CN108471393B

CN108471393B - Double-subcarrier modulation method and wireless station

Info

Publication number: CN108471393B
Application number: CN201810106460.0A
Authority: CN
Inventors: 盖瑞安威尔; 刘剑函; 伍天宇; 皮尔二世汤姆士艾德华
Original assignee: MediaTek Inc
Current assignee: MediaTek Inc
Priority date: 2017-02-02
Filing date: 2018-02-02
Publication date: 2021-10-15
Anticipated expiration: 2038-02-02
Also published as: TWI653862B; CN108471393A; TW201830937A

Abstract

The invention discloses a double-subcarrier modulation method and a wireless station. The dual subcarrier modulation method introduces dual subcarrier modulation DCM in the high-efficiency WLAN. DCM is a solution to handle narrowband interference and range extension. The DCM may introduce frequency diversity into the OFDM system by transmitting the same information on two subcarriers separated in the frequency domain. If DCM is applied, the transmitter modulates the same coded bits onto two frequency-domain separated subcarriers with the same or different constellation mapping schemes. DCM suffers from a higher peak-to-average power ratio PAPR. According to one aspect, a method of transmitting and encoding a HE PPDU frame with a lower PAPR and a dual subcarrier modulation DCM of binary phase shift keying BPSK is presented. By the mode, the invention can expand the range of outdoor scenes and solve the problem of narrow-band interference.

Description

Double-subcarrier modulation method and wireless station

Technical Field

The present invention relates to the field of wireless network communications, and more particularly, to reducing dual subcarrier modulation (DCM) and peak-to-average power ratio (PAPR) in a wireless communication system.

Background

IEEE 802.11 is a set of specifications for Medium Access Control (MAC) and physical layer (PHY) for Wireless Local Area Network (WLAN) communications in Wi-Fi (2.4, 3.6, 5, and 60GHz) bands. The 802.11 family includes a family of half-duplex transmission wireless modulation techniques that use the same basic protocol. Standards and revisions provide a basis for wireless network products that use the Wi-Fi band. For example, IEEE 802.11ac is a wireless networking standard in the IEEE 802.11 family that provides high throughput WLAN over the 5G band. Significantly wider channel bandwidths (20MHz, 40MHz, 80MHz and 160MHz) are proposed in the IEEE 802.11ac standard. The High Efficiency WLAN group (HEW SG) is one of the IEEE 802.11 working groups, and the IEEE 802.11 working group considers improving the spectrum Efficiency to improve the system throughput of the wireless device in a High density scenario. Due to the HEW SG, TGax (an IEEE task group) holds and is responsible for studying the IEEE 802.11ax standard, which will become the successor standard to IEEE 802.11 ac. Recently, the demand for WLANs has grown exponentially in organizations in many industries.

Orthogonal Frequency Division Multiple Access (OFDMA) is introduced in HE WLAN to allow Multiple users to simultaneously perform data transmission by allocating subsets of subcarriers to different users, thereby improving user experience. In OFDMA, each user is allocated a set of subcarriers called Resource Units (RUs). In HE WLAN, a wireless Station (STA) can transmit a minimum size RU (which is about 2MHz bandwidth) in uplink and downlink OFDMA. The power density of the data portion is 9dB higher than that of the preamble portion, compared to its 20MHz preamble. Such a narrowband uplink OFDMA signal is difficult to detect by CCA (Clear Channel Assessment) because the CCA operates over a bandwidth greater than or equal to 20 MHz. Thus, one STA may experience 9dB more interference on a particular narrowband subcarrier than other subcarriers. It can be seen that narrowband interference is inherent in HE WLANs. A scheme capable of handling such narrowband interference is required.

In a Multi-User (MU) transmission, HE-SIG-B is encoded within 1x symbol (symbol) duration. As a result, when the same Modulation and Coding Scheme (MCS) is used, its performance is worse than that of data symbols having a 4x symbol duration (symbol). HE-SIG-B requires a more stable modulation scheme. Furthermore, to extend the range of outdoor scenarios, a new modulation scheme with a lower SNR than MCS0 is desired.

Dual Sub-Carrier Modulation (DCM) modulates the same information on a pair of subcarriers. DCM may introduce frequency diversity into an OFDM system by transmitting the same information on two subcarriers separated by the frequency domain. DCM can be implemented with low complexity and provides better performance than modulation schemes used in current WLANs. DCM enhances transmission reliability, especially under narrowband interference. The Data field of the HE PPDU (Protocol Data Unit) may be encoded using a Binary Convolutional Code (BCC) or a low-density parity check (LDPC) code. The encoder is selected by a coding field in the HE-SIG-A of the HE PPDU.

While DCM has a significant improvement in diversity in multipath fading channels, it suffers from a high peak-to-average power ratio (PAPR). A solution is sought to reduce PAPR in DCM.

Disclosure of Invention

The invention mainly solves the technical problem of providing a low peak-to-average power ratio dual-subcarrier modulation method and a wireless station, and can solve the problem of narrow-band interference.

One aspect of the present invention provides a dual subcarrier modulation method, which includes: coding data information which is sent to a target site by a source site through a resource unit in an orthogonal frequency division multiplexing wireless local area network; modulating the encoded bit stream into a first set of modulation symbols using a first binary phase shift keying modulation scheme, wherein the first set of modulation symbols are mapped onto subcarriers of a first portion of the resource elements; if dual subcarrier modulation is employed, modulating the same encoded bit stream into a second set of modulation symbols using a second binary phase shift keying modulation scheme, wherein the second set of modulation symbols are mapped onto subcarriers of a second portion of the resource elements; and transmitting a data packet containing the first set of modulation symbols and/or the second set of modulation symbols to the destination station.

One aspect of the present invention provides a wireless station, comprising: the encoder is used for encoding data information which is transmitted to a target site by a source site through a resource unit in the orthogonal frequency division multiplexing wireless local area network; a modulator to modulate the encoded bit stream into a first set of modulation symbols using a first binary phase shift keying modulation scheme, wherein the first set of modulation symbols are mapped onto subcarriers of a first portion of the resource elements; if dual subcarrier modulation is employed, the modulator modulates the same encoded bit stream into a second set of modulation symbols using a second binary phase shift keying modulation scheme, wherein the second set of modulation symbols are mapped onto subcarriers of a second portion of the resource units; and a transmitter for transmitting a data packet comprising the first set of modulation symbols and/or the second set of modulation symbols to the destination station.

Wherein the first portion of the resource unit is a first half-band of the resource unit; the second part of the resource unit is a second half-band of the resource unit, wherein the first half-band of the resource unit is one of an upper half-band of the resource unit and a lower half-band of the resource unit; the second half band of the resource unit is the other of the upper half band of the resource unit and the lower half band of the resource unit.

Dual sub-carrier modulation (DCM) is introduced in a High Efficiency (HE) WLAN. DCM is a solution to handle narrowband interference and range extension. The DCM may introduce frequency diversity into the OFDM system by transmitting the same information on two subcarriers separated in the frequency domain. If DCM is applied, the transmitter modulates the same coded bits onto two frequency-domain separated subcarriers using the same or different constellation mapping schemes. DCM is affected by a high peak-to-average power ratio (PAPR). According to one aspect, a method of transmitting and encoding a HE PPDU frame using a Binary Phase Shift Keying (BPSK) DCM and a lower PAPR is proposed. In one embodiment, a first BPSK modulation scheme is used to map the coded bits in the data packet onto the subcarriers of the lower half band; the second BPSK modulation scheme is used to map the same coded bits in the data packet onto the upper half band of subcarriers at frequencies higher or lower than the lower half band of subcarriers. The first and second BPSK modulation schemes are designed to achieve low PAPR. In one example, the first set of modulation symbols consists of s_nRepresenting a second set of modulation symbols by s_mWherein n and m are subcarriersWave index, and s_m＝s_n*e^j*(pi)*m。

In one embodiment, a wireless source station encodes data information to be transmitted from the source station to a destination station in an Orthogonal Frequency Division Multiplexing (OFDM) wireless local area network via Resource Units (RUs). The source station modulates the encoded bit stream into a first set of modulation symbols using a first BPSK modulation scheme, wherein the first set of modulation symbols is mapped onto subcarriers of a first half-band of the RU, wherein the first half-band of the RU may be one of an upper half-band of the RU and a lower half-band of the RU. If dual subcarrier modulation (DCM) is applied, the source station modulates the same encoded bit stream into a second set of modulation symbols using a second BPSK modulation scheme, where the second set of modulation symbols is mapped onto subcarriers of a second half-band of the RU, where the second half-band of the RU may be the other of the upper half-band of the RU and the lower half-band of the RU. The source station transmits a data packet containing the first set of modulation symbols and/or the second set of modulation symbols to the destination station.

According to the invention, the coding bits in the data packet are mapped to the first part of frequency subcarriers of the resource unit by using the first BPSK modulation scheme, the same coding bits in the data packet are mapped to the second part of frequency subcarriers of the resource unit by using the second BPSK modulation scheme, namely the same coding bits are mapped to different subcarriers, so that in the case of narrow-band interference, signals on the subcarriers with better SNR can be selected for subsequent calculation and processing, and therefore, the problem of narrow-band interference can be effectively solved.

Other embodiments and advantages are described in the detailed description below. This summary is not intended to be limiting. The invention is defined by the claims.

Drawings

Fig. 1 is a block diagram of a wireless communication system and a high efficiency HE PPDU frame structure supporting DCM transmission with reduced PAPR according to an aspect;

fig. 2 is a simplified block diagram of a wireless device according to an aspect;

fig. 3 is a simplified schematic diagram of a transmission apparatus applying Dual Carrier Modulation (DCM) according to an aspect;

fig. 4 is an example of a BPSK modulation mapping scheme for DCM with reduced peak-to-average power ratio (PAPR);

fig. 5 is an example of a Cumulative Distribution Function (CDF) of PAPR corresponding to different BPSK modulation schemes;

fig. 6 is a simplified schematic diagram of a receiving apparatus applying DCM demodulation and demapping;

fig. 7 is a flow diagram of a method of transmitting and encoding a frame with DCM and reduced PAPR HE PPDU according to an aspect.

Detailed Description

Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

Fig. 1 is a wireless communication system 100 and high efficiency HE PPDU frame structure supporting DCM (dual carrier modulation) transmission with reduced PAPR (peak-to-average power ratio) according to an aspect. The wireless communication network 100 comprises a wireless access point AP101 and a wireless station STA 102. In a wireless communication system, wireless devices communicate with each other through various well-defined frame structures. The frame includes a Physical Layer Convergence Protocol (PLCP) protocol data unit (PPDU), a frame header, and a payload. The frames are in turn divided into very specific and standard parts. In fig. 1, a High Efficiency (HE) PPDU frame 110 is transmitted from an AP101 to an STA 102. The HE PPDU110 includes a conventional short training field (L-STF) 111, a conventional long training field (L-LTF) 112, a conventional signaling field (L-SIG) 113, a repeated conventional signaling field (RL-SIG) 114, a high efficiency signaling A field (HE-SIG-A) 115, a high efficiency signaling B field (HE-SIG-B) 116, a high efficiency short training field (HE-short training field, HE-STF)117, high efficiency long training fields (HE-long training field, HE-LTF)118 and 119 for data, a high efficiency data payload 120, and a Packet Extension (PE) 121.

Orthogonal Frequency Division Multiple Access (OFDMA) is introduced in HE WLAN to enhance user experience by assigning subsets of subcarriers to different users, allowing Multiple users to transmit data simultaneously. In OFDMA, each user is allocated a set of subcarriers called Resource Units (RUs). In HE WLAN, STAs can transmit a minimum size RU (which is about 2MHz bandwidth) in uplink OFDMA. The power density of the data portion is 9dB higher than that of the preamble portion, compared to its 20MHz preamble. This narrowband uplink OFDMA signal is difficult to detect by CCA. Thus, a STA may experience 9dB more interference on a subcarrier on a particular narrowband than other subcarriers. It can be seen that narrowband interference is inherent in HE WLANs. A solution to deal with narrowband interference is therefore needed. Furthermore, robustness in the face of narrowband interference is important for HE WLANs in the case of dense deployments. Enhancing the PER performance of the HE data portion may extend the range of outdoor scenarios. There is a need to propose new modulation schemes for HE data that can operate at lower SNR than that of MCS 0. Similarly, a more robust modulation scheme for HE-SIG-B is needed.

Therefore, dual sub-carrier modulation (DCM) is introduced in HE WLAN. DCM is a perfect solution to deal with narrowband interference. The DCM may introduce frequency diversity in the OFDM system by transmitting the same information on two frequency-domain separated subcarriers. For transmission of a single user, the DCM scheme modulates the same information on a pair of subcarriers n and m, i.e. 0<n<N_SDN and m is_SDN is 2+ N, wherein N_SDIs the total number of subcarriers in a resource unit. For OFDMA transmission, one frequency resource block is allocated to a given user. The DCM scheme for one frequency block is the same as the OFDM scheme for a single user. A DCM indication scheme may be applied which is simple to encode and decode for DCM. As shown in FIG. 1, the HE SIG-A115 or HE SIG-B116 includes an MCS subfield indicating MCS and a DCM bit for indicating whether DCM is applied to a subsequent HE SIG-B116 or a subsequent data payload 120 for the user if DCM is employed and directed toAs shown, the AP101, which is equivalent to the transmitter, modulates the same coded bits (bits) of the HE PPDU110 on two separate subcarriers using different mapping schemes. On the receiver side, the STA102 receives the HE PPDU110, decodes the MCS and DCM indication bits, and performs demodulation and decoding accordingly.

Since many subcarrier components are added by an Inverse Fast Fourier Transformation (IFFT) operation, a transmission signal in an OFDM system may have a high peak in a time domain. As a result, the OFDM system is considered to have a higher peak-to-average power ratio (PAPR) when compared to the single carrier system. When DCM is employed, it suffers from high PAPR, although it has significant diversity improvement over multipath fading channels. According to one aspect, the modulation and mapping scheme of the dual subcarriers in DCM is selected to reduce PAPR.

Fig. 2 is a simplified block diagram of a wireless device 201 and a wireless device 211 according to an aspect. For the wireless device 201 (e.g., a transmitting device), the

antennas

207 and 208 transmit and receive radio signals. An RF transceiver module 206, coupled to the

antennas

207 and 208, receives RF signals from the

antennas

207 and 208, converts them to baseband signals, and sends them to the processor 203. The RF transceiver module 206 also converts a received baseband signal from the processor 203 into an RF signal and transmits it to the

antennas

207 and 208. The processor 203 processes the received baseband signals and invokes different functional blocks and circuits to perform the functions of the wireless device 201. Memory 202 stores program instructions and data 210 to control the operation of wireless device 201.

Similarly, for wireless device 211 (e.g., a receiving device),

antennas

217 and 218 transmit and receive RF signals. An RF transceiver module 216, coupled to the

antennas

217 and 218, receives the RF signals from the

antennas

217 and 218, converts them into baseband signals, and transmits them to the processor 213. The RF transceiver module 216 also converts a received baseband signal from the processor 213, converts it into an RF signal, and transmits it to the

antennas

217 and 218. Processor 213 processes the received baseband signals and invokes different functional blocks and circuits to perform the functions of wireless device 211. Memory 212 stores program instructions and data 220 to control the operation of wireless device 211.

Wireless devices

201 and 211 also include several functional modules and circuits that may be employed and configured to perform embodiments of the present invention. In the example shown in fig. 2, the wireless device 201 is a transmission device that includes an encoder 205, a symbol mapper/modulator 204, and an OFDMA module 209. Wireless device 211 is a receiving device that includes a decoder 215, a symbol demapper/demodulator 214, and an OFDMA module 219. It is noted that one wireless device may be both a transmitting device and a receiving device. The various functional blocks and circuits may be implemented and configured in software, firmware, hardware, or any combination thereof. When executed by processors 203 and 213 (e.g., by executing program code 210 and 220), the functional blocks and circuits enable wireless device 201 for transmission and wireless device 211 for reception to perform embodiments of the present invention.

In one example, on the transmitter side, the wireless apparatus 201 generates an HE PPDU frame and inserts both MCS and DCM indication bits into a signal field of the HE PPDU frame. The wireless device 201 then employs the corresponding MCS and DCM and sends the HE PPDU to the receiver. On the receiver side, wireless device 211 receives the HE PPDU and decodes MCS and DCM indication bits. If the DCM indicator bit is 0, the receiver calculates a log-likelihood ratio (LLR) of the received bit for each subcarrier based on the indicated MCS. On the other hand, if the DCM indication bit is 1, the receiver calculates an LLR by performing a combination of LLRs for subcarriers of the upper half band and subcarriers of the lower half band of the resource unit. Various embodiments of such transmission and reception devices will now be described below in conjunction with the appended drawings.

Fig. 3 is a simplified schematic diagram of a transmission apparatus 300 applying Dual Carrier Modulation (DCM). The encoded and interleaved bits of the RU output by encoder/interleaver 301 are sent to DCM constellation (constellation) mapper 302. The encoder 301 may be an LDPC encoder or a BCC encoder, wherein a BCC interleaver is located before or after the BCC encoder. A DCM constellation (constellation) mapper 302 modulates the same coded bits on two separate subcarriers with possibly different mapping schemes. For example, as shown in fig. 3, subcarrier n and subcarrier m carry the same bit information. The subcarrier n is a subcarrier in a lower half band of the RU and employs a mapping scheme #1, and the subcarrier m is a subcarrier in an upper half band of the RU and employs a mapping scheme #2, wherein the subcarrier in the lower half band is lower in frequency than the subcarrier in the upper half band or higher in frequency than the subcarrier in the upper half band. The modulated signal is then mapped onto the data subcarriers of the RU, and then sent to the IFFT 303 and transmitted. In general, two frequency subcarriers for DCM may be predetermined. For example, to maximize frequency diversity, if N is subcarrier k, then m is subcarrier k + (N/2), where N is the total number of subcarriers in one OFDM symbol (symbol) or RU used for data transmission.

Fig. 4 is an example of a BPSK (binary phase shift keying) modulation mapping scheme for DCM with a reduced peak-to-average power ratio (PAPR). Suppose that the modulated signals of subcarrier n and subcarrier m are respectively s_nAnd s_mAnd (4) showing. For BPSK with DCM, 1-bit coded bit b can be mapped on two same or different BPSK constellations₀To obtain s_nAnd s_m. According to an aspect, the modulated symbol s_nAnd s_mThe 1-bit coding bit b can be mapped by using BPSK mapping scheme #1 and BPSK mapping scheme #2₀To obtain the final product. BPSK scheme #1 and BPSK scheme #2 are selected such that s_m＝±(s_n). For example, the BPSK DCM mapping scheme may be:

s_n＝1-2b₀ (1)

s_m＝(1-2b₀)e^jmπ (2)

in the example shown in fig. 4, the same coded bit stream is modulated by the DCM constellation mapper and mapped onto the sub-carriers of the lower half band and the sub-carriers of the upper half band of resource unit RU 400, respectively, wherein the frequency of the sub-carriers of the upper half band is higher or lower than the frequency of the sub-carriers of the lower half band. Make N_SDIs data in one Resource Unit (RU)The number of subcarriers. For the coded bit stream, when DCM modulation is used, a DCM constellation mapper is employed. For example, the coded bits are modulated into the first half of a complex number and mapped to the data subcarriers [1, 2,. -, N ] of the RU's lower half band_SD/2]. The coded bits are copied and modulated into the second half of the complex number and mapped to the data sub-carriers [ N ] of the RU's upper half band_SD/2+1、N_SD/2+2、...、N_SD]。

In next generation WLAN systems based on the upcoming ieee 802.11ax standard, each Station (STA) may use one or more Resource Units (RUs) to transmit signals. The RU size may be 26, 52, 106, 242, 484, or 996 subcarriers (tones), with a subcarrier spacing of approximately 78.1 kHz. The generated complex numbers will be mapped to data subcarriers of a first half band (which may also be referred to as a first half band) and data subcarriers of a second half band (which may also be referred to as a second half band) of the frequency band of the RU. The first half band of the RU contains subcarriers 1 through N _SD2 and the second half band of the RU contains subcarrier N _SD2 to subcarrier N_SDIn which N is_SDIs the RU size.

According to one aspect, the proposed DCM for BPSK modulation scheme reduces PAPR of data packets to be transmitted. As can be seen from equations (1) and (2), s is dependent on the value of the subcarrier index m_mIs s_nMultiplied by +1 or-1. If m is an even number, then s_m＝s_n(ii) a If m is an odd number, then s_m＝-s_n. By this operation, the PAPR of the OFDM signal is significantly reduced. In general, the PAPR of signal x (t) is defined as:

PAPR＝max[x(t)*conj(x(t))]/E[x(t)*conj(x(t))]

in one example, to calculate the PAPR of a data packet, the following steps are performed: 1) generating random binary data with the length of 4K bytes; 2) data is modulated using an IEEE 802.11ax transmitter to generate a time sequence of complex samples. The time samples are sampled at 20 MHz; 3) the PAPR is the ratio of the maximum sampled power divided by the average power. If the complex sequence is T and is of length N:

pt ═ tconj (T) -power per sample

avgPt ═ sum (pt)/N-average power

max (pt) -max power

PAPR＝maxPt/avgPt

PAPR(dB)＝10*log10(maxPt/avgPt)

Fig. 5 is an example of a Cumulative Distribution Function (CDF) of the PAPR corresponding to different BPSK modulation schemes. Since the PAPR of each packet is different, in the example shown in fig. 5, the PAPR of 10,000 packets is calculated, and CDFs corresponding to the PAPRs of different modulation schemes are plotted. Three different modulation schemes are used. In the first modulation scheme, non-DCM BPSK is used; in the second modulation scheme, BPSK is used with DCM without a specific mapping; in the third modulation scheme, DCM BPSK with the proposed specific mapping is used.

For non-DCM BPSK modulation, the average PAPR is about 7.25dB as shown by the solid curve. For DCM BPSK modulation, the data is copied and modulated without using special mapping, e.g., the same BPSK mapping is used for the subcarriers in the lower half band and the subcarriers in the upper half band. As shown by the dashed-dotted line, the average PAPR is about 8.5dB, which is higher than non-DCM BPSK modulation. For DCM BPSK with the proposed specific mapping, data is modulated on the subcarriers in the lower half band with a first BPSK mapping scheme #1, and then the duplicated data is modulated on the subcarriers in the upper half band with a second BPSK mapping scheme # 2. As shown by the dashed curve, the average PAPR is very close to the PAPR of a non-DCM BPSK modulation scheme.

Fig. 6 is a simplified schematic diagram of a receiving apparatus 600 applying DCM demodulation and demapping. At the receiver, the received signal through FFT 601 can be written as:

r_n＝h_ns_n+v_nsub-carriers of the upper half band

r_m＝h_ms_m+v_mSub-carriers of the lower half-band

Wherein

-h_nAnd h_mIs the channel response matrix for subcarriers n and m

-v_nAnd v_mIs modeled as AWGN (Additive White Gaussian Noise) Noise

If the SNR of the upper half-band subcarriers and the lower half-band subcarriers is considered to be "good," the receiver's demapper/demodulator 602 may calculate the Log Likelihood Ratio (LLR) of the received bits by combining the received signals from the upper half-band subcarriers and the lower half-band subcarriers. Alternatively, the receiver may choose to calculate the LLRs of the received bits from the received signal of the sub-carrier of the upper half band if the SNR of the sub-carrier of the lower half band is considered "bad", and the receiver may choose to calculate the LLRs of the received bits from the received signal of the sub-carrier of the lower half band if the SNR of the sub-carrier of the upper half band is considered "bad". The demodulated signal is then sent to a decoder 603 to output a decoded signal.

Fig. 7 is a flow diagram of a method of transmitting and encoding a PPDU frame with DCM and reduced PAPR HE according to an aspect. In step 701, a wireless source station encodes data information for transmission from the wireless source station to a destination station via Resource Units (RUs) in an Orthogonal Frequency Division Multiplexing (OFDM) wireless local area network. In step 702, the source station modulates the coded bit stream into a first set of modulation symbols using a first Binary Phase Shift Keying (BPSK) modulation scheme, where the first set of modulation symbols is mapped to frequency subcarriers of a first half-band (which may also be referred to as a first half-band) of the RU, where the first half-band may be one of an upper half-band of the RU or a lower half-band of the RU. In step 703, if Dual Carrier Modulation (DCM) is applied, the source station modulates the same coded bit stream into a second set of modulation symbols using a second BPSK modulation scheme, where the second set of modulation symbols is mapped to frequency subcarriers of a second half-band (also referred to as a second half-band) of the RU, where the second half-band may be an upper half-band of the RU or a lower half-band of the RUThe other of them. In step 704, the source station transmits a data packet containing modulation symbols to the destination station. In one example, the first set of modulation symbols consists of s_nRepresenting a second set of modulation symbols by s_mDenotes where n and m are subcarrier indices, and s_m＝s_n*e^j*(pi)*m。

Different from the prior art, the DCM is introduced in the HE WLAN, and the DCM can send the same information on two subcarriers separated by frequency domains. Mapping the coding bits in the data packet to the sub-carriers of the lower half-band by using a first BPSK modulation scheme; the same coded bits in the data packet are mapped onto the subcarriers of the upper half of the frequency by the second BPSK modulation scheme, which can solve the problem of narrowband interference and extend the range of outdoor scenes.

Although the present invention is described in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of the various features of the described embodiments can be performed without departing from the scope of the invention as set forth in the claims.

Claims

1. A dual subcarrier modulation method, comprising:

coding data information which is sent to a target site by a source site through a resource unit in an orthogonal frequency division multiplexing wireless local area network;

modulating the encoded bit stream into a first set of modulation symbols using a first binary phase shift keying modulation scheme, wherein the first set of modulation symbols are mapped onto data subcarriers of a first portion of the resource elements;

if dual subcarrier modulation is employed, modulating the same encoded bit stream into a second set of modulation symbols using a second binary phase shift keying modulation scheme, wherein the second set of modulation symbols are mapped onto data subcarriers of a second portion of the resource elements;

transmitting a data packet containing the first set of modulation symbols and/or the second set of modulation symbols to the destination station;

wherein the first set of modulation symbols consists of s for data subcarrier n_nIndicating that the second set of modulation symbols is represented by s for data subcarrier m_mIs represented by the formula (I) in which s_m＝s_n*e^j*(pi)*mAnd N and m are data subcarrier indexes, wherein the difference between N and m is N/2, and N is the total number of data subcarriers in the resource unit.

2. The dual subcarrier modulation method of claim 1, wherein the first binary phase shift keying modulation scheme and the second binary phase shift keying modulation scheme are selected to achieve a first peak-to-average power ratio.

3. The dual subcarrier modulation method of claim 2, wherein a second peak-to-average power ratio is obtained if non-dual subcarrier modulation is employed, and wherein the second peak-to-average power ratio is substantially the same as the first peak-to-average power ratio.

4. The dual subcarrier modulation method of claim 2, wherein if the first and second binary phase shift keying modulation schemes are the same, a second peak-to-average power ratio is obtained, and the second peak-to-average power ratio is higher than the first peak-to-average power ratio.

5. The dual subcarrier modulation method of claim 1, wherein the encoding comprises: encoding the data information using low density parity check channel control coding;

alternatively, the first and second electrodes may be,

the encoding includes: and encoding the data information by using a binary convolutional code encoder before a binary convolutional code interleaver.

6. The dual subcarrier modulation method of claim 1, wherein the first portion of the resource unit is a first half frequency band of the resource unit; the second part of the resource unit is a second half-band of the resource unit, wherein the first half-band of the resource unit is one of an upper half-band of the resource unit and a lower half-band of the resource unit; the second half band of the resource unit is the other of the upper half band of the resource unit and the lower half band of the resource unit.

7. A wireless station, comprising:

the encoder is used for encoding data information to be sent to a target site by a wireless site through a resource unit in the orthogonal frequency division multiplexing wireless local area network;

a modulator to modulate the encoded bit stream into a first set of modulation symbols using a first binary phase shift keying modulation scheme, wherein the first set of modulation symbols are mapped onto data subcarriers of a first portion of the resource elements;

if dual subcarrier modulation is employed, the modulator modulates the same encoded bit stream into a second set of modulation symbols using a second binary phase shift keying modulation scheme, wherein the second set of modulation symbols are mapped onto data subcarriers of a second portion of the resource units; and

a transmitter for transmitting a data packet comprising the first set of modulation symbols and/or the second set of modulation symbols to the destination station;

8. The wireless station of claim 7, wherein the first and second binary phase shift keying modulation schemes are selected to achieve a first peak-to-average power ratio.

9. A wireless station according to claim 8, characterized in that a second peak-to-average power ratio is obtained if non-dual subcarrier modulation is employed, and that the second peak-to-average power ratio is substantially the same as the first peak-to-average power ratio.

10. The wireless station of claim 8, wherein if the first and second binary phase shift keying modulation schemes are the same, a second peak-to-average power ratio is obtained, and the second peak-to-average power ratio is higher than the first peak-to-average power ratio.

11. The wireless station of claim 7, wherein the encoder comprises a low density parity check channel control encoder for encoding the data information using a low density parity check channel control encoding;

or, the encoder comprises a binary convolutional code encoder before a binary convolutional code interleaver, and the binary convolutional code encoder encodes the data information.

12. The wireless station of claim 7, wherein the first portion of resource units is a first half-band of the resource units; the second part of the resource unit is a second half-band of the resource unit, wherein the first half-band of the resource unit is one of an upper half-band of the resource unit and a lower half-band of the resource unit; the second half band of the resource unit is the other of the upper half band of the resource unit and the lower half band of the resource unit.