JP2018038063A - Control of modulation and coding scheme for transmission between base station and user equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling a modulation and coding scheme for transmission between a base station (101) and user equipment (102).SOLUTION: The modulation and coding scheme can be selected on the basis of a first modulation and coding scheme table including entries corresponding to a plurality of modulation and coding schemes having a first maximum modulation degree, or can be selected on the basis of a second modulation and coding scheme table including entries corresponding to a plurality of modulation and coding schemes having a second maximum modulation degree. The degree selects, with a base station (101), the first modulation and coding scheme table or the second modulation and coding scheme table, and controls, with the base station (101), a modulation and coding scheme for transmission between the base station (101) and user equipment (102) on the basis of the selected modulation and coding scheme table.SELECTED DRAWING: Figure 1

Description

  The present invention relates to the field of cellular networks, and more particularly to the evolution of LTE networks, and more particularly to networks including LTE networks and evolved LTE networks.

  Further development has been done on LTE, for example on the Beyond 4G (B4G) radio system, which is assumed to be commercially available in 2020. However, LTE evolution may be introduced on any day within a new release.

  LTE exhibits a peak bit rate of 30 bps / Hz by using 64QAM modulation and 8 × 8 MIMO transmission. As a result, B4G requires higher order modulation than 64QAM, eg 256QAM, to meet future requirements. Higher order modulation is suitable for relay backhaul, for example, because of superior channel quality and superior radio frequency (RF) characteristics, which are more relayable than user equipment (UE) or separate indoor cells In which case the UE is close to the access point and thus has a good link to the access point, and interference from other access points is due to wall attenuation. For little or no.

  The determination of the modulation order of LTE release 10 is described in TS 36.213 V10.3, chapter 7.1.7 and CQI definition, chapter 7.2.3. In LTE (and LTE-Advanced), the theoretical spectral efficiency is limited by 64QAM modulation. An extension to 256QAM results in improved spectral efficiency.

  In the LTE standard, a modulation and coding scheme (MCS) index and modulation table and a channel quality indicator (CQI) table are defined. They are used to determine and select an appropriate modulation and coding scheme. Currently the table supports up to 64QAM. The problem is how to introduce 256QAM extensions, or other higher order modulation extensions for LTE, while maintaining upward compatibility and avoiding significant complexity.

  What is needed is an improved and flexible system and method that is adapted to allow extensions to higher order modulation while maintaining upward compatibility for LTE. In particular, it is desired to maintain the signaling format and more particularly to use the same number of bits as it is necessary to use a different encoding scheme and potentially apply so-called blind decoding.

  Said need is met by the subject matter according to the independent claims. Advantageous embodiments of the invention are described in the dependent claims.

  According to a first aspect of the invention, a method for controlling a modulation and coding scheme for transmission between a base station and a user equipment, the modulation and coding scheme comprising a first maximum modulation order. Selectable based on a first modulation and coding scheme table that includes entries corresponding to multiple modulation and coding schemes, or support multiple modulation and coding schemes having a second maximum modulation order A method is provided that is selectable based on a second modulation and coding scheme table that includes entries to be made. The method selects a first modulation and coding scheme table or a second modulation and coding scheme table by a base station and selects a modulation and coding scheme for transmission between the base station and the user equipment. Control by the base station based on the selected modulation and coding scheme table.

  This aspect of the invention is based on the idea of extending the modulation and coding scheme table to higher order modulations while maintaining upward compatibility. The first table supports, for example, up to 64QAM (Quadrature Amplitude Modulation), and the second table supports, for example, up to 256QAM, or other higher order modulation extensions. Here, 256QAM is explicitly stated, but other modulations higher in order than those used in the first table, for example, 128QAM can also be used, or generally by modulation order and / or coding scheme. Note that the higher order modulation and coding schemes (MCS) that are characterized can also be used.

  The idea of this method is to introduce higher order modulation while still supporting the modulation and coding scheme (MCS) table introduced for lower modulation orders.

  In this document, the term “modulation order” is determined by the number of different symbols that can be transmitted using it. In general, MCS also considers different code rates and thus indicates the average number of payload bits that can be transmitted per symbol. The first maximum modulation order and the second maximum modulation order may be the same or different.

  The term “modulation and coding scheme table” refers to an MCS table defined in LTE and is used to determine and select an appropriate modulation and coding scheme. The second table is an extended MCS table based on MCS defined in LTE, but includes entries corresponding to higher-order modulation. For example, upward compatibility is ensured by making the first table as strict as currently defined in the LTE standard.

  The first and second tables may differ in some aspects. For example, one table may be biased toward a lower MCS and the second table may be biased toward a higher MCS value. For example, a table may have more MCS values than a certain threshold MCS. Also, the density of MCS values at low MCS may be high in one table, or the center of gravity or average of MCS values may be low in one table. In one embodiment, one table is a mirror image of the other, eg, mirrored at the central MCS.

  As used herein, the term “base station” refers to any type of physical entity that can communicate with a user equipment or other network equipment by selecting a modulation and coding scheme from such an MCS table. The base station in this document may be any type of network device that provides the required functionality for the method, or it may be a transceiver node that communicates with the central entity. The base station is, for example, a NodeB or an eNB.

  The base station explicitly notifies the UE about changes to the MCS table to use, or informs the UE as part of the capability inquiry procedure and implicitly selects the MCS table.

  According to an embodiment of the present invention, the second maximum modulation order is higher than the first maximum modulation order. In particular, the first maximum modulation order corresponds to 64QAM and the second maximum modulation order corresponds to 256QAM.

  Note that other modulation orders may be used, for example 128QAM.

  In addition, the first table contains a few high MCS so that it can react quickly if the channel suddenly becomes better.

  According to yet another embodiment of the invention, the maximum modulation order corresponds to the highest modulation and coding scheme (MCS). Furthermore, its highest modulation and coding scheme is the same for both tables.

  According to yet another embodiment of the invention, the method further comprises determining, by the base station, the actual channel state of the radio transmission channel used for transmission between the base station and the user equipment. Determining the maximum supported modulation order by the base station based on the actual channel condition and comparing the maximum supported modulation order with the first maximum modulation order and the second maximum modulation order Selecting a first modulation and coding scheme table or a second modulation and coding scheme table based on the base station.

  If the actual channel condition does not support higher order modulation or the user equipment (UE) cannot support higher order modulation, the base station may modulate and code for transmission based on the first table. Carry out. If the actual channel conditions are good enough for higher order modulation and the UE supports higher order modulation, the base station may, for example, a second table that supports higher order modulation up to 256QAM. Perform modulation and coding based on the above.

  According to yet another embodiment of the invention, the method further includes transmitting information representative of the selected modulation and coding scheme table to the user equipment.

  The base station gives the UE a signal containing information about the MCS table that is selected and used. The UE then performs further actions such as CQI reports based on that information.

  According to yet another embodiment of the invention, the transmission of information to the user equipment is based on radio resource control signaling.

  By using a common signal link, the UE is easily informed about the selected MCS table. This information is also included in any information signal consisting of UE information in view of other resource controls.

  According to yet another embodiment of the invention, the transmission of information to the user equipment is based on implicit signaling.

  This refers to the case where the UE receives information from the base station and determines the selected MCS table based on that information. This is the case, for example, as part of a capability inquiry procedure that also makes the capability available to the eNB. During this type of setup procedure in which the eNB determines the UE capabilities, the table is switched and the UE is implicitly notified without specific signaling.

  According to yet another embodiment of the present invention, the method includes receiving confirmation information from a user equipment that represents a change made to a selected modulation and coding scheme table.

  The base station performs a change from one table to the selected MCS table after receiving the confirmation signal from the UE. Thus, the confirmation signal represents the final change in the MCS table performed by the base station.

  According to yet another embodiment of the invention, the first modulation and coding scheme table and the second modulation and coding scheme table are respectively the first modulation and coding scheme table and the second modulation and coding scheme table. Contains a common subset of equal entries located at the same location in the encoding scheme table. In particular, the method includes selecting the selected modulation and coding scheme table after transmitting information representing the selected modulation and coding scheme table to the user equipment and before receiving confirmation information from the user equipment. And controlling a modulation and coding scheme for transmission between the base station and the user equipment based on the common subset of entries.

  By using a common entry in both MCS tables, the base station uses a common entry unless there is a confirmation signal from the UE. This has the effect that both parts (base station and UE) use the same modulation and coding scheme (possibly using different tables), so there is no misunderstanding or wrong modulation and coding.

  According to yet another embodiment of the invention, controlling the initial transmission between the base station and the user equipment is based on a first modulation and coding scheme table.

  The base station and UE use an MCS table with a low maximum modulation order at the beginning of each communication. This has the effect that each communication starts with the same table and then the base station determines whether to change the MCS table. Then, if the UE can support an MCS table that supports higher order modulation, the change is made based on actual channel conditions.

  According to yet another embodiment of the invention, the bits carrying the modulation and coding scheme index are the same for the first modulation and coding scheme table and the second modulation and coding scheme table.

  Thus, there is no need to change the existing form of the MCS table nor to change the encoding and transmission mechanism used to carry selections from that table, ensuring upward compatibility. In a more specific embodiment, the tables have the same size. In particular, a portion of the first MCS table and the second MCS table are equal, giving the common entry described above. Entries in the first MCS table associated with a very low modulation order are exchanged (redefined) for the second MCS table and include higher order modulations.

  According to yet another embodiment of the present invention, the actual channel condition is based on a first channel quality indicator table that supports a first maximum modulation order or a second that supports a second maximum modulation order. Based on a selectable channel quality indicator based on a channel quality indicator table, wherein the method receives a channel quality indicator from a user equipment by a base station and includes in the received channel quality indicator Based on the base station determining the actual channel state of the radio transmission channel used for transmission between the base station and the user equipment.

  Similar to the MCS table, the CQI table is also selected based on the selection of the MCS table. When there is a change or change from the first MCS table to the second MCS table, there is also a change from the first CQI table to the second CQI table. Therefore, the UE determines the CQI based on a table corresponding to the selected MCS table.

  According to yet another embodiment of the present invention, the method selects by a base station a first channel quality indicator table or a second channel quality indicator table based on a selected modulation and coding scheme table. And transmitting information representative of the selected channel quality indicator table to the user equipment.

  Information of the selected CQI table is provided from the base station to the UE. The information may also be given implicitly by notifying the user device of the selected MCS table.

  According to still another embodiment of the present invention, the first channel quality indicator table and the second channel quality indicator table are respectively a first channel quality indicator table and a second channel quality indicator table. Contains a common subset of equal entries located at the same location in

  Similar to the MCS table, the CQI table also includes a common subset. It is thus ensured that there is no misunderstanding between the UE and the base station during the switching.

  According to a second aspect of the invention, a base station for controlling a modulation and coding scheme for transmissions between a base station and a user equipment, the modulation and coding scheme comprising a first maximum A plurality of modulations and codings that are selectable based on a first modulation and coding scheme table that includes entries corresponding to a plurality of modulation and coding schemes having a modulation order or that have a second maximum modulation order A base station is provided that is selectable based on a second modulation and coding scheme table that includes entries corresponding to the scheme. The base station includes a selection unit for selecting a first modulation and coding scheme table or a second modulation and coding scheme table, and a modulation and coding scheme for transmission between the base station and the user equipment. A control unit for controlling based on the selected modulation and coding scheme table.

  A base station is any type of access point or attachment point that can provide wireless access to a cellular network system. Thus, wireless access is to user devices or other network devices that can communicate wirelessly. The base station is a NodeB, eNB, home NodeB or HeNB, or other type of access point or multihop node or relay. Base stations are used in particular for B4G, LTE or 3GPP cells and communications.

  The base station includes a receiving unit, for example a receiver known to those skilled in the art. The base station also includes a transmission unit or a transmission unit, for example a transmitter. The receiver and transmitter may be implemented as a single unit, eg, a transceiver. The transceiver or the receiving unit / transmitting unit is adapted to communicate with the user equipment via an antenna.

  The base station further includes a selection unit and a control unit. The selection unit and the control unit may be implemented as a single unit, or may be implemented as part of a standard control unit such as, for example, a CPU or microcontroller.

  In one embodiment, the base station further determines the actual channel condition of the radio transmission channel used for transmission between the base station and the user equipment and based on the determined actual channel condition. A determination unit is also provided for determining the maximum supported modulation order. The selection unit may select the first modulation and coding scheme table or the second modulation and coding scheme table based on a comparison of the maximum supported modulation order with the first maximum modulation order and the second maximum modulation order. Select.

  The decision unit may be implemented as a single unit or as part of a standard control unit such as a CPU or microcontroller.

  A user equipment (UE) is any type of communication end device that can be connected to the base station described herein. The UE is in particular a cellular mobile phone, a personal digital assistant (PDA), a notebook computer, a printer, and / or any other mobile communication device.

  The user equipment includes a receiving unit or a receiver for receiving a signal from the base station. The user apparatus includes a transmission unit for transmitting a signal. The transmission unit is a transmitter known to those skilled in the art. The receiver and the transmission unit may be implemented as a single unit, eg, a transceiver. The transceiver, or receiver and transmission unit are adapted to communicate with the base station via the antenna.

  The user equipment further comprises a control unit for controlling and configuring transmission based on information received from the base station representing the selected MCS table. This control unit may be implemented as a single unit or may be implemented as part of a standard control unit such as a CPU or microcontroller.

  According to a third aspect of the present invention, a cellular network system is provided. The cellular network system includes the base station described above.

  Here, in general, methods and method embodiments in accordance with the first aspect include performing one or more functions described with respect to the second or third aspect or embodiments thereof. Vice versa, a base station or cellular network system according to the second and third aspects and embodiments thereof is a unit or unit for performing one or more functions described with respect to the first aspect or embodiments thereof. Including equipment.

  According to a fourth aspect of the presently disclosed subject matter, a computer program is provided for controlling a modulation and coding scheme for transmission between a base station and a user equipment, the computer program being provided by a data processor assembly. When executed, it is for controlling the method described in the first aspect or embodiment thereof.

  As used herein, the term computer program is equivalent to the term program element and / or computer readable medium that contains instructions for controlling a computer system to coordinate the execution of the methods described above.

  The computer program is implemented as computer readable instruction code using, for example, a suitable programming language such as JAVA®, C ++, and computer readable media (removable disc, volatile or non-volatile) Memory, embedded memory / processor, etc.). The instruction code serves to program a computer or other programmable device to perform the intended function. Computer programs are available from networks such as the World Wide Web where they are downloaded.

  The gist disclosed herein can be realized by software for each computer program. However, the subject matter disclosed herein may be implemented by hardware in each of one or more specific electronic circuits. Further, the subject matter disclosed herein may be realized in a hybrid form, that is, a combination of software modules and hardware modules.

  Although exemplary embodiments of the subject matter disclosed herein have been described above, hereinafter, a cellular network system, a base station, and a method for controlling a modulation and coding scheme for transmission between a base station and a user equipment Will be described in detail. Of course, it should be pointed out that combinations of features relating to different aspects of the present disclosure are also conceivable. In particular, certain embodiments will be described with reference to device type embodiments, while other embodiments will be described with reference to method type embodiments. However, those skilled in the art will understand from the foregoing and following description, unless otherwise indicated, in addition to combinations of features belonging to one aspect, combinations between features relating to different aspects or embodiments, for example, implementation of apparatus types Combinations of form features and method form embodiment features are considered to be disclosed with this application.

  The aspects and embodiments described above and further aspects and embodiments of the present invention will be apparent from the examples described below and will be described with reference to the drawings. However, the present invention is not limited thereto. Note that in different drawings, the same or similar elements are denoted by the same reference characters.

1 illustrates a cellular network system according to an exemplary embodiment of the present invention. 2 shows spectral efficiency simulations for 64QAM and 256QAM. 4x4 MIMO and 2x2 MIMO spectral efficiency simulations for 64QAM and 256QAM, respectively. 2 illustrates a base station and user equipment in a cellular network system according to an exemplary embodiment of the present invention.

  In the following, embodiments of the subject matter disclosed herein will be described with reference to the accompanying drawings and with reference to aspects of current standards such as LTE and their further developments. However, referring to the current standard is merely illustrative and does not limit the scope of the claims.

  FIG. 1 shows a cellular network system 100. The user equipment 102 receives the service of the first cell 103 of the cellular network system. The first cell is designated as the base station 101.

  Transmissions and communications between the base station and the user equipment are controlled based on the modulation and coding scheme. The modulation and coding scheme can be selected based on a first modulation and coding scheme table including entries corresponding to a plurality of modulation and coding schemes having a first maximum modulation order, or second Based on a second modulation and coding scheme table including entries corresponding to a plurality of modulation and coding schemes with a maximum modulation order of. In one embodiment, the second maximum modulation order is higher (eg, up to 256 QAM) than the first maximum modulation order (eg, up to 64 QAM).

  The base station determines the actual channel state of the radio transmission channel used for transmission between the base station and the user equipment. The base station can then determine the maximum supported modulation based on the determined actual channel conditions and ultimately based on information from the user equipment which modulation order can be supported by the user equipment. Determine the order. The base station may then determine the first modulation and coding scheme table or the second modulation based on a comparison of the maximum supported modulation order with the first maximum modulation order and the second maximum modulation order. And a coding scheme table. Accordingly, the modulation and coding scheme (MCS) for transmission between the base station and the user equipment is controlled based on the selected modulation and coding scheme table.

  The base station may also select the table based on other information, for example, predetermined selection criteria.

  In LTE (and LTE-Advanced), the theoretical spectral efficiency is limited by 64QAM modulation. FIG. 2 shows LTE-advanced throughput (reference number 201) (code rate 8/9) simulated with 8 × 8 MIMO and modulation limited to 64QAM in a 1-tap Rayleigh channel without spatial correlation. FIG. 2 also plots the spectral efficiency obtained by extension to 256QAM (reference number 202) for comparison. It is clear that the extension to 256QAM begins to work in the SNR range of approximately 25 dB. In this figure, the average SINR is plotted against throughput. Even if the average is lower than that region, the channel conditions remain good for some time, regardless of whether 256QAM gives gain due to fading.

  LTE throughput is limited by MCS even in more practical scenarios (eg, relay backhaul cases) where high spatial channel correlations that limit the use of large ranks occur. This is illustrated in FIG. 3, where the spectral efficiency for 2 × 2 and 4 × 4 MIMO schemes with adaptive rank and MCS selection in high spectral correlation scenarios is plotted as a function of average signal-to-noise ratio. . In both the 2 × 2 and 4 × 4 schemes, two curves are shown, while the MCS is limited to 64QAM (2 × 2: 304, 4 × 4: 302) and on the other side the MCS is It is expanded to 256QAM (2 × 2: 303, 4 × 4: 301). It is clear that the extension to 256QAM already increases the throughput from an approximately 10 dB SNR range in these scenarios. This means that we are already concerned that the throughput is much lower than the maximum throughput possible with 64QAM.

  The problem is how to introduce 256QAM for LTE to maintain upward compatibility and avoid significant complexity. The addition of 256QAM needs to be performed for both the MCS index and modulation table defined in the LTE standard and the CQI table.

  In Release 10, a new DCI format 2c was added to support closed-loop MIMO up to 8 layers. One simple solution is to define a new DCI format for 256QAM (and use more than 6 bits for DCI modulation and coding scheme fields). This is not a desirable solution. This is because it doubles the number of DCI formats and significantly increases complexity. UMTS also extends from 16QAM to 64QAM by adding one special signaling bit [R1-070635 R1-070570]. The special bits can be provided by defining a new DCI format at the expense of poor decoding performance and more blind decoding, or at least defining any more DCI size. Alternatively, limit the possibility of bits being stolen from a code assignment table that only supports half of the entries when 64 QAM is enabled when the bits are “stolen” from some other signaling, for example in HSDPA.

  Another possible solution is to take the existing MCS / CQI index table as a basis and switch its use to use only a subset of the current MCS values, eg drop every third, additional 256QAM Make room for the value. This is undesirable as it roughly adapts the channel conditions. Hereinafter, this method is referred to as sub-sampling.

The idea of the method described here is to define a new procedure that allows the use of 256QAM in good channel conditions using the existing DCI format. For this purpose, additional new MCS and CQI index tables with extensions to 256QAM (Q _m = 8) are created. This new table is the same size as the normal one. The determination of whether the original index table or a table with an extension of 256QAM is used is determined by the base station (or eNB) and the switch is indicated to the UE in a signaling message, Or it is judged in an implicit manner.

  In one embodiment, there is a common index area common to both the original table and the table with 256QAM extension, where the MCS / CQI index, modulation order and TBS index are the same and the same location in both tables. It is in. Only this common MCS index area is used during table switching to avoid ambiguity.

  In one embodiment, the MCS / CQI index table with 256QAM extension is formed so that room for TB (Transport Block) size associated with 256QAM is taken from the originally low TB size. In addition, there is some common modulation / TB size in the common MCS index area from the low range modulation set for situations where an extended 256QAM table is used and the channel conditions drop rapidly. These indexes can be sub-sampled from the low TBS area.

  In order to ensure that the UE knows the switch and does not use ambiguous table entries during the switch, a two-step switch procedure is provided for the CQI index table switch. The MCS table is switched in advance to the 256QAM version.

  Also, for example, a high range set for situations where 256QAM must be used quickly before a clear choice is made during initial call setup or to allow a quick response towards good quality. There is also some common modulation / TB size in the common MCS index area from the previous modulation.

The second table described here for the MCS and CQI index tables is generated corresponding to the 36.213 table 7.1.7-1, but with an extension to 256QAM (Q _m = 8). One option is that the original table 7.1.7-1 and the table with the 256QAM extension are switched by the eNB with an RRC message (or MAC or control signaling messages can also be considered). In this case, the algorithm responsible for this switching is eNB vendor specific, but obviously considers the CQI report from the UE. The UE is responsible for switching the MCS index table based on the RRC message and sending confirmation to the eNB regarding the received RRC message (confirmation is not important, but UEs that do not support switching will not confirm the command, so To help avoid upward compatibility issues).

  It takes about 100-200ms for RRC messages to be valid at the UE (upper layer processing delay is not standardized, depending on how often they are retransmitted in case of detection errors) Both tables, which allow data scheduling during the uncertainty time, because (1) the RRC message is lost and (2) there is an uncertainty related to the start time when the new configuration is used by the UE There must be a common MCS index area. This ensures that the MCS from that area is correctly understood regardless of whether the switch has already taken place. This common area is continuous, i.e. it has continuous MCS entries, allowing fine adaptation during switching. The MCS index, modulation order and TBS index are the same in both MCS index tables of this area. For example, during the RRC procedure for switching tables, only this common MCS index area can be used before the eNB receives confirmation from the UE that an RRC message for switching the MCS index table has been received. This common index area is also used when implicit table switching is used, in which case only the common area can be used during the implicit switching procedure.

  In addition, there is some common low modulation / TB size in the common MCS index area for situations where an extended 256QAM table is used and channel conditions drop rapidly. The TB size required to send the switch command is obtained in the common MCS index area.

A new TB size is introduced in the MCS / CQI index table with 256QAM extension to increase spectral efficiency at 256QAM.
• The room for these new TB sizes can be taken from the current low TB sizes (QPSK and possibly low 16QAM).
• The reserved TBS size for QAM is also in the low modulation common MCS area. This MCS is used for retransmissions in bad channel conditions, especially if the previous initial transmission was done with a high MCS, especially with a high modulation order or a different number of designated resources. However, it is not necessary to reserve an entry for the included 256QAM.
Also, in situations such as call setup where it is useful to use 256QAM quickly, there are several 256QAM entries in a common area (because it loses upward compatibility and has less input available in the “normal” range). At the expense). Such a default “compromise” MCS table, where sub-sampling is used to obtain a high dynamic range, can be used as soon as the eNB is aware of the UE capabilities. Switching from a legacy table, i.e., having a low maximum modulation order, to its compromise table, i.e., having a high maximum modulation order, should be done implicitly as part of the capability inquiry procedure to make the capability available to the eNB. Can do. A clear switch to a table focused on low or high MCS is then made, but if the channel conditions change rapidly and a clear switch cannot be achieved, a clear switch to the sub-sampled table is made. Switching is also performed.

  An example of a modulation table with MCS index and 256QAM extension is shown in Table 1. The MCS indexes 12 to 31 indicate continuous common MCS index areas. MCS indexes 0, 5 and 10 refer to the sub-sampled low modulation common MCS index area, and MCS indexes 1 to 4, 6 to 9 and 1 refer to 256QAM extensions.

  Similar to the MCS index table, a new CQI index table with 256QAM extension and common index area is used. The CQI table is switched with the same RRC message that plays the role of switching the MCS index table. In another case, the CQI table is switched implicitly. The eNB serves to handle possible error situations caused by not knowing which table the UE uses at the exact time during this RRC procedure. The eNB may, for example, simply ignore non-common CQI indexes, round them to the nearest common index or take a risk, and determine which table is most likely associated with heuristics can do. Such an error case occurs when the eNB initiates a change and therefore, in contrast to MCS selection, which can avoid ambiguous entries during switching, in CQI, the UE is unaware of the imminent switching and therefore Because it cannot be avoided (unless it is always avoided unnecessarily). In order to increase the likelihood that the eNB will choose the right decision in the case of ambiguous table entries, the minimum difference in TBS relative to the MCS index must be maximized. This is the case for Table 1. This is because entries are arranged to increase the TBS for both 256 and QAM cases. If the case of 256QAM is in reverse order, for MCS index 9, the TBS is 26 (for 256QAM) or 8 (for QPSK), ie the difference is 26−8 = 18, On the other hand, in Table 1, the difference is 33−8 = 25. The greater this difference, the less likely the eNB will not be able to use heuristics (eg, if the channel is actually changed by that amount in 25 steps). For the same reason, it is beneficial to place the reserved 256QAM entry at the highest MCS index, ie, against the MCS index 11 of Table 1. That reserved entry is only involved for the downlink, not the uplink. Therefore, in the uplink table, it can be easily dropped and replaced with a normal entry in the QAM (TBS 10 in Table 1).

  In order to avoid ambiguous CQI reports during the switching time, a two-step switching procedure can be used, and in the first command, the eNB notifies the switching. Then, only CQI reports from the common MCS area are used for the UE. In the second command, the eNB commands execution of switching. The UE then fully uses the high MCS table. Here, despite the fact that there are two ambiguous cycles, there is no risk of misunderstanding. That is, during both ambiguous periods, the UE uses a well-defined MCS table (the original one in the first ambiguous period and the final one in the second period) Alternatively, only MCS from a common MCS area is used, and there is no possibility of misunderstanding in this common area. This is because entries from a common MCS area are encoded identically in both tables. This makes the order of entries in the high MCS area discontinuous, but this is not very complicated and can be solved, for example, by implementing a lookup table.

The message flow according to this embodiment is as follows.
1) RRC message for switching eNB to UE: MCS table and restricting CQI report to common index area. The eNB uses only a common index area for the MCS.
2) UE to eNB: confirmation (and implicit message), eNB now uses the complete index area of the new MCS table, eNB uses the new CQI table (initially only the common index area) ) Know to use.
3) eNB to UE: confirm, the UE now uses the complete index area of the new CQI table.

  Although there are actually two handshakes, there are only two without using four messages. This is because the intermediate message has two meanings in both the CQI and MCS tables.

  Another solution to avoid ambiguous CQI reports is to allow the UE to initiate a table switch for CQI and the eNB to initiate a switch for MCS. Thus, at any given time, the originator of the message can switch to the corresponding table and thus limit its use to a common index area during an ambiguous period.

  To indicate the UE's ability to support 256QAM, a new UE category that includes 256QAM is required. If the UE does not support 256QAM, the process and the MCS / CQI index table with 256QAM extension are not used. Alternatively, the eNB may send a switch command and determine the response regardless of whether the UE supports 256QAM. In the initial access phase, the eNB is not yet aware of the UE's capabilities, so 256QAM, and hence a higher modulation order MCS table should not be used.

  The process described above can be used to extend to higher MCS. This process can also be extended to cover more than two tables and switch between them. A common MCS represented in more than one table must always be in the same position. There is a difference in the size and form of the common index area between tables, for example, different tables can have different levels of sub-sampling. For example, there are three tables: low, medium and high. The intermediate table can contain every other MCS entry in the low modulation area, while the high table uses only every third entry (similar to table 1) and those entries are Also selected from those that exist. This is possible because 2 is a divisor of 4, so high table sub-sampling should not select every second or every fourth entry that does not fit. It may also be used for table 1 that covers a wide range of CQI values.

  The proposed solution has a number of advantages. Existing DCI format designs are unchanged. This allows 256QAM support for each DL DCI format while maintaining the existing DCI blind decoding burden at the UE. The proposed scheme provides a means for the eNB to easily avoid complex error cases due to signaling errors. The proposed design makes it possible to keep the basic functions of the existing DL resource allocation (CQI / MCS index table) unchanged. Therefore, the impact on DL scheduler operation is only minimal.

  FIG. 4 shows a cellular network system 400 according to an exemplary embodiment of the present invention. The cellular network system includes a base station 101 and a user device 102 that receives services of the base station.

  Hereinafter, the base station will be described together with the determination unit. However, it should be noted that the decision unit is optional.

  The base station determines the actual channel condition of the radio transmission channel used for transmission between the base station 101 and the user equipment 102 and determines the maximum supported modulation based on the determined actual channel condition. A determination unit 402 for determining the order is provided. The base station may further include the first modulation and code based on a predetermined criterion or based on a comparison of the maximum supported modulation order with the first maximum modulation order and the second maximum modulation order. A selection unit 403 for selecting a coding scheme table or a second modulation and coding scheme table. In addition, the base station comprises a control unit 404 for controlling the modulation and coding scheme for transmission between the base station and the user equipment based on the selected modulation and coding scheme table.

  A base station is any type of access point or attachment point that can provide wireless access to a cellular network system. Thus, wireless access is to user devices or other network devices that can communicate wirelessly. The base station is a NodeB, eNB, home NodeB or HeNB, or other type of access point.

  The base station includes a receiving unit, for example a receiver known to those skilled in the art. The base station also includes a transmission unit or a transmission unit, for example a transmitter. The receiver and transmitter may be implemented as a single unit, eg, transceiver 401. The transceiver or the receiving unit / transmitting unit is adapted to communicate with the user equipment via an antenna.

  The decision unit 402, the selection unit 403 and the control unit 404 may be implemented as a single unit or may be implemented as part of a standard control unit such as a CPU or microcontroller, for example.

  A user equipment (UE) is any type of communication end device that can be connected to the base station described herein. The UE is in particular a cellular mobile phone, a personal digital assistant (PDA), a notebook computer, a printer, and / or any other mobile communication device.

  The user equipment includes a receiving unit or a receiver for receiving a signal from the base station. The user apparatus includes a transmission unit for transmitting a signal. The transmission unit is a transmitter known to those skilled in the art. The receiver and transmission unit may be implemented as a single unit, eg, transceiver 405. The transceiver, or receiver and transmission unit are adapted to communicate with the base station via the antenna.

  The user equipment further comprises a control unit 406 for controlling and configuring the transmission based on information received from the base station representing the selected MCS table. This control unit may be implemented as a single unit or may be implemented as part of a standard control unit such as a CPU or microcontroller.

  With respect to the subject matter disclosed herein, some embodiments refer to “base stations”, “eNBs”, etc., each of which is referred to by the general term “network component” or in other embodiments the term “network access node”. Is understood to be implicitly disclosed. Also, other terms relating to specific standards or specific communication technologies are also considered to implicitly disclose each general term with the desired functionality.

  Furthermore, it should be noted that the base stations disclosed herein are not limited to the dedicated entities described in some embodiments. Rather, the subject matter described herein can be implemented in various ways at various locations in a communication network while performing desirable functions.

  In accordance with an embodiment of the present invention, the appropriate entities disclosed herein (eg, components, units and devices), eg, the decision unit, each enables the processor device to perform the functions of each entity disclosed herein. It may be provided at least in part in the form of a computer program. According to other embodiments, the appropriate entities disclosed herein may be provided in hardware. According to other hybrid embodiments, certain entities are provided in software, while other entities are provided in hardware.

  It should be noted that the entities (eg, components, units, and devices) disclosed herein are not limited to the dedicated entities described in some embodiments. Rather, the subject matter disclosed herein can be implemented in a variety of ways and with a variety of granularities at the device level, while performing the desired functions. Further, it should be noted that according to embodiments, separate entities (eg, software modules, hardware modules, or hybrid modules) may be provided for each function disclosed herein. According to other embodiments, an entity (eg, a software module, a hardware module, or a hybrid module (software / hardware combined module)) is configured to provide more than one function disclosed herein.

  Note that the word “comprising” does not exclude other elements or steps. It is also possible to combine features from the different embodiments described above in a further refinement of the invention. It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.

DESCRIPTION OF SYMBOLS 100: Cellular network system 101: Base station 102: User apparatus 103: Cell 201: 8 * 8 MIMO of 64QAM
202: 256QAM 8 × 8 MIMO
301: 256QAM 4 × 4 MIMO
302: 4 × 4 MIMO with 64QAM
303: 256QAM 2 × 2 MIMO
304: 64QAM 2 × 2 MIMO
400: Cellular network system 401: Base station transceiver 402: Base station determination unit 403: Base station selection unit 404: Base station control unit 405: User equipment transceiver 406: User equipment control unit

Claims (15)

A method for controlling a modulation and coding scheme for transmission between a base station (101) and a user equipment (102), the modulation and coding scheme comprising a plurality of modulations having a first maximum modulation order and A first selection including an entry corresponding to a plurality of modulation and coding schemes that is selectable based on a first modulation and coding scheme table that includes an entry corresponding to the encoding scheme or that has a second maximum modulation order; In a method that is selectable based on two modulation and coding scheme tables:
Selecting the first modulation and coding scheme table or the second modulation and coding scheme table by the base station (101), and between the base station (101) and the user equipment (102); Controlling the modulation and coding scheme for transmission by the base station (101) based on the selected modulation and coding scheme table;
A method involving that.   The second maximum modulation order is higher than the first maximum modulation order, in particular, the first maximum modulation order corresponds to 64QAM, and the second modulation order corresponds to 256QAM. The method according to 1. The method further comprises:
The base station (101) determines the actual channel state of the radio transmission channel used for transmission between the base station (101) and the user equipment (102),
A maximum supported modulation order is determined by the base station (101) based on the determined actual channel condition, and the maximum supported modulation order and the first maximum modulation order and the first Selecting the first modulation and coding scheme table or the second modulation and coding scheme table by the base station (101) based on a comparison with a maximum modulation order of two. The method described in 1.   4. The method according to any one of claims 1 to 3, wherein the method further comprises transmitting information representative of the selected modulation and coding scheme table to the user equipment (102).   The method according to claim 4, wherein the transmission of information to the user equipment (102) is based on radio resource control signaling.   The method according to claim 4 or 5, wherein the transmission of information to the user equipment (102) is based on implicit signaling.   6. The method according to any one of claims 3 to 5, wherein the method further comprises receiving confirmation information from the user equipment (102) representing a change made in the selected modulation and coding scheme table. The method described. The first modulation and coding scheme table and the second modulation and coding scheme table are respectively in the same position in the first modulation and coding scheme table and the second modulation and coding scheme table. Contains a common subset of equal entries placed in
In particular, the method further comprises:
After transmitting the information representing the selected modulation and coding scheme table to the user equipment (102) and before receiving the confirmation information from the user equipment (102), the selected modulation and Controlling the modulation and coding scheme for transmission between the base station (101) and the user equipment (102) based on a coding scheme table based on a common subset of the entries;
The method of claim 7 comprising:   Controlling an initial transmission between the base station (101) and the user equipment (102) is based on the first modulation and coding scheme table according to any one of the preceding claims. The method described.   10. A bit carrying modulation and coding scheme index is the same for the first modulation and coding scheme table and the second modulation and coding scheme table. The method described in 1. The actual channel condition is based on a first channel quality indicator table that supports the first maximum modulation order or based on a second channel quality indicator table that supports the second maximum modulation order. Determined based on a selectable channel quality indicator, the method comprising:
A channel quality indicator from the user device (102) is received by the base station (101), and between the base station (101) and the user device (102) based on the received channel quality indicator. The base station (101) determines the actual channel state of the radio transmission channel used for transmission of
The method according to claim 1, comprising: The method further comprises:
Based on the selected modulation and coding scheme table, the base station (101) selects the first channel quality indicator table or the second channel quality indicator table, and the selected channel Transmitting information representing a quality indicator table to the user device (102),
12. The method of claim 11 comprising:   The first channel quality indicator table and the second channel quality indicator table are arranged at the same position in the first channel quality indicator table and the second channel quality indicator table, respectively. 13. A method according to any one of claims 11 or 12, comprising a common subset of equal entries. A base station (101) for controlling a modulation and coding scheme for transmission between a base station (101) and a user equipment (102), the modulation and coding scheme comprising a first maximum modulation order Can be selected based on a first modulation and coding scheme table that includes entries corresponding to a plurality of modulation and coding schemes with a plurality of modulation and coding schemes having a second maximum modulation order In a base station that is selectable based on a second modulation and coding scheme table that includes a corresponding entry,
A selection unit (403) for selecting the first modulation and coding scheme table or the second modulation and coding scheme table;
A control unit (404) for controlling a modulation and coding scheme for transmission between the base station (101) and the user equipment (102) based on the selected modulation and coding scheme table;
Base station with 101.   A cellular network system (100) comprising a base station (101) according to claim 14.

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