CN101282160A - Method for collocating OFDM system - Google Patents

Abstract

The present invention discloses a method for configuring a high-bandwidth orthogonal frequency division system. The method comprises the following steps: A. confirming the system bandwidth and the basic subcarrier distance deltaF; B. setting the subcarrier distance to n times of deltaF according to the bandwidth, n is larger than or equal to 1; C. setting other parameters of the physical layer structure according to the new subcarrier distance confirmed in step B; and D. constructing a frame structure indication according to the parameters in steps B and C and transmitting. The problem of overlarge scale of FFT under high bandwidth can be overcome when the plan according to the invention is adopted.

Description

The collocation method of ofdm system

Technical field

The present invention relates to the radio digital communication field, particularly relate to a kind of based on OFDM (Orthogonal Frequency Division Multiplex, OFDM) collocation method of the physical layer signal parameter of the system of technology.

Background technology

As a kind of multi-carrier transmission pattern, OFDM is converted to one group of low-speed parallel data flow transmitted by the data flow with a high-speed transfer, system is reduced greatly to the susceptibility of multidiameter fading channel frequency selectivity, and the introducing of Cyclic Prefix, further strengthened anti-intersymbol interference (the Inter-symbol Interference of system again, ISI) ability, in addition bandwidth availability ratio height, realize that characteristics such as simple make OFDM more and more wider in the application in radio communication basin, such as, wlan system all is based on the system of OFDM technology based on WiMax system of orthogonal frequency division multiplexing multiple access etc.

The wireless communication system of a new generation has mostly adopted the technology based on OFDMA, as the descending employing of LTE OFDMA, and WiMAX, employings such as UMB provisional capital up and down are OFDMA, or the like.

Common system supports the wireless bandwidth in the certain limit, and for example LTE supports the wireless bandwidth of 1.25MHz～20MHz, and WiMAX also supports the wireless bandwidth of this scope.Adopt the Scalability design, no matter wireless bandwidth (in the support scope) what are, can keep subcarrier spacing constant, thereby the OFDM cycle of time domain is consistent, this gives system design and realization brings great convenience and cost advantage.But in the IMT-Advanced system, wireless bandwidth demand and support are reached the high bandwidth of maximum 100MHz.High bandwidth provides material base for the system requirements of high-throughput, but has also brought challenge to system design.

Such as, when the wireless bandwidth maximum was 20MHz in WiMAX and LTE, its basic subcarrier spacing was respectively 10.94kHz, and 15kHz, so be 2048 points as the size of the FFT (fast fourier transform) of the key technology of OFDMA.Adopt Scalability technology commonly used, can expand to high wireless bandwidth (high bandwidth promptly＞bandwidth of 20MHz).When arriving the wireless bandwidth of 80MHz such as system extension, the size of FFT will reach 8192 points.So the FFT of scale in the industry cycle still can not well support at present.If expand to the wireless bandwidth of 100MHz, then FFT's is larger, and system's implementation complexity of this moment is sizable.

Summary of the invention

The purpose of this invention is to provide the collocation method of a kind of orthogonal frequency system, should overcome the too big problem of FFT scale under the high bandwidth above-mentioned, guarantee under the acceptable situation of systematic sampling rate, to improve the efficient of system again.

To achieve these goals, the invention provides the collocation method of a kind of high bandwidth orthogonal frequency system, may further comprise the steps:

A, determine system bandwidth and basic subcarrier spacing Δ F;

B, be n times of Δ F according to the bandwidth settings subcarrier spacing, n is more than or equal to 1;

C, set other parameter of physical layer architecture according to the new subcarrier spacing of determining among the step B;

D, according to the parametric configuration frame structure among step B, C indication and send.

Further, among the described step B:, set n greater than 1 when system bandwidth during greater than 20MHz.

Further, described steps A also comprises: the length of determining basic Cyclic Prefix;

Also comprise among the described step C: the circulating prefix-length of OFDM symbol is taken as basic circulating prefix-length

Doubly.

Further, described step C also comprises: the n frequency multiplication that the control clock of time-domain signal is taken as existing control clock.

Further, also exist behind the described step D:

E, receiver dispose the physical layer parameter of oneself after receiving the frame structure indication;

F, system begin to carry out proper communication.

The present invention has following advantage: (1) avoided large-scale FFT; (2) system realizes that clock only adopts simple frequency multiplication to get final product; (3) can be at smooth evolution in the original system design; (4) do not influence physical layer frame structure, thereby can under constant substantially PHY (physical layer) structure, expand to bigger spectral bandwidth.

Description of drawings

Fig. 1 is the concrete implementing procedure figure of the collocation method of ofdm system of the present invention;

Fig. 2 is the schematic diagram of the OFDM symbol during n=2 and basic OFDM symbol in the application example 1 of the present invention.

Embodiment

Below in conjunction with drawings and Examples technical scheme of the present invention is described in detail.

At first the present invention mainly is applicable to high-throughput under the high bandwidth situation, little covering, and static application scenarios, method of the present invention is based on that such application scenarios carries out.

In the OFDMA system, one frame is divided into several subframes, and the length of subframe is a prior determined value, because the difference of application scenarios, suitable configuration is selected by system from multiple different business demand, application scenarios and wireless bandwidth resource, in the hope of reaching higher system efficient and realizing simplicity.

The concrete implementation step of the collocation method of high bandwidth ofdm system of the present invention is as follows:

A, the wireless bandwidth of determining system and other wireless transmission environmental information, as the time delay expansion and the desired rate of information throughput, and according to prior art definite basic protection interval and basic symbol cycle; Here the implication of " substantially " is meant that these parameters are parameters selected when being 20MHz as bandwidth in the prior art, used parameter in the just present low-bandwidth systems; Wherein, obtain the length of basic cyclic prefix CP at interval according to basic protection; Inverse by the basic symbol cycle obtains basic subcarrier spacing Δ F.

B, be n times of Δ F according to the subcarrier spacing of the bandwidth settings native system of determining in the steps A, n is more than or equal to 1;

When n=1, be equivalent to continue to use the existing systems configuration; N＞1 o'clock can make 1/n that the OFDM symbol period is reduced into the basic symbol cycle doubly, thus under the situation that does not change sample rate, the size reduction of FFT be original 1/n doubly; And when the FFT size was constant, sample frequency was n a times of original sample frequency.The excessive problem of FFT scale when having solved high bandwidth like this, and from the angle that realizes, do not increase how many complexities.Simultaneously, when the present invention is not precluded within the large-scale FFT of industry support, when high bandwidth, still adopt basic subcarrier spacing to realize the possibility of system.

Can but be not limited to determine the value of n by following mode:

If wireless bandwidth is less and wireless environment allows, get n=1, promptly continue to use the existing system design; If wireless bandwidth is bigger, during such as the high bandwidth situation, then get n＞1.

In addition, this step also has another kind of implementation: determine to adopt the symbol period of 1/n basic symbol cycle doubly as native system.Because symbol period and subcarrier spacing are reciprocal each other, thus these two kinds of implementations actual be of equal value.

C, set other parameter of physical layer architecture, other parameters of respective settings physical layer architecture according to the new subcarrier spacing of determining among the step B.

In order better to realize above-mentioned purpose, it is simple that this method is realized, the CP length of OFDM symbol is made as basic CP's Doubly.At this moment, just be basic OFDM symbol period under the original low bandwidth at the OFDM of time domain symbol period (comprising CP)

Doubly, the control clock of time-domain signal only is required to be the n frequency multiplication that has basic controlling clock in the ofdm system now and gets final product like this.

Certainly, non-

CP doubly also can be through well-organized supported, and still needed sampling clock is complicated a little.

D, structure FSI (indication of Frame Structure Indicator frame structure) and broadcasting;

After E, receiver receive FSI, dispose the physical layer parameter of oneself;

F, configuration finish, and system begins to carry out proper communication.

Further be illustrated with of the present invention one application example below with big wireless bandwidth.

A, system determine wireless bandwidth, and obtain basic subcarrier spacing Δ F and basic CP length;

B, set 2 Δ F, i.e. n=2 as subcarrier spacing;

2,4,5 frequencys multiplication of original sampling clock can be respectively as 40MHz, the sampling clock under the wireless bandwidth of 80MHz and 100MHz.The value of each parameter when following table is Δ F=15kHz, the parameter when wherein bandwidth is 20MHz are basic parameter.

Table 1 n=2, the high bandwidth during Δ F=15kHz is handled

Bandwidth (MHz)	20	40	80	100
					Subcarrier spacing	15kHz	30kHz	30kHz	30kHz
Sample rate (MHz)	30.72	61.44	122.88	153.6
					The FFT size	2048	2048	4096	5120

C, the length of CP is made as half of fundamental length; For example, useful OFDM symbol period is T, adopts the CP length of T/8 when low-frequency band, under the application scenarios of high bandwidth, adopts the CP length of T/16 so.The schematic diagram of OFDM symbol during as shown in Figure 1, for n=2 and basic OFDM symbol; Basic OFDM symbol promptly adopts the OFDM symbol of basic symbol cycle and basic CP length.CP partly is the Cyclic Prefix of OFDM symbol among Fig. 1.And Useful OFDM Symbol partly is the useful symbolic component of OFDM symbol, the repetition of the normally useful symbolic component of Cyclic Prefix part back one piece of data.

The control clock of this time domain signal is that 2 frequencys multiplication of original control clock get final product.

All the other physical layer system parameters are done corresponding change, the system's operation under the realization high bandwidth that can be level and smooth.

The subcarrier spacing structure FSI that d, basis set; System broadcasts FSI.

E, receiver receive the system parameters of i.e. configuration oneself after these parameters.

F, beginning normal course of communications.

Certainly; the present invention also can have other various embodiments; under the situation that does not deviate from spirit of the present invention and essence thereof; those of ordinary skill in the art work as can make various corresponding changes and distortion according to the present invention, but these corresponding changes and distortion all should belong to the protection range of the appended claim of the present invention.

Claims (5)

1. the collocation method of an ofdm system comprises:

A, determine system bandwidth and basic subcarrier spacing Δ F;

B, be n times of Δ F according to the bandwidth settings subcarrier spacing, n is more than or equal to 1;

C, set other parameter of physical layer architecture according to the new subcarrier spacing of determining among the step B;

D, according to the parametric configuration frame structure among step B, C indication and send.

2. collocation method as claimed in claim 1 is characterized in that, among the described step B: when system bandwidth during greater than 20MHz, set n greater than 1.

3. collocation method as claimed in claim 1 is characterized in that, described steps A also comprises: the length of determining basic Cyclic Prefix;

Also comprise among the described step C: the circulating prefix-length of OFDM symbol is taken as basic circulating prefix-length

Doubly.

4. collocation method as claimed in claim 3 is characterized in that, described step C also comprises: the n frequency multiplication that the control clock of time-domain signal is taken as existing control clock.

5. collocation method as claimed in claim 1 is characterized in that, also exists behind the described step D:

E, receiver dispose the physical layer parameter of oneself after receiving the frame structure indication;

F, system begin to carry out proper communication.

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