Femtocell Networks: A Survey

The surest way to increase the system capacity of a wireless link is by getting the transmitter and receiver closer to each other, which creates the dual benefits of higher quality links and more spatial reuse. In a network with nomadic users, this inevitably involves deploying more infrastructure, typically in the form of microcells, hotspots, distributed antennas, or relays. A less expensive alternative is the recent concept of femtocells, also called home base-stations, which are data access points installed by home users get better indoor voice and data coverage. In this article, we overview the technical and business arguments for femtocells, and describe the state-of-the-art on each front. We also describe the technical challenges facing femtocell networks, and give some preliminary ideas for how to overcome them.Comment: IEEE Communications Magazine, vol. 46, no.9, pp. 59-67, Sept. 200

LTE performance study

Long Term Evolution (LTE) has been designed with new architecture and features to meet user’s high data rates demand for a longer term in the future. 3rd Generation Part-nership Project (3GPP) has set the goals and targets for LTE with better performance and data rates close to fixed networks. In this thesis outdoor measurements have been conducted in three different environ-ments macro/rural, urban and suburban. This thesis study has been done with single user measurements and performance analysis scenario. The idea of measurements was to analyze LTE performance in three different types of environments. Performance analysis has been done using few key performance indicators and parameters including RSRP, RS SNR, MAC downlink throughput, timing advance and CQI. Vendor/operator specific key performance indicators and parameters were unknown. The results and analysis of this thesis give an idea about LTE performance in three dif-ferent outdoor environments. The output of this thesis study can be beneficial in under-standing LTE behavior and performance in different environments, which can be further useful in planning and deployment phases for LTE

Adaptive MIMO transmission for exploiting the capacity of spatially correlated channels

We consider a novel low-complexity adaptive multiple-input multiple-output (MIMO) transmission technique. The approach is based on switching between low-complexity transmission schemes, including statistical beamforming, double space-time transmit diversity, and spatial multiplexing, depending on the changing channel statistics, as a practical means of approaching the spatially correlated MIMO channel capacity. We first derive new ergodic capacity expressions for each MIMO transmission scheme in spatially correlated channels. Based on these results, we demonstrate that adaptive switching between MIMO schemes yields significant capacity gains over fixed transmission schemes. We also derive accurate analytical approximations for the optimal signal-to-noise-ratio switching thresholds, which correspond to the crossing-points of the capacity curves. These thresholds are shown to vary, depending on the spatial correlation, and are used to identify key switching parameters. Finally, we propose a practical switching algorithm that is shown to yield significant spectral efficiency improvements over nonadaptive schemes for typical channel scenarios. © 2007 IEEE