Long Term Evolution Cellular Systems Research Articles

Enhanced fair earliest due date first scheduling strategy for multimedia applications in LTE downlink framework

SummaryGuaranteeing a certain delay threshold for delay‐sensitive applications in long term evolution (LTE) cellular communication system is a very challenging mission. By implementing an optimal scheduling strategy, this mission will be achieved. In this article, a novel scheduler is introduced in order to meet a predefined level of service quality by guaranteeing a specific delay threshold for delay‐sensitive applications in LTE cellular systems. The proposed scheduler assigns the available resource blocks (RBs) to active user equipments (UEs) tacking into consideration several attributes. The expiration date of each packet, the channel quality, the average data rate previously achieved by each UE, and the number of dropped packets for each UE compared with the average number of packets totally dropped are all considered in the proposed scheduler working mechanism. Consequently, the proposed scheduling strategy reduces the number of packets dropped for multimedia applications, and at the same time maximizes the overall throughput of the network. Simulation results are provided to study and evaluate the performance of the proposed scheduling strategy. A comparative study is presented between the proposed strategy and the most recent scheduling techniques. The obtained results prove that the proposed scheduling strategy has considerably acceptable and appreciated results compared with the results of the state‐of‐the‐art scheduling techniques.

Resource Allocation Scheme for Interference and Throughput Performance Improvement in LTE Femtocell Networks

Femtocells are one of the key enabling technologies for indoorcoverage extension and system capacity enhancement in LongTerm Evolution (LTE) cellular system. Cross-tier interferencebetween femtocells and macrocells is a great challenge. Inthis paper, a resource allocation scheme is proposed tominimize the interference and enhance the LTE femtocellthroughput. The fraction frequency reuse (FFR) scheme isconsidered for LTE cellular system. The proposed scheme isbased on using small number of resource blocks (RBs) whichefficiently selected according to their signal to interferenceplus noise ratio (SINR). Simulation results demonstrate thatthe proposed scheme increases the femtocell throughputusing small number of allocated resource blocks (RBs) andincreases SINR of femtocells users. Also, the proposedscheme significantly outperforms the conventional randomallocation scheme in terms of the achieved throughput andSINR values when the number of allocated RBs is only 20% ofthe total number of the available RBs.

Empirical Statistical Model for LTE Downlink Channel Occupancy

This paper develops an empirical statistical channel occupancy model for downlink long-term evolution (LTE) cellular systems. The model is based on statistical distributions mixtures for the holding times of the channels. Moreover, statistical distribution of the time when the channels are free is also considered. The data is obtained through an extensive measurement campaign performed in Stockholm, Sweden. Two types of mixtures are considered, namely, exponential and log-normal distributions to fit the measurement findings. The log-likelihood of both mixtures is used as a quantitative measure of the goodness of fit. Moreover, finding the optimal number of linearly combined distributions using the Akaike information criterion is investigated. The results show that good fitting can be obtained by using either exponential or log-normal distributions mixture. Even though, the fitting is done for a representative case with a tempo-spatial consideration, the model is yet applicable in general for LTE and other cellular systems in a wider sense.

Cell Coverage Area and Link Budget Calculations in LTE System

The network planning is a significant step in establishment of wireless communication system. For a wireless system the primary setup takes a lot of time for process and also very expensive. Because of this reason it uses a mathematical model before the processing of the system to avoid unknown expenses. The mathematical model calculation mainly includes path loss, link budgets etc. Radio propagation is site specific and it varies substantially depending on geography, frequency at which system will operate mobile terminal speed, interface sources and other dynamic factors. To estimate the signal coverage and to achieve a high data rates, it is very important to illustrate the radio channel through important parameters and with the help of a mathematical model. In this paper we have evaluated the cell coverage area for Long Term Evolution (LTE) technology at 1800 MHz (FDD-LTE) theoretically for different transmitting antenna heights and at different transmitting power levels. This coverage area is then compared with the practical measured coverage area i.e. practical measured path loss. The signal coverage starts within the cell, by predicting the affecting parameters on the signal power level in the uplink and downlink at the practical cases. In this paper the concentration is completely on preprocess of network planning i.e. link budgeting of LTE cellular system. This investigation can also lead the radio planner to a thorough understanding of radio wave propagation for designing mobile communication system.

Hybrid radio resource allocation and interference coordination for type 1a‐relayed long term evolution uplink

Relay technology has been included in long term evolution (LTE) cellular system through 3GPP Release 10. Relay-based LTE cellular system is one of the most promising technologies to enhance the throughput and coverage of access network. Deployment of relays in a cell opens many issues of frequency/time domain radio resource allocation and frequency planning. In this study, the authors consider the uplink of LTE relay-assisted network and formulate the joint scheduling and intra-cell interference mitigation as a non-linear optimisation problem. They take into account the projection of the gradient of user's utility function over the user's rate vector based on Lagrangian method. They propose a novel transformation of scheduling problem into combinatorial Knapsack optimisation to convert the optimisation problem into binary integer non-linear program. Finally, they present an alternate solution through a low complexity algorithm to allocate resources based on group of resource blocks, whereas considering the contiguity constraint. Simulation results show that the proposed scheme is near optimal with a much lower complexity order.

Performance with MIMO for the Downlink 3GPP LTE Cellular Systems

High spectrum efficiency is one of the goals for 3GPP Long-term Evolution (LTE) cellular networks. This paper provides evaluation of the downlink (DL) transmission in LTE. The evaluation is performed for a regular hexagonal multi-cell deployment, universal frequency reuse scheme2x2 Multiple Input Multiple Output (MIMO) antenna configuration and varying packet scheduling algorithm. This study evaluates the advantages and benefits of combining several spectrum efficiency improvement techniques over multipath selective fading channel conditions and various bandwidth sizes (BW). The proposed paper compares MIMO improvements to Single Input Single Output (SISO) scenario in terms of cell and user throughputs. The evaluation is performed through a custom simulation package developed for this purpose. .

Auto-configuration of Physical Cell ID in LTE femtocellular systems using Self Organizing Networks

The commercial success of cellular networks, combined with advances in digital electronics, signal processing, and telecommunications research have lead to the design of next generation 4G-based long term evolution (LTE) wireless systems. The key essence of these emerging, LTE cellular systems lie in deployment of multiple femtocells for improved coverage and higher data rates. However, the arbitrary deployment of a wide number of femtocells makes the configuration, management and planning of LTE systems quite complex and challenging. In order to support dynamic and efficient network configuration, every cell needs to be assigned a particular Physical Cell ID (PCID). In this paper we show that the dynamic, optimal PCID allocation problem in LTE systems is NP-complete. Subsequently we provide a near-optimal solution using Self-Organizing Networks which models the problem using new merge operations and explores the search space using a suitable randomized algorithmic approach. We also discuss two feasible options for dynamic auto-configuration of the system and analyze the algorithm to prove its convergence. Simulation results point out that our proposed near-optimal solution dynamically achieves ~85−90 % of global optimal auto-configuration in computationally feasible time.

Multi-objective handover in LTE macro/femto-cell networks

One of the key elements in the emerging, packet-based long term evolution (LTE) cellular systems is the deployment of multiple femtocells for the improvement of coverage and data rate. However, arbitrary overlaps in the coverage of these femto-cells make the handover operation more complex and challenging. As the existing handover strategy of LTE systems considers only carrier to interference plus noise ratio (CINR), it often suffers from resource constraints in the target femtocell, thereby leading to handover failure. In this paper, we propose a new efficient, multi-objective handover solution for LTE cellular systems. The proposed solution considers multiple parameters like signal strength and available bandwidth in the selection of the optimal target cell. This results in a significant increase in the handover success rate, thereby reducing the blocking of handover and new sessions. The overall handover process is modeled and analyzed by a three-dimensional Markov chain. The analytical results for the major performance metrics closely resemble the simulation results. The simulation results show that the proposed multi-objective handover offers considerable improvement in the session blocking rates, session queuing delay, handover latency, and goodput during handover.

Entropy-based location management in long-term evolution cellular systems

The recently emerging location-based services in long-term evolution (LTE) systems require the accurate and efficient tracking of mobile users. An optimal information-theoretic framework is developed for tracking area update (TAU) for next-generation LTE cellular systems. Shannon's entropy is used to characterise the location uncertainty of the mobile users. Based on this entropy-based tracking framework, two practical location management schemes, Bayesian-based TAU and entropy-coding based TAU, are proposed. The proposed schemes capture the users' mobility patterns online and perform profile-based paging to optimise the TAU cost. Of the two proposed schemes, the Bayesian-based TAU operates as an independently identically distributed process and improves the paging cost with less storage and computational overhead, whereas the entropy-coding-based TAU using the Lempel'Ziv strategy asymptotically minimises both the update and paging costs with higher storage and computational overheads than the Bayesian-based one. There is some trade-off between the update/paging costs and storage/computational overheads in the two proposed schemes. The simulation results demonstrate that both proposed schemes outperform the existing comparable schemes for LTE systems in all of the performance metrics.

Wavelet-based downlink scheduling and resource allocation for long-term evolution cellular systems

This study proposes the use of wavelet transform in long-term evolution (LTE) cellular systems. Mathematical expressions are derived to represent data rate in LTE downlink transmission based on Wavelet and Fourier Transforms. Furthermore, a comparison between these two systems is provided. Simulation results show the proposed orthogonal wavelet division multiplexing (OWDM) approach outperforms the traditional orthogonal frequency division multiplexing-based systems. The data rate can also be increased by the amount of CyclicPrefix/SymbolTime%, as there is no need for a channel prefix in an OWDM-based system.

Multiuser Scheduling on the Downlink of an LTE Cellular System

The challenge of scheduling user transmissions on the downlink of a long-term evolution (LTE) cellular communication system is addressed. In particular, a novel optimalmultiuser scheduler is proposed. Numerical results show that the system performance improves with increasing correlation among OFDMA subcarriers. It is found that only a limited amount of feedback information is needed to achieve relatively good performance. A suboptimal reduced-complexity scheduler is also proposed and shown to provide good performance. The suboptimal scheme is especially attractive when the number of users is large, in which case the complexity of the optimal scheme is high.