Minimising interference in wireless networks
In order to increase quality of service (QoS) and decrease price, engineers must increase the spectral efficiency and reduce interference. Spectral efficiency refers to the total information throughput over a given bandwidth (or corresponding frequency range). Different cells use different frequencies to minimise interference. Re-using frequencies of transmission is one way to increase coverage and capacity but it is plagued by inter-cell interference (ICI). Scientists explored techniques to manage the trade-off between spectral efficiency and ICI through cooperation among base stations with EU funding of the project 'Interference management techniques for multicell wireless networks' (INTERCELL). Full cooperation schemes require sharing of tremendous amounts of information, increasing data loads. INTERCELL therefore focused on partially cooperative paradigms requiring only users' channel state information (CSI). CSI contains the channel properties of the communication link that can be used for optimisation under various conditions. While adaptive feedback is useful for modifying resource allocation without a central unit, the feedback can in itself become a huge load and source of 'noise'. Project partners developed adaptive techniques with limited feedback and partial cooperation among base stations. To enable energy- and spectral-efficient wireless telecommunications systems, several steps were taken. This included reductions in the complexity of user-scheduling combined with an effective power minimisation algorithm and an algorithm to reduce the user feedback load. Designs reduced the feedback load by 50 % and up to 150 % improvement in the capacity of enhanced cell edge networks was achieved. INTERCELL has made important progress in addressing the speed, cost and quality issues faced by future wireless telecommunications services. Sharing frequencies among base stations together with reduced feedback load and power consumption will meet user demands for minimal interference at reasonable cost.
