Distance Calculator Tool for RF Engineers

Distance Calculator Tool for RF Engineers

Very Good tool You can Download.

Distance Calculator.

Its calculate distance between two latitude and longitude.

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Brief describe the advantages and disadvantages of soft handover?

Advantages:

·         Overcome fading through macro diversity.

·         Reduced Node B power which in turn decreases interference and increases capacity.

·         Reduced UE power (up 4dB), decreasing interference and increasing battery life.

Disadvantages:

·         UE using several radio links requires more channelization codes, and more resources on the Iub and Iur interfaces.

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Why is there soft handover gain?

Soft handover gain comes from the following:

• Macro diversity gain over slow fading.
• Micro diversity gain over fast fading.
• Downlink load sharing over multiple RF links.  By maintaining multiple links each link could transmit at a lower power, resulting in lower interference therefore a gain.

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Sometimes we say Ec/Io and sometimes we say Ec/No, are they different?

Io = own cell interference + surrounding cell interference + noise density

No = surrounding cell interference + noise density

That is, Io is the total received power density including CPICH of its own cell, No is the total received power density excluding CPICH of its own cell.  Technically Ec/Io should be the correct measurement but, due to equipment capability, Ec/No is actually measured.  In UMTS, Ec/No and Ec/Io are often used interchangeably.

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What is Ec/Io?

Ec/Io is the ratio of the energy per chip in CPICH to the total received power density (including CPICH itself).

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Why is Eb/No requirement lower for PS than for CS?

PS has a better error correction capability and can utilize retransmission, therefore it can afford to a lower Eb/No.  CS is real-time and cannot tolerate delay so it needs a higher Eb/No to maintain a stronger RF link.

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What are the Eb/No targets in your design?

The Eb/No targets are dependent on the service:

• On the uplink, typically CS is 5 to 6dB and PS is 3 to 4dB – PS is about 2dB lower.
• On the downlink, typically CS has 6 to 7dB and PS is 5 to 6dB – PS is about 1dB lower.

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What is Eb/No?

By definition Eb/No is energy bit over noise density, i.e. is the ratio of the energy per information bit to the power spectral density (of interference and noise) after dispreading.

Eb/No = Processing Gain + SIR

For example, if Eb/No is 5dB and processing gain is 25dB then the SIR should be -20dB or better.

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What is difference between RSCP,RSSI,EcIo?

How to calculate maximum number of users on a cell?

 To calculate the maximum number of users (M) on a cell, we need to know:

W: chip rate (for UMTS 3,840,000 chips per second)

EbNo: Eb/No requirement (assuming 3dB for CS-12.2k)

i: other-cell to in-cell interference ratio (assuming 60%)

R: user data rate (assuming 12,200 kbps for CS-12.2k)

η: loading factor (assuming 50%)

Take 12.2kbps as example:

M = W / (EnNo * (1 + i) * R) * η = 3,840,000 (3 * (1 + 0.6) * 12,200) * 0.5 = 32.8

The number of users could also be hard-limited by OVSF code space.  Take CS12.2k for example:

·         A CS-12.2k bearer needs 1 SF128 code.

·         Total available codes for CS-12.2k = 128 – 2 (1 SF64) – 2 (4 SF256) = 124.

·         Consider soft-handover factor of 1.8 and loading factor of 50%: 124 / 1.8 *.05 = 34 uers/cell.

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