Ray-Guang Cheng

Design of a fuzzy traffic controller for ATM networks

This paper presents the design of a fuzzy traffic controller that simultaneously manages congestion control and call admission control for asynchronous transfer mode (ATM) networks. The fuzzy traffic controller is a fuzzy implementation of the two-threshold congestion control method and the equivalent capacity admission control method extensively studied in the literature. It is an improved, intelligent implementation that not only utilizes the mathematical formulation of classical control but also mimics the expert knowledge of traffic control. We appropriately choose input linguistic variables of the fuzzy traffic controller so that the controller is a closed-loop system with stable and robust operation. We extract knowledge of conventional control methods from numerous analytical data using a clustering technique and then use this knowledge to set parameters of the membership functions and fuzzy control rules via fuzzy set manipulation (linguistically stated but mathematically treated) with the aid of an optimization technique named genetic algorithm (GA). Simulation results show that the proposed fuzzy admission control improves system utilization by a significant 11%, while maintaining the quality of service (QoS) contract comparable with that of the conventional equivalent capacity method. The performance of the proposed fuzzy congestion control method is also 4% better than that of the conventional two-threshold congestion control method.

OVSF code channel assignment for IMT-2000

Code channel assignment deals with the problem that how different codes are allocated to different connections. In the 3GPP technical specifications, the channelization codes used for spreading are orthogonal variable spreading factor (OVSF) codes. It can preserve the orthogonality between users physical channels. OVSF codes are valuable resources in CDMA systems and should be properly managed. The objective of this paper is to find a code channel assignment method to support as many users as possible with less complexity. We proposed a code channel assignment method for user equipment (UE) that has the capability to support multi-rate services using multi-code transmission. A single table is used to allocate codes to a UE according to its requested data rate. Therefore, the allocation and releasing procedures, which can be accomplished in a very short period of time, are efficient.

Performance Analysis of Group Paging for Machine-Type Communications in LTE Networks

Machine-type communication (MTC) is a crucial service for next-generation cellular networks. Mass access to the network by MTC devices may result in the overload of radio access networks (RANs) and degrade the service quality of human-to-human communication. Group paging is one of the mechanisms proposed to alleviate the RAN-overload problem. This paper presents an analytical model based on a recursive contending-users estimation (RCE) method proposed in the literature to derive the performance metrics of collision probability, access success probability, average access delay, statistics of preamble transmissions, statistics of access delay, and utilization of random-access opportunities (RAOs) for group paging with various combinations of group sizes and reserved radio resources in a paging access interval. The optimal group size and required RAOs are subsequently derived based on the given target access success probability. Numerical results demonstrate that the proposed model can accurately estimate the performance of group paging.

RACH Collision Probability for Machine-Type Communications

This paper summarizes the two definitions of the collision probability from the perspective of an MTC device and an RAO were presented in 3GPP TR 37.868. We use the results presented in TR 37.868 to show the inconsistency between the two definitions. It worth to note that the researcher needs to clearly specify the definition they used in presenting the results of their proposed radio access network overload control schemes. This paper further presents an analytical model to derive the collision probability, the success probability, and the idle probability based on the two definitions.

Traffic control in an ATM network using fuzzy set theory

Due to the demand for high-speed and multimedia services, ATM (asynchronous transfer mode) networks have increasingly received high attention. The multimedia services in ATM networks have diverse traffic characteristics and service requirements, appropriate traffic controls of call admission and congestion are needed so as to guarantee the required quality of service (QOS) for services. Previous studies on the traffic control were based on the results of queueing analyses. In the present paper, an alternative traffic control for admission in conjunction with congestion based on fuzzy set theory are proposed for an ATM network. The performance evaluation via simulation shows the effectiveness of the proposed method in comparison with the equivalent capacity in Guerin et al. (1991); link utilization is effectively improved by 8% while keeping the QOS contract.<<ETX>>

Modeling and Estimation of One-Shot Random Access for Finite-User Multichannel Slotted ALOHA Systems

This paper presents a combinatorial model and approximation formulas to estimate the average number of successful and collided users for a one-shot random access in finite-user multichannel slotted ALOHA systems. The proposed model and approximation can be used to evaluate the performance of group paging for machine-type communication (MTC) in 3GPP LTE. Numerical results demonstrate the applicable range of the approximation formulas and the accuracy of the derived performance metrics.

A power-spectrum based connection admission control for ATM networks

The power spectrum of the input process explicitly contains the correlation behavior of input traffic and has a great impact on the queueing behavior of an ATM network. In this paper, we propose a power-spectrum based connection admission control scheme for ATM networks. The DC component, the average power, and the half-power bandwidth are the key factors of the input power spectrum. Here, we use a method to approximate the QoS by the result obtained from the equivalent average power. Finally, we construct an admission control table which contains the performance measure for different loads and the equivalent average power. Whether a new call can be accepted or not is determined by table lookup. Simulation results show that our proposed power-spectrum based connection admission control is an efficient control method for ATM networks.

Ripple: a wireless token-passing protocol for multi-hop wireless mesh networks

This work presents a wireless token-passing protocol, named Ripple, for wireless mesh networks (WMNs). In contrast to existing random-access approaches, Ripple uses a decentralized controlled-access approach to protect nodes from unintentional packet collisions and maximize the spatial reuse. The performance of Ripple under an error-free wireless channel was investigated and the accuracy of the analysis was verified by simulation. Simulation results also indicated that Ripple achieved throughput, stability, and QoS enhancement than that of 802.11 DCF under a highly loaded situation

Modeling and Analysis of an Extended Access Barring Algorithm for Machine-Type Communications in LTE-A Networks

Simultaneous channel accesses from mass machine-type communications (MTC) devices may congest the random-access channels (RACHs) of LTE-A networks. Currently, 3GPP selects extended access barring (EAB) mechanism as the baseline solution to relieve the congestion of RACHs by barring low-priority devices. Different settings of EAB parameters may re-shape the arrival process of MTC traffic and thus, lead to unpredictable performance. This paper presents an analytical model to investigate the performance of the EAB algorithm on the RACHs in LTE-A networks. Computer simulations were conducted to verify the accuracy of the analysis. The optimal values of paging cycle and repetition period of system information block type 14 (SIB14) can then be obtained from the analytical model subject to a target quality-of-service (QoS) constraint.

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