Method and apparatus for generating OFDM signals

Patent metadata

Field	Value
Publication number	US-9998313-B2
Application number	US-201715503882-A
Country	US
Kind code	B2
Filing date	Jan 27, 2017
Priority date	Feb 15, 2016
Publication date	Jun 12, 2018
Grant date	Jun 12, 2018

Abstract

A method in a transmitter circuit ( 200 ) of generating a signal comprising a first sequence of OFDM symbols, which are to be transmitted within a frequency sub band of a second sequence of OFDM symbols is disclosed. A first CP of the second sequence of OFDM symbols has a first duration, and a second CP of the second sequence of OFDM symbols has a second duration. In order to generate both the first and the second cyclic prefix with an integer number of equidistant samples, a first sampling rate is required. The method comprises generating ( 100 ) the signal comprising the first sequence of OFDM symbols at a second sampling rate, lower than the first sampling rate, and adjusting ( 110 ) a sampling phase during CPs.

First claim

The invention claimed is:

1. A method in a transmitter circuit of generating a signal comprising a first sequence of an integer number N sym of OFDM symbols, which are to be transmitted within a frequency sub band of a second sequence of N sym OFDM symbols, wherein
the first sequence of OFDM symbols and the second sequence of OFDM symbols are to be transmitted with the same timing;
a first cyclic prefix of the second sequence of OFDM symbols has a first duration;
a second cyclic prefix of the second sequence of OFDM symbols has a second duration; and
the second duration is shorter than the first duration, such that in order to generate both the first and the second cyclic prefix with an integer number of equidistant samples, a first sampling rate is required;

wherein the method comprises:
generating the signal comprising the first sequence of OFDM symbols at a second sampling rate, lower than the first sampling rate;
adjusting a sampling phase during cyclic prefixes.

2. The method of claim 1 , wherein a subcarrier spacing of the OFDM symbols of the first and second sequences of OFDM symbols are 15 kHz, the first duration is 160/30.72 μs, and the second duration is 144/30.72 μs.

3. The method of claim 1 , wherein the first sampling rate is 1.92 MHz.

4. The method of claim 1 , wherein OFDM symbols of the first sequence of OFDM symbols have 12 subcarriers.

5. The method of claim 1 , wherein the first cyclic prefix is an initial cyclic prefix of the second sequence of OFDM symbols, and all subsequent cyclic prefixes of the second sequence of OFDM symbols have the second duration.

6. The method of claim 5 , wherein the second sequence of OFDM symbols are transmitted in a third-generation partnership project (3GPP) long term evolution (LTE) system and corresponds to a slot.

7. The method of claim 1 , wherein the second sampling rate is 240 kHz.

8. The method of claim 1 , wherein the second sampling rate is 480 kHz.

9. The method of claim 1 , wherein the second sampling rate is 960 kHz.

10. The method of claim 1 , wherein adjusting the sampling phase comprises setting an initial sample instant during an OFDM symbol to occur a non-integer multiple of periods at the second sampling rate after a final sample instant of a preceding OFDM symbol.

11. A transmitter circuit for generating a signal comprising a first sequence of an integer number N sym of OFDM symbols, which are to be transmitted within a frequency sub band of a second sequence of N sym OFDM symbols, wherein
the first sequence of OFDM symbols and the second sequence of OFDM symbols are to be transmitted with the same timing;
a first cyclic prefix of the second sequence of OFDM symbols has a first duration;
a second cyclic prefix of the second sequence of OFDM symbols has a second duration; and
the second duration is shorter than the first duration, such that in order to generate both the first and the second cyclic prefix with an integer number of equidistant samples, a first sampling rate is required;

wherein the transmitter circuit comprises
a digital-to-analog converter configured to generate the signal comprising the first sequence of OFDM symbols at a second sampling rate, lower than the first sampling rate; and
a control circuit configured to adjust a sampling phase of the digital-to-analog converter during cyclic prefixes.

12. The transmitter circuit of claim 11 , wherein a subcarrier spacing of the OFDM symbols of the first and second sequences of OFDM symbols are 15 kHz, the first duration is 160/30.72 μs and the second duration is 144/30.72 μs.

13. The transmitter circuit of claim 11 , wherein the first sampling rate is 1.92 MHz.

14. The transmitter circuit of claim 11 , wherein OFDM symbols of the first sequence of OFDM symbols have 12 subcarriers.

15. The transmitter circuit of claim 11 , wherein the first cyclic prefix is an initial cyclic prefix of the second sequence of OFDM symbols, and all subsequent cyclic prefixes of the second sequence of OFDM symbols has the second duration.

16. The transmitter circuit of claim 15 , wherein the second sequence of OFDM symbols are transmitted in a third-generation partnership project (3GPP) long term evolution (LTE) system and corresponds to a slot.

17. The transmitter circuit of claim 12 , wherein the second sampling rate is 240 kHz.

18. The transmitter circuit of claim 11 , wherein the second sampling rate is 480 kHz.

19. The transmitter circuit of claim 11 , wherein the second sampling rate is 960 kHz.

20. The transmitter circuit of claim 11 , wherein the control circuit is configured to adjust the sampling phase by setting an initial sample instant during an OFDM symbol to occur a non-integer multiple of periods at the second sampling rate after a final sample instant of a preceding OFDM symbol.

21. An electronic device comprising the transmitter circuit of claim 11 .

22. The electronic device of claim 21 , wherein the electronic device is a machine-type communication (MTC) device.

23. The electronic device of claim 21 , wherein the electronic device is a network node for a cellular communication system.

Assignees

• Ericsson Telefon Ab L M

Inventors

• Hill Johan
• Breschel Michael

Classifications

• H03M1/66

  Digital/analogue converters ({H03M1/001 – } H03M1/10 take precedence) · CPC title

• H03M1/004

  Reconfigurable analogue/digital or digital/analogue converters (H03M1/02 takes precedence) · CPC title

• H04L5/0037

  Inter-user or inter-terminal allocation · CPC title

• H04L27/2607 Primary

  Cyclic extensions · CPC title