WO2018157719A1

WO2018157719A1 - Network node, user device, and method for wireless communication system

Info

Publication number: WO2018157719A1
Application number: PCT/CN2018/075873
Authority: WO
Inventors: Hua Xu
Original assignee: Guangdong Oppo Mobile Telecommunications Corp., Ltd.
Priority date: 2017-03-02
Filing date: 2018-02-08
Publication date: 2018-09-07
Also published as: CN109691205A; TW201834488A; TWI696398B

Abstract

A network node, a user device, and a method for a wireless communication system are provided. The network node includes a processor and a transceiver. The processor is configured to allocate a plurality of resource element group (REG) sets of a physical downlink control channel (PDCCH) having PDCCH candidates defined for at least one control channel element (CCE) aggregation level (AL). CCEs are allocated to a user device and include a plurality of REGs. The REG sets including a set of the REGs are a mapping unit of the PDCCH candidates. The processor is configured to map the REGs of the REG sets to a contiguous time and/or frequency resource. The transceiver is configured to transmit the PDCCH on allocated resources to the user device.

Description

NETWORK NODE, USER DEVICE, AND METHOD FOR WIRELESS COMMUNICATION SYSTEM

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates to the field of communication systems, and more particularly, to a network node, a user device, and a method for a wireless communication system.

2. Description of the Related Art

In long term evolution (LTE) , a physical channel of the LTE can be classified into a downlink channel, i.e., a physical downlink shared channel (PDSCH) and a physical downlink control channel (PDCCH) , and an uplink channel, i.e., a physical uplink shared channel (PUSCH) and a physical uplink control channel (PUCCH) .

The PDCCH is used to transfer downlink control information that informs a user device about resource allocations or scheduling related to downlink resource assignments on the PDSCH, uplink resource grants, and uplink power control commands.

PDCCH signal is designed to be demodulated at the user device based on a cell specific reference signal (CRS) . However, use of the CRS does not take into account of increased complexities of the LTE systems. The use of the cell specific reference signal can limit advanced techniques to increase cell capacity.

SUMMARY

An object of the present disclosure is to propose a network node, a user device, and a method for a wireless communication system to balance channel estimation performance as well as various gains including frequency selective gain and time/frequency diversity gain.

In a first aspect of the present disclosure, a network node for a wireless communication system includes a processor and a transceiver. The processor is configured to allocate a plurality of resource element group (REG) sets of a physical downlink control channel (PDCCH) having PDCCH candidates defined for at least one control channel element (CCE) aggregation level (AL) . CCEs are associated with a user device and include a plurality of REGs. The REG sets including a set of the REGs are a mapping unit of the PDCCH candidates and the processor is configured to map the REGs of the REG sets to a contiguous time and/or frequency resource. The transceiver is configured to transmit the PDCCH on allocated resources to the user device.

According to an embodiment in conjunction with the first aspect of the present disclosure, the processor is configured to map the REG sets of the PDCCH candidates to frequencies in a contiguous or distributed manner.

According to an embodiment in conjunction with the first aspect of the present disclosure, the processor is configured to map the REG sets of the PDCCH candidates to time in a contiguous manner.

According to an embodiment in conjunction with the first aspect of the present disclosure, the processor is configured to map the REG sets in a time-first mapping manner to a plurality of orthogonal frequency-division multiplexing (OFDM) symbols, and the REG sets contain demodulation reference signals (DMRS) on every REG for the PDCCH candidates.

According to an embodiment in conjunction with the first aspect of the present disclosure, the REG sets contain DMRS on a first orthogonal frequency-division multiplexing (OFDM) symbol

According to an embodiment in conjunction with the first aspect of the present disclosure, the REG sets contain DMRS on a second OFDM symbol for the PDCCH candidates.

According to an embodiment in conjunction with the first aspect of the present disclosure, the REG sets do not contain DMRS on a second OFDM symbol for the PDCCH candidates.

According to an embodiment in conjunction with the first aspect of the present disclosure, the REG sets contain DMRS on a third OFDM symbol for the PDCCH candidates.

According to an embodiment in conjunction with the first aspect of the present disclosure, the REG sets do not contain DMRS on a fourth OFDM symbol for the PDCCH candidates.

According to an embodiment in conjunction with the first aspect of the present disclosure, the PDCCH candidates are in a nested structure and larger CCE ALs include CCEs of small CCE Als.

According to an embodiment in conjunction with the first aspect of the present disclosure, the processor is configured to map the REG sets in a time-first mapping and the PDCCH candidates are in a nested structure.

According to an embodiment in conjunction with the first aspect of the present disclosure, the processor is configured to map the REG sets in a frequency-first mapping and the PDCCH candidates are in a nested structure.

In a second aspect of the present disclosure, a user device for a wireless communication system includes a processor and a transceiver. The processor is configured to determine a plurality of resource element group (REG) sets for at least one network node. The transceiver is configured to transmit the REG sets in a physical downlink control channel (PDCCH) to the at least one network node. The REG sets are allocated for the PDCCH having PDCCH candidates defined for at least one control channel element (CCE) aggregation level (AL) . CCEs are allocated to a user device and include a plurality of REGs. The REG sets including a set of the REGs are a mapping unit of the PDCCH candidates, and the processor is configured to map the REGs of the REG sets to a contiguous time and/or frequency resource.

According to another embodiment in conjunction with the second aspect of the present disclosure, the transceiver is configured to receive the PDCCH on allocated resources to the user device, and the transceiver is configured to transmit the REG sets in the PDCCH.

According to another embodiment in conjunction with the second aspect of the present disclosure, the processor is configured to map the REG sets of the PDCCH candidates to frequencies in a contiguous or distributed manner or to time in a contiguous manner.

According to another embodiment in conjunction with the second aspect of the present disclosure, the processor is configured to map the REG sets in a time-first mapping manner to a plurality of orthogonal frequency-division multiplexing (OFDM) symbols, and the REG sets contain demodulation reference signals (DMRS) on every REG for the PDCCH candidates.

According to an embodiment in conjunction with the second aspect of the present disclosure, the REG sets contain DMRS on a first orthogonal frequency-division multiplexing (OFDM) symbol for the PDCCH candidates.

According to another embodiment in conjunction with the second aspect of the present disclosure, the REG sets contain DMRS on a second OFDM symbol for the PDCCH candidates.

According to another embodiment in conjunction with the second aspect of the present disclosure, the REG sets do not contain DMRS on a second OFDM symbol for the PDCCH candidates.

According to another embodiment in conjunction with the second aspect of the present disclosure, the REG sets contain DMRS on a third OFDM symbol for the PDCCH candidates.

According to another embodiment in conjunction with the second aspect of the present disclosure, the REG sets do not contain DMRS on a fourth OFDM symbol for the PDCCH candidates.

According to another embodiment in conjunction with the second aspect of the present disclosure, the PDCCH candidates are in a nested structure and larger CCE ALs include CCEs of small CCE ALs.

According to another embodiment in conjunction with the second aspect of the present disclosure, the processor is configured to map the REG sets in a time-first mapping and the PDCCH candidates are in a nested structure.

According to another embodiment in conjunction with the second aspect of the present disclosure, the processor is configured to map the REG sets in a frequency-first mapping and the PDCCH candidates are in a nested structure.

In a third aspect of the present disclosure, a method of a node for a wireless communication system includes allocating a plurality of resource element group (REG) sets of a physical downlink control channel (PDCCH) having PDCCH candidates defined for at least one control channel element (CCE) aggregation level (AL) and transmitting the PDCCH on allocated resources to the user device. CCEs are allocated to a user device and include a plurality of REGs. The REG sets including a set of the REGs are a mapping unit of the PDCCH candidates, and the method further includes mapping the REGs of the REG sets to a contiguous time and/or frequency resource.

According to another embodiment in conjunction with the third aspect of the present disclosure, the method further includes mapping the REG sets of the PDCCH candidates to frequencies in a contiguous or distributed manner or to time in a contiguous manner.

According to another embodiment in conjunction with the third aspect of the present disclosure, the method further includes mapping the REG sets in a time-first mapping manner to a plurality of orthogonal frequency-division multiplexing (OFDM) symbols, and the REG sets contain demodulation reference signals (DMRS) on every REG for the PDCCH candidates.

According to an embodiment in conjunction with the third aspect of the present disclosure, the REG sets contain DMRS on a first orthogonal frequency-division multiplexing (OFDM) symbol for the PDCCH candidates.

According to another embodiment in conjunction with the third aspect of the present disclosure, the REG sets contain DMRS on a second OFDM symbol for the PDCCH candidates.

According to another embodiment in conjunction with the third aspect of the present disclosure, the REG sets do not contain DMRS on a second OFDM symbol for the PDCCH candidates.

According to another embodiment in conjunction with the third aspect of the present disclosure, the REG sets contain DMRS on a third OFDM symbol for the PDCCH candidates.

According to another embodiment in conjunction with the third aspect of the present disclosure, the REG sets do not contain DMRS on a fourth OFDM symbol for the PDCCH candidates.

According to another embodiment in conjunction with the third aspect of the present disclosure, the PDCCH candidates are in a nested structure and larger CCE ALs include CCEs of small CCE ALs.

According to another embodiment in conjunction with the third aspect of the present disclosure, the method further includes mapping the REG sets in a time-first mapping and the PDCCH candidates are in a nested structure.

According to another embodiment in conjunction with the third aspect of the present disclosure, the method further includes mapping the REG sets in a frequency-first mapping and the PDCCH candidates are in a nested structure.

In a fourth aspect of the present disclosure, a method of a user device for a wireless communication system includes determining a plurality of resource element group (REG) sets for at least one network node and transmitting the REG sets in a physical downlink control channel (PDCCH) to the at least one network node. The REG sets are allocated for the PDCCH having PDCCH candidates defined for at least one control channel element (CCE) aggregation level (AL) . CCEs are allocated to a user device and include a plurality of REGs. The REG sets including a set of the REGs are a mapping unit of the PDCCH candidates. The method further includes mapping the REGs of the REG sets to a contiguous time and/or frequency resource.

According to another embodiment in conjunction with the fourth aspect of the present disclosure, the method further includes receiving the PDCCH on allocated resources to the user device and transmitting the REG sets in the PDCCH.

According to another embodiment in conjunction with the fourth aspect of the present disclosure, the method further includes mapping the REG sets of the PDCCH candidates to frequencies in a continuous or distributed manner or to time in a contiguous manner.

According to another embodiment in conjunction with the fourth aspect of the present disclosure, the method further includes mapping the REG sets in a time-first mapping manner to a plurality of orthogonal frequency-division multiplexing (OFDM) symbols, and the REG sets contain demodulation reference signals (DMRS) on every REG for the PDCCH candidates.

According to another embodiment in conjunction with the fourth aspect of the present disclosure, the PDCCH candidates are in a nested structure and larger CCE ALs include CCEs of small CCE ALs.

According to another embodiment in conjunction with the fourth aspect of the present disclosure, the method further includes mapping the REG sets in a time-first mapping and the PDCCH candidates are in a nested structure.

According to another embodiment in conjunction with the fourth aspect of the present disclosure, the method further includes mapping the REG sets in a frequency-first mapping and the PDCCH candidates are in a nested structure.

In the embodiment of the present disclosure, the REG sets are a mapping unit of the PDCCH candidates and the processor is configured to map the REGs to a contiguous time and/or frequency resource to balance channel estimation performance as well as various gains including frequency selective gain and time/frequency diversity gain.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present disclosure or related art, the following figures will be described in the embodiments are briefly introduced. It is obvious that the drawings are merely some embodiments of the present disclosure, a person having ordinary skill in this field can obtain other figures according to these figures without paying the premise.

FIG. 1 is a block diagram of a network node for a wireless communication system according to an embodiment of the present disclosure.

FIG. 2A is a flowchart illustrating a method of a network node for a wireless communication system according to an embodiment of the present disclosure.

FIG. 2B is a flowchart illustrating a method of a user device for a wireless communication system according to an embodiment of the present disclosure.

FIG. 3 is a block diagram of a user device for a wireless communication system according to an embodiment of the present disclosure.

FIG. 4 is a diagram of mapping of control channel elements (CCEs) in a distributed manner on the same orthogonal frequency-division multiplexing (OFDM) symbol according to an embodiment of the present disclosure.

FIG. 5 is a diagram of mapping of CCEs in a distributed manner on different OFDM symbols according to an embodiment of the present disclosure.

FIG. 6 is a diagram of physical downlink control channel (PDCCH) candidates according to an embodiment of the present disclosure.

FIG. 7 is a diagram of a time-first CCE mapping with PDCCH candidates of a CCE aggregation level (AL) according to an embodiment of the present disclosure.

FIG. 8 is a diagram of a time-first CCE mapping with PDCCH candidates of CCE ALs according to an embodiment of the present disclosure.

FIG. 9 is a diagram of a time-first CCE mapping with PDCCH candidates of CCE ALs according to an embodiment of the present disclosure.

FIG. 10 is a diagram of a time-first CCE mapping with PDCCH candidates of CCE ALs according to an embodiment of the present disclosure.

FIG. 11 is a diagram of a nested structure for time-first CCE mapping according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure are described in detail with the technical matters, structural features, achieved objects, and effects with reference to the accompanying drawings as follows. Specifically, the terminologies in the embodiments of the present disclosure are merely for describing the purpose of the certain embodiment, but not to limit the invention.

Referring to FIG. 1, a network node 100 is in communication with a wireless communication system 500. The network node 100 includes a processor 102 and a transceiver 104. The processor 102 is in communication with the transceiver 104. The network node 100 may include one or more optional antennas 106 coupled to the transceiver 104. The processor 102 is configured to allocate a plurality of resource element group (REG) sets of a physical downlink control channel (PDCCH) having PDCCH candidates defined for at least one CCE aggregation level (AL) . A number of CCEs are defined by the at least one CCE AL. The CCEs are associated with a user device 300 (see FIG. 3) of the wireless communication system 500 and include a plurality of resource element groups (REGs) . A REG set can be, such as the CCE. The REG sets including a set of the REGs are a mapping unit of the PDCCH candidates and the processor 102 is configured to map the REGs of the REG sets to a contiguous time and/or frequency resource. The transceiver 104 is configured to transmit the PDCCH on allocated resources to the user device 300.

The network node 100 or base station, e.g. a radio base station (RBS) , which in some networks may be referred to as transmitter such as eNB, eNodeB, NodeB, or B node, depending on the communication technology and terminology used. The radio network nodes may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. The radio network node can be a station (STA) , which is any device that contains an IEEE 802.1 1 -conformant media access control (MAC) and physical layer (PHY) interface to the wireless medium (WM) .

Referring to FIG. 1 and FIG. 2A, a method 200 may be executed in the network node 100. The method 200 includes a block 202 of allocating a plurality of REG sets of a physical downlink control channel (PDCCH) having PDCCH candidates defined for at least one CCE aggregation level (AL) and a block 204 of transmitting the PDCCH on allocated resources to the user device 300. A number of CCEs is defined by the at least one CCE AL. The CCEs are allocated for a user device 300 and include a plurality of resource element groups (REGs) . The REG sets including a set of the RGEs are a mapping unit of the PDCCH candidates, and the processor 102 is configured to map the REGs of the REG sets to a contiguous time and/or frequency resource.

Referring to FIG. 2A and FIG. 3, a method 210 may be executed in the user device 300. The method 210 includes a block 212 of determining a plurality of resource element group (REG) sets for at least one network node 100 and a block 214 of transmitting the REG sets in a physical downlink control channel (PDCCH) to the at least one network node 100. The REG sets are allocated for the PDCCH having PDCCH candidates defined for at least one control channel element (CCE) aggregation level (AL) . CCEs are allocated to the user device 300 and include a plurality of REGs. The REG sets including a set of the REGs are a mapping unit of the PDCCH candidates. The method 210 further includes mapping the REGs of the REG sets to a contiguous time and/or frequency resource.

Referring to FIG. 3, the user device 300 includes a processor 302 and a transceiver 304. The processor 302 is in communication with the transceiver 304. In the embodiment, the user device 300 may further includes one or more optional antennas 306 coupled to the transceiver 304. The processor 302 of the user device 300 is configured to determine REG sets for at least one network nodes 100.

The transceiver 304 of the user device 300 receives uplink control information (UCI) from the processor 302 and is further configured to transmit the REG sets in the PDCCH to the network node 100. The REG sets are allocated for the PDCCH having PDCCH candidates defined for at least one CCE aggregation level (AL) . A number of CCEs are defined by the at least one CCE AL. The CCEs are associated with a user device 300 and include a plurality of resource element groups (REGs) . The REG sets including a set of the REGs are a mapping unit of the PDCCH candidates, and the processor 102 is configured to map the REGs to a contiguous time and/or frequency resource. The transceiver 304 is configured to receive allocation information from the at least one network node 100. The allocation information includes a frequency location and a number of the at least one CCE AL. The transceiver 304 is configured to transmit the REG sets in the PDCCH according to the allocation information.

In some embodiments, a REG bundle is used as a mapping unit, where the REG bundle includes 6 REGs. REG sets including a set of the REGs are a mapping unit, and a REG set can be, such as CCE.

The user device 300 such as mobile station, wireless terminal and/or mobile terminal is in communication with the wireless communication system 500, sometimes also referred to as a cellular radio system. The user device 300 may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability. The user device 300 may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another receiver or a server. The user device 300 can be a STA, which is any device that contains an IEEE 802.1 1 -conformant MAC and PHY interface to the WM.

In fourth generation of mobile phone mobile communication technology standards (4G) long term evolution (LTE) system, control region spans the whole system bandwidth and occupies first several orthogonal frequency-division multiplexing (OFDM) symbols in a subframe. PDCCH is carried by one or multiple CCEs depending on size of payload and channel quality. The CCE further consists of a number of resource element group (REGs) . The REGs of different PDCCHs are interleaved and spread across the whole control region (in both time and frequency) to obtain time and frequency gain. The channel estimation is accomplished based on cell-specific reference signal (CRS) which are transmitted at fixed locations across the whole control region.

In 5G new radio (NR) system, similar channel structure could be used for PDCCH, CCE, REG. However, there are also some new developments in the design of 5G NR PDCCH. For example, there could be different ways of mapping CCE/REG to the time/frequency region for PDCCH (called control resource set in NR) . In PDCCH, there could be a frequency-first mapping, or a time-first mapping or a combination of both. Besides this, mapping elements of PDCCH in contiguous or distributed manners are also supported. There are pros and cons for each way of mapping and the purpose is to exploit various gains such as time/frequency diversity gain, localized frequency selective gain, as well as beamforming (BF) gain. Another aspect that 5G NR is different from 4G LTE is that demodulation reference signals (DMRS) will be used for PDCCH demodulation. The DMRS for PDCCH is transmitted along with intended PDCCH but not across the whole control region. That requires enough amount of DMRS for a good channel estimation. A good design of mapping needs to balance the requirement from these aspects, namely, to benefit from various gains as mentioned above as well as generate good channel estimation for PDCCH decoding.

As PDCCH is carried by one or multiple CCEs and CCE further consists of multiple REGs. There are different ways of conducting the mapping. For example, REGs of PDCCH could be distributed across the time/frequency domain of a control region to exploit time/frequency diversity similar as in LTE. However, that may lead to some channel estimation performance loss due to the limited DMRS transmitted within a REG. To trade off between diversity gain vs channel estimation performance, CCE could be used as the unit for distributed mapping.

Referring to FIG. 4, an example where each CCE is mapped in a distributed manner to different frequency locations on the same OFDM symbol while the REGs in a CCE are mapped together. Such mapping has benefits, CCE is used as the smallest mapping unit, and therefore the REGs in a CCE (e.g., a CCE may contain 4 REGs as shown in the example) are allocated on contiguous resources, this could help with the channel estimation as more DMRS could be used. The distributed CCEs may benefits from frequency diversity gain.

Referring to FIG. 5, to further exploit diversity gain in both time/frequency and allow power boosting, each CCE could be mapped to different OFDM symbols as an example.

Referring to FIG. 6, another design criteria that needs to be considered in 5G NR is the reuse of channel estimation for decoding of different PDCCH candidates to reduce the overall PDCCH decoding efforts. A nested structure as shown in FIG. 6 illustrates an example where PDCCH candidates of different CCE aggregation levels (ALs) are aligned and share the same set of resources. That would allow the reuse of channel estimation for decoding different PDCCH candidates.

The nested structure in FIG. 6 could be seen as a logic structure and CCE could be further mapped to physical resource. The distributed CCE mapping as described in FIG. 4 and FIG. 5 along frequency direction could be used for this purpose as it maintains such nested structure and supports the reuse of channel estimation, while at the same time, exploit the BF and/or frequency diversity gain. However, for time-first REG/CCE mapping, such structure may require some modifications. The time-first mapping is to exploit localized frequency selective gain, allow power boost, and at the same time, may save some DMRS overhead and thus to improve PDCCH performance. This is because if resources used for PDCCH is contiguous in time, the DMRS on the 2nd or the 3rd OFDM symbols could be omitted and thus give more resource element (RE) for PDCCH transmission.

Referring to FIG. 7, an example of time-first CCE/REG mapping is illustrated. In order to maintain certain level of channel estimation performance, CCE can be used at the mapping unit instead of REG because CCE contain more REGs and therefore have more DMRS to provide good channel estimation. The example in FIG. 7 illustrates a number of the at least one CCE AL is equal to 1 (that is CCE AL =1) , the user device includes all CCEs contain DMRS for PDCCH decoding. Referring to FIG. 8, a number of the at least one CCE AL is equal to or greater than 2 (that is CCE AL >=2) , the CCEs on the first OFDM symbol can contain DMRS, while CCEs on the second OFDM symbol do not carry DMRS, thus have more REs for PDCCH. The channel estimation for CCEs on the 2nd symbol could be obtained from those done on the first symbol providing the channel variation along time direction is small enough between symbols. The example in FIG. 5 illustrates the mapping on the 1st and 2nd OFDM symbols for PDCCH candidates of CCE AL >=2, but it can be extended for more OFDM symbols. FIG. 9 illustrates an example of time-first CCE mapping on four OFDM symbols for PDCCH candidates of CCE AL >=2.

The above design could be generalized to map CCEs to an even number of OFDM symbols (e.g., 2 or 4) along time direction first (followed by frequency) , where CCEs on odd numbered of OFDM symbols (e.g., 1st, 3rd OFDM) carry DMRS for channel estimation, while CCEs on even numbered of OFDM symbols (e.g., 2nd, 4th OFDM) do not carry DMRS. If the total number of OFDM symbols in a control region (control resource set) is odd (e.g., 3) , such mapping may only be confined on a pair of 2 OFDM symbols. For example on the 1st and 2nd OFDM symbols, or on the 2nd and 3rd OFDM symbols. In another embodiment, the 2nd OFDM symbol is the first symbol for such mapping and CCEs on the 2nd symbol carry DMRS, while CCE on the 3rd does not. The gNB could configure which OFDM symbols could be used for time-first mapping.

It should be mentioned that columns of CCEs along time direction as shown in FIG. 8 and FIG. 9 could be contiguous in frequency or distributed in frequency.

Referring to FIG. 10, in an embodiment, columns of CCE along time direction could be distributed in frequency and thus may bring more frequency diversity. Referring to FIG. 11, the nested structure for time-first mapping is illustrated. It should be noted that the user device includes

CCE numbers

2, 4, 6, 8 (that is CCE #2, #4, #6 and #8) do not contain DMRS for PDDCH candidates of CCE AL >=2. For PDCCH candidates of CCE AL =1, the user device includes all CCE contain DMRS which could be used for channel estimation and decoding of PDCCH candidates. However, the channel estimation obtained from decoding PDCCH candidates of CCE AL =1 is not used for decoding PDCCH candidates of CCE AL >=2 because the DMRS assumption for these PDCCH candidates are different.

With nested structure as shown in FIG. 11 as part of the design criteria, the time-first CCE/REG mapping as shown in FIG. 9 and FIG. 10 has some restrictions in terms of mapping of CCEs, and which CCE may contain DMRS and which does not. Such restriction is to allow more consistent design for different PDCCH candidates of different CCE AL, and thus lead to similar/consistent performance such as channel estimation when decoding different PDCCH candidates. The nested structure would also allow the reuse of channel estimation for decoding different PDCCH candidates with different CCE AL and thus reduce power consumptions of the user device.

A person having ordinary skill in the art understands that each of the units, algorithm, and steps described and disclosed in the embodiments of the present disclosure are realized using electronic hardware or combinations of software for computers and electronic hardware. Whether the functions run in hardware or software depends on the condition of application and design requirement for a technical plan. A person having ordinary skill in the art can use different ways to realize the function for each specific application while such realizations should not go beyond the scope of the present disclosure.

It is understood by a person having ordinary skill in the art that he/she can refer to the working processes of the system, device, and unit in the above-mentioned embodiment since the working processes of the above-mentioned system, device, and unit are basically the same. For easy description and simplicity, these working processes will not be detailed.

It is understood that the disclosed system, device, and method in the embodiments of the present disclosure can be realized with other ways. The above-mentioned embodiments are exemplary only. The division of the units is merely based on logical functions while other divisions exist in realization. It is possible that a plurality of units or components are combined or integrated in another system. It is also possible that some characteristics are omitted or skipped. On the other hand, the displayed or discussed mutual coupling, direct coupling, or communicative coupling operate through some ports, devices, or units whether indirectly or communicatively by ways of electrical, mechanical, or other kinds of forms.

The units as separating components for explanation are or are not physically separated. The units for display are or are not physical units, that is, located in one place or distributed on a plurality of network units. Some or all of the units are used according to the purposes of the embodiments.

Moreover, each of the functional units in each of the embodiments can be integrated in one processing unit, physically independent, or integrated in one processing unit with two or more than two units.

If the software function unit is realized and used and sold as a product, it can be stored in a readable storage medium in a computer. Based on this understanding, the technical plan proposed by the present disclosure can be essentially or partially realized as the form of a software product. Or, one part of the technical plan beneficial to the conventional technology can be realized as the form of a software product. The software product in the computer is stored in a storage medium, including a plurality of commands for a computational device (such as a personal computer, a server, or a network device) to run all or some of the steps disclosed by the embodiments of the present disclosure. The storage medium includes a USB disk, a mobile hard disk, a read-only memory (ROM) , a random access memory (RAM) , a floppy disk, or other kinds of media capable of storing program codes.

While the present disclosure has been described in connection with what is considered the most practical and preferred embodiments, it is understood that the present disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements made without departing from the scope of the broadest interpretation of the appended claims.

Claims

A network node for a wireless communication system, the network node comprising:

a processor configured to allocate a plurality of resource element group (REG) sets of a physical downlink control channel (PDCCH) having PDCCH candidates defined for at least one control channel element (CCE) aggregation level (AL) , CCEs being allocated to a user device and comprising a plurality of REGs, wherein the REG sets comprising a set of the REGs are a mapping unit of the PDCCH candidates, and the processor is configured to map the REGs of the REG sets to a contiguous time and/or frequency resource; and

a transceiver configured to transmit the PDCCH on allocated resources to the user device.
The network node of claim 1, wherein the processor is configured to map the REG sets of the PDCCH candidates to frequencies in a continuous or distributed manner.
The network node of claim 1, wherein the processor is configured to map the REG sets of the PDCCH candidates to time in a contiguous manner.
The network node of claim 1, wherein the processor is configured to map the REG sets in a time-first mapping manner to a plurality of orthogonal frequency-division multiplexing (OFDM) symbols, and the REG sets contain demodulation reference signals (DMRS) on every REG for the PDCCH candidates.
The network node of claim 1, wherein the PDCCH candidates are in a nested structure and larger CCE ALs comprise CCEs of small CCE ALs.
The network node of claim 1, wherein the processor is configured to map the REG sets in a time-first mapping and the PDCCH candidates are in a nested structure.
The network node of claim 1, wherein the processor is configured to map the REG sets in a frequency-first mapping and the PDCCH candidates are in a nested structure.
A user device for a wireless communication system, the user device comprising:

a processor configured to determine a plurality of resource element group (REG) sets for at least one network node; and

a transceiver configured to transmit the REG sets in a physical downlink control channel (PDCCH) to the at least one network node, wherein the REG sets are allocated for the PDCCH having PDCCH candidates defined for at least one control channel element (CCE) aggregation level (AL) , CCEs being allocated to a user device and comprising a plurality of REGs, wherein the REG sets comprising a set of the REGs are a mapping unit of the PDCCH candidates, and the processor is configured to map the REGs of the REG sets to a contiguous time and/or frequency resource.
The user device of claim 8, wherein the transceiver is configured to receive the PDCCH on allocated resources to the user device, and the transceiver is configured to transmit the REG sets in the PDCCH.
The user device of claim 8, wherein the processor is configured to map the REG sets of the PDCCH candidates to frequencies in a continuous or distributed manner or to time in a contiguous manner.
The user device of claim 8, wherein the processor is configured to map the REG sets in a time-first mapping manner to a plurality of orthogonal frequency-division multiplexing (OFDM) symbols, and the REG sets contain demodulation reference signals (DMRS) on every REG for the PDCCH candidates.
The user device of claim 8, wherein the PDCCH candidates are in a nested structure and larger CCE ALs comprise CCEs of small CCE ALs.
The user device of claim 8, wherein the processor is configured to map the REG sets in a time-first mapping and the PDCCH candidates are in a nested structure.
The user device of claim 8, wherein the processor is configured to map the REG sets in a frequency-first mapping and the PDCCH candidates are in a nested structure.
A method of a network node for a wireless communication system, the method comprising:

allocating a plurality of resource element group (REG) sets of a physical downlink control channel (PDCCH) having PDCCH candidates defined for at least one control channel element (CCE) aggregation level (AL) , CCEs being allocated to a user device and comprising a plurality of REGs, wherein the REG sets comprising a set of the REGs are a mapping unit of the PDCCH candidates, and the method further comprises mapping the REGs of the REG sets to a contiguous time and/or frequency resource; and

transmitting the PDCCH on allocated resources to the user device.
The method of claim 15, further comprising mapping the REG sets of the PDCCH candidates to frequencies in a contiguous or distributed manner or to time in a contiguous manner.
The method of claim 15, further comprising mapping the REG sets in a time-first mapping manner to a plurality of orthogonal frequency-division multiplexing (OFDM) symbols, and the REG sets contain demodulation reference signals (DMRS) on every REG for the PDCCH candidates.
The method of claim 15, wherein the PDCCH candidates are in a nested structure and larger CCE ALs comprise CCEs of small CCE ALs.
The method of claim 15, further comprising mapping the REG sets in a time-first mapping and the PDCCH candidates being in a nested structure.
The method of claim 15, further comprising mapping the REG sets in a frequency-first mapping and the PDCCH candidates being in a nested structure.
A method of a user device for a wireless communication system, the method comprising:

determining a plurality of resource element group (REG) sets for at least one network node; and

transmitting the REG sets in a physical downlink control channel (PDCCH) to the at least one network node, wherein the REG sets are allocated for the PDCCH having PDCCH candidates defined for at least one control channel element (CCE) aggregation level (AL) , CCEs being allocated to a user device and comprising a plurality of REGs, wherein the REG sets comprising a set of the REGs are a mapping unit of the PDCCH candidates, and the method further comprises mapping the REGs of the REG sets to a contiguous time and/or frequency resource.
The method of claim 21, further comprising receiving the PDCCH on allocated resources to the user device and transmitting the REG sets in the PDCCH.
The method of claim 21, further comprising mapping the REG sets of the PDCCH candidates to frequencies in a continuous or distributed manner or to time in a contiguous manner.
The method of claim 21, further comprising mapping the REG sets in a time-first mapping manner to a plurality of orthogonal frequency-division multiplexing (OFDM) symbols, and the REG sets contain demodulation reference signals (DMRS) on every REG for the PDCCH candidates.
The method of claim 21, wherein the PDCCH candidates are in a nested structure and larger CCE ALs comprise CCEs of small CCE ALs.
The method of claim 21, further comprising mapping the REG sets in a time-first mapping and the PDCCH candidates are in a nested structure.
The method of claim 21, further comprising mapping the REG sets in a frequency-first mapping and the PDCCH candidates are in a nested structure.