TTI bundling has been recently introduced as a feature of LTE. Rel. 8 to improve the uplink coverage. In TTI bundling, a VoIP packet is transmitted as a single. TTI Bundling optimizes the uplink (cell edge) coverage for services like VoLTE. For services such as VoIP, the packet size is small and the. TTI Bundling in FDD and TD-LTE Abstract TTI Bundling has been introduced in FDD Alternative Approach The alternative to TTI bundling is.

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Thanks for the chart on explaining it visually. Emeka Ijere February 20, at 7: Adnan Basir April 17, at 2: Re transmission means control plane overhead and specially the delay which is not acceptable for services like VoIP. Isn’t it too much waste of subframes? Why are the durations of the TTIs all common, or equal?

TTI Bundling in FDD and TD-LTE

Therefore, in a case where the communication bjndling for time critical communication and UE is in the area of poor coverage e. Magdalena Mieczkowska November 18, at 7: As shown in Figure 4, TTI bundling enables up to 4 redundancy versions of the same transport block to be sent in 4 consecutive subframes. But I haven’t seen any case in which this is enabled in live network, at least as of now Aug, Is this ‘Not allowed’?

Or is there any misunderstanding from my side?

Should it be always like this i. According to this statement, the PHICH timing for all the case illustrated above the answer is same as follows. Check the following figure to understand bundlnig concept of TTI. Just enable a ttiBundling IE as shown below. This could for example happen at the edge of a cell when the terminal has to send high power but is limited by the power capability of the terminal. DJ May 29, at 3: This way the bunding of successfully decoding the bits improve every time.


Combined processing of the redundant transmissions over multiple buundling leads to a better probability of detection of the transport block. Thus, with limited power, the UE has a better chance of a successful transmission with lesser latency using the TTI bundling method.

All about Wired and Wireless Technology: TTI Bundling

A single RLC PDU is transmitted as multiple redundancy versions in consecutive subframes using a single common allocation. What would be the advantages and drawbacks of TTI bundling compared to this bundlng solution if it is possible to implement? The reciever will combine the previously recieved erroneous data with newly attempted data by the sender. Or only in UL? So the basic idea of TTI bundling is to improve performance of VoIP applications bundlnig cell edge and therefore it happens only in uplink Hope this helps.

Unknown April 25, at When the base station detects that the mobile can’t increase it’s transmission power and reception is getting worse it can instruct the device to activate TTI bundling and send the same packet but with different error detection and correction bits in 2, 3 or even 4 consecutive transmit time intervals.

Normally, a transport block is converted to multiple redundancy versions after coding and the first redundancy version is sent in a subframe.

That is true, but tti kind of normal retransmission mechnism cause a certain time delay e. Or its just implementation difference. TTI bundling is used to achieve successful transmissions from power limited terminals. Sekhar joined Award Solutions inand has over 16 years of experience in wireless telecommunication industry with mobile cellular, digital communications technologies.

Then Why we need this kind of method?

LTE TTI Bundling

One drawback of this method is the potential overhead increase due to RLC segmentation due to multiple RLC headers needed. Unknown December 14, at 2: This triggers the eNB to transmit the various redundancy versions of the same transport block in consecutive subframes or TTIs giving rise to the name TTI bundling.


In case the bundle is not received correctly, it is repeated in the same way as an ordinary transmission of a packet. Ok here is what I understand Since UE has very limited power in uplink 23dbm LTE this means that at cell edge there can be many re transmissions in uplink due to poor radio conditions.

Altamont April 16, at 2: There might be retransmissions of each of those transport blocks which will also potentially increase the control signaling overhead. Latency is also reduced as no waiting time is required between the retransmissions. There must be some technical reason why they are not varied. Overview of TTI Bundling.

There is one drawback however, that it can result in delay and too much control overhead in case of poor radio conditions if the sender has to attempt many transmissions.

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Eric November 29, at 8: The process as shown in Figure 3 is typically triggered by UE informing the eNB about its power limitations at the present state. At first the feature name reminded me of the packet bundling that is done in Wi-Fi, which concatenates several packets into one transmission burst thereby saving a lot of air interface overhead.

There is no way to reduce the waste of subframe caused by retransmission, but there is some way to reduce the wast of subframe caused by scheduling restriction.

In addition, since we are transmitting many small transport blocks, the chances of interpreting a NACK as a ACK also increases proportionately with the increase in the RLC segmentation size. Winnie Lee August 4, at 4: Or is equally applicable to both?

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