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To accommodate current machine type communications (MTC), an uplink waveform is proposed where MTC nodes use one carrier to transmit signal, and central nodes demodulate different nodes' signal jointly. Furthermore, the carrier bandwidth is variable to fit for the channels of nodes. This waveform may reduce the hardware complexity of low cost MTC nodes, and loose the time and frequency domain synchronization...
This paper proposes a filtered multitone modulation with variable subcarrier bandwidths (VSB-FMT). Through using one DFT-IDFT pair, FMT subcarriers with different bandwidths are modulated and demodulated jointly with different subcarrier bandwidths. The VSB may provide subcarriers in one frequency division multiple access band the ability to combat diversity fading channels from multiple users. This...
This paper presents a decision directed frequency and clock tracking scheme to improve the spectrum efficiency of burst mode OFDM transmission with frequency selective channel. OFDM divides one broadband channel to parallel narrowband subchannels of different channel characteristics. In this scheme, the subcarriers with better attenuation are selected out to do the decision-directed based clock and...
This paper proposes an improved initial ranging method for orthogonal frequency division multiple access (OFDMA) system. In initial ranging, though the expected timing offset is quite long, the actual channel spread of specific user equipment (UE) is short. In addition, due to bandwidth limitation of ranging sequence, sidelobe appears which degrades the performance of noise detection. By the two characteristics,...
To improve the system capacity of conventional orthogonal frequency division multiplexing (OFDM) systems, the layered modulation OFDM scheme is proposed. The modulated OFDM symbols are separated into two layers as differential modulated symbols and coherent symbols. The differential symbols are used as pilots, which are combined with the coherent modulated data and sent out by the transmitter. At...
In orthogonal frequency division multiplexing (OFDM) systems, the estimated channel impulse response (CIR) can be recovered by transforming the initial channel frequency response (CFR) to time domain. The CIR is preferred to be filtered before transforming to frequency domain and using as accurate CFR. In orthogonal frequency division multiplexing access (OFDMA) systems, subcarriers are allocated...
In time-domain synchronous (TDS) block transmission systems, known symbols are padded in the guard interval between data blocks using some specific patterns. The complexity of channel estimation is relatively high for the time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) system. As a result, original TDSOFDM is only used for downlink broadcasting. This paper proposes a...
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