802.11ac Wi-Fi Technology Standard
802.11ac Wi-Fi technology standard addresses challenges that apply tremendous stress on the Wi-Fi network - high density environments, BYOD proliferation and bandwidth intensive applications such as video streaming - by delivering Gigabit speeds. This is achieved with 802.11ac Wi-Fi standard by building on technologies such as MIMO, beamforming, channel bonding and many more that were first introduced in 802.11n.
802.11ac OverviewThe newly adopted 802.11ac standard is the first Wi-Fi standard to provide gigabit performance, increasing the maximum data rate from 600Mbps to 1300Mbps and eventually to 6.93Gbps.
While the most obvious result of these higher rates is faster data transfers for individual users, the biggest benefit to network managers may be the ability to handle a higher number of devices without unacceptable degradation in performance. Given the fact that more and more users are not only accessing the Wi-Fi network, but doing so with multiple devices (phones, tablets, and other “smart” devices), upgrading AP’s to new Wi-Fi technology standards can provide welcome relief at reasonable cost. The cumulative benefit of the new Wi-Fi standard features will enable Wi-Fi solutions to meet today’s demand for high capacity and high quality mobile real-time applications such as video and voice.
802.11ac Wi-Fi technology standard achieves its raw speed increase in multiple ways:
- More channel bonding, increased from the maximum of 40MHz in 802.11n, and now up to 80 and soon 160MHz
- Denser modulation, now using 256 quadrature amplitude modulation (QAM), as compared to 802.11n's 64QAM
- Support for eight spatial streams, up from 802.11n’s four streams.
- Simplification of the transmit beamforming capability, that was first introduced with 802.11n
A new MIMO technology, multiuser MIMO (MU-MIMO), allows an AP to send multiple frames to multiple users at the same time on the same frequency. So for the first time, with the new Wi-Fi standard, an AP can act something like an Ethernet switch instead of a hub, supporting more users.
The new Wi-Fi standard operates only in the less crowded 5GHz band, so dual band clients and AP’s will be able to access 802.11n in the 2.4GHz band. The design of 802.11ac Wi-Fi stresses compatibility with existing Wi-Fi standards and can coexist with 802.11a/n devices. Careful design and deployment of the network can maximize the benefit of deploying the new Wi-Fi standard while still supporting older devices.
As with the introduction of any new technology, there are challenges that every user who is responsible for Wi-Fi standard design, deployment and maintenance of the network faces. These design challenges include:
- How to phase new gear into an established wireless LAN and get true performance that rivals what the 802.11ac Wi-Fi technology can do in theory
- Troubleshoot Wi-Fi problems right the first time without costly rework, escalations or downtime.
802.11ac Wi-Fi Technology Design and Deployment
It is important to resist the temptation for a simple 1 to 1 replacement of existing 802.11n or even legacy technologies like 802.11a/b/g Wi-Fi APs with new 802.11ac APs. Users believe that 1 to 1 replacement of APs is the cheapest and fastest method of rolling out the new technology and that the past efforts for deployments can be just be reused for all future technologies without any “real planning”. This fallacy leads to poor & expensive network design and always costly rework later. Also the common “throw in another AP to the problem” attitude is costly, time-consuming and lowers the efficiency of the network.
Users should be defining the migration strategy instead of blindly deploying or throwing APs at the problems later. This includes matching new Wi-Fi technology rollouts with business requirements, estimate budgets and figuring out the location and configuration of the APs to maximize coverage and performance before any AP rollout. Just like 802.11n, along with planning the migration path, it is also important for users to perform real-world surveys to deploy the most accurate network as that takes into account all of the environmental and network conditions of the network.
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In addition to the issues faced in deploying any wireless network, there exist a number of other considerations:
Measuring throughput is the only real indicator of performance
The new Wi-Fi standard builds on technologies introduced in 802.11n such as MIMO, beamforming, wider channels and additional spatial streams. Because of all these capabilities, signal strength is not a true indicator of WLAN performance
Your current 802.11a/n wireless environment adversely impacts 11ac performance
As noted above, the new standard is backwards compatible with 802.11n and 802.11a, and operates in a mixed mode environment supporting 802.11a/n/ac clients in the 5GHz band. Performance for 802.11ac clients may be adversely impacted because of slower transmission rates by 802.11a/n clients.
Developing a channel allocation plan is critical to maximizing performance in a 802.11ac Wi-Fi network
The new Wi-Fi technology standard introduces 80MHz and 160MHz wide channel operation which enables higher throughput. The use of wider channels increases the likelihood of co-channel interference and this adversely impacts performance.
802.11ac Wi-Fi Troubleshooting, Maintenance and Optimization
It is a misconception in the industry that users can use any troubleshooting tool/method available at hand to solve problems in the network. This is due to the myth that all troubleshooting tools have the same capabilities or that the built-in troubleshooting or monitoring capabilities of the WLAN AP infrastructure can do all of the troubleshooting.
Relying on incompetent tools or methods, lead to slow troubleshooting, and in most cases, not being able to solve the problems at all. This is the most common issue faced with free smart device apps that are downloaded onto the user’s phones or tablets. The cost of repeat visits due to ineffective or incomplete troubleshooting methods not only lower user satisfaction of the network, but also impact the performance of mission critical WLAN applications and make the networks vulnerable from security threats and attacks. For system integrators, this not only erodes margins of the project, but also affects their credibility to get future business.
Users are also under the false belief that the AP can monitor and solve all of its problems without the need for a 3rd party tool. Taking infrastructure APs offline for part-time (scanning the air only once in a while) or full-time analysis with the limited capabilities (does not have comprehensive monitoring and troubleshooting capabilities like a 3rd party tool) is neither going to solve real-world problems, nor does it help their “AP infrastructure investments”, but instead is just a “feel-good” or “checkmark” option. For thorough problem solving, customers should be capturing and analyzing the full traffic for 802.11ac, by traveling to the location of the problem (and not a one-sided AP view from a fixed location) and without taking the AP off-line.
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|IEEE 802.11ac Migration Guide
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