Hyu-Dae Kim

Enhanced power-saving mechanism for broadcast and multicast service in WLAN

When a WLAN station has low battery-power, a normal power-saving mechanism is not desirable and sparse wake-up should be used. In that case, the station cannot remain awake throughout every delivery-traffic-indication-message (DTIM) interval, which results in the loss of broadcast and multicast packets. In this letter, we propose a double-buffering power-saving mechanism for stations with low battery power. Broadcast and multicast packets can be delivered to stations with low battery power more reliably with the new scheme.

A prioritized random access with discriminative power ramping step size

Power ramping makes the access more likely to succeed in a contention, so power ramping can be modified to support multi-class services in a random access channel. In this paper, we introduce discriminative router ramping into a slotted-ALOHA channel and 3GPP (Third Generation Partnership Project) common packet channel. The proposed scheme serves the high-priority service more rapidly and more efficiently with few defects in both channels.

Extended-rtPS+ considering characteristics of VoIP codecs in Mobile WiMAX

We review previous resource allocation algorithms for voice over IP (VoIP) services in Mobile WiMAX based on the IEEE 802.16e-2005 standard, and propose a new algorithm that allocates radio resources in the consideration of packet-size and packet-generation period variations of wireless VoIP codecs; hence, we can improve the efficiency of resource utilization in Mobile WiMAX. Through simulations, we demonstrate the outstanding performance of our proposed algorithm with respect to packet dropping probability and VoIP capacity for various VoIP codecs, such as adaptive multi-rate wideband (AMR-WB) codec, enhanced variable rate codec (EVRC), and G.729B codec. In addition, we compare VoIP capacity of each algorithm according to the application of VoIP header compression schemes, such as payload header suppression (PHS) and robust header compression (ROHC).

A New Power-Saving mechanism for WLAN Broadcast/Multicast services

When a WLAN station has low battery-power, a normal power-saving mechanism is not desirable and sparse wake-up should be used. In that case, the station cannot remain awake throughout every delivery-traffic-indication-message (DTIM) interval, which results in the loss of broadcast and multicast packets. In this paper, we propose a double-buffering power-saving mechanism for stations with low battery power. Broadcast and multicast packets can be delivered to stations with low battery power more reliably with the new scheme

Detector SherLOCK: Enhancing TRW with Bloom filters under memory and performance constraints

Computer worms and bots are significant threats to large networks because they can spread very rapidly and are used for DDoS. The first phase of worms and bots begins by scanning vulnerable hosts. Missing on-going scanning activity can significantly deteriorate network performance. We propose a new scanning detection scheme, SherLOCK, based on the connection attempt success ratio. The proposed scheme can detect scanners with guaranteed false positive and false negative probabilities and with a limited memory size. Detection of scanners at high-speed links requires a high-speed memory and such memory devices are expensive and limited in size. We reduce the memory requirement by applying the Bloom filter. We show how slow scanners can be detected with a guaranteed performance for a given offered traffic load and memory size. This study can help to design the system that satisfies the target performance requirement. The detection performance is guaranteed under the assumption that malicious scanners and benign hosts have distinct behaviors in terms of the connection success ratio. We extend the proposed detector with a sampling mechanism to detect more intelligent scanners with guaranteed performance. These include scanners that use a list of pre-acquired IP addresses. We evaluate the performance of the proposed scheme through experiment using well-known traffic traces.

An efficient power-saving protocol for internet traffic in wireless LANs

The main factor of wireless systems, such as Wire- less LAN, is battery-powered terminal, so energy-efficient MAC protocol should be used. The IEEE 802.11 standard adopts Power-saving mechanism in MAC protocol and two kinds of power-conserving mechanism that conform to the standard can be implemented, each of which has advantages and disad- vantages. We analyze the two schemes and propose a hybrid mechanism that is suitable for the current Internet environment. The proposed mechanism reflects the strong points of both schemes. Simulations are done in the heavy and light traffic environments.

A new CPCH access scheme for priority service

CPCH (common packet channel) is an uplink common channel made by 3GPP to support rather a reliable packet transport. In this paper, we propose a new access scheme to provide a prioritized service. Discrimination of the backoff timer is applied and the channel characteristic is described. We also present a simple system model of CPCH for EPA and use it to get a mathematical result. The results show that the multi-class service with different priorities can be, effectively and easily, served by the proposed scheme.

Throughput Enhancement through Arranged Power-saving Mechanism in Wireless LAN

Current PS mechanisms in the IEEE 802.11 infrastructure mode cause reductions in system throughput because additional PS control packets induce more collisions. In this paper, we propose a new PS mechanism that offsets the defect of general PS schemes. The proposed scheme, which we call an arranged PS scheme, reduces the transmissions of redundant control packets and takes a load off the system. The analysis and simulation results show that with the arranged PS scheme, the number of collisions are greatly reduced and system throughput is enhanced in comparison with normal PS scheme without any degradation of power efficiency.

Overhearing based relaying scheme in wireless sensor networks with mobile access points

In sensor networks with mobile access points (MAs), distant sensor nodes cannot communicate directly with the MA when it is path-constrained and sensor area is very wide. For these nodes, we propose a relaying operation based on overhearing, which is very simple and compatible with the conventional operation of MAs. The simulation results show that it enhances coverage and energy efficiency.