Dynamic resource allocation is an important means to increase the sum capacity of fading multiple-access channels (MACs). In this paper, we consider vector multiaccess channels (channels where each user has multiple degrees of freedom) and study the effect of power allocation as a function of the channel state on the sum capacity (or spectral efficiency) defined as the maximum sum of rates of users per unit degree of freedom at which the users can jointly transmit reliably, in an information -theoretic sense, assuming random directions of received signal. Direct-sequence code-division multiple-access (DS-CDMA) channels and MACs with multiple antennas at the receiver are two systems that fall under the purview of our model. Our main result is the identification of a simple dynamic power-allocation scheme that is optimal in a large system, i.e., with a large number of users and a correspondingly large number of degrees of freedom. A key feature of this policy is that, for any user, it depends on the instantaneous amplitude of channel state of that user alone and the structure of the policy is "water-filling." In the context of DS-CDMA and in the special case of no fading, the asymptotically optimal power policy of water-filling simplifies to constant power allocation over all realizations of signature sequences; this result verifies the conjecture made in [28]. We study the behavior of the asymptotically optimal water-filling policy in various regimes of number of users per unit degree of freedom and signal-to-noise ratio (SNR). We also generalize this result to multiple classes, i.e., the situation when users in different classes have different average power constraints.

For wireless cellular and ad hoc networks with QoS constraints, we propose a suite of problem formulations that allocate network resources to optimize SIR, maximize throughput and minimize delay. The distinguishing characteristics of these resource allocation formulations is that, by using convex optimization, they accommodate a variety of realistic QoS and fairness constraints. Their globally optimal solutions can be computed efficiently through polynomial time interior point methods, even though they use nonlinear objectives and constraints.

We propose a new method of power control for interference limited wireless networks with Rayleigh fading of both the desired and interference signals. Our method explictly takes into account the statistical variation of both the received signal and interference power, and optimally allocates power subject to constraints on the probability of fading induced outage for each transmitter/receiver pair. We establish several results for this type of problem.

Several different distributed channel assignment algorithms are compared using Unsupervised FDMA (UFDMA), a multiple access scheme for the land mobile radio environment. All algorithms make use of coexistence etiquettes which allow different users to share common frequency allocation. It is found that using the Least Interfered Channel (LIC) with call reassignment provides considerably better performance than LIC, and LIC better than First Available (FA). A tight interference level threshold, at the transmitter, improves the performance of the FA algorithm, but it is much better to use a loose interference threshold with the LIC algorithms. 1 Introduction Distributed channel assignment algorithms are gaining considerable attention as increasing cellular traffic requires the use of smaller and smaller cells, which mean that, due to localised fading, the port closest to the mobile may no longer be the most suitable transmitter to support the call. For this reason the Federal Communicat...

A Distributed Dynamic Channel Assignment (DDCA) scheme, entitled UFDMA PDA PC has been developed which incorporates power control and which is designed to substantially reduce call dropping without the need for intra-cell handoffs. It has been shown that the scheme increases capacity by at least a factor of 3 compared with the best previous non power control UFDMA scheme. The scheme has been developed with the aid of mathematical analysis and a pictorial model. Results are presented which show that call dropping may be virtually eliminated in a correlated shadowing environment and median transmitter power is reduced by 15dB. Discussion of the different call dropping mechanisms are presented and it is suggested that the residual level of call dropping is now a result of multiple additional call arrivals close to an active link. Methods to make further reductions in the call dropping probability are also explored. I. INTRODUCTION Distributed Dynamic Channel Assignment (DDCA) is being i...

outage probability, interference, impact (effect), radio network planning, cellular systems. As a consequence of rapidly increasing mobile communications, efficient utilization of the scarce radio resources becomes one of the most important issues in the system evolution. Increase of the system capacity has been investigated in two ways. The first way is to replace the fixed channel allocation (FCA), with the more efficient dynamic channel allocation (DCA). The second way is to utilize those traffic channels not being used by voice services to provide a packet data service, like general packet radio service (GPRS) and cellular digital packet data (CDPD). In this thesis, the author have proposed two DCA schemes and developed an analysis method to investigate the GPRS impact on the GSM voice services. In addition, the GPRS downlink performance is investigated and some guidelines or principles for GPRS network planning have been presented. In the proposed DCA algorithms, the effect of the channel allocation on existing calls is considered by the evaluation of the call outage rate or a cost function. In the first proposed algorithm, in order to evaluate the call outage caused by those candidate channels, a method of

In this paper, we integrate the channel assignment and power assignment into a distributed channel access algorithm. A cost-function is introduced to provide some optional channels according to their cost for transmitted power level searching. The simulation results show that this algorithm largely increases capacity compared with the fixed channel allocation (FCA). The proposed algorithm can adapt to the call saturated state of network and does not cause high intracell handover access. It has a short average call setup time even at high traffic loads. We suggest that the intracell handover rate should be a factor in evaluation of an algorithm’s performance, because high handover access will intensively increase the load of switch and cause much higher call dropping and blocking probabilities than those we expect. I.

User capacity of the uplink of a multiple cell synchronous CDMA system is analyzed along with power and channel allocation. For the most part, attention is focussed on the situation when the signature sequences are chosen from an orthogonal sequence set. The user capacity of the system is the maximum number of users per unit processing gain admissible in the system such that each user has its quality of service (QoS) requirement (expressed in terms of its desired signal-to-interference ratio) met. The user capacity depends on the path gains of the users to the base stations and the comparison of the user capacity per unit processing gain with the maximum number of admissible users in a single channel system allows us to describe (in terms of the path gains) scenarios when the user capacity of the system can be increased by having more processing gain. We conclude by conjecturing the user capacity region when the signature sequences are not constrained and the base station estimates the users' symbols with matched filter and linear MMSE receiver structures.

: The effects of interference threshold and SNR acceptance threshold on channel capacity have been determined for several distributed channel assignment algorithms using Unsupervised FDMA (UFDMA), a multiple access scheme for the terrestrial radio environment. It is found that the effect of tightening the interference threshold reduces the call dropping probability at the expense of increasing the blocking probability for a given channel capacity. Introducing hysteresis in the SNR acceptance threshold is only beneficial in improving performance if a high level of call dropping can be tolerated, and in all circumstances reduces capacity for a fixed call blocking grade of service. These effects are then explained using a pictorial model which considers the frequencyreuse behaviour using the concepts of Interference and SNR Exclusion Areas. I. INTRODUCTION Distributed channel assignment algorithms are gaining considerable attention as increasing cellular traffic requires the use of smal...

this paper we investigate one such scheme, which manipulates power based on C/I measurements. The basic scheme is a distributed dynamic channel assignment algorithm [15] and its variants, which manipulate transmitted power in different ways. In section 2, we present the system considered, including the attenuation model, call processing and handoff procedures. In sections 3- 8, we analyze the performance of the basic scheme and its variants. We find that power control based on C/I is achievable, and it leads to greater system capacity, at the expense of call rearrangements. 2 System Description