Method and Arrangement in a Wireless Communication System

TECHNICAL FIELD

0001The present disclosure relates generally to a method and an arrangement in a network node. In particular, it relates to scheduling of data transmission and/or reception.

BACKGROUND

0002Femto base stations, also called home base stations, have attracted much interest recently in the wireless industry. The standardization process for home base stations is ongoing in 3GPP for Universal Terrestrial Radio Access (UTRA), Evolved UMTS Radio Access (E-UTRA) and Worldwide Interoperability for Microwave Access (WiMAX). Furthermore, in both UTRA and E-UTRA, advanced features related to home base stations such as mobility procedures, interference management and control etc are also being introduced. Home base stations are already operational in other technologies such as Global System for Mobile communication (GSM) and 3GPP2 CDMA technologies (e.g. CDMA2000 1×RTT and High Rate Packet Data, HRPD).

0003In legacy UTRAN specifications, four classes of base stations (BS) are defined, namely the wide area BS that serves macro cell deployment, the medium range BS that serves micro cell deployment, the local area BS that serves pico cell deployment and the home base station serving the private localized premises, like a home or an office. In UTRAN, the home BS is also called a home NodeB (HNB). In E-UTRAN specifications three classes of base stations are defined; Wide area BS, local area BS and home base station. In E-UTRAN the home BS is also called a Home eNodeB (HeNB).

0004A home base station may also be referred to as a home access point, femto base station, femto access point, home NodeB, or home eNodeB. Some particular examples of Home Base Stations are UTRAN FDD/TDD home NodeB, E-UTRAN TDD/FDD home eNB (eNodeB), GSM home base station, CDMA2000 1×home BS, HRPD home BS, or WiMAX home base station. For simplicity and consistency, we will use the term home base station (HBS) in the rest of the disclosure. This term is intended to covers all types of home access points, including but not limited to those mentioned above. It should be understood that a home base station may not only deployed in a private residence, but also in other public or private premises such as shopping malls, office buildings, etc.

0005Depending on the operator, a Home Base Station may share the carrier with macro, micro or pico base stations, i.e. non home base stations. This may be referred to as a mixed carrier scenario. Alternatively, the HBS may be assigned a carrier which is used only for the operation of home base stations, i.e. a dedicated carrier scenario.

0006One main difference between a home base station and other base station classes is that a Home Base Station is assumed to be owned by a private subscriber, who has the liberty to install it at any location. Thus, strict network planning is not possible in case of Home Base Station deployment. This is in contrast to other base station classes, which are deployed by an operator according to well-defined principles. The lack of precise network planning of Home Base Stations and their dense deployment may have the following consequences: <ul id="ul0001" list-style="none"><li id="ul0001-0001" num="0000"><ul id="ul0002" list-style="none"><li id="ul0002-0001" num="0007">High interference towards other base stations, including other home BS:s and the surrounding network, e.g. macro base stations.</li><li id="ul0002-0002" num="0008">In case of dense Home BS deployment, the UE may detect, measure and report a large number of cells, which are served by home base stations but are not required for mobility.</li></ul></li></ul>

0009Access to a home base station may be under the control of the operator or the owner of the home base station. The access control mechanism for a home BS decides if a given user may or may not connect to that home base station. The selection of the access control mechanism has a large impact on the performance of the overall network, mainly due to its role in the definition of interference. In UTRAN and E-UTRAN, the concept of a Closed Subscriber Group (CSG) exists. According to the CSG concept, only a subset of users, defined by the owner of the home base station, are allowed to connect to that particular home base station. Because access to a HBS may be restricted only to certain users, appropriate mobility procedures to prevent unnecessary handovers towards the non-allowed home base stations are specified for UTRAN as well as for E-UTRAN. This implies that before initiating a handover to a neighbor cell, the serving network node may need to know whether the target cell is a CSG cell or not, i.e. whether the target cell is served by a HBS using the CSG concept.

0010Currently, network deployments with several layers comprising macro base stations, pico base stations, home base stations etc are gaining popularity. In certain areas, coverage from macro layer deployment overlaps with areas covered by micro, pico or femto network deployments. Such a network or deployment is called a heterogeneous network. These heterogeneous network scenarios are expected to become more and more popular as a direct consequence of the proliferation of pico, femto, and home eNBs. In such heterogeneous network deployments, mobility management is becoming an even more challenging task, because it is quite probable that Physical Cell Identities, PCIs, are frequently reused. Hence, a serving node in many cases may have to know whether the target cell belongs to a macro, pico or home base station etc.

0011Thus, in a scenario with home base stations, as well as in heterogeneous networks, it is beneficial to uniquely determine the identity and/or type of potential target cells. This requires information which is transmitted in the cell's system information. Hence, the user equipment (UE) is expected to acquire system information from surrounding base stations, such as neighboring HBSs, and report this information to the network. One example of system information that the UE may need to acquire is the Cell Global Identifier (CGI), which is a unique identifier of a cell. The CGI or E-UTRAN CGI (ECGI) acquisition is typically performed by the UE in response to an explicit request received from the serving network node. One example scenario where this may occur is when the UE performs neighbor cell measurements on potential target cells for handover, i.e. to support mobility.

0012As part of the neighbor cell measurement procedure, the UE will send a measurement report containing neighbor cell measurements such as Reference Symbol Received Power (RSRP) and/or Reference Symbol Received Quality (RSRQ) in E-UTRAN, or Common Pilot Channel Received Signal Code Power (CPICH RSCP) and/or Common Pilot channel received energy per chip divided by power spectral density (CPICH Ec/No) in UTRAN. The serving network node typically uses these measurements to determine if the UE would be better served by one of the neighbor cells, i.e. whether to initiate a handover (HO).

0013The measurement report also comprises the physical cell identity (PCI) of the target cell to the serving network node, e.g. the serving eNodeB in E-UTRAN. The PCI is an identity which identifies the target cell, but it is typically not unique within the network. In current E-UTRAN specifications, for instance, there are only 504 different PCI:s defined. This is because the PCI is broadcast at frequent intervals in the cell, so its length is restricted to only a few bytes in order to consume less radio resources. As a consequence, in a large network the same PCI may need to be reused in several cells and is therefore not guaranteed to be unique, or even to uniquely identify the type of the cell. In a dense Home Base Station deployment scenario, the PCI:s are more frequently reused, due to the large number of cells and smaller cell sizes.

0014Therefore, in a situation where the serving network node is not able to derive the necessary information from the PCI, the serving network node may also request the UE to decode and report the Cell Global Identifier (CGI) of the target cell. For example, based on the reported PCI, the network node may suspect that the target cell belongs to a CSG, a Home Base Station or to any similar node as part of the heterogeneous network. In order to prevent a HO command to a non-allowed Home Base Station, e.g. a CSG cell to which the UE does not have access, the serving network node needs to be able to uniquely identify the cell, or at least determine with certainty whether the cell is served by a HBS or not, and in particular whether it is associated with a CSG. However, since the PCI is not unique, the network node cannot establish this based on the PCI alone. The CGI, however, is an identity which is unique in the network, thereby allowing the network to distinguish between macro BS:s and home BS:s, or to uniquely identify that the reported cell is associated with a CSG. Hence, to confirm its hypothesis that the target cell is served by a HBS, the network may request the UE to decode and report the target cell's CGI or ECGI.

0015The procedure and the associated requirements for the UE reporting of the target cell's CGI or ECGI are specified in both UTRAN and E-UTRAN. One key aspect of the CGI decoding is that it is performed by the UE during autonomous gaps, which are created by the UE itself. During the autonomous gaps, the UE interrupts its reception and transmission of data in the serving cell. The reason for acquiring the target cell CGI during autonomous gaps is that the typical UE implementation is not capable of simultaneously receiving data from the serving cell and acquiring the target cell's system information, which contains the CGI. Furthermore, the CGI acquisition of an inter-frequency or inter-Radio Access Technology (inter-RAT) target cell requires the UE to switch carrier frequency, which means it cannot communicate with the serving cell at the same time. Hence, the use of autonomous gaps is necessary for acquiring the target cell's CGI. These autonomous gaps are also interchangeably referred to as measurement occasions, because the gaps are the occasions during which the UE measures the CGI of the target cell.

0016The CGI is sent over a system information block (SIB). In E-UTRAN, the CGI is called E-UTRAN CGI (ECGI), and is transmitted in system information block type <b>1</b> (SIB<b>1</b>). However, the acquisition of ECGI requires the UE to first read the master information block (MIB) of the target cell, which is transmitted on the physical broadcast channel (PBCH) with a periodicity of 40 ms. Within the 40 ms period, the PBCH is repeated in every frame. For example, in E-UTRAN, the length of an E-UTRAN frame is 10 ms, and the PBCH will be repeated in every fourth frame. The MIB enables the UE to acquire information such as system frame number (SFN), cell transmission bandwidth etc. Hence, after acquiring the MIB, the UE reads the system information block type <b>1</b> (SIB<b>1</b>), which contains the ECGI and is transmitted with a periodicity of 80 ms on DL-SCH. The home eNodeB can be deployed on a shared carrier or on a dedicated carrier as described earlier. Therefore EGCI requirements in E-UTRAN are specified for the following two scenarios: <ul id="ul0003" list-style="none"><li id="ul0003-0001" num="0000"><ul id="ul0004" list-style="none"><li id="ul0004-0001" num="0017">Intra-frequency ECGI reporting</li><li id="ul0004-0002" num="0018">Inter-frequency ECGI reporting</li></ul></li></ul>

0019The UE is required to report the intra-frequency ECGI within about 200 ms, including processing time of the measurement request, after receiving a request from the serving network node, for a target intra-frequency cell provided that the target cell's SINR experienced by the UE is at least −6 dB or higher, and to report an inter-frequency ECGI within about 200 ms, including processing time of the measurement request, provided that the target cell's SINR is at least −4 dB or higher. During the acquisition of the target cell's ECGI on the serving carrier frequency the UE is allowed to create autonomous gaps in the downlink. Those gaps result in interruptions in the UE downlink reception from the serving node, and uplink transmission to the serving node. That is to say, the UE cannot receive signals from or transmit signals to its serving node during an autonomous gap. The duration of the autonomous gap may vary depending upon the UE implementation, but typically comprises 3 sub-frames.

0020In UTRAN, the CGI is transmitted in the system information block type <b>3</b> (SIB<b>3</b>). But in order to read the SIB<b>3</b> the UE has to first read the MIB. Hence the UE can determine the CGI of a neighbor cell by reading its MIB and system information block type <b>3</b> (SIB<b>3</b>), which are sent on the broadcast channel (BCH). The MIB is transmitted every 20 ms. The SIB<b>3</b> may have different periodicity, which is configured by the network. As compared to E-UTRAN, in UTRAN the target cell's CGI acquisition time is typically much longer, e.g. more than 1 second depending upon the periodicity of the SIB<b>3</b>. Furthermore, due to the autonomous gaps created by the UE to acquire the target cell's CGI, the interruption of the data transmission and reception from the serving cell can be 600 ms or longer.

0021The concepts of autonomous gaps and CGI/ECGI acquisition are also relevant for self organizing networks (SON). The SON function in E-UTRAN and UTRAN allows the operator to automatically plan and tune the network parameters and network nodes. The conventional method is based on manual tuning, which consumes enormous amounts of time and resources, and requires considerable involvement of work force. Due to network complexity, a large number of system parameters, Inter-Radio Access Technologies (IRAT) etc., it is very attractive to have reliable schemes to perform the test of self organization in the network whenever necessary.

0022An operator may also add or delete a cell or an entire base station, which may serve multiple cells. Especially new cells are added more frequently during an early phase of network deployment. In the later stages, an operator can still upgrade the network by adding more carriers or more base stations on the same carrier. It can also add cells related to another technology. The network may automatically detect the new cells and their relationship to existing cells in a process referred to as automatic neighbor cell relation (ANR) establishment, which it is part of the self organizing network (SON) functionality. In order to ensure correct establishment of the neighbor cell relation, the serving cell requests the UE to report the CGI of the new target cell, whose PCI is identified and reported to the said serving cell. The CGI acquisition requires the UE to read the target cell's system information and is thus carried out by the UE during autonomous gaps. As in the case of home inbound mobility, the CGI acquisition for ANR purposes also leads to interruption of data from the serving cell.

0023As explained above, the UE autonomously creates measurement gaps for acquiring the system information of the target cell to decode its CGI in home BS inbound mobility scenarios, for ANR purposes, or in any similar scenario. In other words, the length (L) of the measurement gaps and number (N) of measurement gaps depend upon the UE itself. No signaling or any related information about the autonomous gaps is exchanged between the UE and the serving network node. Since the serving network node is unaware of the exact occasions and number of autonomous gaps created by the UE, it does not know when the UE can be conveniently scheduled without losing data due to the gaps.

0024One solution to this problem is to not allow the serving network node to schedule the UE during the entire time while the UE is acquiring system information, e.g. decoding the CGI, of a target cell. As mentioned above, this period is about 200 ms in E-UTRAN and may be over one second in UTRAN. Thus, this solution leads to a long interruption in the transmission/reception between the serving cell and the UE while the target cell's CGI decoding is performed. This may cause significant degradation of real time services such as voice.

0025Another prior art solution is to use an aggressive approach, i.e. to continue scheduling the UE during the period when the UE is acquiring system information from other cells, without any regard for the autonomous gaps. A drawback of this approach is that if the UE receives an uplink grant which coincides with an autonomous gap, the UE will not be able to use the grant. Thus, the associated uplink resources, which could potentially have been assigned to another UE, will be wasted. If a downlink transmission to the UE coincides with an autonomous gap, the UE will not receive the information and retransmission will be required.

0026The performance degradation resulting from these drawbacks may be significant, in particular in a dense home base station scenario or in heterogeneous networks, where there are many potential target cells for the UE to measure on. It is therefore important to minimize the duration of the data interruption from the serving cell while the UE is acquiring system information, in particular CGI or ECGI.

0027There is thus a need in the art for improving the performance of wireless communication systems, in particular in a scenario when UEs may need to acquire system information from neighboring cells.

SUMMARY

0028It is an object of at least some embodiments of the invention to improve performance by providing a scheduling mechanism, which is able to take into account autonomous gaps created by the UE.

0029Some embodiments of the present invention provide a solution to the above problem, whereby a serving network node is able to determine at what instances the gaps are autonomously created by the UE for the acquisition of the system information. This determination allows the network to schedule the UE based on its knowledge of when the UE is acquiring the target cell's system information.

0030According to one embodiment, the present invention comprises a method implemented in a radio network node. The method comprises the steps of: <ul id="ul0005" list-style="none"><li id="ul0005-0001" num="0000"><ul id="ul0006" list-style="none"><li id="ul0006-0001" num="0031">Requesting the UE to identify the system information of the target cell,</li><li id="ul0006-0002" num="0032">Acquiring at least one UE measurement report of the said target cell,</li><li id="ul0006-0003" num="0033">Determining, based on the said acquired measurement report, the occasions or time instances during which the UE is not acquiring the system information of the said target cell, and</li><li id="ul0006-0004" num="0034">Scheduling the UE for data reception and/or transmission during the time instances when UE is not acquiring the system information.</li></ul></li></ul>

0035Particular embodiments of the invention enable the serving network node to predict or determine the autonomous gaps created by the UE for acquiring the target cell's system information, which contains the CGI. This prediction makes it possible for the serving network node to schedule the UE in the time periods when there is no autonomous gap, which may contribute to performance improvement and/or better utilization of resources.

0036Other particular embodiments provide a method in a radio network node for scheduling data transmission and/or reception. According to the method, the radio network node predicts at least one autonomous gap occurrence in which user equipments served by the radio network node will use autonomously created gaps for acquiring system information from a neighboring base station, and during which the UE is not able to receive data from, and/or transmit data to, the radio network node. The radio network node then schedules a user equipment for data transmission and/or reception in a time period which does not overlap with any predicted autonomous gap occurrence.

0037Other particular embodiments provide a method in a radio network node serving a user equipment. According to the method, the radio network node receives information from the user equipment, which indicates at least one autonomous gap occurrence, during which the user equipment will autonomously create gaps for acquiring system information from a neighboring base station. Furthermore, the radio network node predicts at least one autonomous gap occurrence in which user equipments served by the radio network node will use autonomously created gaps for acquiring system information from the neighboring base station. The radio network node then schedules a user equipment for data transmission and/or reception in a time period which does not overlap with any predicted autonomous gap occurrence.

0038Another embodiment provides a radio network node comprising one or more processing circuits, which are configured to predict at least one autonomous gap occurrence in which user equipments served by the radio network node will use autonomously created gaps for acquiring system information from a neighboring base station and during which the UE is not able to receive data from, and/or transmit data to, the radio network node. Furthermore, the processing circuits are configured to schedule a user equipment for data transmission and/or reception in a time period which does not overlap with any predicted autonomous gap occurrence.

0039Another embodiment provides a radio network node comprising one or more processing circuits, which are configured to receive information from a user equipment being served by the radio network node. The information indicates at least one autonomous gap occurrence, during which the user equipment will autonomously create gaps for acquiring system information from a neighboring base station. The processing circuits are further configured to predict at least one autonomous gap occurrence in which user equipments served by the radio network node will use autonomously created gaps for acquiring system information from the neighboring base station. Furthermore, the processing circuits are configured to schedule a user equipment for data transmission and/or reception in a time period which does not overlap with any predicted autonomous gap occurrence.

0040Another embodiment provides a method in a user equipment, which is being served by a radio network node. According to the method, the user equipment performs a measurement on a signal received from a neighboring base station. Based on this measurement, the user equipment determines at least one autonomous gap occurrence during which the user equipment will autonomously create gaps for acquiring system information from the neighboring base station. The user equipment then transmits information to the radio network node, indicating the at least one autonomous gap occurrence.

0041In another embodiment, a user equipment comprising one or more processing circuits is provided. The processing circuits are configured to perform a measurement on a signal received from a neighboring base station, and to determine, based on the measurement, at least one autonomous gap occurrence during which the user equipment will autonomously create gaps for acquiring system information from a neighboring base station. The processing circuits are further configured to transmit information to the radio network node serving the user equipment, the information indicating the at least one autonomous gap occurrence.

0042An advantage of some embodiments is that the serving cell interruption while the UE acquires the CGI of the target cell is minimized, since the serving cell can still schedule the UE during the occasions when there are no gaps. This is made possible because the radio network node predicts the autonomous gap occurrences that the UE will use to acquire system information from the target cells.

0043A further advantage is that the scheduling grant issued by the serving cell to the UE is not wasted since the serving cell knows when the UE can transmit and/or receive the data when it is acquiring the system information of the target cell.

0044Furthermore, the performance degradation of delay sensitive services such as voice over IP can be minimized by reducing the interruption in scheduling the packets.

BRIEF DESCRIPTION OF THE DRAWINGS

0045<figref idref="DRAWINGS">FIG. 1</figref> is a schematic diagram illustrating a wireless network.

0046<figref idref="DRAWINGS">FIG. 2</figref> is a schematic diagram showing a more detailed view of the wireless network of <figref idref="DRAWINGS">FIG. 1</figref>.

0047<figref idref="DRAWINGS">FIG. 3</figref> is a flow chart illustrating a method in a network node according to some embodiments.

0048<figref idref="DRAWINGS">FIG. 4</figref> is a flow chart illustrating a method according to an embodiment.

0049<figref idref="DRAWINGS">FIG. 5</figref> is a flow chart illustrating a method in a base station according to some embodiments.

0050<figref idref="DRAWINGS">FIG. 6</figref> is a flow chart illustrating a method in a network node according to some embodiments.

0051<figref idref="DRAWINGS">FIG. 7</figref> is a flow chart illustrating a method in a network node according to some embodiments.

0052<figref idref="DRAWINGS">FIG. 8</figref> is a flow chart illustrating a method in a network node according to some embodiments.

0053<figref idref="DRAWINGS">FIG. 9</figref> is a flow chart illustrating a method in a user equipment according to some embodiments.

0054<figref idref="DRAWINGS">FIG. 10</figref> is a flow chart illustrating a method in a network node according to some embodiments.

0055<figref idref="DRAWINGS">FIG. 11</figref> is a schematic block diagram illustrating a base station.

0056<figref idref="DRAWINGS">FIG. 12</figref> is a schematic block diagram illustrating a user equipment.

LIST OF ABBREVIATIONS

0000<ul id="ul0007" list-style="none"><li id="ul0007-0001" num="0057">CPICH: Common pilot channel</li><li id="ul0007-0002" num="0058">CSI Channel state information</li><li id="ul0007-0003" num="0059">E-UTRAN: Evolved UTRAN</li><li id="ul0007-0004" num="0060">GPS: Global Positioning System</li><li id="ul0007-0005" num="0061">RSRP: Reference symbol received power</li><li id="ul0007-0006" num="0062">RSRQ: Reference symbol received quality</li><li id="ul0007-0007" num="0063">UE: User Equipment</li><li id="ul0007-0008" num="0064">UTRAN: Universal Terrestrial Radio Access Network</li><li id="ul0007-0009" num="0065">WCDMA: Wide band code division multiple access</li><li id="ul0007-0010" num="0066">SON: Self organizing network</li><li id="ul0007-0011" num="0067">CGI: Cell global identifier</li><li id="ul0007-0012" num="0068">PCI: Physical cell identifier</li><li id="ul0007-0013" num="0069">ANR: Automatic neighbor relation</li></ul>

DETAILED DESCRIPTION

0070It should be noted that although terminology from 3GPP UTRAN, also known as 3G, and E-UTRAN, also known as Long Term Evolution (LTE), has been used in this disclosure to exemplify the invention, this should not be seen as limiting the scope of the invention to only the aforementioned system. Other wireless systems, including other WCDMA-based systems, WiMax, Ultra Mobile Broadband (UMB) and GSM, may also benefit from exploiting the ideas covered within this disclosure.

0071As explained above, the use of autonomous gaps for acquiring system information may result in service interruption and performance degradation of the ongoing communication between the serving cell and the UE. However, typically the autonomous gaps created by the UE are short, sporadic and sometimes occur periodically. This implies that the network could in principle still maintain active communication with the UE, i.e. transmit and/or receive data, while the UE is acquiring the CGI of a neighbor cell, provided that the communication takes place in the time periods when there is no gap—that is, the serving network node may more intelligently schedule transmissions to or from the UE, based on knowing or at least predicting, with some accuracy, when the measurement gaps are likely to occur.

0072This disclosure uses the terms “occurrence”, “occasion”, and “timing” interchangeably when referring to the UE measurement gaps. Herein, “timing” should be broadly construed to include the times and/or positions of measurement gaps, in an absolute or relative sense (e.g., with respect to synchronized frames), and/or the number, duration, and/or periodicity of such gaps.

0073The term “autonomous gap occurrence”, when used in this disclosure, refers to a time instance or a time period, determined or selected by the UE, when a user equipment is not able to receive data from its serving network node, because the user equipment is acquiring information from another node, e.g. a neighboring base station. In some cases the UE may also not be able to transmit data to its serving network node during the autonomous gap occurrence. As explained above, the time instance or time period may be defined in various different ways, for instance as a starting and ending subframe number, or a starting subframe number and a length, either in milliseconds or in terms of number of subframes. The autonomous gap occurrence may also be defined only by its starting point, e.g. starting subframe number. In this case the length of the gap occurrence may be predefined, e.g. the gap length may be assumed to always be 3 subframes.

0074The following non-limiting example is intended to illustrate the potential improvement in terms of resource utilization, if the serving network node would be able to predict the autonomous gap occurrences of the UE. It is first recalled that in E-UTRAN, the UE is required to acquire and report the CGI of a neighbor cell within about 200 ms, including processing time of the measurement request command. Since the neighbor BS will be transmitting the MIB and SIB1 (which contains CGI) once every 40 ms and 80 ms respectively, there will be either four or five possible occurrences when the UE may attempt to acquire the CGI within this 200 ms period. The contents of MIB and SIB<b>1</b> are repeated every 10 ms and 20 ms during 40 ms and 80 ms periods respectively. This enables UE to improve the decoding performance by soft combining the MIB and SIB<b>1</b> information up to 4 times within their respective periods. The UE reads MIB and SIB<b>1</b> in tandem. This is because in order to read SIB<b>1</b> the UE needs to know some fundamental system parameters like cell transmission bandwidth, system frame number (SFN) etc, which are transmitted in MIB. Assuming that the UE creates an autonomous gap at each CGI transmission occurrence, and each gap is three subframes in length, this means that autonomous gaps will occur only in a total of 12 or 24 subframes, corresponding to 12 or 24 ms out of the entire 200 ms measurement period (the length of a subframe in E-UTRAN is 1 ms). Thus, if the network node would be able to accurately predict when the gaps would occur, it could schedule transmissions to or from the UE in the remaining 200−24=176 ms.

0075In some embodiments of the invention, the serving network node predicts the autonomous gap occurrences based on the knowledge or assumption that the UE will only create a gap when the required system information, e.g. the Master Information Block (MIB), the required SIB (i.e. SIB<b>1</b> in E-UTRAN and SIB<b>3</b> in UTRAN) containing CGI etc, is actually being transmitted in the neighbor cell, e.g. a target cell for handover. Thus, in the serving network node may predict the autonomous gap occurrences by determining timing information for the neighboring base station, and then deducing from the timing information when the required system information, e.g. the ECGI, will be transmitted. That is to say, the serving network node assumes that the timing of the autonomous gaps in the UE coincides with the timing of the transmission of the required system information in the neighbor cell. Various methods that the serving network node may use for determining timing information for neighboring base stations are set forth in this disclosure.

0076In other embodiments, the gaps are predicted based on the absence or presence of an expected transmission from the UE. For instance, if the serving network node does not receive an expected Channel State Information (CSI) report from the UE, or if it does not receive HARQ ACK/NACK feedback following a downlink transmission, the serving network node may assume that an autonomous gap occurred, preventing the UE from receiving or transmitting information. Conversely, if the serving network node does receive feedback from the UE, it may assume that there was no gap created during that particular time period. This information may be used to predict future autonomous gap occurrences, assuming that the gaps recur periodically.

0077<figref idref="DRAWINGS">FIG. 1</figref> is a schematic diagram illustrating a wireless network <b>100</b> in which some embodiments of the invention may operate. The wireless network <b>100</b> comprises three cells <b>110</b>, <b>120</b>, <b>130</b>. A UE may make measurements to determine system information for one or more neighboring cells <b>120</b>, <b>130</b>, such as to enable reporting of the CGI:s of those neighboring cells to its reporting cell, or serving cell, <b>110</b>. Note that the uniformity of cells depicted in the drawing does not imply that the real-world network is so implemented, as different cell types/sizes may be involved. Regardless, according to particular embodiments of the present invention, scheduling of data transmissions to or from the UE is improved, based on determining the timing of service interruptions caused in the serving cell by the UE's measurements of neighboring cell system information.

0078<figref idref="DRAWINGS">FIG. 2</figref> is a schematic diagram which gives a more detailed view of the wireless network <b>100</b> shown in <figref idref="DRAWINGS">FIG. 1</figref>. Three UE:s <b>104</b>, <b>106</b> and <b>108</b> are present within the cell <b>110</b>, and served by the serving base station <b>102</b>. Neighboring cell <b>120</b> is served by base station <b>122</b>, and neighboring cell <b>130</b> is served by base station <b>132</b>. The base stations <b>102</b>, <b>122</b>, and <b>132</b> periodically transmit system information, which can be decoded by UE:s located within the cell coverage area. It is to be understood, with respect to all embodiments set forth herein, that this particular example scenario is not to be construed as limiting, and that the exemplified methods and arrangements may be applied in a network comprising any number of cells, with any number of UE:s being served by each cell. It is further pointed out that while the example scenario in <figref idref="DRAWINGS">FIG. 2</figref> shows a single network node serving each cell, it is equally possible for one network node to serve several cells or sectors.

0079Referring to <figref idref="DRAWINGS">FIG. 2</figref> and the flowchart of <figref idref="DRAWINGS">FIG. 3</figref>, a general method for scheduling data transmission and/or reception according to one embodiment will now be described. The method is performed in a network node <b>102</b>, e.g. an E-UTRAN eNodeB or an UTRAN RNC. In a first step <b>310</b>, the network node <b>102</b> predicts at least one autonomous gap occurrence in which user equipments <b>104</b>, <b>106</b>, <b>108</b> served by the network node <b>102</b> will use autonomously created gaps for acquiring system information from a neighboring base station <b>122</b>. During such an autonomous gap occurrence, the user equipment creating the gap is not able to receive data from, and/or transmit data to, the serving network node <b>102</b>. In a further step <b>320</b>, the network node <b>102</b> schedules a user equipment <b>104</b> for data transmission and/or reception in a time period which does not overlap with any predicted autonomous gap occurrence. In other words, the network node <b>102</b> schedules the UE in the non-gap periods.

0080Another general method according to some embodiments is illustrated in <figref idref="DRAWINGS">FIG. 4</figref>. According to this method, a base station determines gap timing information, and then adapts the downlink and/or uplink scheduling for a user equipment as a function of the gap timing. The expression “gap timing” as used in <figref idref="DRAWINGS">FIG. 4</figref> corresponds to “autonomous gap occurrence” in <figref idref="DRAWINGS">FIG. 3</figref>.

0081In particular embodiments of the invention, one may assume a scenario whereby in active mode, e.g. RRC_CONNECTED mode in E-UTRAN, the serving network node, e.g. serving eNode B in E-UTRAN, requests that the UE: <ul id="ul0008" list-style="none"><li id="ul0008-0001" num="0000"><ul id="ul0009" list-style="none"><li id="ul0009-0001" num="0082">Read the system information of at least one target cell or neighbor cell, which may operate over the intra-frequency carrier, inter-frequency carrier or may belong to another Radio Access Technology (RAT).</li><li id="ul0009-0002" num="0083">Acquire CGI of the target cell or neighbor cell by reading the system information of the target cell during the measurement gaps, which are created autonomously by the UE without the intervention of the network.</li><li id="ul0009-0003" num="0084">Report the acquired CGI to the serving network node.</li></ul></li></ul>

0085According to particular embodiments of the invention, a method in a network node is provided. The method comprises the steps of: <ul id="ul0010" list-style="none"><li id="ul0010-0001" num="0000"><ul id="ul0011" list-style="none"><li id="ul0011-0001" num="0086">I. Determining, based on static/semi-static and dynamic information, the occurrence of at least one autonomous gap, which comprise at least one of the time instances (T<b>0</b>), the length (L) and the number of autonomous gaps which are to be created by the UE while acquiring system information, such as the CGI of a particular target cell.</li><li id="ul0011-0002" num="0087">II. Using the determined knowledge in step I) to determine when the UE can be scheduled without interruption due to the autonomous gaps.</li><li id="ul0011-0003" num="0088">III. Scheduling the UE while taking into account the determined knowledge.</li></ul></li></ul>

0089The subsequent sections describe the use of static, semi-static and dynamic information for the determination of the occurrence of autonomous gaps according to some embodiments.

0090The occurrence of gaps may be determined by using static and/or semi-static information. By static and semi-static information we mean the information which may change over a longer time scale e.g. in the order ranging from hours to several days. This type of information can typically be stored in a database, such as at the time of network planning.

0091The following pieces of static or semi-static information are gathered by the network and one or more elements of this information can be combined with other information to determine various details related to the occurrence of the autonomous gaps: <ul id="ul0012" list-style="none"><li id="ul0012-0001" num="0000"><ul id="ul0013" list-style="none"><li id="ul0013-0001" num="0092">Scheduling of system information (e.g. SFN, MIB and SIB<b>1</b>) in the neighboring cells.</li><li id="ul0013-0002" num="0093">In case of an asynchronous network, the Frame Start Timing of the neighboring cells or the time offset between the frame timing of the serving and the neighbor cells or similar information. In some cases, the network may already have this information, if it supports positioning services such as observed time difference of arrival (OTDOA).</li><li id="ul0013-0003" num="0094">In case of a synchronous network, the accuracy of the frame start timing between the cells and also the cell size, e.g. cell range or cell radius, of the serving and the neighbor cells, because the accuracy between any two cells depends upon the overlapping area between them.</li><li id="ul0013-0004" num="0095">UE receiver type or receiver capability information either explicitly, i.e. by UE indication/capability reporting or implicitly, which is based on the UE reported measurement data/results, i.e. based on past UE reported statistics. This information indicates whether the UE has a baseline receiver or an advanced receiver, e.g. an interference cancellation receiver.</li></ul></li></ul>

0096As mentioned above, the UE creates gaps only when the required system information (e.g. MIB, the required SIB containing CGI etc) are transmitted in the target cell. After synchronization to the target cell and acquisition of the SFN, the UE will only read the necessary SIB which contains the target cell CGI.

0097Thus, the above information enables the network to determine the potential time instances (T<b>0</b>) of the occurrences of the autonomous gaps that can be created by the UE for obtaining the CGI of the target cell, assuming the target cell is at the lowest SNR for which the requirements are specified (e.g. SNR=−6 dB in case of E-UTRAN intrafrequency).

0098The static and semi-static information discussed above provide information about the scheduling and transmission of the neighbor cells' system information, which for instance contains CGI of the neighbor cells. In addition, one or more out of the following set of dynamic information indicated below may be used to assist the network node in determining the number of autonomous gaps and also the length of each gap the UE may use in decoding the CGI of a particular target cell. This dynamic information comprises: <ul id="ul0014" list-style="none"><li id="ul0014-0001" num="0000"><ul id="ul0015" list-style="none"><li id="ul0015-0001" num="0099">Signal quality of the target cell</li><li id="ul0015-0002" num="0100">Relative signal quality between the serving and the target cell</li><li id="ul0015-0003" num="0101">Time required for identifying the physical cell identity of the target cell</li><li id="ul0015-0004" num="0102">Received time difference between the serving and the target cell</li><li id="ul0015-0005" num="0103">HARQ ACK/NACK</li><li id="ul0015-0006" num="0104">Interruption in periodic CSI reports</li></ul></li></ul>

0105A method in a network node for scheduling data transmission and/or reception according to an embodiment of the invention will now be described, with reference to the example scenario of <figref idref="DRAWINGS">FIG. 2</figref> and the flowchart in <figref idref="DRAWINGS">FIG. 5</figref>.

0106The method may be executed in a network node <b>102</b>, comprised within a wireless communication network <b>100</b> as shown in <figref idref="DRAWINGS">FIG. 2</figref>. The network node <b>102</b> may for instance be an E-UTRAN eNodeB, or an UTRAN radio network node such as a NodeB or RNC. The network node <b>102</b> serves a cell <b>110</b>, and within this cell three user equipments <b>104</b>, <b>106</b>, <b>108</b> are located. However, it should be understood that this scenario is not limiting—in particular, the network node <b>102</b> may serve more than one cell, and the cell <b>110</b> may comprise any number of user equipments.

0107In step <b>510</b>, the network node <b>102</b> receives a measurement report from a reporting user equipment <b>104</b>. The measurement report relates to the neighboring cell <b>120</b>, served by base station <b>122</b>. For instance, the measurement report could be a neighbor cell measurement report comprising the PCI of neighboring base station <b>122</b>, as well as other information such as the signal-to-noise ratio, SNR, of neighboring base station <b>122</b> as experienced by UE <b>104</b>.

0108In step <b>520</b>, the network node <b>102</b> determines timing information for the neighboring base station <b>122</b> based on the measurement report received in step <b>510</b>. The timing information comprises the frame start timing and/or the System Frame Number, SFN of neighboring base station <b>122</b>. In one variant, the frame start timing and/or SFN are directly included in the measurement report received from the UE. In another variant, the timing information is determined based on the relative time difference between the serving base station <b>102</b> and the neighboring base station <b>122</b>, as measured by the UE <b>104</b>. Especially in an asynchronous network, the relative time difference between the serving and the target cell, as measured by the UE <b>104</b>, may be used by the serving node <b>102</b> to determine the precise transmit timing of the target cell <b>120</b>. Another possibility is that the serving base station or the serving radio network node determines the timing without user equipment measurement reports. In one variant the serving base station or the serving radio network node determines the timing information of the neighbouring base station from the message received from the said neighbouring base station or by any other network node. The received message contains at least the frame start timing and may also contain the SFN of the neighbouring base station. In yet another variant, the radio network node or the serving base station directly acquires the timing information of the neighbouring base station by performing correlation over a pre-defined set of synchronization and/or pilot signals transmitted by the neighbouring base station. In order to further acquire the SFN of the neighbour cell the radio network node has to also read at least part of the system information (e.g. MIB) of the neighbouring base station. This method requires that the radio network node is equipped with a receiver unit, which is capable of receiving signals transmitted by other radio network node such as base stations. Low power network nodes such as home base stations, relay nodes or pico base stations are generally equipped with a receiver to receive the signals from other base stations, in particular macro base stations.

0109The timing information determined in step <b>520</b> enables network node <b>102</b> to determine when the neighbor cell <b>120</b> is transmitting certain system information, such as a certain SIB, or more specifically the Cell Global Identifier, CGI, contained in SIB<b>1</b> in E-UTRAN. This is because system information is transmitted periodically in certain predefined frames or subframes—for instance, as explained above, in E-UTRAN the MIB and SIB<b>1</b> which contains the CGI are transmitted every 40 ms or every 4^thframe and every 80 ms or every 8^thframe respectively. Thus, by knowing the frame start timing and/or the current SFN of the neighboring base station <b>122</b>, the network node <b>102</b> is able to determine at which future time instances or time periods the neighboring base station <b>122</b> will transmit its system information in neighbor cell <b>120</b>. This information corresponds to the potential occasions or instances when the UE <b>104</b> could create autonomous gaps for acquiring the target cell's <b>120</b> CGI.

0110The network node <b>102</b> thus uses the determined timing information in a step <b>530</b> for predicting at least one autonomous gap occurrence for user equipments served by network node <b>102</b>, which are acquiring system information from the neighbor cell <b>120</b>. In this way, the network node <b>102</b> determines the starting point in time for one or more gap occurrences. However, the timing information does not reveal the duration of each gap, or the total number of gaps used by the UE <b>104</b> for acquiring the system information. The duration and number of gaps are preconfigured in this embodiment. For instance, the duration of each autonomous gap may be preconfigured to be 1, 2, 3, or 4 subframes.

0111Other preconfigured durations are also possible. As for the total number of gaps created, in this embodiment the network node <b>102</b> assumes that the user equipment will use the maximum possible number of autonomous gap occurrences in a measurement period for acquiring the system information such as CGI of the neighbouring base station. For instance, as mentioned above, during a measurement period of 200 ms there will be four or five possible autonomous gap occurrences, depending on when the UE starts to measure. In this embodiment the network node <b>102</b> will assume that all these occurrences will be used. It should be noted that it may be possible for the UE to decode the required system information faster, e.g. using only two out of four possible gap occurrences, in which case the network node <b>102</b> would unnecessarily avoid scheduling the UE during the remaining two or three gaps. However, this is not likely to cause any significant performance reduction.

0112In some variants of this embodiment, the network node <b>102</b> performs a further step <b>550</b>, wherein the network node <b>102</b> requests a user equipment to acquire system information from the neighboring base station <b>122</b>. For example, if the network node <b>102</b> received a PCI in step <b>510</b>, the network node <b>102</b> might determine based on the PCI that the neighboring base station <b>122</b> could be a Home Base Station, but that this cannot be determined with certainty based on the PCI alone. To confirm if the neighbor cell <b>120</b> really is a Home Base Station, the network node <b>102</b> may request UE <b>104</b> to also acquire the CGI of neighbor cell <b>120</b>. However, it should be pointed out that after acquiring timing information for neighboring base station <b>122</b> from UE <b>104</b>, the network node <b>102</b> could alternatively request another UE, e.g. UE <b>106</b> or <b>108</b>, to acquire system information from neighboring base station <b>122</b>. That is to say, network node <b>102</b> may use the timing information from UE <b>104</b> to predict the autonomous gap occurrences for any of the other UEs <b>106</b>, <b>108</b> within cell <b>110</b>.

0113In step <b>560</b>, the network node <b>102</b> schedules a user equipment for data transmission and/or reception in a time period which does not overlap with any predicted autonomous gap occurrence. That is to say, the network node <b>102</b> avoids the gap occurrences during the measurement period when the UE is acquiring system information, by scheduling the UE in a time period that does not coincide with any of the gaps. In one particular variant, the network node <b>102</b> schedules the UE only in time periods that do not coincide or overlap with any of the predicted autonomous gap occurrences. It is pointed out that the user equipment to be scheduled in step <b>560</b> could be the reporting UE <b>104</b>, i.e. the UE that sent the initial measurement report, but it could also be any other UE served by the network node <b>102</b>, provided that the network node <b>102</b> is aware that this UE is currently in a measurement period during which it is attempting to acquire system information from the neighboring base station <b>122</b> using autonomous gaps. That is to say, the predicted gap occurrences for UE <b>104</b> may be used to schedule other UEs. In some variants, the serving network node <b>102</b> may gather statistics from several UEs in order to more accurately determine the timing of the neighboring base station <b>122</b>.

0114A further embodiment of a method in a network node for scheduling data transmission and/or reception will now be described, also with reference to <figref idref="DRAWINGS">FIG. 5</figref>. This embodiment is based on the one described above. However, in this embodiment the duration and/or number of gap occurrences are not preconfigured. Instead, additional information is used to more precisely determine the gap occurrences, i.e., the number of gap instances and/or length, i.e. duration, of each instance.

0115Thus, in the present embodiment steps <b>510</b>, <b>520</b>, <b>530</b>, and the optional step <b>550</b>, are performed in the same way as described above.

0116However, this embodiment comprises an additional step <b>540</b>, wherein the network node <b>102</b> predicts the duration and/or number of the autonomous gap occurrences that will be used by the UE <b>104</b> for acquiring system information from the neighbouring base station <b>122</b>.

0117In some variants of this embodiment, the serving network node <b>102</b> predicts the duration and/or number of gap occurrences based on the SNR of the neighboring base station <b>122</b>. At higher SNR (i.e. higher RSRQ) of the target cell <b>120</b>, the UE requires fewer gaps to decode the CGI. On the other hand, at lower SNR level the UE may require more gaps, and in the worst case may require all possible gaps within the maximum allowed time. The network may maintain a pre-defined mapping between the SNR and the number of measurement gaps required for acquiring the CGI of the target cell for different UE receiver types. The duration of each gap depends on the SNR of neighbor cell <b>120</b> in a corresponding way. That is to say, at a higher SNR, the UE <b>104</b> may be able to decode the system information using fewer subframes than at a lower SNR. At lower SNR levels, a larger gap, i.e. a longer gap, might be needed due to higher noise level and imprecise received timing from a weak target cell.

0118The following paragraphs will describe several ways in which the serving network node <b>102</b> may determine the SNR of the neighboring base station <b>122</b>.

0119In one variant, the serving network node <b>102</b> assumes the lowest allowed SNR of the target cell or neighbor cell <b>120</b> (e.g. SNR=−6 dB) to determine the number of measurement occasions, i.e. autonomous gap occurrences, for a particular receiver type based on the pre-defined mapping.

0120In another variant, the serving network node <b>102</b> determines the SNR based on a signal quality measurement. The signal quality reveals the SNR or signal strength of the target cell. Examples of such measurements are RSRQ and RSRP of the target cell in E-UTRAN and CPICH Ec/No and CPICH RSCP in UTRAN.

0121These signal quality metrics are generally reported with the PCI of the identified target cell in prior art. Alternatively, the serving network node can preconfigure the UE <b>104</b> to report one or more of these measurements whenever a new neighbor cell is identified. Thus, the serving network node <b>102</b> may receive one or more of these metrics as part of the measurement report received in step <b>510</b>. In the present variant, one or more of these signal quality metrics is used in determining or predicting the occurrence of the service gaps, i.e. the autonomous gap occurrences, caused by the UE in decoding the CGI of the target cell. For instance, as mentioned above, the network can maintain a pre-defined mapping between the number of gaps required to decode CGI and the corresponding signal quality, e.g. SNR, RSRQ and RSRP. As stated earlier, the CGI acquisition requires the UE to decode MIB and SIB. Hence, separate pre-defined mapping tables for determining the gaps for decoding the MIB and SIB may be used in some embodiments. Such a mapping table may also be used to predict the size of each gap e.g. whether each gap should be 2 ms or 4 ms long. Hence using the reported measurement and mapping tables, the network node can determine when it is feasible to schedule the UE, i.e., when UE completes the acquisition of CGI. The reported measurement and the mapping table also reveal to the network, i.e. the serving network node <b>102</b>, when the UE will complete the decoding of CGI. For example the UE may require lower overall delay compared to the minimum requirements in case of high SNR. Hence the network can predict when it can resume scheduling a UE which is performing CGI decoding.

0122In another variant, the serving network node <b>102</b> uses the relative quality between the serving cell <b>110</b> and the target cell <b>120</b> to determine the SNR. The UE <b>104</b> may be configured to report an event which is based on the comparison between the serving and target cell signal strength or quality, e.g. when the target cell signal quality is X dB above that of the serving cell <b>110</b>. The UE <b>104</b> also reports the serving cell quality (e.g. RSRQ or RSRP). Using this set of information, the serving network node <b>102</b> may determine the target cell's <b>120</b> signal quality. The derived target cell quality can then be used to determine the number of measurement gaps and/or the length of each gap in time, required for acquiring system information, such as the CGI of the target cell <b>120</b>. It is pointed out that the UE <b>104</b> may report the signal strength or quality of the neighboring base station <b>122</b> relative to that of the serving base station <b>102</b>, or vice versa.

0123In yet another variant, the network node <b>102</b> uses the time required for identifying the PCI of the target cell to determine the signal quality level. For example, at high SNR levels (e.g. 0 dB) the UE <b>104</b> is able to identify the PCI of an unknown neighbor cell in about 50-100 ms in non-DRX, or for DRX in up to 40 ms. However, at a SNR level of −6 dB, the time required to identify the cell is about 800 ms in non DRX state. Thus, by knowing the delay in acquiring the PCI, the network node <b>102</b> may determine the target cell's <b>120</b> SNR, which is turn is used to find the number and/or size, i.e. duration, of each gap for acquiring system information, such as the CGI of that target cell <b>120</b>, for example by using the pre-defined mapping table between SNR and number of gaps and/or length of gaps as described above.

0124In another variant, the serving network node <b>102</b> predicts the duration and/or number of autonomous gap occurrences based on the receiver capability of the user equipment. For instance, if the UE is equipped with a more advanced received, the network node <b>102</b> may assume that it is able to acquire system information using shorter and/or fewer gap occurrences. Advanced receivers, which may be employed in the user equipment, are generally capably of eliminating or minimizing the intra-cell interference or both intra-cell and inter-cell interference. Some of the advanced receivers that may be employed in the user equipment are also capable of eliminating or minimizing the inter-stream interference, which occurs due to the multi-stream transmission in case of Multiple Input Multiple Output (MIMO). These interference cancellation or minimization capabilities of the advanced receivers in the user equipment in turn enhance the measured SINR and enable the acquisition of the information in fewer decoding attempts, i.e. in a shorter time.

0125In another variant, the serving network node <b>102</b> uses knowledge of whether the serving radio base station and the neighboring base station operate on the same or different carrier frequencies to predict the duration of the autonomous gap occurrences. As explained above, the UE is required to switch carrier frequency in order to acquire system information, such as CGI, from an inter-frequency or inter-RAT target cell, and therefore a longer autonomous gap will typically be needed in such situations.

0126In at least one of the variants described above, the network schedules the UE in a step <b>560</b> to avoid sending and/or receiving during the times that the UE is reading the system information. In this regard, the network uses its knowledge of the timing, duration and number of the service gaps, i.e. autonomous gap occurrences, and schedules around those gaps, e.g., the serving node defers scheduling the UE until after the UE reads the system information. It is pointed out that the user equipment to be scheduled in step <b>460</b> could be the reporting UE <b>104</b>, i.e. the UE that sent the initial measurement report, but it could also be any other UE served by the network node <b>102</b>, provided that the network node <b>102</b> is aware that the UE is currently in a measurement period during which it is attempting to acquire system information from the neighboring base station <b>122</b> using autonomous gaps. That is to say, information acquired from one UE may be used to predict autonomous gap occurrences for other UEs. In some variants, the serving network node <b>102</b> may gather statistics from several UEs in order to more accurately determine the timing, duration and/or number of autonomous gap occurrences.

0127In some further variants, the serving network node <b>102</b> uses a predicted duration and/or number of gap occurrences, which has been determined based on measurements from a first UE, only for those other UEs which have similar capabilities as the first UE. and/or are located within a certain distance from the first UE. This is because UEs which have the same or similar receiver capabilities are more likely to require a similar duration and/or number of gaps for decoding, as explained above. Furthermore, UEs which are located closer to each other are more likely to experience a similar SNR with respect to neighboring base station <b>122</b>, and consequently to require a similar duration and/or number of autonomous gaps, than UEs which are located further apart in the cell <b>110</b>. Therefore, in this variant the network node <b>102</b> may be able to predict the duration and/or number of gap occurrences with even higher accuracy.

0128A further embodiment of a method in a network node for scheduling data transmission and/or reception will now be described with reference to <figref idref="DRAWINGS">FIG. 6</figref>. This embodiment is based on the embodiments described above with reference to <figref idref="DRAWINGS">FIG. 5</figref>. Thus, this method may also be executed in a network node <b>102</b>, comprised within a wireless communication network <b>100</b> as shown in <figref idref="DRAWINGS">FIG. 2</figref>.

0129In a first step <b>610</b>, the network node <b>102</b> receives a message from another network node. The message may for instance be received from the neighboring base station <b>122</b>, from a positioning node, or from an O&amp;M node residing within the wireless communication network <b>100</b>. The message comprises information related to the timing of the neighboring base station <b>122</b>, e.g. frame start timing, SFN, relative time difference between the serving cell <b>110</b> and neighbor cell <b>120</b>, or any other data that may be used to derive the neighbor cell timing. In one variant, the message is a positioning-related message.

0130The serving network node <b>102</b> then proceeds to step <b>620</b>, where it determines timing information for the neighbor cell <b>120</b> based on the message received in step <b>610</b>. The determined timing information comprises the frame start timing and/or the System Frame Number, SFN of neighbor cell <b>120</b>.

0131Once the serving network node <b>102</b> has determined the timing of neighboring base station <b>122</b>, it proceeds to predicting one or more gap occurrences in step <b>530</b>, and scheduling the UE in a time period not overlapping with any predicted gap occurrence in step <b>560</b>. Optionally, the serving network node <b>102</b> may also perform steps <b>540</b> and/or <b>550</b>. Steps <b>540</b>-<b>560</b> may be performed in the same way as described in connection with <figref idref="DRAWINGS">FIG. 5</figref> above.

0132A method in a network node for scheduling data transmission and/or reception according to an embodiment of the invention will now be described, with reference to the scenario of <figref idref="DRAWINGS">FIG. 2</figref> and the flowchart in <figref idref="DRAWINGS">FIG. 7</figref>. This embodiment predicts autonomous gap occurrences based on HARQ ACK/NACK feedback from a UE.

0133The method may be executed in network node <b>102</b>, comprised within a wireless communication network <b>100</b> as shown in <figref idref="DRAWINGS">FIG. 2</figref>. The network node <b>102</b> may for instance be an E-UTRAN eNodeB, or an UTRAN NodeB. The network node <b>102</b> serves a cell <b>110</b>, and within this cell three user equipments <b>104</b>, <b>106</b>, <b>108</b> are located.

0134Referring now to <figref idref="DRAWINGS">FIG. 7</figref>, in step <b>710</b> the network node <b>102</b> transmits data to user equipment <b>104</b>, which is located within cell <b>110</b> and being served by network node <b>102</b>.

0135The transmission of data occurs in a time period when the network node <b>102</b> knows or suspects that UE <b>104</b> is attempting to acquire system information from the neighboring base station <b>122</b>. For instance, in an E-UTRAN system the transmission of data in step <b>710</b> may take place during the 200 ms period when UE <b>104</b> is acquiring the CGI of neighboring base station <b>122</b> following a request from the serving network node <b>102</b>.

0136In a variant of this embodiment, the network node <b>102</b> transmits dummy data to the UE in step <b>710</b> to check whether the said UE is currently using autonomous gaps or not for measuring the target cell's CGI, i.e. the transmission does not contain any real data destined for the UE. For instance, in E-UTRAN the network node <b>102</b> may schedule dummy data on PDSCH to UE <b>104</b>. This may be advantageous in a situation where the network node <b>102</b> does not currently have any data pending for transmission to the UE <b>104</b>.

0137In step <b>720</b>, network node <b>102</b> determines whether an autonomous gap occurrence was used by UE <b>104</b> during the time period of the transmission in step <b>710</b>. This determination is based on whether the radio network node <b>102</b> receives HARQ NACK/ACK feedback for the transmitted data.

0138As explained earlier, the HARQ ACK/NACK sent by the UE <b>104</b> to the serving network node <b>102</b> in response to the transmission in step <b>710</b> may reveal whether the autonomous gaps are currently employed by the UE <b>104</b> or not. In particular, if the UE does not respond to downlink transmission from the serving network node <b>102</b> in terms of ACK/NACK feedback, the serving network node <b>102</b> may assume that an autonomous gap occurrence is being used by the UE <b>104</b> for decoding system information, such as the CGI of neighbor cell <b>120</b>. Similarly, if the UE <b>104</b> sends an ACK/NACK response to a downlink transmission, then the network node <b>102</b> may assume that the UE <b>104</b> is not currently creating an autonomous gap occurrence, and hence the network, if needed, may continue scheduling the UE <b>104</b>.

0139Based on the information about past or current gap occurrences which was determined in step <b>720</b>, the network node <b>102</b> predicts in step <b>730</b> at least one autonomous gap occurrence in which its served UEs will autonomously create gaps for acquiring system information from neighboring base station <b>122</b>. That is to say, the network node <b>102</b> predicts that the future gap occurrences will correspond to the past or current gap occurrences. For example, in an E-UTRAN scenario where the UE <b>104</b> is acquiring the ECGI from neighboring base station <b>122</b>, the network node <b>102</b> may predict that the next gap occurrence will occur 40 ms from the last detected gap occurrence, since in E-UTRAN the ECGI is transmitted with a periodicity of 40 ms.

0140In some variants, the network node <b>102</b> may also predict the duration and/or length of the autonomous gaps based on the HARQ ACK/NACK feedback in a step <b>740</b>. For example, the network node <b>102</b> may determine the duration and/or number of times when the UE <b>104</b> did not provide any HARQ feedback, and then predict that the same or a similar duration and/or number of gaps will also apply to future autonomous gap occurrences. As an example, the network node <b>102</b> may repeat steps <b>710</b> and <b>720</b> two or more times to obtain more detailed information as to the duration of the gap and/or the number of occasions. If the network node <b>102</b> has access to UE capability information, this information may also be used to better predict the duration and/or number of gaps required by the UE <b>104</b>, as described in connection with previous embodiments.

0141In other variants, the duration and/or number of the gaps may be preconfigured, e.g. the duration may be assumed to be 2-4 subframes and the number of gaps may be assumed to be all possible gap occurrences, as described above.

0142In some variants of this embodiment, the network node <b>102</b> performs step <b>550</b>, wherein the network node <b>102</b> requests a user equipment to acquire system information from the neighboring base station. This step may be performed in a way similar to that described in connection with previous embodiments.

0143In step <b>760</b>, network node <b>102</b> schedules a user equipment for data transmission and/or reception in a time period which does not overlap with any of the autonomous gap occurrence which were predicted in step <b>730</b>. According to one variant, the UE is scheduled only in time periods which do not coincide with any predicted gap occurrence.

0144In a particular variant of this embodiment, the network node <b>102</b> collects statistics of the HARQ ACK/NACK feedback, i.e. interruption in ACK/NACK when UE <b>104</b> decodes system information such as CGI. This essentially corresponds to performing steps <b>710</b> and <b>720</b> multiple times, and possibly for different user equipments. The network node <b>102</b> uses the statistics to determine the pattern of the autonomous gaps created by the UE <b>104</b> while the UE decodes system information, e.g. CGI, of a target cell <b>120</b> under a certain target cell SNR. A more precise pattern of gaps can be determined by the serving node <b>102</b> by combining the target cell SNR (e.g. RSRQ as explained above) and the HARQ ACK/NACK statistics. Such a pattern based on the statistics and target cell SNR can be used by the network node <b>102</b> in the future when performing scheduling while the UE <b>104</b> acquires system information, e.g. the CGI, of the target cell <b>120</b>.

0145Similarly to previous embodiments, it is pointed out that the user equipment to be scheduled in step <b>760</b> could be the UE <b>104</b>, i.e. the UE that the network node transmitted data to in step <b>610</b>, but it could also be any other UE served by the network node <b>102</b>, provided that the network node <b>102</b> is aware that the UE is currently in a measurement period during which it is attempting to acquire system information from the neighboring base station <b>122</b> using autonomous gaps. That is to say, HARQ ACK/NACK feedback acquired from one or more UEs may be used to predict autonomous gap occurrences for other UEs which are acquiring system information from neighbor cell <b>120</b>, in particular for UEs having similar receiver capabilities.

0146The present embodiment may be combined in various ways with any of the previously described embodiments. As mentioned above, the HARQ ACK/NACK feedback information or statistics described in this embodiment may be combined with SNR and/or UE capability information. Furthermore, the network node <b>102</b> may determine the timing of neighbor cell <b>120</b> in any of the ways described above, and combine this information with HARQ feedback data or statistics to make the prediction of autonomous gap occurrences even more accurate.

0147A method in a network node for scheduling data transmission and/or reception according to an embodiment of the invention will now be described, with reference to the scenario of <figref idref="DRAWINGS">FIG. 2</figref> and the flowchart in <figref idref="DRAWINGS">FIG. 8</figref>. This embodiment predicts autonomous gap occurrences based on CSI feedback reports from a UE.

0148In prior art, the serving network node <b>102</b> may configure a UE <b>104</b> to periodically report one or more types of channel state information (CSI), which reveals downlink channel or radio conditions. These measurements are done over the downlink signals from the serving cell <b>110</b> and reported to the serving radio network node <b>102</b>, which in turn uses this for various purposes such as for scheduling, resource allocation, link adaptation, antenna selection in case of MIMO, rank adaptation in case of MIMO etc. Examples of CSI are channel quality indicator (CQI), pre-coding matrix index (PMI), rank indicator (RI) etc.

0149The method may be executed in network node <b>102</b>, comprised within a wireless communication network <b>100</b> as shown in <figref idref="DRAWINGS">FIG. 2</figref>. The network node <b>102</b> may for instance be an E-UTRAN eNodeB, or an UTRAN NodeB. The network node <b>102</b> serves a cell <b>110</b>, and within this cell three user equipments <b>104</b>, <b>106</b>, <b>108</b> are located.

0150Referring now to <figref idref="DRAWINGS">FIG. 8</figref>, in step <b>810</b> the network node <b>102</b> monitors received reports of Channel State Information, CSI, from a user equipment <b>104</b>, which is served by the network node <b>102</b> and which is currently attempting to acquire system information from the neighboring base station <b>122</b>.

0151In some variants of this embodiment, the serving network node <b>102</b> starts monitoring the CSI reporting pattern from the UE <b>104</b> after requesting the UE <b>104</b> to acquire the target cell's <b>120</b> system information, e.g. CGI.

0152In step <b>820</b>, the network node <b>102</b> determines whether an autonomous gap occurrence was created by the user equipment <b>104</b>, based on the presence or absence of a CSI report in the time period during which the network node <b>102</b> is monitoring received CSI reports. That is to say, if the network node <b>102</b> receives a CSI report it may assume that the UE <b>104</b> was not using an autonomous gap occurrence in the time instance when the CSI report was generated, and conversely if the network node <b>102</b> does not receive a CSI report when expected, the network node <b>102</b> may infer that the UE <b>104</b> was prevented from sending a CSI report because of an autonomous gap occurrence.

0153Based on the information about past or current gap occurrences which was determined in step <b>820</b>, the network node <b>102</b> predicts in step <b>830</b> at least one autonomous gap occurrence in which its served UEs will use autonomously created gap occurrences for acquiring system information from neighboring base station <b>122</b>. That is to say, the network node <b>102</b> predicts that the future gap occurrences will correspond to the past or current gap occurrences.

0154In some variants, the duration and/or number of the autonomous gaps may be preconfigured, i.e. the duration may be assumed to be 2-4 subframes and the number of gaps may be assumed to be all possible gap occurrences, as described above. In other variants, the duration and/or number of gaps is predicted, for instance based on the presence or absence of several CSI reports. The duration and/or number of gaps may also be determined in any of the ways described above, e.g. based on SNR, UE receiver capability, etc.

0155In step <b>860</b>, network node <b>102</b> schedules a user equipment for data transmission and/or reception in a time period which does not overlap with any of the autonomous gap occurrences which were predicted in step <b>830</b>. According to one variant, the UE is scheduled only in time periods which do not coincide with any predicted gap occurrence.

0156In some variants of this embodiment, the network node <b>102</b> collects statistics of the CSI reporting interruptions, and uses these statistics to determine the pattern of the autonomous gaps created by the UE <b>104</b> while the said UE decodes the system information, e.g. CGI, of a target cell <b>120</b> under certain target cell's SNR. A more precise pattern of gaps can be determined by the serving node <b>102</b> by combining the target cell SNR (e.g. RSRQ as explained above) and the CSI interruption statistics. Such a pattern based on the CSI interruption statistics and target cell SNR may be used by the network node <b>102</b> in the future when performing scheduling while the UE <b>104</b> acquires the CGI of the target cell.

0157The present embodiment may be combined in various ways with one or more of the previously described embodiments to obtain more detailed or accurate information about the timing, duration and/or number of gaps. For example, the CSI interruption statistics may be combined with one or more of neighbor cell timing, UE capability information, and/or neighbor cell SNR measurements, which may all be determined as described above.

0158A method in a user equipment according to an embodiment of the invention will now be described, with reference to the scenario of <figref idref="DRAWINGS">FIG. 2</figref> and the flowchart in <figref idref="DRAWINGS">FIG. 9</figref>. In this embodiment, an explicit message is sent from the UE, comprising information about a past or current autonomous cap occurrence. The serving network node may use this information to predict future autonomous gap occurrences.

0159The method is executed in a user equipment <b>104</b>, comprised within a wireless communication network <b>100</b> as shown in <figref idref="DRAWINGS">FIG. 2</figref>, and being served by a radio network node <b>102</b>. The serving radio network node <b>102</b> may be an E-UTRAN eNodeB, an UTRAN NodeB or an UTRAN RNC.

0160In a step <b>910</b>, the user equipment <b>104</b> performs a measurement on a signal received from a neighboring base station <b>122</b>. In one variant the step of performing a measurement comprises reading system information, such as the Cell Global Identifier, CGI, of the neighboring base station <b>122</b>.

0161In step <b>920</b>, the user equipment <b>104</b> determines, based on the measurement, at least one autonomous gap occurrence during which the user equipment will autonomously create gaps for acquiring system information, e.g. CGI, from the neighboring base station <b>122</b>.

0162In some variants of this embodiment, the serving radio network node <b>102</b> explicitly requests the UE <b>104</b> to supply information about the autonomous gap occurrence, and the UE <b>104</b> receives this request in a step <b>930</b>. However, it is also possible for the UE to proceed directly from step <b>920</b> to step <b>940</b> without receiving any request from the network node. Furthermore, it should be noted that the request from the network node may also be received before step <b>910</b> is performed, or alternatively between steps <b>910</b> and <b>920</b>.

0163In step <b>940</b>, the user equipment <b>104</b> transmits information to the network node <b>102</b> indicating the at least one autonomous gap occurrence. For example, the information indicating the autonomous gap occurrence may comprise at least one of the starting time or subframe, the number of gaps, the duration of each gap and the total duration to acquire the system information. In a particular variant of this embodiment, the information about the autonomous gap occurrence signalled by the UE <b>104</b> in step <b>940</b> corresponds to the actual autonomous gap occurrence which was used by the UE <b>104</b> for acquiring the system information of the neighbouring base station <b>122</b>. The information about the autonomous gap occurrence signalled by the user equipment also includes an identifier of the neighbouring base station, e.g. CGI and/or PCI.

0164In a variant of this embodiment, the information about the autonomous gap occurrence is separately reported by the user equipment to the network node <b>102</b> for gaps created in the uplink and downlink. An advantage of this approach is that the user equipment may report the information about the autonomous gap occurrence anytime, without waiting for the normal measurement reporting instances.

0165According to some variants, the information about the autonomous gap occurrence is signalled by the UE <b>104</b> when reporting measurements such as downlink signal quality, downlink signal strength, physical cell identity or global cell identity etc. This approach has an advantage of reduced signalling overhead, since the information about the gap occurrence is piggybacked with the normal measurement reports.

0166The information transmitted to the network node <b>102</b> in step <b>940</b> enables the network node <b>102</b> to make predictions about future gap occurrences for this UE or other served UEs. The reported information about the autonomous gap occurrence may also be used by the network to perform site planning and/or setting radio parameters, such as the transmitted power in the base station. For examples the network can increase the transmit power level of a base station which generally requires user equipments to create more gaps than a certain threshold for acquiring its SI. The increase in the base station's transmitted power level may improve the SINR experienced by the user equipment, thereby reducing the length of the measurement period required for acquiring the SI of the base station.

0167A method in a radio network node for scheduling data transmission and/or reception according to an embodiment of the invention will now be described, with reference to the scenario of <figref idref="DRAWINGS">FIG. 2</figref> and the flowchart in <figref idref="DRAWINGS">FIG. 10</figref>. In this embodiment, the radio network node receives an explicit message from the UE, comprising information about a past or current autonomous cap occurrence, and uses this information to predict future autonomous gap occurrences.

0168The method is executed in a radio network node <b>102</b>, comprised within a wireless communication network <b>100</b> as shown in <figref idref="DRAWINGS">FIG. 2</figref>. The radio network node <b>102</b> serves a user equipment <b>104</b>. The serving radio network node <b>102</b> may be an E-UTRAN eNodeB, an UTRAN NodeB or an UTRAN RNC.

0169In step <b>1020</b>, the network node <b>102</b> receives information from the user equipment (<b>104</b>) indicating at least one autonomous gap occurrence, during which the user equipment <b>104</b> will autonomously create gaps for acquiring system information from a neighboring base station <b>122</b>. For example, the information indicating the at least one autonomous gap occurrence may comprise one or more of: the starting point of the gap occurrence, e.g. in the form of a subframe number, the end point or duration of a gap occurrence, and the number of gap occurrences used during a system information measurement period. In some variants, the information indicating the autonomous gap occurrence is received in conjunction with a measurement report from the user equipment <b>104</b>, for instance a neighbor cell report.

0170In step <b>1030</b>, the network node <b>102</b> predicts at least one autonomous gap occurrence in which user equipments served by the radio network node <b>102</b> will use autonomously created gaps for acquiring system information from the neighboring base station <b>122</b>. The prediction is based on the information received in step <b>1020</b>, i.e. the network node <b>102</b> assumes that future gap occurrences will follow the same pattern as the gap occurrence indicated in step <b>1020</b>. In some variants, the prediction may be further improved by combining this method with any of the previously described embodiments. For instance, timing information related to neighboring base station <b>122</b> may be obtained and used to predict the starting point of the gaps. Furthermore, UE receiver capability information, SNR, or other metrics may be used to more accurately predict the duration and/or number of autonomous gaps. It is also possible to combine the present embodiment with information gathered from HARQ/NACK feedback report, or CSI reporting patterns, as already explained above.

0171In step <b>1040</b>, the network node <b>102</b> schedules a user equipment for data transmission and/or reception in a time period which does not overlap with any predicted autonomous gap occurrence. It should be noted, as for previous embodiments, that the UE to be scheduled may be the user equipment <b>104</b>, or another UE which is acquiring system information from the neighboring base station <b>122</b>.

0172In some variants of this embodiment, a further step <b>1010</b> is performed before step <b>1020</b>. In step <b>1010</b>, the network node <b>102</b> requests the user equipment <b>104</b> to signal the information indicating the at least gap occurrence.

0173As stated earlier, all of the above embodiments may also be used to determine the autonomous gaps which are created by the UE for reading the target cell system information when UE is in DRX state. In E-UTRAN the DRX cycles may range from 10 ms to 2.56 seconds.

0174The network may configure the UE with a DRX cycle such that the DRX ON period does not coincide or overlap with the scheduling of system information (SI), especially the MIB and required SIB (e.g. SIB<b>1</b> in E-UTRAN when reading the CGI), which are to be read by the UE, in the target cell. This will ensure that the UE does not create autonomous gaps during the DRX ON periods of the DRX cycle, since these gaps are meant to read the SI. The UE opens its receiver for the reception of the data from the serving cell during the DRX ON period, which may comprise between a few OFDM symbols up to few sub-frames in E-UTRAN.

0175For instance, the periods when the SI is being transmitted in the target cells, i.e. the periods when autonomous gap occurrences may be used, may be determined using any of the methods described above. Accordingly, the DRX cycle is configured to avoid conflict between the DRX ON period and the autonomous gaps. This can be easily achieved in a synchronous network since all the cells have the same transmit timing. However in an asynchronous network, the serving network node can set the DRX cycle to avoid, to the extent possible, the conflict with the scheduling of the SI and thus with the potential autonomous gaps when the UE reads the SI. The network may also adjust the DRX cycle to avoid such a conflict with the scheduling of the SI at the target cell when the network node requests the UE to read the SI of the target cell. Another possibility is to use the same measurement period for decoding the CGI of the target cell in non DRX and for all DRX cycles, regardless of their length. This will ensure that the UE performs the CGI decoding in a shorter time, and thus the risk that the DRX ON period coincides with the autonomous gaps is minimized.

0176Thus, any of the previously described methods executed in a network node may comprise a further step of configuring the DRX cycle of the user equipment to be scheduled, such that the DRX ON periods do not overlap with any predicted autonomous gap occurrence. In a further variant, the same duration is used for acquiring the system information of the neighbouring base station regardless whether DRX is used or not, and regardless of the length of the DRX cycle when DRX is used.

0177<figref idref="DRAWINGS">FIG. 11</figref> is a block diagram of a base station <b>1100</b> according to particular embodiments of the invention. The example base station provides a non-limiting illustration of communication and processing circuits used in carrying out the network-side of the present invention in one or more embodiments. However, it should be noted that other network nodes may be involved.

0178Further, those of ordinary skill in the art will appreciate that the example base station may well include elements not shown in the simplified illustration—e.g., additional communication interfaces and processing/control circuitry.

0179Those of ordinary skill in the art will also appreciate that the base station may be implemented using fixed and/or programmable circuitry. In one embodiment, the apparatus includes one or more microprocessors, digital signal processors, or other digital processing circuits, along with associated program and data memory. As such, the term “circuitry” should be understood as encompassing discrete electronic circuits and/or integrated electronic circuits (whether fixed or programmable).

0180For example, in the illustration, the apparatus <b>1100</b> comprises one or more processing circuits <b>1120</b> that are configured to implement at least some of the network-side processing disclosed herein for the present invention. Those one or more processing circuits—e.g., the signalling control circuitry, the gap estimation processor, and the scheduling processor—may be at least partly implemented using programmable digital processing circuits. For example, these functions may be implemented in one or more microprocessors, signal processors, or other computer circuits.

0181In a particular example, the base station's processing circuits <b>1120</b> are configured to implement the gap timing estimation and corresponding scheduling controls based on the execution of stored computer program instructions. In that regard, it will be appreciated that these base station processing circuits <b>1120</b> are specially adapted or otherwise configured to carry out the processing disclosed herein, irrespective of whether they comprise fixed or programmable circuitry, or any mix thereof. It will also be appreciated that the base station <b>1100</b> includes or has access to memory or another computer-readable medium, for storing configuration and operating data, which can include information at least some of the static/semi-static and dynamic information described herein—some static information may be provisioned or otherwise pre-stored in the base station for its use during operation.

0182In one embodiment, the illustrated base station <b>1100</b>, or variations of it, is configured to implement a method of improved data scheduling comprising:

0183determining timing information regarding gaps in service with the user equipment, as caused by the user equipment measuring system information for a neighboring target cell; and

0184adapting scheduling of data transmissions to or from the user equipment as a function of the determined timing information.

0185In one embodiment, said determining comprises estimating, calculating, or otherwise predicting the timing, number, period, or other characteristics of such gaps, based on static or semi-static information. Such information comprises knowledge of transmission frame/sub-frame start timing in the neighboring cells, the scheduling of such information in the neighboring cells, the user equipment's capabilities, e.g., as regards its measurement of such information, etc. Further, the determination accuracy is enhanced in one or more embodiments, by basing the determination on dynamic information, such as signal qualities, timing differences, etc.

0186In another embodiment, the one or more processing circuits <b>1120</b> are configured to predict at least one autonomous gap occurrence in which user equipments served by the radio network node <b>1100</b> will use autonomously created gaps for acquiring system information from a neighboring base station and during which the UE is not able to receive data from, and/or transmit data to, the radio network node, and further configured to schedule a user equipment for data transmission and/or reception in a time period which does not overlap with any predicted autonomous gap occurrence. In a variant of this embodiment, the one or more processing circuits <b>1120</b> are further configured to request the user equipment to read system information from the neighboring base station.

0187In a further variant, the one or more processing circuits <b>1120</b> are further configured to determine when the neighboring base station transmits system information. For example, the one or more processing circuits <b>1120</b> may be configured to determine timing information for the neighbouring base station, the timing information comprising at least one of frame start timing and the System Frame Number, SFN. In a variant, the one or more processing circuits <b>1120</b> are further configured to determine timing information based on a measurement report received from a reporting user equipment, which is served by the radio network node, and wherein the measurement report relates to the neighboring base station. In a further variant, the one or more processing circuits <b>1120</b> are configured to determine the frame start timing and the SFN are determined based on a message received from another network node. In an alternative variant, the one or more processing circuits <b>1120</b> are configured to determine the timing information by performing correlation over a pre-defined set of synchronization and/or pilot signals transmitted by the neighbouring base station. In some variants, the one or more processing circuits <b>1120</b> are further configured to predict the duration and/or number of autonomous gap occurrences. For instance, the one or more processing circuits <b>1120</b> may be configured to predict the duration and/or number of autonomous gap occurrences based on the downlink signal strength or quality of the base station reported by the reporting user equipment. Furthermore, the one or more processing circuits <b>1120</b> may be configured to predict the duration and/or number of autonomous gap occurrences based on the time required by the reporting user equipment to identify the physical layer identity of the neighbouring base station. The one or more processing circuits <b>1120</b> may also be configured to predict the duration and/or number of autonomous gap occurrences based on the receiver capability of the reporting user equipment. Furthermore, the one or more processing circuits <b>1120</b> may be configured to predict the duration and/or number of autonomous gap occurrences based on whether the serving radio radio network node and the neighboring base station operate on the same or different carrier frequencies. Alternatively, the duration and/or number of autonomous gap occurrences may be preconfigured. For instance, the preconfigured duration of the autonomous gap occurrences may be between 2 and 4 subframes. The number of autonomous gap occurrences may be configured to be the maximum number of autonomous gap occurrences possible within a measurement period.

0188In some variants, the one or more processing circuits <b>1120</b> are configured to transmit data during a certain time period to a user equipment, which is served by the radio network node and which has been requested to read system information from the neighboring base station. Furthermore, the one or more processing circuits <b>1120</b> are configured to determine, based on whether the radio network node receives HARQ NACK/ACK feedback for the transmitted data, whether an autonomous gap occurrence was used in the certain time period. In some variants, the one or more processing circuits <b>1120</b> are configured to transmit dummy data during the certain time period.

0189In some variants, the one or more processing circuits <b>1120</b> are configured to monitor the received reports of Channel State Information, CSI, from a user equipment, which is served by the radio network node and which has been requested to read system information from the neighboring base station. Furthermore, the one or more processing circuits <b>1120</b> are configured to determine whether an autonomous gap occurrence was created by the user equipment, based on the presence or absence of a CSI report in a certain time period.

0190In some variants, the one or more processing circuits <b>1120</b> are further configured to configure the DRX cycle of the user equipment to be scheduled such that the DRX ON periods do not overlap with any predicted autonomous gap occurrence. In some variants, the one or more processing circuits <b>1120</b> are configured to use the same measurement period for acquiring the system information of the neighbouring base station regardless whether DRX is used or not and regardless of the length of the DRX cycle when DRX is used.

0191In yet another embodiment, the one or more processing circuits <b>1120</b> are configured to receive information from a user equipment being served by the radio network node <b>1100</b>, the information indicating at least one autonomous gap occurrence, during which the user equipment will autonomously create gaps for acquiring system information from a neighboring base station, and further configured to predict at least one autonomous gap occurrence in which user equipments served by the radio network node <b>1100</b> will use autonomously created gaps for acquiring system information from the neighboring base station. Furthermore, the processing circuits <b>1120</b> are configured to schedule a user equipment for data transmission and/or reception in a time period which does not overlap with any predicted autonomous gap occurrence. In some variants, the one or more processing circuits <b>1120</b> are further configured to request the user equipment to signal the information indicating the at least gap occurrence.

0192<figref idref="DRAWINGS">FIG. 12</figref> is a schematic block diagram illustrating an example item of user equipment, such as cellular telephone, smart phone, PDA, network modem card, or essentially any other wireless communication apparatus. One sees that the example UE <b>1200</b> includes a transceiver <b>1230</b> for receiving DL signals, i.e. control and data, from a supporting network, and for sending UL signals, i.e. control and data, to that network. One also sees various processing and control circuits <b>1220</b>, for processing and responding to received control and data, and for generating control and data for transmission. In particular, the UE may include measurement circuitry for measuring various received signal parameters, and for obtaining system information from neighboring target cells.

0193Those ordinarily skilled in the art will appreciate that the UE <b>1200</b> of <figref idref="DRAWINGS">FIG. 11</figref> may be implemented using fixed or programmable circuits, or both, and that in one or more embodiments, the UE <b>1200</b> includes one or more microprocessors, digital signal processors, or other such digital processing circuits, and that the UE <b>1200</b> may store computer program instructions, which, when executed, cause the UE <b>1200</b> to perform as described herein.

0194In one embodiment, the illustrated user equipment <b>1200</b>, or variations of it, comprises one or more processing circuits <b>1220</b>, configured to perform a measurement on a signal received from a neighboring base station, and to determine, based on the measurement, at least one autonomous gap occurrence during which the user equipment will autonomously create gaps for acquiring system information from a neighboring base station, and to transmit information to the radio network node serving the user equipment <b>1200</b>, the information indicating the at least one autonomous gap occurrence.

0195In some variants, the one or more processing circuits <b>1220</b> are further configured to report the information about the autonomous gap occurrence separately for gaps created in the uplink and downlink.

0196In some variants, the one or more processing circuits <b>1220</b> are configured to signal the information about the autonomous gap occurrence when reporting measurements, such as downlink signal quality, downlink signal strength, physical cell identity or global cell identity etc.

0197In some variants, the one or more processing circuits <b>1220</b> are configured to signal the information about the autonomous gap occurrence when requested by the serving radio network node.

0198When using the word “comprise” or “comprising” it shall be interpreted as non-limiting, i.e. meaning “consist at least of”.

0199This disclosure refers interchangeably to acquiring system information from a cell, or from a node (e.g. a NodeB or eNodeB). For completeness, it is pointed out that while the system information is transmitted from a physical node (e.g. NodeB or eNodeB), certain information, such as the CGI or E-CGI may be associated with a particular cell which is being served by that node. In particular, one base station may serve several cells or cell sectors, in which case the base station may transmit different system information in the various cells. Furthermore, a “neighboring base station” or “neighboring node” within the context of this disclosure should be understood as a base station or node which serves a neighboring cell. Thus, the physical base station or node does not necessarily need to be located in close proximity to the measuring user equipment.

0200The present invention is not limited to the above-describe preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appending claims.

0201In particular, it should be noted that the embodiments of the invention in this disclosure apply to various scenarios such as for intra-frequency, inter-frequency, inter-RAT, e.g. when serving and target cells belong to E-UTRA FDD and TDD respectively or vice versa, or when serving and target cells belong to E-UTRA and UTRA respectively or vice versa. Furthermore, the embodiments described above apply to the UE, which is decoding system information such as the CGI of the target cell, when it is in DRX state as well as in non DRX state. In addition, the invention applies when autonomous gaps are used by the UE to acquire the system information of any type of target cell i.e. home base station, pico base station or any base station in a heterogeneous network environment. Also, the underlying aspects of the invention apply when the UE is acquiring the CGI of the target cell for any other purpose such as for automatic neighbor relation as part of a self organizing network (SON). Broadly, the principles of the invention apply to any case where a UE reads the system information of a neighbor cell or target cell for any purpose, and thereby creates gaps in the downlink and/or uplink service with the serving node.