Mohd Dani Baba

A-MSDU real time traffic scheduler for IEEE802.11n WLANs

The IEEE 802.11n network main feature is to support high throughput of more than 100Mbps at the MAC layer. To achieve this, the 802.11n Task Group has introduced frame aggregation technique which reduces the overhead and increases the channel utilization efficiency. The MAC layer defines two frame aggregation mechanisms namely the MAC protocol data unit aggregation A-MPDU and MAC service data unit aggregation A-MSDU. A-MPDU is robust against error due to subframes retransmission and large aggregation size, whereas A-MSDU is effective in error free channel due to small headers. A-MPDU has poor performance in erroneous channel because of the absence of sub frames retransmission. It is worth mentioning that some recent researches have enabled the selective retransmission which makes it robust against error. The AMSDU has becomes compatible and able to fulfill the QoS requirements for applications with small frame size such as VoIP, videos as well as interactive gaming. In this paper, we propose A-MSDU real-time scheduler by exploiting the A-MSDU attributes and adopting the idea of enabling retransmission in our aggregation scheduler algorithm to obtain aggregation with small size to support time sensitive applications and satisfying the QoS requirements.

Performance analysis of transparent and non-transparent relays in MMR WiMAX networks

The main function of relay station is to enhance the network capacity and extend the coverage area. This paper analyses the performance of relay stations in IEEE 802.16j Mobile Multi-hop Relay (MMR) WiMAX for the transparent and non-transparent modes. The performance of these relays is evaluated based on the throughput for the downlink and uplink transmission using National Chiao Tung University - network simulator (NCTU-ns) module. This study shows that the sustained rate for uplink transmission is 0.471 Mbps while for the downlink in the relay mode is about ten times higher either for transparent or non-transparent relay types.

Assigning cognitive radio to the femtocell in LTE based network : A solution for interference mitigation

Recently, femtocell attains a lot of attention for its capability to offer extended coverage from macrocell to indoor subscribers. The deployment of Femtocell may cause Inter Cell Interference (ICI) between Femtocells and Macrocell due to the same set of frequency reuse. The characteristic of cognitive radio helps in efficiently utilizing the frequency spectrum, both in the licensed and unlicensed bands. The aim of this study is to highlight how an efficient Femtocell deployment scheme is presented to mitigate interference and enhance the users capacity in the Femtocell network. This study integrates cognitive radio with the Femtocell in LTE based network. Cognitive Radio (CR) and Femtocell network will complement each other and improve spectrum utilization and cell capacity. The simulation results show that the proposed method has the capability to improve the network capacity for the active Cognitive Femtocell Users (CFUs).

Parameters optimization for handover between femtocell and macrocell in LTE-based network

The challenge of removing redundant handover (HO) has gained more importance after the existence and deployment of femtocell in the network. By nature, the existence of femtocell can lead to the increase of handover initiation. However, 3GPP standard provides Mobility Robustness Optimization (MRO) to optimize handover performance. MRO is a use-case for Self-Organizing Network (SON). The conventional MRO algorithm tunes handover parameters based on counts of handover failures and handover events. In addition, conventional MRO algorithm uses hysteresis only to adjust and improve HO performance. In this paper, we propose an improved MRO algorithm by taking into account new optimization parameters, which is Time To Trigger parameter (TTT) to improve MRO algorithm performance in terms of reducing Ping-Pong rate and lower HO failure rate between femtocell and macrocell. We compared our improved MRO algorithm with the conventional one. The simulation results show remarkable improvement of the improved MRO algorithm over the standard one.

Downlink performance evaluation of multi-mode devices in WiMAX and WiFi environment

The attention on WiMAX and WiFi technologies are rapidly progressing and now it is common to find them not just in laptops and personal digital assistants (PDAs), but in equipment as mobile phones, parking meters, security cameras and home entertainment equipment. A combination of WiFi and WiMAX deployment, will offer more cost-effective solution than a sole WiMAX or WiFi implementation. Its technology is best meets the demand for personal broadband services. This project is focused on the performance evaluation of WiMAX and WiFi systems. It is conducted using open source simulator called NCTUns 6.0. Several scenarios have been created, to evaluate the coexistence of WiMAX and WiFi technology. The data of the simulation results have been gathered and the performance with the effects of transport layer protocol, send rates, packet sizes, distances, bandwidth and queue length were analyzed. Based on the results obtained, the performance of both WiMAX and WiFi technology are not affected due to distances variation but its performance can be improved by using of other parameter such as packet size, bandwidth and queue length.

Performance analysis of the IEEE 802.15.7 CSMA/CA algorithm based on Discrete Time Markov Chain (DTMC)

IEEE 802.15.7 is introduced to standardize the visible light communication system for connecting devices via visible light spectrum. A slotted CSMA/CA MAC protocol defined in the standard to coordinate channel access for numbers of the optical wireless devices. In this paper, we proposed a simple Discrete Time Markov Chain (DTMC) model for modeling the behavior of the Contention Access Period (CAP) of the IEEE 802.15.7 to acquire valuable insights and inner workings of the protocol. The throughput and packet delivery reliability of the Contention Access Period (CAP) of the IEEE 802.15.7 are analyzed. Ns-2 simulations are used to verify the accuracy of the proposed model. The results between the proposed model and ns-2 simulation are closely matched with about 4 percent accuracy. Thus, verify the accuracy of the proposed model.

Performance analysis of fixed and mobile WiMax networks using NCTUns tools

WiMAX is a Worldwide Interoperability for Microwave Access. The technology is specified by the Institute of Electrical and Electronics Engineers Inc., as the IEEE 802.16 standard that works on development of globally standardized protocols for wireless MAN and it has been commercialized under the name “WiMAX”. 802-16-2004 has often been considered the “fixed standard” or “fixed WiMAX” and 802.16-2005 as the “mobile standard” or “mobile WiMAX”. Fixed WiMAX has been used to support fixed and nomadic applications while mobile WiMAX is an amendment to this standard that support mobile, portable, fixed and nomadic applications. This paper presents the simulation of performance of TCP and UDP protocol over fixed and mobile WiMAX using NCTUns simulator version 6.0. NCTUns is an open simulator which is developed by National Chiao Tung University in Taiwan. Three performance metrics such as throughput, delay and packet loss have been determined in this work in varying WiMAX network topologies/scenarios.

Analysis of handover performance in mobile WiMAX networks

The handover performance in mobile network is the most important factor that can influence the Quality of Service (QoS). Today many countries in the world have migrated to more advanced mobile communication system such as the IEEE 802.16e mobile WiMax network. This mobile WiMax has been proven to be more stable and applicable for fixed, portable, nomadic and mobile network. The parameters such as handover time, throughput and packet delay are the main factor which affects the WiMax network performance. With the appropriate system setting, the QoS of the WiMAX system will be achieved. This paper presents handoff analysis in terms of the throughput and delay characteristic for 2 different fading models which involve UDP and TCP protocol.

DESIGN CONSIDERATIONS FOR EFFICIENT MULTICAST WDM NETWORK SCALABLE ARCHITECTURE

In this paper, we present a method for designing a passive optical based single-hop wavelength division multiplexing multicast network architecture that can achieve a scalable structure and form the basis of a wavelength efficient single-hop WDM network. The proposed architecture minimizes the number of wavelengths required for efficient multicast service and also minimizes tunability requirement of the transceivers. The network size scalability is achieved by adding transmitters and receivers to the designated groups. We show that the proposed system can accommodate large tuning delays and keeps with suitable throughput when the number of wavelength is equal to the number of nodes. We also show that the design can lead to a scalable structure while minimizing the number of wavelengths and tunability of the transceivers required for an efficient multicast service resulting in an improved system throughput and delay performance

Cell Breathing and Coverage Prediction in WCDMA

Cell breathing technique is commonly used in cellular network such as Wide Code Division Multiple Access (WCDMA) to overcome load congestion by expanding or shrinking the cell coverage. This paper presents the study of the cell breathing boundary of urban environment for WCDMA. The base station cell coverage may expand or shrink depending on the number of mobile station being served. The COST231 HATA model is used in this study to predict the cell coverage for urban environment. The actual received signal strength indicator (RSSI) obtained by conducting drive test measurement are compared to the received signal code power (RSCP) of the COST231 HATA propagation model. The error calculated in the measurements enables to determine the minimum discrepancy between RSSI and RSCP data. Thus the COST231 HATA model can be used to predict correctly the cell coverage for urban environment. The result also shows that during light load the cell coverage radius is 0.18km and then decreases to 0.15km so as to limit soft handover and hence reduces load congestion.