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Recently, MIMO techniques have been using in active radars,and become a hot topic in radar field, where they improve the performance of detection and parameters estimation greatly. On estimates of direction-of-arrival (DOA) in active radars, generally elements of the receive array were closely spaced to enable direction finding measurements. However, in order to obtain angular diversity, all elements...
In this paper, we propose a robust STBC transmission scheme to combat the timing synchronization errors over frequency-selective multiple-access channels. First, the equivalent channel model in the presence of timing synchronization errors is derived and we find that the synchronization errors result in an equivalent channel model with larger number of correlated channel taps. Based on this correlated...
Li and Xia have recently investigated the design of space-time codes that achieve full spatial diversity for asynchronous cooperative communications. They show that certain of the binary space-time trellis codes derived from the Hammons-El Gamal stacking construction are delay tolerant and can be used in the multilevel code constructions by Lu and Kumar to produce delay tolerant space-time codes for...
In this paper userspsila short-term delay and throughput fundamental properties under basic opportunistic scheduling policies, required to support high throughput wireless communication systems with integrated multimedia services, are studied. Among the objectives of this work is to determine at what extent opportunistic scheduling policies can be used to support real-time services in addition to...
Some communication applications, like multimedia, deliver data of different importance classes allowing unequal error protection (UEP) levels. In this paper, a multiple-input multiple-output (MIMO) system using orthogonal frequency division multiplexing (OFDM) is considered with a new UEP bit-loading algorithm based on the non-UEP algorithm by Chow, Cioffi, and Bingham. In the proposed bit-loading...
This work studies the performance of a data-driven reduced rank scheme for rapid timing acquisition in multiple access communications. Our results show that when only a limited amount of preamble bits are available, instead of the true second-order statistics (SOS), the reduced rank scheme provides reliable timing information. Exploiting the structure of the multiple access interference, the data...
In this work we investigate the effects of multiple access interference (MAI) and polarization mode dispersion (PMD) in optical code division multiplexing (OCDM) lightpaths. These paths are determined by the data encoding with non-coherent optical orthogonal codes (OOC), using a sequence inversion keying (SIK) optical correlator system. Our results show the impact of MAI effects and PMD constraint...
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...
Wireless sensor networks consist of a large number sensors spread across a given geographical area. Each sensor has its own communication capability as well as certain level of intelligence for signal processing and networking. As the sensor nodes are densely populated, communication range requirement for these nodes is smaller. After signal detection, a number of sensor nodes communicate over the...
The next generation of wireless networks (4G) will use OFDMA (Orthogonal Frequency Division Multiple Access) in the reverse link. In OFDMA, the reverse link resources assigned to a user are called tiles each of which consists of a subset of consecutive subcarriers. Since at most one user is assigned to each of these tiles then reverse link transmissions within a sector are orthogonal. However, the...
In this paper, we focus on the security issue of a chaotic digital communication scheme called chaotic-pulse- position modulation. We design a third party intrusion scheme to test to see if CPPM is as secure as is claimed. Experiments are conducted with various chaotic maps, where CPPM is used to modulate the message at the transmitter and a Kalman filter fed with a polynomial approximation is used...
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