Wi-Fi HaLow：我为物联网而生

作为一种无线电技术，Wi-Fi让数码设备不需依靠蜂窝网络就能连接互联网。用不了多久，我们新购入的数码产品就能使用一种新型Wi-Fi了。这种新型Wi-Fi并非为这些数码产品专门设计，而是为我们家里，甚至我们身上的互联设备网络量身打造的。这些设备都将是物联网的组成部分。

Wi-Fi联盟把这种新标准称为Wi-Fi HaLow（发音为“哈喽”），称其传输距离是传统Wi-Fi的两倍，耗能也有所降低。当下，构建智能城市的主要是专有标准化网络和蜂窝网络，而可穿戴设备的个人网络则由蓝牙无线主导，Wi-Fi联盟很乐于看到Wi-Fi成为这些领域的新标准。

到目前为止，Wi-Fi联盟在新标准的耗电量、传输距离和传输数据量大小（速度）等细节上语焉不详。他们只透露这种新标准将使用900兆赫兹的频率，这一频段目前属于未授权频段，被用于微波炉、婴儿监控器和其他无线设备上。这意味着Wi-Fi将会有三个工作频段：2.4GHz频段、5GHz频段和900MHz频段。

然而，HaLow现在和未来都只会有900MHz这个工作频段。这主要是因为这个频段在穿透墙壁和远距离传输方面表现出色，满足了“远距离传输”的前景，不过在耗能上，人们依旧莫衷一是，因为这也是Wi-Fi应用于物联网的最大问题。许多物联网设备都是电池供电，而Wi-Fi则是著名的电量杀手，也就是说大部分厂商都不会在感应器、可穿戴设备、以及其它无法安装大型电池却需要长时间工作的设备上使用Wi-Fi。

当HaLow2015年以802.11ah【这是电气与电子工程师协会（IEEE）的标准名，而不是Wi-Fi联盟的品牌名】的名字开发时，几家芯片公司的工程师对它宣称的低能耗半信半疑。Moor Insights and Strategy公司的分析师帕特里克•摩尔海德表示：“联盟对细节的表述不太清楚，所以，我有点怀疑他们能否实现功耗和传输速度的目标，否则，他们就是在吹牛了。”

不过Wi-Fi联盟确实公布了HaLow的数据传输速率，大约是每秒150KB到18MB，这比传统的Wi-Fi要慢得多。如果带宽足够，传统Wi-Fi的传输速率可以达到每秒1GB。一般来说，耗能越高、干扰越弱，数据传输速率就越快。考虑到一般的家庭环境中，900MHz频段的使用量就如同早上7点星巴克的人一样多，所以想要保持高速率可能很难。当然，在物联网中没必要传输大量数据，所以，这一点可能并不太重要。耗能、可靠性和传输距离才是更重要的指标。

这一标准直到2018年才会正式使用，不过相关设备将会在今年晚些时候面世。我们很快就能看到Wi-Fi HaLow究竟有多么强大和实用。（财富中文网）

译者：严匡正

审校：任文科

Soon your new gadgets will come with a new flavor of Wi-Fi, the radio technology that allows your digital devices to connect to the Internet without blowing through your cellular data cap. This new version isn’t designed for these gadgets, however. Instead, it will be made for the network of connected devices in your home ― and even on your body ― that make up the Internet of Things.

The Wi-Fi Alliance calls this new standard Wi-Fi HaLow (pronounced halo), and says it doubles the distance and cuts the power consumption of traditional Wi-Fi. The Alliance would like to see Wi-Fi become a standard in smart cities where proprietary standards and cellular networks currently reign supreme, and in personal area networks for wearable devices where Bluetooth radios are used now.

So far, the Wi-Fi Alliance is being pretty vague on the details about the new standard in terms of how much power it will consume, how far it will travel, and how much data it will be able to transfer (and how quickly). It does say that the new standard will use the 900 megahertz spectrum, which is currently unlicensed and used by microwave ovens, baby monitors and all sorts of other wireless devices. This means Wi-Fi will now work in three bands; the 2.4 GHz band, the 5 GHz band and the 900 MHz band.

However, HaLow only works in the 900 Mhz band and will do so primarily because that band is great for penetrating walls and going further. So that covers the ‘going the distance’ part, but the jury is still out on the power consumption part, which is where Wi-Fi has really suffered when it comes to the Internet of things. Many of these devices are powered only by batteries, and Wi-Fi is a notorious power suck, which means that most manufacturers don’t use it on sensors, wearables and other devices that don’t have room for a large battery, but are expected to last a long time without a recharge.

When HaLow was being developed around last year as 802.11ah (that’s the IEEE version of the standard as opposed to the Wi-Alliance brand), several engineers at chip companies expressed concern over its claims about being low power. “The Alliance is being a bit vague with the details so I’m a bit skeptical that they will hit their power and speed goals. Otherwise they would be touting the accomplishment,” says Patrick Moorhead, an analyst with Moor Insights and Strategy.

It did, however, provide data rates for HaLow, which are between 150 kilobits per second and 18 megabits per second, which is much less than the traditional Wi-Fi rates (which are hitting up to a gigabit if the underlying broadband speeds are fast enough). Generally, you’ll see faster data rates at higher power consumptions and when there is less interference. Given the average home environment where 900 Mmz is the spectral equivalent of a Starbucks at 7AM those fast rates may prove difficult. Of course, with the Internet of Things, transmitting large amounts of data isn’t necessary, so that may not matter. Power consumption, reliability and distance could be more important.

The standard won’t be official until 2018, but devices will be out later this year. We’ll soon see how robust and useful Wi-Fi HaLow really is.