MIMO 기술의 진화

Long Term Evolution (LTE) and Long Term Evolution-Advanced (LTE-A) support a better data transmission service than 3G dose and are globally commercialized technologies in a cyber world that is essential for constructing a future mobile environment, since network traffics have exponentially increased as people have started to use more than just one mobile device. However, when User Equipment (UE) is executing initial attach processes to access LTE networks, there is a vulnerability in which identification parameters like International Mobile Subscriber Identity (IMSI) and Radio Network Temporary Identities (RNTI) are transmitted as plain texts. It can threat various services that are commercialized therewith in a cyber world. Therefore, a security scheme is proposed in this paper where identification parameters can be securely transmitted and hidden in four cases where initial attach occurs between UE and Mobility Management Entity (MME). The proposed security scheme not only supports encrypted transmission of identification parameters but also mutual authentication between Evolved Node B (eNB) and MME to make a secure cyber world. Additionally, performance analysis results using an OPNET simulator showed the satisfaction of the average delay rate that is specified in LTE standards.

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.

The fifth-generation (5G) mobile network is facing severe challenges of the traffic demand surge and spectrum scarcity. To improve the network capacity and data rate, the deployment of Long Term Evolution (LTE) cellular system on unlicensed band is considered as one of the promising solutions. But the interference problem among LTE and WiFi system on the same unlicensed band hinders the deployment process, which is a critical issue unsolved for network operators. Therefore, a novel channel access scheme integrating the energy detection scheme and back-off mechanism in LTE system has been proposed in this paper, to minimize the interference to WiFi system. The throughput of both LTE and WiFi systems and the optimal sensing time and back-off time are theoretically analyzed with proofs. Furthermore, an efficient adaptive reconfiguration strategy of access parameters is proposed based on the channel occupancy cognition results. Simulation results verify that the proposed channel access scheme with optimal back-off time can double the throughput of WiFi system when coexisting with LTE system on unlicensed band.

Long Term Evolution (LTE) and its revision, Long Term Evolution-Advanced (LTE-A), were designed for high performance communications between devices operated by human users. However, when these networks are used for Machineto- Machine (M2M) traffic, i.e., communications between smart electronic devices that do not need human supervision, performance is far from satisfactory. This is mostly due to the overload condition created when a large number of M2M devices attempts random access using the fourstep handshake prescribed by the LTE standard. In this article, we describe an overlay network that allows M2M devices to access the network without going through the full handshake. We show that the overlay provides much improved performance for M2M traffic, especially when the transmission power of M2M devices is slightly increased to combat the overload condition, and is capable of supporting M2M traffic in device-todevice (D2D) communication mode.

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.

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.

One of the challenges of the mobile industry is to cope with the growth of mobile traffic demand expected for the next years, primarily driven by the increasing usage of mobile video services. Indeed, the existence of increasingly powerful terminals is encouraging the consumption of high-quality video content. Usually, video services are identified with linear Television (TV) and scheduled broadcast (point-to-multipoint (p-t-m)) distribution. However, the consumption of video content over mobile networks is different from traditional fixed TV because contents are mainly consumed on-demand with unicast point-to-point (p-t-p) connections. Then, the convergence of linear TV and on-demand content delivery represents a challenge that requires a combined broadcast/unicast transmission model. This dissertation addresses the use of broadcasting technologies for the provision of mobile multimedia services in Fourth Generation (4G) mobile broadband networks and beyond. Specifically, the dissertation focuses on the broadcast technology included in 4G Long Term Evolution (LTE) and LTE Advanced (LTE-A) networks, known as Enhanced Multicast Broadcast Multimedia Services (eMBMS). It analyses the benefits of the eMBMS physical layer aspects regarding Multimedia Broadcast Multicast Services over a Single Frequency Network (MBSFN) deployments and identifies the current limitations of eMBMS at physical layer by comparing with the broadcast technology of the other 4G mobile system, the Institute of Electrical and Electronics Engineers (IEEE) 802.16m standard. Those limitations are the use of a dedicated carrier and Multiple-Input Multiple-Output (MIMO) techniques for broadcast transmissions. Our investigations employ a complete simulation platform including link-level and system-level simulations to evaluate the performance of broadcast transmissions in these real technologies. The research on eMBMS services is aimed at finding the optimum delivery of streaming and file download services focusing on the Radio Resource Management (RRM) problem and trade-off between Physical layer ? Forward Error Correction (PHY-FEC) and Application Layer - Forward Error Correction (AL-FEC). Concerning streaming services, results show that the use of AL-FEC increases the coverage level and, then, the maximum service data rate. The gain due to AL-FEC is greater in scenarios with high mobility users, although, this gain is limited if low zapping times are desired. Regarding file delivery services, this dissertation analyses the duration of the transmission required to guarantee the correct file reception and the reduction in the mean throughput of unicast users with different delivery modes. They are the unicast delivery, the eMBMS delivery and a hybrid approach, which combines a first eMBMS delivery with a post-delivery error repair phase with unicast transmissions. Our results show that the hybrid delivery is the most efficient configuration in terms of file download time, although it further reduces unicast performance. On the other hand, as an exemplary use case, this dissertation also investigates the use of LTE networks for the provision of vehicular safety services comparing both unicast and eMBMS delivery modes. Results highlight the significant benefits in terms of resource usage, end-to-end latency and cost delivery saving that can be achieved by using eMBMS for the delivery of road safety applications. In addition, research also addresses the problem associated with the support of road safety applications over the current eMBMS architecture, the configuration of the Intelligent Transportation Systems (ITS) server in charge of distributing safety messages as well as on its interaction with the mobile network operator. Finally, this dissertation analyzes feasible options of convergence between mobile and broadcast industry to ensure the success of the mobile broadcasting deployments in the future. A separated evolution of the broadcast technologies of both industries would lead to a scenario with two complete different industries, with different network infrastructures and business models competing for market and spectrum. This dissertation proposes an approach by which the definition of the future Fifth Generation (5G) mobile broadband communication system could bring together the cellular and broadcast industries to form a single fixed and mobile converged network and offer a full alternative to terrestrial TV broadcasting as a universal service

In this paper we discuss about security which is the main element in the wireless communication. As the generation changes many steps are used to improve the security so in this we discuss many security techniques choose, implement and compare two of them which provide better security to customers in LTE Advanced. LTE Advanced is evolved and advanced version of LTE (Long Term Evolution) which is developed by 3GPP. We implement the security techniques which we can use in LTE Advanced. To secure our data we use security algorithms (KASUMI & TDES) which have two parts encryption and decryption. In encryption process we convert our original data in cipher text by using keys and then transmit this encrypted data to the receiver. And at the receiving end we decrypt the encrypted data with the same keys to recover the original data. KASUMI Algorithm is a block cipher that produces a 64-bit output from 64-bit input under the control of a 128-key and three functions. It has 8 rounds. TDES Algorithm is a block cipher that produces a 64-bit output from a 64-bit input under the control of three keys of 64-bits with a function. It has 16 rounds. We implement these techniques in Matlab for verifying our results, and then we conclude that both algorithms are efficient for security purposes, so that no one can crack our data.

C-RAN is the next-generation clean wireless access network architecture, which is based on centralized processing, the Collaborative Radio and Real-time Cloud Infrastructure. In C-RAN architecture, different access technology (eg.GSM / TD-SCDMA / WCDMA / LTE) can be support on the same hardware platform in baseband pool system; C-RAN can be applied to reduce the consumption of operators. LTE (Long Term Evolution) and LTE-A, which are based on OFDM and MIMO technologies, are regarded as the main wireless access technology in the evolution from 3G to 4G. LTE introduces variety of novel technologies to improve the system performance, especially in C-RAN architecture, such as Multi antennas MIMO, Carrier Aggregation, CoMP. However, C -RAN architecture also brings about lager data transmission in the optical fiber. In this paper a low-latency baseband signal compression algorithm used in ALU is introduced to reduce the data rate. Based on the Characteristics of LTE signal data, the algorithm removal redundancies in the spectral domain firstly, and then the block scaling, which is combined with non-linear (nonuniform) quantizer, is designed to minimize quantization error. This algorithm can effectively reduce the amount of data transferred between BBU and RUU in LTE system, to facilitate the deployment of LTE in the CRan architecture. Simulation analysis is given out in the paper; meanwhile TD-LTE system demo verification is also implemented. The results indicate that the scheme introduced can get good performance under a certain compression rate in the real system. Further research is also in progress.

One of the critical components of the Smart Grid (SG) is the Smart Meter (SM), which reports power consumption to a centralized control center at regular intervals. The Long Term Evolution (LTE) network has received much attention as a promising platform for SG communications due to its high bandwidth and low latency over a large coverage area. Nevertheless, when a huge number of SMs access the LTE network, the preamble collision becomes an issue. The negative effects of preamble collision are packet loss, delay, reestablishment attempts, and physical channel utilization, which degrade the performance of the LTE network. Hence, a Random Access (RA) mechanism is required for preamble signature to occupy Resource Blocks (RBs) for SMs. In this paper, we introduce a hybrid procedure that combines contention and non-contention based random access methods. The significance of this method is that, although SMs have fixed periodic communications, preamble signatures do not need to be reserved. The simulation results are compared with LTE standard. Packet loss is reduced by approximately 43%. SM latency is decreased by 11 ms at 90% of probability delay. Re-establishment attempts are lower than standard by proximately 76%. Finally, physical channel utilizations are reduced by around 3%.

High Altitude Platform Station (HAPS) system is one of the recent wireless technologies that exploit many promising advantages from satellite system as well as from terrestrial system. Long Term Evolution (LTE) is a 4G wireless broadband technology developed by Third Generation Partnership Project (3GPP), an industry trade group. 3GPP has been centered on enhancing LTE radio standards to improve the performance of wireless communications link, receive diversity has been proposed by the 3GPP within mode 1 of transmission in the LTE standard. In this paper, we focus on the HAPS-LTE downlink system performance evaluation with optimum receive spatial diversity and has channel side information known at the receiver (CSIR) for different scenarios. Simulation results show that, HAPS channel characteristics such as elevation angle, user mobility, and channel bandwidth greatly affect the performance of the proposed system. It is also shown that, maximal-ratio combining (MRC) diversity algorithm is able to improve the system performance in bad channel conditions.

In this paper, we investigate the feasibility of applying interference alignment (IA) technology to multi-cell coordinated beamforming (CB) in a future release of the Long Term Evolution (LTE) standard. Specifically, we establish a link level model for a two-cell system according to the current LTE- Advanced (LTE-A) specifications, and evaluate the performance of an IA based CB scheme. The link-level performance of the IA based CB scheme is compared to that of conventional coordination schemes to identify the potential gain. We establish different simulation configurations to identify the factors that restrict the practical deployment of the IA based CB scheme and the potential requirements for extra standardization support.

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 deployment of long term evolution (LTE) in the unlicensed spectrum (LTE-U) has been gaining significant industry momentum in recent months. The US 5-GHz Unlicensed National Information Infrastructure (UNII) bands that are currently under consideration for LTE deployment in the unlicensed spectrum contain only a limited number of 20 MHZ channels. Thus, in a dense multi-operator deployment scenario, one or more LTE-U small cells have to coexist and share the same 20 MHz unlicensed channel with each other and with the incumbent Wi-Fi. In this paper, we present the scenario and demonstrate that in the absence of an explicit interference mitigation mechanism, there will be a significant degradation in the overall LTE-U system performance for LTE-U cochannel coexistence in countries that do not mandate listen-before-talk (LBT) requirements. We then present the unlicensed spectrum intercell interference co-ordination (usICIC) mechanism as a time-domain multiplexing technique for interference mitigation for the sharing of an unlicensed channel by multioperator LTE-U small cells. Through extensive simulation results, we also demonstrate that our proposed usICIC mechanism will result in 40% or more improvement in overall LTE-U system performance.

Deployment of Long Term Evolution (LTE) on unlicensed bands has been discussed recently in the 3rd Generation Partnership Project (3GPP) Release 13, which is also called LTE Licensed-Assisted Access (LAA) to unlicensed bands. Due to the unlicensed feature, other systems such as Wi-Fi and radar would operate on these bands. In order to avoid the interference, some management mechanism needs to be considered. In this paper, we propose a novel approach in interference detection, introduce DFS in UE and make the implementation of DFS both in BS and UE. Furthermore, the performance of LAA is studied via a detailed system level simulate with 3GPP simulation parameters and test scenarios. The Simulation results show that DFS in BS can obtain the higher gain in throughput and latency.