Apparatus and method for assigning subchannel in a mobile communication system using orthogonal frequency division multiple access scheme

• US 20050025039A1
• Filed: 07/29/2004
• Published: 02/03/2005
• Est. Priority Date: 07/30/2003
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Sung, Sang-Hoon, Hwang, In-Seok, Yoon, Soon-Young, Cho, Jae-Hee, Huh, Hoon, Roh, Kwan-Hee
• Granted Patent: US 7,502,310 B2
• Time in Patent Office: Days
• US Class Current: 370/206
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601
• CPC Class Codes: H04W 72/00 Local resource management
• CPC Class Codes: H04W 72/02 Selection of wireless resources by user or terminal
• CPC Class Codes: H04W 72/0453 Resources in frequency domain, e.g. a carrier in FDMA

Abstract

A two-dimensional subchannel assigning method and apparatus in a time-frequency domain where a plurality of subcarriers are arranged along a time domain with a plurality of symbols and along a frequency domain with a plurality of subbands in an OFDM communication system. In the subchannel assigning method, the plurality of subcarriers are divided into a plurality of frequency bands and the frequency bands are grouped into the subbands. A plurality of groups are generated by dividing each of the subbands in the frequency domain by the number of the symbols in the time domain. Subcarriers selected from the respective groups in each of the subbands are assigned as an AMC subchannel to which an AMC scheme is applied.

Claims

1. A two-dimensional subchannel assigning method in a time-frequency domain having a plurality of subcarriers arranged along a time domain with a plurality of symbols and arranged along a frequency domain with a plurality of subbands in an orthogonal frequency multiplexing (OFDM) communication system, the method comprising the steps of:

dividing a plurality of subcarriers into a plurality of frequency bands and grouping the frequency bands into subbands;

generating a plurality of groups by dividing each of the subbands in the frequency domain by the number of symbols in the time domain; and

assigning subcarriers selected from the respective groups in each of the subbands as an adaptive modulation and coding (AMC) subchannel to which an AMC scheme is applied.

2. The method of claim 1, further comprising the step of, after the AMC subchannel assigning step, forming a diversity subchannel to which a diversity scheme is applied using second subcarriers selected from subcarriers other than the subcarriers assigned to the AMC subchannel.

3. A subchannel assigning method in an orthogonal frequency division multiplexing (OFDM) communication system having a total frequency band divided into a plurality of subcarriers, comprising the steps of:

generating as many groups as the number of base stations (BSs) of the OFDM communication system by grouping the subcarriers in a time domain;

generating a plurality of subbands by grouping the groups;

detecting subcarriers from each of the groups included in a subband according to a first sequence; and

assigning the detected subcarriers as an adaptive modulation and coding (AMC) subchannel to which an AMC scheme is applied.

4. The method of claim 3, further comprising, after the AMC subchannel assigning step, the steps of:

detecting subcarriers from each of the groups according to a second sequence; and

assigning the detected subcarriers as a diversity subchannel.

5. The method of claim 4, wherein the subcarriers assigned as the diversity subchannel are different from the subcarriers assigned as the AMC subchannel.

6. The method of claim 4, wherein the first sequence indicates the indexes of the subcarriers assigned as the AMC subchannel.

7. The method of claim 4, wherein the second sequence indicates the indexes of the subcarriers assigned as the diversity subchannel.

8. The method of claim 6, wherein the first sequence is defined over a Galois Field.

9. The method of claim 7, wherein the second sequence is defined over a Galois Field.

10. A subchannel assigning method in an orthogonal frequency division multiplexing (OFDM) communication system having a total frequency band divided into a plurality of subcarriers, comprising the steps of:

generating (Q-1) groups for n symbol periods by grouping subcarriers for each of the n symbol periods into (Q-1)/n groups;

generating B subbands by grouping the (Q-1) groups into L groups;

detecting subcarriers from each of (Q-1)/L groups included in a subband according to a first sequence; and

assigning the detected subcarriers as an adaptive modulation and coding (AMC) subchannel to which an AMC scheme is applied.

11. The method of claim 10, further comprising, after the AMC subchannel assigning step, the steps of:

detecting subcarriers from each of the (Q-1) groups according to a second sequence; and

assigning the detected subcarriers as a diversity subchannel.

12. The method of claim 11, wherein the subcarriers assigned as the diversity subchannel are different from the subcarriers assigned as the AMC subchannel.

13. The method of claim 11, wherein the first sequence indicates the indexes of the subcarriers assigned as the AMC subchannel.

14. The method of claim 13, wherein the first sequence is defined over a Galois Field.

15. The method of claim 14, wherein the first sequence is determined by

Sub_carrier index(n,b:

i)=Q×

L×

[(L/B)b+(└

i/B┘

%(L/B))]+S<sub>m,β

0+(i % B)</sub>(└

i/B┘

);

n=└

i/L┘

where b is the index of the subband, i is a subcarrier index, and S<sub>m,β

0</sub> is a sequence that defines a first diversity channel (diversity channel #0) for an m^th base station (BS) from among a plurality of BSs existing in the OFDM communication system.

16. The method of claim 12, wherein the second sequence indicates the indexes of the subcarriers assigned as the diversity subchannel.

17. The method of claim 16, wherein the second sequence is defined over a Galois Field.

18. The method of claim 17, wherein the second sequence is determined by

sub_carrier index(n:

i)=Q×

(i−

L×

└

i/L┘

)+S_m,β

(i);

n=└

i/L┘

where i is a subcarrier index and S<sub>m,β

0</sub> is a sequence that defines each of subchannels for the m^th BS from among a plurality of BSs existing in the OFDM communication system.

19. A subchannel assigning method in an orthogonal frequency division multiplexing (OFDM) communication system where a total frequency band is divided into a predetermined number of subbands, a subchannel is formed a number of subcarriers selected from each of the subbands, a reference signal is transmitted in the subcarriers of the subchannel, and a data signal is transmitted in subcarriers other than the subcarriers of the reference signal in the subchannel, the method comprising the steps of:

modulating and encoding a data signal in a predetermined modulation and coding scheme, upon input of the data signal, inserting a reference signal into the modulated and coded data signal, inverse-fast-Fourier transform (IFFT)-processing the reference signal-inserted signal, and transmitting the IFFT signal to a mobile subscriber station (MSS);

receiving a channel quality information (CQI) of the data signal and the reference signal on a subband basis from the MSS; and

selecting a subband having the best quality by analyzing the received CQI, and selecting a subchannel in the selected subband for the MSS.

20. The method of claim 19, wherein the subband includes a plurality of subcarriers.

21. The method of claim 20, wherein the CQI includes the carrier-to-interference and noise ratio (CINR) of the data signal and the reference signal in the subband.

22. The method of claim 21, wherein the CINR is the average of the CINRs of the reference signals in the subband and the CINRs of data signals in the subband, the CINRs of the data signals calculated by interpolating the CINRs of the reference signals.

23. A two-dimensional subchannel assigning apparatus in a time-frequency domain where a plurality of subcarriers are arranged along a time domain with a plurality of symbols and arranged along a frequency domain with a plurality of subbands in an orthogonal frequency multiplexing (OFDM) communication system, the apparatus comprising:

a subchannel/subband allocator for dividing a plurality of subcarriers into a plurality of frequency bands, grouping the frequency bands into subbands, generating a plurality of groups by dividing each of the subbands in the frequency domain by the number of the symbols in the time domain, and assigning subcarriers selected from the respective groups in each of the subbands as an adaptive modulation and coding (AMC) subchannel to which an AMC scheme is applied; and

a transmitter for, upon generation of data to be transmitted, transmitting the data on the assigned AMC subchannel.

24. The apparatus of claim 23, wherein the subchannel/subband allocator forms a diversity subchannel to which a diversity scheme is applied using subcarriers selected from subcarriers other than the subcarriers assigned to the AMC subchannel, after assigning the AMC subchannel.

25. A subchannel assigning apparatus in an orthogonal frequency division multiplexing (OFDM) communication system where a total frequency band is divided into a plurality of subcarriers, comprising:

a subchannel/subband allocator for generating as many groups as a number of base stations (BSs) of the OFDM communication system by grouping subcarriers in a predetermined time domain, generating a plurality of subbands by grouping the groups, detecting subcarriers from each of the groups included in a subband according to a first sequence, and assigning the detected subcarriers as an adaptive modulation and coding (AMC) subchannel to which an AMC scheme is applied; and

a transmitter for, upon generation of data to be transmitted, transmitting the data on the assigned AMC subchannel.

26. The apparatus of claim 25, wherein the subchannel/subband allocator detects subcarriers from each of the groups according to a second sequence and assigns the detected subcarriers as a diversity subchannel, after assigning the AMC subchannel.

27. The apparatus of claim 26, wherein the subcarriers assigned as the diversity subchannel are different from the subcarriers assigned as the AMC subchannel.

28. The apparatus of claim 26, wherein the first sequence indicates the indexes of the subcarriers assigned as the AMC subchannel.

29. The apparatus of claim 26, wherein the second sequence indicates the indexes of the subcarriers assigned as the diversity subchannel.

30. The apparatus of claim 28, wherein the first sequence is defined over a Galois Field.

31. The apparatus of claim 29, wherein the second sequence is defined over a Galois Field.

32. A subchannel assigning apparatus in an orthogonal frequency division multiplexing (OFDM) communication system where a total frequency band is divided into a predetermined number of subbands, a subchannel is formed from a number of subcarriers selected from each of the subbands, a reference signal is transmitted in subcarriers of the subchannel, and a data signal is transmitted in subcarriers other than the subcarriers of the reference signal in the subchannel, the apparatus comprising:

an encoder for encoding the data signal in a coding method upon input of the data signal;

a modulator for modulating the coded data signal in a modulation method;

a transmitter for inserting a reference signal into the modulated data signal, inverse-fast-Fourier transform (IFFT)-processing the reference signal-inserted signal, and transmitting the IFFT signal to a mobile subscriber station (MSS); and

a subchannel/subband allocator for receiving from the MSS a channel quality information (CQI) of the data signal and the reference signal on a subband basis, selecting a subband having the best quality by analyzing the received CQI, and selecting a subchannel in the selected subband for the MSS.

33. The apparatus of claim 32, wherein the subband includes a number of subcarriers.

34. The apparatus of claim 33, wherein the CQI includes the carrier-to-interference and noise ratio (CINR) of the data signal and the reference signal in the subband.

35. The apparatus of claim 34, wherein the CINR is the average of the CINRs of reference signals in the subband and the CINRs of data signals in the subband, the CINRs of the data signals being calculated by interpolating the CINRs of the reference signals.