A Feasibility Study of Wireless Networks for 17 and 60 GHz and the Impact of Deployment Strategies on the System Performance

Abstract: This thesis addresses the question of how to deploy the infrastructure for wireless networks carrying high data rate services. It starts from the assumption that a major part of the costs for installing wireless infrastructure is caused by antenna site acquisition, planning of network coverage and capacity as well as manpower for setting up and wiring the antenna sites. Specific attention is therefore paid to simplifying the network installation and hence reducing the overall costs. The results show that the proposed user-deployment approach, where Access Points (APs) are set up by the customers themselves, can achieve coverage and data rates comparable to pre-planned networks with properly placed and wired APs. Typical for user-deployment is that APs are set up in an ad-hoc fashion, wherever wireless access is needed and a wired backbone infrastructure is available.A number of typical usage scenarios are developed for identifying characteristic situations and places where high data-rate applications are likely to be used. Service requirements and essential technical parameters are derived and motivated, based on these scenarios. A system design is proposed, featuring an air-interface with multi-carrier modulation and slow link-adaptation. Both coverage and capacity of this system, which achieves link-layer data rates between 40 and 130Mbps, are then studied in the different usage scenarios.The user-deployment approach, a core supposition in this thesis, requires the considered networks to be operated in an unlicensed fashion. Sufficient spectrum for unlicensed wireless services is allocated around 5, 17, 24 and 60GHz. The 5GHz band has been studied thoroughly in conjunction with the development of HiperLAN/2 and IEEE 802.11. This thesis focuses on the 17 and 60GHz bands and assumes that the performance of a system operating at 24GHz can be to some extent approximated from these results.An in-depth investigation of propagation properties at 17 and 60GHz shows that achievable cell radii are rather small. Shadowing severely impairs coverage and achievable data rates of a wireless network. A large number of APs is therefore necessary for providing sufficiently high signal levels to transmit high data rates. The shadowing problem is particularly severe for ad-hoc installations. Two different deployment scenarios and their impact on the system performance are investigated: arbitrary placed, wall-mounted APs and regularly placed, ceiling-mounted APs. The first represents the user-deployment paradigm and is certainly the cheapest method; the latter requires coarse network planning and suitable wiring and will hence be more costly.Results show that both installation methods achieve comparable performance for dense infrastructures, e.g. indoor environments. Since user-deployment is simpler and cheaper, it should be preferred in this case. Sparse networks are typical for large, open buildings or outdoor areas. In that case, regular installation should be favored, since cells typically overlap very little and achieving coverage is difficult. Consequently, some form of network planning is needed.The 60GHz band is best suited for indoor applications with a dense infrastructure, since achievable cell radii are very limited. However, very high data rates and capacities can be offered due to the large amount of bandwidth allocated at 60GHz. If capacity is less important, the 17GHz band should be preferred. The better propagation characteristics allow larger cells and fewer APs are required for reliable coverage, but the attainable network capacity is limited by the rather small amount of unlicensed spectrum.User-deployment is generally suitable for indoor applications. A slightly denser infrastructure will be required to compensate for the lack of network planning, but the costs for additional hardware will be likely insignificant compared to the potential savings by avoiding coverage planning and additional wiring.