Signal Processing for Communication Systems
An important consideration for propagation models are the existence of objects within what is called the first Fresnel zone. Fresnel zones, referenced in Figure 1 are ellipsoids with the foci at the transmitter and the receiver, where the path length between the direct path and the alternative paths are multiples of half-wavelength ($latex \lambda/2$). Rays … Read more
Modeling diffraction loss Propagation environments may have obstacles that hinder the radio transmission path between the transmitter and the receiver. Idealized models for estimating the signal loss associated with diffraction by such obstacles are available. The shape of the obstacles considered in these model are too idealized for real-life applications, nevertheless, these models can serve … Read more
Two-ray ground reflection: direct plus ground-reflected rays, breakpoint distance, and why path loss approaches 40 dB/decade at large range.
Outdoor propagation models involve estimation of propagation loss over irregular terrains such as mountainous regions, simple curved earth profile, etc., with obstacles like trees and buildings. All such models predict the received signal strength at a particular distance or on a small sector. These models vary in approach, accuracy and complexity. Hata Okumura model is … Read more
Pulse-shaping Lab path:Nyquist zero-ISI → Raised cosine → Matched filter + SRRC → Eye diagramsTool: RRC filter & bandwidth calculator Key focus: Let’s learn how to simulate matched filter receiver with square root raised cosine (SRRC) filter, for a pulse amplitude modulation (PAM) system. Simulation Model A basic pulse amplitude modulation (PAM) system as DSP … Read more
Introduction to precoding Intersymbol interference (ISI) is a common problem in telecommunication systems, such as terrestrial television broadcasting, digital data communication systems, and cellular mobile communication systems. Dispersive effects in high-speed data transmission and multipath fading are the main reasons for ISI. To maximize the capacity, the transmission bandwidth must be extended to the entire … Read more
Impulse response and frequency response of PR signaling schemes Consider a minimum bandwidth system in which the filter $latex H(f)$ is represented as a cascaded combination of a partial response filter $latex Q(f)$ and a minimum bandwidth filter $latex G(f)$. Since $latex G(f)$ is a brick-wall filter, the frequency response of the whole system $latex … Read more
Consider the generic baseband communication system model and its equivalent representation, shown in Figure 1, where the various blocks in the system are represented as filters. To have no ISI at the symbol sampling instants, the equivalent filter $latex H(f)$ should satisfy Nyquist’s first criterion. If the system is ideal and noiseless, it can be … Read more
Pulse-shaping Lab path:Nyquist zero-ISI → Raised cosine → Matched filter + SRRC → Eye diagramsTool: RRC filter & bandwidth calculator In digital communications, an eye diagram (or eye pattern) is one of the most intuitive and powerful diagnostic tools for evaluating signal quality. Formed by overlapping consecutive symbol traces of a modulated signal over a … Read more
Why SRRC is used at Tx and Rx: matched filtering, overall raised-cosine Nyquist pulse, roll-off α, and links to the RRC tool.