Frequency division multiple access for wireless communication

[0001] The present invention relates generally to communication and, inter alia, to data transmission in a wireless communication system.

II. Background of the Invention [0002] Orthogonal frequency division multiplexing (OFDM) is a multi-carrier multiplexing scheme that divides a frequency band (e.g., system bandwidth) into multiple (K) orthogonal subbands. These subbands are also called tones, subcarriers, intervals, and so on. In OFDM, each subband is assigned to a corresponding subcarrier, which can be independently modulated by data.

[0003] The OFDM method has some desirable features such as high spectral efficiency and resistance to the multi-path effect. However, the main disadvantage of OFDM is the high ratio of peak power to average power (PAPR), which means that the ratio of peak power to average power of OFDM waveform can be high. The high PAPR ratio for the OFDM waveform results from the possible phase addition of all subcarriers when they are independently modulated by data. Indeed, it can be seen that the peak power can be up to K times greater than the average power for OFDM.

[0004] A high PAPR for an OFDM waveform is undesirable and may reduce performance. For example, high OFDM waveform peaks can cause the power amplifier to operate in an area with high non-linearity, or possibly cut off the signal, which

53 / 55P24748PL00

EP 1 884 096 B1 would then cause intermodulation distortions and other artifacts that may degrade the signal quality. Deteriorated signal quality may adversely affect performance in terms of channel estimation, data detection and the like.

WO 02/49306 describes a method and apparatus for selecting a subcarrier for an orthogonal frequency division multiple access system.

[0005] There is therefore a need in the art for providing a multiplexing scheme that provides good performance and does not have a high PAPR ratio.

SUMMARY OF THE INVENTION [0006] This description describes data transmission and pilot techniques using improved frequency division multiple access (EFDMA). EFDMA is a multiplexing scheme that sends time-domain modulation symbols, has a lower PAPR ratio than the OFDM scheme, and has other advantages. The EFDMA symbol (which is also called the transmission symbol) is formed by a plurality of modulation symbols and occupies a plurality of groups of subbands that are separated from each other in a frequency band, with each subband group having a plurality of adjacent frequency subbands among the K of all subbands.

[0007] In an embodiment, for generating an EFDMA symbol, a plurality of modulation symbols are mapped to the first sequence of symbols, e.g., at locations determined by the groups of subbands used for the EFDMA symbol. A transformation (e.g., discrete Fourier transform (DFT) or fast Fourier transform (FFT)) is performed on the first sequence of symbols to obtain a second sequence of values. The values ​​in the second sequence corresponding to the subbands used for the EFDMA symbol are retained, and the remaining values ​​in the second sequence are

53 / 55P24748PL00

EP 1 884 096 B1 zeroed to obtain a third sequence of values. A reverse transformation is performed on the third sequence (e.g., inverse DFT transform (IDFT) or inverse FFT transform (IFFT)) to obtain a fourth sequence of samples. On the fourth sequence, a phase ramp may be used to obtain the fifth sequence of samples. Then, based on the fifth sequence of samples, the EFDMA symbol is generated, e.g., by appending a cyclic prefix. The EFDMA symbol can also be generated by other methods, as described below. The receiver performs complementary processing to recover modulation symbols sent in the EFDMA symbol.

[0008] Further details of various aspects and embodiments of the invention are provided below.

BRIEF DESCRIPTION OF THE DRAWINGS [0009] The features and nature of the present invention will be more clearly apparent from the detailed description below, taken together with the drawings, which, like reference marks, identify it accordingly.

[0010] FIG. 1 shows a wireless communication system.

[0011] FIG. 2 shows an example subband structure for an IFDMA scheme.

[0012] FIG. 3 shows an exemplary subband structure for the LFDMA scheme.

[0013] FIG. 4 shows an example subband structure for an EFDMA scheme.

[0014] - FIG. 5A and 5B show two processes for generating the EFDMA symbol.

[0015] FIG. 6 shows EFDMA subband sets.

[0016] FIG. 7 shows a time-changing set of subbands for the EFDMA scheme.

[0017] FIG. 8 illustrates the process of generating EFDMA symbols.

53 / 55P24748PL00

EP 1 884 096 B1 [0018] FIG. 9 shows the process of receiving EFDMA symbols.

<td> [0019]</td><td>FIG.</td><td> 10</td><td>presents</td><td>scheme</td><td>jump</td><td>frequency</td>

<td colspan="3">(frequency hopping)</td><td>(FH).</td><td></td><td></td><td></td>

<td> [0020]</td><td>FIG.</td><td> 11</td><td>presents</td><td colspan="2">block diagram</td><td>transmitter and</td>

<td>receiver</td><td> .</td><td></td><td></td><td></td><td></td><td></td>

<td> [0021]</td><td>FIG.</td><td> 12</td><td>presents</td><td>scheme</td><td>block</td><td>transmitter for</td>

<td colspan="3">generating symbols</td><td>EFDMA.</td><td></td><td></td><td></td>

<td> [0022]</td><td>FIG.</td><td> 13</td><td>presents</td><td>scheme</td><td colspan="2">block receiver for</td>

receiving EFDMA symbols.

DETAILED DESCRIPTION [0023] The word "exemplary" as used in the specification means "serving as an example, example or illustration." Any embodiment or structure described herein as "exemplary" is not necessarily considered preferred or recommended among other embodiments or structures.

[0024] FIG. 1 depicts a wireless communication system 100 with multiple base stations 110 and multiple terminals 120. The base station is essentially a fixed station that communicates with the terminals and may also be called an access point, Node B, or other terminology. Each base station 110 provides communication coverage for a specific geographical area 102. The term "cell" may refer to the base station and / or its coverage area depending on the context in which the term is used. To improve system capacity, the base station coverage area can be divided into many smaller areas, e.g., three smaller areas 104a, 104b, and 104c. These smaller areas are defined by bundles of different antennas formed by multiple antennas for the base station. Each smaller area is served by the appropriate base station subsystem (BTS). The term "sector" may refer to the BTS station and / or its coverage area depending on the context in which the term is used. For

53 / 55P24748PL00

EP 1 884 096 B1 or other terminology.

cordless cell phone divided into sectors, BTS stations for all sectors of this cell are usually located within the base station for the cell.

[0025] Terminals 120 are typically distributed throughout the system, and each terminal may be fixed or mobile. The terminal may also be called a mobile station, user equipment, the terminal may be a cellular device, personal digital assistant (PDA), wireless modem card and the like. Each terminal can communicate with one or possibly many base stations via forward and reverse links at any given time. The forward link (or "downlink") refers to the communication link from base stations to terminals, and the reverse link (or "uplink") refers to the communication link from terminals to base stations. For simplicity, FIG. 1 only shows transmissions from terminals on the reverse link.

[0026] In some embodiments, the system controller 130 is coupled to base stations 110 and provides coordination and control for these base stations. For distributed architecture, base stations can communicate with each other as needed.

[0027] System 100 may use single carrier frequency multiple access (SC-FDMA), orthogonal frequency division multiple access (OFDMA), and / or some other multiplexing schemes. The SC-FDMA scheme includes interleaved FDMA (IFDMA), which transmits data on subbands that are arranged in a frequency band, localized FDMA (LFDMA), which transmits data in a group of adjacent subbands, and improved FDMA (EFDMA), which transmits data in many groups of adjacent subbands. The IFDMA scheme is also called and the LFDMA scheme is also called classic FDMA, and FDMA. The OFDMA scheme uses OFDM. Modulation symbols are sent in the time domain using IFDMA, LFDMA, and EFDMA, and in the distributed field of FDMA, narrowband FDMA,

53 / 55P24748PL00

EP 1 884 096 B1 by OFDM. In general, system 100 may use one or more multiplexing schemes for forward and reverse links. For example, system 100 may use (1) an SC-FDMA scheme (e.g., IFDMA, LFDMA or EFDMA) for both forward and reverse links (2) one version of the SC-FDMA scheme (e.g., EFDMA) for one link and another SC-FDMA schema version (e.g. IFDMA) for another link, (3) SC-FDMA scheme for reverse link and OFDMA for forward link, or (4) some other combinations of multiplexing schemes. The SC-FDMA, OFDMA scheme, and / or some other multiplexing schemes, or a combination thereof, can be used for each link to achieve the desired performance. For example, the SC-FDMA and OFDMA scheme can be used for a given link, while the SC-FDMA scheme is used for some subbands and the OFDMA scheme is used on other subbands. It may be desirable to use the SC-FDMA scheme on the reverse link to achieve a lower PAPR ratio and to reduce the power amplifier's requirements for terminals. It may also be desirable to use the OFDMA scheme on the forward link for possible higher system throughput.

[0028] FIG. 2 shows an example subband structure 200 for an IFDMA scheme. The total BW MHz bandwidth of the system is divided into many (K) orthogonal subbands, which are designated by indexes from 0 to K -1, where K can be any integer. For simplicity, the following description for the IFDMA, LFDMA and EFDMA schemes assumes that all K subbands can be used for transmission. The distance between adjacent subbands is BW / K MHz. For a 200 subband structure, K all subbands are organized in S, separable or non-overlapping interlaces. S interlaces are separable, so that each of the K subbands belongs to only one interlacing. For the 200 subband structure, each interlace contains N subbands that are uniformly distributed among all K

53 / 55P24748PL00

EP 1 884 096 B1 subbands; successive subbands in each interlace are separated from each other by S subbands, and interlace u includes the subband u as the first subband, where K = S'N iue {0, ..., S -1}.

[0029] FIG. 3 shows an example subband structure 300 for LFDMA scheme. For a 300 subband structure, K all subbands are organized in S non-overlapping groups. Each group contains N adjacent subbands, and the group ν contains subbands from ν · Ν to (v + 1) · Ν-1, where K = SN and ν e {0, ..., 5-1}.

[0030] FIG. 4 shows an example subband structure 400 for an EFDMA scheme. For a 400 subband structure, K all subbands are organized in S non-overlapping sets. In an embodiment, K all subbands are separated into S sets as follows. K all subbands are first divided into many (L) frequency ranges, with each frequency range containing P = K / L adjacent subbands. Each frequency range is further divided into S groups, each group containing M adjacent subbands. For each frequency range, the first M subbands are allocated to set 0, the next M subbands are allocated to set 1, and so on, and the last M subbands are allocated to set S-1. The set s, for s = 0, ..., S-1, therefore contains subbands having indexes k which meet the following condition:

s M &lt;k modulo (K / L) &lt;(s +1) M. Equation (1) [0031] For the embodiment described above, each set comprises L groups M of adjacent subbands, or in total N = L'M subbands. The L groups for each set are separated by P subbands. Each set of subbands thus comprises a plurality of groups of adjacent subbands, wherein the subband groups are uniformly distributed over the frequency band. S sets

53 / 55P24748PL00

EP 1 884 096 B1 subbands can be assigned to S different users for transmission.

[0032] In general, the subband structure may contain any number of sets, each set may contain any number of subband groups and any number of subbands, and the sets may contain the same or a different number of subbands. For each set, the subband groups may contain the same or a different number of subbands and may be distributed uniformly or heterogeneously across the system bandwidth. Furthermore, L, M, S and N may be the divisor of K or not.

[0033] EFDMA, IFDMA and LFDMA schemes are SC-FDMA schemes that transmit time-domain modulation symbols and have low PAPR ratios that are comparable to single carrier carrier PAPR ratios. This is the opposite of the OFDM scheme, which transmits modulation symbols in the frequency domain and has a high PAPR ratio. The advantage of the IFDMA scheme is that each interlacing covers the entire system bandwidth and thus ensures frequency diversity. However, the interleaving structure is also a disadvantage of the IFDMA scheme because it requires estimation of the entire broadband channel, which may not be efficient for small subband allocation sizes, e.g., for small N values. The LFDMA scheme does not have this disadvantage because the transmission is sent in a group of adjacent subbands . However, the LFDMA scheme does not provide frequency diversity due to its narrowband nature. Furthermore, the IFDMA and LFDMA schemes usually do not provide interference diversity because the user in the sector may be allocated the same subbands as the interference user in the neighbor sector. The EFDMA scheme may provide IFDMA scheme frequency diversity and LFDMA channel estimation performance. The EFDMA scheme can also provide interference diversity while achieving a lower PAPR ratio than a system based on the OFDM scheme.

53 / 55P24748PL00

EP 1 884 096 B1 [0034] FIG. 5A shows a process 500 for generating an EFDMA symbol for one set of subbands. For simplicity, FIG. 5A shows a simple case for K = 16 all subbands, where the set of subbands contains L = 4 groups of subbands, where each group contains M = 2 adjacent subbands, and the set contains a total of N = 8 subbands. However, a different number of subbands, subband sets, subband groups and adjacent subbands can be used.

[0035] The initial sequence of N modulation symbols to be transmitted in one symbol period in the subband set is denoted as {dn} = {d0, d1, d2, ..., dN-1} (block 510). N modulation symbols are mapped to N sample locations in the {xn} sequence. The {xn} sequence has a total of K sample locations that are identified by indexes from n = 0 to K-1. The sample locations that are mapped with modulation symbols have n indexes that satisfy the following equation:

n modulo (K / M) &lt;L. Equation (2)

For the example shown in FIG. 5A, K / M = 8, L = 4, an = 0, 1, 2, 3, 8, 9, 10 and 11 meet the equation (2). Thus, 8 modulation symbols are mapped to sample locations n = 0, 1, 2, 3, 8, 9, 10 and 11. Zero values ​​are mapped to the remaining K - N sample locations to obtain a sequence

K samples, {xn} (block 512).

The K samples, {xn}, is then the frequency domain with K [0036] The sequence is transformed to a point value of the remaining DFT transforms to obtain the sequence in the KN domain of the frequency value, frequency in the {Xk} domain (block 514). is maintained, the frequencies are replaced by zeros to create a sequence of K values, {Yk} (block 516). The frequency domain values ​​that are stored are used for transmission on N subbands. These

53 / 55P24748PL00

EP 1 884 096 B1 subbands have k indexes which satisfy the following equation:

k modulo (K / L) &lt;M. Equation (3)

For the example shown in FIG. 5A, K / L = 4, M = 2, ak = 0, 1, 4, 5, 8, 9, 12 and 13 meet equation (3). Thus, the frequency domain values ​​for the subbands k = 0, 1, 4, 5, 8, 9, 12 and 13 are preserved, and zeros are mapped to the subbands k = 2, 3, 6, 7, 10, 11, 14 and 15.

[0037] The value sequence K, {Yk}, is then transformed to the time domain using the ID-point KFT transform to obtain the sequence of time domain samples K, {yn} (block 518). The K sequence of the samples, {yn}, is then multiplied by the phase edge to obtain the K sequence of the output samples, {zn} (block 520). Each output sample in the {Zn} sequence can be generated as follows:

from_n = y_n · e¹²ⁿⁿ'^s'^M'^K, for n = 0, ... K-1, Equation (4) where yn is the n-th sample in the sequence {yn}, z n the n-th sample in the sequence {z_n}, and s &lt;M is the first subband used for transmission. Multiplication by the edge of phase e¹²ⁿⁿ'^s'^{M / K}, in the time domain results in the sequence {zn} occupying the set of subbands s in the frequency domain.

[0038] The last C output samples of the sequence {zn} are copied to the beginning of the sequence to form an EFDMA symbol that contains K + C output samples (a block of 522 copied output samples is often called a cyclic prefix or a safety space, and a cyclic prefix. A cyclic prefix.

C is a length that may or may not be used, is used to combat intersymbol interference (ISI) caused by selective frequency decay. The K + C output samples of the EFDMA symbol are

53 / 55P24748PL00

EP 1 884 096 B1 transmitted in K + C sample periods, one output sample in each sample period. The EFDMA symbol period (or simply, the symbol period) is the duration of one symbol

EFDMA and is equal to K + C sample periods. The sample period is also called the code period.

[0039] FIG. 5A shows an example transformation for generating an EFDMA symbol. This transformation results in yn equal to xn for all sample locations where xn is not zero. The sequence {yn} therefore contains N modulation symbols in the initial sequence {dn}, which may simplify processing at the receiver. The {yn} sequence additionally contains KN interpolated samples that are created by "interpolating" between non-zero locations {xn} using DFT operations.

[0040] FIG. 5B shows another process 502 for generating an EFDMA symbol for one set of subbands. For simplicity, FIG. 5B also depicts the simple case of K = 16 all subbands, where the set of subbands contains L = 4 groups of subbands, and each group contains M = 2 adjacent subbands. However, a different number of subbands, subband sets, subband groups and adjacent subbands can be used.

[0041] The initial sequence of N modulation symbols to be transmitted in one symbol period in the subband set is denoted as {dn} = {d0, d1, d2, ..., dN-1} (block 530). The sequence of N modulation symbols, {dn}, is transformed into the frequency domain using an N-point DFT transform to obtain a sequence of N values ​​in the frequency domain, {Dk} (block 532). N values ​​in the frequency domain are mapped to N subbands used for transmission, and zeros are mapped to the other KN subbands to form the sequence of K values, {Zk} (block 534). For the example shown in FIG. 5B, s = 1, K / M = 8, L = 4, and the subbands used for transmission have the indices k = 2, 3, 6, 7, 10, 11, 14 and 15. Thus, 8 values ​​in the field

53 / 55P24748PL00

EP 1 884 096 B1 frequency is mapped to subbands k = 2, 3, 6, 7, 10,

11, 14 and 15, and zeros are mapped to the subbands k = 0, 1, 4, 5, 8,

9, 12 and 13.

[0042] The value sequence K, {Zk}, is then transformed into the time domain using the ID-point KFT transform to obtain the sequence of time domain samples K {zn} (block 536). The last C output samples of the sequence {zn} are copied to the beginning of the sequence to form an EFDMA symbol that contains K + C output samples (block 538).

[0043] FIG. 5B shows another example transformation to generate an EFDMA symbol. Sequence {zn} generated by process 502 in FIG. 5B has similar time and spectral characteristics as the sequence {zn} generated by the process 500 of FIG. 5A. However, the samples in the {Zn} sequence generated by the 502 process may not be equal to the corresponding samples in the {Zn} sequence generated by the 500 process.

[0044] In FIG. 5A, locations that contain modulation symbols in the {xn} sequence may be designated by the Nd set, and the subbands used for transmission may be designated by the K set_d. Sequence {x_n} is such that x_n = 0 for n &amp; _N_d.

The transformation may be that the sequence {yn} is equal to the sequence {xn} for all sample locations in the Nd set. This condition can be expressed as:

s_n = x_n for ne N_dd . Equation (5)

The transformation can also be such that the sequence {Yk} is equal to the sequence {Xk} for all subbands in the Kd set and is equal to zero for other subbands. This condition can be expressed as:

X _k for for keKd, ^k £ ^Kd.

Equation (6)

53 / 55P24748PL00

EP 1 884 096 B1 [0045] The {xn} sequence may be represented

1, x = [x₀, xi, ..., x_K-1]^T, and the sequence represented as a vector K χ 1, y = [y₀, y₁,.

"^T"means transposition. The transformation of then be expressed as:

as a vector K χ {yn} can be., yK-1]^Twhere x to y can

Equation (7) where A is the transformation transformation matrix, A transformation matrix is

K χ K. In the example, defined as:

Equation (8) where Q is the transformation matrix K χ K, Q^-1 is the inverse transformation matrix K χ K and D is the diagonal matrix K χ

K. K columns of matrix D correspond to K of all subbands. Matrix D has ones along the diagonal for the columns corresponding to the subbands used for transmission and zero in other places. For the embodiment shown in FIG. 5A, Q is a Fourier matrix K χ K in which (k, n) -th element, wk, n, are defined as:

in_k,_n = e^{-j2nkn / K}, for k = 0, ..., Q-1 and n = 0, ..., Q-1.

Equation (9) [0046] A transformation matrix A may also be determined based on other transformation matrices instead of the Fourier matrix. The transformation matrix A can be determined such that (n₂, n₁) -th element of the matrix A, A (n₂, uf, is equal to δ (n₂ - nf) for all n1 and n2 that are in the Nd set. This condition ensures that y_n = x_n for n eN_d.

53 / 55P24748PL00

[0047] The EFDMA symbol may also be generated by other methods and by means of other transformations, and this is within the scope of the present disclosure.

[0048] For the EFDMA scheme, the modulation symbols in the initial {dn} sequence may be samples of the EFDMA symbol to be transmitted. Thus, after alignment in the receiver, the EFDMA scheme has similar performance as the single carrier FDMA scheme, such as IFDMA and LFDMA. The EFDMA receiver may use frequency domain equalization schemes applicable for IFDMA or LFDMA and may be able to achieve similar performance in the absence of channel estimation errors. The EFDMA scheme is the same as LFDMA when L = 1 and the same as IFDMA when M = 1. Furthermore, EFDMA boils down to classic single-carrier transmission when S = 1 and L &lt;M = K. [0049] In an embodiment, S subband sets were specified for the EFDMA scheme (e.g., as shown in FIG. 4), and neighboring sectors use the same S subband sets for transmission. For this embodiment, the user u1 to whom the subband set s is allocated in the sector experiences interference from another user u2 who is assigned the same set of subbands s in the neighbor sector. Furthermore, user u1 experiences interference from user u2 on all N subbands in set s. If frequency hopping is used, then user u1 experiences interference from user u2 only in time slots in which both users are assigned the same sets of subbands.

[0050] In another embodiment, S subband sets are specified for each sector and different subband sets are defined for adjacent sectors. For this embodiment, a subband set for a given sector may overlap partially, but not entirely over any subband set for an adjacent sector. Thus, no subband set for a given sector contains all subbands in any set of subbands for a neighbor sector. For this embodiment,

53 / 55P24748PL00

User u1 who is assigned a set of subbands in a sector may experience interference from another user u2 in an adjacent sector in some but not all subbands in set s. This embodiment provides interference diversity because user u1 does not experience interference from a single user in another sector among all subbands assigned to user u1.

[0051] FIG. 6 shows an example EFDMA subband structure 600. For the example shown in FIG. 6, L = 2, and each set of subbands contains two groups of M subbands. For sector 1, subband set 0 contains subbands 0 to M-1 and K / 2 to K / 2 + M-1. For sector 2, subband set 0 contains subbands 0 to M-1 and K / 4 to K / 4 + M-1. For sector 3, subband set 0 contains subbands 0 to M-1 and K / 8 to K / 8 + M-1. The other subband sets for each sector can be specified differently. For example, subband set 1 for sector 1 may contain subbands M to 2M-1 and from K / 2 + M to K / 2 + 2M-1, subband set 1 for sector 2 may include subbands K / 2 to K / 2 + M1 and 3K / 4 to 3K / 4 + M-1, and subband set 1 for sector 3 may contain subbands K / 2 to K / 2 + M-1 and ask / 8 to 5K / 8 + M -1. Each set of subbands for each sector may contain some, but not all, subbands in any set of subbands for any adjacent sector.

[0052] Set of subbands 0 in sector 1 assigned to user u1 would overlap partly with set of subbands 0 in sector 2 assigned to another user u2 and would also overlap partly with set of subbands 0 in sector 3 assigned to another user u3. User u1 would then experience interference from users u2 and u3 in subbands 0 to M -1, which are shared by these three users. User resources u1 would also partially overlap subbands K / 2 to K / 2 + M-1 in adjacent sectors assigned to other users, and user u1 would also experience interference from these users in these subbands.

53 / 55P24748PL00

EP 1 884 096 B1 [0053] For the case when L = 2, the distances between two groups of subbands can take the values ​​K / 2, K / 4, K / 8, ..., M.

Thus, the achievable level of interference diversity corresponds to approximately log (K / M) choices.

[0054] EFDMA symbols may be generated for various sets of subbands in FIG. 6 in different ways. For clarity, the following description applies when K = 32 total subbands, where each set of subbands contains L = 2 groups of subbands and each group contains M = 4 adjacent subbands. Subband set 0 for sector 1 contains subbands 0, 1, 2, 3, 16, 17, 18 and 19, subband set 0 for sector 2 contains subbands 0, 1, 2, 3, 8, 9, 10 and 11, and the set Subbands 0 for sector 3 include subbands 0, 1, 2, 3, 4, 5, 6 and 7.

[0055] The EFDMA symbol for subband set 0 in sector 1 may be generated as follows:

1. Map 8 modulation symbols to sample locations 0, 1,

8, 9, 16, 17, 24 and 25, and map zeros to the other 24 sample locations;

2. Perform a 32-point DFT transform on a sequence of 32 samples to obtain a sequence of 32 frequency-domain values;

3. Keep the frequency domain values ​​for subbands 0, 1, 2, 3, 16, 17, 18 and 19 and reset the 24 remaining subbands;

4. Perform a 32-point IDFT transform on a sequence of 32 values ​​to generate a sequence of 32 time-domain samples; and

5. Include a cyclic prefix to create the EFDMA symbol for subband set 0 in sector 1.

[0056] The EFDMA symbol for subband set 0 in sector 2 may be generated as follows:

53 / 55P24748PL00

EP 1 884 096 B1

1. Map 8 modulation symbols to sample locations 0, 2, 8, 10, 16, 18, 24 and 26, and map zeros to 24 other sample locations;

2. Perform a 32-point DFT transform on a sequence of 32 samples to obtain a sequence of 32 frequency-domain values;

3. Keep the frequency domain values ​​for subbands 0, 1, 2, 3, 8, 9, 10 and 11 and reset the 24 remaining subbands;

4. Perform a 32-point IDFT transform on a sequence of 32 values ​​to generate a sequence of 32 time-domain samples; and

5. Include a cyclic prefix to create the EFDMA symbol for subband set 0 in sector 2.

[0057] The EFDMA symbol for subband set 0 in sector 3 may be generated as follows:

1. Map 8 modulation symbols on sample locations 0, 4, 8, 12, 16, 20, 24 and 28, and map zeros to the other 24 sample locations;

2. Perform a 32-point DFT transform on a sequence of 32 samples to obtain a sequence of 32 frequency-domain values;

3. Keep the frequency domain values ​​for subbands 0, 1, 2, 3, 4, 5, 6 and 7 and reset the 24 remaining subbands;

4. Perform a 32-point IDFT transform on a sequence of 32 values ​​to generate a sequence of 32 time-domain samples; and

5. Include a cyclic prefix to create the EFDMA symbol for subband set 0 in sector 3.

53 / 55P24748PL00

[0058] EFDMA symbols can also be generated in other ways for sectors 1, 2 and 3. For example, the EFDMA symbol for subband set 0 in sector 2 can be generated by (1) mapping 8 modulation symbols to sample locations 0, 1, 4, 5, 8, 9, 12 and 13 and zero mapping to locations of samples 2, 3, 6, 7, 10, 11, 14 and 15, (2) performing a 16-point transform

DFT, (3) zeroing subbands 4, 5, 6, 7, 12, 13, 14 and 15, (4) appending 16 zeros to the end to obtain a sequence of 32 values, (5) performing a 32-point IDFT transform, and ( 6) appending a cyclic prefix. The EFDMA symbol is therefore initially generated if it is sent in a set of subbands formed in the first K / 2 subbands (or part of the system bandwidth) and is then extended to cover K of all subbands by zero padding to the required degree.

[0059] As shown in FIG. 6, L groups of subbands for a given set of subbands can be uniformly distributed across the system bandwidth (e.g., as shown for sector 1) or heterogeneously distributed across the system bandwidth (e.g., as shown for sectors 2 and 3).

[0060] In an embodiment, non-uniformly distributed subband groups for a given set of subbands may be defined as follows. Group 0 contains subbands from a₀'L'M to a₀'(L + 1)' M-1, group 1 contains subbands from (a₁^,L + 1) -M to (a₁^,L + 2) 'M-1, group 2 contains subbands from (a / L + 2) &lt;M to (a / L + 3) &lt;M-1, and so on, where each of the values ​​a0, a1, a2, ... can be any non-negative integer. The set may contain different groups of subbands depending on the values ​​selected for a0, a1, a2 ... The set contains subbands (a / L + 1) &lt;M + m, for l = 0, ..., L-1 and m = 0 , ..., M-1. S subband sets can be determined based on S different offsets. For example, al may be a function of the index s of the set and may be specified as al = a ·? + s, where a is the set value for all S subband sets. As an example, for M = 8, L = 4, and a = 5, set s = 0

53 / 55P24748PL00

EP 1 884 096 B1 variable in time For example, it contains subbands 0 to 7, 50 to 57, 100 to 107, and

150 to 157, set s = 1 contains subbands 8 to 15, 58 to

63, 108 to 115, and 158 to 165, and so on.

[0061] The subband groups for a given set may be static, which may simplify operation. The subband groups for a given set may also change dynamically over time, which may provide interference diversity and other benefits. S subband sets for a sector may be static or may change dynamically. Alternatively, only some of the subband sets may change dynamically, and the other subband sets may be static.

[0062] FIG. 7 depicts an example subband set for the EFDMA scheme shown in FIG. 7, the subband set contains two different groups of M subbands at different time slots. For this example, the subband set contains subbands 0 to M -1 and K / 2 to K / 2 + M -1 in time slot 1, subbands K / 8 to K / 8 + M-1 and 3K / 8 up to 3K18 + M-1 in time slot 2, subbands from K / 4 to K / 4 + M-1 and from 7K / 8 to 7K / 8 + M-1 in time slot 3, subbands from 5K / 8 to 5K / 8 + M-1 and from 3K / 4 to 3K / 4 + M-1 in time slot 4, and so on. Basically, the set can contain any subband groups in each time slot, and the groups do not need to start with a multiple of the K / 8 integer. Other subband sets may be specified such that all of the K total subbands are assigned to S subband sets.

[0063] In general, for interference diversity, different sets of subbands may be determined for adjacent sectors. S subband sets for each sector can be static to facilitate frequency planning for a wireless network. Alternatively, the S subband sets for each sector may change dynamically (e.g., as shown in FIG. 7), which may randomize interference. For each sector, L subband groups for each set can be separated from each other behind

53 / 55P24748PL00

EP 1 884 096 B1 using any number of subbands. Furthermore, the subband groups for each set can be static or can change dynamically (e.g., based on a predetermined sequence, a pseudo-random sequence, and so on).

[0064] Interference diversity can also be achieved using the LFDMA scheme. For example, S subband groups for sector 1 may be determined such that group 0 contains subbands 0 to N-1, group 1 contains subbands N to 2N-1, group 2 contains subbands 2N to 3N-1, and so further as shown in FIG. 3. S subband groups for sector 2 may be arranged alternately using N / 2 subbands from the subband groups for sector 1. In this case, for sector 2, group 0 contains subbands N / 2 to 3N / 2-1, group 1 contains subbands 3N / 2 to 5N / 2-1, group 2 contains subbands 5N / 2 to 7N / 2 -1, and so on. A user assigned to a subband group in sector 1 would then experience interference from two users in sector 2. [0065] FIG. 8 shows a process 800 for generating EFDMA symbols. Modulation symbols are generated, e.g., for motion data, signaling, pilot, or a combination thereof (block 812). EFDMA symbols (or transmission symbols) are then generated for these modulation symbols, e.g., as shown in FIG. 5A or 5B. For clarity, FIG. 8 illustrates the generation of an EFDMA symbol based on the process 500 shown in FIG. 5A.

[0066] Block 820 represents the processing for generating one EFDMA symbol. Many modulation symbols are mapped to the first symbol sequence, e.g., at locations determined based on equation (2) (block 822). A transformation (e.g., a DFT transform) is performed on the first symbol sequence to obtain a second sequence of values ​​(block 824). The values ​​in the second sequence corresponding to the subbands used for the EFDMA symbol are retained, and the remaining values ​​are reset to obtain the third sequence of values ​​(block 826). The subbands used for EFDMA symbols can be determined, e.g., based on equation (1) for the structure

53 / 55P24748PL00

EP 1 884 096 B1 of the subband shown in FIG. 4. Inverse transformation (e.g., IDFT transform) is performed on the third sequence to obtain the fourth sequence of samples (block 828). A phase slope can be used on the fourth sample sequence to obtain the fifth sample sequence (block 830). The EFDMA symbol is then generated based on the fifth sequence of samples, e.g., by appending a cyclic prefix to the fifth sequence (block 832).

[0067] FIG. 9 shows a process of obtaining 900 symbols

EFDMA. EFDMA symbols are received from the transmitter (block 912). Each received EFDMA symbol is processed in block 920 to recover modulation symbols sent in that EFDMA symbol.

[0068] For each EFDMA symbol received, the cyclic prefix is ​​removed to obtain the first sequence of input samples (block 922). The transformation (e.g., the K-point DFT transform) is performed on the sequence of input samples to obtain a second sequence of values ​​(block 924). The values ​​in the second sequence corresponding to the subbands used for the received EFDMA symbol are retained and the other values ​​are discarded (block 926). The stored values ​​are processed to obtain symbol estimates for modulation symbols sent in the received EFDMA symbol. This processing can be performed in various ways depending on how the modulation symbols are sent, how the EFDMA symbol is generated, and so on. For example, frequency domain equalization or some other form of data detection may be performed on stored values ​​with a channel estimate for the transmitter to obtain the detected values ​​(block 928). Inverse transformation (e.g., N-point DFT) can then be performed on the detected values ​​to obtain symbol estimates, which are estimates of modulation symbols sent in the received EFDMA symbol (block 930).

53 / 55P24748PL00

EP 1 884 096 B1 assigned a hop, [0069] FIG. 10 shows a frequency hopping (FH) diagram 1000 that can be used in system 100 for the forward and / or reverse link. Frequency hopping can provide frequency diversity and interference randomization. By means of frequency hopping, the user may be a traffic channel that is associated with a pattern that indicates which subband set (s), if any, is to be used in each time slot. The subband sets available for transmission may be determined based on EFDMA or some other multiplexing schemes. The hop pattern is also called the FH pattern or sequence, and the time slot is also called the hop period. The time slot is the amount of time allocated to a given set of subbands and usually extends over many symbol periods. The hop pattern can pseudo-randomly select different sets of subbands at different time slots.

[0070] In an embodiment, one channel set is specified for each link. Each channel set contains S traffic channels that are orthogonal to each other such that no two traffic channels map the same subband in any time slot. This avoids inter-sector interference among users assigned to traffic channels in the same channel set. Each traffic channel is mapped to a specific sequence of time-frequency blocks based on the hop pattern for the traffic channel. A time-frequency block is a specific set of subbands in a specific time slot. For this embodiment, up to S users can be assigned to S traffic channels and they would be orthogonal to each other.

[0071] FIG. 11 shows a block diagram of a transmitter 1110 and a receiver 1150. For a transmit connection, the transmitter 1110 is part of the base station and the receiver 1150 is part of

53 / 55P24748PL00

EP 1 884 096 B1 terminal. For a reverse link, transmitter 1110 is part of the terminal and receiver 1150 is part of the base station.

[0072] At transmitter 1110, the transmitted data (TX) and pilot processor 1120 encodes, interleaves, and the symbol maps data (e.g., traffic and signaling data) and generates data symbols. Processor 1120 also generates pilot symbols and multiplexes data symbols and pilot symbols. The data symbol used here is the modulation symbol for data, the pilot symbol is the modulation symbol for the pilot, the modulation symbol is a complex value for a point in the signal constellation (e.g. for PSK or QAM), and the symbol is a complex value. The EFDMA 1130 modulator performs EFDMA modulations (e.g., as shown in FIGS. 5A or 5B) and generates EFDMA symbols. The transmitter unit (TMTR) 1132 processes (e.g., transforms into analog form, amplifies, filters, and converts the signal frequency to a higher) EFDMA symbols and generates a radio frequency (RF) modulated signal that is transmitted via antenna 1134. [0073] At receiver 1150, the antenna 1 152 receives the transmitted signal and provides the received signal. The receiver unit (RCVR) 1154 conditions (e.g., filters, amplifies, converts to a lower frequency and converts to digital form) the received signal and provides input samples. The FDMA demodulator (Demod) 1160 performs EFDMA demodulation on input samples (e.g., as shown in FIG. 9) and provides received data values ​​and received pilot values ​​for the subbands used for data transmission and pilot transmission. The channel estimator 1180 calculates the channel estimation based on the received EFDMA 1160 demodulator also performs or alignment) on the received values ​​with the channel estimation and provides an estimation of the data symbols for the transmitter 1110. The received data processor (RX) 1170 performs reverse symbol mapping, deinterleaves and decodes estimates of data symbols, and provides decoded data. Basically, processing with the EFDMA demodulator pilot value data detection from

53 / 55P24748PL00

EP 1 884 096 B1

1160 and the RX data processor 1170 at the receiver 1150 is complementary to the processing of the EFDMA modulator 1130 and the TX data processor 1120 and the pilot at the transmitter 1110, respectively.

[0074] Controllers / processors 1140 and 1190 direct the operation of various processing units in transmitter 1110 and receiver 1150, respectively. Memories 1142 and 1192 store program codes and data for transmitter 1110 and receiver 1150, respectively.

[0075] FIG. 12 shows a block diagram of a transmitter for generating EFDMA symbols. Elements 1200 for generating modulation symbols are combined with elements 1210. Elements 1210 are used to generate transmission symbols based on modulation symbols, where each transmission symbol occupies a plurality of groups of subbands, each of which includes a plurality of adjacent frequency subbands: These elements 1210 may operate as described, for example, with reference to FIG. 8.

[0076] FIG. 13 is a block diagram of a receiver for receiving EFDMA symbols. Elements 1300 for receiving transmission symbols, where each transmission symbol occupies a plurality of groups of subbands, each of which comprises a plurality of adjacent frequency subbands, are combined with elements 1310 for processing the received symbols. These elements 1300 may operate as described, for example, with reference to FIG. 9.

[0077] The multiplexing schemes described herein can be implemented using various elements. For example, processing at the transmitter or receiver can be performed in hardware, software, or a combination thereof. For hardware implementation, the processing units used to generate EFDMA symbols in the transmitter can be implemented inside one or more integrated circuits designed to perform a predetermined task (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD),

53 / 55P24748PL00

EP 1 884 096 B1 programmable controllers, electronic programmable logic devices (PLDs), gate matrices (FPGAs), processors, microcontrollers, microprocessors, devices of other electronic units designed to carry out the functions described herein or a combination thereof. Processing units used to process received EFDMA symbols at the receiver can also be implemented within one or more ASICs, DSPs, processors, and the like.

[0078] For software implementation, processing may be implemented using modules (e.g., procedures, functions, and so on) that perform the functions described herein. Program codes may be stored in memory (e.g., memory 1142 or 1192 in FIG. 11) and executed by a processor (e.g., processor 1140 or 1190). The memory can be implemented inside the processor or outside the processor.

[0079] The purpose of the previous description of the presented embodiments is to enable any person skilled in the art to make or use the present invention. Various modifications of these embodiments will be readily apparent to those skilled in the art, and the general principles set forth herein may be applied to other embodiments without departing from the scope of the invention as set forth. Thus, the purpose of this description is not to be limited to the embodiments shown, but to make it correspond to the widest extent consistent with the principles and the new features set forth herein.

53 / 55P24748PL00

EP 1 884 096 B1