GSM technology, GSM RF optimization, GSM Planning and How GSM Works.
The physical channel is the medium over which the information is carried. The logical channel consists of the information carried over the physical channels. A Physical Channel (a TS, defined by a fixed position (0-7) on a given TDMA frame) may be used to broadcast messages containing different kinds of information: traffic messages for speech … Read more
The major basic concept concerned with the radio path transmission of the GSM system is the burst sequence (simplified as Burst). It is a string of transmission units including more than 100 modulation bits. The burst sequence has a restricted duration and seizes a restricted radio frequency spectrum. They can be described as output from … Read more
Actually, during the communication process, the mobile subscriber talks only 40% of the time and there is not much useful information transmitted during rest of the time. If all the information is transmitted to the network, it will not only be a waste of the system resources but also add more interference to the system. … Read more
When the voice signal is transmitted after being processed and modulated, the frequency hopping technique will be used too, i.e. the transmission carrier varies constantly at different timeslots (of course, the variation should comply with the frequency planning principles). The frequency hopping spread spectrum (FHSS) is a method for quickly switching the transmission of radio … Read more
If the voice signal is modulated and transmitted directly after channel coding, due to the condition changes in mobile communication channel, a deep of the fading will influence a successive string of bits and cause high bit error rate. If the bits of a successive string are interfered or lost, the other end of … Read more
To check and correct errors during the transmission, redundancy data and the information calculated from the source data are added to the stream so as to increase the bit rate. For the voice, the length of these codes is 456 bits every 20ms. The bit rate of code stream output from the voice coder is … Read more
The coding mode is called Regular Pulse Excited-Long Term Prediction (RPE-LTP). It works as follow: 8KHZ of sampling is performed first, then divided into frames with 20ms; every frame has 4 sub-frames; the duration of every sub-frame is 5ms; and the pure bit rate is 13kbit/s. The voice compression coding technique is widely used in … Read more
To Improve Error Protection and Security of Data the Data is Interleaved and its type is Diagonal let’s check how it works. The diagram below illustrates, in a simplified form, diagonal interleaving applied to a 9.6 kbit/s data channel. The diagram shows a sequence of ‘data blocks’ after the encoding process previously described, all from … Read more
As All Channel Interleaving in GSM but control channel is some different interleaved its interleaving rectangular lets understand how it. The diagram below illustrates, in a simplified form, the principle of rectangular interleaving. This is applied to most control channels. The diagram shows a sequence of ‘control blocks’ after the encoding process. Each block contains … Read more
Interleaving in gsm used in gsm to reduce error and for speech diagonal types interleaving used here I write how speech in gsm interleaving diagonally. The diagram below illustrates, in a simplified form, the principle of the interleaving process applied to a full-rate speech channel. The diagram shows a sequence of ‘speech blocks’ after the … Read more