WO2018004401A1

WO2018004401A1 - A transmitter and method performed thereby for performing a transmission to a receiver

Info

Publication number: WO2018004401A1
Application number: PCT/SE2016/050639
Authority: WO
Inventors: Alireza Nejatian; Guido Hiertz
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2016-06-28
Filing date: 2016-06-28
Publication date: 2018-01-04

Abstract

A radio communication transmitter and a method performed thereby for performing a transmission to a radio communication receiver over a first channel are provided. The radio communication transmitter and the radio communication receiver are operable in a radio communication network. The method comprises determining (110) power leakage to adjacent channels due to an ongoing transmission on a second channel; and determining (120) an energy threshold based on the determined power leakage to adjacent channels. The method also comprises performing (130) energy detection on one or more first channels; and transmitting (160) data to the radio communication receiver if the detected energy on the one or more first channels does not meet the determined energy threshold.

Description

A TRANSMITTER AND METHOD PERFORMED THEREBY FOR PERFORMING

A TRANSMISSION TO A RECEIVER

Technical field

[0001 ] The present disclosure relates to wireless communication and in particular to a radio transmitter and a method performed thereby for the radio transmitter to perform a transmission to a radio communication receiver over a first channel of a radio communication network.

Background

[0002] The demands on radio or wireless communication networks are constantly increasing with higher demands on capacity, bit rates etc. Generally, the amount of traffic varies substantially over time and designing any

communication network having resources to cope with the most extreme traffic peeks is very expensive and may also be impossible.

[0003] Instead, it is desirable to use any communication system optimally without wasting resources. In many places there may be overlapping radio communication networks employing different technologies. Once such example is Long Term Evolution, LTE, and WiFi which is also known as Wireless Local Area Network, WLAN. As will be explained in more detail below, a wireless device operating in an LTE communication network may simultaneously also operate in a WLAN, which is referred to as LTE Licenced Assisted Access, LTE-LAA.

[0004] Different technologies have different schemes for performing

transmissions. Collisions are to be avoided since they may likely cause

transmissions to be lost, wherein re-transmissions are required. In WLAN, a transmitter may fist sense a channel, or channels, in order to determine whether the channel(s) is/are free or busy. In case the channel is busy, the transmitter backs off and retries to find a free channel. In case the channel is free, the transmitter is free to use the channel for performing a transmission.

[0005] However, due to e.g. imperfections of the transmitter, determining whether a channel truly is free may be tricky. Generally, thresholds which are predetermined are generally very strict so that a transmitter should not erroneously determine the channel free when it is in fact actually busy. As a consequence, instead the channel may be erroneously determined to be busy when it is in fact free, wherein resources are wasted, delays in transmissions may occur etc.

Summary

[0006] The object is to obviate at least some of the problems outlined above. In particular, it is an object to provide a radio communication transmitter and a method performed thereby for performing a transmission to a radio communication receiver over a first channel in a radio communication network. These objects and others may be obtained by providing a radio communication transmitter and a method performed by a radio communication transmitter according to the independent claims attached below.

[0007] According to an aspect a method performed by a radio communication for performing a transmission to a radio communication receiver over a first channel is provided. The radio communication transmitter and the radio

communication receiver are operable in a radio communication network. The method comprises determining power leakage to adjacent channels due to an ongoing transmission on a second channel; and determining an energy threshold based on the determined power leakage to adjacent channels. The method also comprises performing energy detection on one or more first channels; and transmitting data to the radio communication receiver if the detected energy on the one or more first channels does not meet the determined energy threshold.

[0008] According to an aspect, a radio communication for performing a transmission to a radio communication receiver over a first channel is provided. The radio communication transmitter and the radio communication receiver are operable in a radio communication network. The radio communication transmitter is configured for determining power leakage to adjacent channels due to an ongoing transmission on a second channel; and determining an energy threshold based on the determined power leakage to adjacent channels. The radio communication transmitter is also configured for performing energy detection on one or more first channels; and transmitting data to the radio communication receiver if the detected energy on the one or more first channels does not meet the determined energy threshold.

[0009] The radio communication transmitter and the method performed thereby may have several advantages. On possible advantage is that the probability of identifying idle channels may be improved. Another possible advantage is that system capacity may be enhanced since more channels may be used

simultaneously.

Brief description of drawings

[00010] Embodiments will now be described in more detail in relation to the accompanying drawings, in which:

[0001 1 ] Figure 1 a is a flowchart of a method performed by a radio communication transmitter for performing a transmission to a radio communication receiver over a first channel, according to an exemplifying embodiment.

[00012] Figure 1 b is a flowchart of a method performed by a radio communication transmitter for performing a transmission to a radio communication receiver over a first channel, according to yet an exemplifying embodiment.

[00013] Figure 1 c is a flowchart of a method performed by a radio communication transmitter for performing a transmission to a radio communication receiver over a first channel, according to still an exemplifying embodiment.

[00014] Figure 2a is an illustration of an example showing energy level of un- licenced band channels.

[00015] Figure 2b is an illustration of an adaptive wireless communication system.

[00016] Figure 2c is a graph illustrating typical AM/AM performance of a power amplifier. [00017] Figure 2d is a graph illustrating power spectral density of ideal power amplifier and non-linear power amplifier.

[00018] Figure 2e is an illustration of a conventional DPD technique for compensating non-linear effects of a power amplifier.

[00019] Figure 3 is a block diagram of a radio communication transmitter for performing a transmission to a radio communication receiver over a first channel, according to an exemplifying embodiment.

[00020] Figure 4 is a block diagram of a radio communication transmitter for performing a transmission to a radio communication receiver over a first channel, according to yet an exemplifying embodiment.

[00021 ] Figure 5 is a block diagram of an arrangement in a radio communication transmitter for performing a transmission to a radio communication receiver over a first channel, according to an exemplifying embodiment.

Detailed description

[00022] Briefly described, a radio communication transmitter and a method performed thereby for performing a transmission to a radio communication receiver over a first channel are provided. The radio communication transmitter and the radio communication receiver are operable in a radio communication network. Instead of having a static predetermined threshold for determining whether a channel is busy or idle during channel sensing, the transmitter determines a dynamic threshold, called energy threshold, which is determined based on a power leakage to adjacent channels due to an ongoing transmission on another, in this disclosure referred to as a second, channel.

[00023] As will be clear from the description and the drawings, the transmitter may be employed in different networks or combination of networks. In one non- limiting example, the transmitter is operating in a radio communication network based on LTE-LAA, wherein the ongoing transmission is on an LAA channel and the channel on which the transmitter wishes to transmit belongs to another radio communication network based on for example WiFi. However, the transmitter may be operating on a WiFi network only, wherein the second channel on which the ongoing transmission is performed is a WiFi channel and the channel on which the transmitter wishes to transmit belongs to the same WiFi radio communication network.

[00024] Embodiments of such a method performed by a radio communication transmitter for performing a transmission to a radio communication receiver over a first channel will now be described with reference to figures 1a-1c. The radio communication transmitter and the radio communication receiver are operable in a radio communication network. Figure 1a illustrates the method 100 comprising determining 1 10 power leakage to adjacent channels due to an ongoing

transmission on a second channel; and determining 120 an energy threshold based on the determined power leakage to adjacent channels. The method also comprises performing 130 energy detection on one or more first channels; and transmitting 160 data to the radio communication receiver if the detected energy on the one or more first channels does not meet the determined energy threshold.

[00025] When the transmitter is performing a transmission on the second channel, parts of that transmission may leak to one or more adjacent channels due for e.g. non-linearities in one or more power amplifiers of the transmitter.

Consequently, if the transmitter simultaneously senses channel(s) in order to determine whether it/they is/are idle or busy, the transmitter may sense that or those channels suffering from the power leakage to be erroneously busy. When the transmitter senses a channel or channels, the transmitter detects energy on that channel or those channels. Since part of the transmission on the second channel may leak into one or more adjacent first channels, the transmitter may detect energy on the one or more adjacent first channels thereby deeming the one or more adjacent first channels to be busy.

[00026] The transmitter may then determine the energy threshold based on the determined power leakage to adjacent channels. The energy threshold is used by the transmitter to determine if a channel is idle or busy. Once the transmitter has sensed the channel(s), the transmitter may compare the detected energy of each sensed channel to the energy threshold. [00027] The transmitter may then transmit data to the radio communication receiver if the detected energy on the one or more first channels does not meet the determined energy threshold. Since the energy threshold is determined based on the determined power leakage to adjacent channels, the energy threshold takes into account the determined power leakage so that the transmitter does not mistake determined power leakage for one or more first channels being busy.

[00028] The method performed by the radio communication transmitter has several possible advantages. One possible advantage is that the probability of identifying idle channels may be improved. Another possible advantage is that system capacity may be enhanced since more channels may be used

simultaneously.

[00029] The power leakage to adjacent channels may be determined based on a known signal.

[00030] There are various different signals that may be used in order to determine the power leakage to adjacent channels. In order to determine the power leakage to adjacent channels, the transmitter needs to know the power with which the transmission is being transmitted.

[00031 ] In an example, the known signal is a reference signal.

[00032] Various examples may be listed of possible known signals that may be used by the transmitter to determine the power leakage to adjacent channels. One example is a reference signal or reference signals.

[00033] Reference signals are generally transmitted with a known transmission power and also on known frequencies, points in time etc. Consequently, they are a suitable known signal based on which the transmitter may determine the power leakage to adjacent channels.

[00034] The performing 130 of energy detection on one or more first channels may comprise receiving respective energy level of individual one or more first channels. [00035] When the transmitter senses a channel, the transmitter detects energy of that channel. The "amount" of energy the transmitter senses corresponds to the energy level of the channel. Consequently, the transmitter detects a respective energy level on respective one or more first channels.

[00036] The unit of the energy level may be e.g. dBm, which is the same unit as the determined energy threshold.

[00037] The energy level is determined averaging of all energies over a channel bandwidth within predefined time unit.

[00038] The method may further comprise comparing 140 respective received energy level of individual one or more first channels to the determined energy threshold.

[00039] By comparing the energy level of one or more of the one or more first channels to the determined energy threshold, the transmitter may determine whether one or more of the one or more first channels is/are free or busy. Since the energy threshold is determined based on the power leakage to adjacent channels, the energy threshold provides a more correct determination of whether channels are free or busy.

[00040] Still further, the method may comprise ranking 150 the one or more first channels based on their respective energy level.

[00041 ] The ranking means that the transmitter may look at individual first channels that do not meet with the determined threshold, and sort them according to their respective energy level. Individual first channels that do not meet with the determined energy threshold may possibly all be used for the transmission.

Channels not meeting the determined energy threshold means channels for which detected energy level is lower than the determined energy threshold. However, it may be advantageous to transmit on a channel having the lowest detected energy level since that channel may suffer least amount of interference from other channels and/or other transmitters. [00042] The transmitting 160 of data to the radio communication receiver may comprise taking into account the ranking.

[00043] Once the transmitter has ranked the one or more first channels based on their respective energy level, the transmitter selects one or more of the available channels for the transmission.

[00044] The selection may be performed such that the transmitter attempts to minimise interference on other channels and/or to maximise the likelihood that the transmission will be successful. One example of possibly obtaining both those objectives is to select the channel(s) having lowest detected energy level(s).

[00045] The data may be transmitted to the radio communication receiver no later than directly after the ongoing transmission on the second channel has terminated without a backoff period, whereby the ongoing transmission of data is switched from the second channel to the first channel.

[00046] By switching the ongoing transmission from the second channel to the first channel, the transmission may be continued without interruption. Without the method, the transmitter is generally allowed to only transmit for a limited time, e.g. 4 or 8 ms, and then the transmitter needs to back off for a period of time, then to sense the channels in order to find an idle channel and then resume or start a new transmission. However, with the method described herein, the transmitter may sense one or more first channels already as it has the ongoing transmission on the second channel.

[00047] Once the transmitter has found an idle channel, i.e. the first channel(s), the transmitter may switch the ongoing transmission to the found first channel(s) or start a new transmission on the found first channel(s) without backing off in between. This may increase throughput and/or system usage and/or efficiency in system usage.

[00048] It shall be noted that the method may also be performed by the radio communication transmitter in order to find an addition free channel for transmission in case carrier aggregation is supported, wherein the transmitter may simultaneously transmit on more than one channel.

[00049] The power leakage to adjacent channels may be determined by Adjacent Channel Leakage Ratio, ACLR.

[00050] The ACLR is defined as the ratio of the transmitted power to the power in the adjacent radio channel. Both powers are measured after a receiver filter.

[00051 ] The ACLR may be measured and determined e.g. by means of a

Reference Measurement Channel.

[00052] The radio communication network may be based on Orthogonal

Frequency Division Multiplexing, OFDM, and the one or more first channels and the second channel are comprised in a non-licenced frequency band.

[00053] There are different types of radio communication technologies, whereof OFDM is one. The OFDM comprises a licensed frequency band.

[00054] Generally, transmissions in an OFDM-based radio communication network are scheduled, e.g. by a scheduler in a Radio Base Station, RBS.

Generally, there are no dedicated channels in the un-licensed band, instead transmissions in the non-licenced frequency bands are not scheduled Thus the transmitter senses the channels before transmitting and if the transmitter finds an idle channel, the transmitter may transmit on that channel.

[00055] The radio communication network may be a LTE-LAA network and/or the un-licenced frequency band belongs to a Wi-Fi network.

[00056] The LTE and Wi-Fi networks are two examples of radio networks that are generally operating in two difference frequency bands and have very different media access policies, i.e. the way a transmitter gains access to a channel and/or period in time, for performing a transmission. In an example, the Wi-Fi network is an IEEE 802.1 1 network. [00057] Driven by growing number of LTE subscribers worldwide, 3^rd Generation Partnership Project, 3GPP, started a new activity using unlicensed spectrum with LTE alongside licensed spectrum. This is known as LTE-License Assisted Access, LTE-LAA. LTE-LAA allows operators to benefit from additional capacity available in unlicensed spectrum, particularly in hotspots and corporate environments. With LTE-LAA, the extra spectrum resource, especially in the 5 GHz band, may complement licensed band LTE operation.

[00058] In LTE-LAA, a Radio Base Station, RBS (also referred to as eNodeB or eNB) senses unlicensed channels before transmitting data. If it finds a channel as idle, it may schedule data transmissions. Otherwise the eNodeB performs a back off procedure, i.e. it does not transmit any data (including Reference Symbols, RSs).

[00059] Energy detection, as described above, is a technique to detect the state of a medium, e.g. one or more first channels. Sensing a channel for energy, the transmitter may decide whether the medium is idle or occupied (busy). Figure 2a illustrates an example of an energy detection scheme. Without limitation to the generality, assume an example of four channels in the unlicensed band, also denoted as secondary channels. An eNodeB senses energy on each channel. A channel is declared unoccupied if the energy is less than a pre-defined (i.e.

without the method described above) threshold. If the eNodeB senses that there is no transmission from the other eNodeBs or other Radio Local Area Network, RLAN, devices, i.e. the channel is idle, the eNodeB may schedule its downlink transmission. Without limitation to the generality assume the energy detection threshold to be set as -62 dBm.

[00060] In the example in figure 2a, the eNodeB senses channels 1 -4. Based on a threshold of -62 dBm it determines that channels 1 and 4 are busy.

Consequently the eNodeB will not transmit in these channels. However, in channels 2 and 3 the level of energy observed is less than the pre-determined threshold of -62 dBm. Thus, the eNodeB may schedule transmissions in these channels. [00061 ] Figure 2b illustrates a generic block diagram of a radio communication system (LTE/LTE-LAA). Input bits from upper layers are passed through baseband blocks, which typically consist of channel encoder, interleaver and rate matching, modulator, layer mapper, OFDM modulator etc. Once the baseband signal is generated, it passes through the Radio Frequency, RF, chain before it is sent to the antenna ports. The RF chain typically consists of Digital to Analog converter, DAC, l/Q imbalance correction, oscillators, and Power Amplifiers, PAs. Note that the baseband signal generation depends on higher layer scheduler decisions e.g. Medium Access Control, MAC, layer. Scheduler decisions are also influenced by the contents of the feedback channel from the receiver. For example the receiver has knowledge to advice on the most suitable modulation and coding scheme to use. E.g. when the receiver experiences a good signal to noise (plus interference) ratio, it might prefer higher order modulation say 256-QAM

(Quadrature Amplitude Modulation) or 64-QAM, and when the receiver

experiences a low signal to noise ratio, it might prefer a low order modulation such as QPSK (Quadrature Phase Shift Keying) or 16-QAM.

[00062] For acceptable efficiency, power amplifiers in the RF block need to nonlinear operate. Figure 2c shows the typical AM/AM curve of a power amplifier. It can be observed that the input/output curve is highly non-linear.

[00063] However, with non-linear power amplifier operation, some signals are leaked into the other frequency bands (adjacent carrier bandwidths). Figure 2d shows the spectral regrowth due to PA non-linearity. It can be seen from figure 2d that, the power spectral density plot is distorted, and there is leakage of the desired signal to adjacent channels as described above with reference to figures 1a-1c

[00064] The ACLR defines a metric to measure non-linear PA leakage. Figure 2d presents that an ideal PA may achieve down to -100 dBc ACLR, while a nonlinear PA achieves an ACLR of only about -38 dBc.

[00065] One method to compensate for a power amplifier's non-linear behaviour is to distort the input signal to the PA such that the output signal from the PA is transformed to be close to what it would have been if the PA would operate linear. An example of such method is called Digital Pre-Distortion, DPD,

Technique. In general DPD may interchangeably be called as a signal

linearization circuitry, component, mechanism, or scheme.

[00066] Figure 2e illustrates the block diagram of a transmitter employing DPD. Let yi denote the output signal at the output of the PA, xi denote the output signal from the baseband, and zi denote the input signal to the PA. Note that, in this model, only the impact of nonlinear PA behaviour is considered. In practical systems, however, the PA may be preceded by many other blocks such as digital to analogue converter, DAC, local oscillator, LO, etc. All of them may add to non- linearities that reduce ACLR. The output signal may be expressed as y_t = i (zi) , where denotes a non-linear function which characterises the PA.

[00067] With DPD, the above equation may be written as y₂ = Λ (#ι (χι)) , where g^.) denotes the function that characterises the DPD block. Note that DPD extraction block is chosen such that y₂ = Λ (#ι

^Gi- i . where G_t denotes the PA's gain. The above equation indicates that the PAs output signal may be linearized if g_t is chosen accordingly.

[00068] Even with DPD, the achievable ACLR will be limited to -45 dBc to -60 dBc. As consequence, a substantial amount of energy will still be leaked to neighbouring channels. Moreover, DPD techniques have high computational complexity that requires a high amount of power. This renders DPD technologies less useful for low complexity transmitter implementations in radio nodes such as e.g. LTE-LAA base stations or other transmitters that are designed for cost sensitive mass or bulk deployments within a cell. Therefore 3GPP proposes to relax the ACLR requirement of the current LAA standard since LTE-LAA base stations transmit at low power of about 30 dBm to 24 dBm. Note that current 3GPP standards set a minimum ACLR requirement of -45 dBc in licensed band.

[00069] With fixed energy detection per each channel (e.g. -62 dBm) the probability of identifying an unoccupied channel is very limited. In particular, if the same eNodeB schedules wireless devices in more than one unlicensed band (say adjacent channels), adjacent channel interference caused by non-linarites of the transmission chain adds up. This minimises the probability of finding an idle channel. Consequently, overall system efficiency and LAA system's capacity may be reduced, if the method described above is not employed.

[00070] By employing the method described above with reference to figures laic, the transmitter uses an energy detection scheme employing a variable threshold. Using the method described above, the transmitter (e.g. an eNodeB of an LTE-based radio communication network) first computes the amount of self- interference caused by non-linearities of its transmission chain. Once it computes the adjacent channel interference leaked from its operating channels into adjacent channel, the transmitter may compute adjacent channel specific energy detection threshold(s) and perform channel sensing processes accordingly. The impact caused by adjacent channel interference may be minimal when aggressor (system that interfere the other systems) and victim (system that is interfered by other systems) are co-located. In the present case, aggressor and victim may be co- located as transmissions from in adjacent channel originate from the same transmitter.

[00071 ] Explanatory example calculation 1 : Consider 4 channels in the

unlicensed band with energy levels of E1 , E2, E3, and E4. Say the fixed energy detection threshold is Ετ (e.g. -62 dBm). Assume, channel 2 is empty and the transmitter (eNodeB) decides to transmit on channel 2. Then it computes the ACLR to neighbouring channels caused by its channel 2 transmissions. This computation may operate either on current transmissions or derived from previous transmissions, e.g. transmissions in prior subframes. Denote ACLR for channel 1 as A21 dBc, for channel 3 as A23 dBc, and for channel 4 as A24 dBc. Suppose the eNodeB's output power is TPeNodeB dBm. Then the self-interference from channel 2 is computed as:

• (TPeNodeB +A21 ) dBm in channeH ,

• (TPeNodeB +A23) dBm in channel3, and

• (TPeNodeB +A24) dBm in channel 4. [00072] Once the transmitter/eNodeB computes the channel specific energy levels, it may compare them with known reference level. Such a known reference level is the energy level of Reference Symbols. Consequently, the eNodeB may decide if the sensed energy level in the channel indicates an idle or a busy channel condition.

[00073] In LTE, all power related settings stem from Reference Symbol, RS, measurements. In IEEE 802.1 1 an Access Point's, AP's, beacon frame may serve a similar purpose. An 802.1 1 AP operates on a fixed frequency channel. The AP changes this frequency channel only rarely. The vast majority of APs uses the default beacon transmission interval of 100 ms. Thus, frequent measurements of neighbouring APs' beacon signal (strength) is possible. Therefore, in the following RS may serve as synonym of beacon in IEEE 802.1 1 Wireless LANs, WLANs.

[00074] RSs are generally transmitted over the entire channel. Typically, RS power is around 4.5% of the total power (this may depend on configuration), which is around 13 dB below the maximum transmission power.

[00075] Explanatory example calculation 2: Attenuation between an operating channel and an immediately neighbouring channel provides ca. 50 dB separation ACLR. Attenuation towards ACLR between the operating channel and the next but one channel is 55 dB. ACLR with the next but two channels is even higher.

Without loss of generality, assume transmission power to be 24 dBm. Then the RS power is about 1 1 dBm. Thus,

• A21 can be calculated as

1 1 dBm - 50 dB = -39 dBm,

• A24 can be calculated as

1 1 dBm - 55 dB = -44 dBm etc.

[00076] Energy Detection, ED, is performed by a channel sensing mechanism. This mechanism is implemented by a special chain/receiver entity that has at least 30 dB isolation towards downlink transmissions. In addition, RS symbols are modulated as QPSK symbols that have a typical Signal to Noise Ratio, SNR, requirement of about 20 dB for successful reception. [00077] Explanatory example calculation 3: Without loss of generality we assume transmission power to be 24 dBm. Then, the RS power level observable in the first adjacent channel may be calculated as

24 dBm (total power)

- 13 dB (RS power in transmitted channel)

50 dB (first channel ACLR)

₌ 30 dB (isolation between PL and ED measured chain)

-69 dBm

[00078] Explanatory example calculation 4: Assuming that successful reception of QPSK encoded RSs requires an SNR of 20 dB the maximum tolerable noise level must not exceed -69 dBm - 20 dB = -89 dBm. As the typical ED threshold level of -62 dBm/20 MHz is higher than the maximum tolerable noise level of -89 dBm/20 MHz for RS detection it can be assumed that noise coming from measured channels is much higher than Noise within RS signals. This means that it is possible to identify if an adjacent channel is idle or busy as the added noise to RS is measurable.

[00079] Embodiments herein also relate to a radio communication transmitter for performing a transmission to a radio communication receiver over a first channel, wherein the radio communication transmitter and the radio

communication receiver are operable in a radio communication network. The radio communication transmitter has the same technical features, objects and

advantages as the method performed by the radio communication transmitter described above. The radio communication transmitter will therefore be described only in brief in order to avoid unnecessary repetition. The radio communication transmitter will be described with reference to figures 3 and 4.

[00080] Figure 3 illustrates the radio communication transmitter 300, 400 being configured for determining power leakage to adjacent channels due to an ongoing transmission on a second channel; and determining an energy threshold based on the determined power leakage to adjacent channels. The radio communication transmitter 300, 400 is further configured for performing energy detection on one or more first channels; and transmitting data to the radio communication receiver if the detected energy on the one or more first channels does not meet the determined energy threshold.

[00081 ] The radio communication transmitter 300, 400 may be realised or implemented in various different ways. A first exemplifying implementation or realisation is illustrated in figure 3. Figure 3 illustrates the radio communication transmitter 300 comprising a processor 321 and memory 322, the memory comprising instructions, e.g. by means of a computer program 323, which when executed by the processor 321 causes the radio communication transmitter 300 to determine power leakage to adjacent channels due to an ongoing transmission on a second channel; and to determine an energy threshold based on the determined power leakage to adjacent channels. The memory further comprises instructions, which when executed by the processor 321 causes the radio communication transmitter 300 to perform energy detection on one or more first channels; and to transmit data to the radio communication receiver if the detected energy on the one or more first channels does not meet the determined energy threshold.

[00082] Figure 3 also illustrates the radio communication transmitter 300 comprising a memory 310. It shall be pointed out that figure 3 is merely an exemplifying illustration and memory 310 may be optional, be a part of the memory 322 or be a further memory of the radio communication transmitter 300. The memory may for example comprise information relating to the radio

communication transmitter 300, to statistics of operation of the radio

communication transmitter 300, just to give a couple of illustrating examples.

Figure 3 further illustrates the radio communication transmitter 300 comprising processing means 320, which comprises the memory 322 and the processor 321 . Still further, figure 3 illustrates the radio communication transmitter 300 comprising a communication unit 330. The communication unit 330 may comprise an interface through which the radio communication transmitter 300 communicates with other nodes or entities of the communication network as well as other communication units. Figure 3 also illustrates the radio communication transmitter 300 comprising further functionality 340. The further functionality 340 may comprise hardware or software necessary for the radio communication transmitter 300 to perform different tasks that are not disclosed herein.

[00083] An alternative exemplifying implementation of the radio communication transmitter 300, 400 is illustrated in figure 4. Figure 4 illustrates the radio communication transmitter 400 comprising a determining unit 403 for determining power leakage to adjacent channels due to an ongoing transmission on a second channel; and for determining an energy threshold based on the determined power leakage to adjacent channels; and a detection unit 404 for performing energy detection on one or more first channels. The radio communication transmitter 400 further comprises a transmitting unit 405 for transmitting data to the radio communication receiver if the detected energy on the one or more first channels does not meet the determined energy threshold.

[00084] In figure 4, the radio communication transmitter 400 is also illustrated comprising a communication unit 401 . Through this unit, the radio communication transmitter 400 is adapted to communicate with other nodes and/or entities in the radio communication network. The communication unit 401 may comprise more than one receiving arrangement. For example, the communication unit 401 may be connected to both a wire and an antenna, by means of which radio communication transmitter 400 is enabled to communicate with other nodes and/or entities in the radio communication network. Similarly, the communication unit 401 may comprise more than one transmitting arrangement, which in turn is connected to both a wire and an antenna, by means of which the radio communication transmitter 400 is enabled to communicate with other nodes and/or entities in the radio communication network. The radio communication transmitter 400 is further illustrated comprising a memory 402 for storing data. Further, the radio

communication transmitter 400 may comprise a control or processing unit (not shown) which in turn is connected to the different units 403-405. It shall be pointed out that this is merely an illustrative example and the radio communication transmitter 400 may comprise more, less or other units or modules which execute the functions of the radio communication transmitter 400 in the same manner as the units illustrated in figure 4. [00085] It should be noted that figure 4 merely illustrates various functional units in the radio communication transmitter 400 in a logical sense. The functions in practice may be implemented using any suitable software and hardware means/circuits etc. Thus, the embodiments are generally not limited to the shown structures of the radio communication transmitter 400 and the functional units. Hence, the previously described exemplary embodiments may be realised in many ways. For example, one embodiment includes a computer-readable medium having instructions stored thereon that are executable by the control or processing unit for executing the method actions or steps in the radio communication transmitter 400. The instructions executable by the computing system and stored on the computer-readable medium perform the method actions or steps of the radio communication transmitter 400 as set forth in the claims.

[00086] The radio communication transmitter has the same possible

advantages as the method performed by the radio communication transmitter. One possible advantage is that the probability of identifying idle channels may be improved. Another possible advantage is that system capacity may be enhanced since more channels may be used simultaneously.

[00087] According to an embodiment, the radio communication transmitter 300, 400 is further configured for determining the power leakage to adjacent channels based on a known signal.

[00088] According to yet an embodiment, the known signal is a reference signal.

[00089] According to still an embodiment, the radio communication transmitter 300, 400 is further configured for performing of energy detection on one or more first channels by receiving respective energy level of individual one or more first channels.

[00090] According to another embodiment, the radio communication transmitter 300, 400 is further configured for comparing respective received energy level of individual one or more first channels to the determined energy threshold. [00091 ] According to a further embodiment, the radio communication transmitter 300, 400 is further configured for ranking the one or more first channels based on their respective energy level.

[00092] According to an embodiment, the radio communication transmitter 300, 400 is further configured for taking the ranking into account when transmitting data to the radio communication receiver.

[00093] According to still an embodiment, the radio communication transmitter 300, 400 is further configured for transmitting the data to the radio communication receiver no later than directly after the ongoing transmission on the second channel has terminated without a backoff period, whereby the ongoing

transmission of data is switched from the second channel to the first channel.

[00094] According to another embodiment, the power leakage to adjacent channels may be determined by ACLR.

[00095] According to a further embodiment, the radio communication network is based on OFDM, and the one or more first channels and the second channel are comprised in a non-licenced frequency band.

[00096] According to an embodiment, the radio communication network is an LTE-LAA network and/or the non-licenced frequency band belongs to a Wi-Fi network.

[00097] Figure 5 schematically shows an embodiment of an arrangement 500 in a radio communication transmitter 400. Comprised in the arrangement 500 in the radio communication transmitter 400 are here a processing unit 506, e.g. with a Digital Signal Processor, DSP. The processing unit 506 may be a single unit or a plurality of units to perform different actions of procedures described herein. The arrangement 500 of the radio communication transmitter 400 may also comprise an input unit 502 for receiving signals from other entities, and an output unit 504 for providing signal(s) to other entities. The input unit and the output unit may be arranged as an integrated entity or as illustrated in the example of figure 4, as one or more interfaces 401 . [00098] Furthermore, the arrangement 500 in the radio communication transmitter 400 comprises at least one computer program product 508 in the form of a non-volatile memory, e.g. an Electrically Erasable Programmable Read-Only Memory, EEPROM, a flash memory and a hard drive. The computer program product 508 comprises a computer program 510, which comprises code means, which when executed in the processing unit 506 in the arrangement 500 in the radio communication transmitter 400 causes the radio communication transmitter to perform the actions e.g. of the procedure described earlier in conjunction with figures 1a-1c.

[00099] The computer program 510 may be configured as a computer program code structured in computer program modules 510a-510e. Hence, in an

exemplifying embodiment, the code means in the computer program of the arrangement 500 in the radio communication transmitter 400 comprises a determining unit, or module, for determining power leakage to adjacent channels due to an ongoing transmission on a second channel; and determining an energy threshold based on the determined power leakage to adjacent channels. The computer program further comprises a detection unit, or module, for performing energy detection on one or more first channels; and a transmitting unit, or module for transmitting data to the radio communication receiver if the detected energy on the one or more first channels does not meet the determined energy threshold.

[000100] The computer program modules could essentially perform the actions of the flow illustrated in figures 1a-1c, to emulate the radio communication

transmitter 400. In other words, when the different computer program modules are executed in the processing unit 506, they may correspond to the units 403-405 of figure 4.

[000101 ] Although the code means in the embodiments disclosed above in conjunction with figure 4 is implemented as computer program modules which when executed in the respective processing unit causes the radio communication transmitter to perform the actions described above in the conjunction with figures mentioned above, at least one of the code means may in alternative embodiments be implemented at least partly as hardware circuits. [000102] The processor may be a single Central Processing Unit, CPU, but could also comprise two or more processing units. For example, the processor may include general purpose microprocessors; instruction set processors and/or related chips sets and/or special purpose microprocessors such as Application Specific Integrated Circuits, ASICs. The processor may also comprise board memory for caching purposes. The computer program may be carried by a computer program product connected to the processor. The computer program product may comprise a computer readable medium on which the computer program is stored. For example, the computer program product may be a flash memory, a Random-Access Memory RAM, Read-Only Memory, ROM, or an EEPROM, and the computer program modules described above could in alternative embodiments be distributed on different computer program products in the form of memories within the radio communication transmitter.

[000103] It is to be understood that the choice of interacting units, as well as the naming of the units within this disclosure are only for exemplifying purpose, and nodes suitable to execute any of the methods described above may be configured in a plurality of alternative ways in order to be able to execute the suggested procedure actions.

[000104] It should also be noted that the units described in this disclosure are to be regarded as logical entities and not with necessity as separate physical entities.

[000105] While the embodiments have been described in terms of several embodiments, it is contemplated that alternatives, modifications, permutations and equivalents thereof will become apparent upon reading of the specifications and study of the drawings. It is therefore intended that the following appended claims include such alternatives, modifications, permutations and equivalents as fall within the scope of the embodiments and defined by the pending claims.

Claims

1 . A method (100) performed by a radio communication transmitter for performing a transmission to a radio communication receiver over a first channel, wherein the radio communication transmitter and the radio communication receiver are operable in a radio communication network, the method comprising:

- determining (1 10) power leakage to adjacent channels due to an ongoing transmission on a second channel,

- determining (120) an energy threshold based on the determined power leakage to adjacent channels,

- performing (130) energy detection on one or more first channels, and

- transmitting (160) data to the radio communication receiver if the detected energy on the one or more first channels does not meet the determined energy threshold.

2. The method (100) according to claim 1 , wherein the power leakage to adjacent channels is determined based on a known signal.

3. The method (100) according to claim 2, wherein the known signal is a reference signal.

4. The method (100) according to any of claims 1 -3, wherein the performing (130) of energy detection on one or more first channels comprises receiving respective energy level of individual one or more first channels.

5. The method (100) according to claim 4, further comprising comparing (140) respective received energy level of individual one or more first channels to the determined energy threshold.

6. The method (100) according to any of claims 1 -5, further comprising ranking (150) the one or more first channels based on their respective energy level.

7. The method (100) according to claim 6, wherein the transmitting (160) of data to the radio communication receiver comprises taking into account the ranking.

8. The method (100) according to any of claims 1 -7, wherein the data is transmitted to the radio communication receiver no later than directly after the ongoing transmission on the second channel has terminated without a backoff period, whereby the ongoing transmission of data is switched from the second channel to the first channel.

9. The method (100) according to any of claims 1 -8, wherein the power leakage to adjacent channels is determined by Adjacent Channel Leakage Ratio, ACLR.

10. The method (100) according to any of claims 1 -9, wherein the radio communication network is based on Orthogonal Frequency Division Multiplexing, OFDM, and the one or more first channels and the second channel are comprised in a non-licenced frequency band.

1 1 . The method (100) according to any of claims 1 -10, wherein the radio communication network is a Long Term Evolution - Licence Assisted Access, LTE- LAA, network and/or the non-licenced frequency band belongs to a Wi-Fi network.

12. A radio communication transmitter (300, 400) for performing a

transmission to a radio communication receiver over a first channel, wherein the radio communication transmitter and the radio communication receiver are operable in a radio communication network, the radio communication transmitter (300, 400) being configured for:

- determining power leakage to adjacent channels due to an ongoing

transmission on a second channel,

- determining an energy threshold based on the determined power leakage to adjacent channels,

- performing energy detection on one or more first channels, - transmitting data to the radio communication receiver if the detected energy on the one or more first channels does not meet the determined energy threshold.

13. The radio communication transmitter (300, 400) according to claim 12, being configured for determining the power leakage to adjacent channels based on a known signal.

14. The radio communication transmitter (300, 400) according to claim 13, wherein the known signal is a reference signal.

15. The radio communication transmitter (300, 400) according to any of claims 12-14, being configured for performing of energy detection on one or more first channels by receiving respective energy level of individual one or more first channels.

16. The radio communication transmitter (300, 400) according to claim 15, further being configured for comparing respective received energy level of individual one or more first channels to the determined energy threshold.

17. The radio communication transmitter (300, 400) according to any of claims 12-16, further being configured for ranking the one or more first channels based on their respective energy level.

18. The radio communication transmitter (300, 400) according to claim 17, further being configured for taking the ranking into account when transmitting data to the radio communication receiver.

19. The radio communication transmitter (300, 400) according to any of claims 12-18, further being configuring for transmitting the data to the radio communication receiver no later than directly after the ongoing transmission on the second channel has terminated without a backoff period, whereby the ongoing transmission of data is switched from the second channel to the first channel.

20. The radio communication transmitter (300, 400) according to any of claims 12-19, wherein the power leakage to adjacent channels is determined by Adjacent Channel Leakage Ratio, ACLR.

21 . The radio communication transmitter (300, 400) according to any of claims 12-20, wherein the radio communication network is based on Orthogonal Frequency Division Multiplexing, OFDM, and the one or more first channels and the second channel are comprised in a non-licenced frequency band.

22. The radio communication transmitter (300, 400) according to any of claims 12-21 , wherein the radio communication network is a Long Term Evolution - Licence Assisted Access, LTE-LAA, network and/or the non-licenced frequency band belong to a Wi-Fi network.

23. A Computer program (510), comprising computer readable code means, which when run in a processing unit (506) comprised in an arrangement (500) in a radio communication transmitter (400) according to claims 12-22 causes the radio communication transmitter (400) to perform the corresponding method according to any of claims 1 -1 1 .

24. A Computer program product (508) comprising the computer program (510) according to claim 23.