Tom Wheeler, FCC chairman (the Federal Communications Commission, in other words the American mobile industry regulatory body) has recently written that he is asking fellow commissioners to begin investigating frequencies and technologies that may be suitable for 5G network technologies. So far, Tom has asked for research in the 24 GHz and higher frequency bands. Current mobile networks use frequency ranges from 700 MHz to 2.7 GHz and as we here at Android Headlines are always reminding our readers, the lower the frequency, the slower the theoretical data transfer speed but the better the penetration into buildings and solid objects. Networks such as Sprint appear to be planning on using lower frequency LTE coverage as a core network and areas with high frequency coverage for a quicker connection. The problem with using the 24 GHz and higher frequency bands is that the power output used by mobile technologies means, quite simply, the signal won’t go far.
Currently, these frequencies are often used for the infrastructure and backhaul systems: the parts of the network that interconnects masts and buildings with one another. However, these signals are carefully aligned and more powerful. Typical network sites have much broader beams. Some networks have already considered using these high frequencies for very short range (but high performance) cell sites. Such small sites would be a useful way to ensure that urban areas have good coverage, or where high capacity sites are needed such as at sports games and similar and we’ve written about unlicenced spectrum recently.
One of the ideas that has been mooted is to use massive arrays of antennas with beam shaping to send large numbers of parallel low power signals to handsets. These stacked low power signals would reinforce one another, which could be used to significantly increase the effective range. We have seen less sophisticated versions of this technique used across the mobile networks: T-Mobile USA uses four-antenna systems with its LTE networks and Sprint has started using eight-antenna systems for the higher speed Spark network. Samsung have experimented with 64 antenna arrays that achieved a data throughput of 1 Gbps over a mile. There are, of course, problems with this technique, including how to disguise a large, ugly block of antennas! Another plan that has been discussed is to significantly increase the number of cell sites (several in a room) to provide coverage across a very small distance, which could be combined with devices that may connect with multiple networks and cell sites at the same time. We expect the networks to use a combination of different techniques.
One final point from the FCC chairman’s blog is that he is proposing rule changes that could make it much simpler to deploy short range LTE sites – masts hanging from lamp posts, street furniture and similar. These are currently used to provide continuous coverage in city centers or inside large buildings; their deployment should make the mobile data experience much smoother and is a key enabler for technologies such as VoLTE (voice-over-LTE, a way of making and receiving voice calls over the data network, which will ultimately provide a better experience for customers and reduce carrier costs).