Our client is a semiconductor company which has both hardware and software operating solutions for Broadband Power Line modems. Dual core SoC, main processor ARM plus dedicated 32-bit CPU running real time operating system (OS) and handling the BPL protocol. Arm runs on Linux, making use of network stack and facilitating application development.

The implemented protocol was HomePlugAV, the OS was Linux and the number of modems which could effectively interoperate was up to 20. The Channel Access implemented was CSMA, with maximum throughput of 75 Mbps in one cell. Our client needed a solution for Internet Service Providers with a minimum of 32 modems, one dedicated modem connected to Internet backbone (head-end) and traffic limitation per modem.

Although HomePlugAV allows fixed channels between modems and hence traffic shaping, it requires complicated negotiation which is very susceptible to any asynchronism and creates additional load on CPU. We decided to implement TDMA on a dedicated modem (master). We used modified Round Robin polling mechanism, which was giving the priority to the modems which generated more traffic to prevent starvation with mandatory polls. On Physical level it enabled higher data transfer.