Statistical Analysis of CQI Reporting and MIMO Utilization for Downlink Scheduling in Live LTE Mobile Network

Data-centric mobile devices poses challenges to operators on sustaining the rapid growth of mobile traffic. Recently, full-dimensional MIMO (FD-ΜΓΜΟ) emerges as a promising technique to significantly increase spectrum efficiency and has been proposed and investigated in 3GPP LTE (Long Term Evolution) and LTE-advanced (LTE-A). In FD-MIMO systems, an evolved Node B (eNB) deploys a large number of active antenna elements in a 2-dimensional (2D) grid and is capable to support many users on the same bandwidth simultaneously. In this paper, we propose a FD-MIMO framework within LTE/LTE-A standards and discuss key challenges including downlink preceding, antenna virtualization and channel quality indicator (CQI) prediction. Furthermore, we explore feasibility of implementing FD-MIMO in frequency division duplex (FDD) systems. Based on system-level simulations, FD-MIMO is shown to attain 2–5 times cell average throughput gain as well as cell-edge throughput gain, compared with 4G LTE system.

Long Term Evolution (LTE) is an emerging 4G wireless access technology. Multiple-Input Multiple-Output (MIMO) systems are a primary enabler of the high data rate sought to be achieved by LTE. Closed-Loop-Spatial-Multiplexing and Open-Loop-Spatial-Multiplexing are the two primary MIMO transmission modes used in the LTE downlink. An LTE Base Station (eNodeB) is expected to select and switch transmission characteristics of these MIMO modes based on channel quality feedbacks: Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI) and Rank Indicator (RI) reported by the mobile. In this paper, we show analytically as well as through simulations, that is it not optimal to make MIMO transmission mode selection at the eNodeB based solely on mobile feedback. Doing so can result in significant throughput loss. We then describe an algorithm that can prevent such throughput reduction. The algorithm works by enabling the eNodeB to selectively override the mobile's channel feedback and make a better choice of transmission mode. We provide simulation data to show that such an algorithm can improve the downlink throughput by 110% in some cases and by 20-50% on an average. We also show that an eNodeB equipped with this algorithm is able to match a benchmarked “best case” downlink throughput for a wide range of signal quality and channel models. Existing transmission mode selection algorithms described in literature involve the estimation of additional parameters such as mobile speed, channel diversity etc along with the mobile's channel feedback. The algorithm proposed in this paper is computationally much simpler. It does not involve estimation of any of these additional channel parameters. It is also at par or better in performance. This algorithm has been implemented in the Motorola LTE product.

Long Term Evolution (LTE) mobile networks, time-frequency radio resources are allotted with respect to Quality of Service (QoS) requirements using scheduling algorithms. Buffer Occupancy (BO), Average Cellular Throughput (ACT), Average User Throughput (AUT), Blocking Probability (BP) and Fairness Index (FI) are the parameters to be considered when designing a scheduler. A new scheduling policy is proposed in this paper, called “Channel Aware Optimized Proportional Fair (CAOPF)” to optimize the channel behavior based on Channel Quality Indicator (CQI). The performance of the introduced scheduler is investigated and compared with the other schedulers such as Round Robin (RR) and Proportional Fair (PF). Simulation results indicate that the new scheduler gives the best level of QoS performance in terms of the above said parameters when compared with the other schedulers taken into account. It provides no pending data of users in good channel condition, higher ACT, higher improvement in user throughput in good and average channel conditions. In addition, very low blocking of user data in good channel condition and optimized FI and resource block (RB) allocated to the users in all channel conditions are seen.

Long Term Evolution (LTE) of UMTS Terrestrial Radio Access and Radio Access Network is a Fourth Generation wireless broadband technology which is capable of providing backward compatibility with 2G (Second Generation) and 3G (Third Generation) technologies. LTE is able to deliver high data rate and low latency with reduced cost. It uses the frame structure as Time Division Duplexing (TDD) Land Frequency Division Duplexing (FDD). The broadcast channel in LTE is Physical Broadcast Channel (PBCH) information is divided into two categories one is Master Information Block (MIB) consists of a limited number of the most frequently transmitted parameters essential for initial access to the cell, and is carried on the PBCH and the other System Information Blocks (SIB) at the physical layer are multiplexed together with unicast data transmitted. The main objective of this paper is the realization of receiver architectures for PBCH in LTE considering Single Input Single Output (SISO), Multiple Input Single Output (MISO), Single Input Multi Output (SIMO), and Multiple Input Multiple Output (MIMO). The Receiver processing steps involves as channel de-estimation, demodulation, minimum mean square error (MMSE) and among the received data minimum value is calculated using the comparator at receiver side. By applying the following VLSI DSP methods folding to reduce the number of resource elements required and another method consider to reduce the delay is Super scalar processing method and the results are compared between the direct method, folding method and super scalar method. Based on simulation and implementation, results are discussed in terms of Register Transfer Level (RTL) design, Field Programmable Gate Arrays (FPGA) editor, power estimation and resource estimation. To simulate all the modules of all PBCH channel Verilog code, Modelsim is used. For synthesis and implementation of the above architecture PlanAhead 13.4 tool on Virtex-5, xc5vlx50tff1136-1 device board is used.

Long Term Evolution (LTE) Networks are being planned to be upgraded to LTE Advanced along with increasing availability of Release 10 User Equipment (UEs) and Spectrum Availability for Carrier Aggregation. LTE Advanced brings a major step increase in Down Link and Uplink Throughputs and related spectral efficiencies. This paper explains the evolution of Frequency Division Duplex (FDD) throughputs for different Channel Bandwidths. The maximum theoretical physical layer throughputs and expected actual application layer throughputs after removing the necessary overheads by different broadcast, signaling, synchronization & random access channels have been explained with an impact analysis thereof. Throughput gains for upcoming LTE Advanced deployments have been computed for Frame Structure Type 1 (FDD) for Channel Bandwidth of 1.4 MHz, 3MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz along with Carrier Aggregation of 2 & 5 Component Carriers. Impact of increasing Signaling Channels, retransmissions & code rate on throughputs has been explained so that the computations can be extended to any deployment scenario.

This paper study the performance of an orthogonal frequency division multiple access (OFDMA) system under fractional load based in long term evolution (LTE) downlink. Fractional load is defined by a situation where only a fraction of the bandwidth is used for transmission due to lack of traffic. This type of situation should result in a global increase of signal to interference and noise ratio (SINR) conditions in the network. We propose different methods integrating the transmission pattern selection to the packet scheduling functionality of the enode-B depending only on the channel quality indicator (CQI) reports from the user equipments. Fractional load handling is operated without inter eNode-B coordination. We conclude that the system can operate under fractional load conditions if the CQI is calculated with wideband interference. Further gain can be obtained if the CQI is calculated with local interference, however, in that case, it is necessary to inject a certain time correlation in the transmission patterns due to reporting delay.

This paper presents a feature comparison between the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) Release 8 and Institute of Electrical and Electronics Engineers (IEEE) 802.16m and preliminary system performance comparison. As Orthogonal Frequency Division Multiple Access (OFDMA) mobile broadband air interfaces, LTE and IEEE 802.16m are both International Mobile Telecommunications-Advanced (IMT-Advanced) technologies. LTE and IEEE 802.16m, which both make use of Multiple-Input Multiple-Output (MIMO) channels, have their own features and advantages. This paper compares some features between LTE and IEEE 802.16m in terms of frame structure, effective bandwidth, Hybrid Automatic Retransmission Request (HARQ) and Modulation and Coding Scheme (MCS), which is a valuable replenishment to the former work. The system simulation results show that LTE and IEEE 802.16m achieve similar performance although they are different communication evolution systems from different specification work groups.

Traffic capacity planning is a challenging task in multiple input multiple output (MIMO) & orthogonal frequency division (OFDM) based long term evolution (LTE) cellular networks, resulted from emerging diverse multimedia traffic requirement, together with highly open & flexible air interface design in LTE. In this paper, a new methodology for dynamic real-time capacity planning is proposed for LTE radio network dimensioning, based on unified traffic process mechanism, fresh simulation methodology for air interface, and smart self-evaluation and optimization. By corresponding software design and implementation, it provides powerful tool for LTE network planners to get efficient, accurate and professional capacity planning outcome without much manual effort.

Long Term Evolution (LTE) is designed as a wireless broadband technology for a last generation of Universal Mobile for Telecommunication System (UMTS) to provide multimedia services for the users. In order to enhance the performance of LTE system with low complexity for the system, this paper submits Hybrid Adaptive Repeat and Request (HARQ) procedure with one retransmitting and Multiple Input Single Output (MISO) technique using two antenna elements at the transmitter side to improve the capability of the system. The results showed that the block error rate (BLER) and the throughput of the system are improved when the HARQ procedure and MISO technique are employed together in a three cases study of the Channel Quality Indicator (CQI) of the user.

In this paper, we propose a new uplink reference signal (RS) structure and channel estimation scheme for long term evolution (LTE) compatible geostationary earth orbit (GEO) satellite communication systems over dual-polarized multiple-input multiple-output (MIMO) channels. The conventional discrete Fourier transform (DFT) based least square (LS) channel estimator suffers from a spectral leakage, which results in an irreducible inter-antenna interference in MIMO systems. By exploiting the characteristic of satellite channel, we put forward a joint slot RS structure in both code division multiplexing (CDM) and frequency division multiplexing (FDM) modes, ensuring the orthogonality between antennas, the former of which is compatible with the terrestrial LTE system. In order to further eliminate the influence of noise, a simple implementation of the optimal channel estimator in the linear minimal mean square error (LMMSE) sense in discrete cosine transform (DCT) domain is derived. Finally, the effectiveness of the proposed RS structure and channel estimation method is verified via simulations.

Recently, energy efficiency in wireless networks has become an important objective. Aside from the growing proliferation of smartphones and other high-end devices in conventional human-to-human (H2H) communication, the introduction of machine-to-machine (M2M) communication or machine-type communication into cellular networks is another contributing factor. In this paper, we investigate quality-of-service (QoS)-driven energy-efficient design for the uplink of long term evolution (LTE) networks in M2M/H2H co-existence scenarios. We formulate the resource allocation problem as a maximization of effective capacity-based bits-per-joule capacity under statistical QoS provisioning. The specific constraints of single carrier frequency division multiple access (uplink air interface in LTE networks) pertaining to power and resource block allocation not only complicate the resource allocation problem, but also render the standard Lagrangian duality techniques inapplicable. We overcome the analytical and computational intractability by first transforming the original problem into a mixed integer programming (MIP) problem and then formulating its dual problem using the canonical duality theory. The proposed energy-efficient design is compared with the spectral efficient design along with round robin (RR) and best channel quality indicator (BCQI) algorithms. Numerical results, which are obtained using the invasive weed optimization (IWO) algorithm, show that the proposed energy-efficient uplink design not only outperforms other algorithms in terms of energy efficiency while satisfying the QoS requirements, but also performs closer to the optimal design.

We present in this paper a novel proactive interference avoidance scheme for mobile-to-mobile (M2M) communication as an underlay in Long-Term Evolution (LTE) downlink networks. The proposed scheme introduces an intelligent user-selective resource allocation algorithm that aims to proactively avoid interference between M2M pairs and LTE regular users while achieving a satisfactory link budget for both M2M and LTE regular links. The proposed resource allocation algorithm is based on a novel low-complexity interference estimation approach that requires only channel quality indicator (CQI) information (CSI). Since the CQI reporting mechanism has been already implemented in current LTE systems, the proposed algorithm is indeed practical and standard compatible, compared with the existing works that require perfect knowledge of the channel state information (CSI). In this research, achievable data throughput with LTE-compliant adaptive modulation and coding has been adopted as the optimization measurement, rather than the information-theoretic capacity. Therefore, the performance of the proposed scheme is practically realizable in LTE communication systems. Since the performance of the proposed scheme highly relies on the accuracy of CQI feedback, we also carry out performance analysis to evaluate the impact of CQI estimation error and delay. The simulation results show that the total achievable data throughput for LTE networks is dramatically enhanced by M2M communication with this proposed interference avoidance resource allocation scheme.

In order to satisfy constantly increasing user demands, in process of transition towards LTE (Long Term Evolution) mobile networks of 4th generation, for 3G UMTS networks potential solution is exploitation of multi-antenna MIMO (Multiple Input Multiple Output) systems, which provide increase in both capacity and reliability. This paper puts an effort to provide a link between link-level and system-level gains introduced by multi-antenna techniques in UMTS systems. Coverage, capacity and achievable data rates are evaluated and presented for Alamouti scheme, TxAA and D-TxAA. Radio mobile planning tool is used for illustration of coverage improvement achieved by implementation of several multi-antenna techniques. Considering system-level gains, it is seen that implementation of MIMO techniques yields larger service area and/or increase in capacity and available data rates maintaining the same bandwidth. Results presented in this paper help making a clear picture of achievable gains, employment costs and answering the question: Should mobile operators invest in upgrading their 3G networks with MIMO techniques and is that investment justified, considering achievable improvements.

This paper addresses the performance of spatial division multiplexing (SDM) multiple-input multiple-output (MIMO) techniques together with frequency domain packet scheduling (FDPS) based on UTRAN long term evolution (LTE) downlink. Two SDM concepts currently considered in 3GPP are the single-user (SU-) and the multi-user (MU-) MIMO. For MU-MIMO, multiple users can be scheduled on different streams on the same time-frequency resource, while SU-MIMO restricts one time-frequency resource to a single user. Both concepts are analyzed against the 1times2 maximal ratio combining (MRC) case, using the proportional fair (PF) criterion extended to frequency and spatial domains. The realistic finite buffer best effort traffic model is used in the study. Results show that in the macrocell scenario, the combination of FDPS and SDM (SDM-FDPS) without preceding achieves only marginal gain in cell throughput, due to limited SINR dynamic range. The gain is increased to around 20% when precoding is applied. In the micro-cell scenario, the gain of SDM-FDPS over the reference scheme is increased up to 35% with precoding.

The recent wireless communication networks rely on the new technology named Long Term Evolution (LTE) to offer high data rate real-time (RT) traffic with better Quality of Service (QoS) for the increasing demand of customer requirement. LTE provide low latency for real-time services with high throughput, with the help of two-level packet retransmission. Hybrid Automatic Repeat Request (HARQ) retransmission at the Medium Access Control (MAC) layer of LTE networks achieves error-free data transmission. The performance of the LTE networks mainly depends on how effectively this HARQ adopted in the latest communication standard, Universal Mobile Telecommunication System (UMTS). The major challenge in LTE is to balance QoS and fairness among the users. Hence, it is very essential to design a down link scheduling scheme to get the expected service quality to the customers and to utilize the system resources efficiently. This paper provides a comprehensive literature review of LTE MAC layer and six types of QoS/Channel-aware downlink scheduling algorithms designed for this purpose. The contributions of this paper are to identify the gap of knowledge in the downlink scheduling procedure and to point out the future research direction. Based on the comparative study of algorithms taken for the review, this paper is concluded that the EXP Rule scheduler is most suited for LTE networks due to its characteristics of less Packet Loss Ratio (PLR), less Packet Delay (PD), high throughput, fairness and spectral efficiency.