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One of the distinguishing features of wireless communication is its broadcast nature. This creates complicated signal interactions when there are multiple transmitting and receiving nodes, due to superposition of signals at the receivers. In this paper, we focus on wireless relay networks where (relay) nodes facilitate communications between a source and a destination. We review some recent progress...
In many DSP applications (image and voice processing, baseband symbol decoding in high quality communication channels) several dBs of SNR loss can be tolerated without noticeable impact on system level performance. For power optimization in such applications, voltage overscaling can be used to operate the arithmetic circuitry slower than the critical circuit path delay while incurring tolerable SNR...
The decision-directed space-alternating generalized expectation-maximization (SAGE) algorithm is introduced in [1] to estimate the channel and track the channel varying for OFDM systems with transmitter diversity. However, this method is based upon a discrete Fourier transform (DFT), which will cause power leakage and result in an error floor in a multipath channel with non-sample-spaced time delays...
Orthogonal frequency division multiplexing (OFDM) is the modulation scheme of choice for digital video broadcasting-handheld (DVB-H), which is required to operate under high mobility conditions resulting in significant Inter-carrier Interference (ICI). To mitigate ICI, several cancellation schemes have been proposed but they require reliable channel information at the receiver which is quite challenging...
In this paper, we propose a cross-layer optimization approach that exploits retransmission diversity in wireless CDMA communications. Conventionally, data packets that are not correctly detected are usually dropped. These dropped packets can be used to help data packet detection. By exploiting all the retransmitted packets, data packets can be correctly detected with higher probability. The proposed...
This paper investigates the effective gain of antennas in indoor channels. A metric called instantaneous effective gain is proposed, and a multiple-cluster 3D channel model is used to facilitate the proposed antenna effective gain. In the multiple-cluster channel model, Laplacian and double exponential distribution are utilized to model azimuth and elevation signal power distribution respectively,...
While two-dimensional (2-D) orthogonal variable spreading factor (OVSF) codes were proposed for multicarrier direct-sequence code-division multiple-access (MC/DS-CDMA) systems in order to eliminate multiple-access interference, the number of orthogonal sequences (or code cardinality) was restricted by the number of carrier frequencies. Non-orthogonal 2-D frequency-time-spreading (FTS) codes were then...
In this paper, we propose a cognitive radio-based multi-user resource allocation framework for mobile ad hoc networks using multi-carrier DS CDMA modulation over a frequency-selective fading channel. In particular, given pre-existing communications in the spectrum where the system is operating, in addition to potential narrow-band interference, a channel sensing and estimation mechanism is provided...
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