Slotted mode is enabled in those WCDMA cells bordering GSM, creating the possibility of inter RAT handovers. Unlike GSM, where the duty cycle is 12.25%, in WCDMA, the duty cycle of the frames are 100%. Therefore it becomes important to introduce gaps/reduced duty cycle in the frames (slotted mode) to enable the UE to make BCCH measurements of the GSM neigboring cells. These reports are sent to the RNC over the DCCH.
In Compressed Mode idle periods are created in radio frames during which the UE can perform measurements on other frequencies.
The UE can carry out measurements in the neighboring cell, such as GSM cell and cell on another frequency.
Two different methods, HLS or SF/2, are used to create these idle periods depending on the radio bearer combination.
While doing the planning in unet, I came across this term in Site equipment table....
At that time I searched the help and got the following explanation...
Compressed Mode: If you select this option, cells located on sites with this equipment are able to manage compressed mode when radio conditions require it. Compressed mode is generally used to prepare the hard handover of users with single receiver terminals.
Compressed mode aka slotted mode is enabled only for hard-handovers, as in the case of inter-RAT HOs. But, one should note the implications of compressed mode operations: higher power requirements for the individual connection, and also capicity loss, especially in the downlink, due to excess Node B power utilization.
One doubt arises is that if this compressed mode is not enables then will the inter RAT HO(hard handover) will get affected???
How will the inter RAT HO take place in that case?
Please focus on this......
There are other techniques to implement inter RAT handovers apart from compressed mode handovers like a blind handover, wherein the base station hands off the UE by passing it the details of the new cell to the UE without linking to it and setting the timing, etc of the mobile for the new cell. In this mode, the network selects what it believes to be the optimum GSM based station. The UE first locates the broadcast channel of the new cell, gains timing synchronisation and then carries out non-synchronised intercell handover.
Compressed mode is not necessary. If the UE has a second receiver it can make measurements on that receiver while continuing with the transmission/reception on the first receiver. This does not happen in practise as the cost would go up. The UE capabilities define whether a UE requires compressed mode in order to monitor cells on other FDD frequencies and on other modes and radio access technologies. UE capabilities indicate the need for compressed mode separately for the uplink and downlink and for each mode, radio access technology and frequency band.
unlike GSM,Mobile in CDMA based technology like WCDMA is fully lisening to the network & dont get idle periods/time for performing inter-freq & inter RAT measurements.
In compressed mode radio transmission on the currently used radio link is frequently interrupted. Extremely short interruption periods are called gaps and are used to gather measurement results of neighbour cells working on different UTRAN frequencies or different RATs.
Compressed mode is of course not a standard mode for radio transmission and as a rule it needs a special measurement event to trigger the activation of compressed mode measurements.If event-triggered measurement reporting is activated this event is usually described by event-ID 2D: ‘The estimated quality of the currently used frequency is below a certain threshold’.
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Originally Posted by justdream
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