Search space and configuration for short transmission time interval

Abstract

A method in a network node for supporting a predetermined set of aggregation levels for configuring a downlink control channel for one of a slot transmission time interval (TTI) and a sub-slot TTI. The method comprises determining an aggregation level to be monitored by a wireless device (WD) in a communication network; and determining a number of downlink control channel candidates for the WD to monitor within each of the one of a slot TTI and a sub-slot TTI, the number of downlink control channel candidates being based on the aggregation level. A wireless device and corresponding method are also provided for supporting the predetermined set of aggregation levels, and for implementing at least one aggregation level and at least one downlink control channel candidate in order to configure the downlink control channel for one of a slot TTI and a sub-slot TTI.

Description

Technical Field

[0001] Wireless communication, and in particular, a method, network node, and wireless device for configuring a downlink control channel for a short transmission time interval (sTTI). Background Technology

[0002] Packet data latency is one of the performance metrics that vendors, operators, and end users regularly measure (via speed testing applications). Latency measurements are performed at all stages of the radio access network system's lifespan, including when validating new software versions or system components, when deploying systems, and when systems are in commercial operation.

[0003] Shorter latency than previous generations of 3GPP RATs was once a performance metric guiding the design of Long Term Evolution (LTE). LTE is now also considered by end users as a system that provides faster internet access and lower data latency than previous generations of mobile radio technologies.

[0004] Packet data latency is not only important for the perceived responsiveness of a system; it is also a parameter that indirectly affects system throughput. HTTP / TCP is the dominant application and transport layer protocol suite used on the Internet today. According to the HTTP archive (http: / / httpcarchive.org / trends.php), the typical size of HTTP-based transactions on the Internet ranges from tens of kilobytes to one megabyte. Within this size range, the TCP slow start period is a significant portion of the total transmission time of the packet stream. During TCP slow start, performance is latency-constrained. Therefore, for this type of TCP-based data transaction, it is relatively easy to demonstrate improvements in latency in order to improve average throughput.

[0005] Radio resource efficiency can be positively impacted by latency reduction. Lower packet data latency can increase the number of transmissions possible within a certain latency limit; therefore, a higher block error rate (BLER) target can be used to free up radio resources for data transmission, potentially increasing system capacity.

[0006] When it comes to reducing packet latency, one aspect to address is reducing the transmission time of data and control signaling by adjusting the length of the Transmission Time Interval (TTI). In LTE Release 8, the TTI corresponds to a subframe (SF) with a length of 1 millisecond. In the case of a normal cyclic prefix, such a 1ms TTI is constructed using 14 OFDM or SC-FDMA symbols, while in the case of an extended cyclic prefix, it is constructed using 12 OFDM or SC-FDMA symbols.

[0007] Currently, work in the 3rd Generation Partnership Project (3GPP) (see RP-161299) is standardizing “short TTI” or “sTTI” operations, where scheduling and transmission can be completed on a faster time scale. Therefore, traditional LTE subframes are subdivided into several sTTIs. Supported sTTI lengths of 2, 4, and 7 OFDM symbols are currently discussed. Data transmission in the downlink (DL) can occur according to the sTTI via the short physical downlink shared channel (sPDSCH), which may include the control area short downlink control channel (sPDCCH). In the uplink (UL), data is transmitted according to the sTTI via the short physical uplink shared channel (sPUSCH); control can be transmitted via the short physical uplink control channel (sPUCCH).

[0008] Different alternatives may schedule the sTTI in UL or DL ​​to the radio device. In one alternative, each radio device receives information about sPDCCH candidates for sTTI via RRC configuration, informing the radio device where to look for the control channel for sTTI, i.e., the sPDCCH. The DCI for sTTI is actually included directly in the sPDCCH. In another alternative, the DCI for sTTI is divided into two parts: a slow DCI transmitted in the PDCCH and a fast DCI transmitted in the sPDCCH. The slow grant may include frequency allocations for DL ​​and UL short TTI bands for short TTI operation, and it may also include refinement regarding the sPDCCH candidate locations.

[0009] 3GPP Long Term Evolution (LTE) technology is a mobile broadband wireless communication technology that uses Orthogonal Frequency Division Multiplexing (OFDM) to transmit data from a base station (called an eNB) to a mobile station (also called a User Equipment (UE)). OFDM divides the signal into multiple parallel subcarriers in frequency. The basic unit of transmission in LTE is a Resource Block (RB), which, in its most common configuration with a normal cyclic prefix, consists of 12 subcarriers and 7 OFDM symbols (one time slot). With an extended cyclic prefix, the RB consists of 6 OFDM symbols in the time domain. The common term is also Physical Resource Block (PRB) to indicate an RB in physical resources. Two PRBs in the same subframe using the same 12 subcarriers are used to represent a PRB pair. This is the smallest schedulable resource unit in LTE.

[0010] A cell consisting of one subcarrier and one OFDM symbol is called a resource element (RE) (see See [link]). Figure 1 Therefore, a PRB consists of 84 REs. An LTE wireless electronic frame consists of multiple resource blocks on a frequency, where the number of PRBs determines the system bandwidth, and the two time slots on time are as follows: Figure 2As shown in the image.

[0011] In the time domain, LTE downlink transmission is organized into 10ms radio frames, each radio frame consisting of a length of T. subframe It consists of ten equal-sized subframes, each lasting 1 ms.

[0012] Messages transmitted to users via radio links can be broadly classified as control messages or data messages. Control messages facilitate the proper operation of the system and each wireless device within the system. Control messages may include commands for controlling functions such as transmit power from wireless devices and signaling from radio units (RBs), where data is to be received by or transmitted from wireless devices.

[0013] In Rel-8, depending on the configuration, the first one to four OFDM symbols in a subframe are reserved to contain this control information, such as... Figure 2 As shown in the diagram. Furthermore, in Rel-11, an Enhanced Control Channel (EPDCCH) was introduced, in which PRB pairs were reserved specifically for EPDCCH transmissions, although the first one to four symbols, which could contain control information for radio devices with versions earlier than Rel-11, were excluded from the PRB pairs, see [link to diagram]. Figure 3 The illustration is shown in the image.

[0014] Therefore, unlike PDCCH, which uses time multiplexing for PDSCH transmission, EPDCCH uses frequency multiplexing for PDSCH transmission. Depending on the downlink control information (DCI) format, resource allocation (RA) for PDSCH transmission exists in several RA types. Some RA types have the smallest scheduling granularity of Resource Block Groups (RBGs), see 3GPP TS36.211. An RBG is a group of adjacent (frequency-based) resource blocks, and when scheduling a radio device, the radio device is allocated resources in an RBG rather than individual RB aspects.

[0015] When a radio device is scheduled from EPDCCH in the downlink, the radio device assumes that PRB pairs carrying DL assignments are excluded from resource allocation; that is, rate matching is applied. For example, if a radio device is scheduled for PDSCH in a specific RBG of size 3 adjacent PRB pairs, and one of these PRB pairs contains a DL assignment, the radio device assumes that the PDSCH will only be transmitted in the two remaining PRB pairs in that RBG. Also note that multiplexing of PDSCH within a PRB pair and any EPDCCH transmissions is not supported in Rel-11.

[0016] PDCCH and EPDCCH are transmitted over radio resources shared among several user equipments (UEs). Each PDCCH consists of smaller parts (called Control Channel Elements (CCEs)) to enable link adaptation (by controlling the number of CCEs being utilized by the PDCCH). It is stipulated that for a PDCCH, the radio device must monitor four (4) CCE aggregation levels, namely, 1, 2, 4, and 8 for the radio device-specific search space, and two CCE aggregation levels, namely, 4 and 8, for the common search space.

[0017] In Section 9.1.1 of 3GPP TS36.213, the search space at the aggregation level L∈{1,2,4,8} is defined by a continuous set of CCEs given by the following equation.

[0018]

[0019] Where N CCE,k It is the total number of CCEs in the control region of subframe k. Define the beginning of the search space, i = 0, 1, ..., M. (L) ·L-1, and M (L) This represents the number of PDCCHs to be monitored in the given search space. Each CCE contains 36 QPSK modulation symbols. M (L) The value is specified in Table 9.1.1-1 of 3GPP TS36.213, as follows:

[0020] Table 1

[0021]

[0022] Using this definition, search spaces at different aggregation levels can overlap, regardless of system bandwidth. More specifically, device-specific search spaces and common search spaces may overlap, and search spaces for different aggregation levels may also overlap. See the example shown below, where there are a total of 9 CCEs and very frequent overlap between PDCCH candidates:

[0023] Example 1: N CCE ,k =9, for L = {1,2,4,8} respectively (See Table 2 below).

[0024] Table 2

[0025]

[0026] After channel coding, scrambling, modulation, and interleaving of control information, the modulated symbols are mapped to resource elements in the control region. To multiplex multiple PDCCHs onto the control region, control channel elements (CCEs) have been defined, where each CCE maps to 36 resource elements. Depending on the information payload size and the required level of channel coding protection, a PDCCH can consist of 1, 2, 4, or 8 CCEs, and this number is represented as the CCE aggregation level (AL). By selecting the aggregation level, link adaptation of the PDCCH is achieved. There are a total of N... CCE One CCE can be used for all PDCCHs to be transmitted in a subframe, and N CCE The number varies with subframes depending on the number of control symbols n and the number of configured antenna ports.

[0027] Because N CCE The number of CCEs varies with subframes, so the radio device needs to blindly determine the location and number of CCEs used for its PDCCH, which can be a computationally intensive decoding task. Therefore, some limitations have been introduced on the number of possible blind decoding operations that the radio device needs to undergo. For example, CCEs are numbered, and a CCE aggregation level of size K can only begin on CCE numbers divisible by K, such as... Figure 4 As shown in the image.

[0028] The set of candidate control channels formed by CCEs that the wireless device needs to blindly decode and search for valid PDCCHs is called the search space. This is the set of CCEs on the AL, which the wireless device should monitor in response to scheduling assignments or other control information. See [link to relevant documentation]. Figure 5 In the example above, within each subframe and on each AL, the radio device will attempt to decode all PDCCHs that can be formed by the CCEs in its search space. If a CRC check is performed, the contents of the PDCCH are considered valid for the radio device, and it further processes the received information. Two or more radio devices will typically have overlapping search spaces, and the network must select one of them to schedule the control channel. When this happens, the unscheduled radio device is said to be blocked. The search space varies pseudo-randomly with each subframe to minimize this blocking probability.

[0029] The search space is further divided into a common portion and a radio device-specific portion. In the common search space, PDCCHs containing information (paging, system information, etc.) are transmitted to all or a group of radio devices. If carrier aggregation is used, radio devices will only find the common search space existing on the principal component carrier (PCC). The common search space is limited to aggregation levels 4 and 8 to provide sufficient channel code protection for all radio devices in the cell (link adaptation cannot be used because it is a broadcast channel). The first m8 and m4 PDCCHs with AL of 8 or 4 (where the CCE number is the smallest) belong to the common search space respectively. To efficiently utilize CCEs in the system, the remaining search space is radio device-specific at each aggregation level.

[0030] Figure 5 This is a graph illustrating the search space (denoted as "A") that a particular wireless device needs to monitor. In this example, there are a total of N... CCE =15 CCEs, and the public search space is indicated as "B".

[0031] The Cell-Cycle Encoder (CCE) consists of 36 QPSK-modulated symbols, which are mapped to 36 unique Real-Time Exchanges (REs) for that CCE. To maximize diversity and interference randomization, all CCEs are interleaved before cell-specific cyclic shifts and mapping to REs; see [link to relevant documentation]. Figure 6 The processing steps are as follows. Note that in most cases, some CCEs are empty due to the limitations imposed by PDCCH location on the search space and aggregation level of the radio device. Empty CCEs are included in the interleaving process and mapped to REs as any other PDCCH to maintain the search space structure. Empty CCEs are set to zero power, and this power can be used instead by non-empty CCEs to further enhance PDCCH transmission.

[0032] Furthermore, in order to enable diversity using 4 antennas (TX), a group of 4 adjacent QPSK symbols in the CCE is mapped to 4 adjacent REs, denoted as a RE group (REG). Therefore, CCE interleaving is based on quadruplex interleaving (group of 4), and the mapping process has a granularity of 1 REG, and one CCE corresponds to 9 REGs (=36 REs).

[0033] Typically, there will also be a set of REGs, whose size is already determined to be N. CCE The remaining REGs after the CCE set are still considered as surplus resources (although the surplus REGs are always less than 36 REs), because the number of REGs available for PDCCH in the system bandwidth is usually not an even multiple of 9 REGs. These surplus REGs are not used by the system in LTE.

[0034] Similar to PDCCH, EPDCCH is transmitted over radio resources shared by multiple radio devices, and Enhanced CCE (eCCE) is introduced as an equivalent of CCE for PDCCH. eCCE also has a fixed number of REs, but the number of REs available for EPDCCH mapping is typically less than this fixed number because many REs are occupied by other signals such as CRS and CSI-RS. Code chain rate matching is applied whenever an RE belonging to an eCCE contains other conflicting signals, such as CRS, CSI-RS, legacy control areas, or, in the case of TDD, GP and UpPTS.

[0035] consider Figure 7 The examples shown, where (a) illustrates the PDCCH mapping, which avoids CRS, ensuring that the CCE always consists of available REs. In (b), it is shown how the eCCE nominally includes 36 REs, but in the presence of collision signals, the number of available REs is reduced, thus REs are used for the EPDCCH. Since collision signals are subframe dependent, their values ​​also become subframe dependent, and if collisions do not affect the eCCE uniformly, the values ​​of the collision signals can even differ for different eCCEs.

[0036] It should be noted that when the number of eCCEs per PRB pair is 2, the nominal number of REs per eCCE is not 36, but is instead 72 or 64 for normal and extended CP lengths, respectively.

[0037] In 3GPP Rel-11, EPDCCH only supports radio device-specific search spaces, while the common search space is monitored within the PDCCH of the same subframe. In future versions, a common search space may also be introduced for EPDCCH transmission.

[0038] The regulations specify wireless devices monitoring eCCE aggregation levels 1, 2, 4, 8, 16, and 32, with limitations shown.

[0039] In distributed transmission, the EPDCCH is mapped to resource elements in up to D PRB pairs, where D = 2, 4, or 8 (a value of D = 16 is also considered in 3GPP). This allows for frequency diversity in the EPDCCH message. See also Figure 8 An illustrative example.

[0040] Figure 8 The diagram shows a downlink subframe where four parts belonging to the EPDCCH are mapped to multiple enhancement control regions called PRB pairs to enable distributed transmission and frequency diversity or subband precoding.

[0041] In localized transmission, if space permits (which is always possible for aggregation levels one and two, as well as for normal subframes and normal CP lengths, and also for level four), the EPDCCH is mapped to only one PRB pair. If the aggregation level of the EPDCCH is too large, a second PRB pair is also used, and so on, using more PRB pairs until all eCCEs belonging to the EPDCCH have been mapped.

[0042] Figure 9 A diagram of centralized transmission is provided. Specifically, Figure 9 The diagram shows a downlink subframe that illustrates how four eCCEs belonging to the EPDCCH are mapped to one of the enhanced control areas for centralized transmission.

[0043] As an example, in a normal subframe, and utilizing the normal CP length and utilizing n EPDCCH ≥104, centralized transport is using aggregation levels (1, 2, 4, 8), and they are mapped to (1, 1, 1, 2) PRB pairs respectively.

[0044] To facilitate the mapping of eCCEs to physical resources, each PRB pair is divided into 16 Enhanced Resource Element Groups (eREGs), and each eCCE is divided into 4 eREGs for the normal cycle prefix and 8 eREGs for the extended cycle prefix. Therefore, depending on the aggregation level, EPDCCHs are mapped to multiples of four or eight eREGs.

[0045] eREGs belonging to the ePDCCH reside in a single PRB pair (typical for centralized transmission) or multiple PRB pairs (typical for distributed transmission). PRB pairs are precisely divided into eREGs.

[0046] To quickly schedule low-latency data on short TTIs, a new short PDCCH (sPDCCH) can be defined. Since short TTI operations are expected to coexist with traditional TTI operations, the sPDCCH should be placed within the PDSCH band, leaving resources for traditional data.

[0047] Traditional control channels PDCCH and EPDCCH use CRS and DMRS demodulation, respectively. For operation in both environments, sPDCCH should support both CRS and DMRS, and for efficient maintenance, resources not used by sPDCCH should be used by sPDSCH (short PDSCH).

[0048] To facilitate the definition of sPDCCH mapped to resource elements, special entities are defined: Short Resource Element Group (sREG) and sCCE. This follows the approach used to date in the LTE specification for defining PDCCH and ePDCCH, as described above. Note that the same mapping can also be defined without using these terms or by using equivalent terms.

[0049] The primary candidate length for sPDCCH in the time domain is one or two OFDM symbols used for sTTI operations. The REs of the PRB in a given OFDM symbol of sTTI can construct one or more sREGs. The number of REs in the sREG can also be variable to provide allocation flexibility and support good frequency diversity.

[0050] The sREG configuration used for sPDCCH is defined as the full number of REs in the PRB within one OFDM symbol (i.e., 12 REs per sREG in one OFDM symbol). Figure 10 In this context, we consider 1 OFDM symbol sPDCCH, 2 OFDM symbols sPDCCH, and 3 OFDM symbols sPDCCH to depict these sREG configurations. Each index, namely {0, 1, 2} (represented as A, B, and C respectively), represents an sREG group.

[0051] The number of sREGs required to establish an sCCE for a given sPDCCH, and their arrangement, can vary depending on the frequency resources used for sTTI operation. One option is to define an sCCE ideally consisting of 36 REs, such as an eCCE or CCE. For this purpose, and based on... Figure 10 sCCE consists of three sREGs, that is, 1 sCCE = 3 sREGs.

[0052] For DMRS-based sPDCCH, another option to consider to increase the number of REs available within the 2 OFDM symbol SPDCCH is to define sCCE as consisting of 48 REs instead of 36 REs, i.e., 1 sCCE = 4 sREGs. Compared to CRS-based sPDCCH, the 12 additional REs help to compensate for the DMRS overhead.

[0053] To support good frequency diversity or more centralized placement, centralized and distributed placement schemes for sREGs that construct the same sCCE are defined:

[0054] - Centralized approach: The sREGs that construct the same sCCE can be centralized in the frequency domain to take into account the allocation of sPDCCH resources confined to a limited frequency band. This facilitates the use of beamforming for DMRS-based sPDCCHs.

[0055] - Distributed Scheme: Distributed sREG locations can be used to allow for frequency diversity gain. In this case, multiple radio devices can map the sREG of their sPDCCH to the same PRB on different REs. Distribution over a wide frequency range also makes it easier to fit the sPDCCH to a single OFDM symbol. For radio devices with DMRS-based demodulation, user-specific beamforming with distributed sCCE locations is not recommended.

[0056] The schemes described below for constructing sCCE based on 1 OFDM symbol sPDCCH, 2 OFDM symbol sPDCCH, and 3 OFDM symbol sPDCCH can be used for CRS and DMRS transmission.

[0057] Similarly, this takes into account the following factors:

[0058] -CRS and DMRS users can coexist on the same sTTI because the sPDCCH design is identical.

[0059] - If both CRS and DMRS users are given a DCI in the same PRB, this is needed to inform the CRS user. They then know that some REs were not used for sCCE. Otherwise, the DCI must be sent to the CRS and DMRS users in different PRBs.

[0060] Each user configures at least one set of PRBs available for sPDCCH. It has been recommended to support the configuration of several PRB sets for sPDCCH, with one PRB set configured after centralized sPDCCH mapping and another PRB set configured using distributed mapping. The radio device will monitor both sets, and the network node can select the most advantageous configuration / PRB set for a given sTTI and radio device.

[0061] The set of PRBs assigned to sPDCCH can be configured via RRC signaling, which includes PRBs from available sTTI bands (not necessarily contiguous). However, it can include potential resource allocation refinements in slow DCIs transmitted in PDCCH, such as a reduced set of PRBs or a specific set if several sPDCCH sets are defined.

[0062] The PRB set can be configured independently, for example, as a PRB bitmap. The set can also be configured based on a PRB set. An example of a PRB group already defined in LTE is called an RBG, and it can be used as the basis in the proposed sPDCCH mapping. Then, all PRBs within the same PRB group (e.g., RBG) are used in conjunction.

[0063] Before mapping sPDCCH to a wireless device, the PRBs or PRB groups included in the configured PRB set can be sorted according to the sequence of signals sent to the wireless device.

[0064] Due to the advantage of early decoding of two OFDM symbol sTTIs and slot TTIs, one OFDM symbol sPDCCH is defined for CRS-based transmission. Two OFDM symbol sPDCCHs can also be configured for two OFDM symbol sTTIs and slot TTIs as an alternative to allow for smaller sTTI bandwidths, i.e., limiting the number of frequency resources used for sTTI operations.

[0065] For a DMRS-based transmission with a 2-symbol sTTI, assuming a design based on DMRS pairs in the time domain as in conventional LTE, two OFDM-symbol sPDCCHs are defined because the radio device needs to wait for the end of the sTTI to perform channel estimation anyway. In this case, DMRS is therefore not shared between the sPDCCH and sPDSCH in a given PRB of the sTTI. This provides greater flexibility in applying beamforming to the sPDCCH. Furthermore, for some sTTIs in a subframe, the TTI length is 3 symbols instead of 2. To allow for beamforming flexibility, a 3-symbol sPDCCH can be considered for a 3-symbol sTTI.

[0066] For a DMRS with a 1-slot sTTI, a 2-symbol sPDCCH is suitable. Preferably, a DMRS pair used for a 1-slot TTI is capable of channel estimation and early sPDCCH decoding. Similarly, for cases where only a small number of REs are available in the first two symbols of a slot due to reference signals and other types of overhead, a 3-OFDM symbol sPDCCH is also suitable for a 1-slot TTI. Thus, considering the potential reference signals in sTTIs such as DMRS, CRS, or CSI-RS, those REs occupied by these signals within the PRB are not used for a given sREG.

[0067] Assuming the sPDCCH spans only the first OFDM symbol of the 2-symbol sTTI, and the sCCE consists of 36 REs (such as ECCE or CCE), then 3 PRBs are needed to construct the sCCE (i.e., 3 sREGs). These 3 PRBs can be distributed across the sPDCCH-PRB set, or they can be grouped into three consecutive PRBs. Figure 11 In the text, examples of distributed and centralized configurations are described for 4 sCCEs and 1 OFDM symbol sPDCCH. Figure 11The unused PRB shown can be further assigned to build other sCCEs and for the possibility of sPDSCH allocation. Figure 11 In cases where sPDCCH is configured with only one OFDM symbol in time (i.e., only OS1 is considered), for clarity, sCCE0 is indicated as "0", sCCE1 is indicated as "1", sCCE2 is indicated as "2", and sCCE3 is indicated as "3".

[0068] The same considerations described above for a single OFDM symbol sPDCCH can be extended to two OFDM symbols sPDCCH. Two OFDM symbols are suitable for CRS-based sPDCCH transmission in poor channel conditions, or for short TTI operation within a smaller frequency range. Similarly, as mentioned above, two OFDM symbol sPDCCH is more suitable for DMRS-based transmission.

[0069] If three sREGs are needed to construct the sCCE, then for two OFDM symbols sPDCCH, there are two mapping options to consider. Figure 12 In the document, these options, including examples of distributed and centralized configurations, are described for 4 sCCEs and 2 OFDM symbols sPDCCH. Figure 12 The unused PRBs shown can be further assigned to build other sCCEs and possibly for sPDSCH allocations. For clarity, sCCE0 is represented as "0", sCCE1 as "1", sCCE2 as "2", and sCCE3 as "3".

[0070] In option A ( Figure 12 In option A (left), the sREGs forming the sCCE are selected in the following order: time-first-frequency-second. Therefore, it is possible to utilize the two OFDM symbols available for each PRB from the beginning. However, option A includes low-frequency diversity of the sREGs in a distributed configuration. On the other hand, in option B (left) Figure 6 In the right section, select the sREG that forms the sCCE in the following order: frequency - first - time - second. Higher frequency diversity of the sREG can be achieved using option B. For both options, the centralized configuration includes the same conditions.

[0071] exist Figure 11 and 12 In the diagram, the physical resource blocks are numbered sequentially in frequency order and transmitted simultaneously. Symbols (OS1 and OS2) are transmitted sequentially at separate times. Figure 12In this context, "Time-First-Frequency-Second" (Option A) means assigning sREGs to different times (symbols) and the same PRBs (i.e., frequencies) within the sPDCCH until no further time assignments (symbols) are available. Then, the next assigned PRB (from a different frequency set, which can be continuous or discontinuous) is used. Figure 12 Option B reverses the references for time (symbols) and frequency (PRBs). It should be noted that even if PRBs are numbered consecutively in the diagram, they are not necessarily physically consecutive PRBs from the available sTTI bands. It is merely a set of PRBs selected by the network nodes.

[0072] As mentioned above, if 1 sCCE = 4 sREGs, then for 2 OFDM symbols sPDCCH, sCCE consists of 2 complete PRBs, such as... Figure 13 The diagram shows examples of distributed and centralized configurations for four sCCEs. Figure 13 The unused PRB shown can be further assigned to build other sCCEs and possibly for sPDSCH allocations. Figure 12 and 13 The case involves two OFDM symbols sPDCCH (i.e., consider OS1 and OS2). For clarity, sCCE0 is represented as "0", sCCE1 as "1", sCCE2 as "2", and sCCE3 as "3".

[0073] For the case of 3 OFDM symbols, the sPDCCH based on DMRS transmission can be constructed using a single sCCE consisting of 3 sREGs along the 3 symbols for both 2os-sTTI (for the 3-symbol sTTI case) and slot-sTTI (with high reference signal overhead). Figure 14 Examples of distributed and centralized configurations for 4 sCCEs and 3 OFDM symbols sPDCCHs are shown. Figure 14 The unused PRB shown can be further assigned to build other sCCEs and possibly for sPDSCH allocations. Figure 14 The case involves three OFDM symbols sPDCCH (i.e., consider OS1, OS2, and OS3). For clarity, sCCE0 is represented as "0", sCCE1 as "1", sCCE2 as "2", and sCCE3 as "3".

[0074] The configuration of the DL control channel (sTTI) for short TTIs (referred to herein as sPDCCH (PDCCH for short TTIs)) is configured via higher-layer signaling or predefined in the specification. Some configurations, such as the search space and the set of one or more sPDCCH-PRBs for sTTI operation of the radio device, still need to be defined and included in the specification. Summary of the Invention

[0075] This disclosure advantageously provides a method, network node, and wireless device for supporting a predetermined set of aggregation levels for configuring downlink control channels for sTTI, to limit the number of blind decodings to be performed by the wireless device (WD) in some embodiments, and / or to provide flexibility in the transmission of downlink control channels for sTTI in network nodes in some embodiments.

[0076] Some embodiments disclosed herein include a method, network node, and wireless device, thereby enabling the configuration of a limited number of aggregation levels and sPDCCH candidates for the wireless device within a 1ms subframe during sTTI operation. Furthermore, this document proposes sPDCCH-PRB set configuration, including a definition for determining the sPDCCH-PRB set size to be configured for the wireless device or several wireless devices sharing the same PRB set.

[0077] According to one aspect of this disclosure, a method is provided in a network node for supporting a predetermined set of aggregation levels for configuring downlink control channels for short transmission time intervals (sTTIs). The method includes at least determining a subset of the predetermined set of aggregation levels to be monitored by a wireless device (WD) in a communication network; and determining a number of downlink control channel candidates to be monitored by the WD in each sTTI, the number of downlink control channel candidates being at least partially based on at least a subset of the predetermined set of aggregation levels.

[0078] According to this aspect, in some embodiments, the method further includes assigning aggregation level and downlink control channel candidates to the WD. In some embodiments, assigning aggregation level and downlink control channel candidates to the WD includes assigning them via a higher layer and optionally via RRC signaling. In some embodiments, determining the number of downlink control channel candidates that the WD will monitor in each of the time slot TTI and the sub-time slot TTI includes determining the number of downlink control channel candidates that the WD will monitor in each of the time slot TTI and the sub-time slot TTI based at least on a maximum of six downlink control channel candidates to be monitored in each of the time slot TTI and the sub-time slot TTI. The reference to "each of the time slot TTI or the sub-time slot TTI" can refer to the time slot TTI and / or the sub-time slot TTI, i.e., a short TTI.

[0079] In some embodiments, determining the number of downlink control channel candidates to be monitored by the wireless device within each of a time slot TTI and a sub-time slot TTI includes determining up to two downlink control channel candidates in a high aggregation level. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to a predetermined set of aggregation levels is at most six downlink control channel candidates. In some embodiments, one of the time slot TTI and the sub-time slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, the aggregation level includes a number of short control channel elements (sCCEs). In some embodiments, the number of sCCEs supports the number of downlink control channel candidates defined for each aggregation level in a predetermined set of aggregation levels to be monitored by the WD. In some embodiments, the number of sCCEs is determined based on system bandwidth. In some embodiments, the number of sCCEs is selected to avoid control overhead along the available frequency resources of each of a time slot TTI and a sub-time slot TTI. In some embodiments, the method further includes determining the size of the downlink control channel-physical resource block (PRB) set for each WD. In some embodiments, the size of the PRB set for each WD is determined based at least on the number of sCCEs, the number of orthogonal frequency division multiplexing (OFDM) symbols per control channel, and the number of short resource element groups (sREGs) per sCCE. In some embodiments, for a short physical downlink control channel (sPDCCH) based on a demodulation reference signal (DMRS), two PRB sets are defined for the WD, the first PRB set being configured as centralized and the second PRB set being configured as distributed.

[0080] According to another aspect of this disclosure, a network node is provided for supporting a predetermined set of aggregation levels for configuring downlink control channels in one of a time slot transmission time interval (TTI) and a sub-time slot TTI. The network node includes processing circuitry configured to: determine the aggregation level to be monitored by a wireless device (WD) in a communication network; and determine the number of downlink control channel candidates to be monitored by the WD within each of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the aggregation level.

[0081] According to this aspect, in some embodiments, the processing circuitry is further configured to assign aggregation levels and downlink control channel candidates to the WD. In some embodiments, the processing circuitry is further configured to assign aggregation levels and downlink control channel candidates to the WD via a higher layer and optionally via RRC signaling. In some embodiments, the processing circuitry is further configured to determine the number of downlink control channel candidates that the WD will monitor in each of the time slot TTI and the sub-time slot TTI, based at least on a maximum of six downlink control channel candidates to be monitored in each of the time slot TTI and the sub-time slot TTI. In some embodiments, the processing circuitry is further configured to determine up to two downlink control channel candidates in a high aggregation level. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to a predetermined set of aggregation levels to be monitored by the WD is a maximum of six downlink control channel candidates. In some embodiments, one of the time slot TTI and the sub-time slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, the aggregation level includes a number of short control channel elements (sCCE). In some embodiments, the number of sCCEs supports the number of downlink control channel candidates defined for each aggregation level of a predetermined set of aggregation levels to be monitored by the WD. In some embodiments, the number of sCCEs is determined based on system bandwidth. In some embodiments, the number of sCCEs is selected to avoid control overhead along the available frequency resources of each of the time slot TTI and sub-time slot TTI. In some embodiments, the processing circuitry is also configured to determine the size of the downlink control channel-physical resource block (PRB) set for each WD. In some embodiments, the processing circuitry is also configured to determine the PRB set size for each WD based at least on the number of sCCEs, the number of orthogonal frequency division multiplexing (OFDM) symbols for each control channel, and the number of short resource element groups (sREGs) for each sCCE. In some embodiments, the processing circuitry is also configured to define two PRB sets for the WD for a short physical downlink control channel (sPDCCH) based on a demodulation reference signal (DMRS), wherein the first PRB set is configured to be centralized and the second PRB set is configured to be distributed.

[0082] According to another aspect of this disclosure, a method is provided in a wireless device (WD) for supporting a predetermined set of aggregation levels and for implementing at least one aggregation level and at least one downlink control channel candidate to configure a downlink control channel for one of a time slot transmission time interval (TTI) and a sub-time slot TTI. The method includes: receiving from a network node an assigned aggregation level to be monitored by the WD in the communication network; and receiving from the network node an assigned downlink control channel candidate, the network node determining the number of downlink control channel candidates to be monitored by the WD within each of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the assigned aggregation level.

[0083] According to this aspect, in some embodiments, receiving the assigned aggregation level to be monitored by the WD in the communication network from the network node includes receiving the assigned aggregation level to be monitored by the WD in the communication network from the network node via a higher layer and optionally via Radio Resource Control (RRC) signaling. In some embodiments, the method further includes monitoring the assigned aggregation level. In some embodiments, the number of downlink control channel candidates is based at least on a maximum of six downlink control channel candidates to be monitored within each of a time slot TTI and a sub-time slot TTI. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to a predetermined set of aggregation levels to be monitored by the WD is a maximum of six downlink control channel candidates. In some embodiments, one of the time slot TTI and the sub-time slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, the aggregation level includes a number of short control channel elements (sCCEs). In some embodiments, the number of sCCEs supports the number of downlink control channel candidates defined for each aggregation level of the predetermined set of aggregation levels to be monitored by the WD. In some embodiments, the number of sCCEs is determined based on system bandwidth. In some embodiments, the number of sCCEs is selected to avoid control overhead on the available frequency resources along each of the time slot TTI and sub-time slot TTI.

[0084] According to another aspect of this disclosure, a wireless device (WD) is provided for supporting a predetermined set of aggregation levels and for implementing at least one aggregation level and at least one downlink control channel candidate to configure a downlink control channel for one of a time slot transmission time interval (TTI) and a sub-time slot TTI. The WD includes processing circuitry configured to: receive from a network node an assigned aggregation level to be monitored by the WD in a communication network; and receive from the network node an assigned downlink control channel candidate, the network node determining the number of downlink control channel candidates to be monitored by the WD within each of a time slot TTI and a sub-time slot TTI, the number of downlink control channel candidates being based on the assigned aggregation level.

[0085] According to this aspect, in some embodiments, the processing circuitry is further configured to receive, via a higher layer and optionally via Radio Resource Control (RRC) signaling, an assigned aggregation level to be monitored by the WD in the communication network from the network node. In some embodiments, the processing circuitry is further configured to monitor the assigned aggregation level. In some embodiments, the number of downlink control channel candidates is based at least on a maximum of six downlink control channel candidates to be monitored within each of a time slot TTI and a sub-time slot TTI. In some embodiments, at a high aggregation level, the number of downlink control channel candidates is up to two. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to a predetermined set of aggregation levels to be monitored by the WD is a maximum of six downlink control channel candidates. In some embodiments, one of the time slot TTI and the sub-time slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, the aggregation level includes a number of short control channel elements (sCCEs). In some embodiments, the number of sCCEs supports the number of downlink control channel candidates defined for each aggregation level of a predetermined set of aggregation levels to be monitored by the WD. In some embodiments, the number of sCCEs is determined based on system bandwidth. In some embodiments, the number of sCCEs is selected to avoid control overhead on the available frequency resources along each of the time slot TTI and sub-time slot TTI. Attached Figure Description

[0086] A more complete understanding of embodiments of the invention and their accompanying advantages and features will be more readily understood by referring to the following detailed description taken in conjunction with the accompanying drawings, in which:

[0087] Figure 1 It is a time-frequency grid diagram;

[0088] Figure 2 This is a diagram of downlink subframes;

[0089] Figure 3 This is a diagram showing the configuration of 10 RB pairs and three ePDCCH areas in a downlink subframe;

[0090] Figure 4 This is a graph of CCE aggregation;

[0091] Figure 5 This is a diagram showing the search space to be monitored by the wireless device;

[0092] Figure 6 This is a flowchart of the processing steps used for PDCCH formation;

[0093] Figure 7 The differences between CCE and eCCE are shown;

[0094] Figure 8 It is a downlink subframe with four parts belonging to the ePDCCH;

[0095] Figure 9 This shows the downlink subframes with different mappings for the four eCCEs;

[0096] Figure 10 This is a diagram of an sREG configuration based on 12 REs within one OFDM;

[0097] Figure 11 The distributed and centralized configurations of four sCCEs are shown;

[0098] Figure 12 The distributed and centralized configurations of four sCCEs, each consisting of three sREGs, are shown within the 2os-sPDCCH-PRB set.

[0099] Figure 13 The distributed and centralized configurations of four sCCEs, each consisting of four sREGs, are shown within the 2os-sPDCCH-PRB set.

[0100] Figure 14 A 3-os-sPDCCH configuration with w sCCEs is shown;

[0101] Figure 15 This is a block diagram of a network node configured for sTTI based on the principles of this disclosure;

[0102] Figure 16 This is a block diagram of a radio device for implementing aggregation-level sets and downlink control channel candidates in accordance with the principles of this disclosure in order to configure downlink control channels for sTTI;

[0103] Figure 17It is an alternative network node used to configure the downlink control channel for sTTI according to the principles of this disclosure; and

[0104] Figure 18 It is an alternative radio device based on the principles of this disclosure for implementing aggregation-level sets and downlink control channel candidates in order to configure downlink control channels for sTTI;

[0105] Figure 19 This is a flowchart of an exemplary process performed in a network node to configure a downlink control channel for sTTI, based on the principles of this disclosure;

[0106] Figure 20 This is a flowchart of an exemplary process performed in a wireless device according to the principles of this disclosure, the process being used to implement a set of aggregation levels and downlink control channel candidates for configuring downlink control channels for sTTI; and

[0107] Figure 21A -B shows the link performance for different CRC lengths for the extended Vehicle A (EVA) channel and the extended Typical City (ETU) channel, respectively. Detailed Implementation

[0108] Before describing the exemplary embodiments in detail, it should be noted that the embodiments mainly consist of a combination of device components and processing steps relating to defining the aggregation levels to be supported for sTTI operations and the sPDCCH candidates for each aggregation level, as well as defining the size of the sPDCCH-PRB set for sTTI operations.

[0109] Therefore, in the accompanying drawings, components have been indicated by conventional symbols where appropriate, and only those specific details relevant to understanding the embodiments are shown so as not to obscure this disclosure due to details that would be readily apparent to those skilled in the art who benefit from the description herein.

[0110] This disclosure is described in the context of LTE (i.e., E-UTRAN). It should be understood that the problems and solutions described herein are equally applicable to radio access networks and radio devices (user equipment (UE)) implementing other access technologies and standards (e.g., 5G NR). LTE is used as an example technology, and therefore its use in the description is particularly useful for understanding the problems and solutions.

[0111] As used herein, relational terms such as “first” and “second”, “top” and “bottom” may be used only to distinguish one entity or element from another, without requiring or implying any physical or logical relationship or order between these entities or elements.

[0112] The embodiments described herein can be used to limit the number of blind decoding operations performed by a wireless device within a 1ms subframe, thereby facilitating the implementation and capabilities of the wireless device. The proposed sPDCCH-PRB set configuration is wireless device-specific, but it can also be shared among multiple wireless devices. Therefore, network nodes can be given complete flexibility for sPDCCH transmission. Furthermore, the sPDCCH-PRB set size definition is based on providing high-order diversity and avoiding excessive control overhead within a single sTTI.

[0113] Throughout this disclosure, it is assumed that the sPDCCH parameters have been pre-configured via higher-layer signaling such as LTE's RRC, or predefined in, for example, the LTE specification. A typical sPDCCH parameter is the number of time resources (e.g., OFDM symbols) used for sPDCCH transmission. As an example, for short TTI (sTTI) operation, in the following description, the pre-configured or predefined number of OFDM symbols (OS) used for sPDCCH is 1, 2, or 3.

[0114] Now for reference Figure 15 This document illustrates components of an example network node 30 for supporting a predetermined set of aggregation levels to configure a downlink control channel for a Short Transmission Time Interval (sTTI). In one embodiment, the network node 30 includes a communication interface 32 and processing circuitry 34. The processing circuitry 34 includes a processor 36 and a memory 38. The memory 38 may include aggregation level and candidate determination code 40, which in some embodiments may include instructions for implementing one or more of the techniques described herein with respect to the network node 30. The memory 38 may include any kind of volatile and / or non-volatile memory, such as cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory). Such memory may be configured to store code and / or other data executable by the control circuitry, such as communication-related data, such as node configuration and / or address data.

[0115] Processor 36 is configured to perform all or some of the processes described herein with respect to network node 30. In addition to conventional processors and memory and the microcontroller arrangement described above, processing circuitry 34 may include integrated circuits for processing and / or control, such as one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Arrays) and / or ASICs (Application-Specific Integrated Circuits).

[0116] Processing circuitry 34 may include and / or be connected to and / or configured to access (e.g., write to and / or read from) memory 38, which may include any kind of volatile and / or non-volatile memory, such as cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory). Such memory 38 may be configured to store code and / or other data executable by control circuitry, such as communication-related data, such as configuration and / or calibration of input data. Processing circuitry 34 may be configured to control any of the methods described herein and / or cause these methods to be executed, for example, by processor 36, with corresponding instructions stored in memory 38, which may be readable and / or readablely connected to processing circuitry 34. In other words, processing circuitry 34 may include a controller, which may include a microprocessor and / or microcontroller and / or FPGA (Field Programmable Gate Array) device and / or ASIC (Application-Specific Integrated Circuit) device. The processing circuitry 34 may be considered to include, be connected to, or be accessible to a memory that can be configured to be accessed by the controller and / or the processing circuitry 34 for reading and / or writing.

[0117] Now for reference Figure 16 This document provides components of an example wireless device 42 that supports a predetermined set of aggregation levels and is used to implement at least one aggregation level and at least one downlink control channel candidate for configuring a downlink control channel for a Short Transmission Time Interval (sTTI). The wireless device 42 includes a communication interface 44 and processing circuitry 46, which includes a processor 48 and a memory 50. The memory may store aggregation level monitoring code 52, which, in some embodiments, may include instructions for implementing one or more of the techniques described herein with respect to WD 42. The memory 50 may include any kind of volatile and / or non-volatile memory, such as cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory). Such memory may be configured to store code and / or other data executable by control circuitry, such as communication-related data, such as node configuration and / or address data.

[0118] Processor 48 is configured to perform all or some of the processes described herein with respect to wireless device 42. In addition to conventional processors and memory and the microcontroller arrangement described above, processing circuitry 46 may include integrated circuits for processing and / or control, such as one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Arrays) and / or ASICs (Application-Specific Integrated Circuits).

[0119] Processing circuitry 46 may include and / or be connected to and / or configured to access (e.g., write to and / or read from) memory 50, which may include any kind of volatile and / or non-volatile memory, such as cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory). Such memory 50 may be configured to store code and / or other data executable by control circuitry, such as communication-related data, such as configuration and / or calibration of input data. Processing circuitry 46 may be configured to control any methods described herein and / or cause such methods to be executed, for example, by processor 48. Corresponding instructions may be stored in memory 50, which may be readable and / or readablely connected to processing circuitry 46; in other words, processing circuitry 46 may include a controller, which may include a microprocessor and / or microcontroller and / or FPGA (Field Programmable Gate Array) device and / or ASIC (Application-Specific Integrated Circuit) device. The processing circuit 46 may be considered to include, be connected to or be accessible to, a memory that may be configured to be accessible by the controller and / or the processing circuit 46 for reading and / or writing.

[0120] As used herein, the term "wireless device" or mobile terminal may refer to any type of wireless device that communicates with network node 30 and / or with another wireless device 42 in a cellular or mobile communication system. Examples of wireless devices 42 include user equipment (UE), target device, device-to-device (D2D) wireless device, machine-type wireless device or wireless device capable of machine-to-machine (M2M) communication, PDA, tablet computer, smartphone, laptop embedded device (LEE), laptop mounted device (LME), USB dongle, etc.

[0121] As used in this document, the term "network node" can refer to any type of radio base station in a wireless network, and may further include any Base Transceiver Station (BTS), Base Station Controller (BSC), Radio Network Controller (RNC), Evolved Node B (eNB or eNodeB), NR gNodeB, NR gNB, Node B, Multi-Standard Radio (MSR) radio node (e.g., MSRBS), relay node, donor node of control relay, radio access point (AP), transmission point, transmission node, Remote Radio Unit (RRU), Remote Radio Header (RRH), node in Distributed Antenna System (DAS), etc.

[0122] While embodiments are described herein with reference to certain functions performed by network node 30, it should be understood that these functions may be performed in other network nodes and components. It should also be understood that the functions of network node 30 may be distributed across the network cloud, enabling other nodes to perform one or more functions, or even portions of the functions described herein.

[0123] refer to Figure 17 An alternative embodiment of a network node 30 for configuring downlink control channels for short transmission time intervals (sTTIs) is shown. In one embodiment, the network node 30 includes an aggregation level determination module 54 configured to determine a predetermined set of aggregation levels to be monitored by a wireless device 42 in a communication network, each aggregation level including a number of short control channel elements (sCCEs); a downlink control channel candidate determination module 56 configured to determine a number of downlink control channel candidates to be monitored by the wireless device 42 in each sTTI, the number of downlink channel candidates being based at least on the predetermined set of aggregation levels; and a communication interface module 58 configured to assign the set of aggregation levels and downlink control channel candidates to the wireless device 42.

[0124] refer to Figure 18 An alternative embodiment of a wireless device 42 is provided for implementing a set of aggregation levels and downlink control channel candidates for configuring downlink control channels for short transmission time intervals (sTTIs). The wireless device 42 includes a communication interface module 60 configured to receive from a network node 30 an assigned set of aggregation levels, each aggregation level including a number of short control channel elements (sCCEs), and assigned downlink control channel candidates from the network node 30, the network node 30 determining the number of downlink control channel candidates to be monitored by the wireless device 42 in each sTTI, the number of downlink channel candidates being based at least on a predetermined set of aggregation levels. The wireless device 42 also includes an aggregation level monitoring module 62 configured to monitor the assigned set of aggregation levels.

[0125] refer to Figure 19 An exemplary method is provided in network node 30 for supporting a predetermined set of aggregation levels to configure downlink control channels for short transmission time intervals (sTTIs). In one embodiment, the method includes: determining at least a subset of the predetermined set of aggregation levels to be monitored by a wireless device (WD) 42 in the communication network (box S100); and determining the number of downlink control channel candidates to be monitored by the WD in each sTTI, the number of downlink control channel candidates being at least partially based on at least a subset of the predetermined set of aggregation levels (box S110).

[0126] refer to Figure 20A method is provided in a wireless device 42 that supports a predetermined set of aggregation levels and is used to implement at least one aggregation level and at least one downlink control channel candidate to configure a downlink control channel for a short transmission time interval (sTTI). The method includes receiving from a network node 30 at least an assigned subset of the predetermined set of aggregation levels to be monitored by a WD 42 in a communication network (block S120); and receiving from the network node 30 allocated downlink control channel candidates, the network node 30 determining the number of downlink control channel candidates to be monitored by the WD 42 in each sTTI, the number of downlink control channel candidates being based at least on the at least assigned subset of the predetermined set of aggregation levels (block S130).

[0127] Some embodiments of this disclosure have been generally described, and a more detailed description of some embodiments will now be described below.

[0128] Aggregation levels to be supported in sTTI operations

[0129] It has been recognized that short TTIs may be most beneficial under low to medium system loads. It has been noted that sTTI operation can have flexible sPDCCH regions. Under low to medium loads, due to the few co-scheduled users and the high signal-to-interference-plus-noise ratio (SINR) (low interference), only a small amount of resources may be required for the sPDCCH. Therefore, the sPDCCH can be designed such that the amount of resources consumed is suitable for the number of co-scheduled users (in DL and UL) and their required aggregation level. Therefore, it can be expected that the aggregation level configured for the radio device (e.g., WD 42) will remain low during sTTI operation. As mentioned above, the aggregation level includes a certain number of sCCEs. For example, aggregation level 1 includes one sCCE, aggregation level 2 includes two sCCEs, and aggregation level 4 includes four sCCEs.

[0130] Based on this, in one embodiment of this disclosure, three aggregation levels (AL) {1, 2, 4} for sPDCCH can be defined for short TTI operations, for example, up to 4 sCCEs per sPDCCH.

[0131] Therefore, the wireless device (e.g., WD 42) can monitor up to three aggregation levels per sTTI. However, in another embodiment, the wireless device 42 can be configured via a higher layer, such as through LTE RRC, or by signaling in the conventional PDCCH (i.e., in DCI) the number of candidates to monitor for each configured aggregation level, monitoring only one, two, or three sPDCCH aggregation levels per sTTI. For example, a low aggregation level, such as 1 or 2, for efficient resource utilization under good channel conditions, and a high aggregation level, such as 4, for low channel quality. Thus, network node 30 may be able to select the appropriate set of aggregation levels to configure for each wireless device 42.

[0132] sPDCCH candidates to be supported in sTTI operation

[0133] For sTTI operation, dynamic switching between short TTI and 1ms TTI has been considered. This means that radio device 42 can search for 1ms TTI assignment / grant and sTTI assignment / grant within a subframe. Since radio device 42 can monitor additional candidates in sPDCCH multiple times per subframe, the total number of blind decodings that radio device 42 needs to perform may increase. Therefore, the network facilitates radio device 42 to implement, for short TTI operation, it may be beneficial to keep the number of candidates and additional attempts for blind decoding (BD) within a 1ms subframe low. To this end, in one embodiment of this disclosure, each radio device 42 defines four sPDCCH candidates for each sTTI. This embodiment establishes that low aggregation levels, such as AL1 and AL2, may include up to three sPDCCH candidates, while high aggregation levels, such as AL4, may include up to two candidates.

[0134] As another embodiment, candidates for each aggregation level to be monitored by the wireless device 42 are defined according to the set of aggregation levels configured for the wireless device 42, as shown in Table 3 below. The definition of candidates for each aggregation level can be based on the required sPDCCH-PRB set size to be configured. The sPDCCH-PRB set size is further described below in this disclosure.

[0135] Table 3: Candidates to be monitored by wireless device 42 based on its configured aggregation level. This case considers up to four sPDCCH candidates.

[0136]

[0137] In a two-symbol sTTI, there are six sTTIs within a 1ms subframe. If up to four sPDCCH candidates are considered for each sTTI, and assuming the same DL / UL sDCI size, the radio device 42 will need to monitor an additional 24 candidates within a 1ms subframe for sTTI operation. If the DL / UL sDCI sizes are different, then 48 additional candidates will need to be monitored within a 1ms subframe. However, if the processing power of the radio device 42 needs to be further reduced within a 1ms subframe, as an enhancement to the previous embodiment, the number of candidates to be monitored can be defined as three. In this embodiment, low aggregation levels, such as AL1 and AL2, may include up to two candidates, while high aggregation levels, such as AL4, include one candidate.

[0138] As another embodiment, the candidates for each aggregation level to be monitored by the wireless device 42 are based on the set of aggregation levels configured for the wireless device 42, as shown in Table 4 below.

[0139] Table 4: Candidates to be monitored by wireless device 42 based on its configured aggregation level. This case considers up to three sPDCCH candidates.

[0140]

[0141] Tables 3 and 4 illustrate the feature of limiting the number of sPDCCH candidates to a maximum of four. It has then been considered that these candidates are divided among the aggregation levels that can be configured for the wireless device 42. This means that each aggregation level can be defined using the number of candidates as described in Tables 3 and 4, but in one embodiment, the sum of all candidates cannot exceed four or three. For example, in the last option of Table 3, for a total of four candidates for a given aggregation level, the aggregation levels configured for the wireless device 42 are {1, 2, 4}, where aggregation level 1 has two candidates, aggregation level 2 has one candidate, and aggregation level 4 has one candidate.

[0142] Tables 3 and 4 above are merely exemplary. In other embodiments, up to six sPDCCH candidates per WD42 for each sTTI can be considered. For example, low aggregation levels, such as 1 and 2, may include up to three candidates, while high aggregation levels, such as 4, may include up to two candidates (in some embodiments, only one AL 4 candidate may be supported). For example, if WD 42 is configured with aggregation levels {1, 2, 4}, the number of sPDCCH candidates can be defined as {2, 2, 1} so that a total of 5 candidates are generated per sTTI. In yet another embodiment, for an example where only two aggregation levels are configured for WD 42, such as {2, 4}, the number of sPDCCH candidates can be defined as {3, 1} to generate a total of 4 candidates per sTTI. Therefore, some embodiments of the present invention specify limiting the number of sPDCCH candidates to a maximum number of candidates (e.g., 3 candidates as shown in Table 4, 4 candidates as shown in Table 3, 6 candidates as described above, etc.).

[0143] sPDCCH-PRB set configuration for sTTI operations

[0144] As described above, one or more sPDCCH-PRB sets containing the user-specific sTTI search space of the wireless device 42 can be configured to the wireless device 42 via higher-layer signaling. The sPDCCH-PRB sets (one or more) can be configured as centralized or distributed. To define how many PRB sets need to be configured for the wireless device 42, in one embodiment of the invention, for DMRS-based sPDCCH, two PRB sets are defined for the wireless device 42, one set being configured as centralized and the second set being configured as distributed. The centralized sPDCCH-PRB set can be used to allocate sREGs that construct the same sCCE in a limited frequency band. When CSI is available at network node 30, this arrangement can utilize scheduling and beamforming gains for DMRS-based sPDCCH. When CSI is limited or unavailable, the distributed sPDCCH-PRB set can be used to provide robust control signaling and backoff. Furthermore, in this embodiment, for CRS-based sPDCCH, at least one PRB set can be defined as being configured as distributed to achieve frequency diversity gain. The sPDCCH-PRB set configuration selection can be defined by network node 30 for each wireless device 42.

[0145] Since the sPDCCH-PRB set can consist of groups of PRBs, network node 30 has complete flexibility to define an appropriate sPDCCH-PRB set size for each wireless device 42 based on the available system bandwidth. Therefore, as an example, the sPDCCH-PRB set size can be based on:

[0146] - Support for an appropriate number of sCCEs.

[0147] - The number of OFDM symbols per sPDCCH.

[0148] - The number of sREGs per sCCE.

[0149] Therefore, the size of the sPDCCH-PRB set can be defined as follows:

[0150]

[0151] Where, N RB It is the size of the sPDCCH-PRB set, N sCCE The number of sCCEs to be supported (described further below), nr_of_sREG_per_sCCE is the number of sREGs per sCCE, and nr_of_OFDM_symbols_per_sPDCCH is the number of OFDM symbols per sPDCCH. Therefore, the sPDCCH-PRB set can be defined as N sCCE The coefficients and the number of OFDM symbols per sPDCCH and the number of sREGs per sCCE.

[0152] According to this formula, one of the main factors is N. sCCE Therefore, as a further embodiment, N sCCE It can be based on at least:

[0153] -Including the number of sCCEs required to support the number of sPDCCH candidates defined for each aggregation level of each wireless device 42.

[0154] - If needed, a limited number of wireless devices 42 with high aggregation levels of sPDCCH (e.g., AL 4) can be supported within the same sTTI. This is for cases where the same sPDCCH-PRB set can be shared among multiple wireless devices 42.

[0155] -System bandwidth.

[0156] - The number of sCCEs can be selected to avoid excessive control overhead along the available frequency resources of each sTTI.

[0157] Therefore, in one embodiment, for each possible configuration of the number of OFDM symbols per sPDCCH, such as 1OS, 2OS, and 3OS, three different values ​​of N_sCCE are supported: 4sCCE, 6sCCE, and 8sCCE. As described above, N_sCCE = 8sCCE supports up to two candidates, for example, AL 4 (for the case where up to four sPDCCH candidates are defined). Furthermore, using 8 sCCEs, network node 30 can flexibly configure up to two radio devices 42 that share the same sPDCCH-PRB-set with sPDCCHs having AL 4 in the same sTTI. N_sCCE = 6sCCE supports up to three candidates, for example, AL 2 (for the two cases where up to three or four sPDCCH candidates are defined). N_sCCE = 4sCCE supports at least one candidate, for example, having AL 4.

[0158] Based on the above formula, for N_sCCE = 4, 6 and 8sCCE, the size of the sPDCCH-PRB set considering 1os, 2os and 3os sPDCCH and 1sCCE = 3sREG and 1sCCE = 4sREG is defined as an embodiment of this disclosure, as described below in Tables 5, 6 and 7 respectively.

[0159] Table 5: For N sCCE =8sCCE and considering 1os, 2os, and 3os sPDCCH, as well as the cases where 1sCCE = 3sREG and 1sCCE = 4sREG, sPDCCH - PRB - set size

[0160]

[0161] Table 6: For N sCCE =6sCCE and consider 1os, 2os, and 3os sPDCCH, as well as the cases where 1sCCE = 3sREG and 1sCCE = 4sREG, sPDCCH - PRB - set size

[0162]

[0163] Table 7: For N sCCE =4sCCE and considering 1os, 2os, and 3os sPDCCH, as well as the cases where 1sCCE = 3sREG and 1sCCE = 4sREG, sPDCCH - PRB - set size

[0164]

[0165]

[0166] However, as observed, for example for 1os-s PDCCH and low system bandwidth (e.g., 5MHz), N sCCE =8sCCE can represent high sPDCCH overhead. Therefore, as an additional embodiment, network node 30 can carefully configure the sPDCCH-PRB set size based on the available system bandwidth.

[0167] For a normal CP, a 1ms LTE subframe contains 14 OFDM symbols. New Radio (NR) subframes have a fixed duration of 1ms and therefore can contain different numbers of OFDM symbols for different subcarrier intervals. For a normal CP, an LTE slot corresponds to 7 OFDM symbols. NR slots correspond to either 7 or 14 OFDM symbols; at a 15kHz subcarrier interval, a slot with 7 OFDM symbols occupies 0.5ms. For information on the NR terminology, refer to 3GPP TR 38.802v14.0.0 and later versions.

[0168] Alternatively, the reference to short TTI in this document can be considered as a sub-slot or micro-slot according to NR terminology. A micro-slot can have a length of 1 symbol, 2 symbols, 3 or more symbols, or a length between 1 symbol and the NR slot length minus 1 symbol. A short TTI (or sub-slot) can have a length of 1 symbol, 2 symbols, 3 or more symbols, the LTE slot length (7 symbols), or a length between 1 symbol and the LTE subframe length minus 1 symbol. Short TTIs, sub-slots, or micro-slots can be considered to have a length of less than 1 ms or less than 0.5 ms.

[0169] Therefore, as described herein, in one embodiment, there are three aggregation levels for sTTI operation. The wireless device 42 can support these three aggregation levels, but it can be configured via a higher layer (e.g., RRC) to monitor only one set of them.

[0170] In one embodiment, this disclosure defines a finite number of candidates for sPDCCH in sTTI operation, wherein the definition of the number of candidates for each aggregation level depends on the configured set, as shown in Tables 3 and 4.

[0171] In one embodiment, this disclosure provides an sPDCCH-PRB collection configuration, including:

[0172] - For DMRS-based sPDCCH, two PRB sets are defined for wireless device 42, one set can be configured as centralized, and the second set can be configured as distributed;

[0173] - For CRS-based sPDCCH, this disclosure can be defined as configuring at least one PRB set as distributed; and

[0174] The size of the -sPDCCH-PRB set can be based on three factors: the coefficient of N_sCCE, the number of OFDM symbols in each sPDCCH, and the number of sREGs in each sCCE.

[0175] In one embodiment, a method is provided in a network node 30 for supporting a predetermined set of aggregation levels for configuring downlink control channels for one of a slot transmission time interval (TTI) and a sub-slot TTI. The method includes determining an aggregation level to be monitored by a wireless device WD 42 in the communication network (S100); and determining the number of downlink control channel candidates to be monitored by WD 42 within each of the slot TTI and the sub-slot TTI, the number of downlink control channel candidates being based on the aggregation level (S110). References to one of the slot TTI and the sub-slot TTI, or to each of the slot TTI and the sub-slot TTI, may refer to usage in the slot TTI and / or the sub-slot TTI, i.e., one or both of the slot TTI and the sub-slot TTI, i.e., a short TTI. Aspects of this disclosure apply to one or both of the slot TTI and the sub-slot TTI (or micro-slots), i.e., in transmissions using a short TTI length. In one embodiment, the method further includes assigning an aggregation level and downlink control channel candidates to WD 42. In some embodiments, assigning aggregation levels and downlink control channel candidates to WD 42 includes, via a higher layer, and optionally via RRC signaling, assigning aggregation levels and downlink control channel candidates to WD 42. In some embodiments, determining the number of downlink control channel candidates that WD 42 will monitor within each of the time slot TTI and the sub-time slot TTI includes: determining the number of downlink control channel candidates that WD 42 will monitor within each of the time slot TTI and the sub-time slot TTI, based at least on a maximum of six downlink control channel candidates to be monitored within each of the time slot TTI and the sub-time slot TTI. In some embodiments, determining the number of downlink control channel candidates that the radio device will monitor within each of the time slot TTI and the sub-time slot TTI includes: determining up to two downlink control channel candidates in a high aggregation level. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to a predetermined set of aggregation levels to be monitored by WD 42 is a maximum of six downlink control channel candidates. In some embodiments, one of the time slot TTI and the sub-time slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, each aggregation level includes a certain number of short control channel elements (sCCEs). In some embodiments, the number of sCCEs supports the number of downlink control channel candidates defined for each aggregation level of a predetermined set of aggregation levels to be monitored by WD 42. In some embodiments, the number of sCCEs is determined based on system bandwidth.In some embodiments, the number of sCCEs is selected to avoid control overhead on the available frequency resources along each of the time slot TTI and sub-time slot TTI. In some embodiments, the method further includes determining the size of the downlink control channel physical resource block set for each WD 42. In some embodiments, the size of the PRB set for each WD 42 is determined based at least on the number of sCCEs, the number of orthogonal frequency division multiplexing (OFDM) symbols per control channel, and the number of short resource element groups (sREGs) per sCCE. In some embodiments, two PRB sets are defined for the WD 42 for a short physical downlink control channel (sPDCCH) based on a demodulation reference signal (DMRS), the first PRB set being configured as centralized and the second PRB set being configured as distributed.

[0176] In another embodiment, a network node 30 is provided for supporting a predetermined set of aggregation levels for configuring downlink control channels for one of a time slot transmission time interval (TTI) and a sub-time slot TTI. The network node 30 includes processing circuitry 34 configured to: determine an aggregation level to be monitored by a wireless device WD 42 in a communication network; and determine the number of downlink control channel candidates to be monitored by WD 42 within each of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the aggregation level. In some embodiments, the processing circuitry 34 is further configured to assign aggregation levels and downlink control channel candidates to WD 42. In some embodiments, the processing circuitry 34 is further configured to assign aggregation levels and downlink control channel candidates to WD 42 via a higher layer and optionally via RRC signaling. In some embodiments, the processing circuitry 34 is further configured to determine the number of downlink control channel candidates to be monitored by WD 42 within each of the time slot TTI and the sub-time slot TTI, based at least on a maximum of six downlink control channel candidates to be monitored within each of the time slot TTI and the sub-time slot TTI. In some embodiments, processing circuitry 34 is further configured to determine up to two downlink control channel candidates in a high aggregation level. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to a predetermined set of aggregation levels is a maximum of six downlink control channel candidates. In some embodiments, one of the time slot TTI and the sub-time slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, the aggregation level includes a number of short control channel elements (sCCEs). In some embodiments, the number of sCCEs supports the number of downlink control channel candidates defined for each aggregation level in a predetermined set of aggregation levels to be monitored by WD 42. In some embodiments, the number of sCCEs is determined based on system bandwidth. In some embodiments, the number of sCCEs is selected to avoid control overhead along the available frequency resources of each of the time slot TTI and the sub-time slot TTI. In some embodiments, processing circuitry 34 is further configured to determine the size of the downlink control channel physical resource block (PRB) set for each WD 42. In some embodiments, processing circuitry 34 is further configured to determine the PRB set size for each WD 42 based at least on the number of sCCEs, the number of Orthogonal Frequency Division Multiplexing (OFDM) symbols per control channel, and the number of Short Resource Element Groups (sREGs) per sCCE. In some embodiments, processing circuitry 34 is further configured to define two PRB sets for WD 42 for a Short Physical Downlink Control Channel (sPDCCH) based on a Demodulation Reference Signal (DMRS), wherein the first PRB set is configured to be centralized and the second PRB set is configured to be distributed.

[0177] In another embodiment, a method is provided in a wireless device WD 42 for supporting a predetermined set of aggregation levels and for implementing at least one aggregation level and at least one downlink control channel candidate to configure a downlink control channel for one of a slot transmission time interval (TTI) and a sub-slot TTI. The method includes receiving from a network node 30 an assigned aggregation level to be monitored by WD 42 in the communication network (S120); and receiving from the network node 30 an assigned downlink control channel candidate, the network node 30 determining the number of downlink control channel candidates to be monitored by WD 42 within each of a slot TTI and a sub-slot TTI, the number of downlink control channel candidates being based on the assigned aggregation level (S130). In some embodiments, the method of receiving the assigned aggregation level to be monitored by WD 42 in the communication network from the network node 30 includes: receiving, via a higher layer, radio resource control (RRC) signaling for the assigned AT aggregation level to be monitored by WD 42 in the communication network from the network node 30. In some embodiments, the method further includes monitoring the assigned aggregation level. In some embodiments, the number of downlink control channel candidates is based on at least six downlink control channel candidates to be monitored within each of the time slot TTI and sub-time slot TTI. In some embodiments, at high aggregation levels, the number of downlink control channel candidates is up to two. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to a predetermined set of aggregation levels to be monitored by WD 42 is at most six downlink control channel candidates. In some embodiments, one of the time slot TTI and sub-time slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, the aggregation level includes a number of short control channel elements (sCCEs). In some embodiments, the number of sCCEs supports the number of downlink control channel candidates defined for each aggregation level of the predetermined set of aggregation levels to be monitored by WD 42. In some embodiments, the number of sCCEs is determined based on system bandwidth. In some embodiments, the number of sCCEs is selected to avoid control overhead along the available frequency resources of each of the time slot TTI and sub-time slot TTI.

[0178] In another embodiment, a wireless device (WD) 42 is provided for supporting a predetermined set of aggregation levels, and for implementing at least one aggregation level and at least one downlink control channel candidate to configure a downlink control channel for one of a time slot transmission time interval (TTI) and a sub-time slot TTI. The WD 42 includes processing circuitry 46 configured to: receive from a network node 30 an assigned aggregation level to be monitored by the WD 42 in the communication network; and receive from the network node 30 an assigned downlink control channel candidate, the network node 30 determining the number of downlink control channel candidates to be monitored by the WD 42 within each of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the assigned aggregation level. In some embodiments, the processing circuitry 46 is also configured to receive the assigned aggregation level to be monitored by the WD 42 in the communication network from the network node 30 via a higher layer and optionally via Radio Resource Control (RRC) signaling. In some embodiments, the processing circuitry 46 is also configured to monitor the assigned aggregation level. In some embodiments, the number of downlink control channel candidates is based on at least six downlink control channel candidates to be monitored within each of the time slot TTI and sub-time slot TTI. In some embodiments, at high aggregation levels, the number of downlink control channel candidates is up to two. In some embodiments, the sum of the number of downlink control channel candidates for each aggregation level according to a predetermined set of aggregation levels is at most six downlink control channel candidates. In some embodiments, one of the time slot TTI and sub-time slot TTI is a short TTI. In some embodiments, the downlink control channel is a short physical downlink control channel (sPDCCH). In some embodiments, the aggregation level includes a number of short control channel elements (sCCEs). In some embodiments, the number of sCCEs supports the number of downlink control channel candidates defined for each aggregation level of a predetermined set of aggregation levels to be monitored by WD 42. In some embodiments, the number of sCCEs is selected to avoid control overhead along the available frequency resources of each sTTI.

[0179] Some further embodiments may include reusing sPDCCH for different WD42 within the same search space region for sTTI.

[0180] Further embodiments of this disclosure may include limiting blind decoding on the PDCCH. Since the PDCCH can be used to transmit sDCI and supports dynamic switching between short TTI and 1ms TTI, the WD 42 may have to search for both the 1ms DCI and sDCI in the PDCCH in each subframe. Therefore, the total number of blind decodes in the PDCCH may increase. One exemplary method for limiting the number of blind decodes could be a generic format for both sTTI and 1ms TTI. Another exemplary method could be to define the search space for sDCI transmitted on the PDCCH as a subset of the search space for 1ms TTI DCI.

[0181] Other embodiments may include limiting blind decoding on the sPDCCH based on additional techniques. For example, uplink grants and downlink assignments in the DCI may have slightly different fields; for instance, there may be dedicated bits in the DL but not in the UL. Although uplink grants and downlink assignments may have different bit amounts in the DCI, these formats can be blindly decoded on the same sPDCCH. Therefore, to limit blind decoding, the DCI format can be designed to be the same size for all grants, and the bit fields can indicate whether the DCI is an uplink grant or a downlink assignment. This approach can be considered similar to the flags used to distinguish between format 0 and format 1A. In another embodiment, padding bits may be used in addition to the indicator bits when the required number of bits differs for uplink grants and downlink assignments. In one embodiment, a single size may be defined for the DL and UL sDCI to limit the number of blind decodes on the WD 42.

[0182] Other embodiments of this disclosure may include increasing the sPDCCH cyclic redundancy check (CRC) length. For example, increasing the sPDCCH CRC length from 16 bits to 24 bits has been considered, for example, to reduce the false detection rate and avoid the additional pruning algorithm in WD 42. In some embodiments, a longer CRC may have some impact on control channel performance. Figure 21A -B shows the block error rate (BLER) of AL1 in a 10MHz system bandwidth, where the sPDCCH-PRB set size is 18 PRBs, assuming a distributed and centralized configuration of sCCE0. Figure 21A The example results of the extended Vehicle A (EVA) channel are shown in the figure. Figure 21B The figure shows exemplary results for an extended typical city (ETU) channel, both at 3 km / h. Figure 21A-B shows simulations of the performance for both the standard 16-bit CRC and the 24-bit CRC using 8 additional bits. Figure 21A As shown in -B, the 24-bit CRC increases the code rate and BLER, resulting in a loss of approximately 1.5-2 dB. Therefore, Figure 21A -B illustrates the link performance for different sREG mappings of a single sCCE sPDCCH. Both graphs include sets of curves with different payloads (excluding CRC) of 14 and 34 bits and CRC lengths of 16 or 24 bits. In some embodiments, the loss in demodulation performance can be compensated for by using a higher AL, which can also lead to more scheduling constraints and greater control overhead. In some embodiments, it may be advantageous to compare the benefits of increasing the sPDCCH CRC length with the signal-to-noise ratio (SNR) loss caused by the increased coding rate.

[0183] Some embodiments of this disclosure are as follows:

[0184] Example 1. A method for configuring a downlink control channel for a short transmission time interval (sTTI) in a network node, the method comprising:

[0185] A predetermined set of aggregation levels to be monitored by wireless devices in a communication network is determined, each aggregation level comprising a certain number of short control channel elements (sCCEs).

[0186] Determine the number of downlink control channel candidates to be monitored by the wireless device in each sTTI, the number of downlink channel candidates being based at least on a predetermined set at the aggregation level; and

[0187] The aggregation level set and the downlink control channel candidates are assigned to the wireless device.

[0188] Example 2. According to the method described in Example 1, the downlink control channel is a short physical downlink control channel (sPDCCH).

[0189] Example 3. The method according to Example 1 further includes determining the size of the downlink control channel physical resource block (PRB) set for each wireless device.

[0190] Example 4. According to the method of Example 3, wherein the PRB set size for each wireless device is determined based at least on the number of sCCEs, the number of orthogonal frequency division multiplexing (OFDM) symbols per control channel, and the number of short resource element groups (sREGs) per sCCE.

[0191] Example 5. According to the method described in Example 3, for the short physical downlink control channel sPDCCH based on demodulation reference signal DMRS, two PRB sets are defined for the wireless device, wherein the first PRB set is configured as centralized and the second PRB set is configured as distributed.

[0192] Example 6. The method according to Example 1, wherein the number of sCCEs supports the number of downlink control channel candidates defined for the set of aggregation levels of the wireless device.

[0193] Example 7. The method according to Example 1, wherein the number of sCCEs supports wireless devices with an aggregation level greater than a predetermined level.

[0194] Example 8. The method according to Example 1, wherein the number of sCCEs is determined based on system bandwidth.

[0195] Example 9. The method according to Example 1, wherein the number of sCCEs is selected to avoid control overhead of available frequency resources along each sTTI.

[0196] Example 10. The method according to Example 1, wherein the number of aggregation levels to be monitored by each wireless device is three.

[0197] Example 11. The method according to Example 1 further includes assigning the set of aggregation levels and the downlink control channel candidates to the radio device via at least one of Radio Resource Control (RRC) signaling or Physical Downlink Control Channel (PDCCH) signaling.

[0198] Example 12. A network node for configuring a downlink control channel for a short transmission time interval (TTI), the network node comprising:

[0199] Processing circuitry, comprising a memory and a processor, the memory communicating with the processor, the memory having instructions that, when executed by the processor, configure the processor to:

[0200] A predetermined set of aggregation levels to be monitored by wireless devices in a communication network is determined, each aggregation level comprising a certain number of short control channel elements (sCCEs).

[0201] Determine the number of downlink control channel candidates to be monitored by the wireless device in each sTTI, the number of downlink channel candidates being based at least on a predetermined set at the aggregation level; and

[0202] The communication interface is configured as follows:

[0203] The aggregation level set and the downlink control channel candidates are assigned to the wireless device.

[0204] Example 13. The network node according to Example 12, wherein the downlink control channel is a short physical downlink control channel (sPDCCH).

[0205] Example 14. The network node according to Example 12, wherein the processor is further configured to determine the size of the downlink control channel physical resource block (PRB) set for each wireless device.

[0206] Example 15. A network node according to Example 14, wherein the PRB set size for each wireless device is determined based at least on the number of sCCEs, the number of orthogonal frequency division multiplexing (OFDM) symbols per control channel, and the number of short resource element groups (sREGs) per sCCE.

[0207] Example 16. According to the network node of Example 14, for the short physical downlink control channel sPDCCH based on demodulation reference signal DMRS, two PRB sets are defined for the wireless device, wherein the first PRB set is configured as centralized and the second PRB set is configured as distributed.

[0208] Example 17. A network node according to Example 12, wherein the number of sCCEs supports the number of downlink control channel candidates defined for each aggregation level set of the wireless device.

[0209] Example 18. A network node according to Example 12, wherein the number of sCCEs supports wireless devices with an aggregation level greater than a predetermined level.

[0210] Example 19. The network node according to Example 12, wherein the number of sCCEs is determined based on the system bandwidth.

[0211] Example 20. A network node according to Example 12, wherein the number of sCCEs is selected to avoid control overhead of available frequency resources along each sTTI.

[0212] Example 21. A network node according to Example 12, wherein the number of aggregation levels to be monitored by each wireless device is three.

[0213] Example 22. The network node according to Example 12, wherein the processor is further configured to assign an aggregation level set and downlink control channel candidates to the radio device via at least one of Radio Resource Control (RRC) signaling and Physical Downlink Control Channel (PDCCH) signaling.

[0214] Example 23. A method in a wireless device for implementing aggregation-level set-up and downlink control channel candidates to configure downlink control channels for a short transmission time interval (sTTI), the method comprising:

[0215] Receive a set of assignments for aggregation levels from network nodes, each aggregation level including a certain number of short control channel elements (sCCEs).

[0216] Monitor the set of assignments at the aggregation level; and

[0217] The network node receives assigned downlink control channel candidates and determines the number of downlink control channel candidates to be monitored by the wireless device in each sTTI, the number of downlink channel candidates being based at least on the set of assignments at the aggregation level.

[0218] Example 24. The method according to Example 23, wherein the downlink control channel is a short physical downlink control channel (sPDCCH).

[0219] Example 25. The method according to Example 23, wherein the number of sCCEs supports the number of downlink control channel candidates defined for each aggregation level set of the wireless device.

[0220] Example 26. The method according to Example 23, wherein the number of sCCEs supports wireless devices with an aggregation level greater than a predetermined level.

[0221] Example 27. The method according to Example 23, wherein the number of sCCEs is determined based on system bandwidth.

[0222] Example 28. The method according to Example 23, wherein the number of sCCEs is selected to avoid control overhead of available frequency resources along each sTTI.

[0223] Example 29. The method according to Example 23, wherein the number of aggregation levels to be monitored by the wireless device is three.

[0224] Example 30. A wireless apparatus for implementing an aggregation level set and downlink control channel candidates for configuring downlink control channels for a short transmission time interval (sTTI), the wireless apparatus comprising:

[0225] The communication interface is configured as follows:

[0226] Receive a set of assigned aggregation levels from the network node, each aggregation level comprising a certain number of Short Control Channel Elements (sCCEs); and

[0227] The network node receives assigned downlink control channel candidates from the network node, and the network node determines the number of downlink control channel candidates to be monitored by the wireless device in each sTTI, the number of downlink channel candidates being based at least on the set of assignments at the aggregation level; and

[0228] Processing circuitry, comprising a memory and a processor, the memory communicating with the processor, the memory having instructions that, when executed by the processor, configure the processor to:

[0229] The set of aggregation levels assigned to the monitoring;

[0230] Example 31. The wireless device according to Example 30, wherein the downlink control channel is a short physical downlink control channel (sPDCCH).

[0231] Example 32. The wireless device according to Example 30, wherein the number of sCCEs supports the number of downlink control channel candidates defined for each aggregation level set of the wireless device.

[0232] Example 33. The wireless device according to Example 30, wherein the number of sCCEs supports a wireless device with an aggregation level greater than a predetermined level.

[0233] Example 34. The wireless device according to Example 30, wherein the number of sCCEs is determined based on the system bandwidth.

[0234] Example 35. The wireless device according to Example 30, wherein the number of sCCEs is selected to avoid control overhead of available frequency resources along each sTTI.

[0235] Example 36. The wireless device according to Example 30, wherein the number of aggregation levels to be monitored by the wireless device is three.

[0236] Example 37. A network node for configuring a downlink control channel for a short transmission time interval (sTTI), the network node comprising:

[0237] The aggregation level determination module is configured as follows:

[0238] A predetermined set of aggregation levels to be monitored by wireless devices in a communication network is determined, each aggregation level comprising a certain number of short control channel elements (sCCEs).

[0239] The downlink control channel candidate determination module is configured as follows:

[0240] The number of downlink control channel candidates to be monitored by the wireless device within each sTTI is determined, the number of downlink channel candidates being based at least on a predetermined set at the aggregation level; and

[0241] The communication interface module is configured as follows:

[0242] The aggregation level set and the downlink control channel candidates are assigned to the wireless device.

[0243] Example 38. A wireless device for implementing aggregation-level set-up and downlink control channel candidates to configure downlink control channels for short transmission time intervals (sTTI), the wireless device comprising:

[0244] The communication interface module is configured as follows:

[0245] Receive a set of aggregation level assignments from network nodes, each aggregation level including a certain number of short control channel elements (sCCEs); and

[0246] The network node receives assigned downlink control channel candidates, and the network node determines the number of downlink control channel candidates to be monitored by the wireless device in each sTTI, the number of downlink channel candidates being based at least on a predetermined set at the aggregation level; and

[0247] The aggregation-level monitoring module is configured as follows:

[0248] The set of aggregation levels assigned by the monitoring.

[0249] As those skilled in the art will understand, the concepts described herein can be embodied as methods, data processing systems, and / or computer program products. Therefore, the concepts described herein can take the form of entirely hardware embodiments, entirely software embodiments, or embodiments combining software and hardware aspects, all of which are generally referred to herein as “circuit” or “module.” Furthermore, this disclosure can take the form of a computer program product on a tangible computer-readable storage medium having computer program code embodied therein that is executable by a computer. Any suitable tangible computer-readable medium can be utilized, including hard disks, CD-ROMs, electronic storage devices, optical storage devices, or magnetic storage devices.

[0250] This document describes some embodiments with reference to flowchart illustrations and / or block diagrams of methods, systems, and computer program products. It will be understood that each block of the flowchart and / or block diagram, and combinations of blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer (thus creating a special-purpose computer), a special-purpose computer, or other programmable data processing apparatus to produce a machine such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create components for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0251] These computer program instructions may also be stored in a computer-readable storage medium or storage medium that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of writing comprising instruction components that implement the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0252] Computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide steps for implementing the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0253] It should be understood that the functions / actions indicated in the boxes may not occur in the order shown in the operation diagram. For example, depending on the functions / actions involved, two boxes shown consecutively may actually be executed substantially simultaneously, or these boxes may sometimes be executed in reverse order. Although some diagrams include arrows on the communication path to indicate the main direction of communication, it should be understood that communication may occur in the opposite direction to the arrows depicted.

[0254] Computer program code used to perform operations that implement the concepts described in this article can be written in an object-oriented programming language (e.g., The code can be written in languages ​​such as C or C++. However, the computer program code used to perform the operations of this disclosure can also be written in a conventional procedural programming language such as the "C" programming language. The program code can be executed entirely on the user's computer, partially on the user's computer, as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer. In the latter case, the remote computer can be connected to the user's computer via a local area network (LAN) or a wide area network (WAN), or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0255] This document has disclosed numerous different embodiments in conjunction with the foregoing description and accompanying drawings. It will be understood that a literal description and illustration of every combination and sub-combination of these embodiments would be excessively repetitive and obscure. Therefore, all embodiments can be combined in any manner and / or combination, and this specification, including the accompanying drawings, should be construed as a complete written description of all combinations and sub-combinations constituting the embodiments described herein, as well as the ways and processes of making and using them, and should support the claims for any such combination or sub-combination.

[0256] Those skilled in the art will understand that the embodiments described herein are not limited to those specifically shown and described above. Furthermore, unless stated to the contrary above, it should be noted that all drawings are not to scale. Various modifications and variations are possible based on the foregoing teachings, which are limited only by the appended claims.

Claims

1. A method in a network node (30) for supporting a predetermined set of one or more aggregation levels for configuring a downlink control channel for one of a time slot transmission time interval (TTI) and a sub-time slot TTI, the method comprising: Determine (S100) the aggregation level of the predetermined set of one or more aggregation levels to be monitored by the wireless device WD (42) in the communication network; Determine (S110) the number of downlink control channel candidates to be monitored in each of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the aggregation level; as well as The configuration is transmitted to the wireless device, the configuration indicating a predetermined set of one or more aggregation levels to be monitored by the WD, and for each aggregation level of the configuration to be monitored, indicating the number of downlink control channel candidates to be monitored by the WD.

2. The method according to claim 1, further comprising: The aggregation level and the downlink control channel candidate are assigned to the WD (42).

3. The method of claim 2, wherein assigning the aggregation level and the downlink control channel candidate to the WD (42) comprises assigning the aggregation level and the downlink control channel candidate to the WD (42) by RRC signaling.

4. The method according to any one of claims 1-3, wherein determining the number of downlink control channel candidates to be monitored by the WD (42) within each of the time slot TTI and the sub-time slot TTI comprises: Based at least on at least six downlink control channel candidates to be monitored within each of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates to be monitored by the WD (42) within each of the time slot TTI and the sub-time slot TTI shall be determined.

5. The method according to any one of claims 1-3, wherein determining the number of downlink control channel candidates to be monitored by the wireless device within each of the one of the time slot TTI and the sub-time slot TTI comprises: Identify up to two downlink control channel candidates in the high aggregation level.

6. The method according to any one of claims 1-3, wherein the sum of the number of downlink control channel candidates for each of the predetermined set of one or more aggregation levels to be monitored by the WD (42) is at most six downlink control channel candidates.

7. The method according to any one of claims 1-3, wherein one of the time slot TTI and the sub-time slot TTI is a short TTI.

8. The method according to any one of claims 1-3, wherein the downlink control channel is a short physical downlink control channel (sPDCCH).

9. The method of claim 1, wherein the aggregation level includes a number of short control channel elements (sCCEs).

10. The method of claim 9, wherein the number of sCCEs supports the number of downlink control channel candidates defined by each aggregation level of the predetermined set of one or more aggregation levels to be monitored by the WD (42).

11. The method according to any one of claims 9-10, wherein the number of sCCEs is determined based on system bandwidth.

12. The method according to any one of claims 9-10, wherein the number of sCCEs is selected to avoid control overhead on the available frequency resources along each of the time slot TTI and the sub-time slot TTI.

13. The method of claim 1, further comprising determining the size of the downlink control channel physical resource block (PRB) set for each WD (42).

14. The method of claim 13, wherein the size of the PRB set for each WD (42) is determined at least based on the number of sCCEs, the number of orthogonal frequency division multiplexing (OFDM) symbols per control channel, and the number of short resource element groups (sREGs) per sCCE.

15. The method according to any one of claims 13-14, wherein for the short physical downlink control channel sPDCCH based on demodulation reference signal DMRS, two PRB sets are defined for the WD (42), the first PRB set being configured as centralized and the second PRB set being configured as distributed.

16. A network node (30) for supporting a predetermined set of one or more aggregation levels for configuring a downlink control channel for one of a time slot transmission time interval (TTI) and a sub-time slot TTI, the network node (30) including processing circuitry (34) configured to: Determine the aggregation level of the predetermined set of one or more aggregation levels to be monitored by the wireless device WD (42) in the communication network; Determine the number of downlink control channel candidates that the WD (42) will monitor within each of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the aggregation level; and This enables the transmission of configurations to the wireless device, the configurations indicating a predetermined set of one or more aggregation levels to be monitored by the WD, and for each aggregation level of the configurations to be monitored, indicating the number of downlink control channel candidates to be monitored by the WD.

17. The network node (30) of claim 16, wherein the processing circuit (34) is further configured to assign the aggregation level and the downlink control channel candidate to the WD (42).

18. The network node (30) of claim 17, wherein the processing circuit (34) is further configured to assign the aggregation level and the downlink control channel candidate to the WD (42) via RRC signaling.

19. The network node (30) according to any one of claims 16-18, wherein the processing circuitry (34) is further configured to: determine, at least based on a maximum of six downlink control channel candidates to be monitored in each of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates to be monitored by the WD (42) in each of the time slot TTI and the sub-time slot TTI.

20. The network node (30) according to any one of claims 16-18, wherein the processing circuit (34) is further configured to determine up to two downlink control channel candidates in a high aggregation level.

21. The network node (30) according to any one of claims 16-18, wherein the sum of the number of downlink control channel candidates for each of the predetermined set of one or more aggregation levels to be monitored by the WD (42) is at most six downlink control channel candidates.

22. The network node (30) according to any one of claims 16-18, wherein one of the time slot TTI and the sub-time slot TTI is a short TTI.

23. The network node (30) according to any one of claims 16-18, wherein the downlink control channel is a short physical downlink control channel (sPDCCH).

24. The network node (30) according to claim 16, wherein the aggregation level includes a number of short control channel elements (sCCEs).

25. The network node (30) of claim 24, wherein the number of sCCEs supports the number of downlink control channel candidates defined for each of the predetermined set of one or more aggregation levels to be monitored by the WD (42).

26. The network node (30) according to any one of claims 24-25, wherein the number of sCCEs is determined based on system bandwidth.

27. The network node (30) according to any one of claims 24-25, wherein the number of sCCEs is selected to avoid control overhead of available frequency resources along each of the time slot TTI and the sub-time slot TTI.

28. The network node (30) of claim 16, wherein the processing circuit (34) is further configured to determine the size of the downlink control channel physical resource block (PRB) set for each WD (42).

29. The network node (30) of claim 28, wherein the processing circuit (34) is further configured to determine the PRB set size for each WD (42) based at least on the number of sCCEs, the number of orthogonal frequency division multiplexing (OFDM) symbols for each control channel, and the number of short resource element groups (sREGs) for each sCCE.

30. The network node (30) according to any one of claims 28-29, wherein the processing circuit (34) is further configured to: define two PRB sets for the WD (42) for a short physical downlink control channel sPDCCH based on demodulation reference signal DMRS, wherein the first PRB set is configured to be centralized and the second PRB set is configured to be distributed.

31. A method in a wireless device WD (42) for supporting a predetermined set of one or more aggregation levels and for implementing at least one aggregation level and at least one downlink control channel candidate to configure a downlink control channel for one of a time slot transmission time interval (TTI) and a sub-time slot TTI, the method comprising: The configuration is received from the network node, which indicates the predetermined set of one or more aggregation levels to be monitored by the WD, and for each aggregation level of the configuration to be monitored, indicates the number of downlink control channel candidates to be monitored by the WD; Receive (S120) from the network node (30) an aggregation level to be monitored by the WD (42) in the communication network for one or more aggregation levels; The network node (30) receives (S130) assigned downlink control channel candidates, and the network node (30) determines the number of downlink control channel candidates that the WD (42) will monitor in each of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the assigned aggregation level.

32. The method of claim 31, wherein receiving the assigned aggregation level to be monitored by the WD (42) in the communication network from the network node (30) comprises receiving the assigned aggregation level to be monitored by the WD (42) in the communication network from the network node (30) via Radio Resource Control (RRC) signaling.

33. The method according to any one of claims 31-32, further comprising monitoring the aggregation level of the assignment.

34. The method according to any one of claims 31-32, wherein the number of downlink control channel candidates is based at least on a maximum of six downlink control channel candidates to be monitored within each of the one of the time slot TTI and the sub-time slot TTI.

35. The method according to any one of claims 31-32, wherein in the high aggregation level, the number of downlink control channel candidates is up to two downlink control channel candidates.

36. The method according to any one of claims 31-32, wherein the sum of the number of downlink control channel candidates for each aggregation level to be monitored by the WD (42) according to the predetermined set of one or more aggregation levels is at most six downlink control channel candidates.

37. The method according to any one of claims 31-32, wherein one of the time slot TTI and the sub-time slot TTI is a short TTI.

38. The method according to any one of claims 31-32, wherein the downlink control channel is a short physical downlink control channel (sPDCCH).

39. The method of claim 31, wherein the aggregation level comprises a number of short control channel elements (sCCEs).

40. The method of claim 39, wherein the number of sCCEs supports the number of downlink control channel candidates defined by each aggregation level of the predetermined set of one or more aggregation levels to be monitored by the WD (42).

41. The method according to any one of claims 39-40, wherein the number of sCCEs is determined based on system bandwidth.

42. The method according to any one of claims 39-40, wherein the number of sCCEs is selected to avoid control overhead on the available frequency resources along each of the time slot TTI and the sub-time slot TTI.

43. A wireless device WD (42), the WD (42) being configured to support a predetermined set of one or more aggregation levels and to implement at least one aggregation level and at least one downlink control channel candidate for configuring a downlink control channel for one of a time slot transmission time interval (TTI) and a sub-time slot TTI, the WD (42) including processing circuitry (46) configured to: The configuration is received from the network node, which indicates the predetermined set of one or more aggregation levels to be monitored by the WD, and for each aggregation level of the configuration to be monitored, indicates the number of downlink control channel candidates to be monitored by the WD; Receive from the network node (30) an aggregate level to be monitored by the WD (42) in the communication network for one or more aggregate levels; The network node (30) receives assigned downlink control channel candidates and determines the number of downlink control channel candidates that the WD (42) will monitor in each of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the assigned aggregation level.

44. The WD (42) of claim 43, wherein the processing circuit (46) is further configured to receive, via Radio Resource Control (RRC) signaling, the assigned aggregation level to be monitored by the WD (42) in the communication network from the network node (30).

45. The WD (42) according to any one of claims 43-44, wherein the processing circuit (46) is further configured to monitor the aggregation level of the assignment.

46. ​​The WD (42) according to any one of claims 43-44, wherein the number of downlink control channel candidates is based at least on a maximum of six downlink control channel candidates to be monitored in each of the one of the time slot TTI and the sub-time slot TTI.

47. The WD (42) according to any one of claims 43-44, wherein in the high aggregation level, the number of downlink control channel candidates is up to two downlink control channel candidates.

48. The WD (42) according to any one of claims 43-44, wherein the sum of the number of downlink control channel candidates for each aggregation level of the predetermined set of aggregation levels to be monitored by the WD (42) is at most six downlink control channel candidates.

49. The WD (42) according to any one of claims 43-44, wherein one of the time slot TTI and the sub-time slot TTI is a short TTI.

50. The WD (42) according to any one of claims 43-44, wherein the downlink control channel is a short physical downlink control channel (sPDCCH).

51. The WD (42) according to claim 43, wherein the aggregation level includes a number of short control channel elements sCCE.

52. The WD (42) of claim 51, wherein the number of sCCEs supports the number of downlink control channel candidates defined for each of the predetermined set of one or more aggregation levels to be monitored by the WD (42).

53. The WD (42) according to any one of claims 51-52, wherein the number of sCCEs is determined based on system bandwidth.

54. The WD (42) according to any one of claims 51-52, wherein the number of sCCEs is selected to avoid control overhead for each available frequency resource along the one of the time slot TTI and the sub-time slot TTI.

55. A network node (30) supporting a predetermined set of one or more aggregation levels for configuring a downlink control channel for one of a time slot transmission time interval (TTI) and a sub-time slot TTI, the network node including an aggregation level determination module (54) configured to: Determine the aggregation level of a predetermined set of one or more aggregation levels to be monitored by the wireless device WD (42) in the communication network; Determine the number of downlink control channel candidates to be monitored by the WD (42) within each of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the aggregation level; and The configuration is transmitted to the wireless device, the configuration indicating a predetermined set of one or more aggregation levels to be monitored by the WD, and for each aggregation level of the configuration to be monitored, indicating the number of downlink control channel candidates to be monitored by the WD.

56. A wireless device WD (42), the WD (42) being configured to support a predetermined set of aggregation levels and to implement at least one aggregation level and at least one downlink control channel candidate for configuring a downlink control channel for one of a time slot transmission time interval (TTI) and a sub-time slot TTI, the WD (42) including a communication interface module (60) configured to: The configuration is received from the network node, which indicates the predetermined set of one or more aggregation levels to be monitored by the WD, and for each aggregation level of the configuration to be monitored, indicates the number of downlink control channel candidates to be monitored by the WD; Receive from the network node (30) an aggregate level to be monitored by the WD (42) in the communication network for one or more aggregate levels; The network node (30) receives assigned downlink control channel candidates and determines the number of downlink control channel candidates that the WD (42) will monitor in each of the time slot TTI and the sub-time slot TTI, the number of downlink control channel candidates being based on the assigned aggregation level.

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