A TDMA modem design for multiparty communications with the relay function

Abstract

By utilizing the channel bandwidth in a pre-assigned time slot, TDMA is very useful to communicate voice and data for small group. It also provides the increased battery life by transmitting data in an assigned slot. Instead of two party communications, it can be applied to multiparty communications. This paper presents a design of the TDMA baseband modem to support multiparty voice communications with the relay functions to extend the communication distance. The baseband modem supports an ad-hoc function for multiparty communications and relays voice data from a slave node to the master node. The proposed baseband modem is expandable up to 8 relay nodes. The communication distance is extended up to 1.6Km when 2.4GHz frequency is used for a RF transmitter. To implement the multi-party communications and the relay function, the TDMA baseband modem consists of a cycle network controller, a sync time controller, a buffer controller and an asynchronous serial block. The protocol is programmed on Xilinx Zynq 7000 with Verilog HDL. The baseband modem is tested and verified its functions for 8-node relay communications and its measured maximum delay time is about 120msec for 8-node voice relay.