Joint Adaptivity of Pilot Patterns and Channel Estimation in OFDM systems

In wireless communications which are widely applicable nowadays, the channel variation over time and frequency is a major problem. Therefore, the channel estimation and compensation are critical challenges in these systems. The OFDM technique is noteworthy for wireless channels due to robustness, high efficiency and consequently high data rate. Pilot-aided channel estimation is a promising approach in many OFDM systems, including mobile networks, digital audio and video broadcasting standards. The number and the arrangement of pilots in the time-frequency grid affect the accuracy and the period of the channel estimation procedure. Practical OFDM systems utilize fixed pilot patterns that are designed based on typical assumptions of the fading channel. Thus, unnecessary pilot overhead is imposed when the channel is close to a flat slow fading channel, and the performance degrades in the worst condition of the channel. To remedy this issue, adaptive pilot arrangement based on the channel response is introduced in the previous researches. Indeed, finding the best pilot arrangement according to the channel response is an optimization problem and the adaptive approach is exploited to find its answer. In this paper, we develop a novel method for adaptive pilot arrangement based on Kalman filter which is combined with the channel estimation algorithm. Therefore, the position of the pilots and the channel response are jointly estimated in the proposed method. This method is simulated for various channel types and its performance is evaluated by bit error rate (BER) and pilot overhead criteria. Simulation results illustrate that the proposed method obtains the same performance as the previous methods by fewer pilots. This achievement leads to significant increase in the capacity of data transfer.