KR101681784B1 - Method and apparatus of generating ranging preamble code in wireless communication system - Google Patents

Abstract

A method and apparatus for generating ranging ranging preamble codes in a wireless communication system are provided. The terminal generates a Zadoff-Chu (ZC) sequence using a cyclic shift for each OFDMA symbol with a ranging preamble code. The cyclic shift may be applied to each OFDMA symbol.

Description

[0001] The present invention relates generally to a method and apparatus for generating ranging preamble codes in a wireless communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless communication, and more particularly, to a method and apparatus for generating a ranging preamble code in a wireless communication system.

The Institute of Electrical and Electronics Engineers (IEEE) 802.16e standard is a sixth standard for IMT (International Mobile Telecommunication) -2000 in ITU-R (ITU-R) under ITU (International Telecommunication Union) OFDMA TDD '. ITU-R is preparing the IMT-Advanced system as the next generation 4G mobile communication standard after IMT-2000. The IEEE 802.16 WG (Working Group) decided to implement the IEEE 802.16m project with the goal of preparing the amendment specification of the existing IEEE 802.16e as the standard for the IMT-Advanced system at the end of 2006. As can be seen from the above objectives, the IEEE 802.16m standard contains two aspects: continuity of the past, which is the modification of the IEEE 802.16e standard, and future continuity of the standards for the next generation IMT-Advanced system. Therefore, the IEEE 802.16m standard is required to satisfy all the advanced requirements for the IMT-Advanced system while maintaining compatibility with the Mobile WiMAX system based on the IEEE 802.16e standard.

In the case of a broadband wireless communication system, effective transmission and reception techniques and utilization methods have been proposed to maximize the efficiency of limited radio resources. One of the systems considered in the next generation wireless communication system is an Orthogonal Frequency Division Multiplexing (OFDM) system capable of attenuating the inter-symbol interference (ISI) effect with low complexity. OFDM converts serial data symbols into N parallel data symbols, and transmits the data symbols on N separate subcarriers. The subcarriers maintain orthogonality at the frequency dimension. Each of the orthogonal channels experiences mutually independent frequency selective fading, thereby reducing the complexity at the receiving end and increasing the interval of transmitted symbols, thereby minimizing intersymbol interference.

Orthogonal frequency division multiple access (OFDMA) refers to a multiple access method in which a part of subcarriers available in a system using OFDM as a modulation scheme is independently provided to each user to realize multiple access. OFDMA provides a frequency resource called a subcarrier to each user, and each frequency resource is provided independently to a plurality of users and is not overlapped with each other. Consequently, frequency resources are allocated mutually exclusively for each user. Frequency diversity for multiple users can be obtained through frequency selective scheduling in an OFDMA system and subcarriers can be allocated in various forms according to a permutation scheme for subcarriers. And the efficiency of spatial domain can be improved by spatial multiplexing technique using multiple antennas.

An uplink control channel for transmitting an uplink control signal may be defined. A variety of types such as a fast feedback control channel, a Hybrid Automatic Repeat reQuest feedback control channel, a sounding channel, a ranging channel, a bandwidth request channel, The uplink control channel of the uplink control channel can be defined. The fast feedback channel carries feedback of CQI (Channel Quality Indicator) and / or MIMO (Multiple-In Multiple-Out) information, and includes a primary fast feedback channel and a secondary fast feedback channel ). The HARQ feedback control channel is a channel for transmitting ACK (Acknowledgment) / NACK (Non-acknowledgment) signals in response to data transmission. The sounding channel can be used as an uplink channel response for uplink closed-loop MIMO transmission and uplink scheduling. The bandwidth request channel is a channel for requesting radio resources for transmitting uplink data or control signals to be transmitted by the UE.

The ranging channel may be used for uplink synchronization. The ranging channel includes an asynchronous ranging channel (NS-RCH) for a non-synchronized MS and a synchronous ranging channel (S-RCH) for a synchronized MS ). An asynchronous ranging channel may be used for initial access and handover. In the subframe in which the asynchronous ranging channel is supposed to be transmitted, the UE may not transmit any other uplink burst or uplink control channel. The synchronous ranging channel may be used for periodic ranging. A terminal already synchronized with the target base station can transmit a ranging signal for the synchronous terminal.

A ranging preamble code may be transmitted over the ranging channel. Various types of codes or sequences such as a Zadoff-Chu (ZC) sequence can be used as the ranging preamble code, and a cyclic shift can be applied. The ranging preamble code may be mapped to at least one OFDMA symbol allocated to the ranging channel.

There is a need for a method for applying a cyclic shift when a ranging preamble code is mapped to a plurality of OFDMA symbols.

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for generating a ranging preamble code in a wireless communication system.

In an aspect, a method of generating ranging ranging preamble codes in a wireless communication system is provided. The ranging preamble code generation method includes generating a Zadoff-Chu (ZC) sequence to which a cyclic shift is applied to each of a plurality of Orthogonal Frequency Division Multiple Access (OFDMA) symbols using a ranging preamble code, The cyclic shift is applied to each OFDMA symbol.

의수학식에 의해 결정될 수 있다. 단, s_p는 순환 쉬프트 인덱스(cyclic shift index), N_TCS는 시간 영역에서의 순환 쉬프트 단위, N_FFT는 FFT 크기, N_RP는 OFDMA 심벌당 상기 레인징 프리앰블 코드의 길이를 나타낸다. 상기 N_TCS=G*N_FFT일 수 있다. 단, G는 CP(cyclic prefix) 비율(ratio)이며, N_FFT는 FFT 크기이다. 상기 레인징 프리앰블 코드는

의 수학식에 의해 결정될 수 있다. 단, r_p는 상기 ZC 시퀀스의 루트 인덱스(root index), s_p는 순환 쉬프트 인덱스(cyclic shift index), N_TCS는 시간 영역에서의 순환 쉬프트 단위, N_FFT는 FFT 크기, N_RP는 OFDM 심벌당 상기 레인징 프리앰블 코드의 길이, n은 OFDMA 심벌 인덱스를 나타낸다. The cyclic shift

And can be determined by the numerical formula. Here, s _p denotes a cyclic shift index, N _TCS denotes a cyclic shift unit in the time domain, N _FFT denotes an FFT size, and N _RP denotes a length of the ranging preamble code per OFDMA symbol. N _TCS = G * N _FFT . Where G is a cyclic prefix (CP) ratio, and N _FFT is the FFT size. The ranging preamble code

Can be determined by the following equation. R _p is a root index of the ZC sequence, s _p is a cyclic shift index, N _TCS is a cyclic shift unit in the time domain, N _FFT is an FFT size, N _RP is an OFDM symbol The length of the ranging preamble code per symbol, and n denotes an OFDMA symbol index.

The length of the ranging preamble code may be 72. The number of OFDMA symbols may be three. The ranging preamble code generation method may further include mapping the generated ranging preamble code to each OFDMA symbol. The cyclic shift unit to which the cyclic shift is applied may be equal to or less than the length of the ranging preamble code. The ranging preamble code may be used for periodic ranging through a Synchronized Ranging Channel (S-RCH).

In another aspect, a ranging preamble code generation apparatus includes a radio frequency (RF) unit for transmitting or receiving a radio signal, and a processor coupled to the RF unit, wherein the processor is configured to perform, for each of a plurality of OFDMA symbols, To a ranging preamble code, and the cyclic shift is applied to each OFDMA symbol. The length of the ranging preamble code may be 72. The number of OFDMA symbols may be three. The processor may further be configured to map the generated ranging preamble code to each OFDMA symbol.

A ranging preamble code to which a cyclic shift is applied to the base sequence can be used without increasing the detection complexity at the receiving end.

1 shows a wireless communication system.
Fig. 2 shows an example of a frame structure.
3 shows an example of an uplink resource structure.
4 shows the structure of the synchronous ranging channel in the time domain.
5 shows an example in which a ranging preamble code of a synchronous ranging channel is mapped to an OFDMA symbol.
6 is a block diagram of an algorithm for detecting a ranging preamble code.
FIG. 7 shows a case where a cyclic-shifted sequence is mapped to one OFDMA symbol or a plurality of OFDMA symbols.
FIG. 8 shows a mapping of a ranging preamble code generated by the proposed ranging preamble code generating method to a plurality of OFDMA symbols.
9 to 12 show an example of mapping a ranging preamble code according to the proposed ranging preamble code generating method.
13 shows an embodiment of the proposed ranging preamble code generation method.
14 is a block diagram illustrating a base station and a terminal in which an embodiment of the present invention is implemented.

The following description will be made on the assumption that the present invention is applicable to a CDMA system such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), and Single Carrier Frequency Division Multiple Access And can be used in various wireless communication systems. CDMA may be implemented in radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. The TDMA may be implemented in a wireless technology such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented in wireless technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and Evolved UTRA (E-UTRA). IEEE 802.16m is an evolution of IEEE 802.16e, providing backward compatibility with systems based on IEEE 802.16e. UTRA is part of the Universal Mobile Telecommunications System (UMTS). The 3rd Generation Partnership Project (3GPP) LTE (Long Term Evolution) is a part of E-UMTS (Evolved UMTS) using Evolved-UMTS Terrestrial Radio Access (E-UTRA). It adopts OFDMA in downlink and SC -FDMA is adopted. LTE-A (Advanced) is the evolution of 3GPP LTE.

For clarity of description, IEEE 802.16m is mainly described, but the technical idea of the present invention is not limited thereto.

1 shows a wireless communication system.

The wireless communication system 10 includes at least one base station 11 (BS). Each base station 11 provides a communication service to a specific geographical area (generally called a cell) 15a, 15b, 15c. The cell may again be divided into multiple regions (referred to as sectors). A user equipment (UE) 12 may be fixed or mobile and may be a mobile station, a mobile terminal, a user terminal, a subscriber station, a wireless device, a PDA The base station 11 generally refers to a fixed station that communicates with the terminal 12, and may be referred to as a " mobile station " an eNB (evolved-NodeB), a base transceiver system (BTS), an access point, and the like.

A UE belongs to one cell, and a cell to which the UE belongs is called a serving cell. A base station providing a communication service to a serving cell is called a serving BS. Since the wireless communication system is a cellular system, there are other cells adjacent to the serving cell. Another cell adjacent to the serving cell is called a neighbor cell. A base station that provides communication services to neighbor cells is called a neighbor BS. The serving cell and the neighboring cell are relatively determined based on the terminal.

This technique can be used for a downlink or an uplink. Generally, downlink refers to communication from the base station 11 to the terminal 12, and uplink refers to communication from the terminal 12 to the base station 11. In the downlink, the transmitter may be part of the base station 11, and the receiver may be part of the terminal 12. In the uplink, the transmitter may be part of the terminal 12 and the receiver may be part of the base station 11.

Fig. 2 shows an example of a frame structure.

Referring to FIG. 2, a superframe (SF) includes a superframe header (SFH) and four frames (F0, F1, F2, F3). The length of each frame in a superframe may be the same. The size of each super frame is 20 ms, and the size of each frame is 5 ms, but the present invention is not limited thereto. The length of the superframe, the number of frames included in the superframe, the number of subframes included in the frame, and the like can be variously changed. The number of subframes included in a frame may be variously changed according to a channel bandwidth and a length of a CP (Cyclic Prefix).

One frame includes a plurality of subframes (subframes SF0, SF1, SF2, SF3, SF4, SF5, SF6, SF7). Each subframe may be used for uplink or downlink transmission. One subframe includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols or orthogonal frequency division multiple access (OFDMA) in a time domain and includes a plurality of subcarriers in a frequency domain. do. An OFDM symbol is used to represent one symbol period and may be called another name such as an OFDMA symbol and an SC-FDMA symbol according to a multiple access scheme. The subframe may be composed of 5, 6, 7 or 9 OFDMA symbols, but this is only an example and the number of OFDMA symbols included in the subframe is not limited. The number of OFDMA symbols included in the subframe may be variously changed according to the channel bandwidth and the length of the CP. The type of the subframe can be defined according to the number of OFDMA symbols included in the subframe. For example, a Type-1 subframe may be defined as including 6 OFDMA symbols, a Type-2 subframe as 7 OFDMA symbols, a Type-3 subframe as 5 OFDMA symbols, and a Type-4 subframe as 9 OFDMA symbols have. One frame may include all subframes of the same type. Or one frame may include different types of subframes. That is, the number of OFDMA symbols included in each subframe in one frame may be the same or different from each other. Alternatively, the number of OFDMA symbols in at least one subframe in one frame may be different from the number of OFDMA symbols in the remaining subframes in the frame.

A TDD (Time Division Duplex) scheme or an FDD (Frequency Division Duplex) scheme may be applied to the frame. In the TDD scheme, each subframe is used for uplink transmission or downlink transmission at different times at the same frequency. That is, the subframes in the TDD frame are divided into the uplink subframe and the downlink subframe in the time domain. The switching point is a point at which a transmission direction changes from an uplink region to a downlink region or from a downlink region to an uplink region. In the TDD scheme, the number of switching points in each frame may be two. In the FDD scheme, each subframe is used for uplink transmission or downlink transmission at different frequencies at the same time. That is, subframes in a frame of the FDD scheme are divided into an uplink subframe and a downlink subframe in the frequency domain. The uplink transmission and the downlink transmission occupy different frequency bands and can be performed at the same time.

The SFH can carry essential system parameters and system configuration information. The SFH may be located in the first subframe within the superframe. SFH may occupy the last 5 OFDMA symbols of the first subframe. The superframe header can be classified into a primary SFH (P-SFH) and a secondary SFH (S-SFH). The P-SFH is transmitted every super frame. Information transmitted to the S-SFH can be divided into three sub-packets: S-SFH SP1, S-SFH SP2, and S-SFH SP3. Each subpacket can be transmitted periodically with different periods. SFH SP1, S-SFH SP2, and S-SFH SP3 may be different from each other, and the S-SFH SP3 may be transmitted in the shortest cycle and the S-SFH SP3 may be transmitted in the longest cycle. The S-SFH SP1 includes information about network re-entry. The S-SFH SP2 includes information about an initial network entry and network discovery. S-SFH SP3 contains the remaining important system information.

One OFDMA symbol includes a plurality of subcarriers, and the number of subcarriers is determined according to the FFT size. There are several types of subcarriers. The types of subcarriers can be divided into data subcarriers for data transmission, pilot subcarriers for various estimation, guard bands, and null carriers for DC carriers. The parameters that characterize the OFDM symbol are BW, N _used , n, G, and so on. BW is the nominal channel bandwidth. N _used is the number of subcarriers _used (including DC subcarriers). n is a sampling factor. This parameter is used in conjunction with BW and N _used to determine the sub-carrier spacing (spacing) and the effective symbol time (useful symbol time). G is the ratio of CP time to useful time.

Table 1 below shows the OFDMA parameters.

Channel bandwidth, BW (MHz) 5 7 8.75 10 20 Sampling factor, n 28/25 8/7 8/7 28/25 28/25 Sampling frequency, F _s (MHz) 5.6 8 10 11.2 22.4 FFT size, N _FFT 512 1024 1024 1024 2048 Subcarrier spacing, Δf (kHz) 10.94 7.81 9.77 10.94 10.94 Useful symbol time, T _b (μs) 91.4 128 102.4 91.4 91.4 G = 1/8 Symbol time, T _s (μs) 102.857 144 115.2 102.857 102.857 FDD Number of
ODFMA symbols
per 5ms frame 48 34 43 48 48 Idle time (μs) 62.857 104 46.40 62.857 62.857 TDD Number of
ODFMA symbols
per 5ms frame 47 33 42 47 47 TTG + RTG (μs) 165.714 248 161.6 165.714 165.714 G = 1/16 Symbol time, T _s (μs) 97.143 136 108.8 97.143 97.143 FDD Number of
ODFMA symbols
per 5ms frame 51 36 45 51 51 Idle time (μs) 45.71 104 104 45.71 45.71 TDD Number of
ODFMA symbols
per 5ms frame 50 35 44 50 50 TTG + RTG (μs) 142.853 240 212.8 142.853 142.853 G = 1/4 Symbol time, T _s (μs) 114.286 160 128 114.286 114.286 FDD Number of
ODFMA symbols
per 5ms frame 43 31 39 43 43 Idle time (μs) 85.694 40 8 85.694 85.694 TDD Number of
ODFMA symbols
per 5ms frame 42 30 38 42 42 TTG + RTG (μs) 199.98 200 136 199.98 199.98 Number of Guard subcarriers Left 40 80 80 80 160 Right 39 79 79 79 159 Number of used subcarriers 433 865 865 865 1729 Number of PRU in type-1 subframe 24 48 48 48 96

In Table 1, N _FFT is the most small 2 ⁿ in the water is greater than N _used is the least power (Smallest power of two greater than N _used), sampling factor _{F s = floor (n · BW} / 8000) , and × 8000, subcarrier spacing Δf = F _s / a N _FFT, and the effective symbol time T _b = 1 / Δf, CP time T _g = g · a T _b, and OFDMA symbol time T _s = T _b + T _g, the sampling time is T _b / N _FFT .

3 shows an example of an uplink resource structure.

Each uplink subframe can be divided into four or less frequency partitions. In FIG. 3, it is exemplified that the subframe is divided into two frequency partitions FP1 and FP2, but the number of frequency partitions in the subframe is not limited thereto. Each frequency partition is composed of at least one physical resource unit (PRU) over the entire OFDMA symbol usable in the subframe. Each frequency partition may also contain contiguous / localized and / or distributed PRUs. Each frequency partition can be used for other purposes such as fractional frequency reuse (FFR). In FIG. 3, the second frequency partition FP2 includes both continuous resource allocation and distributed resource allocation. 'Sc' means a subcarrier.

The PRU is the basic physical unit for resource allocation, including Psc consecutive subcarriers and Nsym consecutive OFDMA symbols. Psc can be 18 days. Nsym may be equal to the number of OFDMA symbols included in one subframe. Therefore, Nsym can be determined according to the type of the subframe. For example, when one subframe is composed of 6 OFDMA symbols, the PRU can be defined as 18 subcarriers and 6 OFDMA symbols. A logical resource unit (LRU) is a basic logical unit for distributed and continuous resource allocation.

A Distributed Logical Resource Unit (DLRU) can be used to obtain a frequency diversity gain. The uplink DLRU may be composed of subcarriers included in three tiles distributed in one frequency partition. The tile is the minimum unit constituting the uplink DLRU. The size of the uplink tile may be 6 * Nsym, and Nsym may vary depending on the subframe type.

A contiguous logical resource unit (CLRU) may be used to obtain a frequency selective scheduling gain. The DLRU includes a group of consecutive subcarriers within a localized allocated resource. The CLRU consists of data subcarriers in a Contiguous Resource Unit (CRU). The size of the CRU is equal to the size of the PRU.

Hereinafter, the synchronous ranging channel will be described.

The synchronous ranging channel is used for periodic ranging. A terminal having already been synchronized with the target BS transmits a periodic ranging signal to the BS. In a femtocell, a UE can perform an initial ranging, a handover ranging or a periodic ranging using a synchronous ranging channel.

4 shows the structure of the synchronous ranging channel in the time domain. 4- (a) is a structure of a basic unit constituting a synchronous ranging channel, and Fig. 4- (b) is a structure of a synchronous ranging channel composed of the basic unit. The base unit occupies 72 subcarriers and 3 OFDMA symbols, and a signal waveform corresponding to the base unit is generated by the ranging preamble code. The synchronous ranging channel occupies 72 subcarriers and 6 OFDMA symbols from the first OFDMA symbol in the subframe. Two repeated base units constitute a synchronous ranging channel.

A padded ZC (Zadoff-Chu) code can be used as the ranging preamble code of the synchronous ranging channel. Equation (1) is an example of a ranging preamble code used in the synchronous ranging channel.

p is the index of the ranging preamble code for the n-th OFDMA symbol in the basic unit. The ranging preamble code of Equation (1) can be generated by applying an s _p -th cyclic shift with a cyclic shift unit m from a ZC sequence whose root index is r _p . m is a unit of cyclic shift, and N _RP is the length of the ranging preamble code.

The ranging channel allocation information may include ranging configuration information. The ranging configuration information may indicate a subframe offset (O _SF ) to which a resource for a ranging channel is allocated in a time domain. The radio resources in the time domain in which the asynchronous ranging channel and the synchronous ranging channel are allocated can be determined by the subframe offset.

Table 2 shows the ranging channel allocation information of the synchronous ranging channel. The subframe to which the synchronous ranging channel is allocated is determined according to Table 2. At this time, the number of uplink subframes (N _UL ) per frame is greater than one.

Configurations The subframe allocating Ranging channel 0 mod (O _SF +1, N _UL ) ^th UL AAI subframe in every frame One mod (O _SF +1, N _UL ) ^th UL AAI subframes in the first frame in every superframe 2 mod (O _SF +1, N _UL ) ^th UL AAI subframe in the first frame in every 4 ^th superframe 3 mod (O _SF +1, N _UL ) ^th UL AAI subframe of the first frame in every 8 ^th superframe

5 shows an example in which a ranging preamble code of a synchronous ranging channel is mapped to an OFDMA symbol. In FIG. 5- (a), the ranging preamble code is mapped over 72 subcarriers in the frequency domain and 3 OFDMA symbols in the time domain. In Fig. 5- (b), the basic unit of Fig. 5 (a) is repeatedly mapped. That is, the ranging preamble code is mapped to the 4th to 6th OFDMA symbols in the same manner as that mapped to the first to third OFDMA symbols.

The ranging preamble code used in FIG. 5 can be determined by Equation (2).

p is the index of the ranging preamble code for the n-th OFDMA symbol in the basic unit. The ranging preamble code of Equation (2) can be generated by applying an s _p cyclic shift having a cyclic shift unit N _CS from a ZC sequence whose root index is r _p . N _RP is the length of the ranging preamble code and can be defined as N _RP = 214 in Equation (2). The terminal generates a ranging preamble code according to Equation (2) and maps it to a plurality of OFDMA symbols as shown in FIG.

6 is a block diagram of an algorithm for detecting a ranging preamble code. Referring to FIG. 6, a receiving end multiplies a complex conjugate of a ranging preamble code for each OFDMA symbol in a frequency domain, adds OFDMA symbols at a subcarrier level, and transmits a ranging preamble (IFFT) And detects a ranging preamble code by obtaining a correlation of codes. The algorithm for detecting the ranging preamble code is not limited to this, but in the following description, the detection of the ranging preamble code by the detection algorithm of FIG. 6 is taken as an example.

Meanwhile, the ranging preamble code of Equation (2) can be rewritten as Equation (3).

In Equation (3), N _RP = 214 can also be determined. If N _RP = 214 = N _ZC +3, then N _ZC = 211, which is a prime number. (4) can be expressed by Equation (4).

The first term of Equation (4) is a formula for generating a ZC sequence of length N _ZC . Here, k can have a value up to N _ZC + 2, which is cyclically extended by 3 samples, not N _ZC -1, which is the length of the original ZC sequence. The second term in Equation (4) is a formula for cyclically shifting the generated ZC sequence in the time domain by S _p * N _CS with respect to the length N _ZC . That is, the ZC sequence generated by the first term is cyclically shifted by the second term, and since the length of the ranging preamble code is longer than the number of subcarriers in one OFDMA symbol, the ZC sequence is segmented over a plurality of OFDMA symbols. Are mapped.

FIG. 7 shows a case where a cyclic-shifted sequence is mapped to one OFDMA symbol or a plurality of OFDMA symbols. In FIG. 7, the code index represents a sample index in the time domain of the sequence.

FIG. 7- (a) shows a case where a sequence of length 4 is mapped to one OFDMA symbol. In FIG. 7 (a), regardless of whether a basic sequence is used or a sequence to which a cyclic shift is applied, a basic sequence of length 4 is retained in one OFDMA symbol to which a sequence is mapped. On the other hand, the ranging preamble code detection algorithm of FIG. 6 detects a ranging preamble code by obtaining a correlation on an OFDMA symbol basis. Accordingly, when the receiving terminal detects the ranging preamble code, only the correlation with respect to the base sequence can be detected, and the ranging preamble code to which the cyclic shift is applied to the base sequence can be easily detected. In this case, the basic sequence means a sequence to which the cyclic shift is not applied. For example, in a ZC sequence or a padded ZC sequence, sequences having different root indices may all be basic sequences.

FIG. 7- (b) shows a case where a sequence of length 12 is mapped over three OFDMA symbols. In Fig. 7B, the base sequence having a length of 12 is cyclically shifted by 2 samples in the time domain and mapped to three OFDMA symbols. Code indices 10, 11, 0 and 1 are mapped to the first OFDMA symbol, code indices 2 to 5 are mapped to the second OFDMA symbol, and code indices 6 to 9 are mapped to the third OFDMA symbol. In this case, the shape of the base sequence of length 12 in each OFDMA symbol is not maintained. That is, when detecting the ranging preamble code according to the detection algorithm of FIG. 6, since the shape of the basic sequence is not maintained in each OFDMA symbol, the ranging preamble code can not be detected only by correlation with the base sequence. Therefore, we need to find the correlation for all sequences with circular shift applied to the base sequence. For example, assuming that eight cyclic-shifted sequences are used in one base sequence, all eight cyclic shifts are regarded as the base sequence, and detection is performed by obtaining all the correlations for the eight sequences.

As described in the example of FIG. 7, when a long sequence is circularly shifted and mapped to a plurality of OFDMA symbols, it is impossible to properly detect a sequence in each OFDMA symbol. Accordingly, detection complexity ) Is increased. Therefore, a ranging preamble code generation method is required to prevent an increase in detection complexity.

FIG. 8 shows a mapping of a ranging preamble code generated by the proposed ranging preamble code generating method to a plurality of OFDMA symbols. A case in which a sequence of length 12 is circularly shifted and mapped over three OFDMA symbols is explained as in Fig. 7 (b).

Referring to FIG. 8, a sequence to which a cyclic shift is applied to a base sequence is mapped to a plurality of OFDMA symbols, but a cyclic shift can be applied to each OFDMA symbol without being applied to the entire base sequence. That is, the cyclic shift can be applied in units of the same or smaller units of the number of subcarriers included in the OFDMA symbol in each OFDMA symbol. Accordingly, the code indexes 0 to 3 are cyclically shifted by 2 samples in the code indexes 0 to 3, and the code indexes 4 to 7 are cyclically shifted by 2 samples in the second OFDMA symbol. , 7, 4, and 5, and code indexes 10, 11, 8, and 9, which are cyclically shifted by two samples, are mapped to code indexes 8 to 11 in the third OFDMA symbol. By applying the cyclic shift for each OFDMA symbol, it is possible to detect all of the cyclically shifted sequences using only the correlation with the base sequence without having to calculate the correlation for all cyclically shifted sequences.

Equation (5) is an example of a formula for generating a ranging preamble code by the proposed invention.

p is an index of a ranging preamble code constituting a basic unit of a ranging channel determined by cyclic shifting from a ZC sequence whose root index is r _p . r _p and s _p may be defined by Equation (6).

The p < th > ranging preamble code is determined using the root index r _p determined from the starting root index r ₀ . M is the number of cyclically shifted sequences per root index of the ZC sequence and can be defined as M = 1 / G. N _TOTAL is the total number of sector-specific periodic ranging preamble codes, and can be expressed as a sum of N _cont , which is the number of contention-based ranging preamble codes, and _Nden , the number of dedicated ranging preamble codes.

N _TCS is a unit of time-domain cyclic shift per OFDMA symbol according to CP length, and can be defined as N _TCS = G * N _FFT . G and N _FFTs can be defined by Table 1. N _RP is the length of the ranging preamble code per OFDMA symbol and can be defined as N _RP = 72 in this embodiment. n denotes an OFDMA symbol index in a basic unit over 3 OFDMA symbols.

Equation (7) is another example of a formula for generating a ranging preamble code by the proposed invention.

N _RP = 214, U _SC1 = 72, and U _CS2 = 72 in Equation (7). N _CS represents the cyclic shift unit within the length of U _CS2 . N _CS is a value determined according to U _CS2 . For example, if eight cyclic-shifted sequences are used per root index, N _CS = U _CS2 / 8 can be determined. In order to eliminate rounding error, N _CS can be computed as floor or ceil.

Equation (8) is another example of a formula for generating a ranging preamble code by the proposed invention.

N _RP = 216, U _SC1 = 72, U _CS2 = 72 in Equation (8). N _CS represents the cyclic shift unit within the length of U _CS2 . N _CS is a value determined according to U _CS2 . For example, if eight cyclic-shifted sequences are used per root index, N _CS = U _CS2 / 8 can be determined. In order to eliminate rounding error, N _CS can be computed as floor or ceil.

Equation (9) is another form of Equation (7).

N _RP = 214, U _SC1 = 72, and U _CS2 = 72 in Equation (9). N _CS represents the cyclic shift unit within the length of U _CS2 . N _CS is a value determined according to U _CS2 . For example, if eight cyclic-shifted sequences are used per root index, N _CS = U _CS2 / 8 can be determined. In order to eliminate rounding error, N _CS can be computed as floor or ceil.

Equation (10) is another form of Equation (8).

N _RP = 216, U _SC1 = 72, U _CS2 = 72 in Equation (10). N _CS represents the cyclic shift unit within the length of U _CS2 . N _CS is a value determined according to U _CS2 . For example, if eight cyclic-shifted sequences are used per root index, N _CS = U _CS2 / 8 can be determined. In order to eliminate rounding error, N _CS can be computed as floor or ceil. In Equations (9) and (10), U _CS1 and U _CS2 may be different values. For example, U _CS1 = 71 and U _CS2 = 72.

Equations (7) to (10) illustrate the use of 72 subcarriers in the frequency domain, but a smaller number of subcarriers may be used depending on the mapping method of the ranging preamble code. At this time, the number of sequences to be cyclically shifted can be determined by the size of the actual detection window, not by 72.

9 is an example of mapping a ranging preamble code according to the proposed ranging preamble code generating method. A terminal can map a ranging preamble code using 71, 71, and 68 subcarriers of each OFDM symbol as detection windows, and apply circular shift based on the size of a detection window of each OFDMA symbol. Even if the size of the detection window differs for each OFDMA symbol, the ranging preamble code is detected by adding a sequence mapped to each OFDMA symbol on a subcarrier-by-subcarrier basis, so that the cyclic shift unit applied to each OFDMA symbol is preferably the same.

Equation (11) is an example of a formula for generating a ranging preamble code when a ranging preamble code is mapped as shown in FIG.

N _RP = 214, U _SC1 = 71, U _CS2 = 71 in Equation (11). That is, the denominator of the second term constituting Equation (11) differs from Equation (9). N _CS represents the cyclic shift unit within the length of U _CS2 . N _CS is a value determined according to U _CS2 . For example, if eight cyclic-shifted sequences are used per root index, N _CS = U _CS2 / 8 can be determined. In order to eliminate rounding error, N _CS can be computed as floor or ceil. In Equation (11), U _CS1 and U _CS2 may be different values. For example, U _CS1 = 72 and U _CS2 = 71.

FIG. 10 and FIG. 11 show another example of mapping the ranging preamble code according to the proposed ranging preamble code generating method. In each embodiment, the terminal may map the ranging preamble code to three OFDMA symbols by varying the size of the detection window. The formula for generating the ranging preamble code may vary depending on the method to be mapped. For example, when samples of the same sequence are applied to a plurality of OFDMA symbols as shown in FIG. 10- (a), a ranging preamble code can be generated for each OFDMA symbol. Equation (12) is an example of a formula for generating a ranging preamble code when a ranging preamble code is mapped as shown in FIG. 10- (a).

N _RP = 214, U _SC1 = 72, and U _CS2 = 72 in Equation (12). That is, the denominator of the second term constituting Equation (11) differs from Equation (9). N _CS represents the cyclic shift unit within the length of U _CS2 . N _CS is a value determined according to U _CS2 . For example, if eight cyclic-shifted sequences are used per root index, N _CS = U _CS2 / 8 can be determined. In order to eliminate rounding error, N _CS can be computed as floor or ceil. In Equation (12), U _CS1 and U _CS2 may be different values. For example, U _CS1 = 71, U _CS2 = 71.

The cyclic shift is applied to a value equal to or smaller than the number of subcarriers included in each OFDMA symbol in the cyclic shift unit. This is for the sake of convenience, and a value longer than the length of the sequence for each OFDMA symbol is used as a unit A cyclic shift can be applied. For example, in Equations (7) to (12), N _FFT can be substituted for U _CS2 . N _CS denotes a cyclic shift unit within the length of U _CS2 , and N _CS is a value determined according to U _CS2 .

FIG. 12 shows another example in which the ranging preamble code is mapped according to the proposed ranging preamble code generating method. When a ranging preamble code is mapped as shown in FIG. 12, a ranging preamble code can be generated by Equation (13).

N _RP in Equation (13) is the length of the entire sequence, and N _RP2 is the length of the sequence in each OFDMA symbol. N _RP = 216, U _CS1 = 72, U _CS2 = N _FFT , N _RP2 = 72 in Equation (13). The N _FFT represents the FFT size in the OFDMA modulation and demodulation determined by the bandwidth. For example, the N _FFTs are 512, 1024, and 2048, respectively, when the bandwidths are 5 MHz, 10 MHz, and 20 MHz, respectively. N _CS is a value determined according to U _CS2 . For example, if eight cyclic-shifted sequences are used per root index, N _CS = U _CS2 / 8 can be determined.

13 shows an embodiment of the proposed ranging preamble code generation method. In step S100, the terminal generates a ZC sequence to which a cyclic shift is applied for each of a plurality of OFDMA symbols, using a ranging preamble code. The cyclic shift may be applied to each OFDMA symbol.

14 is a block diagram illustrating a base station and a terminal in which an embodiment of the present invention is implemented.

The base station 800 includes a processor 810, a memory 820, and a radio frequency unit 830. Processor 810 implements the proposed functionality, process and / or method. The layers of the air interface protocol may be implemented by the processor 810. The memory 820 is coupled to the processor 810 and stores various information for driving the processor 810. [ The RF unit 830 is coupled to the processor 810 to transmit and / or receive wireless signals.

The terminal 900 includes a processor 910, a memory 920, and an RF unit 930. Processor 910 implements the proposed functionality, process and / or method. The processor 910 generates a ZC sequence to which a cyclic shift is applied for each OFDMA symbol with a ranging preamble code. The cyclic shift may be applied to each OFDMA symbol. The layers of the air interface protocol may be implemented by the processor 910. The memory 920 is coupled to the processor 910 and stores various information for driving the processor 910. [ The RF unit 930 is coupled to the processor 910 to transmit and / or receive wireless signals.

Processors 810 and 910 may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. Memory 820 and 920 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage media, and / or other storage devices. The RF units 830 and 930 may include a baseband circuit for processing radio signals. When the embodiment is implemented in software, the above-described techniques may be implemented with modules (processes, functions, and so on) that perform the functions described above. The modules may be stored in memories 820 and 920 and executed by processors 810 and 910. The memories 820 and 920 may be internal or external to the processors 810 and 910 and may be coupled to the processors 810 and 910 in various well known means.

In the above-described exemplary system, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders . It will also be understood by those skilled in the art that the steps shown in the flowchart are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the invention.

The above-described embodiments include examples of various aspects. While it is not possible to describe every possible combination for expressing various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the invention include all alternatives, modifications and variations that fall within the scope of the following claims.

Claims (15)

A method for generating a ranging preamble in a wireless communication system,
Determining a cyclic shift using a cyclic shift unit in the time domain, determined using a fast Fourier transform (FFT) size of 512, 1024 or 2048 based on the bandwidth;
Generating a Zadoff-Chu (ZC) sequence to which the cyclic shift is applied for each of a plurality of orthogonal frequency division multiple access (OFDMA) symbols as a ranging preamble code; And
And using the ranging preamble code for periodic ranging through a synchronized ranging channel (S-RCH)
The cyclic shift is determined by the following equation,

,
Wherein the ranging preamble code is determined by the following equation.

Where s _p is a cyclic shift index, N _TCS is the cyclic shift unit per OFDMA symbol in the time domain, N _FFT is the FFT size, N _RP is the length of the ranging preamble code per OFDMA symbol, , r _p is a root index of the ZC sequence, and n is an OFDMA symbol index. delete The method according to claim 1,
And the N _TCS = G * N _FFT . Here, G is a cyclic prefix (CP) ratio. delete The method according to claim 1,
Wherein the ranging preamble code has a length of 72. The method according to claim 1,
Wherein the number of the OFDMA symbols is three. The method according to claim 1,
And mapping the generated ranging preamble code to each OFDMA symbol. The method according to claim 1,
Wherein the cyclic shift unit to which the cyclic shift is applied is equal to or less than the length of the ranging preamble code. delete A radio frequency (RF) unit; And
And a processor coupled to the RF unit,
The processor comprising:
Determining a cyclic shift using a cyclic shift unit in the time domain, determined using a fast Fourier transform (FFT) size of 512, 1024 or 2048 based on the bandwidth;
Generating a Zadoff-Chu (ZC) sequence to which the cyclic shift is applied for each of a plurality of orthogonal frequency division multiple access (OFDMA) symbols as a ranging preamble code; And
And to use the ranging preamble code for periodic ranging through a synchronized ranging channel (S-RCH)
The cyclic shift is determined by the following equation,

,
Wherein the ranging preamble code is determined by the following equation.

Where s _p is a cyclic shift index, N _TCS is the cyclic shift unit per OFDMA symbol in the time domain, N _FFT is the FFT size, N _RP is the length of the ranging preamble code per OFDMA symbol, , r _p is a root index of the ZC sequence, and n is an OFDMA symbol index. delete delete 11. The method of claim 10,
Wherein the ranging preamble code has a length of 72 bits. 11. The method of claim 10,
Wherein the number of the plurality of OFDMA symbols is three. 11. The method of claim 10,
Wherein the processor is further configured to map the generated ranging preamble code to each OFDMA symbol.

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