CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Submission Under 35 U.S.C. § 371 for U.S. National Stage Patent Application of International Application Number: PCT/SE2017/050960, filed Sep. 29, 2017 entitled “METHODS AND APPARATUS RELATING TO CONTROL CHANNEL DECODING IN A WIRELESS COMMUNICATIONS NETWORK,” the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to wireless communications, and particularly to methods and apparatus relating to control channel decoding in a wireless communication network.

BACKGROUND

Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.

In an LTE wireless communication network, physical control channels are used to transmit downlink and uplink assignments/grants. The physical downlink control channel (PDCCH) was introduced in the very first release of LTE, while the evolved PDCCH (ePDCCH) was introduced later in Rel-11.

According to current standards, the size of the downlink control region, i.e. the resources where a PDCCH can be located, is adaptive in time domain, typically covering the initial one to three OFDM symbols in each subframe. The size used is signaled to the UEs using the PCFICH (Physical Control Format Indicator CHannel). In the frequency domain the PDCCH is static, covering the whole frequency band.

The ePDCCH is also static, but in the time domain, where the starting OFDM symbol of the ePDCCH is the one following directly after the downlink control region. In the frequency domain the ePDCCH is semi-static, where a UE can be configured with up to two ePDCCH regions (called sets). Each of the ePDCCH sets covers a set of physical resource blocks, not necessarily of equal size.

A search space is a set of time-frequency locations where a UE attempts to receive a PDCCH or a ePDCCH. There are common and UE-specific search spaces. All UEs will attempt to receive a PDCCH/ePDCCH in the common search spaces while only specific UEs will consider the UE-specific search spaces.

Upon a successful reception of a downlink assignment the UE may perform a reception of a data transmission on PDSCH (Physical Downlink Shared CHannel) according to the received assignment. The UE decodes the data and then transmits a HARQ-ACK (Hybrid Automatic Repeat request) indicating whether the data was successfully decoded or not. The HARQ-ACK may be sent on PUSCH (Physical Uplink Shared CHannel) or PUCCH (Physical Uplink Control CHannel) depending on if the UE additionally sends data or not. For FDD (Frequency Division Duplex) the HARQ-ACK is transmitted in sub-frame n+4 acknowledging a data transmission in sub-frame n. When the eNB receives the HARQ-ACK it may determine whether it needs to perform a re-transmission or not. There are 8 HARQ processes in the UEs which allows for a HARQ-RTT (HARQ Round-Trip Time) of 8 sub-frames. Depending on the processing capability of the eNB, the HARQ-RTT may be shortened slightly.

3GPP has started work on 5G new radio (NR) technology where reduced latency is one of the key features. For NR the PDCCH is expected to be in the first OFDM symbol(s) like the LTE PDCCH to allow for early decoding, although this may not necessarily be the case. The PUCCH is proposed to be in the last OFDM symbol of each slot which may make it possible to transmit the HARQ-ACK in the same sub-frame as the acknowledged data transmission.

Certain categories of traffic, e.g. ultra-reliable, low-latency communications (URLLC), put very strict robustness requirements on the control channel, as well as low-latency requirements. For example, the control channel may need to operate at error probabilities significantly lower than 10−5. One way of supporting such high requirements on robustness on the NR-PDCCH is to use a large number of physical resources for the DL control channel, e.g. to use 32 CCEs (control channel elements) for the NR-PDCCH. However, such a large number of CCEs requires that the control region is large enough to contain that many CCEs. The current assumption in 3GPP is that a CCE consists of 6 REGs (Resource Element Groups), where a REG maps to the REs (Resource Elements) in one OFDM symbol and PRB (Physical Resource Block). With a 30 kHz sub-carrier spacing (SCS) numerology, a 20 MHz bandwidth consists of 50 PRBs and hence the total number of CCEs is at most 8 if the control region consists of a single OFDM symbol. With a larger control region covering more OFDM symbols the number of CCEs can be increased, but this means less resources for the PDSCH. It will be noted that the numerology set out above may be different in the eventual release of NR, or in future releases. However, the problem remains, of achieving low error rates for the control channel without utilizing excessive resources at the expense of the shared data channel.

Hence there is a trade-off between control channel resource usage and reliability requirements that may make certain use cases very challenging (e.g. URLLC).

SUMMARY

There are, proposed herein, various embodiments which address one or more of the issues disclosed herein.

In one aspect, there is provided a method in a wireless device for a wireless communications network. The method comprises: receiving a first set of coded control symbols on a physical control channel in a first time slot; receiving a second set of coded control symbols on the physical control channel in a second time slot subsequent to the first time slot; and attempting to decode a control message based on the first set of coded control symbols and the second set of coded control symbols using one or more soft-combining techniques.

In further aspects of the disclosure, there is provided a communication system including a host computer. The host computer comprises: processing circuitry configured to provide user data; and a communication interface configured to forward user data to a cellular network for transmission to a user equipment (UE). The UE comprises a radio interface and processing circuitry, the UE's components configured to perform any of the steps of any of the embodiments described herein, including the method recited above.

In some embodiments, the cellular network further includes a base station configured to communicate with the UE.

In some embodiments, the processing circuitry of the host computer is configured to execute a host application, thereby providing the user data; and the UE's processing circuitry is configured to execute a client application associated with the host application.

A further aspect of the disclosure provides a method implemented in a communication system including a host computer, a base station and a user equipment (UE). The method comprises: at the host computer, providing user data; and, at the host computer, initiating a transmission carrying the user data to the UE via a cellular network comprising the base station. The UE performs any of the steps of any of the embodiments described herein, including the method recited above.

In some embodiments, the method further comprises, at the UE, receiving the user data from the base station.

In a further aspect, there is provided a wireless device configured to perform the method recited above. For example, in one aspect there is provided a wireless device for a wireless communications network. The wireless device comprises processing circuitry and a non-transitory machine-readable medium storing instructions which, when executed by the processing circuitry, cause the wireless device to: receive a first set of coded control symbols on a physical control channel in a first time slot; receive a second set of coded control symbols on the physical control channel in a second time slot subsequent to the first time slot; and, attempt to decode a control message based on the first set of coded control symbols and the second set of coded control symbols using one or more soft-combining techniques.

In another aspect of the disclosure, there is provided a method in a network node for a wireless communications network. The method comprises: determining that a wireless device operable in the wireless communications network is configured to soft-combine a physical control channel transmitted over multiple time slots; initiating transmission of a first set of coded control symbols in a physical control channel to the wireless device in a first time slot; and initiating transmission of a second set of coded control symbols in the physical control channel to the wireless device in a second time slot subsequent to the first time slot. The first set of coded control symbols comprises a control message, and the second set of coded control symbols comprises a duplicate copy of the control message.

In further aspects of the disclosure, there is disclosed a communication system including a host computer. The host computer comprises: processing circuitry configured to provide user data; and a communication interface configured to forward the user data to a cellular network for transmission to a user equipment (UE). The cellular network comprises a base station having a radio interface and processing circuitry, the base station's processing circuitry being configured to perform any of the steps of any of the embodiments described herein, including the method recited above.

In some embodiments, the communication system further includes the base station.

In some embodiments, the communication system further includes the UE, wherein the UE is configured to communicate with the base station.

In some embodiments, the processing circuitry of the host computer is configured to execute a host application, thereby providing the user data; and the UE comprises processing circuitry configured to execute a client application associated with the host application.

In further aspects of the disclosure, there is provided a method implemented in a communication system including a host computer, a base station and a user equipment (UE). The method comprises: at the host computer, providing user data; and, at the host computer, initiating a transmission carrying the user data to the UE via a cellular network comprising the base station. The base station performs any of the steps of any of the embodiments described herein, including the method recited above.

In some embodiments, the method further comprises, at the base station, transmitting the user data.

In some embodiments, the user data is provided at the host computer by executing a host application, and the method further comprises, at the UE, executing a client application associated with the host application.

In a further aspect, there is provided a network node configured to perform the method recited above. For example, in one aspect there is provided a network node for a wireless communications network. The network node comprises processing circuitry and a non-transitory machine-readable medium storing instructions which, when executed by the processing circuitry, cause the network node to: determine that a wireless device operable in the wireless communications network is configured to soft-combine a physical control channel transmitted over multiple time slots; initiate transmission of a first set of coded control symbols in a physical control channel to the wireless device in a first time slot; and initiate transmission of a second set of coded control symbols in the physical control channel to the wireless device in a second time slot subsequent to the first time slot. The first set of coded control symbols comprises a control message, and the second set of coded control symbols comprises a duplicate copy of the control message.

Certain embodiments may provide one or more of the following technical advantages. For example, some embodiments allow for soft-combination of control channel assignments providing high enough reliability for certain error-critical applications. By combining control channel assignments from different time slots this can be achieved without any need for multi-node coordination. However, by allowing for multiple transmission points to provide multiple control channel assignments for the wireless device to soft-combine, very high reliability can be achieved without increasing the decoding delay of the downlink control channel.

