2,464 research outputs found
Adaptive Beamforming and Adaptive Modulation-Assisted Network Performance of Multiuser Detection-Aided FDD and TDD CDMA Systems
The network performance of a frequency division duplex and time division duplex (TDD) code division multiple access (CDMA)-based system is investigated using system parameters similar to those of the Universal Mobile Telecommunication System. The new call blocking and call dropping probabilities, the probability of low-quality access, and the required average transmit power are quantified both with and without adaptive antenna arrays (AAAs), as well as when subjected to shadow fading. In some of the scenarios investigated, the systemâs user capacity is doubled with the advent of adaptive antennas. The employment of adaptive modulation techniques in conjunction with AAAs resulted in further significant network capacity gains. This is particularly so in the context of TDD CDMA, where the systemâs capacity becomes poor without adaptive antennas and adaptive modulation owing to the high base station (BS) to BS interference inflicted as a consequence of potentially using all time slots in both the uplink and downlink of the emerging wireless Internet. Index TermsâAdaptive beamforming, adaptive modulation, code division multiple access (CDMA) systems, Universal Mobile Telecommunication System Terrestrial Radio Access (UTRA), wireless network performance
Uplink User Capacity in a CDMA System with Hotspot Microcells: Effects of Finite Transmit Power and Dispersion
This paper examines the uplink user capacity in a two-tier code division
multiple access (CDMA) system with hotspot microcells when user terminal power
is limited and the wireless channel is finitely-dispersive. A
finitely-dispersive channel causes variable fading of the signal power at the
output of the RAKE receiver. First, a two-cell system composed of one macrocell
and one embedded microcell is studied and analytical methods are developed to
estimate the user capacity as a function of a dimensionless parameter that
depends on the transmit power constraint and cell radius. Next, novel
analytical methods are developed to study the effect of variable fading, both
with and without transmit power constraints. Finally, the analytical methods
are extended to estimate uplink user capacity for multicell CDMA systems,
composed of multiple macrocells and multiple embedded microcells. In all cases,
the analysis-based estimates are compared with and confirmed by simulation
results.Comment: To appear in IEEE Transactions on Wireless Communication
A Central Limit Theorem for the SINR at the LMMSE Estimator Output for Large Dimensional Signals
This paper is devoted to the performance study of the Linear Minimum Mean
Squared Error estimator for multidimensional signals in the large dimension
regime. Such an estimator is frequently encountered in wireless communications
and in array processing, and the Signal to Interference and Noise Ratio (SINR)
at its output is a popular performance index. The SINR can be modeled as a
random quadratic form which can be studied with the help of large random matrix
theory, if one assumes that the dimension of the received and transmitted
signals go to infinity at the same pace. This paper considers the asymptotic
behavior of the SINR for a wide class of multidimensional signal models that
includes general multi-antenna as well as spread spectrum transmission models.
The expression of the deterministic approximation of the SINR in the large
dimension regime is recalled and the SINR fluctuations around this
deterministic approximation are studied. These fluctuations are shown to
converge in distribution to the Gaussian law in the large dimension regime, and
their variance is shown to decrease as the inverse of the signal dimension
Final report on the evaluation of RRM/CRRM algorithms
Deliverable public del projecte EVERESTThis deliverable provides a definition and a complete evaluation of the RRM/CRRM algorithms selected in D11 and D15, and evolved and refined on an iterative process. The evaluation will be carried out by means of simulations using the simulators provided at D07, and D14.Preprin
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