WO2019136697A1

WO2019136697A1 - Signal spreading techniques for multiple access in wireless networks

Info

Publication number: WO2019136697A1
Application number: PCT/CN2018/072411
Authority: WO
Inventors: Jianqiang DAI; Zhifeng Yuan
Original assignee: Zte Corporation
Priority date: 2018-01-12
Filing date: 2018-01-12
Publication date: 2019-07-18
Also published as: CN111434073B; CN111434073A

Abstract

A wireless communication method includes modulating, spreading, and scrambling of signals to be transmitted in an Non-Orthogonal Multiple Access (NOMA) environment. The wireless communication method includes modulating bits to obtain symbol blocks. Each symbol block comprises a number of modulated symbols. The method includes spreading the symbol blocks to obtain spread symbol blocks where the number of the spread symbol blocks is an integer multiple of a number of symbol blocks. The method also includes scrambling the spread symbol blocks using a scrambling sequence.

Description

SIGNAL SPREADING TECHNIQUES FOR MULTIPLE ACCESS IN WIRELESS NETWORKS

TECHNICAL FIELD

This disclosure is directed generally to digital wireless communications.

BACKGROUND

Mobile telecommunication technologies are moving the world toward an increasingly connected and networked society. In comparison with the existing wireless networks, next generation systems and wireless communication techniques will need to support a much wider range of use-case characteristics and provide a more complex and sophisticated range of access requirements and flexibilities.

Long-Term Evolution (LTE) is a standard for wireless communication for mobile devices and data terminals developed by 3rd Generation Partnership Project (3GPP) . LTE Advanced (LTE-A) is a wireless communication standard that enhances the LTE standard. The 5th generation of wireless system, known as 5G, further advances the LTE and LTE-A wireless standards and is committed to supporting higher data-rates, large number of connections, ultra-low latency, high reliability and other emerging business needs.

SUMMARY

An exemplary embodiment discloses a wireless communication method. The exemplary method comprising modulating bits to obtain symbol blocks, where each symbol block comprises a number of modulated symbols, spreading the symbol blocks to obtain spread symbol blocks, where a number of the spread symbol blocks is an integer multiple of a number of symbol blocks, and scrambling, using a scrambling sequence, the spread symbol blocks for transmission.

In some embodiments, the number of modulated symbols in each symbol block is one. In an exemplary embodiment, the number of modulated symbols in each symbol block is at least two.

In some embodiments, one or more scrambling sequences is used by user devices located in a same cell region. In some embodiments, a same scrambling sequence is used by user devices located in the same cell region comprising only one group of user devices. In some embodiments, at least one scrambling sequence is used by user devices located in the same cell region comprising more than one group of user devices. In some embodiments, the one or more scrambling sequences are pre-configured according to an identity of a cell region or an identity of a group of user devices.

In an exemplary embodiment, a length of the scrambling sequence is equal to the number of the spread symbol blocks. In some embodiments, the spreading of the symbol blocks is performed using a spreading sequence. In some embodiments, the spreading sequence includes a complex sequence, a Walsh sequence, a Discrete Fourier Transform (DFT) sequence, a Zadoff-Chu (ZC) sequence, a pseudo-noise (PN) sequence, a sequence whose elements are coming from {1+j, 1-j, -1+j, -1-j} , or a sequence whose elements are coming from {1, -1, j, -j} . In some embodiments, the spreading sequence is chosen from a pre-configured spreading sequence set. In some embodiments, the pre-configured spreading sequence set has a minimum mean cross correlation. In some embodiments, the spreading sequence is randomly chosen.

In some embodiments, the spreading of the symbol blocks is performed using more than one spreading sequences.

In another exemplary embodiment, a wireless communication method is disclosed comprising receiving a signal comprising spreaded and scrambled symbol blocks, descrambling, using a descrambling sequence, the scrambled symbol blocks to recover spread symbol blocks, despreading the spread symbol blocks to recover symbol blocks, wherein a number of the spread symbol blocks is an integer multiple of a number of symbol blocks, and generating bits by demodulating symbols from symbol blocks.

In some embodiments, the despreading of the symbol blocks is performed using match filter (MF) , zero forcing (ZF) , or minimum mean square error (MMSE) methods. In some embodiments, only one inversion computation is processed for MMSE despreading or ZF despreading for one user device detection.

In an exemplary embodiment, each symbol block includes one modulated symbol. In some embodiments, each symbol block includes at least two modulated symbols.

In some embodiments, one or more descrambling sequences are used for user devices located in a same cell region. In some embodiments, a same descrambling sequence is used for user devices located in the same cell region comprising only one group of user devices. In some embodiments, at least one descrambling sequence is used for user devices located in the same cell region comprising more than one group of user devices. In some embodiments, a length of the descrambling sequence is equal to the number of the spread symbol blocks.

Another exemplary wireless communication method comprises generating a transmission signal to transmit from a user device in a wireless communication network. The transmission signal includes symbol blocks each including a number of modulated symbols. The transmission signal being a result of a spreading operation so that a number of spread symbol blocks is an integer multiple of a number of the symbol blocks. Further, the transmission signal being a result of a scrambling operation performed on the spread symbol blocks.

In yet another exemplary aspect, the above-described methods are embodied in the form of processor-executable code and stored in a computer-readable program medium.

In yet another exemplary embodiment, a device that is configured or operable to perform the above-described methods is disclosed.

The above and other aspects and their implementations are described in greater detail in the drawings, the descriptions, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows exemplary mobile user devices and base stations operating in a non-orthogonal multiple access (NOMA) wireless network.

FIG. 2A shows an exemplary embodiment of a block diagram implemented at a transmitter-side in a user device using NOMA.

FIGS. 2B-2C illustrate examples of spreading, and scrambling operations implemented by a user device using NOMA.

FIG. 2D shows some examples of a spreading operation.

FIG. 2E-2F show some examples of a scrambling operation.

FIG. 2G illustrates a spreading sequence applied to a modulated symbol block.

FIG. 3 illustrates another embodiment to spread a number of modulated symbols.

FIG. 4 illustrates yet another embodiment to scramble a number of modulated symbols.

FIG. 5 shows an exemplary flowchart that describes the process of modulating, spreading, and scrambling implemented in a transmitter-side in a user device.

FIG. 6 shows an exemplary flowchart that describes the process of demodulating, despreading, and descrambling implemented at a receiver-side in a base station.

FIG. 7 shows a block diagram of a user device 700 implementing the modulation, spreading, and scrambling features.

FIG. 8 shows a block diagram of a base station 800 implementing the demodulation, despreading, and descrambling features.

DETAILED DESCRIPTION

Conventional wireless technology uses techniques such as time division multiple access (TDMA) or orthogonal frequency division multiple access (OFDMA) where a single user can access an orthogonal resource block, such as a time slot or a frequency channel. In contrast, non-orthogonal multiple access (NOMA) is a technology that can be employed in 5G wireless networks to serve more than one user in each orthogonal resource block. While NOMA technology can improve spectrum efficiency, employing NOMA technology can lead to some technical disadvantages. For example, as further illustrated by FIG. 1, multi-user interference can be introduced as a result of NOMA technology.

FIG. 1 shows exemplary mobile user devices and base stations operating in a non-orthogonal multiple access (NOMA) wireless network. Base station BS1 (120a) is in communication with user devices (105a) , (110a) , and (115a) . Similarly, base station BS2 (120b) is in communication with user devices (105b) , (110b) , and (115b) , and base station BS3 (120c) is in communication with user devices (105c) , (110c) , and (115c) . The user devices shown in FIG. 1 can access their respective base stations using either NOMA or conventional wireless technology. As mentioned above, multi-user interference can be introduced as a result of multiple user devices using NOMA for multiple access. A user device operating in an NOMA wireless environment may experience interference from other user devices located in its own cell region or in adjacent cell regions. For example, in FIG. 1, a user device (105a) using non-orthogonal signals for wireless access may experience interference from user devices (110a) , (105b) and (105c) that may also use non-orthogonal signals for wireless access.

Interference experienced by a user device from another user device located in the same cell region can be referred to as intra-cell interference. Further, interference experienced by a user device from another device located in an adjacent cell can be referred to as inter-cell interference. As further explained herein, intra-cell interference and inter-cell interference can be mitigated by using spreading and scrambling functions, respectively. One benefit of using spreading and scrambling functions in a NOMA wireless environment is that existing receivers located in the base stations are designed to perform the de-spreading and unscrambling functions for effective interference suppression. As a result, the base station receivers can support large number of access of user devices.

In an orthogonal multiple access (OMA) system, a user device can transmit a certain number of source bits per second per Hertz for a given modulation type and code rate. For example, a user device in an OMA system can transmit a certain number of bits per resource element. By contrast, in a NOMA system, a user device can transmit a certain number of source bits in a certain number of times per second per Hertz. For example, a user device can transmit a certain number of bits per certain number of times multiplied by the number of resource elements (e.g., x bits / (k *REs) , (where x is the number of bits, k is the number of times greater than 1, and REs are the number of resource elements) ) . In some embodiments, as further illustrated in the paragraphs below, the value for k can be selected from the set that can include 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16. Using a NOMA scheme, for example, it may be possible to transmitting a fractional number (e.g., x/k) number of bits per RE used for transmission.

An exemplary embodiment describes a wireless communication method that generates a transmission signal having exemplary characteristics to transmit from a user device in a wireless communication network. For example, the transmission signal can include symbol blocks where each symbol block includes a number of modulated symbols, the transmission signal can be a result of a spreading operation so that a number of spread symbol blocks is an integer multiple of a number of the symbol blocks, and the transmission signal can be a result of a scrambling operation performed on the spread symbol blocks.

FIG. 2A shows an exemplary embodiment of a block diagram implemented at a transmitter-side in a user device using NOMA. At the modulation block 202, the coded bits are modulated to obtain symbol blocks (202a in FIG. 2A and 202c in FIG. 2C) . In some implementations, the bits can be modulated by a quadrature modulation scheme such as a Quadrature Phase-Shift Keying (QPSK) modulation scheme or a Quadrature Amplitude Modulation (QAM) scheme. Each symbol block comprises a number of modulated symbols. As shown in 202a in FIG. 2A, in some embodiments, the number of modulated symbols in each symbol block can be one or two. As illustrated in 202c in FIG. 2C, in some other embodiments, the number of modulated symbols in each symbol block can include at least two modulated symbols.

In FIG. 2A, at the spreading block 204, the symbol blocks are spread to obtain spread symbol blocks 204a. A user device can use one spreading sequence (further illustrated in FIG. 2D) to spread each modulation symbol 202a. In the illustrated example, one modulation symbols is spread into four symbols. However, different spreading factors may be used. As illustrated in FIG. 2A, spreading changes the number of modulation symbols, while scrambling does not change the number of input symbols (e.g., four spread symbols are scrambled to output four scrambled symbols) . One benefit of the spreading technology described in this document is to multiplex more transmission streams in the same time-frequency. FIG. 2D further illustrates a spreading sequence used by the spreading block 204, and FIG. 2D shows the relationship between the number of spread symbol blocks and the number of symbol blocks.

FIG. 2D shows an example of a spreading function implemented in the spreading block 204 of FIG. 2A. The number of the spread symbol blocks 204d can be an integer multiple of a number of symbol blocks. In some embodiments, the number of spread symbol 204d can be a length of the spreading sequence 208 multiplied by the number of symbol blocks. In some embodiments, the length k of the spreading sequence 208 can be an integer that can be selected from any one of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, and 16. In some embodiments, the spreading sequence can include a complex sequence. For example, a complex sequence may include at least some coefficients that are represented by complex numbers or imaginary numbers (i) .

Returning to FIG. 2A, at the scrambling block 206, a scrambling sequence can be used to scramble the spread symbol blocks for transmission. In some embodiments, as further illustrated in FIG. 2E, the length of the scrambling sequence can be equal to the number of the spread symbol blocks. In such embodiments, if x number of modulation symbols are spread to obtain (k ·x) symbols, then the (k ·x) symbols can be scrambled to obtain the (k ·x) first symbols. A (k ·x) length scrambling sequence can be used to scramble the (k ·x) spread symbols. Accordingly, each symbol block can be scrambled by a corresponding scrambling sequence having the same length. In some implementations, as further shown in FIG. 2F, an element of a (k ·x) length scrambling sequence can be used to scramble one spread symbol block. In some embodiments, the (k ·x) length scrambling sequence can be generated by a cell-specific scrambler. For example, the spreading sequence can also be a pre-defined sequences, and each spreading sequence can be used by one cell region. In this document, the operator “·” indicates a dot multiplication. In some embodiments, as further explained below, one or more scrambling sequences may be used by user devices located in a same cell region. In some embodiments, two user devices located in two adjacent cell regions may use different scrambling sequences. One benefit of the scrambling technology described in this document is to suppress inter-cell interference.

FIGS. 2E-2F show some examples of scrambling functions implemented in the scrambling block 206 of FIG. 2A. In FIG. 2E, the scrambling sequence 206e uses an eight-length scrambling sequence (r1 to r8) to scrambling eight spread symbols (s1 to s8) . In FIG. 2F, an element of a (k ·x) length scrambling sequence 206f can use (r1) to scramble a spread symbol block, the symbol block includes eight spread symbols (s1 to s8) .

An example is provided to further illustrates a user device employing the modulation, spreading, and scrambling operations described in this document. As an example, a user device can use QPSK modulation to modulate twenty coded bits and obtain ten modulation symbols. Each modulation symbol can be spread by, for example, a four-length spreading sequence (k = 4) to obtain 40 symbol. The four-length spreading sequence can be depicted as (c1, c2, c3, c4) . The four-length spreading sequence can include a complex sequence, such as (1, i, 1, i) . In this example, the 40 spread symbols can be scrambled to obtain 40 first scrambled symbols. The k-length scrambling sequence of the whole scrambling sequence can be depicted as (r1, r2, r3, r4) . Accordingly, the first symbol S can be described using the following equation:

S = s1 · (c1, c2, c3, c4) · (r1, r2, r3, r4) or

S = s1 · (r1, r2, r3, r4) · (c1, c2, c3, c4)

where s1 indicates the modulation symbol. The operation s1 · (r1, r2, r3, r4) yields (s1·r1, s1·r 2, s1·r3, s1·r4) . And, the operation (r1, r2, r3, r4) · (c1, c2, c3, c4) yields (r1·c1, r2·c2, r3·c3, r4·c4) . The operation r1·c1 and s1·r1 means multiplication of r1 and c1, and s1 and r1, respectively.

Returning to FIG. 2A, in some embodiments, after the coded bits are modulated in modulation block 202 to obtain symbol blocks, the modulated symbols can be repeated a certain number of times prior to the spreading operation performed by the spreading block 204. Continuing with the example mentioned above, each modulation symbol can be repeated four times so that a total of 40 modulated symbols is obtained. The 40 modulated symbols are spread by a spreading sequence, for example, (c1, c2, c3, c4) . Subsequently, a k-length scrambling sequence, such as (r1, r2, r3, r4) can be used to scramble the spread modulated symbols. In this embodiment, the first symbol S can be described using the following equation:

S = s1· (c1, c2, c3, c4) · (r1, r2, r3, r4) or

S = s1· (r1, r2, r3, r4) · (c1, c2, c3, c4)

At the modulation block 202, the coded bits are modulated to obtain symbol blocks (202a in FIG. 2A and 202c in FIG. 2C) . In some implementations, the bits can be modulated by Quadrature Phase-Shift Keying (QPSK) modulation scheme. Each symbol block comprises a number of modulated symbols.

FIG. 2B illustrates an example of the spreading, and scrambling operations performed on one or more symbols as described in this patent document and as implemented by a user device using NOMA. For example, a four length spreading sequence (c1, c2, c3, c4) is used to spread the four exemplary modulated symbols. A scrambling sequence, such as (r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15, r16) , can be used to scramble the spread symbols and to obtain the first symbols.

FIG. 2C illustrates an example of the spreading, and scrambling operations performed on symbol blocks as described in this patent document and as implemented by a user device using NOMA. The symbol blocks can include, for example, 12 modulated symbols. As shown as an example in FIG. 2C, a four length spreading sequence (c1, c2, c3, c4) is used to spread the four exemplary symbol blocks where each symbol block comprises a number of modulated symbols. A scrambling sequence, such as (r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15, r16) , can be used to scramble the spread symbol blocks and to obtain the first symbols. In the embodiment of FIG. 2C, all modulated symbols in one symbol block can be multiplied with one element of the scrambling sequence. An advantage of performing spreading and scrambling on symbol blocks comprising at least two modulated symbols is that channel equalization and de-spreading can be performed together that better performance can be obtained at the base station receiver end.

FIG. 2G illustrates a spreading sequence applied to a modulated symbol block. In the example shown in FIG. 2G, coded bits are modulated with a QPSK modulation scheme to obtain a modulation symbol block. Each element of the spreading sequence, such as (a1, a2, ..., a4) can be applied to the modulated symbol block to obtain a number of spread symbol blocks. As depicted, each element of the spreading sequence may generate a portion of the spreaded modulation symbol blocks that is contiguous along one of the time-frequency dimensions.

FIG. 3 illustrates another embodiment to spread a number of modulated symbols. The modulation and spreading operations can be performed as described in this patent document to obtain (k ·x) first symbols. The spreading sequence can be a dot product of the spreading sequence and the scrambling sequence. As an example, the exemplary spreading sequence can be described as follows for a k value chosen to be four:

(c1, c2, c3, c4) · (r1, r2, r3, r4)

where the exemplary first symbol S can be described as:

S = s1 · (c1, c2, c3, c4) · (r1, r2, r3, r4)

In some embodiments, dot multiplying using a sequence can be inserted in one place of the physical channel procession. An advantage may be interference suppression, diversity or reliability improvement.

FIG. 4 illustrates yet another embodiment to scramble a number of modulated symbols. In this embodiment, after modulation, a number of modulation symbols can be repeated k times to obtain (k ·x) symbols. Using the scrambling operations described in this patent document, the (k ·x) symbols are scrambled to obtain (k ·x) first symbol. In this embodiment, the exemplary scrambling sequence can be described as follows for a k value chosen to be four:

(c1, c2, c3, c4) · (r1, r2, r3, r4)

where the exemplary first symbol S can be described as:

S = (s1, s1, s1, s1) · (c1, c2, c3, c4) · (r1, r2, r3, r4)

In some embodiments, a user device may use more than one spreading sequences to spread its modulation symbols. However, in some embodiments, the number of the spreading sequences used by a user device may not be larger than eight because of considerations of receiver complexity. Referring back to FIG. 2A, coded bits can be modulated to obtain symbol blocks comprising a number of modulated symbols. The number of modulated symbols can be spread to obtain (k ·x) symbols. The (k ·x) symbols can be spread using more than one spreading sequence. As an example, a first set of modulated symbols can be spread using a first spreading sequence, and a second set of modulated symbols can be spread using a second spreading sequence. As a further example, the first spreading sequence can be used to spread the first half of modulated symbols and the second spreading sequence can be used to spread the second half of modulated symbols.

Subsequently, a scrambling function can be performed on the spread symbol blocks comprising symbol blocks spread using the first and second spreading sequence. A (k ·x) length scrambling sequence can be used to scramble the (k ·x) symbols. Each k-length symbol can be scrambled by a corresponding k-length scrambling sequences.

In some embodiments, a number of source bits are coded with a low code rate, or a number of first coded bits are repeated k times to obtain the coded bits. After coding or repetition, a number of coded bits are modulated to obtain (k ·x) modulation symbols . Using the scrambling operations described in this patent document, the (k ·x) symbols are scrambled to obtain (k ·x) first symbol. In this embodiment, the exemplary scrambling sequence can be described as follows for a k value that can be chosen to be four:

(c1, c2, c3, c4) · (r1, r2, r3, r4)

where the exemplary first symbol S can be described as:

S = (s1, s1, s1, s1) · (c1, c2, c3, c4) · (r1, r2, r3, r4)

In some embodiments, a number of source bits are coded with a low code rate, or a number of first coded bits are repeated k times to obtain the coded bits. After coding or repetition, a number of coded bits are scrambled using techniques described in this patent document to obtain a number of scrambled bits, then the scrambled bits are modulated to obtain (k ·x) first symbol.

In some embodiments, a number of source bits are coded with a low code rate, or a number of first coded bits are repeated k times or with inserted blanks to obtain the coded bits. After coding or repetition or inserting blanks, a number of coded bits are modulated to obtain (k ·x) modulation symbols . A number of modulation symbols are interleaved to obtain (k ·x) interleaved symbol. Using the scrambling techniques described in this patent document, the (k ·x) symbols can be scrambled to obtain (k ·x) first symbol. In some embodiments, coded bits can be modulated by a Binary Phase-Shift Keying (BPSK) modulation scheme.

In some embodiments, one or more scrambling sequence can be used by user devices located in a same cell region. In this embodiment, the scrambling sequence can be pre-configured according to an identity of a cell, or an identity of a group, or both the identity of a cell and the identity of a group. A group may include one or more user devices. Further, a cell region may include one or more group of user devices. In some embodiments, a same scrambling sequence may be used by user devices located in the same cell region if the cell region contains just one group of user devices. In some embodiments, if a cell region includes more than one group of user devices, then at least one scrambling sequence can be used by user devices located in a same cell region.

In some embodiments, the spreading sequence can be chosen from a pre-configured spreading sequence set. In some embodiments, it can be advantageous to design spreading sequences within the pre-configured spreading sequence set to have a reduced mean cross correlation between different sequences, e.g., a minimum mean cross correlation. In some embodiments, if the number of active user devices is known in advance, a set of spreading sequences whose mean cross correlation is minimum can be configured for the group of user devices. However, if the number of active user devices is not known in advance, a set of spreading sequence set can be configured for all user devices in the cell, and each user device can randomly choose a spreading sequence. In some implementations, the spreading sequence can include a complex sequence, or a Walsh sequence, or a Discrete Fourier Transform (DFT) sequence, or a Zadoff-Chu (ZC) sequence, or a pseudo-noise (PN) sequence, or a sequence whose elements are coming from {1+j, 1-j, -1+j, -1-j} , or a sequence whose elements are coming from {1, -1, j, -j} .

FIG. 5 shows an exemplary flowchart of a wireless communication process implemented in a user device. The process may be used for generating wireless transmission signals for transmission. At the modulating operation 502, bits are modulated to obtain symbol blocks. In some embodiments, each symbol block comprises a number of modulated symbols. At the spreading operation 504, the symbol blocks are spread to obtain spread symbol blocks. A number of the spread symbol blocks can be an integer multiple of a number of symbol blocks. At the scrambling operation 506, a scrambling sequence can be used to scramble the spread symbol blocks for transmission. Various embodiments that use the spreading and the scrambling operations described with reference to FIG. 2A to FIG. 2G, FIG. 3 and FIG. 4 may be used in this process. In some embodiments, a user device may perform the scrambling and spreading operations in one step and may use, for example, a lookup table or a circuit that can implement the final scrambled spreaded signal.

FIG. 6 shows an exemplary flowchart that describes the process of demodulating, despreading, and descrambling implemented at a receiver-side, e.g., in a base station’s receiver function. At the receiving operation 602, a signal is received comprising spreaded and scrambled symbol blocks. At the descrambling operation 604, a descrambling sequence is used to descramble the scrambled symbol blocks to recover spread symbol blocks. A base station may use one or more descrambling sequences for user devices located in a same cell region. In some implementations, a same descrambling sequence may be used for user devices located in the same cell region comprising only one group of user devices. Further, in some implementations, at least one descrambling sequence can be used for user devices located in the same cell region comprising more than one group of user devices. In some embodiments, a length of the descrambling sequence can be equal to the number of the spread symbol blocks. At the despreading operation 606, the spread symbol blocks are despread to recover symbol blocks. In some implementations, the despreading of the symbol blocks can be performed using match filter (MF) , zero forcing (ZF) , or minimum mean square error (MMSE) methods. Further, for MMSE despreading or ZF despreading, only one inversion computation can be processed for one user device detection. If more spreading sequences are used by a user device, then more inversion computation would be processed for MMSE despreading or ZF despreading for one user device detection. In some embodiments, a number of the spread symbol blocks can be an integer multiple of a number of symbol blocks. At the generating operation 608, bits can be generated by demodulating symbols from symbol blocks. Various embodiments that use the despreading and the descrambling operations described with reference to FIG. 2A to FIG. 2G, FIG. 3 and FIG. 4 may be used in this process.

FIG. 7 shows a block diagram of a user device 700 implementing the modulation, spreading, and scrambling features. The user device includes one or more processors 710 that can reads code from the memory 705, and perform operations associated with the other blocks of the user device 700. The user device includes a transmitter 715 that can transmit a NOMA or a conventional orthogonal access signal. The user device also includes a receiver 720 that can receive signals from the base station. The user device includes a modulator 725 that can modulate bits using, for example, QPSK modulation. The module for spreading 730 spreads the modulated bits to obtain spread bits, as described in this patent document. The module for scrambling 735 can use a scrambling sequence to scramble the spread bits, as described in this patent document.

FIG. 8 shows a block diagram of a base station 800 implementing the demodulation, despreading, and descrambling features. The base station 800 includes one or more processors 810 that can reads code from the memory 805, and perform operations associated with the other blocks of the base station 800. The base station includes a transmitter 815 that can transmit signals to one or more user devices. The base station also includes a receiver 820 that can receive NOMA or conventional orthogonal signals from one or more user devices. The module for descrambling 835 can use a descrambling sequence to descramble the scrambled symbol blocks to obtain spread symbol blocks, as described in this patent document. The module for despreading 830 despreads the spread symbol blocks to obtain symbol blocks, as described in this patent document. The base station also includes a demodulator 835 that can demodulate symbols from the symbol block.

The term “exemplary” is used to mean “an example of” and, unless otherwise stated, does not imply an ideal or a preferred embodiment.

Some of the embodiments described herein are described in the general context of methods or processes, which may be implemented in one embodiment by a computer program product, embodied in a computer-readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. A computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM) , Random Access Memory (RAM) , compact discs (CDs) , digital versatile discs (DVD) , etc. Therefore, the computer-readable media can include a non-transitory storage media. Generally, program modules may include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Computer-or processor-executable instructions, associated data structures, and program modules represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes.

Some of the disclosed embodiments, modules and blocks can be implemented as devices or modules using hardware circuits, software, or combinations thereof. For example, a hardware circuit implementation can include discrete analog and/or digital components that are, for example, integrated as part of a printed circuit board. Alternatively, or additionally, the disclosed components or modules can be implemented as an Application Specific Integrated Circuit (ASIC) and/or as a Field Programmable Gate Array (FPGA) device. Some implementations may additionally or alternatively include a digital signal processor (DSP) that is a specialized microprocessor with an architecture optimized for the operational needs of digital signal processing associated with the disclosed functionalities of this application. Similarly, the various components or sub-components within each module may be implemented in software, hardware or firmware. The connectivity between the modules and/or components within the modules may be provided using any one of the connectivity methods and media that is known in the art, including, but not limited to, communications over the Internet, wired, or wireless networks using the appropriate protocols.

While this document contains many specifics, these should not be construed as limitations on the scope of an invention that is claimed or of what may be claimed, but rather as descriptions of features specific to particular embodiments. Certain features that are described in this document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or a variation of a sub-combination. Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results.

Only a few implementations and examples are described and other implementations, enhancements and variations can be made based on what is described and illustrated in this disclosure.

Claims

A wireless communication method, comprising:

modulating bits to obtain symbol blocks, wherein each symbol block comprises a number of modulated symbols;

spreading the symbol blocks to obtain spread symbol blocks, wherein a number of the spread symbol blocks is an integer multiple of a number of symbol blocks; and

scrambling, using a scrambling sequence, the spread symbol blocks for transmission.
The wireless communication method of claim 1, wherein the number of modulated symbols in each symbol block is one.
The wireless communication method of claim 1, wherein the number of modulated symbols in each symbol block is at least two.
The wireless communication method of claim 1, wherein one or more scrambling sequences is used by user devices located in a same cell region.
The wireless communication method of claim 1, wherein a same scrambling sequence is used by user devices located in the same cell region comprising only one group of user devices.
The wireless communication method of claim 1, wherein at least one scrambling sequence is used by user devices located in the same cell region comprising more than one group of user devices.
The wireless communication method of claim 4, wherein the one or more scrambling sequences are pre-configured according to an identity of a cell region or an identity of a group of user devices.
The wireless communication method of claim 1, wherein a length of the scrambling sequence is equal to the number of the spread symbol blocks.
The wireless communication method of claim 1, wherein the spreading of the symbol blocks is performed using a spreading sequence.
The wireless communication method of claim 9, wherein the spreading sequence includes a complex sequence, a Walsh sequence, a Discrete Fourier Transform (DFT) sequence, a Zadoff-Chu (ZC) sequence, a pseudo-noise (PN) sequence, a sequence whose elements are coming from {1+j, 1-j, -1+j, -1-j} , or a sequence whose elements are coming from {1, -1, j, -j} .
The wireless communication method of claim 9, wherein the spreading sequence is chosen from a pre-configured spreading sequence set.
The wireless communication method of claim 11, wherein the pre-configured spreading sequence set has a minimum mean cross correlation.
The wireless communication method of claim 11, wherein the spreading sequence is randomly chosen.
The wireless communication method of claim 1, wherein the spreading of the symbol blocks is performed using more than one spreading sequences.
A wireless communication method, comprising:

receiving a signal comprising spreaded and scrambled symbol blocks;

descrambling, using a descrambling sequence, the scrambled symbol blocks to recover spread symbol blocks;

despreading the spread symbol blocks to recover symbol blocks, wherein a number of the spread symbol blocks is an integer multiple of a number of symbol blocks; and

generating bits by demodulating symbols from symbol blocks.
The wireless communication method of claim 15, wherein the despreading of the symbol blocks is performed using match filter (MF) , zero forcing (ZF) , or minimum mean square error (MMSE) methods.
The wireless communication method of claim 16, wherein only one inversion computation is processed for MMSE despreading or ZF despreading for one user device detection.
The wireless communication method of claim 15, wherein each symbol block includes one modulated symbol.
The wireless communication method of claim 15, wherein each symbol block includes at least two modulated symbols.
The wireless communication method of claim 15, wherein one or more descrambling sequences are used for user devices located in a same cell region.
The wireless communication method of claim 15, wherein a same descrambling sequence is used for user devices located in the same cell region comprising only one group of user devices.
The wireless communication method of claim 15, wherein at least one descrambling sequence is used for user devices located in the same cell region comprising more than one group of user devices.
The wireless communication method of claim 15, wherein a length of the descrambling sequence is equal to the number of the spread symbol blocks.
A wireless communication method, comprising:

generating a transmission signal to transmit from a user device in a wireless communication network, wherein

the transmission signal includes symbol blocks each including a number of modulated symbols,

the transmission signal being a result of a spreading operation so that a number of spread symbol blocks is an integer multiple of a number of the symbol blocks, and

the transmission signal being a result of a scrambling operation performed on the spread symbol blocks.
An apparatus for wireless communication, comprising a memory and a processor, wherein the processor reads code from the memory and implements a method recited in any of claims 1 to 14 or 24.
A computer readable program storage medium having code stored thereon, the code, when executed by a processor, causing the processor to implement a method recited in any of claims 1 to 14 or 24.
An apparatus for wireless communication, comprising a memory and a processor, wherein the processor reads code from the memory and implements a method recited in any of claims 15 to 23.
A computer readable program storage medium having code stored thereon, the code, when executed by a processor, causing the processor to implement a method recited in any of claims 15 to 23.