WO2015146551A1

WO2015146551A1 - Wireless network interference effects

Info

Publication number: WO2015146551A1
Application number: PCT/JP2015/056760
Authority: WO
Inventors: Dorin Panaitopol
Original assignee: Nec Corporation
Priority date: 2014-03-24
Filing date: 2015-03-02
Publication date: 2015-10-01
Also published as: GB201405224D0

Abstract

There are provided a method and related system and apparatus (18) for determining interference effects between first and second signals (14, 24, 26) from competing respective first and second wireless transmitters (12, 20, 22) in a wireless communications environment (10), and including Quiet-Period interference-measurement in relation to the first and second signals (12, 20, 22), determining interference measurement (error) values, and further including detection of the number of negative interference measurement (error) values when expressed as linear values so as to identify reliable error requirements, and thus reliable interference measurements, and thus employ such measurements as required in relation, for example, to transmission and interference control.

Description

DESCRIPTION

Title of Invention

WIRELESS NETWORK INTERFERENCE EFFECTS

Technical Field

[0001]

The present invention relates to a wireless communication environment common to a plurality of transmitting devices and, in particular, to a method and related system and apparatus for determining one or more interference effects between the transmitting devices.

Background Art

[0002]

In order to communicate "over the air", i.e. wireless communication, current

management of the available frequency spectrum involves the permanent or at least long term, assignment of a frequency band within the spectrum to a particular user so as to give

priority-access to that user, e.g. an operator or broadcaster for that band. However, such a spectrum-allocation policy proves problematic due to the finite nature of the available spectrum, and the increasing number of potential users, resulting in exhaustion of the frequency resource.

[0003]

One proposal to address this issue introduces the concept of opportunistic access to bands within the frequency spectrum and which involves the identification/acknowledgement of two different kinds of spectrum users, that is "legitimate" users or primary licensed users (PUs), and secondary users (SUs) that are allowed to access to an allocated band of the spectrum only if the PUs are not using the band, or only if the interference is considered acceptable.

[0004]

Within this context, non-exhaustive examples of PUs comprise DVBT (Digital Video Broadcasting-Terrestrial) systems, PMSE (Programme Making and Special Events) systems, and also some 3GPP (3rd Generation Partnership Project) (e.g. GSM (Global System for Mobile communications), UMTS (Universal Mobile Telecommunications System), HSUPA (High-Speed Uplink Packet Access), HSDPA (High-Speed Downlink Packet Access), LTE (Long Term Evolution), etc.) or non-3GPP (e.g. WiMaX (Worldwide Interoperability for Microwave Access), WiFi (Wireless Fidelity), FlashLinQ.. etc) systems.

[0005] In the same context, one example of many potential SUs is a 3 GPP LTE system that can be similar to, or different from, that comprising a PU.

[0006]

Also, a so-called Cognitive Radio Device (CR Device) is known that comprises a terminal which is aware of its electro-magnetic environment and is able to adapt its

transmissions accordingly. For example, a CR Device can sense specific frequency bands in order to estimate the band occupancy before determining whether or not to attempt a

transmission. Various examples of the required sensing are known involving efficient non-cooperative sensing designs and that use different information acquired during the acquisition phase. However, it is now noted that the primary signals to be detected are subject to different environmentally-related changes such as shadowing, fading and path loss, and so can prove difficult to detect and employ in a reliable manner.

[0007]

In known systems it is generally assumed that once a SU performs the required sensing, and deploys in the opportunistic frequency band, an incumbent PU is unlikely to (re-)appear. However, some known systems can also be arranged such that if the SU is already

communicating in an opportunistic frequency band, the SU can perform at least one of the following methods in order to identify whether any incumbent system (secondary or primary) also exists, or is likely to re-appear.

[0008]

First, a classic signal detection (or spectrum sensing detection) technique can be employed and requiring use of a Quiet Period (QP), that is the entire secondary system has to stop transmitting for PU detection purposes.

[0009]

Secondly, signal classification or other discrimination techniques, can be employed which do not tend to require the provision of a Quiet Period.

[0010]

Thirdly, a geo-location database approach is possible such as that which has been adopted by the US Federal Communications Commission (FCC) to allow "Opportunistic Spectrum Access Systems" use of TV White Space (TV WS), (and as discussed in Federal Communications Commission (FCC), "Second memorandum opinion and order". FCC 10-174, Sept. 2010). This technique restricts the use of the spectrum by a SU (or a SU system) when the PU located in a certain area around the SU Transmitter is registered to a database, and which the SU can access. Therefore, in the FCC scenarios, the devices of the opportunistic systems identify their locations by using a geo-location capability and then query the database to determine which TV channels they can use at their locations. Similar approaches have also been investigated by CEPT (and as discussed in "Radio systems in the white space of the frequency band 470-790 MHz", Annex 3 to Doc. SE43(09)34, September 2010).

[0011]

It is also known to employ spectrum signal detection and/or also signal classification detection within Interference Monitoring techniques that can be employed to determine how much interference is actually caused to the active system, e.g. to the receiver of the PU signals. In order to estimate the interference at the edge of the service area of the active systems, e.g. the PU system, the opportunistic system, e.g. the SU system, can obtain location information of the active systems from the geo-location database, and a monitoring node near the edge of the service area can perform the measurements.

Summary of Invention

Technical Problem

[0012]

Known systems .and methods are disadvantageous particularly in that the

estimation/measurement of (likely) interference levels cannot be achieved with great accuracy and certainty and so inappropriate signalling, and potential overload situations, can arise.

[0013]

The present invention seeks to provide for methods, systems and apparatus for managing wireless network interference effects and having advantages over known such methods, systems and apparatus. As noted, the invention can also provide for a computer program product arranged to execute to provide the method of the invention.

Solution to Problem

[0014]

According to one aspect of the present invention there is provided a method for determining interference effects between first and second signals from competing respective first and second wireless transmitters in a wireless communications environment, the method including Quiet-Period interference-measurement in relation to the first and second signals, determining interference measurement (error) values, and the method further including detection of the number of negative interference measurement (error) values when expressed as linear values. [0015]

The method can prove advantageous in determining the likely accuracy, and reliability, of interference measurements so that subsequent network control can likewise benefit from such improved accuracy.

[0016]

Any inherent potential inaccuracies in the signals detected, such as due to the effect of environmental changes/conditions such as shadowing, fading, path loss, etc. can thereby be mitigated.

[0017]

The reliability of interference measurements can therefore be accurately assessed and only measurements deemed to exceed a "reliability threshold" need be employed in subsequent interference control.

[0018]

In this manner, and with the prevention of the signalling of "unreliable" data, signalling overhead and overload within the network environment can be further optimized.

[0019]

Preferably, the method includes determining the number of negative interference measurement (error) values over a finite period, which period can advantageously be

predetermined.

[0020]

Yet further, the method can include the step of determining the percentage of negative interference measurement (error) values.

[0021]

As will be appreciated from the above, the invention can comprise a method of determining the reliability of interference measurements, and which includes a method for determining interference effects as defined above.

[0022]

Yet further, the present invention can comprise a method of validating interference measurements for subsequent use within wireless communication control, and including a method for determining interference effects as outlined above.

[0023]

Of course, it should also be appreciated that the present invention can provide for a method of controlling/influencing transmission of a second signal, in the likely presence of a first signal, and including a method for determining interference effects as noted above. In this manner, the method of controlling/influencing can include a step of controlling the wireless-transmitter source of the said second signal responsive to the determined interference effects.

[0024]

As a further possible feature, the said number of negative interference measurement

(error) values can be employed to determine noise related ratio values such as for example, but not limited to, signal-to-noise ratio (SNR) values, Signal to Interference plus Noise Ratio (SINR) values and Interference to Noise (INR) values, between the first and second signals.

[0025]

If required, the number of negative interference measurement (error) values can be employed to determine a Root Mean Square Error value (RMSE).

[0026]

Further, the Quiet-Period interference measurement, and determination of the interference measurement (error) values, and the number of negative error values, can

advantageously be determined within a spectrum sensor located within the network environment.

[0027]

It should also be appreciated that the method can be employed with a greater plurality of wireless transmitter devices than just the first and second devices noted above.

[0028]

Of course, the interference measurement can include the provision of Quiet-Period measurement as one of a plurality of measurement methods.

[0029]

For example, the invention can include the combination of Quiet-Period interference measurement technique and a database-related measurement technique.

[0030]

The method can further include the conducting of interference measurement (error) values at one or more terminal devices of a mobile radio communications network.

[0031]

For example, the interference measurement (error) values can be determined at one or more network node device, such as an eNB (evolved Node B), or a mobile terminal device such as a UE (User Equipment) device.

[0032]

In one particular example, the first signal can comprise a primary signal from a PU of an allotted frequency spectrum within the wireless communications environment, and the second signal can comprise an opportunistic signal from a SU competing for access to the allotted part of the spectrum.

[0033]

It should be appreciated that such PU can comprise a licensed user such as the source of DVBT or PMSE signalling, and the SU can comprise the source of a, possibly non-licensed, LTE mobile radio communications signal.

[0034]

The method can include conducting a plurality of discrete measurement cycles within a measurement period. As such, the method can include the step of varying the length of the discrete measurement cycles within the measurement period.

[0035]

Such techniques can prove advantageous in improving the granularity of percentage.

[0036]

Yet further, the method can include employing a Cognitive Radio Manager (CRM) for control of the second transmitter responsive to the determined interference effects.

[0037]

As an option, the CRM can be provided as part of a mobile radio communications system, such as a 3 GPP system. In this manner, the CRM can be provided with, or associated with, a network terminal device such as an eNB, or Core Network device.

[0038]

The method can provide for spectrum sensing to determine the interference effects and which can be provided by way of any appropriate terminal device of, for example, a mobile radio communications network, such as an eNB network terminal device or a UE mobile terminal device.

[0039]

The use of an eNB is particularly advantageous due to its relatively high computation power, the inherent energy resources that are available and its environmental position, such as for example a generally higher-located antenna, and also the directivity advantages arising in relation to the antenna lobes.

[0040]

Still further, the method can employ RRC (Radio Resource Control) messages for reporting the interference measurement (error) values and/or the determined outcome of such measurements.

[0041] Further, the operational characteristics of the Quiet-Period interference measurement, such as the length of the quiet periods, can be allocated, periodically or otherwise, during the transmission periods from the second transmitter.

[0042]

Yet further, the method can provide, subsequent to receiving measurement results relating to the number of negative interference measurement (error) values, any one or more of the steps of: increasing or decreasing the length of each measurement cycle within a

measurement period; increasing or decreasing the length of a quiet period; and/or increasing or decreasing the transmission power of the second signal, such as the opportunistic transmission power.

[0043]

In employing a plurality of discrete measurement cycles within a measurement period, the method can include the step of determining the ratio between such periods based on the granularity of the percentage error values and/or the required accuracy of measurement.

[0044]

According to another aspect of the present invention there is provided a wireless communication system comprising competing first and second wireless transmitters located within a wireless communications environment and the system being arranged to determine interference effects between respective first and second signals from the said first and second transmitters, and the system further being arranged to conduct Quiet-Period interference measurement in relation to the said first and second signals, to determine interference measurement (error) values, and to determine the number of negative interference measurement (error) values when expressed as linear values.

[0045]

As with the method outlined above, the system can prove advantageous in readily determining the likely accuracy and reliability of interference measurements so that subsequent network control can likewise benefit from such improved accuracy.

[0046]

The system can accurately assess the reliability of interference measurements and, since only measurements deemed to exceed a "reliability threshold" need be employed in subsequent transmission control, signalling overhead values within the network environment can be improved.

[0047]

Preferably, the system can be arranged to determine a number of negative interference measurement (error) values over a finite period, which finite period can advantageously be predetermined.

[0048]

The system can also be arranged to determine the percentage of negative interference measurement (error) values.

[0049]

As will also be appreciated from the discussion of the methods of the invention, the invention can comprise a system arranged to determine the reliability of interference

measurements and including a system for determining interference effects as defined above.

[0050]

Again, the present invention can comprise a system for validating interference measurements for use within wireless communication control and including a system for determining interference effects as outlined above. Further, the present invention can provide for a system of controlling/influencing transmission of a second signal, in the likely presence of a first signal, and including a system for determining interference effects as noted above.

[0051]

Such a system for controlling/influencing can be arranged to control the wireless transmitter source of the said second signal responsive to the determined interference effects.

[0052]

Of course, it should be appreciated that the various systems of the present invention can be arranged to exhibit the functionality of any one or more of the method steps noted above and particularly as regards interference measurement.

[0053]

Thus, a system of the invention can include the determining of interference

measurement (error) values at one or more terminal devices of a mobile radio communications network. The interference measurement (error) values can be determined at one or more of a network node device, such as that eNB or a mobile terminal device such as a UE device.

[0054]

The systems of the invention can operate with a first signal comprising a primary signal from a primary user of an allotted portion of the frequency spectrum within the wireless communications environment, and the second signal comprising an opportunistic signal from a secondary user competing for access to the allotted portion of the frequency spectrum.

[0055]

As above in relation to the methods of the invention, such primary user can comprise a license user such as the source of a DVBT or PMSE signal, and the secondary user can comprise the source of a, possibly non-licensed LTE mobile radio communications signal.

[0056]

According to yet another aspect of the present invention there is provided a wireless communications network terminal device arranged for quiet-period interference measurement between competing first and second signals and arranged to determine interference measurement (error) values including determination of a number of negative interference measurement (error) values when expressed as linear values.

[0057]

Advantageously, the network terminal device can comprise a spectrum sensing device.

[0058]

In particular, the network terminal device can comprise a terminal device of a mobile radio communications network. In particular, the network terminal device can comprise an eNB.

[0059]

The said wireless communications network terminal device can be arranged with functionality according to any one or more steps of the interference effects determination noted above.

[0060]

According to still a further aspect of the present invention there is provided a wireless communication device arranged for controlling operation of a wireless transmitter device within a wireless communications environment, and arranged to receive a control signal from a network terminal device such as that outlined above and to vary operation of a network transmitter device responsive to that control signal.

[0061]

Advantageously, any one or more of a measuring period for determining interference effects, quiet periods employed within quiet period interference measurement and/or

transmission power employed by the transmitter device can be varied responsive to the control signal.

[0062]

In particular, the network device can be provided on, or as part of, a node device of a mobile radio communications network, such as an eNB.

[0063]

As will therefore be appreciated, the invention can provide for the control of operation of at least one of the transmitting devices, which control is responsive to one or more of the interference effects identified.

Brief Description of Drawings

[0064]

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings.

[0065]

[Fig- 1]

Fig. 1 is a schematic diagram of a network environment including competing signal transmission systems.

[Fig. 2]

Fig. 2 is an illustration of a Quiet Period transmission pattern.

[Fig- 3]

Fig. 3 is a graphical representation of measurement error monitoring as employed by the present invention.

[Fig. 4]

Fig. 4 is a graphical representation (of the percentage) of negative measurement (error) values in relation to signal to noise ratio and as employed by the present invention.

[Fig. 5]

Fig. 5 is a schematic diagram of a network environment including competing signal-transmission systems, and with spectrum sensors and a radio manager arranged to operate according to an embodiment of the present invention.

[Fig- 6]

Fig. 6 is a schematic representation of a spectrum sensor according to an embodiment of the invention.

[Fig. 7]

Fig. 7 is a schematic representation of a (cognitive) radio manager according to an embodiment of the invention.

Description of Embodiments

[0066]

As will be appreciated, the present invention can apply in the context of incumbent detection (e.g. PU detection or SU detection) when the SU is using a Quiet Period (e.g. when the secondary system stops communicating for a while in order to detect the primary signal), with application to Interference Monitoring. This concept is further exemplified by reference to an illustration in which the measurement during the QP is performed by base stations (e.g. eNBs), and the SU system comprises an LTE system.

[0067]

Also, known systems and methods of primary relevance to the present invention have been derived in relation to the (QoSMOS (Quality of Service and Mobility driven cognitive radio Systems)) project that aims at researching, developing and integrating a Cognitive Radio (CR) framework to enable mobile broadband systems to improve utilization of licensed and/or unlicensed bands, by adding dynamic exploitation of under-utilised spectrum. The technical focus is on opportunistic use of spectrum combined with managed Quality of Service (QoS) and seeking seamless mobility. Efficient use of spectrum and energy resources, co-existence with, and the protection of, other services, a quality and affordable user experience, and expansion of mobile markets are the driving forces behind QoSMOS. A new two-tier process is proposed for spectrum management to simplify, and hence reduce the cost of, the access network management system and yet provide managed QoS. New dynamic spectrum sensing and usage metrics are required so that decisions can be taken on spectrum occupancy.

[0068]

Turning now to Fig. 1, there is illustrated a wireless environment 10 comprising a PU DVB-T incumbent transmitter 12 (licensed user) transmitting a signal 14 towards an incumbent DVB-T receiver 16. A Spectrum Sensor 18 co-located with an eNB base station is arranged to intercept (and measure) the transmitted signal 14. Such interception is usefully employed in order to determine if the incumbent DVB-T receiver 16 will satisfactorily receive the DVB-T PU signal 14 when the Incumbent transmitter 12 and an Opportunistic transmitter SUs 20, 22 are transmitting their respective signals 14, 24, 26 at the same time.

[0069]

Interference from one or more opportunistic LTE transmitter(s) 20, 22 can be measured by the same, or other, Spectrum Sensor 18.

[0070]

In other words, measurements of both the interference signals (e.g. the opportunistic

LTE signals 24, 26) and the incumbent DVB-T signal 14 are carried out and may be used to estimate the Signal to Noise Ratio (SNR) and/or the Signal to Noise plus Interference Ratio (SINR) at the incumbent receiver 16. This measurement can be performed at a monitoring node such as the Spectrum Sensor 18 of the opportunistic system which can be located near the incumbent receiver 16 at the edge of the incumbent service area 28. In this way, the measurements performed by the spectrum sensor 18 can be effectively used to expand white space opportunities for the secondary user SU.

[0071]

If the protection ratio, which in this example comprises the required SIR at the incumbent receiver 16, is 21dB, this means that the incumbent signal level at the incumbent receiver 16 need be at least 21dB higher than e.g. the interference level. Therefore, an accurate interference measurement is important for interference monitoring. If the interference from the opportunistic transmitter 20, 22 is too high, and the required SIR of the incumbent receiver 16 cannot be reached, a CRM (not shown in Fig. 1), which can be provided directly at a base station may decide to decrease one or more (if necessary) opportunistic transmitter power(s) 20, 22, or continue to transmit but via only one of the opportunistic transmitters 20, or 22.

[0072]

The illustrated examples of the invention can employ an interference measurement technique using "Quiet Period". Since a monitoring node such as spectrum sensor 18 receives incumbent signal 14 and opportunistic signals 24, 26 at the same time within a measured band, the monitoring node 18 needs to separate the opportunistic signals 24, 26 from the incumbent signal 14 to measure the received power of the interference. For this purpose, Quiet Periods (QPs) are used by the secondary user SU producing the appropriate signals 24, 26 as outlined further below.

[0073]

QPs are assumed to be periodically allocated during transmission and as illustrated in Fig. 2. The opportunistic transmitter, i.e. SU such as one of the LTE transmitters 20, 22 of Fig. 1 , does not transmit any signal during the QP so that it can perform general spectrum sensing. It is also assumed that the opportunistic system may know if the incumbent system is active by means of e.g. geo-location database information.

[0074]

It is also assumed that the monitoring node knows the timing of QP and its duration. By using this information, the monitoring node can separately measure the received power of signals in QP and that in transmission period. The difference of these received powers corresponds to the interference power. Thus, QP-based power estimation of the interference signals is performed by the following equation (1).

[0075]

In this equation (1), NQP and NON are the number of samples in the QP and in the transmission period, respectively. r[k] denotes the received signal at kth sampling time and is expressed by the following equation (2).

[0076]

In these equations (1) and (2), k=0, i[k], s[k], and n[k] denote the beginning of the Quiet Period, interference signal, the incumbent signal, and white Gaussian noise, respectively. For simplification, it is assumed in equation (2) that the channels for the interference and the incumbent signals are Additive White Gaussian Noise (AWGN) channels.

[0077]

Further, r[k] can be considered the signal received by the Spectrum Sensor which is on the Base Station (and is the sum of a Rx Secondary User SU signal using Quiet Period, and of a Rx Primary User PU signal as clarified in Fig. 2, and of noise at the SS level) and can be used to estimate the power measurement interference I from a SU, according to equation (1).

[0078]

The following parameters are relevant to the illustration of this example of the present invention to evaluate the performance of the measurement technique, namely measurement error of the interference as illustrated in equation (3); RMSE of the measurement error as illustrated in equation (4); and STD of the measurement error as illustrated in equation (5).

[0079]

Turning first to the measurement error of the interference, this can be denoted by the following equation (3).

e dB = 1 ^ dBm -I ^J dBm

[0080]

In this equation (3), I, ^^{dBm ~} ^ ^ ^ , and ^^dBm ^ ^ represent the actual interference power in the linear domain, the actual interference power in dB, and the estimated interference power in dB, respectively.

[0081]

Root Mean Square Error (RMSE) is a frequently used measure of the difference between values predicted by a model and the values actually observed from the environment that is being modelled. RMSE is defined as the square root of the mean squared error. The RMSE of the interference measurement error (see equation (4)) can therefore be used to determine the quality of the measurement. If for example the RMSE (of the measurement error value expressed in dB) is zero, this means that the measurement is perfect.

[0082]

Similarly, the Standard Deviation (STD) noted with reference to equation (5) can be used in addition to the RMSE value. This is, for example, useful in a situation where the mean of the measurement error expressed in dB is non-zero (e.g. the measurement error is biased).

[0083]

Similarly, this situation corresponds to a situation when the mean of the measurement error expressed in linear domain is non-one (1 = 0 dB). A comparison between RMSE and STD can also help to determine when the mean of the measurement error (expressed in dB) becomes non-zero and in which situations (e.g. signal power, interference power, and their ratio., etc).

1 Nbsim

STD =

Nbsim ∑ (=1 (^■

(5)

[0084]

In this equation (5), Nbsim= # of realizations (total # of measurements), and μ_ε= mean of measurement error (here expressed in dB).

[0085]

Both RMSE and STD values can be used as basic metrics for statistically evaluating the accuracy of the measurement techniques.

[0086]

For completeness, the simulation parameters employed for consideration of the error measurements were outlined below but are not limiting features of the invention.

1 transmitter

an LTE bandwidth of 5MHz

1 reception antenna

total measurement duration of 10 & 200 ms; and referred to in the following as to Tl or measuring period 10% Quiet Period (i.e. QP was 1 ms and 20 ms depending on the chosen total measurement duration), i.e. 10% of Tl or of the measuring period

SNR DVB-T= 30dB (Signal to Noise DVB-T level received by the SS and assumed to be of similar value at DVBT Rx Level)

3 GPP Pedestrian A Fading model

incumbent signal (DVB-T) having been approximated by white Gaussian noise (OFDM signals have a noise-like behaviour)

[0087]

The simulation results obtained are illustrated in Fig. 3 and from which it can be seen that the RMSE decreases as ISR increases. Also, when the ISR is higher than - 10 dB, the RMSE of 10 ms measurement and 200 ms measurement is approximately zero. Meanwhile, when e.g. the ISR is lower than -20 dB for 10 ms measurement (and e.g. ISR is lower than -25 dB for 200 ms measurement), it has to be determined, for example by way of a CRM device whether a compensation of the measurement error should be made and/or if the power of the opportunistic signal has to be decreased accordingly. Also, if RMSE is too high, e.g. above 4 dB, the measurement may be considered as no longer reliable.

[0088]

Also, the measurement values, as expressed in linear values, can become negative under lower ISR conditions due to the estimation error which is caused by the inadequate averaging time. Therefore, for the simulation results illustrated in Fig. 3 only the positive measurement values were employed and therefore only positive measurement error values as expressed in linear values have been considered.

[0089]

However, potential problems and limitations can arise for known Interference

Monitoring techniques. For example, when Interference Monitoring employs Quiet Period measurement the reliability of measurement is questionable. Although statistical information can be employed to determine the value of the RMSE, if the exact value of the ISR is not known, any such statistical estimation will still remain unreliable.

[0090]

The present invention appreciates that the value of the estimation error depends, at least partly, on the ISR conditions, and also the total averaging time.

[0091]

The invention further appreciates that the measurement values, expressed as linear values, might become negative under (low) ISR conditions and further are proportional to the ISR value. Of course, any such estimated negative value cannot be used for power estimation, and for Interference Monitoring, since there is no such thing as negative power and therefore a negative power cannot be assumed particularly at the spectrum sensor side nor at the incumbent receiver side. However, the number of such occurrences over a predetermined duration of time can prove a powerful indication of the reliability of a measurement.

[0092]

Referring now to Fig. 4, there is illustrated, as a percentage value, the number of negative measurement values occurrences over a predetermined duration of time as related to ISR. As with Fig. 3, an inversely proportional relationship is illustrated.

[0093]

A comparison of Fig. 3 and Fig. 4 reveals that the horizontal scale is the same with both graphs having a horizontal ISR axis. If for example, using Fig. 3, it is required to keep to a RMSE value below a certain level, for example 4 dB, this would correspond to a certain ISR value for a given measuring duration and a given QR Then, using the same ISR value in Fig. 4, this corresponds to a certain percentage % of negative measurement error values for a given measuring duration and a given QR Therefore, the number of negative measurements values expressed as the % value in Fig. 4 can indicate of how high (or low) the RMSE actually is. A similar relationship is revealed for the STD values also.

[0094]

Of course, in the alternative, and staring from Fig. 4, setting a 20% negative percentage threshold for the QP method with 10% quiet period and 10 ms total measuring duration

(equivalent to NQP+NON from Fig. 2) will lead to -20 dB value ISR value. Likewise setting an 11% of negative percentage threshold for the QP method with 10% quiet period and 200 ms total measuring duration (equivalent to NQP+NON from Fig 2.) will lead to -25 dB value ISR value. Then referring to Fig. 3, noting the two ISR values previously mentioned, for 10 ms and 200 ms measuring duration respectively, an RMSE limitation to 4dB is obtained. It can therefore be concluded that there is a direct relationship between the % of negative measurement error, expressed in the linear domain, and the RMSE and/or STD values.

[0095]

Similarly, instead of representing the % of negative measurement (error) values in terms of ISR, they can be readily represented directly in terms of RMSE (and/or STD).

[0096]

Thus, the invention notes that an evaluation of the % of negative measurement error values expressed in the linear domain for QP techniques establishes that the % value decreases when the measurement duration increases, and the % value provides information with respect to the value of ISR and therefore can comprise useful information to determine the reliability of measurement.

[0097]

Reference is now made to Fig. 5 which provides an illustration within a network environment 30 of the determination of reliability characteristics for interference error measurements according to an exemplary embodiment of the invention.

[0098]

A CRM 32 first sets the Tl period (i.e. measuring period as defined above), the T2 period (i.e. period during which reliability is computed) and a reliability threshold value, for example 10%.

[0099]

One 34 of a plurality of Spectrum Sensors performs measurements over repeated periods Tl as discussed above and evaluates the % of negative measurement values for QP over a period T2»T1 as illustrated in Fig. 5 by arrows Tl and T2. The granularity of measurements used for the % evaluation is a ratio between Tl and T2. The Spectrum Sensor then sends its measurement result only if the % of negative measurement over T2 is e.g. under 10% reliability threshold value that has been set. It should of course be appreciated that, as an option, the Spectrum Sensor 34 could also provide a value of ISR, or the RMSE measurement, and the % of negative measurement values.

[0100]

As also illustrated in Fig. 5, T2 is a reliability period during which the spectrum sensor determines if the measurement is reliable, Tl is the measuring period during which the spectrum sensor performs measurement. Tl is therefore the equivalent to NQP+NON as discussed above in relation to Fig. 2 in particular, and T2»T1, e.g. T2 = 2 s (or more) and Tl is 10 ms (or more). The value of T2 can be selected with respect to a PU experience parameter (e.g. how much an incumbent receiver is able to wait before being able to receive its own data) and system reactivity time (e.g. how much time it takes till the opportunistic transmitter adapts its transmission parameters).

[0101]

It should however be noted that the granularity of the measurement is given by T1/T2, which means that for T2 = 2 s and Tl = 10 ms the percentage can be minimum 0% and maximum 100%, with a granularity of 0.5%. Similarly, if Tl is higher e.g. 0.2 s, the granularity increases to 10% but since the Tl measurement time is higher, the measurement will be improved but to the detriment of the granularity of the percentage.

[0102]

In the example of Fig. 5, and as illustrated in that drawing, the measurements within periods T2 at spectrum sensor 34 indicate that the level of reliability is not sufficient, i.e. below the 10% threshold and so measurements from spectrum sensor 34 are not sent to the CRM 32.

[0103]

However, in the illustrated example of Fig. 5, measurements taken at a second 36 of a plurality of spectrum sensors are determined to be under the 10% reliability threshold and so can be transferred to CRM 32 for subsequent control of transmissions 38 from the opportunistic transmitter 40. The reliable measurements reported from spectrum sensor 36 can then be relied upon by the CRM 32 to vary the transmit power at the opportunistic transmitter 40 as required.

[0104]

The illustrated example of use leads to the advantageous exclusion of spectrum sensor readings with unreliable measurements. Only spectrum sensors such as 36 that provide signals that meet the reliability requirements send their measurement results to the CRM 32.

[0105]

As will therefore be appreciated, the invention can be employed to determine if the current measurement is reliable or not, and advantageously to reduce signalling

o verload/o verhead .

[0106]

In particular, the invention can make use of a % of negative measurement (error) values to determine reliability. That is, the % of negative measurement (error) values can be used to determine signal/noise values such as ISR, SIR, SINR.. etc. Also, the % of negative measurement (error) values can be used to adapt the transmission power of the opportunistic user Tx, such as that 40 of Fig. 5. Further, the % of negative measurement (error) values can be used to determine values such as the RMSE of measurement error. The % of negative measurement (error) values can also be used to restrict the transmission of measurements from spectrum sensors, such as that 34 of Fig. 5, that do not meet measurement requirements.

[0107]

It will be appreciated that a variety of additional and/or alternative features can be employed as required. For example, the spectrum sensor can be located at eNB level or a UE level, and/or multiple eNBs or UEs may be employed for a spectrum sensing.

[0108]

The invention can also employ a combination of the QP method with one or more other methods/techniques which can serve to improve the Interference Monitoring accuracy. For example the QP method can be combined with the data base approach noted above.

[0109]

As noted earlier, the parameters for the simulations are not limiting and many other parameters could apply. For example, instead of 1 incumbent Transmitter, the system could comprise two or more transmitters.

[0110]

Also, instead of a 5MHz LTE bandwidth, one of many possible alternatives such as 10MHz, 20 MHz, or 100 MHz bandwidth could be employed.

[0111]

Further, instead of one reception antenna (located at the spectrum sensor side), two or more reception antennas could be employed.

[0112]

Also, instead of sensing/measuring periods of 10 and 200 ms, various other periods can be employed.

[0113]

Instead of 10% Quiet Period of the sensing period (e.g. 1 ms or 20 ms for the above mentioned cases), the other % values can be employed as required.

[0114]

Instead of a SNR DVBT value of 30dB, a higher SNR or indeed lower SNR received by the DVB-T receiver (i.e. the PU of the above-mentioned examples) can be considered.

[0115]

The spectrum sensor can be co-located with, or nearby, the incumbent receiver and the power (or the Signal to Noise Ratio) at the spectrum sensor can therefore be assumed as similar to that at the incumbent receiver. In any case if required a margin can be taken into account, or a direct estimation can be performed in order to determine the DVB-T Rx SNR or SINR level.

[0116]

Also, instead of a 3 GPP Pedestrian A Fading model, other channel models can be employed for consideration of the invention.

[0117]

Of course, the SU can be any type of opportunistic signal (e.g. non-licensed LTE signal) while the PU can be any type of incumbent signal (e.g. licensed signal such as DVBT or PMSE signal).

[0118] The concept is applicable to both UL and/or DL Bands and an LTE system with Normal Cyclic Prefix or Extended Cyclic Prefix may be used. A given QP will therefore correspond to either fewer, or more, symbols which will not be used. For example for a 10 ms measurement duration with 10% Quiet Period, the 10% Quiet Period corresponds to 1 ms LTE signal which means 7x2 - 14 LTE OFDM symbols for Normal CP and 6x2 = 12 LTE OFDM symbols for Extended CP.

[0119]

For a fixed T2 period one can increase or decrease Tl in order to have a good % granularity.

[0120]

The CRM may be provided on an eNB or in the Core Network or other 3 GPP or non-3 GPP system.

[0121]

Instead of an eNB that performs spectrum sensing, a UE or other device (or a combination between them) can be employed for this functionality.

[0122]

PvRC messages may be used for reporting the information and the QPs can be periodically, or non-periodically, allocated during the transmission duration of a SU.

[0123]

Upon receiving the measurement results, (for example for a fixed duration T2) the eNB

(or the CRM) can be arranged to increase/decrease the measuring time Tl, and/or

increase/decrease QP in order to increase the feasibility of the measurements (and to allow an SU system to transmit less/more); and/or to increase/decrease the opportunistic transmission power.

[0124]

Such configuration can be performed by an eNB through RRC (re)configuration messages if, for example, UEs perform measurements instead of the other eNB equipment.

[0125]

In any case, the eNB or other device as appropriate can chose the ratio between Tl and T2 based on various considerations which can include the granularity of the % values (the higher the ratio between T2 and Tl, the lower (and better) the granularity), and/or the accuracy of the measurement. In particular, for a higher Tl the interference is better estimated (e.g. see Fig. 3 where results obtained for 200 ms measurement duration are compared with results obtained for 10 ms measurement duration for a 10% QP, and it can be noted that RMSE is better (i.e. is lower) for 200 ms than for 10 ms). [0126]

As will be appreciated, at the heart of the invention is functionality to determine interference effects within the network environment, and subsequent control-functionality responsive to such determined effects, particularly having regard to the reliability of such determination.

[0127]

Turning now to Fig. 6, there is provided a schematic illustration of a spectrum sensor apparatus such as, for example, a spectrum sensor 36 illustrated in Fig. 5 and which, in this illustrated embodiment, comprises an eNB of a mobile radio communications network. As such, the spectrum sensor 36 includes transmission reception functionality 42 operatively connected to an antenna 44 and arranged to function in accordance with, for example, the requirements of a LTE communication system and including appropriate memory 46 and processing 48 functionality.

[0128]

However, as will be appreciated, the eNB comprising the spectrum sensor 36 also includes processing functionality which can be provided as hardware or software as required, and so as to conduct determination of interference effects. In the illustrated example in particular, interference measurements can be conducted in a manner also serving to determine the degree of error and likely reliability of such measurement.

[0129]

Such further processing functionality 50 can therefore be provided with any one or more of the measurement functions described above so as to determine whether or not the interference measurements are reliable enough to be forwarded to a control module such as the CRM 32 illustrated in Fig. 5 and further illustrated schematically with reference to Fig. 7.

[0130]

Turning now to Fig. 7, there is provided a schematic illustration of the CRM 32 of Fig. 5 and comprising functionality for providing CRM control of, for example, an opportunistic transmitter, such as the eNB 40 of Fig. 5.

[0131]

As illustrated, the CRM 32 includes a receiver 52 for receiving a signal 54 from a spectrum sensor 36 such as that of Fig. 6 and which signalling 54 can comprise measurement reports if the percentage of negative measurement over the period T2 is under the threshold value, such as the 10% threshold previously mentioned.

[0132] The measurement reports can then be delivered 56 and analysed 58 internally and, if required, a further decision made as to whether as to the nature of control signalling 60 that is delivered to an opportunistic transmitter, such as the transmitter 40 of Fig. 5. Such control signalling 60 can be employed to vary the operational characteristic, such as the transmitting power, of the opportunistic transmitter 40 having regard to the deemed "reliable" measurement results 54 received from the spectrum sensor.

[0133]

The CRM 32 also includes a central processing function 62 serving to not only control the measurement analysis function 58, but also to control measurement parameters such as the values Tl, T2 and the aforementioned reliability threshold employed with the spectrum sensor 36. That is, within the control functionality 64 the appropriate measurement parameters to be employed by a spectrum sensor can be determined and, as required, transmitted 66 to the spectrum sensor as appropriate.

[0134]

Thus, and with particular reference to Figs. 5, 6 and 7, it should be appreciated that one particular example of a method according to the present invention, employing a related system and related measurement devices and software products as appropriate involves potential interference arising from mobile wireless communication systems operating in

crowded-spectrum environments.

[0135]

However, various further potential options are available. That is, the CRM 32 can be arranged to inform the spectrum sensor of the appropriate values such as for example, Tl, T2 and the reliability threshold value by way of the signalling 66 of Fig. 7. The spectrum sensor 36 can simply perform the appropriate measurements over the period Tl in accordance with the control functionality 50. The spectrum sensor 36 can then evaluate the percentage of negative measurement values for quiet period processing over a period T2 wherein the period T2 is greater than Tl . The spectrum sensor then reports the measurement results 54 to the CRM 32 if the percentage of negative measurement values over period T2 is under the, for example, 10% threshold and, as an optional feature, the spectrum sensor 36 can be arranged to inform the measured value of ISR, the RMSE value of measurement, and the percentage of negative measurement values as appropriate and even if suitable "reliability" measurement is not achieved.

[0136]

As a further development of such optional functionality, the CRM 32, can also be arranged to request additional acquisition data, such as the threshold values and Tl and T2 periods from an "unreliable" spectrum sensors such as that of 34 of Fig. 5.

[0137]

To conclude the control function, the CRM 32 can then determine at 58 how to adapt the power of the opportunistic transmitter such as eNB 40 and deliver the appropriate control signal 60 as illustrated in Fig. 7.

[0138]

It should however be appreciated that the above mentioned example is merely illustrative and comprises one of many embodiments of the present invention.

[0139]

Still further the present invention can also provide for a computer program product arranged to perform any one or more of the method steps outlined above when the computer program product is run on a computer device. Further, the computer program product can comprise computer-readable medium on which the relevant software code portions are stored. Yet further, the computer program product can be directly loadable into the internal memory of the computer device and/or transmittable via a network by means of any appropriate

transmission/upload/push procedure.

[0140]

The program can be stored and provided to the computer device using any type of non-transitory computer readable media. Non-transitory computer readable media include any type of tangible storage media. Examples of non-transitory computer readable media include magnetic storage media (such as floppy disks, magnetic tapes, hard disk drives, etc.), optical magnetic storage media (e.g. magneto-optical disks), CD-ROM (Read Only Memory), CD-R, CD-R/W, and semiconductor memories (such as mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory), etc.). The program may be provided to the computer device using any type of transitory computer readable media. Examples of transitory computer readable media include electric signals, optical signals, and electromagnetic waves. Transitory computer readable media can provide the program to the computer device via a wired communication line, such as electric wires and optical fibers, or a wireless communication line.

[0141]

This application is based upon and claims the benefit of priority from United Kingdom patent application No. 1405224.5, filed on March 24, 2014, the disclosure of which is incorporated herein in its entirety by reference. Reference Signs List

[0142]

10 WIRELESS ENVIRONMENT

12 INCUMBENT TRANSMITTER

16 INCUMBENT RECEIVER

18, 34, 36 SPECTRUM SENSOR

20, 22, 40 OPPORTUNISTIC TRANSMITTER 14, 24, 26, 38 SIGNAL

28 INCUMBENT SERVICE AREA

30 NETWORK ENVIRONMENT

32 CRM

42 TRANSMISSION RECEPTION FUNCTIONALITY

44 ANTENNA

46 MEMORY

48 PROCESSING FUNCTIONALITY

50, 64 CONTROL FUNCTIONALITY

52 RECEIVER

54 SIGNAL

58 ANALYSIS FUNCTION

60 CONTROL SIGNALLING

62 CENTRAL PROCESSING FUNCTION

Claims

[Claim 1]

A method for determining interference effects between first and second signals from competing respective first and second wireless transmitters in a wireless communications environment, the method comprising:

conducting Quiet-Period interference-measurement in relation to the first and second signals;

determining interference measurement values; and

detecting the number of negative interference measurement values when expressed as linear values.

[Claim 2]

The method as claimed in Claim 1 , further comprising:

determining the number of negative interference measurement values over a finite period.

[Claim 3]

The method as claimed in Claim 1 or 2, further comprising:

determining the percentage of negative interference measurement values.

[Claim 4]

A method of determining the reliability of interference measurements and including a method for determining interference effects as claimed in any one of Claims 1, 2 and 3.

[Claim 5]

A method for validating interference measurements for subsequent use within wireless communication control and including a method for determining interference effects as claimed in any one of Claims 1, 2 and 3.

[Claim 6]

A method of controlling and/or influencing transmission of a second signal, in the presence of a first signal, and including a method for determining influencing effects as claimed in any one of Claims 1 , 2 and 3.

[Claim 7]

The method as claimed in Claim 6, comprising:

controlling the wireless transmitter source of the said second signal responsive to the determined interference effects.

[Claim 8]

The method as claimed in Claim 6 or 7, comprising:

employing the number of negative interference measurement values to determine „ signal-to-noise ratio values between the first and second signals.

[Claim 9]

The method as claimed in any one of Claims 1 to 8, comprising:

employing the number of negative interference measurement values to determine a root mean square value as required.

[Claim 10]

The method as claimed in any one of Claims 1 to 9, wherein the Quiet-Period interference measurement and determination of the interference measurement values, and the said number of negative values, are determined within a spectrum sensor located within the network environment.

[Claim 11]

The method as claimed in any one of Claims 1 to 10, including the determining of interference measurement values at one or more terminal devices of a mobile radio

communications network.

[Claim 12]

The method as claimed in any one of Claims 1 to 11 , wherein the said first signal comprises a primary signal from a primary user of an allotted frequency spectrum within the wireless communications environment, and the said second signal comprises an opportunistic signal from a secondary user competing for access within the said spectrum.

[Claim 13] The method as claimed in any one of Claims 1 to 12, comprising:

conducting a plurality of discrete measurement cycles within a measurement period.

[Claim 14]

The method as claimed in any one of Claims 1 to 13, comprising:

employing a CRM for control of the second transmitter responsive to the determined interference effects.

[Claim 15]

The method as claimed in any one of Claims 1 to 14, comprising:

spectrum sensing to determine the interference effects.

[Claim 16]

The method as claimed in any one of Claims 1 to 15, comprising:

allocating operational characteristics of the Quiet-Period interference measurement periodically or otherwise during transmission periods from the second transmitter.

[Claim 17]

The method as claimed in any one of Claims 1 to 16, including, subsequent to receiving measurement results relating to the number of negative interference measurement values, any one or more of:

increasing or decreasing the length of each measurement cycle within a measurement period;

increasing or decreasing the length of a quiet period; and/or increasing or decreasing the transmission power of the second signal.

[Claim 18]

The method as claimed in any one of Claims 1 to 18, wherein the said interference measurement values comprise interference measurement error values, and the said negative interference measurement values comprise negative interference measurement error values.

[Claim 19]

A wireless communication system comprising:

competing first and second wireless transmitters located within a wireless communications environment,

wherein the system is arranged to:

determine interference effects between respective first and second signals from the said first and second transmitters;

conduct quiet-period interference measurement in relation to the said first and second signals;

determine interference measurement values; and

determine the number of negative interference measurement values when expressed as linear values.

[Claim 20]

The system as claimed in Claim 19, further arranged to determine a number of negative measurement values over a finite period.

[Claim 21]

The system as claimed in Claim 20, further arranged to determine the percentage of negative interference measurement values arising during the said finite period.

[Claim 22]

A system for determining the reliability of interference measurements and including a system for determining interference effects as defined in any one of Claims 19 to 21.

[Claim 23]

A system for validating interference measurements for use within wireless

communication control and including a system for determining interference effects as defined in any one of Claims 19 to 22.

[Claim 24]

A system of controlling transmission of a second signal, in the presence of a first signal, and including a system for determining interference effects as claimed in any one of Claims 19 to 21.

[Claim 25]

The system as claimed in Claim 24, arranged to control the wireless transmitter source of the said second signal responsive to the determined interference effects.

[Claim 26]

The system as claimed in any one of Claims 19 to 25, arranged to perform the method claimed in any one of Claims 8 to 18.

[Claim 27]

The system as claimed in any one of Claims 19 to 26, wherein the said interference measurement values comprise interference measurement error values, and the negative interference measurement values comprise negative interference measurement error values.

[Claim 28]

A wireless communications network terminal device arranged for quiet-period interference measurement between competing first and second signals, the device being arranged to:

determine interference measurement values including determination of a number of negative interference measurement values when expressed as linear values.

[Claim 29]

The device as claimed in Claim 28, comprising a spectrum sensing device.

[Claim 30]

The device as claimed in Claim 28 or 29, comprising a terminal device of a mobile radio communications network.

[Claim 31]

The device as claimed in any one of Claims 28 to 30, comprising either a network terminal device or mobile terminal device of a mobile communications network.

[Claim 32]

The device as claimed in any one of Claims 28 to 31, arranged to perform the method claimed in any one of Claims 8 to 18.

[Claim 33] The device as claimed in any one of Claims 28 to 32, wherein the said interference measurement values comprise interference measurement error values, and the said negative interference measurement values comprise negative interference measurement error values.

[Claim 34]

A wireless communication device arranged for controlling operation of a wireless transmitter device within a wireless communications environment, the wireless communication device being arranged to:

receive a control signal from a network terminal device as claimed in any one of Claims 28 to 32; and

vary operation of a network transmitter device responsive to that control signal.

[Claim 35]

The wireless communications device as claimed in Claim 34, further arranged to vary any one or more of:

a measuring period for determining interference effects;

quiet periods employed within quiet period interference measurement; and/or transmission power employed by the transmitter device, and responsive to the control signal.

[Claim 36]

A computer program product for a computer device, comprising software code portions for performing the method as claimed in any one of Claims 1 to 18 when said product is run on the computer device.

[Claim 37]

The computer program product according to Claim 36, wherein the computer program product comprises a computer-readable medium on which software code portions are stored. [Claim 38]

The computer program product according to Claim 36 or 37, wherein the computer program product is directly loadable into the memory of the computer device and/or

transmittable via network by means of at least one of upload, download and push procedures.