Sun - 20 Aug 2017     
Search
  
Advanced Search
    Recent Design Document
  Non-inverting operational amplifier circuit

  OFDM Basics Tutorial

  Microwave test bench trainer, microwave telecommunication training system Microwave Bench, Microwave trainers, antenna trainer kit, microwave trainers supplier, antenna trainer kit suppliers, microwave antenna trainers, microwave trainers manufacturer, microwave trainers India, microwave components manufacturer, antenna trainer kit exporters, antenna trainer kit India, waveguide components exporter, microwave part suppliers, waveguide components suppliers, waveguide components manufacturer, microwave waveguide instruments, rotary joints, magic tees, horns, x-band microwave benches, waveguide components, bends, twist, couplers, isolators, instruments, circulators, Gunn oscillator, elbows, flanges and subsystems.

  Satellite Training System

  Wide Area Network Tutorial



    Most Read Document
     Non-inverting operational amplifier circuit

  Flash Memory - A Tutorial

  Satellite Training System

  Introduction to OSI model and Networking Components

  RFID Beginners Guide





    Featured Document
    Non-inverting operational amplifier circuit

  OFDM Basics Tutorial

  Microwave test bench trainer, microwave telecommunication training system Microwave Bench, Microwave trainers, antenna trainer kit, microwave trainers supplier, antenna trainer kit suppliers, microwave antenna trainers, microwave trainers manufacturer, microwave trainers India, microwave components manufacturer, antenna trainer kit exporters, antenna trainer kit India, waveguide components exporter, microwave part suppliers, waveguide components suppliers, waveguide components manufacturer, microwave waveguide instruments, rotary joints, magic tees, horns, x-band microwave benches, waveguide components, bends, twist, couplers, isolators, instruments, circulators, Gunn oscillator, elbows, flanges and subsystems.

  Satellite Training System

  Wide Area Network Tutorial




Bookmark and Share Edit Document
 Category : Articles

OFDM synchronization

overview of the timing and frequency synchronization required for the successful use of OFDM, orthogonal frequency division multiplex.

While OFDM has been successfully deployed in many different radio communications systems, one of the main problems that needs to be overcome is that if OFDM synchronization.

Effective OFDM synchronization enables the data error rates to be kept to a minimum, whereas if the system is not accurately synchronized, then errors will result and the system will become less effective.


The need for OFDM synchronization

OFDM offers many advantages in terms of resilience to fading, reflections and the like. OFDM also offers a high level of spectrum efficiency. However to reap the rewards, it is necessary that the OFDM system operates correctly, and to achieve this, it is necessary for the OFDM synchronization to be effective.

There are a number of areas in which the OFDM synchronisation is critical to the operation of the system:

  • OFDM synchronization in terms of frequency offset:   It is necessary that the frequencies are accurately tracked to ensure that orthogonality is maintained.
  • OFDM synchronisation in terms of clock accuracy:   It is necessary that the sampling occurs at the correct time interval to ensure that the samples are synchronized and data errors are minimised.

In order to ensure that the OFDM system works to its optimum, it is necessary to ensure that there are schemes in place to ensure the OFDM synchronization is within the required limits.


Frequency offset OFDM synchronization

It is particularly important that the demodulator in an OFDM receiver is able to synchronize accurately with the carriers within the OFDM signal. Offsets may arise for a number of reasons including any frequency errors between the transmitter and the receiver and also as a result of Doppler shifts if there is movement between the transmitter and receiver.

If the frequency synchronisation is impaired, then the orthogonality of the carriers is reduced within the demodulation process and error rates increase. Accordingly it is essential to maintain orthogonality to reduce errors and maintain the performance of the link.

First look at the way that sampling should occur. With the demodulator in synchronisation, all the contributions from the other carriers sum to zero as shown. On this way all the carriers are orthogonal and the error rate is at its minimum.

OFDM signal in synchronisation
An OFDM signal where demodulation is in synchronisation

If a situation is encountered where the OFDM synchronisation for the frequency aspects are poor, then the demodulator will centre its samples away from the peak of the signal, and also at a point where the contributions from the other signals do not sum to zero. This will lead to a degradation of the signal which could in turn lead to an increase in the number of bit errors.

OFDM signal with poor synchronisation
An OFDM signal where demodulation has poor synchronisation

Clock offset OFDM synchronization

It is also necessary to maintain OFDM synchronization in terms of the clock. Gain if the clock synchronisation is not accurate, sampling will be offset and again orthogonality will be reduced, and data errors will increase.

When looking at OFDM synchronization with regard to the clock offset, the carrier spacing used within the receiver for sampling the received signal will be based upon the internal clock rate. If this differs from that used within the transmitter, it will be found that even if the first carrier within the multiplex is correct, then there will be a growing discrepancy with each carrier away from the first one. Even small levels of discrepancy will cause the error rate to increase.

OFDM synchronization problem with clock offset problem
OFDM synchronization problem with clock offset problem
This page has been viewed for 5212 times

Key Words : OFDM, Frequency offset, Clock offset,

Review
Please enter your email address to receive our newsletters:

Unsubscribe?



Most Viewed News
 
 Programmable System-on-Chip (PSoC) with Integrated Full-Speed USB: Cypress
 
 160-Gb/s, 16-Channel Full-Duplex, Single-Chip CMOS Optical Transceiver
 200GB And 250GB Parallel And SERIAL ATA With 3.0GB Per Second Hard Disk Drives
 
 
Most Viewed Documents
 CDMA technology basics
 OFDM synchronization
 OFDM Basics Tutorial
 Operational Amplifier / Op Amp Basics
 Non-inverting operational amplifier circuit
 
 
Most Viewed Products
 Ku-BAND VSAT
 SkyWay 5000 Series MultiPoint Base Station
 ANTENNA TRAINING LAB
 Microstrip/MIC/Microwave Trainer
 Antenna Trainer 86-860 MHz
 

  Privacy Policy

  Disclaimer

Copyright 2003-2015 rfdesign.info  

Website design by anandsoft.com