WO2016161597A1

WO2016161597A1 - Adaptive transmission methods for uplink control information

Info

Publication number: WO2016161597A1
Application number: PCT/CN2015/076162
Authority: WO
Inventors: Shaohua Li; Rui Fan; Jinhua Liu; Qianxi Lu; Xinghua SONG
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2015-04-09
Filing date: 2015-04-09
Publication date: 2016-10-13

Abstract

The present invention relates generally to telecommunications, and more particularly, to transmission of uplink control information in wireless telecommunications systems. According to one embodiment of the present invention, a method for switching transmission modes for control channel information in a wireless communication system, be characterized in comprising: receiving an indication for switching transmission for control channel information from a radio access node； and according to the indication, switching the transmission of a UE from a first transmission mode for control channel information to a second transmission mode for control channel information.

Description

ADAPTIVE TRANSMISSION METHODS FOR UPLINK CONTROL INFORMATION

TECHNICAL FIELD

The disclosed subject matter relates generally to telecommunications, and more particularly, to transmission of uplink control information in wireless telecommunications systems.

BACKGROUND

Carrier aggregation (CA) for Long Term Evolution (LTE) was introduced in Release 10 (Rel-10) of the Third-Generation Partnership Project (3GPP) specification, and was subsequently enhanced in Release 11 (Rel-11) . The use of CA can increase peak data rates, system capacity, and user experience by aggregating radio resources from multiple carriers. The multiple carriers may reside in the same band or different bands and, for the case of inter-band time-division-duplex (TDD) CA, may be configured with different uplink/downlink (UL/DL) configurations. In Release 12 (Rel-12) , carrier aggregation between TDD and frequency-division-duplex (FDD) serving cells is introduced to support user equipment (UE) connecting to them simultaneously.

In Release 13 (Rel-13) , Licensed-Assisted Access (LAA) has attracted significant interest in extending the LTE carrier aggregation feature towards capturing spectrum opportunities of unlicensed spectrum in the 5GHz band. Wireless local Access network (WLAN) operating in the 5GHz band nowadays already supports 80MHz in the field and 160MHz is to follow in Wave 2 deployment of IEEE 802.11ac. There are also other frequency bands, such as 3.5 GHz, where aggregation of more than one carrier on the same band is possible, in addition to the bands already widely in use for LTE. Enabling the utilization of at least similar bandwidths for LTE in combination with LAA as IEEE 802.11ac Wave 2 will support calls for extending the carrier aggregation framework to support more than 5 carriers. The extension of the CA framework beyond 5 carriers was approved to be one work item for LTE Rel-13. The objective is to support up to 32 carriers in both UL and DL.

Compared to single-carrier operation, a UE operating with CA may report feedback for more than one DL component carriers. Meanwhile, a UE does not need to support DL and UL CA simultaneously. For instance, the first release of CA capable UEs in the market only supports DL CA but not UL CA. This is also the underlying assumption in the 3GPP RAN4 standardization. Therefore, an enhanced UL control channel, i.e. physical uplink control channel (PUCCH) format 3 was introduced for CA during Rel-10 timeframe. However, to support more component carriers in Rel-13, the UL control channel capacity becomes a limitation.

SUMMARY

According to one aspect of the invention, a method for switching transmission modes for control channel information in a wireless communication system comprising:

-receiving an indication for switching transmission for control channel information from a radio access node； and

-according to the indication, switching the transmission of a UE from a first transmission mode for control channel information to a second transmission mode for control channel information.

Preferably, in the above method, the control channel information is uplink control information (UCI) over physical uplink control channel (PUCCH) or UCI over physical uplink shared channel (PUSCH) .

Preferably, in the above method, the indication is based on a gap between a reached SINR and a desired SINR.

Preferably, in the above method, the indication is based on a power headroom report.

Preferably, in the above method, the indication is based on configuration of component carriers.

According to another aspect of the invention, a radio access node in a wireless communication system being configured to:

-generate an indication for switching transmission for control channel information； and

-send the indication to a UE which, according to the indication, switches its transmission from a first transmission mode for control channel information to a second transmission mode for control channel information.

According to another aspect of the invention, a UE in a wireless communication system being configured to:

-receive an indication for switching transmission for control channel information from a radio access node； and

-according to the indication, switch the transmission from a first transmission mode for control channel information to a second transmission mode for control channel information.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of preferred embodiments as illustrated in the accompanying drawings in which:

Fig. 1 illustrates a communication system.

Fig. 2 illustrates an LTE network.

Fig. 3 illustrates a wireless communication device.

Fig. 4 illustrates a radio access node.

Fig. 5 is a block diagram illustrating method steps for switching transmission for control channel information based on current operating conditions.

DESCRIPTION

In 3GPP TS 36.213, section 5.1.2.1, the setting of UE transmit power P_PUCCH for physical uplink control channel (PUCCH) transmission in subframe i is defined by:

where

● P_CMAX, c (i) is the configured UE transmit power defined in 3GPP TS 36.101 in subframe “i” for serving cell “c” .

● P_{O_PUCCH} is a parameter provided by higher layers

● PL_c is the downlink pathloss estimate calculated in the UE for serving cell_c

● The parameterΔ_{F_PUCCH} (F) is provided by higher layers.

● If the UE is configured by higher layers to transmit PUCCH on two antenna ports, the value of Δ_TxD (F') is provided by higher layers

● g (i) is the current PUCCH power control adjustment state.

● h (n_CQI, n_HARQ, n_SR) is a PUCCH format dependent value, wheren_CQIcorresponds to the number of information bits for the channel quality information defined in Subclause 5.2.3.3 in 3GPP TS 36.212.

■ For PUCCH format 3 and when UE transmits Hybrid automatic repeat request (HARQ) -Acknowledgement (ACK) /Scheduling Request (SR) (HARQ-ACK/SR) and periodic Channel State Information (CSI) .

◆ If the UE is configured by higher layers to transmit PUCCH format 3 on two antenna ports, or if the UE transmits more than 11 bits of HARQ-ACK/SR and CSI

◆ Otherwise

In LTE Rel-8, PUCCH format 1/1a/1b and PUCCH format 2/2a/2b are supported for SR, HARQ-ACK and periodic CSI reporting. The PUCCH resource is represented by a single scalar index, from which the phase rotation and the orthogonal cover sequence (only for PUCCH format 1/1a/1b) are derived. The use of a phase rotation of a cell-specific sequence together with orthogonal sequences provides orthogonally between different terminals in the same cell transmitting PUCCH on the same set of resource blocks. In LTE Rel-10, PUCCH format 3 was introduced for carrier aggregation and TDD, when there are multiple downlink transmissions, (either on multiple carriers or multiple downlink subframes) but single uplink (either single carrier or single uplink subframe) for HARQ-ACK, SR and CSI feedback.

Similarly, the PUCCH format 3 resource is also represented by a single scalar index from which the orthogonal sequence and the resource-block number can be derived. A length-5 orthogonal sequence is applied for PUCCH format 3 to support code multiplexing within one resource-block pair (See, 3GPP TS 36.211) and a length-4 orthogonal sequence is applied for shorted PUCCH. Denoting the PUCCH format 3 resource

the resource block number of the PUCCH format 3 resource m is determined by the following

The orthogonal sequence applied for the two slots are derived by the following

Where

and

are the length of the orthogonal sequence for the two slots respectively,

holds for both slots in a subframe using normal PUCCH format 3 while

holds for the first slot and second slot in a subframe using shortened PUCCH format 3.

The PUCCH format 3 resource is determined according to higher layer configuration and a dynamic indication from the downlink assignment. In detail, the Transmitted Power Control (TPC) field in the Downlink control information (DCI) format of the corresponding physical downlink control channel (PDCCH) /Enhanced physical downlink control channel (ePDCC) (PDCCH/ePDCCH) is used to determine the PUCCH resource values from one of the four resource values configured by higher layers, with the mapping defined in Table 1 (See, 3GPP TS 36.213) . For FDD, the TPC field corresponds to the PDCCH/ePDCCH for the scheduled secondary serving cells. For TDD, the TPC field corresponds to the PDCCH/ePDCCH for the primary cell with Downlink assignment index (DAI) value in the PDCCH/ePDCCH larger than ‘1’ . A UE shall assume that the same PUCCH resource values are transmitted in each DCI format of the corresponding PDCCH/ePDCCH assignments.

Table 1: PUCCH Resource Value for HARQ-ACK Resource for PUCCH

For up to 32 DL CCs, there are up to 64 HARQ Acknowledge/Negative Acknowledge (ACK/NACK) at one time (Rank>＝2) depending on the number of configured DL CCs for FDD. For TDD, the number of HARQ-ACK/NACK bits to be fedback depends on the number of configured CCs and UL/DL subframe configuration of the DL CCs. Assume there are 32 DL CCs with UL/DL subframe configuration 2 and transmission mode 3, there are up to 256 (32 *4 *2) HARQ ACK/NACK bits. Assuming 1/2 coding rate and QPSK modulation are applied, FDD needs 32 REs at least while TDD needs 256 REs (32 symbols for FDD and 128 symbols for TDD respectively if the bundling is applied between two codewords) at least.

In 3GPP up to Rel-12, the maximum downlink component carriers are 5. PUCCH format 1b with channel selection and PUCCH format 3 are introduced for HARQ feedback and corresponding fallback operations are defined. The fallback operation is beneficial not only from HARQ-ACK performance perspective but also useful for UE during the transition period. However, in Rel-13, maximum 32 downlink carriers can be configured for one UE and hence a new PUCCH format will be introduced to carry more HARQ-ACK bits due to the aggregation of 32 DL CCs.

Currently, there are three design options to support larger payload size on PUCCH:

-Opt 1: PUCCH format 3 with multiple Physical resource blocks (PRBs)

-Opt 2: PUCCH format 3 with multiple orthogonal cover codes (OCCs)

-Opt 3: PUCCH format 3 with both multiple PRBs and OCCs

As discussed above, for up to 32 DL CCs, there are up to 256 HARQ ACK/NACKs at one time for some component carrier configuration. If PUCCH format 3 power control equation is reused directly compared with PUCCH format 1a, the power offset is:

The above equation may be not directly applicable for the new format design. With some new format design, as described above, the power offset may be determined as follows.

In the above equation, assume 22 bits are carried in one PUCCH format 3 and use

format 3 PUCCHs to carry the total 256 bits and the same performance is achieved as PUCCH format 1a. This power boost is comparable with the scale between transmitted 100 PRB and 1 PRB, which is 20 dB power differences. With so large power boost, it may lead to the power of a lot of UEs based on

P_calculated＝P_{0_PUCCH}+PL_c+h (n_CQI, n_HARQ, n_SR) +Δ_{F_PUCCH} (F) +Δ_TxD (F') +g (i)

exceeding the maximum transmitted power P_CMAX, c (i) .

As an example shown in Figure 1, there are two UEs in the system, one UE (UE1) is very close to the eNB, and the other UE (UE2) is on the border of the cell. For UE1, because it is very close to the eNB, the PL_c is relatively smaller, and for UE2, the PL_c is very large. For UE2, P_calculated is with higher probability to exceed the maximum transmitted power P_CMAX, c (i) . Hence, for UE2, it is a challenge to maintain the uplink control channel transmission with required quality. If there is no reliable HARQ ACK/NACK feedback, it may have great impact on the downlink performance. The disclosed embodiments provide methods that address this problem.

In consideration of the above, certain embodiments of the disclosed subject matter improve the control channel transmission efficiency for CA operation with a large number of CCs. In some embodiments, a network node, e.g. eNB, transmits an indicator to instructa UEto switch transmission methods for control channel information based on current operating conditions. Such embodiments can potentially improve the uplink control channel transmission efficiency for the Further Enhancement of Carrier Aggregation (FeCA) , reduce the impact of PUCCH quality on the Physical downlink shared channel (PDSCH) performance, and conserve UE power. In conventional approaches, for cell edge UEs, PUCCH cannot be reliably detected. Without reliable PUCCH detection, a lot of retransmission may happen. In some worst cases, it will trigger a lot of high layer retransmissions, which will waste resources.

In case the channel quality of the component carriers have strong correlation, less ACK/NACK bits are possible. With less ACK/NACK feedback bits, fewer resources will be expected to carry these ACK/NACK bits. Consequently, less power is needed to achieve the same target SINR, so UE power can be saved.

The described embodiments may be implemented in any appropriate type of communication system supporting any suitable communication standards and using any suitable components. As one example, certain embodiments may be implemented in an LTE network, such as that illustrated in Figure2.

Referring to Figure 2, a communication network 200 comprises a plurality of wireless communication devices 205 (e.g., conventional UEs, machine type communication (MTC) /machine-to-machine (M2M) UEs) and a plurality of radio access nodes 210 (e.g., eNodeBs or other base stations) . Communication network 100 is organized into cells 215, which are connected to a core network 220 via corresponding to radio access nodes 210. Radio access nodes 210 are capable of communicating with wireless communication devices 205 along with any additional elements suitable to support communication between wireless communication devices or between a wireless communication device and another communication device (such as a landline telephone) .

Although wireless communication devices 205 may represent communication devices that include any suitable combination of hardware and/or software, these wireless communication devices may, in certain embodiments, represent devices such as an example wireless communication device illustrated in greater detail by Figure 3. Similarly, although the illustrated radio access node may represent network nodes that include any suitable combination of hardware and/or software, these nodes may, in particular embodiments, represent devices such as the example radio access node illustrated in greater detail by FIG. 3.

Referring to Figure 3, a wireless communication device 300 comprises a processor305, a memory, a transceiver 315, and an antenna 320. In certain embodiments, some or all of the functionality described as being provided by UEs, MTC or M2M devices, and/or any other types of wireless communication devices may be provided by the device processor executing instructions stored on a computer-readable medium, such as the memory shown in Figure3. Alternative embodiments may include additional components beyond those shown in Figure 3 that may be responsible for providing certain aspects of the device’s functionality, including any of the functionality described herein.

Referring to Figure 4, a radio access node 400 comprises a node processor 405, a memory 410, a network interface 415, a transceiver 420, and an antenna 425. In certain embodiments, some or all of the functionality described as being provided by a base station, a node B, an enodeB, and/or any other type of network node may be provided by node processor 405 executing instructions stored on a computer-readable medium, such as memory 410 shown in Figure 4. Alternative embodiments of radio access node 400 may comprise additional components to provide additional functionality, such as the functionality described herein and/or related supporting functionality.

As indicated above, certain embodiments of the disclosed subject matter improve uplink control channel transmission efficiency for carrier aggregation operation with large number of component carriers. In the description that follows, uplink control information (UCI) over PUCCH is presented as one example. Similar concepts can also be applied for UCI over physical uplink shared channel (PUSCH) . Skilled people may readily extend the application to the UCI transmission over PUSCH.

In general, the described embodiments switch transmission methods for control channel information based on current operating conditions. The switching may be controlled by an eNB transmitting an indication to a UE as illustrated in Figure 5. The switching may be implemented in any of various alternative ways as described below with reference to first through fifth embodiments.

In one embodiment, an eNB sends an indication to a UE to instruct the UE to switch the transmission methods for PUCCH.

In a first variant of the first embodiment, switching the transmission methods for PUCCH comprises the following features.

● Changing a payload size carried by the PUCCH, and/or

■ For the UE whose signal quality cannot maintain the high payload PUCCH transmission, the payload can be reduced. Several schemes can be used for the payload reduction according to the indication from eNB, including bundling schemes, such as spatial domain bundling, and/or frequency bundling, and/or time domain bundling. As a first example:

◆ Indicator ＝ 1, bundling is used

◆ Indicator ＝ 0, no bundling is used.

As a second example:

◆ Indicator ＝ 101, UE performs spatial domain bundling only

◆ Indicator ＝ 110, UE performs spatial domain bundling first and then frequency domain bundling

◆ Indicator ＝ 111, UE performs spatial domain bundling firstly, frequency domain bundling secondly and time domain bundling thirdly

Any bundling scheme or any combination of the bundling scheme can be used for payload reduction.

It may also include some source coding schemes, such as data compression schemes. With some source coding scheme, the efficient feedback bits can be reduced.

● Changing the resource carrying the PUCCH, and/or

The indicator of PUCCH payload adjustment may result in resource changing in PRBs, and/or OCCs, and/or the allocated power, or other related resource to change PUCCH transmission in order to reach the desired SINR for PUCCH.

■ For the UE whose signal quality cannot support the high payload PUCCH transmission, the payload can be reduced following the indicator. With the payload decrease, the number of time-frequency resources, and/or OCCs and/or the allocated TX power may be reduced and the desired SINR can be reached. Or

■ For the UE whose signal quality is sufficient to support high payload PUCCH transmission, the payload maybe increased to provide more detailed HARQ ACK/NACK feedback. With the payload increase, the number of time-frequency resources, and/or OCCs and/or the allocated TX power may be increased in order to reach the desired SINR

● Changing the modulation and coding schemes

With the payload change and the resource change according to the indicator, the modulation and coding scheme may be changed accordingly as well. For example, when the payload is higher than a threshold, convolution code may be used. With the reduction of the payload, other coding scheme may be more efficient, such as Reed-Muller code.

In a second variant of the second embodiment, the transmitter sends the indication based on the gap between the reached SINR and the desired SINR. If the desired SINR cannot be achieved using the power control, for instance, reached SINR-desired SINR <threshold 1, the UE may be identified as the problem UE whose channel quality is not good enough, eNB can indicate the UE to reduce payload size. Otherwise, if the desired SINR can be well achieved or exceeded, for instance, reached SINR -desired SINR > threshold 2, the UE can be indicated to use larger payload size.

In a third variant of the first embodiment, the transmitter sends the indication based on the power headroom report (PHR) . If the PHR is smaller than the given threshold, the transmitter may send the indication to instruct the UE to use smaller payload size so that less power resource is used for PUCCH transmission. Otherwise, if the PHR is larger than another given threshold, the transmitter may send the indication to instruct the UE to use larger payload size and allocate more TX power for PUCCH transmission.

In a fourth variant of the first embodiment, the transmitter sends the indication according to the configuration of the component carriers (CC) . The configuration comprises the number of component carriers, the carrier type of each component carrier and the allocation of each component carrier. As one example, there are two types of component carriers (CC) , one is license carrier and one is unlicensed carrier. If there are a lot of unlicensed carriers, the requirement on the number of feedback bits may be not so tight, thus the payload of PUCCH may be expected to be reduced. In this case, the smaller payload size and less resource PUCCH may be used. In this case, the transmitter may indicate the receiver to use the transmission methods with smaller payload size and/or less resource. Otherwise, the transmitter may indicate the receiver to use transmission methods with large payload size and/or more resource.

In a fifth variant of the embodiment, the indication is signaled by higher layer signaling, it may be also possible to signal by MAC control element or physical layer signaling (for instance, PDCCH order or one field in the DL scheduling DCI) . It may be semi-static configured, and/or it may be dynamically signaled.

In a sixth variant of the first embodiment, the eNB sends the indicator but the UE may miss the indicator, and it is not known for eNB. In this case, eNB may take some enhancement for the PUCCH detection. One possible enhancement is to perform multiple blind detection based on all or partial hypothetic assumptions about the transmission methods for PUCCH. eNB performs blind detection until the right information is obtained.

In a second embodiment, the eNB does not send the indicator, and the UE makes a decision by itself on the transmission methods for PUCCH based on predefined rules. In this case, from eNB side, eNB may perform blind detection on the transmission methods based on the predefined rule. As one example, different payload may be used for UE, eNB may try to use different hypothesis for the payload and decode the PUCCH until the right information is obtained. As another alternative, the PUCCH format indicator can be transmitted by the UE along with the PUCCH information. The eNB will first decode PUCCH format indicator then the corresponding PUCCH transmission.

In a third embodiment, the method performed by the receiver which adjusts the PUCCH transmission according the received indication from the eNB comprises the following features.

● Receiving the indication to switch the transmission methods for PUCCH.

● Switching the transmission method based on the indication

In a fourth embodiment, the terminal switches the transmission method for PUCCH by itself based on the operation condition according to preconfigured rules by the eNB. For example, power limitation based rules may be configured as follows.

● Rule 1: if the transmitted power given based on the equation (see P_calculated given in section -) exceeds the maximum transmission power, the terminal may select the transmission methods with smaller payload size and/or less resource for PUCCH transmission. Otherwise, the terminal may use transmission methods with large payload size and/or less resource for PUCCH transmission. Here, the resource may be the number of time-frequency resources, and/or OCCs and/or the allocated TX power, as discussed in the above-mentioned section.

● Rule 2: the UE can keep monitoring the power headroom, if the power headroom is lower than a first threshold, the UE can reduce the payload size； if the power headroom is higher than a second threshold, the UE can increase the payload size by reduce the bundling.

In a variant of the fourth embodiment, where the transmitted power given on the equation (see P_calculated given in section -) is large than a given threshold, the transmission methods for PUCCH may be switched.

In another variant of the fourth embodiment, the UE indicates if the PUCCH transmission method is changed using one predefined field in UCI, e.g., this indicator can either be encoded together with the PUCCH transmission or separately. In the eNB side, the eNB determines how to interpret the received HARQ ACK bit according the said field.

In a fifth embodiment, the UE supports both the third embodiment and the fourth embodiment at the same time. For example, if the UE receives the indication, the UE may have the behavior according to the third embodiment. Otherwise, if the UE does not receive the indication, UE may take action according to the fourth embodiment.

While the disclosed subject matter has been presented above with reference to various embodiments, it will be understood that various changes in form and details may be made to the described embodiments without departing from the overall scope of the invention.

Claims

A method for switching transmission modes for control channel information in a wireless communication system, be characterized in comprising:

-receiving an indication for switching transmission for control channel information from a radio access node； and

-according to the indication, switching the transmission of a UE from a first transmission mode for control channel information to a second transmission mode for control channel information.
A method according to claim 1, wherein the control channel information is uplink control information (UCI) over physical uplink control channel (PUCCH) or UCI over physical uplink shared channel (PUSCH) .
A method according to claim 1, wherein, the indication is based on a gap between a reached SINR and a desired SINR.
A method according to claim 1, wherein, the indication is based on a power headroom report.
A method according to claim 1, wherein, the indication is based on configuration of component carriers.
A radio access node in a wireless communication system, be characterized in being configured to:

-generate an indication for switching transmission for control channel information； and

-send the indication to a UE which, according to the indication, switches its transmission from a first transmission mode for control channel information to a second transmission mode for control channel information.
A UE in a wireless communication system, be characterized in being configured to:

-receive an indication for switching transmission for control channel information from a radio access node； and

-according to the indication, switch the transmission from a first transmission mode for control channel information to a second transmission mode for control channel information.