Consider a given dynamical system, described by ẋ = f(x) (wheref is a nonlinear function) and [x0] a subset ofR. We present an algorithm, based on interval analysis, able to show that there exists a unique equilibrium statex∞ ∈ [x0] which is asymptotically stable. The effective method also provides a set[x] (subset of[x0]) which is included in the attraction domain of x∞.

Ieee transactions on automatic control

Among the goals of 3GPP LTE networks are higher user bit rates, lower delays, increased spectrum efficiency, support for diverse QoS requirements, reduced cost, and operational simplicity. Resource scheduling and interference mitigation are two functions which are key to achieving these goals. This paper provides a survey of related techniques which have been proposed and shown to be promising. A brief discussion of the challenges for LTE-Advanced, the next step in the evolution, is also provided.

https://downloads.hindawi.com/journals/jece/2010/273486.pdf

A survey of scheduling and interference mitigation in LTE

Review: A survey on interference management techniques in femtocell self-organizing networks

Energy is one of the most fundamental and important parts of the social infrastructure. However, factors such as economic progress and the changing nature of society are making the requirements for energy more diverse. Th e following are fi ve common challenges and customer requirements. (1) Th e provision of reliable electric power in response to rising demand, particularly in emerging economies. (2) Dealing with global warming (3) Maintaining grid stability despite challenges such as the increased use of renewable energy (4) Dealing with aging equipment (5) Introduction of market principles to reduce electricity prices through competition As the nature of these challenges and requirements vary widely depending on the customer’s circumstances and other factors, the solutions lie not only in past business models based on the supply of equipment, but also demand open innovation involving the collaborative creation with customers and other external stakeholders of solutions to shared challenges, and thinking in terms of total solutions that combine operation technology (OT) with information technology (IT). Hitachi established its Energy Solutions Company in April 2015 to engage in businesses in the electric power sector alongside its conventional equipment supply business.

What are power systems

The dense deployment of femtocells has brought new challenges for interference management. Flexible and efficient frequency reuse is one of promising approaches to tackling interference among femtocells. In this paper, we propose a semistatic intercell interference coordination (ICIC) scheme called adaptive frequency reuse (AFR). The proposed AFR scheme involves two algorithms, namely, primary subchannel self-configuration (PSC-SC), that served as ICIC, and interference-aware resource allocation, that served as intracell resource allocation. Compared with the no-ICIC scheme (i.e., Reuse 1), the proposed AFR scheme can achieve around 100% gain in terms of spectrum efficiency of cell-edge users with a minimal impact on the spectrum efficiency of cell-center users. Furthermore, the proposed PSC-SC algorithm is characteristic of low signaling overhead and fast convergence, which is very suitable for femtocell networks with constrained-capacity backhaul.

Interference Mitigation for Femtocell Networks Via Adaptive Frequency Reuse

Inter-cell Interference (ICI) is a key issue in Orthogonal Frequency-Division Multiple Access (OFDMA) systems. Since OFDMA was proposed to be used in next generation networks several schemes have been investigated for mitigating the ICI. One of the techniques that promises improvement in reducing ICI is Partial Frequency Reuse (PFR). In this paper we investigate a Flexible Bandwidth Allocation (FBA) scheme for PFR depending on the network-load, which allocates bandwidth dynamically in the network. The scheme is based on the assumption that a cell is not loaded homogeneously. We develop a suitable network description to obtain the optimum PFR zone partitioning as a function of the dynamic bandwidth allocation. Thus, our paper presents a general framework for intelligent frequency planning in wireless networks. Compared to simpler PFR schemes, our simulation results show that the cell capacity for reuse-1 can be increased by 2 b/s/Hz when our scheme is used by exploiting the inhomogeneities in the load.

/pdf/network-load-dependent-partial-frequency-reuse-for-lte-ka29dofb4m.pdf

Network-load dependent Partial Frequency Reuse for LTE

In this paper we apply constrained optimization techniques to optimally allocate bandwidth and transmit power to the users in a cellular network. We utilize partial frequency reuse as inter-cell interference mitigation technique considering multiple users uniformly located in the cell. Efficient algorithms are proposed to select the user in the cell regions. Moreover, based on user's selection the maximization of the minimum rate is used to optimally allocate the bandwidth and power to the users. We further demonstrate by simulations that using partial frequency reuse as inter-cell interference mitigation technique is more efficient in power use than using frequency reuse-1 or frequency reuse-3.

Efficiency of partial frequency reuse in power used depending on user's selection for cellular networks

We conducted drive test measurements in a live LTE 1800 MHz network to evaluate mobile network performance of User Equipments (UEs) located inside and outside a pickup truck. The measurement campaign is performed in Kosovo, starting from Prishtina to the south-western Albanian border. Knowledge of base station locations and cell load during the measurements is made available from the service provider. This is crucial to determine whether the bit rate is limited by network availability, cell load, or propagation effects. To provide reliable in-vehicle coverage, it is necessary to determine the penetration loss. In this paper, we present the first results and show that the penetration loss varies by up to 10.58 dB.

Measurement and analysis of LTE coverage for vehicular use cases in live networks

We apply constrained optimization techniques to optimally allocate the bandwidth and power to the users in a cellular network. Partial frequency reuse with multiple users in the inner region and the outer region is considered as inter-cell interference mitigation scheme.We show that the maximization of the minimum rate under variable bandwidth and variable power can be transformed into a geometric programming problem and solved efficiently using disciplined convex programming. CVX is used to solve the transformed optimization problem. The optimal solution assigns all available bandwidth to the inner and the outer users and only the satisfactory level of power that the users achieve higher rates that the minimum required rate.

/pdf/maximization-of-the-minimum-rate-by-geometric-programming-4u7ixmsnrz.pdf

Maximization of the Minimum Rate by Geometric Programming for Multiple Users in Partial Frequency Reuse Cellular Networks

In this paper we apply constrained optimization techniques to optimally allocate bandwidth and transmit power to the users in a cellular network We utilize partial frequency reuse with one user in the full and one user in the partial frequency reuse regions as inter-cell interference mitigation technique We show that the non-convex sum-rate maximization problem becomes convex under some simplifying assumptions Moreover, an efficient algorithm is used to solve the problem for a fixed bandwidth allocation Our results show that in the optimum, the full amount of power is assigned to the users We further demonstrate by simulations that re-allocating the outer cell bandwidth to the inner user when no outer user is present, results in a significantly increased sum-rate

/pdf/sum-rate-maximization-by-bandwidth-re-allocation-for-two-142jhmt5na.pdf

Bujar Krasniqi

Papers

Network-load dependent Partial Frequency Reuse for LTE

Efficiency of partial frequency reuse in power used depending on user's selection for cellular networks

Measurement and analysis of LTE coverage for vehicular use cases in live networks

Maximization of the Minimum Rate by Geometric Programming for Multiple Users in Partial Frequency Reuse Cellular Networks

Sum-rate maximization by bandwidth re-allocation for two users in partial frequency reuse cellular networks