MU-MIMO in LTE Systems

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.

3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) Advanced standards are currently under way, where 4×4 MIMO (Multiple Input Multiple Output) scheme is the minimum structure. One of the best solutions to support the maximum data rate transmission is to adopt a MIMO scheme, especially spatial multiplexing mode, which means that each antenna port can transmit separate data. To realize this algorithm, the main issue is to cancel interferences added to each antenna port, and therefore, the algorithm at the receiver should have good performances. In the aspect of implementation, MMSE (Minimum Mean Square Error) detection algorithm is a reasonable method considering both complexity and performance. Furthermore, an iterative receiver (IR) algorithm can also be applied to this system. An IR algorithm has a tradeoff between complexity and performance. In this paper, we designed a reasonable and implementable MIMO receiver structure and showed performance for 3GPP LTE Advanced system, and verified that hard decoded bits, PIC-MMSE (Parallel Interference Cancellation - MMSE) and 1-iteration PIC are enough to meet the required SNR using the implemented test-bed system.

This article presents a framework for performance comparison between Long Term Evolution (LTE) and WiMAX technologies, depended on link level simulation, under different conditions (e.g. a mixture of channel models and modulation coding schemes (MCS)). Two performance metrics have been used: throughput against SNR for both downlink (DL) and uplink (UL) and block error rate (BLER) against SNR for both DL and UL. Simulation results, conducted in network simulator OPNET Modeler ver. 17.1, show that the throughput and the BLER increases as the MCS increase (i.e. MCS=5, 15, 24).

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.

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.

Long Term Evolution (LTE) standard aims for high data rate transmission in the order of several hundreds of Mbps. Non-Orthogonal Multiple Access (NOMA) transmission is proposed in LTE-Advanced (LTE-A) systems to increase the cell throughput. NOMA based transmission allows the eNodeB (eNB) to multiplex the different users' signals in power domain in a frequency-time grid. In this paper, a novel Hybrid Automatic Repeat and reQuest (HARQ) scheme is proposed for NOMA based transmission. In the proposed method, power level of users are adjusted dynamically in re-transmissions in order to reduce the number of attempts for successful transmission of packets. This will increase the overall cell throughput and reduce power consumption at UE. The proposed method is applied on the Incremental Redundancy (IR) form of HARQ scheme. System level simulations are carried out by considering LTE system parameters. Based on the results, the proposed method improves the cell throughput by reducing the number of retransmissions in HARQ process considerably.

Multi-input-multi-output (MIMO) systems along with orthogonal frequency division multiplexing (OFDM) technique plays a crucial role in 4G based wireless networks. The inclusion of MIMO technology enables new types of links such as downlink multi-user communication. Long term evolution (LTE) systems are based on multi-user MIMO technologies, which have flexible bandwidths. In this paper, we derived closed form expression of bit error rate (BER) for multi-user LTE and LTE-Advanced (LTE-A) systems. Moment generating function (MGF) and pair-wise error probability (PEP) based approaches are used to derive these BER expressions. Theoretical results of BER are validated using simulation results for different number of users. Results are plotted on the basis of various features such as coordinated multipoint (CoMP) transmission and reception, multimedia broadcast and multicast services (MBMS) and allocation of Bandwidth in LTE and LTE-A systems.

근래 전 세계적으로 스마트 폰의 수요가 급증하면서 기존의 3G 표준에 비해 높은 데이터 전송률을 제공하는 long term evolution (LTE) 서비스가 활발히 보급되고 있다. 특히, 이동통신 강국인 우리나라는 LTE의 최신 릴리즈인 LTE-Advanced (LTE-A) 서비스를 최근 시작하였다. 높은 데이터 전송률을 얻기 위한 LTE와 LTE-A 시스템의 핵심기술로 다중입출력 안테나 (multiple-input-multiple-output; MIMO)기술을 들 수 있다. MIMO 기술은 주파수와 전력의 증가 없이 안테나 수에 비례하는 채널용량을 얻을 수 있는 장점으로 큰 주목을 받아왔으며 다양한 측면에서 진화 발전이 이루어지고 있다. 본 논문에서는 단일사용자 MIMO에서 다중사용자 MIMO, 그리고 최근 주목받고 있는 대용량 MIMO까지 MIMO기술의 이론적 배경 및 시스템을 구현하기 위해 필요한 고려사항들을 살펴본다. Recent exploration of smart-phone user is fueling the deployment of long term evolution (LTE) service that offers higher data rates service over 3G HSPA networks. In particular, Korea, mobile powerhouse, recently launched the service of LTE-Advanced (LTE-A) which is the latest release in LTE standard. Multiple-input-multiple-output (MIMO) technology is the one of key enablers for LTE and LTE-A for achieving high data rate. MIMO technology has received much attention since it is possible to achieve channel capacity in proportion to the number of antennas without increasing frequency and power. In this paper, we overview of the theoretical background of MIMO technology regarding from single-user MIMO, multiuser MIMO, and massive MIMO and design considerations to implement the communication system.

Multiple-input multiple-output (MIMO) has been adopted by long term evolution (LTE) and its updated version LTE-Advanced (LTE-A) to increase spectrum efficiency. However, the benefits of multi-user (MU) MIMO highly rely on the accurate channel knowledge at transmitter. So proper codebook design is a key problem for frequency division multiplexing (FDD) downlink systems. In this paper, an efficient codebook design based on Hadamard transform is proposed for uniform circular arrays. Then a two-stage feedback scheme is further proposed to reduce the feedback overhead. The average cell spectrum efficiency and cell-edge user spectrum efficiency of the proposed scheme are evaluated through system level simulation and compared with LTE Rel-10 feedback. The results show that the proposed codebook significantly improves feedback efficiency and system performance.

The Long Term Evolution (LTE) standards are generated by the Third Generation Partnership Project (3GPP) for the Fourth Generation (4G) wireless communication systems. The Fourth Generation (4G) wireless communication standards use new physical layer signaling techniques in their physical layer. Single Carrier Frequency Division Multiple Access (SC-FDMA) and Orthogonal Frequency Division Multiple Access (OFDMA) are the two major signaling techniques used in LTE. OFDMA is used in the downlink of the Fourth Generation (4G) wireless communication systems for its high spectral efficiency and SC-FDMA is used in the uplink of the Fourth Generation (4G) wireless communication systems for its high power efficiency. The main objective of this paper is to design and implement the reliable and energy efficient architecture for LTE uplink system using FPGA. IFDMA is the most energy efficient subcarrier mapping scheme of SC-FDMA multiple access scheme. In IFDMA, the data symbols subcarrier mapping is not one to one instead each subcarrier carries a part from each data symbol transmitted at that time instant. The reason for the selection of IFDMA subcarrier mapping along with SC-FDMA multiple access scheme for LTE uplink comes mainly from its advantage to provide a low peak to average power ratio (PAPR) for the transmitted waveform. This results in less power consumption in the mobile station during uplink transmission. The reliability of the system is improved using interleaving process by avoiding packet loss. Convolution codes are less complex and are used to provide error free transmission. The enhancement of energy efficiency is done using the convolution coded IFDMA. The chosen energy efficient architecture must be more power efficient and support high data rates, which is the main requirement for the mobile user. The proposed reliable and energy efficient architecture for LTE uplink system is implemented using Xilinx system generator tool.

Long Term Evolution (LTE) represents the fourth generation (4G) technology which is capable of providing high data rates as well as support of high speed mobility. The EU FP7 Mobile Cloud Networking (MCN) project integrates the use of cloud computing concepts in LTE mobile networks in order to increase LTE's performance. In this way a shared distributed virtualized LTE mobile network is built that can optimize the utilization of virtualized computing, storage and network resources and minimize communication delays. Two important features that can be used in such a virtualized system to improve its performance are the user mobility and bandwidth prediction. This paper introduces the architecture and challenges that are associated with user mobility and bandwidth prediction approaches in virtualized LTE systems.

Advanced Nodes are the main components of Physical Layer based fully-directional networks. They consist of sets of appropriately programmed antenna arrays that enable them to conform to the standards of the radio being used. This paper provides an in-depth comparison of advanced nodes implementations for the two main choices of radios: 3GPP's Long Term Evolution (LTE) and IEEE 802.11 (WiFi). Component-by-component comparison is carried out, investigating several implementation aspects as well as estimated performance (in terms of standard performance metrics such as bit error rate, data rate, capacity, coverage radius) for the two radios. Based on the comparison, the associated implementation trade-offs are analyzed which help in choosing between the two radios.

3rd Generation Partnership Project (3GPP) has recently completed the specification of the Long Term Evolution (LTE) standard. Majority of the world's operators and vendors are already committed to LTE deployments and developments, making LTE the market leader in the upcoming evolution to 4G wireless communication systems. Multiple input multiple output (MIMO) technologies introduced in LTE such as spatial multiplexing, transmit diversity, and beamforming are key components for providing higher peak rate at a better system efficiency, which are essential for supporting future broadband data service over wireless links. Further extension of LTE MIMO technologies is being studied under the 3GPP study item to meet the requirement of IMT-Advanced set by International Telecommunication Union Radiocommunication Sector (ITU-R). In this paper, we introduce various MIMO technologies employed in LTE and provide a brief overview on the MIMO technologies currently discussed in the LTE-Advanced forum.

Long Term Evolution (LTE) is the latest cellular system that is being standardized by the 3rd Generation Partnership Project (3GPP) and is expected to substantially improve end-user throughput and reduce user plane latency, while at the same time significantly improve user experience with full mobility. To realize these expectations, 3GPP is investigating the relay station (RS) usage in LTE networks, which is an intermediate station placed between a Mobile Station (MS) and evolved Node-Bs (eNode-Bs). The RS positioning is an important factor that severely influences the LTE uplink performance. This paper analyses the impact of RS positioning on the LTE uplink performance at flow level by using numerical and simulation experiments.

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.