861 research outputs found
Performance analysis of downlink shared channels in a UMTS network
In light of the expected growth in wireless data communications and the commonly anticipated up/downlink asymmetry, we present a performance analysis of downlink data transfer over \textsc{d}ownlink \textsc{s}hared \textsc{ch}annels (\textsc{dsch}s), arguably the most efficient \textsc{umts} transport channel for medium-to-large data transfers. It is our objective to provide qualitative insight in the different aspects that influence the data \textsc{q}uality \textsc{o}f \textsc{s}ervice (\textsc{qos}). As a most principal factor, the data traffic load affects the data \textsc{qos} in two distinct manners: {\em (i)} a heavier data traffic load implies a greater competition for \textsc{dsch} resources and thus longer transfer delays; and {\em (ii)} since each data call served on a \textsc{dsch} must maintain an \textsc{a}ssociated \textsc{d}edicated \textsc{ch}annel (\textsc{a}-\textsc{dch}) for signalling purposes, a heavier data traffic load implies a higher interference level, a higher frame error rate and thus a lower effective aggregate \textsc{dsch} throughput: {\em the greater the demand for service, the smaller the aggregate service capacity.} The latter effect is further amplified in a multicellular scenario, where a \textsc{dsch} experiences additional interference from the \textsc{dsch}s and \textsc{a}-\textsc{dch}s in surrounding cells, causing a further degradation of its effective throughput. Following an insightful two-stage performance evaluation approach, which segregates the interference aspects from the traffic dynamics, a set of numerical experiments is executed in order to demonstrate these effects and obtain qualitative insight in the impact of various system aspects on the data \textsc{qos}
Optimal Power Control and Scheduling under Hard Deadline Constraints for Continuous Fading Channels
We consider a joint scheduling-and-power-allocation problem of a downlink
cellular system. The system consists of two groups of users: real-time (RT) and
non-real-time (NRT) users. Given an average power constraint on the base
station, the problem is to find an algorithm that satisfies the RT hard
deadline constraint and NRT queue stability constraint. We propose a
sum-rate-maximizing algorithm that satisfies these constraints. We also show,
through simulations, that the proposed algorithm has an average complexity that
is close-to-linear in the number of RT users. The power allocation policy in
the proposed algorithm has a closed-form expression for the two groups of
users. However, interestingly, the power policy of the RT users differ in
structure from that of the NRT users. We also show the superiority of the
proposed algorithms over existing approaches using extensive simulations.Comment: Submitted to Asilomar 2017. arXiv admin note: text overlap with
arXiv:1612.0832
Wireless Cellular Networks
When aiming for achieving high spectral efficiency in wireless cellular networks, cochannel interference (CCI) becomes the dominant performancelimiting factor. This article provides a survey of CCI mitigation techniques, where both active and passive approaches are discussed in the context of both open- and closed-loop designs.More explicitly, we considered both the family of flexible frequency-reuse (FFR)-aided and dynamic channel allocation (DCA)-aided interference avoidance techniques as well as smart antenna-aided interference mitigation techniques, which may be classified as active approach
Life-Add: Lifetime Adjustable Design for WiFi Networks with Heterogeneous Energy Supplies
WiFi usage significantly reduces the battery lifetime of handheld devices
such as smartphones and tablets, due to its high energy consumption. In this
paper, we propose "Life-Add": a Lifetime Adjustable design for WiFi networks,
where the devices are powered by battery, electric power, and/or renewable
energy. In Life-Add, a device turns off its radio to save energy when the
channel is sensed to be busy, and sleeps for a random time period before
sensing the channel again. Life-Add carefully controls the devices' average
sleep periods to improve their throughput while satisfying their operation time
requirement. It is proven that Life-Add achieves near-optimal proportional-fair
utility performance for single access point (AP) scenarios. Moreover, Life-Add
alleviates the near-far effect and hidden terminal problem in general multiple
AP scenarios. Our ns-3 simulations show that Life-Add simultaneously improves
the lifetime, throughput, and fairness performance of WiFi networks, and
coexists harmoniously with IEEE 802.11.Comment: This is the technical report of our WiOpt paper. The paper received
the best student paper award at IEEE WiOpt 2013. The first three authors are
co-primary author
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