PILOT DESIGN FOR WIRELESS SYSTEM

• US 20120224659A1
• Filed: 05/21/2012
• Published: 09/06/2012
• Est. Priority Date: 03/04/2008
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Rockstar Bidco LP (Rockstar Consortium Inc.)
• Inventors: Yu, Dong-Sheng, Fong, Mo-Han, Ma, Jianglei, Vrzic, Sophie, Zhang, Hang
• Granted Patent: US 8,537,915 B2
• Time in Patent Office: Days
• US Class Current: 375/340
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0621 Feedback content
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 27/26 Systems using multi-frequency codes H04L27/32 takes precedence
• 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 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• 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

Abstract

The description herein relates to pilot designs for an Orthogonal Frequency Division Multiplexing (OFDM) based communication system. In the preferred embodiment, the communication system is one operating according to the IEEE 802.16m, or WiMax, standard. In general, an OFDM transmitter operates to insert pilot symbols into a resource of a transmit frame according to a predetermined staggered pilot symbol pattern defining pilot symbol locations within the resource of the transmit frame. The predetermined pilot symbol pattern is defined such that pilot symbols are located at or near time boundaries of the resource, at or near frequency boundaries of the resource, or both. By doing so, when generating a channel estimate for the communication channel between the OFDM transmitter and an OFDM receiver based on the pilot symbols, extrapolations needed to estimate the channel near the boundaries of the resource are optimized, thereby improving overall channel estimation accuracy.

Claims

1. An Orthogonal Frequency Division Multiplexing (OFDM) receiver comprising:

receiver circuitry adapted to process a received OFDM signal to provide symbols for a resource of a transmit frame; and

a channel estimator implemented in hardware and adapted to;

receive the symbols from the receiver circuitry;

extract one or more pilot symbols from the symbols for the resource of the transmit frame according to a predetermined staggered pilot symbol pattern including one or more of a group consisting of;

pilot symbol locations located at or near each time boundary of the resource and pilot symbol locations located at or near each frequency boundary of the resource.

2. An Orthogonal Frequency Division Multiplexing (OFDM) receiver comprising:

receiver circuitry adapted to process a received OFDM signal to provide symbols for one or more modern sub-frames of a transmit frame and symbols for a legacy sub-frame neighboring a modern sub-frame of the one or more modern sub-frames within the transmit frame; and

a channel estimator implemented in hardware and adapted to;

receive the symbols from the receiver circuitry;

extract at least some pilot symbols from the symbols in the legacy sub-frame;

extract pilot symbols from the symbols for the one or more modern sub-frames according to a predetermined staggered pilot symbol pattern for the one or more modern sub-frames; and

generate channel estimates for the one or more modern sub-frames based on the pilot symbols extracted from the one or more modern sub-frames and the at least some pilot symbols extracted from the legacy sub-frame.

3. The OFDM receiver of claim 2 wherein the legacy sub-frame precedes the one or more modern sub-frames in the transmit frame, and the modern sub-frame neighboring the legacy sub-frame is a first modern sub-frame of the one or more modern sub-frames in the transmit frame.

4. The OFDM receiver of claim 3 wherein the predetermined staggered pilot symbol pattern begins at a time offset from a starting time boundary of the first modern sub-frame, the time offset being greater than two OFDM symbols.

5. The OFDM receiver of claim 4 wherein the predetermined staggered pilot symbol pattern is a uniform pilot symbol pattern starting after the time offset from the starting time boundary of the first sub-frame.

6. The OFDM receiver of claim 5 wherein the time offset is such that last pilot symbol locations defined by the predetermined staggered pilot symbol pattern are at or near an ending time boundary of a last modern sub-frame.