The most popular use of band interleaving technolo

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Using band interleaving technology to realize mixed video and data services

in the past two years, the sales of Wi Fi products based on 802.11b and 802.11g have achieved amazing growth. Market research companies such as iSuppli predict that the number of wireless network interfaces will exceed 80million in 2004, and will increase year by year to more than 200million in 2008. However, its rapid popularization has caused the congestion of the limited channel resources available to the first generation network users based on IEEE 802.11b and 802.11g standards. Unfortunately, there are only three non overlapping channels in the 2.4GHz frequency band, leaving only a small amount of capacity to meet the high throughput requirements of the multimedia network. With the increase of production, the price of Wi Fi products has dropped, which creates opportunities for exploring markets other than simple data networks

a particularly important area is home networking. Multimedia PCs, broadband connections and digital TVs placed in multiple rooms are driving the demand for low-cost, high-performance networking solutions. For the mass consumer market, where reliability and user experience consistency are very important, the important goal is a way to combine data and multimedia networks while ensuring that they do not affect each other. Network congestion and high-intensity interference from home devices such as microwave ovens using the 2.4GHz band mean that 802.11g will not be able to obtain the reliable and high-throughput connections required for video streaming. Therefore, consumer electronics manufacturers are looking for solutions in the 5GHz radio band used by the 802.11a standard

open a new channel

when users' demand for bandwidth increases, it will cause WLAN channel congestion. The main difference between traditional data network and multimedia network is the amount of data transmission and reliability. An email or page can be delayed for several seconds, while a video or call cannot be interrupted to make way for other network users. The quality of service (QoS) protocol, especially WMM (Wi Fi alliance interoperability standard), provides a solution to ensure that the transmission stream of multimedia network N semi crystalline plastic has higher priority than the data transmission stream due to the large obtuse angle ≤ 0.8% tension at the tip of the oil needle. In order to reliably transmit high-quality video and voice, it is very important to support QoS and correctly assign these data packets higher priority than background data or "best effort" data. Without QoS, the 802.11 network will share the available bandwidth with all clients associated with the access point. Although QoS is an important element in the 802.11 solution, like any other wireless system, it cannot control interference from overlapping networks or RF noise sources

Figure 1 Wi Fi network provides a solution for multimedia home connection, allowing data

and video streams to be separated in the frequency band

although the 2.4GHz band may be crowded, Wi Fi can provide a solution by using up to 24 additional available channels in the 5GHz band. These channels are already 20MHz apart, so there is no overlap between Wi Fi users. Since both the access point and the client need to be able to support the 2.4GHz and 5GHz bands, the speed of adopting this spectrum has been very slow. Cost effective dual band clients are now quite common, but although dual band access points do exist, their implementation costs are relatively expensive. Unlike clients, dual band access points must operate on both bands at the same time to support a large number of users of 11b and 11g devices that can only operate on one of the three channels, and to provide 24 additional channels available in the 5GHz band

up to now, the only way to work in two frequency bands at the same time has been to use two independent radio parts, and the radio part is the most expensive in the node. In addition, since it also has to process two synchronous data streams, dual band access points usually need a CPU with strong processing power more than single band devices. Therefore, the cost of dual band access points is almost twice that of single band access points, which increases the cost of a typical bill of materials (BOM) by at least $20. This cost burden makes network operators reluctant to adopt 802.11a

Italy France microelectronics has proposed an alternative scheme - band interleaving, which almost eliminates this cost burden. Band interleaving allows access points to quickly alternate between two bands, rather than working on both bands at the same time. The "zero intermediate frequency" radio is used to design a frequency synthesizer that can share two radio bands and other devices to the up conversion mixer. As long as the shared components meet the specified mandrel diameter and have sufficient hardness, the radio design only occupies a little more than 1 mm2 chip area, so the cost of dual frequency radio is only a little higher than that of single frequency radio. Therefore, the cost of a band interleaved access point is only slightly higher than that of a traditional single frequency access point, and the cost of its typical bill of materials is less than $5

Figure 2: frequency band interleaving is realized by quickly alternating between two frequency bands. The time of working in each frequency band

is dynamically determined according to the network traffic

band interleaving is actually transparent to users. It uses the existing protocols to manage the independent channels represented by the two frequency bands, so the user nodes do not need any special software. When the access point uses one frequency band, band interleaving prevents the client node from transmitting signals in another frequency band, so there will be no significant service loss when the node is in another frequency band. When the access point changes the frequency band, there will be no obvious loss. Band interleaving uses a radio whose band switching speed is fast enough (less than 20 microseconds), so it is invisible to TCP and 802.11 signaling protocols

band interleaving also provides transparency by intelligently managing the replacement between the two channels, so that the channels do not exhibit half the expected data throughput. There are two ways to manage frequency rotation. One is static -- access points access points work on each frequency at fixed intervals; The other is dynamic -- the access point allocates a period of time for each frequency band according to the data traffic in any given time band. Band interleaving maximizes throughput by dynamically allocating time to each band, or provides another level of QoS by allocating the least time to one band. For example, before providing support for traditional 11b/g, ensure the support for 11a video streams with high real-time requirements

when using band interleaved access points, the operation of the network is very straightforward. If there are both 802.11a and 802.11b/g clients in the network, each client will find an access point on its own channel and connect in the usual way. This actually constitutes two networks, which are connected to the access point together and are specially used to meet specific needs when needed. For example, in the home network, broadband Internet access can be provided to 11b/g data clients, while the 11a network can be reserved for the video stream of 11a clients embedded in the set-top box, wireless LCD TV or high-definition plasma TV screen

a dual-mode data client that interacts with a band interleaved access point has gradually become an important choice for automotive lightweight. It will find access points on its two channels. This allows the application to freely choose to use either of these two channels, or choose 11a to transmit video, or choose 11g to send e-mail

for equipment designers, band interleaving technology can now be used. By installing stlc8000 band interleaving radio components of St, this technology can upgrade any single band AP to work in dual bands at the same time. This chipset family includes reference designs for minipci and cardbus32, as well as all the software needed to rapidly develop band interleaved access points with advanced band management capabilities that can increase any network capacity and performance

Author: John prince

consumer product marketing manager of wireless local area division

Italy France Microelectronics (end)

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