Adaptive spatial mode of space-time and spacefrequency OFDM system over fading channels

In this paper we present a 2 transmit 1 receive (1 Tx : 1 Rx) adaptive spatial mode (ASM) of space-time (ST) and space-frequency (SF) orthogonal frequency division multiplexing (OFDM). At low signal to noise ratio (SNR) we employ ST-OFDM and switch to SF-OFDM at a certain SNR threshold. We determine this threshold from the intersection of individual performance curves. Results show a gain of 9 dB (at a bit error rate of 10-3) is achieved by employing adaptive spatial mode compared to a fixed ST-OFDM, almost 6 dB to fixed SF-OFDM, 4 dB to Coded ST-OFDM and 2 dB to a fixed coded SF-OFDM, at a delay spread of 700 ns

An enhanced IPv6 anycast routing protocol using Protocol Independent Multicast-Sparse Mode (PIM-SM)

Although the demands for finding an economical routing protocol that provides the service to the clients in shortest time and least cost are increasing. IPv6 Anycast still has a lot of issues and problems in practical applications. One of the problems is that IPv6 Anycast still does not have its own standard protocol. In this paper we develop a new Anycast routing protocol by modifying the existing multicast routing protocol because anycast and multicast have many similar properties. Protocol Independent Multicast-Sparse Mode (PIM-SM) is chosen as a basis to design a new anycast routing protocol. We next improve the design by considering the status (free or busy) of the anycast receivers as an important factor in our design. Besides the metric value of the receiver, we propose a new variable in the routing table called BMF (Best Metric Factor)

Algorithm for enhancing the QoS of video traffic over wireless mesh networks

One of the major issues in a wireless mesh networks (WMNs) which needs to be solved is the lack of a viable protocol for medium access control (MAC). In fact, the main concern is to expand the application of limited wireless resources while simultaneously retaining the quality of service (QoS) of all types of traffic. In particular, the video service for real-time variable bit rate (rt-VBR). As such, this study attempts to enhance QoS with regard to packet loss, average delay, and throughput by controlling the transmitted video packets. The packet loss and average delay of QoS for video traffic can be controlled. Results of simulation show that Optimum Dynamic Reservation-Time Division Multiplexing Access (ODR-TDMA) has achieved excellent utilization of resource that improvised the QoS meant for video packets. This study has also proven the adequacy of the proposed algorithm to minimize packet delay and packet loss, in addition to enhancing throughput in comparison to those reported in previous studies

Location Management Cost Reduction Using Adaptive Velocity-movement Based Scheme

Wireless personal communication networks (PCNs) consist of a fixed wireless network and a large number of mobile terminals. These terminals are free to travel within the PC coverage area without service interruption. Each terminal periodically reports its location to the network by a process called location update (or registration). When a call arrives for a particular mobile terminal, the network will determine the exact location of the destination terminal by a process called terminal paging. One major problem that arises in this scenario is the cost associated with paging and registration. Several papers in the literature attempt to reduce the cost by devising new schemes for paging and registration. One of the many interesting schemes was presented by Wan and Lin (1998) that considers a dynamic paging scheme based on the semi-real time velocity information of an individual mobile user, which allows a more accurate prediction of the user location when a call arrives. In this paper, we modified the scheme presented by Wan and Lin by creating an adaptive velocity timer that changes according to the speed of the mobile and applies the same analysis to the movement-based scheme. The investigation shows that the proposed approach of Wan and Lin has better results than what was reported therein and our new approach helps reduce the total cost drastically compared to the original scheme. Results also show that the movement threshold and the adaptive velocity time unit, when they are adaptive, provide significant savings of cost under different cell sizes and velocities in high and low mobility systems

Peak-to-average power ratio reduction in OFDM systems using smoothing technique

This paper presents a new peak-to-average power ratio (PAPR) reduction technique by smoothing the power components of OFDM signals. The smoothing technique only adds a simple process to the existing OFDM signal processing. Also, there is no need to send side information to the receiver for signal recovery. Smoothed OFDM system with 64 subcarrier and 16-QAM modulation achieved reduction in PAPR in the range of 0.5 to 2.5 dB, with out-of-band shoulder lying less than -15 dB compared to in-band level

A review and comparison of efficient flooding schemes for on-demand routing protocols on mobile ad hoc networks (MANETs)

Since the basic components of ad hoc wireless networks are mostly battery-operated portable devices, power conservation is one of the central issues of such networks. Power-conservative designs for ad hoc networks pose many challenges due to the lack of central coordination facilities. Existing on-demand routing protocols perform route discovery by flooding the network with a query message requesting a route to the destination. Flooding is used because of its simplicity and greater success in finding the best route between the source and destination available at that time of route discovery. However, as flooding involves querying all reachable network nodes, frequent flooding can rapidly deplete the energy reserved at each node. In addition to consuming significant portions of the available network bandwidth. Further, as the number of communicating nodes increases, more congestion, contention, and collisions can be expected. This paper reviews and compares approaches for optimizing bandwidth efficiency of route discovery, where several efficient flooding schemes have been presented based on different techniques to solve the problems related with the traditional blind flooding

The use of agent to incorporate network awareness into dynamic proxy framework: an overview

It has been observed that research in mobile agent focused on the development of platforms and on the application of the concept. Network awareness is one of the applications of mobile agent, concerning of how agent determine and make the most efficient use of network resources. This paper describes the role and functionality of mobile agent in the context of a dynamic proxy framework named the Chek Proxy Framework (CPF). Attention is paid on setting out a multi-agent-based framework to enrich CPF with a Network Awareness Module (NAM), which is implemented in an agent named ObjectBasket (OB). NAM is a single framework that integrates resource discovery, load monitoring and migration, and fault management, to operate in a network with dynamic proxy servers. The main objective of NAM is to deliver robustness and best-effort QoS guarantees into the existing CPF system adaptively, based on the availability of resources in the network. In this paper, we present the architecture of NAM, status generation algorithm, implementation rules, and the management of faults and overloading.Facultad de Informátic

A novel cell-selection optimization handover for long-term evolution (LTE) macrocellusing fuzzy TOPSIS

To satisfy the demand for higher data rate while maintaining the quality of service, a dense long-term evolution (LTE) cells environment is required. This imposes a big challenge to the network when it comes to performing handover (HO). Cell selection has an important influence on network performance, to achieve seamless handover. Although a successful handover is accomplished, it might be to a wrong cell when the selected cell is not an optimal one in terms of signal quality and bandwidth. This may cause significant interference with other cells, handover failure (HOF), or handover ping-pong (HOPP), consequently degrading the cell throughput. To address this issue, we propose a multiple-criteria decision-making method. In this method, we use an integrated fuzzy technique for order preference by using similarity to ideal solution (TOPSIS) on S-criterion, availability of resource blocks (RBs), and uplink signal-to-interference-plus-noise ratio. The conventional cell selection in LTE is based on S-criterion, which is inadequate since it only relies on downlink signal quality. A novel method called fuzzy multiple-criteria cell selection (FMCCS) is proposed in this paper. FMCCS considers RBs utilization and user equipment uplink condition in addition to S-criterion. System analysis demonstrates that FMCCS managed to reduce handover ping-pong and handover failure significantly. This improvement stems from the highly reliable cell-selection technique that leads to increased throughput of the cell with a successful handover. The simulation results show that FMCCS outperforms the conventional and cell selection scheme (CSS) methods