HOME > Research > Wireless Networks Lab
Research Area
IEEE 802.11 Wireless LANs
Cognitive Radio
Software Define Radio
Next Generation Cellular Networks
M2M/D2D Communications
Research Topic
Mobility Management
Cognitive Radio Techniques
Ad Hoc Networks, Multi-Hop Networks
Next Generation Cellular Networks (LTE-Advanced, Mobile WiMAX)
QoS (Quality of Service)
1. IEEE 802.11 Wireless LANs
  • When a mobile station moves from one AP to another, it performs scanning, authentication and re-association after its channel is switched. However, the process called handoff is too long to provide seamless services. We research infra-supported networks based on IEEE 802.11 Wireless LANs for seamless mobility without imposing any requirements on the mobile station side.

  • IEEE 802.11 Wireless LANs have trouble in controlling traffic loads between uplink and downlink. The unfair environment can cause serious problems such as throughput inefficiency, delay increase, and so on. Moreover, IEEE 802.11 standards recommend hybrid coordination function (HCF) mode that includes enhanced distributed channel access (EDCA) and HCF controlled channel access (HCCA) to support QoS requirement. However, HCCA unfortunately have not been widely implemented in currently available stations. We investigate how to improve the limitations mentioned above (throughput degradation, unfairness problem, and QoS).
2. Cognitive Radio (CR)
  • Available channel in TV white space vary over time and space.

  • White space wireless devices must not interfere with incumbents, including TV broadcasts and wireless microphone transmissions.

  • To provide seamless communications in White Space Networking, the networks are required to provide two different handoff types.
        - Channel handoff due to appearance of primary users
        - Inter-AP handoff due to user mobility
3. Software-Defined Radio (SDR)
  • The goal of SDR is to realize a multimode and multiband terminal that can be reconfigured to support various communication protocols.

  • SDR devices can be reconfigured adaptively according to the network situations or the service requirements.

  • What is a novel scheme that can improve network performance through adaptive reconfiguration?