Title of Invention	"METHOD AND APPARATUS FOR REPETITIVE TRANSMISSION USING A PLURALITY OF SUB-CARRIERS"
Abstract	Repetitive transmissions in multi-carrier based wireless access techniques may be achieved by providing multiple cyclic delay values for a plurality of carriers, performing a cyclic delay procedure using the multiple cyclic delay values according to the number of repetitive transmission of data symbols to be transmitted to a receiver, and transmitting the cyclic delayed data symbols to the receiver using the plurality of carriers.

Title of Invention

"METHOD AND APPARATUS FOR REPETITIVE TRANSMISSION USING A PLURALITY OF SUB-CARRIERS"

Abstract

Repetitive transmissions in multi-carrier based wireless access techniques may be achieved by providing multiple cyclic delay values for a plurality of carriers, performing a cyclic delay procedure using the multiple cyclic delay values according to the number of repetitive transmission of data symbols to be transmitted to a receiver, and transmitting the cyclic delayed data symbols to the receiver using the plurality of carriers.

Full Text	Description REPETITIVE TRANSMISSIONS IN MULTI-CARRIER BASED WIRELESS ACCESS TECHNIQUES Disclosure of Invention Technical Solution [1] This disclosure relates to repetitive transmissions in multi-carrier based wireless access techniques. [2] Certain multi-carrier based wireless access techniques do not adequately surport a mobile communication system with various types of antenna structures. [3] The present inventors recognized certain problems related to certain multi-carrier based Wireless access techniques. Based upon such recognition, the following features have been conceived. [4] The features and aspects of the present disclosure have been proposed to irrprove upon certain multi-carrier based wireless access techniques by providing a repetitive transmission scheme that results in additional frequency diversity gain being obtained while requiring low complexity. Such repetitive transmission scheme is applicable re- gardless of the number of antennas, and provides improved performance in a channel environment having low frequency selection. [5] Figure 1 is a block diagram showing a structure of an Orthogonal Frequency Division Multiplexing (OFDM) system having a single transceiving antenna. [6] Figure 2 is a block diagram showing a structure of an Orthogonal Frequency Division Multiplexing (OFDM) system having multiple transceiving antennas. [7] . Figure 3 is a block diagram showing an example of a HARQ scheme. [8] Figure 4 is a block diagram showing another example of the HARQ scheme. [9] Figure 5 is a block diagram showing a cyclic delay diversity scheme. [10] Figure 6 is a drawing to describe a re-transmission method for a space-time coding based HARQ scheme. [11] Figure 7 is a block diagram showing some concepts in applying the repetitive transmission method according to an embodiment of the present disclosure. [12] Figure 8 is a block diagram showing the concept of performiag re-transmissions according to the present embodiment. [13] Figure 9 is a block diagram showing a scheme for performing re-transmissions. [14] Figure 10 is a block diagram showing the concepts of performing re-transmissions through multiple antennas according to the present embodiment. [15] Figure 11 is a block diagram showing how the re-transmission scheme is performed through multiple antennas. [16] Figure 12 is a block diagram showing another concept of performing re- transmissions through multiple antennas according to the present embodiment. [17] Figure 13 is a block diagram showing a scheme of performing re-transmission through multiple antennas. [18] Figure 14 is a block diagram showing another concept of prforming re- transmissions through multiple antennas according to the present embodiment. [19] Figure 15 is a block diagram showing a scheme for performing re-transmissions through multiple antennas. [20] Figure 16 is a block diagram indicating the data included in a single frame. [21] Figure 17 is a block diagram indicating a method for generating the data frame of Figure 16. [22] Figure 18 is a block diagram showing how to implement a cyclic delay transmission method through frequency rotation (circular shifting). [23] Figure 19 shows the changes in signal components when cyclic delay is performed. [24] Figure 20 shows the changes in signal components when 3 respectively different phase sequences are multiplied to a particular signal. [25] Repetitive transmission schemes are essential for increasing the quality of commu- nication systems. Many schemes employ methods for respectively increasing spatial diversity, time diversity, and frequency diversity. Among these, one of the most important methods for increasing system quality is the HARQ scheme [26] The basic concept of the HARQ scheme is to re-transmit the same information during re-transmission if re-transmission is required due to an error occurrence in a first transmitted packet, such mat time diversity gain is obtained while signal power is increased for correcting errors or such that coding gain is increased by transmitting the new parts of the parity portion for correcting packet errors. [27] However, despite the use of such HARQ scheme, in certain OFDM systems employing a single transceiving antenna, because there is no spatial diversity gain, even if re-transmission is performed during a low moving speed environment in which the channel changes slowly, the re-transmitted signal passing through a similar channel again, which results in a high probability that packet errors are not corrected if the channel is not good. This same drawback is suffered in a multiple transceiving antenna system without any multiple antenna schemes being applied thereto. [28] Additionally, when using the space-time coding based HARQ scheme, spatial diversity gain is obtained, but because the related art scheme had been designed with the assumption that the channel does not change during re-transmission, if the moving speed is high, inter-symbol interference occurs due to changes in the channel and the first transmission should be sent at a spatial multiplexing rate of 1 or above, which results in the problem of not being useful for a mobile communication system supporting various types of antenna structures. [29] Figure 1 is a block diagram showing a structure of art Orthogonal Frequency Division Multiplexing (OFDM) system having a single transceiving antenna. Figure 2 is a block diagram showing a structure of an Orthogonal Frequency Division Mul- tiplexing (OFDM) system having multiple transceiving antennas. [30] User data to be transmitted to a receiving side or data bits corresponding to control data are inputted into a channel encoder 101. This channel encoder 101 attaches redundant bits to the data bits in order to reduce the effects with respect to effects or noise coming from the channel. The outputs of the channel encoder 101 are inputted into a mapper ICE and are converted into symbols. These symbols are then inputted into a serial/parallel converter 103. The serial/parallel converter 103 changes serial data into parallel data. The serial/parallel converter 103 can transmit data to a receiving side by using a plurality of orthogonal sub-carriers. If transmitting via a plurality of antennas as shown in Figure 2, the output of the serial/parallel converter 103 is input into a multi-antenna encoder 104. The multiplex antenna encoder 104 performs space- time signal processing for converting data symbols into space-time signals. For the multi-antenna scheme, the transmitting antenna is used to transmit such space-time signal via channels, and the receiving antenna is used to receive such space-time signal from the channels. The multi-antenna decoder 105 performs re-conversion of the received space-time signals into respective data symbols. [31] A system, which employs one or more antennas, inputs the signal received via multiple sub-carriers into a parallel/serial converter 106, which changes parallel signals into serial signals. The output of the parallel/serial converter 106 is input into a demapper 107, which changes the data symbols into a bit sequence. For such bit sequence, the channel decoder 108 performs channel decoding with respect to channel codes in order to deduce the data. [32] In a system as shown in Figures 1 and 2, certain repetitive transmission schemes may be classified in the following manner. [33] Repetitive transmission schemes applicable to all systems in which if the feedback channel is available with one or multiple transceiving antennas may include Automatic Repeat Request (ARQ) schemes, Hybrid ARQ (HARQ) schemes, repetition coding schemes, etc. [34] The ARQ scheme employs a method in which the same signal is re-transmitted when an error occurs in the transmitted packet. The HARQ scheme employs a method in which the same signal or a different type of signal is re-transmitted when an error occurs in the transmitted packet The repetition coding scheme employs a method in which the same signal is repeated many times and transmitted via a single packet, and such scheme is used for transmission of signals that require accurate reception, such as control signals. [35] Hereafter, repetitive transmission schemes applicable to only systems with multiple transceiving antennas will be explained. Such schemes may include a space-time coding scheme, a cyclic delay diversity scheme, a space-time coding based HARQ scheme, etc. [36] The space-time coding scheme employs a method in which the same signal is transmitted via a different transmit antenna in a subsequent time slot. The cyclic delay diversity scheme employs a method in which the same signal is transmitted by using different cyclic delays and different power levels with respect to each antenna. The a space-time coding based HARQ scheme employs a method in which the initial transmission is performed according to a spatial multiplexing method, while re- transmissions are performed in a space-time coding manner if errors occur. [37] In communication systems, repetitive transmission schemes have developed in various ways in order to increase the reliability of the communications environment. Some repetitive transmission schemes described above are methods that are applicable to particular communication systems having only one transceiving antenna or multiple transceiving antennas. Such repetitive transmission schemes operate in the following manner. [38] The ARQ scheme is the most basic method for correcting errors when an error occurs in the transmitted packet. This is a scheme for re-transmitting a packet that is the same as the transmitted packet, whereby the receiving side discards the erroneous packet and waits for a new packet. [39] The HARQ scheme is a combination of the ARQ scheme with channel coding. The HARQ scheme may be generally classified into two types. The first type is a chase combining scheme as shown in Figure 3. As shown: in Figure 3, in the chase combining type HARQ, channel coded packets are transmitted and if the first transmission failed, the same packet is transmitted during re-transmission. This is the same as the ARQ scheme, but in the chase combining HARQ scheme, erroneous packets are not discarded but stored in a buffer and later combined with a re- transmitted packet for error restoration. Thus, errors axe restored by using time diversity and by increasing signal power. [40] Figure 4 is a block diagram that shows another example of the HARQ scheme having an increment redundancy type structure (format). In the increment redundancy type HARQ scheme, re-transmissions are not performed in the same manner as in the initial transmission, but the effects of lowering channel coding rate while correcting errors of a packet are achieved by re-transmitting the additional parity portion of the channel code. [41] The repetition coding scheme enqploys a method in which a low channel coding rate is simply obtained by forming a single packet upon repeating the channel coded blocks and transmitting the same. [42] The space-time coding scheme employs a method in which spatial diversity gain is obtained by transmitting signals via a different transmit antenna with continuously sending the same signal in a multi-antenna environment. The equation below is the most basic space-time code and is typically used in a system having two transmitting antennas. [45] In the above equation, the rows of the matrix represent the transmit antennas while the columns represent time. As shown in the above equation, the S1 data symbol is transmitted via the first antenna and then transmitted via the second antenna in the form of a conjugate complex number, and the S2 data eymbol is transmitted via the second antenna and then transmitted via the first antenna in the form of a conjugate ' complex number of an opposite code in order to keep the orthogonal proprty between date symbols. By transmitting in this manner, each data symbol is transmitted trough all transmit antennas without any inter-symbol interference, thus obtaining full diversity gain. [46] Figure 5 is a block diagram showing a cyclic delay diversity scheme. The cyclic delay diversity scheme is advantageous because when transmitting OFDM symbols in a system having multiple transmission antennas, as signals are transmitted via all antennas with respectively different delays and/or magnitudes, frequency diversity gain can be obtained at the receiving side upon combining each delayed signal, and the complexity of the receiver can be significantly reduced since the signals are combined and detected (extracted) per each transmission antenna. [47] Hereafter, the space-time coding based HARQ scheme described above will be explained. Figure 6 is a drawing to describe a re-transmission method for a space-time coding based HARQ scheme. Figure 6 shows a scheme of a first transmission and a second transmission upon reception of its NACK (negative acknowledgement) signal. [48] As in Figure 6, in a time repetitive re-transmission method using space-time coding, space diversity gain is additionally acquired when re-transmitting such mat the power of the re-transmitted signal is increased while diversity gain is also additionally obtained. [49] The particular characteristics and effects of the present disclosure will be specified in more detail as explained hereafter with respect to an embodiment of the present disclosure. [SO] The present embodiment relates to a repetitive transmission method. The repetitive transmission method refers to a scheme in which particular data are transmitted a plurality of times. When data in transmitted a plurality of times according to the re- petitive transmission method, the data being transmitted may be the same data or may be different data. For example, the same data may be transmitted to the receiving side over a plurality of times. Also, a plurality of same data may be transmitted during a particular single unit of time. Also, particular data may be transmitted in an initial transmission, and data resulting from the initially transmitted data having undergone certain data processing may be transmitted during a second transmission. Also, particular data may be transmitted in an initial transmission, and a portion of the initially transmitted data may be transmitted in the second transmission. [51] As an example of the above-described repetitive transmission method, there is a re- transmission scheme. The re-transmission scheme refers to a method where the transmitting side re-transmits data to the receiving side, if the receiving side was not able to normally reconstruct (decode) the received data. Namely, if the initial transmission failed, a re-transmission is performed. The data being transmitted through such re-transmission may be the same data as the initially transmitted data, or may be data resulting from the initially transmitted data having undergone particular data processing, or may be a portion of the initially transmitted data. [52] Figure 7 is a block diagram showing some concepts in applying the repetitive transmission method according to an embodiment of the present disclosure. Figure 7 is used to describe the most general concepts of the exemplary embodiment [53] The example in Figure 7 shows a repetitive transmission scheme for signals having cyclic delay performed thereto in the time domain with respect to OFDM symbols. This cyclic delay is conceptually the same as a cyclic shift, whereby a sample included in an OFDM symbol is cyclically delayed for a particular number of times. The OFDM symbol refers to a set of data that has been processed using IFFT (Inverse Fast Fourier Transform) or IDFT (Inverse Discrete Fourier Transform) operations, and has the char- acteristic of being typically transmitted during the same time period. The above- mentioned sample refers to the data included in each OFDM symbol, and corresponds to user data or control signals. Figure 7 shows an example where a single OFDM symbol includes N samples, and N may be equivalent to the number of sub-carriers used for communication. [54] In Figure 7, the OFDM symbol refers to an OFDM symbol that has undergone FFT or IDFT operations. Namely, the cyclic delay of Figure 7 shows an OFDM symbol (having undergone FFT or IDFT operations) being cyclically delayed by as much as a particular sample in the time domain. [55] Figure 7 shows an example of transmitting an N number of data streams. For each data stream, a cyclic delay with a respectively different delay value is applied. Namely, a delay of '0' is applied to a first data stream corresponding to data V, and a power of g0 is provided. Also, a delay of 'dt' is applied to a second data stream corresponding to data 's(d1)', and a power of g1 is provided. Also, a delay of 'd N' is applied to an N-th data stream corresponding to data 's(dN)', and a power of gN is provided. Such first through N-th data streams may be transmitted via the antennas upon inserting a cyclic prefix (CP) that equals a certain G number of samples. [56] In the example of Figure 7, an N number of respectively different cyclic delays may be applied. Also, an N number of respectively different power controls may be performed. If the transmissions for a single user are problematic, various cyclic delays or various power controls may be performed according to the changing channel en- vironment. Also, if re-transmissions are problematic, various cyclic delays or various power controls may be performed according to the number of re-transmission oc- currences. Also, if transmissions for multiple users are problematic, various cyclic delays or various power controls that are optimized for each user may be performed. As described above, it is preferable that the cyclic delay or power control values are changed according to various communication environments. In order to adjust the cyclic delay or power control values in a mote active manner, it is more preferably that information fed back from the receiving side is used. Namely, the values d1 through dN or the values g0 through gN can be controlled by using feedback information from the receiving side. [57] In the exanple of Figure 7, the number of antennas is not limited, and various antenna schemes may be applicable. More details regarding such amplication methods are described below. [58] In the example of Figure 7, the data 's' through 's(dN)' may be included in a single data frame or in multiple data frames, and the detailed methods therefor are explained below. [59] In the exanple of Figure 1, the data 's' through 's(dN)' may be re-transmission signals in accordance with ACK/NACK signals transmitted from the receiving side, and the detailed re-transmission method therefor is explained below. [60] In the exanple of Figure 7 may be summarized as follows. The basic concept of a method using cyclic delay diversity for a time repetitive signal that is proposed in this exemplary embodiment is shown in Figure 7. Namely, when transmitting a time re- petitive transmission signal as in Figure 7, it is preferably that each of the repeated signals has the same or different powers, while having different cyclic delays. [61] Hereafter, the re-transmission method according to the present embodiment will be explained with reference to Figures 8 and 9. [62] Figure 8 is a block diagram showing the concept of performing re-transmissions according to the present embodiment. Figure 9 is a block diagram showing a scheme for performing re-transmissions. [63] As shown in Figures 8 and 9, data 's' that has not undergone cyclic delay is transmitted in a first transmission, while data 's(d1)' that has undergone cyclic delay amounting to dl is transmitted in a first re-transmission. Such re-transmission is preferably performed when a NACK signal is received. Such re-transmission may be repeated N times, and if repeated N times, it is preferably that the cyclic delay is performed according to at least N respectively different cyclic delay values. By the N- th re-transmission, s(dN) that has been cyclic delayed by dN is transmitted. [64] For re-transmission, it is preferable that power control is performed. Such power control is performed according to g0 through gN of Figure 9. [65] The present embodiment in which cyclic delay diversity is used for the time re- petitive signal can be applied to any scheme that performs repeated transmissions according to time. [66] When the present embodiment is applied to the HARQ scheme or the repetition code scheme, frequency diversity gain can be increased when compared to the related art methods. [67] Also, during re-transmissions, regardless of whether the same or different channels are employed, frequency selectivity can be adjusted by using various power values and delay values, and thus, frequency diversity gain of a high magnitude can be obtained in any situation, [68] As in Figures 8 and 9, if signals are re-transmitted, the receiving side recognized each signal as a multi-path signal, and simple detection thereof is possible and because frequency selectivity can be increased, the overall system performance can be improved. [69] As described above, the present embodiment supports various systems having various numbers of transceiving antennas. [70] Hereafter, the re-transmission method according to the present embodiment will be explained by example of application to a multiple antenna system. [71] Figure 10 is a block diagram showing the concepts of performing re-transmissions through multiple antennas according to the present embodiment Figure 11 is a block diagram showing how the re-transmission scheme is performed through multiple antennas. [72] The example of Figure 10 relates to performing re-transmissions through re- spectively different antennas. Namely, the first transmission is performed through a first antenna, the first re-transmission is performed through a second antenna, and the second re-transmission is performed through a third antenna. Also, the first transmission is to transmit transmission data 's' that has not undergone any cyclic delay, the first re-transmission is to transmit transmission data s(d1) that has undergone a cyclic delay of d1, and the second re-transmission is to transmit transmission data s(d 2) that has undergone a cyclic delay of d2. [73] The example of Figure 11 shows an example that applies the concept of Figure 10. As shown, re-transmission can be performed for a maximum of N times, and each of the re-transmitted data can be transmitted through respectively different antennas. The example of Figure 11 shows when an N number of antennas are used with respect to an N number of re-transmissions, but the total number of antennas are not limited to such. For example, when there are 4 re-transmissions and 2 transmit antennas, a possible transmission scheme would be that the 1st and 3rd re-transmissions go through the 1st antenna, while the 2nd and 4th re-transmissions go trough the 2nd antenna. [74] The example of Figure 11 shows when certain power control is performed for the data being re-transmitted. As described above, the power control or cyclic delay may be based upon information being fed back from the receiving side. [75] When the re-transmission method of 10 and 11 are employed, respectively different channels are established per each antenna, and space diversity gain as well as frequency diversity gain can be obtained. Re-transmissions can also be performed in a manner other than those shown in Figures 10 and 11. [76] Namely, among the multiple antenna schemes, a spatial multiplexing scheme that increases system capacity by obtaining spatial multiplexing gain can be applied. An exanple thereof is shown in Figures 12 and 13. [77] Figure 12 is a block diagram showing another concept of performing re- transmissions through multiple antennas according to the present embodiment. Figure 13 is a block diagram showing a scheme of performing re-transmission through multiple antennas. [78] Figure 12, unlike the examples of Figures 10 and 11, shows an exanple where data re-transmissions are performed at all of the multiple antennas. In Figure 12, S1, S2,..., SM are respectively different OFDM signals. For exanple, the signals S1 through SM may be independent OFDM signals, or may be signals, for respectively different M users. In the exanple of Figure 12, the 1st antenna through the M-th antenna each transmit particular data. For exanple, the 1st antenna is used for re-transmissions related to S1, the 2nd antenna is used for re-transmissions related to S2, and the M-th antenna is used for re-transmissions related to SM. [79] As shown in Figure 13, data S1 through SM that have not undergone any cyclic delay can be transmitted in a first data transmission. If a first re-transmission is performed thereon, a cyclic delay due to a particular cyclic delay value (d1) may be performed for each of the data S1 through SM. [80] As shown, when the first transmission or a re-transmission thereof is performed, power control may be performed upon determining the gO through gM values according to control information such as channel environment at the like. Also, when performing the N-th data transmission, the data having undergone a cyclic delay by an amount of dN as shown in the drawings, can be transmitted through the multiple antennas. [81] If a time-based antenna rotation scheme is applied to the scheme of Figure 12, data can be repetitively transmitted as in the method of Figures 14 and 15. [82] Figure 14 is a block diagram showing another concept of performing re- transmissions through multiple antennas according to the present embodiment. Figure 15 is a block diagram showing a scheme for performing re-transmissions through multiple antennas. [83] Figure 14 shows an example in which data re-transmissions are performed at all of the multiple antennas. In Figure 14, S1, S2,..., SM are respectively different OFDM signals. In Figure 14, if particular data S1 was transmitted through any one among the multiple antennas, thereafter, other data excluding S1 are then transmitted. For example, for the 1st antenna, after S1 is transmitted, S2 data is transmitted instead of S1, then S3 data and the like may be transmitted thereafter. Also, because particular data is transmitted by multiple antennas, the data S1 through SM are thus transmitted to the receiving side at a particular time. [84] As shown in Figure 15, in the first data transmission, the data S1 through SM that have not undergone any cyclic delay can be transmitted. When performing a first re- transmission thereof, a cyclic delay based upon a particular cyclic delay value (d t) may be performed for each data S1 through SM. Here, the 1st antenna that transmitted SI then transmits SM(d[) instead of S1(d1) in order to apply an antenna rotation scheme. Also, the 2nd antenna that transmitted S2 then transmits Sl(d\|) instead of S2(d!> in order to apply an antenna rotation scheme. Also, the M-th antenna that transmitted SM then transmits SM-l(d1) instead of SM(d1) in order to apply an antenna rotation scheme. [85] As shown, in the first transmission or in performing its related re-transmission, power control may be performed by determining the gO through gM value according to control information, such as the channel environment, etc. Also, when performing the N-th data transmission, the data having undergone cyclic delay (by an amount of dN as depicted) may be transmitted through multiple antennas.. [86] As in Figures 14 and 15, if transmissions are performed upon changing the transmit antenna of each signal according to time, spatial diversity gain can be additionally utilized. [87] As described above, in the examples in Figures 12 and 14, respectively different cyclic delays and respectively different power controls may be performed. Also, unlike what is depicted in Figures 12 and 14, only the signals having error occurrences could be re-transmitted. Also, for re-transmission, each cyclic delay value and power value may be received from the receiver as feedback information, or the transmitter may apply appropriate values therefor. [88] A method applicable to the cyclic delay diversity scheme that proposes repetition coding may be achieved according to the examples of Figures 16 and 17. [89] Figure 16 is a block diagram indicating the data included in a single frame. Figure 17 is a block diagram indicating a method for generating the data frame of Figure 16. [90] Repetition coding is a scheme that repeals the same data and included such into a single frame. As the same data is repeated, the effect of lowering the coding rate upon transmission is created and as a result, the effect of performing accurate data trans- missions is created. [91] The repetition coding method according to the present embodiment can generate the data shown in Figure 16. Namely, a data block including values that have undergone respectively different cyclic delays with respect to the same data is generated and transmitted to the receiving side. [92] The example of Figure 17 depicts a method of generating the data of Figure 16., . Figure 17 shows an example in which data S that has not undergone any cyclic delay with respect to the same data S, data S(d1) that has undergone cyclic delay according to a particular delay value dt, and data S(dN) that has undergone cyclic delay according to a particular delay value dN are included in a single frame. [93] According to the examples of Figures 16 and 17, OFDM symbols that have undergone cyclic delays in a sequential manner are transmitted N times, which is the number of times of repetition. Upon such repetition coding transmission, the receiving side can obtain signal power as well as additional frequency diversity gain, and thus high performance can be obtained. [94] Such repetition coding method can be performed in the time domain or the frequency domain. The examples of Figures 7 through 17 refer to performing cyclic delays upon cycling samples in the time domain, but this is merely exemplary, as the same effect as performing cyclic delay on samples in the time domain may also be obtained by al- locating a phase sequence in the frequency domain. The cyclic delay method employed in the repetition signal transmission scheme proposed in the present embodiments are not intended to be limited to any particular methods, and thus methods for performing cyclic delays through operations in the frequency domain are also within the scope of the present disclosure. [95] Hereafter, a method of transmitting signals in a cyclic delay manner through op- erations in the frequency domain will be described. [96] Figure 18 is a block diagram showing how to implement a cyclic delay transmission method through frequency rotation (circular shifting). [97] In a multi-carrier system such as OFDM, SC-FDMA, etc., an FPT operation (or an equivalent IDFT operation) is performed according to the number of sub-carriers used for data transmission. The cyclic delay transmission method may be achieved by a scheme of performing circular shifting (a particular number of times) on the sanples included within the OFDM symbol in the time domain after the FFT operation is performed, or by a scheme of applying particular phase components with respect to frequency conponents prior to performing the FFT operation. Namely, before the FFT operation are performed, the cyclic delay scheme may be inplemented through frequency circular shifting. [98] As shown in Figure 18, when a certain phase sequence is multiplied to a signal before prforming the FFT operation, the same effect as a cyclic delay in the time domain is generated. [99] Figures 19 and 20 show the changes in signal conponents when cyclic delay is performed. [100] Figure 19 shows the original signal conponents before cyclic .delay is performed. If the original signal undergoes cyclic delay in the time domain by an amount equaling to a certain cyclic delay value d1, the signal conponents of the original signal then change to those shown in Figure 20. Namely, upon performing a time delay amounting to d1, the same effect as performing phase rotation (circular shifting) due to a certain θ1 corresponding to dl is generated. Namely, performing a time delay of d1 in the time domain and applying a certain compooent to each sub-carrier in the frequency domain result in the same effects. [101] In summary, cyclic delay may be performed by multiplying a particular phase sequence C1 to the signal of Figure 19, and such phase sequence C1 may be as shown in the following equation 2. [104] Figure 21 shows the changes in signal conponents when 3 respectively different phase sequences are multiplied to a particular signal. [105] Figure 21 shows the case where a certain phase sequence C(1) is multiplied to a signal corresponding to a frequency index of 1 through 5, a certain phase sequence C(2) is multiplied to a signal corresponding to a frequency index of 6 through 10, and a certain phase sequence C(3) is multiplied to a signal corresponding to a frequency index of 11 or above. The frequency index 1 through 5 may be for a signal of a particular user 1 (UE1), and a particular phase value 6, may be multiplied to the user 1. As depicted, the value that has undergone cyclic delay can have various phases. When a signal that has undergone cyclic delay through a single antenna or multiple antennas is transmitted, the magnitude of the signal may change according to the respectively different phase values. In particular, when cyclic delay is applied to a signal that has undergone channel coding, an advantage that is obtained in that the selectivity at the receiving side is improved according to changes in signal magnitude. [106] The present embodiment provides a repetitive signal transmission method with improved performance through cyclic delays in the time domain or through phase rotations (circular shifting) in the frequency domain. [107] The signal repetitive transmission method using a cyclic delay scheme as proposed by the present disclosure applies cyclic delays to transmit a signal for re-transmission or repetitive transmission. Accordingly, the receiving side detects these transmitted signals upon combining thereof, and frequency diversity gain is obtained by increasing frequency selectivity. [108] The present disclosure is applicable to any signal that is repeated in time, and in an OFDM system having multiple transceiving antennas, additional spatial diversity gain can be obtained by performing transmissions in various forms. [109] As a result, additional frequency diversity gain can be obtained by the features described herein mat require low complexity. [110] The concepts of the present disclosure may be related to Cyclic Shift Transmit Diversity (CSTD), which is an adaptation of the idea of delay diversity to OFDM systems. With CSTD, each antenna element in a transmit array sends a circularly shifted version of the same OFDM time domain symbol. Fere, each antenna adds a cyclic prefix after circularly shifting the OFDM symbol, and thus the delay-spread protection offered by the cyclic prefix is unaffected by the CSTD. [111] The present disclosure provides a method for repetitive transmission using a plurality of carriers, the method comprising: preparing a plurality of cyclic delays that can be applied to a plurality of carriers; performing cyclic delays based upon the number of repetitions for repetitive transmission of data symbols to be transmitted to at least one receiving side; and transmitting the cyclic delayed data symbols using the plurality of carriers. The transmitting step may conprise; repetitively transmitting the cyclic delayed data symbols in a sequential manner in accordance with a reception of a negative acknowledgement signal from the receiving side. The transmitting step may be performed through a plurality of antennas. The transmitting step may be performed through a single antenna. A transmitting side of the data symbols respectively transmitted by the plurality of antennas may be fixed. A transmitting side of me data symbols respectively transmitted by the plurality of antennas may change according to the number of repetitions. The transmitting step may be performed by including the cyclic delayed data symbols into a single frame. [112] Also, the present disclosure provides a method of repetitive transmissions in multi- carrier based wireless access techniques, the method comprising: providing multiple cyclic delay values for a plurality of carriers; performing a cyclic delay procedure using the multiple cyclic delay values according to the number of repetitive transmission of data symbols to be transmitted to a receiver; and transmitting the . cyclic delayed data symbols to the receiver using the plurality of carriers. The transmitting step may comprise: repetitively transmitting the cyclic delayed data symbols in a sequential manner in accordance with feedback information from the receiver. The transmitting step may be performed via multiple antennas. The transmitting step may be performed via a single antenna. The data symbols may be re- spectively transmitted via the multiple antennas of a transmitter that is stationary. The data symbols may be respectively transmitted via the multiple antennas of a transmitter that changes according to the number of repetitions. The transmitting step may be performed upon inserting the cyclic delayed data symbols into one data frame. [113] Additionally, the present disclosure provides an apparatus for performing repetitive transmissions in multi-carrier based wireless access techniques, the apparatus comprising: a processor adapted to provide multiple cyclic delay values for a plurality of carriers and to perform a cyclic delay procedure using the multiple cyclic delay values according to the number of repetitive transmission of data symbols to be transmitted to a receiver; and a transmitter cooperating with the processor and adapted to transmit the cyclic delayed data symbols to the receiver using the plurality of carriers. [114] The features and aspects described herein are related to and can be implemented for various types of communication techniques (such as, but not limited to, broadband wireless air interface techniques, Multiple-Input Multiple-Output (MIMO) techniques, so-called 3.5G or 4G systems designed to provide higher data rates and P-based data services, etc.) and/or various communication standards (such as, but not limited to, OFDM, OFDMA, 3GPP HSDPA, WCDMA, UMTS, IEEE 802.11n, IEEE 802.16, etc.). As such, at least some of the features described herein are applicable to such standards that have been developed or that are continuing to evolve. [115] It should also be understood that the above-described exemplary embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly. Any structural and/or functional changes and modifications that fall within the metes and bounds of the claims or equivalents of such metes and bounds are therefore intended to be embraced by such claims. Claims [1] A method for repetitive transmission using a plurality of carriers, the method comprising: preparing a plurality of cyclic delays that can be applied to a plurality of carriers; performing cyclic delays based upon the number of repetitions for repetitive transmission of data symbols to be transmitted to at least one receiving side; and transmitting the cyclic delayed data symbols using the plurality of carriers. [2] The method of claim 1, wherein the transmitting step comprises: repetitively transmitting the cyclic delayed data symbols in a sequential manner in accordance with a reception of a negative acknowledgement signal from the receiving side. [3] The method of claim 1, wherein the transmitting step is performed through a plurality of antennas. [4] The method of claim 1, wherein the transmitting step is performed through a single antenna. [5] The method of claim 3, wherein a transmitting side of the data symbols re- spectively transmitted by the plurality of antennas is fixed. [6] The method of claim 3, wherein a transmitting side of the data symbols re- spectively transmitted by the plurality of antennas changes according to the number of repetitions. [7] The method of claim 1, wherein the transmitting step is performed by including the cyclic delayed data symbols into a single frame. [8] A method of repetitive transmissions in multi-carrier based wireless access techniques, the method comprising: providing multiple cyclic delay values for a plurality of carriers; performing a cyclic delay procedure using the multiple cyclic delay values according to the number of repetitive transmission of data symbols to be transmitted to a receiver, and transmitting the cyclic delayed data symbols to the receiver using the plurality of carriers. [9] The method of claim 8, wherein the transmitting step conprises: . repetitively transmitting the cyclic delayed data symbols in a sequential manner in accordance with feedback information from the receiver. [10] The method of claim 8, wherein the transmitting step is performed via multiple antennas. [11] The method of claim 8, wherein the transmitting step is performed via a single antenna. [12] The method of claim 10, wherein the data symbols are respectively transmitted via the multiple antennas of a transmitter that is stationary. [13] The method of claim 10, wherein the data symbols are respectively transmitted via the multiple antennas of a transmitter that changes according to the number of repetitions. [14] The method of claim 8, wherein me transmitting step is performed upon inserting the cyclic delayed data symbols into one data frame. [15] An apparatus for performing repetitive transmissions in multi-carrier based wireless access techniques, the apparatus comprising: a processor adapted to provide multiple cyclic delay values for a plurality of carriers and to perform a cyclic delay procedure using the multiple cyclic delay values according to the number of repetitive transmission of data symbols to be transmitted to a receiver, and a transmitter cooperating with the processor and adapted to transmit the cyclic delayed data symbols to the receiver using the plurality of carriers. Repetitive transmissions in multi-carrier based wireless access techniques may be achieved by providing multiple cyclic delay values for a plurality of carriers, performing a cyclic delay procedure using the multiple cyclic delay values according to the number of repetitive transmission of data symbols to be transmitted to a receiver, and transmitting the cyclic delayed data symbols to the receiver using the plurality of carriers.

Full Text

Description
REPETITIVE TRANSMISSIONS IN MULTI-CARRIER BASED
WIRELESS ACCESS TECHNIQUES
Disclosure of Invention
Technical Solution
[1] This disclosure relates to repetitive transmissions in multi-carrier based wireless
access techniques.
[2] Certain multi-carrier based wireless access techniques do not adequately surport a
mobile communication system with various types of antenna structures.
[3] The present inventors recognized certain problems related to certain multi-carrier
based Wireless access techniques. Based upon such recognition, the following features
have been conceived.
[4] The features and aspects of the present disclosure have been proposed to irrprove
upon certain multi-carrier based wireless access techniques by providing a repetitive
transmission scheme that results in additional frequency diversity gain being obtained
while requiring low complexity. Such repetitive transmission scheme is applicable re-
gardless of the number of antennas, and provides improved performance in a channel
environment having low frequency selection.
[5] Figure 1 is a block diagram showing a structure of an Orthogonal Frequency
Division Multiplexing (OFDM) system having a single transceiving antenna.
[6] Figure 2 is a block diagram showing a structure of an Orthogonal Frequency
Division Multiplexing (OFDM) system having multiple transceiving antennas.
[7] . Figure 3 is a block diagram showing an example of a HARQ scheme.
[8] Figure 4 is a block diagram showing another example of the HARQ scheme.
[9] Figure 5 is a block diagram showing a cyclic delay diversity scheme.
[10] Figure 6 is a drawing to describe a re-transmission method for a space-time coding
based HARQ scheme.
[11] Figure 7 is a block diagram showing some concepts in applying the repetitive
transmission method according to an embodiment of the present disclosure.
[12] Figure 8 is a block diagram showing the concept of performiag re-transmissions
according to the present embodiment.
[13] Figure 9 is a block diagram showing a scheme for performing re-transmissions.
[14] Figure 10 is a block diagram showing the concepts of performing re-transmissions
through multiple antennas according to the present embodiment.

[15] Figure 11 is a block diagram showing how the re-transmission scheme is performed
through multiple antennas.
[16] Figure 12 is a block diagram showing another concept of performing re-
transmissions through multiple antennas according to the present embodiment.
[17] Figure 13 is a block diagram showing a scheme of performing re-transmission
through multiple antennas.
[18] Figure 14 is a block diagram showing another concept of prforming re-
transmissions through multiple antennas according to the present embodiment.
[19] Figure 15 is a block diagram showing a scheme for performing re-transmissions
through multiple antennas.
[20] Figure 16 is a block diagram indicating the data included in a single frame.
[21] Figure 17 is a block diagram indicating a method for generating the data frame of
Figure 16.
[22] Figure 18 is a block diagram showing how to implement a cyclic delay transmission
method through frequency rotation (circular shifting).
[23] Figure 19 shows the changes in signal components when cyclic delay is performed.
[24] Figure 20 shows the changes in signal components when 3 respectively different
phase sequences are multiplied to a particular signal.
[25] Repetitive transmission schemes are essential for increasing the quality of commu-
nication systems. Many schemes employ methods for respectively increasing spatial
diversity, time diversity, and frequency diversity. Among these, one of the most
important methods for increasing system quality is the HARQ scheme
[26] The basic concept of the HARQ scheme is to re-transmit the same information
during re-transmission if re-transmission is required due to an error occurrence in a
first transmitted packet, such mat time diversity gain is obtained while signal power is
increased for correcting errors or such that coding gain is increased by transmitting the
new parts of the parity portion for correcting packet errors.
[27] However, despite the use of such HARQ scheme, in certain OFDM systems
employing a single transceiving antenna, because there is no spatial diversity gain,
even if re-transmission is performed during a low moving speed environment in which
the channel changes slowly, the re-transmitted signal passing through a similar channel
again, which results in a high probability that packet errors are not corrected if the
channel is not good. This same drawback is suffered in a multiple transceiving antenna
system without any multiple antenna schemes being applied thereto.
[28] Additionally, when using the space-time coding based HARQ scheme, spatial

diversity gain is obtained, but because the related art scheme had been designed with
the assumption that the channel does not change during re-transmission, if the moving
speed is high, inter-symbol interference occurs due to changes in the channel and the
first transmission should be sent at a spatial multiplexing rate of 1 or above, which
results in the problem of not being useful for a mobile communication system
supporting various types of antenna structures.
[29] Figure 1 is a block diagram showing a structure of art Orthogonal Frequency
Division Multiplexing (OFDM) system having a single transceiving antenna. Figure 2
is a block diagram showing a structure of an Orthogonal Frequency Division Mul-
tiplexing (OFDM) system having multiple transceiving antennas.
[30] User data to be transmitted to a receiving side or data bits corresponding to control
data are inputted into a channel encoder 101. This channel encoder 101 attaches
redundant bits to the data bits in order to reduce the effects with respect to effects or
noise coming from the channel. The outputs of the channel encoder 101 are inputted
into a mapper ICE and are converted into symbols. These symbols are then inputted
into a serial/parallel converter 103. The serial/parallel converter 103 changes serial
data into parallel data. The serial/parallel converter 103 can transmit data to a receiving
side by using a plurality of orthogonal sub-carriers. If transmitting via a plurality of
antennas as shown in Figure 2, the output of the serial/parallel converter 103 is input
into a multi-antenna encoder 104. The multiplex antenna encoder 104 performs space-
time signal processing for converting data symbols into space-time signals. For the
multi-antenna scheme, the transmitting antenna is used to transmit such space-time
signal via channels, and the receiving antenna is used to receive such space-time signal
from the channels. The multi-antenna decoder 105 performs re-conversion of the
received space-time signals into respective data symbols.
[31] A system, which employs one or more antennas, inputs the signal received via
multiple sub-carriers into a parallel/serial converter 106, which changes parallel
signals into serial signals. The output of the parallel/serial converter 106 is input into a
demapper 107, which changes the data symbols into a bit sequence. For such bit
sequence, the channel decoder 108 performs channel decoding with respect to channel
codes in order to deduce the data.
[32] In a system as shown in Figures 1 and 2, certain repetitive transmission schemes may
be classified in the following manner.
[33] Repetitive transmission schemes applicable to all systems in which if the feedback
channel is available with one or multiple transceiving antennas may include Automatic

Repeat Request (ARQ) schemes, Hybrid ARQ (HARQ) schemes, repetition coding
schemes, etc.
[34] The ARQ scheme employs a method in which the same signal is re-transmitted when
an error occurs in the transmitted packet. The HARQ scheme employs a method in
which the same signal or a different type of signal is re-transmitted when an error
occurs in the transmitted packet The repetition coding scheme employs a method in
which the same signal is repeated many times and transmitted via a single packet, and
such scheme is used for transmission of signals that require accurate reception, such as
control signals.
[35] Hereafter, repetitive transmission schemes applicable to only systems with multiple
transceiving antennas will be explained. Such schemes may include a space-time
coding scheme, a cyclic delay diversity scheme, a space-time coding based HARQ
scheme, etc.
[36] The space-time coding scheme employs a method in which the same signal is
transmitted via a different transmit antenna in a subsequent time slot. The cyclic delay
diversity scheme employs a method in which the same signal is transmitted by using
different cyclic delays and different power levels with respect to each antenna. The a
space-time coding based HARQ scheme employs a method in which the initial
transmission is performed according to a spatial multiplexing method, while re-
transmissions are performed in a space-time coding manner if errors occur.
[37] In communication systems, repetitive transmission schemes have developed in
various ways in order to increase the reliability of the communications environment.
Some repetitive transmission schemes described above are methods that are applicable
to particular communication systems having only one transceiving antenna or multiple
transceiving antennas. Such repetitive transmission schemes operate in the following
manner.
[38] The ARQ scheme is the most basic method for correcting errors when an error
occurs in the transmitted packet. This is a scheme for re-transmitting a packet that is
the same as the transmitted packet, whereby the receiving side discards the erroneous
packet and waits for a new packet.
[39] The HARQ scheme is a combination of the ARQ scheme with channel coding. The
HARQ scheme may be generally classified into two types. The first type is a chase
combining scheme as shown in Figure 3. As shown: in Figure 3, in the chase
combining type HARQ, channel coded packets are transmitted and if the first
transmission failed, the same packet is transmitted during re-transmission. This is the

same as the ARQ scheme, but in the chase combining HARQ scheme, erroneous
packets are not discarded but stored in a buffer and later combined with a re-
transmitted packet for error restoration. Thus, errors axe restored by using time
diversity and by increasing signal power.
[40] Figure 4 is a block diagram that shows another example of the HARQ scheme having
an increment redundancy type structure (format). In the increment redundancy type
HARQ scheme, re-transmissions are not performed in the same manner as in the initial
transmission, but the effects of lowering channel coding rate while correcting errors of
a packet are achieved by re-transmitting the additional parity portion of the channel
code.
[41] The repetition coding scheme enqploys a method in which a low channel coding rate
is simply obtained by forming a single packet upon repeating the channel coded blocks
and transmitting the same.
[42] The space-time coding scheme employs a method in which spatial diversity gain is
obtained by transmitting signals via a different transmit antenna with continuously
sending the same signal in a multi-antenna environment. The equation below is the
most basic space-time code and is typically used in a system having two transmitting
antennas.

[45] In the above equation, the rows of the matrix represent the transmit antennas while
the columns represent time. As shown in the above equation, the S1 data symbol is
transmitted via the first antenna and then transmitted via the second antenna in the
form of a conjugate complex number, and the S2 data eymbol is transmitted via the
second antenna and then transmitted via the first antenna in the form of a conjugate
' complex number of an opposite code in order to keep the orthogonal proprty between
date symbols. By transmitting in this manner, each data symbol is transmitted trough
all transmit antennas without any inter-symbol interference, thus obtaining full
diversity gain.
[46] Figure 5 is a block diagram showing a cyclic delay diversity scheme. The cyclic
delay diversity scheme is advantageous because when transmitting OFDM symbols in
a system having multiple transmission antennas, as signals are transmitted via all

antennas with respectively different delays and/or magnitudes, frequency diversity
gain can be obtained at the receiving side upon combining each delayed signal, and the
complexity of the receiver can be significantly reduced since the signals are combined
and detected (extracted) per each transmission antenna.
[47] Hereafter, the space-time coding based HARQ scheme described above will be
explained. Figure 6 is a drawing to describe a re-transmission method for a space-time
coding based HARQ scheme. Figure 6 shows a scheme of a first transmission and a
second transmission upon reception of its NACK (negative acknowledgement) signal.
[48] As in Figure 6, in a time repetitive re-transmission method using space-time coding,
space diversity gain is additionally acquired when re-transmitting such mat the power
of the re-transmitted signal is increased while diversity gain is also additionally
obtained.
[49] The particular characteristics and effects of the present disclosure will be specified in
more detail as explained hereafter with respect to an embodiment of the present
disclosure.
[SO] The present embodiment relates to a repetitive transmission method. The repetitive
transmission method refers to a scheme in which particular data are transmitted a
plurality of times. When data in transmitted a plurality of times according to the re-
petitive transmission method, the data being transmitted may be the same data or may
be different data. For example, the same data may be transmitted to the receiving side
over a plurality of times. Also, a plurality of same data may be transmitted during a
particular single unit of time. Also, particular data may be transmitted in an initial
transmission, and data resulting from the initially transmitted data having undergone
certain data processing may be transmitted during a second transmission. Also,
particular data may be transmitted in an initial transmission, and a portion of the
initially transmitted data may be transmitted in the second transmission.
[51] As an example of the above-described repetitive transmission method, there is a re-
transmission scheme. The re-transmission scheme refers to a method where the
transmitting side re-transmits data to the receiving side, if the receiving side was not
able to normally reconstruct (decode) the received data. Namely, if the initial
transmission failed, a re-transmission is performed. The data being transmitted through
such re-transmission may be the same data as the initially transmitted data, or may be
data resulting from the initially transmitted data having undergone particular data
processing, or may be a portion of the initially transmitted data.
[52] Figure 7 is a block diagram showing some concepts in applying the repetitive

transmission method according to an embodiment of the present disclosure. Figure 7 is
used to describe the most general concepts of the exemplary embodiment
[53] The example in Figure 7 shows a repetitive transmission scheme for signals having
cyclic delay performed thereto in the time domain with respect to OFDM symbols.
This cyclic delay is conceptually the same as a cyclic shift, whereby a sample included
in an OFDM symbol is cyclically delayed for a particular number of times. The OFDM
symbol refers to a set of data that has been processed using IFFT (Inverse Fast Fourier
Transform) or IDFT (Inverse Discrete Fourier Transform) operations, and has the char-
acteristic of being typically transmitted during the same time period. The above-
mentioned sample refers to the data included in each OFDM symbol, and corresponds
to user data or control signals. Figure 7 shows an example where a single OFDM
symbol includes N samples, and N may be equivalent to the number of sub-carriers
used for communication.
[54] In Figure 7, the OFDM symbol refers to an OFDM symbol that has undergone FFT
or IDFT operations. Namely, the cyclic delay of Figure 7 shows an OFDM symbol
(having undergone FFT or IDFT operations) being cyclically delayed by as much as a
particular sample in the time domain.
[55] Figure 7 shows an example of transmitting an N number of data streams. For each
data stream, a cyclic delay with a respectively different delay value is applied. Namely,
a delay of '0' is applied to a first data stream corresponding to data V, and a power of
g0 is provided. Also, a delay of 'dt' is applied to a second data stream corresponding to
data 's(d1)', and a power of g1 is provided. Also, a delay of 'd N' is applied to an N-th
data stream corresponding to data 's(dN)', and a power of gN is provided. Such first
through N-th data streams may be transmitted via the antennas upon inserting a cyclic
prefix (CP) that equals a certain G number of samples.
[56] In the example of Figure 7, an N number of respectively different cyclic delays may
be applied. Also, an N number of respectively different power controls may be
performed. If the transmissions for a single user are problematic, various cyclic delays
or various power controls may be performed according to the changing channel en-
vironment. Also, if re-transmissions are problematic, various cyclic delays or various
power controls may be performed according to the number of re-transmission oc-
currences. Also, if transmissions for multiple users are problematic, various cyclic
delays or various power controls that are optimized for each user may be performed.
As described above, it is preferable that the cyclic delay or power control values are
changed according to various communication environments. In order to adjust the

cyclic delay or power control values in a mote active manner, it is more preferably that
information fed back from the receiving side is used. Namely, the values d1 through
dN or the values g0 through gN can be controlled by using feedback information from
the receiving side.
[57] In the exanple of Figure 7, the number of antennas is not limited, and various
antenna schemes may be applicable. More details regarding such amplication methods
are described below.
[58] In the example of Figure 7, the data 's' through 's(dN)' may be included in a single
data frame or in multiple data frames, and the detailed methods therefor are explained
below.
[59] In the exanple of Figure 1, the data 's' through 's(dN)' may be re-transmission
signals in accordance with ACK/NACK signals transmitted from the receiving side,
and the detailed re-transmission method therefor is explained below.
[60] In the exanple of Figure 7 may be summarized as follows. The basic concept of a
method using cyclic delay diversity for a time repetitive signal that is proposed in this
exemplary embodiment is shown in Figure 7. Namely, when transmitting a time re-
petitive transmission signal as in Figure 7, it is preferably that each of the repeated
signals has the same or different powers, while having different cyclic delays.
[61] Hereafter, the re-transmission method according to the present embodiment will be
explained with reference to Figures 8 and 9.
[62] Figure 8 is a block diagram showing the concept of performing re-transmissions
according to the present embodiment. Figure 9 is a block diagram showing a scheme
for performing re-transmissions.
[63] As shown in Figures 8 and 9, data 's' that has not undergone cyclic delay is
transmitted in a first transmission, while data 's(d1)' that has undergone cyclic delay
amounting to dl is transmitted in a first re-transmission. Such re-transmission is
preferably performed when a NACK signal is received. Such re-transmission may be
repeated N times, and if repeated N times, it is preferably that the cyclic delay is
performed according to at least N respectively different cyclic delay values. By the N-
th re-transmission, s(dN) that has been cyclic delayed by dN is transmitted.
[64] For re-transmission, it is preferable that power control is performed. Such power
control is performed according to g0 through gN of Figure 9.
[65] The present embodiment in which cyclic delay diversity is used for the time re-
petitive signal can be applied to any scheme that performs repeated transmissions
according to time.

[66] When the present embodiment is applied to the HARQ scheme or the repetition code
scheme, frequency diversity gain can be increased when compared to the related art
methods.
[67] Also, during re-transmissions, regardless of whether the same or different channels
are employed, frequency selectivity can be adjusted by using various power values and
delay values, and thus, frequency diversity gain of a high magnitude can be obtained in
any situation,
[68] As in Figures 8 and 9, if signals are re-transmitted, the receiving side recognized
each signal as a multi-path signal, and simple detection thereof is possible and because
frequency selectivity can be increased, the overall system performance can be
improved.
[69] As described above, the present embodiment supports various systems having
various numbers of transceiving antennas.
[70] Hereafter, the re-transmission method according to the present embodiment will be
explained by example of application to a multiple antenna system.
[71] Figure 10 is a block diagram showing the concepts of performing re-transmissions
through multiple antennas according to the present embodiment Figure 11 is a block
diagram showing how the re-transmission scheme is performed through multiple
antennas.
[72] The example of Figure 10 relates to performing re-transmissions through re-
spectively different antennas. Namely, the first transmission is performed through a
first antenna, the first re-transmission is performed through a second antenna, and the
second re-transmission is performed through a third antenna. Also, the first
transmission is to transmit transmission data 's' that has not undergone any cyclic
delay, the first re-transmission is to transmit transmission data s(d1) that has undergone
a cyclic delay of d1, and the second re-transmission is to transmit transmission data s(d
2) that has undergone a cyclic delay of d2.
[73] The example of Figure 11 shows an example that applies the concept of Figure 10.
As shown, re-transmission can be performed for a maximum of N times, and each of
the re-transmitted data can be transmitted through respectively different antennas. The
example of Figure 11 shows when an N number of antennas are used with respect to an
N number of re-transmissions, but the total number of antennas are not limited to such.
For example, when there are 4 re-transmissions and 2 transmit antennas, a possible
transmission scheme would be that the 1st and 3rd re-transmissions go through the 1st
antenna, while the 2nd and 4th re-transmissions go trough the 2nd antenna.

[74] The example of Figure 11 shows when certain power control is performed for the
data being re-transmitted. As described above, the power control or cyclic delay may
be based upon information being fed back from the receiving side.
[75] When the re-transmission method of 10 and 11 are employed, respectively different
channels are established per each antenna, and space diversity gain as well as
frequency diversity gain can be obtained. Re-transmissions can also be performed in a
manner other than those shown in Figures 10 and 11.
[76] Namely, among the multiple antenna schemes, a spatial multiplexing scheme that
increases system capacity by obtaining spatial multiplexing gain can be applied. An
exanple thereof is shown in Figures 12 and 13.
[77] Figure 12 is a block diagram showing another concept of performing re-
transmissions through multiple antennas according to the present embodiment. Figure
13 is a block diagram showing a scheme of performing re-transmission through
multiple antennas.
[78] Figure 12, unlike the examples of Figures 10 and 11, shows an exanple where data
re-transmissions are performed at all of the multiple antennas. In Figure 12, S1, S2,...,
SM are respectively different OFDM signals. For exanple, the signals S1 through SM
may be independent OFDM signals, or may be signals, for respectively different M
users. In the exanple of Figure 12, the 1st antenna through the M-th antenna each
transmit particular data. For exanple, the 1st antenna is used for re-transmissions
related to S1, the 2nd antenna is used for re-transmissions related to S2, and the M-th
antenna is used for re-transmissions related to SM.
[79] As shown in Figure 13, data S1 through SM that have not undergone any cyclic
delay can be transmitted in a first data transmission. If a first re-transmission is
performed thereon, a cyclic delay due to a particular cyclic delay value (d1) may be
performed for each of the data S1 through SM.
[80] As shown, when the first transmission or a re-transmission thereof is performed,
power control may be performed upon determining the gO through gM values
according to control information such as channel environment at the like. Also, when
performing the N-th data transmission, the data having undergone a cyclic delay by an
amount of dN as shown in the drawings, can be transmitted through the multiple
antennas.
[81] If a time-based antenna rotation scheme is applied to the scheme of Figure 12, data
can be repetitively transmitted as in the method of Figures 14 and 15.
[82] Figure 14 is a block diagram showing another concept of performing re-

transmissions through multiple antennas according to the present embodiment. Figure
15 is a block diagram showing a scheme for performing re-transmissions through
multiple antennas.
[83] Figure 14 shows an example in which data re-transmissions are performed at all of
the multiple antennas. In Figure 14, S1, S2,..., SM are respectively different OFDM
signals. In Figure 14, if particular data S1 was transmitted through any one among the
multiple antennas, thereafter, other data excluding S1 are then transmitted. For
example, for the 1st antenna, after S1 is transmitted, S2 data is transmitted instead of
S1, then S3 data and the like may be transmitted thereafter. Also, because particular
data is transmitted by multiple antennas, the data S1 through SM are thus transmitted
to the receiving side at a particular time.
[84] As shown in Figure 15, in the first data transmission, the data S1 through SM that
have not undergone any cyclic delay can be transmitted. When performing a first re-
transmission thereof, a cyclic delay based upon a particular cyclic delay value (d t) may
be performed for each data S1 through SM. Here, the 1st antenna that transmitted SI
then transmits SM(d[) instead of S1(d1) in order to apply an antenna rotation scheme.
Also, the 2nd antenna that transmitted S2 then transmits Sl(d|) instead of S2(d!> in
order to apply an antenna rotation scheme. Also, the M-th antenna that transmitted SM
then transmits SM-l(d1) instead of SM(d1) in order to apply an antenna rotation
scheme.
[85] As shown, in the first transmission or in performing its related re-transmission,
power control may be performed by determining the gO through gM value according to
control information, such as the channel environment, etc. Also, when performing the
N-th data transmission, the data having undergone cyclic delay (by an amount of dN as
depicted) may be transmitted through multiple antennas..
[86] As in Figures 14 and 15, if transmissions are performed upon changing the transmit
antenna of each signal according to time, spatial diversity gain can be additionally
utilized.
[87] As described above, in the examples in Figures 12 and 14, respectively different
cyclic delays and respectively different power controls may be performed. Also, unlike
what is depicted in Figures 12 and 14, only the signals having error occurrences could
be re-transmitted. Also, for re-transmission, each cyclic delay value and power value
may be received from the receiver as feedback information, or the transmitter may
apply appropriate values therefor.
[88] A method applicable to the cyclic delay diversity scheme that proposes repetition

coding may be achieved according to the examples of Figures 16 and 17.
[89] Figure 16 is a block diagram indicating the data included in a single frame. Figure 17
is a block diagram indicating a method for generating the data frame of Figure 16.
[90] Repetition coding is a scheme that repeals the same data and included such into a
single frame. As the same data is repeated, the effect of lowering the coding rate upon
transmission is created and as a result, the effect of performing accurate data trans-
missions is created.
[91] The repetition coding method according to the present embodiment can generate the
data shown in Figure 16. Namely, a data block including values that have undergone
respectively different cyclic delays with respect to the same data is generated and
transmitted to the receiving side.
[92] The example of Figure 17 depicts a method of generating the data of Figure 16., .
Figure 17 shows an example in which data S that has not undergone any cyclic delay
with respect to the same data S, data S(d1) that has undergone cyclic delay according to
a particular delay value dt, and data S(dN) that has undergone cyclic delay according to
a particular delay value dN are included in a single frame.
[93] According to the examples of Figures 16 and 17, OFDM symbols that have
undergone cyclic delays in a sequential manner are transmitted N times, which is the
number of times of repetition. Upon such repetition coding transmission, the receiving
side can obtain signal power as well as additional frequency diversity gain, and thus
high performance can be obtained.
[94] Such repetition coding method can be performed in the time domain or the frequency
domain. The examples of Figures 7 through 17 refer to performing cyclic delays upon
cycling samples in the time domain, but this is merely exemplary, as the same effect as
performing cyclic delay on samples in the time domain may also be obtained by al-
locating a phase sequence in the frequency domain. The cyclic delay method employed
in the repetition signal transmission scheme proposed in the present embodiments are
not intended to be limited to any particular methods, and thus methods for performing
cyclic delays through operations in the frequency domain are also within the scope of
the present disclosure.
[95] Hereafter, a method of transmitting signals in a cyclic delay manner through op-
erations in the frequency domain will be described.
[96] Figure 18 is a block diagram showing how to implement a cyclic delay transmission
method through frequency rotation (circular shifting).
[97] In a multi-carrier system such as OFDM, SC-FDMA, etc., an FPT operation (or an

equivalent IDFT operation) is performed according to the number of sub-carriers used
for data transmission. The cyclic delay transmission method may be achieved by a
scheme of performing circular shifting (a particular number of times) on the sanples
included within the OFDM symbol in the time domain after the FFT operation is
performed, or by a scheme of applying particular phase components with respect to
frequency conponents prior to performing the FFT operation. Namely, before the
FFT operation are performed, the cyclic delay scheme may be inplemented through
frequency circular shifting.
[98] As shown in Figure 18, when a certain phase sequence is multiplied to a signal
before prforming the FFT operation, the same effect as a cyclic delay in the time
domain is generated.
[99] Figures 19 and 20 show the changes in signal conponents when cyclic delay is
performed.
[100] Figure 19 shows the original signal conponents before cyclic .delay is performed. If
the original signal undergoes cyclic delay in the time domain by an amount equaling to
a certain cyclic delay value d1, the signal conponents of the original signal then
change to those shown in Figure 20. Namely, upon performing a time delay amounting
to d1, the same effect as performing phase rotation (circular shifting) due to a certain
θ1 corresponding to dl is generated. Namely, performing a time delay of d1 in the
time domain and applying a certain compooent to each sub-carrier in the frequency
domain result in the same effects.
[101] In summary, cyclic delay may be performed by multiplying a particular phase
sequence C1 to the signal of Figure 19, and such phase sequence C1 may be as shown
in the following equation 2.
[104] Figure 21 shows the changes in signal conponents when 3 respectively different
phase sequences are multiplied to a particular signal.
[105] Figure 21 shows the case where a certain phase sequence C(1) is multiplied to a
signal corresponding to a frequency index of 1 through 5, a certain phase sequence
C(2) is multiplied to a signal corresponding to a frequency index of 6 through 10, and
a certain phase sequence C(3) is multiplied to a signal corresponding to a frequency
index of 11 or above. The frequency index 1 through 5 may be for a signal of a

particular user 1 (UE1), and a particular phase value 6, may be multiplied to the user 1.
As depicted, the value that has undergone cyclic delay can have various phases. When
a signal that has undergone cyclic delay through a single antenna or multiple antennas
is transmitted, the magnitude of the signal may change according to the respectively
different phase values. In particular, when cyclic delay is applied to a signal that has
undergone channel coding, an advantage that is obtained in that the selectivity at the
receiving side is improved according to changes in signal magnitude.
[106] The present embodiment provides a repetitive signal transmission method with
improved performance through cyclic delays in the time domain or through phase
rotations (circular shifting) in the frequency domain.
[107] The signal repetitive transmission method using a cyclic delay scheme as proposed
by the present disclosure applies cyclic delays to transmit a signal for re-transmission
or repetitive transmission. Accordingly, the receiving side detects these transmitted
signals upon combining thereof, and frequency diversity gain is obtained by increasing
frequency selectivity.
[108] The present disclosure is applicable to any signal that is repeated in time, and in an
OFDM system having multiple transceiving antennas, additional spatial diversity gain
can be obtained by performing transmissions in various forms.
[109] As a result, additional frequency diversity gain can be obtained by the features
described herein mat require low complexity.
[110] The concepts of the present disclosure may be related to Cyclic Shift Transmit
Diversity (CSTD), which is an adaptation of the idea of delay diversity to OFDM
systems. With CSTD, each antenna element in a transmit array sends a circularly
shifted version of the same OFDM time domain symbol. Fere, each antenna adds a
cyclic prefix after circularly shifting the OFDM symbol, and thus the delay-spread
protection offered by the cyclic prefix is unaffected by the CSTD.
[111] The present disclosure provides a method for repetitive transmission using a plurality
of carriers, the method comprising: preparing a plurality of cyclic delays that can be
applied to a plurality of carriers; performing cyclic delays based upon the number of
repetitions for repetitive transmission of data symbols to be transmitted to at least one
receiving side; and transmitting the cyclic delayed data symbols using the plurality of
carriers. The transmitting step may conprise; repetitively transmitting the cyclic
delayed data symbols in a sequential manner in accordance with a reception of a
negative acknowledgement signal from the receiving side. The transmitting step may
be performed through a plurality of antennas. The transmitting step may be performed

through a single antenna. A transmitting side of the data symbols respectively
transmitted by the plurality of antennas may be fixed. A transmitting side of me data
symbols respectively transmitted by the plurality of antennas may change according to
the number of repetitions. The transmitting step may be performed by including the
cyclic delayed data symbols into a single frame.
[112] Also, the present disclosure provides a method of repetitive transmissions in multi-
carrier based wireless access techniques, the method comprising: providing multiple
cyclic delay values for a plurality of carriers; performing a cyclic delay procedure
using the multiple cyclic delay values according to the number of repetitive
transmission of data symbols to be transmitted to a receiver; and transmitting the .
cyclic delayed data symbols to the receiver using the plurality of carriers. The
transmitting step may comprise: repetitively transmitting the cyclic delayed data
symbols in a sequential manner in accordance with feedback information from the
receiver. The transmitting step may be performed via multiple antennas. The
transmitting step may be performed via a single antenna. The data symbols may be re-
spectively transmitted via the multiple antennas of a transmitter that is stationary. The
data symbols may be respectively transmitted via the multiple antennas of a transmitter
that changes according to the number of repetitions. The transmitting step may be
performed upon inserting the cyclic delayed data symbols into one data frame.
[113] Additionally, the present disclosure provides an apparatus for performing repetitive
transmissions in multi-carrier based wireless access techniques, the apparatus
comprising: a processor adapted to provide multiple cyclic delay values for a plurality
of carriers and to perform a cyclic delay procedure using the multiple cyclic delay
values according to the number of repetitive transmission of data symbols to be
transmitted to a receiver; and a transmitter cooperating with the processor and adapted
to transmit the cyclic delayed data symbols to the receiver using the plurality of
carriers.
[114] The features and aspects described herein are related to and can be implemented for
various types of communication techniques (such as, but not limited to, broadband
wireless air interface techniques, Multiple-Input Multiple-Output (MIMO) techniques,
so-called 3.5G or 4G systems designed to provide higher data rates and P-based data
services, etc.) and/or various communication standards (such as, but not limited to,
OFDM, OFDMA, 3GPP HSDPA, WCDMA, UMTS, IEEE 802.11n, IEEE 802.16,
etc.). As such, at least some of the features described herein are applicable to such
standards that have been developed or that are continuing to evolve.

[115] It should also be understood that the above-described exemplary embodiments are
not limited by any of the details of the foregoing description, unless otherwise
specified, but rather should be construed broadly. Any structural and/or functional
changes and modifications that fall within the metes and bounds of the claims or
equivalents of such metes and bounds are therefore intended to be embraced by such
claims.

Claims
[1] A method for repetitive transmission using a plurality of carriers, the method
comprising:
preparing a plurality of cyclic delays that can be applied to a plurality of carriers;
performing cyclic delays based upon the number of repetitions for repetitive
transmission of data symbols to be transmitted to at least one receiving side; and
transmitting the cyclic delayed data symbols using the plurality of carriers.
[2] The method of claim 1, wherein the transmitting step comprises:
repetitively transmitting the cyclic delayed data symbols in a sequential manner
in accordance with a reception of a negative acknowledgement signal from the
receiving side.
[3] The method of claim 1, wherein the transmitting step is performed through a
plurality of antennas.
[4] The method of claim 1, wherein the transmitting step is performed through a
single antenna.
[5] The method of claim 3, wherein a transmitting side of the data symbols re-
spectively transmitted by the plurality of antennas is fixed.
[6] The method of claim 3, wherein a transmitting side of the data symbols re-
spectively transmitted by the plurality of antennas changes according to the
number of repetitions.
[7] The method of claim 1, wherein the transmitting step is performed by including
the cyclic delayed data symbols into a single frame.
[8] A method of repetitive transmissions in multi-carrier based wireless access
techniques, the method comprising:
providing multiple cyclic delay values for a plurality of carriers;
performing a cyclic delay procedure using the multiple cyclic delay values
according to the number of repetitive transmission of data symbols to be
transmitted to a receiver, and
transmitting the cyclic delayed data symbols to the receiver using the plurality of
carriers.
[9] The method of claim 8, wherein the transmitting step conprises: .
repetitively transmitting the cyclic delayed data symbols in a sequential manner
in accordance with feedback information from the receiver.
[10] The method of claim 8, wherein the transmitting step is performed via multiple

antennas.
[11] The method of claim 8, wherein the transmitting step is performed via a single
antenna.
[12] The method of claim 10, wherein the data symbols are respectively transmitted
via the multiple antennas of a transmitter that is stationary.
[13] The method of claim 10, wherein the data symbols are respectively transmitted
via the multiple antennas of a transmitter that changes according to the number
of repetitions.
[14] The method of claim 8, wherein me transmitting step is performed upon inserting
the cyclic delayed data symbols into one data frame.
[15] An apparatus for performing repetitive transmissions in multi-carrier based
wireless access techniques, the apparatus comprising:
a processor adapted to provide multiple cyclic delay values for a plurality of
carriers and to perform a cyclic delay procedure using the multiple cyclic delay
values according to the number of repetitive transmission of data symbols to be
transmitted to a receiver, and
a transmitter cooperating with the processor and adapted to transmit the cyclic
delayed data symbols to the receiver using the plurality of carriers.

Repetitive transmissions in multi-carrier based wireless access techniques may be achieved by providing multiple cyclic delay values for a plurality of carriers, performing a cyclic delay procedure using the multiple cyclic delay values according to the number of repetitive transmission of data symbols to be transmitted to a receiver, and transmitting the cyclic delayed data symbols to the receiver using the plurality of carriers.

Documents:

3975-KOLNP-2008-(12-08-2014)-CORRESPONDENCE.pdf

3975-KOLNP-2008-(12-08-2014)-OTHERS.pdf

3975-KOLNP-2008-(15-10-2014)-ABSTRACT.pdf

3975-KOLNP-2008-(15-10-2014)-ANNEXURE TO FORM 3.pdf

3975-KOLNP-2008-(15-10-2014)-CLAIMS.pdf

3975-KOLNP-2008-(15-10-2014)-CORRESPONDENCE.pdf

3975-KOLNP-2008-(15-10-2014)-DESCRIPTION (COMPLETE).pdf

3975-KOLNP-2008-(15-10-2014)-DRAWINGS.pdf

3975-KOLNP-2008-(15-10-2014)-FORM-2.pdf

3975-KOLNP-2008-(15-10-2014)-FORM-3.pdf

3975-KOLNP-2008-(15-10-2014)-FORM-5.pdf

3975-KOLNP-2008-(15-10-2014)-OTHERS.pdf

3975-KOLNP-2008-(15-10-2014)-PA.pdf

3975-KOLNP-2008-(15-10-2014)-PETITION UNDER RULE 137.pdf

3975-kolnp-2008-abstract.pdf

3975-KOLNP-2008-ASSIGNMENT.pdf

3975-kolnp-2008-claims.pdf

3975-KOLNP-2008-CORRESPONDENCE-1.1.pdf

3975-kolnp-2008-correspondence.pdf

3975-kolnp-2008-description (complete).pdf

3975-kolnp-2008-drawings.pdf

3975-kolnp-2008-form 1.pdf

3975-KOLNP-2008-FORM 18.pdf

3975-kolnp-2008-form 3.pdf

3975-kolnp-2008-form 5.pdf

3975-kolnp-2008-gpa.pdf

3975-kolnp-2008-international publication.pdf

3975-kolnp-2008-international search report.pdf

3975-kolnp-2008-pct priority document notification.pdf

3975-kolnp-2008-pct request form.pdf

3975-kolnp-2008-specification.pdf

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Patent Number

265459

Indian Patent Application Number

3975/KOLNP/2008

PG Journal Number

09/2015

Publication Date

27-Feb-2015

Grant Date

25-Feb-2015

Date of Filing

30-Sep-2008

Name of Patentee

LG ELECTRONICS INC.

Applicant Address

20, YOIDO-DONG, YONGDUNGPO-GU, SEOUL

Inventors:

#	Inventor's Name	Inventor's Address
1	CHUN, JIN-YOUNG	JOONGANG HEIGHTSVILLE APT. NA-302, 339-13, GURO 2-DONG, GURO-GU, SEOUL, 152-052
2	LEE, MOON-IL	SAETEO MAUEL HYUNDAI HOMETOWN APT. 717-501, JUKJEON-DONG, SUJI-GU, YONGIN,, GYEONGGI-DO, 448-160
3	CHANG, JAE-WON	BAEKSONG MAEUL 7-DANJI IMGWANG APT. 705-1205, BAEKSEOK-DONG, ILSAN-GU, GOYANG,, GYEONGGI-DO, 410-721
4	JUNG, JIN-HYUK	302, 1250-8, SA 1-DONG, SANGNOK-GU, ANSAN,, GYEONGGI-DO, 426-171

PCT International Classification Number

H04L 1/18

PCT International Application Number

PCT/KR2007/001704

PCT International Filing date

2007-04-06

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10-2006-0064452	2006-07-10	U.S.A.
2	60/790972	2006-04-10	U.S.A.