Chapter 9 GPRS Air interface 9.1 Logical Channels and states 1. Logical Channels in GSM 2. Additional Logical Channels in GPRS 52 TDMA Frame Organisation 3. The halfrate PDTCH 4. 52 TDMA Frame Organisation 5. Multislot operation 6. Radio Resource states 7. DTM operation 8. Relation RR states and GMM states 9.2 The Temporary Block Flow 1. Temporary Block Flows 9.3 The Uplink TBF 1. Temporary Block Flows Uplink State Flag 2. Medium Access Modes for UL TBFs 3. Network Access Messages 4. One Phase or two phase access? 5. UL TBF establishment 6. Uplink Access on PCCCH 7. EGPRS and Uplink Access 8. Packet Resource Request and MS Capabilities 9. Packet Queuing and Packet Polling 10. Uplink RLC Data Block Transmission RLC 11. Acknowledged and Unacknowledged Mode 12. Release of an Uplink TBF 13. Delayed Release of an Uplink TBF
Transcript
Chapter 9
GPRS Air interface9.1 Logical Channels and states
1. Logical Channels in GSM 2. Additional Logical Channels in GPRS 52 TDMA Frame Organisation3. The halfrate PDTCH 4. 52 TDMA Frame Organisation5. Multislot operation6. Radio Resource states7. DTM operation8. Relation RR states and GMM states
9.2 The Temporary Block Flow1. Temporary Block Flows
9.3 The Uplink TBF1. Temporary Block Flows Uplink State Flag 2. Medium Access Modes for UL TBFs 3. Network Access Messages 4. One Phase or two phase access? 5. UL TBF establishment 6. Uplink Access on PCCCH 7. EGPRS and Uplink Access 8. Packet Resource Request and MS Capabilities 9. Packet Queuing and Packet Polling 10. Uplink RLC Data Block Transmission RLC 11. Acknowledged and Unacknowledged Mode12. Release of an Uplink TBF13. Delayed Release of an Uplink TBF
Chapter 9
GPRS Air interface9.4 The Downlink TBF
1. Initiating Downlink Packet Transfer2. Paging3. Paging and Packet Paging 4. Downlink TBF Assignment 5. Downlink Data Transmission6. Example7. Packet Downlink Acknowledgements 8. Release of a Downlink TBF
9.5 Other procedures1. Dummy Control Blocks2. Timing Advance3. Continuous Timing Advance Procedure4. Changing Allocated Transmission Resources 5. System Information6. Evolution of Cell Re-selection 7. Autonomous and Network controlled 8. Network Conrol Order 9. NCCR and NACC 10. Additional enhancements
Chapter 9
(E)GPRS Air interface9.1 Logical Channels and states
1. Logical Channels in GSM 2. Additional Logical Channels in GPRS 52 TDMA Frame Organisation3. The halfrate PDTCH 4. 52 TDMA Frame Organisation5. Multislot operation6. Radio Resource states7. DTM operation8. Relation RR states and GMM states
Logical Channels in GSM
BCCH
FCCH Frequency correction
Signallingand Control
Traffic
CCCH
DCCH
SCH Frame synchronisation + BSIC
PCH Paging mobiles
RACH Requesting dedicated channel
AGCH Allocating dedicated/traffic CH
NCH Notifying MSs (for VGCS & VBC)
Broadcast of cell information,e.g. channel combination
SDCCH Signalling between MS and BTSe.g. Authentication, SMS, LUP
SACCH Measurements, TA, PC, ...
FACCH Extra signalling within 26 TDMA Multiframe
TCH (FR, HR, EFR, 9.6, .... )
BCH
DL
UL
DL
DL
DL
DL & UP
DL & UP
Additional Logical Channels in GPRS
The Packet Broadcast Control Channel (PBCCH) is optional. It carries Packet system information (PSI). If supported MSs will no longer listen to BCCH. MSs get all relevant information (eg about neighbours, paging organisation, ..) here.
Packet Common Control Channels (PCCCH) (require support of PBCCH)-The Packet Paging Channel (PPCH) contain CS or Ps paging. -The Packet Random Access Channel (PRACH) is used by MSs for the random access. -The Packet Access Grant Channel (PAGCH) is used to allocate resources to a mobile. -The Packet Notification Channel (PNCH) will be used to notify a group of mobiles (point-to-
multipoint packet transfer)Packet Dedicated Control Channels (PDCCH)-The Packet Associated Control Channel (PACCH) is used to exchange dedicated signalling
information (e.g. power control, timing advance information, resource (re-)assignment messages etc).
-The Packet Timing advance Control Channel, uplink (PTCCH/U) was introduced in GPRS Phase II (GSM Rel. 99). A MS in the packet transfer mode sends an access burst in a regular interval so that the network can estimate its timing advance. (Continuous Timing Advance update procedure)
-The Packet Timing advance Control Channel, downlink (PTCCH/D) was introduced in GPRS Phase II. It is used to sent timing advance information to MSs. (Continuous Timing Advance update procedure)
-PDTCH/F This logical channel is allocated to a single MS. Several MS can be multiplexed on one physical channel.
-PDTCH/H This is a logical channel allocated to a single MS. Half of a physical channel can be allocated to the MS. It is used by class A MS in DTM.
Additional Logical Channels in GPRS
PTCCH/D
PTCCH/U
PBCCH
Signallingand Control
PacketTraffic Channel
PCCCH
PPCH
PRACH MS initiates uplink transfer
PAGCH Resource assignment to an MS
PNCH Notifying PtM Packet Transfer
Broadcast of packet dataspecific information
PDTCH Packet Data Transfer; (multislot)
PACCH
DL
UL
DL
DL
DL
DL & UPPTCH
Signalling: resource allocation,acknowledgements, PC, TA, etc.
Paging MSs for packet dataand circuit switched services
Used by MS to send random burst to BSS for timing advance
Used to send timing advanceInformation to MSs of one PDCH
UP & DL
UL
DL
PDCCH
The usage of PCCHs depends on the usage of PBCCH which is optional. If PBCCH is not in use existing GSM common channels are used for resource assignment as example.
52 TDMA Frame Organisation
B0 B2 B4 B6 B8 B10B1 B3 B5 B7 B9 B11
PTCCH PTCCH idleidlePDTCH/F
In GPRS the transmission of information is organised in so-called Radio Blocks. A radio block is interleaved on four normal bursts which have to be transmitted in four consecutive TDMA-frames (20 msec). (There is one exception: in the uplink direction, instead of four normal bursts, four random access bursts can be used for PACCH information).
Resources are allocated to one MS on a Radio Block basis. A 52 TDMA multiframe is defined for physical channels used for GPRS. Within a 52 TDMA multiframe 12 Radio Blocks can be found. This gets relevant when PBCCH is configured. Then one can allocate more or less resources for PCCCH or PBCCH. The 52 TDMA multiframe is then used by the MS to calculate the repetition rate of PSI (Packet System Information), calculate the paging group,… . For the data transfer the multiframe is of no relevance!!!
Successive bursts on one physical channel used for GPRS Time
One normal burst, different colours may indicate the resource allocation if two users share the TS
The halfrate PDTCH
B10
B11
B6
B7
B8
B9
B4
B5
B0 B2
B3PDTCH/H B1
The PDTCH/H is only used in DTM (Dual Transfer Mode) in the following channel combination:
That means, the GPRS resources on that physical channel are exclusively allocated to one MS, the one that has an ongoing call on the same timeslot. DTM requires support of networks and MSs! Please note, that DTM is as well possible in seperate resources (see DTM operation) The PDCH/H shall not be shared with other GPRS mobile stations. An uplink PDCH/H shall be assigned in exclusive mode, where the correspondent mobile station has always granted the right to transmit The mix of full and half rate packet data channels is not allowed in the uplink. This mix is only defined for the downlink direction and only supported by mobile stations indicating support for Extended GPRS DTM Multi Slot Class or Extended EGPRS DTM Multi Slot Class respectively
Single slot operation
A type 1 mobile can not receive and transmit simultaneously. Anyway it receives and transmits data, switches between reception and transmission frequencies, and carries out neighbouring cell measurements during one TDMA frame of 8 timeslots. This is done one after the other.
-A TDMA frame (4.615 ms) consists of 8 timeslots (0.577 ms)
-A downlink TDMA frame is three timeslots (minus Timing Advance) ahead of the corresponding uplink TDMA frame.
-During a connection MS (in dedicated or Packet transfer or even in DTM mode!, not in RR idle)
1-Receives downlink radio block on assigned timeslot
2-Changes its radio frequency to uplink frequency
3-Transmits uplink radio block on assigned timeslot
4-Changes to neighbour cell frequencies and makes neighbour cell measurements.
5-Changes its radio frequency to downlink frequency
12345
0 1 2 3 4 5 6 70 1 2 3 4 5 6 7
0 1 2 3 4 5 6 70 1 2 3 4 5 6 7
Single slot operation
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
1 TDMA frame
(4.615 ms)
1 TDMA frame
(4.615 ms)
Time
CS CS
CS CS
A circuit switched voice call as seen by MS (1 TSL allocated).
Tx
Rx
f1
f2
f3
f4 …..Neighbour frequencies
M
M
0 1 2
1 2 3 4 5 1 2 3 4
3GPP 5.02
StandardGSM
Multislot operation
• In a multislot connection MS can use several TSLs for reception or transmission during one TDMA frame
• The MS multislot class defines
– Maximum number of downlink timeslots (Rx)
– Maximum number of uplink timeslots (Tx)
– Maximum sum of downlink and uplink timeslots (Sum)
– Tta relates to the time needed for the MS to perform adjacent cell signal level measurement and get ready to
transmit.
– Ttb relates to the time needed for the MS to get ready to transmit. This minimum requirement will only be
used when adjacent cell power measurements are not required by the service selected.
– Tra relates to the time needed for the MS to perform adjacent cell signal level measurement and get ready to
receive.
– Trb relates to the time needed for the MS to get ready to receive.
– Type 1 MS are not required to transmit and receive at the same time.
– Type 2 MS are required to be able to transmit and receive at the same time.
• 29 multislot classes specified in Rel 99 (1-29) A MS in may belong to different multislot classes when switching from GPRS TBF mode to EGPRS TBF mode. Below example for class 5. (All classes are listed in appendix)
Multislot class
Maximum number of slots
Minimum number of slots Type
Rx Tx Sum Tta Ttb Tra Trb
5 2 2 4 3 1 3 1 1example
0 1 2 3 4 5 6 70 1 2 3 4 5 6 7
0 1 2 3 4 5 6 70 1 2 3 4 5 6 7
Multislot operation
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
1 TDMA frame
(4.615 ms)
1 TDMA frame
(4.615 ms)
Time
example of a multislot configuration as seen by MS (class5, 2 transmit, 2 Receive).
Tx
Rx
f1
f2
f3
f4 …..Neighbour frequencies
M
M
5 6 7
0 1 2
M
Tta =3Ttb =1 (-TA)
3GPP 5.02
Applicable forHSCSD, (E)GPRS, ECSD
Resource Allocation in UL
• If MS transmits data in UL it has to monitor the corresponding DL resources, so it is informed, that it is allowed to transmit, in the case the MS just sends data and it has 2 Resources allocated it has to monitor the 2 DL resources independently. The maximum that can be allocated is so 2 Resources in UL, because otherwise the monitoring and transmission would overlap. The MS would be required to be fully duplex capable, what is not given with todays phones (there are no type 2 phones available at this moment).
• In order to overcome the limitation in UL to 2 radio resources, the standard knows the so called Extended Dynamic Allocation (EDA). This means the MS will have to monitor only one Downlink resource, on which it is informed, that it is allowed to transmit on all higher numbered Timeslots. This allows now to allocate more than 2 Radio Timeslots in Uplink.
• Extended Dynamic Allocation is optionally supported by phones and networks
0 1 2 3 4 5 6 70 1 2 3 4 5 6 7
0 1 2 3 4 5 6 70 1 2 3 4 5 6 7
Resource Allocation in UL
TimeExample of a multislot configuration as seen by MS (class5, 2 transmit)-no EDA.
Tx
Rx
M M
5 6 7
0 1 2
M
0 1 2 3 4 5 6 70 1 2 3 4 5 6 7
0 1 2 3 4 5 6 70 1 2 3 4 5 6 7Tx
Rx
M M
5 6 7
0 1 2
M
Can not be allocated, because the MS would have to monitor DL TSL 6 and transmission+reception would overlap
Example of a multislot configuration as seen by MS with EDA. Depending of MS capabilities (and load, and network) more than 2 Resources can be allocated in UL.
Max 4 UL TSLs can be given with EDA
Monitored by MS, in order to find out whether it is allowed to send in UL o not
MS multislot classes (GPP 05.02 / 45.002)
High Multislot Classes (HMC) enhance the data rates available for type 1 (no simultaneous reception and transmission) (E)GPRS mobiles by increasing the number of radio timeslots that can be allocated to an MS. HMC mobiles switch between reception and transmission frequencies faster than mobiles conforming to non-High Multislot Classes, for example multislot classes 1-12. Non-HMC mobiles are required to use at least three timeslots per TDMA frame for frequency switching and neighbouring cell measurements.
HMC increases the maximum downlink and uplink data rates for a mobile, which is beneficial for many existing mobile services, such as file and mail downloading. However, the real benefit of HMC is the possibility to introduce totally new mobile services, such as video conferencing, that rely on increased throughput.
In uplink, Extended Dynamic Allocation should be also supported by the BSC in order to get the maximum gain.
• 3GPP release 4 or earlier MSs (type1, class 1-12) are limited to a sum of maximum 5 DL plus UL Timeslots.
• 3GPP release 5 (TS 45.002) introduces new MS multislot classes 30-45 which allow a maximum sum of 6 DL/UL Timeslots
– New maximum allocation configurations : • Downlink + Uplink: 5+1 and 4+2
– With Extended Dynamic Allocation • Downlink + uplink: 3+3 and 2+4
Rel 5
High multislot classes 30-45
30 5 1 6
31 5 2 6
32 5 3 6
33 5 4 6
34 5 5 6
35 5 1 6
36 5 2 6
37 5 3 6
38 5 4 6
39 5 5 6
40 6 1 7
41 6 2 7
42 6 3 7
43 6 4 7
44 6 5 7
45 6 6 7
SumTxRx
Maximum Number of slots
MS multislot
class
5+1, 4+2
5+1, 4+2, 3+3
5+1, 4+2, 3+3, 2+4
5+1, 4+2, 3+3, 2+4
5+1, 4+2, 3+3, 2+4
5+1
4+1, 3+2, 2+3
4+1, 3+2, 2+3
4+1, 3+2, 2+3
4+1, 3+2
4+1
5+1, 4+2, 3+3, 2+4
5+1, 4+2, 3+3, 2+4
5+1, 4+2, 3+3
5+1, 4+2
5+1
maximum Downlink+Uplink configurations
e.g. 5+1 Requires support from network for the High Multislot classes
e.g. 3+3 Requires Extended Dynamic Allocation and High Multislot classes
e.g. 4+1 Requires no additional support from network
4+1, 3+2, 2+3, 1+454412
SumTxRx
Maximum Number of slots
MS multislot
class
maximum Downlink+Uplink configurations
e.g. 2+3 Requires Support Extended Dynamic Allocation
Support of Extended Dynamic Allocation is optionally availabe for all phones, it is not restricted to High Multislot classes!!!
Rel 99/4
Rel 5
3GPP 45.002
RR States I
RR (Radio Resource) states are defined between BSS (PCU) and MS. In Packet Transfer mode an MS has an assigned TBF (Temporary Block Flow). Dual Transfer Mode (DTM) is only applicable to class A MSs (simultaneous CS and PS traffic). A class B MS (standard GPRS MS) can only handle CS or PS traffic, can be in Packet Transfer mode or Dedicated mode. (A class C device can only handle PS connections)
RR State ModelRel 99, 4, 5 Class A (DTM)
Class B
Packettransfer
Idle /Packet
idle
Packetaccess
Dedi-cated
Dualtransfer
RRrelease
TBFrelease
PDCH assignment
Packetrequest
Packetrelease
RRestablishment
RR release
3GPP 03.64
RR States II
Enhancements for the Transition from Dual Transfer Mode to Packet Transfer and vice versa are defined in Rel 6
RR State Model Rel 6 3GPP 43.064
Class A (DTM)
Class B
Packet transfer
Idle / Packet
idle
Packet access
Dedi - cated
Dual transfer
RR release
TBF(s) released
PDCH assignment
Packet request
Packet release
RR establishment
RR release
RR establishment
Enhanced DTM CS release procedure
DTM phone capabilities
In dual transfer mode, the mobile station is allocated radio resources providing an RR connection (3GPP TS 44.018) and one or more (Rel 6) Temporary Block Flows on one or more packet data physical channels. The allocation of radio resource for the RR connection and the Temporary Block Flow(s) is co-ordinated by the network in agreement with the capabilities of the mobile station in dual transfer mode.
Different mobile stations may support different DTM capabilities and thus they need to be communicated to the network so that they can be taken into account for the allocation of radio resources. The DTM multislot capabilities are independent from the currently defined 3GPP TS 45.002 multislot capabilities. When EGPRS is supported, DTM multislot capability for EGPRS operation is indicated independently from DTM multislot capability for GPRS operation.
The support of the following four capabilities has to be indicated independently from the DTM class:
Single Slot DTM: single slot DTM operation supported or not; (allways supported by mobile stations indicating Extended GPRS DTM Multi Slot Class or Extended EGPRS DTM Multi Slot Class capability), exclusive allocation in the PDCH/H shall always be used;
E-GPRS: supported or not, a mobile station supporting E-GPRS shall support GPRS.
DTM Handover: supported or not.
The mobile station also indicates support of the following capabilities which, if supported, require the indication of an additional DTM class:
Extended DTM: supported or not. If supported, the Extended DTM multislot class shall also be indicated; a separate indication is provided for GPRS and EGPRS;
DTM High Multislot Class: supported or not. If supported, the DTM high multislot class shall also be indicated; a separate indication is provided for GPRS and EGPRS. Rel 6
Rel 4
Rel 6
0 1 2 3 4 5 6 70 1 2 3 4 5 6 7
0 1 2 3 4 5 6 70 1 2 3 4 5 6 7
DTM Dual Transfer Mode
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
1 TDMA frame
(4.615 ms)
1 TDMA frame
(4.615 ms)
Time
CS CS
CS CS
PS PS
PS PS
PS PS
example of a multislot configuration as seen by MS (2 uplink, 3 downlink).
Tx
Rx
f1
f2
f3
f4 …..Neighbour frequencies
M
M
5 6 7
0 1 2
M
DTM establishment
SGSNMS BSS MSC
DTM Request
Assignment CompleteDTM Assignment Command
UL Unitdata
CS dedicated mode
RLC block(s)
[Old main DCCH]
[New main DCCH][Uplink TBF]
Two DTM assignment messages are defined:· the DTM Assignment Command message: this message shall describe both the CS and packet resources when a reallocation of the CS resource is needed, e.g. when a multislot configuration cannot be accommodated or when an "TCH/H + PDCH/H" configuration is to be used (an intra-cell handover has to be performed.The Packet Assignment message: this message describes the allocated packet resources when no reallocation of the CS resource is necessary, e.g. on an adjacent timeslot.
The GPRS information from upper layers (i.e. GMM or SM) is always sent inside an LLC frame. This LLC frame can now be passed down:- to RLC and transmitted on a TBF; (see below) or- to RR, if the MS is in dedicated mode, and transmitted on the main DCCH.The procedures for the transmission of an LLC frame via RLC are defined in 3GPP TS 44.060. The procedures for the transmission of an LLC frame on the main DCCH are defined in 3GPP TS 44.018.
Class B MS and CS connections
The Suspend/Resume procedure is used to interrupt GPRS data traffic temporarily to allow circuit switched services like e.g. answer to Paging for an incoming call, a periodic Location Update or in our example a mobile Originating Call. It is applicable for a class B MS or a Class MS in the case that DTM is not supported in the Network/cell.
1: The mobile is transferring data.
2: The mobile leaves the Packet data traffic channels and switches to the BCCH. It requests a signaling channel (SDCCH) by sending CHNREQ on the Random Access Channel.
3: If a downlink TBF is active during this time, it will fail because the mobile is no longer watching the PDTCHs. The BSC reports this lost downlink TBF with a Radio Status (RSTA) and the number of not transferred Bytes with a LLC-discarded (LLCD) towards the SGSN.
4: The mobile sends a GPRS Suspend Request on the SDCCH. The BSC forwards the Suspend to the SGSN. The call set-up continues.
5: The call ends and the circuit switched resources are released.
6: In case if the optional Resume Procedure is not implemented. Therefore the MS shall resume GPRS services by sending a Routing Area Update Request message to the SGSN, as described in sub clause "Routing Area Update".
7: Whether data transfer is continued or not depends on the recovery mechanism and time out of the suspended application.
Class B MS and CS connections
Standby
Standby
Ready
Relation between RR and GMM states
Once the MS is in GMM standby (and of course GMM idle) the MS can not be in packet transfer mode.
3GPP 03.64
Correspondence between RR operating modes and MM states (non-DTM capable MS) .
RR BSSDual
transfermode
Dedicated
mode
Packet transfer mode
Measurement report
reception
No state
Dedicated mode
No state
RR MSCS idle and packet idle
CS idle and packet
idleGMM
(NSS and MS)
RR BSSPacket transfer
modeMeasurement
report receptionNo state No state
RR MSPacket transfer
modePacket idle mode
Packet idle mode
MM (NSS and MS)
Ready
Correspondence between RR operating modes and MM states (DTM capable MS) .
Chapter 9
(E)GPRS procedures9.2 The Temporary Block Flow
1. Temporary Block Flows
DL Temporary Block Flow
3 4 5 7 8 9 10 11 0 1 2 3 4 5 6 7 8 9 10 11 0
3 4 5 7 8 9 10 11 0 1 2 3 4 5 6 7 8 9 10 11 0
3 4 5 7 8 9 10 11 0 1 2 3 4 5 6 7 8 9 10 11 0
Which radio blocks are mine?
Radio Resource Allocation:• ARFCN• Timeslot (TSs) allocation• TFI (unidirectional, one for UL, 1 for DL)
TFIMS
TFIRadio Block
The MS monitors the allocated TSs and identifies it’s radio block with the TFI
MS BSS
Example 3TSsallocated
Chapter 9
GPRS Air interface9.3 The Uplink TBF
1. Temporary Block Flows Uplink State Flag 2. Medium Access Modes for UL TBFs 3. Network Access Messages 4. One Phase or two phase access? 5. UL TBF establishment 6. Uplink Access on PCCCH 7. EGPRS and Uplink Access 8. Packet Resource Request and MS Capabilities 9. Packet Queuing and Packet Polling 10. Uplink RLC Data Block Transmission RLC 11. Acknowledged and Unacknowledged Mode12. Release of an Uplink TBF13. Delayed Release of an Uplink TBF
Medium Access Modes
PDCH
PDCH
DL Blocks
PDCH
PDCH
TBFUL
USFif
then
TFI
DynamicAllocation
PDCH
PDCH
PDCH
DL Blocks
PDCH
PDCH
PDCH
TBFUL
USF
if
then
TFI
TFI
ExtendedDynamic
Allocation
(*)
(*) higher numberassigned PDCHs
TFI
USF
TFI
Uplink State Flag
USF= 4
USF= 2
USF= 1
USF=Free
USF= Free
USF“rest”
B(x)
part of the 52 multiframe
Radio Block
B(x+1)
Radio Block
1x or 4x
Network Access Messages
CHANNEL REQUEST
8 or 11 Bits of Information on PRACH
Three different messages can be used to request network access in case of EGPRS. Which message is used depends on availability of PCCCH in the cell and on the radio access capabilities of the mobile station.
PACKET CHANNEL REQUEST
EGPRS PACKET CHANNEL REQUEST
8 Bits of Information on RACH
11 Bits of Information on RACH or PRACH
Causes and content for the 8 bit burst:One-Phase Packet Access Request (MultislotClass, 5bit) Short Access Request (number of blocks,<=8, shall no longer be used starting with Rel 5)Two-Phase Packet Access Request Page ResponseCell UpdateMM ProceduresSingle Block without TBF establishmentOne Phase Access Request in RLC unack mode Dedicated channel request Emergency callSingle block MBMS access
Rel 5
Rel 6
GPRS relevant causes:One phase packet access with request for single timeslot uplink transmission; one PDCH is needed.Single block packet access; one block period on a PDCH is needed for two phase packet access or other RR signalling purpose.
3GPP 4.18
3GPP4.60
44.060
Rel 99
If 11 Bits is in use the MS will indicate forOne-Phase Packet Access RequestShort Access RequestTwo-Phase Packet Access Request
additionally the Radio Priority associated with the access.
EGPRS PACKET CHANNEL REQUEST supported in the cell
EGPRS PACKET CHANNEL REQUEST not supported in the cell (on PRACH)
User data transfer – requested RLC mode = unacknowledged
EGPRS PACKET CHANNEL REQUEST with access type = 'Two-phase access'
PACKET CHANNEL REQUEST with access type = 'Two-phase access‘ 2)*
User data transfer – requested RLC mode = acknowledged and number of RLC data blocks ≤ 8 1)*
EGPRS PACKET CHANNEL REQUEST with access type = 'Short Access' or 'One-phase access' or 'Two-phase access'
PACKET CHANNEL REQUEST with access type = 'Two-phase access'
2)*
User data transfer – requested RLC mode = acknowledged and number of RLC data blocks > 8 1)*
EGPRS PACKET CHANNEL REQUEST with access type = 'One-phase access' or 'Two-phase access'
PACKET CHANNEL REQUEST with access type = 'Two-phase access'
2)*
Upper layer signalling transfer (e.g. page response, cell update, MM signalling, etc)
EGPRS PACKET CHANNEL REQUEST with access type = 'signalling' or PACKET CHANNEL REQUEST with corresponding access type (2)*
PACKET CHANNEL REQUEST with access type = 'Two-phase access' or PACKET CHANNEL REQUEST with corresponding access type (2)*
Sending of a measurement report or of a PACKET CELL CHANGE FAILURE
PACKET CHANNEL REQUEST with access type = 'Single block without TBF establishment‘ 2)*
Sending of a PACKET PAUSE message
PACKET CHANNEL REQUEST with access type = 'Single block without TBF establishment' 2)*, 3)*
3GPP4.60
1)* The number of blocks shall be calculated assuming channel coding scheme MCS-1.2)* The format to be used for the PACKET CHANNEL REQUEST message is defined by the parameter ACC_BURST_TYPE.3)* Upon the first attempt to send a PACKET CHANNEL REQUEST message the mobile station shall start timer T3204. If the mobile station receives a PACKET DOWNLINK ASSIGNMENT message before expiry of timer T3204, the mobile station shall ignore the message.
Is the MS allowed to request a new UL TBF on PACCH? 0 = no, 1 = yes
Packet Control Ackowledgement
when the MS has no new uplink
data to transmit
In order to establish a potential DL TBF faster the final acknowledgement may be delayed (max 400 ms, Problem: during this period it is not possible to establish a new UL TBF!
Extended Release of an Uplink TBF
In the extended uplink TBF mode, the network may initiate the release an uplink TBF by sending a PACKET UPLINK ACK/NACK message with the Final Ack Indicator set to ‘1’. The network shall include a valid RRBP field in the RLC/MAC control block header and clear counter N3103 for the TBF. The network may use the TBF Est field in the PACKET UPLINK ACK/NACK message to allow the mobile station to request the establishment of new TBF. The release of the uplink TBF, using this procedure, may be initiated at a point determined by the network.
The mobile station shall support the extended uplink TBF mode. The extended uplink TBF mode is a part of the GERAN Feature Package 1. A mobile station indicating support of GERAN Feature Package 1 in the Mobile Station Classmark 3 IE, the MS Radio Access Capability IE and the MS Radio Access Capability 2 IE supports the extended uplink TBF mode (see 3GPP TS 24.008).
TBF assignment?, two message assignment?, MS identified in downlink, A Rest Octet?, ....
Downlink RLC Data Block Transmission: an Example
Data Block
BSSMS downlink resource assignment
Data BlockData Block (polling)
Data Block
Data BlockData Block (polling)
(EGPRS) Packet Downlink Ack/Nack
Data BlockData BlockData Block (last, polling)
(EGPRS) Packet Downlink Ack/Nack
(EGPRS) Packet Downlink Ack/Nack (final)
A DL TBF may be delayed by Inserting dummy LLCs for that MS. If there is again data in DL it is sent on the same TBF, If there is data in UL, MS may request an UL TBF in the acknowledgements.
RLC control block based System Information can be transmitted on the PBCCH and on the PACCH. In this course documentation, we can not discuss all defined System Information messages. Therefore, we outline some examples:
Packet System Information Type 1 delivers information for cell selection, for the control of the PRACH, and the available common control channels
Packet System Information: Example
Packet System Information Type 3( ... )
MS
BSS
Normal paging/ extended paging/ paging reorganisation/ ...
Packet System Information Type 3 reports the BCCH allocation of neighbouring cells as well as cell selection parameters.
Evolution of Cell Re-selection
When a GPRS MS is in the Transfer state and has to perform a cell reselection, the MS stops the data transfer, selects the new cell and then has to read particular bits of broadcast information before the MS is permitted to access the RACH or PRACH. Note that this procedure is the same with both “mobile initiated” and “network commanded” cell reselection. Depending of support of MS and network following mechanisms apply:
Autonomous cell re-selection based on:
-pathloss criterion (C1)
-cell priorities (C2) (same criterion for GSM and GPRS)
Supported by every phone, the same mechanism as in GSM idle mode.
Autonomous cell re-selection based on:
-pathloss criterion (C1)
-cell priorities (HCS) (C31 & C32) (specific parameters/criterion for GPRS)
GPRS attached MSs follow the parameters defined on PBCCH. GPRS attached MSs can be separated from GSM MSs and GPRS MSs in GMM idle mode. Requires support of PBCCH!
Network Controlled Cell Re-Selection (NCCR)
Network Assisted Cell Change (NACC)
Gives control over the load, (E)GPRS MSs which are in packet
transfer can be dynamically distributet by the network.
EDGE MSs may be seperated from GPRS MS. NCCR (Rel 99)
and NACC (Rel4, part of the GERAN feature 1 package)
are optionallly supported by MSs.
Rel 4
Rel 99
Autonomous and Network controlled
MS PCU
cell update
FLUSH-LL
SGSNC1, C2, C31 or C32
criterion triggers
MS PCU
cell update
FLUSH-LL
SGSN
NCCR triggers
PACKET ENHANCED MEASUREMENT REPORT
PACKET CELL CHANGE ORDER
Network Controlled Cell Reselection
Autonomous MS cell reselection
With the FLUSH-LL message the SGSN inditcates that MS has changed cell and PCU should move data to the new cell
Evolution of Cell Re-selection
• NC (NC0/NC2) mode is always included in (P)SI messages
• Network control is done during the whole MM ready state
NC 0 – autonomous cell selection
(NC 1- autonomous cell selection with sending measurement reports) -normally not supported
NC2 – network controlled cell reselection with measurements
TBF
time
TBF
ready timer
Packet transfer active Packet transfer inactive
PACKET MEASUREMENT ORDER (PCU to MS)(sent on PACCH when TBF is established)
Periodic measurement reports (MS to PCU), Periodicity is different in Packet -idle and -transfer
Mobiles in the packet idle mode always operate in the NC0 mode, i.e. they perform cell reselection decisions themselves. When a mobile starts a packet transfer (uplink or downlink), the BSC modifies the "Network Control Mode" according to the operator’s configuration and dependent on the mobile's capability.
Evolution of Cell Re-selection
Uplink Packet Data transfer
PACCH Packet Enhanced Measurement Report
MS Serving cell
PACCH Packet Cell Change Order
T3174 starts Target cell
PBCCHOld TBF on serving cell is
aborted!
PBCCH
PBCCH of target cell is received
Waits until it gets PSI1
PBCCHPSI messages
Packet Channel Request(new TBF)
Packet Uplink Assignment
PRACH
PAGCHT3174 stops
2-5seconds
Rel 99
NCCR (Network Controlled Cell Reselection) enables the network to control the resource allocation when the MS performs the cell reselection. NCCR does not affect cell reselection delays.
Evolution of Cell Re-selection
Measurement and NCCRS
information regarding target
cell
Uplink Packet Data transfer
PACCH
Packet Enhanced Measurement Report
MS Serving cell
PACCH
Packet Cell Change Order
T3174 starts
Target cell
Packet Channel Request
Packet Uplink Assignment
PRACH
PAGCH
Packet Neighbour Cell Data 1
Packet Neighbour Cell Data n
OLd TBF on serving cell is aborted!
PACCH
PACCH
T3174 stops
0.3-1 seconds
Rel 4NACC Network Assisted Cell Change (Rel 4) shortens the cell reselection in two ways:
-Sending neighbour cell system information on PACCH to MS in packet transfer mode while it is camped on the serving cell
-By supporting PACKET SI STATUS procedure in a target cell
•Both, autonomous and network controlled cell reselections are supported.
•Support is for intra-BSC cell changes (Support of inter-BSC NACC specification is available in Rel 5)
•NACC support is for MSs in RR Packet Transfer Mode only.
•NACC may be used to move MSs to 3G (there is currently no handover for PS services)
Evolution of Cell Re-selection
PACKET SI STATUS procedure in a target cell After the MS has changed to the target cell, it informs the network about the information already received via the Packet Status Information (PSI) message and requests any missing System Information (SI) necessary for further processing. In addition to reducing the service interruption times during data transfers, this feature when seen from a network point of view also compensates the different patterns of behavior inherent to MSs that are compliant to different standardization versions. The support of PACKET PSI STATUS and PACKET SI STATUS messages are broadcast on BCCH thought SI13 and on PBCCH thought PSI1.
Pkt. PSI/SI status
Pkt. SCD
Pkt. SCD
Target cellMS
Pkt.SCD = Packet Service Cell Data
Additional enhancements defined
New Multislot classes for DTM:
Extended DTM GPRS Multi Slot Class or Extended DTM EGPRS Multi Slot Class MS support a mix of full and half rate packet data channels in the uplink (Rel 4),
DTM GPRS High Multi Slot Class and DTM EGPRS High Multi Slot Class (Rel6). For high multislot classes the network may assign a multislot configuration where USF monitoring is not possible for all assigned uplink PDCHs because of the presence of the dedicated channel.
GERAN Feature Package 2 (Rel 5). The GERAN Feature Package 2 includes Enhanced Power Control (EPC) (see 3GPP TS 45.008) In A/Gb mode, when assigned a TCH or O-TCH, the MS shall configure the channel in enhanced power control (EPC) mode if so commanded by BSS in the channel assignment (see 3GPP TS 44.018). On such a channel, EPC may be used for uplink power control and/or downlink power control.Similarly in Iu mode, when assigned a DBPSCH, the MS shall configure the channel in enhanced power control (EPC) mode if so commanded by BSS in the channel assignment (see 3GPP TS 44.118). On such a channel, EPC may be used for uplink power control and/or downlink power control.
Additional enhancements defined
Additions in release 6:
PS Handover is a feature used by the network to command a mobile station to move from its old (source) cell to a new (target) cell while operating in packet transfer mode and continue the operation of one or more of its ongoing packet switched services in the new cell using TBF resource allocations provided within a PS HANDOVER COMMAND message (i.e. TBF resources in the new cell that have been pre-allocated by the target BSS) . The signalling messages used during PS handover are divided into three groups depending on the utilized interface:· PS handover signalling messages on the Um interface are RLC/MAC signalling blocks.· PS handover signalling messages on the Gb interface are BSSGP signalling messages sent by the PFM entity. PS handover signalling messages on the Gn interface are GTP signalling messages.
The DTM Handover procedure is divided into:- a preparation phase including the allocation of CS and PS resources in the target cell, consisting of parallel CS handover preparation phase as described in 3GPP TS 23.009 and PS handover preparation phase as described in 3GPP TS 43.129; and
-an execution phase which includes the sending of the (RR) DTM HANDOVER COMMAND message from the network to the mobile station on PACCH. The (RR) DTM HANDOVER COMMAND message shall describe both the CS and the PS resources in the target cell.
Multiple TBF A mobile station that supports multiple TBF procedures can support one or more concurrent TBFs in either direction while in packet transfer mode (A/Gb mode). A network that supports multiple TBF procedures can support one or more concurrent TBFs in either direction for a mobile station that supports multiple TBF procedures in packet transfer mode (A/Gb mode).
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