Scattered pilot pattern and channel estimation method for MIMO-OFDM systems

• US 8,891,481 B2
• Filed: 09/14/2012
• Issued: 11/18/2014
• Est. Priority Date: 10/17/2001
• Status: Expired due to Term

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Blackberry Limited
• Inventors: Ma, Jianglei, Jia, Ming, Zhu, Peiying, Tong, Wen
• Primary Examiner(s): Nooristany, Sulaiman
• Application Number:
  US13/617,175
• Publication Number:
  US 20130016693A1
• Time in Patent Office: 795 Days
• Field of Search: None
• US Class Current: 370/330
• 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 7/0684 using different training sequences per antenna
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/022 of frequency response
• CPC Class Codes: H04L 25/0234 by non-linear interpolation
• CPC Class Codes: H04L 25/0244 with inversion
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/26035 Maintenance of orthogonality, e.g. for signals exchanged between cells or users, or by using covering codes or sequences using different training sequence per antenna H04B7/0684; code allocation H04J13/16
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/26134 Pilot insertion in the transmitter chain, e.g. pilot overlapping with data, insertion in time or frequency domain
• CPC Class Codes: H04L 27/2627 Modulators
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

Methods and apparatus are provided for inserting data symbols and pilot symbols in an OFDM (orthogonal frequency division multiplexing) transmission resource utilizing frequency hopping patterns for the data symbols and/or the pilot symbols. Data symbols and pilot symbols are allocated for down link (base station to mobile station) and up link (mobile station to bases station) transmission resources in a two-dimensional time-frequency pattern. For each antenna of a MIMO-OFDM (multiple input multiple output OFDM) communication system, pilot symbols are inserted in a scattered pattern in time-frequency and data symbols are inserted in an identical frequency-hopping pattern in time-frequency as that of other antennas.

Claims

1. A method of inserting data symbols into Orthogonal Frequency Division Multiplexing (OFDM) frames at an OFDM transmitter having at least two pairs of transmitting antennas, the OFDM frames having a time domain and a frequency domain, the method comprising:

for each antenna, sparsely distributing pilot symbols in a respective pattern in time-frequency, the patterns being identical for each pair of antennas, the pattern for a first antenna of each of the two pairs of antennas being offset in frequency with respect to the pattern for a second antenna of that pair of antennas, and a pilot density for a first pair of the two pairs of transmitting antennas is higher than a pilot density for a second pair of the two pairs of transmitting antennas.

2. The method of claim 1, wherein at least one pattern is offset from a pilot pattern of an adjacent base station.

3. The method of claim 1, further comprising mapping each data symbol to at least one respective combination of a selected antenna, a selected OFDM symbol and a selected data sub-carrier.

4. The method of claim 3, further comprising, for each data symbol, permuting the selected data sub-carriers according to a frequency-hopping pattern that is identical for each pair of transmitting.

5. The method of claim 1, further comprising for the first antenna of each pair of antennas, inserting pilot symbols in a first scattered pattern in time-frequency and inserting null symbols in a second scattered pattern in time-frequency;

and for a second antenna of each pair of antennas, inserting pilot symbols in the second scattered pattern in time-frequency and inserting null symbols in the first scattered pattern in time-frequency.

6. The method of claim 1, further comprising transmitting the pilot symbols at a higher power level than the data symbols.

7. An Orthogonal Frequency Division Multiplexing (OFDM) base station of a wireless network, the OFDM base station having at least two pairs of transmitting antennas configured to transmit data symbols in OFDM frames, the OFDM frames having a time domain and a frequency domain, the base station configured to:

for each antenna, sparsely distribute pilot symbols in a respective pattern in time-frequency, the patterns being identical for each pair of antennas, the pattern for a first antenna of each of the two pairs of antennas being in frequency with respect to the pattern for a second antenna of that pair of antennas, and a pilot density for a first pair of the two pairs of transmitting antennas is higher than a pilot density for a second pair of the two pairs of transmitting antennas.

8. The OFDM base station of claim 7, wherein at least one pattern is offset from a pilot pattern of an adjacent base station.

9. The OFDM base station of claim 7, further configured to map each data symbol to at least one respective combination of a selected antenna, a selected OFDM symbol, and a selected data sub-carrier.

10. The OFDM base station of claim 9, further configured to permute, for each data symbol, the selected data sub-carriers according to a frequency-hopping pattern that is identical for each pair of transmitting.

11. The OFDM base station of claim 7, further configured to insert, for the first antenna of each pair of antennas, pilot symbols in a first scattered pattern in time-frequency and inserting null symbols in a second scattered pattern in time-frequency;

and for a second antenna of each pair of antennas, inserting pilot symbols in the second scattered pattern in time-frequency and inserting null symbols in the first scattered pattern in time-frequency.

12. The OFDM base station of claim 7, further configured to transmit the pilot symbols at a higher power level than the data symbols.