These channels are defined by gsm architecture or structure. One topic that often causes confusion in digital radio networks is the difference between physical and logical channels. For example, on one of the physical channels used for traffic, the traffic itself is transmitted using a traffic channel tch message, while a handover instruction is transmitted using a fast associated control channel facch message. Gsm architecture or structure defined various channels in the air interface or radio interface. Traffic channels tchs are intended to carry either encoded speech or user data. Aug 03, 2017 in lte we have 7 logical channel in downlink and 3 logical channels in uplink. Jan 11, 20 logical channels reside between rlc sublayer and mac sublayer which are layer 2 protocols in lte protocol stack. Control channels for the transfer of control plane information traffic channels for the transfer of user plane. In this tutorial different types of logical channels and transport channels and their mappings are described. Followings are the types of burst being used in gsmgprs. This lecture is about how the logical channels are used in global system for mobiles gsm for the mobile terminating call. Use features like bookmarks, note taking and highlighting while reading introduction to gsm. The physical channels are determined by the timeslot, whereas the logical channels are determined by the information carried within the physical channel.
There are broadly two categories of logical channels available. Fdma parts involves the division by frequency of the 25 mhz bandwidth in to 124 carrier frequencies also called arfcn spaced 200 khz for gsm 900. Based on, as mentioned earlier, whether they carry gsm traffic ie, speech or data or. Easily attend job interviews and college exams with these multiple choice questions. A logical traffic channel in gsm is abbreviated by tch. Logical channels the physical channels one timeslot per radio channel shown in the previous slides represent the entity transmitted through the air interface each physical channel is used totrasmit a logical channel with different functions logical channels can be divided in 2 main groups traffic channel tch. It covers fcch, sch, bcch, ccch, rach, agch, pch, cbch, sacch, sdcch and facch. In downlink there are 4 control channel which carried common channel information as well as dedicated channel information. Logical channels reside between radio link control rlc and medium access control mac layer. The cross reference between gsm, umts, 3gpp and etsi identities can be found under. In p25 phase 1, a physical channel and logical channel are the same thing. In the radio subsystem, the physical channel supports the logical channel based on the type of message transmitted.
Logical channels are distinguished by the information they carry and can be classified in two ways. Nu tek india limited channels in gsm air interface logical channels. Gsm logical channels free download as powerpoint presentation. May 26, 2016 this video explains the logical channels in the gsm global system for mobile and their usage. The traffic channels are the resources available to the user for either speech or data. It is most often used in the context of a trunked radio system, where the control channel sends various data which coordinates users in talkgroups. Different time slots will carry different logical channels, depending on the structure the bss uses. Simply put, this means in direct radio to radio communication the same frequency may be used for.
Following table lists the logical channels that are used by lte. February, 28th 2005 overview in this document i make a study of third mobiles generation systems. Naturally the system does use the gsm control and broadcast channels for initial set up, but all the gprs actions are carried out within the gprs logical channels carried within the pdch. Different bursts are mapped to these channels uniquely as per gsm technical specification 05. It is most often used in the context of a trunked radio system, where the control channel sends various data which coordinates users in talkgroups in gsm networks, control channels are divided into three categories. Logical channel type in gsm as we know, every cell has several trx and every trx includes 8 timeslots i. Physical channels, logical channels, network, and operation kindle edition by harte, lawrence. Types of channels used in gsm and there discription. Gsm logical channels gsm logical channels consists of two types. Principles for channel allocation in gsm diva portal. A logical channel will carry information of a specific type and a number of these channels may be combined before being mapped onto the same physical channel. Physical channels, logical channels, network, and operation through a thorough description of key functional sections of a gsm network and how they communicate with each other, you will learn how and why gsm is evolving into 3rd generation broadband systems including gprs, edge, and. I understand the different types of channels common continue reading gsm logical vs physical channels. Halfrate tchs double the capacity of a system effectively by making it possible to transmit two calls in a single channel.
Channel types decide whether to carry traffic or signalling information. Logical channels in gsm are defined by the type of information that is carried over them. There is a variety of channels used within gprs, and they can be set into groups dependent upon whether they are for common or dedicated use. May 20, 2015 all these kinds of messages are classified in logical channels. Firstly, logical traffic channels carry data in the user plane, while logical control channels carry signalling messages in the control plane. There are two main categories of logical channels in gsm. This tutorial on umts covers umts logical channels, transport channels and physical channels. Logical channels can be thought of as just different types of data that is transmitted only on certain frames in a certain timeslot. Download it once and read it on your kindle device, pc, phones or tablets.
Introduction in telecommunications a channel, refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel. Nu tek india limited concepts of channels in gsm a company vehicle is used for several purposes in a day similarly in gsm, the timeslots are used for. Introduction to global system for mobile communication gsm. Depending on the quantity of information to transmit and on their consistency, several logical channels may be mapped onto one physical channel, in order to use its successive time slots as much as possible optimization of the resources number by maximizing the occupancy duration of each. Physical and logical channels gsm uses a mix of frequency division multiple access fdma and time division multiple access tdma. In gsm, these channels are separated into physical channels and logical channels.
These 8 timeslots are further broken up into logical. Mapping in frequency of logical channels onto physical channels. Logical channels it transports either user data during a call or signalling information for ms or base station. The video explains the orderly use of pch, rach, sdcch, sacch and tch. The two categories of logical channels in gsm are control channels and traf. Logical channels define what type of information is being transferred and transport channel defines how the information is being transferred logical channels. The defintion of logical channels and details of traffic channels has been discussed in the previous. Arfcn x, timeslot y, frame number n logical channels control channels traffic channels concepts of channels in gsm.
A physical radio channel is a radio frequency or pair of frequencies that is allocated by the regulatory body to an agency for communication. As they tranverse between layers they map to other layer frames. Umts channels logical,transport,physical umts channels. May 27, 2016 this lecture is about how the logical channels are used in global system for mobiles gsm for the mobile terminating call. Explained are the physical and logical radio channel structures of the gsm system along with the basic frame and slot structures. Logical channels reside between rlc sublayer and mac sublayer which are layer 2 protocols in lte protocol stack. Aug 25, 2009 logical channels define what type of information is being transferred and transport channel defines how the information is being transferred.
This video explains the logical channels in the gsm global system for mobile and their usage. All these kinds of messages are classified in logical channels. In summary, a physical radio channel is the frequency or frequency pair allocated by the regulatory body. Broadcast control channel bcch it used for broadcasting mibssibs. The forward channel is the direction of the communication or mobiletocell downlink path. Gsm, gprs, edge, channel allocation, tdma, time slot. Described are the fundamental capabilities and operation of the gsm radio channel including channel coding, modulation types, speech coding, rf power control, and mobile assisted handover. In lte we have 7 logical channel in downlink and 3 logical channels in uplink. A physical channel may carry different messages, depending on the information that is to be sent. Physical channels, logical channels, network, and operation. There are physical and logical channels in gsm radio system. This page on gsm tutorial covers gsm logical channels and their functions.
Logical channels the data, whether user traffic or signaling information, are mapped onto the physical channels by defining a number of logical channels. A traffic channel tch is used to carry speech and data traffic. Viewing 11 posts 1 through 11 of 11 total author posts 17th august 2008 at 14. However, lte provides additional logical channels for features not yet supported by nr but likely to be introduced in upcoming releases. As shown in the figure, there are three types of umts channels viz. As shown in the figure there are two main types of channels in the gsm. Two types of logical channels map onto physical channels control channels call setup, power adjustment, etc traffic channels voice or data 22. In p25 phase 2, a physical channel is divided into two time slots or logical channels. Followings are the types of burst being used in gsm gprs. This topic has 10 replies, 1 voice, and was last updated 9 years, 3 months ago by deepak. To understand the mapping of the logical channels onto physical channels, it is good to understand the two dimensions in time used by the gsm frame structure for more details on the frame structure, see section 3. These gsm logical channels are responsible for effectively using the radio interface between a mobile and base transceiver station bts. Introduction to global system for mobile communication.
Gsm uses a variety of channels in which the data is carried. Every gsm gprs physical channels are mapped to one of these burst types and the mapping is described below. At first i will center the study in the objectives and main characteristic of. These 8 timeslots are further broken up into logical channels. The above logical channels are in general present also in an lte system and used for similar functionality. Radio channels, physical channels and logical channels. The following picture depicts the logical channel hierarchy. Umts logical channels and transport channels 3glteinfo. Based on, as mentioned earlier, whether they carry gsm traffic ie, speech or data or gsm. Jan 14, 2011 logical channels in gsm are defined by the type of information that is carried over them. In gsm as well, we have many different types of physical and logical channels and each of these channel types are using its own physical structure at the level of a slot burst. Chapter 4, by far the longest chapter in this book, covers the gsm air interface. Introduction to physical and logical channels tel3pedia. Study and learn these interview mcq questions and answers on 2g gsm channels, types and functionalities.
They are used to transport speech, user data, high layer signally, cell specific information to name a few. In radio communication, a control channel is a central channel that controls other constituent radios by handling data streams. Fdma parts involves the division by frequency of the 25 mhz bandwidth in to 124 carrier frequencies also called arfcn spaced 200 khz for gsm900. Carries user data speech and data halfrate channel tchh. These channels assist in call terminations and sms delivery. Study and learn these interview mcq questions and answers on 2g gsm logical channels and types. This chapter explains the functionalities of these channels. Gsm channels part 3 call flow in gsm using logical channels. Control channels control channels further consists of three groups namely broadcast control channel, common control channel and dedicated control channel.
Cellular telephone system, gsm channels, gsm identities. Every gsmgprs physical channels are mapped to one of these burst types and the mapping is described below. Logical channels tells what kind of information is transferred. The channel used in the air interface is divided into two types. From the physical layer, the mac layer uses services in the form of transport channels. Logical channels can be broadly divided into two types. Cdma channels can be broadly categorized as forward channel and reverse channel. Sample is95 system identifiers telcom 2720 30 is95 logical channels cdma systems define multiple channels per frequency channel pilot channel provides a reference to all signals beacon sync channel used for obtaining timing information paging channel used to page the mobile terminal when there is an. For gsm 1800 frequency spectrum of 75 mhz bandwidth is.