Synchronous method of orthogonal freuency division multiplex in broadband radio insertion system

A broadband wireless, orthogonal frequency division technology, applied in the field of communication, can solve problems such as subcarrier interference, high symbol synchronization requirements, system performance degradation, etc., to improve frequency offset estimation performance, overcome interdependence, and reduce algorithm complexity Effect

Inactive Publication Date: 2008-05-21
NANJING UNIV OF POSTS & TELECOMM
View PDF3 Cites 0 Cited by
  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, it has very high requirements for symbol synchronization: OFDM uses orthogonal subcarriers to improve spectrum utilization, and if the timing is not synchronized, the orthogonality of subcarriers will be destroyed; frequency offset causes phase rotation and amplitude fading of useful signals, and more serious It causes interference between subcarriers, and the system performance will be greatly reduced, so it is very important to compensate for the system performance degradation caused by time and frequency asynchronization
[0003] In recent years, people have conducted extensive research on OFDM synchronization, among which the typical algorithms mainly include the following: Moose gives the frequency domain maximum likelihood estimation method to estimate the frequency offset, which essentially uses the repetition of symbols to estimate the frequency domain , Moose's idea based on repeated correlation provided the basic idea for the subsequent frequency offset estimation algorithm, but because his algorithm requires the frame header to use two repeated symbols and the channel coherence time is at least greater than the duration of two symbols, so This method is not used in many practical systems now; Nogami and Nagashima use a null symbol to synchronize the frame by detecting the power drop at the receiving end, but this method is suitable for continuous structures. For burst data structures, it cannot be correct This method is not suitable for distinguishing between Null symbol and idle time; Van de Beek proposed a maximum likelihood estimation algorithm based on CP, which cannot estimate integer frequency offset and cannot provide frame synchronization information, so it is mostly used for timing and frequency offset tracking stage, considering that the synchronous tracking should ensure a simple algorithm, many literatures have proposed various improved algorithms on this basis; M.Schmidl proposed a method based on training sequences, which realized energy detection and Fine synchronization and frequency offset estimation, the algorithm is relatively simple and easy to implement; Classen also proposed a pilot-based method, the premise of which is a slow time-varying channel. This algorithm has introduced ICI when estimating the frequency offset in the frequency domain, so the performance is improved. decrease; there are also many blind estimates currently being studied, because they are based on the average of multiple symbols, requiring slow time-varying channels, and the algorithm is complex and mostly used for frequency offset tracking

Method used

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
View more

Image

Smart Image Click on the blue labels to locate them in the text.
Viewing Examples
Smart Image
  • Synchronous method of orthogonal freuency division multiplex in broadband radio insertion system
  • Synchronous method of orthogonal freuency division multiplex in broadband radio insertion system
  • Synchronous method of orthogonal freuency division multiplex in broadband radio insertion system

Examples

Experimental program
Comparison scheme
Effect test

Embodiment Construction

[0022] The frame header structure of the present invention is as figure 1 As shown, it includes a long training sequence and a short training sequence, where the frame header 1 is a short training sequence including 4 repeated periods, each period has 64 sampling points, and the frame header 2 is a long training sequence including 2 repetition periods , each cycle has 128 sampling points, where CP is the cyclic prefix.

[0023] Specific programs such as figure 2 , mainly divided into the following five steps:

[0024] (1) Rough synchronization

[0025] Coarse synchronization utilizes the periodicity of frame header 1, and this algorithm can be called a delay-related algorithm, such as image 3 shown.

[0026] There are two sliding windows C and P shown in the figure. The C window is the correlation function of the received signal and its delayed signal, so it is called delay correlation, and the delay coefficient Z -D In the present invention, it is equal to the period l...

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to view more

PUM

No PUM Login to view more

Abstract

A synchronization method in OFDM broadband wireless access system includes such steps as utilizing NO.1 frame head as a delay related decision to realize rough synchronization, using the conjugate symmetry of No.2 frame head to realize accurate timing, the frame heads roughly and accurately estimate the decimal frequency deviation separately, the frequency field sequences of the two heads are used to estimate the integer frequency bias and finally synchronous tracing.

Description

technical field [0001] The invention relates to a synchronization realization scheme of Orthogonal Frequency Division Multiplexing (OFDM) especially for 802.16a broadband wireless access network, and belongs to the technical field of communication. Background technique [0002] The OFDM system has attracted more and more attention because of its advantages of strong anti-interference ability and high frequency utilization rate. The wireless broadband access system 806.16a adopts OFDM technology as one of the transmission methods of the system. However, it has very high requirements for symbol synchronization: OFDM uses orthogonal subcarriers to improve spectrum utilization, and if the timing is not synchronized, the orthogonality of subcarriers will be destroyed; frequency offset causes phase rotation and amplitude fading of useful signals, and more serious Therefore, it is very important to compensate for the system performance degradation caused by time and frequency async...

Claims

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to view more

Application Information

Patent Timeline
no application Login to view more
Patent Type & Authority Patents(China)
IPC IPC(8): H04L27/26H04L7/04
Inventor 吴蒙朱琦邵世祥张艳酆广增赵夙
Owner NANJING UNIV OF POSTS & TELECOMM
Who we serve
  • R&D Engineer
  • R&D Manager
  • IP Professional
Why Eureka
  • Industry Leading Data Capabilities
  • Powerful AI technology
  • Patent DNA Extraction
Social media
Try Eureka
PatSnap group products