3. HomeNet Logical Layer Architecture
Figure1 shows the HOMENET logical architecture, the whole system consists of five layers: physical media layer, protocol layer, API layer, APP layer (application program) and UI (user interface) layer. The specifications of the underlying two layers has been distributed and used in practices.
Figure 1 HomeNet architecture
The API layer is the key of HomeNet , the technologies of it is the hot issue of home network development, the Home API and Jini specifications distributed in 1999. The fourth layer APP is a set of applications over the third. The fifth layer is UI, it is a set of various interface tools, it is not limited to PC, but also includes emergent buttons, help switches, remote controlling devices and other visual interfaces.
The HomeNet protocols can be divided into three types: under layer protocols ( media ,protocol layers), API protocols and UI specifications. In UI layer, without proper distributed specifications, with the market enlarging and the increment of user requirement, it is necessary to standardize the UI design. From the view of zone, the HomeNet specifications are distributed by America, Europe and Japan, such as Japan’s HBS, Europe’s BatiBUS, Europe Home System and EIB, America’s X10, CEBus and lonWorks. Addition, some work group also distributed specifications such as HAVI’s IEEE 1394, Bluetooth, HPNP, Home API and Jini[4][5].
4. The Connect Scenarios and Media
There are several communication media at home as following: TP (twisted pair), TL (telephone line), xDSL, Cable Modem, FB (fiber), PL (power line) and wireless trsmission (IEEE802.11, HomeRF, Bluetooth). TP, TL and PL are current prevailing media in HomeNet, FB, xDSL, Cable Modem and wireless media will dominate in the future.
The implement of connection scenarios are relative closely to the communication media . The two rules must be observed in HOMENET construction, the first is the usability and the another is the reasonable cost. Due to HOMENET’S various functions and each family’s affording ability, the connection scenarios will also be various. In the following sections, we discuss ether and fast ether network, home TL network, PL network and wireless network.
Ether and fast ether network: ether network is often used in practice , simplicity and reliability is its advantage, and the cost is lower than other scenarios. The compatibility of it makes it convenient to upgrade from 10mpbs to 100mpbs and 1000mpbs ether network, and it benefits users from protecting the original investigates, so this is a preferred scenario in constructing HomeNet.
TL HomeNet: Home TL technology makes it possible to build a high speed network at home by use already existing telephone lines. The 10mpbs TL specification has been distributed in HomePNA 2.0, a digital product can be easily linked to the network by a interface module which connects the telephone line plug and the product. Addition, the xDSL technology extends the PL communication band, and makes the TL HOMENET can afford the multimedia applications.
PL network: this scenario interconnects the home digital devices by ubiquitous power lines, its biggest advantage is that most of the electronic products have been linked to PLs. Although the old PL network (X-10) have difficulties to carry high speed data information, the new technology has implemented high speed data transmission.
Wireless network: the advantages of it over wire network lie in flexibility, mobility and easy constructing. The technology maturity of the wireless network has been proved in the applications of restaurant communication and stock exchange information transmission, but the defect is its high cost in construction and the narrow communication band. With the appearing of new technologies, the wireless network will dominate the HomeNet market in the future due to its above tributes.
5. The End
There are still a lot things to do to spread the home network currently: first of all is the development of embodied OS and IC, then without the interoperable specifications the different devices can not communicate each other directly, and the integration of HomeNet becomes complicated due to much more protocols in the under lays, so much efforts should be taken to implement the dream of remote learning online, ordering online and so on through the HomeNet.
References
[1] MAURY WRIGHT: "Home-automation Networks mature while the PC industry chases a new home LAN", EDN JUNE 4,1998.
[2] Zhong xichang, Home digital devices PC WORLD CHINA , JAN 3, 2000 NO.1
[3] Cao jiuxin ect., The Technology and Design Strategy of HomeNet User Interface MINI-MICRO SYSTEM, 2000
[4] Home Automation Network Standards and Specs – Alliances and Working Groups . http://www.hometoys.com
[5] Kenneth P.Wacs, PH.D. Introduction to the CEBUS® communications protocol. HTINews Articles 1999