The Evolution of WiFi

Transcription

1 The Verification Experts Air Expert Series The Evolution of WiFi By Eve Danel Senior Product Manager, WiFi Products August 2016 VeEX Inc Lakeview Court, Fremont, CA USA Tel: Fax:

2 Table of Contents 1. Introduction IEEE Standards a and b g and n b and Backward Compatibility ac GHz Frequency Band GHz Frequency Band Summary... 8 About VeEX... 9 VeEX Inc Lakeview Court, Fremont, CA USA Tel: Fax:

3 1. Introduction The Institute of Electrical and Electronic Engineers (IEEE) formed the committee to develop and publish standards for the Wireless LAN (WLAN). The committee released the first IEEE standard specification in June It was the creation of this industry standard that served as the catapult for wireless equipment product creation. In 1999, Apple released the first commercial product using the new standard. Apple (in conjunction with Lucent) added a WiFi slot in its new ibook computers, called AirPort. The ibook was the first consumer computer to have integrated WiFi capability. In addition, they also released a base station for home WiFi use. Widespread use of WiFi quickly followed in offices and homes. In 2005, WiFi shipments reached 100 million annually and the term WiFi was officially added in the Merriam-Webster dictionary. By 2009, one billion WiFi chipsets were sold. There are today an estimated 12 billion WiFi devices shipped around the world. By the end of 2016, shipments are expected to reach 15 billion units. Today, most of the devices that we use do not have an Ethernet connector anymore. This makes WiFi the only networking option we have to communicate, work, or stream audio and video on our local networks. American households have an average of four WiFi enabled devices in their homes. WiFi is the access technology of choice - not only used in homes, but in businesses and public spaces across the globe. Many believe that WiFi is a plug and play technology, but it s actually quite complex, and to get it to work optimally requires some understanding of the underlying technology. 2. IEEE Standards In the 1980s, the FCC (Federal Communications Commission), an American government agency, opened up several bands of the Radio Frequency (RF) spectrum for use without license. These garbage bands, at 900 MHz, 2.4 GHz, and 5 GHz, were taken from the ISM (Industrial, Scientific, and Medical band) and U-NII (Unlicensed National Information Infrastructure band) to open up for communication purposes. This opened the way for communications equipment to use the 2.4 GHz and the 5 GHz frequency bands. The IEEE (Institute of Electrical and Electronics Engineers) started working on the specification documents. The initial 1997 IEEE standard specification used the unlicensed 2.4 GHz RF spectrum and allowed for up to two megabits per second of data transfer using frequency hopping. In 1999 the industry association, Wi-Fi Alliance, was founded. It coined the name Wi-Fi and trademarked it. The WiFi Alliance is responsible for interoperability testing and certification of WiFi products. VeEX Inc Lakeview Court, Fremont, CA USA Tel: Fax:

4 a and b The IEEE ratified both the a and b standards in The a standard used the same data link layer protocol and frame format as the original standard, but added a physical layer of an OFDM-based air interface. OFDM (Orthogonal Frequency Division Multiplexing) is a modulation method used to encode 52 data sub-carriers spread over 20 MHz bandwidth. This method operates a in the 5 GHz band with a maximum data rate of 54 Mbps. Due to the cost and complexity to implement, most of the first commercial deployments used the b standard instead. The b standard could only achieve a maximum data rate of 11 Mbps, but implemented a simpler modulation technique called HR/DSSS (High-Rate Direct Sequence Spread Spectrum). HR/DSSS used a 22 MHz wide bandwidth, but remained backward compatible with DSSS, used by the original standard within the 2.4 GHz frequency band g and n The third generation, g, was published in It operated in the 2.4 GHz frequency band like the b, but could also achieve speeds up to 54 Mbps using the same OFDM technology as a. The g standard was backward compatible with b hardware, making the transition to this new technology easier for the consumer as they could keep some of their equipment while transitioning to newer standards. In 2009, the n amendment was released. The n standard made progress both in data speed (reaching up to 450 Mbps in the 2.4 GHz band) and in reliability by using more antennas and multiple streams of data. Multiple-input and multiple-output, or MIMO (pronounced my-moh ), technology uses multipath propagation to send and receive multiple data signals simultaneously over the same frequency. Using multiple antennas to enhance communication between transmitter and receiver provides significant increases in data rate without the need for higher transmitter power. The n standard supports both the 2.4 GHz and 5 GHz frequency bands and is backward compatible with older a/b/g technologies b and Backward Compatibility Since the beginning, the various standards were designed for backwards compatibility, so that legacy equipment could operate in the same network as newer generation equipment. Network administrators could then slowly evolve their equipment without needing a complete overhaul at each new standard release. This contributed to the success of technology. However, b is the exception to the ease of backward compatibility b is the only standard not using OFDM modulation; therefore, equipment using the newer OFDM standard has to ensure that b equipment is aware that all traffic, including traffic it cannot decode, will be transmitted. This is done by using RTS/CTS messages as a protection mechanism. Each time a device gets ready to send traffic, it first sends a RTS (Request to Send) message that is further acknowledged by a CTS (Clear to Send) message. This means that for every data frame an additional two management frames have to be transmitted. This creates a large traffic overhead and inefficiency on the networks. Some network administrators choose to disable b rates (1, 2, 5.5, and 11 Mbps) from the AP s to avoid this problem. To b or not to b? is a controversial subject b clients have become a rarity. Discontinuing support for b rates makes sense; however, this decision would restrict the WiFi cell s coverage area. Non b equipment could fall back to b rates when signal quality was low. Thus, turning off AP support for the 1, 2, 5.5, and 11 Mbps rates would prevent marginal clients from connecting. VeEX Inc Lakeview Court, Fremont, CA USA Tel: Fax:

5 ac Released in two waves in 2014 and 2015, the ac standard is even faster than previously released standards ac Wave 1 devices are capable of transmitting at 1.3 Gbps, while today s latest Wave 2 devices advertise an amazing 3.4 Gbps ac devices achieve almost 8 times the speed of n by leveraging beamforming technology to increase the number of MIMO streams and increasing the channel bandwidth through further optimized OFDM modulation (up to QAM 256) ac Wave 2 supports up to eight spatial streams and is able to operate on channels up to 160 MHz wide, providing bandwidth well beyond 1 Gigabit per second. It also introduces downlink multi-user, multiple input and multiple output (MU-MIMO) technology. MU-MIMO allows downstream transmission to multiple receivers simultaneously, up to four simultaneous client transmissions. Figure Standard Amendments GHz Frequency Band The b, g and n standards are designed to transmit data over the 2.4 GHz frequency band and use frequencies from 2.4 to 2.5 GHz. The 2.4 GHz frequency band, also called Industrial Scientific and Medical or ISM, has been released by the FCC for unlicensed use. This means many different types of equipment can use it without requiring a license. Besides WiFi, other devices use the 2.4 GHz band, such as Bluetooth and ZigBee enabled devices, cordless phones and even microwave ovens. The 2.4 GHz band is divided into 14 channels spaced 5 MHz apart, beginning with channel 1, centered on GHz. Since it is easier to remember channel numbers than center frequency, people use the channel number from 1 to 14 to describe which channel their device is using. VeEX Inc Lakeview Court, Fremont, CA USA Tel: Fax:

6 Figure GHz Frequency Band Spread The technologies RF modulation techniques require a 22 MHz of channel width for b or 20 MHz channel width for a/g/n/ac to operate. Since the channels are spaced 5 MHz apart, there is significant overlap i.e. interference between adjacent channels. Because of this, it is recommended in the United States to setup Access Points on channels 1, 6, or 11 only, which are the only non-overlapping channels. Channels 12 and 13 are illegal to use in the USA. Channel 14 sits at GHz (12 MHz above channel 13) and is only legal for use in Japan. Figure GHz Frequency Band Allocation Channel Frequency (MHz) North America Japan Most of the World Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes In US, these are recommended to avoid interference Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes No Yes Yes No 11b only No The n standard allows for the bonding of two 20 MHz channels together to achieve a higher data rate and create a 40 MHz channel. This ends up creating less non-overlapping channels and more possible interference with neighboring Access Points. Due to this reason, using n channel bonding is not recommended in the 2.4 GHz band. The allocation of the 2.4 GHz is regulated in each country by its own agency. In the United States, the allocation is regulated by the Federal Communications Commission (FCC). Channels 12 and 13, centered around and GHz respectively, is not allowed in the United States, but is allowed in most of the world. Channel 14, centered around GHz, is allowed in Japan only. VeEX Inc Lakeview Court, Fremont, CA USA Tel: Fax:

7 8. 5 GHz Frequency Band Figure 4. 5 GHz Frequency Band Spread (U.S. and Canada) The Unlicensed National Information Infrastructure (U-NII) 5 GHz band is less crowded than the 2.4 GHz frequency band. It is used by the a, n and ac standards. The channels center frequencies range from GHz to GHz. The channels are 20 MHz wide and there is no overlap between adjacent channels, which means less possible interference from neighboring Access Points. Channel 36 is the first channel in the spectrum, ranging from to GHz, and centered at GHz. The 5 GHz band is further sub-divided into four ranges: UNII-1, UNII-2, UNII-2 extended and UNII-3 bands. Most WiFi devices support UNII-1 (channels 36 to 48) and UNII-3 (channels 149 to 165) only for indoor use. The FCC and other regulatory bodies allow the use of the UNII-2 and 2e bands for indoor and outdoor use, provided that your device s radio can support Dynamic Frequency Selection (DFS) and Transmitter Power Control (TPC). DFS and TPC are designed to detect and adjust WiFi channels automatically if military or weather radar systems are present in order to avoid interfering with these systems. If the DFS channels are used, the 5 GHz band offers 25 non-overlapping 20 MHz channels. The n and ac standards make use of the 5 GHz band s many non-overlapping channels by bonding adjacent channels to transmit even more data. With 40 MHz channel width, the n and ac can roughly double their transmission speed, but at the cost of allowing only four non-overlapping 40 MHz channels (or 12 with DFS enabled). Using the ac standard and bonding two adjacent 40 MHz channels into a single 80 MHz channel, data speeds reach up to 1.3 Gbps, but at the cost of allowing only two non-overlapping channels (or six with DFS enabled). The ac Wave 2 standard defines 160 MHz channel width to achieve up to 3.4 Gbps rates, either by bonding contiguous channels (or discontiguous channels) together. VeEX Inc Lakeview Court, Fremont, CA USA Tel: Fax:

8 9. Summary Once the IEEE formed and began releasing standards for WiFi implementation and usage, the world began to transform as markets opened and new technologies emerged. Each amendment to the standard specification has built upon the last and included major advances in both speed and output. Looking to the future, the IEEE is now working on the ax standard. This standard will build upon the ac standard by adding even higher speed. It is targeted to reach around 10 Gbps, although its official release is not planned until At this point, it may be difficult to imagine which application could reap the full benefit of such high-speed connections. However, history shows us that by the time standards are released, the need will already exist. VeEX Inc Lakeview Court, Fremont, CA USA Tel: Fax:

9 Notes About VeEX Located in the heart of Silicon Valley, VeEX develops innovative test and measurement solutions for nextgeneration communication equipment and networks. Founded in April 2006 by test and measurement industry veterans, VeEX products blend advanced technology and vast technical expertise with the discerning measurement needs of customers. VeEX products diligently address all stages of network deployment, maintenance, field service turn-up, and service verification features across DSL, Fiber Optics, CATV/DOCSIS, Mobile, Next-Generation Transport Network, Fibre Channel, Synchronous and Carrier Ethernet technologies. VeEX s multinational structure consists of several specialized business units operating in different parts of the world. VeEX has shipped more than 100,000 units since volume production began. The VeEX team brings simplicity to tomorrow s networks VeEX Inc. All rights reserved. D A /08 Wi-Fi Alliance and Wi-Fi are registered trademarks of Wi-Fi Alliance. The Verification Experts VeEX Inc Lakeview Court, Fremont, CA USA Tel: Fax: