(A) local area network based on the division miltiple access method

Abstract

In this dissertation work, the use of the code division multiple access (CDMA) technique in local area networking has been proposed and studied. The CDMA method allows overlap of signals both in time and frequency domains. The transmitted signal is recovered by exploiting the orthogonality of the code sequences used. When the CDMA approach is used as the transmission mechanism of a local area network (LAN), it offers many advantages, and can alleviate various shortcomings of existing local area networks based on the time division multiple access (TDMA) method. The proposed CDMA LAN is basically a baseband broadcast bus system (BBS). The medium may be baseband coaxial cables, twisted pair wires or optical fibers. In this dissertation, the use of time (bit)-shifted versions of a binary maximal-length sequence as orthogonal codes is proposed. Also, the use of multi-level data symbols is proposed. Thus, information requiring a higher data rate (e.g., voice) than that of normal interactive data can easily be accommodated in the proposed LAN. By employing a dual-cable configuration and broadcasting a reference code sequence, all the transceivers in the CDMA LAN can operate in a synchronous mode, thereby increasing network efficiency. A transceiver can access others simply by changing the destination code sequence. Multiaccess in the CDMA LAN is based on a simple distributed reservation protocol. The medium can be shared equally among active users on a slot-by-slot basis. The system is inherently stable, and at least one logical channel is guaranted at all times. Unlike TDMA LAN``s, channel utilization and the actual data rate of the CDMA LAN are nearly independent of the effect of end-to-end propagation delay. Mean message delay for the CDMA LAN is comparable to or slightly less than that for other TDMA LAN``s. Also, the message delay is rather insensitive to propagation delay. Thus, the performance of the CDMA LAN is superior to those of all other TDMA LAN``s, espec...