1X3 Frequency Reuse Technology Guideline (v2.0)

1x3 Frequency Reuse Technology (V1.0) Public Use

Documentation Center of Radio

Planning and Design Section,

Huawei Technologies

Document No. Product version Confidentiality level

Product name: M900/M1800 24 pages in total

1X3 Frequency Reuse Technology

Guideline

(Public Use)

Drafted by: Topic Research Study Group

Date: 2002-10-22

Reviewed by: Date: yyyy/mm/ddReviewed by: Date: yyyy/mm/ddApproved by: Date: yyyy/mm/dd

Huawei Technologies

All Rights Reserved

2005-01-19 1


Table of Contents

1 General........................................................................................................................................4

1.1 Application background.....................................................................................................4

1.2 Basic concepts..................................................................................................................4

1.3 The advantages and disadvantages of 1*3......................................................................5

1.3.1 Advantages.............................................................................................................5

1.3.2 Disadvantages........................................................................................................6

2 1*3 tight reuse technology...........................................................................................................6

2.1 Layout of sites...................................................................................................................6

2.2 1*3 improve the capacity of network.................................................................................7

2.3 1*3 tight reuse pattern.......................................................................................................8

2.3.1 The basic concepts of frequency hopping..............................................................9

2.3.2 Continuous allocation mode...................................................................................9

2.3.3 Interval allocation mode........................................................................................10

2.3.4 The comparison of two allocation modes.............................................................10

2.4 1*3 probability of ad-frequency collision.........................................................................12

2.4.1 Distribution of ideal meshes.................................................................................12

2.4.2 Irregular network...................................................................................................14

2.5 1*3 reuse technique impact on network quality..............................................................15

2.5.1 Frequency hopping influence on speech quality..................................................15

2.5.2 Impact on 1*3 network performance caused by C/I.............................................16

2.5.3 Impact on 1*3 caused by layout of sites...............................................................17

2.5.4 Impact on 1*3 network performance caused by engineering parameters............17

2.5.5 Impact on 1*3 network capacity cause by handover............................................21

2.5.6 Impact on 1*3 network cause by load handover..................................................23

3 1*3 frequency-hopping data configuration................................................................................24

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1X3 Frequency Reuse Technology Guideline

Key words: Frequency planning, 1*3, 4*3, tight reuse, base transceiver station layout,

ideal mesh, capacity

Abstract: This document combines radio network layout and application experience of

1*3 reuse. It is a guideline to introduce the principles and measures of 1*3 tight

reuse frequency planning.

Reference List

Name Author Code Released

date

Where and

how to

access

Publisher

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1 General

Due to the shortage of frequency resource, in recent years equipment manufactories and

operators have been focusing on improving the efficiency of frequency utilization in GSM

system, and they try to improve network capability in limited frequency resource.

1.1 Application background

At the beginning of GSM network construction with small capacity, 4*3 reuse pattern or

more loose frequency reuse technology are employed. With the increasing of network

capacity, new tight reuse technologies appear, such as 3*3, MRP, 1*3, and 1*1.

It is hard to decide when to use 1*3 tight reuse in actual network planning, because

different operators have much different frequency resource. The maximal site

configurations under different frequency bandwidth and reuse patterns are listed as follows:

Table1 Frequency bandwidth --tight reuse technology--the maximal configuration

Bandwidth 4*3 MRP 1*3

6 MHz S3/2/2 - S4/4/3

7 MHz S3/3/2 S4/4/4 S5/4/4

8 MHz S4/3/3 S5/5/5 S6/5/5

10MHz S4/4/4 S6/6/6 S8/8/8

Notes:

1. Configurations listed above are theoretic values

2. Because the amount of carriers participated in frequency hopping is equal to frequencies

used under the MRP reuse pattern, so for small configuration site, frequency hopping

obtains small gains. Hereby, MRP is not suitable. 1*3 must adopt radio frequency hopping.

The essence of tight reuse technology is bartering capability with quality. The tighter the

frequency reuse is, the worse network quality will be. Therefore, it is better to adopt loose

reuse frequency.

BCCH carrier frequency must adopt 4*3 pattern in an actual frequency planning, BCCH

needs at least 12 frequencies (because of the importance of BCCH, 14 frequencies are

given to BCCH. So real maximal configuration is less than the value in the above table. For

example, if 6MHz bandwidth adopts 1*3, theoretical maximal configuration can only reach

S4/3/3).

1.2 Basic concepts

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In frequency planning, Frequency Reuse Factor is often used to scale frequency utilization

efficiency or tightness degree of frequency reuse. Frequency Reuse Factor is defined as

below:

K NW/NTRx

K is Frequency Reuse Factor; NW is the number of available frequencies; NTRX is the maximal

amount of carriers in a cell.

When 15 frequencies are used for the carriers participating in frequency hopping and the

number of FH carriers in the cell is 2, Frequency Reuse Factor K = 7.5. When the number

of FH carriers is 3, K = 5.

Figure 1 The overlapped depth of coverage is different in cells

Figure 1 The coverage overlap

Because the different overlapped depth of A and B network, the number of A’s adjacent

cells is less than B’s, so the interference of B is bigger than A’s.

Conclusion: The more adjacent cells are, the bigger the probability of co-frequencies

collision is, and the lower the utilization efficiency is. Therefore, the amount of adjacent cell

should be decreased whichever frequency reuse technology is used.

1.3 The advantages and disadvantages of 1*3

1.3.1 Advantages

1. The 1*3 reuse pattern is tighter than 3*3 and MRP , so capability proportion that can be

improved is higher than the latter.

2. The frequency planning is simple. Only BCCH frequency planning is necessary. During

network optimazation and carrieres expansion, frequency planning needn’t be made again.

3. The technology can improve planning efficiency greatly.

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4. Radio frequency hopping is adopted, frequency hopping gain is higher than baseband

frequency hopping(baseband frequency hopping can’t be used for 1*3 reuse pattern).

1.3.2 Disadvantages

1. Broadband combiner is needed and cavity combiner with the property of frequencies

selection can’t be used on 1*3.

2. Broadband repeater is adopted, because 1*3 has much influence on frequency-selected

repeater.

3. As the reuse distance decreases, interference of ad-frequency and co-frequency will

increase rapidly.

4. Network needs delicate optimizing adjustment. Especially, The overlap of coverage

should be restricted strictly.

It is worthy to point out that most sites configuration can only be S2/2/2 and few of them

can be S3/2/2 while we adopt general 4*3 tight reuse technology and 6MHz band is

available. Otherwise the network performance will be out of control. When 1*3 close reuse

technology is used, the maximal configuration is S4/3/3(but it is a theoretical value, the

actual configuration is S3/3/3 generally). Moreover, the capacity is twice of 3*4 reuse

technology, which can save the invests of operators greatly (the expense of tower,

equipment room, power supply, transmission and other assistant equipment will be higher

than the BTS equipment).

2 1*3 tight reuse technology

As some anti-interference technologies can’t be employed on BCCH carrier, such as

frequency hopping, power control and DTX. Therefore BCCH frequency can only use 4*3

reuse pattern.1*3 tight reuse technology is general used on no-BCCH carriers. How to

make a 1*3 frequency planning is illustrated by an actual planning within 6MHz band.

2.1 Layout of sites

Sites layout is an important work in the prophase of network planning. Whichever frequency

planning technology is used, reasonable distribution of the sites is always concerned, which

is based on the requests of coverage, capacity, network quality and construction invests. In

the premise of meeting coverage and capacity, the urban sites should be distributed in the

ideal meshes in order to absorb the traffic as possible. However due to the constraint of

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landform and tenancy, the actual sites can’t be put on ideal meshes and they are always

distributed irregularly. Comparatively, 4*3, 3*3 and MRP have a more tolerance on irregular

layout of sites, while for 1*3, layout of sites should be as regular as possible. Therefore, we

should decide the technology of Frequency planning according to usable frequency

resource, maximal site configuration which could meet the requisition of capability

nowadays and in the future.

What is ideal mesh? The relative position of ideal meshes must meet some mathematics

relation, the relation of the equilateral triangle.

Figure 2 The allocation of ideal stations

The experience proves that the quality of network and utilization efficiency of frequency will

be best when the sites are based on ideal meshes. In other words, more users will be

contained.

2.2 1*3 improve the capacity of network

1*3 tight reuse technology can improve the capacity greatly. Using general frequency reuse

technology, the maximal configuration is S3/2/2 when bandwidth is 6MHz. Nevertheless,

using 1*3 tight reuse technology the maximal configuration is S4/3/3 with the same

bandwidth. The relation of configuration and capacity is listed below:(6MHz bandwidth,

GOS=2%, 0.02 Earl /user)

Table 2 The capacity increasing

Reuse Configuration Cell 1 Cell 2 Cell 3 Site capacity The amount

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patterncapacity

(Erl)capacity

(Erl)capacity

(Erl)(Erl)

of subscribers

4*3 S2/2/2 8.20 8.20 8.20 24.60 1230

1*3 S3/3/3 14.03 14.03 14.03 42.09 2104

S4/3/3 21.00 14.03 14.03 49.06 2453

Notes:The capacity is theoretical values, in actual planning 70~80 percents of theoretical

capacity above is available.

Diagram3: The capability increase

Figure 3 The capacity increasement

Figure 3 The capacity increasing

The capability will increase 99 percents after using 1*3 tight reuse technology under the

condition the quality of network could be accepted.

2.3 1*3 tight reuse pattern

When using 1x3 frequency reuse pattern, three cells of every site will constitute a cluster.

Reuse pattern of frequency will work in every cluster. In other words, the same cell of

different sites will use the same frequency set. It will be shown in the figure below.

Figure 4 1*3 tight reuse pattern

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While adopting 1*3 tight reuse technology, we must use Radio Frequency Hopping. There

are two kinds of allocation mode of MA: continuous allocation mode and interval allocation

mode. Principles of frequency hopping are expressed as follows:

MAI f（MAIO,FN,MA,HSN,N）

f（FN，HSN，N） f（MA,MAIO）

where MAI is mobile allocation index; N is the amount of frequency in MA; FN is frame

number.

When FN, HSN, N of the three cells in the same site are all the same, MAI is only related to

MA and MAIO. It shows that ad-frequencies collision intra-site can be controlled by

planning MA and MAIO carefully. It also shows that ad-frequencies collision inter-site will be

controlled when the amount of the frequencies in MA of the three cells is the same.

NOTICE: It is different from the FH descriptions in GSM Protocol that the cells of intra-site

share the same HSN. The reason is to avoid inter-cell ad-frequencies collision in the site.

It is determined by BTS equipment that FN of different cells in the same site is the same.

When the number of sites with frequency hopping is more than 63, those sites that are far

apart between them can reuse HSN.

2.3.1 The basic concepts of frequency hopping

MA: Mobile Allocation, (in other words, the set of frequency hopping) is referred to the

hopping frequencies in a cell. MA of max 64 frequencies is supported in HUAWEI BSC.

HSN: Hopping Sequence Number, value range: 0~63. When HSN=0, it is circular frequency

hopping; when HSN=1~63, it is pseudo-random frequency hopping.

MAIO: Mobile Allocation Index Offset, value range is 0~(N-1), N is the number of carriers

participating in frequency hopping.

FN: Frame Number, range: 0~(51*26*2048-1). It is decided by BTS.

2.3.2 Continuous allocation mode

The MA and MAIO planning under continuous allocation mode are listed below:

Table 3 Continuous allocation mode

MA0 MA1 MA2 MA3 MA4 MAIO

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CELL 1 96 97 98 99 100 0, 2

CELL 2 101 102 103 104 105 0, 2

CELL 3 106 107 108 109 110 0, 2

In continuous allocation mode, the maximal configuration is S3/3/3 (BCCH carrier without

frequency hopping + 2 TCH carriers with frequency hopping). For bigger site configuration,

the ad-frequencies collision in a cell is unavoidable.

2.3.3 Interval allocation mode

Under interval allocation mode, planning of MA and MAIO is listed below:

Table 4 Frequency hopping aggregation in interval allocation

MA0 MA1 MA2 MA3 MA4 MAIO

CELL 1 96 99 102 105 108 0, 2, 4

CELL 2 97 100 103 106 109 1, 3

CELL 3 98 101 104 107 110 0, 2

In interval allocation, the maximal site configuration is S4/3/3, .For bigger site configuration,

the ad-frequencies collision in a cell is unavoidable.

2.3.4 The comparison of two allocation modes

For those two frequency allocation modes, BCCH carriers of all cells must take 4*3 reuse

pattern. It is proved that BCCH frequencies should be more than 14. TCH carriers with 1*3

tight reuse must adopt radio frequency hopping. If the site configuration is less than S3/3/3,

both of the two allocation modes could avoid ad-frequency collision in the same site.

Comparison of two allocation modes:

1. MAIO is different between interval allocation and continuous allocation.

2. MA is different between interval allocation and continuous allocation.

3. Whether interval or continuous allocation mode is adopted, the ad-frequency collision

could be avoided among the three cells in the same site by reasonable planning. The

difference is:

1) Probability of co-frequency collision in cells with the same number in adjacent

BTS is same. There is still ad-frequency collision in continuous allocation mode, but

there is no ad-frequency collision in interval allocation mode.

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2) In interval allocation, ad-frequency collision will happen among different cells of

adjacent BTS. In continuous allocation, ad-frequency collision will happen among

frequencies which locate on two ends of hopping frequencies set (for example, in this

example, 100 in Cell 1,101 and 105 in Cell 2,106 in Cell 3), but collision won’t happen

in other frequency

4. Some testing of existing network proves: in 1*3 tight reuse pattern, continuous allocation

mode is better than interval allocation mode (idle BURST testing). But the final conclusion

needs more testing. Till now interval and continuous allocation modes both work normally

online.

5. When bandwidth is 6MHz, the maximal BTS configuration that continuous allocation

mode supports is S3/3/3(theoretical value) and that supported by interval allocation mode is

S4/3/3.

Figure 5 1*3 Instance of two allocation mode

Notice: In the above allocation, BCCH frequency 111 should be used as less as possible.

Especially, it can’t use in the third cell (the cell contained 110 in MA).

When continuous and interval allocation mode are used in one actual network (idle BURST

send testing), there is no difference in coverage. On the other hand, continuous allocation

mode is better than interval allocation mode in receiving quality and their difference is listed

below:

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Figure 6 1*3 quality difference of two allocation mode

Figure 6 The receiving quality of two allocation modes

2.4 1*3 probability of ad-frequency collision

After using 1*3 tight reuse technology, the probability of co-frequency and ad-frequency

collisions will be increased greatly. The collision probability and impact on network

performance are related to the amount of adjacent cells.

2.4.1 Distribution of ideal meshes

The most perfect assumption: engineering parameters of sites are completely consistent.

Propagation environment is identical too. Sites locate on ideal meshes. Load ratio of each

cell is less than 40 percent. The number of the carriers participating in FH in a cell is 1 or 2,

and the number of the frequencies participating in FH is 5.

Cell Load Ratio is defined below:

Cell Load Ratio = The number of carries participating in FH/ The number of frequencies

participating in FH

Figure 7 1*3 tight reuse technology

In this figure, there are no co-frequency collisions in cell A-3, but there are ad-frequency

collision in A-3 with B-1, D-1, D-2 and C-2. In the figure, the number of ad-frequency

2005-01-19

12


collision cells is listed below:

Table 5 The number of cells which there are ad-frequency collisions with A-2

Interference area X X1 X2 X3 X4

Interference cells number 2 2 1 2 1

Because it have been assumed that engineering parameters and propagation environment

are all the same, the receiving levels of A-3 and adjacent cells are same at the receiving

points. Because the interference at X, X1 and X3 is maximal, only calculating the probability

at X is enough (The frequencies number in MA is 5):

1. When there is one carrier participating in FH in A-3, D-1, and D-2, the maximal

probability of ad-frequency collision is:

P 15 1

5 15 1

5 225 8%

2. When there are 2 carriers participating in FH in A-3, D-1, and D-2, the maximal

probability of ad-frequency collision is :

P 25 2

5 25 2

5 825 32%

3. When there are 2 carriers participating in FH in A-3, D-1, and D-2, the maximal

probability of ad-frequency collision is :

P 35 3

5 35 3

5 1825 72%

Notes: when three carriers participate in FH and the frequency number in MA is 5,

continuous allocation mode can't avoid ad-frequency collision intra-cell. But interval

allocation mode can avoid ad-frequency collision intra-cell. When the site configuration is

lower than S4/3/3, interval allocation mode can avoid ad-frequency collision between

adjacent cells of the site. When the configuration is higher than S4/3/3, interval allocation

can’t avoid ad-frequency collision between adjacent cells of a site.

The calculation proves that when MA is fixed, probability of ad-frequency collision has

direct ratio with square of carriers participating in FH. In other words, ad-frequency

interference will increase rapidly with increasing of network capability.

It needs to be pointed out that the calculation above is done when network runs under full

load. Actually the network load is lower than the full. One connection in A-3 cell will cause

ad-frequency interference to connections, which locate on the same timeslots in D-1 and D-

2, and there is no ad-frequency interference to the other timeslots. Therefore, ad-frequency

collision of actual network is related to the number of connections.

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2.4.2 Irregular network

The analysis listed above is based on ideal regular network, but the adjacent-cells of one

service cell are very complicated because of the difference of network structure and

propagation environment. When overlap of coverage can’t be controlled well, the adjacent

cells with ad-frequency and co-frequency collision will appear.

Assumption:

1) One cell has j adjacent cells in some interfered area and the receiving signal strength of

different adjacent cells is same.

2) The cell has j-2 adjacent-cells of other BTS, including k adjacent cells have the same

number with the current cell.

3) The number of frequencies participating in FH is N.

1. When there is one carrier participating in FH,

The probability of co-frequency collision:

P 1n 1

n k k/n2

The probability of ad-frequency collision:

P1n 1

n j 2 k j 2 k/n2

2. When there are two carriers participating in FH,


P 4k/n2


P 4j 2 k/n2

3, when there are m carriers taking part in frequency hopping


P m2k/n2


P m2j 2 k/n2

The probability of collision is related to connections in network.

The key points to garanntee network performance:

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1. The layout of the sites locations should be distributed along the regular meshe, and

antennas height should be almost same during the planning and design period.

2. In optimizing period the coverage should be controlled right to aviod the co-frequnecy

adjacent cells with the same number. According to calculation listed above, C/Ia should be

0 in X area, but the actual C/I is much lower than this value because of the coverage

overlap, the fast fading and handover threshold. Therefore, the key works during

optimization are to reduce the depth of overlap coverage and improve the handover

sensitivity.

2.5 1*3 reuse technique impact on network quality

2.5.1 Frequency hopping influence on speech quality

According to subject evaluation of speech quality, FH has much impact on Rx Qual of MS.

Testing result and subject evaluation is listed below:

Table 6 Rx Qual difference between FH and without FH

Rx_Qual

0 1 2 3 4 5 6 7

Subject

evaluation

Without FH A A B B C D D E

FH A A A B B C D E

Table 7 Subject evaluation grade

Subject evaluation grade Evaluation criterion

A Very clear, no noise

B clear, a little noise

C Understood, noise

D Understood after repeating

E Can’t be understood

Testing result proves: Receiving quality and subject speech quality in FH is different from

that in without FH. When FH is not used, Rx_Qual is 0 or 1, subject speech quality is A;

Rx_Qual is below 3, subject speech quality is clear. When FH is used, Rx_Qual is 0,1 and

2, subject speech quality is A; Rx_Qual is below 4, subject speech quality is clear; Rx_Qual

is above 6, there are no difference between FH and without FH.

Subject evaluation and quality grade between FH and without FH is showed below:

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Figure 8 The difference of Subject evaluation and quality grade

Figure 8 Subject evaluation and Rx_Qulity

2.5.2 Impact on 1*3 network performance caused by C/I

The drive test data of idle BURST sending (at this time interference cell send out data

continuously without power control) is analyzed in detail.

The relation of C/I and receiving quality grade from the driver testing data is

shown as follows:

Table 8 C/I and Rx_Qual

Rx_Qual 7 6 5 4

C/I (dB) 1 2 3 10

When C/I of 1*3 network is greater than 10dB, the subject speech quality can reach B

(clear, a little noise). When C/ I is between 3~10dB, subject speech quality is C

(understood, noise). When C/I is less than 3dB, network performance will deteriorate

rapidly.

Testing data proves that interference source in which quality grade is lower than 3 is

caused by ad-frequency collision between different-numbered cells of adjacent sites.

2.5.3 Impact on 1*3 caused by layout of sites

When 1*3 tight reuse is employed in an actual network, the test result shows the conclusion

2005-01-19 16


that the network performance of regular sites distribution is better than that of irregular sites

distribution.

Figure 9 The comparison of receiving quality ratio between regular cells and irregular cells

The data above is originated from an actual running network, and the conclusion can be

made that the distribution of the sites is very important for 1*3 network.

2.5.4 Impact on 1*3 network performance caused by engineering parameters

Engineering parameters include site location, layout, antenna height, azimuth angle,

downtilt and so on. Once site location and layout are decided and put in practice, they are

difficult to change. Therefore site should locate on the ideal meshes as possible. And the

azimuth angle and downtilt of antennas should be selected properly. When antenna is too

high, the height should be decreased to avoid interference.

The traffic statistic indexes will be compared between the 4*3 network, 1*3 network without

engineering parameters optimization and 1*3 network with engineering parameters

optimization. The comparison is listed as follows:

Table 9 The comparison of traffic statistics indexes

SDCCH call

drop rate

SDCCH

congestion rate

TCH call

drop rate

TCH congestion

rate

Traffic

(Erl)

Handover

success rate

4*3 0.25% 0% 0.92% 1.22% 166.79 93.02%

1*3 without 0.3% 0.3% 0.79% 1.19% 172.93 92.33%

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optimization

1*3 with

optimization0.22% 0.01% 0.66% 1.13% 178.87 93.45%

According to data above, after 4*3 reuse network is changed to 1*3 and before

optimization, SDCCH congestion rate deteriorate greatly, handover success rate drop,

SDCCH call drop rate and TCH congestion rate change little and traffic increase a little.

After optimization 1*3 network, each index is improved. Compared with index before

optimization, five key indexes (SDCCH congestion rate, SCCH call drop rate, TCH call drop

rate, TCH congestion rate and handover success rate) have exceeded or reached indexes

before optimization.

Figure 10 The traffic statistics indexes contrast

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Figure 11 The traffic statistics indexes contrast

Table 10 Other traffic statistics indexes contrast

Traffic Interf.B

and 3

Interf.

Band 4

Interf.

Band 5

HO

Requests of

BQ

HO

Requests

Call set

up

Average HO

times per

connection

4*3 166.79 2.41 0.15 0.16 859 9985 10362 0.96

1*3 before

optimization172.93 2.40 0.28 1.56 2433 12716 11190 1.14

1*3 after

optimization178.87 4.00 0.40 0.11 1832 11895 11935 0.99

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Figure 12 Other traffic statistics indexes contrast

The number of idle channels falling into interference band 5 is much lower than that of

before 1*3 optimization.


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Comparing 1*3 FH network before optimization with 4*3 no FH network, handover times

increased by about 2700 times and total Bad Quality handovers increased by about 1600

times. Comparing 1*3 FH network after optimization with 4*3 no FH network, handover

times increased by about 1900 times and Bad Quality handovers increased by about 1000

times. Compare increase of Call set up times with increase of traffic, the conclusion can be

made that traffic increasing is natural. The increase of handover times makes little

contribution on traffic increasing, and it will be explained in next section.

The increasing proportion of total bad quality handovers is much higher than that of traffic.

On one hand, it is due to the closer reuse frequency and the irregularity of real

experimental network causes interference in some area; on the other hand, interference

handover threshold (50) in 4*3 reuse is equal to 1*3 tight reuse threshold. The subject

speech quality of frequency hopping whose Rx_Qual is equal to 5 is as good as that of no

frequency hopping network whose Rx_Qual is equal to 4(explained in 2.5.1 impact on

network quality caused by frequency hopping). The difference of subject voice-quality

standard is the main cause of the increase of bad quality handovers.

2.5.5 Impact on 1*3 network capacity cause by handover

When MS handover from a cell to another cell in the same BSC, TCH channel of the old

cell won't be released after the target cell TCH channel is activated, until BSC receives HO

Complete message from the new cell. During Channel Activation and RF Chan Release

Ack, TCHs of the old and new cell are occupied by the same connection. In this period,

traffic statistics will repeat to count TCH seizure time. The contribution on traffic caused by

handover will be analyzed.

In order to prove whether handover will increase traffic, The test of synchronous and

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asynchronous handover have been made on GSM1800 network that haven’t been in use

commercially. Signaling time from the new cell's CHANNEL ACTIVATION (caused by

handover) to the old cell's RF CHAN RELEASE ACK is gotten by testing. Synchronous

handover counts 20 times and asynchronous handover counts 11 times. The result is listed

below:

Table 11 The time of two channels are occupied by one connection during HO (1800M)

Average time(ms) Shortest time(ms) Longest time(ms)

Synchronous

handover348 339 420

Asynchronous

handover408 398 450

The test of handover period is done in GSM900 network with large traffic, and handover

times are 18.

Table 12 The time of two channels are occupied by one connection during HO (900M)

Average time(ms) Shortest time (ms) Longest

time(ms)

Handover

time

745 584 1675

Testing of traffic statistics is done in laboratory. Statistic period is 15 minutes and MS

handover between cell A to cell B. During testing period, there are no other subscribers

using the two cells and another MS seizures cell C all the time as the terminated. Testing

results are listed below:

Table 13 Lab tests

Statistic time(min) Handover times Statistic traffic(Erl)

Cell A 15 9 0.1400

Cell B 15 9 0.1125

Add up 15 18 0.2525

Cell C 15 0 0.2500

Only one subscriber occupied the channel in cell A or B during 15 minutes testing period, If

no handover occurs, the traffic should be same between them. But the total traffic of Cell A

and B is 0.2525Erl, and the traffic of cell C is 0.25Erl. The excessive 0.0025Erl traffic is due

to handover, and the average crossed-time every handover is 0.5 seconds. Notice:

because the shortest interval of traffic statistics is 480 ms, handover crossed-time

2005-01-19 22


calculated by traffic statistics has a certain error.

Comparing network with large traffic and low traffic, handover crossed time increases

greatly while traffic become high. It is assumed average handover crossed-time is 0.78s,

and the increasing traffic is 2Erl every 10000 handover (0.75*10000/3600).

Comparing the handover increase of 1*3 network before optimization with that after

optimization, suppositional added traffic is about 0.4Erl caused by 2000 handovers. So

12Erl traffic increasing is natural.

Conclusion: Suppositional added traffic is about 2Erl when 10000 handovers are made.

Impact on traffic caused by suppositional added traffic should be considered when

handover times are extremely high. On the other hand, data above proves that handover

speed is related to traffic (the more traffic, the longer handover time).

2.5.6 Impact on 1*3 network cause by load handover

Table 14 Traffic statistics indexes contrast between enable and disable load handover

Load

handoverDate

Traffic

Erl

TCH call

drop rate %

TCH

Congestion rate %

Handover

success rate %

Handover

failure rate

Enable

16 th, 1 182.98 1.01 0.8 95.59 567

17 th, 1 166.39 0.89 0.44 96.29 412

18 th, 1 171.9 0.93 0.45 96.13 427

Disable

23 rd, 1 180.35 0.54 0.4 96.09 467

24 th, 1 181.8 0.55 0.28 / /

25 th, 1 174.47 0.43 0.49 96.71 385

Comparing traffic statistics indexes between enabling and disabling load handover, TCH

congestion rate is not high, but it hasn’t been lowered greatly after enabling load handover

and call drop rate increases distinctly.

Conclusion: Load handover can’t be employed in 1*3 network. For example the bandwidth

of load handover is 25dB and the connections meet the load HO conditions, they will

handover to second best cell and seize FH channels with serious interference, and call

drop rate will increase distinctly. In order to ensure that MS camp in cells with strongest

signal, cell selection and reselection parameters should be consistent with each other in

1*3 network.

2005-01-19 23


3 1*3 frequency-hopping data configuration

1*3 configuration data related to frequency hopping is same with other frequency hopping.

Table is shown as bellows:

Table 15 1*3 data configuration related to frequency hopping

Menu name Table name Parameter Value Annotation

Local office

Radio Channel

Configuration

Table

FH index No. 0~1023

Index to frequency- hopping data

table. And the value of the FH TRX

carriers in a cell should be same.

MAIO0~N-1

Mobile Allocation Index Offset. In

this case, the same MAIO is

recommended for all channels of a

TRX and different MAIO for

different TRX in the same cell.

Frequency

Hopping Data

Table

FH index No. 0~1023Correspond to item in Radio

channel configuration table

HSN1~63

Hopping Sequence Number. HSN

in different cells of the same site is

the same

TSC0~7

Training Serial Code, Same with

BCC.

ARFCN 1~

ARFCN N

Available

frequency

Frequencies in MA participating in

FH

Site

Carrier

Configuration

Table

ARFCN 1~

ARFCN N

Available

frequency

BCCH frequency and frequencies

in MA participating in FH

Static TRX

Power class

0~10,

unit:2dB

Power class "0" shows that power

is in its maximum. Each class is

2dB less than its former class.

Cell Cell

Configuration

Data Table

FH mode Radio

frequency

hopping

FH mode should be RF FH for 1*3

frequency reuse pattern

2005-01-19 24


Cell Allocation

Table

ARFCN 1~

ARFCN N

Available

frequency

BCCH frequency and frequencies

in MA participating in FH

2005-01-19 25

Documents

1X3 Frequency Reuse Technology Guideline (v2.0)