Journal of High Speed Networks - Volume 18, issue 2

Authors: Ong, Hean-Loong | Natsheh, Essam | Wan, Tat-Chee

Article Type: Research Article

Abstract: Ad-hoc networks can operate even when there is a scarcity of network infrastructure. This research examines ad-hoc networks that have varying node densities. These environments can be found in areas struck by disasters to urban city environments. Mobile nodes would not distribute evenly in such environments. Instead, the nodes would likely concentrate around specific landmarks or areas such as public squares with a high number of pedestrians while connecting roads and highways that have a low density of mobile nodes. The main contribution was the integration of a density based probabilistic scheme on AODV to reduce incurred routing overheads and …improve packet delivery without significantly affecting the throughput and end to end delays. The proposed AODV–P (AODV–Probabilistic) protocol was compared against the AODV and OLSR protocols via simulation. The evaluation was based on three different environments: a high density, a variable density and a sparse density. The study showed that the AODV–P had a 28% higher data throughput than AODV and a 42% higher data throughput than OLSR at the three environments. Other performance parameters also showed that AODV–P performed better than AODV or OLSR in sub-optimal network environments due to the improved link lifetimes and lower routing overheads. Show more

Keywords: Mobile ad-hoc networks, density based probabilistic algorithm, nodes density, nodes connectivity management, broadcast management

DOI: 10.3233/JHS-2012-0450

Citation: Journal of High Speed Networks, vol. 18, no. 2, pp. 83-114, 2011

Authors: Kaddour, Mejdi | Tandjaoui, Amel Faiza

Article Type: Research Article

Abstract: We investigate in this paper the implications of scheduling and adaptive modulation and coding (AMC) on the performance of downlink traffic in OFDMA-based IEEE 802.16 cells. To this end, we model the downlink traffic as a discrete-time Markov chain by assuming exponential interarrival times of packets at the upstream of the unidirectional unbuffered connection maintained by the base station with each associated subscriber station (SS). Various performance metrics are derived by considering two usual scheduling policies: equal-slot sharing (ESS) and equal-throughput sharing (ETS). In particular, the estimated packet access delays provide a lower bound on the achieved delays in case …of buffering. Besides, our model considers the adaptivity of the modulation and coding schemes (MCSs) used by the base station. By assuming uniform distribution of the SSs over the cell and shadowing log-normal radio propagation, we derive the probability density function of the signal-to-noise ratios measured at the level of the SSs. Albeit defined in the context of WiMAX networks, this second contribution can be exploited in more generic wireless settings. Several numerical results are presented and discussed to expose the effects of system parameters and scheduling policies on performance. Show more

Keywords: IEEE 802.16, OFDMA, performance evaluation, Markov model, radio propagation, shadowing

DOI: 10.3233/JHS-2012-0451

Citation: Journal of High Speed Networks, vol. 18, no. 2, pp. 115-129, 2011

Authors: Sadish Sendil, M. | Nagarajan, N.

Article Type: Research Article

Abstract: The need of simple storage access, bandwidth and processing power of computers located at the edges of the network is highly required in advanced computing. Peer to Peer (P2P) satisfies the functional requirements of several applications. The searching of the content and file sharing is perhaps the most popular application of P2P networks. In this application, flooding is used as the prevailing resource location method for content searching and file sharing. Larger volume of unnecessary traffic in the network is created due to flooding mechanism. It is because a peer may receive the same queries multiple times through different paths. …In this paper, the performance of the searching is analyzed and improved using the proposed method namely Super-peer based Innovative Search (SPIS). In this method, the super-peer maintains the local peer's information; in addition it maintains other super-peer's information for reducing the unnecessary search in the P2P networks. During the searching, the number of query packets creates a local traffic inconsistency and congestion. Flooding a query to every peer significantly diminishes the performance and effectiveness of the system. Hence, the new method namely SPIS with Query Filtering is proposed. Here, the query is filtered based on the file availability in the forwarding super-peer for reducing the number of duplication query which reduces the query processing time. Hence, the performance of the P2P networks can be improved and thereby reduces traffic. Show more

Keywords: Peer to peer, flooding, super-peer, P2P traffic, super-peer based Innovative Search (SPIS)

DOI: 10.3233/JHS-2012-0452

Citation: Journal of High Speed Networks, vol. 18, no. 2, pp. 131-140, 2011