Downlink throughput enhancement of an OFDMA cellular system with closed-access indoor relays
We propose user-deployable closed-access indoor relays for throughput improvements in the downlink of LTE (long-term evolution) cellular system. The relays are assumed to be placed proximate to the destination user equipments (UEs). We propose a two-hop non-regenerative relaying scheme where the relay, equipped with multiple antennas, performs optimum combining to maximize the SINR (signal-to-interference-plus-noise ratio) before forwarding to a UE. The relaying is performed in a concurrent manner, where the base station (BS) transmits to some other receiver simultaneously when the relay is transmitting, and is therefore spectrally efficient. In order that the users served by a BS do not experience additional co-channel interference (CCI) because of the transmissions of the closed-access relays, we present an interference management scheme that can be implemented with minimal changes in the scheduling algorithm of a BS. Computer simulations, performed with large-scale deployment of indoor relays in the LTE framework, show that the UEs served by the relays see an improvement of over 100% in their respective throughputs, while the average cellular throughput improves by 24% when compared with a baseline system without relays. Also, the UEs served by the BSs do not experience any loss in their throughputs. © 2013 IEEE.
High Precision Positioning using Multi-cell Massive MIMO system for 5G and beyond
The large number of antennas at the base stations (BSs), the reference signal transmission over a wide bandwidth, and dense network deployment can be used to achieve unprecedented position accuracy in 5G and beyond networks. This work proposes a position estimation method using a full dimension massive multiple-input multiple-output (MaMIMO) system in cellular networks. The user equipment (UE) estimates the time of flight/arrival (ToA) from multiple BSs using estimation of signal parameters via rotational invariant technique (ESPRIT). A novel method that selects a subset of the accurate ToA measurements and uses it to estimate the position of the target UE based on multilateration is proposed. The simulation results demonstrate that there is a significant improvement in positioning accuracy over the conventional methods, and the proposed method closely matches the genie-aided algorithm for small subsets, and outperforms it for large subsets. The proposed method achieves 20 cm positioning accuracy for 90% of the UEs in indoor factory (InF) scenarios using practical 3GPP channel models. It also satisfies the ITU requirement for Industry 4.0 and requires a low transmission and measurement overhead.
Design and implementation of a Multi-Terminal Channel Emulator on LTE TestBed
The radio channel is a critical but independent element affecting a wireless communication system. It is highly time-varying and exhibits behaviors such as path loss, shadowing, multi-path fading and Doppler spread. In this paper, we discuss the design and implementation of a real-time Multi-Terminal Channel Emulator on an SDR (Software Defined Radio) platform for providing controlled variability of channel conditions to test wireless systems. The system design is split into three functions: (i) Channel generation on a PC (ii) Ethernet handling on a DSP (Digital Signal Processor), to receive the channel coefficients and update filters on an FPGA (Field Programmable Gate Array) and (iii) Application of the channel to the data on the FPGA (convolution). We propose a simple technique, where the unit can be used to emulate multiple user scenarios by just modifying the channel generation on the PC. This enables a single hardware unit to emulate multiple users with independent channels.
Deploying IP multimedia subsystem (IMS) services over next generation networks (NGNs): The IU-ATC integrated test bed
The IP Multimedia Subsystem (IMS) is the Third Generation Partnership Project's (3GPP) standardized service platform that enables the deployment of rich and personalized services over fixed and mobile networks whilst allowing end-users ubiquitous access to services such as voice, video, presence and online gaming anytime and anywhere. However, the delivery of these services to the end-users is highly dependent on the available or preferred access network which could range from fixed broadband access to mobile 4G connections. Although the IMS was initially developed as the core network for Third Generation (3G) systems, it has now been adopted as the service platform for the Long Term Evolution (LTE) and System Architecture Evolution (SAE). As this transition of 3G to 4G and beyond evolves, there is an immediate need for a research testbed that facilitates the research, development and early trials of the integration of these technologies. This has motivated us to integrate the IMS based Advanced Next Generation Network (ANGN) testbed at the University of Surrey (UniS), U.K. with the 4G Access Network Testbed at IIT Madras, India via an academic transnational network link to form a fully functional telecommunications mobile network. In this paper, we discuss the rationales, motivations and objectives behind the integrated testbed whilst also investigating how it can be extended to support 4G and future technologies such as LTE/SAE and WiMAX. The testbed as a whole plays a key as role in the future of IMS development as it provides a fully functional platform similar to commercial networks for researchers to investigate and demonstrate the feasibility of their proposal in a realistic environment. © Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2011.