Embodiments presented herein relate to a method, a transmitter, a receiver, a point- to-point microwave system, computer programs, and a computer program product for transmission and reception of a signal in a point-to-point microwave system.

BACKGROUND

Long haul point-to-point microwave hops use microwave bands in the 4-13 GHz bands where susceptibility to fading caused by weather conditions such as rain is comparatively small. Radio propagation conditions that change with the weather conditions, and/or time of day, might nevertheless cause sever frequency selective fading over a given radio transmission path between transmitter and sender of a point-to-point microwave system.

In general terms, diversity receiving schemes might be used as a countermeasure to combat such changing radio propagation conditions during signal reception. A diversity receiver can use either switching or combining networks and Received

Signal Strength Indicator (RSSI) or signal-to-noise-plus-interference ratio (SNIR) as criteria when combating changing radio propagation conditions during signal reception. Common for all realizations is however the need for (at least) two antennas separated by a distance on each side of the hop. To increase capacity in a spectrum efficient way, co-channel dual polarization (CCDP) transmission schemes might be used in combination with cross polar interference cancellation (XPIC). In general terms, XPIC is scheme where imperfect isolation between alternating signal polarizations can be compensated for in the receiver by application of a reciprocal cancellation network in the receiver. With space diversity, both the transmitter and the receiver employ two dual polarized antennas separated by a distance suitable to, together with the diversity combiner, overcome selective fading conditions otherwise limiting link availability. On each side, one transmitter and both receivers are active. This means that the signal from the other side’s transmitter will reach both receivers through somewhat different radio propagation paths. If properly designed, fading will be uncorrelated between the respective radio propagation paths. When the received signals are combined in the diversity combiner the detection performance will sustain even during those conditions. When none of the radio propagation paths are faded, the diversity combiner contributes to a 3 dB processing gain that can e.g. be traded for additional capacity. However, there is still a need for improved mechanisms for efficient point-to-point microwave communications.

SUMMARY

An object of embodiments herein is to provide a transmitter enabling efficient point- to-point microwave communications. According to a first aspect there is presented a transmitter for a point-to-point microwave system. The transmitter comprises baseband circuitry. The transmitter comprises a transmitter branch coupled to the baseband circuitry. The transmitter branch comprises a first antenna arrangement. The first antenna arrangement comprises antenna elements of a first polarization. The transmitter branch further comprises a second antenna arrangement. The second antenna arrangement comprises antenna elements of a second polarization, different from the first polarization. The first antenna arrangement and the second antenna arrangement are physically separated by a first distance, Di, where Di > 5 meters.

According to a second aspect there is a method for transmission of a signal in a point- to-point microwave system. The method is performed by a transmitter according to the first aspect. The method comprises transmitting the signal of the first polarization on the first antenna arrangement. The method comprises transmitting the signal of the second polarization on the second antenna arrangement.

According to a third aspect there is presented a computer program for transmission of a signal in a point-to-point microwave system, the computer program comprising computer program code which, when run on processing circuitry of a transmitter according to the first aspect, causes the transmitter to perform a method according to the second aspect.

According to a fourth aspect there is presented a point-to-point microwave system. The system comprises a transmitter according to the first aspect and configured to transmit a signal. The system further comprises a receiver configured to receive the signal transmitted from the transmitter.

According to a fifth aspect there is presented a method for transmission and reception of a signal in a point-to-point microwave system. The method is performed by a transmitter according to the first aspect and a receiver according to the fifth aspect and a receiver according to the fourth aspect. The method comprises transmitting, by the transmitter, the signal of the first polarization on the first antenna arrangement. The method comprises transmitting, by the transmitter, the signal of the second polarization on the second antenna arrangement. The method comprises receiving, by the receiver, the signal of the first polarization and the second polarization on the third antenna arrangement. The method comprises receiving, by the receiver, the signal of the first polarization and the second polarization on the fourth antenna arrangement.

According to an sixth aspect there is presented a computer program for transmission and reception of a signal in a point-to-point microwave system, the computer program comprising computer program code which, when run on processing circuitry of a transmitter according to the first aspect and a receiver according to the fourth aspect, causes the transmitter and the receiver to perform a method according to the fifth aspect. According to a seventh aspect there is presented a computer program product comprising a computer program according to at least one of the third aspect and the sixth aspect and a computer readable storage medium on which the computer program is stored. The computer readable storage medium could be a non-transitory computer readable storage medium. Advantageously these methods, these transmitters, these receivers, and these computer programs enable efficient point-to-point microwave communications.

Advantageously, by means of these methods, these transmitters, these receivers, and these computer programs, path fading will only affect one of the polarizations. The 3 dB diversity combiner gain will sustain on the unaffected path. This means that path fading will only reduce the total system gain by 1.25 dB (instead of 3 dB). Advantageously, by means of these methods, these transmitters, these receivers, and these computer programs there will be a phase offset introduced on the cross-polar leakage only. In the diversity combiner every phase offset (different from n times 180 degrees) will reduce the cross polar interference level in the combined signal and thus improve the cross polar interference cancellation performance compared to prior art.

Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, module, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic diagram illustrating a point-to-point microwave system

according to embodiments;

Fig. 2 is a schematic illustration of a transmitter according to embodiments;

Fig. 3 is a schematic illustration of a receiver according to embodiments;

Figs. 4 and 5 are flowcharts of methods according to embodiments;

Fig. 6 is a schematic illustration of cross polar cancellation according to prior art; Figs. 7 and 8 are schematic illustrations of cross polar cancellation according to embodiments;

Fig. 9 is a schematic diagram showing functional units of a transmitter according to an embodiment; Fig. 10 is a schematic diagram showing functional modules of a transmitter according to an embodiment;

Fig. li is a schematic diagram showing functional units of a receiver according to an embodiment; Fig. 12 is a schematic diagram showing functional modules of a receiver according to an embodiment; and

Fig. 13 shows one example of a computer program product comprising computer readable means according to an embodiment.

DETAILED DESCRIPTION

The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the

description. Any step or feature illustrated by dashed lines should be regarded as optional.

As noted above there is a need for improved mechanisms for efficient point-to-point microwave communications. In particular, when XPIC is used together with space diversity, transmitters of both polarizations share the same antenna. One reason is that there is a rule of thumb to locate the antenna of the transmitter as high as possible above the ground for best Line of Sight (LoS) conditions, even when this is not required by the actual conditions. If there is a radio propagation path fade (i.e. both polarizations fade identically) the 3 dB diversity combiner gain will be lost for both polarizations. The cross-polarization leakage will always be added worst phase in the receivers. That is, the impact from phase noise on the XPIC performance will result in the worst possible signal to noise ratio (SNR) degradation.

Fig. 1 is a schematic diagram illustrating a point-to-point microwave system too where embodiments presented herein can be applied. The point-to-point microwave system 100 comprises a transmitter 200 and a receiver 300. Thus, the transmitter 200 is configured to transmit signals and the receiver 300 is configured to receive signals. However, as the skilled person understands, both the transmitter 200 and the receiver 300 might be implemented as transceivers and thus be configured to both transmit signals and receive signals. There could be different types of

transmitters 200 and receivers 300. However, since the system too is a point-to- point microwave system it is assumed that the transmitter 200 at least is configured for wireless microwave transmission and that the receiver 300 at least is configured for wireless microwave reception. Each of the transmitter 200 and the receiver 300 comprises its own baseband circuitry 120a, 120b and antenna arrangements 110a, 110b, 110c, liod. Hereinafter, antenna arrangement 110a will be denoted a first antenna arrangements, antenna arrangement 110b will be denoted a second antenna arrangement, antenna

arrangement 110c will be denoted a third antenna arrangements, and antenna arrangement liod will be denoted a fourth antenna arrangement. The transmitter 200 and the receiver 300 are configured to, using the antenna arrangement 110a, 110b, 110c, liod, communicate with each other by transmitting signals over wireless links, as in Fig. 1 schematically illustrated at reference numeral 190. The first antenna arrangement 110a and the second antenna arrangement 110b are physically located at a height, denoted D4, over ground. The transmitter 200 and the receiver 300 are physically separated by a third distance, denoted D3, that extends along a terrain 180.

The embodiments disclosed herein therefore relate to mechanisms for transmission of a signal in a point-to-point microwave system 100 and transmission and reception of a signal in a point-to-point microwave system 100. In order to obtain such mechanisms there is provided a transmitter 200, a method performed by the transmitter 200, a computer program product comprising code, for example in the form of a computer program, that when run on processing circuitry of the transmitter 200, causes the transmitter 200 to perform the method. In order to obtain such mechanisms there is further provided a receiver 300, a method performed by the receiver 300, and a computer program product comprising code, for example in the form of a computer program, that when run on processing circuitry of the receiver 300, causes the receiver 300 to perform the method. Fig. 2 is a schematic illustration of a transmitter 200 according to embodiments. The transmitter 200 comprises baseband circuitry 120a and a transmitter branch 130.

The transmitter branch 130 is coupled to the baseband circuitry 120a. The

transmitter branch 130 comprises a first antenna arrangement 110a. The first antenna arrangement 110a in turn comprises antenna elements 140a of a first polarization. The transmitter branch 130 further comprises a second antenna arrangement 110b. The second antenna arrangement 110b in turn comprises antenna elements 140b of a second polarization. The second polarization is different from the first polarization. The first antenna arrangement 110a and the second antenna arrangement 110b are physically separated by a first distance, denoted Di, where Di > 5 meters.

Further aspects of the transmitter 200 will now be disclosed.

The first distance Di might be a vertical distance and/or a horizontal distance.

According to the embodiment of Fig. 2(a) the first antenna arrangement 110a and the second antenna arrangement 110b are horizontally separated by the first distance Di. According to the embodiment of Fig. 2(b) the first antenna arrangement 110a and the second antenna arrangement 110b are vertically separated by the first distance Di. In further examples the first antenna arrangement 110a and the second antenna arrangement 110b are both horizontally and vertically separated by the first distance Di.

As disclosed above, the first antenna arrangement 110a and the second antenna arrangement 110b are physically separated at least by 5 meters. There might be limitations also on the maximum separation between the first antenna arrangement 110a and the second antenna arrangement 110b. In some aspects, the maximum separation is 60 meters. That is, according to an embodiment, Di < 60 meters.

An alternative formulation of how to select the lower and upper limits of Di will now be disclosed. As will follow, this alternative formulation also results in that 5 meters < Di < 60 meters in most practical applications of the transmitter 200 as used in a point-to-point microwave system too. In general terms, an increased vertical separation of Di as in Fig. 2 improves the diversity gain with respect to atmospheric defocusing phenomena. Nevertheless, this improvement is always asymptotic towards a maximum gain. This, together with practical considerations regarding tower heights (i.e., the distance D4 in Fig. 1) etc., limits real world deployments to an antenna separation of Di < 50-60 meters.

The separation Di should also be selected to ensure that simultaneous fading in both antenna arrangements 110a, 110b caused by ground reflections does not occur. This pattern is periodic with the separation Di. The period depends on hop length (i.e., the distance D3), frequency, and mounting height D4 of the transmitting antenna arrangements 110a, 110b. For short hops (i.e., low values of D3) with low mounted antenna arrangements (i.e., low values of D4) the period may be in the order of 10 meters. This means that an acceptable separation Di in such cases is Di = 5 + n · 10 meters, where n > o is an integer. Thus, even if the desired diversity gain can be reached with less separation, the ground reflections in most practical applications sets the lower limit of Di to in the order of 5 meters.

However, if the antenna arrangements 110a, 110b have high mounting height (i.e. the value of D4 is high) then it could be that Di < 5 meters. In this case, Di = x + n · x/o. meters where x is the distance giving correlating fading because of ground reflection. The value of x increases with increased hop length and decreases with increased mounting height (or tower height). But when the hop length is increased the mounting height (or tower height) should be increased in order to retain a line of sight between the antenna arrangements 110a, 110b of the transmitter 200 and the antenna arrangements 110c, nod of the receiver 300. In most practical applications,

3 meters < x < 15 meters where x might be closer to the lower limit for large hop lengths and closer to the upper limit for small hop lengths. In order to achieve diversity gain with respect to atmospherics, it could be sufficient that Di < 5 meters if the hop length is short enough. But in those cases, x > 10 meters and in order to not lose gain due to ground reflections Di should still be selected as Di = x/2 which yields Di > 5 meters.

There could be different relations between the first polarization and the second polarization. Particularly, according to an embodiment the second polarization is orthogonal to the first polarization. As the skilled person understands, that the polarizations are orthogonal implies that the polarizations are orthogonal within a tolerance, where the tolerance depends on the application. With reference again to Fig. l, there is disclosed a point-to-point microwave system too that comprises a transmitter 200 as disclosed above with reference to Fig. 2, where the transmitter 300 is configured to transmit a signal. The point-to-point microwave system too further comprises a receiver 300 according to Fig. 1, where the receiver 300 is configured to receive the signal transmitted from the transmitter 200.

Further aspects of the point-to-point microwave system too will now be disclosed.

In some aspects, the geometry given by the antenna heights (as defined by the fourth distance D4 and the second distance D2, see below), the antenna separation (as defined by the first distance Di) and the hop distance (as defined by the third distance D3) should be selected so as to decorrelate the risk of simultaneous fading in both radio paths for a given antenna at the receiver 300 (e.g., in the radio path from the first antenna arrangement 110a to the first antenna arrangement 110c and the radio path from the second antenna arrangement 110b to the first antenna

arrangement 110c). Provided a given geometry, there will be equal spaced ideal separation distances.

As noted above, with reference to Fig. 1, the transmitter 200 and the receiver 300 are physically separated by a third distance D3. How much the first antenna arrangement 110a and the second antenna arrangement 110b are physically separated might then depend on the third distance D3. That is, according to an embodiment, the distance Di is dependent on the distance D3.

As noted above, with reference to Fig. 1, the first antenna arrangement 110a and the second antenna arrangement 110b are physically located at a height D4 over ground. How much the first antenna arrangement 110a and the second antenna arrangement 110b are physically separated might then depend on the height over ground D4. As further noted above, with reference to Fig. 1, the transmitter 200 and the receiver 300 are physically separated by a third distance D3 that extends along a terrain 180. How much the first antenna arrangement 110a and the second antenna arrangement 110b are physically separated might then depend on the type of the terrain 180. In this respect, terrain characteristics can affect the antenna separation Di in different ways. The risk and type of diffraction affects the mounting height D4 and thus geometry. Surface conditions can influence design parameters, e.g., when changing the geometry to move the reflection point to a less reflective area (from water or open surfaces to vegetation). A different geometry can also provide advantages in terms of terrain shielding of reflection points.

Further aspects of the receiver 300 will now be disclosed.

Fig. 3 is a schematic illustration of a receiver 300 according to embodiments. The receiver 300 comprises baseband circuitry 120b, a first receiver branch 150a, and a second receiver branch 150b. The first receiver branch 150a and the second receiver branch 150b are coupled to the baseband circuitry 120b. The first receiver branch 150a comprises a third antenna arrangement 110c. The third antenna arrangement 110c comprises antenna elements 140c, i4od of the first polarization and the second polarization. The second receiver branch 150b comprises a fourth antenna

arrangement nod. The fourth antenna arrangement nod comprises antenna elements 140c, i4od of the first polarization and the second polarization. The third antenna arrangement 110c and the fourth antenna arrangement nod are physically separated by a second distance, denoted D2, where the second distance is equal to the aforementioned first distance, that is D2 =Di.

Yet further aspects of the receiver 300 will now be disclosed.

As disclosed above, the first distance Di might be a vertical distance and/or a horizontal distance. Likewise, the third antenna arrangement 110c and the fourth antenna arrangement nod might be vertically separated and/or horizontally separated. According to an embodiment, the third antenna arrangement 110c and the fourth antenna arrangement nod are vertically separated by the second distance D2. According to another embodiment, the third antenna arrangement 110c and the fourth antenna arrangement nod are horizontally separated by the second distance D2. According to yet another embodiment, the third antenna arrangement 110c and the fourth antenna arrangement nod are both horizontally and vertically separated by the second distance D2.

In some aspects, and as will be further disclosed below, the receiver 300 is configured to perform cross polar interference cancellation on received signals (i.e., signals transmitted by the transmitter 200 and received by the receiver 300). Reference is now made to Fig. 4 illustrating a method for transmission of a signal in a point-to-point microwave system 100 as performed by the transmitter 200 according to an embodiment.

S102: The transmitter 200 transmits a signal of the first polarization on the first antenna arrangement 110a.

S104: The transmitter 200 transmits the signal of the second polarization on the second antenna arrangement 110b.

Reference is now made to Fig. 5 illustrating a method for transmission and reception of a signal in a point-to-point microwave system 100 as performed by the transmitter 200 and the receiver 300 according to an embodiment.

S202: The transmitter 200 transmits a signal of the first polarization on the first antenna arrangement 110a.

S204: The transmitter 200 transmits the signal of the second polarization on the second antenna arrangement 110b. It is assumed that the signal of both polarizations is received at each of the third antenna arrangement 110c and the fourth antenna arrangement nod of the receiver 300.

S206: The receiver 300 receives the signal of the first polarization and the second polarization on the third antenna arrangement 110c. S208: The receiver 300 receives the signal of the first polarization and the second polarization on the fourth antenna arrangement nod.

The order of the steps might be changed such that the signal of the first polarization is received before the signal of the second polarization is transmitted. Further, the signal of the first polarization and the signal of the second polarization might be transmitted (and received) in parallel.

Embodiments relating to further details of transmission and reception of a signal in a point-to-point microwave system too as performed by the receiver 300 will now be disclosed. There may be different ways for the receiver 300 to process the signal once it has been received. In some aspects the receiver 300 performs cross polar interference cancellation. That is, according to an embodiment, the receiver 300 is configured to perform (optional) step S210: S210: The receiver 300 performs cross polar interference cancellation on the signal received on the third antenna arrangement 110c and on the signal received on the fourth antenna arrangement nod.

Aspects of application of the herein disclosed transmitter 200 and receiver 300 to cross polar interference cancellation will now be disclosed with reference to Figs. 7, and 8 with Fig. 6 as a reference. In all these figures, a signal of a first polarization (denoted H as in horizontal polarization) and a second polarization (denoted V as in vertical polarization) are transmitted from the first antenna arrangement 110a and the second antenna arrangement 110b. These signals are in Figs. 6, 7, 8 denoted Si and S2, respectively. It is assumed that the signals Si and S2 are received at the third antenna arrangement 110c and the fourth antenna arrangement nod, and that a phase offset a is introduced by the radio propagation channel between the transmitter and the receiver. The positive direction of a (i.e., whether to use +a or -a as a phase offset) is defined according to Figs. 6, 7, 8. Figs. 6, 7, 8 further illustrates how diversity combining is performed on the received signals Si and S2 and how XPIC is performed after diversity combining.

Fig. 6 schematically illustrates cross polar interference cancellation according to prior art.

At Stage 1 the following processing is performed: l-a: The contributions of Si and S2 as received with polarization H at the third antenna arrangement 110c are forwarded to Stage 2. l-b: The contributions of Si and S2 as received with polarization V at the third antenna arrangement 110c are forwarded to Stage 2. l-c: The contributions of Si and S2 as received with polarization H at the fourth antenna arrangement nod are phase offset by -a and then forwarded to Stage 2. 1-d: The contributions of Si and S2 as received with polarization V at the fourth antenna arrangement nod are phase offset by -a and then forwarded to Stage 2.

At Stage 2 the following processing is performed:

2-a: The contributions from l-a and l-c are forwarded to Stage 3. 2-b: The contributions from l-a and l-c are phase offset by 18 o° and scaled such that

51 as received at the third antenna arrangement 110c cancels out Si as received at the fourth antenna arrangement nod and then forwarded to Stage 3.

2-c: The contributions from l-b and l-d are phase offset by 18 o° and scaled such that

52 as received at the fourth antenna arrangement nod cancels out S2 as received at the third antenna arrangement 110c and then forwarded to Stage 3.

2-d: The contributions from l-b and l-d are forwarded to Stage 3.

At Stage 3 the following processing is performed:

3-a: All contributions of Si and S2 as provided from 2-a and 2-c are added.

3-b: All contributions of Si and S2 as provided from 2-b and 2-d are added. No relative phase offset between Si and S2 is introduced on the cross-polarization leakage by this geometry. The XPI will therefore be equivalent to that of a single input single output (SISO) channel also after diversity combining.

Reference is now made to Fig. 7 which schematically illustrates cross polar interference cancellation according to a first embodiment. At Stage 1 the following processing is performed: l-a: The contributions of Si and S2 as received with polarization H at the third antenna arrangement 110c are forwarded to Stage 2. l-b: The contributions of Si and S2 as received with polarization V at the third antenna arrangement 110c are phase offset by -a and then forwarded to Stage 2. l-c: The contributions of Si and S2 as received with polarization H at the fourth antenna arrangement nod are phase offset by -a and then forwarded to Stage 2. 1-d: The contributions of Si and S2 as received with polarization V at the fourth antenna arrangement nod are forwarded to Stage 2.

At Stage 2 the following processing is performed:

2-a: The contributions from l-a are forwarded to Stage 3. 2-b: The contributions from l-a and l-c are phase offset by 18 o° and scaled such that

51 as received at the third antenna arrangement 110c cancels out Si as received at the fourth antenna arrangement nod and then forwarded to Stage 3.

2-c: The contributions from l-b and l-d are phase offset by 18 o° and scaled such that

52 as received at the fourth antenna arrangement nod cancels out S2 as received at the third antenna arrangement 110c and then forwarded to Stage 3.

2-d: The contributions from l-b and l-d are forwarded to Stage 3.

At Stage 3 the following processing is performed:

3-a: All contributions of Si and S2 as provided from 2-a and 2-c are added.

3-b: All contributions of Si and S2 as provided from 2-b and 2-d are added. Due to the phase offset introduced on the cross-polarization leakage by this geometry, the XPI will always be reduced by diversity combining.

Reference is now made to Fig. 8 which schematically illustrates cross polar interference cancellation according to a second embodiment.

At Stage 1 the following processing is performed: l-a: The contributions of Si and S2 as received with polarization H at the third antenna arrangement 110c are forwarded to Stage 2. l-b: The contributions of Si and S2 as received with polarization V at the third antenna arrangement 110c are phase offset by -a and then forwarded to Stage 2. l-c: The contributions of Si and S2 as received with polarization H at the fourth antenna arrangement nod are phase offset by -a and then forwarded to Stage 2. 1-d: The contribution of Si as received with polarization V at the fourth antenna arrangement nod is forwarded to Stage 2.

At Stage 2 the following processing is performed:

2-a: The contributions from l-a are forwarded to Stage 3. 2-b: The contributions from l-a and l-c are phase offset by 18 o° and scaled such that

51 as received at the third antenna arrangement 110c cancels out Si as received at the fourth antenna arrangement nod and then forwarded to Stage 3.

2-c: The contributions from l-b and l-d are phase offset by 18 o° and scaled such that

52 as received at the fourth antenna arrangement nod cancels out S2 as received at the third antenna arrangement 110c and then forwarded to Stage 3 (note: in this example the contribution of S2 as received with polarization V at the fourth antenna arrangement nod is assumed to be zero).

2-d: The contributions from l-b and l-d are forwarded to Stage 3.

At Stage 3 the following processing is performed: 3-a: All contributions of Si and S2 as provided from 2-a and 2-c are added.

3-b: All contributions of Si and S2 as provided from 2-b and 2-d are added.

Here the diversity gain and XPI reduction remains on the upper branch (i.e., resulting at 3-b).

Fig. 9 schematically illustrates, in terms of a number of functional units, the components of a transmitter 200 according to an embodiment. Processing circuitry 210 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 1310a (as in Fig. 13), e.g. in the form of a storage medium 230. The processing circuitry 210 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA). Particularly, the processing circuitry 210 is configured to cause the transmitter 200 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 230 may store the set of operations, and the processing circuitry 210 may be configured to retrieve the set of operations from the storage medium 230 to cause the transmitter 200 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus the processing circuitry 210 is thereby arranged to execute methods as herein disclosed.

The storage medium 230 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

The transmitter 200 may further comprise a communications interface 220 for communications with the receiver 300. As such the communications interface 220 may comprise one or more transmitters and receivers, comprising analogue and digital components. The processing circuitry 210 controls the general operation of the transmitter 200 e.g. by sending data and control signals to the communications interface 220 and the storage medium 230, by receiving data and reports from the communications interface 220, and by retrieving data and instructions from the storage medium 230. Other components, as well as the related functionality, of the transmitter 200 are omitted in order not to obscure the concepts presented herein.

Fig. 10 schematically illustrates, in terms of a number of functional modules, the components of a transmitter 200 according to an embodiment. The transmitter 200 of Fig. 10 comprises a number of functional modules; a transmit module 210a configured to perform steps S102, S202, and a transmit module 210b configured to perform steps S104, S204. The transmitter 200 of Fig. 10 may further comprise a number of optional functional modules. In general terms, each functional module 2ioa-2iob may be implemented in hardware or in software. Preferably, one or more or all functional modules 2ioa-2iob may be implemented by the processing circuitry 210, possibly in cooperation with the communications interface 220 and/or the storage medium 230. The processing circuitry 210 may thus be arranged to from the storage medium 230 fetch instructions as provided by a functional module 2ioa-2iob and to execute these instructions, thereby performing any steps of the transmitter 200 as disclosed herein.

Fig. li schematically illustrates, in terms of a number of functional units, the components of a receiver 300 according to an embodiment. Processing circuitry 310 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 1310b (as in Fig. 13), e.g. in the form of a storage medium 330. The processing circuitry 310 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

Particularly, the processing circuitry 310 is configured to cause the receiver 300 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 330 may store the set of operations, and the processing circuitry 310 may be configured to retrieve the set of operations from the storage medium 330 to cause the receiver 300 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus the processing circuitry 310 is thereby arranged to execute methods as herein disclosed.

The storage medium 330 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

The receiver 300 may further comprise a communications interface 320 for communications with the transmitter 200 As such the communications interface 320 may comprise one or more transmitters and receivers, comprising analogue and digital components. The processing circuitry 310 controls the general operation of the receiver 300 e.g. by sending data and control signals to the communications interface 320 and the storage medium 330, by receiving data and reports from the communications interface 320, and by retrieving data and instructions from the storage medium 330. Other components, as well as the related functionality, of the receiver 300 are omitted in order not to obscure the concepts presented herein. Fig. 12 schematically illustrates, in terms of a number of functional modules, the components of a receiver 300 according to an embodiment. The receiver 300 of Fig. 12 comprises a number of functional modules; a receive module 310a configured to perform step S206, and a receive module 310b configured to perform step S208. The receiver 300 of Fig. 12 may further comprise a number of optional functional modules, such as a cancellation module 310c configured to perform step S210. In general terms, each functional module 3ioa-3ioc may be implemented in hardware or in software. Preferably, one or more or all functional modules 3ioa-3ioc may be implemented by the processing circuitry 310, possibly in cooperation with the communications interface 320 and/or the storage medium 330. The processing circuitry 310 may thus be arranged to from the storage medium 330 fetch

instructions as provided by a functional module 3ioa-3ioc and to execute these instructions, thereby performing any steps of the receiver 300 as disclosed herein.

Fig. 13 shows one example of a computer program product 1310a, 1310b comprising computer readable means 1330. On this computer readable means 1330, a computer program 1320a can be stored, which computer program 1320a can cause the processing circuitry 210 and thereto operatively coupled entities and devices, such as the communications interface 220 and the storage medium 230, to execute methods according to embodiments described herein. The computer program 1320a and/or computer program product 1310a may thus provide means for performing any steps of the transmitter 200 as herein disclosed. On this computer readable means 1330, a computer program 1320b can be stored, which computer program 1320b can cause the processing circuitry 310 and thereto operatively coupled entities and devices, such as the communications interface 320 and the storage medium 330, to execute methods according to embodiments described herein. The computer program 1320b and/or computer program product 1310b may thus provide means for performing any steps of the receiver 300 as herein disclosed.

In the example of Fig. 13, the computer program product 1310a, 1310b is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product 1310a, 1310b could also be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory or a Flash memory, such as a compact Flash memory. Thus, while the computer program 1320a, 1320b is here schematically shown as a track on the depicted optical disk, the computer program 1320a, 1320b can be stored in any way which is suitable for the computer program product 1310a, 1310b.

The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.