is a graph for a simulation comparing PAPR performance for LFDMA and block-lFDMA mappings as described in figure 1a; [074] Figure 1c is a schematic diagram of a wireless communication system in accordance with embodiment(s) of the invention; and [075] Figure 2 is a communication resource structure for use with embodiment(s) of the invention.

[076] Figure 3a is a schematic diagram of an OFDM transmitter structure for wireless communication units; [077] Figure 3b is a schematic diagram of a single-carrier OFDM transmitter structure for wireless communication units in accordance with embodiment(s) of the invention; [078] Figure 3c is a graph illustrating the peak power to average power performance when using symbol branch selection and scrambling in the transmitter structure of figure 3b in accordance with embodiments of the invention; [079] Figure 3d is a graph illustrating the peak power to average power performance when using subframe branch selection and scrambling in the transmitter structure of figure 3b in accordance with embodiments of the invention; [080] Figure 3e is a graph illustrating the peak power to average power performance when using subframe branch selection and interleaving in the transmitter structure of figure 3b in accordance with embodiments of the invention; [081] Figure 4a is a schematic diagram of a multiple-carrier OFDM transmitter structure for wireless communication units [082] Figure 4b is a schematic diagram of a multiple-carrier OFDM transmitter structure for wireless communication units based on figure 4a in accordance with embodiment(s) of the invention; [083] Figure 5 is a flow diagram illustrating process performed at a base station for blind decoding of transmission signals from the transmitters based on figures 3b and 4b in accordance with embodiments of the invention; [084] Figure 6a is a graph illustrating the performance of instant power to average power for transmitters according to embodiments of the invention; [085] Figure 6b is a schematic diagram of a single carrier OFDMA transmitter with control signalling according to embodiments of the invention; [086] Figure 6c is a schematic diagram of a multiple carrier OFDMA transmitter with control signalling according to embodiments of the invention; [087] Figure 6d is a schematic diagram of an example control signalling according to embodiments of the invention; [088] Figure 6e is a schematic diagram of another example control signalling according to embodiments of the invention; [089] Figure 6f is a schematic diagram of a further example control signalling according to embodiments of the invention; and [090] Figure 7 is a flow diagram of another example process for reducing PAPR in UL transmissions according to embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[091] Embodiments of the present invention are described below by way of example only. These examples represent the best ways of putting the invention into practice that are currently known to the Applicant although they are not the only ways in which this could be achieved. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

[092] The inventors have found that it is possible to further reduce peak average power ratio (PAPR) for a wireless communication unit’s transmissions when communicating with an eNB on the UL for LTE LAA systems using unlicensed radio spectrum. In addition, the inventors have found efficient control signalling mechanisms that allow the eNB to receive the wireless communication unit’s transmissions for both single carrier and multiple carrier type transmitter structures. Efficient reduction in PAPR for wireless communication unit transmitters according to the invention is made possible for wireless communication systems where LFDMA, block-lFDMA and/or IFDMA based mappings are used. PAPR may be reduced for UL transmissions using a single carrier and/or multiple carrier type transmitter structures in which multiple sets of modulated data are scrambled or interleaved with different types of scrambling or interleaving, and selecting a set of scrambled or interleaved modulated data bits that minimise an estimated PAPR for transmitting from the SC or MC transmitter. Furthermore, the inventors have found that it is possible for the eNB to either use blind decoding to detect and demodulate the UL transmissions and/or that the SC/MC transmitters may include at least one of various control signalling mechanisms that enable the eNB to determine which scrambling or interleaving was used for each UL transmission from a wireless communication unit.

[093] The inventors have also realised that extremely large PAPR values may occur for a small set of input modulated symbols (or modulated data bits) such that PAPR can be reduced by pre-processing these symbol combinations at the wireless communication unit prior to transmission. The input modulated symbols may first be randomized, by way of example only but not limited to, in various ways such as: scrambling by a set of predefined scrambling sequences or codes (e.g. a set of pseudo-noise sequences); and/or interleaving by a set of predefined interleaving schemes; and/or any other method of randomizing or changing the input modulated symbols that is reversible. That is, there is a reproducible de-randomizing/modification technique that can be used to retrieve the original input modulated symbols. The wireless communication unit sending the input modulated symbols has the capability and/or flexibility to select the randomizing scheme that reduces the PAPR value and/or minimises or brings about a minimum PAPR value. The receiver unit of, by way of example only but is not limited to, a base station (e.g. an eNB) may use the same randomizing scheme to recover the original information symbols. The exact sequence or scheme can be either signalled to the receiver or left for the receiver itself to blindly detect the randomizing scheme.

[094] Reducing PAPR in a wireless communication unit has several technical benefits, such as, by way of example but not limited to, a reduced power back-off from the amplifier circuitry used when transmitting the input modulated symbols, and the wireless communication unit or UE can have an improved wireless connection with the base station or eNB. That is, it will be possible for the UE to transmit at a higher power before encountering the non-linear effects of the amplifier circuitry, which may otherwise severely reduce the UL performance. This will be useful for cell edge UEs where every dB of transmission power is needed to overcome the deleterious effects of the communication channel and also to minimise battery consumption. Other benefits may also include the possibility of using a smaller linear range for the amplifier circuitry used for transmission of the input modulated symbols, which will result in reduced costs for the UE. Further benefits may also occur at the receiver side, where high PAPR requires a higher resolution for analogue-to-digital (A/D) converters, which places further complexity and power burden on the receiver front end. This is particularly so for base stations (e.g. eNBs), which need to be able to simultaneously receive multiple UL transmissions from multiple wireless communication units or UEs within the cell served by the eNB. Thus, reducing the complexity of the receiver front end may further improve the number of UEs that may be supported.

[095] A wireless communication unit or UE may comprise or represent any portable computing device for communications. Examples of wireless communication units or UEs that may be used in certain embodiments of the described apparatus, methods and systems may be wired or wireless devices such as mobile devices, mobile phones, terminals, smart phones, portable computing devices such as laptops, handheld devices, tablets, tablet computers, netbooks, phablets, personal digital assistants, music players, and other computing devices capable of wired or wireless communications.

[096] Figure 1c is a schematic diagram of a wireless communications system or network 100 comprising a core network 102 (or telecommunications infrastructure), a plurality of network nodes 104a-104m (e.g. base stations, eNBs) with cells 106a-106m for serving a plurality of wireless communication units 108a-108e (e.g. UEs). The plurality of network nodes 104a-104m are connected by links to the core network 102. The links may be wired or wireless (for example, radio communications links, optical fibre, etc.). The core network 102 may include one or more core network nodes(s), network entities, application servers or any other network or computing device that may be in communication with one or more radio access network(s) including the plurality of network nodes 104a-104m.

[097] Each cell 106a-106m may include one or more UEs 108b or 108e located at or near the edge of the corresponding cell 106a or 106m. Each cell may have a cell edge region 110a (or 110m) in which a UE 108b (or 108e) is considered to be in the vicinity of the edge of the cell 106a (or 106m). The cell edge region 110a may be bordered by a cell edge threshold border 112a and the cell edge, where UE(s) 108b located within the cell edge region 110a are considered to be cell edge users or UEs 108b. The cell edge threshold border 112a may be based on a transmit/received power threshold in which the eNB 104a considers UEs 108b to be in the the cell edge region 110a because, by way of example only, the transmit/receive power between eNB 104a and the UE 108b may be below and/or equal to a first predefined transmit/receive power threshold. UEs 108a or 108c in cell 106a may be considered by the eNB 104a to be in the cell centre region 114a because the transmit/receive power between eNB 104a and UE 108a or 108c may be above and/or equal to a second predefined transmit/receive power threshold. The first predefined transmit/receive power threshold may be equal to or less than the second predefined transmit/receive power threshold.

[098] Although only two regions 112a and 114a are described in cell 106a, it is to be appreciated by the skilled person that multiple regions may exist within a cell in which UEs within each region may be classified as being in a cell edge region 112a, one or more middle cell region(s) (not shown) and/or a cell centre region 114a based on various one or more predefined transmit/receive power thresholds. Although each region 112a and 114a may be defined by a predefined transmit/receive power threshold, it is to be appreciated by the skilled person that each region 112a and/or 114a may be defined by any other cell property or characteristic such as cell radius and location of the eNB etc.

[099] In this example, the network nodes 104a-104m are illustrated as base stations, which, by way of example only but not limited to, in a Long Term Evolution (LTE) Advanced based telecommunications network may be eNodeBs (eNBs). The plurality of network nodes 104a-104m (e.g. base stations) each have a footprint indicated, for simplicity and by way of example only but it not limited to, schematically in figure 1 as a corresponding circular cells 106a-106m for serving one or more of the UEs 108a-108e. UEs 108a-108e are able to receive services from the wireless communications system 100 such as voice, video, audio and other communication services.

[0100] Wireless communications system or network 100 may comprise or represent any one or more communication network(s) used for communications between UEs 108a-108e and other devices, content sources or servers that are connected to the wireless communications system or network 100. The core network 102 may also comprise or represent any one or more communication network(s), one or more network nodes, entities, elements, application servers, servers, base stations or other network devices that are linked, coupled or connected to form wireless communications system or network 100. The coupling or links between network nodes may be wired or wireless (for example, radio communications links, optical fibre, etc.). The wireless communications system or network 100 and core network 102 may include any suitable combination of core network(s) and radio access network(s) including network nodes or entities, base stations, access points, etc. that enable communications between the UEs 108a-108e, network nodes 104a-104m of the wireless communication system 100 and core network 102, content sources and/or other devices connecting to the system or network 100.

[0101] Examples of wireless communications network 100 that may be used in certain embodiments of the described apparatus, methods and systems may be at least one communication network or combination thereof including, but not limited to, one or more wired and/or wireless telecommunication network(s), one or more core network(s), one or more radio access network(s), one or more computer networks, one or more data communication network(s), the Internet, the telephone network, wireless network(s) such as the WiMAX, WLAN(s) based on, by way of example only, the IEEE 802.11 standards and/or Wi-Fi networks, or Internet Protocol (IP) networks, packet-switched networks or enhanced packet switched networks, IP Multimedia Subsystem (IMS) networks, or communications networks based on wireless, cellular or satellite technologies such as mobile networks, Global System for Mobile Communications (GSM), GPRS networks, Wideband Code Division Multiple Access (W-CDMA), CDMA2000 or Long Term Evolution (LTE)/LTE Advanced networks or any 2nd, 3rd, 4th or 5th Generation and beyond type communication networks and the like.

[0102] In the example of figure 1c, the wireless communications system 100 may be, by way of example only but is not limited to, an LTE/LTE advanced communication network that uses orthogonal frequency division multiplexing (OFDM) technologies for the downlink and UL channels. The downlink may include one or more communication channel(s) for transmitting data from one or more eNBs 104a-104m to one or more UEs 108a-108e. Typically, a downlink channel is a communication channel for transmitting data, for example, from a eNB 104a to a UE 108a. In LTE/LTE advanced communication networks, the multiple access method used in the downlink may be orthogonal frequency division multiple access (OFDMA).

[0103] The UL may include one or more communication channel(s) for transmitting data from one or more UE(s) 108a-108e to one or more eNB(s) 104a-104m. The LTE/LTE advanced UL may use single-carrier frequency division multiple access (SC-FDMA) mode, which is similar to OFDMA. Typically, an UL channel is a communication channel for transmitting data, for example, from a UE 108a to a base station 108a. In OFDM, multi-carrier transmission is used to carry data in the form of OFDM symbols over the UL and downlink channels. For example, an UL channel or downlink channel between UE 108a and eNB 104a may comprise or represent one or more narrowband carriers in which each narrowband carrier may further include a plurality of narrowband subcarriers. This is known as multi-carrier transmission. Each of the narrowband sub-carriers is used for transmitting data in the form of OFDM symbols.

[0104] Both the UL and downlink for LTE/LTE advanced networks are divided into radio frames (e.g. each frame may be 10ms in length), in which each frame may be divided into a plurality of subframes. For example, each frame may include ten subframes of equal length, with each subframe consisting of a number of time slots (e.g. 2 slots) for transmitting data. In addition to the time slots, a subframe may include several additional special fields or OFDM symbols that may include, by way of example only, downlink synchronization symbols (s), broadcast symbol(s), and/or UL reference symbol (s). For OFDMA, the smallest resource unit or element in the time domain is an OFDM symbol for the downlink and an SC-FDMA symbol for the UL.

[0105] Figure 2 is a schematic diagram illustrating a communication resource grid 200 in the frequency and time domain of a time slot 202 of a radio frame for when the wireless communications system 100 as described with reference to figure 1 may be an LTE/LTE Advanced network. The frequency domain is on the y axis of the communication resource grid 200 and the time domain is the x axis of the communication resource grid 200. The communication resource grid 200 for the time slot 202 may represent one carrier of a plurality of carriers in the frequency domain. The communication resource grid 200 includes a plurality of RBs in which each RB 204 may be associated with a particular carrier frequency of the plurality of carriers. Each carrier for UL communications may be divided into a number, NRB, of one or more RBs in which each RB 204 has a plurality of subcarriers, e.g. each RB 204 may have a number, Nsc, of one or more subcarriers, in which each subcarrier may be offset from the carrier frequency associated with the RB 204. Each carrier includes a number of NRB x Nsc subcarriers (i.e. a plurality of subcarriers) associated with one or more RB(s) 204. Each RB 204 may be represented by a subset of the plurality of subcarriers, e.g. NSc subcarriers, in the frequency domain and a plurality of symbols over the time slot 202, e.g. NSymb symbols, in which each symbol has a symbol period. The RB 204 defines a grid in the frequency and time domain of Nsc x NSymb resource elements 206. For RB 204, a resource element 206 corresponds to a particular subcarrier of the NSc subcarriers and a particular symbol of the NSymb symbols over time slot 202. The communications resources that may be assigned to a UE may be based on the communication resource grid 200 and are typically assigned in terms of one or more RBs/subcarriers associated with a corresponding carrier. The communication resources may be described in terms of one or more carrier(s), one or more subcarrier(s), and/or one or more RB(s).

[0106] The communication resource grid 200 for the downlink and UL are effectively the same type of structure, with some slight differences. For example, the downlink for LTE/LTE Advanced networks typically uses OFDM multiple access, hence the downlink may use OFDM symbols in the time domain. The UL for LTE-LTE Advanced networks typically uses SC-FDMA for accessing the UL, and so SC-FDMA symbols may be used in the time domain. Although this may be the case for current LTE/LTE Advanced networks, it is to be appreciated by the person skilled in the art that any type of OFDM/SC-FDMA type symbols and the like may be used in the UL.

[0107] Referring to figures 1c and 2, typically, in LTE networks, communication resources may be assigned by eNBs 104a-104m to UEs 108a-108e in terms of a list of carriers and/or RBs 204. For example, in current LTE network(s), the smallest dimensional unit for assigning resources in the frequency domain is a RB with bandwidth 180kHz, which corresponds to Nsc =12 subcarriers, each at 15kHz offset from the carrier frequency associated with the RB.

[0108] For each of the UE(s) 108a-108c served by the eNB 104a and that requests communication resources, the eNB 104a allocates communication resources to each UE 108a-108c for use over a predetermined frequency bandwidth. The eNB 104a may allocate to each UE 108a-108c served by the eNB 104a one or more communication resources or resource blocks based on the above-mentioned LFDMA, IFDMA or block-lFDMA based mapping techniques. Each UE 108a-108c then uses the allocated communication resources and these mapping techniques in the transmitter units when performing UL transmissions of input modulated symbols or input data from the UE 108a-108c to the eNB 104a.

[0109] Although Orthogonal Frequency-Division Multiple Access (OFDMA), single-carrier and multi-carrier transmitters/receivers based on OFDM and other carrier formats have been described, this is by way of example only, it is to be appreciated by the skilled person that the invention has been described herein for simplicity using OFDM-based, single-carrier-based, and/multi-carrier based technologies, however, this is by way of example only and other communication technologies may be applied such as, by way of example only but it not limited to, CDMA, TDMA, other FDMA, and/or SDMA technologies, systems, or standards, and/or or any other suitable communication system or combinations thereof.

[0110] Figure 3a is a schematic diagram of a transmitter apparatus 300 for use in, by way of example only but not limited to, single carrier (SC) FDMA by each of the wireless communication units or UEs 108a-108e for UL transmission in wireless communication system 100. The transmitter apparatus 300 includes, by way of example only but is not limited to, a channel coding unit 302, a modulation unit 304, a signal generator 306, which in this example is an OFDM signal generator 306, a Cyclic Prefix unit 308, and an radio frequency (RF) unit 310. The channel coding unit 302 that encodes information bits from an information source (not shown) for input to the modulation unit 304. The modulation unit 304 uses a modulating mapping to map the coded information bits into modulated symbols for input to the OFDM signal generator 306. The OFDM signal generator 306 generates an OFDM signal for the time domain for input to the Cyclic Prefix unit 308, which adds a cyclic prefix signal to the output OFDM signal. The resulting signal is then upconverted and transmitted by the radio RF unit 310.

[0111] In operation, the transmitter apparatus 300 receives information bits from an information or data source (not shown). The channel coding unit 302 receives the information bits and introduces redundancies to the information bits (e.g. it typically outputs bits with bit values of “0”/“1 ” bits). The Modulation unit 304 maps the channel coding bits into modulation symbols, whose amplitudes and phases are normally modulated.

[0112] The OFDM signal generator 306 receives the modulation symbols and outputs an OFDM signal. The OFDM signal generator 306 includes a Discrete Fourier Transform (DFT) module 307a, a Subcarrier Mapping module 307b, and an Inverse Fast Fourier Transform (IFFT) module 307c. The DFT module 307a receives the modulated symbols in the time domain from the modulation unit 304 and transfers these time domain symbols (called modulated symbols above) into frequency domain symbols, which are mapped by the subcarrier mapping unit 307b into various subcarriers associated with the communication resources or RBs allocated to each wireless communication unit or UE 108a-108e by its serving eNB 104a-104m.

[0113] After the subcarrier mapping, the resulting frequency domain symbols are retransferred back into the time domain by the IFFT module 307c as an output OFDM signal that represents one or more OFDM symbols. For the LTE UL, the IFFT module 307 typically has, by way of example only but is not limited to, 2048 points. It is to be appreciated by the skilled person that the IFFT module 307c may use a different number of points when retransferring the frequency domain symbols back into the time domain as an output OFDM signal.

[0114] The output OFDM signal from the OFDM Signal Generator 306 is very different to the modulated symbols output by modulation unit 304 prior to input to the OFDM Signal Generator 306. The OFDM signal (or resulting time domain OFDM symbols) has been mapped onto the RBs positions allocated to this UE. The output OFDM signal is input to the Cyclic Prefix unit 308, which adds a cyclic prefix and outputs a baseband OFDM signal with CP. The baseband OFDM signal with CP is sent to the RF unit 310, which completes the analogue processing to transmit the information bits as an OFDM signal from the UE 104a over the UL to an eNB 104a.

[0115] The RF unit 310 includes amplifier circuitry for transmitting the baseband OFDM signal at radio frequencies, so it is essential that the baseband OFDM signal has a low PAPR value. If the PAPR value of the baseband OFDM signal exceeds the maximum linear range of the amplifier circuitry, then harmonics will be generated that will increase outband emissions and samples of the OFDM signal with a high power will be cut-off or distorted, which will further increase the Error Vector Magnitude (EVM) of the output signal of the wireless communication unit. This may further result in decoding errors when the transmitted output signal of the wireless communication unit is received by the base station or eNB. In order to reduce the possibility of having a PAPR value of the baseband OFDM signal that exceeds the maximum linear range of the amplifier circuitry, the following transmitter structures or modules may be used or applied to a wireless communication unit.

[0116] In essence the transmitter apparatus 300 may be modified such that the modulated symbols, X, are copied to several different branches, each branch is associated with an index value, and each branch first scrambles the modulation symbols using a different scrambling code or sequence from the other branches. Each branch also has an OFDM Signal Generator 306 that receives the corresponding scrambled modulation symbols and outputs a different scrambled OFDM signal.

[0117] PAPR values of the output OFDM signals from the OFDM Signal Generator(s) of all branches are calculated within a PAPR checker that then selects the branch with a reduced PAPR value and/or the minimum PAPR value. The PAPR checker uses the index value associated with the selected branch to control a multiplexor or switch to select that branch as the output OFDM signal. Thus, the branch that reduces the PAPR or minimises the PAPR value over all branches is selected as the final output OFDM signal for the baseband.

[0118] A scramble sequence is a set of pre-generated symbols that may be known by both transmitter apparatus and receiver apparatus (e.g. sender and receiver). For practical usage, a number of scramble sequences can be defined and each can be identified by the index value that is associated with each branch. This mapping may be communicated to the receiver apparatus to enable descrambling of the scrambled symbols. Each scramble sequence is no less than the maximum modulated symbols length and when the length of the modulated symbols is less than that of the scramble sequence, the scramble sequence may be truncated such that the front portion of the scramble sequence upto the length of the modulated symbols is used. Multiplicative scrambling may be used where each symbol of the scramble sequence is multiplied with a corresponding modulation symbol to output the scrambled symbols.

[0119] When the transmitter apparatus is used in, by way of example only but is not limited to, a UE 108a, the eNB 104a may indicate to the UE 108a whether scrambling is to be used or not and if it is used, then the eNB 104a may also notify the UE 108a which scramble sequences need to be used. This may be performed when the connection between UE 108a and eNB 104a is being set up. There may be a specific type and set of scrambling sequences that may be specified in the corresponding 3GPP standards to enable a standards compliant UE 108a and eNB 104a to generate the same sequence with the same index value.

[0120] Note that the scrambling step can also be done before the modulation step and the only difference is to use a random “07 “1” sequence to do the XOR with the channel coding bits.

[0121] Alternatively or additionally, the transmitter apparatus 300 may be modified such that the modulated symbols, X, are copied to several different branches, each branch is associated with an index value, and each branch first interleaves the modulation symbols using a different interleaving scheme from the other branches. Each branch also has an OFDM Signal Generator 306 that receives the corresponding interleaved modulation symbols and outputs a different interleaved OFDM signal to the other branches.

[0122] On each branch, the interleaver is used before the OFDM Signal Generator 306 to interleave or randomize the modulated symbols. For example, modulated symbols of one sub-frame can be interleaved using different interleaving schemes on each branch. The branch with the minimum PAPR is selected as the final baseband output OFDM signal and, as described in relation to the above scrambling modification, the receiver can use the same interleaving scheme to recover the modulated symbols.

[0123] Figure 3b is a schematic diagram of an example transmitter apparatus 312 based on the SC-FDMA scenario of figure 3b, but which has been modified to include a number of n>=2 signal processing branches 314a-314n. In this example, the signal processing branches 314a-314n are, by way of example only but is not limited to, scrambling or interleaving (S/l) OFDM signal processing branches 314a-314n, or S/l OFDM branches 314a-314n, in which each of the S/l OFDM branches 314a-314n receives a copy of the modulation symbols, X, from modulator unit 304, scrambles or interleaves the modulation symbols and generates n>=2 modified baseband communication signals 316a-316n, which in this example are OFDM signals 316a-316n. The n>=2 modified OFDM signals 316a-316n are input to a PAPR checker module 318, which estimates a PAPR for each of the n>=2 modified OFDM signals 316a-316n and selects one of the S/l OFDM branches 314a-314n for transmission of the corresponding modified OFDM signal 316a-316n that outputs a reduced PAPR or minimum PAPR over all S/l OFDM branches.

[0124] Each of the S/l OFDM branches 314a-314n includes a corresponding S/l module 315a-315n, in which each of the S/l modules 315a-315n receives a copy of the modulation symbols, X, that were output from modulator unit 304. Each of the S/l modules 315a-315n implements a different S/l scheme on the input modulation symbols to output S/l modulated symbols for input to the corresponding signal generator 306a-306n that outputs baseband communciation signals, which in this example is an OFDM signal generator 306a-306n that outputs modified OFDM signals 316a-314n. A S/l module 315a may implement either scrambling, interleaving, or both scrambling and interleaving on the modulation symbols.

[0125] When scrambling is implemented, each of the S/l modules 315a-315n may use a different scrambling scheme to scramble the modulation symbols or copies thereof. Each scrambling scheme may be based on, by way of example, multiplicative scrambling using scrambling codes (e.g., pseudo-noise code such as a Gold code, a Kasami code, a Hadamard code, m-sequences, etc.) or additive scrambling, and/or any other randomizing code or scheme such that a receiver apparatus with the corresponding descrambling scheme may descramble the scrambled modulation symbols and retrieve the original modulation symbols. Each of the S/l OFDM branches 315a-315n may be associated with a particular scrambling scheme that may also be known or communicated to the receiver apparatus. Each of the S/l OFDM branches 315a-315n may be associated with an index value from 1 to n, which may be communicated to the receiver apparatus for descrambling the corresponding S/l OFDM branches 315a-315n.

[0126] When interleaving is implemented, each of the S/l modules 315a-315n may use a different interleaving scheme to interleave or randomize the modulation symbols or copies thereof. Each interleaving scheme may be based, by way of example only but not limited to, on matrix interleaving schemes or any other interleaving scheme, e.g. random interleaving schemes etc. In matrix interleaving the modulated symbols are written into a matrix row first but read out column first. Different matrix interleaving schemes can be implemented with different matrix sizes. For example, an interleaving matrix with 2 rows and 10 columns would interleave or randomize an original ordering of numbers from 1,2, 3, ..., 20 to an output ordering of 1, 11, 2, 12, 3, 13, ..., 10, 20. Each of the S/l OFDM branches 315a-315n may be associated with a particular interleaving scheme that may also be known or communicated to the receiver apparatus for performing the corresponding de-interleaving operation. For example, each of the S/l OFDM branches 315a-315n may be given an indexing value from 1 to n that is used to map onto the corresponding de-interleaving scheme. The indexing value may be communicated to the receiver apparatus, which may also have the mapping to retrieve the correct de-interleaving information based on the indexing value and perform de-interleaving to retrieve the original modulation symbols.

[0127] When the n>=2 modified OFDM signals 316a-316n are input to the PAPR checker module 318, the PAPR module 318 estimates the PAPR for each of the n>=2 modified OFDM signals 316a-316n. The PAPR module 318 may compare the estimated PAPR of the modified OFDM signals 316a-316n and select the modified OFDM signal 316a-316n that as a minimum PAPR. For example, given that each S/l OFDM branch 314a-314n can be identified with an index value, the PAPR checker 318 uses the index value of the S/l OFDM branch outputting the modified OFDM signal with the minimum estimated PAPR as an output selection signal to multiplexor or switch 320. The multiplexor or switch 320 uses the index value to select the S/l OFDM branch outputting the modified OFDM signal with the minimum estimated PAPR for transmission. Thus, the PAPR is reduced at the output of the transmitter apparatus.

[0128] Alternatively or additionally, when the n>=2 modified OFDM signals 316a-316n are input to the PAPR checker module 318, and the PAPR module 318 may estimate the PAPR for each n>=2 modified OFDM signals 316a-316n and select the first modified OFDM signal with an estimated PAPR that reaches or is less than a predefined and/or minimum PAPR threshold. Thus, the PAPR checker 318 may use the index value of the S/l OFDM branch outputting the modified OFDM signal that was first detected to have a PAPR reaching or less than or equal to the PAPR threshold as an output selection signal to multiplexor or switch 320. The selector, multiplexor or switch 320 has as input modified OFDM signals 317a-317n output from branches 314a-314n and uses the index value to select the S/l OFDM branch (e.g. branch 314a) outputting the modified OFDM signal ( e.g. modified OFDM signal 316a/317a) with the reduced PAPR estimate for transmission. Thus, the PAPR is reduced at the output of the transmitter apparatus. The selected modified OFDM signal 317a is then transferred through to the RF unit 310 for transmission.

[0129] Note that the scrambling or interleaving operations could be performed or implemented prior to the modulation operation. For scrambling based on a multiplicative scrambling scheme, the only difference may be to use a random “07 “1” sequence which are XOR’d with the corresponding channel coding bits output from the channel coding unit 302.

[0130] It is to be appreciated that the above transmitter apparatus 312 may be used in communciation systems other than OFDM communciation systems. For example, transmitter apparatus 312 may be used for uplink PAPR reduction in a wireless communications system 100. The transmitter apparatus 312 may include a plurality of signal processing branches 314a-314n coupled to a PAPR checker 318 and a transmitter 310. The PAPR checker 318 may be configured to: estimate the PAPR of baseband communication signals 316a-316n output from the corresponding signal processing branches 314a-314n. The PAPR checker 318 selects the signal processing branch 314a associated with an output baseband communication signal 316a that has a reduced or minimal PAPR compared with other signal processing branches 314b-314n. The PAPR checker 318 then sends the baseband communication signal 316a output from the selected signal processing branch 314a to the transmitter 310 for uplink transmission.

[0131] The PAPR checker 318 is configured to select the signal processing branch 314a-314n in which the PAPR checker 318 detects the estimated PAPR of the corresponding output baseband communication signal 316a that is minimised over all the output baseband communication signals 316b-316n on the remaining signal processing branches 314b-314n. For example, the PAPR checker 318 may be configured to select the signal processing branch 314a in which the PAPR checker 318 first detects the estimated PAPR of the corresponding output baseband communication signal 316a to have reached a predetermined PAPR threshold (e.g. the PAPR estimate may be less than or equal to the predetermined PAPR threshold). Alternatively or additionally, if the PAPR checker 318 detects that all of the estimated PAPRs of the corresponding output baseband communication signals 316a-316n are above the predetermined PAPR threshold, then the PAPR 318 checker may be further configured to select the signal processing branch (e.g. branch 314n) in which the PAPR checker 318 detects the estimated PAPR of the corresponding output baseband communication signal 316n is minimised over all the output baseband communication signals 316a-316n on the signal processing branches 314a-314n.

[0132] Each of the signal processing branches 314a-314n are configured to receive a plurality of modulation symbols, X, where the plurality of modulation symbols, X, are the same for each signal processing branch 314a-314n. Each of the signal processing branches 314a-314n may include corresponding scrambler or interleaving (S/l) modules 315a-315n that are each coupled to a corresponding communication signal generator 306a-306n for outputting the baseband communication signals 316a-316n. Each of the S/l modules 315a-315n are configured to scramble or interleave the modulation symbols, X, prior to input to the corresponding communication signal generator 306a-306n. In the present example, each of the scrambler or interleaving modules 315a-315n of each of the signal processing branches 314a-314n use a different scrambling scheme or a different interleaving scheme compared to the other signal processing branches 314a-314n. Therefore, the modulated symbols, X, are scrambled or interleaved with n different scrambling or interleaving schemes.

[0133] Given that there are different scrambling or interleaving schemes, each signal processing branches 314a-314n may be associated with a different index value for identifying the scrambling scheme or interleaving scheme used to scramble or interleave the modulated symbols, X, on each branch 314a-314n. The index value for a signal processing branch 314a can be used to identify the scrambling scheme or interleaving scheme used on that signal processing branch 314a and hence may be used to select the output baseband communciation signal 316a out of the plurality of output baseband communication signals 316a-316n associated with the branches 314a-314n. The index value may be stored in memory or in the PAPR checker 318. The PAPR checker 318 may then be configured to use the index value(s) to identify which signal processing branch 314a-314n has been selected and to send the corresponding selected baseband communication signal 316a over signal line 317a of the selected signalling branch 314a to the transmitter 310 for transmission based on the index value.

[0134] The PAPR checker 318 and the signal processing branches 314a-314n may be coupled to a selector 320. The selector 320 may have selection inputs coupled to the output of the signal processing branches 314a-314n and for receiving output baseband communciation signals 316a-316n as signals 317a-317n. An output of the selector 320 is coupled to the transmitter 310. A control input 320a of the selector 320 is coupled to a control output of PAPR checker 318. The PAPR checker 318 outputs an index value to the control input 320a of the selector 320 for selecting which baseband communication signal 316a-316n should be sent to the transmitter 310. The PAPR checker 318 outputs the index value associated with the signal processing branch 314a in which the output baseband communciation signal 316a is selected by the PAPR checker 318 as having a reduced or minimum estimated PAPR as described above. The selector 320 receives the index value via the control input 320a and selects, from the plurality of baseband communciation signal inputs 317a-317n, the baseband communication signal 317a that corresponds to the received index value. This selected baseband communication signal 317a is transferred by the selector 320 towards the transmitter 310 for uplink transmission.

[0135] Each output baseband communication signal 316a-316n may include one or more baseband communication symbols. The PAPR checker 318 may be configured to estimate the PAPR and make the selection of the signal processing branch 314a-314n outputting the baseband signal 316a-316n with reduced or minimum PAPR at a rate of the baseband communciation symbol period. That is, the PAPR checker 318 makes a selection on every one or more baseband communciation symbols that have a reduced or minimal PAPR compared with one or more baseband communication symbols associated with other signal processing branches 314b-314n.

[0136] Alternatively or additionally, the one or more baseband communication symbols for each output baseband communication signal 316a-316n may comprise a subframe of a plurality of baseband communication symbols. The PAPR checker 318 may then be configured to select the signal processing branch 314a-314n that reduces or minimises the PAPR at a subframe rate. That is, the PAPR checker 318 estimates the PAPR of the baseband communication signals 316a-316n for every subframe, and selects the signal processing branch that yields a reduced or minimal PAPR.

[0137] Figure 3c is a graph illustrating the simulated peak power to average power performance of the transmitter apparatus 312 of figure 3b for a different number of S/l OFDM branches 314a-314n, where a branch 314a-314n is selected for every OFDM symbol output in the modified OFDM signals 316a-316n, and where scrambling is used in each of the S/l modules 315a-315n. Figure 3d is a graph illustrating the simulated peak power to average power performance of the transmitter apparatus 312 of figure 3b for a different number of S/l OFDM branches 314a-314n, where a branch 314a-314n is selected every OFDM subframe that is output in the modified OFDM signals 316a-316n, and where scrambling is used in each of the S/l modules 315a-315n.

[0138] For figures 3c and 3d, the PAPRs are simulated with a different number of S/l OFDM branches 314a-314n and the above scramble sequences are random QPSK symbols generated at the beginning of the simulation. Each simulation also used either LFDMA or block IFDMA mapping techniques in the Subcarrier Mapping module 307b of the OFDM Signal Generator 306. Relative gains can be observed in Figures 3c and 3d. The solid line labelled C represents PAPR performance of the transmitter apparatus 312 when using LFDMA mapping, which uses continuously allocated subcarriers.

[0139] For both figures 3c and 3d, the dashed line labelled D1b represents the PAPR performance of the transmitter apparatus 312 when using block-lFDMA and only one S/l OFDM branch is implemented. The dashed line labelled D2b represents the PAPR performance of the transmitter apparatus 312 when using block-lFDMA and two S/l OFDM branches are implemented. The dashed line labelled D3b represents the PAPR performance of the transmitter apparatus 312 when using block-lFDMA and three S/l OFDM branches are implemented. The dashed line labelled D4b represents the PAPR performance of the transmitter apparatus 312 when using block-lFDMA and four S/l OFDM branches are implemented.

[0140] For the simulation performed in figure 3c, the PAPR checker 318 selects the S/l branch 314a-314n for each OFDM symbol of the modified OFDM signal output. For the simulation performed in figure 3d, the S/l OFDM branches 314a-314n are selected for every subframe, which in this simulation was every 14 OFDM symbols. The last digit in the legends means the number of branches and the one with “No scramble” has only one branch so no scramble sequence applied.

[0141] As can be seen, the PAPRs are reduced much more with scramble sequences applied on every OFDM symbol, but the cost is that the receiver may need to either carry out a more complex blind decoding or the transmitter apparatus 312 needs to send more index control signal bits representing the index value of the S/l OFDM branch selected for every OFDM symbol. For both figures 3c and 3d, the more branches there are, the larger the reduction in PAPR. When the number of branches is large enough, the probability that a bigger PAPR is produced is less than that of the SC-FDMA or LFDMA mapping technique (e.g. the continuous case). For example, from figure 3c, the probability for four S/l OFDM branches 314a-314n when using block-lFDMA mapping techniques to produce a PAPR greater than 8dB is 2*1 O'6 while it is 10'4 for the continuous curve case (e.g. LFDMA).

[0142] Figure 3e is a graph illustrating the peak power to average power simulation performance of transmitter apparatus 312 for a different number of S/l OFDM branches 314a-314n, where a branch 314a-314n is selected every OFDM subframe that is output in the modified OFDM signals 316a-316n, and where interleaving is used in each of the S/l modules 315a-315n. As can be seen, the gains between figure 3d and 3e are similar which is because both methods are implemented at the subframe level, so it can be concluded that the different methods have similar gain and the gain is mainly determined by the modulated symbols length based on which the optimal branch is selected.

[0143] Different from the scramble method, the interleaving method has some additional gain from the frequency diversity (especially for frequency fading environments) and also requires less processing capacity. However, interleaving typically introduces an interleaving delay due to, by way of example only but is not limited to, the interleaving matrix needing to read in every row before writing out each column of the interleaving matrix.

[0144] However, for both methods, the receiver apparatus, e.g. at the eNB 104a, needs to use the same scrambling scheme or sequence or the same interleaving scheme to recover the original modulated symbols. The inventors have identified two ways for a receiver apparatus, e.g. the eNB 104a, to obtain the index of the selected S/l OFDM branch that reduces the PAPR. The first method is to implement blind decoding at the receiver apparatus to detect the most possible scrambling scheme or sequence or the most possible interleaving scheme that was used in the transmitter apparatus. This assumes that both the transmitter apparatus and the receiver apparatus have the same list of scrambling sequences or interleaving schemes.

[0145] A second method is for the transmitter apparatus 312 to signal the index value in a robust manner to the receiver apparatus. The receiver apparatus uses this index value to look-up the correct descrambling scheme or the correct deinterleaving scheme to generate the original modulated symbols as used by the sender. This also assumes that both the transmitter apparatus and the receiver apparatus have a suitable scrambling/descrambling or interleaving/de-interleaving look-up table mapping corresponding to each of the scrambling/descrambling or interleaving/de-interleaving schemes to the correct index value of the S/l OFDM branch that is selected for transmission at reduced PAPR.

[0146] Although the above scrambling and interleaving method(s) and corresponding transmitter apparatus 300 and 312 are based on SC-FDMA type transmitter and receiver apparatus, these methods can also be used with multiple carriers (MC) transmitter apparatus to reduce the PAPR.

[0147] Figure 4a is a schematic diagram of an example conventional MC OFDM transmitter apparatus 400, includes multiple signal processing branches 401a-401m, which in this example are essentially multiple SC-FDMA branches 401a-401m. Each of the signal processing branches 401-401m (or SC-FDMA branches 401a-401m ) has a corresponding central carrier frequency (CC#1-CC#m) 402a-402m with a particular frequency bandwidth (e.g. for some LTE systems this may be 20MFIz) within which one or more corresponding RBs and subcarriers have been allocated/mapped as described with reference to figures 1a-2. When there are a number of M>=2 CCs 402a-402m then there will be M>=2 SC FDMA branches 401a-401m. Each of the SC FDMA branches 401a-401m includes corresponding channel coding/modulation units 302a/304a-302m/304m, Signal Generators 306a-306m, which in this case may be OFDM Signal Generators 306a-306m, Cyclic Prefix units 404a-404m (which may be optional depending on the type of communication system) and digital-to-analogue (D/A) convertors 406a-406m in which each baseband OFDM signal is upconverted to the corresponding radio frequency 408a-408m (e.g. fcrfcMi and combined by an adder/summer 409, where the corresponding input signal is passed to a low noise amplifier (LNA) 410 for transmission via antenna 412.

[0148] Although each of the CCs 402a-402m may have the single carrier property with a very low PAPR, their summation via adder/summer 409 does not. Thus, the input signals to the LNA 410 have a higher PAPR. As discussed above with reference to figures 1 a-3e, the PAPR value of one carrier is determined by the number of subcarrier clusters or groups of subcarriers associated with the FDMA mapping techniques used in each OFDM Signal Generator 306a-306m. The PAPR value for MC transmission is determined by the number of CCs 402a-402m. When the number of CCs 402a-402m increases, the linear range of the LNA also needs to increase. As described earlier, this can be problematic once a MC transmitter apparatus 400 has been deployed.

[0149] Figure 4b is a schematic diagram of a multiple-carrier transmitter apparatus 420 according to the invention based on MC transmitter apparatus 400 of figure 4a. The techniques and corresponding transmitter apparatus according to the invention as described with reference to figures 1a-3e may be used to in the MC transmitter apparatus 420 to minimize the PAPR.

[0150] In essence, each SC FDMA branch 401a-401m of MC transmitter apparatus 420 may be modified to form each of MC branches 403a-403m based on the transmitter apparatus 312 as described with reference to figure 3b. That is each MC branch 403a-403m is associated with a particular CC 402a-402m (e.g. CC#1-CC#N). That is MC branch 403a is associated with CC 402a, and MC branch 403m is associated with CC 403m. There may be a number of M>=2 MC branches 403a-403m associated with a number of M>=2 of CCs 402a-402m.

[0151] Each MC branch 403a includes a group of n>=2 scrambling or interleaving (S/l) signal processing branches 314a1-314n1. That is a first MC branch 403a associated with a first CC 402a (e.g. CC#1) includes a first group of n>=2 S/l signal processing branches 314a1-314n1 or a first plurality of S/l signal branches 314a1-314n1. An m-th MC branch 403m associated with an m-th CC 402m includes an m-th group of n>=2 S/l signal processing branches 314am,... ..., 314nm (another plurality of S/l signal processing branches 314am,......, 314nm). For a number of M>=2 CCs 402a-402m, there are a number of M>=2 groups of n>=2 pluralities of S/l signal processing branches 314a1-314n1........ 314am,......, 314nm.

[0152] For example, a first CC 402a corresponds to a first MC branch 403a, which includes channel coding/modulation unit 302a/304a, in which modulated symbols are input to a first group of n>=2 S/l signal processing branches 314a1-314n1, which outputs a first group of n>=2 modified OFDM signals 423a1-423n1. Similarly, the m-th CC 402m corresponds to an m-th MC branch 403m, which includes channel coding/modulation unit 302m/304m, in which modulated symbols are input to a m-th group of n>=2 S/l signal processing branches 314am-314nm, which outputs an m-th group of n>=2 modified OFDM signals 423am-423nm.

[0153] For each CC 402a-402m, each group of S/l signal processing branches

314a1 -314n1,......,314am-314nm outputs a group of output modified OFDM

signals 423a1-423n1,......,423am-423nm from each group S/l branch’s OFDM signal generators 306a1-306n1,......, 306am-306nm. That is, a first CC 402a is associated with a first group of S/l branches 314a1 -314n 1 that outputs a first group of output modified OFDM signals 423a1-423n1, which are output from the first group’s S/l branch’s OFDM signal generators 306a1-306n1. Similarly, an ruth CC 402a is associated with an m-th group of S/l branches 314am-314nm that outputs an m-th group of output modified OFDM signals 423am-423nm, which are output from the m-th group’s S/l branch’s OFDM signal generators 306am-306nm.

[0154] Each of the output modified OFDM signals 423a1-423n1,......, 423am- 423nm, from each group are first modulated on an intermediate frequency (IFci-IFcm) chosen according to the frequency of the corresponding CC 402a-402m and/or the radio frequency 408a-408m (e.g. fcrfcM) associated with each CC 402a-402m. That is a first group of output modified OFDM signals 423a1-423n1 are modulated on a first intermediate frequency (IFci) to form a first group of IF modulated OFDM signals 424a1-242n1. As well, an m-th group of output modified OFDM signals 423am-423nm are modulated on an m-th intermediate frequency (IFcm) to form an m-th group of IF modulated OFDM signals 424am-424nm.

[0155] The groups of IF modulated OFDM signals 424a1-242n1, ..., 424am-424nm are combined into a set of combined OFDM signals 428a-428f for input to the PAPR checker 430. A combined OFDM signal includes a combination or summation of one IF modulated OFDM signal from each group of S/l branches.

Thus, a plurality of output IF modulated OFDM signals 424a1-242n1, ..., 424am-424nm are combined via summers 426a-426f to output combined IF OFDM signals 428a-428f, in which each combination only contains one output IF modulated OFDM signal from each group S/l branches. That is, a combined IF OFDM signal 428a does not contain a combination of more than IF modulated OFDM signal from the same group of S/l branches. Each of the IF modulated OFDM signals that are combined are each from a different group S/l branches and/or a different group of output IF modulated OFDM signals. That is, each of the IF modulated OFDM signals that are combined via a summer to form a combined IF OFDM signal is associated with a different CC 402a-402m.

[0156] This means that, for a number of M CCs (e.g. CCs 402a-402m, m=M), where M>=2, in which each CC had a group containing a number of N S/l branches (e.g. S/l branches 314a1 -314n 1, n=N), then there would be a number of N of output IF modulated OFDM signals (e.g. IF modulated OFDM signals 424a1-242n1, n=N). So, when the plurality of the output IF modulated OFDM signals 424a1-242n1, ..., 424am-424nm are combined such that all possible combinations of the output IF modulated OFDM signals 424a1-242n1, ..., 424am-424nm from different groups have been combined, then there would be a total of hf combined IF OFDM signals 428a-428f.

[0157] Alternatively or additionally, the //* combined IF OFDM signals 428a-428f may be further reduced by selecting a number f < αΛ* of combined IF OFDM signals 428a-428f. This may be advantageous by reducing the complexity of the resulting MC transmitter apparatus 420. The selection may be a predetermined selection or a randomised selection of the combined IF OFDM signals 428a-428f conditioned on at least all CCs 402a-402m being represented in the pairs of output IF modulated OFDM signals 424a1-242n1, ..., 424am-424nm associated with the remaining combined IF OFDM signals 428a-428f after the selection. The selection may be applied when the processing capabilities or power/speed of the MC transmitter apparatus 420 are not enough to handle the number of S/l branches 314a1-314n1,......, 314am,......, 314nm should m=M (M>=2) and n=A/ (N>=2) be excessively high. If the MC transmitter apparatus 420 is implemented in software, then some of the S/l branches 314a1-314n1,......, 314am,......, 314nm may be removed and/or not processed by a processor/modules of the MC transmitter apparatus 420.

[0158] In any event, similarly as with the transmitter apparatus 312 of figure 3b, the PAPR checker 430 selects for each MC branch 403a-403m and associated CC 402a the combination of combined IF OFDM signals 428a-428f that reduces or minimises the PAPR. Alternatively or additionally, the PAPR checker 430 may select only one S/l branch associated with each CC 402a from a selection of the combined IF OFDM signals 428a-428f that minimises or reduces the PAPR of the selected combination. The selection is communicated as a command or an index 432 to multiplexor/switch 434 such that the corresponding output modified OFDM signals from the selected S/l branches are processed for MC transmission via CP 404a-404m, D/A 406a-406m, radio frequency upconversion 408a-408m, summer/adder 409, LNA 410 and antenna 412 as described with reference to Figure 4a For the same reason as described with reference to figures 1a-4a, the selection command or index value of the selected S/l branches, one from each group of S/l branches, needs to be signalled to the receiver apparatus.

[0159] Again there will be a trade-off between complexity and performance gain and for simplicity, as described above, not all combinations or pairs of modified OFDM signals output from the S/l branches of different groups need to be compared. For example, for M=2 and N=2, then ideally there will be 4 combinations of pairs of IF modulated modified OFDM signals from different groups of S/l branches. However, a solution may use only 2 of the 4 combinations above, as long as each CC 402a-402m is represented in the 2 combinations. Another benefit to use a subset of all combinations is the reduced number of the index bits that represent the selection of each S/l branch from each CC 402a-402m. In a similar manner as the transmitter apparatus 312 for the single carrier case, the index bits or index values may be either blind decoded by the receiver apparatus or carried to the receiver apparatus as control signalling which will be further detailed below.

[0160] It is to be appreciated that the above transmitter apparatus 420 may be used in communciation systems other than just OFDM communciation systems. For example, transmitter apparatus 420 may be used for uplink PAPR reduction in a wireless communications system 100. The transmitter apparatus 420 may be a MC transmitter apparatus 420 for uplink PAPR reduction in a wireless communications system, where the MC transmitter apparatus 420 is associated with two or more center carrier (CC) frequency bandwidths 402a-402m. The MC transmitter apparatus 420 may include a plurality of signal processing branches 314a1-314nm including two or more subsets of signal processing branches {(314a1-314n1),......,(314am-314nm)}, where each subset of signal processing branches {(314a1-314n1),......,(314am-314nm)} outputs a subset of baseband communication signals {(424a1-424n1),......,(424am-424nm)}. The baseband communciation signals {(424a1-424n1),......,(424am-424nm)} may be converted to an intermediate frequency as described above. Each subset of signal processing branches {(314a1-314n1),......,(314am-314nm)} is associated with each of the CC frequency bandwidths 402a-402m. Each subset of signal processing branches {(314a1-314n1),......,(314am-314nm)} is coupled to the PAPR checker 430 and an MC transmitter 406a-412. Each signal processing branch in a subset of signal processing branches {(314a1-314n1),......,(314am- 314nm)} is combined with each other signal processing branch in other subsets of signal processing branches {(314a1-314n1),......,(314am-314nm)}, where the other signal processing branches are different and are from different other subsets of signal processing branches {(314a1-314n1),......,(314am-314nm)}.

These combinations form multiple or a plurality of combined signal processing branches 426a-426f, each of which output a combined baseband communication signal 428a-428f for input to the PAPR checker 430.

[0161] The PAPR checker 430 is further configured to estimate the PAPR of each of the combined baseband communication signals 428a-428f. The PAPR checker 430 selects a combined signal processing branch 426a-426f associated with a combined baseband communication signal that has an estimated PAPR that is reduced or minimised compared with the estimated PAPR for other combined baseband communication signals 428a-428f. Each of the combined signal processing branches 426a-426f includes or is associated with signal processing branches that are each associated with a different CC frequency bandwidth 402a-402c and include signal processing branches from all CC frequency bandwidths. The PAPR checker 430 sends the baseband communication signal outputs 431a1-431nm associated with the signal processing branches 314a1-314nm of the selected combined signal processing branches 426a-426f to the MC transmitter 406a-412 for uplink transmission.

[0162] Each of the combined signal processing branches 426a-426f is associated with an index value for identifying the scrambling schemes or interleaving schemes used to scramble or interleave the modulated symbols associated with the plurality of signal processing branches that have been combined to form the combined signal processing branch. The PAPR checker 430 is configured to use the index values to identify which combined signal processing branch has been selected and to send the corresponding baseband communication signals 431 a1-431 nm associated with the selected combined signal processing branch 426a-426f to the transmitter 406a-412 for transmission based on the index values.

[0163] Figure 5 is a flow diagram illustrating process performed at a receiver apparatus such as, by way of example but not limited to, a base station or eNB 104a for blind decoding of transmission signals from transmitter apparatus 312 and 420 based on figures 3b and 4b according to the invention. When the total number of scrambling schemes or sequences or total number of interleaving schemes is not too large, a receiver apparatus may implement blind decoding instead of attempting to download or receive control signalling representing the scrambling or interleaving schemes associated with the selected S/l branches outputting the selected modified OFDM signals that the transmitter apparatus found reduced or minimised the PAPR. In essence, with knowledge of all of the scrambling schemes and interleaving schemes that the transmitter apparatus may use, the receiver apparatus may try every possible combination of scrambling/interleaving scheme until one of them passes the cyclic redundancy check at the channel decoder, which means the correct S/l branch and hence correct scrambling/interleaving scheme was selected. Assuming a plurality of scrambling/interleaving schemes may be used by the transmitter apparatus 312 and 420, which are known to the receiver apparatus, the method may be outlined as follows: [0164] In step 502, the receiver apparatus receives the UL transmission from the transmitter apparatus and demodulates the UL transmission, which contains the transmitted modified OFDM signals, to retrieve the original scrambled modulated symbols. In step 504, the receiver apparatus applies a first selected scrambling/interleaving scheme from the plurality of scrambling/interleaving schemes. In step 506, the descrambled/deinterleaved modulation symbols are passed through the channel decoder to output decoded information bits.

[0165] In 508, if the cyclic redundancy check on the decoded information bits passes, then the selected scrambling/interleaving scheme was used by the transmitter apparatus and may be used to descramble/deinterleave further scrambled/interleaved modulation symbols. However, should the CRC check fail, then in step 510, the receiver apparatus checks whether all scrambling/interleaving schemes are been tried in the plurality of scrambling/interleaving schemes. If not, then proceed to 512.

[0166] In 512 another scrambling/interleaving scheme is selected (e.g. SS#i+1 or Interleaver i+1) and the method proceeds to step 504 with the newly selected scrambling/interleaving scheme. However, in step 510, if all the plurality of scrambling/interleaving schemes have been tried, then the receiver apparatus cannot identify the scrambling/interleaving scheme used by the transmitter apparatus and may request the transmitter apparatus to implement control signalling to send an indication of the selected scrambling/interleaving scheme.

[0167] When the total scramble sequences or total interleaving schemes are too many, blind decoding method 500 may consume too much processing capacity of the eNB 104a, especially since the eNB 104a must handle multiple UEs 108a-108c, and signalling the selection or an index value associated with the scramble sequence or interleaving scheme to the eNB 104a may be a more efficient alternative way for decoding the scrambled/interleaved modulation symbols.

[0168] One other disadvantage of blind decoding is that it is more complicated to support increased redundancy decoding after hybrid-automatic repeat request (HARQ) retransmission and different combinations of possible S/l branches from first transmission and retransmissions need to be considered.

[0169] Given that signalling the selected S/l branch or selected scrambling/interleaving scheme may be required, it is important to consider the number of bits the control signalling may require to allow the receiver apparatus to identify the correct scrambling/interleaving scheme that was used at the transmitter apparatus. For example, in a transmitter apparatus 312 according to figure 3b with 4 S/l branches 315a-315m, 2 bits are required for each of the index values that represent each of the four scrambling/interleaving schemes used in the S/l branches 315a-315m. If scrambling/interleaving is implemented at the symbol level as described with reference to figure 3c, then for a subframe of length 1ms, which has 14 OFDM symbols, a total of 24 bits for the 14 different index values is required to be sent by the transmitter apparatus. However, should the scrambling/interleaving be implemented at the subframe level, then for a subframe of length 1ms, which has 14 OFDM symbols, a total of 2 bits is required for representing the index value. Note that 1ms has 14 OFDM symbols, and excluding the two symbols used for reference symbols (RSs), there are 12 OFDM symbols for user data so the total number is 24 bits for the OFDM symbol scrambling/interleaving. So the actual number of bits needs to be considered based on the trade-off between gain and signalling size.

[0170] Figure 6a is a graph illustrating Complementary Cumulative Distribution Function of a simulation of instant power to average power ratio (IAPR) for transmitters according to embodiments of the invention. The simulation is based on parameters mentioned in the above paragraph and the transmitter apparatus 312 of figure 3b. IAPR is a distribution of the ratio between instant power and the average power and is calculated by: IAPR(n) = |x(n)|2 / E{x(n).*conj(x(n))}. As shown, there is a performance gap between the OFDM symbol scrambling and the subframe scrambling curves.

[0171] The dashed curve labelled D1b is for discontinuous subcarrier mappings (e.g. block-lFMDA mappings) using only one S/l branch. This is the worst performing transmitter apparatus because there can be no selection of the S/l branch having a minimum or reduced PAPR. The dashed curve labelled DSF2b is for discontinuous subcarrier mappings with two S/l branches in the transmitter apparatus when subframe selection is performed or when scrambling/interleaving scheme is selected every subframe period. The dash-dot curve labelled DSF3b is for discontinuous subcarrier mappings with three S/l branches in the transmitter apparatus when subframe selection is performed. The dotted curve labelled DSF4b is for discontinuous subcarrier mappings with four S/l branches in the transmitter apparatus when subframe selection is performed.

[0172] The dashed curve labelled DSS2b is for discontinuous subcarrier mappings with two S/l branches in the transmitter apparatus when symbol selection is performed or when scrambling/interleaving scheme is selected for every OFDM symbol period. The dash-dot curve labelled DSS3b is for discontinuous subcarrier mappings with three S/l branches in the transmitter apparatus when symbol selection is performed. The dotted curve labelled DSS4b is for discontinuous subcarrier mappings with four S/l branches in the transmitter apparatus when symbol selection is performed.

[0173] The number of required index bits is summarized below. The same results occur for the interleaver method which can be implemented over different number of OFDM symbols.

[0174] There are normally two types of uplink control signalling in mobile communication systems, one is data-associated control signalling and the other is control signalling not associated with data. The data associated control signalling includes MCS, puncture schemes and multiple-input multiple-output (ΜΙΜΟ) parameters, etc., which are required to decode the received signals. Control signalling not associated with data includes Channel Quality Indicator (CQI), Ack/Nack and pre-coding matrix indicator (PMI), etc., which will not be used to decode the received uplink signals.

[0175] For LTE, due to the extreme short latency, the eNB 104a can fully control the uplink transmission parameters so there is no data-associated control signalling. User control information (UCI) is an uplink control signalling not associated with data and currently it can be carried by either the physical uplink control channel (PUCCH) or by the physical uplink shared channel (PUSCH) when no PUCCH is scheduled. In order to maintain the SC or MC low PAPR property, prior to LTE Release 10, PUCCH was not transmitted with PUSCH in the same subframe for each UE 108a. From LTE Release 10 onwards, the UE 108a is allowed to multiplex PUCCH and PUSCH in the same subframe but it can only be used by UEs 108a with power redundancy (i.e., UEs 108a close to the eNB 104a).

[0176] Figure 6b is a schematic diagram of a transmitter apparatus 600 based on the transmitter apparatus 312 of figure 3b but which includes control signalling for transmitting the index values being taken into account in the PAPR check according to embodiments of the invention. The UCI including branch index value (or index value) may be carried by PUCCH with the low PAPR benefit of the invention. This may be achieve by adding the PUCCH waveform 602a-602n generated for each index value to the output modified OFDM signals 316a-316n of the corresponding S/l branches 314a-314n (e.g. from the corresponding OFDM Signal Generators 306a-306n). This produces combined OFDM signals 604a-604n for input to the PAPR checker 318, which estimates the PAPR for each of the combined OFDM signals 604a-604n. As described with reference to figure 3b, the PAPR checker selects the optimal S/l branch 314a-314n with PUCCH included that is the first to reduce the PAPR or that minimises the PAPR out of all the combined OFDM signals 604a-604n.

[0177] PUCCH can be mapped in the frequency domain in the same way as specified by the 3GPP. Note that considering the number of possible indexes is normally small, the PUCCH waveform 602a-602n can be pre-generated, stored and reused every time control signals are to be generated due to OFDM symbol scrambling/interleaving or OFDM subframe scrambling/interleaving for each S/l branch 314a-314n.

[0178] The index bits carried by PUCCH are few (much less than that of data bits) and PUCCH must be coded in a very robust way and it is also feasible to select a coding scheme with a low PAPR which will help to reduce the PAPR of combined output signals. With this invention, it is possible to multiplex PUCCH and PUSCH in the same subframe for devices located in a cell edge area or region 110a-110m. Another benefit to use PUCCH to carry the index bits is that PUCCH starts being mapped onto RBs or REs from the two ends of the system bandwidth, which can assist the UE in passing the 80% regulation requirement and channel occupation test.

[0179] There are various ways that the PUCCH waveform 602a-602n may be transmitted along with whichever OFDM signal 316a-316n has been selected for transmission. For example, the PUCCH waveform 602a-602n may be transmitted in a control channel bandwidth in the vicinity of the distal ends of carrier frequency or system bandwidth associated whichever OFDM signal 316a-316n is selected by PAPR checker 318 for transmission. This assists in complying with the 80% bandwidth regulation. Additionally or alternatively, the PUCCH waveform may be transmitted in a control channel bandwidth within the carrier frequency or system bandwidth associated with whichever OFDM signal 316a-316n is selected by PAPR checker 318 for transmission. The PUCCH waveform could also be transmitted in a control channel bandwidth outside the carrier frequency or system bandwidth associated with the OFDM signal selected for transmission, e.g. the control channel bandwidth outside the carrier frequency or system bandwidth may be, by way of example only but is not limited to, one or more guard band(s) associated with the OFDM signal selected for transmission.

[0180] Alternatively, the index values may not need to be transmitted in a control waveform such as the PUCCH waveform 602a-602n. Instead, the OFDM signal generators 306a-306n may each be further configured to puncture one or more resource elements associated with data OFDM symbols within each OFDM signal 316a-316n, and thus insert the control signal waveform or data representative of the index value into the one or more resource elements. Thus a receiver apparatus receiving the punctured OFDM signal transmission may retrieve the index value from the associated resource elements for identifying the descrambling or deinterleaving scheme to retrieve the original modulation symbols.

[0181] Alternatively, the OFDM signal 316a-316n may include two or more resource blocks. Each of the resource blocks may include a block of reference symbols (e.g. for pilot signals or other things). Each of the OFDM signal generators 306a-306n in each of the signal processing branches 314a-314n that are associated with an index value may be further configured to encode the corresponding index value within the reference symbols of two or more of the resource blocks. Thus, a receiver apparatus receiving a selected OFDM signal 316a that is transmitted may blindly detect and decode the index value from the associated reference symbols, which can be used by the receiver apparatus for identifying the descrambling or deinterleaving scheme to retrieve the original modulation symbols.

[0182] It is to be appreciated that the above transmitter apparatus 600 may be used in communciation systems other than OFDM communciation systems. For example, transmitter apparatus 600 may be used for uplink PAPR reduction in any other wireless communications system 100 and which includes control signalling for transmitting the index values (as described with reference to figure 3b) being taken into account in the PAPR checker 318 according to embodiments of the invention. The index value associated with the selected signal processing branch 314a (it is assumed, by way of example only, that signal processing branch 314a outputs the baseband communciation signal 316a that is selected by the PAPR checker 318) is transmitted to a receiver apparatus (not shown) for use in descrambling or deinterleaving the corresponding received transmitted baseband communication signal associated with the baseband communciation signal 316a output from the signal processing branch 314a selected by the PAPR checker 318. A waveform generator (e.g. 602a or 602n) may be configured to generate a control signal waveform comprising data representative of the index value associated with the corresponding signal processing branch 314a.

[0183] However, in order to compensate for the additional transmission power for transmitting the control signal waveform, the PAPR checker 318 may be further configured to combine each output baseband communication signal 316a-316n with the control waveform associated with the corresponding signal processing branch 314a-314n, each of which are associated with a different index value. Thus, the PAPR checker 318 estimates the PAPR of each combined output baseband communication signal 316a-316n and corresponding control signal waveform associated with the index corresponding to the signal processing branch 314a-314n. The PAPR checker 318 selects the signal processing branch 314a associated with a combined output baseband communication signal 316a and corresponding control signal waveform 602a that has a reduced or minimal PAPR compared with other signal processing branches 314b-314n.

[0184] Figure 6c is a schematic diagram of another example transmitter apparatus 610 based on the transmitter apparatus 420 of figure 4b but which includes control signalling for transmitting the index values being taken into account in the PAPR check according to embodiments of the invention. In a similar manner as the transmitter apparatus 600 of figure 6b, the UCI including branch index value (or index value) may be carried by PUCCH with the low PAPR benefit of the invention by adding the PUCCH waveform 602a-602f generated for each index value to each of the corresponding combined IF OFDM signals 428a-428f, to produce combined OFDM signals 606a-606f for input to the PAPR checker 430, which estimates the PAPR for a selected combination of each of the combined OFDM signals 606a-606f, in which the selected combination defines a command based on the combined index values of the corresponding combination of selected combined OFDM signals 606a-606f. The command or combined index value 432 is sent to the multiplexor/switch 434 for selecting which S/l branch form each group of S/l branches associated with corresponding CCs 402a-402m. As described with reference to figure 4b, the PAPR checker selects the optimal S/l branch 314a1-314n1,...,314am-314nm with PUCCH included that is the first to reduce the PAPR or that minimises the PAPR for the selected combined OFDM signals 606a-606f.

[0185] As described in figure 4b, the PAPR checker 430 uses an index value to select the appropriate baseband communciation signals 431 a1 -431 am that were associated with the selected combined signal processing branch 426a-426f in which the corresponding combined baseband communciation signal 428a-428f reduced or minimised the PAPR. This index value may be sent to the receiver apparatus (not shown) to allow the received uplink transmission to be descrambled/deinterleaved. This may be achieved using waveform generators 602a-602f, which may be configured to generate a control signal waveform comprising data representative of the index value associated with the corresponding combined of signal processing branches.

[0186] The PAPR checker 430 is further configured to combine each output baseband communication signals associated with each of the multiple combined signal processing branches with the corresponding control waveform 602a-602f associated with the corresponding combined signal processing branch. The PAPR checker 430 estimates the PAPR of each combined output baseband communication signals and corresponding control signal waveform associated with each of the multiple combined signal processing branches 428a-428f. The PAPR checker 430 selects a combined signal processing branch 428a-428f in which the estimated PAPR of the corresponding combined baseband communication signals and control waveform is reduced or minimised compared with other combined signal processing branches 428a-428f.

[0187] Figure 6d is a schematic diagram of example control signalling frequency bandwidth utilisation for transmitter apparatus 600 or 610 according to embodiments of the invention as described with reference to figures 6b and 6c. The modified OFDM signal selected for transmission out of the modified OFDM signals 316a-316n (or the selected m output modified OFDM signals out of each group of output modified OFDM signals 423a1-423n1,...,423am-423nm) may be mapped into the frequency bandwidth Fbw to occupy the RBs associated with a first bandwidth 612. The associated PUCCH waveforms 602a-602n or 602a-602f that carry the index bits are mapped onto RBs or REs 614a and 614b in the vicinity of the distal two ends of the system bandwidth Fbw, which can assist the UE in passing the 80% regulation requirement and channel occupation test.

[0188] Figure 6e is a schematic diagram of another example control signalling and frequency bandwidth utilisation for transmitter apparatus 600 or 610 according to embodiments of the invention as described with reference to figures 6b and 6c. In this example for performing control signalling, transmitter apparatus 600 or 610 may be to add the index value (or branch index value), which represents the scrambling scheme or sequence or interleaving scheme for a selected S/l branch or that reduces PAPR, to UCI as a type of data-associated control signalling and, so, must be transmitted together with PUSCH. This new UCI can be inserted into the PUSCH data stream into frequency bandwidth potions 622a and 622b such that the data stream frequency bandwidth is divided into portions 612a-612c in the same way as the current UCI does but with the only difference, that the symbols of the branch index are mapped to known resource elements (REs) associated with frequency bandwidth portions 622a and 622b without being scrambled or interleaved so the receiver can decode this UCI without knowing the exact S/l branch or scrambling/interleaving scheme selected by the UE.

[0189] This may be performed by puncturing some REs at frequency bandwidth portions 622a and 622b of the data symbols within each OFDM signal generator 306a-306m and map the modulated symbols of index coding bits (or branch index values) to these positions. The drawback of this method is the degraded performance of the data portion.

[0190] Figure 6f is a schematic diagram of a further example control signalling for the transmitter apparatus 312, 600, 610 according to embodiments of the invention. In this example, each RB 632a-632d allocated to a UE may include reference sequence symbols 634a-634d, respectively. A subframe 636a includes 14 OFDM symbols (e.g. 14 SC-FDMA symbols) and there are two OFDM symbols 634a and 634b reserved per subframe for RS symbols, which are used for channel estimation. Special RS sequences can be chosen to implicitly to carry the index bits but the number of bits could not be as many as the above methods. For instance, there are 2 candidate sequences for each RS symbol so 2 RS symbols together have 4 different sequence combinations which can be used to carry 2 bits.

[0191] Figure 7 is a flow diagram of another example process 700 for use in transmitter apparatus according to the invention for reducing PAPR in UL transmissions. The process introduces some optimisations in that it is possible to simplify the implementation of the transmitter apparatus but by giving up some gains. For example, the multiple S/l branches 315a-35n in figure 3b can be implemented one after another (instead of in parallel). The example process 700 may be as follows: [0192] In step 702, coded information bits are received from a coding unit (not shown) and modulated into modulation symbols, which are input to each S/l branch 315a-315n for scrambling or interleaving and conversion into OFDM symbols. However, each S/l branch 315a-315n is serially processed such that a following S/l branch 315b is only processed if the current S/l branch 315a cannot generate a PAPR below a predefined PAPR threshold. In 704, the current S/l branch 315a performs scrambling/interleaving of the modulated symbols to produce scrambled modulated symbols. In step 706, the OFDM Signal Generator outputs modified OFDM signal for the current S/l branch 315a. In 708, the PAPR checker estimates the PAPR of the output modified OFDM signal for the current S/l branch 315a.

[0193] In step 710, if the estimated PAPR is less than a predetermined/predefined PAPR threshold, then the current S/l branch is selected and the index value associated with the S/l branch and/or scrambling/interleaving scheme of the S/l branch 315a is used to select the current S/l branch 315a. In step 720, the modified OFDM signal output from the current S/l branch 315a is prepared for transmission by adding, for example, a CP in step 720 and subsequent transmission of the modified OFDM signal. All other S/l branches are skipped.

[0194] In step 710, if the estimated PAPR for the modified OFDM signal output from the current S/l branch 315a is greater than or equal to the predefined PAPR threshold, then proceed to step 712. In step 712, the output OFDM signal and associated estimated PAPR are stored in a memory space 712a, for later processing if necessary. As well, from step 712 the method proceeds to step 714, where the scramble/interleaving index is incremented, this index is used by the receiver apparatus to descramble/deinterleave the scrambled/interleaved modulated symbols received at the receiver apparatus.

[0195] In step 716, if the scramble/interleaving index is less than P, then the method proceeds to step 704 in which another S/l branch 315b becomes the current S/l branch 315b. In step 716 if the scrambling/interleaving index is greater than or equal to P, then the method proceeds to step 718. In step 718, then the S/l branch that outputs a modified OFDM signal that minimises the PAPR is selected based on the stored modified OFDM signals and associated estimated PAPR, and the method proceeds to step 720 and subsequent transmission of the modified OFDM signal. It is noted that, in 710, even though the S/l branch that first output a modified OFDM signal with a PAPR below the threshold is selected, it may not be the optimal one of all S/l branches. Flowever, this is the trade-off between speed of processing the received signal.

[0196] Although the method(s), apparatus, transmitter(s) and receiver(s), UEs, wireless communication units, base stations and/or eNBs according to the invention have been described in terms of, by way of example only but are not limited to, the use of Orthogonal Frequency-Division Multiple Access (OFDMA), single-carrier and multi-carrier transmitters/receivers based on OFDM, or LTE and/or other carrier formats, it is to be appreciated by the skilled person that this is for simplicity and by way of example only, and the above-mentioned method(s), apparatus, transmitter(s) and receiver(s), UEs, wireless communication units, base stations and/or eNBs according to the invention may be applied, not only to OFDMA or other related FDMA systems, but also to other communication systems, receivers and transmitters, such as, by way of example only but is not limited to, Code Division Multiple Access (CDMA) systems, time division multiple access (TDMA) systems, any other Frequency Division Multiple

Access (FDMA) systems, or Space Division Multiple Access (SDMA) systems, or any other suitable communication system or combinations thereof.

[0197] The signal processing functionality of the embodiments of the invention, particularly the transmitter apparatus and receiving apparatus as described herein with reference to figures 1-7 may be achieved using computing systems or architectures known to those who are skilled in the relevant art. Computing systems such as, a desktop, laptop or notebook computer, hand-held computing device (PDA, cell phone, palmtop, etc.), mainframe, server, client, or any other type of special or general purpose computing device as may be desirable or appropriate for a given application or environment can be used.

[0198] The computing system can include one or more processors which can be implemented using a general or special-purpose processing engine such as, for example, a microprocessor, microcontroller or other control processor. The computing system can also include a main memory, such as random access memory (RAM) or other dynamic memory, for storing information and instructions to be executed by a processor. Such a main memory also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor.

[0199] The computing system may likewise include a read only memory (ROM) or other static storage device for storing static information and instructions for a processor. The computing system may also include an information storage system which may include, for example, a media drive and a removable storage interface. The media drive may include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, a floppy disk drive, a magnetic tape drive, an optical disk drive, a compact disc (CD) or digital video drive (DVD) read or write drive (R or RW), or other removable or fixed media drive.

[0200] Storage media may include, for example, a hard disk, floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed or removable medium that is read by and written to by media drive. The storage media may include a computer-readable storage medium having particular computer software or data stored therein. In alternative embodiments, an information storage system may include other similar components for allowing computer programs or other instructions or data to be loaded into the computing system. Such components may include, for example, a removable storage unit and an interface , such as a program cartridge and cartridge interface, a removable memory (for example, a flash memory or other removable memory module) and memory slot, and other removable storage units and interfaces that allow software and data to be transferred from the removable storage unit to computing system.

[0201] In this document, the terms ‘computer program product’, ‘computer-readable medium’ and the like may be used generally to refer to tangible media such as, for example, a memory, storage device, or storage unit. These and other forms of computer-readable media may store one or more instructions for use by the processor comprising the computer system to cause the processor to perform specified operations. Such instructions, generally referred to as ‘computer program code’ (which may be grouped in the form of computer programs or other groupings), when executed, enable the computing system to perform functions of embodiments of the present invention. Note that the code may directly cause a processor to perform specified operations, be compiled to do so, and/or be combined with other software, hardware, and/or firmware elements (e.g., libraries for performing standard functions) to do so. In an embodiment where the elements are implemented using software, the software may be stored in a computer-readable medium and loaded into computing system using, for example, removable storage drive. A control module (in this example, software instructions or executable computer program code), when executed by the processor in the computer system, causes a processor to perform the functions of the invention as described herein. Further, the inventive concept can be applied to any circuit for performing signal processing functionality within a communications network element. It is further envisaged that, for example, a semiconductor manufacturer may employ the inventive concept in a design of a stand-alone device, such as a microcontroller of a digital signal processor (DSP), or application-specific integrated circuit (ASIC) and/or any other sub-system element.

[0202] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages.

[0203] Any reference to 'an' item refers to one or more of those items. The term 'comprising' is used herein to mean including the method blocks or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

[0204] The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples without losing the effect sought.

[0205] It will be understood that the above description of a preferred embodiment is given by way of example only and that various modifications may be made by those skilled in the art. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of this invention.

Claims

1. A transmitter apparatus for uplink peak average power ratio, PAPR, reduction in a wireless communications system, comprising: a plurality of signal processing branches coupled to a PAPR checker and a transmitter, wherein the PAPR checker is configured to: estimate the PAPR of baseband communication signals output from the corresponding signal processing branches; select the signal processing branch associated with an output baseband communication signal that has a reduced or minimal PAPR compared with other signal processing branches; and send the baseband communication signal output from the selected signal processing branch to the transmitter for uplink transmission.

2. The transmitter apparatus as claimed in claim 1, wherein the PAPR checker is configured to select the signal processing branch in which the PAPR checker detects the estimated PAPR of the corresponding output baseband communication signal is minimised over all the output baseband communication signals on the remaining signal processing branches.

3. The transmitter apparatus as claimed in claim 1, wherein the PAPR checker is configured to select the signal processing branch in which the PAPR checker first detects the estimated PAPR of the corresponding output baseband communication signal to have reached a predetermined PAPR threshold.

4. The transmitter apparatus as claimed in claim 3, wherein when the PAPR checker detects that all of the estimated PAPRs of the corresponding output baseband communication signals are above the predetermined PAPR threshold, then the PAPR checker is configured to select the signal processing branch in which the PAPR checker detects the estimated PAPR of the corresponding output baseband communication signal is minimised over all the output baseband communication signals on the remaining signal processing branches.

5. The transmitter apparatus as claimed in any of claims 1-4, wherein the signal processing branches are configured to receive a plurality of modulation symbols, wherein the plurality of modulation symbols are the same for each signal processing branch, and each signal processing branch further comprises: a scrambler or interleaving module coupled to an communication signal generator for outputting the baseband communication signal, wherein the scrambler or interleaving module is configured to scramble or interleave the modulation symbols prior to input to the communication signal generator.

6. The transmitter apparatus as claimed in claim 5, wherein the scrambler or interleaving module of each signal processing branch, uses a different scrambling scheme or a different interleaving scheme to the other signal processing branches.

7. The transmitter apparatus as claimed in claim 6, wherein each signal processing branch is associated with an index value for identifying the scrambling scheme or interleaving scheme used to scramble or interleave the modulated symbols.

8. The transmitter apparatus as claimed in claim 7, wherein the PAPR checker is configured to use the index value to identify which signal processing branch has been selected and to send the baseband communication signal of the selected signalling branch to the transmitter for transmission based on the index value.

9. The transmitter apparatus as claimed in claim 8, further comprising a selector with the selection inputs of the selector coupled to the output of the signal processing branches, an output of the selector coupled to the transmitter, and a control input of the selector coupled to a control output of PAPR checker, wherein the PAPR checker outputs the index value to the control input of the selector for sending the baseband communication signal output from the selected signal processing branch to the transmitter.

10. The transmitter apparatus as claimed in claims 7 to 9, wherein each output baseband communication signal comprises one or more baseband communication symbols, and the PAPR checker is configured to: select the signal processing branch for every one or more baseband communciation symbols that have a reduced or minimal PAPR compared with one or more baseband communication symbols associated with other signal processing branches.

11. The transmitter apparatus as claimed in claims 7 to 10, wherein the one or more baseband communication symbols for each output baseband communication signal comprises a subframe of a plurality of baseband communication symbols, and the PAPR checker is configured to: select the signal processing branch for every subframe of baseband communication symbols that have a reduced or minimal PAPR compared with the subframes of baseband communication symbols associated with other signal processing branches.

12. The transmitter apparatus as claimed in claims 7 to 11, wherein the index value associated with the selected signal processing branch is transmitted to a receiver apparatus for use in descrambling or deinterleaving a received transmitted baseband communication signal output from the selected signal processing branch.

13. The transmitter apparatus as claimed in claim 12, further comprising a waveform generator configured to generate a control signal waveform comprising data representative of the index value associated with the corresponding signal processing branch.

14. The transmitter apparatus as claimed in claim 13, wherein the PAPR checker is further configured to: combine each output baseband communication signal with the control waveform associated with the corresponding signal processing branch; estimate the PAPR of each combined output baseband communication signal and corresponding control signal waveform; and select the signal processing branch associated with a combined output baseband communication signal and corresponding control signal waveform that has a reduced or minimal PAPR compared with other signal processing branches.

15. The transmitter apparatus as claimed in claim 14, wherein the baseband communication signal is an OFDM signal and the control signal waveform is a physical uplink control channel, PUCCH, waveform.

16. The transmitter apparatus as claimed in claim 15, wherein the PUCCH waveform is transmitted in a control channel bandwidth in the vicinity of the distal ends of carrier frequency or system bandwidth associated with the OFDM signal selected for transmission.

17. The transmitter apparatus as claimed in claim 16, wherein the PUCCH waveform is transmitted in a control channel bandwidth within the carrier frequency or system bandwidth associated with the OFDM signal selected for transmission.

18. The transmitter apparatus as claimed in claim 15, wherein the PUCCH waveform is transmitted in a control channel bandwidth outside the carrier frequency or system bandwidth associated with the OFDM signal selected for transmission.

19. The transmitter apparatus as claimed in claims 15 to 18, wherein the control channel bandwidth outside the carrier frequency or system bandwidth is one or more guard band(s) associated with the OFDM signal selected for transmission.

20. The transmitter apparatus as claimed in claim 13, wherein the baseband communication signal is an OFDM signal, the communication signal generator is an OFDM signal generator within the signal processing branch associated with the index value, wherein the OFDM signal generator is further configured to: puncture one or more resource elements associated with data OFDM symbols; and insert the control signal waveform or data representative of the index value into the one or more resource elements, wherein a receiver apparatus receiving the punctured OFDM signal transmission retrieves the index value from the associated resource elements for identifying the descrambling or deinterleaving scheme to retrieve the original modulation symbols.

21. The transmitter apparatus as claimed in claim 13, wherein the baseband communication signal is an OFDM signal, the communication signal generator is an OFDM signal generator of the signal processing branch associated with the index value, and the OFDM signal comprises two or more resource blocks, wherein each resource block comprises a block of reference symbols, and the OFDM signal generator of the signal processing branch associated with the index value is further configured to: encode the index value within the reference symbols of two or more of the resource blocks, wherein a receiver apparatus receiving a selected OFDM signal transmission detects and decodes the index value from the associated reference symbols for identifying the descrambling or deinterleaving scheme to retrieve the original modulation symbols.

22. The transmitter apparatus as claimed in any preceding claim wherein the transmitter apparatus is a multi-carrier, MC, transmitter apparatus associated with two or more center carrier, CC, frequency bandwidths, and the plurality of signal processing branches comprises two or more subsets of signal processing branches, wherein each signal processing branch outputs a baseband communication signal, and each subset of signal processing branches associated with each of the CC frequency bandwidths, in which each subset of signal processing branches is coupled to the PAPR checker and the transmitter, wherein the transmitter is a MC transmitter and wherein each signal processing branch from each subset of signal processing branches is combined with signal processing branches from different other subsets of signal processing branches to form multiple combined signal processing branches, wherein each combined signal processing branch outputs a combined baseband communication signal for input to the PAPR checker, wherein the PAPR checker is further configured to: estimate the PAPR of each of the combined baseband communication signals associated with each of the multiple combined signal processing branches; select a combined signal processing branch associated with a combined baseband communciation signal that has an estimated PAPR that is reduced or minimised compared with the estimated PAPR of other combined baseband communciation signals output from other combined signal processing branches, wherein each combined signal processing branch includes signal processing branches that are each associated with a different CC frequency bandwidth and include signal processing branches from all of the CC frequency bandwidths; and send the baseband communication signal outputs associated with the signal processing branches of the selected combined signal processing branch to the MC transmitter for uplink transmission.

23. The transmitter apparatus as claimed in claim 22, wherein each of the combined signal processing branches is associated with an index value for identifying the scrambling schemes or interleaving schemes used to scramble or interleave the modulated symbols associated with the combined signal processing branch.

24. The transmitter apparatus as claimed in claim 23, wherein the PAPR checker is configured to use the index values to identify which combined signal processing branch has been selected and to send the baseband communication signals associated with the selected combined signal processing branch to the transmitter for transmission based on the index values.

25. The transmitter apparatus as claimed in claim 24, further comprising a waveform generator configured to generate a control signal waveform comprising data representative of the index value associated with the corresponding multiple combined of signal processing branches.

26. The transmitter apparatus as claimed in claim 25, wherein the PAPR checker is further configured to: combine each output baseband communication signals of the multiple combined signal processing branches with the control waveform associated with the corresponding multiple combined signal processing branches; estimate the PAPR of each combined output baseband communication signals and corresponding control signal waveform associated with each of the multiple combined signal processing branches; and select a combined signal processing branch in which the estimated PAPR of the corresponding combined baseband communication signals and control waveform is reduced or minimised compared with other combined signal processing branches.

27. A multi-carrier, MC, transmitter apparatus for uplink peak average power ratio, PAPR, reduction in a wireless communications system, wherein the MC transmitter apparatus is associated with two or more center carrier, CC, frequency bandwidths, the MC transmitter apparatus comprising: a plurality of signal processing branches including two or more subsets of signal processing branches, wherein each signal processing branch outputs a baseband communication signal, and each subset of signal processing branches associated with each of the CC frequency bandwidths, in which each subset of signal processing branches is coupled to the PAPR checker and an MC transmitter, and wherein each signal processing branch from each subset of signal processing branches is combined with signal processing branches from different other subsets of signal processing branches to form multiple combined signal processing branches, wherein each combined signal processing branch outputs a combined baseband communication signal for input to the PAPR checker, wherein the PAPR checker is further configured to: estimate the PAPR of each of the combined baseband communication signals associated with each of the multiple combined signal processing branches; select a combined signal processing branch associated with a combined baseband communciation signal that has an estimated PAPR that is reduced or minimised compared with the estimated PAPR of other combined baseband communciation signals output from other combined signal processing branches, wherein each combined signal processing branch includes signal processing branches that are each associated with a different CC frequency bandwidth and include signal processing branches from all of the CC frequency bandwidths; and send the baseband communication signal outputs associated with the signal processing branches of the selected combined signal processing branch to the MC transmitter for uplink transmission.

28. A receiver apparatus for receiving an uplink communication signal from a transmitter apparatus in a wireless communications system, wherein the uplink communciation signal is associated with a particular signal processing branch of the transmitter apparatus that uses a particular scrambling scheme or interleaving scheme for scrambling or interleaving modulation symbols prior to processing the scrambled or interleaved modulation symbols into a baseband communication signal for transmission with a reduced or minimised PAPR, and wherein the receiver apparatus has a set of scrambling or interleaving schemes including the particular scrambling or interleaving scheme used by the transmitter apparatus, the receiver apparatus further comprising: a receiver unit for receiving the uplink communciation signal transmitted from a transmitter apparatus; a demodulator unit configured to demodulate the uplink communication signal into a scrambled or interleaved set of modulation symbols; a blind decoding unit configured to: select a candidate scrambling or interleaving scheme from the set of scrambling or interleaving schemes; decode the scrambled or interleaved set of modulation symbols; perform a cyclic redundancy check on the decoded modulation symbols, and when the cyclic redundancy check passes, output the decoded modulation symbols and proceed to decode any remaining scrambled or interleaved modulation symbols using the candidate scrambling or interleaving scheme whilst performing the CRC check, when the CRC check fails, select another candidate scrambling or interleaving scheme from the set of interleaving schemes to decode and perform the CRC check on the scrambled or interleaved modulation symbols using the other candidate scrambling or interleaving scheme.

29. A receiver apparatus for receiving an uplink communication signal from a transmitter apparatus in a wireless communication communications system, wherein the uplink communciation signal is associated with a particular signal processing branch of the transmitter apparatus that uses a particular scrambling scheme or interleaving scheme for scrambling or interleaving modulation symbols prior to processing the scrambled or interleaved modulation symbols into a baseband communication signal for transmission with a reduced or minimised PAPR, and wherein the uplink communication signal includes a control signal identifying the particular scrambling scheme or interleaving scheme, wherein the receiver apparatus has a set of scrambling or interleaving schemes including the particular scrambling or interleaving scheme used by the transmitter apparatus, the receiver apparatus further comprising: a receiver unit for receiving the uplink communication signal transmitted from a transmitter apparatus; a control detection unit for detecting the control signal identifying the particular scrambling or interleaving scheme; a demodulator unit configured to demodulate the uplink communication signal into a scrambled or interleaved set of modulation symbols; and a decoding unit for decoding the scrambled or interleaved modulation symbols using the identified particular scrambling or interleaving scheme.

30. The receiver apparatus as claimed in claim 29, wherein wherein the uplink communication signal is an uplink OFDM signal and the control signal is a physical uplink control channel, PUCCH, waveform identifying the particular scrambling or interleaving scheme and the control detection unit detects the PUCCH waveform.

31. The receiver apparatus as claimed in claim 30, wherein receiver and control unit are configured to detect the PUCCH waveform is located in a control channel bandwidth in the vicinity of the distal ends of carrier frequency or system bandwidth associated with the received OFDM signal.

32. The receiver apparatus as claimed in claim 30, wherein receiver and control unit are configured to detect the PUCCH waveform located in a control channel bandwidth outside the carrier frequency or system bandwidth associated with the OFDM signal.

33. The receiver apparatus as claimed in claim 32, wherein the control channel bandwidth outside the carrier frequency or system bandwidth is one or more guard band(s) associated with the OFDM signal.

34. The receiver apparatus as claimed in any of claims 29 to 33, wherein each signal processing branch of the transmitter apparatus is associated with an index value for identifying the particular scrambling scheme or interleaving scheme used to scramble or interleave the modulated symbols, wherein the control signal comprises data representative of the index value for use by the control detection unit in identifying the particular scrambling scheme or interleaving scheme.

35. The receiver apparatus as claimed in claim 34, wherein, at the transmitter apparatus an OFDM signal generator of the signal processing branch associated with the index value is further configured to puncture one or more resource elements associated with data OFDM symbols and transmit the baseband communication signal at the output of the OFDM generator as an uplink OFDM signal transmission, and insert the control signal waveform or data representative of the index value into the one or more resource elements, wherein: the receiver unit is further configured to receive the punctured OFDM signal transmission; and the control detection unit is further configured to retrieve the index value from the associated resource elements for identifying the descrambling or deinterleaving scheme for retrieving the original modulation symbols.

36. The receiver apparatus as claimed in claim 33, wherein the received uplink communication signal is a received OFDM signal that comprises two or more resource blocks, wherein each resource block comprises a block of reference symbols, and at the transmitter an OFDM signal generator of the signal processing branch associated with the index value encoded the index value within the reference symbols of two or more of the resource blocks and transmit the baseband communication signal at the output of the OFDM generator as an uplink OFDM signal transmission, wherein: the receiver unit is configured to receive the OFDM signal transmission; and the control detection unit is further configured to detect the encoded index value within the reference symbols; the decoding unit uses the index value from the associated reference symbols for identifying the descrambling or deinterleaving scheme to retrieve the original modulation symbols.

37. A method for uplink peak average power ratio, PAPR, reduction in a wireless communications system, the method, performed by a transmitter apparatus comprising a plurality of signal processing branches coupled a transmitter, the method comprising: estimating the PAPR of baseband communication signals output from the corresponding signal processing branches; selecting the signal processing branch associated with an output baseband communication signal that has a reduced or minimal PAPR compared with other signal processing branches; and sending the baseband communication signal output from the selected signal processing branch to the transmitter for uplink transmission.

38. A method for uplink peak average power ratio, PAPR, reduction in a wireless communications system, the method performed by a multi-carrier, MC, transmitter apparatus associated with two or more center carrier, CC, frequency bandwidths, the MC transmitter apparatus comprising: a plurality of signal processing branches including two or more subsets of signal processing branches, wherein each signal processing branch outputs a baseband communication signal, and each subset of signal processing branches associated with each of the CC frequency bandwidths, in which each subset of signal processing branches is coupled to an MC transmitter, and wherein each signal processing branch from each subset of signal processing branches is combined with signal processing branches from different other subsets of signal processing branches to form multiple combined signal processing branches, wherein each combined signal processing branch outputs a combined baseband communication signal, the method comprising: estimating the PAPR of each combined baseband communication signal associated with each of the multiple combined signal processing branches; selecting a set of multiple combined signal processing branches in which the combined estimated PAPR of the corresponding combined baseband communication signals is reduced or minimised compared with the combined estimated PAPR for other sets of multiple combined signal processing branches, wherein each set of multiple combined signal processing branches includes signal processing branches associated with all of the CC frequency bandwidths; and sending the baseband communication signal outputs associated with the signal processing branches of the selected set of multiple combined signal processing branches to the MC transmitter for uplink transmission.

39. A method for receiving an uplink communication signal from a transmitter apparatus in a wireless communications system, wherein the uplink communication signal is associated with a particular signal processing branch of the transmitter apparatus that uses a particular scrambling scheme or interleaving scheme for scrambling or interleaving modulation symbols prior to processing the scrambled or interleaved modulation symbols to output a baseband communication signal for transmission as the uplink communication signal with a reduced or minimised PAPR, the method comprising: receiving the uplink communication signal transmitted from a transmitter apparatus; demodulating the uplink communication signal into a scrambled or interleaved set of modulation symbols; blind decoding the scrambled or interleaved set of modulation symbols by: selecting a candidate scrambling or interleaving scheme from a set of scrambling or interleaving schemes including the particular scrambling or interleaving scheme used by the transmitter apparatus; decoding the scrambled or interleaved set of modulation symbols; performing a cyclic redundancy check on the decoded modulation symbols; when the cyclic redundancy check passes, outputting the decoded modulation symbols, and proceeding to decode any remaining scrambled or interleaved modulation symbols using the candidate scrambling or interleaving scheme whilst performing the CRC check; when the CRC check fails, selecting another candidate scrambling or interleaving scheme from the set of interleaving schemes and performing the steps of decoding and performing the CRC check on the scrambled or interleaved modulation symbols using the other candidate scrambling or interleaving scheme.

40. A method for receiving an uplink communication signal from a transmitter apparatus in a wireless communications system, wherein the uplink communication signal is associated with a particular signal processing branch of the transmitter apparatus that uses a particular scrambling scheme or interleaving scheme for scrambling or interleaving modulation symbols prior to processing the scrambled or interleaved modulation symbols as a baseband communication signal for transmission as an uplink communication signal with a reduced or minimised PAPR, and wherein the uplink communication signal includes a control signal identifying the particular scrambling scheme or interleaving scheme, the method further comprising: receiving the uplink communication signal transmitted from a transmitter apparatus; detecting the control signal identifying the particular scrambling or interleaving scheme from a set of scrambling or interleaving schemes including the particular scrambling or interleaving scheme; demodulating the uplink communication signal into a scrambled or interleaved set of modulation symbols; and decoding the scrambled or interleaved modulation symbols using the identified particular scrambling or interleaving scheme.

41. Computer readable medium comprising program code stored thereon, which when executed on a processor, causes the processor to perform a method according to claims 37 or 38.

42. Computer readable medium comprising program code stored thereon, which when executed on a processor, causes the processor to perform a method according to any of claims 39 or 40.

43. A UE apparatus comprising a transmitter apparatus as claimed in any one of claims 1 to 27

44. A UE apparatus comprising a processor, a storage unit and a communications interface, wherein the processor unit, storage unit, and communications interface are configured to perform the functions associated with the transmitter apparatus as claimed in any one of claims 1 to 27.

45. A UE apparatus comprising a processor, a storage unit and a communications interface, wherein the processor unit, storage unit, and communications interface are configured to perform the method as claimed in any of claims 37 or 38.

46. A base station apparatus comprising a receiver apparatus as claimed in any one of claims 28 to 36.

47. A base station apparatus comprising a processor, a storage unit and a communications interface, wherein the processor unit, storage unit, communications interface are configured to perform the functions associated with the receiver apparatus as claimed in any one of claims 28 to 36.

48. A base station apparatus comprising a processor, a storage unit and a communications interface, wherein the processor unit, storage unit, communications interface are configured to perform the method as claimed in any one of claims 39 or 40.

49. A telecommunications network comprising a plurality of UEs, each UE configured according to any of claims 43 to 45, a plurality of base stations, each base station configured according to any of claims 46 to 48, wherein each base station serves one or more of the plurality of UEs.