APPARATUS AND METHOD OF ERROR VECTOR MEASUREMENT FOR DIGITAL AND MULTIPLE-INPUT MULTIPLE OUTPUT IMO COMMUNICATION SYSTEMS

• US 20090175181A1
• Filed: 01/08/2008
• Published: 07/09/2009
• Est. Priority Date: 01/08/2008
• Status: Active Grant

• Current Assignee: Microchip Technology Incorporated
• Original Assignee: Integrated System Solution Corp.
• Inventors: Chen, Jeng-Hong, KIM, Pansop
• Granted Patent: US 8,036,298 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0015 characterised by the adaptation strategy
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0031 Multiple signaling transmission H04L1/1664, F15 take precedence
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 27/38 Demodulator circuits; Receiver circuits

Abstract

The present invention discloses an effective apparatus and method to measure the received signal quality for digital communication systems by measuring error vector measurement (EVM) with embedded EVM measurement block in receivers. The distinction of the present invention is that the EVM_SIG and the EVM_DATA are measured in the receiver for the SIGNAL fields and DATA fields, respectively. EVM_SIG is a good indicator for one spatial stream and EVM_DATA is a good indicator for current multiple streams. The receiver determines the optimum number of spatial data streams for feedback to the transmitter based on the combinations of EVM_SIG and EVM_DATA with or without other algorithms such as analysis on periodically requested sounding packet. The receiver also determines the optimum modulation and coding schemes for feedback based on the EVM measurements.

Claims

1. An apparatus in a multiple-input multiple-output (MIMO) receiving station, comprising:

an EVM measurement unit for SIGNAL field, used to measure a combined effect of all spatial streams to achieve the measurement of averaged EVM_SIG; and

an EVM measurement unit for DATA field, electrically connected to the EVM measurement unit for SIGNAL field, used in each spatial stream to support unequal modulation and coding rate (MCS) for multiple streams to achieve the measurement of averaged EVM_DATA.

2. The apparatus in a multiple-input multiple-output (MIMO) receiving station as claimed in claim 1, further comprising:

a rate feedback selector, electrically connected to the EVM measurement unit for SIGNAL field and the EVM measurement unit for DATA field, used to provide a feedback determined by analyzing the two averaged EVM_SIG and EVM_DATA to a transmitting station.

3. The apparatus in a multiple-input multiple-output HO) receiving station as claimed in claim 1, wherein the EVM measurement unit for SIGNAL field measures the combined effect of all spatial streams in preamble.

4. The apparatus in a multiple-input multiple-output (MIMO) receiving station as claimed in claim 1, wherein the EVM measurement unit for DATA field has a payload in each spatial stream to support unequal MCS for multiple streams.

5. The apparatus in a multiple-input multiple-output (MIMO) receiving station as claimed in claim 2, wherein the rate feedback selector obtains a number of the spatial data streams (N_SS) and a data rate for MCS by utilizing the measured EVM_SIG and EVM_DATA and a received power.

6. The apparatus in a multiple-input multiple-output (MIMO) receiving station as claimed in claim 5, wherein the receiving station transmits a request of increasing Nss periodically when required.

7. The apparatus in a multiple-input multiple-output (MIMO) receiving station as claimed in claim 6, wherein the receiving station determines whether the request of increasing Nss received packet is good or not by checking the averaged EVM_SIG and EVM_DATA and/or the maximum possible rates on different numbers of spatial streams.

8. The apparatus in a multiple-input multiple-output (MIMO) receiving station as claimed in claim 6, wherein the receiving station transmit a request for a sounding packet that has all the channel information and the optimum Nss on the current channel is determined by analyzing the channel coefficients.

9. The apparatus in a multiple-input multiple-output (MIMO) receiving station as claimed in claim 5, wherein the receiving station determines the optimum Nss and MCS in terms of the balance of throughput and power saving.

10. The apparatus in a multiple-input multiple-output (MIMO) receiving station as claimed in claim 9, wherein the receiving station determines the optimum Nss and MCS in maximum throughput mode, which is for the maximum throughput by turning on all the Tx and Rx antennas in the receiving station and the transmitting station.

11. The apparatus in a multiple-input multiple-output (MIMO) receiving station as claimed in claim 9, wherein the receiving station determines the optimum Nss and MCS in normal mode, which is for compromising of the power saving and the throughput by turning on partial set of Tx and Rx antennas in the receiving station and the transmitting station.

12. The apparatus in a multiple-input multiple-output (MIMO) receiving station as claimed in claim 9, wherein the receiving station determines the optimum Nss and MCS in power saving mode, which is for the maximum power saving by turning on minimally required set of Tx and Rx antennas in the receiving station and the transmitting station for the current data rate.

13. A method of improving transmit modulation accuracy and receiver performance test in a MIMO system, comprising the steps of:

measuring a combined effect of all spatial streams to achieve the measurement of averaged EVM_SIG in an EVM measurement unit for SIGNAL field, and

supporting an unequal modulation and coding rate (MCS) in each spatial stream for multiple streams to achieve the measurement of averaged EVM_DATA in an EVM measurement unit for DATA field, electrically connected to the EVM measurement unit for SIGNAL field.

14. The method as claimed in claim 13, further comprising the step of:

providing a feedback determined by analyzing the two averaged EVM_SIG and EVM_DATA in a rate feedback selector, electrically connected to the EVM measurement unit for SIGNAL field and the EVM measurement unit for DATA field, to a transmitting station.

15. The method as claimed in claim 13, wherein the EVM measurement unit for SIGNAL field measures the combined effect of all spatial streams in preamble.

16. The method as claimed in claim 13, wherein the EVM measurement unit for DATA field has a payload in each spatial stream to support unequal MCS for multiple streams.

17. The method as claimed in claim 14, wherein the rate feedback selector obtains a number of the spatial data streams (N_SS) and a data rate for MCS by utilizing the measured EVM_SIG and EVM_DATA and a received power.

18. The method as claimed in claim 17, wherein the receiving station transmits a request of increasing Nss periodically when required.

19. The method as claimed in claim 18, wherein the receiving station determines whether the request of increasing Nss received packet is good or not by checking the averaged EVM_SIG and EVM_DATA and/or the maximum possible rates on different numbers of spatial streams.

20. The method as claimed in claim 18, wherein the receiving station transmit a request for a sounding packet that has all the channel information and the optimum Nss on the current channel is determined by analyzing the channel coefficients.

21. The method as claimed in claim 17, wherein the receiving station determines the optimum Nss and MCS in terms of the balance of throughput and power saving.

22. The method as claimed in claim 21, wherein the receiving station determines the optimum Nss and MCS in maximum throughput mode, which is for the maximum throughput by turning on all the Tx and Rx antennas in the receiving station and the transmitting station.

23. The method as claimed in claim 21, wherein the receiving station determines the optimum Nss and MCS in normal mode, which is for compromising of the power saving and the throughput by turning on partial set of Tx and RX antennas in the receiving station and the transmitting station.

24. The method as claimed in claim 21, wherein the receiving station determines the optimum Nss and MCS in power saving mode, which is for the maximum power saving by turning on minimally required set of Tx and Rx antennas in the receiving station and the transmitting station for the current data rate.