DE102013010442A1 - Method of estimating noise power in e.g. physical uplink control channel in wireless communication system, involves identifying noise contribution to wireless signal by dividing received wireless signal into sub-spaces - Google Patents

Abstract

The method involves receiving a wireless signal, identifying a noise contribution to the wireless signal by dividing the received wireless signal into a sub-space that comprises data and control or control signal contribution, and a subspace which is orthogonal to another subspace and comprises a noise signal contribution and no data and control or control signal contribution. The noise power is estimated by using power estimates of subspaces. The division is performed using singular value decomposition analysis. Independent claims are included for the following: (1) wireless communication apparatus; (2) a computer program product of estimating noise power; and (3) a wireless communication system.

Description

TECHNICAL AREA

This patent document relates to systems, apparatus and techniques for estimating noise power in a wireless communication system.

BACKGROUND

In wireless mobile communication systems, the transmitter and receiver often perform operations to maintain or improve the performance of the communication channel. For example, in a cellular network (eg, 2G, 3G, 4G, CDMA, GSM, LTE, etc.), the base station may periodically provide a noise characteristic on a receiving channel (eg, an uplink channel for transmissions or transmissions of mobile Estimate terminals or devices to the base station). The estimation of noise characteristics, such as noise power, may be useful to be able to detect whether the amount of received power corresponds to transmission from a mobile station (MS) or user equipment (UE) or channel noise equivalent.

In current wireless systems, transmission sources (e.g., slots or subcarriers) are reserved for channel noise estimation (ie, mobile stations are not allowed to transmit in these transmission sources send). The noise estimate is often performed during these reserved time slots / subcarriers, which are known to carry no transmissions. However, reserving transmission sources limits bandwidth for user data transmission. There is therefore a need for improved techniques for channel noise performance estimation.

ZUSPMMENFASSUNG

This patent document provides, among other things, systems, apparatus and techniques for estimating noise power in an uplink communication channel in a wireless communication network for wireless communication.

In an exemplary aspect, a method of wireless communication includes receiving a wireless signal, identifying a noise contribution to the wireless signal by decomposing the received wireless signal into a first subspace comprising data and a control signal contribution, and a second subspace which is orthogonal to the first subspace, comprising a noise contribution and no data and no control signal contribution, and estimating a noise power using power estimates on the first subspace and the second subspace.

In another exemplary aspect, a system for wireless communication comprising at least a mobile station and a base station is disclosed. The at least one mobile station is operable to transmit an uplink transmission over an uplink channel. The base station is operable to receive a wireless signal on the uplink channel, making a noise contribution to the wireless signal by decomposing the received uplink transmission into a first subspace comprising data and a control signal contribution, and identify a second subspace that is orthogonal to the first subspace, comprising a noise signal contribution and no data and no control signal contribution, and estimate noise power using power estimates over the first subspace and the second subspace.

These and other aspects and their implementations are described in more detail in the drawings, the description and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

1 FIG. 10 is a block diagram representation of a wireless communication network. FIG.

2 FIG. 10 is a block diagram representation of a wireless communication device. FIG.

3 Fig. 10 is a block diagram of a first embodiment of a noise power estimation technique.

4 Fig. 10 is a block diagram of a second embodiment of a noise power estimation technique.

5 FIG. 10 is a flowchart illustration of a process of wireless communications. FIG.

6 FIG. 10 is a block diagram representation of a portion of a wireless communication device. FIG.

DETAILED DESCRIPTION

This patent document discloses channel noise estimation techniques. In some implementations, the disclosed techniques could be used to estimate noise power on an uplink channel in a wireless communication system. In some implementation, the noise estimates obtained using the disclosed techniques could be used in deciding whether an uplink transmission in a given timeslot and / or a given subcarrier in an Orthogonal Frequency Domain Multiplexed (Orthogonal Frequency division multiplexing, OFDM) transmission scheme was present or not.

The disclosed techniques may be implemented at a base station in a wide area wireless network, such as a Long Term Evolution (LTE) network. While the disclosed techniques have been disclosed to be implemented at a base station in a wireless mobile telephone network, the techniques are equally applicable to any mobile application, such as a wireless local area network, for example based on 802.11x standards or the Wi-MAX standard, etc. applicable.

1 shows an example of a wireless communication system. A wireless communication system may include one or more base stations (BSs) 105a . 105b , one or more wireless device (s) 110a . 110b . 110c . 110d and an access network 125 include. A base station 105a . 105b can provide a wireless service to the wireless devices 110a . 110b . 110c and 110d in one or more wireless sector (s). In some applications, implementations include a base station 105a . 105b Directional antennas to generate two or more directed beams to provide wireless coverage in different sectors.

The access network 125 can with one or more base station (s) 105a . 105b communicate or communicate. In some implementations, the access network includes 125 one or more base station (s) 105a . 105b , In some implementations, the access network is 125 in conjunction with a core network (in 1 not shown), which provides connectivity to other wireless communication systems and wired communication systems. The core network may include one or more service subscription database (s) for information regarding the subscribed wireless devices 110a . 110b . 110c and 110d save. A first base station 105a may provide a wireless service based on a first radio access technology while a second base station 105b provide a wireless service based on a second radio access technology. The base stations 105a and 105b may be co-located or may be installed separately in the field according to the usage scenario. The access network 125 can support several different radio access technologies.

Various examples of wireless communication systems and access networks that can implement the present techniques and systems include wireless communication systems based on Code Division Multiple Access (CDMA) such as CDMA2000 1x, High Rate Packet Data (HRPD), developed HRPD ( eHRPD), Universal Mobile Telecommunications System (UMTS), Universal Terrestrial Radio Access Network (UTRAN), developed UTRAN (E-UTRAN), Long-Term Evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX). In some implementations, a wireless communication system may include multiple networks that use different wireless technologies. A dual-mode or multi-mode wireless device includes two or more wireless technologies that could be used to connect different wireless networks. In some implementations, a wireless device may support Simultaneous Voice Data Operation (SV-DO).

2 is a block diagram representation of a portion of a radio station 205 , A radio station 205 For example, a base station or a wireless device may include processor electronics 210 include, such as a microprocessor, implementing one or more of the wireless technologies presented in this document. The radio station 205 can transceiver or transmit-receive electronics 215 include to wireless signals over one or more communication interface (s), such as an antenna 220 to send and / or receive. The radio station 205 may include other communication interfaces for transmitting and receiving data. The radio station 205 may include one or more memories configured to store information such as data and / or instructions. In some implementations, the processor electronics 210 at least one section or area of the transceiver electronics 215 include.

In an LTE (Long Term Evolution) system, it is often desirable to have an estimate of the received noise plus interference power received in a slot of a PUCCH (Physical Uplink Control Channel) Format 1 / 1A / 1B transmission ,

One use for this information is a determination of whether a PUCCH transmission has been sent by the UE or not. Specifically, for PUCCH format 1 transmissions, the presence of a transmission indicates that the UE is requesting for scheduling, and the absence indicates that no arbitration is desired. Typically, a PUCCH format 1 receiver would compare the received signal power on a particular PUCCH index with the estimated noise power to determine the presence or absence of a PUCCH transmission. If the received signal power is much higher than the noise power, it is very likely that a PUCCH transmission has been performed. If the received signal power is close to the noise power, then it is less likely that a PUCCH transmission has been performed.

Another use for a knowledge of PUCCH received noise power may be for interference coordination among base stations, so-called eNodeBs. When a particular set of PUCCH sources consistently receives high levels of interference, a message may be sent to the neighboring eNodeBs to cause them to tune their transmissions to reduce interference ,

At an RB (Resource Block) configured to contain only formats 1 / 1A / 1B, there can be at most 36 UE's using any mix of formats 1, 1A or 1B (specific in LTE). These transfers are numbered by an index, and assuming that p _{f represents} the PUCCH index of the lowest PUCCH index occupying a particular PUCCH RB, indices p _f to p _f + 35 (inclusive) will all occupy the same RB.

For the purpose of simplifying the discussion in this document, it is assumed that up to 36 UE's have the same PUCCH RB pair (ie Δ PUCCH / shift is 1) can occupy, and that p _f 0. In other words, the discussion in this document focuses on discussing PUCCH format 1 / 1A / 1B indices 0 through 35, which are assumed to occupy the same RB pair. One skilled in the art will appreciate that the same description can be used for any 36 PUCCH indices occupying the same RB.

An exemplary implementation of how to estimate the noise power in a PUCCH RB will now be discussed.

For a given slot with a normal CP (Cyclic Prefix), a series of cyclic shifts or

Shifts α _p (k) for a PUCCH transmission p (numbered 0 to 35) for each OFDM symbol k (numbered from 0 to 6) which is to be transmitted. Details of how the α _p values are calculated can be found in the LTE specifications (eg, Section 5.4.1 of 3GPP TS 36.211, the 3GPP document being incorporated by reference in its entirety in this document) being found.

These cyclic shifts are used to construct a base sequence column vector r with 12 elements to modify as follows:

Details concerning the generation of the r Vector can be found in the LTE specifications (see previously cited section). Specifically, according to the definition of r _{u, v} search.

Based on the PUCCH index p, the sequence becomes w _p from 3 possible sequences: [1 1 1], [1 e ^{j2π / 3} e ^{j4π / 3} ], or [1 e ^{j4π / 3} e ^{j2π / 3} ]. Which sequence is chosen precisely for a given p value is described in the LTE specifications.

In addition, again based on the PUCCH index p, the sequence w _{p is selected} from 3 possible sequences +1 +1 +1 +1, +1 -1 +1 -1, or +1 -1 -1 +1. Which sequence is chosen precisely for a given p value is described in the LTE specifications.

The signal transmitted by a UE on a subcarrier a and an OFDM symbol b at a particular slot may be described as T _p (a, b) as follows:

Where d _{p is} the data that is transmitted by the UE and assumes different values depending on whether an arbitration request or ACK / NACK is to be transmitted. Details regarding the actual generation or generation of the d _p values can be found in the LTE specifications. The absolute value of d _p will be either 0 or 1.

This matrix can be converted into a vector of length 84 as follows: t → _p = [d _p w _p (0) r _{p, 0} ^T d _p w _p (1) r _{p, 1} ^T w → _p (0) r _{p, 2} ^T w → _p (1) r _{p, 3} ^T w → _p (2) r _{p, 4} ^T d _p w _p (2) r _{p, 5} ^T d _p w _p (2) r _{p, 6} ^T ]

Where ^{T represents} the matrix transpose operation.

Two basis vectors can be extracted as follows:

Where the normalization factors exist to ensure that the standards of the basis vectors are 1.

The vectors b → _{p, d} and b → _{p, r} are orthogonal for all p values. In addition, are b → _{p, d} orthogonal for all p values that are assigned within the same PUCCH RB pair according to their design in the LTE specifications. Finally are b → _{p, r} orthogonal for all p values named within the same PUCCH RB pair in turn according to their design in the LTE specifications.

The signal transmitted by the UE on a slot can then be represented as: t → _p = √ 36 b → _{p, r} + √ 48 d _p b → _{p, d} d Eq. 5

The signal received by the eNodeB via a slot of an RB pair can be described as:

Where n → is the received noise (including, inter alia, interference and thermal noise) and hp is the channel response between the UE and the eNodeB. Without loss of generality, the channel is assumed to be flat and the noise is assumed to be a white Gaussian noise with a signal power σ 2 / n is.

Developing the above equation:

The sum can be expressed using a matrix multiplication as follows:

Collecting all basis vectors into a matrix B yields:

All of the columns of B have unit norms and are alternately orthogonal, as previously mentioned.

In order to detect PUCCH transmissions, one can then multiply the received signal by B ^H , where the ^H operator represents the Hermit transpose:

Where n → _z a noise vector with statistics equivalent to B ^H n → is. Since the columns of B have normal and are mutually orthogonal, then n → _z also white, Gaussian distribution with a signal power σ 2 / n ,

With reference to 3 a block diagram illustrating an exemplary embodiment is illustrated 300 for solving the above equations, wherein the input signal r → into a PUCCH channel and data separation module 302 is input, which generates the Z values in the equation ( 306 : used for a channel estimation, 308 : used for a data estimate).

A noise estimate is often done by reserving some PUCCH indices so that no UE ever will be transmitted on these indexes. For example, if the PUCCH index 2 is reserved and it is known that no UE will ever use this index, then for Z (2) and Z (38) it will be known that they contain only noise. The power actually received on these indices can be measured and used as an estimate of the received noise power.

It should be U the set of unused PUCCH indexes 312 be. The received noise power can be estimated as:

Where size (U) is the number of elements in the set U.

Eq. 12 is in 3 illustrates where the unused Z values into a noise power estimation module 310 which estimates the power of the received noise and this value (for example) to the PUCCH detector module 304 forwards.

One possible disadvantage of the embodiment discussed above is that it assumes that certain PUCCH sources are reserved for a noise power estimate that might otherwise be used for communication with the UE.

With reference to 4 A second embodiment of a noise power estimation technique will now be discussed.

This technique first involves solving for a set of basis vectors that span the null space of B ^H. In general, there can be infinitely many sets of basis vectors that span the null space of B ^H , and any of these can be used (as described below). A particular example that may be used involves first solving for the Singular Value Decomposition (SVD) of B ^H as: B ^H = UPS ^H Gl 13

The null space of B ^H is the space of vectors v which satisfy: B ^H ν = 0 GI 14

Using the Singular Value Decomposition (SVD) of B ^H from above: UPS ^H ν = 0 Eq 15 SV ^H ν = 0 Gl 16

The S matrix is of size 84 × 72 and contains only non-zero values on its major diagonal. If v is any linear combination of the last 12 column vectors of V, it will be seen that Eq. 16 will yield zero. Therefore, the last 12 columns of the 84x84 matrix V are a basis for the null space of B ^H.

Another exemplary set of 12 basis vectors which also span the null space of B ^H is:

This is true for m = 0 to 11. It will be appreciated that this in Eq. The given example of a set of 12 basis vectors and the SVD equations provided above are merely to demonstrate that many solutions to null-base basis vectors are possible. Other methods may be used by one skilled in the art to arrive at the base vectors for the null space of B ^H. Also, as will be appreciated, the entire space spanned by B ^{H can be} logically divided into null space and the space spanned by the remaining space, using columns of the above matrix is overstretched.

It is to B _{n is} a representing 84 × 12 matrix containing 12 vectors which span the B ^H null space of ^H B. These vectors could have been generated or generated by any of the above methods or any other method that can generate the null space of B ^H.

An extended version of B, called B _e (a size 84 × 84) can be generated as follows: B _e = [BB _n ] Eq 18

When the received signal with B H / e multiplied, this process can be represented as:

Where n → _x a random noise vector with the same statistics as Bra / s → is. Since the columns of B H / e Norm 1 and are alternately orthogonal is n → _x a white Gaussian distribution with a signal power σ 2 / n ,

Eq. 19 is or will be in 4 illustrates where the input signal r into an advanced PUCCH channel and data separation module 402 which generates the X values in the equation ( 406 : used for a channel estimation, 408 : used for a data estimate).

Let U be the set of unused PUCCH indexes. The received noise power can now be estimated as:

Where size (U) is the number of elements in the set U.

Eq. 21 is in 4 illustrated where X indexes 72 to 83 ( 414 ) and also the unused X values 410 are input to an expanded noise power estimation module, which estimates the power of the received noise, and that value (for example) to the PUCCH detector module 404 forwards. Unused PUCCH indices are identified by a reference numeral 412 designated.

An advantage of the second embodiment discussed above is that it allows all 36 PUCCH indices to be populated by transmissions from different UEs. In such a situation, U is the empty set, and the first embodiment discussed above may not generate an estimate of the noise power in the PUCCH transmission. In the second embodiment, which with reference to 4 is discussed, even if U is the blank set, there are still 12 samples (X (72) to X (83)) which can be used to estimate the received noise power.

Another advantage of this technique is that even if U is not the empty set, this technique still allows the use of multiple samples to estimate the received noise power, and thus would be able to produce a more reliable estimate. For example, if the size of U is 1, refer to 1 be able to average 2 samples to estimate the received noise power. In contrast, the second technique would be capable of averaging 14 samples, which is likely to result in a more reliable estimate of received noise power.

It should be clear to those skilled in that a multiplication with the basis vectors b → _{p, r} and b → _{p, d} which are described in this document can be implemented by a combination of DFT (Discrete Fourier Transform, Discrete Fourier Transform) and Hadamard operations. Any particular implementation of multiplication with the base sectors may be used.

Moreover, although embodiments are described in the context of an LTE uplink communication system, one skilled in the art may use and extend the disclosed techniques for any communication system for which exists a FOE algorithm that satisfies the conditions previously described.

5 is a flowchart representation of a process 500 a wireless communication. at 502 a wireless signal is received. For example, as previously discussed, the signal may be received on PUCCH and may or may not include uplink transmissions from UEs. at 504 For example, a noise contribution to the wireless signal is identified by decomposing the received wireless signal into a first subspace comprising data and a control signal contribution, and a second subspace orthogonal to the first subspace comprising a noise signal contribution and no data and no control signal contribution. As previously described with reference to equations 13-21, the decomposition may be performed using singular value decomposition techniques. at 506 For example, noise power is estimated using power estimates over the first subspace and the second subspace. The estimation may be performed, for example, using sums of absolute squares, as set forth in Equation 21 above.

6 is a block diagram representation of a section 600 a wireless communication device. The module 602 is used to receive a wireless signal. The module 604 is for identifying a noise contribution to the wireless signal by decomposing the received wireless signal into a first subspace comprising data and a control signal contribution, and a second subspace orthogonal to the first subspace comprising a noise contribution and not Data and no control or control signal contribution. The module 606 is for estimating noise power using power estimates over the first subspace and the second subspace.

It will be appreciated that the present patent document discloses various techniques for performing noise power estimation by subdivision into subspaces. It will be appreciated that the techniques are described using the example of the operation of PUCCH in a Long Term Evolution (LTE) network.

The disclosed and other embodiments, modules, and the functional processes described in this document may be implemented in a digital electronic circuit or in computer software, firmware, or hardware including the structures that comprise in this document, and their structural equivalents, or in combinations of one or more thereof. The disclosed and other embodiments may be implemented as one or more computer program product (s), ie, one or more modules of computer program instructions encoded on a computer readable medium for execution, or to govern the operation of a data processing device or too Taxes. The computer-readable medium may be a machine-readable storage device, a machine-readable storage substrate, a storage device, a collection of items that effect a machine-readable forwarded signal, or a combination of one or more of these. The term "data processing device" includes all devices, devices and machines for processing data including, for example, a programmable processor, a computer, or multiple processors or computers. The device may include, in addition to hardware, code that generates an execution environment for the computer program in question, e.g. For example, a code representing or representing processor firmware, a protocol stack, and a database management system, an operating system, or a combination of one or more of these. A propagated or propagated signal is an artificially generated or generated signal, for. As an electrical, optical or electromagnetic signal generated by a machine, which is generated or generated to encode information for transmission to a suitable receiver device.

A computer program (also known as a program, software, software application, script or code) may be written in any form of programming language, including compiled or interpreted languages, and may be used in any form, including as a separate program or as a module, component, subroutine or other entity suitable for use in a computer environment. A computer program does not necessarily have to correspond to a file in a file or folder system. A program may be stored in a section of a file containing other programs or data (eg, one or more script (s) stored in a markup language document) in a single file associated with the program in multiple coordinated files (eg, files storing one or more modules, subprograms, or ranges of codes). A computer program may be employed to run on a computer or on multiple computers which are located in one place or distributed over multiple locations and interconnected by a communication network.

The processes and logic sequences described in this document may be performed by one or more programmable processor (s) that perform one or more computer programs to perform functions by editing Perform input data and generate or generate an output. The processes and logic sequences may also be implemented as a special purpose logic circuit, and the apparatus may be implemented as such a logic circuit, e.g. For example, an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

Processors suitable for executing a computer program include, for example, both general purpose and special purpose microprocessors, and one or more processors of any type of digital computer. In general, a processor will receive instructions and data from read-only memory or random-access memory, or both. The essential elements of a computer are a processor for executing instructions and one or more storage devices for storing instructions and data. Generally, a computer will also include or be operatively coupled to receive data or transmit data or both from one or more mass storage devices for storing data, e.g. As magnetic, magneto-optical disks or optical disks. However, a computer does not need to have such devices. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices including, for example, semiconductor memory devices, e.g. EPROM, EEPROM and flash memory devices; Magnetic disks, z. Internal hard disks or removable disks; magneto-optical disks and CD ROM and DVD ROM disks. The processor and memory may be supplemented or integrated into a special purpose logic circuit.

While this patent document contains many specific features, these should not be construed as limitations upon the scope of an invention which may be claimed or claimed, but rather as descriptions of features specific to particular embodiments. Certain features described in this document in the context of separate embodiments may also be implemented in combination in a single embodiment. In contrast, various features described in the context of a single embodiment may also be implemented separately in several embodiments or implemented in any suitable subcombination. In addition, or For example, while features are described above that work in certain combinations and are themselves originally claimed, one or more features of a claimed combination may, in some cases, be taken from the combination, and the claimed combination may include be a sub-combination or a modification of a sub-combination directed. Similarly, while operations in the drawings are illustrated in a particular order, it should not be construed that such operations are required to be performed in the particular order shown or in a sequential order, or that all illustrated operations are performed to achieve desired results. According to one aspect of the invention, there is disclosed a computer program product tangibly embodied on a computer readable storage medium as a signal and / or as a data stream, comprising a computer readable storage medium having code stored thereon, the code, when stored by a processor causing the processor to implement a wireless communication method, comprising: receiving a wireless signal; identifying a noise contribution to the wireless signal by decomposing the received wireless signal into a first subspace comprising data and a control signal contribution, and a second subspace orthogonal to the first subspace comprising a noise signal contribution and no data and no control signal contribution; and estimating a noise power using power estimates over the first subspace and the second subspace.

In particular, the decomposition is performed using a singular value decomposition analysis.

Only a few examples and implementations are disclosed. Modifications, modifications, and enhancements to the described examples and implementations and other implementations may be made based on the disclosure.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• LTE specifications (eg, Section 5.4.1 of 3GPP TS 36.211, the 3GPP document being incorporated by reference herein in its entirety) [0027]

Claims (10)

A method of wireless communication, comprising: Receiving a wireless signal; Identifying a noise contribution to the wireless signal by decomposing the received wireless signal into a first subspace comprising data and a control signal contribution, and a second subspace orthogonal to the first subspace comprising a noise signal contribution and no data and none Control or control signal contribution; and Estimating a noise power using power estimates on the first subspace and the second subspace. The method of claim 1, wherein said decomposing is performed using a singular value decomposition analysis. Method according to one of the preceding claims, wherein the power estimate in each subspace is performed using a sum of squares of an absolute value of a received signal in that space, and / or wherein no time-frequency sources are reserved for a noise signal estimate. The method of claim 1, wherein the wireless signal comprises uplink transmission over a physical uplink control channel from user equipment to a base station, and / or comprising determining based on the estimated noise power, whether a transmission or a transmission is being performed Transmission from the user equipment was received. Apparatus for wireless communication, comprising: a receiving device receiving a wireless signal; a noise distribution identifying means which identifies a noise contribution to the wireless signal by decomposing the received wireless signal into a first subspace comprising data and a control signal contribution, and a second subspace orthogonal to the first subspace comprising Noise signal contribution and no data and no control or control signal contribution; and a noise power estimator that estimates noise power using power estimates over the first subspace and the second subspace. The apparatus of claim 5, wherein the decomposition is performed using a singular value decomposition analysis, and / or wherein the noise power estimation means estimates the power estimate in each subspace using a sum of squares of an absolute value of a received signal in that subspace , Apparatus for wireless communication, comprising: Means for receiving a wireless signal; Means for identifying a noise contribution to the wireless signal by decomposing the received wireless signal into a first subspace comprising data and a control signal contribution, and a second subspace orthogonal to the first subspace comprising a noise contribution and none Data and no control signal contribution; and Means for estimating a noise power using power estimates over the first subspace and the second subspace. The apparatus of claim 7, wherein the decomposing is performed using a singular value decomposition analysis, and / or wherein the power estimation in each subspace is performed using a sum of squares of an absolute value of a received signal in that subspace. A computer program product comprising a computer readable storage medium having a code stored thereon, the code, when executed by a processor, causing the processor to implement a wireless communication method according to any one of the preceding claims 1 to 4. A wireless communication system comprising a base station and at least one mobile station, wherein the at least one mobile station is operable to transmit an uplink transmission over an uplink channel; and the base station is operable to: receive a wireless signal on the uplink channel; making a noise contribution to the wireless signal by decomposing the received uplink transmission into a first subspace comprising data and a control signal contribution, and identifying a second subspace which is orthogonal to the first subspace comprising a noise contribution and no data and no control signal contribution; and estimate a noise power using power estimates over the first subspace and the second subspace.

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