You have to understand at least the structure of slot, frame, multiframe (Do you remember where the multiframe is located in overall GSM frame structure?. This page on GSM tutorial covers GSM frame structure including concept of slot, frame,multiframe,superframe and hyperframe. It covers both 51 frame multiframe . Global System for Mobile (GSM) Several providers can setup mobile networks following the GSM .. Control Channel Multiframe (Reverse link for TS0). 0. F. 1.

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Superframe – A superframe is multiframee multiframe sequence that combines the period of a 51 multiframe with 26 multiframes 6. This channel makes a mobile station time-synchronized with the base station clock. This counter allows the hyperframe to synchronize frequency hopping sequence, encryption processes for voice privacy of subscribers’ conversations.

GSM Tutorial | Frame Structure

One user uses the slot multiframs at every frame and the other user use the slot 4 at every frame. These mappings are summarized in a table in Quick Reference page. You have to understand at least the structure of slot, frame, multiframe structure in very detail. That is why the synchronization training sequence is very large for this burst comparing to other burst types.

Do this questions and answer by yourself whenever you have chance until your brain automatically pops up a frame structure diagram as soon as you see some key words related to GSM frame. Here in the figure GSM Mobile is allocated You will see a better way to visualize this structure at later section, for now just try to get some ‘sense feeling ‘ of how a multiframe looks like.

One of those frequency channels is defined as the base-frequency beacon frequency or BCCH frequency. Multiframes on the GSM system use established schedules for mulyiframe purposes, such as coordinating with frequency hopping patterns. These include functions such as:. This time slot carries Do you remember where the multiframe is located in overall GSM frame multiframd As mentioned in another page of the tutorial, the slots for transmission and reception for fsm given mobile are offset in time so that the mobile does not transmit and receive at the same time.


Multiframs GSM frame structure provides the basis for the various physical channels used within GSM, and accordingly it is at the heart of the overall system.

GSM Timeslot & Frequency Specifications

This helps avoid need of simultaneous transmission and reception by GSM mobile phone. This division of frequency pool is called FDMA.

Every time slot during a hyperframe has a sequential number represented by an 11 bit counter that is composed of a frame number and a time slot number. As shown in the figure 2 ysm, there are two varients to multiframe structure.

In this example, the two users shares the slot 2 of every frame in alternating fashion. That is, an Gsj message from an MS at a distance of up to 35 km from the base station can reach to the base station antenna without overlapping the next burst.

The GSM frame structure is designated as hyperframe, superframe, multiframe and frame.

All other frequencies are mostly for traffic but can also be used for control channels. The idle time period allows a mobile device to perform other necessary operations such as monitoring the radio signal strength level of a beacon channel from other cells. Slot Allocation in Communication. The duration of a frame traffic channel multiframe is ms 26 TDMA frames. X Like My Work Follow. This is like normal burst but has no meaning of its payload bits.

GSM Frame Structure

multiframee Following is one example showing a control multiframe. This lasts for approximately 4. Each timeslot in a cell allocated to traffic channel usage will follow this format, that is, 12 bursts of traffic, 1 burst of SACCH, 12 bursts of traffic and 1 idle.

The last frame Frame 50 is allocated for Idle. As one carrier is used as guard channel between GSM and other frequency bands carriers are useful RF channels.


This diagram shows that a single GSM frame is composed of 8 time slots. Following is the common example of a Traffic Multiframe. The basic element in the GSM frame structure is the frame itself.

You will also discover how 2nd generation systems are gradually evolving into 3rd generation broadband multimedia systems. Then follows, in timeslot 0 of frames 10 and 11, a repeat of the frequency and synchronising bursts F and Sfour further CCCH bursts C and so on.

GSM Timeslot and Frequency Specifications – RF Cafe

The whole data space bits is used for unmodulated carrier pure sinusoid or carrier modulated with all zero bits. As the traffic multiframes are 26 bursts long and the control multiframes are 51 bursts long, the different number of traffic and control multiframes within the superframe, brings them back into line again taking exactly the same interval.

Frame structure is the division of defined length of digital information into different fields information parts. As I keep telling you, the overall GSM frame structure one cycle is so long in time domain and I haven’t see any material showing even a single multiframe at the full details of each slot. This example shows 2 users using full rate voice traffic channels. Engineers working in GSM should know gsm frame structure for both the downlink as well as uplink.

Here each RF carrier frequency is shared between 8 users hence in GSM system, the basic radio resource is a time slot with duration of about microsec. This structure may be transmitted on any timeslot. A typical use of this type of control channel timeslot is in rural areas, where the subscriber density is low.

These logical channels are time sheduled by BTS. This tutorial section on GSM basics covers following sub topics: