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The prime focus of this work is in describing a symbiotic architecture for a Cognitive Radio network, called Cognitive Relaying with Frequency Incentive. The incumbent Primary User (PU) of the spectrum, with a weak transmission link, seeks cooperation from the cognitive Secondary User (SU) nodes in its vicinity, and in return rewards them with incentive frequency bands for their own communication...
In this paper, we propose a novel asymmetric resource allocation (RA) scheme for the decode-and-forward (DF) multi-relay based Long Term Evolution Advanced (LTE-Advanced) system, with the orthogonal frequency division multiplexing (OFDM) modulation. Given a fixed total transmit time duration, the time slot durations for the two hops via each of the K relays are designed to be asymmetric, which increases...
Recently, the OFDM-based Spectrum-sliced Elastic Optical Path (SLICE) network attracts significant interests due to its elastic band-width allocation. The OFDM technology, on one hand, enables both sub-wavelength and super-wavelength traffic accommodation by allocating appropriate number of sub-carriers. On the other hand, it can provide high signal quality by overcoming various impairments. In SLICE...
In this paper, we propose a dynamic power allocation scheme for a single-relay network based on orthogonal frequency division multiplexing (OFDM) modulation with limited feedback.We consider an Amplify-and-Forward (AF) cooperative diversity model, where one source node communicates with one destination node assisted by one half duplex relay. The power allocation scheme employs a codebook of quantized...
In this paper, joint optimization of subcarrier pairing, relay selection and power allocation is formulated through a capacity maximization problem in orthogonal frequency division multiplexing (OFDM) relay systems, with fairness considerations and individual power constraint on each node. Because achieving the optimal solution is computationally demanding, which is resulted from the excessive possibilities...
This paper considers a multi-source orthogonal frequency division multiplexing (OFDM)-based network of access points wherein dedicated relays use the decode-and-forward relaying. We investigate the joint problem of transmission strategy selection (relaying v/s direct), relay assignment, and power allocation to maximize the minimum rate across sources in two different cooperative scenarios: subcarrier-based...
This paper investigates the user and channel diversity in OFDMA wireless systems with network coding. In particular, the paper introduces an adaptive resource allocation scheme to minimize the total transmit power while maintaining a required end-to-end BER. The proposed adaptive sub-carrier allocation scheme de-couples the bit loading of the network coded OFDMA system into three independent bit loadings...
A new cross-layer design taking advantage of OFDMA in ad hoc networks is presented. OFDMA technology is exploited at the physical layer to improve data rate through multiuser diversity and to enhance network throughput by enabling multiple concurrent transmissions over orthogonal subchannels, each consisting of a group of tones. A new tone-assignment algorithm is presented that takes advantage of...
In this paper, we study an opportunistic subchannel scheduling problem for the relay-based OFDMA cellular network where relay stations (RSs) can perform opportunistic network coding with downlink and uplink sessions of a mobile station (MS). In wireless networks, network coding is one of promising techniques to improve network performance in various aspects. However, previous studies did not provide...
We address the coexistence problem between macrocell and femtocell systems by controlling the aggregated interference generated by multiple femtocell base stations at the macrocell receivers in a distributed fashion. We propose a solution based on intelligent and self-organized femtocells implementing a realtime multi-agent reinforcement learning technique, known as decentralized Q- learning. We compare...
This paper proposes FlashLinQ - a synchronous peer-to-peer wireless PHY/MAC network architecture for distributed channel allocation. By leveraging the fine-grained parallel channel access of OFDM, FlashLinQ develops an analog energy-level based signaling scheme that enables SIR (Signal to Interference Ratio) based distributed scheduling. This new signaling mechanism and the corresponding allocation...
In this paper, we consider the use of fractional frequency reuse (FFR) to mitigate inter-femtocell interference in multi-femtocell environments. The use of universal frequency reuse can be said optimum in terms of the ergodic system spectral efficiency. However, it may cause inter-femtocell interference near the cell edge, making it difficult to serve the whole cell coverage. To alleviate this problem,...
We consider a multi-source mesh network of static access points wherein sources use decode-and-forward to cooperate with each other. All transmissions use orthogonal frequency division multiplexing (OFDM). Our objective is to maximize the minimum achievable rate across all flows. We find a tight upper bound on the performance of the subcarrier-based cooperation and show that selecting a single relay...
In this paper, we will study the joint problem of power allocation, relay selection and subchannel pairing in OFDM based amplify-and-forward multiple relays system. The optimization problem of maximizing system capacity under joint power constraint at source and relays is firstly formulated. Then, based on Lagrangian dual method, an optimal algorithm to the problem is derived with high SNR assumption...
In this paper, we study the resource allocation problem in relay aided two-hop uplink multi-user transmission with a single relay node and a single destination node. The orthogonal frequency division multiple access (OFDMA) is adopted as the main transmission modulation. We investigate the problems of subcarrier allocation, subcarrier coupling, and power allocation. The optimization is formulated...
Capacity and coverage of a Frequency Division Multiple Access (OFDMA) network can be greatly enhanced by dynamically allocate the radio transmission resources. By including the radio resources of cooperative nodes and taking into account the fairness issue, we present a simple suboptimal solution to the problem of radio resource allocation in relaybased OFDMA cellular systems. We restrict our investigation...
To mitigate inter-cell interference (ICI) and achieve higher spectrum efficiency, fractional frequency reuse (FFR) has been widely adopted by the next generation wireless systems, wherein different frequency reuse factors are applied to cell center and cell edge zones. In such conventional FFR, a contiguous radio spectrum is partitioned in a fixed fashion across all cells for edge and cell center...
Designed to adapt spectrum usage on-the-fly, frequency-agile radios can drastically improve performance of wireless networks. Such flexibility, however, comes with a cost of increased hardware complexity. This motivates us to understand when and why having higher degree of frequency-agility helps and how much improvement it can lead to. In this paper, we approach this question by comparing two types...
In this paper, we consider joint end-to-end congestion control and multiuser scheduling in multi-hop wireless networks, where orthogonal frequency-division multiple access (OFDMA) is the air interface. Compared to its single-channel counterpart, this problem is significantly more challenging because subchannel assignment and power allocation for all nodes and network traffic need to be jointly optimized...
This paper proposes a new architecture for cooperative communication in wireless ad-hoc networks particularly suitable to emergency and safety applications. The proposed solution is characterized by the following relevant features: (a) a wireless connection between each couple of network nodes is established via multiple relays; (b) each source-to-destination link is characterized by a double string...
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