Coverage Costs of One Amplify-and-Forward Relaying in Outdoors Urban Environment

The use of fixed relays has previously been shown to enhance the performance of cellular systems, e.g. in terms of improved bit-rate CDFs. Under the assumption that these relays are inexpensive, it has been argued that cellular-relaying architectures can provide high bit-rate services at low infrastructure costs. This paper addresses the question of how inexpensive must a relay be, by converting the performance gains of the relaying architecture into cost constraints. The analysis is numerically exemplified on a study case where 95% downlink outdoor coverage must be provided in an urban environment. The relays are (randomly) placed on lamp-posts along streets. The transmission power, height and gain of the base station antennas, and the complexity of the relaying scheme are used to model the cost-performance trade-off. In this coverage study case, the relay to base station cost ratio must be at most 2 - 15%, depending on the above parameters´ values. In the numerical examples, the relaying scheme type has much smaller impact on the cost ratio constraint than the base station antenna height and gain