From the course: Introduction to Telecommunications: Standards, Networks, and Innovations

Multiplexing

From the course: Introduction to Telecommunications: Standards, Networks, and Innovations

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Multiplexing

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- [Instructor] Imagine trying to watch a live sports game on your phone, but the connection keeps freezing because multiple users are competing for the same bandwidth. What if there were a way to share the bandwidth efficiently? That's where OFDM, Orthogonal Frequency-Division Multiplexing, comes in. It ensures efficient and flexible use of frequency bandwidth. So what is OFDM? It is a technique used in communication systems where a carrier signal is divided into smaller subcarriers. Carrier signal is the main frequency used to transmit data. And OFDM, instead of using a single carrier to send all the data, this carrier is split into multiple subcarriers. And each subcarrier is closely spaced, but they don't interfere with one another due to their unique mathematical properties. Now, how the splitting helps: by splitting the data across multiple subcarriers, where OFDM makes the system more efficient and resistant to interference or noise. If one subcarrier is affected, the others can still deliver the data. Imagine it as a busy highway or carrier signal that is split into many lanes or subcarriers. Each lane carries a part of the traffic, allowing smoother and faster transportation without any congestion. OFDM helps to save bandwidth and reduces interference as compared to the traditional system where a guard band is required between signals to avoid interference. In OFDM, it removes the need for that gaps between signals or the guard bands by using orthogonality. This means each signal reaches its peak at specific times while others stays at zero so that they don't interfere with each other. Imagine people singing at different times during a song. Each person takes turns perfectly, so their voice don't overlap. Similarly, OFDM allows many signals to work together without interference, making it great for handling lots of data. In case of OFDM, all subcarriers are allocated to one user at the same time. Now, imagine if there are multiple users wanting to connect at the same time on the same network. That is where OFDMA, Orthogonal Frequency-Division Multiple Access comes into play. OFDMA improves on OFDM by letting multiple users share the same frequencies and times. Instead of giving one user a fixed lot, it divides the slots so anyone can use any available space. For example, a parking slot where cars can park in any empty spot instead of being assigned fixed spaces. This makes it easier to handle changing traffic and use space efficiently. Just like OFDMA makes network more flexible and efficient, this approach is particularly valuable in high-density areas, such as stadiums or airports, where many users need access at the same time. OFDMA ensures that resources are allocated efficiently so there is less congestion and more consistent services. OFDM and OFDMA help networks handle data efficiently. OFDM reduces interference by arranging signals orthogonally, while OFDMA enhances flexibility by enabling multiple user to share resources dynamically.

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