KR20150077248A - Method and system for station selection and link adaptation for 802.11ac compliant multi user-mimo operation - Google Patents

Abstract

A method and system for providing enhanced link adaptation in an 802.11ac wireless networking standard supporting multi-user-multiple-input multiple-output (MU-MIMO) operation on the downlink is disclosed. The method provides a change in the station (STA) to an access point (AP) 801.11ac feedback element of the 801.11ac standard. This change makes it possible for the access point to select the optimal MCS level to match the channel and interference condition by maintaining the desired packet error rate (PER). The method may be such that each co-scheduled station exhibits a SINR step size that enables the access point to obtain an optimal MCS level based on multi-user interference computed after obtaining a multi-user (MU) precoder. can do. The method further enables link adaptation and joint STA selection to appropriately minimize transmit power or maximize data rate appropriately.

Description

[0001] METHOD AND SYSTEM FOR LINK ADAPTATION AND STATION SELECTION FOR 802.11AC COMPLIANCE WITH MULTI-USER-MIMO OPERATION [0002] METHOD AND SYSTEM FOR LINK ADAPTATION AND STATION SELECTION FOR 802.11AC COMPLIANT MULTI USER-MIMO OPERATION [

And more particularly to the improvement of the link adaptation technique of the 802.11ac IEEE wireless network standard supporting multi-user-multiple-input multiple-output (MU-MIMO).

Electronic communication devices, which create new demands for wireless connectivity more quickly and reliably at all times, anywhere, every day, are widely used everyday. IEEE 802.11ac is a fifth-generation Wireless Fidelity (Wi-Fi) networking that provides near instant data backup and synchronization, and fast, high-quality video streaming to notebooks, tablets, It is standard. Link adaptation (LA) technology significantly increases user throughput by providing an efficient way to maximize the spectral efficiency with the instantaneous quality of wireless channels.

The Wi-Fi 802.11ac specification supports multiple user-multiple-input multiple-output (MU-MIMO) operation on the downlink and uses link adaptation for precoder design for multiple performance enhancements. (Uses link adaptation with precoder design to enhance multiuser performance).

Downlink multi-user MIMO is a technique that allows an access point (AP) to transmit to multiple clients (STAs) using multiple spectrum streams simultaneously.

The mapping between channel quality and modulation and coding scheme levels is one of the important design issues of LA technology. In a WLAN that complies with the 802.11ac specification, the access point performs predefined tasks for downlink in MU-MIMO operation. Operations such as station (STA) selection and pairing, MCS, rank selection for each STA, optimal rate and target packet error rate (PER) matching optimizer precocoder design are performed.

Currently, the feedback elements defined in 802.11ac support the MU-MIMO operation to be transmitted from the STAs to the access point and include the feedback SINR, beamforming matrix and the recommended MCS level (recommended MCS level) of the STA , the feedback elements are defined in 802.11ac, which is conveyed from the STAs to the MU-MIMO operation (STA's feedback SINR, beamforming matrices and recommended MCS level).

However, in the existing method, these defined feedback elements are insufficient for the access point to drive to the optimal MCS level for each of the co-scheduled STAs (However, these defined feedback elements are inadequate for AP to derive an optimal MCS level for each co-scheduled STAs). The access point does not recognize the receiver capability of an individual STA according to the receiver type of each STA.

For the reasons mentioned above, the existing method fails to derive an optimal MCS level that allows for improved link adaptation to provide a stable, high quality radio channel.

The purpose of these embodiments is to provide a method and system for improving link adaptation in the 802.11ac specification that supports multi-user-multiple-input multiple-output operation on the downlink to provide an access point (AP) To allow the access point to select an optimal MCS level that matches the channel and interference conditions.

Another object is to provide a method and system that is capable of feeding back a SINR step size table index to an access point and allowing the access point to select an appropriate SINR step size from the SINR step size table.

Yet another object is to provide a method that enables feedback of the interference suppression capability of the STA to an access point.

Another object is to provide a method for optimal joint STA selection, Multi User precoder design and MCS selection.

According to one aspect, a method for link adaptation and joint station selection is provided for 802.11ac that adheres to a multi-user multiple input multiple output (MU-MIMO) operation on the downlink. The method includes receiving an SINR step size according to a feedback SINR from at least one station to an access point (AP), designing an optimized multi-user precoder matrix for the at least one station, Calculating an optimal MCS level for the at least one station using the post processing SINR and the received feedback SINR for the at least one station, And selecting at least one optimal station from the set of stations as a point.

According to another aspect, an access point is provided that provides link adaptation and joint station selection for an 802.11ac that complies with multi-user-multiple-input multiple-output operation in the downlink. Wherein the access point further comprises at least one processor and at least one memory including computer program code in the circuit, wherein the computer program and the at least one memory having the at least one processor Wherein the access point receives a SINR step size along a feedback SINR from at least one station and designs an optimized multiuser precoder matrix for the at least one station and then obtains a post processing SINR for the at least one station , Calculate the MCS level for the at least one station using the post processing SINR and the received feedback SINR, and select at least one optimized station from the set of stations.

According to another aspect, a station is provided that supports link adaptation and joint station selection for an 802.11ac compliant multi-user-multiple-input multiple-output operation in the downlink. The station is configured to feed back the SINR step size to the access point according to the station's receiver capability, store a plurality of the SINR step size tables, and feedback interference suppression capability to the access point.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of these and other aspects are better understood in view of the following description taken in conjunction with the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments and various specific details, is provided for the purpose of illustration and is not intended to be limiting. Various changes and modifications may be made without departing from the spirit and scope of the embodiments, and these embodiments include all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments herein are better understood from the following description with reference to the drawings.
Figure 1 illustrates STA selection and MU-MIMO feedback in accordance with an embodiment during link adaptation in the 802.11ac specification.
Figure 2 shows a PER versus SNR curve in accordance with an embodiment that complies with the 802.11ac specification.
Figure 3 shows a flow chart for obtaining an optimal MCS level, in accordance with the embodiment described herein.
Figures 4A-4B show proposed changes to the VHT format HT control field of the 802.11ac specification D1.1, according to embodiments.
Figure 5 illustrates the joint encoding of MCS level and SINR step size using a change in the MCS field in the MFB sub-field of the VHT Format HT control field, according to embodiments.
6 illustrates a SINR step size table stored in an access point and STA, according to one embodiment.
7 illustrates a variation of the VHT supported in the MCS set field of the 802.11ac specification D1.2, according to one embodiment.
8 shows a variation of the VTH capabilities of 802.11ac D1.2, according to one embodiment.
9 illustrates a flow diagram illustrating the process of link adaptation and joint STA selection, in accordance with one embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments and various features and preferred details of the present invention will be more fully described with reference to the following non-limitative examples, which are illustrated in detail in the following description, taken in conjunction with the accompanying drawings. The descriptions of well known components and processing techniques are omitted so as not to unnecessarily obscure the embodiments described herein. The embodiments used herein are for the purpose of enabling an understanding of the embodiments described herein to be practicable and are intended to enable those skilled in the art to practice the embodiments described herein. Accordingly, the embodiments should not be construed as limiting the scope of the embodiments.

Embodiments achieve a method and system for providing enhanced link adaptation in an 802.11ac wireless networking standard supporting multi-user-multiple-input multiple-output (MU-MIMO) on the downlink. The method provides a change of station (STA) to an access point feedback element of the 801.11ac standard (AP) feedback elements of the 801.11ac standard. This change may cause the access point to select an optimal Modulation and Coding Scheme (MCS) level to match the interference condition and channel by maintaining the desired Packet Error Rate (PER).

The method further comprises enabling the access point to drive the optimized MCS level based on the calculated multi-user interference after each co-scheduled STA acquires the MU-precoder (after deriving the MU-precoder) The signal to interference noise ratio (SINR) step size can be expressed as a function of the coherent signal to interference noise ratio (SINR) step size. The method further enables link adaptation and joint STA selection to minimize power being properly transmitted or maximize data rate.

During the description, the STA refers to a non-AP STA.

According to one embodiment, the station (STA) may be a mobile device supporting a wireless local area network (WLAN), a laptop, a tablet, a personal computer, a media player, a digital camera, a smart phone, And so on.

Referring to Figures 1 to 9, like reference characters denote features corresponding consistently throughout the Figures and are shown as preferred embodiments.

Figure 1 illustrates STA selection and MU-MIMO feedback during link adaptation in the 802.11ac specification according to one embodiment. Figure 1 shows a feedback element from the STAs to the link adaptation of the access point and shows the scheduling algorithm and the output of the link adaptation and scheduling algorithm. scheduling algorithm and output of the link adaptation and scheduling algorithm. The wireless local area network (WLAN) system includes rank selection and MCS for each STA in accordance with an optimized precoder design to match the target packet error rate and desired data rate of each co-scheduled STA, It complies with the existing 802.11ac specification during downlink MU-MIMO operation to perform STA selection and pairing. In the existing method, the access point receives feedback from STAs. Based on the various received feedback parameters, the access point is scheduled at the designed time interval, followed by a set of STAs to obtain an optimized precoder in each subcarrier of the OFDM frame a set of STAs to be scheduled in the designated time interval and an optimal precoder at each subcarrier of the OFDM frame. In addition, the access point calculates the optimal MCS level for each of the STAs (User Equipment) that can satisfy the desired PER targets according to the individual QoS (Quality of Service) requirements.

In accordance with the 802.11ac specification, the feedback elements that support downlink MU-MIMO operation and must be transmitted from each STA to the access point include an MCS feedback message and a beamforming report. The MCS feedback message is transmitted from the STA called the average SINR (AvgSINR) in the STA and all spatial streams SS and subcarriers SC scrolled to the MCS level MCS _fb Lt; RTI ID = 0.0 > SINR. ≪ / RTI > Beamforming report sub a beamforming matrix (V _sc) compression per carrier (compressed per subcarrier Beamforming matrix (V sc)), SC and ΔSINR (quantized ΔSINR per SC & SS (ΔSINR sc, ss)) quantized per SS, And includes a quantized per spatial stream SINR averaged over all subcarriers (Avg SINR _ss ) averaged over all subcarriers.

The access point receives received feedback elements from a STA specific MCS, an STA specific rank and an SC MU-precoder matrix (per SC MU-precoder matrix) (Q).

A disadvantage of the existing method is that the feedback SINR experienced by the STA during a full swing downlink MU-MIMO operation is less than the actual SINR (post processing SINR) or effective SINR (The feedback SINR differs drastically from the actual SINR experienced by the STA). Thus, the Li Command to STA MCS level is sufficient to determine the specific MCS STA (the STA level recommended MCS (MCS _fb) STA is insufficient to decide the specific MCS). The various factors leading to a change in the feedback SINR (Avg SINR) and the actual experienced SINR are described below.

Multi-User Interface: Null Data Packet (NDP) frames are training frames sent to each STA in a Single User-MIMO (SU-MIMO) mode. Due to the absence of multiple users during the transmission of NDP frames, STAs suffer a communication channel free from multi-user interference. Thus, the SINR feedback from the STAs does not take into account the SINR degradation due to multi-user interference when the access point actually transmits data packets in the MU-MIM mode.

(CSIT): An access point (AP) is a part of a STA (a diagonal matrix of the STA) in the form of a beamforming matrix (V _sc ) and a SINRS per stream SINR)) and from the sub-carriers per Receive spatial CSIT (AP receives per subcarrier partial CSIT from each STA in the form of SINR S (Diagonal matrix of per stream SINR) and beamforming matrix (V sc)). The two matrices can be used to construct a Cingular value diagonal matrix and a Light Cingular matrix of SVD (H = USV ^H ).

However, the receiver side rotation matrix U is not known to the AP. Multi-user (MU) precoders designed with this partial CSIT cause degradation in the post-processing SINR experienced at the STA receiver (cause degradation in post-processing SINR experienced at the STA receiver).

Noisy CSIT (Noisy CSIT): STA beamforming matrix are fed back per (V _sc) and subcarrier (per subcarrier SINR feedback and beamforming matrix (V _sc)) through the compression and quantization. The compression and quantization of the beamforming matrix causes errors in the final decoded beamforming matrix at the access point. This corrupted beamforming matrix (V _sc ) is used at the access point to obtain a post-processing SINR, MU-precoder that is subject to STA degradation (which is used at the AP to derive MU-precoders, the post-processing SINR experienced at the STA degrades).

Subcarrier Grouping: In order to reduce the feedback overhead from the STA to the access point, the sub-carrier grouping is performed such that the beamforming matrix (V _sc ) and SINR are all sub- If a specific set of subcarriers is transmitted for a specific set of subcarriers instead of carriers, it is used for feedback. This results in a single feedback that should be sent to one group of subcarriers. At the access point, the CSIT for the other subcarriers can be obtained by interpolation. These interpolation techniques introduce considerable CSIT errors that further degrade the post-processing SINR experienced by the STA.

Thus, in the existing method, the access point fails to re-select an optimal MCS based on the post processing SINR. Existing methods also do not provide a mechanism for deriving a post processing SINR and can not be used further for scheduling algorithms and link adaptation processing to improve link adaptation in existing 802.11ac specifications. In the conventional method, the post processing SINR of the STA lower than the feedback SINR is not taken into consideration.

In addition, the PER performance can be improved by using a minimum mean square error (MMSE) receiver, interference suppression receivers, successive interference cancellation receivers, and maximum likelihood (ML) vector symbol detectors The maximum likelihood (ML) vector symbol detector and the receiver capability of the STA using such receivers are not considered.

FIG. 2 illustrates a PER versus SNR curve (PER versus SNR curve) that complies with the 802.11ac specification in accordance with one embodiment. Figure 2 shows the PER versus SNR curve for a 4x4 MIMO system for MCS levels 0 to 9 at a channel bandwidth of channel model D of 80MHz for a Minimum Mean Square Error (MMSE) receiver. The PER to SNR is a curve for 80 MHz, 4x4, number of spatial streams (NSS) = 4, NCS 0-9, BCC, perfect CSIT and TxBF, and channel D-NLOS (curve for 80 MHz, 4x4, Number of spatial streams (NSS) = 4, MCS 0-9, BCC, TxBF with perfect CSIT, Channel D-NLOS).

At a target PER of 10 ^-2 , the required SNR step size for the next MCS level is shown (the SNR step size required for subsequent MCS levels is shown). The graphs shown from left to right indicate MCS levels 0 to 9, respectively. The SINR difference between MCS level 0 and MCS level 1 is 2.5 dB, the SINR difference between MCS level 1 and MCS level 2 is 3 dB, and the SINR difference between MCS level 2 and MCS level 3 is 4 dB. This is for the ST's desired PER target of a STA and indicates that the SINR difference (dB in dB) between the following MCS levels is not constant. Therefore, the access point needs information of the MCS versus SINR table for different PER targets for all combinations of receiver type, bandwidth and SS (requires MCS vs. SINR tables).

The existing method does not provide information on the STA receiver function. Thus, the access point is unaware of receiver capabilities in the STA and can not accurately estimate the optimal MCS level corresponding to the post-processing SINR (SINR). All MCS downscaling applied by the access point without the knowledge of receiver capabilities threatens the stability and efficiency of the communication link.

Thus, the predefined feedback elements are inadequate for the access point to obtain an optimal MCS level for each co-scheduled STAs.

Figure 3 shows a flow chart for obtaining an optimized MCS level according to an embodiment as described herein. The described method improves the feedback from the STA to the access point by providing a mechanism for feedback SINR step size (dB) (by providing a mechanism to feedback SINR step size (dB)) and provides a post processing SINR Further estimates the post processing SINR likely to be experienced at the STA receiver. In the downlink MU-MIMO scenario, the access point accepts the feedback SINR from the co-scheduled STA.

로 표현되고, 송신 벡터는 X에 의해 표현되며 스퀘어 컨스텔레이션에서 그려진다(is drawn from a square constellation). MU-프리코더 매트릭스(Q)를 이용하는 액세스 포인트와 함께 STA_k 에서 수신된 신호는 수학식 1과 같이 표현된다.The access point AP calculates an optimal MU-precoder matrix Q (301). The access point then forms an MU-precoder matrix (Q) 302 to calculate a post processing SINR for each co-scheduled STA. For example, it is provided with K N _Rx receive antennas, each of which provides one SS for each of the STAs (serving one SS to each of the K STAs, each equipped with NRx receive antennas) and N _Tx antennas Lt; RTI ID = 0.0 > downlink < / RTI > The channel between the transmitter and the kth STA is

And the transmit vector is represented by X and is drawn in a square constellation. The signal received at the STA _k together with the access point using the MU-precoder matrix (Q) is expressed as Equation (1).

Because the access point has the information of Hk and Q, the post processing SINR that is likely to be a STA _k experiences using the equation (2) below is calculated (it computes post processing SINR _k that STA is likely to experience).

The information of the STA's interference suppression capability assists the AP in constructing an optimal receiver matrix G corresponding to each STA (an assist in constructing an optimal receiver matrix G) It is used for computation in the processing SINR (use in computation in the post processing SINR). The G matrix is formed by factoring in the interference suppression capability of each STA. Thus, the post-processing SINR is lower than the STA feedback SINR.

The method enables a co-scheduled STA to feed back the SINR step size to the access point (SINR step size to the AP). As shown in FIG. 2, the SINR difference between adjacent MCS levels is not constant, and the SINR difference is dependent on the receiver type, number of spatial streams (NSS) and bandwidth in the STA. Thus, the method defines multiple SINR step sizes to cover most SINR differences.

According to one embodiment, the method pre-transfers the SINR step size (SINR step size table) to the access point at the time of association.

According to one embodiment, the SINR step size table may be stored in both the access point and the STA, and the index of the SINR step size table may be conveyed in a feedback message.

The method allows the access point to select an appropriate step size from the SINR step size table. The selected SINR step size is used at the access point to select a lower MCS level that is close to the post processing SINR (to select the immediate lower MCS levels to suit the post processing SINR). The method then calculates (303) the number of MCS levels (N _levels ) to downgrade the MCS _fb (the MCS level that is being committed by the STA) using the SINR step size selected from the SINR step size table, . N _levels are calculated using Equation 3 given below.

In addition, the method derives (304) an optimized MCS level (MCS _optimal ) using the N _levels calculated from Equation (3) and the STA (MCS _fb ) that has been mapped to the MCS level. Equation 4 given below provides an MCS-optimized level that is used by the access point to enable the access point to better match the channel and interference condition (that enables AP to better match the channel and interference conditions).

In the flowchart 300, various operations may be performed in the order presented, in a different order, or simultaneously. In addition, in some embodiments, some of the operations described in FIG. 3 may be omitted.

4A and 4B illustrate changes in the VHT format HT control field of the 802.11ac specification D1.1 according to an embodiment described herein. . FIG. 4A illustrates a change in the VHT format HT control field, where the reserved bit B1 of the existing 802.11ac specification is removed (where the reserved bit (B1) of the existing 802.11ac specification is removed). This acquired bit is used in the MFB sub-field of the VHT format HT control field. The method changes the MFB sub-field size to 16 bits (B8-B23). VHT Format The remaining fields of the HT control field are not unchanged and remain according to the existing 802.11ac specification.

4B shows a change in the MCS field of the MFB sub-field in the VHT format HT control field of the 802.11ac specification. The bits obtained in the MFB sub-field are used to change the size of the MCS field to five bits (B11-B15) as shown in the figure. Along with an MCS field having five bit sizes, the method supports 32 unique MCS levels (supports 32 unique MCS levels).

Figure 5 illustrates the joint encoding of the MCS level and signal to interference and noise ratio (SINR) step size using the proposed MCS field in the MFB sub-field of the VHT format HT control field according to the embodiments described herein (Fig. FIG. 5 depicts a combined interpretation of the SINR step size and MCS level. The method may define the three step sizes given below.

The initial 10 MCS levels (0-9) indicate MCS0-9 with step size -1 (indicate MCS 0? 9 with step size-1).

The next 10 MCS levels (10-19) indicate MCS 0-9 with step size -2 (indicate MCS 0? 9 with step size-2).

The next 10 MCS levels (20-29) indicate MCS 0-9 with step size -3 (indicate MCS 0? 9 with step size-3).

The remaining two levels 30 and 31 are not used and are reserved for future use.

Figure 6 shows a SINR step size table stored in an access point and STA according to embodiments as described herein. Figure 6 shows four SINR step sizes for each table defined by three different step sizes. SINR Step Size Table 1 shows three SINR step sizes of 1dB, 2dB, and 3dB, while SINR Step Size Table 2 defines three step sizes such as 1dB, 2.5dB, and 4dB.

The SINR step size table 3 and the SINR step size table 4 define a plurality of SINR step sizes. The method may enable the access point to be aware of the information of the defined SINR step size tables. The access point knows about the appropriate SINR step size table to be used through the SINR step size table index (the AP is informed about the appropriate SINR step size table index).

FIG. 7 illustrates changes to the VHT supported in the MCS set field of the 802.11ac specification D1.2 according to one embodiment. FIG. 7 shows one MCS set field (B0-B63). The method defines an SINR step size table index field (B29-B31) in the MCS set field. With an index field of size 3 bits, it is supported with 8 step size tables of varying granularity. These eight tables are sufficient to cover most SINR step sizes. STAs feedback the index of the preferred SINR step size table to be used by the access point later to obtain an optimal MCS level.

FIG. 8 illustrates a variation of the VHT capabilities Info field of the IEEE 802.11ac D1.2 according to one embodiment. The method enables the STA to feed back its interference suppression capability to the access point. The information of the interference suppression capability of the ATS allows the access point to construct an optimized receiver matrix G corresponding to each STA that is later used to calculate the post processing SINR.

The method may further comprise the step of transmitting the VHT capability information field (32 bits) using one of the reserved bits to cause the STA to transmit its interference suppression capability to the access point at the time of association. Provide changes. The remaining fields of the VHT feature information field remain unchanged and remain in accordance with the existing 802.11ac specification.

FIG. 9 is a flow diagram illustrating a process of joint adaptive joining STA selection and link adaptation according to one embodiment. The access point performs station selection and pairing for a plurality of STAs. For example, the K stations STA ₁ to STA _k are considered by the access point. Each of STA ₁ to STA _k has a defined or preferred QoS, a target PER, a data rate, a rank and an MCS level.

As shown in the flowchart 900, the access point selects 901 a set of STAs (STA ₁ through STA _k ) based on data availability in the access point's queue. The access point knows the QoS of each STA. Therefore, the AP accesses the target PER and data rate of each required STA (AP asses each STA's target PER and data rate required based on the STA specific QoS).

In addition, for each STA, access points derive the MCS level and rank (NSS) required to support their required data rate. The access point arrives at the required SINR of each STA to satisfy the desired target PER of the STA using the stored PER to SINR table. Thereafter, the access point applies (902) the per user SINR constrain and the per antenna power constraint (902) and verifies if there is an optimized precoder (903 (902) the per user SINR constraint and per antenna power constraint and checks (903) if an optimal precoder exists).

If there is no optimizer precursor for the set of selected STAs, the method loops back to step 901 to select a new set of STAs. If an optimal precoder is present, the access point further designs an optimal precoder (904) (further designs (904) the optimal precoder). Then, the access point obtains a respective co-scheduled post processing SINR (the AP derives the post processing SINR of each co-scheduled).

Then, using the SINR step size and the feedback SINR (feedback SINR) from the STAs, the feedback elements MCS _fb , the access point obtains an _optimal MCS for each co-scheduled STA (905). The access point also calculates the achievable data rate for all co-scheduled STAs and calculates the power required to provide this achievable data rate. The access point stores the achievable data rate and the required power (stores the power required and achievable data rate).

Thereafter, the access point loops through all combinations of STAs 906 and selects a combination that maximizes the achievable data rate rate or minimizes the transmit power that satisfies the delay constraints. Thus, the access point learns 907 the STA that is optimized according to the rank (NSS), MU-precoder, and MCS to provide link adaptation and joint STA selection. The various operations in flowchart 900 may be performed in the order presented, in another order, or concurrently. In addition, in some embodiments, some of the operations shown in FIG. 9 may be omitted.

Embodiments described herein may be performed through at least one software program that performs network management functions to control elements and is executed on at least one hardware device. The elements shown in FIG. 9 may be at least one hardware device or may comprise blocks that can be a combination of a hardware device and a software module.

The descriptions of the specific embodiments described above illustrate the general characteristics of embodiments that can adapt and easily modify various applications, such as specific embodiments, without departing from the general concept. Therefore, such adaptations and modifications should be understood within the same scope and meaning as the described embodiments. The phraseology or terminology used herein is for the purpose of description and not of limitation. Therefore, while the embodiments described herein are described with respect to preferred embodiments, it should be understood by those skilled in the art that the embodiments herein may be practiced within the spirit and scope of the embodiments as described above.

Claims (18)

A method for link adaptation and joint station selection for an 802.11ac compliant multi-user multiple-input multiple-output (MU-MIMO) operation on the downlink,
Receiving an SINR (Signal to Interference and Noise Ratio) step size according to a feedback SINR from at least one station through an access point;
Designing a multi-user precoder matrix (MU) optimized for the at least one station and then obtaining a post-processing SINR for the at least one station with an access point;
Calculating an optimal MCS (Modulation and Coding Scheme) level for the at least one station to the access point using the post processing SINR and the received feedback SINR; And
Selecting at least one optimal station from the set of stations as the access point
≪ / RTI > The method according to claim 1,
The method comprises using at least one of a transmitter of the access point, a receiver of the at least one station, an optimal MU-precoder matrix of the optimal MU and an interference suppression capability of the at least one station To obtain the post processing SINR. 3. The method of claim 2,
Wherein the indication of the interference suppression capability is received through a reserved bit of a Very High Throughput (VHT) capability information field. The method according to claim 1,
The method for calculating an optimal MCS level comprises:
Selecting an appropriate SINR step size from the SINR step size table indicated by the supported SINR step size index field at the VHT supported in the MCS set field received from the at least one station to the access point;
Calculating the number of MCS levels using at least one of the SINR step size, the feedback SINR, and the post processing SINR; And
Calculating the MCS level optimized using at least one of the at least one station, the number of the MCS levels for the at least one station, and the MCS level,
≪ / RTI > 5. The method of claim 4,
Wherein the method calculates the optimal MCS level using the encoded MCS level and the encoded SINR step size. 6. The method of claim 5,
The method includes encoding a plurality of MCS levels and the SINR step size using reserved bits in a VHT format High Throughput (HT) control field for the MCS field of an MFB sub-field. 5. The method of claim 4,
Wherein the SINR step size index is transmitted on a reserved bit of the VHT supported in an MCS set field. 5. The method of claim 4,
The method comprising storing a plurality of the SINR step size tables in at least one of the access point and the at least one station. A system for link adaptation and joint station selection for an 802.11ac compliant multi-user-multiple-input multiple-output operation on the downlink,
The system comprises:
At least one access point (AP); And
At least one station
/ RTI >
The system as claimed in any one of claims 1 to 8, An access point that provides link adaptation and joint station selection for an 802.11ac compliant multi-user multiple-input multiple-output (MU-MIMO) operation on the downlink,
An integrated circuit further comprising at least one processor;
At least one memory containing computer program code within said circuit,
Lt; / RTI >
The at least one processor and the computer program code and the at least one memory,
The access point receiving a SINR step size along a feedback SINR from at least one station and designing a multiuser precoder matrix that is optimized for the at least one station and then sending a post processing SINR for the at least one station And calculating the optimized modulation and MCS levels for the at least one station using the post processing SINR and the received feedback SINR and to select at least one optimizable station from the set of stations. 11. The method of claim 10,
Wherein the access point is configured to obtain the post processing SINR using at least one of a transmitter of the access point, a receiver of the at least one station, an interference suppressor capability of the multiuser precoder matrix and the at least one station Access point. 11. The method of claim 10,
Wherein the access point is configured to receive the SINR step size from the SINR step size table that is included in the SINR step size at a supported Very High Throughput (VHT) in a private MCS set field received from the at least one station, point. 13. The method of claim 12,
The access point
Calculating the number of MCS levels using at least one of the SINR step size, the feedback SINR, and the post processing SINR; And
And calculate the MCS level that is optimized using at least one of the number of MCS levels for the at least one station and the at least one station to be MCS leveled. 14. The method of claim 13,
Wherein the access point is configured to calculate the optimized MCS level using the encoded MCS level encoded SINR step size. 15. The method of claim 14,
Wherein the access point is configured to encode a plurality of the MCS levels and the SINR step size using reserved bits in the VHT format HT control field for the MCS field of the MFB sub-field. 11. The method of claim 10,
Wherein the access point is configured to store a plurality of the SINR step size tables. A station providing link adaptation and joint station selection for an 802.11 ac compliant multi-user multiple-input multiple-output (MU-MIMO) operation on the downlink,
Feedback the SINR step size to the access point according to the receiver capability of the station;
Storing a plurality of the SINR step size tables; And
Wherein the station is configured to feedback interference suppression capabilities to the access point. 18. The method of claim 17,
Wherein the station is configured to transmit the SINR step size index to the access point via a reserved bit of a supported VHT in an MCS set field.

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