This paper applies the concept of balanced capacity, a fair trade-off between individual and global performance, to the uplink of a Gaussian frequency-selective multiuser channel with K users, where K can be much larger than 2. Individual power constraints are applied to each transmitter, which makes the computation of the balanced capacity very complex. The concept of 'equivalent channel' is used to derive an explicit expression of the optimal power allocation, that remains compatible with the individual power constraints. The computation of the balanced capacity is then formulated as a set of 2K nonlinear equations. An iterative algorithm providing the exact solution is firstly introduced. A suboptimal solution, based on the Iterative Multiuser Water-Filling (IMWF) algorithm, is then proposed and shown to be very close to the optimal solution. The idea of this alternative method, called 'balanced water-filling', is to modify the power allocation obtained with the IMWF algorithm in order to get balanced data rates. Results are provided for a wireline access network with 20 users.

In this paper, a complete methodology is proposed for the deterministic modeling of the channel transfer functions associated with underground power line access networks, in the light of the Multiconductor Transmission Line Theory. Some multiconductor power line cables are analyzed in detail, and their fundamental propagation characteristics (definition of eigenmodes, phase velocity, characteristic impedance, lineic attenuation) are related to the geometry of the conductors and the material properties. A multidimensional scattering matrix formalism is then introduced to perform an accurate analysis of the global power line network including multiconductor cable segments, derivation points, and termination loads. An illustrative example of a power line access network with three types of cables (with different numbers of conductors), 20 derivations, and five remote terminals, is finally proposed.

This paper analyzes the multiuser capacity of Gaussian frequency-selective wireline multiaccess channels. Both the uplink (multiple-access channel) and downlink (broadcast channel) capacity regions are considered. The concept of balanced capacity is introduced to characterize the multiuser channel performance. Algorithms for the computation of the balanced multiuser capacity (and the associated power allocations) are proposed for an arbitrary number of users. The optimal power allocation in a K-user memoryless Gaussian channel is analyzed in detail, and an extension to intersymbol interference channels is given with various kinds of power constraints. Results are provided for a wireline access network with 20 users.

This paper studies the impact of timing errors in the receivers for baseband filter bank (FB) modulation techniques, including DMT and multicode modulations. Matched filtering detectors are first investigated, followed by MMSE linear and DF detectors.

We investigate detection structures for a DS-CDMA. multiuser uplink using codes with a period of several symbols, named long codes. We first propose a multirate description of the uplink. Then based on this formalism we revisit a number of popular receiver structures: RAKE receivers, minimum mean square error linear and decision feedback fractionally spaced detectors.

We investigate detection structures for a DS-CDMA multiuser uplink using codes with a period of several symbols, named long codes. We first propose a multirate description of the uplink. Then based on this formalism we revisit a number of popular receiver structures: RAKE receivers, minimum mean square error linear and decision feedback detectors.

This paper compares two multiuser transmission techniques in the context of wideband upstream powerline communications. The first one is based on the combination of CAP (carrierless/amplitude phase modulation) and CDMA, the second one is based on DMT (discrete multitone) and relies on a share of the different carriers among the users. The issue of reception under ideal synchronisation assumptions and a simplified noise environment is addressed. Fractional FIR linear and decision feedback joint detectors are derived. A simple resource (code/tone) allocation method is proposed.