Apparatus and method for dynamically assigning resources in an OFDM communication system

• US 20050068884A1
• Filed: 09/15/2004
• Published: 03/31/2005
• Est. Priority Date: 09/15/2003
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Ro, Jung-Min, Cho, Young-Kwon, Chae, Chan-Byoung, Suh, Chang-Ho, Yoon, Seok-Hyun
• Granted Patent: US 7,535,869 B2
• Time in Patent Office: Days
• US Class Current: 370/203
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling
• CPC Class Codes: H04W 28/06 Optimizing the usage of the radio link, e.g. header compression, information sizing , discarding information system modifying transmission characteristic according to link quality by modifying frame length H04L1/0007; dynamic adaptation of the packet size for flow control or congestion control H04L47/365
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 72/00 Local resource management
• CPC Class Codes: H04W 72/0453 Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 72/542 using measured or perceived quality

Abstract

A mobile communication system and method utilizing Orthogonal Frequency Division Multiplexing (OFDM) receives channel quality information (CQIs) for subcarriers through which reference signals are transmitted and subcarriers through which data signals are transmitted, in subbands, each including a predetermined number of subcarriers among a plurality of the subcarriers. The CQIs are fed back from respective receivers. Resources are dynamically assigned to the respective receivers according to the feedback CQIs, thereby enabling dynamic resource assignment with minimized signaling overhead.

Claims

1. A method for dynamically assigning resources in an Orthogonal Frequency Division Multiplexing (OFDM) wireless communication system that divides an entire frequency band into a plurality of subcarriers, transmits reference signals through a predetermined number of the plurality of subcarriers, transmits data signals through subcarriers, not including the subcarriers through which the reference signals are transmitted, and includes a plurality of subchannels, each of which is a set of a predetermined number of the plurality of subcarriers, the method comprising the steps of:

receiving channel quality informations (CQIs) for the subcarriers through which the reference signals are transmitted and the subcarriers through which the data signals are transmitted, in subbands, each including a predetermined number of the plurality of subcarriers, the CQIs being fed back from respective receivers; and

assigning resources to the respective receivers based on the fedback CQIs.

2. The method of claim 1, wherein the resources include the subchannels, modulation and coding schemes (MCSs), and a transmission power.

3. The method of claim 2, further comprising the steps of:

after assigning the subchannels, the MCSs, and the transmission power to the respective receivers, if there is data to be transmitted to the receivers, modulating and coding the data using the assigned MCSs for the receivers;

performing channel multiplexing such that the modulated and coded data is transmittable through the assigned subchannels; and

separately transmitting the reference signals to the receivers through predetermined subcarriers in the subchannels such that the reference signals have the assigned transmission power.

4. The method of claim 1, wherein the step of assigning the resources based on the fedback CQIs comprises the steps of:

calculating frequency efficiencies to be occurred when a particular subchannel among the subchannels is assigned to the receivers, such that the particular subchannel has a same transmission power, taking the CQIs fed back from the respective receivers into consideration; and

assigning a subchannel such that the particular subchannel is assigned to a receiver where a maximum frequency efficiency among the calculated frequency efficiencies occurs.

5. The method of claim 4, wherein the step of assigning the transmission power according to the feedback CQIs comprises the step of, after assigning the subchannel where the maximum frequency efficiency is occurred to the receivers, assigning transmission power to the receivers such that a sum of frequency efficiencies possibly to be occurred when the subchannels are assigned to the receivers is maximized.

6. A method for dynamically assigning resources in an Orthogonal Frequency Division Multiplexing (OFDM) wireless communication system that divides an entire frequency band into a plurality of subcarriers, transmits reference signals through a predetermined number of the plurality of the subcarriers, transmits data signals through subcarriers, not including the subcarriers through which the reference signals are transmitted, and includes a plurality of subchannels, each of which is a set of a predetermined number of the subcarriers, the method comprising the steps of:

receiving channel quality informations (CQIs) including a first parameter related to a mean channel gain of subcarriers in subbands, each of which includes a predetermined number of subcarriers among a plurality of the subcarriers and noise power, and a second parameter related to a variance of subcarriers in the subbands and the noise power, the CQIs being fed back from respective receivers; and

assigning the subchannels, modulation and coding schemes, and a transmission power to the respective receivers based on the first parameter and the second parameter.

7. The method of claim 6, further comprising the steps of:

modulating and coding the data using the assigned modulation and coding schemes for the receivers, if there is data to be transmitted to the respective receivers;

performing channel multiplexing, such that the modulated and coded data is transmittable through the assigned subchannels; and

separately transmitting the reference signals to the respective receivers through predetermined subcarriers in the subchannels, such that the reference signals have the assigned transmission power.

8. The method of claim 6, wherein the first parameter and the second parameter are expressed respectively as

A^(k)_m=|G^(k)_m|²/N₀, B^(k)_m=(1-Ω

(L))/2N₀

where A^(k)_m is the first parameter, B^(k)_m is the second parameter, L denotes a number of subcarriers included in a subchannel, G^(k)_m denotes a mean of a complex channel gain of an m^th subchannel for a k^th receiver, ‘

1-Ω

(L)’

denotes a variance, and N₀ denotes power noise.

9. The method of claim 7, wherein the step of assigning the subchannels based on the first parameter and the second parameter comprises the steps of:

calculating frequency efficiencies to be occurred when a particular subchannel among the subchannels is assigned to the receivers, such that the particular subchannel has a same transmission power, considering first parameters and second parameters fed back from the respective receivers; and

assigning a subchannel such that the particular subchannel is assigned to a receiver where a maximum frequency efficiency among the calculated frequency efficiencies is occurred.

10. The method of claim 9, wherein the frequency efficiency is calculated using

$U$

( P , a , b ) ≡

∫

0 ∞

⁢

log 2 ⁡

( 1 + P ·

r 2 ) ·

R a , b ⁡

( r ) ·

ⅆ

r

where ‘

a’

denotes A^(k)_m, ‘

b’

denotes B^(k)_m, and P denotes the assigned transmission power.

11. The method of claim 9, wherein the step of assigning the transmission power based on the first parameter and the second parameter comprises the step of, after assigning subchannels where the maximum frequency efficiency is occurred to the receivers, assigning transmission power to the receivers such that a sum of frequency efficiencies possibly to be occurred when the subchannels are assigned to the receivers is maximized.

12. The method of claim 11, wherein the assigned transmission power is calculated using

$\begin{array}{c}\{P_m,m=0,1,\dots \end{array}$

⁢

 

, M - 1 } = ⁢

arg ⁢

 

⁢

max p 0 , p 1 , …

⁢

 

, p M - 1 ⁢

∑

m = 0 M - 1 ⁢

U ⁡

( p m , A m ( κ

m ) , B m ( κ

m ) )

where P_m denotes transmission power assigned to an m^th subchannel, and M denotes the number of the subchannels.

13. A method for transmitting channel quality information (CQI) in an Orthogonal Frequency Division Multiplexing (OFDM) wireless communication system that divides an entire frequency band into a plurality of subcarriers, transmits reference signals through a predetermined number of the plurality of subcarriers, transmits data signals through subcarriers, not including the subcarriers through which the reference signals are transmitted, and includes a plurality of subchannels, each of which is a set of a predetermined number of the subcarriers, the method comprising the steps of:

dividing a received signal into at least one reference signal and at least one data signal;

classifying the at least one reference signal and the at least one data signal according to subbands, each of which includes a predetermined number of the plurality of subcarriers, and determining CQI for each of the subbands; and

feeding back the determined CQIs of the subbands to a transmitter.

14. The method of claim 13, wherein each CQI includes a first parameter considering a mean channel gain of subcarriers in the subbands and noise power, and a second parameter considering a variance of subcarriers in the subbands and the noise power.

15. The method of claim 14, wherein the first parameter and the second parameter are expressed as

A^(k)_m=|G^(k)_m|²/N₀, B^(k)_m=(1-Ω

(L))/2N₀

where A^(k)_m is the first parameter, B^(k)_m is the second parameter, L denotes a number of subcarriers included in a subchannel, G^(k)_m denotes a mean of a complex channel gain of an m^th subchannel for a k^th receiver, ‘

1-Ω

(L)’

denotes a variance, and N₀ denotes power noise.

16. An apparatus for dynamically assigning resources in an Orthogonal Frequency Division Multiplexing (OFDM) wireless communication system that divides an entire frequency band into a plurality of subcarriers, transmits reference signals through a predetermined number of the plurality of subcarriers, transmits data signals through subcarriers, not including the subcarriers through which the reference signals are transmitted, and includes a plurality of subchannels, each of which is a set of a predetermined number of the subcarriers, the apparatus comprising:

a resource assignment controller for receiving channel quality informations (CQIs) for each of the subcarriers through which the reference signals are transmitted and the subcarriers through which the data signals are transmitted, in subbands, each including a predetermined number of the plurality of subcarriers, the CQIs being fed back from respective receivers, and for assigning resources to the respective receivers according to the fed back CQIs.

17. The apparatus of claim 16, wherein the resources include the subchannels, modulation and coding schemes (MCSs), and a transmission power.

18. The apparatus of claim 16, further comprising:

an encoder for coding data using the assigned coding scheme for the respective receivers, upon receiving the data to be transmitted to the receivers;

a symbol mapper for modulating the coded data using the assigned modulation scheme for the respective receivers;

a channel multiplexer for performing channel multiplexing such that the modulated data is transmittable through the assigned subchannels; and

a transmitter for separately transmitting the reference signals to the receivers through predetermined subcarriers in the subbands, for a signal output from the channel multiplexer.

19. The apparatus of claim 16, wherein the resource assignment controller calculates frequency efficiencies to be occurred when a particular subchannel among the subchannels is assigned to the receivers, such that the particular subchannel has a same transmission power, considering the CQIs fed back from the respective receivers, and assigns a subchannel, such that the particular subchannel is assigned to a receiver where a maximum frequency efficiency among the calculated frequency efficiencies is occurred.

20. The apparatus of claim 19, wherein the resource assignment controller, after assigning subchannels where the maximum frequency efficiency is occurred to the receivers, assigns transmission power to the receivers, such that a sum of frequency efficiencies possibly occurring when the subchannels are assigned to the receivers is maximized.

21. An apparatus for dynamically assigning resources in an Orthogonal Frequency Division Multiplexing (OFDM) mobile communication system that divides an entire frequency band into a plurality of subcarriers, transmits reference signals through a predetermined number of the plurality of subcarriers, transmits data signals through subcarriers, not including the subcarriers through which the reference signals are transmitted, and includes a plurality of subchannels, each of which is a set of a predetermined number of the subcarriers, the apparatus comprising:

a resource assignment controller for receiving channel quality informations (CQIs) including a first parameter considering a mean channel gain of subcarriers in subbands, each of which includes a predetermined number of subcarriers among a plurality of the subcarriers, and noise power, and a second parameter considering a variance of subcarriers in the subbands and the noise power, the CQIs being fed back from respective receivers, and for dynamically assigning subchannels, modulation and coding schemes, and transmission power to the respective receivers based on the first parameter and the second parameter.

22. The apparatus of claim 21, further comprising:

an encoder for coding data using the assigned coding scheme for the respective receivers, upon receiving the data to be transmitted to the receivers;

a symbol mapper for modulating the coded data using the assigned modulation scheme for the respective receivers;

a channel multiplexer for performing channel multiplexing, such that the modulated data is transmittable through the assigned subchannels; and

a transmitter for separately transmitting the reference signals to the receivers through predetermined subcarriers in the subbands, for a signal output from the channel multiplexer.

23. The apparatus of claim 21, wherein the first parameter and the second parameter are expressed respectively as

A^(k)_m=|G^(k)_m|²/N₀, B^(k)_m=(1-Ω

(L))/2N₀

where A^(k)_m is the first parameter, B^(k)_m is the second parameter, L denotes a number of subcarriers included in a subchannel, G^(k)_m denotes a mean of a complex channel gain of an m^th subchannel for a k^th receiver, ‘

1-Ω

(L)’

denotes a variance, and N₀ denotes power noise.

24. The apparatus of claim 21, wherein the resource assignment controller calculates frequency efficiencies to be occurred when a particular subchannel among the subchannels is assigned to the receivers, such that the particular subchannel has a same transmission power, considering first parameters and second parameters fed back from the respective receivers, and assigns a subchannel such that the particular subchannel is assigned to a receiver where a maximum frequency efficiency among the calculated frequency efficiencies is occurred.

25. The apparatus of claim 24, wherein the frequency efficiency is calculated using

$U$

( P , a , b ) ≡

∫

0 ∞

⁢

log 2 ⁡

( 1 + P ·

r 2 ) ·

R a , b ⁡

( r ) ·

ⅆ

r

where ‘

a’

denotes A^(k)_m, ‘

b’

denotes B^(k)_m, and P denotes the assigned transmission power.

26. The apparatus of claim 24, wherein the resource assignment controller, after assigning subchannels where the maximum frequency efficiency is occurred to the receivers, assigns transmission power to the receivers such that a sum of frequency efficiencies possibly occurring when the subchannels are assigned to the receivers is maximized.

27. The apparatus of claim 26, wherein the assigned transmission power is calculated using

$\{P_m,m=0,1,\dots$

⁢

 

,  

⁢

M - 1 } = argmax p 0 , p 1 , …

,  

⁢

p M - 1 ⁢

∑

m = 0 M - 1 ⁢

 

⁢

U ⁡

( p m , A m ( κ

m ) , B m ( κ

m ) )

where P_m denotes transmission power assigned to an m^th subchannel, and M denotes the number of the subchannels.

28. An apparatus for transmitting channel quality information (CQI) in an Orthogonal Frequency Division Multiplexing (OFDM) mobile communication system that divides an entire frequency band into a plurality of subcarriers, transmits reference signals through a predetermined number of the plurality of subcarriers, transmits data signals through subcarriers, not including the subcarriers through which the reference signals are transmitted, and includes a plurality of subchannels, each of which is a set of a predetermined number of the subcarriers, the apparatus comprising:

a channel estimator for dividing a received signal into at least one reference signal and at least one data signal, classifying the at least one reference signal and the at least one data signal according to subbands, each of which includes a predetermined number of the plurality of subcarriers, and determining CQIs for the respective subbands; and

a transmitter for feeding back the determined CQIs of the respective subbands to a transmitter.

29. The apparatus of claim 28, wherein the CQI includes a first parameter considering a mean channel gain of subcarriers in the subbands and noise power, and a second parameter considering a variance of the subcarriers in the subbands and the noise power are taken into consideration.

30. The apparatus of claim 29, wherein the first parameter and the second parameter are expressed respectively as

A^(k)_m=|G^(k)_m|²/N₀, B^(k)_m=(1-Ω

(L))/2N₀

where A^(k)_m is the first parameter, B^(k)_m is the second parameter, L denotes a number of subcarriers included in a subchannel, G^(k)_m denotes a mean of a complex channel gain of an m^th subchannel for a k^th receiver, ‘

1-Ω

(L)’

denotes a variance, and N₀ denotes power noise.