Interference Reduction in Single Hop Relay Networks.pdfVIP

Interference Reduction in Single Hop Relay Networks Marcus Bronzel, Wolfgang Rave, Patrick Herhold, Gerhard Fettweis Mannesmann Mobilfunk Chair for Mobile Communications Dresden University of Technology, Helmholtzstrasse 18, D–01062 Dresden, Germany bronzel@ifn.et.tu-dresden.de Abstract The purpose of this paper is to determine the possible capacity increase in single hop relay net- works, where mobile stations are enabled to serve as additional access points for other terminals. The total power used for direct transmission from a central base station to uniformly distributed mobiles is compared with indirect transmission using mobiles as relay nodes for different path loss exponents. The relative decrease in transmitted power is calculated as a function of the number of mobiles. Exact solutions of the permutation problem are compared with approximations which can be obtained with acceptable numerical effort. The analysis for a single cell is carried out assum- ing a circular cell geometry, while interference level simulations are performed on a hexagonal cellular structure. The resulting interference powers are used to estimate the capacity gains in CDMA systems for both uplink and downlink. 1 Introduction It is generally expected, that the overall system capacity is increased in single hop relay (SHR) networks, where mobile terminals can provide ad- ditional access points for other terminals. A mo- bile is termed a relay station (RS), if it serves as a repeater for a target mobile while simultaneously performing its own communication with the base station. The purpose of this paper is to determine the possible capacity increase in SHR-networks. 1 1 This work has been sponsored under the HyperNET Re- search Focus of the German Ministry of Education, Research, and Technology. Starting with a geometrically based analysis, the required average transmit power for SHR is compared to the power needed for direct trans- mission. After considering the asymptotic reduc- tion