Data communication apparatus and method based on orthogonal frequency division multiple access

• US 7,257,166 B2
• Filed: 03/22/2002
• Issued: 08/14/2007
• Est. Priority Date: 03/26/2001
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Yung-Soo
• Primary Examiner(s): Ghayour; Mohammed
• Assistant Examiner(s): GHULAMALI, QUTBUDDIN
• Application Number:
  US10/472,271
• Publication Number:
  US 20040114691A1
• Time in Patent Office: 1,971 Days
• Field of Search: 375/260, 375/261, 375/262, 375/298, 375/347, 375/349, 375/147, 375/316, 375/259, 375/267, 375/284, 375/296, 375/299, 375/325, 375/330, 370/210, 370/486, 329/309, 329/306, 708/403, 708/404, 332/105, 332/123, 332/124, 332/126, 381/330
• US Class Current: 375/260
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601

Abstract

A data communication apparatus and method based on OFDMA are provided. In a first user transmitting unit through which a user transmits user information to a base station in units of first symbol blocks each including M symbols, a first encoder generates a first sub-block composed of M_u user symbols for a u-th user by encoding the user information. A first block repeater repeats the first sub-block L_u times to generate M symbols. A first multiplier multiplies the M symbols by γ_u exp(j2πkm_u/M) and outputs a u-th user signal. A first cyclic extension symbol inserter inserts a cyclic extension symbol into the u-th user signal and generates a single complete first symbol block. Accordingly, data transmission speed can be freely changed, a very small PAR can be provided, influence of the signal interference is greatly reduced, interference occurring between received blocks due to channels can be prevented, and distortion between channels can be effectively compensated for.

Claims

1. A data communication apparatus based on orthogonal frequency division multiple access (OFDMA) comprising a first user transmitting unit through which a user transmits user information to a base station in units of first symbol blocks each including a first predetermined number M of symbols in data communication between the user and the base station, the first user transmitting unit comprising:

a first encoder for generating a first sub-block composed of a second predetermined number M_u of user symbols a_k^(u) for a u-th user by encoding the user information, where M_u is an integer greater than or equal to 1 and no greater than M, “

k”

is a time index and an integer greater than or equal to 0 and no greater than M−

1, “

u”

is a user index and an integer greater than or equal to 1 and no greater than U, and U indicates the number of users sharing the first symbol block and is 1 or a positive integer greater than 1;

a first block repeater for repeating the first sub-block a third predetermined number L_u of times to generate M symbols a_k′

^(u), wherein L_u is M/M_u, k′

=k % M_u, and k % M_u indicates the remainder when “

k”

is divided by M_u;

a first multiplier for multiplying the M symbols a_k′

^(u) generated from the first block repeater by γ

_u exp(j2π

km_u/M) and outputting the result of multiplication as a signal x_k^(u) for the u-th user, wherein γ

_u indicates a magnitude control factor for the u-th user signal x_k^(u), and m_u indicates a unique frequency offset number allocated to the u-th user;

a first cyclic extension symbol inserter for outputting the first symbol block completed by inserting a cyclic extension symbol into the u-th user signal x_k^(u); and

a first signal transmitter for converting the completed first symbol block into a symbol block signal and transmitting the symbol block signal,

wherein M₁+M₂+M₃+ . . . +M_u does not exceed M where M represents the number of symbols in data communication between the user and the base station, Mu is an integer greater than or equal to 1 and no greater than M, ‘

u’

is a user index and an integer greater than or equal to 1 and no greater than U, and U indicates the number of users sharing the first symbol block and is 1 or a positive integer greater than 1.

2. The data communication apparatus of claim 1, wherein the number M_u of symbols a_k^(u) used for generating the first sub-block is an exponential with base 2.

3. The data communication apparatus of claim 1, wherein the number U of users sharing the first symbol block varies with the first symbol block.

4. A data communication apparatus based on orthogonal frequency division multiple access (OFDMA) in data communication between a fourth predetermined number V of users and a base station, V indicating the number of users sharing a second symbol block and being 1 or a positive integer greater than 1, the data communication apparatus comprising a first base station transmitting unit through which the base station transmits base station information to a v-th user in units of the second symbol blocks each including a fifth predetermined number N of symbols “

v”

being a user index and an integer greater than or equal to 1 and no greater than V, the first base station transmitting unit comprising;

second through (V+1)-th encoders;

second through (V+1)-th block repeaters;

second through (V+1)-th multipliers;

a first adder;

a second cyclic extension symbol inserter; and

a second signal transmitter,

wherein the (v+1)-th encoder generates a (v+1)-th sub-block composed of a sixth predetermined number N_v of base station symbols a_k^(v) for a v-th user by encoding the base station information and outputs the (v+1)-th sub-block to the (v+1)-th block repeater, N_v being an integer greater than or equal to 1 and less than or equal to N, “

k”

being a time index and an integer greater than or equal to 0 and less than or equal to N−

1,

the (v+1)-th block repeater repeats the (v+1)-th sub-block a seventh predetermined number L_v of times to generate N symbols a_k′

^(v) and outputs the N symbols a_k′

^(v) to the (v+1)-th multiplier, L_v being N/N_v, k′

=k % N_v, k % N_v indicating the remainder when “

k”

is divided by N_v,

the (v+1)-th multiplier multiplies the N symbols a_k′

^(v) by γ

_v exp(j2π

kn_v/N) and outputs the result x_k^(v) of multiplication to the first adder, γ

_v indicating a magnitude control factor for a v-th user signal, n_v indicating a unique frequency offset number allocated to the v-th user,

the first adder sums the results x_k⁽¹⁾ through x_k^(V) of multiplication received from the second through (V+1)-th multipliers and outputs the result x_k of summation to the second cyclic extension symbol inserter,

the second cyclic extension symbol inserter outputs the single second symbol block completed by inserting a cyclic extension symbol into the result x_k of summation to the second signal transmitter,

the second signal transmitter converts the completed second symbol block into a symbol block signal and transmits the symbol block signal, and

N₁+N₂+N₃+ . . . +N_v does not exceed N where N represents the number of second symbol blocks in data communication between the user and the base station, Nv is an integer greater than or eciual to 1 and less than or equal to N, ‘

v’

is a user index and an integer greater than or equal to 1 and no greater than V, and V indicates the number of users sharing the second symbol block and is 1 or a positive integer greater than 1.

5. A data communication apparatus based on orthogonal frequency division multiple access (OFDMA) comprising a first base station receiving unit which receives a symbol block signal transmitted from each of U first user transmitting units and estimates u-th user symbols from the symbol block signal, U indicating the number of users sharing a first symbol block having M symbols and being 1 or a positive integer greater than 1, “

u”

being a user factor and an integer greater than or equal to 1 and no greater than M, the first base station receiving unit comprising;

a first signal receiver for converting the received symbol block signal into the first symbol block and outputting the first symbol block;

a first pre-processor for finding a start point of the first symbol block received from the first signal receiver, removing a cyclic extension symbol from the first symbol block on the basis of the start point, and outputting the result r_k of removal of the cyclic extension symbol, wherein “

k”

is a time index and an integer greater than or equal to 0 and less than or equal to M−

1;

a first user symbol extractor for extracting only the u-th user symbols from the result r_k received from the first pre-processor; and

a first estimate value detector for detecting an estimate value â

_k^(u) for a u-th user symbol from the u-th user symbols extracted by the first user symbol extractor.

6. The data communication apparatus of claim 5, wherein the first estimate value detector comprises first through U-th detectors and the u-th detector detects the user symbol estimate value â

_k^(u) from the u-th user symbols output from the first user symbol extractor.

7. The data communication apparatus of claim 6, wherein the first user symbol extractor comprises:

(V+2)-th through (U+V+1)-th multipliers; and

first through U-th post-processors,

the (u+V+1)-th multiplier multiplies the result r_k output from the first pre-processor by α

_u exp(−

j2π

km_u/M) and outputs the result of multiplication as a u-th user signal {tilde over (r)}_k^(u) to the u-th post-processor, α

_u indicating a magnitude control factor, m_u indicating a unique frequency offset number previously allocated to the u-th user,

the u-th post-processor folds and adds the u-th user signal {tilde over (r)}_k^(u) output from the (u+V+1)-th multiplier with a period of M_u and outputs the result of folding and addition as the u-th user symbol r_k^(u) to the u-th detector, M_u being an integer greater than or equal to 1 and less than or equal to M, and

the u-th detector detects the user symbol estimate value â

_k^(u) from the u-th user symbol r_k^(u) output from the u-th post-processor.

8. The data communication apparatus of claim 6, wherein the first user symbol extractor comprises:

a Fourier transformer for performing M-point Fourier transform on the result r_k output from the first pre-processor and outputting the result R_n of Fourier transform, “

n”

indicating a frequency factor and being an integer greater than or equal to 0 and less than or equal to M−

1;

first through U-th inverse Fourier transformers;

a first controller for generating a selection signal in response to L_u and a unique frequency offset number m_u previously allocated to the u-th user, L_u being M/M_u, M_u being an integer greater than or equal to 1 and less than or equal to M; and

a distributor for outputting the result R_n output from the Fourier transformer as R_n^(u) to the u-th inverse Fourier transformer in response to the selection signal,

the u-th inverse Fourier transformer performs M_u-point inverse Fourier transform on R_n^(u) and outputs the result of inverse Fourier transform as the u-th user symbol r_k^(u) to the u-th detector, and

the u-th detector detects the user symbol estimate value â

_k^(u) for the u-th user from the u-th user symbol r_k^(u) output from the u-th inverse Fourier transformer.

9. The data communication apparatus of claim 6, wherein the first user symbol extractor comprises:

a Fourier transformer for performing M-point Fourier transform on the result r_k output from the first pre-processor and outputting the result R_n of Fourier transform, wherein “

n”

indicates a frequency factor and is an integer greater than or equal to 0 and no greater than M−

1;

a first frequency equalizer for multiplying the result R_n output from the Fourier transformer by a first predetermined complex number and outputting the result Z_n of multiplication;

first through U-th inverse Fourier transformers;

a first controller for generating a selection signal in response to L_u and a unique frequency offset number m_u previously allocated to the u-th user, L_u being M/M_u, M_u being an integer greater than or equal to 1 and less than or equal to M; and

a distributor for outputting the result Z_n output from the first frequency equalizer as Z_n^(u) to the u-th inverse Fourier transformer in response to the selection signal,

the u-th inverse Fourier transformer performs M_u-point inverse Fourier transform on Z_k^(u) output from the distributor and outputs the result of inverse Fourier transform as the u-th user symbol z_k^(u) to the u-th detector, and

the u-th detector detects the user symbol estimate value â

_k^(u) for the u-th user from the u-th user symbol z_k^(u) output from the u-th inverse Fourier transformer.

10. The data communication apparatus of claim 6, wherein the first user symbol extractor comprises:

a first time equalizer for removing interchannel interference from the result r_k output from the first pre-processor and outputting the result z_k of removal of the interchannel interference;

(V+U+2)-th through (2U+V+1)-th multipliers; and

(U+1)-th through 2U-th post-processors,

the (u+V+U+1)-th multiplier multiplies the result z_k output from the first time equalizer by α

_u exp(−

j2π

km_u/M) and outputs the result of multiplication as a u-th user signal {tilde over (z)}_k^(u) for the u-th user to the (u+U)-th post-processor, α

_u indicating a magnitude control factor, m_u indicating a unique frequency offset number previously allocated to the u-th user,

the (u+U)-th post-processor folds and adds the u-th user signal {tilde over (z)}_k^(u) output from the (u+V+U+1)-th multiplier with a period of M_u and outputs the result of folding and addition as the u-th user symbol z_k^(u) to the u-th detector, M_u being an integer greater than or equal to 1 and less than or equal to M, and

the u-th detector detects the user symbol estimate value â

_k^(u) for the u-th user from the u-th user symbol z_k^(u) output from the (u+U)-th post-processor.

11. The data communication apparatus of claim 10, wherein the first time equalizer comprises a finite impulse response (FIR) filter which performs FIR filtering on the result r_k output from the first pre-processor and outputs the result of filtering as the result of removal of the interchannel interference.

12. The data communication apparatus of claim 10, wherein the first time equalizer comprises:

a Fourier transformer for performing M-point Fourier transform on the result r_k output from the first pre-processor and outputting the result of Fourier transform;

a third frequency equalizer for multiplying M signals output from the Fourier transformer by a third predetermined complex number and outputting the result of multiplication; and

an inverse Fourier transformer for performing M-point inverse Fourier transform on the result of multiplication output from the third frequency equalizer and outputting the result of inverse Fourier transform as the result z_k of removal of the interchannel interference.

13. The data communication apparatus of claim 6, wherein the first user symbol extractor comprises:

(V+2)-th through (U+V+1)-th multipliers;

first through U-th post-processors; and

second through (U+1)-th time equalizers,

the (u+V+1)-th multiplier multiplies the result r_k output from the first pre-processor by α

_u exp(−

j2π

km_u/M) and outputs the result of multiplication as a u-th user signal {tilde over (r)}_k^(u) for the u-th user to the u-th post-processor, α

_u indicating a magnitude control factor, m_u indicating a unique frequency offset number previously allocated to the u-th user,

the u-th post-processor folds and adds the u-th user signal {tilde over (r)}_k^(u) output from the (u+V+1)-th multiplier with a period of M_u and outputs the result r_k^(u) of folding and addition to the (u+1)-th time equalizer, M_u being an integer greater than or equal to 1 and less than or equal to M,

the (u+1)-th time equalizer removes interchannel interference from the result r_k^(u) output from the u-th post-processor and outputs the result of removal of the interchannel interference as the u-th user symbol z_k^(u) to the u-th detector, and

the u-th detector detects the user symbol estimate value â

_k^(u) for the u-th user from the u-th user symbol z_k^(u) output from the (u+1)-th time equalizer.

14. The data communication apparatus of claim 13, wherein each of the second through (U+1)-th time equalizers comprises:

a Fourier transformer for performing M_u-point Fourier transform on the result r_k output from the first pre-processor and outputting the result of Fourier transform;

a third frequency equalizer for multiplying M_u signals output from the Fourier transformer by a third predetermined complex number and outputting the result of multiplication; and

an inverse Fourier transformer for performing M_u-point inverse Fourier transform on the result of multiplication output from the third frequency equalizer and outputting the result of inverse Fourier transform as the result z_k^(u) of removal of the interchannel interference.

15. The data communication apparatus of claim 13, wherein each of the second through (U+1)-th time equalizers comprises:

a first finite impulse response (FIR) filter for performing FIR filtering on the result r_k^(u) and outputting the result of filtering;

a delay unit for delaying the estimate value and outputting the result of delay;

a second FIR filter for performing FIR filtering on the result of delay and outputting the result of filtering; and

a second adder for adding the results of filtering received from the first and second FIR filters and outputting the result of addition as the result z_k^(u) of removal of the interchannel interference.

16. A data communication method based on orthogonal frequency division multiple access (OFDMA) through which the first base station receiving unit of the data communication apparatus of claim 5 estimates a u-th user symbol from the symbol block signal, the data communication method comprising the steps of:

(m1) converting the received symbol block signal into the first symbol block;

(n1) finding a start point of the first symbol block and removing the cyclic extension symbol from the first symbol block on the basis of the start point;

(o1) extracting only the u-th user symbols from the result r_k of removal of the cyclic extension symbol; and

(p1) detecting the estimate value â

_k^(u) of the user symbol for the u-th user from the extracted u-th user symbols.

17. The data communication method of claim 16, wherein the step (o1) comprises:

multiplying the result r_k obtained in step (n1) by α

₁ exp(−

j2π

km₁/M) through α

_U exp(−

j2π

km_U/M) to obtain {tilde over (r)}_k⁽¹⁾ through {tilde over (r)}_k^(U); and

performing folding and addition on each of {tilde over (r)}_k⁽¹⁾ through {tilde over (r)}_k^(U) with a period of M_u to obtain U user symbols r_k⁽¹⁾ through r_k^(U), and going to step (p1).

18. The data communication method of claim 16, wherein step (o1) comprises:

(o11) performing M-point Fourier transform on the result r_k obtained in step (n1); and

(o12) when the result of Fourier transform is for the u-th user, performing M_u-point inverse Fourier transform on the result of Fourier transform to obtain the u-th user symbol r_k^(u), and going to the step (p1).

19. The data communication method of claim 18, wherein step (o1) further comprises (o13) performing compensation on phase and magnitude of the result of Fourier transform obtained in step (o11), and when the result of compensation obtained in step (o13) is for the u-th user, step (o12) comprises performing M_u-point inverse Fourier transform on the result of compensation to obtain the u-th user symbol r_k^(u), and going to step (p1).

20. The data communication method of claim 16, wherein the step (o1) comprises:

removing interchannel interference from the result r_k obtained in step (n1);

multiplying the result z_k of removal of the interchannel interference by α

₁ exp(−

j2π

km₁/M) through α

_U exp(−

j2π

km_U/M) to obtain user signals {tilde over (z)}_k⁽¹⁾ through {tilde over (z)}_k^(U); and

performing folding and addition on each of the user signals {tilde over (z)}_k⁽¹⁾ through {tilde over (z)}_k^(U) with a period of M_u to obtain the user symbols z_k⁽¹⁾ through z_k^(U), and going to the step (p1).

21. The data communication method of claim 20, wherein the interchannel interference is removed by finite impulse response filtering.

22. The data communication method of claim 20, wherein the step of removing the interchannel interference comprises:

performing M- or N-point Fourier transform on the result r_k;

multiplying M or N signals obtained from Fourier transform by a third predetermined complex number; and

performing M- or N-point inverse Fourier transform on the result of multiplication to obtain the result z_k of removal of the interchannel interference.

23. The data communication method of claim 16, wherein the step (o1) comprises the steps of:

multiplying the result r_k obtained in step (n1) by α

₁ exp(−

j2π

km₁/M) through α

_U exp(−

j2π

km_U/M) to obtain user signals {tilde over (r)}_k⁽¹⁾ through {tilde over (r)}_k^(U);

performing folding and addition on the user signals {tilde over (r)}_k⁽¹⁾ through {tilde over (r)}_k^(U) with a period of M_u; and

removing interchannel interference from the results r_k⁽¹⁾ through r_k^(U) to obtain the u-th user symbol z_k^(u), and going to the step (p1).

24. The data communication method of claim 23, wherein the step of removing the interchannel interference comprises:

performing M_u- or N_v-point Fourier transform on the result r_k;

multiplying M_u or N_v signals obtained from Fourier transform by a third predetermined complex number; and

performing M_u- or N_v-point inverse Fourier transform on the result of multiplication to obtain the result z_k^(u) of removal of the interchannel interference.

25. The data communication method of claim 23, wherein the step of removing the interchannel interference comprises:

(t) performing finite impulse response filtering on the result r_k^(u);

(u) delaying the estimate value and performing finite impulse response filtering on the result of delay; and

(v) summing the results of filtering obtained in steps (t) and (u) to obtain the result z_k^(u) of removal of the interchannel interference.

26. A data communication apparatus based on orthogonal frequency division multiple access (OFDMA) comprising a first user receiving unit which receives a symbol block signal transmitted from a first base station transmitting units and estimates a base station symbol for a v-th user from the received symbol block signal, “

v”

being a user factor and an integer greater than or equal to 1 and no greater than V, V indicating the number of users sharing a second symbol block having N symbols and being 1 or a positive integer greater than 1, the first user receiving unit comprising;

a second signal receiver for converting the symbol block signal received from the first base station transmitting unit into the second symbol block and outputting the second symbol block;

a second pre-processor for finding a start point of the second symbol block received from the second signal receiver, removing a cyclic extension symbol from the second symbol block on the basis of the start point, and outputting the result r_k of removal of the cyclic extension symbol, wherein k″

is a time index and an integer greater than or equal to 0 and less than or equal to N−

1;

a first base station symbol extractor for extracting only symbols for the v-th user from the result r_k received from the second pre-processor; and

a second estimate value detector for detecting an estimate value â

_k^(v) of the base station symbol for the v-th user from the symbols for the v-th user output from the first base station symbol extractor.

27. The data communication apparatus of claim 26, wherein the first base station symbol extractor comprises:

a (2U+V+2)-th multiplier for multiplying the result r_k output from the second pre-processor by α

_v exp(−

j2π

kn_v/N) and outputting the result {tilde over (r)}_k^(v) of multiplication, α

_v indicating a magnitude control factor, n_v indicating a unique frequency offset number previously allocated to the v-th user; and

a (2U+1)-th post-processor for folding and adding the results {tilde over (r)}_k^(v) output from the (2U+V+2)-th multiplier with a period of N_v and outputting the result r_k^(v) of folding and addition to the second estimate value detector, N_v being an integer greater than or equal to 1 and less than or equal to N, and

the second estimate value detector detects the estimate value â

_k^(v) of the base station symbol for the v-th user from the result r_k^(v) output from the (2U+1)-th post-processor.

28. The data communication apparatus of claim 26, wherein the first base station symbol extractor comprises:

a Fourier transformer for performing N-point Fourier transform on the result r_k output from the second pre-processor and outputting the result R_n of Fourier transform, “

n”

indicating a frequency factor and being an integer greater than or equal to 0 and no greater than N−

1;

a first controller for generating a selection signal in response to L_v and a unique frequency offset number n_v previously allocated to the v-th user, L_v being N/N_v, N_v being an integer greater than or equal to 1 and no greater than N;

an inverse Fourier transformer for performing N_v-point inverse Fourier transform on R_n^(v) and outputting the result r_k^(v) of inverse Fourier transform to the second estimate value detector; and

a switching unit for sorting out only a signal R_n^(v) for the v-th user from R_n received from the Fourier transformer in response to the selection signal and outputting the signal R_n^(v) to the inverse Fourier transformer, and

the second estimate value detector detects the estimate value â

_k^(v) of the base station symbol for the v-th user from the result r_k^(v) output from the inverse Fourier transformer.

29. The data communication apparatus of claim 28, wherein the first base station symbol extractor further comprises a second frequency equalizer for multiplying the signal R_n^(v) output from the switching unit by a second predetermined complex number and outputting the result Z_n^(v) of multiplication to the inverse Fourier transformer, and

the inverse Fourier transformer performs N_v-point inverse Fourier transform on the result Z_n^(v) output from the second frequency equalizer and outputs the result z_k^(v) of inverse Fourier transform to the second estimate value detector.

30. The data communication apparatus of claim 26, wherein the first base station symbol extractor comprises:

a (U+2)-th time equalizer for removing interchannel interference from the result r_k output from the second pre-processor and outputting the result z_k of removal of the interchannel interference;

a (2U+V+3)-th multiplier for multiplying the result z_k output from the (U+2)-th time equalizer by α

_v exp(−

j2π

kn_v/N) and outputting the result {tilde over (z)}_k^(v) of multiplication, α

_v indicating a magnitude control factor for a v-th user signal, n_v indicating a unique frequency offset number previously allocated to the v-th user; and

a (2U+2)-th post-processor for folding and adding the results {tilde over (z)}_k^(v) output from the (2U+V+3)-th multiplier with a period of N_v and outputting the result z_k^(v) of folding and addition to the second estimate value detector, N_v being an integer greater than or equal to 1 and less than or equal to N, and

the second estimate value detector detects the estimate value â

_k^(v) of the base station symbol for the v-th user from the result z_k^(v) output from the (2U+2)-th post-processor.

31. The data communication apparatus of claim 30, wherein the (U+2)-th time equalizer comprises a finite impulse response (FIR) filter which performs FIR filtering on the result r_k output from the second pre-processor and outputs the result of filtering as the result of removal of the interchannel interference.

32. The data communication apparatus of claim 26, wherein the first base station symbol extractor comprises:

a (2U+V+2)-th multiplier for multiplying the result r_k output from the second pre-processor by α

_v exp(−

j2π

kn_v/N) and outputting the result {tilde over (r)}_k^(v) of multiplication, α

_v indicating a magnitude control factor for a v-th user signal, n_v indicating a unique frequency offset number previously allocated to the v-th user;

a (2U+1)-th post-processor for folding and adding the results {tilde over (r)}_k^(v) output from the (2U+V+2)-th multiplier with a period of N_v and outputting the result {tilde over (r)}_k^(v) of folding and addition, N_v being an integer greater than or equal to 1 and less than or equal to N; and

a (U+3)-th time equalizer for removing interchannel interference from the result {tilde over (r)}_k^(v) output from the (2U+1)-th post-processor and outputting the result z_k^(v) of removal of the interchannel interference to the second estimate value detector, and

the second estimate value detector detects the estimate value â

_k^(v) of the base station symbol for the v-th user from the result z_k^(v) output from the (U+3)-th time equalizer.

33. A data communication method based on orthogonal frequency division multiple access (OFDMA) through which the first user receiving unit of the data communication apparatus of claim 26 estimates the base station symbol from the symbol block signal transmitted from the first base station transmitting unit, the data communication method comprising the steps of:

(m2) converting the received symbol block signal into the second symbol block;

(n2) removing the cyclic extension symbol from the second symbol block;

(o2) extracting only the symbols for the v-th user from the result r_k of removal of the cyclic extension symbol; and

(p2) detecting the estimate value of the base station symbol for the v-th user from the symbols extracted for the v-th user.

34. The data communication method of claim 33, wherein the step (o2) comprises:

multiplying the result r_k obtained in step (n2) by α

_v exp(−

j2π

kn_v/N) to obtain the result {tilde over (r)}_k^(v) of multiplication, where α

_v indicates a magnitude control factor, and n_v indicates a unique frequency offset number previously allocated to the v-th user; and

folding and adding the results {tilde over (r)}_k^(v) of multiplication with a period of N_v to obtain symbols r_k^(v) for the v-th user, where N_v is an integer greater than or equal to 1 and less than or equal to N, and going to the step (p2).

35. The data communication method of claim 33, wherein the step (o2) comprises:

(o21) performing N-point Fourier transform on the result r_k obtained in step (n2); and

(o22) when the result R_n of N-point Fourier transform corresponds to the result R_n^(v) of Fourier transform for the v-th user, performing N_v-point inverse Fourier transform on R_n^(v) to obtain symbols r_k^(v) for the v-th user, and going to the step (p2).

36. The data communication method of claim 35, wherein the step (o21) further comprises (o23) performing compensation on phase and magnitude of the result R_n^(v) of Fourier transform for the v-th user, and the step (o22) comprises performing N_v-point inverse Fourier transform on the result of compensation obtained in step (o23) to obtain symbols z_k^(v) for the v-th user, and going to the step (p2).

37. The data communication method of claim 33, wherein the step (o2) comprises:

removing interchannel interference from the result r_k obtained in step (n2);

multiplying the result z_k of removal of the interchannel interference by α

_v exp(−

j2π

kn_v/N), where α

_v indicates a magnitude control factor for a v-th user signal, and n_v indicates a unique frequency offset number previously allocated to the v-th user; and

folding and adding the results {tilde over (z)}_k^(v) with a period of N_v to obtain symbols z_k^(v) for the v-th user, where N_v is an integer greater than or equal to 1 and less than or equal to N, and going to the step (p2).

38. The data communication method of claim 33, wherein the step (o2) comprises:

multiplying the result r_k obtained in step (n2) by α

_v exp(−

j2π

kn_v/N), where α

_v indicates a magnitude control factor for a v-th user signal, and n_v indicates a unique frequency offset number previously allocated to the v-th user;

folding and adding the results {tilde over (r)}_k^(v) of multiplication with a period of N_v, where N_v is an integer greater than or equal to 1 and less than or equal to N; and

removing interchannel interference from the result r_k^(v) of folding and addition to obtain the symbols z_k^(v) for the v-th user, and going to the step (p2).

44. The data communication apparatus of claim 28, wherein the first diversity equalizer calculates Z_1,n and Z_2,n according to:

$Z_{1,n}=\frac{{\left[H_{1,n}\right]}^{*}<br><br>R_{1,n}+{H_{2,n}<br><br>\left[R_{2,n}\right]}^{*}}{{<br><br>H_{1,n}<br><br>}^2+{<br><br>H_{2,n}<br><br>}^2+1/\mathrm{SNR}},<br><br>Z_{2,n}=\frac{{\left[H_{2,n}\right]}^{*}<br><br>R_{1,n}-{H_{1,n}<br><br>\left[R_{2,n}\right]}^{*}}{{<br><br>H_{1,n}<br><br>}^2+{<br><br>H_{2,n}<br><br>}^2+1/\mathrm{SNR}}$

where SNR indicates a ratio of the u-th user symbol to Gaussian noise.

45. The data communication apparatus of claim 28, wherein the first diversity equalizer calculates Z_1,n and Z_2,n according to:

$Z_{1,n}=\frac{{\left[H_{1,n}\right]}^{*}<br><br>R_{1,n}+{H_{2,n}<br><br>\left[R_{2,n}\right]}^{*}}{{<br><br>H_{1,n}<br><br>}^2+{<br><br>H_{2,n}<br><br>}^2},<br><br>Z_{2,n}=\frac{{\left[H_{2,n}\right]}^{*}<br><br>R_{1,n}-{H_{1,n}<br><br>\left[R_{2,n}\right]}^{*}}{{<br><br>H_{1,n}<br><br>}^2+{<br><br>H_{2,n}<br><br>}^2}.$

39. A data communication apparatus based on orthogonal frequency division multiple access (OFDMA) comprising a second user transmitting unit through which a user transmits user information to a base station in units of two first symbol blocks each including a first predetermined number M of symbols in data communication between the user and the base station, the second user transmitting unit comprising:

a first encoder for generating a first sub-block composed of a second predetermined number M_u of user symbols a_k^(u) for a u-th user by encoding the user information, where M_u is an integer greater than or equal to 1 and no greater than M, “

k”

is a time index and an integer greater than or equal to 0 and no greater than M-1, “

u”

is a user index and an integer greater than or equal to 1 and no greater than U, and U indicates the number of users sharing the first symbol block and is 1 or a positive integer greater than 1;

first and second block transmitters; and

a first diversity signal generator for transforming odd- and even-numbered first sub-blocks received from the first encoder every symbol block time and alternately outputting untransformed and transformed odd- and even-numbered first sub-blocks to each of the first and second block transmitters every symbol block time,

wherein each of the first and second block transmitters comprises a first block repeater, a first multiplier, a first cyclic extension symbol inserter, and a first signal transmitter and generates two symbol block signals from the untransformed and transformed odd- and even-numbered first sub-blocks alternately output from the first diversity signal generator,

the first block repeater repeats the first sub-block a third predetermined number L_u of times to generate M symbols a_k′

^(u), wherein L_u is M/M_u, k′

=k % M_u, and k % M_u indicates the remainder when “

k”

is divided by M_u,

the first multiplier multiplies the M symbols a_k′

^(u) generated from the first block repeater by γ

_u exp(j2π

km_u/M) and outputs the result of multiplication as a signal x_k^(u) for the u-th user, wherein γ

_u indicates a magnitude control factor for the u-th user signal x_k^(u), and m_u indicates a unique frequency offset number allocated to the u-th user,

the first cyclic extension symbol inserter outputs the first symbol block completed by inserting a cyclic extension symbol into the u-th user signal x_k^(u),

the first signal transmitter converts the completed first symbol block into a symbol block signal and transmits the symbol block signal, and M₁+M₂+M₃+ . . . +M_U does not exceed M where M represents the number of symbols in data communication between the user and the base station, Mu is an integer greater than or equal to 1 and no greater than M, ‘

u’

is a user index and an integer greater than or equal to 1 and no greater than U, and U indicates the number of users sharing the first symbol block and is 1 or a positive integer greater than 1.

40. The data communication apparatus of claim 39, wherein the first diversity signal generator comprises:

a first time inverter for receiving odd-numbered first sub-blocks and outputting them in order opposite to the order in which they are input;

a first complex conjugate unit for generating a complex conjugate of the output of the first time inverter and outputting the complex conjugate to the second block transmitter;

a first switching unit for selectively outputting the odd-numbered first sub-blocks to one of the first block transmitter and the first time inverter in response to a first switching signal;

a second time inverter for receiving the even-numbered first sub-blocks and outputting them in order opposite to the order in which they are input;

a second complex conjugate unit for generating a complex conjugate of the output of the second time inverter and outputting the complex conjugate;

a (2U+V+4)-th multiplier for multiplying the output of the second complex conjugate unit by −

1 and outputting the result of multiplication to the first block transmitter;

a second switching unit for selectively outputting the even-numbered first sub-blocks to one of the second block transmitter and the second time inverter in response to a second switching signal; and

a switching signal generator for generating the first and second switching signals so that the first and second switching units can output the odd- and even-numbered first sub-blocks, respectively, to the first and second block transmitters and alternately to the first and second time inverters every symbol block time,

the first block repeater included in the first block transmitter repeats the odd-numbered first sub-block output from the first switching unit or the output of the (2U+V+4)-th multiplier L_u times to generate the M symbols a_k′

^(u), and

the first block repeater included in the second block transmitter repeats the even-numbered first sub-block output from the second switching unit or the output of the first complex conjugate unit L_u times to generate the M symbols a_k′

^(u).

41. The data communication apparatus of claim 39, further comprising a second base station receiving unit which receives one of two symbol block signals transmitted from each of U second user transmitting units and estimates a u-th user symbol from the received symbol block signal, the second base station receiving unit comprising:

a third signal receiver for converting the received symbol block signal into the first symbol block and outputting the first symbol block;

a third pre-processor for finding a start point of the first symbol block received from the third signal receiver, removing the cyclic extension symbol from the first symbol block on the basis of the start point, and outputting the result r_k of removal of the cyclic extension symbol;

a second user symbol extractor for extracting odd- and even-numbered user symbols for the u-th user in a frequency domain from the result r_k of removal output from the third pre-processor; and

a third estimate value detector for detecting estimate values â

_1,k^(u) and â

_2,k^(u) of the odd- and even-numbered user symbols from the odd- and even-numbered user symbols for the u-th user extracted by the second user symbol extractor.

42. The data communication apparatus of claim 41, wherein the second user symbol extractor comprises:

a Fourier transformer for performing M-point Fourier transform on the result r_k output from the third pre-processor and outputting the result R_n of Fourier transform, “

n”

indicating a frequency factor and being an integer greater than or equal to 0 and no greater than M−

1;

a first sorter for classing the result R_n output from the Fourier transformer as a result R_1,n generated in the Fourier transformer during an odd-numbered symbol block time and as a result R_2,n generated in the Fourier transformer during an even-numbered symbol block time in response to a third switching signal and outputting R_1,n and R_2,n;

a first diversity equalizer for calculating the results Z_1,n and Z_2,n of removing interchannel interference using the outputs R_1,n and R_2,n of the first sorter and the characteristics H_1,n and H_2,n of channels through which the two symbol block signals are transmitted;

first through 2U-th inverse Fourier transformers;

a first distributor for outputting the result Z₁,n output from the first diversity equalizer as Z_1,n^(u) to one among the first through U-th inverse Fourier transformers in response to a selection signal;

a second distributor for outputting the result Z_2,n output from the first diversity equalizer as Z_2,n^(u) to one among the (U+1)-th through 2U-th inverse Fourier transformers in response to the selection signal; and

a second controller for generating the third switching signal so that R_n can be alternately output as R_1,n and R_2,n every symbol block time and generating the selection signal in response to the unique frequency offset number m_u and the third predetermined number L_u,

the u-th inverse Fourier transformer performs M_u-point inverse Fourier transform on Z_1,n^(u) and outputs the result z_1,k^(u) of inverse Fourier transform as the odd-numbered user symbol for the u-th user to the third estimate value detector, and

the (u+U)-th inverse Fourier transformer performs M_u-point inverse Fourier transform on Z_2,n^(u) and outputs the result z_2,k^(u) of inverse Fourier transform as the even-numbered user symbol for the u-th user to the third estimate value detector.

43. The data communication apparatus of claim 42, wherein the third estimate value detector comprises first through 2U-th detectors, the u-th detector detects the estimate value â

_1,k^(u) of the odd-numbered user symbol from the result z_1,k^(u) output from the u-th inverse Fourier transformer, and the (u+U)-th detector detects the estimate value â

_2,k^(u) of the even-numbered user symbol from the result z_2,k^(u) output from the (u+U)-th inverse Fourier transformer.

46. A data communication method based on orthogonal frequency division multiple access (OFDMA) through which the second user transmitting unit of the data communication apparatus of claim 39 transmits the user information to the base station in two first symbol block units, the data communication method comprising:

(a3) transmitting the untransformed odd-numbered first sub-blocks to the first block transmitter and simultaneously transmitting the untransformed even-numbered first sub-blocks to the second block transmitter, during an odd-numbered symbol block time;

(b3) transforming the even-numbered first sub-blocks by multiplying complex conjugates of the even-numbered first sub-blocks by −

1 and arranging the results of multiplication in order opposite to the order in which the even-numbered first sub-blocks are input and transmitting the transformed even-numbered first sub-blocks to the first block transmitter, and simultaneously, transforming the odd-numbered first sub-blocks by arranging complex conjugates of the odd-numbered first sub-blocks in order opposite to the order in which the odd-numbered first sub-blocks are input and transmitting the transformed odd-numbered first sub-blocks to the second block transmitter, during an even-numbered symbol block time;

(c3) generating the symbol block signal from the untransformed odd-numbered first sub-blocks transmitted in step (a3) using the first block transmitter and generating the symbol block signal from the untransformed even-numbered first sub-blocks transmitted in step (a3) using the second block transmitter, during the odd-numbered symbol block time;

generating the symbol block signal from the transformed even-numbered first sub-blocks transmitted in step (b3) using the first block transmitter and generating the symbol block signal from the transformed odd-numbered first sub-blocks transmitted in step (b3) using the second block transmitter, during the even-numbered symbol block time; and

simultaneously transmitting the two symbol block signals generated during the odd- or even-numbered symbol block time to the base station.

47. A data communication method based on orthogonal frequency division multiple access (OFDMA) through which the second base station receiving unit of the data communication apparatus of claim 46 receives one of the symbol block signals transmitted from the second user transmitting unit and estimates a u-th user symbol, the data communication method comprising:

(m3) converting the received symbol block signal into the first symbol block;

(n3) removing the cyclic extension symbol from the first symbol block;

(o3) extracting odd- and even-numbered user symbols for the u-th user in a frequency domain from the result r_k of removal of the cyclic extension symbol; and

(p3) detecting estimate values â

_1,k^(u) and â

_2,k^(u) of the odd- and even-numbered user symbols from the extracted odd- and even-numbered user symbols for the u-th user.

48. The data communication method of claim 47, wherein the step (o3) comprises:

(o31) performing M-point Fourier transform on the result r_k of removing the cyclic extension symbol in step (n3);

(o32) classing the result R_n of Fourier transform as the result R_1,n of Fourier transform processed during the odd-numbered symbol block time and as the result R_2,n of Fourier transform processed during the even-numbered symbol block time, where “

n”

indicates a frequency factor and is an integer greater than or equal to 0 and no greater than M−

1;

(o33) removing interchannel interference using R_1,n, R_2,n, and the characteristics H_1,n and H_2,n of channels through which the two symbol block signals are transmitted; and

(o34) when the results Z_1,n and Z_2,n of removal of the interchannel interference correspond to the results Z_1,n^(u) and Z_2,n^(u) for the u-th user, performing M_u-point inverse Fourier transform on Z_1,n^(u) and Z_2,n^(u) to obtain the odd- and even-numbered user symbols, and going to the step (p3).

49. The data communication method of claim 48, wherein the step (p3) comprises detecting the estimate value â

_1,k^(u) of the odd-numbered user symbol from the result z_1,k^(u) of inverse Fourier transform performed in step (o34), and detecting the estimate value â

_2,k^(u) of the even-numbered user symbol from the result z_2,k^(u) of inverse Fourier transform performed in step (o34).

50. The data communication method of claim 48, wherein the step (o33) comprises calculating Z_1,n and Z_2,n according to:

$Z_{1,n}=\frac{{\left[H_{1,n}\right]}^{*}<br><br>R_{1,n}+{H_{2,n}<br><br>\left[R_{2,n}\right]}^{*}}{{<br><br>H_{1,n}<br><br>}^2+{<br><br>H_{2,n}<br><br>}^2+1/\mathrm{SNR}},<br><br>Z_{2,n}=\frac{{\left[H_{2,n}\right]}^{*}<br><br>R_{1,n}-{H_{1,n}<br><br>\left[R_{2,n}\right]}^{*}}{{<br><br>H_{1,n}<br><br>}^2+{<br><br>H_{2,n}<br><br>}^2+1/\mathrm{SNR}}$

where SNR indicates a ratio of the u-th user symbol to Gaussian noise.

51. The data communication method of claim 48, wherein the step (o33) comprises calculating Z_1,n and Z_2,n according to:

$Z_{1,n}=\frac{{\left[H_{1,n}\right]}^{*}<br><br>R_{1,n}+{H_{2,n}<br><br>\left[R_{2,n}\right]}^{*}}{{<br><br>H_{1,n}<br><br>}^2+{<br><br>H_{2,n}<br><br>}^2},<br><br>Z_{2,n}=\frac{{\left[H_{2,n}\right]}^{*}<br><br>R_{1,n}-{H_{1,n}<br><br>\left[R_{2,n}\right]}^{*}}{{<br><br>H_{1,n}<br><br>}^2+{<br><br>H_{2,n}<br><br>}^2}.$

52. A data communication apparatus based on orthogonal frequency division multiple access (OFDMA) in data communication between a fourth predetermined number V of users and a base station, V indicating the number of users sharing a second symbol block and being 1 or a positive integer greater than 1, the data communication apparatus comprising a second base station transmitting unit through which the base station transmits base station information to a v-th user in units of two second symbol blocks each including a fifth predetermined number N of symbols, the second base station transmitting unit comprising:

second through (V+1)-th encoders;

third and fourth block transmitters; and

second through (V+1)-th diversity signal generators,

wherein the (v+1)-th encoder generates a (v+1)-th sub-block composed of a sixth predetermined number N_v of base station symbols a_k^(v) for a v-th user by encoding the base station information and outputs the (v+1)-th sub-block to the (v+1)-th block repeater, N_v being an integer greater than or equal to 1 and less than or equal to N, “

k”

being a time index and an integer greater than or equal to 0 and less than or equal to N−

1,

the (v+1)-th diversity signal generator transforms odd- and even-numbered (v+1)-th sub-blocks received from the (v+1)-th encoder every symbol block time and outputs alternately untransformed and transformed odd- and even-numbered (v+1)-th sub-blocks to the third and fourth block transmitters every symbol block time, and

each of the third and fourth block transmitters comprises second through (V+1)-th block repeaters, second through (V+1)-th multipliers, a first adder, a second cyclic extension symbol inserter, and a second signal transmitter, and generates two symbol block signals from the untransformed and transformed odd- and even-numbered second through (V+1)-th sub-blocks alternately output from each of the second through (V+1)-th diversity signal generators,

the (v+1)-th block repeater repeats the (v+1)-th sub-block a seventh predetermined number L_v of times to generate N symbols a_k′

^(v) and outputs the N symbols a_k′

^(v) to the (v+1)-th multiplier, L_v being N/N_v, k′

=k % N_v, k % N_v indicating the remainder when “

k”

is divided by N_v,

the (v+1)-th multiplier multiplies the N symbols a_k′

^(v) by γ

_v exp(j2π

kn_v/N) and outputs the result x_k^(v) of multiplication to the first adder, γ

_v indicating a magnitude control factor for a v-th user signal, n_v indicating a unique frequency offset number allocated to the v-th user,

the first adder sums the results x_k⁽¹⁾ through x_k^(V) of multiplication received from the second through (V+1)-th multipliers and outputs the result x_k of summation to the second cyclic extension symbol inserter,

the second cyclic extension symbol inserter outputs the single second symbol block completed by inserting a cyclic extension symbol into the result x_k of summation to the second signal transmitter,

the second signal transmitter converts the completed second symbol block into a symbol block signal and transmits the symbol block signal, and N₁+N₂+N₃+ . . . +N_v does not exceed N where N represents the number of second symbol blocks in data communication between the user and the base station, Nv is an integer greater than or equal to 1 and less than or equal to N, ‘

v’

is a user index and an integer greater than or equal to 1 and no greater than V, and V indicates the number of users sharing the second symbol block and is 1 or a positive integer greater than 1.

53. The data communication apparatus of claim 52, wherein the (v+1)-th diversity signal generator comprises:

a first time inverter for receiving the odd-numbered (v+1)-th sub-blocks and outputting them in order opposite to the order in which they are input;

a first complex conjugate unit for generating a complex conjugate of the output of the first time inverter and outputting the complex conjugate to the fourth block transmitter;

a first switching unit for selectively outputting the odd-numbered (v+1)-th sub-blocks to one of the third block transmitter and the first time inverter in response to a first switching signal;

a second time inverter for receiving the even-numbered (v+1)-th sub-blocks and outputting them in order opposite to the order in which they are input;

a second complex conjugate unit for generating a complex conjugate of the output of the second time inverter and outputting the complex conjugate;

a (2U+V+5)-th multiplier for multiplying the output of the second complex conjugate unit by −

1 and outputting the result of multiplication to the third block transmitter;

a second switching unit for selectively outputting the even-numbered (v+1)-th sub-blocks to one of the fourth block transmitter and the second time inverter in response to a second switching signal; and

a switching signal generator for generating the first and second switching signals so that the first and second switching units can output the odd- and even-numbered (v+1)-th sub-blocks, respectively, to the third and fourth block transmitters and alternately to the first and second time inverters,

the (v+1)-th block repeater included in the third block transmitter repeats the odd-numbered (v+1)-th sub-blocks output from the first switching unit or the output of the (2U+V+5)-th multiplier L_v times to generate the N symbols a_k′

^(v), and

the (v+1)-th block repeater included in the fourth block transmitter repeats the even-numbered (v+1)-th sub-blocks output from the second switching unit or the output of the first complex conjugate unit L_v times to generate the N symbols a_k′

^(v).

54. The data communication apparatus of claim 52, further comprising a second user receiving unit which receives one of two symbol block signals transmitted from the second base station transmitting unit and estimates a base station symbol for the v-th user from the received symbol block signal, the second user receiving unit comprising:

a fourth signal receiver for converting the received symbol block signal into a second symbol block and outputting the second symbol block;

a fourth pre-processor for finding a start point of the second symbol block received from the fourth signal receiver, removing the cyclic extension symbol from the second symbol block on the basis of the start point, and outputting the result r_k of removal of the cyclic extension symbol;

a second base station symbol extractor for extracting odd- and even-numbered symbols for the v-th user from the result r_k output from the fourth pre-processor; and

a fourth estimate value detector for detecting estimate values â

_1,k^(v) and â

_2,k^(v) of odd- and even-numbered base station symbols for the v-th user from the extracted odd- and even-numbered symbols.

55. The data communication apparatus of claim 54, wherein the second base station symbol extractor comprises:

a user signal detector for detecting only a signal R_n^(v) for the v-th user from the result of performing Fourier transform on the result r_k output from the fourth pre-processor, “

n”

indicating a frequency factor and being an integer greater than or equal to 0 and no greater than N−

1;

a second sorter for classing the result R_n^(v) output from the user signal detector as a result R_1,n^(v) detected in the user signal detector during an odd-numbered symbol block time and as a result R_2,n^(v) detected in the user signal detector during an even-numbered symbol block time in response to a fourth switching signal and outputting R_1,n^(v) and R^2,n(v);

a second diversity equalizer for calculating the results Z_1,n^(v) and Z_2,n^(v) of removing interchannel interference using the outputs R_1,n^(v) and R_2,n^(v) of the second sorter and the characteristics H_1,n^(v) and H_2,n^(v) of channels through which the two symbol block signals are transmitted;

a third controller for generating the fourth switching signal so that R_n^(v) can be alternately output as R_1,n^(v) and R_2,n^(v) every symbol block time;

a first inverse Fourier transformer for performing N_v-point inverse Fourier transform on Z_1,n^(v) output from the second diversity equalizer and outputting the result z_1,k^(v) of inverse Fourier transform as odd-numbered symbols for the v-th user; and

a second inverse Fourier transformer for performing N_v-point inverse Fourier transform on Z_2,n^(v) output from the second diversity equalizer and outputting the result z_2,k^(v) of inverse Fourier transform as even-numbered symbols for the v-th user.

56. The data communication apparatus of claim 55, wherein the fourth estimate value detector comprises:

a first detector for detecting the estimate value â

_1,k^(v) of the odd-numbered base station symbol for the v-th user from the result z_1,k^(v) output from the first inverse Fourier transformer; and

a second detector for detecting the estimate value â

_2,k^(v) of the even-numbered base station symbol for the v-th user from the result z_2,k^(v) output from the second inverse Fourier transformer.

57. The data communication apparatus of claim 55, wherein the user signal detector comprises:

a (2U+V+6)-th multiplier for multiplying the result r_k output from the fourth pre-processor by α

_v exp(−

j2π

kn_v/N) and outputting the result {tilde over (r)}_k^(v) of multiplication, α

_v indicating a magnitude control factor;

a (2U+3)-th post-processor for folding and adding the results {tilde over (r)}_k^(v) output from the (2U+V+6)-th multiplier with a period of N_v and outputting the result r_k^(v) of folding and addition; and

a Fourier transformer for performing N_v-point Fourier transform on the result r_k^(v) output from the (2U+3)-th post-processor and outputting the result of Fourier transform as R_n^(v) to the second sorter.

58. The data communication apparatus of claim 55, wherein the user signal detector comprises:

a Fourier transformer for performing N-point Fourier transform on the result r_k output from the fourth pre-processor and outputting the result R_n of Fourier transform, “

n”

indicating a frequency factor and being an integer greater than or equal to 0 and less than or equal to N−

1;

a first controller for generating a selection signal in response to the unique frequency offset number n_v and the seventh predetermined number L_v; and

a switching unit for selectively outputting the result R_n output from the Fourier transformer as R_n^(v) to the second sorter in response to the selection signal.

59. The data communication apparatus of claim 55, wherein the second diversity equalizer calculates Z_1,n^(v) and Z_2,n^(v) according to:

$Z_{1,n}^{\left(v\right)}=\frac{{\left[H_{1,n}^{\left(v\right)}\right]}^{*}<br><br>R_{1,n}^{\left(v\right)}+{H_{2,n}^{\left(v\right)}<br><br>\left[R_{2,n}^{\left(v\right)}\right]}^{*}}{{<br><br>H_{1,n}^{\left(v\right)}<br><br>}^2+{<br><br>H_{2,n}^{\left(v\right)}<br><br>}^2+1/\mathrm{SNR}},<br><br>Z_{2,n}^{\left(v\right)}=\frac{{\left[H_{2,n}^{\left(v\right)}\right]}^{*}<br><br>R_{1,n}^{\left(v\right)}-{H_{1,n}^{\left(v\right)}<br><br>\left[R_{2,n}^{\left(v\right)}\right]}^{*}}{{<br><br>H_{1,n}^{\left(v\right)}<br><br>}^2+{<br><br>H_{2,n}^{\left(v\right)}<br><br>}^2+1/\mathrm{SNR}}$

where SNR indicates a ratio of the base station symbol for the v-th user to Gaussian noise.

60. The data communication apparatus of claim 55, wherein the second diversity equalizer calculates Z_1,n^(v) and Z_2,n^(v) according to:

$Z_{1,n}^{\left(v\right)}=\frac{{\left[H_{1,n}^{\left(v\right)}\right]}^{*}<br><br>R_{1,n}^{\left(v\right)}+{H_{2,n}^{\left(v\right)}<br><br>\left[R_{2,n}^{\left(v\right)}\right]}^{*}}{{<br><br>H_{1,n}^{\left(v\right)}<br><br>}^2+{<br><br>H_{2,n}^{\left(v\right)}<br><br>}^2},<br><br>Z_{2,n}^{\left(v\right)}=\frac{{\left[H_{2,n}^{\left(v\right)}\right]}^{*}<br><br>R_{1,n}^{\left(v\right)}-{H_{1,n}^{\left(v\right)}<br><br>\left[R_{2,n}^{\left(v\right)}\right]}^{*}}{{<br><br>H_{1,n}^{\left(v\right)}<br><br>}^2+{<br><br>H_{2,n}^{\left(v\right)}<br><br>}^2}.$

61. A data communication method based on orthogonal frequency division multiple access (OFDMA) through which the second user receiving unit of the data communication apparatus of claim 54 receives one of the symbol block signals transmitted from the second base station transmitting unit and estimates the base station symbol for the v-th user, the data communication method comprising:

(m4) converting the received symbol block signal into the second symbol block;

(n4) removing the cyclic extension symbol from the second symbol block;

(o4) extracting only the odd- and even-numbered symbols for the v-th user from the result r_k of removal of the cyclic extension symbol; and

(p4) detecting the estimate values â

_1,k^(v) and â

_2,k^(v) of the odd- and even-numbered base station symbols for the v-th user from the extracted odd- and even-numbered symbols.

62. The data communication method of claim 61, wherein the step (o4) comprises:

(o41) detecting only a signal R_n^(v) for the v-th user from the result of performing Fourier transform on the result r_k of removing the cyclic extension symbol in step (n4);

(o42) classing R_n^(v) as the result R_1,n^(v) of detection during an odd-numbered symbol block time and as the result R_2,n^(v) of detection during an even-numbered symbol block time;

(o43) removing interchannel interference using R_1,n^(v), R_2,n^(v), H_1,n^(v), and H_2,n^(v); and

(o44) performing N_v-point inverse Fourier transform on the results Z_1,n^(v) and Z_2,n^(v) of removal of interchannel interference to obtain the odd- and even-numbered symbols for the v-th user.

63. The data communication method of claim 62, wherein the step (p4) comprises detecting the estimate value â

_1,k^(v) of the odd-numbered base station symbol for the v-th user from the result z_1,k^(v) of inverse Fourier transform performed in step (o44), and detecting the estimate value â

_2,k^(v) of the odd-numbered base station symbol for the v-th user from the result z_2,k^(v) of inverse Fourier transform performed in step (o44).

64. The data communication method of claim 62, wherein the step (o41) comprises:

multiplying the result r_k obtained in step (n4) by α

_v exp(−

j2π

kn_v/N), where α

_v indicates a magnitude control factor;

folding and adding the results {tilde over (r)}_k^(v) of multiplication with a period of N_v; and

performing N_v-point Fourier transform on the result r_k^(v) of folding and addition and determining the result of Fourier transform as the signal R_n^(v) for the v-th user.

65. The data communication method of claim 62, wherein the step (o43) comprises calculating Z_1,n^(v) and Z_2,n^(v) according to:

$Z_{1,n}^{\left(v\right)}=\frac{{\left[H_{1,n}^{\left(v\right)}\right]}^{*}<br><br>R_{1,n}^{\left(v\right)}+{H_{2,n}^{\left(v\right)}<br><br>\left[R_{2,n}^{\left(v\right)}\right]}^{*}}{{<br><br>H_{1,n}^{\left(v\right)}<br><br>}^2+{<br><br>H_{2,n}^{\left(v\right)}<br><br>}^2+1/\mathrm{SNR}},<br><br>Z_{2,n}^{\left(v\right)}=\frac{{\left[H_{2,n}^{\left(v\right)}\right]}^{*}<br><br>R_{1,n}^{\left(v\right)}-{H_{1,n}^{\left(v\right)}<br><br>\left[R_{2,n}^{\left(v\right)}\right]}^{*}}{{<br><br>H_{1,n}^{\left(v\right)}<br><br>}^2+{<br><br>H_{2,n}^{\left(v\right)}<br><br>}^2+1/\mathrm{SNR}}$

where SNR indicates a ratio of the base station symbol for the v-th user to Gaussian noise.

66. The data communication method of claim 62, wherein the step (o43) comprises calculating Z_1,n^(v) and Z_2,n^(v) according to:

$Z_{1,n}^{\left(v\right)}=\frac{{\left[H_{1,n}^{\left(v\right)}\right]}^{*}<br><br>R_{1,n}^{\left(v\right)}+{H_{2,n}^{\left(v\right)}<br><br>\left[R_{2,n}^{\left(v\right)}\right]}^{*}}{{<br><br>H_{1,n}^{\left(v\right)}<br><br>}^2+{<br><br>H_{2,n}^{\left(v\right)}<br><br>}^2},<br><br>Z_{2,n}^{\left(v\right)}=\frac{{\left[H_{2,n}^{\left(v\right)}\right]}^{*}<br><br>R_{1,n}^{\left(v\right)}-{H_{1,n}^{\left(v\right)}<br><br>\left[R_{2,n}^{\left(v\right)}\right]}^{*}}{{<br><br>H_{1,n}^{\left(v\right)}<br><br>}^2+{<br><br>H_{2,n}^{\left(v\right)}<br><br>}^2}.$

67. A data communication method based on orthogonal frequency division multiple access (OFDMA) through which the second base station transmitting unit of the data communication apparatus of claim 52 transmits the base station information in two second symbol block units, the data communication method comprising:

(a4) transmitting the untransformed odd-numbered second through (V+1)-th sub-blocks to the third block transmitter and simultaneously transmitting the untransformed even-numbered second through (V+1)-th sub-blocks to the fourth block transmitter, during an odd-numbered symbol block time;

(b4) transforming the even-numbered second through (V+1)-th sub-blocks by multiplying complex conjugates of the even-numbered second through (V+1)-th sub-blocks by −

1 and arranging the results of multiplication in order opposite to the order in which they are input, and transmitting the transformed even-numbered second through (V+1)-th sub-blocks to the third block transmitter, and simultaneously, transforming the odd-numbered second through (V+1)-th sub-blocks by arranging complex conjugates of the odd-numbered second through (V+1)-th sub-blocks in order opposite to the order in which they are input and transmitting the transformed odd-numbered second through (V+1)-th sub-blocks to the fourth block transmitter, during an even-numbered symbol block time;

(c4) generating the symbol block signal from the untransformed odd-numbered second through (V+1)-th sub-blocks transmitted in step (a4) using the third block transmitter and generating the symbol block signal from the untransformed even-numbered second through (V+1)-th sub-blocks transmitted in step (a4) using the fourth block transmitter, during the odd-numbered symbol block time;

generating the symbol block signal from the transformed even-numbered second through (V+1)-th sub-blocks transmitted in step (b4) using the third block transmitter and generating the symbol block signal from the transformed odd-numbered second through (V+1)-th sub-blocks transmitted in step (b4) using the fourth block transmitter, during the even-numbered symbol block time; and

simultaneously transmitting the two symbol block signals generated during the odd- or even-numbered symbol block time to the base station.

68. A data communication method based on orthogonal frequency division multiple access (OFDMA) through which a user transmits user information to a base station in units of first symbol blocks each including a first predetermined number of symbols in data communication between the user and a base station, the data communication method comprising:

(a1) generating a first sub-block composed of a second predetermined number M_u of a user symbols a_k^(u) for the u-th user by encoding the user information;

(b1) repeating the first sub-block a third predetermined number L_u of times to generate the M symbols a_k′

^(u);

(c1) multiplying the M symbols a_k′

^(u) by γ

_u exp(j2π

km_u/M) to obtain the u-th user signal x_k^(u);

(d1) inserting the cyclic extension symbol into the u-th user signal x_k^(u) to generate the single complete first symbol block; and

(e1) converting the first symbol block into the symbol block signal and transmitting the symbol block signal.

69. The data communication method of claim 68, wherein a frequency offset number is obtained by the method comprising:

(g) sorting all users in order of ascending L_u or L_v;

(h) initializing the user index and the frequency offset number;

(i) increasing the user index by 1, obtaining the value of b_lε

{0, 1} satisfying

$\stackrel{u-1}{\underset{i=1}{\sum <br><br>}}<br><br>L_i^{-1}=\underset{l}{\sum <br><br>}<br><br>b_l<br><br>2^{-1}<br><br><br><br>\mathrm{or}<br><br><br><br>\stackrel{v-1}{\underset{i=1}{\sum <br><br>}}<br><br>L_i^{-1}=\underset{l}{\sum <br><br>}<br><br>b_l<br><br>2^{-1},$

 

and obtaining the frequency offset number using

$\underset{l}{\sum <br><br>}<br><br>b_l<br><br>2^{l-1};<br><br>$

 

and

(j) determining whether the user index is less than the number of users, and going to the step (i) if it is determined that the user index is less than the number of users.

70. The data communication method of claim 69, wherein step (h) comprises initializing the user index to 1 and initializing the frequency offset number to 0, and step (i) comprises determining

$\sum _{}$

l ⁢

b l ⁢

2 l - 1

as the frequency offset number.

71. The data communication method of claim 69, wherein step (h) comprises initializing the user index to 1 and initializing the frequency offset number to L₁−

1, and step (i) comprises determining

$L_u-1-\underset{l}{\sum <br><br>}<br><br>b_l<br><br>2^{l-1}<br><br><br><br>\mathrm{or}<br><br><br><br>L_v-1-\underset{l}{\sum <br><br>}<br><br>b_l<br><br>2^{l-1}$

as the frequency offset number.

72. A data communication method based on orthogonal frequency division multiple access (OFDMA) in a data communication apparatus between a predetermined number V of users and a base station, V indicating the number of users sharing a second symbol block and being 1 or a positive integer greater than 1, the data communication apparatus including a first base station transmitting unit through which the first base station transmits base station information to a v-th user in units of symbol blocks each including a predetermined number N of symbols “

v”

being a user index and an integer greater than or equal to 1 and no greater than V, the data communication method comprising;

(a2) generating V (v+1)-th sub-blocks each composed of a second predetermined number N_v of base station symbols a_k^(v) for the v-th user by encoding the base station information;

(b2) repeating each of the V (v+1)-th sub-blocks L_v times to generate N symbols a_k′

^(v);

(c2) multiplying the symbols a_k′

⁽¹⁾ through a_k′

^(V), which are obtained with respect to the respective V (v+1)-th sub-blocks in step (b2), by γ

₁ exp(j2π

kn₁/N) through γ

_v exp(j2π

kn_v/N), respectively, to generate x_k⁽¹⁾ through x_k^(V);

(d2) summing x_k⁽¹⁾ through x_k^(V) and obtaining the result x_k of summation;

(e2) inserting a cyclic extension symbol into the result x_k of summation to generate a single complete symbol block; and

(f2) converting the symbol block into a symbol block signal and transmitting the symbol block signal.

73. A data communication method based on orthogonal frequency division multiple access (OFDMA) through which a data communication apparatus based on OFDMA generates a channel estimation pilot symbol including at least 2M (2N) symbols, the data communication method comprising:

(k1) setting a reference pilot symbol sequence d[k] composed of M (N) pilot symbols previously known to a user and a base station, “

k”

being an integer greater than or equal to 0 and no greater than M−

1 (N−

1), “

[ ]”

indicating a set; and

(l1) obtaining the pilot symbol d^(u)[e] (d^(v)[e]) for a u-th (v-th) user according to d^(u)[e]=d[m_u+e·

L_u] (d^(v)[e]=d[n_v+e·

L_v]), where “

u”

(“

v”

) is a user index and an integer greater than or equal to 1 and no greater than U (V), U (V) indicates the number of users sharing a symbol block having M (N) symbols and is 1 or a positive integer greater than 1, “

e”

is an integer equal to or greater than 0 and no greater than M_u−

1 (N_v−

1), M_u (N_v) is an integer equal to or greater than 1 and no greater than M (N), m_u (n_v) indicates a unique frequency offset number of the u-th (v-th) user, L_u (L_v) is M/M_u (N/N_v).

74. The data communication method of claim 73, further comprising the step of (n) when a pilot symbol is a phase shift keying (PSK) symbol, changing the phase of the pilot symbol generated in step (l1) according to d^(u)[e]′

=d^(u)[e]·

exp(jπ

e/M) or d^(v)[e]′

=d^(v)[e]·

exp(jπ

e/N) to obtain a new pilot symbol d^(u)[e]′

or d^(v)[e]′

.

75. The data communication method of claim 73, wherein the steps (k1) and (l1) are performed in first or second user transmitting unit to generate the pilot symbol in units of time slots.

76. The data communication method of claim 73, wherein the steps (k1) and (l1) are performed in first or second base station transmitting unit to generate the pilot symbol for each of all users simultaneously using a given time slot.

77. A data communication method based on orthogonal frequency division multiple access (OFDMA) through which a data communication apparatus based on OFDMA generates a channel estimation pilot symbol including at least 2M (2N) symbols, the data communication method comprising:

(k2) setting a reference pilot symbol sequence d[k] composed of M (2N) pilot symbols previously known to a user and a base station, “

k”

being an integer greater than or equal to 0 and no greater than M−

1 (N−

1), “

[ ]”

indicating a set; and

(l2) obtaining the pilot symbol d^(u)[e] (d^(v)[e]) for a u-th (v-th) user according to d^(u)[e]=d[e+S<sub>u−

1</sub>](d^(v)[e]=d[e+S<sub>v−

1</sub>]), where “

u”

(“

v”

) is a user index and an integer greater than or equal to 1 and less than or equal to U (V), U (V) indicates the number of users sharing a symbol block having M (2N) symbols and is 1 or a positive integer greater than 1, “

e”

is an integer equal to or greater than 0 and less than or equal to M<sub>u−

1</sub> (N_v−

1), M_u (N_v) is an integer equal to or greater than 1 and less than or equal to M (N), m_u (n_v) indicates a unique frequency offset number of the u-th (v-th) user, L_u (L_v) is M/M_u (N/N_v),

$S_u=\stackrel{u}{\underset{i=1}{\sum <br><br>}}<br><br>M_i<br><br><br><br>\mathrm{or}<br><br><br><br>S_v=\stackrel{v}{\underset{i=1}{\sum <br><br>}}<br><br>N_i,$

 

and S₀=0.