Process for the transmission of data by a multi-user, point to multi-point digital data transmission system
The invention describes a data transmission method for a multi-user. multipoint-to-multipoint digital data transmission system involving a plurality of users equipment ( 1 ) which are bidirectionally connected via physical medium ( 6 ). The method is intended to communicate one ( 1 a) user to several ( 1 b - 1 d ) users equipment at different speeds, sending multiple frames, maintaining the bandwidth and maximum latency values required by each destination user ( 1 b - 1 d ). Further, this method consists in using the percentage reserve of the frame, providing a quality of service based on that required by the user equipment and supplying a criterion for dynamically assigning the packets sent to each user equipment in the frame, grouping or dividing them.
1. A process for transmitting data by a multi-user, point to multi-point digital data transmission system, where various user modems are in two-way communication over a power line, a downstream channel being the channel used in the communication between a user modem and numerous addressee user modems, and an upstream channel being that used in the communication to this specific user modem; wherein the process comprises:
carrying out the transmission of information at various speeds to various addressee user modems over said power line;
carrying out time division in the down-stream channel adaptable to the different transmission speeds of the different addressee user modems;
optimizing a size of a packet to the communications means regardless of upper layers packet size of the communication from the transmitter;
carrying out packet transmission with different priorities by means of reservation of channel time based on a quality required by the addressee user modems or groups of addressee user modems;
dividing the downstream link in a series of frames with a fixed length where various percentages of the packets sent in the same frame are reserved for the various groups of addressee user modems that share the same quality of service, in terms of criteria selected from reserved bandwidth, maximum latency and combinations thereof; and
adapting quality of services (QoS) for a communication traffic to different requests for bandwidth and latency.
2. The process according to claim 1 , wherein time division in the downstream channel that is adaptable to the different transmission speeds of the different addressee user modems is undertaken by sending packets of different length in a same channel time, so that information is transmitted at different speeds, depending on a number of usable bits per symbol for each one of the addressee user modems by means of packets with a maximum length fixed in number of bits.
3. The process according to claim 2 , wherein to occupy the same channel time a number of symbols to be sent in a packet transmission unit (Maximum Transfer Unit or MTU) of the transmitter is fixed, said number being adjusted to reach a compromise between transmission efficiency in bits per second and quality of service in terms of latency, adapting selectively different types of traffic selected from traffic without minimum latency and bandwidth requirements, traffic with constant bit rates (CBR), traffic with variable bit rates (VBR) and traffic with reserved bandwidth and fixed maximum latency.
4. The process according to claim 3 , wherein the packets that must be sent to the various addressee user modems are grouped and/or divided in the transmitter occupying the size fixed in number of symbols in the Maximum Transfer Unit (MTU).
5. The process according to claim 1 , wherein if an addressee user modem or group of addressee user modems do not use the percentage reserved for them, said percentage is divided between the rest of the modems or groups of modems to whom information is being transmitted, in function of a determined configuration of selected traffic.
6. The process according to claim 1 , wherein within the percentage of packets in the frame reserved for a group of addressee user modems, each modem has its own percentage of packets depending on the quality of service requirements in terms of a criteria selected from reserved bandwidth, maximum latency and combinations thereof.
7. The process according to claim 1 , wherein the packets that must be transmitted are stored in user queues ordered by priority, where these priorities are fixed by a higher layer protocol to allow extraction of the packets ordered according to a priority established determining which is the next packet to be sent, to which user and the size of that packet.