WO2013156174A1

WO2013156174A1 - Scheduling mode selection in uplink data transmission

Info

Publication number: WO2013156174A1
Application number: PCT/EP2013/052841
Authority: WO
Inventors: Krystian Pawlak; Przemyslaw Czerepinski; Roman Maslennikov; Alexey TRUSHANIN
Original assignee: Nokia Siemens Networks Oy
Current assignee: Nokia Solutions and Networks Oy
Priority date: 2012-04-19
Filing date: 2013-02-13
Publication date: 2013-10-24
Anticipated expiration: 2014-10-19

Description

SCHEDULING MODE SELECTION IN UPLINK DATA TRANSMISSION

This disclosure relates to uplink data transmission in selection in a wireless communication system, and more particularly to scheduling of data transmission in the uplink.

A communication system can be seen as a facility that enables communication sessions between two or more entities such as fixed or mobile communication devices, base stations, servers, machine type communication devices and/or other communication nodes. A communication system and compatible communicating entities typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. For example, the standards, specifications and related protocols can define the manner how various aspects of communication such as access to the communication system and feedback messaging shall be implemented between communicating devices. The various development stages of the standard specifications are referred to as releases.

A communication can be carried on wired or wireless carriers. In a wireless communication system at least a part of communications between stations occurs over a wireless link. Examples of wireless systems include public land mobile networks (PLMN) such as cellular networks, satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). A wireless system can be divided into cells or other radio coverage or service areas provided by a station. Radio service areas can overlap, and thus a communication device in an area can send and receive signals within more than one station. Each radio service area is controlled by an appropriate controller apparatus. Higher level control may be provided by another control apparatus controlling a plurality of radio service area.

A wireless communication system can be accessed by means of an appropriate communication device. A communication device of a user is often referred to as user equipment (UE) or terminal. A communication device is provided with an appropriate signal receiving and transmitting arrangement for enabling communications with other parties. Typically a communication device is used for enabling receiving and transmission of communications such as speech and data. In wireless systems a communication device provides a transceiver station that can communicate with another communication device such as e.g. a base station and/or another user equipment.

In this specification term mobile station (MS) is used for referring to a user equipment, the term base station (BS) is used for referring to a network radio access point including at least some control functionality and the term RNC (radio network controller) is used for referring to a network element that performs control functions over, typically but not necessarily, a number of base stations.

The following non-limiting discussion relates to wireless communication based on the code division multiple access (CDMA), and more specifically to direct sequence CDMA (DS-CDMA) employed, for example, in the 3GPP UTRAN FDD (3^rd Generation Partnership Project Universal Mobile Telecommunication System Radio Access Network Frequency Division Duplex) cellular system to separate the uplink signals originating from different user terminals.

In the context of the 3GPP UTRAN WCDMA (Wideband CDMA) FDD system it is noted that the WCDMA uplink (UL) was initially designed to satisfy low reception carrier to interference (RX C/l). Typically, the UL has been dimensioned for concurrent data transmission from multiple mobile stations (MSs). Each radio link is adapted to achieve the C/l below 0 dB to guarantee system stability. Link adaptation is achieved via power control, which is appropriate in the low C/l regime. The current high speed uplink packed access (HSUPA) link adaption mechanism is based on power control and power-based scheduling where a RNC signals to a base station (BS) the target signal-to- interference ratio (SIR) parameter for each mobile station (MS). The SIR can be defined by measuring it on a UL pilot channel, dedicated physical control channel (DPCCH) as a value proportional to the C/l. An inner loop power control (ILPC) between the BS and MS is responsible for adjusting the MS transmit power so that the SIR target is met. An outer loop power control (OLPC) in the RNC is then responsible for updating the SIR target so that a link quality metric, such as block error rate (BLER) target is met. A radio resource, in the form of the maximum allowed received rise over thermal (RX RoT) level is signalled from the RNC to the BS. The rise over thermal (ROT) parameter is a measure used in the context of wireless communications to indicate the ratio between the total power received from wireless sources at a base station and the thermal noise. The BS scheduler apportions the RX RoT to individual MSs in the cell by means of scheduling grants (SG). A higher grant indicates a higher data rate, for example a higher enhanced dedicated channel (E-DCH) transport format combination (E-TFC) but also leads to a higher interference at the base station (BS) antenna. There is a standardized and deterministic relationship between the scheduling grant (SG) and the E-DCH transport format combination (E-TFC) selected by the mobile station (MS) where in UL scheduling and E-TFC selection a maximum allowed transmission format is assigned for the MS, given the granted SG signalled by the BS. Additional power offset parameters have been proposed to aid the scheduling procedure for UL multiple input multiple output (MIMO) transmission to address inter-stream interference.

UTRAN Release-7 and Release-1 1 introduced high data rate features such as UL 16 Quadrature Amplitude Modulation (QAM), 64QAM and Multiple Input Multiple Output (MIMO). These can demand high RX C/l values, these being significantly higher than what can be provided by the above. Therefore, these features can prohibit normal CDMA system operation as higher order modulation and MIMO may be realized only when a single high rate radio link is active per cell, or even per a group of cells. In addition, as the self-interference and inter- stream interference effects are significant in the high C/l range, the inventors have found that power control may no longer be a suitable basis for link adaptation.

It is noted that the above discussed issues are not limited to any particular communication environment, but may occur in any communication system where transmission points may need to be selected.

Embodiments of the invention aim to address one or several of the above issues.

In accordance with an embodiment there is provided a method for controlling uplink data transmission, comprising operating a control function for uplink data transmissions in an area in one of a first mode and a second mode of scheduling, wherein the second mode provides scheduling of uplink data transmission based on signal quality, determining a condition for switching of the control function between the first and second modes, and causing signalling of information regarding switching between the modes to at least one mobile device.

In accordance with an embodiment there is provided a method for uplink data transmission, comprising receiving at a mobile device in an area information regarding a mode of scheduling, the mobile device being configured for uplink data transmissions in a first mode and a second mode of scheduling, wherein the second mode provides scheduling of uplink data transmission based on signal quality, and switching between the modes accordingly.

In accordance with an embodiment there is provided an apparatus for control of uplink data transmission, the apparatus comprising at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to operate a control function for uplink data transmissions in an area in one of a first mode and a second mode of scheduling, wherein the second mode provides scheduling of uplink data transmission based on signal quality, to determine a condition for switching of the control function between the first and second modes, and to cause signalling of information regarding switching between the modes to at least one mobile device.

In accordance with another embodiment there is provided an apparatus for uplink data transmission, the apparatus comprising at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to control reception, at a mobile device in an area, of information regarding a mode of scheduling, the mobile device being configured for uplink data transmissions in a first mode and a second mode of scheduling, wherein the second mode provides scheduling of uplink data transmission based on signal quality, and to cause switching between the modes accordingly. In accordance with a more detailed embodiment a first target for a ratio of received power and thermal noise is applied in the first mode and a second higher target for the ratio of received power and thermal noise is applied in the second mode.

An enhanced dedicated channel transport format combination may be selected based on the mode.

Scheduling in the second mode may be based on signal to noise and interference ratio. Information of at least one difference in a signal to interference and noise ratio compared to a serving grant may be determined for the second mode at a network node. The information can be communicated in the downlink. The at least one difference can be derived based on post-equalizer signal to noise and interference ratio shortfall.

The second mode may be activated in response to determination that high data rates are possible in the area. At least one predefined feature in the area may be determined and switching between the modes may be provided accordingly. The monitoring may comprise monitoring for at least one of determined number of mobile devices in the area, load, channel quality, buffer occupancy, active set size, system noise level, access by mobile devices, paging, channel activations, radio link set-ups, handovers, and deterioration of radio conditions.

A computer program comprising program code means adapted to perform the methods may also be provided.

Various other aspects and further embodiments are also described in the following detailed description and in the attached claims.

The invention will now be described in further detail, by way of example only, with reference to the following examples and accompanying drawings, in which:

Figure 1 shows a schematic diagram of a system where certain embodiments are applicable;

Figure 2 shows a schematic diagram of a mobile communication device according to certain embodiments; Figure 3 shows a schematic diagram of a control apparatus according to some embodiments;

Figure 4 shows the value of rise over thermal as a function of the number of mobile devices and a target;

Figures 5 - 7 shows flow charts according to certain embodiments; and

Figures 8 - 10 show diagrams in relation to a detailed example.

Certain exemplifying embodiments are explained below with reference to a wireless or mobile communication system serving mobile communication devices. Before explaining in detail the exemplifying embodiments, certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to Figures 1 to 3 to assist in understanding the technology underlying the described examples.

In a wireless communication system mobile devices or user equipment (UE) are provided wireless access via at least one base station or similar wireless transmitting and/or receiving node or point. A mobile device may be located within an area of, and thus communicate with, one or more base stations and the communication devices and stations may have one or more radio channels open at the same time and may send signals to and/or receive signals from more than one source. The example of Figure 1 shows two mobile stations MS1 and MS2 in communication with a base station BS. It shall be understood that the sizes and shapes of radio service areas provided by base stations can vary. A base station site can provide one or more cells. A base station can also provide a plurality of sectors, for example three radio sectors, each sector providing a cell or a subarea of a cell. All sectors within a cell can be served by the same base station.

Base stations are typically controlled by at least one appropriate controller apparatus so as to enable operation thereof and management of mobile communication devices in communication with the base stations. In Figure 1 control apparatus 108 is provided. It is noted that more than one base station may be controlled e.g. by a control apparatus. The control apparatus of a base station can be interconnected with other control entities. The control apparatus is typically provided with memory capacity and at least one data processor. The control apparatus and functions may be distributed between a plurality of control units.

Figure 2 is a schematic, partially sectioned view of a possible mobile device or station 200 for communication with the base station. Such a device is often referred to as user equipment (UE) or terminal. An appropriate mobile device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples include a mobile station (MS) such as a mobile phone or what is known as a 'smart phone', a portable computer provided with a wireless interface card or other wireless interface facility, personal data assistant (PDA) provided with wireless communication capabilities, or any combinations of these or the like. A mobile device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services include two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. Non-limiting examples of the content include various downloads, television and radio programs, videos, advertisements, various alerts and other information. The mobile device 200 may receive signals in the downlink 207 via appropriate apparatus for receiving and may transmit signals in the uplink 209 via appropriate apparatus for transmitting radio signals. In Figure 2 transceiver apparatus is designated schematically by block 206. The transceiver apparatus 206 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device. A wireless communication device can be provided with a Multiple Input / Multiple Output (MIMO) antenna system.

A mobile device is also typically provided with at least one data processing entity 201 , at least one memory 202 and other possible components 203 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications, such as communication of data and control signals with access systems and other communication devices and actions according to the embodiments described in more detail below. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 204. The user may control the operation of the mobile device by means of a suitable user interface such as key pad 205, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 208, a speaker and a microphone can be also provided. Furthermore, a mobile communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto.

Figure 3 shows an example of a control apparatus for a communication system, for example to be coupled to and/or for controlling stations of an access system or to a radio network controller (RNC). The control apparatus 300 can be arranged to provide control on communications in a service area of the system. The control apparatus can be configured to provide control functions in association with generation and communication of instructions to relevant nodes and processing of responses from the nodes and other related information by means of the data processing facility in accordance with certain embodiments described below. For this purpose the control apparatus 300 comprises at least one memory 301 , at least one data processing unit 302, 303 and an input/output interface 304. Via the interface the control apparatus can be coupled to a receiver and a transmitter of a base station. The control apparatus can be configured to execute an appropriate software code to provide the control functions. It shall be appreciated that similar component can be provided in a control apparatus provided elsewhere in the system for controlling reception of sufficient information for decoding of received information.

A non-limiting examples for link adaptation are described below in the context of high data rate features introduced into 3GPP UTRAN WCDMA FDD High Speed Uplink Packet Access (HSUPA). It is noted that although most of the discussion and examples are provided for a case where there is only one RX antenna, the principles can be extended to scenarios with multiple RX antennae. The WCDMA UL was designed based on the principle of concurrent signal transmission from a number of mobile stations (MSs). Signal S/ originating from any MS/ is considered to have random noise characteristics owing to the application of MS-specific pseudo-random scrambling codes. By ensuring that the received signal power, corresponding to an individual MS, is lower than the system noise power it is possible for multiple transmissions to co-exist on one carrier frequency and at the same time. This simplifies certain system operation aspects. For example, radio links can be asynchronous relative to other radio links. A rise over thermal (RoT) is a measure used in the context of wireless communications to indicate the ratio between the total power received from wireless sources at a base station and the thermal noise. Impact on the rise over thermal (RoT) at the base station (BS) antenna port in a CDMA based system as a function of the number of concurrent mobile stations and C/l target is illustrated in Figure 4. As illustrated, it is possible to multiplex a number of mobile stations at RX C/l = -6 dB and ensure system stability i.e. keep a finite RoT value. However, it is not possible to multiplex mobile stations at RX C/l = 3 dB as system stability would be lost as the RoT diverges to infinity as soon as a second MSs is inserted into the cell.

Capping of the C/l to 0 dB implies the theoretical spectral efficiency bound of 1 bit/s/Hz, with practically achievable data rates of the order of 1 Mbps, supported by Orthogonal Variable Spreading Factor (OVSF) spread Quadrature Phase Shift Keying (QPSK) transmission in the approximately 4 MHz WCDMA system bandwidth.

Power control is provided in CDMA to ensure that the required Rx C/l or Signal to Noise and Interference Ratio (SINR) target is met and for interference control. In the low C/l operating regime, power control is considered efficient enough because the receiver (RX) SINR, corresponding to a given mobile station is dominated by the interference originating from other mobile stations. Self- interference effects are marginal and therefore increasing the RX signal power at the BS antenna leads to a proportional increase of the SINR.

Figure 1 shows C/l and SINR reference points in the base station receiver block diagram thereof. The C/l relationship refers to MS signal power and interference power measured at the BS antenna. The SINR relationship refers to the ratio of post-equalizer signal power (P_post-Rx) and the interference terms including noise and other MS interference (/„_0/se) as well as MS self interference (I self) according to: p

SINR =

^ self ^ noise Λ \

The growing demand for broadband radio access has increased the demand for higher data rates. For example, the 16 QAM transmission mode was introduced into UTRAN FDD HSUPA during 3GPP Release 7. With this solution, data rates of up to 1 1 .52 Mbps are possible while the required RX C/l varies between 5 and 15 dB. Further Release 1 1 enhancements include HSUPA 64 QAM and MIMO, increasing the peak data rate up to 34.56 Mbps. However, this demands RX C/l of 20 dB or higher.

It is possible to force the high data rate features into the existing WCDMA

UL operation. However, the inventors have found that this could go against certain current system operation principles. For example, a typical Rise over Thermal (RoT) setting, which guarantees stable WCDMA UL operation, is approximately 6 dB. A higher setting might be required if the new functionalities are to be activated in practice. Concurrent high data rate transmission from multiple MSs may not be possible or is at least difficult to realize. The high C/l requirement means that it is only possible to support a single high data transmission per cell, or even a group of cells. Also, power control may no longer be an appropriate link adaptation mechanism in all applications. This can be explained as follows: the terms P_post-Rx and l_seif of equation (1 ) above are proportional to the received signal strength, C. The proportion itself is dependent on the propagation conditions and transmission mode (single stream or multiple input multiple output (MIMO)). In the high C/l regime the noise and other MS interference term becomes negligible, i.e. /_no/se « I self , hence the SINR saturates. In high C/l range, increasing the carrier power may no longer lead to a commensurate increase of the SINR because of self-interference. This is believed to be due to multipath propagation or inter-stream effects in the case of MIMO.

Power based link adaptation and resource allocation nevertheless continue to be important control mechanisms for systems such as WCDMA HSUPA. In the worst case, this may lead to unstable system operation, with the inner loop power control (ILPC) continually increasing the transmission (TX) power in an attempt to meet the non-achievable RX SINR. A more likely consequence is inefficient radio link and system operation, where the mobile station transmit power, data size, modulation and coding (collectively termed "enhanced transport format combination", E-TFC) selection functions do not account for self-interference, leading to suboptimum link and cell throughputs.

In accordance with an embodiment shown in the flowchart of Figure 5, in a method for controlling uplink data transmission, a control function for uplink data transmissions in an area, for example a cell or a group of cells, is operated at 40 in a mode, for example a first mode. A condition enabling switching of the control function to a second mode is determined at 42. In the second mode scheduling of uplink data transmission is based on signal quality. Information regarding activation of the second mode is signalled at 44 to at least one mobile device in the area. After reception of the information, a mobile device can activate the second mode accordingly at 46. Similarly, switching can be provided from the second mode to the first mode in response to a predetermined event.

An enhanced dedicated channel transport format combination can be selected based on the mode. Scheduling in the second mode can be based on signal to noise and interference ratio.

Figure 6 shows an embodiment where a target for a ratio of received power and thermal noise can be used for scheduling at 50. A first target for the ratio of received power and thermal noise can be applied in a mode and a second target for the ratio of received power and thermal noise can be applied in another mode. For example, a higher target can be applied in a mode for provided higher data rates. A switching between the modes can be provided at 52. Information about the switch can be provided at 54 to mobile stations. Figure 7 shows yet another embodiment for controlling uplink data transmission. In the method a control function for uplink data transmissions in an area in one of a first mode and a second mode of scheduling at 60. In the first mode the scheduling of the uplink transmission is based on power. In the second mode at least a part of the power based scheduling function is deactivated. A condition for switching of the control function between the first and second modes can be determined at 62. Information regarding switching between the modes is then signalled at 64 to at least one mobile device.

In accordance with an embodiment, at least one of the following applies in the second mode: outer loop power control is deactivated, a signal to interference target for inner loop power control is set to a fixed value, a value for signal to interference for inner loop power control is determined based on carrier to interference ratio, received signal strength, and/or total received wideband power, a hold command is provided for inner loop power control, frequency of inner loop power control command is reduced, and inner loop power control is replaced by a closed or open loop path loss and shadow fading compensation mechanism.

It shall be appreciated that changing the scheduling method does not necessarily cause any changes in power control and vice versa.

More detailed embodiments for providing an optimized WCDMA HSUPA operation for higher data rates are described below.

In accordance with an embodiment a high rate uplink mode (abbreviated HRUM for simplicity) is provided. A high C/l (equivalently, high RoT of 15 dB or higher) target may be desired for any Higher Order Modulation (HOM; e.g., 64 QAM) or UL MIMO transmission to take place. Increasing the RoT target beyond the typical range of 3.8 dB can increase the risk of losing system stability as pole capacity is approached in a multi-MS cell. In order to enable the usage of high data rates and avoid the risk of stability loss in a cell, the cell can be provided with ability to apply a high RoT target in a controlled manner when it is safe to do so. The HRUM RoT target can be pre-configured by a controller element (for example a RNC) and the decision to activate it could be made by the BS under favourable conditions. Switching to a higher RoT can be likened to enforcing high geometry conditions that some MSs enjoy in the downlink (DL).

lub signalling may be used between the RNC and the base station, for example a Node B, to pre-configure HRUM parameters. Uu signalling may be used for communication between the base station and the mobile station to activate and de-activate HRUM.

HRUM activation criteria can be implementation dependent. A straightforward example for activating high RoT target is the presence of only a single MS in the cell or group of cells. The criteria may include features such as low MS population (in the limit, a single MS per cell or group of cells), high MS buffer occupancy, high Channel Quality Indicator (CQI) reports, indicative of MS located close to cell centre and hence not causing significant interference into other cells, active set size equal to one or a low system noise level and so on.

In accordance with an embodiment HRUM activation and de-activation procedures may include the following steps:

• Detecting in a network a situation where high data rate uplink (UL) transmission can be realized. For example, it can be detected that a small number of capable MSs is present in a cell or a group of cells so system stability is not compromised. The detection may be based on a predefined threshold for the number of mobile stations.

• Activating the HRUM in the relevant cell (or a group of cells) and MSs.

• Monitoring the relevant cell load to detect the appearance of additional MSs in the relevant cells, e.g. based on Random Access Channel (RACH), paging, CELL_DCH activation (CELL_DCH is a state in the Radio Resource Control (RRC) protocol), radio link setup or handover events. One of more thresholds may be defined for this purpose.

• De-activating HRUM in the relevant cell (or a group of cells) and MSs when the high data rate UL transmission can no longer be realized, e.g. due to an increased number of active MSs in the cell (or group of cells) and the related stability concern.

These actions can be taken by the network i.e. the RNC or BS. Decision by the BS may in certain occasions be more timely and be based on the instantaneous cell conditions. The decisions may be communicated to a MS using new High Speed Shared Control Channel (HS-SCCH) orders or as part of grant signalling. Further, it may be beneficial for the BS to act within the HRUM parameterization pre-configured by a RNC. The parameters may include information elements such as RoT target, SIR target of ILPC and ILPC mode of operation (update frequency, step size, presence of POWER HOLD command).

Signal to Noise and Interference Ratio (SINR) based scheduling can be used to decouple the power control and E-DCH Transport Format Combination (E-TFC) selection mechanisms. This is done to enable adaptive modulation and coding (AMC) tuned to the instantaneous propagation conditions and transmission mode (rank-1 or rank-2). This is motivated by the fact that, for a fixed C/l, the post-equalizer SINR can vary significantly between line-of-sight (LoS) and heavy multipath propagation.

A dynamic SINR Difference (SD) parameter for single and multiple stream high rate transmission may be provided. For example, the decoupling can be achieved by the following types of additional SINR difference (SD) parameters:

• In the case of rank-1 recommendation, a single parameter SD can be provided by the BS to the MS, as shown in Figure 8a.

• In the case of rank-2 recommendation, two parameters SD1 and SD2 can be provided by the BS to the MS, as shown in Figure 8b.

The SD, SD1 and SD2 parameters are provided to perform channel- dependent adaptive E-TFC determination. The "SINR-based scheduling" term used herein stems from the fact that the BS can derive them based on the post- equalizer SINR shortfall due to inter-symbol and/or inter-stream interference.

Signalling relating to scheduling grant (SG) reduction during transmissions overlapping the available RACH access slots may be provided.

The SDi parameters can be signalled in addition to Scheduling Grant (SG) yet they do not affect the MS TX power. This continues to be determined by the SG, with the value SG-SD^'\ determining the E-TFC selection in the MS.

The SDi parameters may increase the amount of DL signalling but this is not a problem as the cell is supporting only a small MS population, possibly only a single MS, during HRUM. The SD\ parameters may also be used to signal an increase of E-TFC beyond the SG. For example, this may be useful in the case of UL macrodiversity reception or interference cancellation, where at least one of the streams could be received with a higher quality (lower Block Error Rate (BLER)) than the target.

Instead of the SD^'\ parameter signalling, AMC could also be achieved by maximum E-TFC indication.

SINR-based scheduling can be used to add another mechanism on top of power control for E-TFC selection and link adaptation. In accordance with an embodiment selectable de-activation of Outer Loop Power Control (OLPC) to achieve SINR-based scheduling is provided. For example, to avoid unpredictable operation because of use of these two mechanisms in parallel, power control operation during HRUM operation may be modified follows such that Outer Loop Power Control (OLPC) updates are stopped and instead the Signal to Interference Ratio (SIR) target for Inner Loop Power Control (ILPC) is set to a fixed value. This should be safely high to ensure reliable control channel decoding, but not significantly higher than the typical operating point in absence of HRUM to avoid convergence delays when HRUM is turned on/off.

SIR may not be calculated as a post-receiver SINR value. Instead, the SIR can be calculated as a C/l related value (e.g. SIR = a ^* C/l), a C (received signal strength) related value (e.g. SIR = b ^* C) or a received total wideband power (RTWP) related value (e.g. SIR = c ^* RTWP).

According to a possibility ILPC command frequency may be reduced from 1500 Hz to e.g. 500, 300 or 100 Hz. Also, a POWER HOLD command can be made possible. The default power control loop operates at slot boundaries and includes +/-1 dB POWER UP and DOWN commands only. In a high SINR range the up/down steps may give rise to increased inter-symbol interference in the presence of multipath propagation and TX/RX pulse shaping filters, as well as impair channel estimation accuracy. The lower ILPC rate and the hold command can the used to reduce or remove this effect. According to a possibility, ILPC may be replaced by a closed or open loop path loss and shadow fading compensation mechanism. In certain embodiments power control can be affected when SIR target selection (/calculation) algorithm changes at the transmission mode switch. For example, dynamic update of the SIR target may be stopped and/or the update may be calculated as a ratio of the received total wideband power to the noise plus interference power.

Although it is possible not to have any power control and migrate towards HSDPA-like pure AMC operation, maintaining at least a rudimentary form of power control, as described above, may be desired for example for the reasons that MS and BS power levels should not deviate too far from the typical CDMA- operation points to avoid convergence delays after HRUM (de-)activation, UL RTWP should be kept within the BS receiver dynamic range, excess MS TX power should be avoided to limit battery drain, and MS TX power should be limited to avoid adjacent carrier interference.

It may be desirable to schedule high rate transmissions, by means of absolute grants, in such a way that RACH access slots are avoided. However, as RACH preamble detection is required at very low C/l (below -15 dB, see 25.104), coexistence of HRUM with an occasional RACH instance is feasible.

In order to improve the coexistence of HRUM with the random access procedure, it may be beneficial to introduce further optional information elements into the HRUM parameterization set. Namely (/^') an element informing the MS that the SG should be reduced during transmissions overlapping access slots available for RACH preamble transmission and (/^'/^') a reduced SG value to be used during such transmissions. The access slots available for RACH transmission are known to the MSs from the broadcast information.

In accordance with an embodiment HRUM activation involves at least some of the following features:

• Switching the serving cell (group of cells) RoT target to a high value so that high data rates can be supported (e.g. from 6 dB to 20 dB).

• Setting the SIR target for ILPC to a fixed value. This should be safely high to ensure reliable control channel decoding, but not significantly higher than the typical operating point in absence of HRUM to avoid convergence delays when HRUM is turned on/off. For example, the HRUM SIR may be a BS internal SINR value or the latest SINR value + offset or an RNC pre-configured value.

• Activating SINR based scheduling. This is achieved by extending the existing power control and power based scheduling principles by additional parameters: SD in the case of rank-1 recommendation and SD1 and SD2 in the case of a rank-2 recommendation.

• Reducing the ILPC command frequency from 1500 Hz to e.g. 500, 300 or 100 Hz and allowing the POWER HOLD command. The default power control loop operates at slot boundaries and includes +/-1 dB POWER UP and DOWN commands only. There is evidence that in the high SINR range the up/down steps give rise to increased inter-symbol interference in the presence of multipath propagation and TX/RX pulse shaping filters, as well as impair channel estimation accuracy. The lower ILPC rate and the hold command are a means of reducing or removing this effect.

• Calculating the RX SIR not as a post-receiver SINR value. Instead, it should be calculated as a C/l related value (e.g. SIR = a ^* C/l), a C related value (e.g. SIR = b ^* C) or an RTWP related value (e.g. SIR = c ^* RTWP).

The above actions can be initiated by a BS. SINR scheduling activation and ILPC mode change may need to be signalled to the MS. An example of HRUM activation and deactivation is shown in Figure 9.

In the above description it was assumed that HRUM operation covers both the rank-1 and rank-2 high rate transmissions. It is noted that another possibility is to operate rank-1 transmissions according to legacy principles (no SD parameter signalling) while operating rank-2 transmissions according to HRUM principles of SINR-based scheduling and, optionally, modified power control.

An example of the SD parameter encoding as part of AGCH is shown in Figure 10.

When SINR scheduling is activated, it may be beneficial for the SIR measurement in the BS to be based on RX signal power rather post-equalizer SINR for example SIR = a ^* C/l. For example, when a single MS is present in the cell, a = 256^*Ec_DPCCH/Ec_total, where Ec_DPCCH is the transmitted per chip DPCCH energy and Ec_total is the total energy transmitted by the MS. Then, the scheduling grant can be derived as follows:

SIRJgt = (256^*Ec_DPCCH / Ecjotal) ^* CJgt / 1

Ec_DPCCH / Ecjotal = SIRJgt / (256 ^* CJgt / 1)

SG = Ecjotal / Ec_DPCCH - 1 = (256 ^* CJgt / 1) / SIRJgt - 1

Now, using CJgt / 1 + 1 = RoTJgt we can write:

SG = (256 ^* (RoTJgt - 1 )) / SIRJgt - 1

Example scenarios where HRUM can be deployed include a single high rate MS in a cell or a group of cells. A straightforward use case for HRUM is the presence of a single active MS in the cell. This is expected to be a frequent occurrence in small cells, e.g. in the home or office environment but may also take place in a macrocell. The term 'active' refers to a MS in the CELL_DCH state. Other MSs may be physically present in the same geographical area but not be 'active' e.g. in the IDLE or CELL_PCH state.

Another example includes one high rate connection and a group of low rate MSs. In this scenario, one high rate connection coexists with a number of low rate connections. The term low rate refers to e.g. an AMR speech or basic radio resource control (RRC) signalling for which a very low RX C/l, below -15 dB is sufficient. Optionally, an interference cancellation mechanism operates in the BS receiver to remove the interference that the high rate transmission causes towards low rate transmissions. Optionally, for the high-rate connection, the RX SIR for ILPC is calculated as proportional to the RX power as SIR = a ^* C_high_rate or SIR = b ^* RTWP.

In accordance with an example TDMA scheduling is provided. In this scenario, a group or active MSs is present in the cell. However, only one of them is granted a high rate transmission by the HSUPA scheduler. The remaining MS not allowed to transmit data, or are allowed to transmit with a very low grant so that system stability is not endangered. Different MSs are activated in the TDMA manner. The TDMA switching could be carried out on a slow basis e.g. on the order of 10 ... 100 transmission time intervals (TTIs), or on a faster basis - possibly with a single TTI granularity. Optionally, an interference cancellation mechanism operates in the BS receiver to remove the interference that the high rate transmission causes towards low rate transmissions. Optionally, for the high- rate connection, the RX SIR for ILPC is calculated as proportional to the RX power as SIR = a ^* C_high_rate or SIR = b ^* RTWP. TDMA scheduling on the slower basis is seen as advantageous for system stability.

To speed up power control convergence times after the grant is taken away from one MS and sent to another, step-wise TX power adjustments may be provided.

The above provides a solution where co-existence of an alternative mechanism with power control loops and power-based link adaptation is enabled. This can be used to avoid multiple interfering mechanisms to cater for the same performance metrics such as UL BLER. The embodiments may provide an ability of a WCDMA system to better support high data rate transmissions in practical deployments in certain conditions and without endangering system stability. In addition to improved throughput, the SDi parameter signalling may extend the E- TFC selection rules in the UE.

In accordance with an embodiment there is provided a method for controlling uplink data transmission, comprising operating a control function for uplink data transmissions in an area in one of a first mode and a second mode of scheduling, wherein in the first mode the scheduling of the uplink transmission is based on power and in the second mode at least a part of the power based scheduling function is deactivated, determining a condition for switching of the control function between the first and second modes, and causing signalling of information regarding switching between the modes to at least one mobile device.

In a related embodiment a method for uplink data transmission comprises receiving at a mobile device in an area information regarding a mode of scheduling, the mobile device being configured for uplink data transmissions in a first mode and a second mode of scheduling, wherein in the first mode the scheduling of the uplink transmission is based on power and in the second mode at least a part of the power based scheduling is deactivated, and switching between the modes accordingly. In a more detailed aspect of this embodiment method, in the second mode, at least one of the following applies: outer loop power control is deactivated, a signal to interference target for inner loop power control is set to a fixed value, a value for signal to interference for inner loop power control is determined based on carrier to interference ratio, received signal strength, and/or total received wideband power, a hold command is provided for inner loop power control, frequency of inner loop power control command is reduced, and inner loop power control is replaced by a closed or open loop path loss and shadow fading compensation mechanism.

The required data processing apparatus and functions of a control apparatus in a network element and a mobile device for the causing configuration, signaling, determinations, and/or control of measurement and reporting and so forth may be provided by means of one or more data processor. The described functions may be provided by separate processors or by an integrated processor. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), gate level circuits and processors based on multi core processor architecture, as non limiting examples. The data processing may be distributed across several data processing modules. A data processor may be provided by means of, for example, at least one chip. Appropriate memory capacity can also be provided in the relevant devices. The memory or memories may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.

An appropriately adapted computer program code product or products may be used for implementing the embodiments, when loaded or otherwise provided on an appropriate data processing apparatus. The program code product for providing the operation may be stored on, provided and embodied by means of an appropriate carrier medium. An appropriate computer program can be embodied on a computer readable record medium. A possibility is to download the program code product via a data network. In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large an automated process. Complex and powerful tools are available for converting a logic level design into a semiconductor circuit design ready to be formed on a semiconductor substrate.

It is noted that whilst embodiments have been described in relation to WCDMA, similar principles can be applied to any other communication system where dynamic switching between lower and higher rates might be desired. Therefore, although certain embodiments were described above by way of example with reference to certain exemplifying architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.

The foregoing description has provided by way of exemplary and non- limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. For example, a combination of one or more of any of the other embodiments previously discussed can be provided. All such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims.

Claims

1 . A method for controlling uplink data transmission, comprising

operating a control function for uplink data transmissions in an area in one of a first mode and a second mode of scheduling, wherein the second mode provides scheduling of uplink data transmission based on signal quality,

determining a condition for switching of the control function between the first and second modes, and

causing signalling of information regarding switching between the modes to at least one mobile device.

2. A method for uplink data transmission, comprising

receiving at a mobile device in an area information regarding a mode of scheduling, the mobile device being configured for uplink data transmissions in a first mode and a second mode of scheduling, wherein the second mode provides scheduling of uplink data transmission based on signal quality, and

switching between the modes accordingly.

3. A method according to claim 1 or 2, wherein a first target for a ratio of received power and thermal noise is applied in the first mode and a second higher target for the ratio of received power and thermal noise is applied in the second mode.

4. A method according to any preceding claim, comprising selecting an enhanced dedicated channel transport format combination based on the mode.

5. A method according to any preceding claim, comprising scheduling in the second mode based on signal to noise and interference ratio.

6. A method according to any preceding claim, comprising communicating in the downlink, for the second mode, information of at least one difference in a signal to interference and noise ratio compared to a serving grant by a network node.

7. A method according to claim 6, wherein the at least one difference is derived based on post-equalizer signal to noise and interference ratio shortfall.

8. A method according to any preceding claim, wherein the second mode is activated in response to determination that high data rates are possible in the area.

9. A method according to any preceding claim, comprising monitoring for at least one predefined feature in the area and switching between the modes accordingly.

10. A method according to claim 9, wherein the monitoring comprises monitoring for at least one of determined number of mobile devices in the area, load, channel quality, buffer occupancy, active set size, system noise level, access by mobile devices, paging, channel activations, radio link set-ups, handovers, and deterioration of radio conditions.

1 1 . A method according to any preceding claim, comprising changing at least a part of power control operation when switching between the modes.

12. A method according to claim 1 1 , wherein, in the second mode, at least one of the following applies: outer loop power control is deactivated, a signal to interference target is maintained at a value, a value for signal to interference is determined based on a combined value of a total received wideband power to the noise and interference, a hold command is provided for inner loop power control, frequency of inner loop power control command is reduced, and inner loop power control is replaced by a closed or open loop path loss and shadow fading compensation mechanism.

13. A method according to any preceding claim, comprising receiving by a base station controller at least one parameter for the second mode from a radio network controller.

14. A method according to any preceding claim, comprising controlling at least one parameter for the second mode by a radio network controller.

15. An apparatus for control of uplink data transmission, the apparatus comprising at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to perform the method according to any preceding claim.

16. An apparatus according to claim 15, comprising a controller for one of a base station, a radio network and a mobile device adapted for operation in accordance with the principles of code division multiple access.

17. A computer program comprising code means adapted to perform the steps of any of claims 1 to 14 when the program is run on a processor.