Lehrinhalte
The learning content includes:
- A brief overview of typical wireless communications scenarios, the main challenges and differences when compared with wired communications
- Wireless channel as a time-varying linear system (time-varying impulse response), large-scale and small-scale fading, multi-path fading, existing approaches to modeling of wireless channels
- Basic principles of stochastic modeling for wireless channels, Rayleigh and Rician channels, log-normal shadowing
- Time-frequency correlation functions, wide-sense stationary uncorrelated scattering model, Doppler spread and coherence time, delay spread and coherence bandwidth, flat versus frequency-selective fading
- Performance measures used in wireless communications: signal-to-noise ratio, rate, ergodic capacity, outage capacity, delay-limited capacity
- Definitions of time, frequency and spatial diversity, other notions of diversity
- Some basic diversity techniques including repetition coding, maximal ratio combiner (RAKE receiver), receive antenna diversity (SIMO), transmit antenna diversity (MISO), the impact of channel state information
- Principles of spread-spectrum techniques and orthogonal frequency division multiplexing (OFDM)
- Basic multiaccess techniques including TDMA, FDMA, DS-CDMA and OFDMA
- Random access techniques including traditional ALOHA/slotted ALOHA and contemporary solutions based on coded random access
- Enabling technologies for massive connectivity and efficient spectrum utilization, including massive MIMO systems and cloud-radio access networks (C-RANs)
- Tradeoffs between throughput, reliability and latency in emerging communication scenarios including massive machine-type communications (mMTC), and ultra-reliable low-latency communications (URLLC)
- Mathematical methods that are used to solve many real-world problems in modern wireless communications systems/networks. As concrete applications that are in the focus of the lectures, we cite interference reduction in spread spectrum and MIMO systems, adaptive beamforming, PAPR reduction in OFDM systems. In particular, a special attention is attached to the following topics: basic principles of (functional) analysis that are relevant in the design of modern communications systems, fundamentals of matrix analysis, fundamentals of (convex) optimization theory, Bayesian inference, graphical models, projection methods, principles of convex relaxation, algorithm design, convergence properties.
