Chapter 2. Determining Range and Clearance. Proxim 65756B, CPN 65756B

Tsunami MP.11a Antenna Installation Guide

Chapter 2. Determining Range and Clearance

When you read about wireless outdoor products, you often encounter the terms output power of the radio and gain of the antenna equipment as measures for the strength of the transmitted signal.

▪ Output power of radio equipment often depends on maximum limits as defined by local radio regulations; consequently, output power is, by definition, not the way to enhance wireless performance.

▪ High gain antennas are larger in size than low gain antennas and are characterized by a narrow focus of the antenna beam. These two characteristics make it more difficult to aim the antennas and adjust antenna alignment to optimize the performance of the wireless point-to-point link.

The Tsunami outdoor solution is based upon the following principles:

▪ An output power and antenna gain that comply with the maximum limits as defined by local governing bodies concerning radio transmissions.

▪ Enhanced radio sensitivity for optimal receive quality of radio signals transmitted by remote antennas.

DETERMINING THE OUTDOOR RANGE

The range of your outdoor antenna installation is closely related to a number of different factors. To let you determine the range of the Tsunami MP.11a antenna system in your situation, we have defined the following formula:

Range = Maximum Range x Cable Factor x Clearance Factor where:

Maximum Range

Cable Factor

Clearance Factor

Identifies the theoretical maximum that could be achieved under optimal circumstances using the available Tsunami MP.11a products according to their specifications and in compliance with local radio regulations.

Identifies a correction value (percentage) that compensates for additional cable losses related to the type of cables used at both ends of the wireless link. (See

“Cable Factor” on page 17.)

Identifies a correction value (in percentage) that should be used in case the signal path of your wireless link does not provide the minimum clearance as

listed in the Maximum Range table. (See “Clearance Factor” on page 18.)

Chapter 2. Determining Range and Clearance

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Issue Date: August 2003


Maximum Range

The maximum range of your Tsunami MP.11a system is based upon:

▪ The Type of Outdoor Antenna Equipment

▪ The Data Speed of the Wireless Link

▪

The clearance of the signal path (see “Clearance Factor” on page 18).

The values in this section are based on calculations that assume optimal radio conditions. They do not represent a guarantee that the same maximum distance can be achieved at your location. Differences in performance figures may result from:

▪

Incorrect alignment of antennas (see “Antenna Alignment” on page 30).

▪ Polarization mismatch of the antennas.

▪ Sources of interference or unexpected reflections in the signal path that affect the communications

quality (see “Antenna Placement” on page 12).

▪ Severe weather conditions such as heavy rain or snow fall, or strong winds.

▪ Seasonal influences such as leaves on trees, or icing on the antennas.

Cable Factor

Determine the Cable Factor from the following table to calculate the probable range for your installation.

One side of link

6 m (20 ft) / 10 mm (0.4 in)

6 m (20 ft) / 5 mm (0.2 in)

15 m (50 ft) / 15 mm (0.59 in)

15 m (50 ft) / 10 mm (0.4 in)

22 m (75 ft)

Table 1. Cable Factor

Other side of link

6 m (20 ft) / 10 mm (0.4 in)

6 m (20 ft) / 5 mm (0.2 in)

15 m (50 ft) / 15 mm (0.59 in)

15 m (50 ft) / 10 mm (0.4 in)

22 m (75 ft)

6 m (20 ft) / 5 mm (0.2 in)

15 m (50 ft) / 15 mm (0.59 in)

15 m (50 ft) / 10 mm (0.4 in)

22 m (75 ft)

15 m (50 ft) / 15 mm (0.59 in)

15 m (50 ft) / 10 mm (0.4 in)

22 m (75 ft)

15 m (50 ft)

22 m (75 ft)

22 m (75 ft)

50%

37%

80%

63%

46%

50%

Cable Factor

100%

71%

89%

71%

52%

50%

63%

37%

27%


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Note: The allowed antenna cables depend upon local radio regulations, the frequency, and the antenna

gain used as listed in Table 5 on page 24 “Minimum Antenna Cable Loss in 5 GHz Bands.”

Clearance Factor

For optimal performance of your outdoor wireless link, the signal path between the Base Station Unit and

Subscriber Unit must provide sufficient clearance.

Note: A outdoor wireless link that lacks sufficient clearance will suffer from poor performance, which is typically perceived as slow network response times. Although your Tsunami MP.11a equipment automatically retransmits every lost data frame due to an out-of-range situation or frame collision, the larger the number of retransmissions, the lower the throughput efficiency of your wireless link.

This section explains how to determine the clearance that applies in your environment and (if applicable) the effect of insufficient clearance on the range of your outdoor wireless link.

In “Chapter 1. Preparing for Installation” on page 8, we described the shape of the antenna beam as being

“bulged” in the middle.

Figure 5. Fresnel Zone

If any significant part of this bulged zone is obstructed, a portion of the radio energy is lost, which can affect the performance of your wireless link in terms of maximum range and transmit rate.


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In Figure 5, you see two variables that determine the shape of the antenna beam, also referred to as Fresnel

Zone:

▪ The distance between the antennas (a)

▪ The clearance required for optimal performance (b), where clearance should be interpreted as:

º Vertical clearance above the ground and the highest buildings or objects in the signal path

º Horizontal clearance from neighboring buildings and objects in the signal path.

For optimal range and throughput performance, you must ensure that your antenna installation provides maximum clearance in both horizontal and vertical direction.

Clearance should be interpreted as follows:

▪ In open areas without obstacles in the signal path, clearance is measured as height above the surface of the earth. For example, if the antenna is mounted on the roof, this height includes the height of the building plus the height of the mast above the rooftop.

▪ In areas with obstacles in the signal path between the two antennas, clearance should be measured as height above the highest obstacle in the signal path.

▪ In dense urban areas, the clearance should be measured as height above the highest rooftop or any other obstacles in the signal path between the two antennas.

For situations in which local authorities, the proprietor of the premises, or other factors do not let you set up an antenna mast that lets you meet the listed clearance requirements, you may be unable to achieve a full line-of-sight clearance. At the same time, however, when the distance that your wireless outdoor installation must cover is less than the listed maximum range, you may not even need full clearance,.

To determine the effect of insufficient signal path clearance, you must determine the Clearance Factor as described below, and calculate its effect on the range for your antenna installation using the formula

described in “Determining the Outdoor Range” on page 16.

▪ If the clearance for your antenna installation is equal to or better than the minimum clearance requirement, the Clearance Factor for your installation is 100%.

▪ If your actual clearance is less than the minimum clearance, use the diagram depicted in the following figure to determine the actual range that applies in your situation.

Note: The Clearance Factor Diagram should be used as a rule-of-thumb for estimating the probable range in case the clearance requirements are not fully met. In real life, using FCC approved products, you will also find it almost impossible to achieve the level of clearance for maximum range.


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Figure 6. Clearance Factor Diagram

CALCULATIONS

Availability of the microwave path is a prediction of the percent of time that the link operates without producing an excessive bit error rate (BER) due to multipath fading. In the absence of direct interference, availability is affected by the following:

▪ Path length

▪ Fade margin

▪ Frequency

▪ Terrain (smooth, average, mountainous)

▪ Climate (dry, temperate, humid)

Depending upon the type of information carried over the link and the overall network design redundancy, you may want to design for a specific availability rate. For example, if the data or voice traffic carried by the radio is critical, the link can be designed for a very high availability rate (for example, 99.999% or 5.3 minutes of predicted outage per year).

Availability can be improved by increasing the fade margin either by making the path shorter or by using the higher gain antennas in conjunction with lower loss transmission line (using a higher quality transmission line, shortening the length, or both).


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Calculating Received Signal Level and Link Budget

Use the following formula to estimate the received signal level (RSL):

RSL (dBm) = P out where:

- L

1

P

L out

1

+ G

1

+ G

2

- L

2

- L p is the transmitter output power (in dBm) is the total loss of all transmission elements between the antenna and the RF Unit on one side of the link (in dB) is the gain of the antenna on one side of the link (in dB) G

1

G

2

L

2

L p is the gain of the antenna on the opposite side of the link (in dB) is the total loss of all transmission elements between the antenna and the RF Unit on the opposite side of the link (in dB) is the Path loss, defined by:Lp (dB) = 96.6 + 20 log

10

F + 20 log

10

D where:

F is the Frequency of the radio system in GHz (5.8 in the case of this model)

D is the Distance of the path in miles

See the following figure for a visual representation of the elements of this equation.


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Procedure:

1. Start with the transmit power and the number of the channel to be used. From the output power tables

(on page 23) find the dBm associated with this output power and channel.

2. Subtract the total loss of all transmission elements between the antenna and the radio on one side of the

link (dB). (See “Minimum Antenna Cable Loss in 5 GHz Bands” on page 24.)

3. Add the dBi of the antenna you will be using. The total is the EIRP (equivalent isotropically radiated power).

4. Determine your link budget from the Distance and Path Loss table, For example, if the distance between the two radios is approximately 5 km, the link budget would be 121. (Note that this is the value for 4.8 km, which is closest to the actual value.)

5. Add the gain of the antenna on the second side of the link.

6. Subtract the total loss of all transmission elements between the antenna and the radio on the second side of the link. The result is the Received Signal Level (RSL).

7. From the Receiver Sensitivity in Table 2 on page 23, find the dBm value for the data rate used for the

link.

8. Add the “Minimum SNR for a Good Link” value of the data rate in use to the Receiver Sensitivity level.

9. Subtract this value from the Received Signal Level; this is the Fade Margin.

Notes:

▪ The RSL must be higher than the Receiver Sensitivity plus the minimum SNR for a good link. See Table

3 on page 23, to have a working link with no excessive errors. The amount of Fade Margin indicates the

reliability of the link; the more Fade Margin, the more reliable the link.

▪ The path loss must be smaller than the link budget minus the minimum required fade margin. The maximum ranges cause the path loss plus the fade margin to be the same as the link budget.

The results of this link budget calculation are very important for determining any potential problems during installation. If you have calculated the expected RSL, you can verify that it has been achieved during installation and troubleshooting, if necessary.

In the USA and Canada, this model radio can be installed with any gain directional antennas, as there is no

Effective Isotropic Radiated Power (EIRP) limit for the application of these systems for fixed point-to-point applications. In other countries, EIRP limits may apply.

In the case of EIRP limits, use the lesser of either (P out

- L

1

+ G

1

) or the EIRP limit within the previous equation. You should check this equation in both directions to assure legal application.


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An EIRP limit is the maximum RF energy that can be transmitted, as measured at the transmitting antenna, and is usually determined by government regulations.

Table 2. Receiver Sensitivity and Minimum SNR for a Good Link

Normal Mode

(Mbps)

54

48

36

24

18

12

9

Receiver

Sensitivity

- 69 dBm

- 73 dBm

- 77 dBm

- 81 dBm

- 84 dBm

- 86 dBm

- 87 dBm

Minimum SNR for a Good Link

21

20

16

12

9

7

5

6 - 88 dBm

* allowed in FCC regulatory domain only

4

Turbo Mode*

(Mbps)

108

96

72

48

36

24

18

12

Receiver

Sensitivity

- 66 dBm

- 70 dBm

- 74 dBm

- 78 dBm

- 81 dBm

- 83 dBm

- 84 dBm

- 85 dBm

Minimum SNR for a Good Link

21

20

16

12

9

7

5

4

The first Fresnel zone size is a list; Proxim’s recommendation is to keep at least 60-70% of this zone free. If the clearance is lower than this percentage, the link budget and achieved fade margin are affected.

Clearances more than 100% of the Fresnel zone can cause reflections that are 180 degrees out of phase and can cancel out the signal. The Fresnel zone works in both the horizontal and vertical paths.

Frequency Band

5.25 – 5.35 GHz

5.25 – 5.35 GHz

5.745 – 5.850 GHz

5.745 – 5.850 GHz

5.745 – 5.850 GHz

Channels

Table 3. Output Power Table for FCC

54 Mbps 48 Mbps 36 Mbps

64

149, 153

157, 161

165

6-24 Mbps

12.5 12.5 12.5 12.5

13.5 15.5 17.5 18.5

13.5 15.5 17.5 17.5

12.5 15.5 17.5 17.5

* 17.4dBm is the FCC certified peak output power of Tsunami MP.11a product at 5.25-5.35GHz band

** 20.8dBm is the FCC certified peak output power of Tsunami MP.11a product at 5.725-5.850 GHz band

These power levels are the levels at the antenna connector of the MP.11, so where the MP.11 has a higher output power than certified, the TPC needs to be used to reduce the output power.


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Table 4. Output Power Table for ETSI

Frequency Band

5.47 – 5.70 GHz

Channels

100, 104, 108, 112, 116, 120,

124, 128, 132, 136

54 Mbps 48 Mbps 36 Mbps 6-24 Mbps

14.5 15.5 17.5 18.5

Table 5. Examples of Antenna Cable Loss Required per Regulatory Domain and Antenna Type

Frequency Band

5.25-5.35 GHz

5.25-5.35 GHz

5.25-5.35 GHz

5.25-5.35 GHz

5.725-5.85 GHz

5.725-5.85 GHz

5.725-5.85 GHz

5.725-5.85 GHz

5.725-5.85 GHz

5.725-5.85 GHz

5.725-5.85 GHz

5.725-5.85 GHz

5.47-5.725 GHz

5.47-5.725 GHz

5.47-5.725 GHz

5.47-5.725 GHz

Antenna

Gain

10

17

23

31

10

17

23

31

10

17

23

31

10

17

23

31

TPC

Setting

0

-6

-10

-10

0

0

0

0

0

-6

-10

-10

0

0

-6

-10

Minimum Cable Loss for

Data up to 24 Mbps*

0

0

1.5

9.5

0

0

0

0

0

0

1.5

9.5

0

0

0

3.5

EIRP

28.5

35.5

41.5

49.5

28.5

29.5

30

30

28.5

29.5

30

30

28.5

35.5

35.5

36

Deployment

USA

USA

USA

USA

USA, PtMP

USA, PtMP

USA, PtMP

USA, PtMP

USA, PtP

USA, PtP

USA, PtP

USA, PtP

ETSI

ETSI

ETSI

ETSI

* Note that higher data rates use lower output power, so less cable loss is required to meet the maximum

EIRP limit.


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Table 6. Distance and Link Budget

Reference Frequency: 5600 MHz Center Frequency for Europe

Link Budget

(dB)

61

62

75

76

77

78

71

72

73

74

67

68

69

70

63

64

65

66

83

84

85

86

79

80

81

82

87

88

89

Distance

(m)

4.8

5.4

24

27

30

34

15

17

19

21

9.5

11

12

13

6.0

6.8

7.6

8.5

60

68

76

85

38

43

48

54

95

107

120

0.9

1.0

1.0

1.1

0.7

0.8

0.8

0.8

0.6

0.6

0.6

0.7

0.5

0.5

0.5

0.5

1.1

1.2

1.3

Fresnel Zone

(m)

Link Budget

(dB)

0.3

0.3

0.4

0.4

0.4

0.4

0.3

0.3

0.3

0.3

91

92

97

98

99

100

93

94

95

96

109

110

111

112

113

114

115

116

101

102

103

104

105

106

107

108

117

118

119

Distance

(m)

151

170

478

537

602

676

758

850

954

1071

190

214

240

269

302

339

380

426

1201

1348

1512

1697

1904

2136

2397

2689

3018

3386

3799

90 135 1.3 120 4263 7.6 150

The distance is based upon the assumption that 60% of the 1st Fresnel is clear.

5.0

5.3

5.7

6.0

4.0

4.2

4.5

4.8

6.4

6.7

7.1

Fresnel Zone

(m)

Link Budget

(dB)

1.4

1.5

121

122

3.2

3.4

3.6

3.8

2.5

2.7

2.8

3.0

2.0

2.1

2.3

2.4

1.6

1.7

1.8

1.9

131

132

133

134

135

136

137

138

123

124

125

126

127

128

129

130

139

140

141

142

143

144

145

146

147

148

149

Distance

(km)

4.8

5.4

15.1

17.0

19.0

21.4

24.0

26.9

30.2

33.9

6.0

6.8

7.6

8.5

9.5

10.7

12.0

13.5

38.0

42.6

47.8

53.7

60.2

67.6

75.8

85.0

95.4

107.1

120.1

134.8

Fresnel

Zone (m)

8.0

8.5

14.2

15.1

16.0

16.9

17.9

19.0

20.1

21.3

9.0

9.5

10.1

10.7

11.3

12.0

12.7

13.4

22.6

23.9

25.3

26.8

28.4

30.1

31.9

33.7

35.7

37.9

40.1

42.5


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Chapter 2. Determining Range and Clearance. Proxim 65756B, CPN 65756B

Chapter 2. Determining Range and Clearance

DETERMINING THE OUTDOOR RANGE

Maximum Range

Cable Factor

Clearance Factor

CALCULATIONS

Calculating Received Signal Level and Link Budget

Related manuals

Table of contents

Chapter 2. Determining Range and Clearance. Proxim 65756B, CPN 65756B