On the performance of slotted ALOHA in a spread spectrum environment

ABSTRACT

We present an extension of the slotted ALOHA protocol for use in a spread spectrum packet radio environment. With spread spectrum, we assume that N distinct codes are available, and that each code can be treated as a separate channel. Running an independent copy of the protocol on each of these channels would be undesirable, since each user would have to select one channel to monitor for packets addressed to it, inducing a logical partitioning of the user population into N groups. To preserve the logical connectivity of the network, we examine the effect of separating packet transmissions into two parts, a short preamble, which is sent over a public channel, and followed by the body,> which is sent over a private channel. We assume that m of the available codes are used as preamble channels, and the remaining N - m codes are used for actual packet transmissions. If m (@@@@) N, then the network can support broadcast and multicast packets, and still make use of all of the available channels.

REFERENCES

• 1: Robert C. Dixon, Spread Spectrum Systems, John Wiley & Sons, Inc., New York, NY, 1990
• 2: R. E. Kahn, S. A. Gronemeyer, J. Burchfiel, and R. C. Kunzelman, "Advances in Packet Radio Technology," Proceedings of the IEEE 66pp. 1468-1496 (November 1978).
• 3: UCLA Packet Radio Analytical Workshop, UCLA Computer Science Department, (August 10-11, 1982).
• 4: L. Kleinrock and F. A. Tobagi, "Packet Switching in Radio Channels: Part I — Carrier Sense Multiple-Access Modes and Their Throughput-Delay Characteristics," IEEE Transactions on Communications COM-23(12)pp. 1400-1416 (December 1975).
• 5: L. Kleinrock, Queueing Systems, Vol II., Computer Applications, Wiley-Interscience, New York (1976).
• 6: M. L. Molle and L. Kleinrock, "Virtual Time CSMA: A New Protocol with Improved Delay Characteristics," CSD Report No. 810113, Computer Science Department, University of California, Los Angeles (January 13, 1981).

INDEX TERMS

Primary Classification:
  C. Computer Systems Organization
  C.2 COMPUTER-COMMUNICATION NETWORKS
      C.2.2 Network Protocols

          Nouns: ALOHA

Additional Classification:
  C. Computer Systems Organization
  C.4 PERFORMANCE OF SYSTEMS
      Subjects: Performance attributes

General Terms:
Performance