JP5480349B2 - Pilot subcarrier allocation method in multi-antenna system - Google Patents

Description

  The present invention relates to wireless communication, and more particularly, to a method for assigning pilot subcarriers in a wireless communication system including a multiple-input multiple-output (MIMO) antenna system.

  The Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard provides techniques and protocols to support broadband wireless access. Standardization has progressed since 1999, and IEEE 802.16-2001 was approved in 2001. This is based on a single carrier physical layer called 'WirelssMAN-SC'. Thereafter, in the IEEE 802.16a standard approved in 2003, 'WirelssMAN-OFDM' and 'WirelssMAN-OFDMA' are further added to the physical layer in addition to 'WirelssMAN-SC'. After the IEEE 802.16a standard was completed, the revised IEEE 802.16-2004 standard was approved in 2004. IEEE 802.16-2004 / Cor1 was completed in 2005 in the form of 'corrigendum' to correct bugs and errors in the IEEE 802.16-2004 standard.

  MIMO (Multiple Input Multiple Output Antennas) technology improves data transmission and reception efficiency using multiple transmission antennas and multiple reception antennas. MIMO technology has been introduced from the IEEE 802.16a standard and continues to be supplemented today.

  The MIMO technology is classified into a spatial multiplexing method and a spatial diversity method. According to the spatial multiplexing method, high-speed data is transmitted without increasing the system bandwidth by simultaneously transmitting different data. According to the spatial diversity method, the reliability of data is increased by transmitting the same data through multiple transmission antennas to obtain diversity.

  The receiver needs to estimate the channel to recover the data received from the transmitter. Channel estimation refers to a process of reconstructing a transmission signal by compensating for signal distortion caused by a rapid environmental change due to fading. In general, for channel estimation, a pilot that is known to both the transmitter and the receiver is required.

  In a MIMO system, the signal passes through a channel corresponding to each antenna. Therefore, it is necessary to arrange pilots in consideration of multiple antennas. If the number of pilots increases as the number of antennas increases, this does not match the intention of increasing the data rate by increasing the number of antennas.

In the prior art, different pilot allocation structures have been designed and used for each permutation (distribution / AMC) method. This is the conventional IEEE 802.1
This is because the permutation method is separated in time in the 6e system, so that an optimized structure can be designed for each permutation. If the permutation methods coexist in time, one unified basic data allocation structure is required.

  In the prior art, the pilot overhead is serious and the transmission rate is lowered. In addition, since the same pilot structure is applied between adjacent cells and sectors, there is a risk of collision between cells and sectors. Therefore, a technique for efficiently assigning pilots in a MIMO system is desired.

  An object of the present invention is to provide a method for efficiently allocating pilot subcarriers in a wireless communication system including a MIMO system.

  The above object of the present invention can be achieved by providing a method for allocating pilot subcarriers for a plurality of antennas in a MIMO antenna system over a plurality of OFDM (Orthogonal Frequency Division Multiplexing) symbols and a plurality of subcarriers. This method assigns the same number of pilot subcarriers for multiple antennas for each OFDM symbol. These pilot subcarriers are assigned to be alternately arranged in the time domain on two adjacent OFDM symbols, forming two pilot subcarrier pairs.

  According to an embodiment of the present invention, a pilot subcarrier allocation method is provided for use in downlink and uplink communications in a MIMO antenna system using OFDM modulation. The method provides a frame structure consisting of time-domain OFDM symbols and frequency-domain subcarriers, and the following equation:

Here, _{P i} represents pilot index of the i-th antenna, k = 0, 1, ..., a _{N pilot, i = (n s} + i) a mod 2,

Represents an integer smaller than n.
Assigning pilot positions according to

  According to an embodiment of the present invention, a pilot subcarrier allocation method for use in at least one of downlink and uplink communication in a MIMO antenna system using OFDM modulation includes a time domain OFDM symbol and a frequency domain subcarrier. Providing a frame structure comprising: alternately assigning a first pilot subcarrier for a first antenna and a second pilot subcarrier for a second antenna in at least one of a time domain and a frequency domain, wherein The alternating first pilot subcarriers and second pilot subcarriers are spaced apart by multiples of a first predetermined number of subcarriers in the frequency domain, and are assigned to adjacent two OFDM symbols, and the first predetermined subcarriers are allocated. The number is nine.

  In one aspect of the present invention, each of the first pilot subcarriers separated by 2 OFDM symbol intervals is shifted by a second predetermined number of subcarrier intervals and separated by 2 OFDM symbol intervals. Are shifted by a second predetermined number of subcarrier intervals to vary the frequency selectivity, and the second predetermined number is a multiple of three. Each OFDM symbol includes the first and second pilot subcarriers. Preferably, the number of the first and second pilot subcarriers in each OFDM symbol is the same. Preferably, the second predetermined number is 3. The frame structure is used for one of uplink and downlink communication.

  In another aspect of the present invention, the method further includes alternately allocating a third pilot subcarrier for the third antenna and a fourth pilot subcarrier for the fourth antenna in the time domain and the frequency domain, where The alternating third pilot subcarrier and fourth pilot subcarrier are each spaced apart by multiples of the first predetermined number of subcarriers in the frequency domain, and assigned to two adjacent OFDM symbols. Preferably, in the frequency domain, the first pilot subcarrier is adjacent to the third pilot subcarrier, and the second pilot subcarrier is adjacent to the fourth pilot subcarrier. Preferably, the first pilot subcarrier and the third pilot subcarrier are separated by at least one subcarrier interval in the frequency domain, and the second pilot subcarrier and the fourth pilot subcarrier are at least one subcarrier in the frequency domain. Separated at intervals.

  In one aspect of the invention, the method comprises alternately allocating a fifth pilot subcarrier for a fifth antenna and a sixth pilot subcarrier for a sixth antenna in the time domain and the frequency domain, the alternating A fifth pilot subcarrier and a sixth pilot subcarrier are each spaced apart in multiples of the first predetermined number of subcarriers in the frequency domain and assigned to two adjacent OFDM symbols; time domain and frequency domain; And alternately assigning a seventh pilot subcarrier for the seventh antenna and an eighth pilot subcarrier for the eighth antenna, the alternating seventh pilot subcarrier and the eighth pilot subcarrier in the frequency domain, respectively. 2 adjacent to each other by a multiple of the first predetermined number of subcarriers. And wherein the fifth pilot sub-carrier is adjacent to the third and seventh pilot sub-carriers in the frequency domain and the third and seventh pilot sub-carriers. And the sixth pilot subcarrier is adjacent to the fourth and eighth pilot subcarriers in the frequency domain and between the fourth and eighth pilot subcarriers. In another aspect of the present invention, the fifth pilot subcarrier and the seventh pilot subcarrier are separated by at least one subcarrier interval in the frequency domain, and the sixth pilot subcarrier and the eighth pilot subcarrier are: They are separated by at least one subcarrier interval in the frequency domain.

  The frame structure may be used for a FUSC (Full Usage of Subchannels) permutation mode type. The frame structure may be used for an AMC (Adaptive Modulation and Coding) permutation mode type. Preferably, the starting position of the first pilot subcarrier of the first OFDM symbol is offset by at least one subcarrier.

  According to an embodiment of the present invention, a wireless communication system using OFDM modulation for downlink and uplink communication includes an antenna, an OFDM modulator operably coupled to the MIMO antenna, and the OFDM modulator. And an operatively coupled processor. The processor provides a frame structure consisting of time-domain OFDM symbols and frequency-domain subcarriers, and has the following formula:

Here, _{P i} represents pilot index of the i-th antenna, k = 0, 1, ..., a _{N pilot, i = (n s} + i) a mod 2,

Represents an integer smaller than n.
Is configured to assign pilot positions according to

  According to an embodiment of the present invention, an OFDM modulation is used for downlink and uplink communication, and a MIMO antenna, an OFDM modulator operably coupled to the MIMO antenna, and the OFDM modulator And a operatively coupled processor, wherein the processor provides a frame structure comprising a time-domain OFDM symbol and a frequency-domain subcarrier, and at least one of the time-domain and the frequency-domain. The first pilot subcarrier for the first antenna and the second pilot subcarrier for the second antenna are alternately assigned, wherein the alternating first pilot subcarrier and second pilot subcarrier are each in frequency Are separated by multiples of the first predetermined number of subcarriers in the region. , Assigned to the adjacent 2 OFDM symbol, the first predetermined number is nine. Preferably, each of the first pilot subcarriers separated by 2 OFDM symbol intervals is shifted by a second predetermined number of subcarrier intervals, and each of the second pilot subcarriers separated by 2 OFDM symbol intervals is Shifting at intervals of the second predetermined number of subcarriers to vary the frequency selectivity, the second predetermined number being a multiple of three.

In one aspect of the invention, the processor includes a subcarrier allocator that assigns symbols and pilots to subcarriers for use in at least one of uplink and downlink communications. The processor encodes an input stream to form a coded word, a mapper for mapping the encoded data to a symbol representing a position on a signal constellation, and And a MIMO processor for processing the symbols.
For example, the present invention provides the following.
(Item 1)
Assignment of pilot subcarriers for use in at least one of downlink and uplink communications in a multiple-input multiple-output (MIMO) antenna system using Orthogonal Frequency Division Multiplexing (OFDM) modulation A method,
Providing a frame structure comprising time-domain OFDM symbols and frequency-domain subcarriers;
The following formula:

Here, _{P i} represents pilot index of the i-th antenna, k = 0, 1, ..., a _{N pilot, i = (n s} + i) a mod 2,

Represents an integer smaller than n.
Assigning pilot positions according to
A method for assigning pilot subcarriers, comprising:
(Item 2)
A pilot subcarrier allocation method for use in at least one of downlink and uplink communications in a MIMO antenna system using OFDM modulation comprising:
Providing a frame structure comprising time-domain OFDM symbols and frequency-domain subcarriers;
Alternately allocating a first pilot subcarrier for the first antenna and a second pilot subcarrier for the second antenna in at least one of the time domain and the frequency domain;
Including
The alternating first pilot subcarriers and second pilot subcarriers are spaced apart by multiples of a first predetermined number of subcarriers in the frequency domain, and are assigned to adjacent two OFDM symbols, and the first predetermined number Is a pilot subcarrier allocation method, wherein 9 is 9.
(Item 3)
Each of the first pilot subcarriers separated by 2 OFDM symbol intervals is shifted by a second predetermined number of subcarrier intervals, and each of the second pilot subcarriers separated by 2 OFDM symbol intervals is each of a second predetermined number. 3. The pilot subcarrier allocation method according to Item 2, wherein the second predetermined number is a multiple of 3 by shifting at a subcarrier interval of the first and second frequencies.
(Item 4)
Item 3. The pilot subcarrier allocation method according to Item 2, wherein each OFDM symbol includes the first and second pilot subcarriers.
(Item 5)
Item 5. The pilot subcarrier allocation method according to Item 4, wherein the number of the first and second pilot subcarriers in each OFDM symbol is the same.
(Item 6)
Item 4. The pilot subcarrier allocation method according to Item 3, wherein the second predetermined number is three.
(Item 7)
Item 3. The pilot subcarrier allocation method according to Item 2, wherein the frame structure is used for one of uplink and downlink communications.
(Item 8)
Further comprising alternately allocating a third pilot subcarrier for the third antenna and a fourth pilot subcarrier for the fourth antenna in the time domain and the frequency domain;
The alternating third pilot subcarrier and fourth pilot subcarrier are spaced apart by multiples of the first predetermined number of subcarriers in the frequency domain, and are allocated to two adjacent OFDM symbols. 3. The pilot subcarrier allocation method according to item 2.
(Item 9)
Item 9. The pilot subcarrier of item 8, wherein in the frequency domain, the first pilot subcarrier is adjacent to the third pilot subcarrier, and the second pilot subcarrier is adjacent to the fourth pilot subcarrier. Carrier allocation method.
(Item 10)
The first pilot subcarrier and the third pilot subcarrier are separated by at least one subcarrier interval in the frequency domain, and the second pilot subcarrier and the fourth pilot subcarrier are separated by at least one subcarrier interval in the frequency domain. Item 9. The pilot subcarrier allocation method according to Item 8, wherein
(Item 11)
Alternately assigning a fifth pilot subcarrier for the fifth antenna and a sixth pilot subcarrier for the sixth antenna in the time domain and the frequency domain, wherein the alternating fifth pilot subcarrier and sixth pilot subcarrier are Respectively, spaced apart by a multiple of the first predetermined number of subcarriers in the frequency domain and assigned to two adjacent OFDM symbols;
Alternating the seventh pilot subcarrier for the seventh antenna and the eighth pilot subcarrier for the eighth antenna in the time domain and the frequency domain, wherein the alternating seventh pilot subcarrier and eighth pilot subcarrier are Respectively, spaced apart by a multiple of the first predetermined number of subcarriers in the frequency domain and assigned to two adjacent OFDM symbols;
Further including
The fifth pilot subcarrier is adjacent to the third and seventh pilot subcarriers in the frequency domain and is disposed between the third and seventh pilot subcarriers, and the sixth pilot subcarrier has a frequency of Item 10. The pilot subcarrier allocation method according to Item 9, wherein the pilot subcarrier allocation method is adjacent to the fourth and eighth pilot subcarriers in a region and is arranged between the fourth and eighth pilot subcarriers.
(Item 12)
Alternately assigning a fifth pilot subcarrier for a fifth antenna and a sixth pilot subcarrier for a sixth antenna in a time domain and a frequency domain, wherein the alternating fifth pilot subcarrier and sixth pilot subcarrier are respectively , Spaced apart by multiples of the first predetermined number of subcarriers in the frequency domain, and assigned to two adjacent OFDM symbols;
Alternating the seventh pilot subcarrier for the seventh antenna and the eighth pilot subcarrier for the eighth antenna in the time domain and the frequency domain, wherein the alternating seventh pilot subcarrier and eighth pilot subcarrier are Respectively, spaced apart by a multiple of the first predetermined number of subcarriers in the frequency domain and assigned to two adjacent OFDM symbols;
Further including
The fifth pilot subcarrier and the seventh pilot subcarrier are separated by at least one subcarrier interval in the frequency domain, and the sixth pilot subcarrier and the eighth pilot subcarrier are at least one subcarrier interval in the frequency domain. 11. The pilot subcarrier allocation method according to item 10, wherein the pilot subcarrier allocation method is characterized in that:
(Item 13)
Item 3. The pilot subcarrier allocation method according to Item 2, wherein the frame structure is used for a FUSC (Full Usage of Subchannels) permutation mode type.
(Item 14)
The above frame structure is AMC (Adaptive Modulation and Coding) permutation
3. The pilot subcarrier allocation method according to item 2, wherein the pilot subcarrier allocation method is used for a transmission mode type.
(Item 15)
3. The pilot subcarrier allocation method according to item 2, wherein the start position of the first pilot subcarrier of the first OFDM symbol is offset by at least one subcarrier.
(Item 16)
Orthogonal frequency division multiplexing (OFDM) for downlink and uplink communications
A wireless communication system using Frequency Division Multiplexing modulation,
A multiple-input multiple-output (MIMO) antenna;
An OFDM modulator operably coupled to the MIMO antenna;
A processor operably coupled to the OFDM modulator;
Including
The processor provides a frame structure consisting of time-domain OFDM symbols and frequency-domain subcarriers, and has the following formula:

Here, _{P i} represents pilot index of the i-th antenna, k = 0, 1, ..., a _{N pilot, i = (n s} + i) a mod 2,

Represents an integer smaller than n.
A wireless communication system, configured to assign pilot positions according to:
(Item 17)
A wireless communication system using OFDM modulation,
MIMO antenna,
An OFDM modulator operably coupled to the MIMO antenna;
A processor operably coupled to the OFDM modulator;
Including
The processor provides a frame structure comprising a time domain OFDM symbol and a frequency domain subcarrier, and a first pilot subcarrier for the first antenna and a second for the second antenna in at least one of the time domain and the frequency domain. Two pilot subcarriers are alternately assigned, wherein the alternating first pilot subcarriers and second pilot subcarriers are each separated by a multiple interval of a first predetermined number of subcarriers in the frequency domain; The wireless communication system, wherein the first predetermined number is 9 assigned to two adjacent OFDM symbols.
(Item 18)
Each of the first pilot subcarriers separated by 2 OFDM symbol intervals is shifted by a second predetermined number of subcarrier intervals, and each of the second pilot subcarriers separated by 2 OFDM symbol intervals is Item 18. The wireless communication system according to Item 17, wherein the second predetermined number is a multiple of 3 by shifting at intervals of a predetermined number of subcarriers to change the frequency selectivity.
(Item 19)
Item 18. The wireless communication system according to Item 17, wherein each OFDM symbol includes the first and second pilot subcarriers.
(Item 20)
Item 20. The wireless communication system according to Item 19, wherein the number of the first and second pilot subcarriers in each OFDM symbol is the same.
(Item 21)
Item 19. The wireless communication system according to Item 18, wherein the second predetermined number is three.
(Item 22)
Item 18. The wireless communication system according to Item 17, wherein the frame structure is used for one of uplink and downlink communication.
(Item 23)
The third pilot subcarrier for the third antenna and the fourth pilot subcarrier for the fourth antenna are alternately assigned in the time domain and the frequency domain, where the alternating third pilot subcarrier and fourth pilot subcarrier are respectively Item 20 is further characterized in that the subcarrier divider is further configured to be allocated to two adjacent OFDM symbols separated by a multiple interval of the first predetermined number of subcarriers in the frequency domain. Wireless communication system.
(Item 24)
24. The wireless communication of item 23, wherein, in the frequency domain, the first pilot subcarrier is adjacent to the third pilot subcarrier, and the second pilot subcarrier is adjacent to the fourth pilot subcarrier. system.
(Item 25)
The first pilot subcarrier and the third pilot subcarrier are separated by at least one subcarrier interval in the frequency domain, and the second pilot subcarrier and the fourth pilot subcarrier are separated by at least one subcarrier interval in the frequency domain. Item 24. The wireless communication system according to Item 23.
(Item 26)
The subcarrier allocator further includes:
In the time domain and the frequency domain, the fifth pilot subcarrier for the fifth antenna and the sixth pilot subcarrier for the sixth antenna are alternately assigned, where the alternating fifth pilot subcarrier and sixth pilot subcarrier are Respectively spaced apart by multiples of the first predetermined number of subcarriers in the frequency domain, and assigned to two adjacent OFDM symbols,
In the time domain and the frequency domain, the seventh pilot subcarrier for the seventh antenna and the eighth pilot subcarrier for the eighth antenna are alternately assigned, but the iron, the seventh pilot subcarrier and the eighth pilot subcarrier are alternately arranged. Are spaced apart by multiples of the first predetermined number of subcarriers in the frequency domain and are assigned to two adjacent OFDM symbols,
The fifth pilot subcarrier is adjacent to the third and seventh pilot subcarriers in the frequency domain and is disposed between the third and seventh pilot subcarriers, and the sixth pilot subcarrier is arranged in the frequency domain. 25. The wireless communication system according to item 24, wherein the wireless communication system is adjacent to the fourth and eighth pilot subcarriers and disposed between the fourth and eighth pilot subcarriers.
(Item 27)
The subcarrier allocator further includes:
In the time domain and the frequency domain, the fifth pilot subcarrier for the fifth antenna and the sixth pilot subcarrier for the sixth antenna are alternately assigned, where the alternating fifth pilot subcarrier and sixth pilot subcarrier are Respectively spaced apart by multiples of the first predetermined number of subcarriers in the frequency domain, and assigned to two adjacent OFDM symbols,
In the time domain and the frequency domain, the seventh pilot subcarrier for the seventh antenna and the eighth pilot subcarrier for the eighth antenna are assigned alternately, where the alternating seventh pilot subcarrier and eighth pilot subcarrier are Respectively spaced apart by multiples of the first predetermined number of subcarriers in the frequency domain and configured to be assigned to two adjacent OFDM symbols,
The fifth pilot subcarrier and the seventh pilot subcarrier are separated by at least one subcarrier interval in the frequency domain, and the sixth pilot subcarrier and the eighth pilot subcarrier are at least one subcarrier interval in the frequency domain. 26. The wireless communication system according to item 25, wherein the wireless communication system is separated by
(Item 28)
Item 18. The wireless communication system according to Item 17, wherein the frame structure is used for a FUSC permutation mode type.
(Item 29)
Item 18. The wireless communication system according to Item 17, wherein the frame structure is used for an AMC permutation mode type.
(Item 30)
Item 18. The wireless communication system according to Item 17, wherein the start position of the first pilot subcarrier of the first FDM symbol is offset by at least one subcarrier.
(Item 31)
Item 18. The wireless communication system of item 17, wherein the processor includes a subcarrier allocator that assigns symbols and pilots to subcarriers for use in at least one of uplink and downlink communications.
(Item 32)
The processor
Encodes input stream to form encoded data (coded word)
A channel encoder to
A mapper for mapping the encoded data to a symbol representing a position on a signal constellation;
A MIMO processor for processing the symbols;
Item 32. The wireless communication system according to Item 31, further comprising:

The accompanying drawings are included to provide an additional understanding of the invention, and illustrate embodiments of the invention together with the description provided to illustrate the principles of the invention.
FIG. 3 is a block diagram illustrating a transmitter having multiple antennas. It is a block diagram which shows the receiver which has a multiple antenna. It is a figure which shows an example of a frame structure. It is an illustration figure which shows the pilot arrangement | positioning with respect to 2 transmission antennas in PUSC. It is an illustration figure which shows the pilot arrangement | positioning with respect to 2 transmission antennas by FUSC. It is an example figure which shows the pilot arrangement | positioning with respect to 4 transmission antennas in PUSC. It is an illustration figure which shows the pilot arrangement | positioning with respect to 4 transmission antennas by FUSC. It is a graph which shows each case of Table 2 by the ratio of a pilot overhead, and the ratio of a protection subcarrier. It is an illustration figure showing an example of pilot arrangement to two transmitting antennas. It is an illustration figure which shows an example of the pilot arrangement | positioning with respect to 4 transmission antennas. It is the illustration figure which formulated the pilot arrangement | positioning with respect to 3 or 4 transmission antennas. It is an illustration figure which shows the other example of the pilot arrangement | positioning with respect to 2 transmission antennas. It is an illustration figure which shows the further another example of pilot arrangement | positioning with respect to 2 transmission antennas. It is an illustration figure which shows the other example of the pilot arrangement | positioning with respect to 4 transmission antennas. It is an illustration figure which shows the further another example of the pilot arrangement | positioning with respect to 4 transmission antennas. FIG. 4 is a diagram illustrating a pilot subcarrier allocation structure in a system using eight antennas according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a pilot subcarrier allocation structure in a system using eight antennas according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a pilot subcarrier allocation structure in a system using eight antennas according to an embodiment of the present invention. It is a figure which shows embodiment which allocates a different pilot subcarrier allocation offset for every cell with a 4Tx system and an 8Tx system, respectively. It is a figure which shows embodiment which allocates a different pilot subcarrier allocation offset for every cell with a 4Tx system and an 8Tx system, respectively. It is a figure which shows the other Example with respect to 8Tx system shown in FIG. FIG. 6 is a diagram illustrating a pilot subcarrier allocation pattern according to another embodiment of the present invention. FIG. 4 is a diagram illustrating a pattern for assigning pilot subcarriers in a 2Tx system according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a pattern for assigning pilot subcarriers in a 2Tx system according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a pattern for assigning pilot subcarriers in a 2Tx system according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a pattern for assigning pilot subcarriers in a 4Tx system according to an embodiment of the present invention; FIG. 4 is a diagram illustrating a pattern for assigning pilot subcarriers in a 4Tx system according to an embodiment of the present invention; FIG. 4 is a diagram illustrating a pattern for assigning pilot subcarriers in a 4Tx system according to an embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same components are denoted by the same reference numerals.

  The following techniques can be used in various wireless communication systems. Wireless communication systems are widely deployed to provide various communication services such as voice and packet data. This technique can be used for downlink or uplink. In general, the downlink means communication from a base station (BS) to a user equipment (UE), and the uplink means communication from the terminal to the base station. A base station usually refers to a fixed station that communicates with a terminal, and may also be referred to as a node B (node-B), a BTS (base transceiver system), an access point, or the like. A terminal can be fixed or mobile, and can also be referred to as terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device.

  In the following, an efficient pilot structure for a new system is proposed. The example of the new system will be described mainly as an IEEE 802.16m system, but can be applied to other systems by the same principle.

  The communication system may be a multiple-input multiple-output (MIMO) system or a multiple-input single-output (MISO) system. The MIMO system uses a plurality of transmission antennas and a plurality of reception antennas. The MISO system uses a plurality of transmission antennas and one reception antenna.

  FIG. 1 is a block diagram illustrating a transmitter having multiple antennas. Referring to FIG. 1, the transmitter 100 includes a channel encoder 120, a mapper 130, a MIMO processor 140, a subcarrier allocator 150, and an OFDM modulator 160.

  The channel encoder 120 encodes an input stream according to a predetermined coding method, and generates encoded data (coded word). The mapper 130 maps the encoded data as a symbol representing a position on a signal constellation. The modulation scheme in the mapper 130 is not limited and can be m-PSK (m-Phase Shift Keying) or m-QAM (m-Quadrature Amplitude Modulation).

  The MIMO processor 140 processes the input symbol by the MIMO scheme using the transmission antennas 190-1,..., 190-Nt. For example, the MIMO processor 140 may perform precoding based on a code book.

  Subcarrier allocator 150 assigns input symbols and pilots to subcarriers. The pilot is arranged for each transmission antenna 190-1,..., 190-Nt. The pilot is a signal known to both the transmitter 100 and the receiver (200 in FIG. 2) used for channel estimation or data demodulation, and is also referred to as a reference signal. The OFDM modulator 160 performs OFDM modulation on the input symbol and outputs an OFDM symbol.

  The OFDM modulator 160 can perform an IFFT (Inverse Fast Fourier Transform) on the input symbol, and can further insert a CP (Cyclic prefix) after performing the IFFT. The OFDM symbol is transmitted from each of the transmission antennas 190-1, ..., 190-Nt.

  FIG. 2 is a block diagram illustrating a receiver having multiple antennas. Referring to FIG. 2, the receiver 200 includes an OFDM demodulator 210, a channel estimator 220, a MIMO post-processor 230, a demapper 240, and a channel decoder 250.

  Signals received from the receiving antennas 290-1,..., 290 -Nr are subjected to FFT (fast Fourier transform) by the OFDM demodulator 210. Channel estimator 220 estimates the channel using the pilot. The MIMO post-processor 230 performs post-processing corresponding to the MIMO processor 140. The demapper 240 demaps the input symbols to the encoded data, and the channel decoder 250 decodes the encoded data to restore the original data.

  FIG. 3 is a diagram illustrating an example of a frame structure. A frame is a sequence of data for a fixed time used by physical specifications. This may be referred to section 8.4.4.2 of IEEE standard 802.16-2004 “Part 16: Air Interface for Fixed Broadband Wireless Access systems” (hereinafter referred to as Reference 1).

Referring to FIG. 3, the frame includes a downlink (DL) frame and an uplink (UL) frame. Time Division Duplex is a scheme in which uplink and downlink transmissions share the same frequency but occur at different times. The downlink frame is earlier in time than the uplink frame. The downlink frame starts in the order of preamble, FCH (Frame Control Header), DL (Downlink) -MAP, UL (Uplink) -MAP, and burst region. The guard time for distinguishing between uplink and downlink frames is the middle part of the frame (between the downlink and uplink frames) and the last part (the part following the uplink frame). Inserted into. TTG (transmit / receive transition gap) is a gap between a downlink burst and a subsequent uplink burst. RTG (receive / transmit transition gap) is a gap between an uplink burst and a subsequent downlink burst.

  The preamble is used for initial synchronization, cell search, frequency offset and channel estimation between the base station and the terminal. The FCH includes the length of the DL-MAP message and DL-MAP coding scheme information. DL-MAP is an area in which a DL-MAP message is transmitted. The DL-MAP message defines the downlink channel connection. The DL-MAP message includes a configuration change count of DCD (Downlink Channel Descriptor) and a base station ID (identifier). The DCD describes a downlink burst profile that is applied to the current map. The downlink burst profile means a characteristic of a downlink physical channel, and the DCD is periodically transmitted by the base station through the DCD message.

  UL-MAP is an area where UL-MAP messages are transmitted. The UL-MAP message defines the uplink channel connection. The UL-MAP message includes a configuration change count of UCD (Uplink Channel Descriptor) and the effective start time of uplink allocation defined by UL-MAP. UCD describes an uplink burst profile. The uplink burst profile refers to the characteristics of the uplink physical channel, and the UCD is periodically transmitted by the base station through the UCD message.

  In the following, a slot is the smallest possible data allocation unit and is defined by time and subchannel. The number of subchannels follows the FFT size and time-frequency mapping. A subchannel includes a plurality of subcarriers, and the number of subcarriers per subchannel varies depending on a permutation scheme. Permutation means mapping logical subchannels to physical subcarriers. In FUSC (Full Usage of Subchannels), the subchannel includes 48 subcarriers, and in PUSC (Partial Usage of Subchannels), the subchannel includes 24 or 16 subcarriers. A segment refers to a set of at least one subchannel.

  In order to map data to physical subcarriers in the physical layer, there are generally two steps. In its first stage, data is mapped to at least one data slot on at least one logical subchannel. In the second stage, each logical subchannel is mapped to a physical subcarrier. This is called permutation. Reference literature 1 discloses permutation schemes such as FUSC, PUSC, O-FUSC (Optimal-FUSC), O-PUSC (Optional-PUSC), and AMC (Adaptive modulation and Coding). A set of OFDM symbols in which the same permutation scheme is used is called a permutation zone, and one frame includes at least one permutation region.

  FUSC and O-FUSC are only used for downlink transmission. The FUSC is composed of one segment including all subchannel groups. Each subchannel is mapped to physical subcarriers distributed throughout the entire physical channel. This mapping varies for each OFDM symbol. A slot is composed of one subchannel on one OFDM symbol. O-FUSC may have a different pilot allocation scheme than FUSC.

  PUSC is used for both downlink and uplink transmissions. On the downlink, each physical channel is partitioned into clusters composed of 14 contiguous subcarriers over 2 OFDM symbols. Physical channels are mapped in units of 6 groups. Within each group, pilots are assigned to fixed positions in each cluster. In the uplink, the subcarrier is divided into tiles composed of 4 adjacent physical subcarriers on 3 OFDM symbols. The subchannel includes 6 tiles. Pilots are assigned to the corners of each tile. O-PUSC is used only for uplink transmission, and a tile is composed of 3 contiguous physical subcarriers over 3 OFDM symbols. The pilot is assigned to the center of the tile.

  4 is an exemplary diagram illustrating pilot arrangement for two transmission antennas in PUSC, FIG. 5 is an exemplary diagram illustrating pilot arrangement for two transmission antennas in FUSC, and FIG. 6 is a pilot arrangement for four transmission antennas in PUSC. FIG. 7 is a diagram illustrating pilot arrangement for four transmission antennas in FUSC. These are the IEEE standard 802.16-2004 / Cor1-2005 “Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access systems; Amendment 2: Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands and Corrigendum 1 (Hereinafter referred to as Reference 2), sections 8.4.8.1.2.1.1, 8.4.8.1.2.1.2, 8.4.8.2.1, and 8.4.8.2.2, respectively.

  Referring to FIGS. 4 to 7, pilot overhead is large when subcarriers are allocated such as PUSC and FUSC. In particular, when one transmission antenna is used, overhead is more serious than two or more transmission antennas when considering pilot overhead per transmission antenna.

  Table 1 shows pilot overhead according to the number of transmission antennas in each permutation scheme.

Here, the pilot overhead is a value obtained by dividing the number of subcarriers allocated to the pilot by the number of total subcarriers used. The value in parentheses represents the pilot overhead per transmit antenna. Moreover, according to Reference 2, when 4 or 3 transmit antennas are used, data is mapped to subchannels after puncturing or truncation is performed on channel-coded data. The problem arises.

Next, a pilot structure according to the present invention for multiple antennas will be described. The design criteria for the optimal pilot structure are as follows:
(1) The pilot overhead in a single antenna is about 4 to 9% in the time-frequency domain. (2) One slot may include 48 subcarriers on 2 adjacent OFDM symbols. (3) The pilot subcarriers are distributed as uniformly as possible in the time-frequency domain. (4) The pilot overhead per transmission antenna is maintained in substantially the same manner, and the overall pilot overhead increases in proportion to the increase in transmission antennas. However, when considering the total pilot overhead, if there are three or more transmission antennas, the total pilot overhead is kept the same so as not to exceed 20%.

  (5) Even if the number of transmission antennas is increased, the data mapping to the subchannel is not affected.

In order to derive a possible candidate group using the above conditions, the requirements can be expressed by mathematical formulas as follows, and a candidate group that satisfies this requirement may be derived.
(1) (Nused-2 * Np) mod Nsub = 0
(2) (Nused-2 * Np) mod Nsub = 0
(3) (Nused-Np) mod Nsub = 0
(4) 0.04 <= Np <= 0.09
(5) Ng = Nfft-Nused-1 (DC subcarrier)
(6) (Nused-Np) / Nsub.sym> = Nsch.pusc
Where Nused is the number of subcarriers used, Np is the number of pilot subcarriers, Ng is the number of guard subcarriers, Nfft is the size of FFT, Nsub is the number of subcarriers per subchannel, and Nsub.sym Is the number of subcarriers allocated to the subchannel on one OFDM symbol, and Nsch.pusc is the number of subchannels that can be generated by the existing DL-PUSC.

  Table 2 shows 26 candidate groups according to the above design criteria.

A usable subcarrier (Used SC), a pilot subcarrier (Pilot SC), and a guard subcarrier (Guard SC) are obtained according to the FFT size, and a subchannel based on the number of transmission antennas is obtained. Here, usable subcarriers are values excluding DC subcarriers. For example, in case (1), the number of subchannels in one transmission antenna is (number of usable subcarriers−number of pilot subcarriers) / (number of subcarriers allocated to subchannels on one OFDM symbol) ) = 1656−72 / 24 = 66.

  FIG. 8 is a graph showing each case of Table 2 as a ratio of pilot overhead and a ratio of guard subcarriers.

  Referring to FIG. 8, among cases (1) to (26) shown in Table 2, when considering the system bandwidth or the resulting FFT size, it is most suitable with the same design criteria for 5 to 20 MHz or 512 to 2048 FFT. The cases are (10), (22) and (26). In Table 2, cases (10), (22), and (26) all have a pilot interval of 9. That is, in one embodiment of the present invention, it is proposed to arrange pilots at 9 subcarrier intervals.

  Table 3 shows the proposed subcarrier allocation.

Subchannels are mapped to the remaining subcarriers of the subcarriers used after assigning pilot subcarriers. At this time, a normal PUSC or FUSC permutation method can be applied.

  According to the proposed method, it is possible to obtain a yield improvement of about 6 to 13% in PUSC / FUSC. For example, according to the prior art, 60 subchannels can be obtained by PUSC and 64 subchannels can be obtained by FUSC, but 68 subchannels can be obtained by the proposed scheme. In addition, when a new permutation method is applied in consideration of multiple antennas, performance degradation due to data puncturing or truncation can be prevented.

  The mathematical formula shown in Pilot Subcarrier Index in Table 3 represents the pilot index Pi of the i-th antenna. This can also be shown by the following mathematical formula 1.

Where k = 0,1, ..., Npilot, mi = (ns + i) mod2, i = 0,1

Represents an integer smaller than n.

  In Equation 1, the factor '18' means that the subcarrier of the subchannel on one OFDM symbol is 18, and the factor '9' means that the pilot subcarriers are arranged at 9 subcarrier intervals. In addition, the factor “3” means that it is shifted by a slot interval of 3 subcarriers.

  FIG. 9 is an exemplary diagram illustrating an example of pilot arrangement for two transmission antennas. Referring to FIG. 9, one slot includes 72 subcarriers on two adjacent OFDM symbols, and on one OFDM symbol, a pilot subcarrier and a second antenna (antenna 1) for the first antenna (antenna 0). Pilot subcarriers for are arranged at 9 subcarrier intervals. In addition, the pilot subcarrier for the first antenna (antenna 0) and the pilot subcarrier for the second antenna (antenna 1) are alternately (switched) in the first OFDM symbol and the second OFDM symbol.

  In the second slot, the pilot subcarriers are arranged by shifting the pilot subcarriers allocated to the first slot by 3 subcarriers as a whole. In the third slot, the pilot subcarriers are arranged by shifting the pilot subcarriers allocated in the second slot by 3 subcarriers as a whole. As a result, the same pilot arrangement is repeated every three slots.

  In a pilot arrangement, pilots can be moved at regular intervals in the time domain or in the frequency domain, and thus have no absolute position. While maintaining the pilot subcarrier spacing, it can be shifted as a whole by a fixed time interval and / or subcarrier spacing.

  FIG. 10 is an exemplary diagram showing an example of pilot arrangement for four transmission antennas. Referring to FIG. 10, pilot subcarriers for four transmit antennas are adjacent in the frequency domain or time domain. The pilot subcarriers for each transmit antenna are arranged at 12 subcarrier intervals.

  In the second slot, the pilot subcarriers are arranged by shifting the pilot subcarriers allocated to the first slot by 6 subcarriers as a whole. As a result, the same pilot arrangement is repeated every two slots.

  In the case of four transmission antennas, since the number of pilots is larger than that of two transmission antennas, the pilot interval is made wider than the pilot arrangement of two transmission antennas, and the cycle period of repeated slots is reduced.

FIG. 11 is an exemplary diagram in which pilot arrangements for three or four transmission antennas are formulated. Referring to FIG. 11, G ₀ , G ₁ , G ₂ , and G ₃ are respectively defined in a 2 × 2 region including 2 OFDM symbols (i = 0, 1) and 2 subcarriers.

  In the case of 4 transmitting antennas, pilot subcarriers are arranged as shown in Table 4 below. This is similar to the arrangement of FIG.

In the case of three transmitting antennas, pilot subcarriers are arranged as shown in Table 5 below.

To formulate the pilot arrangement for four transmit antennas, six pilot subcarrier sets P ⁱ ₀ , P ⁱ ₁ , P ⁱ ₂ , P ⁱ ₃ , P ⁱ ₄ , on each OFDM symbol (i = 0, 1) Consider P ⁱ ₅ and P ⁱ ₆ . At this time, it can be shown as in Table 6 below.

here,

It is. Accordingly, the pilot subcarrier set can be mapped to the four pilot subcarriers G ₀ , G ₁ , G ₂ , and G ₃ in one slot as shown in Equation 2 below.

Here, i = 0,1.

  The proposed pilot structure has a pilot overhead that satisfies the design criteria, and can reduce the overhead by 5% or more compared to the prior art. The pilot overhead is only 5.55% for 2 transmit antennas, 5.55% for 3 transmit antennas, and 4.16% for 4 transmit antennas.

  Also, even if the number of transmission antennas increases, the permutation scheme can be simplified without affecting the data mapping to the subchannel.

  In the case of the distributed subchannel generation scheme used in the existing IEEE 802.16-2004 standard, pilot subcarriers for the first antenna and the second antenna are first allocated, and the remaining subcarriers are used for subchannels. Configure. In the case of the third antenna and the fourth antenna, pilot subcarriers are allocated and used through the allocated subchannels, so that the same number of subchannels are always used regardless of the number of antennas. However, according to the proposed pilot structure, at the time of pilot allocation, only a necessary amount can be allocated according to the number of antennas, and a subchannel can be configured using the remaining portion. Therefore, it has the advantage of increasing the number of subchannels while optimizing the pilot overhead.

  FIG. 12 is an exemplary diagram showing another example of pilot arrangement for two transmission antennas. Referring to FIG. 12, pilot subcarriers for one antenna are arranged at 9 subcarrier intervals on one OFDM symbol. That is, pilot subcarriers for the first antenna (antenna 0) are arranged at 9 subcarrier intervals on the first OFDM symbol, and pilot subcarriers for the second antenna (antenna 1) are arranged on the second OFDM symbol. Arranged at 9 subcarrier intervals.

  In the second slot, the pilot subcarriers are arranged by shifting the pilot subcarriers allocated to the first slot by 3 subcarriers as a whole. In the third slot, the pilot subcarriers are arranged by shifting the pilot subcarriers allocated to the second slot by 3 subcarriers as a whole. As a result, the same pilot arrangement is repeated every three slots.

  FIG. 13 is an exemplary diagram showing still another example of pilot arrangement for two transmission antennas.

  Referring to FIG. 13, the arrangement of pilot subcarriers in one slot is the same as that of the embodiment of FIG. However, in the second slot, the pilot subcarriers are arranged by shifting the pilot subcarriers allocated to the first slot by 4 subcarriers as a whole. As a result, the same pilot arrangement is repeated every two slots.

  Referring to FIG. 14, pilot subcarriers for each transmission antenna (antenna 0 to antenna 3) are arranged at intervals of 12 subcarriers, and frequency slots are arranged in units of 2 OFDM symbols for each slot. In the second slot, the pilot subcarriers are arranged by shifting the pilot subcarriers allocated to the first slot by 6 subcarriers as a whole. As a result, the same pilot arrangement is repeated every two slots.

  FIG. 15 is an exemplary diagram showing still another example of pilot arrangement for four transmission antennas (antenna 0 to antenna 3). Referring to FIG. 15, the pilot subcarriers for each antenna are arranged at intervals of 12 subcarriers, and the pilot subcarriers for each antenna are alternately arranged between two adjacent OFDM symbols within one slot. Is done. By alternately arranging two pilot subcarriers in two adjacent OFDM symbols, that is, by equally arranging pilot subcarriers for each antenna in one OFDM symbol, the transmission power for each antenna is balanced for a certain period of time. be able to. In FIG. 15, two pilot subcarriers for each two antennas form a pair, and the two pairs of pilot subcarriers are alternately arranged in two OFDM symbols.

  In the following, an effective pilot allocation structure according to another embodiment of the present invention is proposed. A structure is proposed that avoids collision between pilots by effectively shifting and allocating pilot structures between neighboring cells.

  In the embodiment of the present invention described below, the case where the basic resource block unit is composed of 18 subcarriers (vertical axis) * 6 OFDM symbols (horizontal axis) will be described. However, the pilot subcarrier allocation method according to the present embodiment can be applied by extending the same method to a subframe or the entire frame even when the basic resource block unit is different from the above.

  In the following embodiments, the horizontal axis indicates a set of time domain OFDM symbols, and the vertical axis indicates a frequency domain subcarrier. P1, P2, P3, P4, P5, P6, P7, and P8 indicate pilot subcarriers corresponding to the antennas 1, 2, 3, 4, 5, 6, 7, and 8, respectively.

  16 to 18 are diagrams illustrating pilot subcarrier allocation structures in a system using eight antennas according to an embodiment of the present invention. As shown in FIGS. 16 to 18, the pilot (P1) of the first transmitting antenna and the pilot (P2) of the second transmitting antenna, the pilot (P3) of the third transmitting antenna and the pilot (P4) of the fourth transmitting antenna, The pilot of the fifth transmitting antenna (P5) and the pilot of the sixth transmitting antenna (P6), and the pilot of the seventh transmitting antenna (P7) and the pilot of the eighth transmitting antenna (P8) are each on two OFDM symbols. Assigned next to each other. On the frequency axis, a structure is proposed in which pilot subcarriers for each antenna are continuously allocated at intervals of 18 subcarriers. That is, pilot subcarriers are allocated at subchannel intervals composed of 18 subcarriers.

  In particular, FIG. 16 shows a pilot pattern allocated by shifting by 2 subcarrier intervals in units of 2 OFDM symbols, and FIG. 17 shows a pilot pattern allocated by shifting by 6 subcarrier intervals in units of 2 OFDM symbols, FIG. 18 shows a pilot pattern allocated by shifting by 2 subcarrier intervals in units of 2 OFDM symbols, similar to FIG. 17, but with an additional 1 subcarrier offset.

  In one aspect of the present invention, a pilot subcarrier for an antenna is assigned to each OFDM symbol, and this pilot subcarrier pattern is assigned by shifting at a constant interval in units of 2 OFDM symbols. In another aspect of the present invention, the pilots for the eight transmit antennas can be all allocated adjacently as shown in FIGS. 16-18, but with constant subcarrier spacing for each antenna or for each pilot pair. You can also assign to shift.

Such pilot allocation can always have the same allocation structure regardless of whether a general subframe (regular subframe) / irregular subframe (irregular subframe). In addition, the pilots allocated according to the present embodiment may be used by distinguishing a part as a common pilot and a part as a dedicated pilot. Also, all assigned pilots can be applied as dedicated pilots, and conversely, all pilots can be applied as common pilots. The important point in such an embodiment is that pilots of all antennas are uniformly allocated in one OFDM symbol in order to achieve power balancing by antenna for each OFDM symbol. In the pilot subcarrier allocation method according to the above-described embodiments, a shift offset for pilot allocation can be applied for each cell.

  FIGS. 19 and 20 are diagrams for describing embodiments in which different pilot subcarrier allocation offsets are assigned to each cell in the 4Tx system and the 8Tx system, respectively. In particular, FIG. 19 illustrates a case where different pilot subcarrier allocation offsets are set for each of cell A, cell B, and cell C in a 4Tx system, and FIG. A case where different pilot subcarrier allocation offsets are set for each of B and cell C is shown.

  That is, different pilot allocation structures can be applied to the cells A, B, and C. The applied shift offset value can be a number in the 1-18 subcarrier range. Here, 18 subcarriers correspond to the size of the basic resource block.

  This shift offset value can be an integral multiple of the size of the basic resource block, if necessary. In the present embodiment, the case where the shift is applied to the frequency axis has been described. However, the present invention can also be applied to the time axis.

  When the above principle is extended and applied when there are three or more adjacent cells, the structure shown in FIGS. 19 and 20 can be used repeatedly, or shifted by a certain subcarrier offset or a certain OFDM symbol offset. Can be applied.

  FIG. 21 is a diagram showing another embodiment of the 8Tx system shown in FIG. FIG. 22 is a diagram illustrating a pilot subcarrier allocation pattern according to another embodiment of the present invention.

  In the case of 8 transmission antennas, the overhead problem can be solved by assigning only the antennas 1, 2, 3, and 4 instead of assigning pilots to all eight antennas in consideration of the problem of pilot overhead. As an example, such a pilot allocation structure can be applied to the SFBC-CDD method. Such an embodiment is shown in FIG. In the pilot allocation pattern shown in FIG. 22, the method of shifting and using the pilot pattern between adjacent cells is as described in the above embodiment.

  23 to 25 are diagrams illustrating patterns for assigning pilot subcarriers in a 2Tx system according to still another embodiment of the present invention. The principle according to the above-described embodiment is basically applied to the pilot patterns shown in FIGS. That is, the pilot subcarrier for the first antenna and the pilot subcarrier for the second antenna make a pair and are arranged adjacent to each other in two adjacent OFDM symbol regions. In addition, pilots for all antennas are included in each OFDM symbol region. This is because the transmission power allocated to each antenna at a specific time is set evenly.

  Also, each pilot subcarrier pair is preferably assigned at 9 subcarrier intervals. This is to obtain the optimal granularity for each pilot subcarrier allocation, taking into account the correlation bandwidth. Note that a pair of pilot subcarriers for the first antenna and pilot subcarriers for the second antenna are allocated with a shift of a certain subcarrier in units of 2 OFDM symbols. 23 and 24 show a case where the constant subcarrier interval to be shifted is 3 subcarrier intervals (specifically, the case where the subcarrier index is increased by 3 subcarriers), the constant subcarrier interval to be shifted is shown. Can be an integer multiple of 3 subcarriers (eg, 6 subcarrier spacing) and can be applied to reduce the index by 3 subcarrier indices.

  As described above, the reason for setting the frequency domain shift as 3 subcarrier intervals or subcarrier intervals corresponding to multiples of 3 is that each pilot subcarrier is allocated in units of 9 subcarrier intervals, and thus at a constant period. This is because the pilot subcarrier allocation pattern is repeated. The pilot patterns shown in FIGS. 23 to 25 can be repeatedly applied to the time / frequency domain in a frame or subframe. Further, the position of the pilot with respect to the antenna 1 and the position of the pilot with respect to the antenna 2 may be interchanged without departing from the principle of the present embodiment.

When the pilot allocation structure shown in FIG. 23 is used, the pilot allocation index for each antenna is specifically shown as follows.
<Pilot allocation index for Fig. 23>
Antenna 1-
18k + 1 when s is 0
18k + 10 when s is 1
18k + 4 when s is 2
18k + 13 when s is 3
18k + 7 when s is 4
18k + 16 when s is 5
Antenna 2-
18k + 10 when s is 0
18k + 1 when s is 1
18k + 13 when s is 2
18k + 4 when s is 3
18k + 16 when s is 4
18k + 7 when s is 5
k: subcarrier index (k = 0, 1, ...),
s: [OFDM symbol index] mod 6
(OFDM symbol index = 0,1,2, ...)
In addition, when the pilot allocation structure shown in FIG. 24 is used, the pilot allocation index for each antenna is specifically shown as follows.
<Pilot allocation index for Fig. 24>
Antenna 1-
18k when s is 0
18k + 9 when s is 1
18k + 3 when s is 2
18k + 12 when s is 3
18k + 6 when s is 4
18k + 15 when s is 5
Antenna 2-
18k + 9 when s is 0
18k when s is 1
18k + 12 when s is 2
18k + 3 when s is 3
18k + 15 when s is 4
18k + 6 when s is 5
k: subcarrier index (k = 0, 1, ...),
s: [OFDM symbol index] mod 6
(OFDM symbol index = 0,1,2, ..)
In addition, when the pilot allocation structure shown in FIG. 25 is used, the pilot allocation index for each antenna is specifically shown as follows.
<Pilot allocation index for Fig. 25>
Antenna 1 -18k when s is 0
18k + 9 when s is 1
18k + 6 when s is 2
18k + 15 when s is 3
18k + 3 when s is 4
18k + 12 when s is 5
Antenna 2-
18k + 9 when s is 0
18k when s is 1
18k + 15 when s is 2
18k + 6 when s is 3
18k + 12 when s is 4
18k + 3 when s is 5
k: subcarrier index (k = 0, 1, ..),
s: [OFDM symbol index] mod 6
(OFDM symbol index = 0,1,2, ..)
In the pilot allocation structure according to the above-described embodiment, when a preamble OFDM symbol is transmitted at a constant period at the beginning of a subframe, the pilot subcarrier can be changed to a form applied from the second OFDM symbol.

  Meanwhile, FIGS. 26 and 27 are diagrams illustrating patterns for assigning pilot subcarriers in a 4Tx system according to still another embodiment of the present invention. 26 and 27, the basic pilot allocation method is as described in the above embodiment. However, in this embodiment, pilot subcarriers for four antennas can be allocated so as to be adjacent in adjacent 4 OFDM symbol regions.

Further, in the case of having the pilot allocation structure shown in FIG. 26, the pilot allocation index for each antenna is specifically shown as follows.
<Pilot allocation index for Fig. 26>
Antenna 1-
18k + 1 when s is 0
18k + 10 when s is 1
18k + 4 when s is 2
18k + 13 when s is 3
18k + 7 when s is 4
18k + 16 when s is 5
Antenna 2-
18k + 10 when s is 0
18k + 1 when s is 1
18k + 13 when s is 2
18k + 4 when s is 3
18k + 16 when s is 4
18k + 7 when s is 5
k: subcarrier index (k = 0, 1, ..),
s: [OFDM symbol index] mod 6
(OFDM symbol index = 0,1,2, ..)
Antenna 3-
18k + 4 when s is 0
18k + 13 when s is 1
18k + 7 when s is 218k + 16 when s is 3
18k + 10 when s is 4
18k + 1 when s is 5
Antenna 4-
18k + 13 when s is 0
18k + 4 when s is 1
18k + 16 when s is 2
18k + 7 when s is 3
18k + 1 when s is 4
18k + 10 when s is 5
k: subcarrier index (k = 0, 1, ..),
s: [OFDM symbol index] mod 6
(OFDM symbol index = 0,1,2, ..)
In the case of having the pilot allocation structure shown in FIG. 27, the pilot allocation index for each antenna is specifically shown as follows.
<Pilot allocation index for Fig. 27>
Antenna 1-
18k when s is 0
18k + 9 when s is 1
18k + 3 when s is 2
18k + 12 when s is 3
18k + 6 when s is 4
18k + 15 when s is 5
Antenna 2-
18k + 9 when s is 0
18k when s is 1
18k + 12 when s is 2
18k + 3 when s is 3
18k + 15 when s is 4
18k + 6 when s is 5
k: subcarrier index (k = 0, 1, ..),
s: [OFDM symbol index] mod 6
(OFDM symbol index = 0,1,2, ..)
Antenna 3-
18k + 3 when s is 0
18k + 12 when s is 1
18k + 6 when s is 2
18k + 15 when s is 3
18k + 9 when s is 4
18k when s is 5
Antenna 4-
18k + 12 when s is 0
18k + 3 when s is 1
18k + 15 when s is 2
18k + 6 when s is 3
18k when s is 4
18k + 9 when s is 5
k: subcarrier index (k = 0, 1, ..),
s: [OFDM symbol index] mod 6
(OFDM symbol index = 0,1,2, ..)
FIG. 28 is a diagram illustrating a pattern for assigning pilot subcarriers in a 4Tx system according to another embodiment of the present invention. The principle explained in the above embodiment is basically applied to the pilot pattern of FIG. However, FIG. 28 shows a case where the subcarrier for the first antenna and the subcarrier for the second antenna are used as one pilot pair, and the subcarrier for the third antenna and the subcarrier for the fourth antenna are used as another pilot pair. An example of assigning two subcarrier intervals between pairs is shown. That is, in this embodiment, two pilot pairs can be assigned so as to be adjacent to each other, or can be assigned so as not to be adjacent.

  The functions described above can be performed by a processor such as a microprocessor, controller, microcontroller, ASIC (Application Specific Integrated Circuit) coded to perform those functions. The design, development and implementation of the code will be apparent to those skilled in the art from the description of the invention.

  The pilot subcarrier allocation method according to the present invention is applicable to an IEEE 802.16m system. As described above, basic principles such as pilot arrangement and pilot shift pattern setting for uniformly allocating transmission power to each antenna can be applied to other wireless communication systems in the same manner.

  Although the present invention has been described with reference to the embodiments, those skilled in the art can make various modifications and changes without departing from the technical idea and scope of the present invention. It is understood that it can be implemented with changes. Accordingly, the invention is not limited to the embodiments described above, but the invention can include any embodiments within the scope of the appended claims.

Claims (18)

Orthogonal frequency division multiplexing (OFDM) A how you assign a pilot in the modulation system,
The method
A first pilot (P1) for the first antenna, a second pilot (P2) for the second antenna, a third pilot (P3) for the third antenna, and a fourth pilot for the fourth antenna. Assigning a pilot (P4) to each of a plurality of OFDM symbols in a basic resource block unit;
The basic resource block unit includes a plurality of OFDM symbols and a plurality of subcarriers,
The first pilot (P1), the second pilot (P2), the third pilot (P3), and the fourth pilot (P4) are defined as shown in Table 1 below. Assigned in two consecutive OFDM symbols to be a first pattern or a second pattern defined as in Table 2 below:
Table 2 shows
And
The method wherein the first pattern and the second pattern alternate with each other along the frequency domain in the two consecutive OFDM symbols . The method of claim 1, wherein the first pattern and the second pattern are separated from each other by a predetermined number of subcarriers along the frequency domain in the two consecutive OFDM symbols . 3. Each of the first and second patterns in the two consecutive OFDM symbols is shifted by an integer multiple of 3 subcarriers in the next two consecutive OFDM symbols. Method. Orthogonal frequency division multiplexing (OFDM) a signal unit sending to assign a pilot in the modulation system,
The transmitter is
A first antenna, a second antenna, a third antenna, a fourth antenna;
An OFDM modulator operatively connected from the first antenna to the fourth antenna;
A processor operably connected to the OFDM modulator;
The processor is
A first pilot (P1) for the first antenna, a second pilot (P2) for the second antenna, a third pilot (P3) for the third antenna, and the fourth antenna Is assigned to each of a plurality of OFDM symbols in the basic resource block unit, and
The basic resource block unit includes a plurality of OFDM symbols in the time domain and a plurality of subcarriers in the frequency domain,
The processor is
The first pilot (P1), the second pilot (P2), the third pilot (P3), and the fourth pilot (P4) are defined as shown in Table 1 below. Is configured to be allocated in two consecutive OFDM symbols to be a first pattern or a second pattern defined as in Table 2 below:
Table 2 shows
And
The transmitter, wherein the first pattern and the second pattern alternate with each other along the frequency domain in the two consecutive OFDM symbols . The processor includes the first pattern and the second pattern such that the first pattern and the second pattern are separated from each other by a predetermined number of subcarriers along the frequency domain in the two consecutive OFDM symbols. a pilot (P1), and the second pilot (P2), and the third pilot (P3), and is configured to assign said fourth pilot (P4), according to claim 4 Transmitter. The processor is arranged such that each of the first and second patterns in the two consecutive OFDM symbols is shifted by an integer multiple of 3 subcarriers in the next two consecutive OFDM symbols. a first pilot (P1), and the second pilot (P2), and the third pilot (P3), and is configured to assign said fourth pilot (P4), according to claim 4 or 5. The transmitter according to 5 .   A method for receiving a pilot by a receiver in an orthogonal frequency division multiplexing (OFDM) modulation system, comprising:
  The method
  In each of the multiple OFDM symbols in the basic resource block unit, a first pilot (P1) for the first antenna, a second pilot (P2) for the second antenna, and a third pilot for the third antenna Receiving a pilot (P3) and a fourth pilot (P4) for a fourth antenna;
  The basic resource block unit includes a plurality of OFDM symbols and a plurality of subcarriers,
  The first pilot (P1), the second pilot (P2), the third pilot (P3), and the fourth pilot (P4) are defined as shown in Table 1 below. Received in two consecutive OFDM symbols in a first pattern or a second pattern defined as in Table 2 below,
Table 2 shows
And
  The method wherein the first pattern and the second pattern alternate with each other along the frequency domain in the two consecutive OFDM symbols.   The method of claim 7, wherein the first pattern and the second pattern are separated from each other by a predetermined number of subcarriers along the frequency domain in the two consecutive OFDM symbols.   9. Each of the first and second patterns in the two consecutive OFDM symbols is shifted by an integer multiple of 3 subcarriers in the next two consecutive OFDM symbols. Method.   A receiver for receiving a pilot in an orthogonal frequency division multiplexing (OFDM) modulation system, comprising:
  The receiver is
  At least one receiving antenna;
  A processor operably connected to the at least one receive antenna;
  Including
  The processor is
  In each of the multiple OFDM symbols in the basic resource block unit, a first pilot (P1) for the first antenna, a second pilot (P2) for the second antenna, and a third pilot for the third antenna Configured to control the at least one receive antenna to receive a pilot (P3) and a fourth pilot (P4) for a fourth antenna;
  The basic resource block unit includes a plurality of OFDM symbols in the time domain and a plurality of subcarriers in the frequency domain,
  The first pilot (P1), the second pilot (P2), the third pilot (P3), and the fourth pilot (P4) are defined as shown in Table 1 below. Received in two consecutive OFDM symbols in a first pattern or a second pattern defined as in Table 2 below,
Table 2 shows
And
  The receiver wherein the first pattern and the second pattern alternate with each other along the frequency domain in the two consecutive OFDM symbols.   The receiver of claim 10, wherein the first pattern and the second pattern are separated from each other by a predetermined number of subcarriers along the frequency domain in the two consecutive OFDM symbols.   12. Each of the first and second patterns in the two consecutive OFDM symbols is shifted by an integer multiple of 3 subcarriers in the next two consecutive OFDM symbols. Receiver.   A first pilot (P1) for the first antenna, a second pilot (P2) for the second antenna, a third pilot (P3) for the third antenna, and a fourth pilot for the fourth antenna. A program programmed to operate a computer of the transmitter to cause the transmitter to assign a pilot (P4) to each of a plurality of orthogonal frequency division multiplexing (OFDM) symbols in a basic resource block unit There,
  The basic resource block unit includes a plurality of OFDM symbols and a plurality of subcarriers,
  The first pilot (P1), the second pilot (P2), the third pilot (P3), and the fourth pilot (P4) are defined as shown in Table 1 below. Assigned in two consecutive OFDM symbols to be a first pattern or a second pattern defined as in Table 2 below:
Table 2 shows
And
  The program in which the first pattern and the second pattern alternate with each other along the frequency domain in the two consecutive OFDM symbols.   The program according to claim 13, wherein the first pattern and the second pattern are separated from each other by a predetermined number of subcarriers along the frequency domain in the two consecutive OFDM symbols.   15. Each of the first and second patterns in the two consecutive OFDM symbols is shifted by an integer multiple of 3 subcarriers in the next two consecutive OFDM symbols. program.   In each of a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the basic resource block unit, a first pilot (P1) for the first antenna, a second pilot (P2) for the second antenna, and a third Programmed to operate the receiver computer to cause the receiver to receive a third pilot (P3) for the second antenna and a fourth pilot (P4) for the fourth antenna. A program,
  The basic resource block unit includes a plurality of OFDM symbols and a plurality of subcarriers,
  The first pilot (P1), the second pilot (P2), the third pilot (P3), and the fourth pilot (P4) are defined as shown in Table 1 below. Received in two consecutive OFDM symbols in a first pattern or a second pattern defined as in Table 2 below,
Table 2 shows
And
  The program in which the first pattern and the second pattern alternate with each other along the frequency domain in the two consecutive OFDM symbols.   The program according to claim 16, wherein the first pattern and the second pattern are separated from each other by a predetermined number of subcarriers along the frequency domain in the two consecutive OFDM symbols.   18. Each of the first and second patterns in the two consecutive OFDM symbols is shifted by an integer multiple of 3 subcarriers in the next two consecutive OFDM symbols. program.