Symbol timing for MIMO OFDM and other wireless communication systems

A receiver for a multiple-input multiple-output (MIMO) system, the receiver comprising:

• a plurality of receiver antennas, each adapted to receive signals from a plurality of transmitter antennas in the MIMO system, each transmitter antenna transmitting multiple channels;
• a receiver branch for each different receiver antenna, each receiver branch having a transform adapted to transform a corresponding received signal into a plurality of transformed components;
• a symbol decoder adapted to receive transformed components from each transform and to detect symbols, wherein:
• processing within each receiver branch is based on symbol timing determined for each receiver branch;
• at least one receiver branch is adapted to determine its symbol timing by
• (a) for each of a plurality of channels originating from the transmit antennas, estimating a CIR value characterizing channel impulse response (CIR) of the channel;
• (b) summing the CIR values for the plurality of channels to generate a plurality of summed CIR values;
• (c) integrating the summed CIR values over a specified window to generate an integrated summed CIR value;
• and
• (d) determining the symbol timing in the received signals based on the integrated summed CIR value;
• a plurality of integrated summed CIR values are generated corresponding to a plurality of different instances of the specified window, each instance corresponding to integrating a different set of summed CIR values for the plurality of channels;
• and
• the determined symbol timing is based on selecting a maximum integrated summed CIR value of the plurality of integrated summed CIR values.

In a receiver of a multiple-input multiple-output (MIMO) system, the receiver having a plurality of receiver antennas, a method comprising:

• (a) receiving signals from a plurality of transmitter antennas;
• (b) for each of a plurality of channels originating from the transmit antennas, estimating a CIR value characterizing channel impulse response (CIR) of the channel;
• (c) summing the CIR values for the plurality of channels;
• (d) integrating the summed CIR values over a specified window;
• (e) determining symbol timing in the received signals based on the integrated summed CIR value;
• and
• (f) processing the received signals based on the determined symbol timing, wherein:
• the plurality of channels corresponds to a single antenna of the receiver;
• a different symbol timing is determined for each different receiver antenna;
• timing of the processing of the received signals for each different receiver antenna is based on the maximum symbol timing for all of the receiver antennas;
• and
• at least one received signal is delayed based on a timing difference between the maximum symbol timing and the symbol timing determined for said at least one received signal.

In a receiver of a multiple-input multiple-output (MIMO) system, the receiver having a plurality of receiver antennas, a method comprising:

• (a) receiving signals from a plurality of transmitter antennas;
• (b) for each of a plurality of channels originating from the transmit antennas, estimating a CIR value characterizing channel impulse response (CIR) of the channel;
• (c) summing the CIR values for the plurality of channels;
• (d) integrating the summed CIR values over a specified window;
• (e) determining symbol timing in the received signals based on the integrated summed CIR value, wherein the determined symbol timing corresponds to minimal CIR power falling outside of the specified window and maximal CIR power falling inside the specified window;
• and
• (f) processing the received signals based on the determined symbol timing.