Patent Description:
This disclosure relates generally to wireless communication, and more specifically, to transport block size for channels with shortened transmission time interval (sTTI).

In some Long Term Evolution (LTE) or New Radio (NR) deployments, base stations and/or UEs may transmit a data packet during a defined time duration, generally referred to as transmission time interval (TTI). Legacy LTE systems (e.g., LTE Release <NUM>) generally use <NUM> millisecond (a duration of a subframe) as TTI. Later LTE releases introduce shortened TTI (sTTI) to support services that provide low latency for wireless transmissions. An sTTI has shorter duration in time relative to the legacy (or non-shorten) TTI. Correspondingly, the amount of available resources for an sTTI transmission may be smaller than that of the legacy TTI, and hence, a transport block (TB) for an sTTI channel may have a smaller transport block size (TBS) relative to a legacy TTI channel. Relatedly, 3GPP R1-<NUM> describes shortened processing time and sTTI, 3GPP R1-<NUM> describes TBS scaling for sTTI, and <CIT> describes a method and apparatus for determining TBS for sTTI.

The invention is defined in the appended independent claims. Embodiments representing specific realisations of the invention are defined in the dependent claims.

Systems, apparatuses, and methods are disclosed for transport block size (TBS) for shortened TTI (sTTI) channels. An initial size may be determined based on one or more TBS tables, such as a baseline table, or a translation table that maps a baseline size from the baseline table to a TBS value for a transport block mapped to more than one layer. The initial size may be scaled by a factor associated with the sTTI channel. A TBS table may be selected based on the one or more TBS tables. The scaled size may be rounded based on the selected TBS table to generate a TBS for the sTTI channel. Embodiments and aspects that do not fall within the scope of the claims are merely examples used for explanation of the invention.

Various features and advantages of this disclosure are described in further details below. Other features will be apparent from the description, drawings, and/or the claims.

Illustrative and non-limiting drawings are provided to aid in the description of various aspects and implementations. Unless specified otherwise, like reference symbols indicate like elements.

TBS for legacy TTI channels may be computed using various TBS tables, such as a baseline and a translation table, that provide a TBS value for a transport block mapped to one or more layers. These tables may be reused to compute TBS for an sTTI channel. An initial size corresponding to a non-shorten channel may be determined based on these TBS tables. The initial size may be scaled by a factor associated with the sTTI channel. The factor may represent a proportional reduction in the amount of available resources afforded by the sTTI channel, relative to a corresponding legacy channel. A TBS table may be selected based on various TBS tables. For example, a translation TBS table may be avoided, in favor of a baseline table, if the scaled size is smaller than a threshold. For another example, a combined table from a baseline table and a translation table may be selected based on a number of layers to which a transport block of the sTTI channel is mapped. The TBS of the sTTI channel may be determined by rounding the scaled size to a TBS value of the selected table.

Aspects of the disclosure introduced above are described below in the context of a wireless communications system. Examples of TBS computation for legacy TTI and sTTI channels are then described. Aspects of the disclosure are further illustrated by and described with reference to various apparatus diagrams, system diagrams, and flowcharts.

<FIG> illustrate an example of wireless communications system <NUM>. The wireless communications system <NUM> includes base stations <NUM>, UEs <NUM>, and a core network <NUM>. In some examples, the wireless communications system <NUM> may be an LTE, LTE-Advanced (LTE-A) network, or a New Radio (NR) network. In some cases, wireless communications system <NUM> may support enhanced broadband communications, ultra-reliable (i.e., mission critical) communications, low latency communications, and communications with low-cost and low-complexity devices.

In an example, a UE <NUM> and a base station <NUM> may support communications via sTTI channels as well as legacy TTI channels. A UE <NUM> and a base station <NUM> may compute TBS for a transport block for sTTI channels by leveraging legacy TBS computation mechanisms.

Each base station <NUM> may provide communication coverage for a respective geographic coverage area <NUM>. Control information and data may be multiplexed on an uplink channel or downlink according to various techniques. Control information and data may be multiplexed on a downlink channel, for example, using time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. In some examples, the control information transmitted during a TTI duration of a downlink channel may be distributed between different control regions in a cascaded manner (e.g., between a common control region and one or more UE-specific control regions).

A UE <NUM> may also be referred to as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. A UE <NUM> may also be a cellular phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a personal electronic device, a handheld device, a personal computer, a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, a machine type communication (MTC) device, an appliance, an automobile, or the like.

In some cases, groups of UEs <NUM> communicating via D2D communications may utilize a one-to-many system in which each UE <NUM> transmits to every other UE <NUM> in the group.

The core network <NUM> may provide user authentication, access authorization, tracking, IP connectivity, and other access, routing, or mobility functions. At least some of the network devices, such as base station <NUM> may include subcomponents such as an access network entity, which may be an example of an access node controller (ANC). Each access network entity may communicate with a number of UEs <NUM> through a number of other access network transmission entities, each of which may be an example of a smart radio head, or a transmission/reception point (TRP).

Multiple-input multiple-output (MIMO) wireless systems use a transmission scheme between a transmitter (e.g., a base station <NUM>) and a receiver (e.g., a UE <NUM>), where both transmitter and receiver are equipped with multiple antennas. Some portions of wireless communications system <NUM> may use beamforming. For example, base station <NUM> may have an antenna array with a number of rows and columns of antenna ports that the base station <NUM> may use for beamforming in its communication with UE <NUM>. Signals may be transmitted multiple times in different directions (e.g., each transmission may be beamformed differently). An mmW (millimeter wave) receiver (e.g., a UE <NUM>) may try multiple beams (e.g., antenna subarrays) while receiving the synchronization signals.

In some cases, the antennas of a base station <NUM> or UE <NUM> may be located within one or more antenna arrays, which may support beamforming or MIMO operation. One or more base station antennas or antenna arrays may be collocated at an antenna assembly, such as an antenna tower. A base station <NUM> may multiple use antennas or antenna arrays to conduct beamforming operations for directional communications with a UE <NUM>.

The MAC layer may also use Hybrid ARQ (HARQ) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE <NUM> and a network device, base station <NUM>, or core network <NUM> supporting radio bearers for user plane data.

Time intervals in LTE or NR may be expressed in multiples of a basic time unit (which may be a sampling period of Ts = <NUM>/<NUM>,<NUM>,<NUM> seconds). Time resources may be organized according to radio frames of length of <NUM> (Tf = 307200Ts), which may be identified by a system frame number (SFN) ranging from <NUM> to <NUM>. Each frame may include ten <NUM> subframes numbered from <NUM> to <NUM>. A subframe may be further divided into two <NUM> slots, each of which contains <NUM> or <NUM> modulation symbol periods (depending on the length of the cyclic prefix prepended to each symbol). Excluding the cyclic prefix, each symbol contains <NUM> sample periods. In some cases, the subframe may be the smallest scheduling unit, also known as a TTI duration. In other cases, a TTI duration may be shorter than a subframe or may be dynamically selected (e.g., in short TTI duration bursts or in component carriers using short TTI durations (for example, sTTIs)).

A resource element may consist of one symbol period and one subcarrier (e.g., a <NUM> frequency range). A resource block may contain <NUM> consecutive subcarriers in the frequency domain and, for a normal cyclic prefix in each OFDM symbol, <NUM> consecutive OFDM symbols in the time domain (<NUM> slot), or <NUM> resource elements. The number of bits carried by each resource element may depend on the modulation scheme (the configuration of symbols that may be selected during each symbol period). Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate may be.

For illustrative purposes, the following examples and figures may be described with reference to UE <NUM> and base station <NUM> of <FIG>; however, other types of UEs or base stations may be used in same or other examples without limiting the scope of the present disclsoure.

<FIG> illustrates an example of a frame structure <NUM> containing shortened transmission time intervals. A transmission timeline may be partitioned into units referred to herein as (radio) frames. Depicted are frames t-<NUM>, t, and t+<NUM>. Each frame <NUM> may have a defined duration (e.g., <NUM> milliseconds (ms)) and may be partitioned into a defined number of subframes <NUM> having corresponding indices (e.g., <NUM> subframes with indices of <NUM> through <NUM>). A subframe <NUM> may be used for uplink communication or downlink communication. In uplink communication, a UE <NUM> transmits to a base station <NUM>. In downlink communication, a base station <NUM> communicates to a UE <NUM>. Each subframe <NUM> may include two slots and each slot may include L symbol periods, e.g., L=<NUM> symbol periods for a normal cyclic prefix or L=<NUM> symbol periods for an extended cyclic prefix. The <NUM> symbol periods in each subframe may be assigned indices of <NUM> through <NUM>-<NUM>.

The available time and frequency resources of each subframe <NUM> may be partitioned into resource blocks (RBs). Each resource block may cover N subcarriers (e.g., <NUM> subcarriers) in one slot. Each subcarrier may occupy a certain frequency bandwidth (e.g., <NUM> kiloHertz (kHz)). One or more resource elements may be available in each symbol period. Each resource element (RE) may cover one subcarrier in one symbol period and may be used to send one modulation symbol, which may be a real or complex value. Resource elements not used for a reference signal in each symbol period may be arranged into resource element groups (REGs). Each REG may include four resource elements in one symbol period.

A TTI <NUM> may be referred to as a duration in time of a subframe <NUM> (e.g., <NUM>). An sTTI <NUM> (e.g., <NUM>-a to <NUM>-d) may have a duration that is less than the duration of TTI <NUM>. In an example, an sTTI <NUM> may include one or more symbols, may correspond to a duration of a single slot, or the like. An sTTI may be referred to as slot TTI for duration equal to a slot, and sub-slot TTI for duration less than a slot. In the depicted example, sTTI <NUM>-a may have slot sTTI, occupying a duration of one slot, and sTTI <NUM>-b, <NUM>-c, and <NUM>-d, each with sub-slot sTTI, may collectively occupy a duration of one slot.

A channel transmitted within a TTI <NUM> may be referred to as non-shortened TTI (or legacy) channel, and one within an sTTI <NUM> an sTTI (or shortened) channel. In some examples, a TTI <NUM> may transport physical downlink shared channel (PDSCH) in the downlink and physical uplink shared channel (PUSCH) in the uplink. An sTTI <NUM> may transport shortened PDSCH (sPDSCH) in the downlink and shortened PUSCH (sPUSCH) in the uplink.

<FIG> illustrates various examples of TBS tables <NUM> for TBS computation of non-shortened TTI channels. A channel may transport data in one or more transport blocks. A transport block may contain one or more units of data. The number of the transported units is referred to as TBS of the transport block. An TBS may be expressed in units of bits, bytes, or the like; for example, TBS is defined in bits for LTE systems. TBS may vary with the amount of available communication resources (including time, frequency, and/or spatial dimension) for a transport block. A ratio of TBS to the amount of available communication resources may provide a measure of efficiency in resource utilization. The larger the TBS for a given amount of resources, the higher the resource utilization but the less the redundancy added to protect against communication errors. Different TBS values may be selected depending on channel conditions, available resources, or other considerations.

A transport block may be mapped to one or more layers over which data of the transport block can be sent. In some cases, multiple layers can be created in spatial dimension using multiple antennas. For example, a <NUM>-by-<NUM> MIMO system may provide two spatial layers on the same time and frequency resources. A transport block may occupy the two layers (i.e., one mapped to two layers), or each of two transport blocks may separately occupy only one of the two layers (i.e., each mapped to one layer).

A baseline table <NUM> may contain one or more TBS values as entries <NUM>. The entries <NUM> may be indexed by an TBS index (e.g., I_TBS) and a PRB index (e.g., N_PRB representing the number of physical resource blocks (PRBs) for a transport block). For the same PRB index, different TBS indices may point to different TBS values. In some cases, the same TBS index may provide for approximately the same level of resource utilization as PRB index varies.

As an example of the baseline table <NUM>, the I_TBS may range from <NUM> to <NUM>, and N_PRB may range from <NUM> to <NUM>. Thus, the baseline table <NUM> has <NUM>-by-<NUM> entries <NUM>. The TBS values of the entries <NUM> may generally increase along with I_TBS or N_PRB. In some cases, the TBS values are byte-aligned, that is, being multiples of eight (<NUM> byte = <NUM> bits).

A baseline table <NUM> may be used to compute TBS for a transport block mapped to one layer. As illustrated by a look-up operation <NUM>, the TBS of the transport block is given by the corresponding entry <NUM> in the baseline table <NUM> indexed by the (I_TBS, N_PRB) pair, wherein the transport block is assigned I_TBS and has N_PRB of RBs.

The baseline table <NUM> may also be used to compute TBS for a transport block mapped to multiple (M) layers (M><NUM>). The number of available resources may generally increase proportionally along with the number of layers. For a given TBS index, the number of available resource may also generally increase proportionally along with the PRB index. In some scenarios, the baseline table <NUM> may accommodate the increased layer without the use of an additional table. Consider a transport block mapped to M layer has assigned an I_TBS and has N_PRB number of PRBs. If N_PRB multiplied by M does not exceed the maximum PRB index of the baseline table <NUM> (e.g., <NUM>), the TBS of the transport block may be given by the TBS value of the baseline table <NUM> indexed by (I_TBS, M times N_PRB).

A translation table <NUM> may be used in conjunction with the baseline table <NUM> to compute TBS when the baseline table <NUM> may not able to accommodate the M-fold increased value of N_PRB. For example, if N_PRB equals to <NUM> and M equals to <NUM>, M times N_PRB, being <NUM>, may exceed the range of PRB indices of the baseline table (e.g., <NUM> to <NUM>). In such a case, the TBS computation first uses the baseline table <NUM> to generate a baseline size (denoted by TBS_L1) as if the transport block were mapped to one layer instead of multiple layers. For example, TBS_L1 may be given by the corresponding entry <NUM> of the baseline table <NUM> indexed by the TBS index (I_TBS) and PRB index (N_PRB) of the transport block.

The translation table <NUM> then maps the baseline size (TBS_L1) from the baseline table <NUM> to a TBS value (denoted by TBS_LM) for the transport block mapped to M layers. The translation table <NUM> may contain one or more TBS values as entries <NUM>, and the entries <NUM> may be indexed by TBS_L1 values. As illustrated by a translation operation <NUM>, after TBS_L1 is computed, the TBS for the transport block may be given by the corresponding TBS_LM value indexed by the TBS_L1 in the translation table <NUM>.

The baseline table <NUM> and the translation table <NUM> together provide a TBS computation mechanism for non-shortened or legacy channels. Legacy systems and implementations may be designed and/or optimized based on these tables. For example, turbo codes interleavers may have fixed sizes corresponding to the TBS values of these tables. It may be beneficial to reuse the baseline table <NUM> and the translation table <NUM> to support TBS computation the sTTI channels.

As illustrative examples in the context of LTE systems, the baseline table <NUM> may be Table <NUM>. <NUM>-<NUM>, and the translation table <NUM> may be Table <NUM>. <NUM>-<NUM> for two layer (or Table <NUM>. <NUM>-<NUM> for three layers, or Table <NUM>. <NUM>-<NUM> for four layers), defined in the 3rd Generation Partnership Project (3GPP) Technical Specification series <NUM> (LTE Release <NUM> or onwards).

<FIG> illustrates an example of a method <NUM> of computing TBS for sTTI channels. The method <NUM> may adapt a baseline table and a translation table originally for legacy channels to sTTI channels which may have relatively fewer number of resources (e.g., symbols in time duration). A UE <NUM>, a base station <NUM>, or a component therein may perform the method <NUM> to determine TBS of a transport block mapped to one or more layers for an sTTI channel (e.g., sPDSCH or sPUSCH). The TBS computation may be implemented in a similar way at both a transmitter and a receiver to process a legacy or sTTI channel between the transmitter and the receiver.

At block <NUM>, an initial size is determined using at least a baseline table. In addition to the baseline table, the TBS computation for legacy channels may also use a translation table, e.g., such as discussed above with reference to <FIG>. The baseline table and the translation table may be examples of the baseline table <NUM> and the translation table <NUM> described with reference to <FIG>. In some examples, the baseline table alone may provide TBS values for a transport block mapped to one layer, or in some scenarios, for a transport block mapped to multiple layers. In other scenarios, the translation table may be used in conjunction with the baseline table to provide TBS values for a transport block mapped to more than one layers. The translation table may map a baseline size from the baseline table to a TBS for a transport block mapped to multiple layers. The baseline table and the translation table may contain all the valid TBS values that a transport block can use.

The initial size may be determined as if the transport block were for a corresponding non-shortened channel for the same TBS index and channel bandwidth (e.g., as measured by the number of allocated PRBs) but with longer transmission duration in time. However, the shorter transmission time interval of the sTTI channel may provide a fewer number of symbols for data transmission. For example, while a legacy PDSCH may have thirteen or more data (OFDM) symbols in a subframe, an sPDSCH may not have more than seven symbols for slot sTTI or three symbols for sub-slot sTTI.

At block <NUM>, the initial size is scaled by a factor associated with the sTTI channel. The scaling factor may be chosen based on the length of an sTTI relative to non-shorten TTI. For example, the scaling factors for downlink channels may be <NUM>/<NUM> for slot sTTI channels or <NUM>/<NUM> for sub-slot sTTI channels; the scaling factors for uplink channels may be <NUM>/<NUM> for slot sTTI channels, <NUM>/<NUM> for sub-slot sTTI channels, or <NUM>/<NUM> for sub-slot sTTI channels containing only one data symbol.

After scaling, the scaled size could be a non-integer value, and even if the scaled size is an integer value, it may not match exactly with any TBS value or entry of the baseline table or the translation table. It may be beneficial to round the scaled size to a suitable entry in the baseline table or the translation table, such that a transport block of the newer sTTI channel can reuse an existing TBS value supported by a legacy system.

In one example, a baseline table is selected if the transport block is mapped to one layer, but if the transport block is mapped to more than one (M><NUM>) layer, a translation table corresponding to M layers is selected irrespective of the value of the scaled size. However, some translation table may have a relatively large minimum TBS value among its table entries, and the scaled size may be substantially smaller than the minimum TBS value. In this case, choosing a TBS value from the translation table may be problematic. For example, the previously referred LTE Table <NUM>. <NUM>-<NUM>, Table <NUM>. <NUM>-<NUM>, Table <NUM>. <NUM>-<NUM> all have minimum value of <NUM> as a (translated) TBS value.

Consider a <NUM>-layer (M=<NUM>) sub-slot sPDSCH with <NUM> RBs (N_PRB=<NUM>) and TBS index of 26A (I_TBS=26A). For N_PRB smaller than or equal to <NUM> (assuming the PRB index of the baseline table ranges from <NUM> to <NUM>), the TBS of the <NUM>-layer for non-shortened channels is the (I_TBS=26A, 2N_PRB=<NUM>) entry of the baseline table, which may have a TBS value of <NUM>. Thus, the initial size is <NUM>. After scaling with <NUM>/<NUM> (the scaling factor associated with the sub-slot sPDSCH), the scaled size is <NUM> (i.e., <NUM>/<NUM>). A TBS value of <NUM> from the translation table may appear to be a relatively close approximation of the scaled size. (The TBS value of <NUM> may originally be a TBS_L2 entry indexed by TBS_L1 value of <NUM> in the translation table.

Now consider a <NUM>-layer (M=<NUM>) sub-slot sPDSCH with <NUM> RBs (N_PRB=<NUM>) and TBS index of <NUM> (I_TBS=<NUM>). The initial size is given by the (I_TBS=<NUM>, 2N_PRB=<NUM>×<NUM>=<NUM>) entry of the baseline table, which may have a TBS value of <NUM>. Accordingly, the scaled size is <NUM> (<NUM>/<NUM>). However, the translation table may have a minimum TBS value of <NUM>, which may be substantially larger than the scaled size (as in this case, <NUM> is more than double of <NUM>). A sub-slot sTTI with <NUM> RBs may carry at most <NUM> coded bits for data transmission. Thus, if the TBS of the transport block were chosen to be <NUM> or any other TBS value in the translation table, the resulting transmission could have a coding rate greater than one, that is, there are more bits to transmit than the channel resources can support.

At block <NUM>, a table is selected from either the baseline table, or a translation table, or a combination thereof. In some cases, considering the value of the scaled size in table selection can avoid the problem discussed above. The scaled size may be compared to a threshold. The threshold may depend on the TBS values of the translation table, for example, being the smallest TBS value of the translation table (e.g., <NUM> in the preceding examples).

In one aspect, the baseline table may be selected if the scaled size is smaller than the threshold. In such case, TBS computation may avoid using the translation table for some TBS and PRB index combinations that may produce small scaled sizes relative to the translation table. In some implementations, if the scaled size is greater than or equal to the threshold, the baseline table may be selected for a transport block mapped to one layer, or the translation table otherwise.

In another aspect, if the scaled size is greater than the threshold, the baseline table or a translation table may be selected depending on a number of layers to which the transport block of the sTTI channel is mapped. For example, if the scaled size is greater than the threshold, then the baseline table is selected if the transport block is mapped to one layer or a translation table associated with M layers is selected if the transport block is mapped to M layers (M><NUM>).

In yet another aspect, the translation table may be selected if the scaled size is greater than the threshold and if the translation table is used to determine the initial size. In some cases, the TBS values of the baseline table may have finer granularity than the TBS values of the translation table. The finer granularity in TBS values of the selected table may provide closer approximation of the scaled size. An implementation may prefer the baseline table, especially if the translation table is not used to determine the initial size, such as when the baseline table may accommodate the M-fold increase in PRB index for a transport block mapped to M layer.

According to the invention, a a combination of the baseline table and one or more translation tables is selected. In particular, a union of the baseline table and a translation table is selected based on a number of layers to which a transport block of the sTTI channel is mapped. In one example, a combined table (e.g., a union of tables) may contain some or all the TBS values of the baseline table (e.g., LTE Table <NUM>. <NUM>-<NUM>) and all the translation tables for the various multiple layers (e.g., LTE Table <NUM>. <NUM>-<NUM>, Table <NUM>. <NUM>-<NUM>, and Table <NUM>. <NUM>-<NUM> for two, three, and four layers respectively) supported by the system, regardless how many layers the transport block is mapped to. In another example (where the selection depends on how many layers to which a transport block is mapped), a combined table (e.g., a union of tables) may contain some or all the TBS values of the baseline table and a translation table for M layers when the transport block is mapped to M layers. For instance, if the transport block is mapped to three layers, the corresponding Table <NUM>. <NUM>-<NUM> may be combined with Table <NUM>. <NUM>-<NUM>. In general, a combined table may be generated from a baseline table and a particular translation table associated with the number of layers to which a transport block is mapped.

As an illustrative example in the LTE context, TBS for downlink sTTI channels may be computed based on LTE legacy TBS tables, including Table <NUM>. <NUM> (baseline table), Table <NUM>. <NUM>-<NUM> (translation table for two layers), Table <NUM>. <NUM>-<NUM> (translation table for three layers), and Table <NUM>. <NUM>-<NUM> (translation table for four layers). In this example, a scaled transport block size for sTTI channels may be quantized or rounded to entries of a combined table depending on the number of layers. A union of a baseline table (e.g., Table <NUM>. <NUM>-<NUM>) and a translation table (e.g., Table <NUM>. <NUM>-<NUM> for two layers, Table <NUM>. <NUM>-<NUM> for three layers, or Table <NUM>. <NUM>-<NUM> for four layer) constitutes the "combined table" for a respective number of layers. More specifically, for a downlink sTTI channel (e.g., scheduled by DCI format <NUM>-1A/<NUM>-1B/<NUM>-1C/<NUM>-1D/<NUM>-1E/<NUM>-1F/<NUM>-<NUM>), an initial size for a transport block (e.g., as determined using baseline table or additionally a translation table when the transport block is mapped to more than one spatial layer) is scaled by a scaling factor α (for slot-PDSCH or subslot-PDSCH), then rounded to the closest valid transport block size in:.

If the scaled TBS is closest to two valid transport block sizes, it is rounded to the larger transport block size.

Although the above example is described for downlink sTTI channels, similar designs can be applied to uplink sTTI channels, and are within the scope of the present disclosure.

The selection of TBS tables may also depend on the scaled size, and additionally or optionally on the number of layers. As an illustrative example, TBS for downlink sTTI channels may be computed based on LTE legacy TBS tables, including Table <NUM>. <NUM> (baseline table), Table <NUM>. <NUM>-<NUM> (translation table for two layers), Table <NUM>. <NUM>-<NUM> (translation table for three layers), and Table <NUM>. <NUM>-<NUM> (translation table for four layers). For a downlink control information (DCI) format associated with downlink scheduling of sTTI channels, e.g., Format <NUM>-1A/<NUM>-1B/<NUM>-1C/<NUM>-1D/<NUM>-1E/<NUM>-1F/<NUM>-<NUM>, an initial size (or a derived transport block size by legacy TBS computation) may be scaled by scaling factor α (e.g., <NUM>/<NUM> for slot-based PDSCH, or <NUM>/<NUM> for subslot-based PDSCH), then rounded to the closest valid transport block size in one of the following ( <MAT> denotes the number of downlink resource blocks):.

If two valid TBS values are the closest, the larger TBS value is selected.

As another illustrative example, TBS for uplink sTTI channels may be computed based on the LTE legacy tables. For a DCI format associated with uplink scheduling of sTTI channels, e.g., DCI format <NUM>-0A/B, an initial size (or a derived transport block size by legacy TBS computation) may be scaled by scaling factor α (e.g., <NUM>/<NUM> for slot-based PUSCH, <NUM>/<NUM> for subslot-based PUSCH with one data symbol in the subslot, or <NUM>/<NUM> for subslot-based PUSCH with two data symbols in the subslot), then rounded to the closest valid transport block size in one of the following ( <MAT> denotes the number of uplink resource blocks):.

In case two valid TBS values are the closest, the lager TBS value is selected.

At block <NUM>, the scaled size is rounded to a TBS value of the selected table. A set of TBS values of the selected table may be determined. The set may contain all or a subset of the TBS values of the selected table. In some examples, the set may be restricted to TBS values of the baseline table corresponding to a same TBS index. Such a restriction may help maintain roughly same level of resource utilization corresponding to the TBS index.

The rounding operation may be performed with respect to the determined set of TBS values. In one aspect, a TBS value from the set may be chosen that is closest to the scaled size among all TBS values from the set. The closest-value rounding may help reduce deviation between the scaled size and the TBS for the sTTI channel, thereby maintaining a proportional reduction of TBS represented by the scaling factor. In another aspect, a TBS value from the set may be chosen that is closest to the scaled size among all the TBS values that are smaller than or equal to the scaled size. The closest-smaller-value rounding may help ensure the chosen TBS value would not exceed the scaled size and hence avoid increasing coding rate due to rounding.

A tie may occur during the rounding; for example, two different TBS values may be equally close to the scaled size. An implementation may pick either one of the two TBS values as the rounded value. In some cases, the scaled size may be rounded to the larger of the two values when a tie occurs. For example, suppose a scaled size being <NUM> is equally closest to two different TBS values (<NUM> and <NUM>), that is, <NUM> is midpoint between <NUM> and <NUM>, the scaled size may be rounded up to <NUM>, the larger of the two TBS values (<NUM> and <NUM>).

<FIG> illustrates an example of an apparatus <NUM> that supports TBS computation for sTTI channels. The apparatus <NUM> may include a receiver <NUM>, a transmitter <NUM>, and a TBS computation logic <NUM>. The apparatus <NUM> may perform various aspects of the method <NUM> described with reference to <FIG>. The apparatus <NUM> may be embodied by, or resides within, a UE <NUM> or a base station <NUM>. For example, a UE <NUM> may compute TBS of a transport block for encoding sPUSCH or decoding sPDSCH. Correspondingly, a base station <NUM> may compute TBS of a transport block for decoding sPUSCH or encoding sPDSCH.

Receiver <NUM> may receive information such as packets, user data, or control information associated with various information channels. Information may be passed on to other components of the apparatus. The receiver <NUM> may utilize a single antenna or a set of multiple antennas. In some respects, receiver <NUM> may receive a transport block of an sTTI channel, such as sPDSCH by a UE <NUM> or sPUSCH by a base station <NUM>. The transport block may be mapped to one or more layers.

Transmitter <NUM> may transmit signals generated by other components of the apparatus. The transmitter <NUM> may utilize a single antenna or a set of multiple antennas. In some respects, transmitter <NUM> may transmit a transport block of an sTTI channel, such as sPUSCH by a UE <NUM> or sPDSCH by a base station <NUM>. The transport block may be mapped to one or more layers.

TBS computation logic <NUM> may be a baseband modem or an application processor or may illustrate aspects of a baseband or application processor. TBS computation logic <NUM> or at least some of its various sub-components may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions of TBS computation logic <NUM> or at least some of its various sub-components may be executed by a general-purpose processor, a DSP, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure. Software may comprise codes or instructions stored in a memory or like medium that is connected or in communication with the process described above. The codes or instructions may cause the processor, the apparatus <NUM>, or one or more components thereof to perform various functions described herein.

TBS computation logic <NUM> or at least some of its various sub-components may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical devices. In some examples, TBS computation logic <NUM> or at least some of its various sub-components may be a separate and distinct component. In other examples, TBS computation logic <NUM> or at least some of its various sub-components may be combined with one or more other hardware components, including but not limited to an I/O component, a transceiver, a server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

TBS computation logic <NUM> may include TBS tables <NUM>, legacy TTI module <NUM>, and sTTI module <NUM>. Together these components may perform TBS computation for sTTI channels, e.g., implementing the method <NUM> described with reference to <FIG>.

TBS tables <NUM> may include a baseline table and a translation table, e.g., as described with reference to <FIG>. One or more entries of TBS tables <NUM> may be stored in memory accessible by the legacy TTI module <NUM> and the sTTI module <NUM>. In some examples, table lookup operations may be implemented entirely or partially in hardware, firmware, or software.

Legacy TTI module <NUM> may be configured to compute TBS for legacy channels and to provide an initial size for an sTTI channel. The initial size may be determined through the baseline table or together with the translation table.

sTTI module <NUM> may be configured to scale the initial size by a factor associated with the sTTI channel, select either the baseline table, or a translation table, or a combination thereof, and/or round the scaled size to a TBS value of the selected table. In some examples, the sTTI module may also compute the legacy TBS to generate the baseline size using the TBS tables <NUM>.

In one aspect, sTTI module <NUM> may be configured to select a union of the baseline table and a translation table based on a number of layers to which a transport block of the sTTI channel is mapped, for example, as described with reference to <FIG>.

In another aspect, sTTI module <NUM> may be configured to compare the scaled size with a threshold and then select a table based on whether the scaled size is smaller than, or alternatively, greater than, the threshold. For example, the baseline table may be selected if the scaled size is smaller than the threshold, or the translation table is selected if the scaled size is greater than the threshold and if the translation table is used to determine the initial size.

The scaled size may be rounded with respect to all or a subset of the TBS values of the selected table. In one aspect, a set of TBS values may be determined. The scaled size may be rounded to a closest value in the set, or a closest smaller value in the set. The scaled size may be rounded to the larger of two different values that are equally closest to the scaled size.

<FIG> illustrates, as an example, a device <NUM> that supports TBS computation for sTTI channels in accordance with the present disclosure. The device <NUM> may be an example of a UE <NUM>, or a base station <NUM>, or components thereof, which may embody various aspects of the apparatus <NUM> described with reference to <FIG>. The device <NUM> may comprise TBS Computation logic <NUM>, processor <NUM>, memory <NUM>, software <NUM>, transceiver <NUM>, antenna <NUM>, and I/O controller <NUM>. These components may be coupled or in electronic communication via one or more buses (e.g., bus <NUM>).

TBS Computation logic <NUM> may perform various functions supporting TBS computation for sTTI channels. For example, the TBS Computation logic <NUM> may be configured to determine an initial size using at least a baseline table; scale the initial size by a factor associated with an sTTI channel; select a table from either the baseline table, or a translation table, or a combination thereof; and/or round the scaled size to a TBS value of the selected table. In some examples, the TBS Computation logic <NUM> may implement the TBS computation logic <NUM> described with reference to <FIG>. Generally speaking, the TBS Computation logic <NUM> may utilize processor <NUM> and memory <NUM> to execute its functionalities.

Processor <NUM> may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a central processing unit (CPU), a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, processor <NUM> may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor <NUM>. Processor <NUM> may be configured to execute computer-readable instructions (e.g., software <NUM>) stored in a memory (e.g., memory <NUM>) to perform various functions.

Memory <NUM> may include random access memory (RAM) and/or read only memory (ROM). The memory <NUM> may store computer-readable, computer-executable software <NUM> including instructions that, when executed, cause the processor <NUM> (or the device <NUM> generally) to perform various functions described herein.

Software <NUM> may include codes implementing aspects of the present disclosure, e.g., described with reference to <FIG> and <FIG>. For example, the software <NUM> may include codes for determining an initial size using at least a baseline; codes for scaling the initial size by a factor associated with the sTTI channel; codes for selecting a table from either the baseline table, or a translation table, or a combination thereof; and/or codes for rounding the scaled size to a TBS value of the selected table. Software <NUM> may be stored in a non-transitory computer-readable medium such as system memory or other memory. In some cases, the software <NUM> may not be directly executable by the processor but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

The transceiver <NUM> may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets from signals received from the antennas. In some examples, the transceiver <NUM> may include both the receiver <NUM> and the transmitter <NUM> described with reference to <FIG>.

I/O controller <NUM> may manage input and output signals for the device <NUM>. I/O controller <NUM> may also manage peripherals not integrated into the device <NUM>. In other cases, I/O controller <NUM> may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or other device. In some cases, a user may interact with the device <NUM> via I/O controller <NUM> or via hardware components controlled by I/O controller <NUM>.

<FIG> illustrates an example of a base station <NUM> in communication with a user equipment <NUM> in a networking system <NUM> that supports TBS computation for sTTI channels. The base station <NUM> or the UE <NUM> may respectively be an example of the base station <NUM> or the UE <NUM> in <FIG>.

In the downlink communication, a transmit processor <NUM> of the base station <NUM> may receive data from a data source <NUM> and control signals from a controller/processor <NUM>. The transmit processor <NUM> provides various signal processing functions for the data and control signals, as well as reference signals (e.g., pilot signals). For example, the transmit processor <NUM> may provide cyclic redundancy check (CRC) codes for error detection, coding and interleaving to facilitate forward error correction (FEC), mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM), and the like). The transmit processor <NUM> may generate transmit waveform symbols corresponding to a ratio access technology, such as spread spectrum or orthogonal frequency division modulation. Channel estimates from a channel processor <NUM> may be used by the controller/processor <NUM> to determine the coding, modulation, and/or waveform generation schemes for the transmit processor <NUM>. These channel estimates may be derived from a reference signal transmitted by the UE <NUM> or from feedback from the UE <NUM>. The symbols generated by the transmit processor <NUM> may be provided to a transmit frame processor <NUM> to create a frame structure. A frame may be further divided into a series of smaller units, such as subframes or slots. The frames are then provided to a transmitter <NUM>, which may provide various signal conditioning functions including amplifying, filtering, and modulating the frames onto a carrier for downlink transmission over the wireless medium through one or more antennas <NUM>. The antennas <NUM> may include beam steering bidirectional adaptive antenna arrays or other similar beam technologies.

At the UE <NUM>, a receiver <NUM> receives the downlink transmission through one or more antennas <NUM> and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver <NUM> is provided to a receive frame processor <NUM>, which may parse each frame and provides information from the frames to a channel processor <NUM> and the data, control, and reference signals to a receive processor <NUM>. The receive processor <NUM> then performs an inverse of the processing performed by the transmit processor <NUM> in the base station <NUM>. More specifically, the receive processor <NUM> may process and demodulate the symbols based on the modulation scheme. These soft decisions may be based on channel estimates computed by the channel processor <NUM>. The soft decisions are decoded and deinterleaved to recover the data or control signals. The CRC codes may be checked to determine whether the frames were successfully decoded. The data carried by the successfully decoded frames may be provided to a data sink <NUM>, which represents applications running in the UE <NUM> and/or various user interfaces (e.g., a display). Control signals carried by successfully decoded frames are provided to a controller/processor <NUM>. When data are unsuccessfully decoded by the receive processor <NUM>, the controller/processor <NUM> may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those data.

In the uplink, data from a data source <NUM> in the UE <NUM>, and control signals from the controller/processor <NUM> are provided to a transmit processor <NUM>. The data source <NUM> may represent applications running in the UE <NUM> and various user interfaces (e.g., keyboard). The transmit processor <NUM> provides various signal processing functions including CRC codes, coding and interleaving to facilitate FEC, mapping to signal constellations, and generating waveform symbols. Channel estimates, derived by the channel processor <NUM> from a reference signal transmitted by the base station <NUM> or from feedback by the base station <NUM>, may be used to select the appropriate coding, modulation, waveform generation schemes. The symbols produced by the transmit processor <NUM> may be provided to a transmit frame processor <NUM> to create a frame structure. The generated frames are provided to a transmitter <NUM>, which provides various signal conditioning functions including amplification, filtering, and modulating the frames onto a carrier for uplink transmission over the wireless medium through the antennas <NUM>.

At the base station <NUM>, a receiver <NUM> receives the uplink transmission through the antennas <NUM> and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver <NUM> is provided to a receive frame processor <NUM>, which parses each frame, and provides information from the frames to the channel processor <NUM> and the data, control, and reference signals to a receive processor <NUM>. The receive processor <NUM> performs an inverse of the processing performed by the transmit processor <NUM> in the UE <NUM>. The data and control signals carried by the successfully decoded frames may be provided to a data sink <NUM> and the controller/processor <NUM>, respectively. If some of the data were successfully or unsuccessfully decoded by the receive processor, the controller/processor <NUM> may use an acknowledgement (ACK) or negative acknowledgement (NACK) protocol to support transmission or retransmission requests for those data.

The controller/processors <NUM> and <NUM> may be used to direct operations at the base station <NUM> and the UE <NUM>, respectively. For example, the controller/processors <NUM> and <NUM> may provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. The computer readable media of memories <NUM> and <NUM> may store data and software for the base station <NUM> and the UE <NUM>, respectively. A scheduler/processor <NUM> at the base station <NUM> may be used to allocate resources to UEs and schedule downlink and uplink transmissions for the UEs.

The controller/processors <NUM> or <NUM> may compute TBS for a transport block of shorten TTI channels, e.g., as described in the method <NUM>. It may provide configuration information for an individual transmit or receiver processor (e.g., the transmit processor <NUM>, the receive processor <NUM>) to compute the TBS. The computed TBS may be used to determine the payload size and may affect various processing (e.g., coding or decoding) in the transmit or receiver processor.

As used herein, the phrase "based on" shall not be construed as a reference to a closed set of conditions.

As used herein, the conjunction "or" shall generally be interpreted as "inclusive" unless the context indicates otherwise. For example, "A or B" would generally mean "either A, or B, or both" (but not necessarily "either A, or B, but not both"); in other words, the presented alternatives ("A" and "B") need not necessarily be mutually exclusive. Certain context, however, can indicate an "exclusive or," as in "whether A or not," for example.

Also, as used herein, including in the claims, "or" as used in a list of items (for example, a list of items prefaced by a phrase such as "at least one of" or "one or more of') indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A processor may also be implemented as a combination of computing devices (e.g., a combination of a digital signal processor and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

By way of example, and not limitation, non-transitory computer-readable media can include random access memory (RAM), read-only memory (ROM), electrically erasable programmable read only memory (EEPROM), compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, digital subscriber line, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium.

Claim 1:
A method of computing transport block size, TBS, for a shortened transmission time interval, sTTI, channel for wireless communication, wherein the sTTI channel has a fewer number of symbols in time duration than a legacy channel, the method comprising:
determining (<NUM>) an initial transport block size, TBS, value using at least a baseline table;
scaling (<NUM>) the initial TBS value by a factor associated with the sTTI channel;
selecting (<NUM>) a union of the baseline table and a translation table based on a number of spatial layers to which a transport block of the sTTI channel is mapped, wherein the union is a combined table that contains at least some TBS values of the baseline table and at least some TBS values of the translation table; and
rounding (<NUM>) the scaled TBS value to a TBS value of the selected union of the baseline table and the translation table.