Yeong-Jun Kim

Channel Estimation for OFDM SYstems with Transparent Multi-Hop Relays

In this letter, the effect of a propagation delay resulting from the use of an OFDM system with a transparent mobile multi-hop relay (MMR) is initially analyzed. Then, a least square (LS) channel estimation technique for the OFDM system with throughput enhancement (TE) MMR or cooperative MMR is proposed. It is demonstrated by computer simulation that the proposed LS channel estimation technique for OFDM systems with transparent MMR is superior to the conventional technique in terms of mean square error (MSE) and bit error rate (BER).

A transmission of paging indicator information for mobile communication systems

In a cellular system, efficient power saving techniques for a mobile station (MS) are necessary because of its inherently limited battery of MS. The paging indicator (PI) transmission scheme in CDMA cellular systems is known to be an effective power saving strategy. However, in OFDM-based cellular systems, the MS has to operate FFT for PI symbol detection, resulting in a significant power consumption. In this paper, a reduced power consumptive PI transmission technique using the preamble in OFDM-based cellular systems, especially for mobile WiMAX systems, is proposed for the MS under power saving mode. Simulations indicate a 30∼50% power saving result from our proposed PI transmission technique, at the expense of a slight increase of paging response delay.