Ching-Neng Lai

A Novel Query Tree Protocol with Bit Tracking in RFID Tag Identification

Tag anticollision has long been an important issue in RFID systems. To accelerate tag identification, some researchers have recently adopted bit tracking technology that allows the reader to detect the locations of collided bits in a collision slot. However, these methods still encounter the problem of too many collisions occurring at the beginning of identification. This paper proposes an optimal query tracking tree protocol (OQTT) that tries to separate all of the tags into smaller sets to reduce collisions at the beginning of identification. Using bit tracking technology, OQTT mainly adopts three proposed approaches, bit estimation, optimal partition, and query tracking tree. Bit estimation first estimates the number of tags based on the locations of collided bits. Optimal partition then determines the optimal number of the initial sets based on this estimation. Query tracking tree splits a set of collided tags into two subsets using the first collided bit in the tag IDs. This paper analyzes the efficiency of OQTT, which represents how many tags can be identified in a slot. Results show that its efficiency is close to 0.614, the highest efficiency published to date. The simulation results further show that OQTT outperforms other existing algorithms.

A GPS navigation system with QR code decoding and friend positioning in smart phones

Global Positioning System (GPS) navigation is a popular assistant during a trip. By using a GPS navigation system, the travelers can easily and quickly arrive to the destination in an unfamiliar area. However, there is no free and open-source GPS navigation system which integrates many useful applications. Thus, this paper proposes a GPS navigation system on the Android platform, called Android Mobile Navigation System (AMNS). AMNS not only provides users the GPS navigation function, but also supports Quick Response (QR) code decoding and friend positioning. Furthermore, AMNS is free and open-source software, so service providers or developers can easily extend their own services on this system.

DCCP partial reliability extension with sequence number compensation

Datagram congestion control protocol (DCCP), possessing congestion control and unreliable transmission, specially suits real-time multimedia applications. Nevertheless, losses of key packets will cause a substantial decline on quality of services (QoS) in some applications. This paper proposes a DCCP partial reliability extension (PR-DCCP) that can retransmit lost packets as needed. Since DCCP uses an incremental sequence number, the retransmitted packets cannot utilize their original sequence number. To solve this problem, PR-DCCP adopts sequence number compensation, which appends an offset to the retransmitted packet; thus the receiver can use the sequence number of this retransmitted packet and the attached offset so as to re-obtain the original sequence number. The simulation uses two performance metrics: decodable frame ratio (DFR) representing QoS, and useless data received ratio (UDRR) representing the bandwidth waste. These are used to evaluate different transport protocols, namely, PR-DCCP, DCCP, SCTP, TCP, and UDP. Simulation results show that PR-DCCP has the better DFR and UDRR than other transport protocols in almost all cases. For various movies, a DFR of PR-DCCP is 1.2-12.4% higher than that of DCCP; while UDRR is lower by 73.2-85.1%. Furthermore, two reliability policies to determine which packets require reliability are investigated. Finally, the comparisons between PR-DCCP and PR-SCTP are examined.

Enhanced Mechanisms for Navigation and Tracking Services in Smart Phones

Combining Global Positioning System (GPS) and Short Message Service (SMS), this paper develops a realistic system, called Mobile Navigation and Tracking System (MNTS), to provide navigation and target tracking services. MNTS is an Android based mobile application which integrated many enhanced mechanisms for navigation and target tracking services. MNTS not only provides users with the GPS navigation capability, but also supports Quick Response (QR) code decoding, nearby scenic spot searching, friend positioning and target tracking. In target tracking, MNTS utilizing SMS mainly adopts two proposed novel approaches: location prediction and dynamic threshold to reduce the number of short message transmissions while maintaining location accuracy within an acceptable range. Location prediction utilizes the current target’s location, moving speed, bearing to predict its next location. When the distance between the predicted location and the actual location exceeds a threshold, the target sends a short message to the tracker to update the actual location. Based on the movement speed of the target, the threshold is dynamically adjusted to balance the location accuracy and the number of short messages. Furthermore, as MNTS is free and open-source software, service providers or developers can easily extend their own services based on this system.

A tracking system using location prediction and dynamic threshold for minimizing SMS delivery

In this paper, a novel method called location-based delivery (LBD), which combines the short message service (SMS) and global position system (GPS), is proposed, and further, a realistic system for tracking a targets movement is developed. LBD reduces the number of short message transmissions while maintaining the location tracking accuracy within the acceptable range. The proposed approach, LBD, consists of three primary features: Short message format, location prediction, and dynamic threshold. The defined short message format is proprietary. Location prediction is performed by using the current location, moving speed, and bearing of the target to predict its next location. When the distance between the predicted location and the actual location exceeds a certain threshold, the target transmits a short message to the tracker to update its current location. The threshold is dynamically adjusted to maintain the location tracking accuracy and the number of short messages on the basisof the moving speed of the target. The experimental results show that LBD, indeed, outperforms other methods because it satisfactorily maintains the location tracking accuracy with relatively fewer messages.

A Channel Quality Aware Algorithm for IEEE 802.16 Uplink Burst Construction

Many burst construction algorithms for Orthogonal Frequency Division Multiple Access (OFDMA) were proposed. However, these algorithms do not meet the uplink burst characteristics specified in the IEEE 802.16 standard. This paper therefore proposes the Best Sub channel Oriented algorithm (BSO). BSO not only complies with uplink burst characteristics, but also obtains high throughput by considering the issues of internal fragmentation, external fragmentation, and good-sub channels exploring. BSO shrinks the burst area to avoid internal fragmentation, if the requested bandwidth has been satisfied. BSO minimizes the external fragmentation by evaluating all divided bandwidth areas and shrinking the burst area to fit into a proper available bandwidth area if no available area can accommodate it. To explore the good sub channels, BSO analyzes the channel quality of sub channels and constructs the burst on the sub channels which provide largest throughput. The simulation results under a heavy load indicate that BSO achieves 2 times the throughput achieved by Raster, a conventional algorithm.

A bandwidth allocation algorithm with channel quality and QoS aware for IEEE 802.16 base stations

SUMMARY Subscriber stations located in different places encounter various interferences in an IEEE 802.16 network, resulting in that their communication channels experience varying channel conditions. Thus, an excellent bandwidth allocation algorithm should not only satisfy various QoS required by heterogeneous traffic, but also consider the channel quality to maximize bandwidth utilization. In this paper, a bandwidth allocation algorithm with channel quality awareness and QoS guarantee, called CQQ, is proposed. CQQ not only satisfies each connections QoS requirement, but also dynamically adjusts the downlink/uplink bandwidth to match current downlink/uplink traffic ratio. CQQ allocates more bandwidth to the connections having better channel quality by applying weighted fair queuing strategy to raise the bandwidth usage. CQQ provides lower delay violation ratio and higher goodput than the previous algorithms, as observed from the simulation results. Copyright

A Group Bandwidth Reservation Scheme for the Control Channel in IEEE 802.11p/1609 Networks

IEEE 802.11p/1609 standards divide the radio spectrum into one control channel (CCH) and six service channels (SCH) for emergent/management frame exchange and service dissemination, respectively. Previous schemes, however, still suffer from enormous collisions of emergency messages or the large overhead of control messages in CCH, leading toward poor bandwidth usage. This paper develops group reservation MAC (GRMAC) to minimize the number of collisions in CCH to increase its overall goodput. GRMAC allows vehicles to reserve the CCH bandwidth while they stay in SCHs in order to reduce the number of collisions in CCH. Also, GRMAC migrates the CCH bandwidth scheduling mechanism from CCH to SCHs to reduce the burden on CCH bandwidth resources. The simulation results under heavy load reveal that GRMAC achieves two times the goodput achieved by the conventional IEEE 802.11p/1609 mechanism.

Retransmission Mechanism for Partially Reliable Transport Protocols Based on Multimedia Applications Transmission

The partially reliable transport protocol can enhance the quality of services (QoS) of multimedia applications because it reliably transmits some packets and unreliably transmits other packets. Nevertheless, determining which packets require reliable, i.e., these packets will be retransmitted if they were lost, significantly influences the performance of multimedia applications. For the determination, existing approaches adopt a fixed threshold or require information from other layers. This paper proposes a Timeliness-aware Retransmission Mechanism (TRM) that dynamically determines which lost packets should be retransmitted without any information provided from other layers. The receiver using TRM determines a threshold, which is the packet sequence number having timeliness, according to the packet consumed rate and the Round-Trip Time (RTT). Thus the sender retransmits lost packets that can timely arrive, namely, the packets have sequence numbers larger than this threshold. Simulation results shows that PR-DCCP, a partially reliable transport protocol, with TRM can efficiently increase the Decodable Frame Ratios (DFRs), which represents QoS, and decrease the Useless Data Received Ratios (UDRRs), which represents the bandwidth waste. In the simulations, TRM can achieve 8.6~10.6% DFR improvement and 15.1%~17.6% UDRR improvement on average, compared with other retransmission methods.

A Timeliness-Aware Retransmission Mechanism for Partially Reliable Transport Protocols to Enhance Performance of Multimedia Applications

The partially reliable transport protocol can enhance the quality of services (QoS) of multimedia applications because it reliably transmits some packets and unreliably transmits other packets. Nevertheless, determining which packets require reliable, i.e., these packets will be retransmitted if they were lost, significantly influences the performance of multimedia applications. For the determination, existing approaches adopt a fixed threshold or require information from other layers. This paper proposes a Timeliness-aware Retransmission Mechanism (TRM) that dynamically determines which lost packets should be retransmitted without any information provided from other layers. The receiver using TRM determines a threshold, which is the packet sequence number having timeliness, according to the packet consumed rate and the Round-Trip Time (RTT). Thus the sender retransmits lost packets that can timely arrive, namely, the packets have sequence numbers larger than this threshold. Simulation results shows that PR-DCCP, a partially reliable transport protocol, with TRM can efficiently increase the Decodable Frame Ratios (DFRs), which represents QoS, and decrease the Useless Data Received Ratios (UDRRs), which represents the bandwidth waste. In the simulations, TRM can achieve 8.6 ~ 10.6% DFR improvement and 15.1% ~ 17.6% UDRR improvement on average, compared with other retransmission methods.