bintec guideline for migrating to ac The technology behind ac

Transcription

1 Whitepaper bintec guideline for migrating to ac The technology behind ac bintec elmeg Teldat Group Company

2 bintec guideline for migrating to ac The technology behind ac Introduction ac is a new wireless networking standard developed to meet the increasing demand for bandwidth. It is an update of the existing n standard and is backward compatible with wireless clients that use older standards (802.11a/b/g/n) ac itself, however, uses the 5 GHz band exclusively. Access points that support.11ac should therefore always be dual-radio access points so that they can simultaneously operate in both the 2.4 GHz and 5 GHz bands MIMO, from 1x1 to 8x8 MIMO (Multiple Input, Multiple Output) technology is already part of the n standard. The different MIMO types describe the number of receive and transmit antennas each type involves. The ac standard defines systems from MIMO 1x1 to MIMO 8x8. Since multiplexing normally involves using a single antenna as both a transmit and a receive antenna simultaneously, we are talking about devices that use anywhere from one antenna (MIMO 1x1) up to as many as eight antennas (MIMO 8x8). The first MIMO number specifies the number of receive antennas. The second numeral in the MIMO notation is the number of transmit antennas this is in most cases also the number of transmission streams. The number of transmission streams has a great influence on the maximum performance a device can achieve. VHT MCS Index Modulation & Coding 20 MHz 40 MHz 80 MHz 0 BPSK 1 / 2 14,4 Mbit/s 30 Mbit/s 65 Mbit/s 1 QPSK 1 /2 28,9 Mbit/s 60 Mbit/s 130 Mbit/s 2 QPSK 3 / 4 43,3 Mbit/s 90 Mbit/s 195 Mbit/s 3 16-QAM 1 /2 57,8 Mbit/s 120 Mbit/s 260 Mbit/s 4 16-QAM 3 / 4 86,7 Mbit/s 180 Mbit/s 390 Mbit/s 5 64-QAM 2 / 3 115,6 Mbit/s 240 Mbit/s 520 Mbit/s 6 64-QAM 3 / 4 130,3 Mbit/s 270 Mbit/s 585 Mbit/s 7 64-QAM 5 / 6 144,4 Mbit/s 300 Mbit/s 650 Mbit/s QAM 3 / 4 173,3 Mbit/s 360 Mbit/s 780 Mbit/s QAM 5 / 6 n/a 400 Mbit/s 867 Mbit/s Raw transfer rates attainable with MIMO 2x2:2 systems Some manufacturers include chipsets in their devices that allow for more transmit antennas than transmission streams for this reason, the notation MIMO 3x3:2 is often used. MIMO 3x3:2 means we are dealing with a model that has three transmit antennas but only two transmission streams. The performance is similar to that of MIMO 2x2:2 devices. As a rule of thumb, a MIMO 2x2:2 device will offer twice as much throughput as a device using MIMO 1x1:1 technology. It is important to keep in mind here that for wireless connections between a wireless access point and a wireless client, the maximum achievable data rate is always determined by the device with the lowest MIMO. Currently available ac access point chipsets support a maximum of MIMO 4x4. Channel bandwidths In addition to MIMO, channel bandwidth has a direct influence on the maximum attainable data rate an devices can operate with channel bandwidths of 20 MHz and 40 MHz. The maximum achievable data rate for an n MIMO 2x2:2 system using 40 MHz channels is 300 Mbps. The new ac standard defines channel bandwidths of 20, 40, 80 and 160 MHz. Current devices support 20,40, and 80 MHz bandwidths.

3 All about modulation from BPSK to 256-QAM Another factor that impacts performance is the chosen modulation. This technology has a considerable impact on the efficiency with which the transmission path is used n can encode signals using BPSK, QPSK, 16 QAM, or 64 QAM modulation. In addition to the modulation procedures defined in n, ac also allows for the use of the more efficient 256 QAM scheme. 256 QAM requires a signal-to-noise ratio that is approximately 6 db better than 64 QAM, but enables data rates that are up to 33% higher. This higher data rate that 256 QAM makes possible can of course only be achieved if the wireless client is not too far from the access point if the signal-to-noise ratio is poor, the access point automatically falls back to a more robust modulation scheme. Spectrum and channels As mentioned above, ac operates exclusively in the 5 GHz band. There are up to 19 channels of 20 MHz each available in the 5 GHz band. For indoor applications, eight 20 MHz channels are available. Of those, the upper four channels (52, 56, 60, and 64) are DFS channels, which require the access point to attempt to detect interference from radar signals. Installing ac indoors results in the following usable channels: ac access points are normally equipped with two radio modules. The first radio module supports clients that can only operate on the 2.4 GHz bgn standards. The second radio module is a 5 GHz ac module. This configuration allows gentle migrations to the new standard without rendering older clients obsolete. The ac radio module is also compatible both with older legacy clients that support a/h (54 Mbps) and with an clients. Mixed-mode operation with legacy a/h, an, and ac clients is also possible. Migrating an existing network to ac In this section we will demonstrate which aspects must be considered when an existing network is to be migrated to the ac standard. Ethernet cabling and switches The cabling and switches on the LAN should be Gigabit Ethernet or faster. Older 100 Mbps switches should be replaced since they can create a bottleneck even on n systems. The bintec W2003ac can perform to its full potential on a single 1 Gbps LAN port. Thus it is no longer necessary to run two Ethernet cables or set up complex in-switch bonding (link aggregation). The decision of whether to use a Gigabit Ethernet or 10 Gbps interface for the uplink must be made on a case-to-case basis. Backward compatible Bandwidth Number of usable non-overlapping Channels indoors Usable Channel combinations 20 MHz 8 36, 40, 44, 48, 52, 56, 60, MHz , 44+48, 52+56, MHz , MHz

4 Power supply The bintec W2003ac requires less than 12.4 watts to operate and can therefore run on PoE and the widely used 802.3af standard. That eliminates the need to perform expensive upgrades to switches or undertake costly installations of new electrical lines and outlets to power the APs via plug-in power supplies. Access points with 3x3 or 4x4 MIMO, on the other hand, require as much as 21 watts of power and generate significant additional expense with the unavoidable upgrades to the PoE infrastructure they require. Operation on PoE switches that can provide a maximum of 12.4 watts, although possible, reduces performance with these devices because they are forced to switch over to a type of safe mode in which they drop down to MIMO 2x2:2. In addition, electricity costs for a MIMO 4x4 access point can be as much 25 a year, an expense that cannot be ignored. Wireless site survey A wireless site survey determines which positions in the building are suitable to install access points in order to achieve seamless wireless coverage throughout the company s facilities. Whether or not a new site survey is required depends on a number of factors. If the customer only wishes to install ac access points in certain areas, for instance in conference rooms, nothing else needs to be done other than replace the existing access point with a bintec W2003ac. Should the customer however prefer to have seamless.11ac coverage with a 5 GHz network and the old wireless network only used the 2.4 GHz band, a new site survey is necessary. If the old network was already surveyed for 5 GHz, a new site survey is not normally required. Capacity planning A site survey determines how many access points are necessary to achieve sufficient field strength in all the areas where coverage is required. For normal office environments or in storage areas, this is sufficient. If however there will be a large number of wireless clients that require connectivity, it s essential to also take capacity into consideration. A wireless radio module can theoretically handle up to 250 clients, but this is impractical because performance would suffer. In most cases, 20 to 30 clients per radio module has proven to be appropriate. bintec access points offer client management features that can prevent APs from exceeding a specified number of clients or reroute clients from access points experiencing heavy loads to other APs in the vicinity that are handling less traffic. For customers who prefer to be cautious when approaching the capacity limits of their wireless networks, the bintec Cloud NetManager offers comprehensive wireless LAN management, analysis, and alert features. Channel planning The first thing is to decide on the bandwidth of the channels. Administrators seek to achieve the maximum performance from their hardware and may therefore be inclined to use the maximum channel bandwidth available (such as 80 MHz). Parameter Function Recommended value Max. number of clients - Once this value is exceeded, all further clients hard limit requesting a connection are rejected. Max. number of clients - soft limit Once this value is exceeded, all clients attempting to connect for the first time are rejected. If the client can t find another AP in the area, it will try to connect to the first AP again. The second connection attempt will be accepted until the hard limit is reached

5 For a wireless infrastructure with multiple access points, however, it s important note that although it is possible to use the same channel for several access points, the field strength of the other access points on that channel must be low enough wherever the next access point will re-use the channel. In other words, two access points on the same channel should be far enough apart. 80 MHz channel bandwidth Since there are only two non-overlapping 80 MHz channels available for indoor applications, this bandwidth only comes into question for areas with a low density of access points. That includes installations with only two access points or those whose access points are far enough apart. There should also be only be a limited number of 5 GHz access points in the area surrounding the installation. 40 MHz channel bandwidth At a channel bandwidth of 40 MHz, there are four non-overlapping channels available. This makes it easy to install access points at normal density throughout the area that requires coverage. This is the standard configuration for larger installations in hotels, offices, conference rooms, etc. 20 MHz channel bandwidth If a large number of wireless clients require connectivity, more access points are used than would be necessary just to provide sufficient radio coverage. To have enough channels without overlap available for this type of application, 20 MHz channels are recommended. 20 MHz channels are especially well-suited to installations in facilities such as convention centers, trade fair installations, and stadiums. Wireless LAN management All bintec wireless management systems support bintec.11ac access points. bintec access points always uncouple the payload so that they don t have to send that data through the WLAN Controller. This eliminates both a potential hardware bottleneck and the need to invest in new controller hardware. Conclusion The current bintec access points are easy to integrate into existing installations and they don t require any large investments. bintec devices running MIMO 2x2 have technological advantages over MIMO 3x3 and MIMO 4x4 access points. An investment in MIMO 3x3 or MIMO 4x4 access points does not make a lot of sense right now because there are only a limited number of client devices that support the technology. Caution is warranted especially with very affordable consumer-grade devices since they only rarely support DFS channels in the 5 GHz band, even though DFS channels are absolutely essential there because of the limited number of channels available. All existing WLAN Controllers and WLAN Controller licenses can continue to be used at no additional cost all that is required is a free software update to enable support for bintec.11ac access points. Customers who manage their wireless LAN installations with the bintec Cloud NetManager or the bintec Virtual Cloud NetManager do not have to do anything at all because these management systems already support bintec ac access points.

6 FLEXIBLE communications solutions that grow with you. green it by bintec bintec W2003ac / bintec W2003ac-ext The bintec W2003ac access point supports the new ac wireless standard. Dual radios allow simultaneous operation in both the 2.4 GHz and 5 GHz frequency bands. bintec Client Management ensures that the wireless client is always able to operate at maximum speed. MIMO 2x2 technology and the ac standard allow for raw data rates of up to 867 Mbps. MIMO 2x2 and its two transmission streams has the considerable advantage that the device can run on existing cost-efficient PoE infrastructure (<12.4 watts). Furthermore, MIMO 2x2 is ideal for the current generation of smart phones and tablet PCs which frequently only support ac with MIMO 1x1. The bintec W2003ac uses internal antennas while the W2003ac-ext comes equipped with external antennas. These APs are compatible with Cloud NetManager, the bintec WLAN Controller, and master AP configurations that include a free WLAN Controller license for up to six APs. Dual radio for simultaneous operation on the 2.4 GHz and 5 GHz bands ac with MIMO 2x2 and up to 867 Mbps raw data rate Standalone operation or management via Cloud NetManager or bintec WLAN Controller bintec elmeg GmbH Südwestpark 94 D Nuremberg Phone: Fax: info@bintec-elmeg.com