This post summarizes some of the content from the author’s “Usage of Millimeter Wave Frequencies for 5G Systems” presentation during the Antenna Evolution Focus Day at 5G North America in Austin, Texas.
The 4G throughput target of 1 Gbps is now being approached through the use of carrier aggregation and MIMO antenna technologies. For 5G, the new target is 10 or 20 times greater.
To reach a throughput speed of 20 Gbps, larger channel bandwidths are required, and this means using millimeter wave (mmWave) spectrum
in the extremely high frequency range above 6 GHz. In the US, the FCC is making mmWave spectrum available at 28 GHz and 39 GHz. At these higher frequencies, operators could see 400 MHz, 800 MHz, or up to 1 GHz of additional bandwidth for their networks. For comparison, the typical operator today has just over a 100 MHz of aggregate channel bandwidth in their network.
The behavior of signals at these higher frequencies has profound implications for radio system and antenna designs. For example, compared to cellular frequencies in use today, the propagation loss of mmWave is greater, the ray scattering is lower, and the building penetration is shallower. Therefore, cell sizes will be smaller and the links will be line of site. MIMO will be used, in fact it will be Massive MIMO, which requires antennas that have 64 or more elements. These antennas will be quite small by today’s standards. They will use analog beamforming that is more akin to the “smart antennas” of the 1990’s rather than the digital MIMO ubiquitous to LTE.
While 5G mmWave will eventually be used for mobility, its first application will be for fixed wireless access, that is, broadband to the home. Internet service providers will deliver Gbps speeds to homes in the service area of a beamsteering mmWave access point. Multiple homes will share the resources of the beam’s “data pipe” as it quickly hops from home-to-home streaming bits.
In contrast, for a mobile system, a moving user will be tracked and served by a beam from a particular base station until that beam is blocked and service is interrupted. Communication will be reinstated from a beam transmitted from another antenna that has an unobstructed path. These beam handovers will be more infrequent than the fast beam scanning implemented in a fixed wireless system.
To see the beam motions compared, check out our new video “mmWave massive MIMO for wireless and broadband.”