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Method and apparatus for packet acquisition

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20140219321 patent thumbnailZoom

Method and apparatus for packet acquisition


Certain aspects of the present disclosure relate to a method for acquisition of a received spread spectrum signal transmitted over a wired or wireless medium.
Related Terms: Wireless Spread Spectrum

Browse recent Adeptence LLC patents - Carlsbad, CA, US
USPTO Applicaton #: #20140219321 - Class: 375148 (USPTO) -
Pulse Or Digital Communications > Spread Spectrum >Direct Sequence >Receiver >Multi-receiver Or Interference Cancellation



Inventors: Ismail Lakkis

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The Patent Description & Claims data below is from USPTO Patent Application 20140219321, Method and apparatus for packet acquisition.

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BACKGROUND

1. Field

Certain aspects of the present disclosure generally relate to signal acquisition, more particularly, to a method for joint packet detection, timing and frequency synchronization of a spread-spectrum signal.

2. Background

Spread-spectrum coding is a technique by which signals generated in a particular bandwidth can be spread in a frequency domain, resulting in a signal with a wider bandwidth. The spread signal has a lower power density, but the same total power as an un-spread signal. The expanded transmission bandwidth minimizes interference to others transmissions because of its low power density. At the receiver, the spread signal can be decoded, and the decoding operation provides resistance to interference and multipath fading.

Spread-spectrum coding is used in standardized systems, e.g. GSM, General Packet Radio Service (GPRS), Enhanced Digital GSM Evolution (EDGE), Code Division Multiple Access (CDMA), Wideband Code Division Multiple Access (WCDMA or W-CDMA), Orthogonal Frequency Division Multiplexing (OFDM), Orthogonal Frequency Division Multiple Access (OFDMA), Time Division Multiple Access (TDMA), Digital European Cordless Telecommunication (DECT), Infrared (IR), Wireless Fidelity (Wi-Fi), Bluetooth, Zigbee, Global Positioning System (GPS), Millimeter Wave (mmWave), Ultra Wideband (UWB), other standardized as well as non-standardized systems, wireless and wired communication systems.

In order to achieve good spreading characteristics in a system using spread spectrum, it is desirable to employ spreading codes which possess a near perfect periodic or aperiodic autocorrelation function, i.e. low sidelobes level as compared to the main peak, and an efficient correlator-matched filter to ease the processing at the receiver side. Spreading codes with high peak and low sidelobes level yields better acquisition and synchronization properties for communications, radar, and positioning applications.

In spread spectrum systems using multiple spreading codes, it is not sufficient to employ codes with good autocorrelation properties since such systems may suffer from multiple-access interference (MAI) and possibly inter-symbol interference (ISI). In order to achieve good spreading characteristics in a multi code DS-CDMA system, it is necessary to employ sequences having good autocorrelation properties as well as low cross-correlations. The cross-correlation between any two codes should be low to reduce MAI and ISI.

Complementary codes, first introduced by Golay in M. Golay, “Complementary Series,” IRE Transaction on Information Theory, Vol. 7, Issue 2, April 1961, are sets of complementary pairs of equally long, finite sequences of two kinds of elements which have the property that the number of pairs of like elements with any one given separation in one code is equal to the number of unlike elements with the same given separation in the other code. The complementary codes first discussed by Golay were pairs of binary complementary codes with elements +1 and −1 where the sum of their respective aperiodic autocorrelation sequence is zero everywhere, except for the center tap.

Polyphase complementary codes described in R. Sivaswamy, “Multiphase Complementary Codes,” IEEE Transaction on Information Theory, Vol. 24, Issue 5, September 1978, are codes where each element is a complex number with unit magnitude.

An efficient Golay correlator-matched filter was introduced by S. Budisin, “Efficient Pulse Compressor for Golay Complementary Sequences,” Electronic Letters, Vol. 27, Issue 3, January 1991, along with a recursive algorithm to generate these sequences as described in S. Budisin “New Complementary Pairs of Sequences,” Electronic Letters, Vol. 26, Issue 13, June 1990, and in S. Budisin “New Multilevel Complementary Pairs of Sequences,” Electronic Letters, Vol. 26, Issue 22, October 1990. The Golay complementary sequences described by Budisin are the most practical, they have lengths that are power of two, binary or complex, 2 levels or multi-levels, have good periodic and aperiodic autocorrelation functions and most importantly possess a highly efficient correlator-matched filter receiver.

However, Golay sequences are not without drawbacks. First, Golay sequences don't exist for every length, for example binary complementary Golay sequences are known for lengths 2M as well as for some even lengths that can be expressed as sum of two squares. Second, an efficient Golay correlator-matched filter exists only for Golay sequences generated by Budisin's recursive algorithm and that are of length that is a power of two (i.e. 2M). Third, the Golay sequences generated using Budisin's recursive algorithm might not possess the desired correlation properties. Furthermore, good spreading sequences such as m-sequences, Gold sequences, Barker sequences and other known sequences do not possess a highly efficient correlator-matched/mismatched filter.

Therefore, there is a need in the art for a method of spread spectrum coding applied at the transmitter and an efficient method for de-spreading at the receiver.

In high speed spread spectrum systems, a known signal, such as a preamble, is transmitted to aid receiver algorithms related to AGC setting, antenna diversity or pattern selection, DC offset and IQ imbalance estimation, packet detection, timing acquisition, frequency offset estimation, frame synchronization and channel estimation. In high speed systems, a large portion of the preamble is allocated for frequency estimation which is typically performed after packet detection.

Therefore, there is a need in the art for a method of joint packet detection and synchronization in order to shorten the preamble and therefore reduce the overhead associated with the preamble.

SUMMARY

Certain aspects provide a method for wireless and wired communications. The method generally includes spreading at least one of the fields of a data stream with one or plurality of spreading sequences wherein at least one of the spreading sequences is based on Golay or generalized Golay sequences, and transmitting the spread data stream.

Certain aspects provide a method for wireless and wired communications. The method generally includes receiving a spread data stream wherein at least one of the fields is spread with one or plurality of spreading sequences, and performing a joint signal detection, timing and frequency synchronization.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects.

FIG. 1 illustrates an example wireless communication system, in accordance with certain aspects of the present disclosure.

FIG. 2 illustrates various components that may be utilized in a wireless device in accordance with certain aspects of the present disclosure.

FIG. 3 illustrates an example transceiver that may be used within a wireless communication system in accordance with certain aspects of the present disclosure.

FIG. 4A illustrates an efficient Golay generator/correlator that may be used to generate a pair of Golay complementary codes or to perform matched filtering operations.

FIG. 4B illustrates an alternative efficient Golay generator/correlator that may be used to generate a pair of Golay complementary codes or to perform matched filtering operations.

FIG. 5A illustrates a preferred Golay generator in accordance with certain aspect of the present disclosure which may be used at a transmitter to generate one or multiple generalized Golay codes that may be used for spreading one or multiple fields of a data stream to be transmitted.

FIG. 5B illustrates one of the stages of the preferred binary Golay generator in accordance with certain aspect of the present disclosure.

FIG. 5C illustrates one of the stages of the preferred non-binary Golay generator in accordance with certain aspect of the present disclosure.

FIG. 6A illustrates a generalized Golay code in accordance to one aspect of the present disclosure which may be used at a transmitter to generate one or multiple generalized Golay codes that may be used for spreading one or multiple fields of a data stream to be transmitted.

FIG. 6B illustrates a preferred generalized Golay generator in accordance to one aspect of the present disclosure which may be used at a transmitter to generate one or multiple generalized Golay codes that may be used for spreading one or multiple fields of a data stream to be transmitted.

FIG. 7 a millimeter wave frame format using Golay and Generalized Golay codes in accordance to one aspect of the present disclosure.

FIG. 8A illustrates an example generalized efficient Golay correlator that may be used within a wireless communication system in accordance with certain aspects of the present disclosure.

FIG. 8B illustrates example implementation generalized efficient Golay correlator that may be used within a wireless communication system in accordance with certain aspects of the present disclosure.

FIG. 9 illustrates an example generalized efficient parallel Golay correlator that may be used within a wireless communication system in accordance with certain aspects of the present disclosure.

FIG. 10A illustrates an acquisition algorithm that may be used within a wireless communication system.

FIG. 10B illustrates an example acquisition algorithm that may be used within a wireless communication system in accordance with certain aspects of the present disclosure.

FIG. 10C illustrates an example differential detector that may be used within the acquisition circuit of FIG. 10B in accordance with certain aspects of the present disclosure.

FIG. 10D illustrates an example accumulator that may be used within the acquisition circuit of FIG. 10B in accordance with certain aspects of the present disclosure.

FIG. 11A illustrates example operations for Golay codes generation and spreading in accordance with certain aspects of the present disclosure.

FIG. 11B illustrates example components capable of performing the operations illustrated in FIG. 11A.

FIG. 11C illustrates an example operations for processing of spread signals at the receiver using preferred Golay generation methods in accordance with certain aspects of the present disclosure.

FIG. 11D illustrates example components capable of performing the operations illustrated in FIG. 11C.

FIG. 12A illustrates example operations for combined spreading and modulation in accordance with certain aspects of the present disclosure.

FIG. 12B illustrates example components capable of performing the operations illustrated in FIG. 12A.

FIG. 12C illustrates an example operations for processing of spread and modulated signals at the receiver in accordance with certain aspects of the present disclosure.

FIG. 12D illustrates example components capable of performing the operations illustrated in FIG. 12C.

FIG. 13A illustrates example operations for spreading in accordance with certain aspects of the present disclosure.

FIG. 13B illustrates example components capable of performing the operations illustrated in FIG. 13A.

FIG. 13C illustrates an example operations for processing of spread signals at the receiver in accordance with certain aspects of the present disclosure.

FIG. 13D illustrates example components capable of performing the operations illustrated in FIG. 13C.

FIG. 14A illustrates an example operations for processing of spread signals at the receiver in accordance with certain aspects of the present disclosure.

FIG. 14B illustrates example components capable of performing the operations illustrated in FIG. 14A.

DETAILED DESCRIPTION

Various aspects of the disclosure are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim.

The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects.

Although particular aspects are described herein, many variations and permutations of these aspects fall within the scope and spirit of the disclosure. Although some benefits and advantages of the preferred aspects are mentioned, the scope of the disclosure is not intended to be limited to particular benefits, uses, or objectives. Rather, aspects of the disclosure are intended to be broadly applicable to different wireless technologies, system configurations, networks, and transmission protocols, some of which arc illustrated by way of example in the figures and in the following description of the preferred aspects. The detailed description and drawings are merely illustrative of the disclosure rather than limiting, the scope of the disclosure being defined by the appended claims and equivalents thereof.

An Example Wireless Communication System

The techniques described herein may be used for various broadband wireless and wired communication systems, including communication systems that are based on a single carrier transmission and OFDM. Aspects disclosed herein may be advantageous to systems employing Ultra Wide Band (UWB) signals including millimeter-wave signals, Code Division Multiple Access (CDMA) signals, and OFDM. However, the present disclosure is not intended to be limited to such systems, as other coded signals may benefit from similar advantages.

FIG. 1 illustrates an example of a wireless communication system 100 in which aspects of the present disclosure may be employed. The wireless communication system 100 may be a broadband wireless communication system. The wireless communication system 100 may provide communication for a number of Basic Service Sets (BSSs) 102, each of which may be serviced by a Service Access Point (SAP) 104. A SAP 104 may be a fixed station or a mobile station that communicates with Stations (STAs) 106. A BSS 102 may alternatively be referred to as cell, piconet or some other terminology. A SAP 104 may alternatively be referred to as base station, a piconet controller, a Node B or some other terminology.

FIG. 1 depicts various stations 106 dispersed throughout the system 100. The stations 106 may be fixed (i.e., stationary) or mobile. The stations 106 may alternatively be referred to as remote stations, access terminals, terminals, subscriber units, mobile stations, devices, user equipment, etc. The stations 106 may be wireless devices, such as cellular phones, personal digital assistants (PDAs), handheld devices, wireless modems, laptop computers, personal computers, etc.

A variety of algorithms and methods may be used for transmissions in the wireless communication system 100 between the SAPs 104 and the STAs 106 and between STAs 106 themselves. For example, signals may be sent and received between the SAPs 104 and the STAs 106 in accordance with CDMA technique and signals may be sent and received between STAs 106 in according with OFDM technique. If this is the case, the wireless communication system 100 may be referred to as a hybrid CDMA/OFDM system.

A communication link that facilitates transmission from a SAP 104 to a STA 106 may be referred to as a downlink (DL) 108, and a communication link that facilitates transmission from a STA 106 to a SAP 104 may be referred to as an uplink (UL) 110. Alternatively, a downlink 108 may be referred to as a forward link or a forward channel, and an uplink 110 may be referred to as a reverse link or a reverse channel. When two STAs communicate directly with each other, a first STA will act as the master of the link, and the link from the first STA to the second STA will be referred to as downlink 112, and the link from the second STA to the first STA will be referred to as uplink 114.

A BSS 102 may be divided into multiple sectors 112. A sector 116 is a physical coverage area within a BSS 102. SAPs 104 within a wireless communication system 100 may utilize antennas that concentrate the flow of power within a particular sector 116 of the BSS 102. Such antennas may be referred to as directional antennas.

FIG. 2 illustrates various components that may be utilized in a wireless device 210 that may be employed within the wireless communication system 100. The wireless device 210 is an example of a device that may be configured to implement the various methods described herein. The wireless device 202 may be a SAP 104 or a STA 106.

The wireless device 202 may include a processor 204 which controls operation of the wireless device 202. The processor 204 may also be referred to as a central processing unit (CPU). Memory 206, which may include both read-only memory (ROM) and random access memory (RAM), provides instructions and data to the processor 204. A portion of the memory 206 may also include non-volatile random access memory (NVRAM). The processor 204 typically performs logical and arithmetic operations based on program instructions stored within the memory 206. The instructions in the memory 206 may be executable to implement the methods described herein.

The wireless device 202 may also include a housing 208 that may include a transmitter 210 and a receiver 212 to allow transmission and reception of data between the wireless device 202 and a remote location. The transmitter 210 and receiver 212 may be combined into a transceiver 214. An antenna 216 may be attached to the housing 208 and electrically coupled to the transceiver 214. The wireless device 202 may include one or more wired peripherals 224 such as USB, HDMI, or PCIE. The wireless device 202 may also include (not shown) multiple transmitters, multiple receivers, multiple transceivers, and/or multiple antennas.

The wireless device 202 may also include a signal detector 218 that may be used in an effort to detect and quantify the level of signals received by the transceiver 214. The signal detector 218 may detect such signals as total energy, energy per subcarrier per symbol, power spectral density and other signals. The wireless device 202 may also include a digital signal processor (DSP) 220 for use in processing signals.

The various components of the wireless device 202 may be coupled together by a bus system 222, which may include a power bus, a control signal bus, and a status signal bus in addition to a data bus.

FIG. 3 illustrates an example of a transmitter 302 that may be used within a wireless communication system 100 that utilizes CDMA or some other transmission technique. Portions of the transmitter 302 may be implemented in the transmitter 210 of a wireless device 202. The transmitter 302 may be implemented in a base station 104 for transmitting data 330 to a user terminal 106 on a downlink 108. The transmitter 302 may also be implemented in a station 106 for transmitting data 330 to a service access point 104 on an uplink 110.

Data 306 to be transmitted are shown being provided as input to a forward error correction (FEC) encoder 308. The FEC encoder encodes the data 306 by adding redundant bits. The FEC encoder may encode the data 306 using convolutional encoder, Reed Solomon encoder, Turbo encoder, low density parity check (LDPC) encoder, etc. The FEC encoder 308 outputs an encoded data stream 310. The encoded data stream 310 is input to the mapper 314. The mapper 314 may map the encoded data stream onto constellation points. The mapping may be done using some modulation constellation, such as binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), 8 phase-shift keying (8PSK), quadrature amplitude modulation (QAM), constant phase modulation (CPM), etc. Thus, the mapper 312 may output a symbol stream 314, which may represents one input into a block builder 310. Another input in the block builder 310 may be comprised of one or multiple of spreading codes produced by a spreading-codes generator 318.

The block builder 310 may be configured for partitioning the symbol stream 314, into sub-blocks and creating OFDM/OFDMA symbols or single carrier sub-blocks. The block builder may append each sub-block by a guard interval, a cyclic prefix or a spreading sequence from the spreading codes generator 318. Furthermore, the sub-blocks may be spread by one or multiple spreading codes from the spreading codes generator 318.

The output 320 may be pre-pended by a preamble 322 generated from one or multiple spreading sequences from the spreading codes generator 324. The output stream 326 may then be converted to analog and up-converted to a desired transmit frequency band by a radio frequency (RF) front end 328 which may include a mixed signal and an analog section. An antenna 330 may then transmit the resulting signal 332.

FIG. 3 also illustrates an example of a receiver 304 that may be used within a wireless device 202 that utilizes CDMA or OFDM/OFDMA. Portions of the receiver 304 may be implemented in the receiver 212 of a wireless device 202. The receiver 304 may be implemented in a station 106 for receiving data 306 from a service access point 104 on a downlink 108. The receiver 304 may also be implemented in a base station 104 for receiving data 306 from a user terminal 106 on an uplink 110.

The transmitted signal 332 is shown traveling over a wireless channel 334. When a signal 332′ is received by an antenna 330′, the received signal 332′ may be down-converted to a baseband signal by an RF front end 328′ which may include a mixed signal and an analog portion. Preamble detection and synchronization component 322′ may be used to establish timing, frequency and channel synchronization using one or multiple correlators that correlate with one or multiple spreading codes generated by the spreading code(s) generator 324′.

The output of the RF front end block 328′ is input to the frequency and timing correction component 326′ along with the synchronization information from 322′. The outputs from 326′ and 322′ are fed to a block detection component 316′. When OFDM/OFDMA is used, the block detection block may perform cyclic prefix removal and fast Fourier transform (FFT). When single carrier transmission is used, the block detection block may perform de-spreading and equalization.

A demapper 312′ may perform the inverse of the symbol mapping operation that was performed by the mapper 312 thereby outputting soft or hard decisions 310′. The soft or hard decisions 310′ are input to the FEC decoder which provides an estimate data stream 306′. Ideally, this data stream 306′ corresponds to the data 306 that was provided as input to the transmitter 302.

The wireless system 100 illustrated in FIG. 1 may be the UWB/millimeter wave system operating in the band including 57-64 GHz unlicensed band specified by the Federal Communications Commission (FCC).

Golay Codes

In one aspect of the disclosure, spreading codes generated by spreading code(s) generator 318 and 324 in a transmitter 302 are based on Golay codes. A summary of Golay codes, their properties, generation and reception is provided next.

A Golay complementary pair of codes of length N=2M, denoted here a and b, are specified by a delay vector D=[D1, D2, . . . , DM] with elements chosen as any permutation of {1, 2, 4, . . . , 2M} and a seed vector W=[W1, W2, . . . , WM]. Binary Golay complementary sequences are generated when the seed vector elements {Wm} are +1 or 1. Polyphase Golay complementary sequences are generated when the seed vector elements {Wm} are arbitrary complex numbers with unit magnitude. Golay complementary pairs of length 1 are defined here as the pair of sequences a=[+1] and b=[±1]. Alternative Golay complementary pairs of length 1 can be used such as a=[+1] and b=[−1].

The following MATLAB code can be used to generate a pair of binary or polyphase Golay complementary codes a and b of length N=2M with M>1, using Budisin\'s recursive algorithm. The inputs to the MATLAB function being the delay vector D and seed vector W.



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stats Patent Info
Application #
US 20140219321 A1
Publish Date
08/07/2014
Document #
14248151
File Date
04/08/2014
USPTO Class
375148
Other USPTO Classes
International Class
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Drawings
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