Multiple access schemes for data communications

Abstract

Four new multiple access schemes for a broadcast channel shared by a finite number of users in packet communications are proposed. Random access schemes (e.g., slotted ALOHA) are efficient at low values of throughput while the performance of fixed assignment TDMA is better when throughput in high. Scheme I has static mixing of S-ALOHA and TDMA slots. In Schemes II, III and IV, the normal accessing mode is S-ALOHA until a collision is detected. Upon detecting a collision, a TDMA frame is reserved in Scheme II; while in Schemes III and IV, slots are reserved for collided users only. Scheme IV is just an extension of Scheme III with the additional capability of sending queue length information of each collided user. Schemes II, III and IV adapt smoothly to traffic variations and the maximum throughput may approach unity in these schemes. Detailed delay and buffer analyses are performed and the results are verified by simulation.