Research

As a member of Antennas & Electromagnetics Research Group and Centre for Intelligent Sensing. My research activity addresses the design, analysis, optimisation and performance evaluation of smart antennas and signal processing techniques:

  • Smart antennas from UHF to millimetre-wave for various applications, e.g. 4G/5G, WiFi, MIMO, massive MIMO, base stations, satellite, RFID, sensors, cognitive radio and white space devices. .
  • Signal processing algorithms for M2M/IoT and 5G wireless networks, e.g. geo-location TV white space database model, compressed sensing, matrix theory, sparse FFT, multicoset sampling theories, etc.
  • System integration and field measurements for M2M/IoT and 5G wireless networks, e.g. software defined radio, TV whites space field trail under Ofcom framework, low power long range M2M testbed.

antenna designs

Queen Mary’s Antenna & Electromagnetics Group, is a world-leading multidisciplinary research group in the field of Antennas and Propagation; Applied Physics; and Metamaterials. Over the past years, I have developped a number of antennas for various applications. For example, the left figure below is a novel design of a circular polarized antenna for multiband L-bands compact receivers. The design employs the concept of multistacked patches fed through a single coaxial probe. The details can be found in our paper [PDF]. Further to this work, an enhanced design with multiple bands was licensed to SSBV Space & Ground Systems Ltd (click for the details). The figure on the right is a dual-element planar inverted-F antenna (PIFA) operating in 2.5 GHz band on a printed circuit board (PCB) of a size of 40mm by 100mm MIMO handset. My paper about this work has been cited for more than 50 times according to Google scholar [PDF].

Dual port diversity antenna for femtocell base stations
The prototype and radiation pattern of a dual-port pattern diversity antenna for femtocell (small cell) applications is shown in the figure below. Both ports of the antenna covers cover GSM1800, UMTS, and WLAN frequency bands. The channel capacities of the proposed antennas and two ideal dipoles with different mutual coupling levels are investigated in an indoor environment. The relation between mutual coupling and channel capacity are observed through investigations of these antennas.

gpsandmimoatennas.png

Spectrum sensing and cognition algorithms

Live spectrum monitoring at Mile End Campus of Queen Mary University of London. For more recorded data for specturm sensing reserach work, please feel free to contact Yue Gao (yue.gao@qmul.ac.uk).

Spectrum sensing & cognition is one of the most challenging tasks in cognitive radio systems as it requires precise accuracy and low complexity. My research is focused on welch's, wavelet, geo-location database TV white space and compressed sensing algorithms for single and multi-nodes which can be applied to wireless sensor and cellular networks. The figures below shows that our optimal threshold setting in Welch's algorithm for sensing OFDM signals can be reached as low as -17dB. A lower error decision probability was obtained for proposed algorithm compared to conventional fixed threshold at SNR ranging from -20dB to -10dB with a balanced point at -15dB. The lowest spectrum efficiency for both primary users and secondary users was obtained when primary users’ spectrum utilization is 50%.

gpsandmimoatennas.png
Cognitive network and cooperative communications are two promising techniques for efficient utilization of scarce radio resources and guaranteeing quality of services (QoS) in wireless heterogeneous networks (HetNet). The following figures present the architecture for the integration of cognitive networks and cooperative communications in wireless HetNet. Under the condition of imperfect channel state information (CSI) estimations of interference links between primary and secondary systems, especially the links from both secondary transmitter and secondary relays to primary users, the exact outage probability has been derived over Rayleigh fading channels and verified through simulations.

Dual port diversity antenna for femtocell base stations

small cell and interference mitigation

Small cells, such as femtocell, have been regarded as the most promising approach to deploying LTE networks by operators. A LTE femtocell station is referred to as the Home eNode B (HeNB). It is an effective approach to improving the indoor coverage and cell capacity. The major challenge in current femtocell deployment is the cross-tier interference between macrocell users and nearby HeNBs. We proposed system architecture of using TV White Space (TVWS) and sequential power allocation algorithms in LTE femtocell networks to mitigate the co-tier and cross-tier interferences, respectively. A Geo-location database model was also developed. Simulation results show that our scheme has achieved better downlink interference mitigation performance in comparison with existing schemes.

Dual port diversity antenna for femtocell base stations