System access and synchronization methods for MIMO OFDM communications systems and physical layer packet and preamble design

• US 8,830,816 B2
• Filed: 06/04/2012
• Issued: 09/09/2014
• Est. Priority Date: 10/17/2001
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Ma, Jianglei, Jia, Ming, Zhu, Peiying, Tong, Wen
• Primary Examiner(s): MATTIS, JASON E
• Application Number:
  US13/487,898
• Publication Number:
  US 20120243626A1
• Time in Patent Office: 827 Days
• Field of Search: 370/208, 370/324, 370/511
• US Class Current: 370/208
• CPC Class Codes: H04B 7/022 Site diversity; Macro-diversity using two or more spaced independent antennas H04B7/04
• CPC Class Codes: H04B 7/04 using two or more spaced independent antennas
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0667 of delayed versions of same signal using space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• CPC Class Codes: H04J 11/0069 Cell search, i.e. determining cell identity [cell-ID] design of multiplexing codes H04J13/00; processing access restriction or access information H04W48/16; discovery of network devices for network data management H04W8/005; sounding signals for channel estimation H04L25/0226; structure of reference signals in multicarrier modulation systems H04L27/2613; frame, time or carrier synchronisation in multicarrier modulation systems H04L27/2655
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/26025 Numerology, i.e. varying one or more of symbol duration, subcarrier spacing, Fourier transform size, sampling rate or down-clocking allocating sub-channels of the transmission path H04L5/003
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/2627 Modulators
• CPC Class Codes: H04L 27/2663 Coarse synchronisation, e.g. by correlation
• CPC Class Codes: H04L 27/2665 Fine synchronisation, e.g. by positioning the FFT window
• CPC Class Codes: H04L 27/2672 Frequency domain
• CPC Class Codes: H04L 27/2675 Pilot or known symbols
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 7/0008 Synchronisation information channels, e.g. clock distribution lines
• CPC Class Codes: H04W 36/08 Reselecting an access point

Abstract

A method and apparatus are provided for performing acquisition, synchronization and cell selection within an MIMO-OFDM communication system. A coarse synchronization is performed to determine a searching window. A fine synchronization is then performed by measuring correlations between subsets of signal samples, whose first signal sample lies within the searching window, and known values. The correlations are performed in the frequency domain of the received signal. In a multiple-output OFDM system, each antenna of the OFDM transmitter has a unique known value. The known value is transmitted as pairs of consecutive pilot symbols, each pair of pilot symbols being transmitted at the same subset of sub-carrier frequencies within the OFDM frame.

Claims

1. A method for use with a plurality of transmit antennas included with each transmitter of a plurality of transmitters in a communication network, comprising:

converting frequency domain representations of sync sequences into time domain representations, wherein each sync sequence is different for each antenna of the plurality of transmit antennas and common for respective transmit antennas of each transmitter; and

transmitting each time domain representation twice, preceded by a cyclic prefix of each respective time domain representation.

2. The method of claim 1, wherein converting the frequency domain representations comprises:

mapping the sync sequences to a set of non-adjacent orthogonal frequency division multiplexing (OFDM) sub-carriers; and

performing an inverse fast Fourier transform (IFFT).

3. The method of claim 1, wherein each transmitter of the plurality of transmitters is used with a different base station.

4. An apparatus for use with a plurality of transmit antennas included with each transmitter of a plurality of transmitters in a communication network, comprising:

means for converting frequency domain representations of sync sequences into time domain representations, wherein each sync sequence is different for each antenna of the plurality of transmit antennas and common for respective transmit antennas of each transmitter; and

means for transmitting each time domain representation twice, preceded by a cyclic prefix of each respective time domain representation.

5. The apparatus of claim 4, wherein converting the frequency domain representations comprises:

means for mapping the sync sequences to a set of non-adjacent orthogonal frequency division multiplexing (OFDM) sub-carriers; and

means for performing an inverse fast Fourier transform (IFFT).

6. The apparatus of claim 4, wherein each transmitter of the plurality of transmitters is used with a different base station.