Part # Technical Article Mobile Computing STLC8201 TA0312 datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics

Part Description: Band Interleaving Benefits, implementation and operation

Part Details:

TA0312 TECHNICAL ARTICLE BAND INTERLEAVING BENEFITS, IMPLEMENTATION AND OPERATION This document explains the advantages and benefits of band interleaving as well asdescribing the implementation of band interleaving. 1 INTRODUCTION According to industry analysts the number of wireless LAN users is growing every year. Todaythe dominant solutions are based on 802.11b or 802.11g standards and are operating in the2.4GHz ISM band. If this growing user base continues to operate only in the 2.4GHz ISM bandthen those users will face growing problems of interference. In fact wireless LAN users at2.4GHz have access to only 3 non overlapping channels and furthermore they must sharethose channels with other systems such as Bluetooth devices, microwave ovens and cordlessphones. The result will be loss of performance for everybody. A potential solution to the chan-nel crowding problem is offered by accessing the 5GHz channels available to 802.11a users. But then the problem comes of how to provide new solutions that will support 802.11a and atthe same time support the millions of legacy users at 2.4GHz using 802.11b and 802.11g. From the client side this looks simple. Dual band multimode wireless LAN solutions, of whichseveral are on the market today, can scan through all available channels in both bands andmake a connection with available networks in either band. Such a solution provides the porta-ble PC user with the ability to connect and operate with whatever network standard exists inthe vicinity. From the infrastructure or access point side the problem is more complicated. Any networkmust support multiple clients and if those clients are a potential mix of 802.11a b or g clientsthen the network must support all of them at the same time. Whereas the client operates inany given channel or frequency at any one time, either 5GHz or 2.4GHz, the access point mustoperate in both simultaneously. Until now access point architectures that support dual bandoperation have been based on the concept of having dual independent radio functions. Thisworks well but makes dual band access points considerably more expensive at the point ofsale and hence limits their adoption. Band interleaving offers a low cost alternative to this ap-proach. Band interleaving provides the ability for an access point to support clients in bothbands and using all standards, but using only a single radio. Obsolete Product(s) - Obsolete Product(s) By providing low cost dual band access point solutions this will pave the way for exploitationof the 5GHz spectrum. The ST band interleaving functionality enables any Access Point equipped with a singleWLAN radio to simultaneously support 802.11a and 802.11b/g clients. This advanced capa-bility dynamically allocates channel resources to any associated WLAN client cards on the2.4GHz and 5GHz bands. The STLC8000 chipset family architecture delivers the rapid bandswitching technology to support this advanced capability. TA0312/2005 1/7 TA0312 TECHNICAL ARTICLE Band interleaving is based on standard 802.11 protocols, is compatible with current Wi-Fi in-teroperability requirements and ensures that any Wi-Fi approved card can connect and oper-ate with a band interleaving Access Point. 2 WHAT IS BAND INTERLEAVING? Band Interleaving is defined as the capability of an Access Point to share its availablethroughput between the 2.4GHz and 5GHz bands using a single WLAN card. This is imple-mented by dividing time into slots and associating each slot to either 2.4GHz or 5GHz opera-tion. Band Interleaving dynamically means that the amount of throughput dedicated to a singlefrequency is calculated according to the network requirement at that moment. This is imple-mented by adjusting the time allocated for each frequency according to the instantaneous datatraffic demands. Using band interleaving, an Access Point or Gateway equipped with a single STLC8000 basedWLAN radio, can support any of the following combinations simultaneously: 802.11a and 802.11b networks 802.11a and 802.11g networks 802.11a and 802.11bg networks Band interleaving is an optional feature and may be disabled by the user. In which case thesame Access Point operates in conventional mode supporting either of the following networks: 802.11a 802.11b 802.11b/g 802.11g 3 HOW DOES BAND INTERLEAVING WORK? It is important to note that a band interleaving access point makes use of the existing standard802.11 protocols therefore ensuring interoperability with any third party Wi-Fi compliant clientimplementation. A proprietary client is not required. The main principle of band interleaving de-pends on the agility of the access point, its ability to rapidly switch frequency and operatingmodes. Figure 1describes the basic mechanisms of operation at the frame level. Figure 1. Band interleaving implementation Fi F xed be e a d be con i o nte t rva v l a NAV NAV a1 S

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