CS and PS SERVICE

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PS Part: 

GPRS Channels and System Information Messages

GPRS traffic uses the same radio resource as CS traffic, and is carried on the same type of physical channel. When a physical channel to carry packet logical channel, it is called a packet data channel or PDCH.

There are have 7 part such as:

1. MPDCH Handling : The number of MPDCH is determined by the operator, and the MPDCHs are established on the BCCH TRE.
2. Master Channel: Are packet channels that carry packet broadcast control channel only on the MPDCH, the packet common control channel, the packet data traffic channel and the packet associated control channel. PDTCH and PACCH are not support by the MPDCH. There allow such as: (1) More performance packet service to be offered through : * Enhanced cell reselection by using optimized cell reselection criteria. * Optimized system information reception, the mobile station does not interrupt its data transfer to acquire or refresh system information from serving and neighbor cells. * Faster TBF establishment, through dedicated PCCCH channels and multislot TBF allocation in on phase. (2) GPRS signaling traffic to be placed on dedicated PCCCH channels. This prevents CCCH channel congestion, and thus degradation of the quality of the CS service, even at a low level of GPRS traffic. Multiple MPDCHs maybe required in case of an increase in the gprs traffic in the cell.
3. Static Allocation: A dedicated O&M parameter allow the operator to configure the MPDCH. only a MPDCH can be configured for static allocation. The MPDCH is permanently established in the cell even if there is no gprs traffic. This is useful if the operators want the mobile station to perform autonomous cell reselection based on the C31 & C32 parameters, or if the paging load is high, independent of the gprs traffic.GPRS Master Channel : this feature can be enabled on a per cell basis. when there is a MPDCH in a cell, it is established as soon as gprs is supported in the cell and is kept even if there if no gprs traffic. The gprs master channel is a packet data channel carrying the packet broadcast control channel to broadcast gprs system information in the cell and the packet common control channel providing gprs-specific channels. when there is a gprs master channel in a cell, the BSS broadcasts its channel description on the BCCH. MS can monitor teh broadcast and thus received all gprs-specific system information pertaining to the cell. The MC is mandatory when the Optimized access on CCCH feature is not used. There can be at most one MC in a cell.         The MC feature allows the operator to set a MC and to benefit from the following advantages, on a per cell basis: * More complete gprs system information is broadcast, which enhances the overall performance of the network. Ex, the permanent broadcast of C31 & C32 criteria enhances cell reselection for all gprs-attached mobile stations. * Better performance in a gprs network by reducing the load on the CCCH. * Shortend access time for multislot MS. * A faster paging cycle. * Higher radio resource efficiency due to the flexibility in the mapping of logical channels on the physical channels.
4. Multiple PCCCH: TO allow an increase in gprs traffic and its associated signaling, more than one MPDCH is required. A secondary MPDCH is required to handle the increase in signaling. The following logical channel can be multiplexed on one MPDCH: PBCCH and PCCCH. The MPDCH carry the PBCCH is the master PDCH.The PBCCH carries is indicated on the BCCH. Up to four MPDCH can be allocated in a cell. When the MPDCH is activated, the BSC broadcast the SI 13 SMS with PBCCH radio configuration. when the MPDCH is de-activated, the SI13 SMS no longer contains a PBCCH description. paging and assignment sms are routed either on the CCCH or PCCCH depending on MPDCH presence.The MPDCHs are established on the BCCH TRX.
5. Logical Channel: The type of logical channels which can be carried on a PDCH are the: * Packet traffic channel: This channel is analogous to a CS traffic channel, and is used for user data transmission and its associated signaling. It has tow sub-channels. + Packet Data Traffic Channel which contains the user data traffic. + packet Associated Control Channel which contains the signaling information. If multiple PDTCHs are assigned to one mobile station, the PACCH is always allocated on one of the PDCHs on which PDTCHs are allocated. the function of these sub channel is  analogous to their CS counterparts. Packet Timing Advance Control Channel: this bi-directional channel is used for maintaining a continuous timing advance update mechanism.
6. Virtual Channels : PS is a mode of operation adapted to transmission of bursty data-that is, data which comes in intense "Burst"separated by periods of inactivity. The network establishes a connection during the transmission of such a burst of data. If there is no activity on this connection, the connection is taken down. when the original user need to send or receive another burst of data, a new temporary connection is set up. this can be on another channel in the same cell, or in anther cell if the MS is in motion. The routing of one burst of data maybe different from the routing of another. The establishment and disestablishment of temporary connections is transparent to the user. The user sees an exchange of data that seems to be a continuous flow, unless the network is over congested. This semblance of continuous flow is a VC. A virtual channel can be represented as the flow of data between two terminals during a user session. The user has the impression of a single continuous connection, but in the network, this is not the case. A single data transfer, either in the uplink or in the downlink direction, can pass between the MFS and the MS via on or more PDCH. A PDCH is shared between multiple MS and the network. It contains asymmetric and independent uplink & downlink channel.
7. System Information Message: GPRS system information messages, like their GSM counterparts, transmit information about the cell to the MS.

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