CN1773897A - Resource distributing method and apparatus of dynamic time-frequency and code sequence - Google Patents

Abstract

A method for resource allocation of dynamic time-frequency and code sequences, comprising the steps of: searching for a suitable time-frequency resource block according to the channel quality, and completing the time-frequency resource allocation to the channel; according to the allocated code sequence information in the time-frequency resource block, completing code sequence assignment. For the multiple access system of OFDM-CDMA, the present invention uses dynamic time-frequency resources to allocate time-frequency resources to channels with good channel quality; The rational allocation of sequence resources maintains the orthogonality of all code sequences of multiple channels in partially overlapping time-frequency resources, reduces MAI interference between multiple channels, and improves the quality of signal transmission. It further provides a method for reducing MAI interference between multiple channels in the case of non-ideal equalization according to the MAI power corresponding function as a judgment condition. The MAI power correspondence function is used to determine the degree of correlation between code sequences.

Description

Resource allocation method and device for dynamic time-frequency and code sequence

technical field

The invention relates to resource allocation technology, in particular to a dynamic channel allocation method and device including time-frequency resources and sequence resources in an OFDM-CDMA multiple access system.

Background technique

Code Division Multiplexing (CDMA) is an advanced wireless spread spectrum communication technology used in digital cellular mobile communication in recent years. The code division multiplexing (CDMA) system adopts direct sequence spread spectrum (DS-SS) to overcome frequency selective fading in the channel, but its capacity is limited by multiple access interference (MAI for short), and MAI comes from incomplete spreading Autocorrelation and cross-correlation properties of frequency codes. A method to suppress inter-chip interference in frequency-selective fading channels is to combine CDMA technology with multi-carrier modulation, such as Orthogonal Frequency Division Multiplexing (OFDM) technology, to form various OFDM-CDMA systems to achieve more High spectral efficiency. Multi-carrier CDMA (MC-CDMA) and Orthogonal Frequency Domain Code Division Multiplexing (OFCDM) are typical representatives of OFDM-CDMA systems. Considering that in the multi-carrier CDMA system, the orthogonal spread spectrum is carried out in the frequency domain, David Mottier and Damien Castelain published "A spreading sequence allocation procedure for MC- In the article "CDMA transmission systems", it is mentioned that in the multi-carrier CDMA (MC-CDMA) system based on Walsh (Walsh) codes, the method of code sequence allocation is provided to reduce the number of channels between multiple channels in the case of non-ideal channel equalization. MAI interference. After that, Qinghua Shi and M.Latva-aho published "Simple spreading code allocation scheme for downlink MC-CDMA" in Electronics letters in July 2002, based on the characteristics of Walsh code distribution in the frequency domain, further A more simplified code sequence allocation method in MC-CDMA system is provided.

Based on CDMA technology and multi-carrier modulation technology, Liao Jingyi, Wang Hai et al. proposed a variable-based Orthogonal Time-Frequency Domain Code Division Multiple Access (VSFH-OTFCDM) with Spread Spectrum and Frequency Hopping. The idea is to use frequency hopping and variable spreading factors to jointly control the orthogonal code channel in the time-frequency domain, adopt variable-rate orthogonal spread spectrum, and map the spread spectrum information to subcarriers in the time-frequency domain, and transmit it through the OFDM system. In the VSFH-OTFCDM system, time, frequency and orthogonal spread spectrum codes together constitute channel resources for data transmission. In order to reduce multiple access interference, the mutual orthogonality of each channel in time, frequency and code domain should be guaranteed.

The VSFH-OTFCDM access scheme is similar to many OFDM-CDMA multiple access systems. The spread spectrum information is transmitted with one or more subcarriers in OFDM symbols. Therefore, in order to reduce multiple access interference, the orthogonality between multiple users Sexuality also needs to be maintained in the time-frequency domain. A channel is defined below as a transmission unit consisting of an orthogonal spreading sequence allocated on one or more time-frequency blocks (TFB). Each time-frequency block is composed of continuous or discontinuous subcarriers in the time domain and frequency domain. To facilitate channel equalization and system design, the time and frequency range of the time-frequency block should be smaller than the channel coherence time and coherence bandwidth.

When the spreading factor (SF) of the orthogonal spreading code is larger than the total number of subcarriers in a TFB block, the time-frequency resource of a channel will consist of multiple time-frequency blocks (TFB). According to the selected method, the TFB block composition of the channel can adopt the static channel allocation method, that is, each channel allocates TFB blocks according to a preset scheme or formula. The advantage of this allocation method is that the resource allocation method is simple, and the disadvantage is that some TFB blocks that make up the channel may encounter deep fading, thereby affecting system performance. Another method for channel composition is to use dynamic channel allocation. The TFB blocks that make up the channel can be assigned to a certain channel according to its channel characteristics, such as allocating TFB blocks with good channel quality to avoid the impact of deep fading. Improve system performance.

However, with this method of dynamic channel allocation, the TFB blocks allocated to each channel will be randomly distributed in the time-frequency domain of OFDM, especially when the SF factor of the orthogonal spreading code is greater than the total number of subcarriers in a TFB block, It is more necessary to effectively select the orthogonal spread spectrum code sequence to meet the orthogonality of time, frequency and code domain of channel allocation, thereby reducing MAI interference. That is to say, it is required that the allocation of the orthogonal spreading codes of the multiple time-frequency blocks composing the channel of the newly allocated channel should guarantee the orthogonality with the originally allocated spreading codes in these time-frequency blocks. In the OFDM-CDMA multiple access system, when using orthogonal spreading codes for spreading transmission, the maintenance of its orthogonal characteristics is closely related to the performance of channel equalization. It is necessary to further propose a method for reducing MAI interference between multiple channels in different situations such as ideal and non-ideal channel equalization.

Contents of the invention

The object of the present invention is to provide a dynamic channel allocation method and device including time-frequency resources and sequence resources, wherein sequence allocation is used to reduce multiple access interference in the system.

According to one aspect of the present invention, a method for resource allocation of dynamic time-frequency and code sequences comprises the steps of:

Find the appropriate time-frequency resource block according to channel quality and other parameters, and complete the time-frequency resource allocation for the channel;

According to the allocated code sequence information in the time-frequency resource block, the allocation of the code sequence in the allocated time-frequency resource block is completed.

According to another aspect of the present invention, a resource allocation device for dynamic time-frequency and code sequences includes:

Modulation module 304, for modulation processing of source information 302 without channel coding or channel coding;

The channel mapping module 312 performs orthogonal spread spectrum on the modulated information, and maps the spread spectrum information to allocated time-frequency resources;

The Fourier inverse transform module 314 performs IFFT processing on the channel-mapped information and transmits it through the OFDM system; the TFB resource allocation module 310 determines the TFB blocks for channel allocation according to the CQI information in each TFB;

The channel allocation and code allocation management module 308 will store and manage the information of the allocated code sets in the TFB;

The sequence allocation module 306, according to the code set information allocated in the corresponding time-frequency resource TFB block provided by the management module 308, according to the requirements of satisfying the orthogonality characteristics of the multi-channel code sequence and reducing the MAI interference between the multi-channels, allocates The sequence allocation is completed in the time-frequency resources.

The present invention is aimed at the multiple access system of OFDM-CDMA, and utilizes dynamic time-frequency resources to allocate time-frequency resources to channels with good channel quality; when the time and frequency resources allocated to channels overlap with other channel time-frequency resources, the Reasonable allocation of code sequence resources maintains the orthogonality of all code sequences of multiple channels in partially overlapping time-frequency resources, reduces MAI interference between multiple channels, and improves signal transmission quality. It further provides a method for reducing MAI interference between multiple channels in the case of non-ideal equalization according to the MAI power corresponding function as a judgment condition. The MAI power correspondence function is used to determine the degree of correlation between code sequences.

Description of drawings

Fig. 1 is the time-frequency resource composition of the channel based on OFDM system;

Fig. 2 is the composition of Walsh code sequence;

Fig. 3 is a dynamic channel allocation model based on OFDM-CDMA multiple access system;

Fig. 4 is the flow of dynamic time-frequency resource and sequence allocation based on OFDM-CDMA multiple access system;

Fig. 5 is an example of dynamic time-frequency resource and sequence allocation (SF=8, number of TFB subcarriers=4).

Detailed ways

The present invention provides a dynamic channel allocation method including time-frequency resources and sequence resources, wherein the sequence allocation is used to reduce multiple access interference (Multiple Access Interference, MAI) in the system. Its core idea is that for OFDM-CDMA multiple access systems, dynamic time-frequency resources are used to allocate time-frequency resources to channels with good channel quality; when the time and frequency resources allocated to channels overlap with time-frequency resources of other channels, Through the reasonable allocation of code sequence resources, the orthogonality of all code sequences of multiple channels in partially overlapping time-frequency resources is maintained, and the MAI interference between multiple channels is reduced. It further provides a method for reducing MAI interference between multiple channels in the case of non-ideal equalization according to the MAI power corresponding function as a judgment condition. The MAI power correspondence function is used to determine the degree of correlation between code sequences. Based on the multiple access system of OFDM-CDMA, the allocation of channel resources will include the allocation of one or more time-frequency resource blocks and code sequence resources.

The dynamic channel and sequence allocation method mentioned in the present invention is mainly aimed at the OFDM-CDMA multiple access system. Figure 1 shows the channel composition based on OFDM time-frequency resources. Fig. 1-(a), Fig. 1-(b), and Fig. 1-(c) respectively show three ways of composition of time-frequency resources of channels based on OFDM system. In the time-frequency resource structure 10 shown in FIG. 1, a time-frequency block (TFB) 104 is composed of one or more subcarriers 102, where the time-frequency block TFB in FIG. 1-(a) consists of multiple subcarriers continuous in the frequency domain Carrier composition, the time-frequency block TFB in Figure 1-(b) is composed of multiple subcarriers that are continuous in the time domain, and the time-frequency block TFB in Figure 1-(c) is composed of multiple subcarriers that are continuous in the time and frequency domains.

The time-frequency resources allocated on the channel 106 may consist of one or more TFB blocks. Using OFDM-CDMA multiple access technology, spread spectrum information will be transmitted using the time-frequency resources of the channel composed of one or more TFB blocks.

When the spreading factor SF is greater than the number of subcarriers in a TFB, a channel will consist of multiple TFBs. When dynamic channel allocation is adopted, multiple TFB blocks constituting each channel will appear as random distribution in the time-frequency domain of OFDM. The present invention will provide dynamic channel allocation and code sequence allocation when the spreading factor SF is larger than the number of subcarriers in one TFB.

The channel allocation including time frequency and sequence resources will jointly complete the resource allocation including time, frequency and spreading code in the OFDM-CDMA multiple access system. Among them, the dynamic time-frequency block (TFB) resource allocation will depend on parameters such as channel quality information (CQI) for allocation. In the case of dynamic time-frequency resource allocation, for different situations such as ideal balance and non-ideal balance, the code sequence allocation will be performed according to the code sequence allocation principle with the least MAI interference.

When the Spread Factor (SF) of the spreading sequence that makes up the channel is greater than the number of subcarriers in a TFB block, a channel will consist of multiple TFBs. Under dynamic time-frequency block (TFB) resource allocation, time-frequency resources constituting a channel can be determined according to information such as the CQI value of each TFB block. Wherein, the CQI value of each TFB block may be a signal-to-noise ratio (SNR) parameter or a signal-to-interference ratio (SIR) parameter of the TFB block. The method for determining the CQI value of each TFB block may be to use channel detection information, blind detection of transmission information, or use channel symmetry characteristics in a time division duplex (TDD) system.

Walsh (Walsh) sequences are used for spread spectrum transmission, and the orthogonality of the Walsh sequences is used at the receiving end to despread the spread spectrum information. Figure 2 shows the composition of the Walsh code sequence when the spreading factors SF are 1, 2, 4, and 8. In order to correctly complete the orthogonal despreading of the spread spectrum information in the OFDM-CDMA system, it is required to maintain the orthogonality of the spread spectrum information during despreading at the receiving end. Assuming that the system is ideally balanced, that is, when the receiving end performs ideal estimation and channel equalization on the transmission channel, when the spreading factor SF is not greater than the number of subcarriers in one TFB, a channel will consist of one TFB. Interaction characteristics will not be destroyed during transmission. And when the spreading factor SF is greater than the number of subcarriers in a TFB, a channel will be composed of multiple TFBs, especially under dynamic time-frequency block (TFB) resource allocation, the multiple TFB blocks that make up each channel will be in OFDM In the time-frequency domain, it appears as a random distribution. In this way, multiple channels may partially overlap in time-frequency resources, so that even under ideal equalization, the allocation of code sequences needs to take into account both the original code sequence allocation in the TFB blocks that make up the channel, and the Wall What (Walsh) sequence characteristics. The following will focus on the composition method of the ideally balanced lower code sequence. Assuming that the spreading factor SF=8, that is, the spreading sequence length is 8, each TFB block contains 4 subcarriers, and the time-frequency resource of one channel will consist of 2 TFBs.

Table 1. Example of allocated TFB resources and code sequences channel number Assigned TFB block number and sequence Assigned TFB block number and sequence Assigned TFB block number and sequence Assigned TFB block number and sequence channel 0 TFB A TFB C a _{1, 0} a _{1, 1} a 1 _{, 2} a _{1, 3} a _{1, 4} a 1 _{, 5} a 1, ₆ a _{1, 7} channel 1 TFB B TFB D b _{1, 0} b _{1, 1} b _{1, 2} b _{1, 3} b _{1, 4} b 1 _{, 5} b 1 _{, 6} b _{1, 7} channel 2 TFB A TFB D c _{1, 0} c _{1, 1} c 1 _{, 2} c _{1, 3} c _{1, 4} c 1 _{, 5} c 1 _{, 6} c _{1, 7} Assume that channel 0 and channel 1 have already been allocated, wherein channel 0 occupies TFB blocks A and C, and the allocated sequence is A=(a _{1, 0} a _{1, 1} a 1 _{, 2} a 1, ₃ a _{1, 4} a _{1, 5} a 1 _{, 6} a _{1, 7} ); channel 1 occupies TFB blocks B and D, and the assigned sequence is B=(b _{1, 0} b _{1, 1} b 1 _{, 2} b _{1, 3} b _{1, 4b1 , 5b1 , 6b1} , ₇ ). Assume that the newly allocated channel 2 will occupy TFB blocks A and B, and assume that the sequence to be allocated is C = (c _{1, 0} c _1, 1 c _{1, 2} c _{1, 3} c 1 _{, 4} c 1, ₅ c _{1 , 6} c _{1, 7} ). Channel 2 will partially overlap channel 0 on TFB block A, and channel 2 will partially overlap channel 1 on TFB block D. Assuming S ₁ , S ₂ and S ₃ are data symbols transmitted on channels 0, 1 and 2, respectively, let C′=[c _1,0 , c _1,1 , c _1,2 , c _1,3 , 0, 0, 0, 0], C″=[0, 0, 0, 0, c ₁ , ₄ , c 1, 5 , c _{1, 6} , c _{1, 7} ], and let C1 and C2 represent the sequence respectively The first half and the second half of C are C1=c _1,0 , c _1,1 , c _1,2 , c _1,3 ], C2=[c _1,4 , c _1,5 , c _{1, 6} , c _{1, 7} ]. Let the expression " be expressed as the sum of dot products between two vectors. Then according to the orthogonal despreading, in order to maintain the orthogonality of channel allocation, the code sequence C allocated to the newly allocated channel 2 will satisfy the following characteristics:

$\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 8</span>}}\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="S"\; filenames="A20041009049800182.png"\; state="\{\{state\}\}">S</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

$\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 8</span>}}\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}^{<span\; class="notranslate">\; \&prime;</span><span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

From equations (1) and (2), it can be deduced that $\left\{\begin{array}{c}A\&CenterDot;C^{\&prime;}=0\\ B\&Center\; Dot;C^{\&prime;\&prime;}=0\end{array}\right....\left(3\right)$ , that is to say, the left half of sequence A and the right half of sequence B should be orthogonal to the left half C1 and right half C2 of sequence C respectively. Meanwhile, because the code sequence C=[C1 C2] is still a Walsh sequence, therefore, C1 and C2 will also have the following characteristics:

C2＝C1 or C2＝-C1 (4)

Combining expressions (3) and (4), the generation method of code C can be deduced:

$\mathrm{<span\; class="notranslate">\; subject</span>}<span\; class="notranslate">\; .</span>\left\{\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="C"\; filenames="A20041009049800182.png"\; state="\{\{state\}\}">C</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; ]</span>& & \\ & \mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; C</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}& \\ & \mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}^{<span\; class="notranslate">\; \&prime;</span><span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}& \\ \mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="C"\; filenames="A20041009049800182.png"\; state="\{\{state\}\}">C</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; or</span>}& \mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="C"\; filenames="A20041009049800182.png"\; state="\{\{state\}\}">C</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right.<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

When the spreading factor SF is greater than the number of subcarriers in the TFB block, the transmission spreading sequence is transmitted in multiple TFBs, and the allocation principle of the spreading sequence when the TFB block resources of different channels overlap is illustrated by the expression (5). That is, when the assigned channel and the existing channel overlap in time-frequency resources, the orthogonality of the codes at the overlapped time-frequency resources should be guaranteed. According to this principle, the code sequence is allocated, which will ensure the orthogonality of the code allocation under ideal balance, and the system has no MAI interference. Further, the code sequence allocation method under ideal equalization can be determined: when the spreading factor SF is greater than the number of subcarriers in the TFB block, in each possible TFB block allocated for a certain channel, according to the part of the Walsh code already allocated on it Or the entire sequence, calculate or look up the table to obtain some or all sequences of other Walsh codes that are orthogonal to it; perform sequence combination according to the characteristics of the Walsh code, such as the case where the spreading factor SF is twice the number of subcarriers of the TFB block, Only the sequences that meet the condition (4) can be combined; continue to calculate or look up the table for various TFB block combinations allocated to the channel to determine the final allocated spreading sequence. This method can be further used in cases where the spreading factor SF is an integer multiple (>2) of the number of subcarriers in a TFB block. In these cases, the time-frequency resources that make up the channel will include multiple (>2) TFB blocks, dynamically Orthogonal sequence resource allocation will need to satisfy the sequence allocation orthogonality of each channel in overlapping TFB blocks.

In the actual environment, due to factors such as channel distortion, MAI interference is caused, and then the orthogonality of Walsh codes is destroyed, and its orthogonal decoding is destroyed. For OFDM-CDMA combined systems, channel equalization will be done in OFDM frequency domain. Commonly used detection techniques, such as equal gain combining (Equal GainCombining, EGC), minimum mean square error combining (Minimum Mean Square ErrorCombining, MMSEC) and other methods can be used for channel equalization of the OFDM-CDMA combined system. However, these methods will still cause a certain channel equalization deviation, which will cause MAI interference, and then affect the orthogonal decoding. In the following, the MAI power corresponding function will be used to make a decision to determine the code allocation process in the channel. Specifically, when there is a partial overlap with the time-frequency resources of other channels, it should be ensured that the found spreading code overlaps the time-frequency resources and the orthogonality of the allocated code set; further according to the For the allocated code set in the allocated time-frequency resources, find a suitable spreading code in the remaining code set according to the method with the minimum value of the MAI power corresponding function. The MAI power corresponding function is used to determine the degree of correlation between code sequences. The corresponding function for seeking the minimum MAI power is expressed by formula (6).

${\mathrm{<span\; class="notranslate">\; \&Omega;</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; opt</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; arg</span>}\underset{{\mathrm{<span\; class="notranslate">\; \&Omega;</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}<span\; class="notranslate">\; \&Element;</span>\mathrm{<span\; class="notranslate">\; \&Omega;</span>}}{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; max</span>}\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; \&Element;</span>{\mathrm{<span\; class="notranslate">\; \&Omega;</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; \&Element;</span>{\mathrm{<span\; class="notranslate">\; \&Omega;</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; \&NotEqual;</span>\mathrm{<span\; class="notranslate">\; k</span>}}{<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; W</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

in $T\left(x\right)=\frac{1}{2}\underset{i=0}{\overset{\mathrm{Nc}-2}{\mathrm{\&Sigma;}}}|\mathrm{sgn}\left(x_{i+1}\right)-\mathrm{sgn}\left(x_i\right)|$

Among them, W ^{(j, k) is} the new vector obtained after multiplying the jth and k sequences, and each vector unit of the new vector is the product value of the corresponding unit of j and k sequences, Ω _K is all possible code sequence sets, T (x) represents the number of transitions of vector x crossing zero.

Figure 3 is a dynamic channel allocation model based on OFDM-CDMA multiple access system. The source information 302 without channel coding or channel coding is modulated by the modulation module 304. In the channel mapping module 312, the orthogonal spread spectrum of the modulated information will be completed, and the spread information will be mapped to the allocated time frequency. resources, the information after the channel mapping is completed will be processed by the IFFT module 314, and then transmitted through the OFDM system. The system will carry out the channel allocation process according to information such as allocated sequence resources and channel conditions. Among them, the TFB resource allocation module 310 will decide according to the CQI information; the selected TFB block information will be communicated to the channel allocation and code allocation management module 308; in the channel allocation and code allocation management module 308, the TFB will be stored and managed Assign code set information; the sequence allocation module 306 reduces the MAI interference between multiple channels according to the code set information allocated in the corresponding time-frequency resource TFB block provided by the management module 308, and according to the orthogonality characteristic that satisfies the multi-channel code sequence and other requirements, the sequence allocation is completed in the allocated time-frequency resources. Sequence allocation will be done according to the respective processes according to ideal and non-ideal equilibrium situations.

The flow of dynamic time-frequency resource and sequence allocation based on OFDM-CDMA system is shown in Fig. 4 . Firstly, the time-frequency resource allocation is completed, and the appropriate TFB resource block 400 can be found according to the channel quality CQI and other information, and the allocated code sequence information 402 can be obtained from it; then the code sequence allocation under ideal equalization is completed. In this process, firstly, in module 404, it is judged whether the newly allocated TFB resource overlaps with the TFB block resource of the allocated channel. If not, then the allocatable code sequence 408 will be determined according to the characteristics of the Walsh sequence. If overlapping occurs, the feasible code sequence 406 can be found and combined according to formula (5); in the judgment of the equalization situation 410 module, if it is an ideal equalization condition, then the feasible TFB block set and code sequence found can be output gather. If it is not ideal equalization, 412 will use the MAI power corresponding function (6) as a decision condition to find and determine the final feasible sequence.

In the above ideal and non-ideal equalization situations, the sequence selection in formula (5) and the MAI power corresponding function in formula (6) are only related to the sequence itself, not to the channel characteristics. or part thereof, the combination of different sequences is calculated and stored in advance, and the sequence information to be allocated can be quickly obtained by looking up the table in dynamic channel allocation.

Example

Figure 5 shows an example of dynamic time-frequency resource and sequence allocation when the spreading factor SF is 8 and the number of TFB subcarriers is 4. Assume that two channels have occupied TFB block A in OFDM symbol 1 and TFB block D in OFDM symbol 2 respectively, and the two channels have respectively occupied TFB block B in OFDM symbol 1 and OFDM symbol 2 The TFB block E of the other two channels also occupy the TFB block C in OFDM symbol 1 and the TFB block F in OFDM symbol 2 respectively. The existing sequence assignments in TFB blocks A, B, F are further shown in FIG. 5 . Assume that in the process of dynamic time-frequency resource allocation, TFB blocks A and B in OFDM symbol 1 and TFB block F in OFDM symbol 2 meet the requirements. See Tables 2 and 3 for the code sequence selection process. Wherein, Table 2 lists the results of allocation of TFB blocks and code sequences obtained according to formula (5) under ideal equalization conditions. The optional TFB block combinations are {TFB-A, TFB-F} and {TFB-B, TFB-F}, and the optional code sequence in the TFB block combination {TFB-A, TFB-F} is c3 or c4 , the optional code sequences in the TFB block combination {TFB-B, TFB-F} are c1, c2, c7 or c8.

Table 3 further lists the results of allocation of TFB blocks and code sequences according to formula (6) in the case of non-ideal equalization. Optional TFB block combinations are {TFB B, TFB F}. The optional code sequence obtained according to the MAI power corresponding function is c1 or c2.

Table 2. Optional TFB blocks and code sequences under ideal equalization In OFDM symbol 1 In OFDM symbol 2 TFB block selected according to CQI A B f Sequences allocated in each corresponding TFB block (1, 1, 1, 1) (1, -1, -1, 1) (1, -1, 1, -1) (1, 1, -1, -1) (1, -1, 1, -1) Sequences allocable in each corresponding TFB block (1, -1, 1, -1) (1, 1, -1, -1) (1, 1, 1, 1) (1, -1, -1, 1) (1,1,-1,-1)(-1,-1,1,1)(1,-1,-1,1)(-1,1,1,-1)(1,1,1 ,1)(-1,-1,-1,-1) Optional TFB block combinations {TFB-A, TFB-F}, {TFB-B, TFB-F} Alternative sequence derived from formula (5) c4=(1,1,-1,-1,-1,-1,1,1) c3=(1,1,-1,-1,1,1,-1,-1) C1=(1,1,1,1,1,1,1,1) C2=(1,1,1,1,-1,-1,-1,-1)C7=(1,-1, -1, 1, 1, -1, -1, 1) C8 = (1, -1, -1, 1, -1, 1, 1, -1)

Table 3. Optional TFB blocks and code sequences under non-ideal equalization The optional code sequence in the TFB block and the weight value obtained by formula (6) TFB-A TFB-B possible code sequence (1, 1, -1, -1) (1, -1, -1, 1) (1,1,1,1) Weight set Ω ^(opt) {-3,-1} {-3,-1} {-3,-1} TFB-F possible code sequences (1, 1, -1, -1) (-1, -1, 1, 1) (1, -1, -1, 1) (-1, 1, 1, -1) (1,1,1,1) (-1, -1, -1, -1) Weight set Ω ^(opt) -2 -2 -1 -1 -3 -3 Optional TFB block combination {TFB B, TFB F} optional sequence {c1,c2}

The present invention provides a channel allocation method including dynamic time-frequency resource allocation and sequence allocation, using dynamic time-frequency resources to allocate time-frequency resources to channels with good channel quality, dynamic sequence allocation is used to reduce multiple access interference (Multiple Access Interference) in the system , MAI). Provides a sequence allocation method that maintains the orthogonality of all code sequences of multiple channels in partially overlapping time-frequency resources under ideal equalization conditions and reduces MAI interference between multiple channels. Among them, the sequence allocation should meet the orthogonality characteristic of the time-frequency resource overlapping part in the multi-channel allocation, and then complete the sequence allocation through sequence combination, so as to satisfy the orthogonality of the sequence allocation of the whole system. In the case of non-ideal equalization, it further provides a sequence allocation method that maintains the orthogonality of all code sequences of multiple channels in partially overlapping time-frequency resources and reduces MAI interference between multiple channels. Among them, according to the MAI power corresponding function as the judgment condition, the sequence allocation should meet the orthogonality characteristics of the time-frequency resource overlap in multi-channel allocation, and have the corresponding function value of the minimum MAI power, and then complete the sequence allocation through sequence combination, reducing the system Multiple Access Interference in . Provides channel allocation procedures for dynamic time-frequency resource allocation and sequence allocation under ideal and non-ideal equalization conditions. The allocation method provided is only related to the sequence itself, and does not involve channel characteristics, so these parameters can be pre-calculated and stored. In dynamic channel allocation, the sequence information to be allocated can be quickly obtained by looking up the table, which is convenient for system application.

Claims (12)

1. the resource allocation methods of dynamic time-frequency and sign indicating number sequence comprises step:

Seek suitable temporal frequency Resource Block (TFB piece) according to parameters such as channel qualities, finish time-frequency resource allocating channel;

According to the sign indicating number sequence information that has distributed in the temporal frequency Resource Block, finish the sign indicating number sequence allocation in the temporal frequency Resource Block that distributes.

2. by the described method of claim 1, it is characterized in that described sign indicating number sequence allocation comprises:

Judge newly assigned temporal frequency Resource Block whether and the temporal frequency Resource Block of allocated channel partly overlap;

Do not overlap if there is part, then the sign indicating number sequence of distributing with decision according to the orthogonal property that satisfies sequence.

3. by the described method of claim 1, it is characterized in that the described yard sequence allocation of finishing comprises:

If judge newly assigned temporal frequency Resource Block and the temporal frequency Resource Block of allocated channel part takes place overlaps;

Then according to sign indicating number sequence of having distributed in the temporal frequency Resource Block that overlaps or part sign indicating number sequence information, in the temporal frequency Resource Block that overlaps, seek assignable and satisfy the sign indicating number sequence or the part yard sequence of orthogonal property, and finish the sequence allocation in the whole newly assigned temporal frequency Resource Block by combined sequence.

4. by the described method of claim 3, it is characterized in that also comprising: if newly assigned temporal frequency Resource Block and the temporal frequency Resource Block of allocated channel the part overlapping takes place, and under imperfect equilibrium,

During sign indicating number sequence of distributing or part sequence sets close, seek the sign indicating number sequence or the part sign indicating number sequence that reach multiple access interference (MAI) power respective function minimum value in each temporal frequency Resource Block;

Finish the sequence allocation in the whole newly assigned temporal frequency Resource Block by combined sequence.

5. by the described method of claim 1, it is characterized in that, determine to form the temporal frequency resource of a channel according to the size of the channel quality value of each temporal frequency piece.

6. by the described method of claim 1, it is characterized in that the TFB piece of forming a channel is one or more.

7. by the described method of claim 3, it is characterized in that, in the Walsh orthogonal sequence distributes, when the spreading factor (SF) of the sequence of distributing equals 2N, and when equaling to form the twice of TFB piece sub-carriers number of channel, make C '=[c _1,0, c _1,1..., c _{1, N-1}, 0,0 ..., 0], C "=[0,0,0,0, c _{1, N}, c _{1, N+1}..., c _1,2N-1], C1 and C2 represent the first half and the latter half of sequence C, C1=[c respectively _1,0, c _1,1.., c _{1, N-1}], C2=[c _{1, N}, c _{1, N+1}..., c _1,2N-1], A and B represent to be assigned to the sequence in the TFB piece of sequence C 1 and C2 correspondence respectively.New assigned sequence C will be the combination of sequence C 1 and C2, and meet the following conditions:

$\mathrm{subject}.\left\{\begin{array}{ccc}C=[C1,C2]& & \\ & A\&CenterDot;C^{\&prime;}=0& \\ & B\&CenterDot;C^{\&prime;\&prime;=0}& \\ C2=C1& \mathrm{or}& C2=-C1\end{array}\right.$

8. by the described method of claim 7, it is characterized in that sequence selection is only relevant with sequence itself.

9. by the described method of claim 4, it is characterized in that, under imperfect equilibrium situation, adopt equalization methods such as equal gain combining and Minimum Mean Square Error merging.

10. by the described method of claim 4, it is characterized in that, seek minimum MAI power respective function and represent with following formula:

${\mathrm{\&Omega;}}_K^{\left(\mathrm{opt}\right)}=\arg \underset{{\mathrm{\&Omega;}}_K\&Element;\mathrm{\&Omega;}}{\min }\underset{j\&Element;{\mathrm{\&Omega;}}_K,k\&Element;{\mathrm{\&Omega;}}_{K,},j\&NotEqual;k}{\left(\max (-T\left(W^{(j,k)}\right))\right)}$

Wherein $T\left(x\right)=\frac{1}{2}\underset{i=0}{\overset{\mathrm{Nc}-2}{\mathrm{\&Sigma;}}}|\mathrm{sgn}\left(x_{i+1}\right)-\mathrm{sgn}\left(x_i\right)|$

W ^{(j, k)}Be j, the new vector that obtains after the k sequence multiplies each other, each vector location of new vector is j, the product value of k sequence corresponding unit, Ω _KFor all possible sequence sets closes, the conversion times of T (x) expression vector x zero passage.。

11., it is characterized in that MAI power respective function is all only relevant with sequence itself, and does not relate to the characteristic of channel by the described method of claim 10.

12. the resource allocation device of dynamic time-frequency and sign indicating number sequence comprises:

Modulation module (304) is to the modulation treatment of the information source information (302) of no chnnel coding or chnnel coding;

Channel Mapping module (312) is carried out orthogonal spectrum expansion to modulation intelligence, and with the running time-frequency resource of the information mapping behind the spread spectrum to distribution;

Fu Liye inverse transformation (IFFT) module (314) is carried out IFFT to the information after the channel Mapping and is handled, and transmits by ofdm system;

TFB resource distribution module (310) decides the TFB piece of channel allocation according to the CQI information among each TFB;

A channel allocation and a sign indicating number allocation manager module (308) are with the information of assigned code collection among storage and the management TFB;

Sequence allocation module (306), according to the administration module 308 sign indicating number collection information of in corresponding running time-frequency resource TFB piece, having distributed of providing, according to the orthogonal property that satisfies multichannel sign indicating number sequence, and the demands such as MAI interference between the minimizing multichannel, in the running time-frequency resource that distributes, finish sequence allocation.

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