Uppsala universitet

Dynamic Reuse Partitioning Within Cells Based on Local Channel and Arrival Rate Fluctuations.

Mathias Johansson, Dirac Research AB

IEEE Transactions on Vehicular Technology, Vol. 57, no. 2, March 2008., pp. 1155-1165.   © IEEE


Outline:
Consider two base stations of a cellular wireless system that are opposite to each other in a traditional hexagonal cell pattern with 60 degree sectors. If both base stations use the same transmission bandwidth, there will be a considerable interference for users near the cell borders, whereas users close to either of the base stations will experience little, if any, interference from the other base station.

At some point, the interference levels become too high for the border users, and it would be better to set aside a certain part of the bandwidth for transmitting to these users using only one base station (or both, employing macrodiversity). That way, total system throughput would increase. The main problem that we will treat here lies in identifying the right amount of bandwidth to use for each transmission mode and dynamically adapting this amount according to the actual demand for capacity and supply thereof (which indirectly measures the interference levels) in different areas of the sector.

Abstract:
It is possible to improve the spectral efficiency of cellular systems by dynamically repartitioning the available band-width between different interfering and noninterfering subareas within and among sectors. Here, we investigate the problem of maximizing the expected system throughput in a two-sector area by dynamic bandwidth partitioning between two transmission modes:

  1. using bandwidth in the low-interference area near either of the base stations and
  2. using bandwidth for macrodiversity or single-base station transmission to avoid interference. Mode 2 is typically useful for giving users near the cell border higher bit rates.

The suggested solution adapts the bandwidth partitioning to reflect local transmission capacities and bandwidth demands. Thus, it automatically decides on whether both trans-mission modes should be used and how much bandwidth should be used in each mode.

The solution requires only limited knowledge of the future arrival rates and channel qualities and uses probability theory to find a robust bandwidth partitioning.

Finally, we discuss access control and when to switch a user between the transmission modes to achieve high spectral efficiency and some minimum average quality of service.

Related publications:
PhD Thesis by Mathias Johansson
IEEE Trans. IT paper on resource allocation under uncertainty using the maximum entropy principle.

Source:
Pdf (249K)

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