Yih-Shen Chen

A utility-approached radio resource allocation algorithm for downlink in OFDMA cellular systems

In this paper, we propose a utility-approached radio resource allocation (RRA) algorithm for downlink transmission in orthogonal frequency division multiple access (OFDMA) cellular systems. The proposed utility-approached RRA algorithm is to efficiently allocate the radio resource to mobiles according to a utility function, which contains a rate-power function, a QoS function, and a priority function to ensure QoS requirements among heterogenous services and improve the system throughput. Also, a simulated-annealing (SA) method is applied to find out the solution within a reasonable time. Simulation result shows that the proposed utility-approached RRA algorithm can allocate the radio resource efficiently and guarantee the QoS requirements of each user under the power constraints of the OFDMA system.

Maximum Freedom Last Scheduling Algorithm for Downlinks of DSRC Networks

This paper proposes a maximum freedom last (MFL) scheduling algorithm for downlinks, from the roadside unit to the onboard unit (OBU), of dedicated short-range communication networks in intelligent transportation systems, to minimize the system handoff rate under the maximum tolerable delay constraint. The MFL scheduling algorithm schedules the service ordering of OBUs according to their degree of freedom, which is determined by factors such as remaining dwell time of service channel, remaining transmission time, queueing delay, and maximum tolerable delay. The algorithm gives the smallest chance of service to the OBU with the largest remaining dwell time, the smallest remaining transmission time, and the largest weighting factor, which is a function of the queueing delay and the maximum tolerable delay. Simulation results show that the MFL scheduling algorithm outperforms the traditional first-come-first-serve and earliest-deadline-first methods in terms of service failure and system handoff rates

Neural fuzzy call admission and rate controller for WCDMA cellular systems providing multirate services

The paper proposes a neural fuzzy call admission and rate controller (NFARC) scheme for WCDMA cellular systems providing multirate services. The NFARC scheme can guarantee the quality of service (QoS) requirements and improve the utilization of the system. Simulation results show that the NFARC scheme achieves low forced termination probability and high system capacity even in the bursty traffic conditions. NFARC accepts users more than intelligent call admission controller (ICAC) by an amount of 45.35%.

A channel effect prediction-based power control scheme using PRNN/ERLS for uplinks in DS-CDMA cellular mobile systems

This paper proposes a channel effect prediction based power control scheme using pipeline recurrent neural network (PRNN)/extended recursive least squares (ERLS) for uplinks in direct sequence code division multiple access (DS-CDMA) cellular mobile systems. Conventional signal-to-interference (SIR) prediction-based power control schemes may incur prediction mistakes caused by the adjustment of transmission power. The proposed power control scheme purely tracks the variation of channel effect and, thus, can be immune to any power adjustment. Furthermore, it adopts the PRNN with ERLS for predicting the channel effect. Simulation results show that the channel effect prediction-based power control scheme using PRNN/ERLS achieves a 40% higher system capacity and a lower outage probability than the conventional SIR prediction-based power control scheme using grey prediction method (IEEE Trans. Veh. Technol., Vol. 49, No. 6, p. 2081, 2000).

A power control scheme with link gain prediction using PRNN/ERLS for DS-CDMA cellular mobile systems

In this paper, a link gain prediction-based power control scheme is designed for DS-CDMA cellular mobile systems. The link gain prediction can help to remove the interference of the power control adjustment itself. The pipeline recurrent neural network (PRNN) with extended recursive least square (ERLS) is adopted for the prediction. This PRNN/ERLS predictor possesses infinite memory of past signals so that it can capture precisely the signal correlation and improve the delay compensation of power control. Simulation results show that the link gain prediction-based power control scheme using PRNN/ERLS has lower outage probability than the received SIR prediction-based power control scheme using grey prediction method [S. L. Su, Y. C. Su, and J. F. Huang, November 2000] and improves the system capacity by an amount of 41.6%.

A Novel Adaptive P-Persistent MAC Scheme for WLAN Providing Low Delay Variance

The paper proposes and analyzes a novel adaptive p-persistent-based (APP) medium access control (MAC) scheme to provide low delay variance for IEEE 802.11 WLAN. The APP MAC scheme can differentiate permission probabilities of transmission for stations being incurred with different packet delays, and the permission probability is designed as a function of the numbers of retransmissions and re-backoffs so that stations being with larger packet delay can attain higher permission probability. Additionally, the scheme is modeled by a Markov-chain and successfully analyzed, where the system throughput and delay are derived. Results show that the proposed APP MAC scheme can achieve lower delay variance than conventional algorithms; it can effectively reduce the collision probability and the mean delay, therefore, the mean throughput is enhanced, as well.

Situation-aware data access manager using fuzzy Q-learning technique for multi-cell WCDMA systems

This paper proposes a novel situation-aware data access manager using fuzzy Q-learning technique (FQ-SDAM) for multi-cell WCDMA systems. The FQ-SDAM contains a fuzzy Q-learning-based residual capacity estimator (FQ-RCE) and a data rate scheduler (DRS). The FQ-RCE can accurately estimate the situation-dependent residual system capacity, and appropriately chooses the received interference powers from the home-cell and adjacent-cell as input linguistic variables, which simplifies the multi-cell environment into a single-cell environment by applying a perceptual coordination mechanism. The DRS can effectively allocate the resource for non-real-time terminals by modifying the exponential rule (S. Shakkottai and A.L. Stolyar, 2001), which considers the effect of interference on adjacent cells. Simulation results show that, compared to the link and interference-based demand assignment (LIDA) scheme proposed in S. Kumar and S. Nanda (1999), FQ-SDAM can effectively reduce the packet error probability and improve aggregate throughput of the non-real-time services in both the homogeneous and non-homogeneous multi-cell WCDMA environments. Additionally, the modified exponential rule achieves better system performance than the original exponential rule

An adaptive p-persistent MAC scheme for multimedia WLAN

The letter proposes an adaptive p-persistent-based (APP) medium access control (MAC) scheme for the IEEE 802.11e distributed WLAN supporting multimedia services. The APP MAC scheme adaptively gives differentiated permission probabilities to transmission stations which are in different access category and with various waiting delay. Simulation results show that the APP MAC scheme can improve the performance of multimedia WLAN, such as small voice packet dropping probability, low delay variation, and high system throughput, compared to conventional MAC algorithms

An Effective APP MAC Scheme for Multimedia WLAN-based DSRC Networks

The paper proposes an effective adaptive p-persistent-based (APP) medium access control (MAC) scheme for WLAN-based dedicated short-range communications (DSRC) networks supporting multimedia services. The APP MAC scheme adaptively gives differentiated permission probabilities to on board units (OBUs) which are in different access category and with various waiting delay. Simulation results show that the APP MAC scheme can improve the performance of multimedia WLAN-based DSRC networks, such as small real-time packet dropping probability, low delay variation, and high system throughput, compared to conventional MAC algorithms

A power-efficient MAC protocol for integrated voice and data services over 802.11e HCF

A novel power-efficient MAC protocol, named on-demand polling (ODP) scheme, is presented for supporting integrated voice and data services over WLAN. The ODP scheme combines the polling-based and the contention-based mechanisms over HCF (hybrid coordination function). In the ODP scheme, a voice station is in the polling list when it is in the active mode. During the idle mode, it is configured to operate in the sleep mode for saving power. Also, it adopts the contention-based mechanism to join the list again when returning from the idle mode. In this paper, we investigate the RR-Brady, the RR-CBR and the proposed ODP schemes and derive the power consumption and the aggregate throughput for voice and data stations, respectively. Simulation results show that the ODP scheme can reduce the power consumption for voice stations and enhance the throughput for data stations.