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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...
We propose a more accurate method to analyze multilevel frequency-shift-keying frequency-hopping code-division multiple-access (MFSK/FH-CDMA) wireless communication systems using ldquoone-hitrdquo FH patterns, instead of random FH patterns. By also removing the over-optimistic symbol-synchronous assumption, the new method provides a more realistic performance analysis as the MFSK modulation may result...
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...
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...
A new construction of a full-diversity full-rate space-time block code (FDFR-STBC) is presented in this paper. The design is for 2 transmit antennas and 2 time slots. The code outperforms the previous FDFR-STBC codes in [3], [4], [5], [6] for 1 receive antenna. We reduce the decoding complexity by exploiting the algebraic structure of the code and using the hybrid maximum-likelihood interference cancellation...
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.
A 53 dB gain limiting amplifier for OC-192 and 10 GbE applications is developed in a 50 GHz fT SiGe SOI complimentary bipolar process, and has 5 mV pk-pk sensitivity, 1.25 V pk-pk maximum input signal, 14 ps (20/80%) rise/fall times and 450 mV pk-pk output into matched differential 50 Ohm loads, consuming 430 mW on a 3.3 V supply. Input Cherry-Hooper gain stages limit the -3 dB bandwidth to 11 GHz...
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...
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). Under these conditions, the conventional one-tap per subcarrier channel estimation and equalization is suboptimal since it does not account for ICI...
A novel compact coupled planar resonator (CCPR) based VCO (voltage controlled oscillator) using mode-coupling technique was developed in response to expensive high Ceramic and SAW resonators based signal source for wireless communications. One of the problems related to the conventional Ceramic/SAW based resonators (with high Q and low phase noise) is the challenge for integration in IC form. Instead...
In this paper we discuss performance results of a novel real-time closed-loop power amplifier (PA) linearization technique that has originally been proposed by Ahmed and Li. The novel approach performs on-the-fly prediction and measurement of the PA AM/AM and AM/PM non-linearity, stores such non-linear characteristics and calculates their inverse functions in order to pre-distort the base-band amplitude...
In this paper the performance of the ESPAR (electronically steerable passive array radiator) antenna in suppressing both the co-channel and inter-symbol interferences is compared with the conventional circular and linear arrays. For this purpose, the STAP (space-time adaptive processing) is implemented in both arrays with equal elements. Simulation results show that when the pattern of the ESPAR antenna...
The difficulty for accurate determination of the angles of arrival (AOA) of signals arises from the optimization of likelihood functions of high dimension. Usually, a gradient-based technique is employed to find the optimum of the function. However, this method requires heavy computational work and the differentiability of the likelihood function. This paper presents two gradient-free methods: One...
The next generation of wireless communication is a ubiquitous radio system concept, providing wireless access from short-range to wide-area, with one single reconfigurable and adaptive system for all envisaged radio environments. This paper presents the design approach of RCO (reconfigurable concurrent oscillator) that simultaneously generates two or more signals of different frequencies that eliminate...
In this paper we derive optimal power allocation (PA) in space and time that minimizes BER for transmitter selection in multi-input-single-output (MISO) Rayliegh fading channels assuming perfect channel state information (CSI) is available at receiver and transmitter. This power allocation scheme achieves exponential diversity order with a single RF front end and requires feedback of the best channel...
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...
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...
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