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Wireless-local-area-networks (WLANs) based on WiFi technology have become a standard part of life for many, whether integrated within a home television or a radio-controlled drone helicopter. The latest commercially available version of WiFi, based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11ac standard, provides significant connectivity improvements. In addition, it is driving upgrades in consumer and enterprise markets from earlier versions, such as IEEE 802.11n. As the use of WLANs has grown, so have feature requests, helping to drive the evolution of WiFi more rapidly than ever.  

The “WiFi” brand name popularized by the WiFi Alliance refers to products based on the IEEE 802.11 family of WLAN standards.1 The IEEE 802.11 standard was first approved in 1997. Subsequent amendments added innovations such as orthogonal frequency division multiplexing (OFDM; from IEEE 802.11a) and multiple-input, multiple-output (MIMO) antenna systems (from IEEE 802.11n) to keep up with market requirements.

As Table 1 shows, the theoretical peak physical layer (PHY) data rate supported by the standard has increased by more than 100× over the past decade: from 54 Mb/s in IEEE 802.11g to 6.9 Gb/s in IEEE 802.11ac. Although these PHY rates do not directly translate to data throughput due to channel access and protocol overheads, improvements in the IEEE 802.11 medium access control (MAC) layer (such as packet aggregation and block acknowledgments) enable present-day IEEE 802.11 devices to achieve 70% to 80% efficiency.2 Improvements in data rate are not the only trend in WiFi evolution. What follows is a review of five important trends expected to shape the WiFi ecosystem over the next decade.

Five Trends Shaping 802.11 WLANs, Table 1

IEEE 802.11ac

The first trend involves the market rollout of products based on the IEEE 802.11ac wireless standard.  The current wave of IEEE 802.11ac products is part of release 1, which added support for wider 80-MHz bandwidth with as many as three MIMO spatial streams, per-frame dynamic bandwidth selection, and higher-order modulation operation, in the form of 256-point quadrature amplitude modulation (256QAM).  In addition, IEEE 802.11ac simplifies and improves a number of features present in IEEE 802.11n, such as transmit beam forming.2 Based on a 3×3 MIMO configuration with 80-MHz bandwidth, the present-day typical release 1 IEEE 802.11ac access point supports a peak PHY data rate of 1.3 Gb/s.

Five Trends Shaping 802.11 WLANs, Fig. 1

Release 2 devices for IEEE 802.11ac are anticipated to support even wider bandwidth (160 MHz) operation and four MIMO spatial streams. Release 2 is also likely to support downlink (DL) multiuser (MU) MIMO (DL MU-MIMO). As illustrated in Fig. 1, today’s WiFi access point can only support one client at a time using single-user MIMO (SU-MIMO) operation. Since devices such as laptop computers and smartphones usually support only one or two antennas and most IEEE 802.11ac access points support three or four antennas, this leads to a “waste” of MIMO resources and lower throughput.

MU-MIMO, also shown in Fig. 1, allows the access point to use spatial separation to send data to multiple clients at the same time and fully utilize its MIMO capabilities. MU-MIMO in IEEE 802.11ac is limited to the “downlink” direction—i.e., for data packets sent from the access point.

MU-MIMO has the potential to increase network capacity since it minimizes packet collisions, reduces network usage, and reduces interference to neighboring networks. Note, however, that performance improvements due to MU-MIMO can vary drastically depending upon the spatial distribution of devices and data traffic patterns.

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