A multiple-choice knapsack based algorithm for CDMA downlink rate differentiation under uplink coverage restrictions

This paper presents an analytical model for downlink rate allocation in Code Division Multiple Access (CDMA) mobile networks. By discretizing the coverage area into small segments, the transmit power requirements are characterized via a matrix representation that separates user and system characteristics. We obtain a closed-form analytical expression for the so-called Perron-Frobenius eigenvalue of that matrix, which provides a quick assessment of the feasibility of the power assignment for a given downlink rate allocation. Based on the Perron-Frobenius eigenvalue, we reduce the downlink rate allocation problem to a set of multiple-choice knapsack problems. The solution of these problems provides an approximation of the optimal downlink rate allocation and cell borders for which the system throughput, expressed in terms of downlink rates, is maximized. \u

Optimal downlink rate allocation in multicell CDMA networks

We study downlink rate allocation for a three cells CDMA system. Based on the discretized cell model, the rate optimization problem that maximizes the total downlink rate allocation is formulated. We propose an approximation procedure for obtaining a rate allocation in three cells case. Via numerical examples, we show that this procedure gives a good approximation of the optimal downlink rate allocation

A combinatorial approximation algorithm for CDMA downlink rate allocation

This paper presents a combinatorial algorithm for downlink rate allocation in Code Division Multiple Access (CDMA) mobile networks. By discretizing the coverage area into small segments, the transmit power requirements are characterized via a matrix representation that separates user and system characteristics. We obtain a closed-form analytical expression for the so-called Perron-Frobenius eigenvalue of that matrix, which provides a quick assessment of the feasibility of the power assignment for a given downlink rate allocation. Based on the Perron-Frobenius eigenvalue, we reduce the downlink rate allocation problem to a set of multiple-choice knapsack problems. The solution of these problems provides an approximation of the optimal downlink rate allocation and cell borders for which the system throughput, expressed in terms of utility functions of the users, is maximized

A combinatorial approximation algorithm for CDMA downlink rate allocation

This paper presents a combinatorial algorithm for downlink rate allocation in Code Division Multiple Access (CDMA) mobile networks. By discretizing the coverage area into small segments, the transmit power requirements are characterized via a matrix representation that separates user and system characteristics. We obtain a closed-form analytical expression for the so-called Perron-Frobenius eigenvalue of that matrix, which provides a quick assessment of the feasibility of the power assignment for a given downlink rate allocation. Based on the Perron-Frobenius eigenvalue, we reduce the downlink rate allocation problem to a set of multiple-choice knapsack problems. The solution of these problems provides an approximation of the optimal downlink rate allocation and cell borders for which the system throughput, expressed in terms of utility functions of the users, is maximized

An analytical model for CDMA downlink rate optimization taking into account uplink coverage restriction

This paper models and analyzes downlink and uplink power assignment in Code Division Multiple Access (CDMA) mobile networks. By discretizing the area into small segments, the power requirements are characterized via a matrix representation that separates user and system characteristics. We obtain a closed-form analytical expression of the so-called Perron-Frobenius eigenvalue of that matrix, which provides a quick assessment of the feasibility of the power assignment for each distribution of calls over the segments. Our results allow for a fast evaluation of outage and blocking probabilities. The result also enables a quick evaluation of feasibility that may be used for capacity allocation. Our combined downlink and uplink feasibility model is applied to determine maximal system throughput in terms of downlink rates. \u

Optimal resource allocation in downlink CDMA wireless networks

This thesis presents a full analytical characterization of the optimal joint downlink rate and power assignment for maximal total system throughput in a multi cell CDMA network. In Chapter 2, we analyze the feasibility of downlink power assignment in a linear model of two CDMA cell, under the assumption that all downlink users in the system receive the same rate. We have obtained an explicit decomposition of system and user characteristics. Although the obtained relation is non-linear, it basically provides an effective interference characterisation of downlink feasibility for a fast evaluation of outage and blocking probabilities, and enable a quick evaluation of feasibility. We have numerically investigated blocking probabilities and have found for the downlink that it is best to allocate all calls to a single cell. Moreover, this chapter has also provided a model for determining an optimal cell border in CDMA networks. We have combined downlink and uplink feasibility model to determine cell borders for which the system throughput, expressed in terms of downlink rates, is maximized. In Chapter 3, we have considered the two cell linear model where the coverage area was divided into small segments. Previously, we have assumed that all users in the cell are using the same rate, regardless their location. In this chapter, we have differentiated rate allocation based on their location. We have assumed that users in the same segment receive the same rate which is chosen from a discrete set. The goal is to assign rates to users in each segment, such that the utility of the system is maximized. In this chapter, we design an algorithm that is actually a fully polynomial time approximation scheme (FPTAS) for the rate optimization problem. The model in this chapter indicates that the optimal downlink rate allocation can be obtained in a distributed way: the allocation in each cell can be optimized independently, interference being incorporated in a single parameter $t$. In Chapter 4, we have analyzed the two cell model under the assumption that the rates are continuous and may be chosen from a given interval. Moreover, we also taken into account the downlink limited transmit power. First, we developed a model for the joint rate and power allocation problem. Despite its non-convexity, the optimal solution in this chapter can be very well characterized. Second, we analyzed several properties of the optimal solutions. We have proved that the optimal rate allocations are monotonic as a function of the path loss. Based on this property, we have showed that in the optimal rate allocation, in each cell, only three rates are given to users. Finally, we have proposed a polynomial time algorithm in the number of users that solves optimally the joint rate and power allocation problem. The results can be extended to non-decreasing utility functions. In Chapter 5, we have extended the model of the previous chapter to a multi-cell setting. We have presented a full analytical characterization of the optimal joint downlink rate and power assignment for maximal total system throughput in a multi cell CDMA network. Moreover, the cell model is a planar model. Chapter 5 has three main contributions. First, we provide an explicit and exact characterization of the structure of the optimal rate and power assignment. Second, we give a characterization of the optimal rate assignment in each cell. Third, based on these results, we give an exact algorithm for solving the rate and power assignment problem and a fast and accurate heuristic algorithm for power and rate assignment to achieve maximal downlink throughput in a multi cell CDMA system

Optimal joint rate and power allocation in CDMA networks

In this paper we propose a polynomial time algorithm for the optimal rate and power allocation problem in a two cell CDMA network. We assume continuous rates and limited powers for the base stations

Optimal joint rate and power allocation in CDMA networks

In this paper we propose a polynomial time algorithm for the optimal rate and power allocation problem in a two cell CDMA network. We assume continuous rates and limited powers for the base stations

CDMA coverage under mobile heterogeneous network load

We analytically investigate coverage (determined by the uplink) under non-homogeneous and moving traffic load of third generation UMTS mobile networks. In particular, for different call assignment policies, we investigate cell breathing and the movement of the coverage gap occurring between cells when a hot spot moves among the cells. These call assignment policies mainly differ in handling non feasible call configurations. To establish the maximally possible coverage, calls at the cell borders are dropped such that the remaining carried calls establish their SIR target. By assigning calls to different base stations according to these policies, the coverage gap differs, especially under moving non-homogeneous load