1 / 7

Predictive and Adaptive Bandwidth Reservation for Hand-Offs in Cellular Networks

This paper proposes a solution to reduce hand-off drops in cellular networks by reserving bandwidth for hand-offs from adjacent cells. The solution includes predictive estimation of ongoing connections and adaptive adjustment of reserved bandwidth. Simulation results show that the proposed adaptive control outperforms static reservation methods.

chamilton
Download Presentation

Predictive and Adaptive Bandwidth Reservation for Hand-Offs in Cellular Networks

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Predictive and Adaptive Bandwidth Reservation for Hand-Offs in Cellular Networks • Goal: provide a probabilistic guarantee on connection hand-off drops as mobile user moves from one cell to another • Naïve solution: for no hand-off drops, reserve bandwidth in all cells a mobile/connection might pass through • Problem: bandwidth quickly consumed and new connection blocking probability increases • Proposed solution: a cell estimates aggregate bandwidth for hand-offs from adjacent cells, to be reserved and used solely for hand-offs, not new connection requests • Predictive: estimate directions and hand-off times of ongoing connections in each cell • Adaptive: dynamically adjust amount of reserved bandwidth to account for estimation inaccuracies and varying traffic/mobility conditions

  2. System Model • Cellular infrastructure with a wired backbone and base stations as access points to mobiles in their cells • A hand-off fails if new cell does not have sufficient bandwidth • Solution: reserve bandwidth in each cell for possible hand-offs from its adjacent cells • Simple admission control of new connection requests: sum of current bandwidths + new bandwidth <= cell capacity – reserved handoff bandwidth • Reserved handoff bandwidth can be static, but then can not effectively handle varying conditions • Want to update it in a predictive and adaptive way before performing the admission test • Note reserved handoff bandwidth is a target, not actual reserved bandwidth • A base station needs to communicate its hand-off load to other other base stations

  3. Hand-Off Estimation • A cell’s base station maintains quadruplets: Time when mobile moved from current cell Previous cell before entering current cell Next cell to which mobile moved Residence time in current cell • Give less weight to quadruplets observed long ago • For a given previous cell, compute probability of going to some next cell given residence time in current cell

  4. Bandwidth Reservation • Given current time and time elapsed in current cell, estimate probability of connection handing off to some next cell within a time (estimation) window • A cell can then estimate the bandwidth required in some next cell for its hand-offs, and inform this adjacent cell • A cell computes its total bandwidth to be reserved for hand-offs from all its adjacent cells • Large (small) estimation window may lead to over-reservation (under-reservation) • Keep track of the proportion of hand-off drops to total observed hand-offs • If it exceeds target, increase estimation window • Otherwise, decrease estimation window

  5. Admission Control • AC1: simple admission control done in current cell only • Problem: cell overloaded with hand-offs from adjacent cells • Solution AC2: check available bandwidths of adjacent cells as well as current cell • Cheaper solution AC3: consider some adjacent cells only; those which “appear” to be overloaded

  6. Simulations • 1-dimensional system (e.g. cars on a highway) • Voice and video connections • Poisson arrivals and exponentially-distributed cell residence times • Static reservation is not effective under varying conditions (voice ratio, mobile speed, offered load) • AC3 is effective in meeting target hand-off dropping probability • Reserved bandwidth increases with offered load, video ratio and user mobility speed increase • As hand-off drops increase, estimation window increases • AC1 gives the most hand-off drops • AC2 and AC3 perform similarly and are fair (i.e. almost same new connection blocking probability in all cells) • AC3 is a better choice since it is less complex

  7. Conclusions • Meet connection-level hand-off dropping requirements by predicting hand-offs and adapting the estimation interval • Robust admission control of new connections • Higher dimensional systems, more realistic mobility patterns, use of readily available path/direction information, routing/re-routing over the wired backbone, … • Hierarchical architecture?

More Related