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The second trend in WiFi is the development of high-efficiency WLANs. WiFi has become so ubiquitous that it is being deployed in dense, high-interference environments, such as airports and office buildings. Use in such environments usually results in lower-than-expected data rates and sluggish performance. For example, WiFi users may experience a WiFi network crash at a tradeshow or other even where the presence of a large number of WiFi devices leads to high interference.

This is because, traditionally, IEEE 802.11 standards have focused on point-to-point link data rate improvements in an indoor network consisting of a single access point and a few clients working under light external interference. This objective needs to be amended to consider total system throughput and fairness, given the market reality of denser indoor and outdoor deployments.

Five Trends Shaping 802.11 WLANs, Table 2

To address this, the IEEE formed a new IEEE 802.11 study group (SG) called High-Efficiency WLAN (HEW) in July 2013.3 The efforts of this study group are expected to lead to the next major evolution of the IEEE 802.11 standard after IEEE 802.11ac. Table 2 compares the key differences in objective between the HEW SG and past IEEE 802.11 efforts. The HEW SG will consider both PHY innovations [such as orthogonal frequency division multiple access (OFDMA) modulation] and uplink MU-MIMO and MAC innovations [such as interference management and dynamic sensitivity control]. The initial target of the HEW SG is to improve average throughput per station by at least 4× in dense deployments.

Update: After this article was published, HEW SG completed its feasibility study. The IEEE standard board moved the effort to the next stage and officially created task group IEEE 802.11ax. This task group will discuss technical solutions needed to meet HEW requirements and reach consensus on updates to the IEEE 802.11 standard.

A HEW Use Case

The cellular ecosystem is preparing for increases of as much as 1000× over present demand in cellular data traffic in future Long-Term-Evolution (LTE) and Fifth-Generation (5G) cellular networks.4 Given this expected volume, offloading some user traffic to a WiFi network represents an attractive solution to meet this data demand. As a result, cellular carriers around the world are deploying or partnering with WiFi networks.

Five Trends Shaping 802.11 WLANs, Fig. 2

Figure 2 shows a simplified example of a next-generation heterogeneous cellular network with integrated WiFi. In addition to the traditional wide-area macrocell tower, the network includes a dense network of indoor and outdoor small cells with varying range servicing areas of high handset density (“hotspots”) such as downtown neighborhoods. Most of the small cells will have integrated cellular and WiFi access-point capabilities, but some may be WiFi- or cellular-only cells.

The network will cooperatively make decisions (e.g., when to offload a user from cellular to WiFi) to meet data traffic demand. In hotspots, it is beneficial to have a very dense deployment. However, carriers have found that efficient scaling of a network based on current WiFi technology is challenging in dense scenarios and, hence, the interest in HEW SG.

There are other pieces to the “carrier-grade WiFi” puzzle, such as RF coexistence testing, integration with cellular network infrastructure, and optimizing handoffs between WiFi and cellular networks. The WiFi Alliance is working on a first version of carrier-grade WiFi certification based on existing WiFi technologies and some incremental changes. But, if HEW SG is successful, it has the potential to revolutionize the performance of carrier-deployed WiFi and beyond.

Internet of Things

The third trend influencing the future of WiFi is the exponential growth expected in the Internet of Things (IoT) and machine-to-machine (M2M) communications. Wireless connectivity is seen as an important enhancement for the sensors and meters used in markets such as smart grid, healthcare, fitness, consumer wearable devices, and industrial monitoring.

IEEE 802.11ah defines a lower-power version of WLAN to better address these use cases. To reduce power requirements, IEEE 802.11ah adds support for lower bandwidths (1 and 2 MHz are mandatory modes), lower data rates (typically less than 2 Mb/s), and uses unlicensed spectrum in the 900-MHz range. MAC layer enhancements in IEEE 802.11ah improve power save modes and network scalability. As a result, access points can support a huge number of very low rate sensors efficiently. An example use case is in smart grids, where IEEE 802.11ah access points attached to electric utility poles connect wirelessly to sensors/meters in nearby homes to collect information on energy usage. The instantaneous information provided can be used for customer billing purposes and to improve power grid performance.

Intelligent Transport Systems

The fourth trend impacting WiFi is the use of intelligent transport systems and the growing application of IEEE 802.11p. The IEEE 802.11p amendment supports vehicle-to-vehicle and vehicle-to-infrastructure communications for intelligent transport system applications. Regulators in the European Union (EU) and in the US have designated spectrum near 5.9 GHz for this application.5 In the US, this spectrum is typically referred to as dedicated short-range communications (DSRC) spectrum.

Five Trends Shaping 802.11 WLANs, Fig. 3

Figure 3 shows an example use case, where the IEEE 802.11p enabled automobiles and traffic infrastructure (e.g., a traffic light) cooperate to avoid any potential collisions in the intersection. Other vehicular safety use cases include such functions as forward collision warning, blind spot warning, etc.

A model deployment of the collision-avoidance system was launched in Ann Arbor, MI by the US Department of Transportation in the Fall of 2012 using a pool of 3000 cars.6 Based on the positive results of this trial, the Department of Transportation announced in February 2014 that it is working on regulations to require this technology in light vehicles such as personal automobiles.

In the future, additional pieces of intelligent transport systems could be enabled, such as connected real-time traffic rerouting, dynamic lane management, etc. Considering the recent research interest in driverless cars, the potential of intelligent transport systems and IEEE 802.11p appears even more promising.

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