JP2024028826A - Control of modulation and coding schemes for transmissions between base stations and user equipment - Google Patents

Abstract

A method for controlling modulation and coding schemes for transmissions between a base station (101) and a user equipment (102) is provided.
The modulation and coding scheme can be selected based on a first modulation and coding scheme table that includes entries corresponding to a plurality of modulation and coding schemes having a first maximum modulation order; The selection can be based on a second modulation and coding scheme table that includes entries corresponding to a plurality of modulation and coding schemes with a maximum modulation order of two. The method includes selecting a first modulation and coding scheme table or a second modulation and coding scheme table by a base station (101), and transmitting between the base station (101) and a user equipment (102). The modulation and coding scheme for the base station (101) is controlled by the base station (101) based on the selected modulation and coding scheme table.
[Selection diagram] Figure 1

Description

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

Further developments are being made for LTE, for example for the Beyond 4G (B4G) radio system, which is assumed to be commercially available in 2020. However, evolution of LTE may be introduced any day within the new release.

LTE delivers a peak bit rate of 30 bps/Hz using 64QAM modulation and 8x8 MIMO transmission. As a result, B4G requires higher order modulation than 64QAM, for example 256QAM, to meet future requirements. Higher order modulation is more suitable for relay backhaul, for example, due to its superior channel quality and better radio frequency (RF) characteristics, which make it more suitable for relay backhaul than for user equipment (UE) or isolated indoor cells. If the UE is close to the access point and therefore has a good link to the access point, and the interference from other access points is attenuated by walls, little or no reason for

Determination of modulation order for LTE Release 10 is described in TS36.213 V10.3, Chapter 7.1.7 and CQI Definition, Chapter 7.2.3. In LTE (and LTE-Advanced), theoretical spectral efficiency is limited by 64QAM modulation. Extension to 256QAM provides improved spectral efficiency.

The LTE standard defines a modulation and coding scheme (MCS) index and table and a channel quality indicator (CQI) table. They are used to determine and select appropriate modulation and coding schemes. Currently the table supports up to 64QAM. The question 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 expansion to higher order modulation while maintaining upward compatibility for LTE. In particular, it is desirable to maintain the signaling format and, more particularly, to use the same number of bits as if a different encoding scheme had to be used and potentially so-called blind decoding had to be applied.

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

According to a first aspect of the invention, there is provided a method for controlling a modulation and coding scheme for transmission between a base station and a user equipment, the modulation and coding scheme having a first maximum modulation order. selectable based on a first modulation and coding scheme table comprising entries corresponding to a plurality of modulation and coding schemes with or a second maximum modulation order. A method is provided that is selectable based on a second modulation and coding scheme table that includes entries for. The method includes selecting a first modulation and coding scheme table or a second modulation and coding scheme table by the base station, and selecting the 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. Although 256QAM is specifically mentioned here, other modulations higher than those used in the first table could also be used, e.g. Note that characterized higher order modulation and coding schemes (MCS) can also be used.

The idea of this method is to introduce higher order modulation while still supporting modulation and coding scheme (MCS) tables 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, the MCS also takes into account different code rates and therefore dictates 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 the MCS table defined in LTE, which is used to determine and select an appropriate modulation and coding scheme. The second table is an extended MCS table based on the MCS defined in LTE, but includes entries corresponding to higher order modulations. For example, upward compatibility is ensured by making the first table strict as currently defined in the LTE standard.

The first and second tables may differ in several respects. For example, one table may be biased towards low MCS and a second table may be biased towards high MCS values. For example, one table may have more MCS values below a certain threshold MCS. Also, the density of MCS values at low MCS may be higher in one table, or the centroid or average of MCS values may be lower 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 kind of physical entity that can communicate with user equipment or other network equipment by selecting a modulation and coding scheme from such an MCS table. A base station in this document may be any kind of network equipment that provides the required functionality for the method, or a transceiver node that communicates with a central entity. The base station is, for example, a NodeB or an eNB.

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

According to an embodiment of the 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 can also be used, for example 128QAM.

Additionally, a small number of high MCSs are included in the first table in order to be able to react quickly if the channel suddenly becomes good.

According to yet another embodiment of the invention, the maximum modulation order corresponds to the highest modulation and coding scheme (MCS). Furthermore, the 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 an actual channel condition of a wireless transmission channel used for transmission between the base station and the user equipment; determining by the base station a maximum supported modulation order based on the actual channel conditions, and comparing the maximum supported modulation order with the first maximum modulation order and the second maximum modulation order; selecting by the base station the first modulation and coding scheme table or the second modulation and coding scheme table based on the base station.

If the actual channel conditions do not support higher order modulation or the user equipment (UE) cannot support higher order modulation, the base station modulates and codes 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 create a second table that supports higher order modulation, e.g. up to 256QAM. Performs modulation and coding based on

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

The base station provides a signal to the UE containing information about the MCS table selected and used. The UE then performs further actions such as CQI reporting 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 signaling link, the UE is easily informed regarding the selected MCS table. This information is also included in any information signal consisting of the UE's 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 capabilities inquiry procedure that also makes capabilities available to the eNB. During this type of configuration procedure, where the eNB determines the UE's capabilities, tables are switched and the UE is implicitly informed without specific signaling.

According to yet another embodiment of the invention, the method includes receiving confirmation information from the user equipment representing the changes made to the selected modulation and coding scheme table.

The base station performs changes from one table to the selected MCS table after receiving a confirmation signal from the UE. The confirmation signal thus represents the final modification of 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 arranged in a first modulation and coding scheme table and a second modulation and coding scheme table, respectively. Contains a common subset of equal entries placed in the same position in the encoding scheme table. In particular, the method includes transmitting information representing the selected modulation and coding scheme table to a user equipment and before receiving confirmation information from the user equipment. control a modulation and coding scheme for transmission between a base station and a user equipment based on a common subset of entries.

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

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 the MCS table with the lower 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 decides whether to change the MCS table. Changes are then made based on the actual channel conditions if the UE can support an MCS table that supports higher order modulation.

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 or the encoding and transmission mechanisms used to convey selections from that table, ensuring upward compatibility. In a more specific embodiment, the tables have the same size. In particular, portions of the first MCS table and the second MCS table are equal, giving the above-mentioned common entries. Entries in the first MCS table associated with very low modulation orders are swapped (redefined) to the second MCS table to include higher order modulations.

According to yet another embodiment of the invention, the actual channel condition is based on a first channel quality indicator table supporting a first maximum modulation order or a second channel quality indicator table supporting a second maximum modulation order. The method includes receiving a channel quality indicator from a user equipment by a base station, and adding the received channel quality indicator to the base station. determining, by the base station, an actual channel condition of a wireless transmission channel used for transmission between the base station and the user equipment based on the base station;

Similar to the MCS table, the CQI table is also selected based on the selection of the MCS table. If there is a switch 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 the table corresponding to the selected MCS table.

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

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

According to yet another embodiment of the invention, the first channel quality indicator table and the second channel quality indicator table are a first channel quality indicator table and a second channel quality indicator table, respectively. Contains a common subset of equivalent entries placed in the same position within.

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

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 having a first maximum selectable based on a first modulation and coding scheme table comprising entries corresponding to a plurality of modulation and coding schemes with a modulation order; or a second plurality of modulation and coding schemes with a 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 schemes. 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 selection unit for selecting a modulation and coding scheme for transmission between the base station and the user equipment. , and 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. Wireless access is thus provided to user equipment 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 multi-hop node or relay. Base stations are used in particular for B4G, LTE or 3GPP cell and communication.

The base station includes a receiving unit, for example a receiver known to those skilled in the art. The base station also includes a transmitter or transmission unit, eg a transmitter. The receiver and transmitter may be implemented as a single unit, eg a transceiver. The transceiver, or receiving and transmitting unit, is adapted to communicate with the user equipment via the 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 as part of a standard control unit, such as for example a CPU or a microcontroller.

In one embodiment, the base station further determines an actual channel condition of a wireless transmission channel used for transmission between the base station and the user equipment, and based on the determined actual channel condition. A decision unit is also provided for determining a maximum supported modulation order. The selection unit selects 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 and 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 a microcontroller.

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

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

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

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

Generally, methods and embodiments of methods according to the first aspect herein include performing one or more of the functions described with respect to the second or third aspect or embodiments thereof. Vice versa, a base station or cellular network system and embodiments thereof according to the second and third aspects may be a unit or unit for performing one or more functions as mentioned in relation to the first aspect or embodiments thereof. Including equipment.

According to a fourth aspect of the subject matter disclosed herein, there is provided a computer program for controlling a modulation and coding scheme for transmissions between a base station and a user equipment, the computer program comprising: It is for controlling the method described in the first aspect or embodiment thereof when executed.

The term computer program as used herein is equivalent to the term program element and/or computer readable medium containing instructions for controlling a computer system to coordinate the execution of the method described above.

A computer program may be implemented as computer readable instruction code by the use of a suitable programming language, such as, for example, JAVA, C++, and stored on a computer readable medium (removable disk, 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 functions. Computer programs are available from networks such as the World Wide Web where they can be downloaded.

The subject matter disclosed herein can be implemented by computer programs or software. However, the subject matter disclosed herein may be implemented in hardware, each with one or more specific electronic circuits. Furthermore, the subject matter disclosed herein may be implemented in a hybrid form, ie, a combination of software and hardware modules.

Having thus described exemplary embodiments of the subject matter disclosed herein, the following describes a cellular network system, a base station, and a method for controlling a modulation and coding scheme for transmission between a base station and user equipment. will be explained in detail. It is of course pointed out that combinations of features relating to different aspects of the subject matter disclosed herein are also possible. In particular, certain embodiments will be described with reference to embodiments in the form of an apparatus, whereas other embodiments will be described with reference to embodiments in the form of a method. However, those skilled in the art will appreciate from the foregoing and the following description that, unless otherwise indicated, in addition to combinations of features belonging to one aspect, combinations of features relating to different aspects or embodiments, such as implementations of device types, Combinations between features of the form and embodiments of the method form are contemplated as being disclosed with this application.

The aspects and embodiments described above and further aspects and embodiments of the invention are evident from the examples described below and will be explained with reference to the drawings, but the invention is not limited thereto. It should be noted that in different drawings the same or similar elements are designated with the same reference characters.

1 illustrates a cellular network system according to an exemplary embodiment of the invention. Figure 3 shows simulations of spectral efficiency for 64QAM and 256QAM. Simulations of spectral efficiency of 4×4 MIMO and 2×2 MIMO are shown for 64QAM and 256QAM, respectively. 1 illustrates a base station and user equipment in a cellular network system according to an exemplary embodiment of the invention.

Embodiments of the subject matter disclosed herein will now be described with reference to the accompanying drawings and with reference to current standards such as LTE and their further developments. However, references to current standards are by way of example only and do not limit the scope of the claims thereto.

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

Transmissions and communications between base stations and user equipment are controlled based on modulation and coding schemes. The modulation and coding scheme is selectable based on a first modulation and coding scheme table that includes entries corresponding to a plurality of modulation and coding schemes having a first maximum modulation order; is selectable based on a second modulation and coding scheme table that includes 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 conditions of the wireless transmission channel used for transmission between the base station and the user equipment. The base station then determines the maximum supported modulation order based on its determined actual channel conditions and ultimately based on the information from the user equipment which modulation orders can be supported by the user equipment. Determine the order. The base station then generates a first modulation and coding scheme table or a second modulation scheme table based on a comparison of its maximum supported modulation order with the first maximum modulation order and the second maximum modulation order. and select the encoding scheme table. Therefore, 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 a table based on other information, such as predefined selection criteria.

In LTE (and LTE-Advanced), theoretical spectral efficiency is limited by 64QAM modulation. FIG. 2 shows simulated LTE-Advanced throughput (reference number 201) (code rate 8/9) with 8×8 MIMO and modulation limited to 64 QAM in a spatially uncorrelated one-tap Rayleigh channel. Also plotted in FIG. 2 for comparison is the spectral efficiency obtained by expanding to 256QAM (reference numeral 202). It is clear that the extension to 256QAM starts to have an effect in the SNR range of approximately 25dB. In this figure, average SINR is plotted against throughput. Even if the average is lower than that region, the channel conditions are still good for some time, regardless of whether 256QAM provides any gain due to fading.

LTE throughput is limited by MCS even in more practical scenarios (eg, relay backhaul cases) where high spatial channel correlation occurs that limits the use of large ranks. This is illustrated in Figure 3, where the spectral efficiency for 2x2 and 4x4 MIMO schemes with adaptive rank and MCS selection in a high spectral correlation scenario is plotted as a function of the average signal-to-noise ratio. . For both 2x2 and 4x4 schemes, two curves are shown, on the one hand the MCS is limited to 64QAM (2x2:304, 4x4:302) and on the other hand the MCS is limited to 64QAM (2x2:304, 4x4:302). Expanded to 256QAM (2×2:303, 4×4:301). It is clear that extending to 256QAM already increases the throughput from an SNR range of approximately 10 dB in these scenarios. This means that the throughput is already likely to be significantly lower than the maximum throughput possible with 64QAM.

The question is how to implement 256QAM for LTE to maintain upward compatibility and avoid significant complexity. The addition of 256QAM needs to be performed to 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 the modulation and coding scheme fields of the DCI). This is not a desirable solution. This is because it doubles the number of DCI formats and significantly increases complexity. In UMTS, the extension from 16QAM to 64QAM is also made by adding one special signaling bit [R1-070635 R1-070570]. That extra bit can be provided by defining a new DCI format, or at least by defining more arbitrary DCI sizes, at the expense of worse decoding performance and more blind decoding. Alternatively, the possibility of bits being "stolen" from some other signaling and from a code allocation table that supports only half of the entries when 64QAM is enabled is limited, for example in HSDPA.

Another possible solution is to take the existing MCS/CQI index table as a basis and switch its use so that it currently only uses a subset of MCS values, e.g. dropping every third Try to make room for value. This is a coarse adaptation of the channel conditions, which is undesirable. Hereinafter, this method will be referred to as sub-sampling.

The idea of the method described here is to use the existing DCI format to define a new procedure that allows the use of 256QAM in good channel conditions. For this purpose, additional new MCS and CQI index tables with extension to 256QAM (Q _m =8) are created. This new table is the same size as the normal one. The decision whether the original index table or the table with 256QAM extension is used is decided by the base station (or eNB), and the switching is indicated to the UE by a signaling message, or or 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 in the same position 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 expansion is formed such that room for the 256QAM-related TB (transport block) size is taken from the originally lower TB size. Additionally, an extended 256 QAM table is used and there are some common modulation/TB sizes in the common MCS index area from the low range modulation set for situations where channel conditions drop rapidly. These indices can be sub-sampled from the lower TBS area.

A two-step switching procedure is provided for CQI index table switching to ensure that the UE is aware of the switch and does not use ambiguous table entries during the switch. The MCS table is pre-switched to the 256QAM version.

Also, a high range set for situations where 256QAM must be used quickly, for example before a clear selection is made during initial call set-up or to allow a quick reaction towards good quality. There are also some common modulations/TB sizes in the common MCS index area from the modulations.

The second table described here for the MCS and CQI index table 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 256QAM extension are switched by the eNB with RRC messages (alternatively, MAC or control signaling messages can also be considered). In this case, the algorithm responsible for this switching is eNB vendor specific, but obviously takes into account the CQI report from the UE. The UE is responsible for switching the MCS index table based on the RRC message and sending an acknowledgment to the eNB regarding the received RRC message (the acknowledgment is not important, since UEs that do not support switching do not acknowledge the command) (helps avoid upward compatibility issues).

RRC messages take about 100-200ms to become valid at the UE (upper layer processing delays are not standardized and depend on how often they are retransmitted in case of detection errors) , and since there is uncertainty associated with the start time when (1) RRC messages are lost and (2) a new configuration is used by the UE, both tables allow data scheduling even during times of uncertainty. There must be a common MCS index area. This ensures that the MCS from that area is understood correctly, regardless of whether a switch has already taken place. This common area is continuous, ie has consecutive MCS entries, allowing fine adaptation even during switching. The MCS index, modulation order and TBS index are the same in both MCS index tables in this area. For example, during an RRC procedure to switch tables, only this common MCS index area can be used before the eNB receives confirmation from the UE that it has received an RRC message to switch MCS index tables. 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.

Additionally, 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 switching 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 with 256QAM.
- Room for these new TB sizes can be taken from current lower TB sizes (QPSK and possibly lower 16QAM).
- The reserved TBS size for QAM is also in the common MCS area of low modulation. This MCS is used for retransmissions in bad channel conditions, especially if the previous initial transmission was performed with a higher MCS, especially a higher modulation order, or a different number of designated resources. However, there is no need to reserve entries for included 256QAM.
Also, in situations such as call setup where quick use of 256QAM is useful, there may be several 256QAM entries in a common area (losing upward compatibility and reducing the number of inputs available in the "normal" range). sacrifice). Such a default "compromise" MCS table, where sub-sampling is used to obtain high dynamic range, can be used as soon as the eNB is aware of the UE's capabilities. The switch from a legacy table, i.e. one with a lower maximum modulation order, to a compromise table, i.e. one with a higher maximum modulation order, shall be done implicitly as part of the capability inquiry procedure to make the capability available to the eNB. I can do it. A clear switch to a table focused on lower or higher MCS is then made, but if channel conditions change rapidly and a clear switch cannot be achieved, a clear switch to a sub-sampled table is made. Switching also takes place.

An example of a modulation table with MCS index and 256QAM extension is shown in Table 1. MCS indexes 12 to 31 refer to consecutive 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 the 256QAM extension.

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 serves as the MCS index table switch. In another case, the CQI table is switched implicitly. The eNB has the role of handling possible error situations caused by not knowing which table the UE will use at the exact time during this RRC procedure. The eNB may, for example, simply ignore non-common CQI indexes, round them up to the nearest common index, or take the risk and decide based on heuristics which tables are most likely to be associated. can do. Such an error case arises because, in contrast to MCS selection where the eNB initiates the change and therefore avoids ambiguous entries during the switch, with CQI the UE is unaware of the impending switch and therefore , because you can't avoid it (unless you constantly avoid it futilely). To increase the likelihood that the eNB will choose the correct decision in case of ambiguous table entries, the minimum difference of TBS to MCS index should be maximized. This is the case in Table 1. This is because the entries are arranged to increase TBS for both the 256 and QAM cases. If the 256QAM case is in reverse order, then for an MCS index of 9, the TBS is 26 (for 256QAM) or 8 (for QPSK), i.e. the difference is 26-8=18; On the other hand, in Table 1, the difference is 33-8=25. The larger this difference is, the less likely it is that the eNB will not be able to use the heuristic (eg, if the channel is actually changed by that amount out of 25). For the same reason, it is beneficial to place the reserved 256QAM entry at the highest MCS index, ie for MCS index 11 of table 1. That reserved entry is only concerned with the downlink, not the uplink. Therefore, in the uplink table, it can be easily dropped and replaced by a normal entry for QAM (TBS10 in Table 1).

To avoid ambiguous CQI reports during the switching time, a two-step switching procedure can be used, in the first command the eNB signals 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 the switch. 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 during the first ambiguous period and the final one during the second period); Alternatively, only MCSs from a common MCS area are used, and in this common area there is no risk of misunderstanding. This is because entries from a common MCS area are coded identically in both tables. This makes the order of entries in high MCS areas non-sequential, but this is less complex and can be solved by implementing a look-up table, for example.

The message flow according to this embodiment is as follows.
1) eNB to UE: RRC message to switch MCS table and restrict CQI reporting to a common index area. The eNB only uses a common index area for the MCS.
2) UE to eNB: confirmation (and implicit message), the eNB now uses the complete index area of the new MCS table; ).
3) eNB to UE: Confirmation, the UE now uses the complete index area of the new CQI table.

Even though there are actually two handshakes, instead of using four messages, there are only two. 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. Therefore, at any time, the sender of a message can switch to the corresponding table and therefore limit its use to the common index area during ambiguous periods.

Indicating the UE's ability to support 256QAM requires a new UE category that includes 256QAM. If the UE does not support 256QAM, the above process and the MCS/CQI index table with 256QAM extension are not used. Alternatively, the eNB can send the switching command and determine the response regardless of whether the UE supports 256QAM. In the initial access phase, 256QAM and therefore higher modulation order MCS tables should not be used since the eNB does not yet know the UE's capabilities.

The process described above can be used for expansion to higher MCS. Also, this process can be extended to cover and switch between more than two tables. Common MCSs represented in two or more tables must always be in the same location. There are differences in the size and shape 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 selected from those that also exist. This is possible because 2 is a divisor of 4, so sub-sampling of the high table should not select every second or fourth entry that is not compatible. It may also be used for Table 1 covering a wide range of CQI values.

The solution proposed here has a number of benefits. The existing DCI format design remains unchanged. This allows 256QAM to be supported for each DL DCI format while maintaining the existing DCI blind decoding burden at the UE. The scheme proposed here provides a means for the eNB to easily avoid complex error cases due to signaling errors. The design proposed here allows the basic functionality of the existing DL resource allocation (CQI/MCS index table) to remain 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 invention. This cellular network system includes a base station 101 and user equipment 102 that receives service from the base station.

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

The base station determines the actual channel conditions of the wireless transmission channel used for transmission between the base station 101 and the user equipment 102, and the maximum supported modulation based on the determined actual channel conditions. A determination unit 402 is provided for determining the order. The base station further determines 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 the modulation scheme table or the second modulation and coding scheme table. Furthermore, 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. Wireless access is thus provided to user equipment 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 transmitter or transmission unit, eg a transmitter. The receiver and transmitter may be implemented as a single unit, eg, transceiver 401. The transceiver, or receiving and transmitting unit, is adapted to communicate with the user equipment via the antenna.

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

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

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

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

With respect to the subject matter disclosed herein, some embodiments may refer to "base station," "eNB," etc.; however, each such reference may refer to the general term "network component" or, in other embodiments, the term "network access node." It is to be understood that this may be considered an implied disclosure of ``. It is also contemplated that other terms relating to a particular standard or a particular communication technology implicitly disclose each general term with desired functionality.

Furthermore, it is noted that the base stations disclosed herein are not limited to the dedicated entities described in some embodiments. Rather, the principles described herein can be implemented in a variety of ways at various locations in a communications network while still providing the desired functionality.

According to embodiments of the present invention, suitable entities (e.g., components, units and devices) disclosed herein, such as a decision making unit, may be used to enable a 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, suitable entities disclosed herein may be provided in hardware. According to other hybrid embodiments, some entities are provided in software, while other entities are provided in hardware.

Note 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 at various granularities at the device level while still achieving the desired functionality. Furthermore, it is noted that, according to embodiments, separate entities (eg, software modules, hardware modules, or hybrid modules) may be provided for each functionality disclosed herein. According to other embodiments, an entity (eg, a software module, a hardware module, or a hybrid module (software/hardware module)) is configured to provide two or more of the functionality 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 further refinements of the invention. It is also noted that any reference signs in the claims shall not be construed as limiting the scope of the claims.

100: Cellular network system 101: Base station 102: User equipment 103: Cell 201: 8x8 MIMO with 64QAM
202: 8x8 MIMO with 256QAM
301: 4x4 MIMO with 256QAM
4x4 MIMO with 302:64QAM
2x2 MIMO with 303:256QAM
2x2 MIMO with 304:64QAM
400: Cellular network system 401: Transceiver of base station 402: Determination unit of base station 403: Selection unit of base station 404: Control unit of base station 405: Transceiver of user equipment 406: Control unit of user equipment

Claims (15)

A method for controlling a modulation and coding scheme for transmissions between a base station (101) and a user equipment (102), the modulation and coding scheme comprising a plurality of modulation and coding schemes having a first maximum modulation order. selectable based on a first modulation and coding scheme table comprising entries corresponding to a coding scheme; or a first modulation and coding scheme table comprising entries corresponding to a plurality of modulation and coding schemes having 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 controlling the modulation and coding scheme for transmission by the base station (101) based on the selected modulation and coding scheme table;
Methods that include. 5. 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. The method described in 1. The method further includes:
determining by the base station (101) an actual channel state of a wireless transmission channel used for transmission between the base station (101) and the user equipment (102);
determining by the base station (101) a maximum supported modulation order based on the determined actual channel conditions; and 2. 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 2. The method described in. 4. A 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). 5. The method of claim 4, wherein the transmission of information to the user equipment (102) is based on radio resource control signaling. 6. A 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, further comprising receiving confirmation information from the user equipment (102) representing the changes made to the selected modulation and coding scheme table. Method described. The first modulation and coding scheme table and the second modulation and coding scheme table are located at the same position in the first modulation and coding scheme table and the second modulation and coding scheme table, respectively. contains a common subset of equal entries located in
In particular, the method further comprises:
After transmitting 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), 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 the common subset of entries;
8. The method according to claim 7, comprising: 9. Controlling the initial transmission between the base station (101) and the user equipment (102) is based on the first modulation and coding scheme table. Method described. 10. Any one of claims 1 to 9, wherein the bits conveying a modulation and coding scheme index are the same for the first modulation and coding scheme table and the second modulation and coding scheme table. The method described in. The actual channel condition is based on a first channel quality indicator table supporting the first maximum modulation order or based on a second channel quality indicator table supporting the second maximum modulation order. determined based on a selectable channel quality indicator, the method comprising:
a channel quality indicator from the user equipment (102) is received by the base station (101), and communication between the base station (101) and the user equipment (102) based on the received channel quality indicator; determining by the base station (101) an actual channel state of a wireless transmission channel used for transmission of;
11. A method according to any one of claims 1 to 10, comprising: The method further includes:
selecting the first channel quality indicator table or the second channel quality indicator table by the base station (101) based on the selected modulation and coding scheme table; and 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 having a first maximum modulation order; selectable based on a first modulation and coding scheme table comprising entries corresponding to a plurality of modulation and coding schemes with a second maximum modulation order; at a base station selectable based on a second modulation and coding scheme table containing corresponding entries;
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 (101) with A cellular network system (100) comprising a base station (101) according to claim 14.

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