The 802.11ac is a complete evolution of the 802.11n. IEEE 802.11acÂ refers to a wirelessÂ known computer networkingÂ standard that is ofÂ 802.11. It is currentlyÂ under development, and will be slated with providing very high-throughputÂ networks in wireless local areaÂ on theÂ given 5Â GHz band. 802.11ac is known to build upon the revered success of the 802.11n that is now the considered predominant WLAN best standard in the whole market. 802.11n did bring many improvements in the data rates and also link efficiencies. This, however, was affected by the consumer and also commercial trends that have created total demand for a very new set of varied capabilities which are greatly addressed by the 802.11ac.
This paper discusses 802.11ac as a type wifi. In today's communication, with an explosive increase of multiple advanced applications802.11ac can be the best solution that is able to handle the ever-increasing of bandwidth demand. The focus of the paper will discuss the 802.11ac technology and why 802.11ac becomes the best solution that overcomes the limitation of other technologies. The discussion will cover several aspects of this technology.
1.1 The Objectives
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There is a variety of wireless technologies were introduced today. The aim of this research is that discussing and analyzing 802.1ac technology as new wifi standard.
This research paper will provide a great overview about the 802.11ac technology discussing it in several points. Thus, the discussion will be organized in chapters as follow:
Chapter 1: Introduction
Chapter 2: Drivers for 802.11ac
Chapter 3: How the 802.11ac goes extremely fast
Chapter 4: Technology Overview
Chapter 5 : Differences between 802.11ac and 802.11n
Chapter 6: RTS/CTS with Bandwidth Indication
Chapter 7: MIMO improving efficiency with multiuser-MIMO
Chapter 8: Conclusion
IEEE 802.11acÂ refers to a wirelessÂ known computer networkingÂ standard that is ofÂ 802.11. It is currentlyÂ under development, and will be slated with providing very high-throughputÂ networks in wireless local areaÂ on theÂ given 5Â GHz band. 802.11ac is known to build upon the revered success of the 802.11n that is now the considered predominant WLAN best standard in the whole market. 802.11n did bring many improvements in the data rates and also link efficiencies. This, however, was affected by the consumer and also commercial trends that have created total demand for a very new set of varied capabilities which are greatly addressed by the 802.11ac. According to a known study, most of the devices with this 802.11ac specification are also expected to be very common by the year 2015 with a total estimated one whole billion spread all over the globe. 802.11ac stems out as a faster and even more scalable version that was of 802.11n. 802.11ac is known to couple the desired freedom of the wireless with all the capabilities of the Gigabit Ethernet.
The Wireless LAN sites are expected to witness significant progress in the given number of all clients that are supported by the access point (AP). This means a better experience for all the clients, and even more available total bandwidth for a given higher number of the parallel video streams. Despite the known issues when the given network is deemed not fully loaded, for this one, users will still experience a great benefit: their whole file downloads and also email sync may happen at very low-lag gigabit deemed speeds. Also, the same device battery life, as witnessed, is purely extended, since this device's known Wi-Fi interface has the ability to even wake up. It can also exchange all data with its given AP, and then also revert to the dozing that really much even more quickly. This is a dream come true for many system networks.
802.11ac greatly achieves its desired raw speed increase by always pushing on the three different and revered dimensions, which include:
â€¢ Extra channel bonding, which are known to have increased from that maximum of a 40 MHz in the 802.11n, and also now up to a high of 80 or even the 160 MHz (for 117% or even 333% many speed-ups, respectively)
â€¢ The denser modulation that is now using the 256 known quadrature amplitude modulation, abbreviated as QAM, up from the 802.11n's 64QAM (that is for a 33% of speed burst at very shorter, and yet still much usable, ranges)
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â€¢ The more multiple input, with multiple outputs (MIMO). In relation to that, whereas the 802.11n really stopped at known four spatial streams, the 802.11ac still goes all the known way to a high of eight (for a given another 100% of speed-up).
This design really constraints and also economics that went on to keep 802.11n and its products at a one, two, or even three spatial streams still have not changed a great deal for the 802.11ac, so people can expect a quality of the same kind in line with product availability. This is expected to be with the first-wave 802.11ac products in that same category built around the 80 MHz and also delivering up to a high of 433 Mbps (low end), then 867 Mbps (on midtier), or even 1300 Mbps (at the high end) basing on the physical layer. The second-generation products also promise still more in line with channel bonding and also spatial streams, with many plausible product and the configurations that are operating at up to a high of 3.47 Gbps. 802.11ac comes out as a 5 GHz-and only technology, that is so dual-band APs and also clients will always continue to use the 802.11n at a 2.4 GHz. However, the 802.11ac clients would operate in a situation deemed less crowded than the 5 GHz band.
The second-generation products are recommended to come with a very new technology that is multiuser MIMO. Whereas the 802.11n is deemed to be like a known Ethernet hub that may only transfer a one frame at any given time to all its known ports. The MU-MIMO allows all the AP to eventually send multiple known frames to very many clients at the same given time over one frequency spectrum. This is also a major development. With the multiple antennas and also smarts, any AP can eventually behave like a known wireless switch. This can lead to great and massive improvements in this field. There are many technical constraints, and this means that the MU-MIMO is considered well suited in line with bringing-your-own-known-device (BYOD) many situations where the same devices like the smartphones and also tablets may only have one single antenna. 802.11ac-enabled known products are also the main culmination of all efforts at that IEEE and also Wi-Fi Alliance slated pipelines. IEEE 802.11ac is known to have delivered a much approved Draft of 2.0 amendments in the January 2012 and also a refined Draft of 3.0 in May of 2012, with the final ratification being planned for the very end of year 2013.
In the parallel, the same Wi-Fi Alliance, as seen by many, is solely expected to always take a very early draft of IEEE , most likely it may be Draft 3.0, and also use that same one as the known baseline for a very interoperability certification of the first-wave products in the early 2013. Later on, and also more in relation to the ratification date of the 802.11ac, the same Wi-Fi Alliance is also expected to eventually refresh its known 802.11ac previous certification to also include sole testing of the all the more advanced and revered 802.11ac features.
This notable second-wave certification is expected to include all features for example channel bonding for a high of160 MHz, then four spatial evident streams, and also MU-MIMO. On the overall, this same arrangement will closely follow how the 802.11n was even rolled out.
All enterprise networks in line with considering a given investment in all infrastructure of the Wi-Fi have two known excellent choices in: (1) buying the 802.11n APs, because they always deliver a very remarkable level of total performance, they are deemed available today, and also 802.11n is also widely deployed in many of the client products, or even (2) wait for the 802.11ac APs and also their known state-of-the-art pure performance. The last one is option (3), which calls for avoiding the wait: investing in a known modular 802.11n AP for example theÂ CiscoÂ®Â AironetÂ®Â 3600 and Access Point that is considered readily field-upgradable in line with the 802.11ac.
2 DRIVERS FOR 802.11AC
802.11ac is intended to deliver higher levels of the performances by using multiple channels that have very high-definition in line. Hence, this chapter will discuss this goal in more details.
2.2 Drivers for 802.11ac
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802.11ac is deemed an evolutionary improvement to the 802.11n. The main goal of 802.11ac is to always deliver extremely higher levels of the performances that are usually commensurate with all the Gigabit Ethernet networking that includes:
â€¢ Very desired "instantaneous" for all data transfer pure experience
â€¢ A known pipe that is fat enough in line with delivering very high quality of all experience (QoE) is also straightforward
In all the consumer spaces, the main target is the multiple channels that have very high-definition in line with content delivered to these given areas of the whole house.
These enterprises have many challenges that vary in nature:
â€¢ Delivering all the network with the same enterprise-class level speeds and also latencies
â€¢ High-density of environments with all the scores of the clients per the given AP
-Â Which are always exacerbated by the very BYODÂ trend in line with the one given employee and might carry two or three 802.11 known devices and must have them before consuming the given network resources at a given instance.
â€¢ The increased and revered adoption of the video streaming that is desired.
802.11ac is all about the delivering of an outstanding desired experience to all the deemed client s that are served by the AP, even when there are any demanding loads.
Meanwhile, the 802.11 acts as an integral part to the hugely broad range of many devices, and also some of them come out as highly costly, power, or even volume constrained. This is based on the fact that one given antenna is always the routine for all these devices, and yet 802.11ac must always still deliver the peak efficiency.
The only noticed one thing that the 802.11ac has bears in its favor is the known evolutionary improvement in line with the silicon technology that has lasted over the given past of half-dozen years: the channel bandwidths that can even be wider, the constellations can also be denser, and also APs can always integrate and be of more functionality.
Figure : How the 802.11ac Accelerates the 802.11n
It is mandatory that 802.11ac deliver higher levels of the performances by using multiple channels that have very high-definition in line.
3 HOW THE 802.11AC GOES EXTREMELY FAST
802.11ac improve the channel bandwidth, the constellation density, and also the number of all spatial streams; therefore it provides high speed in comparison to other standards. This chapter discuss how 802,11ac achieve high-speed data rate.
3.2 802.11ac with high-speed data rate.
The wireless speed refers to the product of the three main factors: the channel bandwidth, the constellation density, and also the number of all spatial streams. 802.11ac always pushes hard on all the boundaries that exist on each of the tackled cases, as represented inÂ the Figure 1.
For all the mathematically inclined, also the physical layer that has a speed of the 802.11ac is known to be calculated according toÂ the given Table 1. For example, a whole 80 MHz and transmission sent at a 256QAM with known three spatial evident streams and also a short guard at interval delivers a whole 234Ã-3Ã-5/6Ã-8 bits/3.6 Î¼s = 1300 Mbps.
Bandwidth (as Number of Data Subcarriers)
Number of Spatial Streams
Data Bits per Subcarrier
Time per OFDM Symbol
PHY Data Rate (bps)
11n or 11ac
56 (20 MHz)
1 to 4
Up to 5/6Ã-log2(64) = 5
3.6 Î¼s (short guard interval)
108 (40 MHz)
4 Î¼s (long guard interval)
234 (80 MHz)
5 to 8
Up to 5/6Ã-log2(256) â‰ˆ 6.67
2Ã-234 (160 MHz)
Table 1.Â Calculating the given Speed of the 802.11n and also the 802.11ac
Immediately it becomes evident see of the increasing channel bandwidth to a high of 80 MHz, it yields a total of 2.16 times speed-up, and also 160 MHz greatly offers a seen further doubling in the whole scenario. Nothing ever comes on a silver platter: it also does consume a lot of spectrum, and on every time people are always splitting a similar scenario of the transmit power over any twice as there may be subcarriers. This means that that speed greatly doubles, but that given range for the doubled speed is deemed slightly reduced.
Going from the 64QAM to the 256QAM also widely benefits, by the other 8/6 = 1.33 times.
Putting them closer together, the constellation points are easily affected to noise, so 256QAM assists most at very small range where 64QAM is already trustworthy. Though, 256QAM require less spectrum and less antennas than 64QAM. Then this speed is also directly proportional to that number of the spatial streams. This means that more spatial streams always require more of the antennas, the RF connectors, and also the RF chains at that transmitter and also the receiver.
The antennas should always be spaced at a1/3 wavelength (3/4") or even more apart, and this means that any additional RF given chains continue to consume a whole extra power As result of that, many mobile devices tend to reduce the number of antennas to one, two, or three.
Altogether, these three speed-ups are deemed very significant. FromÂ Figure 2Â andÂ Table 2, the minimum allowed 802.11ac product is 4.4Ã- faster than the corresponding 802.11n product.
Figure : Evolution of the Cisco APs with the 802.11 Physical Layer and Amendments
Number of Spatial Streams
Constellation Size and Rate
PHY Data Rate (Mbps)
Low-end product (2.4 GHz only+)
802.11ac wave 1
80 MHz amendment max
802.11ac wave 2
*Assuming a 70% efficient MAC, except for 802.11a, which lacks aggregation.
+Assuming 40 MHz is not ready for use due to the presence of other APs.
Table 2.Â Important Data Rates of 802.11a, 11n, and 11ac
The existing sticker on that box that always shows the maximum data rate does not help on a larger scale in this real world, where many devices have to always contend with the interference from any of the non-802.11 devices, and also the preexisting APs that may only apply 20 or even 40 MHz, weak signals at a given range, multipath fading, very few antennas on the mobile devices, and many others. The only main factor when it comes to the raw speed that is evident of the 802.11ac lies on the valuable extensions that always help in line with delivering very reliable rates throughput the under and also matter-of-fact conditions.
802.11ac achieved higher data rate by improving the channel bandwidth, the constellation density, and also the number of all spatial streams.
4 TECHNOLOGY OVERVIEW
802.11ac operates in the 5GHz band, which is universally practicable due to less interference. This chapter discuss the technology that allows 802.11ac to brings a widely encouragement for users to easily upgrade their mobile devices and Access Points in order to be dual band.
4.2 Technology overview
802.11ac is designed in order to work only in the 5 GHz band, as illustrate inÂ Table 3. This leads to have less interference at 2.4 GHz, including both Bluetooth headsets and microwave ovens. Moreover, it brings a strong encouragement for users to easily upgrade their mobile devices and Access Points to be dual band ;therefore, the 5 GHz band is more universally practicable. This choice also makes the IEEE process more efficient by preventing the contention between 802.11 andÂ 802.15Â supports cause. And there is only just 80 MHz of bandwidth at 2.4 GHz anyway.
As it's already illustrated, 802.11 provides higher order modulation, up to 256QAM; Moreover, channel bonding provide up to 80 or 160 MHz; and more spatial streams provide up to eight. There is an alternate way to transmit a 160 MHz signal, which known as "80+80" MHz.
802.11ac keeps providing some of the more important features of 802.11n; such as, the option of short guard interval (for a 10% speed bump) and increasely better rate at range by take advantage of the advanced low-density parity check (LDPC) forward error-correcting codes. These LDPC codes are intended to be an evolutionary extension of the 802.11n LDPC codes; therefore, it is very hard to extend their current hardware designs by implementers.
Various space time block codes (STBCs) are permitted as options, but (1) this list is abbreviated from the overmuch set defined by 802.11n, and (2) STBC is widely made redundant by using beam-forming. Actually, the simplest mode, which is 2Ã-1, has been certified by the Wi-Fi Alliance. What 802.11ac also introduce a one way of performing channel sounding for beam forming: so-called explicit compressed feedback. Although optional, if an implementer intends to provide the benefits of standards-based beam forming, there is no way other than selecting that single mechanism, which may be tested for interoperability later on.
Likely Wave 1 Wi-Fi Alliance Certification
802.11ac (Later Draft)
Potential Wave 2 Wi-Fi Alliance Certification
802.11ac Complete Amendment
5 GHz (varied support by regulatory domain; nearly 600 MHz in the United States)
<6 GHz excluding 2.4 GHz
Mandatory: 20, 40, and 80 MHz
Mandatory: 20, 40, and 80 MHz
Optional: 160 and 80+80 MHz
Mandatory: BPSK, QPSK, 16QAM, 64QAM
Number of spatial streams
Mandatory: 2 (non mobile APs*), 1 (others)
Optional: up to 3 spatial streams
Mandatory: 2 (non mobile APs*), 1 (others)
Optional: up to 4 spatial streams
Forward error correction
Optional: 2Ã-1 AP to client
Optional: 2Ã-1, 4Ã-2, 6Ã-3, 8Ã-4
Short guard interval
Sounding (a single interoperable protocol)
CTS in response to RTS with bandwidth indication
RTS with bandwidth indication
Mandatory: TX and RX of A-MPDU
Optional: RX A-MPDU of A-MSDU
Mandatory: TX and RX of A-MPDU
TBD: RX A-MPDU of A-MSDU
A-MDPU, A-MDPU of A-MSDU
*Additional requirement introduced by the Wi-Fi Alliance.
Table 3.Â Primary Ingredients of 802.11ac
As result of the huge channel bandwidths of 802.11ac, it is most likely that an 80 MHz AP will li with another 20 or 40 MHz AP - and also an 80 or 160 MHz Access Point - or several of them on dissimilar channels. 802.11ac mandates extensions to the RTS/CTS mechanism, stronger clear-channel assessment (CCA) requirements, and new primary channel selection rules in order to allow reliable operation amid this complexity.
802.11ac operates in the 5GHz band, which is universally practicable due to less interference. By using some technologies; such as beamforming, 802.11ac brings a widely encouragement for users to easily upgrade their devices to be dual band.
5 DFFERENCES BWTWEEN 802.11AC AND 802.AAN
802.11ac has great features in comparison to other standards like 802.11n. This chapter illustrates the most common differences between 802.11ac and 802.11n
5.2 802.11ac against 802.11n
The battles of 802.11n have been prevented by 802.11ac. Additionally, 802.11ac concentrate on improving the advances made in 802.11n in order to pass both the generation of robustness and speed.
Actually, every 802.11ac transmission has to be sent as an A-MPDU aggregate and that's one of the 802.11ac's requirements.
In the proposal example, 802.11ac aggrandizes the 802.11n channel access mechanism; virtual carrier sense and back-off happen on a single 20 MHz basic channel and after that CCA can be utilized for the remaining 20 MHz subchannels right away before transmition can occur.
When the power of A-MPDU and the 802.11n channel access mechanism are given , there wasn't need for a lot of innovation in the MACby 802.11ac. Indeed, one of the new mandatory MAC feature is extensions to the RTS/CTS .
802.11n indeed contain a lot of options with decreased value. 802.11ac takes sensible approach to them. There are two cases for "useless" option. First, when a "useless" option is used and the a third-party device is affected, as a rule an 802.11ac device is prevented from using the option by 802.11ac. Second, if a "useless" option is used in 802.11n products or only affects the devices, thus the feature is not updated for 802.11ac but instead it is left to die.
For example, 802.11ac version does not contain any type of the "802.11n greenfield" preamble format. Actually, there is only one preamble format introduced by 802.11ac , which is to legacy 802.11a/11n equipment , will appear securely same as an 802.11a preamble chased by a payload with a poor CRC. This illustrates that neither legacy equipments attempt to send over the top of the 802.11ac transmission, nor transmit a bad payload up the stack.
802.11n defined a "reduced interframe spacing," which in turn decreases overheads between transmissions in sequence, but A-MDPU solves much the same problem efficiently as experience has shown. 802.11ac equipment functioning in 802.11ac mode are not allowed to sen RIFS as of Draft 3.0.
802.11n features that are not brought up to date for 11ac include all the 802.11n sounding options, extension LTFs, the calibration procedure, antenna selection, PCO, LSIG TXOP protection, unequal modulation, 4Ã-3 and 3Ã-2 STBC modes, MCS32, and dual CTS protection.
Although 802.11ac and 802.n have some features in common, 802.11ac is better than 802.11n as discussed above due to the great improvement that added to 802.11ac.
6 RTS/CTS WITH BANDWIDTH INDICATION
RTS/CTS is a technology used to find when channel bandwidth is clear. This chapter shows how 802.11ac get benefits of this such a great technology.
6.2 RTS/CTS with 802.11ac
An 802.11ac AP operating on 80 MHz (or 160 MHz and so on) should still be capable of allowing 802.11a or 802.11n clients to associate. Thus beacons are sent on one 20 MHz channel, known as the primary channel, within that 80 MHz. The AP and all clients associated to the AP receive and process every transmission that overlaps this primary channel and extract virtual carrier sense from the frames they can decode.
However, the AP could be nearby other uncoordinated APs. Those APs could be preexisting 802.11a or 802.11n APs, and their primary channels could be any 20 MHz within the 80 MHz of the 802.11ac AP. Then the different APs and their associated clients have a different virtual carrier sense, so can transmit at different times on the different subchannels, including overlapping times. With the wide 802.11ac channel bandwidths, this scenario becomes much more likely than with 802.11n.
Figure : RTS/CTS Enhanced with Bandwidth Signaling
For this reason, 802.11ac defines an enhanced RTS/CTS protocol. RTS/CTS can be used to find when channel bandwidth is clear and how much, around both the initiator and the responder, as shown inÂ Figure 3.
There are other variations on this protocol, for when the initiator is incapable of switching to a narrower bandwidth on the fly and so forth, but the previous description captures the essence of the enhancement: the recipient can say "these subchannels are busy - don't use them."
802.11ac get benefits from RTS/CTS is a technology used to find when channel bandwidth is clear by using some indicators. Therefore, 802.11ac can achieve great amount of bandwidth.
7 MIMO IMPROVING EFFICIENCY WITH MULTIUSER-MIMO
A new option for the IEEE 802.11ac standard is multiuser-MIMO, which is a new multi-antenna technique used on the downlink only. This chapter discuss how 802.11ac attempt to improve the overall system efficiency by using multiuser-MIM.
In to 802.11ac, Multiuserâ€MIMO was attached to solve the multiâ€STA throughput necessity. In MUâ€MIMO, the independent data streams are transmitted to different STAs at the same time by the Access Point. By way of preparation of the data streams at the sender, the interference that occurs accidentally for a specific STA is deleted at the receiver of each STA. Hence, each STA accept delivery of data that is totally free of interference from the transmissions that are guided towards other STAs at the same time. In MUâ€MIMO, the independent transmissions are created by using the spatial degrees of freedom, whereas in singleâ€user MIMO, the throughput from AP is increased to STA by taking advantage of these spatial degrees of freedom.
The complication of MUâ€MIMO descends mainly on the Access Point, where the preprocessing occurs. The receiving STAs only need the ability to report channel information to the AP; therefore, it is able to compute the preparation matrices. The channel information which is required from the receiving STAs is exactly the same required channel for explicit feedback beamforming. Hence, the complication for the STA doesn't exceed the complexity that already included in providing explicit feedback beamforming as a receiver.
One disadvantage of MUâ€MIMO is that the slowest link among all APâ€STA pairs determines the bundle of time that the medium is busy. If all transmissions to STAs in the MUâ€group have ended, the new data can be transmitted to any of the STAs .If there is huge difference in either the Data bundle or throughput passing to various STAs, the wireless medium cannot be utilized efficiently. At this moment, MUâ€MIMO is really a great concept, but in practical the installation of MUâ€MIMO feature will be delayed to next generations of 802.11ac. One drawback of Mu-MIMO is that the medium is detected to be busy by the slowest link.
Figure : multiuser-MIMO
IEEE 802.11ac can improve the overall system efficiency by using multiuser-MIM which is a new multi-antenna technique used only on the downlink.
The IEEE 802.11ac is a suggested enhancement of the IEEE 802.11 specifications for wireless Local Area Network (WLAN). It operates on 5GHz band and props up backwards compatibility with other 802.11 technologies on the same band such as 802.11n. The main purpose is to provide a high-throughput within Basic Service Set (BSS). The IEEE 802.11ac has some fundamental improvements in both physical and MAC layer; such as (MUâ€MIMO), and has an advanced digital communication concepts to the 802.11technology, such as space division multiplexing. These ameliorations will lead to get a maximum multi-station throughput of at least 1Gbps and a maximum single link throughput of at least 500 Mbps.