11,417 research outputs found
An Adaptive Algorithm to Optimize the Dynamics of IEEE 802.15.4 Networks
Presentado en ICST 2013IEEE 802.15.4 standard is becoming one of the most popular technologies for the deployment of low rate Wireless Personal Area Networks with strong power constraints. In order to reduce the energy consumption, beacon-enabled networks with long network inactive periods can be employed. However, the duration of these inactivity periods, as some other configuration parameters, are conventionally set to default values and remain fixed during the whole network operation. This implies that if they are misconfigured the network will not adapt to changes in the conditions of the environment, particularly to the most determining one, i.e. the traffic load. This paper proposes a simple procedure for the dynamic adaptation of several key parameters of IEEE 802.15.4 networks. Under this procedure, the 802.15.4 parameters are modified as a function of the existing traffic conditions.Spanish National Project No.TEC2009-13763-C02-01
Performance analysis of carrier aggregation for various mobile network implementations scenario based on spectrum allocated
Carrier Aggregation (CA) is one of the Long Term Evolution Advanced (LTE-A)
features that allow mobile network operators (MNO) to combine multiple
component carriers (CCs) across the available spectrum to create a wider
bandwidth channel for increasing the network data throughput and overall
capacity. CA has a potential to enhance data rates and network performance in
the downlink, uplink, or both, and it can support aggregation of frequency
division duplexing (FDD) as well as time division duplexing (TDD). The
technique enables the MNO to exploit fragmented spectrum allocations and can be
utilized to aggregate licensed and unlicensed carrier spectrum as well. This
paper analyzes the performance gains and complexity level that arises from the
aggregation of three inter-band component carriers (3CC) as compared to the
aggregation of 2CC using a Vienna LTE System Level simulator. The results show
a considerable growth in the average cell throughput when 3CC aggregations are
implemented over the 2CC aggregation, at the expense of reduction in the
fairness index. The reduction in the fairness index implies that, the scheduler
has an increased task in resource allocations due to the added component
carrier. Compensating for such decrease in the fairness index could result into
scheduler design complexity. The proposed scheme can be adopted in combining
various component carriers, to increase the bandwidth and hence the data rates.Comment: 13 page
TCP over CDMA2000 Networks: A Cross-Layer Measurement Study
Modern cellular channels in 3G networks incorporate sophisticated power control and dynamic rate adaptation which can have significant impact on adaptive transport layer protocols, such as TCP. Though there exists studies that have evaluated the performance of TCP over such networks, they are based solely on observations at the transport layer and hence have no visibility into the impact of lower layer dynamics, which are a key characteristic of these networks. In this work, we present a detailed characterization of TCP behavior based on cross-layer measurement of transport layer, as well as RF and MAC layer parameters. In particular, through a series of active TCP/UDP experiments and measurement of the relevant variables at all three layers, we characterize both, the wireless scheduler and the radio link protocol in a commercial CDMA2000 network and assess their impact on TCP dynamics. Somewhat surprisingly, our findings indicate that the wireless scheduler is mostly insensitive to channel quality and sector load over short timescales and is mainly affected by the transport layer data rate. Furthermore, with the help of a robust correlation measure, Normalized Mutual Information, we were able to quantify the impact of the wireless scheduler and the radio link protocol on various TCP parameters such as the round trip time, throughput and packet loss rate
A low complexity resource allocation algorithm for multicast service delivery in OFDMA networks
Allocating and managing radio resources to multicast transmissions in Orthogonal Frequency-Division Multiple Access (OFDMA) systems is the challenging research issue addressed by this paper. A subgrouping technique, which divides the subscribers into subgroups according to the experienced channel quality, is considered to overcome the throughput limitations of conventional multicast data delivery schemes. A low complexity algorithm, designed to work with different resource allocation strategies, is also proposed to reduce the computational complexity of the subgroup formation problem. Simulation results, carried out by considering the Long Term Evolution (LTE) system based on OFDMA, testify the effectiveness of the proposed solution, which achieves a near-optimal performance with a limited computational load for the system
Buffer Sizing for 802.11 Based Networks
We consider the sizing of network buffers in 802.11 based networks. Wireless
networks face a number of fundamental issues that do not arise in wired
networks. We demonstrate that the use of fixed size buffers in 802.11 networks
inevitably leads to either undesirable channel under-utilization or unnecessary
high delays. We present two novel dynamic buffer sizing algorithms that achieve
high throughput while maintaining low delay across a wide range of network
conditions. Experimental measurements demonstrate the utility of the proposed
algorithms in a production WLAN and a lab testbed.Comment: 14 pages, to appear on IEEE/ACM Transactions on Networkin
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