Xircom’s Netwave is a Compact Wireless Solution

There is little question about it: state-of-the-art wireless solutions for mobile computers are on the way. One of the most impressive packages is offered by Xircom, a long-time leader in mobile computing solutions. The Calabasas, California-based company introduced Netwave at CeBIT ’94, one of the smallest, self-contained PCMCIA-based, radio frequency (RF) communication systems.

Dubbed by Xircom as a cordless local area network system, the Netwave offers the potential for a new degree of mobility in an office or campus environment. In fact, Xircom officially prefers the word “cordless” in place of the more common wireless to better reflect the local nature of the mobile communication. In this sense, cordless is in sync with mobile telephony where wireless is frequently used for regional or wide-area service, while cordless telephones are more localized.

The Xircom Netwave technology integrates with existing LANs by implementing a modified physical and data link layer to support radio communication. The physical layer is responsible for controlling the radio medium and operates using a frequency hopping, spread spectrum system in the 2.4 GHz band. Using this unlicensed RF band, the system is capable of delivering a raw data rate of 1 Mbps.

Frequency hopping is a technology that permits the system to operate well, even in the presence of interference. The system divides an 83 MHz wide channel (located at 2.4 to 2.4835 GHz in the United States) into 82 one megahertz channels. When transmission occurs, the Netwave transmits on one particular channel for about one tenth of a second before hopping to the next channel. The sender and the receiver agree on this prearranged sequence of channels (or hops) enabling them to communicate.

Using this system, interference on any particular channel affects only a small portion of the exchange, and never lasts for an extended period. Also, stations unaware of the hopping sequence will find the message nearly impossible to decipher, adding to the inherent security of spread spectrum systems. This technology permits Netwave equipped devices to communicate through walls and ceilings within a range of 40 to 50 m (130 to 150 ft.).

At the data link layer, Xircom provides an enhanced Media Access Control (MAC) sub-layer that enables asynchronous data exchange while taking into account the special characteristics of the radio medium. This includes a positive acknowledgement (ACK) protocol that increases the reliability of the data exchange to match those expected by typical LAN-based applications.

The Netwave MAC must also perform the standard medium access functions of any layer 2 protocol. These include determining when a station is permitted to send data, what to do when two stations attempt to transmit at the same time, and how to assure that every device is given reasonable access to the radio channels. Without going into details, LAN-based approaches to these problems, as used by Ethernet for example, fair poorly with radio-based communication.

Xircom introduced three specific products to enable cordless communication for mobile computers:

• CreditCard Netwave Adapter, a PCMCIA 2.0 Type II card that is completely self-contained without the need for external circuitry, antenna, or power cord.
• Pocket Netwave Adapter, the same device which instead connects to a parallel port and supports an EPP (Enhanced Parallel Port).
• Netwave Access Point for Ethernet, an external unit that forms a bridge between a Netwave LAN and a wired, IEEE 802.3 Ethernet LAN. The Token Ring version is planned for late 1994.

The Netwave Access Point includes some additional features that makes it particularly useful as a gateway to traditional wired LANs. Most notably, the Access Point is designed to maintain network connections when the mobile device enters sleep mode, and resumes the connection when the device awakes. This is crucial for portable devices that must take advantage of every power saving feature while still remaining functional on a network.

The Netwave system is compatible with all major network operating systems including Novell’s NetWare and Microsoft’s LAN Manager. European availability for the product, however, depends on ETSI’s (European Telecommunications Standard Institute) final proposal on European-wide wireless data communication, and will therefore push back actual product introduction in Europe until the third quarter of 1994.

The suggested retail price for either the CreditCard Netwave or the Pocket Netwave is US $595, the price for the Netwave Access Point for Ethernet is $1745. For more information, contact Xircom at (818) 878-7600, and Xircom Europe at 32 (0) 3-360-38-11.