This paper investigates the problem of dynamic multiuser subchannel allocation in the downlink OFDM systems. In traditional TDMA or FDMA systems, resource allocation for each user is non-adaptively fixed. Since the subchannel allocations among the users are not optimized, a group of users is likely to suffer from poor channel gains resulting from large path loss and random fading. To resolve th...

We present two detectors which allow multiuser detection without a side channel in a dynamic CDMA system where users are constantly leaving and entering the system. These detectors, the Maximum Likelihood (ML) and Generalized Maximum Likelihood (GML) detectors, optimally detect a new user given only the chip rate and the spreading factor of the new user. Each of these detectors produces maximum...

With a narrowband multiuser detector (MUD), multiple users can simultaneously share the same channel without using a bandwidth expanding signature code when sufficient power differences at the receiver are maintained. In this paper, we estimate the capacity that can be achieved in a hypothetical cellular system with centralized power control, using a narrowband MUD based on successive cancellat...

Cognitive Radio (CR) aims to increase the spectrum utilization by allowing secondary users (SU) to access unused licensed spectrum bands. To maximize the throughput given limited sensing capability, SUs need to strike a balance between sensing the channels that are not heavily used by primary users (PU) and avoiding collisions with other SUs. To randomize sensing decisions without resorting to ...

This paper proposes a novel scalable approach to reduce the feedback for downlink multiuser diversity in multiple input multiple output (MIMO) systems. We propose a feedback protocol that features a contention channel consisting of a fixed number of feedback minislot to convey channel state information. Feedback control parameters such as channel quality threshold and feedback probability are j...

A low complexity dynamic subcarrier and power allocation methodology for downlink communication in an OFDM-based multiuser environment is developed. The problem of maximizing overall capacity with constraints on total power consumption, bit error rate and data rate proportionality among users requiring different QOS specifications is formulated. Assuming perfect knowledge of the instantaneo...

1. Introduction Due to the lack of explicit closed form expressions of the mutual information for binary inputs, which were provided only for the BPSK and QPSK for the single input single output (SISO) case, [1], [2], [3], it is of particular importance to address connections between information theory and estimation theory for the multiuser case. Connections between information theory and esti...