Inwhee Joe

A slotted CDMA protocol with BER scheduling for wireless multimedia networks

In future wireless multimedia networks, there will be a mixture of different traffic classes which have their own maximum tolerable bit error rate (BER) requirements. In this paper, a novel medium access control (MAC) protocol called wireless multimedia access control protocol with BER scheduling (in short form, WISPER) for CDMA-based systems is proposed. WISPER utilizes the novel idea of scheduling the transmission of multimedia packets according to their BER requirements. The scheduler assigns priorities to the packets, and performs an iterative procedure to determine a good accommodation of the highest-priority packets in the slots of a frame so that packets with equal or similar BER requirements are transmitted in the same slots. The proposed WISPER protocol has been validated using a software emulator on the cellular environment. Performance evaluation results based on the implementation are also included.

A Network Selection Algorithm Considering Power Consumption in Hybrid Wireless Networks

In this paper, we propose a novel network selection algorithm considering power consumption in hybrid wireless networks for vertical handover. CDMA, WiBro, WLAN networks are candidate networks for this selection algorithm. This algorithm is composed of the power consumption prediction algorithm and the final network selection algorithm. The power consumption prediction algorithm estimates the expected lifetime of the mobile station based on the current battery level, traffic class and power consumption for each network interface card of the mobile station. If the expected lifetime of the mobile station in a certain network is not long enough compared the handover delay, this particular network will be removed from the candidate network list, thereby preventing unnecessary handovers in the preprocessing procedure. On the other hand, the final network selection algorithm consists of AHP (Analytic Hierarchical Process) and GRA (Grey Relational Analysis). The global factors of the network selection structure are QoS, cost and lifetime. If user preference is lifetime, our selection algorithm selects the network that offers longest service duration due to low power consumption. Also, we conduct some simulations using the OPNET simulation tool. The simulation results show that the proposed algorithm provides longer lifetime in the hybrid wireless network environment.

An adaptive hybrid ARQ scheme with concatenated FEC codes for wireless ATM

Thii paper describes the design and performance of a hybrid ARQ scheme with the concatenated FEC for wireless ATM networks. The wireless channel is characterized by burstier error patterns, and a higher and time-varying error rate when compared with the fiber-based network for which ATM was designed. The purpose of the hybrid ARQ scheme with the concatenated FEC is to provide a capability to dynamically support survivable ATM-based communications on a wireless channel by using a combination of ARQ and FEC schemes. The key ideas of the proposed hybrid scheme are the adaptation of the code rate to the channel conditions using incremental redundancy and the increase of the starting code rate as high as possible with the concatenated FEC to maximize the throughput efficiency. The simulation results show that our proposed scheme outperforms other hybrid ARQ schemes for all SNR values.

A new ARQ protocol for wireless ATM networks

This paper describes the design and performance of a new ARQ protocol for wireless ATM networks. The wireless channel is characterized by a higher and variable error rate in comparison with fiber-based networks for which ATM was designed. The purpose of the protocol is to provide a capability to dynamically support ATM-based communications in a fluctuating transmission environment by using selective retransmission. The key ideas in the protocol design consist of variable packet size and periodic status message. The packet size is changed adaptively with the optimal size according to the time-varying conditions of the wireless channel, as a result maximizing the throughput efficiency. The proposed protocol has been validated using a software emulator which incorporates a wireless channel model. Experimental performance results based on the implementation are presented.

Reservation CSMA/CA for multimedia traffic over mobile ad-hoc networks

This paper describes the design and performance of a medium access control protocol (called reservation CSMA/CA) for multimedia traffic over mobile ad-hoc networks. The reservation CSMA/CA protocol is based on a hierarchical approach consisting of two sublayers. The lower sublayer of the MAC protocol provides a fundamental access method using CSMA/CA to support asynchronous data traffic over mobile ad-hoc networks. The upper sublayer is designed to support real-time periodic traffic by making a slot reservation with the three-way handshake prior to actual data transmission. The proposed protocol has been validated using a software emulator which was carried out with the UNIX implementation. The simulation results show that the reservation CSMA/CA offers higher throughput for real-time periodic traffic compared to the IEEE 802.11 standard, while providing deterministic delay performance.

Packet loss and jitter control for real-time MPEG video communications

Real-time video communication over a packet switching network is subject to packet loss and random delay variation called jitter. For compressed video, packet loss can cause significant performance degradation, and for continuous video regeneration, packet jitter can cause discontinuity and additional packet loss. Therefore, for good reception quality of video, a low jitter and a low loss are required. In this paper, a real-time video transport protocol on top of the UNIX UDP/IP is proposed. To reduce the delay jitter and packet loss effects, the protocol uses new mechanisms of such as selective packet discard, buffering, and constant rate playback for compressed MPEG (Moving Pictures Experts Group) video. Test results over Ethernet and under heavy traffic conditions show satisfactory performance which is unnoticeable from the ideal case.

A Message Priority Routing Protocol for Delay Tolerant Networks (DTN) in Disaster Areas

A delay tolerant network (DTN) is a mobile wireless network that is characterized by frequent partitions and potentially long message delivery delays. Compared with conventional networks, the distinguishing feature is that there is no end-to-end connectivity between source and destination. In this paper, we assume that an earthquake has occurred in a city and roads and nodes have been damaged in the disaster. In this situation, we found performance degradation of existing DTN routing protocols due to damage. To address this problem, we propose a DTN message priority routing protocol. In a disaster situation, the proposed protocol was able to deliver more messages than existing DTN protocols, with a lower overhead ratio and lower latency.

A Network Selection Algorithm considering Power Consumption in Hybrid Wireless Networks

In this paper, we propose a novel network selection algorithm considering power consumption in hybrid wireless networks for vertical handover. CDMA, WiBro, WLAN networks are candidate networks for this selection algorithm. This algorithm is composed of the power consumption prediction algorithm and the final network selection algorithm. The power consumption prediction algorithm estimates the expected lifetime of the mobile station based on the current battery level, traffic class and power consumption for each network interface card of the mobile station. If the expected lifetime of the mobile station in a certain network is not long enough compared the handover delay, this particular network will be removed from the candidate network list, thereby preventing unnecessary handovers in the preprocessing procedure. On the other hand, the final network selection algorithm consists of AHP (analytic hierarchical process) and GRA (grey relational analysis). The global factors of the network selection structure are QoS, cost and lifetime. If user preference is lifetime, our selection algorithm selects the network that stays longer due to low power consumption. Also, we conduct some simulations using the OPNET simulation tool. The simulation results show that the proposed algorithm provides longer lifetime in the hybrid wireless network environment.

QoS-aware MAC with reservation for mobile ad-hoc networks

This paper describes the design and performance of a novel medium access control (MAC) protocol, called reservation CSMA/CA for QoS (quality of service) support over mobile ad-hoc networks. The reservation CSMA/CA protocol is based on an hierarchical approach consisting of two sublayers. The lower sublayer of the MAC protocol provides a fundamental access method using CSMA/CA to support asynchronous data traffic over mobile ad-hoc networks. The upper sublayer is designed to support real-time periodic traffic with QoS requirements by making a slot reservation with the three-way handshake prior to actual data transmission. The proposed protocol has been validated using the ns network simulator with wireless and mobility extensions. The simulation results show that the reservation CSMA/CA offers the higher throughput with the higher load for real-time periodic traffic compared to the IEEE 802.11 standard, while providing deterministic delay performance.

A Novel Anti-Collision Algorithm with Optimal Frame Size for RFID System

In this paper, we propose a novel anti-collision algorithm for generation 2 RFID system to estimate the number of tags and to use the optimal frame size. Depending on the number of tags, there exists the optimal frame size in the sense that the system efficiency is maximized. The number of tags can be estimated from the collision ratio in terms of collided slots per frame. In addition, we compare our proposed algorithm with other existing schemes by simulation. The proposed scheme is easy to implement, and the simulation results show that its performance improves significantly compared to other schemes in terms of the identification time and the number of consumed slots.