Performance Comparison between LTE and WiMAX Based on Link Level Simulation

Long Term Evolution (LTE) networks are designed with overlap between cells to support mobility along the network cells and to avoid out of coverage area; especially in suburban and rural area because high mobility. The overlapping results in interferences which reduce network capacity so this paper aims to bring customer demands for high-quality networks. This paper involves a good understanding of radio network planning and optimization of LTE and perform a case study in Taiz governorate with a selected suburban and rural area of 86.846 km2. Self-organizing networks (SONs) are widely considered to improve the end users’ quality of experience. The simulation was performed using ATOLL software. The radio frequency (RF) optimization involves Inter-Cell Interference Coordination (ICIC). The downlink (DL) LTE coverage area is enhanced and increased to 84 km2 with probability of 97%. In addition, the overlapping zone is reduced to 0.4% and the block error rate (BLER ≥ 0.2) is reduced to 2.1% in the DL and (BLER ≥ 0.2) to 0.6% in the uplink (UL).

Concurrent self-organization of coverage and capacity in both downlink (DL) and uplink (UL) is an ambitious task since 1) Coverage and capacity are conflicting key performance indicators (KPIs), and 2) an adequate DL performance does not necessarily entail an adequate UL performance because the DL and UL interference scenarios are fundamentally different. However, considering the UL when self-organizing the network is crucial because the UL transmission becomes more important due to the emergence of new applications and services, such as social networking, video calls, or sensor networks, which require either parity between DL and UL traffic or even more UL than DL traffic. In this paper, we propose a general concept for the self-organization of multiple KPIs while having only very sparse knowledge about the network. Using this concept, we propose an effective tilt-based algorithm that manages to jointly optimize coverage and capacity in DL and UL. In an urban scenario with real Long-Term Evolution (LTE) site locations, we were able to increase the cell-edge user throughput by 70% (DL) and 24% (UL) while concurrently decreasing the number of uncovered users by 21% (DL) and 25% (UL), compared with a well-chosen reference tilt setting.

The Third Generation Partnership Project (3GPP) has been studying dynamic allocation of sub-frames to uplink (UL) or downlink (DL) in Time Division Duplex (TDD), called ‘Dynamic TDD,’ since the Long Term Evolution (LTE) Rel. 11 timeframe. At the same time, 3GPP is also standardizing Enhanced Local Area (eLA) small-cell heterogeneous architectures for inclusion in LTE-B (LTE Rel. 12) as a solution offering high data rate to user terminals (UEs) along with high system capacity through spatial reuse of spectrum. In this paper, we focus on a particular eLA architecture proposed by DOCOMO, called the Phantom Cell architecture, that has the option to support dynamic TDD. For an arbitrarily-located UE in an eLA cell network, we apply results from stochastic geometry to derive expressions for the distribution of DL signal to interference plus noise ratio (SINR) at an arbitrary UE and the distribution of UL SINR at its serving eLA base station (BS). We use these results to study aspects of eLA cell system design, and the sensitivity of SINR to the extent of coordination across eLA cells employing dynamic TDD.

Relay is a key technique in the 3G long term evolution (LTE), it uses wireless backhaul to communicate with the donor eNodeB. Relay can be deployed to improve the cell-edge coverage and throughput. However, when relay is introduced into the network, it will also cause additional inter-cell interference for both uplink (UL) and downlink (DL). A field test is done to understand the inter-cell interference impacts of TD-LTE in-band relay. The results show that without coordination, relay may increase both UL and DL inter-cell interference to the neighbor cells, and this may impair the cell-edge user throughput of the neighbor cells. Therefore a coordination mechanism tailor made for relay is proposed, and the analyses show that it can help to reduce the inter-cell interference due to the introduction of relay.

The fifth-generation new radio technology (5G NR) introduces improved functions to the air interface. In addition, the 5G NR non-standalone (NSA) will operate with long-term evolution, enabling vehicle-to-everything communications (V2X) for improved infotainment services. V2X includes four main classes of communications: vehicle-to-vehicle, vehicle-to-infrastructure, vehicle-to-pedestrian devices, and vehicle-to-network. However, the stringent transmission frequency, latency, and throughput requirements of infotainment applications constrain the transmitting packets of 5G-V2X-based NSA in highway scenarios. In this paper, the latency is improved by preventing the physical layer of gNodeB and the user equipment (UE) from sending redundant packets for service in a highway scenario. The proposed approach adopts an adaptive neuro-fuzzy inference system (ANFIS), a powerful modeling technique based on artificial neural networks ,and a fuzzy inference system. The performance of ANFIS is compared with that of the traditional 5G V2X NSA architecture in a simulation study using Voice over Internet Protocol (VoIP) traffic. The delays, throughputs, and packet losses of both architectures are determined in radio link control (RLC) and VoIP applications. The switch-modes, signal-to-interference-noise ratios (SINRs), hybrid automatic repeat request (HARQ) error rate, channel quality indicators (CQIs), served blocks, and transmission-state of gNodeB are computed for the two architectures for device-to-device (D2D), uplink (UL) and downlink (DL) traffic directions. The simulation results show comparable SINRs, CQIs, served blocks ,andswitchmodes in both scenarios, but the presented ANFIS model significantly outperforms the traditional architecture in delay by 66% in D2D, 29% in UL, 25% in DL, and packet loss by 21% in UL in RLC, the HARQ error rate by 9% in D2D, 30% in UL, 95% in DL, transmission-state in gNodeB by 29%, and the delay by 4% for UEs, and frame loss by 90%for UE in VoIP.

In this paper, we study the uplink (UL) and downlink (DL) ergodic capacity in the bidirectional dynamic network (BDN). By dynamically allocating the numbers of UL and DL remote radio heads (RRHs), BDN facilitates simultaneous UL and DL communications to accommodate the data traffic asymmetry. Assuming that the number of antennas at each RRH (M) is large, we derive the closed-form expressions for the ergodic achievable rates in BDN systems, and the theoretical results are shown to be accurate compared with the Monte Carlo simulation results. Furthermore, we investigate the performance of the limiting UL and DL rates when M goes to infinity, and it indicates that we can scale down the UL and DL power per user proportionally to 1/M to guarantee a certain UL or DL quality of service in BDN. Numerical results indicate that there exists an optimal ratio between UL and DL RRH numbers for the maximal spectral efficiency in BDN. Thanks to our proposed RRH layout which guarantees the uniformity and symmetry in the whole network, we can find the optimal ratio between UL and DL RRH numbers more easily.

In traditional half-duplex (HD) communication systems, the HD base station (BS) can transmit artificial noise (AN) to jam the eavesdroppers for securing the downlink (DL) communication. However, guaranteeing uplink (UL) transmission is not possible with an HD BS because HD BSs cannot jam the eavesdroppers during UL transmission. In this chapter, we investigate the resource allocation algorithm design for secure multiuser systems employing a full-duplex (FD) BS for serving multiple HD DL and UL users simultaneously. In particular, the FD BS transmits AN to guarantee the concurrent DL and UL communication security. We propose a multi-objective optimization framework to study two conflicting yet desirable design objectives, namely total DL transmit power minimization and total UL transmit power minimization. To this end, the weighted Tchebycheff method is adopted to formulate the resource allocation algorithm design as a multi-objective optimization problem (MOOP). The considered MOOP takes into account the quality-of-service (QoS) requirements of all legitimate users for guaranteeing secure DL and UL transmission in the presence of potential eavesdroppers. Thereby, secure UL transmission is enabled by the FD BS, which would not be possible with an HD BS. Although the considered MOOP is non-convex, we solve it optimally by semidefinite programming (SDP) relaxation. Simulation results not only unveil the trade-off between the total DL transmit power and the total UL transmit power, but also confirm that the proposed secure FD system can guarantee concurrent secure DL and UL transmission and provide substantial power savings over a baseline system.

Coexistence research for LTE systems is indispensable to ensure that the time division duplex (TDD) Long Term evolution (LTE) system can coexist with the frequency division duplex (FDD) LTE system operating at the adjacent frequency band within the same geographical area. Previous studies on this topic only focus on the throughput loss of the victim system from the data channel viewpoint. In this paper, the performance of control channels (CCHs) in the typical coexistence scenario is investigated, since the performance of communication systems is largely dependent on the quality of CCHs. The CCHs' interferences are analyzed in detail, including the coexistence issue for CCHs, Co-Channel Interference (CCI) analysis, and Adjacent Channel Interference (ACI) on CCHs. The simulation results indicate that the ACI generated by the Base Station (BS) of collocated LTE system degrades the performance of the uplink (UL) CCHs of the victim LTE system significantly.

In this paper, performance of two Interference Aware (IA) receivers is assessed in the context of MultiUser-Multiple Input Multiple Output (MU-MIMO) Coordinated MultiPoint (CoMP) in the downlink (DL) of Long Term Evolution (LTE) cellular system. The use of IA receivers is motivated by the poor spatial resolution of the LTE codebook, considered here. Analytical formulation of receivers and Log likelihood Ratios (LLRs) in the context of the study is derived. The performance are measured thanks to link level simulations. It is first shown that interference must be rejected at the receiver. Studied receivers are then shown to be able to reject all the interference due to MU-MIMO. Finally it is demonstrated that these algorithms are robust to a non optimal location of UEs with respect to precoders used.

For the 5G systems, new uplink waveforms enabling low peak-to-average power ratio (PAPR) and low out-of-band emission (OOBE) are required to enhance spectrum efficiency while maintaining power efficiency of mobile terminals. Discrete Fourier transform-spread orthogonal frequency division multiplexing (DFTs-OFDM) is extensively used as an uplink multiple access scheme for existing Long Term Evolution (LTE) and LTE-Advanced systems. Despite lower PAPR of DFTs-OFDM compared to conventional OFDM, its high OOBE limits the spectral availability in adjacent channels. Universal time-domain windowing (UTW) is expected to significantly reduce OOBE, while it is necessary to demonstrate its practicality with a comprehensive evaluation including the communication quality. In this paper, we apply the UTW to the 5 MHz LTE uplink system based on DFTs-OFDM (UTW-DFTs-OFDM) and simulate its performance in respect to OOBE, PAPR, and block error rate (BLER) under the frequency selective fading environment. In addition, we propose new receiver architecture to improve the communication quality and clarify the trade-off between OOBE reduction and the communication quality. The simulation results indicate that UTW-DFTs-OFDM significantly reduces the OOBE by applying a long time-domain window in excess of the CP length with maintaining sufficient communication quality.

In this paper, we find the optimum lengths of T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">UL</sub> , T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DL</sub> and B i.e. the uplink (UL) and downlink (DL) pilots and feedback bits respectively maximizing the sum of the lower bounds of the UL and the DL rates. With the aid of T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">UL</sub> symbols, the Base Station (BS) estimates the UL channel of each user. T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DL</sub> symbols are means of estimating the downlink channel, which after being normalized and quantized with B bits, is made available at the BS. Estimated Channel State Information (CSI) and quantized Channel Direction Information (CDI), which may be received erroneously, are thus available at the BS for computing the receive and the transmit Zero-forcing (ZF) filters, respectively. The use of ZF enables the derivation of analytical DL and UL mean squared error (MSE) expressions that give a lower bound on the DL and UL rates, respectively, needed for our optimization.

Device-to-device (D2D) communication as an underlaying cellular network empowers user-driven rich multimedia applications and also has proven to be network efficient offloading eNodeB traffic. However, D2D transmitters may cause significant amount of interference to the primary cellular network when radio resources are shared between them. During the downlink (DL) phase, primary cell UE (user equipment) may suffer from interference by the D2D transmitter. On the other hand, the immobile eNodeB is the victim of interference by the D2D transmitter during the uplink (UL) phase when radio resources are allocated randomly. Such interference can be avoided otherwise diminish if radio resource allocated intelligently with the coordination from the eNodeB. In this paper, we formulate the problem of radio resource allocation to the D2D communications as a mixed integer nonlinear programming (MINLP). Such an optimization problem is notoriously hard to solve within fast scheduling period of the Long Term Evolution (LTE) network. We therefore propose an alternative greedy heuristic algorithm that can lessen interference to the primary cellular network utilizing channel gain information. We also perform extensive simulation to prove the efficacy of the proposed algorithm.

We consider the problem of UpLink (UL) scheduling in relay-assisted Long Term Evolution (LTE) networks and propose a Buffer-based Channel dependent Scheduler (BCS) for the same. Our objectives are to minimize packet loss due to buffer overflow and increase resource utilization efficiency while ensuring fairness among users. This is achieved by utilizing the Buffer Status Report (BSR) available in Third Generation Partnership Project (3GPP)-LTE. The proposed scheduler comprise three-phases. Phase I partitions the resources between eNB (Base Station in LTE) and Relay Nodes (RNs) while Phase II, between different RNs. This resource partitioning is entailed by Phase III which implements buffer-based channel dependent resource allocation. We perform simulations to illustrate reduction in packet drop probability and increment in resource utilization efficiency when BSR is incorporated in scheduling decision. Further, our simulations show that BCS provides higher degree of fairness and lower outage probability compared to opportunistic and round robin scheduler. We also investigate the impact of buffer based resource partitioning on packet drop probability.

Full duplex (FD) communication has emerged as an attractive solution for increasing the network throughput, by allowing downlink (DL) and uplink (UL) transmissions in the same spectrum. However, only employing FD base stations in heterogeneous cellular networks (HCNs) cause coverage reduction, due to the DL and UL interferences as well as the residual loop interference. We, therefore, propose HCNs with half duplex massive multiuser multiple-input multiple-output macrocell base stations (MBSs) to relax the coverage reduction, and FD small cell base stations (SBSs) to improve spectrum efficiency. A tractable framework of the proposed system is presented, which allows to derive exact and asymptotic expressions for the DL and the UL rate coverage probabilities, and the DL and the UL area spectral efficiencies (ASEs). Monte Carlo simulations confirm the accuracy of the analytical results, and it is revealed that the equipping massive number of antennas at MBSs enhances the DL rate coverage probability, whereas increasing FD SBSs increases the DL and the UL ASEs. The results also demonstrate that by tuning the UL fractional power control, a desirable performance in both UL and DL can be achieved.

This paper addressed the problem of packet scheduling (PS) on the 3GPP Long Term Evolution (LTE) downlink (DL). The main contribution of this work was to propose a new scheduling and resource allocation scheme that deals with QoS requirements. The objectives of this proposed scheduler are to maximize the system’s sum throughput, to allow a fair distribution of available RBs and to handle GBR and NGBR traffic in LTE downlink systems. The performance of the proposed approach was compared with previous resources allocation and scheduling algorithms such as Best-CQI, RR, and QoE downlink schedulers. Simulation results show that it is possible to achieve a considerable gain in both system’s throughput and fairness.KeywordsSchedulingLTEDownlinkThroughputQoS