The hottest ubiquitous access technology of wirele

Wireless digital home network ubiquitous access technology

Abstract: digital home network is an important branch of communication field, which has developed very rapidly in recent years

the architecture of digital home network based on telecommunication network has been standardized in China, but in terms of access mode, it only defines that wireless mode can be used. How to establish wireless digital home network is the focus of future research. This paper puts forward the concept of ubiquitous access of wireless digital home network, gives the architecture of wireless ubiquitous access network, and discusses the key technologies, including cognitive radio, wireless mesh network theory, universal access point link conversion mechanism, service QoS guarantee mechanism, electromagnetic compatibility and heterogeneous system coexistence mechanism, etc

with the rapid development of information technology, human society has entered the information society from the industrial society. The information society has had a great impact on people's lives. It has changed our behavior and way of thinking. In the early 1980s, American scholar Toffler predicted in his book the third wave that people's life center in the information society will return from the society centered industrial society to the family and individual centered [1], From the field of communication, digital home network will become a hot spot and play an important role in the information society

digital home network is established to meet some needs of users and provide users with certain business and application networks. Users' needs can be the information flow between multiple devices in a limited range, between multiple devices in a limited range and the public network, or even between all devices in a limited range and between these devices and the public network. Digital home network can be based on wireless or wired architecture. It should be noted that broadband wireless access is heating up all over the world, and the growth momentum of broadband wireless users in China in recent years is also very strong. As the research focus of broadband wireless access, wireless digital home network has a broad market space. According to the prediction of in stat/MDR, the home network market will grow to $5.3 billion in 2007. In this market, home multimedia wireless network technology will account for about 49% of the market share, that is, $2.6 billion [2]

digital home network has a wide application prospect by using wireless access. With the continuous updating and improvement of home appliances, mobile devices and computer equipment technology, and the seamless interaction between the three, consumers can obtain, view and manage more and more digital media content on home appliances, mobile devices and computer devices. It has become a development trend to easily and conveniently enjoy media content through different devices in different parts of the home, and realize wireless digital home networking. Wireless digital home network has short-range characteristics and pays more attention to the access of the last 10 m. It will take ultra wideband (UWB) as the core of high-speed short-range wireless communication technology, which can ensure the communication speed of consumer electronics, office equipment, computer peripheral equipment and mobile communication terminals in the home environment. However, only with the high-speed transmission speed between links, it can not guarantee the establishment of a high-speed wireless data home network. Its network architecture and the relevant protocols of the media intervention layer must be defined

1 current situation of research and standardization of wireless digital home network

from the perspective of wireless air interface, wireless digital home network belongs to the access sub of digital home network, and from the perspective of its wireless communication distance, it belongs to the technical category of short-range wireless personal domain (WPAN). For short-range wireless personal domain, ultra wideband (UWB) technology is mainly used to provide short-range high-speed information transmission, and can also be used to provide ranging and positioning functions. UWB technology is a new communication method compared with traditional narrowband and wideband communication methods such as spread spectrum communication. From the perspective of signal generation, UWB technology can not use sine wave to modulate baseband signal to the channel, but use baseband signal to directly stimulate the antenna to transmit ultra short time-wide impulse pulse, and use time-domain narrow pulse as the information carrier. At present, UWB mainly has two communication technologies. One is ultra wideband technology based on narrow pulse, which is mainly advocated by Motorola and other companies; The other is pulsed multiwave ultra wideband technology similar to orthogonal frequency division technology, which is mainly advocated by Intel. However, these two UWB communication technologies in China do not have their own intellectual property rights, and their corresponding standards and applications are not yet mature. On the contrary, impulse UWB Technology in China has certain intellectual property advantages, and as for impulse UWB technology itself, it has the characteristics of high data transmission rate, accurate positioning and can support more business types. The technical standards of UWB are mainly carried out in the IEEE 802.15 working group. There are two standards, one is 802.15.3a protocol with very short range and very high data rate, and the other is 802.15.4a protocol with long distance and low data rate

Bluetooth technology is another widely used wireless communication method. It is an open global standard to realize wireless data and voice communication. Its substantive content is to establish a general short-range wireless interface for the communication environment between fixed devices or mobile devices, and further combine communication technology with computer technology, so that various devices can be connected without wires or cables, It can realize mutual communication or operation in a close range. Its standard work is mainly completed by the Bluetooth SIG. The transmission band is the 2.4 GHz license free band (ISM) commonly used by the global public, providing a transmission rate of 1 mb/s and a transmission distance of 10 m

another major short-range wireless personal domain technology is ZigBee technology. ZigBee is a new short-range, low-power, low-speed wireless access technology that requires more complex parameters. It works in the 2.4 GHz ISM band without registration, with a transmission rate of 10 ~ 250 kb/s and a transmission distance of 10 ~ 75 M. It looks closer to Bluetooth, but simpler than Bluetooth. It has lower transmission rate and power consumption, and is in sleep mode most of the time. It is more suitable for those occasions that do not need real-time transmission or continuous update, such as industrial control fields and sensor networks. Langsheng is currently building a 1500 square meter fourth production center in its brilon plant. The main supporters of ZigBee have jointly established the ZigBee alliance to jointly promote the further development and application of this technology. The alliance currently has 70 members. The seven original sponsors of the alliance are emer, Honeywell, Invensys, Mitsubishi, Motorola, Samsung and Philips. ZigBee is an extended set of IEEE 802.15.4 standard. The 802.15.4 working group is mainly responsible for formulating the protocols of physical layer and media access control (MAC) layer. ZigBee defines the specifications of application layer and security, so that devices from different manufacturers can talk to each other

other short-range wireless personal domain standards with development potential include short-range communication (NFC), Wimedia, GPS, DECT, wireless 1394 and dedicated wireless systems. These technologies are based on the special needs of transmission speed, distance and power consumption, or focus on the expansion of functions, or meet the requirements of some single application scenarios, or meet the differentiation of competitive technologies. Table 1 shows the characteristics of three main short-range wireless communication technologies

at present, the standards supporting short-range wireless personal domain are mainly IEEE 802.15 series, which is a standard tailored for specific wireless short-range wireless communication networks, that is, wireless personal domain, although the standard is not yet mature. In 1998, the IEEE 802.15 working group was established to study the standardization of personal area networks and short-range wireless networks. According to the different requirements of data rate, power consumption and quality of service (QoS), the IEEE 802.15 working group defines three different types of wireless personal domain (WPAN) standards, which are high-speed wireless personal domain (hr-wpan) with a transmission rate higher than 20 mb/s, medium speed wireless personal domain (mr-wpan) with a transmission rate of 1 mb/s, and low-speed wireless personal domain (LR-WPAN) with a relatively low transmission rate. The IEEE 802.15 working group also established a special task force to standardize them respectively. IEEE 802.15.1 is the first wireless personal domain technology standard proposed by IEEE to replace wired connection. It is based on Bluetooth technology and belongs to medium speed short-range wireless communication network. IEEE 802.15.2 was established in 1999. Its main goal is to develop recommended applications for IEEE 802.15 wireless personal networks. It can coexist with other wireless devices based on the open frequency band, such as IEEE 802.11 devices. Propose modifications to other 802.15 standards to improve the coexistence performance with other wireless devices working in the open frequency band. The goal of IEEE 802.15.3 is to achieve higher data transmission rate, low cost and low power consumption. At the same time, it is also compatible with Bluetooth, and formulate a high-speed WPAN standard for low-power, low-cost short-range communication. In addition, working group 3A (tg3a) is working on the preparation of IEEE 802.15.3 ultra-high speed WPAN physical layer optional standard to replace the physical layer of high-speed WPAN, and ultra wideband (UWB) technology is currently its main consideration. For some application fields that only need simple wireless connection, the requirements for data rate are not high, and the requirements for power consumption are more stringent, such as industrial control and home network, so the IEEE 802.15.4 working group came into being. The working group researches the application equipment with low data transmission rate to provide comprehensive network solutions for personal area network applications. Working group 4 (TG4) is mainly responsible for formulating the protocols of physical layer and MAC layer, and other protocols mainly refer to existing standards

it should be noted that wireless digital home network is a new wireless application field, and the wireless technology to meet the needs of the home market is still being explored. At present, the Standardization Association of China has officially begun to standardize the digital home network based on the telecommunication network, including the telecommunication services supported by the home network, the reference model of the home network, the functional requirements of the home network, the media format of the home network, the number and address of the home network, the performance of the home network, the electromagnetic compatibility (EMC) requirements of the equipment, the environmental protection requirements of the home network equipment, etc, However, the standardization of wireless digital home network has not yet started

2 wireless digital home access technology

in February 2006, the China Communications Standardization Association (CCSA) approved two communications industry standards for approval, namely, the general technical requirements for home networks based on telecommunications networks and the technical requirements for home network equipment based on telecommunications networks - Family Customs. In these two drafts for approval, the architecture of digital home network based on telecommunication network is defined in detail, the functions of digital home network are expounded, and the services it supports are discussed. It is clearly stipulated in the standard that the access mode of digital home network can be wireless or wired [3]. From the perspective of the future development of communication technology, wireless broadband access is an important development direction of digital home network. Since wireless access technology has not been discussed in the current standard, a wireless ubiquitous heterogeneous access architecture suitable for digital home network is proposed below, and the key technologies are described

the wireless access bearer environment of digital home network is called Pico here. The wireless terminal shown in Figure 1 can be a single-mode or multi-mode node, supporting single or multiple different physical layer access modes of wireless digital home network. Among them, the wireless terminal in the same Pico accesses the dedicated access point in the pico, and the internal communication can adopt the mode of point-to-point or dedicated access point relay; Wireless terminal access stations in heterogeneous Pico