ABSTRACT
Channel Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3 System-Dependent Channel Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.1 General Description of Multipath Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.3.2 Impact of Antenna Directivity and System-Operating Frequency
on Channel Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.4 DAS Topology and Channel Models. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.5 DIV and DOF in Degenerate SCSB Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.5.1 Diversity Gain Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 1.5.2 Degrees-of-Freedom (DOF) Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.6 Complete Model: Multiple-Cluster Multiple-Bounce (MCMB) Channels with Imperfect Receiver Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 1.6.1 Diversity Gain Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 1.6.2 Degrees-of-Freedom Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
1.7 Numerical Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 1.7.1 SCSB Channels with Perfect Receiver Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . 25 1.7.2 SCSB Channels with Imperfect Receiver Conditions . . . . . . . . . . . . . . . . . . . . . . . 27 1.7.3 MCMB Channels with Imperfect Receiver Conditions . . . . . . . . . . . . . . . . . . . . . . 27
1.8 Summary and Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Distributed antenna system (DAS) is a new architecture for future public wireless access, which refers to a generalized multiple-input multiple-output (MIMO) system comprising an antenna array at one side of the link and several largely separated antenna arrays at the other side. With DASs, both diversity and multiplexing gains can be achieved. This chapter presents formulation of diversity (DIV) and degrees-of-freedom (DOF) for a
system-dependent wireless channel by taking a microscopic view of the two measures. As an initial study, we will consider a simple network topology and DAS architecture. Starting with a degenerate single-cluster single-bounce (SCSB) channel and perfect receiving conditions, the analysis is extended to more general scattering and receiver-operating scenarios. The utility of the proposed methodology is demonstrated by presenting various numerical examples to provide insight into the impact of the signal power spectrum on the DIV and DOF estimates. The chapter is concluded by identifying some important open issues in DAS channel measurement and modeling, DIV-DOF tradeoff, and design of an advanced signaling scheme under the rubric of “system-dependent channel modeling.”
