Ho Young Hwang

Enhanced Markov Chain Model and Throughput Analysis of the Slotted CSMA/CA for IEEE 802.15.4 Under Unsaturated Traffic Conditions

In this paper, we propose an analytical Markov chain model of the slotted carrier-sense multiple-access/collision-avoidance (CSMA/CA) protocol for IEEE 802.15.4 under unsaturated traffic conditions. Our proposed Markov chain model reflects the characteristics of the IEEE 802.15.4 medium-access control (MAC) protocol, such as a superframe structure, acknowledgements, and retransmissions with and without limit. We evaluate the throughput performance of the slotted CSMA/CA and verify the analytical model using simulation results.

Effect of Frame Aggregation on the Throughput Performance of IEEE 802.11n

The IEEE 802.11n standard aims at providing a data transmission rate of up to 600 Mbps. The frame aggregation techniques of IEEE 802.11n MAC layer play an important role in the enhancement of channel utilization. In this paper, we investigate the effect of IEEE 802.11n frame aggregation for two aggregation mechanisms: MAC protocol data unit aggregation (A-MPDU) and MAC service data unit aggregation (A-MSDU). We propose an analytical model based on an enhanced discrete time Markov chain (DTMC) model in order to describe the post- backoff behavior due to frame aggregation, and then evaluate the throughput performance. Analytical results based on the mathematical model are verified through simulation. The throughput performance of the A-MSDU mechanism outperforms the A-MPDU mechanism as the frame aggregation size becomes larger under an error-free environment. In addition, the throughput performance is significantly improved as the frame aggregation size increases.

Analysis of throughput in a ZigBee network under the presence of WLAN interference

In this paper, we analyze the operation of ZigBee devices under the presence of WLAN interference and formulate a mathematical model for evaluating the performance of ZigBee devices. Our proposed mathematical model for ZigBee devices is based on a Markov chain concept. We here utilize the fact that the transmission power of WLAN devices is set hundred to thousand times higher than that of ZigBee devices. Thus, we assume WLAN devices interfere with ZigBee devices, but the ZigBee devices do not. The throughput of a ZigBee network is derived for varying the input load of WLAN interference. The result shows that analytical results obtained from the mathematical model agree well with simulation results.

Performance Analysis of IEEE 802.11e EDCA With a Virtual Collision Handler

This paper presents an analytical model of IEEE 802.11e enhanced distributed channel access (EDCA) with a virtual collision handler (VCH). The proposed analytical model provides different access categories (ACs) for supporting the quality of service (QoS) of differentiated services by using different contention window (CW) sizes and arbitration interframe space (AIFS) values in EDCA. The proposed model considers a network of stations, each of which has multiple queues and a VCH for different ACs. Based on the proposed model, we analyze the throughput and delay performance of the EDCA with four different ACs and investigate the effect of the VCH by considering two VCH schemes. The analytical and simulation results show that the proposed analytical model is very accurate for various CW sizes and AIFS values.

Analysis of a mobility management scheme considering battery power conservation in IP-based mobile networks

Mobile hosts (MHs) in all IP-based mobile networks must update their current location to receive incoming packets. The MHs are idle for most of time. Both registration of approximate location information and paging can facilitate efficient power management for the idle MHs. Furthermore, the MHs can be in switch-off state for battery power conservation. Mobile IP, the current standard for IP-based mobility management, needs to be enhanced for use in all IP-based mobile networks. Mobility management in all IP-based mobile networks should consider idle and detached MH states as well as active MH state. A mobility management scheme for all IP-based mobile networks is introduced in this paper. This scheme includes management of communicating, attentive, idle, and detached states. We model MH behavior in the networks when the binding-lifetime-based registrations are utilized as a means of identifying that an MH is switched off. The steady-state probabilities for MH state transitions are derived, and an optimal rate of binding-lifetime-based registrations that results in minimum network cost is derived.

Analysis of Throughput and Energy Consumption in a ZigBee Network Under the Presence of Bluetooth Interference

In this paper, we analyze the operation of ZigBee devices under the presence of Bluetooth interference and formulate a mathematical model for evaluating the performance of ZigBee devices. Our proposed mathematical model for ZigBee devices is based on a Markov chain concept. We here consider Bluetooth devices which adopt class 1 or class 2 Bluetooth chips as an interference source and the transmission power of Bluetooth devices is set several to hundred times higher than that of ZigBee devices. Thus, we assume Bluetooth devices interfere with ZigBee devices, but the ZigBee devices do not. The throughput and energy consumption of ZigBee devices in a ZigBee network are derived for varying the number of actively interfering Bluetooth devices. The result shows that analytical results obtained from the mathematical model agree well with simulation results.

Goodput analysis of a WLAN with hidden nodes under a non-saturated condition

Hidden nodes may severely degrade the performance of wireless LANs. Focusing on the hidden node effect, we analyze goodput in a single cell WLAN environment with hidden nodes under a non-saturated condition. Uplink and downlink goodputs are analytically derived using an approximation technique and are compared with simulation results.

Saturation Performance Analysis of IEEE 802.11 WLAN under the Assumption of No Consecutive Transmissions

To analyze the saturation performance of IEEE 802.11 DCF, several discrete-time Markov chain models for a station and sets of channel equations have been introduced. We take into account a frame retry limit, freezing of backoff counter, and the dependence of backoff procedure on the previous channel status all together. Our method is simple even though it is accurate under the assumption of no consecutive transmissions over the shared channel.

A mobility management scheme for reducing power consumption in IP-based wireless networks

For data communication services gradually dominating in future wireless networks, one crucial problem is to save battery power of data terminals usually requiring much power. A mobility management scheme in IP-based wireless networks is proposed to reduce battery power consumption of mobile hosts. The proposed scheme manages six states: communicating, attention/cell-connected, attention/PA-connected, idle, off/attached, and detached states for efficient management of battery power, radio resources, and network load. Steady state probabilities for mobile host (MH) state transitions are derived using a semi-Markov process approach, and the power-saving effect of the proposed scheme is analyzed. The effects of various input parameters on the steady state probabilities and power consumption are also investigated. The proposed mobility management scheme yields significant power saving in comparison with the current mobility management schemes for Mobile IP-based wireless networks.

Performance comparison of ATM and IP based transmission schemes in the UTRAN

Mobile communication networks can provide various types of services, such as voice, data, video, and multimedia as they evolve toward 3G networks. To increase the efficiency of limited resources in the UTRAN Iub interface, AAL2/ATM link transmission schemes with multiplexing have been introduced. As an all-IP based network technology develops, the AAL2/ATM link transmission schemes will be replaced by IP based link transmission schemes in future to reduce large protocol overheads. Accordingly, CIP, LIPE and PPPmux have been proposed in 3GPP standards. In this paper, we describe a link transmission model in the UTRAN Iub interface and evaluate the performance of ATM based and IP based link transmission schemes in terms of link efficiency and average link transmission delay. Simulation results show that the IP based transmission schemes perform better than the ATM based transmission scheme as the number of users increases.