This paper studies the adaptive coded modulation for OFDM system using punctured convolutional code, channel estimation, equalization and SNR estimation. The estimation based on block type pilot arrangement is performed by sending pilots at every sub carrier this a specific number of following symbols. Signal to noise ratio estimated receiver then transmitted transmitter through feedback ,the a...

Adaptive modulation techniques combat fading by employing a suitable modulation mode depending on the instantaneous channel conditions for improving the Bit Error Rate (BER) performance or the average throughput. Based on a generic model of constant-power adaptive modulation, exact closed form expressions of the average BER and the average throughput are derived, when employing square Quadratur...

Adaptive transmission techniques, such as adaptive modulation and coding, adaptive power control, adaptive transmitter antenna diversity, etc., generally require precise channel estimation and channel state information (CSI) feedback. For fast vehicle speeds, reliable adaptive transmission also requires prediction of future CSI since the channel conditions are rapidly time-variant. In this pape...

The goal for the fourth generation (4G) of mobile communications system is to seamlessly integrate a wide variety of communication services such as high speed data, video and multimedia traffic as well as voice signals. One of the promising approaches to 4G is adaptive OFDM (AOFDM). In AOFDM, adaptive transmission scheme is employed according to channel fading condition with OFDM to improve the...

Adaptive coded modulation is one of the key technologies used to enhance the capabilities of future communication network. Many adaptive modulation techniques have been investigated for the enhancement of transmission rate in combination with OFDM under AWGN channel .OFDM will provide much higher bandwidth efficiency. This is due to the fact that in OFDM the spectra of individual subcarriers ar...

As demand for high quality transmission increases increase of spectrum efficiency and an improvement of error performance in wireless communication systems are important . One of the promising approaches to 4G is adaptive OFDM (AOFDM) . Fixed modulation systems uses only one type of modulation scheme (or order), so that either performance or capacity should be compromised Adaptive modulated sys...