Round-robin Polling Research Articles

Scheduling algorithms for multimedia traffic over high-rate WPANs

The IEEE 802.15.3 standard aims at covering the gaps of current Wireless Personal Area Network (WPAN) technologies in supporting applications with very high-rate and/or quality of service requirements. To this end, the standard encompasses high-rate modulations and a flexible medium access mechanism that permits resource reservation. Whereas the standard defines the general resource management framework, the definition of practical scheduling algorithms is left open to proprietary solutions. In this paper we investigate the potentialities offered by the IEEE 802.15.3 framework for supporting multimedia services. More specifically, we analyze the performance of some classical scheduling policies in presence of intensive real-time and multimedia traffic, in order to identify the most effective strategy for the considered scenarios. The analysis has been performed by using a complete 802.15.3 C++ simulator, where we have realized the different scheduling strategies upon an entirely standard-compliant round robin polling procedure. Results show that the simple and well-known scheduling strategies considered in this study offer very good performance in a large set of realistic application scenarios.

Efficient silence suppression and call admission control through contention-free medium access for VoIP in WiFi networks

In view of the rapidly growing trend of migrating customers from traditional wired phones to mobile phones and then to VoIP services in the recent past, there is a tremendous demand for wireless technologies to support VoIP, specially on WiFi technologies which have already matured commercially. This has put forth great research challenges in the area of wireless VoIP. In this article we have addressed two core issues, efficient silence suppression and call admission control, in QoS provisioning for VoIP services in WiFi networks. In this connection we present a QoS-aware wireless MAC protocol called hybrid contention-free access (H-CFA) and a VoIP call admission control technique called the traffic stream admission control (TS-AC) algorithm. The H-CFA protocol is based on a novel idea that combines two contention-free wireless medium access approaches, round-robin polling and TDMA-like time slot assignment, and provides substantial multiplexing capacity gain through silence suppression of voice calls. The TS-AC algorithm ensures efficient admission control for consistent delay bound guarantees and further maximizes the capacity through exploiting the voice characteristic so that it can tolerate some level of non-consecutive packet loss. We expose the benefits of our schemes through numerical results obtained from simulations.

Performance evaluation of new scheduling methods for the RR/RR CICQ switch

Increasing link speeds and port counts in packet switches demand that methods for minimizing internal speed-up and implementing fast scheduling be developed. Combined input and cross point queued (CICQ) switches with round-robin (RR) polling of virtual output queues (VOQ) and of cross point buffers can natively forward variable-length packets without a required internal segmentation into cells. However, native switching of variable-length packets results in unfairness between ports. To eliminate this unfairness, we propose a block transfer mechanism that transfers up to a predefined number of bytes of packet data from a selected VOQ. This mechanism does not require internal speed-up. We also propose an overlapped RR (ORR) arbiter design that fully overlaps RR polling and scheduling. Using simulation and both synthetic and traced packet traffic as input, we show that the RR/RR CICQ switch with the block transfer mechanism has a lower delay than an input queued (IQ) switch that internally uses cells. We also show that the ORR arbiter is scalable, work conserving, and fair.

블루투스 피코넷에서의 효율적인 전력 및 자원 스케줄링

근거리 무선 개인 네트워크 시스템 즉, 블루투스의 피코넷을 위한 전력 및 차등 대역폭 할당을 고려한다. 대역폭 요구는 어플리케이션/서비스에 또는 시간에 따라서 변할 수도 있으므로, 제한된 자원을 서비스 요구를 만족하면서 다양한 서비스 클래스로 어떻게 할당할 것인가를 결정 하는 것이 중요하다. 본 논문에서는 다양한 서비스 형태의 대역폭 요구를 만족하면서 전력 절약 모드 (즉, 스니프 모드)에 의해 전력 소비를 절약하는 간단하고 효율적인 대역폭 할당 메커니즘을 제안한다. 기존의 (가중치) 라운드 로빈 폴링 방법과 제안된 메커니즘을 비교하고, 전송율, 지연시간, 전력 소비 측면에서의 성능 향상을 보인다. We consider differentiated bandwidth allocation for a piconet in short-range wireless personal network systems : Bluetooth. Since bandwidth requirements nay vary among applications/services, and/or it may change over time, it is important to decide how to allocate limited resources to various service classes to meet their service requirements. We propose a simple and efficient bandwidth allocation mechanism which meets bandwidth requirements of various service types while saving power consumption by a Power saying mode, i.e., sniff node. We compare our proposed mechanism with a conventional (weighted) round-robin polling scheme and show that it achieves significant improvement of hroughput, delay, and power consumption.

A learning-automata-based controller for client/server systems

Polling policies have been introduced to simplify the accessing process in client/server systems by a centralized control access scheme. This paper considers a client/server model which employs a polling policy as its access strategy. We propose a learning-automata-based approach for polling in order to improve the throughput-delay performance of the system. Each client has an associated queue and the server performs selective polling such that the next client to be served is identified by a learning automaton. The learning automaton updates each client's choice probability according to the feedback information. Under the considered approach, a client's choice probability asymptotically tends to be proportional to the probability that this client is ready. Simulation results have shown that the proposed polling policy is beneficial in comparison to the conventional round-robin polling when operating under bursty traffic conditions. The benefits are significant for the delay reduction in the considered client/server system.

Input buffer requirements for round robin polling systems

A packet switched network that can be modeled as a round robin polling system with nonzero switchover times is considered. The input traffic is assumed to obey the (σ, ϱ) regularity conditions recently proposed by Cruz [ IEEE Trans. Inform. Theory 37(1) (1991) 114–141]. These conditions are particularly applicable to traffic from open loop flow control mechanisms, such as the leaky bucket. For partially gated service, upper and lower bounds are provided for buffer requirements to insure no data loss. The bounds are extended to gated and exhaustive service and are modified to provide bounds on guaranteed network delays. Using the bounds, it is demonstrated that partially gated service requires nearly minimal buffering when incoming traffic approaches the capacity of the network. It is also demonstrated that open loop flow control can improve the buffer requirements and guaranteed delays of the network significantly.