This is the continuous Article for Channel Concept here i am going to explain MAPPING OF LOGICAL CHANNELS:

FCCH+SCH+BCCH+CCCH:

An unmoving MS hunt down the recurrence amendment channel. At the point when the MS finds the recurrence rectification burst it realizes this is time space 0 on c0. Note that the BCCH transporter, c0, in one cell need not be equivalent to c0 in another cell utilizing the same channel portion. c0 is just utilized as a part of GSM suggestions to name the recurrence that conveys the BCCH inside of a cell. Furthermore, c0 needs not be the most minimal recurrence utilized as a part of the cell.

Channel blend multiplexing is appeared in below Figure. There is a cycle of 51 TDMA outlines (0-50), albeit just time space 0 from every casing is appeared. The cycle implies that the F, S, B structure is rehashed after the unmoving casing (which shows up in edge number 50). The four casings conveying CCCH data are known as a paging square. In 51 TDMA outlines there are 9 paging pieces.
F (FCCH)        Frequency Correction CHannel
S (SCH)          Synchronization CHannel
B (BCCH - Norm)     Broadcast Control CHannel - normal
C (CCCH)                  Common Control CHannel: Paging CHannel


                                   (PCH) or Access Grant CHannel (AGCH)
I                                  Idle


BCCH augmented implies that the first CCCH piece can be utilized for transmission of framework data rather than PCH or AGCH. The channels are shared on a square by piece premise, and data inside of every square, when de-interleaved and decoded permits a MS to figure out if the square contains paging messages, framework data messages or get to give.

TS 0 on uplink does not contain the channels above. It is utilized by MSs for access. This implies just the RACH is sent on this TS.

SDCCH+SACCH:

Channel combination, SDCCH and SACCH can be transmitted on any TS and any bearer, aside from time space 0 on c0. The default time opening and bearer in Ericsson's GSM framework is TS 2 on c0.
Subsequent to the bit rate amid ring set and enlistment is low, utilizing channel blend eight MSs can share one TS for flagging. The eight channels are called sub-channels.

Multiplexing of channel blend is appeared in Figure 2-3. The structure indicated is cyclic more than 102 casings. The initial four times that TS 2 happens in the 51 TDMA outline, the channel is utilized for the first MS. The following four times TS 2 happens, motioning for the second MS is traded, et cetera. Note that the uplink and downlink examples are time moved, so that SDCCH sub-divert 0 is sent in casings 0-3 on downlink and in edges 15-18 on uplink. The purpose behind this is to accomplish more effective correspondence, by giving the MS time to compute its responses to the solicitations got on downlink SDCCH.


Dx (SDCCH)        Stand alone Dedicated Control CHannel
Ax (SACCH)  Slow Associated Control CHannel
x          Sub-channel number, 0-7
I           Idle

TCH:
With channel combinations (i), (iv) and (vii) in my previous Channel Concept Article used in a cell, TSs 0 and 2 on c0 are occupied by the control channels. This leaves TSs 1 and 3 - 7 free for the use by TCHs.

TCHs are mapped onto the physical channels with the SACCH, as shown in Figure 2-4. In the figure the information in TS 1 forms a TCH. The repetition is cyclic over 26 frames, which means that the repetition time is 120 ms.

T (TCH)          Traffic CHannel
A (SACCH)    Slow Associated Control CHannel
I           Idle

FACCH is additionally utilized together with the TCH, yet it is excluded in the figure since it works in taking mode, taking blasts of discourse and supplanting them with flagging.

At the point when taking a gander at all figures, aside from Figure 2-5, in this part demonstrating the distinctive channels, it is essential to recall that just every eighth TS in each TDMA edge is appeared.

Another method for portraying the channel mixes (i), (iv) and (vii) in my previous Channel Concept Article is appeared in Figure 2-5. Note that the redundancy of channel mix (i), (ii) and (iii) in my previous Channel Concept Article is 26 TDMA outlines, while for (iv) and (vi) in my previous Channel Concept Article it is 51 TDMA outlines and for (v) and (vii) in my previous Channel Concept Article it is 102.

BCCH Carrier:


Carrier C 0







Downlink

















Uplink















































0

1

2


3
4

5
6


7

0

1

2


3


4

5

6

7



Frame 0

F

T

D0


T
T

T
T


T



R

T

A5


T



T

T


T

T






S

T

D0













R

T

A5




















B

T

D0













R

T

A5




















B

T

D0













R

T

A5




















B

T

D1













R

T

A6




















B

T

D1













R

T

A6




















C

T

D1













R

T

A6




















C

T

D1













R

T

A6




















C

T

D2













R

T

A7




















C

T

D2













R

T

A7




















F

T

D2













R

T

A7




















S

T

D2













R

T

A7

















12


C

I

D3


I
A

I
A


I



R

I

I


I



A

I


A

I






C

T

D3













R

T

I




















C

T

D3













R

T

I




















C

T

D3













R

T

D0




















C

T

D4













R

T

D0




















C

T

D4













R

T

D0




















C

T

D4













R

T

D0




















C

T

D4













R

T

D1




















F

T

D5













R

T

D1




















S

T

D5













R

T

D1




















C

T

D5













R

T

D1




















C

T

D5













R

T

D2




















C

T

D6













R

T

D2

















25


C

A

D6


A
I

A
I


A



R

A

D2


A



I

A


I

A






C

T

D6













R

T

D2




















C

T

D6













R

T

D3




















C

T

D7













R

T

D3




















C

T

D7













R

T

D3




















F

T

D7













R

T

D3




















S

T

D7













R

T

D4




















C

T

A0













R

T

D4




















C

T

A0













R

T

D4




















C

T

A0













R

T

D4




















C

T

A0













R

T

D5




















C

T

A1













R

T

D5




















C

T

A1













R

T

D5

















38


C

I

A1


I
A

I
A


I



R

I

D5


I



A

I


A

I






C

T

A1













R

T

D6




















F

T

A2













R

T

D6




















S

T

A2













R

T

D6




















C

T

A2













R

T

D6




















C

T

A2













R

T

D7




















C

T

A3













R

T

D7




















C

T

A3













R

T

D7




















C

T

A3













R

T

D7




















C

T

A3













R

T

A0




















C

T

I













R

T

A0




















C

T

I













R

T

A0

















50


I

T

I












R

T

A0



























































Half rate channels

In this way, this section has depicted full rate TCH and SACCH/T that uses the majority of the dispensed assets (every one of the 26 timeslots in a multiframe). At the point when half rate movement diverts are executed in the framework, activity limit will twofold. Two clients have the same physical channel when channel blends (ii) and (iii) in my previous Channel Concept Article are utilized. This is delineated in Figure 2-6.

Utilizing half rate channels, the Idle edge from the full rate channel will be utilized for SACCH motioning for the second MS. Following the MSs just utilize each other time space for the call, the multiframe will contain 13 unmoving casings for every MS. Utilizing channel blend (iii) in my previous Channel Concept Article, one portable can likewise be allotted two movement channels, for instance, one for discourse and the other for information.


COMBINED CCCH AND EXTRA PAGING CAPACITY


In low limit zones where cells have stand out bearer it might be viable to utilize one and only TS for flagging, and the other seven for activity. The disservice with this method is that the SDCCH flagging limit and the paging limit diminish: 4 SDCCH/SACCH and 3 paging pieces for each 51 TDMA outlines. Figure 2-7 delineates channel blend (v) in my previous Channel Concept Article. Channel mix (vi) in my previous Channel Concept Article is a supplement to channel mix (iv) in my previous Channel Concept Article and is utilized as a part of the inverse case from blend (v) in my previous Channel Concept Article. That is, when more paging limit than one TS can give is required, see Figure 2-8. All CCCHs must utilize TSs on radio recurrence c0 of the cell assignment. The main CCCH must utilize TS number 0, the second TS number 2, the third TS number 4 and the fourth TS number 6.

Paging Groups

From framework data (see part 4) MSs get data about the quantity of BPCs supporting CCCH, if joined mapping is utilized, and the quantity of 51 multiframes in a paging cycle (i.e. the quantity of 51 multiframes between transmission of paging messages to the same paging bunch). The MSs compute which CCCH and which paging bunch they have a place with utilizing this data and the IMSI number (portrayed in GSM TS 05.02). MSs in a particular paging bunch listen for paging messages and make irregular gets to on the particular CCCH just.

The most extreme number of 51 multiframes in a paging cycle is 9. Utilizing non-consolidated mapping this yields a most extreme of 81 (9X9) paging bunches (for each BPCs supporting CCCH). On the off chance that joined mapping is utilized the greatest number of paging gatherings is 27 (9X3)

To guarantee that a MS has acceptable access to the framework, a variable number of the accessible CCCH hinders in each 51 multiframe can be saved for AGCH just. In Ericsson's GSM framework, no squares are saved for AGCH, since AGCH has need over PCH. CCCH pieces are additionally saved if BCCH expanded or CBCH is utilized. The quantity of squares saved is found in the framework data, so that the MS can decide the quantity of paging gatherings accessible.