A maximum-likelihood (ML) channel estimation and preamble design rules for the multiple-input-multiple-output (MIMO) channels are described when orthogonal frequency division multiplexing (OFDM) is employed with null subcarriers at both DC and high frequencies. The ML channel estimator in the time domain is derived assuming the knowledge of the maximum length of channel. To reduce the mean square error (MSE) of the estimation, three design rules are proposed: orthogonality between the preambles of different antennas, orthogonality between the circular shifted preamble sequences, and the condition that the number of subcarriers is larger than the maximum length of channel multiplied by the number of transmit antennas. In addition, we prove that the use of Golay Complementary Sequence (GCS) for preamble limits the peak to average power ratio (PAPR) by 3dB although there are null subcarriers at high frequencies. Numerical results shows that the MSE of the proposed method approaches that of optimum ML estimation when the number of null subcarriers and maximum length of channel are small. GLOBECOM 2003-317 -0-7803-7974-8/03/$17.00

Interference over thermal noise (IoT) level control is crucial to system performance and link quality in interference limited scenarios, especially for cell edge users. This paper proposes a simple and novel technique for IoT control by adopting the concept of load control where load is defined as the total interference impacting on neighbor sectors. The proposed technique is able to control IoT level accurately and is very robust against impairments in practical implementations, while minimizing the required signaling overhead.Keywords-OFDMA, interference limited system; power control; interference over thermal noise (IoT)

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The Control Hold mode from cdma2000 Ix systems has been adapted to the IxEV-D V(Evo1ution Data and Voice) systems because it has a lot of benefits such as power saving, reducing of overload and channel interferences, etc. However IxEV-DV system does not fully capture the bene$ts @om Control Hold mode, because the MS has to do continuous monitoring the F-PDCCH indicating whether the BS sends packet data or not. That is, the MS has to do monitoring the F-PDCCH (Forward Packet Data Control Channel) continuously to capture the MAC-ID while in Control Hold mod like as an operation in Active mode. This continuous monitoring of the F-PDCCH causes higher power consumption and gives an overload to the decoder block at the MS side. In this papel; to resolve these problems, we propose a new channel, F-WUCH (Forward Wake-Up Channel), to maximize the power saving of the MS, to minimize the interferences and to reduce the overhead from the continuous monitoring of the F-PDCCH in the Control Hold Mode.