In this paper, we propose a multi-carrier transmission scheme to overcome the problem of intercarrier interference (ICI) in orthogonal frequency division multiplexing (OFDM) systems. In the proposed scheme, called universal-filtered multi-carrier (UFMC), a filtering operation is applied to a group of consecutive subcarriers (e.g. a given allocation of a single user) in order to reduce out-of-band sidelobe levels and subsequently minimize the potential ICI between adjacent users in case of asynchronous transmissions. We consider a coordinated multi-point (CoMP) reception technique, where a number of base stations (BSs) send the received signals from user equipments (UEs) to a CoMP central unit (CCU) for joint detection and processing. We examine the impact of carrier frequency offset (CFO) on the performance of the proposed scheme and compare the results with the performance of cyclic prefix based orthogonal frequency division multiplexing (CP-OFDM) systems. We use computer experiments to illustrate the efficiency of the proposed multi-carrier scheme. The results indicate that the UFMC scheme outperforms the OFDM for both perfect and non-perfect frequency synchronization between the UEs and BSs.

http://www.ece.tufts.edu/ee/108/Reading7.pdf

Universal-filtered multi-carrier technique for wireless systems beyond LTE

This paper presents the latest progress on cloud RAN (C-RAN) in the areas of centralization and virtualization. A C-RAN system centralizes the baseband processing resources into a pool and virtualizes soft base-band units on demand. The major challenges for C-RAN including front-haul and virtualization are analyzed with potential solutions proposed. Extensive field trials verify the viability of various front-haul solutions, including common public radio interface compression, single fiber bidirection and wavelength-division multiplexing. In addition, C-RANs facilitation of coordinated multipoint (CoMP) implementation is demonstrated with 50%-100% uplink CoMP gain observed in field trials. Finally, a test bed is established based on general purpose platform with assisted accelerators. It is demonstrated that this test bed can support multi-RAT, i.e., Time-Division Duplexing Long Term Evolution, Frequency-Division Duplexing Long Term Evolution, and Global System for Mobile Communications efficiently and presents similar performance to traditional systems.

Recent Progress on C-RAN Centralization and Cloudification

Coordinated scheduling is an efficient resource allocation technique employed to improve the throughput, utilization, and energy efficiency of radio networks. This work focuses on the coordinated scheduling problem for cloud radio access network (CRAN). In particular, we consider the downlink of a CRAN where a central cloud performs the scheduling and synchronization of transmitting frames across the base stations (BSs). For each BS, the transmit frame is composed of several time/frequency slots called resource blocks (RBs). We formulate an optimization problem for joint users to BS association and resource allocation with an objective to maximize the overall network utilization under practical network constraints. The formulated problem is combinatorial and an optimal solution of such a problem can be obtained by performing an exhaustive search over all possible users-to-BSs assignments that satisfy the network constraints. However, the size of search space increases exponentially with the number of users, BSs, and RBs, thus making this approach prohibitive for networks of practical size. This work proposes an interference-aware greedy heuristic algorithm for the constrained coordinated scheduling problem. The complexity analysis of the proposed heuristic is also presented and performance is compared with the optimal exhaustive search algorithm. Simulation results are presented for various network scenarios which demonstrate that the proposed solution achieves performance comparable to the optimal exhaustive search algorithm.

Efficient Joint User Association and Resource Allocation for Cloud Radio Access Networks

The present invention relates to a wireless communication system, and more particularly, discloses a method and an apparatus for mode switching between a multi-cell coordinated communication mode and a single-cell MIMO communication mode. A method for dynamically switching a communication mode according to one embodiment of the present invention comprises: a step of generating and transmitting first feedback information in accordance with a first communication mode; a step of switching the first communication mode into a second communication mode interlocked with the first communication mode; and a step of generating and transmitting second feedback information in accordance with the second communication mode. The first communication mode is one of a multi-cell coordinated multi-point (CoMP) communication mode and a single-cell multi-input multi-output (MIMO) communication mode, and the second communication mode is the other of the multi-cell coordinated multi-point (CoMP) communication mode and the single-cell multi-input multi-output (MIMO) communication mode. The switching step can be performed without signaling from a base station.

Method and apparatus for mode switching between a multi-cell coordinated communication mode and a single-cell mimo communication mode

Long Term Evolution Advanced (LTE-Advanced) is the next step in LTE evolution and allows operators to improve network performance and service capabilities through smooth deployment of new techniques and technologies. LTE-Advanced uses some new features on top of the existing LTE standards to provide better user experience and higher throughputs. Some of the most significant features introduced in LTE-Advanced are carrier aggregation, enhancements in heterogeneous networks, coordinated multipoint transmission and reception, enhanced multiple input multiple output usage and deployment of relay nodes in the radio network. Mentioned features are mainly aimed to enhance the radio access part of the cellular networks. This survey article presents an overview of the key radio access features and functionalities of the LTE-Advanced radio access network, supported by the simulation results. We also provide a detailed review of the literature together with a very rich list of the references for each of the features. An LTE-Advanced roadmap and the latest updates and trends in LTE markets are also presented.

/pdf/lte-advanced-radio-access-enhancements-a-survey-18x62ryvaj.pdf

LTE-Advanced Radio Access Enhancements: A Survey

LTE-Advanced systems which based on orthogonal frequency division multiplexing (OFDM) can eliminate intra-cell interference but still can not mitigate inter-cell interference (ICI). Coordinated Multi-Point transmission/reception (CoMP) is one of the candidate techniques for LTE-Advanced systems to increase the average cell throughput and cell edge user throughput in the both uplink and downlink. Although CoMP naturally increases system complexity, it has potentially significant capacity and coverage benefits, making it worth a more detailed consideration. In this paper, we focus on the downlink CoMP-MU-MIMO transmission scheme and present some system level performance evaluation which shows that the CoMP-MU-MIMO transmission scheme can bring significant gains to both the average cell throughput and the cell edge user throughput.

Zhigang Yan

Papers

Coordinated Multiple Points Transmission for LTE-Advanced Systems