Pingping Zong

Medium access design for LTE in unlicensed band

In this paper, a medium access protocol suitably adapted for the operation of Long term evolution (LTE) in unlicensed band (LTE-U) is proposed. The MAC design considers the impact of LTE-U on the devices operating in unlicensed band, such as WiFi and legacy LTE. The LTE-U design differences from the legacy LTE system, an inherently a synchronized, tightly controlled system are explored. The performance of LTE-U is studied via a detailed system level simulator implementation and 3GPP simulation test scenarios. We show that our proposed MAC design enables high throughput in unlicensed band and achieves co-existence with the incumbent systems. Moreover, the use of channel reservation mechanisms is shown to improve LTE-U cell edge performance.

Performance analysis of LTE and Wi-Fi in unlicensed band using stochastic geometry

In this paper, the multi-channel performance of large scale deployment of Long Term Evolution (LTE) in Unlicensed (LTE-U) band and WiFi using stochastic geometry is studied. LTE-U and WiFi cell placement is modeled as a Poisson Point Process (PPP), while transmission activity is modeled as hardcore simple sequential inhibition (SSI) point processes, which have been shown to accurately model Carrier sense multiple access (CSMA) access. This stochastic geometry based framework is used to analyze the co-existence of LTE-U and WiFi systems operating in the same set of available channels in unlicensed band. Several interesting results are derived. First, it is shown that fair coexistence can be achieved by LTE-U implementing a Listen-Before-Talk (LBT) protocol. Different variations of LBT are explored to improve the co-existence. Secondly, it is shown that the classical hidden node problem can severely affect performance, and that channel selection mechanisms can significantly alleviate the problem.

On the throughput analysis of LTE and WiFi in unlicensed band

In this paper, the co-channel performance of large scale deployment of LTE in Unlicensed (LTE-U) band and WiFi is studied using stochastic geometry. Analytical expressions of LTE-U throughput in presence of WiFi are presented and are partly validated by the simulation results. The LTE-U Low Power Nodes (LPNs) are deployed as Poisson Point Process (PPP), and, the WiFi transmissions are modeled as hardcore Matérn point process. Using this analytical approach the impact of various parameters such as sensing threshold and transmission power on the co-existence of LTE-U and WiFi is studied.

Channel Selection for Licensed Assisted Access in LTE Based on UE Measurements

Licensed Assisted Access (LAA) represents a new paradigm for LTE, where unlicensed bands are used in conjunction with licensed bands to increase network capacity. The main challenge of LAA is ensuring that unlicensed bands are shared with WiFi systems in an efficient manner. In this paper, we study a coexistence solution based on channel selection. A centralized channel selection mechanism which increases network capacity of LTE in unlicensed bands is proposed. We also describe the implementation of our scheme using existing LTE signaling mechanisms. Simulation results show that channel selection can improve the performance of both LTE and WiFi by over 100\%.

Cell detection in high frequency band small cell networks

In this paper, we investigate cell detection schemes for a new high frequency band (HFB) radio access technology (RAT) based small cell network, which employs much wider channel bandwidth (e.g. 100MHz~2 GHz) than current LTE- Advanced systems, in order to provide Gbps-level throughput. Cell detection performances are compared in terms of expected coverage and detection overhead/latency at 28GHz channels. Furthermore, a novel UE polling based cell detection method, which exploits a higher beamforming gain and processing power at a base station, is proposed to guarantee robust coverage and fast cell detection in HFB small cell networks.

Algorithm design and analysis for network coding in D2D underlay communications

Device to Device (D2D) communications are an important part of next generation wireless systems, and a key technology to improve local services and overall system throughput. This paper proposes Optimized Network Coding (ONC) to boost the performance of D2D communications. ONC leverages on using network coding combined with improved scheduling to increase the throughput of D2D links. We describe the proposed ONC approach and verify its performance through extensive system level simulations. We show that ONC-based use of dynamic relay selection and a flow-based proportional fair scheduling significantly improves the system-wide D2D performance.