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Road to wireless Net has bumps

Posted: 16 May 2001     Print Version  Bookmark and Share

Keywords:tcp/ip  wireless ip  wireless data  wireless internet  always-on networks 

While fewer than two percent of Internet users worldwide have wireless access, expect that to change dramatically over the next three years. But mobility will not come without a fight. Before widespread acceptance and availability, the wireless Internet must attain credibility, which means significant advancements in reliability, speed and bandwidth must be made before it is adopted broadly.

Many fundamental obstacles that compromise the promise of the wireless Internet are rooted in the traditional Internet Protocol suite, which was not designed for wireless networks. Although Transport Control Protocol/Internet Protocol (TCP/IP) was envisioned for transmission across any physical channel, the traditional IP suite—specifically, TCP—is built upon a set of fundamental assumptions and optimizations specific to the performance characteristics of wireline physical channels available nearly 30 years ago.

There are obvious performance differences between wireless and wireline physical channels that are obvious in the transport layer of a network stack. And there are other factors that are dramatically different in wireless networks, mainly higher bit error rates (BER), longer latencies and highly variable channel availability. These differences make channel conditions highly dynamic in comparison with the relatively static channel conditions of wireline networks.

Underlying assumptions

The tremendous variance in channel characteristics and conditions created by these differences breaks the underlying assumptions and optimizations upon which TCP is built, causing its machinery to fail. TCP is, in effect, thrashing in mobile cellular networks, throwing away much of what precious little bandwidth is available. Also, wireless networks typically use many different RF channels to facilitate continuous communications; wireless devices are forced to carry out a number of RF channel bookkeeping and administrative tasks that temporarily interfere with data communications. The flow control mechanisms of TCP were not designed to maximize data throughput in the presence of this activity.

These are but a small sampling of the obstacles that interfere with the ability of the traditional Internet Protocol suite to deliver reliable and efficient data communications in mobile cellular networks.

The disparity in reliability and speed between wireline and wireless networks created by these obstacles must be rectified before the Internet, or the Internet as we know it, can be successfully utilized in a wireless environment. To date and for the foreseeable future including second- and third-generation networks, wireline networks will offer at least an order of magnitude greater capacity for data throughput than wireless networks. Because of the differences described above, it is not economically feasible to provide the same level of data throughput in mobile cellular wireless networks as is possible in wireline networks.

Three fundamental matters adversely affect the performance of any data networking system in a mobile environment:

  • Physical channel performance of mobile wireless IP networks is dramatically different and less efficient than the performance of wireline networks.

  • More noise and distinctly different patterns of noise adversely affect data communications, leading to high BER and packet data loss.

  • Wireless networks must employ frequency-agile systems that utilize many physical RF channels dynamically allocated to provide a logical channel structure, thereby giving the appearance of a dedicated physical channel. This will ensure the economic feasibility of wireless networks.

Each presents unique challenges to data communication systems that conform to the Open Systems Interconnection networking model, such as the Internet. In particular, at the transport layer, TCP is ill-equipped to deal with the network performance that results from these fundamental attributes of wireless networking and performs poorly as a result. Key challenges traced to the TCP design include its unreliability in wireless environments and inefficient use of bandwidth.

The challenges of the RF environment push the packet loss ratios in wireless networks beyond 5 percent, the upper limit of the zone where TCP can guarantee reliable transmission. At a 15 percent packet loss, within specifications for normal operation in the cellular digital packet data (CDPD) network, the probability of successful transmission is 90 percent. The protocol will attempt to compensate through multiple retransmission efforts, but incur an expense of increased time.

Traditional telecommunications technology vendors are working on advanced RF technologies driving next-generation wireless networks—third generation, or 3G, and beyond—and will be able to provide greater raw bandwidth. Several new companies are concentrating on the marriage of wireless networking technology and the existing wireline Internet infrastructure. Other companies are developing and deploying exciting mobile-commerce applications. Lastly, companies are producing streaming compression solutions to improve the speed of existing wireless networks.

Innovations concurrently being developed by leading companies are certain to yield futuristic wireless networks, network infrastructure integration, mobile-commerce applications and advanced data compression. However, the arrival of new wireless technologies will be largely disconcerted, just as the development of new innovations have been independent thus far. The creation of a reliable platform that powers new applications and a patented alternative to TCP will enable industry leaders to create an Internet that is completely wireless.

Ed Acosta

President and CEO

BroadCloud Communications Inc.





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