8,215 research outputs found
Power allocation in wireless multi-user relay networks
In this paper, we consider an amplify-and-forward wireless relay system where multiple source nodes communicate with their corresponding destination nodes with the help of relay nodes. Conventionally, each relay equally distributes the available resources to its relayed sources. This approach is clearly sub-optimal since each user experiences dissimilar channel conditions, and thus, demands different amount of allocated resources to meet its quality-of-service (QoS) request. Therefore, this paper presents novel power allocation schemes to i) maximize the minimum signal-to-noise ratio among all users; ii) minimize the maximum transmit power over all sources; iii) maximize the network throughput. Moreover, due to limited power, it may be impossible to satisfy the QoS requirement for every user. Consequently, an admission control algorithm should first be carried out to maximize the number of users possibly served. Then, optimal power allocation is performed. Although the joint optimal admission control and power allocation problem is combinatorially hard, we develop an effective heuristic algorithm with significantly reduced complexity. Even though theoretically sub-optimal, it performs remarkably well. The proposed power allocation problems are formulated using geometric programming (GP), a well-studied class of nonlinear and nonconvex optimization. Since a GP problem is readily transformed into an equivalent convex optimization problem, optimal solution can be obtained efficiently. Numerical results demonstrate the effectiveness of our proposed approach
Jointly Optimal Channel and Power Assignment for Dual-Hop Multi-channel Multi-user Relaying
We consider the problem of jointly optimizing channel pairing, channel-user
assignment, and power allocation, to maximize the weighted sum-rate, in a
single-relay cooperative system with multiple channels and multiple users.
Common relaying strategies are considered, and transmission power constraints
are imposed on both individual transmitters and the aggregate over all
transmitters. The joint optimization problem naturally leads to a mixed-integer
program. Despite the general expectation that such problems are intractable, we
construct an efficient algorithm to find an optimal solution, which incurs
computational complexity that is polynomial in the number of channels and the
number of users. We further demonstrate through numerical experiments that the
jointly optimal solution can significantly improve system performance over its
suboptimal alternatives.Comment: This is the full version of a paper to appear in the IEEE Journal on
Selected Areas in Communications, Special Issue on Cooperative Networking -
Challenges and Applications (Part II), October 201
Joint Bandwidth and Power Allocation with Admission Control in Wireless Multi-User Networks With and Without Relaying
Equal allocation of bandwidth and/or power may not be efficient for wireless
multi-user networks with limited bandwidth and power resources. Joint bandwidth
and power allocation strategies for wireless multi-user networks with and
without relaying are proposed in this paper for (i) the maximization of the sum
capacity of all users; (ii) the maximization of the worst user capacity; and
(iii) the minimization of the total power consumption of all users. It is shown
that the proposed allocation problems are convex and, therefore, can be solved
efficiently. Moreover, the admission control based joint bandwidth and power
allocation is considered. A suboptimal greedy search algorithm is developed to
solve the admission control problem efficiently. The conditions under which the
greedy search is optimal are derived and shown to be mild. The performance
improvements offered by the proposed joint bandwidth and power allocation are
demonstrated by simulations. The advantages of the suboptimal greedy search
algorithm for admission control are also shown.Comment: 30 pages, 5 figures, submitted to IEEE Trans. Signal Processing in
June 201
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