Determination of Packet Data Transmission Parameters when Working in the Meter Range

Abstract

The article considers the possibility of organizing packet TCP/IP exchange in the channel of the frequency range from 30 to 300 MHz, as a basis for implementing a secure VPN connection between two subscribers within one of the communication network modes. The VPN connection, when considered, is a TCP/IP packet transmission, the only difference is that a new special header is attached to the original packet, as well as to the cryptographic encryption of the original packet. Hence, VPN tunnel can be represented as a TCP/IP connection. TCP/IP protocol stacks are oriented to support high-speed interfaces operating at high frequencies (for example, Ethernet/Wi-Fi, speeds from 100 Gb/s, 2.4 GHz frequency). The main problem of such a packet implementation at relatively low frequencies (30-300 MHz) is the sufficient instability of mobile MV radio communication (communication in the meter wave range) at a given frequency range and low transmission rate (up to 32 Kb/s), as a result of which there may be a high probability of data bit errors, loss of information packets and huge time delays in the exchange. The Reno model is used as a model for evaluating packet transmission [rec. ITU-T Y.1541, RFC2001] and such regulated indicators [rec. ITU-T 1.1540, ITU-T Y.1541], as: channel bandwidth, signal-to-noise ratio (SNR), transmission delay (IPTD), transmission delay variation (IPDV), transmission error rate (IPER), packet loss rate (IPLR, SER), maximum packet transport unit (MTU). The simulation of a low-speed communication line with the characteristics: length up to 5 km, transmission speed from 300 bits/s to 32,000 bits/s (V.21 - V.34bis modem protocols), the sizes of transmitted packets is 72, 576 and 1500 bytes (threshold values of the maximum unit of packet transportation), transmitter power 2 W, the signal-code construction is a 4-FSK signal with Reed-Muller encoding RM(30, 14). Based on the analysis of the data obtained, three categories of channels were identified: "bad" - low signal-to-noise ratio (2-5 dB), high packet loss (above 10%) and long transmission delay (above 400 ms); "medium" - SNR from 5 to 10 dB, packet loss less than 1%, the delay varies from 400 to 800 ms; "good" is a channel passing through all regulated TCP/IP parameters, the OSH is more than 10 dB, the error probability is less than 0.1%, the delay fits into the regulated 400 ms.