ACoRN Members Only AreaWireless Data Communications
Vision
Modern wireless communications was born at the end of the nineteenth century when Marconi demonstrated the first radio transmission. Since that time wireless communications has developed at a truly remarkable rate. The exciting opportunities in the application area of wireless data networks look set to continue driving this development.
The ultimate vision for wireless data networks is to enable high-speed and high-quality information exchange between untethered portable devices located anywhere in the world. People will be able to communicate while on the move, wherever they are, using a variety of methods including voice, video, facsimile, E-mail and file transfer.
What is a Wireless Data Network?
See also an ACoRN sponsored article at NOVA http://www.science.org.au/nova/097/097key.htm
In basic terms, a wireless data network has many users or nodes communicating over a shared wireless channel. The data being communicated could be anything but the term "wireless data network" generally refers to networks that transmit generic computer data, rather than voice traffic. While existing cellular networks have "unwired" voice, one could see the driving goal of wireless data networks as unwiring the Internet.
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| WLAN technology is becoming widespread but is limited to low speeds and mostly stationary users. |
Some well known examples of wireless data networks include the radio paging network, which operates over a wide area but transmits small amounts of data at a very low rate, and Wireless Local Area Networks (WLANs) which connect computers in the same local area (offices, coffee shops) at high data rates. The real challenge is too provide high-speed data to mobile users over a wide area.
Where do Cellular Systems Fit?
Existing wireless networks can be classified into those that had their origins in wireless telephony and those that were created to connect computers. The early cellular mobile networks were designed to transmit voice traffic and this is still the main driver of today's cellular networks. (See below for a discussion of the differences between transmitting voice and data.)
Cellular mobile systems have been the big success story in wireless networks with unprecedented growth over the past fifteen years. They have moved from first generation analog systems, through second-generation digital systems and on to third-generation systems which support both voice and data. Cellular networks are not really optimized for transmitting data however and we are far from reaching our original vision.
The Difference between Voice and Data
There are fundamental differences between the transmission requirements of voice and data. These differences make it difficult to design a network to support both voice and data services. Indeed there is great uncertainty whether the next generation cellular systems will dominate the wireless data market or new systems tailored specifically for data will win the day.
The main differences between voice and data communications are:
- Voice communication requires low transmission rates (of the order of 10 kbps) while data communication often requires much higher rates (Mbps and higher).
- Voice transmissions require a steady bit rate while data rate requirements can be very variable with large idle periods followed by big file downloads.
- Voice transmission can tolerate errors in the received bit stream while data networks have very strict error rate requirements.
- Voice communications is sensitive to delay while data is more robust in this regard.
These differences lead to very different design considerations for wired or wireless networks however the impact of the differences is even greater when the access network is wireless.
Key Research Challenges
We are not yet to the point where wide-area wireless data networks are able to offer the speed and quality of wired networks. Fourth-generation systems will aim to meet this challenge by employing new breakthroughs in wireless communications and networking theory including adaptive modulation and coding, multiple-input multiple-output links, channel dependent scheduling (multiuser diversity), and orthogonal frequency division multiplexing (OFDM).
Australian Wireless Data Communications Researchers
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