TECHNICAL FIELD

The present disclosure relates to a wireless device (and a method implemented thereby) that is configured with resources for both Physical Uplink Control Channel (PUCCH) and short PUCCH (sPUCCH), and determines whether or not the sPUCCH performance is equal to the performance of the PUCCH, and based on a result of this determination applies a strategy for determining when to trigger a fallback wherein the strategy is based on a number of failed Scheduling Request (SR) transmissions to a wireless access node. The present disclosure also relates to the wireless access node (and a method implemented thereby) that is configured to determine information associated with the serving cell of the wireless device, and transmit the information associated with the serving cell to the wireless device, wherein the information enables the wireless device to determine whether or not the sPUCCH performs equally well as the PUCCH.

BACKGROUND

The following abbreviations are herewith defined, at least some of which are referred to within the following description of the present disclosure.

3GPP 3rd-Generation Partnership Project

ASIC Application Specific Integrated Circuit

BLER Block Error Rate

BSS Base Station Subsystem

BTS Base Transceiver Station

CE Control Element

CN Core Network

CSI Channel State Information

DCI Downlink Control Information

DL Downlink

DMRS Demodulation Reference Symbols

DSP Digital Signal Processor

eNB Evolved Node B

EDGE Enhanced Data rates for GSM Evolution

EGPRS Enhanced General Packet Radio Service

E-UTRA Evolved Universal Terrestrial Radio Access

E-UTRAN Evolved Universal Terrestrial Radio Access Network

FDMA Frequency Division Multiple Access

gNB Next generation Node B

GSM Global System for Mobile Communication

HARQ Hybrid Automatic Repeat Request

HTTP Hypertext Transfer Protocol

LTE Long-Term Evolution

MAC Medium Access Control

MS Mobile Station

MTC Machine Type Communications

NB Node B

ng-eNB Next generation eNB

NR 5G New Radio

OFDM Orthogonal Frequency Division Multiplexing

PDCCH Physical Downlink Control Channel

PRACH Physical Random Access Channel

PDSCH Physical Downlink Shared Channel

PUCCH Physical Uplink Control Channel

PUSCH Physical Uplink Shared Channel

RAN Radio Access Network

RAT Radio Access Technology

RNC Radio Network Controller

RRC Radio Resource Control

SC Single Carrier

SF Subframe

S-GW Serving Gateway

SIBX SystemInformationBlock TypeX

SINR Signal to Interference and Noise Ratio

SNR Signal to Noise Ratio

SR Scheduling Request

SRS Sounding Reference Symbols

sPDCCH Short Physical Downlink Control Channel

sPDSCH Short Physical Downlink Shared Channel

sPUCCH Short Physical Uplink Control Channel

sPUSCH Short Physical Uplink Shared Channel

sTTI Short TTI

TCP Transmission Control Protocol

TTI Transmission Time Interval

UE User Equipment

UL Uplink

UTRAN Universal Terrestrial Radio Access Network

WCDMA Wideband Code Division Multiple Access

WiMAX Worldwide Interoperability for Microwave Access

Packet data latency is one of the performance metrics that vendors, operators, and end-users regularly measure (e.g., via speed test applications). Packet data latency measurements are done in all phases of a lifetime of a radio access network (RAN) system, such as when verifying a new software release or a system component, when deploying the RAN system, and when the RAN system is in commercial operation.

Shorter packet data latency than previous generations of 3GPP radio access technologies (RATs) was one performance metric that guided the design of Long Term Evolution (LTE). The end-users also now recognize LTE to be a system that provides faster access to the internet and lower packet data latencies than previous generations of mobile radio technologies.

Packet data latency is important not only for the perceived responsiveness of the system but it is also a parameter that indirectly influences the throughput of the system. In this regard, Hypertext Transfer Protocol (HTTP)/Transmission Control Protocol (TCP) is the dominating application and transport layer protocol suite used on the internet today. According to the HTTP Archive the typical size of HTTP-based transactions over the internet are in the range of a few 10's of Kbytes up to 1 Mbyte. In this size range, the TCP slow start period is a significant part of the total transport period of the packet stream. During the TCP slow start the performance is packet data latency limited. Hence, improved packet data latency can rather easily be shown to improve the average throughput, for this type of TCP-based data transaction.

One approach to reduce the packet data latency is the reduction of transport time of data and control signalling, by addressing the length of a transmission time interval (TTI). By reducing the length of a TTI and maintaining the bandwidth (i.e., keeping the frequency domain resources constant), the processing time at the transmitter node and the receiver node is also expected to be reduced due to less data having to be processed within the reduced TTI. In LTE release 8, a TTI corresponds to one subframe (SF) of length 1 millisecond. One such 1 ms TTI is constructed by using 14 Orthogonal Frequency Division Multiplexing (OFDM) or 14 Single Carrier Frequency Division Multiple Access (SC-FDMA) symbols in the case of normal cyclic prefix and 12 OFDM or 12 SC-FDMA symbols in the case of extended cyclic prefix. In LTE release 14 in the 3rd-Generation Partnership Project (3GPP), a study item on packet data latency reduction has been conducted, with the goal of specifying transmissions with shorter TTIs, such as a slot or a few symbols. A work item with the goal of specifying short TTI (sTTI) started in August 2016 (see RP-171468, “Work Item on Shortened TTI and Processing Time for LTE”, 3GPP TSG RAN Meeting #76, West Palm Beach, USA, Jun. 5-8, 2017—the entire contents of which are hereby incorporated herein by reference).

An sTTI can be realized using any duration in time, can comprise resources on any number of OFDM or SC-FDMA symbols, and can start at any fixed symbol position within the overall subframe. For the work in LTE, the focus of the work currently is to only allow the sTTIs to start at fixed positions with time durations of either 2, 3, or 7 symbols. Furthermore, the sTTI is not allowed to cross the slot or subframe boundaries.

One example of an sTTI configuration100is shown in a second row ofFIG. 1(PRIOR ART), where the duration of the uplink short TTI is 0.5 ms, i.e., seven SC-FDMA symbols102for the case with normal cyclic prefix. The third row ofFIG. 1(PRIOR ART) shows an sTTI configuration110with a combined length of 2 or 3 symbols102for each sTTI #0, sTTI #1, sTTI #2, sTTI #3, sTTI #4, and sTTI #5. The first row ofFIG. 1(PRIOR ART) shows a traditional TTI configuration120with 14 symbols102. Here, the “R” inFIG. 1(PRIOR ART) indicates the Demodulation Reference Symbols (DMRS) symbols102, and the “D” indicates the data symbols102. Other sTTI configurations are not excluded, andFIG. 1(PRIOR ART) is only an attempt to illustrate differences in possible sTTI lengths.

Although the use of a sTTI has merits when it comes to reducing packet data latency, it can also have a specifically negative impact to the uplink (UL) coverage since less energy is transmitted by the User Equipment (UE) (i.e., a reduced number of resource elements are transmitted when sTTI is used). For example, when considering the UL control channel, the same Hybrid Automatic Repeat Request (HARQ) information and Channel State Information (CSI) as well as Scheduling Requests which are sent when the legacy TTI is used still need to be sent when the sTTI is used but will be transmitted using less energy.

Due to the potential for reduced UL control channel performance when a UE transmits using sTTI, one possible solution is to configure a longer sTTI length on the UL than for the downlink (DL) to combat these problems. For example, the configured sTTI length combination in the [DL,UL] can consist of {2,7}. In another possible solution, there is also the possibility of the network scheduling the UE with a 1 ms TTI duration (as per the first row ofFIG. 1) dynamically on a subframe-by-subframe basis in support of the most demanding coverage conditions.

The following terms are used in the discussion hereinafter:Physical Uplink Control Channel (PUCCH) denotes the UL control channel on 1 ms TTI while short PUCCH (sPUCCH) denotes the UL control channel on a sTTI.Physical Uplink Shared Channel (PUSCH) denotes the UL data channel on 1 ms TTI while short PUSCH (sPUSCH) denotes the UL data channel on a sTTI.Physical Downlink Control Channel (PDCCH) denotes the DL control channel on 1 ms TTI while short PDCCH (sPDCCH) denotes the DL control channel on a sTTI.Physical Downlink Shared Channel (PDSCH) denotes the DL data channel on 1 ms TTI while short PDSCH (sPDSCH) denotes the DL data channel on a sTTI.

In LTE, the UL control channel PUCCH can be used to carry different types of information: HARQ feedback, scheduling request (SR), and CSI feedback. Different PUCCH formats with different maximum payloads are defined to be able to carry the different information types. For example, PUCCH format 1/1a/1b is suitable for transmitting very low payload of UL control information like HARQ feedback and scheduling request (SR). While, PUCCH format 2/3/4/5 is suitable for larger payload of UL control information, like more than 2 HARQ bits and CSI report. Similarly, different formats with different maximum payloads will be supported for sPUCCH.

Before transmitting the PUCCH, the UE should compute the required transmit power according to the power control equation for PUCCH defined in the 3GPP Technical Specification (TS) 36.213 v14.3.0, June 2017 entitled “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures” (the entire contents of which are hereby incorporated herein by reference) as follows.

For subframe i and serving cell c,

PPUCCH⁡(i)=min⁢{PCMAX,c⁡(i),P0⁢_⁢PUCCH+PLc+h⁡(nCQI,nHARQ,⁢nSR)+ΔF⁢_⁢PUCCH⁡(F)+ΔTxD⁡(F′)+g⁡(i)⁢}
for PUCCH format 1/1a/1b/2/2a/2b/3, and

PPUCCH⁡(i)=min⁢{PCMAX,c⁡(i),P0⁢_⁢PUCCH+PLc+10⁢log10⁡(MPUCCH,c⁡(i))+ΔTF,c⁡(i)+ΔF⁢_⁢PUCCH⁡(F)+g⁡(i)⁢}
for PUCCH format 4/5, wherePCMAX,c(i) is the maximum transmit power.PO_PUCCHis the target of received power.PLcis the downlink path loss estimate.h(nCQI,nHARQ,nSR) is a PUCCH format dependent value that reflects cases with larger payload.MPUCCH,c(i) is the number of resource blocks for PUCCH format 5, equals 1 for all other formats.ΔF_PUCCH(F) is a relation in dB between PUCCH format F and PUCCH format 1a.ΔTF,c(i) is an adjustment factor depending on number of coded bits that is exactly specified in 3GPP TS 36.213.ΔTxD(F′) depends on the number of antenna ports configured for PUCCH.g(i) is the closed loop power control state and is updated using δPUCCHsignaled in the downlink assignment.

It is to be noted that a similar procedure and power control equation will be defined for sPUCCH

A UE that has uplink data in its buffer indicates it wants to be scheduled on the UL by sending the network a “Scheduling Request”, SR. In LTE, the SR can be indicated using any of the PUCCH formats. But, if a UE has no other UL control information to send other than the SR, then the PUCCH format selected for the SR transmission is PUCCH format 1, which is defined so that multiple UEs can transmit SRs simultaneously (i.e., using the same time and frequency domain resources). As such, multiple UEs can transmit SRs simultaneously to indicate to the network that they want to be scheduled for uplink data transmission. The periodicity with which the UE can transmit an SR to the network is configurable. A SR sent using PUCCH is transmitted using 14 SC-FDMA symbols for the case with normal cyclic prefix as per row 1 ofFIG. 1(i.e., a TTI of 1 ms).

The concept of sending a SR using a sPUCCH has been recently introduced wherein a sTTI (e.g., as per the second and third rows ofFIG. 1) is used by the UE to convey the SR to the network, thereby allowing the UE to reduce the time required to inform the network that it wants to be scheduled for uplink data transmission. A UE can be configured with both PUCCH and sPUCCH as separate resources allowing the potential for even further reducing the packet data delay experienced. For example, the location of the periodic transmission opportunities provided by PUCCH and sPUCCH can be staggered in the time domain, thereby allowing a UE to select the next available PUCCH or sPUCCH for SR transmission whenever the UE determines it has uplink data in its buffer.

A UE configured with both PUCCH and sPUCCH needs a process for determining how it should use PUCCH and sPUCCH when transmitting the SR to inform the network that it has uplink data in its buffer. The decision process can take into account the reality that sPUCCH coverage is worse than PUCCH coverage. Possible examples of UE implementations when the UE is configured with only the PUCCH (legacy operation) and when the UE is configured with both PUCCH and sPUCCH (implementations 1 and 2) are as follows:

Legacy Operation:

As per legacy operation, a UE configured with only PUCCH transmits the SR thereon up to K times without success (i.e., a valid grant is not received) before it triggers fallback (i.e., at fallback, the UE releases its PUCCH resources and resorts to contention-based access on the Physical Random Access Channel (PRACH)).

Implementation 1:

A UE configured with PUCCH and sPUCCH transmits on the first available SR resource up to M times before fallback but must still transmit SR on the PUCCH K times (without success) before fallback is allowed (i.e., at fallback, the UE releases its PUCCH and sPUCCH resources and resorts to contention-based access on the Physical Random Access Channel (PRACH)). This implementation requires that M is larger than K to ensure that the probability of successful SR transmission is not affected by poor sPUCCH coverage (e.g., the UE experiences a downlink coverage that is less than 9 dB above the maximum coupling loss allowed for its serving cell). However, if sPUCCH coverage is sufficiently robust (e.g., the UE experiences a downlink coverage that is 9 dB or more above the maximum coupling loss allowed for its serving cell) then the performance of the sPUCCH can be considered as being equal to that of the PUCCH. As such, when sPUCCH and PUCCH provide equal performance, a UE will effectively make up to M equally robust SR transmissions (where M is larger than K) and thereby experience excessive battery consumption before triggering a fallback when compared to the legacy operation.

Implementation 2:

A UE configured with PUCCH and sPUCCH accommodates the possibility of poor sPUCCH coverage by first sending the SR up to K times without success on the sPUCCH only, and if still no valid grant is received, it sends the SR on PUCCH up to N more times without success at which point it triggers fallback (i.e., at fallback, the UE releases its PUCCH and sPUCCH resources and resorts to contention-based access on the Physical Random Access Channel (PRACH)). As with the “Implementation 1” above, if the sPUCCH coverage actually experienced by the UE is sufficiently robust then the performance of the sPUCCH can be considered as being equal to that of the PUCCH. As such, when sPUCCH and PUCCH provide equal performance, a UE will then effectively make up to K+N equally robust SR transmissions and once again experience excessive battery consumption before triggering a fallback when compared to the legacy operation.

Considering these two possible implementation examples, it can be seen that there is a need for a more optimized UE strategy for determining when to trigger a fallback that should take into account whether or not the performance of the sPUCCH can be considered as being equal to that of the PUCCH. This need and other needs are addressed by the present disclosure.

SUMMARY

A wireless device (e.g., UE), a wireless access node (e.g., eNB, eNodeB, ng-eNB, gNB), and various methods for addressing the aforementioned need in the prior art are described in the independent claims. Advantageous embodiments of the wireless device, the wireless access node, and various methods are further described in the dependent claims.

In one aspect, the present disclosure provides a wireless device configured to interact with a wireless access node. The wireless device comprises a transceiver circuit configured with resources for a PUCCH and a sPUCCH, and further comprises a buffer that has uplink data stored therein. In addition, the wireless device comprises a processor and a memory that stores processor-executable instructions, wherein the processor interfaces with the memory to execute the processor-executable instructions, whereby the wireless device is operable to perform a determine operation and an apply operation. In the determine operation, the wireless device determines whether or not the sPUCCH performs equally well as the PUCCH. In the apply operation, based on the determination of whether or not the sPUCCH performs equally well as the PUCCH, the wireless device applies a strategy for determining when to trigger a fallback, wherein the strategy is based on a number of failed SR transmissions to the wireless access node, wherein the SR transmissions are transmitted by the transceiver circuit to the wireless access node due to the buffer having uplink data stored therein, and wherein the fallback if triggered includes releasing the resources for the PUCCH and the sPUCCH. An advantage of this specially configured wireless device is that it will experience improved battery conservation and an improved overall packet delay performance for the pending uplink data transmission whenever the wireless device determines that fallback is necessary.

In another aspect, the present disclosure provides a method implemented by a wireless device configured to interact with a wireless access node. The wireless device comprises a transceiver circuit configured with resources for a PUCCH and a sPUCCH, and further comprises a buffer that has uplink data stored therein. The method comprises a determining step and an applying step. In the determining step, the wireless device determines whether or not the sPUCCH performs equally well as the PUCCH. In the applying step, based on the determination of whether or not the sPUCCH performs equally well as the PUCCH, the wireless device applies a strategy for determining when to trigger a fallback, wherein the strategy is based on a number of failed SR transmissions to the wireless access node, wherein the SR transmissions are transmitted by the transceiver circuit to the wireless access node due to the buffer having uplink data stored therein, and wherein the fallback if triggered includes releasing the resources for the PUCCH and the sPUCCH. An advantage of the wireless device implementing this method is that the wireless device will experience improved battery conservation and an improved overall packet delay performance for the pending uplink data transmission whenever the wireless device determines that fallback is necessary.

In yet another aspect, the present disclosure provides a wireless access node configured to interact with a wireless device, wherein the wireless device is located in a serving cell, and wherein the wireless device is configured with resources for a PUCCH and a sPUCCH, The wireless access node comprises a processor and a memory that stores processor-executable instructions, wherein the processor interfaces with the memory to execute the processor-executable instructions, whereby the wireless access node is operable to perform a determine operation and a transmit operation. In the determine operation, the wireless access node determines information associated with the serving cell. In the transmit operation, the wireless access node transmits, to the wireless device, the information associated with the serving cell, wherein the information enables the wireless device to determine whether or not the sPUCCH performs equally well as the PUCCH. An advantage of this specially configured wireless access node is that the wireless device by utilizing this information will experience improved battery conservation and an improved overall packet delay performance for uplink data transmission whenever the wireless device determines that fallback is necessary.

In yet another aspect, the present disclosure provides a method implemented by a wireless access node configured to interact with a wireless device, wherein the wireless device is located in a serving cell, and wherein the wireless device is configured with resources for a PUCCH and a sPUCCH, The method comprises a determining step and a transmitting step. In the determining step, the wireless access node determines information associated with the serving cell. In the transmitting step, the wireless access node transmits, to the wireless device, the information associated with the serving cell, wherein the information enables the wireless device to determine whether or not the sPUCCH performs equally well as the PUCCH. An advantage of the wireless access node implementing this method is that the wireless device by utilizing this information will experience improved battery conservation and an improved overall packet delay performance for uplink data transmission whenever the wireless device determines that fallback is necessary.

Additional aspects of the present disclosure will be set forth, in part, in the detailed description, figures and any claims which follow, and in part will be derived from the detailed description, or can be learned by practice of the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure.

