Another crucial issue is packet latency, or the time (in milliseconds) that it takes for a packet of video data (in this case) to move from a server up in the network down to the end device. With 3G service latency time can be around the 150 milliseconds, which is too much drag time for high-definition streaming media like video. Mobile HD video requires a fast and steady stream of packets moving down to the end device in order to remain "HD."

In 4G networks latency time is much less. For instance, Verizon's new 4G LTE service is showing latency numbers of around 40 milliseconds. That near instantaneous send-and-receive connection between the end device and the server, combined with much higher raw data speeds, creates a video image that looks rich in color, has obvious dimension, and handles movement in a smooth, liquid way. In short, it looks like what we know as HD video.

You will notice that many (if not most) of the new 4G handsets being announced today have front-facing cameras in addition to the camera on the back. We're even beginning to see a move from one-megapixel front-facing cameras to two-megapixel cameras, to increase the quality of the video of the caller being sent upstream through the network.

is a bit different from HD video streaming in that it is a real-time bi-directional application. Like HD video streaming, videoconferencing requires a certain threshold of download speed--preferably around 1 megabit per second--to pull down the moving image of the person on the other end from a server on the network. The real challenge, however, is upload speed. Because today's networks are configured to serve up far faster download speeds than upload speeds, and because videoconferencing requires adequate downlink and uplink speeds, slow upload speeds are often the bottleneck in sub-standard videoconferencing sessions.