Chang Yong Jung

Interference mediation for coexistence of WLAN and ZigBee networks

In emerging ubiquitous wireless environments, mobile devices can have multiple communication modules such as WLAN and ZigBee. Since IEEE802.15.4 ZigBee devices and IEEE802.11b WLAN devices share the same 2.4 GHz ISM band, a ZigBee network operating in a low power environment can be severely interfered by overlapped WLAN networks with much larger bandwidth due to higher transmission power. To overcome this inter-system interference problem and guarantee the ZigBee communications, we propose an interference mediation scheme in an overlaid network environment of WLAN and ZigBee devices by using an interference mediator, and evaluate the performance of ZigBee and WLAN networks for three different resource allocation schemes in terms of throughput and channel occupancy time.

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.

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.

Orthogonal Time Hopping Multiple Access for UWB Impulse Radio Communications

Recently, UWB technologies have been introduced for low rate wireless personal area networks (LR-WPANs). Since the energy level of the UWB impulse radio signals is very low, it is very hard to apply them to a carrier sensing multiple access with collision avoidance (CSMA/CA) scheme, which was adopted as the MAC protocol in IEEE 802.15.4 standard. In this paper, we propose an orthogonal time hopping multiple access (OTHMA) as a multiple access scheme for UWB impulse radio communications, and compare the MAC performance of the proposed scheme with that of CSMA/CA in terms of throughput, success probability, average delay, and user utilization. Simulation results show that the proposed scheme performs better than CSMA/CA as the number of users increases. Therefore, OTHMA can be applied as a multiple access scheme for low power, large scale, and low activity networks in UWB impulse radio communications

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.

1/spl times/EV-DO system-level simulator based on measured link-level data

1/spl times/EV-DO systems are being deployed widely for high speed wireless data communications. A 1/spl times/EV-DO system-level simulator is developed to evaluate the forward link capacity in an environment of multi-cell, multi-user, and mixed traffic of HTTP, FTP, NRV, and WAP, using measured link-level data, such as data rate transition thresholds and FER from HPEOS (high rate packet data performance evaluation and optimization system for cdma2000 1/spl times/EV-DO). The performance of the 1/spl times/EV-DO system is evaluated in terms of utilization, service throughput, over-the-air (OTA) throughput, and packet delay for four different traffic types, by using the system-level simulator.

QoS-Based AAL2/ATM multiplexing schemes in the UTRAN lub interface

Recently, mobile communication systems have supported various services including voice, data, video, and multimedia services as they evolve toward 3G. An AAL2 multiplexing scheme is introduced for transmission link efficiency in the UTRAN (UMTS terrestrial radio access network). However, limited radio resources and various quality of services (QoS) make it difficult to guarantee QoS requirements at radio access networks. The conventional AAL2/ATM multiplexing systems focused on link efficiency in multiplexing real-time voice and nonreal-time data traffic. In this paper, we classify various services into four classes according to QoS requirements and propose AAL2/ATM multiplexing schemes using statistical multiplexing and scheduling to guarantee the given requirements. Simulation results show that the proposed schemes perform better than the conventional schemes in guaranteeing QoS requirements of various services.

Capacity Analysis of a TH-PPM UWB System using a Near-Interference Erasure Scheme in Multi-User Environments

In this paper, the capacity of a TH-PPM UWB system with an outage constraint in multi-user environments is mathematically analyzed and evaluated. To mitigate a near-far problem, a near-interference erasure scheme is adopted and the capacity of the TH-PPM UWB system using the near-interference erasure scheme is evaluated through numerical analysis and Gaussian approximation. The numerical results show that the capacity of the TH-PPM UWB system using the near-interference erasure scheme is significantly improved and there exists an optimum threshold for the near-interference erasure scheme which maximizes the capacity. The capacity which is mathematically derived is very similar to that of numerical results in the region near the optimum threshold. Furthermore, the results are more accurate as the number of bit repetitions increases.

Link performance evaluation of a TH-PPM UWB system in the presence of multi-user interference

The link performance of a TH-PPM UWB system is evaluated through a more realistic multi-user interference (MUI) model. Instead of unrealistic assumptions such as perfect interference power control and Gaussian MUI distribution, the received power and the propagation delay of each interference signal at a receiver are obtained from the distance between the receiver and an interfering user. Based on the proposed MUI model, a semi-analytical approach of the receiver link performance is also introduced. The estimated E/sub b//(I/sub o/ + N/sub o/) and the bit error probability for a given number of interfering users are numerically obtained by the proposed semi-analytical approach and the results are compared with the simulation results.