Unix Simulator ( Cygwin )

Happy to share one more software called Cygwin with you.

What it is?
I can say it is a UNIX simulator for MS Windows Machine. I come across this with the help of my good friend Chintav just before a week. As its website describes “Cygwin is a Linux-like environment for Windows ". So, you can do little practice on basic commands of Unix/Linux with this Utility and No need to create separate partition for Linux and make your system dual-boot for windows and Linux. You can download it from provided link. And best thing is that it’s absolutely free, no trial and no limitations. So click on it and start practicing UNIX on your favorite windows machine. Software will tell you more about it and I can say it is very helpful tool. Do try it without hesitation. Have a nice day.

Sudoku with Excel

What to do for a time pass?

Today I am on leave & in the noon time with extreme hot condition I decided to solve SUDOKU.
But after some time I realize “why to do such a Majuri daily? Let my Intel Processor work for me." and as a result of such a great thought I started to write code for solving daily headache, and here I am with SUDOKU solver.

Code written here is able to solve all easy level as well as most of medium level puzzles. You can also able to solve difficult level puzzle by giving some manual inputs. It will not solve whole puzzle with a single click but give you some HELP whenever u wanted in the middle of puzzle. By doing so it will intact your fun also. I am also giving complete code for this so that you can also get idea of Excel Programming. To open the code just click on Visual Basic Editor from TOOL-->MACRO Menu of your EXCEL application. The file is available on my group Tech Crazy.

Ec/Io Vs Eb/No

Today I got the query about Ec/I0 and Eb/N0, What is the Difference between these terms? Here are a possible short explanations for them.

What is Ec/I0?

A special term is used to describe the SNR of the pilot channel: energy per chip per interference density, or Ec/I0. The energy per chip Ec is different from energy per bit Eb in that “chips” refer to PN sequences that are spread. Since there is no base-band information contained in the pilot channel, the pilot is not de-spread and bits are not recovered. Therefore, in order to describe the signal strength of the pilot channel, the raw SNR, or Ec/I0, is used. Note that since the pilot is not de-spread, Ec/I0 remains less than 1 most of the time.

The Ec/I0 is the energy per chip per interference density measured on the pilot channel; it is effectively the signal strength of the pilot channel.

Why it is needed?

This mobile-assisted handoff (MAHO) is evident in that the mobile makes a measurement of forward link Ec/I0 and reports the measurement result to the base station. Since each base station transmits its own pilot on a different PN offset, the Ec/I0 of a pilot gives a good indication of whether or not the particular sector should be the serving sector for the mobile. With accordance of Ec/I0 of different pilots, they switched between different sets like Candidate or neighbor set.

The candidate set contains those pilots whose Ec/I0s are sufficient to make them handoff candidates. This means that if the Ec/I0 of a particular pilot is greater than the pilot detection threshold T_ADD, then that pilot will be added to the candidate set. A pilot is removed from this set and placed in the neighbor set if the strength of that pilot drops below the pilot drop threshold T_DROP for more than the duration specified by the handoff drop timer expiration value T_TDROP. The candidate set can contain at least six pilots.

What is Eb/N0?

In digital communication, we are primarily interested in a link metric called Eb/N0, or energy per bit per noise power density. The link requires a particular Eb/N0 to attain an acceptable BER and ultimately an acceptable frame error rate (FER). Capacity is inversely proportional to the required Eb/N0 of the link. The lower the required threshold Eb/N0, the higher the system capacity.

Why it is needed?

FER is a good indicator of link quality. But because it takes a long time for the base station to accumulate enough bits to calculate FER, Eb/N0 is used as an indicator of reverse link quality.

The reverse-link closed-loop power control is as follows:

1. The base station continuously monitors Eb/N0 on the reverse link.
2. If Eb/N0 is too high (i.e., if it exceeds a certain threshold), then the base station commands the mobile to decrease its transmit power.
3. If Eb/N0 is too low (i.e., if it drops below a certain threshold), then the base station commands the mobile to increase its transmit power.



Summary:

Ec/I0: Used for Forward Link (Pilot) Measurement & MAHO.
Eb/N0: Used for Reverse Link Measurement & Power Control.

Signalling Link Calculation

Assumptions :

»the speech channels carry a traffic load of 0.75 Erl
»the average call duration is 100 seconds
»the signaling link is used at a rate of 0.2 Erl
»each call setup and call release involves the transmission of 14 information blocks with 12 bytes each ( per POTS subscriber ) and 24 bytes ( per ISDN subscriber )

Explanation :

»per hour every speech channel carries 3600/100 * 0.75 = 27 calls
»per hour every speech channel 27*14*24 = 9072 bytes of info must be transmitted ( 4536 bytes from exchange A to B and 4536 bytes from exchange B to A )
»a circuit transmits 64000 bits/sec or 8000 bytes/sec or 8000*3600*0.2 bytes/hour I.e 5760000 bytes/hour
»with each voice channel transmits 4536 bytes a signaling circuit can support 5760000/4536 = 1269.84 voice circuits.

CDMA Hard Handoff

What is Hard Handoff?

The hard handoff process here concerns the D-to-D handoff, in which a handoff between CDMA carriers occurs. D-to-D handoff is carried out via the handoff direction message and the process is known as break-before-make. In break-before-make, the call is interrupted before the acquisition of the new carrier. If the acquisition is successful, the call continues; otherwise, the call is interrupted. Hard Handoff can be possible between different system , Different BSC/MSC where direct ATM link is not established and also between CDMA to Analog system (D-to-A).

Advantages of Hard Handoff

● Continue the call beyond the current network.
● Provide expanded service.
● Overlay and integration of new CDMA networks with the existing networks.

How to Implement Hard Handoff?

The different methods for implementing hard handoff are listed below.

1) Pilot Beacon
§ A pilot beacon cell is a signal which can be seen by arriving mobiles from the other system on their own frequency, inducing them to request handoff as soon as it is appropriate
§ When mobiles request soft handoff with the beacon, the old system steps in and instructs the mobiles to do inter system hard handoff to the real cell which the mobiles are approaching on the other system

2) RTD Triggered
§ The out looking sector of cell is tagged in the site database as a “border sector”. Whenever a mobile is served exclusively by a border sector, the system continuously monitors that mobile’s round trip delay (RTD).
§ When the mobile’s RTD passes upward through a data filled threshold, the system steps in and orders a hard handoff to previously defined sector on the other system/same system

3) Ec/Io Triggered
§ Out looking sectors of border cells are tagged as “border sectors” in the system database
§ Whenever a mobile is served exclusively by a border sector, the system frequently interrogates the mobile with pilot measurement request messages
§ When the mobile’s reports the boundary sector’s Ec/Io is below a preset threshold, the system immediately commands a hard handoff to a previously defined sector on the other system/same system.

4) Enhanced Hard Handoff

§ EHHO is a Quality based HHO Trigger, it allows the call to remain on overlay sector(s) as long as possible & only hand down to underlay when call quality is impacted.

§ User configured trigger conditions are defined from many parameters like FER, Forward Traffic Gain or Eb/No. We can set threshold for individual parameters.

How Hard Handoff Works?

The base station directs the mobile station to perform a CDMA-to-CDMA hard handoff by sending an Extended Handoff Direction Message , a General Handoff Direction Message or a Universal Handoff Direction Message in which the mobile station is transitioned between disjoint sets of base stations, different Frequency Assignments, or different frame offsets.

Different Handoff Messages.

Forward Traffic Channel Handoff Messages
1. Pilot Measurement Request Order:
2. Analog Handoff Direction Message:
3. Neighbor List Update Message
4. Extended Handoff Direction Message:
5. Candidate Frequency Search Request Message:
6. Candidate Frequency Search Control Message:
7. Extended Neighbor List Update Message:
8. Supplemental Channel Assignment Message:
9. General Handoff Direction Message:
10. Periodic Pilot Measurement Request Order:
11. Universal Handoff Direction Message:
12. Mobile Assisted Burst Operation Parameters Message:
13. Extended Supplemental Channel Assignment Message:
14. Forward Supplemental Channel Assignment Mini Message:
15. Reverse Supplemental Channel Assignment Mini Message:

Reverse Traffic Channel Handoff Messages
1. Pilot Strength Measurement Message or Extended Pilot Strength Measurement Message:
2. Handoff Completion Message or Extended Handoff Completion Message:
3. Candidate Frequency Search Report Message:
4. Periodic Pilot Strength Measurement Message:
5. Pilot Strength Measurement Mini Message:

Message Flow for the Hard handoff.

Detailed information is Available on Group Tech Crazy