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 gsm gprs. Logical channels can be broadly divided into two types. May 20, 2015 all these kinds of messages are classified in logical channels. Followings are the types of burst being used in gsmgprs. The time slot configuration is declared for each time slot at the operations maintenance center for radio omcr, initially found in gprs phase i. In p25 phase 1, a physical channel and logical channel are the same thing. This page on gsm tutorial covers channel types logical gsm channels,physical gsm channels and mapping between them. There are broadly two categories of logical channels available. Different logical channels are used for different tasks.
Most of these control channels can therefore multiplexed onto a single physical channel. Gsm network architecture, channelisation, signalling and. Revised and updated gsm switching, services and protocols now features the abundant new services and applications that gsm can provide. The operation of the uplink sources is virtually identical. Should the phone wait for a certain moment, or the. Eighthrate tchs are also specified, and are used for signaling. This book starts with the system components and basic services that the gsm system can provide. Types of channels used in gsm and there discription.
Wireless course physical vs logical channels on air interface physical channels. Gsm, gprs, edge, channel allocation, tdma, time slot. In practice, the 2g global system for mobile communications gsm specification supports cell sizes of up to 35km using macro, micro, pico or femto cells 7 9. Given below is a simple pictorial view of the gsm architecture. Gsm channels part 3 call flow in gsm using logical channels.
In gsm networks, control channels are divided into three categories. A tutorial, description, overview of gsm channels including transport and logical channels, sacch, sdcch, facch, etc. 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. They fall into two main categories, dedicated channels and com mon control channels. In the us, gsm operates in the bands 850 mhz and 1900 mhz. American devices were somewhat more sophisticated but only slightly smaller and lighter than the soviet equipment. In summary, a physical radio channel is the frequency or frequency pair allocated by the regulatory body. For example, it tells whether the mac data is for control signal or user data or signaling message etc. The set of logical channel types specified for nr includes. Different bursts are mapped to these channels uniquely as per gsm technical specification 05. Umts logical channels and transport channels 3glteinfo. Gsm switching, services and protocols wiley online books.
Gsm owns a market share of more than 70 percent of the worlds digital cellular subscribers. The following table shows the relationship between frequency band, arfcn, and gsm 10 mhz. Easily attend job interviews and college exams with these multiple choice questions. The cross reference between gsm, umts, 3gpp and etsi identities can be found under. 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. These channels assist in call terminations and sms delivery. Sometimes, it can also be classified as the traffic channel and control channel. 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. If a card supports the logical channel mechanism, then the maximum number of available logical channels is indicated in the card capabilities see 8. The channel used in the air interface is divided into two types. By focusing on the fundamentals of the mobile radio systems, it provides an excellent introductory insight to the whole area of gsm cellular radio. The physical channels are determined by the timeslot, whereas the logical channels are determined by the information carried within the physical channel.
A traffic channel tch is used to carry speech and data traffic. A logical channel is defined by the type of information it carries and is generally classified as a control channel, used for transmission of control and configuration information necessary for operating an nr system, or as a traffic channel, used for the user data. Gsm case study is part of a series of telecommunication case studies produced under the new initiatives program of the office of the secretary general of the international telecommunication union itu. This video explains the logical channels in the gsm global system for mobile and their usage. Based on, as mentioned earlier, whether they carry gsm traffic ie, speech or data or gsm. Apr 20, 2020 in gsm cellular networks, an absolute radiofrequency channel number arfcn is a code that specifies a pair of physical radio carriers used for transmission. Gsm logical channels telecommunications engineering. The physical channel structure is presented in appendix 1. In the gsm recommendations, they are called standalone dedicated control channels sdcch signaling channels.
Study and learn these interview mcq questions and answers on 2g gsm channels, types and functionalities. These gsm logical channels are responsible for effectively using the radio interface between a mobile and base transceiver station bts. In gsm cellular networks, an absolute radiofrequency channel number arfcn is a code that specifies a pair of physical radio carriers used for transmission. Gsm case study is part of a series of telecommunication case studies produced under the new initiatives program of the office of the secretary general of. These logical channels are mapped onto one physical channel. May 27, 2016 this lecture is about how the logical channels are used in global system for mobiles gsm for the mobile terminating call. This lecture is about how the logical channels are used in global system for mobiles gsm for the mobile terminating call. 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. Gsm logical channels traffic channels tch a traffic channel tch is used to carry speech and data traffic. Also, in gsm, identities gives uniqueness to the user, on the bases of subscriber, location, and equipment. There are many different logical channels and the dis tinction between them is based on the purpose and the information transmitted via a channel. Logical channels in gsm are defined by the type of information that is carried over them. Principles for channel allocation in gsm diva portal.
Logical channels reside between radio link control rlc and medium access control mac layer. Traffic channels tchs are intended to carry either encoded speech or user data. For gsm1800 frequency spectrum of 75 mhz bandwidth is. Basic definitions,physical channels,logical channels,layer 3. Throughout this thesis traces of actual gsm traffic will be shown that where.
Study and learn these interview mcq questions and answers on 2g gsm logical channels and types. Gsm adjunct systems gsm standards define that certain adjunct or secondary systems work with gsm technology. The following picture depicts the logical channel hierarchy. Number of logical channels per physical channel number of time slots in tdma frame. Learn more about packet logical channels pdch allocation on globalspec. Mapping in frequency of logical channels onto physical channels. They are used to transport speech, user data, high layer signally, cell specific information to name a few. Lcidlogical channel id lcid is one of the most important component of a mac header.
Gsm case study 2 this case has been prepared by audrey selian, itu. It also covers gsm noncombined channel configuration51 frame multiframe and gsm combined channel configuration51 frame multiframe. 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. Traffic channels, for call data control channels, to communicate service data. Every gsmgprs physical channels are mapped to one of these burst types and the mapping is described below. Packet logical channels pdch allocation engineering360. Catching and understanding gsmsignals institute for computing. Traffic channel traffic channels carries speech and data. Logical channels the data, whether user traffic or signaling information, are mapped onto the physical channels by defining a number of logical channels. There are 124 channels of 200khz each and one channel is left as guard band. 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.
The logical channels carry user information and control signalling data. Jan 14, 2011 they are used to transport speech, user data, high layer signally, cell specific information to name a few. The physical channel is the medium over which the information is carried. There are many different logical channels and the distinction between them is based on the purpose and the information transmitted via a channel. In the radio subsystem, the physical channel supports the logical channel based on the type of message transmitted. It covers fcch, sch, bcch, ccch, rach, agch, pch, cbch, sacch, sdcch and facch. Nu tek india limited channels in gsm air interface logical channels. This page on gsm tutorial covers gsm logical channels and their functions.
The logical channel consists of the information carried over the physical channels. In this way, the physical channels are mapped as different logical channels. The gsm channels are divided in physical and logical channels. In the gsm system, the logical channel is classified as the dedicated channel dch and the common channel cch.
They fall into two main categories, dedicated channels and common control channels. What are the allowed logical channel combinations in gsm. These functions and interfaces are explained in this chapter. The traffic channel tch carries voice or data, which are the fullrate traffic channel tchf and halfrate traffic channel tchh. I am able to place a call and i want to implement that whenever the user picks up the call a wav file should be. Channel types decide whether to carry traffic or signalling information.
A physical channel designates a particular rfc radio frequency channel and timeslot. The additional components of the gsm architecture comprise of databases and messaging systems functions. Logical channel type in gsm as we know, every cell has several trx and every trx includes 8 timeslots i. As shown in figure 65, some time slots are reserved for the gsm system only circuitswitched time slot. The following table shows the relationship between frequency band, arfcn, and gsm 10. Logical channels reside between rlc sublayer and mac sublayer which are layer 2 protocols in lte protocol stack. The signaling channels on the air interface are used for. Session, mobility and location contents radio resource management and logical channels gprs uses the same frequency spectrum as gsm i. The information transmitted on a logical channel depends on a particular task. Arfcn x, timeslot y, frame number n logical channels control channels traffic channels logical channel. Logical channels the reason logical channels are used is because gsm has a number of control channels which do not require to operate at the full rate of a physical channel. Gsm operates on the mobile communication bands 900 mhz and 1800 mhz in most parts of the world. Gsm uses a variety of channels in which the data is carried. Traffic channels are defined using a 26frame multi frame, or group of 26 tdma frames.
I can not understand when the phone can send a rach signal. In p25 phase 2, a physical channel is divided into two time slots or logical channels. Gsm is a circuitswitched system that divides each 200 khz channel into eight 25 khz timeslots. Structure introduction we discuss the logical channels that are used in gsm system. Aug 25, 2009 logical channels define what type of information is being transferred and transport channel defines how the information is being transferred. Logical channels tells what kind of information is transferred. Nu tek india limited logical channel one or more logical channel can be transmitted on a physical channel. Commands referring to a certain logical channel carry the respective logical channel number in the cla byte see tables 8 and 9.
Cellular networks khoury college of computer sciences. In the future there may be more types of services than just voice and packet data and that these services. 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. In gsm, these channels are separated into physical channels and logical channels. These channels are defined by gsm architecture or structure. A little bit of history in around 1986 a military radio transceiver was large 15 x 40 x 60cm and heavy, weighing around 10kg. The diagram below shows the frame structure used to multiframr eight sdcchs, although, as it takes two repetitions of the multiframe to complete the entire sequence, it may be more logical to think of it as a frame structure. The gateway msc or gmsc the purpose of which is to query the hlr and determine the location of the subscriber. Logical channels define what type of information is being transferred and transport channel defines how the information is being transferred logical channels. The video explains the orderly use of pch, rach, sdcch, sacch and tch. At the center of the frame traffic channel multiframe i.
Every gsm gprs physical channels are mapped to one of these burst types and the mapping is described below. Lcid logical channel id lcid is one of the most important component of a mac header. As shown in the figure there are two main types of channels in the gsm. May 26, 2016 this video explains the logical channels in the gsm global system for mobile and their usage. Explained are the physical and logical radio channel structures of the gsm system along with the basic frame and slot structures. The primary difference between the two is the modulation format of the output signal. Basically it tells the characteristics or the destination of the mac data.
Lte logical channels structure and mapping between logical channels and transport channels. In radio communication, a control channel is a central channel that controls other constituent radios by handling data streams. Channel coding and decoding x rate adaptation x encryption and decryption x x paging x x uplink signal measurements x traffic measurement x authentication x location registry, location update x handover management x mario jorge leitao gsm 16 mobile switching center the msc mobile switching center plays a central role in gsm switching functions. Jan 11, 20 lte logical channels structure and mapping between logical channels and transport channels.
339 1128 1283 99 77 919 1078 569 779 1080 663 5 286 643 421 314 1229 91 1296 489 352 108 825 1199 1441 1482 894 183 1162 1434 403 999 992 364 1333 1078 1151 586 1228 128 1426 546 498 7 1070 829