Title of Invention	A METHOD AND APPARATUS FOR SUPPORTING HOPPING OF CAZAC-BASED SEQUENCE WITH MINIMUM IMPLEMENTATION COMPLEXITY
Abstract	A method and apparatus are provided for the selection of sequences used for the transmission of signals from user equipments in a cellular communication system. The sequences can be selected either through planning or through pseudo-random hopping among a set of sequences. With planning, the serving Node B signals the sequence assignment for each cell, which remains invariable in time. With pseudo-random sequence hopping, the serving Node B signals the initial sequence, from a set of sequences, which can be different among cells. The initial sequence used in the control (or data) channel is signaled by the serving Node B. The initial sequence used in the data (or control) channel is selected to be the sequence in a set of sequences with number equal to a shift value relative to the first sequence as signaled by the serving Node B for the control (or data) channel.

Title of Invention

A METHOD AND APPARATUS FOR SUPPORTING HOPPING OF CAZAC-BASED SEQUENCE WITH MINIMUM IMPLEMENTATION COMPLEXITY

Abstract

A method and apparatus are provided for the selection of sequences used for the transmission of signals from user equipments in a cellular communication system. The sequences can be selected either through planning or through pseudo-random hopping among a set of sequences. With planning, the serving Node B signals the sequence assignment for each cell, which remains invariable in time. With pseudo-random sequence hopping, the serving Node B signals the initial sequence, from a set of sequences, which can be different among cells. The initial sequence used in the control (or data) channel is signaled by the serving Node B. The initial sequence used in the data (or control) channel is selected to be the sequence in a set of sequences with number equal to a shift value relative to the first sequence as signaled by the serving Node B for the control (or data) channel.

Full Text	SEQUENCE HOPPING IN SC-FDMA COMMUNICATION SYSTEMS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to wireless communication systems and, more particularly, to a Single-Carrier Frequency Division Multiple Access (SC-FDMA) communication system that is further considered in the development of the 3rd Generation Partnership Project (3GPP) Evolved Universal Terrestrial Radio Access (E-UTRA) long term evolution (LTE). 2. Description of the Art Methods and apparatus are considered for the functionality and implementation of hopping for sequences used in the construction of Reference Signals (RS) or control signals transmitted in SC-FDMA communication systems. The Uplink (UL) of the communication system is assumed, which corresponds to signal transmissions from mobile User Equipments (UEs) to a serving base station (Node B). A UE, also commonly referred to as terminal or mobile station, may be fixed or mobile and may be a wireless device, a cellular phone, a personal computer device, a wireless modem card, etc. A Node B is generally a fixed station and may also be called a Base Transceiver System (BTS), an access point, or some other terminology. A Node B may control multiple cells in a cellular communication system, as it is known in the art. Several types of signals need to be supported for the prope'r functionality of the communication system. In addition to data signals, which convey the information content of the communication, control signals also need to be transmitted from UEs to their serving Node B in the UL and from the serving Node B to UEs in the downlink (DL) of the communication system. The DL refers to the communication from the Node B to UEs. Additionally, a UE having data or control transmission also transmits RSs, also known as pilots. These RSs primarily serve to provide coherent demodulation for the transmitted data or control signals by a UE. The UEs are assumed to transmit data or control signals over a Transmission Time Interval (TTI), which is assumed to correspond to a sub- frame. The sub-frame is the time unit of a frame, which may consist of ten sub- frames. FIG. 1 illustrates a block diagram of the sub-frame structure 110. The sub-frame 110 includes two slots. Each slot 120 further includes seven symbols used for transmission of data or control signals. Each symbol 130 further includes a Cyclic Prefix (CP) in order to mitigate interference due to channel propagation effects. The signal transmission in one slot may be in the same or at a different part of the operating bandwidth (B W) than the signal transmission in the second slot. In addition to symbols carrying data or control information, some symbols are used for Reference Signal (RS) transmission 140. The transmission BW is assumed to include frequency resource units, which will be referred to herein as resource blocks (RBs). Each RB may consist of 12 sub-carriers and UEs are allocated a multiple N of consecutive RBs 150 for Physical Uplink Shared Channel (PUSCH) transmission and 1 RB for Physical Uplink Control Channel (PUCCH) transmission. As the data or control signal transmission is over a BW that can be (orthogonally) shared by multiple UEs, the corresponding physical layer channel may be respectively referred to as PUSCH or as PUCCH. FIG. 1 illustrates a structure for the PUSCH sub-frame while respective ones for the PUCCH will be subsequently described. The UEs are also assumed to transmit control signals in the absence of any data signals. The control signals include, but are not limited to, positive or negative acknowledgment signals (ACK or NAK, respectively) and Channel Quality Indication (CQI) signals. The ACK/NAK signals are in response to the correct or incorrect, respectively, data packet reception by a UE in the DL of the communication system. The CQI signals are sent by a UE to inform its serving Node B of its Signal-to-Interference and Noise Ratio (SINR) conditions in order for the serving Node B to perform channel dependent scheduling in the DL of the communication system. Both ACK/NAK and CQI signals are accompanied by RS signals in order to enable their coherent demodulation at the Node B receiver. The physical layer channel conveying ACK/NAK or CQI control signaling may be referred as the PUCCH. The ACK/NAK, CQI and associated RS signals are assumed to be transmitted by UEs in one RB using CAZAC sequences as it is known in the art and is subsequently described. FIG. 2 shows a structure for the ACK/NAK transmission during one slot 210 in a SC-FDMA communication system. The ACK/NAK information bits 220 modulate 230 a "Constant Amplitude Zero Auto-Correlation (CAZAC)" sequence 240, for example with QPSK or 16QAM modulation, which is then transmitted by the UE after performing an Inverse Fast Fourier Transform (IFFT) operation as it is further subsequently described. In addition to the ACK/NAK, RS is transmitted to enable the coherent demodulation of the ACK/NAK signal at the Node B receiver. The third, fourth, and fifth SC-FDMA symbols in each slot may carry an RS 250. FIG. 3 shows a structure for the CQI transmission during one slot 310 in a SC-FDMA communication system. Similar to the ACK/NAK transmission, the CQI information bits 320 modulate 330 a CAZAC sequence 340, for example with QPSK or 16QAM modulation, which is then transmitted by the UE after performing the IFFT operation as it is further subsequently described. In addition to the CQI, RS is transmitted to enable the coherent demodulation at the Node B receiver of the CQI signal. In the embodiment, the second and sixth SC-FDMA symbols in each slot carry an RS 350. As it was previously mentioned, the ACK/NAK, CQI, and RS signals are assumed to be constructed from CAZAC sequences. An example of such sequences is the Zadoff-Chu (ZC) sequences whose elements are given by Equation (1) below: L is the length of the CAZAC sequence, n is the index of an element of the sequence n = {0, 1, 2 ..., L - 1}, and k is the index of the sequence itself. For a given length L, there are L - 1 distinct sequences, if L is prime. Therefore, the entire family of sequences is defined as k ranges in {1,2 ...,L- 1}. However, it should be noted that the CAZAC sequences used for the ACK/NAK, CQI, and RS transmission need not be generated using the exact above expression as it is further discussed below. For CAZAC sequences of prime length L, the number of sequences is L-l. As the RBs are assumed to consist of an even number of sub-carriers, with 1 RB consisting of 12 sub-carriers, the sequences used to transmit the ACK/NAK, CQI, and RS can be generated, in the frequency or time domain, by either truncating a longer prime length (such as length 13) CAZAC sequence or by extending a shorter prime length (such as length 11) CAZAC sequence by repeating its first element(s) at the end (cyclic extension), although the resulting sequences do not fulfill the definition of a CAZAC sequence. Alternatively, the CAZAC sequences can be directly generated through a computer search for sequences satisfying the CAZAC properties. A block diagram for the transmission through SC-FDMA signaling of a CAZAC-based sequence in the time domain is shown in FIG. 4. The selected CAZAC-based sequence 410 is generated through one of the previously described methods (modulated by the respective bits in case of ACK/NAK or CQI transmission), it is then cyclically shifted 420 as it is subsequently described, the Discrete Fourier Transform (DFT) of the resulting sequence is obtained 430, the sub-carriers 440 corresponding to the assigned transmission bandwidth are selected 450, the Inverse Fast Fourier Transform (IFFT) is performed 460, and finally the CP 470 and filtering 480 are applied to the transmitted signal 490. Zero padding is assumed to be performed by a UE in sub-carriers used for signal transmission by another UE and in guard sub-carriers (not shown). Moreover, for brevity, additional transmitter circuitry such as digital-to-analog converter, analog filters, amplifiers, and transmitter antennas, as they are known in the art, are not shown in FIG. 4. Similarly, for the PUCCH, the modulation of a CAZAC sequence with ACK/NAK or CQI bits is well known in the art, such as for example QPSK modulation, and is omitted for brevity. At the receiver, the inverse (complementary) transmitter functions are performed. This is conceptually illustrated in FIG. 5 where the reverse operations of those in FIG. 4 apply. As it is known in the art (not shown for brevity), an antenna receives the RF analog signal and after further processing units (such as filters, amplifiers, frequency down-converters, and analog-to-digital converters) the digital received signal 510 passes through a time windowing unit 520 and the CP is removed 530. Subsequently, the receiver unit applies an FFT 540, selects 550 the sub-carriers 560 used by the transmitter, applies an Inverse DFT (IDFT) 570, de-multiplexes (in time) the RS and CQI signal 580, and after obtaining a channel estimate based on the RS (not shown) it extracts the CQI bits 590. As for the transmitter, well known receiver functionalities such as channel estimation, demodulation, and decoding are not shown for brevity. An alternative generation method for the transmitted CAZAC sequence is in the frequency domain. This is depicted in FIG. 6. The generation of the transmitted CAZAC sequence in the frequency domain follows the same steps as the one in the time domain with two exceptions. The frequency domain version of the CAZAC sequence is used 610 (that is the DFT of the CAZAC sequence is pre-computed and not included in the transmission chain) and the cyclic shift 650 is applied after the IFFT 640. The selection 620 of the sub-carriers 630 corresponding to the assigned transmission BW, and the application of CP 660 and filtering 670 to the transmitted signal 680, as well as other conventional functionalities (not shown), are as previously described for FIG. 4. The reverse functions are again performed for the reception of the CAZAC-based sequence transmitted as in FIG. 6. This is illustrated in FIG. 7. The received signal 710 passes through a time windowing unit 720 and the CP is removed 730. Subsequently, the cyclic shift is restored 740, an FFT 750 is applied, and the transmitted sub-carriers 760 are selected 765. FIG. 7 also shows the subsequent correlation 770 with the replica 780 of the CAZAC-based sequence. Finally, the output 790 is obtained which can then be passed to a channel estimation unit, such as a time-frequency interpolator, in case of a RS, or can be used for detecting the transmitted information, in case the CAZAC-based sequence is modulated by ACK/NAK or CQI information bits. The transmitted CAZAC-based sequence in FIG. 4 or FIG. 6 may not be modulated by any information (data or control) and can then serve as the RS, as shown, for example, in FIG. 2 and FIG. 3. Different cyclic shifts of the same CAZAC sequence provide orthogonal CAZAC sequences. Therefore, different cyclic shifts of the same CAZAC sequence can be allocated to different UEs in the same RB for their RS or ACK/NAK, or CQI transmission and achieve orthogonal UE multiplexing. This principle is illustrated in FIG. 8. Referring to FIG. 8, in order for the multiple CAZAC sequences 810, 830, 850, 870 generated correspondingly from multiple cyclic shifts 820, 840, 860, 880 of the same root CAZAC sequence to be orthogonal, the cyclic shift value A 890 should exceed the channel propagation delay spread D (including a time uncertainty error and filter spillover effects). If Ts is the duration of one symbol, the number of cyclic shifts is equal to the mathematical floor of the ratio Ts/D. For a CAZAC sequence of length 12, the number of possible cyclic shifts is 12 and for symbol duration of about 66 microseconds (14 symbols in a 1 millisecond sub-frame), the time separation of consecutive cyclic shifts is about 5.5 microseconds. Alternatively, to provide better protection against multipath propagation, only every other (6 of the 12) cyclic shift may be used providing time separation of about 11 microseconds. CAZAC-based sequences of the same length typically have good cross- correlation properties (low cross-correlation values), which is important in order to minimize the impact of mutual interference in synchronous communication system and improve their reception performance. It is well known that ZC sequences of length L have optimal cross-correlation of However, this property does not hold when truncation or extension is applied to ZC sequences or when CAZAC-based sequences are generated through computer search. Moreover, CAZAC-based sequences of different lengths have a wide distribution of cross-correlation values and large values can frequently occur leading to increased interference. FIG 9 illustrates the Cumulative Density Function (CDF) of cross- correlation values for length-12 CAZAC-based sequence resulting from cyclically extending a length-11 ZC sequence, truncating a length-13 ZC sequence and generating length-12 CAZAC-based sequences through a computer search method. Variations in cross-correlation values can be easily observed. These variations have even wider distribution for cross-correlations between CAZAC- based sequences with different lengths. The impact of large cross-correlations on the reception reliability of signals constructed from CAZAC-based sequences can be mitigated through sequence hopping. Pseudo-random hopping patterns are well known in the art and are used for a variety of applications. Any such generic pseudo-random hopping pattern can serve as a reference for sequence hopping. In this manner, the CAZAC-based sequence used between consecutive transmissions of ACK/NAK, CQI, or RS signals in different SC-FDMA symbols, can change in a pseudo-random pattern and this reduces the probability that CAZAC-based generated signals will be subjected to large mutual cross-correlations and correspondingly experience large interference over their transmission symbols. There is therefore a need for supporting hopping of CAZAC-based sequences with minimum implementation complexity in order to reduce the average interference among CAZAC-based sequences. There is another need for assigning CAZAC-based sequences through planning in different Node Bs and different cells of the same Node B in a communication system. Finally, there is a need for minimizing the signaling overhead for communicating sequence hopping parameters or the sequence assignment (planning) from the serving Node B to the UEs. SUMMARY OF THE INVENTION The present invention has been made to address at least the above- mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention provides an apparatus and method for supporting CAZAC-based sequence hopping or sequence planning. Another aspect of the present invention enables CAZAC-based sequence hopping with minimum implementation complexity at a UE transmitter and a Node B receiver by applying the same hopping pattern to the sequences used for signal transmission in all possible channels. Additionally, an aspect of the present invention enables CAZAC-based sequence hopping with minimum implementation complexity at a UE transmitter and a Node B receiver by limiting the total number of sequences in the sets of sequences for the possible resource block allocations to be equal to the smallest number of sequences obtained for one of the possible resource block allocations. A further aspect of the present invention enables CAZAC-based sequence hopping and planning with minimum signaling overhead for communicating the sequence allocation parameters from the serving Node B to UEs. According to one aspect of the present invention, an apparatus and a method are provided for a user equipment to transmit a signal using one sequence in all symbols of a sub-frame where the signal is transmitted if the resource block allocation is smaller than or equal to a predetermined value and to transmit a signal using, respectively, a first sequence and a second sequence in a first symbol and a second symbol of a sub-frame where the signal is transmitted if the resource block allocation is larger than a predetermined value. According to another aspect of the present invention, an apparatus and a method are provided for a user equipment to transmit a signal using a sequence from a full set of sequences in a symbol of a sub-frame where the signal is transmitted if the resource block allocation is smaller than or equal to a predetermined value and to transmit a signal using a sequence from a sub-set of sequences in a symbol of a sub-frame where the signal is transmitted if the resource block allocation is larger than a predetermined value. According to an additional embodiment of the present invention, an apparatus and a method are provided for a user equipment to transmit a signal in a data channel using a sequence from a set of sequences wherein the sequence at each symbol of a sub-frame where the signal is transmitted is determined according to a pseudo-random hopping pattern and to transmit a signal in a control channel using a sequence from a set of sequences wherein the sequence at each symbol of a sub-frame where the signal is transmitted is determined according to same pseudo-random hopping pattern. The signal and the number of symbols where the signal is transmitted may be different between the data and control channels but the sequence hopping pattern remains the same by adjusting the rate of its application (slower rate applies for the channel having the larger number of symbols for the signal transmission using sequence hopping). According to a further embodiment of the present invention, an apparatus and a method are provided for a user equipment to transmit a signal in a control channel using one or more sequences from a set of sequences wherein the first sequence is signaled by the serving Node B, and to transmit a signal in a data channel using one or more sequences from a set of sequences wherein the first sequence is determined from the set of sequences by applying a shift relative to the first sequence in the respective set of sequences used for the control channel as signaled by the serving Node B. The reverse relation may apply in determining the first sequence in the control and data channels. BRIEF DESCRIPTION OF THE DRAWINGS The above and other aspects, features and advantages of the present invention will be more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: FIG. 1 is a diagram illustrating a sub-frame structure for the SC-FDMA communication system; FIG. 2 is a diagram illustrating a partitioning of a slot structure for the transmission of ACK/NAK bits; FIG. 3 is a diagram illustrating a partitioning of a slot structure for the transmission of CQI bits; FIG. 4 is a block diagram illustrating an SC-FDMA transmitter for transmitting an ACK/NAK signal, or a CQI signal, or a reference signal using a CAZAC-based sequence in the time domain; FIG. 5 is a block diagram illustrating an SC-FDMA receiver for receiving an ACK/NAK signal, or a CQI signal, or a reference signal using a CAZAC- based sequence in the time domain; FIG. 6 is a block diagram illustrating an SC-FDMA transmitter for transmitting an ACK/NAK signal, or a CQI signal, or a reference signal using a CAZAC-based sequence in the frequency domain; FIG. 7 is a block diagram illustrating an SC-FDMA receiver for receiving an ACK/NAK signal, or a CQI signal, or a reference signal using a CAZAC- based sequence in the frequency domain; FIG. 8 is a block diagram illustrating a construction of orthogonal CAZAC-based sequences through the application of different cyclic shifts on a root CAZAC-based sequence; FIG. 9 is a diagram illustrating the CDF of cross-correlation values for CAZAC-based sequences of length 12; FIG. 10 is a diagram illustrating the allocation of sequence groups to different cells or different Node Bs through group sequence planning, according to an embodiment of the present invention; FIG. 11 is a diagram illustrating sequence hopping within a sub-frame for allocation larger than 6 RBs when group sequence planning is used, according to an embodiment of the present invention; FIG. 12 is a diagram illustrating the allocation of sequence groups to different cells or different Node Bs through group sequence hopping, according to an embodiment of the present invention; FIG. 13 is a diagram illustrating sequence hopping within a sub-frame when group sequence hopping is used, according to an embodiment of the present invention; FIG. 14 is a diagram illustrating allocating different sequences with different cyclic shifts to cells of the same Node B, according to an embodiment of the present invention; FIG. 15 is a diagram illustrating determining the PUCCH sequence from the PUSCH sequence, according to an embodiment of the present invention; and FIG. 16 is a diagram illustrating determining the PUCCH sequence from the PUSCH sequence by applying a shift, according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention are described in detail with reference to the accompanying drawings. The same or similar components are designated by the same or similar reference numerals although they are illustrated in different drawings. Detailed descriptions of constructions or processes known in the art may be omitted to avoid obscuring the subject matter of the present invention. Additionally, although the present invention assumes a SC-FDMA communication system, it also applies to all Frequency Division Multiplexing (FDM) systems in general and to Orthogonal Frequency Division Multiple Access (OFDMA), Orthogonal Frequency Division Multiplexing (OFDM), Frequency Division Multiple Access (FDMA), Discrete Fourier Transform (DFT)-spread OFDM, DFT-spread OFDMA, Single-Carrier OFDMA (SC- OFDMA), and Single-Carrier OFDM in particular. Methods of the embodiments of the invention solve problems related to the need for enabling sequence planning or sequence hopping for CAZAC-based sequences while minimizing the respective implementation complexity at a UE transmitter and at a Node B receiver and minimizing the signaling overhead required for configuring the sequence planning or the sequence hopping patterns. As discussed in the foregoing background, the construction of CAZAC- based sequences may be through various methods. The number of sequences provided with cyclic extension or truncation of Zadoff-Chu (ZC) sequences depends on the sequence length. Some indicative values for corresponding RB allocations are shown in Table 1 where one RB is assumed to consist of 12 sub- carriers. Since the number of CAZAC-based sequences depend on the corresponding sequence length, a number of sequences of larger length can be associated with each sequence of smaller length. For example, referring to Table 1, for cyclic extension of ZC sequences, each of the 10 sequences of length 12 can be associated (one-to-one mapping) with a set of 7 sequences of length 72 (since there are 70 sequences of length 72). Moreover, the number of sequences for small RB allocations, such as 1 RB or 2 RBs, is the smallest and defines the constraints in allocating different sequences in neighboring cells and Node Bs (a Node B may comprise of multiple cells). For these sequences, if a pseudo-random hopping pattern applies for their transmission, the same sequence may often be used in neighboring cells resulting to full interference of transmissions and associated degradation in the reception reliability of signals transmitted through the use of CAZAC-based sequences. To mitigate the sequence allocation problem resulting from the small number of available CAZAC-based sequences for the smaller RB allocations, CAZAC sequences constructed through computer searches can be used as a larger number of sequences can be obtained in this manner. However, unlike CAZAC- based sequences obtained from cyclic extension or truncation of ZC sequences, a closed form expression for computer generated CAZAC sequences does not exist and such sequences need to be stored in memory. For this reason, their use is typically confined to small RB allocations where the shortage of CAZAC-based sequences is most acute. For the larger RB allocations, CAZAC-based sequences are generated through the implementation of a formula such as the one described for the generation of ZC sequences. About 30 computer generated CAZAC sequences can be obtained for 1 RB allocations and by obtaining the same number of sequences for 2 RB allocations, sequence planning and sequence hopping is then constrained by the number of sequences for 1, 2, or 3 RB allocations. In a preferred embodiment this number is 30. The invention considers cyclic extension of ZC sequences for the generation of CAZAC-based sequences for allocations equal to or larger than 3 RBs and computer generated CAZAC sequences for allocations of 1 RB or 2 RBs. An embodiment of the invention assumes that PUCCH transmissions from a UE occupy one RB and allocations larger than 1 RB are used only for the PUSCH, which, in the embodiment, contains 2 RS transmission symbols per sub- frame. Therefore, only one sequence hopping opportunity exists within a PUSCH sub-frame. For packet retransmissions based on Hybrid Automatic Repeat reQuest (HARQ), as it is known in the art, the interference experienced by the CAZAC- based sequence used for RS transmission will be different among retransmissions as different RB allocations (different size or different BW position leading to partial overlapping between two CAZAC sequences) are likely to be used for UEs in interfering cells during a packet retransmission. Moreover, the channel characteristics are likely to be different between retransmissions and this also leads to different cross-correlation characteristics among interfering CAZAC sequences. Therefore, extending the number of sequences for each RB allocation to more than 2 is of little or no benefit to the PUSCH reception quality. For the above reasons, the invention considers the use of only a sub-set of sequences from the total set of available ones. These sequences may be fixed and selected according to their cross-correlation and/or according to their cubic metric values where small values are desired in both cases. Limiting the number of sequences that can be used for hopping for the larger RB allocations, reduces the number of sequence groups and corresponding hopping patterns that need to be supported and therefore reduces the complexity and signaling overhead to support sequence hopping. Considering that the limitation of sequences, and therefore the limitation in hopping patterns, occurs for the smaller RB allocations and that an embodiment of the invention assumes 2 RS per PUSCH sub-frame, one sequence for small RB allocations can be associated with two sequences for the larger RB allocations. As the embodiment assumes 30 computer generated CAZAC sequences for 1 RB and 2 RB allocations, the grouping of sequences for different RB allocations results in 30 groups where each group includes one CAZAC-based sequence for allocations up to 5 RBs and two CAZAC sequences for allocations larger than 5 RBs (Table 1). The sequences in each group are different. The grouping principle is summarized in Table 2. In an embodiment of the present invention, there are 30 sequence groups (one-to-one mapping is assumed between each sequence group and each sequence in a set of 30 sequences). Considering the number of available sequences from Table 1, it becomes apparent that only a sub-set of sequences is used for allocations of 4 RBs (30 out of set of 46 sequences are used), 5 RBs (30 out of set of 58 sequences are used), and 6 RBs or larger (60 out of a set of 70 or more sequences are used). As previously mentioned, the sub-set of these sequences may be fixed and selected for its cross-correlation and/or cubic metric properties. Therefore, the number of sequence groups is equal to the smallest sequence set size, which in the embodiment is equal to 30, with each group containing one sequence for allocations up to 5 RBs and two sequences for allocations larger than 5 RBs, and each set containing 30 sequences for allocations smaller than or equal to 5 RBs and 60 sequences for allocations larger than 5 RBs. The invention considers that the CAZAC sequence allocation to cells or Node Bs is either through planning or hopping. If both sequence planning and sequence hopping could supported in a communication system, the UEs are informed of the selection for planning or hopping through a respective indicator broadcasted by the Node B (one bit is needed to indicate whether sequence planning or sequence hopping is used). Sequence planning assigns each of the 30 groups of sequences, with each group containing 1 sequence for allocations up to 5 RBs and 2 sequences for allocations larger than 5 RBs, to neighboring cells and Node Bs so that the geographical separation between cells using the same group of sequences is preferably maximized. The assignment may be explicit through broadcasting of group sequence number, which in an embodiment having 30 sequence groups can be communicated through the broadcasting of 5 bits, or it can be implicit by associating the group sequence number to the cell identity. This is equivalent to specifying one sequence from the set of sequences with the smallest size (because a one-to-one mapping between each of these sequences and each group of sequences is assumed). In the embodiment this can be either of the sets of 30 sequences corresponding to 1, 2, or 3 RB allocations. This principle is illustrated in FIG. 10 for cell based and Node B based sequence group allocation (a Node B is assumed to serve 3 cells). For cell based sequence group assignment, different cells, such as, for example cells 1010 and 1020, are assumed to be allocated different sequence groups. For Node B based sequence group assignment, different cells, such as, for example Node Bs 1030 and 1040, are assumed to be allocated different sequence groups. Obviously, after exhausting all sequence groups, having the same sequence group in cells or Node Bs cannot be avoided but the objective is to have large geographical separation among such cells or Node Bs so that the interference caused from using the same sequences is negligible. Sequence hopping may still apply between the pair of sequences for allocations of 6 RBs or larger during the two RS transmission symbols of the PUSCH sub-frame as illustrated in FIG. 11. This provides additional randomization of the cross-correlations among sequences transmitted from UEs in different cells and thereby provides more robust reception reliability than the one achieved purely through sequence planning. No hopping applies for the sequences with length smaller than 6 RBs assuming that all sequence groups are used for planning. Therefore, if the PUSCH allocation to a UE is smaller than 6 RBs, the same CAZAC sequence is used for the RS transmission symbols 1110 and 1120 while if the PUSCH allocation is 6 RBs or larger, a different CAZAC sequence, among 2 possible CAZAC sequences, is used for the RS transmission in each of the symbols 1110 and 1120. transmission in the two symbols of the PUSCH sub-frame in FIG. 1 is based on sequences from two typically different groups of sequences. However, in order to limit the complexity and signaling required to define the sequence hopping patterns and since there is no additional benefit from having more than one sequence per group for allocations larger than 5 RBs when sequence hopping is used, only one sequence for each RB allocation exists for any of the 30 groups of sequences. In other words, only one sequence is selected to be used for each of the possible RB allocations (all entries in Table 2 contain 1 sequence) and all sets of sequences contain the same number of sequences, which is the same as the number of sequence groups. FIG. 12 and FIG. 13 further illustrate this concept. In FIG. 12, different sequence groups such as 1210 and 1230 or 1220 and 1240 are used during different transmission periods in each cell. In FIG. 13, the sequence used by a UE during successive RS transmissions 1310 and 1320 varies according to a sequence hopping pattern which is initialized either explicitly through broadcast signaling in each cell or implicitly through the broadcasted cell identity. The sequence hopping pattern may be the same for all cells and only its initialization may be cell dependent by specifying the initial sequence group or, equivalently, by specifying the initial sequence for an RB allocation since one-to-one mapping between each sequence in a set and each sequence group is assumed. The first transmission period may correspond to the first slot of the first sub-frame in a period of one frame (for example, a frame may comprise of 10 sub-frames) or to any other predetermined transmission instance. The same concept can be trivially extended to Node B specific sequence hopping. Sequence hopping for both PUCCH signals (ACK/NAK, CQI, and RS) and the PUSCH RS can also be supported and the respective signaling is subsequently considered. In order to maximize the PUCCH UE multiplexing capacity, all cyclic shifts (CS) of a CAZAC sequence are assumed to be used for the PUCCH transmission within a cell thereby necessitating the use of different CAZAC sequences in different cells (FIG. 10 with cell based group allocation). However, for the PUSCH, this depends on the extent of the application of Spatial Domain Multiple Access (SDMA) as it is known in the art. With SDMA, multiple UEs share the same RBs for their PUSCH transmission (no SDMA applies for the PUCCH as all CS are assumed to be used in each cell). Without SDMA or with SDMA applied to a maximum of 4 UEs per cell, assuming that 12 CS can be used, the same CAZAC sequence may be used among the adjacent cells of the same Node B with different CS used to discriminate the PUSCH RS in each cell as shown in FIG. 14 which is combined with FIG. 10 for the case of Node B based sequence group allocation. Cells 1410, 1420, and 1430 use the same sequence group, that is the same CAZAC-based sequence for any given PUSCH RB allocation, but use different CS in order to separate the sequences. With SDMA applied to more than 4 UEs per cell (with 3 cells per Node B), it may not be possible to rely on the use of different CS to separate the PUSCH RS from UEs in different cells. Then, a different CAZAC-based sequence needs to be used per cell as is the case for the PUCCH (FIG. 10 with cell based group allocation). Regardless of the separation method for the PUSCH RS from UEs in different cells of a Node B (through different CS of the same CAZAC-based sequence or through different CAZAC-based sequences), the present invention considers that the sequence hopping pattern for the PUCCH is derived from the signaled sequence hopping pattern for the PUSCH (the reverse may also apply). If different CAZAC-based sequences are used for the PUSCH RS transmission in the cells of a Node B (FIG. 10 with cell based group allocation), for example through sequence planning, the invention considers that the same CAZAC sequence can be used for 1 RB allocations of the PUSCH RS and for the PUCCH (for which the signal transmissions are assumed to be always over 1 RB). Therefore, the initial sequence group assignment for the PUSCH, either through explicit signaling in a broadcast channel in the serving cell or through implicit mapping to the broadcasted cell identity, determines the sequence used for the PUCCH transmission. This concept is illustrated in FIG. 15. It should be noted that PUCCH signals (RS and/or ACK/NAK and/or CQI) may allow for more sequence hopping instances within a sub-frame (symbol- based sequence hopping), but the same hopping pattern can still apply as it only needs to have a longer time scale for the PUSCH RS. If the sequence hopping for PUCCH signals is slot based and not symbol based, the PUSCH and PUCCH use the same sequence hopping patterns. If the same CAZAC sequence is used for the PUSCH RS transmission in different cells of the same Node B (FIG. 10 with Node B based sequence group allocation), the sequence hopping pattern for the PUCCH transmission may still be determined by the sequence hopping pattern of the PUSCH RS transmission even though different CAZAC sequences are used in each cell of the same Node B for the PUCCH transmission. This is achieved by the Node B signaling only a shift of the initial sequence applied to the PUSCH RS transmission, with this shift corresponding to initializing the sequence hopping pattern with a different CAZAC sequence in the set of CAZAC sequences over 1 RB for the PUCCH. Clearly, as it is subsequently illustrated in FIG. 16, the addition of a shift value S is cyclical over the set of sequences, meaning that the shift value 5 is applied modulo the size of the sequence set K, wherein the modulo operation is as known in the art. Therefore, in mathematical terms, if the hopping pattern for the PUSCH is initialized with sequence number N, the hopping pattern for the PUCCH is initialized, in the respective sequence set, with sequence number M = (N + S)mod(K) where (N + S)mod(K) = (N + S)-floor((N + S)/K)-K and the "floor" operation rounds a number to its lower integer as it is known in the art. The shift can be specified by a number of bits equal to the number of sequences for the RB allocation of PUCCH signals. If the PUCCH RB allocation is the smallest one corresponding to 1 RB, this number is identical to the number of sequence groups (in the embodiment, 5 bits are needed to specify one of the 30 sequences in a set of sequences or, equivalently, one of the 30 sequence groups). Alternatively, such signaling overhead can be reduced by limiting the range of the shift to only the sequences with indexes adjacent to the ones used for the by the first sequence in the hopping pattern applied to the RS transmission for the data channel. In that case, only 2 bits are needed to indicate the previous, same, or next sequence. The above are illustrated in FIG. 16 where in an embodiment, a shift of 0 1610, 1 1620, and -1 1630 is applied to the sequence hopping pattern of the PUCCH transmission in three different cells relative to the sequence hopping pattern for the PUSCH RS transmission 1640. The different sequence hopping patterns simply correspond to a cyclical shift (the addition of the shift value is modulo the sequence set size) of the same sequence hopping pattern 1640, or equivalently, the different sequence hopping patterns correspond to different initialization of the same hopping pattern. The initialization of the hopping pattern for the PUSCH may be explicitly or implicitly signaled, as previously described, and the shift for the initialization pattern for the PUCCH is determined relative to the initial sequence for the PUSCH (which may be different than the first sequence in the set of sequences). The above roles of the PUSCH and PUCCH may be reversed and the shift may instead define the initialization of the PUSCH, instead of the PUCCH, hopping pattern in a cell. The start of the hopping pattern in time may be defined relative to the first slot in the first sub- frame in a frame or a super-frame (both comprising of multiple sub-frames) as these notions are typically referred to in the art. While the present invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims. WHAT IS CLAIMED IS: 1. A method for allocating sequences used to transmit a signal by a user equipment in a communication system, wherein the signal transmission is over a number of resource blocks in a frequency domain and over a number of symbols in a time domain, wherein a different set of sequences exists for each possible number of resource blocks and a set of sequences with a smallest set size corresponds to at least a first number of resource blocks, the method comprising: selecting a sub-set of sequences with a sub-set size equal to a smallest set size corresponding to a second number of resource blocks; and transmitting the signal in a symbol of the number of symbols and over the second number of resource blocks using only a sequence belonging to the sub-set of sequences. 2. The method of claim 1, wherein the sequences comprise CAZAC- based sequences. 3. The method of claim 1, wherein the signal comprises a reference signal. 4. A method for allocating sequences used to transmit a signal by a user equipment in a communication system, wherein the signal transmission is over a number of resource blocks in a frequency domain and over a number of symbols in a time domain, the method comprising: transmitting the signal using a single sequence in all symbols of the number of symbols if the number of the resource blocks is less than a predetermined value; and transmitting the signal using a first sequence in a first symbol of the number of symbols and using a second sequence in a second symbol of the number of symbols if the number of the resource blocks is equal to or greater than the predetermined value. 5. The method of claim 4, wherein the sequence comprises a CAZAC- based sequence. 6. The method of claim 4, wherein the signal comprises a reference signal. 7. A method for allocating sequences used to transmit a signal by a user equipment in a communication system, wherein the signal transmission is over a number of resource blocks in a frequency domain and over a number of symbols in a time domain, wherein a set of sequences exists for each possible number of resource blocks and a set of sequences with a smallest set size corresponds to at least a first number of resource blocks, the method comprising: selecting a sub-set of sequences with a sub-set size equal to a smallest set size from a set of sequences corresponding to a second number of resource blocks; and transmitting the signal over the second number of resource blocks and over the number of symbols with the sequence used in each symbol of the number of symbols being selected from the sub-set of sequences according to a pseudo- random pattern. 8. The method of claim 7, wherein the sequence comprises a CAZAC- based sequence. 9. The method of claim 7, wherein the signal comprises a reference signal. 10. A method for a user equipment to transmit a first signal or a second signal in a communication system, wherein the first signal is transmitted over a first number of symbols in a first channel using sequences from a first set of sequences and the second signal is transmitted over a second number of symbols in a second channel using sequences from a second set of sequences, the method comprising: selecting a sequence used to transmit the first signal in each symbol of the first number of symbols by applying a pseudo-random pattern over the first set of sequences; and selecting a sequence used to transmit the second signal in each symbol of the second number of symbols by applying the pseudo-random pattern over the second set of sequences. 11. The method of claim 10, wherein the sequence comprises a CAZAC- based sequence. 12. The method of claim 10, wherein the first signal comprises a reference signal and the first channel is used for transmission of data information. 13. The method of claim 10, wherein the second signal comprises a reference signal or a control signal and the second channel is used for transmission of control information. 14. A method for a user equipment to select an initial sequence from a first set of sequences with a set size K for the transmission of a signal in a first channel to a Node B, wherein an initial sequence from a second set of sequences with a set size K for the transmission of a signal in a second channel to the Node B is sequence number N, the method comprising: receiving a shift value S from the Node B; and selecting the initial sequence from the first set of sequences for the transmission of the signal in the first channel to be the sequence whose number M is obtained as (N + S) modulo(K). 15. The method of claim 14, wherein the sequences comprise CAZAC- based sequences. 16. The method of claim 14, wherein the first channel is used for transmission of data information and the second channel is used for transmission of control information. 17. The method of claim 14, wherein the number N of the initial sequence for the transmission of a signal in the second channel is signaled by the Node B. 18. An apparatus for transmitting a signal in a communication system, wherein the signal transmission is through a transmission of sequences over a number of resource blocks in a frequency domain and over a number of symbols in a time domain, the apparatus comprising: a transmitter for transmitting the signal using a single sequence in all symbols of the number of symbols if the number of the resource blocks is less than a predetermined value; and a transmitter for transmitting the signal using a first sequence in a first symbol of the number of symbols and using a second sequence in a second symbol of the number of symbols if the number of the resource blocks is equal to or greater than the predetermined value. 19. The apparatus of claim 18, wherein the sequence comprises a CAZAC-based sequence. 20. The apparatus of claim 18, wherein the signal comprises a reference signal. 21. An apparatus for transmitting a signal in a communication system, wherein the signal transmission is through a transmission of sequences over a number of resource blocks in a frequency domain and over a number of symbols in a time domain, wherein a set of sequences exists for each possible number of resource blocks, wherein a set of sequences with a smallest set size corresponds to at least a first number of resource blocks, the apparatus comprising: a generator for generating a sub-set of sequences, with a sub-set size equal to a smallest set size, from a set of sequences corresponding to a second number of resource blocks; and a transmitter for transmitting the signal over the second number of resource blocks and over the number of symbols with the sequence used in each symbol of the number of symbols being selected from the sub-set of sequences according to a pseudo-random pattern. 22. The apparatus of claim 21, wherein the sequence comprises a CAZAC-based sequence. 23. The apparatus of claim 21, wherein the signal comprises a reference signal. 24. An apparatus for transmitting a first signal or a second signal in a communication system, wherein the first signal is transmitted over a first number of symbols in a first channel using sequences from a first set of sequences and the second signal is transmitted over a second number of symbols in a second channel using sequences from a second set of sequences, the apparatus comprising: a selector for selecting a sequence used to transmit the first signal in each symbol of the first number of symbols in the first channel by applying a pseudo- random pattern over the first set of sequences; a selector for selecting a sequence used to transmit the second signal in each symbol of the second number of symbols in the second channel by applying the pseudo-random pattern over the second set of sequences; and a transmitter for transmitting the first signal or the second signal. 25. The apparatus of claim 24, wherein the sequence comprises a CAZAC-based sequence. 26. The apparatus of claim 24, wherein the first signal comprises a reference signal and the first channel is used for transmission of data information. 27. The apparatus of claim 24, wherein the second signal comprises a reference signal or a control signal and the second channel is used for transmission of control information. 28. An apparatus for transmitting a signal to a Node B of a communication system in a first channel using sequences from a first set of sequences with a set size K, wherein an initial sequence from a second set of sequences with a set size K for the transmission of a signal in a second channel to the Node B is sequence number N, the apparatus comprising: a selector for selecting an initial sequence from the first set of sequences for the transmission of the signal in the first channel to be a sequence with number M obtained as (N + S) modulo(K), where S is a shift value signaled by the Node B; and a transmitter for transmitting the signal in the first channel. 29. The apparatus of claim 28, wherein the sequences comprise CAZAC- based sequences. 30. The apparatus of claim 28, wherein the first channel is used for transmission of data information and the second channel is used for transmission of control information. 31. The apparatus of claim 28, wherein the number N of the initial sequence for the transmission of a signal in the second channel is signaled by the Node B. 32. A method for allocating sequences used to transmit a reference signal (RS) by a user equipment in a communication system, wherein the RS transmission is over a number of resource blocks in a frequency domain and over a number of symbols in a time domain, the method comprising: transmitting the RS using a single non-hopped sequence in the symbols if a size of RS transmission symbols within a sub-frame is less than a size of 6 resource blocks; and transmitting the reference signal using hopped sequences in the symbols if the size of RS transmission symbols within the sub-frame is equal to or greater than the size of 6 resource blocks. A method and apparatus are provided for the selection of sequences used for the transmission of signals from user equipments in a cellular communication system. The sequences can be selected either through planning or through pseudo-random hopping among a set of sequences. With planning, the serving Node B signals the sequence assignment for each cell, which remains invariable in time. With pseudo-random sequence hopping, the serving Node B signals the initial sequence, from a set of sequences, which can be different among cells. The initial sequence used in the control (or data) channel is signaled by the serving Node B. The initial sequence used in the data (or control) channel is selected to be the sequence in a set of sequences with number equal to a shift value relative to the first sequence as signaled by the serving Node B for the control (or data) channel.

Full Text

SEQUENCE HOPPING IN SC-FDMA COMMUNICATION SYSTEMS
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to wireless communication systems
and, more particularly, to a Single-Carrier Frequency Division Multiple Access
(SC-FDMA) communication system that is further considered in the development
of the 3rd Generation Partnership Project (3GPP) Evolved Universal Terrestrial
Radio Access (E-UTRA) long term evolution (LTE).
2. Description of the Art
Methods and apparatus are considered for the functionality and
implementation of hopping for sequences used in the construction of Reference
Signals (RS) or control signals transmitted in SC-FDMA communication systems.
The Uplink (UL) of the communication system is assumed, which
corresponds to signal transmissions from mobile User Equipments (UEs) to a
serving base station (Node B). A UE, also commonly referred to as terminal or
mobile station, may be fixed or mobile and may be a wireless device, a cellular
phone, a personal computer device, a wireless modem card, etc. A Node B is
generally a fixed station and may also be called a Base Transceiver System
(BTS), an access point, or some other terminology. A Node B may control
multiple cells in a cellular communication system, as it is known in the art.
Several types of signals need to be supported for the prope'r functionality
of the communication system. In addition to data signals, which convey the
information content of the communication, control signals also need to be
transmitted from UEs to their serving Node B in the UL and from the serving
Node B to UEs in the downlink (DL) of the communication system. The DL
refers to the communication from the Node B to UEs. Additionally, a UE having
data or control transmission also transmits RSs, also known as pilots. These RSs
primarily serve to provide coherent demodulation for the transmitted data or
control signals by a UE.

The UEs are assumed to transmit data or control signals over a
Transmission Time Interval (TTI), which is assumed to correspond to a sub-
frame. The sub-frame is the time unit of a frame, which may consist of ten sub-
frames. FIG. 1 illustrates a block diagram of the sub-frame structure 110. The
sub-frame 110 includes two slots. Each slot 120 further includes seven symbols
used for transmission of data or control signals. Each symbol 130 further includes
a Cyclic Prefix (CP) in order to mitigate interference due to channel propagation
effects. The signal transmission in one slot may be in the same or at a different
part of the operating bandwidth (B W) than the signal transmission in the second
slot. In addition to symbols carrying data or control information, some symbols
are used for Reference Signal (RS) transmission 140.
The transmission BW is assumed to include frequency resource units,
which will be referred to herein as resource blocks (RBs). Each RB may consist
of 12 sub-carriers and UEs are allocated a multiple N of consecutive RBs 150 for
Physical Uplink Shared Channel (PUSCH) transmission and 1 RB for Physical
Uplink Control Channel (PUCCH) transmission.
As the data or control signal transmission is over a BW that can be
(orthogonally) shared by multiple UEs, the corresponding physical layer channel
may be respectively referred to as PUSCH or as PUCCH. FIG. 1 illustrates a
structure for the PUSCH sub-frame while respective ones for the PUCCH will be
subsequently described.
The UEs are also assumed to transmit control signals in the absence of any
data signals. The control signals include, but are not limited to, positive or
negative acknowledgment signals (ACK or NAK, respectively) and Channel
Quality Indication (CQI) signals. The ACK/NAK signals are in response to the
correct or incorrect, respectively, data packet reception by a UE in the DL of the
communication system. The CQI signals are sent by a UE to inform its serving
Node B of its Signal-to-Interference and Noise Ratio (SINR) conditions in order
for the serving Node B to perform channel dependent scheduling in the DL of the
communication system. Both ACK/NAK and CQI signals are accompanied by RS
signals in order to enable their coherent demodulation at the Node B receiver. The

physical layer channel conveying ACK/NAK or CQI control signaling may be
referred as the PUCCH.
The ACK/NAK, CQI and associated RS signals are assumed to be
transmitted by UEs in one RB using CAZAC sequences as it is known in the art
and is subsequently described.
FIG. 2 shows a structure for the ACK/NAK transmission during one slot
210 in a SC-FDMA communication system. The ACK/NAK information bits 220
modulate 230 a "Constant Amplitude Zero Auto-Correlation (CAZAC)" sequence
240, for example with QPSK or 16QAM modulation, which is then transmitted
by the UE after performing an Inverse Fast Fourier Transform (IFFT) operation
as it is further subsequently described. In addition to the ACK/NAK, RS is
transmitted to enable the coherent demodulation of the ACK/NAK signal at the
Node B receiver. The third, fourth, and fifth SC-FDMA symbols in each slot may
carry an RS 250.
FIG. 3 shows a structure for the CQI transmission during one slot 310 in a
SC-FDMA communication system. Similar to the ACK/NAK transmission, the
CQI information bits 320 modulate 330 a CAZAC sequence 340, for example
with QPSK or 16QAM modulation, which is then transmitted by the UE after
performing the IFFT operation as it is further subsequently described. In addition
to the CQI, RS is transmitted to enable the coherent demodulation at the Node B
receiver of the CQI signal. In the embodiment, the second and sixth SC-FDMA
symbols in each slot carry an RS 350.
As it was previously mentioned, the ACK/NAK, CQI, and RS signals are
assumed to be constructed from CAZAC sequences. An example of such
sequences is the Zadoff-Chu (ZC) sequences whose elements are given by
Equation (1) below:

L is the length of the CAZAC sequence, n is the index of an element of the
sequence n = {0, 1, 2 ..., L - 1}, and k is the index of the sequence itself. For a
given length L, there are L - 1 distinct sequences, if L is prime. Therefore, the

entire family of sequences is defined as k ranges in {1,2 ...,L- 1}. However, it
should be noted that the CAZAC sequences used for the ACK/NAK, CQI, and RS
transmission need not be generated using the exact above expression as it is
further discussed below.
For CAZAC sequences of prime length L, the number of sequences is L-l.
As the RBs are assumed to consist of an even number of sub-carriers, with 1 RB
consisting of 12 sub-carriers, the sequences used to transmit the ACK/NAK, CQI,
and RS can be generated, in the frequency or time domain, by either truncating a
longer prime length (such as length 13) CAZAC sequence or by extending a
shorter prime length (such as length 11) CAZAC sequence by repeating its first
element(s) at the end (cyclic extension), although the resulting sequences do not
fulfill the definition of a CAZAC sequence. Alternatively, the CAZAC sequences
can be directly generated through a computer search for sequences satisfying the
CAZAC properties.
A block diagram for the transmission through SC-FDMA signaling of a
CAZAC-based sequence in the time domain is shown in FIG. 4. The selected
CAZAC-based sequence 410 is generated through one of the previously described
methods (modulated by the respective bits in case of ACK/NAK or CQI
transmission), it is then cyclically shifted 420 as it is subsequently described, the
Discrete Fourier Transform (DFT) of the resulting sequence is obtained 430, the
sub-carriers 440 corresponding to the assigned transmission bandwidth are
selected 450, the Inverse Fast Fourier Transform (IFFT) is performed 460, and
finally the CP 470 and filtering 480 are applied to the transmitted signal 490. Zero
padding is assumed to be performed by a UE in sub-carriers used for signal
transmission by another UE and in guard sub-carriers (not shown). Moreover, for
brevity, additional transmitter circuitry such as digital-to-analog converter, analog
filters, amplifiers, and transmitter antennas, as they are known in the art, are not
shown in FIG. 4. Similarly, for the PUCCH, the modulation of a CAZAC
sequence with ACK/NAK or CQI bits is well known in the art, such as for
example QPSK modulation, and is omitted for brevity.
At the receiver, the inverse (complementary) transmitter functions are
performed. This is conceptually illustrated in FIG. 5 where the reverse operations

of those in FIG. 4 apply. As it is known in the art (not shown for brevity), an
antenna receives the RF analog signal and after further processing units (such as
filters, amplifiers, frequency down-converters, and analog-to-digital converters)
the digital received signal 510 passes through a time windowing unit 520 and the
CP is removed 530. Subsequently, the receiver unit applies an FFT 540, selects
550 the sub-carriers 560 used by the transmitter, applies an Inverse DFT (IDFT)
570, de-multiplexes (in time) the RS and CQI signal 580, and after obtaining a
channel estimate based on the RS (not shown) it extracts the CQI bits 590. As for
the transmitter, well known receiver functionalities such as channel estimation,
demodulation, and decoding are not shown for brevity.
An alternative generation method for the transmitted CAZAC sequence is
in the frequency domain. This is depicted in FIG. 6. The generation of the
transmitted CAZAC sequence in the frequency domain follows the same steps as
the one in the time domain with two exceptions. The frequency domain version of
the CAZAC sequence is used 610 (that is the DFT of the CAZAC sequence is
pre-computed and not included in the transmission chain) and the cyclic shift 650
is applied after the IFFT 640. The selection 620 of the sub-carriers 630
corresponding to the assigned transmission BW, and the application of CP 660
and filtering 670 to the transmitted signal 680, as well as other conventional
functionalities (not shown), are as previously described for FIG. 4.
The reverse functions are again performed for the reception of the
CAZAC-based sequence transmitted as in FIG. 6. This is illustrated in FIG. 7.
The received signal 710 passes through a time windowing unit 720 and the CP is
removed 730. Subsequently, the cyclic shift is restored 740, an FFT 750 is
applied, and the transmitted sub-carriers 760 are selected 765. FIG. 7 also shows
the subsequent correlation 770 with the replica 780 of the CAZAC-based
sequence. Finally, the output 790 is obtained which can then be passed to a
channel estimation unit, such as a time-frequency interpolator, in case of a RS, or
can be used for detecting the transmitted information, in case the CAZAC-based
sequence is modulated by ACK/NAK or CQI information bits.

The transmitted CAZAC-based sequence in FIG. 4 or FIG. 6 may not be
modulated by any information (data or control) and can then serve as the RS, as
shown, for example, in FIG. 2 and FIG. 3.
Different cyclic shifts of the same CAZAC sequence provide orthogonal
CAZAC sequences. Therefore, different cyclic shifts of the same CAZAC
sequence can be allocated to different UEs in the same RB for their RS or
ACK/NAK, or CQI transmission and achieve orthogonal UE multiplexing. This
principle is illustrated in FIG. 8.
Referring to FIG. 8, in order for the multiple CAZAC sequences 810, 830,
850, 870 generated correspondingly from multiple cyclic shifts 820, 840, 860,
880 of the same root CAZAC sequence to be orthogonal, the cyclic shift value A
890 should exceed the channel propagation delay spread D (including a time
uncertainty error and filter spillover effects). If Ts is the duration of one symbol,
the number of cyclic shifts is equal to the mathematical floor of the ratio Ts/D.
For a CAZAC sequence of length 12, the number of possible cyclic shifts is 12
and for symbol duration of about 66 microseconds (14 symbols in a 1 millisecond
sub-frame), the time separation of consecutive cyclic shifts is about 5.5
microseconds. Alternatively, to provide better protection against multipath
propagation, only every other (6 of the 12) cyclic shift may be used providing
time separation of about 11 microseconds.
CAZAC-based sequences of the same length typically have good cross-
correlation properties (low cross-correlation values), which is important in order
to minimize the impact of mutual interference in synchronous communication
system and improve their reception performance. It is well known that ZC
sequences of length L have optimal cross-correlation of However, this
property does not hold when truncation or extension is applied to ZC sequences
or when CAZAC-based sequences are generated through computer search.
Moreover, CAZAC-based sequences of different lengths have a wide distribution
of cross-correlation values and large values can frequently occur leading to
increased interference.

FIG 9 illustrates the Cumulative Density Function (CDF) of cross-
correlation values for length-12 CAZAC-based sequence resulting from cyclically
extending a length-11 ZC sequence, truncating a length-13 ZC sequence and
generating length-12 CAZAC-based sequences through a computer search
method. Variations in cross-correlation values can be easily observed. These
variations have even wider distribution for cross-correlations between CAZAC-
based sequences with different lengths.
The impact of large cross-correlations on the reception reliability of signals
constructed from CAZAC-based sequences can be mitigated through sequence
hopping. Pseudo-random hopping patterns are well known in the art and are used
for a variety of applications. Any such generic pseudo-random hopping pattern
can serve as a reference for sequence hopping. In this manner, the CAZAC-based
sequence used between consecutive transmissions of ACK/NAK, CQI, or RS
signals in different SC-FDMA symbols, can change in a pseudo-random pattern
and this reduces the probability that CAZAC-based generated signals will be
subjected to large mutual cross-correlations and correspondingly experience large
interference over their transmission symbols.
There is therefore a need for supporting hopping of CAZAC-based
sequences with minimum implementation complexity in order to reduce the
average interference among CAZAC-based sequences.
There is another need for assigning CAZAC-based sequences through
planning in different Node Bs and different cells of the same Node B in a
communication system.
Finally, there is a need for minimizing the signaling overhead for
communicating sequence hopping parameters or the sequence assignment
(planning) from the serving Node B to the UEs.
SUMMARY OF THE INVENTION
The present invention has been made to address at least the above-
mentioned problems and/or disadvantages and to provide at least the advantages

described below. Accordingly, an aspect of the present invention provides an
apparatus and method for supporting CAZAC-based sequence hopping or
sequence planning.
Another aspect of the present invention enables CAZAC-based sequence
hopping with minimum implementation complexity at a UE transmitter and a
Node B receiver by applying the same hopping pattern to the sequences used for
signal transmission in all possible channels.
Additionally, an aspect of the present invention enables CAZAC-based
sequence hopping with minimum implementation complexity at a UE transmitter
and a Node B receiver by limiting the total number of sequences in the sets of
sequences for the possible resource block allocations to be equal to the smallest
number of sequences obtained for one of the possible resource block allocations.
A further aspect of the present invention enables CAZAC-based sequence
hopping and planning with minimum signaling overhead for communicating the
sequence allocation parameters from the serving Node B to UEs.
According to one aspect of the present invention, an apparatus and a
method are provided for a user equipment to transmit a signal using one sequence
in all symbols of a sub-frame where the signal is transmitted if the resource block
allocation is smaller than or equal to a predetermined value and to transmit a
signal using, respectively, a first sequence and a second sequence in a first
symbol and a second symbol of a sub-frame where the signal is transmitted if the
resource block allocation is larger than a predetermined value.
According to another aspect of the present invention, an apparatus and a
method are provided for a user equipment to transmit a signal using a sequence
from a full set of sequences in a symbol of a sub-frame where the signal is
transmitted if the resource block allocation is smaller than or equal to a
predetermined value and to transmit a signal using a sequence from a sub-set of
sequences in a symbol of a sub-frame where the signal is transmitted if the
resource block allocation is larger than a predetermined value.

According to an additional embodiment of the present invention, an
apparatus and a method are provided for a user equipment to transmit a signal in a
data channel using a sequence from a set of sequences wherein the sequence at
each symbol of a sub-frame where the signal is transmitted is determined
according to a pseudo-random hopping pattern and to transmit a signal in a
control channel using a sequence from a set of sequences wherein the sequence at
each symbol of a sub-frame where the signal is transmitted is determined
according to same pseudo-random hopping pattern. The signal and the number of
symbols where the signal is transmitted may be different between the data and
control channels but the sequence hopping pattern remains the same by adjusting
the rate of its application (slower rate applies for the channel having the larger
number of symbols for the signal transmission using sequence hopping).
According to a further embodiment of the present invention, an apparatus
and a method are provided for a user equipment to transmit a signal in a control
channel using one or more sequences from a set of sequences wherein the first
sequence is signaled by the serving Node B, and to transmit a signal in a data
channel using one or more sequences from a set of sequences wherein the first
sequence is determined from the set of sequences by applying a shift relative to
the first sequence in the respective set of sequences used for the control channel
as signaled by the serving Node B. The reverse relation may apply in determining
the first sequence in the control and data channels.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other aspects, features and advantages of the present
invention will be more apparent from the following detailed description when
taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a diagram illustrating a sub-frame structure for the SC-FDMA
communication system;
FIG. 2 is a diagram illustrating a partitioning of a slot structure for the
transmission of ACK/NAK bits;

FIG. 3 is a diagram illustrating a partitioning of a slot structure for the
transmission of CQI bits;
FIG. 4 is a block diagram illustrating an SC-FDMA transmitter for
transmitting an ACK/NAK signal, or a CQI signal, or a reference signal using a
CAZAC-based sequence in the time domain;
FIG. 5 is a block diagram illustrating an SC-FDMA receiver for receiving
an ACK/NAK signal, or a CQI signal, or a reference signal using a CAZAC-
based sequence in the time domain;
FIG. 6 is a block diagram illustrating an SC-FDMA transmitter for
transmitting an ACK/NAK signal, or a CQI signal, or a reference signal using a
CAZAC-based sequence in the frequency domain;
FIG. 7 is a block diagram illustrating an SC-FDMA receiver for receiving
an ACK/NAK signal, or a CQI signal, or a reference signal using a CAZAC-
based sequence in the frequency domain;
FIG. 8 is a block diagram illustrating a construction of orthogonal
CAZAC-based sequences through the application of different cyclic shifts on a
root CAZAC-based sequence;
FIG. 9 is a diagram illustrating the CDF of cross-correlation values for
CAZAC-based sequences of length 12;
FIG. 10 is a diagram illustrating the allocation of sequence groups to
different cells or different Node Bs through group sequence planning, according
to an embodiment of the present invention;
FIG. 11 is a diagram illustrating sequence hopping within a sub-frame for
allocation larger than 6 RBs when group sequence planning is used, according to
an embodiment of the present invention;

FIG. 12 is a diagram illustrating the allocation of sequence groups to
different cells or different Node Bs through group sequence hopping, according to
an embodiment of the present invention;
FIG. 13 is a diagram illustrating sequence hopping within a sub-frame
when group sequence hopping is used, according to an embodiment of the present
invention;
FIG. 14 is a diagram illustrating allocating different sequences with
different cyclic shifts to cells of the same Node B, according to an embodiment of
the present invention;
FIG. 15 is a diagram illustrating determining the PUCCH sequence from
the PUSCH sequence, according to an embodiment of the present invention; and
FIG. 16 is a diagram illustrating determining the PUCCH sequence from
the PUSCH sequence by applying a shift, according to an embodiment of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the present invention are described in detail with
reference to the accompanying drawings. The same or similar components are
designated by the same or similar reference numerals although they are illustrated
in different drawings. Detailed descriptions of constructions or processes known
in the art may be omitted to avoid obscuring the subject matter of the present
invention.
Additionally, although the present invention assumes a SC-FDMA
communication system, it also applies to all Frequency Division Multiplexing
(FDM) systems in general and to Orthogonal Frequency Division Multiple
Access (OFDMA), Orthogonal Frequency Division Multiplexing (OFDM),
Frequency Division Multiple Access (FDMA), Discrete Fourier Transform
(DFT)-spread OFDM, DFT-spread OFDMA, Single-Carrier OFDMA (SC-
OFDMA), and Single-Carrier OFDM in particular.

Methods of the embodiments of the invention solve problems related to the
need for enabling sequence planning or sequence hopping for CAZAC-based
sequences while minimizing the respective implementation complexity at a UE
transmitter and at a Node B receiver and minimizing the signaling overhead
required for configuring the sequence planning or the sequence hopping patterns.
As discussed in the foregoing background, the construction of CAZAC-
based sequences may be through various methods. The number of sequences
provided with cyclic extension or truncation of Zadoff-Chu (ZC) sequences
depends on the sequence length. Some indicative values for corresponding RB
allocations are shown in Table 1 where one RB is assumed to consist of 12 sub-
carriers.

Since the number of CAZAC-based sequences depend on the
corresponding sequence length, a number of sequences of larger length can be
associated with each sequence of smaller length. For example, referring to Table
1, for cyclic extension of ZC sequences, each of the 10 sequences of length 12
can be associated (one-to-one mapping) with a set of 7 sequences of length 72
(since there are 70 sequences of length 72). Moreover, the number of sequences
for small RB allocations, such as 1 RB or 2 RBs, is the smallest and defines the

constraints in allocating different sequences in neighboring cells and Node Bs (a
Node B may comprise of multiple cells). For these sequences, if a pseudo-random
hopping pattern applies for their transmission, the same sequence may often be
used in neighboring cells resulting to full interference of transmissions and
associated degradation in the reception reliability of signals transmitted through
the use of CAZAC-based sequences.
To mitigate the sequence allocation problem resulting from the small
number of available CAZAC-based sequences for the smaller RB allocations,
CAZAC sequences constructed through computer searches can be used as a larger
number of sequences can be obtained in this manner. However, unlike CAZAC-
based sequences obtained from cyclic extension or truncation of ZC sequences, a
closed form expression for computer generated CAZAC sequences does not exist
and such sequences need to be stored in memory. For this reason, their use is
typically confined to small RB allocations where the shortage of CAZAC-based
sequences is most acute. For the larger RB allocations, CAZAC-based sequences
are generated through the implementation of a formula such as the one described
for the generation of ZC sequences. About 30 computer generated CAZAC
sequences can be obtained for 1 RB allocations and by obtaining the same
number of sequences for 2 RB allocations, sequence planning and sequence
hopping is then constrained by the number of sequences for 1, 2, or 3 RB
allocations. In a preferred embodiment this number is 30.
The invention considers cyclic extension of ZC sequences for the
generation of CAZAC-based sequences for allocations equal to or larger than 3
RBs and computer generated CAZAC sequences for allocations of 1 RB or 2
RBs.
An embodiment of the invention assumes that PUCCH transmissions from
a UE occupy one RB and allocations larger than 1 RB are used only for the
PUSCH, which, in the embodiment, contains 2 RS transmission symbols per sub-
frame. Therefore, only one sequence hopping opportunity exists within a PUSCH
sub-frame.

For packet retransmissions based on Hybrid Automatic Repeat reQuest
(HARQ), as it is known in the art, the interference experienced by the CAZAC-
based sequence used for RS transmission will be different among retransmissions
as different RB allocations (different size or different BW position leading to
partial overlapping between two CAZAC sequences) are likely to be used for UEs
in interfering cells during a packet retransmission. Moreover, the channel
characteristics are likely to be different between retransmissions and this also
leads to different cross-correlation characteristics among interfering CAZAC
sequences. Therefore, extending the number of sequences for each RB allocation
to more than 2 is of little or no benefit to the PUSCH reception quality.
For the above reasons, the invention considers the use of only a sub-set of
sequences from the total set of available ones. These sequences may be fixed and
selected according to their cross-correlation and/or according to their cubic metric
values where small values are desired in both cases. Limiting the number of
sequences that can be used for hopping for the larger RB allocations, reduces the
number of sequence groups and corresponding hopping patterns that need to be
supported and therefore reduces the complexity and signaling overhead to support
sequence hopping.
Considering that the limitation of sequences, and therefore the limitation in
hopping patterns, occurs for the smaller RB allocations and that an embodiment
of the invention assumes 2 RS per PUSCH sub-frame, one sequence for small RB
allocations can be associated with two sequences for the larger RB allocations. As
the embodiment assumes 30 computer generated CAZAC sequences for 1 RB and
2 RB allocations, the grouping of sequences for different RB allocations results in
30 groups where each group includes one CAZAC-based sequence for allocations
up to 5 RBs and two CAZAC sequences for allocations larger than 5 RBs (Table
1). The sequences in each group are different.
The grouping principle is summarized in Table 2. In an embodiment of the
present invention, there are 30 sequence groups (one-to-one mapping is assumed
between each sequence group and each sequence in a set of 30 sequences).
Considering the number of available sequences from Table 1, it becomes
apparent that only a sub-set of sequences is used for allocations of 4 RBs (30 out

of set of 46 sequences are used), 5 RBs (30 out of set of 58 sequences are used),
and 6 RBs or larger (60 out of a set of 70 or more sequences are used). As
previously mentioned, the sub-set of these sequences may be fixed and selected
for its cross-correlation and/or cubic metric properties. Therefore, the number of
sequence groups is equal to the smallest sequence set size, which in the
embodiment is equal to 30, with each group containing one sequence for
allocations up to 5 RBs and two sequences for allocations larger than 5 RBs, and
each set containing 30 sequences for allocations smaller than or equal to 5 RBs
and 60 sequences for allocations larger than 5 RBs.

The invention considers that the CAZAC sequence allocation to cells or
Node Bs is either through planning or hopping. If both sequence planning and
sequence hopping could supported in a communication system, the UEs are
informed of the selection for planning or hopping through a respective indicator
broadcasted by the Node B (one bit is needed to indicate whether sequence
planning or sequence hopping is used).
Sequence planning assigns each of the 30 groups of sequences, with each
group containing 1 sequence for allocations up to 5 RBs and 2 sequences for
allocations larger than 5 RBs, to neighboring cells and Node Bs so that the
geographical separation between cells using the same group of sequences is
preferably maximized. The assignment may be explicit through broadcasting of

group sequence number, which in an embodiment having 30 sequence groups can
be communicated through the broadcasting of 5 bits, or it can be implicit by
associating the group sequence number to the cell identity. This is equivalent to
specifying one sequence from the set of sequences with the smallest size (because
a one-to-one mapping between each of these sequences and each group of
sequences is assumed). In the embodiment this can be either of the sets of 30
sequences corresponding to 1, 2, or 3 RB allocations.
This principle is illustrated in FIG. 10 for cell based and Node B based
sequence group allocation (a Node B is assumed to serve 3 cells). For cell based
sequence group assignment, different cells, such as, for example cells 1010 and
1020, are assumed to be allocated different sequence groups. For Node B based
sequence group assignment, different cells, such as, for example Node Bs 1030
and 1040, are assumed to be allocated different sequence groups. Obviously, after
exhausting all sequence groups, having the same sequence group in cells or Node
Bs cannot be avoided but the objective is to have large geographical separation
among such cells or Node Bs so that the interference caused from using the same
sequences is negligible.
Sequence hopping may still apply between the pair of sequences for
allocations of 6 RBs or larger during the two RS transmission symbols of the
PUSCH sub-frame as illustrated in FIG. 11. This provides additional
randomization of the cross-correlations among sequences transmitted from UEs in
different cells and thereby provides more robust reception reliability than the one
achieved purely through sequence planning. No hopping applies for the sequences
with length smaller than 6 RBs assuming that all sequence groups are used for
planning. Therefore, if the PUSCH allocation to a UE is smaller than 6 RBs, the
same CAZAC sequence is used for the RS transmission symbols 1110 and 1120
while if the PUSCH allocation is 6 RBs or larger, a different CAZAC sequence,
among 2 possible CAZAC sequences, is used for the RS transmission in each of
the symbols 1110 and 1120.

transmission in the two symbols of the PUSCH sub-frame in FIG. 1 is based on
sequences from two typically different groups of sequences. However, in order to
limit the complexity and signaling required to define the sequence hopping
patterns and since there is no additional benefit from having more than one
sequence per group for allocations larger than 5 RBs when sequence hopping is
used, only one sequence for each RB allocation exists for any of the 30 groups of
sequences. In other words, only one sequence is selected to be used for each of
the possible RB allocations (all entries in Table 2 contain 1 sequence) and all sets
of sequences contain the same number of sequences, which is the same as the
number of sequence groups. FIG. 12 and FIG. 13 further illustrate this concept.
In FIG. 12, different sequence groups such as 1210 and 1230 or 1220 and 1240
are used during different transmission periods in each cell.
In FIG. 13, the sequence used by a UE during successive RS transmissions
1310 and 1320 varies according to a sequence hopping pattern which is initialized
either explicitly through broadcast signaling in each cell or implicitly through the
broadcasted cell identity. The sequence hopping pattern may be the same for all
cells and only its initialization may be cell dependent by specifying the initial
sequence group or, equivalently, by specifying the initial sequence for an RB
allocation since one-to-one mapping between each sequence in a set and each
sequence group is assumed. The first transmission period may correspond to the
first slot of the first sub-frame in a period of one frame (for example, a frame may
comprise of 10 sub-frames) or to any other predetermined transmission instance.
The same concept can be trivially extended to Node B specific sequence hopping.
Sequence hopping for both PUCCH signals (ACK/NAK, CQI, and RS)
and the PUSCH RS can also be supported and the respective signaling is
subsequently considered.
In order to maximize the PUCCH UE multiplexing capacity, all cyclic
shifts (CS) of a CAZAC sequence are assumed to be used for the PUCCH
transmission within a cell thereby necessitating the use of different CAZAC
sequences in different cells (FIG. 10 with cell based group allocation). However,
for the PUSCH, this depends on the extent of the application of Spatial Domain
Multiple Access (SDMA) as it is known in the art. With SDMA, multiple UEs

share the same RBs for their PUSCH transmission (no SDMA applies for the
PUCCH as all CS are assumed to be used in each cell).
Without SDMA or with SDMA applied to a maximum of 4 UEs per cell,
assuming that 12 CS can be used, the same CAZAC sequence may be used
among the adjacent cells of the same Node B with different CS used to
discriminate the PUSCH RS in each cell as shown in FIG. 14 which is combined
with FIG. 10 for the case of Node B based sequence group allocation. Cells 1410,
1420, and 1430 use the same sequence group, that is the same CAZAC-based
sequence for any given PUSCH RB allocation, but use different CS in order to
separate the sequences.
With SDMA applied to more than 4 UEs per cell (with 3 cells per Node
B), it may not be possible to rely on the use of different CS to separate the
PUSCH RS from UEs in different cells. Then, a different CAZAC-based
sequence needs to be used per cell as is the case for the PUCCH (FIG. 10 with
cell based group allocation). Regardless of the separation method for the PUSCH
RS from UEs in different cells of a Node B (through different CS of the same
CAZAC-based sequence or through different CAZAC-based sequences), the
present invention considers that the sequence hopping pattern for the PUCCH is
derived from the signaled sequence hopping pattern for the PUSCH (the reverse
may also apply).
If different CAZAC-based sequences are used for the PUSCH RS
transmission in the cells of a Node B (FIG. 10 with cell based group allocation),
for example through sequence planning, the invention considers that the same
CAZAC sequence can be used for 1 RB allocations of the PUSCH RS and for the
PUCCH (for which the signal transmissions are assumed to be always over 1
RB). Therefore, the initial sequence group assignment for the PUSCH, either
through explicit signaling in a broadcast channel in the serving cell or through
implicit mapping to the broadcasted cell identity, determines the sequence used
for the PUCCH transmission. This concept is illustrated in FIG. 15.
It should be noted that PUCCH signals (RS and/or ACK/NAK and/or CQI)
may allow for more sequence hopping instances within a sub-frame (symbol-
based sequence hopping), but the same hopping pattern can still apply as it only

needs to have a longer time scale for the PUSCH RS. If the sequence hopping for
PUCCH signals is slot based and not symbol based, the PUSCH and PUCCH use
the same sequence hopping patterns.
If the same CAZAC sequence is used for the PUSCH RS transmission in
different cells of the same Node B (FIG. 10 with Node B based sequence group
allocation), the sequence hopping pattern for the PUCCH transmission may still
be determined by the sequence hopping pattern of the PUSCH RS transmission
even though different CAZAC sequences are used in each cell of the same Node
B for the PUCCH transmission. This is achieved by the Node B signaling only a
shift of the initial sequence applied to the PUSCH RS transmission, with this shift
corresponding to initializing the sequence hopping pattern with a different
CAZAC sequence in the set of CAZAC sequences over 1 RB for the PUCCH.
Clearly, as it is subsequently illustrated in FIG. 16, the addition of a shift value
S is cyclical over the set of sequences, meaning that the shift value 5 is
applied modulo the size of the sequence set K, wherein the modulo operation is
as known in the art. Therefore, in mathematical terms, if the hopping pattern for
the PUSCH is initialized with sequence number N, the hopping pattern for the
PUCCH is initialized, in the respective sequence set, with sequence number
M = (N + S)mod(K) where (N + S)mod(K) = (N + S)-floor((N + S)/K)-K and
the "floor" operation rounds a number to its lower integer as it is known in the art.
The shift can be specified by a number of bits equal to the number of
sequences for the RB allocation of PUCCH signals. If the PUCCH RB allocation
is the smallest one corresponding to 1 RB, this number is identical to the number
of sequence groups (in the embodiment, 5 bits are needed to specify one of the 30
sequences in a set of sequences or, equivalently, one of the 30 sequence groups).
Alternatively, such signaling overhead can be reduced by limiting the range of the
shift to only the sequences with indexes adjacent to the ones used for the by the
first sequence in the hopping pattern applied to the RS transmission for the data
channel. In that case, only 2 bits are needed to indicate the previous, same, or next
sequence.
The above are illustrated in FIG. 16 where in an embodiment, a shift of 0
1610, 1 1620, and -1 1630 is applied to the sequence hopping pattern of the
PUCCH transmission in three different cells relative to the sequence hopping
pattern for the PUSCH RS transmission 1640. The different sequence hopping

patterns simply correspond to a cyclical shift (the addition of the shift value is
modulo the sequence set size) of the same sequence hopping pattern 1640, or
equivalently, the different sequence hopping patterns correspond to different
initialization of the same hopping pattern. The initialization of the hopping
pattern for the PUSCH may be explicitly or implicitly signaled, as previously
described, and the shift for the initialization pattern for the PUCCH is determined
relative to the initial sequence for the PUSCH (which may be different than the
first sequence in the set of sequences). The above roles of the PUSCH and
PUCCH may be reversed and the shift may instead define the initialization of the
PUSCH, instead of the PUCCH, hopping pattern in a cell. The start of the
hopping pattern in time may be defined relative to the first slot in the first sub-
frame in a frame or a super-frame (both comprising of multiple sub-frames) as
these notions are typically referred to in the art.
While the present invention has been shown and described with reference
to certain preferred embodiments thereof, it will be understood by those skilled in
the art that various changes in form and details may be made therein without
departing from the spirit and scope of the present invention as defined by the
appended claims.

WHAT IS CLAIMED IS:
1. A method for allocating sequences used to transmit a signal by a user
equipment in a communication system, wherein the signal transmission is over a
number of resource blocks in a frequency domain and over a number of symbols
in a time domain, wherein a different set of sequences exists for each possible
number of resource blocks and a set of sequences with a smallest set size
corresponds to at least a first number of resource blocks, the method comprising:
selecting a sub-set of sequences with a sub-set size equal to a smallest set
size corresponding to a second number of resource blocks; and
transmitting the signal in a symbol of the number of symbols and over the
second number of resource blocks using only a sequence belonging to the sub-set
of sequences.
2. The method of claim 1, wherein the sequences comprise CAZAC-
based sequences.
3. The method of claim 1, wherein the signal comprises a reference
signal.
4. A method for allocating sequences used to transmit a signal by a user
equipment in a communication system, wherein the signal transmission is over a
number of resource blocks in a frequency domain and over a number of symbols
in a time domain, the method comprising:
transmitting the signal using a single sequence in all symbols of the
number of symbols if the number of the resource blocks is less than a
predetermined value; and
transmitting the signal using a first sequence in a first symbol of the
number of symbols and using a second sequence in a second symbol of the
number of symbols if the number of the resource blocks is equal to or greater than
the predetermined value.
5. The method of claim 4, wherein the sequence comprises a CAZAC-
based sequence.

6. The method of claim 4, wherein the signal comprises a reference
signal.
7. A method for allocating sequences used to transmit a signal by a user
equipment in a communication system, wherein the signal transmission is over a
number of resource blocks in a frequency domain and over a number of symbols
in a time domain, wherein a set of sequences exists for each possible number of
resource blocks and a set of sequences with a smallest set size corresponds to at
least a first number of resource blocks, the method comprising:
selecting a sub-set of sequences with a sub-set size equal to a smallest set
size from a set of sequences corresponding to a second number of resource
blocks; and
transmitting the signal over the second number of resource blocks and over
the number of symbols with the sequence used in each symbol of the number of
symbols being selected from the sub-set of sequences according to a pseudo-
random pattern.
8. The method of claim 7, wherein the sequence comprises a CAZAC-
based sequence.
9. The method of claim 7, wherein the signal comprises a reference
signal.
10. A method for a user equipment to transmit a first signal or a second
signal in a communication system, wherein the first signal is transmitted over a
first number of symbols in a first channel using sequences from a first set of
sequences and the second signal is transmitted over a second number of symbols
in a second channel using sequences from a second set of sequences, the method
comprising:
selecting a sequence used to transmit the first signal in each symbol of the
first number of symbols by applying a pseudo-random pattern over the first set of
sequences; and
selecting a sequence used to transmit the second signal in each symbol of
the second number of symbols by applying the pseudo-random pattern over the
second set of sequences.

11. The method of claim 10, wherein the sequence comprises a CAZAC-
based sequence.
12. The method of claim 10, wherein the first signal comprises a
reference signal and the first channel is used for transmission of data information.
13. The method of claim 10, wherein the second signal comprises a
reference signal or a control signal and the second channel is used for
transmission of control information.
14. A method for a user equipment to select an initial sequence from a
first set of sequences with a set size K for the transmission of a signal in a first
channel to a Node B, wherein an initial sequence from a second set of sequences
with a set size K for the transmission of a signal in a second channel to the Node
B is sequence number N, the method comprising:
receiving a shift value S from the Node B; and
selecting the initial sequence from the first set of sequences for the
transmission of the signal in the first channel to be the sequence whose number M
is obtained as (N + S) modulo(K).
15. The method of claim 14, wherein the sequences comprise CAZAC-
based sequences.
16. The method of claim 14, wherein the first channel is used for
transmission of data information and the second channel is used for transmission
of control information.
17. The method of claim 14, wherein the number N of the initial
sequence for the transmission of a signal in the second channel is signaled by the
Node B.
18. An apparatus for transmitting a signal in a communication system,
wherein the signal transmission is through a transmission of sequences over a
number of resource blocks in a frequency domain and over a number of symbols
in a time domain, the apparatus comprising:

a transmitter for transmitting the signal using a single sequence in all
symbols of the number of symbols if the number of the resource blocks is less
than a predetermined value; and
a transmitter for transmitting the signal using a first sequence in a first
symbol of the number of symbols and using a second sequence in a second
symbol of the number of symbols if the number of the resource blocks is equal to
or greater than the predetermined value.
19. The apparatus of claim 18, wherein the sequence comprises a
CAZAC-based sequence.
20. The apparatus of claim 18, wherein the signal comprises a reference
signal.
21. An apparatus for transmitting a signal in a communication system,
wherein the signal transmission is through a transmission of sequences over a
number of resource blocks in a frequency domain and over a number of symbols
in a time domain, wherein a set of sequences exists for each possible number of
resource blocks, wherein a set of sequences with a smallest set size corresponds
to at least a first number of resource blocks, the apparatus comprising:
a generator for generating a sub-set of sequences, with a sub-set size equal
to a smallest set size, from a set of sequences corresponding to a second number
of resource blocks; and
a transmitter for transmitting the signal over the second number of
resource blocks and over the number of symbols with the sequence used in each
symbol of the number of symbols being selected from the sub-set of sequences
according to a pseudo-random pattern.
22. The apparatus of claim 21, wherein the sequence comprises a
CAZAC-based sequence.
23. The apparatus of claim 21, wherein the signal comprises a reference
signal.

24. An apparatus for transmitting a first signal or a second signal in a
communication system, wherein the first signal is transmitted over a first number
of symbols in a first channel using sequences from a first set of sequences and the
second signal is transmitted over a second number of symbols in a second channel
using sequences from a second set of sequences, the apparatus comprising:
a selector for selecting a sequence used to transmit the first signal in each
symbol of the first number of symbols in the first channel by applying a pseudo-
random pattern over the first set of sequences;
a selector for selecting a sequence used to transmit the second signal in
each symbol of the second number of symbols in the second channel by applying
the pseudo-random pattern over the second set of sequences; and
a transmitter for transmitting the first signal or the second signal.
25. The apparatus of claim 24, wherein the sequence comprises a
CAZAC-based sequence.
26. The apparatus of claim 24, wherein the first signal comprises a
reference signal and the first channel is used for transmission of data information.
27. The apparatus of claim 24, wherein the second signal comprises a
reference signal or a control signal and the second channel is used for
transmission of control information.
28. An apparatus for transmitting a signal to a Node B of a
communication system in a first channel using sequences from a first set of
sequences with a set size K, wherein an initial sequence from a second set of
sequences with a set size K for the transmission of a signal in a second channel to
the Node B is sequence number N, the apparatus comprising:
a selector for selecting an initial sequence from the first set of sequences
for the transmission of the signal in the first channel to be a sequence with
number M obtained as (N + S) modulo(K), where S is a shift value signaled by
the Node B; and
a transmitter for transmitting the signal in the first channel.

29. The apparatus of claim 28, wherein the sequences comprise CAZAC-
based sequences.
30. The apparatus of claim 28, wherein the first channel is used for
transmission of data information and the second channel is used for transmission
of control information.
31. The apparatus of claim 28, wherein the number N of the initial
sequence for the transmission of a signal in the second channel is signaled by the
Node B.
32. A method for allocating sequences used to transmit a reference signal
(RS) by a user equipment in a communication system, wherein the RS
transmission is over a number of resource blocks in a frequency domain and over
a number of symbols in a time domain, the method comprising:
transmitting the RS using a single non-hopped sequence in the symbols if a
size of RS transmission symbols within a sub-frame is less than a size of 6
resource blocks; and
transmitting the reference signal using hopped sequences in the symbols if
the size of RS transmission symbols within the sub-frame is equal to or greater
than the size of 6 resource blocks.

A method and apparatus are provided for the selection of sequences used
for the transmission of signals from user equipments in a cellular communication
system. The sequences can be selected either through planning or through
pseudo-random hopping among a set of sequences. With planning, the serving
Node B signals the sequence assignment for each cell, which remains invariable
in time. With pseudo-random sequence hopping, the serving Node B signals the
initial sequence, from a set of sequences, which can be different among cells. The
initial sequence used in the control (or data) channel is signaled by the serving
Node B. The initial sequence used in the data (or control) channel is selected to
be the sequence in a set of sequences with number equal to a shift value relative
to the first sequence as signaled by the serving Node B for the control (or data)
channel.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=4Prc9j6v6tbqlMKfN2qoTg==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

272333

Indian Patent Application Number

610/KOLNP/2010

PG Journal Number

14/2016

Publication Date

01-Apr-2016

Grant Date

30-Mar-2016

Date of Filing

17-Feb-2010

Name of Patentee

SAMSUNG ELECTRONICS CO., LTD.

Applicant Address

416, MAETAN-DONG, YEONGTONG-GU, SUWON-SI, GYEONGGI-DO 442-742 REPUBLIC OF KOREA

Inventors:

#	Inventor's Name	Inventor's Address
1	ARIS PAPASAKELLARIOU	2128 HAROLD STREET UNIT B HOUSTON, TX 77098 U.S.A.
2	JOON-YOUNG CHO	#224-101, HWANGGOLMAEUL 2-DANJI APT. YEONGTONG-DONG, YEONGTONG-GU, SUWON-SI GYEONGGI-DO 443-744 REPUBLIC OF KOREA

PCT International Classification Number

H04B7/26;H04B7/26

PCT International Application Number

PCT/KR2008/005188

PCT International Filing date

2008-09-03

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	60/969,659	2007-09-03	U.S.A.