JP4334274B2 - Multi-carrier transmission transmitter and multi-carrier transmission method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transmitter for multicarrier transmission and a multicarrier transmission method.
[0002]
[Prior art]
In recent years, studies on wireless transmission using multicarrier transmission have been actively conducted.
[0003]
For example, in “IEEE802.11a” that is a wireless LAN standard, wireless transmission is performed by “OFDM (Orthogonal Frequency Division Multiplexing)” which is a kind of multicarrier transmission.
[0004]
In addition, as a wireless transmission method combining multi-carrier transmission and “CDMA (Code Division Multiple Access)”, “MC / DS-CDMA (Multi-Carrier / Direct Sequence-CDMA)” or “MC-CDMA (Multi-Carrier--) Wireless access schemes such as “CDMA” have been proposed.
[0005]
As shown in FIG. 12, MC / DS-CDMA includes a spreading code multiplier 13. ₁ Thru 13 _n The data symbols are spread using spreading codes, the spread data symbols (chips) are arranged (mapped) on the time axis to generate a DS-CDMA signal, and a plurality of DS-CDMA signals are This is a method of parallel transmission using subcarriers.
[0006]
On the other hand, as shown in FIG. ₁ Thru 13 _n In this method, data symbols are spread using spreading codes, and the spread data symbols (chips) are arranged (mapped) on a plurality of subcarriers and transmitted in parallel. Therefore, in MC-CDMA, data symbols are spread and transmitted to a plurality of symbols on subcarriers.
[0007]
As described above, multi-carrier transmission has been actively studied because multi-carrier transmission is used for multi-path propagation in which a signal transmitted by a transmitter reaches a receiver through a plurality of propagation paths. This is because has a proof stress.
[0008]
That is, when multipath propagation occurs, a problem is that a signal that arrives late at the receiver interferes with a signal that has arrived at the receiver first, but as shown in FIG. In this case, since the length of one symbol is long and the amount of delay is small compared to the length of one symbol, the influence of interference due to the above-described multipath propagation is reduced.
[0009]
Here, since the signal transmitted from the transmitter is superimposed with information to be transmitted in the amplitude and phase, if the amplitude or phase varies due to the influence of the propagation path, the signal is propagated in the receiver. It is necessary to remove amplitude and phase fluctuations generated in the path from the received signal and restore information superimposed on the amplitude and phase.
[0010]
In this way, for the purpose of estimating fluctuations in amplitude and phase occurring in the propagation path, symbol patterns (pilot symbol patterns) having known amplitudes and phases are transmitted between the transmitter and the receiver, and the propagation path There is known a method for estimating fluctuations in amplitude and phase generated in the above.
[0011]
Therefore, a pilot channel configuration method for multiplexing pilot symbol patterns is also very important in multicarrier transmission.
[0012]
As a method for configuring a pilot channel in multicarrier transmission, Patent Document 1 discloses a method for configuring a pilot channel in OFDM, and Patent Document 2 discloses a method for configuring a pilot channel in MC / DS-CDMA. Patent Document 3 discloses a method for configuring a pilot channel in MC-CDMA.
[0013]
These pilot channel configuration methods disclose a configuration in which pilot symbol patterns are multiplexed in at least one of a time axis direction, a frequency axis direction (subcarrier direction), and a code axis direction in a radio frame.
[0014]
Non-Patent Document 1 discloses a method of spreading data symbols two-dimensionally in the time axis direction and the subcarrier direction by combining MC / DS-CDMA and MC-CDMA, that is, a plurality of symbols of a plurality of subcarriers. A method for spreading data symbols in a section has been proposed.
[0015]
[Patent Document 1]
JP 2001-203665 A
[0016]
[Patent Document 2]
JP 2001-244913 A
[0017]
[Patent Document 3]
Japanese Patent Laid-Open No. 2001-197037
[0018]
[Non-Patent Document 1]
OFDM-CDMA using time-frequency domain simultaneous spreading (Akira Sumasu, Takao Nihira, Keiichi Kitagawa, Mitsuru Uesugi, Osamu Kato; IEICE Technical Report RCS200-3)
[0019]
[Problems to be solved by the invention]
However, the above-described pilot channel configuration method has a problem that a specific pilot channel multiplexed on a radio frame does not consider interference given to other pilot channels.
[0020]
Further, in the method of spreading the above data symbols in the time axis direction, the subcarrier direction, or two-dimensionally, there is a problem that the superiority or inferiority of signal transmission characteristics in each spreading method greatly depends on the state of the propagation path. It was.
[0021]
Therefore, the present invention has been made in view of the above points, and a multicarrier transmission transmitter and a multicarrier transmission capable of allocating a pilot channel of a symbol pattern in consideration of interference given to other pilot channels on a radio frame. An object is to provide a carrier transmission method.
[0022]
The present invention also relates to a multicarrier transmission transmitter and a multicarrier transmission capable of controlling a spreading method in consideration of a state of a propagation path between a multicarrier transmission transmitter and a multicarrier transmission receiver. It aims to provide a method.
[0023]
[Means for Solving the Problems]
A first feature of the present invention is a transmitter for multicarrier transmission that transmits a plurality of subcarriers having at least one pilot symbol period, and a plurality of pilot symbol patterns orthogonal to each other are transmitted to at least two subcarriers. The gist of the present invention is to provide a pilot symbol allocation unit that allocates to a pilot symbol section to be crossed.
[0024]
According to this invention, the pilot symbol allocating unit allocates a plurality of pilot symbol patterns orthogonal to each other to pilot symbol sections over at least two subcarriers, so that interference given to other pilot channels is considered in multicarrier transmission. A pilot channel of the symbol pattern can be allocated on the radio frame.
[0025]
Further, according to this invention, since the pilot symbol allocating section allocates a plurality of pilot symbol patterns to pilot symbol sections over at least two subcarriers, a symbol section (that is, a pilot section) that can assign pilot symbols in each subcarrier. The number of pilot symbol patterns that can be multiplexed can be increased, the number of pilot symbol patterns that can be multiplexed can be increased, and the number of multi-carriers can be increased. The number of radio channels that can be set between the transmission transmitter and the multicarrier transmission receiver can be increased.
[0026]
In the first aspect of the present invention, the pilot symbol allocation unit can change the period of the pilot symbol pattern according to the number of allocated pilot symbol patterns.
[0027]
In the first aspect of the present invention, the plurality of pilot symbol patterns can be composed of orthogonal variable spreading factor (OVSF) codes.
[0028]
In the first aspect of the present invention, the pilot symbol assigning unit can assign the pilot symbol pattern to a predetermined part in a pilot symbol interval over at least two subcarriers, and the same part in the pilot symbol interval The pilot symbol patterns assigned to are orthogonal to each other.
[0029]
In the first aspect of the present invention, the pilot symbol allocation unit can allocate the pilot symbol pattern to a pilot symbol section over a predetermined number of consecutive subcarriers.
[0030]
A second feature of the present invention is a multicarrier transmission transmitter that transmits a plurality of subcarriers having a plurality of symbol periods, and the symbols to be transmitted are spread in a subcarrier direction and a spreading factor in a time axis direction. And the spreading factor in the subcarrier direction and the time according to the state of the propagation path between the spreading unit that spreads over a plurality of symbol periods over the plurality of subcarriers and the receiver for multicarrier transmission. The gist of the present invention is to include a control unit that changes the diffusion rate in the axial direction.
[0031]
According to this invention, the control unit spreads and transmits the symbols to be transmitted in accordance with the state of the propagation path between the multicarrier transmission receiver and the spreading factor in the subcarrier direction and the time axis direction. Therefore, the diffusion method can be controlled in consideration of the state of the propagation path.
[0032]
In the second aspect of the present invention, the control unit changes the spreading factor in the subcarrier direction and the spreading factor in the time axis direction when a radio channel is set up with a receiver for multicarrier transmission. Is the gist.
[0033]
The gist of the second feature of the present invention is that the control unit changes the spreading factor in the subcarrier direction and the spreading factor in the time axis direction following the change in the state of the propagation path.
[0034]
A third feature of the present invention is a multicarrier transmission method for transmitting a plurality of subcarriers having at least one pilot symbol period, wherein a plurality of pilot symbol patterns orthogonal to each other are piloted over at least two subcarriers. The gist is to have a step of assigning to the symbol interval.
[0035]
According to this invention, since a plurality of pilot symbol patterns orthogonal to each other are allocated to pilot symbol sections over at least two subcarriers, the pilot channel of the symbol pattern in consideration of interference given to other pilot channels in multicarrier transmission Can be allocated on the radio frame.
[0036]
Further, according to this invention, since a plurality of pilot symbol patterns are allocated to pilot symbol sections over at least two subcarriers, the number of symbol sections (that is, pilot symbol sections) to which pilot symbols can be allocated in each subcarrier is reduced. Even in a limited case, it is possible to increase the period of pilot symbol patterns that can be multiplexed, increase the number of pilot symbol patterns that can be multiplexed, It is possible to increase the number of radio channels that can be set up with the carrier transmission receiver.
[0037]
In the third aspect of the present invention, the period of the pilot symbol pattern can be changed according to the number of assigned pilot symbol patterns.
[0038]
In the third aspect of the present invention, the plurality of pilot symbol patterns can be composed of orthogonal variable spreading factor (OVSF) codes.
[0039]
In the third aspect of the present invention, the pilot symbol pattern can be assigned to a predetermined portion in a pilot symbol interval over at least two subcarriers, and is assigned to the same portion in the pilot symbol interval. Are orthogonal to each other.
[0040]
In the third aspect of the present invention, the pilot symbol pattern can be assigned to a pilot symbol interval over a predetermined number of consecutive subcarriers.
[0041]
A fourth feature of the present invention is a multi-carrier transmission method for transmitting a plurality of subcarriers having a plurality of symbol periods, using a subcarrier direction spreading factor and a time axis direction spreading factor for the symbols to be transmitted. The spreading rate in the subcarrier direction and the time according to the state of the propagation path between the step of spreading and transmitting to a plurality of symbol intervals over the plurality of subcarriers and the multicarrier transmission receiver And a step of changing the diffusivity in the axial direction.
[0042]
According to this invention, the spreading factor in the subcarrier direction and the spreading factor in the time axis direction for spreading and transmitting the symbols to be transmitted are changed according to the state of the propagation path with the receiver for multicarrier transmission. The diffusion method can be controlled in consideration of the state of the propagation path.
[0043]
In the fourth aspect of the present invention, the spreading factor in the subcarrier direction and the spreading factor in the time axis direction are changed when a radio channel is set between the transmitter for multicarrier transmission and the receiver for multicarrier transmission. Can be made.
[0044]
In the fourth feature of the present invention, the spreading factor in the subcarrier direction and the spreading factor in the time axis direction can be changed following the change in the state of the propagation path.
[0045]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment of the present invention)
A first embodiment of the present invention will be described with reference to FIGS. 1 and 2. The configuration of the multicarrier transmission transmitter according to the present embodiment is the same as that of the conventional multicarrier transmission transmitter shown in FIG. 12 or 13 except for the pilot symbol pattern allocation method by the pilot symbol allocation unit 17. It is.
[0046]
As shown in FIG. 1, the transmitter for multicarrier transmission according to the present embodiment transmits a radio frame including at least one pilot symbol section using a plurality of subcarriers # 1 to # 8.
[0047]
In this specification, “pilot symbol” refers to 1-bit information having a value of “+1” or “−1”, and “pilot symbol pattern” refers to a configuration in which a plurality of pilot symbols are collected. Point to. For example, “pilot symbol pattern” includes “+ 1, + 1, + 1, + 1, + 1, + 1, + 1, + 1 (pilot symbol pattern # 1)” shown in FIG. It should be noted that the “pilot symbol pattern” can take a symbol period of an arbitrary period (in the above-described pilot symbol pattern # 1, eight symbol periods).
[0048]
In this specification, “orthogonal” means “+ 1, + 1, + 1, + 1, + 1, + 1, + 1, + 1 (pilot symbol pattern # 1)” and “+ 1, −1, + 1, Like the relationship of “−1, +1, −1, +1, −1 (pilot symbol pattern # 2)”, the corresponding pilot symbols in each pilot symbol pattern are multiplied with each other, and the sum of all multiplication results is “ It means “0”.
[0049]
In FIG. 1, there are only “4 symbol intervals” in the time axis direction (pilot symbol intervals) in which “pilot symbols” can be multiplexed in each of the plurality of subcarriers # 1 to # 8.
[0050]
That is, in FIG. 1, the pilot symbol allocating unit 17 of the multicarrier transmission transmitter can allocate pilot symbols to the above-described four symbol intervals (hereinafter referred to as pilot symbol intervals). Data symbols are allocated to other symbol intervals (hereinafter referred to as data symbol intervals).
[0051]
In this case, since there are only 4 symbol periods of pilot symbols for each radio frame, the pilot symbol allocation unit 17 of the conventional multicarrier transmission transmitter uses pilot symbols having symbol patterns orthogonal to each other in each subcarrier. As a pattern (hereinafter referred to as an orthogonal pilot symbol pattern), only a pilot symbol pattern having a period of 4 symbols (4 symbol periods) can be multiplexed, and only a maximum of 4 types of pilot symbol patterns can be multiplexed. It was.
[0052]
On the other hand, the pilot symbol allocating unit 17 of the transmitter for multicarrier transmission according to the present embodiment includes a plurality of orthogonal pilot symbol patterns in a pilot symbol section that spans a plurality of subcarriers, for example, a pilot symbol section that spans two subcarriers. Therefore, even if there are only four symbol periods, it is possible to multiplex eight pilot symbol orthogonal pilot symbol patterns and multiplex up to eight orthogonal pilot symbol patterns. Can do.
[0053]
In particular, in a cellular system, when directional beam transmission using a plurality of antennas is applied to each mobile station in a base station, it is necessary to use an individual pilot channel for each mobile station. By increasing the number of multiplexed orthogonal pilot symbol patterns (pilot channels), it is effective to increase the number of wireless channel connections between the base station and the mobile station.
[0054]
FIG. 1 shows an example in which an orthogonal pilot symbol pattern having an 8-symbol period is allocated, and such orthogonal pilot symbol pattern is repeatedly allocated every two subcarriers.
[0055]
As described above, according to the present embodiment, since the orthogonal pilot symbol pattern can be lengthened by assigning the orthogonal pilot symbol pattern to the pilot symbol sections over the plurality of subcarriers # 1 to # 8, the multiplexing is possible. It is possible to increase the number of possible orthogonal pilot symbol patterns.
[0056]
In addition, when orthogonal pilot symbol patterns are assigned to a plurality of subcarriers # 1 to # 8, orthogonality is reduced between pilot channels received on the multicarrier transmission receiver side. It is necessary that the correlation of propagation path variations received by the subcarriers assigned the pilot symbol pattern is large, but in multicarrier transmission using a large number of subcarriers, the correlation of propagation path variations received by adjacent subcarriers is large. It is possible to reduce the influence of the above-described disruption of orthogonality.
[0057]
Therefore, according to the present embodiment, in multicarrier transmission, orthogonal pilot symbol patterns having orthogonal symbol patterns are multiplexed in a radio frame, and a pilot channel having a symbol pattern with small interference given to other pilot channels is added to the radio frame. Can be assigned to.
[0058]
In addition, according to the present embodiment, since the pilot symbol allocation unit 17 allocates a plurality of pilot symbol patterns to pilot symbol sections over a plurality of subcarriers, the number of pilot symbol sections in each subcarrier (radio frame) is limited. Even if the number of pilot symbol patterns that can be multiplexed can be increased, the number of pilot symbol patterns that can be multiplexed can be increased, and a multicarrier transmission transmitter and a multicarrier transmission The number of radio channels that can be set up with the receiver can be increased.
[0059]
In FIG. 2, the pilot symbol allocating unit 17 of the transmitter for multicarrier transmission according to the present embodiment generates an orthogonal pilot symbol pattern of 4 symbol sections (time axis direction) × 2 subcarriers (subcarrier direction) = 8 symbol periods. An example of assignment is shown.
[0060]
FIG. 2 shows eight types of orthogonal pilot symbol patterns # 1 to # 8. The pilot symbol allocating unit 17 of the multicarrier transmission transmitter according to the present embodiment includes eight types of pilot symbol sections (4 symbol sections × 2 subcarriers) in two subcarriers #i and # i + 1. Pilot symbol patterns (pilot symbol patterns # 1 to # 8) can be multiplexed respectively.
[0061]
(Second embodiment of the present invention)
A second embodiment of the present invention will be described with reference to FIGS. The configuration of the multicarrier transmission transmitter according to the present embodiment is the same as the configuration of the multicarrier transmission transmitter according to the first embodiment.
[0062]
In the present embodiment, an example is shown in which a pilot symbol section of 4 symbol sections exists in each of a plurality of subcarriers # 1 to # 8, and the orthogonal pilot symbol pattern to be assigned is the same as in the first embodiment. This will be described using
[0063]
The pilot symbol assignment unit 17 of the multicarrier transmission transmitter according to the present embodiment can change the number of subcarriers to which each pilot symbol pattern is assigned according to the period of the pilot symbol pattern.
[0064]
In addition, pilot symbol allocating unit 17 varies the period (pilot symbol pattern period) in which the pilot symbol patterns are orthogonal according to the number of multiplexed pilot channels (that is, the number of pilot symbol patterns to be allocated). be able to.
[0065]
Specifically, the pilot symbol allocating unit 17 of the multicarrier transmission transmitter according to the present embodiment, as shown in FIG. 3, performs orthogonality of pilot symbol patterns # 1 to # 8 according to the number of multiplexed pilot channels. A pilot symbol pattern (8 symbol periods) can be assigned to one or two subcarriers in turn.
[0066]
In this allocation method, as shown in FIG. 3, when the number of multiplexed pilot channels is 4, the orthogonal pilot symbol patterns from pilot symbol patterns # 1 to # 4 are orthogonal in four symbol periods within one subcarrier. Can be realized.
[0067]
Further, when the number of multiplexed pilot channels is up to 8, the orthogonal pilot symbol patterns from pilot symbol patterns # 5 to # 8 are added to pilot symbol patterns # 1 to # 4, thereby extending over two subcarriers. Orthogonalization can be realized with a period of 8 symbols.
[0068]
FIG. 4 shows an example using an orthogonal variable spreading factor (OVSF) code as an example of a more general orthogonal pilot symbol pattern. OVSF codes, "Koichi Okawa and Fumiyuki Adachi," Orthogonal forward link using orthogonalmulti-spreading factor codes for coherent DS-CDMA mobile ratio ", IEICE Transactions on Communications, vol.E81-B, no.4, pp.777-784 , April 1998 ”.
[0069]
As shown in FIG. 4, the pilot symbol allocating unit 17 of the multicarrier transmission transmitter according to the present embodiment is based on the hierarchical structure when generating the OVSF code and based on the number of multiplexed pilot channels. If the orthogonal pilot symbol pattern to be assigned is selected, orthogonalization can be realized with a small number of subcarriers when the number of multiplexed pilot channels is small, and orthogonalization is performed using a plurality of subcarriers as the number of multiplexed pilot channels increases. Can be realized.
[0070]
FIG. 4 shows an example in which the number of multiplexed pilot channels is up to 8, but the number of multiplexed pilot channels can be sequentially increased based on the generation pattern of the OVSF code.
[0071]
(Third embodiment of the present invention)
A third embodiment of the present invention will be described with reference to FIG. The configuration of the multicarrier transmission transmitter according to the present embodiment is the same as the configuration of the multicarrier transmission transmitter according to the first embodiment.
[0072]
As shown in FIG. 5, the pilot symbol allocating unit 17 of the multicarrier transmission transmitter according to the present embodiment includes a predetermined portion in a pilot symbol section that spans at least two subcarriers among subcarriers # 1 to # 6. (#A, #B, etc.) are assigned pilot symbol patterns # 1 to # 8 shown in FIG.
[0073]
In FIG. 5, the pilot symbol allocation unit 17 applies the pilot symbol patterns # 1 to # 8 shown in FIG. 2 to pilot symbol sections (#A, #B, etc.) over a predetermined number (two) of consecutive subcarriers. Configured to assign.
[0074]
That is, pilot symbol allocation section 17 allocates pilot symbol patterns # 1 to # 8 shown in FIG. 2 for every two subcarriers over a total of six subcarriers.
[0075]
Here, pilot symbol patterns # 1 to # 8 assigned to the same part (#A, #B, etc.) in the pilot symbol period are orthogonal to each other.
[0076]
Here, the part #A is composed of pilot symbol intervals # 1 to # 4 of the subcarrier # 1 and pilot symbol intervals # 1 to # 4 of the subcarrier # 2 continuous with the subcarrier # 1. .
[0077]
Portion #B is composed of pilot symbol periods # 1 to # 4 of subcarrier # 2 and pilot symbol periods # 1 to # 4 of subcarrier # 3 that is continuous to subcarrier # 2.
[0078]
Portion #C includes pilot symbol periods # 1 to # 4 of subcarrier # 3 and pilot symbol periods # 1 to # 4 of subcarrier # 4 that is continuous to subcarrier # 3.
[0079]
Portion #D is composed of pilot symbol periods # 1 to # 4 of subcarrier # 4 and pilot symbol periods # 1 to # 4 of subcarrier # 5 that is continuous to subcarrier # 4.
[0080]
Portion #E is composed of pilot symbol periods # 1 to # 4 of subcarrier # 5 and pilot symbol periods # 1 to # 4 of subcarrier # 6 that is continuous to subcarrier # 5.
[0081]
That is, portions #A to #E are composed of a 4-symbol section in the time axis direction and a 2-symbol section in the subcarrier direction.
[0082]
In other words, the pilot symbol allocating unit 17 of the multicarrier transmission transmitter according to the present embodiment includes a predetermined symbol section (partial) in a set of a plurality of symbol sections including a predetermined number of subcarriers # 1 to # 6. A plurality of pilot symbols constituting pilot symbol patterns # 1 to # 8 are assigned to #A to #E).
[0083]
Here, pilot symbol patterns composed of pilot symbols assigned to the same symbol section in a set of a plurality of symbol sections are orthogonal to each other.
[0084]
For example, as shown in FIG. 5, pilot symbol patterns # 1 to # 8 assigned to the pilot symbol interval parts #A to #E, for example, “+1, +1, +1, +1, +1, +1, "+1, +1 (pilot symbol pattern # 1)" and "+1, -1, +1, -1, +1, -1, +1, -1 (pilot symbol pattern # 2)" are orthogonal to each other.
[0085]
According to the present embodiment, since orthogonalization can be realized for every two subcarriers, for example, when estimating propagation path fluctuation of each subcarrier, it can be estimated with higher accuracy.
[0086]
(Fourth embodiment of the present invention)
A fourth embodiment of the present invention will be described with reference to FIGS. The configuration of the multicarrier transmission transmitter according to the present embodiment is the same as the configuration of the multicarrier transmission transmitter according to the first embodiment.
[0087]
As shown in FIG. 6, the pilot symbol allocating unit 17 of the transmitter for multicarrier transmission according to the present embodiment includes a predetermined portion in a pilot symbol section that spans at least two subcarriers among subcarriers # 1 to # 6. (#G etc.) are assigned pilot symbol patterns # 1 to # 4 shown in FIG.
[0088]
In FIG. 6, the pilot symbol allocation unit 17 is configured to allocate pilot symbol patterns # 1 to # 4 to the portions #F and #G of the pilot symbol section.
[0089]
Here, pilot symbol patterns # 1 to # 4 assigned to the same part (#F, #G, etc.) in the pilot symbol period are orthogonal to each other.
[0090]
Portion #F is configured by pilot symbol sections # 1 to # 4 of subcarrier # 1. That is, the part #F is composed of 4 symbol intervals in the time axis direction (all symbol intervals constituting the pilot symbol interval) and 1 symbol interval in the subcarrier direction.
[0091]
Portion #G is composed of pilot symbol sections # 1 and # 2 of subcarrier # 1 and pilot symbol sections # 1 and # 2 of subcarrier # 2 that are continuous to subcarrier # 1. That is, the part #G is composed of two symbol intervals in the time axis direction (a part of the symbol interval constituting the pilot symbol interval) and two symbol intervals in the subcarrier direction.
[0092]
As shown in FIG. 6, the pilot symbol assigning unit 17 can assign the above-described pilot symbol patterns # 1 to # 4 to overlapping portions such as the portion #F and the portion #G.
[0093]
In other words, the pilot symbol allocation unit 17 of the multicarrier transmission transmitter according to the present embodiment includes a predetermined symbol interval (#) in a set of a plurality of symbol intervals including a predetermined number of subcarriers # 1 to # 6. F, #G, etc.) are assigned a plurality of pilot symbols constituting pilot symbol patterns # 1 to # 8.
[0094]
Here, pilot symbol patterns composed of pilot symbols assigned to the same symbol interval #F or #G in a set of a plurality of symbol intervals are orthogonal to each other.
[0095]
For example, as shown in FIG. 6, pilot symbol patterns # 1 to # 4 assigned to each of the pilot symbol interval portions #F or #G, for example, “+1, +1, +1, +1 (pilot symbol pattern # 1 ) "And" +1, -1, +1, -1 (pilot symbol pattern # 2) "are orthogonal to each other.
[0096]
In other words, in the present embodiment, as shown in FIG. 6, the pilot symbol allocating unit 17 increases the pilot channel orthogonality between the pilot symbol patterns # 1 to # 4 in four symbol sections in the time axis direction. A pilot symbol pattern can be allocated so as to be maintained, and a pilot symbol pattern can be allocated so that the orthogonality of the pilot channel is maintained in two symbol intervals in the subcarrier direction and two symbol intervals in the time axis direction.
[0097]
By using such a pilot symbol pattern allocation method, for example, as shown in FIG. 7, the radio frame has a 2-slot configuration (configuration consisting of slots # 1 and # 2), and each slot has a 2-symbol section. When two pilot symbols are multiplexed in the pilot symbol section of each slot constituting a radio frame, orthogonalization is realized in four symbol sections in the time axis direction in the radio frame On the other hand, orthogonalization can be realized in two symbol intervals in the subcarrier direction and two symbol intervals in the time axis in the slot, and up to four orthogonal pilot symbol patterns can be used.
[0098]
(Fifth embodiment of the present invention)
A fifth embodiment of the present invention will be described with reference to FIGS. FIG. 8 shows a schematic configuration of the multicarrier transmission transmitter according to the present embodiment. The transmitter for multicarrier transmission according to the present embodiment transmits a radio frame having a plurality of symbol sections using a plurality of subcarriers # 1 to #n.
[0099]
As shown in FIG. 8, the transmitter for multicarrier transmission according to the present embodiment includes a data symbol generator 11, a serial-parallel converter 12, and a spreading code multiplier 13. ₁ Thru 13 _n And the subcarrier frequency multiplier 14 ₁ 14 _n And the synthesizing unit 15 and the duplicating unit 16 ₁ 16 _n And a propagation path state monitoring unit 18 and a control unit 19.
[0100]
Hereinafter, the configuration of the transmitter for multicarrier transmission according to the present embodiment will be described focusing on differences from the configuration of the transmitter for multicarrier transmission according to Embodiments 1 to 4 described above.
[0101]
Spreading code multiplier 13 ₁ Thru 13 _n In this method, symbols to be transmitted (data symbols) are spread over a plurality of symbol intervals over a plurality of subcarriers using a spreading factor in the subcarrier direction and a spreading factor in the time axis direction.
[0102]
Specifically, the spread code multiplier 13 ₁ Thru 13 _n As shown in FIG. _Tim SF (spreading factor) and SF in the subcarrier direction _Freq The symbols (data symbols) to be transmitted are spread with a size (spreading factor). In FIG. 9, SF _Tim = 2 and SF _Freq = 4, an example in which symbols to be transmitted (data symbols) are spread is shown.
[0103]
In this way, when a radio channel is configured by spreading symbols in two dimensions, the spread code multiplier 13 ₁ Thru 13 _n If symbol patterns of different spreading codes are used, a plurality of radio channels can be multiplexed.
[0104]
The propagation path state monitoring unit 18 monitors the state of the propagation path, that is, the state of the radio channel between the multicarrier transmission transmitter and the multicarrier transmission receiver.
[0105]
The control unit 19 determines the spreading factor SF in the subcarrier direction according to the state of the propagation path, that is, the state of the radio channel between the multicarrier transmission transmitter and the multicarrier transmission receiver. _Freq And diffusion factor SF in the time axis direction _Tim Is something that changes.
[0106]
In addition, the control unit 19 sets the spreading factor SF in the subcarrier direction at the time of setting a radio channel with the receiver for multicarrier transmission. _Freq And diffusion factor SF in the time axis direction _Tim Can be changed.
[0107]
Further, the control unit 19 follows the change in the state of the propagation path, and the spreading factor SF in the subcarrier direction. _Freq And diffusion factor SF in the time axis direction _Tim Can be changed.
[0108]
The spread code multiplier 13 ₁ Thru 13 _n If the symbol pattern of the spreading code used by the transmitter is a symbol pattern orthogonal to each other, the orthogonality of the multiplexed radio channels is maintained on the multicarrier transmission transmitter side, but the multicarrier transmission receiver On the side, since the spread symbols are affected by different phase and amplitude fluctuations in the propagation path, the orthogonality of the multiplexed radio channels is lost and interference occurs, so that reception characteristics deteriorate.
[0109]
Also, in the propagation path, for symbols in the time axis direction, the magnitude of phase and amplitude fluctuations changes depending on the magnitude of the maximum Doppler frequency, and for the symbols in the subcarrier direction, the delay spread of the propagation path is changed. The magnitude of the fluctuation of the phase and amplitude changes depending on the magnitude of.
[0110]
Therefore, in order to mitigate the disruption of orthogonality between multiplexed radio channels due to the influence of propagation path fluctuations, the control unit 19 maintains orthogonality according to the maximum Doppler frequency, the size of the delay spread, and the like. SF within the range _Tim And SF _Freq It is effective to adaptively set the size of.
[0111]
For example, the control unit 19 determines that the maximum Doppler frequency f _D SF with respect to fluctuations in symbol amplitude and phase in the time axis direction due to _Tim In order to maintain orthogonality between radio channels multiplexed in the size of SF _Tim <1 / f _D The maximum SF that satisfies the size of _Tim Setting is effective.
[0112]
In addition, the control unit 19 applies SF to the fluctuation of the symbol amplitude and phase in the subcarrier direction due to the delay spread τ. _Freq In order to maintain orthogonality between radio channels multiplexed in the size of SF _Freq <Maximum SF satisfying 1 / τ _Freq Setting is effective.
[0113]
Where SF _Tim And SF _Freq Is defined as the maximum spreading factor that satisfies the above relationship, but this is an example for the purpose of reducing interference from other cells in a cellular environment and is set by other control methods. You can also.
[0114]
As described above, it is possible to perform high-quality transmission with little influence of interference caused by the disruption of the orthogonality of the radio channel due to the influence of the fluctuation of the propagation path with respect to the symbol in the time axis direction or the symbol in the subcarrier direction.
[0115]
10 and 11 are flowcharts showing the operation of the multicarrier transmission transmitter according to this embodiment. FIG. 10 shows the spreading factor SF in the subcarrier direction when the control unit 19 sets a radio channel with the receiver for multicarrier transmission. _Freq And diffusion factor SF in the time axis direction _Tim FIG. 11 shows a flowchart when the control unit 19 follows the change in the state of the propagation path, and the spreading factor SF in the subcarrier direction. _Freq And diffusion factor SF in the time axis direction _Tim The flowchart figure in the case of changing is shown.
[0116]
First, the operation of the multicarrier transmission transmitter shown in FIG. 10 will be described. As shown in FIG. 10, in step 1001, data symbols to be transmitted to a multicarrier transmission receiver are generated. In step 1002, before the control unit 19 transmits the data symbol, the state of the propagation path between the multicarrier transmission receiver and the multicarrier transmission transmitter monitored by the propagation state monitoring unit 18 Based on the diffusivity SF in the time axis direction _Tim And spreading factor SF in the subcarrier direction _Freq Decide.
[0117]
In step 1003, the spread code multiplier 13 ₁ Thru 13 _n Is the spreading factor SF determined by the control unit 19 _Tim And SF _Freq The data symbols are spread based on the subcarrier frequency multiplier 14 ₁ 14 _n The combining unit 15 transmits the spread data symbol to the receiver for multicarrier transmission.
[0118]
In an environment where the state of the propagation path between the receiver for multicarrier transmission and the transmitter for multicarrier transmission does not change frequently, the spreading factor SF for each transmission opportunity of data symbols. _Tim And SF _Freq Is set, it is possible to follow the environment of the above-mentioned propagation path, so the method according to this operation is suitable.
[0119]
Second, the operation of the multicarrier transmission transmitter shown in FIG. 11 will be described. As shown in FIG. 11, in step 1101, data symbols to be transmitted to a receiver for multicarrier transmission are generated. In step 1102, before the control unit 19 transmits the data symbol, the state of the propagation path between the multicarrier transmission receiver and the multicarrier transmission transmitter monitored by the propagation state monitoring unit 18 Based on the diffusivity SF in the time axis direction _Tim And spreading factor SF in the subcarrier direction _Freq Decide.
[0120]
In step 1103, the spread code multiplier 13 ₁ Thru 13 _n Is the spreading factor SF determined by the control unit 19 _Tim And SF _Freq The data symbols are spread based on the subcarrier frequency multiplier 14 ₁ 14 _n The combining unit 15 transmits the spread data symbol to the receiver for multicarrier transmission.
[0121]
In step 1104, the control unit 19 follows the change in the state of the propagation path between the receiver for multicarrier transmission and the transmitter for multicarrier transmission, and the spreading factor SF in the subcarrier direction. _Freq And diffusion factor SF in the time axis direction _Tim To change. Then, the spread code multiplier 13 ₁ Thru 13 _n Is the spreading factor SF updated by the control unit 19 _Tim And SF _Freq The data symbols are spread based on the subcarrier frequency multiplier 14 ₁ 14 _n The combining unit 15 transmits the spread data symbol to the receiver for multicarrier transmission.
[0122]
According to the method of this operation, for example, the state of the propagation path between the multicarrier transmission receiver and the multicarrier transmission transmitter is frequently changed, such as in an environment where the multicarrier transmission receiver is moving at high speed. In an environment that changes to an appropriate spreading factor SF following the propagation path fluctuation, _Tim And SF _Freq As a result, high-quality signal transmission can be realized.
[0123]
In the above embodiment, the number of subcarriers and the number of symbol sections are specifically described. However, the present invention is not limited to the configuration using the number of subcarriers and the number of symbol sections.
[0124]
In the present invention, similarly to the invention according to the above-described embodiment, “n (an integer of 1 or more) determined according to the length of the period of the pilot symbol pattern to be allocated in consideration of interference given to other pilot channels. The present invention can also be applied to a configuration using “m (an integer greater than or equal to 1) symbol section” of “subcarrier”.
[0125]
The transmitter for multicarrier transmission according to the present invention, for example, when using an OVSF code, “n” and “m” are powers of 2 and “n × m” is a pilot symbol pattern. “N” and “m” can be determined so as to be the length of the period. In addition, the transmitter for multicarrier transmission according to the present invention does not need to be configured such that “n” and “m” are powers of 2 when other codes are used.
[0126]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a multicarrier transmission transmitter and a multicarrier transmission method capable of allocating pilot channels in consideration of interference given to other pilot channels on a radio frame. it can.
[0127]
In addition, according to the present invention, a multicarrier transmission transmitter and a multiprocessor capable of controlling a spreading method in consideration of a state of a propagation path between a multicarrier transmission transmitter and a multicarrier transmission receiver. A carrier transmission method can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a specific example when a pilot symbol assignment unit of a transmitter for multicarrier transmission according to a first embodiment of the present invention assigns orthogonal pilot symbols.
FIG. 2 is a diagram illustrating an example of orthogonal pilot symbols allocated by a pilot symbol allocation unit of the transmitter for multicarrier transmission according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating an example of orthogonal pilot symbols allocated by a pilot symbol allocation unit of a transmitter for multicarrier transmission according to a second embodiment of the present invention.
FIG. 4 is a diagram illustrating an OVSF code which is an example of orthogonal pilot symbols allocated by a pilot symbol allocation unit of a multicarrier transmission transmitter according to a second embodiment of the present invention.
FIG. 5 is a diagram illustrating a specific example when a pilot symbol assignment unit of a multicarrier transmission transmitter according to a third embodiment of the present invention assigns orthogonal pilot symbols.
FIG. 6 is a diagram illustrating a specific example when a pilot symbol assignment unit of a transmitter for multicarrier transmission according to a fourth embodiment of the present invention assigns orthogonal pilot symbols.
FIG. 7 is a diagram illustrating a specific example in the case of applying an orthogonal pilot symbol assignment method of a transmitter for multicarrier transmission according to a fourth embodiment of the present invention to a radio frame having a two-slot configuration.
FIG. 8 is a schematic configuration diagram of a multicarrier transmission transmitter according to a fifth embodiment of the present invention.
FIG. 9 is a diagram for explaining a data symbol spreading method by a multicarrier transmission transmitter according to a fifth embodiment of the present invention;
FIG. 10 is a flowchart showing an operation of the multicarrier transmission transmitter according to the fifth embodiment of the present invention.
FIG. 11 is a flowchart showing the operation of the multicarrier transmission transmitter according to the fifth embodiment of the present invention.
FIG. 12 is a schematic configuration diagram of a transmitter for MC / DS-CDMA transmission according to a conventional technique.
FIG. 13 is a schematic configuration diagram of a transmitter for MC-CDMA transmission according to a conventional technique.
FIG. 14 is a diagram for explaining the reason why the influence of interference due to multipath propagation is reduced by multicarrier transmission according to the prior art.
[Explanation of symbols]
11: Data symbol generator
12 ... Series-parallel converter
13: Spreading code multiplier
14: Subcarrier frequency multiplier
15 ... Synthesizer
16 ... Duplicator
17 ... Pilot symbol allocation unit
18 ... propagation path state monitoring unit
19 ... Control unit

Claims (6)

A multicarrier transmission transmitter for transmitting a plurality of subcarriers including at least one pilot symbol period,
A pilot symbol allocating unit for allocating each of a plurality of pilot symbol patterns to each of a plurality of predetermined portions in a block configured by the pilot symbol sections included in the plurality of subcarriers;
Each of the plurality of pilot symbol patterns assigned to each of the plurality of predetermined portions is orthogonal to each other;
The transmitter for multicarrier transmission, wherein the predetermined portions overlap each other.   The transmitter for multicarrier transmission according to claim 1, wherein the pilot symbol allocating unit changes a period of the pilot symbol pattern according to the number of the plurality of pilot symbol patterns to be allocated.   The transmitter for multicarrier transmission according to claim 1 or 2, wherein the plurality of pilot symbol patterns are configured by orthogonal variable spreading factor (OVSF) codes. A multicarrier transmission method for transmitting a plurality of subcarriers having at least one pilot symbol period,
Allocating each of a plurality of pilot symbol patterns to each of a plurality of predetermined portions in a block constituted by the pilot symbol sections included in the plurality of subcarriers,
Each of the plurality of pilot symbol patterns assigned to each of the plurality of predetermined portions is orthogonal to each other;
The multicarrier transmission method, wherein the predetermined portions overlap each other.   5. The multicarrier transmission method according to claim 4, wherein the period of the pilot symbol pattern is changed according to the number of assigned pilot symbol patterns. The multicarrier transmission method according to claim 4 or 5 , wherein the plurality of pilot symbol patterns are configured by orthogonal variable spreading factor (OVSF) codes.

Images