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Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS ERA/SV-01:0976 Rev A 2001-12-11E******* Wide Interna
RADIO NETWORK CONFIGURATION GUIDELINE
FOR EDGE AND GPRS CS3/CS4 IN
E*******'S BSS
E******* WIDE INTERNAL
Contents
1 Revision History................................................................... 2
2 Purpose and scope.............................................................. 2
3 Glossary .............................................................................. 3
3.1 Abbreviations....................................................................... 3
3.2 Concepts ............................................................................. 4
4 Introduction..........................................................................4
5 Requirements for Packet Data............................................. 5
5.1 Software .............................................................................. 5
5.2 Hardware............................................................................. 5
5.3 BSC PCU Capacity and A-bis Configuration........................ 7
5.4 Core Network ...................................................................... 7
6 Channel Allocation...............................................................8
7 Cell Planning Aspects of Packet Data ................................. 8
7.1 General................................................................................8
7.2 Introducing GPRS CS3/CS4 and EDGE in a
Synthesizer Frequency Hopping Network ............................ 9
7.3 Introducing GPRS CS3/CS4 and EDGE in a Baseband
Frequency Hopping Network ............................................. 10
7.4 Network configuration........................................................ 12
8 Output power for GMSK and 8PSK ................................... 13
8.1 Background .......................................................................13
8.2 Non-BCCH TRU carrying EDGE traffic.............................. 13
8.3 BCCH TRU carrying EDGE traffic...................................... 14
9 References ........................................................................ 16
GUIDELINE
2(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
1 Revision History
Rev Date Description
A 2001-12-11 Created.
2 Purpose and scope
The Configuration Guideline describes different configuration aspects which
needs to be considered while implementing the packet data services GPRS
CS3/CS4 and EDGE in an E******* GSM network. The document gives
suggestions on how to configure the networks, but no specific
recommendations.
Note that this is a release independent document, which does not state when
the features will be available.
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
3 Glossary
3.1 Abbreviations
BB Base Band
BCCH Broadcast Control Channel
BSC Base Station Controller
BTS Base Transceiver Station
CS Coding Scheme
DTX Discontinuous Transmission
EDGE Enhanced Data rates for Global Evolution
EGPRS Enhanced GPRS
FLP Fractional Load Planning
GMSK Gaussian Minimum Shift Keying
GoS Grade of Service
GPRS General Packet Radio Service
LQC Link Quality Control
MCS Modulation Coding Scheme
MRP Multiple Reuse Patterns
PDCH Packet Data Channel
PSK Phase Shift Keying
SY Synthesizer
TBF Temporary Block Flow
TCH Traffic CHannel
TRU Transceiver Unit
WWW World Wide Web
GUIDELINE
4(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
3.2 Concepts
8PSK 8 Phase Shift Keying is a new modulation method which enables
higher data rates than GMSK.
IR Incremental Redundancy (IR) is an approach to adapt the code
rate to the channel quality.
LA Link Adaptation (LA) is an approach to select the most optimum
coding scheme based on the radio link quality.
LQC The LQC algorithm controls the selection of coding scheme to
be used for the transmission. LQC can use either IR or LA, see
ref [2].
BB Hop In baseband frequency hopping, each transmitter is assigned
with a fixed frequency. At transmission, all bursts, irrespective
of which connection, are routed to the appropriate transmitter of
the proper frequency.
SY Hop Synthesizer hopping means that one transmitter handles all
bursts that belong to a specific connection. In contrast to
baseband hopping, the transmitter tunes to the correct frequency
at the transmission of each burst.
4 Introduction
The purpose of this document is to present the most important information
regarding the implementation of EDGE and GPRS CS3/CS4 in an E*******
GSM network. A basic requirement for these services is that the BSS and BTS
SW can handle EDGE and CS3/CS4. By introducing EDGE and CS3/CS4 also
new hardware is required. Which HW to use and how this is to be configured
is strongly dependent on the existing HW configuration and the capacity
demand. The impact on the frequency planing varies depending on the
strategies of the operator and the available hardware. Furthermore, the
document describes the effects of the average power reduction on the EDGE
signal due to the 8PSK modulation.
In the E******* R8 version of GPRS the only coding schemes available have
been CS1 and CS2. From release 9.1 it will also be possible to use the coding
schemes CS3 and CS4 on the downlink, meaning that the system can choose
between CS1 to CS4. The higher coding schemes uses less coding bits for
error correction and can therefore be used to increase the throughput for
connection with good radio conditions.
EDGE introduces a new modulation method (8PSK), which enables higher
data rates than GMSK. Compared to GPRS, also the RLC protocol is
enhanced with e.g. an extended transmit window, refined ACK/NACK reports
and the possibility to resegment data and therefore to retransmit with a
different MCS. More information can be found in ref [3 and 6].
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
When dimensioning a network for packet data, it is the general C/I conditions
in the network that is of interest. Given a certain frequency plan, cell plan and
traffic load, the throughput per timeslot can be derived through simulations.
For EDGE this is described in the EDGE bandwidth dimensioning guideline
ref [3].
The coverage of EDGE and GPRS CS3/CS4 will be as good as for GPRS
CS1/CS2 since all the signaling is done using the most robust coding scheme
(MSC1 or CS1). Investigations have shown that wherever there is speech
coverage there will also be packet data coverage, see ref [1]. The header in
packet data is very safe coded and there should be no problems to decode the
Uplink State Flag (USF) giving uplink coverage.
In GPRS the link control is controlled by Link Adaptation. For a network
capable of CS4 this means that the system can choose between the coding
schemes CS1 to CS4, depending on the radio link quality.
In EDGE the Link Quality Control (LQC) algorithm aims at achieving the
highest possible throughput for the end user. This is done by dynamically
selecting the most optimal MCS to be used. In the MCS selection process, two
different modes of operation are used; Incremental Redundancy (IR) or Link
Adaptation (LA). See ref [2].
5 Requirements for Packet Data
5.1 Software
In order to support the higher coding schemes for GPRS (CS3/CS4) and/or
EDGE both the BSC and the BTS require new SW.
5.2 Hardware
The ambition is to introduce packet data at minimal effort and cost. In other
words, the impact of the packet data system on the network architecture must
be small, and the system should permit operators to reuse most of the existing
base station equipment.
All RBS HW available since 1991 (RBS 200 and RBS 2000) supports GPRS
CS1/CS2. To support GPRS CS3/CS4 and EDGE a need for more processing
capacity and memory demands the new HW platform of TRU (sTRU EDGE,
dTRU and dTRU EDGE).
The RBS 2101/2102/2202 macro base stations are hardware prepared to
support EDGE as well as CS3/CS4 using the plug-in single EDGE sTRU. This
transceiver unit will fit in a TRU slot of the current RBS 2000 macro base
stations. No further changes to the cabinet are needed in order to get EDGE
and CS3/CS4 up and running. Back plane, DXU and combiner structures stay
unchanged. However, the maximum number of GPRS and EDGE timeslots
GUIDELINE
6(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
that can be supported in one cabinet are limited by the capacity of the PCMlink
and the architecture of the DXU.
On the RBS 2000 it is possible to increase the EDGE and CS3/CS4 capacity
per sector by replacing the old DXUs (01/02/03/11), that only support one
EDGE sTRU per cell, with the new DXU-21 which supports up to 12 EDGE
sTRUs per cell, see table 1.
Note that by switching form the current DXUs (01/02/03/11) to DXU-21, for
all RBS 2000 base stations, the local bus, timing buss and x bus have to be
replaced by the new "Y bus". An upgrade kit will be available for easy
implementation, see ref [7].
Table 1. Examples of configurations for EDGE with DXU-11 and DXU-21
(#cells X #TRUs).
Sector configuration 1X6 3X2 3X4 1X12
Configuration for EDGE with DXU-11 1X1 3X1 3X1 1X1
Configuration for EDGE with DXU-21 1X6 3X2 3X4 1X12
The RBS 2206/2106 is delivered capable of GPRS CS1 to CS4. As an option
it can be fully equipped to also handle EDGE. Both the dTRU and the EDGE
dTRU support GPRS CS1 to CS4. For EDGE it is required to use the EDGE
dTRU. The base station is equipped with DXU-21.
The new RBS 2205 will support EDGE and GPRS CS1 to CS4 on the sector
part through the EDGE sTRU. This is however not finalised.
The RBS2301 micro supports GPRS CS1/CS2 if a DSP cluster is deployed.
GPRS CS3/CS4 and EDGE is not supported.
The RBS2302 micro supports GPRS CS1/CS2.
The RBS2401 micro micro supports GPRS CS1/CS2. GPRS CS3/CS4 and
EDGE is not supported.
The RBS 200 supports GPRS CS1/CS2. In order to introduce EDGE and/or
GPRS CS3/CS4 to a RBS 200 network it is required to combine the RBS 200
with a RBS 2000 using TG synchronization, see ref [5].
The RBS2308 micro will support EDGE as well as GPRS CS1 to CS4.
All future base stations are planned to support EDGE and GPRS CS1 to CS4.
For detailed information, see ref [7].
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
5.3 BSC PCU Capacity and A-bis Configuration
The processing capacity of the BSC will not be impacted by the introduction
of packet data in terms of number of TRX, the E******* BSC will still support
up to 1020 TRX. In the BSC no extra hardware is needed for the EDGE and
CS3/CS4 support as such. However, if the traffic requirements exceed the
capacity installed, then additional transmission links (E1/T1) are needed. The
PCU, which is situated in the BSC, could of course also be affected when
traffic requirements exceed the installed PCU capacity. In the time frame
when EDGE and CS3/CS4 will be available, the PCU capacity can be
increased. This will be achieved by extending the number of RPP boards. The
PCU will then have sufficient capacity to handle the growth for both GPRS
and for EDGE traffic. The PCU will be enhanced so four 16 kbps GSL
devices can be reserved for each Basic Physical Channel (BPC).
With “normal” GSM, every air timeslot uses 16 kbps transmission capacity to
the BSC. Four air timeslots are combined to a 64 kbps PCM timeslot. The
transmission need for an EDGE air timeslot can be as high as 59.2 kbps. This
requires that one 64 kbps PCM timeslot is assigned to every EDGE air
timeslot. Note that GPRS CS3 and CS4 also require one 64 kbps PCM
timeslot for every air timeslot, whereas CS1 and CS2 only need 16 kbps PCM
timeslot.
Depending on the existing utilisation of the PCM links, it can initially be
possible to use spare 64 kbps transmission timeslots on the existing links for
the EDGE and CS3/CS4 capable timeslots.
5.4 Core Network
When the data rate on the air interface is increased, this increases the demand
for transmission capacity between the BSC and the SGSN node (Gb
interface). However, for EDGE and GPRS CS3/CS4, the same physical links
can be used as in GPRS CS1/CS2, i.e. the Frame Relay protocol.
The SGSN supports the optional “MS Radio Access Capabilities” in terms of
8PSK support or not (1 bit) which has to be reported to the PCU. This new bit
is being set with the down link data unit (LLC PDU).
GUIDELINE
8(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
6 Channel Allocation
In a cell supporting packet data, the BSS system maintains two idle lists (GSM
and the GPRS idle list) over all the available traffic channels. Initially all
these idle channels belong to GSM idle list. When a packet data channel is
required, the system first looks for a dedicated PDCH. If no channel is found
(either there is no dedicated PDCH allocated in the cell or all PDCHs are
busy), the system checks the GSM idle list.
GPRS MSs will share the PDCHs with EDGE MSs. The channel allocation
algorithm will investigate on which timeslots an incoming MS will get the
best throughput and place it there. E.g. if the load on the EDGE capable
timeslot is high this means that an EDGE MS might be allocated to timeslots
that are only GPRS capable and vise versa. If a GPRS capable MS is assigned
timeslots capable of EDGE, it will still only be GPRS capable.
All packet data is assigned to EDGE capable timeslots as first choice.
7 Cell Planning Aspects of Packet Data
7.1 General
Generally packet data is considered to have a better coverage than voice. This
is due to the fact that all signaling is done using CS-1 (GPRS) or MCS-1
(EDGE). Simulation and measurement results show that for noise limited
systems packet data services have at least the same coverage as GSM voice
system.
When introducing EDGE into an already existing cell plan, the radio link
throughput can be estimated with the help of the Radio Link Bandwidth
Dimensioning Guideline, ref [3]. Dependent on cell plan, frequency re-use and
frequency load the throughput per timeslot can be derived.
The higher coding schemes provided by GPRS and EDGE are beneficial since
they make use of good C/I conditions. However, to give certain application
coverage over the whole network, the cell plan may be affected.
In some configurations the output power for GMSK and 8PSK i.e. EDGE may
differ. How this affects the cell plan is described in chapter 8.
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
7.2 Introducing GPRS CS3/CS4 and EDGE in a
Synthesizer Frequency Hopping Network
7.2.1 Strategies
Synthesized frequency hopping allows more frequencies per cell than there
are transceivers. This is normally the case, and since there are more
frequencies than transceivers each frequency is only used a fraction of the
time. Hence it is called fractional load planning. The BCCH carriers are in
most FLP networks non-hopping. For more information about FLP, see ref [4].
There are basically three different strategies when implementing packet data
into a FLP network:
• Put packet data on the BCCH frequency.
• Integrate packet data into the existing hopping CHGR.
• Give dedicated frequency spectrum to packet data.
When configuring packet data on the BCCH frequency, the interference in the
network will not increase since the BCCH is always transmitting. The BCCH
plan can be kept and no re-planning is needed. Depending on the control
channel configuration, up to 7 channels can be used for the packet data. Note
that if either of the 2 highest output power settings are used then timeslot 7
can not carry EDGE traffic. See chapter 8. Furthermore, this power setting
will cause the output power to differ between GMSK and 8PSK. It is believed
that this will have minor effects on the network. See chapter 8.
When integrating CS3/CS4 or EDGE into an existing hopping channel group
there are two options; either to swap an existing TRU for an EDGE TRU or to
expand the channel group with an EDGE TRU. The GoS for speech has to be
taken into consideration when introducing the EDGE TRU.
The packet data traffic will introduce interference into the network, as all
traffic does. Meaning that when the traffic grows, the throughput for packet
data may be lower just as the speech quality may be worsened.
When using dedicated spectrum for packet data, the interference generated by
the data traffic will not affect the speech frequencies. On the other hand, the
frequency re-use probably has to be tightened for the speech traffic in order to
free up some spectrum for packet data. Whilst doing this, the speech quality
measures has to be monitored carefully. Dependent on the amount of packet
data traffic, around 4-12 frequencies using a 1/1 frequency re-use would be
recommended for CS3/CS4 and/or EDGE. By using synthesized frequency
hopping and 1/1 the frequency planning will be easy for packet data.
GUIDELINE
10(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
When using on-demand channels for packet data, the GoS for speech will not
be affected if speech is set to have priority over packet data.
Where to put the packet data channels is dependent on the strategy of the
operator. However, initially it is presumably beneficial to put the data traffic
on the BCCH, because:
• Speech will be unaffected by the data traffic (no interference increase due
to the carrier filling)
• Easy to swap one TRU for an EDGE TRU
• Enough with the timeslots on the BCCH for the initial GPRS and EDGE
traffic
7.3 Introducing GPRS CS3/CS4 and EDGE in a
Baseband Frequency Hopping Network
7.3.1 Strategies
Baseband frequency hopping means that the number of transceivers in a cell is
equal to the number of frequencies. Each transceiver has its own frequency
reuse pattern. An advantage of baseband hopping is that the BCCH carrier can
be included in the hopping sequence.
The following strategies can be used for introducing packet data in a baseband
frequency hopping network:
• Remove one frequency (BCCH TRU or non-BCCH TRU) from the
hopping group and use it for CS3/CS4 and/or EDGE (one frequency group
as no hopping for packet data)
• Add one TRU for packet data and use dedicated spectrum (configured as
no hopping)
• Add one cabinet with EDGE TRU using TG Synchronization (configured
as no hopping or preferably synthesized hopping)
When swapping one TRU for an EDGE TRU, it has to be configured as no
hopping, since the transceiver is locked to one frequency. The benefit with
this solution would be low cost but there are several drawbacks. Since the
EDGE TRU is non-hopping, the speech quality may be poor on that TRU. It
all depends on the frequency re-use and the load of the TRU.
When removing one frequency from the frequency group, the frequency
hopping gain is decreased for the rest of the group. A minimum of 4 TRUs in
one hopping group is recommended in order to utilize the frequency hopping
gain.
If the packet data is placed on a BCCH, having a separate channel group, it is
possible to make CS traffic to choose the BCCH as last choice by setting the
CHALLOC parameter to last preference. Depending on the control channel
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
configuration, up to 7 channels can be used for the packet data. Note that if
either of the 2 highest output power settings are used then timeslot 7 can not
carry EDGE traffic. See chapter 8. Furthermore, this power setting will cause
the output power to differ between GMSK and 8PSK. It is believed that this
will have minor effects on the network. See chapter 8.
When adding one TRU and using dedicated spectrum, the rest of the baseband
hopping frequency plan has to be tightened in order to free up frequencies.
The quality has to be monitored. Furthermore there is also a risk of poor
speech quality on the non-hopping TRU.
When adding a cabinet for EDGE and CS3/CS4, the feature TG
Synchronization can be used to connect the two cabinets to the same cell. The
new EDGE TRU should be configured as synthesized frequency hopping in a
1/1 frequency plan. The frequency planning will then be easy for packet data
and the performance can easily be adjusted (by adding frequencies). Of course
the EDGE TRU can be used for speech as well with good speech quality.
Probably 4-5 frequencies needs to be set-aside for the new CS3/CS4 and
EDGE frequency group which means that the MRP plan has to be tightened.
The suggested method depends on the amount of spectrum:
• Narrow band (<8MHz): FLP methods are recommended, 1/1, 1/3
• Broad band (>8MHz): Free up frequencies for packet data and
configure one extra channel group using SY and 1/1 for the packet
data.
GUIDELINE
12(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
7.4 Network configuration
How to introduce EDGE and/or CS3/CS4 into an existing network is
dependent the predicted load and on the current configuration. E.g. what type
of combiners are used and what types of RBSs. In figure 1 some possible ways
of configurations are presented. The initial configurations are shown to the
left and the site evolution is represented as moving to the right. For a network
consisting of RBS 200 these have to be co-sited or exchanged with RBS 2000
in order to deploy EDGE and/or CS3/CS4. In an RBS 2000 network EDGE
and CS3/CS4 can be implemented on the current equipment.
Detailed configuration examples are presented in Appendix.
Figure 1. The figure shows site evolution for implementing EDGE and/or
CS3/CS4 in a network using either filter combiners or hybrid combiners. The
evolution represented as going from the left to the right. In the figure the
ordinary expansions are separated from the High Cap solutions.
RBS 2206 CDU-G
Filter Combiner
RBS 200/205
RBS 2000
Continue with Filter
Filter + EDGE on
hybrid
RBS 2000 CDU-D/F
RBS 2206 CDU-F
RBS 2000 CDU-C+
RBS 2206 CDU-G
Hybrid Combiner
RBS 200/205
RBS 2000
RBS 2000 CDU-C+
Exchange to
Hybrid
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
8 Output power for GMSK and 8PSK
8.1 Background
Due to the linear 8PSK modulation used for EDGE, it will be difficult to
design power amplifiers that operate with the same average output power for
8PSK and GMSK. An average power decrease, approximately corresponding
to the peak to average ratio for 8PSK can be expected.
A typical example for an E******* TRU is showed below. Figures are in dBm.
Note that the maximum and average output power is the same for GMSK,
whereas for 8PSK the maximum average is used. The output power is set for
GMSK, as usual, and when 8PSK is used the average output power is affected
for the highest and second highest value.
GMSK(max/average) 8PSK(max) 8PSK(average)
47 47 44
45 47 44
43 46 43
41 44 41
etc.
Due to the difference in average output power for 8PSK compared to GMSK
the TRU is automatically compensates the maximum output power for 8PSK.
The GSM standard [GSM 05.08] state that the 8PSK timeslots on the BCCH
carrier may, with the exception of timeslot 7, use a mean power that is at most
4 dB lower than for GMSK timeslots.
The BCCH information on timeslot 0 is always GMSK modulated.
8.2 Non-BCCH TRU carrying EDGE traffic
The circuit switched traffic carried on the EDGE TRU in this type of
configuration will not suffer from the difference in output power.
One concern when the lower output power is used for EDGE is the decoding
of the Uplink State Flag, USF, that’s included in each radio block. The USF is
however very safe coded in all coding schemes and should be able to cope
with really low C/I. The coding of the USF is even more robust than MCS-1.
GUIDELINE
14(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
8.3 BCCH TRU carrying EDGE traffic
8.3.1 General
Timeslot 0 on a BCCH carrier will carry the BCCH information, which has to
be GMSK modulated. The remaining timeslots on the BCCH carrier have to
use carrier filling, i.e. they have to be transmitting at all times.
When timeslots on the BCCH carrier are used for EDGE traffic (8PSK
modulation), they may be transmitting with lower signal strength than when
using GMSK modulation (only when maximum or second maximum output
power is used). This will result in a varying output power of the BCCH carrier
depending on the EDGE load on the BCCH TRU. Circuit switched traffic on
the EDGE TRU will still use the output power specified in the BTS.
According to the standard [GSM 05.08] is no output power variations on the
BCCH timeslot 7 allowed. EDGE can consequently not be transmitted on
timeslot 7 when either of the 2 highest output power levels is used. When
lower output power is used can EDGE also be applied on timeslot 7.
The possible effects of varying signal strength on the BCCH carrier are listed
in section 8.3.2 – 8.3.5. It is however important to stress that for most
networks these effects are considered minor due to the small actual average
variation. An estimation of the actual average variation is performed in section
8.3.6.
8.3.2 Coverage
Due to the power decrease on the BCCH, the coverage area for a cell might be
slightly affected. Note that the effect is considered small for most networks.
8.3.3 Packet Switched Traffic
Varying load on the BCCH carrier may cause mobiles in idle mode (both
packet idle and speech idle) to camp on “non-ideal” cells. As a result of this
the mobiles might start their connections in the wrong cell and thus get
reduced quality.
Continuous cell selections can occur at certain cell borders. This is not a
problem as long as it isn’t along any LA or RA border, which will cause more
LA-updates and RA-updates, which in turn will increase the signaling load.
This should however be possible to avoid by increasing the hysteresis.
Mobiles in packet transfer mode may do their cell re-selection slightly late and
therefore get a somewhat lower throughput. There is also the possibility of
making the cell re-selection too early. This might happen if the BCCH carrier
is used for 8PSK in own cell, but the neighbors are all using GMSK
modulation on their BCCH carriers.
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
8.3.4 Circuit switched traffic
In idle mode the same problems might occur as those for packet switched cell
selection and cell re-selection.
In active mode i.e. speech call ongoing, problems may occur with handover as
the measurements are done on 8PSK connections. Neighbors can be seen as
being weaker than they really are, leading to a delayed handover or maybe
even a handover to the wrong cell.
If the power reduction is in the range of 1dB, these problems can probably be
neglected. For larger power reductions, problems may occur in tight networks
with high traffic load. Not in a big scale, but certain problem areas may occur
locally.
The varying load may also cause ping-pong effects. However by assuming that
the 8PSK traffic is evenly distributed in the network this should not be a
problem.
Although, if a ping-pong behavior occur are the suggested actions to increase
the hysteresis, longer the hand-over filters or reducing the number of PDCHs.
8.3.5 MS Power control
In packet transfer mode, the MS uses the same signal strength measurements
on the BCCH frequency of the serving cell as made for cell selection. In the
case of an average power reduction on the BCCH due to 8PSK this may cause
the packet switched open loop MS power control to slightly underestimate the
BCCH. The result of this would be that the MS transmits with a bit too high
output power.
Circuit switched MS power control will not be affected.
8.3.6 What is the output power difference
The 3dB difference will never occur on more than 6 out of the 8 timeslots.
Meaning that the BCCH carrier will have at maximum 2.3 dB lower output
power (3dB*6/8=2.3dB). For a non-combined configuration, using one
SDCCH/8, the corresponding value would be 1.9dB.
The EDGE traffic will use MCS-1 for signaling which is a GMSK modulated
coding scheme. For bursty applications like web-browsing, one can assume
that the amount of signaling is about 20% per user. This would mean that the
difference in output power would be further decreased. 3dB*6/8*0.8=1.8dB.
A lot of the PS traffic will be bursty, depending of course on the application.
Simulations done with web-browsing for GPRS have shown that the channel
activity (fraction of a time that a PDCH is used) is quite low, see ref [1]. For a
reasonable dimensioning an activity factor of 50% can be assumed.
The EDGE traffic will probably have the same behavior as GPRS traffic. By
estimating the activity factor to be 50% for 8PSK, the 6 TS on the BCCH
carrier using 8PSK will in average be used 50% of the time (dummy bursts
GUIDELINE
16(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
using GMSK will be sent when no transmission is done on a PS connection).
The decrease in output power will be reduced to around 1 dB
(3dB*6/8*0.8*0.5=0.9dB). Web-browsing assumed to be the dominating
application.
The worst case will be an EDGE 6-slot mobile on the BCCH carrier doing an
ftp file download. Assume a file of size 500kb and an average throughput on
45 kbps per TS on the radio link. The download time for the file can be
estimated to be around 1.9 seconds (500/(6*45)=1.9sec, no overhead
included). This would lead to a 2.3dB reduction of the output power for 1,9
seconds.
In all the calculations it has been assumed that all six timeslots on the BCCH
are used for 8PSK modulation. By configuring less timeslots for 8PSK, the
power reduction can be further decreased. For instance 4 EDGE capable TS
on the BCCH would result in a maximum power decrease of 1.5dB.
9 References
1. GPRS Radio Network Dimensioning Guideline for E*******’s GSM
System BSS R8, LVR/D-99:0178 rev C.
2. User Description, Link Quality Control in Enhanced GPRS, 95/1553-
HSC 103 12/3 Uen PA3.
3. EGPRS Radio Link Bandwidth dimensioning guideline for E*******’s
GSM systems, ERA/SV-01:0013 rev A.
4. Fractional Load Planning (FLP) guideline, ERA/LVR/D-99:0201 rev A.
5. An introduction to Transceiver Group Synchronisation Configurations,
ERA/SV-01:1369 rev A.
6. Edge Technology and Implementation Aspects, LRM-00:0107 Uen rev
B.
7. Product Information, http://prodinfo.e*******.se/
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
Appendix
Table A1. The table shows some examples of upgrade scenarios for
introducing EDGE and/or GPRS CS3/CS4.
Initial configuration Solution Antenna
System
Freq.
Plan
Max. TRXs
per sector
[Max. EDGE
TRXs]
a) Add 1 RBS 2202
cabinet for each
sector with CDU-D
equipped with
DXU-11 max 1
EDGE sTRU
2 dual
Antennas
and 3
feeders
needed per
sector if
duplexers
are used
EDGE:
Fixed
reuse
Speech:
MRP
8+6
[1]
b) Add 1 RBS 2202
cabinet for each
sector with CDU-D
equipped with
DXU-21 more than
1 EDGE sTRU
2 dual
Antennas
and 3
feeders
needed per
sector if
duplexers
are used
EDGE:
MRP
Speech:
MRP
8+6
[6]
c) Add 1 RBS 2206
cabinet for each
sector with CDU-F
2 Dual
polarised
Antennas
and 4
feeders
needed per
sector if
duplex are
used
EDGE:
MRP
Speech:
MRP
8+12
[12]
1) RBS 200/205 with
F-comb Up to 3*8
(max RBS 200/205
config. with TG
sych)
d) Add 1 RBS 2206
cabinet for each
sector with CDU-G
> 4 EDGE dTRU
3 Dual
polarised
Antennas
and 4
feeders
needed per
sector if
duplex are
used
EDGE:
FLP
Speech:
MRP
8+4
[4]
GUIDELINE
18(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
a) Add 1 RBS 2202
with CDU-C+ for
all sectors equipped
with DXU-21
2 dual
Antennas
and 3
feeders
needed per
sector if
duplexers
are used
EDGE:
FLP
Speech:
FLP
4+2
[2]
2) RBS 200/205 with
H Up to 3*4
b) Add 1 RBS 2206
with CDU-G for all
sectors
2 dual
Antennas
and 4
feeders
needed per
sector if
duplexers
are used
EDGE:
FLP
Speech:
FLP
4+4
[4]
a) Add / Swap to
max 1 EDGE
sTRU / cell
2 Dual
polarised
Antennas
and 3
feeders
needed per
sector if
duplex are
used
Speech
and
EDGE:
FLP
6
[1]
3) RBS 2000 with
CDU-C+ Up to 3*6
b) Swap to DXU-
21 and add / Swap
to more than 1
EDGE sTRU / cell
2 Dual
polarised
Antennas
and 3
feeders
needed per
sector if
duplex are
used
Speech
and
EDGE:
FLP
6
[6]
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
a) Add / Swap to
max 1 EDGE
sTRU / cell
1 dual
Antenna and
2 feeders
needed per
sector if
duplexers
are used
Speech
and
EDGE:
FLP
2
[1]
b) Swap to DXU-
21 and add / Swap
to > 1 EDGE sTRU
/ cell, gives 3*2 on
EDGE
1 dual
Antenna and
2 feeders
needed per
sector if
duplexers
are used
Speech
and
EDGE:
FLP
2
[2]
4) RBS 2000 with
CDU-C+ Up to 3*2
c) Use Extention to
add 1 cabinet for 3
cells with 3*2
EDGE sTRU / cell
with DXU-21
2 dual
Antennas
and 2
feeders
needed per
sector if
duplexers
are used
Speech
and
EDGE:
FLP
2+2
[2]
a) Add / Swap to 1
EDGE sTRU / cell
1 dual
Antenna and
2 feeders
needed per
sector if
duplexers
are used
Speech
and
EDGE:
MRP
12
[1]
5) RBS 2000 with
CDU-D Up to 3*12
b) Swap DXU-21,
add > 1EDGE
TRU/cell
1 dual
Antenna and
2 feeders
needed per
sector if
duplexers
are used
Speech
and
EDGE:
MRP
12
[12]
GUIDELINE
20(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
c) Add 1 RBS 2202
with CDU-C+ and
3*1 EDGE
sTRU/cell
2 dual
Antenna and
4 feeders
needed per
sector if
duplexers
are used
EDGE:
FLP
Speech:
MRP
12+1
[1]
d) Add 1 RBS 2202
with CDU-C+, 3*2
EDGE sTRU per
cell and DXU-21
2 dual
Antenna and
4 feeders
needed per
sector if
duplexers
are used
EDGE:
FLP
Speech:
MRP
12+2
[2]
a) Add 1 EDGE
dTRU per cell
1 dual
Antenna and
2 feeders
needed per
sector if
duplexers
are used
Speech
and
EDGE:
FLP or
MRP
12
[2]
6) RBS 2206 with
CDU-G or CDU-F
Up to 1*12
b) Add more than 1
EDGE dTRU per
cell
1 dual
Antenna and
2 feeders
needed per
sector if
duplexers
are used
Speech
and
EDGE:
FLP or
MRP
12
[12]:p
RADIO NETWORK CONFIGURATION GUIDELINE
FOR EDGE AND GPRS CS3/CS4 IN
E*******'S BSS
E******* WIDE INTERNAL
Contents
1 Revision History................................................................... 2
2 Purpose and scope.............................................................. 2
3 Glossary .............................................................................. 3
3.1 Abbreviations....................................................................... 3
3.2 Concepts ............................................................................. 4
4 Introduction..........................................................................4
5 Requirements for Packet Data............................................. 5
5.1 Software .............................................................................. 5
5.2 Hardware............................................................................. 5
5.3 BSC PCU Capacity and A-bis Configuration........................ 7
5.4 Core Network ...................................................................... 7
6 Channel Allocation...............................................................8
7 Cell Planning Aspects of Packet Data ................................. 8
7.1 General................................................................................8
7.2 Introducing GPRS CS3/CS4 and EDGE in a
Synthesizer Frequency Hopping Network ............................ 9
7.3 Introducing GPRS CS3/CS4 and EDGE in a Baseband
Frequency Hopping Network ............................................. 10
7.4 Network configuration........................................................ 12
8 Output power for GMSK and 8PSK ................................... 13
8.1 Background .......................................................................13
8.2 Non-BCCH TRU carrying EDGE traffic.............................. 13
8.3 BCCH TRU carrying EDGE traffic...................................... 14
9 References ........................................................................ 16
GUIDELINE
2(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
1 Revision History
Rev Date Description
A 2001-12-11 Created.
2 Purpose and scope
The Configuration Guideline describes different configuration aspects which
needs to be considered while implementing the packet data services GPRS
CS3/CS4 and EDGE in an E******* GSM network. The document gives
suggestions on how to configure the networks, but no specific
recommendations.
Note that this is a release independent document, which does not state when
the features will be available.
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
3 Glossary
3.1 Abbreviations
BB Base Band
BCCH Broadcast Control Channel
BSC Base Station Controller
BTS Base Transceiver Station
CS Coding Scheme
DTX Discontinuous Transmission
EDGE Enhanced Data rates for Global Evolution
EGPRS Enhanced GPRS
FLP Fractional Load Planning
GMSK Gaussian Minimum Shift Keying
GoS Grade of Service
GPRS General Packet Radio Service
LQC Link Quality Control
MCS Modulation Coding Scheme
MRP Multiple Reuse Patterns
PDCH Packet Data Channel
PSK Phase Shift Keying
SY Synthesizer
TBF Temporary Block Flow
TCH Traffic CHannel
TRU Transceiver Unit
WWW World Wide Web
GUIDELINE
4(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
3.2 Concepts
8PSK 8 Phase Shift Keying is a new modulation method which enables
higher data rates than GMSK.
IR Incremental Redundancy (IR) is an approach to adapt the code
rate to the channel quality.
LA Link Adaptation (LA) is an approach to select the most optimum
coding scheme based on the radio link quality.
LQC The LQC algorithm controls the selection of coding scheme to
be used for the transmission. LQC can use either IR or LA, see
ref [2].
BB Hop In baseband frequency hopping, each transmitter is assigned
with a fixed frequency. At transmission, all bursts, irrespective
of which connection, are routed to the appropriate transmitter of
the proper frequency.
SY Hop Synthesizer hopping means that one transmitter handles all
bursts that belong to a specific connection. In contrast to
baseband hopping, the transmitter tunes to the correct frequency
at the transmission of each burst.
4 Introduction
The purpose of this document is to present the most important information
regarding the implementation of EDGE and GPRS CS3/CS4 in an E*******
GSM network. A basic requirement for these services is that the BSS and BTS
SW can handle EDGE and CS3/CS4. By introducing EDGE and CS3/CS4 also
new hardware is required. Which HW to use and how this is to be configured
is strongly dependent on the existing HW configuration and the capacity
demand. The impact on the frequency planing varies depending on the
strategies of the operator and the available hardware. Furthermore, the
document describes the effects of the average power reduction on the EDGE
signal due to the 8PSK modulation.
In the E******* R8 version of GPRS the only coding schemes available have
been CS1 and CS2. From release 9.1 it will also be possible to use the coding
schemes CS3 and CS4 on the downlink, meaning that the system can choose
between CS1 to CS4. The higher coding schemes uses less coding bits for
error correction and can therefore be used to increase the throughput for
connection with good radio conditions.
EDGE introduces a new modulation method (8PSK), which enables higher
data rates than GMSK. Compared to GPRS, also the RLC protocol is
enhanced with e.g. an extended transmit window, refined ACK/NACK reports
and the possibility to resegment data and therefore to retransmit with a
different MCS. More information can be found in ref [3 and 6].
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
When dimensioning a network for packet data, it is the general C/I conditions
in the network that is of interest. Given a certain frequency plan, cell plan and
traffic load, the throughput per timeslot can be derived through simulations.
For EDGE this is described in the EDGE bandwidth dimensioning guideline
ref [3].
The coverage of EDGE and GPRS CS3/CS4 will be as good as for GPRS
CS1/CS2 since all the signaling is done using the most robust coding scheme
(MSC1 or CS1). Investigations have shown that wherever there is speech
coverage there will also be packet data coverage, see ref [1]. The header in
packet data is very safe coded and there should be no problems to decode the
Uplink State Flag (USF) giving uplink coverage.
In GPRS the link control is controlled by Link Adaptation. For a network
capable of CS4 this means that the system can choose between the coding
schemes CS1 to CS4, depending on the radio link quality.
In EDGE the Link Quality Control (LQC) algorithm aims at achieving the
highest possible throughput for the end user. This is done by dynamically
selecting the most optimal MCS to be used. In the MCS selection process, two
different modes of operation are used; Incremental Redundancy (IR) or Link
Adaptation (LA). See ref [2].
5 Requirements for Packet Data
5.1 Software
In order to support the higher coding schemes for GPRS (CS3/CS4) and/or
EDGE both the BSC and the BTS require new SW.
5.2 Hardware
The ambition is to introduce packet data at minimal effort and cost. In other
words, the impact of the packet data system on the network architecture must
be small, and the system should permit operators to reuse most of the existing
base station equipment.
All RBS HW available since 1991 (RBS 200 and RBS 2000) supports GPRS
CS1/CS2. To support GPRS CS3/CS4 and EDGE a need for more processing
capacity and memory demands the new HW platform of TRU (sTRU EDGE,
dTRU and dTRU EDGE).
The RBS 2101/2102/2202 macro base stations are hardware prepared to
support EDGE as well as CS3/CS4 using the plug-in single EDGE sTRU. This
transceiver unit will fit in a TRU slot of the current RBS 2000 macro base
stations. No further changes to the cabinet are needed in order to get EDGE
and CS3/CS4 up and running. Back plane, DXU and combiner structures stay
unchanged. However, the maximum number of GPRS and EDGE timeslots
GUIDELINE
6(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
that can be supported in one cabinet are limited by the capacity of the PCMlink
and the architecture of the DXU.
On the RBS 2000 it is possible to increase the EDGE and CS3/CS4 capacity
per sector by replacing the old DXUs (01/02/03/11), that only support one
EDGE sTRU per cell, with the new DXU-21 which supports up to 12 EDGE
sTRUs per cell, see table 1.
Note that by switching form the current DXUs (01/02/03/11) to DXU-21, for
all RBS 2000 base stations, the local bus, timing buss and x bus have to be
replaced by the new "Y bus". An upgrade kit will be available for easy
implementation, see ref [7].
Table 1. Examples of configurations for EDGE with DXU-11 and DXU-21
(#cells X #TRUs).
Sector configuration 1X6 3X2 3X4 1X12
Configuration for EDGE with DXU-11 1X1 3X1 3X1 1X1
Configuration for EDGE with DXU-21 1X6 3X2 3X4 1X12
The RBS 2206/2106 is delivered capable of GPRS CS1 to CS4. As an option
it can be fully equipped to also handle EDGE. Both the dTRU and the EDGE
dTRU support GPRS CS1 to CS4. For EDGE it is required to use the EDGE
dTRU. The base station is equipped with DXU-21.
The new RBS 2205 will support EDGE and GPRS CS1 to CS4 on the sector
part through the EDGE sTRU. This is however not finalised.
The RBS2301 micro supports GPRS CS1/CS2 if a DSP cluster is deployed.
GPRS CS3/CS4 and EDGE is not supported.
The RBS2302 micro supports GPRS CS1/CS2.
The RBS2401 micro micro supports GPRS CS1/CS2. GPRS CS3/CS4 and
EDGE is not supported.
The RBS 200 supports GPRS CS1/CS2. In order to introduce EDGE and/or
GPRS CS3/CS4 to a RBS 200 network it is required to combine the RBS 200
with a RBS 2000 using TG synchronization, see ref [5].
The RBS2308 micro will support EDGE as well as GPRS CS1 to CS4.
All future base stations are planned to support EDGE and GPRS CS1 to CS4.
For detailed information, see ref [7].
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
5.3 BSC PCU Capacity and A-bis Configuration
The processing capacity of the BSC will not be impacted by the introduction
of packet data in terms of number of TRX, the E******* BSC will still support
up to 1020 TRX. In the BSC no extra hardware is needed for the EDGE and
CS3/CS4 support as such. However, if the traffic requirements exceed the
capacity installed, then additional transmission links (E1/T1) are needed. The
PCU, which is situated in the BSC, could of course also be affected when
traffic requirements exceed the installed PCU capacity. In the time frame
when EDGE and CS3/CS4 will be available, the PCU capacity can be
increased. This will be achieved by extending the number of RPP boards. The
PCU will then have sufficient capacity to handle the growth for both GPRS
and for EDGE traffic. The PCU will be enhanced so four 16 kbps GSL
devices can be reserved for each Basic Physical Channel (BPC).
With “normal” GSM, every air timeslot uses 16 kbps transmission capacity to
the BSC. Four air timeslots are combined to a 64 kbps PCM timeslot. The
transmission need for an EDGE air timeslot can be as high as 59.2 kbps. This
requires that one 64 kbps PCM timeslot is assigned to every EDGE air
timeslot. Note that GPRS CS3 and CS4 also require one 64 kbps PCM
timeslot for every air timeslot, whereas CS1 and CS2 only need 16 kbps PCM
timeslot.
Depending on the existing utilisation of the PCM links, it can initially be
possible to use spare 64 kbps transmission timeslots on the existing links for
the EDGE and CS3/CS4 capable timeslots.
5.4 Core Network
When the data rate on the air interface is increased, this increases the demand
for transmission capacity between the BSC and the SGSN node (Gb
interface). However, for EDGE and GPRS CS3/CS4, the same physical links
can be used as in GPRS CS1/CS2, i.e. the Frame Relay protocol.
The SGSN supports the optional “MS Radio Access Capabilities” in terms of
8PSK support or not (1 bit) which has to be reported to the PCU. This new bit
is being set with the down link data unit (LLC PDU).
GUIDELINE
8(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
6 Channel Allocation
In a cell supporting packet data, the BSS system maintains two idle lists (GSM
and the GPRS idle list) over all the available traffic channels. Initially all
these idle channels belong to GSM idle list. When a packet data channel is
required, the system first looks for a dedicated PDCH. If no channel is found
(either there is no dedicated PDCH allocated in the cell or all PDCHs are
busy), the system checks the GSM idle list.
GPRS MSs will share the PDCHs with EDGE MSs. The channel allocation
algorithm will investigate on which timeslots an incoming MS will get the
best throughput and place it there. E.g. if the load on the EDGE capable
timeslot is high this means that an EDGE MS might be allocated to timeslots
that are only GPRS capable and vise versa. If a GPRS capable MS is assigned
timeslots capable of EDGE, it will still only be GPRS capable.
All packet data is assigned to EDGE capable timeslots as first choice.
7 Cell Planning Aspects of Packet Data
7.1 General
Generally packet data is considered to have a better coverage than voice. This
is due to the fact that all signaling is done using CS-1 (GPRS) or MCS-1
(EDGE). Simulation and measurement results show that for noise limited
systems packet data services have at least the same coverage as GSM voice
system.
When introducing EDGE into an already existing cell plan, the radio link
throughput can be estimated with the help of the Radio Link Bandwidth
Dimensioning Guideline, ref [3]. Dependent on cell plan, frequency re-use and
frequency load the throughput per timeslot can be derived.
The higher coding schemes provided by GPRS and EDGE are beneficial since
they make use of good C/I conditions. However, to give certain application
coverage over the whole network, the cell plan may be affected.
In some configurations the output power for GMSK and 8PSK i.e. EDGE may
differ. How this affects the cell plan is described in chapter 8.
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
7.2 Introducing GPRS CS3/CS4 and EDGE in a
Synthesizer Frequency Hopping Network
7.2.1 Strategies
Synthesized frequency hopping allows more frequencies per cell than there
are transceivers. This is normally the case, and since there are more
frequencies than transceivers each frequency is only used a fraction of the
time. Hence it is called fractional load planning. The BCCH carriers are in
most FLP networks non-hopping. For more information about FLP, see ref [4].
There are basically three different strategies when implementing packet data
into a FLP network:
• Put packet data on the BCCH frequency.
• Integrate packet data into the existing hopping CHGR.
• Give dedicated frequency spectrum to packet data.
When configuring packet data on the BCCH frequency, the interference in the
network will not increase since the BCCH is always transmitting. The BCCH
plan can be kept and no re-planning is needed. Depending on the control
channel configuration, up to 7 channels can be used for the packet data. Note
that if either of the 2 highest output power settings are used then timeslot 7
can not carry EDGE traffic. See chapter 8. Furthermore, this power setting
will cause the output power to differ between GMSK and 8PSK. It is believed
that this will have minor effects on the network. See chapter 8.
When integrating CS3/CS4 or EDGE into an existing hopping channel group
there are two options; either to swap an existing TRU for an EDGE TRU or to
expand the channel group with an EDGE TRU. The GoS for speech has to be
taken into consideration when introducing the EDGE TRU.
The packet data traffic will introduce interference into the network, as all
traffic does. Meaning that when the traffic grows, the throughput for packet
data may be lower just as the speech quality may be worsened.
When using dedicated spectrum for packet data, the interference generated by
the data traffic will not affect the speech frequencies. On the other hand, the
frequency re-use probably has to be tightened for the speech traffic in order to
free up some spectrum for packet data. Whilst doing this, the speech quality
measures has to be monitored carefully. Dependent on the amount of packet
data traffic, around 4-12 frequencies using a 1/1 frequency re-use would be
recommended for CS3/CS4 and/or EDGE. By using synthesized frequency
hopping and 1/1 the frequency planning will be easy for packet data.
GUIDELINE
10(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
When using on-demand channels for packet data, the GoS for speech will not
be affected if speech is set to have priority over packet data.
Where to put the packet data channels is dependent on the strategy of the
operator. However, initially it is presumably beneficial to put the data traffic
on the BCCH, because:
• Speech will be unaffected by the data traffic (no interference increase due
to the carrier filling)
• Easy to swap one TRU for an EDGE TRU
• Enough with the timeslots on the BCCH for the initial GPRS and EDGE
traffic
7.3 Introducing GPRS CS3/CS4 and EDGE in a
Baseband Frequency Hopping Network
7.3.1 Strategies
Baseband frequency hopping means that the number of transceivers in a cell is
equal to the number of frequencies. Each transceiver has its own frequency
reuse pattern. An advantage of baseband hopping is that the BCCH carrier can
be included in the hopping sequence.
The following strategies can be used for introducing packet data in a baseband
frequency hopping network:
• Remove one frequency (BCCH TRU or non-BCCH TRU) from the
hopping group and use it for CS3/CS4 and/or EDGE (one frequency group
as no hopping for packet data)
• Add one TRU for packet data and use dedicated spectrum (configured as
no hopping)
• Add one cabinet with EDGE TRU using TG Synchronization (configured
as no hopping or preferably synthesized hopping)
When swapping one TRU for an EDGE TRU, it has to be configured as no
hopping, since the transceiver is locked to one frequency. The benefit with
this solution would be low cost but there are several drawbacks. Since the
EDGE TRU is non-hopping, the speech quality may be poor on that TRU. It
all depends on the frequency re-use and the load of the TRU.
When removing one frequency from the frequency group, the frequency
hopping gain is decreased for the rest of the group. A minimum of 4 TRUs in
one hopping group is recommended in order to utilize the frequency hopping
gain.
If the packet data is placed on a BCCH, having a separate channel group, it is
possible to make CS traffic to choose the BCCH as last choice by setting the
CHALLOC parameter to last preference. Depending on the control channel
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
configuration, up to 7 channels can be used for the packet data. Note that if
either of the 2 highest output power settings are used then timeslot 7 can not
carry EDGE traffic. See chapter 8. Furthermore, this power setting will cause
the output power to differ between GMSK and 8PSK. It is believed that this
will have minor effects on the network. See chapter 8.
When adding one TRU and using dedicated spectrum, the rest of the baseband
hopping frequency plan has to be tightened in order to free up frequencies.
The quality has to be monitored. Furthermore there is also a risk of poor
speech quality on the non-hopping TRU.
When adding a cabinet for EDGE and CS3/CS4, the feature TG
Synchronization can be used to connect the two cabinets to the same cell. The
new EDGE TRU should be configured as synthesized frequency hopping in a
1/1 frequency plan. The frequency planning will then be easy for packet data
and the performance can easily be adjusted (by adding frequencies). Of course
the EDGE TRU can be used for speech as well with good speech quality.
Probably 4-5 frequencies needs to be set-aside for the new CS3/CS4 and
EDGE frequency group which means that the MRP plan has to be tightened.
The suggested method depends on the amount of spectrum:
• Narrow band (<8MHz): FLP methods are recommended, 1/1, 1/3
• Broad band (>8MHz): Free up frequencies for packet data and
configure one extra channel group using SY and 1/1 for the packet
data.
GUIDELINE
12(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
7.4 Network configuration
How to introduce EDGE and/or CS3/CS4 into an existing network is
dependent the predicted load and on the current configuration. E.g. what type
of combiners are used and what types of RBSs. In figure 1 some possible ways
of configurations are presented. The initial configurations are shown to the
left and the site evolution is represented as moving to the right. For a network
consisting of RBS 200 these have to be co-sited or exchanged with RBS 2000
in order to deploy EDGE and/or CS3/CS4. In an RBS 2000 network EDGE
and CS3/CS4 can be implemented on the current equipment.
Detailed configuration examples are presented in Appendix.
Figure 1. The figure shows site evolution for implementing EDGE and/or
CS3/CS4 in a network using either filter combiners or hybrid combiners. The
evolution represented as going from the left to the right. In the figure the
ordinary expansions are separated from the High Cap solutions.
RBS 2206 CDU-G
Filter Combiner
RBS 200/205
RBS 2000
Continue with Filter
Filter + EDGE on
hybrid
RBS 2000 CDU-D/F
RBS 2206 CDU-F
RBS 2000 CDU-C+
RBS 2206 CDU-G
Hybrid Combiner
RBS 200/205
RBS 2000
RBS 2000 CDU-C+
Exchange to
Hybrid
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
8 Output power for GMSK and 8PSK
8.1 Background
Due to the linear 8PSK modulation used for EDGE, it will be difficult to
design power amplifiers that operate with the same average output power for
8PSK and GMSK. An average power decrease, approximately corresponding
to the peak to average ratio for 8PSK can be expected.
A typical example for an E******* TRU is showed below. Figures are in dBm.
Note that the maximum and average output power is the same for GMSK,
whereas for 8PSK the maximum average is used. The output power is set for
GMSK, as usual, and when 8PSK is used the average output power is affected
for the highest and second highest value.
GMSK(max/average) 8PSK(max) 8PSK(average)
47 47 44
45 47 44
43 46 43
41 44 41
etc.
Due to the difference in average output power for 8PSK compared to GMSK
the TRU is automatically compensates the maximum output power for 8PSK.
The GSM standard [GSM 05.08] state that the 8PSK timeslots on the BCCH
carrier may, with the exception of timeslot 7, use a mean power that is at most
4 dB lower than for GMSK timeslots.
The BCCH information on timeslot 0 is always GMSK modulated.
8.2 Non-BCCH TRU carrying EDGE traffic
The circuit switched traffic carried on the EDGE TRU in this type of
configuration will not suffer from the difference in output power.
One concern when the lower output power is used for EDGE is the decoding
of the Uplink State Flag, USF, that’s included in each radio block. The USF is
however very safe coded in all coding schemes and should be able to cope
with really low C/I. The coding of the USF is even more robust than MCS-1.
GUIDELINE
14(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
8.3 BCCH TRU carrying EDGE traffic
8.3.1 General
Timeslot 0 on a BCCH carrier will carry the BCCH information, which has to
be GMSK modulated. The remaining timeslots on the BCCH carrier have to
use carrier filling, i.e. they have to be transmitting at all times.
When timeslots on the BCCH carrier are used for EDGE traffic (8PSK
modulation), they may be transmitting with lower signal strength than when
using GMSK modulation (only when maximum or second maximum output
power is used). This will result in a varying output power of the BCCH carrier
depending on the EDGE load on the BCCH TRU. Circuit switched traffic on
the EDGE TRU will still use the output power specified in the BTS.
According to the standard [GSM 05.08] is no output power variations on the
BCCH timeslot 7 allowed. EDGE can consequently not be transmitted on
timeslot 7 when either of the 2 highest output power levels is used. When
lower output power is used can EDGE also be applied on timeslot 7.
The possible effects of varying signal strength on the BCCH carrier are listed
in section 8.3.2 – 8.3.5. It is however important to stress that for most
networks these effects are considered minor due to the small actual average
variation. An estimation of the actual average variation is performed in section
8.3.6.
8.3.2 Coverage
Due to the power decrease on the BCCH, the coverage area for a cell might be
slightly affected. Note that the effect is considered small for most networks.
8.3.3 Packet Switched Traffic
Varying load on the BCCH carrier may cause mobiles in idle mode (both
packet idle and speech idle) to camp on “non-ideal” cells. As a result of this
the mobiles might start their connections in the wrong cell and thus get
reduced quality.
Continuous cell selections can occur at certain cell borders. This is not a
problem as long as it isn’t along any LA or RA border, which will cause more
LA-updates and RA-updates, which in turn will increase the signaling load.
This should however be possible to avoid by increasing the hysteresis.
Mobiles in packet transfer mode may do their cell re-selection slightly late and
therefore get a somewhat lower throughput. There is also the possibility of
making the cell re-selection too early. This might happen if the BCCH carrier
is used for 8PSK in own cell, but the neighbors are all using GMSK
modulation on their BCCH carriers.
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
8.3.4 Circuit switched traffic
In idle mode the same problems might occur as those for packet switched cell
selection and cell re-selection.
In active mode i.e. speech call ongoing, problems may occur with handover as
the measurements are done on 8PSK connections. Neighbors can be seen as
being weaker than they really are, leading to a delayed handover or maybe
even a handover to the wrong cell.
If the power reduction is in the range of 1dB, these problems can probably be
neglected. For larger power reductions, problems may occur in tight networks
with high traffic load. Not in a big scale, but certain problem areas may occur
locally.
The varying load may also cause ping-pong effects. However by assuming that
the 8PSK traffic is evenly distributed in the network this should not be a
problem.
Although, if a ping-pong behavior occur are the suggested actions to increase
the hysteresis, longer the hand-over filters or reducing the number of PDCHs.
8.3.5 MS Power control
In packet transfer mode, the MS uses the same signal strength measurements
on the BCCH frequency of the serving cell as made for cell selection. In the
case of an average power reduction on the BCCH due to 8PSK this may cause
the packet switched open loop MS power control to slightly underestimate the
BCCH. The result of this would be that the MS transmits with a bit too high
output power.
Circuit switched MS power control will not be affected.
8.3.6 What is the output power difference
The 3dB difference will never occur on more than 6 out of the 8 timeslots.
Meaning that the BCCH carrier will have at maximum 2.3 dB lower output
power (3dB*6/8=2.3dB). For a non-combined configuration, using one
SDCCH/8, the corresponding value would be 1.9dB.
The EDGE traffic will use MCS-1 for signaling which is a GMSK modulated
coding scheme. For bursty applications like web-browsing, one can assume
that the amount of signaling is about 20% per user. This would mean that the
difference in output power would be further decreased. 3dB*6/8*0.8=1.8dB.
A lot of the PS traffic will be bursty, depending of course on the application.
Simulations done with web-browsing for GPRS have shown that the channel
activity (fraction of a time that a PDCH is used) is quite low, see ref [1]. For a
reasonable dimensioning an activity factor of 50% can be assumed.
The EDGE traffic will probably have the same behavior as GPRS traffic. By
estimating the activity factor to be 50% for 8PSK, the 6 TS on the BCCH
carrier using 8PSK will in average be used 50% of the time (dummy bursts
GUIDELINE
16(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
using GMSK will be sent when no transmission is done on a PS connection).
The decrease in output power will be reduced to around 1 dB
(3dB*6/8*0.8*0.5=0.9dB). Web-browsing assumed to be the dominating
application.
The worst case will be an EDGE 6-slot mobile on the BCCH carrier doing an
ftp file download. Assume a file of size 500kb and an average throughput on
45 kbps per TS on the radio link. The download time for the file can be
estimated to be around 1.9 seconds (500/(6*45)=1.9sec, no overhead
included). This would lead to a 2.3dB reduction of the output power for 1,9
seconds.
In all the calculations it has been assumed that all six timeslots on the BCCH
are used for 8PSK modulation. By configuring less timeslots for 8PSK, the
power reduction can be further decreased. For instance 4 EDGE capable TS
on the BCCH would result in a maximum power decrease of 1.5dB.
9 References
1. GPRS Radio Network Dimensioning Guideline for E*******’s GSM
System BSS R8, LVR/D-99:0178 rev C.
2. User Description, Link Quality Control in Enhanced GPRS, 95/1553-
HSC 103 12/3 Uen PA3.
3. EGPRS Radio Link Bandwidth dimensioning guideline for E*******’s
GSM systems, ERA/SV-01:0013 rev A.
4. Fractional Load Planning (FLP) guideline, ERA/LVR/D-99:0201 rev A.
5. An introduction to Transceiver Group Synchronisation Configurations,
ERA/SV-01:1369 rev A.
6. Edge Technology and Implementation Aspects, LRM-00:0107 Uen rev
B.
7. Product Information, http://prodinfo.e*******.se/
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
Appendix
Table A1. The table shows some examples of upgrade scenarios for
introducing EDGE and/or GPRS CS3/CS4.
Initial configuration Solution Antenna
System
Freq.
Plan
Max. TRXs
per sector
[Max. EDGE
TRXs]
a) Add 1 RBS 2202
cabinet for each
sector with CDU-D
equipped with
DXU-11 max 1
EDGE sTRU
2 dual
Antennas
and 3
feeders
needed per
sector if
duplexers
are used
EDGE:
Fixed
reuse
Speech:
MRP
8+6
[1]
b) Add 1 RBS 2202
cabinet for each
sector with CDU-D
equipped with
DXU-21 more than
1 EDGE sTRU
2 dual
Antennas
and 3
feeders
needed per
sector if
duplexers
are used
EDGE:
MRP
Speech:
MRP
8+6
[6]
c) Add 1 RBS 2206
cabinet for each
sector with CDU-F
2 Dual
polarised
Antennas
and 4
feeders
needed per
sector if
duplex are
used
EDGE:
MRP
Speech:
MRP
8+12
[12]
1) RBS 200/205 with
F-comb Up to 3*8
(max RBS 200/205
config. with TG
sych)
d) Add 1 RBS 2206
cabinet for each
sector with CDU-G
> 4 EDGE dTRU
3 Dual
polarised
Antennas
and 4
feeders
needed per
sector if
duplex are
used
EDGE:
FLP
Speech:
MRP
8+4
[4]
GUIDELINE
18(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
a) Add 1 RBS 2202
with CDU-C+ for
all sectors equipped
with DXU-21
2 dual
Antennas
and 3
feeders
needed per
sector if
duplexers
are used
EDGE:
FLP
Speech:
FLP
4+2
[2]
2) RBS 200/205 with
H Up to 3*4
b) Add 1 RBS 2206
with CDU-G for all
sectors
2 dual
Antennas
and 4
feeders
needed per
sector if
duplexers
are used
EDGE:
FLP
Speech:
FLP
4+4
[4]
a) Add / Swap to
max 1 EDGE
sTRU / cell
2 Dual
polarised
Antennas
and 3
feeders
needed per
sector if
duplex are
used
Speech
and
EDGE:
FLP
6
[1]
3) RBS 2000 with
CDU-C+ Up to 3*6
b) Swap to DXU-
21 and add / Swap
to more than 1
EDGE sTRU / cell
2 Dual
polarised
Antennas
and 3
feeders
needed per
sector if
duplex are
used
Speech
and
EDGE:
FLP
6
[6]
GUIDELINE
Radio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSSERA/SV-01:0976 Rev A 2001-12-11E******* Wide Internal
a) Add / Swap to
max 1 EDGE
sTRU / cell
1 dual
Antenna and
2 feeders
needed per
sector if
duplexers
are used
Speech
and
EDGE:
FLP
2
[1]
b) Swap to DXU-
21 and add / Swap
to > 1 EDGE sTRU
/ cell, gives 3*2 on
EDGE
1 dual
Antenna and
2 feeders
needed per
sector if
duplexers
are used
Speech
and
EDGE:
FLP
2
[2]
4) RBS 2000 with
CDU-C+ Up to 3*2
c) Use Extention to
add 1 cabinet for 3
cells with 3*2
EDGE sTRU / cell
with DXU-21
2 dual
Antennas
and 2
feeders
needed per
sector if
duplexers
are used
Speech
and
EDGE:
FLP
2+2
[2]
a) Add / Swap to 1
EDGE sTRU / cell
1 dual
Antenna and
2 feeders
needed per
sector if
duplexers
are used
Speech
and
EDGE:
MRP
12
[1]
5) RBS 2000 with
CDU-D Up to 3*12
b) Swap DXU-21,
add > 1EDGE
TRU/cell
1 dual
Antenna and
2 feeders
needed per
sector if
duplexers
are used
Speech
and
EDGE:
MRP
12
[12]
GUIDELINE
20(20) E******* Wide InternalRadio Network Configuration Guideline for EDGE and GPRS CS3/CS4 in E*******'s BSS 2001-12-11
c) Add 1 RBS 2202
with CDU-C+ and
3*1 EDGE
sTRU/cell
2 dual
Antenna and
4 feeders
needed per
sector if
duplexers
are used
EDGE:
FLP
Speech:
MRP
12+1
[1]
d) Add 1 RBS 2202
with CDU-C+, 3*2
EDGE sTRU per
cell and DXU-21
2 dual
Antenna and
4 feeders
needed per
sector if
duplexers
are used
EDGE:
FLP
Speech:
MRP
12+2
[2]
a) Add 1 EDGE
dTRU per cell
1 dual
Antenna and
2 feeders
needed per
sector if
duplexers
are used
Speech
and
EDGE:
FLP or
MRP
12
[2]
6) RBS 2206 with
CDU-G or CDU-F
Up to 1*12
b) Add more than 1
EDGE dTRU per
cell
1 dual
Antenna and
2 feeders
needed per
sector if
duplexers
are used
Speech
and
EDGE:
FLP or
MRP
12
[12]:p