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taki
2009-03-26, 04:26 AM
Hi all;

Could you please show me how to optimize network frequencies with
Synthesized Frequency Hopping ???

Thanks in advance

Lesmana
2009-03-26, 06:28 AM
Please see the attached doc. it may help you.

Thanks

venom
2009-03-26, 06:35 AM
Hi all;

Could you please show me how to optimize network frequencies with
Synthesized Frequency Hopping ???

Thanks in advance


Read a simple post here written by me

http://www.finetopix.com/showpost.php?p=42301&postcount=15

kvf
2009-03-26, 06:39 AM
See more user description in the attachment

taki
2009-03-26, 08:08 PM
Hi Friends

Thanks for your help

tok2222
2009-04-21, 05:51 AM
Hi Friends,

we are trialing sfh and have found it has degraded the perf of the network and the 3g irat handover?

why is it?


thanks,


tok2222

gprastomo
2009-05-28, 04:48 PM
hi, if there is no activity on 3G, so you should check which kpi is degraded on 2G.
Or Usually when there are SFH activity, the BCCH and BSIC were changed so ti should be changed on 3G neighbour parameter also...

br


Hi Friends,

we are trialing sfh and have found it has degraded the perf of the network and the 3g irat handover?

why is it?


thanks,


tok2222

hassen
2009-05-28, 09:44 PM
See more user description in the attachment
hi kvf

your doc is for E/// equipment ,and i think taki are looking for a method using tool like
planet or atoll.
do you have doc in this sense

br hassen

Inception
2009-05-28, 09:59 PM
2
Capabilities
2.1 Frequency Diversity
2.2 Interference Diversity
2.3 Conclusions

3
Technical Description
3.1 Methods of Frequency Hopping
3.2 Configuration
3.3 Algorithm
3.4 Limitations at Frequency Allocation
3.5 GPRS/EGPRS Impacts
3.6 Related Counters
3.7 Main Changes in Ericsson GSM System R11/BSS R11

4
Engineering Guidelines
4.1 Applications
4.2 Impact of Frequency Hopping on Frequency Planning
4.3 Channel Configuration
4.4 Frequency Hopping and Subjective Speech Quality

5
Parameters
5.1 Main Controlling Parameters
5.2 Value Ranges and Default Values

6
Concepts

Glossary

Reference List


--------------------------------------------------------------------------------

1 Introduction
During a call connection, a burst can easily be lost when the mobile station happens to be located in a fading dip for that particular frequency, or if it is subjected to interference. There is a high probability for the next burst to be received if it is sent on a different frequency. This can be done by using frequency hopping. The coding and interleaving scheme in GSM is constructed so that loss of a single burst have minimal influence on the speech quality. In frequency hopping, a predefined set of frequencies is used in each cell. The mobile station changes frequencies once every TDMA frame, i.e. 217 times per second.

2 Capabilities
2.1 Frequency Diversity
Frequency hopping can reduce the effect of multipath fading. Multipath fading is frequency and location dependent. With frequency hopping, a non-moving mobile will typically not remain in a specific fading dip longer than one TDMA frame. The low signal strength dips in multipath fading are thus levelled out, and the mobile will perceive a more even radio environment. This is called frequency diversity, see Figure 1 .



Figure 1 Schematic Picture of Multipath Fading at Two Different Frequencies and at Frequency Hopping between the Two Frequencies for a Slow/non-moving Mobile Station

The advantage of frequency diversity is more evident with slow/non-moving mobiles. Fast moving mobiles can obtain similar improvements by their speed alone.

2.2 Interference Diversity
Interference is dependent on time, frequency and mobile location. Without frequency hopping, some cell planning margins must be incorporated so that sufficient service quality can still be provided in an interfered situation. By changing frequency on every TDMA frame, a mobile only experiences interference on a particular frequency once in a number of hops. Similarly, interference on a particular frequency will be spread across many mobiles (i.e. averages out with other mobiles). This is called interference averaging and results in interference diversity. With interference diversity, the perceived radio environment will be more even. As a result of frequency hopping, cell planning margins can be reduced which makes it possible to implement a tighter frequency plan.

Interference diversity is independent of the mobile speed, but is dependent on the mode of hopping, cyclic or random, and the type of frequency hopping used, baseband and synthesizer hopping. The greatest improvement is obtained when the interferer and the interfered connections use uncorrelated hopping sequences (see sec. Section 3.3.4 ) The lower the correlation, the higher the hopping gain. If both server and interferer use the same set of frequencies and also cyclic hopping, it is possible that some mobiles will hop "in phase" with each other. The effect is a total correlation, as if no hopping is done, and the resulting improvement will be very small. On the other hand, random frequency hopping would still show hopping gain, in a fully loaded system, because of its uncorrelated hopping. The number of hopping frequencies also affects interference diversity gain. If interference can be spread over a larger bandwidth (i.e. more frequencies), the interference collisions will be fewer, which results in higher hopping gain.

2.3 Conclusions
From a subscriber point of view, frequency hopping gives an improved speech quality in many situations. From an operator point of view, the benefits are:

tighter frequency reuse and increase in capacity,
a more robust radio environment,
a possibility to give subscribers a more uniform speech quality.
3 Technical Description
3.1 Methods of Frequency Hopping
There are two types of frequency hopping, baseband and synthesizer hopping. Parameter FHOP specifies which method to be used in the entire base station. For each channel group, the parameter HOP is used to switch the frequency hopping feature on and off separately, see Section 3.2.1. In R10 synthesized frequency hopping can be done on up to 32 frequencies in one CHGR. However up to 128 frequencies can be assigned to one cell. Frequency hopping can be performed on the Traffic Channels (TCHs), Stand alone Dedicated Control Channels (SDCCHs) and all Packet Data Channels (PBCCH and PDCH). However, broadcast and common control channels such as e.g. the Broadcast Control Channel (BCCH) are not allowed to hop. These channels are mapped onto timeslot 0 of the BCCH carrier.

In the following, baseband and synthesizer hopping is explained with the use of some simple examples of combiner and antenna configurations. The actual configuration however, depends on the base station (RBS200 or RBS2000) and on the type of combiner that is installed.

3.1.1 Baseband Hopping
In baseband 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, see Figure 2 .



Figure 2 Routing of Bursts from the TRX to the Transmitter at Baseband Hopping

The advantage with this mode is that narrow-band tunable filter combiners can be used. These combiners have up to 12 inputs for RBS2000 and 16 inputs for RBS200. This makes it possible to use many transceivers with one combiner.

3.1.2 Synthesizer Hopping
Synthesizer hopping means that one transmitter handles all bursts that belong to a specific connection. The bursts are sent "straight on forward" and not routed by the bus. In contrast to baseband hopping, the transmitter tunes to the correct frequency at the transmission of each burst, see Figure 3 .



Figure 3 Schematic Picture of Sending Bursts from the TRX to the Transmitter at Synthesizer Hopping

The advantage of this mode is that the number of frequencies that can be used for hopping is not dependent on the number of transmitters. It is possible to hop over a lot of frequencies even if only a few transceivers are installed. The gain from frequency hopping can thereby be increased, see Section 4.1.2 . Synthesizer hopping is often used in fractional load network, which is characterised by tight frequency reuse and high interference. Each TRX is configured to hop over a large number of frequencies in order to obtain the maximum frequency hopping gain and interference averaging.

A disadvantage with synthesizer hopping is that wide-band hybrid combiners have to be used. This type of combiner has approximately 3 dB loss making more than two combiners in cascade impractical.

3.2 Configuration
3.2.1 General
At cell configuration, the cell is assigned with one or several channel groups (CHGRs). The available frequencies for the cell are split and assigned to one of the channel groups. A transceiver group can be connected to one or more channel groups. Furthermore, each channel group can be defined separately as hopping with the parameter HOP. For example, there can be two channel groups in a cell, where one is hopping and the other is not. Within each channel group, the channels will hop over the frequencies defined for that particular channel group. SDCCH/8, TCH and all packet data channels can hop. Timeslot 0 on the BCCH carrier cannot hop, even if it belongs to a channel group that is configured as hopping.

The BCCH carrier must always transmit, in order to allow mobiles in the neighbouring cells to take measurement during active and idle mode. When there is no traffic burst, a dummy burst will be sent instead on the downlink and only on the BCCH carrier. This is provided by the transmitter itself. If it is configured for a single frequency, it can be set up so that it transmits dummy bursts whenever nothing else arrives from the controllers via the bus. This is called carrier-zero (c 0 ) filling when applied to the BCCH frequency f 0 . The c 0 filling is obtained automatically for the channel group containing the BCCH carrier.

For baseband hopping, the c 0 filling is straightforward (see Section 3.2.2 ). For synthesizer hopping, the c 0 filling is more complicated. There are two possible configurations, the first one has the BCCH carrier in a separate non-hopping channel group (see Section 3.2.3 ) and the second one has the BCCH frequency included in the hopping set (see Section 3.2.4 ).

3.2.2 Carrier-zero Filling at Baseband Hopping
As an example, suppose that a base station containing four transceivers shall be configured for baseband hopping. In this case, only four frequencies can be defined. Assume furthermore that only one channel group is defined. One of the transmitters is transmitting on f 0 only (see Figure 2 ). This transmitter is automatically set up for c 0 filling. The resulting configured channels are shown schematically in Figure 4 . Hopping channels are circled.



Figure 4 Channel Configuration for Four Transceivers and Baseband Frequency Hopping

In Figure 4 , four frequencies are used. On the first time slot, TS 0 , the BCCH is not hopping, and transmitted on f 0 only. The remaining three channels on TS 0 , which are all traffic channels (TCH), hop on three frequencies, f 1 to f 3 , indicated by the circle around the TCHs in the positions for f 1 , f 2 and f 3 . On TS 1 all channels, one SDCCH/8 and three TCHs, are hopping on all four frequencies, f 0 to f 3 , as indicated by the circle. On the remaining time slots, there are four TCHs hopping on all four frequencies.

3.2.3 Carrier-zero Filling at Synthesizer Hopping: Two Channel Groups
In this configuration, the cell is configured into two channel groups. One channel group (channel group 0) is defined to contain f 0 only, and parameter HOP is set to OFF. The other channel group is defined to contain the rest of the frequencies f 1 to f n , with HOP = ON for that channel group. This is illustrated in Figure 5 .



Figure 5 Channel Configuration for Four Transceivers and Pure Synthesizer Frequency Hopping in One of Two Channel Groups

In this case, n frequencies (f 1 to f n ) are used for hopping, and with four transceivers available the total number of traffic channels will be 30 (7 of these are non-hopping and 23 are hopping).

This configuration is obtained automatically if two or more channel groups are defined for a cell. If two channel groups are defined, each with two or more frequencies, the one containing f 0 will be configured according to Section 3.2.4 .

3.2.4 Carrier-zero Filling at Synthesizer Hopping: the BCCH Frequency Included
A transmitter configured for synthesizer hopping can not perform filling since it is not configured for a fixed frequency. Furthermore, if the number of frequencies that are configured for a channel group is larger than the number of transceivers, it is not possible to guarantee that f 0 is always transmitted. All channels may be busy and transmitting on a frequency different from f 0 . This is a consequence of the fact that the GSM specifications defines a number of fixed frequency sequences (see Section 3.3 ).

If the BCCH carrier is included in the hopping set, there are two possible configurations for c 0 filling.

The first configuration has been provided so that c 0 filling can be obtained at the same time as f 0 is included in a set of hopping frequencies. With this method, an extra transmitter (TX) operating only as a c 0 filler is used. All traffic bursts that are to be transmitted on the f 0 frequency are routed to this transmitter. If no traffic bursts are transmitted, dummy bursts are sent instead, as usual for a c 0 filler. All other traffic bursts are sent straight on forward, as usual for synthesizer hopping. The method is thus a mixture of synthesizer hopping and baseband hopping.

In Figure 6 , it shows one of the methods when three transceivers and one extra TX are used.



Figure 6 Synthesizer Hopping, Plus Baseband Hopping for Bursts of the BCCH Frequency

The resulting configured channels are shown schematically in Figure 7 , for the case HOP = ON.



Figure 7 Channel Configuration with BCCH Included in the Frequency Hopping. There are Three Transceivers and One Extra Transmitter.

The figure indicates that on TS 1 to TS 7 , all bursts that shall be transmitted on the f 0 frequency are sent to the c 0 filler transmitter instead of to their regular transmitters. If no traffic bursts are transmitted, dummy bursts are sent instead, as usual for a c 0 filler. On TS 1 to TS 7 , all frequencies defined (f 0 to f n ) are used in the hopping sequence. On TS 0 , the frequencies f 1 to f n are used. Note that the number of frequencies used in the set of hopping frequencies is not limited to the number of transceivers (three in Figure 6 and Figure 7 ). The total number of TCHs will be 22 according to Figure 7 .

In the other configuration, an extra transceiver is added (or one of the existing devices is used). The timeslot handler of that transceiver is used for timeslot 0 on the BCCH carrier and filling only, i.e. it carries no traffic. This is shown in Figure 8 .



Figure 8 Synthesizer Hopping Plus Baseband Hopping for Bursts of the BCCH Frequency, Four TRXs

Thus, for a base station containing four transceivers, this option leaves three transceivers for traffic, and the fourth for the BCCH frequency with filling. The resulting configured channels are schematically shown in Figure 9 , for the case HOP = ON.



Figure 9 Channel Configuration for Four Transceivers and Frequency Hopping with the BCCH Frequency Included

In this case, one additional TCH channel is obtained on time slot TS 0 , as compared to Figure 7 .

If a cell is configured for synthesizer hopping, and if f 0 is included in the set of frequencies defined for hopping, one of these two channel configurations is obtained automatically, depending on the hardware.

3.2.5 Mixed HW Configurations
3.2.5.1 General
There is a procedure (Operational Instruction, 12/15431-APT21009 BSC, Optimization of EGPRS or CS-3/4 Configurations when RBS of Mixed Capability, Perform) to reduce the undesirable side-effects resulting from mixing EGPRS or CS-3/4 capable Radio Base Station (RBS) hardware with non-EGPRS or non-CS-3/4 capable RBS hardware within the same TG. If the described steps are not followed the resulting configurations may not be optimal in terms of traffic capacity and recovery.

From BSS R10 and onwards the BSC and BTS are able to handle mixed HW of different capabilities in the same CHGRs. In the case of baseband hopping, it is recommended to have the same HW capability in all TRXs in a CHGR. Otherwise the CHGR will be limited by the HW with less capability.

3.2.5.2 Using micro RBS 2308/2309 together with micro RBS 2302 in the same TG
For certain combinations of micro RBSs, RBS 2308/2309 and RBS 2302 can be used together in the same TG.

However, since the X-bus or Y-link is not supported between RBS 2308/2309 and RBS 2302, due to HW differences, GMSK bursts can not be transported between the RBSs. Because of this the TRXs of RBS 2308/2309 and the TRXs of RBS 2302 can neither baseband hop, synthesizer hop or use non-hopping together. In order to overcome this limitation it is of vital importance that the TRXs of RBS 2308/2309 and RBS 2302 are dedicated to separate CHGRs.

3.3 Algorithm
3.3.1 Cyclic Frequency Hopping
In cyclic hopping, the frequencies are changed for every TDMA frame in a consecutive order. For instance, the sequence of frequencies for cyclic hopping between four frequencies may appear as follows:

________________________________

... , f 4 , f 1 , f 2 , f 3 , f 4 , f 1 , f 2 , f 3 , f 4 , f 1 , f 2 , ...

________________________________

A cyclic sequence is specified by setting parameter HSN (hopping sequence number) to 0. There is only one cyclic sequence defined in the GSM specifications. The sequence of frequencies goes from the lowest absolute frequency number in the set of frequencies specified for that channel group, to the highest, and over again.

3.3.2 Random Frequency Hopping
A random hopping sequence is implemented as a pseudo-random sequence. The sequence is stored in a look-up table in the mobile as well as in the base stations. 63 independent sequences are defined (see Section 3.3.4). Which of the 63 sequences to be used is specified with parameter HSN.

The actual frequency to be used at each instant is obtained by an algorithm with the available frequencies, see Reference [10]

When random hopping is used, the frequencies will be used (pseudo-) randomly, and a hopping sequence for four frequencies may appear as follows:

________________________________

... , f 1 , f 4 , f 4 , f 3 , f 1 , f 2 , f 4 , f 1 , f 3 , f 3 , f 2 , ...

________________________________

The period for a random sequence is approximately 6 minutes.

3.3.3 Orthogonal Hopping Sequences
For each transceiver, in the same channel group, in the same cell, they will be assigned with the same HSN , i.e. they hop in the same way. In order not to interfere with each other, they must not use the same frequency at the same time. This is called orthogonality . All channels in a cell must be orthogonal since non-orthogonal channels will cause co-channel interference to each other.

This problem is solved by using an offset in the hopping sequence, which is referred as the Mobile Allocation Index Offset (MAIO), see Reference [10]. Each transceiver is assigned with a unique MAIO, from the MAIO list, at configuration. In this way, two transceivers bearing the same HSN but different MAIO will never use the same frequency in the same TDMA frame. A random hopping sequence (for consecutive MAIO) may appear as follows:

________________________________

... , f 1 , f 4 , f 4 , f 3 , f 1 , f 2 , f 4 , f 1 , f 3 , f 3 , f 2 , ...

... , f 2 , f 1 , f 1 , f 4 , f 2 , f 3 , f 1 , f 2 , f 4 , f 4 , f 3 , ...

... , f 3 , f 2 , f 2 , f 1 , f 3 , f 4 , f 2 , f 3 , f 1 , f 1 , f 4 , ...

... , f 4 , f 3 , f 3 , f 2 , f 4 , f 1 , f 3 , f 4 , f 2 , f 2 , f 1 , ...

________________________________

If MAIO management (see Reference [6]) is used, operators can choose between a default MAIO list or to define their own. (Operators without the feature MAIO Management will automatically get the default list.) The MAIO list is defined on a channel group level. In the default MAIO list, the even MAIO values, in increasing order, are picked first, and then, the odd values, in increasing order, are used. As an example, for a channel group of 5 frequencies, the default MAIO list is 0, 2, 4, 1, 3. In the manual MAIO allocation, operators can define MAIO values at configuration, from 0 and N-1, where N is the total number of hopping frequencies.

3.3.4 Independent Hopping Sequences
The assignment of HSN depends on whether cells are synchronised or not, and whether MAIO allocation is used.

In unsynchronised cells, for the interference averaging mechanism to work well, the hopping sequence in co-channel cells must be different. This is even more important if the cells use exactly the same set of frequencies. Connections in these cells will then use the same frequencies, but not always at the same time. If the frequencies are independent, they will only interfere with each other, now and then, when two (or more) bursts happen to coincide in frequency. The number of collisions per second will depend on the number of frequencies in the channel group.

The hopping sequences for three connections in three unsynchronised co-channel cells might appear as follows for four frequencies in the hopping set. The frequency collisions, i.e. the instances of co-channel disturbance, are indicated with bold type:

______________________________________

Cell 1: ... , f 1 , f 4 , f 4 , f 3 , f 1 , f 2 , f 3 , f 1 , f 3 , f 4 , f 2 , ...

______________________________________

Cell 2: ... , f 3 , f 1 , f 1 , f 1 , f 4 , f 3 , f 2 , f 1 , f 2 , f 1 , f 4 , ...

______________________________________

Cell 3: ... , f 3 , f 4 , f 3 , f 3 , f 2 , f 1 , f 4 , f 1 , f 3 , f 2 , f 1 , ...

______________________________________

This type of sequences are independent since the correlation between the frequencies is minimal. Since there is only one cyclic sequence, cyclic sequences can be orthogonal (if they have different MAIOs), but never independent. In order to obtain efficient interference averaging, unsynchronised co-channel cells must be assigned different HSN in much the same way as BSIC is planned, especially at very tight reuse (1/1) as the number of co-channel neighbours will be high (see also Section 4.1.3).

For synchronised cells, it is possible to use the same hopping sequence in co-channel cells. For details, please refer to Reference [6].

3.4 Limitations at Frequency Allocation
3.4.1 General Limitations
The maximum number of frequencies per cell is 128. Note that the number of frequencies per channel group is however limited to 32, thus limiting the number of frequencies to hop on per BPC to 32.

It is also possible that a frequency (except the BCCH carrier) in one CHGR can be reused in other CHGRs within the cell. However this requires careful MAIO planning to avoid co-channel interference within the cell. Therefore this is further described in Reference [6].

Note that the GSM800 and GSM900 system types have overlapping frequencies.

3.4.2 Limitations in CA List
For each cell a Cell Allocation list (CA list) is sent to the mobile in which information regarding frequencies used in the cell is defined. This information is needed for the mobile at Immediate Assignment and Packet Assignment to know what frequencies to use (it is also needed for GSM phase 1 mobiles at assignment). In the CA list, only hopping frequencies to be used at Immediate Assignment must be specified. This means that by putting all non hopping BCCH frequencies in one end of the spectrum, the total range can be minimized.

At Immediate Assignment, it is specified which of the ARFCNs in the CA list that are used in the hopping sequence for the specific BPCs. No more than 64 ARFCNs should be encoded in CA list since this is the maximum number of ARFCNs which can be referenced at Immediate Assignment.

Note that this is also the case at Packet Downlink Assignment and Packet Uplink Assignment for GPRS, but then also Direct Encoding could also be used. When CBCH frequency is part of CA list, no more then 32 frequencies can be listed due to the limitations in 3GPP 44.018 (in SI4, only 32 frequencies is allowed in the CA list). In case of different frequency bands this can be as low as 16 (due to ranges, see Section 3.4.3 Limitation of Frequency Range). If PS traffic would continue to use this list, a number of frequencies would never be used for Immediate Assignment. This is solved by using the direct encoding 2 option in Packet Downlink Assignment and Packet Uplink Assignment messages. If MS capabilities are known and MPDCH is present in a cell, direct encoding 2 allows MS to use hopping frequencies not listed in the CA list for PS traffic.

When up to 128 frequencies is to be defined in a cell, not all defined frequencies will be possible to use at Immediate Assignment. The solution to this is to restrict CHGRs to be used for Immediate Assignment. By doing so the CA list can be kept equal or below 64. This is done by choosing which CHGRs frequencies that should not be included (i.e. exclude the CHGR) and thereby sum up the rest of the CHGR's frequencies to equal or below 64. The operator can define which channel groups to include and exclude for Immediate Assignment with the parameter, BCCD. As the maximum number of frequencies in the CA list is 64 the sum of frequencies for all of the hopping CHGRs HFS shall be equal or less than 64. If the sum is higher then 64 then BCCD is used to prevent immediate/packet assignment in one or more CHGRs.

3.4.3 Limitation of Frequency Range
For cells defined with 800/Extended 900/1800/1900 frequencies for hopping there is a limitation of frequencies that can be specified for the CA list. The reason for this is that there is a restriction in the GSM specification that has to do with the frequency range, i.e. the frequencies shall not be allocated too far from each other. By range is meant the distance in ARFCN numbering between the highest and lowest frequency used. If for example ARFCN 5 up to ARFCN 30 is used the range is 26.

These are the frequency ranges for the different system types:

GSM 800: ARFCN 128 - ARFCN 251

GSM 900, P-GSM: ARFCN 1 - ARFCN 124

GSM 900, G1-GSM (Extended): ARFCN 0, ARFCN 975 - ARFCN 1023

GSM 1900: ARFCN 512 - ARFCN 810

GSM 1800: ARFCN 512 - ARFCN 885

For a 900 MHz P-GSM cell there is no practical limitation as the range limitation on the 900 MHz P-GSM is 124 (see Table 1) which is the same as the total range for GSM 900 P-GSM (ARFCN 1 - ARFCN 124). However, the limitation is 112 for all other system types or combinations of system types (e.g. multi band cells 900/1800). If the frequency range is within these limits then all 64 positions in the CA list can be used (see Table 1). Otherwise the range can be limited to 112 by excluding CHGRs with "out of range" frequencies (by using the BCCD parameter).

Table 1 System Type Dependent Frequency Limitations System type
Max frequency range
Max number of frequencies

900 P-GSM
124
64

All other + combinations
112
64


If the range is exceeded, then the consequence will be that the maximum number of frequencies for the CA list is decreased. This decrease depends on by how much the range is exceeded. This is however not a limitation if only a few hopping frequencies are allocated. The result of maximum number of frequencies depending on total range is displayed in Table 2.

Table 2 Number of Frequencies when Exceeding Frequency Range 112 Frequency range
Max number of frequencies

113-256
22

257-512
18

513-1024
16 without ARFCN 0

17 with ARFCN 0


The range stretches over all defined ARFCNs with a so called modulo arrangement that can be visualized with a figure (see Figure 10). The circle represents ARFCNs and in this figure the frequency bands of different system types are marked. The range of the system types assigned to a cell can stretch over the so called Modulo 1024 border. This means that a cell with 900 G1-GSM and 900 P-GSM frequencies with ARFCN 1003, 1005, 1007, 4, 7, 8 has a total range of 29.



Figure 10 This figure shows the ranges of the system types. The range when handling more than one system type can stretch over the modulo 1024 border. For example, the frequencies ARFCN 1003, 1005, 4, 7 and 8 are within the range of 29. Note that the 1800 and 1900 bands are overlapping.

The general (simplified) methodology for allocation of hopping frequencies considering range can be stated as can be seen in Table 3. (More combinations can be found in Table 12.) CHGRs can be excluded for immediate assignment with BCCD to cope with frequencies out of range.

Table 3 Limitations and Considerations at Frequency Allocation Frequency band(s) allocated in a cell that is to be used for Immediate Assignment
Total number of hopping frequencies used
Range considerations
Remarks/Examples

900 P-GSM
Any number
Range is of no importance
-

1800
Up to 18
Range is of no importance
-

1800
19-22
Do not exceed the 256 range limitation.
E.g. do not assign both ARFCN 550 and ARFCN 820 in CHGRs allowed for immediate assignment.

1800
More than 22
Do not exceed the 112 range limitation
E.g. do not assign both ARFCN 550 and ARFCN 750 in CHGRs allowed for immediate assignment.

800
Up to 22
Range is of no importance
-

800
More than 22
Do not exceed the 112 range limitation
E.g. do not assign both ARFCN 128 and ARFCN 250 in CHGRs allowed for immediate assignment.

1900
Up to 18
Range is of no importance
-

1900
19-22
Do not exceed the 256 range limitation.
E.g. do not assign both ARFCN 540 and ARFCN 810 in CHGRs allowed for immediate assignment.

1900
More than 22
Do not exceed the 112 range limitation
E.g. do not assign both ARFCN 550 and ARFCN 750 in CHGRs allowed for immediate assignment.

900 P-GSM and G1-GSM Extended band
Up to 22
Range is of no importance
-

900 P-GSM and G1-GSM Extended band
More than 22
Do not exceed the 112 range limitation.
The range may stretch maximum 112 positions over the Mod 1024 border (ARFCN 1023-ARFCN 0) between ARFCN 975-ARFCN 124. E.g. do not assign both ARFCN 975 and ARFCN 124 in CHGRs allowed for immediate assignment (e.g. exclude extended band).

900 P-GSM and 1800
Up to 16
Range is of no importance
-

900 P-GSM and 1800
17 or 18
Do not exceed the 512 range limitation.
The range may stretch maximum 512 positions between ARFCN 1-ARFCN 885 or over the Mod 1024 border (ARFCN 1023-ARFCN 0) between ARFCN 512-ARFCN 124. E.g. do not assign both ARFCN 5 and ARFCN 550 in CHGRs allowed for immediate assignment.

900 P-GSM and 1800
19-22
Do not exceed the 256 range limitation.
The range may stretch maximum 256 positions between ARFCN 1-ARFCN 885 or over the Mod 1024 border (ARFCN 1023-ARFCN 0) between ARFCN 512-ARFCN 124. E.g. do not assign both ARFCN 5 and ARFCN 550 in CHGRs allowed for immediate assignment.

900 P-GSM and 1800
More than 22
Do not exceed the 112 range limitation.
The range may stretch maximum 112 positions between ARFCN 1-ARFCN 885 or over the Mod 1024 border (ARFCN 1023-ARFCN 0) between ARFCN 512-ARFCN 124. E.g. do not assign both ARFCN 5 and ARFCN 880 in CHGRs allowed for immediate assignment.

900 P-GSM and 1900
Up to 16
Range is of no importance
-

900 P-GSM and 1900
17 or 18
Do not exceed the 512 range limitation.
The range may stretch maximum 512 positions between ARFCN 128-ARFCN 810, or over the Mod 1024 border (ARFCN 1023-ARFCN 0) between ARFCN 512-ARFCN 124. E.g. do not assign both ARFCN 5 and ARFCN 550 in CHGRs allowed for immediate assignment.

900 P-GSM and 1900
19-22
Do not exceed the 256 range limitation.
The range may stretch maximum 256 positions between ARFCN 128-ARFCN 810, or over the Mod 1024 border (ARFCN 1023-ARFCN 0) between ARFCN 512-ARFCN 124. E.g. do not assign both ARFCN 5 and ARFCN 550 in CHGRs allowed for immediate assignment.

800 and 1900
Up to 16
Range is of no importance
-

800 and 1900
17 or 18
Do not exceed the 512 range limitation.
The range may stretch maximum 112 positions between ARFCN 128-ARFCN 810, or over the Mod 1024 border (ARFCN 1023-ARFCN 0) between ARFCN 512-ARFCN 251. E.g. do not assign both ARFCN 128 and ARFCN 550 in CHGRs allowed for immediate assignment.

900 P-GSM and 800
Up to 22
Range is of no importance
Note that these system types have overlapping frequencies

900 P-GSM and 800
More than 22
Do not exceed the 112 range limitation.
Note that these system types have overlapping frequencies

900 P-GSM and G1-GSM Extended band and 800
Up to 18
Range is of no importance
Note that these system types have overlapping frequencies

900 P-GSM and G1-GSM Extended band and 800
19-22
Do not exceed the 256 range limitation.
Note that these system types have overlapping frequencies

900 P-GSM and G1-GSM Extended band and 800
More than 22
Do not exceed the 112 range limitation.
Note that these system types have overlapping frequencies


Note that Phase 1 MSs are not capable of decoding the CA-list if not only P-GSM frequencies are in the CA-list (i.e. Phase 1 MSs are not possible to access this cell). This means that measures have to be taken for Phase 1 MSs when the P-GSM is the BCCH frequency band/sub band, like in single band cells with both P- and G1-GSM or in multi band cells. Because of this, if there is a significant amount of Phase 1 MSs in a BSC, it is recommended to set BCCD to NO for all hopping channel groups that are not using P-GSM frequencies.

3.4.4 Examples
This section deals with restrictions that can be made with the BCCD parameter.

Example 1 (900 MHz P-GSM):

A cell is to be configured with 60 hopping frequencies. Due to operator specific reasons three CHGRs for the hopping frequencies are defined.

A cell with four CHGRs configured with 60 hopping frequencies (900 MHz P-GSM) will not need restrictions at call setup as the CA list can handle both the range and the number of frequencies (see Table 4).

Table 4 Channel Group Configurations for a Cell with 60 Hopping Frequencies (900 MHz P-GSM)
# frequencies in HFS
BCCD
# of SDCCHs/8

CHGR0
1 * 900 MHz

1

CHGR1
20 * 900 MHz
Yes
1

CHGR2
20 * 900 MHz
Yes
1

CHGR3
20 * 900 MHz
Yes
1


Sum = 61 frequencies. 60 of them are hopping.
All CHGRs allowed at call setup. 60 frequencies in the CA (CHGR0 not counted as long as it is non-hopping).
One SDCCH/8 in each CHGR = 4 SDCCH/8s in total


Example 2 (900 MHz P-GSM):

The cell in Example 1 is expanded with ten hopping frequencies to a total of 71.

If one or more of the existing CHGRs are expanded to include more frequencies (above 64) then some of the CHGRs must be avoided for immediate/packet assignment (see Table 5). In the table CHGR2 is now restricted for immediate/packet assignment, but CHGR1 and CHGR3 could have been restricted instead/also as long as the total number of frequencies in the non-restricted CHGRs are equal to or less than 64.

Note that the SDCCHs assigned and dimensioned to handle immediate assignment shall not be allocated to this restricted CHGR. Move these SDCCHs to other CHGRs.

Table 5 Channel Group Configurations for a Cell with 70 Hopping Frequencies (900 MHz P-GSM)
# frequencies in HFS
BCCD
# of SDCCHs/8

CHGR0
1 * 900 MHz

1

CHGR1
20 * 900 MHz
Yes
2 (One SDCCH/8 is moved from CHGR2

CHGR2
30 * 900 MHz
No
0

CHGR3
20 * 900 MHz
Yes
1


Sum = 70 hopping frequencies
CHGR2 not allowed at call setup. 40 frequencies in the CA (CHGR0 not counted as long as it is non-hopping).
SDCCH in CHGR2 is moved to CHGR1 = 4 SDCCH/8s in total


Example 3 (1800 MHz):

A cell is to be configured with 30 hopping frequencies from the 1800 band. The range of frequencies stretches from ARFCN 520 to ARFCN 600.

A 1800 MHz cell configured with 30 hopping frequencies in one CHGR will not need restrictions at call setup as the CA list can handle up to 64 frequencies and the range of frequencies is kept below 112. All 30 hopping frequencies can be used in one CHGR (see Table 6).

Table 6 Channel Group Configurations for a Cell with 30 Hopping Frequencies (1800 MHz)
# frequencies in HFS
BCCD
# of SDCCHs/8

CHGR0
1 * 1800 MHz

1

CHGR1
30 * 1800 MHz
Yes
2


Sum = 30 hopping frequencies

3 SDCCH/8s in total


Example 4 (1800 MHz):

A change of frequencies is performed to the cell in Example 3. The new hopping frequencies are 512-515 and ARFCN 854-885.

As the range is now higher than 112 the frequencies need to be split up in two CHGRs, one containing ARFCN 512-515 and one with ARFCN 854-885 as can be seen in Table 7. Now either of the CHGRs can be restricted with BCCD. Here we have chosen CHGR2. Note that the SDCCH/8 in CHGR 2 has been moved to CHGR1.

Table 7 Channel Group Configurations for a Cell with 36 Hopping Frequencies (1800 MHz)
# frequencies in HFS
BCCD
# of SDCCHs/8

CHGR0
1 * 1800 MHz

1

CHGR1
32 * 1800 MHz
Yes
2

CHGR2
4 * 1800 MHz
No
0


Sum = 36 hopping frequencies

3 SDCCH/8s in total


A second solution to Example 4 is to mix all the frequencies for the two CHGRs. According to Table 2 the total range of 374 still calls for restriction of CHGRs but equal number of frequencies can be used in each CHGR. In Table 8 18 frequencies are chosen for each CHGR.

The conclusion of this example is that equal number of frequencies in hopping CHGRs can still be achieved.

Table 8 Channel Group Configurations for a Cell with 36 Hopping Frequencies (1800 MHz)
# frequencies in HFS
BCCD
# of SDCCHs/8

CHGR0
1 * 1800 MHz

1

CHGR1
18 * 1800 MHz
Yes
2

CHGR2
18 * 1800 MHz
No
0


Sum = 36 hopping frequencies

3 SDCCH/8s in total


Example 5 (multi band cell 900/1800)

A cell is to be defined as a multi band cell with a total of 60 hopping frequencies with ARFCN 41-70 and ARFCN ARFCN 521-550.

The 900 frequencies and the 1800 frequencies are defined in different subcells. Since the range is above 112, the 1800 CHGR (CHGR2) is restricted as can be seen in Table 9.

Table 9 Channel Group Configurations for a Cell with 60 Hopping Frequencies (Multi Band Cell 900/1800 MHz)
# frequencies in HFS
BCCD
# of SDCCHs/8

CHGR0
1 * 900 MHz

1

CHGR1
30 * 900 MHz
Yes
3

CHGR2
30 * 1800 MHz
No
0


Sum = 60 frequencies
CHGR2 not allowed at call setup.
4 SDCCH/8s in total.


3.5 GPRS/EGPRS Impacts
In frequency hopping, all GPRS/EGPRS channels are treated as traffic channels.

It will not be possible to have dedicated PDCHs in channel groups with BCCD equal to NO.

3.6 Related Counters
There is no counter that is directly related to frequency hopping. For further information, please refer to Reference [8].

3.7 Main Changes in Ericsson GSM System R11/BSS R11
Support for Mixed HW configurations: a chapter has been added that emphasizes the need to dedicate RBS 2302 TRXs to a different channel group than the RBS 2308 TRXs.

4 Engineering Guidelines
4.1 Applications
4.1.1 General
Frequency hopping should always be enabled in every cell since it introduces frequency and interference diversity. The frequency diversity balances the quality between slow and fast moving mobile stations, i.e. the quality for slow moving users is increased. Slow and fast users can thereby be treated in the same way when designing the radio network. Frequency diversity can be seen as a C/N (carrier to noise) gain. The interference diversity implies that the network can cope with a higher interference level and thereby a tighter frequency reuse. This implies increased capacity compared to a non-hopping network. The interference diversity can, in turn, be expressed as a C/I (carrier to interference) gain. Frequency hopping is the most important feature for supporting high capacity networks with maintained quality, though efficient use of DTX, MAIO allocation, MS and BTS power control are also essential.

4.1.2 Frequency Hopping Gain
The gain from frequency hopping depends on factors such as propagation environment, number of hopping frequencies and interference characteristics (e.g. time and location).

The number of hopping frequencies affects the gain from both frequency and interference diversity. The hopping gain increases with the number of hopping frequencies, but there is a "law of diminishing returns". For example, increasing the number of frequencies in the hopping group from seven to eight does not give as much improvement as increasing it from two to three. Three hopping frequencies per cell results in a substantial gain. With four frequencies per cell, it will work even better. It is because the interference will then spread over a larger bandwidth and the probability of MS being inside a fading dip is reduced. The frequency hopping gain is summarised in Table 10 .

The interference diversity gain is also dependent on the efficient use of interference reduction features such as DTX, MAIO management, MS and BTS power control. Using DTX and power control increases the gain from the interference averaging. In addition, the time variation of the interference is also important. The channel coding and interleaving schemes are not efficient when being hit by interference too often.

Frequency diversity for slowly moving mobile stations also depends on the coherence bandwidth of the radio link, i.e. the correlation of fading dips between different frequencies. Hopping over as few as two frequencies will give frequency diversity if the two frequencies are separated by more than the coherence bandwidth. In urban environments with a lot of reflections present, there will be a substantial gain if the hopping frequencies are separated 1 MHz or more. The coherence bandwidth is strongly dependent upon the propagation environment and the presence of reflections (reflecting objects). More reflections are better in this case. A line of sight connection will have a smaller gain, but fewer fading dips implying that a gain is really not needed. Full frequency diversity gain is achieved for the TCH when hopping over 8 frequencies since a speech frame is interleaved over 8 bursts (for the SDCCH the corresponding limit is 4).

Table 10 Gain from Frequency Hopping Number of hopping frequencies
Interference diversity
Frequency diversity

(C/I gain)
(C/N gain)

2
Small gain
Substantial if carrier frequencies separated by coherence bandwidth: around 1 MHz, dense urban and urban scenarios

3
Significant gain
Larger than with 2 frequencies per cell

>=4
Larger than with 3 frequencies per cell and increasing if the traffic load is kept low
Significantly larger than with 2 frequencies per cell


4.1.3 Cyclic Versus Random Hopping
The random hopping mode has a cycle that runs for 6 minutes. The cyclic hoping has a cycle duration that depends on the number of frequencies in the HFS (Number of frequencies * the duration of a TDMA frame). As neighbouring unsynchronised cells using the same frequencies may have an offset of current FN which corresponds to the number of frequencies in the HFS, the cells will have a higher probability to actually be synchronised by accident when using cyclic hopping compared to using random hopping. This means that random hopping is superior to cyclic hopping for limiting the co-channel interference in high capacity networks.

If random hopping is applied, co-channel cells (cells which have the same carrier frequencies in the hopping sequence) may need to have different HSNs, especially at very tight reuse (1/1) as the number of co-channel neighbours will be high. (see also Section 3.3.4).

In a 1/1 network with synchronised cells within a site, all cells within the site should use the same HSN if MAIO management is used, (see Reference [6]). In this way orthogonal frequency hopping is achieved within the site. In the case that MAIO management is not used 1/1 can not be utilized fully within a site and each sector must use different HSN. In this way the co-channel hits are randomly distributed. This is also true to non co-sited cells that are network synchronized, see also Reference [9].

4.1.4 Baseband or Synthesizer Hopping
The choice between baseband hopping and synthesizer hopping depends on the available hardware. Some properties of the synthesizer and baseband hopping are summarized below:

Number of TXs
In a synthesizer hopping system, the required number of TXs can be less than the number of frequencies. In a baseband hopping system, a dedicated TX is needed for each frequency.

Combiner type
For the synthesizer hopping system, a hybrid combiner solution is required. Baseband hopping can also be specified if hybrid combiners are used. If a filter combiner is used then only baseband hopping can be specified.

RBS200
The minimum channel separation in a hybrid combiner is 400 kHz, while the minimum channel separation in a filter combiner is 600 kHz (900 MHz band) and 1200 kHz (1800/1900 MHz band).

RBS2000
The minimum channel separation for CDU-A, CDU-C/C+, CDU-F & CDU-G is 400 kHz, while the minimum channel separation for CDU-D is 600 kHz (900 MHz band) and 1000 kHz (1800/1900 MHz band).

Faulty TX
In a synthesizer hopping system, a fault on a TX will affect up to eight Basic Physical Channels (BPCs) assigned to that TX. In a baseband hopping system, a fault on a TX will affect every BPC that uses the frequency that the faulty TX was transmitting on.

A lost transceiver, included in a frequency hopping sequence, is isolated and hopping is restored without the faulty transceiver, but the transceiver will not automatically be included in the hopping sequence after a recovery unless the feature to automatic expand the HFS is used, see Reference [4].

It should be noted that the requirement on channel separation for different combiner types can be disregarded in some cases. For example, in the 1/1 fractional load network, it is common to assign adjacent frequencies within a cell. However, if the Hopping Frequency Set is large, these adjacencies can be avoided with MAIO Management.

4.2 Impact of Frequency Hopping on Frequency Planning
4.2.1 General
Frequency planning in a network is done with respect to an acceptable interference level. This level can be set to a lower value in a frequency hopping network compared to a network without frequency hopping.

Even if sufficient frequency hopping gain is achieved at a relative small number of frequencies in the HFS, a large number of frequencies, compared to the number of TRXs in the cells, will simplify the frequency planning work when using synthesizer hopping. The installation of an extra cell or a TRX for a cell will be easy as only concerns regarding the BCCH carrier frequency has to be taken. If e.g. 27 frequencies are initially assigned to the hopping CHGR, the cell will be prepared for many future TRX upgrades.

4.2.2 BCCH Frequency Planning
Because of the importance of the BCCH, great care should be taken to protect these channels from interference. The BCCH frequency can not be planned according to a tight reuse pattern. An approximate 12 reuse is possible for the BCCH frequencies for macrocells, especially if using the feature BCCH in Overlaid subcell. It is further recommended to use a separate (dedicated) band for the BCCH frequencies.

4.2.3 High Capacity Networks
The general strategy is to boost the macrocell network capacity as a first step. Deploying microcells in the later phases enables the operator to perform site hunting and establish procedures for the microcell roll-out.

The macrocell network capacity is increased by planning the TCH frequencies using a tighter frequency reuse, significantly tighter than 12. Features like DTX, MAIO allocation, BTS and MS power control are then applied with frequency hopping to reduce interference. Different high capacity strategies can be employed depending on factors such as the combiner type used in the network, the number of available frequencies and number of transceivers per cell.

In networks using filter combiners and configured with many transceivers per cell (3 or more), the Ericsson Multiple Reuse Patterns (MRP) methodology is preferred using baseband hopping. An average reuse of typically 7-8 can be applied (the average reuse including the BCCH frequency reuse of 12). If DTX and power control are applied, an average reuse of down to 6 or even less is possible.

For networks using wide-band combiners, such as CDU-A, CDU-C, CDU-C+ & CDU-G it might be better to apply fractional loading using synthesizer hopping (especially if only a few frequencies are available). Thereby the hopping can be performed over more frequencies than there are installed transceivers per cell in order to achieve a sufficient frequency hopping gain. In this case, very tight reuse patterns like 1/3 or 1/1 can be applied on the TCH frequencies. Other features, like DTX, MAIO allocation, MS and BTS power control should also be applied to reduce interference further.

As a second step, hot spot microcells with synthesizer hopping can be introduced to further boost the network capacity. In order to make the implementation easy, a few frequencies can be reserved for the microcell BCCH frequencies. TCH frequencies for the microcells can be borrowed from the macrocell layer. As the microcell network grows, it is a good option to further reserve frequencies for the microcells. A total allocation of 5-8 frequencies is normally sufficient for a contiguous microcell layer configured with 2 transceivers per cell.

4.3 Channel Configuration
4.3.1 Baseband Hopping
The following example illustrates the channel structure for a cell with baseband frequency hopping.

Example:

Consider a cell without subcell structure using one channel group. Four frequencies are assigned to the cell in the 900 MHz band, defined by ARFCN 75, 78, 81, and 84. The following parameter setting is defined for the cell:

Table 11 Parameter Setting, Example Parameter
Value
Description

BCCHNO
75
The frequency defined by ARFCN 75 is defined as the BCCH frequency (f 0 ).

CHGR
0
Channel group 0 is defined in the cell.

HOP
ON
Channel group 0 is hopping.

HSN
0
Cyclic hopping mode is specified.

DCHNO
78, 81, 84
Three frequencies are assigned to CHGR0, defined by ARFCN 78, 81, and 84 (f 1 , f 2 and f 3 ).


The following relation between ARFCNs and frequencies is assumed:


ARFCN =
75
f 0


ARFCN =
78
f 1


ARFCN =
81
f 2


ARFCN =
84
f 3


For the previous parameter setting, the system automatically defines three Hopping Frequency Sets (HFS):


HFS1
{f 0 },


HFS2
{f 1 , f 2 , f 3 },


HFS3
{f 0 , f 1 , f 2 , f 3 }.


HFS1 contains frequency f 0 , which is the BCCH frequency which is non-hopping. HFS1 is assigned to TS0 on the transceiver handling the BCCH frequency.

HFS2 contains all frequencies except the BCCH frequency and it is assigned to TS0 on the TCH frequency transceivers.

HFS3 contains all frequencies defined in the channel group and it is assigned to TS1-TS7 on all transceivers in the cell.

The BPC (basic physical channel) in TS0 on the BCCH frequency transceiver is non-hopping (HFS1). The other BPCs in TS0 on the other transceivers are hopping (HFS2). All other BPCs in TS1-TS7 on all transceivers are hopping, (HFS3). This leads to 31 hopping BPCs.

Figure 11 , which is based on Figure 4 , shows this configuration.



Figure 11 Channel Configuration Example for Four TRXs and Baseband Frequency Hopping

4.3.2 Synthesizer Hopping
With synthesizer hopping, TS1-TS7 on the TX that supports the BCCH frequency might not be used (refer Section 3.2.4 ). The total number of supported BPCs can be reduced by seven which would be a clear limitation for synthesizer hopping configurations. The following two methods can be used to eliminate this limitation:

Use two channel groups
Define the available frequencies in two channel groups, one channel group which contains only the BCCH frequency and another channel group that contains the other frequencies. This configuration is described in Section 3.2.3 .

An example of this procedure: consider a configuration with two transceivers and four frequencies (f 0 , f 1 , f 2 , and f 3 ). Define two channel groups: CHGR0 and CHGR1. CHGR0 contains only the BCCH frequency (f 0 ). CHGR1 contains the other frequencies (f 1 , f 2 , and f 3 ). With this configuration, one TX supports CHGR0 with the broadcast channels in TS0 and seven non-hopping TCHs in TS1-TS7. The other TX supports CHGR1, with 8 BPCs hopping over three frequencies.

Add extra hardware
An extra TX can be added to the configuration. The BSC supports base station configurations with an extra TX. This additional TX supports the BCCH frequency. This configuration is described in Section 3.2.4 .

4.3.3 Support for Extended Frequency Bands
A channel group is not restricted to one frequency band, it is possible to mix the frequencies from different GSM bands in one channel group. When defining frequencies in channel group 0, they must be defined in the primary GSM band (P-GSM) if the BCCH frequency is defined in the P-GSM band. Otherwise the P-GSM only mobiles will not work properly. If the BCCH frequency is defined in the G1-GSM band, the other frequencies can be defined in the P-GSM or G1-GSM band. The BCCH frequency can be defined in any GSM band (P-GSM or G1-GSM).

4.4 Frequency Hopping and Subjective Speech Quality
In frequency hopping networks, there is no distinct mapping between the estimated raw bit error rate, i.e. rxqual , and speech quality making it difficult to estimate the network speech quality performance. However, the following rule-of-thumb can still be used.

The rxqual limit for poor subjective speech quality is:

rxqual >= 4.5 for a network without frequency hopping
rxqual >= 5.5 for a network with frequency hopping
These limits will approximately correspond to a speech Frame Erasure Rate (FER) of 2%.

The feature Measurement Result Recording (MRR) (see Reference [7]) can be used for collecting rxqual in order to assess the speech quality in both up- and downlink of a network. With this feature, data can be gathered from a lot of cells in network providing very significant values, statistically.

An alternative solution for the downlink is to use the Speech Quality Index (SQI) measure present in TEMS. This speech quality measure is based on both rxqual and FER and it is independent of the use of frequency hopping which is advantageous. A SQI less than 15 dBQ usually reflects poor speech quality.

5 Parameters
5.1 Main Controlling Parameters
HOP is the switch for turning frequency hopping on or off, defined per channel group. HOP = ON defines that all channels except the BCCH hop. HOP = OFF defines that the hopping status for the channel group is non-hopping.

HSN is the hopping sequence number, defined per channel group. This parameter specifies which hopping sequence to be used. All timeslots in one channel group are configured with the same HSN. HSN = 0 yields a cyclic sequence. HSN = 1 to 63 yields pseudo-random sequences. Due to the procedure used by the mobile stations for measurement reporting, the use of cyclic hopping with a multiple of 13 frequencies should be avoided when DTX is used, see Reference [1]. (For measurement reporting when using DTX, a subset of TDMA frames, SACCH, are used for the measurements which is sent every 13:th TDMA frame. Cyclic hopping on 13 frequencies will in this case only consider one of the frequencies.)

FHOP selects which hopping method to be used, baseband hopping (FHOP = BB) or synthesizer hopping (FHOP = SY). It is defined per transceiver group. At synthesizer hopping, the hopping method including c 0 filling mentioned in Section 3.2.4 , is obtained by default in the channel group that contains the BCCH frequency.

COMB specifies which combiner type that has been connected, a wide-band hybrid combiner (COMB = HYB) or a narrow-band filter combiner (COMB = FLT). It is defined per transceiver group. If a filter combiner is connected, only baseband hopping can be used.

MAIO This parameter allows operators to specify a MAIO list of, up to 16 MAIO values (with a range of 0-31), in the order of allocation, to a channel group or specify the channel group to use default MAIO list (MAIO = DEFAULT).

BCCD Defines if the channel group frequencies are allowed (YES) or not (NO) for Immediate Assignment. It might not be possible to set BCCD=YES for all channel groups in the cell. This is due to restrictions on the maximum number of hopping frequencies allowed for Immediate Assignment and their maximum ranges for different frequency bands (1x00 stands for 1800 or 1900):

Table 12 Range Limitations at Frequency Allocation Frequency band(s) in the cell
Number of hopping freqs for ImmAss
Max range

800
1-22
any

800
23-64
112

900,P
1-64
any

900,P&G1
1-22
any

900,P&G1
23-64
112

1x00
1-18
any

1x00
19-22
256

1x00
23-64
112

800 & 900,P
1-22
any

800 & 900,P
23-64
112

800 & 900,P&G1
1-18
any

800 & 900,P&G1
19-22
256

800 & 900,P&G1
23-64
112

800 & 1x00
1-16
any

800 & 1x00
17-18
512

900,P & 1x00
1-16
any

900,P & 1x00
17-18
512

900,P & 1x00
19-22
256

900,P&G1 & 1x00
1-16
any

900,P&G1 & 1x00
17-18
512

900,P&G1 & 1x00
19-22
256

900,P&G1 & 1x00
23-64
112


Note: The range stretches over the modulo 1024 border. For example, the frequencies ARFCN 1003, 1005, 4, 7 and 8 are within the range of 29.

5.2 Value Ranges and Default Values
Table 13 Controlling Parameters Parameter name
Default value
Recommended value
Value range
Unit

HOP
OFF
ON
OFF, ON


HSN

1-63
0 to 63


FHOP

-
BB, SY


COMB

-
HYB, FLT


MAIO
DEFAULT
-
0 to 31 or DEFAULT


BCCD
NO
-
YES,NO



6 Concepts
Cell Allocation Information element included in the System Information and used to instruct the mobile terminal about the resources allocated by the network, in case of frequency hopping, during immediate assignments and packet assignments. It represents the set of frequencies allocated within a cell. Also called CA-list.

E-GSM Extended GSM900 band including the P-GSM and the G1-GSM sub bands.

EGPRS 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.

Filter Combiner The filter combiner is a narrow band combiner where the filter of each transmitter is tuned to the transmitting frequency. This tuning can be done automatically but takes some time. For this reason, filter combiner can only be used with baseband hopping. The advantage of filter combiner compared to a hybrid combiner is it can combine more than 2 TRXs into one antenna.

G1-GSM A GSM900 sub band operating between 880 and 890 MHz for uplink and between 925 and 935 MHz for downlink (ARFCN 975 to 1023, 0).

GSM800 GSM frequency band operating between 824 and 849 MHz for uplink and between 869 and 894 MHz for downlink (ARFCN 128 to 251). Also known as GSM850.

GSM900 GSM frequency band operating between 880 and 915 MHz for uplink and between 925 and 960 MHz for downlink (ARFCN 0 to 124 and 975 to 1023). It consists of two sub bands P-GSM and G1-GSM. Also known as E-GSM, or Extended GSM.

GSM1800 GSM frequency band operating between 1710 and 1785 MHz for uplink and between 1805 and 1880 MHz for downlink (ARFCN 512 to 885). Also known as DCS1800.

GSM1900 GSM frequency band operating between 1850 and 1910 MHz for uplink and between 1930 and 1990 MHz for downlink (ARFCN 512 to 810). Also known as PCS1900.

GPRS GPRS 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.

Hybrid Combiner A Hybrid combiner is a broadband combiner and does not require tuning. It is therefore suitable for both synthesizer hopping and baseband hopping. A hybrid combiner can combine at most 2 TRXs into one antenna.

MAIO It is the offset index to the ARFCN with the allocated frequencies.

Multi band cell A cell with more than one frequency band. When the frequency capability of the MSs is discussed, the term multi band cell also includes the single band cells with both P-GSM and G1-GSM frequency bands.

Multipath Fading Multipath fading occurs when signals arrive at the receiver both directly from the transmitter, and, indirectly, due to propagation through objects or reflection. These signals arrive at slightly different times, with different amplitudes and phases. They sum together constructively and also destructively (fading dips). The fading dips appear at different spatial locations for different frequencies, i.e. they are frequency and location dependent. This phenomenon is called multipath fading. Fading dips are separated by approx. 17 cm for GSM 900, and approx. 8 cm for GSM 1800 and GSM 1900.

P-GSM A GSM900 sub band operating between 890 and 915 MHz for uplink and between 935 and 960 MHz for downlink (ARFCN 1 to 124). It is also known as the Standard GSM900 or Primary GSM900 band

Sub band There are two sub bands within the GSM 900: P-GSM band and G1-GSM band.

Transceiver Group GSM requires that all channels within a cell are synchronised on the air interface. This is a basic requirement of an air interface based on TDMA principles and supports use of logical channels and baseband hopping. This requirement is met in the BTS. All TRXs within a Transceiver Group (TG) are synchronised by a common Timing Function.

TS0 to TS7 Time slot position within a TDMA frame.



Glossary
8-PSK
8-Phase Shift Keying

ARFCN
Absolute Radio Frequency Channel Number

BCCH
Broadcast Control CHannel

BPC
Basic Physical Channel

BSC
Base Station Controller

BTS
Base Transceiver Station

CA
Cell Allocation

CDU
Combining and Distribution Unit

CHGR
Channel Group

DTX
Discontinuous Transmission

EGPRS
Enhanced GPRS

FER
Frame Erasure Rate

GMSK
Gaussian Minimum Shift Keying

GPRS
General Packet Radio Service

HFS
Hopping Frequency Set

MAIO
Mobile Allocation Index Offset

MCS
Modulation and Coding Scheme

MRP
Multiple Reuse Pattern

MS
Mobile Station

PBCCH
Packet Broadcast Control CHannel

RBS
Radio Base Station

RxQual
Received Quality

SDCCH
Standalone Dedicated Control CHannel

SQI
Speech Quality Index

TCH
Traffic CHannel

TG
Transceiver Group

TRX
Transceiver


Reference List
Ericsson Documents
[1] User Description, Discontinuous Transmission.
[2] User Description, Dynamic BTS Power Control.
[3] User Description, Dynamic MS Power Control.
[4] User Description, Frequency Re-configuration with Minimum Disturbance.
[5] User Description, Locating.
[6] User Description, MAIO Management.
[7] User Description, Measurement Result Recording (MRR)
[8] User Description, Radio Network Statistics.
[9] User Description, Synchronized Radio Networks.
Standards
[10] 3GPP Technical Specification 45.002.



Hi all;

Could you please show me how to optimize network frequencies with
Synthesized Frequency Hopping ???

Thanks in advance

Mazari
2009-05-29, 02:47 AM
That's the biggest post I've ever seen

Khairul
2009-06-21, 10:58 PM
That's the biggest post I've ever seen

Ya right buddy.. your quote make me laugh a loud.. :p

justdream
2009-11-01, 11:29 PM
this document can help :hug:

edmond
2009-11-02, 12:07 AM
See more user description in the attachment

Kindly i ask if you can upload it for rapid share cause of user limitation.
Thanks in advance .

Anyway is great post

Boys
2009-11-28, 03:27 AM
Thanks for forum Wire free

Boys
2009-11-28, 03:54 AM
Thanks for forum Wire free

Processor
2009-11-30, 07:09 PM
@ Lavin80

You may try pasting in notepad or word next time and upload.

Nice share anyway!:p