Techniques for transmitting/receiving portions of received signal to identify preamble portion and to determine signal-distorting characteristics

• US 10,149,263 B2
• Filed: 10/27/2015
• Issued: 12/04/2018
• Est. Priority Date: 10/29/2014
• Status: Active Grant

• Current Assignee: Freewave Technologies Incorporated
• Original Assignee: Freewave Technologies Incorporated
• Inventors: McMeekin, Steven E., Mester, Timothy G.
• Primary Examiner(s): Nawaz, Asad M
• Assistant Examiner(s): Ali, Syed
• Application Number:
  US14/924,372
• Publication Number:
  US 20160128010A1
• Time in Patent Office: 1,134 Days
• CPC Class Codes: H04W 56/005 compensating for timing error by adjustment in the receiver
• CPC Class Codes: H04W 56/0055 determining timing error of reception due to propagation delay

Abstract

A method for operating a receiver in a wireless communication system to synchronize the receiver to a received signal. The received signal is preamble correlated to identify a preamble portion of the signal. Portions of the received signal near the identified preamble portion are processed to determine signal-distorting channel characteristics, such as multipath channel delay spread, of the channel over which the received signal propagated. A digital filter is configured based on the determined channel characteristics to compensate for the signal-distorting channel characteristics, and the received signal is filtered with the configured digital filter. The filtered received signal is second preamble correlated with a second preamble that is different than the first preamble to produce a second preamble correlation. The second preamble correlation is processed to identify delay in the filtered received signal. Portions of the filtered received signal are identified and processed based on the identified delay.

Claims

1. A method for operating a receiver in a wireless communication system to synchronize the receiver to a received signal, comprising:

receiving a signal defining a downlink frame portion including a plurality of slots, including a broadcast control channel (BCCH) slot including information used to control parameters of an associated uplink frame portion, wherein the parameters include one or more of transmission time, slot time and length, frequency or modulation method, and wherein one or more of the slots includes a first preamble, a second preamble that is at a location after the first preamble and separated from the first preamble by a guard interval, and a data portion, wherein the second preamble precedes the data portion; and

digitally processing the received signal, including;

frequency shifting the downlink frame portion of the received signal from an intermediate frequency to base band;

demodulating the downlink frame portion

first preamble correlating the one or more of the slots of the received signal to identify the first preamble;

processing the one or more of the slots of the received signal, including at least a portion of the identified first preamble, to determine signal-distorting channel delay spread characteristics of the channel over which the one or more of the slots of the received signal propagated;

configuring a digital filter based on the determined channel delay spread characteristics to compensate for the signal-distorting channel characteristics;

filtering the one or more of the slots of the received signal with the configured digital filter;

second preamble correlating the filtered one or more of the slots of the received signal to identify the second preamble and to produce a second preamble correlation;

processing the filtered one or more of the slots of the received signal using the second preamble correlation to identify remaining delay error in the filtered one or more of the slots of the received signal; and

identifying and processing the data portions of the filtered one or more of the slots of the received signal based on the identified remaining delay error.

2. The method of claim 1 wherein the received signal has communication frames.

3. The method of claim 1 wherein the received signal has a single carrier frequency.

4. The method of claim 1 wherein one or more of the steps of first preamble correlating, processing to determine the channel delay spread characteristics, configuring the digital filter, filtering the received signal and second preamble correlating are done on digital samples of the received signal.

5. The method of claim 1 wherein processing the one or more of the slots of the received signal to determine signal-distorting channel delay spread characteristics includes processing the one or more of the slots of the received signal from a location preceding the identified first preamble through a location following the identified first preamble.

6. The method of claim 1 wherein identifying and processing the data portions of the filtered one or more of the slots of the received signal based on the identified remaining delay error includes identifying samples of the received signal.

7. The method of claim 1 wherein second preamble correlating includes correlating the second preamble at a beginning of the data portion of the one or more of the slots of the signal.

8. The method of claim 7 wherein second preamble correlating includes correlating the second preamble that is shorter than the first preamble.

9. The method of claim 1 and further including operating a transmitter to produce a transmit signal defining the uplink frame portion including a plurality of slots;

comprising;

inserting a first preamble into one or more of the slots of the transmit signal; and

inserting a second preamble in one or more of the slots of the transmit signal, wherein each second preamble is inserted into the one or more of the slots at a location that is after the first preamble and separated from the first preamble by a guard interval; and

transmitting the transmit signal having the first and second preambles.

10. The method of claim 9 wherein inserting the second preamble includes inserting a second preamble that is shorter than the first preamble.

11. The method of claim 10 wherein inserting the second preamble includes inserting the second preamble at a location adjacent to the data portion.

12. The method of claim 11 wherein inserting the second preamble includes inserting the second preamble at a location preceding the data portion of the signal.

13. A transceiver comprising:

a receiver providing a received signal defining a downlink frame portion including a plurality of slots, including a broadcast control channel (BCCH) slot including information used to control parameters of an associated uplink frame portion, wherein the parameters include one or more of transmission time, slot time and length, frequency or modulation method, and wherein one or more of the slots includes a first preamble, a second preamble that is at a location after the first preamble and separated from the first preamble by a guard interval, and a data portion, wherein the second preamble precedes the data portion; and

a digital processor configured to;

frequency shift the downlink frame portion of the received signal from an intermediate frequency to base band;

demodulate the downlink frame portion;

first preamble correlate the one or more slots of the received signal to identify the first preamble;

process the one or more slots of the received signal, including at least a portion of the identified first preamble, to determine signal-distorting channel delay spread characteristics of the channel over which the one or more slots of the received signal propagated;

configure a digital filter based on the determined channel delay spread characteristics to compensate for the signal-distorting channel characteristics;

filter the one or more slots of the received signal with the configured digital filter;

second preamble correlate the filtered one or more slots of the received signal to identify the second preamble and to produce a second preamble correlation;

process the filtered one or more slots of the received signal using the second preamble correlation to identify remaining delay error in the filtered one or more slots of the received signal; and

identify and process the data portions of the filtered one or more slots of the received signal based on the identified remaining delay error.

14. A transceiver comprising:

a receiver providing a received signal defining a downlink frame portion including a plurality of slots, including a broadcast control channel (BCCH) slot including information used to control parameters of an associated uplink frame portion, wherein the parameters include one or more of transmission time, slot time and length, frequency and/or modulation method, and wherein one or more of the slots includes a first preamble, a second preamble that is at a location after the first preamble and separated from the first preamble by a guard interface, and a data portion, wherein the second preamble precedes the data portion;

a transmitter to transmit a transmit signal defining the uplink frame portion including a plurality of slots; and

a digital processor configured to;

frequency shift the downlink frame portion of the received signal from an intermediate frequency to base band;

demodulate the downlink frame portion;

first preamble correlate the one or more slots of the received signal to identify the first preamble;

process the one or more slots of the received signal, including at least a portion of the identified first preamble, to determine signal-distorting channel delay spread characteristics of the channel over which the one or more slots of the received signal propagated;

configure a digital filter based on the determined channel delay spread characteristics to compensate for the signal-distorting channel characteristics;

filter the one or more slots of the received signal with the configured digital filter;

second preamble correlate the filtered one or more slots of the received signal to identify the second preamble and to produce a second preamble correlation;

process the filtered one or more slots of the received signal using the second preamble correlation to identify remaining delay error in the filtered one or more slots of the received signal;

identify and process the data portions of the filtered one or more slots of the received signal based on the identified remaining delay error;

insert a first preamble into the one or more slots of the transmit signal;

insert a second preamble in the one or more slots of the transmit signal, wherein the second preamble is inserted into the one or more slots of the transmit signal at a location that is after the first preamble and separated from the first preamble by a guard interval; and

transmit the transmit signal having the first and second preambles.