MIMO communication system and method capable of adaptive user scheduling

• US 20060146755A1
• Filed: 12/30/2005
• Published: 07/06/2006
• Est. Priority Date: 12/30/2004
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Chen, Lan, Pan, Zhengang
• Granted Patent: US 7,688,789 B2
• Time in Patent Office: Days
• US Class Current: 370/334
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04B 7/0691 using subgroups of transmit antennas

Abstract

A MIMO communication system capable of adaptive user scheduling. The MIMO communication system comprises a transmitting terminal, which sends data frames containing at least channel estimation signal and user data, and at least one receiving terminal, which recovers the user data and generates corresponding feedback information. The feedback information comprises an optimal transmitting antenna set dedicated to the receiving terminal, the achievable channel capacity by each antenna within the antenna set, and the degradation factors caused by each of other unselected antennas to each of the selected antennas. Depending on the feedback information, the transmitting terminal generates scheduling information based on which the adaptive user scheduling is conducted. The scheduling information comprises the scheduled users, number of data streams supported by each scheduled user, and the corresponding transmitting antenna for each of the data streams. The MIMO system can achieve the optimal channel capacity through adaptive user scheduling.

Claims

1. A MIMO communication system capable of adaptive user scheduling, comprising:

a transmitting terminal to transmit data frames containing at least channel estimation signal and user data;

and at least one receving terminal to receive the data frames transmitted by the transmitting terminal and produce corresponding feedback information as well as recover the user data,

wherein the feedback information comprises an optimal transmitting antenna set dedicated to the receiving terminal, the achievable channel capacity by each antenna within the antenna set, and the degradation factors caused by each of other unselected antennas to each of the selected antennas,

the transmitting terminal produces scheduling information based on the feedback information, the scheduling information being used to adaptively schedule the users, and wherein the scheduling information comprises the scheduled users, number of data streams supported by each scheduled user, and the corresponding transmitting antenna for each of the data streams.

2. A MIMO communication system capable of adaptive user scheduling as claimed in claim 1, wherein

the transmitting terminal comprises:

a duplexer group and corresponding mounted transmitting antennas to transmit the data frame and receive the feedback information from the receiving terminal;

a MIMO scheduler to produce the scheduling information based on the feedback information; and

a MIMO signal processor to schedule the users according to the scheduling information and to transmit data of the scheduled users through the selected transmitting antennas, and

wherein the receiving terminal comprises;

a duplexer group and corresponding mounted receiving antennas to recieve the data frame from the transmitting terminal and transmit feedback information;

a receiving signal processor to produce user feedback information and recover the user data from the received data frame; and

a feedback information processor to convert the user feedback information into the feedback signals.

3. A MIMO communication system capable of adaptive user scheduling as claimed in claim 2, wherein,

the MIMO scheduler comprises:

a receiving RF chain group to convert the received RF signals to the corresponding code streams;

a MIMO receiving signal processor to produce the scheduling information through a layered space-time signal processing on the obtained code streams; and

a scheduler to control the signal processing of the MIMO signal processor.

4. A MIMO communication system capable of adaptive user scheduling as claimed in claim 2, wherein

the MIMO signal processor comprises:

a user selector to select the users according to the scheduling information;

a plurality of parallel de-multiplexer to de-multiplex the user data of the scheduled users to generate a plurality of separated code streams;

a MIMO transmitting signal processor to conduct the layered space-time processing on the obtained plurality of separated code streams according to the scheduling information;

a transmitting RF chain group to convert the plurality of code streams processed by the MIMO transmitting signal processor into the corresponding RF signals; and

a transmitting antenna selector to select transmitting antennas depending on the scheduling information.

5. A MIMO communication system capable of adaptive user scheduling as claimed in claim 4, wherein

the transmitting RF chain group comprises:

a plurality of transmitting RF chains each of which is used to modulate one of the code streams generated by the MIMO transmitting signal processor to the corresponding RF signal,

wherein each transmitting RF chain comprises a modulator, an upconverter, and a power amplifer connected in serial.

6. A MIMO system capable of adaptive user scheduling as claimed in claim 5, wherein the power amplifer is a high power linear amplifier.

7. A MIMO system capable of adaptive user scheduling as claimed in claim 6, wherein the number of the transmitting RF chains is less than or equal to the number of the transmitting antennas.

8. A MIMO communication system capable of adaptive user scheduling as claimed in claim 2, wherein

the receiving signal processor comprises:

a receiving RF chain group to demodulate and convert the received RF signals to obtain the corresponding code streams;

a MIMO receiving signal processor to produce the corresponding user feedback information depending on the code streams and recover the user data, and

wherein the feedback information processor comprises

a MIMO transmitting signal processor to convert the user feedback information into the feedback signals; and

a transmitting RF chain group to convert the feedback signals into the corresponding RF signals.

9. A MIMO system capable of adaptive user scheduling as claimed in claim 8, wherein the power amplifer is a high power linear amplifier.

10. A MIMO system capable of adaptive user scheduling as claimed in claim 9, wherein the number of the transmitting RF chains is less than or equal to the number of the transmitting antennas.

11. An adaptive user scheduling method for MIMO communication system, comprising:

a) the receving terminal producing feedback information based on the channel fading condition between transmitted antennas and receiving antennas and feeding the feedback information to the transmitting terminal,

b) the transmitting terminal receiving the feedback information and producing scheduling information and adaptively scheduling the users according to the obtained scheduling information,

wherein the the feedback information comprises an optimal transmitting antenna set dedicated to the receiving terminal, the achievable channel capacity by each antenna within the antenna set, and the degradation factors caused by each of other unselected antennas to each of the selected antennas,

and wherein the scheduling information comprises the scheduled users, number of data streams supported by each scheduled user, and the corresponding transmitting antenna for each of the data streams.

12. An adaptive user scheduling method as claimed in claim 11, wherein the channel fading conditions are obtained via channel estimation signal received by the receiving terminal.

13. An adaptive user scheduling method as claimed in claim 11, wherein the channel fading conditions are obtained via data frames received by the receiving antennas.

14. An adaptive user scheduling method as claimed in any one of claim 11, wherein receiving the feedback information further comprises:

initializing the set of scheduled users and set of assigned antennas as null set;

comparing channel capacities in the feedback information, and selecting a user having the maximum channel capacity, then adding the selected user to the set of scheduled users, and adding the transmitting antenna corresponding to the selected user to set of assigned antennas;

selecting a transmitting antenna with the least degradation factor to the user in the set of scheduled users, and identifying another user corresponding to the selected transmitting antenna and having the maximum channel capacity;

calculating the total capacity of the system when another user is added to the system, and if the total capacity is increased, adding the user to the scheduled user set and adding the corresponding antenna to the assigned antenna set and proceeding to selecting the transmitting antenna if the total capacity is decreased, ending the scheduling process; and

scheduling users in the system according to the final scheduled users set and the assigned antennas set.

15. An adaptive user scheduling method as claimed in any one of claim 12, wherein receiving the feedback information further comprises:

initializing the set of scheduled users and set of assigned antennas as null set;

comparing channel capacities in the feedback information, and selecting a user having the maximum channel capacity, then adding the selected user to the set of scheduled users, and adding the transmitting antenna corresponding to the selected user to set of assigned antennas;

selecting a transmitting antenna with the least degradation factor to the user in the set of scheduled users, and identifying another user corresponding to the selected transmitting antenna and having the maximum channel capacity;

calculating the total capacity of the system when another user is added to the system, and if the total capacity is increased, adding the user to the scheduled user set and adding the corresponding antenna to the assigned antenna set and proceeding to selecting the transmitting antenna if the total capacity is decreased, ending the scheduling process; and

scheduling users in the system according to the final scheduled users set and the assigned antennas set.

16. An adaptive user scheduling method as claimed in any one of claim 13, wherein receiving the feedback information further comprises:

initializing the set of scheduled users and set of assigned antennas as null set;

comparing channel capacities in the feedback information, and selecting a user having the maximum channel capacity, then adding the selected user to the set of scheduled users, and adding the transmitting antenna corresponding to the selected user to set of assigned antennas;

selecting a transmitting antenna with the least degradation factor to the user in the set of scheduled users, and identifying another user corresponding to the selected transmitting antenna and having the maximum channel capacity;

calculating the total capacity of the system when another user is added to the system, and if the total capacity is increased, adding the user to the scheduled user set and adding the corresponding antenna to the assigned antenna set and proceeding to selecting the transmitting antenna if the total capacity is decreased, ending the scheduling process; and

scheduling users in the system according to the final scheduled users set and the assigned antennas set.