GB2493290A - Forming a common relative grant channel monitoring set of neighbour cells up to an upper limit of neighbour cells - Google Patents

Abstract

A wireless device receives an upper limit from a network entity which indicates a maximum number of neighbour cells to be monitored (200). Common pilot channels from a plurality of neighbour cells in a neighbour cell list are monitored (202) and those neighbour cells which have a common pilot channel that satisfies a predetermined criterion (204) are included in a common relative grant monitoring set (206), the common relative grant channel monitoring set having a number of neighbour cells less than or equal to the upper limit. If the number of neighbour cells exceeds the upper limit, then the best quality neighbour cells are included in the common relative grant channel monitoring set up to the upper limit. The common relative grant channels of the neighbour cells in the common relative grant channel monitoring set are monitored to receive relative grant information from those neighbour cells (208).

Description

METHOD, APPARATUS AND

COMPUTER PROGRAM FOR A WIRELESS DEVICE

Technical Ficid The present invention relates to a method of operating a wireless device in a communications network, and apparatus and a computer program therefor.

Background

The following is a list of acronyms that have been uscd throughout this

specification:

3GPP 3rd Gcncration Partnership Project Ec/No a ratio of the reccivcd energy per chip to thc total received powcr spectral density F-DC-I Enhanced Dedicated Channel E-RGCI-1 E-DCH Relative Grant Channel EUTRAN Evolved UMTS Terrestrial Radio Access Network FACH Forward Access Channel NCL Neighbour Cell List RF radio frequency RGCH Relative Grant Channel RSCP Received Signal Code Power tiE user equipment UMTS Universal Mobile Telecommunications System UTRAN UMTS Terrestrial Radio Access Network Wireless networks have in recent years experienced a considerable increase in the amount of data bcing transmitted to and from wirelessly connected devices or "user equipment" (HE). The traffic characteristics of this data traffic are very different from that of traditional mobile phones, and can be characterised by its use of a lot of background signalling and bursty traffic consisting of relatively small data packets. The introduction of machine-type communications to the networks can also be expected to IblIow this trend. As a result, wireless networks need to implement new mechanisms to cope with this new traffic and make efficient use of the available resources while providing high capacity and thmughputs and minimum delays. Of particular concern in improving the support of this low volume, bursty data is mininiising the signalling load on the network and improving the power consumption of the user equipment.

In general, in many types of wireless systems, the user equipment is typically in one of a number of predefined activity states. These may be fbr example an idle state, a paging state in which the user equipment checks a paging channel for incoming paging messages at predefined time intervals, and one or more data connection states in which the user equipment can actively transmit and receive data.

In general, these states use increasingly more power at the user equipment and also more network signalling. In order to minimise power consumption, particularly to maximise battery life before recharging is required, the user equipment is often caused to operate in a state having a low or the lowest power consumption possible, depending on fbr example the operational demands of the user equipment and/or network requirements. A particular concern from the perspective of the wireless network operator is to keep down the amount of control signals that have to be passed to and flDm the user equipment in order to cause the user equipment to transition between states, and/or to allow the user equipment to send or receive data, and/or to locate the user equipment.

Therefore, when a TIE is sending or receiving data, although there are advantages to the UE operating in a particular state that happens to be a high power state, it may be desirable for the Ut to operate in a lower power state so that the Ut's power consumption is minimised. For example, in UTRAN, a UE can operate either in a CELL_DCH state or in a lower power CELL_FACH state when transmitting or receiving data. In general, a CELL_DCH state is a state in which the UE has a dedicated channel 1kw transmitting and receiving data to and from a Node B. In contrast, a UE operating in a CELL_FACH state uses a channel which is shared with other UEs when transmitting and receiving data.

A TIE that is operating in CELL DCH state that is near a cell edge can cause interference with transmissions from a neighbour cell (known as "inter-cell interference"). To mitigate inter-cell interference, the TJE in the CELL DCH state adds neighbour cells to an "E-DCH active set". The neighbour cells of the E-DCH active set are thcn used in a power control mechanism for controlling the UE's transmission powcr.

It has been proposed that, for a UE in a CELL EACH state, a common Enhanced-Dedicated Channcl (E-DCH) resource can be aflocated to the UE. A common E-DCH rcsourcc is a plurality of E-DCH channels (transport channels used to transport data), which can be temporarily allocated to a UE in thc CELL FACH statc. Historically, a LIE in CELL_EACH state has not had any mechanisms to control inter-cell interfercnce. This was bccausc the TIE was not cxpccted to occupy a common E-DCH resource for lengthy periods of time and therefore was not expected to contribute significantly to inter-cell interference. More recently, it has been proposed that when a TIE is in the CELL FACH state and has been allocated a common E-DCH resource, the UE can determine which of the relative grant channels of neighbour cells included in a neighbour cell list (NCL) should be monitored based on determined measurements of those neighbour cells satisfying specified criteria (which could be all of the neighbour cells in the NCL) in order to deal with inter-cell interference. The liE receives relative grants via the relative grant channels of the neighbour cells. The received relative grants indicate whether the TIE should decrease or maintain its transmission power and, assuming that this particular UE is contributing to inter-cell interference (i.e. the neighbour cell does not know which TIE is contributing to inter-cell interference but merely broadcasts its relative grants to all TIEs who are monitoring the common relative grant channels, the relative grants can thereby be used to help mitigate inter-cell interference. The liE monitors the relative grant channels until the common E-DCH resource is released, at which point these channels are no longer monitored.

However, the liE tends to consume high levels of battery power when monitoring these neighbour cells. Also, as the UE continues to monitor these neighbour cells up until the common E-DCH is released, it is possible that, over time, the transmissions from one or more neighbour cells could weaken (e.g. due to the liE moving away from particular neighbour cells). This could result in the liE receiving false information from the one or more neighbour cells having weak transmissions and the received false information could therefore negatively impact any desired adjustment to the UE's transmission power.

Summary

According to a first aspect the present invention, there is provided a method of operating a wireless device in a cellular comnmnications network, the method comprising: receiving an upper limit from a network entity, the upper limit indicating a maximum number of neighbour cells to be monitored by the wireless device monitoring common pilot channels from a plurality of neighbour cells in a neighbour cell list; determining which of the plurality of neighbour cells have a common pilot channel that satisfies a predetermined criterion; forming a common relative grant channel monitoring set of neighbour cells, wherein the common pilot channel of each of said neighbour cells satisfies the predetermined criterion, the common relative grant channel monitoring set having a number of neighbour cells less than or equal to the upper limit, wherein if thc number of neighbour cells whose common pilot channel satisfies the predetermined criterion exceeds the upper limit, then the best quality neighbour cells are included in the monitoring set up to the upper limit of neighbour cells; and monitoring common relative grant channels of the neighbour cells in the common relative grant channel monitoring set to receive relative grant information from those neighbour cells.

Receiving an upper limit from a network entity, such as a Radio Network Controller (RNC) or the like, allows the network entity to have an element of control over a maximum number of neighbour cells that can be monitored by a wireless device such as a UE.

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The method may comprise determining that a neighbour cell listed in the common relative grant channel monitoring set has a common pilot channel that satisfies a second predetermined criterion and, in response, stopping the monitoring of the common relative grant channel of that neighbour cell.

The method may comprise removing the neighbour cell that satisfies the second predetermined criterion from the common relative grant channel monitoring set. This ensures that the common relative grant channel monitoring set is kept up-to-date so that the UE does not take into account the relative grants from neighbour cells that satisfy the second predetermined criterion.

The quality of a neighbour cell may be determined according to a measured result of the common pilot channel, the measured result relating to a measurement quantity comprising at least one of a Ec/No, a received signal code power, and a pathloss between the neighbour cell and the user equipment. These are measured results or parameters of a Common Pilot Channel (CPICH) of a neighbour cell that can be assessed to establish whether the common relative grant channel of that neighbour cell is suitable for monitoring.

The common relative grant channel monitoring set may comprise neighbour cells for which common Enhanced Dedicated Channel Relative Grant Channels are monitored. Relative grant information may be received via the common Enhanced Dedicated Channel Relative Grant Channels. The UE may control its traasmission power in accordance with the relative grant information received from the neighbour cells in the common RGCH monitoring set.

The common pilot channel may satis' the predetermined criterion when a measured result of the common pilot chann& is determined to be within a specified reporting range.

The received upper limit may comprise a reporting deactivation threshold, which is provided to the wireless device for event-triggered measurement. The reporting deactivation threshold is a parameter that is defined in 3GPP as the maximum number of cells allowed in an "active set" in order for measurement reports to be triggered by "event IA" criteria, which may for example be used in a handover procedure. Therefore, re-using this parameter to limit the size of the number of neighbour cells that are to be monitored for relative grants reduces the complexity of the UTRAN system because thither parameters do not need to be defined. This also keeps down the amount of signalling across the network that is required.

According to a second aspect of the present invention there is provided apparatus comprising a processing system for a wireless device constructed and arranged to cause the wireless device to: monitor common pilot channels from a plurality of neighbour cells in a neighbour cell list; determine which of the plurality of neighbour cells have a common pilot channel that satisfies a predetermined criterion; form a common relative grant channel monitoring set of neighbour cells, wherein the common pilot channel of each of said neighbour ccfls satisfies the predetermined criterion, the common relative grant channel monitoring set having a number of neighbour cells less than or equal to an upper limit provided by a network entity, wherein if the number of neighbour cells whose common pilot channel satisfies the predetermined criterion exceeds the upper limit, then the best quality neighbour cells arc included in the common relative grant channel monitoring set up to the upper limit of neighbour cells; and monitor common r&ativc grant channels of the neighbour cells in the common relative grant channel monitoring set to receive relative grant information from those neighbour cells.

The processing system described above may comprise at least one processor and at least one memory including computer program instructions, the at least one memory and the computer program instructions being configured to, with the at least one processor, cause the apparatus at least to perform as described above.

According to a third aspect of the present invention there is provided a computer program comprising instructions such that when the computer program is executed on a wireless device, the wireless device is arranged to: monitor common pilot channels from a plurality of neighbour cells in a neighbour cell list; determine which of the plurality of neighbour cells have a common pilot channel that satisfies a predetermined criterion; form a common relative grant channel monitoring set of neighbour cells, wherein the common pilot channel of each of said neighbour cells satisfies the predetermined criterion, the common relative grant channel monitoring set having a number of neighbour cells less than or equal to an upper limit provided by a network entity, wherein if the number of neighbour cells whose common pilot channel satisfies the predetermined criterion exceeds the upper limit, then the best quality neighbour cells are included in the common relative grant channel monitoring set up to the upper limit of neighbour cells; and monitor common relative grant channels of the neighbour cells in the common relative grant channel monitoring set to receive relative grant information from those neighbour cells.

There may be provided a non-transitory computer-readable storage medium having the instructions mentioned above stored thereon.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 shows a schematic block diagram of an example of a system architecture according to an embodiment of the present inventiom

S

Figure 2 shows a schematic state flow diagram of processes that occur in an example of a method according to an embodiment of the present invention; and Figure 3 shows a schematic state flow diagram of processes that occur in a second example of a method according to an embodiment of the present invention.

Detailed Description

"Wireless devices" include in general any device capablc of connecting wirelessly to a network, and includes in particular mobile devices including mobile or cell phones (including so-called "smart phones"), personal digital assistants, pagers, tablet and laptop computers, content-consumption or generation devices (for music and/or video for example), data cards, USB dongles, etc., as well as fixed or more static devices, such as personal computers, game consoles and other generally static entertainment devices, various other domestic and non-domestic machines and devices, etc. The term "user equipmcnt" or UE is often used to refer to wireless devices in general, and particularly mobile wireless devices.

Reference will sometimes be made in this specification to "network", "network control apparatus" and "base station". In this respect, it will be understood that the "network control apparatus" is the overall apparatus that provides for general management and control of the network and connected devices, Such apparatus may in practice be constituted by several discrete pieces of equipment. Moreover for convenience and by convention, the terms "network", "network control apparatus" and "base station" will often be used interchangeably, depending on the context.

Figure 1 shows schematically a UE or wireless device, in this case in the form of a mobile phone/smartphone 100. The user equipment 100 contains the necessary radio module 102, processor(s) and memorytmemories 104, antenna 106, etc. to enable wireless communication with the network. The user equipment 100 in use is in communication with a radio mast 108. As a particular example in the context of UMTS (Universal Mobile Telecommunications System), there may be a network control apparatus 110 (which may be constituted by for example a so-called Radio Network Controller) operating in conjunction with one or more Node Bs (which, in many respects, can be regarded as "base stations"). As another example, LTE (Long Term Evolution) makes use of a so-called evolved Node B (eNB) where the RF transceiver and resource management/control frmnctions are combined into a single entity. The term "base station" is used in this specification to include a "traditional" base station, a Node B, aa evolved Nodc B (cNB), or any other access point to a network, unless thc contcxt requires othcrwisc. The network control apparatus 110 (of whatever typc) may have its own proccssor(s) 112 and memory/memories 114, etc. Figure 2 shows a schematic state flow diagram of an example of a method of operating a wireless device such as a UE in a ceflular communications network such asLJTRAN.

At step 200, the UE receives an upper limit from a network entity, the upper limit indicating a maximum number of neighbour cells whose common relative grant channels can be monitored by the wireless device.

At step 202, the liE begins monitoring common pilot channels (CPICHs) from a plurality of neighbour cells in a neighbour cell list (NCL). A CPICH is a channel having a constant power and known bit sequence enabling a UE to make relative mcasurcmcnts of different CPICHs from different ncighbour cells and make comparisons bctwccn thc neighbour cclls. The NCL is a list of neighbour cells provided by the network to the UE, typically to facilitate mobility of the tilE so that the UE can use cell reselection from one cell to another as the tiE moves. In broad terms, a liE in a CELL FACH state first receives the NCL from a Radio Network Controller (RNC). If a neighbour cell in the NCL satisfies cell reselection criteria, then the tiE can autonomously perform a cell reselcction using that neighbour cell.

The NCL that is broadcast to the tiE is currently specified to have a maximum length of 32 cells. In this example, the NCL is a list of intra-frequency neighbour cells. In measuring and reporting of intra-frequency neighbour cells, the UE makes measurements on cells that use the same carrier frequency as the current serving cell for the UE. The monitoring of the CPICHs enables to TIE to determine a measured result or a characteristic associated with each monitored CPICH.

At step 204, the TIE determines which of the plurality of neighbour cells have a CPICH that satisfies a predetermined criterion. The predetermined criterion is cffectively used to determine if a measurcd result determined from a CPICH is within a predetermined range of measured result values, described in further detail below.

The CPICH measured results can relate to one or more measurement quantities such as CPICH Ec/No, CPICH received signal code power (RSCP) or pathloss between the particular neighbour cell and the UE. The predetermined criterion can therefore be one or more of a range of Ec/No values, a range of RSCP values and a range of pathloss values.

At step 206, the TIE forms a monitoring set, and more specifically, a common relative grant channel monitoring set. The UE includes each neighbour cell determined to have met the predetermined criterion in the monitoring set. The monitoring set is limited by the upper limit parameter received from the network entity so that once the upper limit is reached, no further neighbour cells are added to the monitoring set. When the number of neighbour cells that have been deemed to satisfy the predetermined criterion exceeds the upper limit, the UE ensures that only the neighbour cells having the best quality measured results (the "best quality neighbour cells") arc included in the monitoring set. This ensures that only the best quality neighbour cells arc monitored when there arc a number of neighbour cells (that satis1' the predetermined criterion) in excess of the upper limit. This is done by selecting n' neighbour cells having the highest determined measured results from a list of candidate neighbour cells determined to have satisfied the predetermined criterion, where n' is the upper limit.

The liE at step 208 then monitors the neighbour cells in the monitoring set in order to receive relative grant information from those neighbour cells. More particularly, the UE monitors common relative grant channels of the neighbour cells.

The relative grant information, in general, indicates that a neighbour cell would like the liE to either decrease or keep the same transmission power so as to minimise inter-cell interference to that neighbour cell.

In Figure 2, as the network entity can determine an optimum maximum number of neighbour cells that can be monitored, the network entity can assist the liE to conserve battery power (i.e. because the UE is told to monitor up to a limited number of neighbour cells in the NCL rather than all of them).

The neighbour cells do not know which TiEs contribute to inter-cell interference and it is probable that only the neighbour cells that have good quality signals relative to the liE would be affected by transmissions from the liE (and hence possible inter-cell interference). Hence, creating a monitoring set with "best quality neighbour cells" means that a TiE will only monitor neighbour cells having good quality signals that the TiE is likely to interfere with. The UE can therefore control its transmission power based on these monitored cells. A neighbour cell that is not in the monitoring set is unlikely to be a cell the tiE interferes with and therefore should not be allowed to affect the transmission power of the liE.

In (JTRAN, when a tiE is transmitting or receiving data, it is desirable, where possible, for the tiE to reside in a CELL FACFI state as opposed to a CELL_DCH state in order to minimise power consumption by the liE and free up network resources for use by other UEs. In general, a CELL FACH state is a state in which the FE shares a channel with other liEs, where the shared channel is used for sending and receiving data to and from a Node B. A CELL DCH state is a state in which the liE has a dedicated channel for communications with a Node B. The transmissions of a UE in CELL FACH state close to a ccli edge may cause significant interference to its neighbour cells (known as "inter-cell interference"). The UE can use an interference control mechanism to minimise this inter-cc!] interference. The interference control mechanism works by enabling the UE to monitor common E-RGCHs (E-DCH Reiative Grant Channel) from neighbour cells and receive, via the E-RGCHs, relative grants. The relative grants allow non-serving neighbour cells to indicate to or request the UB to modifj its transmission power to effectively reduce thc inter-cell interference.

The relative grants operate somewhat similarly to power control. More particularly, relative grants are used to adjust a UE's transmission power and can take one of three values: liP, DOWN or HOLD. A value of UP indicates that the UE may increase its transmission power. A value of DOWN indicates that the TiE may decrease its transmission power. A value of HOLD is indicative that the TIE need not change its transmission power. A liE in the CELL_EACH state therefore listens to and monitors one or more common E-RGCI-ls from one or more neighbour cells as a part of a common E-RGCH based interference control mechanism. The interference mechanism is applied to DTCH (Dedicated Transport Channel) transmission and DCCH (Dedicated Control Channel) transmissions but is not applied to CCCH (Common Control Channel) transmissions.

A relative grant from a non-serving cell can only take the values DOWN and HOLD. If a UE receives a DOWN from any of the non-serving cells, it is an indication that the cell in question is overloaded and the UE should therefore reduce its transmission power, even if absolute grants from the serving cell suggest an increase. Thus, the relative grant from a neighbour cell serves as an "overload indicator". The overload indicator is broadcast to all UEs having the cell in question as a non-serving cc!!.

Referring now to a more detailed example a shown schematically in Figure 3, the tiE first receives an intra-frcquency neighbour cell list from a network entity such as a Radio Network Controller (RNC) (step 300). The NCL is determined by the RNC and is a list of cefls that are considered to neighbour a serving cefl of the UE.

This list may typically comprise a maximum of thirty two neighbour cells.

At step 302, the UE then receives a common E-RGCH configuration signal from a network entity such as the RNC. The common E-RGCH configuration signal comprises an "N" signal. N is a number that is predetermined by the network entity and is chosen so as to ensure that significant inter-cell interference is minimised whilst also ensuring that the UE does not need to monitor all of the cells listed in the NCL, thus allowing the UE's power consumption due to monitoring E-RGCHs to be minimised. In some examples N is set to 3. In other examples, N may be less or more than 3. In general, N is less than or equal to the maximum number of neighbour cells that can be listed in the NCL, and is therefore less than or equal to 32.

N may comprise a "reporting deactivation threshold", which reporting deactivation threshold is an existing parameter defined in 3GPP TS25.331 section 14.1.2.1. The reporting deactivation threshold is defined as being a threshold, at which an "event la" is triggered. More particularly, the threshold is satisfied when a CPICH of a neighbour cell has been determined to satisl an "event la" criterion or criteria and thus determined to have entered a "reporting range". The reporting range is defined as a range of measured result, such that a neighbour cell is deemed to have entered the reporting range when a determined measured result of a neighbour cell (i.e. the measured result of the CPICI-I measurement) is within the reporting range.

When the neighbour cell has entered the reporting range, the liE can trigger a measurement report (i.e. relating to that neighbour cell) to be sent to the UE's serving cell Node B. Therefore, rather than defining a new parameter in 3GPP. example embodiments of the present invention may re-use the already-defined reporting deactivation threshold. By using an existing definition, there is no need to include further definitions in 3GPP and therefore the inter-cell interference control mechanism of example embodiments of the present invention is easier to implement and does away with extra signalling across the network that might be required.

At step 304, the UE monitors primary Common Pilot Channels (CPICHs) from the cells listed in the NCL to determine a measured result or characteristic of the primary CPICHs. The primary CPTCHs are downlink channels broadcast by the Node B of each neighbour cell, the primary CPICH having a constant power and known bit sequence. The constant power and known bit sequence allows the UE to determine a measured resuh relating to the neighbour cell and thereby determine whether the neighbour cell associated with the primary CPICI-l has entered the reporting range.

The UE does this by comparing the determined measured result with the event Ia critenon or criteria to see whether or not the measured result satisfies the criterion or criteria and thus determining that the neighbour cell has entered the reporting range.

The triggering of event Ia, and thus the entering of the reporting range, is therefore used to determine whether the neighbour cell is a candidate for being added to a common E-RGCH monitoring set (a set of cells that the UE is listening to and can communicate with) (step 306). The measured result determined from CPICH for use in triggering event la can relate to one or more of the measurement quantities CPICH Ec/No, CPICH RSCP or pathloss between the neighbour cell and the liE. CPICH Ec/No is the ratio of the received energy per chip (or modulating bit) for the CPICH to the total received power spectral density at the UE antenna. The Received Signal Code Power (RSCP) is the absolute power level of the CPICH as received by the UE.

The pathloss is the loss measured between the cell and UE. For Frequency Division Duplexing (FDD), the pathloss is determined by calculating the difference between the UEs measurement of CPICH RSCP and the value of Primary CPICH transmission power (the power level of the CPTCH at the neighbour cell, as reported by the network).

The triggering condition for event I a, when the measurement quantity is pathloss, is govemed by the following equation: «=H7.l0.Lo[l/(1/iVI)J+(1_W).10.LogMst+(Ria_Hi/2) The triggering condition for event I a, when the measurement quantity is other than pathloss, is governed by the following equation: 10-LogM + ClO »= W -10 Lo[M19 + (1-W) 10 LogM, -(R1 -H /2), The variables in the above equations are defined as follows: Mvew is the measurement result of the neighbour cell entering the reporting range.

CIONew is the individual cell offset for the neighbour cell entering the reporting range if an individual cell offset is stored for that cell. Otherwise it is equal to 0. Cell Individual Ofthet (ClO) is configured for each neighbouring cell. A positive offset increases the probability of the neighbour cell triggering event Ia. This can be useful in high mobility scenarios in which case it is desirable to trigger event I a earlier than usual. The ClO is signalled as part of the information element (IE) "Cell-Info" inside the IE "Intra-Frequency Cell Info List".

M, is a measurement result of a neighbour cell not forbidden to affect reporting range in the monitoring set.

NA is the number of cells not forbidden to affect reporting range in the current monitoring set.

For pathioss, MBt is the measurement result of the cell not forbidden to affect reporting range in the monitoring set with the lowest measurement result, not taking into account any cell individual offset.

For other measurements quantities, Mfit is the measurement result of the cell not forbidden to affect reporting range in the monitoring set with the highest measurement result, not taking into account any cell individual offset.

W is a weighting coefficient parameter sent from UTRAN to UE, which may be set to nil for the common RGCH monitoring or will be considered absent.

R1 is the reporting range constant, which may be signalled from the network.

H1 is the hysteresis parameter for the event Ia, which may be set to nil for the common RGCH monitoring or will be considered absent.

If the measurement results are pathloss or CPICH-Ec/No then Mwew, M1 and are expressed as ratios.

If the measurement result is CPICH-RSCP then M1 and MB5 are expressed in mW.

Unlike in 3GPP TS25.331 section 14.1.2.1, the above parameters Wand JJ,, in addition to a "time to trigger" parameter, may not be signalled by the network to the UE but may instead be considered as absent or hardcoded to zero. This is because these parameters are not necessary when forming a common E-RGCH monitoring set for this purpose. The network does however signal to the liE a reporting range parameter, a filter coefficient and a minimum serving grant. Some of these parameters are signalled using dedicated messages.

The UE will form the monitoring set by including the best quality neighbour cells that satisfy the event la criterion or criteria, up to the number specified by the reporting deactivation threshold (step 308). If there are more than the limit specified by the reporting deactivation threshold, then the UE selects the best quality neighbour cells from the candidate cells.

In some examples, the UE orders the neighbour cells in the NCL by measured result such that the N best cells can be readily selected from the list. For example, the monitoring set could be listed by Ec/No (or by another desired measurement quantity or by one or more combinations of the measurement quantities) and the desired number of neighbour cells (i.e. according to the reporting deactivation threshold) can be selected from that list in the order that the list is presented in. This list is maintained regularly so that it is kept up-to-date. This is done by applying the event I a criteria to the cells listed in the NCL according to a regular time interval and storing the results in an ordered list in memory (either in the processor or eLsewhere in the IJE). Preferably, the neighbour cell in the monitoring list that is compared with the new neighbour cell is one in which the measured result is the least desirable out of the neighbour cells in the monitoring set.

At step 310, the UF monitors the E-RGCI-Is of the neighbour cells in the common E-RGCI-1 monitoring set.

The UE can thereby determine at step 312, based on relative grant information received in the E-RGCHs, whether or not to adjust its transmission power in order to minimise inter-cell interference.

In some examples, the monitoring of an E-RGCH of a neighbour cell ceases when the CPICH of that neighbour cell has satisfied a "leaving triggering condition" of the event la criteria. The common E-RGCFI monitoring set can be a dynamic list that is kept updated such that, if a neighbour cell has been determined to satisfy the leaving triggering condition, then that neighbour cell, in some example embodiments, is removed from the common E-RGCFI monitoring set so that the common E-RGCH of that neighbour cell is no longer monitored. This ensures that the UE only takes into account relative grants received from cells that have good quality signals. The UE is morc likely to cause interference to these neighbour cells as opposed to neighbour cells having poorer quality signals. Neighbour cells with poorer quality or weaker signals are not placed in the common E-DCH monitoring set and therefore cannot contribute their relative grant information to the UE common E-RGCH based interference control mechanism. This is desirable because, as these neighbour cells that are not included in the common E-RGCH monitoring list are likely to experience less or no interference from the TJE (i.e. compared with a better quality neighbour cell), the liE should not take these neighbour cells into account when controlling its transmission power.

When thc measured resuh of thc CPICH and the predetcrmincd criterion use pathloss as a measurement quantity, a neighbour cell is deemed to satisfy the leaving triggering condition according to the following equation: 1OLogM+CIO > W.1O.Lo[ 1/(l/M;)9+(l_W).10.LoMB +(R10 +H/2), When the measured result of the CPICH and the predctermined criterion use a measurement quantity other than pathloss, a neighbour cell is deemed to satisIv the leaving triggering condition according to the following equation: 10LogM + CfO <W 10 +(1 -W)l0 LogilfB, -(R10 + U0 /2), The above embodiments arc to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. For example, in the above example embodiment, the upper limit was described as being provided by the R}C. It other example embodiments, the UE may determine the upper limit without any network input.

In the above example embodiment, a liE in a CELL FACH state uses specific measurement parameters in order to form a common E-RGCEI monitoring set. In another example embodiment, the LIE uses measurement parameters that have afready been provided to the LIE for CELL DCH mobility in order to form the common E-RGCH monitoring set from event la measurement configuration. These CELL_DCH measurement parameters are defined in 3GPP TS25.331.

In the above example embodiment, the NCL comprised intra-frequency neighbour cells. In another example embodiment, the NCL may comprise inter-frequency neighbour cells. In measuring and reporting of inter-frequency neighbour cells, the neighbour cells that are measured by the LiE operate on a carrier frequency that is different from the carrier frequency of the current serving cell for the LIE.

Although at least some aspects of the embodiments described herein with reference to the drawings comprise computer processes performed in processing systcms or processors, the invention also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice.

The program may be in the form of non-transitory source code, object code, a code intermediate source and object code such as in partially compiled form, or in any other non-transitory form suitable for use in the implementation of processes according to the invention. The carrier may be any entity or device capable of carrying the program. For example, the carrier may comprise a storage medium, such as a solid-state drive (SSD) or other semiconductor-based RAM; a ROM, for example a CD ROM or a semiconductor ROM; a magnetic recording medium, for example a floppy disk or hard disk; optical memory devices in general; etc. It will be understood that the processor or processing system or circuitry referred to herein may in practice be provided by a single chip or integrated circuit or plural chips or integrated circuits, optionally provided as a chipset, an application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), digital signal processor (DSP), etc. The chip or chips may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor or processors, a digital signal processor or processors, baseband circuitry and radio frequency circuitry, which are configurable so as to operate in accordance with the exemplary embodiments. In this regard, the exemplary embodiments may be implemented at least in part by computer software stored in (non-transitory) memory and executable by the processor, or by hardware, or by a combination of tangibly stored software and hardware (and tangibly stored firmware).

It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not descnl,cd above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims (1)

1. <claim-text>CLAIMS1. A method of operating a wireless device in a cellular communications network, the method comprising: receiving an upper limit from a network entity, the upper limit indicating a maximum number of neighbour cells to be monitored by the wireless device; monitoring common pilot channels from a plurality of neighbour cells in a neighbour cell List; determining which of the plurality of neighbour cells have a common pilot channel that satisfies a predetermined criterion; forming a common relative grant channel monitoring set of neighbour cells, wherein the common pilot channel of each of said ncighbour cells satisfies the predetermined criterion, the common relative grant channel monitoring set having a number of neighbour cells less than or equal to the upper limit, wherein if the number of neighbour cells whose common pilot channel satisfies the predetermined criterion exceeds the upper limit, then the best quality neighbour cells are included in the common relative grant channel monitoring set up to the upper limit of neighbour cells and monitoring common relative grant channels of the neighbour cells in the common relative grant channel monitoring set to receive relative grant information from those neighbour cells.</claim-text> <claim-text>2. A method according to claim I, comprising determining that a neighbour cell listed in the common relative grant channel monitoring set has a common pilot channel that satisfies a second predetermined criterion and, in response, stopping the monitoring of the common relative grant channel of that neighbour cell.</claim-text> <claim-text>3. A method according to claim 2, comprising removing the neighbour cell that satisfies the second predetermined criterion from the common relative grant channel monitoring set.</claim-text> <claim-text>4. A method according to any of claims 1 to 3, wherein the quality of a neighbour cell is determined according to a measured result of the common pilot channel, the measured result relating to a measurement quantity comprising at least one of a Ec/No, a received signal code power, and a pathhss between the neighbour S cell and the user equipment.</claim-text> <claim-text>5. A method according to any of claims 1 to 4, wherein the common relative grant channel monitoring set comprises neighbour cells for which common Enhanced Dedicated Channcl Relative Grant Channels arc monitored.</claim-text> <claim-text>6. A method according to claim 5, comprising receiving, via the common Enhanccd Dedicated Channel Relative Grant Channels, the rehtive grant information to control a transmission power of the wireless device.</claim-text> <claim-text>7. A method according to any of claims 1 to 6, wherein the common pilot channel satisfics the predetermined critcrion when a measured result of the common pilot channel is determined to be within a specified reporting range.</claim-text> <claim-text>8. A method according to any of claims Ito 7, wherein the received upper limit comprises a reporting deactivation threshold which is provided to the wireless device for event-triggered measurement.</claim-text> <claim-text>9. Apparatus comprising a processing system for a wireless device constructed and arranged to cause the wireless device to: monitor common pilot channels from a plurality of neighbour cells in a neighbour cell List; determine which of the p'urality of neighbour cells have a common pilot channel that satisfies a predetermined critcrion; form a common relative grant channel monitoring set of neighbour cells, wherein the common pilot channel of each of said neighbour cells satisfies the predetermined criterion, the common relative grant channel monitoring set having a number of neighbour cells less than or equal to an upper limit provided by a network entity, wherein if the number of neighbour cells whose common pilot channel satisfies the predetermined criterion exceeds the upper limit, then the best quality neighbour cells are included in the common relative grant channel monitoring set up to the upper limit of neighbour cells; and monitor comnon relative grant channels of the neighbour cells in the common relative grant channel monitoring set to receive relative grant information from those neighbour cells.</claim-text> <claim-text>10. Apparatus according to claim 9, arranged to cause the wireless dcvice to stop monitoring a neighbour cell if that neighbour cell has a common pilot channel that satisfies a second predetermined criterion.</claim-text> <claim-text>11. Apparatus according to claim 10, arranged to remove the neighbour cell that satisfies the second predetermined criterion from the common relative grant channel monitoring set.</claim-text> <claim-text>12. Apparatus according to any of claims 9 to 11, wherein the quality of a neighbour cell is determined according to a measured result of the common pilot channel, the measured result relating to a measurement quantity comprising at least one of a Be/No, a received signal code power, and a pathioss between the neighbour cell and the user equipment.</claim-text> <claim-text>13. Apparatus according to any of claims 9 to 12, wherein the common relative grant channel monitoring set comprises neighbour cells for which common Enhanced Dedicated Channel Relative Grant Channels are monitored.</claim-text> <claim-text>14. Apparatus according to claim 13, arranged to cause the wireless device to receive, via the common Enhanced Dedicated Channel Relative Grant Channels, the relative grant information to control a transmission power for the wireless device.</claim-text> <claim-text>15. Apparatus according to any of claims 9 to 14, wherein the common pilot channel satisfies the predetermined criterion when a measured result of thc common pilot channel is determined to be within a specified reporting range.</claim-text> <claim-text>16. Apparatus according to any of claims 9 to 15, wherein the received upper limit comprises a reporting deactivation threshold which is provided to the wireless device for event-triggered measurement.</claim-text> <claim-text>17. A computcr program comprising instructions such that whcn thc computer program is executcd on a wireless device, thc wireless device is arrangcd to: monitor common pilot channels from a plurality of neighbour cells in a neighbour cell list determinc which of the plurality of neighbour cells have a common pilot channel that satisfies a predetermined criterion; form a common relative grant channel monitoring set of neighbour cells, wherein the common pilot channel of each of said neighbour cells satisfies the predetermined criterion, the common relative grant channel monitoring set having a number of neighbour cells less than or equal to an upper limit provided by a network entity, wherein if the number of neighbour cells whose common pilot channel satisfies the predetermined criterion exceeds the upper limit, then the best quality neighbour cells are included in the common relative grant channel monitoring set up to the upper limit of neighbour cells; and monitor common relative grant channels of the neighbour cells in the common relative grant channel monitoring set to receive relative grant information from those neighbour cells.</claim-text> <claim-text>18. A computer program according to claim 17, wherein the wireless device is caused to stop monitoring the common relative grant channel of a neighbour cell if that neighbour cell has a common pilot channel that satisfies a second predetermined criterion.</claim-text> <claim-text>19. A computer program according to claim 18, wherein wireless device is caused to remove the neighbour cell that satisfies the second predetermined criterion from the common relative grant channel monitoring set.</claim-text> <claim-text>20. A computer program according to any of claims 17 to 19, wherein the quality of a neighbour cell is determined according to a measured result of the common pilot channel, the measured result relating to measurement quantity comprising at least one of a EcINo, a received signal code power, and a pathloss between the neighbour cell and the user equipment.</claim-text> <claim-text>21. A computer program according to any of claims 17 to 20, wherein the common relative grant channel monitoring set comprises neighbour cells for which common Enhanced Dedicated Channel Relative Grant Channels are monitored.</claim-text> <claim-text>22. A computer program according to claim 21, arranged to cause the wireless device to receive, via the common Enhanced Dedicated Channel Relative Grant Channels, the relative grant information to control a transmission power for the wireless device.</claim-text> <claim-text>23. A computer program according to any of claims 17 to 22, wherein the common pilot channel satisfies the predetermined criterion when a measured result of the common pilot channel is determined to be within a specified reporting range.</claim-text> <claim-text>24. A computer program according to any ofclaims 17 to 23, wherein the received upper limit comprises a reporting deactivation threshold provided to the wireless device for event-triggered measurement.</claim-text> <claim-text>25. A method of operating a wireless device substantially in accordance with any of the examples as described herein with reference to and illustrated by the accompanying drawings.</claim-text> <claim-text>26. A wireless device substantially in accordance with any of the cxamples as described herein with reference to and illustrated by the accompanying drawings.</claim-text>