In response to my posting The Short, Smart Play, and presentations I’ve made on the topic, a number of folks have asked what other key areas are seeing rapid growth (and thus opportunity). For those of us involved in the world of RF/Wireless, there are two key technologies which are going to continue to be utilized which we should have at least a fundamental understanding of: OFDM and MIMO.
Orthogonal Frequency Division Multiplexing (OFDM) and MIMO (Multiple Input, Multiple Output) are used in a number of wireless technologies including WLAN (802.11a/b/g), WiMAX (802.16) and LTE (Long Term Evolution, the 4G standard). Rather than focus on the applications, as in which technology is going to win the ‘4G war’ – LTE or WiMAX, focus on understanding the underlying technology and challenges.
In OFDM, the concept is the same regardless of application; data is divided into parallel streams at a reduced rate (which allows for longer symbol duration) and the bandwidth is divided into subcarriers upon which the data streams are modulated. There are a number of great OFDM tutorials and books on-line so I won’t write another one here, suffice it to say that if you understand the variables (i.e. subcarrier spacing, symbol duration, code type/rate, etc.) then it’s much easier to wrap you head around the details for a specific standard/application.
MIMO is a family of techniques for multi-antenna wireless transmission and reception that increases the achievable data throughput within the same occupied bandwidth, increases quality of communication, and allows dramatically increased spectral efficiency. The most popluar implementation is for WLAN, enabling the 802.11n compliant wireless modems we see more and more of. Understand the fundamentals of propagation delay, multipath fading and transfer function as it applies to combining multiple receivers and then the rest becomes much easier.
It reminds me of one of my Calculus professors who shared with me that many of his students did poorly in Calculus because they did not thoroughly grasp Algebra. In fact, he would often work a problem to a certain point then swipe the board with the chalk or whiteboard pen and declare, “and the rest is just algebra…” before moving on. You have no idea how badly I wanted to write this on my final exam instead of solving down to a final answer! 🙂
I’ll post some nice OFDM and MIMO tutorials on my website once I finished my latest recorded presentation: “The True Schematic – Understanding & Correcting for Component Behavior at High Frequencies”.
Ah, I almost forgot, one last technique to be familiar with…turbo coding. Again, there are a variety of flavors but, as Led Zeppelin says, “The song remains the same”. Here is a great book on the matter which I recommend to get you started.