User Description, GPRS/EGPRS Channel Administration USER DESCRIPTION

Transcription

1 User Description, GPRS/EGPRS Channel Administration USER DESCRIPTION E

2 Copyright Ericsson AB All Rights Reserved Disclaimer No part of this document may be reproduced in any form without the written permission of the copyright owner. The contents of this document are subject to revision without notice due to continued progress in methodology, design, and manufacturing. Ericsson shall have no liability for any error or damage of any kind resulting from the use of this document.

3 Contents 1 Introduction 1 2 Glosary Concepts Abbreviations and acronyms 4 3 Capabilities 6 4 Technical Description General Service oriented Allocation of Resources on the Abis interface (SARA) Configuration of dedicated PDCHs in Packet Switched Domain (PSD) Handling of Packet Data traffic Channel selection in Cicuit Switched Domain (CSD) Return of PDCHs to Cicuit Switched Domain (CSD) Main changes in Ericsson GSM system R10/BSS R Engineering guidelines 24 6 Parameters Main controlling parameters Parameters for special adjustments Value ranges and default values 28 7 References 29

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5 1 Introduction GPRS/EGPRS packet data sessions are scheduled over the air interface as Temporary Block Flows (TBFs). When a TBF shall be set up in order to support a certain service for a mobile user, transmission resources will be reserved on one or more Packet Data Channels (PDCHs). The PDCHs can have different capabilities. They may support only the low speed coding schemes CS-1 to CS-2, which will only require 16 kbits/s Abis connections per timeslot, or also CS-3 to CS-4 and/or EGPRS which will require 64 kbits/s Abis per timeslot. The PDCH reservation will be made taking into account the Mobile Station s (MS) capabilities (Multislot Class, and support for EGPRS). PDCHs are chosen for the reservations also in accordance with the requested Quality of Service) (QoS) Class for the service. The QoS attributes are negotiated with the Core Network (the node SGSN). To be able to reserve GPRS/EGPRS channels for an MS, they must first be allocated as PDCHs. PDCHs may be fixed allocated as dedicated PDCHs or they may be allocated temporary as on-demand PDCHs. The allocation of dedicated PDCHs will be made by the system according to operator request (ordered number of dedicated PDCHs). On-demand PDCHs will be automatically allocated by the system when more resources for Packet Data traffic are needed. PDCHs will be allocated according to certain rules (best channels are allocated first). Several other features impact on the GPRS/EGPRS Channel Administration feature see references to other User Descriptions Section 7 References on page Glosary 2.1 Concepts B-PDCH B-TCH CHGR A Packet Data Channel (PDCH) used for the transfer of GPRS CS-1 to CS-2. Traffic Channel (TCH), which in the PSD is capable of carrying GPRS CS-1 to CS-2. A Channel Group (CHGR) is a group of frequencies within one cell. CHGRs are operator controlled and facilitate control over groups of frequencies in a cell. 1

6 CHGR-0 contains BCCH and is defined automatically at cell definition. Channel set indicator CSD EDGE EGPRS E-PDCH E-TCH G-PDCH GPRS GPRS Attach GPRS Network operation mode GPRS paging message The channel set indicator says if new channels are to be established or if the old channels should be kept. The channels may be kept at a resource level upgrade. The Circuit Switched Domain (CSD) is where the circuit switched calls are handled (speech, data, signalling). Enhanced Data rates for GSM Evolution (EDGE) is a standardized set of improvements to the GSM radio interface. It defines a new modulation method (8-PSK) and new radio protocols that bring higher maximum data rates and increased spectral efficiency. EDGE is applicable to both GPRS traffic (EGPRS) and circuit switched traffic. Enhanced GPRS (EGPRS) supports the GMSK and 8-PSK modulation methods and defines nine Modulation and Coding Schemes (MCSs). MCS-1 to MCS-4 are modulated with GMSK and MCS-5 to MCS-9 are modulated with 8-PSK. EGPRS supports net bit rates up to 59.2 kbps per timeslot. A Packet Data Channel (PDCH) used for the transfer of EGPRS and GPRS CS-1 to CS-4. Traffic Channel (TCH), which in the PSD is capable of carrying EGPRS and GPRS CS-1 to CS-4. A Packet Data Channel (PDCH) used for the transfer of GPRS CS-1 to CS-4. GPRS is a feature that makes it possible to send packet data over the GSM network with GMSK coding schemes (CS-1 to CS-4). GPRS supports net bit rates up to 20.0 kbps per timeslot. An MS shall perform a GPRS Attach to the network in order to obtain access to the GPRS/EGPRS services. The network may provide coordination of paging for Circuit Switched (CS) and Packet Switched (PS) services in different ways depending on if the Gs interface is present or not. See Section on page 14 Allocation of the Master PDCH for a detailed explanation of the different operation modes. This concept is valid also for EGPRS. This message is used to page an MS supporting GPRS/EGPRS. 2

7 GSM 900 bands There are two sub-bands within the GSM 900: P-GSM band: sub-band with frequency range MHz uplink and MHz downlink. G1-GSM band: sub-band with frequency range MHz uplink and MHz downlink. G-TCH Idle rank value Traffic Channel (TCH), which in the PSD is capable of carrying GPRS CS-1 to CS-4. The idle rank value gives an indication of how well one TCH group fulfils the allocation request for a new channel set to be used as on-demand PDCHs. The Idle Rank Value is then compared with other TCH groups in order to find the best TCH group. The components of the Idle Rank Value are listed below in preference order. 1 Number of idle channels within the TCH group. 2 The highest number of consecutive idle channels within the TCH group. 3 The distance from the largest set of consecutive idle channels to the other idle channels within the TCHGRP. 4 The position of the largest set of idle consecutive channels. For example, consecutive channels on TN5 to TN7 is ranked higher than consecutive channels on TN2 to TN4. Master PDCH MS multislot class PCU PS capable TCH PSD A PDCH carrying the Packet Broadcast Control Channel and the Packet Common Control Channel. PS traffic can also be carried on the Master PDCH. The Master PDCH is a dedicated PDCH. MS capability to handle multiple time slots. The multislot classes 1-29 are defined. They are all supported but classes and are handled as class 10. See reference 6 on Page 29. Unit in the BSC responsible for all PDCH allocated channels. Channels capable of carrying PS connections. The Packet Switched Domain (PSD) where the GPRS/EGPRS connections are handled. The PSD is dependent on the CSD to provide it with channels usable for PS connections. 3

8 PSD idle list PSET Selection indicator TAI individual TBF TBF limit TCHGRP A list of on-demand PDCHs not carrying traffic. A set of PDCHs possible to use together for a Temporary Block Flow (TBF). A PSET can contain up to eight on-demand and/or dedicated PDCHs. It is complete when no more PDCHs is possible to allocate in the TCHGRP due to the number of deblocked TCHs. Maximum one PSET can be allocated on the same TCHGRP. The selection indicator indicates whether dedicated or on-demand PDCHs are to be allocated. The PDCH, among the PDCHs used by a TBF, that is chosen to carry the TAI. A Temporary Block Flow (TBF) is a logical connection between the BSS and the MS. A TBF is set up when there is data to send at the BSS or MS side. The parameters in the uplink or downlink direction for when new on-demand PDCHs shall be requested. The limits correspond to the average amount of TBFs on all PDCHs in a cell. They are however calculated separately for E-,G- and B-PDCHs. Thus if the TBF limit is exceeded for any type of PDCHs, then new on-demand PDCHs will be requested from the CSD. All deblocked channels are grouped into TCHGRPs. TCHs within the group shall be located in the same cell or subcell, and be of the channel type TCH. The TCHs within a TCHGRP shall also have the same frequency capabilities. Non frequency hopping channels shall have the same Training Sequence Code (TSC) and ARFCN. Frequency hopping channels shall have the same TSC, Hopping Sequence Number (HSN) and Mobile Allocation Index Offset (MAIO). A TCHGRP can contain maximum one PSET. PDCHs can only be allocated on TCHGRPs with PS capable TCHs. 2.2 Abbreviations and acronyms 8-PSK ARFCN BCCH CHGR CS 8-Phase Shift Keying Absolute Radio Frequency Channel Number Broadcast Control Channel Channel Group Circuit Switched 4

9 CSD EGPRS GBR GMSK GPRS GSL HSN MAIO MS PBCCH PCCCH PCU PDCH PS PSD PSET QoS RP SARA SGSN TAI TBF TCH TCHGRP THP TFI Circuit Switched Domain Enhanced GPRS Guaranteed Bit Rate Gausian Minimum Shift Keying General Packet Radio Service GPRS Signalling Link Hopping Sequence Number Mobile Allocation Index Offset Mobile Station Packet Broadcast Control Channel Packet Common Control Channel Packet Control Unit Packet Data Channel Packet Switched Packet Switched Domain PDCH Set Quality of Service Regional Processor Service oriented Allocation of Resources on the Abis interface Serving GPRS Support Node Timing Advance Index Temporary Block Flow Traffic Channel Traffic Channel Group Traffic Handling Priority Temporary Flow Identity 5

10 TN TRU TSC USF Timeslot Number Transceiver Unit Training Sequence Code Uplink State Flag 3 Capabilities The capability of this feature is to allocate and reserve PDCHs. All PS capable TCHs may be used for dedicated or on-demand PDCHs. 4 Technical Description 4.1 General In order to support GPRS/EGPRS, multiple channels can be allocated for Packet Switched (PS) connections. Channels are allocated for GPRS/EGPRS traffic from the Circuit Switched Domain (CSD) as Packet Data Channels (PDCHs). These PDCHs will then belong to the Packet Switched Domain (PSD). Multislot and PS capable TCHs are used for PDCH allocation. In a cell, PDCHs will coexist with traffic channels for CS. The Packet Control Unit (PCU) is responsible for all PDCH allocated channels. In the PSD, several PS connections can share the same PDCH. One PS connection is defined as a Temporary Block Flow (TBF) and is either uplink or downlink. An MS can have up to two TBF at the same time, one uplink and one downlink. When a TBF is to be set up for a MS, a reservation is put on one or more PDCHs. PDCHs are allocated in sets of PDCHs (PSET) and only PDCHs in the same PSET can be used for a MS. Before a reservation can take place, one or more PDCHs must be present in the PSD. There are two situations in which a set of PDCHs can be allocated for GPRS/EGPRS: 6

11 Allocation of dedicated PDCHs The operator sets the number of dedicated PDCHs in a cell. These PDCHs are allocated from the CSD to the PSD, and will be dedicated for GPRS/EGPRS traffic only. Allocation of on-demand PDCHs On-demand PDCHs are allocated from the CSD only when there is need for more PDCHs for PS traffic. After allocation of PDCHs, the PDCHs can be reserved to carry packet data traffic. PDCH reservation Resources are provided for PS connections by PDCH reservation. PDCHs are reserved for a TBF, uplink or downlink, in accordance with the MS capabilities (MS multi-slot class, support for EGPRS and frequency band capabilities). The on-demand PDCHs are only temporary allocated for GPRS/EGPRS and are returned to the CSD when they have had no reservations for a certain time, or whenever CS needs them. The following two situations can occur: Deallocation of idle on-demand PDCHs PDCHs that are not reserved for GPRS/EGPRS traffic, are put in a PSD idle list. After a limited time in the PSD idle list, the PDCHs are deallocated from the PSD and returned to the CSD. Deallocation of on-demand PDCHs due to pre-emption If there is a shortage of traffic channels in the CSD, a request for PDCH pre-emption is sent to the PSD, in the case there are any on-demand PDCH in the cell. A suitable PDCH may be returned to the CSD, depending on the PDCHPREEMPT setting. The number of dedicated PDCHs can be decreased by the operator: Deallocation of dedicated PDCHs The dedicated PDCHs that are removed by operator command are not returned to the CSD immediately, but will be marked as on-demand PDCHs. If the PDCHs to be marked as on-demand do not carry PS traffic they are put in the PSD idle list. 7

12 Each PSET can contain up to eight on-demand and/or dedicated PDCHs. PDCHs are allocated as a PSET on the very same TCHGRP using any deblocked TCH. As a maximum a PSET consists of up to eight PDCHs, but in some cases less channels are allocated as PDCHs to a PSET. Either it is not possible to allocate channels as PDCHs, for example some TCH are busy with CS traffic, or some BPCs are configured as BCCH or SDCCH, see Figure 1 on page 8. Only PDCHs in the same PSET can be used for the same PS connection and for each MS the multislot class determines which PDCHs that can be used. PSET 1 B S T T P P P P PSET 2 P T P T P T P P B = BCCH P = PDCH S = SDCCH T = TCH Figure 1 Allocation of PSET 4.2 Service oriented Allocation of Resources on the Abis interface (SARA) In order to support higher data rates for PS traffic (CS-3 to CS-4) and EGPRS it is not sufficient with 16 kbits/s per TCH on Abis. G-TCHs and E-TCHs need 64 kbits/s on Abis, which is handled by the SARA functionality. The following parameters can be set at cell configuration: NUMRE- QCS3CS4BPC NUMREQEGPRS- BPC is set per CHGR, and is used to set the wanted amount of BPCs for a CHGR to be G-TCHs. is set per CHGR, and is used to set the wanted amount of BPCs for a CHGR to be E-TCHs. 8

13 TN7BCCH is set per cell, and is used to define if TN7 is allowed to carry EGPRS on the BCCH frequency. Note that the parameter will affect all TN7 in CHGR-0 if Frequency Hopping is used. If there is not enough capacity on Abis to use 64 kbits/s connections for all the 64 kbits/s capable timeslots in a Transciever Group, then the EGPRS capable TRUs have higher priority for 64 kbits/s Abis connections than the only GPRS (CS-1 to CS-4) capable TRUs. At CHGR configuration the network will configure as many EGPRS capable BPCs as possible, in the basic TN priority order 6, 5, 7, 4, 3, 2, 1, 0 on the same carrier before configuring EGPRS capable BPCs on another carrier. If frequency hopping is used the carrier with the highest prioritized MAIO is configured as EGPRS capable first. In order to utilize all possible EGPRS capable timeslots, if limited, for all MAIOs within a CHGR, the TN priority order may be different when E-TCHs are configured on certain MAIOs. The GPRS (CS-1 to CS-4) capable BPCs will be configured when all the EGPRS capable BPCs have been configured. Example: If 24 BPCs are requested, where 9 are to support both GPRS (CS-1to CS-4) and EGPRS and 4 are to support only GPRS (CS-1 to CS-4) for a non hopping CHGR-1, it would look like: Table 1 TN0 TN1 TN2 TN3 TN4 TN5 TN6 TN7 f0 E-TCH E-TCH E-TCH E-TCH E-TCH E-TCH E-TCH E-TCH f1 B-TCH B-TCH B-TCH G-TCH G-TCH G-TCH E-TCH G-TCH f2 B-TCH B-TCH B-TCH B-TCH B-TCH B-TCH B-TCH B-TCH Note that for CHGR-0, the network will not configure 64K Abis for the BCCH or SDCCH timeslots. Note: According to 3GPP specifications 8 PSK (EGPRS) is not allowed to be used on TN7 on the BCCH frequency if the maximum 8 PSK output power in the cell is lower than the maximum GMSK output power. To avoid that situation the parameter TN7BCCH can be set to GPRS. When TN7BCCH=GPRS, TN7 on the BCCH frequency will not carry EGPRS traffic, i.e. E-TCH will not be configured on TN7 for that carrier. TN7 can however be configured as a G-TCH if all the other BPCs in CHGR-0 are configured as G-TCH or E-TCH. 9

14 4.3 Configuration of dedicated PDCHs in Packet Switched Domain (PSD) General In order to secure resources for GPRS/EGPRS, the operator can configure up to eight dedicated PDCHs per cell by setting the parameter FPDCH. The dedicated PDCHs are only available for GPRS/EGPRS traffic. The dedicated PDCHs in a cell can either be placed on non hopping TCHs on the BCCH frequency as a first choice, last choice or as no preference according to the parameter PDCHALLOC Adding dedicated PDCHs When the operator requests an increased number of dedicated PDCHs, a PSET where these PDCHs will reside is selected. There can be up to eight dedicated PDCHs in a cell and a PSET can accommodate up to eight PDCHs. Maximum two PSETs can be selected to add dedicated PDCHs to. The first PSET to be selected is called the primary dedicated PSET, and the second PSET to be selected is called the secondary dedicated PSET. The primary dedicated PSET will always be placed in accordance with the parameter PDCHALLOC. A secondary PSET is allocated when the primary PSET is allocated on a TCHGRP with less deblocked TCHs than the requested number of PDCHs. 10

15 Primary PSET B S DP DP DP DP DP DP Secondary PSET T T T T T DP DP T B = BCCH DP = Dedicated PDCH S = SDCCH T = TCH Figure 2 first Allocation of eight dedicated PDCHs when PDCHALLOC is set to Before any dedicated PDCHs are added in a cell, a check is made to see if it is possible to add more dedicated PDCHs in the RP handling the cell. An RP can handle several cells, but a cell can only be handled by one RP. The check is made against the parameters ONDEMANDGPHDEV and ONDEMANDGPHDV64. The parameter ONDEMANDGPHDEV is a limit of the minimum number of B-PDCHs reserved for on-demand PDCHs for each RP (16 kbits/s GSL sub-devices), i.e. for all the cells handled by each RP. This is to make sure that the total number of possible PDCHs in an RP is not allocated as dedicated PDCHs. If this would be the case, no on-demand PDCHs can be allocated in any of the cells handled by that RP and the cells without dedicated PDCHs will not be able to handle any PS traffic at all. The parameter ONDEMANDGPHDV64 is the corresponding limit of the minimum number of E-PDCHs and G-PDCHs reserved for on-demand E-PDCHs or G-PDCHs for each RP (64 kbits/s GSL devices), i.e. for all the cells handled by each RP. All GSL devices in a RP (both 64 kbits/s and 16 kbits/s), which are reserved for on-demand PDCHs belong to the same pool of resources. Before any dedicated E-PDCHs, G-PDCHs or B-PDCHs are added in the cell, a check is made if the on-demand PDCHs capacity will still exceed both operator thresholds (ONDEMANDGPHDV64 and ONDEMANDGPHDEV) after the allocation the dedicated PDCHs. In that case the requested number of dedicated E-PDCHs, G-PDCHs or B-PDCHs are allocated in the cell, otherwise an attempt to move a cell from this RP shall be made. The selected cell to 11

16 be moved is the cell with the largest amount of GSL resources occupied by dedicated PDCHs and with the least number of TBF. When adding a dedicated PDCHs to the PSD, the following actions are made: 1 If there is a primary PSET containing less than the requested number of PDCHs, and it is possible to upgrade it according to the amount of deblocked E-TCH/G-TCH/B-TCH, then this PSET is selected for adding dedicated PDCHs to. If there are suitable on-demand PDCHs in the primary PSET, then those on-demand PDCHs are marked as dedicated, up to the number the operator has requested. If there are no suitable or not enough on-demand PDCHs in the primary PSET, then PDCH channels are allocated from the CSD towards the number the operator has requested, see Note below and Section on page If the primary dedicated PSET was not possible to upgrade fully according to the request, but there exist a secondary dedicated PSET which is not complete, and it is possible to upgrade it according to the amount of deblocked E-TCH/G-TCH/B-TCH, then that PSET is selected for adding dedicated PDCHs to. If there are on-demand PDCHs in the secondary PSET, then those on-demand PDCHs are marked as dedicated up to the number the operator has requested. If there are no suitable or not enough on-demand PDCHs in the secondary PSET, then PDCH channels are allocated from the CSD towards the number the operator has requested, see Note below and Section on page If no dedicated PSET exist, but the most suitable TCHGRP for allocating a primary PSET (see Section on page 19) is already in use in the PS domain as a set of on-demand PDCHs, then an attempt to transform this PSET into a primary dedicated PSET is initiated. The on-demand PDCHs in the PSET shall be transformed to dedicated PDCHs, up to the number the operator has requested. If there are no suitable or not enough on-demand PDCHs in the PSET according to the operator request, then PDCH channels are allocated from the CSD towards the number the operator has requested, see Section on page If no dedicated PSET exists and if no on-demand PSET, which is possible to upgrade, belongs to the best TCHGRP for allocating a primary PSET on, then an attempt to create a new primary dedicated PSET is made.the PSET, has to be in accordance with the strategy for non hopping PDCHs on the BCCH frequency, according to parameter PDCHALLOC. PDCH channels are allocated from the CSD up to the number the operator has requested, see Note below and Section on page If the request for dedicated PDCHs cannot be fulfilled in the primary PSET, and no secondary PSET exists, but the most suitable TCH group for allocating a secondary PSET (see Section on page 19) is already in use in the PS domain as a set of on-demand PDCHs, then an attempt to transform this PSET into a secondary dedicated PSET is initiated. The on-demand PDCHs in the PSET shall be transformed to dedicated PDCHs towards the number the operator has requested. If there are no suitable or not enough on-demand PDCHs in the PSET according to the operator 12

17 request, then PDCH channels are allocated from the CSD up to the number the operator has requested, see Note below and Section on page If the request for dedicated PDCHs cannot be fulfilled in the primary PSET, and no secondary PSET exists, and if no on-demand PSET, which is possible to upgrade, belongs to the best TCH group for allocating a secondary PSET on, then an attempt to create a new secondary dedicated PSET is made. PDCH channels are allocated from the CSD up to the number the operator has requested, see Note below and Section on page 19. Note: In the transformation of on-demand PDCHs to dedicated PDCHs, the timeslot number priority order is normally used. However if TN7 support less coding schemes than any of TN0 to TN4, then TN7 will be transformed after the TNs which support more coding schemes Fixed PDCH Addition Timer (FAT) Channels chosen for allocation of dedicated PDCHs may be impossible to allocate immediately, since they are busy with CS calls. Pre-allocation of dedicated PDCHs will then take place, which means that the channels will not be allocated for new CS calls. The status of these channels will be periodically checked (FAT interval). When any of these channels has been found idle, it will be allocated as a dedicated PDCH and the pre-allocation status will cease Periodic Check for best Primary Dedicated PSET Depending on application parameter PSETCHKPERIOD the periodic check may be activated. A periodic check whether a better TCHGRP exists for the allocation of a primary dedicated PSET will then be performed. If a better TCHGRP is found (see allocation criteria in Section on page 19), then the PDCHs in the current primary PSET will be marked as on-demand PDCHs and a new primary PSET will be allocated in the best TCHGRP. As a consequence the secondary PSET (if existing) may be removed or re-allocated differently Removing dedicated PDCHs When the operator orders a decrease in the number of dedicated PDCHs in a cell, a PSET is selected from where the dedicated PDCHs are to be removed. If there is a secondary dedicated PSET, then that PSET is selected. Otherwise the primary dedicated PSET is selected. In the selected PSET, a number of dedicated PDCHs are marked as being on-demand PDCHs, in order to decrease the number of dedicated PDCHs in the cell according to the requested number of dedicated PDCHs. 13

18 If the secondary PSET was selected and there were too few dedicated PDCHs in that PSET to fulfil the request, the primary dedicated PSET is selected in order to complete the request. Timeslots are removed in the reversed order they have been allocated Allocation of the Master PDCH A Master PDCH may be allocated in a cell to carry the packet broadcast channel and the packet common control channel, the PBCCH and the PCCCH. The Master PDCH will also carry packet data traffic. The Master PDCH is a dedicated PDCH and can only be set up if there are dedicated PDCHs in the cell. Whether the Master PDCH is allocated or not when at least one dedicated PDCH is configured, is dependent on the chosen GPRS network operation mode (also valid for EGPRS), parameter GPRSNWMODE. The GPRS network operation mode I requires the optional Gs interface between the MSC and the SGSN, while the GPRS network mode II and III should be chosen when the Gs interface is not present. If network mode I is chosen, there are two choices; either no Master PDCH will be allocated in the cell even if there are dedicated PDCHs, GPRSNWMODE = 0, or a Master PDCH is allocated when there are dedicated PDCHs, GPRSNWMODE = 1. The network sends CS paging message for a GPRS-attached MS, either on the same channel as the GPRS paging channel (i.e. the packet paging channel or the Common Control Channel, CCCH, paging channel), or on a GPRS/EGPRS traffic channel. This means that the MS must only monitor one paging channel, and that it receives CS paging messages on the packet data channel when it has been assigned a packet data channel. If network mode II is chosen, GPRSNWMODE = 2, no Master PDCH will be allocated in the cell even if there are dedicated PDCHs. Common control signalling are performed on CCCH for both CS and PS. This means that the MS must only monitor the CCCH paging channel, but that CS paging continues on this paging channel, even if the MS has been signed a packet data channel. If network mode III is chosen, GPRSNWMODE = 3, a Master PDCH will be allocated in the cell when there are dedicated PDCHs. The network sends CS paging message for a GPRS-attached MS on the CCCH paging channel, and sends a GPRS paging message on either the packet paging channel (if allocated in the cell) or on the CCCH paging channel. This means that an MS that wants to receive pages for both CS and PS must monitor both paging channels if the packet channel is allocated in the cell. The network performs no paging coordination. If a Master PDCH is allocated in the cell, one of the dedicated PDCHs that is successfully allocated on the primary dedicated PSET becomes the Master PDCH in the cell. The primary dedicated PSET is allocated in accordance with 14

19 the chosen strategy for non hopping TCH on the BCCH frequency, parameter PDCHALLOC, see Section 4.5 Channel selection in Cicuit Switched Domain (CSD) on page Handling of Packet Data traffic General When resources are needed for PS connections, PDCHs are reserved for those TBF. PDCHs are reserved in accordance with the MS type (EGPRS or GPRS) and the multislot class. If the feature Multiband cell is used also the frequency band capabilities of the MS may be considered. See reference 9 on Page 30. Each PDCH can carry traffic for more than one connection at a time, both uplink and downlink. There is a limit of 32 TFI per PSET and direction. Besides there is a limit of 6 USF per PDCH on uplink traffic using MPDCH and 7 USF per PDCH for non MPDCH channels PDCH reservation General At channel request for a GPRS/EGPRS user, channels in a PSET are selected where the PDCH reservations will be made for the TBF. If the MS already has PDCHs reserved for a TBF in the opposite direction, new reservations are made on the same PSET in accordance with the MS multislot class, (which does not always mean that channels are reserved on the maximum number of PDCHs according to the class), as well as the QoS requirements. The PDCH reservations are continuously supervised and any TBF may be upgraded (on the same PSET) in order to fulfill the QoS requirements and/or the MS multislot class. Channel reservations are made according to the following: MS type (EGPRS or GPRS), frequency capabilities, and multislot class QoS attributes of the packet data session to be set up Available channel resources (E-, G- and B-PDCHs) Channel load from ongoing traffic A TBF will generally be reserved on channels that will provide as much capacity (bandwith) as possible. If GPRS/EGPRS Quality of Service handling is on, the interaction between packet data sessions with different weights must be regarded, since ongoing packet data traffic will be scheduled over the air interface according to their relative QoS weights. QoS class interactive has generally higher weight than the background class and there can be different Traffic Handling Priorities (TPHs) within the Interactive class. See reference 5 on Page

20 Depending on the mobile capabilities, test reservations will be performed for different types of TBFs. There are: E-TBF reservations which can only use E-PDCHs G-TBF reservations which can only use E-PDCHs and G-PDCHs B-TBF reservations which can use all PDCHs All types of TBFs which are applicable for a certain MS (according to the MS type) will be tested if PDCHs of the proper type are allocated in the cell. The type of TBF (E-, G, or B) that will be chosen depends on the capacity each type of reservation can provide. If GPRS/EGPRS Quality of Service handling is on, QoS weights must also be regarded, and the weights are fetched from QoS in relation to the TBF request. See reference 6. Quality of Service class Streaming The streaming class has the highest priority. It will regard the Guaranteed BitRate attribute, which has been negotiated with the SGSN node. Only one streaming TBF will be reserved per PDCH. The rest of the PDCH capacity may be used for Interactive Class or Background Class TBFs, if possible, in order to fulfill the GBR for the Streaming TBF. Quality of Service class Interactive With a TBF request for an EGPRS capable MS three weights are received, these weights correspond to the three possible TBF-modes (E-TBF, G-TBF and B-TBF). With a TBF request for a GPRS only capable MS two weights are received (G-TBF and B-TBF). These weights are received from QoS for Traffic Class Interactive. Quality of Service class Background If the TBF request indicates Traffic Class Background, the weight will be calculated by this function as: weight = 0.1 * (the lowest of the current interactive weights within the cell). If no interactive weight is existing in the cell, the weight 1 is used as the lowest current Interactive weight in the cell. If GPRS/EGPRS QoS is off, all TBF requests are considered as Traffic Class Background and will thus be given the same weight. Selection of all possible combinations of PSET and possible TBF-mode One PSET may have up to three possible TBF-modes depending on the requested TBF-mode and the types of PDCH resources in the PSET. In the case an EGPRS TBF (E-TBF) is requested then: 16

21 a In a PSET containing at least one E-PDCH as the most capable, then E-, G- and basic GPRS TBF (B-TBF) is tested. b In a PSET containing at least one G-PDCH as the most capable, then G- and B-TBF is tested. c In a PSET containing only B-PDCHs, only B-TBF is tested. In the case an GPRS TBF (G-TBF) is requested then: a b In a PSET containing at least one E-PDCH or at least one G-PDCH as the most capable, then G- and B-TBF is tested. In a PSET containing only B-PDCHs, only B-TBF is tested. PDCHs which are not possible to use in a PDCH-reservation are not considered. An example is a PDCH with no available USFs, which therefore may not be part of an Up Link PDCH-reservation. The reservation must also be done according to the MS multislot class and MS type. If the MS capabilities are not known at reservation time, only one B-PDCH will be reserved. For all the combinations above all unnecessary combinations are removed. Test Reservations Test Reservations are performed on all combinations selected in the previous part selection of all possible combinations of PSET and Possible TBF-mode. The Test Reservation algorithm ranks all meaningful reservation patterns within each selected combination and among all selected combinations. The reservation that will give the highest bandwith for a TBF in accordance with the QoS scheduling (if QoS is active) and the capabilities of the different PDCHs that may be reserved, will be ranked highest. Reservation A PDCH-reservation will be made on the best test reservation pattern (highest rank) and with the selected TBF-mode. Upgrade of PDCH reservation The reservations of TBFs on PSETs are continuously supervised in order to check if it is possible to upgrade any reservation according to the MS multislot class. Upgrade will be made, if possible, in accordance with the MS multislot class when more PDCHs are available compared to when the previous reservation was made. Upgrade of a TBF reservation is only possible within the PSET where the initial reservation was made. Dynamic downlink/uplink PDCH reservation 17

22 This feature can be activated/deactivated by parameter DYNULDLACT. It is deactivated by default. If the traffic load is indicated to be mainly uplink, an uplink upgrade can be performed if possible. Since as many as possible downlink PDCHs of the PSET were reserved in the downlink direction during the initial reservation, it may then be necessary to first execute a downgrade of the downlink reservation in order to achieve a possible uplink upgrade in accordance with the MS multislot class. Re-Reservation of PDCH Reservation A TBF reservation that do not fulfill the GBR for streaming or is not reserved on as many timeslots as possible according to the MS multislot class may be re-reserved. A re-reservation attempt will be made if an upgrade is not possible or not enough in order to reach GBR or to handle as many timeslots as the MS multislot class admits. (EIT excluded). TBF reservations on heavy loaded PDCHs may be subject for re-reservation, with the purpose to even out the load on the available PDCHs. A request for new on-demand PDCHs may be part of the re-reservation strategy if the existing PSETs do not fulfill the requirements for the reservation. Only the needed number of PDCHs will be requested from the CSD Request for on-demand PDCHs from the CSD On-demand PDCHs are requested from the CSD when: There are no PDCHs in a cell and a GPRS/EGPRS MS requests channels. MS reservations were made up to one of the TBF limits (uplink or downlink) in average for the PDCHs in a cell. This is checked individually for PDCHs capable of supporting E-, G-, and B-TBFs. MS reservations are made on less PDCHs than the MS is capable of according to its multislot class. An MS has been reserved using a lower TBF mode than the MS can handle according to its capabilities. (For instance an EGPRS mobile has been reserved in B-TBF mode). Note: This case is not valid for upgrade of running TBFs or for re-reservation, since change of TBF mode of a running TBF is not allowed according to 3GPP standard. 18

23 If the PSET is not complete, an attempt is made to upgrade the PSET. Otherwise, if there are no incomplete PSET, an attempt is made to allocate a new PSET of up to four PDCHs. The new on-demand PDCHs are for future use. 4.5 Channel selection in Cicuit Switched Domain (CSD) General In the allocation request from the PCU, the cell, channel set indicator and selection indicator are provided. In the case of adding channels to a PSET, the number of already allocated channels is also provided. If the feature Multi Band Cell is used, the frequency band capabilities of the mobile are considered (if known) if the allocation of new PDCHs is done in order to serve a certain mobile (re-reservation of PDCHs on another PSET or initial PDCH setup). See User Description, Multi Band Cell Also if E-GSM is used the frequency band capabilities of the mobile (P-band or G1 band) are considered (if known) if the allocation of new PDCHs is done in order to serve a certain mobile. General PDCH allocation as a new PSET, (not for individual mobile support), can be performed only in the BCCH frequency band if the parameter MBCRAC is set to 0 (default value). To allow general allocation of PDCHs in other bands in a cell must MBCRAC be set to 1 see Page 26. Dedicated PDCHs are always allocated according to the MBCRAC setting. Extension of an already existing on-demand PSET is however generally allowed regardless of the MBCRAC setting. The non BCCH band is generally preferred if other constrictions not prevent this. The MBCRAC setting is applicable also if E-GSM is used. The GSM 900 P-band and the G1 band are handled in the same way as other different bands in a multi band cell. If the feature Packet Data in Overlaid Subcell is used, PDCHs will be allocated in any of the subcells which are allowed according to the parameter SCALLOC see Page 27. The allocation algorithms will also consider if any subcell is preferred according to this parameter. If the feature Packet Data in Overlaid Subcells is not in use, PDCH allocation is only possible in underlaid subcells. See User Description, Overlaid/Underlaid Subcells. Among the multislot and PS capable TCHs, a TCHGRP is selected according to what type of allocation is requested. If the allocation request is adding channels to an existing PSET, the TCHGRP where the already allocated channel(s) belong is selected. If a new channel set is requested, PS capable TCHs are selected depending on if the selection criteria is dedicated PDCHs or on-demand PDCHs. 19

24 Only TCH groups that are non-hopping or belong to CHGRPs with parameter BCCD set to yes, see User Description, Frequency Hopping, are considered for the primary PSET Selection of dedicated PDCHs When the selection indicator is set to allocation of dedicated PDCHs, the requested number of channels are selected within the allowed frequency band and subcell(s) according to the following algorithm: 1 In the case of adding PDCHs to a PSET, then select the TCHGRP where the other PDCHs in the PSET are located. Then proceed to step For the primary PSET Select the TCHGRPs that fulfil the operator chosen strategy regarding non hopping TCH on the BCCH frequency, according to parameter PDCHALLOC. 3 Among these TCHGRPs, select the TCHGRPs that have the highest number of deblocked E-TCHs (idle or busy). 4 Among these TCHGRPs, select the TCHGRPs where the E-TCHs have the highest TNs. 5 Among these TCHGRPs, select the TCHGRPs that have the highest number of deblocked G-TCHs (idle or busy). 6 Among these TCHGRPs, select the TCHGRPs that have the highest number of deblocked B-TCHs (idle or busy). 7 Among these TCHGRPs, select the TCHGRPs that have TN6 idle. 8 Among these TCHGRPs, select the TCHGRPs that have the highest number of idle TCH among TN4 to TN7. 9 Among these TCHGRPs, select the TCHGRPs that have the highest number of idle TCH among TN0 to TN3. 10 If the function Idle Channel Measurements is active, select among these TCHGRPs the TCHGRPs with the lowest interference level. (This refers to the channel with the highest interference level within the TCHGRP.) 11 If frequency hopping is used, select among these TCHGRPs the TCHGRPs hopping over as many frequencies as possible. 12 Select a non BCCH frequency band first, and the BCCH band as second choice if the prerequisites mentioned above will admit this. 13 If Packet Data in Overlaid subcell is used, select among these TCHGRPs the TCHGRPs in the preferred subcell according to the parameter SCALLOC. 14 Among these TCHGRPs, select the first found TCHGRP and allocate as many as requested or as many as possible, if less, PDCHs. 20

25 Note: The normal TN allocation order is 6, 5, 7, 4, 3, 2, 1, 0. However, if TN7 support less coding schemes than any of TN0 to TN4, then TN7 will be allocated after the TNs which support more coding schemes. If only one PDCH was requested and if TN7 support less coding schemes than any of TN0 to TN4, the allocation order starts with TN5 before TN6 instead. First E-TCHs are allocated. If there are not enough deblocked E-TCHs compared to the requested number of channels then the search continues for G-TCHs in the preferred TN order. If there are not enough deblocked E-TCHs and G-TCHs compared to the requested number of channels the search continues for B-TCHs Selection of on-demand PDCHs When the selection indicator is set to allocation of on-demand PDCHs, the requested number of channels are selected within the allowed frequency band and subcell(s) according to the following algorithm: 1 In the case of adding PDCHs to a PSET, then select the TCHGRP where the other PDCHs in the PSET are located. Then proceed to step Among these TCHGRPs, select the TCHGRPs that have the best idle rank value of idle E-TCH. 3 Among these TCHGRPs, select the TCHGRPs that have the best idle rank value of idle G-TCH. 4 Among these TCHGRPs, select the TCHGRPs that have the best idle rank value of idle B-TCH. 5 Select the TCHGRP that fulfil the operator chosen strategy regarding non hopping TCH on the BCCH frequency, according to parameter PDCHALLOC. 6 If the function Idle Channel Measurements is active, select among these TCHGRPs the TCHGRPs with the lowest interference level. (This refers to the channel with the highest interference level within the TCHGRP.) 7 If frequency hopping is used, select among these TCHGRPs the TCHGRPs hopping over as many frequencies as possible. 8 Select a non BCCH frequency band first and the BCCH band as second choice if the prerequisites mentioned above will admit this. 9 If Packet Data in Overlaid subcell is used, select among these TCHGRPs the TCHGRPs in the preferred subcell according to the parameter SCALLOC. 10 Among these TCHGRPs, select the first found TCHGRP and allocate four or as many as possible, if less, PDCHs. 21

26 Note: If the request was for a new PSET, then first E-TCHs are allocated and the allocation starts from the highest TN in the group of idle consecutive E-TCHs. If there are less than 4 idle consecutive E-TCH, then the remaining E-TCHs are allocated as close as possible to the largest set of consecutive idle E-TCHs. If there are not enough idle E-TCHs compared to the requested number of channels then the search continues for G-TCHs in the preferred order. If there are not enough idle E-TCHs and G-TCHs compared to the requested number of channels the search continues for B-TCHs. The same search criteria is used if there is no idle E-TCHs but idle G-TCHs and/or B-TCHs exists. If the allocation request stated that there must exist at least one idle E-TCH or at least one idle G-TCH in the TCH group, then channels are only allocated in this case. If the request was that channels should be added to a PSET the channels shall be allocated so that as large consecutiveness as possible is achieved. Idle E-TCHs shall be allocated first, secondly idle G-TCHs and as a last priority B-TCHs. 4.6 Return of PDCHs to Cicuit Switched Domain (CSD) General The on-demand PDCHs can be returned to the CSD in two ways, either when they have been idle for a limited time or whenever CS needs them. They are then returned in reversed priority order (first B-PDCHs, G-PDCHs and then E-PDCHs as last choice). Dedicated PDCHs that are removed by operator order will not be returned to the CSD directly, but will be marked as on-demand PDCHs, see section Section on page Deallocation of idle on-demand PDCHs On-demand PDCHs that become idle in both directions, are linked into the PSD idle list after which the timer PILTIMER is started. When the timer expires for a PDCH, the PDCH is deallocated in the PSD and returned to the CSD. The timer PILTIMER is restarted for all PDCHs in a PSET if a reservation is put on one or more PDCHs in the PSET. The value range of the PILTIMER is 1 s. to 3600 s. When the PILTIMER is set to a low value, the idle on-demand PDCHs will only stay in the PSD idle list for a short time before they are deallocated in the PSD and returned to the CSD. This implies more allocations and deallocations of PDCHs and requires more CP capacity. On the other hand a low value of the PILTIMER will make the allocation of on-demand PDCHs more dynamic in the cells handled by the same RP. The cells, handled by the same RP, share the maximum number of possible PDCHs and by deallocating idle on-demand PDCHs the possibility to allocate PDCHs for other cells, handled by the same RP, will increase. When setting the PILTIMER, the number of RP handling cells in the PCU, the number of cells and the CP capacity should be taken into consideration. 22

27 4.6.3 Deallocation of on-demand PDCHs due to pre-emption When there is a shortage of channels in the CSD, a request for PDCH pre-emption is sent to the PSD in case there are any on-demand PDCHs in the cell. The pre-emption procedure can be controlled by the parameter PDCHPREEMPT. Thus the operator can choose to allow either pre-emption of: Only idle PDCHs Only non essential PDCHs (not carrying TAI) and idle PDCH Only on-demand PDCHs that are not marked as used for streaming or are non-essential Only on-demand PDCHs that are not marked as used for streaming All PDCHs If pre-emption of busy PDCHs are allowed, the operator can also decide if PDCHs carrying TAI can be pre-empted, which will cause the whole packet data data session connected to the pre-empted TAI to stop. If the PDCHPREEMPT parameter allows pre-emption of all types of on-demand PDCHs (idle or busy), an on-demand PDCHs to be returned is selected as follows: 1 If there exist any idle on-demand PDCHs, then select those PDCHs and proceed to 5. 2 Select the on-demand PDCHs that are chosen as TAI individual for the least number of TBF. 3 Among those on-demand PDCHs, select B-PDCHs firstly, G-PDCHs secondly and E-PDCHs as last choice. 4 Among those on-demand PDCHs, select the PDCHs having the least number of PDCH reservations. 5 Among those on-demand PDCHs, select the on-demand PDCHs residing on the PSETs with the least dedicated PDCHs. 6 Among those on-demand PDCHs, select the PDCHs residing on the PSET containing the fewest PDCHs. 7 Among those on-demand PDCHs, select the PDCHs residing on the PSETs with the least deblocked E-TCHs. 8 Among those on-demand PDCHs, select the PDCHs residing on the PSETs with the fewest E-PDCHs. 9 Among those on-demand PDCHs, select the PDCHs residing on the PSETs with the least deblocked G-TCHs. 23

28 10 Among those on-demand PDCHs, select the PDCHs residing on the PSETs with the fewest G-PDCHs. 11 Among those on-demand PDCHs, select the PDCHs residing on the PSETs with the least deblocked B-TCHs. 12 Among those on-demand PDCHs, select the PDCHs in reversed priority order (B, G and last E-PDCHs). 13 Among those on-demand PDCHs, select the first found PDCH after search in reversed TN order ( ). If only non essential PDCHs (not carrying TAI) and idle PDCHs are allowed for pre-emption, then start on 2 above, but do only regard PDCHs not carrying TAI. Then follow the list from 3 until 13. If only idle PDCHs are allowed for pre-emption, then start on 1and select all idle PDCHs, then follow the list from 5 until Main changes in Ericsson GSM system R10/BSS R10 The following new functionality affecting the GPRS/EGPRS channel allocation stratagy have been introduced: Improved upgrade of TBF reservation (both uplink and downlink) TBF re-reservation Dynamic downlink/uplink PDCH reservation (de-activated by default) QoS Class Streaming Packet Data in Overlaid Subcell Multiband Cell 5 Engineering guidelines The recommended parameter value of PILTIMER (20 s) is chosen as a compromise between keeping the number of reserved on-demand PDCHs low, thereby reducing the number of engaged GSL devices, and still admit good performance of traffic throughput and delay. A lower setting of the PILTIMER value (down to 1 s) may significantly further reduce the number of engaged GSL devices in case of pure PS traffic in the cell. Instead on-demand PDCHs must be allocated more often, which may cause increased delays for some types of 24

29 PS traffic. In case of mixed CS and PS traffic in a cell, the reduction of engaged GSL devices due to very low PILTIMER settings is negligible, so such settings are recommended only in case of shortage of GSL devices in combination with pure PS traffic. A higher value of PILTIMER than the recommended may slightly increase the throughput performance to the cost of more engaged GSL devices. The parameters TBFDLLIMIT and TBFULLIMIT have a default value of 2. A low value will ensure sufficient channel allocation for PS traffic when CS traffic is low, thereby maintaining an adequate transmission rate. A high value may cause lower transmission rate per MS, since several MS may share the same PDCH, but on the other hand it will reduce the risk of preemption if CS traffic is high. The default value is chosen in order to get a reasonable fast PS transmission with a limited risk of preemption. If the cell normally has overcapacity for GPRS/EGPRS, it may be an adequate choice to set these parameters to 1, thus improving the data transmission rate in general per mobile station. The default value of FPDCH is 0. This will give as many channels as possible free for CS allocation. This may be an optimal solution if the GPRS/EGPRS traffic is low whereas the CS traffic is close to congestion and if CS service is prioritized, but if it is important to guarantee GPRS/EGPRS service in the cell under such conditions FPDCH may be set to 1, thus avoiding allocation attempts of a new PSET for every cell update. If the GPRS/EGPRS traffic is significant it may be a better choice to set FPDCH to 4 to ensure adequate capacity for multi-slot mobile stations. If EGPRS is used it is recommended to allocate at least 4 dedicated E-PDCHs on the non hopping BCCH CHGRP. This will be achieved by setting NUMREQEGPRSBPC (for CHGRP number 0) to the value 4.The parameter PDCHALLOC should then be set to first and FPDCH to 4. The preference parameter PDCHALLOC, which determines whether non hopping TCHs on the BCCH frequency are first choice or not for allocation of PDCHs, has some interaction with the corresponding parameter for allocation of CS channels CHALLOC, see User Description, Channel Administration. If PDCHALLOC is set to first, and PDCHs are allocated using non hopping TCHs on the BCCH frequency, then the probability to also get CS channels there will decrease even if CHALLOC also is set to first. This is due to the fact that TCHs adjacent to the TCHs allocated as PDCHs are reserved for PS as a first choice, since they could be part of a larger PSET together with the PDCHs already allocated. CS channels will be allocated there only if there are no other idle TCHs left in the cell. In order to maintain acceptable GPRS/EGPRS performance on on-demand PDCHs, it is recommended to only allow pre-emption of non essential on-demand PDCHs (not carrying TAI). This is achieved by setting the PDCHPREEMPT parameter to 1. Pre-emption of a PDCH carrying TAI will crash the on-going TBF, but pre-emption of other PDCHs will only reduce the data throughput. See Page 9 regarding setting of the parameter TN7BCCH. 25