RU2774062C2 - Semi-orthogonal multiple access with power-adaptive constellation - Google Patents

Abstract

FIELD: communication.

SUBSTANCE: invention relates to a system and a method for using combined constellations of symbols in wireless local area networks (WLAN). The power distribution coefficient is determined from a set of possible power distribution coefficients; energy is distributed based on the power distribution coefficient between the first and the second composite constellations combined to form a quadrature amplitude modulation (hereinafter – QAM) constellation. QAM constellation includes a sub-constellation of symbols in each of four quadrants, wherein an increase in the power distribution coefficient increases distances between symbols within each sub-constellation and reduces distances between sub-constellations. The first data and the second data are displayed in QAM constellation symbol, wherein the first data is displayed in the first sub-symbol of the symbol corresponding to the first composite constellation, and the second data is displayed in the second sub-symbol of the symbol corresponding to the second composite constellation; and the constellation symbol is transmitted in a frame in the form of a radio frequency (RF) signal.

EFFECT: improvement of the use of the wireless communication spectrum using combined constellations.

23 cl, 19 dwg, 1 tbl

Description

The field of technology to which the invention belongs

The present disclosure relates generally to digital communications, and more particularly to a system and method for using co-located symbol constellations in wireless local area networks (WLANs).

State of the art

The overall goal of subsequent generations of radio frequency communication systems is to increase the amount of information transmitted in a given range of communication frequencies. As an example, US Patent Application Publication No. 2016/0204969 discloses a Semi-Orthogonal Multiple Access (SOMA) system that allows multiple electronic devices to use co-located constellations to share wireless spectrum. In SOMA, co-located symbol constellations are formed from multiple constellations that use different modulation layers. The resulting symbols include higher modulation level and lower modulation level sub-symbols that have different decoding reliability. Higher modulation level subsymbols have lower reliability and may be more suitable for high signal to noise ratio (SNR) channels. Lower modulation level sub-symbols have higher reliability and may be more suitable for lower SNR channels. The term "semi-orthogonal" in SOMA derives from the property that, from the point of view of a high SNR receiver decoding lower reliability sub-symbols, the higher reliability sub-symbols can be considered non-interfering and thus orthogonal in towards subsymbols with lower reliability. However, from the point of view of a low SNR receiver decoding the higher reliability sub-symbols, the lower reliability sub-symbols may be considered as interference that is not orthogonal to the higher reliability sub-symbols. For example, SOMA can be used in modern radio access technologies. Currently, proposed SOMA systems use a QAM constellation which is the same as for the corresponding radio access technologies, IEEE 802.11ac.

Thus, there is a need for systems that can further improve the use of wireless spectrum using co-located constellations.

Disclosure of the essence of the invention

Exemplary embodiments provide a system and method for controlling the power allocated to each of the multiple constellations that make up a co-located symbol constellation. In some examples, co-located constellations with adaptive power allocation are used in wireless local area networks (WLANs).

The first aspect of the disclosure provides for a method performed at a network node. The method includes determining a power sharing factor from a plurality of possible power sharing factors, allocating, based on the power sharing factor, energy between the first and second constituent constellations that are combined to form a quadrature amplitude modulation (QAM) constellation, and displaying the first data and the second data into a QAM constellation symbol, wherein the first data is mapped to a first symbol sub-symbol that corresponds to the first composite constellation, and the second data is mapped to a second symbol sub-symbol that corresponds to the second composite constellation. The constellation symbol is transmitted in the frame as a radio frequency (RF) signal.

Alternatively, in any of the previous aspects, increasing the power sharing factor increases the energy allocated to the first constituent constellation by an amount that is proportional to the decrease in the energy allocated to the second constituent constellation.

Alternatively, in any of the previous aspects, the QAM constellation includes a sub-constellation of symbols in each of the four quadrants, whereby increasing the power sharing factor increases the distances between symbols within each sub-constellation and decreases the distances between the sub-constellations.

Alternatively, in any of the previous aspects, the power sharing factor is the average power of each symbol in the QAM constellation.

Alternatively, in any of the previous aspects, the set of power sharing factors includes at least one power sharing factor that corresponds to the 801.11ac QAM constellation.

Alternatively, in any of the previous aspects, the QAM constellation is a 16-QAM constellation representing 16 possible 4-bit symbols (b ₀ b ₁ b ₂ b ₃ ), with each symbol a 4-bit symbol (b ₀ b ₁ b ₂ b ₃ ) represents bits and has the relative coordinates of the in-phase (I) and quadrature (Q) axes, represented as follows:

SYMBOL
(b ₀ b ₁ b ₂ b ₃ ) COORDINATES
I+jQ 0000

0001

0010

0011

0100

0101

0110

0111

1000

1001

1010

1011

1100

1101

1110

1111

where:

α - power distribution coefficient, 0 < α <1,

, и

, and

.

.

Alternatively, in any of the previous aspects, the first sub-symbol contains the b ₀ and b ₂ bits of the b ₀ b ₁ b ₂ b ₃ symbol, and the second sub-symbol contains the b ₁ and b ₃ bits of the b ₀ b ₁ b ₂ b ₃ symbol.

Alternatively, in any of the previous aspects, one of the many possible power distribution factors is α = 0.2.

), и относительную координату квадратурной (Q) оси, выбранную из множества (

) Alternatively, in any of the previous aspects, the QAM constellation is a 64-QAM constellation representing 64 possible 6-bit symbols (b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ ), with each of the 6-bit symbols (b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ ) has a relative coordinate of the in-phase (I) axis, selected from the set (

), and the relative coordinate of the quadrature (Q) axis, selected from the set (

)

where:

α - power distribution coefficient, 0 < α < 1,

,

,

,

,

Alternatively, in any of the previous aspects, one of the many possible power distribution factors is α = 0.2381.

Alternatively, in any of the previous aspects, the first sub-symbol contains bits b ₀ , b ₂ and b _{4 of} symbol b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ and the second sub-symbol contains bits b ₁ , b ₃ and b _{5 of} symbol b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ .

), и относительную координату квадратурной (Q) оси, выбранную из множества (

).Alternatively, in any of the previous aspects, the QAM constellation is a 256-QAM constellation representing 256 possible 6-bit symbols (b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ b ₆ b ₇ ), with each of the symbols in the first constellation quadrant 256-QAM has a relative in-phase (I) axis coordinate selected from the set (

), and the relative coordinate of the quadrature (Q) axis, selected from the set (

).

α is the power sharing factor, 0 < α < 1,

,

,

,

,

Alternatively, in any of the previous aspects, one of the many possible power distribution factors is α = 0.247.

Alternatively, in any of the previous aspects, the frame includes a multi-bit field, the method comprising populating the multi-bit field with an index value that is a power sharing factor.

According to a second aspect, an access point (AP) is provided that includes a memory, an interface for wireless communication, and a processing device configured to execute instructions stored in the memory. The executable instructions cause the AP to execute, determine a power sharing factor from a plurality of possible power sharing factors, distribute, based on the power sharing factor, energy between the first and second constituent constellations that are combined to form a quadrature amplitude modulation (QAM) constellation, and display the first data and second data into a QAM constellation symbol, wherein the first data is mapped to a first symbol sub-symbol that corresponds to the first composite constellation, and the second data is mapped to a second symbol sub-symbol that corresponds to the second composite constellation. The constellation symbol is transmitted in the frame as a radio frequency (RF) signal using an interface.

Alternatively, in any of the previous aspects, increasing the power sharing factor increases the energy allocated to the first constituent constellation by an amount that is proportional to the decrease in the energy allocated to the second constituent constellation.

Alternatively, in any of the previous aspects, the QAM constellation includes a sub-constellation of symbols in each of the four quadrants, whereby increasing the power sharing factor increases the distances between symbols within each sub-constellation and decreases the distances between the sub-constellations.

Alternatively, in any of the previous aspects, the QAM constellation is a 16-QAM constellation representing 16 possible 4-bit symbols (b ₀ b ₁ b ₂ b ₃ ), with each symbol a 4-bit symbol (b ₀ b ₁ b ₂ b ₃ ) represents bits and has the relative coordinates of the in-phase (I) and quadrature (Q) axes, represented as follows:

SYMBOL
(b ₀ b ₁ b ₂ b ₃ ) COORDINATES
I+jQ 0000

0001

0010

0011

0100

0101

0110

0111

1000

1001

1010

1011

1100

1101

1110

1111

where:

α - power distribution coefficient, 0 < α <1,

, и

, and

.

.

Alternatively, in any of the previous aspects, the first sub-symbol contains the b ₀ and b ₂ bits of the b ₀ b ₁ b ₂ b ₃ symbol, and the second sub-symbol contains the b ₁ and b ₃ bits of the b ₀ b ₁ b ₂ b ₃ symbol.

Alternatively, in any of the previous aspects, one of the many possible power distribution factors is α = 0.2.

), и относительную координату квадратурной (Q) оси, выбранную из множества (

) Alternatively, in any of the previous aspects, the QAM constellation is a 64-QAM constellation representing 64 possible 6-bit symbols (b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ ), with each of the 6-bit symbols (b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ ) has a relative coordinate of the in-phase (I) axis, selected from the set (

), and the relative coordinate of the quadrature (Q) axis, selected from the set (

)

where:

α - power distribution coefficient, 0 < α <1,

,

,

,

,

Alternatively, in any of the previous aspects, one of the many possible power distribution factors is α = 0.2381.

), и относительную квадратурную (Q) координату оси, выбранную из множества (

),Alternatively, in any of the previous aspects, the QAM constellation is a 256-QAM constellation representing 256 possible 6-bit symbols (b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ b ₆ b ₇ ), with each of the symbols in the first constellation quadrant 256-QAM has a relative in-phase (I) axis coordinate selected from the set (

), and a relative quadrature (Q) axis coordinate selected from the set (

),

α - power distribution coefficient, 0 < α <1,

,

,

,

,

Alternatively, in any of the previous aspects, one of the many possible power distribution factors is α = 0.247.

According to a third aspect, a method and station (STA) is provided for receiving an RF signal that includes a frame containing a QAM constellation symbol having first data mapped to a first sub-symbol and second data mapped to a second symbol sub-symbol, the first the sub-symbol corresponds to the first constituent constellation, and the second sub-symbol corresponds to the second constituent constellation, wherein the frame includes power distribution information identifying a relative power distribution between the first sub-symbol and the second sub-symbol. In the STA, the power sharing factor is determined from a plurality of possible power sharing factors based on the power allocation information in the frame. The symbol is decoded to recover at least one of the first and second sub-symbols based on the power sharing factor.

According to a fourth aspect, a method is provided which includes: generating a quadrature phase shift keying (QPSK) symbol stream, each symbol having a first bit representing a corresponding data bit and a second bit representing a corresponding bit of a parity; and transmitting the QPSK symbols in the frame as a radio frequency (RF) signal. In the examples, the QPSK symbols form the middle part of the frame that follows the frame preamble. In some cases, the middle part is preceded and followed by QAM symbols, which have a higher modulation than QPSK. In some examples, the pilot sequence is a channel state estimation sequence. The method may be performed by an appropriately configured access point.

According to a fifth aspect, a method is provided at a receiver, which includes: receiving, over a wireless communication channel, a frame that includes a plurality of quadrature phase shift keying (QPSK) symbols, each symbol having a first bit representing a corresponding data bit and a second bit A that represents the corresponding bit of the parity. The frame is decoded in order to recover the data bits and parity bits. In some examples, channel state estimation is performed over a wireless communication channel based on the bits of the control sequence.

According to a sixth aspect, there is provided a method performed at a network node, including: mapping first data for a first station to a first bit of a quadrature phase shift keying (QPSK) symbol and second data for a second station to a second bit of a QPSK symbol; and transmitting the QPSK symbol in the frame as a radio frequency (RF) signal for the first station and the second station.

Alternatively, in any of the previous aspects, the method further comprises allocating power between the first bit and the second bit based on a power sharing factor.

Brief description of the drawings

Reference will now be made, by way of example, to the accompanying drawings, which show exemplary embodiments of the present application and in which:

Fig. 1 is an exemplary communication system according to exemplary embodiments;

figure 2 - QPSK constellation 802.11ac;

Fig.3 - constellation QAM-16 802.11ac;

4 is a diagram of channel resources for a WLAN using SOMA;

Fig.5 - QPSK constellation according to an exemplary variant;

6 is a block diagram of a QAM modulator;

Fig.7 - frame diagram;

8A is a flowchart showing actions taken at an access point and stations according to an exemplary embodiment;

8B is a flowchart showing actions taken at an access point and stations according to another exemplary embodiment;

Fig. 9 is a 16-QAM co-constellation according to an exemplary embodiment;

Fig. 10 shows a 16-QAM co-constellation (Fig. 9) with two different power distribution factors;

11 is a 64-QAM co-constellation according to an exemplary embodiment;

12 is a subconstellation of a co-located 256-QAM constellation according to an exemplary embodiment;

Fig.13 is a diagram of a frame similar to that shown in Fig.7, illustrating additional details;

14 shows operations performed at an access point according to an exemplary embodiment;

Fig.15 - operations performed in stations according to an exemplary variant;

Fig.16 - operations performed in the access point, according to another exemplary variant of implementation;

Fig.17A - an example of a station that can be used in the network (Fig.1)

Fig.17B is an example of an access point that can be used in the network (Fig.1).

Like reference numerals may be used throughout the various figures to refer to like components.

Implementation of the invention

The operation and structure of exemplary embodiments are described in detail below. However, it should be understood that the present disclosure provides for many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of the specific structures of the embodiments and modes of operation of the embodiments disclosed herein and do not limit the scope of the disclosure.

Exemplary embodiments are described in the context of WLAN communication systems that use co-located symbol patterns to improve communication performance. Embodiments may apply to standards compliant WLAN communication systems, such as systems that conform to specifications in the IEEE 802.11 standards group, and to non-standards compliant communication systems.

Figure 1 shows an exemplary wireless communication system 100. Communication system 100 includes an access point (AP) 102 that can serve a plurality of stations (STA) such as STA1, STA 2, STA 3-STA N (which are collectively referred to as STA). AP 102 may schedule transmission opportunities for the STA and signal information regarding transmission opportunities to the STA. STAs may receive transmissions or make transmissions according to scheduled transmission capabilities. AP 102 and STA may implement the exemplary embodiments presented in this disclosure.

In exemplary embodiments, APs 102 may be base stations, Node Bs (NodeBs), evolved NodeBs (eNBs), controllers, base terminal stations, and other transceiver devices. Similarly, STAs can be receivers, electronic devices, mobile stations, mobile phones, terminals, user equipment (UEs), machine-type communication devices, and other devices that can receive RF signals. While it is understood that communication systems may use multiple APs 102 capable of communicating with multiple STAs, only one AP 102 and a corresponding group of STAs is shown in FIG. 1 for simplicity.

STAs may have different quality links to AP 102. For example, different STAs may be located at different distances from AP 102. STA 1 may be located in close proximity to AP 102 and may have a high signal-to-noise ratio (SNR), such as 20 dB, and STA 2 may be located remotely from AP 102 and may have a low SNR, such as 5 dB or 8 dB. It should be noted that the distance between the AP 102 and the STA is not the only factor in link quality (low SNR versus high SNR). For example, intermediate objects such as structures, walls, vegetation, and precipitation can also affect the quality of the received signal. Although the present discussion focuses on two STAs (high SNR STA 1 and low SNR STA 2), the exemplary embodiments presented herein are designed to operate with any number of STAs.

In an exemplary embodiment, adaptive power allocation is combined with SOMA superposition symbol constellations to create a multiple access radio technology that provides increased link capacity and unequal data protection for different STAs. In exemplary embodiments, new Quadrature Amplitude Modulation (QAM) constellation formats are introduced. To provide context for the embodiments to be described below, FIG. 2 shows an example of a QAM constellation (also known as 4-QAM) according to the IEEE.802.11ac specification, and FIG. 3 shows an example of a 16-QAM constellation in according to the IEEE.802.11ac specification.

. Таким образом, мощность символа пропорциональна квадрату амплитуды символа. Энергия символа равна мощности, умноженная на длительность символа:

. Так как каждый символ несет в себе b битов, средняя энергия бита равна

. Среднюю энергию

символа для данного созвездия можно вычислить в виде среднего значения по всем символам. В примере, показанном на фиг.2, синфазные и квадратурно-фазовые координаты масштабируются или нормируются, поэтому средняя энергия для всех символов равна 1. В случае QPSK 802.11ac нормирующий множитель равен

. Например, на фиг.2 символ созвездия, который представляет собой пару битов b₀b₁ 11, имеет полярные координаты (Si=1, θ=45°) и прямоугольные координаты

. Символы созвездия отображаются в биты с использованием кода Грея, так что соседние символы созвездия изменяются только на один бит.In the 802.11ac QPSK constellation shown in FIG. 2, each constellation point is a symbol b ₀ b ₁ that encodes 2 bits. Each constellation point (and its corresponding symbol) can be represented with respect to the (I) axis of in-phase amplitudes and the (Q) axis of quadrature-phase amplitudes as real and imaginary rectangular coordinates (Si*cosθ, Si*sinθ) or Si*cosθ+ j (Si*sinθ), where Si is the symbol amplitude (e.g., the distance from the origin O to the constellation point), and θ is the phase angle of the symbol about the in-phase axis I. The symbol power is

. Thus, the symbol power is proportional to the square of the symbol amplitude. The energy of a symbol is equal to the power multiplied by the duration of the symbol:

. Since each character carries b bits, the average bit energy is

. average energy

symbol for a given constellation can be calculated as an average over all symbols. In the example shown in Figure 2, the in-phase and quadrature-phase coordinates are scaled or normalized so that the average energy for all symbols is 1. In the case of QPSK 802.11ac, the normalization factor is

. For example, in figure 2, the constellation symbol, which is a pair of bits b ₀ b ₁ 11, has polar coordinates (Si=1, θ=45°) and rectangular coordinates

. The constellation symbols are mapped to bits using Gray code so that adjacent constellation symbols change by only one bit.

In the 16-QAM 802.11ac constellation shown in FIG. 3, each constellation point is a symbol 302 that encodes 4 bits (b ₀ b ₁ b ₂ b ₃ ). In exemplary embodiments, the 16-QAM constellation shown in FIG. 3 is the result of a superposition of two composite constellations, each using a corresponding modulation level. As used herein, the term "composite constellation" refers to a constellation that is combined with one or more other composite constellations to form a superposition constellation. The term "subconstellation" refers to the symbols of a constellation in one quadrant of a constellation.

Symbol 302 may be divided into a first sub-symbol 304 that includes bits b ₀ , b ₂ , and a second sub-symbol 306 that includes bits b ₁ , b ₃ . The first sub-symbol 304 (b ₀ , b ₂ ) corresponds to the first composite constellation that uses a lower modulation level, namely QPSK. As shown in FIG. 3, the first bits of the sub-symbols b ₀ , b ₂ remain the same in each quadrant Q1, Q2, Q3 and Q4, but are different in the other quadrants. For example, b ₀ , b ₂ = 1.1 for all four symbols in the Q1 quadrant and b ₀ , b ₂ = 0.1 for all four symbols in the Q2 quadrant. The second sub-symbol 306 (b ₁ , b ₃ ) corresponds to the second composite constellation that uses a higher modulation level, namely 16-QAM. As shown in FIG. 3, the bits of the second sub-symbol b ₁ , b ₃ are different for each symbol in the quadrant.

, и уровень амплитуды Ah равен

.Accordingly, sub-symbol 304 that includes bits b ₀ , b ₂ can be decoded based on which quadrant it falls in. The inter-quadrant energy differences among sub-symbols 304 representing different bit values for bits b ₀ and b ₂ are greater than the intra-quadrant energy differences among sub-symbols 306 representing different bit values for bits b ₂ and b ₄ . As shown in FIG. 3, the log-likelihood ratio (LLR) for bits b ₀ and b ₂ is the same and is based on the signal amplitude (Al) represented by the distance from the constellation origin 0 to the quadrant subconstellation center SC. The LLR for bits b ₁ and b ₃ is based on the lower amplitude value (Ah) represented by the distance from the sub-quadrant constellation center SC to the sub-constellation symbol. In 802.11ac, the A1 amplitude level is

, and the amplitude level Ah is equal to

.

In 802.11ac, each QAM symbol consists of bits for the same STA. However, in a system that considers a constellation as a set of superimposed composite constellations (such as SOMA), the QAM symbols may be composed of bits for different STAs. More reliable bits in the 302 QAM symbol may be scheduled for the STA by the lower SNR channel, and less reliable bits may be scheduled for the STA by the higher SNR channel. Assigning more reliable bits to the lower SNR channel increases the probability of successful decoding. By assigning less reliable bits to a channel with a higher SNR, the probability of successful decoding is sacrificed for higher data rates. FIG. 4 shows a channel resource diagram 450 for a WLAN using a superposition constellation. Using superposition constellation, two or more STAs can be scheduled on the same channel or on the same carrier. As shown in FIG. 4, one channel or one carrier may carry a frame for STA 1455 as well as a frame for STA 2 460. Alternatively, padding 465 may be used to match the frame size for STA 1455 and the frame for STA 2 460. Although FIG. 4B shows the case where two transmissions are supported, transmissions to two or more stations may be supported with an upper limit on the number of simultaneous transmissions that is set by the size of the superposition QAM constellation used.

,

и

, соответственно.In 802.11ac QAM constellations, the relative in-phase and quadrature-phase amplitudes of each symbol 302 remain constant for that symbol 302, and thus the relative position of each symbol in the constellation remains constant. In 802.11ac, the constellation symbols are normalized such that the average energy of all symbols in each quadrant is 1. In 802.11ac 16-QAM, 64-QAM, and 256-QAM, each constellation symbol is normalized with a normalization factor

,

and

, respectively.

. Однако в QPSK-созвездии 500 символов квадратурные и синфазные значения амплитуды для каждого символа могут изменяться в соответствии с заранее определенной зависимостью на основе коэффициента α адаптивного распределения мощности. Как показано на фиг.5, уровень квадратурной фазовой амплитуды каждого символа созвездия равен

, и уровень синфазной амплитуды равен

. QPSK-созвездие 500 является суперпозицией созвездия двоичной фазовой манипуляции (BPSK) и созвездия квадратурной двоичной фазовой манипуляции (QBPSK), причем созвездие BPSK существует только по синфазной или действительной оси, и созвездие QBPSK существует только по квадратурной фазовой или мнимой оси.The exemplary embodiments described herein present new symbol constellations that differ from known 802.11ac constellations in that an adaptive power distribution factor can be applied to control the power allocation for each constituent constellation. In this regard, FIG. 5 shows an example of a new QPSK constellation 500 symbols according to an exemplary embodiment. In an 802.11ac QPSK constellation, the quadrature and in-phase amplitude values for each symbol are the same, namely

. However, in the QPSK constellation 500 symbols, the quadrature and in-phase amplitude values for each symbol may change according to a predetermined relationship based on the adaptive power distribution factor α. As shown in FIG. 5, the quadrature phase amplitude level of each constellation symbol is

, and the common-mode amplitude level is equal to

. The QPSK constellation 500 is a superposition of a binary phase shift keying (BPSK) constellation and a quadrature binary phase shift keying (QBPSK) constellation, where the BPSK constellation exists only along the in-phase or real axis, and the QBPSK constellation exists only along the quadrature phase or imaginary axis.

, и данные (-1 или 1) для QBPSK-подсимвола b₁ могут быть применены к квадратурному фазовому входу Q и скорректированы до уровня амплитуды, что приводит к следующим возможным QPSK-символам: FIG. 6 shows a block diagram of a QAM modulator 600 that outputs a signal that includes consecutive QPSK symbols b ₀ b _{1 of} the QPSK constellation 500. As indicated in FIG. 6, data (-1 or 1) for BPSK - sub-symbol b ₀ can be applied to the common mode input I and corrected to the amplitude level

, and the data (-1 or 1) for the QBPSK subsymbol b ₁ can be applied to the quadrature phase input Q and adjusted to an amplitude level, resulting in the following possible QPSK symbols:

In case α = 0.5, the QPSK constellation 500 will be identical to the QPSK 802.11ac constellation.

In the superposition QPSK constellation 500, power can be distributed adaptively between the BPSK and QBPSK constituent constellations by adjusting the power distribution factor α. Increasing the power distribution factor α increases the distance between QBPSK sub-symbols in constellation 500 (increasing the reliability of QBPSK sub-symbol b ₁ ) and decreases the distance between BPSK sub-symbols in constellation 500 (decreasing the reliability of BPSK sub-symbol b ₀ ). Reducing the power distribution factor α has the opposite effect.

амплитуды может использоваться для кодирования битов данных, которые предназначены для одной STA, и QBPSK-подсимвол b₁ с квадратурным фазовым уровнем

амплитуды может использоваться для кодирования битов данных, которые предназначены для другой STA. В случае, когда коэффициент распределения мощности α < 0,5, BPSK-подсимвол b₀ будет самым надежным битом (MRB) и может использоваться для канала с более низким SNR (например, для дальней STA 2), и QBPSK-подсимвол b₁ будет наименее надежным битом (LRB) и может использоваться для канала с более высоким SNR (например, для ближней STA1). В примере, где BPSK-подсимвол b₀ предназначен для дальней STA 2, и QBPSK-подсимвол b₁ предназначен для ближней STA1, каждая из дальней STA 2 и ближней STA 1может демодулировать принятый суперпозиционный QPSK-символ таким же образом, как станция демодулировала бы традиционный QPSK-символ, и игнорировать бит, который не предназначен для нее. Альтернативно, удаленная STA 2 может просто обрабатывать принятый суперпозиционный QPSK-символ как BPSK-символ и обрабатывать квадратурную фазовую часть сигнала как шум. В некоторых примерных вариантах осуществления принятый QPSK-символ может быть разделен в приемной STA на синфазные и квадратурные фазовые компоненты во время RF обработки до цифровой обработки в основной полосе частот.In some exemplary embodiments, the BPSK subsymbol b ₀ with in-phase level

amplitude can be used to encode data bits that are destined for one STA, and QBPSK subsymbol b ₁ with quadrature phase level

amplitude can be used to encode data bits that are destined for another STA. In the case where the power sharing factor α < 0.5, BPSK sub-symbol b ₀ will be the most reliable bit (MRB) and can be used for a lower SNR channel (for example, far STA 2), and QBPSK sub-symbol b ₁ will be Least Reliable Bit (LRB) and can be used for a higher SNR channel (eg near STA1). In the example where BPSK subsymbol b ₀ is for far STA 2 and QBPSK subsymbol b ₁ is for near STA1, far STA 2 and near STA 1 can each demodulate the received superimposed QPSK symbol in the same manner as a station would demodulate a traditional QPSK character, and ignore the bit that is not intended for it. Alternatively, the remote STA 2 may simply process the received QPSK superposition symbol as a BPSK symbol and process the quadrature phase portion of the signal as noise. In some exemplary embodiments, a received QPSK symbol may be split at a receiving STA into in-phase and quadrature phase components during RF processing prior to baseband digital processing.

In some embodiments, an alternative to using each of the bits b ₀ and b _{1 of} the sub-symbols of the QPSK symbol b ₀ b ₁ as data bits for different stations may be that each of the bits may be used for different purposes. For example, one bit can be used as a data bit and another bit as a training signal to estimate the channel condition. The data bit and the training bit may be used by the same STA, or the data bit may be used by one STA and the training bit may be used for another STA.

In the context of using one bit of the QPSK symbol b ₀ b ₁ for a reference signal for channel state estimation, in one example, the QPSK symbol may be included in a Physical Layer Convergence Protocol (PLCP) data unit (PPDU). In this regard, FIG. 7 shows an example frame 700, which is similar to the 802.11ac PPDU structure. Frame 700 may include legacy fields 702 for backward compatibility with stations that are not configured to handle superposition constellations. The legacy fields are followed by a preamble 701 intended for legacy stations that are capable of handling superposition constellations, such as the QPSK constellation 500. A preamble 701, which may be encoded, for example, using lower layer modulation such as BPSK, QBSK, or a combination thereof. , includes a SIG-A field 704, a short training field (STF) 706, a long training field (LTF) 708, and a SIG-B field 710. Data field 712 follows preamble 701. SIG-A field 704 may be used to signal that frame 700 is a non-legacy frame. Data field 712 may also contain information required to interpret subsequent frames, including, for example, bandwidth, number of streams, guard interval, modulation and coding scheme (MCS), and beamforming. The STF field 704 is used to improve automatic gain control estimation in multi-input multi-output (MIMO) transmission. The LTF field 708 includes long training sequences that provide the receiver with a means to estimate the channel condition between the transmit and receive antennas. The number of LTF fields 708 may vary depending on the total number of space-time streams. Field 710 SIG-B includes information that describes the data length and modulation and coding scheme (MCS) for single or multi-user modes.

In some exemplary embodiments, data field 712 may include a plurality of consecutive QPSK symbols b ₀ b ₁ having one bit allocated for data and one bit for channel state estimation purposes. In some examples, QPSK symbols b ₀ b ₁ having a channel state estimation bit may only be included at selected locations in data field 712, including, for example, as one or more middle portions 714 at locations directly in the middle portion or near the middle of the data field 712, or at locations at predetermined intervals in the data field 712. In cases where data field 712 is long, the channel state estimate made during preamble 701 may not remain accurate for the duration of the transmission. Accordingly, the middle portion 714 provides the receiver with an opportunity to update a previous channel state estimate.

In one example, the same LTF bit sequence used for BPSK modulated LTF field 708 of preamble 701 is retransmitted in middle portion 714 using consecutive QPSK symbols b ₀ b ₁ . One bit of each QPSK symbol b ₀ b ₁ is used for one of the bits of the LTF sequence, and the other bit of the QPSK symbol b ₀ b ₁ is used to carry data. For example, bit b _{1 of} the QBPSK sub-symbol may be a data bit, and bit b ₀ of the BPSK sub-symbol may be used as a bit of the LTF sequence. In exemplary embodiments, the receiver STA is pre-informed of the location of the middle portion of the preamble 714 within the data field 712, as well as the specific power allocation and expected constellation location for the reference signal bit in QPSK symbols b ₀ b ₁ . After receiving and decoding the QPSK symbols b ₀ b _{1 of} the middle portion 714, the receiving STA may perform a channel state estimate using the bits of the LTF sequence, and this information may then be used by the receiving STA to supplement and refine the channel state estimate previously made with respect to the sequence, included in field 708 LTF. In this regard, the QPSK symbol b ₀ b ₁ can be used as a training signal of the middle part 714, which can, among other things, be used to compensate for any channel changes that may have occurred after receiving the preamble 701. As noted above, the bit of the QPSK symbol b ₀ b ₁ , which is not allocated for channel state estimation purposes, may be used to encode data for the receiving STA. The use of the superimposed QPSK symbol b ₀ b ₁ still allows data to be transmitted during the intermediate period 714 and therefore can reduce the overhead associated with turning on the middle portion 714.

In another embodiment, one bit of the QPSK symbol b ₀ b ₁ may be used for control signaling, including, for example, to indicate the number of middle portions 714 of the training signal in frame 700. In some examples, the control signaling bit may be used to indicate which the QAM constellation type will be used for data after the middle part 714 in cases where a QPSK constellation is used for the middle part and another QAM constellation is used after the middle part.

FIG. 8A shows a method 800A performed in the AP 102 and a method 800B performed in each of STA 1 and STA 2, according to the first exemplary embodiment. In methods 800A, 800B, superposition QPSK constellation 500 is used for consecutive QPSK symbols b ₀ b ₁ included in a downlink message frame 820 transmitted from AP 102 simultaneously to STA 1 and STA 2. When method 800A starts, AP 802 has data to be delivered simultaneously to STA 1 and STA 2 on respective channels 822A, 822B. The AP determines channel information for channels 822A, 822B (block 801). The channel information may be obtained from various sources, including the STA. The channel information may be in the form of channel quality indicators (CQIs), channel state information (CSIs), or other information related to channel quality, channel state, and the like.

The AP 104 determines the power distribution factor α that is used for the QPSK constellation 500 according to the channel information, and also determines which modulation (BPSK or QBPSK) will be assigned to each STA (step 802). As noted above, the power distribution factor α determines the relative distribution of energy along the quadrature amplitude axis and the common mode amplitude axis. As an illustrative example, the AP 104 may select a power sharing factor α < 0.5 (e.g., 0.4), in which case, as noted above, the BPSK sub-symbol b ₀ is an MRB and may be assigned to a channel with a lower SNR (eg, far STA 2), and QBPSK sub-symbol b ₁ is an LRB and may be assigned to a channel with a higher SNR (eg, near STA1).

AP 104 then generates frame 820 (block 804). In exemplary embodiments, information identifying the power distribution factor α is embedded in frame 820 along with information indicating which sub-symbol has been assigned to each station. One or more QPSK symbols b ₀ b ₁ are included in frame 820 after the power distribution factor α and station assignment information. The data bits for one STA are encoded using one of the bit subsymbols b ₀ or b ₁ , and the data bits for another STA are encoded using the other bit subsymbol b ₀ or b ₁ . Frame 806 is then transmitted to AP 104 on channels 822A, 822B (block 806). In the example, channels 822A, 822B are respective spatial streams that use the same time-frequency resources. In some examples, AP104 transmits a common stream for both channels 822A, 822B.

With reference to method 800B, STA 1 on the receiver side receives frame 820 on channel 822A, and STA 2 receives frame 820 on channel 822B (step 808). Each STA decodes the symbols included in frame 820 as they are received, allowing each STA to determine the power sharing factor α and station subsymbol assignment (block 810) prior to decoding any received QPSK symbols b ₀ b ₁ . Then, STA 1 and STA 2 each decode the received QPSK symbols b ₀ b ₁ to extract their respective data bits (block 812). As suggested above, different decoding configurations are possible. In one example, both or one of STA1, STA 2 may be configured to decode both bits of the received QPSK symbols b ₀ b ₁ and then ignore the bit that is not assigned to them. In another example, both or one of STA1, STA 2 can only be configured to decode the subsymbol assigned to them. For example, STA 2 may simply process the received QPSK superposition symbol as a BPSK symbol and process the quadrature phase portion of the signal as noise.

As stated above, in an alternative embodiment, superposition QPSK constellation 500 is used for consecutive QPSK symbols b ₀ b ₁ included in a frame for the dual purpose of transmitting a data bit and a signaling bit for a receiving STA (eg, STA1). In one example, the signaling bit is a bit from a sequence used to evaluate the channel state. In this regard, FIG. 8B illustrates methods 800C and 800D performed at AP 104 and STA1, respectively, in the context of this alternate embodiment. When method 800C begins, AP 802 has data to deliver to STA 1 on channel 822A. The AP determines the channel information for channel 822A (block 801) in a manner similar to that above. The AP 104 determines the power sharing factor α which is used for the QPSK constellation 500 according to the channel information, and also determines which modulation (BPSK or QBPSK) is assigned to be used as a data bit and which one as a signaling bit. As an illustrative example, AP 104 may assign an MRB for a data bit and an LRB for a signaling bit.

The access point 104 then generates a frame (step 804), which in the illustrated embodiment has the format as described above with respect to frame 700 shown in FIG. In exemplary embodiments, information identifying the power distribution factor α is embedded in frame preamble 701 (eg, in SIG-B field 710) along with information indicating which sub-symbol has been assigned to the data bit, and which sub-symbol has been assigned as the signaling bit. . In some examples, information identifying the location of the QPSK symbols b ₀ b ₁ in the data field 712 is also included in the preamble 701. One or more QPSK symbols b ₀ b ₁ are included in the middle part of the frame 714. The data bits are encoded using one of the sub-symbols b ₀ or b ₁ bits, and the signal bits are encoded using another sub-symbol b ₀ or b ₁ bits. Frame 700 is then transmitted to AP 104 on channels 822A (block 806).

With reference to method 800D, STA 1 on the receiver side receives frame 700 on channel 822A. STA 1 decodes the symbols included in the frame as they are received. In an exemplary embodiment, preamble 701 includes one or more training fields (eg, 708 LTFs) that include channel state estimation sequences, and STA 1 uses this information to estimate channel state 822A (block 809). In exemplary embodiments, STA 1 also decodes information in preamble 701 that identifies power distribution factor α, sub-symbol assignments, and location of middle portion 714 (block 810). Next, STA 1 decodes the received QPSK symbols b ₀ b ₁ in the middle portion 714 to recover the data bit and signaling bit included in each symbol (step 812). In the case where signaling bits are used to transmit a channel state estimation sequence, STA 1 may perform an updated channel state estimate (block 814).

In some examples of methods 800c, 800d, one or more of the power distribution factor, subsymbol assignments, and midsection location is known to STA 1 in advance of frame transmission and thus does not need to be included in the transmitted frame. In some examples, the signaling bit may be used by one STA and the data bit may be used by another STA.

, и уровень амплитуды от центра SC подсозвездия квадранта до символа 110 созвездия Q1 равен

. Соответственно, увеличение коэффициента α распределения мощности приводит к большему выделению мощности для составного созвездия более высокого уровня модуляции, связанного с подсимволом 306 (b₁, b₃), и, наоборот, приводит к меньшему выделению мощности для составного созвездия более низкого уровня модуляции, связанного с подсимволом 304 (b₀, b₂). Таким образом, увеличение коэффициента α распределения мощности увеличивает надежность наименее надежных битов (LRB) b₁, b₃ подсимвола 306 с более высокой модуляцией, а также снижает надежность самых надежных битов (MRB) b₀ и b₂ подсимвола 304 с более низкой модуляцией. Уменьшение коэффициента α распределения мощности приводит к противоположному эффекту.Next, other QAM constellations will be described according to additional exemplary embodiments. FIG. 9 shows an example of a 16-QAM symbol constellation 900 according to an exemplary embodiment. The 16-QAM symbol constellation 900 is Gray-coded in the same way as the 802.11ac 16-QAM constellation, with each constellation symbol being a four-bit symbol 302 (b ₀ b ₁ b ₂ b ₃ ). The four-bit symbol 302 b ₀ b ₁ b ₂ b ₃ includes a lower modulation sub symbol 304 (b ₀ , b ₂ ) and a higher modulation sub symbol 306 (b ₁ , b ₃ ). In exemplary embodiments, the relative power distribution for the constituent constellations may be adjusted in accordance with the power distribution factor α. Each Q1, Q2, Q3 quadrant includes a corresponding 4-character subconstellation square. As shown in FIG. 9, in the Q1 quadrant, the amplitude level from the constellation origin O to the subconstellation center SC of the quadrant is

, and the amplitude level from the quadrant subconstellation center SC to Q1 constellation symbol 110 is

. Accordingly, an increase in the power sharing factor α results in more power allocation for the higher modulation level composite constellation associated with subsymbol 306 (b ₁ , b ₃ ), and conversely results in less power allocation for the lower modulation level composite constellation associated with with subcharacter 304 (b ₀ , b ₂ ). Thus, increasing the power sharing factor α increases the reliability of the least reliable bits (LRB) b ₁ , b ₃ of the higher modulation subsymbol 306, and also reduces the reliability of the most reliable bits (MRB) b ₀ and b ₂ of the lower modulation subsymbol 304. Reducing the power distribution factor α leads to the opposite effect.

As an example, FIG. 10 graphically illustrates two examples of a 16-QAM constellation 900 having a different power distribution factor α. The left side of FIG. 10 illustrates a constellation 900A with a power sharing factor α=0.4, and the right side illustrates a constellation 900B with a power sharing factor α=0.1. As shown in FIG. 10, a constellation 900A with a higher power sharing factor corresponds to a larger spacing between subconstellation symbols in each corresponding quadrant and a smaller spacing between the subconstellation center points SC of the respective quadrants, which improves the reliability of the LRB and reduces the reliability of the MRB. In contrast, constellation 900B with a lower power sharing factor corresponds to closer sub-constellation symbols in each respective quadrant and additional sub-constellation center points SC between respective quadrants, which improves MRB reliability and reduces LRB reliability.

The power distribution factor α is the average power of each constellation symbol. As the power sharing factor α increases, the average symbol energy in each subconstellation increases proportionally, and as the power sharing factor α decreases, the average symbol energy in each subconstellation decreases proportionally. On the contrary, the energy offset between the centers of the subconstellations decreases proportionally with an increase in the power sharing factor α and proportionally with a decrease in the power sharing factor α.

Referring again to FIG. 9, in an exemplary embodiment, the following two relationships can be used to provide rectangular coordinates for 16-QAM symbols in constellation 900:

, Уравнение (1)

, Equation (1)

where:

K _f is both the in-phase distance and the quadrature phase distance measured from the origin O of the constellation coordinates to the sub-constellation center point SC of any of the sub-constellations of the Q1, Q2, Q3 and Q4 quadrants;

α is the coefficient of adaptive power distribution, and 0 < α <1.

, Уравнение (2)

, Equation (2)

where:

K _n is both the in-phase distance and the quadrature phase distance from the center point SC of the quadrant that contains the symbol to the symbol in the quadrant.

Using K _f and K _n , the symbols for constellation 900 can be represented in the following table:

Table 1. Constellation 16-QAM

INDEX SYMBOL
(b ₀ b ₁ b ₂ b ₃ ) COORDINATES
I+jQ 0 0000

one 0001

2 0010

3 0011

four 0100

5 0101

6 0110

7 0111

eight 1000

9 1001

ten 1010

eleven 1011

12 1100

13 1101

fourteen 1110

fifteen 1111

In case α = 0.2, the 16-QAM constellation 900 is the same as the 802.11ac 16-QAM constellation.

In exemplary embodiments, a lower modulation subsymbol 304 that includes MRB b ₀ , b ₂ is used for a lower SNR STA, which in the present example is far STA 2, and a higher modulation subsymbol 306 that includes itself LRB b ₁ , b ₃ , is used for the lower SNR STA, which in the present example is adjacent to STA1. A station that is the target receiver (eg, far STA 2) for MRB b ₀ b ₂ may treat the received symbol 302 as a QPSK symbol for decoding MRB b ₀ b ₂ and may treat LRB b ₁ b ₃ as noise. A station that is a target receiver (eg, near STA1) for LRB b ₁ b ₃ must demodulate received symbol 302 as a 16-QAM symbol to decode LRB b ₁ b ₃ . Accordingly, at least the station that is the target receiver (eg, near STA1) for LRB b ₁ b ₃ is pre-informed about the adaptive power distribution factor α in order to enable the station to demodulate the received symbol 302 and appropriately compute the LLR to determine LRB b ₁ b ₃ .

The adaptive power allocation between multiple constellations, which is described above with respect to the 900 QAM constellation, can also be applied to higher modulation level QAM constellations, including but not limited to 64-QAM and 256-QAM. In this regard, FIG. 11 shows an example of a 64-QAM symbol constellation 1100 according to an exemplary embodiment. As shown in FIG. 11, each quadrant includes a sub-constellation of sixteen 6-bit symbols b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ arranged in a 4 by 4 grid, and each of the four sub-constellations has a corresponding sub-constellation center (e.g. marked as SC in quadrant Q1),

The 1100 symbol 64-QAM constellation uses the same Gray coding scheme as the 64-QAM 802.11ac constellation. A constellation of 1100 64-QAM symbols may be divided into a different number of component constellations, each corresponding to a respective modulation level and having a respective power allocation.

представляет собой среднее значение между X12 и X32, так что

. Соответственно,

In the example shown in FIG. 11, the 6-bit symbol b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ includes two composite constellations that have respective power allocations. One composite constellation includes the most reliable three-bit subsymbol b ₀ b ₂ b ₄ with lower modulation corresponding to power allocation 1-α, and the other composite constellation includes the least reliable three-bit subsymbol b ₁ b ₃ b ₅ with higher modulation, corresponding to the release of power. The relationship between the power distribution factor α and the distances between constellations can be represented using equations (1) and (2) for K _f and K _n , respectively. K _f is the same size for the 1100 QAM constellation as the 900 QAM constellation, namely the in-phase distance and the quadrature phase distance from the constellation origin O to the quadrant center point SC. K _n is defined as follows. In the 1100 64-QAM constellation, X1 is half the in-phase distance and half the quadrature phase distance between adjacent symbols in a quadrant, and X3 is 3 times X1.

is the average between X12 and X32, so that

. Respectively,

As shown in FIG. 11, the positive (real) values along the in-phase I coordinate axis for the four columns of constellation symbols located in each of Q1 and Q4 are, respectively:

.

.

The positive (imaginary) values along the quadrature phase axis Q coordinates for the four strings of constellation symbols located in each of Q1 and Q2 are, respectively:

The negative (real) values along the in-phase I coordinate axis for the four column symbols located in each of Q2 and Q3 are, respectively:

The negative (imaginary) values along the quadrature phase axis Q coordinates for the four strings of constellation symbols located in each of Q3 and Q4 are, respectively:

Accordingly, each of the 64 constellation symbols has an in-phase (I) position value and a quadrature-phase position value selected from the following set of possible position values:

In case α = 0.2381, the 6400 QAM 1100 constellation is the same as the 64-QAM 802.11ac constellation.

FIG. 12 shows an example of a 256-QAM symbol constellation 1200 according to an exemplary embodiment. In particular, FIG. 12 shows the first quadrant Q1 of a constellation 1200 of 256-QAM symbols. The 256-QAM 1200 symbol constellation uses the same Gray coding scheme as the 802.11ac 256-QAM constellation and each constellation symbol is an 8-bit symbol b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ b ₆ b ₇ . A constellation of 1200 256-QAM symbols may be divided into a different number of component constellations, each corresponding to a respective modulation level and having a respective power allocation.

представляет собой медианное значение среди X1² , X3², X5² и X7², так что

. Соответственно.In the example shown in FIG. 12, the 8-bit symbol b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ b ₆ b ₇ includes two composite constellations that have respective power allocations. One composite constellation includes the most reliable four-bit subsymbol b ₀ b ₂ b ₄ b ₆ with lower modulation corresponding to the 1-α power distribution, and the other composite constellation includes the four-bit subsymbol b ₁ b ₃ b ₅ b ₇ with lower modulation. modulation corresponding to the power distribution factor α. The relationship between the power distribution factor α and the distances between constellations can be represented using equations (1) for K _f and (2) for K _n . The value of K _f is the same dimension for the 256-QAM constellation 1200 as for the QAM constellation 900, namely the in-phase distance and the quadrature phase distance from the origin O of the constellation coordinates to the center point of the SC quadrant. K _n is defined as follows. In the 1200 256-QAM constellation, X1 is half the in-phase distance and half the quadrature phase distance between adjacent symbols in a quadrant, and X3 is 3 times X1; X5 is 5 times larger than X1; and X7 is 7 times larger than X1.

is the median value among X1 ² , X3 ² , X5 ² and X7 ² , so that

. Respectively.

As shown in FIG. 12, the positive (real) in-phase I-axis coordinates for the eight columns of constellation symbols located in each of Q1 and Q4 are, respectively:

Similarly, the positive quadrature phase Q (imaginary) coordinate axis values for the eight rows of constellation symbols located in each of Q1 and Q2 are, respectively:

Negative coordinate values are the negative values specified above.

Therefore, in quadrant Q1 in FIG. 12, each constellation symbol has an in-phase I coordinate value and a quadrature phase coordinate value selected from the following set of possible coordinate values:

In case α = 0.247, the 1200 256-QAM constellation is the same as the 256-QAM 802.11ac constellation.

A frame format to support the use of power adaptive superposition QAM constellation symbols will now be described. In exemplary embodiments, a PPDU frame, such as frame 700 (reproduced in FIG. 13), is used to transmit symbols that may be located in data field 712, for example. Information allowing the receiving STA to decode the symbols is embedded in the preamble 701. For example, in the case of both 64-QAM and 256-QAM, and at least for the receiving STA LRB in 16-QAM, the receiving STA must be informed of the value of the coefficient α power distribution. Additional information that may be provided in preamble 701 may include: information indicating that frame 700 includes superposition constellation symbols (eg, indication bit); assignment information indicating assignment of the composite constellations (eg, sub-symbol bits) to respective STAs (eg, which bit positions in a symbol are assigned to each STA); and constellation information identifying the type of superposition QAM constellation (eg, 16, 64, or 128-QAM). In an exemplary embodiment, this information is embedded in SIG-B field 710. FIG. 13 shows an example where the SIG-B field 710 includes the STA attribute portion 740 for each STA (eg, for STA 1 and STA 2).

Each STA attribute part 740 includes: an STA_ID field 750 that identifies the STA to which the information in the STA attribute part 740 applies; an indication bit 752 that indicates that frame 700 includes superposition constellation symbols; an MCS field 754 that identifies the type of coding and modulation scheme used for the STA (eg, if the superposition constellation is QPSK, 16-QAM, 64-QAM, or 256-QAM); a bit level field 756 that identifies which bits in the constellation were assigned by the STA (eg, MSB or LSB); and a power sharing factor indication field 758 that identifies the power sharing factor. In some examples, power sharing factor field 758 has a size of N bits, with each unique bit pattern acting as an index for a unique power sharing factor α. For example, for N=2, 3, or 4, power sharing factor field 758 can be used as an index for 4, 8, or 16 different levels of power sharing factor α, respectively. In an exemplary embodiment, at least one of the possible index values for power sharing factor field 758 is assigned to indicate that the superposition constellation is an 802.11ac constellation. For example, a particular bit pattern in power sharing factor field 758 indicates that α = 0.5 for the SOMA QPSK constellation, α = 0.2 for the SOMA 16-QAM constellation, α = 0.2381 for the SOMA 64-QAM constellation, and α = 0.247 for SOMA 256-QAM constellation.

14 shows, according to an exemplary embodiment, baseband operations 131 that are performed at AP 104 to populate frame 700 with station-specific data scheduled for multiple STAs. Baseband operations 131 represent operations that can be performed in a single input, single output (SISO) scheduling environment.

Prior to baseband operations 131, the AP 104 will determine the channel information for each of the scheduled STAs. As noted above, channel information may be obtained from various sources, including STAs, and may be in the form of CQI, CSI, or other information related to channel quality. Then, the AP determines the attributes to be used for encoding data for the respective STAs according to the channel information, including, for example, the power spreading factor α, the QAM modulation level, and the station's sub-symbol assignments.

In the example shown in FIG. 14, AP 104 receives a corresponding data bitstream (STA 1Data, STA 2 Data, STA N Data) for each of the plurality of stations STA1, STA 2, and STA N. STA-specific data bitstreams, STA 1Data, STA 2 Data, STA N Data are processed separately and independently of each other in the respective Forward Error Correction (FEC) encoder operations 132(1), 132(2) and 132(N) and in operations 134(1), 132 (2) and 132 (N) bit interleaving. Then, the corresponding interleaved FEC-coded data bitstreams are combined in a superposition constellation mapping operation 136, after which a single constellation symbol stream is obtained. In exemplary embodiments, constellation superposition mapping operation 136 maps respective station data bits to respective constellation symbols based on constellation attributes 135, which include: (1) power distribution factor α; (2) QAM modulation level (eg, QPSK, 16-QAM, 64-QAM, 256-QAM); and (3) station sub-symbol assignments (ie, sub-symbol bits assigned to each of the respective stations). By way of illustration, in one example, constellation attributes 135 may be: (1) power distribution factor α; (2) modulation level = 16-QAM; and (3) two stations in total, wherein STA 1 is assigned an LRB sub-symbol 306 (b ₁ , b ₃ ) with a higher modulation and STA 2 is assigned an MRB sub-symbol 304 (b ₀ , b ₄ ) with a lower modulation. In exemplary embodiments, constellation mapping operation 136 may be performed by AP 104 based on constellation lookup tables, such as 16-QAM coordinate table 1 shown above.

Accordingly, in exemplary embodiments, superposition constellation mapping operation 136 generates a superposition constellation symbol baseband stream for data field 712 of frame 700. In some examples, all or part of preamble 701 is pre-added to data field 701, including the STA attribute portion 740 for each of the respective STAs. Then, in exemplary embodiments, the resulting baseband frame symbols are modulated onto a plurality of subcarriers (eg, modulated using orthogonal frequency division multiplexing (OFDM)) using an inverse fast Fourier transform (IFFT) operation 138 . In examples where spatial mapping is used to direct messages transmitted from specific directions, spatial mapping operation 140 is applied. The resulting baseband stream may then be upconverted to the appropriate carrier frequency and transmitted to the AP 104.

FIG. 15 shows, according to an exemplary embodiment, baseband operations 1500 that are performed in respective STAs in order to recover STA-specific data from a received frame 700. In particular, FIG. performed in STA 1 to recover the data bitstream of STA 1Data, however, similar operations are performed in other stations that have data in frame 700. As shown in FIG. 15, STA 1 performs a Fast Fourier Transform (FFT) operation 150 on the symbols baseband frame 700 in order to convert the symbols of the frame into the time domain. The resulting frame symbols are then subjected to channel state estimation and channel equalization operations 152, which are performed based on the information contained in at least some of the fields of the preamble 701 (including, for example, STF field 708 and LTF field 708).

Then, LLR calculation operation 154 is performed. The symbols that the LLR calculation operation 154 takes as input are values that represent relative coordinate points in the superposition constellation, and the LLR calculation operation 154 uses log-likelihood ratios to convert these values into actual bits. In order to do this, LLR calculation operation 154 uses the information included in the STA attribute part 740 of frame 700 for the receiving STA (e.g., (1) power distribution factor α; (2) QAM modulation level, and (3) station sub-symbol assignment) . As noted above, the STA attribute portion 740 is typically modulated using very low level modulation such as BPSK, allowing the STA to extract the information required for LLR calculation operation 154 . In the example shown, where: (1) power distribution factor α, (2) modulation level = 16-QAM, and (3) STA 1 is a higher modulation LRB subsymbol 306 (b ₁ , b ₃ ), LLR calculation operation 154 will be decode the LRB and MRB sub-symbols into the corresponding bits, but will ignore the bits of the MRB sub-symbol 304 (b ₀ , b ₂ ).

Accordingly, although the data for all STAs have been included in the symbols input to the LLR calculation operation 154, only the bits that correspond to the STA1 data are output by the LLR calculation operation 154 so that the resulting bit stream is permuted to place the bits in the original order by the deinterleaving operation 156, and then subjected to the FEC decoding operation 158, resulting in the recovery of the STA 1Data.

The examples shown in Fig. 14 and Fig. 15 illustrate the SISO environment. FIG. 16 shows an example of baseband operations 1600 that are performed by AP 104 in a multi-input-multi-output (MIMO) environment in which M spatial streams are transmitted by AP 104. In the example shown in FIG. 16, AP 104 receives a corresponding data bit stream (STA 1Data - STA N Data) for each of the plurality (N) stations STA 1 - STA N. Each of the data bit streams STA 1 Data - STA N Data is divided into multiple data streams through a sequence of operations 162 coding and interleaving, which are performed separately for each data bit stream. For example, in FIG. 16, the data for STA 1, namely the data bit stream STA 1 Data, undergoes encoding and interleaving operations 162 in which the data bits are scrambled by a scrambling operation 164 and then parsed into two or more streams in a first operation 166 parsing. Each of the parsed streams is then passed to the respective operations 168 of a binary convolutional code (BCC) encoder. The BCC encoded streams are then passed to a stream parsing operation 170, in which the BCC encoded streams are further parsed to provide a total of M data streams, each of which is then individually subjected to a BCC interleaving operation 172. As shown in FIG. 16, as a result of the encoding and interleaving operations 162, the STA 1 Data bit stream is divided into M parallel STA 1 Data (1) to STA 1 Data (M) data streams. Similar operations are performed for other STAs, resulting in N sets of M data streams. The respective data streams from each STA are processed as a group by the respective superposition constellation mapping operations 174(1)-174(M). As an illustrative example, as shown in FIG. 16, data streams STA 1Data (1) and STA N Data (N) are processed together through a superposition constellation mapping operation 174 (1) to generate a corresponding single constellation symbol stream (symbol stream (1) ), each of which includes data for stations STA1-STA N. Similarly, data streams STA 1Data (M) and STA N Data (M) are processed together with superposition constellation mapping operation 174 (M) to generate a corresponding single stream constellation symbols (symbol stream (M)), each of which also includes data for stations STA1 to STA N. Superposition constellation mapping operation 174 (1) to 174 (N), which is performed for each group of station-specific data streams , is generally identical to the superposition constellation mapping operation 136 described above with respect to the SISO environment.

A stream-specific preamble (eg, preamble 701) may be added to each (1)-(M) symbol stream to form frames 700(1)-700(M), each including respective attribute information 135 constellations for the stream. Each symbol stream (1) - (M) can then be processed in a manner consistent with known MIMO transmitter operations. For example, each stream may be subjected to a respective cyclic shift delay (CSD) operation followed by a spatial mapping operation 178 and then an OFDM modulation operation 180. The resulting M baseband streams are upconverted to their assigned spatial stream frequency and transmitted to the AP 104.

In other embodiments, different operations may be performed. For example, low density parity check (LDPC) code protocols may be used in exemplary embodiments, in which case the encoding and interleaving operations 162 may be replaced by parsing the output of the LDPC encoder into M streams.

At the receiving station (eg, STA1), each of the M streams may be separated using known MIMO detection techniques, and then each individual stream may be processed in a manner similar to that discussed above with reference to FIG. 15, except that in some examples the individual bit streams of data may be joined again before FEC decoding, and FEC decoder operation 158 is performed on the combined stream.

On figa and 17B show exemplary devices that allow you to implement the methods and ideas according to the present disclosure. In particular, FIG. 17A shows an example of an STA 1310, and FIG. 17B shows an example of an AP 1370.

As shown in FIG. 17A, STA 1310 includes at least one processing unit 1400. The processing unit 1400 implements various processing operations of the STA 1310. For example, the processing unit 1400 may perform signal coding, data processing, power control, I/O processing, or any other functions that allow the STA 1310 to operate in the communication system 1300. The processing unit 1400 may also be configured to implement some or all of the functionality and/or embodiments described in more detail above. Each processing unit 1400 includes any suitable processing device or computing device configured to perform one or more operations. Each processing unit 1400 may, for example, include a microprocessor, microcontroller, digital signal processor, programmable logic array, or ASIC.

STA 1310 also includes at least one transceiver 1402. The transceiver 1402 is configured to modulate data or other content for transmission by at least one antenna or network interface controller (NIC) 1404. The transceiver 1402 is also configured to demodulate data or other content received by at least one antenna 1404. Each transceiver 1402 includes any suitable structure for generating signals for wireless or wired transmission and/or processing signals received wirelessly or wired. Each antenna 1404 includes any suitable structure for transmitting and/or receiving wireless or wired communication signals. One or more transceivers 1402 may be used in STA 1310, and one or more antennas 1404 may be used in STA 1310. Although shown as a single functional block, transceiver 1402 may also be implemented using at least one transmitter and at least one separate receiver.

STA 1310 further includes one or more input/output devices 1406 or interfaces (such as a wired Internet interface 1350). I/O devices 1406 provide interaction with the user or other devices on the network. Each input/output device 1406 includes any suitable structure for providing information to or receiving information from a user, such as a speaker, microphone, keyboard, keypad, display, or touch screen, including network interface communication.

In addition, STA 1310 includes at least one memory 1408. Memory 1408 stores instructions and data used, generated, or collected by STA 1310. For example, memory 1408 may store program instructions or modules configured to implement some or all of the functionality and/or the embodiments described above and which are executed by the processing unit(s) 1400. Each memory 1408 includes any suitable one or more volatile and/or nonvolatile storage and retrieval devices. Any suitable type of memory may be used, such as random access memory (RAM), read only memory (ROM), hard disk, optical disk, subscriber identity module (SIM) card, memory card, secure digital (SD) memory card, etc. P.

As shown in FIG. 17B, AP 1370 includes at least one processor 1450, at least one transmitter 1452, at least one receiver 1454, one or more antennas 1456, at least one memory 1458, and one or more input/output devices or interfaces 1466. A transceiver (not shown) may be used instead of transmitter 1452 and receiver 1454. Scheduling block 1453 may be connected to processing block 1450. A scheduling unit 1453 may be included in or separate from the AP 1370. The processing unit 1450 implements various processing operations of the AP 1370 such as signal coding, data processing, power control, and I/O processing, or any other functions. Processing unit 1450 may also be configured to implement some or all of the functionality and/or embodiments described in more detail above. Each processing unit 1450 includes any suitable processing device or computing device configured to perform one or more operations. Each processing unit 1450 may, for example, include a microprocessor, microcontroller, digital signal processor, programmable logic array, or ASIC.

Each transmitter 1452 includes any suitable structure for generating signals for wireless or wired transmission to one or more STAs or other devices. Each receiver 1454 includes any suitable structure for processing signals received wirelessly or wired from one or more STAs or other devices. Although the components are shown as separate, at least one transmitter 1452 and at least one receiver 1454 may be combined into a transceiver. Each antenna 1456 includes any suitable structure for transmitting and/or receiving wireless or wired communication signals. Although a common antenna 1456 is shown herein as being connected to both transmitter 1452 and receiver 1454, one or more antennas 1456 may be connected to transmitter(s) 1452 and one or more separate antennas 1456 may be connected to receiver(s). 1454. Each memory 1458 includes any suitable one or more volatile and/or nonvolatile storage and retrieval devices, such as those described above in relation to STA 1310. Memory 1458 stores instructions and data used, created, or collected by AP 1370 For example, memory 1458 may store program instructions or modules configured to implement some or all of the functionality and/or embodiments described above and executed by processing unit(s) 1450.

Each I/O device 1466 allows interaction with the user or other devices on the network. Each input/output device 1466 includes any suitable structure for providing information or receiving/providing information from a user, including a network communication interface.

Those skilled in the art can easily understand various modifications of the embodiments described herein, and the general principles of the methods and apparatuses described herein can be applied to other embodiments. Thus, the present disclosure is not intended to limit the embodiments shown herein and is to be kept to the broadest scope consistent with the principles and new features disclosed herein. In the described embodiments, certain adaptations and modifications can be made. Therefore, the embodiments discussed above are considered illustrative and not restrictive.

Claims (70)

1. The method of power distribution implemented by the network node, containing the steps at which: determining a power distribution factor from a plurality of possible power distribution factors; allocate, based on the power sharing factor, energy between the first and second constituent constellations aligned to form a quadrature amplitude modulation (QAM) constellation, wherein the QAM constellation includes a subconstellation of symbols in each of the four quadrants, and increasing the power sharing factor increases the distances between symbols within each sub-constellation and reduces the distances between sub-constellations; mapping the first data and the second data to a QAM constellation symbol, the first data being mapped to the first subsymbol of the symbol corresponding to the first composite constellation, and the second data being mapped to the second subsymbol of the symbol corresponding to the second composite constellation; and transmitting the constellation symbol in the frame as a radio frequency (RF) signal. 2. The power distribution method of claim 1, wherein increasing the power sharing factor results in an increase in energy allocated to the first constituent constellation by an amount proportional to a decrease in energy allocated to the second constituent constellation. 3. The power distribution method according to claim 1 or 2, wherein the power distribution factor represents the average power of each symbol in the QAM constellation. 4. The power distribution method according to any one of claims 1 to 3, wherein the QAM constellation is a 16-QAM constellation representing 16 possible 4-bit symbols (b ₀ b ₁ b ₂ b ₃ ), each 4-bit symbol (b ₀ b ₁ b ₂ b ₃ ) represents bits and has the relative coordinates of the in-phase (I) and quadrature (Q) axes, represented as follows: SYMBOL
(b ₀ b ₁ b ₂ b ₃ ) COORDINATES
I+jQ 0000

0001

0010

0011

0100

0101

0110

0111

1000

1001

1010

1011

1100

1101

1110

1111

where: α – power distribution coefficient, 0 < α <1,

, and

. 5. The power allocation method according to claim 4, wherein the first sub-symbol contains bits b ₀ and b _{2 of} the symbol b ₀ b ₁ b ₂ b ₃ , and the second sub-symbol contains bits b ₁ and b _{3 of} the symbol b ₀ b ₁ b ₂ b ₃ . 6. The power distribution method according to claim 4, wherein one of the plurality of possible power distribution factors is α = 0.2. 7. The power distribution method according to any one of claims 1 to 6, wherein the QAM constellation is a 64-QAM constellation representing 64 possible 6-bit symbols (b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ ), each of 6-bit symbols (b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ ) has a relative in-phase (I) axis coordinate selected from the set (

), and the relative coordinate of the quadrature (Q) axis, selected from the set (

) where: α – power distribution coefficient, 0 < α <1,

,

,

8. The power distribution method according to claim 7, wherein one of the plurality of possible power distribution factors is α = 0.2381. 9. The power allocation method according to claim 7, wherein the first sub-symbol contains bits b ₀ , b ₂ and b _{4 of} the symbol b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ and the second sub-symbol contains bits b ₁ , b ₃ and b ₅ characters b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ . 10. The power distribution method according to any one of claims 1 to 9, wherein the QAM constellation is a 256-QAM constellation representing 256 possible 6-bit symbols (b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ b ₆ b ₇ ), with each of the symbols in the first quadrant of the 256-QAM constellation having a relative in-phase (I) axis coordinate selected from the set (

), and the relative coordinate of the quadrature (Q) axis, selected from the set (

). α is the power sharing factor, 0 < α < 1,

,

,

11. The power distribution method according to claim 10, wherein one of the plurality of possible power distribution factors is α = 0.247. 12. The power distribution method according to any one of claims 1 to 11, wherein the frame includes a multi-bit field, the method further comprising filling the multi-bit field with an index value representing a power distribution factor. 13. Access point (AP), containing: memory; wireless communication interface; and a processing device configured to execute instructions stored in memory causing the AP to be executed: determining a power sharing factor from a plurality of possible power sharing factors; distributing, based on the power sharing factor, energy between the first and second constituent constellations aligned to form a quadrature amplitude modulation (QAM) constellation, wherein the QAM constellation includes a subconstellation of symbols in each of the four quadrants, with increasing power sharing factor increasing distances between symbols within each sub-constellation and reduces the distances between sub-constellations; mapping first data and second data to a QAM constellation symbol, the first data being mapped to a first symbol subsymbol corresponding to the first composite constellation and the second data being mapped to a second symbol subsymbol corresponding to the second composite constellation; and transmitting the constellation symbol in the frame as a radio frequency (RF) signal using the interface. 14. The AP of claim 13, wherein an increase in the power sharing factor results in an increase in the energy allocated to the first constituent constellation by an amount proportional to a decrease in the energy allocated to the second constituent constellation. 15. The AP according to any one of claims 13, 14, wherein the QAM constellation is a 16-QAM constellation representing 16 possible 4-bit symbols (b ₀ b ₁ b ₂ b ₃ ), each 4-bit symbol (b ₀ b ₁ b ₂ b ₃ ) represents bits and has the relative coordinates of the in-phase (I) and quadrature (Q) axes, represented as follows: SYMBOL
(b ₀ b ₁ b ₂ b ₃ ) COORDINATES
I+jQ 0000

0001

0010

0011

0100

0101

0110

0111

1000

1001

1010

1011

1100

1101

1110

1111

where: α – power distribution coefficient, 0 < α <1,

, and

. 16. The AP of claim 15, wherein the first sub-symbol contains bits b ₀ and b _{2 of} b ₀ b ₁ b ₂ b ₃ and the second sub-symbol contains bits b ₁ and b _{3 of} symbol b ₀ b ₁ b ₂ b ₃ . 17. The AP of claim 15, wherein one of the many possible power distribution factors is α = 0.2. 18. An AP according to any one of claims 13-17, wherein the QAM constellation is a 64-QAM constellation representing 64-QAM representing 64 possible 6-bit symbols (b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ ) , and each of the 6-bit symbols (b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ ) has a relative in-phase (I) axis coordinate selected from the set (

), and the relative coordinate of the quadrature (Q) axis, selected from the set (

) where: α – power distribution coefficient, 0 < α <1,

,

,

19. The AP of claim 18, wherein one of the many possible power distribution factors is α = 0.2381. 20. The AP of any one of claims 13-19, wherein the QAM constellation is a 256-QAM constellation representing 256-QAM representing 256 possible 6-bit symbols (b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ b ₆ b ₇ ), with each of the symbols in the first quadrant of the 256-QAM constellation having a relative in-phase (I) axis coordinate selected from the set (

), and a relative quadrature (Q) axis coordinate selected from the set (

), α – power distribution coefficient, 0 < α <1,

,

,

21. The AP of claim 20, wherein one of the many possible power distribution factors is α = 0.247. 22. A method implemented by a station (STA) for receiving an RF signal comprising a frame including a QAM constellation symbol having first data mapped to a first sub-symbol and second data mapped to a second sub-symbol of the symbol, the first sub-symbol corresponding to the first the composite constellation, and the second subsymbol corresponds to the second composite constellation, wherein the frame includes power allocation information identifying the relative energy distribution between the first subsymbol and the second subsymbol, the method comprising: determine, at the STA, a power sharing factor from a plurality of possible power sharing factors based on the frame power allocation information, wherein the QAM constellation includes a subconstellation of symbols in each of the four quadrants, whereby increasing the power sharing factor increases the distances between symbols within each sub-constellation and reduces the distances between sub-constellations; decoding the symbol to recover at least one of the first and second sub-symbols based on the power distribution factor. 23. Station (STA) for an access point (AP), comprising: memory; wireless communication interface; and a processing device configured to execute instructions stored in memory causing the execution of the STA: receiving, via the RF interface, a signal comprising a frame including a QAM constellation symbol having first data mapped to a first sub-symbol and second data mapped to a second symbol sub-symbol, the first sub-symbol corresponding to the first composite constellation and the second sub-symbol corresponding to a second composite constellation, the frame including power allocation information identifying a relative power distribution between the first sub-symbol and the second sub-symbol; determining a power sharing factor from a plurality of possible power sharing factors, wherein the QAM constellation includes a sub-constellation of symbols in each of the four quadrants, wherein increasing the power sharing factor increases the distances between symbols within each sub-constellation and decreases the distances between sub-constellations; and decoding the symbol to recover at least one of the first and second sub-symbols based on the power distribution factor.

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