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Thursday, April 28, 2011

Rake receiver and Multipath signal propagation

Because of the natural obstacles, signals transmitted may take multiple paths and reach destination at different time. As the chip rate is 3.84Mcps leads to time duration 0.26MicroSecs. If the time difference between multipath signal is 0.26 Micro seconds then receiver can separate those signals and combine them.

Power Control

Open loop power control make rough estimate of path loss by means of a downlink beacon signal. This may not be accurate.
Closed loop power control is performed in the uplink; base station performs frequent estimates of the received Signal-to-Interference Ratio (SIR) and compares it to a target SIR. If the measured SIR is higher than the target SIR, the base station will command the mobile station to lower the power; if it is too low it will command the mobile station to increase its power.

Outer loop power control a procedure where target SIR is changed based on signal quality. Based on the quality of radio link measure in the uplink for each user data channel regulates the target SIR.

Monday, April 25, 2011

Engineering mode/Field test mode in various mobiles using codes

LG Mobile:
Most of the LG Models have similar field test menu:
  1. Version
  2. Factory Reset
  3. Device Test
  4. Port Setting
  5. Modem Setting
  6. SIM Test
  7. IMS Setting
  8. IM Client ID
Engineering mode (field test mode) could be found under Modem Setting. Modem setting has various options including the Network mode, Engineering Mode, GPRS Attach and many more. In some of the LG Models if you want to get into Engineering mode directly using code *748#96


Model : LG CU720 (LG Shine), LG CU575, LG CU500, LG CU400 (many other models)
Code : 3845#*360#
Model:  LG CF360(This model has more options in the field test mode like GPS, DRM test menus, Calibration data)

Samsung Mobile:
Code: *#0011#
Model: SGH-A707, SGH-A717, SGH-A727, SGH-i617 and many other models support this code.

Apple iPhone:
Code : *3001#12345#* then press call
Various field test information could be seen under the menus.

Blackberry Mobile:
Code: Menu->Settings->Options->status
This would show some of field test information on blackberry phones.

Nokia Mobile:
Code: *3001#12345#.
Code changes on some of the Model. Some time field test displays as Net monitor in Nokia mobiles.  Most of the models like Nokia 12xx, 51xx (except 5125), 61xx, 62xx, 71xx,3285, 63xx are supported with this code. To get out the engineering mode, you need to either dial 00/01 in some models, in some models in net monitor, you many dial 0000.

You contact me if you need more information or field test mode for any other phone/model, I would try to look and get the information back to you.

What is WPS - Wireless Priority Service

WPS means Wireless Priority Service which is priority calling service provided to the subscribers by the operators. This service is add-on service which shall be subscribed by the subscriber.  User must be having WPS feature enabled to make the WPS call.
To make WPS call, dial, *272 + Destination Number

Remember you do not need a special cellphone to make WPS call, only need to subscribed to WPS package from operator. Receiver of the WPS call does not need to subscribe for the WPS feature. *272 enables the priority access to local channels, High probability of completion  features (HPC). If the terminating end is mobile user the then priority channels are allocated for terminating call.