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Showing posts from February, 2012

Hard Handover

Soft handover refers to the intra-frequency handover, but not all intra-frequency handovers are soft handovers. If the target cell and the former cell have the intra-frequency but belong to different RNC, and there is no Iur interface between RNCs, the intra-frequency hard handover will occur. Besides, the internal code handover in the same cell is also hard handover. Inter-system hard handover consists of the handover between FDD mode and TDD mode, the handover between WCDMA system and GSM system in R99, and the handover between WCDMA and cdma2000 in R4.


Soft Handover

Soft handover refers to that a MS begins to connect with a new BS (Base Station), the communication between the mobile station and the former base station is still on. Soft handover is only applying to the CDMA cells with the same frequency.

Comparison between 3G Technologies

In this post we will compare different 3G technologies. Comparison is done using Receiver structure, Support closed-loop power control, Handoff, Demodulation mode, Chip rate, Transmit diversity mode, Synchronization mode and Core network. This is shown in the following table. WCDMA cdma2000 TD-SCDMA Receiver structure Rake Rake Rake Support closed-loop power control Yes Yes Yes Handoff Soft handoff and hard handoff Soft handoff and hard handoff Relay handoff Demodulation mode Coherence demodulation Coherence demodulation Coherence demodulation Chip rate (Mcps) 3..8 N*1228 1.2 Transmit diversity mode TST, STT, and FBT OT and ST None Synchronization mode

WCDMA ( Wideband Code Division Multiple Access)

WCDMA ( Wideband Code Division Multiple Access) is a wideband spread-spectrum 3G mobile telecommunication system to support wideband services like high-speed Internet access, video and high quality image transmission with the same quality as the fixed networks. 

Handover

As the MS (Mobile station) gets out of the service cell and goes into another service cell, the link between the former base station and the MS will be substituted for the link between the new base station and the MS. Handover, in mobility management, is mostly performed by RRC layer protocol in 3G.

WCDMA Power Control

In terms of power management, the QOS (Quality of Service) of a subscriber can be improved by increasing the transmit power of the subscriber. However, such improvement may result in deteriorating other subscriber’s receiving quality due to the self-interference feature of the CDMA system. WCDMA adopts the broadband spreading technology with all signals sharing the same spectrum and the signal energy of each MS is allocated within the frequency band, thus for other MSs it is a kind of wideband noise. Therefore, the use of power in the CDMA system is conflicting.

Smart Antenna

Smart antenna is one of the key enhanced technologies in the 3G system. SA (Smart Antenna) reduces the effects of time delay spread, Rayleigh fading, multi-path, channel interference, distinguishes the signals from the same frequency and timeslot, and combines with other multiple access technologies to maximize the use of frequency spectrum resources.

Rake Receiver

Signals sent over the air can take multi-paths to the receiver. It can result in the receiving several versions of the same signal but at slightly different times. Multi-paths can cause a loss of signal through cancellation in other technologies. WCDMA rake receiver is multiple receivers in one. The rake receiver identifies the three strongest multi-path signals and combines them to produce one very strong signal.

Paper Ruler

Everyone must have come across the problem of searching for a ruler to measure something. Unfortunately you can't carry a foot ruler with you all the time. So what can you do?

Find Large Number of Duplicate Files on Your Computer

You might have come across the problem of identifying and removing the duplicate files in your computer. These duplicates file could be created by yourself or by some applications. If the number of  files to be identified is in small amount then you can do it manually. But if it is bulk then this process will be time consuming and boring. 

Shaolin warrior training

Shaolin warrior training:
Shaolin Kung Fu is a collection of Chinese martial arts that might have  affiliation with the Shaolin Monastery. Some of the different styles of kung fu and wushu are actually related to Shaolin temple. Due to the loss of records during the 20th Century Cultural Revolution, it is very difficult for a particular style to conclusively establish a connection to Shaolin temple.

Mathemagic 01

In this post we are presenting some mathmagics to you.