Bora Kim

Cell Range Expansion and Time Partitioning for Enhanced Inter-cell Interference Coordination in Heterogeneous Network

In this paper, we propose a cell selection scheme and interference management scheme in Heterogeneous Network (HetNet). The cell selection scheme is based on the SINR, and the cell expansion range can vary through the offset value. We can manage the interference between the macro cell and Picocell, using ABS in the time domain. Also, a flexible ABS density is applied, to increase the spectrum efficiency. We show the simulation results of the selection scheme based on SINR with different offset values (6dB, 12dB) and the interference management scheme. Simulation results show that the proposed scheme can improve the user spectrum efficiency of the macro cell and Pico cell user. Eventually, the proposed scheme can improve overall user performance.

Novel MCS Based Relay Protocols for Throughput Optimization Using AMC in LTE-Advanced System

In this paper, we propose a throughput optimization scheme for relay protocols based on Adaptive Modulation and Coding (AMC). The performance of relay protocols with the AMC scheme and show that relay protocols with the AMC scheme are capable of providing better average throughput at a lower Signal to Noise Ratio (SNR) level as compared to the conventional scheme with no AMC. We perform 3GPP Long Term Evolution-Advanced (LTE-A) parameters based simulations to prove the performance comparison of adaptive Modulation and Coding Scheme (MCS) relay protocols with non-adaptive MCS relay protocols. The simulation results of the proposed system with adaptive MCS prove that among the Amplify-and-Forward (AF), Decode-and-Forward (DF) and De-Modulate-and-Forward (DMF), the DMF protocol performs best, at a lower SNR value and higher average throughput.

Interference Management with Cell Selection Using Cell Range Expansion and ABS in the Heterogeneous Network Based on LTE-Advanced

Long term evolution-advanced has developed the heterogeneous network (HetNet) that consists of a mix of macrocells and low-power nodes, such as picocells, to improve the system performance. Also, to encourage data offloading in HetNet, cell range expansion has been introduced. In this paper, we propose a cell selection scheme based on signal to interference plus noise ratio for optimal offloading effect. Also, we manage interference for the user located cell range expanded region using almost blank subframe (ABS) with flexible ABS ratio, to improve the spectrum efficiency in the time domain. Simulation results show that the proposed scheme can improve the spectrum efficiency of the macrocell and picocell user. Eventually, the proposed scheme can improve overall user performance.

Performance Analysis of Coordinated Multi-point with Scheduling and Precoding Schemes in the LTE-A System

To meet the requirements of users for quality of data services, techniques which can support a high data rate to users located within the cell edge as well as the cell center would be indispensible. Accordingly, the need for efficient methods to control the interference between transfer points is increasing. In current standards and academic issues the way of how to control the interference from point-to-point transmission naming coordinated multi-point (CoMP) was selected as the work items for 3rd Generation Partnership Project (3GPP) long term evolution-advanced (LTE-A) Release 11. This paper proposes a combined system of CoMP with Scheduling and Precoding, which solves the problem of conventional cellular system and improves the spectral efficiency of overall system. We design and analyze the performance of the Coordinated Beamforming technique, which is one major category of CoMP. The parameters are included in order to fulfill the requirements of the 3GPP LTE-A Standard. Finally, we make a performance analysis of the proposed system through the system level simulation in Homogeneous Network and Heterogeneous Network. We confirm the performance through a graph of the cumulative distribution function about signal to interference plus noise ratio.

Cell Selection and Resource Allocation for Interference Management in a Macro-Picocell Heterogeneous Network

A heterogeneous network (HetNet) based on the long-term evolution advanced standard has been developed to improve the system performance; in this HetNet, macrocells and low-power nodes, such as picocells, coexist. Further, cell range expansion has been introduced to encourage data offloading in a HetNet. In this paper, we propose a cell selection scheme based on the signal-to-interference-plus-noise ratio to achieve an optimal offloading effect. We also propose a resource allocation scheme in the frequency and time domains, to reduce interference in a HetNet. In the frequency domain, the macrocells allocate a frequency band by using soft frequency reuse, and the picocells choose the sub-bands that are not used in the macrocell sector, to avoid interference. In addition, we found that it was difficult to allocate a limited frequency resource. Therefore, the cross-tier interference can be managed by using an almost blank subframe (ABS) with a flexible ABS ratio, to improve spectrum efficiency in the time domain. The simulation results show that the proposed schemes can improve the spectrum efficiency of both the macro-user equipment and the pico-user equipment, as well as improve the overall UE performance.

Smart cooperative relay schemes in LTE-advanced system

Cooperative relaying is considered as the most cost-efficient method in 3GPP LTE-Advanced in terms of coverage prolongation and transmission efficiency. In this paper, we analyze the best performing cooperative relaying scheme between the Amplify-- and--Forward (AF) and Decode-and--Forward (DF) schemes for LTE-Advanced systems. The comparison between AF and DF Relay Nodes (RN) is important because both approaches are currently under consideration for 3GPP LTE-Advanced (LTE-A). The performance analysis of these two relay nodes considers the criteria of: (1) Linear equalization techniques such as Zero Forcing (ZF) and Minimum Mean Square Error (MMSE) and (2) Cooperative Diversity using 2x2 Multiple Input and Multiple Output (MIMO) Alamouti scheme also termed as Space Frequency and Block Coding. Simulation results show that the Bit Error Rate (BER) performance of AF RN and DF RN improves in LTE-Advanced system and that DF RN clearly outperforms AF RN.

Novel Hybrid Receiver for Interference Cancellation and Suppression in Sidehaul System

Recently, the 3rd Generation Partnership Project (3GPP) has developed a sidehaul system to cope with rapidly increasing mobile data traffic. Nevertheless, numerous challenging technical problems remain. One of the major problems is interference management between small cells. In this paper, we propose a novel hybrid receiver for full suspension cancellation to reduce the interference from neighboring cells in the sidehaul system. The proposed receiver can cancel and suppress interference by integrating the interference rejection combining technique with successive interference cancellation. We perform a simulation based on the 20-MHz bandwidth of the 3GPP LTE-Advanced technology. Simulation results show that the proposed receiver can achieve a lower error rate and a higher throughput compared to conventional receivers.

New Relay Protocols with AMC Scheme for Throughput Enhancement in LTE-Advanced System

Abstract We propose an adaptive modulation and coding (AMC) scheme using relay protocols AF, DF and DMF. The AMC scheme is used for improving the throughput and reliability of a communication system, using different modulation and coding schemes. We analyze the performance of relay protocols with the AMC scheme and observe that relay protocols with the AMC scheme are capable of providing better average throughput at a lower signal to noise ratio (SNR) level as compared to the conventional scheme with no AMC. We perform Monte Carlo simulations based on 3GPP long term evolution-advanced parameters to prove the performance comparison of adaptive modulation and coding scheme (MCS) relay protocols with non-adaptive MCS relay protocols. The simulation results of the proposed system with adaptive MCS prove that among the amplify-and-forward (AF), decode-and-forward (DF) and de-modulate-and-forward (DMF), the DMF protocol performs best, at a lower SNR value and higher average throughput.

Novel Detection Scheme for LSAS Using Power Allocation in Multi User Scenario with LTE-A and MMB Channels

Massive MIMO (also known as the “Large-Scale Antenna System”) enables a significant reduction of latency on the air interface with the use of a large excess of service-antennas over active terminals and time division duplex operation. For large-scale MIMO, several technical issues need to be addressed (e.g., pilot pattern design and low-antenna power transmission design) and theoretically addressed (e.g., channel estimation and power allocation schemes). In this paper, we analyze the ergodic spectral efficiency upper bound of a large-scale MIMO, and the key technologies including channel uplink detection. We also present new approaches for detection and power allocation. Assuming arbitrary antenna correlation and user distributions, we derive approximations of achievable rates with linear detection techniques, namely zero forcing, maximum ratio combining, minimum mean squared error (MMSE) and eigen-value decomposition power allocation (EVD-PA). While the approximations are tight in the large system limit with an infinitely large number of antennas and user terminals, they also match our simulations for realistic system dimensions. We further show that a simple EVD-PA detection scheme can achieve the same performance as MMSE with one order of magnitude fewer antennas in both uncorrelated and correlated fading channels. Our simulation results show that our proposal is a better detection scheme than the conventional scheme for LSAS. Also, we used two channel environment channels for further analysis of our algorithm: the Long Term Evolution Advanced channel and the Millimeter wave Mobile Broadband channel.

Design and Analysis of Novel Precoding Scheme for LSAS Using Power Allocation

Massive MIMO systems (also known as “large-scale antenna system” and “full-dimension MIMO”) significantly reduce air interface latency by using a large excess of service antennas over active terminals and time-division duplex operation. We consider the downlink of a time-division duplexing multicell multiuser MIMO system in which the base transceiver stations are equipped with a very large number of antennas. Assuming channel estimation through uplink pilots, arbitrary antenna correlations, and user distributions, we derive approximations of achievable rates with linear precoding techniques—namely, zero forcing, matched filtering, eigen-beamforming (EBF), and regularized zero-forcing (RZF). The approximations are tight in the large system limit with an infinitely large number of antennas and user terminals, but they match our simulations for realistic system dimensions. We further show that a simple EBF precoding scheme can achieve the same performance as RZF with one order of magnitude fewer antennas in both uncorrelated and correlated fading channels. Our simulation results show that our proposed precoding scheme is better than the conventional scheme. Moreover, we have used two channel environments for further analysis of our algorithm—long-term evolution advanced and millimeter wave mobile broadband channels.