Chil-youl Yang

Multi-connectivity strategy for agile service delivery with low power discovery

To deliver services using wireless connectivity on mobile devices, service discovery with low power and service execution with fast connection are the essential factors. However, no single connectivity technology satisfies fast service execution with low power discovery because agile service delivery fundamentally requires consuming high power. Therefore, we propose a synergetic multi-connectivity strategy utilizing Bluetooth Low Energy (BLE) discovery and Wi-Fi Peer to Peer (P2P) fast connection for agile service delivery. Furthermore, we develop an adaptive BLE discovery algorithm to enhance the discovery performance. Finally, the experiment of the multi-connectivity scheme and the theoretical simulation of the discovery algorithm show that the proposed approach excellently provides the fast service delivery with low power discovery.

Enhanced polling scheme with IEEE 802.11a WLAN

Although the distributed coordination function is the fundamental access protocol of IEEE 802.11, it cannot guarantee quality of service requirements in general. In fact, the point coordination function is aimed to support QoS related services by using polling schemes. However, it has an inherent problem. In this paper, we introduce an enhanced polling scheme to overcome the problem. We compare the enhanced polling scheme with three popular polling schemes, non-preemptive, round-robin and first-in-first-out under various channel situations including error prone environments.

A cognitive link adaptation strategy with differentiated responses on Wi-Fi System-on-Chip

The dynamic change of wireless channel condition causes poor Wi-Fi quality of service. To cope with the channel variation of wireless communication, the essential strategy for the physical layer with multi-rate capability is the link adaptation. However, because definite guidelines for rate changes do not exist, most link adaptation algorithms can misleadingly increase transmission rates. Therefore, we propose a cognitive link adaptation scheme, sensing link adaptation urgency and responding with differentiated rate control such as the long-term rate adaptation with a short-term rate drop. To evaluate the proposed scheme, we implement the link adaptation scheme on Wi-Fi System-on-Chip, applying the optimal HW/SW partitioning technique to reduce the SW processing delay from heavy operating calculation for the algorithm. The experiment shows that the proposed algorithm increases the packet arrival rate in a real Wi-Fi environment by reducing transmission failure due to wrong rate changes.

An 18ms-latency wireless high quality codec SoC for full HD streaming

An SoC integrating both an IEEE 802.11n Wireless LAN (WLAN) and a high quality codec is implemented using 90nm CMOS technology for wireless connectivity between full HD video-supporting devices. The WLAN operates with up to 270-Mbps data rates using 2×3 MIMO technologies and the codec supports up to 1080P 60Hz resolution with 30-bit RGB color format. The system achieves total 18ms latency, which enables this SoC to be used in gaming consoles and PCs as well as full-HD digital TVs with 1.5W power consumption.

Performance analysis of polling schemes with IEEE 802.11a WLAN

IEEE 802.11 MAC consists of the distributed coordination function, the point coordination function and their coexistence. The DCF provides contention services and the PCF provides contention-free services. Although DCF is the fundamental access protocol of IEEE 802.11, it can not support various classes of traffic while guaranteeing quality of service requirements in general. In fact, the point coordination function is aimed to support QoS related services by using polling schemes. However, it has an inherent problem. The point coordinator has no mechanism to know the queue status of the station buffer and this may cause a lot of troubles. We introduce an enhanced polling scheme to overcome the problem. We compare the enhanced polling scheme with three popular polling schemes, non-preemptive, round-robin and first-in-first-out under various channel situations including error prone environments.