Who will be the best choice for wireless transmiss

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Who will be the ideal choice for wireless transmission of digital home network

from the information collected from all aspects, digital home will undoubtedly be the next hot spot in the consumer electronics industry. Almost all major semiconductor companies have made efforts in this field, and semiconductor giant Ti has taken this field as a stage to continue its DSP brilliance. Around the control right of digital home, the print experiment report shows three factions: TV (with TV as the core), Telecom (with Internet as the core) and it (with PC as the core). However, what is the digital home? What is the connotation? How many "stories" can be deduced for users around the digital home? Although both industry experts and consumers have unlimited reverie, it is still difficult to give a unified explanation in a few words. But it is certain that the connotation given by the digital family will be more and more rich, but this is the thing of the application layer! What will be the underlying technology, or group technology, that supports these rich applications

wired media are restricted in digital home transmission

although for many newly installed homes, there may be a variety of wiring, including lines, coaxial lines, network lines and even optical fibers. Although these cabling can play some role in the hybrid group, the biggest problem is that it can not meet the mobility, can not be upgraded, and the cost is very high. As the transmission medium of digital home, power line has been verified in the form of Homeplug standard. Many companies including arkados have launched Homeplug module, and the data transmission test effect is good. In terms of coverage, it is wider than other wired technologies, and seems to be more suitable for a large number of low-end mainstream users. However, in terms of the actual situation in China, The surge and high-voltage safety problems on the line restrict its good performance in the short term. Thus, the constraints of wired media will enable wireless media to play an important role in the digital home

Figure 1: build digital home network transmission based on WiFi

wifi can become an ideal support for home network

when it comes to WiFi, there is a very interesting thing. A few years ago, many experts believed that WiFi was about to die out because it had too many limitations. In the final analysis, it had no roaming function and could not organize itself, so it could only become a vassal of other technologies. Then there is the lack of competitive profit model of the technology. However, the development in recent years has made many experts fall short of their glasses, and the shipment of WiFi has surged year after year. At present, it has become the mainstream technology of wireless communication. However, on the other hand, operators who invested heavily in the construction of WiFi networks were unprofitable and even kept losing money. In the end, only chip manufacturers were happy because WiFi was squeezed by other technologies and there was no clear independent profit model

however, it seems that the digital home has found a place for WiFi to play its role alone. It uses open frequency band and direct sequence spread spectrum. The maximum data transmission rate is 11Mbps. It can also dynamically adjust the transmission rate to 5.5mbps, 2Mbps and 1Mbps bandwidth according to the link fading state. The transmission range without straight-line transmission is up to 300 meters outdoors and 100 meters indoors in case of obstacles, which is enough to meet home applications. The original intention of "wireless fidelity" seems to be more in line with the needs of home entertainment. Therefore, both the transmission rate and coverage seem to be in line with the application of digital home. Of course, there is no lack of technologies that compete fiercely with them. UWB in the Wimedia camp is one of them. This technology is used in cwave of plex link. UWB adopts many advantageous underlying technologies, including MIMO and OFDM, and the data rate has reached nearly 1Gbps. However, this technology focuses on the high data rate, and its too short coverage distance will restrict its performance in the digital home

an essential function of the digital home is the interconnection with the outside world. Today, 802.11g is the most successful wireless standard for WiFi. Based on the characteristics of WiFi, this technology is more friendly to the wireless technology of network layer. This may be one of the reasons why this technology currently occupies a large share in the field of digital home. Michael hurlston, vice president and general manager of wireless local area network (WLAN) division of wireless connectivity group of Broadcom, believes that WiFi has now become the most ideal supporting technology for digital homes. His reason is simple: for today's applications, Wi Fi can provide sufficient bandwidth and coverage distance at a price that consumers can afford. In recent years, Wi Fi manufacturers have made gratifying progress in product security and ease of use. The direct result of this is the continued expansion of the Wi Fi market and the emergence of different variants for various special applications. In addition, he believes that with the declining price, power consumption and technology integration of 802.11g, it will continue to push it into the digital home application market, including mobile, printer and media player

another factor that cannot be ignored is that 802.11n is rapidly becoming the de facto standard for wireless PCs and routers, which will provide additional support for high-speed data transmission applications. These applications include video streaming in digital homes, 3D games, etc. The 5g band provided by 802.11n for WiFi has added new impetus to WiFi, enabling it to enter the consumer electronics field including set-top box, high-definition TV, media player and so on, mainly depending on the detection accuracy and service life. "Through the complementarity of the two standards, the WiFi ecological environment will continue to improve the way people communicate at home and the experience of enjoying media programs," hurlston said

on the other hand, whether 802.11g or 802.11n, its frequency fading characteristics will be tested in the digital home, especially the latter. Two aspects should be considered. On the one hand, the impact of building fading characteristics on application QoS should be considered, and on the other hand, the comprehensive EMI problem caused by increasing power should be considered. In particular, the structure of unit housing in China is very different from that in western countries

whether ZigBee can catch up with the feast of digital family

a large part of the task in the digital home belongs to the control domain, that is, the category of sensor networks. It involves safety monitoring, automatic meter reading, remote control and maintenance, control of various electronic and electrical equipment, etc. Such tasks do not require too high transmission rate, but reliability and network system are more important. These characteristics seem to determine that ZigBee is the most ideal choice. Kuang Jingliang, marketing manager of wireless and mobile systems division of Freescale Hong Kong Co., Ltd., thinks so. He said: "ZigBee has the main functions of path selection, automatic network connection and self recovery. It is very suitable for monitoring, control and sensing network applications in digital homes.". However, he also believes that ZigBee will only be applied in lighting control due to equipment renewal and cost problems

Figure 2: three device types in ZigBee network

zigbee protocol defines three node types - network coordinator, router and terminal device. ZigBee network coordinator is the center of the whole network. Its functions include establishing, maintaining and managing networks, assigning network addresses, etc. The coordinator can start a Zigbee network by selecting the working channel of the network and the personal domain identifier (Pan ID). Once the network is started, routers and terminal devices can join the network and transmit and route data through the network. The network has strict level management. The terminal equipment cannot participate in routing data, so it can sleep when it does not transmit and receive data. These characteristics exactly match the control function in the digital home. ZigBee has a maximum coverage distance of nearly 100 meters, which is also suitable for home applications

in fact, ZigBee has another advantage, that is, the operating frequency band. In addition to ISM frequency band, this technology also supports multiple other frequency bands. It can be seen from the lower part of the force measuring cylinder that many engineers believe that 400m and 800m frequency bands may be good frequency choices for data home networks. Indeed, these frequency bands have advantages for medium and low speed data transmission, especially many companies have very low-cost transceiver modules. Thus, various contradictions and problems are intertwined with each other in terms of cost. In addition, it is also conducive to the development of relevant products by radio enthusiasts, and on the other hand, it promotes the promotion of digital home network

however, ZigBee network also has some problems, such as the defect of addressing mechanism caused by repeated and changed network addresses. Facing the increasing group capacity and security requirements, the storage capacity in the protocol is difficult to meet the 802.15.4mac/phy, ZigBee network layer and other expected application function requirements. Another key defect is that ZigBee cannot support dynamic channel switching like Bluetooth technology. This will be a challenge for WiFi, ZigBee hybrid group and QoS guarantee in the future digital home

in addition to the technology itself, ZigBee alliance's own problems also cast a shadow on whether the technology can play its role in the digital home. That is how to upgrade the existing protocol standards. Due to commercial interests, several key initiators of the standard have their own words and are unwilling to give up their own favorable terms, so it is always difficult to reach an effective compromise. It is precisely this point that makes the progress of the standard as slow as an old bull pulling a broken cart

it is precisely because of the above factors that many manufacturers are forced to open up new paths, and many quasi ZigBee solutions continue to emerge. Such as the simple ZigBee solutions of St, jennic, maxstream and Fuchang electronics. These simple schemes have been applied in many aspects such as home control

from the current situation, it seems that the pressure of market demand on ZigBee is not large enough, because the digital home technology is still in the exploration stage. Restricted by the social server network and management system, China's digital home market does not seem to expand so fast, which provides ZigBee with a breathing space. However, the author believes that at any time, we should not forget the advanced habits of Chinese consumers in this regard, and early cultivation is conducive to accumulation

QoS and security in home networks are more critical

although different from operator level networks, QoS in digital home networks is also very critical. As for Mac to guarantee QoS, few people seem to mention it in today's digital home solutions. Instead, they focus on bandwidth. In fact, the importance of QoS in digital home networks will only be higher than that of existing local networks. Just imagine, when you are absorbed in watching HD programs on demand, who is willing to be constantly disturbed by other unrelated businesses

it is gratifying that some companies have noticed the importance of this issue. Some companies have launched chips that support ieee802.15.3b Mac. This MAC supports IP and is designed from the bottom. Using this Mac, we can support the synchronous data flow and realize the reliable distribution of high-capacity entertainment content in different places in the digital home

another key is the security technology in the digital home network. At present, many people have included personal finance or home banking as an indispensable part of the digital home. Indeed, it seems very safe to handle all kinds of financial businesses and wealth management at home. There is no need to worry about the acts that infringe on financial security, such as secretly photographing and recording, and the problem of any time is solved. But then comes the problem of network security. This is not only the security of the transmission network

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