A Fair and Efficient Packet Scheduling Scheme for IEEE 802.16 Broadband Wireless Access Systems

This paper proposes a fair and efficient QoS scheduling scheme for IEEE 802.16 BWA systems that satisfies both throughput and delay guarantee to various real and non-real time applications. The proposed QoS scheduling scheme is compared with an existing QoS scheduling scheme proposed in literature in recent past. Simulation results show that the proposed scheduling scheme can provide a tight QoS guarantee in terms of delay, delay violation rate and throughput for all types of traffic as defined in the WiMAX standard, thereby maintaining the fairness and helps to eliminate starvation of lower priority class services. Bandwidth utilization of the system and fairness index of the resources are also encountered to validate the QoS provided by our proposed scheduling scheme

Wireless broadband access: WiMAX and beyond - Investigation of bandwidth request mechanisms under point-to-multipoint mode of WiMAX networks

The WiMAX standard specifies a metropolitan area broadband wireless access air interface. In order to support QoS for multimedia applications, various bandwidth request and scheduling mechanisms are suggested in WiMAX, in which a subscriber station can send request messages to a base station, and the base station can grant or reject the request according to the available radio resources. This article first compares two fundamental bandwidth request mechanisms specified in the standard, random access vs. polling under the point-to-multipoint mode, a mandatory transmission mode. Our results demonstrate that random access outperforms polling when the request rate is low. However, its performance degrades significantly when the channel is congested. Adaptive switching between random access and polling according to load can improve system performance. We also investigate the impact of channel noise on the random access request mechanism

Characteristics of chicken slaughterhouse wastewater

The chicken slaughterhouse wastewater is a class of wastewater, which is heavily polluted with organic matters including proteins, blood residues, fats and lard. Therefore, the direct discharged of untreated chicken slaughterhouse wastewater into the environment is associated with the occurrence of eutrophication phenomenon. In the present study, the characteristics of chicken slaughterhouse wastewater were investigated to ascertain the role of these wastes in the adverse effect on the environment and natural water system. The parameter tested included biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solid (TSS), total nitrogen (TN), total organic carbon (TOC), orthophosphate (PO4 3-), temperature and pH. The results revealed available high concentrations of BOD (1,341 - 1,821 ± 242.7 mg L1 ), COD (3,154.19 - 7,719.3 ± 2,282.69 mg L-1), TSS (377.67 - 5,462 ± 2,696.1 mg L-1) which have exceeded the EQA1974 standard limits for disposal of wastewater into the environment. The concentrations of TN (162.6 -563.8 ± 215 mg L-1) and PO4 3- (7.047 - 17.111 ± 4.25 mg L-1) were within the range required for microalgae growth which confirm their role in the occurrence of eutrophication phenomenon. It can be concluded that the direct discharge of chicken slaughterhouse wastewater contributes negatively on the environmental biodiversity and thus they should be subjected for an effective treated before the final disposal

WIMAX Basics from PHY Layer to Scheduling and Multicasting Approaches

WiMAX (Worldwide Interoperability for Microwave Access) is an emerging broadband wireless technology for providing Last mile solutions for supporting higher bandwidth and multiple service classes with various quality of service requirement. The unique architecture of the WiMAX MAC and PHY layers that uses OFDMA to allocate multiple channels with different modulation schema and multiple time slots for each channel allows better adaptation of heterogeneous user’s requirements. The main architecture in WiMAX uses PMP (Point to Multipoint), Mesh mode or the new MMR (Mobile Multi hop Mode) deployments where scheduling and multicasting have different approaches. In PMP SS (Subscriber Station) connects directly to BS (Base Station) in a single hop route so channel conditions adaptations and supporting QoS for classes of services is the key points in scheduling, admission control or multicasting, while in Mesh networks SS connects to other SS Stations or to the BS in a multi hop routes, the MMR mode extends the PMP mode in which the SS connects to either a relay station (RS) or to Bs. Both MMR and Mesh uses centralized or distributed scheduling with multicasting schemas based on scheduling trees for routing. In this paper a broad study is conducted About WiMAX technology PMP and Mesh deployments from main physical layers features with differentiation of MAC layer features to scheduling and multicasting approaches in both modes of operations