Browsing by Author "Lo, BC"

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A collision resolution paradigm for Random Access Channel control in multi-access wireless networks
(2002)
Yuang, MC
;
Lo, BC
;
Chen, JY
;
資訊工程學系
;
Department of Computer Science
The Random Access Channel (RACH) incurs a collision if more than one user make signaling requests over the same time slot, spreading code, or antenna element, in TDMA, CDMA, or SDMA wireless networks, respectively. In this paper, we propose a Hexanary-Feedback Collision Resolution Paradigm (HFCRP), capable of leveraging access efficiency of the RACH for all above wireless networks. HFCRP performs incremental contention resolution, managing a small subset of users at a time via a two-phase process. In the first phase, a group of users is probabilistically admitted, with a negligible probability of the group size greater than five. In the second phase, all users in the group are efficiently resolved. The two-phase process is augmented with hexanary feedback control facilitated by an nvelope-pdf-based Multi-user stimator ( M R) implemented at the physical layer. significantly, the M R measures the exact number of transmitting users (zero to five) in a contention slot by matching the envelope pdf s histograms of received signals to a library of pre-constructed pdf s. These six outcomes comprise the hexanary feedback being broadcast to users during the real-time operation of the two-phase process. Analytic and simulation results delineate that, performing in con unction with the M R, HFCRP achieves high performance with respect to maximum stable throughput, saturated throughput, access delay, and blocking probability.
A perfectly stable contention access scheme for wireless access networks
(2001)
Yuang, MC
;
Lo, BC
;
Chen, JY
;
資訊工程學系
;
Department of Computer Science
Existing TDM-based contention access schemes exhibit the unstable or load-susceptible problem in which throughput exponentially deteriorates as the traffic offered load increases or fluctuates. In this paper, we propose a persistently stable, efficient Hexanary-Feedback-based Contention Access (HFCA) scheme, aiming to provide QoS guarantee while retaining stable and maximal network throughput. Unlike existing schemes that consider all contending mobile terminals as a whole, HFCA incrementally resolves a small group of terminals each time via a two-phase selection/resolution process. The incremental resolution repeats until the minimum non-blocking probability (QoS for signaling traffic) is satisfied. To accelerate resolution within the process, the number of simultaneously transmitting terminals is estimated based on an Envelope-pdf-based Estimator (EPER), by matching the corresponding normalized envelope histogram of the receiving signal with the priori envelope-pdf library. Facilitated with incremental resolution and the EPER, HFCA achieves the highest maximum throughput (0.574) and saturated throughput (0.52) reported to date irrespective of traffic increase and variation.
A QoS-guaranteed MAC protocol using variable frame granularity for wireless access networks
(2001)
Yuang, MC
;
Lo, BC
;
資訊工程學系
;
Department of Computer Science
In this paper, we propose a MAC protocol, called QMAC+, which adopts variable frame granularity, aiming to provide bandwidth-on-demand and QoS guarantees while retaining maximal network throughput QMAC+ supports three traffic types- CBR, VBR, and Reservation Request (RVR) for making CBR/VBR connection reservation. Essentially, QMAC+ governs weight-based reservation access (for VBR/CBR) and premier contention access (for RVR) over dynamically allocated reservation and premier contention bandwidths, respectively. In particular, the premier contention access performs incremental contention resolution by means of feedback control using an envelope-pdf-based estimator for the estimation of the number of concurrently transmitting users. As a result, the frame granularity is dynamically changed adapting to traffic fluctuation. Simulation results demonstrate that QMAC+ achieves superior performance with respect to throughput, delay, and blocking probability.
A synchronization paradigm with QoS guarantees for multimedia communications
(1999)
Yuang, MC
;
Lo, BC
;
Chen, YG
;
Tien, PL
;
資訊工程學系
In this paper, we propose a synchronization paradigm, called SYNC*, offering two Quality of Service (QoS) requirements, skew and throughput, for multimedia communications. SYNC* is composed of three components: Intelligent Video Smoother (IVS), Synchronizer, and Multi-thread Priority Manager (MPM). While IVS and Synchronizer achieves intramedia and Intermedia synchronization, respectively, MPM ensures satisfactory throughput before playout. The main goal of the paper is to present in detail the design and performance analysis of the second component, Synchronizer. Synchronizer is aimed to achieve bounded skew between different media through periodic marking of correlated frames. The minimum marking interval yielding a given skew is analytically determined based on a Markov Batch Bernoulli Process (MBBP)/D/K/1 queueing model. We demonstrate the profound agreement between analytic and simulation results. The results also indicate that, the playout quality with respect to skew is highly relevant to the traffic burstiness and decoder buffer size. On the basis of a fixed marking interval, the greater the burstiness and buffer size, the poorer the playout quality.
Hexanary-feedback contention access with PDF-based multiuser estimation for wireless access networks
(2004-01-01)
Yuang, MC
;
Lo, BC
;
Chen, JY
;
資訊工程學系
;
Department of Computer Science
Most existing contention access schemes are inherently unstable resulting in exponentially deteriorating throughput under increased traffic loads. In this paper, we propose a wide-sense stable (WSS) efficient hexanary-feedback contention access (HFCA) scheme, capable of providing signaling traffic high performance while retaining maximal throughput for wireless access networks. HFCA performs incremental contention resolution, managing a small subset of users at a time via a two-phase process. In the first phase, a group of users is probabilistically admitted, with a negligible probability of the group size greater than five. In the second phase, all users in the group are efficiently resolved. The two-phase process is augmented with hexanary feedback control facilitated by a probability density function (pdf)-based multiuser estimator (PMER) implemented at the physical layer. Basically, PMER measures the exact number of transmitting users (zero to five) in a contention slot by matching the envelope-phase pdf's histograms of received signals to a preconstructed pdf's library. To formally justify the performance of HFCA, we present throughput and stability analysis in which HFCA is shown WSS and the strict-sense stability condition is derived. Finally, analytic and simulation results delineate that, HFCA is highly robust against estimation discrepancy. Significantly, HFCA achieves high performance with respect to maximum stable and saturated throughputs, access delay, and blocking probability.
Wide-sense stable hexanary-feedback contention access for wireless networks
(2003)
Yuang, MC
;
Lo, BC
;
Chen, JY
;
資訊工程學系
;
Department of Computer Science
Most existing contention access schemes are inherently unstable resulting in exponentially deteriorating throughput under increased traffic loads. In this paper, we propose a wide-sense stable, efficient Hexanary-Feedback Contention Access (HFCA) scheme, capable of providing signaling traffic high performance while retaining maximal throughput for wireless access networks. HFCA performs incremental contention resolution via a two-phase process. The two-phase process is augmented with hexanary feedback control facilitated by a Pdf-based Multi-user Estimator (PMER) implemented at the physical layer. We present throughput and stability analyses in which HFCA is shown wide-sense stable, and the strict-sense stability condition is derived. Finally, analytic and simulation results delineate that, HFCA achieves high performance with respect to maximum stable and saturated throughputs, access delay, and blocking probability.