خفض تداخل الحوامل الفرعية باستخدام الترويسة القصيرة في المعيار IEEE 802.11a

Abstract EN

Orthogonal Frequency Division Multiplexing (OFDM) is a Multi-carrier Modulation (MCM) scheme.

OFDM is a modulation technique to achieve transmission of high data rates, increase the bandwidth effi- ciency and robustness of the communication system in multipath environments.

However, the OFDM transmission has some disadvantages; such as large peak to average power ratio (PAPR) self-interference.

This work intends to highlight the self-interference.

In the OFDM systems, and Inter-symbol Interference (ISI) and Inter-carrier Interference (ICI) are two types of self-interference.

The cyclic prefix is one meth- od to prevent the ISI, where is the interference of the echoes of a transmitted signal with the original transmitted signal.

The required length of cyclic prefix to remove ISI depends on the channel conditions, and usually it is chosen according to the worst case channel scenario.

The other common self-interference in the OFDM systems is the ICI, where the power leakage among differentsub-carriers degrades the per- formance of both symbol detection and channel estimation.

The OFDM is very sensitive to frequency off- set and this causes ICI and a reduction in the amplitude of the desired subcarrier that results in loss of orthogonality for subcarriers.

In this paper, the short preamble technique in IEEE 802.11a standard is studied to estimate the frequency offset in the received signal and its cancelation.

The results of the short preamble technique is presented and validated by computer simu- lations with MATLAB.