Understanding Interference and System Capacity in Cellular Communications — Lesson 5

This lesson covers the fundamental aspects of wireless communications. It begins with an introduction to the concept of wireless communication, explaining how it involves transmitting and receiving voice and data using electromagnetic waves in open space. The lesson then delves into the cellular concept, frequency planning, mobile radio propagations, and fading. It also discusses large scale path loss, multipath small scale fading, modulation techniques, channel coding, and multiple access. The lesson concludes with an introduction to wireless networking and wireless communication standards. It uses the example of GSM phones to illustrate various aspects of wireless communications.

Video Highlights

01:15 - Introduction to interference and system capacity in cellular communications.
03:04 - Overview of channel assignment strategies.
05:06 - Discussion on the effects of interference on voice and control channels.
06:09 - Introduction to co-channel interference (CCI) and adjacent channel interference (ACI).
10:33 - Introduction to multiple input multiple-output systems (MIMO) for interference reduction.
31:38 - Explanation of the worst case and average case scenarios for signal to interference ratio.
42:58 - Discussion on adjacent channel interference and the near far effect.
47:50 - Example of frequency separation for reducing adjacent channel interference.
51:44 - Conclusion and summary of the lecture.

Key Takeaways

- Interference is a major limiting factor in the performance of cellular radio systems, affecting capacity and increasing the number of dropped calls.
- Co-channel interference and adjacent channel interference are the two main types of interference in cellular communications.
- The signal to interference ratio impacts the number of users a system can support.
- Cell capacity and the reuse factor are interlinked - as the cluster size decreases, the capacity of the system increases.
- Erlang B and C formulas are used to calculate the probability of an arriving call being blocked or delayed.
- Interference reduction can be achieved through techniques like multiple input multiple-output systems and coding.
- Careful channel assignment can help reduce adjacent channel interference.