WiFi Through 2018 - Industry focus and emerging prospects

WiFi_in right perpectives_2018 from Saurabh Verma

Unlicensed integration with 5G Networks

Unlicensed integration-with-5 g-networks from Saurabh Verma

WiFi 802.11ax - what is Resource Unit?

A 20 MHz OFDMA channel consists of a total of 256 subcarriers (tones). These tones are grouped into smaller sub-channels, known as resource units (RUs). As shown in Figure 1, when subdividing a 20 MHz channel, an 802.11ax access point designates 26, 52, 106, and 242 subcarrier resource units (RUs), which equates roughly to 2 MHz, 4 MHz, 8 MHz, and 20 MHz channels, respectively. The 802.11ax access point dictates how many RUs are used within a 20 MHz channel, and different combinations can be used.

Figure 1- OFDMA resource units – 20 MHz channel

An 802.11ax AP may allocate the whole channel to only one client
 at a time, or it may partition the OFDMA channel to serve multiple clients simultaneously. For example, an 802.11ax AP could simultaneously communicate with one 802.11ax client using 8 MHz of frequency space while communicating with three additional 802.11ax clients using 4 MHz sub-channels. These simultaneous communications can be either downlink or uplink.

Figure 2 – OFDMA transmissions over time

In the example shown in Figure 2, the 802.11ax AP first simultaneously transmits downlink to 802.11ax clients 1 and 2. The 20 MHz OFDMA channel is effectively partitioned into two sub-channels. Remember that an ODFMA 20 MHz channel has a total of 256 subcarriers; however, the AP simultaneously transmitted to clients 1 and 2 using two different 106-tone resource units. In the second transmission, the AP simultaneously transmits downlink to clients 3, 4, 5, and 6. In this case, the ODFMA channel had to be partitioned into four separate 52-tone sub-channels. In the third transmission, the AP uses a single 242-tone resource unit to transmit downlink to a single client (5). Using a single 242-tone resource unit is effectively using the entire 20 MHz channel. In the fourth transmission, the AP simultaneously transmits downlink to clients 4 and 6 using two 106-tone resource units. In the fifth transmission, the AP once again transmits only downlink to a single client, with a single 242-tone RU utilizing the entire 20 MHZ channel. In the sixth transmission, the AP simultaneously transmits downlink to clients 3, 4, and 6. In this instance, the 20 MHz channel is partitioned into three sub-channels; two 52-tone RUs are used for clients 3 and 4, and a 106-tone RU is used for client 6.

For backward compatibility, 802.11ax radios will still support OFDM. Keep in mind that 802.11 management and control frames will still be transmitted at a basic data rate using OFDM technology that 802.11a/g/n/ac radios can understand. Therefore, the transmission of management and control frames will be transmitted using the standard 64 OFDM subcarriers of an entire primary 20 MHz channel. OFDMA is only for 802.11 data frame exchanges between 802.11ax APs and 802.11ax clients. Please check back every week and read future 802.11ax blogs, where we will discuss in more detail the mechanisms of ODMA including resource unit allocation and trigger frames. We also discuss the differences between downlink OFDMA and uplink OFDMA.

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OFDM & OFDMA in context of WiFi 802.11ax technology.

802.11a/g/n/ac radios currently use Orthogonal Frequency Division Multiplexing (OFDM) for single-user transmissions on an 802.11 frequency. 802.11ax radios can utilize orthogonal frequency-division multiple access (OFDMA) which is a multi-user version of the OFDM digital-modulation technology. OFDMA subdivides a channel into smaller frequency allocations, called resource units (RUs). By subdividing the channel, parallel transmissions of small frames to multiple users can happen simultaneously.

Think of OFDMA as a technology that partitions a channel into smaller sub-channels so that simultaneous multiple-user transmissions can occur. For example, a traditional 20 MHz channel might be partitioned into as many as nine smaller sub-channels. Using OFDMA, an 802.11ax AP could simultaneously transmit small frames to nine 802.11ax clients. OFDMA is a much more efficient use of the medium for smaller frames. The simultaneous transmission cuts down on excessive overhead at the MAC sublayer as well as medium contention overhead. The goal of OFDMA is better use of the available frequency space. OFDMA technology has been time-tested with other RF communications. For example, OFDMA is used for downlink LTE cellular radio communication.

To illustrate the difference between OFDM and OFDMA, please reference both Figures 1 and 2. When an 802.11n/ac AP transmits downlink to 802.11n/ac clients on an OFDM channel, the entire frequency space of the channel is used for each independent downlink transmission. In the example shown in Figure 1, the AP transmits to six clients independently over time. All 64 subcarriers are used when an OFDM radio transmits on a 20 MHz channel. In other words, the entire 20 MHz channel is needed for the downlink communication between the AP and a single OFDM client. The same holds true for any uplink transmission from a single 802.11n/ac client to the 802.11n/ac AP. The entire 20 MHz OFDM channel is needed for the client transmission to the AP.

Figure 1- OFDM transmissions over time

 As shown in Figure 2, an 802.11ax AP can partition a 20 MHz OFDMA channel into smaller sub-channels for multiple clients on a continuous basis for simultaneous downlink transmissions. In a future blog, you will learn that an 802.11ax AP can also synchronize 802.11ax clients for simultaneous uplink transmissions. It should be noted that the rules of medium contention still apply. The AP still has to compete against legacy 802.11 stations for a transmission opportunity (TXOP). Once the AP has a TXOP, the AP is then in control of up to nine 802.11ax client stations for either downlink or uplink transmissions. The number of resource units (RUs used can vary on a per TXOP basis.

Figure 2- OFDMA transmissions over time

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Terragraph - Facebooks New Plan along with Qualcomm to Test the 10 gbps WiFi based backbone networks

The two tech companies announced the joint effort for test of, Facebook's mesh network technology, Called  Terragraph. it already has announced tow field trials in Europe. Now Tests are also expected to begin in partnership with Qualcomm in the U.S. next year.

The technology could deliver significantly higher bandwidth via Wi-Fi — perhaps as fast as 10 gigabits per second at peak speeds. If this gets a successful feat it would do wonder much like 'fiber in the air'.

"With Terragraph, our goal is to enable people living in urban areas to access high-quality connectivity that can help create new opportunities and strengthen communities," said Yael Maguire, vice president of connectivity with Facebook.

The technology is complicated. But it taps 60 gigahertz unlicensed airwaves — know as millimeter wave — to bring high speed Internet to big cities.

Millimeter wave spectrum can deliver a lot of data fast. But it's prone to interference and doesn't travel very far — only a few hundred feet at best — before degrading. It needs to be within line of sight of devices, small cells and access points.

The Terragraph system would use advanced and future generations of Wi-Fi standards to generate uber-fast speeds. Qualcomm is producing the chips and software to enable outdoor operation and avoid interference.

"Our collaboration with Facebook will bring advanced 11ad and pre-11ay technologies to market, increasing broadband penetration and enabling operators to reduce their capital expenses for last-mile access," said Irvind Ghai, a vice president with Qualcomm Atheros.

There ar obvious challenges with the deployment of such WiFi hotspots across the cities and delivering millimeter waves technology, but these challenges are there with others smallcell centric technology too, like 5G fixed broadband systems. 

"There are licensed and unlicensed approaches," said Jesse Burke, a product marketing manager at Qualcomm. "The point is our customers are looking for increasing capacity. There are various approaches in both the licenses and unlicensed bands, and we are providing solutions, along with our customers."

A Comprehensive Outlook on WiFi and Cellular Integration and holistic approach for WiFi in 5G. From Fundarc-Comm (xgnlab)

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Is WiFi with WBA and WiFi Alliance sufficiently focused to come for 5G?

This is a discussion with industry experts Oscar Bexell.

Oscars Linkedin profile is - https://www.linkedin.com/in/oscar-bexell-9462922/

Q. 5G still seams to be dimensionless, where do you see Wi-Fi fitting with 5G?

A. Residential and for enterprises (how long depends on how well 11ax plays out). In the longer run, and with new types of gadgets coming in, I don't think anything LBT/CS fits the bill. CBRS will take off in the US and take the indoor enterprise space. In China the MNOs have been doing this with small cells for quite some time. In other countries there will be other approaches. Different markets will also take longer/shorter time to adopt. For many Wi-Fi system integrators and vendors, there will be market shares to take with CBRS.

Q. Wi-Fi in current wireless access technology space is on hype or settled, why?

A. I only follow them from a distance. I like the NGH initiative. I think they should get into CBRS+4G/5G. That's where the MSOs and many service providers will be able to take footprints over time. Build ecosystem and drive standardization/harmonization.

Q.How relevant Wi-Fi Alliance has been so far, and what you think about its future role should be?

A.It's probably the main factor behind the success of Wi-Fi. I see their work as critical, both for new standards, but maybe even more for driving interoperability work and harmonization of frequencies. They should keep on doing exactly this, but I also think they should drive CBRS spectrum harmonization in more markets and the ecosystems around this. That is the future for enterprise/venue in-building networks.

Q. Wi-Fi access would be catching what kind of segments of IOT?

A.It's already used a lot, especially in in-home deployments and as backhaul to many Bluetooth/Zigbee/Z-wave/gateway applications. It will play a very big role in the coming years as it's already present in most environments. I think mainly as backhaul. I'm also looking forward to see how 802.11ah takes off. I see that mainly as an in-home competitor to Bluetooth 5.0 and Zigbee.

Q.Do you feel for any need of collaboration or association for Wi-Fi ecosystem development with a fresh view (may be like use case basis/software defined/cloud based)?

A. N/A

HEW - WiFi 802.11ax gearing up for ecosystem gain

802.11ax, also called High-Efficiency Wireless (HEW), has the challenging goal of improving the average throughput per user by a factor of at least 4X in dense user environments. This new standard focuses on implementing mechanisms to serve more users a consistent and reliable stream of data (average throughput) in the presence of many other users.

Looking beyond the raw link speeds of 802.11ac, this new standard implements several mechanisms to serve more users consistent and reliable data throughput in crowded wireless environments.

High-Efficiency Wireless includes the following key features:

• Backwards compatible with 802.11a/b/g/n/ac
• Increase 4X the average throughput per user in high-density scenarios, such as train stations, airports and stadiums. -Data rates and channel widths similar to 802.11ac, with the exception of new Modulation and Coding Sets (MCS 10 and 11) with 1024-QAM.
• Specified for downlink and uplink multi-user operation by means of MU-MIMO and Orthogonal Frequency Division Multiple Access (OFDMA) technology.
• Larger OFDM FFT sizes (4x larger), narrower subcarrier spacing (4X closer), and longer symbol time (4X) for improved robustness and performance in multipath fading environments and outdoors.
• Improved traffic flow and channel access
• Better power management for longer battery life

802.11ax provides greater Wi-Fi speed and does it through making capacity improvements in congested network environments, by supporting more users in dense networks and making more efficient use of spectrum. the difference between 802.11ax and previous Wi-Fi generations may not be very noticeable for a residential Wi-Fi user, compared to the improvements in a dense network with many users. The goal is to increase the data rate in a congested environment by 4x or more."

802.11ax also offers significant power usage improvements. Qualcomm, for instance, claims that its WCN3998 chipset reduces Wi-Fi power consumption by up to 67% compared to 802.11ac Wave 2.

The Wi-Fi technology so far has been based on one-on-one device-to-access point conversations. 802.11ax changes that to multi-user simultaneous support. The capacity increases will make for a better user experience, with 10x more users able to be supported.

802.11ac with MU-MIMO hasn't achieved its full commercial deployment potential and was based on beam-steering. In contrast, 802.11ax makes Wi-Fi more like cellular through the use of OFDM, and scheduling. The technology comes in closer to what LTE is today in competition, also same time cellular is moving to 5G, where also it [802.11ax] usher to write place.

Testing and standardization of 802.11ax

Testing 802.11ax offers up some unique challenges that Wi-Fi testing hasn't previously had to navigate. One of those is synchronization of devices in the uplink using the AP, in order to avoid interference. A trigger frame is sent from the AP to the devices and they must respond for coordination of timing, frequency and power levels. Rohde & Schwarz gives some of the basics of uplink accuracy testing.

802.11ax along with 802.11ac and previous generations, at both 2.4 and 5 GHz, means that test times "could go up dramatically."

Meanwhile, the path to a final standard for 802.11ax has been a rocky one, and the work is still ongoing. As Intel's Dan Artisu, vice president of its client computing group and GM of Intel's connected home division, noted, the standards work continues and the draft which is ultimately adopted — and on which certification is based — may differ enough from earlier drafts that product interoperability could be an issue. The next draft is expected to be voted on mid-2018.

Some in the industry believe that due to the additional complexity of the 802.11ax standard, it is important to get 802.11ax chipsets into the hands of engineers sooner rather than later to help them build devices around the new features. If an OEM does decide to hold back, their first devices integrating an 802.11ax chipset may come 6 to 18 months behind that of the competition. the question for OEMs is whether they should wait until the standard is more stable before adopting an 802.11ax-ready solution. A wait-and-see approach could arguably result in a longer lead time, and some OEMs may lose out to those who are proactive in getting their designs ready for the full version of the standard.

WBA impacting 5G with WiFi.

5 g networks-role-of-wi-fi-and-unlicensed-technologies-v2 from Saurabh Verma