141 research outputs found
QoS and channel-aware packet bundeling for capacity improvement in cellular networks
We study the problem of multiple packet bundling
to improve spectral efficiency in cellular networks. The packet
size of real-time data, such as VoIP, is often very small. However,
the common use of time division multiplexing limits the number
of VoIP users supported, because a packet has to wait until it
receives a time slot, and if only one small VoIP packet is placed
in a time slot, capacity is wasted. Packet bundling can alleviate
such a problem by sharing a time slot among multiple users. A
recent revision of cdma2000 1xEV-DO introduced the concept
of the multi-user packet (MUP) in the downlink to overcome
limitations on the number of time slots. However, the efficacy
of packet bundling is not well understood, particularly in the
presence of time varying channels. We propose a novel QoS and
channel-aware packet bundling algorithm that takes advantage
of adaptive modulation and coding. We show that optimal
algorithms are NP-complete, recommend heuristic approaches,
and use analytical performance modeling to show the gains
in capacity that can be achieved from our packet bundling
algorithms. We show that channel utilization can be significantly
increased by slightly delaying some real-time packets within their
QoS requirements while bundling those packets with like channel
conditions. We validate our study through extensive OPNET
simulations with a complete EV-DO implementation.Supported in part by U.S. National Science Foundation under grant no. 072971
Analytical evaluation of higher order sectorization, frequency reuse, and user classification methods in OFDMA networks
Higher order sectorization (HOS), which splits macrocells into a larger number of smaller sectors, are receiving significant interest as a cost-effective means of improving network capacity. Potentially, the capacity gain with HOS is proportionally linear to the number of sectors per cell due to spatial reuse, but factors such as non-ideal antenna radiation patterns together with inter-cell interference can significantly reduce this capacity gain. We develop a statistical model to theoretically characterize the performance of HOS deployments in wireless networks using orthogonal frequency division multiple access. Moreover, a fractional frequency reuse scheme is considered, which aids to mitigate inter-cell interference. The model provides a fast and effective tool for studying network performance in terms of user signal quality, site throughput, and outage probability, and it can be used to speed up network planning and optimization. In addition, we consider the impact of user classification methods in the analysis, and propose a new spectrum efficiency-based user classification method that improves resource utilization and allocation fairness. Performance results indicate that the proposed model is accurate, and shows a diminishing performance gain of HOS deployments with the number of sectors. The proposed user classification method improves network performances with respect to the state-of-the-art approaches
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