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The routing and spectrum assignment in nonlinear flexible-grid networks is extended by optimizing the power separately for each connection. This yields 24% bandwidth reduction for large networks. An Optimization formulation and decomposition strategy are proposed to solve the problem.
Nowadays, the spread of wireless applications has led to the need of new spectrum resources and to the need to exploit in a more dynamic and efficient way those already in use. Several recent research works have confirmed the presence of unused spectrum portions in the range 30 MHz-3 GHz. As a consequence, developing new techniques to assure the utilization of these unused resources has become a key...
In this paper, an energy efficient adaptive modulation scheme is proposed for a wireless cognitive radio ad hoc network, where each node is equipped with cognitive radio and the network is an OFDMA system operating on time slots. In each slot, the users with new traffic demand will sense the spectrum and locate the available subcarrier set. Then they choose subcarriers with favorable channel condition...
In this paper, we develop an approach toward joint source-channel coding (JSCC) for JPEG compressed image transmission. First, a data partition (DP) technique is employed to divide the JPEG bitstream into three groups, namely, Huffman codes, DC coefficients and AC coefficients. Second, we combine the rate-compatible punctured convolutional (RCPC) codes to protect the coded data according to channel...
Three applications in wireless networks where model-free stochastic learning is applicable, are discussed. The learning based optimization problems are formulated and simulation results are presented. Some open issues are also discussed.
This paper investigates effects of pilot assisted channel estimation on dynamic resource allocation in a multiuser orthogonal frequency division multiplexing (OFDM) system. The channel estimation is done in each OFDM symbol through least-squared error (LSE) or minimum mean-squared error (MMSE) algorithm. The performance of each of these algorithms is evaluated through computer simulations. The maximal...
More and more users subscribing to wireless broadband services are seeking to have access to both WLAN and UMTS networks. We study individually optimal user-network association in an integrated WLAN and UMTS hybrid cell. The association problem is formulated within a non-cooperative game framework. In the formulation, mobile arrivals are assumed to follow the Poisson process and each mobile considers...
This paper explores the attributes, layering models and objective functions in cross layer designs for mobile ad hoc wireless networks by taking all the statistical characteristics and constraints from the physical (PHY) layer, media access control (MAC) layer and network (NET) layer into consideration. This paper reviews the entire network optimization across all the PHY/MAC/NET layers. At the PHY...
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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